| 1. |
- Zhu, Zhaolong, et al.
(författare)
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Built-up edge formation mechanisms in orthogonal cutting of wood-plastic composite
- 2022
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280. ; 17:5, s. 388-396
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Tidskriftsartikel (refereegranskat)abstract
- This project aims to improve the machinability of wood-plastic composites by understanding chip and built-up edge formation, so as to help manufacturers optimize cutting performance and product quality. Chip formation and built-up edge were studied during orthogonal cutting of wood polyethylene composite with cemented carbide cutters under different conditions. During the orthogonal cutting process, segmental, ribbon, and element chips were generated. The cutting depth was found to have a great impact on the types of chips that formed. Additionally, a built-up edge was found during wood-plastic composite machining, with debris only attaching to the tool's rake face due to thermo-mechanical coupling. Such built-up edges hinder cutting stability and surface quality. Furthermore, variations in the accumulation of debris on the built-up edge corresponded to changes in cutting force and temperature. In fact, both cutting force and temperature proved to be inversely related to the rake angle and positively correlated to the cutting speed and depth. Therefore, to achieve better cutting stability and surface quality for wood-plastic composites, a larger rake angle and a reduced cutting depth are recommended because they reduce the accumulation of debris and the formation of built-up edge.
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| 2. |
- Guo, Xiaolei, et al.
(författare)
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Cutting forces and cutting quality in the up-milling of solid wood using ceramic cutting tools
- 2021
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Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer. - 0268-3768 .- 1433-3015. ; 114:5-6, s. 1575-1584
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Tidskriftsartikel (refereegranskat)abstract
- Although many studies have focused on the cutting performance of ceramic blades in processing different materials, few have reported on their application in wood processing. Thus, it is necessary to explore the cutting performance of ceramic tools in solid wood machining. The aims of this paper were to evaluate the cutting performance of Al2O3 and Si3N4 ceramic tools in the process of machining Manchurian ash (Fraxinus mandshurica Rupr.) and Chinese fir (Cunninghamia lanceolata) by means of analysing cutting force and surface roughness and to provide guidelines for factories for applying ceramic tools in the manufacture of solid wood furniture. Up-milling tests were conducted for each combination of cutting speed, tool material, and workpiece material, and each combination was replicated five times. Results showed that (1) cutting force and surface roughness decreased with increase of cutting speed and (2) cutting force and surface roughness resulting from using Al2O3 ceramic cutting tools were larger than those of Si3N4 ceramic cutting tools, especially when cutting Manchurian ash with its extractives. Overall, ceramic tools can be used in high-speed cutting of solid wood. Compared with Al2O3 ceramic cutting tools, Si3N4 ceramic cutting tools are more suitable for cutting solid wood, especially those with extractives. Si3N4 ceramic tools provided not only chemical stability, but improved final product quality.
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| 3. |
- Guo, Xiaolei, et al.
(författare)
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Machinability of wood fiber/polyethylene composite during orthogonal cutting
- 2021
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Ingår i: Wood Science and Technology. - : Springer. - 0043-7719 .- 1432-5225. ; 55:2, s. 521-534
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Tidskriftsartikel (refereegranskat)abstract
- Wood fiber/polyethylene composite (WFPEC) is composed of a natural wood fiber and a recyclable polyethylene plastic, which is normally used as an environmental protection composite material. However, better knowledge of chip formation and surface damage mechanism of WFPEC is essential to improve its machinability for extending exterior and interior applications. In this article, machinability of WFPEC was investigated by analyzing the disparity between cutting efficiency and surface quality through a group of orthogonal cutting experiments with change of cutting depth. The chip formation process was recorded by a high-speed camera system with 5000 frames per second. Surface topography was observed by a scanning electron microscope. The results showed that the chip morphology changed from continuous cutting governed by a continuous shearing process under the shallow cutting depth, to a discontinuous cutting governed by plastic fracture under the deep cutting depth ahead of the tool tip. Flattened matrix was the main form of surface topography caused by shallow cutting depth, while matrix-fiber tearing was caused by deep cutting depth. Pullout/fracture and debonding of fibers were related to the fiber orientation angle and the diameter of fiber bundles, but not to the cutting depth. Taken together, the toughness of the workpiece material in the cutting region decreased with the increase in cutting depth. To avoid matrix-fiber tearing, shallow cutting depth should be used during finishing to maintain surface quality. In contrast, pre-cutting can be performed with a deep cutting depth in order to improve the cutting efficiency.
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| 4. |
- Jia, Zhenrong, et al.
(författare)
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Near-infrared absorbing acceptor with suppressed triplet exciton generation enabling high performance tandem organic solar cells
- 2023
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Ingår i: Nature Communications. - : NATURE PORTFOLIO. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Reducing the energy loss of sub-cells is critical for high performance tandem organic solar cells, while it is limited by the severe non-radiative voltage loss via the formation of non-emissive triplet excitons. Herein, we develop an ultra-narrow bandgap acceptor BTPSeV-4F through replacement of terminal thiophene by selenophene in the central fused ring of BTPSV-4F, for constructing efficient tandem organic solar cells. The selenophene substitution further decrease the optical bandgap of BTPSV-4F to 1.17 eV and suppress the formation of triplet exciton in the BTPSV-4F-based devices. The organic solar cells with BTPSeV-4F as acceptor demonstrate a higher power conversion efficiency of 14.2% with a record high short-circuit current density of 30.1 mA cm(-2) and low energy loss of 0.55 eV benefitted from the low non-radiative energy loss due to the suppression of triplet exciton formation. We also develop a high-performance medium bandgap acceptor O1-Br for front cells. By integrating the PM6:O1-Br based front cells with the PTB7-Th:BTPSeV-4F based rear cells, the tandem organic solar cell demonstrates a power conversion efficiency of 19%. The results indicate that the suppression of triplet excitons formation in the near-infrared-absorbing acceptor by molecular design is an effective way to improve the photovoltaic performance of the tandem organic solar cells. Reducing energy loss of sub-cells is critical for high performance tandem organic solar cells. Here, the authors design and synthesize an ultra-narrow bandgap acceptor through replacement of terminal thiophene by selenophene in the central fused ring, achieving efficiency of 19% for tandem cells.
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| 5. |
- Jiang, Shangsong, et al.
(författare)
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Cutting Force and Surface Roughness during Straight-Tooth Milling of Walnut Wood
- 2022
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Ingår i: Forests. - : MDPI. - 1999-4907. ; 13:12
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Tidskriftsartikel (refereegranskat)abstract
- Walnut (Juglans regia L.) is widely used in wood furnishings, and machinability is a key factor for improving product quality and enterprise benefits. This work focused on the influence of the rake angle, depth of cut, and cutting speed on the cutting force and machined surface roughness during the straight-tooth milling of walnut. On the basis of the experimental findings, a mathematical model was created using a response surface methodology to determine the relationship between the cutting force and the cutting conditions, as well as the relationship between the surface roughness and the cutting conditions. Variance analysis was used to study the significant contributions of the interactions of various factors and two-level interactions to the cutting force and surface roughness. The optimized combination of milling conditions, resulting in lowest cutting force and surface roughness, was determined to be a rake angle of 5°, a depth of cut of 0.6 mm, and a cutting speed of 45 m/s.
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| 6. |
- Jin, Tingting, et al.
(författare)
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Efficient heterogeneous integration of InP/Si and GaSb/Si templates with ultra-smooth surfaces
- 2022
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Ingår i: Science China Information Sciences. - : Springer Science and Business Media LLC. - 1869-1919 .- 1674-733X. ; 65:8
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Tidskriftsartikel (refereegranskat)abstract
- Heterogeneous integration of InP and GaSb on Si substrates holds a huge potential interest in near-infrared and mid-infrared optoelectronic devices. In this study, 2-inch 180-nm-thick InP and 185-nm-thick GaSb thin layers were successfully transferred onto the Si substrates to form high-quality and ultra-smooth InP/Si and GaSb/Si templates using molecular beam epitaxy (MBE) and the ion-slicing technique together with selective chemical etching. The relocation of the implantation-introduced damage in the sacrificial layer enables the transfer of relatively defect-free InP and GaSb thin films. The sacrificial layers were completely etched off by selective chemical etching, leaving ultra-smooth epitaxial surfaces with a roughness of 0.2 nm for the InP/Si template and 0.9 nm for the GaSb/Si template, respectively. Thus, the chemical mechanical polishing (CMP) process was not required to smooth the surface which usually introduces particles and chemical contaminations on the transferred templates. Furthermore, the donor substrate is not consumed and can be recycled to reduce the cost, which provides a paradigm for the sustainable and economic development of the Si integration platform.
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| 7. |
- Li, Junjie, et al.
(författare)
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A Novel Dry Selective Isotropic Atomic Layer Etching of SiGe for Manufacturing Vertical Nanowire Array with Diameter Less than 20 nm
- 2020
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 13:3
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Tidskriftsartikel (refereegranskat)abstract
- Semiconductor nanowires have great application prospects in field effect transistors and sensors. In this study, the process and challenges of manufacturing vertical SiGe/Si nanowire array by using the conventional lithography and novel dry atomic layer etching technology. The final results demonstrate that vertical nanowires with a diameter less than 20 nm can be obtained. The diameter of nanowires is adjustable with an accuracy error less than 0.3 nm. This technology provides a new way for advanced 3D transistors and sensors.
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| 8. |
- Liang, Xiaoyan, et al.
(författare)
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Exosomal miR-532-5p induced by long-term exercise rescues blood–brain barrier function in 5XFAD mice via downregulation of EPHA4
- 2023
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Ingår i: Aging Cell. - : Wiley. - 1474-9718 .- 1474-9726. ; 22:1
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Tidskriftsartikel (refereegranskat)abstract
- The breakdown of the blood–brain barrier, which develops early in Alzheimer's disease (AD), contributes to cognitive impairment. Exercise not only reduces the risk factors for AD but also confers direct protection against cognitive decline. However, the exact molecular mechanisms remain elusive, particularly whether exercise can liberate the function of the blood–brain barrier. Here, we demonstrate that long-term exercise promotes the clearance of brain amyloid-β by improving the function of the blood–brain barrier in 5XFAD mice. Significantly, treating primary brain pericytes or endothelial cells with exosomes isolated from the brain of exercised 5XFAD mice improves cell proliferation and upregulates PDGFRβ, ZO-1, and claudin-5. Moreover, exosomes isolated from exercised mice exhibit significant changes in miR-532-5p. Administration or transfection of miR-532-5p to sedentary mice or primary brain pericytes and endothelial cells reproduces the improvement of blood–brain barrier function. Exosomal miR-532-5p targets EPHA4, and accordingly, expression of EphA4 is decreased in exercised mice and miR-532-5p overexpressed mice. A specific siRNA targeting EPHA4 recapitulates the effects on blood–brain barrier-associated cells observed in exercised 5XFAD mice. Overall, our findings suggest that exosomes released by the brain contain a specific miRNA that is altered by exercise and has an impact on blood–brain barrier function in AD.
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| 9. |
- Song, Meiqi, et al.
(författare)
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Effects of Tool Tooth Number and Cutting Parameters on Milling Performance for Bamboo–Plastic Composite
- 2023
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Ingår i: Forests. - : MDPI. - 1999-4907. ; 14:2
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Tidskriftsartikel (refereegranskat)abstract
- Cutting force and temperature are critical indicators for improving cutting performance and productivity. This study used an up-milling experiment to ascertain the effect of tool tooth number, cutting speed, and depth on the machinability of bamboo–plastic composite. We focused on the changes in the resultant force and cutting temperature under different milling conditions. A response surface methodology was used to build prediction models for the resultant force and temperature. A verification test was conducted to prove the model’s reliability. The empirical findings suggested that the number of tool teeth had the most significant impacts on both the resultant force and the cutting temperature, followed by the depth of cut and the cutting speed. Moreover, the resultant force and cutting temperature showed increasing trends with decreasing numbers of tool teeth and increasing cut depths. However, cutting speed had a negative relationship with the resultant force and a positive relationship with temperature. We also determined the optimal milling conditions with the lowest force and temperature: four tool teeth, 300 m/min cutting speed, and 0.5 mm depth. This parameter combination can be used in the industrial manufacture of bamboo–plastic composite to improve tool life and manufacturing productivity.
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| 10. |
- Wang, Jinxin, et al.
(författare)
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Machining Properties of Stone-Plastic Composite Based on an Empirically Validated Finite Element Method
- 2023
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Ingår i: Advanced Engineering Materials. - : John Wiley & Sons. - 1438-1656 .- 1527-2648. ; 25:8
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Tidskriftsartikel (refereegranskat)abstract
- High-cutting performance is an essential metric for improving the suitability of materials for industrial applications. Herein, the machining properties of stone-plastic composite are assessed through a finite element method to explore orthogonal cutting behavior by diamond cutters. The key aspects examined in this work are the effects of tool geometry and cutting parameters on the cutting force, temperature, chip formation, von Mises stress, and surface quality finish. Primary findings show that chip continuity increases proportionally with increase in rake angle but decreases with cutting speed and depth. Meanwhile, both cutting stability and surface quality are negatively correlated with cutting speed and depth but positively correlated with rake angle. These results support the adoption of cutting conditions using greater rake angle, higher cutting speed, and shallower cutting depth to obtain higher cutting performance, that is, greater cutting stability and surface quality in the finishing machining of stone-plastic composites.
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