• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.47 no.8
• /
• pp.99-107
• /
• 2010

In a single frequency network (SFN) for Advanced Television Systems Committee (ATSC) terrestrial digital television (DTV) system, the interferences induced by the multiple transmitters and/or repeaters using the same frequency are inevitable. Since the presence of interferences results in performance degradation of the SFN, it is crucial to manipulate the interferences by adjusting the transmit power and timing of each transmitter and repeater. In the ATSC terrestrial DTV system, in order to facilitate the interference manipulation process, a transmitter identification (TxID) signal which is uniquely embedded in the signal to be transmitted from each transmitter and repeater is recommended. Even though the injection level of the TxID signal is much lower than the DTV signal, the TxID signal injection infects the DTV signal. Hence, the effect of the TxID signal on the DTV signal must be investigated before deployment. In this paper, the effect of the TxID signal on the performance of legacy DTV receivers under additive white Gaussian noise and multipath channel environments is investigated not only with computer simulation but also with laboratory and field tests. The test results show that the average threshold of visibility degradation of the legacy DTV receivers due to the TxID signal injection is less than 0.2 dB at the TxID injection level of -30 dB.

• Structural Engineering and Mechanics
• /
• v.63 no.3
• /
• pp.361-370
• /
• 2017

Through the use of finite element analysis and acoustic emission techniques we have evaluated the interfacial failure of a carbon fiber reinforced polymer (CFRP) repair patch on a notched aluminum substrate. The repair of cracks is a very common and widely used practice in the aeronautics field to extend the life of cracked sheet metal panels. The process consists of adhesively bonding a patch that encompasses the notched site to provide additional strength, thereby increasing life and avoiding costly replacements. The mechanical strength of the bonded joint relies mainly on the bonding of the adhesive to the plate and patch stiffness. Stress concentrations at crack tips promote disbonding of the composite patch from the substrate, consequently reducing the bonded area, which makes this a critical aspect of repair effectiveness. In this paper we examine patch disbonding by calculating the influence of notch tip stress on disbond area and verify computational results with acoustic emission (AE) measurements obtained from specimens subjected to uniaxial tension. The FE results showed that disbonding first occurs between the patch and the substrate close to free edge of the patch followed by failure around the tip of the notch, both highest stress regions. Experimental results revealed that cement adhesion at the aluminum interface was the limiting factor in patch performance. The patch did not appear to strengthen the aluminum substrate when measured by stress-strain due to early stage disbonding. Analysis of the AE signals provided insight to the disbond locations and progression at the metal-adhesive interface. Crack growth from the notch in the aluminum was not observed until the stress reached a critical level, an instant before final fracture, which was unaffected by the patch due to early stage disbonding. The FE model was further utilized to study the effects of patch fiber orientation and increased adhesive strength. The model revealed that the effectiveness of patch repairs is strongly dependent upon the combined interactions of adhesive bond strength and fiber orientation.

• Journal of Korean Society of Transportation
• /
• v.22 no.5
• /
• pp.123-137
• /
• 2004

The study on traffic assignment is actively being performed which reflect networks status using time. Its background is increasing social needs to use traffic assignment models in not only hardware area of road network plan but also software area of traffic management or control. In addition, multi-class traffic assignment model is receiving study in order to fill a gap between theory and practice of traffic assignment model. This model is made up of two, one of which is multi-driver class and the other multi-vehicle class. The latter is the more realistic because it can be combined with dynamic model. On this background, this study is to build multidynamic model combining the above-mentioned two areas. This has been a theoretic pillar of ITS in which dynamic user equilibrium assignment model is now made an issue, therefore more realistic dynamic model is expected to be built by combining it with multi-class model. In case of multi-vehicle, FIFO would be violated which is necessary to build the dynamic assignment model. This means that it is impossible to build multi-vehicle dynamic model with the existing dynamic assignment modelling method built under the conditions of FIFO. This study builds dynamic network model which could relieve the FIFO conditions. At the same time, simulation method, one of the existing network loading method, is modified to be applied to this study. Also, as a solution(algorithm) area, time dependent shortest path algorithm which has been modified from existing shortest path algorithm and the existing MSA modified algorithm are built. The convergence of the algorithm is examined which is built by calculating dynamic user equilibrium solution adopting the model and algorithm and grid network.

• Journal of Preventive Medicine and Public Health
• /
• v.21 no.1 s.23
• /
• pp.195-206
• /
• 1988

Two major issues of the blood bank management are quality assurance and inventory control. Recently, in Korea blood donation has gained popularity increasingly to allow considerable improvement of the quality assurance with respect to blood collection, transportation, storage, component preparation skills and hematological tests. Nevertheless the inventory control, the other issue of blood bank management, has been neglected so far. For the supply of blood by donation barely meets the demand, the blood bank policy on the inventory control has been 'the more the better.' The shortage itself by no means unnecessitate inventory control. In fact, in spite of shortage, no small amount of blood is outdated. The efficient blood inventory control makes it possible to economize the blood usage in the practice of state-of-the-art medical care. For the efficient blood inventory control in Korean hospitals, this tudy is to develop formulae forecasting the standard blood inventory level and suggest a set of policies improving the blood inventory control. For this study informations of $A^+$ whole bloods and packed cells inventory control were collected from a University Hospital and the Central Blood Bank of the Korean Red Cross. Using this informations, 1,461 daily blood inventory records were formulated.48 varieties of blood inventory control environment were identified on the basis of selected combinations of 4 inventory control variables-crossmatch, transfusion, inhospital donation and age of bloods from external supply. In order to decide the optimal blood inventory level for each environment, simulation models were designed to calculate the measures of performance of each environment. After the decision of 48 optimal blood inventory levels, stepwise multiple regression analysis was started where the independent variables were 4 inventory control variables and the dependent variable was optimal inventory level of each environment. Finally the standard blood inventory level decision rule was developed using the backward elimination procedure to select the best regression equation. And the effective alternatives of the issuing policy and crossmatch release period were suggested according to the measures of performance under the condition of the standard blood inventory level. The results of this study' were as follows ; 1. The formulae to calculate the standard blood inventory level($S^*$)was $S^*=2.8617X(d)^{0.9342}$ where d is the mean daily crossmatch(demand) for a blood type. 2. The measures of performace - outdate rate, average period of storage, mean age of transfused bloods, and mean daily available inventory level - were improved after maintenance of the standard inventory level in comparison with the present system. 3. Issuing policy of First In-First Out(FIFO) decreased the outdate rate, while Last In-First Out(LIFO) decreased the mean age of transfused bloods. The decrease of the crossmatch release period reduced the outdate rate and the mean age of transfused bloods.

• Korean Security Journal
• /
• no.47
• /
• pp.85-117
• /
• 2016

These days, ISIS terrorists have been expanding not only to european countries, but also to asian countries so South Korea is no longer safe from terrorists' attacks. Especially, 'soft target terrorism' makes many people maximizing fear of terrorism because it is caused by small groups - those who are armed with small arms and light weapons - and they are able to carry out hit and run attacks on civilian targets. It poses even more dangerous to kill massively. That is why November 2015 Paris attacks and January 2016 Jakarta attacks killed and injured many people because of 'soft target terrorism.' Therefore, the South Korea has also recognized the seriousness of terrorism by ISIS. The study has shown the precautionary measures about 'soft target terrorism' and how to defend against 'soft target terrorism' by looking through overseas examples. It is for the possibilities of 'soft terrorism' in South Korea because of the expansion of ISIS. As a result, 'soft target terrorism', caused by ISIS, could happen in South Korea. The counterplan is as in the following. First of all, 'soft target terrorism', which is collaborated with ISIS and domestic terrorists, could be caused by negative awareness of foreign residents and xenophobia so the public should change stereotypes about the foreign residents and there should be legislation about racial discrimination enacted by parliament and the government must practice the law. Second, the Korean anti-terrorism laws should be modified to minimize violations of human rights, related to the Korean citizens' personal information, and to stop the concentration of power into the hands of one law enforcement. Third, the government has to develop and to initiate the refuge&evacuation simulation, which prepares for 'soft target terrorism' and minimizes the damages if terrorists attack hot spots like central commercial areas or event halls.

• Journal of Korean Society of Transportation
• /
• v.22 no.2 s.73
• /
• pp.121-130
• /
• 2004

In these days, multiple-path generation method is highly demanded in practice and research areas, which can represents realistically travelers behavior in choosing possible alternative paths. The multiple-path generation algorithm is one of the key components for policy analysis related to ATIS, DRGS and ATMS in ITS. This study suggested a method to generate multiple Possible paths from an origin to a destination. The approach of the suggested method is different from an other existing methods(K-shortest path algorithm) such as link elimination approach, link penalty approach and simulation approach. The result of the multi-label vine-building shortest path algorithm(MVA) by Kim (1998) and Kim(2001) was used to generate multiple reasonable possible paths with the concept of the rational upper boundary. Because the MVA algorithm records the cost, back-node and back-back node of the minimum path from the origin to the concerned node(intersection) for each direction to the node, many potential possible paths can be generated by tracing back. Among such large number of the potential possible paths, the algorithm distinguishes reasonable alternative paths from the unrealistic potential possible paths by using the concept of the rational upper boundary. The study also shows the very simple network examples to help the concept of the suggested path generation algorithm.

• The Journal of the Korea Contents Association
• /
• v.14 no.6
• /
• pp.247-254
• /
• 2014

For the purpose of early diagnosis of the breast cancer, the attention on the screening mammography has been increasing-with supply of digital mammography day by day. Image quality is decided by target materials and filter combinations. Optimized selection by a glandular density and a thickness is needed, because these combinations change x-ray spectrum and effect to image quality. The purpose of this study is to find out optimized target and filter combinations through the evaluation of quantitative image quality and to suggest means which minimize patient dose through MCNPX. In results, spatial frequency resolution evaluation which is quantitative image quality evaluation method, MTF, NPS, DQE shows that we have to select Mo/Mo combinations or Mo/Rh combinations when compressed breast is thin. but in case of that when compressed breast is thick, we have to select Rh/Rh combinations or W /Rh combinations. In a comprehensive evaluation, W!Rh combinations which are not used in thin breasts in practice was superior to all image quality evaluation. This result is somewhat different-with clinical examination results. Secondary end point was organ dose evaluation, radiation dose of opposite breast was approximately 47 ~73% effectiveness when selecting standard breast. In conculsion, the most important point is that we have to select the optimal combinations-with considering dose evaluation and various thickness.

• Journal of Wetlands Research
• /
• v.19 no.4
• /
• pp.375-382
• /
• 2017

In this study, general characteristics of dynamic behavior of stormwater runoff from a small impervious catchment was investigated from a series of simulations for a radial type surface runoff. Based on the simulation results, a better placement strategy for stormwater inlets to improve performance of a structural best management practice (BMP) was suggested. The degree of pollutant first flush from an ideal radial type impervious catchment was simulated using a 1-D diffusion wave equation coupled with a pollutant transport equation. The results showed that the first flush of the chemical oxygen demand was the strongest when the catchment length ranged 30-50m at a bed slope of 0.02. This result suggested that a required degree of the first flush can be intentionally obtained by just changing the locations and numbers of stormwater inlets, and thereby adjusting the catchment length. Particularly, the overall performance of a structural BMP in reducing pollutant load can be improved by placing the stormwater inlets at locations for obtaining a required first flush strength.

• Korean Journal of Construction Engineering and Management
• /
• v.19 no.2
• /
• pp.38-49
• /
• 2018

Since the ratification of the Paris Agreement (COP21), the government is continuously strengthening policies for the reduction of greenhouse gas of the construction industry in accordance with the growing importance of reducing greenhouse gas and obligation of the government. Especially, the government emphasizes the need to improve the energy performance of old public buildings. Since 2014, the government is running a pilot project in which the government supports the construction cost of the green remodeling project of old public buildings and it is intended to develop the best practice of green remodeling and activate the green remodeling in the private sector. In this study, we analyzed the economical efficiency of the old public buildings by each level through green remodeling and conducted building related investigation and equipment measurement to plan the alternatives of the corresponding buildings. The improvement plan is a green remodeling plan that integrates alternatives. Five improvement plans were developed for each level to analyze the economic feasibility of each plan. As for the analysis method, the first energy demand amount calculation and the LCC analysis were performed through ECO2. In the LCC aspect, the improved 3/4 plan (middle level plan) was the most excellent and results were obtained in the order of the highest cost plan followed by the lowest cost plan. As a result, it is expected that it can be utilized as a basic data for future green remodeling performance plan and economic feasibility analysis in the future.

• Information Systems Review
• /
• v.9 no.3
• /
• pp.99-132
• /
• 2007

As customer management rises by important issue in electronic commerce, virtue study about CRM have proceeded much. However, because existent researches were positive researches of most statistical base, There are some limitation that does not show dynamic change with CRM flow by flowing of time, and can not forecast propriety and future result about CRM strategy. Therefore, in order to overcome existent limitation on these CRM study, this study designed dynamic model which draws factors that compose CRM strategy of on-line shopping mall, and do based on technique in system dynamics so that can analyze dynamic change between these factors. Concretely, atomized customer focuses in the on-line shopping mall and does based on Permission marketing theory, and applied CRM of different level to atomized customers and know change of customer satisfaction measurement and discomfort degree accordingly. According to the result of Simulation practice, situation that achieve CRM strategy of different level by atomize customer more increase the customer satisfaction than situation that is not so. Dynamic pattern that presented in this study is expected that can verify validity about CRM achievement strategy of different level at each CRM point of contact & how Internet enterprise including on-line shopping mall is establishing CRM strategy reasonably.