Investigation on operational stability of main shaft of a prototype reversible pump turbine in generating mode based on ensemble empirical mode decomposition and permutation entropy

Xianghao Zheng,Suqi Zhang,Yuning Zhang,Jinwei Li,Yuning Zhang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.12

Evaluation of the operational stability of the main shaft is of great significance to ensure the security and reliability of the prototype reversible pump turbine (RPT). In the present paper, the experimental study was carried out using the sensors with high accuracy to obtain the shaft displacement signals under different load conditions of the RPT in the generating mode. A set of signal extraction procedure based on ensemble empirical mode decomposition, permutation entropy (PE) and modified wavelet soft-threshold de-noising method is proposed to reduce the influences of the random noises and extract the effective components within the signal. The PE values of the extracted shaft displacement signals are all below 0.3, illustrating that good extraction results have been achieved. Meanwhile, the typical shape evolution of the extracted shaft orbit with load variations at the turbine guide bearing is also depicted in detail. And the PE analysis result of the extracted shaft orbit can effectively reflect the evolution of different internal flow patterns under different load partitions of the RPT, which are 0.33-0.36 for low partial load partition, 0.22-0.30 for medium load partition and 0.30-0.32 for high partial load partition, respectively.

Experimental research on the collapse dynamics of the cavitation bubble near two spherical particles

Xiaoxiao Zheng,Xiaoyu Wang,Xuan Lu,Jin Yuan,Yuning Zhang,Yuning Zhang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5

In this paper, the collapse dynamics of the cavitation bubble located in the middle position of two spherical particles of the same size are studied with the help of a high-speed photography experimental system. According to a large number of experimental results, the effects of several important parameters (the bubble size and the distance between the bubble and any particle) on the bubble collapse characteristics are revealed. For the process of the bubble collapse, four representative situations (gyro-shaped, drum-shaped, olive-shaped and spherical-shaped collapse) are defined, and three critical parameters of different situations are given based on the dimensionless distance between the bubble and any particle, which are 0.27, 1.17 and 1.56, respectively. Finally, through quantitative research, it is found that the dimensionless distance and the bubble size have a significant impact on the deformation degree of the bubble and the contractive rates at the characteristic bubble wall positions.

중국 주요 물류기업의 운영 효율성 분석

장광홍(Zhang, Guang-Hong),이윤(Lee, Yune) 한국물류학회 2022 물류학회지 Vol.32 No.2

중국의 35개 상장물류기업들은 2015∼2020년의 5년간 효율성이 매우 빠르게 증가하였다. 중국 정부의 물류산업 중장기발전계획을 비롯한 다양한 지원정책들이 효과를 나타내고 있음을 시사한다. 하지만 중국 물류기업들의 효율성 증가는 일부 기업들의 매우 빠른 성장에 기인하고 기업별로 편차가 크다. 기업들의 흥망성쇠도 비교적 빈번할 뿐만 아니라 규모에 대한 효율성도 최근까지크게 개선되지 않고 있다. 총요소생산성지수(TFPI)로 산정한 생산성 역시 5년간 매우 빠르게 상승하였는데, 기술변화지수(TCI)와변화 양상이 매우 유사하였다. 반면 기술적효율성변화지수(TEI)는 같은 기간에 거의 변동이 없었다. 결국, 중국 상장물류기업의 총요소생산성은 내부적인 생산요소의 효율적 결합에 의한 효율화보다는 외부환경 요인으로서 기술 변화가 주도한 것으로 판단된다. This paper analyzes the efficiency and productivity of the leading 35 logistics companies in China from 2015 to 2020 based on the DEA Model and Malmquist Index Method. We use assets, capital, and operating cost of the 35 logistics companies as input variables, while operating revenue, net profit, earning per share, and inventory turnover rate as output ones. In this analysis, we find that China’s leading logistics companies have increased operational efficiency measured by DEA methodology very fast, while the increase was led by a few companies. Furthermore the disparity of increasing rate between them was very big, and the companies have often risen and fallen. The increase in total factor productivity index (TFPI) of the companies during the same period has also been very fast and parallel with that of the Technical Change Index (TCI) whereas the technical Efficiency Change Index (TEI) has little changed, which implies that the productivity increase has been driven not by the endeavor of the companies to combine production factors more efficiently but by the technology change external to the companies.

Experimental and Mechanism Study of a Polymer Foaming Grouting Material for Reinforcing Broken Coal Mass

Junxiang Zhang,Yuning Sun 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.1

To study the mechanism of grouting reinforcement of broken coal mass, simulation experiments on grout reinforcing of broken coal mass were performed by using traditional materials, namely, Superfine Cement (SC) and Aluminate Cement (CA), and selfdeveloped Polymer Foaming (PF) grouting material. The macromechanical test results of the different grouting reinforced specimens showed that the residual strength of broken coal increased by different degrees after grouting, and the reinforcement effect was improved most notably by the PF material, which caused obvious plastic deformation characteristics of the coal mass that highly adapted to the deformation of the surrounding rocks, moreover, the long-term reinforcement effect was beneficial. Scanning Electronic Microscopy (SEM) showed that the grout-coal interfaces of the SC and CA materials were relatively loose and mainly affected by the types, quantities, and existence forms of cement hydration products, but had little relation to the properties of the injected medium. However, SEM showed a close combination at the interface with the PF material, which presented acceptable molecular compatibility. Moreover, FTIR indicated that some chemical grafting reactions occurred between the PF and coal mass, thereby leading to a firm polymer coating on the coal surface; thus, the grouting reinforcement effect of the broken coal mass was improved.

한국 산업단지의 효율성과 생산성 : 2001-2019

장광홍(Zhang, Guang-Hong),이윤(Lee, Yune) 한국물류학회 2021 물류학회지 Vol.31 No.1

한국 국가산업단지들은 효율성에서 차이가 확연하며, 수도권과 영남권의 산업단지들이 상대적으로 규모에 비하여 효율적이다. 총요소생산성은 그다지 빠르게 증가하지 않았으며, 내부적인 기술적 효율성 변화보다는 외부적인 기술 변화에 의하여 주도되었다. 총요소생산성과 기술적 효율성은 권역 간에 차이가 크고, 특히 충청호남권이 여타 권역에 비하여 낮은 것으로 나타났지만, 기술 변화는 권역 간에 차이를 확인하기 어렵다. 국가산업단지의 효율성을 높이기 위해서 규모에 비하여 효율성이 낮은 산업단지들을 대상으로 효율성이 높은 수도권과 영남권 산업단지들을 벤치마킹하도록 할 필요가 있으며, 생산성 향상을 위하여 기술의 도입과 적용 및 확산을 촉진하는 정책을 적극 추진하는 것이 바람직하다. This paper analyzes the efficiency and productivity of the main 20 industrial complexes in Korea from 2001 to 2019 based on the DEA Model and Malmquist Index Method. Production amount and export sales value of the 20 National Industrial Complexes are used as output variables, while industrial land area, number of operating companies, rate of operation, and the number of employees are used as input variables. In this analysis, the industrial complexes show a big difference in their efficiency and those of the Capital Area and the Southeastern(Youngnam) area are revealed to be comparatively efficient relative to their scale. The increase of total factor productivity has not been so fast, and it was driven not by that of technical efficiency but by technical change. Out of the 3 main areas in Korea Western area (Chungcheong & Honam) has been clearly lower in their total factor productivity and technical efficiency, but we can not confirm there has been clear difference in their technical change among them.

한국 자유무역지역의 운영효율성 분석

이윤(Lee, Yune),장광홍(Zhang, Guanghong),안영효(Ahn, Young Hyo) 한국물류학회 2020 물류학회지 Vol.30 No.2

이 연구는 한국의 7개 산업단지형 자유무역지역들의 운영효율성을 계량적 방법으로 비교·분석하는 데 목적을 둔다. DEA모형 으로 분석한 결과, 한국 자유무역지역의 운영효율성은 2014년 이래 대체로 증가하여 왔다. 운영효율성의 증가는 내수효율성의 증 가에 기인하며, 수출효율성은 운영효율성 증가에 기여하지 못하고 있는 것으로 판단된다. 자유무역지역은 지역 간의 효율성의 격 차가 커서, 상대적으로 효율이 높은 군집과 낮은 군집으로 양분되는 양상이다. 따라서 향후 자유무역지역의 운영효율성을 높이기 위해서는 수출효율성을 높이는 한편, 효율성이 낮은 자유무역지역들의 전반적인 운영효율성을 높이는 정책적 노력이 요구된다. This paper analyzed the relative efficiency of the Free Trade Zones in Korea from 2014 to 2018 based on the DEA Model. In this analysis, export sales value and domestic sales value of the 7 Free Trade Zones were used as output variables, while foreign investment, domestic investment, industrial land area, and the number of employees in the same year were used as input variables. The results of the analysis were as follows; The overall efficiency of the Free Trade Zones has generally been increasing since 2014. The efficiency was affected mainly by domestic demand-oriented efficiency rather than export-oriented efficiency. The efficiency gap among the 7 Free Trade Zones was relatively huge and they were mostly divided into by two groups, the favorable and the unfavorable. Therefore, it is highly recommended to increase the export-oriented efficiency of all the Tree Trade zones and further increase the overall efficiency of the unfavorable zones.

CT Experimental Study on the Damage Characteristics of Anchored Layered Rocks

Junyang Teng,Jianxin Tang,Yuning Zhang,Xinyi Li 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.9

A laboratory physical simulation and a CT scan test were conducted to analyze the anchoring mechanism of a system anchor bolt and a steel floral pipe in a layered rock mass. The following conclusions were drawn: (1) The anchoring effect of the system anchor bolt and steel floral pipe improves the strength parameter of the layered rock, and the system anchor bolt provides higher improvement. Neglecting the jointing effect, the improvement in the strength parameter of the layered rock due to the anchor bolt is primarily reflected by the following three aspects: the compressive zone effect of the preload, the repairing effect of the anchoring agent on defects in country rocks, and the reinforcement effect of the anchor bolt on the overall strength and density of the anchoring object. Considering the jointing effect, the improvement in the strength parameter of the layered rock due to the anchor bolt is reflected by improvement in the deformability and shear strength of the joint surface. (2) The stress-strain curves of the anchored specimens can be divided into different stages of damage evolution, based on the angles of bedding. (3) The crack-arresting effect of the anchor bolt is due to the weakening, cutting, and arresting of the cracks in the anchorage zone. The larger the anchorage zone, the better is the crack-arresting effect.

Recognition of Radar Emitter Signals Based on SVD and AF Main Ridge Slice

Qiang Guo,Pulong Nan,Xiaoyu Zhang,Yuning Zhao,Jian Wan 한국통신학회 2015 Journal of communications and networks Vol.17 No.5

Recognition of radar emitter signals is one of core elements in radar reconnaissance systems. A novel method based on singular value decomposition (SVD) and themain ridge slice of ambiguity function (AF) is presented for attaining a higher correct recognition rate of radar emitter signals in case of low signal-tonoise ratio. This method calculates the AF of the sorted signal and ascertains the main ridge slice envelope. To improve the recognition performance, SVD is employed to eliminate the influence of noise on the main ridge slice envelope. The rotation angle and symmetric Holder coefficients of the main ridge slice envelope are extracted as the elements of the feature vector. And kernel fuzzy cmeans clustering is adopted to analyze the feature vector and classify different types of radar signals. Simulation results indicate that the feature vector extracted by the proposed method has satisfactory aggregation within class, separability between classes, and stability. Compared to existing methods, the proposed feature recognition method can achieve a higher correct recognition rate.

Construction of Eukaryotic Vector Expressing shRNA of Lycopene Cyclase Gene carRA

( Ye Li ),( Lihua Jin ),( Qing Wei ),( Xiaojie Wang ),( Bo Li ),( Yuning Zhang ),( Liqing Zhang ) 조선대학교 공학기술연구원 2012 공학기술논문지 Vol.5 No.2

To construct eukaryotic vector expressing shRNA (short hairpin RNA) of carRA. Methods: Designing three different shRNA targeting the coding sequence of the car RA, the mU6-carRA shRNA was constructed by inserting the designed shRNA to the eukaryotic expression vector mU6pro. The constructed eukaryotic vector expressing shRNA of carRA was transformed into DH5 strain. Finally, the recombinant plasmid identified by restriction endonuclease was used for sequence analysis. Results: It was verified by partial nucleotide sequencing and restriction endonuclease digestion that the constructed eukaryotic vector expressing shRNA of carRA was correct. Conclusion: The results of study lay the foundation for further studying on its inhibitive effect on cycling of lycopene.