• Journal of Ecology and Environment
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• 제38권1호
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• pp.95-107
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• 2015

Because an ecological community consists of diverse species that vary nonlinearly with environmental variability, its dynamics are complex and difficult to analyze. To investigate temporal variations of benthic macroinvertebrate community, we used the community data that were collected at the sampling site in Baenae Stream near Busan, Korea, which is a clean stream with minimum pollution, from July 2006 to July 2013. First, we used a self-organizing map (SOM) to heuristically derive the states that characterizes the biotic condition of the benthic macroinvertebrate communities in forms of time series data. Next, we applied the hidden Markov model (HMM) to fine-tune the states objectively and to obtain the transition probabilities between the states and the emission probabilities that show the connection of the states with observable events such as the number of species, the diversity measured by Shannon entropy, and the biological water quality index (BMWP). While the number of species apparently addressed the state of the community, the diversity reflected the state changes after the HMM training along with seasonal variations in cyclic manners. The BMWP showed clear characterization of events that correspond to the different states based on the emission probabilities. The environmental factors such as temperature and precipitation also indicated the seasonal and cyclic changes according to the HMM. Though the usage of the HMM alone can guarantee the convergence of the training or the precision of the derived states based on field data in this study, the derivation of the states by the SOM that followed the fine-tuning by the HMM well elucidated the states of the community and could serve as an alternative reference system to reveal the ecological structures in stream communities.

• 대한산업공학회지
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• 제41권5호
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• pp.481-487
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• 2015

In the product development stage, it is very important to ensure demanded quality level before moving to the full-scale manufacturing. For example, in developing guided weapons, live-fire tests are required to verify the final performance of the weapons which are very expensive. The quality evaluation of the guided weapons needs destructive testing, which makes it necessary to test as small number of samples as possible. This paper presents sampling inspection plans and calculating system for finite population guided weapons, which can meet the demanded quality level and confidence level with the minimum number of performance tests. The result of this paper can be useful for any kind of costly destructive testing.

• 한국컴퓨터그래픽스학회논문지
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• 제26권3호
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• pp.123-131
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• 2020

본 연구는 10만 개 이상의 움직이는 파티클 각각이 발광원으로서 존재할 때 라이팅을 위한 실시간 렌더링 알고리즘을 제안한다. 각 라이트의 영향 범위를 동적으로 파악하기 위해 2개의 3D 텍스처를 사용하며 첫 번째 텍스처는 라이트 색상 두 번째 텍스처는 라이트 방향 정보를 가진다. 각 프레임마다 두 단계를 거친다. 첫 단계는 Compute shader 기반으로 3D 텍스처 초기화 및 렌더링에 필요한 파티클 정보를 갱신하는 단계이다. 이때 파티클 위치를 3D 텍스처의 샘플링 좌표로 변환 후 이 좌표를 기반으로 첫 번째 3D 텍스처엔 해당 복셀에 대해 영향을 미치는 파티클 라이트들의 색상 총합을, 그리고 두 번째 3D 텍스처에 해당 복셀에서 파티클 라이트들로 향하는 방향벡터들의 총합을 갱신한다. 두 번째 단계는 일반 렌더링 파이프라인을 기반으로 동작한다. 먼저 렌더링 될 폴리곤 위치를 기반으로 첫 번째 단계에서 갱신된 3D 텍스처의 정확한 샘플링 좌표를 계산한다. 샘플링 좌표는 3D 텍스쳐의 크기와 게임 월드의 크기가 1:1로 대응하므로 픽셀의 월드좌표를 그대로 샘플링 좌표로 사용한다. 샘플링한 픽셀의 색상과 라이트의 방향벡터를 기반으로 라이팅 처리를 수행한다. 3D 텍스처가 실제 게임 월드와 1:1로 대응하며 최소 단위를 1m로 가정하는데 1m보다 작은 영역의 경우 해상도 제한에 의한 계단 현상 등의 문제가 발생한다. 이러한 문제를 개선하기 위한 텍스처 샘플링 시 보간 및 슈퍼 샘플링을 수행한다. 한 프레임을 렌더링하는데 소요된 시간을 측정한 결과 파티클이 라이트의 개수가 262144개일 때 Forward Lighting 파이프라인에서 146ms, deferred Lighting 파이프라인에서 46ms 가 소요되었으며, 파티클 라이트의 개수가 1024576개일 때 Forward Lighting 파이프라인에서 214ms, Deferred Lighting 파이프라인에서 104ms 가 소요되었다.

• 한국운동역학회지
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• 제17권4호
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• pp.115-125
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• 2007

Grould Reaction force(GRF) is important in human movements and GRF measurements are one of the most frequently used tool in biomechanical studies. In the studies of the golf swing motion, people refer to GRF as weight transfer. A successful golf swing motion requires many segments activation sequences which are controled by the nerve system. Due to the inter- and intra-individual variability of the human movement and the movement strategies, reliability of the measurements are important in human movement studies. Previous golf researches were based on group studies and certain events' values were analyzed. The purposes of this study were to determine the number of trials for the reliable golf swing GRF data collection, to reveal the variability level of the meaningful components of the golf swing GRF, and to classify the types of the golf swing GRF patterns. Twenty three male professional golfers($26.4{\pm}6.6$ years, $174.3{\pm}5.2\;cm$, $71.3{\pm}6.5\;kg$) signed an informed consent form prior to participation in this study. GRFs of driver swings were collected with Kistler 9285 force platform and 9865A amplifier, and calculated by the KwonGRF program(Visol, Korea). Sampling frequency was 1080 Hz. GRF data were trimmed from 1.5 s prior to the impact to 0.5 s after the impact. The number of trials for the reliable GRF collection was determined when the change in floating mean overs the 25 % of the standard deviation of that variable. Variabilities of the variables were determined by the coefficient of variation(CV) of 10 %. The types of GRF patterns were determined by visual inspection of the peak GRF shapes. The minimum number of trials for the reliable golf swing GRF data collection was five. Ten-trial seems more conservative. The value of the peak GRF was more reliable than the value of the impact GRF. The CV of the peak GRF and impact GRF were 7.4 %, 15.2 %, respectively. Because of the +/- sigh of the peak GRF appearance time, it was impossible to calculate CV of the peak GRF appearance time. Golf swing GRF patterns were classified as sing peak type, double peak type, and plateau peak type. This classification suggests the presence of the different golf swing weight transfer strategies.

• Corrosion Science and Technology
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• 제4권4호
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• pp.155-163
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• 2005

Heavy duty coating are required to have minimum durable period of 15 years under average usage environment because these paints are coated with purpose of anti-corrosion, antifouling, plastering etc. Onto steel structures constructed upon land and sea and other ferrous structures of electric power generation plants, electricity transmission towers, large structures of various plants, etc. Therefore we tried to estimate heavy duty coating longevity through reliability evaluation method and used combined cyclic anti-conrrosion test method composed of drying, moisturizing and salt spray as for accelerated life test to estimate longevity. Accelerated life test hours to heavy duty coating of first grade (with longevity not less than 15 years) specification may be obtained from troubleless test hours $t_n=\frac{B_p}{n^{1/\beta}}\left[\frac{1n(1-CL)}{1n(1-p)} \right]^{1/\beta}=19.671$ (yr) where shape parameter $\beta=1.1$, confidence level CL=80 %, warranty life $B_{10}=15$ yr and sampling size n=10 (2 sets). Because acceleration factor {AF} found by accelerated test is 41.7, accelerated life test hours required may be represented about 4,132 hr so that if this amount of hours is converted to number of cycles(6 hr/cycle) of complex cycle corrosion resistance test then the amount is tantamount about 690 cycles. That means if there does not occur trouble failure (with defect factor sum not more than 20) during when there is performed 690 cycles of combined cyclic anti-corrosion test to heavy duty coating specimen then it signifies that there can be warranted longevity $B_{10}$ of 15 yr under condition of confidence level CL=80 %.

• Asian-Australasian Journal of Animal Sciences
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• 제15권4호
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• pp.504-508
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• 2002

The effects of fetal number (single or twin) on blood glucose and plasma NEFA during pregnancy and around parturition were studied on ten Alpine ${\times}$ Beetal crossbred goats in their first to third lactation. The animals were divided in-groups 1(carrying single fetus, n=4) and 2(twin fetus, n=6). The samples were drawn on day1 after estrus and then at 14 days interval (fortnight) for 10 fortnights. Around parturition the samples were taken on days -20, -15, -10, -5, -4, -3, -2, -1 prior to kidding and on day 0 and +1, +2, +3, +4, +5, +10, +15, +20 days post kidding. In twin bearing goats the blood glucose concentration continued to increase from 1st until 4th fortnight and thereafter gradually decline from 5th upto 8th fortnight. In single bearing goats there was increase in levels from 2nd upto 4th fortnight and thereafter it declined from 5th uptill 9th fortnight. The difference in sampling interval was highly significant (p<0.01) in both the groups. However the values were higher in single than in twin bearing goats. The plasma NEFA concentration was low in both the groups' upto 4th fortnight and thereafter it is continuously increased upto 9th fortnight. During prepartum period the blood glucose was higher in single than in twin bearing goats. The values were minimum on the day of kidding in both the groups. During postpartum period the values were significantly (p<0.01) higher in twin than in single fetus bearing goats. The plasma NEFA was significantly (p<0.05) higher in twin than in single fetus bearing goats. The blood glucose and plasma NEFA concentration can be used as index of nutritional status during pregnancy and around parturition in goats.

• 대한토목학회논문집
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• 제8권2호
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• pp.99-107
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• 1988

과압밀점토(過壓密粘土)에 대한 일련의 입방형삼축시험(立方型三軸試驗)이 실시되었다. 삼축시험(三軸試驗)은 세 주응력(主應力)을 서로 독립적으로 제어시킬 수 있는 입방체형삼축시험기(立方體型三軸試驗機)를 사용하여 실시되었다. 점토공시체(粘土供試體)로는 현장(現場)에서 직접 채취된 자연시료(自然試料)를 삼축(三軸) chamber 내(內)에서 과압밀비(過壓密比)가 5가 되게 만든 입방체형공시체(立方體型供試體)가 사용되었으며 본연구결과(本硏究結果), 중간주응력(中間主應力)은 과압밀점토(過壓密粘土)의 응력변형률(應力變形率), 비배수강도(非排水强度), 유효강도(有效强度), 유효내부마찰각(有效內部摩擦角) 및 간극압(間隙壓)에 큰 영향을 미치고 있음이 구명(究明)되었다. 중간주응력(中間主應力)이 최소주응력(最小主應力)과 같지 않은 경우의 과압밀점토파괴강도(過壓密粘土破壞强度)는 Mohr-Coulomb 파괴규준(破壞規準)에 의하여 과소평가(過小評價)되나 Lade규준(規準)에 의하여는 대단히 양호하게 산정된다. 또한 과압밀점토(過壓密粘土)의 비배수강도(非排水强度)는 Tresca규준(規準)에 일치하지 않는다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제12권1호
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• pp.36-43
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• 2007

토양위해성평가를 위한 토양조사방법의 목적은 오염정도와 범위를 파악하여 부지의 대표적인 토양노출농도를 결정해야 하는 것은 물론이고 부지의 물리화학적 특성을 조사하여 노출평가시 사용될 수 있는 주요 정보를 제공하는데 있다. 앞으로 우리나라도 토양위해성평가를 위한 토양조사시 두 가지 점을 고려해야 할 것으로 나타났다. 첫째, 현재 우리나라의 토양조사는 오염정도와 범위 확인을 위한 조사에 국한하고 있으므로 차후 위해성평가를 위해서는 부지의 물리화학적 특성파악을 위한 조사가 추가되어야 한다. 둘째, 국내와 외국의 토양조사방법에 있어 가장 큰 차이는 외국의 현장조사계획에서는 모든 데이터에 대해 통계학적 개념을 반영하여 시료채취 개수 결정 및 오염여부 판단에 신뢰성을 확보하고 있다는 점으로 우리도 이에 대한 보완이 필요할 것으로 판단된다. 본 연구에서는 토양위해성평가를 위한 토양조사방법을 별도로 마련하는 것보다 기존 토양정밀조사지침과 연계하여 토양위해성평가의 목적을 이룰 수 있는 토양조사방안을 제안하였다.

• Safety and Health at Work
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• 제14권1호
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• pp.66-70
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• 2023

Background: Online teaching and learning extend the duration of using gadgets such as mobile phones and tablets. A prolonged usage of these gadgets in a static position can lead to musculoskeletal disorders (MSD). Therefore, this study aims to identify the risk factors related to musculoskeletal symptoms while using gadgets during work from home due to the COVID-19 pandemic. Method: A cross-sectional survey with online-based questionnaires was collected from the University of Indonesia, consisting of lecturers, students, and managerial staff. The minimum number of respondents was 1,080 and was defined by stratified random sampling. Furthermore, the dependent variable was musculoskeletal symptoms, while the independent were age, gender, job position, duration, activity when using gadgets, and how to hold them. Result: Most of the respondents had mobile phones but only 16% had tablets. Furthermore, about 56.7% have used a mobile phone for more than 10 years, while about 89.7% have used a tablet for less than 10 years. A multivariate analysis found factors that were significantly associated with MSD symptoms while using a mobile phone, such as age, gender, web browsing activity, work, or college activities. These activities include doing assignments and holding the phone with two hands with two thumbs actively operating. The factors that were significantly associated with MSD symptoms when using tablets were gender, academic position, social media activity, and placing the tablet on a table with two actively working index fingers. Conclusion: Therefore, from the results of this study it is necessary to have WFH and e-learning policies to reduce MSD symptoms and enhance productivity at work.

• 보건행정학회지
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• 제23권2호
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• pp.152-161
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• 2013

Korea has a single National Health Insurance program and all citizens are covered under this program, accounting 97% of the population, approximately 50 million people. Claims submitted by Health care providers are reviewed by Health Insurance Review and Assessment (HIRA) for the reimbursement. HIRA database contains not only individual beneficiary's information, but also healthcare service information such as diagnosis, procedures, prescriptions and tests for them. HRA database has gained attention as importance source for research due to its rich healthcare information and the demand of HIRA database has increased. Due to its tremendous size, however, researchers have had problems in accessing the database to conduct research. To meet this demand, we conducted a study to develop the inpatient sample data from HIRA database for research. This study has two purposes: 1) to determine a needed sample size; 2) to test reliability and validity of the sample data. We determined an adequate sample size to ensure representativeness and generality with additional consideration for convenience of calculation. The minimum sample size was 729,904 for the generality, and 488,861 for representativeness. After considering the convenience of calculation, our final sample size was 13% of the population, which was about 7.7 million beneficiaries. Age (5 years interval) and gender were used as stratification variables for sampling. In order to examine whether this sample data appropriately reflect population, we tested the reliability and validity of the sample data. From the sample data, we computed average expenditure of total claims per inpatient for 2011, frequency of top 30 disease, estimation of the number of stroke patients from the sample data, and then compared them to those from the population. Results confirmed reliability and validity of the sample data.