• Wind and Structures
• /
• v.10 no.4
• /
• pp.383-398
• /
• 2007

The paper describes a study of the effects of structural coupling on the wind-induced response of twin tall buildings connected by a skybridge. Development of a dual high-frequency force balance used in wind tunnel investigation and background information on the methodology employed in analysis are presented. Comparisons of the wind-induced building response (rooftop acceleration) of structurally coupled and uncoupled twin buildings are provided and the influence of structural coupling is assessed. It is found that the adverse aerodynamic interference effects caused by close proximity of the buildings can be significantly reduced by the coupling. Neglecting of such interactions may lead to excessively conservative estimates of the wind-induced response of the buildings. The presented findings suggest that structural coupling should be included in wind-resistant design of twin tall buildings.

• Wind and Structures
• /
• v.4 no.1
• /
• pp.63-72
• /
• 2001

This paper presents results of a study on wind loads and wind induced dynamic response of bridge jointed twin-towered buildings. Utilizing the high-frequency force balance technique, the drag and moment coefficients measured in wind tunnel tests, and the maximum acceleration rms values on the top floor of towers, are analyzed to examine the influence of building's plan shapes and of intervals between towers. The alongwind, acrosswind and torsional modal force spectra are investigated for generic bridge jointed twin-towered building models which cover twin squares, twin rhombuses, twin triangles, twin triangles with sharp corners cut off, twin rectangles and individual rectangle with the same outline aspect ratio as the twin rectangles. The analysis of the statistical correlation among three components of the aerodynamic force corroborated that the correlation between acrosswind and torsional forces is significant for bridge jointed twin-towered buildings.

• Physical Therapy Rehabilitation Science
• /
• v.10 no.4
• /
• pp.387-397
• /
• 2021

Objective: The purpose of this case study was to investigate selective region high-frequency diathermy at trigger points with therapeutic exercises on pain, function, balance and gait in older patients with degenerative knee osteoarthritis (DKO). Design: A case report. Methods: The patient who participated in this study was a 71-year-old woman, who had been diagnosed with moderate osteoarthritis with grade II Kellgren & Lawrence grading scale. The intervention consisted of selective region high-frequency diathermy at trigger points, with hip and knee stretching and strengthening exercises. The participant was given assessments before and after every intervention session using the Visual Analogue Scale (VAS), Western Ontario and McMaster Universities Arthritis Index (WOMAC), the Timed Up and Go test (TUG) and the 10 Meter Walk Test (10MWT). The participant performed the intervention 18 times for a total of 30 minutes each. Results: As a result of this study, the patient VAS decreased to 3 points, and the WOMAC decreased to 53 points. In addition, the TUG decreased to 3.25 s and the 10MWT decreased to 1.14 s. Conclusions: The results of this study suggest that selective region high-frequency diathermy at trigger points with therapeutic exercises may be an effective intervention to decrease pain, improve knee function, balance and gait in patients with DKO. The selective region high-frequency diathermy with therapeutic exercises may be feasible and provide potential benefits for rehabilitation of DKO.

• Journal of Biomedical Engineering Research
• /
• v.18 no.1
• /
• pp.37-44
• /
• 1997

In this paper, the power spectral analysis of heart rate variability(HRV) was performed to evaluate effects of orthostatic stress with head-up tiIt on autonomic nervous system(ANS) for 25 healthy male subjects(age : 24 $\pm$ 5 yr.) and a new method was proposed to assess the autonomic balance. The ECG and respiration signals were recorded at tiIt angles of $0^{\circ}$, $45^{\circ}$, $90^{\circ}$and $0^{\circ}$ successively for 10 minutes per each stage under the condition of frequency controlled respiration(0.25Hz). Heat rate(HR) gradually increased ils the angle increased Similarly, according to the increment of angle, normalized low frequency component(0.05-0.15Hz) gradually increased, whereas normalized high frequency component (0.20-0.30Hz) was reduce4 From these results it is speculated that orthostatic stress head-up tiLt, results in the prevalence of sympathetic tone in autonomic balance with the increment of sympathetic tone and the decrement of parasympathetic tone, which seems to meanthat autonomic nervous system plays a major role in compensating for disturbances of cardiovascular system due to it.

• The Journal of Korean Physical Therapy
• /
• v.25 no.3
• /
• pp.136-142
• /
• 2013

Purpose: The application of transcutaneous electrical nerve stimulation (TENS) is beneficial for joint movements, inhibition of spasticity, and the improvement of walking ability in patients with chronic hemiplegia. This study aimed to identify the effect of the application of TENS to the knee extensor on the affected side with respect to postural-sway distance and velocity during the sit-to stand movement. Methods: We included 19 patients with post-stroke hemiplegia in this study. They underwent measurements during the sit-to stand movement on a force plate with 5 different stimulation dosages applied over 7 s:No TENS, high-frequency and high intensity TENS, high-frequency and low intensity TENS, low-frequency and high intensity TENS, and low-frequency and low intensity TENS The 5 different condition were administered in random order. Results: The group that received TENS application exhibited a significant decrease in path length and average velocity of center of pressure (COP) displacement compared with the group that did not receive TENS application. TENS dosage at low frequency (3Hz) and high intensity yielded a significant decrease in path length, average velocity, mediolateral distance and anteroposterior distance of COP displacement (p<0.05). Conclusion: Our results demonstrated the effectiveness of the application of low-frequency TENS on STS performance. These findings provide useful information on the application of TENS for the reduction of postural sway during the sit-to-stand movement after stroke.

• Proceedings of the KIPE Conference
• /
• 1998.07a
• /
• pp.90-94
• /
• 1998

The parallel inverter is popularly used because of its fault-tolerance capability, high-current outputs at constant voltages and system modularity. The conventional parallel inverter usually employes active and reactive power control or frequency and voltage droop control. However, these approaches have the disadvantages that the response time of parallel inverter control is slow against load and system parameter variation to calculate active, reactive power, frequency and voltage. This paper describes a novel control scheme for power equalization in parallel connected inverter. The proposed scheme has a fast power balance control response, a simplicity of implementation, and inherent peak current limiting capability since it employes a instantaneous current/voltage control with output voltage and current balance and output voltage regulation. A design procedure for the proposed parallel inverter controller is presented. Futhermore, the proposed control scheme is verified through the simulation in various cases such as the system parameter variation, the control parameter variation and the nonlinear load condition.

• Proceedings of the KIPE Conference
• /
• 1998.10a
• /
• pp.176-181
• /
• 1998

The parallel inverter is popularly used because of its fault-tolerance capability, high-current outputs at constant voltages and system modularity. The conventional parallel inverter usually employs active and reactive power control of frequency and voltage droop control. However, these approaches have the disadvantages that the response time of parallel inverter control is slow against load and system parameter variation to calculate active, reactive power, frequency and voltage. This paper describes a novel control scheme for power equalization in parallel-connected inverter. The proposed scheme has a fast power balance control response, a simplicity of implementation, and inherent peak current limiting capability since it employees an instantaneous current/voltage control with output voltage and current balance and output voltage regulation. A design procedure for the proposed parallel inverter controller is presented. Furthermore, the proposed control scheme is verified through the experiment in various cases such as the system parameter variation, the control parameter variation and the nonlinear load condition.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.3
• /
• pp.1207-1212
• /
• 2013

The purpose of this study was to examine the effect of transcutaneous electrical nerve stimulation (TENS) according to frequency and intensity on postural sway distance and velocity. TENS was applied to posterior aspect of the dominant leg with postural sway during one leg stance. Twenty-four healthy participants were measured while standing on a force platform with 5 different stimulation dosages of no TENS, high frequency and high intensity, high frequency and low intensity, low frequency and high intensity, low frequency and low intensity applied in 30 seconds. The five different dosages were performed with vision in random order. The results indicated that TENS dosage in the high frequency and low intensity had a significant decrease in postural sway(p<.05). From these results, we concluded that TENS delivered a high frequency and low intensity enhanced the postural sway in healthy adults. We expect that the postural sway of patients with decreased balance will reduce by application of TENS.

• Journal of Power Electronics
• /
• v.18 no.6
• /
• pp.1683-1696
• /
• 2018

Under the conventional control strategy, the asymmetry of arm impedances may result in the poor operating performance of modular multilevel converters (MMCs). For example, fundamental frequency oscillation and double frequency components may occur in the dc and ac sides, respectively; and submodule (SM) capacitor voltages among the arms may not be balanced. This study presents an enhanced control strategy to deal with these problems. A mathematical model of an MMC with asymmetric arm impedance is first established. The causes for the above phenomena are analyzed on the basis of the model. Subsequently, an enhanced current control with five integrated proportional integral resonant regulators is designed to protect the ac and dc terminal behavior of converters from asymmetric arm impedances. Furthermore, an enhanced capacitor voltage control is designed to balance the capacitor voltage among the arms with high efficiency and to decouple the ac side control, dc side control, and capacitor voltage balance control among the arms. The accuracy of the theoretical analysis and the effectiveness of the proposed enhanced control strategy are verified through simulation and experimental results.

• Current Applied Physics
• /
• v.18 no.11
• /
• pp.1368-1374
• /
• 2018

In this paper, forced vibration was used to regulate the droplet migration, fully recording the transient migration of droplets on a micro-textured substrate under the resonance frequency by a high-speed camera. The influence of resonance frequency and dynamic migration characteristics of droplets on the solid micro-texture surface under lateral vibration were researched. The experiment demonstrates that the driving force is caused by the difference between the left and right contact angles made the droplet oscillate and migrate, and as time t increases, the left and right contact points are periodically shifted and the amplitude of migration increases. Therefore, based on the droplet migration behavior and its force balance mechanism, a spring vibration model of migration behavior of the vibrating droplet micro unit was set up to predict the complete trajectory of its migration on a solid surface. The calculation results show that the theoretical displacement is less than the experimental displacement, and the longer the time, the larger the difference. Affected by the vibration, part of the droplet permeates through the micro-texture, resulting in the droplet losing height and the contact angle becoming smaller as well. While the other part of droplet overcomes the internal surface tension to migrate.