• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.2
• /
• pp.603-608
• /
• 2014

In many manufacturing such as the components of airplane and automobile, aluminum alloys(Al2024) which remarkable in low specific gravity and high strength have been utilized effectively. Face milling machining technology for surface roughness quality of workpiece has been applied in these fields. A face milling machining with chamfered throw away type insert tip can produce a perfect flat surface only in theory. But It is impossible because of many unwanted factors, namely, cutting temperature, plastic deformation, dynamic effect, etc. In this paper, experimental investigations are performed to improve surface roughness after high speed machining of Al2024 using qualified face milling cutter body for high speed machining.

• Transactions of Materials Processing
• /
• v.14 no.6 s.78
• /
• pp.520-526
• /
• 2005

In recent years, there has been a growth of the manufacture and application of magnesium products because of its small specific gravity as well as its relatively high strength. However, there are so many studies to assure good formability because magnesium sheet alloy is difficult to form. In this study, uniaxial tensile and biaxial tensile tests of AZ31 magnesium sheet alloy with thickness of 1.2mm were performed at room temperature. Uniaxial tensile tests were performed until $7{\%}$ of engineering strain. Lankford values and stress-strain curve were obtained. Biaxial tensile tests with cruciform specimen were performed until the breakdown of the specimen occurs. The yield loci were calculated by application of plastic work theory. The results are compared with the theoretical predictions based on the Hill and Logan-Hosford model. In this study, Hill's 1979 yield function for the case of m=2.8 and Logan-Hosford yield function for the case of M=8 give good agreements with experimental results. However, next study will be performed at warm-temperature because the specimens are broken under the $0.5{\%}$ of equivalent strain at biaxial tensile test.

• Current Optics and Photonics
• /
• v.6 no.1
• /
• pp.69-78
• /
• 2022

A high-resolution camera is a precise optical system. Its vibrations during transportation and launch, together with changes in temperature and gravity field in orbit, lead to different degrees of defocus of the camera. Thermal refocusing is one of the solutions to the problems related to in-orbit defocusing, but there are few relevant thermal refocusing mathematical models for systematic analysis and research. Therefore, to further research thermal refocusing systems by using the development of a high-resolution micro-nano satellite (CX6-02) super-resolution camera as an example, we established a thermal refocusing mathematical model based on the thermal elasticity theory on the basis of the secondary mirror position. The detailed design of the thermal refocusing system was carried out under the guidance of the mathematical model. Through optical-mechanical-thermal integration analysis and Zernike polynomial calculation, we found that the data error obtained was about 1%, and deformation in the secondary mirror surface conformed to the optical index, indicating the accuracy and reliability of the thermal refocusing mathematical model. In the final ground test, the thermal vacuum experimental verification data and in-orbit imaging results showed that the thermal refocusing system is consistent with the experimental data, and the performance is stable, which provides theoretical and technical support for the future development of a thermal refocusing space camera.

• Journal of English Language & Literature
• /
• v.56 no.4
• /
• pp.719-751
• /
• 2010

While Lukacs advocated the progressive effect that Darwin's evolutionary theory had on Goethe and Balzac, he was convinced that the "influences of Nietzsche, Freud, or Spengler on the writers" of his own time were "devastating." He maintains that to the "'vacuous' reality" of bourgeois life, "the bourgeois writer counterposes 'the life of the soul,' which is 'alone decisive.' This life of the soul then becomes the centre of gravity, and sometimes the sole content of his portrayal." Naming this creative tendency psychologism, he warns against the danger of "depicting only the 'inner life,' and carrying on a more or less conscious education in the direction of political and social indifferentism, of ignoring and pushing aside the 'inessential,' 'external' struggles of the world, in favour of the 'life of the soul,' which is all that matters." However, Frantz Fanon's analysis of the psychology of the colonized in Black Skin, White Masks displays that after all, "the life of the soul" cannot be separated from the "external' struggles of the world." Pat Barker's Regeneration Trilogy, which criticizes the conduct of World War I by British leaders and the British society in general with its patriarchal, gender, and class repression by depicting the psychopathology of the shell shock victims of the same war amply shows the possibility of portraying the "external struggles of the world" through the in-depth probing into "the life of the soul" and finding political and social relevance in the process.

• Advances in aircraft and spacecraft science
• /
• v.10 no.5
• /
• pp.419-437
• /
• 2023

This paper presents the study of the effects of rigid-body motion simultaneously with the presence of the effects of temporal variation due to the existence of morphing speed on the aeroelastic stability of the two-stage telescopic wings, and hence this is the main novelty of this study. To this aim, Euler-Bernoulli beam theory is used to model the bending-torsional dynamics of the wing. The aerodynamic loads on the wing in an incompressible flow regime are determined by using Peters' unsteady aerodynamic model. The governing aeroelastic equations are discretized employing a finite element method based on the beam-rod model. The effects of rigid-body motion on the length-based stability of the wing are determined by checking the eigenvalues of system. The obtained results are compared with those available in the literature, and a good agreement is observed. Furthermore, the effects of different parameters of rigid-body such as the mass, radius of gyration, fuselage center of gravity distance from wing elastic axis on the aeroelastic stability are discussed. It is found that some parameters can cause unpredictable changes in the critical length and frequency. Also, paying attention to the fuselage parameters and how they affect stability is very important and will play a significant role in the design.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.8 no.1
• /
• pp.87-95
• /
• 1988

In the arctic offshore regions, massive offshore gravity platforms are recommended to be construced because of severe environments. In such structures which is so large that its characteristic length is of the order of the wave length, wave-structure interaction problem has been solved using linear diffraction theory. Structural analysis of the large scale offshore structures requires wave force distribution along depth and wave pressure distribution on the body surface. In this study, existing computer program which calculates the total wave force acting on axisymmetric bodies has been modified to calculate wave force distribution along depth and wave pressure distribution on the body surface. Numerical results of pressure distribution for a fixed vertical cylinder obtained from this analysis has been compared with the results of an analytic solution of MacCamy-Fuchs, and good agreements has been obtained. It is desirable to use 6 in the case of analytic solution, and 5 in the case of numerical solution as the Fourier Mode of Green function. The results in this study are expected to be utilized for structural analysis such as pseudo-static analysis, dynamic analysis and fatigue analysis.

• Geomechanics and Engineering
• /
• v.28 no.3
• /
• pp.299-311
• /
• 2022

Water-resisting key stratum (WKS) between coal seams is an important barrier that prevents water inrush from goaf in roof under multi-seam mining. The occurrence of water inrush can be evaluated effectively by analyzing the fracture of WKS in multi-seam mining. A "long beam" water inrush mechanical model was established using the multi-seam mining of No. 2+3 and No. 8 coal seams in Xiqu Mine as the research basis. The model comprehensively considers the pressure from goaf, the gravity of overburden rock, the gravity of accumulated water, and the constraint conditions. The stress distribution expression of the WKS was obtained under different mining distances in No. 8 coal seam. The criterion of breakage at any point of the WKS was obtained by introducing linear Mohr strength theory. By using the mechanical model, the fracture of the WKS in Xiqu Mine was examined and its breaking position was calculated. And the risk of water inrush was also evaluated. Moreover, breaking process of the WKS was reproduced with Flac3D numerical software, and was analyzed with on-site microseismic monitoring data. The results showed that when the coal face of No. 8 coal seam in Xiqu Mine advances to about 80 m ~ 100 m, the WKS is stretched and broken at the position of 60 m ~ 70 m away from the open-off cut, increasing the risk of water inrush from goaf in roof. This finding matched the result of microseismic analysis, confirming the reliability of the water inrush mechanical model. This study therefore provides a theoretical basis for the prevention of water inrush from goaf in roof in Xiqu Mine. It also provides a method for evaluating and monitoring water inrush from goaf in roof.

• Journal of Korean Society of Water and Wastewater
• /
• v.22 no.5
• /
• pp.531-540
• /
• 2008

The main advantage of dissolved air flotation (DAF) in water treatment process is the small dimension compared with conventional gravity sedimentation and it can be basically reduced by the separation zone performed with the short solid-liquid separation time. Fine bubbles make such a short time possible to carry out solid from liquid separation as a collector on the course of water treatment. Therefore, the dimension of separation zone in DAF process is practically determined by the rise velocity of the bubble-floc agglomerates, which is a floc attached with several bubbles. To improve flotation velocity and particle removal efficiency in DAF process, many researchers have tried to attach bubbles as much as possible to flocs. Therefore, the maximum number of attached bubble on a floc and the rise velocity of bubble-floc agglomerates considered as the most important factor to design the separation zone of flotation tank in DAF process was simulated based on the population balance theory. According to the simulation results of this study, the size and volume concentration of bubble influenced on the possible number of attached bubble on a floc. The agglomerates attached with smaller bubble was more sensitive to hydraulic loading rate in the separation zone of DAF process. For the design of a high rate DAF process applied over surface loading 40 m/hr. it is required a precise further study on the variation of bubble property and behavior including in terms of bubble size distribution.

• Journal of KIISE:Computer Systems and Theory
• /
• v.28 no.10
• /
• pp.499-506
• /
• 2001

Terrain Following means that a mobile object, such a user's avatar, must follow terrain, remaining in contact with the ground at all times in virtual environments. This makes a virtual environment have the effects of gravity. Terrain Following is often done using collision detection: however this is inefficient, because general collision detection solves a problem that is inherently more complex than merely determining terrain contact points. Many virtual environments avoid the expense by utilizing a flat terrain with a constant altitude everywhere. This makes a terrain following trivial, but lacks realism. This paper provides as algorithm and a data structure for a terrain following using a neighboring area search as a way to search neighboring polygons. Because this algorithm uses a pre-processing step that stores the terrain polygons for calculating, it results in reducing overheads to workstations that is used to construct and maintain a virtual environment. Consequently, workstation can be used to apply not only a terrain following but also other things.

• Korean Institute of Interior Design Journal
• /
• no.11
• /
• pp.57-63
• /
• 1997

In the early 20'c, scientific thoughts make a change the absolute and separate concept of space-time into relative concept of continual entity; a kind of ideal world. It suggests that the meaning of geometry as absolute truth with which has endowed human beings would changed to a relative meaning of accumulation in intellectual work on 'nature'. This cognitive changes appeared into absolute arts in 20'c like Cubism, Superematism or Constructivism. De Stijl movement which had recepted the relative concepts like Einstein's 'theory of relativity' as a developed thought from Newton-Cartesian cognition on the world. Abstration would be adequate method for expressing the dynamics and interrelationship between forms and for giving values to indivisual elements in a compositiov. This method had appeared Modern architectural form, as a common framework. The expression characteristics of geometrical design in Deconstructive and Experimental architecture were summerized in four features through the results of the analysis. First, the relation of architectural element and intertextuality is expressed in discontinuation of context and refusal of functional building. Second, the concept of trace expresses as connection of place, decomposing of excavation of trace, trace of axis, trace of fragments. Third, anti-gravity expression is there to express of open cubic, to outgrow of rectangular system, to outgrow of volume, to separate of ground connectiov. Fourth, the complex composition of abstracted geometric form is these to abstracted geometry about indefinite shape, to layer through the overlap and collage, to de-meaning and amusement of form through the pursuit of uncertainty, to indeterminate of formal meaning through operation and composition of similar form cause to the diverse of meaning.