加卸载下原煤力学特性及渗透演化规律

基于自主研发的煤岩热流固耦合试验系统,在考虑实际开采方式的条件下,进行轴压升高和围压降低的加卸载试验,分析研究不同加卸载速率下原煤的力学特性和渗透演化规律.结果表明:加卸载过程中,轴向应力的加载速率越大,峰值应力附近的曲线平台越长,峰值应力、轴向应变和环向应变也越大,体应变则越小.不同加卸载速率比下含瓦斯煤变形模量均先迅速减小后缓慢减小,到破坏时再迅速降低,而后逐渐保持稳定趋势;在相同轴向应变时,加卸载速率比越小,煤样的变形模量越大.加卸载过程中,煤样的偏应力、渗透率与应变的关系可分为三个阶段:初始压密与弹性阶段、屈服破坏阶段和破坏后阶段.加卸载速率比越小,煤样达到峰值应力时,含瓦斯煤的渗透率和体积变形越大.      

Some features of DNA-tRNA hybrids in the rat

The importance and value of manometry are presented with examples of patients in labour. It is important to distinguish between the pressures and the forces working on the fetus, especially as far as the causes of fetal bradycardia are concerned. Graphs of magnetic lag are shown in order to demonstrate that the tension on the fetus and sometimes on the placenta and the cord precedes and lasts longer than the increase in hydrostatic pressure which accompanies a contraction. The paper includes the following subjects: Introduction and general observations. The patient and the monitoring device and the tolerance to external and internal manometry by the patient. The concepts of pressure and force. The distrubution of pressures and forces in obstetrics. The measure of forces by their conversion into pressure in a manometric system. The interpretation of the results of the measure of pressure and force in obstetrics.     

浅谈高炉用冲压焊接冷却板的损坏原因及改进

冲压焊接冷却板存在许多缺点,这将大大降低冲压焊接冷却板的使用寿命。对冲压焊接冷却板的设计结构和在高炉中的使用工况进行总结,重点分析冲压焊接冷却板的结构和材质失效原因,探讨采用球墨铸铁冷却板来代替冲压焊接冷却板,改善冷却板的冷却性能,从而提高冷却板的使用寿命。并设计密封板和垫板,球墨铸铁冷却板铸造好后,把密封板和球墨铸铁冷却板的冷却箱套焊接在一起,然后再把垫板和密封板、套管焊接在一起。解决了球墨铸铁冷却板本体和冷却箱套之间漏煤气的问题。     

长流程钢铁企业检化验设施的现代化设计

检化验系统对钢铁企业的进厂原料检验、中间产品检测、出厂产品质量判定等有着重要意义。对钢铁企业检化验系统的设置原则、组成和发展趋势进行了介绍,集中化、智能化和信息化是现代化钢铁企业检化验系统的特点。重点论述了原料取制样系统、原料分析中心、冶炼分析中心和轧钢检测中心的建设设计理念。随着中国智能制造发展,全自动智能检测系统、信息流过程自动化及实验室管理自动化已成为当今钢铁企业检化验系统设计不可避免的趋势。     

钛渣酸解过程中物相变化特征探讨

明确物相变化是剖析钛渣酸解机理和改进酸解工艺的关键点之一.综合应用化学分析、X射线衍射(XRD)分析、矿物解离分析以及扫描电镜形貌分析对某74钛渣酸解过程中主要物相的含量、形貌变化以及Ti、Si两种元素的含量及赋存变化进行了研究.结果表明:钛渣主要由黑钛石和辉石组成,酸解过程中黑钛石含量逐渐减小,辉石含量逐渐增加;反应...     

Ni和Nb元素对Fe-Cr-Mo合金力学和阻尼性能的影响

摘要：采用光学显微镜、扫描电镜、透射电镜、弯曲共振试验机和万能材料试验机等分析了复合添加质量分数0.8%Ni元素和0.1%Nb元素的Fe-Cr-Mo合金组织和析出相的大小、形态,研究了Ni和Nb元素的添加对Fe-Cr-Mo合金力学性能和阻尼性能的影响。结果表明,Ni和Nb元素的加入不但使合金晶粒显著细化,而且有效抑制了富Cr析出物的析出,使析出物明显细化且分布弥散。晶粒和析出物的细化同时提高了合金的强度和塑韧性,尤其是显著地提高了材料的塑性。1000和1100℃退火后,Ni和Nb元素的加入将提高减振合金的矫顽力,降低磁致伸缩系数,使减振合金的阻尼性能降低。900℃退火后,Ni和Nb元素的添加虽然提高了合金的矫顽力,但由于Mo元素的回溶使磁致伸缩系数增大,阻尼性能获得提高。     

空间机械臂在轨插、拔孔操作基于力/位姿跟踪指数型阻抗控制

讨论了空间机械臂在轨插、拔孔操作的阻抗控制问题。为此,结合系统动量守恒关系,空间机械臂替换部件末端输出插、拔孔主动力与孔内所受摩擦阻力作用关系,以及第二类拉格朗日方程,推导得到了载体位置、姿态均不受控制情况下,空间机械臂在轨插、拔孔操作过程系统动力学方程。同时,根据相关操作控制系统设计需要,利用系统位置几何关系分析、建立了空间机械臂替换部件末端相对基联坐标系的相对运动雅可比关系。之后,由空间机械臂替换部件末端位姿与末端输出插、拔孔主动力之间的动态关系并结合阻抗控制原理,建立了二阶线性阻抗模型。在上述工作基础上,针对空间机械臂在轨插、拔孔操作过程同时存在运动学与动力学不确定性的情况,设计了空间机械臂替换部件末端力/位姿跟踪指数型阻抗控制策略;并通过李雅普诺夫理论,证明了控制系统的稳定性。提到的控制策略具有结构简单、收敛速度快、稳定性好的特点。系统数值仿真,验证了上述控制策略的有效性。      

阳极板载运车提升卸载装置改进与优化

介绍了贵溪冶炼厂极板转运设备阳极板载运车提升卸载装置的组成及工作原理,并从提升卸载装置缺乏自由度、限位支架损坏摆动撞击、提升装置倾斜重力、硬性碰撞冲击四个方面分析了提升卸载装置产生变形的原因,最终确定是由于提升装置倾斜重力、硬性碰撞冲击导致提升卸载装置产生变形。通过分析,采用加强立板的方式进行改进优化,经计算验证,改进方式是可行的,可以解决阳极板载运车提升卸载装置变形的问题。     

低氧铜杆线铜粉剥离原因分析及其对策措施

表面铜粉剥离,导致铜杆线表面损伤,其对铜杆线拉伸过程具有较大影响。通过扫描电镜分析,剥离铜粉厚度可达25μm,经物相分析确定其主要成分为铜及铜的氧化物。通过对剥离物和杆线表面缺陷进行形貌分析,以铜杆线的生产、加工各环节作为研究对象,并确认了铜杆轧制工艺、无酸清洗工艺、线表擦伤、拉伸角度及拉丝模具等5方面影响因素,制定了相应的对策措施。研究表明,铜杆氧化物剥落和机械损伤是铜粉剥离的主要原因,在铜杆线生产、加工环节,防止氧化物带入铜基体和避免铜线表面损伤能有效减少铜杆线铜粉剥离。     

Intramembrane structure of the sensory axon terminals in bullfrog muscle spindles

Much physiologic and morphologic research has been done into the sensory mechanism of the frog muscle spindle. However, no freeze-fracture study has described in detail the shape and intramembrane structure of the nonmyelinated sensory axon terminals of the frog muscle spindle. In this study, muscle spindles were isolated from the red part of bullfrog semitendinous muscles. Chemically fixed spindles were subjected to freeze fracturing. The sensory axon endings were reconstructed, and the size and density of intramembrane particles (IMPs) were measured along the sensory nerve endings. The axon terminals had four distinctive parts: parent trunks (>0.5 microm in diameter), primary branches (0.15-0.5 microm), terminal branches (<0.1 pm), and varicosities (0.02-0.5 microm). IMPs ranged from 5 nm to 21 nm in diameter and were present in the intramembrane space of the plasma membrane all throughout the nonmyelinated sensory nerve endings. Mean IMP sizes in the protoplasmic face (PF) and the external face (EF), respectively, were 8.1 nm and 8.4 nm in the parent trunks, 8.8 nm and 8.8 nm in the primary branches, 9.4 nm and 9.0 nm in the varicosities, and 8.7 nm and 8.7 nm in the terminal branches. Mean IMP size in the PF was smallest in the parent trunk and largest in the varicosity. Mean IMP densities (numbers of IMPs per microm2) in the PF and the EF, respectively, were 2,500 and 700 in the parent trunks, 2,200 and 500 in the primary branches, 1,700 and 400 in the varicosities, and 1,000 and 300 in the terminal branches. Density decreased with the tapering of the axon terminal, with IMPs distributed evenly in the PF and the EF. The characteristic intramembrane structure of sensory nerve endings is discussed.     

氧氮分析仪的热导检测器及热敏元件选择

讨论了金属中氧氮分析仪所用热导检测器及其核心热敏元件的选择。基于NTC热敏电阻阻值大,所需桥流小,且元件采用惰气保护密闭封装,能够抵御恶劣的环境条件,很好地保持热导检测器测量电桥的对称性、稳定性,具有应用灵活、简单的特点,选择NTC热敏电阻作为热导检测器的热敏元件,并应用于金属中氧氮分析仪,其线性和灵敏度均符合仪器使用和分析要求。采用NTC热敏电阻作为热敏元件、选择扩散型热导池结构研制的热导检测器应用于ON-2008氧氮分析仪中。分别采用高含量和低含量氮的标准物质对仪器的高氮和低氮两个测量通道的线性和精密     

河钢石钢智能制造的思考

对工业革命的发展特点进行了评述,对3.0和4.0的建设过程进行了描述,强调了信息化建设期间应注意的几个问题。在此基础上分析了河钢石钢公司的现状,对河钢石钢公司的发展阶段进行了定义。讨论了河钢石钢公司发展智能制造的必要性和可行性。在阐述作者对智能制造的理解之后,提出了河钢石钢应借搬迁之良机按发展智能制造的思路规划建设。还就河钢石钢建设智能制造3.0和4.0的若干问题提出了具体建议,指出智能制造建设将是一个长期的、持续的升级过程。     

Long time follow-up of flexor tendons of the hand after reconstructive operations. Part 1. Monitoring method

OBJECTIVE: To assess whether it is possible to make accurate vertical measurements of the jaws from panoramic radiographs. METHODS: Five dry skulls were shifted 5 mm forwards and backwards and tilted 5 degrees up and down in the sagittal plane. Panoramic radiographs of each skull were obtained in nine different positions. In the maxilla, three reference lines were used and vertical measurements were made at the distal surfaces of the first premolar and first molar and in the midline. In the mandible, measurements were made at the distal surfaces of the first premolar and first molar, and at the mental foramen on both sides, and in the midline. The points and lines were marked manually and the radiographs were digitized, magnified and measured. RESULTS: Sagittal shifting and tilting had only a slight effect on measurements in the mandible. Sagittal tilting of the head had the greatest effect on all the measurements made from the line between the articular eminences to the alveolar crest, as well as measurements in the maxillary midline. CONCLUSIONS: The line between the articular eminences is unsuitable as a reference line for measurements of the tooth-bearing areas. A slight misalignment of the head does not significantly affect the vertical measurements in the mandible or of the posterior maxilla if the reference lines are in the same vertical plane as the teeth.     

Three-dimensional reconstructions of the developing forebrain in rat embryos

Using a computerized three-dimensional reconstruction technique with serially sectioned rat embryos, changes in the size and form of the forebrain were studied on Embryonic Days (E) 12 (1 day after closure of the neural tube), E15, E18, and E21 (2 days before birth). During this time, the forebrain changes from a relatively simple tubular structure with thin walls surrounding a large ventricular system to a thick-walled brain with a highly convoluted but reduced ventricular system. On E12, the two components of the forebrain, the telencephalon and the diencephalon, cannot be distinguished. Considering the forebrain as a whole (the embryonic prosencephalon), its volume continually increases between E12 and E21 due to the generation, differentiation, and maturation of neurons and glia. Attention was paid to changes in the sizes of the ventricles, the neuroepithelium and the parenchyma. Volumes of the ventricles and the surrounding neuroepithelium rapidly expanded from E12 to E18 and then decreased by E21, while the volume of the parenchyma continually increased. Differential growth of the telencephalon and that of the diencephalon were compared between E15 and E21. The expansion of the telencephalon was much larger than that of the diencephalon. In the telencephalon, the volumes of the lateral ventricles and the surrounding neuroepithelium increased between E15 and E18 and decreased by E21, while in the diencephalon the volumes of the third ventricle and its surrounding neuroepithelium continually declined between E15 and E21. That observation is compatible with previous work showing that the majority of diencephalic structures develop earlier than those in the telencephalon. It is important to note that volume changes in the ventricles and the neuroepithelium are maintained in "lock-step," suggesting a close relationship between the size of the ventricle and the size of the neuroepithelium.     

Diagnostic imaging in otorhinolaryngology--assessment of current status

BACKGROUND: The first conventional x-rays of the paranasal sinuses were received in 1897, just two years after the detection of x-rays. During the following decades several modifications and extensions of conventional radiologic techniques were developed, but routine imaging procedures of the head and neck were mainly restricted to pictures of the paranasal sinuses and the temporal bone. In the fifties, tomography was developed, which gave us a more detailed insight of the anatomy and pathology of the paranasal sinuses and temporal bone. During the last two decades the development of new techniques, i.e. computed tomography (CT) and magnetic resonance imaging (MRI), has significantly increased the importance of modern imaging for the diagnostic evaluation of head and neck diseases. These diagnostic tools enable us to visualize anatomical structures and pathological entities with an accuracy never been expected beforehand. The pace of the improvement of these diagnostic tools, however, requires that both radiologist and otorhinolaryngologist keep up with the adequate indications of CT and MRI in the different areas of the head and neck. A close relationship and cooperation between radiologist and ENT surgeon is therefore indispensible for a fruitful and cost-effective use of modern imaging. Otherwise the patient is exposed to modern medical technology without an equivalent benefit. The purpose of the present paper is mainly to give an update and state of the art of modern imaging techniques in otorhinolaryngology, head and neck surgery. Different areas i.e. paranasal sinuses, temporal bone, salivary glands, oral cavity and oropharynx as well as the neck are discussed in terms of adequate indications for modern imaging in the diagnostic evaluation of different lesions.     

模糊层次分析法在我国深空探测方案优选应用探究

中国深空探测是复杂的系统工程，涉及领域多、技术难度大、经费需求高，目前方案优选方法是论证组论证和中介机构专家评估后形成，该方法论证周期长，不易快速做出科学决策。本文基于模糊层次分析模型，考虑技术、科学、经费等多指标多层次结构，建立系统指标评价模型。以中国探月工程中嫦娥四号任务方案为具体算例，综合专家判断和理论分析，建立各层次指标的判断矩阵，计算权重系数，进而实现总体方案的优选应用评价。结果表明，技术、科学和经费这三个因素相对于周期和效益更为重要。在4个备选方案中，由长征四号丙发射中继星，长征三号乙发射着陆器和巡视器组合体的方案，排序权值最大，因此该方案为最优方案，这也与实际情况一致。本研究可为我国后续各类深空探测方案制定提供快速及科学的理论支撑。      

甘肃洛坝铅锌矿选矿流程考察与优化

我国铅锌矿产资源丰富,但其自然禀赋差且矿物组成复杂,导致其综合回收利用难度大。甘肃洛坝铅锌矿是一座含铅锌且伴生有少量银、硫的泥岩—细碎屑岩型铅锌矿床,因其矿石性质复杂,较早期形成的矿石性质发生明显变化,导致铅锌分选指标及精矿质量下降。为解决现有选矿生产过程中存在的问题,寻找适宜的改进措施和方法,以提高铅锌资源综合利用效率,在研究矿石性质的基础上开展了详细的工艺流程考察。研究结果表明：矿石中碳质、硅质等脉石矿物含量升高,碎磨过程易于泥化,且吸附性能和可浮性好,这些是影响铅锌分选指标的主要因素;通过优化碎磨工艺参数,减少了碳质、硅质等脉石矿物的泥化程度;在浮选工艺中添加适宜抑制剂,并采用高选择性的铅、锌矿物捕收剂,可显著提高铅、锌精矿品位和质量,大幅提高铅、锌回收率,从而实现该复杂含碳低品位铅锌资源的高效综合回收,并为同类矿产资源的选矿回收提供参考依据。     

次级发射相关研究及应用的发展与现状

本文简述了次级发射的理论研究。次级发射理论在于研究影响次级发射的相关因素及对离子轰击下的次级发射现象的研究,以及对氧在金属表面的覆盖率与二次电子发射性能的关系的研究。介绍了几种成熟的有效次级发射体的性能研究、实际应用和与这些发射体相关的理论探讨。本文根据新型稀土钼热阴极材料发射理论研究成果,提出稀土钼次级发射材料研究的一些设想。     

Design and optimisation of charging ingredients and structure in an ironmaking system (Part II)

In order to maximise the reduction of pig iron cost in an ironmaking process, and at the same time ensure the output and quality of the pig iron, a design and optimisation system for the charging ingredients and structure in an ironmaking system was established using metallurgical theory. The system includes six modules, namely, sinter metallurgical performance testing and analysis, sintering burdening design, sinter component and property prediction, blast furnace burdening design, blast furnace batching calculation and ironmaking system burden optimisation. Based on actual production, testing and material balance theory, the system integrated these modules on VB and MATLAB using a series of intelligent algorithms, such as the BP neural network, multiple objective linear programming, genetic algorithms and so on. As a result, the optimum burden composition and structure of the sinter and blast furnace that satisfied all the constraint conditions could be obtained. Standing as a pinnacle of the global ironmaking production, the system can design and optimise not only the sintering burden, but also the blast furnace burden. Compared with the traditional production testing and hand calculation in the ironmaking system, the project can greatly reduce the production risk and greatly increase the calculation accuracy. Industrial application shows that the system is especially beneficial to reduce the ironmaking cost and at the same time ensure the output and quality.