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Detection of long-chain branches in polyethylene via rheological measurements

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Chinese Chemical Letters 2016年第4期27卷 588-592页

作者： yun-Fan Mei bao-Hua Guo Jun Xu Department of Chemical Engineering Tsinghua University Beijing 100084 China

The detection of long-chain branches（LCB） in polyethylene is of considerable importance as the processing properties of polyethylene are strongly affected by even a small amount of LCB. While the conventional characterization techniques such as GPC-MALS and13 C NMR fail or take very long time to detect low content of LCB, we turn to the rheological method, which is more sensitive to LCB. In our study, we performed oscillatory shear test, creep test and stress relaxation test on two series of metallocene linear low density polyethylene（LLDPE）, revealing that the resins with LCB show higher zero-shear-rate viscosity, retarded relaxation and higher flow activation energy than those without or with less LCB. The resins with LCB showed shear thinning at very low shear rate and their zero-shear-rate viscosities were obtained via creep test. The content of LCB was quantitatively estimated from the flow activation energy. In addition, the modulus-time curves during stress relaxation of melt of the different resins obeyed the power law. The exponent of the resins with more LCB was 0.7, different from that of the resins with less LCB, around 1.7.

关键词： Metallocene polyethylene Long-chain branch Rheology Stress relaxation

NUMERICAL ANALYSIS OF SATURATED-UNSATURATED SEEPAGE FLOW IN FRACTURED ROCK MASS DUE TO SURFACE INFILTRATION

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Journal of Hydrodynamics 2001年第4期13卷 28-33页

作者： Hu, yun-Jin Su, bao-Yu zha., Mei-Li Dept. of Hydraulic Eng. Tsinghua Univ. Beijing 100084 China

Seepage flow in fractured rock mass due to surface infiltration is a saturated-unsaturated seepage process. Aimed at rock mass with large fracture density, which can be equivalent to continuum, a mathematical model for saturated-unsaturated seepage flow in fractured rock mass due to surface infiltration was established in this paper. The Galerkin finite element method was used in numerical simulation and a finite element program used to calculate saturated-unsaturated seepage flow due to surface infiltration was worked out. A model experiment was used to examine the reasonableness of the program. The results show that the proposed model and program are reasonable. The application of the analysis method in an engineering project shows that the method is reliable and feasible.

关键词： Computer simulation Mathematical models Seepage

气相色谱法测定鱼肉中指示性多氯联苯的不确定度评定

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食品工业科技 2024年第6期45卷 289-296页

作者：杨冉冉左惠君王忠一都芸鲍治成周雁楠王开宇烟台市食品药品检验检测中心山东烟台264000

为了提高实验室检测结果的准确性,对气相色谱法测定鱼肉中指示性多氯联苯含量进行了不确定度的评定。依据食品安全国家标准GB 2762-2022《食品安全国家标准食品中污染物限量》,识别“被测量”为样品中“以2,4,4’-三氯联苯(PCB 28)、2,2... 详细信息

为了提高实验室检测结果的准确性,对气相色谱法测定鱼肉中指示性多氯联苯含量进行了不确定度的评定。依据食品安全国家标准GB 2762-2022《食品安全国家标准食品中污染物限量》,识别“被测量”为样品中“以2,4,4’-三氯联苯(PCB 28)、2,2’,5,5’-四氯联苯(PCB52)、2,2’,4,5,5’-五氯联苯(PCB101)、2,3’,4,4’,5-五氯联苯(PCB118)、2,2’,3,4,4’,5’-六氯联苯(PCB138)、2,2’,4,4’,5,5’-六氯联苯(PCB153)和2,2’,3,4,4’,5,5’-七氯联苯(PCB180)总和计”的多氯联苯含量,根据“被测量”及检测标准,重新建立多氯联苯测量模型,分析测量模型中对结果有影响的不确定度分量,并进行评定。经评定,质控鱼肉样品中多氯联苯的测量结果为149.1μg/kg,相对扩展不确定度Ur=2.9%,k=2。不确定度贡献为:测量重复性70.8%、称样质量0.025%、加入内标体积1.8%、样品溶液中各目标物浓度比值之和27.3%。

关键词：鱼肉多氯联苯不确定度气相色谱法内标法

Deformation resistance of Fe-Mn-V-N alloy under different deformation processes

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Rare Metals 2017年第10期36卷 833-839页

作者： yun-Li Feng Jie Li Li-Qun Ai bao-Mei Duan College of Metallurgy and Energy North China University of Science and Technology Tangshan 063009 China Key Laboratory of the Ministry of Education for Modem Metallurgy Technology Tangshan 063009 China

The deformation resistance of Fe-Mn-V-N alloy under different deformation conditions was investigated by hot compression method on thermal simulator. Effects of deformation degree, deformation temperature, and strain rate on deformation resistance were analyzed. The results show that when other conditions are constant, the deformation resistance increases with the increase in deformation degree and strain rate and decreases with the increase in deformation temperature. At the same time, the mathematical model of deformation resistance for Fe-Mn- V-N alloy was established by lstOpt software using the Levenberg-Marquardt optimization algorithm carried out on the fitting of regression coefficients, which has higher fitting precision.

关键词： Fe-Mn-V-N alloy Deformation process Deformation resistance Mathematical model

Asymmetric Fuzzy Control of a Positive and Negative Pneumatic Pressure Servo System

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Chinese Journal of Mechanical Engineering 2017年第6期30卷 1438-1446页

作者： Gang Yang Jing-Min Du Xiao-yun Fu bao-Ren Li School of Mechanical Science and Engineering Huazhong University of Science and Technology Wuhan 430074China

The pneumatic pressure control systems have been used in some fields. However, the researches on pneumatic pressure control mainly focus on constant pressure regulation. Poor dynamic characteristics and strong nonlinearity of such systems limit its application in the field of pressure tracking control. In order to meet the demand of generating dynamic pressure signal in the application of the hardware-in-the-loop simulation of aerospace engineering, a positive and negative pneumatic pressure servo system is provided to implement dynamic adjustment of sealed chamber pressure. A mathematical model is established with simulation and experiment being implemented afterwards to discuss the characteristics of the system, which shows serious asymmetry in the process of charging and discharging. Based on the analysis of the system dynamics, a fuzzy proportional integral derivative （PID） controller with asymmetric fuzzy compensator is proposed. Different from conventional adjusting mecha- nisms employing the error and change in error of the controlled variable as input parameters, the current cham- ber pressure and charging or discharging state are chosen as inputs of the compensator, which improves adaptability. To verify the effectiveness and performance of the pro- posed controller, the comparison experiments tracking sinusoidal and square wave commands are conducted. Experimental results show that the proposed controller can obtain better dynamic performance and relatively consis- tent control performance across the scope of work （2-140 kPa）. The research proposes a fuzzy control method to overcome asymmetry and enhance adaptability for the positive and negative pneumatic pressure servo system.

关键词： Pneumatic pressure control system Positiveand negative pressure Asymmetric control Fuzzy control

DOCK8 deficiency with mediastinal lymph node tuberculosis

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World Journal of Pediatrics 2020年第2期16卷 213-214页

作者： Lin-Qian zha.g Xiao-Bing Li yun-Guang bao Jinhua Hospital of Zhejiang University Jinhua 321300China

A 12-year-old girl presented with a history of unexplained persistent fever,accompanied by paroxysmal dry cough,skin *** patient had a past medical history of recurrent fever,pneumonia(at least four times per year),eczema,accompanied by diarrhea,repeated skin Staphylococcus aureus infection since 6 months of *** examination revealed broad nasal bridge and scoliosis,and chest computed tomography(CT)showed pneumonia,partial bronchiectasis of the right lung,and multiple mediastinal lymph node enlargement with confluence(Fig.1).Laboratory studies demonstrated significantly increased blood eosinophils and serum level of total *** biopsy of the rashes on the buttocks suggested eosinophil infiltration.

关键词： diarrhea tuberculosis fever

25例新生儿分娩性臂丛神经损伤医疗损害法医学鉴定评价

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法医学杂志 2024年第1期40卷 43-49页

作者：俞勇王英杰贾云飞黄宝静何颂跃刘川川北京法源司法科学证据鉴定中心北京100062 重庆市公安局大渡口区分局刑事侦查支队重庆400084

目的分析新生儿分娩性臂丛神经损伤的高危因素,探讨在医疗损害法医学鉴定中如何评价过错诊疗行为与新生儿分娩性臂丛神经损伤之间的关系。方法对北京法源司法科学证据鉴定中心2017—2021年25例新生儿分娩性臂丛神经损伤医疗损害责任... 详细信息

目的分析新生儿分娩性臂丛神经损伤的高危因素,探讨在医疗损害法医学鉴定中如何评价过错诊疗行为与新生儿分娩性臂丛神经损伤之间的关系。方法对北京法源司法科学证据鉴定中心2017—2021年25例新生儿分娩性臂丛神经损伤医疗损害责任纠纷相关案例进行回顾性分析,总结医院在胎儿体质量评估、分娩方式选择、产程观察与肩难产处置等方面存在的不足之处及其与患儿损害后果之间的关系。结果过错医疗行为评定为主要原因2例,同等原因10例,次要原因8例,轻微原因1例,无因果关系1例,未明确原因力3例。结论新生儿分娩性臂丛神经损伤医疗损害法医学鉴定过程中,从产前评估、分娩方式告知、规范使用缩宫素、肩难产操作规范性等环节,客观分析医疗行为是否履行诊疗义务,同时需充分考量不同危险因素的客观风险性和损伤预防的困难性,综合评价过错医疗行为在损害结果中的原因力大小。

关键词：法医学分娩性臂丛神经损伤医疗损害案例分析

10份豌豆种质在青海半干旱和高寒地区适应性评价的研究

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草地学报 2024年第9期32卷 2910-2918页

作者：冯晓云李媛张鹏刘文辉鲍根生李春刚青海大学青海西宁810003 青海省畜牧兽医科学院青海西宁810016 青海省青藏高原优良牧草种质资源利用重点实验室青海西宁810016 青海兴青工程监理咨询有限公司青海西宁810000

为筛选出适宜青海半干旱和高寒区种植的优良豌豆(Pisum sativum)资源,本研究选取10份豌豆种质资源,系统评价供试豌豆资源的13个农艺性状及产量在同仁(半干旱区)和泽库(高寒区)种植区的田间表现。结果表明:10份豌豆种质的表型变异范围在... 详细信息

为筛选出适宜青海半干旱和高寒区种植的优良豌豆(Pisum sativum)资源,本研究选取10份豌豆种质资源,系统评价供试豌豆资源的13个农艺性状及产量在同仁(半干旱区)和泽库(高寒区)种植区的田间表现。结果表明:10份豌豆种质的表型变异范围在同仁为3%~24%,在泽库为7%~23%。其中,荚数(24%)和每荚籽粒数(23%)的变异系数最高;10份豌豆种质资源在同仁和泽库农艺性状存在差异,且泽库‘A-61’豌豆的干草和种子产量最高,同仁49豌豆干草产量、‘中原5号’种子产量最高;灰色关联度分析表明,84豌豆和‘A-61’豌豆分别在同仁和泽库种植区综合性状最优。因此,‘中原5号’和49豌豆可分别作为同仁地区饲用型和种用型豌豆种质资源,而‘A-61’豌豆可作为泽库地区饲用型兼种用型豌豆种质资源。

关键词：豌豆种质资源农艺性状相关性分析灰色关联度分析

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Si、Mn元素对ZG06Cr13Ni4Mo组织及性能的影响研究

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铸造 2024年第2期73卷 167-173页

作者：徐芳宋蕾王宇高云保赵岭陈瑞曹衡王增睿沈阳飞机工业(集团)有限公司辽宁沈阳110850 高端装备铸造技术全国重点实验室辽宁沈阳110022

以ZG06Cr13Ni4Mo低碳马氏体不锈钢为原料,设计不同Si、Mn元素添加量,通过微观组织及力学性能检测,探究Si、Mn元素对该材料组织及力学性能的影响及作用机制,为超高水头水轮机用高强低碳马氏体不锈钢的制备及工程应用提供理论参考。试验... 详细信息

以ZG06Cr13Ni4Mo低碳马氏体不锈钢为原料,设计不同Si、Mn元素添加量,通过微观组织及力学性能检测,探究Si、Mn元素对该材料组织及力学性能的影响及作用机制,为超高水头水轮机用高强低碳马氏体不锈钢的制备及工程应用提供理论参考。试验结果表明:Si添加量为1.1wt%时,材料的强韧性最佳,力学性能指标为:Rm=850 MPa,Rp0.2=608 MPa,A=19.5%,Z=59%,Akv=73J;添加Mn元素可以在一定程度上提升ZG06Cr13Ni4Mo不锈钢的抗拉强度,材料的屈服强度会有所下降。Mn添加量为1.0wt%时,材料的强韧性最佳,力学性能指标为:Rm=845MPa,Rp0.2=546MPa,A=19%,Z=64%,Akv=105J。

关键词：马氏体不锈钢合金强化显微组织力学性能

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