Impact resistance performance and optimization of the sand-EPE composite cushion in rock sheds

Rock sheds are widely used to prevent rockfall disasters along roads in mountainous areas.To improve the capacity of rock sheds for resisting rockfall impact,a sand and expandable polyethylene(EPE)composite cushion was proposed.A series of model experiments of rockfall impact on rock sheds were conducted,and the buried depth of the EPE foam board in the sand layer was considered.The impact load and dynamic response of the rock shed were investigated.The results show that the maximum impact load and dynamic response of the rock shed roof are all significantly less than those of the sand cushion.Moreover,as the distance between the EPE foam board and rock shed roof decreases,the maximum rockfall impact force and impact pressure gradually decrease,and the maximum displacement,acceleration and strain of the rock shed first decrease and then change little.In addition,the vibration acceleration and vertical displacement of the rock shed roof decrease from the centre to the edge and decrease faster along the longitudinal direction than that along the transverse direction.In conclusion,the buffering effect of the sand-EPE composite cushion is better than that of the pure sand cushion,and the EPE foam board at a depth of 1/3 the thickness of the sand layer is appropriate.

PbrARF4 contributes to calyx shedding of fruitlets in ‘Dangshan Suli’ pear by partly regulating the expression of abscission genes

Fruitlet calyx shedding in pear plants is apparently regulated via numerous pathways that involve both environmental triggers and phytohormones cues such as auxin. In this study, we found at 10 days after full bloom (DAFB) higher levels of indoleacetic acid (IAA) and tryptophan (Trp) in calyx persistence fruitlet (CPF) than calyx shedding fruitlet (CSF) ofDanshan Suli’ pear (Pyrus bretschneideri Rhed.). Consisting with this, the activity of indolealdehyde oxidase (IAAIdO), which promotes IAA synthesis, was remarkably increased, and that of peroxidase(POD), which degrades IAA, dropped markedly in CPF but not in CSF. Further, qRT-PCR results revealed that most of 31 PbrARFs (encoding auxin response factors) in Pyrus bretschneideri were highly expressed in CPF, whereas PbrARF4, PbrARF24 and PbrARF26 were significantly downregulated in CPF vis-a-vis CSF. Phylogenetic analysis revealed that 6 PbrARFs clustered in the group III, where PbrARF4 showed the closest affinity with AtARF1 that promotes organ abscission, indicating a putative role of PbrARF4 in mediating the process of calyx shedding in pear. In fact, the ectopic overexpression of PbrARF4 in Solanum lycopersicum resulted in an earlier-formed and deeper abscission layer (AL) in the transgenic plants, whose calyxes were more prone to wilt at the mature red stage (MR) compared with the control plants (wild-type). More importantly, expression levels of the abscission genes SILS and Sl Cel2 in transgenic plants overexpressing PbrARF4 were significantly upregulated in comparation with the WT, whereas those of Sl BI and Sl TAPG2 were considerably inhibited. Further, PbrJOINTLESS and PbrIDA,the two genes related to calyx shedding in pear, were up-regulated more in CSF than CPF. The findings contribute to a better understanding of PbrARFs involved in fruitlet calyx shedding of pear, which could prove beneficial to improving the quality of pear fruit.

Coupled DEM-FDM analyses of the effects of falling rock’s shape and impact angle on response of granular cushion and rock shed

Rock shed is an effective protection measure against rockfall.To investigate the influences of falling rock’s shape and impact angle on the impact effect of the cushioned rock shed,a modeling approach for a rock shed with a cushion layer using PFC-FLAC.The granular cushion is modeled as an aggregate of discrete non-cohesion particles,while the concrete plate and the beam are modeled as zones.The falling rock with different sphericities and impact angles is modeled as a rigid assembly.The numerical model is validated by comparing the simulation results with experimental and numerical results from previous literature.This model is applied to analyze the effects of rock shape and impact angle on the dynamic interaction effects between falling rock and cushioned rock shed,including the impact force,transmitted bottom force,penetration depth,and plate deflection.The numerical results show that the variation in the falling rock’s shape has different effects on the falling rock with different impact angles.These findings could support rock shed design by revealing the limitations of the assumptions in the past research,which may result in unsafe rock sheds for some rockfall cases.

Load Profile Analysis for Mitigating Load-Shedding in Central Africa: Case of Kinshasa

Load shedding is a major problem in Central Africa, with negative consequences for both society and the economy. However, load profile analysis can help to alleviate this problem by providing valuable information about consumer demand. This information can be used by power utilities to forecast and reduce power cuts effectively. In this study, the direct method was used to create load profiles for residential feeders in Kinshasa. The results showed that load shedding on weekends results in significant financial losses and changes in people’s behavior. In November 2022 alone, load shedding was responsible for $ 23,4 08,984 and $ 2 80,9 07,808 for all year in losses. The study also found that the SAIDI index for the southern direction of the Kinshasa distribution network was 122.49 hours per feeder, on average. This means that each feeder experienced an average of 5 days of load shedding in November 2022. The SAIFI index was 20 interruptions per feeder, on average, and the CAIDI index was 6 hours, on average, before power was restored. This study also proposes ten strategies for the reduction of load shedding in the Kinshasa and central Africa power distribution network and for the improvement of its reliability, namely: Improved load forecasting, Improvement of the grid infrastructure, Scheduling of load shedding, Demand management programs, Energy efficiency initiatives, Distributed Generation, Automation and Monitoring of the Grid, Education and engagement of the consumer, Policy and regulatory assistance, and Updated load profile analysis.

Modeling ash deposition and shedding during oxy-combustion of coal/rice husk blends at 70%inlet O_(2)

Co-firing rice husk(RH)and coal with carbon capture using oxy-combustion presents a net carbon negative energy produc-tion opportunity.In addition,the high fusion temperature of the non-sticky,silica rich,RH can mitigate ash deposition as well as promote shedding of deposits.To identify the optimum operating conditions,fuel particle sizes,and blend ratios that minimize ash deposition,a Computational Fluid Dynamic methodology with add-on ash deposition and shedding models were employed to predict outer ash deposition and shedding rates during co-combustion of coal/RH in AIR and O2/CO_(2)(70/30 vol%,OXY70)oxidizer compositions.After ensuring that the fly-ash particle size distributions and particle Stokes numbers near the deposition surface were accurately represented(to model impaction),appropriate models for coal ash and RH ash viscosities that were accurate in the temperature region(1200-1300 K)of interest in this study were identified.A particle viscosity and kinetic energy(PKE)based capture criterion was enforced to model the ash capture.An erosion/shed-ding criterion that takes the deposit melt fraction and the energy consumed during particle impact into account was also implemented.Deposition rate predictions as well as the deposition rate enhancement(OXY70/AIR)were in good agreement with measured values.While the OXY70 scenario was associated with a significant reduction(60%-70%)in flue gas velocities,it also resulted in larger fly-ash particles.As a result,the PKE distributions of the erosive RH ash were similar in both scenarios and resulted in similar shedding rates.

Discussion on the Main Reasons for a Large Number of Père David s Deer ( Elaphurus davidianus ) with Abnormal Antler Shedding

[Objectives]This study was conducted to find out the causes of abnormal antler shedding in Père David s deer(Elaphurus davidianus).[Methods]Abnormally-shed antlers were compared with normally-shed antlers in terms of light condition,antler development and bone nutritional status during the abnormal shedding season in the growth area of Père David s deer.[Results]Abnormally-shed antlers had no significant differences in the development of shed antlers,or even in the overall composition of antlers,from those of normal Père David s deer.[Conclusions]Insufficient light was the main cause of abnormal antler shedding in Père David s deer.

Energy Efficiency in Periods of Load Shedding and Detrimental Effects of Energy Dependence in the City of Maroua, Cameroon

During the years 2021 and 2022, the city of Maroua experienced repeated power blackouts. However, this locality has significant photovoltaic energy potential. Nevertheless, the evaluation of the electrical performance showed the dependence of the population on these fluctuations, which could be bypassed or suppressed. In most cases, the blackout occurs during high energy demand. In this paper, a method for evaluating electrical efficiency is proposed and its credibility has been demonstrated on the one hand, and on the other hand, a renewable energy production system is proposed. The Homer software has made possible the analysis of the proposed system and its impact on the environment has also been carried out. The techno-economic study of the system has proved that a solar photovoltaic farm associated with an energy storage system, with a capacity of 47 MW, can meet the energy demand of the town of Maroua. This alternative is profitable for this locality which lives in a precarious situation and a continuous need.

Pilomatrixoma causing irreversible peripheral eyebrow shedding:A case report

Pilomatrixomas are benign tumors derived from hair stromal cells;however,their exact etiology is unknown.A 31-year-old woman presented with a subcutaneous mass located precisely above the left eyebrow,with shedding of eyebrow hair around the mass,and the shedding area gradually expanded.Surgical removal of the mass failed to prevent eyebrow loss,and the entire left eyebrow shed 6 months postoperatively.Pathology and histology of the biopsy specimen revealed a pilomatrixoma comprising basaloid cells and ghost cells,with basaloid cells expressing high bcl-2 levels.Instead of apoptosis,the emergence and growth of pilomatrixoma-induced microinflammation around the hair follicles of the eyebrow may lead to eyebrow loss.

Optimal integration of solar home systems and appliance scheduling for residential homes under severe national load shedding

In developing countries like South Africa,users experienced more than 1030 hours of load shedding outages in just the first half of 2023 due to inadequate power supply from the national grid.Residential homes that cannot afford to take actions to mitigate the challenges of load shedding are severely inconvenienced as they have to reschedule their demand involuntarily.This study presents optimal strategies to guide households in determining suitable scheduling and sizing solutions for solar home systems to mitigate the inconvenience experienced by residents due to load shedding.To start with,we predict the load shedding stages that are used as input for the optimal strategies by using the K-Nearest Neighbour(KNN)algorithm.Based on an accurate forecast of the future load shedding patterns,we formulate the residents’inconvenience and the loss of power supply probability during load shedding as the objective function.When solving the multi-objective optimisation problem,four different strategies to fight against load shedding are identified,namely(1)optimal home appliance scheduling(HAS)under load shedding;(2)optimal HAS supported by solar panels;(3)optimal HAS supported by batteries,and(4)optimal HAS supported by the solar home system with both solar panels and batteries.Among these strategies,appliance scheduling with an optimally sized 9.6 kWh battery and a 2.74 kWp panel array of five 550 Wp panels,eliminates the loss of power supply probability and reduces the inconvenience by 92%when tested under the South African load shedding cases in 2023.

砂卵石地层矿山法隧道长管棚支护机理及应用

研究目的:砂卵石地层由于卵石强度高且颗粒分布无序,因此长管棚施工地层扰动大且支护效果难以保证,已成为制约隧道实际应用的一大瓶颈。本文以某轨道交通暗挖法车站为依托工程,采用理论分析、现场测试与数值模拟相结合的方法,对不同直径、不同环向间距条件下长管棚的支护效果进行了深入研究,以期揭示砂卵石地层矿山法隧道长管棚支护机理,提出最佳支护参数。研究结论:(1)砂卵石地层,暗挖隧道管棚超前支护条件下,地层沉降变形在向地表传递过程中,沿高度方向的折减率约为0.91 mm/m;(2)管棚超前支护效果对矿山法隧道工程安全具有决定性作用,须采取措施减小管棚施工扰动及相应地层变形;(3)根据单因素敏感性分析结果,地表沉降随管棚支护长度的增加而增大,随管棚环向间距的增大而增加,且基本呈正相关;(4)为有效控制地表沉降并提高工程经济效益,建议直径127 mm管棚环向间距宜为35 cm,支护长度宜为40 m;直径159 mm管棚建议环向间距宜为40 cm,支护长度宜为40 m;直径209 mm管棚建议环向间距宜为45 cm,支护长度宜为50 m;管棚直径与其最佳打设长度正相关;(5)本研究结论可为砂卵石地层矿山法隧道支护措施提供借鉴与参考。

基于空中回收的运载火箭尾舱挂取方案设计及仿真分析

运载火箭空中回收的挂取过程是整个回收过程中最关键的环节之一。针对运载火箭尾舱空中挂取的全流程,开展了将直升机作为回收平台的钩取装置设计,主要包括拉力传感器、过载保护装置、减载装置以及末端的执行机构。翼伞和减速伞从火箭尾舱的底部弹出,挂取装置可通过挂取翼伞顶部的牵顶伞实现对回收体的挂取操作。通过对挂取过程的仿真分析可以看出,回收体的质量增大时,过载显著增加,而当翼伞的收伞时间增加时,减载效果明显。

连杆曲线导引的织机开口机构设计

传统连杆开口机构难以使梭口保持停歇,无法适应高速、宽幅的现代新型织机的工艺要求。引入特殊连杆曲线导引的概念,利用带鲍尔点和带圆点连杆曲线能使从动件产生停歇的原理,设计了两种新型连杆开口机构。该机构由四连杆机构和综框导引组件组成,四连杆机构的曲柄、连杆、摇杆和机架杆杆长比分别为1∶2∶2∶2.76、1∶2∶2∶2.3,连杆点的位置角分别为62.49°、49.15°,其与摇杆相连的连接杆与连杆等长。综框运动规律显示:两种机构梭口满开时主轴的相对静止角分别为约150°,40°和200°;综框处于最高和最低位时速度和加速度均为0,表明综框运动平稳,无冲击。该机构突破了传统连杆开口机构的局限,为低成本新型织机的开发创造了条件。

含减载控制和虚拟惯量控制的直驱风电场等值建模方法

为建立准确的具有主动支撑能力的直驱风电场等值模型,提出一种含减载控制和虚拟惯量控制的直驱风电场等值建模方法。首先,建立包含减载控制和虚拟惯量控制的直驱风机并网系统模型;其次,依据适应性分析选取转速、减载系数、惯性系数和阻尼系数作为分群指标;然后,基于分群指标利用改进K-means算法对直驱风电场中的机组进行聚类分群,得到直驱风电场的等值模型;最后,利用实际算例在不同场景下进行仿真和计算,对等值建模方法的准确性进行验证。

盘锦市夏季高温闷棚土壤消毒技术

通过盘锦市部分农户反映问题和长期生产调研,发现盘锦市部分农户种植的温室内由于长期连作及不科学的病虫害防治方式,导致温室内病虫害极为严重,尽管当地农户采用多种防治手段,温室内病虫害始终难以根除。为解决这一生产难题,2022—2023年辽宁省农业科学院蔬菜研究所与当地农户对接,在盘锦市菜根堂培训基地农户种植的温室内进行了夏季高温闷棚土壤消毒试验。为加强防治效果,试验增加了不同剂量的石灰氮和98%棉隆颗粒进行了不同组合处理。结果显示,35 g/m^(2)98%棉隆颗粒+135 g/m^(2)石灰氮高温闷棚土壤消毒效果最好,但35 g/m^(2)98%棉隆颗粒+105 g/m^(2)石灰氮高温闷棚土壤消毒防治效果和成本投入最易为农户接受。

早熟陆地棉金垦1402脱叶效果的比较研究

[目的]针对早熟陆地棉品种金垦1402,研究棉花叶片形态学指标与药剂脱叶催熟效果的规律研究,为生产中提供脱叶催熟效果优良的早熟机采棉品种提供理论依据。[方法]分析金垦1402不同类型叶片脱叶规律及催熟效果,寻找影响该品种在脱叶剂作用下单株叶片脱落率的重要影响因素。[结果]金垦1402主茎叶、果枝叶、叶枝叶叶量均高于新陆早61号,但脱叶速度、脱叶率均高于新陆早61号,在药后21 d,脱叶效果优于新陆早61号;金垦1402药后单株吐絮铃数较新陆早61号多,且单株吐絮率高,优于新陆早61号;纤维品质指标达到“双31”以上,优于新陆早61号。[结论]金垦1402生育期119 d左右,在喷施脱叶剂后21 d,脱叶效果好,说明该品种属于对脱叶剂敏感型品种;该品种施药后,吐絮率高,纤维品质优。

应对极端冰灾的电力系统多阶段韧性提升策略

为提升冰灾下电力系统的韧性,降低系统负荷削减量,提高系统恢复速率,提出一种应对极端冰灾的电力系统多阶段韧性提升策略。对冰灾场景以及受冰灾影响的线路故障率进行建模;从线路抗冰能力、系统负荷损失、系统恢复情况、线路受损情况、维修资源充裕度多个角度构建电力系统综合韧性评估指标,以定位冰灾下系统的薄弱环节;在此基础上,通过灾前线路故障风险预测、灾中机组出力调整以及除冰线路筛选和主动停运除冰、灾后维修顺序规划等策略提升冰灾下的系统韧性。基于IEEE 39和IEEE 118节点系统进行仿真分析,结果验证了所提韧性评估方法和提升策略的有效性。

从ITMA ASIA+CITME 2022看织造机械的技术进步

总结2022中国国际纺织机械展览会暨ITMA亚洲展览会上织造机械及织造准备的最新技术进展。织造机械的结构与性能不断优化,发展更加贴近市场需求。国产剑杆、喷气、喷水织机的制造水平发展迅速,提高了国产设备的核心竞争力。随着人工智能的爆发式增长,织造机械的数字化转型步伐加快,先进的信息技术和自动化工具的运用使织造机械呈现出个性化、智能化、绿色化发展新趋势。认为:近几年织造机械在高速化、自动化、绿色化方面进步显著。

基于落石模型试验的棚洞垫层力学响应及优化设计

结合边坡落石灾害现状,基于落石模型试验,系统分析落石质量、下落高度、垫层厚度、加筋位置、加筋材料等因素对落石冲击力及其动态演化的影响,揭示落石冲击棚洞的动力响应规律,结合垫层自重与落石冲击作用双因素影响确定垫层最优厚度,并对垫层设计提出优化建议。结果表明:随着垫层厚度增加,棚洞所受落石冲击力呈非线性减小,减小幅度先大后小而后趋于稳定;在同一垫层厚度下,棚洞所受落石冲击力随落石高度和落石质量近似呈线性增大;当复合垫层设计为“5 cm河砂+聚苯乙烯泡沫(EPS)+10 cm河砂”时,落石中心处土压力峰值相较于纯河砂垫层降低约60%,缓冲耗能效果最佳;通过多元回归分析得到了落石冲击力计算公式,且计算结果与实验数据吻合良好。

高寒区隧道洞口段覆雪波纹钢棚洞减载方法研究

高寒区隧道洞口段易受上方覆雪及落石影响,采用现有大跨径波纹钢棚洞会产生较大变形和失稳,影响边疆公路运行安全。为此,依托某线路隧道洞口段波纹钢防雪棚洞项目,从拱效应及加筋桥减载原理出发,运用有限元软件构建了EPS板、EPS板+加筋雪、EPS板+加筋冰等10种减载方案的三维波纹钢棚洞模型,研究不同减载方案对棚洞应力、棚洞变形和覆雪压力的影响,对比分析棚洞受力变形特征及减载效果,筛选出最优减载方案。结果表明:施加减载材料后,棚洞上方覆雪压力均不同程度分散到棚洞两侧,减小了棚洞结构的受力;随着覆雪高度增加,减载效果更显著,其中30 cmEPS板+加筋冰组合式方案的减载效果最佳,棚顶应力减少32.72%,棚顶位移减小22.63%;针对波纹钢棚洞的减载问题,建议隧道洞口30 m范围内采用30 cmEPS板+加筋雪方案,距隧道口30 m以外范围可采用30 cmEPS板+加筋冰方案。

结合风速预测的直驱风电机组减载调频策略

直驱永磁风电机组常用的减载调频控制策略缺乏对风电机组运行经济性和调频能力的考虑,易导致系统出现调频能力不足或备用功率冗余的问题,对此提出了一种基于变减载率的优化减载调频策略。首先划分不同的风速模式,确立不同模式下的超速与变桨距协调控制方案;其次考虑系统调频能力和发电量两因素,设计函数求取不同工况下的最优减载率;由于风速波动频繁,风机控制具有延迟,因此利用风速预测和滑动窗口法对最优减载率做进一步调整;最后搭建系统仿真模型,通过改进的频率控制动态调整减载率参与系统调频。仿真实验表明,所提控制策略与常用的策略相比在实时风速、负荷扰动下系统频率动态偏差减小、达到最低值的时间延长,风机发电量增加,桨距角变化量减小。该策略能满足调频需求,提升调频质量,减小机械磨损,提高风机运行的经济性。