• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.424-432
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• 1989

A mathematical model is developed for determination of the dynamic cutting force from static cutting data. The dynamic cutting force is analytically expressed by the static cutting coefficient and the dynamic cutting coefficient which can be determined from the cutting mechanics. The proposed model is verified by the chatter stability charts. A good agreement was shown between the stability limits predicted by the theory and the critical width of cut determined by experiments. The static cutting coefficient dominates high speed chatter stability, while the dynamic cutting coefficient dominates low speed chatter stability.

• The Journal of Korean Physical Therapy
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• v.28 no.1
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• pp.1-7
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• 2016

Purpose: The aim of this study was to evaluate the effect of Bridge exercise with abdominal drawing-in on static and dynamic balance in patients with stroke. Methods: Forty patients with stroke participated in this study. Participation was randomly assigned to the Bridge exercise group (n=20) and the Bridge exercise with abdominal drawing-in group (n=20). A bio-feedback device was used when patients performed the Bridge exercise with abdominal drawing-in. This training was performed without any motion on the patient's spine and upper belly part, and the pressure was held with the biofeedback device as 40-70 mmHg. Both groups received training 30 minutes per day, three times per week, for four weeks. Weight bearing, anterior limit of stability, and posterior limit of stability for static balance ability were measured, and Berg balance scale (BBS), Timed up and go test (TUG) for dynamic balance ability were also measured. Results: Participants showed significant differences between pre- and post-mediation in terms of weight bearing, anterior limit of stability, posterior limit of stability, Berg balance scale, and Timed up and go test (p<0.05). The Bridge exercise with abdominal drawing-in group showed a more significant increase (p<0.05). Conclusion: According to the results of this study, both exercises were effective for improving the static and dynamic balance ability. However we suggest that the Bridge exercise with abdominal drawing-in is more efficient for increasing balance ability in patients with stroke.

• Geomechanics and Engineering
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• v.29 no.5
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• pp.567-582
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• 2022

In the present study, a series of physical experiments and numerical simulations were conducted to investigate the effects of mode I and mixed-mode I/II cracks on the fracture modes and stability of roadway tunnel models. The experiments and simulations incorporated different inclination angle flaws under both static and dynamic loads. The quasi-static and dynamic testing were conducted by using an electro-hydraulic servo control device and drop weight impact system (DWIS), and the failure process was simulated by using rock failure process analysis (RFPA) and AUTODYN software. The stress intensity factor was also calculated to evaluate the stability of the flawed roadway tunnel models by using ABAQUS software. According to comparisons between the test and numerical results, it is observed that for flawed roadways with a single radical crack and inclination angle of 45°, the static and dynamic stability are the lowest relative to other angles of fractured rock masses. For mixed-mode I/II cracks in flawed roadway tunnel models under dynamic loading, a wing crack is produced and the pre-existing cracks increase the stress concentration factor in the right part of the specimen, but this factor will not be larger than the maximum principal stress region in the roadway tunnel models. Additionally, damage to the sidewalls will be involved in the flawed roadway tunnel models under static loads.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.11
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• pp.963-969
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• 2005

An advanced method of Relaxed Static Stability (RSS) is utilized for improving the aerodynamic performance of modem version supersonic jet fighter aircraft. The flight control system utilizes RSS criteria in both longitudinal and lateral-directional axes to achieve performance enhancements and improve stability. The T-50 advanced trainer employs the RSS concept in order to improve the aerodynamic performance and the flight control law in order to guarantee aircraft stability, The T-50 longitudinal control laws employ the dynamic inversion and proportional-plus-integral control method. This paper details the design process of developing longitudinal control laws for the RSS aircraft, utilizing the requirement of MIL-F-8785C. In addition, This paper addresses the analysis of aircraft characteristics such as damping, natural frequency, gain and phase margin about state variables for longitudinal inner loop feedback design.

• The korean journal of orthodontics
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• v.19 no.2
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• pp.109-120
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• 1989

We tend to consider only static occlusion such as molar relationship, canine key, and interdigitation at finishing stage. Of course, this static occlusion is important for post-orthodontic stability. But we should remember that mandible is always on the move during its various functions. If no pressure or too much pressure is put on during its functions, untoward tooth movement could occur. And tooth mobility, periodontitis, wear facet, bruxism, and far worse temporomandibular disorder could occur. After many studies have been done on what is a desirable occlusal scheme to strengthen post-orthodontic stability, today, "mutually protective occlusion" is recommended. If an orthodontist does not have understanding about this occlusal scheme during orthodontic treatment, the following conditions will be resulted after orthodontic treatment. I. Centric discrepancy 1. centric prematurity 2. sunday bite 3. molar fulcrum II. Eccentric discrepancy 1. posterior interference 2. anterior interference If we have deep understanding about these discrepancies that can happen after orthodontic treatment and their causes, corrections, and especially preventions against them, post-orthodontic stability could be strengthened and further temporomandibular disorder could be prevented.

• Steel and Composite Structures
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• v.28 no.6
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• pp.671-679
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• 2018

The paper is devoted to the stability analysis of a simply supported five layer sandwich beam. The beam consists of five layers: two metal faces, the metal foam core and two binding layers between faces and the core. The main goal is to elaborate a mathematical and numerical model of this beam. The beam is subjected to an axial compression. The nonlinear hypothesis of deformation of the cross section of the beam is formulated. Based on the Hamilton's principle the system of four stability equations is obtained. This system is approximately solved. Applying the Bubnov-Galerkin's method gives an ordinary differential equation of motion. The equation is then numerically processed. The equilibrium paths for a static and dynamic load are derived and the influence of the binding layers is considered. The main goal of the paper is an analytical description including the influence of binding layers on stability, especially on critical load, static and dynamic paths. Analytical solutions, in particular mathematical model are verified numerically and the results are compared with those obtained in experiments.

• Journal of Electrical Engineering and Technology
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• v.5 no.3
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• pp.415-422
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• 2010

The distributed flexible alternative current transmission system (D-FACTS) is a recently developed FACTS technology. Distributed Static Series Compensator (DSSC) is one example of DFACTS devices. DSSC functions in the same way as a Static Synchronous Series Compensator (SSSC), but is smaller in size, lower in price, and possesses more capabilities. Likewise, DSSC lies in transmission lines in a distributed manner. In this work, we designed a fuzzy logic controller to use the DSSC for enhancing transient stability in a two-machine, two-area power system. The parameters of the fuzzy logic controller are varied widely by a suitable choice of membership function and parameters in the rule base. Simulation results demonstrate the effectiveness of the fuzzy controller for transient stability enhancement by DSSC.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.6
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• pp.82-89
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• 2011

Reactive power support is considered to be necessary for dealing with a voltage stability issue with wind turbine system employing squirrel-cage induction generator(SCIG). This paper analyses steady-state characteristics of the SCIG wind turbine system by simulating torque-slip characteristics of SCIG with respect to variations of interconnecting network strength and generator terminal voltage. It also presents dynamics analysis of SCIG wind turbine system on Simulink to investigate the impact of static var compensator(SVC) and static synchronous compensator(STATCOM) on transient stability enhancement. It analysed transient stability with varying fault duration times and compared the transient stability characteristics with varying rated capacities of SVC and STATCOM. It is shown that the STATCOM has a better performance and reactive power support compared to SVC.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.7
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• pp.1187-1193
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• 2010

This paper provides the methods for enhancing the stability with normal or emergency operating conditions in real power systems and copes with the unbalance of demand of reactive power due to the loss of facility, such as 765kV transmission line. In this paper, we focused on the maximum allowable transmission power(hereafter, MAXTP) in the metropolitan area. In order to increase the MAXTP, the application of reactive power compensators, SVC, and Shunt compensator and reactor, is analyzed as an enhancing method of stability and MAXTP. Particularly, the f-V analysis was performed for the postulated contingency, in order to evaluate the effects on SVC. Conclusively, the stability of power systems could be enhanced and the MAXTP is increased effectively with Dongseoul SVC which has the capacity 200MVAr.

• JSTS:Journal of Semiconductor Technology and Science
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• v.10 no.2
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• pp.118-129
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• 2010

A lower-threshold-voltage (LVth) SRAM cell with an elevated cell biasing scheme, which enables to reduce the random threshold-voltage (Vth) variation and to alleviate the stability-degradation caused by word-line (WL) and cell power line (VDDM) disturbed accesses in row and column directions, has been proposed. The random Vth variation (${\sigma}Vth$) is suppressed by the proposed LVth cell. As a result, the LVth cell reduces the variation of static noise margin (SNM) for the data retention, which enables to maintain a higher SNM over a larger memory size, compared with a conventionally being used higher Vth (HVth) cell. An elevated cell biasing scheme cancels the substantial trade-off relationship between SNM and the write margin (WRTM) in an SRAM cell. Obtained simulation results with a 45-nm CMOS technology model demonstrate that the proposed techniques allow sufficient stability margins to be maintained up to $6{\sigma}$ level with a 0.5-V data retention voltage and a 0.7-V logic bias voltage.