• Journal of Institute of Control, Robotics and Systems
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• v.10 no.6
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• pp.510-518
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• 2004

The PID trajectory tracking controller for robotic systems shows performance limitation imposed by inverse dynamics according to desired trajectory. Since the equilibrium point can not be defined for the control system involving performance limitation, we define newly the quasi-equilibrium region as an alternative for equilibrium point. This analysis result of performance limitation can guide us the auto-tuning method for PID controller. Also, the quasi-equilibrium region is used as the target performance of auto-tuning PID trajectory tracking controller. The auto-tuning law is derived from the direct adaptive control scheme, based on the extended disturbance input-to-state stability and the characteristics of performance limitation. Finally, experimental results show that the target performance can be achieved by the proposed automatic tuning method.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.6
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• pp.523-530
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• 2017

In this study, a method of probabilistic evaluation of the performance point of the structure obtained by capacity spectrum method (CSM) is presented. The performance point of the 4-story and 1-bay steel structure was determined by using CSM according to ATC-40. In order to analyze whether the demand spectrums exceed the performance limit of the structure, the limit displacements are derived for the performance limit of the structure defined from the plastic deformation angle of the structural member. In addition, by selecting a total of 30 artificial seismic wave having the response spectrum similar to the design response spectrum, the fragility curves were derived by examining whether the response spectrum obtained from the artificial seismic wave were exceeded each performance limit according to the spectral acceleration. The maximum likelihood method was used to derive the fragility curve using observed excess probabilities. It has been confirmed that there exists a probability that the response acceleration value of the design response spectrum corresponding to each performance limit exceeds the performance limit. This method has a merit that the stochastic evaluation can be performed considering the uncertainty of the seismic waves with respect to the performance point of the structure, and the analysis time can be shortened because the incremental dynamic analysis (IDA) is not necessary.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.383-383
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• 2011

Generally, field emitters can be categorized into two types according to the emitter shape, one is a planar field emitter and the other is a point emitter. The planar field emitter is used for displays, flat lamps and signage boards. On the other hands, the point field emitter is expected to play a significant role in x-ray sources and electron beam sources. Such applications of the point field emitters, especially, need large emission current and high emission stability with a small electron beam size. A few reports announced point emitters made by carbon nanotubes (CNTs). However, they still have suffered from poor reproducibility and low emission current. Here, we demonstrated high performance CNT point emitters by attaching CNTs onto graphite rod. Graphite rod exhibited good electrical conductivity and chemical stability. In this method, the shape of the point emitter could be easily controlled by changing the length and diameter of the graphite rod. The CNT point emitter showed emission current over 1 mA at an applied electric field of 1.4 V/${\mu}m$. We consider that the stable emission performance is attributed to the stable contact between CNTs and graphite rod.

• Journal of Construction Engineering and Project Management
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• v.1 no.2
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• pp.18-27
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• 2011

Egyptian construction firms (ECF) started recently to adopt quality management system (QMS) as a way to develop and improve their performance as previous studies have shown. However, considering all the firm's aspects in a competitive way is a crucial process for the ECF's culture. This research is trying to indicate the role of the QMS implementation in measuring performance (MP) through developing a model for measuring performance at the organizational level, and to explore its impact on the organizations that adopt QMS. This model is based on specific elements and their related indicators which have been derived from national approaches and models of MP. This model determines the performance level (PL) of the organization that is measured by means of a point system. Weights of the elements in the point system considered both the elements' importance in the international models and its real practice in the ECFs. This model has been validated using another questionnaire and the majority of surveyed experts agreed that the proposed model can be applied effectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.472-479
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• 2006

Recently, various methods have been developed to improve the performance of gas turbines for combined cycle power plants. This paper especially focused on the gas turbine with a reheat process. The purpose of this study is to analyze performance characteristics of a reheat-cycle gas turbine on both a design point and off-design operations. Results of the parametric study of this model show how operating and design parameters influence on the performance of the gas turbine. Moreover, possibilities for the analysis of off-design performance based on a self-generated compressor performance characteristic map are presented.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.7 no.1
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• pp.29-50
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• 2001

This research have been made to define how the IADL (Instrumental Activity of Daily Living) performance and the subjective health index of the Aged are affected by their residential circumstance, gender and age, and how deeply these two factors are related and interact. For the period of June 1 to July 31, 2000, we had conducted a questionnaire and direct interview with 693 persons over age sixty-five (65) in Daejon and in other adjacent area, grouping into three different residential types The Aged living at home, The Aged living at welfare facilities and The Aged living alone, and studied on how the IADL performance and the subjective health index of the Aged are influenced and interact as per their characteristics, daily activity and mentality. We had analyzed all the data obtained through this research by the method of : - analysis of frequency as per specific factors by SPSS 1O.0/PC+, - $x^2$ test, - t-test, - ANOVA, - multiple regression analysis by factors. The research concludes followings : a. It appears that the three (3) factors such as gender, age and residential circumstance of the Aged deeply affect the IADL performance and subjective health index of the Aged. (p<0.01) b. With regard to IADL performance of the Aged by the gender, it was analyzed that the female-Aged gains 23.8 point on average, which shows the performance of the female-Aged is less independent. (p<0.01). In addition, it was also found that the IADL performance is becoming less and less independent following their age increasing. In analyzing IADL performance by the residential type, it appears that the Aged living at welfare facilities gains the lowest 21.5 points and is least independent. It was also found that the Aged living at welfare facilities need some assistances from others for their performing IADL. (20-24 point) (p<0.001) c. With regard to the subjective health index of the all-Aged participated in this research, the analysis indicates 8.8 point and this is considered as a point of general standard (7-10 point). In analyzing this index by the gender, the female-Aged gains only 8.6 point which explains a lot of female-Aged consider they are not really healthy. (p<0.001) In analyzing this index by the residential type, the Aged living at welfare facilities and the Aged living alone gain the comparatively lower point, - respectively 8.4 point for the Aged living at welfare facilities and 8.8 point for the Aged living alone. The Aged living at these two residential types express they are obviously in a bad situation of health. (p<0.001) d. With regard to the factors affecting the IADL performance and the subjective health index of the Aged, it was analyzed that the IADL performance can largely be affected by the factors such as depression, frequency of going-out and age rising, and that the subject health index can also deeply be affected by depression, pain and by how much they are satisfied with their current living conditions. e. It was analyzed that the interacting between the IADL performance and the subjective health index is not that strong but even weak. As a result, we were able to conclude that the IADL performance is less independent in case of the female-Aged, the Aged living at welfare facilities, and following the age rising. As for the subjective health state the Aged themselves are aware of, we concluded that the female-Aged, the Aged living at welfare facilities and the Aged living alone, are more critical about their health. From this research, we were able to realize that, when the OMT (Orthopedic Manual Therapy) needed, the physical therapists are really required to have a correct and cautious understanding of the situation in which the aged persons are, and take care of them with more concerns and more improved treatment.

• International Journal of Highway Engineering
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• v.15 no.4
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• pp.127-133
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• 2013

PURPOSES : The impact performance of flexible barrier system such as structural response, vehicular motion and occupant safety vary depending on the impact point. Thus, to properly evaluate the performance of a flexible barrier system, impact should be made to a point which will lead to the worst possible results. This point is called the Critical Impact Point (CIP). This paper presents the way to determine the CIP for a SB2 class flexible barrier system which is consisted of Thrie-Beam rail and circular hollow tube post of 2m span. METHODS: Barrier VII simulations were made for impact points; Case 1 at a post, Case 2 at 1/3 span downstream from a post, Case 3 at middle of the span, Case 4 at 2/3 span downstream from a post. For the structural performance (deflections), impact simulation of 8000kg-65km/h-15degree was used, and for vehicle motion and occupant safety, simulation of 1300kg-80km/h-20degree impact was made and analysed. RESULTS: Case 1 gave the largest dynamic deflection of 75.72cm and also gave the largest snag value of 44.3cm. Occupant safety and exit angle of the vehicle after the impact were not sensitive to the impact point and were all below the allowable limit. CONCLUSIONS : For the SB2 class flexible barrier system's CIP can be regarded as a post which is sufficiently away from the end of Length of Need in order to avoid the end-effect of the barrier system. It can be more economic in the long run because the normal concrete pavement material is likely to cost more due to higher probability of maintenance and repair and higher social cost due to traffic accident, etc.

• 한국데이터정보과학회:학술대회논문집
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• 2004.10a
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• pp.25-32
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• 2004

In this study, we use various change-point detection methods to detects Korea economic crisis of 1997, and then compares their performance. In change-point detection method, there are three major categories: (1) the parametric approach, (2) the nonparametric approach, and (3) the model-based approach. Through the application to Korea foreign exchange rate during her economic crisis, we compare the employed change-point detection methods and, furthermore, determine which of them performs better.

• Journal of the Korean Data and Information Science Society
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• v.15 no.3
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• pp.585-592
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• 2004

This study detects Korea economic crisis of 1997 using various change-point detection methods and then compares their performance. In change-point detection method, there are three major categories: (1) the parametric approach, (2) the nonparametric approach, and (3) the model-based approach. Through the application to Korea foreign exchange rate during her economic crisis, we compare the employed change-point detection methods and, furthermore, determine which of them performs better.

• Communications for Statistical Applications and Methods
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• v.14 no.1
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• pp.155-167
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• 2007

Knowing the time of the process change could lead to quicker identification of the responsible special cause and less process down time, and it could help to reduce the probability of incorrectly identifying the special cause. In this paper, we propose the maximum likelihood estimator (MLE) for the process change point when a control chart is used in monitoring the mean of a process in which the observations can be modeled as an AR(1) process plus an additional random error. The performance of the proposed MLE is compared to the performance of the built-in estimator when they are used in EWMA charts based on the residuals. The results show that the proposed MLE provides good performance in terms of both accuracy and precision of the estimator.