Über die Säuren HOOCCH(SX)CH(SX)COOH (X  CH2COOH,C6H5) und ihre Methylester

The Acids HOOCCH(SX)CH(SX)COOH (X  CH₂COOH, C₆H₅) and their Methyl Esters The acids HOOCCH(SX)CH(SX)COOH with X  CH₂COOH and C₆H₅ and their methyl esters have been prepared by addition of thiols to acetylene dicarboxylic acid as salt and methyl ester. The structures and configurations have been discussed.     

Design and evaluation of fundamental-mode and polarization-stabilized VCSELs with a subwavelength surface grating

We demonstrate 850-nm oxide-confined vertical-cavity surface-emitting lasers (VCSELs) with a locally etched subwavelength surface grating that are single-mode and polarization stable from threshold up to thermal roll-over, reaching /spl sim/4 mW of output power. The side-mode suppression ratio (SMSR) is >30 dB and the orthogonal polarization suppression ratio (OPSR) is /spl sim/20 dB. Moreover, no distortion of the far-field beam profile is observed as a result of the surface grating. Our numerical calculations show that a carefully designed VCSEL can have a high simultaneous mode and polarization selectivity without a significant increase in loss for the favored fundamental mode with polarization state perpendicular to the grating lines. This indicates characteristics such as threshold current and resonance frequency will not be notably degraded. The calculations also show a low sensitivity to variations in grating etch depth and duty cycle, which relaxes fabrication tolerances. In our experimental parametric study, where the oxide aperture diameter, surface grating diameter, and grating duty cycle were varied, the combined mode and polarization selection was investigated. For an optimum combination of oxide aperture and surface grating diameters of 4.5 and 2.5 /spl mu/m, respectively, the device is found to be single-mode and polarization stable for a broad range of grating duty cycles, from 55% to 75%, with only a small variation in other laser performances, which is in line with theory.     

Single fundamental-mode output power exceeding 6 mW from VCSELs with a shallow surface relief

A single fundamental-mode output power of 6.5 mW was achieved from an 850-nm vertical-cavity surface-emitting laser (VCSEL) with a shallow surface relief, the highest single-mode power ever reported using this technique. The VCSELs were fabricated from epitaxial material grown to yield an antiphase reflection from the topmost layer. A circular surface relief, acting as a mode discriminator, was etched in the center to reduce the mirror loss for the fundamental mode. This "inverted" surface-relief technique offers relaxed etch depth control and, therefore, improves reproducibility and yield.     

综放工作面垮落带高度测定方法研究

为解决高瓦斯矿井综放工作面垮落带高度难以精确测定,造成工作面两端头难维护、预抽钻孔终孔位置难以确定等问题,依据工作面采动后顶板岩层破断垮落、弯曲下沉对采空区煤层底板施加压力的情况,结合采空区上覆各岩层的厚度和密度,提出了垮落带发育高度的测定方法。以大平矿N1S2综放工作面为例,现场测试结果表明：利用该测定方法测得的垮落带高度为88.65 m,钻孔冲洗液法测得的垮落带高度为88.20 m,二者绝对误差仅为0.45 m。     

Effect of geometry and green density on the anisotropic sintering shrinkage of axisymmetric iron parts

Sintering shrinkage of prior cold compacted iron rings with different geometry (height to wall thickness ratio) and green density in the 6.5–7.3?g/cm³ range was investigated. It displays a minimum at an intermediate green density. Axial, tangential and radial shrinkages are different, due to the gradients of green density along the axial and the radial directions. Therefore, the effect of height on shrinkage and its anisotropy is the result of their effect on the stress distribution in the green parts during cold compaction, and the resulting green density and deformation experienced by the powder. Anisotropy decreases on increasing shrinkage.     

Bark as feedstock for dual fluidized bed gasifiers—Operability,efficiency, and economics

The demand for biofuels and biochemicals is expected to increase in the future, which will in turn increase the demand for biomass feedstock. Large gasification plants fueled with biomass feedstock are likely to be a key enabling technology in a resource‐efficient, bio‐based economy. Furthermore, the costs for producing biofuels and biochemicals in such plants could potentially be decreased by utilizing inexpensive low‐grade residual biomass as feedstock. This study investigates the usage of shredded tree bark as a feedstock for the production of biomethane in the GoBiGas demonstration plant in Gothenburg, Sweden, based on a 32 MW_th industrial dual fluidized bed gasification unit. The plant was operated with bark feedstock for 12 000 hours during the period 2014 to 2018. Data from the measurement campaign were processed using a stochastic approach to establish the plant's mass and energy balances, which were then compared with operation of the plant with wood pellets. For this comparison, an extrapolation algorithm was developed to predict plant performance using bark dried to the same moisture content as wood pellets, ie, 8%_w.b. Plant operation with bark feedstock was evaluated for operability, efficiency, and feedstock‐related cost. The gas quality achieved during the test period was similar to that obtained for operation with wood pellets. Furthermore, no significant ash sintering or agglomeration problems were observed more than 750 hours of operation. The calculated biomass‐to‐biomethane efficiency is 43% to 47% (lower heating value basis) for operation with wet bark. However, the predicted biomass‐to‐biomethane efficiency can be increased to 55%–65% for operation with bark feedstock dried to 8% moisture content, with corresponding feedstock costs in the range of 24.2 to 32.7 EUR/MWh; ie, a cost reduction of about 40% compared with wood pellets.     

Evaluation of <Emphasis Type="Italic">flaA</Emphasis> Short Variable Region Sequencing,Multilocus Sequence Typing,and Fourier Transform Infrared Spectroscopy for Discrimination between <Emphasis Type="Italic">Campylobacter jejuni</Emphasis> Strains

Discriminatory and robust typing methods are needed to improve the understanding of the dynamics of food-borne Campylobacter infections and epidemiology in primary animal production. To evaluate the strain discriminatory potential of typing methods, flaA short variable region (SVR) sequencing and Fourier transform infrared (FTIR) spectroscopy were applied on a collection of 102 epidemiologically related and unrelated Campylobacter jejuni strains. Previous application of FTIR spectroscopy for subtyping of Campylobacter has been limited. A subset of isolates, initially discriminated by flaA SVR sequencing, were further subjected to multilocus sequence typing (MLST). It was found that flaA SVR sequencing had a slightly higher discriminatory power than FTIR spectroscopy, based on the Simpson diversity index. The clustering of strains indicated that FTIR spectroscopy is indeed a suitable method for discrimination of Campylobacter. The isolates were assigned to six clusters based on flaA SVR sequences and nine clusters based on the FTIR spectroscopy profiles. Furthermore, the cluster analysis of flaA SVR sequences, MLST, and FTIR spectroscopy profiles showed a high degree of congruence, assigning the isolates to similar cluster structures. In conclusion, FTIR spectroscopy can be applied for subtyping of Campylobacter, and the high discriminatory potential of both flaA SVR sequencing and FTIR spectroscopy render them suitable screening methods for large numbers of strains.     

Polylactide latex/nanofibrillated cellulose bionanocomposites of high nanofibrillated cellulose content and nanopaper network structure prepared by a papermaking route

Previous attempts to use polylactide (PLA) latex particles and nanofibrillated cellulose (NFC) in papermaking processing have been limited to low NFC content. In the present study, a bionanocomposite material was successfully produced using a PLA latex and NFC. The components were mixed using a wet mixing method and bionanocomposite films were made by filtration followed by hot pressing. In composite materials, the dispersion of the reinforcing component in the matrix is critical for the material properties. Biopolymers such as PLA are non-polar and soluble only in organic solvents; NFC is, however, highly hydrophilic. By utilizing latex, i.e., an aqueous dispersion of biopolymer micro-particles, wet mixing is possible and the problem of aggregation of the hydrophilic nanocellulose in organic solvent is avoided. The properties of the resulting NFC/PLA latex bionanocomposite films were analyzed. Thorough blending resulted in good dispersion of the reinforcing component within the matrix. Adding increasing amounts of NFC improved the Young's modulus, tensile strength, and strain at break of the bionanocomposite material. The increase in the tensile properties was linear with increasing NFC content as a result of the good dispersion. The NFC also improved the thermal stability of the bionanocomposite material. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Integral Equation Method for Evaluation of Eddy-Current Impedance of a Rectangular,Near Surface Crack Inside a Cylindrical Hole

An integral equation method for solving the eddy-current nondestructive evaluation problem of a flat, rectangular, near surface crack inside of a cylindrical hole in a conducting material is presented. The method involves expanding the Green’s tensor, the incoming field, and the jump in electric potential over the crack in suitable basis functions. Here, plane waves, cylindrical waves, and basis functions related to the Chebyshev polynomials, are used. The way of discretization in this method leads to a formulation where the scattering is defined by a scattering matrix, independent of the incoming field. This presents an advantage, when conducting numerical simulations, since the scattering matrix does not have to be recalculated for every probe position. The numerical calculations are straightforward to perform and model predictions are compared with finite element results.