• Journal of Powder Materials
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• v.22 no.3
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• pp.181-186
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• 2015

In this study, the effect of the friction stir welding (FSW) was compared with that of the gas tungsten arc welding (GTAW) on the microstructure and microhardness of Cu-Ni alloy weldment. The weldment of 10 mm thickness was fabricated by FSW and GTAW, respectively. Both weldments were compared with each other by optical microstructure, microhardness test and grain size measurement. Results of this study suggest that the microhardness decreased from the base metal (BM) to the heat affected zone (HAZ) and increased at fusion zone (FZ) of GTAW and stir zone (SZ) of FSW. the minimum Hv value of both weldment was obtained at HAZ, respectively, which represents the softening zone, whereas Hv value of FSW weldment was little higher than that of GTAW weldment. These phenomena can be explained by the grain size difference between HAZs of each weldment. Grain size was increased at the HAZ during FSW and GTAW. Because FSW is a solid-state joining process obtaining the lower heat-input generated by rotating shoulder than heat generated in the arc of GTAW.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.7
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• pp.695-701
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• 2008

In this paper, we propose the efficient Doppler removal method using map-based partial-time common intermediate frequency removal technique. In the proposed algorithm, the 2-stage carrier removal process was used. First, the component of common intermediate frequency is removed. Next the component of Doppler was removed with averaging and approximation. For the evaluation of the proposed algorithm, The real-time software GPS L1 C/A-code receiver was implemented. When the proposed algorithms are used, 12 tracking channels with 3 track arm(early, prompt, late) is operated real-time on PC using a Intel Pentium-III 1.0GHz CPU. Also, the requirement of memory was less than 2Mbytes. The real-time software GNSS receiver using the proposed algorithms provides the navigation solution with below 10 meter rms error. Especially, in spited of using the various approximations for implementing the algorithms, the high sensitivity capability (able to track the weak signal with -159dBm) was achieved.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.3
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• pp.239-254
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• 1988

In this paper an exciter which performs modulation and amplification is composed of high power(30dBm) VCO(Voltage Controlled Oscillator) using push-pull circuit. Modulation is FSK using PLL(Phase Locked Loop). A single loop PLL synthesizer having sequency range of 42.5-100.5MHz, 25KHz channel spacing and switching time of 1msec converts down the exciter VCO frequency to 1.25MHz. This signal mixed with the FSK modulated signal coming in the phase detector of exciter. The acquisition time of exciter for frequency hoppng is less than 200usec, so the total acquisition time for transmission is less that 1.5msec. There is no need of additional power amplification because power amlifiction by high power VCO is high enough to communicate within near distance. The proposed frequency synthesizer is not complex so it is suitable for low cost slow frequency hopping spread spectrum communication.

• The Research Journal of the Costume Culture
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• v.15 no.6
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• pp.996-1007
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• 2007

This study was focused on recognitive reaction. The purposes of this study was to analyze the fashion brands through correlation analysis between top of mind, recall, recognition, impact index and consumer behavior, and to identify the graveyard brand, niche brand and core brand. 33 questions about 20 fashion brands were asked to 442 males and females from the middle school students to age of 40. Data were analyzed mean, standard deviation, frequency, and correlation by using SPSS 12.0. The results were as follows: 1. Top of mind, recall and recognition affected recognizing the brands and including evoked setting, but it didn't lead the customer to purchase the brand. 2. Although top of the mind and recall are high, the percentage of purchasing the brand is relatively low if a consumer doesn't own the brand. 3. Brands 'B', 'L', 'PF', 'D' and 'BM' were represented as niche Brands which had high recognition and memory. 4. Brands 'TB', 'I', 'EN', 'ML', 'E' could be Graveyard brands that need special management. 5. Brands with the high impact index were 'A', 'T', 'I', 'C' and 'B'. These brands were recognized as the core brands by consumers.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.118-121
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• 2003

A new approach, using MEMS, for improving the performance of high efficiency amplifiers is proposed in this paper. The MEMS tuning element is described as a variable-length shorted CPW stub. Class-E amplifiers can be optimally tuned by these MEMS tuning elements because their operation varies with the impedance of the output tuning circuit. A MEMS tuning element was simulated using full-wave EM simulators to obtain its S-parameters. A Class-E amplifier with the MEMS was designed at 8GHz. The non-linear operation of this amplifier was simulated to explore the effect of the MEMS tuning. Comparing the initially designed amplifier without MEMS, the Power Added Efficiency (PAE) of the amplifier with MEMS is improved from 46.3% to 66.9%. For the amplifier with MEMS, the nonlinear simulation results are PAE = 66.90%, $\eta$(drain efficiency) = 75.89%, and $P_{out}$ = 23.37 dBm at 8 GHz. In this paper, the concept of the MEMS tuning element is successfully applied to the Class E amplifier designed with transmission lines.

• Journal of electromagnetic engineering and science
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• v.17 no.4
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• pp.178-180
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• 2017

This study presents a 2-20 GHz monolithic distributed power amplifier (DPA) using a $0.25{\mu}m$ AlGaN/GaN on SiC high electron mobility transistor (HEMT) technology. The gate width of the HEMT was selected after considering the input capacitance of the unit cell that guarantees decade bandwidth. To achieve high output power using small transistors, a 12-stage DPA was designed with a non-uniform drain line impedance to provide optimal output power matching. The maximum operating frequency of the proposed DPA is above 20 GHz, which is higher than those of other DPAs manufactured with the same gate-length process. The measured output power and power-added efficiency of the DPA monolithic microwave integrated circuit (MMIC) are 35.3-38.6 dBm and 11.4%-31%, respectively, for 2-20 GHz.

• The Inventors News
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• no.46
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• pp.1-16
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• 2006

'2006 대한민국 여성 발명품 박람회' 개최/'발명의 달 5월' 행사 풍성히 열려/'제12회 여성발명 우수사례 발표회' 열려/;꽃꽃이 용기' 출원동향 급격히 늘어나/특허청 '소멸특허정보 서비스' 제공한다/김열 특허청 차장 승진 임명/BM 특허 출원, 개인은 줄고 기업은 늘고/5월부터 특허료, 우선심사신청료 인하/현장 스케치/특허청과 한국전력 기술.특허정보 공유 양해각서 체결/독일과 '장미전쟁', 한국 승리/'제34회 제네바 국제발명전'에서 전원 수상 기록/국제 특허 전문가 한 자리에 모였다/특허청, 해외지재권 침해 소송비용 지원/국가연구 개발사업 지원하는 'R&D 특허센터' 출범/'특허 고객 고층 해결 안방 서비스' 개시/한국특허정보원, 다양한 캠페인 통해 사회공헌 활동/특허청, 과학기술 전문인력 50명 특별채용/'특허기술이전 박람회' 개최/취업 위해 일본 기업에 IT특허 기술 유출/부조리 신고자에 포상금 지급/역사 속의 발명품/하루 10분 발명교실/특허Q&A/'주부에서 발명가로, 필요에 의해 발병이 시작됐습니다'/여주초등학교 발명교실/아이디어 착상 및 발명 기법/여성 발명 활동 더욱 장려해야/무리에의 마가린/세계 상표제도 더욱 가까워져/특허청,'아시아 특허정보 허브'로 급부상/'2006 발명 특허 페스티벌' 개최/지리적 명칭, 신문제호 상표등록 안된다/리빙 아이디어/특허기술사업화에 3천89척원 지원/'찾아가는 심사 서비스' 대리인 사무소까지 확대/문화콘텐츠 식별체계 첫 선 보여/한국여성발명협회 회원사 발명품 가이드/

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.2
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• pp.238-246
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• 2024

Modern military operations rely heavily on broadband communication and data transmission. Recently, the rising use of intelligent unmanned technology necessitates more frequencies. Free-space optical(FSO) communication can offer high-data-rate communications with high security and no need for licensing. Therefore, the FSO communication holds significant interest and potential in the defense industry. In this paper, we present design of a FSO communication terminal taking Korean domestic weather conditions into account. The domestic atmospheric attenuation is analyzed using several models and two-year meteorological information for a city in Korea, and this analysis is utilized to design the FSO communication terminal. The design results were verified using an FSO communication test bed, and we achieved an Ethernet bandwidth of approximately 1.86 Gbps at a distance of 1.3 km with the optical amplifier output power of the test bed set to about 20 dBm.

• Korean Journal of Materials Research
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• v.13 no.6
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• pp.389-393
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• 2003

The effect of antireflection layer on the reduction of optical loss has been investigated in Si photodiodes detecting red light with central wavelength of 670 nm. The theoretical analysis showed minimum reflection loss of 6% for the $SiO_2$thickness of about $1100∼1200\AA$ in the $SiO_2$-Si system with the single antireflection layer and no reflection loss for the X$N_3$N$_4$$SiO_2$thickness of $2000\AA$/$1200\AA$ in the $Si_3$$N_4$$SiO_2$-Si system with double antireflection layer. In our experiments, Si photodiodes with the web-patterned $p^{＋}$-shallow diffusion region were fabricated by bipolar IC process technology and the devices were classified into three kinds according to the structure of $Si_3$$N_4$/$SiO_2$antireflection layer. The fabricated devices showed maximum spectral response in the optical spectrum of 650∼700 nm. The average photocurrents of the devices with the $Si_3$$N_4$$SiO_2$thickness of $1000\AA$/X$SiO\AA$, and $2000\AA$$1800\AA$ under the incident power, of -17 dBm were 3.2 uA, 3.5 uA and 3.1 uA, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.9
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• pp.1037-1044
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• 2010

In this paper, a new size-reduced, wideband ring-hybrid coupler is presented, and a design of a planar single-balanced doubler using the ring-hybrid is shown. This ring-hybrid coupler employs a pair of ultra-wideband transitions for phase inversion, which consists of in-phase and out of-phase transitions providing a good amplitude and phase balances for wide frequency ranges. The implemented ring-hybrid is 65 % smaller than conventional ring-hybrids, and provides 92.5 % and 81.3 % bandwidth at $\sum$ and $\Delta$ ports, respectively. Thanks to good amplitude and phase balances over wide bandwidth, the ring-hybrid can be applied to implement various balanced components. The implemented single-balanced doubler utilizing the ring-hybrid exhibits typical conversion loss of 10.5 dB for the output frequency range of 4~12 GHz with fundamental suppression level of 30 dB. The performance was also well-predicted with the nonlinear circuit simulation.