Predictability of Al-Mn Alloy Exposure Time Based on Its As-Cast Weight and Corrosion Rate in Sea Water Environment

This paper presents the predictability of aluminium-manganese alloy exposure time based on its as-cast weight and corrosion rate in sea water environment. The validity of the derived model: α = 26.67γ + 0.55β?- 0.29 is rooted on the core expression: 0.0375α = γ + 0.0206β?- 0.0109 where both sides of the expression are correspondingly approximately equal. Statistical analysis of model-predicted and experimentally evaluated exposure time for each value of as-cast weight and alloy corrosion rate considered shows a standard error of 0.0017% & 0.0044% and 0.0140% & 0.0150% respectively. The depths of corrosion penetration (at increasing corrosion rate: 0.0104 - 0.0157 mm/yr) as predicted by derived model and obtained from experiment are 0.7208 × 10-4 & 1.0123 × 10-4 mm and 2.5460 × 10-4 & 1.8240 × 10-4 mm (at decreasing corrosion rate: 0.0157 - 0.0062 mm/yr) respectively. Deviational analysis indicates that the maxi- mum deviation of the model-predicted alloy exposure time from the corresponding experimental value is less than 10%.

Machine learning noise exposure detection of rail transit drivers using heart rate variability

Previous studies have found that drivers’physiological conditions can deteriorate under noise conditions,which poses a potential hazard when driving.As a result,it is crucial to identify the status of drivers when exposed to different noises.However,such explo-rations are rarely discussed with short-term physiological indicators,especially for rail transit drivers.In this study,an experiment involving 42 railway transit drivers was conducted with a driving simulator to assess the impact of noise on drivers’physiological responses.Considering the individuals’heterogeneity,this study introduced drivers’noise annoyance to measure their self-noise-adaption.The variances of drivers’heart rate variability(HRV)along with different noise adaptions are explored when exposed to different noise conditions.Several machine learning approaches(support vector machine,K-nearest neighbour and random forest)were then used to classify their physiological status under different noise conditions according to the HRV and drivers’self-noise adaptions.Results indicate that the volume of traffic noise negatively affects drivers’performance in their routines.Drivers with different noise adaptions but exposed to a fixed noise were found with discrepant HRV,demonstrating that noise adaption is highly associated with drivers’physiological status under noises.It is also found that noise adaption inclusion could raise the accuracy of classifications.Overall,the random forests classifier performed the best in identifying the physiological status when exposed to noise conditions for drivers with different noise adaptions.

Minimum Bedrock Exposure Ages and Their Implications:Larsemann Hills and Neighboring Bolingen Islands,East Antarctica

Considerable controversy exists over whether or not extensive glaciation occurred during the global Last Glacial Maximum（LGM） in the Larsemann Hills.In this study we use the in situ produced cosmogenic nuclide ^（10）Be（half life 1.51 Ma） to provide minimum exposure ages for six bedrock samples and one erratic boulder in order to determine the last period of deglaciation in the Larsemann Hills and on the neighboring Bolingen Islands.Three bedrock samples taken from Friendship Mountain（the highest peak on the Mirror Peninsula,Larsemann Hills;～2 km from the ice sheet） have minimum exposure ages ranging from 40.0 to 44.7 ka.The erratic boulder from Peak 106（just at the edge of the ice sheet） has a younger minimum exposure age of only 8.8 ka.The minimum exposure ages for two bedrock samples from Blundell Peak（the highest peak on Stornes Peninsula,Larsemann Hills;～2 km from the ice sheet） are about 17 and 18 ka.On the Bolingen Islands（southwest to the Larsemann Hills;～10 km from the ice sheet）,the minimum exposure age for one bedrock sample is similar to that at Friendship Mountain（i.e.,44 ka）.Our results indicate that the bedrock exposure in the Larsemann Hills and on the neighboring Bolingen Islands commenced obviously before the global LGM（i.e.,20-22 ka）,and the bedrock erosion rates at the Antarctic coast areas may be obviously higher than in the interior land.

Currency exposures of the oil and natural gas stock prices in the Hushen-300 stock market： A nonlinear model approach

The paper embarks to investigate the relationship between currency risk and stock prices of the oil and natural gas exploitation industry in the value-weighted Hushen-300 stock market, by applying the standard Capital Asset Pricing Model （CAPM） and nonlinear exchange rate exposure model to the Renminbi against US dollar. The results show that the currency exposure does vary in the oil-gas stock prices throughout the bull and bear market. The study suggests that the models of the equilibrium exchange rate exposure must be extended to considering the nonlinear exchange rate exposure, the regime periods of bull and bear market, and the industry types that is sensitive to the currency exposures. The nonlinear dynamic relationship between the exchange rate changes and the Chinese energy stock prices throughout the bull and bear market add to the recent empirical evidences that foreign exchange markets and stock markets are closely correlated.

Selected Trace Elements in Domestic Water Boreholes and Their Implications on Human Health, in Huruma Estate, Eldoret Municipality, Uasin-Gishu County, Kenya

Trace elements constitute less than 1% of the rocks in the crust (Stumm and Morgan, 1991). In the human body, they constitute less than 100 mg/kg (0.01%). These elements are released to the environment naturally by weathering and volcanic activities (Flint and skinner, 1997). It has been observed that trace elements are greatly absorbed and retained in the body when in liquid diet. This phenomenon also influences the risk to human health, especially of infants and children whose immature digestive system further promote absorption of toxic heavy metals. The study was based on the analysis of domestic borehole water supplies in Huruma estate of Eldoret Municipality for selected trace elements and their implications on human health. The boreholes were systematically selected for sampling points and trace elements, Cr, Cu and Se analyzed using AAS. Statistical analysis for mean, standard deviation and confidence interval limits was done using SPSS. The statistical t-test was used to test for significance differences at (p = 0.05). The graphs were drawn using the Microsoft Excel package. The resulting data obtained from analysis were compared with WHO data for drinking water. In the study, the mean values of the following parameters were as follows: Chromium 17.9 μg/L, Copper 563 μg/L and Selenium 22.7 μg/L. There was a significant difference at 5% level of significance (p = 0.000) in all the parameter values among the sampling points in Huruma estate. The above mean values were far below the WHO recommended limits for drinking water. It was concluded that the borehole water from Huruma was fit for drinking and therefore could not cause cancer and cardiovascular diseases. However, borehole water should be used if other water sources (tap water etc.) were not available. All the industries near Huruma estate should carefully analyze and regularly monitor their liquid waste effluents to ensure that no harmful discharges get into the soil.

Use of Ventilation-Index in the Development of Exposure Model for Indoor Air Pollution—A Review

In indoor environment, emission factor of the cooking fuel plays a vital role in determining correlation between exposure assessment and health effects. Both indoor and outdoor air pollution exposures are widely influenced by the ventilation status. An optimum control of the air change rate has also significant impact on the exposure pattern. A number of studies revealed that the indoor particulates and gaseous exposures, resulting from the combustion of various cooking fuels, are associated with significant adverse health effects on pregnant mothers and new born babies. The impacts of ventilation status on air pollution exposure in households’ kitchens or living rooms have not been explored enough. Except a few studies with concrete rooms, especially in industries, no other studies have been established on the correlation between the ventilation index and air pollution exposure. The intent of this review is to discuss reported findings focused on the ventilation and exposure to air pollution. This will obviously help better understanding to modulate exposure profile in household condition using simple tool of ventilation measurement.

天山中段2次6级地震前钻孔应变高频异常分析

2014年以来,天山中段分量钻孔应变仪空前增多,这些高采样率的应变观测资料蕴含着丰富的构造信息。如何从高采样率观测资料中提取有效的前兆异常信息,是分析研究人员亟待解决的问题。文章通过对天山中段分量钻孔应变观测数据进行S变换和超限率分析发现,在天山中段2次6级地震前有5套应变资料出现高频信息异常。这些异常均在震前出现,随后达到峰值,临震前或地震后衰减,其中短周期异常信号主要集中在10~720 min频段,且S变换与超限率分析结果具有很好的同步性。结合精河地震震源区及附近的GPS分析结果,发现高频异常信息的分布与该地区地壳运动场具有很好的一致性,进一步验证了高频信息异常的可信度。

桂北典型岩溶区植物alpha和beta多样性特征及影响因素

母岩对景观演化和生物定植起着决定性作用,但母岩对区植物多样性是否产生影响是地学、植物学和生态学共同关注的热点。以桂北冠岩、恭城两个典型岩溶区3种母岩(灰岩、碎屑岩、灰岩夹白云岩)天然次生林为研究对象,基于野外调查数据,分析了岩溶区植物alpha和beta多样性特征及影响因素。结果显示:(1)研究区内物种相对丰富,共记录乔木86种、灌木93种、草本56种,灰岩植物alpha多样性最高,碎屑岩次之,灰岩夹白云岩最低;(2)不同母岩和同一母岩区的植物群落相异性均较高,物种周转组分对beta多样性贡献(82.86%—84.49%)显著高于物种丰富度组分(15.51%—17.14%);(3)Pearson和Mantel分析表明,母岩、基岩裸露率和土壤厚度与桂北岩溶区植物alpha和beta多样性显著相关(P<0.05)。综上所述,桂北岩溶森林林分异质性较高,碳酸岩混合沉积区植物多样性显著低于纯灰岩和碎屑岩。植物组成差异主要取决于物种周转过程,母岩、基岩裸露和土壤厚度是主要影响因素。本研究从母岩的角度评估了岩溶森林的植物多样性特征及主要影响因素,为桂北乃至中国西南岩溶地区植被保护和重建提供科学依据和理论支持。

持续湿热暴露下人体认知表现的响应规律分析

近年来不断加剧的全球变暖引起热浪频发,带来了持续的高温高湿天气,由此导致的人体认知能力受损的问题越来越受到社会关注。为了探索湿热暴露下人体认知表现响应规律,在温度分别为32、35、38、41℃,相对湿度为70%的湿热环境暴露下进行了5种持续认知测试,期间观察了14名男性受试者的认知测试结果(平均反应时间和平均正确率)随环境温度的变化特征。暴露期间认知测试不间断,直到受试者拒绝继续试验。结果表明:受试者处理认知任务的平均反应时间随环境温度升高而增加,平均正确率随环境温度升高而降低;在暴露时间内,平均反应时间在前3段测试中依次增加,然后在第4、5段测试中减少;而平均正确率在前3段测试中持续降低,在第4、5段测试中快速升高;此外,观察到相对认知表现随环境温度升高而降低,但环境温度高于35℃后降低速率减缓;相对认知表现在暴露时间内呈近似U形分布,且环境温度越高,U形曲线最低点对应的时间越靠前。该研究为湿热环境下认知能力的评估提供了一种潜在的解决方案。

运用队列研究观察抑郁障碍心肾不交型复发率的多中心前瞻性研究

目的:评价滋阴降火、除烦安神功效中医药治疗方案对心肾不交型抑郁障碍(MDD)2年复发率的疗效。方法:运用队列研究方法,选取2017年1月至2018年12月全国13个分中心的心肾不交型MDD患者,根据患者接受干预方案的不同,自然形成中医、中西医结合及西医队列,比较3个队列复发率。并根据患者接受中医药方案干预时间的不同,将中医和中西医结合队列分为低、中、高3个暴露水平,比较3种暴露水平的复发率,以评价中医药方案降低心肾不交型MDD远期复发率的疗效。结果:共纳入506例患者,其中中医队列172例、中西医结合队列166例、西医队列168例。2年复发率方面,中医队列25.6%、中西医结合队列21.1%、西医队列35.1%。复发风险方面,中医队列中水平暴露比低水平暴露低63.0%(HR=0.370,95%CI为0.170~0.808,P<0.05),高水平暴露比低水平暴露低94.5%(HR=0.055,95%CI为0.016~0.192,P<0.01);中西医结合队列中水平暴露比低水平暴露低72.3%(HR=0.277,95%CI为0.111~0.689,P<0.01),高水平暴露比低水平暴露低83.9%(HR=0.161,95%CI为0.058~0.446,P<0.01)。结论:滋阴降火、除烦安神治法的中医药综合方案能有效降低心肾不交型MDD远期复发率,同时随接受中医药干预时间的增加,MDD复发率亦有逐渐下降趋势。

1980—2020年登陆中国热带气旋及其人口暴露度演变特征

热带气旋频发于人口密集的中国沿海地区,造成严重的人员伤亡。基于1980—2020年西北太平洋热带气旋数据,研究生成、登陆中国热带气旋的时空分布特点。结合空间化后的同期中国人口数据,采用敏感性实验分析热带气旋暴露人口变化的主要影响因素及其贡献率,揭示登陆中国热带气旋及其人口暴露度演变特征。(1)1980—2020年,西北太平洋海域共生成1 217个热带气旋,270个登陆中国,生成和登陆气旋频数均呈减少趋势;其中,台风及以上等级登陆气旋共计88个,呈缓慢增加趋势,且强台风频数增加明显。(2)台风及以上等级热带气旋登陆地按登陆频次递减为:广东、浙江、海南、福建和江苏,超强台风登陆地集中在广东、浙江、福建和海南。(3)1980—2020年中国台风及以上等级热带气旋的人口暴露总数为35.8亿人,2016年暴露人口共2.5亿人,为历年最多;同期影响面积累计9.5×10^(6)km^(2),广西区累计暴露范围最大,为2.1×10^(6)km^(2)。(4)热带气旋致灾因子对人口暴露度的贡献率在各个时期均最高,超过60%,且随年代际先增后减,2000—2009年贡献率达峰值80.3%;人口和其他因素的贡献率呈现出同步变化,随时间先减后增,且人口因素增幅更大。

注浆压力对顺层抽采钻孔封孔质量影响研究

为研究不同注浆压力下各顺层钻孔的封孔质量,以轩岗煤电有限责任公司刘家梁煤矿2214工作面为试验对象,根据矿井煤层实际赋存情况,采用COMSOL数值模拟软件,模拟不同注浆压力下浆液在煤层中的扩散范围,数值模拟结果表明,在1~4 MPa注浆压力范围内,浆液在煤层中的扩散半径与其注浆压力的大小成正相关关系,而浆液扩散半径的增加幅度随注浆压力的增加呈现逐渐减小的变化趋势。同时在钻孔始封深度、封孔长度等封孔参数一定的情况下,按照1、2、3和4 MPa四个等级进行现场顺层钻孔封孔试验,并利用漏气率对各抽采钻孔的封孔质量进行评价和对比,现场试验表明,采用1 MPa和2 MPa注浆压力的顺层钻孔分别有4个和2个钻孔出现漏气,其平均漏气率分别为32.76%和28.65%,而采用3 MPa和4 MPa注浆压力的钻孔均未出现漏气现象。综合数值模拟及现场试验结果表明,该工作面顺层钻孔封孔时其注浆压力应不小于3 MPa。

持续近高温暴露下基于心率变异性的认知表现评价方法

目的探究持续高温暴露对人体认知表现的影响规律,为因高温应急导致的认知表现降低提供解决方案,减少高温应急时航天员的误操作问题甚至安全事故。方法本研究招募了14名右利手男性受试者,在32℃、35℃、38℃、41℃这四种热环境下均连续暴露150 min,其间持续进行5种不同的认知任务(Posner Cueing Task、Deary-liewald Task、N-back Task、Wisconsin Card Task、Visual Search Task)得到相对认知表现;同时在认知测试过程中使用便携式2导联动态心电仪连续捕捉心电R波信号,并且基于心电数据进行心率变异性非线性分析,探索非线性指标SD1、Shannon entropy、α2、D2与相对认知表现的定量关系。结果结果表明,所有非线性指标均随着暴露时间与环境温度的变化而发生一定规律的变化。此外,通过相对认知表现与非线性指标的相关性分析得到相关系数最高的指标α2(相关系数为0.7)。在此基础上分析了α2与相对认知表现的定量关系,发现非线性指标α2与相对认知表现呈近似U型函数关系,当α2=0.98时,相对认知表现最差。结论本研究表明心率变异性非线性指标α2可较准确地预测近高温暴露下人的认知表现,能够为高温暴露下各行业作业人员的工效与健康评价提供一种较为可靠的客观指标。

The corrosion characteristic and mechanism of Mg-5Y-1.5Nd-xZn-0.5Zr(x=0,2,4,6 wt.%)alloys in marine atmospheric environment

The microstructure and precipitated phases of as-cast Mg-5Y-1.5Nd-x Zn-0.5Zr(x=0,2,4,6 wt.%)alloys were investigated by optical microscopy,scanning electron microscopy,energy-dispersive spectrometry and X-ray Diffraction.The exposure corrosion experiment of these magnesium alloys was tested in South China Sea and KEXUE vessel atmospheric environment.The corrosion characteristic and mechanism of magnesium alloys of Mg-5Y-1.5Nd-x Zn-0.5Zr(x=0,2,4,6 wt.%)alloys were analyzed by weight loss rate,corrosion depth,corrosion products and corrosion morphologies.The electrochemical corrosion tests were also measured in the natural seawater.The comprehensive results showed that Mg-5Y-1.5Nd-4Zn-0.5Zr magnesium alloy existed the best corrosion resistance whether in the marine atmospheric environment and natural seawater environment.That depended on the microstructure,type and distribution of precipitated phases in Mg-5Y-1.5Nd-4Zn-0.5Zr magnesium alloy.Sufficient quantity anodic precipitated phases in the microstructure of Mg-5Y-1.5Nd-4Zn-0.5Zr alloy played the key role in the corrosion resistance.

Impact of Spatial Scale and Building Exposure Distribution on Earthquake Insurance Rates:A Case Study in Tangshan,China

In order to examine the effect of spatial scale and building exposure distribution on the pure rate of earthquake catastrophe insurance,this study described three modules for rate determination,put forward the general assumptions and principles for calculating the pure insurance rate,and introduced three types of building distribution and their calculation.Taking Tangshan City of Hebei Province in China as an example,we analyzed the pure rate of regional earthquake insurance in terms of spatial scale and building exposure distribution by using the method of control variables.The results show that for districts(or counties)with large differences in seismic risk,the risk areas can be further divided to apply differential rates.In areas with a diverse distribution of potential earthquake source areas and large differences in building density,there is a risk of overestimating or underestimating the pure rate of earthquake insurance when buildings are distributed evenly or partially evenly.This violates the break-even principle of rate setting.This study also provides a reference for earthquake catastrophe insurance companies to choose the spatial scale and the detailed level of exposure distribution in rate determination.

工程项目中岩溶发育强度的有效估计

基于岩溶的空间分布特征,对岩溶在水平方向上的分布不均一性和垂直分带性特征进行总结,并分析其对岩溶率统计的影响。以某地埋式污水厂的勘察数据为基础,分析了见洞隙率、线岩溶率的垂直分带性,并基于抽样误差原理,分析了不同勘察阶段见洞隙率、线岩溶率统计数据间的概率关系。研究认为,各勘察阶段应在充分考虑岩溶发育的水平向不均一性、垂直分带性基础上,结合钻遇灰岩孔数、入岩深度等实际情况,通过区间估计的方式对岩溶率进行有效估计。

车载手机无线充电模块对人体电磁辐射安全性的仿真评估

采用电磁仿真软件FEKO建立人体模型、手机无线充电模块以及汽车车身的联合仿真模型,运用矩量法(MoM),计算手机无线充电模块在工作频率为127.82 kHz时,人体内部感应电场强度、比吸收率(specific absorption rate,SAR)以及外部磁场分布,并与相关标准限值进行对比,分析主驾位置人体模型的电磁辐射安全性。研究表明:汽车内手机无线充电模块在搜寻手机的过程中,所产生的内部电场和SAR剂量均未超过ICNIRP和IEEE规定的水平,驾驶员位置的磁场强度也未超过较为严格的国标GB 8702-2014限值。通过仿真分析预测了人体在车内的辐射剂量水平,能够帮助人们更好地了解所处的电磁场环境对人体健康的影响。

缓倾斜中厚矿体微贫损动态控制技术研究

缓倾斜中厚矿体赋存条件较为特殊,采场空顶高度较高,顶板管理困难,采准工程量大,开采难度较大,普遍存在采矿损失率高、矿石贫化率高等问题。针对鑫达黄金矿业公司囫囵图矿区32-2号脉采场桃形矿柱难回收、贫损指标不理想等问题,研发缓倾斜中厚矿体微贫损动态控制技术,系统运用全方位钻孔测斜技术,反演设计炮孔与实际炮孔的三维空间模型,研究钻孔偏斜规律,大幅度降低矿石贫化率,在回采过程中2条凿岩巷道之间的桃形矿柱采用多孔深协同组合开采技术,有效降低了采矿损失率,显著提升资源利用率和技术经济指标,可为类似矿山安全高效开采提供新的技术途径。

设备曝光率对电缆绝缘厚度检测结果的影响分析

为确保正常的电力运转,避免因电缆质量而造成人力及财力损失,需严格控制电缆指标,提高其检测准确性。以电缆绝缘厚度检测的影响因素为例,分析了样品制备、仪器选择和检测人员主观因素对检测结果产生的影响。同时,通过大量试验找出智能平面影像测量仪的最佳参数设置,规避设备测量误差。试验结果表明:当该设备曝光率参数设置为10时,电缆绝缘厚度检测结果最为准确和稳定。

延安典型丹霞地貌景观特征及发育演化研究

本文是在延安典型丹霞地貌景观特征分析的基础上,采用宇宙成因核素^(10)Be和^(26)Al技术获得暴露年龄和侵蚀速率,研究“黄土覆盖型沟谷丹霞”地貌景观的演化历史。研究结果显示:延安典型丹霞地貌的类型有狭缝式、石蘑菇式、天生桥式,其中狭缝式丹霞的景观特征为“窄狭、多弯、韵律、多彩”,同时也是典型的“黄土覆盖型沟谷丹霞”,石蘑菇式丹霞造型奇特,天生桥式丹霞地貌整体规模宏大,这两者发育都严格受控于垂直节理和外力作用的侵蚀;运用宇宙成因核素^(10)Be和^(26)Al技术,计算获得志丹猫巷狭缝式丹霞地貌的暴露年代有两期,分别为(0.75±18)~(0.83±0.14)ka和(1.14±13)~(1.29±0.30)ka,安塞王家湾石蘑菇式丹霞地貌暴露年代为(1.76±0.45)~(1.77±0.15)ka,这两处丹霞地貌暴露地表的年代都在全新世(Qh),前者晚于后者,地貌较年青;运用宇宙成因核素^(10)Be-^(26)Al计算获得两处典型丹霞地貌侵蚀速率为(39±3.3)~(104±24.4)cm·ka~(-1),与目前国内外学者研究地表和基岩得到的侵蚀速率对比,这两处典型丹霞地貌的侵蚀速率较大,结果还有待进一步研究;延安典型丹霞地貌景观发育的演化始于白垩纪红层的堆积,大致都经历了四个演化阶段,初步揭示了地质构造、上覆黄土盖层以及流水等多种因素共同控制和影响延安典型丹霞地貌的形成,演化阶段总体都处于青年晚期。