Wyniki wyszukiwania - BazTech

1

PIV measurement of tube-side in a shell and tube heat exchanger

Wang K., Zhang Z., Liu Q., Tu X., Hyoung-Bum K.

Polish Journal of Chemical Technology

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2018

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Vol. 20, nr 1

60--66

EN

In order to improve the performance of the shell and tube heat exchanger, a porous baffle and a splitter bar are employed in this research. Through the arrangement of the porous baffle in the tube-side inlet and the splitter bar in the tube, the flow distribution of liquid in the heat exchanger is improved. PIV technology is used to investigate the unsteady flow in the tube-side inlet and the outlet of different models. The porous baffle significantly improves the flow of fluid in the shell and tube heat exchanger, especially by eliminating/minimizing the maldistribution of fluid flow in the tube-side inlet. The performance of the arc baffle is better than that of the straight baffle. The splitter bar has a minimal effect on the flow field of the tube-side inlet, but it effectively improves the flow in the tube bundle and restrains the vortex generation in the tube-side outlet.

2

Real-time optical demultiplexing with the chirped pulses

Li Y., Zhang X., Yuan J., Kang Z., Sang X., Kang S., Kang X., Yan B., Wang K., Yu C.

Optica Applicata

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2018

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Vol. 48, nr 4

621--632

EN

A scheme for real-time optical demultiplexing is proposed by utilizing the time-broadened and linearly chirped pulses instead of the conventional mode-locked pulses. The copies of the optical-time-division-multiplexed signal are acquired through a dual-pump parametric gate and used as the parametric multicast block. Simulation results show that the demultiplexing from 160 Gb/s down to sixteen 10 Gb/s tributaries can be achieved only by using a sampling source of 10 GHz. The proposed scheme can effectively reduce the complexity of parallel processing, and find important applications in the high-speed all-optical signal processing.

3

Comparative Theoretical Investigation on Energetic Substituted Furazanyl Ethers

Liu N., Wang K., Shu Y., Zeman S., Wang B., Wang W.

Central European Journal of Energetic Materials

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2018

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Vol. 15, no. 1

47--71

EN

Furazanyl ether has great potential to be an important candidate as a casting explosive and energetic plasticizer. The density functional theory (DFT) method was used to investigate the heats of formation (HOFs), molecular stability, detonation performance and melting point of a series of substituted furazanyl ethers at B3LYP/6-311G(d,p) level. The results show that the introduction of –N3 or –N(O)=N– groups significantly improves the HOFs values of the derivatives. The bond dissociation energies (BDEs) were analyzed, showing that the N–O bond in the furazan ring is the weakest for most compounds and the ring is vulnerable to cleavage in thermal decomposition. The calculation of density, detonation velocities and detonation pressures suggests that the substitution of –NF2, –CF(NO2)2, furoxan or –N(O)=N– group is an effective method for enhancing their detonation performance. The melting points were determined according to the variation of specific heat capacity, and good estimates were obtained in comparison with the available experimental data. Taking into account the detonation performance and melting point, four compounds are favoured for application in melt cast explosive or energetic plasticizers.

4

Wpływ glukonianu i cytrynianu sodu na konsystencję zaczynów z półwodnego gipsu α upłynnianego superplastyfikatorem polikarboksylanowym

Wang K., Yang L., Ren L.

Cement Wapno Beton

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2018

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R. 21/83, nr 2

144--158

PL

W pracy przedstawiono wyniki badań wpływu cytrynianu oraz glukonianu sodu na właściwości zaczynów z półwodnego siarczanu wapnia odmiany alfa, upłynnianych dodatkiem superplastyfikatora polikarboksylanowego [PA]. Na podstawie uzyskanych wyników stwierdzono, że zdolność do adsorpcji cytrynianu sodu jest znacznie większa od glukonianu, ze względu na większą zdolność tego pierwszego do tworzenia kompleksów chelatowych z jonami wapnia. W przypadku równoczesnego dodatku plastyfikatora i opóźniacza zachodzi adsorpcja wymienna. Cytrynian oraz glukonian sodu opóźniają hydratację gipsu, przy czym efekt opóźniający cytrynianu jest znacznie większy niż glukonianu, ze względu na większą zdolność tego pierwszego do adsorpcji na ziarnach półwodzianu. Przyczyną poprawy konsystencji jest mniejsza ilość zużytej wody i PA, spowodowana działaniem opóźniającym, a przyczyną pogorszenia konsystencji jest mniejsza ilość zaadsorbowanego PA wynikająca z adsorpcji wymiennej cytrynian lub glukonian i PA. W przypadku glukonianu sodu dominuje pierwszy efekt co powoduje poprawę płynności zaczynu, a dla cytrynianu przeważa drugi efekt co wpływa na jej pogorszenie.

EN

The effect of sodium gluconate and sodium citrate on the fluidity of gypsum paste of α hemihydrate plasticized by polycarboxylate superplasticizer [PCE] was investigated. The results have shown that both retarders are adsorbed on the surface of gypsum particles, and the adsorption ability of citrate is much higher than that of gluconate, probably due to the more developed ability of citrate to form chelate complexes with calcium ions. In the case of simultaneous addition of PCE and retarder to hemihydrate paste, the competitive adsorption takes place. The retarding effect of citrate is much stronger than that of gluconate, because of the higher adsorption ability of citrate. Sodium gluconate increase the fluidity of the gypsum paste plasticized by PCE, while citrate reduce it. The reason for the increase of fluidity is due to the reduced consumption of free water and PCE caused by hydration of hemihydrate. Retarding effect is due to the reduced adsorption of PCE, resulting from competitive adsorption with retarder. The latter effect dominates for citrate, resulting in decreased fluidity, while first effect is dominating for gluconate, resulting in increased fluidity.

5

Tensile Damage Mechanism of 3-D Angle-Interlock Woven Composite using Acoustic Emission Events Monitoring

Ma Q., Wang K., Wang S. D., Liu H., Jin B. C., Jin L. M., Ma P.

Autex Research Journal

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2018

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Vol. 18, no. 1

46--50

EN

The quasi-static tensile damage behavior of one type of layer-to-layer 3-Dimensional Angle-interlock Woven Composite (3DAWC) was tested and analyzed in this paper. Incorporated with the acoustic emission (AE) events monitoring, the mechanical behavior of the 3DAWC under tensile loading condition was characterized. The Load-Extension curve, Load/AE events-Time curves occurred during the entire testing process and tensile damage modes were recorded to characterize and summarize the mechanical properties and damage mechanism of the 3DAWC subjected to tensile loading. It was found that the tensile damage of the 3DAWC could be summarized into 3 steps. And each step has a distinct primary damage mode. Moreover, the resin cracks, resin-yarn interface debonding and yarn breakages were the main damage modes for the 3DAWC.

6

Dual reference beam digital off-axis holography for exact suppression of zero-order term and twin image without spectrum loss

Wang M., Wang K., Zheng M., Li F., Wu J.

Optica Applicata

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2017

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Vol. 47, nr 3

435--443

EN

In this paper, we describe an effective approach to suppressing zero-order term and twin image by using pixel-by-pixel multiplication of double holograms in digital off-axis holography. This method records two holograms, respectively, by using the reference waves in different directions. It shows not only a simpler algorithm and easier implementation in experiment, but also exact and complete suppression of the zero-order term and twin image without any spectrum loss of the object in the image reconstruction, particularly when the image and the zero-order term are fairly close to each other. The experimental result approves of the theoretical prediction very well. This approach provides an effective solution to suppressing undesired noises in the digital off-axis holography.

7

An Enhanced Run-Length Encoding Compression Method for Telemetry Data

Shan Y., Ren Y., Zhen G., Wang K.

Metrology and Measurement Systems

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2017

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Vol. 24, nr 3

551--562

EN

The telemetry data are essential in evaluating the performance of aircraft and diagnosing its failures. This work combines the oversampling technology with the run-length encoding compression algorithm with an error factor to further enhance the compression performance of telemetry data in a multichannel acquisition system. Compression of telemetry data is carried out with the use of FPGAs. In the experiments there are used pulse signals and vibration signals. The proposed method is compared with two existing methods. The experimental results indicate that the compression ratio, precision, and distortion degree of the telemetry data are improved significantly compared with those obtained by the existing methods. The implementation and measurement of the proposed telemetry data compression method show its effectiveness when used in a high-precision high-capacity multichannel acquisition system.

8

Computational Investigation on the Structure and Performance of Novel 4,7-dinitro-furazano-[3,4-d]-pyridazine Derivatives

Wang K., Shu Y., Liu N., Ding X., Wu Z., Lu Y.

Central European Journal of Energetic Materials

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2017

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Vol. 14, no. 1

26--46

EN

Seven novel energetic 4,7-dinitro-furazano-[3,4-d]-pyridazine derivatives were designed, and their optimized structures and performances were studied by density functional theory (DFT) at B3LYP/6-311g(d,p) level. The detonation performances were estimated by the Kamlet-Jacobs equations. The results show that these compounds have high crystal densities (1.818-1.925 g·cm−3), detonation velocities (8.51-9.56 km·s−1) and detonation pressures (32.28-41.70 GPa). The bond dissociation energies (BDEs) of the weakest bond (N–O bond) vary from 70.889 kJ·mol−1 to 173.283 kJ·mol−1, and some of them exhibit higher BDEs than that of RDX (N–NO2 bond, 149.654 kJ·mol−1) and HMX (N–NO2 bond, 154.905 kJ·mol−1). M4 and M5 exhibit similar and higher detonation performance than RDX (8.81 km·s−1, 34.47 GPa). The detonation performance of M7 (9.56 km·s−1, 41.70 GPa) even surpasses that of HMX (9.10 km·s−1, 39.00 GPa). Otherwise, the specific impulse values of M1-M7 (266-279 s) outperform HMX (266 s) by 0-13 s, which indicates that M1-M7 may show better performance as monopropellants. It is concluded that density, heat of formation, stability, detonation performance and specific impulse of the designed compounds depend on the position and number of the N→O oxidation bonds.

9

Biodiversity Versus Stability: the Biological Effect of Plant Functional Traits on Ecosystem Functioning in Grasslands Dominated by Leymus chinensis

Zhao N., Shao X., Wang K.

Polish Journal of Ecology

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2016

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Vol. 64, nr 3

339--349

EN

Although diversity-ecosystem theory predicts that ecosystem functioning is strongly determined by species number, species traits play an important role in regulating ecosystem-level dynamics. We analyze responses of species attributes to diversity level and resource availability, and explore their consequences for ecosystem functioning and ultimately assess the contributions of five traits (vegetative plant height, clonal growth, root depth, cespitose habit and seed mass) to ecosystem functioning defined by spatial stability of community biomass. We found that functional traits disproportionately affected spatial stability. Relationships between species functional traits and spatial stability of community biomass indicated that diversity of vegetative plant height facilitated stability of a nitrogen fertilized undisturbed natural community (NAT), and that of a phosphorus fertilized forb, legume and bunchgrass community (FLB). The clonal growth form was also identified as a stabilizing trigger for a unfertilized undisturbed natural community (NAT), whereas diversity in root depth, cespitose habit and seed mass were related to destabilization of a nitrogen fertilized rhizomatous grass community (RRR). Studies quantifying interactions among plant traits, community structure and ecological functioning will contribute much more to understanding of the effects of the ecological behavior of specific traits on the ecosystem functioning.

10

Synthesis and Characterization of Four Energetic Transition Metal Complexes of 3,4-Diamino-1,2,4-triazole

Yin X., Jin X., Xu C.-X., He P., Wang K., Zhang J.-G.

Central European Journal of Energetic Materials

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2016

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Vol. 13, no. 2

301--320

EN

Four complexes with the formula of [M5(DATr)12~14(H2O)6](ClO4)10 (M = Mn (1), Co (2), Ni (3), Zn (4)) about their synthesis, structures and some energetic properties (such as sensitivities tests) have been described, where the DATr here denotes 3,4-diamino-1,2,4-triazole. These four compounds are all light metallic complexes with good thermal stability. The structures of 2-4 were determined by single-crystal X-ray diffraction, and the crystal structures mainly consist of penta-nuclear units. All the structures have a common interesting property in which DATr plays a role of bi-dentate ligand. Besides, it is observed from the crystal structure of 4 that DATr can be also act as a mono-dentate ligand. Thermodynamic studies of their decomposition properties and kinetic parameters show that the four complexes have high thermal stabilities. Furthermore, tests of their impact and friction sensitivities show that complexes (2) and (3) can be potential candidates as primary explosives to replace toxic lead azide.

11

A high performance distributed sensor system with multi-intrusions simultaneous detection capability based on phase sensitive OTDR

Zhan Y., Yu Q., Wang K., Yang F., Kong Y., Zhao X.

Opto-Electronics Review

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2015

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Vol. 23, No. 3

187-194

EN

A high performance distributed sensor system with multi-intrusions simultaneous detection capability based on phase sensitive OTDR (Φ-OTDR) has been proposed and demonstrated. To improve system performance, three aspects have been investigated. Firstly, a model of one-dimensional impulse response of backscattered light and a Monte Carlo method have been used to study how the laser line width affects the system performance. Theoretical and experimental results show that the performances of the system, especially the signal-noise-ratio (SNR), decrease with the broadening of laser linewidth. Secondly, a temperature-compensated fibre Bragg grating with a 3 dB linewidth of 0.05 nm and a wavelength stability of 0.1 pm has been applied as an optical filter for effective denoising. Thirdly, a novel interrogation method for multi-intrusions simultaneous detection is proposed and applied in data denoising and processing. Consequently, benefiting from the three-in-one improvement, a high performance Φ-OTDR has been realized and four simultaneous applied intrusions have been detected and located at the same time along a 14 km sensing fibre with a spatial resolution of 6m and a high SNR of 16 dB. To the best of our knowledge, this is the most multifunctional Φ-OTDR up to now and it can be used for perimeter and/or pipeline intrusion real-time monitoring.

12

Focusing properties of partially coherent dark hollow Gaussian beams through a thin lens system

Dong Y., Zhao C., Wang K., Zhao C., Cai Y.

Optica Applicata

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2015

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Vol. 45, nr 2

151--161

EN

This paper investigated the focal shift of partially coherent dark hollow Gaussian beams through a thin lens system. An analytic expression of the irradiance distribution of the focusing partially coherent dark hollow Gaussian beams in the back focal plane has been given by using the Collins formula. The focus shift of focused partially coherent dark hollow Gaussian beams in different parameters is studied in detail by numerical calculations. It is found that the absolute value of the focal shift of partially coherent dark hollow Gaussian beams decreases as the transverse coherence width or the order of the dark hollow Gaussian beams or a parameter of the dark hollow Gaussian beams increases.

13

Method of regularized sources for two-dimensional Stokes flow problems based on rational or exponential blobs

Wen S., Wang K., Zahoor R., Li M., Šarler B.

Computer Assisted Methods in Engineering and Science

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2015

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Vol. 22, no. 3

289--300

EN

The solution of Stokes flow problems with Dirichlet and Neumann boundary conditions is performed by a non-singular method of fundamental solutions (MFS) which does not require artificial boundary, i.e., source points of fundamental solution coincide with the collocation points on the boundary. The fundamental solution of the Stokes pressure and velocity is obtained from the analytical solution due to the action of the Dirac delta- type force. Instead of Dirac delta force, a non-singular function called blob, with a free parameter epsilon is employed, which is limited to Dirac delta function when epsilon is limited to zero. The analytical expressions for related Stokes flow pressure and velocity around such regularized sources have been derived for rational and exponential blobs in an ordered way. The solution of the problem is sought as a linear combination of the fields due to the regularized sources that coincide with the boundary and with their intensities chosen in such a way that the solution complies with the boundary conditions. A numerical example for two-dimensional (2D) driven cavity and a flow between parallel plates are chosen to assess the properties of the method. The results of the posed method of regularized sources (MRS have been compared with the results obtained by the fine-grid second-order classical finite difference method (FDM) and analytical solution. The results converge with finer discretisation; however, they depend on the value of epsilon. The method gives reasonably accurate results for the range of epsilon between 0.1 and 0.5 of the typical nodal distance on the boundary. Exponential blobs give slightly better results than the rational blobs; however, they require slightly more computing time. A robust and efficient strategy to find the optimal value of epsilon is needed in the perspective.

14

Phytoremediation of phenol using Polygonum orientale and its antioxidative response

Wang K., Cai J., Xie S., Feng J., Wang T.

Archives of Environmental Protection

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2015

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Vol. 41, no. 3

39--46

EN

Polygonum orientale with beautiful red flowers can be found as one dominant species in the vicinity of most water bodies and wetlands in China. However, its phytoremediation potential has not been sufficiently explored because little is known about its resistance to inorganic or organic pollutants. We investigated P. orientale response to low and moderate levels of phenol stress (≤ 80 mg L-1). Endpoints included phenol tolerance of P. orientale and the removal of the pollutant, antioxidant enzyme activities, damage to the cell membrane, osmotic regulators and photosynthetic pigments. In plant leaves, phenol stress significantly increased the activities of peroxidase (POD) and catalase (CAT), as well as the contents of proline, soluble sugars and carotenoids, whereas superoxide dismutase (SOD), H2O2 and electrolyte leakage (EL) levels remained unaltered. On the other hand, there were significant decreases of soluble protein and chlorophyll contents. We demonstrated that, in combination with phenol tolerance and its removal, P. orientale has efficient protection mechanisms against phenol-induced oxidative damage (≤ 80 mg L-1). We propose that P. orientale could be used as an alternative and interesting material in the phytoremediation of phenol.

15

A Curvature-Tensor-Based Perceptual Quality Metric for 3D Triangular Meshes

Torkhani F., Wang K., Chassery J. M.

Machine Graphics and Vision

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2014

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Vol. 23, No. 1/2

59--82

EN

Perceptual quality assessment of 3D triangular meshes is crucial for a variety of applications. In this paper, we present a new objective metric for assessing the visual difference between a reference triangular mesh and its distorted version produced by lossy operations, such as noise addition, simplification, compression and watermarking. The proposed metric is based on the measurement of the distance between curvature tensors of the two meshes under comparison. Our algorithm uses not only tensor eigenvalues (i.e., curvature amplitudes) but also tensor eigenvectors (i.e., principal curvature directions) to derive a perceptually-oriented tensor distance. The proposed metric also accounts for the visual masking effect of the human visual system, through a roughness-based weighting of the local tensor distance. A final score that reflects the visual difference between two meshes is obtained via a Minkowski pooling of the weighted local tensor distances over the mesh surface. We validate the performance of our algorithm on four subjectively-rated visual mesh quality databases, and compare the proposed method with state-of-the-art objective metrics. Experimental results show that our approach achieves high correlation between objective scores and subjective assessments.

16

Nonlinear motion law of coalbed gas seepage under the combined effects of stress field and temperature field

Li B., Wei J., Li P., Wang K., Borisyuk Y. A.

Journal of Power Technologies

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2014

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Vol. 94, nr 2

106--113

EN

The shrinkage and swelling of the coal matrix due to the effects of temperature were investigated through the performance by Henan Province Key Lab of Gas Geology & Gas Control of a permeability test of loaded coal under various temperature and working conditions using its own seepage equipment for thermo-fluid-solid-mechanical coupling of methane-containing coal. The variation of coal permeability under the combined effects of stress and temperature was investigated, and the gas motion law in the coal samples was tested. The variation equations of coal permeability under the combined effects of stress and temperature, as well as the motion equations describing the nonlinear gas seepage law in coal seams were established. The established equations were proved to fit well with the experimental data, which demonstrated that the motion equations and the research methods were both reasonable. Study on the seepage nonlinear motion law of gas in the coal seam is great significance to mineral gas extraction.

17

DC-Link Voltage Balancing Method with Reduced CommonMode Voltage for a Five-Level ANPC Inverter

Wang K., Li Y., Zheng Z., Xu L., Feng J.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 3b

32--34

EN

This paper presents a DC-link voltage balancing method with reduced common-mode voltage for a five-level active neutral-point clamped (ANPC) inverter. The DC-link voltage balancing method is based on zero-sequence voltage injection using carrier-based PWM. By further limiting the range of injected zero-sequence voltages, the amplitude of common-mode voltage can be reduced to 1/4 of the dc-link voltage. Experimental results are presented to verify the validity of this method.

PL

W artykule przedstawiono metodę balansowania napięciami kondensatorów obwodu pośredniczącego DC dla pięcio-poziomowego falownika Active NPC z redukcją napięcia common-mode. W metodzie wykorzystywana jest modulacja PWM z falą nośną i sygnałem kolejności zerowej, o regulowanym zakresie aplikacji. Przedstawiono wyniki eksperymentalne.

18

A Condition Assessment Model of Oil-immersed Transformers Using Cloud and Matter Element Integrated Method

Liao R., Zhang Y., Zheng H., Yang L., Wang K., Akram S.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 4

142-146

EN

High voltage oil-immersed transformers are the most important components in the power system. If there is a potential fault in the transformer it may cause a power failure even a catastrophe. Therefore, it is important to assess the condition of the transformer accurately and to make some relative maintenance to minimize the risk of premature failure. However, condition assessment of transformers can be considered as a multiple-attribute decision-making (MADM) problem which is full of uncertain, fuzzy and randomness information. Aiming at this intricate problem, this paper presents a cloud and matter element integrated approach for assessing the condition of transformers. An assessing index system is established, which includes dissolved gas analysis (DGA), electrical testing and oil testing. An integrated model based on matter element approach and cloud approach is applied to assess the condition of the transformer. Cases study show that the proposed approach is practical and effective. The assessing result can be regarded as a useful suggestion to condition based maintenance of high voltage oil-immersed transformers.

PL

W artykule przedstawiono metodę oceny stanu technicznego transformatora olejowego, opartą na analizie elementów chmury oraz tzw. Matter-Element Analysis. Opracowany został zintegrowany model oraz wskaźnik szacujący stan transformatora, uwzględniający czynniki takie jak: analiza rozpuszczonych gazów (DGA), testy elektryczne i olejowe. Przeprowadzone badania potwierdziły skuteczność metody.

19

Theoretical Studies of High-nitrogen-containing Energetic Compounds Based on the s-Tetrazine Unit

Man T. T., Wang K., Zhang J.G., Niu X. Q., Zhang T. L.

Central European Journal of Energetic Materials

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2013

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Vol. 10, no. 2

171-189

EN

In order to develop new high-energy-density materials (HEDMs), we have investigated 12 substituted s-tetrazine (TZ) compounds, where s-tetrazine was substituted by amino, amido and related groups. Density functional theory (DFT) was used to predict the optimized geometries, electronic structures, total energy, heats of formation (HOFs) and densities. In addition the detonation properties were evaluated by using the VLW equation of state (EOS). The standard enthalpy of formation, the Gibbs free energy, entropy and equilibrium constants were used to estimate the success of the synthetic substitution reactions, which provided theoretical support for practical work. The bond dissociation energy (BDE) of bond C-R was calculated at each stage of the substitution reaction. The calculated results showed that substitution of amino, amido and their derivatives in the TZ ring enhances the HOF values and is favorable for increasing the thermal stability. The calculated detonation properties indicated that incorporating the above groups into the TZ ring is benefcial for improving the explosive performance. Considering the detonation properties and thermal stability, the 12 derivatives may be regarded as promising candidates as high-energy-density materials (HEDMs).

20

Investigation on Chaotic Characteristic of PD Magnitude Series during Propagation of Electrical tree in XLPE Power Cables

Liao R., Wang K., Liu L., Zhou T., Zhou Q.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 5b

213-217

EN

The electrical tree propagation experiments were performed under high voltages with a frequency of 50Hz and amplitudes ranging from 12kV to 21kV at room temperature by utilizing an actual XLPE cable as the test sample, where the concentration of electrical field was simulated by a metal needle tip. The chaotic theory was introduced to analyze the PD magnitude series during the propagation process of electrical tree. Experimental results show that deterministic chaos exists in the propagation of electrical tree in XLPE cables, and the largest Lyapunov exponent and correlation of the strange attractors increase with the decrease of electrical tree fractal dimension. The results may provide a new approach for online diagnosis of electrical tree morphology.

PL

rzedstawiono wynika badania wyładowania w kablu XPLE przy częstotliwości 50 Hz i napięciu 12 – 21 kV. Stwierdzono chaotyczny charakter drzewienia elektrycznego. Zaproponowano opis teoretyczny umożliwiający łatwe rozpoznanie typu wyładowania.