• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1549-1551
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• 1998

We have designed and developed narrow bandpass multipole filters for satellite communication using $YBa_2Cu_3O_{7-x}$(YBCO) thin films on MgO substrates. The superconducting film used in this study was prepared by laser ablation on one side polished MgO (100) substrates. A Nd:YAG laser was used to fabricate YBCO thin films. The wave length of the laser was 355 nm. The laser beam was focused onto a YBCO target rotating linearly to avoid deep craters that may eject macroscopic YBCO particles. The YBCO films were grown at $750^{\circ}C$ in the oxygen partial pressure of 200 mTorr. The deposited YBCO thin films were patterned by conventional wet-etching method. The transition temperatures of YBCO thin films were 85 - 88 K and the film thicknesses were about 5,000 $\AA$. By comparing the performances of normal-metal filters and YBCO filters, we observed that superconducting YBCO multipole filters have been showed superior performances at 77 K.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.183-190
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• 2017

Recently, BIM (Building Information Modeling) has been attracting attention as a next-generation architectural design tool. The strength of BIM technology is that it enables collaborative work and it is shared in real time. The Revit program, an architectural design program for BIM technology, enhances the information input side, making it possible to know the information of components at the design stage. However, in the use of the Revit program, it is impossible to share or reuse a family created by one designer with another designer. In order to overcome this inefficiency, we designed the design drawing as an Excel file and made it easy to create.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.620-623
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• 2014

Network topology for communication between vehicles are quickly changing because vehicles have a special movement pattern, especially character which is quickly changed by velocity and situation of road. Because of these feature, it is not easy to apply reliable routing on VANET(Vehicular Ad-hoc Network). Clustering method is one of the alternatives which are suggested for overcoming weakness of routing algorithm. Clustering is the way to communicate and manage vehicles by binding them around cluster head. Therefore choosing certain cluster head among vehicles has a decisive effect on decreasing overhead in relevant clustering and determining stability and efficiency of the network. This paper introduces new cluster head selection algorithm using RSU(Road Side Unit) different from existing algorithms. We suggest a more stable and efficient algorithm which decides a priority of cluster head by calculating vehicles' velocity and distance through RSU than existing algorithms.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.93-102
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• 2018

This paper reports a Surge Protective Device (SPD) that is used to protect an automatic metering interface (AMI) power supplies of communication equipment on a low-voltage distribution system from a lightning current. The surge protective device (SPD) can be classified as one-port SPDs and two-port SPDs with decoupling elements depending on the connection type. The protection of internal systems against the lightning current may require a systematic approach consisting of coordinated SPDs. To deal with this, the definition of a lightning protection zone (LPZ) was studied and interpreted through a theoretical review. Because the lightning current resulting from a lightning surge is considerably high, there is limited protection from one SPD; therefore, coordinated cascaded MOV-based SPDs are installed to solve this problem. Regarding the power grid mentioned in this paper, a class II SPD for the low-voltage distribution system installed on the border of LPZ1 and LPZ2, which establish a protection coordination with the Arrester (LA, SA) that corresponds to the LPZO installed on the MOF stage connected to one system were designed to protect various communication (control) equipment, including the automatic meter reading system inside the branch-type electric supply panel of a building, not the incoming side of one system. In addition, performance-related tests were done by a comparison with the existing method through testing, and the optimal design was achieved for the 1-port SPD that uses a series connection and can bleed load current without any decoupling element.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.6 no.1
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• pp.9-20
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• 1981

The organization of Ministry of communications shall be remarkably reorganized, in accordance with the inauguration of Korea Telecommunication corporation which will operate independently from the Ministuy, starting from on the 1st of January, 1982. On this accasion. I, as one of communication scientists, would like to recommend some suggestions for the development of Telecommunications policy and Radio Administration which should be the most important departments of Korea, particularly confined to the organizational structure and personnel administration of the Ministry of Communications. With a view to make a comparative perspective, I took the model of Japanese Telecommunications Administration because of its efficient performance by way of coordinationg between business side of Corporation (N.T.T.) and regulatory side of the Ministry of Post and Telecommunication. This study is mainly based on domestic and foreign books and documents.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.12
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• pp.1-6
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• 2004

In this study, heat and discharge treatments are arbitrary simulated for finding out the initiations and processes of surface degradation on the surface of polymer for using as a PCB substrate. Thermal-treatment changed the surface to the hydrophobic one with the increase of contact angle and surface potential decay, respectively. The XPS spectrum showed that the increased hydrophobicity in thermal treatment was originated from the continuous decrease of side-chains caused by secessions of oxygen groups and the increase of unsaturated double bond in carbon chains. Also, thermal-treatment caused the discoloration on the point of treated surface. These phenomena were attributed to the generation of ether group. In the chemical change by discharge treatment, a lot of side-chains occurred on the treated surface, and so the hydrophilicity increased as time elapsed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.4
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• pp.671-690
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• 2010

The continuous growth of attacks in the Internet causes to generate a number of rules in security devices such as Intrusion Prevention Systems, firewalls, etc. Policy anomalies in security devices create security holes and prevent the system from determining quickly whether allow or deny a packet. Policy anomalies exist among the rules in multiple security devices as well as in a single security device. The solution for policy anomalies requires complex and complicated algorithms. In this paper, we propose a new method to remove policy anomalies in a single security device and avoid policy anomalies among the rules in distributed security devices. The proposed method classifies rules according to traffic direction and checks policy anomalies in each device. It is unnecessary to compare the rules for outgoing traffic with the rules for incoming traffic. Therefore, classifying rules by in-out traffic, the proposed method can reduce the number of rules to be compared up to a half. Instead of detecting policy anomalies in distributed security devices, one adopts the rules from others for avoiding anomaly. After removing policy anomalies in each device, other firewalls can keep the policy consistency without anomalies by adopting the rules of a trusted firewall. In addition, it blocks unnecessary traffic because a source side sends as much traffic as the destination side accepts. Also we explain another policy anomaly which can be found under a connection-oriented communication protocol.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.3
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• pp.162-169
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• 2018

Net neutrality, which has not been a problem, has recently become a problem for ISPs (Internet Service Providers), and their complaints have been paid by domestic platform companies, but overseas global IT companies such as Google and YouTube, generate huge revenues from domestic markets. In this situation, domestic IT companies claim that it is natural to impose more expensive charges or restrict speed on users who generate huge traffic. On the other side, however, the telecommunication network has become an essential public good that is essential to our everyday life, and because it has been given a monopoly position by a private company to efficiently respond to the explosive demand for telecommunication services, It is necessary to provide equal and universal service and fulfill public duty. In this paper, we deal with the network neutrality problem, focusing on the price elasticity between the CP (Contents Provider) and the ISP, rather than the user who is one side of the two-sided market for the already saturated satellites communication market. We present a game model that determines the optimal price for each platform by Nash equilibrium and analyze how the net neutrality affects CP according to the change of exogenous variables through the proposed game model.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.2
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• pp.450-454
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• 2015

In this paper, when points with weights are given in a plane, for an arbitrary constant r, we shall find a square area S such that the sum of weights of points belonging to S is maximized. If the length of the side of S is not given, the problem to find arbitrary rectangular area has been studied. In this paper, we will consider the problem to find a square area with a side of a length r when a constant r is given. We will solve the one dimensional problem in dynamic environment and propose an algorithm with the time complexity of O(nlogn+rn).

• Journal of Broadcast Engineering
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• v.16 no.4
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• pp.635-646
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• 2011

In distributed video coding, low complexity encoder can be realized by shifting encoder-side complex processes to decoder-side. However, not only motion estimation/compensation processes but also complex LDPC decoding process are imposed to the Wyner-Ziv decoder, therefore decoder-side complexity has been one important issue to improve. LDPC decoding process consists of numerous iterative decoding processes, therefore complexity increases as the number of iteration increases. This iterative LDPC decoding process accounts for more than 60% of whole WZ decoding complexity, therefore it can be said to be a main target for complexity reduction. Previously, HDA (Hard Decision Aided) method is introduced for fast LDPC decoding process. For currently received parity bits, HDA method certainly reduces the complexity of decoding process, however, LDPC decoding process is still performed even with insufficient amount of parity request which cannot lead to successful LDPC decoding. Therefore, we can further reduce complexity by avoiding the decoding process for insufficient parity bits. In this paper, therefore, a parity request estimation method is proposed using bit plane-wise correlation and temporal correlation. Joint usage of HDA method and the proposed method achieves about 72% of complexity reduction in LDPC decoding process, while rate distortion performance is degraded only by -0.0275 dB in BDPSNR.