• Korean Journal of Environment and Ecology
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• v.34 no.3
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• pp.259-270
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• 2020

Plants Social Network (PSN) was first used in recent studies to incorporate the plant sociology methods for the understanding of plant society with the social network analysis methods that have recently attracted attention in the social science and visualize and analyze a PSN. The process of construction and analysis on PSN proceeds in the order of setting up the survey area, investigating the appearance plants species on plots of 100㎡, analyzing the interspecific association, building the sociogram, and analyzing the network structure and centrality. This study established a PSN by investigating the appearance species after installing 708 plots to include various dominant vegetational physiognomies in Busan Metropolitan City, where coastal and inland vegetation could be observed simultaneously. The survey found a total of 195 species, including 42 species of evergreen, 151 species of deciduous trees, and 2 species of semi-evergreen trees. The interspecies binding analysis was performed with the focus on the total number of species. It showed the number of friendly species in the order of Eurya japonica (47 species), Trachelospermum asiaticum (46 species), Linder glauca (44 species), Sorbus alnifolia (44 species), and Ligustrum japonicum (41 species). Based on it, we generated a sociogram using Gephi 0.9.2 program. The sociogram was divided into groups that appeared mostly on the coast and those that did not, reflecting the geographical distribution characteristics of forest vegetation in Busan. The analysis of the network structured showed 1,709 links and an average of 17.5 species having interspecies binding with a species. The density was 0.09, the diameter was 5, and the average path distance was 2.268. We concluded that various PSNs should be established in the future for precise comparative analysis of network characteristics in the social science field. In the PSN of Busan Metropolitan City, Eurya japonica, Linder glauca, Ligustrum japonicum, and Trachelospermum asiaticum showed high centrality.

• Journal of Practical Agriculture & Fisheries Research
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• v.22 no.1
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• pp.113-129
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• 2020

In this study we examined the topic analysis and correlation analysis by text mining to extract meaningful information or rules from the self introduction letter of freshman at Korea National College of Agriculture and Fisheries in 2020. The analysis items are described in items related to 'academic' and 'in-school activities' during high school. In the text mining results, the keywords of 'academic' items were 'study', 'thought', 'effort', 'problem', 'friend', and the key words of 'in-school activities' were 'activity', 'thought', 'friend', 'club', 'school' in order. As a result of the correlation analysis, the key words of 'thinking', 'studying', 'effort', and 'time' played a central role in the 'academic' item. And the key words of 'in-school activities' were 'thought', 'activity', 'school', 'time', and 'friend'. The results of frequency analysis and association analysis were visualized with word cloud and correlation graphs to make it easier to understand all the results. In the next study, TF-IDF(Term Frequency-Inverse Document Frequency) analysis using 'frequency of keywords' and 'reverse of document frequency' will be performed as a method of extracting key words from a large amount of documents.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5452-5457
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• 2012

It is saving material cost and construction cost by replacing conventional building materials, and It has advantages for aesthetic value. In the Europe, the United States, Japan and other country research about BIPV is actively being carried out and marketability is also being infinity expanding. Arch type PV systems efficiency characteristics is different depending on PV array's directly connection, parallel connection and arches angle, but is a lack of analysis on this nowadays. When the arch type PV system design up, they consider about aesthetic value and they didn't consider about generation efficiency. In this paper, we try to improve the efficiency through optimization of arch type PV system and estimation of the efficiency parameters of the arch type PV system, such as latitude, longitude, temperature, insolation, arch angle and each kind loss from system organization. For improving Arched PV system efficiency, proposed multiple control inverter system, and using simulation tool of Arched PV system "Solar pro", flat-plate type and many arch type PV system configuration the driving characteristics were compared and analyzed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.430-439
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• 2007

In this paper, we propose a broadband TEM horn antenna optimized using a genetic algorithm. The characteristics required for the TEM horn are the broad matching bandwidth from 2 GHz to 10 GHz and high gain in broadside with a small gain deviation within that bandwidth. In addition, a broadband balun is designed to improve the portability and to reduce the total size of the antenna. The measured return loss of the proposed TEM horn with the broadband balun is less than -10 dB(VSWR<2) from 2 GHz to 10 GHz. Compared to a conventional triangular type TEM horn, the proposed antenna shows about 80 % reduced volume and gives the broadside gain about 12 dBi with a gain deviation less than 6 dB from 2 GHz to 10 GHz. The time domain measurement shows less than 0.4 ns group delay and the pulse measurement using the transmitting signal with the rising time of 58.5 ps shows the received pulse with the rising time of 66.5 ps, which is less than 10 % rising time variation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.122-131
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• 1992

An expert system is developed which can design the power transmission involute cylindrical gears on the basis of strength and durability. Bending strength, surface durability, scoring, and wear probability are considered as the basis. The basic components of the expert system are knowledge base, inference engine, and working memory. The knowledges in knowledge base are classified hierarchically into the knowledges used in selection of gear type, selection of materials, and determination of K factor and are represented by rules. In the inference engine two inference methods are implemented with the depth first search method. For-ward chaining method is introduced in the selection of gear type and materials and in the determination of K factor. Backward chaining method is introduced in the detailed design of module and face width in accordance with the validation of strength. And inference efficiency is achieved by constructing the part needing a lot of numerical calculations in strength estimation separately from inference mechanism. The working memory is established to save the results during inference temporarily. In addition, design database of past design results is built for consultation during design and knowledge acquisition facility, explanation facility, and user interface are included for the usefulness of user. This expert system is written with the PROLOG programming language and the FORTRAN language in numerical calculation part which interfaced with PROLOG and can also be executed on IBM-PC compatible computer operated by MS-DOS alone.

• Journal of Bio-Environment Control
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• v.20 no.3
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• pp.176-181
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• 2011

The fan and pad evaporative cooling system is one of the main cooling methods in greenhouses. Its efficiency is very high, but it has some disadvantages as temperature gradient in greenhouse is large. This study was conducted to reduce the internal temperature gradients in the fan and pad cooling greenhouses. Experiments on cooling performance were carried out in a greenhouse equipped with air duct and integrated fan and pad system as an idea of this study. It showed that the cooling efficiency of an integrated fan and pad system was 75.7% in the first stage and 88.6% in the second stage. When this cooling system was operated for an unshaded and a shaded greenhouse, there were cooling effects of $5.7\sim7.6^{\circ}C$ and $7.4\sim9.7^{\circ}C$ to the control greenhouse, respectively. Maximum temperature differences in a cooling greenhouse, with a length of 18m, were $1.6\sim1.7^{\circ}C$ for shaded conditions and $2.3\sim2.7^{\circ}C$ for unshaded conditions. This greenhouse cooling method, with air duct and integrated fan and pad system, can reduce about 40~50% of the internal temperature gradients in the usual fan and pad cooling greenhouses.

• Journal of the Korean Chemical Society
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• v.54 no.3
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• pp.261-268
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• 2010

In this account, three synthetic methodologies that serve as the basis for new strategies for the preparation of selected natural products are briefly introduced. One process, involving ruthenium carbene catalyzed ring rearrangement metathesis developed by Grubbs and his coworkers, transforms alkene-tethered cycloalkenes to thermodynamically more favored alkene-tethered cycloalkenes. Another ruthenium carbene promoted reaction, referred to as dienyne metathesis, was uncovered in early studies by Grubbs and his collaborators. This process converts dienynes to fused bicyclic conjugated dienes. Finally, a novel photo-electrocyclization reaction of pyridinium salts, which leads to the formation of 4-aminocyclopenten-3,5-diol derivatives, is discussed. Examples are provided to show the utility of these methodologies in natural product synthesis. Emphasis is given to studies in which pyridinium salt photochemistry is coupled with ring rearrangement and dienyne metathesis in routes for the synthesis of polyhydroxyalted indolizidine alkaloids and the construction of the tricyclic core of the lepadiformine and cylindricine alkaloids.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.1
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• pp.72-79
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• 2013

In the paper, a pattern analysis to decide whether the 1st local peak power point near open circuit voltage is the global peak power point or not, in case that the voltage and current at the 1st local peak power point are in a specific range, for Maximum Power Point Tracking on the photo voltaic power conversion system. When a solar cell panel array is shaded partially, multi-local peak power points can occur. That makes it hard to search the global peak power point. Through Tableau analysis using by piecewise linear solar cell model, V-I characteristic of a solar cell panel array circuit when partial shading problem happens, is simulated. The global peak power and the local peak power points is confirmed by simulations. Voltage and current values and patterns of V-I characteristic are analyzed. The generating efficiency of the solar cell panel array is improved, when the solar cell panel array circuit is operated at the power point estimated by setting up specific range.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.4
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• pp.425-442
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• 2004

Statement of problem: A difficulty in achieving a passive-fitting prosthesis can be overcome by individual crown restoation of multiple implants. But individualized crown has another difficulty in control of contact tightness and stress distribution. Purpose: This in vitro study is to evaluate the stress distribution and the magnitude in the supporting tissues around Endopore implants with different crown lengths, interproximal contact tightness, and the splinting effects. Material & methods: Three Endopore implants($4.1{\times}9mm$) were placed in the mandibular posterior edentulous area distal to the canine and photoelastic model was made with PL-2 resin(Measurements Group, Raleigh, USA). Restorations were fabricated in two crown lengths: 9, 13 mm. For non-splinted restorations, individual crowns were fabricated on three custom-milled titanium abutments. After the units were cemented, 4 levels of interproximal contact tightness were evaluated: open, ideal($8{\mu}m$ shim stock drags without tearing), medium($40{\mu}m$), and heavy($80{\mu}m$). For splinted restorations, 3-unit fixed partial dentures were fabricated. This study was examined under simulated non-loaded and loaded conditions(6.8 kg). Photoelastic stress analysis was carried out to measure the fringe order around the implant supporting structure. Results: 1. When restorations were not splinted, the more interproximal contact tightness was increased among the three implants, the more stress was shown in the cervical region of each implant. When crown length was increased, stresses tended to increase in the apex of implants but there were little differences in stress fringes. 2. When nonsplinted restorations were loaded on the first or third implant, stresses were increased in the apex and cervical region of loaded implant. Regardless of interproximal contact tightness level, stresses were not distributed among the three implants. But with tighter interproximal contact, stresses were increased in the cervical region of loaded first or third implant. 3. When the nonsplinted restorations were not loaded, there were little stresses on the supporting structure of implants, but low level stresses were shown in the splinted restorations even after sectioning and soldering. 4. With splinted restorations, there were little differences in stresses between different crown lengths. When splinted restorations were loaded, stresses were increased slightly on the loaded implant, but relatively even stress distribution occurred among the three implants. Conclusions: Splinting the crowns of adjacent implants is recommended for Endopore implants under the overloading situation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.4
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• pp.659-666
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• 2006

Servo-motors are used as key components of automated system by performing precise motion control as accurate positioning and accurate speed regulation in response to the commands from computers and sensors. Especially, the linear brushless servo-motors have numerous advantages over the rotary servo motors which have connection with the friction induced transfer mechanism such as ball screws, timing belts, rack/pinion. This paper proposes an estimation method of unknown motor system parameters using the informations from the sinusoidal driving type linear brushless DC motor dynamics and outputs. The estimated parameters can be used to tune the controller gain and a disturbance observer. In order to meet this purpose high performance Digital Signal Processor, TMS320F240, designed originally for implementation of a Field Oriented Control(FOC) technology is adopted as a controller of the liner BLDC servo motor. Having A/D converters, PWM generators, rich I/O port internally, this servo motor application specific DSP play an important role in servo motor controller. This linear BLDC servo motor system also contains IPM(Intelligent Power Module) driver and hail sensor type current sensor module, photocoupler module for isolation of gate signals and fault signals.