• The KSFM Journal of Fluid Machinery
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• v.19 no.5
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• pp.5-11
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• 2016

The purpose of this study is to design the transonic centrifugal compressor impeller with splitter blades and analyze the flow fields with respect to various splitter blades. Seven impellers with different splitter chord length or pitchwise location were tested by using CFD method. To investigate aerodynamic performance, Mach number distribution and entropy distribution were confirmed. As a result, it is found that the size of transonic region and shock wave location are related to the splitter chord length and pitchwise location. Also the impeller with long chord length of splitter shows higher total pressure ratio but lower efficiency than those of the impeller with short chord length of splitter. In terms of pitchwise location, the impeller with the splitter located in mid-pitch of main blades shows the best performance with respect to pressure ratio and efficiency.

• Journal of Astronomy and Space Sciences
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• v.19 no.2
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• pp.151-162
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• 2002

Two approximate calculation models for a cosmic radiation shielding in satellite are compared with detailed 3-dimensional calculation results. One is a sectoring method and the other is a chord-length distribution method. Shielding caltulation is performed for KITSAT-1 under the assumed environment at SAA (South Atlantic Anomaly) location with AP-8 radiation spectrum model. When both approximate models are applied, calculation error is expected compared with 3-D detailed geometry calculation because of straight knock-on assumption neglecting the deflection of incident proton. However, both approximate models showed good agreements with 3-dimensional detailed Monte Carlo calculation in two dose detector locations.

• Journal of Korean Institute of Industrial Engineers
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• v.20 no.1
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• pp.87-98
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• 1994

This paper describes a method of constructing VC2 Chord-length spline surface from semi-evenly spaced 3D point array. The suface uses Hermite interpolant as Ferguson surface, and it is an extention of chord-length spline curve to surface The proposed surface may be widely used in interpolating smoothly 3D point data obtaind by measurement or engineering design.

• Bulletin of the Korean Mathematical Society
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• v.58 no.2
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• pp.433-444
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• 2021

In this paper a new generating procedure of a random chord is presented. This problem has its roots in the Bertrand's paradox. A study of the limit behaviour of its maximum length and the rate of convergence is conducted. In addition, moments of record values of random chord length are obtained for this case, as well as other cases of solutions of Bertrand's paradox.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.5 s.170
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• pp.45-54
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• 2005

The purpose of this research is to find a simple and accurate NURBS interpolator for CNC systems such as robot, CMM and CNC machine tools. This paper presents a new design of NURBS interpolator for CNC system. The proposed algorithm used the recursive characteristics of NURBS equation, the previous incremental value and chord length for the sake of a constant chord length. Simulation study was conducted to see the performance of the proposed interpolator with reference-word and reference-pulse method. Consequently, an accurate and simple NURBS interpolator was possible for modem CNC systems.

• Nuclear Engineering and Technology
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• v.47 no.5
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• pp.546-558
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• 2015

Chord length sampling method in Monte Carlo simulations is a method used to model spherical particles with random sampling technique in a stochastic media. It has received attention due to the high calculation efficiency as well as user convenience; however, a technical issue regarding boundary effect has been noted. In this study, after analyzing the distribution characteristics of spherical particles using an explicit method, an alternative chord length sampling method is proposed. In addition, for modeling in finite media, a correction method of the boundary effect is proposed. Using the proposed method, sample probability distributions and relative errors were estimated and compared with those calculated by the explicit method. The results show that the reconstruction ability and modeling accuracy of the particle probability distribution with the proposed method were considerably high. Also, from the local packing fraction results, the proposed method can successfully solve the boundary effect problem. It is expected that the proposed method can contribute to the increasing of the modeling accuracy in stochastic media.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1647-1652
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• 2008

Track geometry consists of tangent and curved lines, which caused undesirable changes in initial track geometry by traffic loads. The bigger the changes are, the worse the riding comfort and running stability of train. This is so-called track irregularity and is the most important quality parameters of ballasted track. To be able to objectively assess track irregularity, track geometry should be able to be measured. Practically, railway companies use moving chord method, this method determine versine values via a chord. The versine is the vertical distance to curve measured in the middle of the chord. This type of method measures only versine of track irregularity curve by transfer function from specific property of measuring tool. In this report, review the characteristics of two types of measuring tools by comparing the measurements. The one is GRP-1000 system, optical surveying system with Total station and lazar prism trolly. This calculates track geometry by surveying absolute coordinates of two points each on both rail heads. The other is Trackmaster, measures versine with 2m of chord length.

• 한국가시화정보학회:학술대회논문집
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• 2001.12a
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• pp.53-61
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• 2001

Highly swept leading edge extensions(LEX) applied to delta wings have greatly improved the subsonic maneuverability of contemporary fighters. Fundamental approach by PIV method was adopted to study the basic flow of the vortex pair formation appearing on a delta wing model with or without LEX. Three angles of attacks$(16^{\circ},\;24^{\circ},\;28^{\circ})$ and four measuring section of chord length(LEX-on) and three section(LEX-off) were selected as experimental conditions. From the PIV analysis, maximum vorticity was found at a given chord length and maximum velocity was also detected at larger chord length where stronger vortex was generated. Furthermore, the effect of LEX was remarkable at the vortex pair distance indicating narrower distance at LEX-on case.

• Steel and Composite Structures
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• v.21 no.2
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• pp.323-342
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• 2016

To study the effect of collar-plate reinforcement on the static strength of tubular T-joints under axial loading, fundamental research work is carried out from both experimental test and finite element (FE) simulation. Through experimental tests on 7 collar-plate reinforced and 7 corresponding un-reinforced tubular T-joints under axial loading, the reinforcing efficiency is investigated. Thereafter, the static strengths of the above 14 models are analyzed by using FE method, and it is found that the numerical results agree reasonably well with the experimental data to prove the accuracy of the presented FE model. Additionally, a parametric study is conducted to analyze the effect of some geometrical parameters, i.e., the brace-to-chord diameter ratio ${\beta}$, the chord diameter-to-chord wall thickness ratio $2{\gamma}$, collar-plate thickness to chord wall thickness ratio ${\tau}_c$, and collar-plate length to brace diameter ratio $l_c/d_1$, on the static strength of a tubular T-joint. The parametric study shows that the static strength can be greatly improved by increasing the collar-plate thickness to chord wall thickness ratio ${\tau}_c$ and the collar-plate length to brace diameter ratio $l_c/d_1$. Based on the numerical results, parametric equations are obtained from curving fitting technique to estimate the static strength of a tubular T-joint with collar-plate reinforcement under axial loading, and the accuracy of these equations is also evaluated from error analysis.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1090-1095
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• 2008

Track geometry changes by traffic loads. The bigger the changes are, the worse the riding comfort and running stability of train. This is so-called track irregularity and is the most important quality parameters of ballasted track. To objectively assess track irregularity, track geometry should be able to be measured. Practically, railway companies use moving chord method, which determine versine values via a chord. The versine is the vertical distance to curve measured in the middle of the chord. This type of method measures only versine of track irregularity curve by transfer function from the characteristics of measuring device. In this report, review the characteristics of two types of measuring tools by comparing the measurements. The one is GRP-1000 system, optical surveying system with Total station and lazar prism trolley. This calculates track geometry by surveying absolute coordinates of two points each on both rail heads. The other is EM-120, measures versine with 10m of symmetrical chord length.