An experimental method for quantitative analysis of real contact area based on the total reflection optical principle

The simulation of real contact area between materials is foundationally important for the contact mechanics of mechanical structures. The Greenwood and Williamson(GW) model and the Majumdar(MB) model are the basic models in this field, which are widely accepted and proven to be valid in many experiments and engineering. Although the contact models have evolved considerably in recent years, the verifications of the models are most based on the indirect methods such as electrical conductivity and contact stiffness, because of the lack of effective methods to directly measure the variation of contact surface. In this paper, the total reflection(TR) method is introduced into the verification of contact models.An experiment system based on TR method is constructed to measure the real contact area of two PMMA specimens. The comparison analysis between the results of experiment and models suggests that the experiment result has the same trend with simulation, the MB model has better agreement with the experimental result because this method can take into account the variation of radius and the merging of asperities, while the GW model has a huge deviation because of the dependence on resolution and the lack of considering the variation of radius and asperity's merging process. Taking the interaction of asperities into account could give a better result that is closer to the experiment. Our results and analysis prove that the experimental methods in this paper could be used as a more direct and valid method to quantitatively measure the real contact area and to verify the contact models.

Evolution of real contact area during stick-slip movement observed by total reflection method

We build an experiment system based on total reflection(TR) method to observe the evolution of real contact area of polymethyl methacrylate(PMMA) in the continual stick-slip movement. The bilateral friction is adopted to overcome the bending moment in the lateral friction movement. Besides some classical phenomena of stick-slip movement such as periodical slow increase of frictional force in sticking phase and a sudden drop when slipping, a special phenomenon that the contact area increases with the tangential force is observed, which was called junction growth by Tabor in 1959.Image processing methods are developed to observe the variation of the junction area. The results show that the center of the strongest contact region will keep sticking under the tangential force until the whole slipping, the strongest point undergoes three stages in one cycle, which are named as sticking stage, fretting stage, and cracking stage, respectively. The combined analysis reveals a physical process of stick-slip movement: the tangential force causes the increase of the real contact area, which reduces the pressure between the contact spots and finally leads to the slipping. Once slipping occurs,the real contact area drops to the original level resulting in the pressure increase to the original level, which makes the sticking happen again.

The scaling relationship of leaf area and total mass of sample plots across world trees

The scaling relationship between leaf area and total mass of plant has important implications for understanding resource allocations in the plant.The model of West,Brown and Enquist(WBE model)considers that a 3/4 scaling exponent of metabolic rate versus total mass to be optimal for each plant and has been confirmed numerous times.Although leaf area is a better proxy of the metabolic rate than leaf mass,few studies have focused on the scaling exponent of leaf area versus total mass and even fewer have discussed the diversification of this scaling exponent across different conditions.Here,I analyzed the scaling exponent of leaf area versus total mass of sample plots across world plants.I found that as the plant grows,it allocates fewer resources to photosynthetic tissues than expected by the WBE model.The results also empirically show that this scaling exponent varies significantly for different plant leaf habit,taxonomic class and geographic region.Therefore,leaf strategy in response to environmental pressure and constraint clearly plays a significant role.

Distribution Characteristics of Soil Total Nitrogen in Low-efficiency Forest Land in the Northern Windy Desert Area of Jingbian County

[Objectives]The paper was to investigate the distribution characteristics of soil total nitrogen in low-efficiency forest land in the northern windy desert area of Jingbian County.[Methods]The distribution of soil total nitrogen in the 0-40 cm soil layer of 5 towns in the northern windy desert area of Jingbian County was studied through field sampling and laboratory detection.[Results]The average soil total nitrogen contents of Hongdunjie Town,Haizetan Town,Huanghaojie Town,Ningtiaoliang Town,Dongkeng Town and windy desert area in the 0-20 cm soil layer were 0.259,0.224,0.242,0.248,0.431 and 0.275 g/kg,respectively.The soil total nitrogen content in Dongkeng Town was higher than those in other towns,while there was little difference among other regions.The average total nitrogen contents in the 20-40 cm soil layer were 0.239,0.285,0.113,0.262,0.349 and 0.241 g/kg,respectively.The soil total nitrogen content in Huanghaojie Town was slightly lower than those in other towns,while that in Dongkeng town was higher.The variation coefficient of soil total nitrogen content in the survey area was greater than 30%,and there was great difference in spatial distribution.With the increase of soil depth,there was little change in soil total nitrogen content,namely the soil total nitrogen contents in 5 towns and windy desert area were not statistically different in the 0-40 cm soil layer.According to the nutrient grading standard of the second national soil survey,the soil total nitrogen content in the survey area was in the deficiency grade.[Conclusions]The research will provide a scientific guidance for the healthy and sustainable development of vegetation in arid regions.

Content Determination of Total Flavonoids in Tetracera asiatica from 10 Different Production Areas in Guangxi

[Objectives] To determine the content of total flavonoids in Tetracera asiatica from different production areas in Guangxi and provide a basis for improving the quality standards of crude drug. [Methods] Using 50% ethanol as extractor,NaNO_2-Al(NO_3)_3-NaOH as chromogenic system and rutin as the reference substance,the content of total flavonoids from the crude drug was determined. [Results] A method for determining the content of total flavonoids was established,the content of total flavonoids was 11.35-21.35 mg·g^(-1),and the average content was 17.64 mg·g^(-1). [Conclusions] The method had high repeatability and stability,and the method was simple,rapid and sensitive and suitable for quantitative analysis.

Spatial Distribution of Soil Salinization Based on GIS in Tianjin Binhai New Area

The distribution of soil salinization was investigated based on GIS and field sampling in Tianjin Binhai New Area. The results showed that the average soil total salt content was 0.818%, with an average pH of 8.43, and the average CI and Na＋ contents were 0.27% and 0.22%, respectively. Presenting zonal distribution feature, the soil total salt content increased gradually from west to east of Binhai New Area. Statistics on the distribution areas of different salinization degrees showed that the area of non-salinzed soils only accounted for 3.18% of the total area; with an area of 107.43 km2, mild saline soil accounted for 6.34% of the total area; the area of moderate saline soil was 173.51 km2, accounting for 10.24%; and the area of sal- inzed soils was 217.36 km2, accounting for 12.82% of the total soil area. The area of saline soils （total salt content 〉0.6%） was 1 142.8 km2, accounting 67.42% of the total land area in Binhai New Area. And the areas for the soils with total salt content of 0.6%-1.0%, 1.0%-1.5%, 〉1.5% were respectively 388.47, 411.82, 342.51 km2, accounting for 22.92%, 24.3%, 20.21% of the total area.

基于Total多分类支持向量机的小麦产地判别分析

采用近红外光谱分析的方法快速鉴别小麦的产地,可为小麦流通监管、优质小麦生产基地保护和国际贸易提供理论和技术支持。以来自中国不同地域的202份小麦样品为例,在已知样品组分含量(蛋白质、湿面筋、沉降值、硬度)的前提下,结合样品的近红外光谱信息,利用Total多分类支持向量机对小麦产地进行判别分析。在构建分类模型的过程中,使正确分类的小麦样品尽可能地远离分类超平面,使错误分类的小麦样品尽可能地靠近分类超平面,可获得较高的分类精度。通过100个小麦样品构建分类模型,对另外的102个小麦样品产地进行预测,有80个与实际产地相符,预测精度为78.43%。为小麦产地鉴别提供一种新的方法。

基于SWMM模型的海绵城市建设效果评估

为定量评估广州市荔湖片区海绵城市建设成效,研究通过本底分析、资料收集等构建了片区排水分区尺度上的SWMM模型,并从年径流总量控制率、管网过流能力和内涝风险方面对广州市荔湖片区海绵城市建设效果进行了模拟分析,以期验证该区域按照海绵城市建设实施方案开发建设后,片区防灾减灾能力,同时本研究成果可为南方高密度地区海绵城市建设对缓解城市内涝提供理论参考。通过对广州市荔湖片区模拟计算得出主要结论如下:(1)广州市荔湖片区低影响开发建设后,年径流总量控制率显著提升,2022年片区年径流总量控制率为81.46%,较2019年低影响开发建设前提升了15.37%;(2)对广州市荔湖片区低影响开发建设前后排水管网过流能力模拟分析,结果表明片区在低影响开发建设前,在不同重现期降雨条件下,管网均出现溢流情况,且随着设计重现期的增大,管网溢流比例增加。片区低影响开发建设后,在不同重现期降雨条件下,管网溢流情况均明显降低;(3)对广州市荔湖片区低影响开发建设后内涝风险模拟分析,结果显示在发生百年一遇24 h降雨(累计降雨量322 mm)时,片区基本为无风险区域,极少部分为低风险区域,荔湖片区海绵城市建设后能有效应对百年一遇暴雨。广州市荔湖片区通过海绵城市建设可有效降低雨水外排,提升了片区防灾减灾能力。

Spatial distributions of organic carbon and nitrogen and their isotopic compositions in sediments of the Changjiang Estuary and its adjacent sea area

The spatial distribution patterns of total organic carbon and total nitrogen show significant correlations with currents of the East China Sea Shelf. Corresponding to distributions of these currents, the study area could be divided into four different parts. Total organic carbon, total nitrogen, and organic carbon and nitrogen stable isotopes in sediments show linear correlations with mean grain size, respectively, thus ＂grain size effect＂ is an important factor that influences their distributions. C/N ratios can reflect source information of organic matter to a certain degree. In contrast, nitrogen stable isotope shows different spatial distribution patterns with C/N and organic carbon stable isotope, according to their relationships and regional distributions. The highest contribution （up to 50%） of terrestrial organic carbon appears near the Changjiang Estuary with isolines projecting towards northeast, indicating the influence of the Changjiang dilution water. Terrestrial particulate organic matter suffers from effects of diagenesis, benthos and incessant inputting of dead organic matter of plankton, after depositing in seabed. Therefore, the contribution of terrestrial organic carbon to particulate organic matter is obviously greater than that to organic matter in sediments in the same place.

The migration of total dissolved solids during natural freezing process in Ulansuhai Lake

High total dissolved solids （TDS） content is one of the most important pollution contributors in lakes in arid and semiarid areas. Ulansuhai Lake, located in Urad Qianqi, Inner Mongolia, China, was selected as the object of study. Temperatures and TDS contents of both ice and under-ice water were collected together with corresponding ice thickness. TDS profiles were drawn to show the distribution of TDS and to describe TDS migration. The results showed that about 80% （that is 3.602x108 kg） of TDS migrated from ice to water during the whole growth period of ice. Within ice layer, TDS migration only occurred during initial ice-on period, and then perished. The TDS in ice decreased with increasing ice thickness, following a negative exponential-like trend. Within un- der-ice water, the TDS migrated from ice-water interface to the entire water column under the effect of concentra- tion gradient until the water TDS content was uniform. In winter, 6.044x 107 kg （16.78% of total TDS） TDS migrated from water to sedirnent, which indicated that winter is the best time for dredging sediment. The migration effect gives rise to TDS concentration in under-ice water and sediment that is likely to affect ecosystem and water quality of the Yellow River. The trend of transfer flux of ice-water and water-sediment interfaces is similar to that of ice growth rate, which reveals that ice growth rate is one of the determinants of TDS migration. The process and mechanism of TDS migration can be referenced by research on other lakes with similar TDS content in cold and arid areas.

A measurement method for distinguishing the real contact area of rough surfaces of transparent solids using improved Otsu technique

An experimental method of measuring the real contact area of transparent blocks based on the principle of total internal reflection is presented, intending to support the investigation of friction characteristics, heat conduction, and energy dissipation at the contact interface. A laser sheet illuminates the contact interface, and the transmitted laser sheet is projected onto a screen. Then the contact information is acquired from the screen by a camera. An improved Otsu method is proposed to process the data of experimental images. It can compute the threshold of the overall image and filter out all the pixels one by one. Through analyzing the experimental results, we describe the relationship between the real contact area and the positive pressure during a continuous loading process, at different loading rates, with the polymethyl methacrylate（PMMA）material. A hysteresis phenomenon in the relationship between the real contact area and the positive pressure is found and explained.

Assessment of Industrial Land Use Intensity: A Case Study of Beijing Economic-technological Development Area

In recent years, great economic output of land has been achieved in economic-technological development areas in China, but the intensity of land use in some of these areas is very low. The degree of the low intensity of land use needs to be evaluated. The current method of comprehensive evaluation and grading by one index system has the limitations due to the existence of differences between regions and industries. This paper evaluates industrial land use intensity by Total Factor Productivity (TFP) analysis, which not only measures the intensity but also illustrates the ef-ficiency of input factors. This method is applied to the Beijing Economic-technological Development Area (BDA). A comparison analysis on factor use efficiency and input structure of capital and labor between industries is also carried out in the absence of a labor-income ratio.

Eco-Friendly Selection of Diesel Generator Based on Genset-Synchro Technology for Off-Grid Remote Area Application in the North of Quebec

For most of their energy requirements, greater part of remote communities and small islands around the world rely on imported fossil fuels. The economical cost of energy is therefore very high not only due to inherent cost of fuel, but also due to transportation and due to maintenance costs. One solution for saving fuel in a diesel generator is to allow the engine to operate directly in relation to the request for electrical load at variable speeds. Genset-Synchro Technology has developed an innovative variable speed?generator technology (patent pending) that allows applications where power demand varies widely to benefit from the new technology that maintains constant voltage and frequency while adjusting the generator stator speed to power demand. This paper will present an innovative approach for optimizing the energy production based from the fact that the structure that contains the stator windings of the generator is mounted on roller bearings, which allows its free rotation around the axis of the rotor, consequently stopping the stator structure from being static and aims to minimize the unit cost of electricity. Case study on application in remote area in the north of Quebec is described. A saving of 7%?-?9% on fuel consumption and greenhouse gas (GHG) under low winter ambient temperatures has been registered.

Correlation between Surface Area Ratio of Medial to Lateral Tibial Plateau and Knee Alignment in Adults

Objective This study aimed to investigate the correlation between the surface area ratio of medial tibial plateau(MTP)to lateral tibial plateau(LTP)and the mechanical tibiofemoral angle(mTFA).Methods Lower limb computed tomography(CT)images were collected at our hospital.Then,the original CT data were analyzed and reconstructed using medical image processing software.The proximal and distal centres of the femur and tibia were marked.The surface areas of MTP and LTP were identified using image processing software.GraphPad Prism 8.0.2 was used to perform the statistical analysis.Results The surface area ratio of MTP to LTP was significantly correlated with the mTFA in all patients(P<0.0001),male group(P<0.0001),female group(P<0.0001),varus group(P<0.0001),and valgus group(P=0.002).Furthermore,the surface area of MTP and LTP was significantly greater in the male group than in the female group(P<0.0001).There was significant difference in the surface area of the MTP between the varus and valgus groups(P<0.0001).Significant difference was also observed in the surface area ratio of MTP to LTP between the varus and valgus groups(P<0.0001).Conclusion The surface area ratio of MTP to LTP was correlated with the mTFA.Within a certain range,the smaller the mTFA,the greater the surface area ratio of MTP to LTP.For patients undergoing total knee arthroplasty,of whom the surface area of the MTP was basically equal to that of the LTP,it is recommended that the osteotomy should be performed in accordance with mechanical alignment standards,and that a symmetrical tibial plateau prosthesis should be used.For patients whose surface area of MTP is significantly greater than that of the LTP,it is recommended that the osteotomy should be performed in accordance with kinematic alignment standards,and that an anatomical tibial plateau prosthesis should be used.

基于声发射断层总面积和b值的钢筋混凝土梁损伤表征

为研究钢筋混凝土构件破坏过程中的声发射特性,对钢筋混凝土梁进行四点弯曲加载破坏试验,利用声发射技术对破坏过程进行监测。为综合考虑声发射信号的事件数、幅度和能量等因素所反映的损伤特性,引用地震学领域的断层总面积理论与声发射b值理论进行联合表征。断层总面积反映事件数和能量的关系,声发射b值反映事件数和幅度的关系,两者的结合可以更好地反映钢筋混凝土梁的破坏规律。实验表明,该损伤表征方法可进一步提升对混凝土结构损伤预警识别的精准性,从而在实际工程运用声发射技术进行损伤识别和预警提出合理的声发射信号监测方法。

广西农业全要素生产率的时空差异及影响因素分析

【目的】测算广西农业全要素生产率(TFP)并分析其时空特征和影响因素,为推动广西农业科技创新及赋能农业强区建设提供决策依据。【方法】运用DEA-Malmquist指数法对2005—2021年广西农业全要素生产率进行测算,将其分解为技术效率和技术进步,分析其时空变化情况,构建面板数据回归模型,分析广西农业全要素生产率的影响因素,并进行稳健性检验。【结果】从时间趋势来看,2005—2021年广西农业全要素生产率稳步增长,特别是“十三五”以来增长速度明显加快,且形成了广西农业全要素生产率增长的技术进步和技术效率“双驱动”模式。从空间分布来看,广西14个地级市的农业全要素生产率增长差异较明显,其中,有11个市实现增长,增长最多的是南宁市,增长最少的是贺州市。从影响因素来看,农村人力资本、农业生产规模、农业机械化水平和财政支农水平是影响广西农业全要素生产率增长的主要因素。从与周边省份对比结果来看,广西农业全要素生产率平均增长速度落后于广东省2.3%,落后于云南省0.9%。【建议】建议广西以市场需求为导向,推动农业技术进步;以生产需求为导向,提升农业技术效率;以协调发展为导向,合理布局创新资源;以优先发展为导向,强化支农强农措施,从而加快提升农业全要素生产率,助力农业强区建设。

单元感知测试的优化方案

越来越多的半导体公司采用新型故障模型——单元感知测试(Cell Aware Test,CAT)来提高库单元内部覆盖率和低缺陷率,但CAT在自动测试向量生成(Auto Test Pattern Generation,ATPG)过程中使用的测试向量数量多,运行时间长,显著地增加测试成本。为了优化CAT,在ATPG流程中加入了总临界区域(Total Critical Area,TCA)和合并时钟域命名捕获过程(Named Capture Procedure,NCP)方法。TCA根据故障类型和最有可能出现故障的位置进行排序,合并时钟域NCP方法为被测知识产权(Intellectual Property,IP)管理时钟域、控制时钟、定义捕获方案。结果表明,结合TCA和合并时钟域NCP方法的CAT达到了提高覆盖率、降低测试向量数量、减少运行时间的优化目标。与以往的CAT优化研究相比,结合了TCA和合并时钟域NCP的CAT优化流程在优化覆盖率和测试向量方面达到了更好的效果。

政府行为和技术创新如何影响金融服务实体经济效率?——基于长三角四大都市圈的实证研究

当前区域间金融资源配置不平衡现象突出,地区金融服务实体经济效率存在较大差异。基于2012-2022年相关数据,以长三角四大都市圈为研究对象,从全要素生产率角度测算金融服务实体经济效率水平及区域差异;对政府行为和技术创新对金融服务实体经济效率水平的影响进行实证分析,并探究不同地区呈现的差异。研究发现,加强技术创新对提高金融服务实体经济效率有显著的促进作用,而政府过度干预则会降低金融服务实体经济效率。基于研究结论提出以下建议:促进金融资源跨区域流动,缩小地区间效率差异;政府适度干预,由“生产型政府”向“服务型政府”转型;以实体经济融资需求为导向,激励企业持续技术创新;改善实体经济融资结构,提高直接融资比重。

白芍总苷胶囊联合益生菌芦荟发酵凝胶治疗复发性阿弗他溃疡的疗效分析

目的探讨白芍总苷胶囊联合益生菌芦荟发酵凝胶治疗复发性阿弗他溃疡的临床疗效。方法选取2023年1月至12月在西安市红会医院治疗的复发性阿弗他溃疡患者80例进行随机对照试验,采用随机数字表法分为两组,各40例。对照组男22例、女18例,年龄(31.88±6.12)岁,病程(11.15±2.70)个月,采用益生菌芦荟发酵凝胶治疗,共治疗2周;观察组男20例、女20例,年龄(31.76±6.00)岁,病程(11.22±2.16)个月,采用白芍总苷胶囊联合益生菌芦荟发酵凝胶治疗,共治疗2周。对比两组患者临床疗效、用药后疼痛评分[采用视觉模拟评分法(VAS)]、溃疡面积、炎性因子[肿瘤坏死因子-α(TNF-α)、白细胞介素-2(IL-2)、γ干扰素(IFN-γ)]与不良反应发生情况。统计学方法采用t检验、χ^(2)检验。结果观察组治疗总有效率为95.00%(38/40),高于对照组的80.00%(32/40),差异有统计学意义(χ^(2)=4.114,P=0.043)。治疗前,两组患者VAS评分、溃疡面积及炎性因子水平比较,差异均无统计学意义(均P>0.05)。治疗后,观察组VAS评分及TNF-α、IL-2水平均低于对照组[(1.30±0.22)分比(2.20±0.36)分、(3.58±0.81)g/L比(5.35±1.48)g/L、(0.30±0.07)g/L比(0.62±0.10)g/L],溃疡面积小于对照组[(0.68±0.12)cm^(2)比(1.45±0.28)cm^(2)],FN-γ水平高于对照组[(77.50±12.97)mmol/L比(63.68±12.49)mmol/L],差异均有统计学意义(t=13.492、6.635、16.580、15.986、4.854,均P<0.05)。两组患者不良反应发生率比较,差异无统计学意义(χ^(2)=0.263,P=0.608)。结论白芍总苷胶囊联合益生菌芦荟发酵凝胶治疗复发性阿弗他溃疡可提高治疗效果,减轻疼痛程度与炎性反应,缩小溃疡面积,且不会明显增加不良反应的发生。

全面抗战时期陕甘宁边区乡村党员教育研究

全面抗战时期,陕甘宁边区持续开展党员教育,以提高农民党员的思想认识与政治水平,引导广大乡村党员干部坚定理想信念和政治方向,围绕党的政治路线和中心工作,坚持抗日民族统一战线,一切为战胜日本帝国主义而奋斗。在中共中央、西北局(边区党委、边区中央局)领导下,边区乡村党员教育以西北局高干会为界,分为前后两个阶段。前一阶段,乡村党员教育中的教条主义、主观主义比较严重,教学方式以照本宣科为主,教育形式主要是流动训练班,教材内容艰深、枯燥无味。后一阶段,结合全党整风,较好地纠正了党员教育中存在的偏差,面向乡村党员干部的扫盲教育与政治教育取得显著效果,基本实现了巩固和发展党员的目标。