Optical pulse shaper with integrated slab waveguide for arbitrary waveform generation using optical gradient force

Integrated optical pulse shaper opens up possibilities for realizing the ultra high-speed and ultra wide-band linear signal processing with compact size and low power consumption. We propose a silicon monolithic integrated optical pulse shaper using optical gradient force, which is based on the eight-path finite impulse response. A cantilever structure is fabricated in one arm of the Mach–Zehnder interferometer（MZI） to act as an amplitude modulator. The phase shift feature of waveguide is analyzed with the optical pump power, and five typical waveforms are demonstrated with the manipulation of optical force. Unlike other pulse shaper schemes based on thermo–optic effect or electro–optic effect, our scheme is based on a new degree of freedom manipulation, i.e., optical force, so no microelectrodes are required on the silicon chip,which can reduce the complexity of fabrication. Besides, the chip structure is suitable for commercial silicon on an insulator（SOI） wafer, which has a top silicon layer of about 220 nm in thickness.     

A comparative first-principles study on electronic structures and mechanical properties of ternary intermetallic compounds Al8Cr4Y and Al8Cu4Y: Pressure and tension effects

An investigation into the bulk properties, elastic properties and Debye temperature under pressure, and deformation mode under tension of Al₈Cu₄Y and Al₈Cr₄Y compounds was investigated by using first principles calculations based on density functional theory. The calculated lattice constants for the ternary compounds (Al₈Cu₄Y and Al₈Cr₄Y) are in good agreement with the experimental data. It can be seen from interatomic distances that the bonding between Al1 atom and Cr, Y, and Al2 atoms in Al₈Cr₄Y are stronger than Al₈Cu₄Y. The results of cohesive energy show that Al₈Cr₄Y should be easier to be formed and much stronger chemical bonds than Al₈Cu₄Y. The bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν can be obtained by using the Voigt–Reuss–Hill averaging scheme. From the results of elastic properties, Al₈Cr₄Y has the stronger mechanical behavior than Al₈Cu₄Y. Our calculations also show that pressure has a greater effect on mechanical behavior for both compounds. The ideal tensile strength are obtained by stress-strain relationships under [001](001) uniaxial tensile deformation, which are 15.4 and 23.4 GPa for Al₈Cu₄Y and Al₈Cr₄Y, respectively. The total and partial density of states and electron charge density under uniaxial tensile deformations for Al₈Cu₄Y and Al₈Cr₄Y compounds are also calculated and discussed in this work.     

Effect of external pressure on the Kβ/Kα X-ray intensity ratios of 3d metals

The occupation numbers of the 3d transition metals are calculated as a function of pressure by means of the linear muffin-tin-orbital method. This data is used with the multiconfiguration Dirac-Fock (MCDF) X-ray intensity ratios (R) to estimate the variation of the intensity ratios of 3d metals with pressure. It is found that R decreases with pressure for the early 3d metals whereas it increases for the heavier 3d transition metals.     

非低温法的稀有气体纯化技术概述

稀有气体广泛应用于工业生产中,如离子刻蚀、检漏等。但是它们在地球上的含量比较少,属于稀有资源,因此需要对它们进行纯化以循环再利用。首先介绍了不同气体纯化的原理,然后以实际生产中的不同稀有气体使用范围为例,说明纯化装置的设计方法和需要考虑的问题。为以后气体纯化装置的设计提供借鉴。     

Effect of flame-sprayed Al–12Si coatings on the failure behaviour of pressurized fibre-reinforced composite tubes

Internal pressurization testing at room temperature was performed to evaluate the effect of flame-spraying aluminum-12silicon on the leakage behavior of fibre-reinforced composite tubes fabricated by filament winding, and covered with garnet sand. A group of specimens were completely coated with flame-sprayed metal particles and another set remained uncoated. t-tests were conducted at a significance level of α = 0.05 to analyze the effect of the coating on the leakage behavior of the specimens. Ultraviolet imaging was used to illustrate a characteristic leakage pattern of the composite tubes. Coated specimens exhibited slightly higher mean leakage and burst pressures than the uncoated specimens. The t-test results provided strong statistical evidence that the flame spraying process employed did not damage the filament wound tubes covered with garnet sand.     

Structural properties of rutherfordium: An ab-initio study

The structural and electronic properties of rutherfordium, the latest group IV B element, have been evaluated by first principles density functional theory in scalar relativistic formalism with and without spin-orbit coupling and compared with its 5d homologue Hf. It is found that Rf will crystallize in the hexagonal close packed structure as in Hf. However, under pressure, it will have different sequence of phase transitions than Hf: hcp→bcc instead of hcp→ω→bcc. An explanation is offered for this difference in terms of the competition between the band structure and the Ewald energy contributions.     

Instant Controlled Pressure Drop technology: From a new fundamental approach of instantaneous transitory thermodynamics to large industrial applications on high performance–high controlled quality unit operations

Solvent extraction processes have been largely used in various industries. They recently were improved through new physical concepts such as CO₂ Supercritical Fluid Extraction, Ultrasound assisted process, Microwave-assisted extraction, Instant Controlled Pressure Drop DIC-assisted extraction… Systematically, a pretreatment stage of grinding takes place in order to improve the exchange surface increasing the starting accessibility. Swelling of the material structure implies an increase of the porosity thus leading to higher solvent diffusivity within the solid matrix. A new concept of expanded granule powder has recently been defined using Instant Controlled Pressure Drop DIC technology. Whatever the type of solvent is (even CO₂-SFE), such a swelled structure dramatically intensifies the kinetics through a higher specific exchange surface thanks to the open pores, while improving the solution solvent–solute diffusivity within the solid. Coupled to ultrasound, the internal transfer of solute within the pore solvent can likewise be intensified by replacing molecular diffusion within the pores by an effective convection transfer. In this work, we carried out a first approach of modeling of solvent extraction kinetics of expanded granules involving higher exchange surface and greater internal diffusion process.     

Structural and electronic properties of type-I and type-VIII Ba8Ga16Sn30 clathrates under compression

The total energy and electronic structures for type-I (β phase) and type-VIII (α phase) Ba₈Ga₁₆Sn₃₀ clathrates under hydrostatic pressure have been investigated using density functional theory (DFT) calculations. It was found that the type-VIII phase is more stable than the type-I one at ambient conditions and that β→α phase transition can not occur under hydrostatic pressure. The band structures show that the type-I and type-VIII Ba₈Ga₁₆Sn₃₀ are indirect semiconductors with band gaps of 0.24 eV and 0.19 eV, respectively. The results suggested that type-I clathrate Ba₈Ga₁₆Sn₃₀ has a larger value of the thermoelectric (TE) power than that of type-VIII clathrate. We found that pressure tuning changes the k-point of conduction band minimum (CBM) in the Brillouin zone for β-phase, but it is not the case for α-phase. Furthermore, the results show that the pressure can change the interaction between guest atoms and the host lattice, and consequently results in the decrease of the band gap of β-phase and the increase of the band gap of α-phase, indicating that the pressure effect can play an important role in the magnitude of the TE power.     

Split injection: A simple introduction of subnanoliter sample volumes for chip electrophoresis

The ability to accurately inject small volumes of sample into microfluidic channels is of great importance in electrophoretic separations. While electrokinetic injection of nanoliter scale volumes is commonly utilized in microchip capillary electrophoresis (MCE), mobility and matrix bias makes quantitation difficult. Herein, we describe a new injection method based on the simple patterning of the crossing of channels that does not require sophisticated instrumentation. The sample volume injected into the separation channel is dependent on the ratio of the widths of the crossing channels. This injection method is capable of introducing, into a separation channel, multiple plugs of sample on a large scale. This injection technique is tested for zone electrophoresis in native and surface modified poly(dimethylsiloxane) (PDMS) chips.     

Hydration forces between bilayers in the presence of dissolved or surface-linked sugars

We analyse the experimental evidence of the hydration force near phospholipid bilayers when the “solvent” is a solution of carbohydrates. Two cases must be clearly distinguished: when sugar is dissolved, depletion causes a supplementary attractive force, while in the case of sugar linked to the lipid the contact pressure increases by orders of magnitude. Attractive interaction inferred between bilayers is sometimes derived from indirect evidence, i.e. scattering, attraction between layers adsorbed, shape of phase boundary limits, and without the simultaneous determination of the osmotic compressibility. Generally, water molecules in the first hydration shell of sugar compete with water molecules bound (by more than one kT in free energy) to lipid head-groups. A general result is that the decay length of any repulsive effect remains close to 0.2 nm, even in concentrated sugar solutions. A tentative general explanation of this experimental fact is given together with consequences, such as the possibility of several types of critical points appearing in bilayer stacks. Decay length as well as effective contact pressure is considered with respect to carbohydrate activity.