• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1172-1172
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• 2001

Compact Near Infrared Diode Array Spectrometers offer new possibilities for on line quality assurance in the agricultural sector. Due to their speed and complete robustness towards temperature fluctuations and mechanical shock Diode Array Spectrometers are suitable for the use on Agricultural Harvest Machines. The growing consumer consciousness of food quality in combination with falling manufacturing prices demands procedures for an effective quality control system. The various conventional types of NIR instruments which have so far been used in laboratories are unsuitable for mobile applications under the rough conditions of field cropping not only because of their slow speed of measurement but also because of their shock sensitive filter wheels and monochromators necessary for fractionating polychromatic light. Another advantage of the on line use is the reduction of the sampling error because of the continuously measurement of the whole product. Considering the large economic importance of the dry matter content on agricultural products it is of particular advantage that water belongs to those constituents which are most easily assessed in the near infrared. While other constituents of economic importance such as starch, oil and protein in grains and seeds have a much lesser effect on NIR signals, their contents can nonetheless be assessed with high analytical precision on freshly harvested grains and seeds. In the last years several applications for on line quality assessment on harvesting machines were developed and tested. The talk will give an overview and outlook on existing and future possibilities of this new field of NIR applications.

• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.106-112
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• 1994

The injection-locking of the broad-area diode laser was analysed by using the Fabry-Perot model. The far-field pattern of the output beam was able to be treated by superposing the individual beams emitted from the front facet due to the multiple reflections between the front and rear facets. and the exact near and far field patterns were obtained. The angle-steering effect according to change of the incident frequency was changed was calculated and found to be 0.022 degree/GHz with a bandwidth of 120 GHz.20 GHz.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.53-58
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• 2008

Film cooling effectiveness on a flat plate was measured with pressure sensitive paint. The pressure sensitive paint(PSP) changes the intensity of its emissive light with pressure and the characteristic was used in film cooling effectiveness measurement. The film coolants were air and nitrogen, and by comparing the intensity of PSP coated surface with each coolant, the film cooling effectiveness was calculated. Three blowing ratio of 0.5, 1, and 2 were tested with two mainstream turbulence intensities. Results clearly showed the effect of blowing ratio and mainstream turbulence intensity. As the blowing ratio increases, the film cooling effectiveness was decreased near the film cooling holes. However, the film cooling effectiveness far downstream from the injection hole was higher for higher blowing ratio. As the mainstream turbulence intensity increased, the film cooling effectiveness was decreased at far downstream from the injection hole.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.12
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• pp.969-976
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• 2014

Nowadays, it is required for naval ships to estimate 3D underwater radiated noise pattern in all direction at peak frequencies of hull vibration for the reduction of being detected and doing the effective operation. For this purpose, the numerical method has to be developed to calculate 3D underwater radiated noise pattern with experimental data. It is very difficult to obtain the experimental data for the real ship. Alternative to get the experimental results is to use NAH(near-field acoustic holography) in acoustic tank with experimental model. Application of NAH in acoustic tank for the experimental model needs some investigation of reflection wave from the wall of the acoustic tank and unmeasured zone of the experimental model due to the supporting structure for it. In this study, the effect of reflection wave in the acoustic tank and unmeasured area of the experimental model when using the NAH was investigated with experiment and numerical model. From these, it is known for the error due to reflection wave can be reduced when the distance between the measurement plane and source is being shorten. Also, unmeasured area of the experimental model gives rise to some error in the estimation of the far-field acoustic pressure.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.3
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• pp.263-269
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• 2003

Magnetic flux leakage (MFL) signals were used for corrosion inspection of buried oil and gas pipeline. 3D finite element analysis was used to examine the effects of far and near-side pit depth and tensile stress on MFL signals. Anisotropci materials were used, and the effects of simulated tensile stress on MFL were investigated. The axial and radial MFL signals depended on far and near-side single pit depth and on the bulk stress, but the circumferential MFL signal did not depend on them. The axial and radial MFL signals increased with increasing pit depth and the bulk stress, but the circumferential MFL signal was scarcely changed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.8 s.101
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• pp.891-896
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• 2005

On the basis of theoretical studies on the effect of the cylinders attached to semi-infinite screens, the tangential sound power-transport parallel to the surface of the attached cylinder is minimized by means of a secondary sound field, which is generated from a part of the attached cylinder. The numerical study shows the possibility of deflecting the incident sound by minimizing the sound field of the upper sections. The acoustical shadow region was more pronounced in both near- and far-field compared to the passive case with rigid surface, i.e. without active control. For a relatively wide frequency range it was possible to enhance shielding effects only with few secondary sources and error microphones. In this paper effects of control parameters on the actively controlled sound field near the top edge of noise barriers are studied. Results of numerical study and model measurements are shown and discussed.

• Journal of computational fluids engineering
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• v.2 no.1
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• pp.37-45
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• 1997

벽면 근처에 가까이 위치하는 회전와류쌍을 음원으로 갖는 비정상 유동장에서 벽면이 음장에 미치는 효과를 알아보기 위해 이차원 음장 수치해석을 시도하였다. 비압축성 유동장에 대한 비정상 수력정보를 기반으로 오일러식에서 교란 압축성 소음항을 도출하였다. 원거리 자유 경계면은 비반사 경계조건을 이용하였으며, 벽면에서는 벽면 효과를 음향장에 고려하였다. 자유흐름장에 놓인 와류쌍이 대칭인 나선팔을 갖는 반면에, 벽면이 있는 경우엔 음파가 전달되는 경로를 따라 방향성이 존재함을 알 수 있었다. 본 연구를 통하여 벽면이 존재하는 경우에 비정상 수력정보를 이용하여 근거리와 원거리 음장을 동시에 수행할 수 있음을 알아내었다.

• Earthquakes and Structures
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• v.15 no.2
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• pp.203-214
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• 2018

Deflection control in tall buildings is a challenging issue. Connecting of the towers is an interesting idea for architects as well as structural engineers. In this paper, two reinforced concrete core-wall towers are connected by a truss bridge with buckling restrained braces. The buildings are 40 and 60-story. The effect of the location of the bridge is investigated. Response spectrum analysis of the linear models is used to obtain the design demands and the systems are designed according to the reliable codes. Then, nonlinear time history analysis at maximum considered earthquake is performed to assess the seismic responses of the systems subjected to far-field and near-field record sets. Fiber elements are used for the reinforced concrete walls. On average, the inter-story drift ratio demand will be minimized when the bridge is approximately located at a height equal to 0.825 times the total height of the building. Besides, because of whipping effects, maximum roof acceleration demand is approximately two times the peak ground acceleration. Plasticity extends near the base and also in major areas of the walls subjected to the seismic loads.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.548-554
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• 2000

The aim of this paper is to understand the time averaged pressure distributions in a high-speed centrifugal compressor channel diffuser at design and off-design flow rates. Pressure distributions from the impeller exit to the channel diffuser exit are measured and discussed far various flow rates from choke to near surge condition, and the effect of operating condition is discussed. The strong non-uniformity in the pressure distribution is obtained over the vaneless space and semi-vaneless space caused by the impeller-diffuser interaction. As the flow rate increases, flow separation near the throat, due to large incidence angle at the vane leading edge, increases aerodynamic blockage and reduces the aerodynamic flow area downstream. Thus the minimum pressure location occurs downstream of the geometric throat, and it is named as the aerodynamic throat. And at choke condition, normal shock occurs downstream of this aerodynamic throat. The variation in the location of the aerodynamic throat is discussed.

• Wind and Structures
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• v.15 no.1
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• pp.43-64
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• 2012

Many potential small wind turbine locations are near obstacles such as buildings and shelterbelts, which can have a significant, detrimental effect on the local wind climate. A neural network-based model has been developed which predicts mean wind speed and turbulence intensity at points in an obstacle's region of influence, relative to unsheltered conditions. The neural network was trained using measurements collected in the wakes of 18 scale building models exposed to a simulated rural atmospheric boundary layer in a wind tunnel. The model obstacles covered a range of heights, widths, depths, and roof pitches typical of rural buildings. A field experiment was conducted using three unique full scale obstacles to validate model predictions and wind tunnel measurements. The accuracy of the neural network model varies with the quantity predicted and position in the obstacle wake. In general, predictions of mean velocity deficit in the far wake region are most accurate. The overall estimated mean uncertainties associated with model predictions of normalized mean wind speed and turbulence intensity are 4.9% and 12.8%, respectively.