SOLUTION OF GENERALIZED COORDINATE FOR WARPING FOR NATURALLY CURVED AND TWISTED BEAMS

A theoretical method for static analysis of naturally curved and twisted beams under complicated loads was presented, with special attention devoted to the solving process of governing equations which take into account the effects of torsion-related warping as well as transverse shear deformations. These governing equations, in special cases, can be readily solved and yield the solutions to the problem. The solutions can be used for the analysis of the beams, including the calculation of various internal forces, stresses, strains and displacements. The present theory will be used to investigate the stresses and displacements of a plane curved beam subjected to the action of horizontal and vertical distributed loads. The numerical results obtained by the present theory are found to be in very good agreement with the results of the FEM results. Besides, the present theory is not limited to the beams with a double symmetric cross-section, it can also be extended to those with arbitrary cross-sectional shape.

Exact solution for warping of spatial curved beams in natural coordinates

The purpose of the paper is to present an exact analytical solution of a spatial curved beam under multiple loads based on the existing theory. The transverse shear deformation and torsion-related warping effects are taken into account. By using this solution, a plane curved beam subjected to uniform vertical loads and torsions is analyzed. Accuracy and efficiency of present theory are demonstrated by comparing its numerical results with Heins＇ solution. Furthermore, the effects of the transverse shear deformation and torsion-related warping on deformation of the beam are discussed.

NANOMECHANICAL MAPPING OF CARBON BLACK REINFORCED NATURAL RUBBER BY ATOMIC FORCE MICROSCOPY

Atomic force microscopy （AFM） has the advantage of obtaining mechanical properties as well as topographic information at the same time. By analyzing force-distance curves measured over two-dimensional area using Hertzian contact mechanics, Young＇s modulus mapping was obtained with nanometer-scale resolution. Furthermore, the sample deformation by the force exerted was also estimated from the force-distance curve analyses. We could thus reconstruct a real topographic image by incorporating apparent topographic image with deformation image. We applied this method to carbon black reinforced natural rubber to obtain Young＇s modulus distribution image together with reconstructed real topographic image. Then we were able to recognize three regions; rubber matrix, carbon black （or bound rubber） and intermediate regions. Though the existence of these regions had been investigated by pulsed nuclear magnetic resonance, this paper would be the first to report on the quantitative evaluation of the interfacial region in real space.

Natural Radioactivity Assessment and Radiological Hazards in Soils from Qarun Lake and Wadi El Rayan in Faiyum, Egypt

The activity concentrations of naturally occurring 238U, 232Th and 40K in surface soils along Qarun Lake and Wadi El Rayan located in Faiyum, Egypt were determined. The measurements were carried out through gamma-ray spectrometry using a coaxial HPGe detector. The results were compared with those reported in the literature. The radiological hazard radium-equivalent activity index, external and internal indices, radioactivity level index, absorbed dose rate, annual effective dose rate and total absorbed dose rate associated with radioactivity in all samples were evaluated and compared with recommended values. Correlation studies between pairs of radionuclides were performed and discussed.

Assessment of Natural Radioactivity in Rivers Sediment and Soil from the Copper Belt Artisanal Mining Region, Democratic Republic of the Congo

The concentrations and distribution of naturally occurring radionuclides (238U, 235U, 234U, 230Th, 226Ra, 210Pb, 232Th, 228Ra, and 40K) were determined by alpha and gamma spectrometry in soil and sediments collected from Luilu and Dilala rivers located in the mining district of Kolwezi (Lualaba Province) of the Democratic Republic of the Congo. The average concentrations of 238U and 226Ra in the analyzed samples were 5 - 10 times higher than the world average values for soil provided by the United Nations Scientific Committee on the Effects of Atomic Radiation. However, the average concentrations of 232Th were found similar to the world average. In both river basins, artisanal mining activities and mineral washing sites displayed the higher concentration values of radionuclides. The mean values of health risk indices calculated for those sites were found significantly higher compared to world average levels. Radiation protection measures seem needed to ensure the radiation safety of local populations. Graphical Abstract

A Study of Chemical, Mineral Compositions (of Some Metals) and Natural Radioactivity in Porcelain and Ceramic Dinner Ware

Fifteen Porcelain and Ceramic Dinner Wares samples (collected from local commercial suppliers—Jeddah Saudi Arabia) were studied applying X-Ray Diffraction and Atomic Absorption techniques were used to study the Chemical, Mineral, Compositions Concentrations (of Some Metals). In addition, the Natural Radioactivity measurements of 226Ra, 232Th and 40K, was used by a high-purity germanium (HPGe) detector. X-ray diffraction results showed that the major mineral constituents of 15 samples were quartz (SiO2) (except one), minor and trace elements vary from sample to sample. Atomic absorption spectroscopy results of the concentrations for (Al, Pb, Bi, U, Th and K) in (ppm) showed that Al2O average was 10.3 (ppm) (10%) less than the acceptable value. PbO, its average was 1.65 ppm which was slightly greater than the allowed value 1.35 ppm. Bi concentrations for all samples were lower than (DL < 10). For most samples U, concentrations were lower than (DL < 5) except samples C9 and C11. Th concentrations ranged from LDL (<1 to 52.88) and were much greater than the acceptable value 7.24 ppm except samples P1, P2, P4. The potassium concentration average was greater than the acceptable value. The average concentrations of 238U, 232Th and 40 K were (83.83, 91.05 and 751.07) Bq/kg dry. The radium equivalent activity concentration Raeq (Bq/kg) (302.61) was less than recommended value (370), gamma dose rate D (nGy/h) average (140.15) was much higher than the recommended value (60) (UNSCEER). Deff (mSv/year) and Hix were below the published admissible limit ≤ 1 and the risk is negligible. This study offers needed information for consumers at exposure risk and is useful to be found in terms of radiation protection.

Evaluation of Natural Radioactivity in Dust Storms Samples from AI-Najaf//Iraq

Abstract： 40K, 238U and 232Th in dust storms samples from AI-Najaf Holy Area - lraq in year 2013 were measured using a high efficiency gamma ray spectroscopy NaI（Tl） detector. From the measured gamma rays spectra, the specific activity were determined for 40K （range from 237.166 to 368.689 Bq/kg）, 23SU （range from 11.531 to 34.997 Bq/kg） and 232Th （range from 2.805 to 11.162 Bq/kg）. Hazard indices （external hazard index, internal hazard index, radium equivalent activities and absorbed effective dose rates） were calculated for the measured samples to assess the radiation hazards arising from dust storms samples, which is the average of Hazard indices equal （0.214, 0.192, 25.359 nG/y and 50.855 Bq/Kg）, respectively. All results of Hazard indices were compared with safe limit values recommended by UNSCEAR （2008） below the safe limit.

Measurement of Natural Radioactivity in Sand Samples Collected from Ad-Dahna Desert in Saudi Arabia

Natural radioactivity is a source of continuous exposure to human beings. The natural radioactivity due to the presence of 226Ra, 232Th and 40K in sand samples collected from Ad-Dahna was measured by means of HPGe. The measured activity concentrations of radionuclides were compared with the worldwide reported data. Mean measured activity concentrations of 226Ra, 232Th and 40K varied between 16.2 - 30.6, 15.8 - 36.7 and 285.3 - 533.2 Bq·kg–1 respectively with a mean value of 23.4 ± 4.3 Bq·kg–1, 29.7 ± 5.9 Bq·kg–1 and 380 ± 65 Bq·kg–1 respectively. Mean values of radium equivalent activity, absorbed dose rate and external radiation hazard index were 106 ± 8 Bq·kg–1, 51.4 nGy·h–1 and 0.29 respectively. The annual effective radiation dose was calculated to be 0.32 mSv·y–1. The Raeq values of sand samples are lower than the limit of 370 Bq·kg–1, equivalent to a gamma dose of 1.5 mSv·yr–1.This study shows that the measured sand samples do not pose any significant source of radiation hazard and are safe for use in building materials.

Study and Simulated the Natural Radioactivity (NORM) U-238, Th-232 and K-40 of Igneous and Sedimentary Rocks of Al-Atawilah (Al-Baha) in Saudi Arabia

In this work, gamma-ray spectroscopy based on semiconductor hyper pure germanium (HPGe) detector was used to evaluate the activity concentrations of the natural radionuclides (U-238 (Ra-226), Th-232 and K-40) and the fallout nuclide (Cs-137) for thirty samples of igneous and sedimentary rocks of Al-Atawilah (Al-Baha). The mean values of the activity concentrations of U-238 (Ra-226), Th-232, K-40 and Cs-137 in the igneous samples are found as (11.0, 11.50, 1172.71, 1.47) Bq/Kg respectively. In the sedimentary rocks, the mean values of the activity concentrations of the natural radionuclides (U-238 (Ra-226), Th-232 and K-40) and the fallout nuclide (Cs-137) equal to (12.04, 13.18, 1131.36, 1.60) Bq/Kg respectively. The averages of radiological hazards (Raeq, Hex and Iγ) were calculated and found to be within the UNSCEAR permissible limit values (370 Bq/kg for Raeq, and 1 for Hex and Iγ), except for a slight increase of average value of Iγ in the igneous rock samples (1.36). The results indicate that the dose rate values depend on the kind of rocks (high in some igneous rock samples, and most of sedimentary rock samples have low dose rate). The activities of naturalnuclides were predicted and simulated in T time using a written MATLAB R2020a script based on the average activity concentrations and respective half-lives of U-238 and Th-232 series, and K-40, this is to evaluate the future effects of natural radionuclides on the population and estimate the human inputs in the future.

Dynamic test methods for natural frequency of footbridge

Using environmental random vibration as the excitation,traditional accelerometer method,non-contact video method and non-contact laser method were employed to determine the natural frequency of Kunyu River footbridge.All the results of these three methods are close to 2.70 Hz,which are concordant with each other and hence credible.

冲积性弯曲河道造床过程及演变机制

冲积性弯曲河道独特的几何边界特征,使得弯曲河道的水沙运动特性和河床演变特性与其他类型河道显著不同。为模拟自然条件下的冲积性弯曲河道河床冲淤演变特性,采用自然模型法的理念在试验水槽中塑造出近似的弯曲河道,探究不同水沙条件对弯曲河道形成和发育过程的影响。试验表明:进口水沙循环周期长、来水来沙强度较小时,弯曲河道达到动态平衡状态所需的时间相对较短,河道形成稳定河宽也较小。弯曲河道在形成和发育过程中,河道的形态要素主要由水沙作用条件决定,在一定变化范围内,当水沙作用循环变换周期较短、来流流量较小、含沙量较大时,有利于形成弯曲度较大的河道;而当来流量较大、水位漫滩冲刷浅滩时,所塑造的弯曲河道会偏向于宽浅形断面形态。在河道弯曲程度和河道横断面形态的调整中,水沙作用变化对横断面形态塑造的作用相对较强。

湖南省自然灾害风险可接受程度研究

自然灾害是湖南省面临的主要灾害之一,确定自然灾害风险可接受程度对该省的可持续发展意义重大。通过分析湖南省2010~2020年因灾死亡人数与经济损失、总人口、GDP等数据,参照国内外相关研究,开展自然灾害风险可接受水平研究。取意愿系数β=0.01,确定个人生命可接受风险标准;使用人均GDP这一指标,量化个人可接受经济风险;根据最低合理可行准则,分别构建社会生命与经济风险可接受准则模型。结果表明:个人可接受和可容忍生命风险分别为10^(-6)/a和10^(-5)/a;个人可接受经济风险指数为0.01,即个人经济风险的可接受风险范围不超过人均GDP的1%;因灾死亡100人的概率大于10^(-9)、经济损失10亿元的概率大于10^(-2)都属于不可接受风险。研究结果可用于辅助湖南省自然灾害风险的评估、决策与管理,也为其他地区相关研究提供参考。

电子圆二色光谱图的模拟与软件开发

有机小分子化合物,尤其是天然产物具有复杂和多样的结构,且一般含有多个手性中心,确定其绝对构型一直是结构鉴定的难点之一。电子圆二色光谱(ECD)具有样品无损、曲线简洁等优势,是鉴定绝对构型的强有力的手段之一。利用密度泛函理论(DFT)和含时密度泛函理论(TDDFT)等量子化学理论以及计算机技术,对化合物的理论ECD计算模拟,与实验值对比确定绝对构型是目前主流技术。计算模拟流程如下:首先确定化合物的相对构型,其次运用构象搜索软件对化合物进行构象分析,然后对搜索得到的多个最低能量态构象(如能量阈值在2.0 kcal·mol^(-1)以内)进行几何优化和振动分析,将已经优化完成的优势构象投入ECD计算,计算ECD相关参数,得到电子激发能(eV)和转子强度(10^(-40) erg-esu-cm)等数据,最终根据数据进行多构象谱图拟合。该研究主要对ECD曲线的模拟方法、ECD计算结果的评价标准进行了全面总结。在此基础上,运用Python语言开发了一款自动化处理高斯ECD计算结果、模拟ECD曲线的软件,该软件能够对计算得到的输出文件进行定位,对于化合物几何优化和振动分析得到的输出文件,可以抓取各个构象的吉布斯自由能数据,并且依据此数据进行玻尔兹曼分布的加权,对于计算ECD相关性质的输出文件,可以抓取ECD计算相关的电子激发能和转子强度的数据,依据以上数据得到的ECD计算理论光谱图,能够进行实时模拟参数调节并与实测曲线对比,方便了计算ECD的数据处理和结果评价。

洞庭湖生态水位与生态需水量研究

为保护洞庭湖生态系统,基于洞庭湖鹿角、杨柳潭和南咀水文站1961~2020年逐日水位监测数据,开展洞庭湖生态水位和生态需水量的研究。运用天然水位资料法、湖泊形态法、生物空间最小需求法、年保证率法、最低年平均水位法和频率曲线法等6种分析方法计算得出洞庭湖生态水位,利用功能法计算得出洞庭湖生态需水量。结果表明:(1)洞庭湖东、南、西3个湖区最低生态水位分别为24.20,27.78,29.42 m,适宜生态水位分别为25.80,29.07,30.08 m。(2)洞庭湖东、南、西3个湖区最低生态需水量分别为6.31亿,10.02亿,3.83亿m^(3),适宜生态需水量分别为12.66亿,13.99亿,4.61亿m^(3),洞庭湖最低与适宜生态需水量分别为20.16亿m^(3)和31.26亿m^(3)。研究成果可为洞庭湖区域水资源合理配置、湖区生态系统健康运转和洞庭湖治理与保护提供参考依据。

水沙变化条件下不同边界弯曲河道演变特征研究

弯曲河道具有迂回曲折的外形和蜿蜒蠕动的动态特征,其形成、发展和演变是受多种因素综合影响的复杂过程。为研究水沙变化条件下弯曲河流的河道演变特征,采用自然模型法在室内水槽中塑造出相对自然的弯曲河道,设置有、无护岸措施两种工况进行模型试验。结果表明:在有护岸措施条件下,河道纵剖面上游段冲刷下切、下游段变化不大,河道整体比降呈减小趋势,河道深泓弯曲度减小,其演变响应特性对含沙量的变化更敏感;在无护岸措施条件下,河道滩槽演变调整作用较强,纵剖面呈整体式下切,且下游段纵剖面下切幅度较上游段大,河道深泓弯曲度逐渐增大,其演变响应特性对流量的变化更敏感。弯曲河道发生演变的实质是变化的水沙条件与河道形态调整之间相互适应的过程,演变的最终趋势是河道的形态结构与水沙条件达到相互协调的平衡状态。

低计数特征的自然伽马能谱测井数据滤波方法研究

岩石天然放射性强度较弱,自然伽马能谱测井所测得的能谱计数较低,低计数特征使得地层衰变随机误差影响被放大,造成测量能谱质量差、测井曲线统计噪声大的情况。该文通过对比多种能谱滤波结果,使单深度点能谱最大程度还原准确能谱信息;利用曲线形态,针对求解的U、Th、K含量曲线进行深度域的滤波处理,综合从高噪声、低计数的数据中准确提取地层信息;利用中国石油集团测井有限公司的过钻具自然伽马能谱仪器的实测数据验证该方法的有效性。结果表明:对于计数低、谱形差的自然伽马能谱,高斯滤波、卷积滤波效果相对较好,该文提出结合这2种方法的复合滤波可以准确地还原出高保真的能谱形状;深度域的滤波,卡尔曼滤波相对自适应滤波方法有一定优势;依次经过能谱滤波和深度滤波后,结果的准确性和重复性有了大幅提升。该文所介绍的针对低计数特征的自然伽马能谱测井滤波方法,可以有效提高U、Th、K的测量精度。

孕晚期血清松弛素、分娩方式对初产妇产后早期盆底功能障碍影响的交互作用分析

目的分析孕晚期血清松弛素、分娩方式对初产妇产后早期盆底功能障碍(PFD)影响的交互作用。方法选取2019年3月—2022年12月收治的203例初产妇,根据产后42 d有无PFD分为PFD组(43例)和无PFD组(160例)2组,比较2组基线资料、孕晚期血清松弛素;采用Logistic回归分析探讨初产妇产后早期PFD的相关危险因素,交互作用系数γ、比值比(OR)分析孕晚期血清松弛素、分娩方式对初产妇产后早期PFD影响的交互作用,受试者工作特征曲线(ROC)分析孕晚期血清松弛素、分娩方式及二者联合预测初产妇产后早期PFD的价值。结果PFD组自然分娩产妇占比高于无PFD组(P<0.05)。PFD组孕晚期血清松弛素为(657.33±178.56)ng/L高于无PFD组(460.81±142.35)ng/L(P<0.05)。Logistic回归分析显示,自然分娩、血清松弛素均是初产妇产后早期PFD的相关危险因素(P<0.01)。自然分娩产妇血清松弛素高于剖宫产初产妇(P<0.05)。单独孕晚期血清松弛素所致OR为132.000,单独自然分娩所致OR为6.919,孕晚期血清松弛素与自然分娩联合所致OR为198.000,交互作用OR小于单独孕晚期血清松弛素与单独自然分娩OR的乘积,为次相乘模型,孕晚期血清松弛素对自然分娩的效应具有正向交互作用。孕晚期血清松弛素联合分娩方式预测PFD的ROC曲线下面积大于单独血清松弛素、分娩方式(P<0.05),预测敏感度为86.05%,特异度为86.87%。结论孕晚期血清松弛素、分娩方式对初产妇产后早期PFD的影响符合次相乘模型,孕晚期血清松弛素对自然分娩的效应具有正向交互作用,联合孕晚期血清松弛素、分娩方式可提高对初产妇产后早期PFD的预测能力。

天然气水合物生成要素影响研究

研究水合物生成影响因素有助于预测管道中的水合物生成风险,并制定相应的管道管理策略。采用PVTsim软件研究了不同组分及抑制剂对水合物生成过程的影响规律。结果表明,氮气和二氧化碳对天然气水合物生成的影响很小,可忽略不计。硫化氢对天然气水合物形成具有促进作用,增大了现场水合物堵塞事故发生的风险,对于高含硫天然气的生产处理,要注意节流、压缩等工艺部位的运行情况。随着甲醇和乙二醇质量分数占比增大,天然气水合物临界形成压力升高,水合物形成的工况范围明显缩小,可有效抑制天然气水合物形成。

准噶尔盆地玛中地区砂砾岩储层特征及非线性反演方法的应用

随着近年来在玛湖凹陷斜坡区下三叠统百口泉组砂砾岩储层中发现越来越多的油气藏,有关砂砾岩优质储层的预测技术也受到很多学者的关注。文章分析了研究区砂砾岩储层的岩石铸体薄片、矿物成分分析和氦气孔隙度测量结果,发现塑性碎屑含量对该类岩石的物性有较大的影响,随着岩石中塑性碎屑含量的增加,岩石的孔隙度和渗透率都会降低。同时,利用测井数据开展了优质储层的敏感参数优选,优质储层在常规测井曲线上表现为低自然伽马和高电阻率的特征,并构建了可以表征塑性碎屑含量的特征曲线,该曲线可以有效识别研究区的优质储层。利用人工智能反演技术在研究区开展了基于该特征曲线的非线性反演,结合敏感曲线交会分析认为,当特征曲线小于0.3的地区是研究区优质砂砾岩储层的发育区。

潍坊地区地层频散特征与分析研究

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