• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.43 no.7
• /
• pp.1206-1213
• /
• 1994

This paper presents the operation principle and design rule of the Rogowski coil which can measure the transient current and describes the calibration and application experimental results for performance evaluation. It is obtained that the response curves of the Robowski coil with the turns of 300 and the passive integrator to sinusoidal input give a good linearity up to the frequency of 500 [kHz] and the current measurement system gaving the Rogowski coil is the frequency bandwidth of 40 [Hz]~700 [kHz]. As an application experiment for the fabricated modeling power transmission line, the impulse current, which limitates the direct lightning return stroke to overhead ground wire, is measured by the Rogowski coil and its fast Fourier transformation is carried out. The equivalent circuit of the Rogowski coil considering the stray capacitances is proposed, and the theoretical analysis is in good agreement with the measurement results. Also, it is found that for high frequency domain the stray capacitance such as a distributed capacitance to the shield and the capacitance between windings of coil should be considered in designing the Rogowski coils since the resonance originates from the stray capacitance and the self-inductance of the Rogowski coil.

• Journal of the Korean Society of Combustion
• /
• v.19 no.1
• /
• pp.29-38
• /
• 2014

This paper described an experimental investigations of combustion instability mode in a lean premixed dual swirl combustor for micro-gasturbine system. When such the instability occurs, a strong coupling between pressure oscillations and unsteady heat release excites a self-sustained acoustic wave which results in a loud, annoyed sound and may also lead a structural damage to the combustion chamber. The detailed period of flame behavior and heat release in combustion instability mode have been examined with high speed OH and CH-PLIF system and $CH^*$ chemiluminescence measurement, flame tomography with operated at 10 kHz and 6 kHz each. Experiment results suggest that unstable flame behavior has a specific frequency with 200 Hz and this frequency is accords with about 1/2 sub-harmonic of combustor resonance frequency, not fundamental frequency. This is very interesting phenomenon that have not reported yet from other previous works. Therefore, when a thermo-acoustic instability with Rayleigh criterion occurs, the fact that the period of heat release and flame behavior are different each other was proposed for the first time through this work.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.23 no.7
• /
• pp.624-630
• /
• 2013

In this study, a parametric study is performed to investigate the squeal noise of an automobile water pump. The squeal noise studied in this paper is generated by the self-excited torsional resonance of the rotating shaft, and this noise is related to the stick-slip phenomenon of the mechanical seal in the water pump. The mechanical seal friction has the characteristics of the negative velocity-gradient. The equations of motion of multiple-degree-of-freedom torsional vibration model is constructed by the Holzer's method and then the equation is transformed to an equivalent single-degree-of-freedom torsional resonance simulation model. A squeal noise criteria is determined by the simulation model to perform the parametric study. The design parameters(the mass moment of inertia of the pulley, the mass moment of inertia of the impeller, the length of the shafts, the radius of the shafts, spinning speed of the shafts, the position of the mechanical seal, radius of the mechanical seal, and normal load of the mechanical seal) are investigated to confirm the stability for the squeal noise.

• Journal of the Society of Naval Architects of Korea
• /
• v.43 no.1 s.145
• /
• pp.22-31
• /
• 2006

Recent studies have shown that the short time solution of the equation of motion for the rolling of ships is important in deciding the possibility of capsize of ships due to the excessive heel. Since most of known solutions for nonlinear equations of motion are long time or steady periodic solutions, here a simple way is described to get the short time solutions of the Duffing equation, which was chosen for deriving a criterion for the capsize of the ship. With the small external rolling moment, we first assume the state of the small damping and near resonance. Then, for cases when the frequency of the external moment is higher than the resonant one, an inequality was derived as a criterion for the capsize. This gives the range of the initial condition and the magnitude of the external moment which should be avoided for a ship to be safe from capsize. Furthermore, from the linearized equation, it is also shown that a simple and self-explanatory solution can be obtained consistent with that for the case of no damping, which yields the well-known linear growth with time.

• Journal of Powder Materials
• /
• v.28 no.5
• /
• pp.429-434
• /
• 2021

Magnetic nanoparticles have a significant impact on the development of basic sciences and nanomedical, electronic, optical, and biotech industries. The development of magnetic structures with size homogeneity, magnetization, and particle dispersibility due to high-quality process development can broaden their utilization for separation analysis, structural color optics using surface modification, and energy/catalysts. In addition, magnetic nanoparticles simultaneously exhibit two properties: magnetic and plasmon resonance, which can be self-assembled and can improve signal sensitivity through plasmon resonance. This paper reports typical examples of the synthesis and properties of various magnetic nanoparticles, especially magnetoplasmonic nanoparticles developed in our laboratory over the past decade, and their optical, electrochemical, energy/catalytic, and bio-applications. In addition, the future value of magnetoplasmonic nanoparticles can be reevaluated by comparing them with that reported in the literature.

• Nuclear Engineering and Technology
• /
• v.55 no.12
• /
• pp.4518-4526
• /
• 2023

NECP-SARAX is a neutronics analysis code system for advanced reactor developed by Nuclear Engineering Computational Physics Laboratory of Xi'an Jiaotong University. In past few years, improvements have been implemented in TULIP code which is the cross-section generation module of NECP-SARAX, including the treatment of resonance interface, considering the self-shielding effect in non-resonance energy range, hyperfine group method and nuclear library with thermal scattering law. Previous studies show that NECP-SARAX has high performance in both fast and thermal spectrum system analysis. The accuracy of TULIP code in fast and thermal spectrum system analysis is demonstrated preliminarily. However, a systematic verification and validation is still necessary. In order to validate the applicability of TULIP code for full energy range, 147 fast spectrum critical experiment benchmarks and 170 thermal spectrum critical experiment benchmarks were selected from ICSBEP and used for analysis. The keff bias between TULIP code and reference value is less than 300 pcm for all fast spectrum benchmarks. And that bias keeps within 200 pcm for thermal spectrum benchmarks with neutron-moderating materials such as polyethylene, beryllium oxide, etc. The numerical results indicate that TULIP code has good performance for the analysis of fast and thermal spectrum system.

• Investigative Magnetic Resonance Imaging
• /
• v.17 no.1
• /
• pp.59-62
• /
• 2013

There are various types of foreign body reactions, such as inflammation, edema, fluid collection, hematoma, infection, abscess and granulomas. There are various imaging findings according to types of foreign bodies and depending on the lapse of time. Therefore, correct diagnosis of a foreign body reaction is difficult and easily confused with soft tissue neoplasm. The MRI is ideal for the detection of foreign bodies regardless of radiolucency or acoustic impedance. It is especially very useful in the evaluation of the surrounding tissue reaction. The authors report a case of a 26-year-old female patient with both forearm swelling due to self-injection of a mixture of powdered tablets and saline. The lesion shows numerous internal T1 and T2 dark signal intensity micro-spots with surrounding fluid collection, which are diagnosed as foreign bodies with surrounding inflammatory changes during an operation.

• Journal of the Korean Magnetics Society
• /
• v.24 no.6
• /
• pp.191-196
• /
• 2014

The purpose of this study is to evaluate the reproducibility and usefulness of an image through the fusion of the computed tomography image and the magnetic resonance image by using a self-produced phantom when planning the treatment, and also to compare and analyze the target dose on the acquired image. The size of small hole and the reproducibility of capacity existed in the phantom on the image of the phantom obtained by the computed tomography and the magnetic resonance image of the phantom scanning with different intensity of magnetic field are compared, and the change of dose in the random target is compared and analyzed.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.42 no.2 s.302
• /
• pp.33-38
• /
• 2005

In this paper, the sensing unit of a non-invasive blood glucose sensor for home users, using a magneto-resonance absorption method, have been designed and manufactured. The sensor is capable of non-invasively determining blood glucose levels through measuring the 1H spin-lattice relaxation time in human body, The comparison of initial models, with different dimensions and shapes, for the sensing unit has led us to select the materials of the final model, which has adequate size and weight for home use. Through the design optimization using the FEM model, the dimension of final model has been determined to satisfy the required strength and uniformity of the magnetic field in the detecting area.

• The Journal of the Korea Contents Association
• /
• v.18 no.9
• /
• pp.346-356
• /
• 2018

The Purpose of this study is to examine the effect of communication competence and empathy on stress coping in college students. The research problems were verified by correlation analysis and multivariate regression analysis. A questionnaire survey was conducted on 292 college students. The findings are as follows. First, college students who have high communication competence show more problem-focused coping, social-support seeking coping, and self-soothing coping in stressful conditions, but less emotion-oriented coping and avoidance-oriented coping. Particularly, it is found that behavioral flexibility in communication competence has the greatest effect on problem-focused coping and emotion-oriented coping. Similarly, affiliation/support influences social support seeking coping, interaction management influences self-soothing coping and avoidance-oriented coping. Second, college students who have high empathy are also found more problem-focused coping, social-support seeking coping, and self-soothing coping in stressful conditions. Especially it is found that role-taking in empathy has the greatest effect on problem-focused coping self-soothing coping. Similarly, emotion recognition influences avoidance-oriented coping, emotional resonance influences emotion-oriented coping, authenticity influences social-support seeking coping.