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He Zhanhao and Chen Gang: "The Butterfly Lovers" violin concerto.
No full textMusical study of The Butterfly Lovers violin concerto by He Zhanhao and Chen Gang. Tracing its cultural background in China, analyzing in terms of the concerto's form, melody, scale, mode, harmony, and orchestration and discussing the more unusual technical demands of violin playing made by this concerto
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Politics of renewable energy in China /
No full textIn this book, Chen Gang examines the real-world effectiveness of China's approach to the promotion of green technologies and practices, and discusses the political landscape in which it is situated
Thermoelectric Energy Conversion: Materials, Devices, and Systems
Full text linkThis paper will present a discussion of challenges, progresses, and opportunities in thermoelectric energy conversion technology. We will start with an introduction to thermoelectric technology, followed by discussing advances in thermoelectric materials, devices, and systems. Thermoelectric energy conversion exploits the Seebeck effect to convert thermal energy into electricity, or the Peltier effect for heat pumping applications. Thermoelectric devices are scalable, capable of generating power from nano Watts to mega Watts. One key issue is to improve materials thermoelectric figure- of-merit that is linearly proportional to the Seebeck coefficient, the square of the electrical conductivity, and inversely proportional to the thermal conductivity. Improving the figure-of-merit requires good understanding of electron and phonon transport as their properties are often contradictory in trends. Over the past decade, excellent progresses have been made in the understanding of electron and phonon transport in thermoelectric materials, and in improving existing and identify new materials, especially by exploring nanoscale size effects. Taking materials to real world applications, however, faces more challenges in terms of materials stability, device fabrication, thermal management and system design. Progresses and lessons learnt from our effort in fabricating thermoelectric devices will be discussed. We have demonstrated device thermal-to-electrical energy conversion efficiency ~10% and solar-thermoelectric generator efficiency at 4.6% without optical concentration of sunlight (Figure 1) and ~8-9% efficiency with optical concentration. Great opportunities exist in advancing materials as well as in using existing materials for energy efficiency improvements and renewable energy utilization, as well as mobile applications
Nanoscale heat transfer - from computation to experiment
Full text linkHeat transfer can differ distinctly at the nanoscale from that at the macroscale. Recent advancement in
computational and 5 experimental techniques has enabled a large number of interesting observations and
understanding of heat transfer processes at the nanoscale. In this review, we will first discuss recent
advances in computational and experimental methods used in nanoscale thermal transport studies,
followed by reviews of novel thermal transport phenomena at the nanoscale observed in both
computational and experimental studies, and discussion on current understanding of these novel
10 phenomena. Our perspectives on challenges and opportunities on computational and experimental
methods are also presented.University of Notre Dame (Startup fund)United States. Dept. of Energy. Office of Basic Energy Sciences (Solid-State Solar-Thermal Energy Conversion Center
Theoretical efficiency of solar thermoelectric energy generators
No full textThis paper investigates the theoretical efficiency of solar thermoelectric generators (STEGs). A model is established including thermal concentration in addition to optical concentration. Based on the model, the maximum efficiency of STEGs is a product of the opto-thermal efficiency and the device efficiency. The device efficiency increases but the opto-thermal efficiency decreases with increasing hot side temperature, leading to an optimal hot-side temperature that maximizes the STEG efficiency. For a given optical concentration ratio, this optimal hot-side temperature depends on the thermoelectric materials’ nondimensional figure-or-merit, the optical properties of wavelength-selective surface and the efficiency of the optical system. Operating in an evacuated environment, STEGs can have attractive efficiency with little or no optical concentration working in the low temperature range (150–250 °C) for which Bi[subscript 2]Te[subscript 3]-based materials are suitable.United States. Dept. of Energy. Office of Basic Energy Sciences (Award DE-SC0001299
Nanocomposites for thermoelectrics and thermal engineering
No full textThe making of composites has served as a working principle of achieving material properties beyond those of their homogeneous counterparts. The classical effective-medium theory models the constituent phases with local properties drawn from the corresponding bulk values, whose applicability becomes questionable when the characteristic size of individual domains in a composite shrinks to nanometer scale, and the interactions between domains induced by interfacial and size effects become important or even dominant. These unique features of nanocomposites have enabled engineering of extraordinary thermoelectric materials with synergistic effects among their constituents in recent years. For other applications requiring high thermal conductivity, however, interfacial and size effects on thermal transport in nanocomposites are not favorable, although certain practical applications often call for the composite approach. Therefore, understanding nanoscale transport in nanocomposites can help determine appropriate strategies for enhancing the thermal performance for different applications. We review the emerging principles of heat and charge transport in nanocomposites and provide working examples from both thermoelectrics and general thermal engineering.United States. Dept. of Energy. Office of Science (Solid-State Solar-Thermal Energy Conversion Center Award DE-FG02-09ER46577)United States. Air Force Office of Scientific Research. Multidisciplinary University Research Initiative (Grant FA9550-10-1-0533)United States. Department of Energy. Office of Energy Efficiency and Renewable Energy (Advanced Manufacturing Program Award DE-EE0005756
Minimum thermal conductivity in superlattices: A first-principles formalism
No full textThe thermal conductivity of silicon-germanium superlattices is computed from density-functional perturbation theory using relaxation times that include both anharmonic and interface roughness effects. A decrease in the group velocity of low-frequency phonons in addition to the interface-disorder-induced scattering of high-frequency phonons drives the superlattice thermal conductivity to below the alloy limit. At short periods, interplay between decrease in group velocity and increase in phonon lifetimes with increase in superlattice period leads to a minimum in the cross-plane thermal conductivity. Increasing the mass mismatch between the constituent materials in the superlattice further lowers the thermal conductivity below the alloy limit, pointing to avenues for higher efficiency thermoelectric materials.United States. Dept. of Energy. Office of Science (Award DE-SC0001299/DE-FG02-09ER46577
Thermal conductivity of bulk nanostructured lead telluride
Full text linkThermal conductivity of lead telluride with embedded nanoinclusions was studied using Monte Carlo simulations with intrinsic phonon transport properties obtained from first-principles-based lattice dynamics. The nanoinclusion/matrix interfaces were set to completely reflect phonons to model the maximum interface-phonon-scattering scenario. The simulations with the geometrical cross section and volume fraction of the nanoinclusions matched to those of the experiment show that the experiment has already reached the theoretical limit of thermal conductivity. The frequency-dependent analysis further identifies that the thermal conductivity reduction is dominantly attributed to scattering of low frequency phonons and demonstrates mutual adaptability of nanostructuring and local disordering.United States. Dept. of Energy. Office of Science (Solid-State Solar-Thermal Energy Conversion Center Grant DE-SC0001299/DE-FG02-09ER46577
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