• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39B no.9
• /
• pp.620-628
• /
• 2014

Various on-demand manner routing protocols have been proposed for efficient energy consumption in mobile ad-hoc networks. Some of the protocols tried to extend the network lifetime by periodically rerouting paths according to the energy consumption rate of nodes. However, those protocols suffer from frequent flooding and high overhead. This paper proposed a new routing protocol called ALPMR (Adaptive Local Path Modification Routing) that extends the network lifetime by using local path rerouting. The proposed ALPMR protocol performs local rerouting around nodes with little remaining energy as well as data congestion, thus reduces flooding and routing overhead and can extend the network lifetime. The performance of ALPMR protocol is observed using ns-2 simulator.

• Journal of Integrative Natural Science
• /
• v.14 no.4
• /
• pp.162-175
• /
• 2021

Recently, due to global warming, the average temperature of the earth has risen, and the glaciers in the Antarctic and Arctic melt, leading to a rise in sea level, which is accompanied by powerful natural disasters such as strong typhoons and tsunamis around the world. Accordingly, a precipitation in summer in Korea also increased, and changes in the form of precipitation were showed with the increase. Compared to the past, the frequency of localized heavy rain is increasing, and the damage from flooding and flooding is increasing day by day. In this study, based on the precipitation data measured in hours from May to September from 2016 to 2021 according to the change in the precipitation form, according to the nature of the torrential rain investigated the change in the summer precipitation form. In addition, the trend of localized heavy rain from 2016 to 2021 was confirmed by classifying them into two types: localized heavy rains caused by cyclones and weather front, and by typhoons and large-scale cyclones. Through this, the change in precipitation due to the climate crisis should not be viewed as a single phenomenon, it should be reflected and discussed on our life focused on scientific and technological development, and it should be used as a stepping stone for realizing a humanistic.

• International Journal of Computer Science & Network Security
• /
• v.21 no.12
• /
• pp.1-8
• /
• 2021

In Mobile Ad-Hoc Network (MANET) Application, routing protocol is essential to ensure successful data transmission to all nodes. Ad-hoc On-demand Distance Vector (AODV) Protocol is a reactive routing protocol that is mostly used in MANET applications. However, the protocol causes Route Request (RREQ) message flooding issue due to the broadcasting method at the route request stage to find a path to a particular destination, where the RREQ will be rebroadcast if no Request Response (RREP) message is received. A scalable neighbor-based routing (SNBR) protocol was then proposed to overcome the issue. In the SNBR protocol, the RREQ message is only rebroadcast if the number of neighbor nodes less than a certain fix number, known as drop factor. However, since a network always have a dynamic characteristic with a dynamic number of neighbor nodes, the fix drop factor in SNBR protocol could not provide an optimal flooding problem solution in a low dense network environment, where the RREQ message is continuously rebroadcast RREQ message until reach the fix drop factor. To overcome this problem, a new broadcasting method as Dynamic SNBR (DSNBR) is proposed, where the drop factor is determined based on current number of neighbor nodes. This method rebroadcast the extra RREQ messages based on the determined dynamic drop factor. The performance of the proposed DSNBR is evaluated using NS2 and compared with the performance of the existing protocol; AODV and SNBR. Simulation results show that the new routing protocol reduces the routing request overhead, energy consumption, MAC Collision and enhances end-to-end delay, network coverage ratio as a result of reducing the extra route request messages.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.57 no.3
• /
• pp.228-235
• /
• 2021

Marine accidents caused by ships are very diverse, such as collision, sinking, stranding, grounding and fire. In particular, persons on passenger ship are unspecified and not trained, so it makes evacuation harder. For this reason, an evacuation plan that considers diverse situation in ship is needed. Effective evacuation planning requires training in consideration of various evacuation situations. In this paper, we investigated the time elapsed on evacuation in various situations from "HANMIR," the fishery training ship of the Korean Institute of Maritime and Fisheries Technology, using a Ship Evacuation Analysis Program (SEA-Pro) which is introduced to the society. We assumed a situation that has not only inconveniences for real training but also the possibilities of happening. Not all trainees are resting in their cabin, so we assumed positions such as they are in the bridge or engine room and applied fire and flooding situations. We assumed that the time for alerting the situation would be short, so we applied only elapsed time of movement. Those analyses could be helpful in three ways. The first is predicting the consequence of possible accidents. There are some conditions that can be appliable to this model, such as the decreased area of sight in those situations. The second is concluding the optimal limit of carriage and placement of safety instruments on building a new ship. The third is to be a base data for ships to make a new effective evacuation plan based on these analyses.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.25 no.3
• /
• pp.440-448
• /
• 2021

This paper presents problems of network technology in smart grid and implements a blockchain-based LoRa multi-hop network to solve them. Since some smart grid applications are operated in harsh environments, it is difficult to establish communication infrastructure. We propose a LoRa network with multi-hop using the Flooding routing protocol. Smart grid environment composes an independent network using various power grid protocols depending on the application. Since this has a problem that an independent infrastructure must be established for each network, a single gateway device supports multiple power grid protocols to implement a method for network integration. Lastly, the author applied Hyperledger-based blockchain to the LoRa network to ensure the integrity of data in a smart grid environment, and strengthened security by physically distributing it. After constructing the three suggestions on the actual test bed, we confirmed that the network operates normally through experiments.

• Journal of Ecology and Environment
• /
• v.47 no.2
• /
• pp.49-62
• /
• 2023

Background: Over the past three decades, gradual eustatic sea-level rise has been considered a primary exogenous factor in the increased frequency of flooding and biological changes in several salt marshes. Under this paradigm, the potential importance of short-term events, such as ocean storminess, in coastal hydrology and ecology is underrepresented in the literature. In this study, a simulation was developed to evaluate the influence of wind waves driven by atmospheric oscillations on sedimentary and vegetation dynamics at the Skallingen salt marsh in southwestern Denmark. The model was built based on long-term data of mean sea level, sediment accretion, and plant species composition collected at the Skallingen salt marsh from 1933-2006. In the model, the submergence frequency (number yr^-1) was estimated as a combined function of wind-driven high water level (HWL) events (> 80 cm Danish Ordnance Datum) affected by the North Atlantic Oscillation (NAO) and changes in surface elevation (cm yr^-1). Vegetation dynamics were represented as transitions between successional stages controlled by flooding effects. Two types of simulations were performed: (1) baseline modeling, which assumed no effect of wind-driven sea-level change, and (2) experimental modeling, which considered both normal tidal activity and wind-driven sea-level change. Results: Experimental modeling successfully represented the patterns of vegetation change observed in the field. It realistically simulated a retarded or retrogressive successional state dominated by early- to mid-successional species, despite a continuous increase in surface elevation at Skallingen. This situation is believed to be caused by an increase in extreme HWL events that cannot occur without meteorological ocean storms. In contrast, baseline modeling showed progressive succession towards the predominance of late-successional species, which was not the then-current state in the marsh. Conclusions: These findings support the hypothesis that variations in the NAO index toward its positive phase have increased storminess and wind tides on the North Sea surface (especially since the 1980s). This led to an increased frequency and duration of submergence and delayed ecological succession. Researchers should therefore employ a multitemporal perspective, recognizing the importance of short-term sea-level changes nested within long-term gradual trends.

• Korean Journal of Cognitive Science
• /
• v.13 no.3
• /
• pp.33-46
• /
• 2002

Recently, unstructured random data such as website logs, texts and tables etc, have been flooding in the internet. Among these unstructured data there are potentially very useful data such as bulletin boards and e-mails that are used for customer services and the output from search engines. Various text mining tools have been introduced to deal with those data. But most of them lack accuracy compared to traditional data mining tools that deal with structured data. Hence, it has been sought to find a way to apply data mining techniques to these text data. In this paper, we propose a text mining system which can incooperate existing data mining methods. We use text mining as a preprocessing tool to generate formatted data to be used as input to the data mining system. The output of the data mining system is used as feedback data to the text mining to guide further categorization. This feedback cycle can enhance the performance of the text mining in terms of accuracy. We apply this method to categorize web sites containing adult contents as well as illegal contents. The result shows improvements in categorization performance for previously ambiguous data.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.12 no.5
• /
• pp.891-898
• /
• 2017

Climate changes consistently cause coastal accidents such as coastal flooding, so the studies on monitoring the marine environments are progressing to prevent and reduce the damage from coastal accidents. In this paper, we propose a new method to estimate the sea level which can be applied to the tidal sensors to monitor the variation of sea level. Existing sea level models are very complicated and need a lot of tidal data, so they are not proper for tidal sensors. On the other hand, the proposed algorithm is very simple but precise since we use the measured data from the sensor to estimate the sea level value in short period such as one or two hours. It is shown by experimental results that the proposed method is simple but predicts the sea level accurately.

• Journal of Environmental Impact Assessment
• /
• v.20 no.2
• /
• pp.249-256
• /
• 2011

Causing by green house gas emission, global warming is being accelerated significantly. This global warming cause world climate to change quiet different than before and we call this phenomenon is Climate Change. Environmental Impact Assessment being implemented in Korea is to prevent predicted environmental impacts from deteriorating within the domestic information and situation. As the climate change is getting severe, new meteorological records can be occurred which is exceeded existing statistical data. According to KMA(Korea Meteorological Administration) data, maximum value of precipitation and temperature in many regions changed with new data within last decade. And these events accompanied with landslides and flooding, and these also affected on water quality in rivers and lakes. According to impacts by climate change, disasters and accidents from heavy rain are the most apprehensive parts. And water pollution caused by overflowed non-point sources during heavy rain fall, fugitive dust caused by long-term drought, and sea level rise and Tsunami may affect on seaside industrial complex should be worth consideration. In this review, necessity of mutual consideration with influences of climate change was considered adding on existing guideline.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.41 no.3
• /
• pp.37-45
• /
• 2004

In this paper we propose Clustered Group Multicast by Clustering Algorithm in Wireless Mobile Ad-hoc Network. The proposed scheme applies to Weighted Cluster Algorithm Ad-hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any centralized administration or reliable support services such as wired network and base station. In ad hoc network muting protocol because of limited bandwidth and high mobility robust, simple and energy consume minimal. WCGM method uses a base structure founded on combination weighted value and applies combination weight value to cluster header keeping data transmission by seeped flooding, which is the advantage of the exiting FGMP method. Because this method has safe and reliable data transmission, it shows the effect to decrease both overhead to preserve transmission structure and overhead for data transmission.