ABS对POM结晶行为及力学性能的影响研究

考察了丙烯腈–丁二烯–苯乙烯塑料(ABS)含量和相形态对聚甲醛(POM)结晶行为及力学性能的影响。结果表明,POM球晶生长时将ABS相作为异物排除在晶格外,使其在球晶间隙间富集或囊裹在球晶中。ABS使POM结晶完善程度稍降低,但晶型及负光性未变。ABS含量及相形态影响POM结晶行为:ABS含量在0~50%时,ABS稍促进POM结晶;ABS含量在60%~90%时,强烈干扰POM结晶,呈现分步结晶现象。ABS使POM的拉伸性能和冲击强度显著下降,但弯曲性能出现协同效应。     

GFRP筋与再生混凝土粘结性能试验研究

为了系统研究GFRP直径、再生混凝土粗骨料取代率、立方体抗压强度及劈裂强度四因素对GFRP筋再生混凝土间粘结性能的影响,按照CSA标准设计制作了12组标准粘结试验并进行抗拔试验。试验结果表明,再生混凝土粗骨料取代天然骨料对粘结破坏形态影响不大,破坏形态以拔出破坏为主;但平均粘结强度随着再生混凝土粗骨料取代率的增大而下降;立方体抗压强度、劈裂强度两者对平均粘结强度的影响较为相似,均显示出随强度下降而下降的趋势;由于剪力滞后的影响,平均粘结强度随GFRP筋直径的增大而下降。     

GA-g-PAMPS/APT复合高吸水性树脂的合成和溶胀行为

以阿拉伯胶(GA)、2-丙烯酰胺基-2-甲基丙磺酸(AMPS)、凹凸棒石黏土(APT)为原料,采用微波辐射法,通过接枝共聚合成生物质GA-g-PAMPS/APT高吸水性树脂。利用FTIR、XRD和TG分析了树脂的结构和热稳定性能,探讨了树脂在各种盐溶液和不同p H溶液中的溶胀行为,研究了树脂的溶胀速率和反复吸水性能。结果显示:GA、APT与AMPS之间发生了接枝共聚反应,w(GA)=7.5%、w(APT)=10%时树脂在去离子水和生理盐水中的最大吸水倍率分别为783 g/g和91 g/g。树脂在各种盐溶液和不同p H溶液中表现出良好的响应性和可逆性能。适量引入APT能显著提高树脂的热稳定性、溶胀速率、反复吸水性能和p H稳定性。     

The formation of the S‐shaped edge‐on lamellae on the thin porous polylactic acid membrane via phase separation induced by water microdroplets

Biodegradable polymers have received increased attention due to their potential application in the medicine and food industries; in particular, poly(lactic acid) (PLA) is a primary biopolymer because of its excellent biocompatibility and absorbability features. In this study, a porous PLA membrane was fabricated by phase separation using water microdroplets produced by an ultrasonic atomizer as a coagulation bath. The formation of S‐type clusters was attributed to the slow exchange rate between solvent and coagulant, which provided time for the movement of polymer molecules. The effect of preparation conditions on the structure of S‐type clusters, including polymer concentration in solution and ambient temperature was investigated. The PLA porous membrane prepared from water micro‐droplets with different morphology compared with the sample fabricated from distilled water has potential application in fields of tissue engineering and artificial organ generation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43355.     

磁流变阻尼器非线性动力学行为的实验研究

磁流变阻尼器具有阻尼力大范围高度可控且耗能功率小的优点,在结构的半主动控制中有广泛的应用。磁流变流体及其元器件的动力学行为因其磁流变现象而存在滞回效应,对这种滞回效应的研究是其相关应用的基础。对磁流变阻尼器在多种激励电流与加载频率下的滞回动力学行为进行了实验研究,并进行了数学建模与参数识别。结果表明:磁流变阻尼器的阻尼力大小由激励电流控制,其非线性滞回特性具有频率依赖性;实验数据与模型仿真值的比较显示,模型可以准确模拟磁流变阻尼器滞回阻尼特性。     

The FKBP5 Gene Affects Alcohol Drinking in Knockout Mice and Is Implicated in Alcohol Drinking in Humans

FKBP5 encodes FK506-binding protein 5, a glucocorticoid receptor (GR)-binding protein implicated in various psychiatric disorders and alcohol withdrawal severity. The purpose of this study is to characterize alcohol preference and related phenotypes in Fkbp5 knockout (KO) mice and to examine the role of FKBP5 in human alcohol consumption. The following experiments were performed to characterize Fkpb5 KO mice. (1) Fkbp5 KO and wild-type (WT) EtOH consumption was tested using a two-bottle choice paradigm; (2) The EtOH elimination rate was measured after intraperitoneal (IP) injection of 2.0 g/kg EtOH; (3) Blood alcohol concentration (BAC) was measured after 3 h limited access of alcohol; (4) Brain region expression of Fkbp5 was identified using LacZ staining; (5) Baseline corticosterone (CORT) was assessed. Additionally, two SNPs, rs1360780 (C/T) and rs3800373 (T/G), were selected to study the association of FKBP5 with alcohol consumption in humans. Participants were college students (n = 1162) from 21–26 years of age with Chinese, Korean or Caucasian ethnicity. The results, compared to WT mice, for KO mice exhibited an increase in alcohol consumption that was not due to differences in taste sensitivity or alcohol metabolism. Higher BAC was found in KO mice after 3 h of EtOH access. Fkbp5 was highly expressed in brain regions involved in the regulation of the stress response, such as the hippocampus, amygdala, dorsal raphe and locus coeruleus. Both genotypes exhibited similar basal levels of plasma corticosterone (CORT). Finally, single nucleotide polymorphisms (SNPs) in FKBP5 were found to be associated with alcohol drinking in humans. These results suggest that the association between FKBP5 and alcohol consumption is conserved in both mice and humans.     

高功率激光照射致材料气化与熔池行为

激光深熔焊接小孔内前沿孔壁上的动态行为与焊接小孔的动态波动关系密切。为了进一步探明激光照射在前沿孔壁上产生的物理现象,设计激光倾斜照射在板材上的试验以模拟激光照射在倾斜的小孔内前沿孔壁上的状态。拍摄观察激光照射作用下材料的熔化与气化行为,深入分析熔池流动状态与蒸气特征在不同的激光照射角度与不同的照射能量密度时的变化规律。结果显示,激光照射作用下材料熔化形成的熔池表面易产生波动涟漪,且涟漪产生的频率与移动速度随照射激光功率密度的增加而增加。由于涟漪的存在使得涟漪处局部激光照射倾角发生改变,材料对激光的吸收率大幅提高,局部可产生更多蒸气,在气化反冲作用力下,涟漪可被剥离形成飞溅熔滴。     

近β钛合金中两相组织不协调变形行为的晶体塑性有限元研究

本文基于晶体塑性模型,研究了近β钛合金中(α β) 两相组织的不协调变形行为。首先,双晶体模型的计算结果表明(α β) 两相组织中的塑性变形是不协调的,而且α相的变形行为与晶体取向和加载方向密切相关。另外,通过耦合三维Voronoi几何模型,探讨了近β钛合金中球状初生α相对宏观力学响应的影响。利用该CPFE-VT数值模型,研究发现α相与β相的不协调变形导致了合金强度随α相体积分数的增加而成线性降低。此外,β基体中α相的分布对合金应力-应变响应也有较大的影响。本文针对具有两相组织的近β钛合金建立的晶体塑性有限元模型为钛合金组织控制技术的发展以及性能预测提供了重要的技术途径。     

等离子蒸发制备的纳晶镍的压缩变形机理

与传统粗晶金属材料相比,纳晶金属具有特殊的变形机理。为了探索纳晶金属的变形机理,本文以等离子蒸发结合热压烧结制备的块体纳晶镍为研究对象,进行了准静态压缩力学性能测试,并且利用XRD和TEM技术对试样压缩前和压缩后的微结构演化进行了研究。结果表明：块体纳晶镍表现出较高的压缩强度和较好的韧性,且强度和韧性均具有率相关性。同时,纳晶镍压缩变形后晶粒尺寸较压缩前减小,但其微应变增加。结合纳晶镍的力学行为和压缩过程中微结构的演化,本文预测晶界位错运动和晶界滑移的联合机制是块体纳晶镍压缩过程中塑性变形的主要机理。     

Corrosion behavior of Ti-35Nb-7Zr-5Ta alloy prepared by spark plasma sintering in Hank’s artificial body fluid北大核心CSCD

Biomedical Ti-35Nb-7Zr-5Ta(Ti-Osteum) alloys was prepared by spark plasma sintering (SPS). Corrosion behavior and mechanism of the alloys was investigated in Hank’s solution by means of open-circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Both commercially pure titanium (TA1) and Ti-6Al-4V (TC4) alloy were also investigated to make a comparison. The results showed that, in comparison with TA1 and TC4 alloy, the Ti-Osteum alloy prepared by SPS exhibited a good corrosion resistance with lower corrosion current, lower passive current density and higher polarization resistance, but more or less the similar corrosion potential. As a result, the corrosion resistance of the three materials may be ranked as follows: Ti-Osteum＞TC4＞TA1. The excellent corrosion resistance of Ti-Osteum alloy prepared by SPS in simulated artificial body fluid may be attributed to its higher sintered density, β-type single phase microstructure, and a stable passive film mainly consisted of titanium oxide, nio bium oxide, zirconium oxide, and tantalum oxide on its surface. © 2016, Corrosion Science and Protection Technology. All rights reserved.