• Steel and Composite Structures
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• 제49권1호
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• pp.19-30
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• 2023

Steel-concrete composite slabs represent a very efficient floor solution combining the key performance of two different materials: the steel and the concrete. Composite slab response is governed by the degree of the interaction between these two materials, mainly depending by chemical and mechanical bond. The latter is characterized by a limited degree of confinement if compared with the one of the rebars in reinforced concrete members while the former is remarkably influenced by the type of concrete and the roughness of the profiled surface, frequently lubricated during the cold-forming manufacturing processes. Indeed, owing to the impossibility to guarantee a full interaction between the two materials, a key parameter governing slab design is represented by the horizontal shear-bond strength, which should be always experimentally estimated. According to EC4, the design of the slab bending resistance, is based on the simplified assumption that the decking sheet is totally yielded, i.e., always in plastic range, despite experimental and numerical researches demonstrate that a large part of the steel deck resists in elastic range when longitudinal shear collapse is achieved. In the paper, the limit strain for composite slab, which corresponds to the slip, i.e., the debonding between the two materials, has been appraised by means of a refined numerical method used for the simulation of experimental results obtained on 8 different composite slab types. In total, 71 specimens have been considered, differing for the properties of the materials, cross-section of the trapezoidal profiled metal sheets and specimen lengths.

• 한국컴퓨터정보학회논문지
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• 제22권2호
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• pp.45-50
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• 2017

This paper proposes a novel resource allocation scheme which allows to guarantee the user-perceived service quality for various high-quality mobile multimedia service such as interactive game, tactile internet service, remote emergency medical service or remote disaster handling robot control to a certain level in the mobile networks. In our proposed scheme, Mean Opinion Score(MOS), which represents the degree of user satisfaction for perceived quality, is determined based on the delay limit allowable to each service. Moreover resources are allocated in consideration of this MOS. Simulation results show that our proposed scheme can decrease the outage probability in comparison with existing schemes Moreover it can increase the total throughput as well.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.159-163
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• 2004

The KNR(Korean National Railroad) has a speed limit regulation(130km/h) for the train passing the turnout to guarantee a safety. Since that speed is set as below the maximum commercial speed(140km/h), it has been regarded as a major factor to obstacle the total efficiency. The crossing rail part of the turnout system is formed into a antisymmetric, furthermore, there are several discontinuous part. Thus, measuring the strain signals of this part is impossible actually and it must be in the most difficult work related the turnout research. In this research, the program that can anticipate the signals at the various conditions with considering its own shape was developed and the preciousness of its results had been examined by comparing analyzed and measured ones at the other parts. The simulation was performed with varying the factors such as train speed and contact depth. As a results, it was proved that the regulation was not useless and very important guide at least up to now.

• 한국물환경학회지
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• 제23권5호
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• pp.766-775
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• 2007

The use of toxic chemicals was extended as the industry in Korea has grown dramatically during the last three decades. However, list of toxic substances and limit concentrations in the water environment are not consistent within management of ambient water, drinking water and industrial effluent. This article suggests the systematic framework to classify toxic substances in the water environment and deriving their effluent limits. The most important factor for decision-making to classify toxic substances is whether their concentrations in the water environment are higher than the reference concentrations, estimated by considering human health risk and ecological risk. Using a risk-based reference concentration, the ambient water quality criterion, it is possible to derive the regulatory limit concentrations of toxic substances in drinking water and in industrial effluent. The goal concentrations in the effluent, which guarantee the human and ecological safety, should be determined with scientific investigation, balancing environmental benefit and economical effect, considering availability of treatment technology and identifying characteristics of wastewater from different industries.

• 한국경영과학회지
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• 제32권1호
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• pp.93-104
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• 2007

We consider a supply chain where products are shipped to warehouse from manufacturing system to customers. Products are supplied from either in-house regular manufacturing or the secondary source such as subcontractor. The inventory in warehouse is controlled by base-stock policy, that is, whenever a demand arrives from customer, an order is released to the manufacturing system. Unsatisfied demand is backlogged. The manufacturing system is modeled as M/M/s+1/c queueing system, and the orders exceeding the given limit care blocked and lost. The steady state distribution of the outstanding orders and the throughput of the manufacturing system are functions of the level of engagement In the secondary source. There is a profit obtained from throughput and cost not only due to the engagement of the secondary source in the manufacturing system but also inventory positions. We want to maximize the total production profit minus the total cost of the production system by simultaneously determining the optimal level of engagement of the secondary source and the optimal base-stock level of the inventory. We develop two algorithms : one without guarantee of the optimal solution but with the small number of computations, the other optimal but with more computations.

• Journal of Communications and Networks
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• 제18권1호
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• pp.84-94
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• 2016

Design of effective cooperative jamming (CJ) algorithm is studied in this paper to maximize the achievable secrecy rate when the total transmit power of the source and multiple trusted terminals is constrained. Recently, the same problem was studied in [1] and an optimal algorithm was proposed involving a one-dimensional exhaustive searching.However, the computational complexity of such exhaustive searching could be very high, which may limit the practical use of the optimal algorithm. We propose an asymptotically optimal algorithm, involving only a fast line searching, which can guarantee to achieve the global optimality when the total transmit power goes to infinity. Numerical results demonstrate that the proposed asymptotically optimal algorithm essentially gives the same performance as the algorithm in [1, (44)] but with much lower computational complexity.

• 한국안전학회지
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• 제11권4호
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• pp.135-142
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• 1996

Prolonged in-plant personnel exposure to high noise levels results in permant hearing damage. There are no way to correct this hearing damage by treatment or use of hearing aids. Therefore, every employer is responsible for providing a workplace free of such hazards as excessive noise. This study was carried out to evalute and predict a given noise environment based on specific limit as the noise guarantee for a newly-founded petrochemical plant. The maximum total sound level should not exceed 85dBA in the work area, except where the area is defined as a restricted area and 70dBA at the plant boundary. Prediction of the noise levels within the plant area for a newly-founded petrochemical plant was achieved by dividing all plant area into 20m$\times$20m regular grid spaces and noise level inside the area or unit that in-plant personel exposure to high noise levels was estimated computed into 5m$\times$5m regular grid spaces. The noise level at the grid point that was propagated from each of the noise sources(equipments) computed using the methematical formula was defined as follows : $SPL_2$=$SPL_1-20log{\frac{r_2}{r_1}}$(dB) where $SPL_1$ =sound pressure level at distance $r_1$ from the source $SPL_2$=sound pressure level at distance $r_2$ from the source As a result, the equipments exceeded noise limit or irritaring noise levels were identified on the specific grid coordinates. As for equipments in the area that show high noise levels, appropriate counter-measures for noise control (by barriers, enclosure, silencers, or the change of equipments, for example) should be reviewed. Methods for identifying sources of noise applied in this study should be the model for prediction of the noise levels for any newly-founded plant.

• 한국식품영양학회지
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• 제34권1호
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• pp.132-136
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• 2021

The purpose of this study is to measure the levels of eluted and dissolved CO2, and CO, volatile organic substances and radiation composition of Cheongsong mineral water which were collected from November 2019 to July 2020 during the autumn, spring, and summer seasons at collection points located in the upper, middle and lower spring waters. Data of the upper, middle and lower spring waters include the following: the amount of eluted water (average value±standard deviation, mL/min) was 30.07±0.52, 15.03±0.16, 23.73±0.42, and the amount of CO2 gas was 1,000 ppm or more. In addition, there was no detection of CO or total volatile organic substances (TVOC) and the radiation dose was 0.08 to 0.13. μSv/h. A blank test value of 0.08 to 0.10 μSv/h, when compared with the median value, showed a high value of 0.02 μSv/h, and the uranium test results provided by the Cheongsong-gun Office were 0.0118 mg/L (date 2019.06.18) and 0.0091 mg/L (date 2020.06.04.) respectively, which was less than the permission limit of 0.03 mg/L. However, it is believed that further research using more precise devices is needed in order to guarantee the safety and health of the water.

• Journal of Communications and Networks
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• 제11권1호
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• pp.26-35
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• 2009

In this paper, we investigate how to do resource allocation to guarantee a minimum user data rate at low signaling overhead in multi-cell orthogonal frequency division multiple access (OFDMA) wireless systems. We devise dynamic resource allocation (DRA) algorithms that can minimize the QoS violation ratio (i.e., the ratio of the number of users who fail to get the requested data rate to the total number of users in the overall network). We assume an OFDMA system that allows dynamic control of frequency reuse factor (FRF) of each sub-carrier. The proposed DRA algorithms determine the FRFs of the sub-carriers and allocate them to the users adaptively based on inter-cell interference and load distribution. In order to reduce the signaling overhead, we adopt a hierarchical resource allocation architecture which divides the resource allocation decision into the inter-cell coordinator (ICC) and the base station (BS) levels. We limit the information available at the ICC only to the load of each cell, that is, the total number of sub-carriers required for supporting the data rate requirement of all the users. We then present the DRA with limited coordination (DRA-LC) algorithm where the ICC performs load-adaptive inter-cell resource allocation with the limited information while the BS performs intra-cell resource allocation with full information about its own cell. For performance comparison, we design a centralized algorithm called DRA with full coordination (DRA-FC). Simulation results reveal that the DRA-LC algorithm can perform close to the DRA-FC algorithm at very low signaling overhead. In addition, it turns out to improve the QoS performance of the cell-boundary users, and achieve a better fairness among neighboring cells under non-uniform load distribution.

• 헤리티지:역사와 과학
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• 제55권1호
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• pp.111-132
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• 2022

2014년 불거진 숭례문 부실수리 논란에 대응하고자 문화재청은 2016년 문화재수리 종합심사낙찰제·종합평가낙찰제를 전격 도입하였다. 동 제도의 도입취지는 문화재수리업체에게 적정한 문화재수리비용을 제공하고 보다 나은 문화재수리 품질을 확보하고자 한 것이다. 이렇게 2016년부터 도입된 종합심사낙찰제·종합평가낙찰제는 운영된 지 벌써 5년이 넘어가고 있어 동 낙찰제도의 운영결과를 중간 점검하고 새로운 입찰제도의 도입취지인 수리이행능력이 높은 업체에게 적정한 대가를 보장한다는 목표가 현재 달성되고 있는지 확인할 필요가 있다. 이에 본 연구에서는 2016년부터 2020년까지 문화재수리 종합심사낙찰제·종합평가낙찰제로 입찰된 총 114개의 입찰사례를 위주로 통계적접근 등을 통해 분석하고자 하였다. 조사분석 기간 중 발주된 114건의 분석결과, 첫 번째로 수리이행능력이 높은 문화재수리업체 선정 여부에 대해서는 낙찰자의 과반수가 문화재수리능력평가액 순위 중 상위 20%에 위치해 있어 '수리이행능력이 좋은 문화재수리업체 선정'이라는 목표를 전반적으로 달성하였다고 판단된다. 두 번째로 적정한 대가가 보장되었는지에 대해 문화재수리 종합심사낙찰제·종합평가낙찰제의 도입취지와는 달리 2017년 86.847%에서 2020년 85.488%로 매년 낙찰률이 저하되고 있고, 문화재수리 종심제·종평제 대상의 94.7%가 속하는 50억원 미만의 문화재수리의 경우에는 예상되는 시설공사 적격심사 낙찰하한율 보다도 낙찰률이 낮아 이를 개선할 필요가 있을 것으로 판단된다. 세 번째로, 2019년 개정된 문화재수리 종합심사낙찰제·종합평가낙찰제 경제성평가 배점구조의 변화로 경제성 평가의 영향력 즉, 변별력이 더 강해졌음을 알 수 있다. 문화재수리 종합심사낙찰제·종합평가낙찰제 시행 이후 낙찰률 하락의 원인을 분석한 결과, 첫 번째로 투찰률이 매년 하락하는 추세인 '1등 초과 그룹'과 '1등 그룹'이 전체 투찰자 수의 과반 이상이기 때문이며, 둘째로 낙찰률을 상향시켜 주는 역할을 하는 '1등 초과 그룹' 내에서도 높은 투찰가격을 써낸 투찰자를 '1등 미만 그룹'의 균형가격 배제범위보다 상대적으로 많이 배제시키기 때문인 것으로 보인다 결론적으로 상위 투찰가격의 과도한 배제를 지양해야 하고, 시설공사 적격심사제도의 낙찰하한율과 같이 낙찰률 저하를 막아줄 장치가 필요하다.