• Journal of the Microelectronics and Packaging Society
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• v.31 no.2
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• pp.63-68
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• 2024

With the increasing use of transparent displays and flexible devices, polymer substrates offering excellent flexibility and strength are in demand. Since polymers are sensitive to heat, precise temperature control during the process is necessary. The study proposes a temperature measurement system for the laser processing area within the polymer base, aiming to address the drawbacks of using these polymer bases in laser-based selective processing technology. It presents the possibility of optimizing the process conditions of the polymer substrate through local temperature change measurements in the laser processing area. We developed and implemented the PDPT (Photodiode-based Planck Thermometry) to measure temperature in the laser-processing area. PDPT is a non-destructive, contact-free system capable of real-time measurement of local temperature increases. We monitored the temperature fluctuations during the laser processing of the polymer substrate. The study shows that the proposed laser-based temperature measurement technology can measure real-time temperature during laser processing, facilitating optimal production conditions. Furthermore, we anticipate the application of this technology in various laser-based processes, including essential micro-laser processing and 3D printing.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.5
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• pp.175-182
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• 2022

Rare-earth elements were doped with Mg to enhance the temperature stability of dielectric properties of BaTiO₃ for its application to MLCC (Multi-Layer Ceramic Capacitor). The additives strongly affect both grain growth and densification behaviors during sintering, and hence dielectric properties. The additive effects therefore should be examined in each system with different additives. This study investigated the crystal structure, grain growth and densification behaviors and related variations in dielectric constant with respect to sintering temperature. Dielectric constant appears to be varied with grain size in a temperature range between 1200 and 1300℃, suggesting the importance of grain size control. The temperature dependence of grain size variation was well explained by an established theory correlating the grain growth behavior with grain boundary structure. This accordance provides a basis for sintering technique to control grain growth thus to improve dielectric constant in rare-earth doped BaTiO₃.

• Resources Recycling
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• v.30 no.1
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• pp.35-43
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• 2021

In this study, Na2SO4 and KCl reagents were used to synthesize K2SO4 as a basic study for recycling byproducts generated during the manufacture of steel and cement. The mole ratio of Na2SO4 to KCl, the saturation of the solution, and the stirring temperature were controlled to derive the optimal manufacturing conditions. The microstructure and crystallinity of the materials prepared were evaluated using scanning electron microscopy and X-ray diffraction analysis. Pure K2SO4 was obtained when the mole ratio of Na2SO4 to KCl was 1:6-18, the saturation of the solution was less than 160%, and the stirring temperature was 20℃, 50℃. The optimal manufacturing conditions to maximize the crystallinity and yield of K2SO4 while minimizing the energy consumption were 1:6 mole ratio of Na2SO4 to KCl, 140% saturation of the solution, and 20℃ stirring temperature.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2951-2957
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• 2015

The development of worldwide harmful algal blooms(HAB) is a serious problem for public health and fisheries industries. To evaluate the algicidal impact on the HAB species, algicide thiazolidinedione derivative (TD49) and yellow clay were examined, which is focus on assess the algicidal effects and inhibition to photosynthesis of HAB species. To obtain the detailed information, we analyzed the viability of target species related to activity Chl. a, photosynthetic efficiency($F_v/F_m$), and electron transport rate(ETR). Culture experiment was conducted to evaluate the algicidal effects of three harmful species(raphidophyceae Heterosigma akashiwo, Chattonella marina, and dinophyceae Heterocapsa circularisquama) and one non-harmful species (cryptophyceae Rhodomonas salina). Our experiments revealed that three HAB species were easily destroyed of the cell walls after TD49 dosing. Also, they had significantly reducing values of active Chl. a, $F_v/F_m$, and ETR, due to the damage of photosystem II by inter-cellular disturbance. As a result, the algicidal effect(%) for the three HABs were as follows, in the order of greatest to the least: H. circularisquama> C. marina> H. akashiwo. However, the algicidal effect for yellow clay remained to be <30% (p>0.01), implying that it may not have damaged the photosystem II. On the other hand, non-HAB R. salina was promoted at both TD49 and yellow clay treatments. Our results demonstrated that the TD49 is a good agent for the control of HABs H. akashiwo, C. marina, and H. circularisquama, whereas the yellow clay would not be suitable for the field application based on our experimental results.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.1
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• pp.51-58
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• 2016

As semiconductor technology has developed, device performance has been improved. However, since device structures became smaller, circuit aging due to operational and environmental conditions can be accelerated. Circuit aging causes a performance degradation and eventually a system error. In reliable systems, a failure due to aging might cause a great disaster. Therefore, these systems need a performance degradation prediction function so that they can take action in advance before a failure occurs. This paper presents an on-line circuit performance degradation monitoring scheme for predicting a failure by detecting performance degradation during circuit normal operation. In our proposed scheme, IEEE 1149.1 output boundary scan cells and TAP controller are reused. The experimental result shows that the proposed architecture can monitor the performance degradation during normal operation without stopping the circuit.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.5
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• pp.772-778
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• 2018

Due to the recent advances in computing, communication and micro-electromechanical technology, Wireless Sensor Networks (WSNs) applications have been extended from military to many commercial areas such as object tracking, wire detection, and vehicular sensor networks. In some applications bursty data from many sensor nodes may be generated and the generated data from the monitoring area may be sent in a limited time to the final destination, sink node. In this paper, we present a BTF-MAC protocol adequate for WSNs applications in which bursty data packets are required to be transmitted in a limited time. The BTF-MAC is a synchronous duty-cycle MAC protocol and uses a slot-reserved and operational period extension mechanism adapted to the traffics. Our numerical analysis and simulation results show that BTF-MAC outperforms other related protocols such as DW-MAC and SR-MAC in terms of energy consumption and transmission delay.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.29-34
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• 2019

Silicon carbide is considered to be a potentially useful material for high-temperature electronic devices, as its large energy band gap and the p-type and/or n-type conduction can be controlled by impurity doping. Particularly, electric conductivity of porous n-type SiC semiconductors fabricated from ${\beta}-SiC$ powder at $2000^{\circ}C$ in $N_2$ atmosphere was comparable to or even larger than the reported values of SiC single crystals in the temperature region of $800^{\circ}C$ to $1000^{\circ}C$, while thermal conductivity was kept as low as 1/10 to 1/30 of that for a dense SiC ceramics. In this work, for the purpose of decreasing sintering temperature, it was attempted to fabricate porous reaction-sintered bodies at low temperatures ($1400-1600^{\circ}C$) by thermal decomposition of polycarbosilane (PCS) impregnated in n-type ${\beta}-SiC$ powder. The repetition of the impregnation and sintering process ($N_2$ atmosphere, $1600^{\circ}C$, 3h) resulted in only a slight increase in the relative density but in a great improvement in the Seebeck coefficient and electrical conductivity. However the power factor which reflects the thermoelectric conversion efficiency of the present work is 1 to 2 orders of magnitude lower than that of the porous SiC semiconductors fabricated by conventional sintering at high temperature, it can be stated that thermoelectric properties of SiC semiconductors fabricated by the present reaction-sintering process could be further improved by precise control of microstructure and carrier density.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2002.11a
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• pp.29-29
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• 2002

공구강 등 산업용 재료로 널리 사용되는 카바이드 계 재료는 입자 크기 및 분포에 따라 기계적 성질이 변화하므로, 이를 제어하고 조절하는 기술에 관하여 많은 연구가 진행되어 왔다. 본 연구에서는 TiCN-WC-Co 복합초경계 에서 소결 공정 및 조성변화에 따른 입자 모양을 관찰하고 이에 따른 업자 성장 거동을 고찰하였다. 일반적으로 입자 조대화 양상과 고상 입자의 모양과는 밀접한 관계가 있다. 각진 입자의 경우에 는 계면이 원자적으로 singular 하여 원자의 홉착이 어렵기 때문에 임계값 이상의 성장 구동력을 받 는 몇몇 입자만 성장하는 비정상 입자 성장이 일어날 수 있다. 반면에 계면이 rough한 퉁큰 엽자의 경우에는 원자 홉착에 필요한 구동력이 존재하지 않아 성장 구동력을 받는 모든 입자들이 성장하기 때문에 정상 입자 성장을 하게 된다. 이와 같이 입자 모양에 따른 입자 성장 거동은 전체 미세구조를 결정하게 되며, 이에 따른 물리 화학적 물성을 변화시킨다. 이러한 입자 성장 원리를 적용하 면 복합초경계 (TiCN-WC-Co)에서도 입자성장이 억제되고 치밀한 소결체를 제조할 수 있을 것이다. 본 실험에서는 평균입도가 각각 0.1, 1.33, 2$\mu\textrm{m}$인 TiCN, WC, Co 분말을 사용하여 $((I00_{-x)}TiCN+_xWC)-30Co$ (wt%) 조성에서 TiCN/WC 비를 변화시키면서 업자 모양과 입자성장 거동을 관찰하였다. 청량된 분말은 WC 초경 볼로 밀렁하고, 건조한 후, 100 mesh 체로 조립화 하였다. 이 분말을 100 MPa의 압력으로 냉간정수압성형 하고 $10^{-2}$ torr의 진공분위기의 graphite f furnace에서 carbon black으로 packing 하여 액상형성 온도 이상에서 소결하였다. 소결된 시편은 경면 연마하여 주사전자현미경으로 미세 조직을 관찰하였다. TiCN-30Co 조성 시편은 corner-round 모양의 입자 모양으로 소결 시간 증가에 따라 빠른 입자 성장을 나타내었다 .(7STiCN+2SWC)-30Co 조성 시변의 경우 일반적으로 보고된 바와 같이 core/shell 구조를 나타내었으며, core는 TiC-rich 상이었고, shell은 (Ti,W)(C,N) 복합 탄화물 상이었다. WC 함량이 중가함에 따라 입자의 corner-round 영역이 증가하였으며 (SOTiCN-SOWC)-30Co 조성 근처에서는 거의 둥근 형태의 입자 모양을 나타내었다. 또한 TiCN - 30Co 조성 시편에 비하여 WC가 첨가된 시펀들은 작은 평균입자크기를 나타내었다. 본 연구의 결과는 shell 영역 조성 변화는 계면에너지 이방성과 기지상 내의 펑형 입자 모양을 변화시키고 나아가 입자 성장 속도 에도 영향을 미친다는 것을 보여준다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.2
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• pp.139-145
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• 2024

This paper presents the design of a voltage controlled oscillator (VCO) which is one of the key building blocks in modern wireless communication systems with small VCO gain (K_vco) variation. To compensate conventional large K_vco variation, a series varactor bank has been added to the conventional LC-tank with parallel capacitor bank array. And also, in order to achieve excellent phase noise performance while maintaining wide tuning range, a mixed coarse/fine tuning scheme(series varactor array and parallel capacitor array) is chosen. The switched varactor array bank is controlled by the same digital code for switched capacitor array without additional digital circuits. For use at a low voltage of 1.2V, the proposed current reference circuit in this paper used a current reference circuit for safety with the common gate removed more safely. Implemented in a TSMC 0.13㎛ CMOS RF technology, the proposed VCO can be tuned from 4.4GH to 5.3GHz with the K_vco (VCO gain ) variation of less than 9.6%. While consuming 3.1mA from a 1.2V supply, the VCO has -120dBc/Hz phase noise at 1MHz offset from the carrier of the 5.3 GHz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.257-257
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• 2007

고밀도 FeRAM (Ferroe!ectric Random Access Memory) 소자를 개발하기 위해서는 강유전체 물질을 이용한 안정적인 스텍형의 커패시터 개발이 필수적이다. 특히 $(Bi,La)_4Ti_3O_{12}$ (BLT) 강유전체 물질을 이용하는 경우에는 낮은 열처리 온도에서도 균질하고 높은 값의 잔류 분극 값을 확보하는 것이 가장 중요한 과제 중의 하나이다. 불행히도, BLT 물질은 a-축으로는 약 $50\;{\mu}C/cm^2$ 정도의 높은 잔류 분극 값을 갖지만, c-축 방향으로는 $4\;{\mu}C/cm^2$ 정도의 낮은 잔류 분극 값을 나타내는 동의 강한 비등방성 특성을 보인다. 따라서 BLT 박막에서 각각 입자들의 크기 및 결정 방향성을 세밀하게 제어하는 것은 무엇보다 중요하다. 본 연구에서는 16 Mb의 1T/1C (1-transistor/1-capacitor) 형의 FeRAM 소자를 BLT 박막을 적용하여 제작하였다. 솔-젤 (sol-gel) 용액을 이용하여 스핀코팅법으로 BLT 박막을 증착하고, 후속 열처리 공정을 RTP (rapid thermal process) 공정을 이용하여 수행하였다. 커패시터의 하부 전극 및 상부 전극은 각각 Pt/IrOx/lr 및 Pt을 적용하였다. 반응성 이온 에칭 (RIE: reactive ion etching) 공정을 이용하여 커패시터를 형성시킨 후, 32k-array (unit capacitor: $0.68\;{\mu}m$) 패턴에서 측정한 스위칭 분극 (dP=P*-P^) 값은 약 $16\;{\mu}C/cm^2$ 정도이고, 웨이퍼 내에서의 균일도도 2.8% 정도로 매우 우수한 특성을 보였다. 그러나 단위 셀들의 특성을 평가하기 위하여 bit-line의 전압을 측정한 결과, 약 10% 정도의 커패시터에서 불량이 발생하였다. 그리고 이러한 불량 젤들은 매우 불규칙적으로 분포함을 확인할 수 있었다. 이러한 불량 원인을 파악하기 위하여 양호한 젤과 불량이 발생한 셀에서의 BLT 박막의 미세구조를 분석하였다. 양호한 셀의 BLT 박막 입자들은 불량한 셀에 비하여 작고 비교적 균일한 크기를 갖고 있었다. 이에 비하여 불량한 셀에서의 BLT 박막에는 과대 성장한 입자들이 존재하고 이에 따라서 입자 크기가 매우 불균질한 것으로 확인되었다. 또 이러한 과대 성장한 입자들은 거의 모두 c-축 배향성을 나타내었다. 이상의 실험 결과들로부터, BLT 박막을 이용하여 제작한 FeRAM 소자에서 발생하는 불규칙한 셀 불량의 주된 원인은 c-축 배향성을 갖는 과대 성장한 입자의 생성임을 알 수 있었다. 즉 BLT 박막을 이용하여 FeRAM 소자를 제작하는 경우, 균일한 크기의 입자 및 c-축 배향성의 입자 억제가 매우 중요한 기술적 요소임을 알 수 있었다.