Yi Cui

Bio: Yi Cui is an academic researcher from Stanford University. The author has contributed to research in topics: Anode & Lithium. The author has an hindex of 220, co-authored 1015 publications receiving 199725 citations. Previous affiliations of Yi Cui include KAIST & University of California, Berkeley.

The unique chemistry of thiuram polysulfides enables energy dense lithium batteries

Abstract: Organosulfur compounds are cheap and abundant cathode materials that can offer high specific energies. Herein, we explore for the first time, the common vulcanization accelerators viz. thiuram polysulfides embedded in carbon nanotubes as binder-free cathodes in lithium batteries that show 3 highly reversible redox reactions (3 discharge plateaus) and high material utilization (up to 97%). We use electrochemical characterization techniques, first-principles calculations, XPS, XRD, FTIR, and SEM to gain insight into the chemical transformations occurring during battery cycling. We identify that the mesomeric form of lithium pentamethylene dithiocarbamate with a positive nitrogen center, formed in the discharge, can act as polysulfide and sulfide anchors through strong coulombic interactions thus enabling a capacity retention of 87% after 100 cycles at C/5 rate. A high loading cathode with an areal capacity of 5.3 mA h cm−2 tested under a low electrolyte to active material ratio of 3 μL mg−1 yields an active material specific energy of 1156 W h kg−1 thus demonstrating the potential of this class of compounds in high specific energy lithium batteries.

Radar imaging by using GTD near-field model and antenna array-factor

Abstract: As one of the image processing method of radar sensor, it is most typical method which employs synthetic aperture radar (SAR) processing. In this paper we investigate radar image of scattering models by using an extended idea of array-factor (AF) in antenna theory. Applying phase difference between each element of the array becomes so-called phased array beam-forming and weighting to each element becomes adaptive beam processing [1], [2]. Also, regarding AF as near sources, it has been directly applied to far-field transforming algorithm [3]. Since AF is considered as a sum of delayed phase signals from each antenna element, we can construct image of the signal from the sum which depends on degree of phase matching between the receiving signal and its coordinate. This procedure is a kind of aperture synthesis, also known as delay and sum (DAS), especially in the field of ultrasound medical imaging and acoustics [4].

Symmetrical MnO 2 Carbon NanotubeTextile Nanostructures for Wearable Pseudocapacitors with High

Abstract: While MnO2 is a promising material for pseudocapacitor applications due to its high specific capacity and low cost, MnO2 electrodes suffer from their low electrical and ionic conductivities. In this article, we report a structure where MnO2 nanoflowers were conformally electrodepositedontocarbonnanotube(CNT)-enabledconductivetextile fibers.Suchnanostructures effectively decrease the ion diffusion and charge transport resistance in the electrode. For a given arealmassloading,thethicknessofMnO2onconductivetextile fibersismuchsmallerthanthatona flat metal substrate. Such a porous structure also allows a large mass loading, up to 8.3 mg/cm 2 , which leads to a high areal capacitance of 2.8 F/cm 2 at a scan rate of 0.05 mV/s. Full cells were demonstrated, where the MnO2� CNTtextile was used as a positive electrode, reduced MnO2� CNTtextile as a negative electrode, and 0.5 M Na2SO4 in water as the electrolyte. The resulting pseudocapacitor shows promising results as a low-cost energy storage solution and an attractive wearable power.

Unsupervised Speckle Level Estimation of SAR Images Using Texture Analysis and AR Model

Abstract: In this paper, a new method is proposed for unsupervised speckle level estimation in synthetic aperture radar (SAR) images. It is assumed that fully developed speckle intensity has a Gamma distribution. Based on this assumption, estimation of the equivalent number of looks (ENL) is transformed into noise variance estimation in the logarithmic SAR image domain. In order to improve estimation accuracy, texture analysis is also applied to exclude areas where speckle is not fully developed (e.g., urban areas). Finally, the noise variance is estimated by a 2-dimensional autoregressive (AR) model. The effectiveness of the proposed method is verified with several SAR images from different SAR systems and simulated images. key words: AR model, equivalent number of looks (ENL), synthetic aperture radar (SAR), texture analysis.

On exact model-based scattering decomposition of polarimetric SAR data

Abstract: Model-based scattering decomposition [1–4] is an effective and popular tool for analyzing polarimetric SAR (PolSAR) data due to its clear physical explanation, convenient implementation, and easy visual interpretation. This technique aims to express the measured PolSAR data as the combination of different scattering mechanisms. However, the original three-component model proposed by Freeman and Durden [1] assumes azimuthal reflection symmetry and consequently does not use the complete information of the covariance or coherency matrix. Recent advances focused on increasing component numbers (e.g., the four-component model [2]) or reducing the number of knowns (e.g., by matrix rotation [3]), with the purpose to account for more elements in the matrix data. Nevertheless, it is to the best knowledge of the authors that finding a physically meaningful matrix expansion (i.e., model-based) that exactly (but not approximately) matches the measured data remains an unresolved task.

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。