• 한국전기전자재료학회논문지
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• 제19권7호
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• pp.655-661
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• 2006

Dielectric and piezoelectric properties of PMN-PZT ceramics with a high mechanical quality factor$(Q_m)$ and a low temperature sintering temperature were investigated as a function of PZN substitution in order to develop multilayer piezoelectric transformer for AC-DC converter. Multilayer piezoelectric transformers were subsequently manufactured using the PMN-PZN-PZT ceramic offering the optimal behavior and then the electrical performance were invetigated. At the sintering temperature of $940^{\circ}C$, density, electromechanical coupling factor$(k_p)$, mechanical qualify factor$(Q_m)$ and dielectric constant$(\varepsilon_r)$ of 8 mol% PZN substituted specimen were $7.73g/cm^3$, 0.524, 1573 and 1455, respectively. The PZN substitution caused a increase in the dielectric constant and the electromechnical coupling factor. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value at near the resonant frequency of 76.55 kHz and increased according to the increase of load resistance. The multilayer piezoelectric transformer with the output impedance coincided with the load resistance showed the temperature increase of less than $20^{\circ}C$ at the output power of 10 W. Based on the results, the manufactured multilayer transformer using the low temperature sintered PMN-PZN-PZT ceramics can be stably driven for both step-up and down transformers.

• 한국전기전자재료학회논문지
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• 제18권2호
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• pp.136-141
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• 2005

In this study, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, PCW-PMN-PZT ceramics using Li$_2$CO$_3$, Bi$_2$O$_3$, and CuO as sintering aids were manufactured according to the amount of MnO$_2$ addition. Their microstructural, dielectric and piezoelectric properties were investigated. When the sintering aids were added, specimens could be sintered below 95$0^{\circ}C$, but mechanical qualify factor decreased. Therefore, MnO$_2$ was added excessively to the PCW-PMN-PZT ceramics to increase mechanical quality factor. At the sintering temperature of 95$0^{\circ}C$, the density, dielectric constant($\varepsilon$$_{r}$), electromechanical coupling factor(k$_{p}$), mechanical quality factor(Q$_{m}$) and Curie temperature(T$_{c}$) of 0.1 wt% MnO$_2$ added specimen showed the optimal values of 7.75 g/㎤, 1503, 0.57, 1502, and 337, respectively, for multilayer piezoelectric transformer application.ation.n.

• 대한방사선치료학회지
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• 제14권1호
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• pp.187-199
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• 2002

This descriptive study was undertaken to measure quality of life score and investigate the correlation between the demographic characteristics, the diagnostic related characteristics, physical symptom and quality of life of breast cancer patients undergoing radiation therapy as on attempt to provide basic data to help them attain better qualify of life. The subjects for this study were 74 out-patients undergoing radiation therapy at C University hospital in Gwangju, from June, 1998 to July, 2000. The data were obtained using a convenient sampling technique. The tool of this study was the quality of life scale developed by Ro Yoo Ja. The data were analyzed using the SAS program for percentage, mean, standard deviation, Pearson Correlation Coefficient, GLM. The results were as follows: 1. The total average score for quality of life of the subjects was 137.22 and the range was from 38 to 227, item mean score(range 1-5) was 3.15. For each factor in qualify of life of life score, the mean scores(range 1-5) were as follows; family relationship 3.69, relationship with neighbors factor 3.40, self esteem 3.10, physical state and function 2.95, economic life 2.91, emotional fate 2.88. 2. The incidence of physical symptoms was seen fatigue($82.4\%$), skin change($43.2\%$), alopecia($41.9\%$), pain($41.9\%$), anorexia($39.2\%$), anemia($39.2\%$), and headache($31.1\%$) in that order. 3. The result of the analysis of the relationships between the quality of life scores and demogaphic characteristics were as follows : there were significant differences, between age(F=3.44, p=0.013), educational level(F=3.84, p=0.007), duration of marriage((F=5.06, p=0.003) and monthly income(F=4.72, p=0.005). 4. The result of the analysis of the relationships between quality of life scores and diagnostic related characteristics was as follows: there was a significant difference between incidence durations(F=5.02, p=0.003). 5. The correlation of emotional state, economic life, self esteem, physical sate & function, relationship with neighbors, relationship with family in quality of life of cancer patients revealed a positive correlation.

• 대한전자공학회논문지SD
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• 제44권7호통권361호
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• pp.9-15
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• 2007

본 논문에서는 UHF 대역 수동 RFID 태그(UHF-band passive RFID tag) 칩 제작에 필수적인 요소인 쇼트키(Schottky) 다이오드를 CMOS 공정으로 제작하고 크기에 따른 특성을 분석하였으며 이를 이용하여 전압체배기를 설계하였다. 쇼트키 다이오드는 Titanium-Silicon 접합을 이용하여 제작되었으며, $4{\times}10{\times}10\;{\mu}m^{2}$의 면적을 가지는 쇼트키 다이오드는 $20\;{\mu}A$의 전류 구동에 대해 약 0.15 V의 순방향 전압 강하의 우수한 특성을 나타내었다. 역방향 파괴전압(breakdown)은 약 -9 V로 수동 RFID 태그칩의 전압체배기에 사용될 수 있는 충분한 값을 나타내었다. 제작된 쇼트키 다이오드의 소신호 등가모델을 이용하여 다이오드의 크기에 따른 순방향 전압강하와 입력 임피던스간의 trade-off에 대해 분석하였다. 이를 이용하여 제작된 6-단 전압체배기는 900 MHz 주파수, 200mV 최대 입력 전압에 대해 1.3 V이상의 출력 전압 특성을 나타내어 인식거리가 비교적 큰 수동형 태그에 적합한 특성을 나타내었다.

• Radiation Oncology Journal
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• 제14권3호
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• pp.237-244
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• 1996

목적 : 의료용 선형가속기의 Independent Collimator는 현재 광범위하게 사용되고 있다. 그러나 방사선량의 계산과 MU(Monitor Unit)의 계산에 사용되는 모든 기본 자료는 대칭 조사면를 기준으로 작성되었기 때문에 independent collimator를 사용한 비대칭적인 조사면의 경우 현재 사용하고 있는 계산 방식을 그대로 적용함에 무리가 있을 것으로 생각된다. 따라서 이러한 의문에 대한 체계적이고 과학적인 검토가 필요할 것으로 사료되어 본 연구를 진행하였다. 대상 및 방법 :본 연구는 Dual Photon Beam(6MV와 15MV)을 산출(産出)하는 선형가속기(Linac 1800, Varian Co)에서 collimator 사용시 산란 방사선의 총채로 표현되어지는 field size factor, beam qualify에 영향을 미치는 HVL와 PDD를 조사하였다. 먼저 field size factor는 water phantom(WP 600C Wellhofer, Germany)내의 Dmax에서 field size $3{\times}3cm$에서 $35{\times}35cm$까지의 방사선량의 변화를 square field로 $1cm^2$씩 증가시켜 가며 0.6cc ion chamber(NE 2571)로 측정하였다. Beam quality는 100cm SSD(source-surface distance)에서 $5{\times}5$, $10{\times}10$, $15{\times}15$ 및 $20{\times}20cm$ field size로 0, 3 및 10cm off-axis distance와 dmax 4, 10, 15 및 20cm의 깊이에서 측정하였다. Dose distribution을 분석하기 위하여 film densitometer와 water phantom(IC 10 ion chamber)을 사용, $10{\times}10cm$ field size에서 5, 10 및 15cm의 off-axis distance까지의 방사선량의 분포를 관찰하고 대칭 방사선 조사면와 비교 분석하여 실제 isodose 분포에 미치는 영향을 관찰하였다. 결과: 1) Relative field size factor는 중심 축에서 off-axis lateral distance에 따라 다양하게 변화하였는데 6MV X-선의 경우 최대 $3.1\%$, 15MV X-선의 경우 최대 $5\%$까지의 변화를 보였다. 이때 off-axis factor를 구하여 교정을 하였을 경우 중심 축의 field size factor와 거의 유사한 값에 도달할 수 있었다. 2) Beam qualify의 변화를 관찰하기 위한 실험에서 HVL는 off-axis distance가 멀어질수록 감소하였고 PDD도 off-axis distance가 멀어지고 측정 깊이가 깊어질수록 감소되는 현상을 보였다. 통상적인 방사선 치료시에 이용되는 $5{\times}5cm$ 이상의 field size와 15cm 이내의 깊이에서는 3cm 와 l0cm의 off-axis에서 6MV X-선은 평균 $0.5\%$와 $2\%$, 15MV X선은 $0.4\%$와 $1.4\%$의 감소 현상을 보여 큰 편차를 관찰할 수 없었다. 3) Isodose distribution은 off-axis distance가 멀어질수록 depth dose의 증가치가 감소되었으며 특히 central axis의 가장자리 부위에서는 isodose curve의 위축이 확연하였다. 결론 : Independent collimator를 사용하여 비대칭 방사선 치료를 할 경우 MU의 계산은 off-axis factor와 PDD 보정이 필수적이며 임상적으로는 중심 축에서의 과소조사에 대한 정밀한 주의가 필요할 것으로 사료된다.

• 한국ITS학회 논문지
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• 제3권1호
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• pp.13-19
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• 2004

본 논문에서는 낮은 위상잡음과 고신뢰성을 갖는 전압제어 발진기를 비선형 설계하였으며 그 위상잡음을 Lesson식과 비교하여 잘 일치함을 확인하였다. 전압제어 발진기의 위상잡음을 개선하기 위하여 유전체 공진기와 결합하는 마이크로 스트립 라인을 고임피던스 변환기를 이용함으로써 공진회로의 Q값이 그대로 능동소자에 전달되도록 하였다. 또한 worst case 해석 및 part stress 해석을 수행함으로써 전압제어 발진기의 신뢰도를 높였다. 제작된 전압제어 발진기는 0$\~$12 V의 제어전압에서 0.56 MHz/V의 튜닝대역을 가지고 있으며 160 mW의 DC 전력을 소모한다. 또한 -116.5 dBc/Hz @100KHz와 -96.51 dBc/Hz @10KHz의 우수한 위상잡음 특성과 7.33 dBm의 출력을 얻었다.

• 한국전기전자재료학회논문지
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• 제19권1호
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• pp.35-39
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• 2006

In this study, in order to develop the multilayer piezoelectric actuator and ultrasonic resonator, PMN-PNN-PZT ceramics were fabricated by sintering with $Li_2CO_3-Na_2CO_3$ as sintering aids at $950^{\circ}C$ and their piezoelectric and dielectric characteristics were investigated as a function of PNN substitution. With increasing PNN substitution, dielectric constant(${\epsilon}_r$), electromechanical coupling factor(kp), and piezoelectric d constant($d_{33}$) were increased to $12 mol\%$ PNN substitution and then showed a tendency to decrease rapidly With increasing PNN substitution, crystal structure changed from tetragonal to rhombohedral at $12 mol\%$ PNN substitution and then secondary phase was appeared and its intensity was increased. At the $12 mol\%$ PNN substituted PMN-PZT composition ceramic sintered at $950^{\circ}C$, density, kp, $d_{33}$ and Qm showed the optimum value of $7.79 g/cm^3$, 0.599, 419 pC/N, and 894, respectively for multilayer piezoelectric actuator application.

• 한국시뮬레이션학회논문지
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• 제16권1호
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• pp.1-9
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• 2007

고속 네트워크에서 QoS 라우팅은 수많은 사용자의 요구를 만족하기가 매우 어렵다. 네트워크의 경로설정 알고리즘에서 측도로써 단지 링크지연시간만을 고려한다면 그 경로는 최소지연시간 경로가 될 것이며, 링크비용만을 고려한다면 최소비용경로를 찾을 것이다. 지연시간 한계의 최소비용(Delay Constrained Least Cost; DCLC)문제는 NP-hard 문제로 알려져 있으며, 두 개의 인자 경로비용과 지연시간을 혼합한문제로 생각할 수 있다. 경로설정 시 최소지연시간을 생각하면 그 경로는 상대적으로 높은 비용의 경로이며, 반대로 최소비용만을 생각하면 그 경로는 상대적으로 높은 지연시간을 얻는다. 따라서 DCLC문제를 풀기위해서는 단 하나의 인자만을 고려해서는 안 되며 두 개의 인자를 동시에 고려할 수 있는 새로운 인자를 요구하게 되었다. 따라서 본 논문에서는 DCLC 문제를 풀기위해 경로비용과 지연시간을 동시에 확률적으로 고려한 새로운 인자를 소개한다. 시뮬레이션 결과는 새로운 인자가 DCLC 문제에 적절하다는 것을 보여주었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.547-550
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• 2000

The (1-x)MgTiO$_3$-xSrTiO$_3$(x=0.03~0.04) ceramics were fabricated by the conventional mixed oxide method. The sintering temperature and time were 125$0^{\circ}C$~135$0^{\circ}C$, 2hr., respectively. From the X-ray diffraction patterns, it was found that the perovskite SrTiO$_3$ and ilmenite MgTiO$_3$ structures coexisted in the (1-x)MgTiO$_3$-xSrTiO$_3$(x=0.03~0.04) ceramics. The dielectric constant($\varepsilon$$_{r}$) was increased with addition of SrTiO$_3$. The temperature coefficient of resonant frequency($\tau$$_{f}$) was gradually varied from negative value to the positive value with increasing the SrTiO$_3$. The negative temperature coefficient of resonant frequency of the magnesium titanate was adjusted to near zero at x=0.036, where the dielectric constant, quality factor, and $\tau$$_{f}$ were 20.65, 95120, and +1.3ppm/$^{\circ}C$, respectively. The temperature stability of qualify factor in (1-x)MgTiO$_3$-xSrTiO$_3$(x=0.03~0.04) ceramics increased as the amount of MgTiO$_3$./TEX>.

• 복식문화연구
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• 제11권1호
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• pp.1-10
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• 2003

The purpose of this study is to identify differences that married exist between married women´s buying motivations for imported and domestic formal two piece suits and to test the role of socioeconomic variables on those differences. Sample selection criteria included married women lit in8 in ,seoul. Korea, between ages 30∼59. Purposive sampling method was used to secure respondents It with experience with imported formal two-piece suits. Of 400 distributed. 246 usable questionnaires were returned. Statistical analysis of results included factor analysis, and paired t-tests. For both imported and domestic suits, the most important buying motivation was utilitarian, with qualify the most important consideration. Purchases of domestic suits were more influenced by factors such as advertisements, economics, impulse buying, approval of others, and current fashionability of style than were the purchases of imported suits. On the other hand, purchases of imported suits u·ere more influenced by factors such as prestige and utilitarian motivation than were purchases of domestic suits. For most socioeconomic variables, respondents indicated significant differences in their motivations for buying imported suits and domestic suits. The results of this study suggest the need for implementing different marketing strategies for imported suits and domestic suits.