Daryoosh Vashaee

Bio: Daryoosh Vashaee is an academic researcher from North Carolina State University. The author has contributed to research in topics: Thermoelectric effect & Thermoelectric materials. The author has an hindex of 48, co-authored 225 publications receiving 15724 citations. Previous affiliations of Daryoosh Vashaee include University of California, Santa Cruz & Oklahoma State University–Tulsa.

Thermoelectric Properties of Mg2Si Doped with Bi and Al with Conductive Glass Inclusion

Abstract: The thermoelectric (TE) properties of magnesium silicide (Mg2Si) fabricated through mechanical alloying and hot-pressing have been characterized by measurements of electrical resistivity (ρ), Seebeck coefficient (S) and thermal conductivity (κ) between 300 K and 970 K. TE samples of 2-at% Bi doped and 2-at% Al doped specimens were sintered at 1173 K and 1123 K, respectively. Structural analysis of the sintered samples was performed by scanning electron microscopy. The effect of inclusion of a minuscule quantity (0.25-vol%) of Mg-Si-B-R based conductive glass-frit in order to reduce the brittleness of samples has been investigated on the Al-doped Mg2Si samples. Power factors (S2σT) of greater than 2 W/mK were obtained from samples doped with Al. The samples mixed with conductive glass frit have also exhibited higher stability at temperatures greater than 900 K when compared to samples doped with Bi. The Mg2Si:Bi and Mg2Si:Al samples showed a maximum figure-of- merit (ZT) of 0.53 and 0.66 at 970 K, respectively.

Differential Thermal Analysis of Nanostructured Si0.80Ge0.20 Thermoelectric Material

Abstract: Thermoelectric effect becomes one of the important elements in sustainable energy due to its capability in green conversion of waste heat into electrical energy. Among various thermoelectric materials, nanostructured-Si0.80Ge0.20 is being widely investigated owing to its efficient thermoelectric effect at high temperature. In this manuscript, we studied differential thermal analysis (DTA) of Si0.80Ge0.20 thermoelectric alloy in detail. Our DTA study revealed the fact that in almost all alloys of nanostrcutured Si0.80Ge0.20 prepared with mechanical ball milling, the sample is not in Si0.80Ge0.20 phase but is in composite mixed phases of Si0.88Ge0.12 and small amount of Si0.55Ge0.45. This phase impurity can hardly be seen in X-ray diffraction patterns and is often neglected.

Enhancement of Thermoelectric Efficiency of MnSi1.75 with the Addition of Externally Processed Nanostructured MnSi

Abstract: Higher manganese silicide is one of the promising thermoelectric materials for waste heat recovery at medium temperature (500-700 °C). Improvement on thermoelectric performance of bulk thermoelectric higher manganese silicide MnSi1.75 is introduced by externally mixing 1 at% nanostructured MnSi to MnSi1.75. This method can reduce the thermal conductivity above 400 °C more than reducing the power factor of the higher manganese silicide. This would enhance the figure-of-merit ZT of MnSi1.75 to ZT0.5 without any doping at 570 °C. In comparison, the figure-of-merit of conventional MnSi1.75 is ZT0.3. This method can be easily applied to industrial manufacturing of this material to enhance its efficiency.

Economical FeSi2-SiGe Composites for Thermoelectric Power Generation

Abstract: Clean energy production and its efficient usage is one of the most important issues in the world today. Thermoelectric materials, which can convert heat into electricity, have drawn significant attention for waste-heat harvesting. In this report, FeSi2 and SiGe thermoelectric materials were used to make a new composite with enhanced efficiency/cost factor relative to pure FeSi2 and SiGe compounds.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Complex thermoelectric materials.

Abstract: Thermoelectric materials, which can generate electricity from waste heat or be used as solid-state Peltier coolers, could play an important role in a global sustainable energy solution. Such a development is contingent on identifying materials with higher thermoelectric efficiency than available at present, which is a challenge owing to the conflicting combination of material traits that are required. Nevertheless, because of modern synthesis and characterization techniques, particularly for nanoscale materials, a new era of complex thermoelectric materials is approaching. We review recent advances in the field, highlighting the strategies used to improve the thermopower and reduce the thermal conductivity.