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PL
Nieliniowy chemiczny „odcisk palca” NCF (nonlinear chemical fingerprint) to nowa metoda analityczna szeroko ostatnio stosowana do identyfikacji i oceny materiałów. Zastosowano ją do oceny jakości różnych odmian zielonej herbaty. Po raz pierwszy zaprezentowano koncepcję wykorzystania widma NCF rośliny złożonej do rozpoznawania jej odmiany, jak również szczegółowo omówiono właściwości NCF.
EN
Seven various Chinese green teas were characterized by using the nonlinear chem. fingerprint method with electrochem. detection. The aq. suspensions of tea were treated with H2SO4, MnSO4 and Me2CO. The 1st grade Maojian tea (green bamboo mountain tea) showed the highest quality.
EN
Seismic impedance inversion is a well-known method used to obtain the image of subsurface geological structures. Utilizing the spatial coherence among seismic traces, the laterally constrained multitrace impedance inversion (LCI) is superior to trace-by-trace inversion and can produce a more realistic image of the subsurface structures. However, when the traces are numerous, it will take great computational cost and a lot of memory to solve the large-scale matrix in the multitrace inversion, which restricts the efficiency and applicability of the existing multitrace inversion algorithm. In addition, the multitrace inversion methods are not only needed to consider the lateral correlation but also should take the constraints in temporal dimension into account. As usual, these vertical constraints represent the stratigraphic characteristics of the reservoir. For instance, total-variation regularization is adopted to obtain the blocky structure. However, it still limits the magnitude of model parameter variation and therefore somewhat distorts the real image. In this paper, we propose two schemes to solve these issues. Firstly, we introduce a fast algorithm called blocky coordinate descent (BCD) to derive a new framework of laterally constrained multitrace impedance inversion. This new BCD-based inversion approach is fast and spends fewer memories. Next, we introduce a minimum gradient support regularization into the BCD-based laterally constrained inversion. This new approach can adapt to sharp layer boundaries and keep the spatial coherence. The feasibility of the proposed method is illustrated by numerical tests for both synthetic data and field seismic data.
EN
The convergence and divergence are two common phenomena in swarm intelligence. To obtain good search results, the algorithm should have a balance on convergence and divergence. The premature convergence happens partially due to the solutions getting clustered together, and not diverging again. The brain storm optimization (BSO), which is a young and promising algorithm in swarm intelligence, is based on the collective behavior of human being, that is, the brainstorming process. The convergence strategy is utilized in BSO algorithm to exploit search areas may contain good solutions. The new solutions are generated by divergence strategy to explore new search areas. Premature convergence also happens in the BSO algorithm. The solutions get clustered after a few iterations, which indicate that the population diversity decreases quickly during the search. A definition of population diversity in BSO algorithm is introduced in this paper to measure the change of solutions’ distribution. The algorithm’s exploration and exploitation ability can be measured based on the change of population diversity. Different kinds of partial reinitialization strategies are utilized to improve the population diversity in BSO algorithm. The experimental results show that the performance of the BSO is improved by part of solutions re-initialization strategies.
4
Content available remote Partial Discharge Location in Oil Using Ultrasonic Phased Array
EN
A new PD-locating method based on an ultrasonic phased array was proposed. First, a PD-locating system was established. Second, TCT algorithm was used to focus the wide-band signals on the narrowband signals. Then, the improved MUSIC algorithm was used to detect the direction and elevation angles. Finally, we performed a global search of the min-distance function with the genetic algorithm to obtain the accurate geometric space coordinates of the PD source. The result from the experiment shows that the location error was 5.6 cm.
PL
W artykule przedstawiono metodę lokalizacji wyładowań niezupełnych, opartą na metodzie ultradźwiękowej PA. Opis składa się z czterech części, odnoszących się do etapów opracowywania. Algorytm poddano weryfikacji eksperymentalnej.
PL
W artykule omówiono możliwe przyczyny niezbalansowania napięcia punktu neutralnego w przekształtniku z diodami poziomującymi oraz wpływ na to napięcie nakładania się fal nośnych w modulacji. W przedstawionym schemacie modulacji nakładanie się fal jest wynikiem zwiększenia amplitudy jednej z tych fal. Przedstawiono dyskusję wpływu proponowanej techniki na zmiany napięcia punktu neutralnego oraz zależności między współczynnikiem modulacji, stopniem nakładania się fal i współczynnikiem mocy. Wyniki badań symulacyjnych potwierdzają skuteczność działania.
EN
To address the neutral point voltage balance problem of the diode clamped three-level inverter, this paper analyzes the causes of unbalanced neutral point voltage and studies the impact of the carriers overlap on the neutral point voltage. A simple neutral point voltage control scheme using carrier overlapping sinusoidal pulse width modulation (SPWM) is proposed. The proposed scheme does not change the modulation waves, the amplitude of one carrier is increased to overlap the other carrier, and the neutral point voltage can be maintained balance by increasing the carriers amplitudes. The influence of the vertical overlap of carriers on neutral point balance is investigated in depth. The relationship among the neutral point voltage variation, modulation index, overlap of the carriers, and power factor is discussed in this paper. Simulation results show the neutral point voltage balancing control strategy based on SPWM is effective.
EN
A multi-objective optimization model which effectively replicates different perspectives is presented to address the optimal allocation of DG units. To offer diverse solutions, NSGA-II is applied to the nonlinear, combinatorial three-objective optimization problem. The encouraging simulation results suggest that the proposed approach not only optimally allocate DG units with benefits of reducing power loss, improving system’s reliability and decreasing pollutant emissions simultaneously but also provide alternative options and facilitate to make more rational evaluations.
PL
W artykule zaproponowano model optymalizacji wielozadaniowej na potrzeby rozmieszczenia rozproszonych generatorów energii. Dla zapewnienia różnorodności aplikacji, zastosowano algorytm NSGA-II do nieliniowej, kombinacyjnej optymalizacji trzyzadaniowej. Przedstawiono wyniki badań symulacyjnych potwierdzających skuteczność działania, ograniczenie strat mocy i redukcję emisji zanieczyszczeń.
7
Content available remote Application of flywheel energy storage to damp power system oscillations
EN
Flywheel energy storage system (FESS) is believed to be a potential solution for power quality improvements. This paper proposed a new idea of using a large-mass varying-speed flywheel as an energy storage element to damping power system electromechanical oscillations. In the paper, the FESS is studied in the context of a single-machine infinite-bus (SMIB) power system. The mathematical model of the SMIB power system including a FESS is established, and the Phillips-Heffron controI structure of the power system is described. Based on the principle of the complex torque coefficient (CTC) method, the expression of the complex electromagnetic torque of the entire power system inctuding the FESS unit is derived. A 10 kW prototype of FESS, which consists of a double-fed induction machine (DFIM) and a voltage-source pulse width modulation (PWM) rectifier-inverter used as an AC exciter, is developed. Simulation and experiment results demonstrate that it is effective in damping the power system oscillations.
PL
System magazynowania energii typu FESS (z kołem zamachowym) może być potencjalnym rozwiązaniem problemu poprawy jakości energii. Artykuł omawia zastosowanie systemu FESS do tłumienia oscylacji w systemach mocy. Przedstawiono model matematyczny systemu ze strukturą sterowania typu Philips-Heffron. Bazując na metodzie współczynnika momentu wyprowadzono model momentu elektromagnetycznego w systemie mocy. Zabadano model prototypu 10 KW z podwójnie zasilaną maszyną indukcyjną i żródłem napięcia typu PWM. Symulacje i eksperymenty potiwrdziły zdolnosć tłumienia oscylacji.
EN
ZnO thin films doped with aluminum (AZO) were deposited on silicon dioxide covered type texturized Si substrates by radio frequency magnetron sputtering, to fabricate AZO/SiO2/p-Si heterojunction, as an absorber for ultraviolet cell. The microstructure, optical and electrical properties of the Al-doped ZnO films were characterized by XRD, SEM, UV-VIS spectrophotometer, current-voltage measurement, and four point probe technique, respectively. The results show that AZO films are of good quality. The electrical junction properties were investigated by I-V measurement, which reveals that the heterojunction shows rectifying behavior under a dark condition. The ideality factor and the saturation current of this diode are 24.42 and 8.92×10-5 A, respectively. And the values of IF/IR (IF and IR stand for forward and reverse current, respectively) at 10 V are found to be as high as 38. It shows fairly good rectifying behavior indicating formation of a diode between AZO and p-Si.
EN
A novel ITO/SiO2/np-silicon violet and blue enhanced photovoltaic device with SINP structure has been fabricated by thermal diffusion of phosphorus. The shallow junction was formed to enhance the spectral responsivity within the wavelength range of 400-600 nm. An ultrathin silicon dioxide was thermally grown at low temperature and RF sputtering of ITO antireflection coating to reduce the reflected light and enhance the sensitivity. The crystalline structure, optical and electric properties of ITO film were determined by an XRD, UV-VIS spectrophotometer, a four point probe and the Hall effect measurement, respectively. The results show that ITO film has high quality. The current-voltage (I-V) characteristics, spectral response and responsivity of the photovoltaic device with high quantum efficiency of violet SINP and deep junction SINP structure were calculated and analyzed in detail.
10
Content available remote A Picard theorem for iterative differential equations
EN
A Picard type existence and uniqueness theorem is established for iterative differential equations of the form y'(x) - f(x,y(h(x) + g (y (x)))), a special case of which is y'(x) = f(x,y(y(x))). Such iterative differential equations can be used to model infective disease processes, pattern formation in the plane, and in investigations of dynamical systems.
EN
The hydrolysis of PNPP was investigated in the presence and absence of Co(II), Cu(II), Ni(II), Zn(II), La(III) at 25°C and ionic strength of 0.1 mol dm-3. The results indicate that the spontaneous hydrolysis of PNPP was catalyzed by hydronium ion, hydroxide ion and water molecule, because of the existence of the pyridium nitrogen, while the metal ion catalyzed hydrolysis of PNPP at zero buffer concentration fulfills the equation: k obsd=K a [H+]+K a (k H[H+]+k 0+k OH K W [H+] showing that the reaction proceeds via nucleophilic attack by external OH- on the metal ion complex of PNPP. The order of catalytic ability of different metal ions was interpreted by the stability of the complex structure relative to the structure of the groundstate intermediate, employing the method devised by Kurz for catalyzed reaction.
12
Content available remote Periodic solutions of two-species difusion models with continuous time delays
EN
Two-species prey-predator diffusion models with periodic coefficients and continuous time delays are investigated. We derive sufficient conditions that guarantee the existence of positive periodic solutions which are globally asymptotically stable.
13
Content available remote On connected half-linear differential equations
14
Content available remote Note on an iterative functional differential equation
EN
This note is concerned with an iterative functional differential equation xI(z)=c1x(z) + . . . + Cmx(m) (z), where x(k) (z)=x(x(. . . x(z))) is the k-th iterate of the function x (z) . We apply the techniques developed in a previous paper [1] which deals with the simpler equation xI (z)=x (m) (z) and obtain analytic solutions for the more general equation.
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