复杂性后尿道狭窄81例治疗分析

目的探讨复杂性后尿道狭窄或闭锁的手术治疗方法,提高手术治疗效果。方法 1991～2008年收治的81例复杂性后尿道狭窄/闭锁患者,狭窄/闭锁段长度为3～10cm,其中>5cm者27例;66例曾有1～4次手术史;62例行改良尿道套入术,19例尿道端端吻合术;73例经会阴或腹会阴切口,8例经耻骨或切除部分耻骨下缘切口。15例应用尿道替代物成形。结果 76例(93.8%)术后排尿满意,5例失败,其中改良尿道套入术和尿道端端吻合术成功率分别为95.2%(59/62)、89.5%(17/19)(P>0.05)。15例应用尿道替代物成形术均取得成功。结论复杂性后尿道狭窄/闭锁的治疗应根据尿道病变情况选择不同的手术径路及术式,改良尿道套入术具有创伤小、操作简便、成功率高等优点。尿道狭窄段>5cm者应考虑应用尿道替代物成形

Prefabricated crack propagation in alumina ceramic during flame thermal shock

陶瓷材料因其在高温下具有稳定的化学和力学性能，被广泛应用在航空航天的高温构件中。但是，由于陶瓷材料固有的脆性，当环境温度急剧升高或降低（热震）时容易在结构内部或表面产生裂纹，降低结构的性能，还可能导致结构直接失效而造成巨大的损失，严重制约了陶瓷材料在高温领域的应用。 另外，陶瓷材料在制备和加工过程中或多或少地会产生一些缺陷（微气孔、微裂纹等），热震过程中缺陷处因应力集中而容易产生裂纹扩展，进而影响材料的抗热震性能和使用寿命。因此，研究缺陷对陶瓷材料热震裂纹萌生和扩展的影响对提高其抗热震性能具有重要的科学意义。本文通过实验和数值模拟研究了预制裂纹氧化铝陶瓷在火焰热冲击下的裂纹扩展过程，分析了预制裂纹的角度和位置对裂纹形貌和裂纹扩展速度的影响。 实验上，实现了火焰热冲击下含不同角度和位置预制裂纹氧化铝陶瓷裂纹扩展过程的实时观测。实验结果表明，不同角度和位置预制裂纹的两个尖端都出现了翼形裂纹，裂纹快速扩展并最终贯穿试样，试样的完全破坏是一个高速过程；预制裂纹尖端的裂纹扩展速度开始很快，然后逐渐减慢。另外，随着预制裂纹角度的增加，近火焰裂纹尖端和远火焰裂纹尖端的最大扩展速度都呈现出增加的趋势；近火焰裂纹尖端的最大扩展速度随着预制裂纹到加热表面的距离增加而增加，而远火焰裂纹尖端则观察到相反的趋势。大部分实验结果表明，近火焰裂纹尖端在火焰热冲击下会率先扩展，然后远火焰裂纹尖端才开始扩展。 本文基于动态断裂力学建立了火焰热冲击过程的数值模型，以期重现热冲击下裂纹扩展的过程。通过部分实验和数值模拟相结合的方式，确定了100m/s~2600m/s范围内临界动态应力强度因子与裂纹扩展速度的关系。将该关系用于模拟其它实验的裂纹扩展过程，最终模拟的结果与实际观察的结果一致。数值模型可以如实地再现含预制裂纹氧化铝陶瓷在火焰热冲击下的裂纹演化过程。</p

Cracking in the translucent alumina ceramic during flame thermal shock

Crack measurement after thermal shock is usually considered as a replacement because real-time observation of thermal shock experiments is difficult to achieve. This paper presents an experimental approach for real-time displaying thermal shock cracking using oxygen-acetylene flame and high-speed imaging of translucent ceramic. We capture the crack propagation process, calculate the crack propagation speed, discuss the effect of sample size and flame heat flux on the crack propagation, and analyze the difference between the crack propagation under cold shock and hot shock. This paper further improves the mechanism of thermal shock damage of ceramic materials

The Mechanism for Vapor-phase Hydrogenation of Benzoic Acid to Benzaldehyde

通讯作者: [email protected][中文文摘]通过改变苯甲酸和苯甲醛催化加氢的氢气流量、预还原时间、反应温度来研究苯甲酸催化加氢的反应机理,为取代苯甲酸催化加氢的理论研究提供参考模型,同时也为加氢催化剂的设计和工艺条件的选择提供实验理论依据.副产物甲苯主要是来自于主产物苯甲醛的进一步加氢反应,而少部分来自于苯甲酸双氧空位吸附.研究表明,苯甲酸单氧空位催化加氢符合M.v.K机理,而苯甲醛的深度加氢和苯甲酸的双氧空位加氢并不完全符合M.v.K机理.根据催化剂层三段反应的分析,可将反应器设计成漏斗状或在上、中、下三层中采用不同粒径的催化剂,达到同时提高苯甲酸转化率和苯甲醛选择性的目的.[英文文摘]By optimizing reaction conditions,such as GHSV,pre-reduction time and reaction temperature,the reaction mechanism of catalytic hydrogenation of benzoic acid to benzaldehyde was investigated,the results not only provided reference for theoretical model of hydrogenation of substituted benzion acids,but also set up theoretical basis for catalyst design and choice of process conditions.Moreover,the present work showed that toluene as by-product was mainly from further hydrogenation of benzaldehyde,while a small part of toluene was from hydrogenation of benzoic acid adso rbed at double oxygen vacancy sites. The results indicated that the catalytic hydrogenation of benzoic acid adso rbed at single oxygen vacancy site was consistent with M.v.K mechanism,but the catalytic hydrogenation of benzaldehyde and benzoic acid at double oxygen vacancy sites were not fully consistent with the M.v.K mechanism.A nalysis of three stage reactions in catalyst bed suggested that, to improve both the conversion of benzoic acid and the selectivity of benzaldehyde at the same time, the reactor can be designed as funnelshaped , and/or be filled with different size of catalyst in the upper, middle and lower lay er, respectively.福建省重点科技项目(99-2-53)资

Prefabricated crack propagation in translucent alumina ceramic sheets during flame thermal shock

The prefabricated cracks propagation of ceramic under flame thermal shock was studied by realtime observation. The experimental results show that wing cracks are generated from both tips of the prefabricated crack, and the complete failure of the samples is a high-speed process. The crack propagation speed is fast at first and then gradually slows down. The maximum propagation speed of the near flame tip increases with the prefabricated crack distance to the heated surface, while an inverse trend is observed for the far flame tip. The effect of prefabricated crack angle on thermal shock crack propagation was also considered. In addition, numerical simulations based on dynamic fracture mechanics were carried out to reproduce the entire cracking process. To this end, the relation between the dynamic stress intensity factors and the crack growth speed in the speed range of 100 m/s to 2600 m/s was identified by combing experiments and numerical simulations. The simulation results and the above-mentioned relation are consistent with the experimental observations. The numerical model can faithfully reproduce the crack evolution process of the thermal shock, which is difficult to observe in an experiment due to the high speed of the cracking process

Effect of material parameters on thermal shock crack of ceramics calculated by phase-field method

Based on alumina ceramics, we employ the phase-field method to study the effects of thermal conductivity, specific heat, density, thermal expansion coefficient, Young's modulus, and fracture toughness on thermal shock cracks. The results show that increasing thermal conductivity and fracture toughness will reduce thermal shock damage. That is, the long crack length becomes shorter, or the crack density becomes smaller. However, increasing the thermal expansion coefficient and Young's modulus will increase thermal shock damage. It is consistent with the previous thermal shock theory. The effect of material parameters on crack propagation speed was also considered. In addition, we carried out a thermal shock test of the zirconia. The results of the phase-field calculation are the same as the thermal shock results of the zirconia. This paper verifies that the phase-field method is suitable for simulating thermal shock cracks in other ceramics

Measurement of ceramics cracking during water quenching by digital image correlation

Measuring the thermal shock crack growth process is crucial for revealing ceramic materials and structures' thermal shock failure mechanisms and evaluating their reliability. We used a self made water quenching system to conduct thermal shock tests on alumina and zirconia ceramics. The thermal shock process was recorded by high speed digital image correlation (DIC) during the test. The process of thermal shock crack initiation and propagation in two kinds of ceramics was determined by analyzing the speckle image change on the sample's surface. It is found that the crack growth rate of alumina is faster than that of zirconia, which is caused by different material parameters. This paper presents an in situ measurement method for the initiation and prop agation of thermal shock cracking in ceramic materials. It can provide a measurement method to identify and predict the thermal shock damage of ceramic components

甲烷空气催化部分氧化制合成气与含氮合成气制二甲醚的研究

采用常规浸渍法制备了经镧和镁改性的镍基催化剂，以铜锌铝甲醇合成催化剂和HZSM－5分子筛通过机械混合制造了二甲醚合成催化剂，采用固定床流动反应色谱装置研究了甲烷空气催化部分氧化制合成气的催化性能，同时开展了以含氮合成气制备二甲醚的研究，结果说明，镍基催化剂对甲烷空气部分氧化制合成气在常压下具有高的转化率，随压力升高，随压力升高，转化率明显下降，并且催伦剂严重积炭，通过向反应体系添加H2O和CO2可以提高加压条件下的CH4转化率并抑制催化剂积炭，还可获得n(H2)/n(CO)接近2的合成气，满足合成二甲醚的要求，采用含氮合成气制备二甲醚，在压力7．0MPa，空速1000h^-1条件下，催化剂连续使用200h性能基本稳定，CO转化率在93％左右，DME选择性在77％左右，DME收率在72％左右

内蒙古呼伦贝尔市饮茶型氟铝联合中毒研究

目的探讨饮茶型氟中毒是否为砖茶型氟铝联合中毒。方法对饮茶型氟中毒病区进行饮水、砖茶、奶茶、主食、副食及牧民发、血、尿氟铝水平检测,对饮茶型氟中毒病区儿童和成人进行临床检查和拍摄 X 线片,同时对成人进行血液生物化学检查,以饮水型病区及非病区居民为对照组。结果呼伦贝尔市饮茶型病区饮水、主食、副食氟铝水平均在正常范围,砖茶氟铝水平分别为(541.3±48.8)、(4351±724)mg/kg,奶茶氟铝水平分别为(3.83±0.73)、(4.28±1.56)mg/L。饮水型病区饮水氟铝水平分别为(3.68±1.05)、(0.45±0.25)mg/L。饮茶型病区牧民氟总摄入量96.15%、铝总摄入量89.60%来源于砖茶。儿童氟斑牙检出率饮茶型病区为25.24%,饮水型病区为63.17%,饮茶型病区非常显著低于饮水型病区(P<0.01);成人氟中毒检出率饮茶型病区为42.61%,饮水型病区为28.83%,饮茶型病区显著高于饮水型病区(P<0.01)。结论呼伦贝尔市饮茶型氟中毒发病机理较为复杂,可能是砖茶型氟铝联合中毒