• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.5
• /
• pp.1227-1236
• /
• 1993

In conventional thermodynamics, energy is regarded as a physical quantity transferring from one system to another, but in present study, the real energy is regarded as a physical quantity coming out from one interaction and absorbing into another interaction between two systems. To reconstruct thermodynamics with such a point of view, available work is distinguished from half work in conventional work concepts, and a special space named reversible world is proposed in which every process is reversible and the only measurable quantity is available work and just the equality between the intensities of two systems can be verified. As results, thermodynamic laws are arranged into two principles in the reversible world-conservations of energy elements and conservation of available energy. It means the exsistences of state properties corresponding to transferring energy elements and the available work. The former are extensive properties and the later is named potential work which is a property of the composite system and a kind of mathematical distance. The conventional available energy (exergy) and internal energy can be explained as the special cases of potential work, and the conventional first law of thermodynamics can be derived from the principle of the conservation of available energy. With these new concepts, the description of thermodynamic processes is more comprehensive. The second law of thermodynamics is no longer needed in the reversible world.

• Applied Chemistry for Engineering
• /
• v.2 no.4
• /
• pp.311-329
• /
• 1991

Electrochemical behavior of surface active Osmium bipyridine complex adsorbed in a monomolecular layer on tin oxide electrodes by the Langmuir-Blodgett method was studied. Theoretical equation of cyclic voltammetry of electrode reactions for redox species adsorbed as monolayer form was discussed by reversible and quasi-reversible waves. The film was transferred onto the $SnO_2$ electrode surface and then amounts of charge on the electrode were measured in the technique of cyclic voltammetry. The electron transfer mediation of these monolayer with $Fe^{2+}$, TEMPOL and others were studied. And the cyclic voltammetry were simulated by taking into account the interaction parameters. From these values, we found it possible to fit almost all measured cyclic voltammograms with these parameters. The recent works and directions using LB method were introduced with various applicable field.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.13 no.4
• /
• pp.737-744
• /
• 2018

The RSA cryptosystem is a one of the first public-key cryptosystems and is widely used for secure data transmission and electric signature. The security of the RSA cryptosystem is based on the difficulty of factoring large numbers.. Though many studies on finding methods for factoring large numbers are going on, the results of that are all experimental or probabilistic. We, in this paper, construct an algorithm for finding large prime factors of integers without factoring integers using properties of the structure of semigroup of imaginary quadratic order and non-invertible ideal, then propose our methods foe deterministic attack against RSA cryptosystem.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.10 no.1
• /
• pp.55-61
• /
• 2000

The electrochemical properties of hard carbon anodes in lithium ion batteries were improved by carbon coating using polyvinyl chloride (PVC). The reduction in irreversible capacity occured and the reversible capacity increased. It is suggested that the PVC carbon coating modifies the surface of hard carbon and reduces the surface reaction with species from air. The degree of the graphitization of PVC carbon was controlled by an addition of Ni, and the effect of the amount of Ni addition on the electrochemical properties was discussed.

• Applied Chemistry for Engineering
• /
• v.10 no.2
• /
• pp.196-200
• /
• 1999

The electrochemical properties of 9-methyl-2,3,6,7-tetramethoxyfluorene have been investigated by cyclic voltammetry in acetonitrile, dichloromethane, trifluoroacetic acid (TFA) and trifluoroacetic acid anhydride (TFAn). The first charge transfer for the compound in $CH_3CN$ appeared to be a quasi-reversible one-electron step. The second oxidation step from cation to dication was irreversible. However, the oxdition of the compound in a mixture of solvents containing $CH_2Cl_2$, TFA and TFAn was reversible for both the first and second charge transfer reactions. Since the electrolytic products display a darkblue color and can be stabilized in the solvent mixture, they may be used as an electrochromic material.

• The Korean Journal of Nuclear Medicine
• /
• v.32 no.4
• /
• pp.325-331
• /
• 1998

Purpose: We evaluated the importance of redistribution and 24 hour reinjection images in T1-201 SPECT assessment of myocardial viability after acute myocardial infarction (AMI). Materials and Methods: We performed dipyridamole stress-4 hour redistribution-24 hour reinjection T1-201 SPECT in 43 patients with recent AMI (4-16 days). The myocardium was divided into 16 segments and perfusion grade was measured visually with 4 point score from 0 to 3 (absent uptake to normal uptake). A perfusion defect with stress score 2 was considered moderate. A defect was considered severe if the stress score was 0 or 1 (absent uptake or severe perfusion decrease). Moderate defect on stress image were considered viable and segments with severe defect were considered viable if they showed improvement of 1 score or more on redistribution or reinjection images. We compared the results of viability assessment in stress-redistribution and stress-reinjection images. Results: On visual analysis, 344 of 688 segments (50%) had abnormal perfusion. Fifty two (15%) had moderate perfusion defects and 292 (85%) had severe perfusion defects on stress image. Of 292 severe stress defects, 53 were irreversible on redistribution and reversible on reinjection images, and 15 were reversible on redistribution and irreversible on reinjection images. Two hundred twenty four of 292 segments (76.7%) showed concordant results on stress-redistribution and stress-reinjection images. Therefore 24 hour reinjection image changed viability status from necrotic to viable in 53 segments of 292 severe stress defect (18%). However, myocardial viability was underestimated in only 5% (15/292) of severe defects by 24 hour reinjection. Conclusion: The 24 hour reinjection imaging is useful in the assessment of myocardial viability. It is more sensitive than 4 hour redistribution imaging. However, both redistribution and reinjection images are needed since they complement each other.

• Composites Research
• /
• v.21 no.2
• /
• pp.8-14
• /
• 2008

Decrease of strength in composite material is generally caused by water absorption. It makes fracture of material, and loss of money or human lives. The objective of this study is to investigate the causes of decrease in strength by water absorption. Mechanism of water absorption was supposed as three steps. This mechanism is consisted of absorption into resin, absorption between resin and surface treatment agent, and delamination between fiber and resin. Conditions of test were supplied differently; kinds of fiber and resin, immersion time etc. Both of reversible reaction and irreversible reaction occurred simultaneously. Most of decrease in strength was finished at 2.5% water absorption, and the strength was recovered. At 4% water absorption, most of decrease was caused by irreversible reaction, therefore, there was a tendency not to be recovered in strength.

• Applied Chemistry for Engineering
• /
• v.5 no.2
• /
• pp.285-294
• /
• 1994

Some supported gold catalysts were prepared by impregnation and coprecipitation methods. Effect of gold addition and active sloe formation were studied by investigating particle sizes of gold, amounts of oxygen adsorbed, adsorption properties of CO and NO, and reduction and oxidation properties, etc.. The gold particles of the catalyst by impregnation were irregular and very large as 30~100 nm, but those by coprecipitation were uniform and ultra-fine as about 4 nm. On $Au/Al_2O_3$ catalyst, the addition of gold to inactive $Al_2O_3$ caused the decomposition of $N_2O$, and CO was not irreversibly adsorbed while $O_2$ was atomically and irreversibly adsorbed. The adsorption sites of oxygen were attributed to the active sites which were restricted to the circumference of hemispherical gold particle-support interface rather than all atoms on the surface of gold particle. Also, CO was reversibly and irreversibly adsorbed on $Al_2O_3$ at low temperature, and the addition of gold weakened both reversible and irreversible adsorptions. The affinity for CO on $Au/Co_3O_4$ catalyst decreased conspicuously compared to $Co_3O_4$. The effect of gold addition did not appear in reduction step but did remarkably in reoxidation step; the added gold promoted the reoxidation of the reduced cobalt atoms.

• Journal of Soil and Groundwater Environment
• /
• v.6 no.2
• /
• pp.49-56
• /
• 2001

Benzene, one of the aromatic hydrocarbons, can be degraded by physical, chemical and biological processes in aquifers. This study aimed at analyzing separately the three different forms of degradation by performing column tests. Column tests using KCl and benzene as tracers were conducted for four different cases: 1) no hydrogen peroxide and no microorganism, 2) hydrogen peroxide only; 3) microorganism only; 4) hydrogen peroxide and microorganism to investigate the sorption and degradation of benzene. The observed BTCs of KCl and benzene in all cases showed that the arrival times of the peaks of both tracers coincided well but the peak concentration of benzene was much lower than that of KCl. This reveals that a predominant process affecting the transport of benzene in a sandy soil is an irreversible sorption and/or degradation rather than retardation. Decay of benzene through sorption and degradation increased with the addition of hydrogen peroxide and/or microorganism. Dissolved oxygen decreased with the increase of benzene in all cases indicating that degradation of benzene was also influenced by dissolved oxygen. For BTCs with the addition of microorganisms (case 3 and case 4), microorganism showed much lower concentrations compared to the initial levels and an increasing tendency with time although concentrations of benzene returned to zero, indicating a possible retardation of microorganism due to reversible and irreversible sorption to the particle surfaces.

• Journal of the Korean Ceramic Society
• /
• v.40 no.11
• /
• pp.1085-1089
• /
• 2003

In the present study effects of SnO$_2$-impregnation on the cell performance of Mesocarbon Microbeads (MCMB) electrode in the Li-ion battery have been investigated. Sn element was impreganted into MCMB powders by the chemical titration, and then post annealed at 250$^{\circ}C$ for 1 h in ambient atmosphere to be transformed as tin-oxide. From the measurement for the cell performance with the half cell in which the SnO$_2$-impregnated MCMB was used as an anode, the SnO$_2$-impregnated MCMB showed higher charge/discharge capacities, higher reversible specific charge capacity and better cycleability than a raw MCMB. As the amount of impregnated SnO$_2$ increased, both reversible and irreversible capacities increased.