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      • 수술을 시행한 요추간판탈출증에 있어서 척수조영술의 가치

        백지현 충남대학교 의과대학 지역사회의학연구소 1978 충남의대잡지 Vol.5 No.2

        All who deal with the problem of ruptured lumbar discs know that both false-negative and false-positive myelograms occur. Many retrospective analysis have been made of the number of times myelograms agreed or disagreed with surgical findings, and an over all accuracy of lumbar myelography from 60% to 80% has been report: What the surgeon really needs to know for any given patient having certain signs and symptoms of a ruptured lumbar disc, is the likelihood that a positive myelogram truely predicts a ruptured dise or, if normal, that it truely predicts the abscence of a ruptured disc. To obtain the data necessary for such an analysis, a clinical study was done. The results of that study are reported here. During January 1974 to September 1978, 134 lumbar intervertebral discs were revealed on 120 herniated lumbar intervertebral disc patients at the department of neurosurgery of Chungnam National University Hospital. Myelography was done in all 120 patinents. The myelographic study showed unilateral smooth round filling defect in 46 cases, unilateral wedge shaped defect in 44 cases, block type defect in 19 cases, bilateral wedge shaped defect in 12 cases and hourglass defect in 1.0 cases. The operative finding revealed protruded disc in 70. 9%, bulging one in 14.2%, extruded 11.2%, and migrated 3.7%. The major discrepancies between myelographic and the operative finding were found in 10% while the minor discrepancies were 4. 2%. In 103 patients of the present series of 120 cases the operative findings were in complete accord with. the myelagraphic findings, giving an accuracy of 85.8 percent. The myelographic finding of bulging type disc usually showed smooth round filling defect while those of protruded was wedge shape filliing defect, and the extruded type revealed smooth round and hourglass defect in the most of case, A positive myelogram is more important than a negative myelogram. A negative or normal myelogram in the face of cliinical evidence of a ruptured disc sometimes will be wrong. Myelography can be a valuable aid in accurately localzing herniated discs and showing multiple discs, and may be very helpful in borderline cases. now believe that myelography should routinely precede surgery for lumbar disc Lesions.

      • KCI등재

        히스토그램의 변곡점을 이용한 영상 신호의 잡음 제거

        백지현,김남호 한국정보통신학회 2020 한국정보통신학회논문지 Vol.24 No.11

        In modern society, various video devices such as CCTV and black boxes are used for convenience. However, noise is frequently generated in the process of transmitting and receiving video images and video signals photographed at night. If such noise is not eliminated, the problem that the image is difficult to identify is generated. Accordingly, noise elimination of images in the image information is an indispensable step. Salt and Pepper noises are typical impulse noises among image noises. Previous research has been carried out as a method for eliminating noise, and CWMF, MMF and A-TMF are typical methods. In common, such a filter exhibits excellent performance in a low-density noise area, but a disadvantage is that noise elimination performance in a high-density noise area is somewhat insufficient. Accordingly, the proposed algorithm uses the inflection point of the histogram graph to separate areas and remove singular points, and proposes a weighting filter utilizing histogram distribution. PSNR was used for objective judgment. 현대사회에서 CCTV, 블랙박스 등 다양한 영상기기로 편리함을 도모한다. 하지만 야간에서 촬영된 영상이나 영상 신호가 송, 수신되는 과정에서 잡음이 빈번하게 발생한다. 이러한 잡음을 제거하지 않으면 영상의 식별이 어렵다는 문제점이 발생한다. 따라서 영상 정보에서 영상의 잡음 제거는 필수불가결한 단계이다. 영상 잡음 중 대표적인 임펄스 잡음으로 Salt and Pepper 잡음이 있다. 잡음을 제거하기 위한 방법으로 선행연구가 진행되어져 왔고 그중 대표적인 방법으로 CWMF, MMF, A-TMF 등이 있다. 이러한 필터들은 공통적으로 저밀도 잡음 영역에서는 우수한 성능을 보이지만 고밀도 잡음 영역에서 잡음 제거 성능이 다소 부족하다는 단점이 있다. 따라서 제안한 알고리즘은 히스토그램 그래프의 변곡점을 이용하여 영역을 나누어 특이점을 제거하고, 히스토그램 분포를 이용한 가중치 필터를 제안한다. 객관적인 판단을 위해 PSNR을 이용하였다.

      • KCI등재후보

        Salt and Pepper 잡음 환경에서 히스토그램의 분포를 이용한 스위칭 필터

        백지현,박준모,김남호 한국융합신호처리학회 2020 信號處理·시스템學會 論文誌 Vol.21 No.3

        최근 통신장비가 발달함에 따라 통신장비의 수요가 점차 늘어나고 있는 추세이다. 이에 따라 다양한 신호 처리가 연구되어져 왔다. 그 중 영상은 전처리 과정에서 잡음을 제거하지 않으면 오류의 전파라는 문제를 야기할 수 있기 때문에 잡음 제거가 필수불가결한 단계이다. Salt and Pepper 잡음의 경우 두 개의 극값을 가지는 대표적인 임펄스 잡음이다. 이러한 잡음을 제거하기 위해 다양한 연구가 진행되어 왔으며 CWMF, MF, MMF 등이 있다. 하지만 기존의 방법들은 고밀도 잡음 영역에서 다소 미흡한 모습을 보인다. 따라서 본 연구에서는 7×7 마스크 내부의 잡음개수에 따라 마스크의 크기를 다르게 하고, 영상의 히스토그램 분포를 이용하여 변형된 스위칭 필터로 필터링하는 알고리즘을 제안하였다. 제안한 알고리즘의 경우 고밀도 잡음 영역에서 효과적으로 잡음을 제거할 수 있으며, 객관적인 판단을 위해 PSNR을 이용하여 기존의 알고리즘들과 비교, 분석하였다. With the recent development of communication equipment, the demand for communication equipment is gradually increasing. Accordingly, various signal processing has been studied. In the case of an image, noise removal is an indispensable step because noise propagation problems may occur if noise is not removed in the pre-processing process. Salt and Pepper noise is a typical impulse noise with two extremes. Various studies have been conducted to remove such noise, and there are CWMF, MF and MMF. However, the existing methods are somewhat insufficient in the high-density noise region. Therefore, in this study, we have proposed an algorithm that filters the size of the mask according to the number of noises inside the 7x7 mask and filters it with a modified switching filter using the histogram distribution of the image. In the case of the proposed algorithm, noise can be effectively removed in a high-density noise region. For objective judgment, PSNR was used to compare and analyze with existing algorithms.

      • KCI등재

        고밀도 잡음 환경에서 엔트로피를 이용한 잡음 제거 방법

        백지현,김남호 한국정보통신학회 2020 한국정보통신학회논문지 Vol.24 No.10

        Currently, the spread of mobile devices is gradually increasing. Accordingly, various techniques using images or photos are actively being researched. However, image data generates noise for complex reasons, and the accuracy of image processing increases according to the performance of removing noise. Therefore, noise reduction is one of the essential steps. Salt and pepper noise is a typical impulse noise in the image, and various studies are being conducted to remove the noise. However, existing algorithms have poor noise rejection performance in high frequency areas, and average filters have blurring. Therefore, in this paper, we propose an algorithm that effectively removes salt and pepper noise in the high frequency region as well as the low frequency region using entropy. For objective and accurate judgment of proposed algorithms, MSE and PSNR were used to compare and analyze existing algorithms. 현재 모바일 기기의 보급이 점차 확대되어 지고 있다. 그에 따라 영상이나 사진을 활용한 다양한 기술들이 활발히 연구되어지고 있다. 하지만 영상 데이터는 복합적인 이유로 잡음이 발생하게 되며, 잡음의 제거 성능에 따라 영상처리의 정확도가 높아진다. 따라서 전 처리 과정으로 잡음의 제거는 필수불가결한 단계중 하나이다. 영상의 대표적인 임펄스 잡음으로 Salt and Pepper 잡음이 있으며, 이러한 잡음을 제거하기 위해 다양한 연구가 진행되고 있다. 하지만 기존의 알고리즘의 경우 고주파 영역에서 잡음제거 성능이 떨어지고, 평균 필터의 경우 블러 현상이 나타난다. 따라서 본 논문에서는 엔트로피를 이용하여 저주파영역 뿐만 아니라 고주파 영역에서도 효과적으로 Salt and Pepper 잡음을 제거하는 알고리즘을 제안한다. 제안한 알고리즘의 객관적이고 정확한 판단을 위해 MSE 및 PSNR을 이용하여 기존의 알고리즘들과 비교, 분석하였다.

      • KCI등재

        Smart Stress Care: Usability, Feasibility and Preliminary Efficacy of Fully Automated Stress Management Application for Employees

        백지현,Jeong Hyun Kim,Sohee Oh,Ju Young Kim,Soyoung Baik 대한신경정신의학회 2018 PSYCHIATRY INVESTIGATION Vol.15 No.11

        Objective We developed a fully automated smartphone-based stress management application and explored its usability, potential feasibility, and preliminary efficacy for stress management in Korean employees. Methods Healthy employees working in large public enterprises were enrolled. Participants used our automated stress management application for four weeks. With the application, they monitored their stress level and life style factors. Personalized stress management techniques, including psychoeducation and cognitive behavioral technique, were also provided based on their stress level and lifestyle pattern. In 2014, additional relaxation techniques were incorporated. Participants’ mental health status and lifestyle pattern were self-assessed at baseline and at 4 weeks after using the application. Results A total of 68 subjects were recruited. The application generally received high satisfaction rating. After the intervention, perceived stress level was significantly decreased, both in 2013 and 2014 (BEPSI-K score pre. vs. post. 14.27 vs. 11.00, F=12.49, p=0.001 in 2013; 12.05 vs. 10.00, F=17.18, p<0.001). In 2014, depression symptom severity was also significantly decreased (CES-D score pre- vs. Post-, 17.66 vs. 11.95, F=9.76, p=0.004). The effects were more significant in females and in those <35 years. Conclusion Our fully automated stress management application is acceptable and usable, showing preliminary efficacy for reducing employees’ stress levels.

      • 친환경복합타운, 선진국가들의도시개발트렌드로부상

        백지현,Baek, Ji-Hyeon 한국주택협회 2006 주택과 사람들 Vol.198 No.-

        미국, 일본, 유럽 등 선진국들은 신도시 건설보다 낙후된 도심 개발에 주력하고 있다. 대표적인 예가 도쿄 롯폰기 힐스, 뉴욕 배터리 파크 시티, 베를린 포츠다머 플라츠, 그리고 영국의 도클랜드다. 주거·상업·업무 기능을 아우르는 복합 타운으로 개발된 이들 지역을 살펴보고, 앞으로 우리나라 재개발 사업의 나아갈 방향에 대해 알아본다.

      • KCI등재

        Optimization of the Scan Protocol for the Reduction of Diaphragmatic Motion Artifacts Depicted on CT Angiography: a Phantom Study Simulating Pediatric Patients with Free Breathing

        백지현,장기현,정진욱,박재형,이활 대한영상의학회 2009 Korean Journal of Radiology Vol.10 No.3

        Objective: This study was designed to optimize the scan protocol of CT angiography to reduce diaphragmatic motion artifacts in pediatric patients with free-breathing. Materials and Methods: A phantom with twelve tubes with different diameters was constructed. To simulate free-breathing, the phantom was connected to a motor, and the phantom moved along the axis of scan. Scans were performed under several conditions: different pitch (1, 1.5) and gantry rotation time (0.37 and 0.75 sec), and different movement range (1 cm, 3 cm) and rates (20/min, 40/min). For CT scanning, a 16-channel CT scanner was used and fixed factors of the CT protocol were as follows: 100 effective mAs, 80 kVp, reconstruction with a softalgorithm, beam collimation 16×75 mm, reconstruction thickness of 1 mm, and an interval of 0.5 mm. CT scans were repeated five times. Each tube was evaluated with the use of a grading system (0 for images where tubes were not discriminable and 2 for images where tubes were clearly discriminable). Results: A higher pitch and shorter gantry rotation time produced images with a higher grade. Average grades for the higher pitch (1.5) and faster gantry rotation time (0.37 sec) for each combination of movement were as follows: 1.94 (range 1 cm and rate 20/min), 1.42 (range 1 cm and rate 40/min), 0.86 (range 3 cm and rate 20/min) and 0.52 (range 3 cm and rate 40/min). Average grades for the lower pitch (1) and slower gantry rotation time (0.75 sec) for each combination of movement were 1.08, 0.56, 0.32 and 0.08, respectively. Conclusion: The scanning speed and especially the pitch are important parameters for CT scans to overcome a respiratory motion artifact. Objective: This study was designed to optimize the scan protocol of CT angiography to reduce diaphragmatic motion artifacts in pediatric patients with free-breathing. Materials and Methods: A phantom with twelve tubes with different diameters was constructed. To simulate free-breathing, the phantom was connected to a motor, and the phantom moved along the axis of scan. Scans were performed under several conditions: different pitch (1, 1.5) and gantry rotation time (0.37 and 0.75 sec), and different movement range (1 cm, 3 cm) and rates (20/min, 40/min). For CT scanning, a 16-channel CT scanner was used and fixed factors of the CT protocol were as follows: 100 effective mAs, 80 kVp, reconstruction with a softalgorithm, beam collimation 16×75 mm, reconstruction thickness of 1 mm, and an interval of 0.5 mm. CT scans were repeated five times. Each tube was evaluated with the use of a grading system (0 for images where tubes were not discriminable and 2 for images where tubes were clearly discriminable). Results: A higher pitch and shorter gantry rotation time produced images with a higher grade. Average grades for the higher pitch (1.5) and faster gantry rotation time (0.37 sec) for each combination of movement were as follows: 1.94 (range 1 cm and rate 20/min), 1.42 (range 1 cm and rate 40/min), 0.86 (range 3 cm and rate 20/min) and 0.52 (range 3 cm and rate 40/min). Average grades for the lower pitch (1) and slower gantry rotation time (0.75 sec) for each combination of movement were 1.08, 0.56, 0.32 and 0.08, respectively. Conclusion: The scanning speed and especially the pitch are important parameters for CT scans to overcome a respiratory motion artifact.

      • KCI등재

        단백분해효소 억제제를 포함한 항레트로바이러스 병용 치료중인 HIV 감염 한국인에서 Atazanavir로 변경 후 지질 수치의 변화

        백지현,송영구,김창오,정수진,구남수,김혜원,한상훈,최준용,김준명 대한감염학회 2012 Infection and Chemotherapy Vol.44 No.5

        Dyslipidemia, one of the major disadvantages of use of protease inhibitor (PI), is a risk factor for cardiovascular disease in HIV-infected patients receiving antiretroviral treatment. Little is known about the effect of a switch from another PI to unboosted atazanavir (ATV) on the lipid profile. The aim of this study was to evaluate changes in the lipid profile after switching from another PI to either unboosted or boosted ATV in HIV-infected Koreans. We retrospectively collected data on the serum lipid profile at the time of the switch (week 0), and weeks 12 and 24 after the switch, as well as clinical characteristics at week 0 in a total of 27 patients. Triglyceride (TG) showed a significant decrease at weeks 12 and 24 in all patients (196 vs. 174 mg/dL, P=0.048and 196 vs. 150 mg/dL, P=0.021, respectively). However, these effects were only observed in the unboosted ATV group (N=14; 239 vs. 125 mg/dL, P=0.017 and 239vs. 87 mg/dL, P=0.021, respectively). For total cholesterol, only the unboosted ATV group at 24 weeks showed a significant decrease (184 vs. 158 mg/dL, P=0.031). No significant changes were observed in LDL- and HDL-cholesterol at weeks 12 and 24in both the unboosted and boosted ATV groups. These results suggest that changing to unboosted ATV from another PI may ameliorate high TG and total cholesterol in HIV-infected Koreans.

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