检索结果-南通市图书馆

Glacier Changes during the Past 40 Years in the West Kunlun Shan

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2015年第2期12卷 344-357页

作者： bao Wei-jia LIU Shi-yin WEI jun-feng GUO Wan-qin State Key Laboratory of Cryospheric Sciences Cold and Arid Regions Environmental and Engineering Research InstituteChinese Academy of Science University of Chinese Academy of Sciences

Recent studies on glaciers in the West Kunlun Shan, northwest Tibetan Plateau, have shown that they may be stable or retreating slightly. Here, we assess changes in the mass of the glaciers in the West Kunlun Shan(WKS) in an attempt to understand the processes that control their behavior. Glaciers over the recent 40 years(1970-2010) have shrunk 3.4±3.1%in area, based on a comparison between two Chinese glacier inventories. Variations of surface elevations, derived from ICESat-GLAS(Ice, Cloud, and Land Elevation Satellite-Geoscience Laser Altimeter System) elevation products(GLA14 data) using the robust linear-fit method, indicate that the glaciers have been gaining mass at a rate of 0.23±0.24 m w.e./a since 2003. The annual mass budget for the whole WKS range from 2003 to 2009 is estimated to be 0.71±0.62 Gt/a. This gain trend is confirmed by MOD10A1 albedo for the WKS region which shows a descent of the mean snowline altitude from 2003 to 2009.

关键词： Glacier change Mass balance West Kunlun Shan

Synthesis of an antimetastatic tetrasaccharide β-D-Gal-(1→4)-β-d-GlcpNAc-(1→6)-α-D-Manp-(1→6)-β-D-Manp-OMe

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2012年第12期23卷 1371-1374页

作者： Kai jun Liao Xiao feng Jin Xiang bao Meng Chen Li Zhong jun Li State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical SciencesPeking University

An antimetastatic tetrasaccharide β-D-Gal-（1 → 4）-β-D- GlcpNAc-（1 →6）-α-D-Manp-（1 → 6）-β-D-Manp-OMe, was syn- thesized with two approaches. The first approach was a conventional method employing thioglycoside and Koenigs-Knorr glycosylation reaction in 24% overall yield. The second one was a novel route through the azidoiodo-glycosylation strategy by using 2-iodo-2-deoxylactosyl azide as the donor in 36% overall yield.

关键词： Antimetastatic tetrasaccharide Thioglycoside Koenigs-Knorr method Azidoiodo-glycosylation 2-Iodo-2-deoxyl-actosyl azide β-Methyl mannoside

A Model-Based Soft Decision Approach for Speech Enhancement

在线全文

学校读者我要写书评

暂无评论

China Communications 2017年第9期14卷 11-22页

作者： Xianyun Wang Changchun bao feng bao Speech and Audio Signal Processing Laboratory Faculty of Information TechnologyBeijing University of Technology Department of Electrical and Computer Engineering The University of Auckland

Many speech enhancement algorithms that deal with noise reduction are based on a binary masking decision(termed as the hard decision), which may cause some regions of the synthesized speech to be discarded. In view of the problem, a soft decision is often used as an optimal technique for speech restoration. In this paper, considering a new fashion of speech and noise models, we present two model-based soft decision techniques. One technique estimates a ratio mask generated by the exact Bayesian estimators of speech and noise. For the second technique, we consider one issue that an optimum local criterion(LC) for a certain SNR may not be appropriate for other SNRs. So we estimate a probabilistic mask with a variable LC. Experimental results show that the proposed method achieves a better performance than reference methods in speech quality.

关键词： speech enhancement soft masks CASA threshold

Energy Expenditure of Trotting Gait Under Different Gait Parameters

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2017年第4期30卷 943-950页

作者： Xian-bao Chen feng Gao State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong University Shanghai 200240 China

Robots driven by batteries are clean, quiet, and can work indoors or in space. However, the battery endurance is a great problem. A new gait parameter design energy saving strategy to extend the working hours of the quadruped robot is proposed. A dynamic model of the robot is established to estimate and analyze the energy expenditures during trotting. Given a trotting speed, opti- mal stride frequency and stride length can minimize the energy expenditure. However, the relationship between the speed and the optimal gait parameters is nonlinear, which is difficult for practical application. Therefore, a simplified gait parameter design method for energy saving is pro- posed. A critical trotting speed of the quadruped robot is found and can be used to decide the gait parameters. When the robot is travelling lower than this speed, it is better to keep a constant stride length and change the cycle period. When the robot is travelling higher than this speed, it is better to keep a constant cycle period and change the stride length. Simulations and experiments on the quadruped robot show that by using the proposed gait parameter design approach, the energy expenditure can be reduced by about 54% compared with the 100 mm stride length under 500 mm/s speed. In general, an energy expenditure model based on the gait parameter of the quadruped robot is built and the trotting gait parameters design approach for energy saving is proposed.

关键词： Quadruped robot Energy expenditure Gait Bezier curve

Discovering genes responsible for silk synthesis in Bombyx moriby piggyBac-based random insertional mutagenesis

在线全文

学校读者我要写书评

暂无评论

Insect Science 2019年第5期26卷 821-830页

作者： Xing-bao feng Zi-Wen Zheng Xian Zhang jun Gu Qi-Li feng Li-Hua Huang Guangzhou Key Laboratory of Insect Development Regulation and Applied Research Institute of Insect Science and TechnologySchool of Life SciencesSouth China Normal UniversityGuangzhouChina

Silkworm mutants are valuable resources for both transgenic breeding and gene discovery. PiggyBac-based random insertional mutagenesis has been widely used in gene functional studies. In order to discover genes involved in silk synthesis, a piggyBac-based random insertional library was constructed using Bombyx mori, and the mutants with abnormal cocoon were particularly screened. By this means, a “thin cocoon” mutant was identified. This mutant revealed thinner cocoon shell and shorter posterior silk gland (PSG) compared with the wild type. The messenger RNA (mRNA) levels of all the three fibroin genes, including Fib-H, Fib-L and P25, were significantly down-regulated in the PSG of mutants. Four piggyBac insertion sites were identified in Aquaporin (AQP), Longitudinals lacking protein-like {Lola), Glutamyl aminopeptidase-like (GluAP) and Loc101744460. The mRNA levels of all the four genes were significantly altered in the silk gland of mutants. In particular, the mRNA amount of AQP, a gene responsible for the regulation of osmotic pressure, decreased dramatically immediately prior to the spinning stage in the anterior silk gland of mutants. The identification of the genes disrupted in the “thin cocoon” mutant in this study provided useful information for understanding silk production and transgenic breeding of silkworms in the future.

关键词： aquaporin Bombyx mori development mutant piggyBac silk gland

Modular assembly of Co4-thiacalix[4]arene units and Keggin-type SiW12O40 for visible-light photothermal conversion

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Tungsten 2025年第1期 112-119页

作者： Jia-Hui Li Qing Zhao Dong-Ao Mao Kun Zhou bao-Kuan Chen Yan-feng Bi School of Petrochemical Engineering Liaoning Petrochemical University

The construction of metal-organic coordination clusters（MCCs） using modular secondary building units is an important method for preparing functional *** this study,two new MCCs modularly assembled from Keggin-type {SiW12O40}H4TC4A=p-tert-Butylthiacalix[4]arene(SiW12) units and thiacalixarene-supported Co4-thiacalix[4]arene(Co4-TC4A polynuclear second-building units（PSBUs,H4TC4A=p-tert-Butylthiacalix[4]arene） are *** two MCCs,abbreviated as Co4-SiW12and Co8-SiW12,were structurally characterized by single-crystal X-ray *** Co4-SiW12is a supramolecular structure involving cation-anion interactions between Co4-TC4A PSBUs and ***8-SiW12features "barbell-like" shapes with two Co4-TC4A coordinatively linked to a Keggin-type SiW12unit on opposite via W-O_t-Co *** coordination of Co4-TC4A to SiW12in Co8-SiW12resulted in significantly improved photothermal conversion performances compared with Co4-SiW12and pure SiW12or ***-gap determination and photophysical analysis combined with density functional theory calculations indicated the binding mode between Co4-TC4A PSBUs and SiW12,which considerably influences the way of electron transport and the conversion ability of visible light to heat.

关键词：

Effect of Glutinous Rice Flour on Mechanical Properties and Microstructure of Cement-based Materials

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2023年第2期38卷 394-400页

作者： feng Qi LU bao WANG Dan Guangxi Key Lab of Road Structure and Materials Guangxi Transportation Science and Technology Group Co.LtdNanning5300007China Key Laboratory for Advanced Technology in Environment Protection of Jiangsu Province Yancheng Institute of TechnologyYancheng224051China Special Glass Key Lab of Hainan Province&State Key Laboratory of Marine Resource Utilization in South China Sea Hainan UniversityHaikou570228China

The mechanism of glutinous rice flour,a kind of natural admixture,on the hydration process,setting time,and microstructure of the Portland cement was *** experimental results show that the glutinous rice flour has an obvious setting retarding effect on cement *** optimal dosage of the glutinous rice flour is 3wt%.In this case,the initial and final setting time of the paste are delayed by 140 and185 min,*** flexural and compressive strengths of the hardened paste are increased by 0.35%and 0.07%after 56 d of *** glutinous rice flour hinders the mineral dissolution process and decreases the concentration of calcium ion at the initial stage of hydration due to the complexation effect,thereby hindering the nucleation and growth of CH and C-S-H phases and prolonging the hydration ***,C-S-H phases combine with the glutinous rice flour to contribute the bonding effect together,which compacts the microstructure of hardened cement pastes at the later hydration stage of cement ***,in-depth investigation on the utilization of glutinous rice flour as the admixture for the Portland cement is expected to be meaningful for the control of hydration exothermic rate and setting time.

关键词： glutinous rice flour cement-based materials mechanical properties setting time

Limited ecological risk of insect-resistance transgene flow from cultivated rice to its wild ancestor based on life-cycle fitness assessment

在线全文

学校读者我要写书评

暂无评论

Science Bulletin 2016年第18期61卷 1440-1450页

作者： Lei Li Xiao Yang Lei Wang Huanxin Yan jun Su feng Wang bao-Rong Lu Ministry of Education Key Laboratory for Biodiversity and Ecological Engineering Institute of Biodiversity Science Fudan University Fujian Province Key Laboratory of Genetic Engineering for Agriculture Fujian Academy of Agricultural Sciences

Ecological impact caused by transgene flow from genetically engineered （GE） crops to their wild rela- tives is largely determined by the fitness effect brought by a transgene. To estimate such impact is critical for the eco- logical risk assessment prior to the commercialization of GE crops. We produced F1 and F2 hybrid descendants from crosses of two insect-resistant GE rice lines （Bt, Bt/CpT1） and their non-GE rice parent with a wild rice （Oryza ruff- pogon） population to estimate the transgenic fitness. Insect damages and life-cycle fitness of GE and non-GE crop- wild hybrid descendants as well as their wild parent were examined in a common-garden experiment. No significant differences in insect damages were observed between the wild rice parent and GE hybrid descendants under high- insect pressure. The wild parent showed significantly greater relative survival-regeneration ratios than its GE and non-GE hybrid descendants under both high- and low-in- sect pressure. However, more seeds were produced in GE hybrid descendants than their non-GE counterparts under high-insect pressure. Given that the introduction of Bt and Bt/CpT1 transgenes did not provide greater insect resistance to crop-wild hybrid descendants than their wild parent, we predict that transgene flow from GE insect-resistant rice to wild rice populations may not cause considerable ecolog- ical risks.

关键词： Environmental impact Fecundity andsurvival Genetically modified organisms Lepidopteran - Oryza sativa Wild relative

Boundary layer structure in turbulent rayleigh-bénard convection in a slim box

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2019年第4期35卷 713-728页

作者： Hong-Yue Zou Wen-feng Zhou Xi Chen Yun bao jun Chen Zhen-Su She State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering Science College of Engineering Peking University Beijing 100871 China Department of Mechanics College of Engineering Sun Yat-sen University Guangzhou 510275 China

Logarithmic boundary layers have been observed in different regions in turbulence. However, how thermal plumes correlate to the log law of temperature and how the velocity profile changes with pressure gradient are not fully understood. Here, we perform three-dimensional simulations of turbulence in a slim-box without the front and back walls with aspect ratio, width:depth:height=L:D:H=1:1/6:1width:depth:height=L:D:H=1:1/6:1 (respectively corresponding to xx, yy and zz coordinates), in the Rayleigh number Ra=[1×10^8,1×10^10]Ra=[1×10^8,1×10^10] for Prandtl number Pr=0.7Pr=0.7. To investigate the structures of the viscous and thermal boundary layers, we examine the velocity profiles in the streamwise and vertical directions (i.e. UU and WW) along with the mean temperature profile throughout the plume-impacting, plume-ejecting, and wind-shearing regions. The velocity profile is successfully quantified by a two-layer function of a stress length, e^+u=e^+0(z^+)3/2[1+(z^+/z^+sub)4]^1/4eu+=e^+0(z+)3/2[1+(z+/zsub+)4]1/4, as proposed by She et al.(J Fluid Mech, 2017), though it is neither \pb type nor logarithmic. In contrast, the temperature profile in the plume-ejecting region is logarithmic for all simulated cases, being attributed to the emission of thermal plumes. The coefficient of the temperature log-law, AA, can be described by composition of the thermal stress length ■■θ0■θ0■ and the thicknesses of thermal boundary layer z■subzsub■ and z?bufzbuf■, i.e. A■z?sub/(■■θ0z■buf3/2)A■zsub?/(■θ0■zbuf^3/2). The adverse pressure gradient responsible for turning the wind direction contributes to intensively emitting plumes and the logarithmic temperature profile at the plume-ejecting region. The Nusselt number scaling and the local heat flux in the slim box are consistent with previous results of the confined cells. Therefore, the slim-box RBC is a preferable system for investigating in-box kinetic and thermal structures of turbulent convection with the large-scale circulation

关键词： Rayleigh-Bénard convection Wall-bounded turbulence Heat transport Direct numerical simulation