• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.119-128
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• 1993

Effective machine capacity is affected by the physical and geometrical conditions of the fields. In the small and scattered farmland structure field efficiency is greatly influenced by plot geometry. In this paper, a method for estimating field efficiency and effective machine capacity was developed . The developed method was applied to Korean paddy cultivation. Various time elements related to farm operations for small and scattered plots are discussed in this paper . Available working time is divided into two parts, viz. the preparation time for machine operation and actual working time. Two kinds of machine efficiencies, namely , Machine Efficiency 1, applicable on a single large plot or set of well consolidated plots ; and Machine Efficiency 2, applicable on small and scattered multiple plots, are considered. Based assumptions made and steps followed to construct the model are discussed. Effective capacity of each machine based on different plot geometries are calculated y the model. Machine efficiency on a single plot increases with increase in the dimension of longer side of the plot . Low speed, low theoretical capacity machines have higher machine efficiency which is only slightly influenced by plot geometry. As plot geometry is improved , the machine efficiency of high speed, high capacity machines increases rapidly. The effects of short side length and plot size on machine efficiency on a single plot depend on the type of farm operation. For a particular plot shape, as plot size increases, machine efficiency on multiple plots increases rapidly. The effects of consolidation on machine efficiency is highly significant if the plot size is small and/or machine size is large.

• The Journal of the Korea Contents Association
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• v.7 no.4
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• pp.30-38
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• 2007

In this paper, UHF band RFID reader antenna using filbert curve fractal structure and adding the partially grounded plane at the bottom of antenna, which has a resonant frequency at 910MHz, is proposed. Input impedance of antenna is matched with the feed line of 50ohm by varying the length and width of line segment making up the antenna, and by moving the position of via hole. The gain and directivity of antenna is enhanced as varying the dimension of the partially grounded plane and adding the line segment. The size of fabricated antenna is $68mm\times68mm$. The impedance band width(VSWR<2) is $882\sim942MHz$. The return loss and the gain of fabricated antenna are -18.2dB, 5.3dBi at 910MHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2373-2377
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• 2009

In this paper, the threshold voltage characteristics have been analyzed using three dimensional Poisson's equation for FinFET. The FinFET is extensively been studing since it can reduce the short channel effects as the nano device. We have presented the short channel effects such as subthreshold swing and threshold voltage for PinFET, using the analytical three dimensional Poisson's equation. We have analyzed for channel length, thickness and width to consider the structural characteristics for FinFET. Using this model, the subthreshold swing and threshold voltage have been analyzed for FinFET since the potential and transport model of this analytical three dimensional Poisson's equation is verified as comparing with those of the numerical three dimensional Poisson's equation.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.178-180
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• 2006

In general, camera calibration has to be gone ahead necessarily to estimate a position and an orientation of the object exactly using a camera. Autonomous land system in order to run a vehicle autonomously needs a camera calibration method appling a camera and various road environment. Camera calibration is to prescribe the confrontation relation between third dimension space and the image plane. It means to find camera calibration parameters. Camera calibration parameters using the paved road and the unpaved road are estimated. The proposed algorithm has been detected through the image processing after obtaining the paved road and the unpaved road. There is able to detect easily edges because the road lanes exist in the raved road. Image processing method is two. One is a method on the paved road. Image is segmentalized using open, dilation, and erosion. The other is a method on the unpaved road. Edges are detected using blur and sharpening. So it has been made use of Hough transformation in order to detect the correct straight line because it has less error than least-square method. In addition to, this thesis has been used vanishing point' principle. an algorithm suggests camera calibration method using Hough transformation and vanishing point. When the algorithm was applied, the result of focal length was about 10.7[mm] and RMS errors of rotation were 0.10913 and 0.11476 ranges. these have the stabilized ranges comparatively. This shows that this algorithm can be applied to camera calibration on the raved and unpaved road.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.23 no.1
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• pp.7-14
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• 2001

Purpose : The lateral cephalometric Korean norms of the skeletal and pharyngeal dimension were analyzed for the diagnosis of obstructive sleep apnea syndrome(OSAS). Materials and Methods : The lateral cephalometric radiographies were taken in male(n=53) and female(n=50), who had a normal profile, class I occlusion, normal ANB $(0{\sim}4^{\circ})$ and normal Wits $Appraisal(-4{\sim}0mm)$. The X-rays were traced by two oral and maxillofacial surgeons twice. The significant differences between male-female and examiners were tested. Results : The angle of mandibular line to Nasion-Sella line was $31.12^{\circ}/33.79^{\circ}$ (in male/in female, p=0.0018). The lower Gonion angle was $73.74^{\circ}/73.74^{\circ}(p=0.9978)$. The length of the soft palate was 36.93mm/34.35mm(p=0.0002). The pharyngeal airway space was 13.42mm/11.55mm at mandibular plane level(PAS(ML))(p=0.0025). The hyoid was placed inferiorly to mandibular plane 10.18mm/7.72mm(p=0.0051). The results from this study are to be used for the diagnosis of OSAS.

• Journal of ILASS-Korea
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• v.13 no.4
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• pp.212-219
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• 2008

To develop the twin-fluid atomizer having the excellent performance of painting, the spray characteristics of how a wide area can be painted efficiently by one time spraying were studied in this paper. Spray phenomena are affected by the many factors determining the spray field such as the spraying pressure of gas, the spraying pressure and viscosity of liquid paints, the opening duration of needle valve, the design dimension of nozzle, and so on. As the results of experiments, these factors affecting on spray characteristics were suggested as followings; 1) The optimum spraying pressure of gas was $0.015{\sim}0.02\;kPa$, and the appropriate spraying pressure of liquid paint was 0.01kPa, In these situations, the setting up pressures must be compensated as much as the losing amount of pressure because a decompression occurred when operating valves. 2) The duration of opening the needle valve must be sustained for $1{\sim}2$ seconds to inject gas after spraying the liquid paint. This operating of the needle valve was necessary to avoid the affect on the changing of liquid column length, and to prevent the droplet deposit at the initial time of spraying. 3) The spray tip penetration was gained form the experimental equation, and the effective spraying angle was $85^{\circ}{\pm}5^{\circ}$ just at he appropriate spraying pressure of gas. The distribution of the area sprayed had the variation in $350{\pm}50\;mm$ because of the spraying pressure of gas, the its distance from the spray tip, and the lift of the needle valve.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.6 no.3
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• pp.95-100
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• 2007

In this paper, a twice folded TEM horn antenna for 70 kV impulse high power system is proposed. The length reduction of 50 % is achieved by folding a conventional TEM horn antenna twice. The array elements are fed by the stripline power divider using the Chebyshev transformer. The power divider feeds four TEM horn antenna elements with an in-phased uniform power, and it covers a wide bandwidth ($150\;MHz\;{\sim}\;768\;MHz$, VSWR<2.0). Considering the air breakdown at peak 70 kV impulse, the proposed antenna maintains the 25 mm gaps between conducting plates. The dimension of the twice folded horn antenna is $1730\;{\times}\;1600\;{\times}\;300$ (mm3), and the operating frequency is from 152 MHz to 750 MHz under 10 dB return loss. The peak gains are measured from 6.77 dBi to 10.70 dBi at $400\;MHz\;{\sim}\;750\;MHz$.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.2
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• pp.1-8
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• 2017

In order to analyze combustion characteristics of methane-oxygen diffusion flame in a model combustor, combustion experiments were carried out under various spray conditions of propellant scrutinizing combustion stability limit and flame shapes. As the propellant approached the theoretical equivalence ratio condition, a stable detached flame was observed even under high oxygen Reynolds number. And the length of the visible flame increased and the lift-off distance of the flame exhibited a tendency toward decrease. Due to the swirl effect of the propellant by the swirl-coaxial injector, a wide and short flame was produced. Thus, it may be appropriate to employ the swirl-coaxial injector in thrusters having a limited physical dimension.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.3
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• pp.239-248
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• 2007

The accuracy and dimensional stability of rubber impression materials are very important for the fitness of the final restoration. The purpose of this investigation was to evaluate the effects of the storage time and pouring frequency of the additional silicone materials on dimensional stability. Total 30 impressions were made of tooth prepared single crown. The dies had 1 buccolingual, 1 mesiodistal and 1 occlusogingival lines. Two additional silicone materials(examixfine, aquasil) were included. 15 specimens were made of each impression material and poured by type IV stone over times(1hour, 24hours, 72hours) after mixing. 5 impressions poured after 1 hour were used for second pouring after 24hours and third pouring after 72hours. The same examiner measured each specimen 3 times after lazer scanning. All statistical tests were performed with the level of significance set at 0.05. The results indicated that significant difference at any measuring point of stone dies except the buccolingual and mesiodistal lines of the specimen made at 1hour after mixing with examixfine when measurements at 1hour, 24hours and 72hours were campared. There were significant difference between two impression materials and at every measuring point of stone dies made at second and third pouring. The length of measuring point increased significantly as time passed by and increase of the pouring frequency. However, this results are clinically acceptable except the dies of the third pouring. Under the conditions of this study, the shrinkage rate of the additional silicone rubber impression materials significantly increased as time passed by and increase of the pouring frequency.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.471-472
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• 2015

In this paper, a design method for enhancing the gain of a series-fed dipole pair (SDP) antenna using mutiple directors is studied. Strip-type directors are located above the second dipole of the SDP antenna, and the variations of the input VSWR bandwidth and gain depending on the length of the second dipole and the number of directors are analyzed. The antenna is optimized to obtain gain > 8 dBi in the frequency range of 1.7-2.7 GHz, which has three directors in the optimum design. The optimized antenna is designed on an FR4 substrate with a dimension of 86.2 mm by 152.3 mm, and it has frequency bands of 1.67-2.79 GHz for a VSWR < 2 and 1.69-2.72 GHz for a gain > 8 dBi.