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91.
Dhananjay Kumar K M Satyalakshmi S S Manoharan M S Hegde 《Bulletin of Materials Science》1994,17(6):625-632
Microstructural and superconducting properties of YBa2Cu3O7−x
thin films grownin situ on bare sapphire by pulsed laser deposition using YBa2Cu3O7−x
targets doped with 7 and 10 wt% Ag have been studied. Ag-doped films grown at 730°C on sapphire have shown very significant
improvement over the undoped YBa2Cu3O7−x
films grown under identical condition. A zero resistance temperature of 90 K and a critical current density of 1·2×106 A/cm2 at 77 K have been achieved on bare sapphire for the first time. Improved connectivity among grains and reduced reaction rate
between the substrate and the film caused due to Ag in the film are suggested to be responsible for this greatly improved
transport properties. 相似文献
92.
93.
Parallel cascade controllers are used in chemical processing industries to improve the dynamic performance of a control system in the presence of disturbances. In the present work, a delay compensator has been incorporated in the primary loop of the parallel cascade control system. The secondary controller is designed using the internal model control (IMC) method. The primary controller is designed based on a direct synthesis method for the delay-free system. Design of controllers for slow (when the secondary loop dynamics is slow i.e. process contains poles sufficiently slower than the desired closed loop response) as well as fast dynamics (when the inner loop dynamics is fast i.e. process contains poles sufficiently faster than the desired closed loop response) of the secondary process is considered. The method provides robust control performances. Significant improvement in the closed loop performances are obtained with the delay compensator over that of a conventional parallel cascade control system. Several case studies are considered to show the advantage of the proposed method when compared to other recently reported methods. 相似文献
94.
95.
96.
N Chidambaram A Mazzalai P Muralt 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2012,59(8):1624-1631
Interdigitated electrode (IDE) systems with lead zirconate titanate (PZT) thin films play an increasingly important role for two reasons: first, such a configuration generates higher voltages than parallel plate capacitor-type electrode (PPE) structures, and second, the application of an electric field leads to a compressive stress component in addition to the overall stress state, unlike a PPE structure, which results in tensile stress component. Because ceramics tend to crack at relatively moderate tensile stresses, this means that IDEs have a lower risk of cracking than PPEs. For these reasons, IDE systems are ideal for energy harvesting of vibration energy, and for actuators. Systematic investigations of PZT films with IDE systems have not yet been undertaken. In this work, we present results on the evaluation of the in-plane piezoelectric coefficients with IDE systems. Additionally, we also propose a simple and measurable figure of merit (FOM) to analyze and evaluate the relevant piezoelectric parameter for harvesting efficiency without the need to fabricate the energy harvesting device. Idealized effective coefficients e(IDE) and h(IDE) are derived, showing its composite nature with about one-third contribution of the transverse effect, and about two-thirds contribution of the longitudinal effect in the case of a PZT film deposited on a (100)-oriented silicon wafer with the in-plane electric field along one of the <011> Si directions. Randomly oriented 1-μm-thick PZT 53/47 film deposited by a sol-gel technique, was evaluated and yielded an effective coefficient e(IDE) of 15 C???m(???2). Our FOM is the product between effective e and h coefficient representing twice the electrical energy density stored in the piezoelectric film per unit strain deformation (both for IDE and PPE systems). Assuming homogeneous fields between the fingers, and neglecting the contribution from below the electrode fingers, the FOM for IDE structures with larger electrode gap is derived to be twice as large as for PPE structures, for PZT-5H properties. The experiments yielded an FOM of the IDE structures of 1.25 × 10(10) J/m(3) and 14 mV/μ strain. 相似文献
97.
98.
This paper presents a method for realizing cooperative control of dual-arm manipulators (RM-10A by Remotec Inc.) handling
the same object in the presence of dynamic parameter uncertainties of both robots and object. When multiple robots handle
the same object, both the position and the internal forces between the robots and the object should be controlled. In this
paper, a sliding mode controller is derived for trajectory tracking of object position and internal forces. To show the effectiveness
of the proposed controller, numerical simulations are performed for 12 axis dual-arm manipulators.
This work was presented, in part, at the Third International Symposium on Artificial Life and Robotics, Oita, Japan, January
19–21, 1998 相似文献
99.
Zonios G Perelman LT Backman V Manoharan R Fitzmaurice M Van Dam J Feld MS 《Applied optics》1999,38(31):6628-6637
Diffuse reflectance spectra were collected from adenomatous colon polyps (cancer precursors) and normal colonic mucosa of patients undergoing colonoscopy. We analyzed the data by using an analytical light diffusion model, which was tested and validated on a physical tissue model composed of polystyrene beads and hemoglobin. Four parameters were obtained: hemoglobin concentration, hemoglobin oxygen saturation, effective scatterer density, and effective scatterer size. Normal and adenomatous tissue sites exhibited differences in hemoglobin concentration and, on average, in effective scatterer size, which were in general agreement with other studies that employ standard methods. These results suggest that diffuse reflectance can be used to obtain tissue information about tissue structure and composition in vivo. 相似文献
100.