• 한국정보통신학회논문지
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• 제14권9호
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• pp.2143-2149
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• 2010

본 논문에서는 지리정보 라우팅 프로토콜 중 가장 잘 알려진 GPSR의 성능을 향상시키기 위한 에이전트 기반의 로드 분산 알고리즘을 제안한다. 제안된 방법은 싱크 노드 주변 노드 중에 하나를 에이전트 노드로 설정하고 데이터 패킷을 싱크로 직접 전송하는 대신에 에이전트 노드에게 전송하고 이 패킷들은 에이전트 노드에 의하여 싱크로 전달되게 하게 함으로써 트래픽의 분산을 자동적으로 유도한다. 또한, 데이터 포워딩시에는 위치 정보뿐만 아니라 주변 노드의 현재 버퍼 사용량을 기준으로 다음 홉을 선택하게 함으로써 혼잡을 효율적으로 예방함으로써 로드 분산을 수행한다. 이러한 기능들은 패킷의 손실의 줄이게 되고 결국 패킷 전송 성공률이 높아지게 된다. 제안된 메커니즘의 성능 평가를 위하여 싱크노드로의 연결 수와 홉 수에 따른 패킷 전송 성공율을 측정한 결과 기존 GPSR 프로토콜에 비하여 향상된 성능을 확인하였다.

• Journal of Communications and Networks
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• 제14권4호
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• pp.434-442
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• 2012

Several gateway selection schemes have been proposed that select gateway nodes based on a single Quality of Service (QoS) path parameter, for instance path availability period, link capacity or end-to-end delay, etc. or on multiple non-QoS parameters, for instance the combination of gateway node speed, residual energy, and number of hops, for Mobile Ad hoc NETworks (MANETs). Each scheme just focuses on the ment of improve only a single network performance, i.e., network throughput, packet delivery ratio, end-to-end delay, or packet drop ratio. However, none of these schemes improves the overall network performance because they focus on a single QoS path parameter or on set of non-QoS parameters. To improve the overall network performance, it is necessary to select a gateway with stable path, a path with themaximum residual load capacity and the minimum latency. In this paper, we propose a gateway selection scheme that considers multiple QoS path parameters such as path availability period, available capacity and latency, to select a potential gateway node. We improve the path availability computation accuracy, we introduce a feedback system to updated path dynamics to the traffic source node and we propose an efficient method to propagate QoS parameters in our scheme. Computer simulations show that our gateway selection scheme improves throughput and packet delivery ratio with less per node energy consumption. It also improves the end-to-end delay compared to single QoS path parameter gateway selection schemes. In addition, we simulate the proposed scheme by considering weighting factors to gateway selection parameters and results show that the weighting factors improve the throughput and end-to-end delay compared to the conventional schemes.

• Journal of Information Processing Systems
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• 제5권1호
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• pp.33-40
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• 2009

Ever since the network-based malicious code commonly known as a 'worm' surfaced in the early part of the 1980's, its prevalence has grown more and more. The RCS (Random Constant Spreading) worm has become a dominant, malicious virus in recent computer networking circles. The worm retards the availability of an overall network by exhausting resources such as CPU capacity, network peripherals and transfer bandwidth, causing damage to an uninfected system as well as an infected system. The generation and spreading cycle of these worms progress rapidly. The existing studies to counter malicious code have studied the Microscopic Model for detecting worm generation based on some specific pattern or sign of attack, thus preventing its spread by countering the worm directly on detection. However, due to zero-day threat actualization, rapid spreading of the RCS worm and reduction of survival time, securing a security model to ensure the survivability of the network became an urgent problem that the existing solution-oriented security measures did not address. This paper analyzes the recently studied efficient dynamic network. Essentially, this paper suggests a model that dynamically controls the RCS worm using the characteristics of Power-Law and depth distribution of the delivery node, which is commonly seen in preferential growth networks. Moreover, we suggest a model that dynamically controls the spread of the worm using information about the depth distribution of delivery. We also verified via simulation that the load for each node was minimized at an optimal depth to effectively restrain the spread of the worm.

• 생체재료학회지
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• 제22권4호
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• pp.235-248
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• 2018

Background: Injectable hydrogels have been extensively researched for the use as scaffolds or as carriers of therapeutic agents such as drugs, cells, proteins, and bioactive molecules in the treatment of diseases and cancers and the repair and regeneration of tissues. It is because they have the injectability with minimal invasiveness and usability for irregularly shaped sites, in addition to typical advantages of conventional hydrogels such as biocompatibility, permeability to oxygen and nutrient, properties similar to the characteristics of the native extracellular matrix, and porous structure allowing therapeutic agents to be loaded. Main body: In this article, recent studies of injectable hydrogel systems applicable for therapeutic agent delivery, disease/cancer therapy, and tissue engineering have reviewed in terms of the various factors physically and chemically contributing to sol-gel transition via which gels have been formed. The various factors are as follows: several different non-covalent interactions resulting in physical crosslinking (the electrostatic interactions (e.g., the ionic and hydrogen bonds), hydrophobic interactions, ${\pi}$-interactions, and van der Waals forces), in-situ chemical reactions inducing chemical crosslinking (the Diels Alder click reactions, Michael reactions, Schiff base reactions, or enzyme-or photo-mediated reactions), and external stimuli (temperatures, pHs, lights, electric/magnetic fields, ultrasounds, or biomolecular species (e.g., enzyme)). Finally, their applications with accompanying therapeutic agents and notable properties used were reviewed as well. Conclusion: Injectable hydrogels, of which network morphology and properties could be tuned, have shown to control the load and release of therapeutic agents, consequently producing significant therapeutic efficacy. Accordingly, they are believed to be successful and promising biomaterials as scaffolds and carriers of therapeutic agents for disease and cancer therapy and tissue engineering.

• International Journal of Internet, Broadcasting and Communication
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• 제14권1호
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• pp.85-94
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• 2022

Recently, consumers who prefer contactless consumption are increasing due to pandemic trends such as Corona 19. This is the driving force for developing the last mile-based logistics ecosystem centered on the online e-commerce market. Lastmile led to the continued development of the logistics industry, but increased the amount of cargo in urban area, and caused social problems such as overcrowding of logistics. The courier service in the logistics base area utilizes the process of visiting the delivery site directly because the courier must precede the loading work of the cargo in the truck for the delivery of the ordered product. Currently, it's carried out as automated logistics equipment such as conveyor belt in unloading or classification stage, but the automation system isn't applied, so the work efficiency is decreasing and the intensity of the courier worker's labor is increased. In particular, small-scale courier workers belonging to the sub-terminal unload at night at underdeveloped facilities outside the city center. Therefore, the productivity of the work is lowered and the risk of safety accidents is exposed, so robot-based loading technology is needed. In this paper, we have derived the top-level concept and requirements of robot-based loading system to increase the flexibility of logistics processing and to ensure the safety of courier drivers. We defined algorithms and motion concepts to increase the cargo loading efficiency of logistics sub-terminals through the requirements of end effector technology, which is important among concepts. Finally, the control technique was proposed to determine and position the load for design input development of the automatic conveyor system.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.413-422
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• 1993

Air shipment affords the quickest possible delivery of horticultural products. The price of air shipped horticultural products are relatively high as most of these products are perishable. Usually the temperature in the cargo compartment is not controlled during flight. Thus, special attention should be paid to procooling prior to shipment. The environmental condition during transportation of horticultural products is an essential parameter for maintaining the quality of perishable products. Commonly horticultural products were loaded by ULD(Unit Load Devices) as a container or pallet in the aircraft (except for small aircraft) . Therefore, inside temperature of the container and cargo compartment came into question. Scarce literature on the relationship between environmental condition and quality changes of horticultural products during air shipment can be found. By the stand point of keeping fresh quality, investigations on the actual condition of air shipments were carried out to improve the technique during the distribution process of fresh horticultural products. Temperature, humidity, atmospheric pressure, carbon dioxide, ethylene, impacts, and changes in quality during the air shipment of snapbeans, okras and chrysanthemums were measured. Temperature was measured by recording thermometers, relative humidity by recording hygrometers, atmospheric pressure by a strain -guage type pressure sensor, carbon dioxide by testing tubes, ethylene by sampling bags and a gaschromatograph, impacts and vibrations by impact recorders and a 3D accelerometer. Relationships between environmental conditions and quality changes during air shipments were clarified. It was expected from investigations into actual shipments that the ventilation and insulation properties of air freight containers were related to the quality of agricultural products. Aircraft can no directly load and unload trucks into them. The transshipment is inclined to cause shocks and vibrations, and to invite damages within a short time.

• 대한전기학회논문지:전력기술부문A
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• 제51권9호
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• pp.433-440
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• 2002

The addition of switches to a distribution feeder does, in general, increase reliability by decreasing the duration of the outage of many to the customers on the feeder. To cover its service area so that feeder-level delivery reaches sufficiently close to all customers, feeders typically split their routes many times, in what is often called a lateral feeder. It is interesting to note, however, that the effectiveness of a switch is very much dependent on the types of lateral feeder. The types of lateral are classified into two types. The first is loop lateral feeder that can connect its load to an adjacent feeder through a tie line in case that a fault occurs in its feeder and it is laid out so that every feeder has complete fault backup through re-switching of its loads to other sources like a main feeder The second is the radial lateral feeder cannot connect its load to an adjacent line, no provision is made for contingency backup of feeders. There are no other circuits in the radial lateral feeder form which to restore power. In this study, we evaluate the effectiveness of a switch installation between on the radial and loop lateral feeders to increase reliability by decreasing the duration of the outage. These results can help power utility to design the switch layouts on the radial and loop lateral feeder system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권2호
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• pp.683-701
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• 2012

IEEE 802.11 standard has achieved huge success in the past decade and is still under development to provide higher physical data rate and better quality of service (QoS). An important problem for the development and optimization of IEEE 802.11 networks is the modeling of the MAC layer channel access protocol. Although there are already many theoretic analysis for the 802.11 MAC protocol in the literature, most of the models focus on the saturated traffic and assume infinite buffer at the MAC layer. In this paper we develop a unified analytical model for IEEE 802.11 MAC protocol in ad hoc networks. The impacts of channel access parameters, traffic rate and buffer size at the MAC layer are modeled with the assistance of a generalized Markov chain and an M/G/1/K queue model. The performance of throughput, packet delivery delay and dropping probability can be achieved. Extensive simulations show the analytical model is highly accurate. From the analytical model it is shown that for practical buffer configuration (e.g. buffer size larger than one), we can maximize the total throughput and reduce the packet blocking probability (due to limited buffer size) and the average queuing delay to zero by effectively controlling the offered load. The average MAC layer service delay as well as its standard deviation, is also much lower than that in saturated conditions and has an upper bound. It is also observed that the optimal load is very close to the maximum achievable throughput regardless of the number of stations or buffer size. Moreover, the model is scalable for performance analysis of 802.11e in unsaturated conditions and 802.11 ad hoc networks with heterogenous traffic flows.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권4호
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• pp.1256-1275
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• 2014

As one of the new self-organizing and self-configuration broadband networks, wireless mesh networks are being increasingly attractive. In order to solve the load balancing problem in wireless mesh networks, this paper proposes a novel multi-path routing algorithm based on clustering (Cluster_MMesh) for wireless mesh networks. In the clustering stage, on the basis of the maximum connectivity clustering algorithm and k-hop clustering algorithm, according to the idea of maximum connectivity, a new concept of node connectivity degree is proposed in this paper, which can make the selection of cluster head more simple and reasonable. While clustering, the node which has less expected load in the candidate border gateway node set will be selected as the border gateway node. In the multi-path routing establishment stage, we use the intra-clustering multi-path routing algorithm and inter-clustering multi-path routing algorithm to establish multi-path routing from the source node to the destination node. At last, in the traffic allocation stage, we will use the virtual disjoint multi-path model (Vdmp) to allocate the network traffic. Simulation results show that the Cluster_MMesh routing algorithm can help increase the packet delivery rate, reduce the average end to end delay, and improve the network performance.

• 한국산업정보학회논문지
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• 제19권2호
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• pp.1-13
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• 2014

In IEEE 802.11p/1609-based vehicular networks, vehicles are allowed to exchange safety and control messages only within time periods, called control channel (CCH) interval, which are scheduled periodically. Currently, the length of the CCH interval is set to the fixed value (i.e. 50ms). However, the fixed-length intervals cannot be effective for dynamically changing traffic load. Hence, some protocols have been recently proposed to support variable-length CCH intervals in order to improve channel utilization. In existing protocols, the CCH interval is subdivided into safety and non-safety intervals, and the length of each interval is dynamically adjusted to accommodate the estimated traffic load. However, they do not consider the presence of hidden nodes. Consequently, messages transmitted in each interval are likely to overlap with simultaneous transmissions (i.e. interference) from hidden nodes. Particularly, life-critical safety messages which are exchanged within the safety interval can be unreliably delivered due to such interference, which deteriorates QoS of safety applications such as cooperative collision warning. In this paper, we therefore propose a new interference-aware Dynamic Safety Interval (DSI) protocol. DSI calculates the number of vehicles sharing the channel with the consideration of hidden nodes. The safety interval is derived based on the measured number of vehicles. From simulation study using the ns-2, we verified that DSI outperforms the existing protocols in terms of various metrics such as broadcast delivery ration, collision probability and safety message delay.