引燃柴油量及喷射间隔对直喷天然气发动机排放的影响

为优化直喷天然气发动机的喷射策略,在一台六缸电控直喷天然气发动机上,用试验方法研究了引燃柴油量及柴油摘/天然气喷射间隔对发动机 HC、CO和 NO_x排放的影响。试验结果表明:喷射间隔一定时, HC排放随引燃柴油喷射量的增加而降低；在引燃柴油喷射量为 4.0 mg时, HC排放随喷射间隔的增加而增加；引燃柴油喷射量在 6.0～11.5 mg范围内, HC排放在喷射间隔从 0.5 ms变化到 1.1 ms时,变化较小；喷射间隔增加到 1.4 ms时, HC排放升高趋势明显。 CO排放随引燃柴油喷射量的变化规律为先降低后升高；在不同的柴油喷射量下增加喷射间隔, CO排放均降低。 NO_x排放随引燃柴油喷射量的增加先降低后升高；在喷射间隔为 0.5 ms时, NO_x排放相对较小,在喷射间隔为 1.4 ms时, NO_x排放最高。增加引燃柴油喷射量有利于 HC的减排,对 CO排放的影响较小,但会导致 NO_x排放的恶化；增加喷射间隔会促使 HC和 NO_x排放的升高,但 CO排放有所降低。     

Development and performance test of a miniature movable mixed-refrigerant liquid nitrogen generator

In order to cover long-term but small quantity liquid nitrogen requirements of laboratory or field users, a miniature movable mixed-refrigerant liquid nitrogen generator (MRLN) was developed and tested here, based on a precooled mixed-refrigerant J-T (MRJT) refrigerator. With the full air-cooled, skid-mounted structure, this MRLN was built utilizing off-the-shelf refrigeration components like commercial single-stage oil-lubricated compressors to reduce construction cost greatly. Bottled pure N₂, pressure swing adsorption (PSA) unit and mini cryogenic rectification column could be employed to supply N₂ in different operation modes respectively. In pure N₂ mode, N₂ was directly liquefied by the MRJT refrigerator. With feed N₂ at 0.8 MPa, the specific power consumption (SPC) was 1.79 kWh L⁻¹, and figure of merit (FOM) was 6.27%. The estimated SPC in PSA mode was 2.68 kWh L⁻¹. For column mode, the SPC was 4.59 kWh L⁻¹, with FOM of 3.38%. A closed N₂ cycle could convey cooling capacity between flammable refrigerant and air. This MRLN could be a convenient and low-costing choice for some liquid nitrogen users.     

超滤膜对微污染原水处理的研究进展

文章介绍了微滤膜、超滤膜、反渗透膜、纳滤膜技术的主要特点,着重介绍了超滤膜材料、膜组件的研究现状,论述了近年来超滤膜新技术及其与预处理联用在自来水净化中的研究进展,展望了超滤新技术在我国自来水处理方面的应用前景和发展方向。     

Optimum Cut of Separating Element as a Function of Total Separation Factor

Calculation of one of the SIMBATH experiments was performed using the SIMMER-II code. The experiments were intended to simulate the fuel pin disintegration, the molten materials relocation and following materials redistribution that could occur during core disruptive accidents assumed in fast breeder reactors. The calculation by SIMMER-II showed that the incorporated step-wise fuel pin disintegration model and the modified particle jamming model were capable of reproducing the course of materials relocation within the identified ranges of the parameters which governed the blockages formation, i.e. the characteristic radius of solid particles jamming and/or sieving out in the flow and the effective particle viscosity. In particular the final materials redistribution calculated by SIMMER-II very well reproduced the experiment. This fact made it possible to interpret theoretically the mechanisms of flow blockages formation and related materials redistribution.     

Effect of annealing on the structure and magnetic properties of CoFe2O4:SiO2 nanocomposites

The decomposition of succinate type precursors obtained by a modified sol-gel method using cobalt and iron nitrates, 1,4-butanediol and tetraethylorthosilicate, followed by the formation of single phase cobalt ferrite embedded in the silica matrix by annealing at 400–1100 °C was studied. The thermal analysis indicated the formation temperature of succinate type precursors, while the Fourier transform infrared spectroscopy (FT-IR) data confirmed the formation of the precursors in the pores of silica matrix. The formation of CoFe₂O₄ was investigated by X-ray diffraction and FT-IR, the size and shape of the nanoparticles by transmission electron microscopy, while the resulted microstructures by scanning electron microscopy. The crystallinity and crystallites size increased with the annealing temperature. The hysteresis loops revealed a direct relationship between annealing temperature and saturation magnetization in constant coercive field. The particle size of ferrite powders is critically dependent on the annealing temperature.     

Enhanced microwave-absorbing properties of FeCo magnetic film-functionalized silicon carbide fibers fabricated by a radio frequency magnetron method

Silicon carbide (SiC) fibers have potential application in microwave absorption materials in recent years. In this study, we provide a new method for improving the microwave-absorbing properties of SiC fibers. Magnetic FeCo films were fabricated on SiC fibers at low temperature and high vacuum by a radio frequency magnetron sputtering method. The properties of FeCo film/SiC fiber (FeCo/SiC_f) composites were investigated. When compared with SiC fiber, the FeCo/SiC_f composites exhibit excellent microwave-absorbing properties in the microwave range, with enhancements in the optimal reflectivity loss from −5.03 to −25.51 dB. This excellent performance may be because of the magnetic loss due to ferromagnetic resonance and interfacial polarization, thus inducing dielectric relaxation. In addition, the magnetic properties of FeCo/SiC_f composites are significantly improved: the value of saturation magnetization reaches up to 41.45 emu/g and the coercivity is 116.27 Oe. In addition, the strength of SiC fiber remains at 99.17% after the fabrication process. The method provided in this study for enhancing the microwave-absorbing properties of FeCo/SiC_f composites will pave a new way for the development of SiC microwave-absorbing materials.     

Control of a magnetic levitation system with communication imperfections: A model-based coupling approach

This work presents a control strategy to control a magnetic levitation system under the influence of coupling imperfections (disturbances). To overcome problems arising whenever the interconnections between plant and controller have a non-negligible influence on the control-loop behavior a so-called model-based coupling approach is used. The main idea of this coupling approach is to use prediction schemes based on recursively identified plant and controller models which compensate for performance degradation due to coupling imperfections. Coupling failures such as time-delays, data-losses and noise drastically influence the control-loop performance. Especially when systems in form of real hardware (real-time systems) are present such disturbances have to be handled adequately. To demonstrate the effectiveness of the model-based coupling approach, a control-loop of a magnetic levitation system is analyzed in simulation as well as in real world laboratory setup (HiL simulation). Furthermore a first insight into the stability analysis of closed-loop systems including the model-based coupling technique is performed for a simplified configuration.     

Structural,morphological, optical,and magnetic properties of Ni-doped CuO nanostructures prepared by a rapid microwave combustion method

In the present paper, we report a facile and rapid microwave-assisted combustion synthesis method for the preparation of pure and Ni-doped CuO nanostructures with different weight ratios (0.5, 1.0, 1.5, and 2.0 at wt% of Ni). The structure and morphology of the pure and Ni-doped CuO samples were investigated by X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), energy dispersive x-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). XRD patterns refined by the Rietveld method indicated the formation of single-phase monoclinic structure and also confirmed that Ni ions are successfully doped into CuO crystal lattice by occupying Cu ionic sites. Interestingly, the morphology was found to transform substantially from nanoflowers to nanoparticles with close-packed periodic array, and then into nanocrystals with the variation of Ni content. The optical band gap estimated using DRS was found to be 3.9 eV for pure CuO and then increases up to 4.3 eV with increasing Ni content. PL spectra at room temperature showed a strong green emission band, and thereby confirmed the above results. Magnetic measurements reveal a room temperature ferromagnetism (RTFM) with an optimum value of saturation magnetization of 1.3140×10⁻³ emu/g for 2.0 wt% of Ni.     

Application of A4F-MALS for the Characterization of Polymers Prepared by Emulsion Polymerization: Comparison of the Molecular Structure of Styrene-Acrylate and Methyl Methacrylate-Acrylate Copolymers

In this paper, organic asymmetric flow field flow fractionation coupled to a multi-angle light scattering detector is presented as a very efficient tool for the characterization of copolymers prepared by emulsion polymerization. The molar mass distribution and the extent of branching of styrene–acrylate copolymers have been compared with corresponding copolymers of methyl methacrylate. It has been found that the presence of acrylate monomer results in the increase of molar mass and formation of branched macromolecules due to intermolecular chain transfer to polymer similarly as in case of methyl methacrylate–acrylate copolymers. However, the effect is far less pronounced.     

Polymerization induced viscoelastic phase separation of porous phenolic resin from solution

The porous structure evolution of thermosetting phenolic resin controlled by polymerization induced viscoelastic phase separation from solution was investigated in this work. The ultimate morphology and the evolution of a porous texture for the resol resin/solvent system were characterized by digital camera and optical microscopy. In-situ Fourier transform infrared spectroscopy and a rheological method were used to trace the curing reaction of the resol resin/solvent system. The impacts of solvent content and curing temperature on the foaming behavior were quantitatively and systematically investigated. Based on the relationship between the morphology evolution and curing dynamics, the foaming mechanism of the polymerization induced viscoelastic phase separation was elucidated. The present work provides new insight into the foaming mechanism of thermosetting materials and may be helpful for morphological control in the preparation of lightweight porous phenolic material. © 2016 Society of Chemical Industry