• Steel and Composite Structures
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• 제51권1호
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• pp.73-91
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• 2024

This paper has focused on presenting vibration analysis of trapezoidal sandwich plates with a damaged core and FG wavy CNT-reinforced face sheets. A damage model is introduced to provide an analytical description of an irreversible rheological process that causes the decay of the mechanical properties, in terms of engineering constants. An isotropic damage is considered for the core of the sandwich structure. The classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The First-order shear deformation theory of plate is utilized to establish governing partial differential equations and boundary conditions for the trapezoidal plate. The governing equations together with related boundary conditions are discretized using a mapping-generalized differential quadrature (GDQ) method in spatial domain. Then natural frequencies of the trapezoidal sandwich plates are obtained using GDQ method. Validity of the current study is evaluated by comparing its numerical results with those available in the literature. After demonstrating the convergence and accuracy of the method, different parametric studies for laminated trapezoidal structure including carbon nanotubes waviness (0≤w≤1), CNT aspect ratio (0≤AR≤4000), face sheet to core thickness ratio (0.1 ≤ ${\frac{h_f}{h_c}}$ ≤ 0.5), trapezoidal side angles (30° ≤ α, β ≤ 90°) and damaged parameter (0 ≤ D < 1) are carried out. It is explicated that the damaged core and weight fraction, carbon nanotubes (CNTs) waviness and CNT aspect ratio can significantly affect the vibrational behavior of the sandwich structure. Results show that by increasing the values of waviness index (w), normalized natural frequency of the structure decreases, and the straight CNT (w=0) gives the highest frequency. For an overall comprehension on vibration of laminated trapezoidal plates, some selected vibration mode shapes were graphically represented in this study.

• 수산해양기술연구
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• 제38권2호
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• pp.119-128
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• 2002

우리 나라 연안에서 주로 서식하고 있는 조피볼락(Schlegel's Black Rockfish, Sebastes schlegeli)과 참돔(Red Seabream, Pagrus major) 의 자원량을 추정할 때 보다 더 정확히 추정할 수 있는 기초 자료를 얻기 위하여 in situ TS 측정법과 유사한 환경 속에서 망과 3개의 주파수를 이용하여 어체의 크기와 자세별 및 주파수 특성에 따른 TS 에 대하여 조사하여 얻어진 결과를 요약하면 다음과 같다. 1. 전장(L, cm)에 따른 최대 TS 값을 이용한 조피볼락의 변환 계수(A) 값은 38kHz에서 -63.7dB, 120kHz에서 -64.4dB, 200kHz에서 -62.4 dB로 나타났으며, 참돔은 38kHz에서 -62.6dB, 120kHz에서 -65.4dB, 200kHz에서 -65..dB이었다. 또한, 평균 TS 값을 이용한 조피볼락의 변환 계수 값은 38kHz에서 -68.4dB, 120kHz에서 73.4dB, 200kHz에서 -70.8dB로 나타났으며, 참돔은 38kHz에서 -67.9dB, 120kHz에서 -72.7 dB, 200kHz에서 -73.4dB로 각각 나타났다. 2. 어체 1g당 최대 TS 값을 이용한 조피볼락의 변환 계수( B) 값은 38kHz에서 -52.0dB, 120 kHz에서 -52.7dB, 200kHz에서 -50.7dB로 나타났으며, 참돔은 38kHz에서 -50.9dB, 120kHz 에서 -53.7dB, 200kHz에서 -53.3dB이었다. 또한 평균 TS 값을 이용한 조피볼락의 변환 계수 값은 38kHz에서 -56.7dB, 120kHz에서 -61.7 dB, 200kHz에서 -59.IdB로 나타났으며, 참돔은 38kHz에서 -56.2dB, 120kHz에서 -61.0dB, 200 kHz에서 -61.6dB로 각각 나타났다. 3. 참돔 2마리를 대상으로 한 자세각 분포는 -26$^{\circ}$~25$^{\circ}$로 나타났으며, 그 때의 주파수에 따른 자세별 표적 강도는 38kHz에서 변화 폭이 비교적 적었으며, 120kHz에서는 Head down 되었을때 보다 Head up 되었을 때 3~6dB 정도 높게 나타났다.

• 한국정보통신학회논문지
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• 제21권6호
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• pp.1075-1082
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• 2017

본 논문에서는 새로운 해쉬 알고리듬인 SHA-3과 출력 길이 확장함수인 SHAKE256을 구현하는 해쉬 프로세서를 설계하였다. 해쉬 프로세서는 성능을 극대화하기 위해 Padder 블록, 라운드 코어 블록, 출력 블록이 블록 단계에서 파이프라인 구조로 동작한다. Padder 블록은 가변길이의 입력을 여러 개의 블록으로 만들고, 라운드 코어 블록은 on-the-fly 라운드 상수 생성기를 사용하여 SHA-3와 SHAKE256에 대응하는 해쉬 및 출력 확장 결과를 생성하며, 출력 블록은 결과 값을 호스트로 전달하는 기능을 수행한다. 해쉬 프로세서는 Xilinx Virtex-5 FPGA에서 최대 동작 속도는 220 MHz이며, SHA3-512의 경우 5.28 Gbps의 처리율을 갖는다. 프로세서는 SHA-3 와 SHAKE-256 알고리듬을 지원하므로 무결성, 키 생성, 난수 생성 등의 암호 분야에 응용이 가능하다.

• 한국전자파학회지:전자파기술
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• 제2권3호
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• pp.10-16
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• 1991

마이크로파용 소자를 측정하기 위해서 test fixture를 이용하는데, 소자 특성화에 앞서 측정시스댐과 test fixture에 따른 오차회로망을 우선적으로 보정하여야 한다. 본 논문에서는 길이가 다른 두개의 보정용 마이크로 스트립 선로만으로 오차회로망을 특성화하는 방볍을 제시하였다. 보정용 두 선로의 길이가 정확히 주어진다면, 전파상수의 지식없이도 정확한 보정 데이타를 제공할 수 있다. 보정용 선로 제작시 end effect를 전혀 고려할 필요가 없다. 이 방볍에 의한 보정작업에 따라 A TF13736 MESFET를 특성화 하였다. 측정주파수 범위는 2 2-18 GHz이고, 바이어스는 VDs=2. 5V, IDs=20mA이었다. 보정데이타와 데이타 용지를 비교할 때, 상대적 으로 낮은 주파수에서 그 크기는 거의 일치하고 단지 $0.1^{\circ}$~$12^{\circ}$의 위상차를 보였다.

• 한국학교보건학회지
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• 제3권2호
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• pp.63-87
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• 1990

The purpose of this study was to investigate the performance rate of regular health instruction by school nurses and its related factors. These data were collected by questionnaire in Mar. 1990. Total 986 school nurses who have been working primary, secondary schools in Seoul were given the questionnaire, and 672 school nurses' respectively, were finally analyzed. Analysis of the data was done utilizing SPSS/PC+for percentage, frequency, mean, $X^2$-test, t-test, ANOVA, correlation, regression. The major findings of this study were as follows : 1. Thc performance rate of regular health instruction by school nurses was 77.7% of 552 respondents. 2. The school nurses in primary school(87.0%) were more likely to perform regular health instruction than the school nurses in secondary school (63.8%). 3. The teachers of regular health instruction were more likely to display favorable attitudes toward need of health instruction. The school level was not statistically significant(P>0.05). 4. The evidence from the data analysis supported the proposition that the teachers of regular health instruction had more positive attitude toward the establishment of health subject(80.3%). The school level was statistically significant(P<0.05). 5. The school principal was a highly significant factor as it affected the performance rate of regular health instruction by school nurses. The school level was statistically significant(P<0.001). 6. The length of past career, the degree of self confidence on health instruction, the need of health instruction did affect the performance rate of regular health instruction by school nurses. On the basis of the above mentioned, so as for regular health instruction of school to be activated more throughly, regular class must be introduced in the form of establishment of health subject, enhancement of quality on the part of school nurses, made and various methods for enhancing perception toward the regular health instruction on the part of school principal are to be carried out.

• 한국정보통신학회논문지
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• 제17권2호
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• pp.397-404
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• 2013

본 논문에서는 Adaboost알고리즘을 이용한 얼굴인식 하드웨어 시스템의 구조를 제안하였다. 제안된 하드에어 구조는 초당 30프레임을 가지며 실시간 처리가 가능하다. 또한 Adaboost알고리즘을 이용하여 얼굴 특징 데이터를 학습하였고, 영상 크기 축소부와 적분 영상 추출부 그리고 얼굴 비교부, 메모리 인터페이스부, 데이터 그룹화, 검출결과 표시부 등으로 구성되었다. 제안된 하드웨어 구조는 사이클당 1포인트를 계산 할 수 있는 구조로 속도의 향상을 가져오며 full HD($1920{\times}1080$)의 경우에는 총 사이클 수 $2,316,087{\times}30=69,482,610$로 약 70MHz의 속도를 가진다. 제안된 하드웨어 구조는 Verilog HDL로 디자인되었고, Mentor Graphics Modelsim을 이용하여 검증하였으며, 합성은 FPGA Xilinx Virtex5 XC5VLX330을 이용하여 칩의 대략 35%인 74,757 Slice LUT와 45MHz의 주파수에서 동작한다.

• 부모자녀건강학회지
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• 제5권2호
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• pp.177-190
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• 2002

This study were conducted to assess the physical growth and developmental status of infants in orphanage in order to provide an empirical data. The subjects for this study were 104 infants and toddlers who were reared in an orphanage in D Metropolitan city. The instrument used for this study were anthropometric assessment and DDST for normative data of development. Data has been collected from September 1st, 1998 to August 31st, 2000 and were analyzed using SPSS/PC(Version 10.0) with frequency, mean, standard deviation, ANOVA and Chi-square test. The results of this study were as follows; 1. 30.8% of infants in orphanage had abnormal weight, 26.9% had abnormal length, and 22.1% had abnormal head circumference and most of them were distributed below 50 percentile of growth chart. 2. 53.8% of infants in orphanage had normal, 27.9% had qustionable, and 18.3% had abnormal developmental screening test results, especially, 31.5% of infants in orphanage ages 3 to 5 years had abnormal developmental screening test results, according to the Denver Developmental Screening Test(DDST). There was a significant developmental delay noted in the language and fine motor-adaptive sector. 3. It is anticipated that developmental delays would increase in severity by older the mean age of orphanage infants and longer the time being raised in orphanage. It would be concluded that the physical growth and developmental status of orphaned infants were very vulnerable and serious and it is suggested that there needed an effective intervention strategies to promote growth and development of infants in orphanage.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권6호
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• pp.2160-2179
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• 2015

In many Radio Frequency Identification (RFID) applications, the reader recognizes the tags within its scope repeatedly. For these applications, some algorithms such as the adaptive query splitting algorithm (AQS) and the novel semi-blocking AQS (SBA) were proposed. In these algorithms, a staying tag retransmits its ID to the reader to be identified, even though the ID of the tag is stored in the reader's memory. When the length of tag ID is long, the reader consumes a long time to identify the staying tags. To overcome this deficiency, we propose a slot allocated blocking anti-collision algorithm (SABA). In SABA, the reader assigns a unique slot to each tag in its range by using a slot allocation mechanism. Based on the allocated slot, each staying tag only replies a short data to the reader in the identification process. As a result, the amount of data transmitted by the staying tags is reduced greatly and the identification rate of the reader is improved effectively. The identification rate and the data amount transmitted by tags of SABA are analyzed theoretically and verified by various simulations. The simulation and analysis results show that the performance of SABA is superior to the existing algorithms significantly.

• 한국간호교육학회지
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• 제6권2호
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• pp.199-217
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• 2000

This descriptive longitudinal study was done to identify the ethical value of nursing students and to compare the differences of results with one year interval. The data were collected twice in 1999 and in 2000, from the 82 first year and 64 second year nursing students who have been attending at C college in Chonnam province. The analysis of data was done by frequency, mean, paired t-test, t-test, and ANOVA. The results of data were summarized as follows: 1. The total ethical value score of the first year students was 3.48 (maximum : 5) and, one year later, the score was lowered to 3.26. Especially, the degree of their ethical value was significantly decreased in the sub-areas of human-life and nurse-nursing task. 2. The total ethical value score of the second year students was 3.24 and, one year later, the score was increased to 3.39. The degree of their ethical value was significantly increased in the subarea of nurse- client relationship. 3. In the subarea of human-life, the mean score of ethical value was 3.25 and, one year later, the score was 2.95. The degree of ethical value was significantly lowered among the first year students with an utilitarian position. 4. In the subarea of nurse-client relationship, the mean score of ethical value was 3.39 and, one year later, the score was 3.67. The degree of ethical value was significantly increased among the second year students with a deontological position. 5. In the subarea of nurse-nursing task relationship, the mean score of ethical value was 3.38 and, one year later, the mean score was 3.08. The degree of ethical value was significantly decreased among the first year students. 6. In the subarea of nurse-collaboration relationship, the mean score of ethical value was 3.96 and, one year later, the mean score was 4.08 in second year students. There was no statistically significant difference. 7. The ethical values of nursing students were significantly different depending on their religion, length of study, attitude toward nursing and the experience of dying during their clinical practice.

• 생물정신의학
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• 제9권2호
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• pp.129-139
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• 2002

Objective:This study was performed to investigate the prescribing patterns of antimanic agents in the treatment of acute bipolar disorder inpatients in Korea from 1990 through 2000. The results will serve as the basic data for the practice guideline for the pharmacotherapy of bipolar disorder patients in Korea. Method:Retrospective chart review of bipolar disorder inpatients of Soonchunhyang Medical Center in Seoul and Chun-An was conducted for each of the year 1990, 1995, and 2000. The following data are collected ; 1) demographic data, 2) history of bipolar disorder, 3) length of hospital stay, 4) detailed drug titration records of antimanic agents and antipsychotic agents. Results:During the last decade, the frequency of lithium monotherapy was decreased obviously. Instead, more than half of the patients in 2000 were on combination therapy of lithium and anticonvulsants. Lithiumvalproate combination was the preferred strategy and the use rate of carbamazepine has been decreased. In addition, most of the patients were given antipsychotic agents during the last 10 years. And recently, atypical antipsychotics were increasingly prescribed. These changes in the field of pharmacology of bipolar disorder have resulted neither in shorter hospital stays nor lower dosages of concurrent neuroleptics. Conclusions:The results indicate the trends in the prescribing of antimanic agents for the treatment of bipolar disorder in Korea across the past 10 years. Mostly, the change seems to correspond to the international practice guideline. More systematic research is needed to find out the clinical benefits of the anticonvulsants in the real practice of treatment of bipolar disorder.