• The Korean Journal of Applied Statistics
• /
• v.15 no.2
• /
• pp.233-250
• /
• 2002

Cox's proportional hazard model is highly-used for the regression analysis of survival data in various fields. Regression diagnostics for the proportional hazards model, however, is not as well-known as the diagnostics for the classical linear models and so these diagnostic methods are not used widely in our practical data analyses. For this reason, we review the residuals proposed by several authors, and investigate how to use them in assessing the model. We also provide the results and interpretation with the analysis of PBC data using S-plus 2000 program.

• Transactions of The Korea Fluid Power Systems Society
• /
• v.8 no.4
• /
• pp.9-16
• /
• 2011

Because of the increasing demand on the high precision and high response of a machinery, proportional control valves are widely adopted at various application fields. This paper studies on the static and dynamic characteristics of a pilot proportional pressure control valve. An experimental apparatus including hydraulic pump, variable speed inverter, pressure and flow sensors and data aquisition system was set up. And various experiments such as P-Q-V curves, step responses due to input voltage and flow rate, hysteresis, frequency response of the proportional valve was carried out and the results are discussed.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.19 no.2
• /
• pp.191-197
• /
• 2010

In spite of a large amount of previous research, detail study on modified mass in proportional damping system is not well understood. It is common to predict structural dynamic design parameters due to the change of mass, but to predict the amount of modified mass and the location where the mass is being modified are rarely found in previous literature. Such inverse problem required detail analytical study in order to understand structural modification in proportional damping system. This paper predicts the modified mass and the modified mass location in proportional damping system using sensitivity coefficients and iterative method. The sensitivity coefficients are obtained from the change of eigenvectors due to mass modification. This method is applied to a horizontal beam and three degree of freedoms system. To validate the predicted changing mass and its location, the obtained results are compared to the reanalysis result which shows good agreement.

• Communications for Statistical Applications and Methods
• /
• v.24 no.6
• /
• pp.583-604
• /
• 2017

The most popular regression model for the analysis of time-to-event data is the Cox proportional hazards model. While the model specifies a parametric relationship between the hazard function and the predictor variables, there is no specification regarding the form of the baseline hazard function. A critical assumption of the Cox model, however, is the proportional hazards assumption: when the predictor variables do not vary over time, the hazard ratio comparing any two observations is constant with respect to time. Therefore, to perform credible estimation and inference, one must first assess whether the proportional hazards assumption is reasonable. As with other regression techniques, it is also essential to examine whether appropriate functional forms of the predictor variables have been used, and whether there are any outlying or influential observations. This article reviews diagnostic methods for assessing goodness-of-fit for the Cox proportional hazards model. We illustrate these methods with a case-study using available R functions, and provide complete R code for a simulated example as a supplement.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2001.06a
• /
• pp.212-217
• /
• 2001

This paper presents the stability characteristics of a rotor-bearing system supported by actively controlled hydrodynamic journal bearing. The proportional and derivative controls including coupled motion are adopted for the control algorithm to control the hydrodynamic journal bearing with a circumferentially groove. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than conventional analysis which uses the Reynolds condition. The stability characteristics are investigated with the Routh-Hurwitz criteria using the linear dynamic coefficients which are obtained from the perturbation method. The stability characteristics of the rotor-bearing system supported by active controlled hydrodynamic journal bearing are investigated for various control gain. It is found that the speed at onset of instability is increased for both proportional and derivative control of the bearing, and the proportional and derivative control of coupled motion is more effective than proportional and derivative control of uncoupled motion.

• Journal of Fashion Business
• /
• v.10 no.6
• /
• pp.91-109
• /
• 2006

This study aims at strengthening the national competitiveness of Korea's clothing industry as it provides substantial information on the human body proportion and proportional dimension standards for Chinese women and improves the fitness of clothing, considering human proportion in the production of clothing products for export to China. This study selected by simple random sampling Chinese women in Beijing and Shanghai, China, whose age is between 19-50 from June 23 to August 7, 2004. The stature of the average Chinese woman belonging to the High Frequency group is 7.09 times as long as the length of the head. We developed the body proportional dimension standards with the same proportion with High-Frequence group. The basic size of proportional dimension standards for Chinese women has the stature of 159cm, (chest circumference)/2 of 42.8cm.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.12
• /
• pp.1607-1612
• /
• 2011

In this study, dynamic analysis of a proportional solenoid valve is performed, and an LQG/LTR controller with an integrator is designed to control the proportional solenoid valve. The dynamic characteristic of a valve is identified using experimental data by employing the frequency-domain modeling technique. The purpose of LQG/LTR control with an integrator is to enhance the system response and to improve the tracking accuracy for a complex input signal. Experimental tests are performed to verify the performance of the controller, and the results prove the high performance of the controller.

• Tunnel and Underground Space
• /
• v.8 no.2
• /
• pp.79-86
• /
• 1998

This study was performed to suggest to suggest suitable design conditions of water curtain system through analysis on pressure down in boreholes by hydraulic tests carried out I construction fields for underground oil storages. The influence by hydraulic conductivities of rock mass around boreholes on pressure down in boreholes was analysed. The relationship between array of boreholes and their pressure down was also analysed. Groundwater flow analysis on crude oil and LPG storages was carried out to evaluate results of field tests and to investigate distribution of hydraulic gradient in rock mass around cavern using finite difference method. As the results, hydraulic tests showed that pressure down in boreholes was inverse proportional to the hydraulic conductivity of surrounding rock mass. The rate of pressure down of boreholes was not influenced by water curtain system more than 20m over cavern and was proportional to installation interval of boreholes. The hydraulic gradient in rock mass around cavern was proportional to distance and interval of boreholes and its value was not satisfactory to oil tightness condition in case of no water curtain system.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.5 s.110
• /
• pp.470-478
• /
• 2006

An efficient method for change of eigenvectors and eigenvalues due to the modifying proportional damping structure using sensitivity coefficients is presented. Sensitivity coefficients are determined by iteration with eigenvalue and eigenvectors before modification of system. The proposed method is applied to examples of 3 degrees of freedom system and plate by modifying mass and stiffness. The predicted change of eigenvectors and eigenvalues are in a good agreement with these from the structural re-analysis after modification of mass and stiffness.

• Journal of the Korean Data and Information Science Society
• /
• v.9 no.2
• /
• pp.119-138
• /
• 1998

The case of proportional cell frequencies for the two-way cross-classification with interaction is considered. Several types of hypotheses for the general unbalanced data that are commonly used in the literature are shown, and they are written out for this particular case. A reparameterized form of the cell means model is defined to establish the reparameterized model, and orthogonal property of the model is shown using the augmented matrix and the numerator sums of squares are computed. Different ways of producing the same analysis of variance tables are shown in both orthogonal and nonorthogonal situations.