• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.6
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• pp.585-597
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• 2014

In this study, the cutter acting forces were measured by 3-directional load cell at two different skew angles and various S/d ratios during a series of linear cutting tests using a slim conical pick. The analysis for cutting performance were carried out after calculating average values of the measured results. The increase of penetration depth results in the decrease of specific energy. And the variations of the cutter acting forces depending on penetration depth in the case of 6 degree skew angle were smaller than in the case of 0 degree skew angle. From this results, 6 degree skew angle is more effective than 0 degree skew angle in designing optimal specifications of cutting head. In addition, $F_c/F_n$ under the setting of 6 degree skew angle was smaller than under the setting of 0 degree skew angle. However, it should be considered that the increase of cutter acting force in the cutting direction accompanied the increase of driving force in the case of the setting for 6 degree skew angle.

• Coupled systems mechanics
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• v.8 no.6
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• pp.473-488
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• 2019

The present work is the study of mechanical behavior due to variation of the geometrical parameters in the core of the sandwich honeycomb panel. This study has allowed us to increase or decrease the strains and stresses of the panel, in changing the angle of alveolus, as explained and described below. In taking into consideration the results obtained previously to improve the mechanical properties and increase the adhesion of different parts of the panel, without changing the adhesive, we have conceived two new models, in increasing the contact surfaces in boundary of each part of the panel and giving a conical hexagonal shape in his corp.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1-6
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• 2008

Due to the self-similarity of Berkovich and conical indenters, different materials may show the same loaddepth curve for single indentation. In this study, we first compare the load-depth characteristics of conical and Berkovich indenters via finite element method. We also analyze the variation of load-depth curves with angle of Berkovich indenter, indentation parameters, and material properties. With numerical regressions of obtained data, we then propose dual-Berkovich indentation formulae for material property evaluation. The proposed approach provides the values of elastic modulus, yield strength and strain-hardening exponent and corresponding stress-strain curve with an average error of less than 3%. The method is valid for any elastic indenters made of tungsten carbide and diamond for instance.

• International Journal of Aerospace System Engineering
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• v.7 no.2
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• pp.1-5
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• 2020

When a rigid wedge is indented in to a semi-infinite block, the material is bulged up around the wedge that is generally called lip. The previous works in this filed considered the outer profile of the lip to be linear. But, present authors observed both experimentally and with the aid of finite element analysis that the profile of the lip is not always linear, and it depends on the angle of the wedge and friction parameters. So, in this work, attempts have been made to calculate hardness of indentation for different wedge angles and friction parameters. As hardness is intrinsic property of material, consideration of either linear or parabolic lip will not be affected much. A comparative study of hardness for linear and parabolic free surface profiles of the piled up material around the cone is analyzed in this work.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.1
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• pp.60-65
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• 2000

The virtual mass of net is an important parameter in the analysis and control of net movement in the water. This experiment was performed with the purpose of getting a relation on the quantity of netting and virtual mass of trawl nets using the circulating water channel that can control flow speed. Twelve types of conical nets were examined. Resistance of the conical net at the steady and acceleration state was recorded as text on the personal computer through the tension meter and current meter. The results were obtained as follows ;1. Resistance(R) of the conical net is proportional to the degree of attack angle in the sam e amount of twine material.2. Coefficient of the resistance(Cd)could be defined by the following regression model as a function of Reynolds Number(Re). Cd=0.039Re-0.14743. Resistance(R) is proportional to TSA(Twine surface area) and defined as follows; R=21.398TSA-0.12194. Coefficient of virtual mass(CM) could be calculated by the following first order regression model. CM=37.557U-8.96845. Virtual mass is directly proportional to Volume of net(V) or d/l.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.5
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• pp.637-649
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• 1997

Effects of cone angle, pressure-hole orientation and Reynolds number on the five-hole probe calibration have been investigated for eight large-scale conical five-hole probes, which have either perpendicular pressure holes or forward-facing pressure holes for the cone angles of 45 deg, 60 deg, 75 deg and 90.deg. Pitch and yaw angles are changed from -40 deg to +40 deg with an interval of 5 deg, respectively, when the probe Reynolds numbers are 1.77*10$^{4}$, 3.53*10$^{4}$ and 7.06*10$^{4}$. The result shows that larger cone angle results in more sensitive changes in the calibration coefficients. In the case that the cone angle is 45 deg, the pitch-angle and yaw-angle coefficients of the five-hole probe with the perpendicular pressure holes show a very different trend compared with those of the five-hole probe with the forward-facing pressure holes. On the other hand, when the cone angle is more than 60 deg, each calibration coefficient is nearly independent of the pressure-hole orientation. Additionally, the effects of the Reynolds number on the calibration coefficients are also reported in detail.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.4
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• pp.393-404
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• 2003

Statement of problem. Higher incidence of prosthetic complications such as screw loosening, screw fracture has been reported for posterior single tooth implant. So, there is ongoing research regarding stability of implant-abutment interface. One of those research is increasing the implant diameter and prosthetic table width to improve joint stability. In another part of this research, internal conical type implant-abutment interface was developed and reported joint strength is higher than traditional external hex interface. Purpose. The purpose of this study is to compare stress distribution in single molar implant between external hex butt joint implant and internal conical joint implant when increasing the implant diameter and prosthetic table width : 4mm diameter, 5mm diameter, 5mm diameter/6mm prosthetic table width. Material and method. Non-linear finite element models were created and the 3-dimensional finite element analysis was performed to see the distribution of stress when 300N static loading was applied to model at $0^{\circ},\;15^{\circ},\;30^{\circ}$ off-axis angle. Results. The following results were obtained : 1. Internal conical joint showed lower tensile stress value than that of external hex butt joint. 2. When off-axis loading was applied, internal conical joint showed more effective stress distribution than external hex butt joint. 3. External hex butt joint showed lower tensile stress value when the implant diameter was increased. 4. Internal conical joint showed lower tensile stress value than external hex butt joint when the implant diameter was increased. 5. Both of these joint mechanism showed lower tensile stress value when the prosthetic table width was increased. Conclusion. Internal conical joint showed more effective stress distribution than external hex joint. Increasing implant diameter showed more effective stress distribution than increasing prosthetic table width.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.291-294
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• 2002

This study describes the external spray characteristics of deflector nozzle such as the breakup procedures of liquid sheet, spray angle, discharge coefficient and bubble behaviors of spray and SMD at deflector nozzle. In order to visualize the spray behaviors shadow graphy technique were used. According to the increase of injection pressure, development of the spray passes through the dribbling, distoted jet, closed bubble due to the contraction by surface tension forces, the bubble opens into hollow tulip shape, and the curved surface straightened to form a conical sheet like as the simplex swirl atomizer. Spray cone angle was nearly 90 deg. Variations of SMD were examined in order to describe the dependency of SMD on the injection pressure and orifice diameter. The shape of deflector and oriffice diameter had an effect on the discharge coefficient.

• Journal of ILASS-Korea
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• v.7 no.1
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• pp.29-35
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• 2002

This study describes the external spray characteristics of deflector nozzle such as the breakup procedures of liquid sheet, spray angle, breakup length and bubble behaviors of spray at deflector nozzle. In order to visualize the spray behaviors shadow graphy technique were used. According to the increase injection pressure, deveopment of the spray passes through the dribbling, distoted jet, closed bubble due to the contraction by form a conical sheet like as the simplex swirl atomizer. As trying the analysis of the ratio of bubble length and width it was found that the ratios is comparable. Spray cone angle was nearly $90^{\circ}$.

• Journal of ILASS-Korea
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• v.4 no.4
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• pp.24-29
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• 1999

In the pressure swirl atomizer, the liquid is injected through tangential passages into a swirl chamber, from which it emerges with both tangential and axial velocity components to form a thin conical sheet at the nozzle exit. This sheet rapidly attenuates, finally disintegrating into ligaments and then drops. The purpose of this study is to measure the spray characteristics according to variation of viscosity of the spray produced by the pressure swirl atomizer. The nozzle tested here were especially designed for this investigation. The discharge coefficient is determined by measuring the volume flow rate with a flow meter and the cone angle of the liquid sheets issuing from the nozzle is obtained from series of photographs of the sheet for various liquid viscosity and injection pressure. And mean drop size is measured by image processing method. It is found that the geometrical characteristics of the nozzle and the variation of viscosity were the influential parameters to determine the spray characteristics such as the cone angle, discharge coefficients and SMD.