• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.62-65
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• 2001

The effects of the initial torture of workpiece as well as the process conditions such as punch speed and lubrication on the formablity of sheet stretching are investigated by experiments. Two types of the initial textures of aluminum sheet plane strain compression torture and recrystallization texture are chosen since those are the most common in practice. Punch loads vs depth and thickness strain distributions along radial directions having the slope of $0^{\circ},\;45^{\circ},\;90^{\circ}$ with rolling directions are reported for hemishperical punch stretchings under a variety of process conditions.

• Journal of Korean Physical Therapy Science
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• v.28 no.1
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• pp.11-22
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• 2021

Background: This study was to investigate the effects of active stretching and stability exercise on piriformis muscle thickness and low back pain of male patients with chronic low back pain. Design: Randomized Controlled Trial. Methods: 45 male patients participated in this study. All subjects were randomly assigned. Subjects divided into 15 who underwent contract relaxation (CR) of the proprioceptive neuromuscular facilitation (PNF) to their hip joints, 15 who underwent a combination of isotonic (CI) of the PNF, and the rest 15 who underwent the two techniques (CR+CI). Real-time diagnostic ultrasound was used to measure thickness of the piriformis muscles. The visual analogue scale (VAS) was used to measure degrees of low back pain. A two-way repeated measures ANOVA was used to compare the average values. The SPSS 24.0 was used as the statistical program, and the significance level was set at .05. Results: The CR and the CR+CI groups had more decreased thickness of piriformis muscle when compared to the CI group. The CR+CI group had more decreased pain when compared to the CR and the CI groups. Conclusion: These results suggest that combination of stretching and stability exercise was effective on male patients with chronic low back pain showing limited hip medial rotation.

• Steel and Composite Structures
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• v.18 no.3
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• pp.793-809
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• 2015

In this scientific work, constructing of a novel shear deformation beam model including the stretching effect is of concern for flexural and free vibration responses of functionally graded beams. The particularity of this model is that, in addition to considering the transverse shear deformation and the stretching effect, the zero transverse shear stress condition on the beam surface is assured without introducing the shear correction parameter. By employing the Hamilton's principle together with the concept of the neutral axe's position for such beams, the equations of motion are obtained. Some examples are performed to demonstrate the effects of changing gradients, thickness stretching, and thickness to length ratios on the bending and vibration of functionally graded beams.

• Archives of Plastic Surgery
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• v.46 no.2
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• pp.167-170
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• 2019

Full-thickness scalp burns secondary to hair coloring are rare; however, such defects can be large and complex reconstruction of hair-bearing tissue may be necessary. Many skin-stretching devices that use gradual traction have been applied to take advantage of the viscoelastic properties of the skin. A 21-year-old female patient was seen with a burn defect on her occipital scalp leading to exposed subcutaneous tissue after chemical application of hair coloring in a salon. The dimensions of the wound were $10cm{\times}5cm$, and a skin graft or flap would have been necessary to close the defect. Two long transfixing K-wires (1.4 mm) and paired 3-wire threads (23 gauge), which are readily available in most hospitals, were applied over a period of 12 days for trichophytic closure of the defect. The remaining scalp scars after primary trichophytic closure with this skin-stretching method were refined with hair follicle transplantation. This skin-stretching method is simple to apply and valuable for helping to close problematic areas of skin shortage that would otherwise require more complicated procedures. This case shows a relatively unknown complication of hair coloring and its treatment.

• Advances in nano research
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• v.10 no.3
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• pp.271-280
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• 2021

The present work deals with an investigation on longitudinal wave propagation in nanobeams made of graphene sheets, for the first time. The nanobeam is modelled via a higher-order shear deformation theory accounts for both higher-order and thickness stretching terms. The general nonlocal strain gradient theory including nonlocality and strain gradient characteristics of size-dependency in order is used to examine the small-scale effects. This model has three-small scale coefficients in which two of them are for nonlocality and one of them applied for gradient effects. Hamilton supposition is applied to obtain the governing motion equation which is solved using a harmonic solution procedure. It is indicated that the longitudinal wave characteristics of the nanobeams are significantly influenced by the nonlocal parameters and strain gradient parameter. It is shown that higher nonlocal parameter is more efficient than lower nonlocal parameter to change longitudinal phase velocities, while the strain gradient parameter is the determining factor for their efficiency on the results.

• Structural Engineering and Mechanics
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• v.84 no.6
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• pp.783-798
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• 2022

This study attempts to investigate the impact of thickness stretching and nonlinear hygro-thermo-mechanical loading on the bending behavior of FG beams. Young's modulus, thermal expansion, and moisture concentration coefficients vary gradually and continuously according to a power-law distribution in terms of the volume fractions of the constituent materials. In addition, the interaction between the thermal, mechanical, and moisture loads is involved in the governing equilibrium equations. Using the present developed analytical model and Navier's solution technique, the numerical results of non-dimensional stresses and displacements are compared with those obtained by other 3D theories. Furthermore, the present analytical model is appropriate for investigating the static bending of FG beams exposed to intense hygro-thermo-mechanical loading used for special technical applications in aerospace, automobile, and civil engineering constructions.

• Smart Structures and Systems
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• v.19 no.2
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• pp.115-126
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• 2017

In this paper, size dependent bending and free flexural vibration behaviors of functionally graded (FG) nanobeams are investigated using a nonlocal quasi-3D theory in which both shear deformation and thickness stretching effects are introduced. The nonlocal elastic behavior is described by the differential constitutive model of Eringen, which enables the present model to become effective in the analysis and design of nanostructures. The present theory incorporates the length scale parameter (nonlocal parameter) which can capture the small scale effect, and furthermore accounts for both shear deformation and thickness stretching effects by virtue of a hyperbolic variation of all displacements through the thickness without using shear correction factor. The material properties of FG nanobeams are assumed to vary through the thickness according to a power law. The neutral surface position for such FG nanobeams is determined and the present theory based on exact neutral surface position is employed here. The governing equations are derived using the principal of minimum total potential energy. The effects of nonlocal parameter, aspect ratio and various material compositions on the static and dynamic responses of the FG nanobeam are discussed in detail. A detailed numerical study is carried out to examine the effect of material gradient index, the nonlocal parameter, the beam aspect ratio on the global response of the FG nanobeam. These findings are important in mechanical design considerations of devices that use carbon nanotubes.

• Steel and Composite Structures
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• v.18 no.1
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• pp.235-253
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• 2015

In this research, a simple but accurate sinusoidal plate theory for the thermomechanical bending analysis of functionally graded sandwich plates is presented. The main advantage of this approach is that, in addition to incorporating the thickness stretching effect, it deals with only 5 unknowns as the first order shear deformation theory (FSDT), instead of 6 as in the well-known conventional sinusoidal plate theory (SPT). The material properties of the sandwich plate faces are assumed to vary according to a power law distribution in terms of the volume fractions of the constituents. The core layer is made of an isotropic ceramic material. Comparison studies are performed to check the validity of the present results from which it can be concluded that the proposed theory is accurate and efficient in predicting the thermomechanical behavior of functionally graded sandwich plates. The effect of side-to-thickness ratio, aspect ratio, the volume fraction exponent, and the loading conditions on the thermomechanical response of functionally graded sandwich plates is also investigated and discussed.

• Earthquakes and Structures
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• v.16 no.5
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• pp.547-561
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• 2019

In this work, a new analytical approach using a theory of a high order hyperbolic shear deformation theory (HSDT) has been developed to study the free vibration of plates of functionally graduated material (FGM). This theory takes into account the effect of stretching the thickness. In contrast to other conventional shear deformation theories, the present work includes a new displacement field that introduces indeterminate integral variables. During the manufacturing process of these plates defects can appear as porosity. The latter can question and modify the global behavior of such plates. The materials constituting the plate are assumed to be gradually variable in the direction of height according to a simple power law distribution in terms of the volume fractions of the constituents. The motion equations are derived by the Hamilton principle. Analytical solutions for free vibration analysis are obtained for simply supported plates. The effects of stretching, the porosity parameter, the power law index and the length / thickness ratio on the fundamental frequencies of the FGM plates are studied in detail.

• Physical Therapy Korea
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• v.2 no.2
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• pp.56-65
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• 1995

The purpose of this study was to compare the effects of one proprioceptive neuromuscular facilitation technique and static stretching on calf muscle tightness. The subjects consist of 9 hemiplegics, and 9 quadriplegics. The eighteen subjects were randomly divided into 3 groups: prorioceptive neuromuscular facilitation(6 persons), static stretching(6 persons) and control(6 persons). Contract relax antagonist contract and static stretching techniques were applied continuously for twenty minutes each. Of the many proprioceptive neuromuscular facilitation techniques, only the contract relax antagonist contract technique was applied. The static stretching technique was applied with the subject placed in standing on a seventy degree inclined tilt table for twenty minutes. A wedge was placed under the feet to obtain maximum dorsiflexion. Wedge thickness varied with each subject. Results revealed: (1) a significant difference between the experimental and the control groups(p<0.05). (2) a significant difference between contract relax antagonist contract and static stretching groups(p<0.05). (3) At day five, the final increments were: contract relax antagonist contract $11.9{\pm}1.90^{\circ}$, static stretching $7.7{\pm}2.3^{\circ}$(mean${\pm}$standard deviation).