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나이브 베이지안 환경에서 미분류 데이터를 이용한 성능향상
이창환,Lee Chang-Hwan 한국정보처리학회 2006 정보처리학회논문지B Vol.13 No.4
많은 경우에 분류데이터의 생성은 사람의 시간과 노력에 의존하기 때문에 많은 비용과 시간을 요구한다. 이에 반하여 미분류 데이터는 거의 비용을 들이지 않고 무제한의 데이터를 쉽게 획득할 수 있다. 따라서 기계학습에 있어서 이러한 미분류 데이터를 이용하여 분류학습의 성능을 향상시킬 수 있는 준감독자(semi-supervised)학습 방법이 최근 관심을 끌고 있다. 본 논문에서는 미분류 데이터가 분류학습의 성능향상에 마치는 영향을 분석하기 위하여 나이브 베이지안의 환경에서 미분류 데이터를 이용한 학습방법을 제시하고 이를 이용하여 미분류 데이터의 효용성을 실험적으로 조사하였다. 미분류 데이터는 나이브 베이지안의 환경에서 분류데이터의 숫자가 적을 때 특히 많은 효과를 보임을 알 수 있었다. In many applications, an enormous amount of unlabeled data is available with little cost. Therefore, it is natural to ask whether we can take advantage of these unlabeled data in classification learning. In this paper, we analyzed the role of unlabeled data in the context of naive Bayesian learning. Experimental results show that including unlabeled data as part of training data can significantly improve the performance of classification accuracy. The effect of using unlabeled data is especially important in case labeled data are sparse.
Phonological Recoding in Multi-syllabic Words : Using the Delaying Letter Priming Task
이창환 한국자료분석학회 2008 Journal of the Korean Data Analysis Society Vol.10 No.4
An experiment was conducted in order to investigate the role of phonological information in multisyllabic word processing. Korean multisyllabic words were used as the main stimuli because Korean words have an unique characteristic as compared to English: The phonoloigcal form of the first syllable itself in many words is different from the same syllable within the corresponding word. Thus, delaying such first letter before presenting a target word would provide a clue on phonological recoding (e.g., "국" in "국난"). Presenting phonologically consistent first syllable as the prime was more advantageous in processing the target than presenting phonologically inconsistent first syllable. These results support the phonologial recoding in multisyallabic word recognition.
Hellinger 엔트로피를 이용한 다차원 연속패턴의 생성방법
이창환,Lee, Chang-Hwan 한국정보처리학회 2004 정보처리학회논문지B Vol.11 No.4
데이터 마이닝에서 연속패턴(sequential pattern) 생성기술은 시차를 두고 발생한 사건들에 대하여 잠재해있는 패턴을 발견하는 기술을 의미한다. 본 연구는 정보이론을 이용하여 데이터베이스로부터 연속패턴을 자동으로 발견하는 방법에 관한 내용이다. 기존의 방법들이 한 속성내에서의 연속패턴만을 탐지하는 일차원 연속패턴을 생성하는데 비하여 본 연구에서 제시하는 방법은 데이터베이스내의 모든 속성간의 연속패턴 관계를 탐지할 수 있는 다차원 연속패턴을 생성할 수 있다. 본 연구에서는 연속패턴 생성을 위하여 헬링거(Hellinger) 변량을 사용하였으며 이를 이용하여 발견된 연속패턴들의 중요도를 측정할 수 있었다. 또한 헬링거 변량의 함수적인 특성을 분석하여 연속패턴 추출의 복잡도를 줄이기 위한 두 가지의 법칙이 제안되었고 다수의 실험 데이터를 통하여 다차원의 연속패턴을 생성할 수 있음을 보였다. The technique of sequential pattern mining means generating a set of inter-transaction patterns residing in time-dependent data. This paper proposes a new method for generating sequential patterns with the use of Hellinger measure. While the current methods are generating single dimensional sequential patterns within a single attribute, the proposed method is able to detect multi-dimensional patterns among different attributes. A number of heuristics, based on the characteristics of Hellinger measure, are proposed to reduce the computational complexity of the sequential pattern systems. Some experimental results are presented.
신증후성 출혈열 환자에서 유식세포분석기를 이용한 림프구 아형에 대한 연구
이창환,김원,임성희,이대열,박성광,강성귀,고정곤 대한신장학회 1994 Kidney Research and Clinical Practice Vol.13 No.3
Korean hemorrhagic fever, known as hemorrhagic fever with renal syndrome, is an acute infectious disease caused by Hantaan virus. Pathogenesis of Korean hemorrhagic fever (KHF) is not clearly delineated to date. Recently the immunologic mechanisms of KHF have been investigated by many authors. To clearify the role of immunemechanism in the pathogenesis of KHF, lymphocyte subsets were measured by Flow cytomerty in the peripheral blood with 8 patients during the acute phase of KHF and 10 months later. During the acute phase of KHF the percentage of CD4 decreased and CDS and activated T cell increased significantly compared to 10 months later of acute phase of KHF. These results suggest that variation of lymphoctye subsets distribution occurred in acute phase of KHF and it may be related to pathogenesis of KHF.
이창환,김원,곽재용,박성광,강성귀 대한신장학회 1993 Kidney Research and Clinical Practice Vol.12 No.4
Objectives: Systemic lupus erythematosus (SLE) is a multisystem inflammatory disorder characterized by the production of antibodies that react with many different self-antigens. Lupus nephritis has long been considered one of the most ominous components of SLE. The extreme diversity of the renal changes indicates that many variables are likely to be involved. So lupus nephritis is characterized by various chlinicl course, histologic and immunologic patterns. So, we evaluated the clinical characteristics of 32 lupus nephritis patients in Chonbuk National University Hospital. Methods: Forty patients whose clinical findings fulfilled The American Rheumatism Association Criteria for SLE were studied between May 1979 and December 1992 in our hospital retrospectively. Results: In 40 systemic lupus erythematosus patients, lupus nephritis occurred in 32 patients (80%). Subjects mean age was 31.2 (18 to 67 years). Three cases were male and 37 cases were female making the male to female ratio of about 1:12.3. The most common renal manifestation was proteinuria and mean GFR (Ccr) is 78.2 ml/min. Renal failure was developed in 4.8% The most common histological finding by renal biopsy was diffuse proliferative glomerulonephritis (70%). In the only steroid therapeutic group, rate of complete remission and no-response rate were 19.0% and 28.6% Respectively. In the steroid and cyclophosphamid combination group, rate of complete remission and no-response were 54.5%, 9.1% respectively. Conelusion: Treatment with prednisolone and cyclophosphamide improve the clinical outcome in patients with lupus nephritis, as compared with steroid alone.
Polypropylene Melt Blown Nonwovens for Plate-Type Enthalpy Exchanger
이창환,김성훈,손은종,임태환 한국고분자학회 2012 Macromolecular Research Vol.20 No.1
An enthalpy exchanger made of melt blown nonwoven fabrics was prepared using various chemical and physical treatments, and its characteristics were compared with those of a paper exchanger. Water vapor transmission rate and air permeability, the major properties that determine enthalpy exchanger index performance, were investigated. Various measurements were conducted as a function of calendering temperature and speed, moisture content absorbance, and water soluble polymer concentration. The optimum conditions for the enthalpy exchanger made of melt blown nonwoven fabrics included 95 oC calendering temperature and 5% poly(vinyl alcohol) concentration. A commercial melt blown type heat exchanger could potentially replace the paper type.