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조동혁,박종우 한국IT서비스학회 2015 한국IT서비스학회지 Vol.14 No.3
The spread of mobile commerce due to popularization of smartphones not only broke down the boundary between online and offline, but also changed the consumer life, and hence brought change of commerce paradigm that creates new demand. The success of innovative information technology such as mobile shopping can be defined as an individual accepting the technology and continuously using it, but the studies on the usage behavior after the acceptance have been done in very restrictively, despite its importance. In this study, in order to empirically investigate the factors that influence the continuance in mobile shopping usage experience and its causal relationship, Social Cognitive Theory and Habit Theory were applied to IS Continuance Model,and the extended IS Continuance Model was suggested and proved. As a result, the usefulness, enjoyment, and self-efficacy perceived in usage experience significantly influence satisfaction, and usefulness, self-efficacy, and satisfaction influence habit. Also, usefulness, self-efficacy, satisfaction, and habit significantly influence continuance intention. This study provides a valuable asset in providing an opportunity to understand the usage behavior of mobile shopping service users after the acceptance, and furthermore proving directionality in improving customer loyalty.
조동혁,장윤찬,이영석 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.9
In this study, we selected six ductile fracture (DF) criteria to assess their capability to predict material fracture when high-alloy steel was cold drawn at a wide range of reduction ratios and die semi-angles in a single-pass drawing process. A user-defined subroutine VUSDFLD for each DF criterion was coded in Fortran and integrated into ABAQUS. Twenty-eight drawing tests were performed using a combination of reduction ratio (r) range (10-49 %) and die semi-angle (a) range (4°-25°). Test results were compared with the results of finite element simulations. The results showed that, if three macroscopic variables (namely, stress triaxiality, maximum principal stress, and equivalent stress) and a cut-off value are combined in a DF criterion, the fracture of the material being drawn can be predicted at a sufficient level. This DF criterion showed a much higher prediction accuracy than the other five DF criteria, especially in the operating region (a < 10° and r > 40 %) where the producer of cold-drawn steel bar (or rod) products prefers to increase productivity and improve quality.
조동혁,Young-seog Lee 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.Supp
This study proposes a fast running model that interconnects input and output data for a single-pass cold bar drawing process through the use of Artificial Neural Network (ANN) and automatically generated a large volume of elasticplastic finite element (FE) analysis results. The prediction accuracy of the FE analysis was verified by comparing the FE analysis with measurements from a drawing experiment. A Python-based script that automatically controls ABAQUS was coded to sequentially produce output data that varies according to the input data, which is a combination of 18 grades of steel and 1,000 process conditions. The ANN was trained using input and output data, and then a nine-dimensional fast running model was developed. The fast running model predicted the values of output variables (drawing force, strain at the center, strain on the surface, accumulated damage at the center, contact pressure, and the fracture (or non-fracture) of the material) in 0.1 second no matter how the mechanical properties of the steels and process conditions change. With this fast running model, engineers in the drawing industry can easily determine or modify the process conditions to improve productivity and product quality even when a grade of steel that has never been employed before is drawn.
하추체정맥동 채혈검사 후 발생한 Raymond-Cestan 증후군 1예
조동혁 대한내분비학회 2003 Endocrinology and metabolism Vol.18 No.1
Inferior petrosal sinus sampling (IPSS) plays an important role in the assessment of patients with ACTH-dependent Cushing's syndrome. IPSS has been described as an innocuous, essentially risk-free procedure. Neurological complications associated with IPSS are rare. Previously reported neurological complications include brain stem infraction, pontine hemorrhage and subarachnoid hemorrhage.A 26-year-old woman was admitted to the hospital because of a moon face and a buffalo hump. A MRI showed a suspicious, but uncertain, area on the left side of the sella turcica. IPSS was performed as an appropriate means of providing more information about the side of the ACTH source. Immediately after the procedure, the woman experienced double vision, caused by a complete sixth nerve palsy of the left eye, together with a contralateral hemiparesis. From a clinical point of view, abducens nerve palsy and contralateral hemiparesis corresponded to Raymond-Cestan syndrome. I report a case of Raymond-Cestan syndrome, following petrosal sinus sampling in a female patient with ACTH-dependent Cushing's syndrome. To the best of our knowledge, this complication associated with petrosal sinus sampling has only been described in one previous case report. Although IPSS may provide essential information in the investigation of Cushing's syndrome, the possibility of very occasional but devastating complications should be remembered(J Kor Soc Endocrinol 18:73~78, 2003). 저자는 4년 전에 하추체정맥동채혈검사 등을 시행하여 쿠싱병으로 진단받고 종양제거 후에 완치 판정을 받아 외래추적관찰 중이던 26세 여자에서 재발한 ACTH 의존성 쿠싱증후군의 원인적 감별 진단을 위하여 하추체정맥동채혈검사 후에 좌안의 외전신경마비와 우측부전마비가 발생하여 Raymond-Cestan 증후군으로 진단하고 항응고요법 등의 치료 후에 호전된 1예를 경험하였기에 문헌고찰과 함께 보고하는 바이다.
An Exploratory Study on Success Factors of Technology-based start-ups
조동혁,김종영 한국인터넷정보학회 2018 인터넷정보학회논문지 Vol.19 No.6
This study was conducted to empirically verify the effect of the technological entrepreneurship, network capability and technological innovation capability on the innovative performance of technology-based start-ups with the aim of determining the success factors of technology-based start-ups by defining the success of technology-based start-ups as the innovative performance through technology innovation activities. For the significance of this study, it suggested the importance of technology innovation as a survival strategy of technology-based start-ups, verified the dimensions, relationship and roles of technological entrepreneurship, network capability and technology innovation capability, thereby proving the theoretical expansion. This study has determined the success factors of technology-based start-ups and thereby suggested the strategic directions for enhancing the competitiveness of technology-based start-ups.
Reference Intervals for Bone Turnover Markers in Korean Healthy Women
조동혁,정진욱,Min-Young Chung,Jeong-Ran Cho,정동진 대한골대사학회 2020 대한골대사학회지 Vol.27 No.1
Background: Adequate suppression of bone turnover rate is important to decrease fracture risk without mineralization defect due to oversuppression. This study was performed to determine reference intervals (RIs) for 2 bone turnover markers, serum C-terminal telopeptide of type I collagen (CTX) and osteocalcin, in Korean women. Methods: A total of 461 Korean women (287 premenopausal and 174 postmenopausal) without any disease or drug history affecting bone metabolism was included. Serum CTX and osteocalcin were measured after overnight fasting. Bone mineral density (BMD) was measured at the 1st to 4th lumbar vertebra using dual energy X-ray absorptiometry. Subjects with normal spinal BMD (T-score ≥-1.0) were included in this study. Results: After stable concentrations were maintained, both CTX and osteocalcin were abruptly increased in 50 to 59 years, and then decreased with increasing age. Median levels and interquartile range of serum CTX and osteocalcin in all subjects were 0.322 (0.212-0.461) ng/mL and 15.68 (11.38-19.91) ng/mL. RIs for serum CTX and osteocalcin in all subjects were 0.115 to 0.861 ng/mL and 6.46 to 36.76 ng/mL. Those were higher in postmenopausal women (CTX, 0.124-1.020 ng/mL, osteocalcin, 5.42-41.57 ng/mL) than in premenopausal women (CTX, 0.101-0.632 ng/mL, osteocalcin, 6.73-24.27 ng/mL). If we use target reference levels as lower half of premenopausal 30 to 45 years in patients with antiresorptive drugs, those were 0.101 to 0.251 ng/mL and 6.40 to 13.36 ng/mL. Conclusions: We established RIs for serum CTX and osteocalcin in healthy Korean women with normal lumbar spine BMD. Premenopausal RIs for serum CTX and osteocalcin would be useful to monitor patients with low bone mass using osteoporosis drugs.