Passivation controller design for turbo-generators based on generalised Hamiltonian system theory

A method of pre-feedback to formulate the generalised forced Hamiltonian system model for speed governor control systems is proposed. Furthermore, passivation controllers are designed based on the scheme of Hamiltonian structure for single machne infinite bus and multimachine power systems. In particular, in the case of multimachine systems, all the variables in the control law are only relevant to the state variables of the local generator, which means that a decentralised controller is achieved. Simulation results of a four-machine system show that the controller can enhance power system transient stability

Effect of Carburizing and Shot Peening on the Microstructure and Surface Properties of 17-CrNi6-Mo Steel

Carburizing and shot peening are commonly accepted surface treatment methods used to improve the surface properties of materials. Researchers are making attempts to optimize their application for obtaining superior mechanical properties. However, there are few comprehensive reports on this problem. The combination of carburizing and shot peening is used for the surface treatment of 17-CrNi6-Mo steel. This is followed by detailed analysis employing optical and scanning electron microscopy, microhardness testing, surface roughness measurements, and the measurement of residual stresses using X-ray diffraction. The results show that shot peening can further improve the microstructure and surface properties of carburized specimens since it induced the phase transformation of a carburized layer. Moreover, simulation of the phase composition variation curve along with the change in the carbon content and the continuous cooling transformation (CCT) curve of the specimen is also presented. The results are used to elucidate the carburizing effect on a 17-CrNi6-Mo steel surface microstructure.Цементация и дробеструйная обработка общепринятые методы поверхностной обработки, используемые для улучшения поверхностных свойств материалов. Ученые проводят работы в направлении оптимизации их применения с целью обеспечения высоких механических свойств. Однако существует лишь несколько подробных исследований, посвященных их применению. Комбинацию цементации и дробеструйной обработки используют для поверхностной обработки стали 17-CrNi6-Mo. После обработки проводили подробный анализ поверхности материала с использованием оптической и сканирующей электронной микроскопии, измерений ее микротвердости и шероховатости, а также остаточных напряжений с помощью рентгенографии. Результаты показывают, что дробеструйная обработка может дополнительно улучшить микроструктуру и поверхностные свойства науглероженных образцов, поскольку она вызывает фазовое превращение науглероженного слоя. Выполнено моделирование кривой вариации фазового состава с одновременным изменением содержания углерода, а также кривой превращения при непрерывном охлаждении образца. Полученные результаты используются для установления эффекта влияния цементации на микроструктуру поверхности стали 17-CrNi6-Mo

Symmetry in the insulator - quantum Hall - insulator transitions observed in a Ge/SiGe quantum well

We examine the magnetic field driven insulator-quantum Hall-insulator transitions of the two dimensional hole gas in a Ge/SiGe quantum well. We observe direct transitions between low and high magnetic field insulators and the $\nu=1$ quantum Hall state. With increasing magnetic field, the transitions from insulating to quantum Hall and quantum Hall to insulating are very similar with respect to their transport properties. We address the temperature dependence around the transitions and show that the characteristic energy scale for the high field transition is larger.Comment: 4 page

Effect of Phosphorus and Strontium Additions on Formation Temperature and Nucleation Density of Primary Silicon in Al-19 Wt Pct Si Alloy and Their Effect on Eutectic Temperature

The influence of P and Sr additions on the formation temperature and nucleation density of primary silicon in Al-19 wt pct Si alloy has been determined, for small volumes of melt solidified at cooling rates _T of ~0.3 and 1 K/s. The proportion of ingot featuring primary silicon decreased progressively with increased Sr addition, which also markedly reduced the temperature for first formation of primary silicon and the number of primary silicon particles per unit volume �Nv: When combined with previously published results, the effects of amount of P addition and cooling rate on �Nv are in reasonable accord with �Nv� _T ¼ ðp=6fÞ1=2 109 [250 � 215 (wt pct P)0.17]�3, where �Nv is in mm�3, _T is in K/s, and f is volume fraction of primary silicon. Increased P addition reduces the eutectic temperature, while increased Sr appears to generate a minimum in eutectic temperature at about 100 ppmw Sr

Alternative splicing and genetic diversity of the white collar-1 (wc-1) gene in cereal Phaeosphaeria pathogens

The white collar-1 (wc-1) gene encodes an important light-responsive protein (wc-1) that maintains circadian clocks and controls numerous light-dependent reactions including sporulation in ascomycete fungi. The structure and expression of the wc-1 gene in wheat-biotype Phaeosphaeria nodorum (PN-w) was studied. It was shown that the full-size (3,353 bp in length) wc-1 gene in PN-w contained 4 introns in which introns 1 and 2 were flanked by GC-AG splice borders and were spliced constitutively. However, introns 3 and 4 of the wc-1 gene were alternatively spliced. As the result of alternative splicing (AS), six transcript variants were identified, encoding different lengths of deduced polypeptides (from 1,044 to 1,065aa). Ratios of the wc-1 gene transcript variants in the RNA population were the same in the sporulated and non-sporulated PN-w isolate Sn37-1 and the sporulated PN-w isolate S-79-1, grown under light/dark conditions. The AS of the wc-1 gene may control various light-dependent reactions in PN-w, which leads to diverse morphological, physiological and pathological characters for pathogen infection and spread. Based on the nucleotide and deduced amino acid sequences, the wc-1 gene in cereal Phaeosphaeria pathogens was diverse. It appeared that the deduced wc-1 polypeptide sequences of P. avenaria f. sp. avenaria (Paa), P. avenaria f. sp. triticea (Pat1 and Pat3) and barley biotype P. nodorum (PN-b) were more closely related than PN-w and Phaeosphaeeria sp. (P-rye) from Poland. Based on the wc-1 deduced polypeptide sequences, P. avenaria f. sp. triticea (Pat2) from foxtail barley (Hordeum jubatum L.) was evolutionary well separated from the other cereal Phaeosphaeria pathogens

Mode oscillation and harmonic distortions associated with sinusoidal modulation of semiconductor lasers

This paper investigates mode dynamics, operation characteristics and signal distortions associated with sinusoidal modulation of semiconductor lasers. The study is based on intensive integrations of the multimode rate equation model of semiconductor lasers over wide ranges of the modulation frequency and depth. The rate equations take into account both spectral symmetric and asymmetric suppressions of modal gain. The higher harmonic distortions as well as the half harmonic distortion associated with the period doubling effect are investigated. The study is applied to both cases of single-mode and multimode oscillations of the non-modulated laser. The obtained results showed that the modulated signal has six distinct waveforms depending on the modulation conditions; three types have continuous periodic waveforms and the others have periodic pulsing waveforms. The modulated laser is found to oscillate in a single mode under weak modulation where the modulated signal is continuous, whereas the pulsing signals are associated with multimode oscillation. The higher harmonic distortions of single-mode laser are lower than those of two-mode lasers, and become serious at modulation frequencies around the relaxation oscillation frequency. These distortions are highest when the laser output is pulsating and the pulses are superposed by relaxation oscillations. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2012

Partial Wave Analysis of J/ψ→γ(K+K−π+π−)J/\psi \to \gamma (K^+K^-\pi^+\pi^-)

BES data on $J/\psi \to \gamma (K^+K^-\pi^+\pi^-)$ are presented. The $K^*\bar K^*$ contribution peaks strongly near threshold. It is fitted with a broad $0^{-+}$ resonance with mass $M = 1800 \pm 100$ MeV, width $\Gamma = 500 \pm 200$ MeV. A broad $2^{++}$ resonance peaking at 2020 MeV is also required with width $\sim 500$ MeV. There is further evidence for a $2^{-+}$ component peaking at 2.55 GeV. The non-$K^*\bar K^*$ contribution is close to phase space; it peaks at 2.6 GeV and is very different from $K^{*}\bar{K^{*}}$.Comment: 15 pages, 6 figures, 1 table, Submitted to PL