• Journal of KIISE:Information Networking
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• v.35 no.2
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• pp.120-129
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• 2008

The purpose of sensor network is gathering the information from sensor nodes. If there are selfish node that deliberately avoid packet forwarding to save their own energy, the sensor network has trouble to collect information smoothly. To solve this problem we suggest a mechanism which uses credit payment schema according to the amount of forwarding packets. Sensor nodes use credits to send their own message and they forward packets of other sensor nodes to get credits. To offer authenticity we combined the roles of sink node and server, also we used piggybacking not to send additional report message. The packet trace route is almost fixed because sensor node doesn't have mobility. In this case, it happens that some sensor nodes which don't receive forwarding packets therefore they can't get credit. So, we suggested the way to give more credits to these sensor nodes. Finally, we simulated the suggested mechanism to evaluate performance with ns2(network simulator). As a result, packet transmission rate was kept on a high rate and the number of arrival packets to sink node was increased. Also, we could verify that more sensor nodes live longer due to deceasing the energy consumption of sensor nodes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.2014-2025
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• 2015

Wireless Sensor Networks (WSNs) are special network which has purpose of usage for gathering information of certain area and observing situation. WSNs consist of small nodes with sensing event such as temperature, movement or certain objects. The sensor has the capabilities to collect data and route data back to the sink. The sensors route data either to other sensors or back to a sink in one direction. That is, traditional WSNs communicate asymmetrically. However, under the new paradigm of the Internet of Things (IoTs) or Cyber Physical system (CPS), WSNs have potential to be used as important area. So, more research is necessary to communicate with each moving objects symmetrically in WSNs. In this paper, we proposed symmetric communication scheme among mobile objects in wireless sensor network. Simulation results show that our scheme is superior th the existing ones in terms of energy consumption and transmission success ratio.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.3
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• pp.155-161
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• 1998

Retardation effect of heavy metals in soils caused by adsorption onto the surfaces of solids particles is well known phenomenon. In this study, we investigated the retardation effect on the mobility of a Zn in a sandy soil by conducting batch and column tests. The column test consisted of monitoring the concentrations of effluent versus time known as a breakthrough curve (BTC). We used NaCl and ZnCl$_2$ solutions with the concentration of 10 g/L as a tracer, and injected them respectively into the inlet boundary of the soil sample as a square pulse type, and monitored the effluent concentrations at the exit boundary under a steady state condition using an EC-meter and ICP-AES. The batch test was conducted based on the standard procedure of equilibrating fine fractions collected from the soil with various initial ZnCl$_2$ concentrations, and analysis of Zn ions in the equilibrated solutions using ICP-AES. The results of column test showed that i) the peak concentration of ZnCl$_2$analyzed by ICP was far less than that of either NaCl or bulk electrical conductivity and ⅱ) travel times of peak concentrations for two tracers were more less identical. The relatively low concentration of Zn can be explained by ion exchange between Zn and other cations, and possible precipitation of Zn in the form of Zn(OH)$_2$due to high pH range (7.0∼7.9) of the effluent. The identical result of travel times of peak concentrations indicates that the retardation effect is not present in the soil. The only way to describe the prominent decrease of Zn ion was to introduce decay or sink coefficient in the CDE model to account for irreversible decrease of Zn ions in the aqueous phase.

• Korean Journal of Agricultural Science
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• v.43 no.3
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• pp.353-359
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• 2016

Soil organic carbon (SOC) retention has gradually gotten attention due to the need for mitigation of increased atmospheric carbon dioxide and the simultaneous increase in crop productivity. We estimated the statistical maximum value of soil organic carbon (SOC) fixed by clay content using the Korean detailed soil map database. Clay content is a major factor determining SOC of subsoil because it influences the vertical mobility and adsorption capacity of dissolved organic matter. We selected 1,912 soil data of B and C horizons from 13 soil series, Sangju, Jigog, Jungdong, Bonryang, Anryong, Banho, Baegsan, Daegog, Yeongog, Bugog, Weongog, Gopyeong, and Bancheon, mainly distributed in Korean upland. The ranges of SOC and clay content were $0-40g\;kg^{-1}$ and 0 - 60%, respectively. Soils having more than 25% clay content had much lower SOC in subsoil than topsoil, probably due to low vertical mobility of dissolved organic carbon. The statistical analysis of SOC storage potential of upland subsoil, performed using 90%, 95%, and 99% maximum values in cumulative SOC frequency distribution in a range of clay content, revealed that these results could be applicable to soils with 1% - 25% of clay content. The 90% SOC maximum values, closest to the inflection point, at 5%, 10%, 15%, and 25% of clay contents were $7g\;kg^{-1}$, $10g\;kg^{-1}$, $12g\;kg^{-1}$, and $13g\;kg^{-1}$, respectively. We expect that the statistical analysis of SOC maximum values for different clay contents could contribute to quantifying the soil carbon sink capacity of Korean upland soils.

• Journal of Environmental Science International
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• v.29 no.1
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• pp.95-108
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• 2020

Silver nanoparticles were loaded onto g-C₃N₄ (CN) with a nanoroll-type morphology (Ag/CN) synthesized using a co-polymerization method for highly selective conversion of toxic nitrobenzene to industrially-valuable aminobenzene. Scanning electron microscopy and high-resolution transmission electron microscopy (HRTEM) images of Ag/CN revealed the generation of the nanoroll-type morphology of CN. Additionally, HRTEM analysis provided direct evidence of the generation of a Schottky barrier between Ag and CN in the Ag/CN nanohybrid. Photoluminescence analysis and photocurrent measurements suggested that the introduction of Ag into CN could minimize charge recombination rates, enhancing the mobility of electrons and holes to the surface of the photocatalyst. Compared to pristine CN, Ag/CN displayed much higher ability in the photocatalytic reduction of nitrobenzene to aminobenzene, underscoring the importance of Ag deposition on CN. The enhanced photocatalytic performance and photocurrent generation were primarily ascribed to the Schottky junction formed at the Ag/CN interface, greater visible-light absorption efficiency, and improved charge separation associated with the nanoroll morphology of CN. Ag would act as an electron sink/trapping center, enhancing the charge separation, and also serve as a good co-catalyst. Overall, the synergistic effects of these features of Ag/CN improved the photocatalytic conversion of nitrobenzene to aminobenzene.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.6
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• pp.1728-1742
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• 2023

In this paper, we extended a hierarchical clustering technique, which is the most researched in the sensor network field, and studied a dynamic differential clustering technique to minimize energy consumption and ensure equal lifespan of all sensor nodes while considering the mobility of sinks. In a sensor network environment with mobile sinks, clusters close to the sinks tend to consume more forwarding energy. Therefore, clustering that considers forwarding energy consumption is desired. Since all clusters form a hierarchical tree, the number of levels of the tree must be considered based on the size of the cluster so that the cluster size is not growing abnormally, and the energy consumption is not concentrated within specific clusters. To verify that the proposed DDC protocol satisfies these requirements, a simulation using Matlab was performed. The FND (First Node Dead), LND (Last Node Dead), and residual energy characteristics of the proposed DDC protocol were compared with the popular clustering protocols such as LEACH and EEUC. As a result, it was shown that FND appears the latest and the point at which the dead node count increases is delayed in the DDC protocol. The proposed DDC protocol presents 66.3% improvement in FND and 13.8% improvement in LND compared to LEACH protocol. Furthermore, FND improved 79.9%, but LND declined 33.2% when compared to the EEUC. This verifies that the proposed DDC protocol can last for longer time with more number of surviving nodes.

• Korean Institute of Interior Design Journal
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• v.21 no.1
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• pp.258-268
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• 2012

The bathroom is a space where humans fulfil certain daily needs, but for the disabled, it can be the most difficult space to use and may even be a cause of accidents and a source of danger. Previous studies on the bathroom have mostly proposed an ideal model of bathroom, but the majority of disabled people live in small homes of about $50m^2$ in size. As their bathrooms are usually very small, and existing houses have various structural limitations, more research should be conducted on the remodeling of residential bathrooms. This study analyzed a number of remodeling items in bathrooms, all of which were listed in previous studies. Based on 17 cases of residential bathroom remodeling in the homes of disabled people residing in Incheon in 2009, this study analyzed several remodeling items required according to the subject's characteristics, such as a lifestyle, gender, and family composition; and proposed the following remodeling requirements and improvement measures for ambulatory-disabled persons and sedentary-disabled people. First, as ambulatory-disabled people have lower-limb impairments, they required bathroom remodeling designed to improve their mobility in the bathroom. These subjects desired the installation of grab bars, as well as the elimination of floor level differences, the installation of non-slip flooring, a counter-top, a sink stand, and a shower holder whose height can be adjusted. Second, sedentary-disabled people move around in a sitting or crawling position, so many of them asked to eliminate floor level differences and vertically-installed bathroom furnishings. Basically, both people with ambulatory disabilities and people with non-ambulatory impairments requested the elimination of floor level differences and the installation of non-slip flooring and grab bars for the toilet and bathtub. They also asked for the heights of sinks, faucets, mirrors, shower holders, and cabinets to be adjusted to suit their needs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.4
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• pp.1224-1248
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• 2022

In various sensor network applications, such as climate observation organizations, sensor nodes need to collect information from time to time and pass it on to the recipient of information through multiple bounces. According to field tests, this information corresponds to most of the energy use of the sensor hub. Decreasing the measurement of information transmission in sensor networks becomes an important issue.Compression sensing (CS) can reduce the amount of information delivered to the network and reduce traffic load. However, the total number of classification of information delivered using pure CS is still enormous. The hybrid technique for utilizing CS was proposed to diminish the quantity of transmissions in sensor networks.Further the energy productivity is a test task for the sensor nodes. However, in previous studies, a clustering approach using hybrid CS for a sensor network and an explanatory model was used to investigate the relationship between beam size and number of transmissions of hybrid CS technology. It uses efficient data integration techniques for large networks, but leads to clone attacks or attacks. Here, a new algorithm called SBEA (Snowball Endurance Algorithm) was proposed and tested with a bow. Thus, you can extend the battery life of your WSN by running effective copy detection. Often, multiple nodes, called observers, are selected to verify the reliability of the nodes within the network. Personal data from the source centre (e.g. personality and geographical data) is provided to the observer at the optional witness stage. The trust and reputation system is used to find the reliability of data aggregation across the cluster head and cluster nodes. It is also possible to obtain a mechanism to perform sleep and standby procedures to improve the life of the sensor node. The sniffers have been implemented to monitor the energy of the sensor nodes periodically in the sink. The proposed algorithm SBEA (Snowball Endurance Algorithm) is a combination of ERCD protocol and a combined mobility and routing algorithm that can identify the cluster head and adjacent cluster head nodes.This algorithm is used to yield the network life time and the performance of the sensor nodes can be increased.

• Journal of the Mineralogical Society of Korea
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• v.27 no.4
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• pp.301-310
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• 2014

To investigate the role of fault gauge in the behavior of heavy metals caused by the acid rock drainage in the area of pyrite-rich andesite, XRD, pH measurement, XRF, SEM-EDS, ICP, and sequential extraction method were used. Bed rock consists of quartz, pyrophyllite, pyrite, illite, and topaz, but the brown-colored fault gouge is composed of quartz, illite, chlorite, smectite, goethite, and cacoxenite. The mineral composition of bed rock suggests that it is heavily altered by hydrothermal activity. The concentrations of heavy metals in the bed rock are as follows, Zn > As > Cu > Pb > Cr > Ni > Cd, and those in fault gouge are As > Zn > Pb > Cr > Cu > Ni > Cd. The concentrations of the heavy metals in the fault gouge are generally higher than those in the bed rock, especially for Pb, As, and Cr, which were more than twice as those in the bed rock. It is believed that the difference in the amount of heavy metals between the bed rock and the fault gouge is mainly due to the existence of goethite which is the main mineral composition in the fault gouge and can play important role in sequestering these metals by coprecipitation and adsorption. The low pH, caused by oxidation of pyrite, also plays significant role in fixation of those metals. It is confirmed that the fractions of labile (step 1) and acid-soluble (step 2), which can be easily released into the environment, were higher in the bed rock. Those fractions were relatively low in fault gauge, suggesting that fault gauge can play important role as a sink of heavy metals to prevent those ones from being released in the area where the acid rock drainage can have an influence.