• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.2 no.4
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• pp.17-25
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• 1991

Slotted coaxial cables are used for a wide variety of radio communications and control applications within buildings, subways, tunnels and outdoors. They function as continuous antennas to solve RF coverage problems in difficult or confined areas. In this paper the electric and magnetic field distributions inside and outside of axially slotted coaxial cables are analyzed numerically. This paper gets the fields from the equivalent potentials which are obtained by grid relaxation method. The slot electric field configurations are consistent with Essam E. Hassan's results. The field distributions in the slotted coaxial cables show that the TEM mode doesn't propagate any longer in them. But the fields don't variate with the frequencies that are under the first higher order mode cutoff frequency of shielded coaxial cable of the same dimension The fields inside of the tunnel ($3\times4$) including the slotted coaxial cable axially are similar to those of $TE_{10}$ mode at 38.75 MHz. This method offers the basis for theoretical analysis of coaxial cables with nonuniform slots as well as coaxial cables in tunnels and buildings.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.9-14
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• 2006

Estimations of depth, magnetic orientation, and strength of dipole moments aid discrimination between unexploded ordnance (UXO) and non-UXO using magnetic surveys. Such estimations may be hindered by geologic noise, magnetic clutter, and overlapping tails of nearby dipole fields. An improved method of inversion for anomalies of single or multiple dipoles with arbitrary polarization was developed to include intra-inversion filtering and estimation of background field gradients. Data interpolated to grids are flagged so that only nodes nearest to measurement stations are used. To apply intra-inversion filtering to such data requires a gapped filter. Moreover, for data with significant gaps in coverage, or along the edges or corners of survey areas, intra-inversion filters must be appropriately modified. To that end, edge-adaptive and gapped gradient-nulling filters have been designed and tested. Applications are shown for magnetic field data from Chongcho Lake, Sokcho, Korea and the U. S. Army's Aberdeen Proving Ground in Maryland.

• Journal of Biosystems Engineering
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• v.38 no.1
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• pp.1-8
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• 2013

Purpose: Path planning and tracking algorithms applicable to various agricultural operations, such as tillage, planting, and spraying, are needed to generate steering angles for auto-guidance tractors to track a point ahead on the path. An optimal coverage path algorithm can enable a vehicle to effectively travel across a field by following a sequence of parallel paths with fixed spacing. This study proposes a path generation and tracking algorithm for an auto-guided Korean tractor with a tillage implement that generates a path with C-type turns and follows the generated path in a paddy field. A mathematical model was developed to generate a waypoint path for a tractor in a field. This waypoint path generation model was based on minimum tractor turning radius, waypoint intervals and LBOs (Limit of Boundary Offsets). At each location, the steering angle was calculated by comparing the waypoint angle and heading angle of the tractor. A path following program was developed with Labview-CVI to automatically read the waypoints and generate steering angles for the tractor to proceed to the next waypoint. A feasibility test of the developed program for real-time path tracking was performed with a mobile platform traveling on flat ground. The test results showed that the developed algorithm generated the desired path and steering angles with acceptable accuracy.

• Journal of Broadcast Engineering
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• v.15 no.1
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• pp.40-51
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• 2010

This paper presents and analyzes field test results of distributed translator (DTxR) for distributed frequency network (DFN) in the ATSC (Advanced Television Systems Committee) terrestrial digital TV broadcasting system. In the field test, according to types of antennas and receivers in areas where are overlapped by two DTxRs' coverage, we measured reception power, noise margin reception possibility, and ease of reception at each test point. By the field test results, when two DTxRs are on, reception power and noise margin are increased than when one DTxR is on. However, reception rate and ease of reception are similar or increased according to types of receivers.

• Journal of Korean Society of Rural Planning
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• v.12 no.4 s.33
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• pp.83-88
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• 2006

Recently, management and restoration efforts using the plants promote the disturbed habitats such as a set-asides or field boundaries. But, side effects are coming out because of using the exotic plants in restoration process. This study was conducted to select the native plant species used for restoration through the vegetation survey and plant community analysis at small stream-side in rural villages. We surveyed at two small stream-sides in open field and high land area in 2005 as a case study. Total 126 species was found at small stream side in open field area. As the result of important value' calculation, Persicaria thunbergii 23.0%, Humulus japonicus 18.6%, Phragmites communis 4.4%, Bromus japonicus 4.2%, and Rosa multiflora 3.4% were in the order of important value. Total 92 species were found at small stream side in high land area. As the result of important value' calculation, Dactylis glomerata 16.1%, Artemisia princeps var. orientalis 11.0%, Persicaria thunbergii 10.9%, Humulus japonicus 9.3%, Phragmites japonica 5.2% and Phragmites communis 3.5% were in the order of important value. We selected some plant species to use in restoration after due consideration of problems of exotic plant and high coverage and density species, and ecological process; Persicaria thunberii, Phragmites communis, Bromus japonicus, Rosa multiflora, Equisetum arvense, Digtaria sanguinalis, Impatiens textori, and Artemisia princeps var. orientalis in open field stream-side, and Artemisia princeps var. orientalis, Persicaria thunbergii, Phragmites japonica, Phragmites communis, Artemisia selengensis, Panicum bisulcatum, Rorippa indica, and Equisetum arvense at hghland stream-side. We will verify the selected native plants and plan the utilization of the native plants in restoration at stream-side in rural village.

• Journal of Environmental Science International
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• v.14 no.11
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• pp.1005-1014
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• 2005

The purpose of this research was to present multi-criteria which were related to the heat island and find methods which decreased heat island affection on the ecological landscape planning. The results of this study were as follows. According to the analysis of surface temperatures, the first grade was the outside-city like a mountain and its temperature was less than $13.0^{\circ}C$. The fifth grade was the downtown, industrial area and its temperature was more than $26.9^{\circ}C$. Therefore, the result was seen the serious heat-island effect. The results of field survey, the closer to the first grade, the higher the value of green coverage. The closer to the fifth grade, the higher the value of impermeability surface, paving materials and colors. According to the correlation analysis, the temperature had high correlation with impermeability surface, paving materials and colors. According to the simple regression analysis, permeability surface, green coverage, topography, impermeability surface, paving materials f: colors, human impact related with surface temperatures. To plan for the decrease of Heat-Island Effect needed the extension of green space, decrease of impermeability surface. This research suggested data for urban green plan and decrease of heat island effect, but there was a limit to get the objective method for grade classification because of lacking in the basic data, the research of multi-criteria will be accomplished continuously.

• Journal of Advanced Navigation Technology
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• v.20 no.3
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• pp.182-189
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• 2016

In this paper, we propose a buoy system based on multi-hop relay networks for ocean observation. The proposed system consists of various sensor modules, a gateway, wireless communication modules, and a remote monitoring site. The sensor modules are integrated with various communication interfaces and connected to the gateway of the proposed buoy system with an unified protocol based on controller area network (CAN)-bus. In order to communicate with the remote monitoring site and extend the coverage, the proposed system uses long-term evolution (LTE) router and XBee mesh network modules. The field test results show that the proposed system can extend the coverage using the proposed multi-hop relay network.

• Korea journal of population studies
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• v.12 no.1
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• pp.19-29
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• 1989

It is well known that vital statistics is of great importance as basic data for establishing various range of national policies. Especially, vital statistics is important among demographic information for monitoring and evaluating the population policy, for constructing life table, for making population projection, and for studying various aspects of the society. In principle, the production of vital statistics is based on the registration system. It is, however, still observed that there are some limitations in utilizing fully the registration system due to the inherent problems such as problems in its coverage, accuracies and timeliness. Thus, as an alternative, many countries conduct survey on vital statistics in order to supplement the registration system and obtain in-depth data. Korea is no exception in this aspect. The National Bureau of Statistics carries out the so-called Continuous Demographic Survey. This is a kind of multi-round retrospective survey, covering 32, 000 households and having reference period of one month. The survey has also characteristics of multi-subject sample. Thus, surveys on economic activity status of population, house-hold income & expenditure, and social indicators are together conducted with the same sample. It is, however, found that the survey itself tends to have some quality problems. Especially, the quality problems connected with field data collection are summarized as coverage error, non-response error and response error. Although it is inevitable not to be free from these errors, we should make all our efforts to reduce the errors. The probable schemes pointed out in this paper are as follows : 1) the strengthening formal quality control activities, 2) the review of the survey method, i. e., the combining interview method with mail-sending and mail-back method or pick-up method, 3) well documentation for various cases found in every stage of data collection, and 4) the strengthening the analytical activities. It is, also, emphasized that sincerity of planners and interviewers is the most important factor among other things.

• Journal of Korean Society on Water Environment
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• v.24 no.6
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• pp.709-717
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• 2008

The field scale experiment which is constructed with four sets (0.88 ha for each set) of wetland (0.8 ha) and pond (0.08 ha) systems was performed to examine the effect of plant coverage on the constructed wetland performance and to recommend the optimum development and management of macrophyte communities. After six growing seasons of wetlands, plant coverage was about 100%. And the concentration of DO showed low value (1.0~5.4 mg/L). This is caused by a blighted plant consumed dissolved oxygen with decay in water column. As the result, water column went to be anaerobic conditions and T-N removal rate are 58~67%. Dead vegetation increased nitrogen removal during winter because it is a source of organic carbon which is an essential parameter in denitrification. However, wetland released phosphorus caused by a blighted plant and accumulation, the removal rate of phosphorus might be decreased. To rise of DO concentration, the three open-waters were constructed in cell 3 and 4. Cell 3 has two open-waters (width 10 m, depth 1.8 m) and cell 4 has one open-water (width 20 m, depth 1.8 m). As the result, DO concentration and treatment efficiency of nutrient and BOD were improved. In case that constructed wetland is operated for a long time, physical circulation structure such as open water help continuous circulation of aerobic and anaerobic conditions. Through the constructed open-water, treatment efficiency of phosphorus and nitrogen in wetland could be improved effectively.

• Journal of Navigation and Port Research
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• v.26 no.1
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• pp.15-21
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• 2002

Re Ministry of Maritime Affairs and Fisheries in Korea completed the installation of 8 maritime DGPS station mfd is to going install 3 additional Maritime DGPS station for the enhancement of dual coverage in Korean coasts until Oct. 2002. Moreover, Korean government decided to provide the NDGPS service over the whole Korean inland area, which will be schedule to complete until June. 2004. On this paper to evaluate the propagation characteristics of using maritime DGPS site as un element of NDGPS ann to evaluate the required number of additional NDGPS sites, the propagation characteristics of the radio waves of 300kHz bands on sea and land nth are studied With the result of study, the conceptional design of Korean NDGPS System is proposed, which consists of 5 NDGPS sites with modified antenna and tかee coverage monitoring sites.