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81.
A voltage-controlled chaotic oscillator based on carbon nanotube field-effect transistor for low-power embedded systems 下载免费PDF全文
This paper presents a compact and low-power-based discrete-time chaotic oscillator based on a carbon nanotube field-effect transistor implemented using Wong and Deng's well-known model. The chaotic circuit is composed of a nonlinear circuit that creates an adjustable chaos map, two sample and hold cells for capture and delay functions, and a voltage shifter that works as a buffer and adjusts the output voltage for feedback. The operation of the chaotic circuit is verified with the SPICE software package, which uses a supply voltage of 0.9 V at a frequency of 20 kHz. The time series, frequency spectra, transitions in phase space, sensitivity with the initial condition diagrams, and bifurcation phenomena are presented. The main advantage of this circuit is that its chaotic signal can be generated while dissipating approximately 7.8 μW of power, making it suitable for embedded systems where many chaos-signal generators are required on a single chip. 相似文献
82.
Hoon Kim Sung-Geun Park Buyoung Jung Junphil Hwang Woochul Kim 《Applied Physics A: Materials Science & Processing》2014,114(4):1201-1208
Low-quality heat is generally discarded for economic reasons; a low-cost energy conversion device considering price per watt, $/W, is required to recover this waste heat. Thin-film based thermoelectric devices could be a superior alternative for this purpose, based on their low material consumption; however, power generated in conventional thermoelectric device architecture is negligible due to the small temperature drop across the thin film. To overcome this challenge, we propose new device architecture, and demonstrate approximately 60 Kelvin temperature differences using a thick polymer nanocomposite. The temperature differences were achieved by separating the thermal path from the electrical path; whereas in conventional device architecture, both electrical charges and thermal energy share same path. We also applied this device to harvest body heat and confirmed its usability as an energy conversion device for recovering low-quality heat. 相似文献
83.
This study employs the self-consistent Green's function method to study the magnetic properties of diluted CoxCu1-x alloys from a consideration of their spin dynamics characteristics. The numerical results show that in dilute cobalt concentrations (i.e. x?0.4), the critical temperatures vary linearly with x for different itinerant carrier concentration conditions. Interestingly, the carrier concentration does not affect the degree of dependency of the temperature on the cobalt concentration when the carrier concentration is less than the atomic number concentration of the alloy. 相似文献
84.
Modeling of ultrasonic testing has been paid a great attention in nondestructive evaluation community recently since it can provide thorough understanding of underlying physics of ultrasonic testing. As a result, there have been developed various modeling approaches up to now. Especially, many practical models have been developed based on either the multi-Gaussian beam or the Rayleigh-Sommerfeld integral. This paper discusses the modeling of ultrasonic testing with oblique incidence at the near critical angles using these two approaches. The theoretical models that can predict the reflection signals from side drilled cylindrical holes in solid specimen immersed in water are developed. Then, the theoretical predictions for the oblique incidence at the near critical angles are compared to the experiments for the investigation of model behavior. 相似文献
85.
Lee KI Joo SJ Lee JH Rhie K Kim TS Lee WY Shin KH Lee BC LeClair P Lee JS Park JH 《Physical review letters》2007,98(10):107202
Tunneling magnetoresistance was found to be suppressed with decreasing temperature for magnetic tunnel junctions (MTJs) oxidized under high plasma power. A strong temperature dependence of the junction resistance was observed, along with zero-bias anomalies of dynamic resistance at low temperatures. Resistance shows a logarithmic dependence on temperature, and resistance versus temperature exhibits a scaling behavior. Our experimental data can be explained in a consistent way by the Kondo effect in the MTJs with the Kondo temperature TK=20-30 K. 相似文献
86.
We have demonstrated the synthesis of one-dimensional (1D) structures of bismuth oxide (Bi2O3) by a reaction of a trimethylbismuth (TMBi) and oxygen (O2) mixture at 450 °C. Scanning electron microscopy showed that the product consisted of 1D materials with width or diameters less than 1 μm and lengths up to several tens of micrometers. The X-ray energy dispersive spectroscopy revealed that the materials contained elements of Bi and O. The results of X-ray diffraction and selected area electron diffraction pattern indicated that the obtained Bi2O3 were crystalline with monoclinic structure. 相似文献
87.
Yong-Goo Yoo Seong-Gi Min Ho-Jun Ryu Nam-Seok Park Seong-Cho Yu 《Journal of magnetism and magnetic materials》2006
Exchange biased IrMn/NiFe/IrMn thin films were studied as a function of NiFe thickness. In plane angular dependence of a resonance field distribution which is measured by FMR was analyzed as a combined effect of an unidirectional anisotropy and an uniaxial anisotropy. The unidirectional anisotropic field and the uniaxial anisotropic field were linearly varied with NiFe thickness while the films with a thicker NiFe layer do not follow the linear variation. Resonance field and linewidth variations were also analysed with NiFe thickness. 相似文献
88.
Nam Park Jingyeong Seo Kihyun Kim Jihyun Sim Yonggu Kang Minhyeon Han 《Composite Interfaces》2016,23(8):781-796
AbstractTo improve the endurance performance of run-flat tires by preventing the sidewall from folding at zero air pressure, a master batch of natural rubber and ZnO-treated aramid pulp (AP) is applied to the rubber sidewall-insert-layer compound. The mechanical, viscoelastic, and fatigue properties of the compounds are investigated by varying the AP content, and the endurance performance of actual run-flat tires is assessed. The results indicate that the mechanical properties are improved and the hysteresis is reduced as the AP content increased. The overall trend of the endurance times of the run-flat tires is consistent with the results of the DeMattia tests, constant-strain fatigue tests, and high-temperature tensile tests. The run-flat endurance time of the tire containing one part per hundred rubber (phr) of AP is superior to that of the tire containing 3 phr of AP because of the enhanced dispersion of the AP fibers. 相似文献
89.
Jooung-Hyun Jo Hyun-Cheol Ko Byeong-Woo Kim Hyun Park In-won Lee Ho-Hwan Chun 《Composite Interfaces》2016,23(8):797-805
AbstractMarine fouling can be a serious problem in the shipping industry, since it increases the surface roughness of the hull and hence its frictional resistance to its movement through water. Antifouling paint can be defined as preventing the attachment of marine organisms onto surfaces. However, the most commonly used antifouling coating which is the tributyltin-based self-polishing copolymer causes the severe pollution of marine environment. Ammonium salt-based paints include tertiary amines as biocides which have effective biocidal and biodegradable properties without accumulation in the sea environment. However, ammonium salt-based coatings were too sensitive to seawater and became swollen. In this study, polyurethane-acrylic copolymers were synthesized by radical polymerization. These hybrid materials were found to form core–shell structures in aqueous media. Synthesis and properties of copolymers were investigated by Fourier transform-infrared spectrometer, proton-nuclear magnetic resonance, transmission electron microscopy, and dynamic light scattering. The polishing rate of self-polishing copolymer was determined from the reduction in dry film thickness after artificial seawater immersion under a dynamic condition. 相似文献
90.
A novel water-soluble solvatochromic molecule, 7-(dimethylamino)-2-fluorenesulfonate (2,7-DAFS), was prepared by a three-step
reaction from 2-nitrofluorene in good overall yield. The pH and solvent effects on the UV-VIS absorption and fluorescence
spectra of 2,7-DAFS have been studied. Protonation of the dimethylamino group switches the absorption from intramolecular
charge-transfer (ICT) to π → π* transition. The ground state pKa value of 2,7-DAFS was determined as 4.51. The fluorescence spectrum of the excited basic form, *(DAFS), shows a structureless
single band with a large Stokes shift, whereas that of the acidic form, *(+HDAFS), exhibits a structured band with a small Stokes shift. The emission intensities of the basic and acidic forms versus
pH/Ho plots show stretched sigmoidal curves and indicate that (1) the rate of deprotonation of *(+HDAFS) is comparable to the fluorescence decay of the species, and (2) the efficient proton-induced quenching of *(DAFS) fluorescence
occurs. The pKa* was estimated as −1.7 from the fluorescence titration curve. The fluorescence maximum of *(DAFS) is blue-shifted as the
polarity of solvent decreases. However, no clear dependency of the emission intensity and spectral half width, and thus fluorescence
quantum yield, on the solvent polarity was revealed. It appears that the fluorescence sensitivity of 2,7-DAFS is 15 ∼ 25 times
greater than the sensitivity of a widely utilized fluorescent probe, 5-(dimethylamino)-1-naphthalenesulfonate. This higher
sensitivity, together with the ease of derivatization, would provide the fluorene-based fluorescent molecules significant
advantages for a variety of applications. 相似文献