Papers by Keyword: Tunable

Abstract: This research proposes an improved tunable piezoelectric harvester structure which is constructed by a cantilever base beam and piezoelectric elements working in d33 mode. Our previous work on tunable piezoelectric harvester structure showed a frequency variation ratio of 3.17% with piezoelectric elements working in d31mode coupling. In this work, by changing the working mode of the piezoelectric elements from d31 to d33 mode, the frequency variation ratio was shown to be much higher. Theoretical analysis of the improved structure was investigated and verified with simulations. The results showed that the d33 mode coupling surpasses the d31 mode coupling with a frequency variation ratio of 29.74%.

Abstract: A modeling analysis and verification of tunable metamaterial absorbers (MA) comprised of a new combination shaped metal elements printed on a dielectric substrate loaded with PIN diodes were presented. Unlike conventional transmission line analysis, new modeling analysis allows arbitrarily shaped elements to be calculated. A qualitative analysis by a simple equivalent circuit model is carried out on the parameters of the tunable MA. Thus, samples of the tunable MA are fabricated. The measured results are in good agreement with the predicted ones. The study shows that the modeling analysis is simple and practicable to describe the working principle of the tunable MA structure.

Abstract: This research proposes a novel piezoelectric harvester structure which is constructed by a cantilever base beam and piezoelectric elements bonded with the base beam in a certain manner. By changing the electrical boundary conditions of the piezoelectric elements, the resonant frequency of the beam structure changes accordingly. Two kinds of manners in which piezoelectric elements are bonded with the beam are investigated and compared with ANSYS simulations and experiments. The results showed that the embedded manner surpasses the surface-bonded manner with the frequency variation ratio of 3.17%.

Abstract: In this paper, we successfully designed a pH-responsive micelles based on hybrid polypeptide copolymers of poly (L-lysine-4-Azepan-1-yl-butyric)-b-poly (ethylene glycol)-b-poly (L-lysine-Diisopropylamide)-b-poly (L-leucine) (PLL(A)-PEG-PLL(B)-PLLeu) for efficient drug delivery. This pH-responsive nanoparticles were able to response to different pH values (pH=6.8 and 5.5). In vitro, these nanoparticles exhibited a stable and evenly distributed approximately 51 nm, a slightly positive potential about 10.3 mv at pH 7.4, which were crucial for the circulation of drugs in blood. While size and potential were about 130 nm and 34.7 mv at pH 6.8, which were good for drugs in membrane. Furthermore, the loading capability of DOX was up to 11.3%, and the pH-responsive release efficiency reached to 68.3% at pH 5.5. The results indicated that these micelles had huge potential application in cancer delivery.

Abstract: In order to reach soft x-ray wavelength starting from the UV seed laser, we used the recently Echo-Enabled Harmonic Generation (EEHG) scheme proposed by D. Xiang. This scheme uses two laser modulators in combination with two dispersion sections to generate higher harmonic radiation as compared with the normal limit arising from energy spread for HGHG. Using representative, realistic and optimized parameters, finally, we get the beam density modulation at the 88th harmonic of the seed laser. The performance of the above event is estimated by means of GENESIS.

Abstract: This paper presents a tunable inductor using MEMS technology .This tunable spiral inductor is designed in order to be used in RF circuits such as : controlled oscillators with voltage (VCO) , matching networks ,amplifiers etc . The electrostatic method is employed for tuning the inductor by the movement of cantilever beam downward and changing the value of magnetic flux. Value of inductance varies fram 1.15nh to 0.561 nh .therefore ,tunablity of 66.21% was achieved .Maximum quality factor in the above inductor was achieved az 13.88 in the frequency 0f 12 GHz and the value of resonance frequency was achieved as 19.5 GHz

Abstract: In this paper, the liquid crystal grating-based 3D display will be introduced, and emphasis on the ‘movable’ characteristic of the LC grating. To make LC grating tunable, the required lighted LC grating pixels would be controlled via programming in order to solve the following questions: the pixels loss or the single viewing point.

Abstract: The fabrication of the single-negative (SNG) metamaterials involving the tunable SNG metamaterials based on coplanar waveguide is investigated. First, the SNG metamaterials are fabricated by periodically loading lumped-element series capacitors and shunt inductors on coplanar waveguide. Moreover, based on it, the tunable SNG metamaterials in which the center frequency and frequency region of the SNG gap can be tuned conveniently is also realized through loading the varactor diodes in place of the lumped-element capacitors.

Abstract: We present a new concept for compact, tunable antennas. Traditional approaches have circuits and switchable elements which can be bulky and lossy. Here we investigate structures which offer direct tuning through voltage-controlled deformation of the radiating structure itself. The antenna is a dielectric resonator (DRA), where the antenna impedance and tuning depends on the shape of the dielectric. The deformation action is through using electro-active polymer (EAP) for the dielectric. EAPs have promising properties for smart antennas and ongoing developments are continuing to improve its suitability.

Abstract: Pure barium strontium titanate (Ba0.65Sr0.35TiO3) and MnO2-modified barium strontium titanate (Ba0.65Sr0.35TiO3-MnO2) thick films were fabricated by electrophoretic deposition technique. The structures and morphologies of the films were analyzed. The dielectric measurements were conducted on metal-insulator-metal capacitors using platinum as the bottom electrodes and gold as the top electrodes. The dielectric constants and dissipation factors of Ba0.65Sr0.35TiO3 and Ba0.65Sr0.35TiO3-15wt% MnO2 thick films were measured at a frequency of 1 MHz. The tunabilities of 12.5% and 9.3% were obtained for Ba0.65Sr0.35TiO3 and Ba0.65Sr0.35TiO3-MnO2 thick films under an applied electric field of 15 kV/cm, respectively. The dielectric properties of the present thick films were suitable for tunable microwave device applications.