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송형근,양규현,유제현,변영수 연세대학교의과대학 2014 Yonsei medical journal Vol.55 No.3
Purpose: Among patients over 50 years of age, separate vertical wiring alone may be insufficient for fixation of fractures of the inferior pole of the patella. Therefore, mechanical and clinical studies were performed in patients over the age of 50 to test the strength of augmentation of separate vertical wiring with cerclage wire (i.e., combined technique). Materials and Methods: Multiple osteotomies were performedto create four-part fractures in the inferior poles of eight pairs of cadaveric patellae. One patella from each pair was fixed with the separate wiring technique, while the other patella was fixed with a combined technique. The ultimate load to failure and stiffness of the fixation were subsequently measured. In a clinical study of 21 patients (average age of 64 years), comminuted fractures of the inferior pole of the patellae were treated using the combined technique. Operative parameters were recorded from which post-operative outcomes were evaluated. Results: For cadaveric patellae, whose mean age was 69 years, the mean ultimate loads to failure for the separate vertical wiring technique and the combined technique were 216.4±72.4 N and 324.9±50.6 N, respectively (p=0.012). The mean stiffness for the separate vertical wiring technique and the combined technique was 241.1±68.5 N/mm and 340.8±45.3 N/mm, respectively (p=0.012). In the clinical study, the mean clinical score at final follow-up was 28.1 points. Conclusion: Augmentation of separatevertical wiring with cerclage wire provides enough strength for protected early exercise of the knee joint and uneventful healing.
송형근,양규현,윤한국 연세대학교의과대학 2014 Yonsei medical journal Vol.55 No.5
Purpose: Presence of a cephalomedullary nail (CMN) in the medullary canal has been thought as advantageous in the control of femoral neck shortening (FNS) and lag screw sliding in trochanteric fracture compared to extramedullary fixation system. However, researches on the factors that influence the degree of FNS after cephalomedullary nailing are lacking. Materials and Methods: We observed 95 patients (mean age, 75±2.8 years) with trochanteric fractures who were treated with a CMN, and evaluated the relationship between FNS and patient factors includingage, gender, fracture type (AO/OTA), bone mineral density, medullary canaldiameter, canal occupancy ratio (COR=nail size/canal diameter), and tip-apex distance using initial, immediate postoperative, and follow-up radiography. Results:Univariate regression analyses revealed that the degree of FNS was significantlycorrelated with fracture type (A1 versus A3, p<0.001), medullary canal diameter(p<0.001), and COR (p<0.001). Multiple regression analyses revealed that FNS was strongly correlated with fracture type (p<0.001) and COR (p<0.001). Conclusion: Presence of a CMN in the medullary canal could not effectively preventFNS in patients with low COR and in A3 type fracture.
Organic semiconductor based on phenylethynyl end-capped anthracene for OTFT
송형근,김슬옹,박정훈,이상봉,박광훈,김윤희 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
Organic thin film transistors (OTFTs) based on molecular and polymeric organic semiconductors have attracted considerable interest due to their lower cost deposition processes and higher compatibility with plastic substrates compared to silicon-based thin film transistors (TFT). In this study, a new molecular having anthracene core and phenylethynyl end groups is designed and synthesized. This molecular was expected to have deep highest occupied molecular orbital (HOMO) level, leading to higher stability than that of pentacene. Moreover, rigid rod structure with a high aspect ratio due to triple bond, leads to a higher long range ordering and a higher intermolecular π-π stacking compared to that of pentacene. Thus, the device incorporating this molecular shows a high charge mobility, stability and device reproducibility.
모바일 어플리케이션 업데이트 분석 : 사용자 반응과 의도하지 않은 결과를 중심으로
송형근,고병완 한국경영정보학회 2019 Information systems review Vol.21 No.2
모바일 어플리케이션 시장에서 업데이트는 (i) 어플리케이션의 가시성을 높이거나, (ii) 기존 사용자 들의 충성도를 높이고 가치를 제고하거나, (iii) 기능 추가를 통해 시장을 확대하는 등 다양한 목적을 위한 전략적 마케팅 도구로 활용되고 있다. 많은 연구와 사례들은 이러한 업데이트가 모바일 어플리 케이션 시장에서 생존하기 위해 중요하다는 점을 강조하고 있다. 그러나, 일부 다른 사례들은 업데이트가 오히려 사용자들의 반발과 이탈을 불러오기도 한다는 것을 보여주었다. 본 연구는 모바일 어플리 케이션의 실제 사용량 데이터를 통해 어플리케이션의 이용 목적과 시장경쟁 환경에 따라 업데이트가 사용자들의 어플리케이션 이용패턴에 사용자수 측면에서, 이용빈도수 측면에서, 그리고 이용시간 측면에서 어떠한 영향을 주는지를 분석하였다. The updates in the mobile application market have been widely used as strategic marketing tools. It has been used to (i) improve the visibility of an application, (ii) enhance the value of an applicationand strengthen the loyalty of current users, and (iii) expand the market by adding additional features or functions. A number of studies and anecdotal evidence have highlighted the importance of these updates in the mobile application market. However, not all updates in the mobile application market have been successful. Snapchat, for instance, lost 3 million users in three months after it rolled out a major update in November 2017. In this study, we investigate the impact of updates on the usage patterns of users in the mobile application market using MAU (Monthly Active Users), usage frequency, and usage time that we collected from a company that provides mobile application usage statistics.
송형근,김연수,박광훈,이예슬,김봉수,김경곤,김윤희 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
Polymer solar cells have attracted great attention for their potential utility in the production of large-area, low-cost, and flexible photovoltaic devices via solution processing. To achieve high power conversion efficiencies, electron-donor polymers should have the following desirable characteristics: good absorption spectral overlap with the solar spectrum, optimal energy level alignment with respect to electron-acceptor fullerene derivatives to facilitate efficient exciton separation, formation of a nanoscale interpenetrating network of the polymer and fullerene domains inside the photoactive layer, and provision of effective charge transport carriers toward the electrodes. Herein, we report synthesis and characterization of polymers. This work demonstrates that the newly designed materials moiety is a promising building block for high performance PSCs.