• The Journal of Korean Physical Therapy
• /
• v.26 no.5
• /
• pp.280-289
• /
• 2014

Purpose: This study was conducted in order to determine the stimulation variables which should be considered when neuromuscular electrical stimulation (NMES) is applied for a muscle under the normal innervation to minimize muscle fatigue and increase force-generating ability. Methods: A total of 23 healthy men participated in the study and all subjects were randomly assigned to the 1:1 group, 1:3 group, 1:5 group, and control group with on-off ratio of NMES. The subjects performed a fatigue task, consisting of 10 times of isometric contraction sustained by NMES. NMES using Russian current stimulation was applied to muscle fatigue and divided into three sessions by pulse frequency (10 bps, 30 bps, 90 bps). The EMG was recorded using an MP 100 system from the quadriceps femoris muscle in four groups. Results: The differences of delta MdF and delta MF of between on-off ratio groups of 10 bps, 30 bps, and 90 bps pulse frequencies were very significant (p<0.05). According to the results of post hoc of 10, 90 bps, it was greater in the 1:1 group and the 1:3 group compared with the 1:5 group, and no fatigue was observed in the control group. In 30 bps, it was greater in the 1:1 group compared with 1:3, 1:5, and control group (p<.05). Conclusion: Among NMES variables to minimize muscle fatigue, the larger on-off ratio by pulse frequency showed the lower muscle fatigue. Therefore, on-off ratio needs to be great enough, and will be more efficient with the frequency 30 bps rather than of 10 bps and 90 bps.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.31 no.5
• /
• pp.543-551
• /
• 2011

Steam generator tubes for nuclear power plants contain the local shape transitions on their inner or outer surface such as dent, bulge, over-expansion, eccentricity, deflection, and so on by the application of physical force during the tube manufacturing and steam generator assembling and by the sludge (that is, corrosion products) produced during the plant operation. The structural integrity of tubes will be degraded by generating the corrosive crack at that location. The profilometry using the traditional bobbin probes which are currently applied for measuring the profile change of tubes gives us basic information such as axial locations and average magnitudes of deformations. However, the three-dimensional quantitative evaluation on circumferential locations, distributional angle, and size of deformations will have to be conducted to understand the effects of residual stresses increased by local deformations on corrosive cracking of tubes. Steam generator tubes of Korean standard nuclear power plants expanded within their tube-sheets by the explosive expansion method and suffered from corrosive cracks in the early stage of power operation. Thus, local deformations of steam generator tubes at the top of tube-sheet were measured with an advanced rotating probe and a laser profiling system for the two cases where the tubes expanded by the explosive expansion method and hydraulic expansion. Also, the trends of eccentricity, deflection, and over-expansion of tubes were evaluated. The advanced eddy current profilometry was confirmed to provide accurate information of local deformations compared with laser profilometry.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.23 no.3
• /
• pp.313-322
• /
• 2005

Rapid advances in technology and changes in human and cultural activities bring about changes to the earth surface in terms of spatial extension as well as time frame of the changes. Such advances introduce shorter updating frequency of maps and geospatial database. To satisfy these requirements, recent research efforts in the geoinformatics field have been focused on the automation and speeding up of the mapping processes which resulted in products such as the digital photogrammetric workstation, GPSIINS, applications of satellite imagery, automatic feature extraction and the LiDAR system. The possibility of automatically extracting buildings and generating contours from airborne LiDAR data has received much attention because LiDAR data produce promising results. However, compared with the manually derived building footprints using traditional photogrammetric process, more investigation and analysis need to be carried out in terms of accuracy and efficiency. On the other hand, generation of the contours with LiDAR data is more efficient and economical in terms of the quality and accuracy. In this study, the effects of various conditions of the pre-processing phase and the subsequent building extraction and contour generation phases for digital mapping have on the accuracy were investigated.

• Journal of Korea Multimedia Society
• /
• v.9 no.9
• /
• pp.1131-1138
• /
• 2006

This paper proposes a novel method for grading of underground communication conduits by laser projection image analysis. The equipment thrust into conduit consists of a laser diode, a light emitting diode and a camera, the laser diode is utilized for generating projection image onto pipe wall, the light emitting diode for lighting environment and the image of conduit is acquired by the camera. In order to segment profile region, we used a novel color difference model and multiple thresholds method. The shape of profile ring is represented as a minimum diameter and the Fourier descriptor, and then the pipe status is graded by the rule-based method. Both local and global features of the segmented ring shaped, the minimum diameter and the Fourier descriptor, are utilized, therefore injured and distorted pipes can be correctly graded. From the experimental results, the classification is measured with accuracy such that false alarms are less than 2% under the various conditions.

• Tribology and Lubricants
• /
• v.33 no.2
• /
• pp.52-58
• /
• 2017

An ultra-high precise ejection process is essential in a dispensing system for fabricating various precision parts such as a semiconductor, LED, and camera module. The size of such parts has been decreasing, which implies that a precise ejecting technique is required. A phosphor-containing liquid is ejected via a dispenser using dual piezoelectric actuators that are used for generating a high-speed dispensing mechanism. The rod and nozzle continuously contact in high speed to eject the liquid. However, the high-strength filler or phosphor in the liquid causes wear on the surfaces of the rod and nozzle during the dispensing process. As a result, the ejection reliability decreases as the wear on the surfaces increases. Therefore, it is necessary to estimate the wear characteristics of the rod and nozzle via an experiment and FE analysis. Reliability rests up to 1,000 cycles are conducted under relatively severe conditions. The flow rate and surfaces roughness of the rod and nozzle are measured in each ejection cycle. The surface images and wear volume are obtained before and after the tests and the ejection reliability is confirmed by measuring the flow rate of the liquid. The experimental results show that the ejection reliability is maintained up to 1,000k cycles; these results are validated by the simulation results.

• Journal of the korean society of oceanography
• /
• v.37 no.3
• /
• pp.154-159
• /
• 2002

Satellite remote sensing technology for ocean observation has evolved considerably in these last twenty years. Ocean color is one of the most important parameters of ocean satellite measurements. This paper describes a remote sensing of ocean color data project - Asian I-Lac Project; it also introduces several case studies using satellite images in the Asian waters. The Asian waters are related to about 30 Asian countries, representing about 60% of the world population. The project aims at generating long-term time series images (planned for 10 years from 1996 to 2006) by combining several ocean color satellite data, i.e., ADEOS-I OCTS and SeaWiFS, and some other sensors. Some typical parameters that could be measured include Chlorophyll- a (Chl-a), Colored Dissolved Organic Matter (CDOM), and Suspended Material (SSM). Reprocessed OCTS images display spatial variation of Chl-a, CDOM, and SSM in the Asian waters; a short term variability of phytoplankton blooms was observed in the Gulf of Oman in November 1996 by analyzing OCTS and NOAA sea surface temperature (SST)； Chl-a concentrations derived from OCTS and SeaWiFS have also been evaluated in coastal areas of the Taiwan Strait, the Gulf of Thailand, the northeast Arabian Sea, and the Japan Sea. The data system provides scientists with capability of testing or developing ocean color algorithms, and transferring images for their research. We have also analyzed availability of OCTS images. The results demonstrate the potential of long-term time series of satellite ocean color data for research in marine biology, and ocean studies. The case studies show multiple applications of satellite images on monitoring of coastal environments in the Asian Waters.

• Journal of Environmental Science International
• /
• v.23 no.4
• /
• pp.561-569
• /
• 2014

The water resources system of Jeju-do Island entirely depends on groundwater. This study is making a precision observation of baseflow, surface water, water shortage that might be vulnerable to climate change and drought in future. The field observation of baseflow discharges in Akgeuncheon stream has regularly been made with ADCP and ADC and Flowmate every two weeks for twenty-two (22) months (July 8, 2011 to April 27, 2013). This paper represent the results of calculating discharge of a number of hydraulic structures (broad-crested weirs) with comparing and has been calculated more accurate discharges with suitability of different observation methods. The average discharge has been observed 0.851 $m^3/s$, whereas the average ADC and Flowmate is 0.709 $m^3/s$. Meanwhile, stream discharge has been calculated 0.709 $m^3/s$ through the broad-crested weir equation. The discharge has calculated with the weir equation greatly changed according to even a small change in the water level. However, it showed a similar trend to one of the observed discharge. Although, in past there were generating errors caused by observers' strides, vertical and horizontal flow velocity distribution when the average flow velocity had been measured, non-prismatic flow, turbulent flow and others in ADC. This study comes up with the weir equation is more suitable for the characteristics of Jeju-do could be presented through an observations of baseflow discharge.

• Journal of Convergence for Information Technology
• /
• v.12 no.4
• /
• pp.9-13
• /
• 2022

In this paper, the tracking error of monopulse radar caused by cross-eye jamming using terrain bounce is analyzed. Cross-eye jamming is a method of generating an error in a radar tracking system by simultaneously transmitting two signals with different phases and amplitudes. When the monopulse radar receives the cross-eye jamming signal generated by the terrain bounce, a tracking error occurs in the elevation direction. In the presence of multipath, this signal is a combination of the direct target return and a return seemingly emanating from the target image beneath the terrain surface. Terrain bounce jamming has the advantage of using a single jammer, but the space affecting the jamming is limited by the terrain reflection angle and the degree of scattering of the terrain. This study can be usefully used to protect ships from low-altitude missiles or aircraft in the sea.

• Progress in Medical Physics
• /
• v.34 no.3
• /
• pp.33-39
• /
• 2023

Purpose: FLASH radiotherapy (RT) using ultra-high dose rate (>40 Gy/s) radiation is being studied worldwide. However, experimental studies such as preclinical studies using small animals are difficult to perform due to the limited availability of irradiation devices and methods for generating a FLASH beam. In this paper, we report the initial dosimetry results of a prototype electron linear accelerator (LINAC)-based irradiation system to perform ultra-high dose rate (UHDR) preclinical experiments. Methods: The present study used the prototype electron LINAC developed by the Research Center of Dongnam Institute of Radiological and Medical Sciences (DIRAMS) in Korea. We investigated the beam current dependence of the depth dose to determine the optimal beam current for preclinical experiments. The dose rate in the UHDR region was measured by film dosimetry. Results: Depth dose measurements showed that the optimal beam current for preclinical experiments was approximately 33 mA, corresponding to a mean energy of 4.4 MeV. Additionally, the average dose rates of 80.4 Gy/s and 162.0 Gy/s at a source-to-phantom surface distance of 30 cm were obtained at pulse repetition frequencies of 100 Hz and 200 Hz, respectively. The dose per pulse and instantaneous dose rate were estimated to be approximately 0.80 Gy and 3.8×10⁵ Gy/s, respectively. Conclusions: Film dosimetry verified the appropriate dose rates to perform FLASH RT preclinical studies using the developed electron-beam irradiator. However, further research on the development of innovative beam monitoring systems and stabilization of the accelerator beam is required.

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.6
• /
• pp.476-483
• /
• 2016

An organic Rankine cycle for ocean thermal energy conversion system is a generating cycle using the temperature difference between surface water and deep water of the ocean. The working fluid is an important factor in the thermodynamic performance of an organic Rankine cycle. There is pinch point analysis as thermodynamic analysis of an organic Rankine cycle. This study performed a thermodynamic performance analysis according to variation in the pinch point temperature difference in heat exchangers and variation of outlet temperature of heat source and heat sink. It analyzed the thermodynamic performance by applying seven types of simple working fluids in a simple Rankine cycle for ocean thermal energy conversion that was designed according to pinch point analysis. As a result of the performance analysis, cycle irreversibility and total exergy destruction factor more decreased, and second law efficiency more increased in the lower pinch point temperature difference and temperature variation of heat source and heat sink in heat exchangers. In addition, the irreversibility changed greatly at a point that occurred in the thermodynamic variation. Among the selected working fluids, RE245fa2 showed the best thermodynamic performance, and the performance of all working fluids was observed to be similar. It needs a strict theoretical basis about diverse factors with thermodynamic performances in selecting heat exchangers and working fluids.