• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.2B
• /
• pp.76-81
• /
• 2008

LEACH (Low Energy Adaptive Clustering Hierarchy) has been proposed as a routing protocol with a hierarchical structure, in order to achieve the energy efficiency that is of primary importance in the wireless sensor networks. A wireless sensor network adopting LEACH is composed of a few clusters, each of which consists of member nodes that sense the data, and head nodes that deliver the collected data from member nodes to a sink node that is connected to a backbone network. A head node in a cluster allocates TDMA slots to its member nodes without taking into account whether they have data to transmit or not, thus resulting in inefficiency of energy usage of head node that remains in active mode during the entire round time. This motivates us to propose a scheme to improve the energy efficiency of LEACH, by assigning TDMA slots only to those member nodes who have data to send. As a result, the head node can remain sleep during the period of no data transmission from member nodes, leading to the substantial energy saving. By using the ns-2 simulator, we evaluate the performance of the proposed scheme in comparison with the original LEACH. Experimental results validate our scheme, showing a better performance than original LEACH in terms of the number of outliving nodes and the quantity of energy consumption as time evolves.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.6
• /
• pp.4322-4327
• /
• 2015

Improper backfill materials and compaction controls under pipelines have become one of the major causes of failure in many sewage pipeline systems. A study on backfill materials and compaction controls has been considered for a long time. However, structural supporters under the pipe were recently concerned because of pipeline repair and maintenance. This paper presents a prefabricated plastic foundation for supporting a sewage pipe system and increasing the performance function of the pipes. Several analytical models for the plastic foundations were investigated using finite-element program, ABAQUS, for checking safety. Comparing with the results of analyses, some of economic design sections based on the sizes of pipe diameters, 600mm, 700 and 600mm, were evaluated. These results could be applied to a pipeline system with a prefabricated plastic foundation with respect to pipe diameters and buried depths.

• Journal of the Korea Computer Industry Society
• /
• v.6 no.3
• /
• pp.465-476
• /
• 2005

The wireless sensor network consists of a number of sensor nodes which have physical constraints. Each sensor node senses surrounding environments and sends the sensed information to Sink. In order to alleviate the inherent vulnerability in security of the wireless sensor nodes with the hardware constraints, the lightweight security protocol is needed and a variety of research is ongoing. In this paper, we propose a non-hierarchical sensor network and a security protocol that is suitable for monitoring man-made objects such as bridges. This paper, furthermore, explores a two-layer authentication, key distribution scheme which distributes the key and location of a sensor node in advance, and an effective security routing protocol which can take advantage of the Sleep and Awake state. This also results in the increased data transfer rate by increasing the number of alternative routing paths and the reduced energy consumption rate.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.17 no.6
• /
• pp.224-239
• /
• 2018

Autonomous vehicles can significantly reduce accidents due to 'driver's carelessness', which occupies the majority of causes for traffic accidents, but they may fail to avoid traffic accidents due to unexpected situations, such as "trolley dilemma", vehicle defects and road defects. Therefore in situations Autonomous vehicles need to be made ethical choices. This study assumes that Autonomous vehicles can not avoid traffic accidents due to unexpected sink holes. In this situation, the traffic accident costs was analyzed for the ethical choices of Autonomous vehicles. In the process, Autonomous vehicles were made to choose one of three ethical choices : (1) Egoism with priority on passenger safety, (2) Deontology for minimizing human damages, (3) Utilitarianism with minimizing traffic accident costs. As a result of the analysis, egoism had the highest traffic accident costs, and deontology for minimizing human damages had the lowest traffic accident costs.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.26 no.1
• /
• pp.122-127
• /
• 2022

Currently, the drone is considered as a mobile base station of USN as a method to act as a base station using USN in existing LTE-M and LTE networks for data transmission in unmanned ships. Therefore, the drone, which is a mobile base station, is a sink node equipped with an LTE modem or a short-range communication modem, and can collect safety information of ship operation from the sensor node and transmit the safety information to the ship or transmit the information between the ships. As, if a short-range network is formed by using drones, it will form a communication network around unmanned ships and will be advantageous for collecting information using security and environmental sensors. In this paper, we propose a method to transmit environmental sensor data and to utilize communication between ships using drones to secure the surrounding information necessary for AI operation of unmanned ships in the future.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2011.11a
• /
• pp.606-608
• /
• 2011

무선 센서 네트워크는 특정지역에 센서 노드를 설치하여 주변 정보 또는 특정 목적의 데이터를 수집하고, 그 정보를 수집하는 싱크(Sink)로 구성되어 있다. 무선 센서 네트워크의 수명은 망을 구성하는 센서 노드의 베터리 소비에 따라 수명이 결정 되고 하나의 노드가 죽기 시작하면서부터 급격하게 센서 노드의 베터리 소비가 커져 빠르게 죽는다. 무선 센서 네트워크를 구성하는 센서노드는 라우팅, 센싱을 수행하기 때문에 베터리 소비에 많은 부담을 가지고 있다. 본 논문은 무선 센서 네트워크의 대표적 클러스터링 기반 라우팅 기법인 LEACH(Low - Energy Adaptive Clustering Hierarchy)프로토콜에 SVM(Support Vector Machine)을 적용하여 센서노드의 균형적인 베터리 소비로 망을 효율적으로 관리하고 망의 수명을 개선 할 수 있는 방법을 제안 한다. 이러한 센서 노드의 균형적인 베터리 소비로 무선센서 네트워크의 수명을 개선 한다. 실험결과 기존의 LEACH 프로토콜보다 우수한 성능을 보인다.

• Journal of the Microelectronics and Packaging Society
• /
• v.22 no.4
• /
• pp.65-70
• /
• 2015

A study on thermal properties for a single-layer metal and two-layer composites was investigated for the heat-sink application. For the single-layer metal, an aluminum alloy (Al6061) was selected. A screen printed aluminum nitride (AlN) layer on the Al6061 substrate was chosen for the two-layer composites. The thermal conductivity of the sample was determined from the thermal diffusivity measured by the light flash analysis (LFA), specific heat and density. Measured thermal property values were compared to calculated values using the data from the references. The thermal conductivity of composites with screen printed AlN layer on the Al6061 substrate decreased linearly with increasing the thickness of AlN layer. Measured values of the thermal conductivity for composites with $53{\mu}m$ and $163{\mu}m$ thick AlN layers were $114.1W/m{\cdot}K$ and $72.3W/m{\cdot}K$, respectively. In particular, the thermal conductivity of the screen-printed AlN layer was demonstrated by appling the rule of mixture in view point of thermal resistivity. Measured values of the thermal conductivity for AlN layers with the thickness of $53{\mu}m$ and $163{\mu}m$ showed $9.35W/m{\cdot}K$ and $12.40W/m{\cdot}K$, respectively.

• Journal of Korean Society of Environmental Engineers
• /
• v.38 no.12
• /
• pp.641-646
• /
• 2016

Soil organic matter (SOM) is an important soil component releasing nutrients to the plants and reducing risks of soil contamination to the human and ecosystem. Much attention has been recently paid to SOM investigation and management because SOM holds the most of carbon in the earth and sequestrate carbon as a sink tank. The first objective of the study was to investigate SOM of 495 soil samples taken at the Korea Soil Quality Monitoring Network. Soil samples were collected from 16 regions and 8 land use types. The second objective of the study was to find a relationship between the Tyurin method and loss-on-ignition (LOI) method for SOM. The means of SOM by Tyurin and LOI methods were 1.90 and 2.92 % (w/w), respectively. Land uses such as forest, religious area and park where organic matters continuously supply to normally showed higher SOMs than residential and school areas having sandy soils. A regression equation of the relationship between Tyurin and LOI methods was y(Tyurin) = 0.6257x(LOI) + 0.0602 (P-value < 0.001). The coefficient of determination was $R^2=0.749$, relatively linearly related. Although LOI may result in higher SOMs than the Tyurin method, LOI may be a preference for the SOM investigation if various kinds of land uses and many soil samples should be measured.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.11
• /
• pp.7250-7255
• /
• 2015

The objective of this study is to experimentally investigate the heating performances of the portable air combustion heater using diesel fuel for auxiliary cabin heating of the battery electric vehicle. In order to evaluate the heating performances of the air combustion heater, the heating capacity was calculated by the temperature at inlet and outlet parts of the considered heater and the inner temperature distribution characteristics of the vehicle were measured during 1600 seconds with an interval of 1 second. The theoretical efficiency of the tested heater was calculated by temperature data of the air of supplying and exhausting to the cabin. As the air passed the heat-sink, the air temperature at the end of heat-sink reached to $101.3^{\circ}C$ and the difference of temperature on heat-sink was 67.8%. The average heating capacity of the air combustion heater showed 2.0 kW. After 1800 seconds, the inner temperature of the vehicle cabin was continuously increased. The temperatures of the top side and the bottom side of the car cabin under consideration were increased upto $42.5^{\circ}C$ and $24.3^{\circ}C$, respectively, and the theoretical efficiency of the tested heater was on average 63.7%.

• Journal of the Korea Society for Simulation
• /
• v.19 no.4
• /
• pp.11-19
• /
• 2010

ZigBee is a standard for wireless personal area networks(WPANs) based on the IEEE 802.15.4 standard. It has been developed for low cost and low power consumption. There are two alternative routing schemes that have been proposed for the ZigBee standard: Ad-hoc On-Demand Distance Vector(AODV) and tree routing. The tree routing forwards packets from sensors to a sink node based on the parent-child relationships established by the IEEE 802.15.4 MAC topology formation procedure. In order to join the network, a sensor node chooses an existing node with the strongest RSSI(Received signal strength indicator) signal as a parent node. Therefore, some nodes carry a large amount of traffic load and exhaust their energy rapidly. To overcome this problem, we introduce a new metric based on link quality and traffic load for load balancing. Instead of the strength of RSSI, the proposed scheme uses the new metric to choose a parent node during the topology formation procedure. Extensive simulation results using TOSSIM(TinyOS mote SIMulator) show that the CFR scheme outperforms well in comparison to the conventional tree routing scheme.