Showing papers by "Bao Yang published in 2016"
TL;DR: In this article, a transparent wood composite is proposed as a future building material, especially as a replacement of glass toward energy efficient building with sustainable materials, which can create a uniform and consistent daylight distribution over the day.
Abstract: Among many other requirements, energy efficient building materials require effective daylight harvesting and thermal insulation to reduce electricity usage and weatherization cost. The most commonly used daylight harvesting material, glass, has limited light management capability and poor thermal insulation. For the first time, transparent wood is introduced as a building material with the following advantages compared with glass: (1) high optical transparency over the visible wavelength range (>85%); (2) broadband optical haze (>95%), which can create a uniform and consistent daylight distribution over the day without glare effect; (3) unique light guiding effect with a large forward to back scattering ratio of 9 for a 0.5 cm thick transparent wood; (4) excellent thermal insulation with a thermal conductivity around 0.32 W m−1 K−1 along the wood growth direction and 0.15 W m−1 K−1 in the cross plane, much lower than that of glass (≈1 W m−1 K−1); (5) high impact energy absorption that eliminates the safety issues often presented by glass; and (6) simple, scalable fabrication with reliable performance. The demonstrated transparent wood composite exhibits great promise as a future building material, especially as a replacement of glass toward energy efficient building with sustainable materials.
210 citations
TL;DR: It is shown that cooling fluxes of 258 W cm−2 can be achieved in thin-film Bi2Te3-based superlattice thermoelectric modules, which will have far-reaching impacts in diverse applications, such as advanced computer processors, radio-frequency power devices, quantum cascade lasers and DNA micro-arrays.
Abstract: In present-day high-performance electronic components, the generated heat loads result in unacceptably high junction temperatures and reduced component lifetimes. Thermoelectric modules can, in principle, enhance heat removal and reduce the temperatures of such electronic devices. However, state-of-the-art bulk thermoelectric modules have a maximum cooling flux qmax of only about 10 W cm−2, while state-of-the art commercial thin-film modules have a qmax <100 W cm−2. Such flux values are insufficient for thermal management of modern high-power devices. Here we show that cooling fluxes of 258 W cm−2 can be achieved in thin-film Bi2Te3-based superlattice thermoelectric modules. These devices utilize a p-type Sb2Te3/Bi2Te3 superlattice and n-type δ-doped Bi2Te3−xSex, both of which are grown heteroepitaxially using metalorganic chemical vapour deposition. We anticipate that the demonstration of these high-cooling-flux modules will have far-reaching impacts in diverse applications, such as advanced computer processors, radio-frequency power devices, quantum cascade lasers and DNA micro-arrays. Current thermoelectric modules provide cooling fluxes that are insufficient for high-heat flux applications. Here, the authors demonstrate thin-film-based thermoelectric modules capable of providing cooling fluxes more than double that of the current state-of-the-art.
150 citations
TL;DR: In this paper, a theoretical model for contact-mode triboelectric nanogenerators based on the principles of charge conservation and zero loopvoltage is illustrated. And the effect of the moving speed on output voltage, current, and power are illustrated in three cases, that is, the motion with constant speed, the sinusoidal motion cycles, and the real walking cycles by human subject.
Abstract: Harvesting mechanical energy from human activities by triboelectric nanogenerators (TENGs) is an effective approach for sustainable, maintenance-free, and green power source for wireless, portable, and wearable electronics. A theoretical model for contact-mode triboelectric nanogenerators based on the principles of charge conservation and zero loop-voltage is illustrated. Explicit expressions for the output current, voltage, and power are presented for the TENGs with an external load of resistance. Experimental verification is conducted by using a laboratory-fabricated contact-mode TENG made from conducting fabric electrodes and polydimethylsiloxane/graphene oxide composite as the dielectric layer. Excellent agreements of the output voltage, current, and power are demonstrated between the theoretical and experimental results, without any adjustable parameters. The effects of the moving speed on output voltage, current, and power are illustrated in three cases, that is, the motion with constant speed, the sinusoidal motion cycles, and the real walking cycles by human subject. The fully verified theoretical model is a very powerful tool to guide the design of the device structure and selection of materials, and optimization of performance with respect to the application conditions of TENGs.
132 citations
TL;DR: Simultaneously enhanced thermally conductive and electrically insulating properties of wax-BNNS composites demonstrate their promising application for thermal management in electronic systems.
Abstract: Phase change materials (PCMs) possessing ideal properties, such as superior mass specific heat of fusion, low cost, light weight, excellent thermal stability as well as isothermal phase change behavior, have drawn considerable attention for thermal management systems. Currently, the low thermal conductivity of PCMs (usually less than 1 W mK−1) greatly limits their heat dissipation performance in thermal management applications. Hexagonal boron nitride (h-BN) is a two-dimensional material known for its excellent thermally conductive and electrically insulating properties, which make it a promising candidate to be used in electronic systems for thermal management. In this work, a composite, consisting of h-BN nanosheets (BNNSs) and commercialized paraffin wax was developed, which inherits high thermally conductive and electrically insulating properties from BNNSs and substantial heat of fusion from paraffin wax. With the help of BNNSs, the thermal conductivity of wax–BNNS composites reaches 3.47 W mK−1, which exhibits a 12-time enhancement compared to that of pristine wax (0.29 W mK−1). Moreover, an 11.3–13.3 MV m−1 breakdown voltage of wax–BNNS composites was achieved, which shows further improved electrical insulating properties. Simultaneously enhanced thermally conductive and electrically insulating properties of wax–BNNS composites demonstrate their promising application for thermal management in electronic systems.
67 citations
TL;DR: For the first time, a thermally conductive, electrically insulating, and optically transparent nanopaper using a bilayer design where a thin layer of boron nitride nanosheets were coated on the CNF-nanopaper is reported.
Abstract: Cellulose nanofiber (CNF) from abundant and renewable wood is an emerging material with excellent mechanical, chemical, and optical properties. Transparent nanopaper made of CNF (CNF-nanopaper) could potentially replace plastics in electronics due to its excellent optical transparency, mechanical strength, and biodegradability. However, CNF-nanopaper normally has a low thermal conductivity and poor stability in increasing temperatures, which is not suitable for long-term stability and reliability in devices. Herein, for the first time, we report a thermally conductive, electrically insulating, and optically transparent nanopaper using a bilayer design where a thin layer of boron nitride (BN) nanosheets were coated on the CNF-nanopaper. An optical transparency (70%) and a thermal conductivity (0.76 W/m/K) were successfully achieved through a solution-based process at room temperature. Such an optically transparent, electrically insulating, and thermally conductive bilayer nanopaper can find applications in...
48 citations
TL;DR: This wearable anthropometric device provides a useful index, the limb circumferential strain, for upper arm muscle contraction in isometric mode, and provides a linear relationship was found during isometric contraction.
Abstract: Fabric-based wearable technology is highly desirable in sports, as it is light, flexible, soft, and comfortable with little interference to normal sport activities. It can provide accurate information on the in situ deformation of muscles in a continuous and wireless manner. During elbow flexion in isometric contraction, upper arm circumference increases with the contraction of elbow flexors, and it is possible to monitor the muscles' contraction by limb circumferential strains. This paper presents a new wireless wearable anthropometric monitoring device made from fabric strain sensors for the human upper arm. The materials, structural design and calibration of the device are presented. Using an isokinetic testing system (Biodex3®) and the fabric monitoring device simultaneously, in situ measurements were carried out on elbow flexors in isometric contraction mode with ten subjects for a set of positions. Correlations between the measured values of limb circumferential strain and normalized torque were examined, and a linear relationship was found during isometric contraction. The average correlation coefficient between them is 0.938 ± 0.050. This wearable anthropometric device thus provides a useful index, the limb circumferential strain, for upper arm muscle contraction in isometric mode.
21 citations
TL;DR: In this article, the authors studied the pathway and energetics of thermally-induced structural change in water-in-oil microemulsions using microsecond-long molecular dynamics simulations.
3 citations