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Niu M.,China Ship Development And Design Center | Zang S.,Shanghai JiaoTong University
Experimental Thermal and Fluid Science | Year: 2011

This investigation presents detailed experimental measurements of an active tip-clearance control method based on tip injection in a high-turning axial turbine cascade. Besides that, numerical investigations are also conducted to study phenomena which are not easily measured in the experiments. It aims to study the influence of tip injection on tip clearance flow, with emphasis on the effects of injection locations. Detailed flow field measurements were made downstream of the cascade using a three-hole probe. Static pressure distributions were also measured on the blade surface at 50% and 97.5% span, respectively. The results suggest that tip injection can weaken tip clearance flow, reducing the tip clearance mass flow and its associated losses. Meanwhile, the heat transfer condition on the blade tip surface can be also improved significantly. It also can be found that injection chordwise location plays an important role in the redistribution of secondary flow within the cascade passage. When the same number of injection holes and injection mass flow are applied, holes located in the aft part of blade can perform much better than that in the front part. © 2011 Elsevier Inc. Source


Sun F.,Harbin Engineering University | Tang L.-J.,China Ship Development And Design Center
Kongzhi yu Juece/Control and Decision | Year: 2013

In order to select the appropriate filtering method from the UKF and CKF for the different dimensions nonlinear systems estimation, the two filters are analyzed and compared through the Taylor expansion of function and the numerical stability. Due to the different dimension, the captured high-order item degree of function Taylor expansion and the numerical stability are different to appear different filter precisions, so that the filter choice ways of different dimension are acquired. Simulation results show the correctness of with the theoretical analysis. Source


Zhu Z.,China Ship Development And Design Center
Journal of Medical Systems | Year: 2012

To ensure patients' privacy, such as telephone number, medical record number, health information, etc.; authentication schemes for telecare medicine information systems (TMIS) have been studied widely. Recently, Wei et al. proposed an efficient authentication scheme for TMIS. They claimed their scheme could resist various attacks. However, in this paper, we will show their scheme is vulnerable to an off-line password guessing attack when user's smart card is lost. To improve the security, we propose a new authentication scheme for TMIS. The analysis shows our scheme could overcome the weaknesses in Wei et al.'s scheme and has better performance than their scheme. © 2012 Springer Science+Business Media, LLC. Source


Cheng Y.,Central China Normal University | Yang H.,Central China Normal University | Cheng Z.,Xianning University | Wu N.,China Ship Development And Design Center
Applied Physics A: Materials Science and Processing | Year: 2011

In this paper, we present a polarization-insensitive metamaterial (MM) absorber which is composed of the dielectric substrate sandwiched with split-ring-cross resonator (SRCR) and continuous metal film. The MM absorber is not limited by the quarter-wavelength thickness and can achieve near-unity absorbance by properly assembling the sandwiched structure. Microwave experiments demonstrate the maximum absorptivity to be about 99% around 10.91 GHz for incident wave with different polarizations. The surface currents distributions of the resonance structure are discussed to look into the resonance mechanism. Importantly, our absorber is only 0.4 mm thick, and numerical simulations confirm that the MM absorber could achieve very high absorptivity at wide angles of incidence for both transverse electric (TE) wave and transverse magnetic (TM) wave. The sandwiched structure is also suitable for designing of a THz and even higher frequency MM absorber, and simulations demonstrate the absorption of 99% at 1.105 THz. © 2010 Springer-Verlag. Source


Ren P.,China Ship Development And Design Center
Applied Mathematics and Information Sciences | Year: 2015

In this paper, a virtual token passing protocol has been proposed, in which sensor nodes join in the different subnets according to the received signal strength and the number of sensor nodes in the subnet to decrease the transmitting power to reduce energy consumption as far as possible. Secondly, router nodes adopt different RF to polling for new sensor node and neighboring subnets use different channels to realize internal communication, and this can not only improve the network capacity, but also reduce the interference between subnets and sensor nodes. Thirdly, the address of sensor nodes in subnet is allocated by the router in a unified way. By making full use of the continuity of address and the negotiation mechanism, sensor nodes impartially access the wireless channel according to the virtual token passing method, and this has greatly reduced the effect on network performance brought by token passing and maintenance. In addition, the introduction of node priority and second competition state make the higher sensor nodes have priority to access wireless channel and then send packet as soon as possible, and this will enhance the real-time performance and reliability further when there is an emergency happened. OPNET simulation experimental results show that the proposed MAC protocol has improved the throughput, increased the traffic load, decreased the network delay, reduced the amount of dropped packets and the wireless channel access delay, and this is of great importance to the wireless sensor network under manufacturing environment. © 2015 NSP Natural Sciences Publishing Cor. Source

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