• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3191-3196
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• 2013

Ultrasonic transducer is the sensor which is measuring distance. Piezo ceramic of ultrasonic sensor and adhesive technique of matching layer are the most core techniques. With the study of relation on matching layer which takes off the ultrasonic wave into the air, this paper aims to find the second useful frequency as the results which can be changed are extracted in case piezo ceramic and matching layer are bonded. And the experiment is done with piezo ceramic as real piezoelectric element and matching layer of chemical wood. OD of piezo ceramic has designed by ${\Phi}50{\times}3T$ and OD of matching layer is designed by ${\Phi}62{\times}12t$ with ${\lambda}=1/4$. Acoustic impedance is generated at the most optimum resonant frequency of 53 Khz. As experimental result, more available frequency can be generated by using the adhesive close to solid than the flexible one.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.11
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• pp.874-882
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• 2003

The condition assessment of engineering systems has increased in importance because the manpower needed to operate and supervise various plants has been reduced. Especially, induction motors are at the core of most engineering processes, and there is an indispensable need to monitor their health and performance. So detection and diagnosis of motor faults is a base to improve efficiency of the industrial plant. In this paper, a model-based fault detection system is developed for induction motors, using steady state vibration signals. Early various fault detection systems using vibration signals are a trivial method and those methods are prone to have missed fault or false alarms. The suggested motor fault detection system was developed using a model-based reference value. The stationary signal had been extracted from the non-stationary signal using a data segmentation method. The signal processing method applied in this research is FFT. A reference model with spectra signal is developed and then the residuals of the vibration signal are generated. The ratio of RMS values of vibration residuals is proposed as a fault indicator for detecting faults. The developed fault detection system is tested on 800 hp motor and it is shown to be effective for detecting faults in the air-gap eccentricities and broken rotor bars. The suggested system is shown to be effective for reducing missed faults and false alarms. Moreover, the suggested system has advantages in the automation of fault detection algorithms in a random signal system, and the reference model is not complicated.

• Journal of Environmental Science International
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• v.29 no.1
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• pp.1-13
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• 2020

Recently, a heavy rainfall with high spatial variation occurred frequently in the Korean Peninsula. The meteorological event that occurred in Busan on 3 May 2016 is characterized by heavy rain in a limited area. In order to clarify the reason of large spatial variation associated with mountain height and location of low level jet, several numerical experiments were carried out using the dynamic meteorological Weather Research and Forecasting (WRF) model. In this case study, the raised topography of Mount Geumjeong increased a barrier effect and air uplifting due to topographic forcing on the windward side. As a result, wind speed reduced and precipitation increased. In contrast, on the downwind side, the wind speed was slightly faster and since the total amount of water vapor is limited, the precipitation on the downwind side reduced. Numerical experiments on shifting the location of the lower jet demonstrated that if the lower jet is close to the mountain, its core becomes higher due to the effect of friction. Additionally, the water vapor convergence around the mountain increased and eventually the precipitation also increased in the area near the mountain. Hence, the location information of the lower jet is an important factor for accurately predicting precipitation.

• Journal of the Korean earth science society
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• v.37 no.4
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• pp.200-210
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• 2016

Geoacoustic modeling is used to predict sound transmission through submarine bottom layers of sedimentary strata and acoustic basement. This study reconstructed four geoacoustic models for sediments of 50 m thick at the Jeongdongjin area in the western continental margin of the East Sea. Bottom models were based on the data of the highresolution air-gun seismic and subbottom profiles (SBP) with sediment cores. P-wave speed was measured by the pulse transmission technique, and the resonance frequency of piezoelectric transducers was maintained at 1MHz. Measurements of 42 P-wave speeds and 41 attenuations were fulfilled in three core sediments. For actual modeling, the P-wave speeds of the models were compensated to in situ depth below the sea floor using the Hamilton method. These geoacoustic models of coastal bottom strata will be used for geoacoustic and underwater acoustic experiments reflecting vertical and lateral variability of geoacoustic properties in the Jeongdongjin area of the East Sea.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.5
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• pp.409-416
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• 2006

Operating Characteristics of LLC Series resonant converter with a LLT(Inductor-Inductor-Transformer) transformer is presented. LLT transformer used to combine the inductor and transformer into one unit has the increased leakage inductance in the primary and secondary due to the winging method and the use of the gaped core. The increased leakage inductance in the primary and secondary of LLT transformer can be impacted on the DC voltage gain characteristics of LLC series resonant converter. In the paper, DC gain characteristics and the experimental results of the LLC series resonant converter with a LLT transformer are verified on the simulation based on the theoretical analysis and the 400W experimental prototype.

• Textile Coloration and Finishing
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• v.22 no.2
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• pp.173-179
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• 2010

In this study, we determine the stretch and shrinkage properties of conjugated yarns. The shrinkage(%) and elasticity(%) were determined by applying twist conditions of 0, 350, 800, 1000, 1200, 1400, 1600, 2000 T/M (twisting per meter). It is found that the shrinkage(%) and elasticity(%) gradually decreased with increasing T/M. Especially the elasticity(%) dramatically decreased over 1400 T/M condition. In contrast, it is showed that the handle and drapery properties decreased below 1000 T/M, which indicates that the optimal T/M condition could be 1000~1400. The effect of shrinkage(%) and elasticity(%) with different steam setting temperatures (60, 70, 80 and $90^{\circ}C$) was also determined. The shrinkage(%) decreased with increasing setting temperature, while the elasticity not changed. In this context, the optimal steam setting temperature could be $80^{\circ}C$ because it is not easy to weave with the yarns which was set below $80^{\circ}C$. The elasticity(%) decreased with increasing the density of warp and weft. To produce soft handle, excellent drapery and good stretch fabrics, the warp density needs to be reached by 90% of the ideal warp density. In the case of NaOH treatments to the fabrics, the elasticity(%) increased with increasing weight reduction. Therefore, this study have demonstrated that the conjugated yarns with core yarn and the SDY CD(cation dyeable spindraw yarn) as an effect yarn would be appropriate to produce excellent mixture-yarn, which displays clean appearance, good handle and excellent elasticity, The optimized conditions are as follows; 1000~1200 twist per meter, $80^{\circ}C$ steam setting temperature, 90% of ideal warp density and relaxation condition treated with 5g/l NaOH concentration.

• Journal of Broadcast Engineering
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• v.11 no.1 s.30
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• pp.107-115
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• 2006

In the environment of single application data broadcasting, only one application can be serviced at a specific time on one channel. To overcome this, we developed the structure and the method of operation for multi-applications which are fully conformant to the ACAP (Advanced Common Application Platform), and modified data broadcasting system to support multi-applications. In multi-application environment, broadcasters can service multiple applications simultaneously at a specific airtime on one channel so users can enjoy services selectively according to their preferences. In this paper, we present an example of multi-application service which was developed to make an experiment before servicing them to users on the air. The core of the multi-application is a manager application which manages other ordinary applications, so we describe the function and structure of the manager application, and then present the experimental results to show that the proposed method is the proper model for multi-applications.

• Korean Journal of Medicinal Crop Science
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• v.7 no.3
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• pp.172-176
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• 1999

The saponins are considered the main effective components in Platycodon grandiflorum (Jacq.) A. DC.. In order to obtain the basic information for producing the high quality medicinal plant and processing, the crude saponin contents were analyzed with platycodi radix, the root of Platycodon grandiflorum by different cultivating years, parts, harvesting times and drying methods. The crude saponin contents were decreased by increasing cultivating years. The crude saponin contents were 2.74% in tail of root and 1.65 % in head of root, respectively. Besides, the contents of the crude saponin in cortex were 1.8 times more than that in core of root. The crude saponin contents in different harvesting times were 2.82% and 2.74% at March 10 and December 10, showing higher than that being harvested at June 10 and September 10. The crude saponin contents among drying methods were not significantly different at 5% level DMRT, but the hot air drying after steam showed the least crude saponin.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.11-17
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• 2011

A major source of durability problems in concrete structures is the corrosion of steel by the damage of passivity layer around steel bars. As chloride ion penetration is major cause of the destruction of passivity layer, evaluation of depth and concentration profile of chloride ion is the essential factor for the service-life estimation of concrete structure. To estimate chloride ion penetration characteristics, this paper on the basis of in-situ experimental data investigated the depth and concentration profile of chloride ion penetration. The core specimens are obtained at air-zone, splash zone, and tidal zone in Wando, Masan, Incheon, Gwangyang, and donghae harbors. Colorimentric method measured the chloride ion penetration depth and ASTM C 114 evaluated the concentration profile of chloride ion. Based on experimental data, the influence of harbor location and exposure condition on chloride ion penetration is evaluated.

• Journal of the Korean Institute of Rural Architecture
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• v.22 no.3
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• pp.49-60
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• 2020

The purpose of this study utilizes the service design methodology centered on the lives and experiences of rural residents, who are the main beneficiaries of the service, to derive specific problems and needs, and to propose a service improvement plan suitable for the rural residential environment. The study selected Dosan 2-ri Village, Hongseong-gun, Chungcheongnam-do as the target of the survey, used personas and Customer Journey map of service design method to derive specific core issues and insights from the village residents. By developing this, the final five service directions for 'Air care service', 'Self-driving garbage collection and treatment service', 'Emergency/disaster networking service', 'Contaminant removal service' and 'Mobility share service' were derived and presented according to each key keyword. This study is not just a study to grasp the actual conditions of the rural residential environment, but it focuses on the lives and experiences of rural residents and extracts elements that can respond to changes in the lifestyles and patterns of the residents. It can be used as a basic material for more realistic improvement of rural residential environment and service development research. Most of the existing studies on residential environments and spaces is focused on urban areas, and there is a limit to the use of rural areas in residential areas. Therefore, by making recommendations for improvement of residential environment services suitable for rural areas and by creating residential spaces and environments in rural areas in a comfortable and safe manner, it is thought that it is possible to contribute to improvement of satisfaction in rural areas and improvement of healthy housing welfare as well as to improvement of the quality of life of residents of rural areas.