• Design & Manufacturing
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• v.15 no.3
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• pp.19-25
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• 2021

The bending process of a press die is to bend a flat blank to the required angle. There are V-bending, U-bending, Z-bending, O-bending etc. for bending processing, and the basic principle of calculating the unfolding length of die processing is used as the neutral plane length. Since the constant of the length value of the neutral surface is different depending on the type of bending, it is impossible to accurately calculate it. In particular, Z-bending processing is performed twice, and it is set on the upper and lower surfaces of the blank, and bending processing occurs at the same time as the upward and downward bending, and the elongation of the material occurs and the material increases. It is not possible to check with the calculated value, and it occurs in many cases where the mold is modified after start-up. This study aims to minimize die modification by developing a formula to calculate the development length of Z-bend.

• Steel and Composite Structures
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• v.28 no.5
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• pp.589-606
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• 2018

The previous studies reflected the significant effect of neutral-axis position and coupling of in-plane and out-of-plane displacements on behavior of functionally graded (FG) nanobeams. In thin FG beam, this coupling can be eliminated by a proper choice of the reference axis. In shear deformable FG nanobeam, not only this coupling can't be eliminated but also the position of neutral-axis is dependent on through-thickness distribution of shear strain. For the first time, in this paper it is avoided to guess a shear strain shape function and the exact shape function and consequently the exact position of neutral axis for arbitrary gradation of higher order nanobeam are obtained. This paper presents new methodology based on differential transform and collocation methods to solve coupled partial differential equations of motion without any simplifications. Using exact position of neutral axis and higher order beam kinematics as well as satisfying equilibrium equations and traction-free conditions without shear correction factor requirement yields to better results in comparison to the previously published results in literature. The classical rule of mixture and Mori-Tanaka homogenization scheme are considered. The Eringen's nonlocal continuum theory is applied to capture the small scale effects. For the first time, the dependency of exact position of neutral axis on length to thickness ratio is investigated. The effects of small scale, length to thickness ratio, Poisson's ratio, inhomogeneity of materials and various end conditions on vibration and buckling of local and nonlocal FG beams are investigated. Moreover, the effect of axial load on natural frequencies of the first modes is examined. After degeneration of the governing equations, the exact new formulas for homogeneous nanobeams are computed.

• Bulletin of the Korean Chemical Society
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• v.22 no.8
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• pp.833-836
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• 2001

Infrared absorption spectra of $\alpha\omega-diphenylpolyenyl$, anions Ph(CH)nPh- (DPn-, n=7, 9, and 13) in the tetrahydrofuran-d6 solutions was measured in the range of 1700 and 1200 cm-1 . The infrared spectra obtained from anions (DPn) showed considerable difference from their neutral species (DPn); their intensities were enhanced at least two orders of magnitude stronger than their neutral species. The in-plane CH bending modes at 1464 and 1375 cm-1 are correspondingly strengthened with the chain length increased, but the C=C stretching at 1541 cm-1 is weakened and frequencies are not changed. We provide an IR evidence for the first time that the bond order or bond alternations of the anions (soliton) are different from those of radical anions (polaron) as well as neutral species.

• The korean journal of orthodontics
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• v.25 no.3 s.50
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• pp.273-286
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• 1995

The purpose of this study was to compare the difference of the growth aspects in three facial growth patterns. The biennial serial cephalometric radiographs of 33 samples(19males, 14females) with normal occlusion from 8.5 years to 18.5 yews of age were used in this study. The facial growth patterrn was categorized in 3 types(Drop type, Neutral type, Forward type) by the total amounts of the Y-axis which changed from 8.5 years to 18.5 years of age. The growth change of the craniofacial area during 10 years in each growth type was analyzed and was compared among the 3 growth types. The results of this study might be summarized as follows. 1. The samples that were classified by total change of the Y-axis during this study period were distributed to 52% of the neutral type, 27% of the forward type, 21% of the drop type. 2. The anterior growth of the maxilla to the cranial base(N per A) showed larger in the forward type than in other 2 types(p<0.05). 3. The palatal plane to the FH plane showed more anterior-superior inclination in the forward type with age during this study period. 4. The anterior growth of the mandible to the cranial base(N per Pog) appeared large in rank order, of largest the forward type, second the neutral type, and third the drop type(p<0.05). 5. During this study period the mandibular plane(SN/MN,FMA) showed more counterclockwise rotation in the forward type than in the drop type(p<0.05), and this tendency was stronger in males than in females(p<0.05). 6. The growth of the mandibular corpus length(Go-Me) showed smaller in the drop type than in the other 2 types(p<0.05). 7. In the forward type and the neutral type, the anterior growth of the mandible was larger than that of the maxilla(p<0.05). 8. In the craniofacial growth distances and angulations turned out to be somewhat variable, but the vertical proportion had a strong tendency whose original relation was maintained consistently during this study period. 9. Through these analyzed data, the profilograms on each growth type were constructed to evaluate individual growth pattern in the orthodontic diagnosis.

• Magazine of the Korea Concrete Institute
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• v.10 no.4
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• pp.113-124
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• 1998

Numerical study using nonlinear finite element analysis is done for investigating behavior of isolated reinforced concrete walls subject to combined in-plane and out-of-plane bending moments and axial force. A method for estimating the ultimate strength of wall is developed, based on the analytical results. For the nonlinear finite element analysis, a computer program addressing material and geometric nonlinearities is developed. An existing unified method combining plasticity theory and damage model is used for material model of reinforced concrete. By numerical studies, the internal force distribution in the cross section is idealized, and a new method for estimating the ultimate strength of wall is developed. According to the proposed method, variation of the interaction curve of in-plane bending moment and axial force depends on the range of the permissible axial force per unit length that is determined by the given amount of out-of-plane bending moment. As the out-of-plane bending moment increases, the interaction curve shrinks, which indicates a decrease in the ultimate strength. The proposed method is compared with an existing method using the general assumption that strain shall be directly proportional to the distance from the neutral axis. Compared with the proposed method, the existing method overestimates the ultimate strength for walls subject to low out-of-plane bending moments, and it underestimates the ultimate strength for walls subject to high out-of-plane bending moments.

• Journal of the Korean GEO-environmental Society
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• v.10 no.2
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• pp.29-36
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• 2009

A series of two-dimensional (2D) finite element analyses have been performed to study the behaviour of single piles in consolidating ground. The analysis was conducted based on coupled analyses by considering changes of pore water pressure in the clay. In the analyses the soil slippage at the pile and the soil interface has been included. The method widely used in practice somewhat overestimates dragload by about 25% compared to the rigorous numerical analysis since partial mobilization of skin friction near neutral plane and reductions in the vertical soil stress is not incorporated. When soil slip develops at most of the pile length at the pile-soil interface during consolidation, further increases in dragload is not significant. Application of coating on the pile surface can reduce dragload and pile settlement substantially, but under an axial load on the pile head very large pile settlement can be developed unless pile tip is located to a stiff bearing layer.