Real-Time Amplitude and Phase Imaging of Optically Opaque Objects by Combining Full-Field Off-Axis Terahertz Digital Holography with Angular Spectrum Reconstruction

Terahertz digital holography (THz-DH) has the potential to be used for non-destructive inspection of visibly opaque soft materials due to its good immunity to optical scattering and absorption. Although previous research on full-field off-axis THz-DH has usually been performed using Fresnel diffraction reconstruction, its minimum reconstruction distance occasionally prevents a sample from being placed near a THz imager to increase the signal-to-noise ratio in the hologram. In this article, we apply the angular spectrum method (ASM) for wavefront reconstruction in full-filed off-axis THz-DH because ASM is more accurate at short reconstruction distances. We demonstrate real-time phase imaging of a visibly opaque plastic sample with a phase resolution power of λ/49 at a frame rate of 3.5 Hz in addition to real-time amplitude imaging. We also perform digital focusing of the amplitude image for the same object with a depth selectivity of 447 μm. Furthermore, 3D imaging of visibly opaque silicon objects was achieved with a depth precision of 1.7 μm. The demonstrated results indicate the high potential of the proposed method for in-line or in-process non-destructive inspection of soft materials.     

Photobiological hydrogen production

The principles and recent progress in the research and development of photobiological hydrogen production are reviewed. Cyanobacteria produce hydrogen gas using nitrogenase and/or hydrogenase. Hydrogen production mediated by native hydrogenases in cyanobacteria occurs under in the dark under anaerobic conditions by degradation of intracellular glycogen. In vitro and in vivo coupling of the cyanobacterial photosynthetic system with a clostridial hydrogenase via cyanobacterial ferredoxin was demonstrated in the presence of light. Genetic transformation of Synechococcus PCC7942 with the hydrogenase gene from Clostridium pasteurianum was successful; the active enzyme was expressed in PCC7942. The strong hydrogen producers among photosynthetic bacteria were isolated and characterized. Coculture of Rhodobacter and Clostriudium was applied for hydrogen production from glucose. A mutant strain of Rhodobacter sphaeroides RV whose light-harvesting proteins were altered was obtained by UV irradiation. Hydrogen productivity by the mutant was improved when irradiated with monochromatic light of some wavelengths. The development of photobioreactors for hydrogen production is also reviewed.     

LSI implementation of a low-power 4×4-bit array two-phase clocked adiabatic static CMOS logic multiplier

As the density and operating speed of complementary metal oxide semiconductor (CMOS) circuits increases, dynamic power dissipation has become a critical concern in the design and development—of personal information systems and large computers. The reduction of supply voltage, node capacitance, and switching activity are common approaches used in conventional CMOS. In adiabatic switching circuits, the current flow through transistors can be significantly reduced by ensuring uniform charge transfer over the entire available time. This paper presents the simulation of this current in two-phase clocked adiabatic static CMOS logic (2PASCL) and conventional CMOS. From the SPICE simulations, at transition frequencies from 1 to 12 MHz, a 4×4-bit array 2PASCL multiplier shows a maximum reduction in power dissipation of 77% relative to that of a static CMOS. The measurement results of a 4×4-bit array 2PASCL multiplier demonstrate a 57% reduction compared to a 4×4-bit array two-phase clocked adiabatic dynamic CMOS logic (2PADCL). These results indicate that 2PASCL technology can be advantageous when applied to low-power digital devices operated at low frequencies, such as radio-frequency identification (RFID) tags, smart cards, and sensors.     

Transport-Coefficient Dependence of Current-Induced Cooling Effect in a Two-Dimensional Electron Gas

The dependence of the current-induced cooling effect on the electron mobility??? _e is explored for a two-dimensional electron gas (2DEG) subjected to a perpendicular magnetic field. We calculate the distributions of the electrochemical potentials and the temperatures under a magnetic field, fully taking account of thermoelectric and thermomagnetic phenomena. Whereas the electrochemical potential and the electric current remain qualitatively unchanged, the temperature distribution exhibits drastic mobility dependence. The lower-mobility system has cold and hot areas at opposite corners, which results from the heat current brought about by the Ettingshausen effect in the vicinity of the adiabatic boundaries. The cooling effect is intensified by an increase in??? _e. Intriguingly, the cold and hot areas change places with each other as the mobility??? _e is further increased. This is because the heating current on the adiabatic edges due to the Righi?CLeduc effect exceeds that due to the Ettingshausen effect in the opposite direction.     

A Hybrid Decoupled Power Flow Method for Balanced Power Distribution Systems

This paper proposes a hybrid decoupled power flow method for balanced power distribution systems with distributed generation sources.The method formulates the power flow equations in active power and reactive power decoupled form with polar coordinates.Second-order terms are included in the active power mismatch iteration,and constant Jacobian and Hessian matrices are used.A hybrid direct and indirect solution technique is used to achieve efficiency and robustness of the algorithm.Active power correction is solved by means of a sparse lower triangular and upper triangular(LU) decomposition algorithm with partial pivoting,and the reactive power correction is solved by means of restarted generalized minimal residual algorithm with an incomplete LU pre-conditioner.Typical distribution generation models and distribution load models are included.The impact of zero-impedance branches is explicitly modeled through reconfiguring of the adjacent branches with impedances.Numerical examples on a sample distribution system with widespread photovoltaic installations are given to demonstrate the effectiveness of the proposed method.     

Fabrication of carbon nanofibers using only ion beam irradiation to glassy carbon

Carbon nanofibers (CNFs) and carbon nanotubes (CNTs) are new carbon-based materials. However, the production of CNFs and CNTs is very difficult due to the complicated processes and high temperature involved. Therefore, a method of fabrication is required that enables high throughput at a low cost.Our previous study reported that oxygen ion beam energy of 500 eV applied to glassy carbon (GC) forms the finest pitch conical anti-reflection (AR) structures, and that an irradiation time of more than 24 min fabricates conical AR structures with heights of more than 250 nm. After the fabrication of the AR structures, irradiation by an argon ion (Ar⁺ beam changes the surface morphology, and oblique angle irradiation can form CNFs. Thus, we carried out oblique Ar⁺ beam irradiation on conical carbon protrusions on GC fabricated by oxygen ion beam irradiation. As a result, CNFs have been formed using oxygen and argon ion beam irradiation at room temperature. In addition, multi-wall CNT can be obtained by two-step ion beam irradiation.     

A highly integrated 40-MIPS (peak) 64-b RISC microprocessor

A 1-million transistor 64-b microprocessor has been fabricated using 0.8-μm double-metal CMOS technology. A 40-MIPS (million instructions per second) and 20-MFLOPS (million floating-point operations per second) peak performance at 40 MHz is realized by a self-clocked register file and two translation lookaside buffers (TLBs) with word-line transition detection circuits. The processor contains an integer unit based on the SPARC (scalable processor architecture) RISC (reduced instruction set computer) architecture, a floating-point unit (FPU) which executes IEEE-754 single- and double-precision floating-point operations a 6-KB three-way set-associative physical instruction cache, a 2-KB two-way set-associative physical data cache, a memory management unit that has two TLBs, and a bus control unit with an ECC (error-correcting code) circuit     

Ge quantum dots light-emitting devices

Si photonics becomes one of the research focuses in the field of photonics.Si-based light-emitting devices are one of the most important devices in this field.In this paper,we review the Si-based light...     

Numerical simulation of oscillatory flow in melt during InSb single crystal growth by RF heating Czochralski method

Oscillatory flow present in the melt during InSb single crystal growth using an RF-heating Czochralski method has been numerically investigated by means of the finite difference method using the HSMAC algorithm. The thermal boundary conditions required for the numerical simulation model were obtained experimentally by measuring the temperature profile along the crucible of a Czochralski system by means of thermocouples mounted in the crucible. Results of numerical simulations showed that the use of a third-order upwind discretization scheme was necessary to catch the oscillatory behaviour of the fluid flow in the melt. It was shown that this oscillatory behaviour strongly depends on the crystal rotation rate. Indeed, the oscillation period increases when the crystal rotation rate is above a critical rotation rate. In order to avoid such oscillations, crystal rotation rates lower than this critical value of crystal rotation rate must be selected for the growth of high quality crystals free of striations. © 1998 John Wiley & Sons, Ltd.     

Oxidation of Fe (II) in sulfuric acid solutions with dissolved molecular oxygen

The oxidation of Fe(II) with dissolved molecular oxygen was studied in sulfuric acid solutions containing 0.2 mol . dm^-3 FeSO₄ at temperatures ranging from 343 to 363 K. In solutions of sulfuric acid above 0.4 mol . dm^-3, the oxidation of Fe (II) was found to proceed through two parallel paths. In one path the reaction rate was proportional to both [Fe²⁺]² and po₂, exhibiting an activation energy of 51.6 . kJ mol^-1. In another path the reaction rate was proportional to [Fe²⁺]², [SO_4-], and po₂ with an activation energy of 144.6 kJ . mol^-1. A reaction mechanism in which the SO_4- ions play an important role was proposed for the oxidation of Fe(II). In dilute solutions of sulfuric acid below 0.4 mol . dm^-3, the rate of the oxidation reaction was found to be proportional to both [Fe(II)]² and Po₂, and was also affected by [H⁺] and [SO_2- ⁴]. The decrease in [H⁺] resulted in the increase of reaction rate. The discussion was further extended to the effect of Fe (III) on the oxidation reaction of Fe (II).