• Journal of the Korean Society for Marine Environment & Energy
• /
• v.5 no.1
• /
• pp.3-10
• /
• 2002

Quantifying the settling velocities of fine-cohesive sediments is very essential in the study of ocean pollutions as well as sedimentations. Settling properties of fine-cohesive sediments are influenced largely by aggregation which occurs as a consequence of interparticle collision and cohesion of particles. Since the degree of cohesion of fine-cohesive sediments depends on physico-chemical properties such as grain size distribution, percentage of organic materials, and mineralogical compositions, and these physico-chemical properties varies regionally, the settling velocities of fine-cohesive sediments for a specific site should be determined through field or laboratory experiment. Recently, settling velocities of fine-cohesive sediments in Saemankeum coasts and Kunsan Estuary have been measured through laboratory experiments. Using these data, the previously proposed well-known settling velocity equations for fine-cohesive sediments are examined and a new equation is developed for better representation of the measured data in this study. The newly developed settling velocity equation is simpler in the form and easier in determining the related coefficients than the previous well-known equations.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.10
• /
• pp.2088-2096
• /
• 2009

This paper deals with hybrid MAC protocol design for underwater acoustic networks. The proposed MAC protocol has the cluster structure with a master node and slave nodes, and the hybrid network structure that combines a contention free period based on TDMA(Time Division Multiple Access) with a contention period. The suggested MAC protocol has a beacon packet for supervising network, a guard period between time slots for packet collision, time tag for estimation of propagation delay with a master node, the time synchronization of nodes, entering and leaving of network, and the communication method among nodes. In this paper, we adapt the proposed hybrid MAC protocol to AUV network, that is the representative mobile device of underwater acoustic network, and verify this protocol is applicable in real underwater acoustic network environment.

• Journal of the Korean institute of surface engineering
• /
• v.54 no.1
• /
• pp.25-29
• /
• 2021

The fabrication of nanopore membrane by deposition of Al2O3 film using electron-beam evaporation, which is fast, cost-effective, and negligible dependency on substance material, is investigated for potential applications in water purification and sensors. The decreased nanopore diameter owing to increased wall thickness is observed when Al2O3 film is deposited on anodic aluminum oxide membrane at higher deposition rate, although the evaporation process is generally known to induce a directional film deposition leading to the negligible change of pore diameter and wall thickness. This behavior can be attributed to the collision of evaporated Al2O3 particles by the decreased mean free path at higher deposition rate condition, resulting in the accumulation of Al2O3 materials on both the surface and the edge of the wall. The reduction of nanopore diameter by Al2O3 film deposition can be applied to the nanopore membrane fabrication with sub-100 nm pore diameter.

• The Journal of Korea Robotics Society
• /
• v.16 no.3
• /
• pp.250-259
• /
• 2021

Path planning is one of the important technologies for automated parking. It requires to plan a collision-free path considering the vehicle's kinematic constraints such as minimum turning radius or steering velocity. In a complex parking lot, Rapidly-exploring Random Tree^* (RRT^*) can be used for planning a parking path, and Reeds-Shepp or Hybrid Curvature can be applied as a tree-extension method to consider the vehicle's constraints. In this case, each of these methods may affect the computation time of planning the parking path, path-tracking error, and parking success rate. Therefore, in this study, we conduct comparative analysis of two tree-extension functions: Reeds-Shepp (RS) and Hybrid Curvature (HC), and show that HC is a more appropriate tree-extension function for parking path planning. The differences between the two functions are introduced, and their performances are compared by applying them with RRT^*. They are tested at various parking scenarios in simulation, and their advantages and disadvantages are discussed by computation time, cross-track error while tracking the path, parking success rate, and alignment error at the target parking spot. These results show that HC generates the parking path that an autonomous vehicle can track without collisions and HC allows the vehicle to park with lower alignment error than those of RS.

• Structural Engineering and Mechanics
• /
• v.84 no.5
• /
• pp.619-632
• /
• 2022

Reinforced concrete (RC) structures may be subjected to sudden dynamic impact loads such as explosions occurring for different reasons, the collision of masses driven by rockfall, flood, landslide, and avalanche effect structural members, the crash of vehicles to the highway and seaway structures. Many analytical, numerical, and experimental studies focused on the behavior of RC structural elements such as columns, beams, and slabs under sudden dynamic impact loads. However, there is no comprehensive study on the behavior of the RC column-beam connections under the effect of sudden dynamic impact loads. For this purpose, an experimental study was performed to investigate the behavior of RC column-beam connections under the effect of low-velocity impact loads. Sixteen RC beam-column connections with a scale of 1/3 were manufactured and tested under impact load using the drop-weight test setup. The concrete compressive strength, shear reinforcement spacing in the beam, and input impact energy applied to test specimens were taken as experimental variables. The time histories of impact load acting on test specimens, accelerations, and displacements measured from the test specimens were recorded in experiments. Besides, shear and bending crack widths were measured. The effect of experimental variables on the impact behavior of RC beam-column connections has been determined and interpreted in detail. Besides, a finite element model has been established for verification and comparison of the experimental results by using ABAQUS software. It has been demonstrated that concrete strength, shear reinforcement ratio, and impact energy significantly affect the impact behavior of RC column-beam connections.

• Journal of the Korea Society for Simulation
• /
• v.19 no.2
• /
• pp.91-98
• /
• 2010

Conventional path-finding has focused on finding short collision-free paths. However, as computer games become more sophisticated, it is required to take tactical information like ambush points or lines of enemy sight into account. One way to make this information have an effect on path-finding is to represent a heuristic function of a search algorithm as a weighted sum of tactics. In this paper we consider the problem of learning heuristic to optimize path-finding based on given tactical information. What is meant by learning is to produce a good weight vector for a heuristic function. Training examples for learning are given by a game level-designer and will be compared with search results in every search level to update weights. This paper proposes a learning algorithm integrated with search for tactical path-finding. The perceptron-like method for updating weights is described and a simulation tool for implementing these is presented. A level-designer can mark desired paths according to characters' properties in the heuristic learning tool and then it uses them as training examples to learn weights and shows traces of paths changing along with weight learning.

• Journal of Internet Computing and Services
• /
• v.15 no.3
• /
• pp.63-69
• /
• 2014

For the safety messages in IEEE 802.11p vehicles network environment(WAVE), strict periodic beacon broadcasting requires status advertisement to assist the driver for safety. WAVE standards apply multiple radios and multiple channels to provide open public road safety services and improve the comfort and efficiency of driving. Although WAVE standards have been proposed multi-channel multi-radio, the standards neither consider the WAVE multi-radio environment nor its effect on the beacon broadcasting. Most of beacon broadcasting is designed to be delivered on only one physical device and one control channel by the WAVE standard. also conflict-free channel assignment of the fewest channels to a given set of radio nodes without causing collision is NP-hard, even with the knowledge of the network topology and all nodes have the same transmission radio. Based on the latest standard IEEE 802.11p and IEEE 1609.4, this paper proposes an interference aware-based channel assignment algorithm with Nash bargaining solution that minimizes interference and increases throughput with wireless mesh network, which is deigned for multi-radio multi-cahnnel structure of WAVE. The proposed algorithm is validated against numerical simulation results and results show that our proposed algorithm is improvements on 8 channels with 3 radios compared to Tabu and random channel allocation algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.11
• /
• pp.2305-2315
• /
• 2015

Frequency resource value is growing more and more with the development of the wireless communication. With the advent of the current information society comes a serious shortage of frequency resource, as the amount of supply is far from meeting its demands. Thus, cognitive radio (CR) technique is receiving more attention as a way to make use of the temporarily unoccupied frequency resource. In this paper we propose a novel out-of-band spectrum sensing and dynamic channel access scheme for frequency hopping-based cognitive radio ad-hoc networks. At the beginning of each current channel hopping time, member nodes perform spectrum sensing for the next hopping channel. Based on the proposed collision free primary detection notification, member nodes can determine whether they should execute a hopping time extension procedure of the current channel or not. When the primary detected hopping channel is re-idled, the hopping pattern recovery procedure is performed. In this paper we evaluated the performance of the proposed dynamic sensing and hopping channel extension mechanism for the various wireless network conditions. As a result, we show that the proposed method can increase channel utilization and provide reliable channel management operation.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
• /
• v.15
• /
• pp.169-209
• /
• 2001

As a domain name can be registered simply by filing an application for registration, disputes over the domain name between the holder of domain name and the holder of trademark increased. Since the holder of trademark who was late for registering domain name is willing to pay for the return of domain name, cybersquatters increased. Cybersqatters are not genuine users of the Internet. This article is to compare the construction of law by American Courts and by Korean Courts and to assert the creation of the law similar to the law of US as to anti-cybersqatting. American Courts applied the Trademark Act and the Anti-Dilution Act to resolve the disputes over domain name. To apply the Trademark Act, the Court required the plaintiffs to prove that the goods or the services expressed by the domain name should be identical or similar to the goods or the services represented by the trademark. However, there were many cases where the holder of domain name used it for the goods or the services irrelevant to those of the holder of trademark. Also, the Anti-Dilution Act could not successfully protect the holder of trademark from cybersquatters because it required that the trademark should be famous or distinctive. As a result, the US promulgated a new law which is designed to prohibit cybersquatters from being free of sanction by the existing laws. Korea Courts applied the Trademark Act and the Unfair Competition Prohibition Act to the cases disputing domain name. Likewise in the US, Korean Courts must cope with the issue of identity of the goods or the services, and the famousness or distinctiveness of trademark. The Courts hesitate to give a winning judgement to the holder of trademark simply because the domain name of alleged violator confused the trademark. Some scholars advocate the broadening of construction of the Unfair Competition Prohibition Act to illegalize cybersquatting but it is beyond the meaning of the law. Accordingly, it is a time to make a law similar to the Anti-Cybersquatting Act of the US. The law must be a fair and reasonable compromise to resolve the collision between system of registration of domain name and the system of registration of trademark. Some commentators advocate that the registration of domain name should be examined just as the one of trademark and to facilitate it, the Patent and Trademark Office should have jurisdiction of registration of domain name. But it abandons the distinction of domain name and trademark and results in obstructing e-commerce. By adopting the Anti-Cybersqatting Act, we can prohibit it. In other cases, we get a reasonable adjustment between the holder of domain name and the holder of trademark through the Trademark Act and the Unfair Competition Prohibition Act.

• The Journal of Industrial Distribution & Business
• /
• v.2 no.1
• /
• pp.29-37
• /
• 2011

It remains that South and North Korea are the most conflict ridden region of the world and at high risk of military collision despite the appropriateness and necessity of unification between South and North Korea. Meanwhile, our government has pushed ahead with exchange between the two countries in many different fields to defuse this conflict and tension. But, these efforts have made it less meaningful as South-North relations are strained again. This can be because temporary recovery of political relation didn't proceed to system improvement and economic cooperation. This study on exchange cooperation of circulation · distribution between South and North Korea begins with expectation that this study will be based on realizing free circulation · distribution for the unification and making an economic bloc through exchange cooperation of circulation · distribution. To expand economy exchange and cooperation between the two nations, the field of circulation · distribution should be developed. On the basis of this discussion, this study suggests that cooperation relation and the mood of reconciliation created by political declaration are institutionalized in the national consensus and exchange should be expanded in the economic field as well as political field.