检索结果-南通市图书馆

Novel Poly(methyl methacrylate)-based Ionomers Used as Multifunctional Aids to Modify Poly(vinyl chloride)

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2016年第4期34卷 483-490页

作者： li-na zhang 宋义虎郑强 Department of Polymer Science and Engineering Zhejiang University Hangzhou 310027 China MOE Key Laboratory of Macromolecular Synthesis and Functionalization Zhejiang University Hangzhou 310027 China

Poly（methyl methacrylate）（PMMA） based ionomers with different lanthanum （La（III）） contents （PMMA-XLa） synthesized by free radical solution polymerization were applied to poly（vinyl chloride）（PVC） resins as a kind of multifunctional aids, and their performances were evaluated by measuring the static stability time, initial discoloration, transparency, fusion behavior and tensile strength of the modified PVC. The ionomers with proper lanthanum （La（III）） contents show a better thermal stability efficiency in comparison with traditional stabilizer lanthanum stearate. Meantime, they can accelerate PVC plasticization more efficiently than PMMA. The rigid PVC products stabilized with the ionomers present good transparency and enhanced tensile strength.

关键词： Rigid PVC Ionomers Thermal stability Plasticization Multifunction.

New Exact Solutions for Konopelchenko-Dubrovsky Equation Using an Extended Riccati Equation Rational Expansion Method

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2006年第5期45卷 I0003-I0003,770-776页

作者： SONG li-na zhang Hong-Qing Department of Applied Mathematics Dalian University of Technology Dalian 116024 China

Taking the Konopelchenko-Dubrovsky system as a simple example, some familles of rational formal hyperbolic function solutions, rational formal triangular periodic solutions, and rational solutions are constructed by using the extended Riccati equation rational expansion method presented by us. The method can also be applied to solve more nonlinear partial differential equation or equations.

关键词： Konopelchenko-Dubrovsky equation extended Riccati equation rational expansion method nonlinear partial differential equation or equations

Extended sine-Gordon Equation Method and Its Application to Maccari＇s System

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2005年第5X期44卷 783-788页

作者： SONG li-na zhang Hong-Qing Department of Applied Mathematics Dalian University of Technology Dalian 116024 China

An extended sine-Gordon equation method is proposed to construct exact travelling wave solutions to Maccari's equation based upon a generalized sine-Gordon equation. It is shown that more new travelling wave solutions can be found by this new method, which include bell-shaped soliton solutions, kink-shaped soliton solutions, periodic wave solution, and new travelling waves.

关键词： Maccari's system exact travelling wave solution extended sine-Gordon equation method

Extended Jacobi Elliptic Function Rational Expansion Method and Its Application to （2＋1）-Dimensional Stochastic Dispersive Long Wave System

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2007年第6期47卷 969-974页

作者： SONG li-na zhang Hong-Qing Department of Applied Mathematics Dalian University of Technology Dalian 116024 China

In this work, by means of a generalized method and symbolic computation, we extend the Jacobi elliptic function rational expansion method to uniformly construct a series of stochastic wave solutions for stochastic evolution equations. To illustrate the effectiveness of our method, we take the （2＋ 1）-dimensional stochastic dispersive long wave system as an example. We not only have obtained some known solutions, but also have constructed some new rational formal stochastic Jacobi elliptic function solutions.

关键词： stochastic evolution equations (2+ 1)-dimensional stochastic dispersive long wave system rational formal stochastic Jacobi elliptic function solutions

Fast segmentation approach for SAR image based on simple Markov random field

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2010年第1期21卷 31-36页

作者： Xiaogang Lei Ying li na Zhao Yanning zhang Department of Computer Science Northwestern Polytechnical University Xi'an 710072 E R. China

Traditional image segmentation methods based on MRF converge slowly and require pre-defined weight. These disadvantages are addressed, and a fast segmentation approach based on simple Markov random field （MRF） for SAR image is proposed. The approach is firstly used to perform coarse segmentation in blocks. Then the image is modeled with simple MRF and adaptive variable weighting forms are applied in homogeneous and heterogeneous regions. As a result, the convergent speed is accelerated while the segmentation results in homogeneous regions and boarders are improved. Simulations with synthetic and real SAR images demonstrate the effectiveness of the proposed approach.

关键词： SAR image segmentation simple Markov random field coarse segmentation maximum a posterior iterated condition mode.

Effect of kaolin on tensile strength and humidity resistance of a water-soluble potassium carbonate sand core

在线全文

学校读者我要写书评

暂无评论

China Foundry 2016年第1期13卷 15-21页

作者： Long zhang li-na zhang Yuan-cai li School of Metallurgical Engineering Anhui University of Technology School of Material Science and Engineering Huazhong University of Science and Technology

Water soluble cores(WSCs) have been widely applied in manufacture of complex metal components with hollow configurations or internal channels. However, the WSCs without any additons have low tensile strength and low humidity resistance. The purpose of this study is to prepare a water-soluble potassium carbonate sand core with addition of kaolin by the hot-temping method. The effects of kaolin on tensile strength, humidity resistance, fracture mechanism, as well as the gas evolution and collapsibility of WSCs were investigated. Results show that both the crystal morphology and the fracture mechanism of the inorganic salt are changed under the participation of kaolin, contributing to the increase of the tensile strength and the humidity resistance of the core. With the addition of 3wt.% kaolin, the tensile strength could be increased by a factor of 2, reached 1.50 MPa and the hygroscopic rate could be decreased by 14%, achieved 0.559%(after stored for 8 h), respectively. As the addition amount of kaolin increases from 0wt.% to 3wt.%, the main fracture mechanism changes from a adhesive to a cohesive fracture mechanism. The water-soluble potassium carbonate core obtained has the low gas evolution and excellent collapsibility, which makes it suitable for casting low melting metal with complex cavities and crooked channels.

关键词： water-soluble core kaolin tensile strength humidity resistance strengthening mechanism

Pathogenic changes of community-acquired pneumonia in a children’s hospital in Beijing,China before and after COVID-19 onset:a retrospective study

在线全文

学校读者我要写书评

暂无评论

World Journal of Pediatrics 2022年第11期18卷 746-752页

作者： li-na zhang ling Cao ling-Hui Meng Department of Pulmonology Children’s HospitalCapital Institute of PediatricsBeijingChina Center for Evidence-Based Medicine Office of Science and TechnologyCapital Institute of PediatricsBeijingChina

Background This study aimed to analyze the pathogenic characteristics of community-acquired pneumonia(CAP)in a children’s hospital before and after the coronavirus disease 2019(COVID-19)pandemic and to provide testimony for preventing CAP in the *** A retrospective analysis was *** information was collected from the electronic medical record system of the hospital.A total of 2739 children were included from February 1,2019,to January 31,*** Among these 2739 patients were 1507(55.02%)males and 1232(44.98%)females;the median age was 3.84 *** were 2364 cases during the pre-COVID-19 period and 375 cases during the post-COVID-19 *** number of hospitalized children after the pandemic was 84.14%*** median age after the onset was 1.5 years younger than that before the onset(4.08 years old)(Z=−7.885,Pbacteria(50.42%)>viruses(29.57%)>fungi(3.43%).During the post-COVID-19 period,the pathogen proportions were bacteria(56.53%)>viruses(53.60%)>MP(23.47%)>fungi(3.73%).Conclusions There was a significant decrease in the number of children with CAP hospitalized after the pandemic,especially among school-age children,and the pathogen proportions of CAP with MP and IV were significantly *** inferred that CAP was effectively prevented in school-age children because of the strong mitigation measures.

关键词： Community-acquired pneumonia Comparison Coronavirus disease 2019 Pathogen

The prognostic value of clinical and pathologic features in nonmetastatic operable male breast cancer

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

Asian Journal of Andrology 2016年第1期18卷 90-95页

作者： Bo Sun li-na zhang Jun zhang Ning zhang lin Gu The Second Department of Breast Cancer Tianjin Medical University Cancer Institute and Hospital National Clinical Research Center for Cancer Key Laboratory of Breast Cancer Prevention and Therapy Tianjin Medical University Ministry of Education Key Laboratory of Cancer Prevention and Therapy Tianjin China Laboratory of Cancer Cell Biology fianjin Medical University Cancer Institute and Hospital National Clinical Research Center for Cancer Key Laboratory of Breast Cancer Prevention and Therapy Tianjin Medical University Ministry of Education Key Laboratory of Cancer Prevention and Therapy Tianjin China Laboratory of Translational Cancer Biology Research Center of Basic Medical Science Tianjin Medical University No. 22 Qixiangtai Road Heping District Tianjin China

Compared with female breast cancer, male breast cancer is a rare disease, and the relationship between clinical/pathologic features and prognosis is controversial, or even largely unknown. In this study, we performed a retrospective analysis using clinical and pathologic data from 109 nonmetastatic operable male breast cancer patients treated from January 1996 to December 2011 at Tianjin Medical University Cancer Institute and Hospital. Log-rank test showed that lower tumor stage, no lymph node involvement, and positive estrogen/progesterone receptor status were good predictors of both disease-free survival and overall survival on univariate analysis. However, hormonotherapy is only a good predictive factor of disease-free survival, and not of overall survival. In addition, based on a Cox proportional hazard regression model, only lymph node involvement, and estrogen/progesterone receptor status were statistically significant predictive factors on multivariate analysis. Our results demonstrated that although adjuvant systemic therapy is used extensively in male breast cancer patients and prognosis has improved over the last few decades, lymph node involvement, and estrogen/progesterone receptor status are still the most important prognostic factors. A prospective multi-center study with a larger sample size is urgently needed to further understand male breast cancer.

关键词： breast neoplasms clinical/pathologic features male prognosis

Uniform to Accelerated Crystal Twisting Transition in Deuterate Polyethylene/Poly(ethylene-alt-propylene) Blend Films

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 2014年第9期32卷 1260-1270页

作者： li-na zhang Wei-chao Shi 韩志超程贺 State Key Laboratory of Polymer Physics and Chemistry Institute of Chemistry Chinese Academy of Sciences China Spallation Neutron Source Institute of High Energy Physics Chinese Academy of Sciences

A uniform to accelerated crystal twisting transition is observed in deuterate polyethylene/poly（ethylene-alt- propylene）（d-PE/PEP） blend films. And the band period is a function of initial d-PE concentration, quench depth and annealing time of phase separation. As Keith and Padden suggested, twisting of lamella is due to the unbalanced stress on its both sides, which can supply a satisfying explanation to banded spherulites formed in homogeneous systems. When it comes to d-PE/PEP blend system, in homogeneous 99% d-PE/PEP （weight fraction of d-PE） blend film, the formation of banded spherulite is observed as a result of uniform twisting of ribbon like d-PE lamellae along the radial direction. With the amorphous PEP piling up, it transfers into accelerated edge-on to fiat-on twisting due to crystallization assisted phase separation. The mechanism can be interpreted as following： d-PE molecules must inter-diffuse to the twisting growth front to continue the secondary nucleation and growth process. Meanwhile, the amorphous PEP molecules are rejected and accumulated at the twisting growth front. Once the d-PE lamella begins to twist because of unbalanced stress on both sides, the accumulated rubber phase at the growth front strengthens the unbalance and accelerates the edge-on to flat-on twisting. The concentration wave propagates further away with constant speed, and leads to concentric ring pattern with periodic nonuniform twisting along the radial direction. Since this is a kinetic effect, the band period can be controlled through initial d-PE concentration, quench depth and annealing time of phase separation. Our result shows that crystallization assisted phase separation can modify lamella growth kinetic pathway, thereby assisting concentric ring pattern formation.

关键词： Polyethylene/poly(ethylene-alt-propylene) (d-PE/PEP) blend Phase separation Crystallization.