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The modular multilevel converter (MMC) is attractive for medium-/high-voltage and high-power applications because of the advantages of its high modularity, availability, and high power quality. Due to the chemical process, aging effect, etc., the capacitor in the submodule (SM) of the MMC would gradually deteriorate and the capacitance would drop, which would cause unbalanced SM power losses distribution in the same arm of the MMC and affect the reliability of the MMC. This paper proposed an equivalent-reference (ER) control method, which can effectively realize balanced SM power losses distribution in the same arm of the MMC through the voltage-balancing control for the virtual capacitor voltages (VCVs) in the MMC under the capacitor deterioration. The proposed ER control can effectively improve the reliability of the MMC with the balanced SM power losses distribution in the MMC under capacitor deterioration. The simulation studies with the time-domain professional tool PSCAD/EMTDC are conducted, and a down-scale MMC prototype is also tested with the proposed control strategy. The study results confirm the effectiveness of the proposed control strategy.

Songke Well No.2, one of the main part of the scientific drilling project in Songliao Basin, which was drilled 7018 m and acquired the part of cores continuously from the Low Cretaceous to the Carboniferous and the Permian from the 2843 m deep, can be considered as the deepest continental drilling project in Asia. Aiming at the features of longer well sections, larger diameters and multiple spud-ins for coring of Songke Well No.2, this project broke through the “coring in small diameter and reaming in large diameter” spud-in drilling-completion procedures which are always used in large-diameter-well coring for continental scientific drilling projects in domestic and overseas and the drilling method of short-single-cylinder roundtrip footage. At the same time, “coring in the same diameter and completing drilling at one single diameter” was achieved at all φ311 mm and φ216 mm coring sections of more than one thousand meters long, high-efficient operation with “drilling long footage with drill tools combined in multi-cylinders” was achieved at deep coring section. Four world drilling records were created which include more than a thousand meters continuous coring at φ311 mm, and the footage per roundtrip footage at φ311 mm, φ216 mm and φ152 mm is all more than 30 m, all of these breakthroughs reduced at least 300 days for this project; moreover, considering the characteristics of formations that the geothermal gradient is high in the drilled sections and the inside-well temperature is over 240°C after drilling completion, a formate-polymer water-based mud system was developed by compounding attapulgite and sodium bentonite and by adding independently developed high-temperature stabilizer, which can provide critical technical support for successful well completion at 7018 m in the super-high-temperature environment It is the first time that the water-based mud is operated at the working temperature higher than 240°C in China; Besides, considering the high-quality requirement on cores imposed by the project, the method “mechanical cored is charge” to discharge core nondestructively on the ground was worked out, and more than 4000 m scatheless cores were discharged out of the drill pipes while maintaining original stratum structures.

Based on the PBA construction method of Changchun Liberation Road station metro line No.2, in order to get the optimization of construction sequence of six pilot tunnels, we use numerical simulation method and finite element software MIDAS GTS to establish the construction model of the station pilot tunnel. After comparing four excavation methods of the surface subsidence, we come to a conclusion that first up then down and first side then middle is the optimal excavation scheme. At the same time, we make models to analysis the necessity of making advance support before pilot tunnel construction. Pipe shed and small duct grouting pre support is very significant to the control of the subsidence of ground surface and vault.

The characteristics of process mineralogy of some pyrite cinders were studied with optics microscopes, scanning electron microscope, and x-ray diffraction. The chemical composition and the phase composition of the pyrite cinders were analyzed. The occurrence and chemical phase analysis of molybdenum of iron, copper, and gold were also studied. The behaviors of various minerals and mineralogical factors affecting the separation had been explained clearly. The investigation results were favorable to reasonable selection of technological process.

The characteristics of process mineralogy of the some lead-zinc mine were studied with scanning electron microscope, optics microscopes，and x-ray diffraction. The species of lead minerals and zinc minerals and the chemical composition of the minerals were analyzed. The liberations at different grinding finenesses and the particle sizes of the minerals had been also determined. The phase shape of lead and zinc in the ore was also analyzed. The behaviors of various minerals and mineralogical factors affecting the flotation had been explained clearly. The investigation results were favorable to reasonable selection of flotation parameters and would provide theoretical guidance to lead-zinc separation.

AbstractOne hundred two pathogenic Escherichia coliisolates from diseased pigs were analyzed for serotypes, virulence genes, antimicrobial susceptibility, and the molecular basis of phenicol resistance. Of these 102 E. coliisolates, 101 were typeable and belonged to 27 different O serogroups. However, 69% of these isolates belonged to one of the following eight serogroups: O8, O54, O64, O65, O92, O108, O119, and O120. Serogroups O8 (23%) and O64 (10%) were the most prevalent among typeable isolates. High-resistance phenotypes were observed in all the isolates, with the majority displaying resistance to chloramphenicol (89%), streptomycin (83%), enrofloxacin (78%), and doxycycline (60%). The chloramphenicol resistance genes cat1, cat2, and cmlAwere detected in 58%, 49%, and 65%, respectively, of the chloramphenicol-resistant isolates. The floRgene was detected in 57% of the florfenicol-resistant isolates and in 52% of chloramphenicol-resistant isolates. Pulsed-field gel electrophoresis showed that the 32 floR-positive isolates with florfenicol minimum inhibitory concentration ≥8 μg mL−1belonged to 25 different pulsed-field gel electrophoresis profiles, indicating the spread of floRamong swine pathogenic E. coliisolates.

The title compounds, {Cu[CH3C6H4N(CH2COO)2]}-2H2O (I) and {Cu[CH3OC6H4N(CH2COO)2]}-2H2O (II) have been prepared and crystal structures determined. The crystallographic data are as follows: (I) Mr = 320.8, monoclinic, P21/c, a = 12.523(2), b = 7.481(2), c = 15.126(4) Å, β = 111.85(2)°, V=1314.9Å3, Z = 4, δ(CuKa)=1.5410 Å, F(000) = 660, room temperature, R = 0.052 for 1952 observed reflections with I > 3s`(I); (II) Mr = 336.39, monoclinic, P21/c, a = 11.452(2), b = 7.595(2), c = 15.416(2) Å, β = 101.60(1)°, V = 1313.4 Å3, Z = 4, δ(MoKα) = 0.7107 Å, F(000) = 692, room temperature, R = 0.052 for 1091 observed reflections with 1 > 3s`(I).The Cu atom is five coordinate (N(1), O(1), 0(2), O(10) and O(20)) in (I) to form a distorted square pyramid in which O(20) is at the apical site. The Cu(1)-O(20) bond is much longer than the basal bond lengths. In (II), the Cu atom is six coordinate (N(1), 0(1), 0(2), O(10), O(20) and O(01)) in the form of an unsymmetrical and elongated tetragonal bipyramid, manifesting an obvious Jahn-Teller effect.The results of EHMO calculations are very similar to those for the ligand field theory model. The total charge at Cu is approximately +2. The electron population numbers indicate that there is approximately one electron in the d2x—y2 orbital, but approximately two electrons in the other orbitals. It can be ascertained that the ligand mainly provided the field, with few of its electrons being donated to the central atom.