• Wind and Structures
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• v.23 no.2
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• pp.127-142
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• 2016

Aerodynamic effects, such as drag force and flow-induced vibration (FIV), on civil engineering structures can be minimized by optimally modifying the structure shape. This work investigates the turbulent wake of a square prism with its faces modified into a sinusoidal wave along the spanwise direction using three-dimensional large eddy simulation (LES) and particle image velocimetry (PIV) techniques at Reynolds number $Re_{Dm}$ = 16,500-22,000, based on the nominal width ($D_m$) of the prism and free-stream velocity ($U_{\infty}$). Two arrangements are considered: (i) the top and bottom faces of the prism are shaped into the sinusoidal waves (termed as WSP-A), and (ii) the front and rear faces are modified into the sinusoidal waves (WSP-B). The sinusoidal waves have a wavelength of $6D_m$ and an amplitude of $0.15D_m$. It has been found that the wavy faces lead to more three-dimensional free shear layers in the near wake than the flat faces (smooth square prism). As a result, the roll-up of shear layers is postponed. Furthermore, the near-wake vortical structures exhibit dominant periodic variations along the spanwise direction; the minimum (i.e., saddle) and maximum (i.e., node) cross-sections of the modified prisms have narrow and wide wakes, respectively. The wake recirculation bubble of the modified prism is wider and longer, compared with its smooth counterpart, thus resulting in a significant drag reduction and fluctuating lift suppression (up to 8.7% and 78.2%, respectively, for the case of WSP-A). Multiple dominant frequencies of vortex shedding, which are distinct from that of the smooth prism, are detected in the near wake of the wavy prisms. The present study may shed light on the understanding of the underlying physical mechanisms of FIV control, in terms of passive modification of the bluff-body shape.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.1
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• pp.15-20
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• 2008

Contaminated sediments are the actual cause for deterioration of coastal-ecosystem. So the developed countries have been in the process of making an effort to develop new techniques for monitoring and solving this problem since 1960. In this research, suction type pump dredging system of pilot size for collecting the filth from the seabed has been designed and manufactured that can prevent or minimize the secondary pollution by filth diffusion. For the practical use, the application possibility of the developed system has been checked through a system performance test. And, the evaluation of system performance according to the underwater body type has been carried out for system optimization by using CFD. The performance tests for checking the efficiency of sediment collecting system are done under two conditions i.e. when the system is non-operational and when the system is self-propelled. The results of this research showed the possibility of the development of dredging system to remove just the upper parts of filth from seabed.

• The Journal of Society for e-Business Studies
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• v.15 no.3
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• pp.85-98
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• 2010

The prevailing infrastructure of ubiquitous computing paradigm on the one hand making significant development for integrating technology in the daily life but on the other hand raising concerns for privacy and confidentiality. This research presents a new privacy-preserving spatio-temporal query processing technique, in which location based services (LBS) can be serviced without revealing specific locations of private users. Existing location cloaking techniques are based on a grid-based structures such as a Quad-tree and a multi-layered grid. Grid-based approaches can suffer a deterioration of the quality in query results since they are based on pre-defined size of grids which cannot be adapted for variations of data distributions. Instead of using a grid, we propose a location-cloaking algorithm which uses the R-tree, a widely adopted spatio-temporal index structure. The proposed algorithm uses the MBRs of leaf nodes as the cloaked locations of users, since each leaf node guarantees having not less than a certain number of objects. Experimental results show the superiority of the proposed method.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.4
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• pp.26-32
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• 2016

An autonomous car(driverless car, self-driving car, robotic car) is a vehicle that is capable of sensing its environment and navigating without human input. Autonomous cars can detect surroundings using a variety of techniques such as radar, lidar, GPS, odometry, and computer vision. Advanced control systems interpret sensory information to identify appropriate navigation paths, as well as obstacles and relevant signage. Autonomous cars have control systems that are capable of analyzing sensory data to distinguish between different cars on the road, which is very useful in planning a path to the desired destination. An issue tree, also called a logic tree, is a graphical breakdown of a question that dissects it into its different components vertically and that progresses into details as it reads to the right.Issue trees are useful in problem solving to identify the root causes of a problem as well as to identify its potential solutions. They also provide a reference point to see how each piece fits into the whole picture of a problem. Using Issue-Tree menthods, transportation safety policies were developed with autonompus vehicle in mind.

• Journal of the Korea Society of Computer and Information
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• v.19 no.12
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• pp.161-169
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• 2014

Digital forensics is the process of proving criminal charges by collecting and analyzing digital evidence which is related to the crime in question. Most digital forensic research is focused on digital forensic techniques themselves or cyber crime. In this paper, we designed a digital forensics-criminal investigation linked model in order to effectively apply digital forensics to various types of criminal investigations. Digital forensic ontology was developed based on this model. For more effective application of digital forensics to criminal investigation we derived specific application fields. The ontology has legality rules and adequacy rules, so it can support investigative decision-making. The ontology can be developed into an intelligent criminal investigation system.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.573-580
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• 2003

In Taiwan there are 21 Municipal Solid Waste Incinerators (MSWI) built to treat 80% of the MSW nationwide. Approximately 2,000 tons of incineration ashes of municipal waste contain reaction ash and fly ash (3:1 by weight)will be produced daily, and this may cause a serious waste problem. According to EPA regulations, reaction ash and fly ash produced after incineration should be properly treated. Landfill capacity barely meets the general demands. More efficient actions should be planned and taken. The study found 'reclamation' should be the optimal solution to this problem. Only limited research and previous successful experiences are available among other countries. An incinerator in Northern Taiwan is chosen for this study to make environmental bricks from the reaction ash and fly ash. From the previous tests, the results of strength test were measured. From the previous test results, the fly ash products have not reached the desired strength; hence, reaction ash is chosen for further pilot study. In the experiment, incineration ashes, cement and gravel are mixed in the ratio of 1:1:1(by weight), to ground concretization aggregate and pelletization aggregate, the concrete products made from the aggregates were of the strength of 108 $kgf/cm^2$ and 142 $kgf/cm^2$ individually. For the purpose of making nonstructural walls which met the State Building Standards. In the study, 50 tons of concrete products was yielded from aggregate and environmental bricks. Further observation and supervision are recommended to ascertain the resource recycling and reclamation. EPA has planned to build three 'Recycling Plants' in northern, middle and southern Taiwan to develop efficient techniques to produce concrete products, sub-base course, soundproofing wall, gravel, artificial fishing reefs, tiles, drainage, bricks and etc. This experiment of the demonstrative plant solves the problem of the incineration ashes and opens another opportunity to reclaim them.

• Journal of the Korea Society for Simulation
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• v.17 no.3
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• pp.9-18
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• 2008

Unlike conventional researches, we are able to i) compare the fuzzy logic based BBA with non-fuzzy BBA for verifying the effective performance of the proposed fuzzy logic application ii) dynamically respond to the intrusion using BBA whereas the previous IDS was responding statically and iii) expect that this would be a cornerstone for more practical application researches (analyzing vulnerability and examining countermeasures, etc.) of security simulation. Several simulation tests performed on the targer network will illustrate our techniques. And this paper applies fuzzy logic to reduce the false negative that is one of the main problems of IDS. Intrusion detection is complicated decision-making process, which generally involves enormous factors about the monitored system. Fuzzy evaluation component model, which is a decision agent in the distributed IDS, can consider various factors based on fuzzy logic when an intrusion behavior is detected. The performance obtained from the coordination of intrusion detection agent with fuzzy logic is compared against the corresponding non fuzzy type intrusion detection agent. The results of these comparisons allow us to evaluate a relevant improvement on the fuzzy logic based BBA.

• Journal of Internet Computing and Services
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• v.13 no.5
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• pp.21-31
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• 2012

Threat Evaluation(TE) which has air intelligence attained by identifying friend or foe evaluates the target's threat degree, so it provides information to Weapon Assignment(WA) step. Most of TE data are passed by sensor measured values, but existing techniques(fuzzy, bayesian network, and so on) have many weaknesses that erroneous linkages and missing data may fall into confusion in decision making. Therefore we need to efficient Threat Evaluation system that can refine various sensor data's linkages and calculate reliable threat values under unpredictable war situations. In this paper, we suggest new threat evaluation system based on information fusion JDL model, and it is principle that combine fuzzy which is favorable to refine ambiguous relationships with bayesian network useful to inference battled situation having insufficient evidence and to use learning algorithm. Finally, the system's performance by getting threat evaluation on an air defense scenario is presented.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.12 no.2
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• pp.106-113
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• 2009

In this study, stability of the new gabion system with vegetation base materials was analysed. New gabion system with vegetation base materials is a new approach which has been developed to achieve lope stabilization and revegetation of forest road cut-slope by making the best use of advantages of gabion systems with vegetation base materials. Results from stability analysis are as follows. For the soil density, the angle of internal friction and unit weight of the rock fill was assumed to be $1.90g/cm^3$, $30^{\circ}$ and $2.30t/m^3$, respectively, the slope stability analysis showed that the new gabion system couldn't require any poles to fix it up, and could keep stable during both rainy and dry seasons. As the results of checks against overturning and sliding, the retaining wall with. the new gabion system could produce suitable factors of safety for overturning and sliding. Vegetation established on the surface of the new gabion systems indirectly can help to increase slope stability by prevention of surface erosion. Consequently, the new gabion system with vegetation base materials could achieve the desired effect on slope stabilization as much as existing gab ion system could do, and could promote rapid establishment of vegetation on cut-slopes.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.65-65
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• 2010

In shipbuilding industry, welding position are usually flat and vertical position at the erection stage. Application of SAW and EGW for these positions makes it possible to achieve enhanced productivity and high quality. But owing to their large size and weight it is difficult to apply these techniques in short and narrow regions. To overcome this problem, our company developed light weight and compact size 4-axis welding carriage which perform 3D weaving. The purpose of this study is to explain the development and application of intelligent welding carriage using 3D weaving pattern that can fill a large amount of welds and thereby making it possible to achieve high quality of welding. This study shows 3D weaving pattern, development of weaving database, and skill of adaptive control response for the variable gap. Also, it shows the results of procedure qualification test for the AH-grade steel when applied to the intelligent welding carriage.