• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.2
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• pp.259-269
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• 2015

The issue of the longitudinal stability of a WIG vehicle has been a very critical design factor since the first experimental WIG vehicle has been built. A series of studies had been performed and focused on the longitudinal stability analysis. However, most studies focused on the longitudinal stability of WIG vehicle in cruise phase, and less is available on the longitudinal static stability requirement of WIG vehicle when hydrodynamics are considered: WIG vehicle usually take off from water. The present work focuses on stability requirement for longitudinal motion from taking off to landing. The model of dynamics for a WIG vehicle was developed taking into account the aerodynamic, hydrostatic and hydrodynamic forces, and then was analyzed. Following with the longitudinal static stability analysis, effect of hydrofoil was discussed. Locations of CG, aerodynamic center in pitch, aerodynamic center in height and hydrodynamic center in heave were illustrated for a stabilized WIG vehicle. The present work will further improve the longitudinal static stability theory for WIG vehicle.

• The Journal of Korean Physical Therapy
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• v.27 no.1
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• pp.7-11
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• 2015

Purpose: This study was conducted in order to determine the effects of knee malalignment including genu varum, valgum, and recurvatum on static and dynamic postural stability. Methods: A total of 80 subjects were enrolled in this study. Subjects who showed over 3 cm in the distance between the knees were classified as the genu varum group, and subjects who showed over 3 cm in the distance between the ankles were classified as the genu valgum group. Subjects who showed over 1 cm in the distance between the patella and a table in prone position were classified as the genu recurvatum group. Static and dynamic stability were measured as overall, anterioposterior, and mediolateral balance index using a Biodex Balance System. Results: This study showed that knee alignment affected static and dynamic postural stability. In particular, there were significant differences in the mediolateral stability index among genu varum, valgum group, and the other groups, but no differences in overall and anteriolateral stability index. Significant differences in the anterioposterior stability index were observed between genu recurvatum and the other groups, however, there were no differences in overall and mediolateral stability index. Conclusion: The findings were that knee malalignment affects postural stability toward a specific direction. Treatment to improve postural stability for treatment of knee malalignment or to prevent falling or injuries is needed and postural stability toward a specific direction according to the knee alignment conditions should be considered.

• Bulletin of the Society of Naval Architects of Korea
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• v.2 no.1
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• pp.15-19
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• 1965

The stability curves are very important data to decide the seaworthiness of all kinds of ships among waves. Both statical and dynamical stability curves on a rectangular coordinate system have broadly been handled at ship yards or at the government concerned, up to data. As concerns a method of obtaining a statical stability curve on polar coordinate system, the papers were presented once. Also, it is of use to research the dynamical stability curve on polar coordinate system. Author treated of the dynamical stability curve by four different methods, and tried to set the stability indicator inboard, adopted those proposals, in order to give some aids for good navigation on the sea. Fig. 1. shows a drawing method in case of the position of centre of buoyancy can be previously pointed out on the line corresponding to its inclination. Fig. 2. shows a method used a statical stability curve on polar coordinate. Fig. 3. shows a method obtained by the most simplified means. Fig. 4. shows dynamical stability curve made by geometrical expression method, instead of dynamical lever. A simple stability indicator which was mechanized above characteristics is attempted by author as shown Fig. 5 and Fig.6. It is demanded at hand, for more advanced improvement of such indicator.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.411-418
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• 2009

So far the Limit Equilibrium Method has been widely used by way of 2-D slope stability analysis for the evaluation of land slides and slope failures. However recently the evaluation of 3-D slope stability analysis has been comparatively possible owing to the developments of obtaining the terrain data and geological data and of 3-D slope stability analysis softwares. In Japan the evaluation of the 3-D slope stability analysis has been necessary for the stability analysis of the tunnel mouth. In this study we inspected the economic effects introducing the 3-D slope stability analysis for larger scale landslides and slope failures. In case of 3-D slope stability analysis of landslides we acquired the results that we reduce the cost of the countermeasure work of pile work by 40% comparing the 2-D slope stability analysis. Moreover in case of the stability analysis of slope failures we figured out the results that we reduce the cost of the countermeasure work of anchor works by 20%. Furthermore we proved that 3-D slope stability analysis is effective for the stability analysis of tunnel mouths around the sides of landslides and large scale embankment which we could have not evaluated by conventional 2-D section stability analysis.

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.48-54
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• 2009

Structures to support against slop failures or resist earth pressure like masonry retaining walls or retaining walls have continued to advance and evolve to new eco-friendly, easy-to-construct, crib retaining walls with varied forms and construction methods, meeting the needs of the times. Researches until now, however, have focused on the analyses of site displacement or stability of the whole site including structures like retaining walls, and thus, researches on rational design or method for stability analysis are lacking. Therefore, this study was conducted on a number of stability analyses, such as the visual power line or stability on sliding, being presented for bin walls, which enable vegetation to grow and were developed and applied in varied forms, meeting the development demands for eco-friendly retaining wall structures. This study compared the results of stability analyses, determined their feasibility, and evaluated their stability according to the height and facade slope of retaining walls. According to the results of this study, traditional masonry retaining wall analysis showed rather conservative stability evaluation results in the stability evaluation of bin walls, and the method using the visual power line seems to be objective because it produced similar results to the stability evaluation method on sliding or turnover.

• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.443-451
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• 2015

The stability of a multi-terminal direct current (MTDC) system is often influenced by its control strategy. To improve the stability of the MTDC system, the control strategy of the MTDC system must be appropriately adopted. This paper deals with estimating stability of a MTDC system based on the line-commutated converter based high voltage direct current (LCC HVDC) system with an inverter with constant extinction angle (CEA) control or a rectifier with constant ignition angle (CIA) control. In order to evaluate effects of two control strategies on stability, a MTDC system is tested on two conditions: initialization and changing DC power transfer. In order to compare the stability effects of the MTDC system according to each control strategy, a mathematical MTDC model is analyzed in frequency domain and time domain. In addition, Bode stability criterion and transient response are carried out to estimate its stability.

• The Journal of Korean Physical Therapy
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• v.24 no.6
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• pp.419-422
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• 2012

Purpose: Malalignment of the lower limbs may increases the difficulty of maintaining equilibrium. The purpose of this study was to study the effects of genu varum and poor posture in the sagittal plane on postural stability. Methods: We had 27 subjects with varus and 27 normal subjects participate in this study. Subjects for whom the distance between the medial epicondyles in the knee joint was more than 3 cm were classified as varus group, and subjects for whom the distance was less than 3 cm were classified as normal group. The measurements of static and dynamic stability were used overall stability index (OSI), anterioposterior stability index (APSI), and mediolateral stability index (MLSI) using a Biodex balance system. Results: When measuring the static stability index, there were significant differences in the mediolateral stability index between the varus and control groups. When measuring the dynamic stability index, there were significant differences in the overall, anteriorposterior, and mediolateral stability index between the varus and control groups. These results demonstrated that genu varum affects mediolateral movement in static stability, and overall, anterioposterior and mediolateral movements in dynamic stability. Conclusion: As genu varum affects static and dynamic stability in young adults, it increases the risk of injuries or falls. Exercise and surgery are required for realigning the genu varum. Future studies about postural stability in young children and elderly people who have a risk of falls due to lower postural control ability, are needed, as well as in young adults.

• Journal of the Chungcheong Mathematical Society
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• v.19 no.2
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• pp.159-175
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• 2006

This paper is a survey on the Hyers-Ulam-Rassias stability of the Jensen functional equation in $C^*$-algebras. The concept of Hyers-Ulam-Rassias stability originated from the Th.M. Rassias' stability theorem that appeared in his paper: On the stability of the linear mapping in Banach spaces, Proc. Amer. Math. Soc. 72 (1978), 297-300. Its content is divided into the following sections: 1. Introduction and preliminaries. 2. Approximate isomorphisms in $C^*$-algebras. 3. Approximate isomorphisms in Lie $C^*$-algebras. 4. Approximate isomorphisms in $JC^*$-algebras. 5. Stability of derivations on a $C^*$-algebra. 6. Stability of derivations on a Lie $C^*$-algebra. 7. Stability of derivations on a $JC^*$-algebra.

• Korean Journal of Mathematics
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• v.23 no.1
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• pp.181-197
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• 2015

In this paper, we investigate Lipschitz and asymptotic stability for perturbed nonlinear differential systems.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.45 no.1
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• pp.29-33
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• 2019

Objectives: Bone density seems to be an important factor affecting implant stability. The relationship between bone density and primary and secondary stability remains under debate. The aim of this study was to compare primary and secondary stability measured by resonance frequency analysis (RFA) between different bone types and to compare implant stability at different time points during 3 months of follow-up. Materials and Methods: Our study included 65 implants (BioHorizons Implant Systems) with 3.8 or 4.6 mm diameter and 9 or 10.5 mm length in 59 patients. Bone quality was assessed by Lekholm-Zarb classification. After implant insertion, stability was measured by an Osstell device using RFA at three follow-up visits (immediately, 1 month, and 3 months after implant insertion). ANOVA test was used to compare primary and secondary stability between different bone types and between the three time points for each density type. Results: There were 9 patients in type I, 18 patients in type II, 20 patients in type III, and 12 patients in type IV. Three implants failed, 1 in type I and 2 in type IV. Stability values decreased in the first month but increased during the following two months in all bone types. Statistical analysis showed no significant difference between RFA values of different bone types at each follow-up or between stability values of each bone type at different time points. Conclusion: According to our results, implant stability was not affected by bone density. It is difficult to reach a certain conclusion about the effect of bone density on implant stability as stability is affected by numerous factors.