• Journal of the Korean Solar Energy Society
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• v.29 no.5
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• pp.73-80
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• 2009

A tidal current turbine is designed and analyzed numerically by using blade element momentum theory. The rated power has a limitation because the diameter of the tidal current turbine cannot exceed the depth of sea water. This study investigates a horizontal axis tidal-current turbine with a rated power of 500 kW. NACA-6 series laminar foil shape is used for basic airfoil along the blade span. The distributions of chord length and twist angle along the blade span are obtained from the hydrodynamic optimization procedure. Prandtl's tip loss correction and angle of attack correction considering the three-dimensional effect are applied for this study. The power coefficient curve shows maximum peak at the rated tip speed ratio of 6.0, and the maximum torque coefficient is developed at the tip speed ratio of 4. The drag coefficient reaches about 0.85 at the design tip speed ratio.

• The Journal of the Korea Contents Association
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• v.15 no.3
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• pp.168-173
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• 2015

Use of forearm and hip joint bone density scan and find the clinical usefulness of the results that can be inferred as a result of any other region sites injured by a correction factor which if One part up. Groups of 60 patients, 10 patients by age 20-70 were composed of patients measured with the forearm and lumbar spine bone mineral density T-score and Z-score of the survey for each of the three factors that it was Find the correction factor to obtain the relationship. Bone mineral density of the correlation coefficient R = 0.8 correction factor is Y = 1.341X + 0.146. T-score of correlation coefficient R = 0.804 and the correction factor Y = 0.565X - 0.327 is Z-score of the correlation coefficient R = 0.637 correction factor Y = 0.539X - 0.225. It is regarded that there will be a clinical availability which can analogize the result of a part by using the result of the other part. It will be able to determine an auxiliary role in the clinical diagnosis. Correction factor to the equation Y = 1.341X + 0.146 is recommended.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.3
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• pp.133-139
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• 2020

In order to study the resistance test technique for the submerged body in Large Cavitation Tunnel (LCT), DARPA Suboff, submarine model publicly available was manufactured. DTRC released the resistance test data of DARPA Suboff conducted at ship speeds up to 18.0 knots in high-speed towing tank in 1990. As LCT is considered restricted waterways with walls, the resistance test results must be corrected with three wall blockage effects called buoyancy effect, solid blockage effect and wake blockage effect. Before correction, the resistance of LCT was 16~20 % higher than that of DTRC. After correction, the resistance and the resistance coefficients were compared with those of DTRC. The corrected resistance of LCT shows good agreement with that of DTRC. The residual resistance coefficient shows the difference according to the calculation method of buoyancy and frictional resistance coefficient. This paper suggests the best way for the calculation of residual resistance coefficient, On the basis of the present study, it is thought that the operating conditions for the propeller cavitation and noise tests can be drawn through LCT tests.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.6
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• pp.1402-1410
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• 1995

An influence coefficient method with an optimal correction balancing algorithm is developed for balancing a high-speed flexible rotor system. Conventional flexible balancing algorithms such as least square and weighted least square algorithms may not satisfy allowable residual vibration levels in certain speed ranges, while the optimal correction balancing method can be more effective in controlling vibration levels in a target speed. Related analyses were reviewed and applied to a test rig to show the effectiveness of the optimal correction balancing method.

• Bulletin of the Society of Naval Architects of Korea
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• v.12 no.1
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• pp.91-93
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• 1975

• Nuclear Engineering and Technology
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• v.48 no.3
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• pp.642-649
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• 2016

Important safety parameters such as the fuel temperature coefficient (FTC) and the power coefficient of reactivity (PCR) of the CANada Deuterium Uranium (CANDU-6) reactor have been evaluated using the Monte Carlo method. For accurate analysis of the parameters, the Doppler broadening rejection correction scheme was implemented in the MCNPX code to account for the thermal motion of the heavy uranium-238 nucleus in the neutron-U scattering reactions. In this work, a standard fuel lattice has been modeled and the fuel is depleted using MCNPX. The FTC value is evaluated for several burnup points including the mid-burnup representing a near-equilibrium core. The Doppler effect has been evaluated using several cross-section libraries such as ENDF/B-VI.8, ENDF/B-VII.0, JEFF-3.1.1, and JENDL-4.0. The PCR value is also evaluated at mid-burnup conditions to characterize the safety features of an equilibrium CANDU-6 reactor. To improve the reliability of the Monte Carlo calculations, we considered a huge number of neutron histories in this work and the standard deviation of the k-infinity values is only 0.5-1 pcm.

• Geomechanics and Engineering
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• v.15 no.5
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• pp.1081-1089
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• 2018

The deformation and strength of brittle rocks are significantly influenced by the crack closure behavior. The relationship between the strength and deformation of rocks under uniaxial loading is the foundation for design and assessment of such scenarios. The concept of relative crack closure strain was proposed to describe the influence of the crack closure behavior on the deformation and strength of rocks. Considering the crack compaction effect, a new damage constitutive model was developed based on accumulated AE counts. First, a damage variable based on the accumulated AE counts was introduced, and the damage evolution equations for the four types of brittle rocks were then derived. Second, a compaction coefficient was proposed to describe the compaction degree and a correction factor was proposed to correct the error in the effective elastic modulus instead of the elastic modulus of the rock without new damage. Finally, the compaction coefficient and correction factor were used to modify the damage constitutive model obtained using the Lemaitre strain equivalence hypothesis. The fitted results of the models were then compared with the experimental data. The results showed that the uniaxial compressive strength and effective elastic modulus decrease with an increase in the relative crack closure strain. The values of the damage variables increase exponentially with strains. The modified damage constitutive equation can be used to more accurately describe the compressive deformation (particularly the compaction stage) of the four types of brittle rocks, with a coefficient of determination greater than 0.9.

• Journal of the Korea Society of Computer and Information
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• v.15 no.7
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• pp.83-90
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• 2010

In vocabulary recognition system has reduce recognition rate unrecognized error cause of similar phoneme recognition and due to provided inaccurate vocabulary. Input of inaccurate vocabulary by feature extraction case of recognition by appear result of unrecognized or similar phoneme recognized. Also can't feature extraction properly when phoneme recognition is similar phoneme recognition. In this paper propose vocabulary recognition post-process error correction system using phoneme likelihood based on phoneme feature. Phoneme likelihood is monophone training phoneme data by find out using MFCC and LPC feature extraction method. Similar phoneme is induced able to recognition of accurate phoneme due to inaccurate vocabulary provided unrecognized reduced error rate. Find out error correction using phoneme likelihood and confidence when vocabulary recognition perform error correction for error proved vocabulary. System performance comparison as a result of recognition improve represent MFCC 7.5%, LPC 5.3% by system using error pattern and system using semantic.

• The Korean Journal of Nuclear Medicine Technology
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• v.17 no.2
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• pp.10-14
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• 2013

Purpose: Due to developed simultaneous PET/MRI, it has become possible to obtain more anatomical image information better than conventional PET/CT. By the way, in the PET/CT, the linear absorption coefficient is measured by X-ray directly. However in case of PET/MRI, the value is not measured from MRI images directly, but is calculated by dividing as 4 segmentation ${\mu}-map$. Therefore, in this paper, we will evaluate the SUV's difference of attenuation correction PET images from PET/MRI and PET/CT. Materials and Methods: Biograph mCT40 (Siemens, Germany), Biograph mMR were used as a PET/CT, PET/MRI scanner. For a phantom study, we used a solid type $^{68}Ge$ source, and a liquid type $^{18}F$ uniformity phantom. By using VIBE-DIXON sequence of PET/MRI, human anatomical structure was divided into air-lung-fat-soft tissue for attenuation correction coefficient. In case of PET/CT, the hounsfield unit of CT was used. By setting the ROI at five places of each PET phantom images that is corrected attenuation, the maximum SUV was measured, evaluated %diff about PET/CT vs. PET/MRI. In clinical study, the 18 patients who underwent simultaneous PET/CT and PET/MRI was selected and set the ROI at background, lung, liver, brain, muscle, fat, bone from the each attenuation correction PET images, and then evaluated, compared by measuring the maximum SUV. Results: For solid $^{68}Ge$ source, SUV from PET/MRI is measured lower 88.55% compared to PET/CT. In case of liquid $^{18}F$ uniform phantom, SUV of PET/MRI as compared to PET/CT is measured low 70.17%. If the clinical study, the background SUV of PET/MRI is same with PET/CT's and the one of lung was higher 2.51%. However, it is measured lower about 32.50, 40.35, 23.92, 13.92, 5.00% at liver, brain, muscle, fat, femoral head. Conclusion: In the case of a CT image, because there is a linear relationship between 511 keV ${\gamma}-ray$ and linear absorption coefficient of X-ray, it is possible to correct directly the attenuation of 511 keV ${\gamma}-ray$ by creating a ${\mu}$map from the CT image. However, in the case of the MRI, because the MRI signal has no relationship at all with linear absorption coefficient of ${\gamma}-ray$, the anatomical structure of the human body is divided into four segmentations to correct the attenuation of ${\gamma}-rays$. Even a number of protons in a bone is too low to make MRI signal and to localize segmentation of ${\mu}-map$. Therefore, to develope a proper sequence for measuring more accurate attenuation coefficient is indeed necessary in the future PET/MRI.

• Journal of Ocean Engineering and Technology
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• v.27 no.1
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• pp.80-84
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• 2013

This study is to develop the simplified formulae for added mass coefficient of a 2-D floating body with a semi-circle section in a finite water depth. The semi-circle floating body may represent a simplified midship section transformed by Lewis form, which can be used for the ship motion analysis by strip theory. Since the added mass coefficient varies with motion frequencies and sea bottom effect, the correction factor representing the effect of water depth and frequencies is developed for accurate prediction of added mass. Using a two-dimensional numerical wave tank (NWT) technique based on the boundary element method (BEM) including sea bottom boundary the reference values of added mass are calculated to develop the correction factor. For verification and effectiveness of the formulae, the predicted added mass coefficients for various frequencies and water depth ratios are compared with the calculated values from NWT technique.