• Honam Mathematical Journal
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• v.42 no.3
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• pp.591-600
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• 2020

A module M is called ss-semilocal if every submodule U of M has a weak supplement V in M such that U∩V is semisimple. In this paper, we provide the basic properties of ss-semilocal modules. In particular, it is proved that, for a ring R, _RR is ss-semilocal if and only if every left R-module is ss-semilocal if and only if R is semilocal and Rad(R) ⊆ Soc(RR). We define projective ss-covers and prove the rings with the property that every (simple) module has a projective ss-cover are ss-semilocal.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.219-224
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• 2011

The new MPV type reagent, Al-trifluoromethanesulfonyldiisobutylalane ($DIBAO_3SCF_3$), has been prepared and its reducing characteristics in the reduction of selected organic compounds containing representative functional groups have been examined, and compared its reactivity with that of Al-methanesulfonyldiisobutylalane ($DIBAO_3SCH_3$) in order to understand the fluorine-substituent effect on its reactivity. In general, the reactivity of $DIBAO_3SCF_3$ appears to be much higher than that of $DIBAO_3SCH_3$, apparently due to the acidity increase by the electron-withdrawing fluorine-substituent. The reagent reduced aldehydes and ketones readily, but showed a perfect selectivity in the reduction of $\alpha,\beta$-unsaturated aldehydes and ketones to produce the corresponding allylic alcohols in an absolutely 100% purity. In addition, the reagent achieved the regioselective cleavage of phenyl- or/and alkyl-substituted epoxides to the less substituted alcohols in a perfect regioselectivity. Moreover, the reagent also showed an high stereoselectivity in the reduction of substituted cycloalkanones to produce the thermodynamically more stable alcohol epimers exclusively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1047-1054
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• 2004

One of the fundamental problems in computer science is how to store information so that it can be searched and retrieved efficiently. Hashing is a technique which solves this problem. In this paper, we propose a tree construction algorithm using linear two-predecessor single attractor cellular automata C and its complemented cellular automata. Also by using the concept of MRT we give a perfect hasing algorithm based on C.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.04a
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• pp.1-8
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• 1996

Many studies showed that small imperfections can also have a considerable influence on the behaviour of structures. Especially, in Single-Layer Latticed Domes, initial imperfection occurred by human error and construction error is very important to the buckling load. The definition of imperfection is that a node of structure shifts from perfect condition. For example, in the case of truss structures, imperfections are represented by shifting the location of nodal points relative to the position in which they would be for a perfect structure. This paper uses Arc-length Method in nonlinear iteration analysis, choosing star dome, in which many studies have been accomplished, as a model. The results of analysis show that initial imperfection can reduce the buckling load of structures.

• Nuclear Engineering and Technology
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• v.25 no.3
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• pp.394-402
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• 1993

A novel framework for quantitative estimates of the benefits of signals on nuclear power plant availability and economics has been developed in this work. The models developed in this work quantify how the perfect signals affect the human operator's success in restoring the power plant to the desired state when it enters undesirable transients. Also, the models quantify the economic benefits of these perfect signals. The models have been applied to the condensate feedwater system of the nuclear power plant for demonstration.

• Nuclear Engineering and Technology
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• v.34 no.3
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• pp.202-210
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• 2002

The details of the electronic structure of the perfect crystal provides a critically important foundation for understanding the various defect states in uranium dioxide. In order to understand the local defect and impurity mechanism, the calculation of electronic structure of UO$_2$ in the one-electron approximation was carried out, using a semi-empirical tight-binding formalism(LCAO) with and without f-orbitals. The energy band, local and total density of states for both spin states are calculated from the spectral representation of Green’s function. The bonding mechanism in Perfect lattice of UO$_2$ is discussed based upon the calculations of band structure, local and total density of states.

• International Journal of Railway
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• v.1 no.2
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• pp.59-63
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• 2008

The maintenance effect is a peculiar factor applied to repairable systems such as rolling stocks. Conventional statistical analysis for failure times takes into account one of the two following extreme assumptions, namely, the state of the system after maintenance is either as "good as new" (GAN, perfect maintenance model) or as "bad as old" (BAO, minimal maintenance model). Most of the papers concerning the stochastic behavior of railroad systems assume two types of maintenance: perfect and minimal maintenance. However, Lee, Kim & Lee (2008) analyzed the failure data of a door system in Metro EMU and the effect of preventive maintenance was imperfect. It is seen that the imperfect maintenance is of great significance in practice. This article describes how to deal with the maintenance effect in reliability studies of rolling stocks. Maintenance policies under imperfect maintenance are described and the method is proposed to evaluate their performance.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.18 no.36
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• pp.275-285
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• 1995

In recent years there has been increasing interest in the issue of process centering in manufacturing process, The traditional process capability indices Cp, Cpk and Cpu are used to provide measure of process performance, but these indices do not represent the issue of process centering. A new measure of the process capability index Cpm is proposed that takes into account the proximity to the target value as well as the process variation when assessing process performance. However, Cpm only considers acceptance cost for deviation from target value within specification limits, do not includes economic consideration for rejected items. This paper proposes flexible process performance measures that considered quadratic loss function caused by quality deviation within specification limits, rejection cost associated with the disposition of rejected items, and inspection cost. In this model disposition of rejected items are considered under perfect corrective procedures and the absence of perfect corrective procedures.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2005.11a
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• pp.97-100
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• 2005

The handicapped as a member of a society should possess the same opportunity of a perfect participation in public affairs and an equal opportunity in parity of treatment. All sorts of physical and social barriers surrounding the handicapped who can not having a impairment and disability give a less chance to have a share in their society. Therefore, this discrimination barriers must be phased off not only by handicapped but also by normal social members so as to perfect and free access to movement, all of social institution and social activities. Therefor, this paper provides a basic data which conducts investigation and analysis on the outdoor access environment for the handicapped's easy access to public building or facilities. It would be most import rules to make a decision between improvement rate and object for public building or public facilities.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.129-133
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• 2005

While everyone who uses electric power desires perfect frequency, voltage, stability, and reliability at all times, this cannot be realized in practice. The supplying utility cannot be expected to provide a perfect power supply because many of the causes of power supply disturbances are beyond the control of the utility. The outage happens but due to many reason. The electricity equipment requires consequently the emergency power supply. We classify the subordinate for quick supply of the emergency power supply and must grope the supply plan. We will find out in this paper through the case study about the emergency power efficient operation plan.