Impact of Education on Productivity:A Model in China

Improving the quality of human resources through edu-cation and training is of great strategic significance.However, few people have done in depth and systematicstudies on the relationship between education and pro-ducttvity in China. This study developed an educationproductivity transform model and empirically tested themodel using data on the most districts of China. The ba-sic notion is that the effect depends both on the capabilityresulted from education, and on the environment inwhich this capability can be exercised, the effect is a re-sult of two factors combined.

Using Multivariable Linear Regression Technique for Modeling Productivity Construction in Iraq

Productivity is a very important element in the process of construction project management especially with regard to the estimation of the duration of the construction activities, this study aims at developing construction productivity estimating model for marble finishing works of floors using Multivariable Linear Regression technique (MLR). The model was developed based on 100 set of data collected in Iraq for different types of projects such as residential, commercial and educational projects. Which these are used in developing the model and evaluating its performance. Ten influencing factors are utilized for productivity forecasting by MLR model, and they include age, experience, number of the assist labor, height of the floor, size of the marbles tiles, security conditions, health status for the work team, weather conditions, site condition, and availability of construction materials. One model was built for the prediction of the productivity of marble finishing works for floors. It was found that MLR have the ability to predict the productivity for finishing works with excellent degree of accuracy of the coefficient of correlation (R) 90.6%, and average accuracy percentage of 96.3%. This indicates that the relationship between the independent and independent variables of the developed models is good and the predicted values from a forecast model fit with the real-life data.

Reliability Sensitivity-based Correlation Coefficient Calculation in Structural Reliability Analysis

The correlation coefficients of random variables of mechanical structures are generally chosen with experience or even ignored,which cannot actually reflect the effects of parameter uncertainties on reliability.To discuss the selection problem of the correlation coefficients from the reliability-based sensitivity point of view,the theory principle of the problem is established based on the results of the reliability sensitivity,and the criterion of correlation among random variables is shown.The values of the correlation coefficients are obtained according to the proposed principle and the reliability sensitivity problem is discussed.Numerical studies have shown the following results：（1） If the sensitivity value of correlation coefficient ρ is less than（at what magnitude 0.000 01）,then the correlation could be ignored,which could simplify the procedure without introducing additional error.（2） However,as the difference between ρs,that is the most sensitive to the reliability,and ρR,that is with the smallest reliability,is less than 0.001,ρs is suggested to model the dependency of random variables.This could ensure the robust quality of system without the loss of safety requirement.（3） In the case of ｜Eabs｜ρ0.001 and also ｜Erel｜ρ0.001,ρR should be employed to quantify the correlation among random variables in order to ensure the accuracy of reliability analysis.Application of the proposed approach could provide a practical routine for mechanical design and manufactory to study the reliability and reliability-based sensitivity of basic design variables in mechanical reliability analysis and design.

Impact coefficient and reliability of mid-span continuous beam bridge under action of extra heavy vehicle with low speed

To analyze the dynamic response and reliability of a continuous beam bridge under the action of an extra heavy vehicle, a vehicle–bridge coupled vibration model was established based on the virtual work principle and vehicle–bridge displacement compatibility equation, which can accurately simulate the dynamic characteristics of the vehicle and bridge. Results show that deck roughness has an important function in the effect of the vehicle on the bridge. When an extra heavy vehicle passes through the continuous beam bridge at a low speed of 5 km/h, the impact coefficient reaches a high value, which should not be disregarded in bridge safety assessments. Considering that no specific law exists between the impact coefficient and vehicle speed, vehicle speed should not be unduly limited and deck roughness repairing should be paid considerable attention. Deck roughness has a significant influence on the reliability index, which decreases as deck roughness increases. For the continuous beam bridge in this work, the reliability index of each control section is greater than the minimum reliability index. No reinforcement measures are required for over-sized transport.

Analysis of burnup performance and temperature coefficient for a small modular molten‑salt reactor started with plutonium

In a thorium-based molten salt reactor(TMSR),it is difficult to achieve the pure 232Th–^(233)U fuel cycle without sufficient^(233)U fuel supply.Therefore,the original molten salt reactor was designed to use enriched uranium or plutonium as the starting fuel.By exploiting plutonium as the starting fuel and thorium as the fertile fuel,the high-purity^(233)U produced can be separated from the spent fuel by fluorination volatilization.Therefore,the molten salt reactor started with plutonium can be designed as a^(233)U breeder with the burning plutonium extracted from a pressurized water reactor(PWR).Combining these advantages,the study of the physical properties of plutonium-activated salt reactors is attractive.This study mainly focused on the burnup performance and temperature reactivity coefficient of a small modular molten-salt reactor started with plutonium(SM-MSR-Pu).The neutron spectra,^(233)U production,plutonium incineration,minor actinide(MA)residues,and temperature reactivity coefficients for different fuel salt volume fractions(VF)and hexagon pitch(P)sizes were calculated to analyze the burnup behavior in the SM-SMR-Pu.Based on the comparative analysis results of the burn-up calculation,a lower VF and larger P size are more beneficial for improving the burnup performance.However,from a passive safety perspective,a higher fuel volume fraction and smaller hexagon pitch size are necessary to achieve a deep negative feedback coefficient.Therefore,an excellent burnup performance and a deep negative temperature feedback coefficient are incompatible,and the optimal design range is relatively narrow in the optimized design of an SM-MSR-Pu.In a comprehensive consideration,P=20 cm and VF=20%are considered to be relatively balanced design parameters.Based on the fuel off-line batching scheme,a 250 MWth SM-MSR-Pu can produce approximately 29.83 kg of ^(233)U,incinerate 98.29 kg of plutonium,and accumulate 14.70 kg of MAs per year,and the temperature reactivity coefficient can always be lower than−4.0pcm/K.

新质生产力水平的统计测度与时空演变特征研究

文章基于新质生产力的内涵和主要特征,测算了2010—2021年中国30个省份的新质生产力水平,并分析了新质生产力水平的区域差异及动态演变特征,结果显示:(1)研究期内,中国新质生产力水平整体上呈现上升趋势,地区间差异较大,形成“东高西低”的区域发展格局。(2)新质生产力水平存在显著的区域异质性特征,东部地区内部的新质生产力水平差异大于中西部地区,东-西部及东-中部的地区间差异是导致中国新质生产力水平区域差异扩大的主要原因。(3)从新质生产力水平的分布及演变特征来看,全国及东西部地区的新质生产力水平均存在极化现象。从时空动态演进特征看,中国新质生产力水平不存在跨越式跃迁,整体上呈现梯度上升趋势,新质生产力水平较高的省份能够发挥辐射带动作用,促进邻近省份的发展,而当邻近省份的新质生产力水平较低时,该省份将趋于保持相对稳定的状态。

中国新质生产力水平、区域差异与时空演进特征

文章构建新质生产力水平测度指标体系,运用熵值法测算2012—2021年中国31个省份的新质生产力水平,通过Dagum基尼系数法分析其差异及来源,最后采用空间相关性检验探索中国新质生产力的时空集聚特征和动态跃迁情况。研究发现:中国新质生产力水平逐年上升,但整体水平不高且存在区域差异;劳动者维度和劳动对象维度中的新质产业发展是制约新质生产力水平提升的主要因素;四大地区新质生产力水平差异较大,区域差异的主要来源始终是区域间差异;中国新质生产力水平明显集聚于高效型和低效型,且具有较强的空间稳定性;中国新质生产力水平跃迁更多转向极化型和空心型,较少转向高效型,区域协调发展战略效果不同,虹吸效应与带动效应并存。

基于允许可靠度的薄壁圆筒静强度安全系数

为建立钢制单层承压薄壁圆筒静强度的可靠性设计技术,当圆筒静强度与载荷分别符合正态分布且静强度分布参数为区间值时,应用概率论知识,构建了圆筒静强度在不同工况的可靠度系数、安全系数和工况系数三者之间的关系。研究表明:1)在一般气压试验或气液组合试验时,圆筒屈服强度的允许可靠度系数应不小于1.549且不超过2.115,爆破强度的允许可靠度系数应不小于4.081且不超过5.414。2)在一般液压试验时,圆筒屈服强度的允许可靠度系数应不小于0.605且不超过1.005,爆破强度的允许可靠度系数应不小于3.304且不超过4.430。3)在正常操作时,圆筒屈服强度的允许可靠度系数应不小于1.961且不超过2.484,爆破强度的允许可靠度系数应不小于4.280且不超过5.456。4)在允许可靠度系数满足上述取值范围,且工况系数符合中国标准时,圆筒屈服安全系数可取1.40,爆破安全系数可取2.00。

基于可靠性的疲劳试验数据处理方法

本文基于疲劳可靠性的基本原理,在疲劳寿命对数正态分布的假设下,根据t分布理论,结合船舶及海洋工程一般构件具有95%置信度和97.72%可靠度下的P-S-N曲线的基本要求,推算出了具有95%置信度和误差限度5%内的疲劳试件个数与允许的最大变异系数数值对应关系,以此作为成组法疲劳试验的最少试件个数的判据开展典型节点的疲劳试验,得到具有95%置信度的百位估计值Np;并通过线性相关系数r判断对数疲劳应力Y=log S与X=log Np之间线性相关的程度,采用最小二乘法对对数疲劳寿命lg Np和对数疲劳应力lg S线性拟合,得到具有95%置信度的P-S-N曲线,并与IIW规范中相应的曲线进行对比分析,验证了本文试验方法的可行性和可靠性。

炉腹煤气量指数和透气阻力系数在马钢2号高炉的应用

对炉腹煤气量指数X_(BG)和透气阻力系数K在马钢2号高炉的应用进行了总结。通过对2号高炉1年多的生产数据跟踪分析,结果表明:X_(BG)控制在63~64m/min,对应炉腹煤气量V_(BG)控制在6300~6400m^(3)/min时,高炉稳定顺行,燃料比较为稳定;针对2号高炉炉腹渣皮厚、炉腹温度整体偏低现象,风压控制在靠上限水平,K值实际控制在4.25~4.75为宜,高炉运行状态良好。认为炉腹煤气量指数和透气阻力系数都是综合操作参数,在高炉日常操作中,可以用此来判断炉况,衡量强化程度,使炉况保持稳定顺行,技术经济指标改善。

成组法疲劳试件个数选取方法研究

目的 在成组法疲劳试验过程中,确定最少疲劳试件个数判据,获取有效可靠的疲劳试验结果。方法基于疲劳可靠性的基本原理,在疲劳寿命对数正态分布的假设下,根据t分布理论,结合船舶及海洋工程一般构件具有95%置信度和可靠度p=97.72%下的P-S-N曲线的基本要求,推算出相应置信度和可靠度下5%误差限度内的疲劳试件个数与允许的最大变异系数数值的对应关系,以此作为成组法疲劳试验最少试件个数的判据,开展典型节点的疲劳试验。结果 得到了具有95%置信度的百位估计值Np,并通过线性相关系数r,判断对数疲劳应力Y=lg S与X=lg Np之间线性相关的程度,采用最小二乘法对对数疲劳寿命lg Np和对数疲劳应力lg S进行线性拟合,得到了具有95%置信度的P-S-N曲线,与IIW规范中相应的曲线一致。结论 文中给出的成组法疲劳试验个数确定方法是合理、可靠的,为船舶与海洋工程结构物典型焊接接头成组法疲劳试验个数的确定提供了依据。

改进和优化黑果枸杞及其制品中花青素测定的pH示差法

建立一种基于美国官方分析化学师协会(Association of Official Analytical Chemists,AOAC)方法检测黑果枸杞及其制品中花青素含量的改进pH示差法。考察了黑果枸杞及其制品中花青素的最佳提取和检测条件,通过液相色谱-三重四级杆串联质谱法鉴别出黑果枸杞中花青素的具体化学结构,并计算出混合花青素的平均摩尔质量。通过分光光度法测得混合花青素的平均摩尔消光系数,对改进后的pH示差法进行方法学验证和花青素的含量测定。结果显示,最佳提取和检测条件如下:黑果枸杞花青素提取溶剂为盐酸-80%(体积分数)乙醇(3∶97,体积比),料液比为1∶100(g∶mL),提取温度为50℃,提取时间为30 min,缓冲溶液稀释5倍后静置平衡20 min。液相色谱-三重四级杆串联质谱法鉴别黑果枸杞中主要以矮牵牛素类花青素为主(占97.96%),黑果枸杞特有的混合花青素平均摩尔质量为912.7 g/mol,平均摩尔消光系数为29591 L/(mol·cm)。pH示差法改进后能够满足方法学验证要求,固体样品和液体样品最低检出限分别为28.2 mg/100 g、0.282 mg/100 mL。方法改进后花青素提取增长率均大于20%,静置平衡20 min后单次检测结果精密度小于0.3%。以矮牵牛素类花青素代替矢车菊素-3-O-葡萄糖苷计算花青素含量平均提高了2.41倍,能真实地反映黑果枸杞及其制品中花青素的含量。

多向加权Tsallis熵最大化导向的自动阈值分割方法

受噪声或随机细节、目标和背景的大小比例、成像时的点扩散等不同因素的影响,许多图像的灰度直方图呈现为无模态、单模态、双模态或者多模态样式.为了在统一框架内处理这4种不同模态情形下的自动阈值选择问题,本文提出了一种多向加权Tsallis熵最大化导向的自动阈值分割方法(Multi-directional Weighted Tsallis Entropy,MWTE).基于新设计的反正切方向性卷积核的多尺度乘积效应,该方法将不同模态的灰度直方图转化为统一的单模态右偏灰度直方图.在4个不同方向上提取出这种特殊的单模态右偏灰度直方图后,通过多向加权策略构建出与原始图像灰度值紧密相关的加权Tsallis熵目标函数,并以该目标函数取最大值时对应的灰度值作为最终分割阈值.本文将提出的方法和3个阈值分割方法、1个软分割方法、1个活动轮廓分割方法以及1个自动聚类分割方法进行了比较.在4种不同模态情形下的4幅合成图像和50幅真实世界图像上的实验结果表明,本文提出的方法虽然在计算效率方面不占有优势,但它对不同模态的测试图像具有更稳健的分割适应性,且在量化分割精度所用的马修斯相关系数方面优于其他6个分割方法.

断控缝洞型碳酸盐岩立式板状油藏注采井网构建

断控缝洞型碳酸盐岩油藏缝洞结构和连通关系复杂,传统井网部署易产生低产能井,需构建立体注采井网以提高产能。通过油藏数值模拟研究了不同因素对塔里木富满油田满深3和满深4井区立体注采井网波及系数的影响,并设计了先导试验方案预测产能。结果表明,满深3井区注气井与采油井单个交错排状分布时波及系数最大;采油井纵向深度越大,波及系数越大;平面注采井距在500~1000m波及系数相对稳定,井距增至1500m时,波及系数大幅度减小。满深4井区注气井、注水井与采油井单个交错排状分布时波及系数最大。先导试验中,满深3和满深4井区分别采取“浅部注N_(2),深部采油”和“顶部注N_(2),底部注水,中部采油”的井网构建方案,阶段末采出程度分别达到21.3%与22.4%,相比于基础衰竭式开发和注水开发方案有了显著提升。

考虑消费者偏好和可替代产品的供应链绿色开发投资与协调策略

文章针对一个同时生产传统产品和绿色产品的制造商和一个零售商构成的二级结构供应链,分析集中模式、分散模式下的最优决策,探究消费者偏好、产品替代作用以及节税系数对最优决策的影响,通过决策模式的比较提出了协调策略以实现帕累托改进。研究发现:集中决策下的最优利润要优于分散决策;随着消费者偏好及产品替代作用的增加,制造商的绿色开发程度会大幅增加;在消费者偏好和产品替代作用较低时,绿色产品较传统产品的价格更低,但随着其增加,绿色产品的价格会超过传统产品并且价格差会逐渐增大;节税系数能够对供应链利润、产品价格以及绿色开发程度产生正向影响;零售商可以通过向制造商支付固定费用来实现分散决策下的帕累托改进。

基于数据简化与关键链路选择的无线通信网络存储加密

无线通信网络数据结构复杂,通信系统协议种类多、差异大,提取无线网络加密数据链路层和网络层特征存在的大量冗余数据,在数据存储过程中,加密代价高,加密效率低,为此研究基于数据简化与关键链路选择的无线通信网络存储加密。首先计算无线通信网络中需要加密的数据在尺度空间中的加密系数,以加密系数值为约束条件,简化需要加密的数据;其次利用链路可靠性分析的方法,选择关键链路,以可靠性为基础,简化需要加密的链路;最后通过设计非对称加密算法对简化后的数据和链路进行加密,设置非对称加密算法的公钥,进行非对称加密节点的分配,完成加密存储。实验结果表明:运用该方法能够在加密过程中获得更高的存储加密效率。

小样本积木式可靠性评估与更新方法

针对工程上只能进行极少甚至无法进行整机寿命试验,导致可靠性评估精度不高的情况,提出一种小样本积木式可靠性评估与更新方法。首先建立了能够根据机电产品子系统当前试验、以往试验和以往服役寿命数据,对其整机高置信度、高可靠度的可靠寿命进行评估的方法,从而解决了机电产品无法进行整机寿命试验时的可靠性评估难题,为其外场使用提供了科学依据。然后给出了能够根据该机电产品整机试验寿命数据和外场服役寿命数据对上述可靠寿命评估结果进行更新的方法,从而增大了信息量,显著提高其可靠性评估精度。文中针对工程上常用的指数分布、Weibull分布和对数正态分布情况进行了详细讨论,给出了相应的整机高置信度、高可靠度的可靠寿命评估与更新公式。

水泥混凝土道面可靠性设计指标计算方法

基于水泥混凝土道面可靠性设计指标的计算方法,分析目前计算方法存在的问题与不足,并提出算法的改进。我国工程结构设计标准提供的可靠指标基本采用安全系数换算、分项系数基本采用安全系数或可靠指标换算,该算法可能存在不同设计状况的设计结果不符合可靠性宏观规律、不同设计指标的设计结果不具有一致性的问题,原因在于可靠性设计指标的计算忽视了设计变量之间的相关性;将变量间相关性纳入工程整体可靠度考虑,改进得到的可靠指标与分项系数计算式具有更好的适用性;应用到水泥混凝土道面工程,通过抗力性质判断变量之间是否具有相关性,再分别定量统计相关系数值,最后通过改进算法计算可靠性指标的适宜值。

基于Faster R⁃CNN的无人超市商品自动化识别技术

无人超市商品自动化识别过程中易受到背景复杂化、亮度不均匀、角度多变等的干扰。为此,提出一种基于Faster R-CNN的无人超市商品自动化识别方法。首先利用Haar小波提升模型,将商品图像分为低频图像和高频图像;然后通过仿生彩色图像法对图像进行增强处理,并采用Faster R-CNN中的特征融合结构,将图像深度信息与浅度信息融合到一起;最后将融合的特征输入到自动化识别网络中,输出自动化识别结果。实验结果表明,所提方法的识别效率高、图像增强效果好、抗噪能力强。

支路开关自放电对大型多路并联FLTD脉冲源可靠性的影响

快脉冲直线型变压器驱动源(fast linear transformer driver,FLTD)是建设下一代大型Z箍缩装置最有前景的技术路线之一。大型FLTD脉冲源中数以万计气体开关的可靠运行是提高Z箍缩装置可靠性的重要因素。该文基于15 MAZ箍缩科学实验装置的FLTD脉冲源设计,采用Monte-Carlo方法建立考虑支路开关自放电及其载荷共享效应的FLTD脉冲源可靠性计算模型,分析开关故障模式及其触发策略对脉冲源可靠性的影响。结果表明,主支路开关自放电产生的故障电压会引起开关级联自放电,降低装置可靠性。若主支路开关工作系数设定在0.5~0.7范围内,FLTD脉冲源故障率可低于1×10^(-4)。此外,触发器及触发支路开关的高可靠性对于提升脉冲源可靠性至关重要,增加触发器脉冲数量、降低触发器自放电故障率能够有效提升脉冲源可靠性,当触发器脉冲数量提升至4倍后,FLTD脉冲源故障率有望降低至1×10^(-5)以下。研究结果为大型FLTD脉冲源的开关工作系数及触发策略的选取提供参考,具有重要的工程应用价值。