Wyniki wyszukiwania - BazTech

1

RoFa : A Robust and Flexible Fine-Grained Access Control Scheme for Mobile Cloud and IoT based Medical Monitoring

Chen Y., Lei M., Ren W., Ren Y., Qu Z.

Fundamenta Informaticae

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2018

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Vol. 157, nr 1/2

167--184

EN

Cloud computing paradigm is becoming very popular these days. However, it does not include wireless sensors and mobile phones which are needed to enable new emerging applications such as remote home medical monitoring. Therefore, a combined Cloud-Internet of Things (IoT) paradigm provides scalable on-demand data storage and resilient computation power at the cloud side as well as anytime, anywhere health data monitoring at the IoT side. As both the privacy of personal medical data and flexible data access should be provided,attackers exploit diverse social engineering and technology attacks ways, access to personal privacy information stored in the home medical monitoring cloud, with more and more social engineering attacks.Therefore, the data in the Cloud are always encrypted and access control must be operated upon encrypted data together with being fine-grained to support diverse accessibility. Since a plain combination of encryption before access control is not robust and flexible, we propose a scheme referred to as RoFa, with tailored design. The scheme is introduced in a step-by-step manner. The basic scheme (BaS) makes use of cipher-policy attributes based encryption to empower robustness and flexibility. We further propose an advanced scheme (AdS) to improve the computation efficiency by taking the advantages of proxy-reencryption. AdS can greatly decrease the computation overhead on hospital servers due to operation migration. We finally propose an enhanced scheme (EnS) to protect integrity by using aggregate signature. RoFa describes a general framework to solve the secure requirements, and leaves the flexibility of concrete constructions intentionally. We finally compare the robustness and the flexibility of the proposed schemes by performance analysis.

2

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.

3

Accurate Frequency Estimation Based On Three-Parameter Sine-Fitting With Three FFT Samples

Liu X., Ren Y., Chu C., Fang W.

Metrology and Measurement Systems

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2015

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Vol. 22, nr 3

403--416

EN

This paper presents a simple DFT-based golden section searching algorithm (DGSSA) for the single tone frequency estimation. Because of truncation and discreteness in signal samples, Fast Fourier Transform (FFT) and Discrete Fourier Transform (DFT) are inevitable to cause the spectrum leakage and fence effect which lead to a low estimation accuracy. This method can improve the estimation accuracy under conditions of a low signal-to-noise ratio (SNR) and a low resolution. This method firstly uses three FFT samples to determine the frequency searching scope, then – besides the frequency – the estimated values of amplitude, phase and dc component are obtained by minimizing the least square (LS) fitting error of three-parameter sine fitting. By setting reasonable stop conditions or the number of iterations, the accurate frequency estimation can be realized. The accuracy of this method, when applied to observed single-tone sinusoid samples corrupted by white Gaussian noise, is investigated by different methods with respect to the unbiased Cramer-Rao Low Bound (CRLB). The simulation results show that the root mean square error (RMSE) of the frequency estimation curve is consistent with the tendency of CRLB as SNR increases, even in the case of a small number of samples. The average RMSE of the frequency estimation is less than 1.5 times the CRLB with SNR = 20 dB and N = 512.

4

Investigation on the preparation and mechanical properties of porous Cu35Ni15Cr alloy for a molten carbonate fuel cell

Li C., Chen J., Li W., Ren Y., He J.

Materials Science Poland

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2015

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Vol. 33, No. 4

887--893

EN

The preparation process of porous Cu35Ni15Cr alloy was studied in this paper. The effect of ball milling time and sintering temperature on the porosity of Cu35Ni15Cr alloy was identified. It was found that 18 h ball milling and 950 degrees C sintering are the most promising parameters for the preparation of porous Cu35Ni15Cr alloy. The products have a similar to ~62 % porosity. The alloy consists of an alpha phase and beta phase. The influence of deformation temperature and loading rate on the mechanical properties of Cu35Ni15Cr alloys was investigated. The results show that with decreasing deformation temperature, the yield strength and elastic modulus of the porous alloy increase. With the increase of loading rate, the yield strength of these alloys shows an increasing trend, but the elastic modulus is on a steady level.

5

A novel logic-based approach for failure modes mitigation control and quantitative system reliability analyses

Yang D., Ren Y., Wang Z., Liu L., Sun B.

Eksploatacja i Niezawodność

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2015

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Vol. 17, no. 1

100--106

EN

The core idea of reliability design is to mitigate the product’s failure modes. However, for the cross-links among potential failure modes of a complex product, it is very difficult to establish the mapping relationship between failure modes mitigation and quantitative values of reliability, and the decision of failure modes mitigation have to be performed by virtue of experience, which always increase design period. In order to solve these problems, a novel logic-based approach for failure modes mitigation control and quantitative system reliability analyses is provided. Firstly, a hybrid of active and passive control process of reliability design is proposed. Secondly, a novel concept of failure modes correlation set (FMCS) and a determination approach based on deductive theory are presented. According to the changes in failure modes probabilities of occurrence, the reliability formulas of the components and assemblies are provided to depict the effects of failure mode mitigation on reliability of components and assemblies. And then the FMCS mitigation sequence is decided to determine reliability design activities. Thirdly, a closed control process of FMCS mitigation is provided integrated with logic decision method. By exposing the design of a helicopter fuel system, the present study demonstrates that all approaches are feasible, and the relationship between reliability parameters and qualitative design exists. Hence the failure modes mitigation could be controlled for the achievement of quantitative reliability requirements.

PL

Podstawowym problemem w procesie projektowania niezawodności jest ograniczenie przyczyn uszkodzeń produktu. Jednakże, w przypadku sieci połączeń pomiędzy możliwymi przyczynami uszkodzeń złożonego produktu, trudno jest ustalić mapę zależności pomiędzy ograniczaniem przyczyn uszkodzeń i ilościowymi wartościami niezawodności, a decyzje względem ograniczania przyczyn uszkodzeń muszą bazować na własnym doświadczeniu, co znacznie wydłuża okres projektowania. W celu rozwiązania powyższych problemów, zaproponowano oryginalną, opartą na logice, metodę kontroli ograniczania przyczyn uszkodzeń i ilościowej analizy niezawodności systemu. Na wstępie, zaproponowano mieszany proces aktywnej i pasywnej kontroli niezawodności projektu. Następnie, zaprezentowano oryginalną koncepcję zbioru korelacji przyczyn uszkodzeń (FMCS) i metodę oznaczania opartą o teorię dedukcji. Na podstawie zmian dotyczących prawdopodobieństwa występowania przyczyn uszkodzeń, określono wzory niezawodności części i układów w celu pokazania wpływu ograniczania przyczyn uszkodzeń na niezawodność części i układów. Określono następnie ograniczającą sekwencję FMCS, ażeby ustalić założenia dla projektowania niezawodności. Na koniec zaprezentowano zamknięty proces kontroli ograniczania FMCS w powiązaniu z logiczną metodą podejmowania decyzji. Analizując pod tym kątem projekt systemu paliwowego helikoptera, wykazano w niniejszej pracy przydatność wszystkich powyższych metod, jak również związek pomiędzy parametrami niezawodności a projektowaniem jakościowym. Dlatego też ograniczanie przyczyn uszkodzeń powinno być kontrolowane w celu osiągnięcia wymaganej niezawodności ilościowej.

6

Preparation of ITO films using a spray pyrolysis solution containing an acetylacetone chelating agent

Gao Y., Zhao G., Duan Z., Ren Y.

Materials Science Poland

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2014

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Vol. 32, No. 1

66--70

EN

Indium tin oxide (ITO) films were deposited on soda-lime glass substrates by the spray pyrolysis method using a spray solution of InCl33H2O as a precursor, SnCl45H2O as a dopant and acetylacetone (AcAcH) as a chelating agent. The effect of the addition of AcAcH to the spray solution on the surface morphology of the ITO film was investigated. The surface quality of the film prepared from the spray solution with AcAcH was better than that without AcAcH. The ITO film with the thickness of 230 nm, using the spray solution with AcAcH, exhibited the lowest resistivity of 4.75 × 10􀀀4 Wcm and higher optical transmittance of 85 %, respectively.

7

Investigation on compressive behavior of Cu-35Ni-15Al alloy at high temperatures

Li C., Chen J., Li W., Hu Y., Ren Y., Qiu W., He Junjie, Chen J.

Materials Science Poland

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2014

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Vol. 32, No. 3

341--349

EN

Microstructures and mechanical properties of Cu–35Ni–15Al alloy in cast and porous states were studied by scanning electron microscopy and compression tests. The influence of porosity, deformation temperature and loading rate on mechanical properties of the two kinds of alloys was investigated. The results show that the as cast alloy and porous alloys have almost the same phase constitution: Cu rich phase, Ni rich phase and K intermetallics. The yield strength of porous alloys increases continuously with decreasing porosity, the relationship between porosity and yield stress follows Gibson-Ashby equation.With decreasing deformation temperature, the yield strength of as cast alloy and porous alloy increase. With the increase of loading rate, the yield strength of these alloys shows an increasing trend. After compression, the microstructure of as cast alloy is more uniform, and porous alloys are more prone to have localized deformations.

8

Location allocation planning of logistics depots using genetic algorithm

Ren Y., Awasthi A.

Research in Logistics & Production

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2012

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Vol. 2, No. 3

247-257

EN

Location planning of logistics depots and customer allocation are important decisions in supply chain network design. A carefully planned network design positively impacts the economics of business organizations and their competitivity in national and international markets. In this paper, we present a genetic algorithm based approach for solving location allocation planning problem of logistics depots. The problem is solved considering multiple criteria such as minimal distance, travel cost, travel time etc. A numerical application is provided to demonstrate the proposed approach.

9

Development of Near Sets Within the Framework of Axiomatic Fuzzy Sets

Wang G., Ren Y., Liu X.

Fundamenta Informaticae

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2012

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Vol. 118, nr 3

291-304

EN

Near sets result from a generalization of rough sets, which introduced by Peters in 2006, and later formally defined in 2007. Near set theory provides a new framework for representation of objects characterized by the features that describe them. AFS (Axiomatic Fuzzy Set) theory was proposed by Liu (1998), which is a semantic methodology relating to the fuzzy theory. In this paper, a new version of near sets based on AFS theory is established, in which every object has an AFS fuzzy description with definitely semantics. The proposed approach to assessing the nearness (closeness) of objects is not defined directly using a distance metric, but depend on similarity of their fuzzy descriptions. It is also a natural linguistic description that is similar to humans perception. Moreover, an approach to set approximation based on the union of families of objects with similar fuzzy descriptions is given. The near sets based on AFS theory can be viewed as a new development of near sets within the fuzzy context.

10

Four positive periodic solutions of a discrete time Lotka-Volterra competitive system with harvesting terms

Liu X., Ren Y., Li Y.

Opuscula Mathematica

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2011

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Vol. 31, no. 2

257-267

EN

In this paper, by using Mawhin's continuation theorem of coincidence degree theory, we establish the existence of at least four positive periodic solutions for a discrete time Lotka-Volterra competitive system with harvesting terms. An example is given to illustrate the effectiveness of our results.

11

Ontological multi-view failure modeling for ippd

Ren Y., Sun B., Feng Q., Zeng S.

Eksploatacja i Niezawodność

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2011

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nr 2

35-41

EN

Reliability engineering includes series of failure focused technology and management activities running throughout the entire product development cycle. Only these activities are effectively integrated and numerous relevant failure data is synthetically applied, the intent for progressively identifying failure and continuously improving reliability can be obtained. In current engineering practice, the reliability data and knowledge produced in different development phases cannot be efficiently shared and reused. There still exist difficulties in interoperating between different reliability activities. This paper establishes the failure ontology models that contain global failure ontology model, functional failure ontology model and hardware failure ontology model. In virtue of this ontology model, the reliability activities are seamlessly integrated into the integrated product and process development (IPPD). In this model, the evolution process of failure cognition during each development phases is considered. Base on this ontology model, a reliability engineering environment is constructed with the support of PLM (Product Lifecycle Management) platform to verify the ontology model's correctness and applicability.

PL

Inżynieria niezawodności zajmuje się prowadzeniem licznych działań w zakresie technologii uszkodzeń i zarządzania uszkodzeniami w ciągu całego cyklu rozwoju produktu. Stopniowa identyfikacja uszkodzeń oraz ciągła poprawa niezawodności jest możliwa tylko wtedy, gdy działania te zostaną skutecznie zintegrowane, przy syntetycznym uwzględnieniu szeregu istotnych danych dotyczących uszkodzeń. Obecna praktyka inżynieryjna nie pozwala na efektywną wymianę i ponowne wykorzystanie danych i wiedzy pochodzących z różnych faz rozwoju produktu. Ciągle jeszcze napotyka się trudności dotyczące interoperacyjności różnych działań ukierunkowanych na utrzymanie niezawodności. W artykule opracowano model ontologii uszkodzeń obejmujący modele ontologii uszkodzeń globalnych, funkcjonalnych i sprzętowych. Za sprawą tego modelu ontologicznego, działania niezawodnościowe stają się spójną częścią zintegrowanego rozwoju produktu i procesów (IPPD). Proponowany model uwzględnia ewolucję wiedzy na temat uszkodzenia w ciągu poszczególnych faz rozwoju. Na podstawie prezentowanego modelu ontologicznego stworzono środowisko inżynierii niezawodności oparte na platformie PLM (Zarządzanie Cyklem Życia Produktu) pozwalające zweryfikować poprawność i możliwość zastosowania omawianego modelu.