光伏微网逆变器的数字前馈PI控制方法

首先介绍光伏微网逆变器的电路模型及其工作原理,并对电路模型进行简化分析,得到微网逆变器的信号矢量关系,然后通过数学分析,研究和探讨了数字前馈PI控制方法的递推算法,最后基于Matlab平台建立其仿真模型,将数字前馈PI控制方法与滞环控制方法进行对比仿真研究。通过仿真,对两种方法的控制误差、总谐波失真度两个指标进行考察,实验结果表明,在控制误差相同的情况下,光伏微网逆变器的数字前馈PI控制方法的总谐波失真度远小于滞环控制方法,表明数字前馈PI控制方法具有更好的输出电能质量,性能表现更优越。     

基于EHD的聚酰亚胺打印工艺研究

针对目前多数增材制造设备在加工聚酰亚胺(PI)聚合物材料时成型分辨率低、精度差等缺点,课题组提出将电流体动力学(electro-hydro dynamics,EHD)打印方法应用于PI的高精度成型,并对此进行了研究.采用控制变量的方法探究了打印喷嘴处施加的工作电压以及收集板移动速度对PI线条成型分辨率的影响;在分析其打...     

高光洁处理对聚酰亚胺短纤纱及其织物性能的影响

针对聚酰亚胺(PI)短纤维纺纱静电大、成纱毛羽多、后加工摩擦剧烈导致纱线品质大幅恶化的问题,创新提出了在后加工终端对多毛羽PI单纱进行高光洁处理的方法。通过研制纱线高光洁处理装置和理论模拟,分析了该装置引纱区与涡流包缠关键区的作用机制,应用装置的湿热涡流处理多毛羽PI单纱,并将处理前后的PI单纱实施倍捻和织造,获得PI股线及其织物。结果表明：与处理前相比,高光洁处理后的PI单纱有害毛羽去除率为97.69%、耐磨性提高48.84%,PI股线有害毛羽去除率为64.67%、耐磨性提高40.89%;处理后纱线所织造织物的柔软性、透气性、抗起毛起球性、抗静电性均得到改善。     

高耐热聚酰亚胺纤维的制备及其性能

为进一步提升聚酰亚胺(PI)纤维的耐热性能,以全刚性的二酐和二胺合成了可纺性良好的聚酰胺酸纺丝液,通过干法纺丝方法以及高温热环化和热牵伸处理制备了力学性能优良的PI纤维,对PI纤维的热性能和机械性能进行分析。结果表明:所制备的PI纤维具有优越的热稳定性,二酐和二胺内部结构中的全刚性链结构苯环密度大,使PI纤维的化学结构稳定;在氮气氛围下,PI纤维质量损失5%和最大质量损失温度分别达600 和649 ℃,PI纤维的拉伸强度为2.1 GPa,在温度为300 ℃分别热老化处理24、48和72 h后,其拉伸强度保持率可分别达到99.8%、87.3%和76.3%;同时,PI纤维具有优异的尺寸稳定性,在50~350 ℃范围内,其热膨胀系数为 -9.1 μm/(m·℃)。     

靶向磷脂酰肌醇-3-激酶抗肿瘤转移的研究进展

肿瘤转移是肿瘤死亡的首要原因,约占肿瘤死亡的90%。目前临床上对肿瘤转移的治疗方法有限且收效甚微。磷脂酰肌醇-3-激酶（PI3K）信号转导是细胞内最重要的通路之一,在肿瘤的发生、发展及转移中发挥至关重要的作用。因此PI3K抑制剂的研发得到国内外众多药企的广泛关注,目前已有5种PI3K抑制剂被批准上市,更多的抑制剂正在进行临床研究。迄今为止的临床试验结果表明PI3K抑制剂单独用药的抗肿瘤疗效并不理想,因此与其他药物的联合用药受到研究人员和临床医生的关注。本文概述了PI3K信号通路及其在肿瘤转移各个过程中的作用,总结了PI3K抑制剂单独及与其他药物联用抗肿瘤转移的研究进展,为PI3K抑制剂的进一步开发和应用提供参考。     

PI教学法在“数据结构”课程教学中的运用

美国哈佛大学Eric Mazur教授创立并实践了同学间互动(Peer-Instruction,简称PI)教学方法,鼓励学生基于问题进行自主学习和协作探究,取得了良好的教学效果。文章阐述PI教学法的主要思想及实施方法,通过对"数据结构"课程"遍历二叉树"一节导学案的设计,探讨PI教学法在"数据结构"课程教学中的运用。     

PBO纤维纸基复合材料的热老化及高温力学性能研究

本研究采用湿法成形技术制备了聚对苯撑苯并二噁唑（PBO）纸,将其浸渍聚酰亚胺（PI）树脂后,得到PBO纤维纸基复合材料（PBO/PI),随后对PBO/PI进行300℃的老化,并在300℃下测试了其拉伸性能。将PBO/PI与模拟蜂窝格壁的间位芳纶浸渍纸（PMIA/PI）进行对比,分析了老化和高温对PBO/PI和PMIA/PI力学性能的影响。结果表明,在300℃的高温老化下,由于材料微裂纹的产生及扩展,二者拉伸强度均呈下降趋势,但老化前后PBO/PI的强度均比PMIA/PI更强。动态力学性能显示,老化前后PBO/PI的储能模量大于PMIA/PI的储能模量,说明PBO/PI的刚性比PMIA/PI大,在高温下仍不易发生变形。在300℃的高温拉伸测试下,PBO/PI的拉伸强度和保持率均比PMIA/PI要高。PBO/PI在常温及300℃高温下的力学性能均优于PMIA/PI,PBO纤维制备的复合材料可用于需要高的抗变形和热稳定性的承重结构和蜂窝部件中。     

聚酰亚胺气凝胶的研究进展

讨论聚酰亚胺(PI)气凝胶的制备方法,首先是使用的溶剂种类,包括有机溶剂和水溶剂;其次是凝胶干燥的方式,包括冷冻干燥和超临界二氧化钛干燥。对PI气凝胶的应用领域进行归纳总结,包括油水分离、催化载体、电线/缆绝缘层、摩擦电纳米发电机、天线贴片基底,以及防寒作战被装和热红外伪装材料等。最后,对PI气凝胶的发展进行展望。     

超声波辅助酸/碱溶解等电点沉淀法提取鸡架分离蛋白的组成及其凝胶特性

利用高强度超声（high intensity ultrasound,HIU）辅助酸/碱溶解等电点沉淀（isoelectric solubilization/precipitation,ISP）法提取鸡架分离蛋白（protein isolate,PI）,采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳研究PI组成,并分析PI凝胶特性。结果表明：PI主要由肌原纤维蛋白组成;酸溶解会导致肌球蛋白重链降解,HIU可减弱降解程度;碱溶PI凝胶的硬度、蒸煮损失率、离心损失率与对照（鸡胸肉糜凝胶,后同）无显著差异,显著高于酸溶PI凝胶（P＜0.05）;HIU显著提高了酸溶PI凝胶的硬度和弹性（P＜0.05）,降低了蒸煮损失率及离心损失率（P＜0.05）;PI凝胶白度均显著低于对照（P＜0.05）。碱溶PI凝胶对水分子的结合力和束缚力均优于酸溶PI凝胶;碱溶PI凝胶与对照凝胶均具有均匀致密微观结构,而酸溶PI凝胶微观结构明显粗糙、不均匀。结论：HIU辅助碱溶ISP法可高效提取鸡架中肌原纤维蛋白并保持其凝胶特性,有助于鸡架增值利用。     

不同品种（系）红花芽苗菜产量和品质研究

旨在研究红花种子不同亚油酸含量与其芽苗菜的质量关系,为红花芽苗菜的科学生产提供参考。对8个不同亚油酸含量的品种(系)红花芽苗菜产量和品质进行分析比较。结果显示,种子中PI305192亚油酸含量最高,其芽苗菜下胚轴长度和可食鲜重均最大,鲜重显著(P0.05)高于PI544040及其他品种(系)。川红1号和PI198294亚油酸含量极显著(P0.01)低于PI305192,但又极显著高于PI401479和PI470942,其中川红1号芽苗菜可溶性蛋白含量最高,与PI305192和PI198294相比差异不显著;游离氨基酸和可溶性糖含量,PI198294和川红1号极显著高于其他品种(系);总多酚含量以川红1号、PI198294和PI544040较其他品种(系)高;川红1号总黄酮含量高,PI198294总黄酮含量也不低。说明川红1号和PI198294芽苗菜品质较优。试验还发现,红花种子亚油酸含量与芽苗菜的可食鲜重、可食干重及可溶性蛋白含量极显著正相关,而种子油酸含量则与上述指标呈极显著负相关。总体上,种子亚油酸含量高的品种(系),其芽苗菜产量和部分品质较油酸含量高的品种(系)相对更好。     

金属丝杨氏模量的测量方法

介绍金属丝杨氏弹性模量的概念和计算的理论依据,探讨测量金属丝微小伸长量的方法。详述光杠杆放大法和光电传感器法检测杨氏弹性模量的工作原理,给出检测原理图,并分别用2种方法测量长1.10 m、直径0.608 mm钢丝的杨氏模量。使用证明:光杠杆放大法测量精度高,但仪器调整难度大;光电传感器法用激光做光源,利用光电传感器作为接收器,可以直接读出伸长量的对应数值,是测量杨氏模量的简便方法,但测量精度不及光杠杆放大法。     

Protein denaturation in frozen fish. 13. A modified cell fragility method insensitive to the pH of the fish

A modified cell fragility method is described for estimating the deterioration which occurs during the storage of frozen fish. A sample of only 100 mg is needed and this is homogenised in a medium consisting of 2% trichloroacetic acid in 1.2% formaldehyde. The results obtained by the new modification are almost unaffected by the pH of the fish, so can give a more truthful estimate of the time-temperature history than those of the original method. Experimental points on optical density/time curves obtained by the new modification show less scatter than those by the original method. Values decrease during storage rather more rapidly than by the original method, to an asymptote which is lower. Modified cell fragility values do not correlate with the length of the fish or its water content. It appears that the escape of myofilaments from the fibrils of high-pH cod accounted for the drop in optical density (scattering) seen in the original method, while in the modified method such proteinaceous material is precipitated and contributes to the optical density of the homogenate. Good curves of optical density/storage time were obtained with other non-fatty fish species, but fatty fish were not satisfactory. Advanced bacterial spoilage of the fish before freezing reduces the optical density in both methods.     

扩大光纤位移传感系统测量范围的综合判据

从强度调制型光纤位移传感系统的各个组成部分出发,研究提高其测量范围的方法.指出,可控光源法与程控增益放大器法结合使用可突破光电探测器和A/D模数转换器器件特征范围对测量量程的限制,解决光纤位移传感器低、高端盲区探测问题.不同的测量范围要求,可采取不同的方法组合以达到扩大传感量程的目的.     

基于景深成像的孔洞纸病检测

为了克服传统光学方法对孔洞纸病检测的局限性,提高孔洞纸病的检测准确性,采用景深成像方法进行孔洞纸病检测。首先建立测量模型,包括光学景深模型、成像几何模型;然后通过CCD成像测量过程推导得出,视频输出信号只与缺陷点深度有关;最后利用像差模型的残余因子来提高测量精度。实验仿真结果表明,与传统的光学方法测量及手动测量相比,景深成像测量方法所得结果比较接近孔洞纸病的实际尺寸(千分尺测量),测量精度较高。     

No. 5Vol. 42, No. 2, pp. 110–120, 2008Design and development of an innovative hybrid powder based on a computer simulation and its application to base make up products

An innovative hybrid powder prepared through computer simulation allowed a new foundation to be developed having a fine, smooth texture that has never been achieved before. The optical structure/design of the powder was based on the results of measurements and analyses conductedon the optical characteristics of a baby's fine skin that is the envy of many women. In order to achieve the optimal optical characteristics, the Finite Differential Time Domain (FDTD) method to solve Maxwell's differential equation by difference and time domain was applied to the computer simulation method. For the synthesis of the hybrid powder based on the optical model, a proprietary shape regulation coating technology was used, in which flaky substrates were coated with micro-spherical forms of barium sulfate crystals. The developed hybrid powder exhibited optical characteristics that showed a significant diffusion characteristic in the visible light region. The foundation containing this powder could conceal pores, fine wrinkles, freckles, and spots, and provided a fine, smooth texture owing to its microscopic reflection characteristics that has never been available from a conventional foundation.     

原壳小球藻生物量快速测定方法的对比研究

通过分光光度计和酶标仪分别测定不同浓度小球藻藻液的吸光度(A)和光密度(OD),用显微镜对细胞精确计数和用烘干法测量细胞干质量,分别在吸光度/光密度和细胞密度、吸光度/光密度和细胞干质量之间建立了良好的线性关系,相关系数较显著。经过一系列波长的筛选,确定在波长440nm处测定吸光度/光密度最佳,进而确定生物量。两种仪器对比显示：酶标仪测得的结果线性关系更加显著。与细胞计数法等传统方法相比,光密度法更加便捷,能极大地提高检测效率和准确度,可作为小球藻实验室研究和工业化生产的有效检测手段。     

Comparison of total milk-clotting activity measurement precision using the Berridge clotting time method and a proposed optical method

An objective measurement technique is needed to simplify the determination of total milk-clotting activity (a_t) of rennets and other milk coagulating enzymes. IDF Standard 157: 2007/ISO 11815 is the current standard method for bovine rennets and measures milk-clotting activity by visually determining the Berridge clotting time (i.e., time of appearance of flocks of renneted standard milk substrate on the wall of a rotating test tube). The IDF Standard 157: 2007 method is somewhat subjective because it depends on an operator’s skill to consistently identify milk flocculation. An optical method based on changes in infrared light backscatter at 880 nm during milk coagulation is proposed as an alternative, objective method to Berridge clotting time to eliminate the operator’s subjectivity from the IDF Standard 157: 2007. The Berridge clotting time method and a proposed optical method were compared using 29 replications to determine the precision of a_t measurements. The light backscatter profiles collected during the coagulation process were analyzed with five optical time parameters determined for each profile. The a_t, expressed in International Milk-Clotting Units (IMCU mL⁻¹), was calculated using Berridge clotting time and each of the five optical time parameters. The calculated milk-clotting activities were compared statistically to determine differences between measurement methods. No significant differences were found between the a_t determined using the Berridge clotting time and the optical time parameters, t_2min and t_2min2. Preferred optical time parameters t_max and t_2min were recommended. The results show that the proposed optical method based on measurement of changes in infrared light backscatter is a potential objective method for a_t measurement.     

Methods of Starch Analysis

The Ewers method, based on the partial acid hydrolysis of starch, followed by measurement of the optical rotation of the resulting solution, is an official E. C. method and used for determination of starch purity (regulation 2169/86). Short reviews of the evolution of this method, the method based on calcium chloride dissolution followed by optical rotation measurement, and enzymatic methods, have been made. Several of the key parameters of the acid hydrolysis method have been examined, namely solution clarity, clarifier level, degree of hydrolysis, and evolution of optical rotation with time. Results confirm that starches from different plant origins do not behave similarly during acid hydrolysis. The present factors for the respective starches may need some minor refinement. Application of both polarimetric methods and the AFNOR enzymatic method to four different starch types, give mostly acceptable results. For ease of use, the calcium chloride method has advantages over its acid hydrolysis counterpart.     

一种用焦散线确定材料弹性光学系数的新方法

采用内插法将光学各向异性材料的问题转化成准光学各向同性材料的问题,提出了一种用焦散线确定材料弹性光学系数的新方法.以有机玻璃、环氧树脂及聚碳酸脂为例,运用文中所述原理和方法测量了它们的弹性光学系数,并将所得结果与有关资料所给结果进行了比较.     

Design and development of an innovative hybrid powder based on a computer simulation and its application to foundation makeup products

An innovative hybrid powder prepared using computer simulation allowed development of a new foundation having a fine, smooth texture that has never been achieved before. The optical structure/design of the powder was based on the results of measurements and analyses conducted on the optical characteristics of a baby's delicate skin, which is the envy of many women. To obtain the optimal optical characteristics, the finite differential time domain (FDTD) method for solving Maxwell's differential equation by difference and time domain was applied to the computer simulation method. For synthesis of the hybrid powder based on the optical model, a proprietary shape regulation coating technology was used in which flaky substrates were coated with microspherical forms of barium sulfate crystals. The hybrid powder developed exhibited optical characteristics that showed a significant diffusion characteristic in the visible light region. The foundation containing this powder could conceal pores, small wrinkles, freckles, and age spots and owing to its microscopic reflection characteristics provided a fine, smooth texture that has never before been available with a conventional foundation.