• Journal of Preventive Medicine and Public Health
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• 제43권6호
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• pp.543-548
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• 2010

Objectives: The objective of this study was to calculate sample size and power in an ongoing cohort, Korea radiation effect and epidemiology cohort (KREEC). Method: Sample size calculation was performed using PASS 2002 based on Cox regression and Poisson regression models. Person-year was calculated by using data from '1993-1997 Total cancer incidence by sex and age, Seoul' and Korean statistical informative service. Results: With the assumption of relative risk=1.3, exposure:non-exposure=1:2 and power=0.8, sample size calculation was 405 events based on a Cox regression model. When the relative risk was assumed to be 1.5 then number of events was 170. Based on a Poisson regression model, relative risk=1.3, exposure:non-exposure=1:2 and power=0.8 rendered 385 events. Relative risk of 1.5 resulted in a total of 157 events. We calculated person-years (PY) with event numbers and cancer incidence rate in the nonexposure group. Based on a Cox regression model, with relative risk=1.3, exposure:non-exposure=1:2 and power=0.8, 136 245PY was needed to secure the power. In a Poisson regression model, with relative risk=1.3, exposure:non-exposure=1:2 and power=0.8, person-year needed was 129517PY. A total of 1939 cases were identified in KREEC until December 2007. Conclusions: A retrospective power calculation in an ongoing study might be biased by the data. Prospective power calculation should be carried out based on various assumptions prior to the study.

• Asian Pacific Journal of Cancer Prevention
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• 제15권16호
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• pp.6929-6934
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• 2014

Background: To analyze the mortality distribution of esophageal cancer in China from 1991 to 2012, to forecast the mortality in the future five years, and to provide evidence for prevention and treatment of esophageal cancer. Materials and Methods: Mortality data for esophageal cancer in China from 1991 to 2012 were used to describe its epidemiological characteristics, such as the change of the standardized mortality rate, urban-rural differences, sex and age differences. Trend-surface analysis was used to study the geographical distribution of the mortality. Curve estimation, time series, gray modeling, and joinpoint regression were used to predict the mortality for the next five years in the future. Results: In China, the incidence rate of esophageal cancer from 2007 and the mortality rate of esophageal cancer from 2008 increased yearly, with males at $8.72/10^5$ being higher than females, and the countryside at $15.5/10^5$ being higher than in the city. The mortality rate increased from age 45. Geographical analysis showed the mortality rate increased from southern to eastern China, and from northeast to central China. Conclusions: The incidence rate and the standardized mortality rate of esophageal cancer are rising. The regional disease control for esophageal cancer should be focused on eastern, central and northern regions China, and the key targets for prevention and treatment are rural men more than 45 years old. The mortality of esophageal cancer will rise in the next five years.

• Asian Pacific Journal of Cancer Prevention
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• 제14권1호
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• pp.11-13
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• 2013

Background: Esophagus cancer, the third most common gastrointestinal cancer overall, demonstrates high incidence in parts of Iran. The counties of Iran vary in size, shape and population size. The aim of this study was to account for spatial support with Area-to-Area (ATA) Poisson Kriging to increase precision of parameter estimates and yield correct variance and create maps of disease rates. Materials and Methods: This study involved application/ecology methodology, illustrated using esophagus cancer data recorded by the Ministry of Health and Medical Education (in the Non-infectious Diseases Management Center) of Iran. The analysis focused on the 336 counties over the years 2003-2007. ATA was used for estimating the parameters of the map with SpaceStat and ArcGIS9.3 software for analysing the data and drawing maps. Results: Northern counties of Iran have high risk estimation. The ATA Poisson Kriging approach yielded variance increase in large sparsely populated counties. So, central counties had the most prediction variance. Conclusions: The ATAPoisson kriging approach is recommended for estimating parameters of disease mapping since this method accounts for spatial support and patterns in irregular spatial areas. The results demonstrate that the counties in provinces Ardebil, Mazandaran and Kordestan have higher risk than other counties.

• Asian Pacific Journal of Cancer Prevention
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• 제16권15호
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• pp.6391-6396
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• 2015

Background: To analyze cervical cancer mortality trends in China from 1991-2013 and forecast the mortality distribution in future five years (2014-2018), and provide clues for prevention and treatment. Materials and Methods: Mortality data for cervical cancer in China from 1991 to 2013 were used to describe the epidemiological characteristics and distribution, including the trend of the standardized mortality rate, urban-rural differences, and age variation. Trend-surface analysis was used to analyze the geographical distribution of mortality. Curve estimation, time series, gray modeling, and joinpoint regression were performed to predict and forecast mortality trends. Results: In recent years, the mortality rate of cervical cancer has increased, and there is also a steady increase in the incidence from 2003 to 2013 in China. Mortality rates in rural areas are higher than in urban areas. The mortality dramatically increases in the 40+ yr age group, reaching a peak in the >85 yr age group. In addition, geographical analysis showed that the cervical cancer mortality increased from the southwest to west-central and from the southeast to northeast of the country. Conclusions: The incidence rate and the mortality rate are increasing from 1991 to 2013, and the predictions show this will continue in the future. Thus, implementation of prevention and management programs for cervical cancer are necessary in China, especially for rural areas, young women in urban areas, and high risk regions (the west-central).

• Diabetes and Metabolism Journal
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• 제42권6호
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• pp.488-495
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• 2018

Background: Skeletal muscle plays a major role in glucose metabolism. We investigated the association between thigh muscle mass, insulin resistance, and incident type 2 diabetes mellitus (T2DM) risk. In addition, we examined the role of body mass index (BMI) as a potential effect modifier in this association. Methods: This prospective study included 399 Japanese Americans without diabetes (mean age 51.6 years) who at baseline had an estimation of thigh muscle mass by computed tomography and at baseline and after 10 years of follow-up a 75-g oral glucose tolerance test and determination of homeostasis model assessment of insulin resistance (HOMA-IR). We fit regression models to examine the association between thigh muscle area and incidence of T2DM and change in HOMA-IR, both measured over 10 years. Results: Thigh muscle area was inversely associated with future HOMA-IR after adjustment for age, sex, BMI, HOMA-IR, fasting plasma glucose, total abdominal fat area, and thigh subcutaneous fat area at baseline (P=0.033). The 10-year cumulative incidence of T2DM was 22.1%. A statistically significant interaction between thigh muscle area and BMI was observed, i.e., greater thigh muscle area was associated with lower risk of incident T2DM for subjects at lower levels of BMI, but this association diminished at higher BMI levels. Conclusion: Thigh muscle mass area was inversely associated with future insulin resistance. Greater thigh muscle area predicts a lower risk of incident T2DM for leaner Japanese Americans.

• Wind and Structures
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• 제32권2호
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• pp.127-142
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• 2021

Wind load acting on a standalone structure is different from that acting on a similar structure which is surrounded by other structures in close proximity. The presence of other structures in the surrounding can change the wind flow regime around the principal structure and thus causing variation in wind loads compared to a standalone case. This variation on wind loads termed as interference effect depends on several factors like terrain category, geometry of the structure, orientation, wind incident angle, interfering distances etc., In the present study, a three building configuration is considered and the mean pressure coefficients on each face of principle building are determined in presence of two interfering buildings. Generally, wind loads on interfering buildings are determined from wind tunnel experiments. Computational fluid dynamic studies are being increasingly used to determine the wind loads recently. Whereas, wind tunnel tests are very expensive, the CFD simulation requires high computational cost and time. In this scenario, Artificial Neural Network (ANN) technique and Support Vector Regression (SVR) can be explored as alternative tools to study wind loads on structures. The present study uses these data-driven approaches to predict mean pressure coefficients on each face of principle building. Three typical arrangements of three building configuration viz. L shape, V shape and mirror of L shape arrangement are considered with varying interfering distances and wind incidence angles. Mean pressure coefficients (Cp mean) are predicted for 45 degrees wind incidence angle through ANN and SVR. Further, the critical faces of principal building, critical interfering distances and building arrangement which are more prone to wind loads are identified through this study. Among three types of building arrangements considered, a maximum of 3.9 times reduction in Cp mean values are noticed under Case B (V shape) building arrangement with 2.5B interfering distance. Effect of interfering distance and building arrangement on suction pressure on building faces has also been studied. Accordingly, Case C (mirror of L shape) building arrangement at a wind angle of 45º shows less suction pressure. Through this study, it was also observed that the increase of interfering distance may increase the suction pressure for all the cases of building configurations considered.

• Journal of Preventive Medicine and Public Health
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• 제29권2호
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• pp.331-346
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• 1996

Exploring the epidemiological trend of HIV/AIDS is required for making the national AIDS policy. In this study, the trend of HIV/AIDS incidence, rout of transmission and some characteristics of AIDS for the past 11 years in Korea using the reported cases from the national STD screening scheme were reviewed. Based on the results, the trend of main route of transmission according to the year was established by stage and the HIV/AIDS cases in this year was estimated and that to the year 2000 was projected by 'Epimodel' programme. The results were as follows : 1. Of the total infected persons, 76% were in their twenties and thirties, socioeconomically and sexually active age groups. While the transmission by sexual contact overseas was decreasing, the infection through domestic heterosexual and homosexual contact was increasing. 2. In the middle of the 1980's, the infected persons were mainly prostitutes infected through heterosexual contact with the HIV positive foreigner in this county(stage 1). And in the late of the 1980's the main source of infection was the sexual contact overseas and the domestic heterosexual contact(stage 2). Since the early of the 1990's, the infection through the heterosexual contact with non-regular sexual partner in this country has increased rapidly(stage 3), which was the evidence of the possibility of HIV epidemics. After that, it was expected that the infection through the homosexual contacts, the heterosexual contacts with commercial sex workers outside and the non-regular sexual contact inside of this country would increase continuously. In the result, the occurrence of neonatal infection by vertical transmission was expected(stage4). 3. The number of HIV/AIDS was estimated at 572 to 2,313 and the projected number of HIV/AIDS to the you 2000 was around 5,800 including 627 AIDS patients. For the further study on the estimation and projection of HIV/AIDS, it was suggested that the sampling survey on the HIV infection rate in the high risk groups and the sentinel hospital surveillance system should be conducted.

• 대한교통학회지
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• 제24권4호
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• pp.117-127
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• 2006

국내외 각급 도시에서 시행중인 실시간 버스정보시스템(BIS)에 있어 버스도착예정시간 정보의 정확도는 시스템에 대한 가치평가의 가장 중요한 요소 중 하나이다. FTMS나 RTMS에서의 VMS정보와는 달리 개별버스의 도착예정시간 정보의 경우는, 가공 및 제공주기 그리고 시스템의 가공과정에서 불가피한 오차가 발생한다. 이를 '시스템 오차'라 규정하고 이들 오차의 평균값을 통계적 기법으로 도출하여, 버스도착예정시간 정보에 보정하는 방안을 제시하였다. 또한 검증을 위해 'A'시의 버스정보시스템에 동 기법에 따라 보정을 수행한 결과, 보정전보다 오차율이 23%감소한 것으로 나타났다. 이처럼 버스도착예정시간 정보의 정확도의 제고를 위해서는 시스템오차를 낮추는 방안이 적용해야 하는데 특히, 위치정보수집 빈도를 높이고, GPS 음영지역 해소 등 분산 값에 영향을 미치는 결측을 줄이기 위한 노력을 강구해야 한다.

• Journal of Gastric Cancer
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• 제15권4호
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• pp.262-269
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• 2015

Purpose: Intraabdominal abscess is one of the most common reasons for re-hospitalization after gastrectomy. This study aimed to develop a model for estimating the probability of intraabdominal abscesses that can be used during the postoperative period. Materials and Methods: We retrospectively reviewed the clinicopathological data of 1,564 patients who underwent gastrectomy for gastric cancer between 2010 and 2012. Twenty-six related markers were analyzed, and multivariate logistic regression analysis was used to develop the probability estimation model for intraabdominal abscess. Internal validation using a bootstrap approach was employed to correct for bias, and the model was then validated using an independent dataset comprising of patients who underwent gastrectomy between January 2008 and March 2010. Discrimination and calibration abilities were checked in both datasets. Results: The incidence of intraabdominal abscess in the development set was 7.80% (122/1,564). The surgical approach, operating time, pathologic N classification, body temperature, white blood cell count, C-reactive protein level, glucose level, and change in the hemoglobin level were significant predictors of intraabdominal abscess in the multivariate analysis. The probability estimation model that was developed on the basis of these results showed good discrimination and calibration abilities (concordance index=0.828, Hosmer-Lemeshow chi-statistic P=0.274). Finally, we combined both datasets to produce a nomogram that estimates the probability of intraabdominal abscess. Conclusions: This nomogram can be useful for identifying patients at a high risk of intraabdominal abscess. Patients at a high risk may benefit from further evaluation or treatment before discharge.

• 한국환경생태학회지
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• 제22권2호
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• pp.119-127
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• 2008

본 연구는 북한산 국립공원을 대상으로 산사태 발생인자들에 대한 공간정보를 구축하였으며, 중첩분석 및 합산평가 매트릭스분석을 이용한산사태 취약성 지도 및 생태적 위험 지표 작성을 통해 향후산사태 재해 예방을 위한 기초자료를 제시하고자 하였다. 산사태 평가 인자로는 사면경사, 사면방향, 경사길이, 토양배수, 식생활력도(NDVI), 토지이용도가 선택되었으며, 공간데이터베이스는 $30m\times30m$ 해상도로 구축되었다. 분석결과, 우이동 및 도봉계곡 일대의 산사태 취약성이 높은 것으로 분석되었으며, 생태적 위험도는 도봉계곡, 용어천계곡 및 정릉계곡, 평창계곡 등이 높은 것으로 분석되어 향후 이들 지역의 관리계획 수립 시 산사태 위험에 대한 영향도 고려되어져야 할 것으로 판단된다.