• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.2
• /
• pp.169-177
• /
• 2017

In this paper, classification of spall and crack faults of gear teeth is studied by applying the ensemble empirical mode decomposition(EEMD) for the gear transmission error(TE). Finite element models of the gears with the two faults are built, and TE is obtained by simulation of the gears under loaded contact. EEMD is applied to the residuals of the TE which are the difference between the normal and faulty signal. From the result, the difference of spall and crack faults are clearly identified by the intrinsic mode functions(IMF). A simple test bed is installed to illustrate the approach, which consists of motor, brake and a pair of spur gears. Two gears are employed to obtain the TE for the normal, spalled, and cracked gears, and the type of the faults are separated by the same EEMD application process. In order to quantify the results, crest factors are applied to each IMF. Characteristics of spall and crack are well represented by the crest factors of the first and the third IMF, which are used as the feature signals. The classification is carried out using the Bayes decision theory using the feature signals acquired through the experiments.

• Korean Journal of Food Science and Technology
• /
• v.33 no.1
• /
• pp.33-39
• /
• 2001

To develop a method for separation process using Sep-pak $C_18$, simultaneous and systematic analysis of 8 permitted and 11 non-permitted synthetic food colors in Korea, optimization of analysis conditions for reverse phase ion-pair high performance liquid chromatography was carried out. For the best result of Sep-pak $C_18$ separation the pH of color standard mixture solution was $5{\sim}6$ and 0.1% HCl-methanol solution were set as eluent. The colors eluated from Sep-pak $C_18$ cartridge were determined and confirmed by high performance liquid chromatography with a photodiode array detector at 420 nm for yellow colors type, at 520 nm for red colors type, at 600 nm for blue and green colors type and at 254 nm for mixed colors. Conditions for HPLC analysis were as follows: column, Symmetry $C_18$ (5 m, 3.9 mm $i.d.{\times}150\;mm$); mobile phase, 0.025 M ammonium acetate (containing 0.01 M tetrabutylammonium bromide) : acetonitrile : methanol (65 : 25 : 10) and 0.025 M ammonium acetate(containing 0.01 M tetrabutylammonium bromide) : acetonitrile : methanol (40 : 50 : 10); flow rate, 1 mL/min. It takes 35 minutes for simultaneaus analysis and 18 minutes for systematic analysis. The detection limits range of each colors were $0.01{\sim}0.05\;{\mu}g/g$.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.7 no.6
• /
• pp.63-69
• /
• 2008

Reconfigurable RF one-chip solutions have been researched with the objective of designing for smaller-sized and more economical RF transceiver and it can be applied to a vehicular wireless terminal. The proposed voltage-controlled oscillator satisfies the targeted frequency range ($4.2{\sim}5.4\;GHz$) and the frequency planning which correspond to the standards such as CDMA(IS-95), PCS, GSM850, EGSM, WCDMA, WLAN, Bluetooth, WiBro, S-DMB, DSRC, GPS, and DVB-H/DMB-H/L(L Band). In order to improve phase noise performance, PMOS is adopted in the cross-coupled pair, the tail current source and MOS varactor in this VCO and differential-typed switching is proposed in capacitor array. Based on the measurement results, a total power dissipation is $5.3{\sim}6.0\;mW$ at 1.8 V power supply voltage. The oscillator is tuned from 4.05 to 5.62 GHz; The tuning range is 33%. The phase noise is -117.16 dBc/Hz at 1 MHz offset frequency and the FOM (Figure Of Merit) is $-180.84{\sim}-180.5$.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.44 no.6 s.360
• /
• pp.19-27
• /
• 2007

This paper presents power supply-insensitive Gbps low power LVDS I/O circuits. The proposed LVDS I/O has been designed and simulated using 1.8V, $0.18\;{\mu}m$ TSMC CMOS Process. The LVDS I/O includes transmitter and receiver parts. The transmitter circuits consist of a differential phase splitter and an output stage with the switched capacitor common mode feedback(SC-CMFB). The differential phase splitter generates a pair of differential signals which provides a balanced duty $cycle(50{\pm}2%)$ and phase difference$(180{\pm}0.2^{\circ})$ over a wide supply voltage range. Also, $V_{OD}$ voltage is 250 mV which is the smallest value of the permissible $V_{OD}$ range for low power operation. The output buffer maintains the required $V_{CM}$ within the permissible range$(1.2{\pm}0.1V)$ due to the SC-CMFB. The receiver covers a wide input DC offset $range(0.2{\sim}2.6\;V)$ with 38 mV hysteresis and Produces a rail-to-rail output over a wide supply voltage range. Beside, the designed receiver has 38.9 dB gain at 1 GHz, which is higher than conventional receivers.

• Journal of electromagnetic engineering and science
• /
• v.9 no.2
• /
• pp.85-97
• /
• 2009

As operating frequency is raised and as more integration with active and passive elements is required, it becomes difficult to fabricate more than 120 ${\Omega}$ characteristic impedance of a mierostrip line. To solve this problem, an equivalent high impedance transmission-line section is suggested, which consists mainly of a pair of coupled-line sections with two shorts. However, it becomes a transmission-line section only when its electrical length is fixed and its coupling power is more than half. To have transmission-line characteristics(perfect matching), independently of coupling power and electrical length, two identical open stubs are added and conventional design equations of evenand odd-mode impedances are modified, based on the fact that the modified design equations have the linear combinations of conventional ones. The high impedance transmission-line section is a passive component and therefore should be perfectly matched, at least at a design center frequency. For this, two different solutions are derived for the added open stub and two types of high impedance transmission-line sections with 160 ${\Omega}$ characteristic impedance are simulated as the electrical lengths of the coupled-line sections are varied. The simulation results show that the determination of the available bandwidth location depends on which solution is chosen. As an application, branch-line hybrids with very weak coupling power are investigated, depending on where an isolated port is located, and two types of branch-line hybrids are derived for each case. To verify the derived branch-line hybrids, a microstrip branch-line hybrid with -15 dB coupling power, composed of two 90$^{\circ}$ and two 270$^{\circ}$ transmission-line sections, is fabricated on a substrate of ${\varepsilon}_r$= 3.4 and h=0.76 mm and measured. In this case, 276.7 ${\Omega}$ characteristic impedance is fabricated using the suggested high impedance transmission-line sections. The measured coupling power is -14.5 dB, isolation and matching is almost perfect at a design center frequency of 2 GHz, showing good agreement with the prediction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2013.04a
• /
• pp.835-841
• /
• 2013

Modern solid-state gyroscopes (HRG) with hemispherical resonators from high-purity quartz glass and special surface superfinishing and ultrathin gold coating become the best instruments for precise-grade inertial reference units (IRU) targeting long-term space missions. Designing of these sensors could be a notable contribution into development of Korea as a space nation. In participial, 40mm diameter thin-shell resonator from high-purity fused quartz, fabricated as a single-piece with its supporting stem has been designed, machined, etched, tuned, tested, and delivered by STM Co. (ATS of Ukraine) several years ago; an extremely-high Q-factor (upto 10~20 millions) has been shown. Understanding of the best way how to match such a unique sensor with inner glass assembly of the gyro means how to use the high potential in a maximal extent; and this has become the urgent task. Inner quartz glass assembly has a very thin indium (In) layer soldered the resonator and its silica base (case), but effects of internal resonances between operational modal pair of the shell-cup and its side (parasitic) modes can notable degrade the potential of the sensor as a whole, instead of so low level of resonator's intrinsic losses. Unfortunately, there are special combinations of dimensions of the parts (so-called, "resonant sizes"), when intensive losses of energy occurs. The authors proposed to use the length of stem's fixture as an additional design parameter to avoid such cases. So-called, a cyclic scheme of finite element method (FEM) and ANSYS software were employed to estimate different combinations of gyro assembly parameters. This variant has no mismatches of numerical origin due to FEM's discrete mesh. The optimum length and dangerous "resonant lengths" have been found. The special attention has been paid to analyses of 3D effects in a cup-stem transient zone, including determination of a difference between the positions of geometrical Pole of the resonant hemisphere and of its "dynamical Pole", i.e., its real zone of oscillation node. Boundary effects between the shell (cup) and 3D short "beams" (inner and outer stems) have been ranged. The results of the numerical experiments have been compared with the classic model of a quasi-hemispherical shell band with inextensional midsurface, and the solution using Rayleigh's functions of the $1^{st}$ and $2^{nd}$ kinds. To guarantee the truth of the recommended sizes to a designer of the real device, the analytical and FEM results have been compared with experimental data for a party of real resonators. The consistency of the results obtained by different means has been shown with errors less than 5%. The results notably differ from the data published earlier by different researchers.

• Journal of Korean Medical Science
• /
• v.33 no.43
• /
• pp.277.1-277.10
• /
• 2018

Background: To examine survival rates and renal function after partial nephrectomy (PN) and radical nephrectomy (RN) in patients with chronic kidney disease (CKD). Methods: We studied 4,332 patients who underwent PN or RN for pathological T1a-T2N0M0 renal cell carcinoma from 1988 to 2014. Patients were divided into two subgroups of CKD stage I-II and stage III. Kidney function, and survival outcomes were compared between groups. Results: We included 1,756 patients with CKD I-II and 276 patients with CKD III in the final pair-matched analysis. Kidney function was significantly better preserved in the PN than in the RN group among all patients. However, the beneficial effect of PN on kidney function gradually disappeared over time in CKD III patients. The 5-year overall survival (OS) rates after PN and RN differed in patients with CKD I-II disease (99.4% vs. 96.5%, respectively, P = 0.015). The 5-year OS rates after surgery were not affected by mode of nephrectomy in CKD III patients (97.8% vs. 93.5%, P = 0.103). The 5-year cancer-specific survival rates did not differ between treatment groups in all CKD stage. Cox hazard analysis showed that the operative method was a significant factor for OS in CKD I-II patients (hazard ratio [HR], 0.320; confidence interval [CI], 0.122-0.840; P = 0.021). However, PN was not beneficial in terms of OS in CKD III patients (HR, 0.395; CI, 0.086-1.172; P = 0.117). Conclusion: PN is associated with a higher OS rate and better kidney function in patients with preoperative CKD stage I and II, but not in those with CKD stage III.

• International Area Studies Review
• /
• v.20 no.1
• /
• pp.53-78
• /
• 2016

This study is to analyze the effects of both the bilateral FTA and a home and its trade partner's FTAs on the trade with 62 country-pair panel data over the period of 2003-2013 using the gravity model and the spatial autoregressive model. First, the study analyzes how the bilateral FTAs affect the trade using the gravity model and the spatial model. Next, the article analyzes how the home and its trade partners' FTAs affect their trade using only the spatial model under controlling the bilateral FTA. The empirical results are summarized as the followings: first, the spatial mode fits well more than the gravity model in analyzing the relationship between the bilateral FTA and trade. It implies that the spatial spillover effect of FTA is important in the international trade with FTA. Second, the bilateral FTA plays a role in expanding the trade between or among the FTA members as proved by the previous studies. Third, the more the home and its trade partners' FTAs, the more the bilateral trade are extended. Fourth, with the bilateral FTAs, as the home and its trade partners enter into more FTAs, the bilateral trade reduces due to trade diversion effects. In conclusion, this study provides a political implication that in order to increase the trade volume, a country enters into as many FTAs as possible because the effects of the bilateral FTAs would decrease.

• The Journal of the Acoustical Society of Korea
• /
• v.40 no.6
• /
• pp.587-592
• /
• 2021

Change in the cortical thickness of long bones occurring with aging and osteoporosis is known to be a risk factor for fracture. The present study aims to investigate the dependencies of phase velocities of ultrasonic guided waves on the cortical thickness in 7 soft tissue-bone mimicking phantoms consisting of acrylic plates covered by a 2 mm-thick silicone rubber layer by using the axial transmission technique with a pair of transducers with a center frequency of 200 kHz and a diameter of 12.7 mm. Two distinct propagating waves with different velocities, the First Arriving Signal (FAS) and the Slow Guided Waved (SGW), were consistently observed for all the soft tissue-bone mimicking phantoms. The FAS velocity decreased slightly with increasing thickness, whereas the SGW velocity increased strongly with increasing thickness. The FAS and the SGW velocities were found to be closely consistent with the S0 and the A0 Lamb mode velocities for a free acrylic plate, respectively, suggesting that the presence of the soft tissue mimicking material (2 mm-thick silicone rubber layer) covering the acrylic plates does not influence significantly the velocity measurements.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.5 no.2
• /
• pp.141-149
• /
• 2004

The aim of this study was to test the validity of the hypothesis that the karyotypes of four species of Lepilemuridae were formed spontaneously from their ancestral hybrid karyotype. Hypothetical ancestral haploid Karyotype of Lepilemuridae is composed of 18 autosomes and X chromosomes. Lepilemur mustelinus karyotype has four tandem fused chromosomes and one Robertsonian translocated chromosome pairs. Lepilemur septentrionalis septentrionalis karyotype has only two pairs of translocated chromosomes. We reconstruct and suggest ancestral karyotype of LMU(ancLMU) and LSS(ancLSS), from which all four studied species were derived. Hybrids of ancLMU and ancLSS were formed and produce differently fused equilibrated gametes via circular form arrangement during gametogenesis. Five unit of trivalent homologous chromosome pairs were engaged in a circular form to give new gamete corresponding to the karyotype of L. dorsalis, orientation of one unit of trivalent was inversed in the circle to gave new gamete corresponding to the karyotype of L. leucopus. Seven homologous chromosome pairs were engaged in circular form to give haploid karyotype of Lepilemur ruficaudatus. Only one homologous chromosome pair is dissociated and the other chromosome pairs rearranged in the circle to form haploid karyotype of Lepilemur edwardsi. The new gametes could be produced from these circular forms. When the new gamete fertilized with the same type of gamete, The new homozygote is produced as existing L. dorsalis, L. leucopus, L. edwardsi and L. ruficaudatus. These results support the theory that new species could be formed in hybrid population through activated chromosome fusion, chromosome rearrangement in circular from at zygotene stage and production of equilibrated gametes to form homozygote new species.