| 1. |
- Du, Yong, et al.
(författare)
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Flexible n-Type Tungsten Carbide/Polylactic Acid Thermoelectric Composites Fabricated by Additive Manufacturing
- 2018
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Ingår i: Coatings. - : MDPI AG. - 2079-6412. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Flexible n-type tungsten carbide/polylactic acid (WC/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated. The preparation of an n-type polymer-based thermoelectric composite with good stability in air atmosphere via additive manufacturing holds promise for application in flexible thermoelectric devices. For WC/PLA volume ratios varying from similar to 33% to 60%, the electrical conductivity of the composites increased from 10.6 to 42.2 S/cm, while the Seebeck coefficients were in the range -11 to -12.3 V/K. The thermal conductivities of the composites varied from similar to 0.2 to similar to 0.28 Wamp;lt;boldamp;gt;mamp;lt;/boldamp;gt;-1amp;lt;boldamp;gt;Kamp;lt;/boldamp;gt;-1 at similar to 300 K.
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| 2. |
- Du, Yong, et al.
(författare)
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Flexible ternary carbon black/Bi2Te3 based alloy/polylactic acid thermoelectric composites fabricated by additive manufacturing
- 2020
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Ingår i: Journal of Materiomics. - : ELSEVIER. - 2352-8478 .- 2352-8486. ; 6:2, s. 293-299
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Tidskriftsartikel (refereegranskat)abstract
- Flexible ternary carbon black/Bi2Te3 based alloy/polylactic acid (CB/BTBA/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated from 300 K to 360 K. At 300 K, as the mass ratios of BTBAs in the composites increased from 38.5% to 71.4%, both the electrical conductivity and Seebeck coefficient of the composites increased from 5.8 S/cm to 13.3 S/cm, and from 60.2 mV/K to 119.9 mV/K, respectively, and the thermal conductivity slightly increased from 0.15 W m(-1)K(-1) to 0.25 W m(-1)K(-1), as a result, the ZT value of the composites increased from 0.004 to 0.023. As the temperature increased from 300 K to 360 K, the electrical conductivity of all the composites slightly decreased, while the thermal conductivity slowly increased, and a highest ZT value of 0.024 was achieved for the composites with 71.4% BTBAs at 320 K. Unlike traditional sterolithography, fused deposition modeling, selective laser melting, etc., this additive manufacturing process can directly print the solutions which contain inorganic fillers and polymer matrixes into almost any designed intricate geometries of thermoelectric composites, therefore this process has great potential to be used for fabrication of flexible polymer based thermoelectric composites and devices. (C) 2020 The Chinese Ceramic Society. Production and hosting by Elsevier B.V.
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| 3. |
- Du, Yong, et al.
(författare)
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Flexible Thermoelectric Double-Layer Inorganic/Organic Composites Synthesized by Additive Manufacturing
- 2020
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Ingår i: Advanced Electronic Materials. - : WILEY. - 2199-160X. ; 6:8
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Tidskriftsartikel (refereegranskat)abstract
- This study shows an approach to combine a high electrical conductivity of one composite layer with a high Seebeck coefficient of another composite layer in a double-layer composite, resulting in high thermoelectric power factor. Flexible double-layer-composites, made from Bi2Te3-based-alloy/polylactic acid (BTBA/PLA) composites and Ag/PLA composites, are synthesized by solution additive manufacturing. With the increase in Ag volume-ratio from 26.3% to 41.7% in Ag/PLA layers, the conductivity of the double-layer composites increases from 12 S cm(-1)to 1170 S cm(-1), while the Seebeck coefficient remains approximate to 80 mu V K(-1)at 300 K. With further increase in volume ratio of Ag until 45.6% in Ag/PLA composite layer, the electrical conductivity of the double-layer composites increases to 1710 S cm(-1), however, with a slight decrease of the Seebeck coefficient to 64 mu V K-1. The electrical conductivity and Seebeck coefficient vary only to a limited extent with the temperature. The high Seebeck coefficient is due to scattering of low energy charge carriers across compositionally graded interfaces. A power factor of 875 mu W m(-1) K(-2)is achieved at 360 K for 41.7 vol.% Ag in the Ag/PLA layers. Solution additive manufacturing can directly print this double-layer composite into intricate geometries, making this process is promising for large-scale fabrication of thermoelectric composites.
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| 4. |
- Du, Yong, et al.
(författare)
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Flexible thermoelectric materials and devices
- 2018
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Ingår i: APPLIED MATERIALS TODAY. - : ELSEVIER SCIENCE BV. - 2352-9407. ; 12, s. 366-388
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Forskningsöversikt (refereegranskat)abstract
- Thermoelectric generators (TEGs) can directly convert waste heat into electrical power. In the last few decades, most research on thermoelectrics has focused on inorganic bulk thermoelectric materials and corresponding devices, and their thermoelectric properties have been significantly improved. An emerging topic is flexible devices, where the use of bulk inorganic materials is precluded by their inherent rigidity. The purpose of this paper is to review the research progress on flexible thermoelectric materials and generators, including theoretical principles for TEGs, conducting polymer TE materials, nanocomposites comprised of inorganic nanostructures in polymer matrices and fully inorganic flexible TE materials in nanostructured thin films. Approaches for flexible TEGs and components are reviewed, and remaining challenges discussed. (C) 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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| 5. |
- Du, Yong, et al.
(författare)
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Preparation and Thermoelectric Properties of Graphite/poly(3,4-ethyenedioxythiophene) Nanocomposites
- 2018
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 11:10
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Tidskriftsartikel (refereegranskat)abstract
- Graphite/poly(3,4-ethyenedioxythiophene) (PEDOT) nanocomposites were prepared by an in-situ oxidative polymerization process. The electrical conductivity and Seebeck coefficient of the graphite/PEDOT nanocomposites with different content of graphite were measured in the temperature range from 300 K to 380 K. The results show that as the content of graphite increased from 0 to 37.2 wt %, the electrical conductivity of the nanocomposites increased sharply from 3.6 S/cm to 80.1 S/cm, while the Seebeck coefficient kept almost the same value (in the range between 12.0 V/K to 15.1 V/K) at 300 K, which lead to an increased power factor. The Seebeck coefficient of the nanocomposites increased from 300 K to 380 K, while the electrical conductivity did not substantially depend on the measurement temperature. As a result, a power factor of 3.2 Wm(-1) K-2 at 380 K was obtained for the nanocomposites with 37.2 wt % graphite.
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| 6. |
- Du, Yong, et al.
(författare)
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Thermoelectric Properties of Reduced Graphene Oxide/Bi2Te3 Nanocomposites
- 2019
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 12:12
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Tidskriftsartikel (refereegranskat)abstract
- Reduced graphene oxide (rGO)/Bi2Te3 nanocomposite powders with different contents of rGO have been synthesized by a one-step in-situ reductive method. Then, rGO/Bi2Te3 nanocomposite bulk materials were fabricated by a hot-pressing process. The effect of rGO contents on the composition, microstructure, TE properties, and carrier transportation of the nanocomposite bulk materials has been investigated. All the composite bulk materials show negative Seebeck coefficient, indicating n-type conduction. The electrical conductivity for all the rGO/Bi2Te3 nanocomposite bulk materials decreased with increasing measurement temperature from 25 degrees C to 300 degrees C, while the absolute value of Seebeck coefficient first increased and then decreased. As a result, the power factor of the bulk materials first increased and then decreased, and a power factor of 1340 mu Wm(-1)K(-2) was achieved for the nanocomposite bulk materials with 0.25 wt% rGO at 150 degrees C.
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| 7. |
- Jiang, Ruijie, et al.
(författare)
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Substantial increase in future fluvial flood risk projected in China’s major urban agglomerations
- 2023
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Ingår i: Communications Earth and Environment. - 2662-4435. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Urban land will face high fluvial flood risk against the background of climate change and urban expansion. The effect of urban spatial expansion, instead of densification of assets within existing urban cells, on flood risk has rarely been reported. Here, we project the future flood risk of seven urban agglomerations in China, home to over 750 million people. The inundated urban land areas in the future are projected to be 4 to 19 times that at present. Without considering the urban spatial expansion, the inundated urban land areas will be underestimated by 10-50%. Urban land is more likely to be inundated than non-urban land, and the newly-developed urban land will be inundated more easily than the historical urban land. The results demonstrate the urgency of integrating climate change mitigation, reasonable urban land expansion, and increased flood protection levels to minimize the flood risk in urban land.
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| 8. |
- Xu, Jiayue, et al.
(författare)
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A genetic variant in the catechol-O-methyl transferase (COMT) gene is related to age-dependent differences in the therapeutic effect of calcium-channel blockers
- 2017
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Ingår i: Medicine. - : LIPPINCOTT WILLIAMS & WILKINS. - 0025-7974 .- 1536-5964. ; 96:30
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Tidskriftsartikel (refereegranskat)abstract
- Hypertension is the leading risk factor for cardiovascular disease and one of the major health concerns worldwide. Genetic factors impact both the risk for hypertension and the therapeutic effect of antihypertensive drugs. Sex- and age-specific variances in the prevalence of hypertension are partly induced by estrogen. We investigated 6 single nucleotide polymorphisms in genes encoding enzymes involved in estrogen metabolism in relation to sex- and age-specific differences in the systolic and diastolic blood pressure (SBP and DBP) outcome under the treatment of diuretics, calcium-channel blockers (CCBs), angiotensin-converting-enzyme inhibitors, and angiotensin-receptor blockers (ARBs). We included 5064 subjects (age: 40-82) from the population-based CoLaus cohort. Participants were genotyped for the catechol-O-methyltransferase gene (COMT) variants rs4680, rs737865, and rs165599; the uridine-diphospho-glucuronosyltransferase 1A gene family (UGT1A) variants rs2070959 and rs887829; and the aromatase gene (CYP19A1) variant rs10046. Binomial and linear regression analyses were performed correcting for age, sex, body mass index, smoking, diabetes, and antihypertensive therapy to test whether the variants in focus are significantly associated with BP. All investigated COMT variants were strongly associated with the effect of diuretics, CCBs, and ARBs on SBP or DBP (P<.05), showing an additive effect when occurring in combination. After Bonferroni correction the polymorphism rs4680 (Val(158)Met) in COMT was significantly associated with lower SBP in participants treated with CCBs (P=.009) with an especially strong impact in elderly individuals (age >= 70) alone (Delta=-14.08 mm Hg, P=.0005). These results underline the important role of estrogens and catecholamines in hypertension and the importance of genotype dependent, age-related adjustments of calcium-channel blocker treatment.
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| 9. |
- Xu, Lei, et al.
(författare)
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Quantized Distributed Nonconvex Optimization with Linear Convergence
- 2022
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Ingår i: 2022 IEEE 61ST CONFERENCE ON DECISION AND CONTROL (CDC). - : IEEE. ; , s. 5837-5842
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Konferensbidrag (refereegranskat)abstract
- This paper considers distributed nonconvex optimization for minimizing the average of local cost functions, by using local information exchange over undirected communication networks. Since the communication channels often have limited bandwidth or capacity, we first introduce a quantization rule and an encoder/decoder scheme to reduce the transmission bits. By integrating them with a distributed algorithm, we then propose a distributed quantized nonconvex optimization algorithm. Assuming the global cost function satisfies the Polyak-Lojasiewicz condition, which does not require the global cost function to be convex and the global minimizer is not necessarily unique, we show that the proposed algorithm linearly converges to a global optimal point. Moreover, a low data rate is shown to be sufficient to ensure linear convergence when the algorithm parameters are properly chosen. The theoretical results are illustrated by numerical simulation examples.
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