• Smart Structures and Systems
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• v.33 no.2
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• pp.165-175
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• 2024

Rotating beams play a crucial role in representing complex mechanical components that are prevalent in vital sectors like energy and transportation industries. These components are susceptible to the initiation and propagation of cracks, posing a substantial risk to their structural integrity. This study presents a two-stage methodology for detecting the location and estimating the size of an open-edge transverse crack in a rotating Euler-Bernoulli beam with a uniform cross-section. Understanding the dynamic behavior of beams is vital for the effective design and evaluation of their operational performance. In this regard, modal parameters such as natural frequencies and eigenmodes are frequently employed to detect and identify damages in mechanical components. In this instance, the Frobenius method has been employed to determine the first two natural frequencies and corresponding eigenmodes associated with flapwise bending vibration. These calculations have been performed by solving the governing differential equation that describes the motion of the beam. Various parameters have been considered, such as rotational speed, beam slenderness, hub radius, and crack size and location. The effect of the crack has been replaced by a rotational spring whose stiffness represents the increase in local flexibility as a result of the damage presence. In the initial phase of the proposed methodology, a damage index utilizing the slope of the beam's eigenmode has been employed to estimate the location of the crack. After detecting the presence of damage, the size of the crack is determined using a Genetic Algorithm optimization technique. The ultimate goal of the proposed methodology is to enable the development of more suitable and reliable maintenance plans.

• Membrane Journal
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• v.16 no.4
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• pp.252-258
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• 2006

A numerical analysis was performed for a separation process of carbon dioxide from a flue gas stream using polyethersulfone hollow fiber membranes. Countercurrent flow governing equations were regarded to be two point boundary-value problem and the nonlinear ordinary differential equation were simultaneously solved using the finite- difference method. A computer program was developed using the Compaq Visual Fortran 6.6 software. The carbon dioxide permeate driving force and the fred gas residence time at the inside of membrane were found to be very important factors affecting the permeation characteristics of carbon dioxide. The carbon dioxide concentration in the permeate and the flow rate of the permeate were found to be slightly larger by a few percent with a countercurrent flow analysis than those with a cocurrent flow analysis.

• Journal of Astronomy and Space Sciences
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• v.2 no.1
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• pp.19-33
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• 1985

The singularities of differential Newtonian equation of motion in three body problem cause the loss of accuracy and the considerable increase of the computer time. These singularities could be eliminated during the process of regularization to transform the independent variables and the coordinate of Newtonian equations of motion. In this study, we calculated the positions and velocities of three body along the time scale to find out the unique solution of regularized Newtonian equations of motion with the $5^{th}$ order Runge-Kutta method by assuming the suitable initial velocities and positions. As the results of these calculations it is shown that the tripe stellar system eventually distintegrated, two of them formed a binary, and the last one escaped from this system with a hyperbolic orbit. This may suggest one possible explanation for the binary formation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.10 s.253
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• pp.1194-1201
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• 2006

All the loads in the real world are dynamic loads and structural optimization under dynamic loads is very difficult. Thus the dynamic loads are often transformed to static loads by dynamic factors, which are believed equivalent to the dynamic loads. However, due to the difference of load characteristics, there can be considerable differences between the results from static and dynamic analyses. When the natural frequency of a structure is high, the dynamic analysis result is similar to that of static analysis due to the small inertia effect on the behavior of the structure. However, if the natural frequency of the structure is low, the inertia effect should not be ignored. Then, the behavior of the dynamic system is different from that of the static system. The difference of the two cases can be explained from the relationship between the homogeneous and the particular solutions of the differential equation that governs the behavior of the structure. Through various examples, the difference between the dynamic analysis and the static analysis are shown. Also dynamic response optimization results are compared with the results with static loads transformed from dynamic loads by dynamic factors, which show the necessity of the design considering dynamic loads.

• Korean Journal of Social Welfare
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• v.47
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• pp.206-242
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• 2001

A survey research was conducted for a sample of 306 adult children who have an elderly parent or both parents alive. The purpose of the research was to test a structural equation model which specified the effects of early family relationships on comtemporary relationships and assistance patterns between adult children and their parents. The data were analyzed using EQS for Windows 5.7, utilizing maximum likelihood method. The results showed that early family relationships affected filial concern first, which in turn affected the level of assistance provided by adult children for elderly parents. No direct effect has been found between early family relationships and the level of assistance by adult children for elderly parents. Filial concern was played as an intervening variable. Early family relationships gave no direct effects to adult children's intention to assist their parents. Here again, filial concern was played as an intervening factor. Adult children's intention to assist their parents had not been led directly to provision of actual support to parents by their adult children. Thus, it was identified that intention to support is one thing, and the actual support is another. Controlling for the effects of filial concern, overall, early family relationship patterns gave no differential effects to the different aspects of support provided to parents by their adult children. On the basis of these results, this paper provided both discussions and suggestions for some strategies of intervention in the present family relationships in order for the inter-generational exchange of supports to happen in the future.

• Korean Journal of Veterinary Research
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• v.24 no.1
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• pp.91-98
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• 1984

A total of 466 foremilk from dairy farms in Chonnam district was examined for the subclinical mastitis over a period of one year, using a method of the electrical conductivities(EC); absolute conductivity(AC) and differential conductivity(DC) and quarter difference value(QD), in relation to the California mastitis test(CMT) and the direct somatic cell count(DSCC). The compatibility and efficiency rating between the EC values and the other screening tests was conducted. Obtained results are summarized as follows. 1. A linear relationship was found between the EC values and the CMT scores and direct somatic cell counts and it was found that electrical conductivity measurements were comparable with other screening tests for diagnosing animals with mastitis. 2. Compatibilities between the EC and CMT were 70.4% in AC, 74.6% in DC and 70.7% in QD, and that of the EC and DSCC were 53.0% in AC, 63.1% in DC and 53.2% in QD. On the other hand, relative efficiency ratings of Postle's equation between EC and CMT were 37.3% in AC, 26.5% in DC and 13.6% in QD, and that of the EC and DSCC were 33.1% in AC, 20.2% in DC and 11.9% in QD. 3. In the foremilk samples collected from damaged quarters determined by EC, the false positive rate wart higher than the false negative rate, and consequently tests of EC produced lower compatibility or efficiency rating scores. These tendencies suggested that any factors other than the mastitic condition influencing the EC values might be existed.

• Journal of Energy Engineering
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• v.5 no.1
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• pp.50-55
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• 1996

A numerical simulation on a primary calcinator of porcelain was performed with using Fluent to calculate the heat efficiency by studying velocity vector and temperature profile according to variables such as the location of outlet and porcelain. Control-Volume based Finite Difference Method and Up-wind scheme are used for discretization of differential equation. SIMPLEC Algorithm and standard k-$\varepsilon$ turbulent model are selected to resolve the pressure-velocity coupling and the turbulent. The result of simulation showed that the whole velocity vector field in a calcinator was varied greatly according to the location of outlet. But the whole temperature profile at each zone was still high regardless of the location of outlet because of the radiation. But the temperature of a case with a outlet at sidepart of preheating or cooling zone was little high compared to the case with a outlet on the top of preheating zone. The velocity vector field and temperature profile in a calcinator were almost not affected by the location of porcelain, but the temperature inside a porcelain was much affected according to the place where it was located. The heat efficiency in a calcinator was 44.6% and the gas temperature in the outlet was about 1000 K.

• Journal of the Mineralogical Society of Korea
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• v.24 no.3
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• pp.195-204
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• 2011

Exsolution intergrowth of ilmenite and hematite was studied by the Rietveld refinement method. According to the analysis on these two structural analog minerals, it was found that octahedron (M2) of Ti in ilmenite is in the least deformation, then that (M1) of Fe in ilmenite is deformed next, and octaheron deformation of Fe in hematite is between M1 and M2. High pressure compression experiment was performed up to 5.8 GPa, where two minerals' XRD peaks merged completely. Ilmenite shows normal compression behavior, whereas hematite shrinks in very small amount. This kind of abnormal behavior might be due to the differential response to the applied pressure corresponding to the different compressibilities of the minerals each other.

• Korean Journal of Metals and Materials
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• v.46 no.6
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• pp.338-344
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• 2008

The crystallization kinetics of the $Cu_{43}Zr_{43}Al_7Be_7$ bulk metallic glass were studied by differential scanning calorimetry(DSC) in the continuous heating and isothermal annealing modes. Only one major peak could be detected on the DSC traces of $Cu_{43}Zr_{43}Al_7Be_7$ bulk amorphous alloy, and the activation energy for crystallization corresponding to the peak determined by the Kissinger method was resulted of 239 kJ/mol. The isothermal kinetic, analyzed by the Johnson-Mehl-Avrami equation yielded values for the Avrami exponents in the range 1.69 to 2.37, which implied a crystallization governed by a three-dimensioned growth. Primary phases were essentially the cubic structure CuZr together with the $Cu_{10}Zr_7$ phase. At higher temperature, the CuZr disappeared while the $Cu_{10}Zr_7$ became predominant. After long term annealing at 731 K, the phases were $Cu_{10}Zr_7$, $Cu_2ZrAl$ and $Al_3Zr_5$.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.8
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• pp.45-53
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• 1999

Electromagnetic scattering by finite number of conducting strips loaded on a grounded dielectric is considered for the TM polarization case from the viewpoints of transmitting(receiving) leaky wave antenna and grating coupler. An integro-differential equation whose unknowns are the induced currents over the strips is derived and solved by use of the method of moments. In order to construct the non-uniform leaky wave structures with specific source(current) distributions over the strips, distances between two adjacent strips and strip width are simultaneously varied along the structure. From some results for the current distributions over the strips and surface wave powers, it is observed that the maximum coupling efficiencies of the appropriately constructed non-uniform leaky wave structures from the viewpoints of both a receiving leaky wave antenna and a grating coupler amount upto 95%, which are about 15% improvements compared with those(80%) of the uniform structures.