• Journal of Korean Society of Industrial and Systems Engineering
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• v.24 no.68
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• pp.37-50
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• 2001

Although the study of OCB has increased greatly in recent years, a little works have focused on the relationship between leadership and extrarole behavior, and the moderating effects of the situational factors on the relationship between two factors. For the analytical purpose of this article, Fisher＇s Z-transformation and SGC(split groups correlations) methods were introduced. Generally 2 leadership styles are found to have influenced on altruism and conscientiousness respectively. Out of 36 cases, only 2 cases were significant in moderating effects. Based on empirical results, there is no moderating effects in conscientiousness. But altruism is found to be more closely related with employee-centered leadership in low centralized group than in high centralized group, and more closely related with job-centered leadership in low growth-needs group than in high growth-needs group.

• Journal of the Korean Ceramic Society
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• v.35 no.8
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• pp.850-856
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• 1998

The dynaamic fatigue behavior of alumina ceramics was observed at room temperature using four-point bending method. Dynamic fatigue fracture strength was observed as function of down speed and notch length. The crack growth exponent of the specimens was calculated from the fracture strength and lifetime in dynamic fatigue test. After loading the stresses in the range of 0% to 105% compared with the average in-ert strength the value of residual fracture strength was measured for unnotched and 0.5mm notched speci-mens at the 0.001 and 0.0005 mm/min down speed respectively. After the 95% stress of the average inert strength was applied repeatedly the value of rsidual fracture strength was measured for 0.5mm notched specimens at the 0.001 and 0.0005 mm/min down speed respectively. The material constant A was found to be almost the same and not to depend on the loading mode or the down speed for unnotched and notched specimen. The value of fracture strength with time calculated from the constants n and A was in good agreement with the measured value.

• Journal of the Korean Society of Safety
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• v.10 no.2
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• pp.120-128
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• 1995

The fatigue failure of rail is a principal source of derailment accidents. The reduction of fatigue failures can be achieved by Intensive track maintenance and periodic safety assessments for the railway. For the safety assessments, it is required to have more accurate knowledge for fatigue behavior such as the crack initiation, propagation, crack growth rate and the remaining service life in rail. In this paper, the mean stress effects for the fatigue behavior of rail steel are studied. For this study, the fatigue test is conducted and some equations for fatigue evaluation are applied and compared. From the results, we can see that the fatigue crack growth rate is the more increased as the men stress Is the more increased, the mean stress effect is represented well by the combination of stress intensity factor range and maximum stress intensity factor and Crooker and Range's equation represented by ${\Delta}K, K_{max}$ is the best fit for fatigue evaluation and safety assessment of rail.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.4
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• pp.117-124
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• 2003

The lightness of components required in automobile and machinery industry is requiring high strength of components. In particular, manufacturing process and new materials development for solving the fatigue fracture problem attendant upon high strength of suspension of automobile are actively advanced. In this paper, the effect of compressive residual stress of spring steel(JISG SUP-9) by shot-peening on fatigue crack growth characteristics in high temperatures($100^{\circ}C$, $150^{\circ}C$, $180^{\circ}C$) was investigated with considering fracture mechanics. So, we can obtain followings. (1)Compressive residual stress decreases in high temperature, that is, with increasing temperature. (2)The effect of compressive residual stress on fatigue crack growth behavior in high temperature increases below $\Delta$K=17~19MPa (3)It was investigated by SEM that the constraint of compressive residual stress for plastic zone of fatigue crack tip was decreased in high temperature as compared with room temperature.

• Journal of Korean Institute of Industrial Engineers
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• v.6 no.1
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• pp.9-15
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• 1980

By the mid 1960's the rate of productivity growth in the manufacturing industries of the United States reached the lowest level ever recorded in the American economy. As a result the cost-offsetting operations that had been a century-long part of cost minimizing became less feasible. U.S. manufacturing firins apparently embarked on a pattern of a cost pass-along management. Accounting for price variation as a function of a shift from cost minimizing to cost pass-along is the main subject of this investigation. An econometric model of the inflation process is presented which indicates a clear shift in the modal behavior of manufacturing industries from cost minimizing (1948-1964) to cost pass-along (1965-1975). The latter behavior, initially triggered by the drag of resource diversion on the productivity growth process, undermines the pressure toward productive efficiency that is at the core of industrial engineering, and at the center of U.S. industry's ability to remain competitive.

• Journal of the Korean Vacuum Society
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• v.4 no.3
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• pp.270-274
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• 1995

The growth structure of Fe on CU(001) was studied by scanning tunneling microscope. An analysis of size distribution of Fe islands on Cu(001) surface was made to determine whether Fe atoms mix with substrate Cu. The size distribution deviates from the standard scaling behavior, indicating that atomic density of Fe decreases with coverage up to 1 ML. The growth can be characterized by layer-by-layer scheme from 1 ML to 5 ML. This result agrees well with previously studied, Auger spectroscopy and RHEED result.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 2000.06a
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• pp.233-242
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• 2000

Cordierite/ZrO$_2$ composites with 5 to 25wt% ZrO$_2$ were fabricated by prssureless sintering, and their densification behavior, fracture strength, fracture toughness, microstructure and thermal expansion behavior were studied. The ZrO$_2$ addition into cordierite matrix affects the densification behavior and mechanical properties of the composites. By dispersing 25wt% ZrO$_2$, densified cordierite/ZrO$_2$ composite with a relative density of 98.5% was obtained at optimum sintering condition of 144$0^{\circ}C$/2H. Both fracture strength and toughness were increased from 140 to 290MPa and from 1.6 to 3.5 MPam$\frac{1}{2}$, respectively, by dispersing 25wt% ZrO$_2$ into the cordierite matrix. ZrO$_2$ particles were homogenously dispersed into cordierite matrix, which intragranular particles were fine(<100nm) and intergranular particles were coarse. The toughening mechanisms in the present composites were mainly attributed to martensitic transformation toughening. Then, the addition of ZrO$_2$ is likely to have little deleterious effect upon thermal expansion coefficient of cordierite.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.7
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• pp.899-906
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• 2011

Generally, load conditions of machine or structure in fatigue destruction is occurred not under single load conditions but under mixed load conditions. However, the experiment under mixing mode is insufficient because of no having test standard to the behavior of crack under mixing mode and variety of test methods, and many tests are required. In this paper measured crack direction path by created figure capture system when a experiment. Also, we studied by comparison the behavior of crack giving the change of stress ratio and inserting beach mark. Through the test under mixing mode, advancing path of crack is indicated that advancing inclined angle ${\Theta}$ (direction of specimen length) has increased depending on the increase of mixed mode impaction. It is indicated that according to the increase of mixed mode loading condition impaction under mixing mode, advancing speed of crack gets slow. Also, we found that inner crack(cross section of specimen) is progressed more rapidly than outer crack based on data through beach mark.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.119-125
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• 1999

This research has been studied in terms of investigating the reaction behavior of pyrite with a cyclone reactor. The Mathematical model has developed pyrite oxidation and lime sulfation in this reactor. The model assumes a chemical control shrinking core behavior for the pyrite and a fluid film control shrinking core behavior for the lime. The model was solved and characterized numerically. Experiments have been performed to study the influence of reaction parameters such as reactor temperatures, pyrite particle sizes, air flow rates, feeding rates, and mixing ratio of pyrite and lime. The oxidation and sulfation products were characterized chemically and physically.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.4
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• pp.599-609
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• 1997

The phase behavior and dynamics of colloid suspensions and the resulting structures and properties of powder compacts were examined by a computer experimental method for cooperative packing processes. A wide range of properties and process conditions such as arbitrary particle size, medium densities, field strength, and temperature could be examined using the Peclet number (Pe). We demonstrated that an optimum range of Peclet number for the ordering of sediments was present and that the phenomena related to the ordering such as the onset of crystallization, the phase behavior, etc. strongly depend on process conditions. The present work appears to be useful to design the processing method of ceramic spherical submicron powders for the preparation of high-density green compacts.