• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.2
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• pp.138-144
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• 2013

Large and small marine accidents which are related to vessel's navigation are happening continuously and these maritime accidents have caused loss of lives and properties, and serious maritime environmental pollution damage. It is also true that maritime pollution damage is increasing due to these accidents, probability of growth of seaborne volume and complicated maritime traffic environment. Korea, recently, is developing an evaluation index which can assess sea risk through the evaluation of maritime traffic environment and provide danger and general information with relation to maritime traffic environment on target sea area to evaluate maritime traffic safety. In this paper, we intend to confirm the validity of maritime traffic safety on the basis of vessel navigator's risk consciousness and various sailing conditions by using the ship handling simulator. To confirm the validity of sailing vessel's maritime traffic safety, we use analysis of variance. By using analysis of variance, we analyze vessel navigator's characteristics, distance, speed and encounter type between vessels. Through multiple comparison of each factor's risk difference, we can confirm the change of numerical value of risk difference in statistical aspect.

• Journal of Internet Computing and Services
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• v.13 no.2
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• pp.41-49
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• 2012

Wireless network support and extended mobile network environment with exponential growth of smart phone users allow us to utilize the network anytime or anywhere. Malicious attacks such as distributed DOS, internet worm, e-mail virus and so on through high-speed networks increase and the number of patterns is dramatically increasing accordingly by increasing network traffic due to this internet technology development. To detect the patterns in intrusion detection systems, an existing research proposed an efficient algorithm called the jumping window algorithm and analyzed approximately 2,000 patterns in Snort 2.1.0, the most famous intrusion detection system. using the algorithm. However, it is inappropriate from the number of TCAM lookups and TCAM memory efficiency to use the result proposed in the research in current environment (Snort 2.9.0) that has longer patterns and a lot of patterns because the jumping window algorithm is affected by the number of patterns and pattern length. In this paper, we simulate the number of TCAM lookups and the required TCAM size in the jumping window with approximately 8,100 patterns from Snort-2.9.0 rules, and then analyse the simulation result. While Snort 2.1.0 requires 16-byte window and 9Mb TCAM size to show the most effective performance as proposed in the previous research, in this paper we suggest 16-byte window and 4 18Mb-TCAMs which are cascaded in Snort 2.9.0 environment.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.251-258
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• 2012

Recently, NAND Flash memory structure is evolving from SDR (Single Data Rate) to high speed DDR(Double Data Rate) to fulfill the high performance requirement of SSD and SSS. Accordingly, the proper ways of transferring data that latches valid data stably and minimizing data skew between pins by using PHY(Physical layer) circuit techniques have became new issues. Also, rapid growth of speed in NAND flash increases the operating frequency and power consumption of NAND flash controller. Internal voltage variation margin of NAND flash controller will be narrowed through the smaller geometry and lower internal operating voltage below 1.5V. Therefore, the increase of power budge deviation limits the normal operation range of internal circuit. Affection of OCV(On Chip Variation) deteriorates the voltage variation problem and thus causes internal logic errors. In this case, it is too hard to debug, because it is not functional faults. In this paper, we propose new architecture that maintains the valid timing window in cost effective way under sudden power fluctuation cases. Simulation results show that the proposed technique minimizes the data skew by 379% with reduced area by 20% compared to using PHY circuits.

• Structural Engineering and Mechanics
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• v.63 no.3
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• pp.361-370
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• 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 Forest Science
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• v.81 no.4
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• pp.383-392
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• 1992

The objective of this study is to evaluate the impacts on the domestic timber supply potential of forest resources management policies such as the extention of forest management infrastruture and setting aside more forest lands for the provision of environmental goods. To this end, the domestic timber supply functions were estimated using time series data for the period 1970-1990 and were used to predict the future trends in timber production in the Republic of Korea. For this purpose, a set of scenarios based on the forest road density and forest inventory growth were designed for the next 40 years. The timber supply behavior in Korea was found to be different by species group : domestic supply of softwood roundwood is inelastic with respect to its ovum price while that of hardwood elastic. The effect of forest road construction on the domestic timber production seems to be insignificant yet. The model simulation aided by policy scenarios revealed that the future timber supply potential will be largely restricted if the policy option with emphasis on the provision of environmental goods from the forest resources were adopted.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.1
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• pp.127-140
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• 1988

The management of sewage and rainfall runoff becomes an emerging problem with the growth of urban communities. From the uncontrollable excess intensity or amount of rainfall, the conditions of sewer surcharge or manhole overflow could be generated in the combined sewer network where municipal or industrial wastewaters and rainfall runoff flow. The predictive model far the prevention of property and human life losses from this inundation was studied in this research. In the development of a mathematical flow model for the combined sewer surcharge and overflow, the Preissmann Slot concept and the four-point implicit method of finite difference were utilized. For the usage in personal computer, the overlapping segment method that required less memory storage was adopted. Through the simulation of hypothetical sewer network, the conservation of discharge volume was checked, and the usefulness of the Preissmann Slot was assured from the temporal distribution of discharge and depth along the sewer network. Also the possible field application for the correction of sewer diameters and slopes in the design of sewer network which has no surcharge/overflow condition was suggested.

• Archives of design research
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• v.13 no.4
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• pp.11-21
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• 2000

Due to the explosive growth of the internet, terminology like "information society" and "virtual space" is frequently used, but often in a confusing manner. Some Social theorists and many people are fascinated by "information" and "media" as key characteristics of the contemporary world and rely on the unproven opinion that "Knowledge is a source of value and information moves the world". In this regard, Boudllian defines contemporary culture as a culture of signs and insists that we are surrounded by signs and forms of meaning. There isn't anything behind the signs but signs only exsist, so we cannot escaped from its inauthenticity and consider it improper to insist on it. If people can understand that signs are just simulation of reality, that would be alright. But in fact anything cannot be alright.In this matter Boudllian's conclusion is that we produce images in bulk which are not worthy seeing. Today we reach the conclusion that most images are the letter(character) image itself which shows nothing special.Consequently, this kind of world is a postmodern-world that seems meaningless but has signs to experience and enjoy, many examples of which are shown in the media, such as the internet. We can get to the conclusion that the audience neither sees nor hears anything, but they just can experience many interesting things which characterize the present age. The purpose of this research is to help you to understand current design philosophy and the direction of media while considering both a positive social phenomenon about the new design paradigm of information and media, as well as critical thinking about it.

• Fire Science and Engineering
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• v.32 no.2
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• pp.7-16
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• 2018

In this study, the previous design fire curve for fire simulation was modified and re-suggested. Numerical simulations with the FDS and CFAST were performed for the n-heptane and n-octane pool fires in the ISO 9705 compartment to evaluate the prediction performances of the previous 1-stage and modified 2-stage design fire curves. The numerical results were compared with the experimental temperature and concentrations of $O_2$ and $CO_2$. The FDS and CFAST simulations with the 2-stage design fire curve showed better prediction performance for the variation of temperature and major species concentration than the simulations with 1-stage design fire curve. Especially, the simulations with the 2-stage design fire curve agreed with the experimental temperature more reasonably than the results with the 1-stage design fire curve. The FDS and CFAST simulations showed good prediction performance for the temperature in the upper layer of compartment and the results with the FDS and CFAST were similar to each other. However, the FDS and CFAST showed poor and different prediction performance for the temperature in the lower layer of compartment.

• Journal of KIISE:Information Networking
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• v.31 no.6
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• pp.673-684
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• 2004

As the wireless mobile communication is being widespread, mobile technologies will have important roles in the communication with the explosive growth of demanding for wireless portable devices. Among the mobile technologies, a great deal of interest has been taken in mobile ad hoc network (MANET), which is a collection of wireless mobile nodes forming a temporary network without the aid of stationary infrastructure in recent. Furthermore, considering characteristic of ad hoc networks, the design of efficient routing protocols is an important issue. In recent years, on-demand protocols among routing protocols have noticed because of the low routing overhead. However, on-demand protocols suffer from production of the enormous query Packets by broadcasting in order to setup routes, that is, a flooding scheme. The flooding scheme is very costly and results in serious problem, which we refer as the broadcast storm problem. In this paper, we propose a Dynamic Adaptation Query flooding Using Neighbor Topology (NT-DAQ) scheme, in order to resolve the broadcast storm Problem. When a route discovery is in progress, each mobile node decides on the basis of neighbor topology information whether discovery process participates or not. Therefore, our proposed scheme enables to improve network performance in which minimize the number of query rackets. We evaluate the efficiency of our proposed scheme through simulation.

• Journal of Korean Society of Transportation
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• v.22 no.2 s.73
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• pp.145-154
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• 2004

The growing demand for customer-responsive, made-to-order manufacturing is stimulating the need for improved dynamic decision-making processes in commercial fleet operations. Moreover, the rapid growth of electronic commerce through the internet is also requiring advanced and precise real-time operation of vehicle fleets. Accompanying these demand side developments/pressures, the growing availability of technologies such as AVL(Automatic Vehicle Location) systems and continuous two-way communication devices is driving developments on the supply side. These technologies enable the dispatcher to identify the current location of trucks and to communicate with drivers in real time affording the carrier fleet dispatcher the opportunity to dynamically respond to changes in demand, driver and vehicle availability, as well as traffic network conditions. This research investigates key aspects of real time dynamic routing and scheduling problems in fleet operation particularly in a truckload pickup-and-delivery problem under various settings, in which information of stochastic demands is revealed on a continuous basis, i.e., as the scheduled routes are executed. The most promising solution strategies for dealing with this real-time problem are analyzed and integrated. Furthermore, this research develops. analyzes, and implements hybrid algorithms for solving them, which combine fast local heuristic approach with an optimization-based approach. In addition, various partitioning algorithms being able to deal with large fleet of vehicles are developed based on 'divided & conquer' technique. Simulation experiments are developed and conducted to evaluate the performance of these algorithms.