• Journal of Mechanical Science and Technology
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• v.19 no.2
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• pp.487-495
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• 2005

Mechanical properties of in-service facilities are required to evaluate the integrity of power plants and chemical plants. Non-destructive technique can be used to evaluate the mechanical properties. To investigate the mechanical properties using ultrasonic technique, the four classes of thermally aged specimens were prepared using an artificially accelerated aging method. Ultrasonic tests, tensile tests, fracture toughness tests, and hardness tests were performed for the specimens. Then the mechanical properties were compared with ultrasonic parameters such as attenuation and non-linear parameter. From the investigation, we confirm that the ultrasonic parameter can be used to evaluate the mechanical properties.

• Steel and Composite Structures
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• v.7 no.3
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• pp.185-200
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• 2007

Tubular construction is widely used in a range of civil and structural engineering applications. To date, the principal product range has comprised square, rectangular and circular hollow sections. However, hot-rolled structural steel elliptical hollow sections have been recently introduced and offer further choice to engineers and architects. Currently though, a lack of fundamental structural performance data and verified structural design guidance is inhibiting uptake. Of fundamental importance to structural metallic design is the concept of cross-section classification. This paper proposes slenderness parameters and a system of cross-section classification limits for elliptical hollow sections, developed on the basis of laboratory tests and numerical simulations. Four classes of cross-sections, namely Class 1 to 4 have been defined with limiting slenderness values. For the special case of elliptical hollow sections with an aspect ratio of unity, consistency with the slenderness limits for circular hollow sections in Eurocode 3 has been achieved. The proposed system of cross-section classification underpins the development of further design guidance for elliptical hollow sections.

• The Korean Journal of Applied Statistics
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• v.24 no.4
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• pp.709-719
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• 2011

We investigate the latent stage-sequential patterns of drinking behaviors of U.S. adolescents who have started to drink by age 14 years (seven years before the legal drinking age). A multiple-group latent transition analysis(LTA) with logistic regression is employed to identify the subsequent patterns of drinking behaviors among early-onset drinkers. A sample of 1407 early-onset adolescents from the National Longitudinal Survey of Youth(NLSY97) is analyzed using maximum-likelihood estimation. The analysis demonstrates that early-onset adolescents' drinking behaviors can be represented by four latent classes and their prevalence and transition are influenced by demographic factors of gender, age, and race.

• Korean Journal of Child Studies
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• v.31 no.5
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• pp.167-191
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• 2010

The purpose of this study is to examine how science activities using nonfiction literature affectspreschool children's scientific process skills, attitudes and concepts. For the purposes of this study, two classes, consisting of four and five-year-old children in a kindergarten located in D city were selected. One class was designated as the experimental group and the other as the control group. The experimental group performed science activities using nonfiction literature, while the control group did not. Thisexperimental study was conducted over the course of 8 weeks. Analysis of data was performed by ANCOVA. The results of the posttest indicated that the experimental group which performed science activities using nonfiction literature showed an improvement in their process skills, scientific attitudes and scientific concepts compared with the control group.

• Journal of Korean Home Economics Education Association
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• v.7 no.1
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• pp.1-10
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• 1995

This study was intended to provide an improved method for testing textiles in high school. Four kinds of test subjects were selected and applied to the classes. Problems of the methods in the textbooks were corrected as follows: 1)Burning test: The number of specimen is reduced to 3 kinds of fibers(cotton, wool, and polyester) and recommends are given to make result by comparing with the burning characteris-tics of paper and hair. 2) Absorbency test: Test Method is changed to drop test. The result is recorded by measuring time required for the water drops absorbed to the specimen. 3) Wrinkle recovery test: A glass is provided instead of metal weight. The method of measuring angle which is made by the specimen is shown in figure. 4) Effects of Detergent: 0.2% of detergent solution is provided before class. The amount of oil and carbon black is specified. Students have generally agreed that the improved methods were better than those in the text-books after they made the above 4 recommendable experiments(p<.001)

• Journal of the Korean Home Economics Association
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• v.32 no.4
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• pp.135-147
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• 1994

The purpose of this study is to get the data on the day-care type of the employed mothers in urban area and to make it improve the day care service program. I classified day care type into four classes accoding to existing one. And we surveyed 401 employed mothers with the child under age of six who lived at Seoul. the major results were as follows; 1) Most of employed mothers felt the burden of day care expenses and payed it of their own earning 2) The common type of day care is 'by family' and the users of this type more satisfied with the condition than any other types. 3) the difficulty of day care is that can't apply the tool and materials sufficiently, except day care center, 4) The reason that they use day care center or not is thier family. 5) Accoding to child age, family composition, educational level, job, income level, employed mothers choose day care type differently. So I suggest the social support for the employed mothers.

• Journal of the Korean Mathematical Society
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• v.45 no.2
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• pp.559-573
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• 2008

In this paper, two classes of functions, involving a parameter and the classical Euler gamma function, and two functions, involving the classical Euler gamma function, are verified to be logarithmically completely monotonic in $(-\frac{1}{2},\infty)$ or $(0,\infty)$; some inequalities involving the classical Euler gamma function are deduced and compared with those originating from certain problems of traffic flow, due to J. Wendel and A. Laforgia, and relating to the well known Stirling's formula.

• Journal of Drive and Control
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• v.13 no.3
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• pp.53-66
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• 2016

New non-hybrid approaches to improve energy efficiency of construction machineries are reviewed in this paper. Hydraulic systems are classified into four classes according to Backe's classification and commercially promising new technologies are carefully chosen in each class. IMV, 3-Line CPR, Closed Circuit Displacement Control of Differential Cylinder, and Throttle-less Secondary Control are chosen as representative non-hybrid new technologies. Key principle of each technology is explained and representative references which run through each technology are selected. Advantages and weaknesses of each technology are discussed and compared from the view point of construction machinery manufacturers.

• Journal of Korean Library and Information Science Society
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• v.34 no.1
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• pp.217-237
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• 2003

This study investigates the general problems in classifying materials by and related to Shakespeare in the university libraries and suggests a new analytico-synthetic system based on the analysis on the related classes on the major classification systems including DDC, LCC, CC, etc. and other studies and hompages In the area or Shakespeare study. New system consists of four facets, and Its facet formula is “generalities + form ＋ works + language,” each of which includes Its own foci.

• The Korean Journal of Malacology
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• v.1 no.1
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• pp.1-4
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• 1985

The investigation of freshwater molluscs in the South Han River was carried out from 1984 and in 1985. The authors selected 12 stations and collected freshwater snails and mussels. We here publish the catalogue of molluscs in South and North Han River. The catalogue of molluscs in the South Han River is as follows; two classes, four orders, six families including twenty species(Semisulcospira coreana, Semisulcospira globus, Semisulcospira gottschei, Semisulcospira forticosta, Parafossarulus manchouricus, Gabbia misella, Radix auricularia coreana, Austroppepleaollura, Limnoperma lucustris, Lamprotula gottschei, Lanceolariaacrorhyncha, Unio douglasiae, Unio sp, Solenaia triangulalis, Anodonta fukudai, Anodonta woodiana, Corbicula felnouilliana, Corbiculafluminea, Corbicula sp).