• Journal of Engineering Education Research
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• v.14 no.5
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• pp.75-82
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• 2011

The Emergence of german mechanical engineer group is related to the development of polytechnical schools which were founded by the german state governments. Following the model of vienna polytechnical schools, the german polytechnical schools aimed also to educate engineers for private industries. For this purpose, the practices and workshop experiences were more emphasized than the theoretical education. With the further industrialization, the demand for higher educated engineers grew, and the level of theories taught in the polytechnical schools approached to that of university. On the base of mathematicalization of technical and mechanical knowledge, the professors of polytechnical schools succeeded in the establishment of Technische Hochschule which ranked as university. The german mechanical engineers could differentiate themselves from the traditional technicians with the establishment of polytech schools and Technische Hochschule.

• Structural Engineering and Mechanics
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• v.65 no.5
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• pp.573-585
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• 2018

This article presents strain gradient elasticity-based procedures for static bending, free vibration and buckling analyses of functionally graded rectangular micro-plates. The developed method allows consideration of smooth spatial variations of length scale parameters of strain gradient elasticity. Governing partial differential equations and boundary conditions are derived by following the variational approach and applying Hamilton's principle. Displacement field is expressed in a unified way to produce numerical results in accordance with Kirchhoff, Mindlin, and third order shear deformation theories. All material properties, including the length scale parameters, are assumed to be functions of the plate thickness coordinate in the derivations. Developed equations are solved numerically by means of differential quadrature method. Proposed procedures are verified through comparisons made to the results available in the literature for certain limiting cases. Further numerical results are provided to illustrate the effects of material and geometric parameters on bending, free vibrations, and buckling. The results generated by Kirchhoff and third order shear deformation theories are in very good agreement, whereas Mindlin plate theory slightly overestimates static deflection and underestimates natural frequency. A rise in the length scale parameter ratio, which identifies the degree of spatial variations, leads to a drop in dimensionless maximum deflection, and increases in dimensionless vibration frequency and buckling load. Size effect is shown to play a more significant role as the plate thickness becomes smaller compared to the length scale parameter. Numerical results indicate that consideration of length scale parameter variation is required for accurate modelling of graded rectangular micro-plates.

• Journal of the Korean Society of Safety
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• v.29 no.1
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• pp.86-92
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• 2014

This paper provides an integrated view on human and system interaction in advanced and automated systems, which adopting computerized multi-functional artifacts and complicated organizations, such as nuclear power plants, chemical plants, steel and semi-conduct manufacturing system. As current systems have advanced with various automated equipments but human operators from various organizations are involved in the systems, system safety still remains uncertain. Especially, a human operator plays an important role at the time of critical conditions that can lead to catastrophic accidents. The knowledge on human error helps a risk manager as well as a designer to create and control a more credible system. Several human error theories were reviewed and adopted for forming the integrated perspective: gulf of execution and evaluation; risk homeostasis; the ironies of automation; trust in automation; design affordance; distributed cognition; situation awareness; and plan delegation theory. The integrated perspective embraces human error theories within three levels of human-system interactions such as affordance level, psychological logic level and trust level. This paper argued that risk management process should dealt with human errors by providing (1) reasoning improvement; (2) support to situation awareness of operators; and (3) continuous monitoring on harmonization of human system interaction. This approach may help people to understand risk of human-system interaction failure characteristics and their countermeasures.

• Journal of the Korean Society for Library and Information Science
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• v.20
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• pp.223-270
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• 1991

To give any science or discipline an assured status, the most important and fundamental thing is to establish the method of research. 'Bibliography' is an ambiguous and much-abused term in any area, oriental, anglo-american, or latin countries. This study is a little essay to examine the different theories of these three areas and to synthesize the common factors. It is devised three parts : the definition of the term itself and the transition of its concept, the introduction of each theory, and a proposition of methodology based on these theories. In all, bibliography is commonly understood to mean (i) a list of books and other graphic materials arranged according to some system, (ii) the study of books as material objects include historical and textual problems, (iii) as a science of books, the systematic study of all conditions of its production, diffusion, and utilisation, including the study of factors of explication of phenomenon, on the political, economical, technical, social and culturel plans.

• Journal of Astronomy and Space Sciences
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• v.39 no.3
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• pp.99-108
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• 2022

There are two models that explain the rotation curves of galaxies: dark matter, which gives the missing contribution to the gravitational potential of the standard theory of gravity, and modified theories of gravity, according to which the gravitational potential is created by ordinary visible mass. Both models have some disadvantages. The article offers a new look at the problem of galactic rotation curves. The author suggests that the moment of inertia creates an additional gravitational potential along with the mass. The numerical simulation carried out on the example of fourteen galaxies confirms the validity of such an assumption. This approach makes it possible to explain the constancy of gas velocities outside the galactic disk without involving the hypothesis of the existence of dark matter. At the same time, the proposed approach lacks the disadvantages of modified theories of gravity, where the gravitational potential is created only by the mass of visible matter.

• Bulletin of the Korean Chemical Society
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• v.11 no.5
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• pp.446-449
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• 1990

A phenomenological theory of viscosity which has been proposed by authors is applied to liquid metals for which the calculation is a severe test for liquid theories. The thermodynamic properties used in the calculations can be obtained by using the Roulette liquid theory. The calculated values of the viscosities for liquid metals are in good agreements with the observed values.

• International Journal of Concrete Structures and Materials
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• v.10 no.2
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• pp.143-147
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• 2016

In recent years, some modifications were introduced in the stress-strain relationship of the steel in order to develop a more efficient shear model for reinforced concrete members. The last contribution in this sense corresponding to the Refined Compression Field Theory (RCFT, 2009); this theory proposed a steel constitutive model that has account the tension stiffening area prescribed by technical codes, what simplifies all the design process. However, under certain design conditions supported by such codes, the RCFT model does not provide a real (non-complex) solution for the steel yield strain when the prescribed tension stiffening area is considered; then the load-strain response cannot be computed. In this technical note, the tension stiffening area is fixed in order to guarantee the application of the embedded steel constitutive model for all the standard design range.

• Journal of Korea Game Society
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• v.7 no.3
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• pp.1-12
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• 2007

This paper attempts to pursue the internal characters of gambling games. After examining the concepts of gambling and arranging related theories, we found that gambling games have 3 factors of technical intervention, betting and ratio of payment. The betting is subdivided 3 factors of existence of betting, unit speed of betting and extendibility of betting. These factors may be used to a framework of conceptual analysis to gambling games. If social and cultural factors can be added to these factors, gambling games can be comprehensively and empirically analyzed.

• Advances in materials Research
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• v.12 no.3
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• pp.193-210
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• 2023

This paper aims to analyze the dynamic response of a double nanobeam system with a medium viscoelastic layer under a moving load. The governing equations are based on the Eringen nonlocal theory. A thin viscoelastic layer has coupled two nanobeams together. An exact solution is derived for each nanobeam, and the dynamic deflection is achieved. The effect of parameters such as nonlocal parameter, velocity of moving load, spring coefficient and the viscoelastic layer damping ratio was studied. The results showed that the effect of the nonlocal parameter is significantly important and the classical theories are not suitable for nano and microstructures.

• Computers and Concrete
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• v.32 no.6
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• pp.553-565
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• 2023

This work is the first to apply nonlocal theory and a variety of deformation plate theories to study the issue of forced vibration and buckling in organic nanoplates, where the effect of the drag parameter inside the structure has been taken into consideration. Whereas previous research on nanostructures has treated the nonlocal parameter as a fixed value, this study accounts for its effect, and finds that its value fluctuates with the thickness of each layer. This is also a new point that no works have mentioned for organic plates. On the foundation of the notion of potential movement, the equilibrium equation is derived, the buckling issue is handled using Navier's solution, and the forced oscillation problem is solved using the finite element approach. Additionally, a set of numerical examples exhibiting the forced vibration and buckling response of organic nanoplates are shown. These findings indicate that the nonlocal parameter and the drag parameter of the structure have a substantial effect on the mechanical responses of organic nanoplates.