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TiO₂첨가에 따른 Mg₄Ta₂O₉ 세라믹스의 마이크로파 유전특성과 유전체 공진기 거동에 관한 연구
金再植(Jae-Sik Kim),崔義善(Eui-Sun Choi),柳基元(Ki-Won Ryu),李永熙(Young-Hie Lee) 대한전기학회 2007 전기학회논문지 Vol.56 No.4
The (l-x)Mg₄Ta₂O?-xwt%TiO₂ (x=5~20) microwave dielectric ceramics were prepared by solid-state reaction method and sintered at 1450℃. According to the X-ray diffraction data, the Mg₄Ta₂O?-xwt%TiO₂ ceramics had main phase of Mg₄Ta₂O? and MgTi₂O? peaks were added by increasing of TiO₂ addition. Microwave dielectric properties of the Mg₄Ta₂O?-xwt%TiO₂ ceramics were influenced by MgTi₂O? phase and properties of TiO₂. There was a little decrement of the quality factor from 116,800㎓ of pure Mg₄Ta₂O? to 100,100㎓ of 15wt% TiO₂ added one. But there was excellent improvement in temperature coefficient of the resonant frequency (TCRF) by addition of 15wt% TiO₂. The dielectric constant, quality factor and TCRF of the Mg₄Ta₂O?-xwt%TiO₂ ceramics sintered at 1450℃ were 13.08~16.41, 45,000~165,410㎓, -24.82~ +3.88ppm/℃, respectively, depending on the value of x. Simulated dielectric resonator (DR) with Mg₄Ta₂O?-15wt%TiO₂ ceramics had the operating frequency of 11.97㎓ and S2.1 of -35.034㏈.
김재식,이창룡,이기서,Kim, Jae-Sik,Li, Chang-Long,Lee, Key-Seo 한국전자통신학회 2014 한국전자통신학회 논문지 Vol.9 No.2
We have studied on the possibility of railway stability system using RFID tag. UHF RFID tag was desinged, manufactured and tested. Proposed UHF tag antenna has PIFA type structure and inset feed multi matching technique was attempted for impedance matching of antenna. The impedance bandwidth (VSWR < 3) of the proposed tag antenna covers 917~923 MHz. Measured peak gain is 3.225 dBi and UHF band with an omni-directional radiation pattern. RFID reader and tag installed in motor car and track, respectively. Then, tag recognition rate according to velocity of car (under 45 km/h) represented 100 %. 본 논문에서는 RFID 태그를 설계하여 철도 안정화 시스템으로의 적용 가능성에 대하여 연구하였다. UHF 대역에서 동작하는 태그를 설계 제작, 현장 테스트를 진행하였다. 제안된 UHF 대역 태그 안테나는 PIFA형 안테나 구조를 가지며 인셋 급전 다중 정합기술로 주파수와 임피던스 정합을 시도하였다. 제안된 안테나는 UHF 대역인 917~923 MHz에서 VSWR 3:1 이하의 주파수 특성을 나타내었으며, 또한 전방향적인 방사패턴(Omni-directional radiation pattern)을 가진다. 917~923 MHz의 동작주파수에서 안테나의 최대 이득은 3.225 dBi 이었다. 모터카에 RFID 리더를 거취하고 선로에 태그를 설치한 후, 속도에 따른 태그 인식률을 테스트한 결과 45 km/h 이하의 속도에서 100 %의 인식률을 나타내었다.
김재식(Jae SIK, Kim) 한국조형디자인학회 2005 조형디자인연구 Vol.8 No.2
The present study is a recollection of human relations in the past, taking note of contemporary social phenomena. Going against the advanced mechanical civilization, this study purposed to discover our changed looks by reflecting upon the culture of manual tools. Living tools in the past were neither precise nor solid due to lack of technologies but they were sufficiently helpful for human life. They were created and handled directly by human beings, so contained the warm breath of their masters. On the contrary, contemporary living tools are precise, handy and highly effective but because they are mass-produced they are not loved or valued. They are merely material tools without life. The task of the present study is to confront living tools in the past with those in the preset, to analyze meanings and phenomena coming from the confrontation, and to express them humorously. Arts are symbolical express ions of artist s' expenences and thoughts. The symbols are the language of images. Linguistic express ion is based on rhetoric. If art symbolizes a language, the basic of its expression methods is rhetorical methods. Accordingly, this study attempts analysis through rhetorical methods. Another task of the present study is humorous expression. Humor is one of representative Korean beauties, creating smile. In this study, the combination of several elements of smile is recognized as humor. It is because different elements of smile play basic roles in creating smile, they are identical by nature. Smile has the function of brightening and purifying the society . Humorous expression 10 this study, which is a catalyst inducing smile, is to make audience feel humorous smile. It is the core of this study to relieve contemporary people' s mental pain through smile evoked by meanings and humorous expressions coming form the comparison between traditional and contemporary living tools.
$(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ 세라믹스의 마이크로파 유전 특성
김재식,최의선,배선기,이영희,Kim, Jae-Sik,Choi, Eui-Sun,Bae, Seon-Gi,Lee, Young-Hie 대한전기학회 2006 전기학회논문지C Vol.55 No.7
The effect of x on microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics for microwave components were investigated. All spcecimens prepared by the conventional mixed oxied method and sintered at $1450^{\circ}C$. Microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-xTiO_2$ ceramics were influenced by $MgTi_2O_5$ phase. Also the microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics were dominated with an addition of $CaTiO_3\;and\;SrTiO_3$. The dielectric constant $(\varepsilon_r)$, quality factor $(Q{\times}f_r)$ and temperature coefficient of the resonant frequency $(TCRF,\;\tau_f)$ of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics were $12.96\sim70.98,\;5,132\sim186,410GHZ$ and $-35.82\sim+75.96ppm/^{\circ}C$, respectively, and depend on x and addition materials.
안테나 소형화를 위한 Co₂ 페라이트의 마이크로파 특성
김재식(Jae-Sik Kim),최의선(Eui-Sun Choi),김강(Kang Kim),이영희(Young-Hie Lee),송성호(Sung-Ho Song),안종복(Jong-Bok Ahn),김병환(Byung-Hwan Kim),최지영(Ji-Young Choi) 대한전기학회 2011 전기학회논문지 Vol.60 No.12
The sintering behavior and microwave properties of ferrite (Ba3Co2-2xZn2xFe24O41 ceramics) were investigated for microwave applications. Also PIFA type antenna with ferrite was simulated. All samples were prepared by the solid state reaction method and sintered at 1350℃. All ceramics had relatively density above of 92% compare with theoretical density of Ba₃Co₂Fe24O41 ceramics. From the XRD pattens, the Z-type phase was existed as main phase in Ba₃Co2-2xZn2xFe24O41 ceramics. The permittivity and permeability of Ba₃Co2-2xZn2xFe24O41 ceramics were increased with Zn additions and decreased rapidly over frequency of 200~600 ㎒. Several PIFA type antennas with ferrite and FR4 were simulated. All antenna structure had return loss of less than -10 ㏈ at each resonant frequency. Simulated antenna using both ferrite and FR4 showed size reduction of 25% without a significant decrement of efficiency.
김재식 ( Jae Sik Kim ) 한국산업식품공학회 2014 산업 식품공학 Vol.18 No.1
Grape seed tea (GST) was prepared by roasting grape seed at 150-190℃ for 10-60 minutes and then soaking in water at 100℃ for 20 minutes. GSTs made with grape seed with an L value of 19.5-20.5 were the best in terms of color, flavor, and sensory test. GSTs prepared using roasted grape seeds had higher total phenolics and antioxidant activity than GST prepared from raw grape seed. Roasting times to reach an L value of 19.5-20.5 were over 60 minutes at 160℃, 40-50 minutes at 170℃, 30-40 minutes at 180℃, and below 10 minutes at 190℃. In a sensory test, the total preference increased depending on the degree of roasting. GSTs with the highest preference used grape seed roasted at 170℃ and 180℃ for 30 minutes.
소결온도에 따른 0.7Mg<sub>4</sub>Ta<sub>2</sub>O<sub>9</sub>-0.3SrTiO<sub>3</sub> 세라믹스의 마이크로파 유전특성
김재식,최의선,이문기,이영희,배선기,Kim, Jae-Sik,Choi, Eui-Sun,Lee, Moon-Kee,Lee, Young-Hie,Bae, Seon-Gi 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.6
The structural and microwave dielectric properties of $0.7Mg_4Ta_2O_9-0.3SrTiO_3$ ceramics with sintering temperature were investigated. All the sample of the $0.7Mg_4Ta_2O_9-0.3SrTiO_3$ ceramics were prepared by conventional miked oxide method and the sintering temperature was $1425\~1500^{\circ}C$. The hexagonal phase of $Mg_4Ta_2O_9$ and the cubic phase of $SrTiO_3$ were coexisted. The porosity of $0.7Mg_4Ta_2O_9-0.3SrTiO_3$ ceramics were reduced with increasing sintering temperature. In the case of $0.7Mg_4Ta_2O_9-0.3SrTiO_3$ ceramics sintered at $1475^{\circ}C$, dielectric constant, quality factor and temperature coefficient of resonant frequency were 14.51, 82,596 GHz and $-3.14\;ppm/^{\circ}C$, respectively.