[en] Highlights: • Sacrificial layer assisted microfabrication method was developed for CO₂ laser engraving. • Six thermoplastics were found compatible with sacrificial layer assisted laser engraving technique. • Microchannel width as small as ∼ 40 μm was attainable by a laser beam that was 5 times larger in diameter. • Inherent bulging issue of laser engraved microchannel has been solved such that good bonding quality can be achieved. - Abstract: Since polydimethylsiloxane (PDMS) is notorious for its severe sorption to biological compounds and even nanoparticles, thermoplastics become a promising substrate for microdevices. Although CO₂ laser engraving is an efficient method for thermoplastic device fabrication, it accompanies with poor bonding issues due to severe bulging and large feature size determined by the diameter of laser beam. In this study, a low-cost microfabrication method is proposed by reversibly sealing a 1 mm thick polymethylmethacrylate (PMMA) over an engraving substrate to reduce channel feature size and minimize bulges of laser engraved channels. PMMA, polycarbonate (PC), polystyrene (PS), perfluoroalkoxy alkane (PFA), cyclic-olefin polymers (COP) and polylactic acid (PLA) were found compatible with this sacrificial layer assisted laser engraving technique. Microchannel width as small as ∼40 μm was attainable by a laser beam that was 5 times larger in diameter. Bulging height was significantly reduced to less 5 μm for most substrates, which facilitated leak proof device bonding without channel deformation. Microdevices with high aspect ratio channels were prepared to demonstrate the applicability of this microfabrication method. We believe this fast and low-cost fabrication approach for thermoplastics will be of interest to researchers who have encountered problem with polydimethylsiloxane based microdevices in their applications.

[en] The 300 MW unit of a power plant is resistant to fuel, and its color is reddish brown. The acid value and resistivity are in line with the standard requirements. However, a large amount of sludge appears in the same grade of oil, causing the filter to be blocked and unable to supply oil. After the oil is filtered by the online oil filtering device, the degraded anti-fuel oil and the new oil are mixed and there is still sludge. In order to solve this problem, the components in the anti-fuel oil were tested and the acid value, moisture, resistivity, particle size and sludge precipitation test were tested. The cause of the sludge in the mixed oil was found and the treatment method was found. The oil samples were adsorbed by diatomaceous earth, activated clay and strong polar silica-alumina, and the parameters were analyzed after treatment. It was found that both activated clay and polar silica-alumina adsorbent have better purification functions, but the polar silica-alumina adsorbent is better and effectively solves the problem of fuel resistance degradation. (paper)

[en] Objective: To evaluate the therapeutic effects and influential factors of percutaneous lumbar diskectomy (PLD) as a treatment of lumbar disc protrusion. Methods: In total PLD was performed on 1912 protruded lumbar discs in 1282 cases in this series, including the unsuccessful intervention on 3 discs in 3 cases. The retrospective study was made on: (1) the correlation between the clinical effects and the indication as well as the contraindication; (2) the correlation between the therapeutic effects and the degree and types of the lumbar disc protrusion; (3) the correlation between the therapeutic effects and the clinical symptom; (4) the correlation between the therapeutic effects and the duration of the disorder and the age of the patient; (5) the correlation between the therapeutic effects and the amount of disc tissue removed. Results: The successful rate was 99.5%, and the curative and effective rates were 79.7% and 15.3% re- spectively. The overall effective rate was 95%. Conclusion: (1) The stenosis of the lateral recess, the intervertebral space, or the disc with calcification might be indication for PLD; while 'post- operative intervertebral disc' was not a strict contraindication. (2) The therapeutic effects of the contained lumbar disc protrusion was good. (3) The presence of irreversible motor nerve paralysis was a contraindication. (4) Young patient who have traumatic injury and severe symptom must be carefully selected as a candidate of PLD procedure. (5) The mine amount of disc tissue has been removed, the better therapeutic effects will be obtained. While excellent therapeutic effects can be obtained in some cases after a mere annulus fibrosus trepanation is performed to decrease the pressure of the intervertebral disc. (authors)

[en] The subband structures and edge magnetism of α-, β-, γ- and (6, 6, 12)-graphyne nanoribbons with zigzag edges are studied by means of ab initio calculations. Dispersionless subbands and antiparallel edge magnetic ordering occur in these nanostructures, just like in zigzag-edged graphene nanoribbons. More importantly, a very simple tight-binding model is established which can accurately describe the subband structures of these ribbons. From such a model we find that β-graphyne nanoribbon has many more transport modes than other graphyne and graphene nanoribbons, hence it can carry a much larger current. Such a tight-binding model provides a simple but effective way to study further the transport and optical properties of these graphyne nanoribbons. (paper)

[en] Motor made of electrical steel sheet is sometimes used in extreme environments, for example, submersible motors are operated at temperatures and pressures coupling environment. However, most related reports only consider the effect of single environmental factor (temperature or stress) on the magnetic properties of electrical steel sheets. Therefore, in order to accurately design a motor that can operate at temperatures and pressures coupling environment, the magnetic properties of electrical steel sheets used in the motor should be clarified firstly. In the paper, two kinds of specimens (ring specimen and rolled specimen) are used to measure the magnetic properties under temperature and pressure coupling environment. It not only reveals the influence of temperature and pressure coupling environment on the magnetic properties, but also analyzes the difference between the measurement results obtained by two kinds of measurement samples. The measurement results show that the effect of pressure on magnetic properties decreases with increasing temperature under the conditions of temperature and pressure coupling. According to the domain theory, a reasonable explanation for the influence of temperature and pressure coupling environment on electrical steel sheet is given. Meanwhile, combining the shape and size of the two measurement samples, the possible causes of the differences in the measurement results of the two measurement samples were analyzed in detail.

[en] A new linked mirror device for magnetic confinement experiments is proposed. The new linked mirror device consists of two straight magnetic mirrors connected by two half-torus. The structure of the configuration as a whole is three dimensional because the two linear mirror sections are not parallel. The angle between the two mirror sections generates rotational transform which results in good magnetic confinement of toroidally passing particles. In this way the usual loss cone of the traditional linear mirror machines is eliminated. The single particle confinement is similar to that of tokamaks with most of particles well confined. The calculated neoclassical confinement is very good and is even better than that of an equivalent tokamak. (paper)

[en] Highlights: • The proposed measurement system is suitable for unconventional specimens. • The coupling effects of magnetic field, temperature and pressure are discussed. • The electrical resistivity will fluctuate instantaneously. • Ignoring fluctuations, the effect of temperature and pressure can be analyzed. In order to analyze the performance of magnetic device which operate at high temperature and high pressure, such as submersible motor, oil well transformer, the electrical resistivity of non-oriented silicon steel sheets is necessary for precise analysis. But the reports of the examination of the measuring method suitable for high temperature up to 180 °C and high pressure up to 140 MPa are few. In this paper, a measurement system based on four-probe method and Archimedes spiral shape measurement specimens is proposed. The measurement system is suitable for measuring the electrical resistivity of unconventional specimens under high temperature and high pressure and can simultaneously consider the influence of the magnetic field on the electrical resistivity. It can be seen that the electrical resistivity of the non-oriented silicon steel sheets will fluctuate instantaneously when the magnetic field perpendicular to the conductive path of the specimens is loaded or removed. The amplitude and direction of the fluctuation are not constant. Without considering the effects of fluctuations, the electrical resistivity of the non-oriented silicon steel sheets is the same when the magnetic field is loaded or removed. And the influence of temperature on the electrical resistivity of the non-oriented silicon steel sheet is still the greatest even though the temperature and the pressure are coupled together. The measurement results also show that the electrical resistivity varies linearly with temperature, so the temperature coefficient of resistivity is given in the paper.

[en] By means of ab initio calculations within density-functional theory, the structural, electronic and magnetic properties of a zigzag-edged graphene nanoribbon (ZGNR) with 3d transition-metal atoms (TMAs) (Sc–Zn) embedded in the periodically distributed single vacancies are systematically studied. Different from the pristine ZGNR, all of these composite structures show the subband structures with nontrivial spin polarizations, regardless of the type and the embedding position of the TMA. Embedding one kind of these atoms (V, Cr, Ni, Cu or Zn) near one ribbon edge can cause a notable edge distortion. Except for the cases of Sc, Fe and Co doping, other kinds of TMAs embedded near an edge of the ribbon can suppress the inherent magnetism of the zigzag edge. By further analysis, we find that two effects are responsible for the suppression of edge magnetism. One is the variation of the occupied spin-polarized subbands due to the hybridization of the edge state of the ZGNR and 3d atomic states of the dopant. The other is the delocalization of the edge state caused by the exotic TMA. The unilateral magnetism of these TMA-embedded ZGNRs can be utilized to realize the spin-polarized electronic transport, which is the key electronic property in the context of spintronics applications of carbon-based materials. (paper)

[en] The RKKY interaction between two magnetic impurities absorbed on the surface layer of half-filled AB-stacked multilayer graphene (ABSMLG) is theoretically studied based on the lattice Green’s function technique. In comparison with the case of monolayer graphene, the RKKY interaction in such multilayer graphene presents distinct properties in some aspects. Firstly, from the numerical results, we find that the thickness of the ABSMLG influences the RKKY interaction in a complicated manner, depending on the odd/even parity of the number of layers and the sublattice attribution of the positions of the two magnetic impurities. Then, we derive the asymptotic expressions of the RKKY interactions in ABSMLG in the long-distance limit. For even-layered ABSMLG, we find that the RKKY interactions of the 1A-1A, 1B-1A and 1B-1B couplings fall off as 1/R², 1/R⁴ and 1/R⁶ (1A and 1B stand for, respectively, the sublattice points in the surface layer, which are positioned directly on the plaquette and on a lattice point of the layer underneath). On the other hand, in odd-layered ABSMLG, the decays of these interactions follow the 1/R², 1/R³ and 1/R³ power laws respectively. In addition, we also find that these analytical expressions are quantitatively valid to describe the RKKY interaction in ABSMLG when the distance between the two magnetic impurities is larger than the lattice constant of graphene by one order of magnitude. (paper)

[en] By means of density functional theory calculations, we predict a new two-dimensional phosphorus allotrope with the Kagome-like lattice(Kagome-P). It is an indirect gap semiconductor with a band gap of 1.64 eV. The gap decreases sensitively with the compressive strain. In particular, shrinking the lattice beyond 13% can drive it into metallic state. In addition, both the AA and AB stacked Kagome-P multi-layer structures exhibit a bandgap much smaller than 1.64 eV. Edges in the Kagome-P monolayer probably suffer from the edge reconstruction. An isolated zigzag edge can induce antiferromagnetic (AF) ordering with a magnetic transition temperature of 23 K. More importantly, when applying a stretching strain beyond 4%, such an edge turns to possess a ferromagnetic ground state. A very narrow zigzag-edged Kagome-P ribbon displays the spin moment distribution similar to the zigzag-edged graphene nanoribbon because of the coupling between the opposites edges. But the inter-edge coupling in the Kagome-P ribbon vanishes more rapidly as the ribbon width increases. These properties make it a promising material in spintronics. (paper)