• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.324-325
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• 2014

Quantum wells infrared photodetectors (QWIPs) have been used to detect infrared radiations through the principle based on the localized stated in quantum wells (QWs) [1]. The mature III-V compound semiconductor technology used to fabricate these devices results in much lower costs, larger array sizes, higher pixel operability, and better uniformity than those achievable with competing technologies such as HgCdTe. Especially, GaAs/AlGaAs QWIPs have been extensively used for large focal plane arrays (FPAs) of infrared imaging system. However, the research efforts for increasing sensitivity and operating temperature of the QWIPs still have pursued. The modification of heterostructures [2] and the various fabrications for preventing polarization selection rule [3] were suggested. In order to enhance optical performances of the QWIPs, double barrier quantum well (DBQW) structures will be introduced as the absorption layers for the suggested QWIPs. The DBWQ structure is an adequate solution for photodetectors working in the mid-wavelength infrared (MWIR) region and broadens the responsivity spectrum [4]. In this study, InGaAs/GaAs/AlGaAs double barrier quantum well infrared photodetectors (DB-QWIPs) are successfully fabricated and characterized. The heterostructures of the InGaAs/GaAs/AlGaAs DB-QWIPs are grown by molecular beam epitaxy (MBE) system. Photoluminescence (PL) spectroscopy is used to examine the heterostructures of the InGaAs/GaAs/AlGaAs DB-QWIP. The mesa-type DB-QWIPs (Area : $2mm{\times}2mm$) are fabricated by conventional optical lithography and wet etching process and Ni/Ge/Au ohmic contacts were evaporated onto the top and bottom layers. The dark current are measured at different temperatures and the temperature and applied bias dependence of the intersubband photocurrents are studied by using Fourier transform infrared spectrometer (FTIR) system equipped with cryostat. The photovoltaic behavior of the DB-QWIPs can be observed up to 120 K due to the generated built-in electric field caused from the asymmetric heterostructures of the DB-QWIPs. The fabricated DB-QWIPs exhibit spectral photoresponses at wavelengths range from 3 to $7{\mu}m$. Grating structure formed on the window surface of the DB-QWIP will induce the enhancement of optical responses.

• Journal of Preventive Medicine and Public Health
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• 제30권4호
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• pp.840-851
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• 1997

To perform voluntary occupational health program in worksites, regulational supports are necessary. The regulational supports include assessment of current occupational health program and appropriate incentives. The purpose of this study is to find out the requirements of voluntary occupational health program and conditions to be improved. Study population was industrial health managers of both industries with less than 300 workers and over 300 workers, and the member of labor union who is responsible for safety and health in worksite. Two different questionnaire were used to find out the requirements and conditions to be improved respectively, The results were; 1. The category which prevalence rate of occupational injuries and occupational disease should be lower than national average was most important in health managers employed in industries over 300 workers and followed by reporting system, education, worksite policy, work environment assessment, protective equipment, consequently. But those employed in industries less than 300 workers showed high importance in prevalence rate of occupational injuries and disease, reporting system, worksite policy, work environment assessment, protective equipment, education, consequently 2. The members of labor union thought that worksite policy was most important and the next is education, reporting system, work environment assessment, protective equipment, prevalence rate of occupational injuries and disease. 3. There were difference in importance of education and worksite policy according to the size of industries. Reporting system, prevalence rate of occupational injuries and disease, and worksite policy had different importance between members of labor union and health managers. 4. In the results of quiestionnaire for conditions to be improved, the most important condition was top manager's willingness except personal protective equipments, and followed by financial support, legal support. The limitations of this study were the problems of representativeness of study population. but voluntary health program should be performed in worksites which have relatively good occupational health system. So, this selection bias could not disrupt our results.

• Korean Journal of Acupuncture
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• 제35권3호
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• pp.130-138
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• 2018

Objectives : The purpose of this study is to explore patients' perceptions that deserve attention when designing core questions for a clinical practice guideline of Korean medicine(KM) for degenerative lumbar spinal stenosis (LSS). Methods : Patients who had been admitted to Pusan National Korean Medicine Hospital from November 1, 2015 to October 31, 2016 were invited to the survey. Patients were eligible if they were both clinically and radiologically confirmed as degenerative LSS. The structured questionnaire was distributed by mail and outpatient visits. Questions included types of experienced Korean/Western medical interventions for LSS, their perceived effectiveness on symptoms, the necessity for studies of KM for degenerative LSS, the types of KM interventions to be investigated and the types of outcome measures after treatments. Data were descriptively analysed. Results : Twenty of thirty-one invited participants responded to the questionnaire. Acupuncture and herbal medicine were the most frequently used KM interventions. Eighteen respondents reported that KM treatments were helpful for their improvement. Sixteen patients who mentioned that research on KM is needed chose acupuncture as the top priority(88%) among KM interventions. The most important outcomes in the view of nineteen respondents included functional recovery (68%) and pain relief (53%). Thirteen respondents (65%) replied that both short-term and long-term outcome were important for them. Conclusions : Our findings may have limited validity due to the small number of respondents and the potential selection and information bias. Further qualitative studies and large-scale surveys to comprehensively identify patients' views are warranted.

• 한국콘텐츠학회논문지
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• 제12권6호
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• pp.380-389
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• 2012

본 연구는 국내 작업치료사의 직무스트레스에 영향을 미치는 요인들에 대한 여러 선행 연구들의 결과에 대해 체계적 고찰 및 메타분석을 실시하여 스트레스 관련 요인들의 차이를 비교해 봄으로써 향후 작업치료사의 직무스트레스 예방 및 완화, 효과적인 대처 방법 마련에 대한 정보를 제공해 작업치료의 질 향상과 작업치료 인력관련 정책을 수립하는데 기초자료를 제시하고자 하였다. 선정기준에 적합한 총 8건의 논문이 선정되었고, 이중 메타분석을 위해 크기의 변환이 가능한 통계치를 밝히고 있는 연구 5건을 대상으로 상관계수를 이용한 메타분석을 실시해 전체 상관계수 값과 요인별 상관계수 값을 구하였으며 대상 논문들의 동질성 검정과 출판편견 검정을 실시하였다. 그 결과 작업치료사의 직무스트레스 요인에 대한 전체 효과크기에 대한 95%의 신뢰구간은 .27에서 .34로 이 값은 통계적으로 유의하였다. 직무스트레스 요인들 중 조직관련 요인이 가장 높은 상관관계를 보였고, 그 다음으로 조직외관련 요인, 물리적환경 요인, 직무관련 요인, 개인관련 요인 순으로 상관관계를 나타내었다. 또한 출판편견을 배제할 수 있어 본 연구 결과는 신뢰할 수 있음을 뒷받침 해주고 있다. 이 연구는 작업치료사의 직무스트레스 예방 및 완화, 효과적인 대처 방법 마련을 위해 참고할 수 있는 자료를 제공하였다는데 의의가 있다.

• Strategy21
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• 통권46호
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• pp.123-157
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• 2020

이번 연구는 국제해사국의 연례 보고서를 바탕으로 2009~2014년 동안 아프리카 인근 해역에서 발생한 771건의 해적사건을 음이항 회귀분석(Negative binomial regression)을 이용하여 분석했다. 이번 연구를 통해 소말리아 인근에서 작전하는 다국적 해군함정의 숫자가 증가할수록 소말리아 인근에서 발생하는 해적사건이 감소하는 사실을 정량적으로 확인했다. 이를 통해 청해부대를 비롯하여 소말리아 인근에서 실시되고 있는 다국적 해군의 대(對)해적 작전이 실제로 해적사건 감소에 효과가 있음을 증명했다.

• 정보화정책
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• 제21권2호
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• pp.67-88
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• 2014

이 논문의 연구가설은 스마트기기 활용 교육이 장애인들의 교육 및 학습효과로 스마트기기에 대한 사용능력과 활용 정도의 수준을 높여줄 수 있을 것이라는 것이다. 한국정보화진흥원의 '2012년 정보격차 실태조사 원자료' 중 장애인 데이터를 사용하고, 표본선택편의문제 해결을 위해 Heckman의 2단계 추정법을 활용하였다. 실증 분석결과, 스마트기기 활용 교육을 받은 장애인일 경우 종합적인 스마트기기 사용능력과 활용도 수준이 각각 더 높다는 가설이 채택되었다. 스마트기기 사용능력 및 활용도 측면에서는 스마트기기 활용 교육과 높은 학력 가구소득, 전문사무직, 젊은 연령층 등이 긍정적인 유의미한 영향을 미쳤고, 특히 지체장애에 비해서 시각장애일 경우 스마트기기 사용능력 및 활용도 수준이 낮아지는 것으로 나타났다. 이는 시각장애의 경우 특수 보조기기 및 어플리케이션 없이는 생활이 거의 불가능하므로 지체장애의 경우 두 팔 또는 두 손 전체에 이상이 있는 중증장애가 아닌 한 스마트기기 활용 교육을 통해 스마트기기 사용능력 및 활용도 수준이 높아짐을 알 수 있었다. 본 연구결과는 장애인의 스마트기기 활용도를 높이기 위한 공공 정책 또는 민간 협력의 교육프로그램 진행이 그 목적을 달성하면서 교육의 긍정적인 효과를 보여주면서, 한편 장애유형에 따라 보다 정교한 교육내용과 방법이 필요하다는 것을 보여준다.

• 디자인학연구
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• 제19권2호
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• pp.91-98
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• 2006

제품의 융합과 그 사용 환경의 복잡화로 인하여 다양한 감각을 활용해서 제품과 교감하는 다중 인터페이스의 필요성이 제기되고 있다. 전통적이고 일반적인 정보의 습득에는 시각이 압도적으로 많이 활용되었으나 디지털 네트워크 기술을 기반으로 발달할 미래 정보 사회에서는 보다 편리하고 합리적인 제품의 사용을 위하여 다양한 감각의 활용이 요구될 것이다. 정보 전달에 있어서 시각과 더불어 점차적으로 활용 가능성이 높아지고 있는 청각은 그 쓰임새가 더욱 넓어지고 또한 다양한 방식으로 발전될 것이다. 이러한 배경을 바탕으로 본 연구에서는 정보의 전달에서 사용되는 문자언어와 음성언어의 특성과 그에 대한 반응에 있어서 남성과 여성의 차이점의 비교분석에 관한 연구가 수행되었다. 이를 위하여 일단 언어를 구성하는 여러 가지 요소에 대한 문헌자료의 연구를 수행하였다. 이어서 시각과 청각의 특성을 검토한 후 선행 연구를 기반으로 하여 적절한 실험이 설계 및 수행되었다. 수행된 실험은 객관적인 분석방법을 통하여 실험 결과가 검토되었다. 금번 연구의 결과로는 첫째, 문자언어에 대한 반응 시간이 음성언어에 대한 그것보다 짧다는 것, 둘째 각 자극에 대한 반응에 있어서 남녀간의 차이가 존재한다는 것, 셋째, 시각이 청각에 비하여 선택적인 측면에서 절대적 우위를 점하지 못한다는 점등을 들 수 있다. 이번 연구를 기반으로 하여 보다 다양한 감각에 대한 폭 넓은 연구 방법의 개발이 필요할 것으로 사료된다.

• 한국정보통신학회논문지
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• 제19권1호
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• pp.149-155
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• 2015

본 논문에서는 선형성이 개선된 5MHz의 샘플링 주파수를 가지는 10-비트 디지털/아날로그 변환기를 제안한다. 제안하는 디지털/아날로그 변환기는 10-비트 R-2R 기반 디지털/아날로그 변환기, rail-to-rail 입력 범위의 차동 전압증폭기를 이용하는 출력버퍼, 그리고 바이어스 전압을 위한 밴드-갭 기준전압 회로로 구성된다. R-2R 디지털/아날로그 변환기의 2R 구현에 스위치를 위해 사용되는 인버터의 turn-on 저항 값을 포함하여 설계함으로 선형성을 개선시킨다. DAC의 최종 출력 전압 범위는 출력버퍼에 차동전압증폭기를 이용함으로 R-2R의 rail-to-rail 출력 전압으로부터 $2/3{\times}VDD$로 결정된다. 제안된 디지털/아날로그 변환기는 1.2V 공급전압과 1-poly, 8-metal을 이용하는 130nm CMOS 공정에서 구현되었다. 측정된 디지털/아날로그 변환기의 동적특성은 9.4비트의 ENOB, 58dB의 SNDR, 그리고 63dBc의 SFDR이다. 측정된 DNL과 INL은 -/+0.35LSB 미만이다. 제작된 디지털/아날로그 변환기의 면적과 전력소모는 각각 $642.9{\times}366.6{\mu}m^2$과 2.95mW이다.

• 유통과학연구
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• 제12권8호
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• pp.113-121
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• 2014

Purpose - Recently, the number of corporations that practice environmental and social responsibility, besides engaging in traditional profit-seeking activities, has been growing steadily, as interest in Corporate Social Responsibility (CSR) is increasing. Recent research on CSR practices has identified the relationship between CSR activities and corporate value as one of the main issues in this respect. Considering that donations constitute a large proportion of a company's charitable activities, we considered the extent of donation expenses as a charitable activity in order to mitigate sample selection bias. Specifically, we analyzed the impact of donation expenses on firm value, while investigating if this impact varied in response to the level of corporate governance of firms. Research design, data, and methodology - We used non-financial firms listed on the Korean Stock Exchange, having their fiscal year end in December, and the sample period was 2006-2013. For the dependent variable, Tobin's q was used as the corporate value, and for the independent variable, donations were measured as the donation-expense-to-sales ratio. Corporate governance scores, as rated by the Korea Corporate Governance Service, were used to measure corporate governance levels because they consider the overall aspects of governance, including ownership structure, the board of directors, and the audit mechanism of individual companies. To examine the impact of donations on a company in relation to the level of corporate governance, we estimated regression models using the interaction terms of the governance dummy and donation variables. Then, we further estimated the regression models of two sub-samples that were classified according to the level of corporate governance. Similar to previous studies, the study uses variables that affect firm value, such as R&D expenditure, advertising expenses, EBITDA, debt-to-equity ratio, sales growth, company age, and company size as control variables. Results - The empirical results show that firm value significantly increased in response to an increase in donation expenses. Upon including the interaction terms of governance level dummy variables and donations, the coefficients of the interaction terms show significant positive values, while those of donation variables show significant negative values. In the strong governance sub-sample, the relationship between the donation expenses and corporate value was statistically positive (+) and significant. However, in the weak governance sub-sample, the relationship between the donation expenses and corporate value was statistically insignificant and negative (-). Conclusions - The empirical results suggest that donation expenses are significantly linked to an enhanced corporate value if firms have a good corporate governance structure. However, if the corporate governance structure is weak, the same relationship is not necessarily observed. The results of this study show that if a firm has high corporate governance, CSR practices enhance the company's reputation such that it has a positive (+) relationship with corporate value. If a firm has weak corporate governance, on the other hand, CSR practices are recognized as an agency cost and do not increase corporate value.

• Journal of Korean Neurosurgical Society
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• 제65권4호
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• pp.539-548
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• 2022

Objective : Although full-endoscopic lumbar interbody fusion (Endo-LIF) has been tried as the latest alternative technique to minimally invasive transforaminal lumbar interobody fusion (MIS-TLIF) since mid-2010, the evidence is still lacking. We compared the clinical outcome and safety of Endo-LIF to MIS-TLIF for lumbar degenerative disease. Methods : We systematically searched electronic databases, including PubMed, EMBASE, and Cochrane Library to find literature comparing Endo-LIF to MIS-TLIF. The results retrieved were last updated on December 11, 2020. The perioperative outcome included the operation time, blood loss, complication, and hospital stay. The clinical outcomes included Visual analog scale (VAS) of low back pain and leg pain and Oswestry disability index (ODI), and the radiological outcome included pseudoarthosis rate with 12-month minimum follow-up. Results : Four retrospective observational studies and one prospective observational study comprising 423 patients (183 Endo-LIF and 241 MIS-TLIF) were included, and the pooled data analysis revealed low heterogeneity between studies in our review. Baseline characteristics including age and sex were not different between the two groups. Operation time was significantly longer in Endo-LIF (mean difference [MD], 23.220 minutes; 95% confidence interval [CI], 10.669-35.771; p=0.001). However, Endo-LIF resulted in less perioperative blood loss (MD, -144.710 mL; 95% CI, 247.941-41.478; p=0.023). Although VAS back pain at final (MD, -0.120; p=0.586), leg pain within 2 weeks (MD, 0.005; p=0.293), VAS leg pain at final (MD, 0.099; p=0.099), ODI at final (MD, 0.141; p=0.093) were not different, VAS back pain within 2 weeks was more favorable in the Endo-LIF (MD, -1.538; 95% CI, -2.044 to -1.032; p<0.001). On the other hand, no statistically significant group difference in complication rate (relative risk [RR], 0.709; p=0.774), hospital stay (MD, -2.399; p=0.151), and pseudoarthrosis rate (RR, 1.284; p=0.736) were found. Conclusion : Relative to MIS-TLIF, immediate outcomes were favorable in Endo-LIF in terms of blood loss and immediate VAS back pain, although complication rate, mid-term clinical outcomes, and fusion rate were not different. However, the challenges for Endo-LIF include longer operation time which means a difficult learning curve and limited surgical indication which means patient selection bias. Larger-scale, well-designed study with long-term follow-up and randomized controlled trials are needed to confirm and update the results of this systematic review.