Seismic Performance of Kiewitt-Sunflower Single Layer Spherical Reticulated Shells

Sheng He,Siliu Yu,Weijing Yun,Stéphane P. A. Bordas,Peng Yu 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.5

In this paper, seismic behavior of Kiewitt-Sunflower single layer spherical reticulated shells is examined within the time history method, based on our proposed damage constitutive model for thin-walled circular steel tubes. According to a large number of numerical examples, the failure mode of this kind of single layer spherical reticulated shell in the case of earthquake is figured out. In addition, the effect of the damage accumulation, rise-span ratio, initial geometric imperfection, types of seismic wave and amplitude modulation ratio on the dynamic response of the shell structure is explored. Finally, a structural damage factor is proposed and it has a good match with the numerical results, which is productive to assess the damage and failure behavior of such structures suffering the earthquake and post-earthquake.

Microstructural Evolution of T91, T92 and X20 Steel Used as Superheater and Reheater in Power Plants (초)

He Yin Sheng,Jung Chel Chang,Sung Ho Lee,Ji Ling Dong,Dae Hwang Yoo,Kee Sam Shin 대한금속ㆍ재료학회 2009 대한금속재료학회 학술대회 개요집 Vol.2009 No.-

Investigation on Simulation Methods of Initial Geometric Imperfection Distribution in Elasto-plastic Stability Analysis of Single-layer Reticulated Shells

Sheng He,Zhengrong Jiang,Jian Cai 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.4

Based on the theory of probability and mathematical statistics and on the results of nearly 2000 cases of elasto-plastic stabilityanalysis for single-layer reticulated shells, a new simulation method of initial geometric imperfection distribution, N-ordereigenmode imperfection method, is developed. The elasto-plastic stability analyses of four types of commonly used single-layerreticulated domes were conducted with the random imperfection mode method, the eigenmode imperfection method and the N-ordereigenmode imperfection method, respectively, by means of ANSYS. The results show that, though the random imperfection modemethod can simulate the initial geometric imperfection distribution realistically, the calculation cost of this method is too large topopularize in design practice. Adopting the first order eigenmode to simulate the distribution of initial geometric imperfection mayfail to derive the most unfavorable buckling load. The reliability of buckling load obtained from the eigenmode imperfection methodcannot be guaranteed effectively. The N-order eigenmode imperfection method can evaluate the influence of initial geometricimperfection on structural stability reasonably, and capture the buckling load satisfying the requirement of the ‘3σ’ principle with lesscalculation. This method is a convenient and efficient way for designers to estimate stability performance of single-layer reticulatedshells accurately and safely.

Controlling the Fluid Induced Instability of a Supercritical CO₂ Compressor Supported by Magnetic Bearing

김성학(Sheng-He Jin),차재은(Jae-Eun Cha),장지욱(Jee-Uk Chang),최상현(Sang-Hyun Choi),안형준(Hyeong-Joon Ahn) Korean Society for Precision Engineering 2020 한국정밀공학회지 Vol.37 No.10

Since sCO₂ (Supercritical Carbon Dioxide) turbomachinery are generally small and operate at high rotational speed, the bearings remain a significant challenge to the design of the turbomachinery for the sCO₂ power cycles. However, a fluid induced instability similar to the oil whirl may occur even with the magnetic bearing under high pressure and high speed conditions of the sCO₂ turbomachinery. This paper presents experimental investigation on the instability of a sCO₂ compressor supported by the magnetic bearing. First, we introduce the sCO₂ compressor supported by the magnetic bearing. The procedure to guarantee the rotordynamic performance of the sCO₂ compressor supported by the magnetic bearing is provided. Then, the effects of the working condition such as the pressure and rotating speed on the fluid induced instability are investigated experimentally. Finally, a strategy to resolve the fluid-induced instability with conventional PID control is proposed and experimentally verified.

Efficacy and Safety of Endoscopic Resection Therapies for Rectal Carcinoid Tumors: A Meta-Analysis

Lei He,Tao Deng,He-Sheng Luo 연세대학교의과대학 2015 Yonsei medical journal Vol.56 No.1

Purpose: Several endoscopic resection therapies have been applied for the treatment of rectal carcinoid tumors. However, there is currently no consensus regarding the optimal strategy. We performed a meta-analysis to compare the efficacy and safety of endoscopic mucosal resection (EMR) or modified EMR (m-EMR) versus endoscopicsubmucosal dissection (ESD) for the treatment of rectal carcinoid tumors. Materials and Methods: PubMed, Web of Science, Medline, Embase and CNKI were searched up to the end of January 2014 in order to identify all studies on the effectsof EMR (or m-EMR) and ESD on rectal carcinoid tumors. Results: A total of fourteen studies involving 782 patients were included. The pooled data suggested a significantly higher rate of pathological complete resection among patients treated with ESD or m-EMR than those treated with EMR [odds ratio (OR)=0.42, 95% confidenceinterval (CI): 0.25‒0.71; OR=0.10, 95% CI: 0.03‒0.33, respectively], while there was no significant difference between the m-EMR group and ESD group (OR=1.19, 95% CI: 0.49‒2.86); The procedure time of ESD was longer than EMR or m-EMR groups [mean differences (MD)=-11.29, 95% CI: -14.19 ‒ -8.38, MD= -10.90, 95% CI: -18.69 ‒ -3.11, respectively], but it was insignificance between the EMR and m-EMR groups. No significant differences were detected among the treatmentgroups with regard to complications or recurrence. Conclusion: The results of this meta-analysis suggest that treatment of rectal carcinoid tumors with ESD or m-EMR is superior to EMR, and the efficacy of m-EMR is equivalence to ESD treatment. However, more well-designed studies are needed to confirm these findings.

Prospective UNCITRAL Technical Assistance for Asian Countries in International Arbitration

( Qi Sheng He ),( Da Yong Zhou ) 고려대학교 법학연구원 2011 The Asian Business Lawyer Vol.7 No.-

The United Nations Commission on International Trade Law (UNCITRAL) is a core legal body established by the United Nations, which takes the mandate to harmonize the international and regional trade law, and to create an environmentfacilitating international trade and commercial transactions. In the field of international commercial arbitration, UNCITRAL conducts cooperation programs and provides technical assistance to facilitate its mission. In Asia, facing a rapid regional economic boost but divergent legal systems, improving the professional quality and credibility of regional arbitral institutes shall meet the continual increased regional need for commercial arbitrations and guarantee the accurate application of international law. This article introduces the function of UNCITRAL, gives a brief analysis of the demand for improving international commercial arbitration in Asia, and suggests that UNCITRAL as an appropriateorganization may prospectively contribute to promote the competences of regional arbitral institutes and arbitral participants by means of providing active technical assistance and cooperative projects. Two tentative proposals are put forward in this article from a practical perspective.

A Collocated Eddy-Current Displacement Sensor for Magnetic Bearings

김성학(Sheng He Jin),보응옥부(Vo Ngoc Vu),안형준(Hyeong-Joon Ahn) Korean Society for Precision Engineering 2022 한국정밀공학회지 Vol.39 No.1

Magnetic bearings use electromagnetic force to support the rotating shaft without any mechanical contact and actively control shaft vibration; hence, there is no mechanical friction and wear due to contact during the operation, and it has a semi-permanent lifespan. Because magnetic bearings are unstable by themselves, a gap sensor is necessary to stably control the position of objects. However, there is a limit to the improvement in control performance because the sensor is installed on one side of the bearing and is not aligned with the electromagnet. This paper presents a newly developed collocated eddy-current PCB displacement sensor for magnetic bearings. The PCB sensor is designed and built to install between the poles of a magnetic bearing and to minimize the electromagnetic interference. A sensor calibration test is performed to evaluate the sensitivity and noise of the collocated PCB sensor. In addition, the control performance of the collocated PCB sensor is evaluated by measuring the closed-loop sensitivity function of a 1 DOF magnetic suspension test rig. The collocated PCB sensor has noise within ±1 μm and excellent vibration suppression performance.

시간 지연이 있는 변위 센서로 제어되는 자기베어링의 안정성에 대한 실험적 연구

김성학(Sheng-He Jin),장지욱(Jee-Uk Chang),안형준(Hyeong-Joon Ahn) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.12

A Global Online Dispute Resolution System: Is China Ready to Join?

( Qi Sheng He ),( Ji Ping Song ) 고려대학교 법학연구원 2011 The Asian Business Lawyer Vol.7 No.-

In recent years, Online Dispute Resolution (ODR) is in a period of active development and change. United Nations Commission on International Trade Law (UNCITRAL) and other international organizations are actively promoting the establishment of a global ODR system. Facing small value, large volume claims, traditional dispute resolution system in China also can not resolve effectively these disputes arising out of electronic commerce. With an increasing demand of ODR and a favorable legal circumstance for it, ODR practice in China has developed rapidly during the past several years. It can be mainly represented by three categories: Domain Name Dispute Resolution Center of China International Economic and Trade Arbitration Commission (CIETAC), China Online Dispute Resolution Center and Alipay Internal Complaint Mechanism. As for the prospects of China working with UNCITRAL on a Global ODR System, on the one hand, China`s participation in UNCITRAL work on a global ODR system can facilitate its ODR development; on the other hand, China can play an active role in establishing a global ODR system.

Uncovering Microstructure Evolution and Dynamic Softening Mechanism of Spray-Deposited AlZnMgCu Alloy Under Thermal Deformation

Guoai He,Cunxiao He,Yu Liu,Chao Liu,Zhiqiang Fu,Shuanghui Xu,Xiaofei Sheng,Zhu Xiao,Qinghong Wen 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.9

Dynamic softening behavior has been of great concern in the aluminum alloys, which served a vital role in affecting themicrostructure, deformation resistance and the final mechanical properties. In this paper, spray deposition was applied tomanufacture AlZnMgCu alloy to refine the casting microstructure and reduce segregation. The microstructure responses andcorresponding mechanism during the thermal compression with various temperatures and various strain rates were multiscalecharacterized and uncovered using high-resolution EBSD. The results revealed that many broken and fine grains wereobserved in the uneven and jagged grain boundaries under the low temperatures and high strain rates, which indicated theoccurrence of partial discontinuous dynamic recrystallization (DDRX). In addition, high density dislocations were formedat original grain boundaries, where great amount of low angle grain boundaries (LAGBs) were appeared. With temperatureincreased and strains rate decreased, the LAGBs would evolve to the high angle grain boundaries (HAGBs) owing to theconsiderable dislocations migrated to the grain boundaries then accumulated, which triggered the occurrence of continuousdynamic recrystallization (CDRX). Two different dynamic recrystallization types were observed and factors that influenceddifferent dynamic recrystallization behaviors were clearly elaborated, and the corresponding mechanism was indicateddetailly.