• Journal of ILASS-Korea
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• v.13 no.1
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• pp.9-15
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• 2008

This experimental study was carried out to examine the heat transfer characteristics of impinging air jet on a flat plate with a set of right angled triangle rods. Each right angled triangle rod in the array was positioned normal to the flow direction and parallel to the flat plate surface. The clearances from a right angled triangle rod to flat plate surface (C=1, 2 and 4 mm) and the distance from nozzle exit to flat plate (H=100 and 500 mm) were changed for the pitch between each right angled triangle rods (P=40 mm). As a result, heat transfer shows best performance at the clearance of C=1 mm, in case clearance changed, and the average heat transfer enhancement rate increased up to 47% compared to the result of a flat plate without a right angled triangle rod.

• Journal of the Korean Mathematical Society
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• v.59 no.4
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• pp.717-731
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• 2022

We introduce the notion of quasi-roots and study their uniqueness in right-angled Artin groups.

• Bulletin of the Korean Mathematical Society
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• v.49 no.5
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• pp.1057-1065
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• 2012

We prove that if $\widehat{\Gamma}$ is a co-contraction of ${\Gamma}$, then the right-angled Coxeter group $C(\widehat{\Gamma})$ embeds into $C({\Gamma})$. Further, we provide a graph ${\Gamma}$ without an induced long cycle while $C({\Gamma})$ does not contain a hyperbolic surface group.

• The Journal of the Korean bone and joint tumor society
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• v.11 no.2
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• pp.175-182
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• 2005

Purpose: Bone tumor occurred in femur frequently involve proximal intertrochanteric region or distal metaphyseal region. Sometimes, the pathologic fracture can happen according to the size of tumor due to the substantial biomechanical stresses. Therefore, the prognosis can be improved biomechanically by the angled blade plate considering the anatomic configuration after the excision of tumor. Materials and Methods: Between October 1991 and April 2005, there were a total of 16 patients(17 cases) who were treated by the excision of tumor and internal fixation with the angled blade plate for bone tumor occurred in femur. After the excision of tumor, we filled the cavity by bone graft in 11 cases and bone cement in 6 cases. The internal fixation was used by angled blade plate in all cases. Result: The average follow-up time was 55.5 months(6-144 months) in 16 patients(17 cases). No metal failure occurred after the operation. Reoperation was performed in 4 cases due to tumor recurrence, and the internal fixation was firm until that. Conclusion: The angled blade plate can prevent the fracture until grafted bone incorporated to host bone, and protect fragile connection between cement and host bone.

• Structural Engineering and Mechanics
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• v.56 no.4
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• pp.589-603
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• 2015

The mixed-mode stress intensity factors of 2-D angled cracks are evaluated by Petrov-Galerkin natural element (PG-NE) method in which Voronoi polygon-based Laplace interpolation functions and CS-FE basis functions are used for the trial and test functions respectively. The interaction integral is implemented in a frame of PG-NE method in which the weighting function defined over a crack-tip integral domain is interpolated by Laplace interpolation functions. Two Cartesian coordinate systems are employed and the displacement, strains and stresses which are solved in the grid-oriented coordinate system are transformed to the other coordinate system aligned to the angled crack. The present method is validated through the numerical experiments with the angled edge and center cracks, and the numerical accuracy is examined with respect to the grid density, crack length and angle. Also, the stress intensity factors obtained by the present method are compared with other numerical methods and the exact solution. It is observed from the numerical results that the present method successfully and accurately evaluates the mixed-mode stress intensity factors of 2-D angled cracks for various crack lengths and crack angles.

• The KSFM Journal of Fluid Machinery
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• v.20 no.2
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• pp.5-10
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• 2017

In this study, the Coanda effect inducing bump was applied to improve the film cooling effectiveness on the flat plate with $30^{\circ}$ and $45^{\circ}$ angled rectangular slots. The slot length to width ratio was 6. A cylindrical cap shaped structure, called Coanda bump, was installed at the exit of the slot to generate Coanda effect. The width and height of the bump was 10.5 mm and 1 mm, respectively. The film cooling effectiveness was measured at the fixed blowing ratio, M=2.0, using pressure sensitive paint (PSP) technique. The mainstream velocity was 10 m/s and the turbulence intensity was about 0.5%. Results showed that the film cooling effectiveness for case of $30^{\circ}$ angled slot was higher than that of $45^{\circ}$ angled slot. It was found that there was no positive effect of Coanda effect on the overall averaged film cooling effectiveness for the $30^{\circ}$ angled slot. On the other hand, for the $45^{\circ}$ angled slot, the film cooling effectiveness was improved with the installation of the Coanda bump.

• Korean Journal of Mathematics
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• v.29 no.3
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• pp.577-580
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• 2021

For a finite simplicial graph 𝚪, let G(𝚪) denote the right-angled Artin group on the complement graph of 𝚪. For path graphs P_k, cycle graphs C_ℓ and complete bipartite graphs K_n,m, this article characterizes the embeddability of G(K_n,m) in G(P_k) and in G(C_ℓ).

• Tribology and Lubricants
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• v.25 no.5
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• pp.298-304
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• 2009

An angled labyrinth seal is used for the diaphragm-packing-ring seal design of steam turbine due to its leakage reduction characteristic. CFD analysis using FLUENT has been performed to predict leakage and determine an optimum slanted angle which yields the best leakage reduction. Results show that the optimum value of slanted angle is $-30^{\circ}$ independent of number of labyrinth teeth, inlet pressure, and tooth height to pitch ratio. 3D CFD analysis has been performed for predicting leakage of the angled labyrinth seal. Comparing with the result of 2D CFD analysis, 3D CFD analysis shows 1.4% smaller.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.5
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• pp.445-450
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• 2002

We analyzed and measured a CPW(coplanar waveguide)-to-microstrip right-angled transition. Asymmetric CPW-to-microstrip transitions show significant resonances by the slot mode generation at the discontinuities. The air-bridge just shifting the resonance frequency can not fundamentally suppress the occurrence of the slot mode. So, we proposed the structure using offset microstrip section to eliminate the resonance. The proposed structure may be useful for the application of multi-layed structure.

• Tribology and Lubricants
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• v.25 no.2
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• pp.96-101
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• 2009

In order to improve leakage characteristic, angled-circumferential-groove pump seal is suggested. CFD analysis using FLUENT has been performed to predict leakage and determine an optimum slanted-groove angle $\alpha$ which yields the best leakage reduction. The optimum value of $\alpha$ ranges from $45^{\circ}$ to $60^{\circ}$ and depends on the pressure difference of seal and number of grooves for the same groove geometry. The maximum leakage reduction ratio increases as increasing the pressure difference of angled-circumferential-groove pump seal with the optimum value of $\alpha$.