• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2007.06a
• /
• pp.349-350
• /
• 2007

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.305-308
• /
• 2005

Linear motor has been developed for linear motion of machine tools. Linear motor is useful to design the linear motion, high speed and high accuracy, because of the simple system not required the additional mechanical part such as coupling and ballscrew. This paper tested performance of linear motor such as velocity response, position tracing performance, subordinate Traction force change and positional accuracy.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2005.11a
• /
• pp.407-410
• /
• 2005

Acoustic coupling between combustion chamber and gas-liquid scheme injectors are studied numerically in liquid rocket engine adopting linear acoustic analysis. The injectors can play a role as half-wave resonators. The combustion chamber with numerous injectors shows peculiar acoustic coupling with the injectors. As the injector length approaches a half wavelength or the original tuning length, new injector-coupled acoustic modes show up in the chamber and thereby, the acoustic-damping effect of the tuned injectors is appreciably degraded.

• Coupled systems mechanics
• /
• v.9 no.6
• /
• pp.539-562
• /
• 2020

In this paper the linear elastic coupling between a 2 degree of freedom shear-type frame system and a rigid block is analytically and experimentally investigated. As demonstrated by some of the authors in previous papers, it is possible to choose a coupling system able to guarantee advantages, whatever the mechanical characteristics of the frame. The main purpose of the investigation is to validate the analytical model. The nonlinear equations of motion of the coupled system are obtained by a Lagrangian approach and successively numerically integrated under harmonic and seismic excitation. The results, in terms of gain graphs, maps and spectra, represent the ratio between the maximum displacements or drifts of the coupled and uncoupled systems as a function of the system's parameters. Numerical investigations show the effectiveness of the nonlinear coupling for a large set of parameters. Thus experimental tests are carried out to verify the analytical results. An electro-dynamic long-stroke shaker sinusoidally and seismically forces a shear-type 2 d.o.f frame coupled with a rigid aluminium block. The experimental investigations confirm the effectiveness of the coupling as predicted by the analytical model.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.7
• /
• pp.59-67
• /
• 2013

The radiation characteristics of an E-plane linear array antenna composed of inductive loaded patch antennas (ILPAs) are investigated. The radiation characteristics of an ILP array antenna are significantly improved compared to those of a conventional array antenna because the mutual coupling of an ILP array antenna is very small. The patch length of a $5{\times}2$ ILPA for the enhancement of the radiation characteristics of a 5-element E-plane linear array antenna composed of ILPAs is presented.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37C no.12
• /
• pp.1296-1302
• /
• 2012

In this research, optimization of a dual-band dipole array was performed using genetic algorithm. A non-uniform, aperture-shared linear array was configured with dipoles which resonate at 4 GHz and 9.5 GHz. The excited current distributions on dipoles were computed considering mutual coupling between dipole elements. The current distributions were also computed using method of moment (MoM). The optimization using genetic algorithm was performed to obtain the low sidelobe levels in two operating frequency band. The PSLs of the optimized array for 4 GHz and 9.5 GHz are -15.7 dB and -17 dB, respectively. Comparison between computed and simulated results are also discussed.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.5 s.248
• /
• pp.609-614
• /
• 2006

Recently linear motor has been used mainly for high speed feeding performance of machine tools. The advantages of linear motor are not only high speed but high accuracy, because it is not required the coupling and ballscrew for converting rotary to liner motion. Before applying in different moving system, the dynamometer is necessary to test the performance. In Korea, the linear motor is producing in a couple of company However, the liner motor dynamometer is not commercialized yet, like as rotary motor dynamometer. In this paper, a linear motor dynamometer is designed and manufactured using a MR damper. The dynamometer system developed in this study could be used for testing the positioning accuracy fur different loading conditions, traction forces, dynamic performance and so on.

• Polymer(Korea)
• /
• v.33 no.2
• /
• pp.158-163
• /
• 2009

In this study, we synthesized a series of dendritic polystyrene-b-linear poly (t-butyl acrylate) copolymers with well-defined molecular architectures. The hydroxyl group located at the focal point of the second generation dendron bearing polystyrene ($M_n$ = 1000 g/mol) peripheries was converted into amine group via the following stepwise reactions: 1) tosylatoin, 2) azidation, and 3) reduction. On the other hand, the linear poly (t-butyl acrylate)s were prepared by an atom transfer radical polymerization (ATRP) of t-butyl acrylate where benzyl 2-bromopropanoate and Cu(I)Br/PMDETA were used as initiator and catalyst, respectively. To convert the end group of prepared poly (t-butyl acrylate) s into carboxylic acid, a debenzylation was performed using Pd/C catalyst under $H_2$ atmosphere. In the final step, dendritic-linear block copolymers were obtained through a simple amide coupling reaction mediated by 4-(dimethylamino) pyridine(DMAP) and N,N'-diisopropylcarbodiimide(DIPC). The resulting diblock copolymers were shown to have well-defined molecular weights and narrow molecular weight distributions as supported by $^1H$-NMR spectroscopy and gel permeation chromatography(GPC).

• Elastomers and Composites
• /
• v.12 no.1
• /
• pp.27-32
• /
• 1977

The kinetics of azo-coupling reaction of N-acetyl-H-acid (1-acetamino-8-hydroxynaphthalene-3, 6-disulfonic acid) with several heterocyclic diasonium compounds such as diazotiged 3-aminopyridine, 3-aminoquinoline, 8-aminoauinoline and aniline was studied. It was found that reactions proceeded at remarkably different rate. Reaction rate was in increasing order; 3-aminopyridine, 3-aminoquinoline, 8-aminoauinoline and aniline. And the activation energies were 9.62, 10.10, 10.39, 10.70 Kcal/mole, respectively. Especially, the rate constant of 3-aminopyridine was 100 times larger than that of benzene diasonium compound even in strong acidity. Hammett plot was also made of the rate constants obtained against the heterocyclic substituent constants reported in the literature. A good linear relationship was obtained and the reaction constant of N-acetyl H-acid was calculated to be 3.14.

• Journal of computational fluids engineering
• /
• v.14 no.1
• /
• pp.35-44
• /
• 2009

To adequately analyze flows in pipe or duct network system, traditional node-based junction coupling methods require the junction loss which is specified by empirical or analytic correlations. In this paper, a new finite volume junction coupling method using a ghost junction cell is developed by considering the interchange of linear momentum as well as the important wall-effect at junction without requiring any correlation on the junction loss. Also, boundary treatment is modified to preserve the stagnation enthalpy across boundaries, such as pipe-end and the interface between junction and branch. Also, the computational accuracy and efficiency of the Godunov-type finite volume schemes are investigated by tracing the total mechanical energy of rapid transients due to sudden closure of valve at downstream end.