基于断裂力学的腐蚀钢丝疲劳S-N曲线研究

高强冷拔钢丝因其优异的力学性能被广泛应用于缆索承重结构,服役过程中钢丝腐蚀与断裂威胁着结构安全。钢丝腐蚀后表面的蚀坑因应力集中效应易产生疲劳裂纹,因此腐蚀钢丝剩余疲劳寿命主要取决于裂纹的扩展阶段,且裂纹扩展受到腐蚀程度(初始损伤)的显著影响。精确表征腐蚀程度并准确评估服役期钢丝腐蚀后的剩余寿命,仍是亟待解决的维修难题。首先采用蚀坑最大深度表征钢丝腐蚀程度,以应力强度因子幅作为裂纹扩展驱动力指标,基于断裂力学的Paris公式建立受拉钢丝裂纹扩展理论模型,进而推导腐蚀钢丝的疲劳S-N曲线。大量既有的腐蚀钢丝疲劳试验结果与理论预测值的比较验证了所提理论模型及疲劳S-N曲线的合理性和有效性。含多个蚀坑的钢丝裂纹扩展有限元模拟表明,等效单裂纹适用于多腐蚀坑钢丝疲劳寿命的简化分析。参数分析表明,蚀坑深度和腐蚀环境是腐蚀钢丝疲劳强度的关键影响因素,而应力比和疲劳加载频率影响较小,所提出的S-N曲线在钢丝常规服役条件下适用于评估其剩余寿命,可得到合理的预测结果。基于断裂力学所提的理论方法和疲劳S-N曲线可为腐蚀钢丝的疲劳强度和寿命评估提供参考。

基于剩余电流和不平衡电流突变向量比的TN-C-S系统漏电故障检测方法

TN-C-S系统在我国应用广泛,但由于固有剩余电流大,无法区分负荷投切和故障引起的剩余电流变化,漏电总保和中保无法投运,存在安全隐患。针对该问题,提出一种基于剩余电流和不平衡电流突变量之比的漏电故障保护方法。首先,分析剩余电流回路,剩余电流和不平衡电流突变量之比在单相接地故障发生时刻突变,在负荷投切时不变。其次,基于中性线阻抗和接地阻抗不会发生突变的特征,计算故障电流突变量幅值,以故障电流突变量幅值越限作为故障判别依据,实现漏电故障检测。仿真及试验证明,所提方法可有效区分负荷投切和漏电故障,实现大幅值固有剩余电流下的漏电故障检测,在单支路和多支路系统中的检测灵敏度分别为70、150 mA,满足TN-C-S系统多级漏电保护的灵敏度要求。

Isolation of an acid producing Bacillus sp. EEEL02: Potential for bauxite residue neutralization

Bauxite residue deposit area(BRDA)is a typical abandoned mining wasteland representing extreme hostile environment with increased alkalinity.Microbially-driven neutralization of bauxite residue,based on the microbial acid producing metabolisms,is a novel strategy for achieving rapid pH neutralization and thus improving its environmental outcomes.The hypothesis was that these extreme conditions promote microbial communities which are capable of novel ecologically relevant functions.Several alkaliphilic acid producing bacteria were isolated in this study.One strain was selected for its superior growth pattern and acid metabolism(termed EEEL02).Based on the phylogenetic analysis,this strain was identified as Bacillus thuringiensis.The optimized fermentation conditions were as follows:pH 10;NaCl concentration 5%;temperature 25℃;EEEL02 preferred glucose and peptone as carbon and nitrogen sources,respectively.Based on optimal fermentation conditions,EEEL02 induced a significant pH reduction from 10.26 to 5.62 in 5-day incubation test.Acetic acid,propionic acid and CO2(g)were the major acid metabolites of fermentation,suggesting that the pH reduction in bauxite residue may be caused by acid neutralization derived from microbial metabolism.This finding provided the basis of a novel strategy for achieving rapid pH neutralization of bauxite residue.

A comparative analysis of Japanese firm productivity： Solow residual and Malmquist productivity index

For some time, two major kinds of Total Factor Productivity （TFP） have existed independently of each other： the Solow residual and the Malmquist Productivity Index （MPI）. The Solow residual was introduced in macro economic growth models, and the MPI has been used in micro economics and management studies. As both indices were developed independently, few studies utilize both together and compare the results. This paper uses the same data to compare the two productivity indices by setting to determine the economic implications of combining the two indices. We discovered that we could decompose TFP with each aspect of the Soiow residual and MPI. We could then interpret their relationship in the business cycle. Our results indicated that the frontier shift in MPI of Japanese firms often occurred when the Solow residual increased, meaning that improving oroductivitv with the Solow residual could be generated by a firm that could shift new production frontiers.

Analysis of the Bacterial Communities in Lime Concretion Black Soil upon the Incorporation of Crop Residues

To analyze the bacterial communities in lime concretion black soil upon the incorporation of crop residues for two years in wheat-maize system, total DNA was directly extracted and PCR-amplified with the F357GC and R518 primers targeting the 16S rRNA genes of V3 region. The amplified fragments were analyzed by perpendicular DGGE. Analyzing of species richness index S and Shannon diversity index H revealed that there was a high diversity of soil bacterial community compositions among all treatments after incorporation of crop residues and fertilizing under field conditions. Eleven DGGE bands recovered were re-amplified, sequenced. Phylogenetic analysis of the representative DGGE fingerprints identified four groups of the prokaryotic communities in the soil by returning wheat residues and fertilizing under field conditions. The bacterial communities belonged to gamma proteobacterium, Cupriavidus sp, halophilic eubacterium, Acidobacterium sp, Sorangium sp, delta proteobacterium, Streptococcus sp and Streptococcus agalactiae were main bacterial communities. Principal Component Analysis (PCA) showed that there were the differences in DNA profiles among the six treatments. It showed that wheat residue returning, maize residue returning and fertilizing all can improve bacterial diversity in varying degrees. As far as improvement of bacterial diversity was concerned, wheat residue returning was higher than fertilizing, and fertilizing higher than maize residue returning.

基于双分辨率S变换和改进的多尺度ResNet模型的电能质量扰动检测方法

准确的电能质量扰动检测对改善智能电网中电能质量问题、保证电网安全可靠运行具有重要意义。对此,提出一种基于双分辨率S变换和改进的多尺度ResNet模型的电能质量扰动信号的检测方法。首先,利用双分辨率S变换准确提取电能质量扰动信号的时频特征向量;其次,提出利用Mish函数代替传统ReLU激活函数来改进ResNet,再利用不同卷积核大小的改进ResNet模型对复杂电能质量扰动信号进行特征学习与扰动分类;然后,在不增加网络参数的情况下,提出利用轻量级通道注意力(efficient channel attention,ECA)对电能质量扰动检测分类结果影响较大的重要特征分配更大的权重值,提升模型的分类性能。最后,实验结果表明,与其他电能质量扰动检测方法相比,所提方法具有更高的准确率和抗噪性。

经济增长模型中Solow余值的研究

通过对生产函数的前提条件的理论分析,证明了在完全竞争条件下,“余值”不存在,Solow的假设性前提错误,但“余值”存在于现实之中的非完全竞争条件下。“余值”是内生的,不是外生的,其取值范围为[0,1/(α+β)],随价格偏离边际成本的程度δ增大而增大。狭义A的确切涵义既不是“知识进步”,也不是“智能进步”,更不是“全要素生产率”,而是与k,L密切关联,由市场的不完全竞争程度通过价格偏离边际成本,影响k,L的投入,进而影响α,β,最后影响经济增长,具有动态和影响“全方位”特征的变量。

基于Solow余值理论的河北农业科技创新贡献率的测算分析

基于Solow余值理论,利用农业生产总值、农业生产资本存量和劳动力投入量3个指标,对河北省1986—2010年间的农业科技创新速度和农业科技创新贡献率进行了测算,得出此时间段河北省农业科技创新年均速度和年均贡献率分别为4.95%和38.57%。并在此基础上分析了河北省农业经济发展的特征:河北省农业经济仍没有脱离依赖生产资本存量扩张的外延式粗放型增长方式,但是农业科技创新的贡献份额逐年增加。最后提出,河北省要正确处理好科技创新与农业生产之间的关系,充分发挥科技创新对提高农业投入产出比的作用,走依靠科技创新为支撑的农业经济增长新道路。

基于Solow余值的安徽省环境规制与经济发展分析

根据C-D生产函数,论文使用Solow余值法,利用安徽省2000年—2014年的地区生产总值、人力劳动投入量、资本投入量与环境规制成本这4个指标,对安徽省技术进步贡献率进行了测算,分析得出2005年之后资本贡献率、人力劳动贡献率逐渐降低,相反技术进步贡献率逐渐提高。进一步分析安徽省环境规制对于经济发展的影响效应,得出安徽省环境规制强度的提高并没有抑制经济的发展,技术进步对于经济的发展作用比重越来越高,资本与人力劳动的投入刺激经济发展力度减小。因此,安徽省要着重关注资本的投入与利用效率,并注重高素质人才的培养,同时鼓励企业进行自主创新。

基于改进Faster RCNN的驾驶员手持通话检测

针对现有驾驶员通话行为识别误判率较高的问题,提出一种基于改进Faster RCNN的驾驶员行为检测方法,对驾驶员的违规手持通话进行检测.介绍了针对区域建议网络(RPN)及其损失函数的优化策略,并在原始Faster RCNN上运用多尺度训练、增加锚点数量以及引入残差扩张网络的方法增强网络检测不同尺寸目标的鲁棒性.基于车载平台上采集的驾驶员行为图像,对文中提出的方法进行仿真试验.结果表明:RPN和Faster RCNN通过交替优化共享特征提取网络部分,实现高效的目标检测,相较于原始Faster RCNN,检测精确度提高了3.8%,对环境的适应性更强.

Magnetic Technique Estimation of Weld Residual Stress Failure Due to Tensile Loading

In Nigeria, most welding activities are carried out by road side welders, majority of this welders are ignorant of weld residual stress and its adverse effect on weldment. Residual stress (RS) measuring device is vital in the measurement of inherent stresses in material. The aim of this research was to employ proof of principle in analyzing the weld residual stresses in a material. This was achieved by measuring samples with magnetic residual stress device and then subjecting the weld samples to mechanical tensile test with hope that materials with more residual stresses fail first. Finally the result from both procedures was compared to establish a relationship. Four (4) pieces of mild steel coupons measuring 100 × 40 × 3 mm were welded, producing two specimens, A11 and B11 of 200 × 40 × 3 mm, respectively. The specimens were measured using the Magnetic device developed and 37 signals were obtained per specimen, thereafter, the welded specimens were subjected to tensile testing and results analyzed. From the results obtained, Specimen A11 was observed to have the highest signal peak at the weld zone with RS signal of 20.3983 mV compared to B11 with 19.358 mV. While under tensile loading, it took 1.63 kN to cause failure to specimen A11 and 8.65 kN for specimen B11. From this simple experiment, it implies that the Magnetic RS device was able to mimic the behavior of residual stress and also predicted that A11 would fail first.

基于动态剩余S-N曲线的线性疲劳寿命预测模型

为估算结构在变幅载荷下的疲劳寿命,在动态剩余S-N曲线的基础上,结合材料的退化规律,对材料受载过程中的累积疲劳损伤进行了量化,提出了一种预测变幅载荷下线性疲劳损伤预测模型。根据热轧16Mn钢和20Cr2Ni4A标准圆柱齿轮多级载荷下疲劳寿命试验数据,对提出模型的疲劳寿命预测能力进行了验证。结果表明:基于强度退化的线性疲劳寿命预测模型相对传统Miner法则和材料记忆退化累积模型的预测结果更接近试验结果,具有较高的预测精度。

Study and practice of decreasing residual stress with residual heat of casting

A new technique for reducing the residual stress within a casting by using of the residual heat in the casting is presented.The new technique has been applied by Guangxi Yuchai Machinery Company Limited and the result shows remarkably applicable.The casting’s residual stress can be reduced to less than 60 MPa while the saving in energy can be about 101.1 kW.h per ton of castings,as compared with traditional technique.

Residual Stresses and Micro-Hardness Testing in Evaluating the Heat Affected Zone’s Width of Ferritic Ductile Iron Arc Welds

Shielded Metal Arc Welding (SMAW) in Ductile Irons (DI) is often required by foundries for practical manufacturing reasons. The mechanical properties of the welded structures are strongly dependent on their HAZ’s width. A model based on the behaviour of the ferritic matrix of high-Si DIs in order to make an approach in measuring their HAZ’s width is developed in this study. A series of thermal treatments on 3.35 and 3.75 wt% Si as-cast DIs and spot SMAWs is applied on these materials. The applied SMAWs are done on non-preheated and preheated samples (150℃ - 300℃). For welding we modify the amperage (100 - 140A). The micro-hardness Vickers changes in the ferrite of the as-cast samples and inside the HAZ of the welded ones can be attributed to the existence of residual stresses (RS) in the ferritic matrix and assist in estimating the HAZ’s width.

Quantitative Estimation of Altimetric Variations Using Residual DEM from Topographical Maps between Two Epochs 1893 and 1985: Case Study: The Endorheic Basin of Enfidha-Tunisia

This article endeavours to analyse the recent deformation in the Enfidha region. This analysis has been carried out using the Residual Digital Elevation Model (DEM). It is the altimetric difference between two DEM generated from the contour lines of two topographical maps over a period of 100 years. This deformation has been studied by some authors who report the presence of recent ground movements by comparing contour lines with a downward trend in elevation from 1893 to 1985. In 2006, this study area was marked by the presence of two earthquakes that occurred in several coastal cities located in the northeastern part of Tunisia. Our study involves a quantitative estimation of altimetric variations under a Geographic Information System (GIS) environment. Our proposed methodology aims at the mapping of residual (DEM) and the extraction of parameters that have a morphological and morphostructural signature. The extraction of quantitative morphostructural parameters requires the integration of multi-source and multi-scale data. This can only be done if the problem of heterogeneity at the level of scale and coordinate system is solved through the use of GIS tools and the obtainment of the vectorial shapefile format. Then, in order to compare the DEM generation errors with reference to recent and old data, they must be projected in the same projection system and on the same scale. The available data are two topographic maps of Enfidha which represent two different epochs. The first one is an old topographic map of 1893 (type 1922) at a scale of 1:50,000 and the second one is a recent topographic map of 1985 at a scale of 1:25,000. These topographical maps have the Lambert (IGN) projection system. This methodological approach, based on residual (DEM), allows to highlight an estimated subsidence of 3 m/100years located in the Enfidha plain and extends to the south coast of Cap Bon area in Tunisia. The variation of the contour lines shape between the old and the recent map can be studied in correlation with a relay structure fault observed and recognized by some analysts in this area. These relay accidents remain active according to the results obtained by the residual (DEM) and validated by the field observations of two sites that we have carried out in the Enfidha endorheic basin.

基于Savitzky-Golay滤波的雷暴天气大气电场信号分析

基于重庆市南川区金佛山野外雷电观测场2021年大气电场数据及重庆市ADTD闪电定位资料,利用Savitzky-Golay卷积平滑滤波、快速傅里叶变换等信号处理方法对大气电场信号从时域、频域两方面进行分析。分析结果表明:选取窗口宽度n=33,拟合阶次k=3时,滤波效果较为理想;大气电场信号能量主要存在于0~0.05 Hz的低频部分;地闪是引起大气电场突变的重要因素,残差信号不能简单地作为噪声予以去除,选取雷暴天气时不同波形的大气电场数据进行滤波得到的残差信号与ADTD定位数据作对比,验证了其中包含较为丰富的闪电信息。

Cr应力缓释层对柔性Cu_(2)ZnSn(S,Se)_(4)薄膜太阳电池性能的影响

柔性Cu_(2)ZnSn(S,Se)_(4)(CZTSSe)薄膜太阳电池中的应力是阻碍其发展的一大瓶颈。采用磁控溅射法在柔性Ti衬底和Mo背电极之间引入不同厚度的Cr缓释层,研究其对CZTSSe薄膜应力的影响。结果表明,当Cr应力缓释层厚度为80 nm时,薄膜的结晶质量最好,电池具有最佳的光电性能,相比没有Cr应力缓释层存在的情况,薄膜的残余应力从-7.15 GPa降低至-3.61 GPa,电池的光电转换效率(PCE)从2.89%提高至4.65%,增加了60.9%。Cr应力缓释层的引入不会影响CZTSSe薄膜的晶体结构,相反可有效提高薄膜的结晶质量,降低薄膜的残余应力,最终提高电池的光电性能。

人工智能时代高新技术企业存在索洛悖论吗?

在人工智能时代,为了有效利用新一代通用目的技术,企业会进行大量的无形资本投资,包括重新设计业务流程、构建新商业模式以及相关的人力资本投资。虽然这些无形资本为企业创造了有价值的资产,但在增长核算中通常难以计量,从而导致“索洛悖论”。基于中国高新技术企业的股票市场估值,对其无形资本价值大小进行测算的结果表明:中国高新技术企业存在大量未被计量的无形资本,从而导致了人工智能时代的“索洛悖论”。因此,应积极活跃资本市场,特别是大力发展人工智能企业密集的创业板和科创板,满足人工智能企业的直接融资需求,以此支持人工智能技术的扩散与创新,克服“索洛悖论”,提升生产率。

我国省际全要素生产率的对比分析研究

传统的按照索洛方法计算的广义技术进步率并不是本来意义上的全要素生产率。因此,本文重新构建全要素生产率的测度框架。一是明确定义全要素生产率,即一定时期内,按照现有的技术条件和产业结构比例,每投入一个单位的全部生产要素所能够带来的最终产出。二是利用有关统计数据估算省级层面有效资本存量,并分别构建各省份合适的计量模型估计其在不同发展阶段的要素产出弹性系数,进而测度各省份全要素生产率以及因全要素生产率变动所带来的经济增长率(简称全要素经济增长率)。实证分析结果表明,一般情况下,经济越发达省份的全要素生产率也越高,但是经济发达省份的全要素经济增长率并不一定高于经济欠发达省份。该结果不仅与常识相符,而且也合理解释了各省份生产效率与技术进步之间的联系与区别,验证了本文所提出的测度框架及方法的可行性。

科技创新驱动第二产业增长的路径探索——以安徽省为例

文章聚焦科技创新与第二产业的关系,以安徽省为例,基于柯布-道格拉斯生产函数和索洛余值法,测算第二产业科技进步贡献率,并运用灰色关联度法分析第二产业科技进步贡献率的影响因素。研究表明,观测期内安徽省第二产业科技进步贡献率由2006年的-71.13%波动上升至2021年的50.13%,规上工业企业技术获取和技术改造、工业固体废物综合利用率与第二产业科技进步贡献率的关联度分别为0.898和0.881。为此提出科技创新驱动第二产业增长的三大路径:第一,利用新一代信息技术带动第二产业数字化、智能化转型;第二,助推重点领域国有企业以技术改造、技术改进等手段引领技术革新;第三,以绿色低碳经济为方向、创新与完善全产业资源综合利用体系。