• Bulletin of the Korean Mathematical Society
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• v.42 no.2
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• pp.295-305
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• 2005

In this paper, we investigate exchange ideals and get some new characterization of exchange rings. It is shown that an ideal I of a ring R is an exchange ideal if and only if so is $QM_2$(I). Also we observe that every exchange ideal can be characterized by exchange elements.

• Bulletin of the Korean Mathematical Society
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• v.42 no.1
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• pp.45-51
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• 2005

In this paper, we establish necessary and sufficient conditions for an exchange ideal to be a qb-ideal. It is shown that an exchange ideal I of a ring R is a qb-ideal if and only if when-ever $a{\simeq}b$ via I, there exists u ${\in} I_q^{-1}$ such that a = $ubu_q^{-1}$ and b = $u_q^{-1}$. This gives a generalization of the corresponding result of exchange QB-rings.

• Journal of the Korean Mathematical Society
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• v.47 no.1
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• pp.1-15
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• 2010

We introduce, in this article, the quasi-stable exchange ideal for associative rings. If I is a quasi-stable exchange ideal of a ring R, then so is $M_n$(I) as an ideal of $M_n$(R). As an application, we prove that every square regular matrix over quasi-stable exchange ideal admits a diagonal reduction by quasi invertible matrices. Examples of such ideals are given as well.

• Honam Mathematical Journal
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• v.26 no.3
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• pp.247-256
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• 2004

Buchmann and Williams[1] proposed a key exchange system making use of the properties of the maximal order of an imaginary quadratic field. $H{\ddot{u}}hnlein$ et al. [6,7] also introduced a cryptosystem with trapdoor decryption in the class group of the non-maximal imaginary quadratic order with prime conductor q. Their common techniques are based on the properties of the invertible ideals of the maximal or non-maximal orders respectively. Kim and Moon [8], however, proposed a key-exchange system and a public-key encryption scheme, based on the class semigroups of imaginary quadratic non-maximal orders. In Kim and Moon[8]'s cryptosystem, a non-invertible ideal is chosen as a generator of key-exchange ststem and their secret key is some characteristic value of the ideal on the basis of Zanardo et al.[9]'s quantity for ideal equivalence. In this paper we propose the methods for finding the non-invertible ideals corresponding to non-primitive quadratic forms and clarify the structure of the class semigroup of non-maximal order as finitely disjoint union of groups with some quantities correctly. And then we correct the misconceptions of Zanardo et al.[9] and analyze Kim and Moon[8]'s cryptosystem.

• Bulletin of the Korean Mathematical Society
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• v.46 no.5
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• pp.873-884
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• 2009

We characterize QB-ideals of exchange rings by means of quasi-invertible elements and annihilators. Further, we prove that every $2\times2$ matrix over such ideals of a regular ring admits a diagonal reduction by quasi-inverse matrices. Prime exchange QB-rings are studied as well.

• Bulletin of the Korean Mathematical Society
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• v.46 no.3
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• pp.489-498
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• 2009

We obtain two new characterizations of separativity of refinement monoids, in terms of comparability-type conditions. As applications, we get several equivalent conditions of separativity for exchange ideals.

• Communications of the Korean Mathematical Society
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• v.17 no.3
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• pp.409-422
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• 2002

We investigate the relationship between various generalizations of von Neumann regularity condition and the condition that every prime ideal is maximal in exchange rings.

• Journal of the Korean Electrochemical Society
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• v.19 no.1
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• pp.14-20
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• 2016

Vanadium redox flow battery (VRFB) is an energy conversion device in which charging and discharging are alternatively carried out by oxidation and reduction reactions of vanadium ions with different oxidation states. VRFB consists of electrolyte, electrode, ion-exchange membrane, etc. The role of ion-exchange membranes in VRFB separates anolyte and catholyte and provides a high conductivity to hydrogen ions. Recently much attention has been devoted to develop ideal ion-exchange membranes for VRFB. A number of developed ion-exchange membranes should be evaluated to find out ideal ion-exchange membranes for VRFB. Long-term durability test is a crucial characterization of ion-exchange membranes for commercialization, but is very time-consuming. In this study, the life time prediction protocol of ion-exchange membranes in VRFB cell tests was developed through short-term single cell performance evaluation (real total operation time, 87.5 hrs) at three different current densities. We confirmed a decrease in test time up to 96.2% of real durability tests (expected total operation time, 2,296 hrs) and 5~6% of relative error discrepancy between the predicted and the real life time in a unit cell.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.28 no.2
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• pp.190-199
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• 2018

Objectives: The purpose of this case study is to assess the current airflow and find the ideal ventilation conditions in tank reactors for minimizing the possibility of exposure respiratory dusts(size of $2.5{\mu}m$, $10{\mu}m$) when workers exchange catalysts in the tank reactors. Methods: A Numerical study was performed to determine ideal ventilation conditions, We considered two sizes of airborne respiratory particles($2.5{\mu}m$, $10{\mu}m$) at 12points from the bottom of tank reactor. We changed input & output ventilation conditions and analyzed the particle motion in the tank reactor. The star-ccm+, computational fluid dynamics tool was used to predict air & particle flow patterns in the tank reactor and a numerical simulation was achieved by applying the realized ${\kappa}-{\varepsilon}$ turbulence model and the Lagrangian particle tracking method. Results: From the results, the increase of recirculation air had a significant impact on removing dusts because they are removed by HEPA filter. To the contrary, Increasing the clean air quantity or changing the input position of clean air is not good for workers because it causes the exit of respiratory dusts through workers' entrance or cause it to remail suspended in the air in the workplace tank.

• Journal of Nutrition and Health
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• v.22 no.4
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• pp.275-289
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• 1989

The purpose of this study is to develop a computer system with data file and computerized programs for nutrition counseling. In this research, a 16 / XT personal computer (word : COBOL) compatible with IBM-PC/XT was used. Computer system developed for this study was as follows: Data files(food composition list, food exchange list, nutrition management comment, special diet therapy) were used for analysis the nutritional status and the ntrition education comment. (1) Programs for the nutritional status assessment 1) General information a) Name, age, sex, higher, weight, activity, disease and special diet b) Ideal body weight and Obesity assessment(Kaup index and Broca index) c) Rest and athletics status d) Biochemical data comparision with standard 2) Food Intakes 3) Nutrient Intakes a) Comparison of the amounts intaked with the recommended dietary allowances for present weight. b) Comparison of the energy composition rate intaked with the recommended dietary allowances for present weight. b) Comparison of the energy composition rate intaked with the recommended for present weight and ideal weight. c) Nutrient analysis by each meal and snack. 4) Food intakes from each food group and comparison with recommended 5) Special nutrient analysis. (2) Programs for the nutrition education based on nutritional status assessment. 1) Suggestion of number of food exchange group 2) Nutritional assessment and advise comments 3) Nutritional management comments 4) Special diet therapy In the study, the nutritioal status and nutrition education comments are based on individual data from nutrition counseling.