• Smart Structures and Systems
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• v.13 no.4
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• pp.659-683
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• 2014

The static analysis of structures with arbitrary cross-section geometry and material lamination via a refined one-dimensional (1D) approach is presented in this paper. Higher-order 1D models with a variable order of expansion for the displacement field are developed on the basis of Carrera Unified Formulation (CUF). Classical Euler-Bernoulli and Timoshenko beam theories are obtained as particular cases of the first-order model. Numerical results of displacement, strain and stress are provided by using the finite element method (FEM) along the longitudinal direction for different configurations in excellent agreement with three-dimensional (3D) finite element solutions. In particular, a layered thin-walled cylinder is considered as first assessment with a laminated conventional cross-section. An atherosclerotic plaque is introduced as a typical structure with arbitrary cross-section geometry and studied for both the homogeneous and nonhomogeneous material cases through the 1D variable kinematic models. The analyses highlight limitations of classical beam theories and the importance of higher-order terms in accurately detecting in-plane cross-section deformation without introducing additional numerical problems. Comparisons with 3D finite element solutions prove that 1D CUF provides remarkable three-dimensional accuracy in the analysis of even short and nonhomogeneous structures with arbitrary geometry through a significant reduction in computational cost.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.933-940
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• 2024

A macroscopic cross section generation model was developed for the conceptual horizontal, compact high temperature gas reactor (HC-HTGR). Because there are many sources of spectral effects in the design and analysis of the core, conventional LWR methods have limitations for accurate simulation of the HC-HTGR using a neutron diffusion core neutronics simulator. Several super-cell model configurations were investigated to consider the spectral effect of neighboring cells. A new history variable was introduced for the existing library format to more accurately account for the history effect from neighboring nodes and reactivity control drums. The macroscopic cross section library was validated through comparison with cross sections generated using full core Monte Carlo models and single cell cross section for both 3D core steady-state problems and 2D and 3D depletion problems. Core calculations were then performed with the AGREE HTR neutronics and thermal-fluid core simulator using super-cell cross sections. With the new history variable, the super-cell cross sections were in good agreement with the full core cross sections even for problems with significant spectrum change during fuel shuffling and depletion.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.4
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• pp.73-82
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• 2016

Recently, automobile industries have been developing many structural automotive parts made of thin, high-strength steel strips to produce safer and more environmentally friendly cars. The roll forming process has been considered one of the most efficient processes in manufacturing high-strength steel parts because it is a high-speed process that forms sheets in increments. However, most automotive parts vary longitudinally in their cross-sections. Therefore, it is difficult to apply the roll forming process to automotive parts made of high-strength steel. A variable section roll forming process has been proposed in recent studies. The rotational axes of the forming rolls are fixed, and the forming rolls have three-dimensional shape. As such, the cross-section of the part varies linearly along its length, and the angle between the bend line and longitudinal axis is less than 1 degree. Thus, the rate of cross-sectional variation along the length is relatively small. In this study, the rate of cross-sectional change along the length of a forming roll has been increased. Moreover, the angle between the bend line and longitudinal axis has been increased up to 15 degrees. The variable sections of the forming rolls have been designed for high strength steel parts with a symmetric u-type cross-section that varies linearly and symmetrically along the longitudinal axis.

• Transactions of Materials Processing
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• v.23 no.6
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• pp.369-375
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• 2014

Flexible roll forming allows profiles to have variable cross-sections. However, the profile may have some shape errors, such as, warping which is a major defect. The shape error is induced by geometrical deviations in both the concave zone and the convex zone. In the current study, flexible roll forming was modeled with FE simulations to analyze the shape error and the longitudinal strain distribution along the flange section over the profile. A distribution of analytically calculated longitudinal strains was used to develop relationships between the shape error and the longitudinal strain distribution as a function of the defined shape parameters for the profile. The FE simulations showed that the shape error is primarily affected by the deviations between the distribution of analytically calculated longitudinal strain and the longitudinal strain distribution of the profile. The results show that the shape error can be controlled by designing the shape parameters to control the geometrical deviations at the flange section in the transition zones.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.3
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• pp.77-85
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• 2015

In this paper, we present the result of investigations pertaining to the elastic buckling of simply supported columns with various cross-sectional dimensions but the same length and volume. In the investigations the accuracy of the analysis methods is studied and it was found that the result obtained by the successive approximations technique is the most accurate. In addition, the elastic buckling loads of columns with variable cross-section dimensions are obtained by the theoretical and numerical methods. From the results, it was found that the buckling loads obtained by the numerical methods are close to the buckling loads obtained by the successive approximations technique for the practical standpoints. Moreover, the buckling load of column with convexity in its middle is the highest while the buckling load of the tapered column is the lowest as expected.

• ALGAE
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• v.30 no.2
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• pp.103-119
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• 2015

Photosynthetic rates of the large centric diatom Coscinodiscus granii were measured by means of multicolor variable chlorophyll fluorescence imaging, single cell $^{14}C$ assimilation, and optical $O_2$ sensor measurements during light acclimatization of cultures grown at five different irradiances: 50, 150, 235, 332, and $450{\mu}mol$ photons $m^{-2}\;s^{-1}$. Photo-acclimatization was evident from changes of cellular chlorophyll a content, growth rates, and light response curves. Each of the applied methods evaluates different parts and reactions in the photosynthetic apparatus, which makes a direct quantitative comparison of rates difficult, although a different degree of correlation were found between all three methods. However, when used in combination, they provide information about the internal relationship of photosynthetic pathways as well as the variation in photosynthetic capacity between individual cells within a single algal culture.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.2
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• pp.39-45
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• 2022

In this study, we investigated whether the interference occurring in forming roll surfaces could be eliminated by increasing the radius of the variable section forming rolls. The surfaces of the rolls capable of forming products with different flange heights and bend angles with the bend line tilted at an angle of 1° from the longitudinal axis were created using the general CAD software CATIA. Roll interferences were determined for the change in the forming roll radius. The minimum gaps between the upper and lower roll surfaces were measured for the change in the forming roll radius, and the roll interferences were calculated from the difference between the measured value and the thickness of the product. It was observed that the thickness of the product had a slight effect on the roll interference when the thickness was between 0.8 and 1.2 mm. It was also observed that the roll interference could be eliminated by increasing the roll radius.

• Research in Community and Public Health Nursing
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• v.11 no.2
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• pp.499-512
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• 2000

The number of deliveries by cesarean section has increased internationally. However, The cesarean section rate is different by country to country. It is because each country has different social and cultural background and. practices its unique delivery policies. Hence, it is very important to understand the uniqueness that one country faces related with the cesarean section. In Korea, there have been many researches on the clinical. maternal. hospital and community factors and so on. However, few studies have attempted to reveal the physician factors in Korea because it is difficult to approach hospital records. So, in this study, the physician factors that influence the increase of cesarean section rate in Korea was investigated, and preliminary research agenda for policy establishment to keep the cesarean section rate from excessive increase was provided. In this study, all 2744 cesarean section deliveries performed by 36 physicians at the hospital was considered. and detailed delivery records of 12 months selected randomly from January 1996 to August 1998 was reviewed retrospectively. Chi-square analysis is used to examine the homogeneity of distribution of maternal, fetal, and clinical factors. In addition, multiple regression analysis is used to examine the effect of physician characteristics on the cesarean section rate. Physician characteristics as independent variable and the cesarean section rate as dependent variable was put in this analysis. Follows are the results of this study. 1) Total cesarean section rate is 34.8%. primary cesarean section rate is 12.5 % and repeated cesarean section rate is 22.3 %. Among the indications for the primary cesarean section, 15.6 % is for breech presentation. 40.2 % is for dystocia. 7.6 % is for fetal distress. and 36.6 % is for others. 2) There is positive correlation between physician's age and the cesarean section rate (p<0.001). And statistically significant correlation is found between the physician's educational attainment and the cesarean section rate (p<0.001). A physician with Ph.D degree has lower cesarean section rate than a physician with B.A only and M.A. degree (p<0.001). However. physician's gender, location of graduated university. position at the hospital, and the religious belief were not shown statistically significant relations with the cesarean section rate. 3) Among all cesarean sections in this study, only 15.4 % is performed during weekend. While 18.2 % is performed on monday only. This suggests that physicians may not prefer weekend operation of cesarean section. In addition, 86.1 % among all cesarean section operations is performed from 6 a.m. to 6 p.m. So the cesarean section rate could be related with a day of the week and a time of the day. From this results. there is a possibility that the physicians' personal comfort may influence the cesarean section rate.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.2
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• pp.131-139
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• 1988

The thermoacoustic oscillation induced in an air column with variable cross section area is investigated theoretically and experimentally. The onset condition of the oscillation is derived by equating the acoustic power production to the power dissipation. The power production at the heater is predicted by using the efficiency factor obtained by heat transfer analysis for a single wire in a uniform cross flow and considering the interference between heater wires. The power dissipation is estimated by measuring the attenuating coefficient from the pressure decay curve. The theoretical prediction to the onset condition of the oscillation is confirmed experimentally. The effect of the variation of the column cross section area on the onset condition is presented.

• Journal of Aerospace System Engineering
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• v.8 no.1
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• pp.12-17
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• 2014

In this paper, optimal design of composite rotor blade cross-section to consider manufacturability was performed. Skin thickness, torsion box thickness and skin lay-up angle were adopted as discrete design variables and The position and width of a torsion box were considered as continuous variables. An object function of optimal design is to minimize the mass of a rotor blade, and various constraints such as failure index, center mass, shear center, natural frequency and blade minimum mass per unit length were adopted. Finally, design variables such as the thickness and lay-up angles of a skin, and the thickness, position and width of a torsion box were determined by using an in-house program developed for the optimal design of rotor blade cross-section.