Improving recovery in sublevel top coal caving mining by using partially reverse drawing technique

The sublevel top coal caving(SLTCC)mining technology is extensively employed in steeply inclined thick coal seams.Because of the typical characteristics of the short coal face in this mining method,a signifi-cant portion of the top coal is lost at the face end.For reducing the coal loss,the partially reverse drawing technique(PRDT)is proposed as a novel top coal drawing technique.Meanwhile,based on the Bergmark-Roos model(B-R model),a theoretical method for calculating the recovery ratio of top coal based on the top coal boundary equation and residual top coal amount is proposed.The mechanism of PRDT to reduce top coal loss at the face end is revealed by comparing with single-round sequential drawing technique(SSDT).Physical experiments and in-site observation data were used to verify the theoretical model.The results show that PRDT can effectively reduce the amount of residual coal near the roof by optimizing the shape characteristics of top coal boundary.Suggestions for improve recovery ratio in Wudong Coal Mine were given based on its face parameters.

Effect of wire diameter compression ratio on drawing deformation of micro copper wire

A crystal plasticity finite element model was developed for the drawing deformation of pure copper micro wire,based on rate-dependent crystal plasticity theory.The impact of wire diameter compression ratio on the micro-mechanical deformation behavior during the wire drawing process was investigated.Results indicate that the internal deformation and slip of the drawn wire are unevenly distributed,forming distinct slip and non-slip zones.Additionally,horizontal strain concentration bands develop within the drawn wire.As the wire diameter compression ratio increases,the strength of the slip systems and the extent of slip zones inside the deformation zone also increase.However,the fluctuating stress state,induced by contact pressure and frictional stress,results in a rough and uneven wire surface and diminishes the stability of the drawing process.

Modeling asymmetric fracture mechanics of Mg alloy wire in drawing process

In this study,a numerical analysis was conducted on the ductile fracture of a 2-mm diameter Mg-1Zn-0.5Mn-0.5Sr-0.1Ca alloy wire during drawing.The hexagonally close-packed crystal structure of Mg alloys causes asymmetric fracture behavior,especially in the compression region.The aim of this study is to develop a comprehensive damage model for Mg alloy wire that accurately predicts ductile fracture,with a focus on the compression region.A novel experimental method was introduced to measure the ductile fracture of Mg alloy wires under different stress states.The wire drawing process was simulated using the Generalized Incremental Stress-State dependent damage(GISSMO)Model and the Semi-Analytical Model for Polymers(SAMP)model.The damage model's prediction and the experimental results were found to be in excellent agreement,especially in determining crack initiation.Computational analysis established a safe zone diagram for die angle and reduction ratio,and experimental validation confirmed the feasibility of this approach.The proposed damage model can provide a practical and reliable analysis for optimizing the drawing process of Mg alloy wire.

Exploration and Practice of the“One Core,Two Lines,Four Dimensions”Ideological and Political Teaching Model:Taking the Interpretation of Concrete Plane Construction Drawings Course as an Example

This paper first deeply interprets the connotation of the“One Core,Two Lines,Four Dimensions”ideological and political teaching model in courses.Then,it explores the significant meaning of integrating this teaching model into the Interpretation of Concrete Plane Construction Drawings course.Finally,based on the challenges faced in this work,corresponding educational countermeasures are proposed to help improve the effectiveness and quality of ideological and political construction in the Interpretation of Concrete Plane Construction Drawings course and enhance the level of talent cultivation.

基于BIM技术的福建木结构文物建筑修缮保护研究——以华林寺大殿为例

以福州市华林寺大殿为研究对象,该文首先对2016年华林寺大殿的现状勘察病害与修缮措施进行了分类分析。其次,搭建和添加了更适宜福建官式木结构文物建筑保护修缮设计的BIM与参数。再次,实现了在BIM中呈现华林寺大殿现状病害以及分别生成现状图纸和方案图纸的技术过程。最后,基于相关标准尝试建立福建官式木结构文物建筑信息模型修缮设计标准框架,可为福建地区建筑遗产保护修缮工程中建筑信息模型的建立、交付提供参考。将BIM技术运用到福建官式木结构文物建筑修缮是一次完美的尝试,为该地区的官式文物建筑保护提供了一定的技术支撑。

Influence of drawing process parameters on forming of micro copper tube with straight grooves

Using high-speed oil-filled spinning method,high quality micro copper tube with straight grooves（MCTSG） with an outer diameter of 6 mm was obtained.Then,MCTSG with an outer diameter of 3-6 mm was fabricated successfully by multi-pass drawing processing method.The influence of drawing parameters on the forming of micro straight grooves was investigated based on the forming mechanism.The results show that the values of groove depth and width decrease,while the wall thickness increases as the drawing diameter decreases.At the same time,the groove depth and width increase,while the wall thickness decreases as the die angle increases.The drawing force increases as the reduction increases.Excessive copper tube reduction may results in groove folding and segmental teeth.The drawing force decreases firstly and then increases with the increases in die angle.When the die angle α is 16°,the drawing force is the smallest,indicating 16° is the optimal angle.

Microstructure and texture of commercially pure titanium in cold deep drawing

The development of microstructure and texture during cold deep drawing of commercially pure titanium（CP-Ti） was investigated.Three parts,stretching region,drawing region and flange region,were sequentially formed in the deep drawing process of the hemispheric surface part,with reference to deformation modes and strain regimes.Results show that the plastic strain is accommodated by dislocation slip and deformation twinning in the whole deep drawing process.The texture of the CP-Ti sheet and its drawn part consists of rolling texture component and recrystallization texture component.The intensity and type of the initial texture varied during the drawing process are related to the production of deformation twinning and dislocation slip.Twinning weakens the initial texture by randomizing the orientations of crystals,especially for the recrystallization texture.The recrystallization texture in the drawing region disappears due to the significant forming of twinning.Furthermore,over drawing would result in the predominance of dislocation slip and the texture is strengthened.

Texture evolution and its simulation of cold drawing copper wires produced by continuous casting

The texture evolution of cold drawing copper wires produced by continuous casting was measured by X-ray diffractometry and electron back-scatter diffractometry,and was simulated using Taylor model.The results show that in the drawn poly-crystal copper wires produced by traditional continuous casting,111 and 100 duplex fiber texture forms,and with increasing strain,the intensities of 111 and 100 increase.In the drawn single-crystal copper wires produced by Ohno continuous casting,100 rotates to 111,and there is inhomogeneous distribution of fiber texture along radial direction of the wires,which is caused by the distribution of shear deformation.Compared with 100,111 fiber texture is more stable in the drawn copper wires.Comparison of the experimental results with the simulated results shows that the simulation by Taylor model can analyze the texture evolution of drawn copper wires.

Effect of electropulsing on deformation behavior of Ti-6Al-4V alloy during cold drawing

Electron backscattered diffraction （EBSD） and transmission electron microscopy （TEM） were used to investigate effect of electropulsing on microstructure and texture evolution of Ti-6Al-4V during cold drawing. Research results demonstrate that the electropulsing treatment （EPT） can enhance the deformability of the grains with unfavorable orientations, which makes the compatibility of deformation among grains much better. A comparison in texture evolution between conventional cold drawing and EPT cold drawing indicates that the EPT promotes prismatic 〈a〉 slip moving, restricts pyramidal 〈c＋a〉 slip occurring and accommodates the deformation with c-component by grain boundary sliding. The fraction decrease of low-angle grain boundaries for samples deformed with EPT reveals that the application of electropulsing restricts the formation of the incidental dislocation boundaries and the geometrically necessary boundaries.

Effects of stress state on texture and microstructure in cold drawing-bulging of CP-Ti sheet

Three different stress states of the combination of tensile（t） stress and compressive（c） stress,t t,t c and t c c,exist in the deformed commercially pure titanium（CP-Ti） sheet during cold drawing-bulging.The textures and microstructures in the different stress state regions were investigated by means of XRD and TEM analysis.Similar development of texture and microstructure is achieved with less thickness strain under multiaxial stresses in drawing-bulging than in cold rolling.The results show that texture and microstructure are much sensitive to multiaxial stresses.Twinning is more easily activated under compressive stress than tensile stress.Prism a slip is heavily affected by tensile stress,resulting in a remarkable change of the intensity of（0°,35°,0°） texture,while pyramidal c＋a slip,forming（20°,35°,30°） texture,weakens with the increase of thickness strain in spite of stress state.

基于虚拟现实及BIM的泛土木工程制图教改探索

随着我国智能制造产业的不断发展,作为土木工程专业重要的基础课程,土木工程制图课程的教学模式势必向智能化和信息化迈进。将虚拟现实技术与BIM建模技术结合起来,针对工程制图的理论教学、实践教学及考查方式开展多维度课程改革。对现有“多媒体+实物教具展示”的教学方式进行优化,以虚拟模型库为纽带,串联虚拟现实理论教学以及三维建模、手工绘图实践教学,探讨土木工程制图开展虚拟测绘课程的模式,为学生提供具有交互性、沉浸感及趣味性的教学体验,充分开发学生的空间想象及动手能力,提升学生自主学习能力。进一步根据不同学生构建不同的虚拟学习场景,实现差异化教学,提高教学效果,为培养满足智能制造要求的优秀工科学生奠定基础。

Application of ultra-smooth composite diamond film coated WC-Co drawing dies under water-lubricating conditions

A specific revised HFCVD apparatus and a novel process combining HFCVD and polishing technique were presented to deposit the micro-and nano-crystalline multilayered ultra-smooth diamond（USCD） film on the interior-hole surface of WC-Co drawing dies with aperture ranging from d1.0 mm to 60 mm.Characterization results indicate that the surface roughness values（Ra） in the entry zone,drawing zone and bearing zone of as-fabricated USCD coated drawing die were measured as low as 25.7,23.3 and 25.5 nm,respectively.Furthermore,the friction properties of USCD films were examined in both dry sliding and water-lubricating conditions,and the results show that the USCD film presents much superior friction properties.Its friction coefficients against ball-bearing steel,copper and silicon nitride balls（d4 mm）,is always lower than that of microcrystalline diamond（MCD） or WC-Co sample,regardless of the lubricating condition.Meanwhile,it still presents competitive wear resistance with the MCD films.Finally,the working lifetime and performance of as-fabricated USCD coated drawing dies were examined under producing low-carbon steel pipes in dry-sliding and water-lubricating conditions.Under the water-lubricating drawing condition,its production significantly increases by about 20 times compared with the conventional WC-Co drawing dies.

Flexible die drawing of magnesium alloy sheet by superimposing ultrasonic vibration

Combining solid granule medium forming technology with ultrasonic vibration plastic forming technology, ultrasonic vibration granule medium forming （UGMF） technology was proposed. To reveal the effect of ultrasonic vibration on flexible-die deep drawing, an ultrasonic vibration with a frequency of 20 kHz and a maximum output of 1.5 kW was on the solid granule medium deep drawing of AZ31B magnesium alloy sheet. The results revealed that ultrasonic vibration promotes the pressure transmission performance of the granule medium and the formability of the sheet. The forming load declines with the ultrasonic amplitude during the drawing process as a result of the combined influence of the ＂surface effect＂ and the ＂softening＂ of the ＂volume effect＂.

Effects of tribological behavior of DLC film on micro-deep drawing processes

To decrease the size effects of friction in microforming, three kinds of surface coatings, such as diamond-like carbon（DLC）, TiN and MoS2, were deposited on surfaces of dies with plasma based ion implantation and deposition（PBII D） method and magnetron sputtering technique, respectively. The tribological behavior of surface coatings was analyzed considering plastic deformation of specimen at contact interface. The analyses indicate that there is a lower coefficient of friction（COF） and a high wear resistance under the condition of large strain/stress when using the DLC film. The graphitization of DLC film occurs after 100 times of tests. The mechanism of graphitization was analyzed considering energy induced by friction work. The effects of DLC film properties on qualities of micro-deep drawn parts were investigated by analyzing the reduction of wall thickness, etc. The results indicate that DLC film is very helpful for improving the qualities of the micro-parts.

基于Visio Drawing Control控件的图形化潮流计算软件开发

针对VC,Delphi等工具开发电力系统分析计算软件图形可视化的缺陷,提出并研究了一种基于VisioDrawing Control图形控件,利用VC进行二次开发的图形化电力系统潮流计算软件开发的技术,研究了基于该控件的图形化建模方法及电网拓扑结构的自动识别,开发了实用的电力系统图形化潮流计算软件.实践表明,基于Visio Drawing Control的二次开发技术为图形化电力系统潮流计算软件的开发提供了新的有效的途径.

高位肛瘘挂线疗法研究进展

肛瘘也称肛管直肠瘘,是肛肠科常见基础疾病,亦是仅次于痔病的第二大肛肠类疾病。其好发于男性,多数患者年龄为20~40岁。肛瘘的主要症状是疼痛、反复性流脓或粪便排出、瘙痒和周边皮屑脱落。高位肛瘘是一类常见的肛瘘类型,其瘘管及分支都在肛提肌与肛管直肠环的上方,具有走行复杂、位置高、瘘管弯曲等特点,临床缺乏有效治愈手段,其术后并发症和肛门功能的减退严重影响了患者的生活质量。高位肛瘘挂线术是传统的手术方式,其以“简、便、廉、验”的特点成为中国现代肛肠科治疗高位肛瘘的常规手段,并根据病情的不同,遵循“因瘘而异”原则给予治疗,可获得不错的临床效果。

工程图协同审议与存档管理系统VHDrawings的设计与实现

工程设计单位的审图工作是一个需要多人参与、多次往复的过程。用传统的方法传递设计图与修改意见,速度慢且易出错,限制了工程设计单位工作效率的提高。该文介绍了一个计算机辅助的工程图协同审议与存档管理系统VHDrawings的设计与实现。着重讨论了协同审图工作流的管理以及工程图自动识别技术在图档管理中的应用。为设计单位提高工作效率、优化管理流程提供了一种参考。

飞腾平台上高效的OpenGL文字绘制方法

针对飞腾CPU平台上OpenGL文字绘制性能较低的问题,提出一种高效文字绘制方法。基于对基础绘制流程的分析,设计文字的全属性缓存策略,减少绘制数据传输和OpenGL状态切换;并行化CPU端计算密集的过程,提升文字属性处理效率;构建实例化渲染模式,实现GPU端批量化渲染。测试结果表明,在飞腾终端平台上,该文字绘制方法的绘制性能明显优于现有工作,绘制的帧率可大幅提升,资源的利用率更加合理。

Graphical Simulator for Chinese Ink-Wash Drawing

Simulating the traditional painting art by computer graphics is a challenging and attractive subject. Basing on the experience in the ink wash drawing, in this paper, we expound the artistic characters of ink wash painting and particularly analyze the characteristics of the materials used in the ink wash drawing and the relationships between them. A simulation model is presented and some typical visual effects of the ink wash painting are realized.

0Cr17Ni7Al弹簧钢丝的残余应力分析与翘距控制

为了解决0Cr17Ni7Al弹簧钢丝在拉拔过程中出现的残余应力问题及钢丝卷曲后的回弹现象,通过实验观测和有限元模拟相结合的方法,分析了拉拔工艺参数对残余应力及钢丝翘距的影响,并构建了残余应力与翘距之间的量化关系模型。结果表明:卷丝过程中丝圈轴向的塑性变形是翘距产生的主要原因,而残余应力的分布特征对翘距有显著影响;通过调整拉拔参数可以有效控制翘距;翘距与残余应力之间的关系模型准确度高达0.97。研究结果深化了对拉拔工艺中残余应力影响的理解,为钢丝的后续加工和应用提供了技术参考。