• The KIPS Transactions:PartC
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• v.14C no.6
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• pp.519-524
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• 2007

One of the most important issues on the sensor network with resource limited sensor nodes is prolonging the network lifetime by effectively utilizing the limited node energy. The most representative mechanism to achieve a long lived sensor network is the clustering mechanism which can be further classified into the single hop mode and the multi hop mode. The single hop mode requires that all sensor nodes in a cluster communicate directly with the cluster head(CH) via single hop md, in the multi hop mode, sensor nodes communicate with the CH with the help of other Intermediate nodes. One of the most critical factors that impact on the performance of the existing multi hop clustering mechanism is the cluster size and, without the assumption on the uniform node distribution, finding out the best cluster size is intractable. Since sensor nodes in a real sensor network are distributed non uniformly, the fixed size mechanism may not work best for real sensor networks. Therefore, in this paper, we propose a new dynamic size multi hop clustering mechanism in which the cluster size is determined according to the distance from the sink to relieve the traffic passing through the CHs near the sink. We show that our proposed scheme outperforms the existing fixed size clustering mechanisms by carrying out numerical analysis and simulations.

• Journal of Navigation and Port Research
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• v.30 no.1 s.107
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• pp.53-59
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• 2006

Recently, 8,000TEU class containerships has started operating the shipping service and the mega-containership of over 10,000TEU is on planning. A unit cost in relation to shipping service is decreased by the bigger ship based on the economy of scale. Most of the previous studies have been performed and focused on the total operation cost from mega port to mega port. However, the purpose of this paper is to estimate economic efficiency of selected hub ports from point of view of total cost such as service cost(or operation cost), port charge and feeder cost, etc. First, the service-network of mega containerships is based on data of a domestic shipping company operated main line and economic analysis of individual scenarios on the cost and traffic when 10,000TEU mega containerships offer the services. The three scenarios presented in this paper set up the hub ports which are the port of Busan, Shanghai and Yokohama The results show that port of Busan is economically the most efficient one among others.

• Journal of Society of Preventive Korean Medicine
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• v.17 no.2
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• pp.29-46
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• 2013

A survey conducted on 1,103 patients or caretakers visited Korean medical clinics and hospitals between August 25, 2011 to September 30, 2011 by the Ministry of Health and Welfares and Korea Institute for Health and Social Affairs was analyzed and obtained following results: 1. For sociodemographic distribution, female(813) outnumbered male(290) patients with majority of patients ranging from 30s to 60s. Married patients(793) outnumbered unwed(150) patients and 65.0% with higher than high school education. Statistical significance was seen in gender, age, marital status, and education level but no significant difference for status of employment, income level, and types of insurance between the clinics and hospitals. (P<0.05). 45.1% had less than \2,000,000 in monthly salary and most of coverage was provided by either regional or work insurance. 2. 67.9% of the patients rated health conditions to be better than average and 32.1% listed as poor. People in good health showed tendency to visit Korean medical facilities. Musculo-skeletal conditions such as arthritis, ankle sprain, lumbago, muscular injury, and frozen shoulder were common conditions, followed by gastric disorders, common cold and herbal tonics. No significant difference was observed between the clinics and hospitals for above conditions, but significance was seen in atopic dermatitis, stroke, and sequela from traffic accidents (P<0.05). 3. Ten most common conditions addressed at Korean medical facilities were lumbago, arthritis, muscular injury, back sprain, gastric disorders, ankle sprain, common cold, herbal tonics, frozen shoulder and stroke. Major treatment modalities rendered were herbal medicine, herbal supplements, acupuncture and moxibustion, cupping, tuina, and Korean midical physical therapy. No significant difference existed between the clinics and hospitals. 4. All modalities showed at least 85% effectiveness. No statistical significant difference between the clinics and hospitals except for herbal decoction. (P=0.0452) 5. 88.3% of responses showed treatment satisfaction with significant difference between the clinics and hospitals (P=0.002). The occurrence of side effects was at 2%, mostly corning from treating digestive, skin, kidney disorders and neurological issues. No significant difference was observed between the clinics and hospitals. From the above results, the typical population visiting Korean medical facilities can be summarized as being middle aged female with relatively higher education and moderately low income. The health condition is generally good and the purpose of visit is to receive traditional treatments of acupuncture, herbal medicine, and physical therapy. Treatment efficacy and satisfaction were high with no significant differences between the clinics and hospitals.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5585-5593
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• 2014

This study tested the hypothesis that the significance of the heterogeneous dispersion parameter in safety performance function (SPF) used to estimate the expected crashes is affected by the endogenous heterogeneous prior distributions, and analyzed the impacts of the mis-specified dispersion parameter on the evaluation results for traffic safety countermeasures. In particular, this study simulated the Poisson means based on the heterogeneous dispersion parameters and estimated the SPFs using both the negative binomial (NB) model and the heterogeneous negative binomial (HNB) model for analyzing the impacts of the model mis-specification on the mean and dispersion functions in SPF. In addition, this study analyzed the characteristics of errors in the crash reduction factors (CRFs) obtained when the two models are used to estimate the posterior means and variances, which are essentially estimated through the estimated hyper-parameters in the heterogeneous prior distributions. The simulation study results showed that a mis-estimation on the heterogeneous dispersion parameters through the NB model does not affect the coefficient of the mean functions, but the variances of the prior distribution are seriously mis-estimated when the NB model is used to develop SPFs without considering the heterogeneity in dispersion. Consequently, when the NB model is used erroneously to estimate the prior distributions with heterogeneous dispersion parameters, the mis-estimated posterior mean can produce large errors in CRFs up to 120%.

• Asian Journal of Atmospheric Environment
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• v.12 no.2
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• pp.109-126
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• 2018

This paper presents seasonal variation of $PM_{10}$ over five urban sites in Sabah, Malaysia for the period of January through December 2012. The variability of $PM_{10}$ along with the diurnal and weekly cycles of CO, $NO_2$, $SO_2$, and $O_3$ at Kota Kinabalu site were also discussed to investigate the possible sources for increased $PM_{10}$ concentration at the site. This work is crucial to understand the behaviour and possible sources of $PM_{10}$ in the urban atmosphere of Sabah region. In Malaysia, many air pollution studies in the past focused in west Peninsular, but very few local studies were dedicated for Sabah region. This work aims to fill the gap by presenting the descriptive statistics on the variability of $PM_{10}$ concentration in the urban atmosphere of Sabah. To further examine its diurnal and weekly cycle pattern, its responses towards the variations of CO, $NO_2$, $SO_2$, and ozone were also investigated. The highest mean value of $PM_{10}$ for the whole study period is seen from Tawau ($35.7{\pm}17.8{\mu}g\;m^{-3}$), while the lowest is from Keningau ($31.9{\pm}18.6{\mu}g\;m^{-3}$). The concentrations of $PM_{10}$ in all cities exhibited seasonal variations with the peak values occurred during the south-west monsoons. The $PM_{10}$ data consistently exhibited strong correlations with traffic related gaseous pollutants ($NO_2$, and CO), except for $SO_2$ and $O_3$. The analysis of diurnal cycles of $PM_{10}$ levels indicated that two peaks were associated during the morning and evening rush hours. The bimodal distribution of $PM_{10}$, CO, and $NO_2$ in the front and at the back of ozone peak is a representation of urban air pollution pattern. In the weekly cycle, higher $PM_{10}$, CO, and $NO_2$ concentrations were observed during the weekday when compared to weekend. The characteristics of $NO_2$ concentration rationed to CO and $SO_2$ suggests that mobile sources is the dominant factor for the air pollution in Kota Kinabalu; particularly during weekdays.

• The KIPS Transactions:PartC
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• v.13C no.2 s.105
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• pp.219-226
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• 2006

The shortest path is only maintained during short time because network topology changes very frequently and each mobile nodes communicate each other by depending on battery in MANET(Mobile Ad-hoc Network). So many researches that are to overcome a limitation or consider a power have executed actively by many researcher. But these protocols are considered only one side of link stability or power consumption so we can make high of stability but power consumption isn't efficient. And also we can reduce power consumption of network but the protocol can't make power consumption of balancing. For that reason we suggest RBSSPR(Residual Battery Capacity and Signal Strength Based Power-aware Routing Protocol in MANET). The RBSSPR considers residual capacity of battery and signal strength so it keeps not only a load balancing but also minimizing of power consumption. The RBSSPR is based on AODV(Ad-hoc On-demand Distance Vector Routing). We use ns-2 for simulation. This simulation result shows that RBSSPR can extense lifetime of network through distribution of traffic that is centralized into special node and reducing of power consumption.

• Journal of KIISE:Information Networking
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• v.37 no.3
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• pp.204-216
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• 2010

Since Sensor nodes around a fixed sink have huge concentrated network traffic, the battery consumption of them is increased extremely. Therefore the lifetime of sensor networks is limited because of huge battery consumption. To address this problem, a mobile sink has been studied for load distribution among sensor nodes. Since a mobile sink changes its location in sensor networks continuously, the mobile sink has time limits to communicate with each sensor node and unstable signal strength from each sensor node. Therefore, a fair and stable data collection method between a mobile sink and sensor nodes is necessary in this environment. When some sensor nodes are not able to send data to the mobile sink, a real-time application in sensor networks cannot be provided. In this paper, the new scheduling method, FQMS (Fair Queuing for Mobile Sink), is proposed for fair and stable data collection for mobile sinks in sensor networks. The FQMS guarantees balanced data collecting between sensor nodes for a mobile sink. In out experiments, the FQMS receives more packets from sensor nodes than legacy scheduling methods and provides fair data collection, because moving speed of a mobile sink, distance between a mobile sink and sensor nodes and the number of sensor nodes are considered.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.18 no.6
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• pp.211-221
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• 2019

The death toll for every 10,000 cars registered in Korea is 1.4, which is still the lowest among OECD members, and the need for rescue and response systems is emerging. In response, the company is developing a vehicle ICT-based emergency rescue system (e-Call) that can handle accidents such as rapid and accurate life saving by automatically sending accident detection and related information to the central center in the event of a traffic accident. However, ordinary citizens are negative about the installation and cost of e-Call services. To solve these problems, various introduction and operation methods of e-Call were proposed for activation of terminal distribution. In addition, the effect of introducing e-Call was analyzed by predicting the penetration rate of e-Call terminals. Analysis shows that 463 to 926 deaths and 3,335 to 6,66.9 billion won will be saved in 10 years after the introduction of e-Call terminals.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.1
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• pp.110-122
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• 1993

When voice is transmitted through packet switching network, there needs a overload control, that is, a control for the congestion which lasts short periods and occurrs in local extents. In this thesis, we analyzed the performance of the statistical packet voice multiplexer using the overload control strategy by bit dropping. We assume that the voice is coded accordng to (4,2) embedded ADPCM and that the voice packet is generated and transmitted according to the procedures in the CCITT recomendation G. 764. For the performance analysis, we must model the superposed packet arrival process to the multiplexer as exactly as possible. It is well known that interarrival times of the packets are highly correlated and for this reason MMPP is more suited for the modelling in the viewpoint of accuracy. Hence the packet arrival process in modeled as MMPP and the matrix geometric method is used for the performance analysis. Performance analysis is similar to the MMPP IG II queueing system. But the overload control makes the service time distribution G dependent on system status or queue length in the multiplexer. Through the performance analysis we derived the probability generating function for the queue length and using this we derived the mean and standard deviation of the queue length and waiting time. The numerical results are verified through the simulation and the results show that the values embedded in the departure times and that in the arbitrary times are almost the same. Results also show bit dropping reduces the mean and the variation of the queue length and those of the waiting time.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.389-401
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• 2016

This study attempted to present the monthly distribution of the inshore gill netters for the prevention of propeller failure caused by the damage of fishing gear by the merchant vessels in the West Sea. This study was conducted using the transmitting device of fishing location (V-Pass) data for 1 year in 2014. The grid intervals are $30minute{\times}30minute$ ($latitude{\times}longitude$) based on the section of the sea. A total of 56 sections were analyzed by constructing a grid. The results revealed that the section no. 194 with the highest density index showed no fishing gear damage accident. But the section no. 193 with a relatively lower density index showed more frequent fishing gear damage accident. It is because the section no. 193 is included in the main route of the merchant vessels. Based on this analysis, it is found that the fishing gears are not damaged in proportion to density index but risk of damage exists according to the main routes of merchant vessels. Therefore, for the safe navigation of the merchant vessels, notifying the waters of $34.5^{\circ}{\sim}35.5^{\circ}$ at latitude and $125.67^{\circ}{\sim}126^{\circ}$ at longitude, as a navigational warning area from May through September, will prevent marine accident, such as propeller failure and fishing gear damage. Accordingly, when the merchant vessels navigate in the section no. 193 and 203, the area of $34.5^{\circ}{\sim}35.5^{\circ}$ at latitude and $125.5^{\circ}{\sim}125.67^{\circ}$ at longitude is recommended for the safe navigation.