• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.676-681
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• 2000

This study describes a hydraulic fluid property compensator under the various operating conditions. Because hydraulic fluid systems have much more excellent features than other control systems, they are used in many fields. However, the characteristics of hydraulic fluid are changed due to various operating conditions. This phenomenon is called uncertainty. Especially, bulk modulus is considered as the most dominant parameter in this study. Under the wide range of temperature and pressure, bulk modulus is changed. In order to overcome the uncertainty, $H_{\infty}$ technique will be used for this study. Spectral factorization, model-matching problem and controller parametrization are also applied to achieve the desired robust control action. Designed controller using the $H_{\infty}$ technique, is adopted for the hydraulic fluid valve-motor system.

• 산경연구논집
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• 제15권8호
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• pp.1-12
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• 2024

Purpose: Marketing networks are essential for firms to gain new information and resources, yet their effect on innovation performance under uncertainty remains unclear. This study aims to elucidate the effects of technological and demand variability on the innovation performance of first-tier suppliers, considering different levels of structural holes. It particularly explores how structural holes moderate the relationship between uncertain factors and innovation performance. Research design, data and methodology: To assess the hypotheses, a survey was conducted with the first-tier suppliers. The survey targeted internal networks and the relationships between manufacturers, suppliers, and subsuppliers. Structural equation modeling was employed to validate the hypotheses using measures from previous research. Results: The findings indicate that the impact of technological uncertainty and demand variability on innovation performance varies based on the extent of structural holes in the network. Conclusions: This study provides both theoretical and practical insights for distribution channels, highlighting the competitive advantage of interfirm networks in uncertain conditions. However, the focus on the engineering industry may limit the generalizability of the findings. Future research should explore a broader range of industries to improve result applicability.

• 대한간호학회지
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• 제30권4호
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• pp.1006-1017
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• 2000

The purpose of this study was to provide basic information for developing a nursing intervention that helps patients learn how to acquire coping to reduce post operation uncertainty and anxiety by investigating the level of uncertainty and anxiety experienced by mastectomy patients. The subjects were 134 patients selected from St. Mary's Kangnam and St. Mary's hospital, and the data collection period was from October to December of 1998. Uncertainty was measured by using Mishel Uncertainty in Illness Scale (MUIS), anxiety measured by using State-Trait Anxiety Inventory(STAI), and coping by using a questionnaire developed by Kim & Yoo (1996). Data were analyzed with SAS program by t-test, ANOVA, Duncan's multiple range test, Pearson correlation coefficients, and stepwise multiple regression. The results were as follows : 1. The mean uncertainty score was 57.6. The results of the correlation between the compliance of medical regimen and demographic characteristics were as follows ; Those who monthly income over 2,010,000 won had lower than above 1,000,000 won, and those with the experience of chemotherapy had higher than those without, and the patient who has 7∼12 months(1 yr.) post operation period had higher than the one below 6months, 25∼36 months(3 yrs.), 37∼60 months(5 yrs.), and over 61 months. 2. The mean anxiety score was 45.9. Anxiety tended to be increased slightly in subjects with low educational background, poor monthly income, experience of chemotherapy, and 7∼12 months(1 yr.) post operation period, but there was no significant difference by general characteristics 3. The mean value of the coping score was 100.7. The study revealed higher score in problem-focused coping than emotion-focused coping. In regard to coping by demographic characteristics were as follows ; those who had monthly income over 2,010,000 won had higher level of coping than those whose monthly income was between 1,010,000 and 2,000,000 won. In terms of problem- focused coping, those who had 25∼36 months of post operation period showed significantly lower level of coping than those below 6 months or 37∼60 months(5 yrs.) or over 61 months of post operation period. Regarding the emotion-focused coping, those with the christianity had significantly lower level of coping than those without it. Also, those whose monthly income over 2,010,000 won had significantly higher coping level than those with income of between 1,010,000 and 2,000,000 won. 4. A positive relationship was found between uncertainty and anxiety. Patients who experienced more uncertainty also showed more anxiety. Problem-focused coping was inversely related to uncertainty and anxiety. 5. The major variable that affected uncertainty was anxiety, explaining 63.3% of the uncertainty. In addition to this, it would explain 66.4% in total when experience of chemotherapy was added.

• Child Health Nursing Research
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• 제4권2호
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• pp.274-285
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• 1998

Improvements in therapy have resulted in increasing numbers of children being successfully treated for cancer. However the agrressiveness of therapy & uncertainty about prognosis are associated with many adverse effects, psychological as well as physical for both the child & family. The purpose of this study were to measure the degree of perceived uncertainty, self-efficacy & coping, and then to examine the relationship between the perceived uncertainty, self-efficacy & coping in parents of children cancer patients. The subjects of this study consist of 140 parents with pediatric cancer, registered at pediatric cancer ward & Out Patient Department. Data was collected from July 1st to August 15th 1998. The tools used in this study were Mishel's the Parents' Perception of Uncertainty Scale (28 item, 4 likert scale), Shere's Self-Efficacy Scale (17 item, 5 likert scale) & Folkman & Lazarus Ways of Coping Checklist(34 items, 4 likert scale). Data was analyzed by t-test, Anova, Pearson Correlation coefficient. Results of this study are summerized as follows 1. Parents perceived their uncertainty to be slightly high(Mn 2.41). The degree of perceived uncertainty by the four components were followed as lack of clarity (2.60), unpredictability(2.59), ambiguity(2.51) & lack of information(1.90). The degree of perceived uncertainty of parents with pediatric cancer revealed to be influenced significantly by the family outcome, reliability about health care provider & perceived severity of illness. 2. The range of parents' self-efficacy was measured iron 35 to 85 point, so revealed slightly high. The degree of self-efficacy related to be Influenced signiicantly by the sequency of child birth, family religion & degree of perceived support. 3. The degree of parents' coping was measured slightly high (Mn 2.78). The degree of coping related to be influnced significantly by the sequency of child birth, number of sible & degree of perceived support. 4. parents' uncertainty was related inversely to the parents' self-efficacy(r=-.38, p<.001) & coping(r=-.26, p<.001). And also parents' self-efficacy was positively related to coping(r=.56, p<.001) From the above results, it can be concluded that predicting & controlling parents' uncertainty with children cancer are necessary to improve positive coping strategies. This information may be used as a foundation for developing nursing interventions to decrease perceived uncertainty & to foster self-efficacy & coping for parents with children cancer.

• 재활간호학회지
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• 제7권2호
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• pp.207-212
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• 2004

Purpose: This study was to investigate the relationship between mastery and activity of daily life in rheumatoid arthritis patients. Method: The subjects for this study were 222 patients registered in H University Hospital Rheumatoid Arthritis Center, and the period of data collection was from August 15, 2003 to September 30, 2003. Reliability coefficients of instruments were found Cronbach's Alpha =.74~.94. In data analysis, SPSSWIN 10.0 program was utilized for descriptive statistics, Pearson's correlation, and multiple regression analysis. Result: The results were as follows. 1) The range of total uncertainty scores was from 33 to 87 and the mean score of the uncertainty in rheumatoid arthritis patients was 63.27. 2) The range of total mastery scores was from 10 to 27 and the mean score of the mastery in rheumatoid arthritis patients was 18.70. 3) The range of total activity of daily life scores was from 22 to 80 and the mean score of the activity of daily life in rheumatoid arthritis patients was 72.56. 4) The level of mastery was significant correlation with activity of daily life(r=.395, p<.01).

• 센서학회지
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• 제22권6호
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• pp.415-420
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• 2013

Calibration capabilities for thermometer calibration by comparison method were assessed using high-precision industrial platinum resistance thermometers (IPRT). It was found in the performance assessment that out of 31 laboratories who participated, 28 laboratories resulted magnitude of En number less than 1 at every calibration points they submitted results in the range from 50 to $500^{\circ}C$. The results of about 75% of the laboratories showed the difference from the assigned values less than 1/10 of the tolerance level of the class B IPRT. This indicates that the participating calibration laboratories performed with satisfactory level that was enough to calibrate IPRTs to significant precision. The sensors used in this work were manufactured and chosen by the criteria of long-term instability less than 4 mK and hysteresis less than 8 mK in the temperature range used in this work. Furthermore, the change in the resistance of the sensors in the calibration temperature range were less than the uncertainty of the calibration, 25 mK (k=2).

• 한국해양공학회지
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• 제36권4호
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• pp.251-269
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• 2022

The process-based XBeach model has numerous empirical parameters because of insufficient understanding of hydrodynamics and sediment transport on the nearshore; hence, it is necessary to calibrate parameters to apply to various study areas and wave conditions. Therefore, the calibration process of parameters is essential for the improvement of model performance. Generally, the trial-and-error method is widely used; however, this method is passive and limited to various and comprehensive parameter ranges. In this study, the Generalized Likelihood Uncertainty Estimation (GLUE) method was used to estimate the optimal range of three parameters (gamma, facua, and gamma2) using morphological field data collected in Maengbang beach during the four typhoons that struck from September to October 2019. The model performance and optimal range of empirical parameters were evaluated using Brier Skill Score (BSS) along with the baseline profiles, sensitivity, and likelihood density analysis of BSS in the GLUE tools. Accordingly, the optimal parameter combinations were derived when facua was less than 0.15 and simulated well the shifting shape, from crescentic sand bar to alongshore uniform sand bars in the surf zone of Maengbang beach after storm impact. However, the erosion and accretion patterns nearby in the surf zone and shoreline remain challenges in the XBeach model.

• 한국연초학회지
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• 제27권1호
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• pp.114-119
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• 2005

The study was carried out to develope quantitative analysis method of individual sugars in licorice extract. Individual sugars were analyzed by HPLC equipped with Refractive Index(RI) Detector. R values of sucrose and glucose were 1.0000 and R values of fructose and maltose were 0.9999. Standard calibration curve showed good linearity. Detection limit of sugars was in the range of 1.58 to 3.92 ${\mu}g$. Recovery rate of fructose, glucose, sucrose and maltose was $99.4\~102.2\%,\;92.3\~97.9\%,\;99.4\~102.0\%,\;91.1\~101.0$ respectively. Measure uncertainty was calculated to confirm trust and accuracy of analytical results. Main uncertainty factors were standard purity and HPLC replication injection. In $95\%$ trust level expanded uncertainty of sugars in licorice extract were fructose $1.98\pm0.047,\;glucose\;1.32\pm0.065,\;sucrose\;11.69\pm1.177,\;maltose\;1.06\pm0.042\;g/100\;g$.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.438-443
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• 2003

In this paper, we propose a control algorithm for two-wheel mobile robot that can move the rider to his or her command and autonomously keep its balance. The control algorithm is based on a mixed $H_2/H_{\infty}$ control scheme. In this control problem the main issue is to move the rider while keeping its balance in the presence of disturbances and parameter uncertainties. The disturbance force caused by uneven road surfaces and the uncertainty due to different rider's heights are considered. To this end we first consider a state feedback controller as a basic framework. Secondly, we obtain the state feedback gain $K_2$ minimizing the $H_2$ norm and the state feedback gain $K_{\infty}$ minimizing the $H_{\infty}$ norm over the whole range of parameter uncertainty. Finally, we select mixed $H_2$/$H_{\infty}$ state feedback controller K as the geometric mean of $K_2$ and $K_{\infty}$. Simulation results show that the mixed $H_2/H_{\infty}$ state feedback controller combines the effects of the optimal $H_2$ state feedback controller and robust $H_{\infty}$ controller state feedback controller efficiently in the presence of disturbance and parameter uncertainty.

• Architectural research
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• 제9권1호
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• pp.31-37
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• 2007

This study presents the so-called Modified Allowable Stress Design (MASD) method for structural designs. The objective of this study is to qualitatively estimate uncertainties of tensile steel member's cross-sectional structural designs and find the optimal resulting design which can resist all uncertainty cases. The design parameters are assumed to be interval associated with lower and upper bounds and consequently interval methods are implemented to non-stochastically produce design results including the structural uncertainties. By seeking optimal uncertainty combinations among interval parameters, engineers can qualitatively describe uncertain design solutions which were not considered in conventional structural designs. Under the assumption that structures have basically uncertainties like displacement responses, the safety range of resulting designs is represented by lower and upper bounds depending on given tolerance error and structural parameters. As a numerical example uncertain cross-sectional areas of members that can resist applied loads are investigated and it demonstrates that the present design method is superior to conventional allowable stress designs (ASD) with respect to a reliably structural safety as well as an economical material.