检索结果-南通市图书馆

The rate of period change in DAV stars

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2017年第7期17卷 11-24页

作者： Yan-Hui Chen Cai-Yun Ding wei-wei na Hong Shu Institute of Astrophysics Chuxiong Normal University School of Physics and Electronical Science Chuxiong Normal University Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences School of Physics and Electronic Engineering Yuxi Normal University

Grids of DAV star models are evolved by WDEC, taking the element diffusion effect into account. The grid parameters are hydrogen mass log（MH/M＊）, helium mass log（MHe/M＊）, stellar mass M＊and effective temperature T_（eff） for DAV stars. The core compositions are from white dwarf models evolved by MESA. Therefore, DAV star models evolved by WDEC have historically viable core compositions. Based on those DAV star models, we studied the rate of period change（P˙（k）） for different values of H, He, M_＊and Teff. The results are consistent with previous work. Two DAV stars G117-B15A and R548 have been observed for around 40 years. The rates of period change of two large-amplitude modes were obtained through the O-C method. We conducted an asteroseismological study on the two DAV stars and then obtained a best-fitting model for each star. Based on the two best-fitting models,the mode identifications（l, k） of the observed modes for G117-B15A and R548 are consistent with previous work. Both the observed modes and the observedP˙ s can be fitted by calculated ones. The results indicate that our method of evolving DAV star models is feasible.

关键词： stars oscillations (including pulsations) - stars individual (G117-B 15A and R548) -white dwarfs

ASAS J174406+2446.8 is identified as a marginal-contact binary with a possible cool third body

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2020年第6期20卷 265-272页

作者： Xiang-Dong Shi Sheng-Bang Qian Lin-Jia Li wei-wei na Xiao Zhou Yunnan Observatories Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China Yuxi Normal University Yuxi 653100China

ASAS J174406+2446.8 was originally found as aδScuti-type pulsating star with the period P=0.189068 d by ASAS ***,the LAMOST stellar parameters reveal that it is far beyond the red edge of pulsational instability strip on the log g-T diagram ofδScuti pulsating *** understand the physical properties of the variable star,we observed it by the 1.0-m Cassegrain reflecting telescope at Yunnan ***-color light curves in B,V,R_c and I_c bands were obtained and are analyzed by using the W-D *** is found that this variable star is a shallow-contact binary with an EB-type light curve and an orbital period of 0.3781 d rather than aδScuti *** is a W-subtype contact binary with a mass ratio of 1.135(±0.019)and a fill-out factor of 10.4%(±5.6)%.The situation of ASAS J174406+2446.8 resembles those of other EB-type marginal-contact binaries such as UU Lyn,ⅡPer and GW *** of them are at a key evolutionary phase from a semi-detached configuration to a contact system predicted by the thermal relaxation oscillation *** linear ephemeris was corrected by using 303 new determined times of light *** is detected that the O-C curve shows a sinusoidal variation that could be explained by the light-travel-time effect via the presence of a cool red *** present investigation reveals that some of theδScuti-type stars beyond the red edge of pulsating instability strip on the log g-T diagram are misclassified eclipsing *** understand their structures and evolutionary states,more studies are required in the future.

关键词： stars binaries close-stars binaries eclipsing-stars δScuti-stars individual(ASAS J174406+2446.8)

CRABP1-mediated non-canonical retinoic acid signaling in motor neurons and neural stem cells

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2024年第6期19卷 1169-1170页

作者： Li-na wei Department of Pharmacology University of Minnesota Medical SchoolMinneapolisMNUSA

Retinoic acid(RA),the active metabolite of vitamin A(the retinoids),elicits a wide spectrum of biological activities critical to the development and health of most of the organ systems including the nervous systems(Corcoran et al.,2002).The effects of RA are mediated by two very distinct pathways;the first is manifested in the nucleus by binding to a large family of nuclear RA receptors(RARs)to regulate proper expression of RAtargeted genes.

关键词： canonical spectrum critical

Properties of collective flow and pion production in intermediate-energy heavy-ion collisions with a relativistic quantum molecular dynamics model

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2024年第1期35卷 155-169页

作者： Si-na wei Zhao-Qing Feng School of Physics and Optoelectronics South China University of TechnologyGuangzhou 510640China

The relativistic mean-field approach was implemented in the Lanzhou quantum molecular dynamics transport model(***). Using the ***, the properties of collective flow and pion production were investigated systematically for nuclear reactions with various isospin asymmetries. The directed and elliptic flows of the *** are able to describe the experimental data of STAR Collaboration. The directed flow difference between free neutrons and protons was associated with the stiffness of the symmetry energy, that is, a softer symmetry energy led to a larger flow difference. For various collision energies, the ratio between the π^(-) and π^(+) yields increased with a decrease in the slope parameter of the symmetry energy. When the collision energy was 270 MeV/nucleon, the single ratio of the pion transverse momentum spectra also increased with decreasing slope parameter of the symmetry energy in both nearly symmetric and neutron-rich ***, it is difficult to constrain the stiffness of the symmetry energy with the double ratio because of the lack of threshold energy correction on the pion production.

关键词： Heavy-ion collision Collective flow Pion production Symmetry energy Relativistic mean field

Metabolomic Study on Vitamins B_1, B_2, and PP Supplementation to Improve Serum Metabolic Profiles in Mice under Acute Hypoxia Based on ~1H NMR Analysis

在线全文

学校读者我要写书评

暂无评论

Biomedical and Environmental Sciences 2010年第4期23卷 312-318页

作者： JIN LIU JIAN-QUAN WU JI-JUN YANG JING-YU wei wei-na GAO CHANG-JIANG GUO Institute of Hygiene and Environmental Medicine Tianjin 300050 China

Objective To explore metabolic changes after acute hypoxia and modulating effect of vitamins B1, B2, and PP supplementation in mice exposed to acute hypoxia. Methods Fifty male Kunming mice were randomly divided into 5 groups： normal, acute hypoxia, acute hypoxia with 2, 4 and 8 time- vitamins B1, B2, and PP supplementation . All mice were fed with corresponding diets for two weeks and then were exposed to a simulated altitude of 6 000 meters for 8 h, except for the normal group. Nuclear magnetic resonance analysis was used to identify the changes of serum metabolic profiles. Results There were significant changes in some serum metabolites under induced acute hypoxia, essentially relative increase in the concentrations of lactate, sugar and lipids and decrease in ethanol. The serum levels of choline, succinate, taurine, alanine, and glutamine also increased and phosphocholine decreased in the acute hypoxia group. After vitamins B1, B2, and PP supplementation, all these metabolic changes gradually recovered. Conclusion Significant changes in serum metabolic profile were observed by metabolomics in mice exposed to acute hypoxia, and vitamins B1, B2, and PP supplementation proved to be beneficial to improving some metabolic pathways. It is suggested that the dietary intakes of vitamins B1, B2, and PP should be increased under hypoxia condition.

关键词： Vitamins B1 B2 and PP Acute hypoxia 1H NMR Mice

Anomalies of Precipitation over China on Days with Tropical Cyclone Activity over the Bay of Bengal: Role of Moisture Transport

在线全文

学校读者我要写书评

暂无评论

Journal of Meteorological Research 2024年第2期38卷 368-382页

作者： na wei Ying LI Xiaoting FAN nanjing Joint Institute for Atmospheric Sciences Nanjing 210041 State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesChina Meteorological AdministrationBeijing 100081 Department of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences Fudan UniversityShanghai 200433

Tropical cyclones over the Bay of Bengal(BoBTC)affect the precipitation over China,with distinct seasonal and daily *** study quantitatively examines the daily standardized precipitation anomalies(SPAs)over China on the days with BoBTC activities(storm-days)and related circulations,based on rainfall measurements at surface meteorological stations and ECMWF reanalysis data on a 0.25°×0.25°resolution during *** positive SPA is found over the stations in the two adjacent regions around BoB(Southwest China in May/November and southern Tibetan Plateau in October)and three distant regions(Southeast China and the northeastern boundary of the Qinghai-Tibet Plateau in May,and central North China in October).The SPA distributions are remarkably consistent with the integrated water vapor transport(IVT)*** IVT is found associated with the interaction between southwesterly(southerly)of the BoBTC circulation and low-level monsoonal flow in May(midlevel westerly in winter months).The probabilities of extreme precipitation(EP)occurrences over the above regions all increase on *** adjacent regions,EP is significantly correlated with the northward IVT anomalies to the east of BoBTC circulation,which strengthen the water vapor input through the southern *** IVT anomalies are stronger in May,benefited by the deep monsoonal southwesterlies than those in *** distant regions,EP is more closely related to the IVT anomaly extending back from *** moisture from BoB concentrates along a local low-level convergence line over Southeast China,being further facilitated by coexistence of the BoBTC depression and midlevel westerly trough in *** results highlight the interactions between BoBTCs and local weather systems that influence the general precipitation anomalies and occurrence of EP over China,especially over distant regions.

关键词： tropical cyclone Bay of Bengal precipitation anomaly moisture transport

Land use change and its driving factors in the ecological function area:A case study in the Hedong Region of the Gansu Province,China

在线全文

学校读者我要写书评

暂无评论

Journal of Arid Land 2024年第1期16卷 71-90页

作者： wei Zhudeng DU na YU Wenzheng School of Geographical Science Nanjing University of Information Science&TechnologyNanjing 210044China

Land use and cover change(LUCC)is important for the provision of ecosystem *** increasing number of recent studies link LUCC processes to ecosystem services and human well-being at different scales ***,the dynamic of land use and its drivers receive insufficient attention within ecological function areas,particularly in quantifying the dynamic roles of climate change and human activities on land use based on a long time *** study utilizes geospatial analysis and geographical detectors to examine the temporal dynamics of land use patterns and their underlying drivers in the Hedong Region of the Gansu Province from 1990 to *** indicated that grassland,cropland,and forestland collectively accounted for approximately 99% of the total land *** initially increased and then decreased after 2000,while grassland decreased with *** contrast,forestland and construction land were continuously expanded,with net growth areas of 6235.2 and 455.9 km^(2),*** 1990 to 2020,cropland was converted to grassland,and both of them were converted to forestland as a *** expansion of construction land primarily originated from *** 2000 to 2005,land use experienced intensified temporal dynamics and a shift of relatively active zones from the central to the southeastern *** yield,economic factors,and precipitation were the major factors accounting for most land use *** impacts on land use changes were stronger before 1995,succeeded by the impact of animal husbandry during 1995-2000,followed by the impacts of grain production and gross domestic product(GDP)after ***,agricultural and pastoral activities,coupled with climate change,exhibited stronger enhancement effects after 2000 through their interaction with population and economic *** patterns closely correlated with ecological restoration projects in China since *** study implies the importance of synergy be

关键词： land use land type geographic detector driving mechanism Hedong Region

Dynamic Response Impact of Vehicle Braking on Simply Supported Beam Bridges with Corrugated Steel Webs Based on Vehicle-Bridge Coupled Vibration Analysis

在线全文

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2024年第6期139卷 3467-3493页

作者： Yan Wang Siwen Li na wei School of Civil Engineering Zhengzhou UniversityZhengzhou450001China

A novel approach for analyzing coupled vibrations between vehicles and bridges is presented,taking into account spatiotemporal effects and mechanical phenomena resulting fromvehicle *** modeling and solution of bridge vibrations induced by vehicle deceleration are realized using this *** method’s validity and reliability are substantiated through numerical examples.A simply supported beam bridge with a corrugated steel web is taken as an example and the effects of parameters such as the initial vehicle speed,braking acceleration,braking location,and road surface roughness on the mid-span displacement and impact factor of the bridge are *** results show that vehicle braking significantly amplifies mid-span displacement and impact factor responses in comparison to uniform vehicular motion across the ***,the influence of wheelto-bridge friction forces is of particular significance and cannot be *** the vehicle initiates braking near the middle of the span,both the mid-span displacement and impact factor of the bridge exhibit substantial increases,further escalating with higher braking *** favorable road surface conditions,the midspan displacement and the impact factor during vehicle braking may exceed the design values stipulated by *** is important to note that road surface roughness exerts a more pronounced effect on the impact factor of the bridge in comparison to the effects of vehicle braking.

关键词： Corrugated steel web girder bridges simply supported beam bridges vehicle-bridge coupled vibration braking impact factor

Critical Role of Ethylene-Propylene Block Copolymer in Impact Polypropylene Copolymer

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

Chinese Journal of Polymer Science 2024年第3期42卷 344-351,I0007页

作者： Yu-Hui Tang na Zhang wei Bao wei Jiang Yuan Lin Zhao-Hui Su State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China School of Applied Chemistry and Engineering University of Science and Technology of ChinaHefei 230026China

Ethylene-propylene block copolymer(EbP) is a vital component in impact polypropylene copolymer(IPC), yet its distribution in the multiphase composite material and how it influences the phase structure and the mechanical properties are not well understood. In this work,four IPCs were investigated by atomic force microscopy-infrared(AFM-IR) to assess the phase compositions in situ, based on which in conjunction with the chain microstructure information obtained ex situ the distributions of the copolymer components were derived for each alloy. For the IPCs whose EbP comprises long P and long E segments, the EbP fraction was found to phase separate from the rubber and the PP matrix to form the cores of the disperse particles with the E-P segmented copolymer(EsP). In contrast, in the IPC with EbP composed of long P and short E segments, the EbP fraction formed an outer shell for the rubber particles with the cores comprising the EsP alone, and this IPC, containing a lower E comonomer content than its counterpart, exhibited both better impact resistance and higher flexural modulus. These results clarify how the chain structure of EbP governs the phase morphology in IPC, which in turn impacts the properties of the composite material.

关键词： Impact polypropylene copolymers AFM-IR Ethylene-propylene block copolymers Core-shell rubber particles