• Bulletin of the Korean Chemical Society
• /
• v.29 no.8
• /
• pp.1485-1490
• /
• 2008

Dumbbell-shaped aromatic amphiphilic molecules consisting of a dodeca-p-phenylene as a rigid segment and oligoether dendrons as a flexible chains were synthesized, characterized, and their aggregation behavior was investigated in the bulk and at the air-water interface. In contrast to the molecule 2 which shows a nematic liquid crystalline state, molecule 1 based on shorter dendritic chains was observed to self-assemble into a 3-D primitive orthorhombic supercrystal. And molecule 1 at the air-water interface was observed to reorganize from circular plates to ring structures by lateral compressions.

• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 2003.10a
• /
• pp.138.1-138
• /
• 2003

Potato mop-top virus(PMTV) was identified from Solanum tuberosum cv. Gawon showing bright chlorotic mottle symptom in Namwon, Korea. Samples were collected green-house in February, 2003. Electron microscopic examination of negatively stained preparation revealed that PMTV were rigid-rod shaped particles about 100-150, 250-300 nm x 18-20 nm in length. In ultrathin sections of leaf tissue from diseased potato plants, cluster of viruses particles were observed in the cytoplasm. TAS-ELISA determined that the virus was serologically related to PMTV. PMTV produced double ring necrotic local lesion in inoculated leaf of Chenopodium amaranticolor in incubated at 15$^{\circ}C$. The PMTV could be detected with RT-PCR using PMTV detectable primer set designed to amplify about 540 bp of the partial CP gene of PMTV

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 1998.10a
• /
• pp.223-238
• /
• 1998

In this study, to investigate the effect of process variables such as reduction in area, semi-die angle and the rectangular ratio to the corner filling which influences the dimensional accuracy of the final product in the drawing of the cluadrangle rod from a round bar, it has been simulated by three dimensional rigid-plastic finite element method. In order to reduce the number of simulation artificial neural network has been introduced. Also, through the experimental investigation, the present results have been implemented on the industrial product. In results, the main process variable is the combination of the semi-die angle in case of the irregular shaped drawing process and reduction in area in the event of regular shaped drawing process, respectively.

• Transactions of Materials Processing
• /
• v.8 no.5
• /
• pp.482-490
• /
• 1999

7000 series Al alloy with good mechanical properties has been focused with tendency to reduce the components weight of aircraft and automobile. However, it is difficult to manufacture a sound extruded product because of segregation, grain growth, casting defect, surface defect, decreasing extrudability and so on. The objective of this study is to manufacture a new 7000 al alloy more than the extrudability of A7N01 and A7003 through controlling the weight (%) Mg, Zn, Si. Hot extrusion experiments on the axisymmetric rod are performed in 500℃ and also performed analysis of the same process using unmerical analysis method, a coupled rigid-thermoviscoplastic finite element method. Extrusion limit diagram was obtained for the developed alloy by FE-simulation in order to define the relationship of extrusion speed and initial billet temperature.

• KIEE International Transactions on Power Engineering
• /
• v.4A no.4
• /
• pp.227-235
• /
• 2004

This paper presents a new theoretical approach to energy-based power system analysis for multibus power transmission systems. On the basis of mechanical analogy, an exact energy integral expression is derived for lossy multi-bus systems through rigorous energy analysis. A simple rigid rod model of mechanical power transfer system is introduced to address the physical meanings of potential energy terms associated with transfer conductances as well as transfer susceptances. Finally, energy-based analysis has been proposed to show that the energy function has all information of the power system characteristics.

• Bulletin of the Korean Chemical Society
• /
• v.22 no.9
• /
• pp.999-1004
• /
• 2001

(1-Chloro-2,2-dicyanovinyl)benzene or 1,4-bis(1-chloro-2,2-dicyanovinyl)benzene was reacted with 2-amino-phenol to give the model compound, hydroxy enaminonitrile, which was found to undergo thermal cyclization reaction to form the corresponding benzoxazole. This intramolecular cyclization reaction is expected to occur through nucleophilic attack to electropositive enamine carbon by ortho-hydroxy group on the phenyl ring, which is accompanied by the release of neutral malononitrile through rearrangement. From each bifunctional monomer, o-hydroxy substituted polyenaminonitrile was prepared and characterized as a new precursor polymer for well-known aromatic polybenzoxazole. Also the unusual macrocyclic dimer formation from the 1,4-bis(1-chloro-2,2-dicyanovinyl)benzene and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane polymerization reaction system was discussed. The thermal cyclization reactions and the properties of polymers were investigated using FT-IR and thermal analysis (DSC & TGA).

• Bulletin of the Korean Chemical Society
• /
• v.21 no.4
• /
• pp.434-440
• /
• 2000

We present the results of computer simulation for the steady shear flows of rodlike molecules using nonequi-librium molecular dynamics simulation (NEMD) method. The model particle is a rigid rod composed of lin-early connected 6-sites and the Lennard-Jones 12-6 potential governs interactions between sites in different molecules. The system of rodlike molecules exhibits the change of orientational structure, that is, isotropic-nematic transition at high shear rates. We elucidate the nature of the ordered system developed from an isotro-pic phase by steady shear through an analysis of various quantities: orientational order parameters, orientational pair correlation functions, orientational distribution function, and snapshots of configurations. The effects of temperature and density on the shear rate dependence of orientational structure are described.

• Earthquakes and Structures
• /
• v.24 no.6
• /
• pp.405-413
• /
• 2023

Various methods have been used to strengthen structures against earthquakes. Isolator systems are among the methods to control the structure's response. Instead of increasing the strength and capacity of the structure, these systems react to earthquakes. In this paper, an isolator system was investigated with the flexible piers of ∨ and ∧ elements, which were perpendicular to each other and connected by a rod hinged at both ends. The behavior of the isolator system was studied. Many structures have non-rigid connections; the effect of this issue was considered in the pendulum column's performance in this paper. Its mathematical equations were derived, solved with MATLAB software, and compared with ABAQUS results. Later on, the isolator system was investigated during different earthquakes. The results show that this mechanism is suitable as an isolator. The period was found to be longer in the flexible pier form. The flexible piers have an influential role in the system's response by reducing the system's stiffness considerably. Among the different damping ratios, those with more than 15% had better results. Finally, the tested model verified the theory.

• Design & Manufacturing
• /
• v.7 no.1
• /
• pp.11-18
• /
• 2013

This paper presents the plastic inhomogeneous deformation behavior of bimetal composite rods during the axisymmetric and steady-state extrusion process through a conical die. The rigid-plastic FE model considering frictional contact problem was used to analyze the co-extrusion process with material combinations of Cu/Al. Different cases of initial geometry shape for composite material were simulated under different conditions of co-extrusion process, which includes the interference and frictional conditions. The main design parameters influencing on deformation pattern are diameter ratio of the composite components and semi-die angle. Efforts are focused on the deformation patterns, velocity gradient, predicted forming load and the end distance through the various simulations. Simulation results indicate that there is an obvious difference of forming pattern with various diameter ratio and semi-die angle. The analysis in this paper is concentrated on the evaluation of the design parameters on the deformation pattern of composite rod.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.11a
• /
• pp.365-368
• /
• 2006

RBSN Method, Rigid-Body-Spring Network Method, is a structural analysis method that overcomes the problems faced in FEM analysis of concrete or crack forming structures. In RBSN, irregular lattices are used to model structural components consisting of bulk material, curvilinear reinforcements, and their interfaces. Because reinforcements and their interfaces in the bulk material are freely positioned, meshing is irrespective of the geometry of the representing bulk material. In this paper, RBSN method of 3D is applied in simulating the pull-out test of FRP (Fiber Reinforced Polymer) embedded in concrete. The comparison of analysis results to experimental results shows that RBSN method simulates the shear-slip behavior very precisely. From the analysis results, 3D RBSN method is proven to be an effective and accurate analysis method for concrete structural analysis. Also, the results show that RBSN method can be a potential analysis method for concrete structures that can replace the current FEM analysis.