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Jianjian Wang,Pingfa Feng,Tijian Zha 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.2
The precision cylindrical traverse grinding process of slender bar is very complex for the strongly time dependent properties of the wheel. Therefore, it is very difficult for operators to properly judge the grinding state using naked eyes and ears. This calls for automatic monitoring technology that can monitor the process in precision cylindrical traverse grinding to guarantee machining quality and productivity as well as reduction in cost. This study developed an automatic monitoring system for precision cylindrical traverse grinding of slender bar using Acoustic emission (AE) technology. Grinding tests on molybdenum were conducted under traverse conditions in a conventional cylindrical grinder. It was found that larger radial material removal depth results in larger root mean square value of Acoustic emission signals (AE RMS ). Based on this, the AE RMS was analyzed and used to determine the finishing of spark-out process and the pre-processing of tool alignment. The variation tendency of AE RMS in one spark-out process was applied to determine when a wheel wears out and has to be dressed. The experimental results showed that the AE system was effective to monitor the pre-processing of tool alignment, spark-out and wheel wear in precision cylindrical traverse grinding of slender bar.
Pengyan Zhang,Jianjian He,Wang Huili,Zhimin Zhou 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.9
With the acceleration of urbanization, the resources and environment problem has become more and more prominent in Zhongyuan urban agglomerations. Based on evaluation model of resources and environment coordination degree of Pressure-State-Response (PSR), this study adopted the coordination degree analysis methods to calculate and evaluate the resources and environment coordinated development of nine central cities in Zhongyuan Urban Agglomerations from 2006 to 2013. Results showed that: (1) from 2006 to 2013, the statuses of the nine central cities in Zhongyuan Urban Agglomerations were in moderate coordination, elementary coordination, on the verge of imbalance and moderate imbalance, the economic development and the resources and environment statuses were not optimistic; (2) from 2006 to 2009, those cities’ statuses were in moderate imbalance, on the verge of imbalance and elementary coordination, the overall development coordination degree was not high, could not reach the state of coordinated development. Luoyang, Jiaozuo, Xuchang and Luohe’s coordinated development situation was not up to standard, whose status was in moderate imbalance; (3) from 2010 to 2013, the nine cities were on the verge of imbalance, elementary coordination and moderate coordination, coordinated development was improved.
Study on slope stability of waste dump with a weak layer using finite element limit analysis method
Chong Chen,Huayong Lv,Jianjian Zhao,Zhanbo Cheng,Huaiyuan Wang,Gao Xu 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.89 No.3
Slope stability is generally paid more attention to in slope protection works, especially for slope containing weak layers. Two indexes of safety factor and failure model are selected to perform slope stability. Moreover, the finite element limit analysis method comprehensively combines the advantage of the limit analysis method and the finite element method obtaining the upper and lower bounds of the safety factor and the failure mode under the slope stability limit state. In this study, taking a waste dump containing a weak layer as an engineering background, the finite element limit analysis method is adopted to explore the potential failure mode. Meanwhile, the sensitivity analysis of slope stability is performed on geometrical and geotechnical parameters of the waste dump. The results show that the failure mode of the waste dump slope is two wedges if the weak layer is located on the ground surface (Model A), while the slope can be observed as three wedges failure if the weak layer is below the ground surface (Model B). In addition, both failure modes are highly sensitive to the friction angle of the weak layer and the shear strength of waste disposal, and moderately sensitive to the heap height, the dip angle and cohesion of the weak layer, while the toe cutting has limited effect on the slope stability. Moreover, the sensitivity to the excavation of the ground depends on the location of the weak layer and failure mode.
Axial Hole Air-Entraining Cooling Technique of Radial-Flow Turbines
Ma Chao,Zhang Jianjian,Wang Ningning,Zhu Zhifu 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.5
In response to the continually increasing thermal load caused by the rising gas temperature in the inlet of radial-flow turbines, this paper proposes the use of axial hole air-entraining cooling to cool the turbine shaft and turbo wheel back-disc. The cooling effect of this technique, as well as its influence on the aerodynamic performance of turbines, were investigated through numerical simulations. The results demonstrate that the axial hole air-entraining cooling technique can significantly improve the local cooling efficiency of the turbine back-disc. Under a blowing ratio of 0.25 %, the local cooling efficiency increased by 154 %, and the temperature decreased by up to 233 K. The maximum temperature on the surface of the turbine shaft at the floating bearing location decreased significantly, thus reducing the coking risk of the lubricating oil. When the blowing ratio was within 0.5 %, the impact of this cooling technique on the overall turbine performance was negligible.
Ziyin Zhang,Kun Yang,Chaohua Wang,Changwei Zhang,Xiaodong Xie,Jianjian Tang 대한영상의학회 2013 Korean Journal of Radiology Vol.14 No.3
This report concerns a 4-month-old infant with progressive prominent and redness of his left eye since birth. This report concerns a 4-month-old infant with progressive prominent redness of his left eye since birth. Angiography revealed a congenital pial arteriovenous fistula between the temporal branch of the left posterior cerebral artery and left cavernous sinus through the sphenoparietal sinus, a condition not reported in the literature. The fistula was successfully occluded with two micro-coils by vertebrobasilar approach.
Sang Xuehan,Zhao Xiuhong,Yan Lianqi,Jin Xing,Wang Xin,Wang Jianjian,Yin Zhenglu,Zhang Yuxin,Meng Zhaoxiang 한국조직공학과 재생의학회 2022 조직공학과 재생의학 Vol.19 No.3
BACKGROUND: Intra-articular injection is a classic strategy for the treatment of early osteoarthritis (OA). However, the local delivery of traditional therapeutic agents has limited benefits for alleviating OA. Exosomes, an important type of extracellular nanovesicle, show great potential for suppressing cartilage destruction in OA to replace drugs and stem cellbased administration. METHODS: In this study, we developed a thermosensitive, injectable hydrogel by in situ crosslinking of Pluronic F-127 and hyaluronic acid, which can be used as a slow-release carrier to durably retain primary chondrocyte-derived exosomes at damaged cartilage sites to effectively magnify their reparative effect. RESULTS: It was found that the hydrogel can sustainedly release exosomes, positively regulate chondrocytes on the proliferation, migration and differentiation, as well as efficiently induce polarization of M1 to M2 macrophages. Intraarticular injection of this exosomes-incorporated hydrogel significantly prevented cartilage destruction by promoting cartilage matrix formation. This strategy also displayed a regenerative immune phenotype characterized by a higher infiltration of CD163? regenerative M2 macrophages over CD86? M1 macrophages in synovial and chondral tissue, with a concomitant reduction in pro-inflammatory cytokines (TNF-a, IL-1b, and IL-6) and increase in anti-inflammatory cytokine (IL-10) in synovial fluid. CONCLUSION: Our results demonstrated that local sustained-release primary chondrocyte-derived exosomes may relieve OA by promoting the phenotypic transformation of macrophages from M1 to M2, which suggesting a great potential for the application in OA.