Bio‐composites for structural applications: Poly‐l‐lactide reinforced with long sisal fiber bundles

Fully bio‐based and biodegradable composites were compression molded from unidirectionally aligned sisal fiber bundles and a polylactide polymer matrix (PLLA). Caustic soda treatment was employed to modify the strength of sisal fibers and to improve fiber to matrix adhesion. Mechanical properties of PLLA/sisal fiber composites improved with caustic soda treatment: the mean flexural strength and modulus increased from 279 MPa and 19.4 GPa respectively to 286 MPa and 22 GPa at a fiber volume fraction of V_f = 0.6. The glass transition temperature decreased with increasing fiber content in composites reinforced with untreated sisal fibers due to interfacial friction. The damping at the caustic soda‐treated fibers‐PLLA interface was reduced due to the presence of transcrystalline morphology at the fiber to matrix interface. It was demonstrated that high strength, high modulus sisal‐PLLA composites can be produced with effective stress transfer at well‐bonded fiber to matrix interfaces. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40999.     

荔枝果皮色差a*值与其他品质指标的关联性

褐变是影响荔枝销售的主要因素之一,为掌握荔枝颜色变化与荔枝品质指标的关联关系,以"桂味"为试验材料,采用带孔PE袋进行包装,分别将其贮藏于气调和冷藏2种贮藏保鲜模式30d,研究了荔枝果皮色差a*值与其他品质指标的变化关系,并拟合成线性关系式。研究结果表明:气调模式比冷藏模式有利于抑制荔枝果皮色差a*值变化,荔枝果皮色差a*值分别从35.0降至28.97和20.96;荔枝果皮色差a*值与果皮失水率、褐变指数、花色素苷含量、果实失重率以及感官评定值成线性关系,平均相关系数为0.8609;荔枝果皮色差a*值与其电导率、pH值线性关系不显著,平均相关系数分别只有0.5392和0.4977;冷藏模式下,除感官评定值外,荔枝果皮色差a*值与其他品质指标的线性相关性要高于气调模式,平均相关系数分别为0.9465和0.7752。研究结果对研究以果皮色差预测荔枝贮藏期及货架期具有一定的参考价值。     

Fabrication of elastic composite hydrogels using surface‐modified cellulose nanofiber as a multifunctional crosslinker

We fabricate composite hydrogels using surface‐modified cellulose nanofiber (CNF) and N‐isopropylacrylamide (NIPAm) as a multifunctional crosslinker and monomer, respectively. We expect to produce unique network structures that lead to elastomeric properties rarely reported for CNF‐based materials. The modification of CNF is performed to introduce polymerizable vinyl groups onto the surface of CNF via condensation between the surface hydroxyl groups and 3‐(trimethoxysilyl)propylmethacrylate. The modification and morphology of the surface‐modified CNF (mCNF) are confirmed by FTIR, solid‐state NMR, and FE‐SEM, respectively. We conduct in situ radical polymerization under various conditions using mixtures of the mCNF aqueous suspension, NIPAm monomer, radical initiator, and catalyst. The mechanical properties of the obtained hydrogels (water content = 90 wt %) are evaluated. The gels can be elastically stretched to more than 700 times their original lengths and exhibit an apparent shape recovery with a small permanent deformation (～1/5 of the applied deformation under the gravity field). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42906.     

以信息化带动西部水电建设大发展

在对西部地区水电建设的信息化现状进行初步分析的基础上，提出了提高西部水电信息化工作的指导思想和战略目标，以及应采取的相关措施。文章还着重指出：水电企业信息化建设是一项复杂的系统工程，离不开各级政府的鼓励和支持及企业的重视和全体员工的积极参与。这样才能逐步提高信息化建设的水平和质量，从而带动西部水电建设的大发展。     

光伏电池MPPT扰动观察法的研究现状

为了提高太阳电池的利用率并降低系统成本,需要采用最大功率跟踪(MPPT)控制策略使光伏阵列获得最大功率输出。在众多的MPPT控制方法中,扰动观察法由于原理简单、易于实现而成为MPPT控制中应用和研究最为广泛的方法之一。但传统的扰动观察法在稳态下由于其固定的扰动步长会在最大功率点(MPP)附近形成振荡,并且当外界环境发生快速变化时会出现误判断的现象。为了克服以上不足,研究者们提出了很多改进方案。文章对这些改进方案进行了综述,这些改进方案主要包括以下三类:变步长的改进方法、改进的新方法以及与其他方法结合的扰动观察法。     

冲击载荷下轨道炮刨削形成机理及仿真分析

针对电磁轨道炮的发射特点,提出了微凸体引起的刨削形成机理;根据实际轨道炮的结构和载荷特点,利用ABAQUS有限元软件在不同的参数条件下进行了仿真计算;发现刨槽的尺寸主要取决于枢轨间相对滑动速度和电枢长度,滑动速度越高刨槽就越宽,而且刨槽尺寸随着电枢长度的加长而变长,但是枢轨界面载荷对刨槽尺寸的影响不大;轨道刨削形成机理的提出及仿真计算,为电磁轨道炮的抗刨削技术研究提供了参考和指导。     

枪械实战射击方法

为研究和考证现行枪械定型试验国军标中规定的枪械射击方法的合理性,从最典型的战斗类型——进攻战与防御战出发,经实战分析与研究,结合部队、院校广泛调研情况,确定了既可满足试验要求也可指导实战的各种枪械射击方法。     

战斗机高空综合环境模拟舱压カ控制策略研究

高空综合环境模拟舱能够实现高空温度、压力和湿度等参数模拟,对军用战斗机环控系统研究具有重要意义。在多参数综合模拟试验时,传统的试验方法和控制策略不能很好地实现压力与其它环境参数的解耦控制,造成无法快速准确地实现多综合参数模拟。为此,提出单独采用抽气阀控制环境舱压力的试验方法,结合提出的基于非线性补偿的二自由度PID压力控制策略快速控制舱内高度。该控制策略引入非线性补偿环节克服抽气阀的非线性流量特征,同时引入二自由度PID克服压力超调,提高压力调节速度。新的试验方法和压力控制策略为实现多环境参数解耦控制提供了保证,同时能提高模拟舱内无超调压力控制精度和响应速度。该压力控制篥略同样适用于其它压力控制场合。     

Study on Higher Efficiency Thermal Cycling Profile for HALT

HALT (highly accelerated life test) is a new reliability test technique. This paper uses nonlinear finite element method to analyze the stress strain characteristic of solder joints of PQFP (plastic quad flat packaging) and BGA (ball grid array) under thermal cycle test, and studies influences of profile parameters of the thermal cycle, such as hot and cold soak temperature, hot and cold soak time and temperature change rate, on elastic strain range, accumulated plastic strain, fatigue life and test efficiency of two types of solder joints. Based on the above research and experimental verification, this paper presents the method to build an optimal thermal cycling profile for HALT of electronic components.     

Loving yourself abundantly: Relationship of the narcissistic personality to self- and other perceptions of workplace deviance, leadership, and task and contextual performance.

The authors report results from 2 studies assessing the extent to which narcissism is related to self- and other ratings of leadership, workplace deviance, and task and contextual performance. Study 1 results revealed that narcissism was related to enhanced self-ratings of leadership, even when controlling for the Big Five traits. Study 2 results also revealed that narcissism was related to enhanced leadership self-perceptions; indeed, whereas narcissism was significantly positively correlated with self-ratings of leadership, it was significantly negatively related to other ratings of leadership. Study 2 also revealed that narcissism was related to more favorable self-ratings of workplace deviance and contextual performance compared to other (supervisor) ratings. Finally, as hypothesized, narcissism was more strongly negatively related to contextual performance than to task performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)