• JSTS:Journal of Semiconductor Technology and Science
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• 제4권3호
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• pp.189-195
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• 2004

A 10 Gb/s limiting amplifier IC with the emitter area of $1.5{\times}10{\mu}m^2$ for optical transmission system was designed and fabricated with a AIGaAs/GaAs HBTs technology. In this stud)', we evaluated fine pitch bump using WL-CSP (Wafer Level-Chip Scale Packaging) instead of conventional wire bonding for interconnection. For this we developed WL-CSP process and formed fine pitch solder bump with the $40{\mu}m$ diameter and $100{\mu}m$ pitch on bonding pad. To study the effect of WL-CSP, electrical performance was measured and analyzed in wafer and package module using WL-CSP. In a package module, clear and wide eye diagram openings were observed and the riselfall times were about 100ps, and the output" oltage swing was limited to $600mV_{p-p}$ with input voltage ranging from 50 to 500m V. The Small signal gains in wafer and package module were 15.56dB and 14.99dB respectively. It was found that the difference of small signal gain in wafer and package module was less then 0.57dB up to 10GHz and the characteristics of return loss was improved by 5dB in package module. This is due to the short interconnection length by WL-CSP. So, WL-CSP process can be used for millimeter wave GaAs MMIC with the fine pitch pad.

• 설비공학논문집
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• 제25권7호
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• pp.377-385
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• 2013

In this study, the performance of an impeller according to blade length and pitch angle was studied experimentally by building a variable pitch impeller while changing blade length to review the effect of blade length and pitch angle on a fan's performance. The pitch angle was changed in six steps from $20^{\circ}{\sim}45^{\circ}$ at intervals of $5^{\circ}$ while the blade lengths were changed to 90 mm, 100 mm, 110 mm and 120 mm with an identical airfoil shape while carrying out the experiment. The results are summarized as follows : The air flow per static pressure of axial fans increased linearly with increase of pitch angle, but the high static pressure showed a decrease at a pitch angle of $35^{\circ}$. The shaft power increased proportionally to the pitch angle at all blade lengths; the larger the pitch angle, the larger the measured increase of shaft power. This is because the drag at the fan's front increases with the pitch angle. In the axial fans considered in this research, the flow and incre.

• 한국음향학회지
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• 제13권5호
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• pp.77-82
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• 1994

음성신호 처리에서, 피치를 정확하게 찾아내는 것이 매우 중요하다. 현재까지 많은 피치 검출 방법들이 제안되어 왔지만, 광범위한 화자와 다양한 음성 데이터로부터 정확한 피치를 찾는 것은 어렵다. 따라서 본 논문에서는 G-peak 검출을 이용한 새로운 피치 검출 알고리즘을 제안한다. 이 방법은 G-peak 의 MZCI (최대 영교차 간격) 을 LPF (low-pass filter)의 차단대역폭으로 결정하여 음성신호의 피치를 검출하는 방법이다. 본 알고리즘은 0dB SNR 환경 하에서 3.36%의 그로스 에러를 나타내는 잡음에 강인한 방법이다. 또한 잡음이 없는 음성의 그로스 에러는 0.18%였고, 모든 과정은 고속 처리가 가능하다.

• International Journal of Aeronautical and Space Sciences
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• 제9권1호
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• pp.111-120
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• 2008

A particle image velocimetry (PIV) technique was employed to investigate the effects of blowing jet on the flow characteristics over stationary and pitch-oscillating airfoils. The Reynolds number was $7.84{\times}10^5$ based on the chord length. It was found that for stationary airfoil cases, continuous and pulsating blowing jets successfully reduced separated wake region at high angles of attack. A comparison study of two different types of jet blowing indicated that pulsating jet is more effective than continuous jet for flow separation control. Pulsating leading-edge blowing postpones flow separation and increased stall angle of attack by $2^{\circ}{\sim}3^{\circ}$. For pitch-oscillating airfoil cases, the PIV results showed that blowing jet efficiently delays the separation onset point during pitch-up stroke, whereas it does not prevent flow separation during pitch-down stroke, even at angles of attack smaller than static ones.

• 음성과학
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• 제10권4호
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• pp.41-55
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• 2003

This paper investigates the tonal patterns of English information structure composed of topic and focus. It has been argued in previous theories that there is a significant relationship between English topic-focus structure and intonation. The English topic is marked with L+H* pitch accent and focus is marked with H* pitch accent. These theories, however, are oversimplified ones since they do not consider the contextual differences of topic and focus. To examine more concrete tonal patterns of English topic and focus, we classified topic into two subcategories of reminding topic and old-information topic. Focus was categorized into three: information focus, contrastive focus, and reference focus. The overall results show that native English speakers are inclined to use both the L+H* and H* pitch accent for the topic and focus of an utterance. We also observe a tendency to deaccentuate the topics given as old information and to mark the topics given as noun phrase with H* pitch accent. As for the intonation of focus, H* pitch accent is the most frequent type of accent, but L+H* also shows a high percentage of implementation especially in the context of correction or contrast.

• Carbon letters
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• 제16권2호
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• pp.78-85
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• 2015

Activated carbons (ACs) were prepared by activation of coal tar pitch (CTP) in the range of $700^{\circ}C-1000^{\circ}C$ for 1-4 h using potassium hydroxide (KOH) powder as the activation agent. The optimal activation conditions were determined to be a CTP/KOH ratio of 1:4, activation temperature of $900^{\circ}C$, and activation time of 3 h. The obtained ACs showed increased pore size distribution in the range of 1 to 2 nm and the highest specific capacitance of 122 F/g in a two-electrode system with an organic electrolyte, as measured by a charge-discharge method in the voltage range of 0-2.7 V. In order to improve the performance of the electric double-layer capacitor electrode, various mixtures of CTP and petroleum pitch (PP) were activated at the optimal activation conditions previously determined for CTP. Although the specific capacitance of AC electrodes prepared from CTP only and the mixtures of CTP and PP was not significantly different at a current density of 1 A/g, the AC electrodes from CTP and PP mixtures showed outstanding specific capacitance at higher current rates. In particular, CTP-PP61 (6:1 mixture) had the highest specific capacitance of 132 F/g, and the specific capacitance remained above 90% at a high current density of 3 A/g. It was found that the high specific capacitance could be attributed to the increased micro-pore volume of ACs with pore sizes from 1 to 2 nm, and the high power density could be attributed to the increased meso-pore volume.

• 한국응용과학기술학회지
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• 제31권3호
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• pp.408-415
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• 2014

In order to prepare high-quality activated carbons (ACs), coal tar pitch (CTP), and mixtures of CTP and petroleum pitch (PP) were activated with KOH. The ACs prepared by activation of CTP in the range of $700{\sim}1000^{\circ}C$ for 1~5 h had very porous textures with large specific surface areas of $2470{\sim}3081m^2/g$. The optimal activation conditions of CTP were determined as CTP/KOH ratio of 1:4, activation temperature of $900^{\circ}C$, and activation time of 3 h. The obtained AC showed the highest micro-pore volume, and pretty high specific surface area and meso-pore volume. The micro-pore volumes and specific areas of activated mixtures of CTP and PP were similar to each other but the meso-pore volume could be increased. In order to change the degree of crystallinity of precursors before KOH activation process, the CTPs were carbonized in the range of $500{\sim}900^{\circ}C$. As the carbonization temperature increased, the specific surface area and pore volume of the activated ACs with the same activation conditions for CTP decreased dramatically. It was demonstrated that the increased pore size distribution of AC electrodes in the range of 1 to 2 nm plays an important role in the performance of electric double-layer capacitor.

• 한국염색가공학회지
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• 제30권4호
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• pp.313-320
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• 2018

As carbon fiber reinforced composites(CFRP) are widely used in aerospace, automobile, marine, and sports goods applications, they have been studied extensively by various researchers. However, CFRP have been pointed out because of machining problems such as delamination and burr phenomenons. Especially, hole machining process, drilling, has non-smooth features on inlet and outlet surfaces of drilled hole. This kind of machining problem can be controlled to some extent by using high modulus pitch-CF, which has considerable effects on fracture behavior of composite compared with only PAN CF composite. Therefore, PAN and pitch hybridized CF composites were prepared having high strength and modulus. The results demonstrate that the hybrid CFRP specimens with pitch CF offer the good potential to enhance modulus as well as strength properties. Dynamic mechanical, flexural, and impact properties were measured and analyzed. Morphological surface of the composites were also observed by IFS-28, canon after hole machining.

• Carbon letters
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• 제15권4호
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• pp.247-254
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• 2014

In this work, thermal treatment accompanied with different acid treatments was applied to a commercial coal tar pitch (CTP) to obtain a spinnable precursor pitch for carbon fiber. In the case of thermal treatment only, a relatively high reaction temperature of between $380^{\circ}C$ and $400^{\circ}C$ was required to obtain a softening point (SP) range of $220^{\circ}C-260^{\circ}C$ and many meso-phase particles were created during the application of high reaction temperature. When nitric acid or sulfuric acid treatment was conducted before the thermal treatment, the precursor pitch with a proper SP range could be obtained at reaction temperatures of $280^{\circ}C-300^{\circ}C$, which were about $100^{\circ}C$ lower than those for the case of thermal treatment only. With the acid treatments, the yield and SP of the precursor pitch increased dramatically and the formation of meso-phase was suppressed due to the lower reaction temperatures. Since the precursor pitches with acid and thermal treatment were not spinnable due to the inhomogeneity of properties such as molecular weight distribution and viscosity, the CTP was mixed with ethanol before the consecutive nitric acid and thermal treatments. The precursor pitches with ethanol, nitric acid, and thermal treatments were easily spinnable, and their spinning and carbon fiber properties were compared to those of air blowing and thermal treated CTP.

• Journal of the Korean Wood Science and Technology
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• 제35권6호
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• pp.13-22
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• 2007

주요 조림수종으로 도입 식재된 리기다소나무의 고부가가치 이용을 위한 구조용 집성재 이용 가능성을 검토하고, 이에 적합한 기술을 개발하기 위하여 본 연구를 수행하였다. 국산 리기다소나무 제재목의 기계응력등급은 대부분 E7에서 E9등급으로 집성재 제조에는 다소 불량한 것으로 나타났다. 반면 단일수종 및 혼합수종 구조용 집성재 제조에 필수적인 리기다소나무 및 낙엽소 판재의 접착성을 평가한 결과 전단접착력, 목파율, 침지 및 삶음박리율 모두 KS기준 이상으로 나타났다. 리기다소나무 단일수종 집성재의 휨성능을 측정해본 결과 휨강도는 KS의 집성재 강도등급에 따른 휨성능 합격기준을 만족한 반면 휨 탄성계수는 기준에 다소 못 미치는 결과를 나타내었다. 그러나 낙엽송 층재와의 혼합구성을 통해 리기다소나무 집성재의 휨성능(휨강도와 휨탄성계수)을 20% 향상시킬 수 있었으며, 층재 구성방법에 있어서는 판재의 탄성계수가 높고 품질이 우수한 낙엽송 층재를 외층에 배치하는 방법이 보다 효과적인 것으로 확인되었다. 결론적으로 리기다소나무의 부가가치 증진을 위한 구조용 집성재 이용은 그 가능성이 매우 컸다.