• Journal of the Institute of Electronics Engineers of Korea TC
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• 제43권11호
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• pp.149-158
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• 2006

We proposed a method for improving a performance of TCP downstream between a desktop PC as a fixed host and a PDA as a mobile host in a wired and wireless network based on IEEE 802.11x wireless LAN. With data transmission between these heterogeneous terminals a receiving time during downstream is slower than that during upstream by 20% at maximum. The reason is that their congestion window size will be oscillated due to a significantly lower packet processing rate at receiver compared to a packet sending rate at sender. Thus it will cause to increase the number of control packets to negotiate their window size. To mitigate these allergies, we proposed two distinct methods. First, by increasing a buffer size of a PDA at application layer an internal processing speed of a socket receive buffer of TCP becomes faster and then the window size is more stable. However, a file access time in a PDA is kept nearly constant as the buffer size increases. With the buffer size of 32,768bytes the receiving time is faster by 32% than with that of 512bytes. Second, a delay between packets to be transmitted at sender should be given. With an inter-packet delay of 5ms at sender a resulting receiving time is faster by 7% than without such a delay.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 한국농업기계학회 2017년도 춘계공동학술대회
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• pp.169-169
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• 2017

스마트 돈사 내의 열환경 분석에 필수적으로 고려되어야 인자는 가축의 복사 에너지 변화로 볼 수 있다. 열환경 제어의 대상이기도 하지만 회귀적으로 열환경 변화의 인자이기도 하다. 이러한 가축의 복사 에너지 분석을 위하여 시설 내에 용이하게 배포가 가능한 열화상 계측 시스템을 개발하였다. 초소형 마이크로 열화상 계측 시스템에 부가적으로 IOT(Internet of Thing) 기반 기술을 이용한 모듈화 개발을 병행하였다. 열화상 계측 센서로 LWIR(Longwave infrared)영역에 해당하는 $8{\mu}m{\sim}4{\mu}m$의 영역에서 $0.05^{\circ}C$의 분해능을 보이는 $Lepton^{TM}$ (500-0690-00, FLIR, Goleta, CA)모델을 사용하였다. SPI(Serial Peripheral Interface) 속도 2 Mhz로 마이크로프로세서(NanoPi NEO Air, FrendlyArm, CA, USA)와 고속 통신을 수행하여 9 Hz의 계측이 가능하다. 열화상 센서와 마이컴으로 구성되는 단위 계측 시스템의 통신 기능 확장을 위하여 다음과 같이 세 단계의 정보 전달 시나리오를 설계하였다. 1) 단독적으로 열화상을 계측 하고 내장된 메모리에 저장하는 형식 2) 인접한 사용자 인터페이스에서 1번 단독 모듈에 접속하여 열화상을 실시간으로 전송하여 화면에 도시하는 형식 3) 2번 사용자 도시모듈과 병행적으로 Local WI-FI 통신을 이용한 모바일 기기에 화면을 도시하는 형식. 이와 같은 계층적이며 모듈화된 계측 시스템을 구성하기 위해서 1번 모듈에 공개 소프트웨어인 Hostapd 2.5(http://w1.fi/hostapd)버전을 설치하였다. 외부 인터넷 환경이 없는 상황에 1번 모듈 단독으로 AP(Access Point) 기능을 제공하여 지근 거리에 있는 2번 모듈과 3번 모바일 기기의 접속을 관리할 수 있다. 2번 모듈의 경우 화면 다수의 1번 모듈에 접속을 교차적으로 수행하는 방식과 2번 모듈 자체가 AP가 되어 1번 모듈의 접속을 허용하는 형태로 구성되어 있다. 계측 시스템의 계측 매트릭스 구성에 따라 선택적으로 결정할 수 있다. 1번 2번 모듈 공통적으로 TCP/IP Listener와 Client 서비스를 병렬적으로 수행할 수 있도록 개발을 하였다. 3번 모바일 기기에서 사용자 인터페이스 구현을 위하여 범용 Android 기반 GUI 프로그램과 Socket 통신을 연동시켰다. 1개의 열화상 Frame의 전송량은 9,600 Byte ($=80{\times}60{\times}2Byte$) 로 WI-FI 통신 전송 시 2회 ~ 6회 정도 내외로 가변적인 통신 수행 횟수를 나타내었다. 센서 계측 시스템과 정보 전송 시스템을 병렬적으로 구성한 모듈화 된 계측시스템의 전 요소에서 센서에서 제공하는 최대 계측 주기인 9 Hz 구현이 일반적으로 가능하였다. 이를 이용한 추후 연구를 통해 가축 객체의 열복사 정보와 돈사 내 열환경 간의 역학성을 연구할 것이다.

• Journal of the korean academy of Pediatric Dentistry
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• 제26권1호
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• pp.96-102
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• 1999

Tooth avusion implies total displacement of teeth out of its socket. Its frequency range from 0.5 to 16% of traumatic injuries. Replantation procedure is used for the treatment of avulsed tooth. However, its major complications are pulp necrosis, inflammatory root resorption and replacement root resorption. This paper describes 10 years and 2 months old male patient whose both maxillary central incisors were avulsed due to fall-down with slightly underdeveloped root apices. Teeth were replanted 2 hours after accident. Right central incisor's pulp tissues were extirpated and filled with $Vitapex^{(R)}$(calcium hydroxide) at 3-4 weeks after replantation, but left central incisor was filled at 8-9 weeks. Right central incisor showed little inflammatory resorption in apical portion, whereas left central incisor showed severe root resorption. During 18 months' follow-up period, left central incisor showed slightly ankylosis while right central incisor did not. Based upon the above-mentioned results, the following conclusions can be drawn: 1. Inflammatory resorption could be suppressed by endodontic treatment with calcium hydroxide. 2. When apex formation is doubted in replanted tooth due to avulsion, early endodontic treatment with calcium hydroxide seems to act positively for better prognosis.

• Imaging Science in Dentistry
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• 제50권1호
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• pp.1-7
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• 2020

Purpose: This study was performed to evaluate the magnitude of artifacts produced by gutta-percha and metal posts on cone-beam computed tomography (CBCT) scans obtained with different tube currents and with or without metal artifact reduction (MAR). Materials and Methods: A tooth was inserted in a dry human mandible socket, and CBCT scans were acquired after root canal instrumentation, root canal filling, and metal post placement with various tube currents with and without MAR activation. The artifact magnitude was assessed by the standard deviation (SD) of gray values and the contrast-to-noise ratio (CNR) at the various distances from the tooth. Data were compared using multi-way analysis of variance. Results: At all distances, a current of 4 mA was associated with a higher SD and a lower CNR than 8 mA or 10 mA (P<0.05). For the metal posts without MAR, the artifact magnitude as assessed by SD was greatest at 1.5 cm or less (P<0.05). When MAR was applied, SD values for distances 1.5 cm or closer to the tooth were reduced (P<0.05). MAR usage did not influence the magnitude of artifacts in the control and gutta-percha groups(P>0.05). Conclusion: Increasing the tube current from 4 mA to 8 mA may reduce the magnitude of artifacts from metal posts. The magnitude of artifacts arising from metal posts was significantly higher at distances of 1.5 cm or less than at greater distances. MAR usage improved image quality near the metal post, but had no significant influence farther than 1.5 cm from the tooth.

• The Journal of Korean Academy of Prosthodontics
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• 제55권2호
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• pp.151-155
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• 2017

Purpose: The aim of this study was to evaluate screw removal torque of the two-piece zirconia abutment with the novel titanium component compared to the conventional one-piece titanium abutment in the internal connection implant before and after dynamic cyclic loading. Materials and methods: Two types of the abutment assemblies with internal connection were prepared and divided into the groups; titanium abutment-titanium abutment screw assemblies as control, and zirconia abutment-titanium socket-titanium abutment screw assemblies as experimental group. A total of 12 abutments and implants were used of six assemblies each group. Each assembly was tightened to 30 Ncm. A cyclic load of 300 N at an angle of 30 degrees in reference to the loading axis was applied until one million cycles or failure. The removal torque values (RTVs) of the abutment screws were measured with a digital torque gauge before and after cyclic loading. The RTVs of the pre load and post load were analyzed with t-test, and P-values < .05 were considered statistically significant. Results: The assemblies of both groups survived all after the dynamic cyclic loading test without screw loosening. The statistically significant differences were found between the mean RTVs before and after the cyclic loading in both groups (P < .05). The RTV differences for the control and the experimental group were $-7.25{\pm}1.50Ncm$ and $-7.33{\pm}0.93Ncm$, respectively. Statistical analysis revealed that the RTV differences in both groups were not significantly different from each other (P > .05). Conclusion: Within the limitation of this study, the two-piece zirconia abutment with the titanium component did not show a significant RTV difference of the abutment screw compared to the titanium abutment after dynamic cyclic loading.

• Clinics in Shoulder and Elbow
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• 제2권1호
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• pp.41-46
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• 1999

Glenoid labrum acts as one of static stabilizer of the glenohumeral joint. It deepens the glenoid socket and may also serve as a chock, acting as a wedge in preventing glenohumeral translation. Two types of variations in labral anatomy were noted by Detrisac and Johnson. Type A has a superior labrum that is detached centrally but well attached peripherally. The type B labrum is well attached centrally and peripherally at all sites. A meniscoid-type labrum is thought to be normal unless there are splits or fragmentation of the overlying labral tissue. Meniscoid type labrum is different from SLAP II lesion in that it has a firm anchoring on the superior labrum. We observed four cases that had a meniscoid variant superior labrum, which covered the superior glenoid unusually larger than normal in the arthroscopic treatment of shoulder pathology including instability and rotator cuff diseases. We did arthroscopic reshaping and debridement of meniscoid variant superior labrum combined with pathologic change of the glenohumeral joint. Further study would be required for understanding the mechanism of the development of meniscoid variant labrum and its clinical significance.

• Journal of Korea Multimedia Society
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• 제15권4호
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• pp.540-551
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• 2012

Recently, the W3C has developed the HTML5 standard which gives the basis for providing various web applications on the web environments. Because of the advent of the smart devices and the broadband wireless network, users can accesse the web applications on the smart devices at anytime and anywhere. In addition, the demand on the multiscreen services, which enables users to use the appropriate device to their situation, has increased, since users have various smart devices. In this paper, we propose the grouping mechanism of web objects on the HTML5 based web platform, the extraction mechanism of the web object information which is used to create the web object on other devices, and the web object creation mechanism based on the received web object information. In addition, we propose the web service migration architecture between devices on the open web platform and implement the grouping, extraction and creation mechanism of the web objects on the test web document and generic web document with Chrome extension. Finally, we implement the delivery mechanism of the web object information between devices using the node.js and the WebSocket technologies.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제19권1호
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• pp.705-713
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• 2018

An automotive ball joint connects the suspension system to the steering system and helps to enable rotational and linear motion between the two elements for steering. This study examines a ball joint used in medium and large-sized pickup trucks. Ball joints consist of a stud, socket, bearing, and plug. The main structural performance metrics of ball joints are the pull-out strength and push-out strength. These structural parameters must meet certain criteria to avoid serious accidents. Test and simulation methods are used to investigate the design requirements, but tests are time-consuming and costly. In this study, we modeled ball joints in SolidWorks and performed a finite element analysis in Abaqus to predict structural performance. The analysis was used to obtain the structural performance required for the static analysis of a 2D axisymmetric model. The uncertainties in the manufacturing of the ball joint were assumed to be the manufacturing tolerances, and the dimensional design variables were identified through case studies. The manufacturing tolerances at each level were defined, and the results were compared with experimental results.

• The Journal of the Korea Contents Association
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• 제13권8호
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• pp.324-333
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• 2013

The purpose of this study was to investigate the need of home modification for outpatient with stroke and spinal cord injury. The subjects of this study were 54 outpatients who have experience in rehabilitation therapy at hospitals in Seoul and Gyeonggi-do. A questionnaire was distributed and collected form January 2th to February 4th, 2012. Descriptive statistics and $x^2$-test were used to analyze data. There were statistically significant difference in stairs of access, in width of front door, in bathroom, space of room according diagnosis. There were statistically significant difference in light of sensor, tissue holder and socket cover in bathroom for the comparison of demands for home modification by living type. There were statistically significant difference in width and threshold of front door, tissue holder and towel bar, nonslip floor in bathroom, space and table, chair of kitchen, space and threshold of porch, light for the comparison of demands for home modification according score of MBI. Based on the results of the survey, needs of home modification is different according disability level, diagnosis, living type, ADL performance. The results of this study show a need for the further occupational therapy of home modification and supporting policies in home modification.

• Journal of KIISE:Computer Systems and Theory
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• 제37권4호
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• pp.226-238
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• 2010

OpenSSL is an open-source library implementing SSL that is a secure communication protocol. However, the library has a severe vulnerability that its security information can be easily exposed to malicious software when the library is used in a form of shared library on Linux and UNIX operating systems. We propose a scheme to attack the vulnerability of the OpenSSL library. The scheme injects codes into a running client program to execute the following attacks on the vulnerability in a SSL handshake. First, when a client sends a server a list of cryptographic algorithms that the client is willing to support, our scheme replaces all algorithms in the list with a specific algorithm. Such a replacement causes the server to select the specific algorithm. Second, the scheme steals a key for data encryption and decryption when the key is generated. Then the key is sent to an outside attacker. After that, the outside attacker decrypts encrypted data that has been transmitted between the client and the server, using the specified algorithm and the key. To show that our scheme is realizable, we perform an experiment of collecting encrypted login data that an ftp client using the OpenSSL shared library sends its server and then decrypting the login data.