• Journal of Information Technology Applications and Management
• /
• 제14권3호
• /
• pp.169-178
• /
• 2007

The next generation mobile multimedia network is expected to provide higher-rate multimedia communication services to versatile mobile terminals moving in even higher speed. For achieving more efficient reusability of scarce radio resources and thereby accommodating more user population in this network, the smaller cell such as micro or pico cell structure is used. More efficient and faster hand-over schemes are necessary to prevent the degradation of QoS of multimedia services caused by hand-over processing delay and packet loss during frequent hand-over. This paper proposes a faster and more effective hand-over scheme for high-rate multimedia services in the future mobile multimedia networks. by utilizing the GPS information on the position of the mobile terminal and its estimated moving directions. The simulation results show that our proposed method provides a better performance than the conventional method.

• 한국통신학회논문지
• /
• 제32권7A호
• /
• pp.770-777
• /
• 2007

차세대 이동 통신망에서는 광대역의 멀티미디어 서비스를 요구하는 다수의 사용자를 수용하기 위해 마이크로-셀 또는 피코-셀 구조를 채택하므로 핸드오버가 빈번히 발생한다. 또한 핸드오버 처리에 허용될 수 있는 시간이 단말기의 고속 이동에 의해 감소됨으로써 서비스 절단 가능성이 높아지게 되어 매우 짧은 시간의 서비스 중단으로도 치명적인 영향을 받을 수 있다. 더욱이 패킷의 손실을 보상하기 위한 재전송으로 인해 시스템 성능의 추가적인 저하를 초래한다. 본 논문에서는 차세대 이동 멀티미디어 통신망에서 단말기의 핸드오버 시에 기지국 기반 위치 정보와 GPS 위치 정보를 복합적으로 이용하여 멀티미디어 서비스의 지속성을 증대시키기 위한 방안을 제안한다. 제안된 방법의 성능을 평가하기 위해 핸드오버 실패율과 패킷 손실률을 시뮬레이션에 의해 분석하였다.

• 한국컴퓨터정보학회논문지
• /
• 제18권2호
• /
• pp.59-68
• /
• 2013

LTE-Advanced 망에서 핸드오버가 발생하면 멀티미디어 트래픽의 전송이 지연 및 손실에 의하여 영향 받기 때문에, 일관된 QoS를 유지하기 위한 효율적인 자원 관리 방안이 필요하다. 본 논문은 핸드오버 시에 OFDMA 시스템에서 이종 트래픽의 QoS를 보장하기 위한 부하제어 기반의 자원 관리 방안을 제안한다. 이를 통하여 음성, 영상, 데이터 서비스 등 자원할당 요구 사항이 서로 다른 멀티미디어 서비스들의 서비스 연속성을 지원할 수 있다. 핸드오버 실패율과 패킷 손실률을 성능척도로 하여 수행된 시뮬레이션 결과에 의하면 제안된 방안은 기존 방안에 비하여 더 우수한 성능을 가짐이 확인된다.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제2권1호
• /
• pp.45-56
• /
• 2010

Polymer composite materials offer high strength and stiffness to weight ratio, corrosion resistance, and total life cost reductions that appeal to the marine industry. The advantages of composite construction have led to their incorporation in U.S. yacht hull structures over 46 meters (150 feet) in length. In order to construct even larger hull structures, higher quality composites with lower cost production techniques need to be developed. In this study, the effect of composite hull fabrication processes on mechanical properties of glass fiber reinforced plastic (GFRP) composites is presented. Fabrication techniques investigated during this study are hand lay-up (HL), vacuum infusion (VI), and hybrid (HL+VI) processes. Mechanical property testing includes: tensile, compressive, and ignition loss sample analysis. Results demonstrate that the vacuum pressure implemented dining composite fabrication has an effect on mechanical properties. The VI processed GFRP yields improved mechanical properties in tension/compression strengths and tensile modulus. The hybrid GFRP composites, however, failed in a sequential manor, due to dissimilar failure modes in the HL and VI processed sides. Fractography analysis was conducted to validate the mechanical property testing results.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
• /
• pp.282-285
• /
• 2006

This study is to examine bond strength of beam reinforced with GFRP rebar under 4-point bending test by adopting BRITISH STANDARD. The variables were made to have bonding length of 5times$(5d_b)$, 10times$(10d_b)$ and 15times$(15d_b)$ of the nominal diameter of GFRP rebar and were done to analyze the relationship between the bonding strength and the slip. In the result of the test, pull-out failure was dominant in the $5d_b$ and $10d_b$ specimen, both patterns of the pull-out failure and concrete splitting failure appeared in the $10d_b$. On the other hand, the $15d_b$ specimen showed only concrete splitting failure at the end of bonding length. Therefore, it was prove that available bonding length of the GFRP rebar under bending condition on static test is over $15d_b$ then farther research such as fatigue bending test, development of bonding model, FEM parameter study should be performed.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• 제29권2호
• /
• pp.102-107
• /
• 2003

At orthodontic treatment, we have made every effort to get rigid anchorage which is not stirred when teeth move. As a result, the miniscrew that is rigid anchorage was invented recently, and now it is used widely. Concerning the advantage of miniscrew, it is reduced dependence of extraoral anchorage and it shortens treatment time for rapid tooth movement. In contrast, the defect of miniscrew is falling off it resulted from increasing of the mobility. So the purpose of this research is to be of help to prognose clinical use of miniscrew, which is inserted for intraoral anchorage, by investigating and comparing the failure rate of miniscrew for loading time. This study researches the failure rate of miniscrew for teeth movement at the orthodontic treatment. The failure rate of miniscrew in mid course, after inserting 147 miniscrews in 51 patients, is 13%(20/147). It showed no statistically significant differences as compared man with woman, maxilla with mandible, double-head with uni-head miniscrew, and drilling and non-drilling before inserting the miniscrew. In comparison below twenties with over twenties and the times that we give load to miniscrew, it produced that the failure rate of miniscrew is 9.7% higher in the case of below the twenties than over the twenties. Also, the failure rate of loading immediately is 10.8% higher than loading after 7 days. According to using driver for the insertion of miniscrew, the failure rate of miniscrew is higher in the case of using machined driver than in the case of using hand driver when the level of significance is 95%. According to the research, we can suppose that the failure rate has no concern with using miniscrew on man or woman, maxilla or mandible, the shape of head, and drilling or non-drilling before insertion of miniscrew. Therefore, we can choose eclectic miniscrew as demands. In addition, we must notify the patient, below twenties, to be possibility of high failure rate. And It is strongly recommended to give load after $1{\sim}2$ weeks for healing of the insertion area.

• 한국해양공학회지
• /
• 제38권1호
• /
• pp.30-42
• /
• 2024

This study examined the jack-up spudcan penetration for a new type of offshore wind substructure newly proposed using the jack-up concept to reduce construction costs. The jack-up spudcan for offshore wind turbines should be designed to penetrate a stable soil layer capable of supporting operational loads. This study evaluated multi-layered soil conditions using centrifuge tests: loose sand over clay and loose sand-clay-dense sand. The penetration resistance profiles of spudcan recorded at the centrifuge tests were compared with the ISO and InSafeJIP methods. In the tests, a spudcan punch-through effect slightly emerged under the sand-over-clay condition, and a spudcan squeezing effect occurred in the clay-over-sand layer. On the other hand, these two effects were not critically predicted using the ISO method, and the InSafeJIP result predicted only punch-through failure. Nevertheless, ISO and InSafeJIP methods were well-matched under the conditions of the clay layer beneath the sand and the penetration resistance profiles at the clay layer of centrifuge tests. Therefore, the ISO and InSafeJIP methods well predict the punch-through effect at the clay layer but have limitations for penetration resistance predictions at shallow depths and strong stratum soil below a weak layer.

• The Journal of Asian Finance, Economics and Business
• /
• 제8권5호
• /
• pp.851-861
• /
• 2021

This study aims to explore the specific risks in family small-medium enterprises (SMEs) and explain how they manage these risks to sustain and expand. In Indonesia, family business composes around 95 percent of all businesses and contributes about 80 percent to the country's economy. SMEs contribute approximately 57.8 percent to the nation's gross domestic product. Risk management poses challenges to the family business's survival, as family members do not take actions on risk. The assessment of risk is difficult and family businesses lack the ability to determine risk management priorities, including risk management review processes to evaluate risk, thus leading to family business failures. Applying the case study approach, in-depth semi-structured interviews were conducted in seven family SMEs comprising fifteen informants. Additionally, a focus group discussion consisting of three experts is conducted to reaffirm the findings from the interviews, observations, and field notes. The research identified the specific risks and how the family owners strategize to safeguard against these risks such as cash flow deficiency, operations dysfunction, cultural frailty, disharmony, transgenerational entrepreneurship failure, political uncertainty, and unprofessionalism. Comprehending these risks and their strategic decisions elucidated in this research could enable the family owners and key non-family professionals to work hand-in-hand to thrive over the family business risks together. Further avenues of research regarding family business risk management are also suggested in this study.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1999년도 하계종합학술대회 논문집
• /
• pp.25-28
• /
• 1999

Consider connection-oriented wireless cellular net-works. To establish a circuit or virtual circuit in such a network, a paging message is broadcast over a region at which the destined mobile station is presumed to reside, (identified as a paging area). For an effective paging mechanism, it is desirable to provide the location information of mobile stations to the network. In this paper, we consider a mobile controlled location update scheme under which each mobile station periodically reports its current location information to the network by using an inherent timer (without measuring the power of signals transmitted from base stations). Based on the latest information about a mobile station's location, a paging area is selected to page the mobile station. Note that under this scheme, a mobile station may not yet have reported its location change while sojourning out of the current paging area. In such situation, the mobile station can not receive a paging message destined to it. Frequent location updates can reduce the paging failure rate incurred by mobile stations'sojourning out of the paging area. However, larger bandwidth is needed for location update as the location update rate is increased. On the other hand, as the size of the paging area is increased, the paging failure rate is decreased, while larger bandwidth is required for paging. Thus, we first present a model for mobility, paging and location update processes, and secondly investigate the effect of network parameters on the paging failure rate and the amount of bandwidth used for paging and location update. Finally, we formulate problems to find proper values for the location update rate and paging area size under the constraints on the bandwidth usage levels for location update and paging.

• 한국건축시공학회지
• /
• 제22권1호
• /
• pp.115-123
• /
• 2022

최근 10년간 주거시설에서 발생한 화재 중 공동주택이 약 40%를 차지하고 있다. 공동주택에서 화재 확산 방지와 피난을 위해 방화문의 내화성능과 성능설계가 중요해지고 있다. 본 연구는 화재성능시험을 통과한 2016년부터 2020년까지 품질검사보고서 395건의 DB를 구축하고 방화문의 구조(12개 요소)를 분석을 통하여 방화문 성능영향인자를 도출하였다. 결과로서, 287건의 합격사례에서 내화충진재와 밀도, 접착제, 발포제의 영향을 확인하였다. 한편, 불합격 사례 108건에서 화염발생과 틈새발생이 방화문 내화시험에서 가장 큰 불합격 요소임을 확인하였다. 방화문은 내화성능 불합격을 방지하기 위하여 복합자재들로 구성이 되어 있으며, 구성 요소들의 위치 등 형태를 정형화하여 일률적인 품질관리가 필요하다. 본 연구의 DB 분석 결과를 바탕으로 공동주택의 대피공간문 및 공용부 방화문에 대하여도 추가적인 비교분석이 필요하다.