InGaAsP multiple quantum well edge-emitting light-emitting diode showing low coherence characteristics using selective-area metalorganic vapor phase epitaxy

Low coherence multiple-quantum well edge-emitting light-emitting diodes were obtained using selective-area metalorganic vapor-phase epitaxial growth, which utilized growth rate enhancement on an open stripe region between mask stripes. An optical absorption region, which was controlled by selective-area growth, was introduced to suppress optical feedback. At a driving current of 100 mA and an ambient temperature of 25°C, a power of 55 μW was coupled into a single-mode fiber, and a broad spectrum without spectral ripple was observed. Low coherence characteristics and very small temperature dependence were obtained in the temperature range from -40°C to 85°C. The modulation bandwidth was 210 MHz at a bias current of 100 mA.     

Synthesis,structure and biological activity studies of 2‐[(1H‐1,2,4‐triazol‐1‐yl)methyl]‐1‐aryl)‐3‐ferrocenyl prop‐2‐en‐1‐one derivatives

Fifteen new ferrocene derivatives containing 1H‐1,2,4‐triazole moiety were synthesized in various yields by the condensation of ferrocenecarboxaldehyde with 1‐aryl‐3‐(1H‐1,2,4‐triazo‐1‐yl)‐propen‐1‐ones in toluene. Their structures have been confirmed by ¹H NMR, IR, MS and elemental analysis. In addition, the crystal structure of 4l was determined. The antifungal and plant growth regulatory activities of the title compounds are discussed. Copyright © 2005 John Wiley & Sons, Ltd.     

ON SOLUTIONS TO SEMILINEAR INTEGRODIFFERENTIAL EQUATIONS WITH NONLOCAL CONDITIONS

In this paper, using the theory of resolvent operators, Banach,s contraction prin-ciple and Schauder,s fixed point theorem, we study the existence of integral solutions to semilinear integrodifferential equations under nonlocal conditions in Banach space. An example is provided to illustrate the results obtained.     

Inverse nodal and inverse spectral problems for discontinuous boundary value problems

Inverse nodal and inverse spectral problems are studied for second-order differential operators on a finite interval with discontinuity conditions inside the interval. Uniqueness theorems are proved, and a constructive procedure for the solution is provided.     

Synthesis, growth and characterization of a new laser upconversion crystal Ba2ErCl7

A modified method to synthesize the new laser upconversion material Ba₂ErCl₇ using Er₂O₃, BaCl₂ 2H₂O and NH₄CI is reported for the first time in this paper. Single crystals up to 5–8mm in diameter and 10–20 mm in length have been grown by Czochralski method. The transmittance spectra of Ba₂ErCl₇ single crystal has first been measured by using an HITACHI U-3500 spectrophotometer. There are three intense absorption peaks ⁴I_9/2⁴I_11/2 and ⁴I_13/2 in the infrared range which can be excited by 803nm, 980nm and 1.5μm laser diodes (LDs), respectively. The cut-off wavelength of the crystal is 230mn. Intense green luminescence can be observed when the crystal is pumped by a ED at 803nm. The formation of the defects is also discussed.     

Poly(arylene sulfide)s by nucleophilic aromatic substitution polymerization of 2,7‐difluorothianthrene

Poly(thianthrene phenylene sulfide) and poly(thianthrene sulfide) have been prepared by nucleophilic aromatic substitution polymerization of the activated monomer 2,7‐difluorothianthrene with bis thiophenoxide and sulfide nucleophiles, respectively. The resulting polymers are thermally stable, amorphous materials that have been characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), gel permeation chromatography (GPC), matrix‐assisted laser desorption/ionization‐time‐of‐flight (MALDI‐TOF) mass spectrometry, UV‐Vis spectroscopy, refractometry, and intrinsic viscosity (IV) measurements. The polymers produced exhibit 5% weight loss values approaching 500 °C in inert and air atmospheres and glass transition temperatures that range from 149 to 210 °C. Poly(thianthrene phenylene sulfide) with a number average molecular weight of 22,100 g/mol has been synthesized with an IV in DMPU of 0.62 dL/g at 30 °C. Creasable films of this polymer have been prepared by solvent casting and melt pressing at 250 °C. Films of poly(thianthrene phenylene sulfide) exhibit transparencies greater than 50% at wavelengths exceeding 400 nm and a high refractive index value of 1.692 at a wavelength of 633 nm, making the polymer interesting for optical applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2453–2461, 2009     

Simulated Annealing Algorithms for Continuous Global Optimization: Convergence Conditions

In this paper, simulated annealing algorithms for continuous global optimization are considered. After a review of recent convergence results from the literature, a class of algorithms is presented for which strong convergence results can be proved without introducing assumptions which are too restrictive. The main idea of the paper is that of relating both the temperature value and the support dimension of the next candidate point, so that they are small at points with function value close to the current record and bounded away from zero otherwise.     

生长条件对KDP 晶体激光损伤阈值的影响

 研究了各种生长条件对晶体激光损伤阈值的影响, 发现提纯原料用的EDTA对晶体的光损伤阈值没有显著的影响, 溶液陈化能够降低晶体的散射强度,从而使光损伤阈值提高。多磷酸盐阻碍晶体锥面生长, 影响晶体的生长习性, 并降低晶体的激光损伤阈值。     

Some remarks concerning stability for nonstationary quantum systems

The problem of characterizing stability and instability for general nonstationary quantum systems is investigated. Some characterizations are reported and some elementary properties of a topological characterization are established. Then, it is proven, by considering a simple example, that there are nonperiodic driven systems whose orbits are neither precompact nor leave on average any compact set. Autocorrelation measures are computed and the possible roles of the generalizes quasienergy operator and energy growth are briefly discussed.     

A comparative study of inflow conditions for two‐ and three‐dimensional spatially developing mixing layers using large eddy simulation

A series of spatially developing mixing layers are simulated using the large eddy simulation (LES) technique. A hyperbolic tangent function and data derived from boundary layer simulations are used to generate the inflow condition, and their effects on the flow are compared. The simulations are performed in both two and three dimensions. In two‐dimensional simulations, both types of inflow conditions produce a layer that grows through successive pairings of Kelvin–Helmholtz (K–H) vortices, but the composition ratio is lower for the hyperbolic tangent inflow simulations. The two‐dimensional simulations do not undergo a transition to turbulence. The three‐dimensional simulations produce a transition to turbulence, and coherent structures are found in the post‐transition region of the flow. The composition ratio of the three‐dimensional layers is reduced in comparison to the counterpart two‐dimensional runs. The mechanisms of growth are investigated in each type of simulation, and amalgamative pairing interactions are found in the pre‐transition region of the three‐dimensional simulations, and throughout the entire computational domain of those carried out in two‐dimensions. The structures beyond the post‐transition region of the three‐dimensional simulations appear to behave in a much different manner to their pre‐transition cousins, with no pairing‐type interactions observed in the turbulent flow. In order to accurately simulate spatially developing mixing layers, it is postulated that the inflow conditions must closely correspond to the conditions present in the reference experiment. Copyright © 2007 John Wiley & Sons, Ltd.