• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.129-137
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• 2016

Transmission Control Protocol as a transport layer protocol provides steady data transfer service. There are some serious concerns about the performance of TCP over diverse networks. The vital concern in TCP network environment is congestion which may occur due to quick transmission rates or because of large number of new connections entering the network at the same time. Size of queues in routers grows thus resulting in packet drops. Retransmission of the dropped packets, and reduced throughput can prove costly. Explicit Congestion Notification (ECN) in conjunction with Active Queue Management mechanisms (AQM) such as Random early detection (RED) is used for packet marking rather than dropping. In IP packet header ECN bits can be added as a sign of congestion thus avoiding needless packet drops. The proposed ECN and AQM mechanism can be implemented with help of ns2 simulator and the performance can be tested on different TCP variants.

• Journal of The Korean Society of Clinical Toxicology
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• v.1 no.1
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• pp.59-64
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• 2003

Objective: This study was conducted for the nationwide statistical survey of poison exposure to provide the rationale for establishing and developing the poison control center (PCC) in Korea. Design: Study group for Korea PCC in National Medical Center reviewed the medical literature on poison exposure of Korea from death reports of National Statistical Office (NSO), the toxic exposure statistics from the report of National Health Insurance Corporation (NHIC), and poison related data from 119 ambulance services (FD) for the purpose of obtaining the poison and its related data. We also conducted questionnaire from the expert who work in emergency medicine department at the designated 320 emergency medical centers in Korea for the preparedness and acknowledgement about necessity of PCC and their need for that. Results: We reviewed the reliable data from the death report of NSO, poison exposure data from NHIC, and running report from FD. Poisoning death occured at home ($36.7\%$) and hospital ($46.3\%$). Poisoning are more common in rural area than the city area. Patients were seen more frequently in the local clinics than in any hospital. The drugs ($45.7\%$) and pesticide ($18.1\%$) are common poison. Common place to poison exposure were residential area ($39.9\%$), industry ($9\%$). mass residential area ($7\%$). and farm ($6\%$). The education level were primary school ($33.2\%$), high school ($23.7\%$), and middle schol ($21.3\%$) in order. We have to provide the poison guideline for lay public to understand easily, and for medical experts. The medical facilities need to be invested and have more interest for toxicology. All medical staff who work in the designated emergency medical center want PCC to establish. They want to have poison information from hospital ($91.3\%$), regional poison information center ($45.0\%$), regional poison control center ($52.5\%$), nationwide poison information center ($48.8\%$), nationwide poison control center ($46.25\%$), as a role of poison control center. They also want that pcc have poison epidemiologic study and statstics, training program for the experts, registration of rare case of posion on website, reflection of policies to activities for antidote production etc., speedy consultation system for poison analysis, public education, establishment of both regional and national pee, etc. Conclusion: Poison center must be established to provide poison information for all the public and medical experitise, focusing rural area and private clinic, to detoxify, to reduce the cost, time, morbity, and mortality through the whole country.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.139-145
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• 2016

Dumbbell is the most basic topology that can be used in almost all kind of network experiment within it or just by little expansion. While Transmission Control Protocol TCP is the basic protocol that is used for the connectivity among networks and stations. TCP major and basic goal is to provide path and services to different applications for communication. For that reason TCP has to transfer a lot of data through a communication medium that cause serious congestion problem. To calculate the congestion problem, different kind of pre-cure solutions are developer which are Loss Based Variant and Delay Based Variant. While LBV keep track of the data that is going to be passed through TCP protocol, if the data packets start dropping that means congestion occurrence which notify as a symptom, TCP CUBIC use LBV for notifying the loss. Similarly the DBV work with the acknowledgment procedure that is used in when data ACK get late with respect to its set data rate time, TCP COMPOUND/VAGAS are examples of DBV. Many algorithms have been purposed to control the congestion in different TCP variants but the loss of data packets did not completely controlled. In this paper, the congestion control algorithms are implemented and corresponding results are analyzed in Dumbbell topology, it is typically used to analyze the TCP traffic flows. Fairness of throughput is evaluated for different TCP variants using network simulator (NS-2).

• Spatial Information Research
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• v.15 no.4
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• pp.363-370
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• 2007

This study has been carried for the development of the basic algorithm of helicopter navigation system based on TRN (Terrain Referenced Navigation) with information input from the GPS. The helicopter determines flight path due to Origination-Destination analysis on the Cartesian coordinate system of 3-D DTM. This system shows 3-D mesh map and the O-D flight path profile for the pilot's acknowledgement of the terrain, at first. The system builds TCF (terrain clearance floor) far the buffer zone upon the surface of ground relief to avid the ground collision. If the helicopter enters to the buffer zone during navigation, the real-time warning message which commands to raise the body pops up using Matlab menu. While departing or landing, control of the height of the body is possible. At present, the information (x, y, z coordinates) from the GPS is assumed to be input into the system every 92.8 m of horizontal distance while navigating along flight path. DTM of 3" interval has been adopted from that which was provided by ChumSungDae Co., Ltd..

• Journal of KIISE:Information Networking
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• v.27 no.2
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• pp.160-174
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• 2000

Nowadays, most widely used transport protocol, TCP is tuned to perform well in traditional networks where packet losses occur mostly because of congestion. TCP performs reliable end-to-end packet transmission under the assumption of low packet error rate. However, networks with wireless links suffer from significant losses due to high error rate and handoffs. TCP responds to all losses by invoking congestion control and avoidance algorithms, resulting in inefficient use of network bandwidth and degraded end-to-end performance in that system. To solve this problem, several methods have been proposed. In this paper, we analyse and compare these methods and propose appropriate model for improving TCP performance in the network with wireless links. This model uses TCP selective acknowledgement (SACK) option between TCP ends, and also uses caching method at the base station. Our simulation results show that using TCP SACK option with base station caching significantly reduces unnecessary duplicate retransmissions and recover packet losses effectively.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.1
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• pp.1-9
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• 2010

The research which needs when the traffic accident occurs, the assailant and the victim as the assault person the gain and loss as the damage person does in necessity. Produces shame information which is scientific about the traffic accident which occurs, importance in the effect of visual, about the program which based on the fact that provides the tool which is used from the process which reappears an accident embodies is a thing in the objective self-acknowledgement assailant and the victim. From the research which sees traffic accident site easily, will compose and the fact that applies according to in necessary accident investigation process of the simulation program will be able to reappear goal. From the insurance company and the police station expressed the frame about traffic accident and the sample result to apply reappears from the side of visual the application value was expected with the tool which appropriate in accident control is easy very and is.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.6
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• pp.897-906
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• 2022

In this paper, we propose a novel MAC protocol based on the harmonic transmission of ACK, called HAT-LoRa, for improving the reliability and the utilization in multiple gateway LoRa Networks. LoRa is basically vulnerable to collision due to the primitive pure ALOHA-like MAC. Whereas data frame delivery can be guaranteed by the transparent bridge of multiple receiving gateways, ACK is still transmitted by a single gateway in LoRa Network. HAT-LoRa provides the augmented reception opportunity of ACK via the simultaneous transmissions of identical ACK in multiple spreading factors. The proposed method reduces the expected transmission times of ACK double gateway environment as well as single gateway environment, by 55 and 60% in maximum, by 35% and 40% in average, in a single- and double-gateway environment, respectively. Especially, it outperforms under the environment where the distance between end device and gateways are similar to each other.

• The Journal of Korean Society for School & Community Health Education
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• v.3
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• pp.1-13
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• 2002

Female university students generally have a lower intake of nutrition compared to other age groups due to their adverse interests in their appearance. Drinking, smoking, too much weight control, accumulation of psychological and physical stress are causes of inadequate diet. The result is deterioration of hair health. Establishment of good diet and hair care is the foundation of a healthy hair in adulthood. For this reason, there is a great need for a healthy hair care. The data from a questionnaire survey was analyzed with 800 female undergraduate students responding. Seventeen universities were included in the study, 8 of which were from Seoul, 6 from other large cities and 3 from smaller towns. The objective of this study is to investigate the correlations of these factors and to provide preliminary data for developing an effective hair care education program. Results include the following: 1. Knowledge score of hair care based on general characteristics were higher for students in larger cites compare to small cites or regions. Also, students in higher academic year, more allowance, interest in their apparence and family income showed higher knowledge in this field. These factors had meaningful effect on the statistics of this study. 2. Attitude score towards hair care based on general characteristics were higher for students in larger cites compare to small cites or regions. Also, students in higher academic year, more allowance, interest in their apparence and family income showed higher knowledge in this field. These factors had meaningful effect on the statistics of this study. 3. Behavior score towards hair care was higher for students with greater family income, allowance, interest in appearance. These factors had meaningful effect on the statistics of this study. 4. The correlation study between knowledge, attitude and behavior showed that higher the knowledge and attitude, better the behavior. 5. The analysis of factors effecting hair care behavior showed that interest in health, acknowledgement of current hair condition, total family income were a viable factor in predicting hair care behavior. The predictability of regression model is 38.9 %($R^2$) Therefore, in order to maximize the hair care behavior, consistent and systematic study should be earned out to develope an effective education program to improve health interest.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.12
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• pp.1195-1207
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• 2012

Fast and reliable message broadcasting is critical for safety critical applications of VANET due to the urgency and/or significance of the messages for passengers and drivers. For reliable message delivery, a mechanism for checking the reception of message at the neighboring vehicles and retransmitting it if necessary is required. Especially, in urban environments, where the traffic density tends to be high, mechanisms that minimize control message overhead such as beacon are appropriate in order to minimize the message collisions. Furthermore, broadcast delivery is especially difficult at the intersection due to the road side obstacles such buildings, and hence, a mechanism that enables effective and efficient delivery across intersections is required. In this paper, we propose a beaconless reliable and efficient broadcast approach which specifically taking into account the urban streets. The proposed approach checks the message reception of neighboring vehicles implicitly by taking into account the broadcast of message by next vehicle as the acknowledgement. When retransmissions is necessary around the intersections, vehicles located within the intersection area, where the chance of successful signal propagation toward every branch of the intersection is higher due to less signal attenuation caused by road side obstacles, are to do the retransmissions. Simulation results show that the proposed approach can provide better reliability while consume less resources than the existing approaches.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.7
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• pp.612-622
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• 2013

In this paper, we propose a coding packet group-based ARQ scheme (rNC) for file delivery in wireless networks. rNC assumes multiple network coding points between the source and the destination. Each network coding point gathers and codes a group of packets according to the queue polling system. A queue polling system makes a few or several packets available for coding in a queue while polling the other queues in the system. Thus, we assuem a queue polling system at each network coding point. We call this group of packets as coded packet group. Each coding point acknowledges the reception of every code packet group to its previous coding point for reliable delivery. Thus, the intermediate coding points including the source can release its buffer before the packet is delivered to the destination. To guarantee the ultimate file delivery to the destination, the destination sends acknowledgement to the sender. We evaluate our proposed scheme using ns-2 and compare the performance with CodeCast. The results show that rNC works better than CodeCast in terms of packet delivery ratio and control overhead in unreliable wireless networks.