• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2309-2311
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• 2005

A broadband microstrip balun is proposed and designed using a ${\lambda}/4$short-stub in order to compensate phase imbalance. For the demonstration, two baluns are proposed and designed using a ${\lambda}/4$ shorted stub. One is a modified form of the conventional Wilkinson balun, and the other is a modified ring hybrid. Baluns are implemented on TLX-9 substrate of which the dielectric constant is 2.54 and the thickness is 0.5mm. The measurements show a bandwidth of 500MHz at the center frequency of 2GHz.

• Bulletin of the Korean Chemical Society
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• 제18권2호
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• pp.156-161
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• 1997

Aqueous 6-hydroxyquinoline in the first excited singlet state undergoes protonation to the imine group first in 15 ps, then in the time scale of 40 ps deprotonation from the enol group and finally, however, quickly as in 11 ps electron rearrangement to change into a resonance hybrid structure of quinoid-prevailing forms. Despite the fact that the decay time constant is smaller than the formation time constant, fluorescence from excited protropic zwitterion is observed to assign its maximum at 510 nm. The electron rearrangement is basically an intramolecular charge transfer from the deprotonated oxygen atom to the positively charged iminium ring without any notable change in nuclear geometry, producing a zwitterionic quinoid structure with much a smaller electric dipole moment than the zwitterionic protropic species. This photoproduct formed by consecutive excited state proton and electron transfers shows a smaller dipole moment in S1 than in S0 and a hypsochromic shift although its S1 state has (π, π*) character.

• 소성∙가공
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• 제30권3호
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• pp.149-156
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• 2021

Fine blanking is a high-precision process combining principles of metal stamping and cold forming. Unlike conventional metal stamping, fine blanking uses a special triple action such as V-ring force, counter force, shearing force. This study performed the effect of pocket-shaped compression molding on the mold life of the fine blanking using the 7.4mm thick SM45C material. In order to determine the lifespan of the punch and die in the fine blanking molds, a trial mold was manufactured and various punch materials were selected to perform the mold life test. A study on the life of a fine blanking mold by applying a thick plate material was experimentally performed through a mold test.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제10권7호
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• pp.191-198
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• 2021

분산 딥러닝은 각 노드에서 지역적으로 업데이트한 지역 파라미터를 동기화는 과정이 요구된다. 본 연구에서는 분산 딥러닝의 효과적인 파라미터 동기화 과정을 위해, 레이어 별 특성을 고려한 allreduce 통신과 연산 오버래핑(overlapping) 기법을 제안한다. 상위 레이어의 파라미터 동기화는 하위 레이어의 다음 전파과정 이전까지 통신/계산(학습) 시간을 오버랩하여 진행할 수 있다. 또한 이미지 분류를 위한 일반적인 딥러닝 모델의 상위 레이어는 convolution 레이어, 하위 레이어는 fully-connected 레이어로 구성되어 있다. Convolution 레이어는 fully-connected 레이어 대비적은 수의 파라미터를 가지고 있고 상위에 레이어가 위치하므로 네트워크 오버랩 허용시간이 짧고, 이를 고려하여 네트워크 지연시간을 단축할 수 있는 butterfly all-reduce를 사용하는 것이 효과적이다. 반면 오버랩 허용시간이 보다 긴 경우, 네트워크 대역폭을 고려한 ring all-reduce를 사용한다. 본 논문의 제안 방법의 효과를 검증하기 위해 제안 방법을 PyTorch 플랫폼에 적용하여 이를 기반으로 실험 환경을 구성하여 배치크기에 대한 성능 평가를 진행하였다. 실험을 통해 제안 기법의 학습시간은 기존 PyTorch 방식 대비 최고 33% 단축된 모습을 확인하였다.

• 약학회지
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• 제52권1호
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• pp.20-26
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• 2008

2-Aminothiazole ring as a bioisoster of catechol in dopamine has provided with good oral availability and lipophilic property. Selenium was reported to have an improved antioxidant ability and to reduce the loss of dopamine. 2-Aminoindan, is a rigid form of dopamine, was evaluated as a dopamine agonist with low neurotoxocity. In order to develop a novel dopamine agonist, we tried to synthesize the selenazoloaminoindan derivative that is a hybrid structure of aminoindan and aminoselenazole instead of aminothiazole. 2-Indanone-2-oxime was reduced with $TiCl_4$ and $NaBH_4$ to form 2-aminoindan, which was reacted with propionyl chloride to give 2-N-n-propionylaminoindan (2). Compound 2 was reduced with $TiCl_4$ and $NaBH_4$ to afford 2-N-n-propylaminoindan (3) and it was nitrated and reduced to form 5-amino-2-N-n-propylaminoindan (5), which was reacted with KSeCN, $Br_2$, and glacial acetic acid to give 4,6-dibromo-5- amino-2-N-n-propylaminoindan (7) instead of selenazole ring formation. Otherwise, compound 2 was nitrated and hydrogenated to form 5-amino-2-N-n-propionylaminoindan (9), which was treated with KSeCN, $Br_2$, and glacial acetic acid to give 4,6-dibromo-5-amino-2-N-n-propionylaminoindan (10). Compound 9 was cyc1ized with KSeCN and glacial acetic acid in the absence of $Br_2$ to give 6-amino-2-N-(n-propionylamino)selenazolo[4,5-f]indan (11).

• 대한화학회지
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• 제55권2호
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• pp.183-188
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• 2011

Ni$(C_6H_{4-n}F_n)(CO)_2$ ($C_6H_4$=benzyne, n=1-4) 착물의 전자구조 및 성질을 혼성 밀도 함수 B3LYP 이론을 이용하여 조사하였다. Benzyne 고리에 대한 방향족 성질과 벤젠핵과 무관한 화학적이동(NICS)을 분석하였다. 일-, 이- 및 삼-플루오르화 착물 중에서 3-F, 3, 6-F, 및 4-H는 각기 가장 안정한 이성질체였다. 고리 중심 상단의 여러 점에서 계산한 NICS 수치는 이들 착물의 상대 에너지에 의해 구한 값들과 일치하였다. 분자-내-원자(AIM) 분석에서 얻어진 Ni-C 결합거리는 모든 화학종에 대한 고리 임계점의 전자밀도(${\rho}_{rcp}$)와 좋은 상관성을 보였다.

• 한국전자파학회논문지
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• 제20권12호
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• pp.1325-1332
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• 2009

본 논문에서는 인체의 호흡 및 심박수 측정을 위해 2.4 GHz에서 동작하는 바이오 레이더 시스템의 소형화 및 성능 개선 방안으로서 하나의 원형 편파 안테나와 PLL 회로를 갖는 시스템을 설계하고 그 측정 결과를 제시 하였다. 제작된 바이오 레이더는 $90^{\circ}$ 하이브리드를 이용하여 원형 편파 특성과 송수신 격리 특성을 갖는 마이크 로스트립 안테나, 저잡음 증폭기, 전력 증폭기, 위상 고정 루프를 갖는 전압 제어 발진기, 직교 복조기 및 아날로그 회로로 구성된다. 특히, 단일 원형 편파 안테나를 소형화하기 위하여 annular-ring 형태의 마이크로스트립 안 테나를 송수신 회로와 적층함으로써, $40\times40mm^2$의 크기로 소형화할 수 있었다. 또한, 누설 송신 신호에 인한 수신부의 위상 잡음의 영향을 최소화하기 위하여 PLL 회로를 채용함으로써, 개선된 신호대 잡음비 성능을 갖도록 하였다. 설계된 바이오 레이더 시스템은 특별한 신호 처리 없이 50 cm 떨어진 사람의 호흡 및 심박수를 측정할 수 있음을 확인하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.925-928
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• 2005

In this study, we fabricated the DAMLs using surface micromachining technology as well a low loss coupler for the millimeter-wave band applications using these DAMLs. The structure of DAML is that a signal line is supported on ground plane by dielectric posts. Therefore it has advantages about the loss characteristic and the stable structure. The other advantage of the DAML process is a simple and convenient technique using 4 mask steps, even if it has a micromachining technology. The lowest loss of the fabricated DAML was obtained 2.2 dB/cm at 110 GHz. To obtain the low loss characteristic, couplers were designed and fabricated by using DAMLs. The fabricated ring hybrid coupler has the coupling of 3.58 dB and the thru of 3.31 dB at 60 GHz. We can also obtain the coupling of 3.42 dB, the thru of 3.82 dB from fabricated branch line coupler at 60 GHz.

• 한국자기공명학회논문지
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• 제21권4호
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• pp.139-144
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• 2017

Ni(II) containing coenzyme F430 catalyzes the reduction of $CO_2$ in methanogen. Macrocyclic Ni(II) complexes with N,O shiff bases have been received a great attention since metal ions play an important role in the catalysis of reduction. The reducing power of metal complexes are supposed to be dependent on oxidoreduction state of metal ion and structural properties of macrocyclic ring moiety that can enhance electrochemical properties in catalytic process. Six different ${\alpha}$-oximinoketone compounds, precursor of macrocyclic ligands used in $CO_2$ reduction coenzyme F430 model complexes, were synthesized with yields over 90% and characterized by NMR. The molecular geometries of ${\alpha}$-oximinoketone analogues were fully optimized at Beck's-three-parameter hybrid (B3LYP) method in density functional theory (DFT) method with $6-31+G^*$ basis set using the ab initio program. In order to understand molecular planarity and substitutional effects that may enhance reducing power of metal ion are studied by computing the structure-dependent $^{13}C$-NMR chemical shift and comparing with experimental results.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 춘계학술대회 논문집
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• pp.250-253
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• 2007

Gas Discharge Tubes (GDTs) are widely used as surge protectors for commnuication applications due to their small internal capacitance. In these days, however, they are mostly used in combined configurations, because the activation voltage required to initiate the discharge process in the GDTs for sufficient amount of time can be large enough to damage surge-sensitive protected circuits. For GDTs with a considerably high initial over-voltage value, we should limit the peak voltage using a TVS or filter. As for ZnO varistors, even though their performance for voltage restriction is excellent, their applications in high-frequency commnuication circuits have been limited because of higher internal capacitance when compared to the GDTs. In order to develop a surge protector for commnuication applications by taking advantages of these two devices, we built a combination circuit that connects a GDT and a ZnO varistor along with a choke coil in common and differential modes. We describe how the applied SPDs operate in protection process steps with the actual data obtained from the residual voltage measurements at each step. The experiment results show that the surge voltage restriction with the choke coil is more effective in 100 [kHz] RingWave voltage than in lightning impulse voltage.