• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12A
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• pp.1225-1232
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• 2008

In this paper, we describe a compensation method of diurnal effect which is one of the factors giving large effect on the performance when using ground-wave signals like Loran-C for a backup and substitute navigation system of global satellite navigation system such as GPS, and currently many researches of the topics are doing in USA and in Europe. In order to compensate diurnal effect, we find periodic frequency components by using the Least Square Spectral Analysis (LSSA) method at first and then compensate the effect by subtracting the estimated compensation signal, obtained by using the estimated amplitude and phase of the individual frequency component, from the original signal. In this paper, we propose a simple compensation algorithm and analysis the performance through simulations. From the results, it is observed that the amplitude and phase can be estimated with under 5 % and 0.17 % in a somewhat poor receiving situation with 0 dB Signal to Noise Ratio (SNR). Also, we analyze the obtainable performance improvement after compensation by using the measured Loran-C data. From the results, it is observed that we can get about 22 % performance improvement when a moving average with 5 minutes interval is employed.

• Journal of the Korean Ceramic Society
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• v.45 no.11
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• pp.701-706
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• 2008

High frequency dielectric ceramics have potential for applications in mobile and satellite communications systems at frequencies higher than 10GHz. The Ba$(Zn_{1/3}Ta_{2/3})O_3$ ceramics are known to have a high quality factor, a small temperature coefficient of the resonance frequency and a high dielectric constant. On the other hands, sintering at high temperature for extended time is required to obtain the ordered structure for high quality factor. In this study, the microwave dielectric properties of $ZrO_2$ and NiO-added Ba$(Zn_{1/3}Ta_{2/3})O_3$ ceramics prepared by solid-state reaction have been investigated. Adding $ZrO_2$ and NiO could effectively promote the densification even the case of decreasing the sintering time. At the surface of samples, secondary phase of Ba-Ta compounds was formed possibly due to the evaporation of ZnO, however, the interior of the samples remained as pure Ba$(Zn_{1/3}Ta_{2/3})O_3$. The samples sintered at $1600^{\circ}C$ for 2h exhibited 1:2 ordering of Zn and Ta cations. Excellent microwave dielectric properties of $Q{\cdot}f$(>96,000 GHz) and ${\varepsilon}_r$=30 has been obtained.

• Journal of Distribution Science
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• v.6 no.1
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• pp.47-62
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• 2008

Joining the WTO in 2001, China became a number of the global economic system. China succeeded in vying to host Beijing 2008 Olympic Games and World Expo 2010 Shanghai. It is China's honor and opportunity to have high economic growth in the coming future. In 2007, the total cost of public logistics decreased by 18.2% than 2006 to 4540.6 billion RMB, accounting for 18.4% of the GDP. So, China logistics is a huge industry and a growing market full of charm. The statistic ratios of China's logistics and growth trends show us it is an important issue to build and run an effective logistics system. However, research on China's logistics systems and supply chain is lacked. This study is focus on the logistic location strategy in China including the study of factories and warehouses geographic strategy concerned with SCM. The core of this study is to propose a New Multi-Facilities Location Decision Model. This study banded the revised gravity center, the standard single facility location decision model(Gravity Center Model) and the transportation model into a new Multi-Facilities Location Decision Model. In addition, this study suggested the gravity center of population, the gravity center of each industry, the location decision graded-list of each industry of china using the gravity center model and the revised gravity center model. The new Multi-Facilities Location Decision Model proposed in this study can be used to solve the location decision problem of more than two facilities. And it can be used in the fields such as the location decision of production facility and service facility, the location of distribution and logistics, the location of broadcast and satellite communications, the location of wireless communication tower and so on.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.517-531
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• 1999

This paper presents the development of the 2-mode variable gain high power amplifier for a transmitter of INMARSAT-M operating at L-band(1626.5-1646.5 MHz). This SSPA(Solid State Power Amplifier) is amplified 42 dBm in high power mode and 36 dBm in low power mode for INMARSAT-M. The allowable error sets +1 dBm of an upper limit and -2 dBm of a lower limit, respectively. To simplify the fabrication process, the whole system is designed by two parts composed of a driving amplifier and a high power amplifier, The HP's MGA-64135 and Motorola's MRF-6401 are used for driving amplifier, and the ERICSSON's PTE-10114 and PTF-10021 are used the high power amplifier. The SSPA was fabricated by the circuits of RF, temperature compensation and 2-mode gain control circuit in aluminum housing. The gain control method was proposed by controlling the voltage for the 2-mode. In addition, It has been experimentally verified that the gain is controlled for single tone signal as well as two tone signals. The realized SSPA has 42 dB and 36 dB for small signal gain within 20 MHz bandwidth, and the VSWR of input and output port is less than 1.5:1 The minimum value of the 1 dB compression point gets 5 dBm for 2-mode variable gain high power amplifier. A typical two tone intermodulation point has 32.5 dBc maximum which is single carrier backed off 3 dB from 1 dB compression point. The maximum output power of 43 dBm was achieved at the 1636.5 MHz. These results reveal a high power of 20 Watt, which was the design target.the design target.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1C
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• pp.86-93
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• 2008

The Galileo system, a global navigation satellite system(GNSS) developed by E.U., uses the direct sequence/spread spectrum(DS/SS) modulation. A DS/SS-based system performs a fine synchronization between the received and locally generated spreading signals, via attacking process. In the absence of multipath signals, using the symmetric characteristic of the correlation function, the delay lock loop with the early minus late discriminator(EL-DLL) offers the best performance in tracking. However, in the presence of multipath signals, the symmetry of the correlation function could be lost, causing a tracking bias. In this paper, we observe that the correlation values in the advanced offset range remain almost unchanged, due to the multipath signals being received later than a line-of-sight signal. Based on this observation, we propose a novel tracking scheme for a Galileo BOC(1,1) system.

• Journal of the Korean Society for Library and Information Science
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• v.13
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• pp.39-71
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• 1986

Interlibrary loan has been a very common library service in the developed countries but it is yet to be actualized formerly in Korea. As Korea is moving toward an information society where all the individual user's request in the library should be met, we need to understand, in detail, the theory and practice of interlibrary loan service. As various information technology has been applied to the libraries, the libraries became the open system. Thus, the libraries become more cooperative, form networks, and make interlibrary loan service available. This study is based on the following three hypothesis formulated from the systems theory. 1. If libraries cooperate each other and form some kind of networks by mail, computers or telecommunications, they become the open system. 2. If a library develops as the open system, interlibrary loan becomes available in the library. 3. If the interlibrary loan system works, the role of the librarians will be changed. The research was carried out by analyzing the various studies about interlibrary loan service and by examining the interlibrary loan systerns presently working in the U.S.. The conclusions are reached deductively from the data. Some of the terminology used are defined as follows: System: a network of interrelated procedures that are joined together to perform an activity or to accomplish a specific objective. It is, in effect, all the ingredient which make up the whole. Cooperation: Working together to benefit participant libraries. Network: a much more structured type of cooperation in which definite regions or areas are connected by electronic or other means to promote interlibrary loaning of materials, in-service traing & other sharing of resources. Interlibrary loan: the lending of books between libraries. The model of cooperation or networks was used to be (1) a star type, (2) a hieranchical type, (3) a distributed type or (4) the combination of aforementioned three. However, the development of the telecommunications and computers enables all kinds of libraires cooperate together. Interlibrary loan service starts with the needs of user's information. The information have to be logically accessed through bibliographies, computers, electronic mails and satellite communications. And the logical access requires the information technology and the libraries become cooperative. The physical access to the information follows next but only traditional method of mail and some commercial service are currently available for this purpose. Therefore, researches are needed to develop this physical access. If the libraries form networks, the microaspect of library changes accordingly as the macroaspect changes. If the libraries . cooperate to become one large world library, the librarians plan, organize, control library operations and report the results. And the librarians work inside and outside of the library to cooperate with other libraries. Only the cooperation of the libraries will enhance interlibrary loan and the Korean librarians have to be prepared to accept the new role of librarianship for the interlibrary loan service.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.1
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• pp.110-121
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• 2016

Link-16 is a representative TDL operated by US air force and NATO and supports structure of Multi-net. Under Multi-net, military operation can be conducted effectively since terminal nodes in Link-16 hop over total frequency band simultaneously. As air traffic is rapidly increasing, new aeronautical system is introduced or existing system should be expanded to accommodate increasing air traffic and frequency band assigned for operating this system is scarce. It is scheduled to implement frequency remapping to solve frequency scarcity. With limited frequency band for operating Link-16, as frequency remapping is implemented, degradation of Multi-net performance can happen since multiple access interference in Link-16 is increasing so it is difficult to conduct multiple military operations. Thus, Group-based frequency hopping scheme is proposed to solve this problem. We verified the performance of the proposed scheme is improved.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.2
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• pp.179-192
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• 2019

Additional frequencies are allocated in maritime digital data exchange to alleviate overload of the VHF data link. The shipborne ad-hoc network (SANET) for this frequencies was subsequently proposed, which provides various IP-based services to ships on behalf of satellite communications. In SANET, a ship should determine its own IP address to achieve IP connectivity to the shore. Accordingly, this paper proposes a SANET configuration (SANETconf) protocol as an IP configuration protocol. SANETconf propagates non-overlapping IP addresses across the network from the shore to ships. A ship obtains its IP address by exchanging Request and Response messages with its neighbors. Therefore, SANETconf eliminates the process of DAD and managing the movement of ships. Extensive simulations were performed to verify the applicability of SANETconf. Based on results, 85% of the ships can determine their own IP address within one frame. Also, SANETconf has a high resource efficiency by using 0.024 percent of resources for IP configuration.

• Korean Security Journal
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• no.41
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• pp.37-66
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• 2014

In recent years, with the development of computers and electronics, electronics and communication technology in a growing and each part is dependent on the cross-referencing makes all electronic equipment is obsolete due to direct or indirect damage EMP. Korea and the impending standoff North Korea has a considerable level of technologies related to the EMP, EMP weapons you already have or in a few years, the development of EMP weapons will complete. North Korea launched a long-range missile and conducted a nuclear test on several occasions immediately after, when I saw the high-altitude nuclear blackmail has been strengthening the outright offensive nuclear EMP attacks at any time and practical significance for the EMP will need offensive skills would improve. At this point you can predict the damage situation of Korea's security reality that satisfy the need, more than anything else to build a protective system of the EMP. The scale of the damage that unforeseen but significant military damage and socio-economic damage and fatalities when I looked into the situation which started out as a satellite communications systems and equipment to attack military and security systems and transportation, finance, national emergency system, such as the damage elsewhere. In General, there is no direct casualties reported, but EMP medical devices that rely on lethal damage to people who can show up. In addition, the State power system failure due to a power supply interruption would not have thought the damage would bring State highly dependent on domestic power generation of nuclear plants is a serious nuclear power plant accident in the event of a blackout phenomenon can lead to the plant's internal problems should see a forecast. First of all, a special expert Committee of the EMP, the demand for protective facilities and equipment and conduct an investigation, he takes fits into your budget is under strict criteria by configuring the contractors should be sifting through. He then created the Agency for verification of performance EMP protection after you have verified the performance of maintenance, maintenance, safety and security management, design and construction company organized and systematic process Guard facilities or secret communications equipment and perfect for the EMP, such as protective equipment maneuver system should take.

• Journal of the Korean earth science society
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• v.28 no.3
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• pp.298-310
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• 2007

Intercomparison between eight radiative transfer codes used for the studies of COMS (Communications, Ocean, and Meteorological Satellite) in Korea was performed under pure molecular, i.e., Rayleigh atmospheres in four shortwave fluxes: 1) direct solar irradiance at the surface, 2) diffuse irradiance at the surface, 3) diffuse upward flux at the surface, and 4) diffuse upward flux at the top of the atmosphere. The result (hereafter called the H15) from Halthore et al.'s study (2005) which intercompared and averaged 15 codes was used as a benchmark to examine the COMS models. Uncertainty of the seven COMS models except STREAMER was ${\pm}4%$ with respect to the H15, comparable with ${\pm}3%$ of Halthore et al.'s (2005). The uncertainty increased under a large $SZA=75^{\circ}$. The SBDART model generally agreed with the H15 better than the 6S model, but both models in the shortwave infrared region were equally good. The direct solar irradiance fluxes at the surface, computed by the SBDARTs of four different users, were different showing a relative error of 1.4% $(12.1Wm^{-2})$. This reason was partially due to differently installing the wavelength resolution in the flux integration. This study may be useful for selecting the optimum model in the shortwave region.