• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1996년도 춘계학술대회 논문집
• /
• pp.551-555
• /
• 1996

The continuing demand for quality products requires better understanding and improved control of the production process. And, in recent year requirements for flatness control in strip rolling have become increasinglysevere because of the control for flatness of cold rolled strip is essential for further down stream processing. Also a speeds of rolling mills to meet productivity requirements puts a demanding requirement on the control of flatness of rolled strip. The demands on a total flatness control system therefore are a measuring and indication system consisting of a measuring roll that is robust, accurate, reliable and require a minimum of maintenance. The critical prt of any control system is the quality of the information being provided by the measurement instrument or device. It is therfore of utmost importance to have an accurate, repeatable and reliable measuring system. So, in this paper, The measuring roll for automatic flatness control system of contact type has been investigated.

• Advances in materials Research
• /
• 제7권1호
• /
• pp.1-16
• /
• 2018

Thermal bifurcation buckling behavior of fully clamped Euler-Bernoulli nanobeam built of a through thickness functionally graded material is explored for the first time in the present paper. The variation of material properties of the FG nanobeam are graded along the thickness by a power-law form. Temperature dependency of the material constituents is also taken into consideration. Eringen's nonlocal elasticity model is employed to define the small-scale effects and long-range connections between the particles. The stability equations of the thermally induced FG nanobeam are derived via the principal of the minimum total potential energy and solved analytically for clamped boundary conditions, which lead for more accurate results. Moreover, the obtained buckling loads of FG nanobeam are validated with those existing works. Parametric studies are performed to examine the influences of various parameters such as power-law exponent, small scale effects and beam thickness on the critical thermal buckling load of the temperature-dependent FG nanobeams.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
• /
• pp.173-178
• /
• 2001

The materials processing factors such as remelting and casting, heat treatment and microstructure, sheet rolling and can body forming in the aluminum can-to-can recycling procedure have been investigated. Aluminum used beverage can(UBC) was remelted together with virgin aluminum. The ceramic filter was used during casting to remove large impurities. As-cast microstructure was composed of large intermetallic compound (mainly $\beta$ -phase) distributed in the aluminum matrix. By heat treatment, $\beta$ -phase was transformed to $\alpha$ -phase which was also formed from $Mg_2$Si particles. The heat treated ingots were hot-rolled at 48$0^{\circ}C$ and cold-rolled to thin sheets. Can making from this thin sheets was successful and earing was measured after can making. There was a critical cold reduction rate for minimum earing. Some cracks were initiated from the impurity particles which was not removed during filtering.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1999년도 하계종합학술대회 논문집
• /
• pp.333-336
• /
• 1999

In this paper, a new high speed parallel input and parallel output GF(2$^{m}$ ) multiplier based on standard basis is proposed. The concept of the multiplication in standard basis coordinates gives an easier VLSI implementation than that of the dual basis. This proposed algorithm and method of implementation of the GF(2$^{m}$ ) multiplication are represented by two kinds of basic cells (which are the generalized and fixed basic cell), and the minimum critical path with pipelined operation. In the case of the generalized basic cell, the proposed multiplier is composed of $m^2$ basic cells where each cell has 2 two input AND gates, 2 two input XOR gates, and 2 one bit latches Specifically, we show that the proposed multiplier has smaller complexity than those proposed in 〔5〕.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1999년도 추계종합학술대회 논문집
• /
• pp.388-391
• /
• 1999

This Paper presents an efficient algorithm that minimizes the area of the combinational system through cell replacement. During the minimization, it maintains the circuit speed same. For the minimization, the proposed algorithm defines the criticality of each cell, based on the critical delay and the number of paths passing through the cell. Then, it visits the cells of the system, one by one, from the one with the lowest criticality, and replaces it with the minimum area cell that satisfies the delay constraint. Experimental results, using the LGsynth91 benchmark circuits synthesized by misII, show that the proposed algorithm reduces the circuit area further by 17.54% on the average without sacrificing the circuit speed.

• Nuclear Engineering and Technology
• /
• 제38권6호
• /
• pp.489-504
• /
• 2006

A review has been made for the previous studies on safety of a geologic repository for high-level radioactive wastes (HLW) related to autocatalytic criticality phenomena with positive reactivity feedback. Neutronic studies on geometric and materials configuration consisting of rock, water and thermally fissile materials and the radionuclide migration and accumulation studies were performed previously for the Yucca Mountain Repository and a hypothetical water-saturated repository for vitrified HLW. In either case, it was concluded that it would be highly unlikely for an autocatalytic criticality event to happen at a geologic repository. Remaining scenarios can be avoided by careful selection of a repository site, engineered-barrier design and conditioning of solidified HLW. Thus, criticality safety should be properly addressed in regulations and site selection criteria. The models developed for radiological safety assessment to obtain conservatively overestimated exposure dose rates to the public may not be used directly for the criticality safety assessment, where accumulated fissile materials mass needs to be conservatively overestimated. The models for criticality safety also require more careful treatment of geometry and heterogeneity in transport paths because a minimum critical mass is sensitive to geometry of fissile materials accumulation.

• 대한교통학회지
• /
• 제9권1호
• /
• pp.47-56
• /
• 1991

With respect to stochastic delays at linked signals the solid quantitative information has not been available as yet. On the basis of field data the values of "I" (variance-mean ration of flow) were related with the rate of flow. The stochastic delays with specific "I" values were obtained from the distribution of overflow queue, which were calculated by the use of Markov chains. This examination of the results led to the derivation of a simple method for calculating stochastic dclays through the introduction of "I" into Miller's model. The good agreement was shown between the model and the field. The relationships between the cycle lengths and delays were examinated in a large number of conditions with regard to degree of saturation. signal split and link length. Within the practical range of cycle length uniform delays were dominant and no critical point was found in terms of minimum, delay. In highly saturated conditions however the weight of stochastic delay is noticeable.

• 한국강구조학회 논문집
• /
• 제8권3호통권28호
• /
• pp.55-65
• /
• 1996

For stability analysis of stifened rectangular thin plates with various boundary conditions, Ritz method is presented. An energy method is especially useful in those cases where a rigorous solution of the diferential eqution is unknown or where we have a plate reinforced by stiffeners and it is required to find only an approximate value of the critical load. The strain energy due to the plate bending and the work done by the in-plane forces are taken into account in order to apply the principle of the minimum potential energy. The buckling mode shapes of flexural beams with various boundary conditions are derived, and shape functions consistent with the given boundary conditions in the two orthogonal directions are chosen from those displacement functions of beams. The matrix equations for stability of stiffened rectangular thin plates are determined from the stationary condition of the total potential energy. Numerical example for stability behaviors of horizontally and vertically stiffened plates subjected to uniform compression, bending and shear loadings are presented and the obtained results are compared with other researchers' results.

• Structural Engineering and Mechanics
• /
• 제60권4호
• /
• pp.615-631
• /
• 2016

In this paper, an analytical method for the Post-buckling response of cylindrical shells with spiral stiffeners surrounded by an elastic medium subjected to external pressure is presented. The proposed model is based on two parameters elastic foundation Winkler and Pasternak. The material properties of the shell and stiffeners are assumed to be continuously graded in the thickness direction. According to the Von Karman nonlinear equations and the classical plate theory of shells, strain-displacement relations are obtained. The smeared stiffeners technique and Galerkin method is used to solve the nonlinear problem. To valid the formulations, comparisons are made with the available solutions for nonlinear static buckling of stiffened homogeneous and un-stiffened FGM cylindrical shells. The obtained results show the elastic foundation Winkler on the response of buckling is more effective than the elastic foundation Pasternak. Also the ceramic shells buckling strength higher than the metal shells and minimum critical buckling load is occurred, when both of the stiffeners have angle of thirty degrees.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회A
• /
• pp.1934-1938
• /
• 2008

Formation of air bubble is the one of common defects in UV nano imprint lithography. Location of dispensing and volume of droplets are among the most important parameters in the process. ]n this study, UV curable resin droplets with different volumes were dispensed at different locations and pressed to investigate air bubble formation. By varying volume of droplet and dispensing location, process conditions were found for minimum air bubble area.