检索结果-南通市图书馆

BIOCELL 2022年第1期46卷 185-193页

作者： JIANBO LU XIAOHAN sun XU MA Human Genetics Resource Center National Research Institute for Family PlanningBeijing100081China Graduate School Peking Union Medical CollegeBeijing100730China Beijing University of Technology Beijing100124China

The concentration of cell-free fetal DNA fragments should be detected before noninvasive prenatal testing(NIPT).The fetal DNA molecules have significant clinical potential in determining the overall performance of NIPT and clinical *** is important to measure fetal DNA fraction before ***,there is still little research on how to calculate the concentration of female *** estimation approaches were proposed to calculate fetal DNA fraction,including the fragments size-based approach,aneuploid-based approach,which are all approaches based on chromosome *** on high-throughput sequencing data,two approaches to calculate the DNA fraction of male fetuses were tested and obtained the experiment values,which were close to the actual *** correlation coefficient of fragments size-based approach was 0.9243(P<0.0001)and the aneuploid-based approach reached 0.9339(P<0.0001).We calculated the concentration of female fetuses and obtained remarkable experimental *** came up with two approaches for calculating the fetal DNA fraction of female *** provides an important theoretical basis for the detection of female fetal concentration in future clinical diagnosis.

关键词： Fetal DNA fraction Noninvasive prenatal testing Cell-free fetal DNA Female fetus

Review of Denitrogenation of Algae Biocrude Produced by Hydrothermal Liquefaction

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Transactions of Tianjin University 2017年第4期23卷 301-314页

作者： Jinsheng sun Jie Yang Ming Shi School of Chemical Engineering and Technology Tianjin University Wuhan Jinzhong Petrochemical Engineering CO. LTD

Recently, algae biocrude has drawn considerable attention as algae are considered to be one of the major fuel feedstocks of the future. Based on some impressive results achieved under appropriate conditions, the algae hydrothermal liquefaction (HTL) process has proven to be energy efficient. However, the HTL of biocrude is characterized by a high nitrogen content, which prevents its use in the field of transportation due to the associated nitrogen oxide emissions. Despite this toxicity, few research efforts have focused on the denitrogenation of algae biocrude. In this study, we review the effect of different strain-specific operation parameters and process upgrades with respect to the nitrogen content of biocrude. To achieve denitrogenation, chemical engineering may be required, although some improvements in biocrude properties have been achieved in a number of process upgrades. The use of similar successful pathways has the potential to improve the field of HTL biocrude denitrogenation. These methods, including the adsorptive and extractive denitrogenations of fossil fuels and the hydrodenitrogenation of the main nitrogen compounds, are helpful for developing a better understanding of the potential of denitrogenation for algae HTL biocrude. We also recommend the use of some available catalysts and corresponding operation parameters to promote continued research on denitrogenation. © 2017, The Author(s).

关键词： Energy efficiency Fossil fuels Liquefaction Nitrogen compounds Nitrogen oxides

Oligomerization of 1-Decene: Catalyzation by Immobilized AlCl_3/γ-Al_2O_3 Catalyst in Fixed-bed Reactor

在线全文

学校读者我要写书评

暂无评论

China Petroleum Processing & Petrochemical Technology 2014年第3期16卷 50-55页

作者： Li Deng Shen Benxian sun Hui Petroleum Processing Research Center East China University of Science and Technology

1-Decene was oligomerized over the supported AlCl3/γ-Al2O3 catalyst in a fixed-bed reactor. The effects of temperature and LHSV on oligomerization of 1-decene were investigated and the synthetic PAO was characterized with GC technique. Furthermore, the life of immobilized catalyst was tested and the mechanism of catalyst deactivation was discussed. The results showed that with an increasing temperature, the PAO yield increased and the kinematic viscosity of oil decreased. The GC results indicated that the synthesized PAO was a mixture consisting of dimers, trimers, tetramers and pentamers. The results of chloride content measurements and BET tests showed that catalyst deactivation could be mainly attributed to the loss of active components.

关键词： poly-alpha-olefins 1-decene AlCl3/γ-Al2O3 catalyst oligomerization lubricant base stocks

Collocation Methods for Hyperbolic Partial Differential Equations with Singular Sources

在线全文

学校读者我要写书评

暂无评论

Advances in Applied Mathematics and Mechanics 2009年第6期1卷 769-780页

作者： Jae-Hun Jung Wai sun Don Department of Mathematics the State University of New York at BuffaloBuffaloNY 14260-2900USA Department of Mathematics Hong Kong Baptist UniversityHong KongChina

A numerical study is given on the spectral methods and the high order WENO finite difference scheme for the solution of linear and nonlinear hyperbolic partial differential equations with stationary and non-stationary singular *** singular source term is represented by theδ-*** the approximation of theδ-function,the direct projection method is used that was proposed in[6].Theδ-function is constructed in a consistent way to the derivative *** sine-Gordon equation with a stationary singular source was solved with the Chebyshev collocation ***δ-function with the spectral method is highly oscillatory but yields good results with small number of collocation *** results are compared with those computed by the second order finite difference *** modeling general hyperbolic equations with a non-stationary singular source,however,the solution of the linear scalar wave equation with the nonstationary singular source using the direct projection method yields non-physical oscillations for both the spectral method and the WENO *** numerical artifacts arising when the non-stationary singular source term is considered on the discrete grids are explained.

关键词： Singular sources Dirac-δ-function Direct projection method Chebyshev collocation method WENO scheme

Biological control of a predator-prey system through provision of an infected predator

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Biomathematics 2018年第8期11卷 191-215页

作者： Hui Zhang Genjiu Xu Hao sun Department of Applied Mathematics School of Natural and Applied Sciences Northwestern Polytechnical University Xi 'an Shaanxi 710072 P. R. China

Epidemic transmission has a substantial effect on the dynamics and stability of the predator-prey system, in which the transmission rate plays an important role. The probabilistic cellular automaton (PCA) approach is used to investigate the spatiotemporal dynamics of a predator-prey system with the infected predator. Remarkably, it is impossible to achieve a coexistence state of prey, susceptible predators, and infected predators in a spatial population. This is different from the analysis from a non-spatial population with the mean-field approximation, where Hopf bifurcation arises and the interior equilibrium becomes unstable, and a periodic solution appears with the increasing in feet i on rate. The results show that the introduction of the infected predator with a high transmission rate is beneficial for the persistence of the prey population in space. However, a low transmission rate will promote the coexistence state of the prey and the susceptible predator populations. In summary, it is possible to develop management strategies to manipulate the transmission rate of the infected predator for the benefit of biological control.

关键词： Epidemic transmission probabilistic cellular automaton spatiotemporal dynamics management strategies

CFD performance analysis of finned-tube CO_(2)gas coolers with various inlet air flow patterns

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Energy and Built Environment 2020年第3期1卷 233-241页

作者： Xinyu Zhang Yunting Ge Jining sun Sustainable Environment Research Centre Faculty of ComputingEngineering and ScienceUniversity of South WalesPontypridd CF371DLUnited Kingdom RCUK National Centre for sustainable Energy Use in Food Chains(CSEF) Institute of Energy FutureBrunel University LondonUxbridgeMiddlesex UB83PHUnited Kingdom

A detailed model of three-dimensional computational fluid dynamics(CFD)on a finned-tube CO_(2)gas cooler has been developed and *** model is then applied to investigate the effect of uniform and mal-distribution inlet airflow profiles on the coil *** airflow mal-distribution velocity profiles include linear-up,linear-down and parabolic while the effected coil performance parameters contain airside pressure drop,average airside heat transfer coefficient,approach temperature and coil heating *** model also enables to predict the CO_(2)refrigerant temperature profile along the coil pipes from refrigerant inlet to outlet at different operation *** simulation results reveal that different types of inlet airflow velocity profiles have significant effects on the gas cooler *** uniform airflow velocity profile case shows the best thermal performance of gas *** with the cases of linear-up and parabolic air velocity profiles,the linear-down airflow profile can influence more on the coil heat transfer *** to the thermal conduction between neighbour tubes through coil fins,reversed heat transfer phenomenon exists which can be detected and simulated by the CFD *** is predicted that the linear-down airflow profile can increase greatly the reversed heat transfer phenomenon and thus lead to the highest approach temperature and the lowest heating capacity amongst these four types of airflow *** research method and outcomes presented in this paper can have great potentials to optimize the performance of a CO_(2)gas cooler and its associated refrigeration system.

关键词： CO_(2)finned-tube gas cooler Airflow misdistributions Heat transfer coefficient CO_(2)refrigeration system Computational Fluid Dynamics(CFD) modelling

Heat wave mitigation of ecosystems in mountain areas-a case study of the Upper Yangtze River basin

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Ecosystem Health and Sustainability 2022年第1期8卷 370-382页

作者： Yuxin Zhang Bin Fu Juying sun Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengduChina State Key Laboratory of Hydraulics and Mountain River Engineering College of Water Resource and HydropowerSichuan UniversityChengduChina Ecological Value Evaluation Centre China Quality Certification CentreBeijingChina

Background:Natural ecosystems,such as forests and grasslands,can mitigate heat waves,but research on heat wave mitigation in mountain ecosystems is *** the upper reaches of the Yangtze River basin(URYB)as the study area,we first divided the URYB into mountainous and non-mountainous areas based on a digital elevation model(DEM).Then,we used temperature to identify heat waves and used the temperature and humidity index to identify suitable ***,the differences between mountainous and non-mountainous areas were compared,and regional development strategies are ***:(1)The frequency and duration of heat waves increased by 0.433/y(P<0.1),0.07/y(P<0.05),while the number of suitable days in June,July,and August gradually decreased slightly by 0.0096/y(P<0.1),0.0125/y(P<0.1),0.004/y(P<0.1),respectively from 1986 to 2015.(2)The average monthly number of suitable days was the highest in mountainous areas during the summer from 1986 to *** areas have an advantage in mitigating heat waves owing to landform-based changes in the local climate.(3)In addition to the landform,altitude was the main factor responsible for mitigating heat waves in mountainous ***:Parts of the plateau and whole mountain areas were found to be best for avoiding extremely high temperatures based on the number of suitable summer days from 1986 to *** suggest formulating tourism promotion strategies,and strengthening tourism infrastructure,considering landscape protection and creation to promote sustainable regional development.

关键词： Ecosystem services thermal comfort livability summer temperature mountains tourism

Optimization for entransy dissipation minimization in heat exchanger

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 Science Bulletin 2009年第19期54卷 3587-3595页

作者： XIA ShaoJun CHEN LinGen sun FengRui Postgraduate School Naval University of Engineering Wuhan 430033 China

A common of two-fluid flow heat exchanger, in which the heat transfer between highand low-temperature sides obeys Newton's law [q∝Δ(T)], is studied in this paper. By taking entransy dissipation minimization as optimization objective, the optimum parameter distributions in the heat exchanger are derived by using optimal control theory under the condition of fixed heat load. The condition corresponding to the minimum entransy dissipation is that corresponding to a constant heat flux density. Three kinds of heat exchangers, including parallel flow, condensing flow and counter-flow, are considered, and the results show that only the counter-flow heat exchanger can realize the entransy dissipation minimization in the heat transfer process. The obtained results for entransy dissipation minimization are also compared with those obtained for entropy generation minimization by numerical examples.

关键词：物理学有限时间热力学研究

Microstructure characterization of PAN preoxidation fibers prepared with radio frequency plasma

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2006年第10期51卷 1255-1260页

作者： XU Haiping sun Yanping CHEN Xinmou Department of Chemical Engineering Talyuan University of Technology Talyuan 030024 China Xinmou New Technique Corporation General Director S.J.Z. Development Areas Shijiazhuang 050091 China

The microstructures of preoxidation fibers prepared with radio frequency plasma were charac- terized in terms of micron, nano and atomic scales through scanning electron microscopy (SEM), high resolving transmission electron microscopy (HRTEM), scanning tunneling microscopy (STM), X-ray diffrac- tion (XRD), etc. The polyacrylonitrile (PAN) precur- sors were first soaked in the oxygen-enriched solvent and polarized in radio frequency electric field, and then were oxidized in the atmosphere of oxygen plasma. The morphology of SEM at micron scales shows that the wrinkles on the surface of preoxida- tion fibers prepared with plasma are shallower, and the surfaces are more tidy and smoother than the unsoaked samples prepared with usual electric fur- nace, and the uneven radial structure is improved. The results of XRD calculation show that the graph- itization degree and microcrystalline size get larger and the interlayer spacing gets smaller. Also, the lattice stripe and edge of bedding plane (002) can be observed from HRTEM at nano scales. From STM images at nano and atom scales, the microfibrils were found to be composed of ultrafibrils that closely twined and arranged, forming the left spiral structures spreading to fiber axis, and the carbon atoms on the surface of microcrystalline were found to have the trend of directional arrangement. All the above characterization results indicate that the plasma method effectively makes the internal and external oxidation of PAN precursors at the same level, so that the radial structure difference of preoxidation fibers is reduced.

关键词：射频等离子体显微结构 PAN光纤 SEM HRTEM

A KNN-based two-step fuzzy clustering weighted algorithm for WLAN indoor positioning

在线全文

学校读者我要写书评

暂无评论

High Technology Letters 2011年第3期17卷 223-229页

作者： Xu Yubin sun Yongliang Ma Lin Communication Research Center Harbin Institute of Technology Harbin 150080 P. R. China

Although k-nearest neighbors （KNN） is a popular fingerprint match algorithm for its simplicity and accuracy, because it is sensitive to the circumstances, a fuzzy c-means （FCM） clustering algorithm is applied to improve it. Thus, a KNN-based two-step FCM weighted （KTFW） algorithm for indoor positioning in wireless local area networks （WLAN） is presented in this paper. In KTFW algorithm, k reference points （RPs） chosen by KNN are clustered through FCM based on received signal strength （RSS） and location coordinates. The right clusters are chosen according to rules, so three sets of RPs are formed including the set of k RPs chosen by KNN and are given different weights. RPs supposed to have better contribution to positioning accuracy are given larger weights to improve the positioning accuracy. Simulation results indicate that KTFW generally outperforms KNN and its complexity is greatly reduced through providing initial clustering centers for FCM.

关键词： wireless local area networks (WLAN) indoor positioning k-nearest neighbors (KNN) fuzzy c-means (FCM) clustering center