• Title/Summary/Keyword: low-order control

Search Result 2,298, Processing Time 0.033 seconds

Effects of Hydrogeomorphology and Watershed Land Cover on Water Quality in Korean Reservoirs (우리나라 저수지 수질에 미치는 수문지형 및 유역 토지피복의 영향)

  • Cho, Hyunsuk;Cho, Hyung-Jin;Cho, Kang-Hyun
    • Ecology and Resilient Infrastructure
    • /
    • v.6 no.2
    • /
    • pp.79-88
    • /
    • 2019
  • In order to study the water quality status and its causal environmental factors, the water quality variables of chemical oxygen demand (COD), chlorophyll a (Chl a), Total phosphorus (TP), and total nitrogen (TN), the hydrogeomorphologic variables of water level fluctuation, total water storage, dam elevation, watershed area, and shoreline development index, and the land cover variables of forest, agricultural area, and urbanized area in the watershed were investigated in total 73 reservoirs with various operational purposes, water level fluctuation and geographical distribution in South Korea. The water quality was more eutrophic in the reservoirs of the more urbanized and agricultural area in the watershed, the low altitude, the narrow water level fluctuation, the narrowed watershed area, and the more circular shape. In terms of the purposes of reservoir operation, the reservoirs for agricultural irrigation were more eutrophic than the reservoirs for flood control. The results of the variable selection and path analysis showed that COD determined by Chl a and TP was directly affected by water level fluctuation and the shoreline development of the reservoirs. TP was directly affected by the urbanized area of the watershed which was related to the elevation of the reservoir. TP was also influenced by the water level fluctuation and the shoreline development. In conclusion, the eutrophication of the reservoirs in Korea would be influenced by the land use of the watershed, hydrological and geographical characteristics of the reservoir, water level fluctuation by the anthropogenic management according to the reservoir operation purpose, and the location of the reservoirs.

A Study on Heat Transfer and Pressure Drop Characteristics according to Block Size and Turbulence Generator's Placement in a Horizontal Channel (블록 크기 및 난류발생기 배치에 따른 수평채널내의 열전달 및 압력강하 특성에 관한 연구)

  • Seo, Kyu-Won;Lim, Jong-Han;Yoon, Jun-Kyu
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.20 no.4
    • /
    • pp.639-647
    • /
    • 2019
  • Recently, as the semiconductor integration technology due to miniaturization and high density of electronic equipment have developed, it is importantly recognized the application of thermal control system in order to release inner heat generated from chips, modules, In this study, we considered the heat transfer and pressure drop characteristics in a horizontal channel with four blocks using k-${\omega}$ SST turbulence model During CFD (Computational Fluid Dynamics) analysis, the parameters applied block width, block height, heat source and turbulence generator placement etc. As the boundary conditions of analysis, the channel inlet temperature and flow velocity were respectively 300 K and 3.84 m/s, the heat flux was $358W/m^2$. As a result, the heat transfer performance was decreased as the block width ratio (w/h) was increased, while it was increased as the block height ratio (h/w) was increased. In addition, as the arrangement of heat source size was increased to high heat flux from low heat flux, it was influenced by heat source size and the heat transfer coefficient showed a tendency to increase, When the turbulence generator was installed in the upper part of block No. 1 position the closely to the channel entrance, the heat transfer characteristics was greatly influenced on the whole of four heating blocks. and in oder to consider the pressure drop characteristics, we are able to select the most appropriate turbulence generator's position.

Studies on the Development of Soybean Cheeses (대두를 이용한 소이 발효 치즈 개발에 관한 연구)

  • Hwang, Hyo-Jeong;Kang, Chin-Yang;Choi, Kwang-Jin;Lee, Yu-Lim;Shin, Kyung-Ok
    • The Korean Journal of Food And Nutrition
    • /
    • v.31 no.6
    • /
    • pp.811-820
    • /
    • 2018
  • This study suggests a method of making cheese using soybeans for healthy food for people that are allergic to animal proteins, vegetarians, people on a diet, infants and toddlers. Additionally, the study was conducted to provide basic data that can contribute to the development of a quality control class of Korean cheese and underdeveloped cheese industry. Soybean cheeses have a high protein content and low fat. The free amino acids of soybean cheeses contained 11.48 mg of arginine per 100 g, 9.33 mg of glutamate, and leucine 4.91 mg, in that order. The free amino acids of Company A's milk cheese contained 20.95 mg of glutamate, 8.95 mg of proline and 8.02 mg of lysine per 100 g. In soybean cheeses, there were 2.21 mg of tryptophan and 0.73 mg of cysteine, which were not analyzed in the milk cheese of company A. The contents of the constituent amino acids was 1,070.22 mg of glutamate, 467.30 mg of aspartate and 446.30 mg of leucine in 100 grams of soybean cheeses per 100 grams. The milk cheese of Company A was 1,715.97 mg of glutamate, 798.72 mg of leucine and 685.31 mg of proline. The mineral contents of the soybean cheese were 120.29 mg/100 g of calcium, 0.92 mg/100 g of iron, 0.78 mg/100 g of zinc and 0.40 mg/100 g of selenium, respectively. The contents of vitamin $B_1$ and ${\beta}$-glucan in soybean cheese were higher than that of the milk cheese in Company A at 0.08 mg/100 g and 13.73 mg/g, respectively. Therefore, it is considered that the soy cheese is excellent in nutritional aspect and will contribute to health promotion. It is also suitable for people that are allergic to animal proteins, vegetarians, people on a diet and healthy foods for infants.

Analysis of Major Management Factors Affecting Crew Productivity in Road Bridge Construction Site Using IPA (IPA를 이용한 도로교량 골조공사의 작업조 생산성 관리요인의 중요도 및 실행도 분석)

  • Huh, Young-Ki;Lee, Sang-Ho
    • Korean Journal of Construction Engineering and Management
    • /
    • v.20 no.3
    • /
    • pp.39-45
    • /
    • 2019
  • Crew productivity in the construction industry is an important indicator of soundness and efficiency of work process, since all works in a site are conducted as groups of people. A survey was conducted in order to reveal importance and performance of major management factors affecting crew productivity in road bridge construction site using IPA. As a result of the analysis, it was found that 'Construction equipment' and 'Human resource related' factors among five major-categories are most important but with low performance. Furthermore, from another analysis with 27 factors of sub-categories, it is revealed that factors needed sustained attention are four, namely 'Just-in-time machinery delivery', 'Formation of a crew members', 'Skill of workers', and 'Site control and management', whereas those needed much more improvement are five, such as 'Machinery performance', 'Clearity of Design', 'Clearity of shop drawing', 'Timing of work instruction and approval', and 'Clearity of work instruction'. Findings from this study will enable road agencies as well as road construction experts to enhance crew productivity in a site.

Experimental study of the air emission effect in the tangential and the multi-stage spiral inlet (접선식 유입구와 다단식 나선 유입구의 공기 배출 효과에 관한 실험적 연구)

  • Seong, Hoje;Rhee, Dong Sop;Park, Inhwan
    • Journal of Korea Water Resources Association
    • /
    • v.52 no.4
    • /
    • pp.235-243
    • /
    • 2019
  • Recently, urban inundation was frequently occurred due to the intensive rainfall exceeding marginal capacity of the flood control facility. Furthermore, needs for the underground storage facilities to mitigate urban flood are increasing according to rapidly accelerating urbanization. Thus, in this study, drainage efficiency in drain tunnel connecting to underground storage was investigated from the air-core measurements in the drop shaft against two types of inlet structure. In case of the spiral inlet, the multi-stage structure is introduced at the bottom of the inlet to improve the vortex induction effect at low inflow discharge (multi-stage spiral inlet). The average cross-sectional area of the air-core in the multi-stage spiral inlet is 10% larger than the tangential inlet, and show the highly air emission effect and the highly inflow efficiency at the high inflow discharge. In case of the tangential inlets, the air emission effect decreased after exceeding the maximum inflow discharge, which is required to maintain the inherent performance of the tangential inlet. From the measurements, the empirical formula for the cross-sectional area of the air-core according to locations inside the drop shaft was proposed in order to provide the experimental data available for the inlet model used in experiments.

Design and Development of IoT-based Indoor Environment Management Platform (IoT 기반의 실내환경 관리 플랫폼 설계 및 개발)

  • Lee, Wan-Jik;Kim, Se-Jin;Yoon, Jun-Keun;Jeong, Ja-Woon;Heo, Seok-Yeol
    • The Journal of the Convergence on Culture Technology
    • /
    • v.7 no.1
    • /
    • pp.654-661
    • /
    • 2021
  • Air pollution caused by industrial development has become a level that can seriously threaten human health. In general, indoor air pollution is considered to be lower than outdoors, but modern people live indoors most of the time, thus it is essential to keep the indoor air quality comfortable in order to take care of one's own health and improve the quality of life. Therefore, the development of an indoor environment management platform using Internet of Things and data processing technology, which is currently drawing attention, is considered a very meaningful study. In this paper, we designed an IoT-based management platform that can remotely monitor and control indoor environments. In addition, the functions of the IoT terminal, gateway, and data server constituting the platform were implemented using open source and open libraries, and all functional operations were also verified. In particular, the IoT terminal and the gateway in this paper exchange data using BLE communication, so they can operate with relatively low power and since the gateway uses the BLE Advertising mode, it has the advantage of automatically recognizing IoT terminals that have not been previously configured.

Exploring of Resilience in Emergency Infectious Diseases to Moderate Job Stress, Job Burnout, and Turnover Intention of Childcare Teachers (보육교사의 직무스트레스와 직무소진, 이직의도 조절을 위한 긴급 감염병 상황에서의 회복탄력성 탐구)

  • Lee, Jae-Moo;Cho, Kyung-Seu
    • The Journal of the Korea Contents Association
    • /
    • v.21 no.4
    • /
    • pp.509-519
    • /
    • 2021
  • This study was conducted in order to acquire useful information regarding the resilience of childcare educators amidst an emergency pandemic to adjust their job stress, job burnout, and turnover intention. A questionnaire was conducted for analysis from August 19th to the 30th in 2020 and 201 responses ended up being used for analysis. The analysis results revealed that job stress, job burnout, and turnover intention of childcare educators were low while resilience was high and it was acknowledged that all of them mostly differed according to the types of personal traits. Although the job stress of childcare educators had a positive (+) influence on job burnout at a statistically significant level, it turns out that job stress does not have an influential relationship with turnover intention. Furthermore, the emotion regulation ability, impulse control, and active conductivity among resilience displayed a moderating effect in the relationship between job stress and job burnout. Amidst an emergency pandemic known as the COVID-19 virus, it has been confirmed that job stress and turnover intention of childcare educators deteriorated, and the prominent reason for this was identified as the difficulty in carrying out smooth job performances. Accordingly, measures to strengthen resilience such as countermeasures against quarantine-based job stress and turnover intent, daily management over job burnout and resilience, as well as counseling or programs based on self-focused attention have been suggested.

Research on The Crash Location and Speed Distribution of Low Altitude Fixed-Wing Aircraft (저고도 운용 고정익 항공기의 고장 시 추락지점 및 속도 분포 연구)

  • Nam, Hong-Su;Park, Bae-Seon;Lee, Hak-Tae
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.50 no.1
    • /
    • pp.59-66
    • /
    • 2022
  • In order to solve the problem of urban traffic congestion, Urban Air Mobility (UAM) concept using Electric Vertical Take-off and Landing (eVTOL) aircraft has been gaining popularity, and many domestic and international studies are underway. However, since these aircraft inevitably fly over densely populated areas, it is essential to ensure safety, which starts with accurately analyzing the crash risk. In this paper, the locations and impact speeds of crash are computed using six degree-of-freedom simulations of an eVTOL aircraft in a fixed-wing mode. System malfunction was modeled by a sudden loss of thrust with control surfaces being stuck during cruise. Because most of these eVTOL aircraft are still under development, a methodology of constructing a six degree-of-freedom dynamics model from generic specification is also developed. The results show that the crash locations are highly concentrated right under the aircraft within a square that has an edge length similar to the cruise altitude. Speed distribution is more complicated because almost identical crash locations can be achieved by two very different paths resulting in a large variation in the speeds.

The effect of self-regulation ability on fear of dental treatment among male high school students (남자 고등학생의 자기조절능력이 치과 치료공포감에 미치는 영향)

  • Kim, Young-Sun;Lee, Jung-Hwa
    • Journal of Korean Dental Hygiene Science
    • /
    • v.4 no.2
    • /
    • pp.89-98
    • /
    • 2021
  • Background: To analyze the effect of self-regulation on the fear of dental treatment in order to use it as basic data for efficient oral health care among male adolescents. Methods: A survey was administered to 241 first graders of specialized high schools in Daegu using a self-entry method. Twenty questions about fear of dental treatment and fifteen questions about self-regulation were included. The higher the score, the higher the fear of dental treatment and the self-regulation ability, showing a high reliability of 0.972 and 0.750, respectively. Results: The mean score of the participants' self-regulation ability was 3.25±0.51 and that of the degree of fear for dental treatment was relatively low at 1.72±0.85. It was confirmed that the higher the academic performance (F=7.635, p<0.01), the better was the self-regulation based on self-diagnosis (F=3.142, p<0.05), and was associated with higher health awareness (F=5.894, p<0.01). The degree of fear for dental treatment was significantly higher in the self-diagnosis-induced poor health group (F=4.933, p<0.01) and associated with a lower awareness of health (F=3.093, p<0.05). The participants' self-regulation ability was significantly negatively correlated with the degree of fear regarding dental treatment (r=-0.269, p<0.01). Regression analysis was performed using the degree of fear as a dependent variable and including sub-area variables of self-diagnosis-based health status, perception of health, and self-regulation ability as independent variables (β=-0.163, p<0.05). Among the self-regulation abilities, controlled composition (β=-0.232, p<0.01) had a significant effect; the higher the composition, the lower the degree of fear. The total explanatory power of this variable was 8.5%. Conclusion: An appropriate customized education program that can encourage individuals to practice self-care and maintain oral hygiene along with a clear understanding of underlying individual oral health conditions during adolescence is essential for promoting oral health.

Engineering Properties of CB Cut-off Walls Mixed with GGBS (고로슬래그 미분말을 혼합한 CB 차수벽의 공학적 특성)

  • Kim, Taeyeon;Lee, Bongjik
    • Journal of the Korean GEO-environmental Society
    • /
    • v.23 no.5
    • /
    • pp.33-39
    • /
    • 2022
  • For a slag-cement-bentonite (slag-CB) cut-off wall, GGBS replaces a part of the cement mixed to build a CB cut-off wall, which is used to block the flow and leakage of pollutants or groundwater; prevent seawater infiltration; and repair or reinforcement an aged embankments. Slag-CB cut-off walls are used in various applications in different fields where groundwater control is required due to its excellent characteristics. Such properties include high strength, low permeability, high durability and chemical resistance. However, despite these advantages, slag-CB cut-off walls are not extensively studied in Korea and thus are not applied in many cases. Particularly, GGBS, which replaces cement in a mixture, has different properties depending on its country of production. Consequently, it is necessary to perform various studies on slag-CB cut-off walls that use GGBS produced in Korea in order to increase its usability. This study has evaluated the bleeding rate, setting time, strength, and permeability in relation to the cement replacement rate of GGBS produced in Korea for slag-CB cut-off walls, with the aim to increase its usability. The evaluation found that slag-CB cut-off walls, made of a mixture containing GGBS produced in Korea, have a lower bleeding rate and permeability, and higher strengththan CB cut-off walls. It was also analyzed that such improved performance is more effective with a higher cement replacement rate of GGBS.