| 1. |
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| 2. |
- Deng, Min, et al.
(författare)
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Genome-wide association analyses in Han Chinese identify two new susceptibility loci for amyotrophic lateral sclerosis
- 2013
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Ingår i: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 45:6, s. 697-
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Tidskriftsartikel (refereegranskat)abstract
- To identify susceptibility genes for amyotrophic lateral sclerosis (ALS), we conducted a genome-wide association study (GWAS) in 506 individuals with sporadic ALS and 1,859 controls of Han Chinese ancestry. Ninety top SNPs suggested by the current GWAS and 6 SNPs identified by previous GWAS were analyzed in an independent cohort of 706 individuals with ALS and 1,777 controls of Han Chinese ancestry. We discovered two new susceptibility loci for ALS at 1q32 (CAMK1G, rs6703183, P-combined = 2.92 x 10(-8), odds ratio (OR) = 1.31) and 22p11 (CABIN1 and SUSD2, rs8141797, P-combined = 2.35 x 10(-9), OR = 1.52). These two loci explain 12.48% of the overall variance in disease risk in the Han Chinese population. We found no association evidence for the previously reported loci in the Han Chinese population, suggesting genetic heterogeneity of disease susceptibility for ALS between ancestry groups. Our study identifies two new susceptibility loci and suggests new pathogenic mechanisms of ALS.
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| 3. |
- Zhou, Guang-Quan, et al.
(författare)
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Automatic Myotendinous Junction Identification in Ultrasound Images Based on Junction-Based Template Measurements
- 2023
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Ingår i: IEEE transactions on neural systems and rehabilitation engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 1534-4320 .- 1558-0210. ; 31, s. 851-862
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Tidskriftsartikel (refereegranskat)abstract
- Tracking the myotendinous junction (MTJ) motion in consecutive ultrasound images is essential to assess muscle and tendon interaction and understand the mechanics' muscle-tendon unit and its pathological conditions during motion. However, the inherent speckle noises and ambiguous boundaries deter the reliable identification of MTJ, thus restricting their usage in human motion analysis. This study advances a fully automatic displacement measurement method for MTJ using prior shape knowledge on the Y-shape MTJ, precluding the influence of irregular and complicated hyperechoic structures in muscular ultrasound images. Our proposed method first adopts the junction candidate points using a combined measure of Hessian matrix and phase congruency, followed by a hierarchical clustering technique to refine the candidates approximating the position of the MTJ. Then, based on the prior knowledge of Y-shape MTJ, we finally identify the best matching junction points according to intensity distributions and directions of their branches using multiscale Gaussian templates and a Kalman filter. We evaluated our proposed method using the ultrasound scans of the gastrocnemius from 8 young, healthy volunteers. Our results present more consistent with the manual method in the MTJ tracking method than existing optical flow tracking methods, suggesting its potential in facilitating muscle and tendon function examinations with in vivo ultrasound imaging.
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| 4. |
- Luo, Lei, et al.
(författare)
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An experimental investigation on the thermal augmentation of internal endwall in a two-pass duct using an array of delta-winglet vortex generator pair
- 2022
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Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 182
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Tidskriftsartikel (refereegranskat)abstract
- The present study experimentally demonstrates a novel design for an internal endwall in a two-pass duct heat exchanger. An array of delta-winglet vortex generator pairs with different aspect ratio, angle of attack, configuration are mounted on the internal endwall in a U duct. Liquid crystal thermalgraphy and static pressure measurements are utilized in this study to evaluate the heat transfer, thermal-hydraulic performance, and pressure drop penalty. The Reynolds number is varied from 10,000 to 20,000. A comparison between the current novel design and traditional enhanced heat transfer turbulators in the open literature is also included. The results show that the endwall heat transfer is enhanced greatly as the longitudinal vortex generator array is located on the endwall. The variation of the attack angle has great influence on the endwall heat transfer, The endwall fitted with turbulators with an aspect ratio (length/height) of 2 and attack angle of 45-deg provides the highest thermal-hydraulic performance with a relatively low pressure drop penalty as long lasting longitudinal vortices might be induced at this attack angle and the heat transfer is observed to be enhanced at the downstream part of the endwall. In addition, for the temperature uniformity on the endwall, the local heat transfer at the upstream part still has the potential to be further improved for all studied cases. The optimal thermalhydraulic performance is increased by more than 24% compared with that on the endwall in the smooth U duct. This novel design presents a rather high overall thermal performance compared with the traditional design in the open literature.
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| 5. |
- Qiu, Dandan, et al.
(författare)
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On heat transfer and flow characteristics of jets impingement on a concave surface with varying pin-fin arrangements
- 2021
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Ingår i: International Journal of Thermal Sciences. - : Elsevier BV. - 1290-0729. ; 170
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Tidskriftsartikel (refereegranskat)abstract
- Numerical simulations have been conducted to investigate the effects of pin-fin arrangement and jet Reynolds number on heat transfer enhancement and flow characteristics of a concave confined jet impingement cooled surface conjugated with pin-fins. The results without a pin-fin are used as a baseline. Vortices and different sections of streamlines in the channel are employed to understand the flow structures in this cooling system. Based on this, topology pictures are obtained with skin-friction lines to discuss the fluid flow near the target and pin-fin surface. The local and averaged heat transfer characteristics are analyzed using the flow characteristics. The overall parameters (friction factor, thermal performance, pumping power) are also obtained. The results show that the appearance of the pin-fin plays a positive role in heat transfer enhancement and uniformity. The case of a 35° pin-fin arrangement angle reaches the highest overall Nusselt number and heat transfer uniformity. The far away movement of the pin-fin is beneficial to decrease pumping power at a constant heat transfer. The thermal performance is highest for 55° pin-fin arrangement angle at a jet Reynolds number of 40,000 in this work.
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| 6. |
- Qiu, Dandan, et al.
(författare)
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On heat transfer and flow characteristics of jets impinging onto concave surface with varying bleeding arrangements
- 2021
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Ingår i: International Journal of Numerical Methods for Heat and Fluid Flow. - 0961-5539. ; 31:12, s. 3642-3660
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose of this study is to investigate the effects of film holes’ arrangements and jet Reynolds number on flow structure and heat transfer characteristics of jet impingement conjugated with film cooling in a semicylinder double wall channel. Design/methodology/approach: Numerical simulations are used in this research. Streamlines on different sections, skin-friction lines, velocity, wall shear stress and turbulent kinetic energy contours near the concave target wall and vortices in the double channel are presented. Local Nusselt number contours and surface averaged Nusselt numbers are also obtained. Topology analysis is applied to further understand the fluid flow and is used in analyzing the heat transfer characteristics. Findings: It is found that the arrangement of side films positioned far from the center jets helps to enhance the flow disturbance and heat transfer behind the film holes. The heat transfer uniformity for the case of 55° films arrangement angle is most improved and the thermal performance is the highest in this study. Originality/value: The film holes’ arrangements effects on fluid flow and heat transfer in an impingement cooled concave channel are conducted. The flow structures in the channel and flow characteristics near target by topology pictures are first obtained for the confined film cooled impingement cases. The heat transfer distributions are analyzed with the flow characteristics. The highest heat transfer uniformity and thermal performance situation is obtained in present work.
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| 7. |
- Wang, Dandan, et al.
(författare)
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Porcine ZBED6 regulates growth of skeletal muscle and internal organs via multiple targets
- 2021
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Ingår i: PLOS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 17:10
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Tidskriftsartikel (refereegranskat)abstract
- ZBED6 (zinc finger BED domain containing protein 6) is a transcription factor unique to placental mammals and its interaction with the IGF2 (insulin-like growth factor 2) locus plays a prominent role in the regulation of postnatal skeletal muscle growth. Here, we generated lean Bama miniature pigs by generating ZBED6-knockout (ZBED6(-/-)) and investigated the mechanism underlying ZBED6 in growth of muscle and internal organs of placental mammals. ZBED6(-/-) pigs show markedly higher lean mass, lean mass rate, larger muscle fiber area and heavier internal organs (heart and liver) than wild-type (WT) pigs. The striking phenotypic changes of ZBED6(-/-) pigs coincided with remarkable upregulation of IGF2 mRNA and protein expression across three tissues (gastrocnemius muscle, longissimus dorsi, heart). Despite a significant increase in liver weight, ZBED6(-/-) pigs show comparable levels of IGF2 expression to those of WT controls. A mechanistic study revealed that elevated methylation in the liver abrogates ZBED6 binding at the IGF2 locus, explaining the unaltered hepatic IGF2 expression in ZBED6(-/-) pigs. These results indicate that a ZBED6-IGF2-independent regulatory pathway exists in the liver. Transcriptome analysis and ChIP-PCR revealed new ZBED6 target genes other than IGF2, including cyclin dependent kinase inhibitor 1A (CDKN1A) and tsukushi, small leucine rich proteoglycan (TSKU), that regulates growth of muscle and liver, respectively. Author summary The lean meat rate is an important economic trait for the swine industry and it is determined by muscle growth and development. A single base change in intron 3 of the insulin-like growth factor 2 (IGF2) gene increases meat production in pigs by disrupting a binding site for zinc finger BED domain containing protein 6 (ZBED6). Chinese indigenous pig breeds carrying the homozygous IGF2 wild-type allele produce low lean meat. We thus generate a lean pig model in Chinese Bama pig by knocking out ZBED6. In this model, we demonstrate that ZBED6 KO increases muscle and internal organ growth through ZBED6-IGF2 axis and other target genes. These results not only open new strategies for lean meat breeding in Chinese indigenous pigs, but also provide new insights to the global function of ZBED6 in organ growth and development.
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| 8. |
- Wang, Dandan, et al.
(författare)
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Ultrafast carrier dynamics of near-band-edge emission in single-crystal ZnO nanorods
- 2011
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Ingår i: Materials research bulletin. - : Elsevier Science B.V., Amsterdam.. - 0025-5408 .- 1873-4227. ; 46:6, s. 937-940
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Tidskriftsartikel (refereegranskat)abstract
- We report on rational synthesis and optical characteristics of highly crystallined ZnO nanorods which were grown by a facile chemical vapor transport method. Temperature-dependent photoluminescence spectra of as-fabricated ZnO nanorods are dominated by near-band-edge emission with a characteristic fine structure due to high crystallinity. Furthermore, the recombination emission involving carrier dynamics of near-band-edge emission in ZnO nanorods was systematically investigated by temperature-dependent time-resolved photoluminescence spectroscopy. Recombination peaks pertaining to the exciton emissions are monitored and resolved in both temporal and spatial regimes.
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| 9. |
- Zhao, Dandan, et al.
(författare)
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Investigation of ion irradiation hardening behaviors of tempered and long-term thermal aged T92 steel
- 2018
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115. ; 511, s. 191-199
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Tidskriftsartikel (refereegranskat)abstract
- 9Cr ferritic/martensitic steels are promising materials for in-core components in advanced Gen-IV reactors. In these applications, their long-term microstructural stability under thermal exposure and resistance to neutron irradiation are essential. Tempered (unaged) and long-term thermal aged T92 samples were used to evaluate the effects of thermal aging and ion irradiation on the microstructure and micromechanical properties of the steel. Both the tempered and aged samples were irradiated with 3 MeV Fe11+ions to 0.25, 0.50, 1.00 and 5.00 dpa at room temperature. Using the nanoindentation technique, the irradiation hardening behaviors of T92 steel were investigated. The irradiation hardening effect was observed in both the tempered and aged T92 samples. To eliminate the soft substrate effect, the critical indentation depth was determined using the ratio of the average hardness of irradiated and unirradiated samples at the same depth. Under the same irradiation conditions, the macroscopic hardness values of the aged T92 samples after irradiation were lower than those of the tempered samples. The irradiation hardening effect was more significant in the aged T92 due to the decreased dislocation density and the coarsened martensitic lath after long-term thermal aging.
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| 10. |
- Zhao, Dandan, et al.
(författare)
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Proton irradiation induced defects in T92 steels: An investigation by TEM and positron annihilation spectroscopy
- 2019
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 442, s. 59-66
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Tidskriftsartikel (refereegranskat)abstract
- In order to investigate proton irradiation damage on ferritic/martensitic T92 steels, both the unaged and aged (650 °C for 15,000 h) T92 steels were irradiated with 250 keV protons to 0.01, 0.05 and 0.20 dpa at room temperature due to the lower dose rate of protons compared with heavy-ions. The microstructural evolution induced by thermal aging and proton irradiation was studied by transmission electron microscopy and positron annihilation spectroscopy, and the corresponding micromechanical property changes were investigated by nano-indentation. After 0.20 dpa proton irradiation, the dominant irradiation-induced dislocation loops were a0100 type loops for both the unaged and aged samples. The dislocation-type defects in the aged T92 sample were larger in size and higher in number density, compared with those in the unaged samples. Less vacancy-type defects induced by protons were detected in the aged than the unaged T92 samples under the same irradiation conditions. The higher number density of dislocation-type defects led to more severe irradiation hardening in the aged T92 samples.
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| 11. |
- Zhao, Zhiqi, et al.
(författare)
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Effect of divider wall-to-end wall distance on the vortical structures and heat transfer characteristics of two-pass channel using topological analysis
- 2022
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Ingår i: International Journal of Numerical Methods for Heat and Fluid Flow. - 0961-5539. ; 32:1, s. 219-240
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: This study aims to explore the 3 D separated flow fields and heat transfer characteristics at the end wall of a serpentine channel with various turn clearances using topological analysis and critical points principles of three-dimensional vortex flow. Design/methodology/approach: This aims to explore the 3 D separated flow fields and heat transfer characteristics at the end wall of a serpentine channel with various turn clearances using topological analysis as well as critical points principles of three-dimensional vortex flow. Findings: The endwall heat transfer in the narrow spacing passage is significantly stronger than that in a wide spacing channel. As the gap clearance is kept at 0.87 times of the hydraulic diameter, the endwall heat transfer and thermal performance can be accordingly enhanced with low pressure drops, which is because a relatively strong concentrated impingement flow for the medium gap clearance helps to restrain the downstream fluid flow and enhance the shear effect of the secondary flow. Practical implications: The numerical results can be applied in designing sharp turn of serpentine channel in heat exchangers, heat sinks, piping system, solar receiver and gas turbine blades. Originality/value: The evolution mechanism of the vortices in the turning region under different gap clearance was analyzed, and thermal enhancement characteristics were predicted innovatively using topological analysis method.
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| 12. |
- Zhao, Zhiqi, et al.
(författare)
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Influence of spacing of a delta-winglet vortex generator pair on the flow behavior and heat transfer at the internal tip of gas turbine blades
- 2022
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Ingår i: International Journal of Thermal Sciences. - : Elsevier BV. - 1290-0729. ; 175
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Tidskriftsartikel (refereegranskat)abstract
- The hot erosion of turbine tip and the maintenance of tip reliability and service times have always been great challenges for researchers. This work presents a novel design of a tip wall with the internal surface fitted with delta-winglet vortex generator pairs (DVGP). Various spacing of DVGP is considered to study the influence of spacing on the internal tip heat transfer and flow behavior in the turn region of a serpentine cooling channel inside a blade. A smooth internal cooling channel is regarded as the Baseline. Five spacings of the leading edge of the DVGP, i.e., 0.03Dh(hydraulic diameter), 0.07Dh, 0.13Dh, 0.2Dh, 0.27Dh, respectively, are considered. Topological analysis in the skin friction field is introduced to better illustrate the 3D fluid flow. The inlet Reynolds number is set in the range of 10,000 to 50,000. Results show that the variation of the spacing between the DVGPs has a remarkable influence on the thermal performance of the internal blade tip. The heat transfer on each side of the DVGP is weakened increaseing spacing, which is caused by the movement of the attachment line on the surface of the DVGP and the weakening of the vortex energy. The optimal thermal performance appears for the narrow spacing (0.03Dh) of the leading edge of the DVGP, and the heat transfer augmentation is approximately 7.90% compared with the two-pass channel with a smooth tip. The delta-winglet vortex generator arranged narrowly on the internal tip is aimed for enhancement of heat transfer. The analysis and results of this work are beneficial to the tip design of internal passages in gas turbine blades.
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| 13. |
- Zhao, Zhiqi, et al.
(författare)
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On the topology of vortex structures and heat transfer of a gas turbine blade internal tip with different arrangement of delta-winglet vortex generators
- 2021
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Ingår i: International Journal of Thermal Sciences. - : Elsevier BV. - 1290-0729. ; 160
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Tidskriftsartikel (refereegranskat)abstract
- This paper aims to provide a novel enhanced heat transfer method for the internal tip surface of a U bend channel of relevance for a gas turbine rotor blade. The DWVGs (delta-winglet vortex generators) pair is arranged at multiple locations on the tip surface. Two types of vortex generators are studied, including common-flow-up and common-flow-down configurations. The inlet channel Reynolds number varies from 10,000 to 50,000. The topological analysis method is used to determine the formation and evolution of the vortices and to better understand the mechanism of the heat transfer enhancement. Results of skin-friction lines, topological portrait, Nusselt number, friction factor, thermal performance are included. The results show that due to the interaction among the vortices surrounding the vortex generators, the DWVGs pair in common-flow-up configuration has a slight heat transfer improvement, and is not sensitive to the tip location. However, the DWVGs pair in common-flow-down configuration placed at the downstream of the tip surface improved the heat transfer significantly as the induced vortices between the turbulator pairs effectively reduce the thickness of the boundary layer. Compared with the smooth U bend channel, the optimal design shows that the heat transfer and overall thermal performance can be increased by up to 7.4% and 6.8%, respectively. This study elaborates the flow and heat transfer processes from the perspective of topology, which is helpful in the design of cooling procedures of turbine blades.
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| 14. |
- Zhao, Zhiqi, et al.
(författare)
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Vortical structures and heat transfer augmentation of a cooling channel in a gas turbine blade with various arrangements of tip bleed holes
- 2021
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Ingår i: Numerical Heat Transfer; Part A: Applications. - : Informa UK Limited. - 1040-7782 .- 1521-0634. ; 79:1, s. 40-67
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the internal cooling processes affected by the tip bleed holes in gas turbine blades. Double bleed holes are fixed at the center of the blade tip near the pressure side and suction side, respectively. Five different arrangements of the holes along the center line of the tip are studied. The purely double holes are set as the Baseline. The purpose of the present study is to provide a new perspective of the tip film cooling to understand the internal flow processes, vorticity evolution and the mechanism of the heat transfer augmentation. A topological analysis and the boundary layer analysis methods are introduced to better understand the tip heat transfer. The total extraction area and volume is kept at the same level for all the studied cases. The results show that the Dean vortices and the near-wall vortices induced by the secondary flow contribute to the high heat transfer coefficient on the tip surface. The mixing effect of the Dean vortices and the hole extraction helps to enhance heat transfer upstream of the tip. Different arrangement of the bleed holes can affect the internal flow processes and heat transfer performance. The suction effect of the center-line bleed hole can accelerate the near-hole flow and reduce the thickness of the boundary layer. The center-line hole fitted at the middle of the tip affects significantly the rear side of the hole. Thus, the holes aligned in the middle of the tip provide the highest heat transfer and thermal performance. The thermal performance is enhanced by up to 4.7% compared with the Baseline.
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| 15. |
- Chen, Baowei, et al.
(författare)
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Methylation mechanism of tin(II) by methylcobalamin in aquatic systems
- 2007
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 68:3, s. 414-419
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Tidskriftsartikel (refereegranskat)abstract
- The methylation reaction of tin(II) with methylcobalamin (CH(3)B(12)) in aquatic systems was modeled in the laboratory. The products were detected by a sensitive gas chromatography-flame photometric detector (GC-FPD), and further identified by gas chromatography-mass spectrometry (GC-MS). Both monomethyltin (MMT) and dimethyltin (DMT) were found as methylation products. Three important effecting factors during the methylation reaction, salinity, pH and aerobic or anaerobic, were studied. The results showed that methyl group can be transferred from CH(3)B(12) to tin in aquatic solutions as a radical or carbonium, as well as a carbanion. Two explanations for the pH-dependency of the methylation reaction between tin(II) and CH(3)B(12) were proposed: pH-dependency of the equilibrium states of CH(3)B(12), and pH-dependency of inorganic tin(II) species whose reactivity vary with the redox potential in the solution. Salinity can influence the activity of the methyl donor, which cause changes in the methylation efficiency. Kinetic experiments showed that the methylation reaction was pseudo-first-order for CH(3)B(12).
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| 16. |
- Eilert, Johan, 1980-, et al.
(författare)
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Complexity Reduction of Matrix Manipulation for Multi-User STBC-MIMO Decoding
- 2007
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Ingår i: IEEE Sarnoff Symmposium,2007. - 9781424424832 ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- This paper studies efficient complex valued matrix manipulations for multi-user STBC-MIMO decoding. A novel method called Alamouti blockwise analytical matrix inversion (ABAMI) is proposed for the inversion of large complex matrices that are based on Alamouti sub-blocks. Another method using a variant of Givens rotation is proposed for fast QR decomposition of this kind of matrices. Our solutions significantly reduce the number of operations which makes them more than 4 times faster than several other solutions in the literature. Furthermore, compared to fixed function VLSI implementations, our solution is more flexible and consumes less silicon area because the hardware is programmable and it can be reused for many other operations such as filtering, correlation and FFT/IFFT. Besides the analysis of the general computational complexity based on the number of basic operations, the computational latency is also measured in clock cycles based on the conceptual hardware for real-time matrix manipulations.
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| 17. |
- He, Dandan, et al.
(författare)
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Design of a Low Sidelobe Monopulse Array Antenna with Hybrid Feeding Structure
- 2019
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Ingår i: 2019 International Symposium on Antennas and Propagation, ISAP 2019 - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- A low sidelobe monopulse array antenna with hybrid feeding structure is proposed. The array consists of four subarrays which employ 6 × 8 microstrip patch elements on the top layer. The feed network, which is hybrid feeding structure, is composed of 1-to-48 microstrip power dividers on the top layer, microstrip to groove gap waveguide transitions and a gap waveguide-based monopulse comparator. The microstrip unequal power dividers are compact to achieve unequal amplitude distribution. And the monopulse comparator based on groove gap waveguide has low insertion loss. Hence, the array antenna achieves low sidelobe and high efficiency. The array antenna is designed with size of 400 × 320 mm2. The simulated VSWR is less than 1.5 from 10.52 - 10.68 GHz, the simulated gain is 28.7 dBi at 10.6 GHz and the sidelobe level is less than -19 dB. The null depth in the difference pattern is less than -35 dB.
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| 18. |
- Kresge, Hailey A, et al.
(författare)
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Lower Left Ventricular Ejection Fraction Relates to Cerebrospinal Fluid Biomarker Evidence of Neurodegeneration in Older Adults.
- 2020
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Ingår i: Journal of Alzheimer's disease : JAD. - 1875-8908. ; 74:3, s. 965-974
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Tidskriftsartikel (refereegranskat)abstract
- Subclinical cardiac dysfunction is associated with decreased cerebral blood flow, placing the aging brain at risk for Alzheimer's disease (AD) pathology and neurodegeneration.This study investigates the association between subclinical cardiac dysfunction, measured by left ventricular ejection fraction (LVEF), and cerebrospinal fluid (CSF) biomarkers of AD and neurodegeneration.Vanderbilt Memory & Aging Project participants free of dementia, stroke, and heart failure (n=152, 72±6 years, 68% male) underwent echocardiogram to quantify LVEF and lumbar puncture to measure CSF levels of amyloid-β42 (Aβ42), phosphorylated tau (p-tau), and total tau (t-tau). Linear regressions related LVEF to CSF biomarkers, adjusting for age, sex, race/ethnicity, education, Framingham Stroke Risk Profile, cognitive diagnosis, and apolipoprotein E ɛ4 status. Secondary models tested an LVEF x cognitive diagnosis interaction and then stratified by diagnosis (normal cognitive (NC), mild cognitive impairment (MCI)).Higher LVEF related to decreased CSF Aβ42 levels (β=-6.50, p=0.04) reflecting greater cerebral amyloid accumulation, but this counterintuitive result was attenuated after excluding participants with cardiovascular disease and atrial fibrillation (p=0.07). We observed an interaction between LVEF and cognitive diagnosis on CSF t-tau (p=0.004) and p-tau levels (p=0.002), whereas lower LVEF was associated with increased CSF t-tau (β=-9.74, p=0.01) and p-tau in the NC (β=-1.41, p=0.003) but not MCI participants (p-values>0.13).Among cognitively normal older adults, subclinically lower LVEF relates to greater molecular evidence of tau phosphorylation and neurodegeneration. Modest age-related changes in cardiovascular function may have implications for pathophysiological changes in the brain later in life.
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| 19. |
- Li, Xiaojuan, et al.
(författare)
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Climate and soil properties drive soil organic and inorganic carbon patterns across a latitudinal gradient in southwestern China
- 2023
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Ingår i: Journal of Soils and Sediments. - : Springer Science and Business Media LLC. - 1614-7480 .- 1439-0108. ; 23:1, s. 91-102
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Tidskriftsartikel (refereegranskat)abstract
- PurposeDrylands account for 47.2% of land area and contain 15.5% of global carbon (C). However, the variation in organic and inorganic C stocks across latitudinal gradients in arid and semiarid shrubland ecosystems remains understudied, and we lack in-depth understanding of the main drivers of C variation at this spatial scale.MethodsHere, we sampled soils from 95 sites across a latitudinal gradient to explore both the latitudinal patterns and potential drivers of soil organic carbon density (SOCD) and soil inorganic carbon density (SICD). We also assessed variation in SOCD and SICD down the soil profile, by sampling soils at four depths (0 – 10 cm, 10 – 20 cm, 20 – 30 cm, and 30 – 50 cm).ResultBoth SOCD and SICD exhibited a binomial relationship with latitude (P < 0.01). Soil properties accounted for the greatest variation in SOCD, with the most important explanatory factor being exchangeable calcium, followed by mean annual temperature, pH, plant diversity, and silt content. Soil pH and plant diversity were more important in explaining variation in SOCD in the subsoil (> 20 cm depth) than the topsoil. For SICD, soil properties explained the greatest variation at all depths. Soil pH explained the most variance in SICD, followed by exchangeable calcium and mean annual temperature in the topsoil (i.e., 0 – 10 cm and 10 – 20 cm). In the subsoil (i.e., 20 – 30 cm and 30 – 50 cm), exchangeable calcium was the most important predictor, followed by soil organic carbon, mean annual temperature, and pH.ConclusionOur study shows that soil properties are a strong predictor of latitudinal patterns of soil organic and inorganic C in arid and semiarid shrubland ecosystems. We also identified differences in potential drivers of SOCD and SICD with depth, advancing our understanding of large-scale patterns of C storage in arid and semiarid soils.
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| 20. |
- Li, Xiaojuan, et al.
(författare)
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Latitudinal patterns of light and heavy organic matter fractions in arid and semi-arid soils
- 2022
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Ingår i: Catena. - : Elsevier BV. - 0341-8162. ; 215
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Tidskriftsartikel (refereegranskat)abstract
- Semi-arid and arid ecosystems are important for the global C cycle. Despite this, it remains unclear how organic matter fractions vary across latitudinal gradients, and what drives this variation, in dry ecosystems. In this study, we sampled soils from 100 sites across a latitudinal gradient in the dry valleys of southwestern China to explore the latitudinal patterns of light fraction organic matter (LFOM) and heavy fraction organic matter (HFOM) at two soil depths (0–10 cm and 10–20 cm). Across the studied gradient, HFOM accounted for a larger fraction of soil organic matter than LFOM. LFOM increased exponentially with increasing latitude at both 0–10 cm and 10–20 cm depths. Heavy fraction organic C increased linearly with increasing latitude at both depths, while heavy fraction organic N only increased with latitude in soils from 10 to 20 cm depth. Latitudinal patterns of LFOM were mainly explained by climate, with the most important driver being mean annual temperature, followed by mean annual precipitation. Soil physicochemical factors – in particular cation exchange capacity and silt content – explained the most variation in HFOM. Total microbial biomass was also important in explaining variation in HFOM, especially in the 10–20 cm soil layer. Overall, our results shed light on the spatial distribution of organic matter fractions in arid and semi-arid regions. We also identify candidate drivers of the variation in LFOM and HFOM in arid and semi-arid regions, finding that climate primarily explains variation in LFOM while soil physiochemistry primarily explains variation in HFOM.
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| 21. |
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| 22. |
- Lu, Yehu, et al.
(författare)
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A novel personal cooling system (PCS) incorporated with phase change materials (PCMs) and ventilation fans: An investigation on its cooling efficiency
- 2015
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Ingår i: Journal of Thermal Biology. - : Elsevier BV. - 0306-4565. ; 52, s. 137-146
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Tidskriftsartikel (refereegranskat)abstract
- Personal cooling systems (PCS) have been developed to mitigate the impact of severe heat stress for humans working in hot environments. It is still a great challenge to develop PCSs that are portable, inexpensive, and effective. We studied the performance of a new hybrid PCS incorporating both ventilation fans and phase change materials (PCMs). The cooling efficiency of the newly developed PCS was investigated on a sweating manikin in two hot conditions: hot humid (HH, 34 °C, 75% RH) and hot dry (HD, 34 °C, 28% RH). Four test scenarios were selected: fans off with no PCMs (i.e., Fan-off, the CONTROL), fans on with no PCMs (i.e., Fan-on), fans off with fully solidified PCMs (i.e., PCM+Fan-off), and fans on with fully solidified PCMs (i.e., PCM+Fan-on). It was found that the addition of PCMs provided a 54∼78 min cooling in HH condition. In contrast, the PCMs only offered a 19–39 min cooling in HD condition. In both conditions, the ventilation fans greatly enhanced the evaporative heat loss compared with Fan-off. The hybrid PCS (i.e., PCM+Fan-on) provided a continuous cooling effect during the three-hour test and the average cooling rate for the whole body was around 111 and 315 W in HH and HD conditions, respectively. Overall, the new hybrid PCS may be an effective means of ameliorating symptoms of heat stress in both hot-humid and hot-dry environments.
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| 23. |
- Luo, Lei, et al.
(författare)
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Computational investigation of curvature effects on jet impingement heat transfer at internally cooled turbine vane leading edge regions
- 2020
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Ingår i: Heat Transfer Research. - 1064-2285. ; 51:4, s. 333-357
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Tidskriftsartikel (refereegranskat)abstract
- This study is carried out by using numerical simulations to investigate the effect of target surface curvature and the nozzle-to-target surface distance on the flow structure and heat transfer characteristics in a pin-finned double-wall cooling structure. The flow is directly impinging on the target surface and is disturbed by the pin fins, and then released from the film holes after passing the double-wall chamber. The ratio between the radius of the concave outer surface and the chord length of the concave outer surface is varied from 0.500 to 1.300 and the ratio between nozzle-to-target surface distance and diameter of impingement hole is ranging from 0.5 to 2.0. The Reynolds number is between 10,000 and 50,000. Results of the flow structure in the chamber, heat transfer on the target surface, and friction factor of the pin-fi nned channel are included. It is found that an increase of the target surface curvature has signifi cant effects on the flow structure and thus the heat transfer on the target surface is augmented. The Taylor-Görtler vortices near the pin fins are also influenced by the target surface curvature. On the other hand, the nozzle-to-target surface distance influences the jet impingement and the vortices, which are generated by the curvature, remarkably. It is found that the area goodness factor and volume goodness factor are improved by the surface curvature.
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| 24. |
- Luo, Lei, et al.
(författare)
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Surface temperature reduction by using dimples/protrusions in a realistic turbine blade trailing edge
- 2018
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Ingår i: Numerical Heat Transfer; Part A: Applications. - : Informa UK Limited. - 1040-7782 .- 1521-0634. ; 74:5, s. 1265-1283
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Tidskriftsartikel (refereegranskat)abstract
- In this article, numerical simulations have been conducted on the heat transfer effect of dimple/protrusion layouts of a pin-finned wedge duct. Conjugate heat transfer calculations are further performed to investigate the cooling effect of modified schemes with dimples and protrusions added. Comparisons are carried out with a turbine second stage guide vane employed as the prototype. The dimple/protrusion-pin fin arrangement is set as the optimum one obtained above, and dimple depth/protrusion height varies from 0.2 to 0.3 times the structure diameter. It is found that the side-by-side arrangement and protrusion structure is more beneficial for the wedge duct endwall heat transfer. Comparison with the prototype blade shows that the addition of both dimples and protrusions are helpful in enhancing the trailing edge cooling effect. The cooling effect is increased with an increase in dimple depth/protrusion height. The results also show that the modified blade with protrusions attached at 0.3 height saves 0.48 g/s cooling mass flow and reaches the most positive performance with a 17 K, 14 K average temperature reduction, 0.022, 0.018 cooling effect increasing for pressure, suction side, respectively.
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| 25. |
- Qiu, Dandan, et al.
(författare)
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Analysis of heat transfer and fluid flow of a slot jet impinging on a confined concave surface with various curvature and small jet to target spacing
- 2019
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Ingår i: International Journal of Numerical Methods for Heat and Fluid Flow. - 0961-5539. ; 29:8, s. 2885-2910
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: This study aims to focus on the surface curvature, jet to target spacing and jet Reynolds number effects on the heat transfer and fluid flow characteristics of a slot jet impinging on a confined concave target surface at constant jet to target spacing. Design/methodology/approach: Numerical simulations are used in this research. Jet to target spacing, H/B is varying from 1.0 to 2.2, B is the slot width. The jet Reynolds number, Rej, varies from 8,000 to 40,000, and the surface curvature, R2/B, varies from 4 to 20. Results of the target surface heat transfer, flow parameters and fluid flow in the concave channel are performed. Findings: It is found that an obvious backflow occurs near the upper wall. Both the local and averaged Nusselt numbers considered in the defined region respond positively to the Rej. The surface curvature plays a positive role in increasing the averaged Nusselt number for smaller surface curvature (4-15) but affects little as the surface curvature is large enough (> 15). The thermal performance is larger for smaller surface curvature and changes little as the surface curvature is larger than 15. The jet to target spacing shows a negative effect in heat transfer enhancement and thermal performance. Originality/value: The surface curvature effects are conducted by verifying the concave surface with constant jet size. The flow characteristics are first obtained for the confined impingement cases. Then confined and unconfined slot jet impingements are compared. An ineffective point for surface curvature effects on heat transfer and thermal performance is obtained.
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| 26. |
- Wang, Enlin, et al.
(författare)
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Wideband High-Gain Circularly Polarized Antenna Array on Gap Waveguide for 5G applications
- 2019
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Ingår i: 2019 International Symposium on Antennas and Propagation, ISAP 2019 - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- A wideband circularly polarized (CP) antenna array based on gap waveguide (GW) is presented in this paper. Firstly, a CP antenna based on septum polarizer is designed as the element for the array. Secondly, the feeding network is composed of T-junctions and realized by ridge gap waveguide (RGW). Then a 16 × 16 antenna array is built up by the elements. The novelty of this antenna is the combination of planar array and septum polarizer based on GW technology to achieve circularly polarization, high gain and high efficiency in wide bandwidth. The proposed array antenna achieves wide impedance bandwidth of 34.5% with the reflection coefficient below -10 dB, and a wide 3-dB axial ratio (AR) bandwidth of 26.5%. The simulated gain is higher than 32 dBic from 24.5 to 32.0 GHz, and the antenna efficiency is larger than 90%.
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| 27. |
- Wang, Kui, et al.
(författare)
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Efficient electro-demulsification of O/W emulsions and simultaneous oil removal enabled by a multiscale porous biocarbon electrode
- 2024
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 481
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Tidskriftsartikel (refereegranskat)abstract
- Emulsion wastewater contain substantial amounts of oil and various additives, which pose threats to the environment and human health. Demulsification is a crucial pretreatment stage for wastewater. This study aims to identify a novel electro-demulsification method with high oil removal efficiency and low energy consumption. Modified carbonized birch wood with a unique isotropic multiscale pore structure is used as a self-standing electrode to treat a toluene oil-in-water (O/W) emulsion. The electrode must have a highly porous structure to facilitate efficient water diffusion and oil adsorption. It must also have high electronic conductivity to expedite polarized molecular electrophoresis to realize penetration into the pores and, subsequently, demulsification. Guided by an applied electric field force, polarized O/W droplets are drawn toward the electrode, revealing electrical characteristics distinct from those of polarized organic molecules. This electric field force augments the capture and adhesion of droplets by the electric double layer at the electrode interface. Consequently, adsorbed droplets in close proximity to the electrode rupture due to the combined influence of the electric field force and the electrostatic effects stemming from the electrode's multiscale porous structure. This synergistic action enables demulsification to occur efficiently at low energy consumption levels. This study has revealed that electro-demulsification can effectively treat toluene emulsions stabilized by various surfactants and microemulsion containing toluene. Therefore, this electro-demulsification technology can be further developed for various types of water pollution.
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| 28. |
- Wu, Di, 1979-, et al.
(författare)
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Fast Complex Valued Matrix Inversion for Multi-User STBC-MIMO Decoding
- 2007
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Ingår i: IEEE Computer Society Annual Aymposium on VLSI, ISVLSI,2007. - : IEEE. - 0769528961 ; , s. 325-330
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Konferensbidrag (refereegranskat)abstract
- This paper studies the efficient complex matrix inversion for multi-user STBC-MIMO decoding. A novel method called Alamouti blockwise analytical matrix inversion (ABAMI) and its programmable VLSI implementation are proposed for the inversion of (in this context) large complex matrices with Alamouti sub-blocks. Our solution significantly reduces the number of operations which makes it more than 4 times faster than several other solutions in the literature. Furthermore, compared to these fixed function VLSI implementations, our solution is more flexible and consumes less silicon area because the hardware can be reused for many other operations. In addition to the routine analysis of the general computational complexity based on the number of basic operations, the computational latency is also measured in clock cycles based on the conceptual hardware for real-time matrix inversion.
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| 29. |
- Wu, Dandan, et al.
(författare)
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Green technology investment and supply chain coordination strategies considering marketing efforts and risk aversion under carbon tax policy
- 2024
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Ingår i: Journal of Industrial and Management Optimization. - : American Institute of Mathematical Sciences. - 1547-5816 .- 1553-166X.
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Tidskriftsartikel (refereegranskat)abstract
- In response to increasing environmental concerns, many governments have implemented carbon tax policies to incentivize green technology investments. However, the impact of such policies on supply chain coordination, particularly when retailers are risk-averse, remains underexplored. This study investigates a two-tier supply chain where manufacturers invest in green technology and retailers engage in marketing activities within the framework of a carbon tax policy. Motivated by the need to understand how carbon taxes affect strategic decisions and profitability, we analyze the decisions of risk-averse retailers using a mean-variance approach. Our findings indicate that carbon tax policy significantly influences green initiatives and may present challenges to manufacturers and overall supply chain profitability. To address these challenges, we propose both non-contractual and contractual coordination strategies aimed at enhancing the performance of decentralized channels for risk-averse retailers. The comparison of these strategies reveals that the optimal coordination approach is contingent upon the marketing effect and the level of retailer risk aversion. Specifically, a green investment cost-sharing strategy is optimal for maximizing supply chain profit when both retailer risk aversion and the marketing effect are high. Conversely, a marketing effort cost-sharing strategy is more effective in minimizing environmental impact when retailer risk aversion is medium or high and the marketing effect is substantial. This study makes significant contributions by elucidating the interplay between risk aversion, marketing effects, and green technology investments. It provides valuable managerial insights for decision-makers seeking to foster sustainable development in supply chains through the selection of appropriate coordination strategies.
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| 30. |
- Xing, Guozhong, et al.
(författare)
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Correlated d(0) ferromagnetism and photoluminescence in undoped ZnO nanowires
- 2010
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Ingår i: APPLIED PHYSICS LETTERS. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 96:11, s. 112511-
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Tidskriftsartikel (refereegranskat)abstract
- We report the correlated d(0) ferromagnetism and photoluminescence in undoped single-crystalline ZnO nanowires synthesized by using a vapor transport method. We systematically tune the oxygen deficiency in the ZnO nanowires from 4% to 20% by adjusting the growth conditions, i.e., selecting different catalyst (Au or Ag) and varying the growth temperature. Our study suggests that oxygen vacancies induce characteristic photoluminescence and significantly boost the room-temperature ferromagnetism. Such undoped ZnO nanowires with tunable magnetic and optical properties are promising to find applications in multifunctional spintronic and photonic nanodevices.
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| 31. |
- Xu, An, et al.
(författare)
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Rewired m6A epitranscriptomic networks link mutant p53 to neoplastic transformation
- 2023
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- N6-methyladenosine (m6A), one of the most prevalent mRNA modifications in eukaryotes, plays a critical role in modulating both biological and pathological processes. However, it is unknown whether mutant p53 neomorphic oncogenic functions exploit dysregulation of m6A epitranscriptomic networks. Here, we investigate Li-Fraumeni syndrome (LFS)-associated neoplastic transformation driven by mutant p53 in iPSC-derived astrocytes, the cell-of-origin of gliomas. We find that mutant p53 but not wild-type (WT) p53 physically interacts with SVIL to recruit the H3K4me3 methyltransferase MLL1 to activate the expression of m6A reader YTHDF2, culminating in an oncogenic phenotype. Aberrant YTHDF2 upregulation markedly hampers expression of multiple m6A-marked tumor-suppressing transcripts, including CDKN2B and SPOCK2, and induces oncogenic reprogramming. Mutant p53 neoplastic behaviors are significantly impaired by genetic depletion of YTHDF2 or by pharmacological inhibition using MLL1 complex inhibitors. Our study reveals how mutant p53 hijacks epigenetic and epitranscriptomic machinery to initiate gliomagenesis and suggests potential treatment strategies for LFS gliomas.
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| 32. |
- Xu, Fengqin, et al.
(författare)
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Effects of an Innovative Training Program for New Graduate Registered Nurses : A Comparison Study
- 2021
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Ingår i: SAGE Open. - : SAGE Open. - 2158-2440. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- New graduate registered nurses (NGRNs) face a great challenge during the transition from school to clinical practice. We conducted a quasi-randomized controlled study to evaluate the effects of a new training mode for newly recruited NGRNs in a Chinese teaching hospital. A total of 150 NGRNs were recruited from a teaching hospital and assigned into two groups. The conventional training and a new training program were taken for the control group and the research group, respectively. At the end of the training, the two groups were evaluated and compared for theoretical knowledge and operation skills using a mutual-evaluation examination and the Chinese Registered Nurse Core Competency Scale. The scores of theoretical knowledge (88.4 vs. 81.7, p < .001) and operation skills (94.8 vs. 90.3, p < .001), and the total core competencies score (156.2 vs. 148.8, p < .05) in the research group were statistically significantly higher than those in the control group. Compared with the control group, the research group also had statistically significantly higher scores in education and consultation (2.47 vs. 2.40), clinical nursing (2.87 vs. 2.62), interpersonal relationship (2.56 vs. 2.43), and critical thinking and scientific research (2.78 vs. 2.61). The innovative pre-job training program for NGRNs conducted in Chinese clinical nursing skill training bases might significantly improve the training effects and is worthy of broader implementation.
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| 33. |
- Yang, Jinghai, et al.
(författare)
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Investigation on the origin of green light emission in ZnO bulk materials
- 2009
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Ingår i: INTERNATIONAL JOURNAL OF MATERIALS and PRODUCT TECHNOLOGY. - 0268-1900. ; 34:3, s. 360-368
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Tidskriftsartikel (refereegranskat)abstract
- ZnO bulk materials were implanted by O and Zn with different concentration and their photoluminescence (PL) properties were investigated in detail. The results clearly show that O and Zn implantation indeed have great influence on the green light emission. By comparing the PL spectra for the samples with different implantations, O-i, Zn-i and Cu-related defects have been excluded from the possibility of the origin of green light emission step by step. Finally, it can be concluded that V-Zn is responsible to the observed green light emission, which has good agreement with the theoretical results from first principle calculation.
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| 34. |
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| 35. |
- Zhang, Lei, et al.
(författare)
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Discovery of a radio jet in the Cloverleaf quasar at z = 2.56
- 2023
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Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 524:3, s. 3671-3682
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Tidskriftsartikel (refereegranskat)abstract
- The fast growth of supermassive black holes and their feedback to the host galaxies play an important role in regulating the evolution of galaxies, especially in the early Universe. However, due to cosmological dimming and the limited angular resolution of most observations, it is difficult to resolve the feedback from the active galactic nuclei (AGNs) to their host galaxies. Gravitational lensing, for its magnification, provides a powerful tool to spatially differentiate emission originating from AGN and host galaxy at high-redshifts. Here, we report a discovery of a jet-like radio structure in a strongly lensed starburst quasar, H1413+117 or Cloverleaf at redshift z = 2.56, based on observational data at optical, submillimetre, and radio wavelengths. With both parametric and non-parametric lens models and with reconstructed images in the source plane, we find a well-separated, kpc-scaled, single-sided radio jet located at projected to the north-west of the host galaxy in the source plane. This could indicate the co-existence of feedback from the AGN by both wind and jet in the Cloverleaf quasar.
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| 36. |
- Zhao, Yuxuan, et al.
(författare)
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Design of Wideband Dual-Circularly Polarized Endfire Antenna Array on Gap Waveguide
- 2019
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Ingår i: 13th European Conference on Antennas and Propagation, EuCAP 2019.
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Konferensbidrag (refereegranskat)abstract
- A wideband dual-circularly polarized (CP) linear antenna array is presented in this paper. Firstly, a dual-CP endfire antenna based on septum polarizer is designed as the element for the array. Secondly, the feeding network is realized by ridge gap waveguide. Then a 1×8 linear antenna array is built up by the elements. The proposed array antenna achieves wide impedance bandwidth of 44.6% with the reflection coefficient below -10 dB, the isolation between ports greater than 15 dB, and a wide 3-dB axial ratio (AR) bandwidth of 46.2%.
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| 37. |
- Zhao, Zhiqi, et al.
(författare)
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Experimental evaluation of longitudinal and transverse vortex generators on the endwall of a serpentine passage
- 2022
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Ingår i: International Journal of Thermal Sciences. - : Elsevier BV. - 1290-0729. ; 176
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Tidskriftsartikel (refereegranskat)abstract
- A 180-deg turning channel can be seen in many heat exchange systems, and a strong three-dimensional flow phenomenon will occur at the turning point. In order to strengthen the heat transfer inside the turn and considering the lack of relevant enhanced endwall heat transfer approach, the present study innovatively demonstrates the measures of enhanced internal endwall heat transfer using arrays of delta-winglet and conical vortex generators. The studied parameters of the vortex generators include aspect ratio (AR), spacing, and angle of attack, etc. The experimental results indicate that the longitudinal vortex generators have more advantages in increasing the heat transfer than the transverse conical vortex generators in certain configurations with the same order of magnitude of the increased area. Besides, transverse conical vortex generators are more helpful to improve the endwall heat transfer uniformity than longitudinal vortex generators. The array of longitudinal vortex generators with 45-deg angle of attack, 0.02 m pitch, and 2 aspect ratio provides the highest thermal performance for all studied cases, indicating that the longitudinal delta-winglet vortex generators can induce near-wall flow turbulence as well as convective heat transfer of the endwall with a modest pressure loss penalty. For this optimally designed endwall, the Nusselt number is augmented by up to 35%. From the perspective of energy saving, the present studied vortex generators provide a superior thermal performance at identical pumping power, which can be useful in the future design of endwalls in sharp-turn channels.
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| 38. |
- Zhao, Zhiqi, et al.
(författare)
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On the solar air heater thermal enhancement and flow topology using differently shaped ribs combined with delta-winglet vortex generators
- 2021
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Ingår i: Energy. - : Elsevier BV. - 0360-5442. ; 224
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Tidskriftsartikel (refereegranskat)abstract
- A numerical investigation has been conducted to study the convective heat transfer enhancement and friction loss behaviors for turbulent flow by using arrays of differently shaped ribs combined with delta-winglet vortex generators (DWVGs) pair on the absorber plate of a solar air heater. Four transverse vortex generators arrays, i.e., 90° continuous ribs, 90° truncated ribs, 60° V-shaped continuous ribs, and 60° V-shaped truncated ribs, are studied to investigate the mixing effect with the DWVGs pair. The aspect ratio (AR = Lv/Hv) of the DWVGs is 2:1 while the geometrical condition of the ribs is height of 0.003 m and pitch of 0.028 m. The Reynolds number ranges from 4000 to 20,000. Results of temperature, Nusselt number, vortical structure, topological portrait, turbulent kinetic energy (TKE), friction factor and thermal performance evaluation are included. The results show that the adoption of DWVGs and the shape type of the ribs have great impact on the heat transfer and flow structure in the solar air heater. It is found that the DWVGs combined with the 60° V-shaped continuous ribs contributes the best heat transfer performance, and the heat transfer is enhanced by 39.4% compared with the only DWVGs case.
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| 39. |
- Zhao, Zhiqi, et al.
(författare)
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The augmentation of internal tip heat transfer in gas turbine blades using a pair of delta-winglet vortex generators
- 2021
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Ingår i: Journal of Enhanced Heat Transfer. - 1065-5131. ; 28:3, s. 17-40
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Tidskriftsartikel (refereegranskat)abstract
- A novel method to enhance the heat transfer on the internal tip surface of gas turbine blades was developed. Effects of delta-winglet vortex generators (DWVG) and their angle of attack on the vortical structures and mechanism of enhanced heat transfer were investigated. Seven different angles of attack were considered: 0°, 15°, 30°, 45°, 60°, 75°, and 90°. The Reynolds number varies from 10,000 to 50,000. Flow topology analysis was employed to better understand the evolution of vortices in the turn region. Results showed that a vortex was induced on the leeward side of the DWVG as the angle of attack was greater than 0°, which significantly enhanced the local heat transfer. Also, an extra saddle point was generated at the tip surface on the windward side of the DWVG as the angle of attack is greater than 45°, indicating that a vortex wass formed. The internal tip heat transfer increased as the angle of attack of the DWVG increased. The optimal design was reached when the angle of attack is greater than 60°. Compared with the smooth channel, the heat transfer and overall thermal performance are enhanced by up to 9.5% and 8.1%, respectively.
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| 40. |
- Zhou, Xin, et al.
(författare)
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3D-imaging of selective laser melting defects in a Co-Cr-Mo alloy by synchrotron radiation micro-CT
- 2015
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Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454 .- 1873-2453. ; 98, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- Microstructure defects set the mechanical property limits for solid Co-Cr-Mo alloy prepared by selective laser melting (SLM). Previous studies were mainly based on 2D SEM images and thus not able to provide information of the 3D morphologies of the complex defects. In this paper, the remaining porosities in Co-Cr-Mo alloy parts prepared by selective laser melting were presented in relation to the laser processing parameters. In order to understand the defect forming mechanism, accurate 3D images of defects inside SLM fabricated Co-Cr-Mo samples were provided by synchrotron radiation micro-CT imaging of 300 pm thick slices cut from a 10 mm cube. With 3D reconstructed images distinctive morphologies of SLM defects spanning across the consolidated powder layers were generated. The faults can be classified as single layer or multi-layers defects. The accidental single layer defects form as gaps between adjacent laser melt tracks or melt track discontinuousness caused by inherent fluid instability under various disturbances. The first formed single layer defect generates often a multi-layer defect spanning for 2-3 subsequent powder layers. By stabilizing the melt pool flow and by reducing the surface roughness through adjusting processing parameters it appears possible to reduce the defect concentrations.
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