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Anderson Acceleration of Gradient Methods with Energy for Optimization Problems

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Communications on Applied Mathematics and Computation 2024年第2期6卷 1299-1318页

作者： Hailiang Liu Jia-Hao He Xuping Tian Department of Mathematics Iowa State UniversityAmesIAUSA Department of Agricultural and Biosystems Engineering Iowa State UniversityAmesIAUSA

Anderson acceleration(AA)is an extrapolation technique designed to speed up fixed-point *** optimization problems,we propose a novel algorithm by combining the AA with the energy adaptive gradient method(AEGD)[arXiv:2010.05109].The feasibility of our algorithm is ensured in light of the convergence theory for AEGD,though it is not a fixed-point *** provide rigorous convergence rates of AA for gradient descent(GD)by an acceleration factor of the gain at each implementation of *** experimental results show that the proposed AA-AEGD algorithm requires little tuning of hyperparameters and exhibits superior fast convergence.

关键词： Anderson acceleration(AA) Gradient descent(GD) Energy stability

Thermal transports in the MXenes family:Opportunities and challenges

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Nano research 2024年第8期17卷 7700-7716页

作者： Yurui Liu Yue Wu Xinwei Wang Department of Chemical and Biological Engineering Iowa State University618 Bissell AmesIA 50011USA Department of Mechanical Engineering 271 Applied Science Complex II1915 Scholl RoadIowa State UniversityAmesIA 50011USA

The carbides and nitrides of transition metals known as“MXenes”refer to a fast-growing family of two-dimensional materials discovered in *** to their unique nanolayer structure,superior electrical,mechanical,and thermal properties,MXenes have shown great potential in addressing the critical overheating issues that jeopardize the performance,stability,and lifetime of high-energy-density components in modern devices such as microprocessors,integrated circuits,and capacitors,*** outstanding intrinsic thermal conductivity of MXenes has been proved by experimental and theoretical *** MXenes-enabled high thermal conductivity composites incorporated with polymer matrix have also been reported and widely used as thermal management *** the booming heat dissipation demands,MXenes-enabled thermal management material is an extremely valuable and scalable option for modern electronics ***,the fundamental thermal transport mechanisms behind the MXenes family remain *** MXene thermal conductivity disparities between the theoretical prediction and experimental results are still *** better understand the thermal conduction in MXenes and provide more insights for engineering high-performance MXene thermal management materials,in this article,we summarize recent progress on thermal conductive *** essential factors that affect MXenes intrinsic thermal conductivities are tackled,selected MXenes-polymer composites are highlighted,and prospects and challenges are also discussed.

关键词： transition metal carbide(MXene) thermal transport two-dimensional materials thermally conductive composites

Population genomic analysis reveals key genetic variations and the driving force for embryonic callus induction capability in maize

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Journal of Integrative Agriculture 2024年第7期23卷 2178-2195页

作者： Peng Liu Langlang Ma Siyi Jian Yao He Guangsheng Yuan Fei Ge Zhong Chen Chaoying Zou Guangtang Pan Thomas Lübberstedt Yaou Shen State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China/Maize research Institute Sichuan Agricultural UniversityChengdu 611130China Department of Agronomy Iowa State UniversityAmesIA 50011USA

Genetic transformation has been an effective technology for improving the agronomic traits of ***,it is highly reliant on the use of embryonic callus(EC)and shows a serious genotype *** this study,we performed genomic sequencing for 80 core maize germplasms and constructed a high-density genomic variation map using our newly developed pipeline(MQ2Gpipe).Based on the induction rate of EC(REC),these inbred lines were categorized into three *** low-REC germplasms displayed more abundant genetic diversity than the high-REC *** integrating a genome-wide selective signature screen and region-based association analysis,we revealed 95.23 Mb of selective regions and 43 REC-associated *** variants had phenotypic variance explained values ranging between 21.46 and 49.46%.In total,103 candidate genes were identified within the linkage disequilibrium regions of these REC-associated *** genes mainly participate in regulation of the cell cycle,regulation of cytokinesis,and other functions,among which MYB15 and EMB2745 were located within the previously reported QTL for EC *** leaf area-associated variants with large effects were closely linked to several REC-related loci,implying a potential synergistic selection of REC and leaf size during modern maize breeding.

关键词： maize genetic transformation embryonic callus selective signal association analysis

Unveiling a new regulator: Vacuolar V-ATPase mediates brassinosteroid signaling in Arabidopsis

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Molecular Plant 2024年第2期17卷 227-229页

作者： Shikha Malik Justin W.Walley Department of Plant Pathology Entomologyand Microbiologylowa State UniversityAmesIA 50011USA

Plant growth and development are intricately regulated by hormones such as auxins,gibberellins,jamonates,cytokinins,and brassinosteroids(BRs).BRs are a group of plant steroid hormones that play a vital role in plant growth and response to the *** regulate many biological processes including cell elongation,cell division,and male fertility,as well as abiotic and biotic stress responses.

关键词： media fertility brassinosteroid

A novel 10-nm physical gate length double-gate junction field effect transistor

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Chinese Physics B 2008年第2期17卷 685-689页

作者：侯晓宇黄如陈刚刘晟张兴俞滨王阳元 Institute of Microelectronics Peking University nasa ames research center

A novel double-gate （DG） junction field effect transistor （JFET） with depletion operation mode is proposed in this paper. Compared with the conventional DG MOSFET, the novel DG JFET can achieve excellent performance with square body design, which relaxes the requirement on silicon film thickness of DG devices. Moreover, due to the structural symmetry, both p-type and n-type devices can be realized on exactly the same structure, which greatly simplifies integration. It can reduce the delay by about 60% in comparison with the conventional DG MOSFETs.

关键词： MOSFET double-gate MOSFET depletion operation mode

On-the-fly dopant redistribution in a silicon nanowire p-n junction

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Nano research 2017年第8期10卷 2845-2855页

作者： Dong-II Moon Myeong-Lok Seol Jin-Woo Han M. Meyyappan center for Nanotechnology NASA Ames Research Center Moffett Field CA 94035 USA

Dopant redistribution in a silicon nanowire （SiNW） p-n junction is found to occur owing to self-heating effects. A SiNW is doped to form back-to-back diodes and is thermally isolated by an oxide layer on its bottom side and by air on the other sides. When a high level of current flows, the inner body temperature is found to increase enough to cause dopant diffusion and even to reach the silicon melting point due to Joule heating. This experimentally observed electrothermal behavior is also validated through numerical simulation. The conductivity change is dependent on the total power density and the change becomes permanent once the device suffers self-heating beyond a threshold point. Finally, the dopant redistribution is directly visualized using scanning capacitance microscopy for the first time.

关键词： nanowire degradation Joule heating dopant redistribution scanning capacitance microscopy

Substitution of Pb with (Li_(1/2)Bi_(1/2)) in PbZrO_(3)-based antiferroelectric ceramics

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Journal of Advanced Dielectrics 2024年第1期14卷 74-81页

作者： Binzhi Liu Anand P.S.Gaur Jun Cui Xiaoli Tan Department of Materials Science and Engineering Iowa State University AmesIA 50011USA

PbZrO_(3)-based antiferroelectric(AFE)ceramics are promising dielectrics for high-energy-density capacitors due to their reversible phase transitions during charge-discharge *** this work,a new composition series,[Pb_(0.93-x)La_(0.02)(Li_(1/2)Bi_(1/2))_(x)Sr_(0.04)][Zr_(0.57)Sn_(0.34)Ti_(0.09)]O_(3),with Li^(+)and Bi^(3+)substitution of Pb^(2+)at x=0,0.04,0.08,0.12,0.16 is investigated for the microstructure evolution,ferroelectric(FE)and dielectric *** is found that Li^(+) and Bi^(3+) substitution can significantly reduce the sintering temperature and simultaneously enhance the dielectric breakdown *** ultrahigh energy efficiency(94.0%)and a large energy density(3.22 J/cm^(3))are achieved in the composition of x=0.12 with a low sintering temperature(1075℃).

关键词： PbZrO_(3)-based antiferroelectrics LiþBi substitution energy storage energy efficiency

Abomasal infusion of branched-chain amino acids or branched-chain keto-acids alter lactation performance and liver triglycerides in fresh cows

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Journal of Animal Science and Biotechnology 2024年第3期15卷 1145-1157页

作者： Kristen Gallagher Isabelle Bernstein Cynthia Collings David Main Ghayyoor Ahmad Sarah Naughton Jayasimha Daddam Vengai Mavangira Mike Vandehaar Zheng Zhou Department of Animal Science Michigan State UniversityEast Lansing 48824USA Department of Veterinary Diagnostic and Production Animal Medicine Ames 50011USA

Background Dairy cows are at high risk of fatty liver disease in early lactation,but current preventative measures are not always *** with fatty liver have lower circulating branched-chain amino acid(BCAA)concentra-tions whereas cows with high circulating BCAA levels have low liver triglyceride(TG).Our objective was to determine the impact of BCAA and their corresponding ketoacids(branched-chain ketoacids,BCKA)on production performance and liver TG accumulation in Holstein cows in the first 3 weeks *** Thirty-six multiparous Holstein cows were used in a randomized block design *** were abomasally infused for the first 21 d postpartum with solutions of 1)saline(CON,n=12);2)BCA(67 g valine,50 g leu-cine,and 34 g isoleucine,n=12);and 3)BCK(77 g 2-ketovaline calcium salt,57 g 2-ketoleucine calcium salt,and 39 g 2-ketoisoleucine calcium salt,n=12).All cows received the same *** effects were determined using PROC GLIMMIX in *** No differences were detected for body weight,body condition score,or dry matter intake averaged over the first 21 d *** receiving BCK had significantly lower liver TG concentrations compared to CON(6.60%vs.4.77%,standard error of the mean(SEM)0.49)during the first 3 weeks of *** of BCA increased milk yield(39.5 vs.35.3 kg/d,SEM 1.8),milk fat yield(2.10 vs.1.69 kg/d,SEM 0.08),and lactose yield(2.11 vs.1.67 kg/d,SEM 0.07)compared with *** to CON,cows receiving BCA had lower plasma glucose(55.0 vs.59.2 mg/dL,SEM 0.86)but higherβ-hydroxybutyrate(9.17 vs.6.00 mg/dL,SEM 0.80).Conclusions Overall,BCAA supplementation in this study improved milk production,whereas BCKA supplementa-tion reduced TG accumulation in the liver of fresh cows.

关键词： Branched-chain amino acids Branched-chain ketoacids Fatty liver Fresh cow

Dynamic Responses of Atmospheric Carbon Dioxide Concentration to Global Temperature Changes between 1850 and 2010

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Advances in Atmospheric Sciences 2016年第2期33卷 247-258页

作者： Weile WANG Ramakrishna NEMANI Department of Science and Environmental Policy California State University at Monterey Bay Earth Science Division NASA Ames Research Center nasa Advanced Supercomputing Division NASA Ames Research Center

Changes in Earth＇s temperature have significant impacts on the global carbon cycle that vary at different time scales, yet to quantify such impacts with a simple scheme is traditionally deemed difficult. Here, we show that, by incorporating a tem- perature sensitivity parameter （1.64 ppm yr-1 ℃-1） into a simple linear carbon-cycle model, we can accurately characterize the dynamic responses of atmospheric carbon dioxide （CO2） concentration to anthropogenic carbon emissions and global temperature changes between 1850 and 2010 （r2 〉 0.96 and the root-mean-square error 〈 1 ppm for the period from 1960 onward）. Analytical analysis also indicates that the multiplication of the parameter with the response time of the atmospheric carbon reservoir （-12 year） approximates the long-term temperature sensitivity of global atmospheric CO2 concentration （-15 ppm ℃ 1）, generally consistent with previous estimates based on reconstructed CO2 and climate records over the Little Ice Age. Our results suggest that recent increases in global surface temperatures, which accelerate the release of carbon from the surface reservoirs into the atmosphere, have partially offset surface carbon uptakes enhanced by the elevated atmo- spheric CO2 concentration and slowed the net rate of atmospheric CO2 sequestration by global land and oceans by -30% since the 1960s. The linear modeling framework outlined in this paper thus provides a useful tool to diagnose the observed atmospheric CO2 dynamics and monitor their future changes.

关键词： atmospheric CO2 dynamics climate-carbon interactions climate change carbon cycle