Physical and Electrolytic Properties of Monofluorinated Ethyl Acetates and Their Application to Lithium Secondary Batteries

Ethyl acetate (EA) shows low viscosity for its relative permittivity. Monofluorinated organic solvents exert the polar effect on the various properties. We have investigated the effect of position isomerism on the physical and electrochemical properties of two monofluorinated carboxylates: 2-fluoroethyl acetate (2FEA) and ethyl fluoroacetate (EFA). Relative permittivity of 2FEA was lower than that of EFA, whereas viscosity of 2FEA was higher. Electrolytic conductivity of a LiPF6 solution in 2FEA was lower than that in EFA, but higher than that in EA at high temperatures. The use of 2FEA as a co-solvent improved cycling efficiency and suppressed fading of discharge capacity of a Li|LiCoO2 coin cell at high cycle numbers.

Assessment of the Protective Capacity of Vadoze Zone over Aquifer Systems Using Secondary Geoelectrical Parameters: A Case Study of Kaltungo Area North East, Nigeria

An assessment of the protective capacity of the vadose zone overlyingthe aquifer systems in the Kaltungo area was carried out to determine itsinfluence on groundwater quality. Applying the schlumberger array with amaximum electrode spread AB/2 = 100m through VES, thirty water wellpoints were surveyed using Omega terrameter (PIOSO1) resistivity meter.The field data was first subjected to manual interpretation through curvemarching and then digitized modeled curves using computer software. Theinterpreted data revealed that the area is characterized by eleven differentcurve types representing three to five geo electrical layers. In order toassess the protective capacity of the vadoze zone over the aquifer systems,the longitudinal conductance (S) and transverse resistance (T) (secondarygeoelectric parameters) were computed from the primary data using theDar Zarouk formula. The values of S obtained range from 0.0018 to 0.4056ohms with a mean value of 0.0135 ohms while the values of T range from0.55 ohms to 1195.68 ohms with a mean value of 39.84 ohms. The valuesof S and T obtained reveal that 90% of probed points has poor protectivecapacity, 10 % has moderate protective capacity and 83 % has hightransmissivity, 17 % has intermediate transmissivity. The T and S values areskewed towards poorly protective capacity thus making groundwater in thearea highly vulnerable to contamination from the surface. To achieve goodgroundwater quality in the area, proper completion of newly constructedwells should install protective casing through the entire vadose zone.

Synthesis of LiNi_(0.8)Co_(0.2)O_2 in Air Atmosphere and its Characterization

The commercialized lithium secondary cells need the electrode materials with high speeific capacity, lower pollution and lower price. Certain industrial materials ( NiSO_4, CoSO_4 , LiOH·H_2O)were used to synthesize Ni_(0.8)Co_(0.2)(OH)_2 of a stratified structure, when various synthesis conditions such as pH, reaction temperature et al. were controlled strictly. After LiOH·H_2O and Ni_(0.8)Co_(0.2) (OH)_2were calcinated in air atmosphere, LiNi_(0.8)Co_(0.2)O_2 positive electrode materials with good layered crystal structure was obtained. Tests showed that the optimal calcination temperature in air atmosphere was about at 720℃ and LiNi_(0.8)Co_(0.2)O_2 synthesized in the above conditions had good electrochemical properties and a low cost. The first specific: discharge capacity of the material was 186 mAh/g, and the specific discharge capacity was 175 mAh/g after 50 cycles at a 0.2C rate, between 3.0～4.2 V with a discharge deterioration ratio of 0.22% each cycle. Tests showed that LiNi_(0.8)Co_(0.2)O_2 positive electrode materials was a promising candidate to replace the commereialized LiCoO_2 for lithium secondary batteries.

基于电容自然充电换相的混合式直流断路器设计与仿真

以晶闸管作为主断器件是降低混合式直流断路器造价和技术难度的手段之一,电容电压是此类直流断路器能够顺利开断直流故障的关键影响因素。现有结构中电容大多为预充电型,但预充电方式和电容电压的维持较为复杂。因此,该文提出一种基于电容自然充电换相的混合式直流断路器,利用母线电压与预充电电容的电压差值实现电容的预充电和电容电压的自动维持,从而保证断路器的开断能力。此外该断路器还具备二次开断能力,可以满足极短时间内重复开断的需求。针对所提断路器的工作过程和元器件参数进行了详细的理论推导,基于PSCAD/EMTDC建立单端等效和四端柔性直流电网模型验证了所提结构的适用性。最后与其他方案进行比较,结果表明,所提方案在开断速度、电容预充电方式和二次开断方面具备一定优势。

考虑二次受力的UHPC加固RC墩偏压极限承载力

为揭示考虑二次受力UHPC加固桥墩偏压受力的损伤机理和极限状态,设计制作了UHPC加固RC墩和未加固墩构件,并进行了相应的试验研究和理论分析,并与未加固墩进行了比较。开展了考虑二次受力的UHPC增大截面法加固RC桥墩的小偏压试验,研究了不同初始受力条件下加固墩的破坏模式和极限承载力。结合有限元模型讨论了UHPC抗压强度、加固层的厚度和配筋率对极限承载力的影响。根据极限状态下的受力特性和平衡关系,推导了UHPC加固RC墩偏压极限承载力计算公式。结果表明:UHPC搭配钢筋网加固墩小偏压承载力与未加固墩相比,提升幅度达到了183%以上。UHPC强度对试件极限承载力的影响较大,UHPC厚度增大对加固试件承载力提高也较明显,加固层配筋率对构件承载力的提高影响较小。初始荷载的增大会降低原墩的混凝土利用率,降低加固墩的极限承载力。所提出考虑二次受力公式的计算承载力与实测值误差在3%之内,与有限元计算值误差在8%之内,具有较高的计算精度。研究结果可以为UHPC加固RC墩偏压承载力计算提供理论依据。

公路隧道二衬钢筋装配化螺栓的接头设计

针对公路隧道二衬钢筋现场焊接、绑扎效率低、质量控制难度大的弊端,基于直线型混凝土软化本构模型及钢筋应力应变关系,推导得到钢筋混凝土衬砌截面的极限承载力计算式.结合螺栓连接面极限承载力,以应力分布系数作为控制因素,将轴心压缩状态、大小偏心分界点以及纯弯状态时的最危险截面作为特征截面,控制钢筋混凝土截面极限承载力以及螺栓连接面极限承载力在特征截面处的大小,得到连接面处螺栓的设计方法 .选取某隧道隧址围岩参数及其断面尺寸、支护参数,运用得到的螺栓设计方法进行螺栓选型并设计连接面处的螺栓分布,给出钢筋预制节段的划分方案,通过数值模拟验证了二衬钢筋装配化螺栓的接头设计的合理性.研究结果表明:钢筋骨架采用螺栓装配化预制连接后,二衬结构的应力进行了重分布,应力与变形的增长速率放缓,并逐渐稳定.最终,左拱肩和左拱脚处的应力分别降低58%和53%,位移量同样有不同程度的降低;在拱底螺栓连接面,应力相较提高,但由于螺栓的高承载性能,隆起量反而有所降低,充分发挥了螺栓的性能,实现了结构优化.

基于新质生产力视野,提升二级医院康复服务能力的思考

康复服务能力是指以康复医学为主导,解决功能障碍为核心,提高伤、病、残人士的生存质量,并最大限度地恢复身体功能,改善其生活能力,努力回归社会,重新融入生活与工作。二级医院通常是指区县级以下医院,以及一些大型的社区卫生服务中心,既能处理常见病、多发病,也能处理一些较为复杂的疾病,在医疗服务体系中扮演着承上启下的角色。近年来,康复医学科在一些二级医院中已初具规模,但医疗资源不平衡,以致部分二级医院康复医学科在设施设备、人力配备等方面处于弱势,康复服务能力明显不足。新质生产力由技术革命性突破所催生,这为康复医学领域带来了广阔的发展机遇。二级医院康复医学科可以通过数智化等技术进行模式创新、重构特色化康复项目等,进而提升康复服务能力。

大容量高效超超临界二次再热锅炉关键技术研究

依据大量的已投运高效超超临界二次再热机组实际运行经验,结合清洁、高效、灵活运行的先进煤电火电技术,本文从为了保证燃煤二次再热锅炉在宽负荷比下达到额定参数及提高机组经济性方面,具体从炉型选择、炉膛关键的特征参数选取、系统布置、高效低氮燃烧系统优化设计选型、热偏差精准控制和多种手段耦合汽温调节关键技术等方面,系统的阐述了先进的高效超超临界二次再热锅炉设计关键技术。

地被物调控对川西亚高山次生林枯落物持水性能的影响

为弄清地被物调控对次生林地水源涵养能力的影响,对阿坝州米亚罗林区3个退化程度(轻度、中度、重度)的岷江冷杉次生林分别进行了7个地被物调控处理,其中移出3个梯度(10%-C1、30%-C2、50%-C3)、输入3个梯度(10%-R1、30%-R2、50%-R3)、对照-CK,监测其枯落物持水性能的变化,结果显示:次生林的枯落物蓄积量受林分密度和林分结构以及分解速率影响,表现为中度退化>重度退化>轻度退化,枯落物最大持水量与蓄积量呈正相关,也表现为中度退化>重度退化>轻度退化,且中度退化次生林枯落物最大持水量比重度退化次生林高出50.45%,比轻度退化次生林高出57.42%。地被物调控后不同次生林蓄积量、最大持水量和有效拦蓄量均是R2处理(移入30%)最高,其中轻度退化次生林R2的最大持水量比CK(对照)高出35.48%;中度退化次生林R2的最大持水量比CK高出312.24%;重度退化次生林R2的最大持水量比CK高出47.93%。不同次生林最大持水率与最大持水量、蓄积量没有相关性,其中中度退化次生林R3的最大持水率(移入30%)最高,比CK高71.66%。从监测数据来看,R2处理能较快地对提升枯落物持水性能作出响应,且在中度退化次生林的效果最好。

星形级联H桥STATCOM直流侧电容容值设计

为降低成本与提高功率密度,星形级联H桥静止同步补偿器(STATCOM)的直流电容设计越来越小。然而,小容值将会增加直流电压的二次纹波,二次纹波又将通过调制影响STATCOM的输出电压。因此,输出电压的范围发生变化,同时改变STATCOM的输出补偿电流能力。因此,为了保证STATCOM的正常工作,在设计电容时需要考虑直流电压二次纹波对容量的影响,这一点是传统的电容设计方法没有考虑到的。为解决该问题,此处根据基尔霍夫定律,在考虑直流电压二次纹波的前提下建立了 STATCOM可输出的电流范围与直流电容容值的关系。基于此关系,提出一种新的电容设计方法,据此,在保证输出容量不变时,可以设计出最小的直流电容容值。由此,系统可以在正常运行的同时降低系统成本且提高系统的功率密度。最后,搭建400 V/7 kvar的星形级联H桥STATCOM样机验证所提推导的关系与电容设计方法。

1991—2019年青岛市中小学生肺活量动态变化及城乡差异分析

目的:了解青岛市中小学生肺活量动态变化趋势和城乡差异,为制定增进青少年体质健康的干预策略提供参考。方法:采用1991年、2000年、2010年、2019年全国学生体质健康调研中青岛市的数据,对7~17岁中小学生肺活量近30年的动态变化及城乡差异进行分析。结果:1991—2019年,青岛市7~17岁男生平均肺活量上升270.8 mL,女生平均肺活量下降184.9 mL。1991年城市学生平均肺活量较乡村学生低174.0 mL,2000年较乡村学生高105.7 mL,2010年较乡村学生低4.2 mL,2019年较乡村学生高81.5 mL。结论:近30年来,青岛市中小学生肺活量呈现先下降后上升的趋势,2019年较1991年,男生肺活量上升,女生肺活量下降;城市和乡村学生肺活量交替领先,城乡差异依然存在,应针对不同性别、年龄段的学生制定相应干预策略以提升学生肺活量水平,重视乡村学校体育课,进一步缩小城乡差距。

电流互感器极性、容量选择等工程应用问题

目前,电流互感器在10~35 kV开关柜设备中应用广泛,但实际工程设计中存在互感器极性朝向多样、绕组定义不清、二次接地不规范、用户要求不同等问题,导致二次接线错误从而引发现场保护误动作,另外选型设计时互感器容量要求过大,对互感器制作和柜体安装造成不便。基于此,从柜子结构形式来论述互感器的安装方式,归纳总结互感器极性朝向、二次绕组排序以及接线注意事项,并根据标准给出了测量、保护绕组常用容量及具体算法,以供设计时参考使用。

用于火电机组二次调频的混合储能系统容量配置优化方法

现代经济与社会发展的同时,对电力的需求也不断增加,并且世界范围内的环境问题、能源短缺问题越来越受到关注,新能源发展迅速,风能、太阳能等可再生能源大规模并网。但由于并网的不确定性、波动性、弱惯性等,不利于电力系统的安全、稳定运行。受响应速度慢、爬坡率低等的影响,传统机组不符合电网的调频需求,需更加优质的调频资源。混合储能系统对火电机组的二次调频可发挥辅助作用,可解决其二次调频能力不足的问题。

VBA二次开发在水库大坝防洪能力复核中的应用

采用VBA二次开发技术,针对水库大坝防洪能力复核中的防洪标准复核、设计洪水复核、调洪计算等环节开发了相应程序,实现了集查询、计算、分析和生成报告等功能于一体的分析软件,促进了工作效率和设计成果质量的大幅提高,同时为其他编程技术在设计工作中的应用提供了新的思路。

Secondary aerosol formation and oxidation capacity in photooxidation in the presence of Al_2O_3 seed particles and SO_2

To investigate the sensitivity of secondary aerosol formation and oxidation capacity to NOx in homogeneous and heterogeneous reactions, a series of irradiated toluene/NOx/air and ?-pinene/NOx/air experiments were conducted in smog chambers in the absence or presence of Al2O3 seed particles. Various concentrations of NOx and volatile organic compounds(VOCs) were designed to simulate secondary aerosol formation under different scenarios for NOx. Under "VOC-limited" conditions, the increasing NOx concentration suppressed secondary aerosol formation, while the increasing toluene concentration not only contributed to the increase in secondary aerosol formation, but also led to the elevated oxidation degree for the organic aerosol. Sulfate formation was suppressed with the increasing NOx due to a decreased oxidation capacity of the photooxidation system. Secondary organic aerosol(SOA) formation also decreased with the presence of high concentration of NOx, because organo-peroxy radicals(RO2) react with NOx instead of with peroxy radicals(RO2 or HO2), resulting in the formation of volatile organic products. The increasing concentration of NOx enhanced the formation of sulfate, nitrate and SOA under "NOx-limited" conditions, in which the heterogeneous reactions played an important role. In the presence of Al2O3 seed particles, a synergetic promoting effect of mineral dust and NOx on secondary aerosol formation in heterogeneous reactions was observed in the photooxidation. This synergetic effect strengthened the positive relationship between NOx and secondary aerosol formation under "NOx-limited" conditions but weakened or even overturned the negative relationship between NOx and secondary aerosol formation under "VOC-limited" conditions. Sensitivity of secondary aerosol formation to NOx seemed different in homogeneous and heterogeneous reactions, and should be both taken into account in the sensitivity study. The sensitivity of secondary aerosol formation to NOx was further investigated under "winter-like" and NH3-rich conditions. No obvious difference for the sensitivity of secondary aerosol formation except nitrate to NOx was observed.

Improved electrochemical hydrogen storage properties of Mg-Y thin films as a function of substrate temperature

Pd-capped Mg78Y22 thin films have been prepared by direct current magnetron co-sputtering system at different substrate temperatures and their electrochemical hydrogen storage properties have been investigated.It is found that rising substrate temperature to 60 ℃ can coarsen the surface of thin film,thus facilitating the diffusion of hydrogen atoms and then enhancing its discharge capacity to 1725 mAh·g-1.Simultaneously,the cyclic stability is effectively improved due to the increased adhesion force between film and substrate as a function of temperature.In addition,the specimen exhibits a very long and flat discharge plateau at about —0.67 V,at which nearly 60%of capacity is maintained.The property is favorable for the application in metal hydride/nickel secondary batteries.The results indicate that rising optimal substrate temperature has a beneficial effect on the electrochemical hydrogen storage of Mg-Y thin films.

Effect of pH on Antioxidant and Phytochemical Activities of Mulhatti Roots (Glycyrrhiza glabra L.)

Glycyrrhiza glabra L.is the most widely used herb in the ancient history of Ayurvedic medicine,as a medicinal value as well as an aromatic herb,and it is commonly known as Mulhatti.Mulhatti roots are useful for medically and are also a good source of phytoproducts and secondary metabolites present in Mulhatti roots are triterpenoid saponin,glycosides,glycyrrhizin,prenylated biaurone,licoaagrone,7-acetoxy-2-methylisoflavone,4-methylcoumarin,liqcoumarin,glycyrrhetinic acid,quercetin,liquiritigenin,isoliquiritigenin,etc.This study was carried out to study the evaluation of phenolic compounds,2,2-diphenyl-1-picrylhydrazyl(DPPH)free radical activity and general antioxidant capacity of water extracts of Mulhatti roots prepared at different pH values,namely 2,4,7 and 9.Data have shown great differences in terms of results.Most of the phenolic compounds are at pH 7(19.25),followed by pH 9(17.25),pH 2(14.62)and pH 4(8.89 mg GAE/g),respectively.Similarly,the flavonoid data also showed variations,the maximum has been present in pH 2(5.39),then pH 7(3.02),pH 9(1.79)and pH 4(1.40 mg CE/g),respectively.The value for DPPH IC50 free radical scavenging activity was the lowest at pH 7(82.22),followed by pH 2(110.40),pH 4(111.99)and pH 9(146.24μg/mL)and IC50 reference standard(ascorbic acid)was 59.52μg/mL in distilled water.The total capacity of the antioxidant was the highest at pH 2(9.93)followed by pH 4(5.54),pH 7(5.34)and pH 9(4.23 mg AAE/g).According to current research,pH 7 is the best for phytochemicals as well as antioxidants that catch harmful radicals.

智慧教学背景下中小学教师信息化教学能力提升研究

教育信息化步入“智慧化”发展阶段,应运而生的智慧教学在给传统课堂教学带来更多可能的同时,对教师的信息化教学能力提出新的挑战,该文从教师、学校、教育行政部门三个层面探讨教师信息化教学能力提升路径。

区域森林水源涵养功能评价模型的开发与应用

区域尺度上毁林、虫害、火灾以及造林等多种类型森林变化伴随森林植被恢复生长,使森林及其水源涵养功能恢复具有时空累积性。而传统森林水源涵养功能评价方法难以直接刻画森林时空累积变化及其对水源涵养功能的影响,且存在模型计算量大、效率低等问题。针对上述难题,集成自主开发的森林恢复评价模型(ERA模型)与经典的综合蓄水法能力,结合GIS二次开发平台,设计与实现区域森林水源涵养功能评价模型(RFWCFAM)用于不同森林恢复情境下森林景观和森林水源涵养功能的时空动态评价和预测。该模型通过输入降水、植被类型、土壤、森林恢复措施等数据,生成森林变化、水源涵养量变化、恢复措施布局等空间分布图以及相应的统计数据,可以快速、准确定量评估区域尺度森林变化及其恢复过程中水源涵养功能的时空累积变化,辨识影响森林恢复的关键因子。区域森林水源涵养功能评价模型应用于杂谷脑流域,结果表明:1)2010年流域森林总水源涵养量为679.37 t/hm^(2);2)2010—2030年间在自然恢复和人工恢复情景下流域森林土壤层、枯枝落叶层、林冠层及总水源涵养量均呈增加趋势;3)人工恢复效果较自然恢复更明显,预计到2030年人工恢复措施下森林水源涵养总量较自然恢复措施下约高5.19%。本模型的开发及成功应用能够为林业部门和水资源管理部门快速准确评估森林恢复工程对水源涵养功能的提升效果提供高效的评价工具,同时为我国森林资源适应性管理提供科学依据,为水土保持工程的评价和管理提供科学支撑。

不同破碎工艺对低脂肉糜品质的影响

为探究不同破碎工艺对低脂肉糜蛋白质性质和食用品质的影响,在打浆机和斩拌机上,采用不同刀具(钝刀和利刀)制备肉糜,测定肉糜的pH、盐溶性蛋白质含量、蛋白质二级结构、粒径分布、色泽、流变特性和肉糜凝胶的蒸煮损失、持水力、质构特性、微观结构。结果表明:4种破碎工艺对肌肉纤维的破碎程度不同,使低脂肉糜及所形成的凝胶呈现不同性质。与打浆机相比,斩拌机处理的低脂肉糜在温度扫描中拥有更高的G'值。钝刀打浆处理的低脂肉糜在频率扫描中拥有最低的粘度,呈现较差的稳定性。斩拌机高强度的切割作用使得破碎的肉糜的终点温度更低、颗粒粒径更小,煮制形成低脂肉糜凝胶的持水力更高。与其他3种工艺相比,钝刀斩拌低脂肉糜有最高的红度值、pH、盐溶性蛋白质含量和β折叠的相对含量,分别为15.95、6.66、77.05 mg/mL、43.71%,所形成低脂肉糜凝胶的蒸煮损失最低和硬度、胶黏性、咀嚼性、感官评分最高,分别为17.48%、4147.72 g、2883.35、2496.02 g,这可能归因于该处理对肌肉的适度破碎所形成的低脂肉糜凝胶具有更加紧密的微观结构。因此,钝刀斩拌工艺适用于低脂肉糜的破碎生产,可提高其盐溶性蛋白质含量、β折叠相对含量、红度、持水力和质构特性。