• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.292-297
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• 2015

In this paper, we reported the bypass unit for ship area networks in order to detour the communication failure regions and poor communication links. The device was composed of three parts of circuits for power cut-off, protection, and coupling transformer. Since the coupling transformer exerts a dominant influence on the performance of the by-pass unit, we have tried to find the optimal magnetic core materials and its dimensions. The prototype was passed through the performance test of insertion loss, temperature, and vibration characteristics. The insertion loss was around -2 dB in the range of 90 kHz ~ 30 MHz and the average communication speed was 59.2 Mbps in the laboratory. A pilot communication test using the developed tool was conducted in the training ship of the Korea Maritime and Ocean University. As a results of experiment, we showed that the wired communication among the heterogeneous-links in the ship area networks are possible by the bypass unit and also a high speed communication services are available in ~ Mbps by using a power-line.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.5
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• pp.461-466
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• 2015

Atomic force microscopy (AFM) is powerful tool for determining properties of samples based on interactions between the sample surface and an approaching probe tip. In this study, we modeled the interactions between the sample and the tip of the AFM microcantilever as a single nonlinear spring with an equivalent stiffness element and simulated the dynamic behaviors of the AFM microcantilevers using the finite element method (FEM) and ANSYS software. With the simulation results, we analyzed the complex dynamic responses of the AFM cantilever using proper orthogonal decomposition (POD). In addition, we compared the simulation and experimental results using the same method. Consequently, we suggest an effective method to express the interaction between the tip and sample, and we confirm that the influence of the higher order model due to the interaction between the tip and sample is increased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.3
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• pp.317-323
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• 2011

We use the finite element method to analyze the seismic design of a liquid storage tank for a polar crane at a nuclear power plant. We obtained the natural frequency and vibration modes by modal analysis, and we evaluated the seismic stability by response spectrum analysis. Furthermore, the seismic analysis of the tank was accomplished by analyzing not only the forces applied to the wall by the sloshing of the liquid, but also the safe-shutdown earthquake condition for the tank. We propose a seismic-design process and a seismic-analysis method for liquid storage tanks based on the commercial finite element analysis program, ANSYS.

• Journal of KSNVE
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• v.8 no.2
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• pp.260-266
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• 1998

According to the conventional method of analysis for the seismic sliding of equipment submerged in a pool, in general, only the initial condition of fluid gap is used to estimate the hydrodynamic effect between the two structures throughout the seismic analysis. This is based on the assumption of small displacement relative to the fluid gap thickness during earthquakes. In a narrow fluid gap condition, however, this method may lead to a result of unconservative side. Through example seismic analyses for equipment submerged in a pool of a building, in this paper, it is studied when and how much the sliding response can be underestimated. And method of updating the hydrodynamic effect in each step of time integration is proposed to avoid excessive error in estimation of peak sliding response in such a case.

• Journal of the Korean Society of Visualization
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• v.14 no.1
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• pp.57-61
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• 2016

We report a finding of fast(exceeding 2,000 K/s) heating of polydimethylsiloxane(PDMS), one of the most commonly-used microchannel materials, under cyclic loadings at high(~MHz) frequencies. A microheater was created based on the finding. The heating mechanism utilized vibration damping of sound waves, which were generated and precisely manipulated using a conventional surface acoustic wave(SAW) microfluidic system, in PDMS. The penetration depths were measured to range from $210{\mu}m$ to $1290{\mu}m$, enough to cover most microchannel heights in microfluidic systems. The energy conversion efficiency was SAW frequency-dependent and measured to be the highest at around 30 MHz. Independent actuation of each interdigital transducer(IDT) enabled independent manipulation of SAWs, permitting spatiotemporal control of temperature on the microchip. All the advantages of this microheater facilitated a two-step continuous flow polymerase chain reaction(CFPCR) to achieve the billion-fold amplification of a 134 bp DNA amplicon in less than 3 min. In addition, a technique was developed for establishing dynamic free-form temperature gradients(TGs) in PDMS as well as in gases in contact with the PDMS.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.3
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• pp.338-344
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• 2016

The study is actively being performed to increase fuel injection pressure of common rail system among countermeasures to meet the emission regulation strengthen of the Diesel engine. The common rail fuel injection tube in such ultra high pressure common rail system has the weakest structural characteristics against vibration that is generated by fuel injection pressure and pulsation during engine operation and driving. Thus the extreme durability is required for common rail fuel injection tube, and the drawing process is being magnified as the most important technical fact for strength of seamless pipe that is the raw material of common rail tube. In this respect, we analyzed the characteristic of dimension and stress variation of the ultra high pressure common rail fuel injection tube by variation of Die and Plug angle in drawing process. Based on the analysis, we tried to obtain the raw material strength of common rail fuel injection tube for applying to the ultra high pressure common rail system. As a result, Plug angle is more important than entry angle of Die and we could obtain the target dimension and strength of the ultra high pressure common rail fuel injection tube through optimization of Plug angle.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.1
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• pp.28-34
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• 2017

The vehicle stabilizer link is one of the suspension components that reduces the bumping and rolling during vehicle driving. However, this stabilizer link could be a source of the abnormal noises when its free gaps have higher than normal values. Therefore, the current study aims at investigating the quantitative relationships between the abnormal noises and free gaps of the vehicle stabilizer links, as well as the length of time that the vehicle stabilizer links could be used without generating abnormal noises. In this study, the abnormal noises were measured based on the magnitude of the stabilizer link vibration, while the free gaps were quantified through the force-displacement curves of the stabilizer links. Harsh durability tests were also conducted in order to quantify the operating cycles of the stabilizer links before generating the abnormal noises, along with the concomitant measurements of the free gaps. The current results showed that the abnormal noises of the stabilizer links were detected when its free gaps were larger than 0.12 mm. However, the free gaps of the stabilizer links, which are bigger than 0.1 mm, produced the abnormal noises at 1.5 million cycles under harsh durability test conditions. A parametric study in the future that would reflect the different shapes and sizes of the stabilizer links for diverse vehicles could determine more generalized relationships between the abnormal noises and free gaps of the vehicle stabilizer links.

• Journal of Korean Society of Disaster and Security
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• v.6 no.3
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• pp.1-8
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• 2013

Based on random vibration theory, a procedure for calculating the dynamic response of the tall building to time-dependent random excitation is developed. In this paper, the fluctuating along- wind load is assumed as time-dependent random process described by the time-independent random process with deterministic function during a short duration of time. By deterministic function A(t)=1-exp($-{\beta}t$), the absolute value square of oscillatory function is represented from author's studies. The time-dependent random response spectral density is represented by using the absolute value square of oscillatory function and equivalent wind load spectrum of Solari. Especially, dynamic mean square response of the tall building subjected to fluctuating wind loads was derived as analysis function by the Cauchy's Integral Formula and Residue Theorem. As analysis examples, there were compared the numerical integral analytic results with the analysis fun. results by dynamic properties of the tall uilding.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.2018-2030
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• 2015

A two stage ac drive configuration consisting of a single-phase line commutated rectifier and a three-phase voltage source inverter (VSI) is very common in low and medium power applications. The deterministic pulse width modulation (PWM) methods like sinusoidal PWM (SPWM) could not be considered as an ideal choice for modern drives since they result mechanical vibration and acoustic noise, and limit the application scope. This is due to the incapability of the deterministic PWM strategies in sprawling the harmonic power. The random PWM (RPWM) approaches could solve this issue by creating continuous harmonic profile instead of discrete clusters of dominant harmonics. Insufficient filtering at dc link results in the amplitude distortion of the input dc voltage to the VSI and has the most significant impact on the spectral errors (difference between theoretical and practical spectra). It is obvious that the sprawling effect of RPWM undoubtedly influenced by input fluctuation and the discrete harmonic clusters may reappear. The influence of dc link fluctuation on harmonics and their spreading effect in the VSI remains invalidated. A case study is done with four different filter capacitor values in this paper and results are compared with the constant dc input operation. This paper also proposes an ingenious RPWM, a ripple dosed sinusoidal reference-random carrier PWM (RDSRRCPWM), which has the innate capacity of suppressing the effect of input fluctuation in the output than the other modern PWM methods. MATLAB based simulation study reveals the fundamental component, total harmonic distortion (THD) and harmonic spread factor (HSF) for various modulation indices. The non-ideal dc link is managed well with the developed RDSRRCPWM applied to the VSI and tested in a proto type VSI using the field programmable gate array (FPGA).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.8-12
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• 2017

This paper presents the mobile phone case for self-power generation and recharge for emergency calls or text messages at the discharge of a battery. If the user shakes his smart phone case, the interaction of electromagnetic coil and permanent magnet in an electric generator produces electric energy, which charges the lithium-ion battery. This enables the user to give a few calls or text messages. In addition, the vibration energy from humans walking at a frequency of 2 ~ 3Hz charges the battery. The electric generator was simulated using MAXWELL, a commercial electromagnetic analysis program, to analyze the electric power generation. Finally a prototype of the mobile phone case for self-power generation was built based on the analysis and its performance was verified.