Stability behavior of the Lanxi ancient flood control levee after reinforcement with upside-down hanging wells and grouting curtain

The stability of the ancient flood control levees is mainly influenced by water level fluctuations, groundwater concentration and rainfalls. This paper takes the Lanxi ancient levee as a research object to study the evolution laws of its seepage, displacement and stability before and after reinforcement with the upside-down hanging wells and grouting curtain through numerical simulation methods combined with experiments and observations. The study results indicate that the filled soil is less affected by water level fluctuations and groundwater concentration after reinforcement. A high groundwater level is detrimental to the levee's long-term stability, and the drainage issues need to be fully considered. The deformation of the reinforced levee is effectively controlled since the fill deformation is mainly borne by the upside-down hanging wells. The safety factors of the levee before reinforcement vary significantly with the water level. The minimum value of the safety factors is 0.886 during the water level decreasing period, indicating a very high risk of the instability. While it reached 1.478 after reinforcement, the stability of the ancient levee is improved by a large margin.

Effects of dust controls on respirable coal mine dust composition and particle sizes:case studies on auxiliary scrubbers and canopy air curtain

Control of dust in underground coal mines is critical for mitigating both safety and health hazards.For decades,the National Institute of Occupational Safety and Health(NIOSH)has led research to evaluate the effectiveness of various dust control technologies in coal mines.Recent studies have included the evaluation of auxiliary scrubbers to reduce respirable dust downstream of active mining and the use of canopy air curtains(CACs)to reduce respirable dust in key operator positions.While detailed dust characterization was not a focus of such studies,this is a growing area of interest.Using preserved filter samples from three previous NIOSH studies,the current work aims to explore the effect of two different scrubbers(one wet and one dry)and a roof bolter CAC on respirable dust composition and particle size distribution.For this,the preserved filter samples were analyzed by thermogravimetric analysis and/or scanning electron microscopy with energy dispersive X-ray.Results indicate that dust composition was not appreciably affected by either scrubber or the CAC.However,the wet scrubber and CAC appeared to decrease the overall particle size distribution.Such an effect of the dry scrubber was not consistently observed,but this is probably related to the particular sampling location downstream of the scrubber which allowed for significant mixing of the scrubber exhaust and other return air.Aside from the insights gained with respect to the three specific dust control case studies revisited here,this work demonstrates the value of preserved dust samples for follow-up investigation more broadly.

Research Progress of Aromatic Bed Curtains for Aiding Sleep Based on Lavender Microcapsule Technique

In this paper, the preparation technique of lavender essential oil microcapsules and the construction method of aromatic textiles were expounded, and the research status of bed curtains and lavender microcapsules at home and abroad was analyzed and studied from the perspective of application in textiles. The application of lavender essential oil to bed curtains through the microcapsule technique was put forward to allow lavender essential oil to play its role of helping sleep in bed curtains. This paper expounded the material selection and preparation technique of lavender microcapsule agents, and put forward the preparation method of microcapsules with mixed solutions of pure Chinese medicine extracts and natural essences as core material and high-viscosity epoxy resin as wall materials. The post-processing techniques and the spray ironing method for clothing were studied and developed, and these techniques and methods were applied to bed curtains, and good results were obtained.

Cut-off value of glycated hemoglobin A1c for detecting diabetic retinopathy in the Chinese population

BACKGROUND Glycated hemoglobin A1c(HbA1c)is considered the most suitable for diabetes mellitus diagnosis due to its accuracy and convenience.However,the effect of HbA1c on diabetic retinopathy(DR)in the Han and Korean populations in Jilin,China,remains inconclusive.AIM To determine the best cut-off of HbA1c for diagnosing DR among the Chinese.METHODS This cross-sectional study included 1933 participants from the Yanbian area of Jilin Province,China.Trained investigators employed a questionnaire-based survey,physical examination,laboratory tests,and fundus photography for the investigation.The best cut-off value for HbA1c was established via the receiver operating characteristic curve.The factors associated with HbA1c-associated risk factors were determined via linear regression.RESULTS The analysis included 887 eligible Chinese Han and Korean participants,591 of whom were assigned randomly to the training set and 296 to the validation set.The prevalence of DR was 3.27% in the total population.HbA1c of 6.2% was the best cut-off value in the training set,while it was 5.9% in the validation set.In both Chinese Han and Korean populations,an HbA1c level of 6.2% was the best cut-off value.The optimal cut-off values of fasting blood glucose(FBG)≥7 mmol/L and<7 mmol/L were 8.1% and 6.2% respectively in Han populations,while those in Korean populations were 6.9%and 5.3%,respectively.Age,body mass index,and FBG were determined as the risk factors impacting HbA1c levels.CONCLUSION HbA1c may serve as a useful diagnostic indicator for DR.An HbA1c level of 6.2% may be an appropriate cut-off value for DR detection in the Chinese population.

Innovative Techniques Unveiled in Advanced Sheet Pile Curtain Design

This thorough review explores the complexities of geotechnical engineering, emphasizing soil-structure interaction (SSI). The investigation centers on sheet pile design, examining two primary methodologies: Limit Equilibrium Methods (LEM) and Soil-Structure Interaction Methods (SSIM). While LEM methods, grounded in classical principles, provide valuable insights for preliminary design considerations, they may encounter limitations in addressing real-world complexities. In contrast, SSIM methods, including the SSI-SR approach, introduce precision and depth to the field. By employing numerical techniques such as Finite Element (FE) and Finite Difference (FD) analyses, these methods enable engineers to navigate the dynamics of soil-structure interaction. The exploration extends to SSI-FE, highlighting its essential role in civil engineering. By integrating Finite Element analysis with considerations for soil-structure interaction, the SSI-FE method offers a holistic understanding of how structures dynamically interact with their geotechnical environment. Throughout this exploration, the study dissects critical components governing SSIM methods, providing engineers with tools to navigate the intricate landscape of geotechnical design. The study acknowledges the significance of the Mohr-Coulomb constitutive model while recognizing its limitations, and guiding practitioners toward informed decision-making in geotechnical analyses. As the article concludes, it underscores the importance of continuous learning and innovation for the future of geotechnical engineering. With advancing technology and an evolving understanding of soil-structure interaction, the study remains committed to ensuring the safety, stability, and efficiency of geotechnical structures through cutting-edge design and analysis techniques.

Subseasonal Prediction of Early-summer Northeast Asian Cut-off Lows by BCC-CSM2-HR and GloSea5

Northeast Asian cut-off lows are crucial cyclonic systems that can bring temperature and precipitation extremes over large areas.Skillful subseasonal forecasting of Northeast Asian cut-off lows is of great importance.Using two dynamical forecasting systems,one from the Beijing Climate Center(BCC-CSM2-HR)and the other from the Met Office(GloSea5),this study assesses simulation ability and subseasonal prediction skill for early-summer Northeast Asian cut-off lows.Both models are shown to have good ability in representing the spatial structure of cut-off lows,but they underestimate the intensity.The skillful prediction time scales for cut-off low intensity are about 10.2 days for BCC-CSM2-HR and 11.4 days for GloSea5 in advance.Further examination shows that both models can essentially capture the initial Rossby wave train,rapid growth and decay processes responsible for the evolution of cut-off lows,but the models show weaker amplitudes for the three-stage processes.The underestimated simulated strength of both the Eurasian midlatitude and East Asian subtropical jets may lead to the weaker local eddy-mean flow interaction responsible for the cut-off low evolution.

A new DRIE cut-off material in SOG MEMS process

The silicon on glasses process is a common preparation method of micro-electro-mechanical system inertial devices,which can realize the processing of thick silicon structures.This paper proposes that indium tin oxides(ITO)film can serve as a deep silicon etching cut-off layer because ITO is less damaged under the attack of fluoride ions.ITO has good electrical conductivity and can absorb fluoride ions for silicon etching and reduce the reflection of fluoride ions,thus reducing the foot effect.The removal and release of ITO use an acidic solution,which does not damage the silicon structure.Therefore,the selection of the sacrificial layer has an excellent effect in maintaining the shape of the MEMS structure.This method is used in the preparation of MEMS accelerometers with a structure thickness of 100μm and a feature size of 4μm.The over-etching of the bottom of the silicon structure caused by the foot effect is negligible.The difference between the simulated value and the designed value of the device characteristic frequency is less than 5%.This indicates that ITO is an excellent deep silicon etch stopper material.

Multifractal estimation of NMR T_(2) cut-off value in low-permeability rocks considering spectrum kurtosis: SMOTE-based oversampling integrated with machine learning

The transverse relaxation time (T_(2)) cut-off value plays a crucial role in nuclear magnetic resonance for identifying movable and immovable boundaries, evaluating permeability, and determining fluid saturation in petrophysical characterization of petroleum reservoirs. This study focuses on the systematic analysis of T_(2) spectra and T_(2) cut-off values in low-permeability reservoir rocks. Analysis of 36 low-permeability cores revealed a wide distribution of T_(2) cut-off values, ranging from 7 to 50 ms. Additionally, the T_(2) spectra exhibited multimodal characteristics, predominantly displaying unimodal and bimodal morphologies, with a few trimodal morphologies, which are inherently influenced by different pore types. Fractal characteristics of pore structure in fully water-saturated cores were captured through the T_(2) spectra, which were calculated using generalized fractal and multifractal theories. To augment the limited dataset of 36 cores, the synthetic minority oversampling technique was employed. Models for evaluating the T_(2) cut-off value were separately developed based on the classified T_(2) spectra, considering the number of peaks, and utilizing generalized fractal dimensions at the weight <0 and the singular intensity range. The underlying mechanism is that the singular intensity and generalized fractal dimensions at the weight <0 can detect the T_(2) spectral shift. However, the T_(2) spectral shift has negligible effects on multifractal spectrum function difference and generalized fractal dimensions at the weight >0. The primary objective of this work is to gain insights into the relationship between the kurtosis of the T_(2) spectrum and pore types, as well as to predict the T_(2) cut-off value of low-permeability rocks using machine learning and data augmentation techniques.

Lipoprotein (a) Cut-Off in Chronic Kidney Disease Patients with a History of Cardiovascular Disease in Center Hospital University Souro SANOU, Burkina Faso

Patients living with chronic kidney disease (CKD) are at high risk of cardiovascular events. Our aim in this study was to assess the cut-off value for lipoprotein (a) (Lp(a)) in CKD patients with a history of cardiovascular disease (CVD). This was a cross-sectional study. Variables including age, sex, history of CVD, body mass index and CKD stage, were collected during CKD patient’s first admission in the nephrology dialysis department. Blood samples were collected for quantitative determination of Lp(a) by immunoturbidimetric method. They were divided into two groups: CKD patients without history of CVD and CKD patients with history of CVD. Fisher’s exact test was used to assess associations with a significance level of 0.05%. Area under the curve (AUC) and new cut-off value for Lp(a) were identified by drawing Receiver Operating Characteristic (ROC) curve. A total of seventy CKD patients with median age of 43 years [minimum-maximum = 15 - 78 years] were included. Patients with history of CVD were 65.71% (46/70). New Lp(a) cut-off point in CKD patients with history of CVD was 66.50 nmol/L [sensitivity, 87.00%;specificity, 58.30%;AUC = 0.727;p = 0.000]. ROC curve demonstrated good performance of Lp(a) to screen CKD patients with history of CVD. Further research is needed to determine an LPA gene polymorphism’s contribution to increasing risk for CVD at each kidney disease stage.

光伏幕墙辅助双源热泵系统在不同地区的多目标优化配置

为克服单一可再生能源应用的局限性,提出一种光伏幕墙辅助双源热泵系统。利用TRNSYS建立仿真模型,以系统能耗和生命周期成本为目标函数,采用非支配排序遗传算法(NSGA-Ⅱ),对不同地区系统配置规模进行多目标优化设计,并利用加权和法确定均衡解。结果表明:哈尔滨、长春、沈阳3个地区优化后的系统运行能耗比优化前分别增加5.9%、5.0%和3.9%,生命周期成本降低13.6%、17.1%和12.9%;与单目标优化相比,多目标优化在兼顾性能的前提下能明显降低生命周期成本,具有明显的优势。

盾构隧道下穿高铁路基变形影响规律及加固优化研究

为研究盾构隧道下穿高铁路基施工时对路基的影响规律,探究在隧道开挖过程中运用不同加固措施对既有高铁路基的影响程度。以西安市某地铁工程为依托,利用室内模型试验对比分析盾构隧道下穿高铁CFG桩复合路基过程中,无加固、超前管幕工法加固与地表袖阀管注浆加固3种隧道施工条件下,地表沉降值和沉降槽的空间分布规律;采用数值模拟分析验证超前管幕工法加固工况下盾构隧道下穿时,高铁路基、道床的位移变化规律。室内模型试验结果表明:盾构隧道施工中采用管幕工法加固后复合地基正上方的地表沉降最大值减小28.6%,采用袖阀管注浆加固后减小18.0%,并且采用两种加固措施后的CFG桩最大附加轴力均减小20%以上。因此,在隧道掘进过程中采用一定加固措施,可改善围岩稳定性,其中管幕工法加固效果更为显著。数值模拟分析表明:采取管幕工法加固施工与不采取加固措施相比,路基最大沉降量减少33.78%,道床最大沉降量减少45.08%。因此,管幕工法加固能够有效减小对既有高铁路基的影响。

某儿童医院病床隔帘污染情况调查与分析

目的:了解某儿童医院病床隔帘清洗后使用不同时间的污染情况,为制定隔帘清洗频率提供依据。方法:采用分层随机抽样法随机抽取急诊科及普通病区7个科室的隔帘标本,分别于清洗后立即、使用1周、使用1~5个月分7次对隔帘进行采样,并记录菌落数。结果:隔帘清洗后使用不同时间、不同科室、不同病区的污染率差异均有统计学意义(P<0.05),普通病区的隔帘污染率显著高于急诊科;内科隔帘的菌落数最多,急诊科最少。结论:清洗后的病床隔帘在使用1周后就有不同程度的污染,使用时间越长,污染越严重,应根据污染情况对隔帘定期清洗,对于污染较为严重的科室应增加隔帘清洗频次。

排烟口朝向与挡烟垂壁对地铁站台排烟效果的影响

为提高地铁站台的排烟效果,采用数值模拟方法,对地铁站不同排烟口朝向的机械排烟系统排烟效果进行分析,并进一步对比挡烟垂壁高度对排烟效果影响。研究结果表明:排烟口朝向不是影响烟气控制效果的主要因素,顶面排烟的排烟效果最佳,其总排热量是底面排烟的1.32倍,总排烟量是底面排烟的1.19倍;并通过分析3种排烟系统吸入烟气的方式和温度解释排烟效果产生差异的原因;增设挡烟垂壁可起到良好的控烟效果,当挡烟垂壁下沿高度分别降低至3.5,3.0,2.5 m时,顶面排烟,侧面排烟和底面排烟能够将烟气控制在起火防烟分区;挡烟垂壁与机械排烟系统具有协同作用,设置挡烟垂壁可以有效改善排烟效果,因此建议采用排烟管道顶面开口的排烟方式,并可通过设置一定高度的挡烟垂壁提高现有排烟系统的排烟效果。研究结果可为地铁站台排烟系统设计提供参考与借鉴。

基于帷幕注浆理论的瓦斯抽采钻孔封孔技术研究及应用

瓦斯抽采钻孔封孔效果直接决定了矿井瓦斯治理效果,是高瓦斯突出矿井安全生产的重要保障。为解决主焦煤矿2301工作面瓦斯抽采底板巷围岩裂隙发育、钻孔封孔难题,基于矿井防治水经验提出瓦斯抽采钻孔帷幕注浆封孔技术。首先通过数值模拟和钻孔窥视法确定了2301工作面底板巷松动圈范围为0.8~1.7 m。然后根据矿井注浆扩散半径设计施工帷幕注浆钻孔,利用巷道围岩帷幕注浆技术提高瓦斯抽采钻孔的封孔效果。经过现场应用取得了良好效果,71.1%的瓦斯抽采浓度较原抽采浓度得到大幅提高,对类似地质条件的瓦斯抽采岩巷钻孔封孔具有很好的指导意义。

气幕均匀性影响因素及其隔尘效果研究

近年来,空气幕作为一种有效隔绝易于扩散粉尘的装置,被频繁地用于矿山、隧道施工过程中产尘较多的场所,而均匀的气幕会带来更佳的隔尘效果。运用Fluent数值模拟结合相似实验的方法分析了气幕直径和气幕内部风道结构变化对气幕均匀性的影响,并将设计后可以均匀供风的气幕安装在实际施工隧道模型中模拟分析其隔尘效果。结果表明:直径增加,供风装置内气流轴向惯性力降低,有充足的时间改变流出方向,气幕装置轴向静压更加均匀,形成气幕更加均匀,但直径的变化对气幕均匀性的影响不是线性变化的,即存在一个临界直径使直径继续增加对均匀性的改善效果不明显,并且气幕临近直径的范围会随供风装置长度的增加而增加;在长度1 m、临界直径180 mm的气幕装置基础上,依据风道设计原理安装计算出的弧高为149.9 mm的楔形扇面阻体后,气幕装置内部平均压力梯度从38.4 Pa/m降低到19.3 Pa/m,出口风速均匀度从87.6%提高到93.2%,气幕均匀性显著提升;安装气幕后,隔尘区域内回弹的含尘气流被阻隔,区域内风流变得混乱复杂、涡流增加,粉尘停留时间增加,相对较大的粉尘颗粒有更长的时间沉降。整个隔尘区域粉尘浓度明显升高,气幕隔尘效果显著。

露天矿地下水控制技术及对边坡稳定性的影响

我国富水露天矿多且涌水量大,若矿山地下水或边坡处治不当,将面临着“水患难止、边坡难固、有矿难采”的窘境。为解决露天矿遇到的水患和边坡失稳的问题,基于我国露天矿先后发展的垂直疏水孔、水平疏水孔、坑下大口径疏水孔和井群疏水等抽排方式,坑底泄水巷、基坑降水和辐射井疏干等疏放方式以及钻孔注浆帷幕、地下混凝土连续墙帷幕、钻孔咬合桩帷幕、防渗膜帷幕等截水帷幕和地层回灌水帷幕等多种地下水控制技术;开展了不同露天矿地下水控制技术对地下水位、端帮边坡岩土体力学性质变化、坡体应力变化和边坡稳定性系数影响的研究,分析了截水帷幕作用下地下水位抬升与边坡稳定性变化规律。研究结果表明:通过抽排方式、疏放方式将露天矿山地下水疏干或疏降可有效降低地下水位,减少边坡岩土体含水率,提高边坡岩土体黏聚力和内摩擦角,减小坡体的静水压力和水平推力,整体提高边坡稳定性系数,但大量疏排地下水又造成水资源的浪费和污染;截水帷幕能够解决疏排降水造成的地下水位下降幅度太大、疏排水量巨大、水资源浪费和污染的问题;在截水帷幕作用下,露天矿截水帷幕外侧水位不断抬升,引起截水帷幕外侧边坡岩土体含水率增加、黏聚力和内摩擦角减小、坡体的静水压力和水平推力增大,而截水帷幕内侧边坡岩土体含水率减小、黏聚力和内摩擦角增大、坡体的静水压力和水平推力减小,从而引起露天矿边坡稳定性系数略有降低;通过截水帷幕可以控制露天矿边坡地下水位,进而保持边坡岩土体力学参数在合理范围,维持边坡稳定性系数在安全区间,实现露天矿地下水资源保护与边坡安全的平衡。

建筑幕墙装饰装修工程施工探讨

在当前建筑工程及技术水平高度发展的背景下,大众对各种建筑的功能性、装饰性与实用性的需求有所增高。这一点在建筑幕墙装饰装修工程中体现得十分明显。对此,通过探讨建筑幕墙工程施工中影响工程质量、工程效率的关键因素,总结能够用于建筑幕墙装饰装修工程的关键技术,提高工程建设效果的有效方法。

附壁旋流风幕集尘系统数值模拟与试验研究

大型设备工作时产生的粉尘浓度过高、粉尘扩散等问题,会影响工作人员的身体健康,甚至可能造成“粉尘爆炸”等安全问题。基于此现状提出了一种新型风幕集尘系统并介绍了其构造及应用。为了使系统的集尘效果更好,采用计算流体力学FLUENT软件进行数值模拟分析并对风幕集尘系统的工作参数进行了试验研究,得到最佳的设备工作参数及风幕的集尘效率。结果表明:(1)附壁旋流集尘风幕系统可形成稳定的螺旋风流场,大部分粉尘可以控制在风幕内侧,达到良好的集尘效果;(2)附壁旋流风幕集尘系统的射流腔条缝口的喷射角度对风幕形成效果影响最明显,风幕闭合性会随着射流腔工作角度变化而变化;(3)当射流腔条缝口角度为45°、风幕入口速度为15~25 m/s时,风幕的闭合性最好;(4)风幕的入口速度过大或过小都会使风幕的集尘效果下降;(5)吸尘盘的负压区域与风幕交界处会产生微弱湍流,但对风幕整体闭合性影响较小;(6)模拟与试验结果吻合,验证了新型附壁旋流集尘风幕技术的有效性。

基于物联网的温室大棚卷帘智能控制系统设计

随着农业技术的快速发展,智能化、自动化的温室大棚管理系统成为现代农业的重要发展方向。卷帘机控制系统作为温室大棚管理的关键部分,对于调节大棚内的光照、温度和湿度等环境因素、优化作物生长条件起着至关重要的作用。该文设计一套基于物联网技术的卷帘智能控制系统,该系统实时监测温室内部的环境参数,根据控制逻辑自动控制卷帘升降,从而提高温室大棚的管理效率,有助于促进作物的生长,实现农业的可持续发展,推动农业强国的建设进程。

岩溶凹陷式露天矿山大流量涌水治理技术

我国岩溶地质分布广泛,岩溶突涌水已成为石灰石矿山安全生产的巨大灾害与挑战。以广西某岩溶凹陷式露天矿山大流量涌水为研究对象,针对该矿山地质条件复杂、集中涌水量大、流速高等特点,利用岩溶发育特征、资料分析与地球物理探查等方法初步圈定矿山径流带区域;进一步通过钻探、跨孔CT和示踪联通试验等精准查找到矿山Y01特大涌水点岩溶管道的具体位置,在此基础上研究并实施了矿山涌水治理技术与工艺。研究表明:(1)针对复杂岩溶凹陷式露天矿山大流量、高流速的涌水特征,提出并实施了“非连续帷幕截流+关键通道探查与封堵+止浆垫控流降速”的岩溶矿山涌水综合治理体系。依据岩溶发育的不均匀性,提出了非连续帷幕封堵裂隙型涌水区域的思想;对大流量岩溶管道型集中涌水设计采用止浆垫控流装置,通过控流能有效降低关键过水通道内水流速度,为注浆材料的有效留存沉积和工程的成功封堵提供了重要条件。(2)关键孔联合注浆工艺是岩溶管道型涌水成功封堵的保证,关键孔是指直接揭露岩溶涌水管道或与涌水管道联通性极强并对注浆堵水起主要作用的钻孔。针对矿山Y01岩溶管道型特大涌水精准查找到2个关键孔,均在矿坑南部:一个是距涌水点直线距离约50 m的近距离钻孔(以下简称“近孔”),另一个是距涌水点直线距离约150 m的远距离钻孔(以下简称“远孔”)。现场采用近孔、远孔2个关键孔联合注浆工艺:近孔以粗骨料和自主研发的可控凝结新型材料进行注浆,远孔仅注水泥浆液;近孔粗骨料和新型材料既能降低管道内的水流速度为远孔浆液起到更好的留存沉积作用,又能作为封堵材料起到增强的功能,远孔因其离涌水点距离长、辐射范围广、浆液扩散充分而能确保封堵长度和效果。近孔、远孔协同配合同步注浆是封堵管道型大流量涌水的有效组合工艺。(3)涌水口止浆垫控流降速装置的合理有效调控,配合关键孔联合注浆工艺的同步实施,进一步确保了注浆浆液的有效快速留存和沉积,是岩溶地区封堵管道型大流量涌水的创新性技术和方法。项目实施后,彻底封堵矿坑内集中涌水量达7.12万m^(3)/d的Y01特大涌水点,实现总减水量8.43万m3/d(含非连续帷幕注浆封堵),保证了矿山的正常安全开采,大幅降低了抽排水费用,同时保护了周边环境和地下水资源,具有显著的经济效益和社会效益。研究成果可为我国矿山涌水灾害治理提供理论价值和经验借鉴。