• Title/Summary/Keyword: stepwise

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A Study on Determining Fares for Rail Transit in Tour Regions Using a Stepwise Optimization (단계적 최적화 기법을 통한 관광지역 내 궤도교통수단의 요금결정 연구)

  • Yang, Jae Ho;Kim, Eungcheo;Choi, Eunjin
    • Journal of Korean Society of Transportation
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    • v.31 no.6
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    • pp.12-21
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    • 2013
  • Fare is critical variable when deciding project feasibility for a monorail system in tour regions. This study aims to estimate optimal fare balancing operators and users. An object of this study is Wolmi-eunha circulation monorail at Jung-Gu, Wolmido in Incheon metropolitan city. This study introduces a stepwise optimization technique to decide relevant fare ranges between operator's cost and user's cost. We found that the optimized station interval is 0.532km, the optimized headway is 0.206hour, optimal number of stations is 12, optimal number of vehicles is 3. Using these optimized variables, minimum user cost and minimum operator cost can be calculated. Optimal fare range is calculated from 1,261 Won to 5,063 Won. It is also found that sightseeing transport system has less sensitivity on access cost because distance differences among sightseeing transport stations located in the tour regions are negligible.

Effect of Step Pressure on Shape Forming of Alumina by Pressure-Vacuum Hybrid Slip Casting (가압-진공 하이브리드 주입 성형에 의한 알루미나의 성형에 미치는 다단 가압의 영향)

  • Cho, Kyeong-Sik;Lee, Hyun-Kwuon;Woo, Byeong-Joon
    • Journal of the Korean Ceramic Society
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    • v.50 no.2
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    • pp.142-148
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    • 2013
  • Conventional cold isostatic pressing, slip casting, and filter pressing are not completely suitable for fabricating large plates because of disadvantages such as the high cost of equipment and formation of density gradient. These problems could be avoided by employing pressure-vacuum hybrid slip casting (PVHSC). In the PVHSC, the consolidation occurs not only by the compression of the slip in casting room, but also by vacuum sucking of the dispersion medium around the mold. We prepared the alumina bodies by the PVHSC in a static- or stepwise-pressure manner for loading up to 0.5 MPa using an aqueous slip. The green bodies were dried at $30^{\circ}C$ with 40 ~ 80% relative humidity. Under static pressure, casting induced a density gradient in the formed body, resulting in cracking and distortion after the firing. However, the stepwise pressure loading resulted in green bodies with homogeneous density, and the minimization of the appearance of those defects in final products. Desirable drying results were obtained from the cast bodies dried with 80% RH environment humidity. When sintered at $1650^{\circ}C$ for 4 h, the alumina plate made by stepwise-pressure casting reached full density (> 99.7% relative density).

Effect of Patients with Colon Polypectomy on Health Behavior Practices (대장용종수술환자의 건강행태 실행에 영향을 미치는 요인)

  • Lee, Seong-Ran
    • Journal of Digital Convergence
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    • v.10 no.1
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    • pp.385-389
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    • 2012
  • This study was performed to determine the effect of patients with colon polypectomy on health behavior practices. Data were surveyed using interview and questionnaires by 112 patients with colon polypectomy in a general hospital who were located in Seoul from December 6, 2010 to January 31, 2011. Data were evaluated with t-test, ANOVA, Pearson correlation coefficient, and Stepwise multiple regression. The results were as follows: First, the higher control of life habit was, the more positive attitude(r=.350, p<.01) and the less inconvenience was significant correlation(r=-.263, p<.05). Secondly, in the stepwise multiple regression analysis, the most important factors influencing health behavior practices were control of life habit(${\beta}$=.392, p=.000), and then inconvenience of life(${\beta}$=-.265, p=.007), weight gain(${\beta}$=-.248, p=.024). In conclusion, positive attitude and control of life habit are necessary to improve the health behavior of patient with colon polypectomy.

A Study of Factors Influencing Health Promoting Behavior and Quality of Life in the Nursing Students (간호학생의 건강증진 행위 및 삶의 질에 영향을 미치는 요인)

  • Choi Hee Chung
    • Journal of Korean Public Health Nursing
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    • v.14 no.1
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    • pp.161-171
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    • 2000
  • The purpose of this study was to investigate the factors influencing health promoting behavior and quality of life in the nursing students, to provide the basic data for health promoting intervention in order to improve quality of life. The subjects of this study were 199 nursing students, living in M city, during the period from May 18 to 25, 1999. The instruments for this study were the health promoting behavior scale developed by Walker et al.(1987), the quality of life scale by Ro(1988), the self efficacy scale by Sherer(1982), the health locus of control scale by Wallston et al. (1978) and the self esteem scale by Rogenberg(1965). The data were analyzed using descriptive statistics, Pearson correlation coefficients, stepwise multiple regression, t-test, ANOVA. The results of this study are as follows; 1. The health promoting behavior showed significant positive correlation with self efficacy, self esteem, internal health locus of control and quality of life. 2. The quality of life showed significant positive correlation with self efficacy, self esteem, internal health locus of control. 3. Stepwise multiple regression analysis revealed that the most powerful predictor of health promoting behavior was self efficacy. A combination of self efficacy, self esteem, health locus of control and quality of life accounted for $41\%$ of the variance in health promoting behavior. 4. Stepwise multiple regression analysis revealed that the most powerful predictor of quality of life was self esteem. A combination of self esteem, self efficacy and health promoting behavior accounted for $40\%$ of the variance in quality of life. Based on the above findings, it is suggested to develop nursing intervention to improve Self Efficacy, Self Esteem of nursing students enhance health promoting lifestyle.

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Collaborative Stepwise Movement of Mobile Sensor Nodes for Energy Efficient Dynamic Sensor Network Coverage Maintenance (모바일 센서노드들의 협동형 단계적 이동기법 기반의 에너지 효율적인 동적 센서네트워크 커버리지 관리)

  • Han, Ngoc-Soc;Kim, Seong-Whan
    • The KIPS Transactions:PartC
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    • v.16C no.4
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    • pp.535-542
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    • 2009
  • Wireless Sensor Network (WSN) is a wireless network consisting of spatially distributed autonomous devices, using sensors to cooperatively monitor physical or environmental conditions. WSNs face the critical challenge of sustaining long-term operation on limited battery energy. Coverage maintenance has been proposed as a promising approach to prolong network lifetime. Mobile sensors equipped with communication devices can be leveraged to overcome the coverage problem. In this paper, we propose a stepwise movement scheme using perimeter coverage property for the coverage maintenance problem. In our scheme, each sensor monitors neighboring dead nodes, determines vulnerable node (i.e. dead node which makes uncovered area), computes the center of uncovered area HC, and makes a coordinated stepwise movement to compensate the uncovered area. In our experimental results, our scheme shows at least 50 % decrease in the total moving distance which determines the energy efficiency of mobile sensor.

Hybrid Reference Function for Stable Stepwise Inertial Control of a Doubly-Fed Induction Generator

  • Yang, Dejian;Lee, Jinsik;Hur, Kyeon;Kang, Yong Cheol
    • Journal of Electrical Engineering and Technology
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    • v.11 no.1
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    • pp.86-92
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    • 2016
  • Upon detecting a frequency event in a power system, the stepwise inertial control (SIC) of a wind turbine generator (WTG) instantly increases the power output for a preset period so as to arrest the frequency drop. Afterwards, SIC rapidly reduces the WTG output to avert over-deceleration (OD). However, such a rapid output reduction may act as a power deficit in the power system, and thereby cause a second frequency dip. In this paper, a hybrid reference function for the stable SIC of a doubly-fed induction generator is proposed to prevent OD while improving the frequency nadir (FN). To achieve this objective, a reference function is separately defined prior to and after the FN. In order to improve the FN when an event is detected, the reference is instantly increased by a constant and then maintained until the FN. This constant is determined by considering the power margin and available kinetic energy. To prevent OD, the reference decays with the rotor speed after the FN. The performance of the proposed scheme was validated under various wind speed conditions and wind power penetration levels using an EMTP-RV simulator. The results clearly demonstrate that the scheme successfully prevents OD while improving the FN at different wind conditions and wind power penetration levels. Furthermore, the scheme is adaptive to the size of a frequency event.

Stepwise Inertial Control of a Doubly-Fed Induction Generator to Prevent a Second Frequency Dip

  • Kang, Mose;Lee, Jinsik;Hur, Kyeon;Park, Sang Ho;Choy, Youngdo;Kang, Yong Cheol
    • Journal of Electrical Engineering and Technology
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    • v.10 no.6
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    • pp.2221-2227
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    • 2015
  • To arrest a frequency nadir, a stepwise inertial control (SIC) scheme generates a constant active power reference signal of a wind turbine generator (WTG) immediately after a disturbance and maintains it for the predetermined time. From that point, however, the reference of a WTG abruptly decreases to restore the rotor speed for the predefined period. The abrupt decrease of WTG output power will inevitably cause a second frequency dip. In this paper, we propose a modified SIC scheme of a doubly-fed induction generator (DFIG) that can prevent a second frequency dip. A reference value of the modified SIC scheme consists of a reference for the maximum power point tracking control and a constant value. The former is set to be proportional to the cube of the rotor speed; the latter is determined so that the rotor speed does not reach the minimum operating limit by considering the mechanical power curve of a DFIG. The performance of the modified SIC was investigated for a 100 MW aggregated DFIG-based wind power plant under various wind conditions using an EMTP-RV simulator. The results show that the proposed SIC scheme significantly increases the frequency nadir without causing a second frequency dip.

Effects of E-book-based Flipped Learning Education on Critical Thinking Disposition, Academic Self-Efficacy, and Major Satisfaction of Nursing Students (E-book 기반 플립드 러닝(Flipped Learning) 수업이 간호대학생의 비판적 사고성향, 학업적 자기효능감 전공만족도에 미치는 효과)

  • Jung, Mi-Ra;Jeong, Eun
    • The Journal of the Korea Contents Association
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    • v.18 no.2
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    • pp.490-501
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    • 2018
  • This study was conducted to develop and test effects of E-book based Flipped Learning education for nursing students. This study was one-group pretest-posttest design. The data were collected from 54 second-year nursing students in the located Y city and August 28 2017 to October 16 2017. The data were analyzed by descriptive statistics, paired t-test, Pearson's correlation coefficient, and stepwise multiple regression with SPSS 20.0 program. The results showed that the program was effective in increasing the critical thinking disposition (t=-8.62, p<.001), academic self-efficacy (t=-9.62, p<.001) and major satisfaction (t=-8.11, p<.001). The result of the stepwise multiple regression indicates the critical thinking disposition predict 13.4% (F=9.22, p<.001) of major satisfaction. The result of the stepwise multiple regression indicates the critical thinking disposition predict 13.4% (F=9.22, p<.001) of major satisfaction. Therefore, strategies for enhancing critical thinking disposition is needed by applying various teaching and learning strategies for nursing students.

Studies on the Chemical Compositions and Distributions of Ambient Sumicron Aerosols (Submicron 부유분진의 화학적 조성 및 분포에 관한 연구)

  • 황인조;김동술
    • Journal of Korean Society for Atmospheric Environment
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    • v.14 no.1
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    • pp.11-23
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    • 1998
  • The purpose of this study was to survey chemical distribution of inorganic elements and ions in the submicron particles, to characterize qualitatively emitting sources by factor analysis, and finally to reveal existing patterns in terms of chemical compounds by a stepwise multiple regression analysis. Total of 141 samples were collected by a cascade impactor from 1989 to1996. Fifteen chemical species (Al, Ba, Cd, K, Pb, Cu, Fe, Ni, $Cl^-, NO_3^-, SO_4^{2-}, K^+, Mg^{2+}, Ca^{2+}, and Na^+$) were characterized by AAS and IC. The study showed that average seasonal levels of submicron particulate matters $(d_p<0.43 \mum)$ were 18.7 $\mug/m^3$ in spring, 15.5 $\mug/m^3$ in summer, 15.7 $\mug/m^3$ in fall, and 24.5 $\mug/m^3$ in winter, respectively. All of the anion concentrations in the particle were highest in the winter season. By applying a factor analysis, 5 source patterns were qualitatively obtained, such as sulfate related source, nitrate related source, oil burning source, calcium related source, and coal combustion source. Finally, when applying a stepwise multiple regression analysis, the results clearly showed that $Na^+ and Ca^{2+}, K^+ and Ca^{2+}, NO_3^-$ and relative humidity, $Cl^-$ and ambient temperature, $Ca^{2+} and Cl^-, Mg^{2+} and SO_4^{2-}, Na^+ and NO_3^-, and Ca^{2+} and NO_3^-$, respectively, are negatively contributed to each other. As a result of those statistical analysis, we could suggest that some chemical compounds in the submicron particles such as$NaNO_3, MgSO_4, Ca(NO_3)_2, and CaCl_2$ may not exist on the filter as final composing products; however, other compounds may possibly exist in the form of $Mg(NO_3)_2, CaSO_4, Na_2SO_4, K_2SO_4, MgCl_2, NaCl, and KCl$. Thus, it must be necessary to identify differences between the results of above statistical analysis and of the real world by laboratory experiments.

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Taste Characteristics of Kanjang Made with Barley Bran (보리등겨로 제조한 간장의 맛성분 특성)

  • Son, Dong-Hwa;Kwon, O-Jun;Choi, Ung-Kyu;Kwon, O-Jin;Lee, Suk-Il;Im, Moo-Hyeg;Kwon, Kwang-Il;Kim, Sung-Hong;Chung, Yung-Gun
    • Applied Biological Chemistry
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    • v.45 no.1
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    • pp.18-24
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    • 2002
  • This study was conducted to find out optimum conditions for kanjang fermented with barley bran. The correlation between taste components and sensory evaluation score was analyzed with stepwise multiple regression analysis. It was revealed that the taste of kanjang was explained with the mix of free amino acids, free sugars and organic acids. The highest multiple correlation coefficient was obtained from absolute value transformed with logarithm. Thus, stepwise multiple regression analysis was conducted with absolute value transformed with logarithm, for which F-value was highest and standard error of estimation was lowest among the multiple regression models transformed with six variables. The stepwise multiple regression analysis showed that the taste components which most contribute to the quality of taste of kanjang fermented with barley bran was salty taste component followed by palatable taste component, and bitter taste component.