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Challenges of a negative work load and implications on morale,productivity and quality of service delivered in NHS laboratories in England 被引量:1
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作者 Erhabor Osaro Njemanze Chima 《Asian Pacific Journal of Tropical Biomedicine》 SCIE CAS 2014年第6期421-429,共9页
The National Health Service(NHS)is a term used to describe the publicly funded healthcare delivery system providing quality healthcare services in the United Kingdom.There are several challenges militating against the... The National Health Service(NHS)is a term used to describe the publicly funded healthcare delivery system providing quality healthcare services in the United Kingdom.There are several challenges militating against the effective laboratory service delivery in the NHS in England.Biomedical scientists work in healthcare to diagnose disease and evaluate the effectiveness of treatment through the analysis of body fluids and tissue samples from patients.They provide the"engine room"of modern medicine with 70%of diagnosis based on the laboratory results generated by them.This review involved the search of literature for information on working condition of biomedical scientist in the NHS in England.Laboratory service delivery in the NHS in England faces numerous daunting challenges;staffing levels in the last few years have become dangerously low,less remunerated,relatively less experienced and predominantly band 5's,multidisciplinary rather than specialty based,associated with working more unsocial hours without adequate recovery time,de-banding of staff,high staff turnaround,profit and cost driven rather than quality.These factors has resulted in burn out,low morale,high sickness absences,increased error rate,poor team spirit,diminished productivity and suboptimal laboratory service delivery.There is the urgent need to retract our steps on unpopular policies to ensure that patient care is not compromised by ensuring adequate staffing level and mix,ensuring adequate remuneralion of laboratory staff,implementing evidenced-based specialty oriented service,determining the root cause/s for the high staff turnover and implementing corrective action,identifying other potential sources of waste in the system rather than pruning the already dangerously low staffing levels and promoting a quality delivery side by side cost effectiveness. 展开更多
关键词 Laboratory staffs National Health SERVICE ENGLAND NEGATIVE work load MORALE PRODUCTIVITY SERVICE delivery
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On the Study of Translation Approaches of Culture-loaded Words in Literary Works 被引量:1
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作者 李福珍 《海外英语》 2016年第23期143-144,147,共3页
Culture-loaded words refer to expressions and idioms that carry typically culture messages. The peculiarity of one culture cannot be understood or accepted by readers from another culture. The uniqueness very likely m... Culture-loaded words refer to expressions and idioms that carry typically culture messages. The peculiarity of one culture cannot be understood or accepted by readers from another culture. The uniqueness very likely makes misunderstanding and may lead to cultural vacancy in other cultures. Due to the culture differences between Chinese and English, it is hard for a translator to achieve complete equivalence at the level of word. This paper discusses the translation approaches of Chinese cultureloaded words in literary works. 展开更多
关键词 Culture-loaded Words Translation Approaches Literary works
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基于InfoWorks ICM水力模型的排水管道负荷分析方法 被引量:1
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作者 张辰 《工程建设与设计》 2025年第2期31-33,共3页
采用InfoWorks ICM水力模型,通过构建量化模型,对排水管道在不同降雨强度条件下的负荷进行分析。结果表明,新建雨水系统能满足5年一遇降雨标准,且在10年一遇降雨标准下,路面积水不超150 mm。
关键词 排水管道 负荷分析 Info works ICM 管道沉积物
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Tensile Strength Characteristics of GFRP Bars in Concrete Beams with Work Cracks under Sustained Loading and Severe Environments 被引量:4
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作者 何雄君 YANG Jingnan Charles E Bakis 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2013年第5期934-937,共4页
To investigate the effect of different environmental conditions of GFRP bars in concrete beams with work cracks subjected to sustained loads, the beams were exposed in indoor, freeze/thaw cycles and immersed in alkali... To investigate the effect of different environmental conditions of GFRP bars in concrete beams with work cracks subjected to sustained loads, the beams were exposed in indoor, freeze/thaw cycles and immersed in alkaline solution at elevated temperature. The bars were carefully extracted from the beams and tested in order to evaluate residual tensile properties. The results show that the tensile strength decreased significantly in the highly aggressive conditions but not in the natural conditions. The effect of GFRP bars casting in concrete beams demonstrated approximately 2.5% decrease of tensile strength caused by pore water environment in concrete beams on basis of those of the original bars. The effect of sustained loading plus work cracks demonstrated about 10.5% tensile strength decrease on basis of those of the bars only casted in concrete beams. The effect of environments under sustained loading plus work cracks demonstrated about 17% tensile strength decrease caused by a saturated solution of Ca(OH)2 and 60-2 ℃ tap water (pH=12-13) and about 8% tensile strength decrease caused by freezing and thawing cycle (F/T), both on basis of those of the bars of the indoor beams only under sustained loading plus work cracks. The results demonstrate the effects of the tensile strengths under different environmental conditions of GFRP bars in concrete beams with work cracks subjected to sustained loads. 展开更多
关键词 GFRP bars concrete beams working cracks sustained loading and severe environments tensile strength
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Rolling Bearing Fault Diagnosis Based on 1D Convolutional Neural Network and Kolmogorov–Arnold Network for Industrial Internet
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作者 Huyong Yan Huidong Zhou +1 位作者 Jian Zheng Zhaozhe Zhou 《Computers, Materials & Continua》 2025年第6期4659-4677,共19页
As smart manufacturing and Industry 4.0 continue to evolve,fault diagnosis of mechanical equipment has become crucial for ensuring production safety and optimizing equipment utilization.To address the challenge of cro... As smart manufacturing and Industry 4.0 continue to evolve,fault diagnosis of mechanical equipment has become crucial for ensuring production safety and optimizing equipment utilization.To address the challenge of cross-domain adaptation in intelligent diagnostic models under varying operational conditions,this paper introduces the CNN-1D-KAN model,which combines a 1D Convolutional Neural Network(1D-CNN)with a Kolmogorov–Arnold Network(KAN).The novelty of this approach lies in replacing the traditional 1D-CNN’s final fully connected layer with a KANLinear layer,leveraging KAN’s advanced nonlinear processing and function approximation capabilities while maintaining the simplicity of linear transformations.Experimental results on the CWRU dataset demonstrate that,under stable load conditions,the CNN-1D-KAN model achieves high accuracy,averaging 96.67%.Furthermore,the model exhibits strong transfer generalization and robustness across varying load conditions,sustaining an average accuracy of 90.21%.When compared to traditional neural networks(e.g.,1D-CNN and Multi-Layer Perceptron)and other domain adaptation models(e.g.,KAN Convolutions and KAN),the CNN-1D-KAN consistently outperforms in both accuracy and F1 scores across diverse load scenarios.Particularly in handling complex cross-domain data,it excels in diagnostic performance.This study provides an effective solution for cross-domain fault diagnosis in Industrial Internet systems,offering a theoretical foundation to enhance the reliability and stability of intelligent manufacturing processes,thus supporting the future advancement of industrial IoT applications. 展开更多
关键词 Bearing fault diagnosis Kolmogorov-Arnold network adaptivity under various working load transfer generalization
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基于MTAM-LSTM的采煤工作面支架载荷预测方法
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作者 张杰 杨科 范超尘 《中国安全科学学报》 北大核心 2026年第3期144-152,共9页
为有效预测液压支架载荷、评估支架运行状态,提出一种基于多尺度卷积时间注意力模块(MTAM)-长短时记忆(LSTM)神经网络的液压支架载荷预测模型。首先,采用自适应噪声完备集合经验模态分解(CEEMDAN)算法分解支架载荷数据获取本征模态分量... 为有效预测液压支架载荷、评估支架运行状态,提出一种基于多尺度卷积时间注意力模块(MTAM)-长短时记忆(LSTM)神经网络的液压支架载荷预测模型。首先,采用自适应噪声完备集合经验模态分解(CEEMDAN)算法分解支架载荷数据获取本征模态分量,基于K-L散度准则剔除本征模态分量中的冗余分量形成支架载荷预测输入序列;其次,建立MTAM捕捉支架载荷变化特征,静态注意力生成数据特征信息的注意力权重,动态注意力优化不同序列特征的关注度,并引入残差学习保持特征信号的完整性;然后,利用LSTM构建特征信息与支架载荷之间的深层依赖关系,实现支架载荷数据的超前预测;最后,选取陕西某冲击地压矿井402102工作面液压支架载荷数据进行实证分析,对比不同模型均方根误差、决定系数和平均绝对误差3种评价指标,结果表明:MTAMLSTM模型的均方根误差(RMSE)和平均绝对误差(MAE)均明显小于对比模型,RMSE整体降低0.16~0.45,MAE降低0.16~0.45,不同场景下决定系数R^(2)达到0.91,验证了MTAM-LSTM的预测准确率和模型泛化能力。 展开更多
关键词 多尺度卷积时间注意力模块(MTAM) 长短时记忆神经网络(LSTM) 采煤工作面 载荷预测 液压支架 泛化能力
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护生实习后期工作投入现状及其影响因素
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作者 刘丽杰 李进 +2 位作者 覃利英 邹玉珺 伍敏玲 《循证护理》 2026年第2期391-396,共6页
目的:调查护生实习后期工作投入现状及其影响因素。方法:采用便利抽样法选取2025年1月—2月广州市某三级甲等综合医院的180名实习护生为研究对象,采用一般资料调查表、工作投入量表、工作倦怠量表、一般自我效能感量表、任务负荷指数、... 目的:调查护生实习后期工作投入现状及其影响因素。方法:采用便利抽样法选取2025年1月—2月广州市某三级甲等综合医院的180名实习护生为研究对象,采用一般资料调查表、工作投入量表、工作倦怠量表、一般自我效能感量表、任务负荷指数、护生临床学习环境量表进行横断面调查。结果:回收有效问卷167份,有效回收率为92.78%(167/180)。实习护生后期工作投入量表总分为(35.49±8.62)分。多因素分析结果显示,学历、毕业后从事护理工作意愿、工作倦怠、一般自我效能感、任务负荷、临床学习环境是护生实习后期工作投入的影响因素(P<0.05)。结论:实习护生实习后期工作投入水平处于中等水平,影响因素较多,建议护理教育者优化临床教学策略,促进实习护生在实习后期维持良好的工作投入水平。 展开更多
关键词 实习护生 后期 工作投入 工作倦怠 一般自我效能感 任务负荷 临床学习环境 影响因素 护理
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工作姿势和负荷组合对上肢疲劳交互影响效应的幅频联合分析
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作者 薛恩凯 徐红旗 《中国组织工程研究》 北大核心 2026年第16期4115-4124,共10页
背景:上肢工作相关肌肉骨骼疾患因对个人健康和社会经济的危害而备受关注,而肌肉疲劳是主要诱因。目的:通过幅频联合分析法探讨姿势和负荷交互效应对静态上肢作业中肌肉疲劳特征的影响,为上肢工作相关肌肉骨骼疾患的预防提供多维度生物... 背景:上肢工作相关肌肉骨骼疾患因对个人健康和社会经济的危害而备受关注,而肌肉疲劳是主要诱因。目的:通过幅频联合分析法探讨姿势和负荷交互效应对静态上肢作业中肌肉疲劳特征的影响,为上肢工作相关肌肉骨骼疾患的预防提供多维度生物力学依据。方法:14名健康受试者执行肩关节前屈20°,40°,60°的静态任务,任务负荷设置为其最大重复次数(1RM)的10%,30%和50%。同步采集表面肌电信号及Borg主观疲劳感知评估量表数据。采用幅频联合分析计算均方根斜率和中位频率斜率量化肌肉疲劳程度;应用配对样本t检验分析疲劳前后的疲劳状态占比;采用方差分析评估姿势、负荷及其交互效应对疲劳状态占比的影响。结果与结论:①姿势-负荷组合会显著影响作业耐受性(P<0.05),60°50%最大重复次数组合最大保持时间最短(P<0.001);②特定组合下疲劳前后肌肉疲劳状态改变:20°10%最大重复次数组合下,冈上肌和斜方肌上部疲劳状态占比显著下降(P<0.05);40°10%最大重复次数组合下,斜方肌上部疲劳状态占比差异极显著(P<0.01);③姿势与负荷对肌肉疲劳的影响相互独立,在20°姿势下,三角肌前束的疲劳占比在10%最大重复次数与30%最大重复次数、10%最大重复次数与50%最大重复次数的负荷对比中有显著性差异(P<0.05);而在10%最大重复次数负荷条件下,三角肌前束及中束的疲劳占比仅在20°与60°角度间、在疲劳前与全程阶段表现出显著性差异(P<0.05);④姿势与负荷无显著交互效应(P>0.05);⑤提示高负荷与高角度显著加速肌肉疲劳;姿势与负荷独立影响疲劳进程,二者交互效应不显著;幅频联合分析对于姿势与负荷影响下的肌肉疲劳特征敏感性有限。 展开更多
关键词 肌肉骨骼疾患 上肢疲劳 工作姿势 外部负荷 交互影响 最大保持时间 幅频联合分析
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Load Assessment of the Static Posture and Weight Holding inTerms of Pulmonary Ventilation and Heart Rate
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作者 杨磊 林宇声 +2 位作者 刘卫东 刘杰 刘鹤云 《Journal of Huazhong University of Science and Technology(Medical Sciences)》 SCIE CAS 1997年第3期156-159,共4页
The aim of this study was to explore appropriate index for load evaluation by analyzing.the changes of pulmonary ventilation (VE) and heart rate (HR)in 35 student volunteers under the condition of static posture and w... The aim of this study was to explore appropriate index for load evaluation by analyzing.the changes of pulmonary ventilation (VE) and heart rate (HR)in 35 student volunteers under the condition of static posture and weight holding.Each subject was asked to perform 7 kinds of static postures and 2 kinds of weight holdings. The HR was continuously measured by a remote detecting device. VE was recorded by a ventimeter for an average of 5 min. The results showed that HR was positively correlated to VE under static activities (r=0. 89), which suggested that VE as well as HR could to some degrees reflect the static load. It was better to use VE to indicate the load of weight holdings than to use HR, which, on the other hand, was more sensible in reflection of the posture load. It is better to use relative value of both of VE and HR to reflect the static load. In addition,arm-overheaded posture increase HR more significantly than any other activities. 展开更多
关键词 static activity pulmonary ventilation heart rate work load evaluation
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厚松散层薄基岩开采“梁-拱”结构动态演化规律
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作者 李振华 任浩 +5 位作者 杜锋 卢飞飞 王文强 翟明磊 石建行 孙荘 《煤炭学报》 北大核心 2026年第2期887-904,共18页
以新桥煤矿厚松散层薄基岩厚煤层开采为研究背景,采用相似模拟、现场实测、数值模拟、理论分析相结合的方法对厚松散层薄基岩采场覆岩运动规律进行研究,提出了松散层垮落拱-假塑性岩梁复合结构,建立了厚松散层薄基岩采场上覆岩层破断力... 以新桥煤矿厚松散层薄基岩厚煤层开采为研究背景,采用相似模拟、现场实测、数值模拟、理论分析相结合的方法对厚松散层薄基岩采场覆岩运动规律进行研究,提出了松散层垮落拱-假塑性岩梁复合结构,建立了厚松散层薄基岩采场上覆岩层破断力学模型、工作面支架阻力计算模型。结果表明:厚松散层薄基岩煤层开采时,基岩处于风氧化带、覆岩强度小,致使覆岩自稳定性能与承载能力降低、处于垮落带的覆岩范围大,工作面支架阻力具有高静压-低动压的持续来压现象;在覆岩结构演化过程中,采动覆岩破坏分为基本顶破断、假塑性岩梁形成、松散层垮落拱形成、松散层垮落拱横向发育4个阶段,在假塑性岩梁形成阶段之前,工作面支架阻力主要来源于已垮落的破碎岩体,假塑性岩梁形成阶段后,工作面支架阻力由垮落岩体静载和假塑性岩梁给定变形共同组成;数值模拟过程中,通过力链分布和应力分布对覆岩承载过程进行分析,发现假塑性岩梁承载范围并非上方所有已垮落的岩土体,松动岩土体间所具有的力学传递机制使得假塑性岩梁的承载范围得以减小。在覆岩裂隙演化过程中,裂隙扩展分为偏应力张量主导和土拱效应主导2个阶段,结合覆岩裂隙演化过程提出了厚松散层薄基岩覆岩破断机理与破断力学模型,建立了厚松散层薄基岩工作面液压支架工作阻力计算公式,与现场监测结果具有较好的一致性。研究总结了厚松散层薄基岩“梁-拱”结构动态演化规律,可为我国厚松散层薄基岩综采工作面支架选型和顶板控制提供一定的理论参考。 展开更多
关键词 岩层控制 厚松散层薄基岩 承载机理 平面力学模型 支架工作阻力
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并行分治计算中的一种Work-stealing策略 被引量:2
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作者 杨际祥 谭国真 +1 位作者 王荣生 江德 《小型微型计算机系统》 CSCD 北大核心 2010年第3期408-412,共5页
在机群尤其是共享式多用户机群环境中提高非规则问题的并行计算效率是一项具有挑战性的工作.给出了一种适于多核处理器节点构成的机群的层次Work-stealing负载均衡策略(简称HWS),它能够有效利用节点的动态变化的可用计算资源.分析了分... 在机群尤其是共享式多用户机群环境中提高非规则问题的并行计算效率是一项具有挑战性的工作.给出了一种适于多核处理器节点构成的机群的层次Work-stealing负载均衡策略(简称HWS),它能够有效利用节点的动态变化的可用计算资源.分析了分治计算问题中的动态性与非规则性,并使用HWS策略对分治计算问题进行了动态负载均衡(DLB)实验.实验表明,HWS在加速比、CPU利用率和负载分布等性能指标上均优于Work-sharing和Satin-CRS策略. 展开更多
关键词 动态负载均衡(DLB) 层次work-stealing策略(HWS) 多核 分治法(D&C)
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电网负荷侧变压器多工况无功节能优化方法
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作者 张杰 刘生春 +1 位作者 马勇飞 侯元红 《西安邮电大学学报》 2026年第2期56-65,共10页
针对电网负荷侧变压器在多工况运行下因无功补偿不足导致的功率因数低下、能耗增加问题,提出一种电网负荷侧变压器多工况无功节能优化方法。计算电网负荷侧变压器多工况无功节能优化参数,考虑多差异性进行寻优,确定变压器的开关操作允... 针对电网负荷侧变压器在多工况运行下因无功补偿不足导致的功率因数低下、能耗增加问题,提出一种电网负荷侧变压器多工况无功节能优化方法。计算电网负荷侧变压器多工况无功节能优化参数,考虑多差异性进行寻优,确定变压器的开关操作允许上限,生成平衡约束式;进行负载与温升调整,考虑潮流约束关系计算优化潮流,对各个优化节点进行线性化近似处理;对负荷等级进行分类,融合流动特性结合近端优化算法构建电网负荷侧变压器多工况无功节能优化模型,计算此时的适应度,将目标函数映射到较大的取值空间中,判断约束条件,获取每个个体求解的变量值,完成电网负荷侧变压器多工况无功节能优化。实验结果表明,所提方法在轻载、中载、重载工况下可将功率因数分别提升至0.92、0.95、0.91,且电压波动率降至1.2%。所提方法能够显著提升变压器多工况下的无功优化能力与经济运行水平,为电力系统节能降耗提供有效技术支撑。 展开更多
关键词 复杂工况适配 动态约束 负荷时序波动 温升调整 电压稳定
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超长工作面液压支架受不均衡载荷影响研究
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作者 李明忠 邢有望 +4 位作者 张金虎 杨征 乔永力 闫汝瑜 米牧石 《煤炭科学技术》 北大核心 2026年第3期292-309,共18页
工作面长度的增加会使采场出现异于普通工作面的新矿压特征,如随着工作面长度的增加,液压支架支护阻力呈现出单峰值向多峰值转变,更多的支架处于高应力区,降低了液压支架在超长工作面的稳定性与适应性,不利于矿井高产高效建设。针对超... 工作面长度的增加会使采场出现异于普通工作面的新矿压特征,如随着工作面长度的增加,液压支架支护阻力呈现出单峰值向多峰值转变,更多的支架处于高应力区,降低了液压支架在超长工作面的稳定性与适应性,不利于矿井高产高效建设。针对超长工作面液压支架顶梁载荷不明晰、受载后的力学特性不明确等问题,以小保当2号井132202超长工作面为背景,根据支架与围岩关系,建立支持在弹性支座上的二维连续梁模型,利用矩阵位移法计算顶板全长挠度分布。利用单跨梁的微分方程求解了液压支架顶梁的挠度分布及其上沿宽度方向的载荷分布函数,通过与沿梁长方向的载荷函数耦合,得到顶梁上方不均衡载荷分布函数。分析了顶梁上方不均衡载荷等效为集中力后在大小、作用位置等方面的分布特征。利用插入桩结构单元充当支护的3DEC数值模拟结果及现场液压支架压力数据为理论提供支撑,分析结果做到了理论计算、数值模拟及现场数据三者的统一。将不均衡载荷导入ANSYS中进行液压支架受不均衡载荷影响的力学响应分析,并与等效载荷水平下的顶梁偏载、顶梁扭转工况相比较,与工作面其他位置不同不均衡载荷情况下支架工况相比较。结果表明:二维连续梁模型能够在一定程度上解释超长工作面三峰值来压特征,超长工作面不均衡载荷表现出在两端的载荷不均匀但载荷强度小、峰值处的载荷均匀但载荷强度大的分布特点。同时,有限元分析结果证明:位于超长工作面两端的不均衡载荷对液压支架的影响更偏向于顶梁扭转加载工况,支架横向倾覆风险与载荷不均衡程度呈负相关。研究深化了梁模型在采场方面的应用,结果有助于为超长工作面液压支架设计提供理论指导。 展开更多
关键词 超长工作面 顶板挠度 液压支架 矩阵位移法 不均衡载荷
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基于SolidWorks和ADAMS的装车机械手运动仿真 被引量:25
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作者 武金艺 黄金凤 +1 位作者 李炜 田雪珂 《机床与液压》 北大核心 2016年第9期52-56,共5页
针对当今水泥装载运输行业中存在的实际问题,开发设计一种结构简单、控制容易的自动袋装水泥装车机械手。利用三维建模软件SolidWorks建立装车机械手的实体模型,将模型导入仿真软件ADAMS环境中,并进一步的添加约束和驱动等,通过对该模... 针对当今水泥装载运输行业中存在的实际问题,开发设计一种结构简单、控制容易的自动袋装水泥装车机械手。利用三维建模软件SolidWorks建立装车机械手的实体模型,将模型导入仿真软件ADAMS环境中,并进一步的添加约束和驱动等,通过对该模型进行运动学仿真分析,得到关键构件的运动学参数,绘出构件的运动特性曲线,验证机构设计的合理性和可行性,为机械手的运动控制及机械结构的优化设计提供参考依据。 展开更多
关键词 水泥装载 机械手 SOLIDworkS ADAMS 仿真
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SWN: An SDN Based Framework for Carrier Grade WiFi Networks 被引量:1
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作者 LEI Tao WEN Xiangming +3 位作者 LU Zhaoming ZHAO Xing LI Yangchun ZHANG Biao 《China Communications》 SCIE CSCD 2016年第3期12-26,共15页
With the rapid growth of mobile data traffic and vast traffic offloaded from cellular network, Wi-Fi has been considered as an essential component to cope with the tremendous growth of mobile data traffic. Although op... With the rapid growth of mobile data traffic and vast traffic offloaded from cellular network, Wi-Fi has been considered as an essential component to cope with the tremendous growth of mobile data traffic. Although operators have deployed a lot of carrier grade Wi-Fi networks, but there are still a multitude of arrears for nowadays Wi-Fi networks, such as supporting seamless handover between APs, automatic network access and unified authentication, etc. In this paper, we propose an SDN based carrier grade Wi-Fi network framework, namely SWN. The key conceptual contribution of SWN is a principled refactoring of Wi-Fi networks into control and data planes. The control plane has a centralized global view of the whole network, can perceive the underlying network state by network situation awareness(NAS) technique, and bundles the perceived information and network management operations into northbound Application Programming Interface(API) for upper applications. In the data plane, we construct software access point(SAP) to abstract the connection between user equipment(UE) and access point(AP). Network operators can design network applications by utilizing these APIs and the SAP abstraction to configure and manage the whole network, which makes carrier grade Wi-Fi networks more flexible, user-friendly, and scalable. 展开更多
关键词 SWN carrier grade Wi-Finet works SDN seamless handover load balancing Hotspot 2.0 traffic offloading
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Describing failure in geomaterials using second-order work approach
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作者 Franois Nicot Félix Darve 《Water Science and Engineering》 EI CAS CSCD 2015年第2期89-95,共7页
Geomaterials are known to be non-associated materials. Granular soils therefore exhibit a variety of failure modes, with diffuse or localized kinematical patterns. In fact, the notion of failure itself can be confusin... Geomaterials are known to be non-associated materials. Granular soils therefore exhibit a variety of failure modes, with diffuse or localized kinematical patterns. In fact, the notion of failure itself can be confusing with regard to granular soils, because it is not associated with an obvious phenomenology. In this study, we built a proper framework, using the second-order work theory, to describe some failure modes in geomaterials based on energy conservation. The occurrence of failure is defined by an abrupt increase in kinetic energy. The increase in kinetic energy from an equilibrium state, under incremental loading, is shown to be equal to the difference between the external second-order work,involving the external loading parameters, and the internal second-order work, involving the constitutive properties of the material. When a stress limit state is reached, a certain stress component passes through a maximum value and then may decrease. Under such a condition, if a certain additional external loading is applied, the system fails, sharply increasing the strain rate. The internal stress is no longer able to balance the external stress, leading to a dynamic response of the specimen. As an illustration, the theoretical framework was applied to the well-known undrained triaxial test for loose soils. The influence of the loading control mode was clearly highlighted. It is shown that the plastic limit theory appears to be a particular case of this more general second-order work theory. When the plastic limit condition is met, the internal second-order work is nil. A class of incremental external loadings causes the kinetic energy to increase dramatically, leading to the sudden collapse of the specimen, as observed in laboratory. 展开更多
关键词 Failure in geomaterials Undrained triaxial loading path Second-order work Kinetic energy Plastic limit condition Control parameter
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Compressive and Sealing Characteristics of PTFE under Cyclic Loading-unloading
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作者 张宁 LI Qiang +1 位作者 HU Kang 李青 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2015年第1期181-184,共4页
Compressive and sealing characteristics of PTFE under cyclic loading-unloading at room temperature are studied in order to evaluate the cyclic sealing performance of control valve comprehensively. The unloading charac... Compressive and sealing characteristics of PTFE under cyclic loading-unloading at room temperature are studied in order to evaluate the cyclic sealing performance of control valve comprehensively. The unloading characteristics are different from the loading ones, therefore there is hysteresis between the unloading and loading curves. Compressive hysteresis is the main factor that causes sealing hysteresis. The leakage rate of PTFE complies with the power law before it enters the relatively stable region. Lastly, the effect of working pressure on the compressive and sealing characteristics is discussed. The experimental results show that the working pressure has little effect on compressive deformation but has a great influence on leakage rate. 展开更多
关键词 PTFE compression SEALING cyclic loading-unloading working pressure
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Mechanism of rock burst caused by fracture of key strata during irregular working face mining and its prevention methods 被引量:17
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作者 Zengqiang Yang Chang Liu +3 位作者 Hengzhong Zhu Fuxing Xie Linming Dou Jianhang Chen 《International Journal of Mining Science and Technology》 SCIE EI CSCD 2019年第6期889-897,共9页
To study the occurrence mechanism of rock burst during mining the irregular working face,the study took irregular panel 7447 near fault tectonic as an engineering background.The spatial fracture characteristic of over... To study the occurrence mechanism of rock burst during mining the irregular working face,the study took irregular panel 7447 near fault tectonic as an engineering background.The spatial fracture characteristic of overlying strata was analyzed by Winkler elastic foundation beam theory.Furthermore,the influence law of panel width to suspended width and limit breaking span of key strata were also analyzed by thin plate theory.Through micro-seismic monitoring,theoretical analysis,numerical simulation and working resistance of support of field measurement,this study investigated the fracture characteristic of overlying strata and mechanism of rock burst in irregular working face.The results show that the fracture characteristic of overlying strata shows a spatial trapezoid structure,with the main roof being as an undersurface.The fracture form changes from vertical‘‘O-X"type to transverse‘‘O-X"type with the increase of trapezoidal height.From the narrow mining face to the wide mining face,the suspended width of key strata is greater than its limit breaking width,and a strong dynamic load is produced by the fracture of key strata.The numerical simulation and micro-seismic monitoring results show that the initial fracture position of key strata is close to tailgate 7447.Also there is a high static load caused by fault tectonic.The dynamic and static combined load induce rock burst.Accordingly,a cooperative control technology was proposed,which can weaken dynamic load by hard roof directional hydraulic fracture and enhance surrounding rock by supporting system. 展开更多
关键词 ROCK BURST IRREGULAR working FACE Key STRATA Dynamic and static combined load Cooperative control
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锚杆动静耦合力学性能与抗冲机制
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作者 王琦 许硕 +1 位作者 江贝 刘竞轩 《煤炭学报》 北大核心 2025年第11期5043-5053,共11页
锚杆支护是深部地下工程常用的围岩控制技术。为对深部复杂条件围岩进行安全控制,需对锚杆施加预应力,同时受到围岩大变形、开采扰动和强冲击等影响,使锚杆处于动静耦合的工作状态。因此,研究锚杆在不同工作荷载状态下的抗冲性能与安全... 锚杆支护是深部地下工程常用的围岩控制技术。为对深部复杂条件围岩进行安全控制,需对锚杆施加预应力,同时受到围岩大变形、开采扰动和强冲击等影响,使锚杆处于动静耦合的工作状态。因此,研究锚杆在不同工作荷载状态下的抗冲性能与安全储备对深部地下工程支护设计至关重要。基于此,利用自主研发的锚杆动静耦合力学性能试验系统,开展了现场常用普通锚杆与高强锚杆在0~200 kN初始荷载条件下的动静耦合力学性能试验,明确了锚杆动静耦合力学性能与抗冲吸能特性。结果表明:在冲击能量方面,动静耦合条件下不同锚杆抵抗的冲击能量随初始荷载的增大具有相同的衰减规律。在吸收能量方面,锚杆的吸收总能量未随初始荷载条件改变而显著改变。同时,锚杆单次吸收能量随着初始荷载的增大而增大,导致了锚杆冲击能量显著下降,安全储备降低。在0~200 kN初始荷载条件下,普通锚杆与高强锚杆的冲击能量衰减率最大分别为58.8%、50.0%,二者吸收总能量的均值分别为13.0×10^(4)、14.4×10^(4) J,吸能系数随着强度利用率增加均呈现先缓慢、后快速的“阶段性增长”特征。通过综合分析,明确了锚杆动静耦合抗冲吸能机制,提出了锚杆动静耦合强度-能量设计理念,建立了动静耦合条件锚杆预应力“双折线”设计模型,可为深部地下工程动力灾害安全控制提供新思路。 展开更多
关键词 锚杆支护 工作荷载 动静耦合 冲击能量 吸收能量 设计理念
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PHEV副车架焊缝疲劳试验加速载荷谱研究
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作者 赵礼辉 魏绪国 +3 位作者 梁山 翁硕 冯金芝 张东东 《机械强度》 北大核心 2025年第8期1-10,共10页
针对新能源汽车副车架的焊缝疲劳试验问题,提出一种基于失效主导载荷的程序载荷谱编制方法。首先,建立后副车架有限元模型,将单位载荷下应力分布与各连接点载荷相耦合,运用结构应力法对副车架焊缝进行疲劳寿命评估,并筛选出容易失效的6... 针对新能源汽车副车架的焊缝疲劳试验问题,提出一种基于失效主导载荷的程序载荷谱编制方法。首先,建立后副车架有限元模型,将单位载荷下应力分布与各连接点载荷相耦合,运用结构应力法对副车架焊缝进行疲劳寿命评估,并筛选出容易失效的6处危险点;其次,通过对比各连接点载荷损伤大小,确定焊缝危险单元对应的失效主导连接点;然后,通过焊缝处主应力分析、时域相关性和单轴损伤贡献量确定失效主导载荷,实现多轴载荷降维,降低台架试验加载难度;最后,基于失效主导载荷输出伪损伤矩阵,挑选特征工况及其比例得到疲劳加速试验程序载荷谱,根据损伤等效原则确定其最小循环次数。数值仿真结果表明,程序载荷谱能够复现危险点损伤,且具有较高的加速系数,验证了加速试验谱的有效性。 展开更多
关键词 后副车架 焊缝疲劳 主应力分析 失效主导载荷 特征工况 程序载荷谱
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