Nowadays, hydrogen is being utilized massively in industries as a clean fuel. Displacing of hydrogen due to unique chemical and physical properties has adversely affect on pipeline network, hence ...increases the potential risk of explosion. This study was carried out to determine the flame propagation of hydrogen/air and hydrogenamethane/air mixtures in pipeline. A 90ADG pipeline with L/D ratio of 40 was used. Pure hydrogen/air mixture with equivalence ratio, I = 0.13, 0.17, 0.2, 0.24, 0.27 and 0.30 were used in this work. Different composition of hydrogenamethaneaair mixtures were tested in this study i.e. 3%H2 + 97CH4, 4%H2 + 96CH4, 6%H2 + 94CH4 and 8%H2 + 92CH4. All mixtures were operated at ambient condition. The results show that bending is the critical part of pipeline and higher concentration of hydrogen can affect on maximum overpressure, flame speed and temperature rise of both pure hydrogen/air and methane-hydrogen/air mixtures.
Structural investigation of the seeding process for the physical vapor transport (PVT) growth of 4HaSiC single crystals was conducted by high-resolution x-ray diffraction (HRXRD) and synchrotron ...x-ray topography. Characteristic lattice plane bending behavior was observed in the near-seed regions of the grown crystals. The bending of the (112I0) lattice plane was localized near the seed/grown crystal interface, and the (0001) basal plane bent convexly in the growth direction near the interface, indicative of the insertion of extra-half planes pointing toward the growth direction during the seeding process for PVT growth. This study discusses a possible mechanism for the observed lattice plane bending and sheds light on defect formation processes during the PVT growth of 4HaSiC single crystals.
A single-foot linear piezoelectric actuator is proposed in this paper, and a new exciting method for the stepping motion is discussed. The proposed actuator works in the hybrid modes of the second ...horizontal bending vibration and the second vertical bending vibration. Two intermittent sinusoidal signals with a phase difference of 90° are applied on the horizontal and vertical PZT elements, respectively, to obtain a discontinuous elliptical motion at the driving foot, which can move the runner linearly step by step. The structure of a single-foot linear piezoelectric actuator is designed and the mechanism for the linear driving is clarified. Then, modal and transient analyses are carried out by using ANSYS software to get the resonance frequencies of the bending modes and the movement trajectory of the driving foot. Finally, a prototype of the piezoelectric actuator is fabricated, and experiments are carried out. The experiment results show that the displacement resolution, the maximum velocity, and the maximum thrust of the proposed piezoelectric actuator are about 0.21 μm, 827.5 mm/s, and 27 N, respectively.
Flexible electronics is a rapidly growing technology for a multitude of applications. Wearables and flexible displays are some application examples. Various technologies and processes are used to ...produce flexible electronics. An important aspect to be considered when developing these systems is their reliability, especially with regard to repeated bending. In this paper, the frequently used methods for investigating the bending reliability of flexible electronics are presented. This is done to provide an overview of the types of tests that can be performed to investigate the bending reliability. Furthermore, it is shown which devices are developed and optimized to gain more knowledge about the behavior of flexible systems under bending. Both static and dynamic bending test methods are presented.
We performed scanning tunneling spectroscopy on an as-grown Cu(InGa)Se sub(2) (CIGS) thin film and photo-assisted Kelvin probe force microscopy on a CIGS solar cell. From these measurements, we ...estimated the band profile around the grain boundaries (GBs). The results indicate both downward bending of the conduction band edge and broadening of the band gap near GBs. We can therefore conclude that photo-generated electrons and holes are easily separated by the built-in field near GBs, and consequently their recombination at the GBs should be suppressed. Copyright copy 2011 John Wiley & Sons, Ltd. The band profile around the grain boundaries (GBs) in Cu(InGa)Se sub(2) was estimated from scanning tunneling spectroscopy and photo-assisted Kelvin probe force microscopy. The results indicate both downward bending of the conduction band edge and broadening of the band gap near GBs, and consequently we can conclude that photo-generated electrons and holes are easily separated by the built-in field near GBs and that their recombination at the GBs should be suppressed.
Based on the neo-classical elastic energy of liquid crystal elastomers, the opto-mechanical behavior is modeled by considering the effect of photoisomerization on the nematic-isotropic transition of ...liquid crystal phase. Linearized stressastrain relation is derived for infinitesimal deformations with a very unusual shear stress that does not vanish identically as in the case of the soft behavior but is proportional to the rotation of directors. In other words, the shear stress depends on both the shear strain and the skew symmetric part of the displacement gradient with the shear modulus induced by the effect of photoisomerization. Finite element implementation for plane stress problems is obtained through a self-defined material subroutine in ABAQUS FEA tool. Numerical simulations show that the light induced deformations of two dimensional specimens consist of contractions, expansions and bending in different directions. The stress distributions indicate that the driving force for the light induced bending is produced by the bending moment of the normal stress along the director, while the other stress components are much smaller for two dimensional beam shaped specimens. However, the shear stress of the soft LCE is generally nonzero under light illumination due to the inhomogeneity of the opto-mechanical effect. It can be concluded from the strain distributions that the transversal plane cross section could remain plane after deformation if the light intensity or the decay distance is not too small and the sample is in the deep nematic phase. However, the shear strain and in plane rotation are of the same order as the other strain components, and thus should not be neglected. This indicates that the classical simple bending assumptions such as the Euler-Bernoulli beam theory should not be directly applied to model the light induced bending of neo-classical liquid crystal elastomers due to the soft behavior of the materials.
In a high-T(c) superconducting magnetic levitation system, an object can levitate without control and contact. So it is expected to be applied to magnetically levitated transportation. To use it ...safely, lightening the levitated object is necessary. But this reduces the bending stiffness of the object. Besides, the system has nonlinearity. Therefore nonlinear elastic vibration can occur. This study focused on how plural nonlinear elastic vibrations of the 1st, 2nd and 3rd modes simultaneously occur. Our numerical calculation and experiment found out that the three modes simultaneously resonate when the amplitude of the 2nd mode is large enough whereas only the 2nd mode resonates when it is small.
Copolymeric hydrogels of polyacrylic acid (PAA) a polyacrylonitrile (PAN) was radiolytically synthesized from their respective monomers with trimethyloltrimethacrylate (TMPTMA) as the crosslinker ...wherein both polymerization and crosslinking could be achieved in a single step reaction using 60Co I3-radiation under varying doses and dose rates. The formation of the hydrogels was confirmed by their FT-IR analysis, while their thermal degradation patterns were investigated through thermogravimetric analysis in both the dry and swelled state. The water sorption studies showed rapid swelling behavior of these hydrogels, where swelling (%EWC) was found to be strongly dependent on the ratio of the two monomers in the hydrogels and the swelling kinetics dependent on the dose rates of hydrogel synthesis. These radiolytically synthesized hydrogels responded to electrical stimulus both in terms of the bending speed as well as bending angle under an applied voltage. The nature of the deformation was reversible and can be controlled through switching the voltage on and off.
The Raman and the infrared wavenumbers in the Aurivillius structure BaBi sub(2)Ta sub(2)O sub(9) (BBT) having space group 14/mmm (no. 139-D super(1) sub(4) super(7) sub(h)) are investigated using ...normal coordinate analysis. The calculation of zone center phonons incorporates seven stretching and seven bending force constants. The Raman and the infrared frequencies for BBT have been assigned for the first time in 14/mmm phase. The calculated Raman and infrared wavenumbers are in very good agreement with the observed ones. The potential energy distributions (PED) are also investigated for each normal mode in BBT and the contributions of different force constants to various frequencies are determined.
A planar piezoelectric actuator with large travel range is presented in this paper. The actuator is composed of four uniform piezoelectric transducers, and each transducer can bend along the ...horizontal direction or vertical direction independently. Trapezoidal-wave signals are used to excite the hybrid bending of the transducers and form rectangular movements on their driving feet. The actuator can move step by step by the static friction forces in nonresonant mode, and a long reliability life is obtained as there is no wear and tear problem. The operating principle is simulated by finite-element method, which reveals the generation of rectangular trajectory on each driving foot and the large structure stiffness of the actuator. A prototype is fabricated and its experiment system is established. A resolution of 16 nm is achieved at the quasi-static mode, a minimum step distance repeatability error rate of 1.06% is obtained at the stepper mode; the maximum output speed and carrying load of 300 μm/s and 35 kg are achieved at voltage of 400 V<inline-formula><tex-math notation="LaTeX">_{{\text{p-p}}}</tex-math></inline-formula> and frequency of 40 Hz. The experiments also shows that the output speed is linearly related to the exciting voltage; the motion along any direction in the platform is achieved by controlling the voltage signals.
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