品种和加工方式对双低菜粕有效能和氨基酸有效性的影响_注

用精确饲喂技术评价了 3个品种的中国双低油菜和 1个加拿大卡诺拉的脱脂种籽和商品饼粕的能量和氨基酸的有效性。结果表明 ,4个脱脂种籽的氮校正真代谢能和氨基酸真消化率没有差异 (P >0 .0 5 ) ;而 4个商品饼粕的脱脂样品的氮校正真代谢能和氨基酸真消化率有极显著或显著差异。研究结果证实 ,不适当的加工方式不仅降低了氨基酸的有效性 ,而且影响家禽对能量的利用效率。     

Thermal conductivity of 4He vapor as a function of density

Measurements of the dependence of the thermal conductivity (T, ) of ⁴He vapor on the density are presented at 3.3 and 4.5 K. The initial dependence upon near = 0 agrees with the prediction of the modified Enskog theory; but at higher densities there are departures from the prediction. The excess thermal conductivity (T, ) – (T, 0) is independent of T within experimental error.     

CO2 Capture for Fossil Fuel‐Fired Power Plants

An overview of technologies for fossil fuel‐fired power plants with drastically reduced CO₂ emissions is given. Post‐combustion capture, pre‐combustion capture, and oxyfuel technology are introduced and compared. Current research results indicate that post‐combustion capture may lead to slightly higher losses in power plant efficiency than the two other technologies. However, retrofitting of existing plants with oxyfuel technology is complex and costly, and retrofitting of pre‐combustion capture is not possible. On the other hand, post‐combustion capture can be retrofitted to existing power plants with only minimal effort. Based on the mature technology of reactive absorption, it can be implemented on a large scale in the near future. Therefore, post‐combustion capture using reactive absorption is discussed here in some detail.     

Ball screw drives with enhanced bandwidth by modification of the axial bearing

The bandwidth of the ball-screw drive is limited by the first natural frequency of the mechanical structure. As opposed to conventional drives where the axial bearing stiffness is kept high to obtain higher natural frequencies, this paper proposes to use lower axial bearing stiffness accompanied by a strong damper in parallel with the ball-screw structure. The proposed method, which is experimentally demonstrated, increases the bandwidth of the drive considerably provided that a cost effective and practical damper is available.     

On the attenuation and dispersion of first sound near the superfluid transition in He4

In this paper available measurements of the attenuation and dispersion of first sound near the superfluid transition in He⁴ are re-examined. Particular attention is given to the effect of the gravitational inhomogeneity upon the measurements, and the thermodynamic velocity is used to obtain the dispersion contribution from measured velocities at nonzero frequencies. The re-interpreted results are discussed in terms of current theories. Although there is partial agreement between experiment and theory, a number of aspects of the problem requires further theoretical and experimental investigation.     

An Iterative Model for the Steady-State Current Distribution in Oxide-Confined VCSELs

This paper presents an iterative model for the analysis of the current distribution in vertical-cavity surface-emitting lasers (VCSELs) using a SPICE-like approach. The model includes a degeneracy correction for operation at and above threshold. The effect of the resistance due to the p-distributed Bragg reflector (p-DBR) mirror layers and the oxide layer on performance is investigated. Higher sheet resistance under the oxide layer reduces the threshold current, but reduces the current range over which single transverse mode operation occurs. The voltage drop across the p-DBR region dominates spatial hole burning, which is moderated by lateral drift and diffusion. This simple iterative model is applied to commercially available oxide-confined VCSELs.     

Emissions of perfluorinated alkylated substances (PFAS) from point sources--identification of relevant branches

Effluents of wastewater treatment plants are relevant point sources for the emission of hazardous xenobiotic substances to the aquatic environment. One group of substances, which recently entered scientific and political discussions, is the group of the perfluorinated alkylated substances (PFAS). The most studied compounds from this group are perfluorooctanoic acid (PFOA) and perfluorooctane sulphonate (PFOS), which are the most important degradation products of PFAS. These two substances are known to be persistent, bioaccumulative and toxic (PBT). In the present study, eleven PFAS were investigated in effluents of municipal wastewater treatment plants (WWTP) and in industrial wastewaters. PFOS and PFOA proved to be the dominant compounds in all sampled wastewaters. Concentrations of up to 340 ng/L of PFOS and up to 220 ng/L of PFOA were observed. Besides these two compounds, perfluorohexanoic acid (PFHxA) was also present in nearly all effluents and maximum concentrations of up to 280 ng/L were measured. Only N-ethylperfluorooctane sulphonamide (N-EtPFOSA) and its degradation/metabolisation product perfluorooctane sulphonamide (PFOSA) were either detected below the limit of quantification or were not even detected at all. Beside the effluents of the municipal WWTPs, nine industrial wastewaters from six different industrial branches were also investigated. Significantly, the highest emissions or PFOS were observed from metal industry whereas paper industry showed the highest PFOA emission. Several PFAS, especially perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluorododecanoic acid (PFDoA) and PFOS are predominantly emitted from industrial sources, with concentrations being a factor of 10 higher than those observed in the municipal WWTP effluents. Perfluorodecane sulphonate (PFDS), N-Et-PFOSA and PFOSA were not detected in any of the sampled industrial point sources.     

The effect of chlorine and oxygen concentrations on the removal of mercury at an FGD-batch reactor

A series of laboratory scale experiments were conducted in an FGD-batch reactor. A synthetic flue gas was produced and directed through a CaCO₃ suspension contained in a glass reactor vessel. The suspension temperature was set at 54 °C through a water bath. In order to observe the distribution of mercury species in the system, solid, liquid and gaseous samples were taken and analysed. For gaseous mercury determination, continuous measurements were carried out, up and downstream the reactor. Furthermore, the concentration of chlorine in the scrubber solution of the system was varied from 0 to 62 g/l under different oxidative conditions.In a first approach, a concentration drop of elemental mercury coming out of the system was observed. The latter occurs only when high concentrations of Cl⁻ are present, combined with a high O₂ availability in the scrubber. It was also observed that mercury species distribution in the different phases varies, depending on the available chemical form of chlorine and oxygen concentration.     

Hybridization effect of cellulose paper and postcuring conditions on the mechanical properties of flax fiber reinforced epoxy biocomposite

An ever-increasing rise in demand for sustainable materials has received significant attention in developing biocomposites for structural applications. In this regard, natural fibers replacing synthetic fibers as reinforcement in epoxy composite could be a significant gain toward sustainability, especially in automobile and structural applications. Herein, flax fiber/cellulose paper–reinforced epoxy biocomposite (FREC-X) was fabricated via a vacuum infusion process. The influence of postcuring conditions (time and temperature) and cellulose paper density on the mechanical properties of FREC-X was studied. The tensile strength and modulus of FREC-X increased by 37% and 64%, respectively, upon the integration of paper. Postcuring FREC-X further augmented the tensile and flexural properties of the composite, which could be attributed to the increase in cross-linking of the epoxy and yields a strong polymer network. Fractography analysis confirmed that the composites integrated with paper showed fewer defects with improved interfacial adhesion. In addition, the water absorption and thickness swelling results revealed that the presence of cellulose paper marginally increased the water uptake and thickness swelling of FREC-X. Furthermore, there was no significant change in the tensile and flexural properties of FREC-X observed even after immersing in water for >200 h. Such properties of FREC-X seen as a fascinating alternative to synthetic fibers and petroleum-based epoxy and are promising material for sustainable development.