• Journal of Educational Research in Mathematics
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• v.12 no.4
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• pp.473-491
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• 2002

This article analyzes mathematics education from dialectical materialism acknowledging the objectivity of knowledge. The thesis that knowledge is objective advances to the recognition that knowledge will be internalized, and an idea of zone of proximal development(ZPD) is established as a practice program of internalization. The lower side of ZPD, i.e. the early stage of internalization takes imitation in a large portion. And in the process of internalization the mediational means play an important role. Hereupon the role of mathematics teacher, the object of imitation, stands out significantly. In this article, treating the contents of study as follows, I make manifest that teaching and learning in mathematics classroom are united dialectically: I hope to findout the method of teaching-learning to mathematical knowledge from the point of view that mathematical knowledge is objective; I look into how analysis into units, as the analytical method of Vygotsky, has been developed from the side of mathematical teaching-learning; I discuss the significance of mediational means to play a key role in attaining the internalization in connection with ZPD and re-illuminate imitation. Based on them, I propose how the role of mathematics teachers, and the principle of organization to mathematics textbook should be.

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.319-322
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• 2008

The viability of acetylene addition in each step of aromatic formation initiated by vinyl radical and acetylene also with its competition with structure rearrangement is investigated by determining optimal geometries and barrier and reaction energies using quantum mechanical methods. In principle, the addition reaction has more difficult in term of free energy and enthalpy compared to geometry arrangement. Under combustion conditions, i.e. T = 1200 K, acetylene addition is unfavorable mechanism as the barrier energy values rise much higher than that of geometry arrangement. However, in longer chain hydrocarbon case, e.g. n-CxHx+1 where x ³ 8, C-C bond rotation is rather difficult and requires high energy to form a ring structure, elongation chain is preferable.

• Journal of The Korean Association For Science Education
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• v.28 no.3
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• pp.253-268
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• 2008

This paper has two major purposes. One is to introduce the essentialist methodology as a way to articulate subjective aspects of human beings (e.g. teachers' personal values and concerns, philosophies, subjective experiences, etc.) at a deeper level. And the other is to present two portraits, as examples, of science teachers who actively address socioscientiifc issues (SSI) out of their own motivations. The primary data source was consecutive in-depth interviews with two science teachers, Jenna and Thomas, and the interviews were conducted on the basis of the principle of the "participant as ally" (Witz, 2006). The articulation based on the essentialist methodology shows that teachers' deep-rooted values and convictions often play a significant role as a personal social capital enough to expand their teaching practice (i.e. teaching SSI). Namely, this study confirms that teachers who are motivated out of their own convictions are likely to actively develop their own personal practical knowledge, and to implement particular topics or teaching strategies.

• Journal of The Korean Astronomical Society
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• v.32 no.2
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• pp.137-147
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• 1999

Recent studies show the importance of understanding three-dimensional magnetic reconnect ion on the solar surface. For this purpose, I consider non-coplanar magnetic reconnection, a simple case of three-dimensional reconnect ion driven by a collision of two straight flux tubes which are not on the same plane initially. The relative angle e between the two tubes characterizes such reconnection, and can be regarded as a measure of magnetic shear. The observable characteristics of non-coplanar reconnection are compared between the two cases of small and large angles. An important feature of the non-coplanar reconnect ion is that magnetic twist can be produced via the re-ordering of field lines. This is a consequence of the conversion of mutual helicity into self helicities by reconnection. It is shown that the principle of energy conservation when combined with the production of magnetic twist puts a low limit on the relative angle between two flux tubes for reconnect ion to occur. I provide several observations supporting the magnetic twist generation by reconnection, and discuss its physical implications for the origin of magnetic twist on the solar surface and the problem of coronal heating.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.110-110
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• 2017

Biological systems offer unique principles for the design and fabrication of engineering platforms (i.e., popularly known as "Biomimetics") for various applications in many fields. For example, the lotus leaves exhibit unique surfaces consisting of evenly distributed micro and nanostructures. These unique surfaces of lotus leaves have the ability of superhydrophobic property to avoid getting wet by the surrounding water (i.e., Lotus effect). Inspired by the surface topographies of lotus leaves, the artificial superhydrophobic surfaces were developed using various micro- and nanoengineering. Here, we propose new platforms that can control hydrophilic and hydrophobic property of surfaces by mimicking micro- and nanosurfaces of various natural leaves such as common camellia, hosta plantaginea, and lotus. Using capillary force lithography technology and polymers in combination with biomimetic design principle, the unique micro- and nanostructures mimicking natural surfaces of common camellia, hosta plantaginea, and lotus were designed and fabricated. We also demonstrated that the replicated polymeric surfaces had different hydrophilic and hydrophobic properties according to the mimicking the natural leaf surfaces, which could be used as a simple, but powerful methodology for design and fabrication of controlled hydrophilic and hydrophobic platforms for various applications in the field of agriculture and biological engineering.

• Structural Engineering and Mechanics
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• v.8 no.6
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• pp.607-622
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• 1999

Being a significant mode of deformation, shear effect in addition to the other modes of stretching and bending have been considered to develop two finite element models for the analysis of beams on elastic foundation. The first beam model is developed utilizing the differential-equation approach; in which the complex variables obtained from the solution of the differential equations are used as interpolation functions for the displacement field in this beam element. A single element is sufficient to exactly represent a continuous part of a beam on Winkler foundation for cases involving end-loadings, thus providing a benchmark solution to validate the other model developed. The second beam model is developed utilizing the hybrid-mixed formulation, i.e., Hellinger-Reissner variational principle; in which both displacement and stress fields for the beam as well as the foundation are approxmated separately in order to eliminate the well-known phenomenon of shear locking, as well as the newly-identified problem of "foundation-locking" that can arise in cases involving foundations with extreme rigidities. This latter model is versatile and indented for utilization in general applications; i.e., for thin-thick beams, general loadings, and a wide variation of the underlying foundation rigidity with respect to beam stiffness. A set of numerical examples are given to demonstrate and assess the performance of the developed beam models in practical applications involving shear deformation effect.

• Structural Engineering and Mechanics
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• v.74 no.6
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• pp.723-735
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• 2020

This study is reported the adhesion failure in adhesive bonded composite and specifically for the T-joint structure. Three-dimensional finite element analysis has been performed using a commercial tool and the necessary outcomes are obtained via an eight noded solid element (Solid 185-element) from the library of ANSYS. The structural analysis input has been incurred through ANSYS parametric design language (APDL) code. The normal and shear stress distributions along different layers of the joint structure have been evaluated as the final outcomes. Based on the stress distributions, failure location in the composite joint structure has been identified by using the Tsai-Wu stress failure criterion. It has been found that the failure index is maximum at the interface between flange and web part of the joint (top layer) which indicates the probable location of failure initiation. This kind of failures are considered as adhesion failure and the failure propagation is governed by strain energy release rate (SERR) of fracture mechanics. The different adhesion failure lengths are also considered at the failure location to calculate the SERR values i.e. mode I fracture (opening), mode II fracture (sliding) and mode III fracture (tearing) along the failure front. Also, virtual crack closure technique (VCCT) principle of fracture mechanics steps is used to calculate the above said SERRs. It is found that the mode I SERR is more dominating compared to other two modes of failure for the joint considered. Finally, the influences of various parametric (geometrical and material) effect on SERR of the joint structure are evaluated and discussed in details.

• Smart Structures and Systems
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• v.3 no.2
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• pp.147-172
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• 2007

The present paper is concerned with the design of distributed sensors and actuators. Strain type sensors and actuators are considered with their intensity continuously distributed throughout a continuous structure. The sensors measure a weighted average of the strain tensor. As a starting point for their design we introduce the concept of collocated sensors and actuators as well as the so-called natural output. Then we utilize the principle of virtual work for an auxiliary quasi-static problem to assign a mechanical interpretation to the natural output of the sensors to be designed. Therefore, we take the virtual displacements in the principle of virtual work as that part of the displacement in the original problem, which characterizes the deviation from a desired one. We introduce different kinds of distributed sensors, each of them with a mechanical interpretation other than a weighted average of the strain tensor. Additionally, we assign a mechanical interpretation to the collocated actuators as well; for that purpose we use an extended body force analogy. The sensors and actuators are applied to solve the displacement tracking problem for continuous structures; i.e., the problem of enforcing a desired displacement field. We discuss feed forward and feed back control. In the case of feed back control we show that a PD controller can stabilize the continuous system. Finally, a numerical example is presented. A desired deflection of a clamped-clamped beam is tracked by means of feed forward control, feed back control and a combination of the two.

• Wind and Structures
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• v.29 no.6
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• pp.371-387
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• 2019

In the present paper, a simple refined nth-higher-order shear deformation theory is applied for the free vibration analysis of laminated composite plates. The proposed displacement field is based on a novel kinematic in which include the undetermined integral terms and contains only four unknowns, as against five or more in case of other higher-order theories. The present theory accounts for adequate distribution of the transverse shear strains through the plate thickness and satisfies the shear stress-free boundary conditions on the top and bottom surfaces of the plate, therefore, it does not require problem dependent shear correction factor. The governing equations of motion are derived from Hamilton's principle and solved via Navier-type to obtain closed form solutions. The numerical results of non-dimensional natural frequencies obtained by using the present theory are presented and compared with those of other theories available in the literature to verify the validity of present solutions. It can be concluded that the present refined theory is accurate and efficient in predicting the natural frequencies of isotropic, orthotropic and laminated composite plates.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.64
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• pp.155-185
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• 2014

Liability for the manufacture or supply of defective products can arise in two principle ways, in tort and in contract. English law has long regarded shipbuilding contract as agreement for the sale and purchase of goods. The consequence of which is that unless the Buyer and Builder agree otherwise, terms will automatically be implied into the contract between them as to the quality and performance of the completed vessel. The same principle applies to sub-contracts allied to the shipbuilding contract. On the other hand, one case decisions established that ".... a contract to build a ship, though a contract of sale of goods, has also some characteristics of a building contract", Recently the liability of a manufacturer in tort for physical damage i.e. personal injury and damage to property other than alleged to be defective is now well settled in most countries. Accordingly the Builder may face third party claims in tort more regularly than they have in the past, if the statutory implied terms have not been expressly excluded in contract. In such circumstances, it is necessary for the Builder to be prepared with counter measures to secure the stability of the vessel from its design development, building process, delivery and operation etc. The purpose of this paper is, from the case of "MSC Carla", to review product liability, jurisdiction and the initial date of extinctive prescription, then to suggest counter measures to the Builder.