• Fashion & Textile Research Journal
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• v.14 no.4
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• pp.641-647
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• 2012

This study investigates the sound properties of fabric frictional sound (SPL, ${\Delta}L$, ${\Delta}f$) according to the film type of PTFE laminated vapor-permeable water-repellent fabrics in order to understand the relationship between SPL and the basic properties of fabrics such as layer, yarn type, and thickness of fiber. This study accesses their mechanical properties and determines how to control them to minimize SPL. Eight PTFE laminated water-repellent fabrics, composed of four different film types (A, B, C, D) and with two different fabrics, were used as test specimens. Frictional sounds generated at 1.21m/s were recorded by using a fabric sound generator and SPLs were analyzed through Fast Fourier Transformation (FFT). The mechanical properties of fabrics were measured by KES-FB. The SPL value was lowest at 74.4dB in film type A and highest as 85.5dB in type D. Based on ANOVA and post-hoc test, specimens were classified into less Loud Group (A, B) and Loud Group (C, D). It was shown that SPL was lower when 2 layer (instead of 3 layer), filament yarn than staple, and thin fiber than thick were used. In Group I, shearing properties (G, 2HG5), geometrical roughness (SMD), compressional properties (LC, RC) and weight (W) showed high correlation with SPL however, elongation (EM) and shear stiffness (G) did with SPL in Group II.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.489-494
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• 2008

The measurement of magnetic field is performed about DC and AC magnetic field in electric railway line. The test point is cap, on the converter/inverter box, on the traction motor and on the SIV, the height of measurement is bottom and 60 cm height. In case of AC magnetic field, the selected specific frequency is measured on the converter/inverter box. The AC magnetic field is checked and analysis through BNC output, DAQ cad and notebook PC.

• International Journal of Automotive Technology
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• v.6 no.2
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• pp.149-159
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• 2005

A full nonlinear finite element P185/70Rl4 passenger car radial-ply tire model was developed and run on a 1.7-meter-diameter spinning test drum/cleat model at a constant speed of 50 km/h in order to investigate the tire transient response characteristics, i.e. the tire in-plane free vibration modes transmissibility. The virtual tire/drum finite element model was constructed and tested using the nonlinear finite element analysis software, PAM-SHOCK, a nonlinear finite element analysis code. The tire model was constructed in extreme detail with three-dimensional solid, layered membrane, and beam finite elements, incorporating over 18,000 nodes and 24 different types of materials. The reaction forces of the tire axle in vertical (Z axis) and longitudinal (X axis) directions were recorded when the tire rolled over a cleat on the drum, and then the FFT algorithm was applied to examine the transient response information in the frequency domain. The result showed that this PI 85/70Rl4 tire has clear peaks of 84 and 45 Hz transmissibility in the vertical and longitudinal directions. This result was validated against more than 10 previous studies by either theoretical or experimental approaches and showed excellent agreement. The tire's post-impact response was also investigated to verify the numerical convergence and computational stability of this FEA tire model and simulation strategy, the extraordinarily stable scenario was confirmed. The tire in-plane free vibration modes transmissibility was successfully detected. This approach was never before attempted in investigations of tire in-plane free vibration modes transmission phenomena; this work is believed to be the first of its kind.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.2
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• pp.190-198
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• 1995

Many industrial servo amplifiers employ power transister as output device. Thyristor converters are not adopted to drive servo motor, although thyristor is superior to power TR in power rating, noise immunity, price, and size. The reason is, thyristor has no ability of self turn - off. Here in this paper line commutation, in which thyristor is turned off naturally since cathode voltage is higher than anode as time goes by, is employed to turn on thyristor with a delicate sequence. We developed thyristor servo amplifier which does not cause any damage on thyristor because it is designed to prevent triggering the two SCRs in the same arm simultaneously. And it was made clearly how to trigger SCR without any power line shorting and also harmonic analysis is carried out with the aid of FFT analyzer and proved that it can be used even severe reactive load. The designed circuit operated as a good DC amplifier in conventinal servomotor and the results can be use as a position control system application.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.306-307
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• 2011

Franz Keldysh Oscillation (FKO)은 p-n 접합 구조의 공핍층(depletion zone)에서 전기장(electric field)에 의해 발생되며, Photoreflectance (PR) spectroscopy를 통하여 관측된다. InAs/GaAs 양자점 태양전지(Quantum Dot Solar Cells, QDSCs)에서 PR 신호에 대한 Fast Fourier Transform (FFT)을 통하여 FKO 주파수들을 관측할 수 있고, 각각의 FKO 주파수들은 태양전지 구조에 대응하는 표면 및 내부전기장(internal electric field) 들로 분류할 수 있다. InAs/GaAs 양자점 태양전지에서 AlGaAs potential barrier의 두께에 따른 내부전기장의 변화를 조사하기 위해, GaAs-matrix에 8주기의 InAs 양자점 층이 삽입된 태양전지를 molecular beam epitaxy (MBE) 방법으로 성장하였다. 양자점의 크기는 2.0 monolayer (ML)이며, 각 양자점 층은 1.6 nm에서 6.0 nm의 AlGaAs potential barrier들로 분리되어 있다. 또한 양자점 층의 위치에 따라 내부전기장 변화를 조사하기 위해, p-i-n 구조에서 양자점 층이 공핍층 내에 위치한 경우와 p+-n-n+ 구조에서 양자점 층이 공핍 층으로부터 멀리 떨어진 n-base 영역에 삽입하여 실험결과를 비교분석하였다. PR 실험결과로부터, p-i-n 구조에서 InAs 양자점 태양전지의 내부전기장 변화는 potential barrier 두께에 따라 다소 복잡한 변화를 보였으며, 이는 양자점 층이 공핍층 내에 위치함으로써 격자 불일치(lattice mismatch)로 발생된 응력(strain)의 영향으로 설명할 수 있다. 이러한 결과들을 각각의 태양전지 구조에서 표면 및 내부전기장에 대해 계산된 값들에 근거하여, p+-n-n+ 구조에서 양자점 층이 공핍 층으로부터 멀리 떨어진 영역에 삽입된 경우의 결과와 비교해 보면 내부전기장의 변화는 더욱 분명해진다. 즉, 양자점 층의 potential barrier의 두께를 조절하거나, 양자점 층의 위치를 변화시킴으로써 양자점 태양전지의 내부전기장을 조작할 수 있으며, 이는 PR 실험을 통해 FKO를 관측함으로써 확인할 수 있다.

• Journal of Bio-Environment Control
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• v.21 no.4
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• pp.437-444
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• 2012

This study was aimed to minimized the impact force and vibration transmitted to transporting agricultural product from the power tiller trailer by installing vibration absorption device. The vibration absorbable trailer (I) mounted with leaf spring suspension and shock absorber was developed and compared on vibration absorption performance with the existing trailer (E) equipped no vibration absorption device. In order to identify the vibration absorption effect of the trailer developed in this study, the vibration accelerations, occurred during driving on paved road with loading 360 kg of pear, were measured and analyzed using FFT analyzer. The magnitude of average vibration acceleration was decreased highly for the improved trailer mounted with vibration absorption device in comparing with existing trailer in the frequency range under 60 Hz and under 80 Hz. And similar vibration absorption effect was represented for the improved trailer in all frequency range. Especially, in the frequency range between 40 Hz and 80 Hz, the magnitude of vibration acceleration for the improved trailer was decreased with 1/3 times in comparing with existing trailer. So, the transporting loss including damage of agricultural product could be decreased highly by using the improved vibration absorbable trailer mounted with leaf spring suspension and shock absorber simultaneously, designed in this study.

• Journal of Sensor Science and Technology
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• v.14 no.1
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• pp.33-41
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• 2005

For more convenient electrode-electrolyte interface impedance analysis in biosensor, a stand-alone impedance measurement system is required. In our study, we developed a PC-based portable system to analyze impedance of the electrochemical cell using microprocessor. The devised system consists of signal generator, programmable amplifiers, A/D converter, low pass filter, potentiostat, I/V converter, microprocessor, and PC interface. As a microprocessor, PIC16F877 which has the processing speed of 5 MIPS was used. For data acquisition, the sampling rate at 40 k samples/sec, resolution of 12 bit is used. RS-232 with 115.2 kbps speed is used for the PC communication. The square wave was used as stimuli signal for impedance analysis and voltage-controlled current measurement method of three-electrode-method were adopted. Acquired voltage and current data are calculated to multifrequency impedance signal after Fourier transform. To evaluate the implemented system, we set up the dummy cell as equivalent circuit of which was composed of resistor, parallel circuit of capacitor and resistor connected in parallel and measured the impedance of the dummy cell; the result showed that there exist accuracy within 5 % errors and reproduction within 1 % errors compared to output of Hioki LCR tester and HP impedance analyzer as a standard product. These results imply that it is possible to analyze electrode-electrolyte interface impedance quantitatively in biosensor and to implement the more portable high speed impedance analysis system compared to existing systems.

• Economic and Environmental Geology
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• v.18 no.4
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• pp.309-320
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• 1985

The crustal structure of the southern part of the Korean peninsula has been investigated based on the results of processing and anlaysis of gravity data. The processing techniques involve i) seperation of regional and residual anomalies by polynomial fittings, ii) power spectral analyses to determine the mean depth to the crustal base, iii) a filtering operation called "high-cut filtering and resampling," and iv) downward continuation to determine the undulation of the crustal base. The Bouguer anomalies show a lineation in the NE-SW direction which is the same as that of most mountains and tectonic lines of this area. The mean crustal depth is found to be 34km. The depth of the crustal base is varying in the estimated range of 26km to 36km with a thinner crust below the east coast than that of the west coast. The relief of the crustal base is appeared to be correlated with the regional surface topography. The linear regression relations computed between elevations and gravity anomalies indicate that the crust of this area seems to be not in perfect isostatic equilibrium but a little undercompensated state.

• Journal of Korean Clinical Health Science
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• v.8 no.1
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• pp.1362-1368
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• 2020

Purpose. In this study, The change of the accommodation function due to the use of a smartphone was objectively evaluated using an Auto Refractokeratometer and was to investigate the effect of accommodation response and microfluctuations of accommodation on stable fatigue. Methods. Twenty subjects (20 males, 20 females) who had no abnormalities in ophthalmic disease and strabismus, diplopia, suppression, convergence and ocular movement, and corrected visual acuity and unaided visual acuity of 0.8 or more were performed. The average age of the participants is (21.78 ± 1.78) years old. The refractive power of the eye was measured using an Auto Refractokeratometer (Speedy-i K-model, Righton Mfg Co. Tokyo Japan), and the equivalent spherical power was automatically calculated from the measured refractive power. The accommodation response amount was calculated for the accommodation stimulation amount in 8 steps in 0.5D increments from + 0.50D to -3.00D in the calculated equivalent spherical power. The microfluctuations of accommodation in the high frequency region was calculated according to the change in the amount of the accommodation stimulus. At this time, the spectral power of the microfluctuations of accommodation was analyzed by Fast Fourier Transformation (FFT). Results. After using the smartphone, it was found that the accommodation response to accommodation stimulation decreased and the microfluctuations of accommodation increased. Conclusions. It can be said that the use of a smartphone affects the accommodation response and the microfluctuations of accommodation, thereby causing a accommodative stable fatigue. Therefore, it is thought that the use of a smartphone for a long time may bring about a change in the accommodation function.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.45-52
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• 2002

An experimental investigation on the structure and dynamic behavior of two dimensional over-expanded air jets exiting into water was carried out. The hish speed digital video imaging and static pressure distribution measurement were made to characterize the structure and time-dependant behavior of the jets. Mach number at the jet exit was 2.0 and was slightly less than the value predicted by the ideal nozzle calculation. Variance of jet spreading angle at different stagnation condition was measured as a function of mass flow rate. Periodic nature of the air jet distortion in water was observed and the frequency of the repetition was approximately 5-6 Hz for all cases tested. Three characteristic length scales were defined to characterize jet structure. $L_1$, maximum width of the plume when the periodic instability occurs, $L_2$, width of the jet where secondary reverse flow entrained jet flow and $L_3$, distance from the jet exit to the location where entrainment of the secondary reverse flow occurs. The ratio of $L_1$ and $L_2$ decreased with increasing stagnation pressure, i.e. mass flow rate. $L_3$ increased with increasing stagnation pressure. The temporal behavior of static pressure measurements also showed peak around frequency of 5, which corresponds the frequency obtained by visual measurements