• Industrial Engineering and Management Systems
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• 제2권1호
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• pp.63-70
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• 2003

In this study, we employed an arithmetic process (AP) approach to resolve gearbox maintenance problems. The approach is realistic and direct in modelling the characteristics of a deteriorating system such as a gearbox since a decreasing AP can model a gearbox's successive operating times and an increasing AP can model the corresponding consecutive repair times. First of all, two test statistics were used to check whether the process is arithmetic or not. Next, model parameters of the AP were estimated using the simple linear regression method. Finally, the optimal replacement policy based on minimising the long-run average cost per day was determined for each type of gearbox.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2012년도 한국컴퓨터종합학술대회논문집 Vol.39 No.1(C)
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• pp.269-271
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• 2012

무선 네트워크의 급속한 성장과 더불어 스마트폰(Smart Phone) 사용자들이 급증함에 따라 카페나 지하철역 등 곳곳에서 무선LAN을 이용할 수 있게 되었다. 그러나, 무선LAN 이용자의 증가는 심각한 보안 문제를 야기시킨다. 공격자 AP(Access Point)의 SSID를 합법적인 무선 AP의 SSID와 동일하게 설정한 후, 클라이언트의 접속을 유도하여 공격할 수 있는데, 이러한 공격을 에빌 트윈(evil twin)공격이라고도 한다. 에빌 트윈 공격을 함으로써 공격자의 무선 AP를 이용하는 사용자들의 비밀번호를 스니핑 하거나, 피싱등의 공격을 할 수 있게 된다. 특히, 모바일 AP기능이 가능한 스마트폰 사용자들이 급증하고 있는 가운데, 스마트폰을 이용하면 이러한 공격을 더욱 은밀하고 간편하게 수행할 수 있다. 본 논문에서는 IP주소를 이용하여, 스마트폰을 이용한 에빌 트윈 공격 탐지 방법을 제안하였다.

• 한국방사선학회논문지
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• 제7권3호
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• pp.233-238
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• 2013

Chest lateral decubitus 촬영은 일반적으로 PA 검사를 시행하여 왔으나, 응급환자나 몸이 불편한 환자의 검사에 있어 많은 불편이 있었다. 이에 본 연구에서는 AP 검사와 PA 검사를 비교하여 영상의 질, 환자의 안전성, 검사 효율성을 분석하고 두 검사간의 유용성을 알아보고자 하였다. 본원에서 2011.10.1 ~ 2012.7.30까지 늑막염 또는 기흉으로 의심되거나 진단된 환자들 중 chest lateral decubitus 촬영을 시행한 30명(남자 20명, 여자 10명)을 대상으로 하였다. 영상 화질 평가방법은 폐야의 미세구조, 진단영역의 넓음, air-fluid 경계면의 명확 유무, 환자 회전유무, 심장음영과 횡격막의 선명유무를 기준으로 하였으며, 영상의학과 전문의 2명, 호흡기내과 전공의 2명이 blind test로 평가하였다. 환자 안정성 및 방사선 검사의 효율성 평가는 환자 position의 안정성, 환자 상태 확인 등의 기준으로 일반촬영 5년 이상 경력의 방사선사 15명이 5점 척도로 평가를 하였고, 통계 분석은 Paired T-test로 분석하였다. Chest decubitus 촬영 시 AP와 PA자세에 따른 검사의 유용성을 비교 분석한 결과 영상의 화질에서 AP와 PA자세는 큰 차이가 없었던 반면, 환자의 안정성 및 방사선사의 검사 효율성에 있어 PA자세에 비해 AP자세의 평가 점수가 높게 나타났다. 이에 특별히 PA자세가 요구되지 않는다면 AP자세로 검사하여도 무방할 것으로 사료된다.

• Journal of Electrical Engineering and Technology
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• 제8권1호
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• pp.183-189
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• 2013

In this paper, we propose a capacity modeling method for Bluetooth based LBSs (Location Based Services) between Bluetooth APs(Access Points) and mobile phones. In order to do this, we consider the entrance and exit of the users to and from the AP. Using parameters such as the connection time, data transmission time and number of users in the AP zone, we analyze the capacity of a Bluetooth AP using an appropriate queuing model. The required number of APs in a certain zone is estimated from the number of users in the zone using the proposed queuing model. By performing simulations and experiments, the validity and applicability of the proposed method are verified.

• 한국CDE학회논문집
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• 제8권2호
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• pp.122-132
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• 2003

STEP AP218 has a standard schema to represent the structural model of a midship section. While it helps to exchange ship structural models among heterogeneous automation systems, most shipyards and classification societies still exchange information using 2D paper drawings. We propose a feature parameter input method to generate a 3D STEP model of a ship structure from 2D drawings. We have analyzed the ship structure information contained in 2D drawings and have defined a data model to express the contents of the drawing. We also developed a QUI for the feature parameter input. To translate 2D information extracted from the drawing into a STEP AP2l8 model, we have developed a shape generation library, and generated the 3D ship model through this library. The generated 3D STEP model of a ship structure can be used to exchange information between design departments in a shipyard as well as between classification societies and shipyards.

• 대한족부족관절학회지
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• 제17권3호
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• pp.189-195
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• 2013

Purpose: We investigated a statistical difference of tibial-articular surface (TAS) angles between radiographs of standing ankle anteroposterior (AP) and whole lower extremity view, and evaluated whether the tibial axis obtained from the standing ankle AP view reflects the original mechanical axis of lower extremity. Materials and Methods: Both the standing ankle AP and whole lower extremity view were taken from 60 legs of 30 healthy volunteers without a history of ankle surgery or deformity of lower limb. To determine the tibial axis, Takakura's and Hintermann's method were employed in the standing ankle AP view. To compare these results with the original TAS angle, ANOVA and multiple comparison test were used. Results: The mean TAS angle was 88.3 degrees(from hip joint to ankle), 89.5 degrees (from knee joint to ankle), 88.5 degrees (Takakura's method), and 90.2 degrees(Hintermann's method). Although there was a statistical significance (p=0.000) between these results, Takakura's method had no significant difference, compared to the results of whole extremity view by the multiple comparison test. Conclusion: The tibial axis obtained by Takakura's method reflects the original mechanical axis of lower extremity. When a surgical procedure is planned, however, it is necessary to consider that the ankle radiographs do not provide any information on the proximal deformity without the whole lower extremity view.

• 대한화학회지
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• 제57권1호
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• pp.109-114
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• 2013

The effects of aluminum nanoparticles (AlNs) on the thermal decomposition of ammonia perchlorate (AP) were investigated by DSC, TG-DSC and DSC-TG-MS-FTIR. Addition of AlNs resulted in an increase in the temperature of the first exothermic peak of AP and a decrease in the second. The processing of non-isothermal data at various heating rates with and without AlNs was performed using Netzsch Thermokinetics. The dependence of the activation energy calculated by Friedman's isoconversional method on the conversion degree indicated the decomposition process can be divided into three steps. They were C1/D1/D1 for neat AP, determined by Multivariate Non-linear Regression, and changed to C1/D1/F2 after addition of AlNs into AP. The isothermal curves showed that the thermal stability of AP in the low temperature stage was improved in the presence of AlNs.

• 공업화학
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• 제28권2호
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• pp.214-220
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• 2017

결정화/응집(drowning-out/agglomeration, D/A) 공정을 이용하여 평균 입도 $550{\mu}m$인 구형 Al/RDX/AP 에너지 복합체를 제조하였다. SEM과 X-선 분광분석을 이용해 복합체의 표면 구조와 Al의 분포를 분석하였다. 열분석 결과 D/A 공정에 의해 제조된 Al/RDX/AP 복합체는 물리적 혼합에 의한 복합체와 비교하여 분해 개시 온도가 약 $50^{\circ}C$ 정도 낮아졌으며, 동시에 활성화 에너지의 증가에 의해 열적 안정성도 상승하는 것으로 확인되었다. AP의 1차 분해 구간에서는 물리적 혼합과 D/A 공정에 의한 복합체 모두 Prout-Tompkins 모델에 의해 잘 모사되었다. 그러나 AP의 2차 분해 구간에서는 물리적 혼합에 의해 제조된 복합체는 zero-order 모델로 해석되는 반면, D/A 공정에 의해 제조된 복합체는 contracting volume 모델로 해석됨을 알 수 있었다.

• Journal of Korean Dental Science
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• 제2권2호
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• pp.5-11
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• 2009

Objectives : This study investigated the hypothesis that the dentin bond strength of self-etching adhesives (SEAs) may be improved by applying a coat of hydrophobic, neutral adhesive resin in addition to SEA. Method and Materials : The bond strengths of two SEAs - Experimental SEA (EX) and Adper Prompt (AP) - were measured with three bonding protocols. The D/E resin of All-Bond 2 was applied as the hydrophobic, neutral adhesive. Clearfil SE Bond (SE, self-etching primer system) and All-Bond 2 (AB, total etching system) were used as references. The following protocols were used: (1) EX1 (EX 1 coat); (2) EX2 (EX 2 coats); (3) EX+ (EX 1 coat + D/E resin); (4) AP1 (AP 1 coat); (5) AP2 (AP 2 coats); (6) AP+ (AP 1 coat + D/E resin); (7) SE (SE primer + SE bond); (8) SE+ (SE primer + D/E resin); (9) AB (etching + AB primer + D/E resin). Filtek Z250 composite resin was built up and the microtensile bond strength (MTBS) values of the specimens were compared. The fractured surfaces were observed using SEM. Results : When SEA was used as self-etching primer and hydrophobic, neutral adhesive was applied as well, MTBS was significantly higher than that when either one coat or two coats of SEA only were used (p < 0.05). Conclusion : The hydrophobic, neutral adhesive improved the integrity of the bonded interface obtained with SEA.

• 한국운동역학회지
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• 제27권2호
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• pp.133-140
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• 2017

Objective: The purpose of this study was to determine the relationship between center of pressure (CoP) and local stability of the lower joints, which was calculated based on approximate entropy (ApEn) during walking in elderly women. Method: Eighteen elderly women were recruited (age: $66.4{\pm}1.2yrs$; mass: $55.4{\pm}8.3kg$; height: $1.56{\pm}0.04m$) for this study. Before collecting data, reflective marker triads composed of 3 non-collinear spheres were attached to the lateral surface of the thigh and shank near the mid-segment to measure motion of the thigh and shank segments. To measure foot motion, reflective markers were placed on the shoe at the heel, head of the fifth metatarsal, and lateral malleolus, and were also placed on the right anterior-superior iliac spine, left anterior-superior iliac spine, and sacrum to observe pelvic motion. During treadmill walking, kinematic data were recorded using 6 infrared cameras (Oqus 300, Qualisys, Sweden) with a 100 Hz sampling frequency and kinetic data were collected from a treadmill (Instrumented Treadmill, Bertec, USA) for 20 strides. From kinematic data, 3D angles of the lower extremity's joint were calculated using Cardan technique and then ApEn were computed for their angles to evaluate local stability. Range of CoP was determined from the kinetic data. Pearson product-moment and Spearman rank correlation coefficient were applied to find relationship between CoP and ApEn. The level of significance was determined at p<.05. Results: There was a negative linear correlation between CoP and ApEn of hip joint adduction-abduction motion (p<.05), but ApEn of other joint motion did not affect the CoP. Conclusion: It was conjectured that ApEn, local stability index, for adduction/abduction of the hip joint during walking could be useful as a fall predictor.