• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.6
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• pp.189-196
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• 1996

We have studied sngle-frequency yield of 1.55${\mu}$m DFB lasers with uniform sinusoidal grating using an effective index transfer matrix method considering both threshold gain difference and spatial hole-burning effect. Optimum grating height and mirror reflectivities that maximize the single-frequency yield are found for a low-reflection (LR)/high-reflection(HR) mirror structure and a LR/as-cleaved miror structure for an assumed basic waveguide structure. LR/HR structure has a high yield of about 80% in a narrow range of grating height while LR/as-cleaved mirror structure has a low yield of about 50% in a relatively wide range of grating height. The effect of the low-reflection facet reflectivity is also studied.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.3
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• pp.177-187
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• 1990

This paper presents that in the Korean Ondol Heating System using hard coal as an usual fuel, what effects an insulation of chimney with the low temperature gas flow has on the optimum chimney height which gives a maximum gas weight flow rate under the general weather data and actual design condition of chimney is compared with the bared chimney and studied. And also, the effects of chimney materials and diameter, dimensionless temperature difference, insulating materials and thickness which have on the optimum chimney height were researched and a good results increasing a maximum gas weight flowrate is obtained by insulating the chimney.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.262-267
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• 2008

The type used mainly in present our country in the superstructure of the railway bridge including the high speed railway is classified by the box girder and the I-type girder, greatly. The box girder is mainly used by the high speed railway bridge, and the I-type girder is used mostly by general railway bridge style. In this study, according to current railway bridge design code, we execute design by the span length of each considered bridge form. Also we analyze the suitable girder height by the span length and calculate the construction costs. The comparative analysis of the structural efficiency is produced by the span length. From this study, it is exposed that the girder height by the span length is the biggest in box girder. Also it is evaluated that the construction costs of the box girder is higher than that of the I-type girder although there is a difference between more or less according to adopted construction method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.3 s.234
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• pp.368-375
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• 2005

We have presented characteristics of a transitional behavior from a premixed flame to a triple flame in a lifted flame according to the change of equivalence ratio. The experimental apparatus consisted of a slot burner and a contraction nozzle for a lifted flame. As concentration difference of the both side of slot burner increases, the shape of flame changed from a premixed flame to a triple flame, and the liftoff height decreased to the minimum value and then increased again. Around this minimum point, it is confirmed a transition regime from premixed flame to triple flame. Consequently, the experimental results of the liftoff height, flame curvature, and luminescence intensity showed that the stabilized laminar lifted flame regime is categorized by regimes of premixed flame, triple flame and critical flame.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.05a
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• pp.58-62
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• 2001

A numerical investigation was performed to determine the effect of airfoil on the optimum flap. height using NACA 0006, 0009, 0012, 0015, 0018, 0021 and 0024 airfoils. The six flaps which have 0.5% chord height difference were used. A Navier-Stokes code, FLUENT, was used to calculate the flow field of the airfoil. The code was first tested as a benchmark by modelling flow around a NACA 4412 airfoil. Predictions of local pressure coefficients are found to be in good agreement with the result of the experimental result. For every NACA 00XX airfoil, flap heights ranging from 0.0% to 2.5% chord were changed by 0.5% chord interval and their effects were also studied. Representative results from each case are presented graphically and discussed. It is concluded that this initial approach gives a promise for the future development of wind turbine optimum design.

• Korean Institute of Interior Design Journal
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• v.21 no.5
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• pp.106-113
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• 2012

A study on techniques to evaluate auditorium assignment visible efficiency using three-dimensional simulation. The most important thing to be considered is to ensure the visibility to the podium upon assigning auditorium of venues, classrooms or seminar rooms. However, since there are so many variables to be considered such as the form of the stage, the area and height of the stage, size of screen, and the distance and angle of the auditorium from the podium, the methods to assign auditorium are staying at the level of basic for a long time. Thus, in this study, we proposed simulation methodology to quantitatively evaluate the three-dimensional visible efficiency based on Visual Graph Analysis (VGA) theory. After analytical methodology manufactures application, it sets examples of visibility depending on location of screen, visibility depending on degree of height difference and visibility about three-dimensional Mass Zoning like a stage and verifies the efficacy. In addition, based on results, visibility expectation curve is drawn and the method to calculate the stepped height depending on necessary visibility is proposed.

• Journal of the Korean Institute of Navigation
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• v.19 no.1
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• pp.9-16
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• 1995

We are confronted with the serious EMI(electromagnetic interference) problems in company with the development of electronic equipments. Accordingly it is also required to construct some anechoic chambers for EMI measurement. Furthermore it is very important to evaluate the chamber characteristics in advance of its construction. For that purpose we have analyzed the characteristics by computer simulation in base on the image method, and compared the results with the measured ones. In case of 3-meter method as a result, the curved line of height pattern of open site varies similarly as that of height pattern of anechoic chamber. When we measure the electromagnetic strength and can get the height pattern curves by frequencies, we utilized it effectively because we can protect instrumental errors in measurement. On the other hand, there is a little difference in site attenuation above 700MHz. When the ferrite grid was used however, the calculated values agree well with the measured values up to 1000MHz with the exception of 30-40 MHz range. The reason is that we don't consider the antenna coupling in the low frequencies of 30-100MHz range.

• Journal of Preventive Medicine and Public Health
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• v.16 no.1
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• pp.35-40
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• 1983

The author investigated the modified Broca's index that could be applied to Korean adults, what is called Korean Broca's Index, with 2322 apparently healthy subjects of 20-59 years old in order to obtain the index which could be used to estimate the standard body weight of Korean adults. The obtained results were as follows: 1. Linear regression equation of body weight to height was Y (weight in kg)=0.7195 X (height in cm)-57.9746 in male, and V (weight in kg)=0.4288 X (height in cm)-16.6528 in female. 2. Estimated constant that could be applied to Korean Broca's Index was 0.93 in male and 0.89 in female, and these sexual difference was statistically significant. (P<0.01)

• Korean Journal of Applied Biomechanics
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• v.16 no.4
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• pp.21-30
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• 2006

The purpose of the study is to search for the possibility of the application of kinematics analysis to physical education at schools and expand its scope of application. This study chose 9 college students majoring in physical education and classified them into type A group who can make the straight, vertical handstand, type B group whose waist is bent, type C group who cannot handstand completely. The center of mass, distance between hand and leg, and the angle and angular velocity of each joint were obtained. The result of this study is this. 1. The time for CM showed 6:4 for A group and 5:5 for B and C groups. The distance between hand and foot in the event 3 was 44% of the height for A group, and 41% for B and C groups. A Group showed the higher CM positional significant difference, it was vertically direction below the hip joint at front. For significant difference of the B Group showed horizontal and vertical velocity of the CM, the highest vertical was obtained in phase 3. The difference of angle of shoulder join in the flexion/extension was showed gradually extension event 2 and the height angular velocity was at phase 3 in the A group. 2 The analysis of the handstand motion revealed that the phase 3, but the maintenance of posture start part the handstand is also very important. Through these results, this study confirmed that the time for phase of the CM, horizontal and vertical positions, velocity, the distance between hands and foot, and the difference of the angle and angular velocity of hip joint and shoulder joint can be set as the variables of analysis. It was also definite cause that the handstand motions of college students majoring in physical education had many difference in performance.

• The Journal of Advanced Prosthodontics
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• v.6 no.6
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• pp.528-538
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• 2014

PURPOSE. The purpose of this prospective study was to evaluate the effectiveness of newly developed autogenous tooth bone graft material (AutoBT)application for sinus bone graft procedure. MATERIALS AND METHODS. The patients with less than 5.0 mm of residual bone height in maxillary posterior area were enrolled. For the sinus bone graft procedure, Bio-Oss was grafted in control group and AutoBT powder was grafted in experimental group. Clinical and radiographic examination were done for the comparison of grafted materials in sinus cavity between groups. At 4 months after sinus bone graft procedure, biopsy specimens were analyzed by microcomputed tomography and histomorphometric examination for the evaluation of healing state of bone graft site. RESULTS. In CT evaluation, there was no difference in bone density, bone height and sinus membrane thickness between groups. In microCT analysis, there was no difference in total bone volume, new bone volume, bone mineral density of new bone between groups. There was significant difference trabecular thickness ($0.07{\mu}m$ in Bio-Oss group Vs. $0.08{\mu}m$ in AutoBT group) (P=.006). In histomorphometric analysis, there was no difference in new bone formation, residual graft material, bone marrow space between groups. There was significant difference osteoid thickness ($8.35{\mu}m$ in Bio-Oss group Vs. $13.12{\mu}m$ in AutoBT group) (P=.025). CONCLUSION. AutoBT could be considered a viable alternative to the autogenous bone or other bone graft materials in sinus bone graft procedure.