• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.53-59
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• 2010

Recently, NDTs (Non-Destructive Techniques) using infrared camera are widely studied for detection of damage and void in RC (reinforced concrete) structures and they are also considered as an effective techniques for maintenance of infrastructures. The temperature on concrete surface depends on material and thermal properties such as specific heat, thermal conductivity, and thermal diffusion coefficient. Different porosity on cement mortar due to different mixture proportions can show different heat behavior in cooling stage. The porosity can affect physical and durability properties like strength and chloride diffusion coefficient as well. In this paper, active thermography which uses flash for heat induction is utilized and thermal characteristics on surface are evaluated. Samples of cement mortar with W/C (water to cement ratio) of 0.55 and 0.65 are prepared and physical properties like porosity, compressive strength, and chloride diffusion coefficient are evaluated. Then infrared thermography technique is carried out in a constant room condition (temperature $20{\sim}22^{\circ}C$ and relative humidity 55-60%). The mortar samples with higher porosity shows higher residual temperature at the cooling stage and also shows reduced critical time which shows constant temperature due to back wall effect. Furthermore, simple equation for critical time of back wall effect is suggested with porosity and experimental constants. These characteristics indicate the applicability of infrared thermography as an NDT for quality assessment of cement based composite like concrete. Physical properties and thermal behavior in cement mortar with different porosity are analyzed in discussed in this paper.

• Journal of Advanced Navigation Technology
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• v.11 no.4
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• pp.437-446
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• 2007

In this paper, we numerically induced the optimal values of optical phase conjugator (OPC) position and dispersion coefficients of fiber sections, which can improve the bit error rate (BER) and design the adaptive WDM transmission system, as a function of the extinction ratio (ER) of 10 dB and 20 dB in $16{\times}40$ Gb/s WDM transmission system. It is confirmed that these optimal parameter values for effectively compensating overall WDM channels are dependence on the extinction ratio of signals as well as modulation format, transmitted channel numbers, which were investigated in previous researches. It is also confirmed that ER of 20 dB has the advantage of designing flexible WDM systems using optimal parameters than ER of 10 dB.

• Korean Journal of Childcare and Education
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• v.8 no.3
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• pp.229-247
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• 2012

The purpose of this study is to investigate the level of mothers' parenting stress according to the knowledge and behaviors that mothers have on infant development. The subjects of this study are 145 mothers whose infants range in age from 18 to 36 months. The instruments used are: 1) Knowledge of Child Development Inventory (KCDI) (Larsen & Juhasz, 1986), 2) Q-sort modified by Ahn (2001), 3) Parenting Stress Scale (PSS) (Kim & Kang, 1997), and a demographic questionnaire. The data analyses used SPSS 12.0 which employs basic statistics, a reliability test, ANOVA and Pearson's correlation. The results of this study indicate a correlation (r= -.20*) between behaviors of child-rearing and parenting stress of mothers. Specifically, mothers behaviors of child-rearing related to cognition development could predict parenting stress.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.6
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• pp.128-134
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• 2009

In this paper, we propose a new lumped Wilkinson power divider which is designed to have lower quality-factors in the impedance transformation. Therefore, it can provide wider bandwidth than the conventional one. Moreover, the proposed power divider consists of fewer number of elements so that the circuit size can be further reduced. Simulation results show that the proposed lumped power divider allows a 50% wider bandwidth in the return loss and isolation performance. The conventional and new Wilkinson power was designed and fabricated based on the derived equations at 2.0 GHz. In the measurement, the proposed divider achieved a good performance with an input return loss ($S_{11}$) of -23.0 dB, an isolation ($S_{23}$) of -29.0 dB and an insertion loss ($S_{21}$) of -3.12 dB at the design frequency with wider bandwidth than the conventional one.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.10 s.113
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• pp.959-966
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• 2006

This paper proposes a new concept about dual band predistortion linear power amplifier(PD LPA) using diplexer for digital cellular ($f_o$=880 MHz) and IMT-2000($f_o$=2,140 MHz) base stations. The diplexer is composed of low pass filter having defected ground structure(BGS) microstrip line and high pass filter having high-Q lumped capacitors and distributed elements. The proposed predistorter adopts a reflection type intermodulation signal generator with 3 dB hybrid coupler for good reflection characteristic. for a forward link one carrier CDMA IS-95A 1FA and WCDMA 1FA signal, the proposed dual band PD LPA shows the adjacent channel leakage ratio(ACLR) improvement about 10 dB and 9.36 dB for digital cellular and IMT-2000 band, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.5
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• pp.1299-1309
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• 1998

In this paper, we propose a new approach for reducing the blocking artifact that is one of drawbacks of the block-based Discrete Cosine Transform (DCT) without introducing additional information or significant blurring. We modify the inter-block discontinuity minimization technique to preserve edges within a block as well as to reduce visible block boundaries. The homogeneity of each block is decided by the threshold value reated to Q-factor, which is included in a JPEG as well as MPEG streams. The quantization error is estimated by minimizing the discontinuity, which is weighted in proportion to block discontinuity and added to each pixel in the block to compensate block artifacts. The proposed algorithm reconstructs images which have less noticeable block boundaries from a subjective viewpoit without anyconstraints.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.961-966
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• 2009

In this paper, a novel voltage-controlled oscillator(VCO) using the metamaterial broadside coupled spiral resonators(BC-DSRs) is presented for reducing the phase noise. For reducing of the phase noise, the series spiral structures have been applied for the signal plane and ground plane at each in order to have the large coupling. Compared with the conventional VCO, the proposed VCO has the larger coupling coefficient constant, which makes a higher Q-factor and has reduced the phase noise of the VCO. The proposed VCO has the phase noise of $-121{\sim}-117.16\;dBc$/Hz at 100 kHz in the tuning range, $5.749{\sim}5.853\;GHz$. The figure of merit(FOM) of this VCO is $-198.45{\sim}-194.77\;dBc$/Hz at 100 Hz in the same tuning range, respectively.

• Journal of Environmental Policy
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• v.14 no.4
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• pp.63-101
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• 2015

Banking and borrowing under the ETS may affect the low carbon technology investment level. If the indirect implementation measures are allowed, firms can gradually adjust their carbon reduction costs between implementation periods based on their carbon reduction costs and emission price forecasts. This implies that banking and borrowing may reduce or increase the level of low carbon technology R&D investment. In an oligopoly market, the effects of the measures are quite different from the ones in a perfectly competitive market. This is because the indirect implementation measures can shift market competition in Cournot competition model. The effects of banking and borrowing on the carbon reduction R&D investments depend on emission reduction costs, marginal production costs, discount rate, initial free allocation, and the cost reduction effects of R&D investment.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.4
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• pp.59-65
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• 2008

This paper proposed a H.264 deblocking filter for the portable low-power multimedia. In H.264 deblocking filter, total 8 input pixels in filtering operations needs own filtering operation process respectively, and each filtering process has common structures for each filtering operation. By sharing common filter coefficients and registers, we have designed and implemented an smaller gated module, and moreover filtering operations are skipped on some or whole pixels what if we use some specific condition to operate filtering modules that need lots of operations. In the core of filtering modules, we achieve 33.31% and 10.85% gate count reduction compared with those of filtering modules of the conventional deblocking filter papers. The proposed low-power deblocking filter is implemented by using samsung 0.35um standard cell library technology, the maximum operationh frequency is 108MHz, and the maximum throughput is 33.03 frames/s with CCIR601 image format.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.195-195
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• 2008

CAS계 유리에 $CaCO_3-Al_2O_3$ 혼합물 및 화합물을 10, 30 wt% 첨가하여 저온 소걸 및 마이크로파 유전 특성을 고찰하였다. CAS계 유리의 연화온도는 $841^{\circ}C$ 이며, CAS계 유리에 $CaCO_3$ 와 30 wt%의 $CaCO_3-Al_2O_3$ 혼합물을 melting되며, 10 wt%의 $CaCO_3$, $Al_2O_3$, $1CaCO_3-1Al_2O_3$ 혼합물 및 $CaAl_2O_4$ 화합물를 10 wt% 첨가하였을 때 $900^{\circ}C$ 이하에서 소걸이 가능하였다. 복합체의 XRD 상 분석 결과, CaCO3를 첨가하였을 때에는 모든 조성이 비정질을 나타내었고, $Al_2O_3$와 $1CaCO_3-1Al_2O_3$ 혼합물은 $Al_2O_3$ 결정상이 생성되었고, $CaAl_2O_4$ 화합물은 $CaAl_2Si_2O_8$의 hexagonal와 anorthite 결정상이 생성되었다. 따라서 CAS-10 (A, C-A, CA) 복합체는 $900^{\circ}C$에서 각각 유전율 ($\varepsilon_r$) 6.4, 6.9, 5.15 와 품질계수 ($Q^*f$) 2,400, 1,500, 3,000의 마이크로파 유전 특성을 나타내어 LTCC 기판 재료로 사용이 가능하며, 특히 $CaAl_2O_4$ 화합물을 사용하였을 때 가장 우수한 유전 특성을 나타내는 것을 확인하였다.