• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.4
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• pp.1692-1711
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• 2016

Energy is a scarce resource in wireless sensor networks (WSNs). A variety of clustering protocols for WSNs, such as the zone-based stable election protocol-enhanced (ZSEP-E), have been developed for energy optimization. The ZSEP-E is a heterogeneous zone-based clustering protocol that focuses on unbalanced energy consumption with parallel formation of clusters in zones and election of cluster heads (CHs). Most ZSEP-E research has assumed probabilistic election of CHs in the zones by considering the maximum residual energy of nodes. However, studies of the diverse CH election parameters are lacking. We investigated the performance of the ZSEP-E in such scenarios using a fuzzy logic approach based on three descriptors, i.e., energy, density, and the distance from the node to the base station. We proposed an efficient ZSEP-E scheme to adapt and elect CHs in zones using fuzzy variables and evaluated its performance for different energy levels in the zones.

• Journal of The Korean Digital Architecture Interior Association
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• v.7 no.2
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• pp.25-32
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• 2007

Cities should be developed and managed deliberately since reckless development and selfish expansion deteriorate the quality of life in the cities by creating various problems in transportation, residence and environment. In particular, the semi-agricultural zones have been designated in order to address such problems as the overpopulation caused by the influx of people into the cities and promote balanced regional development and eco-friendly cultivation of the land across the nation. But the problems of metropolitan areas, such as the overpopulation and lack of infrastructure, are spreading even to the semi-agricultural zones, which should be the last areas to be developed into cities. We should blame the indolence of our policies on land first, rather than the selfish cities that slip from the grip of the law. This study concludes that the self-agricultural zones should be developed and managed with plans by the public sector rather than the autonomous development by the private sector.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.5
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• pp.11-21
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• 2002

A series of model tests is performed to evaluate the relationship between soil and a buried pipe in soil undergoing lateral movement. As the result of the model tests, a wedge zone and plastic flow zones could be observed in front of the pipe. And also an arc failure of cylindrical cavity could be observed at both upper and lower zones. Failure shapes in both cohesionless and cohesive soils are nearly same, which was investigated failure angle of $45^{\circ}+{\phi}/2$. In the cohesionless soil, the higher relative density produces the larger arc of cylindrical cavity. On the basis of failure mode observed from model tests, the lateral earth pressure acting on a buried pipe in soil undergoing lateral movement could be applying the cylindrical cavity extension mode. The deformation behavior of soils was typically appeared in three divisions, which are elastic zones, plastic zones and pressure behavior zones.

• Water for future
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• v.28 no.2
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• pp.137-143
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• 1995

The location and the shape of freshwater-saltwater transition zones in coastal aquifers are affected by many hydraulic variables. To date most work to determine the effects of these variables are limited to qualitative comparison of transition zones. In this work characteristics of transition zones (maximum intrusion length, thickness, and degree of stratification) are quantified, and effects of principal hydraulic variables(velocity and dispersivity) on these characteristics are studied using a numerical model. Dimensional analysis is used to assemble entire model results. Effects of velocity and dispersivity are seen clearly. From this study, increase in velocity is found to cause shrinkage of transition zones. This observation contradicts claims by some that, because dispersion is proportional to velocity, increase in velocity would cause expansion of transition zones.

• Journal of Welding and Joining
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• v.14 no.4
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• pp.89-98
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• 1996

This study was performed to establish the characteristics of the heat affected zones from view point of the repair weldability for a damaged CrMoV steam turbine rotor steel. Characterization of the heat affected zones of the weldment was conducted with respect to various of postweld heat treatment temperatures, $566^{\circ}C$, $621^{\circ}C$ and $677^{\circ}C$. The evaluations of the heat affected zones were carried out in terms of microstructural characterization, microhardness measurements, Charpy v-notch impact, tensile and stress-rupture tests. The results indicated that the effect of the postweld heat treatment at $677^{\circ}C$ exhibited the favorable microstructure and mechanical properties for the stability of the heat affected zones. While the heat affected zone of the weldment, produced without postweld heat treatment, displayed the inferior toughness and microstructure indicating localized carbide precipitations on the grain boundary. It was also indicated that the stability of the heat affected zones were deteriorated by the formation of the cavitation on the grain boundaries.

• Journal of the Korean institute of surface engineering
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• v.46 no.1
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• pp.48-53
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• 2013

In the present work, it was investigated a behavior of hydrogen embrittlement at the subsurface zones of 590 DP steels by using the micro-Vickers hardness test. The micro-Vickers hardnessess of DP steels were measured to evaluate the degree of embrittlement as the effective hardening depths of subsurface zones with hydrogen charging conditions. The results showed that the distributions of micro-Vickers hardness in width varied from maximum hardness 239.5 Hv to minimum hardness 174 Hv, while the depth of effective hardening layer at the subsurface zones of DP steels was from $320{\mu}m$ to $460{\mu}m$ with hydrogen charging conditions, respectively. It was proposed that the distribution of microhardness be used as the evaluation index of the degree of embrittlement. But the variations of martensite volume fractions were not affected along depth of hardening at the same changing time, hydrogen charging times were appeared as an effective factor of the degree of embrittlement. Therefore, the micro-Vickers hardness test is an attractive tool for evaluation of hydrogen embrittlement at the subsurface zones of these DP steels.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.294-299
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• 2010

Two types of welding methods were performed on austenitic 304 stainless steel: laser welding and TIG welding. The differences of the corrosion characteristics of the welded zones from the two welding methods were investigated with electrochemical methods, such as measurement of the corrosion potential, polarization curves, cyclic voltammogram, etc. The vickers hardness of all laser-welded zones (WM:Weld Metal, HAZ:Heat Affected Zone, BM:Base Metal) was relatively higher while their corrosion current densities exhibited a comparatively lower value than those which were TIG welded. In particular, the corrosion current density of the TIG-welded HAZ had the highest value among all other welding zones, which suggests that chromium depletion due to the formation of chromium carbide occurs in the HAZ, which is in the sensitization temperature range, thus it can easily be corroded with an active anode. Intergrenular corrosion was also observed at the TIG-welded HAZ and WM zones. Consequently, we can see that corrosion resistance of all austenitic 304 stainless steel welding zones can be improved via the use of laser welding.

• Proceedings of the Korea Society of Environmental Biology Conference
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• 2002.11a
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• pp.137-140
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• 2002

To determine if fish density, biomass, species richness, and species diversity were greater in ecotone than the stream and littoral zones, I sampled fish monthly in the Ledbetter Creek through Ledbetter Creek Embayment in Kentucky Lake, Kentucky, from April to October 1996 by using throw traps. During the first four months (daytime only) fish density did not vary significantly among zones or among months. However, there were significant differences among zones during the last three months and the stream zone had significantly higher mean fish density than both the littoral zone and the ecotone. Fish biomass also differed significantly among zones during the last three months. The stream zone had the highest mean fish biomass among zones, significantly higher than the ecotone, but not different than the littoral zone. There were no statistically significant differences among zones during the first four months, but mean fish biomass in the stream zone was about eight times higher than the ecotone, The stream zone had the highest fish species richness among zones. Differences were significant among zones during the last three months, and the stream zone (0.98 $\pm$ 0.04) had significantly greater mean fish species richness than the ecotone (0.45 $\pm$ 0.01), but not significantly than the littoral zone (0.56 $\pm$ 0.17). Fish species richness differed significantly among months during the first four months, Monthly species diversities ranged from 0.62 to 1.96 in the stream zone, 0 to a.57 in the ecotone, and 0 to 2.60 in the littoral zone. Combined species diversities in the stream, the ecotone , and the littoral zones were 2.72, 3.58, and 3.10, respectively, There were five families of fishes captured frequently enough for their individual numbers to comprise at least 8 % of the total. Family rankings in the stream zone were opposite of the littoral zone. Percidae was the most abundant family and Clupeidae was absent in the stream zone, whereas Percidae was uncommon and Clupeidae was the most abundant family in the littoral zone. Atherinidae was dominant in the ecotone. Five of the most abundant species comprised 65 % of the total number. The guardian darter occurred only in the stream zone, and it was consistently found in riffles. Longear sunfish and central stoneroller also had significant differences of mean fish densities among zones, and they were found mostly in the stream zone. Threadfin shad and bullhead minnow were almost exclusively caught in the littoral zone. I finally concluded that the ecotone between the stream and the littoral zone in this small-scale freshwater aquatic ecosystem was not as productive as the ones in other ecosystems.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.2
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• pp.118-126
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• 2023

In accordance with the increased demand for ocean use, the Marine Spatial Planning system was introduced to rationally allocate ocean space, under which fishing activity protection zones have been designated to protect fishery activities and promote fishery resource protection. However, fishing vessels that mainly sail in fishing activity protection zones are exposed to risk, such that they account for about 70% of marine accidents that occur in Korea, Proper risk management is thus required. This study aims to analyze marine accidents in fishing activities protection zones and port and navigation zones to secure the safety of fishing vessels passing within fishing activity protection zones. To this end, the traffic volume in marine use zones was investigated, and marine accidents were investigated by ship type, accident type, tonnage, accident cause, and loss of life. Analysis determined that most of the marine accidents per unit area of each type occurred in port and navigation zones, but overall most marine accidents occurred in fishing activity protection zones. In particular, it was found that traffic safety management was necessary because many human accidents occurred.

• Journal of the Korean Association of Geographic Information Studies
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• v.18 no.2
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• pp.45-58
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• 2015

The aim of this study is to find out major accumulation zones through field survey and moving route tracking trials on floating debris of Nakdong River. It also identified composition and accumulated amount of the floating debris by sample survey for accumulation zones. As a result, total 5 accumulation zones were selected from the midstream and downstream of the Nakdong River. There was a large amount of floating debris, including vegetation debris, in the accumulation zones. And two accumulation zones located in the downstream region, it is much more likely to flow into the ocean along river. From the sample survey on the major accumulation zones, more than $40{\ell}$ of floating debris were collected including vegetation and artificial debris. As a result of composition analysis for artificial debris, plastic(49%) and styrofoam(36%) were the majority in number. The present study is expected to help to plan an efficient pre-collecting activity and to reduce floating debris flowing into the ocean from the Nakdong River.