Numerical investigation on the caving mechanism with different standard deviations of top coal block size in LTCC

The size distribution of the broken top coal blocks is an important factor,affecting the recovery ratio and the efficiency of drawing top coal in longwall top coal caving(LTCC)mining panel.The standard deviation of top coal block size(dt)is one of the main parameters to reflect the size distribution of top coal.To find the effect of dt on the caving mechanism,this study simulates experiments with 9 different dt by using discrete element software PFC.The dt is divided into two stages:uniform distribution stage(UDS)whose dt is less than 0.1(Schemes 1–5),and nonuniform distribution stage(NDS)whose dt is more than 0.1(Schemes 6–9).This research mainly investigates the variation of recovery ratio,drawing body shape,boundary of top coal,and contact force between particles in the two stages,respectively.The results showed that with the increasing dt,the recovery ratio of the panel increases first and then decreases in UDS.It is the largest in Scheme 3,which mainly increases the drawing volume at the side of starting drawing end.However,the recovery ratio decreases first and then increases quickly in NDS,and it is the largest in Scheme 9,where the drawing volume at the side of finishing drawing end are relatively higher.In UDS,the major size of top coal is basically medium,while in NDS,the size varies from medium to small,and then to large,with a distinct difference in shape and volume of the drawing body.When the major size of top coal is medium and small,the cross-section width of the initial boundary of top coal at each height is relatively small.Conversely,when the top coal size is large,the initial boundary of top coal has a larger opening range,the rotating angle of lower boundary is relatively small in the normal drawing stage,which is conducive to the development of drawing body and reduces the residual top coal,and the maximum particle velocity and the particles movement angle are both larger.This study lays a foundation for the prediction of recovery ratio,and suggests that the uniform top coal is more manageable and has a larger recovery ratio.

大尺寸非标碟簧承载性能仿真分析

以某锤击式振打系统中的大尺寸非标碟簧为研究对象,对其在不同载荷作用下的响应特性进行了研究。分别采用理论及仿真模拟方法,对标准碟簧及大尺寸非标碟簧的载荷-变形及载荷-应力状态进行了分析;并采用仿真分析方法,研究了对合状态下重载非标碟簧的响应特征。研究结果表明,对于大变形工况,有限元法能更准确地描述大尺寸非标碟簧的承载性能;大尺寸非标碟簧承受载荷小于额定载荷时,其载荷-变形量呈现线性特征;承受载荷超过额定载荷后,载荷-变形量呈现非线性特征。分析认为,碟簧载荷与变形量的理论计算方法适用于结构的小变形状态,当载荷超过额定载荷时,碟簧的变形较大,小变形的线弹性理论已经不适用于大载荷工况。随着载荷变大,对合状态碟簧接触面的接触状态会发生突变,从面-面接触变成线-面接触,接触状态的改变会造成碟簧局部应力产生变化,影响碟簧的安全使用。

Statistical Characteristics of Raindrop Size Distribution in the Tibetan Plateau and Southern China

The characteristics of raindrop size distribution （DSD） over the Tibetan Plateau and southern China are studied in this paper, using the DSD data from April to August 2014 collected by HSC-PS32 disdrometers in Nagqu and Yangjiang, com- prising a total of 9430 and 63661-rain raindrop spectra, respectively. The raindrop spectra, characteristics of parameter variations with rainfall rate, and the relationships between reflectivity factor （Z） and rainfall rate （R） are analyzed, as well as their DSD changes with precipitation type and rainfall rate. The results show that the average raindrop spectra appear to be one-peak curves, the number concentration for larger drops increase significantly with rainfall rate, and its value over southern China is much higher, especially in convective rain larger drops, especially for convective rain in southern China. Standardized Gamma distributions better describe DSD for All three Gamma parameters for stratiform precipitation over the Tibetan Plateau are much higher, while its shape parameter （,u） and mass-weighted mean diameter （Dm）, for convective precipitation, are less. In terms of parameter variation with rainfall rate, the normalized intercept parameter （Nw） over the Tibetan Plateau for stratiform rain increases with rainfall rate, which is opposite to the situation in convective rain. The/1 over the Tibetan Plateau for stratiform and convective precipitation types decreases with an increase in rainfall rate, which is opposite to the case for Dm variation. In Z-R relationships, like ＂Z = ARb＇＇, the coefficient A over the Tibetan Plateau is smaller, while its b is higher, when the rain type transfers from stratiform to convective ones. Furthermore, with an increase in rainfall rate, parameters A and b over southern China increase gradually, while A over the Tibetan Plateau decreases sub- stantially, which differs from the findings of previous studies. In terms of geographic location and climate over the Tibetan Plateau and southern China, the precipitation in the pre-flood seasons is dominated by strong convective rain, while weak convective rain occurs frequently in northern Tibet with lower humidity and higher altitude.

Fluidization Characteristics of Silicon Particles with a Wide Size Distribution

Fluidization characteristics of silicon particle system are studied by the pressure fluctuation method.The existence of fine particles in the system can improve fluidization. Silicon particles with a wide size distribution,preferably with some fines, behave as Group A particles according to Geldart classification, although the system belongs to Group B actually. The system is also approved to be suitable for organochlorosilane monomer production using a fluidized bed reactor. Experimental data obtained in this work are important for the design and operation of commercial fluidized bed reactors for the production of organochlorosilane monomers.

Impact of Different Grinding Aids on Standard Deviation in X-Ray Fluorescence Analysis of Cement Raw Meal

X-ray fluorescence (XRF) analysis utilizes particle size which is resulted from milling of a material. The milling ensures uniform and fine grained powder. The finer and more uniform the particle size is, the better the result and easier it is for material quality control. To ensure uniformity in particle size and finer powder, a comparative analysis was conducted with different grinding aids and pressed pellet method was used in obtaining analysis results. Pressed pellets of cement raw meal sample milled with different grinding aids (graphite, aspirin and lithium borate) were subjected to XRF. Graphite produced better particle size uniformity with a corresponding standard deviation that made quality control of raw meal easier and better than aspirin and lithium borate.

Simulation of Melt Blown Web and the Effect of Its Pore Size Distribution on Filtration Performance

In this paper melt blown webs with different fiber dis-tributing density were simulated by the computer,and then their pore size distribution was calculated with the image analysis.Based on simulated fiber webs,the effect of 10% big pores on the filtration properties was ana-lyzed theoretically.It is found that the pore radius be-comes smaller and its distribution becomes more uniformwith increasing line density,i.e.,the fiber distributing density.The flow proportion in these 10% big pores is linearly increased with increasing the standard

Study on the Diffusion Performance of Standard E-Government Information Systems

Standard e-government information system(SEIS) including mobile-government applications are playing more and more important roles in the establishing of national e-government framework. It can be beneficial not only for avoiding redundant e-government IS development but also for improving collaboration among government agencies. Two research questions were explored: what are the factors influencing the performance of SEIS? Will mandatory SEIS create a better performance than non-mandatory SEIS? Specifically, the use of five categories of IS aspects--information system quality, online service quality, offline service quality, diffusion modes and standard network size—is proposed to understand the performance of SEIS through applying both survey study and simulation study. The results show that information system quality and online service quality of SEIS have strong effects on users' expectation and users' satisfaction, which thereafter promotes the performance of SEIS. Government agencies' offline service quality shows a significant effect on users' satisfaction while not on users' expectation. Furthermore, the diffusion speed of SEIS in non-mandatory and mandatory modes and the standard network size also have great influence on the utility of SEIS.

Simulation Program to Determine Sample Size and Power for a Multiple Logistic Regression Model with Unspecified Covariate Distributions

Binary logistic regression models are commonly used to assess the association between outcomes and covariates. Many covariates are inherently continuous, and have a variety of distributions, including those that are heavily skewed to the left or right. Existing theoretical formulas, criteria, and simulation programs cannot accurately estimate the sample size and power of non-standard distributions. Therefore, we have developed a simulation program that uses Monte Carlo methods to estimate the exact power of a binary logistic regression model. This power calculation can be used for distributions of any shape and covariates of any type (continuous, ordinal, and nominal), and can account for nonlinear relationships between covariates and outcomes. For illustrative purposes, this simulation program is applied to real data obtained from a study on the influence of smoking on 90-day outcomes after acute atherothrombotic stroke. Our program is applicable to all effect sizes and makes it possible to apply various statistical methods, logistic regression and related simulations such as Bayesian inference with some modifications.

中国西南彝族男性体型分类及胸腰覆盖率研究

为研究并细分中国特定地区男性体型及服装标准体型覆盖率,选择中国四川、云南、贵州3个地区年龄在18~80岁的930名彝族男性作为人体测量样本。采用服装人体测量的质量控制规定进行手工测量,利用SPSS软件进行K-均值聚类分析,将数据与GB/T 1335.1—2008《服装号型男子》中体型分类范围进行比较,对该地区彝族男性的体型特征重新分类,并计算出3个地区彝族男性不同体型胸腰覆盖率。研究结果丰富了中国西南地区的服装人体数据,对中国男性服装标准号型数据库进行了补充和细化,为服装企业和产品研发提供了更准确的数据支持。

动态光散射测量仪粒度标准物质的研制

【目的】解决国内尚缺动态光散射测量法专用粒度标准物质的问题。【方法】采用微乳液聚合法合成标称粒径为40、80 nm的态光散射粒度标准物质,标准物质编号分别是QBW12001和GBW12011b;采用动态光散射多家定值法测定2种粒度标准物质的散射光强调和平均粒径,定值结果溯源至动态光散射法(ISO 22412:2017)。【结果】合成的2种粒度标准物质均匀且稳定,散射光强调和平均粒径分别为(40.0±0.5)、(80±2)nm。【结论】不同厂家生产的激光粒度仪测的散射光强度调和平均粒径一致性最好;散射光强度平均粒径一致性较好;体积平均粒径一致性较差;颗粒数目平均粒径一致性最差。

碘量法测定天然气中硫化氢标准适应性研究

GB/T 11060.1—2010中碘量法是天然气气质中硫化氢限制指标的测定方法之一,是GB 17820—2018《天然气》中硫化氢含量的仲裁方法。现行GB/T 11060.1—2010被广泛应用,在应用中发现存在的主要技术问题:(1)硫代硫酸钠标准滴定溶液配制和标定与GB/T 601—2016规定不完全相同;(2)对于产品天然气中硫化氢含量低,按该标准要求分析一个样品需要4~9 h,方法使用受到限制;(3)按标准规定的试样参考用量,吸收硫化氢的溶液中硫化锌沉淀多、颗粒大,滴定终点的颜色不明显,影响测量结果准确度。通过开展GB/T 11060.1—2010标准适应性研究,考察了标准溶液的配制和标定方法,以及不同的取样量、取样流速和吸收器等对测量结果的影响。研究结果表明:按照GB/T 601—2016配制的0.1 mol/L硫代硫酸钠标准滴定溶液并标定,由于滴定管校准、滴定速度和分析天平精度原因,标定结果不能完全符合GB/T 601—2016要求;硫化氢含量<28.7 mg/m^(3)试样参考用量降低为50 L,其重复性和再现性完全满足标准要求。根据实验结果、标准适用性和操作性等因素,提出了GB/T11060.1—2010的修订内容并修订发布GB/T 11060.1—2023。针对GB/T1106.1—2023新标准进行解读,以便使用者能更好地理解和掌握新标准,确保新标准的有效实施。

高碳铬轴承钢球化退火碳化物尺寸评级标准的对比讨论

本文对比分析制造业现行以下各标准关于高碳铬轴承钢碳化物尺寸规定:GB/T 18254-2016高碳铬轴承钢第5级别图退火组织,SEP 1520-1998钢中碳化物图谱系列显微检验法(斯凯孚公司D33标准总则采用同一标准),ASTM A892-09(2020)高碳轴承钢显微组织的定义和等级的标准导引及其附录金相图谱,舍弗勒公司轴承钢100Cr6球化退火显微组织标准(图谱)S 261010。对于球化退火碳化物尺寸评级,可见我国标准比国外标准级数少,且碳化物尺寸级差不均匀;我国企业通常要求第2级合格,碳化物尺寸偏大,并且显示偏聚程度较大和存在个别大颗粒;没有对超细球化退火组织碳化物级别的界定。需要结合我国轴承企业发展现状并参照国际先进标准,适当修订相关标准。

激光粒度仪测定Y型分子筛粉体粒度的影响因素

采用带有湿法分散单元的马尔文激光粒度仪,对Y型分子筛粉体粒度进行测试,考察了加样方式、超声时间、折射率、吸收率、转速、遮光度等因素对粉体粒度的影响。结果表明:Y型分子筛粉体粒度的最佳测试条件为:预分散加样法,超声功率为40 W,超声处理时间为60 s,进样器转速为2500 r/min,样品遮光度为8%~15%,折射率为1.46,吸收率为0.001;经5次重复测定,D10,D50,D90(样品累计粒径分布百分数为10%,50%,90%时相对应的粒径)的相对标准偏差最高为6.275%,加权残差值最高为0.429。

就业促进还是就业抑制:对接国际环境标准与企业劳动雇佣

对接国际环境标准是推进更高水平的制度型开放和更深层次的生态文明建设的本质要求。该研究以ISO 14001环境标准为准绳,创新性地构建了对接国际环境标准的评价体系,并运用2010—2021年沪深A股上市公司的经验数据,探讨了对接国际环境标准的就业效应。研究发现:①对接国际环境标准显著促进了企业劳动雇佣,表现为“就业促进效应”。②影响机制分析表明,对接国际环境标准的就业促进效应是通过经营风险机制和资源获取机制实现的,其中经营风险机制表现为降低了企业环境处罚、企业环境税收等政策风险,供应商集中度、客户集中度等供应链风险;资源获取机制表现为提高了企业政府补助、企业信贷融资、企业商业信用融资等资源获取。③边界条件分析发现,当产权性质为非国有、行业竞争激烈以及金融生态环境较差时,对接国际环境标准的就业促进效应更显著。④拓展性分析表明,对接国际环境标准显著优化了企业劳动力结构,表现出企业劳动力学历结构和岗位结构明显改善;对接国际环境标准的就业促进效应具有市场溢出效应,表现出市场类型为国际市场和国内市场的企业劳动雇佣均明显增加。该研究的政策含义在于:①政府层面,加快对接国际环境标准,推进国内和国际环境标准的协同联动,改善劳动力市场。②企业层面,积极对接国际环境标准,扩大劳动力规模,优化劳动力结构。③劳动者层面,优化对接国际环境标准新形势下的择业就业观,提升就业竞争力。

贵州省中型灌区与高标准农田建设协同推进的研究与分析

【目的】阐明贵州省在建中型灌区续建配套、节水改造项目与高标准农田建设协同推进之间的关系,提出二者协同推进的建议与对策。【方法】基于2023年在建17个中型灌区续建配套与节水改造项目的实施,统计实施灌区内高标准农田面积覆盖范围,分析灌区与高标准农田的重合度,得出二者在实施过程中的优化方案与对策。【结果】全省在建17个中型灌区项目,涉及8个市(州)17个县(市、区),总投资3.6亿元,总设计灌溉面积49.4万亩,截止2023年,灌区内已建高标准农田面积42.19万亩,重合度达85.48%。【结论】根据目前在建灌区和高标准农田建设协同推进的要求,二者重合度较高,建议各级水务和农业农村部门要进一步提高政治站位,切实落实工作主体责任,确保将高标准农田建设优先安排在中型灌区范围内实施,实现水源、输水、用水环节工程同步改造,协同推进实施中型灌区现代化改造与高标准农田建设。

全国中小河流治理模式和投资规律研究

中小河流治理是保障区域防洪安全的重要举措,是满足人们美好生活需要的重要载体。优化中小河流治理模式,合理安排中小河流治理资金,有利于高质量推动中小河流系统治理,充分发挥中小河流治理效益。基于全国中小河流基本特征、治理现状、投资情况等调查统计数据,分析了中小河流的数量、分布和特点,研究了中小河流治理的重点、模式和投资规律。结果表明,不同地区、不同类型中小河流的治理模式不同,采取的治理措施和治理标准不同,单公里治理投资存在明显差异。本研究分区分类提出了中小河流的治理重点和适宜模式,揭示了中小河流治理投资的影响因素和时间演变规律,为推动实现中小河流治理提质增效提供了理论参考。

电气化铁路接触网滑轮补偿装置轮径选型

通过对多个滑轮生产厂家的数据调研,揭示滑轮尺寸的差异可能导致兼容性、性能、维护和安全隐患等方面的问题。结合接触网滑轮补偿装置工作原理、组成结构、滑轮尺寸,参考起重机滑轮与钢丝绳标准,提出标准化滑轮补偿装置尺寸建议,并给出统一的尺寸数据,从而提高电气化铁路系统的整体稳定性和可维护性。

GB/T 43293-2022《鞋号》标准解读

从范围、术语和定义、世界鞋号及中国鞋号体系的基本特性、鞋号表示方法、鞋号标识、位置6个方面,对GB/T3293.1-1998与GB/T43293-2022《鞋号》进行对比解读;详细分析了新旧标准的异同点。指出修订后的GB/T43293-2022《鞋号》在术语和定义、鞋号表示方法、鞋号标识、位置等方面都有较大变化。新增了“世界鞋号”“中国鞋号”的术语和定义,鞋号标识格式,不同鞋号体系之间的转换要求。删除了“所用字体的高度至少3mm”的要求。该解读能够帮助生产企业及检测机构更准确和全面地理解标准、应用标准.

安全生产标准化在中小企业管理中的应用与问题分析

随着企业安全生产标准化体系建设的推进,中小企业对安全生产标准化工作逐渐重视。体系的落地实施受到更深层次的关注,与此同时,越来越多的企业在体系建设与实施方面出现了“纸上达标”的现象。本文对此提出一些建议措施和方法,以期对推动中小企业安全标准化工作的建设与落地有所帮助。

鲁西北平原大中型灌区标准化管理研究

大中型灌区标准化管理在当前农村水利和农业生产领域扮演着重要角色。位于鲁西北平原的韩家灌区长期以来存在管理体制不完善、日常维护管理不到位、工程监测及巡护资料不规范、档案及资产管理缺乏等一系列问题,无法满足现代化农业生产的需求。本文针对灌区的实际情况,进行了标准化管理建设和改革。经过努力,韩家灌区的标准化管理工作成功通过验收,成为山东省首批实现标准化建设的大中型灌区。在此基础上,对大中型灌区标准化管理经验进行了深入总结,涵盖了组织管理、安全管理、工程管理、农业节水与供水管理、信息化管理和经济管理方面。以期为鲁西北平原大中型灌区标准化管理提供经验和工程参考。