Wyniki wyszukiwania - Biblioteka Nauki

1

On the Generative Power of !-Grammars and ω-Automata

100%

Chen Z.

Fundamenta Informaticae

|

2011

|

tom Vol. 111, nr 2

119-145

EN

An ω-grammar is a formal grammar used to generate ω-words (i.e. infinite length words), while an ω-automaton is an automaton used to recognize ω-words. This paper gives clean and uniform definitions for ω-grammars and ω-automata, provides a systematic study of the generative power of ω-grammars with respect to ω-automata, and presents a complete set of results for various types of ω-grammars and acceptance modes. We use the tuple (σ, ρ, π) to denote various acceptance modes, where σ denotes that some designated elements should appear at least once or infinitely often, ρ denotes some binary relation between two sets, and π denotes normal or leftmost derivations. Technically, we propose (σ, ρ, π)-accepting ω-grammars, and systematically study their relative generative power with respect to (ρ,π)-accepting ω-automata. We show how to construct some special forms of ω-grammars, such as ε-production-free ω-grammars. We study the equivalence or inclusion relations between ω-grammars and ω-automata by establishing the translation techniques. In particular, we show that, for some acceptance modes, the generative power of ω-CFG is strictly weaker than ω-PDA, and the generative power of ω-CSG is equal to ω-TM (rather than linearbounded ω-automata-like devices). Furthermore, we raise some remaining open problems for two of the acceptance modes.

2

Zastosowanie sieci komórkowych do wykrywania konturów w obrazach medycznych

100%

Chen Z.

Przegląd Elektrotechniczny

|

2009

|

tom R. 85, nr 4

56-58

PL

Artykuł przedstawia teoretyczne i praktyczne aspekty sieci komórkowych w zastosowaniu do wykrywania konturów w obrazach medycznych. Na podstawie obrazu wycinka skóry zwierzęcej przedstawiono i przedyskutowano różne aspekty metodologii obliczeń naturalnych przy użyciu sieci komórkowych.

EN

There is a strong need for integrated study of both theoretical and practical aspects of cellular automata (CA). In this article we report our ongoing work of exploring the nature of CA through an experimental study, focusing on an application of CA for edge detection in medical images. Through an example we describe the algorithm developed, followed by a discussion. The main theme of this paper is to advocate a thorough analysis of the methodology in the context of natural computing. We also point out the indication of such integrated study to education.

3

Wind turbines - a cost effective power source

63%

Chen Z. , Blaabjerg F.

Przegląd Elektrotechniczny

|

2004

|

tom R. 80, nr 5

464-469

EN

The global electrical energy consumption is steadily rising and consequently, there is a demand to increase the power generation capacity. A significant percentage of the required capacity increase can be based on renewable energy sources. Wind turbine technology, as the most cost effective renewable energy conversion system, will play an important part in our future energy supply. In this paper, firstly the basic principle of wind power conversion is briefed, then various configurations of wind turbine technology are presented. Finally, the developments and tends are discussed.

PL

Cafkowita konsumpcja energii stale wzrasta i dlatego istnieje potrzeba zwiększania mozliwosci generowania energii. Znaczącą wartością generowanej energii może być energia pozyskiwana ze źródeł odnawialnych. Turbiny wiatrowe, jako najbardziej efektywne kosztowo źródło konwersji energii mogq odgrywać znaczacą rolę w przyszłych systemach zasilania. W prezentowanej pracy przedstawiono podstawowe zasady konwersji energii wiatrowej, a następnie zaprezentowano różne konfiguracje turbin wiatrowych. Przedstawiono też dyskusję tendencji rozwojowych w tej dziedzinie.

4

Phylogenetic positions of Aspidisca steini and Euplotes vannus within the order Euplotida [Hypotrichia: Ciliophora] inferred from complete small subunit ribosomal RNA gene sequences

63%

Chen Z. , Song W.

Acta Protozoologica

|

2002

|

tom 41

|

nr 1

5

Complete Assignment of All 13C NMR Signals of Cs Symmetric Monoazafullerene Derivatives by Comparison of Experimental and Calculated Spectra

51%

Hauke F. , Chen Z. , Hirsch A.

Polish Journal of Chemistry

|

2007

|

tom Vol. 81, nr 5-6

971-983

EN

The complete assignment of all 31 13C NMRsignals which are due to the fullerene carbon atoms of monoazafullerene derivatives has been carried out for the first time by the systematic comparison of experimental and theoretical spectra calculated by high level DFT methods (GIAO-B3LYP/6-31G*/B3LYP/6-31G*). The assignment is facilitated by the striking similarities of the signal patterns of the sp2-fullerene carbon atoms of two different families of such heterofullerene derivatives with both aryl and alkyl addends.

6

Comparative investigations of nonlinear and linear observers for a highly manoeuvrable target in sliding mode guidance

51%

Wang Y. , Sun M. , Du S. , Chen Z.

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2017

|

tom Vol. 65, nr 2

233--245

EN

Target manoeuvre is one of the key factors affecting guidance accuracy. To intercept highly maneuverable targets, a second-order sliding-mode guidance law, which is based on the super-twisting algorithm, is designed without depending on any information about the target motion. In the designed guidance system, the target estimator plays an essential role. Besides the existing higher-order sliding-mode observer (HOSMO), a first-order linear observer (FOLO) is also proposed to estimate the target manoeuvre, and this is the major contribution of this paper. The closed-loop guidance system can be guaranteed to be uniformly ultimately bounded (UUB) in the presence of the FOLO. The comparative simulations are carried out to investigate the overall performance resulting from these two categories of observers. The results show that the guidance law with the proposed linear observer can achieve better comprehensive criteria for the amplitude of normalised acceleration and elevator deflection requirements. The reasons for the different levels of performance of these two observer-based methods are thoroughly investigated.

7

Engineering example of the constraint forces in non-holonomic mechanical: forklift-truck robot motion. Part I

51%

Haddout S. , Guennoun M. A. , Chen Z.

Archives of Control Sciences

|

2018

|

tom Vol. 28, No. 3

483--506

EN

In the presented paper, a problem of nonholonomic constrained mechanical systems is treated. New methods in nonholonomic mechanics are applied to a problem of a Forklift-truck robot motion. This method of the geometrical theory of general nonholonomic constrained systems on fibered manifolds and their jet prolongations, based on so-called Chetaev-type constraint forces. The relevance of this theory for general types of nonholonomic constraints, not only linear or affine ones, was then verified on appropriate models. On the other hand, the equations of motion of a Forklift-truck robot are highly nonlinear and rolling without slipping condition can only be expressed by nonholonomic constraint equations. In this paper, the geometrical theory is applied to the above mentioned mechanical problem. The results of numerical solutions of constrained equations of motion, derived within the theory, are presented.

8

Forecasting Modeling and Analysis of Power Engineering in China Based on Semi-Parametric Regression Model

51%

Wang X. , Yu B. , Chen Z. , Hou L.

Przegląd Elektrotechniczny

|

2013

|

tom R. 89, nr 3b

161--169

EN

Electricity consumption forecasting is considered one of the most important tasks in energy planning, and it has great significance on management decision-making for power generation organizations and power policy adjustments for governments. In this paper, we present a new semi-parametric regression model for consumption forecasting in electrical power systems. We have used the distribution function of student residuals to replace the nonparametric component of the traditional semi-parametric model, thus eliminating the effects of the residual disturbance term according to the change trend of the consumption data themselves. Then, we use differential element theory set information aggregation intervals to create a dynamic weight distribution and improve the forecasting accuracy of the prediction models. Compared with general linear models, our models make statistical inferences and can automatically regulate the boundary effect, which gives the forecast result a higher accuracy. To present a case study, we use the historical data of electricity consumption and related influential factors in China from 1981 to 2010. The simulation results show that both in the model building stage and in the testing stage for this particular case, the SPRM prediction approach proposed in this paper outperforms the other two contrast models, the MAPE of SPRM is 3.21%, much lower than the other two values 3.84% and 13.07%.

PL

W artykule opisano model regresji semiparametrycznej do przewidywania zużycia energii elektrycznej w systemach elektroenergetycznych. W celu eliminacji wywołujących zakłócenia, nieparametrycznych składowych w tradycyjnym modelu semiparametrycznym, zastosowano rozkład studenta. Wykorzystano także metodę różnicową w ustalaniu interwałów zbierania danych, analizowanych przy przewidywaniu. Działanie i skuteczność modelu zweryfikowano z wykorzystaniem prawdziwych danych z lat 1981 do 2010.

9

A Low-Loss Ka-Band Distributed Metal-Air-Metal MEMS Phase Shifter

51%

Chen A. , Jiang W. , Chen Z. , Li Y.

Przegląd Elektrotechniczny

|

2013

|

tom R. 89, nr 7

77--80

EN

A 4-bit wideband distributed phase shifter has been developed for Ka-band operation. The design results show that the digital shifter has four basic phases of 11.25o, 22.5o, 45o, 90o and thus 16 kinds of phase states can be constructed from the combination of them. The simulation results also demonstrates that the insertion coefficient is better than -1.37 dB, the phase error is less than 3.983o at 30GHz, and the reflection coefficient is lower than -10dB from 25GHz to 35GHz for each state. This low-loss distributed metal-air-metal MEMS phase shifter can be well applied to phased arrays.

PL

W artykule opisano 4-bitowy szerokopasmowy przesuwnik fazy zaprojektowany do pasma Ka. Przesuwnik ma cztery ]główne fazy: 11.25o, 22.5o, 45o, 90o i 16 kombinacji między nimi. Błąd jest mniejszy niż 3.983o przy 30GHz.

10

Grey state model and forecasting control of complicated systems

51%

Chen M.-Y. , Chen W. , Chen Z.

Systems Science

|

2005

|

tom Vol. 31, no 3

37-47

EN

This paper presents an outline of complicated system and the use of grey system theory. An approach to grey forecasting control of complicated systems is proposed. At the same time, a grey forecasting controller, which is to control the system's behaviour in advance, is designed. Such a system designed here may be expected to get good control effects, especially it is suitably applied to the controlled objects with long time lag and without complete model information.

11

Robotic contaminated soil excavation with dust suppression

51%

Danko G. , Daemen Z. , Chen Z.

Prace Naukowe Instytutu Górnictwa Politechniki Wrocławskiej. Konferencje

|

1998

|

tom Vol. 82, nr 21

74-84

EN

A closed-process, continuous, Robotic Excavator (REX) with fine depth control is being developed for the selective excavation of plutonium-contaminated soil. A layer of soil of adjustable thickness, typically 1-5 cm in depth, can be cut with REX until background radiation is reach behind the excavator. Contamination sensor can be mounted on the excavator for in situ evaluation of the cleanup. Selective soil excavation may reduce the volume of the harvested soil. Due to fine cutting depth adjustment, the soil volume to be excavated can be kept to a minimum, reducing disposal cost as well as the adverse effects of disturbance to the natural ecosystem. REX is provided with a Rotating Cutting and Loading Head (RCLH), which includes two counterrotating, high-angle conveyor belts to lift the soil as well as vegetation up to 1 meter, the height of the pneumatic loading hopper. Soil and vegetation are moved by the hydraulically powered belts which are equipped with cutting blades. The continuous, closed materials handling system of REX eliminates dust generation and contaminated material spill, and provides consistent excavation quality. Test results with REX on an uncontaminated natural as well as a simulated desert surface have shown that soil as well as light vegetation can be excavated without spoilage. The closed material transport an high effiecient dust control system can reduce radioactive recontamination during the cleanup operation.

PL

Opracowywana jest koparka-robot (REX) z zamkniętym procesem i z możliwością dokładnej regulacji głębokości kopania, przeznaczona do pracy ciągłej przy selektywnym usuwaniu gruntu skażonego plutonem. Warstwa gruntu o regulowanej grubości, typowo głęboka na 1-5 cm, może być usuwana za pomocą koparki REX aż grunt za koparką będzie charakteryzował się naturalnym promieniowaniem. Do oceny in situ oczyszczania, na koparce można zainstalować czujniki skażenia promieniotwórczego. Selektywne usuwanie ziemi może zredukować objętość zbieranej ziemi. Dzięki precyzyjnie regulowanej głębokości ścinania, objętości gruntu do wykopania można ograniczyć do minimum, zmniejszając przez to koszty usuwania jak i ujemne skutki zakłócenia naturalnego ekosystemu. REX wyposażony jest w Obrotową Głowicę Kopiącą i Ładującą (RCLH), która skład się z przeciwbieżnych taśm przenośnikowym o dużym kącie nachylenia do podnoszenia gleby i roślinności na wysokość 1m, na jakiej znajduje się pneumatyczny lej załadowczy. Gleba i roślinność przenoszone są przez hydraulicznie napędzane taśmy wyposażone w ostrze tnące. Ciągły, zamknięty system transportu i przeładunku materiału REXa eliminuje powstawanie kurzu i wycieku skażonego promieniotwórczo materiału, zapewniając stałą jakość kopania. Wyniki prób REXa przeprowadzonych na nieskażonej naturalnej oraz symulowanej powierzchni pustyni wykazały, że ziemia i drobna roślinność mogą być usuwane bezodpadowo. Zamknięty transport materiału i wysoce wydajny układ kontroli kurzu mogą zmniejszyć ponowne skażenie radioaktywne w trakcie operacji oczyszczania.

12

An integrated inverter for a single-phase single-stage grid-connected PV system based on Z-source

51%

Chen Z. , Zhang X. , Pan J.

|

13

A quantum chemical study on thermolysis initiation mechanisms and impact sensitivity of energetic materials

51%

Xu X. , Xiao H. , Fan J. , Chen Z.

Central European Journal of Energetic Materials

|

2005

|

tom Vol. 2, nr 4

5-21

EN

Thermolysis initiation mechanisms of polynitro compounds, tetrazole derivatives and their metallic salts, and cage high energy density compounds have been investigated using quantum chemical approaches. Our calculations showed that the trigger bonds whose breaking initiate a decomposition or an explosion were C-NO2 or N-NO2 bonds for nitro derivatives of benzene and aminobenzenes, CL-20 and polynitroadamantanes. Explosion of nitro derivatives of phenol and toluene were most likely triggered by the isomerization reactions involving the H-shift. Due to larger strain energy, the trigger bond was found to be the C-C bond in the framework of polynitrocubanes. Regarding tetrazoles and their metallic salts, opening of the tetrazole ring, i.e., scission of the N-N bond, followed by formation of N2 molecules, initiate explosive reactions. We found for energetic materials having similar molecular structures and following similar thermal decomposition mechanisms, the bond orders of the trigger bond and the activation energy to break the bond were directly related to the impact sensitivity. We thus proposed two criteria used to evaluate the relative ordering of impact sensitivity for energetic materials with similar structures: the smaller the bond order, the more sensitive an energetic material, which was called the principle of the smallest bond order (PSBO). And the higher the activation energy, the less sensitive a material was. We demonstrated that in most cases the PSBO was equivalent to the activation energy criterion. The former was more convenient and easier to obtain while the latter could be applied more universally.

14

Prognozowanie uszkodzeń przekładni mostu napędowego z wykorzystaniem wstępnego przetwarzania sygnału drgań w połączeniu z sieciami neuronowymi typu RBF

51%

Shao Y. , Li X. , Mechefske C. K. , Chen Z.

Eksploatacja i Niezawodność

|

2009

|

tom nr 4

57-64

PL

Przekładnia mostu pędnego stanowi kluczową część samochodowego układu przeniesienia napędu, a trafne przewidywanie uszkodzeń jest istotne dla bezpiecznego użytkowania samochodu. Jednakże precyzja przewidywania uszkodzenia przekładni jest obecnie niska ze względu na zmienne prędkości obrotowe i zmieniające się obciążenia występujące podczas używania pojazdu. W celu zredukowania zmienności drgań i zwiększenia trafności przewidywania trwałości resztkowej przekładni, w artykule zaproponowano nową metodę predykcyjną, która łączy sieć neuronową o radialnych funkcjach bazowych (RBF) i rekurencyjne przetwarzanie wstępne. Metoda rekurencyjnego przetwarzania wstępnego zmniejsza wpływ zmienności chwilowego obciążenia i prędkości na charakterystyczne parametry uzyskane z sygnałów drganiowych. Sieć neuronowa typu RBF modeluje nieliniowe charakterystyki przenoszenia napędu przez przekładnię mostu pędnego. Sieć taka charakteryzuje się zachowaniem samoadaptacyjnym i szybką zbieżnością. Wyniki badań symulacyjnych i eksperymentalnych pokazują, że ta nowa metoda może pozwolić na udoskonalenie tradycyjnych metod predykcyjnych oraz osiąganie wysokiej precyzji w przewidywaniu uszkodzeń przekładni mostu pędnego.

EN

The rear axle gear is a key part of the automobile transmission system and accurate damage prediction is important for car safety. However, the precision of gear damage prediction is currently low because of the varying rotating speeds and the changing loads when a truck is in use. In order to reduce the fluctuation of vibrations and enhance the predicting accuracy of gear residual life, a new predictive method, which combines the Radial Basis Function (RBF) neural network with recursive preprocessing is proposed in this paper. The recursive preprocessing method reduces the effects of instantaneous load and speed fluctuations on the characteristic parameters extracted from vibration signals. The RBF neural network models the non-linear characteristics of the rear axle gear transmission. The RBF neural network is characterized by its self-adaptive behavior and its rapid convergence. The simulated and experimental results have shown that this new method can enhance traditional prediction methods and obtain high precision for the damage prediction of rear axle gears.

15

Surfactant assisted removal of engine oil from synthetic soil

51%

Ramamurthy A. S. , Chen Z. , Li X. , Azmal M.

Environment Protection Engineering

|

2015

|

tom Vol. 41, nr 2

67--79

EN

Effectiveness of surfactants SDS (sodium dodecyl sulfate), AOT (sodium dioctyl sulfosuccinate) and Brij 35 (polyoxyethylene lauryl ether) in removing residual oil from soils have been determined. Experimental results indicated that oil desorption efficiencies with surfactants are 7 to 18 times higher than using water alone. 0.6% Brij 35 at was the most effective surfactant to remove oil from soil, and it did not display any significant change in oil desorption with pH changes. A comparison study also showed that pore volume was a more significant parameter than soil washing flow rate to improve oil desorption.

16

Research on excitation control system of multi-functional flexible power conditioner

51%

Chen Z. , Zou X. , Duan S. , Wei H.

Przegląd Elektrotechniczny

|

2011

|

tom R. 87, nr 4

172-175

EN

A new kind of FACTS equipment, the multi-functional Flexible Power Conditioner (FPC), is proposed in this paper. The proposed equipment makes use of an advanced synchronous condenser and a flywheel with an AC excitation and vector control technology based power electronics device. It can perform multi--functions including energy storage, active and reactive power generation when used in power systems to enhance the stability of it. A 10kVA excitation control system of FPC was developed. Based on the analysis of control strategy, the start, steady and dynamic performances are studied experimentally. Experimental results show that soft start and various operation states can be implemented. And the excitation control system can be applied to flywheel type FPC system.

PL

Zaproponowano nowy rodzaj urządzenia FACTS - wielofunkcyjny, elastyczny kondycjoner mocy FPC. Kondycjoner wykorzystuje koło zamachowe jako zasobnik energii. Urządzenie umożliwia magazynowanie energii, generację bierną lub czynną do poprawy stabilności systemu. Opracowano system sterowania o mocy 10 kVA. Start, ciągła praca i właściwości dynamiczne systemu były analizowane eksperymentalnie.

17

Effects of factor price distortion oniIndustrial environmental efficiency: evidence from environmental pollution in China

51%

Sun X. , Chen Z. , Huang L.

Polish Journal of Environmental Studies

|

2020

|

tom 29

|

nr 5

18

A Simple Modeling Method to Identify the Kinematic Errors of Machine Tool Rotary Table

51%

Zhang Y. , Fu J. , Chen Z.

Przegląd Elektrotechniczny

|

2013

|

tom R. 89, nr 3b

134--135

EN

A Simple modelling method to identify the kinematic errors of machine tool table is proposed. According to the structure of the machine tool, based on rigid body kinematics, the motion coordinates of major components of the machine tool table was reasonable set up, and the error propagation of the machine tool rotary table was described. The mathematical expression of this model is simple, and the physical meaning is understandable. It is a theoretical foundationon for further error recognition and error compensation.

PL

W artykule przedstawiono metodę rozpoznania błędów kinematycznych stołu do obrabiarki. Wyznaczono funkcje ruchu najważniejszych elementów oraz opisano sposób dalszej propagacji powstałego uchybu. Na tej podstawie możliwe było rozpoznanie błędu i jego kompensacja.

19

An efficient provably secure certificateless aggregate signature applicable to mobile computation

51%

Xiong H. , Wu Q. , Chen Z.

Control and Cybernetics

|

2012

|

tom Vol. 41, no. 2

373-391

EN

An aggregate signature scheme allows a public algorithm to aggregate n signatures on n distinct messages from n signers into a single signature. By validating the single resulting signature, one can be convinced that the messages have been endorsed by all the signers. Certificateless aggregate signatures allow the signers to authenticate messages without suffering from the complex certificate management in the traditional public key cryptography or the key escrow problem in identity-based cryptography. In this paper, we present a new efficient certificateless aggregate signature scheme. Compared with up-to-date certificateless aggregate signatures, our scheme is equipped with a number of attracting features: (1) it is shown to be secure under the standard computational Diffie-Hellman assumption in the random oracle model; (2) the security is proven in the strongest security model so far; (3) the signers do not need to be synchronized; and (4) its performance is comparable to the most efficient up-to-date schemes. These features are desirable in a mobile networking and computing environment where the storage/ computation capacity of the end devices are limited, and due to the wireless connection and distributed feature, the computing devices are easy to be attacked and hard to be synchronized.

20

Middle Eocene flora of Huadian, Jilin Province, Northeastern China

51%

Manchester S. R. , Chen Z. , Geng B. , Tao J.

Acta Palaeobotanica

|

2005

|

tom 45

|

nr 1