• 대한조선학회논문집
• /
• 제51권4호
• /
• pp.321-327
• /
• 2014

A wide scope of numerical simulations was performed to predict model-ship resistances by using STAR-CCM+ and OpenFOAM. The numerical results were compared with experimental measurements in towing tank to analyze statistical reliability of the present simulations. Based on the normal distribution of resistance errors in 113 cases of container carriers, tankers and very large crude-oil carriers, the confidence intervals of numerical error were estimated as [-2.64%,+2.32%] and [-1.82%, +1.87%] with 95% confidence in STAR-CCM+ and OpenFOAM, respectively. The resistance errors of liquefied natural gas carriers with single- and twin-skeg were confident in the ranges of [-2.51%,+2.64%] and [-2.29%, +1.46%], respectively. The grid uncertainty of resistance coefficients for KCS was also quantitatively analyzed by using a grid verification procedure. The grid uncertainty of OpenFOAM (5.1%) was larger than 4.4% uncertainty of STAR-CCM+ although OpenFOAM provided statistically more confident results than those of STAR-CCM+. It means that a grid system verified under a specific condition does not automatically lead to statistical reliability in general cases.

• ETRI Journal
• /
• 제26권4호
• /
• pp.321-331
• /
• 2004

In this paper, we propose a new dynamic bandwidth allocation (DBA) algorithm for multimedia services over Ethernet PONs (passive optical networks). The proposed algorithm is composed of a low-level scheduler in the optical network unit (ONU) and a high-level scheduler in the optical line terminal (OLT). The hierarchical DBA algorithm can provide expansibility and efficient resource allocation in an Ethernet PON system in which the packet scheduler is separated from the queues. In the proposed DBA algorithm, the OLT allocates bandwidth to the ONUs in proportion to the weight associated with their class and queue length, while the ONU preferentially allocates its bandwidth to queues with a static priority order. The proposed algorithm provides an efficient resource utilization by reducing the unused remaining bandwidth caused by the variable length of the packets. We also define the service classes and present control message formats conforming to the multi-point control protocol (MPCP) over an Ethernet PON. In order to evaluate the performance, we designed an Ethernet PON system on the basis of IEEE 802.3ah "Ethernet in the first mile" (EFM) using OPNET and carried out simulations. The results are analyzed in terms of the channel utilization, queuing delay, and ratio of the unused remaining bandwidth.

• 한국결정성장학회지
• /
• 제11권4호
• /
• pp.148-153
• /
• 2001

새로운 압전체인 $Ca_{3}NbGa_{3}Si_{2}O_{14}$(CNGS) 단결정은 Czochralski 법을 사용하여 결정성장을 이루었다. CNGS의 결정 구조는 $A_{3}BC_{3}D_{2}O_{14}$와 동방구조를 이루고 있음이 조사되어졌고, 단위 셀의 격자상수는 각각 a = 8.0873과 c = 4.979이었으며, 공간군은 P321이었다. 각각의 양이온의 분포는 각 자리에 규칙배멸을 이루고 있음을 보였다. CNGS 결정은 Langasite 보다 높은 품질계수, 전기기계결합계수, 압전성수를 나타내었으며, 이는 Langasite와 비교하여 낮은 탄성손실과 우수한 압전특성을 가짐을 보여주고 있다.

• 대한인간공학회지
• /
• 제29권3호
• /
• pp.321-329
• /
• 2010

Unlike production line works, construction work is non-repetitive in nature. In this study, a checklist was developed to characterize the ergonomic hazards of construction work. Eight existing checklists including OWAS, RULA, and REBA were integrated, and a new version was designed to include more postures of lower extremities. The analysis results obtained using the new checklist showed that manual materials handling (MMH) is the most common risk factor. About 62% of the MMH was done below the knee level or above the elbow level, and 22% was carried out with the trunk twisted more than $60^{\circ}$. The next risk factors were the works done with the knee bent or squatted, or with the shoulders abducted. It can be concluded that the new checklist is successful as a quick and easy tool for screening risk factors of construction works, although it is not capable of determining action levels. Further studies on validation of the checklist are expected.

• 대한기계학회논문집A
• /
• 제33권4호
• /
• pp.321-328
• /
• 2009

Shock absorption performances of various rubbers were investigated by using drop impact test. Several types of rubber such as NR, NBR, EPDM, SR and PUR with three respective levels of shore hardness were used for the test. As in the cases, the absorbed impact energies in rubbers were measured under seven different loads against impact energy between 5-80J. The impact absorption efficiencies of the rubbers then were evaluated by means of both single impact energy condition and summation of all impact energy applied condition. As shown in the results, PUR and EPDM have better shock absorption performances than other rubbers. Further analysis was extended to determine a shear modulus of SR through the finite element implementation with Blatz-Ko model. As can be seen, relatively higher level of absorption energy results in a decreasing shear modulus.

• International Journal of Advanced Culture Technology
• /
• 제7권4호
• /
• pp.321-326
• /
• 2019

As AI technology is recently introduced into various fields, it is being applied to the fashion field. This paper proposes a system for recommending cody clothes suitable for a user's selected clothes. The proposed system consists of user app, cody recommendation module, and server interworking of each module and managing database data. Cody recommendation system classifies clothing images into 80 categories composed of feature combinations, selects multiple representative reference images for each category, and selects 3 full body cordy images for each representative reference image. Cody images of the representative reference image were determined by analyzing the user's preference using Google survey app. The proposed algorithm classifies categories the clothing image selected by the user into a category, recognizes the most similar image among the classification category reference images, and transmits the linked cody images to the user's app. The proposed system uses the ResNet-50 model to categorize the input image and measures similarity using ORB and HOG features to select a reference image in the category. We test the proposed algorithm in the Android app, and the result shows that the recommended system runs well.

• 한국정보통신학회논문지
• /
• 제14권2호
• /
• pp.321-328
• /
• 2010

본 논문은 수동형 RFID 시스템에서 리더 충돌을 회피시킬 수 있는 코디네이터 기반 TDMA 프로토콜을 제시한다. 제시한 프로토콜에서는 코디네이터가 포아송 분포로 네트워크에 참여하는 리더에게 슬롯을 효율적으로 할당하고 관리하여 빈 슬롯 발생을 최소화하며 프레임 크기 제한을 통해서 네트워크에 참여하는 리더의 대기 시간을 줄 일 수 있다. 제안된 프로토콜은 이동식 및 고정형 RFID 네트워크 형태로 구현이 가능하며 이를 위한 프레임 및 슬롯구조를 제시한다. 모의실험을 통해서 제시한 프로토콜이 성공적으로 동작하며 특히 프레임 크기의 한계 값과 네트워크에 참여하는 리더의 통계적 분포가 총 슬롯 및 리더의 평균대기 시간에 결정적인 역할을 함을 보인다.

• 정보처리학회논문지A
• /
• 제12A권4호
• /
• pp.321-326
• /
• 2005

본 논문에서는 질점-스프링 모델(mass-spring model)에 기반한 대화형 천 시뮬레이션(interactive cloth simulation) 기법을 제시하며, 특히 소수의 질점들(mass-points)에 상대적으로 강한 힘이 가해졌을 경우 사실적으로 천을 시뮬레이션하는 방법에 초점을 맞추었다. 본 논문에서 제시하는 방법은 소수의 점들에 대해 가해진 힘을 모든 질점들에 분산시킴으로써 의사 실시간(pseudo real-time) 내에 시뮬레이션을 수행하며, 이는 기존의 방법들에 비해 수행속도 면에서 매우 효율적이다. 또한, Provot[9]의 역동역학 방법(inverse dynamic method)을 사용하여 초탄성(super-elasticity) 현상을 해결한 뒤, 인접한 질점 간의 각도를 조정함으로써 초탄성 효과에 의해 발생하는 지그재그(zigzag) 현상을 제거하여 사실적으로 천을 시뮬레이션한다.

• 한국전기전자재료학회논문지
• /
• 제33권4호
• /
• pp.321-325
• /
• 2020

Atmospheric environmental problems have a major impact on human health and lifestyle. In humans, inhalation of nitrogen oxides causes respiratory diseases, such as bronchitis. In this paper, thermal analysis of a gas sensor was carried out to design and fabricate a wearable nylon-yarn gas sensor for the detection of NO_x gas. In the thermal analysis method, the thermal diffusion process was analyzed while operating the sensors at 40 and 60℃ to secure a temperature range that does not cause thermal runaway due to temperature in the operating environment. Thermal diffusion analysis was performed using the COMSOL software. The thermal analysis results could be useful for analyzing gas adsorption and desorption, as well as the design of gas sensors. The thermal energy diffusion rate increased slightly from 10.05 to 10.1 K/mm as the sensor temperature increased from 40 to 60℃. It was concluded that the sensor could be operated in this temperature range without thermal breakdown.

• The Plant Pathology Journal
• /
• 제26권4호
• /
• pp.321-327
• /
• 2010

We performed diagnostic PCR assays and a phylogenetic analysis using partial sequences of TEF1 (translation elongation factor-1) to determine the trichothecene chemotypes and genetic diversity of F. graminearum isolates from maize and rice samples collected in 2009 in Korea. PCR using a species-specific primer set revealed a total of 324 isolates belonging to the putative F. graminearum species complex. PCR with trichothecene chemotypespecific primers revealed that the nivalenol (NIV) chemotype was predominant among the fungal isolates from rice (95%) in all provinces examined. In contrast, the predominant chemotype among the corn isolates varied according to region. The deoxynivalenol (DON) chemotype was found more frequently (66%) than the NIV chemotype in Gangwon Province, whereas the NIV chemotype (70%) was predominant in Chungbuk Province. Phylogenetic analysis showed that all DON isolates examined were clustered into lineage 7, while the NIV isolates resided within lineage 6 (F. asiaticum). Compared with previous studies, the lineage 6 isolates in rice have been predominantly maintained in southern provinces, while the dominance of lineage 7 in maize has been evident in Gangwon at a slightly reduced level.