Wyniki wyszukiwania - Biblioteka Nauki

1

A review of void formation and its effects on the mechanical performance of carbon fiber reinforced plastic

100%

Liu X. , Chen F.

Engineering Transactions

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2016

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tom Vol. 64, iss. 1

33--51

EN

Carbon fiber reinforced plastic (CFRP) is ideal for high performance of mechanical properties. However, during the manufacturing process of CFRP, defects or flaws can easily be introduced into the material, among which void is the most common one. Many factors contribute to the formation of void including the curing pressure, resin system, environmental conditions and so on, some of which are almost unavoidable. The presence of voids results in a reduction of the mechanical properties of CFRP, which has been the subject of many researchers for several decades. The aim of this paper is to summarize state-of-the-art studies on void formation and its effects on the mechanical properties of CFRP.

2

Numerical investigation of temperature distribution of thermal discharge in a river-type reservoir

80%

Wang S. , Chen F. , Zhang W.

Polish Journal of Environmental Studies

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2019

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tom 28

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nr 5

EN

A 3-D thermal discharge numerical model based on the Navier-Stokes equation, the k–ε turbulence model, and the temperature diffusion-controlled equation was developed to simulate the 3-D distribution of thermal discharge along a river-type reservoir under different discharge conditions, hydrological conditions and reservoir water levels. Results showed that the thermal discharge from the power plant would have a smaller effect on a deep-water reservoir. Neither 1ºC, 2ºC nor 3ºC isotherm appear in any scenario conditions. For dam water depths of 155 m and 175 m, a small envelope area of 0.05ºC isothermal line was predicted. The isothermal lines of 0.05ºC and 0.1ºC covered a small area in all scenario conditions. The temperature increase 500 m downstream of the discharge point was predicted to be less than 0.05ºC during dry seasons. The predicted stability time of the temperature increase in each layer was 20 days. It evidences the thermal impact intensity and the extent is different under three scenario conditions. The predicted space–time distribution of the cooling water and the temperature increase provide scientific bases for designing water intake and water management. In the future, the influence of thermal discharge on water quality and aquatic organisms of the reservoir will be discussed based on the simulation results of this study, that is, the variation law of water temperature caused by thermal discharge.

3

An On-Line Method for Thermal Diffusivity Detection of Thin Films Using Infrared Video

80%

Dong H. , Zheng B. , Chen F.

Metrology and Measurement Systems

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2016

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tom Vol. 23, nr 1

59--70

EN

A novel method for thermal diffusivity evolution of thin-film materials with pulsed Gaussian beam and infrared video is reported. Compared with common pulse methods performed in specialized labs, the proposed method implements a rapid on-line measurement without producing the off-centre detection error. Through mathematical deduction of the original heat conduction model, it is discovered that the area s, which is encircled by the maximum temperature curve rTMAX(θ), increases linearly over elapsed time. The thermal diffusivity is acquired from the growth rate of the area s. In this study, the off-centre detection error is avoided by performing the distance regularized level set evolution formulation. The area s was extracted from the binary images of temperature variation rate, without inducing errors from determination of the heat source centre. Thermal diffusivities of three materials, 304 stainless steel, titanium, and zirconium have been measured with the established on-line detection system, and the measurement errors are: −2.26%, −1.07%, and 1.61% respectively.

4

Performance Measurement Model of Multi-Source Data Fusion Based on Network Situation Awareness

80%

Guo L. , Chen F. , Gao C. , Xong W.

Przegląd Elektrotechniczny

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2012

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tom R. 88, nr 7b

315--319

EN

In order to solve the problem of the energy optimization and assessment with situational awareness performance in the wireless sensor network, the function model is proposed based on the potential relationship between the trend of events and trend assumptions. Research from data integration, correlation analysis, events and prediction method, this paper analyzes the ability of the decision node to obtain and process information. It derivates the multi-sensor network situational awareness performance measurement formula, integrates network situation element, draws a trend calculation curve to achieve the network trend prediction. Experiments show that the proposed method can effectively predict the future trend of the network, the trend calculation results and time series analysis results is better than other network trend assessment algorithms.

PL

Zaproponowano model sieci bezprzewodowej czujników bazujący na potencjalnych zależnościach między trendami i zdarzeniami. Artykuł analizuje możliwość decyzji węzłów do realizacji przesyłu informacji. Eksperymenty potwierdziły, że metoda pozwala na efektywne prognozowanie trendu.

5

Research on the Mechanism of Pin-to-Pin ESD to SCB Initiators

80%

Chen F. , Zhou B. , Qin Z.

Przegląd Elektrotechniczny

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2011

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tom R. 87, nr 12a

169-172

EN

By ESD experiment, SEM-EDXA and firing experiment, the electrostatic-response characteristic of SCB was studied and the electrical explosion performance after ESD was measured. Results show that surface-damage of bridge is not obviously visible when lower than 25kV, but part of samples coated with explosive fire; the V-type angles start to be damaged at 25kV. After ESD, the function time and firing energy required decrease significantly. 25kV is the critical damage-voltage of the bridge. When less than 25kV, the electrical energy can only make the polysilicon melting and at 25kV, the temperature reaches the boiling point of silicon to generate plasma.

PL

Analizowano odpowiedź elektrostatyczną i parametry inicjatora eksplozji. Uszkodzenia mostka są nie zawsze widoczne jeśli napięcie jest poniżej 25 kV. Dlatego stwierdzono że napięcie 25 kV jest krytyczne, poniżej powoduje topienie polisilikonu, ale powyżej skutkuje tworzeniem się plazmy.

6

Decomposition and Approximation of Loopy Bayesian Networks

80%

Dong J. , Chen F. , Huo Y. , Liu H.

Fundamenta Informaticae

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2013

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tom Vol. 125, nr 2

135--152

EN

This paper proposes a new method, conditional probability table (CPT) decomposition, to analyze the independent and deterministic components of CPT. This method can be used to approximate and analyze Baysian networks. The decomposition of Bayesian networks is accomplished by representing CPTs as a linear combination of extreme CPTs, which forms a new framework to conduct inference. Based on this new framework, inference in Bayesian networks can be done by decomposing them into less connected and weighted subnetworks. We can achieve exact inference if the original network is decomposed into singly-connected subnetworks. Besides, approximate inference can be done by discarding the subnetworks with small weights or by a partial decomposition and application of belief propagation (BP) on the still multiply-connected subnetworks. Experiments show that the decomposition-based approximation outperforms BP in most cases.

7

Extraction of Discriminative Patterns from Skeleton Sequences for Accurate Action Recognition

80%

Thanh T. T. , Chen F. , Kotani K. , Le B.

Fundamenta Informaticae

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2014

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tom Vol. 130, nr 2

247--261

EN

Emergence of novel techniques devices e.g., MS Kinect, enables reliable extraction of human skeletons from action videos. Taking skeleton data as inputs, we propose an approach to extract the discriminative patterns for efficient human action recognition. Each action is considered to consist of a sequence of unit actions, each of which is represented by a pattern. Given a skeleton sequence, we first automatically extract the key-frames, and then categorize them into different patterns. We further use a statistical metric to evaluate the discriminative capability of patterns, and define them as local features for action recognition. Experimental results show that the extracted local descriptors could provide very high accuracy in the action recognition, which demonstrate the efficiency of our method in extracting discriminative unit actions.

8

Optimal resource allocation for safety in distributed complex electromechanical systems

80%

Han Z. , Gao J. , Xing L. , Chen F.

Eksploatacja i Niezawodność

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2011

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tom nr 2

4-12

EN

Existing optimal resource allocation for system safety mainly concentrates on series/parallel systems or systems that can be converted into series/parallel models. However, for some distributed complex electromechanical systems, it is very difficult or even impossible to refine them into a series/parallel model; in addition, the safety of some system units is immeasurable because of the coupling relationship complexity in the system composition structure. In this paper, a novel method based on complex networks and path set-based dynamic programming is proposed for the optimal resource allocation for maximal safety of distributed complex electromechanical systems with non-series-parallel structures. As a measurement of the system safety, safety importance is defined, which is a function of two safety feature parameters - accident loss and accident probability. A practical system is taken as an example to illustrate and verify the feasibility and applicability of the proposed method.

PL

Istniejące strategie optymalnej alokacji zasobów służące zapewnieniu bezpieczeństwa systemów skupiają się głównie na systemach szeregowo-równoległych lub na systemach, które można przekształcić w modele szeregowo-równoległe. Jednakże, w przypadku niektórych złożonych rozproszonych systemów elektromechanicznych, przetworzenie na model szeregowo-równoległy może być bardzo trudne lub wręcz niemożliwe. Dodatkowo, z powodu złożoności relacji sprzężeń w fizycznej strukturze tego rodzaju systemów, bezpieczeństwo niektórych jednostek systemowych jest niemierzalne. W niniejszym artykule przedstawiono nową metodę optymalnej alokacji zasobów gwarantującą maksymalne bezpieczeństwo złożonych rozproszonych systemów elektromechanicznych o strukturze innej niż szeregowo-równoległa. Metoda ta oparta jest na sieciach złożonych i wykorzystuje dynamiczne programowanie bazujące na zbiorach ścieżek. Jako miarę bezpieczeństwa systemu zastosowano pojęcie hierarchii bezpieczeństwa, zdefiniowane jako funkcja dwóch parametrów bezpieczeństwa: strat z tytułu awarii oraz prawdopodobieństwa awarii. Dla zilustrowania proponowanej metody i weryfikacji jej przydatności i możliwości zastosowania, przedstawiono przykład rzeczywistego systemu.

9

Characterizing the Inter-Thread Interference of Multi-Core Architectures for Accurate WCET Estimations of Real-Time Applications

80%

Chen F. , Zhang D. , Wang Z.

Przegląd Elektrotechniczny

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2012

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tom R. 88, nr 7b

332--335

EN

Worst-Case Execution Time (WCET) estimation of an application in a real-time system becomes more difficult due to inter-thread interference in shared resources multi-core architectures. This paper proposes an iterative approach to analyze cache interference based on circular dependencies between inter-thread interference and instruction fetch time. Our experiments indicate that the proposed approach can reasonably estimate inter-thread interference in shared caches and improve the tightness of WCET estimation by an average of 17.5%.

PL

W artykule zaproponowano iteracyjną metodę do analizy ukrytych interferencji bazującą na cyrkularnych zależnościach między wątkiem interferencji i czasie dostarczania instrukcji.

10

Ternary wavelets and their applications to signal compression

80%

Mustafa G. , Chen F. , Huang Z.

International Journal of Applied Mathematics and Computer Science

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2004

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tom Vol. 14, no 2

233-240

EN

We introduce ternary wavelets, based on an interpolating 4-point C2 ternary stationary subdivision scheme, for compressing fractal-like signals. These wavelets are tightly squeezed and therefore they are more suitable for compressing fractal-like signals. The error in compressing fractal-like signals by ternary wavelets is at most half of that given by four-point wavelets (Wei and Chen, 2002). However, for compressing regular signals we further classify ternary wavelets into 'odd ternary' and 'even ternary' wavelets. Our odd ternary wavelets are better in part for compressing both regular and fractal-like signals than four-point wavelets. These ternary wavelets are locally supported, symmetric and stable. The analysis and synthesis algorithms have linear time complexity.

11

Research on Damage Mechanism of SCB Initiators under RF

80%

Chen F. , Zhou B. , Qin Z. , Shen R.

Przegląd Elektrotechniczny

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2012

|

tom R. 88, nr 11a

188-190

EN

In order to elucidate the response characteristic of semiconductor bridge(SCB) initiators under radio frequency(RF), RF measurement system was used to test the RF sensitivity of SCBs, after that the energy stored in a 22?F was used to activate the SCB. It is inferred from the results of Bruceton-method firing experiment that RF energy does not damage the SCB chip, but can lead to the accidental ignition of SCB initiators or change the color of normal lead styphnate(NLS). RF can also passivate SCB significantly and the all-fire voltage increases from 6.71V to 7.72V. The experimental data of X-ray photoelectron spectroscopy(XPS) analysis, directly indicated that heat generated by RF changes the valence of Pb in NLS from +2 to +4. The decomposition of NLS is responsible for the loss in sensitivity of SCBs. The research results provide a theoretical guidance for the electromagnetic compatibility(EMC) design of SCB initiators.

PL

W artykule opisano badanie oddziaływania sygnałów częstotliwości radiowej (ang. Radio Frequency) na zapalniki zbudowane z mostka półprzewodnikowego. Przedstawiono omówienie teoretyczne oraz wyniki badań eksperymentalnych.

12

Fabrication and thermal properties of Al2TiO5/Al2O3 composites

80%

Li M. , Chen F. , Shen Q. , Zhang L.

Materials Science Poland

|

2010

|

tom Vol. 28, No. 3

663--670

EN

Al2TiO5/Al2O3 composites with various Al2O3 contents were prepared. The phase compositions and microstructure evolution of the samples were observed via XRD and SEM, respectively. The thermal properties, including thermal expansion ratios and the erosion resistance of the Al2TiO5/Al2O3 composites to molten Al, were investigated. The experimental results show that the relative densities of the prepared Al2TiO5/Al2O3 composites are proportional to the Al2O3 content, and that the composite samples with high Al2TiO5 contents have good erosion resistance to molten Al.

13

Analysis of Markov Boundary Induction in Bayesian Networks: A New View From Matroid Theory

80%

Feng D. , Chen F. , Xu W.

Fundamenta Informaticae

|

2011

|

tom Vol. 107, nr 4

415-434

EN

Learning Markov boundaries from data without having to learn a Bayesian network first can be viewed as a feature subset selection problem and has received much attention due to its significance in the wide applications of AI techniques. Popular constraint based methods suffer from high computational complexity and are usually unstable in spaces of high dimensionality. We propose a new perspective from matroid theory towards the discovery of Markov boundaries of random variable in the domain, and develop a learning algorithm which guarantees to recover the true Markov boundaries by a greedy learning algorithm. Then we use the precision matrix of the original distribution as a measure of independence to make our algorithm feasible in large scale problems, which is essentially an approximation of the probabilistic relations with Gaussians and can find possible variables in Markov boundaries with low computational complexity. Experimental results on standard Bayesian networks show that our analysis and approximation can efficiently and accurately identify Markov boundaries in complex networks from data.

14

The effect of surface functional groups of nanosilica on the properties of polyamide 6/SiO2 nanocomposite

80%

Xu Q. , Chen F. , Li X. , Zhang Z.

Polish Journal of Chemical Technology

|

2013

|

tom Vol. 15, nr 3

20-24

EN

The present study investigated the effect of the surface functional groups of nanosilica on the interfacial, crystallization, and thermal stability of polyamide 6/SiO2 (PA6/SiO2) nanocomposite, in which nanosilica was modified in situ with both 3-triethoxysilylpropylamine and 3-methacryloxypropyltrimethoxy silane¬ (KH-550 and KH-570). The FTIR analysis results showed the chemical bonding action between the reacting amino groups of nanosilica and end carboxyl groups of polyamide 6 enhanced with increasing the ratio of KH-550 and KH-570. The XRD spectrum indicated that the crystal structure of PA6/SiO2 nanocomposites tended to form α crystal type that was beneficial to an improvement of mechanical properties, and which was in agreement with the results of mechanical strength measurements. It was also found that crystallization temperature and crystallization rate of PA6/SiO2 nanocomposites were lower than that of neat polyamide 6.

15

Research of Integrated Control Methods and its Simulation for Freeway Mainline and Related Ramp

80%

Chen F. , Jia Y. , Li J.

Przegląd Elektrotechniczny

|

2012

|

tom R. 88, nr 1b

119-122

EN

To relieve traffic congestion during peak hours on freeways, various ramp metering models have been attempted for regulation of the inputs to freeway from entry ramps. Integrated control is a new development to find the combination of control measures for the best road performance and control effectiveness. In consideration of some weaknesses of current intelligent metering, this study proposes an innovative concept and associated local ramp metering approach. From results of a comparative case study with real world traffic flow data in Beijing, the new Intelligent control approach of freeway mainline and related ramp that is proven to significantly output from traditional models, particularly in regards to its effectiveness in minimizing the waiting time of multiple cycles.

PL

W artykule przeanalizowano słabości obecnie stosowanych metod do kontroli przepełnienia w czasie ruchu drogowego i zaproponowano nowa metodę oceny zwalniania tego ruchu. Zaproponowano też inteligentne metody kontroli tego ruchu w tym wjazdu na autostrady.

16

QoE Optimized Resource Allocation in Multiuser OFDM Systems

80%

Chen F. , Qin X. , Wei G.

Przegląd Elektrotechniczny

|

2012

|

tom R. 88, nr 7b

328--331

EN

The resource allocation in multiuser Orthogonal Frequency Division Multiplexing (OFDM) systems is addressed, which aims to maximize the user-perceived quality of services instead of the conventional objective metrics. By introducing the previous application-centric Mean Opinion Score (MOS) assessment model, the problem is formulated as a bounded optimization problem, which is non-concave and difficult to develop a closed-form solution. A heuristic algorithm, which couples bound relaxation technique with further fix and drop operations is then proposed for the final solution. Simulation results indicate that our proposal can improve the overall perceived quality from users’ perspective as well as the fairness between users, in comparison with the classical throughput-oriented algorithm.

PL

Artykuł analizuje system OFDM (orthogonal frequency division multiplexing) do alokacji zasobów przy wielu użytkownikach i przesyle dużych wielkości danych. Metoda wykorzystuje serwisy QoS – Quolity of service i QoE – quality of experience.

17

Microstructure and dielectric properties of La2O3 doped Ti-rich barium strontium titanate ceramics for capacitor applications

71%

Zhang C. , Chen F. , Ling Z. , Jian G. , Li Y.

Materials Science Poland

|

2017

|

tom Vol. 35, No. 4

806--815

EN

Microstructure and dielectric properties of La2O3 doped Ti-rich barium strontium titanate ceramics, prepared by solid state method, were investigated with non-stoichiometric level and various La2O3 content, using XRD, SEM and LCR measuring system. With an increase of non-stoichiometric level, the unit cell volumes of perovskite lattices for the single phase Ti-rich barium strontium titanate ceramics increased due to the decreasing A site vacancy concentration V″A. The unit cell volume increased and then decreased slightly with the increasing La2O3 content. Relatively high non-stoichiometric level and high La2O3 content in Ti-rich barium strontium titanate ceramics contributed to the decreased average grain size as well as fine grain size distribution, which correspondingly improved the temperature stability of the relative dielectric constant. The relative dielectric constant єrRT, dielectric loss tanδRT and the maximum relative dielectric constant єrmax decreased and then increased with the increasing non-stoichiometric level. With the increase of La2O3 doping content, the relative dielectric constant єrRT increased initially and then decreased. The maximum relative dielectric constant єrmax can be increased by applying low doping content of La2O3 in Ti-rich barium strontium titanate ceramics due to the increased spontaneous polarization.

18

Photosystem II activity in the leaves and assimilative branches of alhagi sparsifolia Shap. under brief elevated temperature

71%

Li L. , Li X. , Xu X. , Lin L. , Chen F.

Acta Physiologiae Plantarum

|

2014

|

tom 36

|

nr 07

EN

Leaves and assimilative branches are crucial to the life cycle of Alhagi sparsifolia Shap. that is one of the main shrubs in the southern fringe of the Taklamakan desert. They reduce photosynthesis at midday during summer and exhibit different degrees of adaptability to severe environments. We investigated the changes in the PSII activity of leaves and assimilative branches of under elevated temperature and whether they have the same response and level of tolerance to different temperatures, thus to understand the roles of leaves and assimilative branches of A. sparsifolia in global warming. In this study, the kinetics of induced chlorophyll a fluorescence under heat-stress-induced inhibition of photosystem II in leaves and assimilative branches of A. sparsifolia after 15 min of treatment was investigated. The results show that both the activity and density of reaction centers of leaves are higher than assimilative branch at 35–48°C, and both in the leaves and assimilative branches were decreased above 45°C, the assimilative branches adapted better to the severe environment in terms of light energy transfer, light usage efficiency, and electron transport at 52°C. Assimilative branches had better adaptability to elevated temperature than leaves of A. sparsifolia suggesting that assimilative branches might be more adaptive to severe environment.

19

Spatio-temporal variability of microbial eukaryotic community composition in a large shallow subtropical lake, assessed by 18SrRNA gene sequences

71%

Chen M. , Chen F. , Zhao B. , Qinglong L. W. , Kong F.

Acta Protozoologica

|

2009

|

tom 48

|

nr 3

245-264

20

Expiration date prediction of biocontrol agent prepared with Bacillus subtilis B579 using the accelerated aging method

71%

Zheng Y. , Jiao X. , Chen F. , Wang X. , Wang M.

Polish Journal of Microbiology

|

2016

|

tom 65

|

nr 4

EN

The expiration date of biopesticidal products is an essential feature of their use and storage. In the present work, the expiration date of biocontrol agent was predicted using the accelerated aging method. The available bacteria in Bacillus subtilis B579 biocontrol agent were 3.7 ± 0.2 × 10¹¹ CFU/g. It is calculated that the expiration date of the agent was about 17 months at 25°C. During this period, the available bacteria retained more than 90% of the value in the initial product. Thus, this work suggests the expiration date of biocontrol agents composed with spores could be estimated using the accelerated aging method.