• Journal of the Korean Data and Information Science Society
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• v.6 no.1
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• pp.105-110
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• 1995

In this paper, we shall convey preservation of some partial orderings and closures of some positive ageing classes under k-out-of-n systems of like components. That is, if the life time of a component A is larger than that of a component B in any of the NBU, DMRL, NBUE, HNBUE, NBUFR and NBUFRA orderings, then a k-out-of-n system formed by i.i.d.. components of type A has larger life time, in that ordering, than that of a similar system consisting of n i.i.d. components type of B. And using these partial orderings, closures of positive aging classes(NBU, DMRL, NBUE, HNBUE, NBUFR and NBUFRA) under the coherent system like components.

• International Journal of Reliability and Applications
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• v.7 no.1
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• pp.13-25
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• 2006

A new class of life distributions is studied. This class is defined based on comparing the residual life time to the whole life in the moment generating function order giving 'the new better than used in the moment generating function order ageing class $(NBU_{mgf})$'. Fundamental properties of this class are given including some closure properties and characterizations. Finally, we consider new results about comparisons of age and block replacement policies when the underlying distribution belongs to $NBU_{mgf}$ aging classes.

• International Journal of Reliability and Applications
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• v.8 no.1
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• pp.95-109
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• 2007

The purpose of this paper is to study new notions of stochastic comparisons and ageing classes based on the total time on test transform order. We give relationships to other stochastic orders and aging classes given previously. Several preservation properties under the reliability operations of random minima and series system are given.

• International Journal of Reliability and Applications
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• v.10 no.1
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• pp.59-62
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• 2009

We comment on a new testing procedure for testing exponentiality against different ageing classes. We show that the proposed test is inappropriate at least for two alternatives. We point out the subtle flaw in their argument.

• Journal of the Korean Data and Information Science Society
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• v.7 no.1
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• pp.119-127
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• 1996

The concepy of positive aging describles the adverse effects of age on the lifetime of units. Various aspects of this concepts are described in terms of conditional probability distribution of residual life times, failure rates, equilibrium distributions, etc. In this paper we will consider some partial ordering relations of life distribution under residual life functions and equilibrium distributions.

• Communications for Statistical Applications and Methods
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• v.2 no.2
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• pp.20-32
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• 1995

The concept of positive ageing describes the adverse effects of age on the lifetime of units. Various aspects of this concept are described in terms of conditional probability distribution of residual life times, failure rates, equilibrium distributions, etc. In this paper, we will consider some partial ordering relations of life distributions under residual life functions and equilibrium distributions. Under residual life distributions, we study the relationships of IFR, NBU and NBUFR classes and that of DMRL and NBUE classes, By using WLR ordering comparison between F and its equilibrium $H_F$, we can decide if F belongs to NBUFR class.

• Journal of Forest and Environmental Science
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• v.29 no.4
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• pp.282-291
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• 2013

Rapid loss in viability of neem (Azadirachta indica A. Juss.) seed is a major problem. Present effort was undertaken for developing a set pattern for assessing of viability and vigour in seed of various mother tree age of neem (Age I-06 years, Age II-15 years, Age III-25 years and Age IV->30 years old). Various viability test viz. triphenyle tetrazolium chloride test, electrical conductivity, excised embryo test, and germination test have been performed on seeds obtained from mother tree age classes. Inconsistency was observed with the TTC and EC test in germination of seed in laboratory as well as nursery. While various vigour tests viz. cold test, chemical stress test (methanol stress test), and accelerated ageing test alongwith ageing index, germination test (G%, MGT and GV) and various seedling growth parameters like seedling length (cm), number of leaves, collar diameter (cm), total biomass (g) alongwith mathematical indices i.e. vigour index, sturdiness quotient, volume index, quality index, root shoot ratio in nursery as well have been taken for study and showed better consistency. On the basis present study results of various viability and vigour test indicated that mother tree age class II performed better in comparison to others and it can be recommended for seed collection. Further it is also recommended that viability of neem seed may be assessed using various laboratory tests like excise embryo test and germination test (G%, MGT and GV) and vigour test may be taken preferably by cold germination test, chemical (methanol) stress test, accelerated ageing test in laboratory and germination alongwith various seedling growth parameters seedling length (cm), number of leaves, collar diameter (cm), total biomass (g) alongwith mathematical indices like Vigour Index, Sturdiness quotient, Volume Index, Quality index, root shoot ratio in nursery as discussed in this study.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.359-360
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• 2002

A methodology was developed for evaluation of oxidation stability of base stocks and engine oils. Analytical procedures for both classes of lubricants were based on the ASTM standards D 6186 and/or E 2009. The procedures were applied to a set of engine oils of the SAE 5W-30 specification, and to a set of several hydrocracked and solvent neutral base oils, both with and without addition of antioxidant. A potential of a pressure DSC for diagnostic purposed was also demonstrated by monitoring the engine oil ageing during its operation in heavy-duty engine.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.4
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• pp.151-159
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• 2001

As huge energy transfer systems like a nuclear power plant, steam power plant and petrochemical plant are operated for a long time, mechanical properties are changed by degradation. The life time of the systems can be affected by the mechanical properties. BI(Ball Indentation) test has a potential to replace conventional fracture tests like a uniaxial tensile test, fracture toughness test, hardness test and so on. In this paper, we would like to present the ageing evaluation technique by the BI method. The four classes of the thermally aged 1Cr-!mo-0.25V specimens were prepared using an artificially accelerated aging method. Tensile tests, fracture toughness tests, hardness tests and BI tests were performed. The results of the BI tests were in good agreement with fracture characteristics by a standard fracture test method within 5%. The IDE(Indentation Deformation Energy) of a BI technique as a new parameter for evaluating a degradation was suggested and the new IDE parameter clearly depicts the degradation degree.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.27 no.1
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• pp.53-72
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• 2001

Dry skin is caused mainly by the perturbation of stratum corneum lipids which affected by ageing, change of season, excess use of surfactant and the effect of disease like atopic dermatitis and psoriasis. Intercellular lipid structures in stratum corneum are responsible for the barrier function of mammalian skin. The major lipd classes that can be extracted from stratum corneum are ceramides, cholesterol and fatty acid, which make up approximately 50, 25, 10 percent of the stratum corneum lipid mass, respectively. Small amount of cholesterol sulfate, phospholipids, glycosylceramide and cholesterol esters are also present. Recent studies have shown that application of one or two these lipids to the perturbed skin delays barrier recovery; only equimolar mixtures allow normal recovery. We observed that barrier recovery rate was improved in hairless mouse by topical application of single neutral lipids (ceramide, free fatty acid, cholesterol) and lipid mixtures. Whereas the application of single lipid didn’t allows a significant enhancement comparing with normal barrier repair, the equimolar mixtures of 3 components(including synthetic pseudoceramide PC104) improved barrier repair, as assessed by the transepidermal water loss. At clinical study to the volunteers aged over sixty, skin dryness recuperated by the increase of moisture(capacitance) and the reduction of scaling. Utilization of physiologic lipid mixture containing natural ceramides or synthetic pseudoceramide could lead to new forms of topical therapy for the dryness and dermatoses(e.g., psoriasis, atopic dermatitis and irritant dermatitis).