Two problems in Web Services composition has been tackled in this paper: firstly, decoupling flow execution and Web Services invocation in WebServices Composition Execution Engine--WebJetFlow; secondly, changing services invocation model of Service Proxy from synchronous invocation model to pure asynchronous invocation model. Then NS2 has been adopted to test the performance of WebJetFlow under five different circumstances as well as the performance of WebJetFlow with Service Proxy and without Service Proxy respectively. The simulation results show that the access throughputs of WebJetFlow with Service Proxy are larger than those without Service Proxy under the same thread resources. Moreover, decoupling flow execution and Web Services invocation and using pure asynchronous invocation model greatly increase the concurrence of flow execution, enhance the utilization efficiency and improve the performance of WebJetFlow.
A new type of radial ultrasonic transducer was fabricated in this study. The performances of five radial ultrasonic transducers of different thickness were investigated in this paper. It was found that the radial ultrasonic transducers possess the greatest sensitivity when the matching layer thickness is 2.5 mm. The addition of tungsten powder in the backing layer could effectively absorb noise, which improved the acoustic attenuation performance of the backing layer and their sensitivity. To study the directivity, the ultrasonic transducer was put into water. It was found that the transducer could achieve transmitting ultrasound in all radial directions and the ultrasonic signal is similar along all radial directions, i.e., the transducer exhibits isotropic properties, which makes it a good candidate for nondestructive testing of concrete when embedded in concrete elements and structures.
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