• 융합정보논문지
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• 제10권11호
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• pp.148-155
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• 2020

본 연구는 한국어판 피츠버그 수면의 질 지수(PSQI-K) 도구의 신뢰도와 타당도를 검증하고 수면장애군의 최적 절단점을 탐색하기 위한 목적으로 수행되었다. 초기 성인 64명을 대상으로 PSQI-K와 Fitbit charge 3^TM을 이용하여 주관적 수면의 질과 수면양상을 측정하였다. 도구의 신뢰도는 Cronbach's alpha coefficient 계수로, 도구의 타당도는 요인분석 및 PSQI-K 점수와 Fitbit tracker 간의 Spearman's rho 상관계수로 분석하였다. 연구결과, PSQI-K 점수의 Cronbach's alpha coefficient는 0.69였고, PSQI-K와 Fitbit tracker의 각 지표값과의 correlation은 0.67 이상으로 유의하였다. 수면장애군 구분을 위한 절단점은 ≥6일 때 민감도 0.93, 특이도 0.84로 가장 적합하였다. PSQI-K는 초기 성인의 수면장애군을 스크리닝함에 있어서 신뢰도와 타당도가 양호한 도구임이 확인되었다.

• Journal of Ecology and Environment
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• 제43권4호
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• pp.364-375
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• 2019

Background: Ecologists continue to investigate the factors that potentially affect the pattern and magnitude of tree damage during catastrophic windstorms in forests. However, there still is a paucity of research on which trees are more vulnerable to direct damage by winds rather than being knocked down by the fall of another tree. We evaluated this question in a mixed hardwood-softwood forest within the Big Thicket National Preserve (BTNP) of southeast Texas, USA, which was substantially impacted by Hurricane Rita in September 2005. Results: We showed that multiple factors, including tree height, shade-tolerance, height-to-diameter ratio, and neighborhood density (i.e., pre-Rita stem distribution) significantly explained the susceptibility of trees to direct storm damage. We also found that no single factor had pervasive importance over the others and, instead, that all factors were tightly intertwined in a complex way, such that they often complemented each other, and that they contributed simultaneously to the overall susceptibility to and patterns of windstorm damage in the BTNP. Conclusions: Directly damaged trees greatly influence the forest by causing secondary damage to other trees. We propose that directly and indirectly damaged (or susceptible) trees should be considered separately when assessing or predicting the impact of windstorms on a forest ecosystem; to better predict the pathways of community structure reorganization and guide forest management and conservation practices. Forest managers are recommended to adopt a holistic view that considers and combines various components of the forest ecosystem when establishing strategies for mitigating the impact of catastrophic winds.

• 한국항해학회지
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• 제10권2호
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• pp.97-114
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• 1986

Ship's maneuverability is very important factor in safe ship handling and economical ship operation. Steering characteristics are consisted of course stability and maneuverability. Today in many advanced ship-building countries, they study ship's course stability, using model ship tests, such as straight line tests, rotating arm tests and Planar Motion Mechanism (PMM) etc., in tow in tanks. It is the purpose of this paper to provide ship's handlers with better understanding of steering characteristics and to help them in safe controlling and manevering . In this paper, the author simulated response of various vessels, running straight course with constant speed, and they are disturbed by small external disturbance of one degree yaw angle with no angular velocity . The author used the hydrodynamic derivtives resulted at tests of Davidson's laboratory in Stevens Institute of Technology, New Jersey, U.S.A. Course stability was evaluated and analyzed in various respects, such as block coefficient, ratio of ship's length to beam, draft and rudder area ratio etc. The obtained results are as follows : (1) The ship's course stability is affected by magnitude of block coefficient greatly. In case that the block coefficient is more than 0.7, the deviation varies at nearly same rate but the requistite time to reach the steady course is different. (2) The ship's course stability is affected by magnitude of L/B. When the dimensionless time reaches about 3, the deviation and requisite time to reach the steady course are influenced nearly same. After the dimensionless time is about 3, they change on invariable ratio. (3) The effect to course stability by L/T and RA' can be neglected. (4) The reason why thy VLCC and container feeder vessel are unstable on their course is that their block coefficient is generally more than 0.8 and the ratio of ship's length to beam is about 6.0.

• 센서학회지
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• 제5권3호
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• pp.65-73
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• 1996

수액을 장시간 환자에게 주입할 때 적절한 주입량, 주입률을 조절하는 것이 중요하다. 부적절한 주입량은 환자의 회복에 좋지 않은 영향을 끼칠 수 있으므로 주입량을 감지하는 센서의 신뢰도는 인퓨전 펌프 시스템에 많은 영향을 미친다. 본 연구에서는 인퓨전 펌프 시스템에 사용될 3가지 센서의 성능을 검토하였다. 피에조 필름, 광트렌지스터 및 광 다이오드 어레이의 3가지 센서가 비교되었으며 제안하는 신호 처리 기법과 광 다이오드 어레이를 사용한 기법을 이용하여 간섭과 진동 조도변화 센서의 위치에 따른 감도 변화등의 영향을 줄일 수 있었다. 실험 결과 광 다이오드 어레이가 다른 센서들에 비하여 높은 신지도를 보여 주었다.

• 한국환경복원기술학회지
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• 제13권6호
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• pp.161-172
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• 2010

As the interest on biodiversity has increased around the world, researches about evaluating potential for habitat are also increasing to find and comprehend the valuable habitats. This study focus on comprehending the significance of stream in evaluating habitat's potential. The purpose of this study is to evaluate habitat potential with applying stream as a main variable, and to comprehend the relationship between the variables and habitat potential. Basin is a unit that has hydrological properties and dynamic interaction with ecosystem. Especially, biodiversity and suitability of habitat in basin area has direct correlation with stream. Existing studies also are proposing for habitat potential evaluation in basin unit, they applied forest, slope and road as main variables. Despite stream is considered the most important factor in basin area, researchers haven't applied stream as a main variable. Therefore, in this study, three variables that can demonstrate hydrological properties are selected, which are, riparian distance, stream order and land use disturbance, and evaluate habitat potential. Habitat potential is analyzed by using Maxent (Maximum entropy model), and vertebrate's presence data is used as dependent variables and stream order map and land cover map is used as base data of independent variables. As a result of analysis, habitat potential is higher at riparian and upstream area, and lower at frequently disturbed area. Result indicates that adjacent to stream, upstream, and less disturbed area is the habitat that vertebrate prefer. In particular, mammals prefer adjacent area of stream and forest and reptiles prefer upriver area. Birds prefer adjacent area of stream and midstream and amphibians prefer adjacent area of stream and upriver. The result of this research could help to establish habitat conservation strategy around basin unit in the future.

• 한국물환경학회지
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• 제32권2호
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• pp.135-141
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• 2016

This study investigated changes of hydrology, soil characteristics, riparian vegetation communities, and geomorphology in sandbars before and after sand-mining to determine the effect of sand-mining at upstream of Guemgang and Bochungcheon streams in Korea. Sand-mining events affected the mining area. They supplied organic matters and nutrients during flood. Sediment deposition caused soil texture change and expansion of vegetation area. However, riverbeds were stabilized after the disturbance. According to the analyses of aerial photographs, the vegetation area was significantly expanded in both dam-regulated streams and dam-unregulated streams after sand-mining. Willow shrubs advanced in disturbed area at an average of 10 years after sand-mining. It took willows trees 10.6 years to become dominant communities. Therefore, it took a total of 20.6 years for new riparian forest to form in sandbar after sand-mining. Our results confirmed that stream flow condition were dependent on vegetation recruitment in dam-regulated streams and dam-unregulated streams. For willow recruitment in unregulated streams, calculation of water level below dimensionless bed shear stress is important because low water level variation is a limiting factor of vegetation recruitment.

• 한국지반환경공학회 논문집
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• 제19권12호
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• pp.33-39
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• 2018

본 연구에서는 토목섬유-점토의 접촉면 압밀 전단거동 평가를 위하여 상재하중 및 해수와 담수를 이용해 토목섬유-점토의 경계면에 대한 중요 특성인자를 규명하였다. 또한 폐기물 매립으로 바다에 매립공간을 확보하고 폐기물 처리 및 향후 토지이용 등 새롭게 필요 공간으로 변모가 가능하다. 토목섬유-점토의 접촉면에 거동특성을 분석한 결과 표준 압밀시험기를 이용하여 분석한 경우 해수보다 담수에서 압밀응력이 크게 증가하는 경향을 보였고, 동적 접촉면 전단 시험기를 이용하여 분석한 경우 해수와 담수 두 개의 조건에서 모두 동일하게 하부모듈에 가까운 와이어게이지일수록 변위값이 증가하고, 담수보다 해수의 조건에서 전단파괴가 급격히 일어나는 경향을 볼 수 있다. 따라서 토목섬유-점토의 접촉면에 작용하는 해수와 담수, 차수시설 설치여부(토목섬유)는 차수 시설 동적설계인자에 반드시 필요한 중요 변수로써 고려하여야 한다.

• Journal of Nutrition and Health
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• 제54권5호
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• pp.474-488
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• 2021

Purpose: Malnutrition in children with cerebral palsy (CP) is a significant factor affecting their adequate growth and development. This study aimed at conducting surveys and evaluating the dietary intake of children with CP according to their BMI classification and to thereby highlight the dietary factors affecting the nutritional status of these children. Methods: A total of 16 children were enrolled between the age of four and twelve. These subjects were further classified into three groups, namely underweight, normal and obese, with 6, 8, and 2 children in each group, respectively. The general characteristics, motor disturbances, body composition, feeding problems, eating habits, nutritional intake, dietary variety, and food frequency for children with CP were evaluated. Results: It was observed that motor disturbances tended to increase in underweight children with CP. A significant decrease (p < 0.05) in disturbances related to oral feeding was observed with an increase in obesity. The pattern of eating habits revealed that subjects in the underweight group consumed unbalanced meals, while those in the obese group tended to consume larger meals at a faster pace. The feeding disturbance data revealed that those in the underweight group could not prepare their meals while the obese group had the problem of overeating and consuming an unbalanced diet (p < 0.05). Conclusion: It is necessary for both children with CP, who have a high degree of disability, and their caregivers to take lessons on adequate nutrient intake to prevent malnutrition. Moreover, it is necessary for the caregivers and children with CP having a low degree of disability to take lessons on providing and consuming a balanced diet and to focus on the intake of sufficient calcium in order to prevent obesity.

• Earthquakes and Structures
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• 제20권1호
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• pp.39-53
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• 2021

By means of installing sloped rolling-type seismic isolators (SRI), the horizontal acceleration transmitted to the to-be-protected object above can be effectively and significantly reduced under external disturbance. To prevent the maximum horizontal displacement response of SRI from reaching a threshold, designing large and conservative damping force for SRI might be required, which will also enlarge the transmitted acceleration response. In a word, when adopting seismic isolation, minimizing acceleration or displacement responses is always a trade-off. Therefore, this paper proposes that by exploiting the possible information provided by an earthquake early warning system, the damping force applied to SRI which can better control both acceleration and displacement responses might be determined in advance and accordingly adjusted in a semi-active control manner. By using a large number of ground motion records with peak ground acceleration not less than 80 gal, the numerical results present that the maximum horizontal displacement response of SRI is highly correlated with and proportional to some important parameters of input excitations, the velocity pulse energy rate and peak velocity in particular. A control law employing the basic form of hyperbolic tangent function and two objective functions are considered in this study for conceptually developing suitable control algorithms. Compared with the numerical results of simply designing a constant, large damping factor to prevent SRI from pounding, adopting the recommended control algorithms can have more than 60% reduction of acceleration responses in average under the excitations. More importantly, it is effective in reducing acceleration responses under approximately 98% of the excitations.

• 한국안전학회지
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• 제39권1호
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• pp.62-69
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• 2024

Ensuring swift on-site access to fire engines is crucial in preserving the golden time and minimizing damage. However, various mobility constraints in alleyways hinder the timely entry of fire engines to the fire scene, significantly impairing their initial response capabilities. Therefore, this study analyzed the significant mobility constraints of fire engines, focusing on Seoul, which has many old town areas. By leveraging survey responses from firefighting experts and actual observations, this study quantitatively assessed the frequency and severity of mobility constraint factors affecting the disaster responses of fire engines. Survey results revealed a consistent set of top five factors regarding the frequency and disturbance level, including illegally parked cars, narrow paths, motorcycles, poles, and awnings/banners. A comparison with actual road-view images showed notable consistency between the survey and observational results regarding the appearance frequency of mobility constraint factors in vulnerable areas in Seoul. Furthermore, the study emphasized the importance of tailored management strategies for each mobility constraint factor, considering its characteristics, such as dynamic or static. The findings of this study can serve as foundational data for creating more detailed fire safety maps and advancing technologies that monitor the mobility of fire engines through efficient vision-based inference using CCTVs in the future.