• International Journal of Ocean System Engineering
• /
• v.3 no.1
• /
• pp.16-21
• /
• 2013

This paper presents a design of fuzzy PD depth controller for the autonomous underwater vehicle entitled KAUV-1. The vehicle is shaped like a torpedo with light weight and small size and used for marine exploration and monitoring. The KAUV-1 has a unique ducted propeller located at aft end with yawing actuation acting as a rudder. For depth control, the KAUV-1 uses a mass shifter mechanism to change its center of gravity, consequently, can control pitch angle and depth of the vehicle. A design of classical PD depth controller for the KAUV-1 was presented and analyzed. However, it has inherent drawback of gains, which is their values are fixed. Meanwhile, in different operation modes, vehicle dynamics might have different effects on the behavior of the vehicle. In this reason, control gains need to be appropriately changed according to vehicle operating states for better performance. This paper presents a self-tuning gain for depth controller using the fuzzy logic method which is based on the classical PD controller. The self-tuning gains are outputs of fuzzy logic blocks. The performance of the self-tuning gain controller is simulated using Matlab/Simulink and is compared with that of the classical PD controller.

• Physical Therapy Korea
• /
• v.19 no.4
• /
• pp.24-31
• /
• 2012

The aim of this study was to investigate the effectiveness of self-stretching exercises for iliotibial band (ITB) (Side-lying; right hip and knee were flexed to support the pelvis while left hip was extended and adducted, Standing A; side-bending of the trunk on standing with crossed leg, Standing B; same as Standing A, except the hands were clasped overhead and shifted right side, and Standing C; same as Standing B, except moving the arms diagonally downward) to help determine the most effective self-stretching method to stretch ITB. Twenty-one healthy subjects who do not have ITB shortness from Yonsei University (14 men and 7 women) between the ages of 18 to 28 years voluntarily participated. Ultrasound was performed to measure the thickness of the ITB between the long axis of the ITB and the level parallel to the lateral femoral epicondyle during four self-stretching exercises. All data were found to approximate a normal distribution. We used a one-way repeated-measures analysis of variance (ANOVA) to compare the thickness of the ITB among all self-stretching exercises. The level of significance was set at ${\alpha}$=.05. The ANOVA was followed by Bonferroni's correction. The overall mean of ITB thickness was $1.14{\pm}.4$ mm (${\pm}$ standard deviation) in resting status. The change in the ITB thickness in percentages between the tested position of each self-stretching exercises and resting status was significant (p<.05) (Side-lying $26.62{\pm}10.18%$ with 95% confidence interval [CI]=21.99~31.25%; Standing A $29.46{\pm}16.19%$ with 95% CI=22.09~36.84%; Standing B $44.06{\pm}14.82%$ with 95% CI=37.31~50.81%; Standing C $53.76{\pm}12.1%$ with 95% CI=48.25~59.29%). Results indicated significant differences among four self-stretching exercises except Side-lying versus Standing A (p<.01). Based on these findings, the Standing C self-stretching exercise was the most effective in stretching the ITB thickness among four types of ITB self-stretching exercises. Additionally, the Side-lying self-stretching exercise using gravity to stretch the ITB is recommended as a low-load (low-intensity), long-duration stretch.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.3
• /
• pp.518-526
• /
• 2008

The fuzzy self-tuning PID controller is a PID controller with a fuzzy logic mechanism for tuning its gains on-line. In this structure, the proportional, integral and derivative gains are tuned on-line with respect to the change of the output of system under control. This paper deals with two types of fuzzy self-tuning PID controllers, rule-based fuzzy PID controller and learning fuzzy PID controller. As a medical application of fuzzy PID controller, the proposed controllers were implemented and evaluated in a laparoscopic surgery robot system. The proposed fuzzy PID structures maintain similar performance as conventional PID controller, and enhance the position tracking performance over wide range of varying input. For precise approximation, the fuzzy PID controller was realized using the linear reasoning method, a type of product-sum-gravity method. The proposed controllers were compared with conventional PID controller without fuzzy gain tuning and was proved to have better performance in the experiment.

• The Bulletin of The Korean Astronomical Society
• /
• v.43 no.1
• /
• pp.62.1-62.1
• /
• 2018

Galaxies in the cluster environment interact with the intracluster medium (ICM), losing the interstellar medium (ISM) and alternating their evolution. Observational evidences of the extraplanar ISM stripped by the ICM's ram pressure are prevalent in HI imaging studies of cluster galaxies. However, current theoretical understanding of the ram pressure stripping (or ICM-ISM interaction in general) is still limited mainly due to the lack of numerical resolution at ISM scales in large-scale simulations. Especially, self-consistent modeling of the turbulent, multiphase ISM is critical to understand star formation in galaxies interacting with the ICM. To achieve this goal, we utilize the TIGRESS simulation suite, simulating a local patch of galactic disks with high resolution to resolve key physical processes in the ISM, including cooling/heating, self-gravity, MHD, star formation, and supernova feedback. We then expose the ISM disk to ICM flows and investigate the evolution of star formation rate and the properties of the ISM. By exploring ICM parameter space, we discuss an implication of the simple ram pressure stripping condition (so called the Gunn-Gott condition) to the realistic ISM.

• Journal of the Korean Chemical Society
• /
• v.19 no.3
• /
• pp.149-155
• /
• 1975

Pivalic acid, which has a globular shape and is a plastic crystal, has been examined by means of temperature-dependent with-line proton magnetic resonance spectroscopy. Results of temperature-dependent line width, second moment, and spin-lattice relaxation time studies of pivalic acid were interpreted in terms of dynamic behavior and hydrogen bonding. The dynamic behavior consists of superimposed reorientation of the methyl groups about their three-fold axes$(C_3) and of the molecule about the central C-C bond(C_3'),$ general molecular reorientation about the center of gravity, and molecular self-diffusion. Activation energies for the motional processes have been obtained from line width measurements using the modified Bloembergen, Purcell, and Pound theory and from spin-lattice relaxation time measurements. The results were compared with the Pople-Karasz theory of fusion and the agreement was found to be poor. The discrepancy was interpreted in terms of hydrogen bonding in this molecule.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.10a
• /
• pp.1251-1258
• /
• 2008

The purpose of this research is to introduce the new temporary earth retaining wall system using landslide stabilizing piles. This system is a self-supported retaining wall(SSR) without installing supports such as tiebacks, struts and rakers. The SSR is a kind of gravity structures consisting of twin parallel lines of piles driven below dredge level, tied together at head of soldier piles and landslide stabilizing piles by beams. There are three types of excavation wall structures: standard method for medium retained heights(<8.0m), internal excavation method and slope excavation method for deep-excavation applications(>8.0m). In the present study, the measured data from seven different sites which the SSR was used for excavation were collected and analyzed to investigate the characteristic behavior lateral wall movements associated with urban excavations in Korea.

• Journal of the Optical Society of Korea
• /
• v.11 no.2
• /
• pp.76-81
• /
• 2007

The compound refractive X-ray lens (CRL) for focusing hard X-rays is investigated to determine the parameters such as the focal length, the focal spot size, and spatial distribution at the focal spot using a simple theoretical calculations and CRLs fabricated by the self-assembly method. The number of individual compound lenses are defined for the given focal length of 1 m. The X-ray energy of 1 to 40 keV is used in the calculations. The CRL for focusing hard X-rays which generated from the X-ray tube is fabricated by nanoparticle-polymer composite in the form of circular concaves. The self-assembly method is applied to form the nanoaluminum-poly (methly meth-acrylate) composite and carbon-polymer composite CRL lenses. Aluminum nanoparticles of 100 nm and carbon microparticles are diffused in the polymer solution then the high gravity up to 6000G is applied in it to form the concave lens shape. X-ray energy at 8 keV is used for characterization of the composite CRLs. The FWHM of intensity for the fabricated nanoaluminium composite CRL system, N=10 is measured as 1.8 mm, which would give about $70{\mu}m$ in FWHM at 1 m of the focal length.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.1
• /
• pp.54.1-54.1
• /
• 2011

Formation of self-gravitating gas clouds and hence stars in galaxies is a consequence of both thermal and dynamical evolution of a gaseous medium. Using hydrodynamics simulations including cooling and heating explicitly, we follow simultaneously thermal and dynamical evolution of galactic gas disks to study dynamics and structures of galactic spiral shocks with thermal instability and regulation of the star formation rates (SFRs). We first perform one-dimensional simulations in direction perpendicular to spiral arms. The multiphase gas flows across the arm soon achieve a quasi-steady state characterized by transitions from warm to cold phases at the shock and from cold to warm phases in the postshock expansion zone, producing a substantial fraction of intermediate-temperature gas. Next, we allow a vertical degree of freedom to model vertically stratified disks. The shock front experiences unsteady flapping motions, driving a significant amount of random gas motions, and self-gravity promotes formation of bound clouds inside spiral arms. Finally, we include the star formation feedback in both mechanical (due to supernova explosion) and radiative (due to FUV heating by young stars) forms in the absence of spiral arms. At saturation, gravitationally bound clouds form via thermal and gravitational instabilities, which are compensated by disruption via supernova explosions. We find that the FUV heating regulates the SFRs when gas surface density is low, confirming the prediction of the thermal and dynamical equilibrium model of Ostriker et al. (2010) for star formation regulation.

• Journal of International Academy of Physical Therapy Research
• /
• v.11 no.4
• /
• pp.2197-2202
• /
• 2020

Background: If there is a difference in leg length, the center of gravity shifts unilaterally toward the short leg, causing loss of balance and secondary postural imbalance, trunk muscle tone changes, gait abnormalities and pelvic imbalance. Objectives: To investigate effects of self exercise program on leg length, balance in adults with leg-length discrepancy. Design: Single blind randomized controlled trial. Methods: Twenty-eight participants were selected and divided into resistance exercise, flexibility exercise, and core exercise. Each exercise was performed for 40 minutes, 3 times a week for 6 weeks. Leg length and balance before and after exercise were measured and analyzed. Results: Following the interventions, resistance exercise group showed significant improvement in balance, but leg length difference did not show significant results. Flexibility exercise group showed significant improvement in leg length difference, but balance did not show significant results. Core exercise group showed significant improvement in leg length difference and balance. There was no significant difference in the comparison between the three groups. Conclusion: This study suggests that customized exercise according to the patient's level is beneficial to the patients.

• Journal of Distribution Science
• /
• v.17 no.3
• /
• pp.107-116
• /
• 2019

Purpose - Why, why is it difficult to predict the appropriateness of self-employment, and what are the countermeasures and policy proposals to overcome. This study intends to further develop the field of statistical variables. It is necessary to overcome the limitation of existing proper scale research in Korea. We need to find statistical variables that can determine the appropriateness of self-employment in Korea. These efforts will be helpful in evaluating OECD countries and statistics and developing domestic economic indicators. Research design, data, and methodology - It is the discovery of statistical indicators and complementary indicators that have not been revealed in previous studies. Therefore, we sought to find new statistical parameters based on the statistics of the Korea National Statistical Office, the Bank of Korea, and overseas OECD statistics. (Proper Size of Adequacy) is defined as the specific gravity or number of the self-employed in Korea, which is shown as "Out Put" by statistical analysis of STATA panel statistical data. It is possible to further develop variables such as gross domestic product, gross national product, economic growth rate, unemployment rate, income tax rate, consumer price, tax level, exports, import amount, bill default I want to dig. Results - In addition to expanding economic indicators that can be explained by self-employment determinants, we have developed a variety of methods such as linear and non-linear (U-shaped, inverted U-shaped). It is the improvement of the self-employment determinants and the analysis method to estimate the appropriate scale. Conclusions - The proposed contents are reflected in self - employment appropriateness evaluation data and hope to help the government to select the policy support and to evaluate the government business after the policy support. These efforts are expected to be of great help to operators operating their own businesses, and to government and related institutional practitioners who support them. In this way, self-employment will be created in accordance with the Korean situation, where the happy life of all the people becomes the premise and the inclusive economic activities are guaranteed. It will improve the method of analyzing proper scale of small business owners and self-employed in Korea.