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STANDARDS PRISM (2) 표준시론(時論) - 전기자동차와 기술표준 -전기자동차 개발과 실용화에 뒤처지지 않으려면 표준화 선행돼야
허훈,Heo, Hun 기술표준원 2011 기술표준 Vol.114 No.-
대체에너지 개발과 탄소에너지 규제에 발맞추기 위한 전기자동차의 개발과 실용화가 전 세계적으로 가속화되고 있다. 이번 8월호에서는 허훈 전기자동차 국가표준 코디네이터로부터 전기자동차의 개요와 현황, 세계 각국의 동향과 표준화작업의 필요성에 대해 알아본다. 2012년 2월호에 게제될 다음 연재에서는 전기자동차의 표준화작업과 연구개발 실태와 현황에 관해 보다 자세히 소개할 예정이다.
허훈,안창욱,변철수,신호정,김영배,손상용,한상욱 대한위암학회 2017 Journal of gastric cancer Vol.17 No.3
Purpose: Although Roux-en-Y (R-Y) reconstruction after distal gastrectomy has several advantages, such as prevention of bile reflux into the remnant stomach, it is rarely used because of the technical difficulty. This prospective randomized clinical trial aimed to show the efficacy of a novel method of R-Y reconstruction involving the use of 2 circular staplers by comparing this novel method to Billroth-I (B-I) reconstruction. Materials and Methods: A total of 118 patients were randomly allocated into the R-Y (59 patients) and B-I reconstruction (59 patients) groups. R-Y anastomosis was performed using two circular staplers and no hand sewing. The primary end-point of this clinical trial was the reflux of bile into the remnant stomach evaluated using endoscopic and histological findings at 6 months after surgery. Results: No significant differences in clinicopathological findings were observed between the 2 groups. Although anastomosis time was significantly longer for the patients of the R-Y group (P<0.001), no difference was detected between the 2 groups in terms of the total surgery duration (P=0.112). Endoscopic findings showed a significant reduction of bile reflux in the remnant stomach in the R-Y group (P<0.001), and the histological findings showed that reflux gastritis was more significant in the B-I group than in the R-Y group (P=0.026). Conclusions: The results of this randomized controlled clinical trial showed that compared with B-I reconstruction, R-Y reconstruction using circular staplers is a safe and feasible procedure. This clinical trial study was registered at www.ClinicalTrials.gov (registration No. NCT01142271).
DYNAMIC HARDENING EQUATION OF THE AUTO-BODY STEEL SHEET WITH THE VARIATION OF TEMPERATURE
허훈,H. J. LEE,J. H. SONG 한국자동차공학회 2012 International journal of automotive technology Vol.13 No.1
This paper is concerned with the empirical hardening equation of steel sheets for an auto-body at intermediate strain rates with the variation of temperature. In order to identify the temperature dependence of the strain-rate sensitivity of steel sheets such as SPRC35R, SPRC45E and TRIP60, uniaxial tensile tests have been performed with the variation of the strain rate from 0.001/sec to 200/sec and the environmental temperature from –40oC to 200oC. The thermo-mechanical response at the quasi-static state is obtained from static tensile tests and that at the intermediate strain rate is obtained from high speed tensile tests. The effects of both the strain rate and the temperature on the flow stress and the fracture elongation are investigated with the experimental data. Experimental results provide the variation of the strain-rate sensitivity with respect to the temperature. They also show that as the strain rate increases, the variation of flow stress becomes sensitive to the temperature. A phenomenological constitutive model is newly proposed by modifying the well-known Khan–Huang–Liang model. Based on the experimental data, both the strain rate and the temperature dependent sensitivity of the flow stress are considered in the proposed model by coupling the strain, the strain rate and the temperature. In order to verify the accuracy of the proposed model quantitatively, the standard error between the experimental data and the fitted one is compared with other empirical constitutive models such as the Johnson–Cook and the Khan–Huang–Liang models. The comparison demonstrates that the model proposed gives relatively accurate description of the experimental data at the various strain rates and temperatures.