• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.152-160
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• 2008

Since wall system apartment used the shear wall as main lateral resistance member, installation of openings which causing section loss of walls may cause significant problem to structure. Also, there are few studies for inducing coupling beam or slabs which are occurred by installing openings. Therefore, this study planned isolated 2-story shear walls which are reduced three half-scale specimen to find out walls behavior characteristic. The test results showed that strength reduction caused by loss of effective section of walls and different result of stiffness and energy dissipation regarding to the coupling beam and coupling slabs.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.88-94
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• 2014

In this paper, Thermal Shock tests were performed varying the composition of the solder and ribbon thickness (A-type:0.2mm/60Sn40Pb, B-type:0.25mm/60Sn40Pb, C-type:0.2 /62Sn36Ag2Pb, D-type:0.25mm/62Sn36Ag2Pb) for evaluating the long-term reliability about Ribbon junction of Silicon solar cells. Thermal Shock test condition was performed during the 600cycles having $-40^{\circ}C{\sim}85^{\circ}C$ temperature range each 15 minutes; One cycle time was 30min. As a result, the initial efficiency of the A-type, B-type, and C, D-type were showed 15.0%, 15.4% and 15.8% respectively. After thermal shock test, the efficiency decreasing-rate of each type were as follow that A-type was 13.8%, B-Type was 15.4%. C-Type and D-Type was 15.3% and 16.2%, respectively. Also, degradation of surface changes and I-V characteristic curves were showed that the series resistance of the A, C-type was increased. Also, current lowering starting point of C-type shown 0.05volt[v] earlier than that of A-type. And B, D-type shown characteristics of composite lowering efficiency such as increase of series resistance, decrease of parallel resistance and cell damage. Therefore Initial solderability and efficiency of specimens using the solder with SnAgPb were superior. But, It has inferior the long-term reliability. The test was confirmed that as the ribbon thickness increases, long-term reliability of solar cell will decrease.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.7
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• pp.683-693
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• 2011

In this paper, a design of high current and broad-band microwave bias-tee was presented for a stable bias of a high power amplifier. An input impedance of bias-tee should be shown to 50 ohm with the wideband in order to be stably-biased the amplifier. For this design of the bias-tee, a capacitor of bias-tee for a DC block was designed with a high wide-band admittance by a parallel sum of capacitors, and a inductor for a RF choke and a DC feeding was designed with a high wide-band impedance by a series sum of inductors. As this inductor and capacitor for the sum has each SRF, band-limitation of lumped element was driven from SRF. This limitation was overcome by control of a resonance's quality factor with adding a resistor. 1608 SMD chips for design's element was mounted on the this pattern for the designed bias-tee. The fabricated bias-tee presented 10 dB of return loss and wide-band about 50 ohm input impedance at 10 MHz~10 GHz.

• Journal of Energy Engineering
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• v.21 no.3
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• pp.249-253
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• 2012

In this study, The report analysed the characteristics of power drop in solar cell through thermal shock test. The solar cells were tested 500 cycles in $-40^{\circ}C$ lowest temperature and $120^{\circ}C$ highest temperature by thermal shock test on ironbound conditions, that excerpted standard of PV Module(KS C IEC-61215). The result of the efficiency analysis through measure of I-V, efficiency of Cell decreased from 13.9% to 11.0% and decreasing rate was 20.9% after test. The result of the surface analysis through EL, solar cell has damage of gridfinger and ribbon joint. Cell cracks were founded in damage of cells through cross section of solar cells. Also, Fill factors were decreased from 72.3% to 62.0% after thermal shock test and decreasing rate is 11.8%. therefore, Yearly power drop is aggravated with facts that cell crack, damage of surface and power loss of cell by change of I-V characteristic curve with decreasing of parallel resistance.

• Magazine of the Korea Concrete Institute
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• v.7 no.3
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• pp.187-198
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• 1995

This paper develops practical and reallstic reliabllity models and methods for the evaluation of system rehability and system rellabllity based ratlng of R.C box glrder bridge superstructures. The precise prediction of reberved carrying capacity of bridge as d system is extremely difficult especially when the brldges are highly redundant and slgnlficantly deter 1or;itcd or dainagetl. Thls papel proposes a nt2w approach for the evaluation of reseived system c,drrying capaaty of br~dges in terms ot equ~vdleiit system strength, which may b~ ddcflned as a brtdge system strength correipcmdlng tu the system rehability of the bridge. This cm be ticrAvcd from an Inverse process bami or1 the con~ept of FOSM(F1rst Order Second Moment) form of system reliabihty index. The sf rength llmt state models for K C box girder br~dges suggested In the paper dre based on the basi~ bending and shear strength And thc system reliatxllty pro,~lerri of box gritier super structure 1s formuldted as parallel serles models obtalncd f ~ o m thc FMA(Fdilure blode Rp proath) based on major failure mc>clmusrns or c~itlcal fdure ,>tatcs of each nuder .WOSM(Ad-vanced First Order Second Moment) and IST(1mportance Sampling Technique) simulation algorithm are used for the reliability analysis of the proposed models.

• Journal of Biomedical Engineering Research
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• v.25 no.4
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• pp.269-275
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• 2004

Different biological tissues have different values of electrical resistivity. In EIT (electrical impedance tomography), we try to provide cross-sectional images of a resistivity distribution inside an electrically conducting subject such as the human body mainly for functional imaging. However, it is well known that the image reconstruction problem in EIT is ill-posed and the quality of a reconstructed image highly depends on the measurement error. This requires us to develop a high-performance EIT system. In this paper, we describe the development of a 16-channel digital EIT system including a single constant current source, 16 voltmeters, main controller, and PC. The system was designed and implemented using the FPGA-based digital technology. The current source injects 50KHz sinusoidal current with the THD (total harmonic distortion) of 0.0029% and amplitude stability of 0.022%. The single current source and switching circuit reduce the measurement error associated with imperfect matching of multiple current sources at the expense of a reduced data acquisition time. The digital voltmeter measuring the induced boundary voltage consists of a differential amplifier, ADC, and FPGA (field programmable gate array). The digital phase-sensitive demodulation technique was implemented in the voltmeter to maximize the SNR (signal-to-noise ratio). Experimental results of 16-channel digital voltmeters showed the SNR of 90dB. We used the developed EIT system to reconstruct resistivity images of a saline phantom containing banana objects. Based on the results, we suggest future improvements for a 64-channel muff-frequency EIT system for three-dimensional dynamic imaging of bio-impedance distributions inside the human body.

• Korean Journal of Materials Research
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• v.8 no.5
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• pp.424-428
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• 1998

Mn-Ni oxide thin films for NTC thermistor application were deposited on alumina substrates by using rf magnetron sputter. Effects of various substrate temperatures and annealing temperatures on the microstructure. crystal phase, resistivity and B constant were investigated. Microstructure of the films deposited below 178$^{\circ}C$ was fibrous microcrystalline and at 32$0^{\circ}C$and 40$0^{\circ}C$their microstructure was changed to columnar grain structure. After annealing at 90$0^{\circ}C$, the microstructure was transformed to equiaxed grain structure. Most of the phases were mixture of cubic spinel and $Mn_2O_2$ The crystal phase of the film deposited at 40$0^{\circ}C$ was changed to cubic spinel after annealing above 700"c. As the substrate temperature increased, the resistivity and B constant were greatly decreased, and these values become low and stable after annealing between $600^{\circ}C$and $700^{\circ}C$, All thin films deposited in the present study showed NTC thermistor characteristicsstics.

• Korean journal of applied entomology
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• v.40 no.4
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• pp.337-344
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• 2001

The house fly (Musca domestica L.) strains were derived from the Yumenoshima III strain by selecting with cypermethrin and methomyl for 19 and 16 generations, respectively. The resulting strains, cypermethrin resistance strain (Cyp-R19) and methomyl resistance strain (Met-R16), showed high level of resistance by 12906 and 51 times, respectively, comparing with the susceptible SRS strain. The Cyp-R19 strain was resistant to synthetic pyrethroids such as deltamethrin, esfenvalerate, fenpropathrin, $\beta$-cyfluthrin, showing > 11000, 1231, 103, 292 times higher $LD_{50}$ values than the SRS strain, respectively. It was also resistant to 3 organophosphates and 2 carbamates such as fenitrothion, profenofos, pyridaphenthion, benfuracarb, methomyl, showing resistance ratios fo 51, 17, 49, 39 and 62 comparing to SRS strain. The Met-R16 strain was resistant to synthetic carbamate benfuracarb, showing 6 times higher $LD_{50}$ value than SRS strain. It was also resistant to 4 organophosphates such as acephate, fenitrothion, profenofos and pyridaphenthion, showing > 40, 103, 19, 60 times higher $LD_{50}$ value. It was also resistant to 5 pyrethroids and a pyrrole such as cypermethrin, deltamethrin, esfenvalerate, fenpropathrin, $\beta$-cyfluthrin and chlorfenapyr, showing 3030, 249, 4063, 34, 330 and 86 times higher $LD_{50}$ values than the SRS strain. Cyp-R14 strain which was selected for 14 generations by cypermethrin and developed 11014 times higher resistance to the SRS strain was used in the dominance and linkage group analysis. Cypermethrin resistance inheritance was incompletely dominant in house fly as judged by the reciprocal cross between the resistant and susceptible strains. The linkage group analysis for the major factors responsible for this resistance was carried out by the$ F_1$male-backcross method, using susceptible multi-chromosomal marker aabys strain. The major factors for cypermethrin resistance were located on the 1st, the 3rd and the 4th chromosomes, and the effect of the 3rd chromosome was most prominent.

• Korean Journal of Materials Research
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• v.9 no.12
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• pp.1263-1269
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• 1999

An FBAR(Solidly Mounted Resonator) was fabricated using reflector layers which prohibit the penetration of bulk acoustic wave into substrate. The SMR consisted of top and bottom electrodes(Al films), a piezoelectric layer (ZnO film), reflector layers(W/$Si_2$ films) and Si substrate. The electrodes were deposited by dc sputtering. The piezoelectric layer and the reflector layers were deposited by rf magnetron sputtering. The control of crystallinity, microstructures and electric properties of each layer was essential for attaining the optimum FBAR characteristics. Under the best deposition conditions for FBAR devices, the ZnO films had highly c-axis preferred orientation(${\sigma}=2.17^{\circ}$), resistivity of $10^4\;{\omega}cm$, and surface roughness of 10.6 ${\AA}$. On the other hand, the surface roughness of W and $Si_2$ films was 16 ${\AA}$ and 33 ${\AA}$, respectively, and the resistivity of Al film was $5.1{\times}10^{-6}\;{\Omega}cm$. The SMR devices were fabricated by the conventional semiconductor processes. In the resonance conditions of the SMR, the series resonance frequency (fs) and the parallel resonance frequency(fp) were 1.244 GHz and 1.251 GHz, respectively and the quality factor(Q) was 1200.

• Journal of the Korean Institute of Telematics and Electronics
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• v.11 no.4
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• pp.23-28
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• 1974

One of the consistent nuisances in accurate design of circuits containing coils with core is how to take into account the frequency dependence of Q of actual coils. The conventional equivalent circuit consisting of an inductance and a series (constant) resistance and possibly a parallel (constant) capacitance is of little use in this situation since the core loss itself is strongly dependent on the frequency. In order to circumvent this difficulty, in this paper, a mathematical expression for Q of a given core as a function of inductance and frequency is first assumed and parameters in this expression are optimiged so as to best fit the data provided by the core manufacturer or obtained experimentally. This expression is then utilized in accurate calculation of the frequency response of a given circuit required in the optimal design of circuits containing coils. In other words the proposed approach is an effective combination of an approximate expression of coil's Q and circuit optimisation technique, which seems to have solved, to a great extent, the stated difficulty associated with actual coils. As for the optimization technique, ths Fletcher-Powell procedure was employed and one example was given to illustrate the proposed approach.