• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2310-2314
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• 2007

Stable molecular conformations were calculated for the p-tert-butylcalix[4]arene crown ether bridged at the lower rim with pyridyl unit (1) in the various conformers and their potassium-ion complexes. The structures of three distinct conformations have been optimized using DFT B3LYP/6-31G(d,p) method. Relative stability of free host 1 is in following order: cone (most stable) > partial-cone > 1,3-alternate conformer. For two different kinds of complexation mode, the potassium cation in the crown-ether moiety (cr) has much better complexation efficiency than in the benzene-rings (bz) pocket for all three kinds of conformation of host molecule 1. The relative stability of complex (1+K+) in the cr-binding mode is in following order: partial-cone (most stable) ~ cone > 1,3-alternate conformer.

• Journal of information and communication convergence engineering
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• v.7 no.4
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• pp.516-520
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• 2009

RSA crypto-processors equipped with more than 1024 bits of key space handle the entire key stream in units of blocks. The RSA processor which will be the target design in this paper defines the length of the basic word as 128 bits, and uses an 256-bits register as the accumulator. For efficient execution of 128-bit multiplication, 32b*32b multiplier was designed and adopted and the results are stored in 8 separate 128-bit registers according to the status flag. In this paper, an efficient method to execute 128-bit MAC (multiplication and accumulation) operation is proposed. The suggested method pre-analyzed the all possible cases so that the MAC unit can remove unnecessary calculations to speed up the execution. The proposed architecture prototype of the MAC unit was automatically synthesized, and successfully operated at 20MHz, which will be the operation frequency in the RSA processor.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.5
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• pp.43-51
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• 1993

A new Hangul code called Truecode is developed for accomodating to the future computing environments of graphical user interface and multimedia as well as for corresponding with the invention principle of Hangul. Truecode is not a forced two-byte code of syllable unit, as completion-type of combination-type, currently used, but a one byte code of phoneme unit, which can represent initial consonant, vowel, and final consonant each. It is quite different from three-byte code of syllable unit and also does not require the fill code used for three-byte code. We expect great contribution to the Hangul culture from Truecode's some important following features. It can express all the Korean characters we may imagine and does not cause any problem in communication. As well as we may use direct connection font, we can assign ont-to-one correspondence between Truecode and a keyboard with three sets. Truecode has a good advantage in developing application softwares of Hangul and it can nicely be applied to the fields of speech recognition and artificial intelligence using natural language.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.9
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• pp.1149-1156
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• 2001

The objective of the present study is to investigate the performance of electronic scale mitigation unit(ESMU), which reduces the amount of scale in a heat exchanger. The circular tube with diameter of 19mm and plate-and-frame heat exchangers with 20 thermal plates were used for the tests. In order to accelerate the rate of scale in a laboratory test, artificial hard water of 1000ppm(as CaCO$_3$) was recirculated at a flow rate of 5 lpm, 7 lpm, and 9 lpm throughout the tests. The effect of ESMU on the scale thickness and overall heat transfer coefficients was examined. The test results showed that the ESMU could reduce the scale deposits even in the acceleated test.

• Kyungpook Mathematical Journal
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• v.60 no.3
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• pp.485-505
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• 2020

We present a complete description of all the extreme points of the unit ball of 𝓛_s(²𝑙³_∞) which leads to a complete formula for ║f║ for every f ∈ 𝓛_s(²𝑙³_∞)^∗. We also show that $extB_{{\mathcal{L}}_s(^2l^3_{\infty})}{\subset}extB_{{\mathcal{L}}_s(^2l^n_{\infty})}$ for every n ≥ 4. Using the formula for ║f║ for every f ∈ 𝓛_s(²𝑙³_∞)^∗, we show that every extreme point of the unit ball of 𝓛_s(²𝑙³_∞) is exposed. We also characterize all the smooth points of the unit ball of 𝓛_s(²𝑙³_∞).

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.745-752
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• 2009

This paper presents the optimized mixing design of lightweight aerated concrete using hydrogen peroxide. Design of experiments in order to the optimized mixing design was applied and commercial program (MINITAB) was used. Statistical analysis was used to Box-Behnken (B-B) method in response surface analysis. The influencing factors of experimental are unit cement content, water ratio and hydrogen peroxide ratio. According to the analysis of variance, at the hardened state, water ratio and hydrogen peroxide ratio affects on dried density, compressive strength and bending strength of lightweight aerated concrete, but unit cement content affects on only dried density. In the results of response surface analysis, to obtain goal performance, the optimized mixing design for lightweight aerated concrete using hydrogen peroxide were unit cement content of 800 kg/$m^3$, water ratio of 44.33% and hydrogen peroxide ratio of 10%.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.8
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• pp.730-739
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• 2015

In this paper, a wideband circular polarizer operating in the frequency range of 6~18 GHz is designed and fabricated using a multilayer structure with meanderlines. A T matrix expression for the unit structure, which consists of meanderline, dielectric substrate and spacer, was derived using the boundary value solution. A proposed meanderline structure was modeled as an array of unit meanderline cell in order to apply the waveguide model with PEC and PMC boundary conditions. The calculation procedures to obtain an equivalent susceptance of the unit meanderline cell using HFSS was also suggested. Using a hybrid method, which combines the T matrix with the HFSS results, and cut-and-try method, a wideband circular polarizer with low insertion loss and good AR performance was designed. The fabricated polarizer has the return loss less than -10 dB within 92 % bandwidth, the average insertion loss less than -0.24 dB, and the average AR below 2.6 dB for full 3:1 bandwidth.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3399-3404
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• 2013

A new accepter unit, pyrrolo[3,2-b]pyrrole-2,5-dione, was prepared and utilized for the synthesis of the conjugated polymers containing electron donor-acceptor pair for OPVs. Pyrrolo[3,2-b]pyrrole-2,5-dione unit, regioisomer of the known pyrrolo[3,4-c]pyrrole-1,4-dione, is originated from the structure of stable synthetic pigment. The new conjugated polymers with 1,4-diphenylpyrrolo[3,2-b]pyrrole-2,5-dione, thiophene and carbazole were synthesized using Suzuki polymerization to generate P1 and P2. The solid films of P1 and P2 show absorption bands with maximum peaks at about 377, 554 and 374, 542 nm and the absorption onsets at 670 and 674 nm, corresponding to band gaps of 1.85 and 1.84 eV, respectively. To improve the hole mobility of the polymer with 1,4-bis(4-butylphenyl)-pyrrolo[3,2-b]-pyrrole-2,5-dione unit, which was previously reported by us, the butyl group at the 4-positions of the N-substituted phenyl group was substituted with hydrogen and methyl group. The field-effect hole mobility of P2 is $9.6{\times}10^{-5}cm^2/Vs$. The device with $P2:PC_{71}BM$ (1:2) showed $V_{OC}$ value of 0.84 V, $J_{SC}$ value of 5.10 $mA/cm^2$, and FF of 0.33, giving PCE of 1.42%.

• Journal of Korean Society of Forest Science
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• v.4 no.1
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• pp.26-29
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• 1965

1. The purpose of this study was to find out the best sampling form and sampling unit in forest survey. 2. The value of small sampling unit was over estimated in comparison with that of large sampling unit. 3. The value of circular form was over estimated in comparison with that of the others. 4. The smallest unit for estimation in area sampling were as follows. a) 0.06 ha. in the rectangular plot. b) 0.08 ha. in the square plot. c) 0.10 ha. in the circular plot. 5. Conclusion was as follows. The best sampling unit was 0.06 hectoare in the rectangular plot, which was most economic above all and gave preferable result for in the forest survey.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.832-936
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• 1996

In this paper, we study a dynamic characteristics of HDD. HDD is constructed by spindle motor/disk unit, cover, base, E-block arm/suspension unit, and rotary actuator/voice coil motor. First, we make a FE model of spindle motor/disk unit and analyzed natural frequency/mode analytically and experimentally. Especially, the change of natural frequecy of spindle motor unit according to change of B.C is considered. Second, FE model of cover, base is made. Third, we assemble the above three FE mode, we get HEE assembly and dynamic analysis of HDD assembly is accomplished.