• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.303-306
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• 2000

복잡한 형상을 지닌 터빈 블래이드의 결함을 검사하기 위해 현재 $35^\circ,\; 38^\circ,\; 40^\circ$의 횡파 굴절각을 지닌 탐촉자를 사용하고 있다. 이와 같은 굴절각은 초음파 빔의 경로를 Snell의 법칙에 의해 설정하고 있다. 그러나 터빈 블래이드 검사용 초음파 탐촉자를 제작하는 과정에서 $35^\circ$의 횡파 굴절각을 갖는 경사각 탐촉자는 제작이 어려움을 알았다. 이러한 원인은 철강재료의 종파임계각이 $33.2^\circ$의 횡과굴절각에 대응되며, 종파임계각 근처에서는 전반사 현상 때문에 에너지 투과율이 매우 작아 실제 시험대상체에 입사되는 에너지가 거의 없으며 또한 횡파굴절각이 약 $37.5^\circ$ 일때에 휭파의 에너지 투과율이 최대가 되어 wedge를 $37.5^\circ$ 이하의 횡파굴절각을 갖도록 설계하더라도 측정을 하면 $37.5^\circ$ 근처의 횡파굴 절각을 갖게된다. 즉, 종파임계각 근처에서는 전반사 현상에 의해 경계면에서의 에너지 투과가 매우 작아 횡파 굴절각은 Snell의 법칙이 아닌 초음파 에너지의 투과 정도를 나타내는 echo transmittance의 크기에 의해 결정된다.

• Journal of The Korean Association For Science Education
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• v.43 no.1
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• pp.29-36
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• 2023

This study investigates the effects of the operation of science activity program on scientific literacy focusing on science cultural literacy and core competencies for pre-service teachers. 255 pre-service teachers of K University participated, and the effects of the program were examined through a paired-sample t-test with one group pretest-posttest design for science cultural literacy. Only the post-test was conducted on core competency growth perception, and differences in growth perceptions by competency were compared using ANOVA. As a result of the study, the average of pre-service teachers was higher than the pre-test for science culture literacy, and this difference was statistically significant (p<.05). In the core competency growth perception, 70.6% of pre-service teachers reported growth in scientific communication ability, and as a result of the post-hoc test using LSD, it shows statistically significant growth compared to other competencies (p<.05). Through this, it was possible to confirm the educational value of the science activity program as a way to develop pre-service teachers' scientific literacy.

• Proceedings of the Korean Society of Computer Information Conference
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• 2016.07a
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• pp.281-282
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• 2016

본 논문에서는 IoT 디바이스를 안전하게 관리하고 인가되지 않은 접근과 같은 위협에 대응할 수 있는 보안 메커니즘을 제안한다. 이 메커니즘은 IoT 디바이스의 시스템 특징 및 네트워크 특징을 조합하여 개별적인 시그니처를 생성하고 이를 네트워크에서 지속적이고 주기적으로 검사를 수행함으로써 허가되지 않은 디바이스의 접근을 근본적으로 차단하는 방안이다. 본 논문에서는 제안한 메커니즘을 확인하기 위해 실험망을 구성하여 정상 IoT 디바이스와 비정상 IoT 디바이스를 정책적으로 구별하여 차단하여 보안 메커니즘의 우수함을 보인다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.628-630
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• 2003

오늘날의 규모가 매우 크고 복잡한 시스템 및 네트워크 환경 하에서 컴퓨터 시스템의 보안 관리는 매우 중요하다. 역할기반 접근제어 (RBAC : Role-Based Access Control)는 시스템 상의 역할을 기반으로 하는 접근제어 메커니즘으로 복잡한 접근정책을 기술하고, 시스템 관리상의 에러와 비용을 줄일 수 있다. 본 논문은 리눅스 커널에 보안 강화를 지원하는 리눅스 보안 모듈(LSM: Liunx Security Module) 프레임워크 상에서 확장된 역할기반 접근제어 보안 시스템 (LSM-Based Extended RBAC Security Module)을 제안한다. 본 고에서 제안된 시스템은 보안의 강화를 위하여 원 타임 패스워드 (One-Time Password)의 강화된 인증 방식과 부분적 다중 계층 보안 (Partial Multi-Level Security), 임의적 접근 제어(Discretionary Access Control) 및 감사 정보를 통한 보안 정책 오류 검사 및 대응 (Security Policy Validation and Response) 기능을 지원한다.

• The KIPS Transactions:PartA
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• v.18A no.4
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• pp.151-158
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• 2011

For the purpose of cost saving and sales promotion, various industry companies have introduced logistics management techniques in their field. However, enterprises faced to damages because proper products can not be provided to customers in basic logistics 3S1L(speedy, safely, surely, and low) principles for environments changing rapidly and inflexible business processes. So, we need the ability in coping with risk to handle this phenomenon. In particular, the shipper of key decisions of supply chain risk management requires continuous exchange and collection of logistics information in the third-party logistics. However the current SCRMS(Supply Chain Risk Management System) is not sufficient to cover the shipper's various needs and to recognize and respond to emergency situations. Therefore, this paper proposes an active SCRMS framework through the reconsideration about the previous research on SCRM and rearrangement of risk factors for coping with those problems. in addition, it verifies an efficiency through a stability comparison with the current system.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.1
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• pp.205-214
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• 2019

Android uses app cache files to improve app execution performance. However, this optimization technique may raise security issues that need to be examined. In this paper, we present a practical design of "Android app cache manipulation attack" to intentionally modify the cache files of a target app, which can be misused for stealing personal information and performing malicious activities on target apps. Even though the Android framework uses a checksum-based integrity check to protect app cache files, we found that attackers can effectively bypass such checks via the modification of checksum of the target cache files. To demonstrate the feasibility of our attack design, we implemented an attack tool, and performed experiments with real-world Android apps. The experiment results show that 25 apps (86.2%) out of 29 are vulnerable to our attacks. To mitigate app cache manipulation attacks, we suggest two possible defense mechanisms: (1) checking the integrity of app cache files; and (2) applying anti-decompilation techniques.

• 대한공업교육학회지
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• v.43 no.1
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• pp.1-19
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• 2018

As the BIM designing technology has been applied recently in the construction field, architectural design education in the field of work and university has been changing to 3D modeling. Nevertheless, architectural design & drafting education in the construction specialized vocational high school is not responding appropriately to change. Despite the fact that students need to have 3D modeling design ability, there is a very lack of 3D housing design instructional material that can satisfy the change. The purpose of this study is to develop BIM-based 3D modeling instruction material and apply to analyze effect on interest and task performance ability on Housing Design. The 3D modeling instruction material used in this study was developed through four stages of preparation, development, implementation and evaluation according to the PDIE model procedure. Also, the experimental design model for hypothesis testing was used nonequivalent control group pretest-posttest design. Based on the experimental design model, BIM-based 3D modeling instruction material was performed in the experimental group and 2D CAD-based standard instruction material was taught in the control group. Experimental treatment was conducted on the students of construction specialized vocatinonal high school, and applied to the subject of Professional Drafting in the 12 hours. Before and after the experimental treatment, the interest and task performance ability on Housing Design were tested. Based on the test results, we analyzed the effects of the 3D modeling instruction material through the independent samples t-test. The results of the study are as follows. First, BIM-based 3D modeling instruction material was developed of 'Housing Design & Drafting' unit on the subject of Professional Drafting in construction specialized vocational high school. Second, the application of 3D modeling instruction material has shown to be effective in improving students' interest. Third, the application of 3D modeling instruction material has shown to be effective in improving students' task performance ability on Housing Design.

• Journal of Engineering Education Research
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• v.10 no.1
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• pp.60-76
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• 2007

In this study, the effect of a sustainable energy design project on academic achievement for engineering freshmen at Virginia Tech in fall semester 2006 in the United States was examined by experimental method. The department of engineering education at Virginia Tech was opened in 2004. In this experiment the population was approximately 1200 freshmen, and 5 classes were sampled. Subject name is engineering exploration, a theme of the instruction is sustainable energy design, the project was performed throughout a 6 weeks period with one by 50 minutes lecture conducted by faculty and one 90 minutes workshop conducted by GTAs (Graduate Teaching Assistants) every week. The statistical results using SPSS (ver. 15.0) are as follows: A paired-samples t test analysis was run on the pre- and posttest to determine academic achievement, the results indicated a significant increase in 4 classes of mixed gender at .05 significance level, but there was no significance at 1 group of female class. A paired-samples t test analysis was run on the pre- and posttest to get an attitude score, the results showed, the posttest scores decreased for 5 groups even though it was not statistically significant. Finally, in responses to an open-ended question about students' perceptions of their improvement in skills, the 3 most frequently identified skills were teamwork, design process, knowledge.

• Korean Journal of Optics and Photonics
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• v.29 no.1
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• pp.7-12
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• 2018

In the field of machine vision, a variety of lenses are used to inspect a product for defects. Only part of the appearance of an object can be photographed with a general lens. Optical components such as mirrors, multiple lenses and cameras are required to inspect the entire exterior. This increases the size of the optical system, and has the disadvantage of high cost. In this paper, we design a hypercentric lens, which can photograph the top and side of an object, and various sizes of objects while maintaining the image size. Also, the validity of the design is verified through the performance analysis of the product.

• Journal of the Korea Convergence Society
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• v.12 no.11
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• pp.185-191
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• 2021

The purpose of this study is to develop middle school English classes using Problem-Based Learning(PBL) based on flipped learning and to examine its effects. Recently, various attempts to combine flipped learning and PBL have been made; however, many studies have not been applied to middle and high school curriculums yet. The attempt of this study is expected to have theoretical and practical significance. The instructional model was derived from the review of previous studies, and the development of instructional program followed the general design procedure(analysis-design-development-implement-evaluation), and its validity was secured with the advice of related experts. To verify the effectiveness of the program, the English academic achievement test and the English key competency test were conducted before and after the program. Changes in English academic achievement were analyzed by the paired-sample t-test, and the effect of key competency and the level of achievement test performance (high vs, low) on the pre-post score change was analyzed by the mixed effects repeated measures ANOVA. As a result of the analysis, both academic achievement and key competencies increased, and the low-level students in the pre-academic achievement test showed more improvements. In conclusion, the PBL class based on flipped learning is effective in improving the English academic achievement and key competencies of middle school students, and in particular, it is shown to be an effective teaching method for students with low academic achievement.