Theoretical description of drawing body shape in an inclined seam with longwall top coal caving mining

Understanding the characteristics of drawing body shape is essential for optimization of drawing parameters in longwall top coal caving mining.In this study,both physical experiments and theoretical analysis are employed to investigate these characteristics and derive a theoretical equation for the drawing body shape along the working face in an inclined seam.By analyzing the initial positions of drawn marked particles,the characteristics of the drawing body shape for different seam dip angles are obtained.It is shown that the drawing body of the top coal exhibits a shape-difference and volume-symmetry characteristic,on taking a vertical line through the center of support opening as the axis of symmetry,the shapes of the drawing body on the two sides of this axis are clearly different,but their volumes are equal.By establishing theoretical models of the drawing body in the initial drawing stage and the normal drawing stage,a theoretical equation for the drawing body in an inclined seam is proposed,which can accurately describe the characteristics of the drawing body shape.The shape characteristics and volume symmetry of the drawing body are further analyzed by comparing the results of theoretical calculations and numerical simulations.It is shown that one side of the drawing body is divided into two parts by an inflection point,with the lower part being a variation development area.This variation development area increases gradually with increasing seam dip angle,resulting in an asymmetry of the drawing body shape.However,the volume symmetry coefficient fluctuates around 1 for all values of the seam dip angle variation,and the volumes of the drawing body on the two sides are more or less equal as the variation development volume is more or less equal to the cut volume.Both theoretical calculations and numerical simulations confirm that the drawing body of the top coal exhibits the shape-difference and volume-symmetry characteristic.

Critical Analysis of Children’s Drawings as a Diagnostic Tool for Body Schema and Body Image Disorder in Cerebral Palsy

Cerebral palsy is a multiple disability manifested by motor deficits and impairments of cognition, language, and body perception. To assess if body schema and body image distortion in children and youth with cerebral palsy can be represented through draw-a-person-test, outcome measure of conscious and subconscious body awareness, visual perception and cognition in two age-matched groups, one with cerebral palsy and other with developmental disability, were collected. The outcome was compared within the two groups and with reference data (healthy population) and correlated with the outcome of draw-a-person test. Decreased scores in the draw-a-person test in subjects with cerebral palsy compared both to subjects with developmental disorders and to healthy population had strongly correlated with decreased scores in visual perception. This suggests that draw-a-person test may provide a preliminary guidance for the assessment of visual perception. No statistically significant effect of cognitive abilities on performance in the draw-a-person test was found. The influence of both conscious and subconscious body awareness on the scores in the draw-a-person test was not significant, which confirms that this test alone is not fully reliable to detect the body schema and body image disorder in cerebral palsy.

Three-dimensional experimental study of loose top-coal drawing law for longwall top-coal caving mining technology

Based on the loose medium flow field theory, the loose top-coal drawing law of longwall top-coal caving（LTCC） mining technology is studied by using self-developed three-dimensional（3D） test device. The loose top-coal drawing test with shields and the controlled test without shields are performed in the condition without any boundary effect. Test results show that shields will cause reduction in drawing volume of coal in the LTCC mining. The deflection phenomenon of drawing body is also observed in the controlled test, which is verified that the deflection of drawing body is caused by shield. It is found that the deflection angle decreases with increasing caving height, with the maximum value of atailand the minimum value of 0. In addition, the formula to calculate the drawing volume is proposed subsequently.The deflection of drawing body is numerically simulated using particle flow code PFC3 Dand the proposed formula to calculate drawing volume in LTCC is also verified.

Numerical and theoretical investigations of the effect of the gangue-coal density ratio on the drawing mechanism in longwall top-coal caving

Discrete element calculations of the top-coal drawing process for diferent gangue-coal density ratios were conducted to investigate the efect of the gangue-coal density ratio on the drawing mechanism in longwall top-coal caving.The efects were analyzed for the drawing body,the top-coal boundary,and the recovery of top coal.The results show that for increasing density ratio,the initial drawing body on the goaf side is farther away from the drawing support and its width and volume gradually increase.The upper part of the sickle-shaped drawing body extends near the initial drawing body with increasing density ratio in the normal cycling stage,and the distance from the drawing body to the initial drawing body is its maximum width.The larger the density ratio,the smaller the height of the top coal above the goaf at the end of the initial drawing process.The height of the top-coal boundary decreases with increasing density ratio,until it reaches a limit.In a normal cycle,due to hysteretic development,the top-coal boundary moves toward the goaf until the density ratio is approximately 2.0,which is consistent with the physical experiment results.Finally,increasing the advance length of the working face is benefcial for increasing the overall recovery of top coal.

丝绸之路交融下早期于阗佛寺壁画中的人体图像研究——以和田达玛沟出土晋代壁画为中心

21世纪以来在新疆和田策勒县达玛沟古代佛寺遗址的考古发掘中,出土了7块绘制于晋代的壁画残片。这组壁画残片中蕴含着7个裸体、半裸体的伎乐天神人体形象。达玛沟晋代佛寺壁画的艺术风格具有早期犍陀罗艺术的特质,人体造型具有秣菟罗艺术的因素。壁画注重以线描表现人体的审美取向是受中原人体绘画的影响。这组壁画采用倒“U”形图式构图是对大夏—亚里克艺术中“列龛立佛”模式的模拟,线描与晕染相结合的绘画方法,展现出在中原文化影响下早期于阗佛教绘画创作的本土化实践。

多策略检视问题设计 确保试题命制质量——由一道错题引发的思考

在命题实践中,一味求新求异,致使试题所考查的知识点超出中学物理范畴,难以达到检测学生核心素养的发展过程与现有水平的目的.以一个考查连接体的经典错题为例,尝试采用微元法、求导法、极坐标法及Origin绘图4种策略厘清连接体中加速度关联情景,剖析该题错误成因,分析相同知识点在高考题中应如何设问,以规避错误的发生.希望引起一线命题者的共鸣,以此促进命题质量的提升.

轿车侧围提高材料利用率工艺方案探讨

本文主要着重讨论轿车侧围零件的材料利用率提升问题。针对的问题点在于轿车侧围顶盖侧和门槛侧、拉延筋工艺方案、板料开卷棑样方案。之所以选择顶盖侧和门槛侧做为提升材料利用率的重点,因为顶盖侧工艺方案的选择、拉伸深度、开卷棑样等对整个零件的品质和材料利用率有很大的影响,并且对于模具的设计制造调试有重要意义。

THE SEEPAGE CHARACTERISTICS OF HETEROGENEOUS BODY WITH DIFFERENT SPREADING SOLUTION MODES AND ITS APPLICATIONS

As the dump was a typically heterogeneous body, the seepage was different with varied spreading solution modes. The phenomenon of lamination that occured in the site was simulated using three layers in an indoor experiment, and the seepage effect comparison experiment of the inside spreading solution model and the top spreading solution model have been carried out. In the inside spreading solution mode, the phreatic planar flew without infiltration and the parallel layer motion model was used to calculate the seepage coefficient and equivalent seepage coefficient of each state respectively. In the top spreading solution model, the phreatic planar flew with an even infiltration on the surface, and the vertical layer motion model was adopted to calculate the above coefficient. The results showed that the seepage coefficient of the inside model was larger than the top model in the heterogeneous body, The ratio of them was between 1.42 and 3.07. On the basis of these results, the following new technologies were discussed： installing a few small diameter mechanical pore sand piles with every lamination in the using dump; drilling some holes one-off in the unused dump. These two methods could changed the top spreading solution into the inside model, thus the seepage in the dump was improved.

X-Ray Vision: The Mental Genealogy of the Anatomy of the Interior of the Human Body

Background: The concepts of the Young Person and of an Elderly Person go through an evolutionary diversification during the Human lifecycle and are permeable to diverse biopsychosocial factors involved in the definition of the lifecycle stages. Therefore, assessing this subjectivity in different stages of development and population fringes may be a determinant key factor to assist the implementation of successful disease prevention and health promotion strategies. Aim: The aim of the present study was to discern how Fine Arts’ college students of the Anatomy class mentally represent the inner morphology of the human body of the Young Person and of an Elderly Person. Method: For such, 126 students were asked to draw the interior of the body of a Young Person and of an Elderly Person. In all, 252 drawings were collected and analysed, based on a coding data grid designed for this purpose. Hence, a comparative analysis of these two different vital lifecycle phases was achieved. Results: The results suggest anatomical differences in the pictorial representation of the Young Person and of the Elderly Person, namely in the accentuation of the curvatures of the vertebral column, retrusion of the lower jaw and muscle flaccidity. Conclusions: Although the body schema was the same for all individuals, the body image was singularly depicted and linked to each individual’s history, representing a synthesis of his idiosyncratic perceptions, experiences and particularities.

Body Image Disturbance and Dissatisfaction, Scorn and Stigma in Severely Obese Individuals, a Case-Control Study

Background: The obesity rate is rising. The aims of this study were to elucidate the connection among body image disturbance and dissatisfaction, scorn and stigma in severely obese individuals using a case-control method. Method: The study group consisted of 112 individuals receiving permanent disability pensions primarily for obesity. The controls were selected by random sampling. The controls were matched with the subjects by place of residence, gender, age, the time since the pension was granted and occupation. Psychiatric interviews and psychological assessments were conducted with all participants. The results were analyzed via chi-squared tests (χ2-tests) and percent distributions. The subject and control groups were compared via paired t-tests. Conditional logistic regression analysis was also conducted. Results: In the Draw a Person test, we found disorganization of the body image to some degree in the subject group. Some significant differences were found between the Machover index and the wholeness index. The Rorschach variables obtained some differences in the responses between the subject and control groups. Obesity was a problem in all age groups. In the study group, half of the participants thought that they were obese. Most of the participants had endured scorn and contempt directed at them due to being overweight. Conclusions: We believe that our study provides a novel and necessary overview of the connection among body image disturbance and dissatisfaction, scorn and stigma.

水平分段综放开采顶煤放出体理论计算模型

水平分段综放开采是急倾斜特厚煤层的主要开采方法之一。水平分段综放开采工作面相对较短,导致顶、底板边壁对放煤规律的影响较大。基于BBR理论,采用Bergmark-Roos (B-R)模型分析了存在倾斜边壁影响时的顶煤运移规律及放出体形态变化机理;建立了水平分段综放开采受顶、底板侧边壁影响的放出体理论计算模型,推导了包含轴倾角参数的放出体边界方程;通过颗粒流离散元数值分析得出了轴倾角参数与边界条件的定量关系,采用物理相似实验数据对理论模型进行了验证,提出了不同煤层倾角范围内的合理分段高度及放煤方式优化建议。研究结果表明:倾斜边壁的存在使得散体顶煤受到更大的横向应力,从而改变了顶煤颗粒运移加速度的方向;近边壁处放煤口两侧散体顶煤递补潜力的差异,导致其运移加速度的大小不同;顶煤加速度大小和方向的改变导致放出体轴线方向偏离重力方向。受倾斜边壁影响,放出体形态在轴线两侧呈现非对称性,与近底板侧相比,近顶板侧放出体受边界影响的程度更大;放出体轴倾角β随着煤层倾角的增大呈线性增大关系。随着不放煤段长度的增大,近顶、底板侧放出体的轴倾角均逐渐趋近于90°。物理模拟试验结果验证了理论模型的准确性;采用“底板单轮、中部多轮”、端头逆序放煤方式可有效利用放出体形态特征,减少近顶、底板侧残煤损失。

特厚煤层综放开采多口同时放煤三维实验研究

为提高特厚煤层综放工作面顶煤回收率及放煤效率,重点研究了多口同时放煤的放煤方式。根据塔山煤矿8222工作面实际情况,进行了多口同时放煤三维相似模拟实验。结果表明:首次放煤时,单口放煤放出体大致呈下窄上宽的漏斗状,多口同时放煤放出体呈现中部宽、两端窄的特点,放煤量呈现单口>双口>三口的现象。首次放煤时,开口数目越多煤岩分界线的斜率越大,对顶煤的扰动范围越大,煤岩分界线的最低点越高,损失的低位顶煤越多,且煤岩分界线最低点基本在该组支架的中心位置;放煤结束后,三口组放出更多支架上方及前方的中低位顶煤,放煤量总体呈现三口>双口>单口的现象。

浅析人体结构线与服装结构制图

目前,我国社会经济平稳运行,人们的生活质量不断提升,对服装要求也越来越高,更加注重服装的舒适度、美观度及个性化。作为连接服装设计和服装制作的关键节点,服装结构制图是服装设计师的必备素养之一。将人体结构线用于服装结构制图中,有利于实现“量体裁衣”。开展服装结构制图前,相关人员需先分析人体的体表特征,了解人体结构线,如此方能确保制图的合理性。文章简述人体结构线与服装结构制图的基本概念,分析二者间的关系,探讨人体结构线在服装结构制图中的具体应用,以期为提升服装结构设计与人体特点间的结合度、推动服装行业可持续发展提供助力。

项目化教学在中职时装画课程中的实践研究

服装绘画是表达服装设计理念的重要手段。以时装画技法课程为例,基于项目化教学的目的创设情境,分析实际产品从调研、开发到落地的系统性任务,探讨任务的落实方法,引导学生完成能够展现设计师的设计意图和构思的服装款式图和效果图的绘制,以帮助学生增强对岗位工作能力需求的了解,完善对工作任务流程的认知,提升绘画技法,促进学生养成积极地学习习惯,为学生的职业能力综合发展奠定坚实的基础。

急倾斜特厚煤层走向长壁综放工作面顶煤运动规律研究

通过相似材料模拟试验及FLAC数值模拟,对宝积山煤矿急倾斜厚煤层走向长壁综放开采顶煤运移规律进行了研究。通过分析顶煤运移及主应力分布特点表明,不同角度下松散放出体仍为近似椭球体,在煤层倾斜方向上轴线并未偏移;工作面角度对放出体发育高度及形态有较大影响,同时影响高位顶煤放出。研究对704工作面放煤工艺的参数优化具有指导意义。

板材液压成形技术与装备新进展

随着板材零件向大尺寸、薄壁、深腔、复杂曲面以及难变形材料方向发展,具有低成本、高柔性的板材液压成形技术在航空、航天、汽车等制造业受到高度重视,并面临新的机遇和挑战。介绍板材液压成形技术的发展现状,重点介绍近年发展的径向主动加压充液拉深、预胀充液拉深、正反向加压充液拉深、双板成对液压成形和热态液压成形技术。分析国内外板材液压成形技术在汽车、航空航天等领域的应用现状,综述板材液压成形装备的研制进展,介绍正在研制的世界最大的吨位为150 MN、液体容积为5 m3的液压成形装备,对板材液压成形技术的发展趋势进行展望。

车身覆盖件模具数字化制造技术

根据车身覆盖件的产品特点 ,进行工艺补充面、压料面、拉延筋、凹模圆角的设计 ,得到完整的三维工艺数模 ;对车身覆盖件进行拉延成形数值模拟 ,通过板料成形极限图、厚度分布图、应力应变分布图 ,保证覆盖件的工艺数模具有良好的成形性能 ;根据验证的工艺数模 ,进行模具三维结构设计和数控加工 ;对覆盖件模具进行了CAD/CAE/CAM一体化集成。

覆盖岩层下矿岩流动过程数值模拟

利用离散元中刚性块体模型 ,模拟了多种放矿制度下 ,覆盖岩层与矿石的相互作用及移动过程 ,反映了矿岩的流动特点和接触线变化过程。研究表明 ,用离散元方法模拟非均匀矿岩散体运动过程是适合的 ,能够用于采场结构参数优化、出矿方式选择、放矿管理和对矿石的损失与贫化指标进行预测。

综放开采顶煤放出体理论计算模型

从理论上描述了综放开采顶煤放出体的形态及影响因素,引用散体介质力学中的Berg-mark-Roos模型(B-R模型),考虑了综放支架对顶煤放出过程及放出体的影响,通过散体顶煤三维放出相似模拟和PFC3D数值模拟,得到了重力加速度修正系数K,对B-R模型进行了改进,改进后的模型可以准确描述顶煤放出过程,得到了顶煤放出体理论形态。支架掩护梁-散体顶煤和顶煤-顶煤之间摩擦因数f的差异会导致顶煤放出体左右两侧散体颗粒临界运移角度θG的不同,使放出体向支架前方超前发育,这一放出体理论形态与BBR研究中顶煤放出体呈"切割变异椭球体"的形态相吻合,使用该理论模型可预测不同顶煤厚度条件下的放煤时间。

基于BBR的特厚煤层综放开采放煤方式优化研究

合理的放煤方式是特厚煤层综放开采顶煤充分放出的关键。基于BBR研究体系,对特厚煤层综放开采的放煤方式进行了优化研究,提出了分段大间隔放煤方式;给出了特厚顶煤条件下合理放煤间隔的确定公式,并讨论了其关于破碎顶煤厚度、破碎直接顶厚度和松动体偏心率的敏感性;最后采用PFC数值模拟的方法比较了不同放煤方式的放煤效果。结果表明,与顺序放煤和普通间隔放煤方式相比,分段大间隔放煤方式扩大了可放出区域,减少了架间残煤,使顶煤采出率分别提高了18.2%和9.1%。