• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.4
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• pp.327-343
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• 2004

During tunnel construction, ground failures often occur due to existence of weak zones, such as faults, joints, and cavities, ahead of tunnel face. It is hard to detect effectively weak zones, which can lead underground structure to fail after excavation and before supporting, by using conventional characterization methods. In this study, an enhanced analytical method of predicting weak zones ahead of tunnel face is developed to overcome some problems in the conventional geophysical exploration methods. The analytical method is based on Coulomb's and Gauss' laws with considering the characteristics of electric fields subjected to rock mass. Using the developed method, closed form solutions are obtained to detect a spherical shaped zone and an oriented fault ahead of tunnel face respectively. The analytical results suggest that the presence of weak zones and their sizes, location, and states can be accurately predicted by combining a proper inversion process with resistance measured from several electrodes on the tunnel face. It appears that the skin depth or resistivity in rock mass is affected by the diameter of tunnel face, natural electric potential and noises induced by experimental measurement and spatial distribution of uncertain properties. The developed analytical solution is verified through experimental tests. About 1800 concrete blocks of 5cm by 5cm by 5cm in size are prepared and used to model a joint rock mass around tunnel face. Weak zones are simulated ahead of tunnel face with a material which has relatively higher conductivity than concrete blocks. Experimental results on the model test show a good agreement with analytical results.

• Steel and Composite Structures
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• v.24 no.2
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• pp.151-176
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• 2017

This paper deals with general equations of motion for free vibration analysis response of thick three-layer doubly curved sandwich panels (DCSP) under simply supported boundary conditions (BCs) using higher order shear deformation theory. In this model, the face sheets are orthotropic laminated composite that follow the first order shear deformation theory (FSDT) based on Rissners-Mindlin (RM) kinematics field. The core is made of orthotropic material and its in-plane transverse displacements are modeled using the third order of the Taylor's series extension. It provides the potentiality for considering both compressible and incompressible cores. To find these equations and boundary conditions, Hamilton's principle is used. Also, the effect of trapezoidal shape factor for cross-section of curved panel element ($1{\pm}z/R$) is considered. The natural frequency parameters of DCSP are obtained using Galerkin Method. Convergence studies are performed with the appropriate formulas in general form for three-layer sandwich plate, cylindrical and spherical shells (both deep and shallow). The influences of core stiffness, ratio of core to face sheets thickness and radii of curvatures are investigated. Finally, for the first time, an optimum range for the core to face sheet stiffness ratio by considering the existence of in-plane stress which significantly affects the natural frequencies of DCSP are presented.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.2
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• pp.476-481
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• 1998

It is generally known that in high speed work with more than 1000 m/min cutting speed, according to the work material phenomenon of tool wearing is increased due to the some produced neat and as a result this makes the cutting work impossible. In this study, the high speed cutting is possible because of the different cutting from the presently known fact. That is, most of generated heats influence on the quantity flowing in chip greatly. Therfore, this study aims at the behavior of cutting heat generated at high speed cutting. It makes clearly the euqntity of heat flowing in chip, work materal, tool, and inflowing ratio. The cutting mechanism varies by the changing of cutting depth, slant face and contact area through this study. And it is exammined that the influence of heat of all parts is greatly due to the change the contact length of clearance face. It is confirmed from the exp[eriment that the inflowing heat ratio influences the cutting speed greatly and the heat of clearance face can not be disregarded.

• Structural Engineering and Mechanics
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• v.67 no.6
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• pp.565-578
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• 2018

This research article reported the nonlinear finite solutions of the nonlinear flexural strength and stress behaviour of nano sandwich graded structural shell panel under the combined thermomechanical loading. The nanotube sandwich structural model is derived mathematically using the higher-order displacement polynomial including the full geometrical nonlinear strain-displacement equations via Green-Lagrange relations. The face sheets of the sandwich panel are assumed to be carbon nanotube-reinforced polymer composite with temperature dependent material properties. Additionally, the numerical model included different types of nanotube distribution patterns for the sandwich face sheets for the sake of variable strength. The required equilibrium equation of the graded carbon nanotube sandwich structural panel is derived by minimizing the total potential energy expression. The energy expression is further solved to obtain the deflection values (linear and nonlinear) via the direct iterative method in conjunction with finite element steps. A computer code is prepared (MATLAB environment) based on the current higher-order nonlinear model for the numerical analysis purpose. The stability of the numerical solution and the validity are verified by comparing the published deflection and stress values. Finally, the nonlinear model is utilized to explore the deflection and the stresses of the nanotube-reinforced (volume fraction and distribution patterns of carbon nanotube) sandwich structure (different core to face thickness ratios) for the variable type of structural parameter (thickness ratio, aspect ratio, geometrical configurations, constraints at the edges and curvature ratio) and unlike temperature loading.

• Journal of the Korean Society of Costume
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• v.57 no.2 s.111
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• pp.143-154
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• 2007

This study's purpose is how express gender image according to sex in editorial fashion photography. This study's objectives are the women's magazine Vogue, Harper's Bazaar and man's magazine GQ, Esquire published 2000-2005 within the country. The photography was classified with established a standard based on the precede studies. The photo is classified Gender image according to dress and its ornaments, model character and atmosphere by Sex Expression of femininity woman has exposure of body parts and emphasizing thin eyebrows and red lips, soft and mild image, modest and static pose. Man expressed femininity used ladylike color and pattern, erotic exposure of body and long hair style. Commonly emphasizing red lips, natural background of flower plant, S-line. For expression of masculinity man and woman are used masculinity item, short hair-style and thick eyebrows. And also emphasize square like chin and shoulder. Specially, woman used direct silhouette to conceal soft body curved line. The expressions of androgynous woman and man are colorful dress and make-up. Woman emphasized male face to show and man expressed soft image through hull of abundant material of fur. All two sex selected method that conceal body curved line and face to express sexless. Hiding characteristics of body and face make indistinct of sex. The gender is affected by atmosphere such as model and illumination background as much as clothes because of the editorial fashion photography.

• Journal of Technologic Dentistry
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• v.11 no.1
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• pp.95-102
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• 1989

This study was performed to study the efficiency of a local ventilation system, installed in dental laboratories, and of two types of protecting face masks. The dust originating from the workpiece as well as from the wheels and stones was collected on air filters in the cutting cycle during coarse and fine grinding, and in the subsequent polishing procedures of each specific dental material. The efficiency of the ventilation system was measured on the basis of weight reduction of dust in the breathing air at a distance about 20-40 cm from workpiece. The results were as follows: 1. Use of the local ventilation system reduced the amounts of respirable dust to an average level of 21.4%, although the efficiency of the local ventilation system varied depending upon materials used. 2. Mounting a nozzle on the tube improved the efficiency of the ventilation system considerably. The efficiency of the local ventilation system also increased as the workpiece was closing to the tube inlet. 3. With or without the local ventilation system, the distance between the position of the workpiece and sampler greatly affected the dust level. 4. The face masks covering the sampler improved the efficiency of the ventilation system considerably.

• Structural Engineering and Mechanics
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• v.78 no.5
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• pp.557-572
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• 2021

The current study considers free vibration of the spherical panel with magnetorheological (MR) fluids core and magneto-electro-elastic face sheets. The panel is subjected to electro-magnetic loads and also is located on an orthotropic visco-Pasternak elastic foundation. To describe the displacement components of the structure, the first-order shear deformation theory (FSDT) is used and the motion equations are extracted by employing Hamilton's principle. To solve the motion differential equations, Navier's method is selected as an exact analytical solution for simply supported boundary conditions. Effect of the most important parameters such as magnetic field intensity, loss factor, multi-physical loads, types of an elastic medium, geometrical properties of the panel, and also different material types for the face sheets on the results is considered and discussed in details. The outcomes of the present work may be used to design more efficient smart structures such as sensors and actuators.

• Advances in nano research
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• v.14 no.3
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• pp.261-271
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• 2023

The present study follows three main goals. First, an analytical solution with high accuracy is developed to assess the effects of embedding pre-strained shape memory alloy (SMA) wires on the critical buckling temperatures of rectangular sandwich plates made of soft core and graphite fiber/epoxy (GF/EP) face sheets based on piecewise low-order shear deformation theory (PLSDT) using Brinson's model. As the second goal, this study compares the effects of SMAs on the thermal buckling of sandwich plates with those of carbon nanotubes (CNTs). The glass transition temperature is considered as a limiting factor. For each material, the effective ranges of operating temperature and thickness ratio are determined for real situations. The results indicate that depending on the geometric parameters and thermal conditions, one of the SMAs and CNTs may outperform the other. The third purpose is to study the thermal buckling of sandwich plates with advanced hybrid SMA/CNT/GF/EP composite face sheets. It is shown that in some circumstances, the co-incorporation of SMAs and CNTs leads to an astonishing enhancement in the critical buckling temperatures of sandwich plates.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.3
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• pp.161-167
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• 1993

This paper deals with a new method for the machining of a die cavity defined by sculptured surfaces. In machining die cavities or pockets, process planners have been faced with some troulbes. One of the troubles ius to rebove a great deal of material within a given boundary while avoiding cutter interference. Cutter interference is a ciritical problem in NC machining of a die cavity. Even though this cavity machining has been implemented in many CAM systems, most of them can handle limited shapes of cavities or pockets. In this paper, a procedure has been developed to machine die cavity or pocket of a sculptured surface. The offset surfaces of the part surfaces and boundary surfaces are determined to calculate the intersection curves. These intersection curves form a FACE on the part surface, and the interference free tool pathe is generated by eliminating the points outside the FACE when computing the cutter contact (CC) data. Additionally, the cutter location (CL) data obtained from the CC data convert to an NC data. The NC data generated through this algorithm are verified on the CINCINNATI milling machine. A propotype die cavity machining system has been implemented in FORTRAN language and FIGARO graphics library on IRIS workstation.

• Journal of Mechanical Science and Technology
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• v.16 no.7
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• pp.873-881
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• 2002

In this paper, a on-line estimation method of the radial immersion angle using cutting force is presented. The ratio of cutting forces in feed and cross-feed directions acting on the single tooth at the immersion angle is a function of the immersion angle and the ratio of radial to tangential cutting force. It is found that the ratio of radial to tangential cutting force is not affected by cutting conditions and axial rake angle, which implies that the ratio determined by one preliminary experiment can be used regardless of the cutting conditions for a given tool and workpiece material. Using the measured cutting force during machining and predetermined ratio, the radial immersion ratio is estimated in process. Various experimental results show that the proposed method works within 5% error range.