• Journal of KIISE:Information Networking
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• v.30 no.5
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• pp.595-603
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• 2003

To provide mobile nodes with continuous communication services, it is important to reduce the packet losses during handoffs. The handoffs of mobile nodes cause packet losses and decrease of TCP throughput on account of a variety of factors. One of those is the congestion in the new cell. Due to the congestion, not only the node moving into the cell but also the already existing nodes that were successfully communicating in the cell suffer the performance degradation. In this paper we propose a new handoff mechanism called‘packet freeze control’, which avoids the congestion caused by handoffs by regulating the influx of traffic burst into the new cell. Packet freeze control is applicable to a wireless network domain in which FAs(Foreign Agents) are connected hierarchically and constitute a logical tree. It gradually increases the number of packets transferred to the new cell by buffering packets in the FAs on the packet delivery path over the wireless network domain. The simulation results show that the proposed mechanism not only reduces the packet losses but also enhances the TCP throughput of other mobile nodes in the cell.

• Journal of the Korean Geographical Society
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• v.38 no.2
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• pp.237-256
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• 2003

The main aim of this paper is to provide a plan for building an effective and competitive innovation system of Daeduck Valley in Korea through analysing the process of knowledge production and commercialisation of venture firms in the perspective of industry-(university) research networks. Since 1997, with the willingness of the government aimed at building' second Sillicon Valley', an ostensible innovation system cantered around the existing science technology town has been able to be built in Daeduck Valley. Nonetheless, some fundamental problems with the knowledge production and commercialisation of venture firms were appeared as the results of this study. It is led tv not only the lack of network agents and institutes that are able to facilitate and coordinate the networks of economic actors comprised of the innovation system, but also the impertinent roles of economic actors. In particular, these problems were differentiated in accordance with the growth stage of venture firms and the processes of knowledge production. Therefore, several policy implications for building innovation system are suggested in the perspective of the complement of existing innovation system of Daeduck, rather than constructing a new innovation system. At the same time, they are provided in accordance with different growth stages and knowledge production processes.

• Journal of the Korean Society for Railway
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• v.11 no.6
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• pp.550-561
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• 2008

The purpose of this paper is to propose a new transit assignment model for intercity rail networks. The characteristics of intercity rail are different from that of public transit in urban area. Line selection probability on route section is introduced to include the characteristics of intercity rail into transit assignment model. Network expansion is more simplified by a assumption line selection probability is externally given. The generalized cost is used to decide the volume of each transit line in most of existing transit assignment models. But, many variables have influence on the volume of each line such as time schedule of transit lines, inter-station distance, passengers' income, seasonal variation of demand and regional characteristics. The influence of these variables can be considered to decide the volume of each line by introducing line selection probability on route section. The tests on a small scale network show that the model proposed in this paper is superior to existing models for predicting intercity rail demand. Proposed model is suitable to consider the complicated fare structure of intercity rail and to draw inter-station demand directly as a result of assignment procedure.

• The Journal of the Korea Contents Association
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• v.21 no.11
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• pp.20-29
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• 2021

This study aims to explore the issue of drones and crime in newspaper articles. BIG KINDS, an online news archive of the Korea Press Foundation, collected 1,213 newspaper articles that met the terms of "drone" and "crime" in 11 central and 28 regional comprehensive newspapers between January 1, 1990 and May 1, 2021. Among them, we perform keyword frequency, centrality analysis, network structure construction, CONCOR analysis, and density matrix analysis on 117 key keywords. According to the analysis, the main issues were classified into eight, and the report analysis on drones and crimes in newspaper articles showed that the government's policy-making and social problems on protecting people's privacy, preventing illegal filming, securing navigation safety, social security and resolution. This study attempts to expand the field of humanities and social studies related to drones and crime, and specifically suggests the current status and counterplan against drone-related crimes as policy implications and media implications.

• Imaging Science in Dentistry
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• v.52 no.3
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• pp.239-244
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• 2022

Purpose: Despite the proliferation of numerous morphometric and anthropometric methods for sex identification based on linear, angular, and regional measurements of various parts of the body, these methods are subject to error due to the observer's knowledge and expertise. This study aimed to explore the possibility of automated sex determination using convolutional neural networks(CNNs) based on lateral cephalometric radiographs. Materials and Methods: Lateral cephalometric radiographs of 1,476 Iranian subjects (794 women and 682 men) from 18 to 49 years of age were included. Lateral cephalometric radiographs were considered as a network input and output layer including 2 classes(male and female). Eighty percent of the data was used as a training set and the rest as a test set. Hyperparameter tuning of each network was done after preprocessing and data augmentation steps. The predictive performance of different architectures (DenseNet, ResNet, and VGG) was evaluated based on their accuracy in test sets. Results: The CNN based on the DenseNet121 architecture, with an overall accuracy of 90%, had the best predictive power in sex determination. The prediction accuracy of this model was almost equal for men and women. Furthermore, with all architectures, the use of transfer learning improved predictive performance. Conclusion: The results confirmed that a CNN could predict a person's sex with high accuracy. This prediction was independent of human bias because feature extraction was done automatically. However, for more accurate sex determination on a wider scale, further studies with larger sample sizes are desirable.

• Journal of the Economic Geographical Society of Korea
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• v.27 no.1
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• pp.53-73
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• 2024

While global production supply chains are expected to shift toward friendly or allied countries, pandemic-shoring such as nearshoring and friendshoring, due to increased protectionism and the reorganization of regional value chains in the wake of the global pandemic, the study found that economic rather than political factors are still at play in consumer supply chains. In the case of Chinese e-commerce market (C-commerce), the study attributes the rapid growth of the market to (1) related regulatory relaxations introduced to stimulate consumption after the end of COVID-19, (2) an increasing pattern of wanting to consume more for a limited income and (3) unconventional business activities to increase their share of the global consumption market. Through these phenomena, the production-consumption network is likely to develop into a more fragmented form, and the consumption network in particular is expected to become more fragmented, influenced by the digital technology war, a phenomenon of re-globalization.

• The Journal of Bigdata
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• v.9 no.1
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• pp.115-126
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• 2024

The scale and cost of disasters are increasing globally, emphasizing the importance of logistics activities in disaster response. A disaster response logistics system must place logistics hub centers in regions relatively safe from disasters and ensure the stable supply of relief goods and emergency medicines to the affected areas. Therefore, this study focuses on locating drone delivery centers that minimize disaster vulnerability when designing a disaster response delivery network. To facilitate the transport of relief supplies via drones, the maximum delivery range of drones is considered and we employed a natural disaster vulnerability index to develop optimization models for selecting drone delivery center locations that minimize disaster vulnerability. The analysis indicates that while the optimization models to minimize disaster vulnerability increase the number of hub investments, these approaches mitigate disaster vulnerability and allows the safe and effective operation of a disaster response logistics system utilizing drone deliveries.

• Journal of the military operations research society of Korea
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• v.11 no.1
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• pp.87-110
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• 1985

This paper presents optimum policy of water supply distribution of the Osaka Prefecural Waterworks System located in the midwest of Japanese Islands. Owing to the ever increasing demand for water, the Osaka Prefectural Government endeavors to expand potable and industrial water distribution system to satisfy the growing water demand of the constituents under its jurisdiction. In this regard, the paper discusses a problem of establishing an efficient and effective water distribution system. The criteria to be considered are stability of water level at the reservoirs, stability of flow in the network, and the water treatment and distribution cost. These objective functions may be combined to form a multiple objective optimization problem or may be used independently and formulated into single objective optimization problems.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.205-207
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• 1998

본 논문은 유선망에서의 {{{{ {SM}^{ 2}A }}}} 무선 ATM 망으로 확장한 방안의 소개한다. {{{{ {SM}^{ 2}A }}}}는 기본적으로 양방향성 공유트리방식의 CBT(Core Baeed Tree)구조를 갖는다. 각 지역망(Regional Network))은 하나의 통신그룹단위를 형성하여 자체적인 코어스위치를 보유하고 이들 코어가 공붕망을 통해 연결되므로써 결과적으로 다중코어 구조를 갖는다. 한편, 무선 ATM 망에서 멀티캐스트 서비스를 제공은 유선망에서의 멀티캐스트 서비스제공방식과는 몇가지 점에서 차이를 가지며 보다 복잡하다. 즉, 동적 그룹관리, 멀티캐스트 채널의 재설정문제, 멀리캐스트 가입 호스트의 핸드오프(Handoff) 문제들이 해결되어야 하는데. {{{{ {SM}^{ 2}A }}}}에는 위의 다양한 문제들을 해결하였으며 더불어 인터넷 멀티캐스트 서비스를 무선망에서 수용하기 위한 안정적 데이터 전송 메커니즘도 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.441-443
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• 1998

본 논문은 유무선 환경에서 ATM 멀티캐스트 서비스를 제공하기위한 방안으로서{{{{ { SM}^{2 }A }}}} 를 제안한다. 기존의ATM 멀티캐스트 서비스는 ATM자체의 제약으로 멀티캐스트 서비스가 제한적이며 비효율적이다. 한편, ATM의 중용한 응용으로서 인터넷서비스를 심각하게 고려해야하는데 {{{{ { SM}^{2 }A }}}}는 특히 인터넷 서비스를 제공하는데 적합한 구조를 갖도록 설계되었다.{{{{ { SM}^{2 }A }}}}는 기본적으로 양방향성 공유트리방식인 CBT(Core Based Tree)구조를 갖되 각 지역망 (Regional Network)에서 자체적인 코어스위치( Core Switch)를 보유함으로써 결과적으로 다중 코어 구조를 갖는다. 각 지역망을 잇기 위하여 PNNI 프로토콜을 이용하며 PGL(Peer Group Leader)에 가상 루트(Virtual Root) 및 가상 리프(Virtual Leaf)의 개념을 새로 도입한다. 멀티캐스트 통신의 경우 가장 문제되는 것이 셀끼워넣기(Interleaving)문제인데.{{{{ { SM}^{2 }A }}}}에서는 ITU-T표준 ATC(ATM Transfer Capability)인 ABT/IT(ATM Block Transfer/Immediate Transmission)