• KIPS Transactions on Computer and Communication Systems
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• v.8 no.7
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• pp.167-176
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• 2019

Recently, as the types of services that can be enjoyed in mobile telecommunication networks such as social networks and video streaming are increasing, mobile users(MUs) can access mobile contents easily by consuming mobile data. However, under a mobile telecommunication environment, MUs have to pay a high data fee to a network service provider(SP) in order to enjoy contents. The 'data sponsor' technique, introduced as a way to solve this problem, has attracted attention as a breakthrough method for enhancing contents accessibility of MUs. In this paper, we propose an algorithm that determines the optimal discount rate through the Stackelberg game in the data sponsor environment. We also propose an algorithm to design edge caching, which caches highly popular content for MUs on edge server, through many-to-many matching game. Simulation results clearly indicate that the profit for CP's content consumption is improved by about 6~11%, and the profit of CP according to the ratio of edge caching is improved by about 12% than the other existing schemes under data sponsor environment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.1-8
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• 2019

Medical information is an important personal information for patients, and it must be protected. In particular, when medical personnel approach electronic medical records, authentication for enhanced security is essential. However, the existing public certificate-based certification model did not reflect the security characteristics of the electronic medical record(EMR) due to problems such as personal key management and authority delegation. In this study, we propose a fingerprint recognition-based authentication model with enhanced security to solve problems in the approach of the existing electronic medical record system. The proposed authentication model is an EMR system based on fingerprint recognition using PEMS (Private-key Escrow Management Server), which is applied with the private key commission protocol and the private key withdrawal protocol, enabling the problem of personal key management and authority delegation to be resolved at source. The performance experiment of the proposed certification model confirmed that the performance time was improved compared to the existing public certificate-based authentication, and the user's convenience was increased by recognizing fingerprints by replacing the electronic signature password.

• Geophysics and Geophysical Exploration
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• v.25 no.4
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• pp.252-265
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• 2022

Subsurface velocity is critical for the accurate resolution geological structures. The estimation of acoustic impedance is also critical, as it provides key information regarding the reservoir properties. Therefore, researchers have developed various inversion approaches for the estimation of reservoir properties. The Markov chain Monte Carlo method, which is a stochastic method, has advantages over the deterministic method, as the stochastic method enables us to attenuate the local minima problem and quantify the uncertainty of inversion results. Therefore, the Markov chain Monte Carlo inversion method has been applied to various kinds of geophysical inversion problems. However, studies on the Markov chain Monte Carlo inversion are still very few compared with deterministic approaches. In this study, we reviewed various types of reversible jump Markov chain Monte Carlo applications and explained the key concept of each application. Furthermore, we discussed future applications of the stochastic method.

• Journal of Korean Society of Steel Construction
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• v.27 no.4
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• pp.371-376
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• 2015

This study was conducted for the torsional behavior of catwalk system which is a temporary structure on a suspension bridge. The torsional deformation of the catwalk structure has a significant effect on the workability and safety of workers during main cable erection. For this reason, the torsional deformation of catwalk is controlled to be acceptable levels below by adjusting the cross bridge interval in design stage. This study analyzed the effect of separation between cross bridge associated with twist safety of catwalk system. For the analytical approach, a detailed analysis model was created including cross bridge. Both wind load within the wind velocity range that allows the construction and eccentric load of Prefabricated Parallel Wire Strand were analyzed by analysis model. Result of study shows that separation between cross bridges has a significant effect on the torsional behavior of the catwalk.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.6
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• pp.55-64
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• 2001

Industrial machines are sometimes exposed to the danger of earthquake. In the design of a mechanical system, this factor should be accounted for from the viewpoint of reliability to analyze a complex nonlinear structure system under random excitation is proposed. First, the actual random excitation, such as earthquake, is approximated to the corresponding Gaussian process for the statistical analysis. The modal equations of overall system are expanded sequentially. Then, the perturbed equations are synthesized into the overall system and solved in probabilistic way. Several statistical properties of a random process that are of interest in random vibration are evaluated in each substructure. Comparing with the results of the numerical simulation proved the efficiency of the proposed method.

• Journal of Korean Society of Transportation
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• v.34 no.3
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• pp.207-221
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• 2016

In Korea, older pedestrian accounted for 57% of all pedestrian deaths although a ratio of older pedestrian accidents to total pedestrian accidents was only 25.9%. Though ageing population problem becomes more challenging for road safety, little is know about the behaviour of older pedestrian's behaviour. This study aimed to identify road crossing behaviour of older pedestrian at three-lane unsignalized crosswalks using video image analysis and to compare the behaviour of older pedestrian to younger one by indicators including approaching speed, the number of walking steps and other factors. The results showed that there was a difference of approaching time at kerb, waiting time at kerb, the number of glances at kerb, and the number of glances at crossing between two groups under the situation of car approaching to crosswalks. It also showed that older pedestrian usually spent 1.16 times more than younger pedestrian to walk across the crosswalk with only 84.4% of walking speed of younger pedestrian. The number of steps of older pedestrian for road crossing was 1.12 times higher with 90% shorter steps than younger pedestrian. It was concluded that older pedestrian usually decided to walk across in case of 1.67 times longer headway than younger pedestrian's decision. These results could be applied in road and facility design for better safety of older pedestrians.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.2
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• pp.143-150
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• 1984

This paper is a study on effectiveness of weight in analytical positioning of oblique photography. Oblique photographies are more economical than normal photographies as it has a larger ground coverage and as it can be applied in situations where objects of interest are difficult to be approached. But the comparatively complex methods involved, present a problem in obtaining the desired results. In view of this fact, analytical rectification was applied in normalizing the oblique photographs. As oblique photographies are extensively used in slops and mountainous regions, a number of difficulties are encountered during the control surveying. The photocoordinates of the oblique photographs, taken at $30^{\circ}$, were weighted during rectification. They were weighted as inversely proportionate to the derived formular of ${\gamma}_y=f{\cdot}tan{\frac{\theta}{2}}+y_a$, the distance of each point from the isocenter along the Y axis. By applying the weights, coordinates errors conld be reduced and the error difference between oblique and normal photographs could be reduced upto 53.2%.

• Journal of the Korean Society of Radiology
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• v.9 no.7
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• pp.495-500
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• 2015

Health care privatization will have a very significant impact on the quality of medical service and income redistribution and risk diversification. This study was conducted to improve the situation without too much insistence that one did not understand the essence rife about the privatization of health care. In this study, grasp the implications of the current health care debate to be privatized, and dealing with the claims accordingly. Seeks to help establish an objective perspective, looking at the pros and cons at the same time claims for medical privatization policy. The Health and diversification through the capitalist market access as part of the transition process is being overlooked as a new growth engine industries. But health care is constrained to follow the growth of universal access and how to deal with life because it is practical conduct of the person. In addition to services that are not only for the benefit of the profit or government institutions.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.7-7
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• 2009

TIG 용접에서는 후판 용접의 경우 용입의 한계 때문에 깊고 넓은 그루브 가공을 하여 다층 용접을 한다. 이 때, 그루브를 채우는 용착금속에 의한 응고 수축과 과대한 입열로 인한 변형이 문제시 되고 있다. 변형을 줄이기 위해서는 용착금속의 양과 입열량을 줄여야 한다. 이러한 문제를 해결하기 위해 그루브의 루트패이스를 두껍게 하고 그루브각을 줄여서 용착량을 줄인다. 이때, 좁은 그루브에서 두꺼운 루트패이스를 완전 용입할 수 있는 용접 프로세스가 필요하다. 비드가 좁고 깊은 용입 특성을 가지는 Plasma welding(PAW) 경우에는 좁은 그루브 속에 토치가 접근하기 어려워 적용하기 어렵다. 따라서 접근성이 용이한 TIG 용접에서 높은 용입형상비를 가지는 용접공정 개발이 필요하다. 선행연구로 높은 용입 형상비를 가지는 Active flux Tungsten Inert Gas(ATIG) 용접이 연구되었다. ATIG의 용입 증가 메커니즘으로는 Marangoni effect, 음이온들로 인한 아크 수축 효과, 절연 플럭스에 의한 아크 수축효과 등으로 알려져 있다. 또한 선행연구에서 ATIG에서 Ar가스에 He 또는 $H_2$ 가스를 첨가하면 용입이 더욱 증가하는 것을 확인하였다. 본 연구에서는 A-TIG에 He 가스를 적용하고 아크길이 0.5mm, 1.0mm, 2.0mm와 전극 선단각 30도, 60도, 90도에 따른 용입 형상비와 변형량을 검토하기 위해 실험을 하였다. 실험 결과는 아크길이가 감소할수록 전극 선단각이 증가할수록 용입 형상비는 증가하였고, 변형량은 감소하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.455-461
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• 2008

Enhanced Distributed Channel Access (EDCA) is a channel access scheme adopted by the IEEE 802.11e draft standard for QoS-enabled wireless local area networks. It classifies traffic into separate Access Categories (ACs) and achieves service differentiation by allowing each AC to have its own values of channel access parameters. This paper proposes a scheme to dynamically adapt the EDCA parameters to traffic environment so that they both maximize the throughput of non real-time traffics and meet the delay and throughput constraints of real-time traffics. For this purpose, we develop a design algorithm for efficient exploration of the EDCA parameter space. Using the algorithm, we derive a Pareto curve fur delay-throughput trade-off in each anticipated traffic environment. The Pareto database can then be used to optimally adjust the parameter according to the traffic environment and administrative policies. Simulation results show that compared with the default parameter configuration, the proposed scheme is better for delay, throughput guarantee and can improve the throughput of non real-time traffics by 12% on average.