• 한국항행학회논문지
• /
• 제23권1호
• /
• pp.69-76
• /
• 2019

본 논문에서는 평면 유전체 기판의 유전율 측정을 위해 마이크로스트립 결함 접지구조를 기반으로 한 고감도 마이크로파 센서의 설계 방법에 대하여 연구하였다. 제안된 센서는 H-모양 개구의 리지 구조를 커패시터 기호 모양으로 변형하여 설계하였다. 제안된 센서의 감도를 기존의 이중 링 상보형 분할 링 공진기를 기반으로 한 센서의 감도와 비교하였다. 두 센서는 피 시험 기판이 없는 상태에서 전송 계수가 1.5 GHz에서 공진하도록 0.76 mm 두께의 RF-35 기판 상에 설계하고 제작하였다. 피 시험 기판으로 비유 전율이 2.17에서 10.2 범위에 있는 타코닉 기판 5종을 선택하였다. 실험 결과, 전송계수 공진주파수의 이동으로 측정된 제안된 센서의 감도는 기존 이중 링 상보형 분할 링 공진기를 기반으로 한 센서와 비교할 때 1.31배에서 1.62배 증가하는 것을 확인하였다.

• 한국항행학회논문지
• /
• 제23권5호
• /
• pp.415-423
• /
• 2019

본 논문에서는 유전율 측정을 위한 구부러진 슬롯이 추가된 고감도 마이크로스트립 패치 센서 안테나의 설계 방법에 대하여 연구하였다. 유전율에 대한 감도를 향상시키기 위해 단일 링 CSRR 구조와 유사한 구부러진 슬롯이 패치의 한쪽 방사면에 추가되었다. 제안된 마이크로스트립 패치 센서 안테나의 감도를 기존의 직사각형 마이크로스트립 패치 센서 안테나와 얇은 직사각형 슬롯이 추가된 마이크로스트립 패치 센서 안테나와 비교하였다. 세 마이크로스트립 패치 센서 안테나는 피 시험 상판이 없는 상태에서 전송 계수가 2.5 GHz에서 공진하도록 0.76 mm 두께의 RF-35 기판 상에 설계하고 제작하였다. 피 시험 상판으로 비유전율이 2.17에서 10.2 범위에 있는 타코닉 기판 5종을 사용하여 실험한 결과, 입력 반사계수의 공진 주파수의 이동으로 측정된 제안된 마이크로스트립 센서 안테나의 감도는 기존의 직사각형 마이크로스트립 패치 센서 안테나와 비교할 때 4.1배에서 6.1배 증가하는 것을 확인하였다.

• 한국표면공학회지
• /
• 제54권4호
• /
• pp.178-183
• /
• 2021

The temperature and frequency dependence of the dielectric constant of the BaTiO₃ substituted with two types of donor dopants, Nb⁵⁺ and Ta⁵⁺, respectively, were compared and analyzed. Dielectric specimens of four specific compositions, Ba_0.95Nb_0.05TiO₃, Ba_0.90Nb_0.10TiO₃, Ba_0.95Ta_0.05TiO₃, and Ba_0.90Ta_0.010TiO₃ were prepared by calcining at 1100 ℃ and sintering at 1300 ℃ to have a perovskite structure to measure capacitance. XRD and SEM analysis were used to observe the structure, with particular focus on the integration into the Nb⁵⁺ and Ta⁵⁺ substituted BaTiO₃ crystal lattice. X-ray diffraction peaks in the (200) and (002) planes were observed between 45.10° and 45.45° of the BaTiO₃ solid solution substituted with different fractions of Nb⁵⁺ and Ta⁵⁺. The dielectric properties were analyzed and the relationship between the properties and structure of the substituted BaTiO₃ was established. The fine particles and high density of the substituted BaTiO₃ were maintained like pure BaTiO₃, and in particular, a shift toward the low temperature side of the phase transition temperature range was clearly found, unlike pure BaTiO₃. In addition, the phase transition at a temperature higher than the Curie temperature relatively satisfies the modified Curie-Weiss law.

• 한국정보전자통신기술학회논문지
• /
• 제14권6호
• /
• pp.479-486
• /
• 2021

본 논문에서는 신호감지회로(Signal Sensing Circuit : SSC)를 추가하여 2개의 루프로 구성된 단일 커패시터 루프필터를 가진 극소형 위상고정루프(Phase Locked Loop : PLL)를 제안하였다. 위상고정루프 크기를 극단적으로 줄이기 위하여 가장 많은 면적을 차지하는 수동소자 루프필터를 극소형 단일 커패시터(2pF)로 설계하였다. 신호감지회로가 포함된 내부 부궤환 루프 출력이 외부 부궤환 루프의 단일 커패시터 루프필터 출력에 부궤환 역할을 하여 제안한 극소형 위상고정루프가 안정적으로 동작하도록 설계하였다. 위상고정루프 출력 신호 변화를 감지하는 신호 감지 회로는 루프필터의 커패시턴스 전하량을 조절하여 위상고정루프 출력 주파수의 초과 위상변이를 줄였다. 제안된 구조는 기존 구조에 비해 1/78 정도의 작은 커패시터를 가짐에도 불구하고 지터 크기는 10% 정도 차이가 난다. 본 논문의 위상고정루프는 1.8V 180nm 공정을 사용하였고, Spice를 통해 안정하게 동작하는 시뮬레이션 결과를 보여주었다.

• 한국음향학회지
• /
• 제41권4호
• /
• pp.410-418
• /
• 2022

터보 부호화 같은 반복 부호에서 채널 신뢰도 추정은 시변하는 수중 음향 채널에서 성능 향상을 위한 중요한 요소로서, 부정확한 채널 신뢰도 추정은 오히려 성능을 더욱 악화시킨다. 따라서 본 논문에서는 시변 수중 음향 채널에서 부호화율 1/3을 가지는 터보 부호화된 Frequency Shift Keying(FSK) 신호의 최적의 채널 신뢰도 추정 방식을 분석하였다. 추정(Estimation Bit Error Rate, E-BER) 알고리즘은 복호된 데이터를 재부호화시켜 수신된 신호와의 차이를 산정하는 방식이며, 채널 신뢰도의 변화에 따른 E-BER을 구하여 최적의 채널 신뢰도를 결정할 수 있다. 성능 분석을 위해 문경의 호수에서 거리 300 m ~ 500 m의 이동성 실험을 하였으며, 데이터를 복호하지 못하는 패킷에 대해 최적의 채널 신뢰도를 추정하여 적용한 결과, 모두 복호하였음을 확인하였다.

• Advances in concrete construction
• /
• 제12권5호
• /
• pp.377-389
• /
• 2021

Reinforced concrete vertical silos are universal structures that store large amounts of granular materials. Due to the asymmetric structure, heavy load, uneven storage material distribution, and the difference between the storage volume and the storage material bulk density, the corresponding earthquake is very complicated. Some scholars have proposed the calculation method of horizontal forces on reinforced concrete vertical silos under the action of earthquakes. Without considering the effect of torsional effect, this article aims to reveal the expansion factor of the silo group considering the torsional effect through experiments. Through two-way seismic simulation shaking table tests on reinforced concrete column-supported group silo structures, the basic dynamic characteristics of the structure under earthquake are obtained. Taking into account the torsional response, the structure has three types of storage: empty, half and full. A comprehensive analysis of the internal force conditions under the material conditions shows that: the different positions of the group bin model are different, the side bin displacement produces a displacement difference, and a torsional effect occurs; as the mass of the material increases, the structure's natural vibration frequency decreases and the damping ratio Increase; it shows that the storage material plays a role in reducing energy consumption of the model structure, and the contribution value is related to the stiffness difference in different directions of the model itself, providing data reference for other researchers; analyzing and calculating the model stiffness and calculating the internal force of the earthquake. As the horizontal side shift increases in the later period, the torsional effect of the group silo increases, and the shear force at the bottom of the column increases. It is recommended to consider the effect of the torsional effect, and the increase factor of the torsional effect is about 1.15. It can provide a reference for the structural safety design of column-supported silos.

• 대한지역사회영양학회지
• /
• 제28권3호
• /
• pp.220-234
• /
• 2023

Objectives: This study aimed to assess the adherence to dietary guidelines among college students in the post-COVID-19 era and examine the changes in their dietary habits as the learning environment transitioned from remote to in-person classes. Methods: We conducted a survey involving 327 college students in Daejeon from March to April 2023. The survey questionnaires included various factors, including age, gender, type of residence, frequency of use of delivery food, convenience food, and eating out. In addition, we investigated the extent of adherence to the dietary guidelines for Koreans and the degree of dietary changes following the post-COVID-19 shift in class format were investigated. For comparative analysis of the level of adherence to dietary guidelines in relation to dietary habit changes, an ANOVA and a post hoc Scheffe test were employed. We also performed a multiple linear regression analysis to identify dietary factors influencing the level of adherence to dietary guidelines. Results: The study revealed a high rate of convenience food consumption and a low rate of homemade food intake among students. There was a marked increase in the consumption of processed foods, convenience foods, dining out, sweet foods, high-fat fried foods, beverages, and alcohol following the transition from online to in-person classes. When examining adherence to Korean dietary guidelines, the highest scored practice was 'Hydration', and the lowest was 'Breakfast habit'. Increased consumption of convenience foods, late-night snacks, and dining out were negatively correlated with adherence levels to dietary guidelines, specifically correlating with 'Healthy weight', 'Hydration', 'Breakfast habit', and the total score of adherence. The adoption of 'regular meals' was positively associated with increased adherence levels to dietary guidelines. Conclusions: The transition from remote to in-person classes post-COVID-19 led to increased intake of convenience foods, dining out, sweet foods, high-fat fried foods, and alcohol. The rise in convenience food and late-night snack consumption negatively influenced several aspects of the dietary guidelines adherence, thereby suggesting the need for strategies to encourage healthy dietary habits among college students.

• 한국전기전자재료학회논문지
• /
• 제36권6호
• /
• pp.582-587
• /
• 2023

The effects of the annealing temperature on the structural, morphological, and luminescent properties of SrWO₄:Sm³⁺ thin films grown on quartz substrates by radio-frequency magnetron sputtering were investigated. The thin films were annealed at various annealing temperatures for 20 min in a rapid thermal annealer after growing the thin films. The experimental results showed that the annealing temperature has a significant effect on the properties of the SrWO₄:Sm³⁺ thin films. The crystal structure of the as-grown SrWO₄:Sm³⁺ thin films was transformed from amorphous to crystalline after annealing at 800℃. The preferred orientation along (112) plane and a significant increase in average grain size by 820 nm were observed with increasing the annealing temperature. The average optical transmittance in the wavelength range of 500~1,100 nm was decreased from 72.0% at 800℃ to 44.2% at an annealing temperature of 1,000℃, where the highest value in the photoluminescence intensity was obtained. In addition to the red-shift of absorption edge, a higher annealing temperature caused the optical band gap energy of the SrWO₄:Sm³⁺ thin films to fall rapidly. These results suggest that the structural, morphological, and luminescent properties of SrWO₄:Sm³⁺ thin films can be controlled by varying annealing temperature.

• 한국음향학회지
• /
• 제28권4호
• /
• pp.308-317
• /
• 2009

본 논문에서는 오실레이터 센서와 램파 센서를 결합하여 구조물 손상 진단을 위한 통합된 압전 센서 시스템을 제안한다. 구조물 손상으로 인한 공진주파수 변화를 관측 할 수 있는 오실레이터 센서는 손상 정도에 민감하게 반응하고 구조가 단순한 장치이지만 측정 범위가 센서 주위로 제한되는 특성을 가진다. 반면에 램파를 이용한 진단 시스템은 원거리에 위치한 구조물의 손상부를 감지하기에 유용하다. 본 논문에서는 오실레이터 센서를 이용한 취약 지점의 국부적인 손상 진단 방식과 램파를 이용한 광역적인 손상 진단 방식을 결합하여 각 시스템의 장점들을 활용할 수 있는 센서 시스템의 적용가능성을 연구하였다. PZT소자를 알루미늄 판에 적용하여, 알루미늄 판의 손상 정도에 따른 오실레이터 공진주파수의 변화와 램파 신호의 Time of flight 그리고 진폭의 변화를 이용하여 크랙의 위치와 크기, 개수의 판별 가능성을 제시하고 실험을 통하여 그 타당성을 검증하였다.

• Annals of Occupational and Environmental Medicine
• /
• 제35권
• /
• pp.46.1-46.12
• /
• 2023

Background: As unpredictable work schedule (UWS) has increased worldwide, various studies have been conducted on the resulting health effects on workers. However, research on the effect of UWS on workers' well-being in Korea is still insufficient. This study aimed to investigate the relationship between UWS and work-family conflict (WFC) using 6th Korean Working Conditions Survey (KWCS). Methods: Both UWS and WFC were measured using self-reported questionnaires, using data from the 6th KWCS conducted between 2020 and 2021, including 31,859 participants. UWS was measured by questions regarding the frequency of changes in work schedules and limited advanced notice. WFC was measured by questions regarding work to family and family to work conflicts. Logistic regression analysis was conducted to investigate the association between UWS and WFC. Results: The prevalence of UWS was higher among men, those under 40 years old, service and sales workers and blue-collar workers, and those with higher salaries. Workplace size also influenced UWS prevalence, with smaller workplaces (less than 50 employees) showing a higher prevalence. The odds ratio (OR) for WFC was significantly higher in workers with UWS compared to workers without UWS after adjusting for gender, age, marital status, occupation, salary, education, weekly working hours, shift work, company size, and having a child under the age of 18 years, employment status (OR: 3.71; 95% confidence interval: 3.23-4.25). Conclusions: The analysis of nationwide data revealed that UWS interferes with workers' performance of family roles, which can lead to WFC. Our findings suggest that it is crucial to implement policies to address unfair work schedule management, promoting a healthier work-life balance and fostering a conducive environment for family responsibilities.