The utilization of LH2 and LNG cold for generation of electric power by a cryogenic type stirling engine

The design of a LH₂ and LNG regasification system for a 100 MW power station is discussed. The Cryogenic Stirling Engine is chosen to operate the electrical generator. The results indicate that a system which recovers cold and generates power in parallel is economic, the problem lies in developing a large scale system.     

Shielding study on iron and concrete assemblies of bremsstrahlung photons and photoneutrons from copper target bombarded by 18, 28 and 38 MeV electrons

Following the angular distribution measurements of bremsstrahlung photons and photoneutrons, we measured the distributions of photon and neutron dose rates in the iron and concrete assemblies using a copper target bombarded by 18, 28 and 38 MeV electrons at the electron linear accelerator (linac) of Hokkaido University. In this experiment, seven types of shielding assemblies of iron and concrete layers were used and the photon and neutron dosemeters were inserted into the assemblies to get the depth–dose distribution. The measured results were compared with the results calculated using the Monte Carlo code MCNP5 to verify the calculated results. The calculated results of the ambient dose equivalent rates were in agreement with the measured results within 30% accuracy. Since no work on the radiation behavior in the shielding wall of medical linac room has ever been reported, this work gives valuable benchmark data for the detailed shielding design with high accuracy.     

Effect of spin-orbit split-off bands on GaInP/AlGaInP strainedquantum well lasers

We theoretically analyzed the effect of the spin-orbit split-off band on GaInP/AlGaInP strained quantum well lasers using 6×6 Luttinger-Kohn Hamiltonian. Because of the small spin splitting energy of GaInP, we show that the spin-orbit split-off subbands strongly couple with heavy and light hole subbands, and linear gain properties are greatly different from those without the effect of spin-orbit split-off bands. The unstrained quantum well structure is most influenced by the spin-orbit split-off bands, and laser characteristics such as the differential gain and threshold current are degraded. The compressive-strained quantum well has the lowest threshold current, and the tensile-strained quantum well has largest differential gain, which is improved by the effect of the spin-orbit split-off bands     

Characterization of the medium-range structure of Si-Al-C-O, Si-Zr-C-O and Si-Al-C Tyranno fibers by small angle X-ray scattering

The medium-range structures of Si-Al-C-O, Si-Zr-C-O and Si-Al-C Tyranno fibers, which were prepared by pyrolysing polymetalocarbosilane organic fibers, were observed by means of small angle X-ray scattering using a point-collimated Cu K incident beam and a two-dimensional imaging plate detector. Single Si-Al-C-O and Si-Zr-C-O Tyranno fibers of a few m in diameter have an anisotropic structure comprising thousands of fine filaments of about 10 nm in diameter bundled together along with the long axis of the fibers. The anisotropic structure is not sensitive to the pyrolysing temperature during the organic-to-inorganic conversion process. However, the anisotropic structure of the Si-Al-C-O fibers is totally modified to an isotropic one in Si-Al-C fibers prepared by heating the Si-Al-C-O fibers above 1700°C in an argon gas stream, because of the formation of an aluminum oxide-rich phase at the grain boundaries of -SiC nanoclusters.     

A high accuracy current component detection method for fullydigital vector-controlled PWM VSI-fed AC drives

A high-accuracy, differential-type current component detection method is described, and test results are presented. The method is suitable for vector-controlled pulse-width-modulated (PWM) voltage-source-inverter-(VSI) fed adjustable-speed AC drives. Its features include elimination of high-frequency current harmonics appearing in PWM VSIs and correction of the detection error caused by the lag time of time-sharing processing. Since this method allows current loop calculations to be made at a slower rate with a conventional microprocessor, it realizes a fully digital speed regulator with a minor current component loop     

Theoretical studies of GaInP-AlGaInP strained quantum-well lasersincluding spin-orbit split-off band effect

We studied the GaInP-AlGaInP strained quantum-well laser characteristics, taking into account the spin-orbit split-off bands. When the well width is kept constant at 85 Å, the threshold current of the unstrained quantum-well structure is most degraded by the effect of the spin orbit split-off subbands, due to the larger hole density of states near the band-edge. While the linear gain of the compressive-strained quantum well is slightly changed by the effect, it has the lowest threshold current with the lower threshold gain. In the tensile-strained quantum-well structure, the spin-orbit split-off bands improve the differential gain because they increase the density of states at the valence band-edge. When the lasing wavelength is fixed at 630 nm, the threshold current of the compressive-strained quantum well is the lowest as well. The tensile-strained quantum well has lower threshold current than the unstrained quantum well, and this phenomena is not observed in the analysis without the spin-orbit split-off bands. However, the reduction of threshold current of the tensile-strained quantum well is smaller than that of compressive-strained quantum well, The tensile strain is more preferable for high speed modulation because of its large differential gain, due to the mixing between the light hole and the spin-orbit split-off subbands     

Robust gain-scheduled control for vibration suppression

Limited control authority is a key issue in the field of structural control and is a major research area since most of the practical control problems are dominated by constraints on the control signal. The paper presents a simple and practical gain-scheduled controller design procedure for active vibration suppression of a three-storey flexible structure. First, system identification experiments are performed and the plants uncertainty is derived. Next, robust controller design with constraint on the control signal is presented. For a better trade-off between control performance and control constraint a gain-scheduling approach is investigated. Stability analysis of the gain-scheduled controller is analysed using a parameter-independent Lyapunov function (quadratic stability) as well as a parameter-dependent Lyapunov function (biquadratic stability). Finally, the gain-scheduled controller is tested experimentally when the flexible structure is excited with a scaled historical earthquake record (1940 El Centro record). Successful experimental results show that the proposed robust gain-scheduled control approach offers good performance in the case of control authority limitation.Nomenclature M mass matrix - C damping matrix - K stiffness matrix - q relative displacement vector to base - m_a active mass - active mass acceleration - ground (base) acceleration - K_gap transfer gain of the displacement sensor - K_acc transfer gain of the acceleration sensor - K_AMD transfer gain of the active mass damper - _id frequency range of system identification experiments - r control reference - u control signal - d external disturbance - y control output - e control error - x state vector - p(t) time-varying parameter - N_p parameter boxs dimension - V(x) Lyapunov function - V(x,p) parameter-dependent Lyapunov function - largest parameter box where quadratic stability holds - S(s),T(s) sensitivity and complementary sensitivity transfer functions - G_n(s),G(s) transfer function of nominal and real plant - K_rate rate feedback gain - P_n(s) transfer function of nominal plant modified by rate feedback - P(s) transfer function of real plant modified by rate feedback - G_red transfer function of the reduced-order plant - _m(s) multiplicative uncertainty - W_S(s),W_T(s) performance and robustness weighting functions - G_c(s) controllers transfer function - G_c1(s),G_c2(s) transfer function of robust controller for vertex 1 and vertex 2 - G_cs(p,s) transfer function of the gain-scheduled controller - u_A amplitude of the control signal - K_min,K_max minimum and maximum controller gain - K(p) scheduled controller gain - J₁,J₂,J₃,J₄,J₅ performance evaluation parameters