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51.
Mechanism of heterogeneous catalytic ozonation of nitrobenzene in aqueous solution with modified ceramic honeycomb 总被引:2,自引:0,他引:2
The degradation efficiencies of nitrobenzene in aqueous solution were investigated by semi-continuous experiments in the processes of ozone alone, ozone/ceramic honeycomb (CH) and ozone/modified ceramic honeycomb (MCH). MCH with 1.0% Mn and 0.5% Cu had more pronounced catalytic ability than CH to accelerate the degradation of nitrobenzene, to increase the utilization efficiency of ozone, to improve the concentrations of hydrogen peroxide (H2O2) formation and hydroxyl radical (OH) initiation, and to enhance the removal efficiency of TOC. The modification process of CH with the metals enhanced the density of surface hydroxyl groups, which determines the initiation of OH from ozone decomposition and the generation of intermediate species on heterogeneous catalytic surface, yielding the acceleration of the degradation of nitrobenzene in aqueous solution. Possible reaction mechanism of ozone with heterogeneous catalytic surface in aqueous solution was proposed, and the formation mechanism of H2O2 and OH was also discussed according to the combined reactions in heterogeneous and homogeneous catalytic systems. 相似文献
52.
Recent experimental and computational work by Link and associates has demonstrated that relatively small (W = 150 mm) single edge notched tension specimens (SE(T)) can be used to obtain crack arrest data high in the ductile-to-brittle transition of ferritic structural steel using dynamic computational techniques if a thermal gradient is utilized to aid in the crack arrest. Testing has been reported on two important navy structural steels that clearly defines the relative capability of the two materials to arrest rapidly growing cracks. The HY100 material demonstrated the expected large difference between the initiation and crack arrest toughnesses which has made it impossible in the past to measure crack arrest toughness for this material using the standard ASTM procedure (E1221). The HSLA-100 steel, however demonstrated a much higher crack arrest toughness and a correspondingly smaller drop in toughness below the initiation toughness. This small difference between initiation toughness and arrest toughness suggested that the E1221 procedure, using wedge loaded, compact crack arrest (CCA) specimens would be applicable to this material. Two important issues could then be investigated using this material. First, having completed the expensive and relatively complex testing of the SE(T) specimens using tensile loading and a thermal gradient, a second, quite different geometry could be tested using the E1221 procedure, allowing an important comparison between the crack arrest measurements made using these two distinct geometries. Historically, obtaining crack arrest results using one test configuration has been so difficult, that there have been very few reports of results for the same material using two different test geometries. Transferability of the laboratory results to structural applications has thus been a matter of conjecture. Furthermore, if the E1221 CCA specimens were strain gaged to obtain crack velocity data, and analyzed using the dynamic computational procedure used by Link on the SE(T) specimens, it would be possible to compare the results the E1221 static analysis with the results of the dynamic computation procedure to determine the degree of conservatism present in the E1221 standard procedure.The results of this work have shown that the crack arrest toughness results obtained on these two specimen geometries are similar and hence insensitive to the test geometry and the difference resulting from the application of the complex dynamic computational procedure or the E1221 static analyses is small. 相似文献
53.
《工程爆破》2022,(5)
为了研究起爆方式对截底椭圆形罩LSC射流成型性能影响的特点和规律,运用ANSYS/LSDYNA对不同起爆方式下截底椭圆形罩LSC射流成型过程进行了三维数值模拟,获得了不同时刻射流横断面和正面的成型图片、射流最大速度时程曲线和射流最大速度及其出现的时刻。结果表明,对于顶部中线均布多起爆点,两端起爆时差在3μs以内时,形成的射流最大速度较大,约为42604290m/s,成型性能较好,当起爆点数量大于4时,可以认为是顶部中线线起爆;对于两侧棱上均布多起爆点,两端4点同时起爆时形成的射流最大速度较大,约4800m/s,当两侧棱上均布起爆点数量大于6时,可以认为是两侧棱上线起爆;就射流最大速度而言,两侧棱上均布多起爆点普遍大于顶部中线均布多起爆点。因此,起爆方式对LSC射流成型性能影响较大,研究结果在丰富LSC射流成型理论的同时,为实际应用LSC时选择合适的起爆方式提供了参考。 相似文献
54.
Session mobility is one of new critical issues in the ubiquitous mobile networking environment. Session mobility provides a user changing its ongoing multimedia session, e.g., Voice-over-Internet Protocol (VoIP), from the currently using device to another by adapting user’s demand. In session Initial Protocol (SIP)-based multimedia services supporting session mobility, SIP serves as a signaling control protocol to negotiate session control, whereas media is transmitted using Real-time Transport Protocol (RTP). For securing multimedia sessions, Multimedia Internet Keying (MIKEY) is embedded in SIP signaling to negotiate security parameters for Secure RTP (SRTP), whereas SRTP is used to protect media stream. Since session mobility allows an ongoing multimedia session to be transferred from one device to another, a new security problem is raised, i.e., sensitive parameters may remain in the previous device when the ongoing multimedia session has been transferred to the current device. Unfortunately, current MIKEY cannot bear the aforementioned security problem in session mobility. Therefore, we propose Multimedia Internet Rekeying (MIRKEY) for session mobility in the ubiquitous mobile networking environment. Although MIKEY can be executed again to carry out the rekeying of the session key and Crypto Session bundle (CSB) update, the sensitive parameters still remain in previous devices. MIRKEY contains a SBK to bind the participated user and multimedia session. Besides, SBK can persist in rekeying based on the key chain whenever a multimedia session is transferred to other devices. As a result, SBK is operative only in the specific device. As a result, MIRKEY can solve the newly raised security problem in session mobility. Furthermore, we verify MIRKEY using Burrows–Abadi–Needham (BAN) logic and realize it in the implemented ubiquitous multimedia service platform (UMSP). 相似文献
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以往的IP电话设备主要采用H.323协议实现,但是H.323协议实现过程较复杂,在实际使用中存在很多的问题.提出一种基于FFD2112的VoIP网关的实现方法,阐述了基于FFD2112的VoIP网关的软硬件设计过程,电话接口的性能测试结果表明,所提出的方案在因特网上运行良好. 相似文献
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