• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
• /
• pp.552-554
• /
• 1995

In long-haul high speed optical communications, the distance between a transmitter and a receiver depends on the amount of light coupled to a single mode optical fiber from the laser diode(LD) as well as the LD characteristic itself. And the transmitter module must have long lifetime. high reliability, and even simple structure. Such points have induced laser welding technique to be a first choice in opto-electronic module packaging because it can provide strong weld joint in a short time with very small coupling loss. In this paper, packaging considerations and characteristics for high speed LD modules are discussed. They include optical path design factors for larger aligning tolerance, and novel laser welding processes for component assembly. For low coupling loss after laser welding processes, the optical path for optimum coupling of a single mode optical fiber into the LD chip was designed with the GRIN lens system providing sufficiently large aligning tolerance both in the radial and axial directions. The measured sensitivity of the LD module was better than -33.7dBm(back to back) at a BER of $10^{-10}$ with a 2.5Gbps NRZ $2^{23}-1$ PRBS.

• 한국의학물리학회:학술대회논문집
• /
• 한국의학물리학회 2002년도 Proceedings
• /
• pp.457-460
• /
• 2002

The image quality of three-dimensional (3D) images has been widely investigated by the qualitative analysis method. A need remains for an objective and quantitative method to assess the image quality of 3D volume-rendered images. The purpose of this study was to evaluate the quantitative accuracy of distance measurements on 3D volume-rendered images of a dry human skull by using multi-detector computed tomography (MDCT). A radiologist measured five times the twenty-one direct measurement line items composed among twelve reference points on the skull surface with a digital vernier caliper. The water filled skull specimen was scanned with a MDCT according to the section thicknesses of 1.25, 2.50, 3.75, and 5.00 mm for helical (high quality; pitch 3:1) scan mode. MDCT data were reconstructed with its acquisition section thickness and with 1.25 mm section thickness for all scans. An observer also measured seven times the corresponding items on 3D volume-rendered images with measuring tools provided by volumetric analysis software. The quantitative accuracy of distance measurements on the 3D volume-rendered images was statistically evaluated (p-value < 0.05) by comparatively analyzing these measurements with the direct distance measurements. The accuracy of distance measurements on the 3D volume-rendered MDCT images acquired with 1.25, 2.50, 3,75 and 5.00 mm section thickness and reconstructed with its section thickness were 48%, 33%, 23%, and 14%, respectively. Meanwhile, there were insignificant statistical differences in accuracy of distance measurements among 3D volume-rendered images reconstructed with 1.25 mm section thickness for the each acquisition section thickness. MDCT images acquired with thick section thickness and reconstructed with thin section thickness in helical scan mode should be effectively used in medical planning of 3D volume-rendered images. The quantitative analysis of distance measurement may be a useful tool for evaluating the quantitative accuracy and the defining optimal parameters of 3D volume-rendered CT images.

• Journal of Welding and Joining
• /
• 제33권4호
• /
• pp.37-43
• /
• 2015

Characteristics of dissimilar metal welds between STS 316L and carbon steel ASTM A516 Gr.70 made with GTAW have been evaluated in terms of microstructure, ferrite content, chemical analysis, hardness and corrosion resistance. Three heat inputs of 9.00, 11.25, 13.00kJ/cm were employed to make joints of dissimilar metals with ER309 wire. Based on microstructural examination, the amount of vermicular type of ${\delta}$-ferrite was increased with increasing heat input due to the increase of Creq/Nieq in the second layer of welds. Based on the EDX analysis of weld metals, Cr and Ni content in the 2nd layer increased while those content in the first layer of welds decreased with heat inputs. Cellular solidification mode in the 1st layer and dendritic solidification mode in the 2nd layer due to different cooling rates were prevailed, respectively. Heat affected zone which formed hard microstructure showed higher hardness than the weld metal. The salt spray test of dissimilar metals weld joints showed that the carbon steel surfaces only corroded. The weight loss rate due to corrosion increased up to 100hours but it decreased above 100 hours. There was little difference in the weight loss caused by corrosion regardless of heat inputs.

• 보건교육건강증진학회지
• /
• 제11권2호
• /
• pp.33-47
• /
• 1994

AIDS preventional efforts need to be guided by well trained health care personnel especially by school nurses for the adolescents. This study was designed to get basic data about AIDS educational program development for school nurses. The objectives of this study were to 1) identify AIDS knowledg of school nurses 2) identify AIDS attitudes of school nurses and 3) identify association between AIDS knowledge and sociodemographic characteristics. Data were collected from 173 subjects in Chonbuk province. Self-reporting questionnaire were administered during the period from 1st of June to 30th of June, 1994. AIDS related knowledge was measured by using 44 questions on cause(3 items), testing(3 items), mode of transmission(15 items), clinical manifestations(5 items), treatment(3 items), prevention(5 items), complication(4 items), infection control(3 items) and Using resources(3 items). AIDS related attitudes were measured by five point Likert scales using 13 questions on perceived threats from AIDS crisis (4 items), perceived severity to AIDS(2 items), perceived needs about psychosocial care for HIV infected patients(3 items) and perceived educational needs of AIDS(4 items). The collected data were analyzed by SPSS/PC/sup +/, using percentages, Mean and S.D. descriptive purpose and t-test or F for comparing the variables. The major findings were as follows: 1. Respondents ranged in knowledge of AIDS between 0 and 44 with the 33.79 mean score. Percentage of correctly answered respondents to each categories - mode of transmission : 87.0% - clinical manifestation : 85.0% - cause : 82.5% - prevention : 81.5% - treatment : 76.1% - infection control : 72.8% - testing of HIV infection 71.8% - using community resourses : 50.9% - complication : 45.8% 2. The respondents' attitudes of AIDS The majority(70%) showed higher perceived threat The majority(91.3%) showed higher perceived severity to AIDS crisis As a whole, perceived needs about psychosocial care for HIV infected patients negative The majority (over 96.5%) showed highly perceived educational needs of AIDS. 3. The relationship between AIDS knowledge and each of those general character. AIDS knowledge shows significant difference with age(F=3.50, p<.016), years of professional experience(F=4.14, p<.007) and received lecture about AIDS(F=4.54, p<.000). There was no significant difference between AIDS knowledge and job satisfaction.

• Journal of Welding and Joining
• /
• 제33권2호
• /
• pp.69-77
• /
• 2015

High strength steels have been continually being developed to improve in fuel economy in automotive and ensure safety of passengers. New bonding and welding methods have been required for improving weldability on high strength steels. In this study, resistance spot welding and Weld-bond with nugget diameters of 4.0mm, 5.0mm, 6.0mm and 7.0mm were produced and tested, respectively. In order to confirm the effect of nugget diameters on tensile shear characteristic of the Weld-bond, tensile shear characteristics of Weld-bond were compared with those of resistance spot welding and adhesive bonding. Peak load of Weld-bond were increased as the nugget diameter increases. After appearing maximum peak load continuous fracture followed with second peak owing to load being carried by resistance spot weldment. Fracture modes of the adhesive layer in Weld-bond fractures were represented by mixed fracture mode, which are cohesive failure on adhesive part and button failure at resistance spot welds. The results showed that the tensile shear properties can be improved by applying Weld-bond on TRIP steel, and more apparent with nugget diameter higher than 5${\surd}$t.

• 전기전자학회논문지
• /
• 제22권1호
• /
• pp.127-135
• /
• 2018

본 논문에서는 MNR(Mu-negative) Metamaterial 단일 셀을 사용하여 700 MHz UHD 방송 대역과 2.45 GHz/5 GHz WiFi 대역에서 동작하는 삼중대역 폴디드 모노폴 안테나 설계에 관하여 연구하였다. MNG metamaterial 단일셀이 MZR(Mu zero resonator)에서 동작하도록 안테나 기판 뒷면에 커패시터를 형성하고, 스트립선로와 비아홀을 통해서 접지면과 연결하여 구현하였다. 이를 통해서 700 MHz대역에서 영차모드에서 공진하도록 공진점을 제어할 수 있고, 대역폭을 개선할 수 있다. 최종적으로 700 MHz UHD방송 대역과 2.45 GHz/5 GHz WiFi 대역에서 동작하는 안테나를 구현하였다. 설계 제작한 안테나의 크기는 $100{\times}100mm^2$이고, 실험 결과 첫 번째 공진점에서 10 dB 대역폭과 이득은 각각 309 MHz(41.2%), 5.298 dB이며, 두 번째 공진점에서 10 dB 대역폭과 이득은 각각 821.9 MHz(33.5%), 2.7840 dB이며, 세번째 공진점에서 10 dB 대역폭과 이득은 각각 1.1314 GHz(20.6%), 2.9484 dB의 결과를 확인하였다. 안테나의 공진주파수는 이론과 실험이 일치함을 확인하였다. 그리고 방사패턴은 대체적으로 전방향 특성을 가지고 있으며, 0.75 GHz와 2.45 GHz에서는 측면보다 전방향과 후방향으로 방사특성이 양호하며, 5.5 GHz에서는 다중로브를 갖는 방사패턴 특성을 확인하였다.

• Structural Engineering and Mechanics
• /
• 제33권2호
• /
• pp.239-255
• /
• 2009

In the companion paper, a simple but effective analysis procedure termed an Improved Modal Pushover Analysis (IMPA) is proposed to estimate the seismic capacities of multi-span continuous bridge structures on the basis of the modal pushover analysis, which considers all the dynamic modes of a structure. In contrast to previous studies, the IMPA maintains the simplicity of the capacity-demand curve method and gives a better estimation of the maximum dynamic response in a bridge structure. Nevertheless, to verify its applicability, additional parametric studies for multi-span continuous bridges with large differences in the length of adjacent piers are required. This paper, accordingly, concentrates on a parametric study to review the efficiency and limitation in the application of IMPA to bridge structures through a correlation study between various analytical models including the equivalent single-degree-of-freedom method (ESDOF) and modal pushover analysis (MPA) that are usually used in the seismic design of bridge structures. Based on the obtained numerical results, this paper offers practical guidance and/or limitations when using IMPA to predict the seismic response of a bridge effectively.

• 대한의용생체공학회:의공학회지
• /
• 제33권1호
• /
• pp.32-38
• /
• 2012

Recently, several ultrasound imaging techniques for tissue characterization have been developed. Among them, ultrasound elastography is regarded as the most promising modality and has been rapidly developed. One of ultrasound elastography techniques is shear modulus imaging. Normal and cancerous tissues show big difference of shear moduli and they have good image contrast. However shear wave elastography requires more complicated hardware and more computations for image reconstruction algorithm. Therefore new efficient techniques are being developed. In this paper, we have developed a very flexible ultrasound system for elastography experiments. The developed system has capabilities to acquire ultrasound RF data of all channels and generate arbitrary ultrasound pulse sequences. It has a huge amount of memories for RF data acquisition and a simple and flexible pulse generator. We have verified the performance of the system showing conventional B-mode images and preliminary results of elastography. The developed system will be used to verify our own reconstruction algorithm and to develop more efficient elastography techniques.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1997년도 추계학술대회 논문집
• /
• pp.149-152
• /
• 1997

High-power piezoelectric materials are being developed for applications such as actuators and ultrasonic motors. In this paper, ferroelectric property of iron-doped 0.57 (Sc$_{1}$2//Nb$_{1}$2/)O$_3$-0.43 PbTiO$_3$. which is the morphotropic phase boundary composition for the PSN-PT system, was investigated. The maximum dielectric constant ( $\varepsilon$$_{33}$/$\varepsilon$$_{0}$ = 2551) and the minimum dielectric loss(tan $\delta$ = 0.51 %) at room temperature were obtained at 01. wt% and 0.3 wt% of iron additions. With additions of the Fe$_2$O$_3$ the electromechanical coupling factor of radial mode k$_{p}$ and the piezoelectric coefficient d$_{33}$ were slightly decreased, on the other hand the mechanical quality factor was increased significantly. The highest mechanical quality factor (Qm= 297) was obtained at 0.3 wt% Fe$_2$O$_3$, which is 4.4 times larger than that of pure 0.57 PSN-0.43PT ceramics. The temperature dependence of the dielectric constant and dielectic loss was observed between 2$0^{\circ}C$ and 35$0^{\circ}C$ .X> .X> .

• 한국융합학회논문지
• /
• 제4권3호
• /
• pp.27-33
• /
• 2013

기존의 바코드는 정보 배열이 나란히 나열된 선 모양을 가지며 이를 1차원 바코드라 부른다. 이에 반해 2차원 바코드는 점자방식 또는 모자이크방식 코드로 작은 정사각형 도는 직사각형 안에 정보를 표현한다. 2차원 바코드는 기존의 1차원 바코드보다 작은 공간에 많은 데이터를 표현 가능함으로써 보다 효율적인 바코드의 구현이 가능하다. 현재 ISO 국제 표준화된 2차원 바코드는 총 4가지로 분류되는데 QR Code, Data Matrix, PDF417, MaxiCode가 있다. 본 논문에서는 ISO 국제 표준화된 바코드 중 하나인 Data Matrix의 Base 256 모드에 대한 기본 개념, 구성 방법, 인코딩 및 디코딩 방법을 상세히 제안한다. Data Matrix 심벌에 저장된 데이터를 보다 효율적으로 구성하기 위해 숫자, Alphanumeric 문자, 이진법에 따라 다른 인코딩, 디코딩 방법을 사용하게 되는데 본 논문에서는 이를 고려한 디코딩 방법에 초점을 맞춰 기술할 것이다.