• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.8
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• pp.47-54
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• 2006

In this paper, numerical algorithms applied in two-step eulerian scheme are investigated and implemented. Element quantities are advected with donor or van Leer algorithm. Nodal quantities are advected with Simplifed ALE [SALE] algorithm. Material interfaces are determined with Simple Line Interface Calculation [SLIC] algorithm. Practical aspects considered for code development are addressed in detail. The results of developed two-step Eulerian code are verified by comparing with those from pure lagrangian scheme and commercial code.

• Journal of Digestive Cancer Research
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• v.2 no.2
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• pp.45-51
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• 2014

Gastric cancer is the second most common cancer and the third leading cause of cancer-related deaths in Korea. Many cases of gastric cancer are detected in the early stages on standard medical examinations; complete surgical and endoscopic resection is the most recommended treatment for early-stage gastric cancer. Nevertheless, many patients have already progressed to advanced gastric cancer (AGC) upon diagnosis, and the prognosis of such patients is very poor. Combination chemotherapy has been shown to produce a better quality of life (QOL) and to increase overall survival in AGC patients. However, approximately 50% of patients do not respond to the current first-line chemotherapy, while most patients who do respond eventually show disease progression. Accordingly, various second-line regimens have been investigated, and active salvage chemotherapy has been shown to improve the QOL and clinical outcomes in select AGS patients who can tolerate it. There is also an increasing need for neoadjuvant therapy for treating gastric cancer; therefore, various clinical trials have been set up to investigate different regimens. Neoadjuvant therapy is currently established as the standard treatment for locally AGC in Europe; it has contributed to lowering the nodal stages and has reduced overall mortality rates. Despite these benefits, many uncertainties remain. Therefore, further prospective, high quality randomized controlled trials for neoadjuvant therapies are needed to clarify their clinical benefits and to establish the most effective treatment strategies for AGC.

• The Journal of Engineering Geology
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• v.4 no.1
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• pp.29-42
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• 1994

Discrimination studies between microearthquakes and underground explosions are carried out in the pure-continental path of north-south within the Korean Peninsula. The characteristic waveforms for explosions and microearthquakes are investigated in the light of observation and synthetic seismograms. The characteristic waveform generation is minnly a function of source mechanism and ray-path and former influences more strongly than the latter.A double-couple source mechanism for microeatthquakes and a single-couple(force) mechanism for explosions are presented in this study. It is found for very shallow events to have outstanding of $L_g$ waves in the transverse components that pass through the upper crust with period of 1 - 6 seconds and fundamental modes of Rayleigh waves, $R_g$ in the vertical component with period 8-12 seconds. Furthermore it is pointed out that the first arrival amplitudes of SH waves for explosions are always srnall regardless of azimuth of stations since there is non-existence of nodal lines for the explosion mechanism. Theoretical seismograms for explosions show the first motions of compression with short wavelengths as well as mostly fundamental modes of Rayleight waves, $R_g$ waves and $L_g$ waves, whereas those of micro-earthquakes give either compression or dilatation according to the ack azimuth epicenter to stations and poor or non $R_g$ waves and complicated $L_g$ waves, depending on the focal depth.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.12
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• pp.4853-4858
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• 2015

Background: Colorectal cancer is the most common gastrointestinal cancer in Oman with an increasing incidence. We here report the presenting features, treatment outcomes and survival in a University hospital in Oman and compare our data with regional and international studies. Materials and Methods: Medical records of patients with colorectal cancer were reviewed retrospectively between June 2000 and December 2013 and were followed until June 2014. Results: A total of 162 patients were diagnosed with colorectal cancer. The majority were males (58.6%), with a median age of 56 years. Rectum was involved in 29.6% of patients, followed by ascending and sigmoid colon. The majority of patients had stage III (42.6%) and stage IV (32.7%) disease at presentation. K-Ras status was checked for 79 patients, and 41 (51.9%) featured the wild type. Median relapse free survival was 22 months. Median overall survival for all patients was 43 months. Observed 5 year overall survival (OS) for stages I, II and III was 100%, 60% and 60% respectively. On Log rank univariate analysis, age, BMI, diabetes, hypertension, metformin use, stage, clinical nodal status for rectal cancer, pathological T and nodal status, site of metastasis, surgical intervention, chemotherapy, radiotherapy, chemotherapy regimen, no of cycles of chemotherapy, response, RFS, site of recurrence and administration of $2^{nd}$ line chemotherapy were significant factors affecting OS. On Cox regression multivariate analysis none of the factors independently affected the OS. Conclusions: The majority of patients present with advanced disease and at young age. The survival rates are comparable to the published regional and international literature.

• Advances in aircraft and spacecraft science
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• v.3 no.3
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• pp.351-366
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• 2016

Macroperforations improve the sound absorption performance of porous materials in acoustic cavities and in waveguides. In an acoustic cavity, enhanced noise reduction is achieved using porous materials having macroperforations. Double porosity materials are obtained by filling these macroperforations with different poroelastic materials having distinct physical properties. The locations of macroperforations in porous layers can be chosen based on cavity mode shapes. In this paper, the effect of variation of macroporosity and double porosity in porous materials on noise reduction in an acoustic cavity is presented. This analysis is done keeping each perforation size constant. Macroporosity of a porous material is the fraction of area covered by macro holes over the entire porous layer. The number of macroperforations decides macroporosity value. The system under investigation is an acoustic cavity having a layer of poroelastic material rigidly attached on one side and excited by an internal point source. The overall sound pressure level (SPL) inside the cavity coupled with porous layer is calculated using mixed displacement-pressure finite element formulation based on Biot-Allard theory. A 32 node, cubic polynomial brick element is used for discretization of both the cavity and the porous layer. The overall SPL in the cavity lined with porous layer is calculated for various macroporosities ranging from 0.05 to 0.4. The results show that variation in macroporosity of the porous layer affects the overall SPL inside the cavity. This variation in macroporosity is based on the cavity mode shapes. The optimum range of macroporosities in poroelastic layer is determined from this analysis. Next, SPL is calculated considering periodic and nodal line based optimum macroporosity. The corresponding results show that locations of macroperforations based on mode shapes of the acoustic cavity yield better noise reduction compared to those based on nodal lines or periodic macroperforations in poroelastic material layer. Finally, the effectiveness of double porosity materials in terms of overall sound pressure level, compared to equivolume double layer poroelastic materials is investigated; for this the double porosity material is obtained by filling the macroperforations based on mode shapes of the acoustic cavity.

• Structural Engineering and Mechanics
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• v.48 no.1
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• pp.77-91
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• 2013

The paper presents the formulation of 3-nodal line semi-analytical Mindlin-Reissner finite strip in the buckling analysis of thin-walled members, which are subjected to arbitrary loads. The finite strip is simply supported in two opposite edges. The general loading and in-plane rotation techniques are used to develop this finite strip. The linear stiffness matrix and the geometric stiffness matrix of the finite strip are given in explicit forms. To validate the proposed model and study its performance, numerical examples of some thin-walled sections have been performed and the results obtained have been compared with finite element models and the published ones.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1953-1955
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• 2002

An efficient automatic mesh generator suitable for the harsh model, which contains abrupt regions and thin layers, is implemented. It adopts two kinds of node placement scheme. In the beginning, the initial nodes on the boundary are generated automatically by an efficient boundary node generation scheme. And then the inner nodes are placed using nodal spacing value technique repeatedly from the initial mesh to final mesh. The effectiveness of the proposed technique is verified by a thin film micro-strip line modeling, where the final mesh contains no sliver elements.

• Journal of Power System Engineering
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• v.9 no.1
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• pp.42-49
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• 2005

The vibration analysis of a rectangular plate with stiffeners is formulated by using the transfer stiffness coefficient method (TSCM). This method is based on the concept of the successive transmission of stiffness coefficients which are defined as the relationship between the force vector and the displacement vector at an arbitrary nodal line. In order to confirm the validity of the present method, bending vibration analysis for a rectangular plate with stiffener is carried out on a personal computer by using the present method and the finite element method (FEM). Through comparing computational results of the TSCM and the FEM, the effectivness of the TSCM from the viewpoint of computational cost, that is, computational time and storage is demonstrated.

• Journal of Mechanical Science and Technology
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• v.19 no.5
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• pp.1116-1122
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• 2005

A finite element method was used to simulate the wave propagation of laser-generated ultrasound and its interaction with surface breaking cracks in an elastic material. Thermoelastic laser line source on the material surface was approximated as a shear dipole and loaded as nodal forces in the plane-strain finite element (FE) model. The shear dipole- FE model was tested for the generation of ultrasound on the surface with no defect. The model was found to generate the Rayleigh surface wave. The model was then extended to examine the interaction of laser generated ultrasound with surface-breaking cracks of various depths. The crack-scattered waves were monitored to size the crack depth. The proposed model clearly reproduced the experimentally observed features that can be used to characterize the presence of surface-breaking cracks.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1376-1378
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• 2006

Numerical and experimental study were carried out to characterize sound fields of low frequency in a scaled reverberation chamber for measurement of sound insulation of panels. By using BEM, lower modes of the chamber are identified and then predicted the effect of diffusers in order to destruct lower modes. Compared results with measurements show reasonable agreements, especially at the first end second modes. Based on numerical prediction, the diffuser are installed in order to improve sound fields to be more diffuse than ever. It is found that the diffuser put in nodal line of the chamber destruct evidently the first mode. Consequently, the measuring error at the low frequency can be relatively reduced compare to the case of without diffuser.