[en] We have been investigated HCPD(Hypocycloidal Pinch Device) for NUV(Near Ultraviolet) dye laser pumping source. HCPD is an useful NUV pumping source, because the spectral distribution of radiation from it has very wide range in the NUV region. For the improvement of characteristics of HCPD, we modified materials of its insulators and electrodes. Insulators were changed from PE (polyethylene) to ceramic glass, and electrodes were also changed from Brass to Mo(Molybdenum). Modified HCPD shows more enhanced characteristics. First, the lifetime of the dye cell was extended so much than as before, due to the reduction of carbon contamination and metal coating. Second, HCPD's spectral irradiance shows that it is proper pumping source for NUV laser, because its NUV intensity is higher than visible region. Characteristics of NUV dye laser pumped by HCPD was also investigated. Peak wavelengh of the dye laser observed in spectrum is 385nm and untuned spectral width of the laser is 3nm. The observed laser energy per one pulse under the optimum condition is 34.5mJ

[en] In this paper, a new technique of time-delay compensation is proposed for active control of a flexible hub-beam system. The first-order approximation coupling (FOAC) model proposed recently for dynamics of hub-beam systems is used to verify the applicability of this technique. The FOAC model is first linearized to obtain a linearized equation. The linearized equation with time delay is then transformed into a standard form with no time delay by a particular integral transformation. The time-delay controller is designed based on this standard equation using the classical optimal tracking control theory. Since the controller is a function of modal coordinates, a modal filter is presented to estimate the modal coordinates from physical sensor measurements. The effectiveness of the proposed technique for time delay is demonstrated by numerical simulations. Simulation results indicate that a very small time delay may result in instability of the control system if it is not compensated in control design. The proposed time-delay controller is effective in controlling the system even when the maximum time delay for stability without time-delay compensation is greatly exceeded. Moreover, for the system without time delay, the proposed time-delay controller may possibly obtain much better control effectiveness than the controller without time delay

[en] CoSi₂ layers, <40 nm thick, were grown on Si(001) by reactive deposition epitaxy (RDE) in which Co was deposited at 700 deg.C by magnetically unbalanced ultrahigh vacuum magnetron sputtering. X-ray diffraction pole figures and transmission electron microscopy (TEM) reveal that the layers, which exhibit a cube-on-cube epitaxial relationship with the substrate (001)_CoSi2(parallel sign)(001)_Si and [100]_CoSi2(parallel sign)[100]_Si, contain fourfold symmetric (111) twinned domains oriented such that (221)_CoSi2(parallel sign)(001)_Si and <110>_CoSi2(parallel sign)[110]_Si. We demonstrate that high-flux low-energy (E_Ar⁺=9.6 eV) Ar⁺ ion irradiation during deposition dramatically increases the area fraction f_u of untwinned regions from 0.17 in films grown under standard magnetically balanced conditions in which the ratio J_Ar⁺/J_Co of the incident Ar⁺ to Co fluxes is 1.4 to 0.72 with J_Ar⁺/J_Co=13.3. TEM analyses show that the early stages of RDE CoSi₂(001) film growth proceed via the Volmer-Weber mode with independent nucleation of both untwinned and twinned islands. Increasing J_Ar⁺/J_Co results in larger values of both the number density and area of untwinned with respect to twinned islands. The intense Ar⁺ ion bombardment creates additional low-energy adsorption sites that favor the nucleation of untwinned islands while collisionally enhancing Co surface mobilities which, in turn, increases the probability of itinerant Co adatoms reaching these sites

[en] The conventional HCP (hypocycloidal pinch) device has been proven to have significant advantages over traditional flashlamps in terms of output power, life expectancy and selectivity of spectra in the UV (ultraviolet) region. However, the conventional HCP device's electrical discharge was contaminated with dye cuvette due to vaporization of the electrodes and the insulators. As a result, we improved the electrode and the insulator of the conventional HCP device and investigated the electrical and the optical properties of the improved HCP device. The pumping light intensity of the improved HCP device was compared with that of the conventional HCP device. The optimum operating pressure output power of the UV dye laser pumped by the HCP was 192 kW at input energy of 900 J. In addition, the untuned laser wavelength was 385 nm and the half width of the laser was 3 nm

[en] This paper investigates the natural frequency, steady-state resonance and stability for the transverse vibrations of a nanobeam subjected to a variable initial axial force, including axial tension and axial compression, based on nonlocal elasticity theory. It is reported that the nonlocal nanoscale has significant effects on vibration behavior, which results in a new effective nonlocal bending moment different to but dependent on the corresponding nonlocal bending moment. The effects of nonlocal nanoscale and the variation of initial axial force on the natural frequency as well as the instability regions are analyzed by the perturbation method. It concludes that both the nonlocal nanoscale and the initial tension, including static and dynamic tensions, cause an increase in natural frequency, while an initial compression causes the natural frequency to decrease. Instability regions are also greatly influenced by the nonlocal nanoscale and initial tension and they become smaller with stronger nonlocal effects or larger initial tension

[en] This paper investigates the free vibration characteristics of micro-switches under combined electrostatic, intermolecular forces and axial residual stress, with an emphasis on the effect of geometric nonlinear deformation due to mid-plane stretching and the influence of Casimir force. The micro-switch considered in this study is made of either homogeneous material or non-homogeneous functionally graded material with two material phases. The Euler–Bernoulli beam theory with von Karman type nonlinear kinematics is applied in the theoretical formulation. The principle of virtual work is used to derive the nonlinear governing differential equation. The eigenvalue problem which describes free vibration of the micro-beam at its statically deflected state is then solved using the differential quadrature method. The natural frequencies and mode shapes of micro-switches for four different boundary conditions (i.e. clamped–clamped, clamped–simply supported, simply supported and clamped–free) are obtained. The solutions are validated through direct comparisons with experimental and other existing results reported in previous studies. A parametric study is conducted to show the significant effects of geometric nonlinearity, Casimir force, axial residual stress and material composition for the natural frequencies

[en] Mirage effect, a common phenomenon in nature, is a naturally occurring optical phenomenon in which lights are bent due to the gradient variation of refraction in the temperature gradient medium. The theoretical analysis of mirage effect generated by heated carbon nanotube thin film is presented both for gas and liquid. Excellent agreement is demonstrated through comparing the theoretical prediction with published experimental results. It is concluded from the theoretical prediction and experimental observation that the mirage effect is more likely to happen in liquid. The phase of deflected optical beam is also discussed and the method for measurement of thermal diffusivity of medium is theoretically verified. Furthermore, a method for measuring the refractive index of gas by detecting optical beam deflection is also presented in this paper.

[en] We present a compactly integrated, 625 MHz clocked coherent one-way quantum key distribution system which continuously distributes secret keys over an optical fibre link. To support high secret key rates, we implemented a fast hardware key distillation engine which allows for key distillation rates up to 4 Mbps in real time. The system employs wavelength multiplexing in order to run over only a single optical fibre. Using fast gated InGaAs single photon detectors, we reliably distribute secret keys with a rate above 21 kbps over 25 km of optical fibre. We optimized the system considering a security analysis that respects finite-key-size effects, authentication costs and system errors for a security parameter of ε_QKD = 4 × 10⁻⁹. (paper)