• Geomechanics and Engineering
• /
• v.20 no.2
• /
• pp.121-129
• /
• 2020

In the design of geotechnical structures, engineers choose either peak or critical state friction angles. Unfortunately, this selection is based on engineer's preference for economy or safety and lacks the assessment of the expected level of deformation. To fill this gap in the design process, this study proposes a strain based empirical method. Proposed method is founded on the experimentally supported assumption that higher dilatancy angles result in more brittle soil response. Using numerous triaxial test data on ten different soils, an empirical design chart is developed that allows the estimation of shear strain at failure based on soil's peak dilatancy angle and mean grain diameter. Developed empirical chart is verified by conducting a small scale retaining wall physical model test. Finally, a design methodology is proposed that makes the selection of design friction angle in structured way possible based on the serviceability limits of the proposed structure.

• Proceedings of the KIEE Conference
• /
• 1994.07b
• /
• pp.1435-1438
• /
• 1994

The effects of Ge composition variation in $a-Si_{1-x}Ge_x:H$ alloy p-i-n solar cells on the physical properties and current density-voltage characteristics are analyzed by a new simulation modelling based on the update published experimental datas. The simulation modelling includes newly formulated density of gap density spectrum corresponding to Ge composition variation and utilizes the newly derived generation rate formulars which include the reflection coefficients and can apply to multijunction structures as well as single junction structure. The effects in $a-Si_{1-x}Ge_x:H$ single junction are analyzed through the efficiency, fill factor, open circuit voltage, short circuit current density, free carriers, trap carriers, electric field, generation rate and recombination rate. Based on the results analyzed in single junction structure, the applications to multiple junction structures are discussed and the optimal conditions reaching to a high performance are investigated.

• Honam Mathematical Journal
• /
• v.35 no.2
• /
• pp.225-234
• /
• 2013

Many studies of experimental economics have produced outcomes which contradict the predictions of Nash equilibrium, which relies heavily upon the premise of selfishness of an individual. In the games involving contexts of social conflicts represented by the prisoners' dilemma game, the experiments yields outcomes quite different from what are predicted by the conventional wisdom. In order to fill this gap between the conventional Nash Equilibrium and experimental outcomes, non-selfish (or other-regarding) motives of human behavior are introduced and then a new equilibrium concept, RAE-equilibrium is developed. It is also proved that an RAE-equilibrium exists under quite general conditions. Then it is applied to the prisoners' dilemma game that some of the experimental outcomes can be explained.

• Structural Engineering and Mechanics
• /
• v.54 no.5
• /
• pp.877-890
• /
• 2015

This paper aims to fill the technical gap on the elastic buckling behavior of functionally graded material (FGM) grid systems under inplane loads on which few research has been done. Material properties of an FG beam are assumed to vary smoothly in the thickness direction according to power and exponential laws. Based on a hybrid-stress finite element formulation, buckling solutions for FGM grid systems consisting of various aspect ratios and material gradation are provided. The numerical results demonstrate that the aspect ratio and material gradation play an important role in the buckling behavior of FGM grid systems. We believe that the new results obtained from this study, will be very useful to designers and researchers in this field.

• Korean Journal of Computational Design and Engineering
• /
• v.22 no.2
• /
• pp.190-201
• /
• 2017

This paper proposes how to solve a problem of FDM 3D printer's irregular output when changing volume of extrusion, adjusting movement speed of the printer's head and a way to fill new inner part. Existing slicers adjust directly to change the rotation speed of the stepper. In this method, the change of the extrusion area is delayed due to the gap between the stepper and the nozzle, so that precise control is difficult. We control the extrusion area adjusting the moving speed of the print head and making constantly the rotation speed of the stepper. Thus, the output time can be shortened by generating an efficient path having a short travel distance. For evaluation, we applied our method to lithophanes with detailed variation. Comparing existing methods, our method reduced output time at least 30%.

• Steel and Composite Structures
• /
• v.20 no.2
• /
• pp.447-468
• /
• 2016

Despite of the growing number of built examples, the analysis of non-symmetrical cable-stayed bridges has not received considerable attention from the researchers. In fact, the effects of the main design parameters in the structural behavior of these bridges are not addressed in detail in the literature. To fill this gap, this paper studies the structural response of a number of non-symmetrical cable-stayed bridges. With this aim, a parametric analysis is performed to evaluate the effect of each of the main design parameters (the ratio between the main and the back span length, the pylon, the deck and backstay stiffnesses, the pylon inclination, and the stay configuration) of this kind of bridges. Furthermore, the role of the geometrical nonlinearity and the steel consumption in stays are evaluated.

• Computers and Concrete
• /
• v.13 no.4
• /
• pp.483-499
• /
• 2014

Most of the methods presented in the literature to define the target service stresses (Objective Service Stage, OSS) of cable-stayed bridges rarely include the time-dependent phenomena effects. Nevertheless, especially in concrete structures, this assumption might be on the unsafe side because time-dependent phenomena usually modify service stresses. To fill this gap, this paper studies the time-dependent phenomena effects into service stresses of concrete cable-stayed bridges. After illustrating the important role of these phenomena in an asymmetrical cable-stayed bridge without backstay, a new method to include their effects into the OSS is presented. An important issue to be considered in this method is the target time in which the OSS is defined to be achieved. The application of this method to two different structures showed the convenience of defining the OSS to be achieved at early times because that way the envelope of service stresses is reduced.

• Journal of Information Technology Services
• /
• v.9 no.3
• /
• pp.45-63
• /
• 2010

To examine the role IM plays, We focus on the factors that promote or hinder communication within a Korean organization when instant messenger is used. These factors were examined through two research questions. To understand these issues, a survey consisting of 33 categories was given to government and corporate office workers in Seoul, Korea. The survey results showed that Instant Messenger is recognized as a powerful communication tool in official organizations, but is only used effectively within groups or generations that do not follow the hierarchical relationships characterized by Confucian values. The results of this study fill a gap in our understanding of the important role of IM use in organizational effectiveness and may prove useful when developing tools and strategies to help promote communication within organizations using information technology media.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.11a
• /
• pp.209-212
• /
• 2001

Polyimide(PI) films have been considered as the interlayer dielectric materials due to low dielectric constant, low water absorption, high gap-fill and planarization capability. The PI film was etched with using inductively coupled plasma (ICP). The etching characteristics such as etch rate and selectivity were evaluated to gas mixing ratio. High etch rate was 8300$\AA$/min and vertical profile was approximately acquired 90$^{\circ}$ at CF$_4$/(CF$_4$+O$_2$) of 0.2. The selectivies of polyimide to PR and SiO$_2$ were 1.2, 5.9, respectively. The etching profiles of PI films with an aluminum pattern were measured by a scanning electron microscope (SEM). The chemical states on the PI film surface were investigated by x-ray photoelectron spectroscopy (XPS). Radical densities of oxygen and fluorine in different gas mixing ratio of 07CF4 were investigated by optical emission spectrometer (OES).

• Transactions on Electrical and Electronic Materials
• /
• v.3 no.3
• /
• pp.14-17
• /
• 2002

The HDP (High Density Plasma) CVD process consists of a simultaneous sputter etch and chemical vapor deposition. As CMOS process continues to scale down to sub- quarter micron technology, HDP process has been widely used fur the gap-fill of small geometry metal spacing in inter-metal dielectric process. However, HBP CVD system has some potential problems including plasma-induced damage. Plasma-induced gate oxide damage has been an increasingly important issue for integrated circuit process technology. In this paper, thin gate oxide charge damage caused by HDP deposition of inter-metal dielectric was studied. Multiple step HDP deposition process was demonstrated in this work to prevent plasma-induced damage by introducing an in-situ top SiH$_4$ unbiased liner deposition before conventional deposition.