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- 저자 : Songhua Hu (검색결과 3 건)
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Songhua Ma,Tianliang Hu,Zhenqi Xiong 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.6
Tolerance analysis methods, which are important to achieve a balance between manufacturing costs and functional requirements, have been studied and improved over the last 30 years. This paper proposes a new method to improve the precision of assembly simulation for statistical assembly simulation; by investigating the effect of the geometric deviations and mechanical behaviors of assembly contact on the stack-up assembly deviation by combining the recent theories on the tolerance analysis of rigid bodies and local contact deformation. To improve the precision of the tolerance analysis, real parts with form defects were simulated with the help of non-nominal skin model shapes. The SMSs were first considered to be rigid, and a quadratic optimization-based method for the rigid body displacement was used to calculate the initial contact points of all the SMSs. Next, contact deformation, following Hertzian contact theory, occurred at the initial contact points, which changed the relative positions of the SMSs in the subsequent interactions. The iteration process was convergent, and the final simulation for tolerance analysis could be generated after several iterations. Case studies demonstrated the practicality of the proposed method. Their actual assembly deviations were simulated by combining the effects of geometric deviations and local surface deformations. Since the proposed tolerance analysis framework based on statistical assembly simulation, it is expected to control the functional requirements of mechanical assemblies with much rough tolerance design and help optimize the tolerance in the future.
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Wu, Jiusheng,Liu, Yuehuan,Hu, Songhua,Zhou, Jiyong Asian Australasian Association of Animal Productio 2008 Animal Bioscience Vol.21 No.1
Streptococcus (Strep.) agalactiae is one of the major pathogens of bovine mastitis and is the main cause of subclinical infection. This study attempted to develop a rapid PCR diagnosis procedure using milk samples collected on filter paper disks. Chromatographic filter paper was employed as the preservation media and kept at room temperature for one to four weeks. The revival rate of Strep. agalactiae kept on dried filter paper disks was affected by the pretreatment preservation time. The revival test suggested that not all the bacteria in artificially contaminated milk samples on the filter paper disks could be recovered. After that, a PCR based on the 16-23S intergenic spacer region of Strep agalactiae was performed. The results distinguished the strep. agalactiae from major pathogens of bovine mastitis at a $2{\times}10^2$ colony forming units (CFU)/ml level, which showed similar sensitivity to the results from liquid milk samples. The results also showed that milk samples collected on filter paper disks could be kept at room temperature for one to four weeks with little negative effect on sensitivity and specificity. The field test showed that the diagnostic sensitivity and specificity was 96.15% and 98.60%, respectively. In conclusion, the protocol will provide a rapid and economic procedure for the detection of bovine mastitis.
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Co-DDTMA : Cooperative Distributed TDMA for Vehicular Networks
Zhen Chen,Zhengyu Liu,Jianghong Han,Songhua Hu,Yang Lu 보안공학연구지원센터 2016 International Journal of Future Generation Communi Vol.9 No.2
In recent years, Vehicular Ad Hoc Networks (VANET) has experienced a rapid development due to the advancement of wireless communication technologies, and now emerges as a promising way to provide road safety, traffic efficiency and infotainment applications. However, it is a challenge to design a reliable and efficient Medium Access Control (MAC) protocol for VANET due to its frequent topology changes and unreliable wireless links. Cooperative communication, on the other hand, can enhance the reliability of wireless links by exploiting the broadcast nature of the wireless communication. A cooperative scheme for MAC is proposed for VANET in this paper, referred to as Cooperative Distributed TDMA (Co-DTDMA). In the Co-DTDMA, neighboring nodes utilize its idle slots for cooperatively retransmitting a packet which has failed to reach the destination. Since the cooperative retransmission is conducted in node's own idle slot, the proposed scheme does not interrupt the normal transmission. Both theoretical analysis and simulation results demonstrate that the proposed scheme greatly increases the probability of successful packet transmission and decreases the packet transmission delay.
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