大型多跨厂房及烟囱定向爆破拆除

采用延时爆破技术,一次定向拆除了大型多跨厂房及烟囱。利用厂房中间的框架结构定向爆破形成的倾倒趋势,前推汽机房,后拉锅炉房,促进框架结构前后两侧排架结构的定向倒塌,从而实现多跨厂房的定向爆破拆除。克服了大型多跨排架结构厂房整体性差、不利于定向倾倒的难题,避免了排架结构后排支撑立柱不倒甚至反倒的问题。合理的延时控制,使烟囱定向倒塌在厂房的废碴上,减缓了塌落冲击振动。本文阐述了厂房及烟囱的爆破参数和延时起爆网路的设计、爆破安全控制与防护措施,成功的经验可供类似工程参考。     

100 m高钢筋混凝土烟囱双向切口爆破时差研究

由于场地大小的限制,高耸烟囱的爆破拆除需采用折叠倒塌的方式,为进一步研究复杂环境下100 m钢筋混凝土烟囱的双向折叠定向倾倒爆破拆除中上下爆破切口的最优延时起爆时差,利用LS-DYNA联合Hypermesh的数值模拟方法,采用直接法建立共节点分离式模型,将钢筋节点与混凝土节点直接产出单元体,进行数值模拟仿真,同时与工程实际进行对比分析.通过对烟囱上下切口不同起爆时差下的倒塌过程和结果进行模拟分析,得出起爆时差分别为1s、1.5s、2s、2.5s、3s下的倒塌过程、烟囱倒地破碎程度、爆堆范围和烟囱触地速度,分析比较后确定上下切口的最优起爆时差为2.5 s,并且数值模拟计算的结果与工程实际高度吻合.     

45m钢筋混凝土烟囱同向折叠爆破拆除

为了安全实施45m钢筋混凝土烟囱在距33m处高压线和倒塌空间受限环境中的爆破拆除,采取双切口同向折叠爆破拆除技术,最终确定上、下切口延时时间5s,超长的延时时间保证了烟囱上段筒体倾倒加速后下段筒体才开始倾倒,避免烟囱上段筒体倒塌发生前倾现象,缩短了烟囱的倒塌长度,使其在32m以内,确保了高压线的安全。该工程对于烟囱双切口同向折叠及延时时间的选择具有一定的借鉴意义。     

45m钢筋混凝土烟囱同向折叠爆破拆除

为了安全实施45m钢筋混凝土烟囱在距33m处高压线和倒塌空间受限环境中的爆破拆除,采取双切口同向折叠爆破拆除技术,最终确定上、下切口延时时间5s,超长的延时时间保证了烟囱上段筒体倾倒加速后下段筒体才开始倾倒,避免烟囱上段筒体倒塌发生前倾现象,缩短了烟囱的倒塌长度,使其在32m以内,确保了高压线的安全。该工程对于烟囱双切口同向折叠及延时时间的选择具有一定的借鉴意义。     

120m超高塔架式钢结构烟囱定向爆破拆除

介绍了一座120m高钢结构烟囱的定向爆破拆除工程。通过对烟囱自身结构特点及周围环境的分析,合理的选择爆破切口、爆破参数、延时起爆网路及安全防护等技术措施。为了确保起爆后烟囱沿设计方向顺利倒塌,预先对爆破部位钢板进行机械切割预处理,并针对各爆破部位钢板形状设计出相配合尺寸的聚能切割器。爆破拆除的钢结构烟囱倒塌在设计范围内,四周建(构)筑物和设施完好无损。该烟囱的爆破拆除在安全和质量上都达到了预期效果,可为类似爆破工程提供经验。     

烟囱折叠拆除爆破切口高程与起爆时差优化模拟

针对烟囱折叠爆破拆除的两个最重要的因素,上部切口高程和上、下切口起爆时差优化配置才能保障工程安全、可控的情况。利用Ansys/LS-dyna非线性有限元软件首先模拟了50m高烟囱在上部切口20m高程时,0.1、1.0、2.0s的起爆时差对烟囱倒塌过程和倒塌后爆堆范围的影响;然后模拟上部切口10、15、20m高程的烟囱双向折叠爆破,在0.1、1.0、2.0s起爆时差方案下,得到不同切口高程的爆堆范围,最后比较了4种高程的爆破效果及爆堆范围。上部切口位于15m处时,烟囱倒塌过程更为合理,爆堆范围也比较接近参考范围。通过模拟和分析表明,对于50m高烟囱体双向折叠爆破拆除,上部切口高程和上、下切口起爆时差是决定爆破效果好坏的两个关键控制点,上切口高程为20m处时,随着起爆时差的增大,爆堆范围也增大。上部切口位置的选取使上部筒体质量占烟囱总质量的59.4%左右时,更有利于保障工程的安全性和倒塌过程、爆堆范围的可控性。     

120m超高塔架式钢结构烟囱定向爆破拆除

介绍了一座120m高钢结构烟囱的定向爆破拆除工程。通过对烟囱自身结构特点及周围环境的分析,合理的选择爆破切口、爆破参数、延时起爆网路及安全防护等技术措施。为了确保起爆后烟囱沿设计方向顺利倒塌,预先对爆破部位钢板进行机械切割预处理,并针对各爆破部位钢板形状设计出相配合尺寸的聚能切割器。爆破拆除的钢结构烟囱倒塌在设计范围内,四周建(构)筑物和设施完好无损。该烟囱的爆破拆除在安全和质量上都达到了预期效果,可为类似爆破工程提供经验。     

烟囱折叠拆除爆破切口高程与起爆时差优化模拟

针对烟囱折叠爆破拆除的两个最重要的因素,上部切口高程和上、下切口起爆时差优化配置才能保障工程安全、可控的情况。利用Ansys/LS-dyna非线性有限元软件首先模拟了50m高烟囱在上部切口20m高程时,0.1、1.0、2.0s的起爆时差对烟囱倒塌过程和倒塌后爆堆范围的影响;然后模拟上部切口10、15、20m高程的烟囱双向折叠爆破,在0.1、1.0、2.0s起爆时差方案下,得到不同切口高程的爆堆范围,最后比较了4种高程的爆破效果及爆堆范围。上部切口位于15m处时,烟囱倒塌过程更为合理,爆堆范围也比较接近参考范围。通过模拟和分析表明,对于50m高烟囱体双向折叠爆破拆除,上部切口高程和上、下切口起爆时差是决定爆破效果好坏的两个关键控制点,上切口高程为20m处时,随着起爆时差的增大,爆堆范围也增大。上部切口位置的选取使上部筒体质量占烟囱总质量的59.4%左右时,更有利于保障工程的安全性和倒塌过程、爆堆范围的可控性。     

复杂环境下两座烟囱交叉定向爆破拆除

为了确保电厂生产区内高150 m和180 m两座钢筋混凝土烟囱在一次性爆破拆除中的安全倒塌,在周围环境复杂、设备正常运行的条件下,采用了高位切口控制爆破和延时起爆技术,交叉定向倾倒爆破拆除两座烟囱的爆破技术方案,切口位置分别位于距地面25.0 m和30.0 m处,两烟囱间起爆延期时间为5 s。实践表明,爆破参数、切口位置、倒塌方向和5 s延期时间的选择合理可行,爆破效果良好。     

30m高砖烟囱单向折叠爆破拆除

介绍了复杂条件下的砖烟囱单向折叠爆破拆除。阐述了在倾倒空间不足情况下,为保证烟囱准确倾倒,确定了两段不同段高,单向折叠爆破的技术方案。同时介绍了爆破方案的选择和爆破切口的设计,通过两切口的起爆时差,减弱上下两节烟囱的相互影响,并结合爆破网路设计和有效的安全防护措施,较好地实现了爆破拆除。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.