• Journal of Power Electronics
• /
• v.11 no.6
• /
• pp.880-889
• /
• 2011

In this paper, a novel Active Voltage Quality Regulator (AVQR) topology with a thyristor rectifier and an adaptive dclink voltage control strategy are proposed. The proposed AVQR can efficiently mitigate the long duration variations (e.g. undervoltages/overvoltages), voltage imbalances and voltage harmonics. Compared with conventional AVQRs, it can regulate the load voltage very well with a much lower dc-link voltage. This is accomplished by replacing the diode rectifier with a thyristor rectifier. Moreover, its dc-link voltage can vary with the deviations of the supply voltage through the proposed adaptive dc-link voltage control strategy. All of these contribute to its significantly higher efficiency for online operating, which is very important and attractive for many applications. The proposed topology and control strategy are theoretically analyzed in detail. Simulation results are also provided in the paper. Finally, the feasibility and effectiveness of the proposed method are verified by means of experimental results from a 2kVA prototype. Both of the simulation and experimental results show that the proposed AVQR can achieve a much higher efficiency and similar regulation performance when compared with the conventional ones.

• Physical Therapy Rehabilitation Science
• /
• v.13 no.1
• /
• pp.8-17
• /
• 2024

Objective: This study aims to explore the relationship between isokinetic strength training and the enhancement of physical function in older adults. It also evaluates the effectiveness of isokinetic strength training equipment. Method: This study randomly divided twenty healthy adults into two groups.The experimental group engaged in isokinetic strength training for 30 minutes, three times a week, over a four-week period. In contrast, the control group did not participate in any exercise regimen. We assessed several outcome measures including physical functions (sit-to-stand test, flexibility, Timed Up and Go test), grip strength, balance, thigh circumference, the Korean version of the Patient Health Questionnaire-9 (PHQ-9), and the Korean version of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Additionally, the experimental group's self-perceived improvement in lower limb condition was evaluated using the Global Rating of Change (GROC) scale. Results: The experimental group showed significant improvements compared to the control group in various aspects: reduced sit-to-stand test duration (7.00±2.05 seconds), increased flexibility (4.69±3.90 cm), improved grip strength (1.54±1.74 kg), increased thigh circumference (left: 1.29±1.19 cm, right: 1.19±1.27 cm), enhanced Timed Up and Go test performance (-1.47±0.86 seconds), better balance (eyes open stance: -8.08±4.03 cm, eyes closed stance: -0.27±0.13 cm/s), and a decrease in depression severity (-0.15±1.51 points). Furthermore, significant increases were observed in the experimental group's maximal isokinetic strength at 90°/s for both flexion (19.62±7.03 Nm) and extension (19.60±14.65 Nm) over the study period. Conclusion: The findings suggest that isokinetic strength training equipment can significantly enhance physical functions in seniors when incorporated into an exercise regimen.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.8
• /
• pp.620-626
• /
• 2006

Recently, indoor air quality (IAQ) is one of the greatest problems in our modern societies. Although research for IAQ is made rapid progress but IAQ problems concerning in door microorganism contamination is required to be studied still more. So we have investigated the indoor microorganism concentration of a variety of department store, subway station, underground shopping center, kindergartens, library where people complain about the in-door air quality. The experiment on microorganism concentration of indoor air was carried out and the average of total microorganisms was measured. Comparing the experimental results with existing foreign criterion, the experimental results show that the ministry of environment recommendation microorganism concentration value ($800 CFU/m^3$) is in need of revision in the near future.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.22 no.1
• /
• pp.119-124
• /
• 2013

In this paper, we analysed fatty acid methyl ester contents in the biodiesel which is produced from the newly developed biodiesel production equipment. The lard oil was used as the raw material through various experimental conditions. Thirty one experiments were conducted, which were based on the experimental conditions that designed by central composite design method. The effects of four independent variables, including reaction temperature, reaction time, oil to methanol molar ratio, and catalytic amount, were investigated at five levels using central composite design (CCD). Fatty acid methyl ester content was chosen dependent variable. Although the results of analysis of the surface with an irregular surface geometry showed that the biodiesel was partially impure after the reaction due to the natural characteristics of the lard oil as the raw material, we could confirm the relationship between them from the facts that the production amount of fatty acid methyl ester changes according to reaction temperature, reaction time, oil to methanol molar ratio, and catalytic amount.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.8 no.4
• /
• pp.97-103
• /
• 2009

Since a demand for an extensive range of earthmoving equipment like a hydraulic excavator with a capacity of 85tons has been asked in construction fields, a performance of its track drive unit has to be verified experimentally. Among the verification of the performances, a torque measurement is at issue, in which a torque meter is utilized widely. However, the very large scaled torque meter is necessary when a discharged torque from the track drive unit is increased significantly. In addition, the price for experimental set-up of a torque meter is too high due to its limitation of the geometry such as long length, and a break down in operation occurs frequently. In this study, to measure a high torque up to 200,000Nm, a new technique was proposed as an alternative of conventional measurement by using a torque meter. The new technique enables to measure the high torque stably in a compact space via a torque arm and two load cells. The experimental results showed a propriety of the proposed torque measuring technique for a track drive unit with very large capacity.

• Journal of Institute of Control, Robotics and Systems
• /
• v.14 no.2
• /
• pp.205-211
• /
• 2008

This paper describes the method aimed at establishing the equipment measuring the parameter of Cable Network by Best proper Cable Modem and PDA through RS232 interface. In this paper, we propose our creative experimental configuration and develope the Cable Modem (DOCSIS 2.0) superior more performing than the referred Cable Modem (DOCSIS 1.0, 1.1) and the measuring equipment of HFC network compositing of Cable Modem and PDA through RS232 interface. This equipment analyzes Upstream (U/S) and Downstream (D/S) Signal quality and generates the signal of Upstream by CW signal. The paper also provides the experimental results to check the Best Proper Cable Modem and the displayed screen for parameters for SNR, BER and the demodulated IQ diagram of 256QAM through LCD of PDA. Henceforth, it'll be possible to support a variety of the functions for E-mail, Internet, the speed test of WEB connection and the transmission of the measured result real time by PDA.

• Journal of Sensor Science and Technology
• /
• v.28 no.5
• /
• pp.323-328
• /
• 2019

Recently, a sound wave phase meter (SWPM) that can directly measure the pressure waveform of sound waves in free space has been reported, and the development of educational experimental equipment using this meter is in progress. One of the main advantages of using this meter is that wavelengths can be obtained directly from the crests and troughs of the measured pressure waveforms in space without expensive equipment. However, there are times when the measurement wavelength does not exactly match the actual wavelength value, and the pressure waveform differs from the actual shape. This study was conducted to identify and analyze the causes of such errors occurring in SWPM. As a result, it was found that wavelength errors occur when the propagation direction of sound waves and the measurement direction of SWPM do not coincide. It has also been found that an error in the pressure waveform is generated when the induction and sound wave signal outputs from the SWPM interfere with each other to produce a composite signal. We have shown that we can develop educational experimental equipment by suggesting ways to reduce such errors.

• International journal of advanced smart convergence
• /
• v.12 no.4
• /
• pp.378-385
• /
• 2023

The importance of wearing respiratory protective equipment has been highlighted even more during the COVID-19 pandemic. Even if the suitability of respiratory protection has been confirmed through testing in a laboratory environment, there remains the potential for leakage points in the respirators due to improper application by the wearer, damage to the equipment, or sudden movements in real working conditions. In this paper, we propose a method to detect the occurrence of leak holes by measuring the pressure changes inside the mask according to the wearer's breathing activity by attaching an IoT sensor to a full-face respirator. We designed 9 experimental scenarios by adjusting the degree of leak holes of the respirator and the breathing cycle time, and acquired respiratory data for the wearer of the respirator accordingly. Additionally, we analyzed the respiratory data to identify the duration and pressure change range for each breath, utilizing this data to train a neural network model for detecting leak holes in the respirator. The experimental results applying the developed neural network model showed a sensitivity of 100%, specificity of 94.29%, and accuracy of 97.53%. We conclude that the effective detection of leak holes can be achieved by incorporating affordable, small-sized IoT sensors into respiratory protective equipment.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.157.1-157
• /
• 2001

A new methodology is presented to diagnose faults in equipment plasma. This is accomplished by using neural networks as a pattern recognizer of radio frequency(rf) impedance match data. Using a realtime match monitor system, the match data were collected. The monitor system consisted mainly of a multifunction board and a signal flow diagram coded by Visual Designer. Plasma anomaly was effectively represented by electrical match positions. Twenty sets of fault-symptom patterns were experimentally simulated with experimental variations in process factors, which include rf source power, pressure, Ar and O$_2$ flow rates. As the inputs to neural networks, two means and standard deviations of positions were used ...

• 제어로봇시스템학회:학술대회논문집
• /
• 1989.10a
• /
• pp.663-668
• /
• 1989

Control methods to achieve efficient and accurate deburring robots are proposed. For efficiency, cutting speed is controlled adoptively with the cutting load. For accuracy, it adopts repetitive control. Since usual repetitive control cannot afford dynamical speed changes, the proposed method controls in an interpolating manner using several waveforms stored in the controller. Successful experimental results axe shown.