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1

A numerical approach to predict the rotating stall in the vaneless diffuser of a centrifugal compressor using the eigenvalue method

Hu C., Liu P., Zhu X., Chen H., Du Z.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 2

635--647

EN

A two-dimensional incompressible flow model is presented to study the occurrence of rotating stall in vaneless diffusers of centrifugal compressors. The diffuser considered has two parallel walls, and the undisturbed flow is assumed to be circumferentially uniform, isentropic, and to have no axial velocity. The linearized 2D Euler equations for an incompressible flow in a fixed frame of the coordinate system are considered. After discretization by a spectral collocation method based on Chebyshev-Gauss-Lobatto points, the generalized eigenvalue problem is solved through the QZ algorithm. The compressor stability is judged by the imaginary part of the eigenvalue obtained. Based on the 2D stability analysis, the influence of inflow angle, radius ratio and wave number are studied. The results from the present stability analysis are compared with some experimental measurement and Shen’s model. It is showed that diffuser instability increases rapidly and the stall rotational speed decreases quickly with an increase in the diffuser radius ratio. The largest critical inflow angle can be obtained when the wave number is around 3 ∼ 5 for the radius ratio between 1.5 to 2.2. It is also verified that the stability model proposed in this paper agrees well with experimental data and has the capability to predict the onset of rotating stall, especially for wide diffusers.

2

First principles study of structure, electronic and optical properties of Y3Fe5O12 in cubic and trigonal phases

Shen T., Hu C., Dai H., Yang W., Liu H., Wei X.

Materials Science Poland

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2015

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Vol. 33, No. 1

169--174

EN

First principles calculations have been performed to investigate the structure, electronic and optical properties of Y3Fe5O12. Both the cubic and trigonal phases have been considered in our calculation. The calculated structural parameters are slightly larger than the experimental values. The band structures show that Y3Fe5O12 in cubic and trigonal phases have direct band gaps of 0.65 and 0.17 eV. The calculations of dielectric function, absorption, extinction coefficient, refractive index, energy loss function and reflectivity are presented.

3

Determination of spectinomycin and related substances by HPLC coupled with evaporative light scattering detection

Wang Y, Wang M. J, Li J., Yao S. C, Xue J, Zou W. B, Hu C.

Acta Chromatographica

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2015

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Vol. 27, no. 1

93--109

EN

An improved ion-pairing reversed-phase high-performance liquid chromatography method coupled with evaporative light scattering detection (HPLC-ELSD) was developed to determine spectinomycin and its related substances in commercial samples. The method was validated in accordance with International Conference on Harmonization (ICH) guidelines. The specificity of the HPLC-ELSD method was similar to that of the European Pharmacopoeia (Ph. Eur.) method, and repeatability and robustness were markedly improved relative to other reported methods due to our empirical evaluation of separation columns. Indeed, it is a more specific assay of spectinomycin than traditional microbiological techniques. The HPLC-ELSD method was used to evaluate the impurity profiles of eight compounds in seven spectinomycin batches from five different companies. Liquid chromatography coupled with electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) was employed to characterize the structures of these compounds. Though the HPLC-ELSD method was not as sensitive as the Ph. Eur. method, its limit of quantitation (LOQ) (0.16%) was lower than the disregard limit (0.3%) described by the Ph. Eur. 7.0. This suggests that the HPLC-ELSD method is appropriate for routine analysis of spectinomycin and its related substances.

4

Research on Coverage Performance of GNSS

Zhang P., Xu C., Hu C., Chen Y.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 1b

67--70

EN

The theory of Ground Coverage Performance (GCP) and Space Coverage Performance (SCP) of GNSS constellations is analysed. These performances are influenced by restriction of both the signal’s beam angle and the mask angle which is used by the receivers of users. Then the judgment methods and simulation results are acquired. In practical application, relevant constellations should be selected according to different tasks which are based on the simulation results to ensure the maximum number of visible satellites at the same time.

PL

Przeanalizowano teoretycznie obszary zasięgu naziemne (GCP) i w przestrzeni około-ziemskiej (SCP) dla konstelacji nadajników satelitarnych systemów nawigacji (GNSS). Sprawność zasięgu jest ograniczona zarówno przez kąt promieniowania nadajnika, jak i przez kąt zasięgu odbiorników użytkownika. Przedstawiono metody oceny i wyniki symulacji. W praktycznych zastosowaniach, w zależności od różnych zadań i wyników symulacji, konstelacja satelitów musi być dobrana tak, aby była widoczna maksymalna ich ilość w tym samym czasie. Badania dotyczą systemów: GPS, GLONASS, GALILEO i chińskiego BD2.

5

Geological defect and its geophysical prediction method in Karst Tunel

Li L., Li S., Zhou Z., Xu Z., Shi S., Zhang Q., Zhou Y., Hu C.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 1b

116--119

EN

With the rapid development of traffic tunnels construction in mountain area in the world, hydrogeological conditions are becoming unprecedentedly complex, water inrush and mud gushing is one of the typical common geologic hazards for the karst tunnel construction. .Based on the analyzing karst tunnel water inrush examples in recent years in china, the mechanism of geologic structure for water inrush has been explained through analyzing different karst hydrogeological storage structures. The unfavorable geologic bodies can be forecasted by geophysical method, and the detecting device and the signal receiving sensor would be selected for different water-bearing structure. The seismic wave, electromagnetic wave will be reflected and received by sensor when encountered geological defect, and the attributes of unfavorable geologic bodies were identified based on the returned signal. Risk assessment of water inrush must be done firstly during tunnel construction, an optimal system for water-bearing structure detecting in which prediction methods vary with the risk level of water inrush can be probed. As a result, the hazard prevention & controlling technological system of water inrush of karst tunnel is composed of risk evaluation system and comprehensive geological prediction system. It has been successfully used for hazards prevention and control for water inrush of Qiyueshan Tunnel in Hurong highway, including risk assessment and hazard source detection. Conclusions will benefit further research on hazards control of underground construction.

PL

Wraz z szybkim rozwojem budowy tuneli w terenach górskich rośnie znaczenie oceny warunków hydrogeologicznych: W szczególności, w przypadku tuneli w terenach krasowych, typowym niebezpieczeństwem jest napór wody i tryskające błoto. Na podstawie analizy wypadków w tunelach krasowych w Chinach w ostatnich latach, wyjaśniono mechanizm naporu wody przez analizę różnych formacji hydrogeologicznych w obszarach krasowych. Niekorzystne warunki geologiczne można prognozować metodami geofizycznymi, przez zastosowanie urządzenia detekcji sygnałów odbitych od różnych struktur wodonośnych. Podczas projektowania tunelu należy ocenić ryzyko wystąpienia naporu wody i przeprowadzić wszechstronną prognozę geologiczną. Przy budowie tunelu Qiyushan linii kolejowej Hurong przeprowadzono badania obejmujące oszacowanie ryzyka i wskazano źródła niebezpieczeństw.

6

Electronic Circuit Optimization Design Algorithm based on Particle Swarm Optimization

Yan X., Hu C., Yao H., Fan Y., Liang Q., Liu C.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 3b

50--52

EN

A major bottleneck in the evolutionary design of electronic circuits is the problem of scale and the time required to evaluate the individuals, traditional genetic algorithm cannot solve these problems well. Particle Swarm Optimization (PSO) algorithm was developed under the inspiration of behavior laws of bird flocks, fish schools and human communities. In this paper, we use the PSO algorothm to solve the electronic circuit optimization design. The new algorithm keeps not only the fast convergence speed, but effectively improves the capability of global searching as well. The experiment results show that the PSO algorithm is efficient than traditional genetic algorithm.

PL

W artykule opisano zastosowanie algorytmu optymalizacji rojem cząstek w rozwiązywaniu zagadnienia optymalnego projektowania układów elektronicznych. Proponowane rozwiązanie pozwala na uzyskanie dużej szybkości konwergencji oraz efektywne polepszenie możliwości wyszukiwania globalnego. Wyniki eksperymentalne pokazują, że algorytm PSO jest efektywniejszy niż typowy algorytm genetyczny.