• Restorative Dentistry and Endodontics
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• v.33 no.4
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• pp.323-331
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• 2008

Flexibility and fracture properties determine the performance of NiTi rotary instruments. The purpose of this study was to evaluate how geometrical differences between three NiTi instruments affect the deformation and stress distributions under bending and torsional conditions using finite element analysis. Three NiTi files (ProFile .06 / #30, F3 of ProTaper and ProTaper Universal) were scanned using a Micro-CT. The obtained structural geometries were meshed with linear, eight-noded hexahedral elements. The mechanical behavior (deformation and von Mises equivalent stress) of the three endodontic instruments were analyzed under four bending and rotational conditions using ABAQUS finite element analysis software. The nonlinear mechanical behavior of the NiTi was taken into account. The U-shaped cross sectional geometry of ProFile showed the highest flexibility of the three file models. The ProTaper, which has a convex triangular cross-section, was the most stiff file model. For the same deflection, the ProTaper required more force to reach the same deflection as the other models, and needed more torque than other models for the same amount of rotation. The highest von Mises stress value was found at the groove area in the cross-section of the ProTaper Universal. Under torsion, all files showed highest stresses at their groove area. The ProFile showed highest von Mises stress value under the same torsional moment while the ProTaper Universal showed the highest value under same rotational angle.

• Resources Recycling
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• v.29 no.3
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• pp.11-23
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• 2020

This study aims to investigate breakage and liberation characteristics of iron ore from Shinyemi mine, Jeongseon by ball mill. Parameters of breakage functions for three grade samples of iron ore were obtained using single-sized-feed breakage test and back-calculation based on nonlinear programming. The results showed that with the increase in the grade of iron ore, the breakage rate factor decrease whereas the particle size sensitivity decreases. This results from retardation of microcrack-propagation by magnetite grain in the ore. Breakage distribution analysis showed that the breakage mechanism appear to be impact fracture dominant with the increase of grade owing to the stress distribution effect by magnetite grain. Degree of liberation (DOL) increased with the increase in grade and decrease in particle size, respectively. Using the breakage function and size-DOL relationship, a model that can predict time-dependent-DOL is established. When scale-up factors from operating condition are available, the model is expected to be capable of predicting size and DOL with time in actual mining process.

• The KIPS Transactions:PartC
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• v.14C no.5
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• pp.417-424
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• 2007

Mesh networks using WLAN technology have been paid attention as a key wireless access technology. However, many technical issues still exist for its successful deployment. One of those issues is the routing problem that addresses the path setup through a WLAN mesh network for the data exchanges between a station and a wired network. Since the characteristics of a WLAN mesh network can be very dynamic, the use of single routing protocol would not fit for all environments whether it is reactive or proactive. Therefore, it is required to develop an adaptive routing protocol that modifies itself according to the changes in the network parameters. As a logical first step for the development, an analytical model considering all the dynamic features of a WLAN mesh network is required to evaluate the performance of a reactive and a proactive routing scheme. In this paper, we propose an analytical model that makes us scrutinize the impact of the network and station parameters on the performance of each routing protocol. Our model includes the size of a mesh network, the density of stations, mobility of stations. and the duration of network topology change. We applied our model to the AODV that is a representative reactive routing protocol and DSDV that is a representative proactive routing protocol to analyze the tradeoff between AODV and DSDV in dynamic network environments. Our model is expected to help developing an adaptive routing protocol for a WLAN mesh network.

• Journal of Energy Engineering
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• v.23 no.2
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• pp.62-73
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• 2014

This research was focused to apply response surface methodology for optimization of bio-methane production by biogas upgrading process. Methane concentration(Y1) and methane efficiency(Y2) on biogas upgrading process were mathematically described as being modeled by the use of the Box-Behnken design on response surface methodology. The results of ANOVA(analysis of variance) about models, the probability value of the methane concentration and methane recovery response surface model are 0.0001 and 0.0001, respectively and coefficient of determination($R^2$) are 0.9788 and 0.9710, respectively. The response surface model is proved of high reliability and suitability. The operation pressure had the greatest influence to methane concentration than other operation parameters and the PSA rotary valve velocity had the greatest influence to methane recovery than other operation parameters. Optimal condition of biogas upgrading process for production of $100Nm^3/hr$ bio-methane were operation pressure 8.0bar and outlet flow rate 31.55RPM, respectively. At that operation condition the methane concentration of bio-methane was 97.13% and methane recovery in biogas upgrading process was 75.89%.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.1
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• pp.75-90
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• 1995

A mathematical model for the dynamic analysis of a riser system with the inclusion of internal flow and nonlinear effects due to large structural displacements is developed to investigate the effect of internal flow on marine riser dynamics. The riser system accounts fir the nonlinear boundary conditions and includes a steady flow inside the pipe which is modeled as an extensible or inextensible. tubular beam subject to nonlinear three dimensional hydrodynamic loads such as current or wave excitation. Galerkin's finite element approximation and time incremental operator are implemented to derive the matrix equation of equilibrium for the finite element system and the extensibility or inextensibility condition is used to reduce degree of freedom of the system and the required computational time in the case of a nonlinear model. The algorithm is implemented to develop computer programs used in several numerical applications. The investigations of the effect of infernal flow on riser vibration due to current or wave loading are performed according to the change of various parameters such as top tension, internal flow velocity, current velocity, wave period, and so on. It is found that the effect of internal flow can be controlled by the increase of top tension. However, careful consideration has to be given in the design point particularly for the long riser under the harmonic loading such as waves. And it is also found that the consideration of nonlinear effects due to large structural displacements increases the effect of internal flow on riser dynamics.

• Cartoon and Animation Studies
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• s.36
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• pp.493-510
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• 2014

From game consoles to TV and Hollywood films, 3D rendering technology is involved in various fields. Up until the late 90s, the computer image rendering method was rasterization that mainly used Phong Shading, and up until recently it was the go-to method for movies and film animation. In the 21st century, the quality provided by Ray Tracing and the development of Global Illumination was much more realistic and thus became popularized. However, despite its growing use in architectural rendering to the markets, Global Illumination in film animation and movies was limited due to its long render time. So, in this thesis, if one were to take the concept from each rendering method and consider it from a mathematical perspective, one could adapt the Ambient Occlusion's equation to the illumination loop equation used in rasterization. This algorithm modification has the capability to reflect the lighting of a diverse array of colors, like in Global Illumination, with a fast render time, as in rasterization, and the example RenderMan Shader is based upon this new algorithm. In conclusion, with Global Illumination's naturalistic lighting and rasterization's rendering speed, the combination of the best points of each is a new method with a short rendering time while producing good quality. I hope animations and films can benefit from this algorithm by the reduction of budget with an overall better quality output in VFX production.

• Economic and Environmental Geology
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• v.50 no.3
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• pp.195-214
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• 2017

Statistical landslide susceptibility analysis, which is widely used among various landslide susceptibility analysis approaches, predicts the unstable area by analyzing statistical relationship between landslide occurrence locations and landslide controlling factors. However, uncertainties are involved in the procedures of the susceptibility analysis and therefore, fuzzy approach has been used to deal properly with uncertainties. The fuzzy approach used fuzzy set theory and fuzzy membership function to quantify uncertainties involved in landslide controlling factors. Various fuzzy approaches were suggested in the procedure of the membership value determination and fuzzy operation in the previous researches. However, few studies were carried out to compare the analysis results obtained from various approaches for membership function determination and fuzzy operation. Therefore, in this study, the authors selected Jinbu area, which a large number of landslides were occurred at in 2006, to apply two most commonly used methods, the frequency ratio and the cosine amplitude method to derive membership values for each controlling factor. In addition, the integration of different thematic layers to produce landslide susceptibility map was performed by several fuzzy operators such as AND, OR, algebraic product, algebraic sum and Gamma operator. The results of the landslide susceptibility analysis using two different methods for the determination of fuzzy membership values and various fuzzy operators were compared on the basis of ROC graph to check the feasibility of the fuzzy based landslide susceptibility analysis.

• Archives of design research
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• v.12 no.4
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• pp.191-200
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• 1999

Improving the design ability of idea developing and creative problem solving should be started from the primary school. Design education in the primary school should be not education for design but education by design. It helps students can naturally understand the basic concept of design and experience the process of activities. Therefore primary educational circle use the term of 'Design-related activities', or 'Design-Based Education'. It can be applied to variable themes of mathematics, science, music, society as well as Art. On the Basis of these literature review, the traditional design education as a part of the art education is analyzed in two aspects of its contents and behaviors. The contents in design education involve aesthetic·symbolic, useful·functional, and scientific·technological area. And, the basic design behaviors are classified with 'know', 'perceive', 'inquire', and so on. This concept becomes the analytic frame of the present condition of design education in Korean primary school. Through the analysis, it is found that the portion of scientific·technological area in contents and 'inquire' related behaviors are relatively very low. Also, the planning and teaching methods for leading children's opportunity of creative expression are found inadequate. This study proposes the potential capability and the integrative contents of design education in primary school.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.5
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• pp.436-442
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• 2020

ESS(energy storage system) has recently become an important power source in various areas due to increased renewable energy resources. The more ESS is used, the less the effective capacity of the ESS. Therefore, it is important to manage the remaining useful lifetime(RUL). RUL can be checked regularly by inspectors, but it is common to be monitored and estimated by an automated monitoring system. The accurate state estimation is important to ESS operator for economical and efficient operation. RUL estimation model usually requires complex mathematical calculations consisting of cycle aging and calendar aging that are caused by the operation frequency and over time, respectively. A lightweight RUL estimation model is required to be embedded in low-performance processors that are installed on ESS. In this paper, a lightweight ESS RUL estimation model is proposed to operate on low-performance micro-processors. The simulation results show less than 1% errors compared to the original RUL model case. In addition, a performance analysis is conducted based on ATmega 328. The results show 76.8 to 78.3 % of computational time reduction.

• 대한공업교육학회지
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• v.33 no.1
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• pp.44-66
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• 2008

As the way to intensify vocational education, the places to learn and work merge into one educational system and teaching-learning methods that were pointed at lecturer level are adjusted to learners level. However, the current education environment of vocational highschool doesn't keep up with a new teaching and learning paradigm due to the lack of government-level support and the lecturer level education as well. In this paper, we present a novel learner-leading e-Learning teaching & learning contents framework that intensifying self leading education. In this framework, we concern the ability of self leading, space perception and lesson preparation, preferences of multimedia, scholastic aptitude level and achievement level of students in vocational highschool. Moreover, with following the protocol of the suggested model, we generate a new e-learning contents applying to the subject "Introduction to industry". Especially, to perform better quality of contents, we have survey the whole content of the subject and assorted part of it that would work best with learner-leading e-Learning teaching and learning contents. As we tentatively apply e-learning contents to students in vocational highschool, 79% of them replied that contents brought advantages to get school accomplishment, whereas 19% of students answered in negative that contents wasn't helpful than we've expected. Therefore, the statistical results probe that the e-learning contents we proposed show positive effect, and we analyzed the reasons that deteriorate the effects of contents as shortage of budget and copyright limitation.