• Restorative Dentistry and Endodontics
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• v.26 no.2
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• pp.134-140
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• 2001

The polymerization shrinkage of composite resins is an important drawback although the composites have many advantages-more esthetic and conservative than metallic restoratives etc. The purposes of this research were to develop a new measurement method and to manufacture an instrument that can measure the initial dynamic volumetric shrinkage of composite resins during polymerization. The instrument was basically an electromagnetic balance that constructed with a force transducer using position sensitive photo detector(PSPD) and a negative feedback servo amplifier of proportional-derivative(PD) controller. The volumetric change of composites during polymerization was detected continuously as buoyancy change in distilled water by means of Archimedes's principle. It was converted to continuous electrical voltage signal in real time. The signal was properly conditioned and filtered and then it was stored in computer by a data acquisition(DAQ) board. By using this electronic instrument. the dynamic patterns of the polymerization shrinkage of eight commercial(Z-100, DenFil, AeliteFil, Z-250, P-60, SureFil, Synergy compact, and Tetric ceram) composite resins were measured and compared. The results were as follows. 1. From this project of developing instrument, the ability has been achieved that can acquire and process data of electrical signal transformed from various physical phenomenon by using temperature, displacement. photo. and force transducer. As a consequence, the instrumentation and measurement system used to analyze the physical characteristics of various dental materials in dental research field can be designed, manufactured and implemented in lab. 2. This instrument has some advantages. It was insensible to temperature change and could measure true dynamic volumetric shrinkage in real time without complicated process. It showed accuracy and high precision results with small standard deviation. 3. The polymerization shrinkage of composites was significantly different between brands and ranged from 2.47％ to 3.89％, The order of polymerization shrinkage was as follows, in order of increasing shrinkage, SureFil, P60, Z250, Z100, Synergy compact. DenFil, Tetric ceram, and AeliteFil. 4. The polymerization shrinkage rate per unit time, dVol％/dt, showed that the instrument can provide an indirect research method for polymerization reaction kinetics.

• Journal of the Korean Magnetics Society
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• v.25 no.3
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• pp.87-91
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• 2015

This paper reports the design of solenoid in a coilgun for high velocity of projectile in a coilgun system, according to diameter of coil. Coilgun using a magnetic force means a mechanism that can control the magnetic material. When momentarily supply a large current to the solenoid instantaneous magnetic field is created around the coil, the projectile is fired by receiving a magnetic force towards the center of the coil, based on the right-hand rule of Fleming. The velocity of projectile is proportional to the magnetic force generated by the electromagnetic coil. The current affects the life of the coil and the current limit exists. Therefore, the coilgun design, which does not exceed the current limit and the magnetic forces are at the maximum, is required. In this paper, whether it is possible fire looking for the optimal number of turns according to the diameter of the coil from AWG #6 to AWG #18 for the design of the solenoid coil, and comparative analysis firing rate associated with it.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.2
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• pp.115-118
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• 2020

As interest in the reduction of energy loss has increased in recent years, analysis of losses in power cables is becoming more important. The overall loss in the transmission system can be measured, but there are many difficulties in researching the loss in each internal structure. There are various factors in the type of loss, and the loss of external factors by previous research has been studied. However, there is little research on the cable internal loss. Since the metal sheath inside the cable is made of aluminum having a high conductivity, an eddy current is generated due to the current flowing in the conductor, thereby causing an eddy current loss inevitably. In this paper, the eddy current loss in metal sheath of 154 kV Cable was researched through FEM (Finite Element Method) electromagnetic analysis.

• Journal of the Korea Society for Simulation
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• v.24 no.4
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• pp.29-34
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• 2015

Electronic of military vehicle that had relied on pure machinery system is ongoing. A large part of electronic of small-sized military vehicle has been already commercialized, which will expand to large-sized military vehicle field. Design of solenoid valve for automatic transmission is significantly important for stable driving performance of military vehicle. This research aims to develop simulation method which is capable of predicting performance of solenoid valve quantitatively according to its variation of ATF temperature. The research has been conducted in line with Maxwell, a magnetic field analysis program, and AMESim, a hydraulic analysis program. After simulation, it turned out to have been very similar to the test result in temperature range which excludes high temperature (over $120^{\circ}C$) and extremely low temperature (below $-20^{\circ}C$).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.3
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• pp.411-418
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• 2016

In accordance with global energy conservation policies such as MEPS(Minimum Energy Performance Standard), electric motor industry is moving to super-high-efficiency machines and research to develop IE4 (International Energy Efficiency Class4) motors has been launched. In this situation, SynRM (Synchronous Reluctance Motor) has been attracting attention in place of induction motor which hardly provides super premium efficiency. As a result, much research on SynRM is being performed at home and abroad. Also, some products have already been appearing in the market. Compared to induction motor, SynRM has better efficiency per unit area and wider operating range. Although the utilization of control system in synchronous motor results in higher prices, we still need to concentrate on developments of SynRM so as to comply with the new policies. This study demonstrated the electromagnetic design methods of super-premium SynRM while maintaining the frame of existing IE3 induction motor for blower. We documented the design procedures for generating high saliency which is the most essential and mechanical stress analysis is also treated. In conclusion, we proved the validity of our design by manufacturing and testing our SynRM models.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.12
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• pp.1892-1897
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• 2012

Modern electronic circuits are of importance for the function of communication, traffic systems and security systems. An intentional threat to these systems could be of big casualties and economic disasters. This study has examined susceptibility of electronic circuits inside the cavity by HPEM(High Power Electromagnetics). The UWB measurements were done at an anechoic chamber using a RADAN voltage source, which can generate a transient impulse of about 200 kV. The HPEM wave penetrated inside the metal case appeared to the long damped ringwave of pulse length compared with the incident wave. In addition, the resonant frequency generated inside the metal case occurred primarily in the range of 1~3 GHz. The frequency band of 1~3 GHz was influenced on the electronic circuit, which was confirmed by an external antenna and an internal absorber. The electronic circuit was influenced by HPEM infiltrated into the cavity at the 86 kV/m out of the metal cases. Also in case of an absorber the susceptibility of an electronic circuit was smallest among other cases(aperture, antenna). It is considered that absorber has a function absorbing electromagnetic wave infiltrated into the cavity and simultaneously limiting resonance by varying a boundary condition inside the cavity. Based on the results, electronic equipment systems could be applied to protection that has suited system requirements.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.22 no.53
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• pp.69-78
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• 1999

We developed an apparatus for odorous stimuli control to record olfactory evoked potentials from human scalp. The characteristics of the apparatus were as follows. 1. Translating the subjects respiration into electric signals with a sensor attached to the nose. The period and timing of odorous stimuli could be adjusted, so that stimuli could be synchronous with respiration. 2. The respirations translated into electric signals were made constant in amplitude by using an auto gain control circuit. 3. The interstimulus interval of odorous could be arbitrarily selected once every 1 to 9 respirations so that adaptation could be prevented. We obtained olfactory - evoked potentials (OEPs) to odorous stimuli using this apparatus from the site of Cz, whose positive peak latencies were approximately $180{\pm}23ms$. Such response were not recorded if oxygen stimuli were used instead of odorous or with click sounds produced by the switching electromagnetic valve.

• Journal of the Korean Society for Railway
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• v.14 no.4
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• pp.364-369
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• 2011

For the safety management of tunnel, effective measurements should be continuously carried out. Most of sensors currently being applied for tunnels measure only the local status, thus many of them are needed to monitor an entire tunnel. For the railway tunnel where trains of same conditions are regularly operated, dynamic responses of tunnel structure to train operations can be a good index to estimate the deformation of tunnel structure in wide area. Meanwhile, the electromagnetic interference caused by overhead centenary in railway tunnel obstructs the use of electric-based sensors. In this study a brand new accelerometer using FBG optical fiber sensors is developed to solve these problems. Sensitivity and capacity of the accelerometer are enhanced with effective structural design of its components and verified with laboratory tests. A case history where the developed accelerometers were applied to a safety monitoring system of a high-speed train tunnel is presented. The performances of the developed accelerometers are validated from the measured acceleration data.

• Journal of IKEEE
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• v.16 no.4
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• pp.297-303
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• 2012

This paper proposes the effective design procedure for a broadband, double-ridged horn antenna for evaluating the performance of the RF energy harvesting system with a multi-band rectenna. Using multi-mode network analysis, the higher-mode scattering parameters of the transition and horn were acquired and applied to the antenna design, respectively. As a result, the computing time could be reduced and the calculated VSWR(voltage standing wave ratio) of the antenna was very similar to the analyzed result using fully electromagnetic simulation. And there was also good agreement between the simulated and measured results. The designed broadband antenna has a bandwidth of 660~6360 MHz and 6~13.7 dBi peak radiation gain.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.577-587
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• 2004

A coaxial pulsed plasma thruster (PPT) with a Teflon cavity was designed, and its performance characteristics were examined varying stored energy, cavity length and capacitance. The PPT was tested as the entire system including the discharge circuit, and the results were explained with both the transfer efficiency and the acceleration efficiency. The transfer efficiency is defined as the fraction of energy in capacitors supplied into plasma, and the acceleration efficiency as the fraction of energy supplied into plasma converted to thrust energy. To estimate these efficiencies, the equivalent plasma resistance was defined and calculated using energy conservation during discharge. The equivalent plasma resistance proportionally increased with cavity length, and therefore the current peak increased with decreasing cavity length. The energy density calculated by the transfer efficiency was increased with decreasing cavity length. As a result, higher acceleration efficiency and lower transfer efficiency were obtained with shorter cavity length. Accordingly, there was an optimal cavity length for the thrust efficiency. The specific impulse and the impulse bit per unit stored energy ranged from 390 s and 50 $\mu$ Ns/J for a cavity length of 34 mm to 825 s and 11 $\mu$ Ns/J for a cavity length of 4 mm when the stored energy was fixed to 21.4J. Thus, it was showed that the performance of this PPT approached that of electromagnetic-acceleration-type PPT with decreasing cavity length. The PPT achieved thrust efficiencies of 10-12% at 21.4 J and 6-7% at 5.35 J at cavity lengths between 14 mm and 29 mm.