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EN
The purpose objective of this study was to investigate the influence of finite element meshing accuracy on modal analysis which is one of the basic factors affecting the accuracy of finite element analysis and mostly preoccupies the working staff in pre-processing finite element simulation models. In this paper, we established several finite element models of a welding machine for offshore platform, with the meshing accuracy as the variable and workbench software as the platform for modal analysis, as the same time, comparing the analysis results. The results indicated that for some specific structures and simulation types, mesh refinement alone does not achieve desired results, and the authors indicate that mesh refinement is rarely related to the equipment’s low-frequency modal analysis but it’s great related to the equipment’s high-frequency modal analysis. The findings of this study may serve as breaking the opinion that smaller mesh size means higher calculation precision and provides references for mesh division practices in low frequency modal analysis.
EN
Coastline is one type of valuable non-renewable resources. From the perspective of economic theory, it can gather population, promote traffic construction, and then improve the level of international trade. The research object of this paper is the coastline resource in Dafeng area. Firstly, we have a brief summary of the existing coastline evaluation literature, then introduce the location and natural attributes of the coastline resources in Dafeng. Following that, the Analytic Hierarchy Process (AHP) model is used to build the economic evaluation index system based on the characteristics of coastline in Dafeng. Specially, this index system consists of 6 factors, and a total of 41 detailed indicators were chosen including water depth, GDP, etc. On this basis, we use the assignment method to quantify the weight of each index, and calculate the comprehensive score of coastline resource by using the YAAHP software. The final conclusion is as follows: The total score of economic evaluation of coastline resource in Dafeng is 0.87. Therefore, the coastline resource in Dafeng will eventually be constructed a unique coastal economic zone, where the implemented port industrial projects will include shipbuilding, logistics, mechanical processing etc.
3
Content available remote Working principle analysis and control algorithm for bidirectional DC/DC converter
EN
A bidirectional DC/DC converter is an important part of the DC micro grid system, playing a key role in the stable operation of the system and the coordinated distribution of power. To solve the problem of unstable busbar voltage when the energy transforms bidirectionally in the DC micro grid system, a control algorithm based on closed-loop proportion integral derivative was proposed in this study. The hardware cinarcuit of the bidirectiol DC/DC converter was designed in the DC micro grid energy storage system, and the characteristics of converter efficiency in charging mode and constant voltage output were studied by small-signal modeling of the bidirectional DC/DC converter in charging and discharging systems. Experimental data were used to prove the correctness of the theoretical analysis. The results demonstrate that the current-controlled precision changes steadily in the charging mode when the output voltage is constant and the charging current is adjustable in ranges between 1 A and 2 A. When the charging current is 2 A and the output voltage ranges from 24 V to 36 V, the change rate of the charging current undergoes stable changes. In the discharge mode, when the output voltage is stable, the converter conversion rate changes steadily. When the output voltage changes in the range between 32 V and 38 V, the bidirectional DC/DC circuit automatically switches over the work patterns and maintains the stability of the output voltage. This study achieves bidirectional transmission of energy by rational hardware design of a bidirectional DC/DC converter and improves the reliability of the DC micro grid energy storage system. The proposed method provides a good prospect of a control scheme for the bidirectional DC/DC converter to optimize practical engineering design.
4
Content available remote Estimating root zone moisture from surface soil using limited data
EN
For estimation of root-zone moisture content from EO-1/Hyperion imagery, surface soil moisture was first predicted by hyperspectral reflectance data using partial least square regression (PLSR) analysis. The textures of more than 300 soil samples extracted from a 900 m × 900 m field site located within the Hetao Irrigation District in China were used to parameterize the HYDRUS-1D numerical model. The study area was spatially discretized into 18,000 compartments (30 m × 30 m × 0.02 m), and Monte Carlo simulations were applied to generate 2000 different soil-particle size distributions for each compartment. Soil hydraulic properties for each realization were determined by application of artificial neural network analysis and used to parameterize HYDRUS-1D to simulate averaged soil-moisture contents within the root zone (0-40 cm) and surface (approximately 0-4 cm). Then the link between surface moisture and root zone was established by use of linear regression analysis, resulting in R and RMSE of 0.38 and 0.03, respectively. Kriging and co-kriging with observed surface moisture, and co-kriging with surface moisture obtained from Hyperion imagery were also used to estimate root-zone moisture. Results indicated that PLSR is a powerful tool for soil moisture estimation from hyperspectral data. Furthermore, co-kriging with observed surface moisture had the highest R (0.41) and linear regression model, and HYDRUS Monte Carlo simulations had a lowest RMSE (0.03) among the four methods. In regions that have similar climatic and soil conditions to our study area, a linear regression model with HYDRUS Monte Carlo simulations is a practical method for root-zone moisture estimation before sowing and it can be easily coupled with remote sensing technology.
EN
An explosive co-crystal of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) was prepared by the ball milling method. The raw materials and co-crystals were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Raman spectroscopy. Impact and friction sensitivity of the co-crystals were tested and analyzed. The results showed that the HMX/TATB co-crystals are spherical in shape and 100-300 nm in size. The co-crystals are different from anintimate mixture of HMX/TATB and they exhibit a new co-crystal structure. HMX/TATB co-crystals are formed by N-O···H hydrogen bonding between −NO2 (HMX) and −NH2 (TATB). The drop height of ultrafine HMX/TATB explosive co-crystals is 12.7 cm higher than that of ultrafine HMX, whilst the explosion probability of friction is 20% lower than that of ultrafine HMX. Ultrafine HMX/TATB explosive co-crystals are difficult to initiate under impact and friction conditions.
EN
For improving the understanding of interactions between hyperspectral reflectance and soil salinity, in situ hyperspectral inversion of soil salt content at a depth of 0-10 cm was conducted in Hetao Irrigation District, Inner Mongolia, China. Six filtering methods were used to preprocess soil reflectance data, and waveband selection combined by VIP (variable importance in projection) and b-coefficients (regression coefficients of model) was also applied to simplify model. Then statistical methods of partial least square regression (PLS) and orthogonal projection to latent structures (OPLS) were processed to establish the inversion models. Our findings indicate that the selected sensitive wavebands for the 6 filtering methods are different, among which the multiplicative signal correction (MSC) and standard normal variate methods (SNV) have some similar sensitive wavebands with unfiltered data. Derivatives (DF1 and DF2) could characterize sensitive wavebands along the scale of VNIR (350-1100 nm), especially the second derivative (DF2). The sensitive wavebands for continuum-removed reflectance method (CR) have protruded many narrow absorption features. For orthogonal signal correction method (OSC), the selected wavebands are centralized in the range of 565-1013 nm. The calibration and evaluation processes have demonstrated the second order derivate filtering method (DF2) combined with waveband selection is superior to other processes, for it has high R2 (larger than 0.7) both in PLS and OPLS models for calibration and evaluation, by choosing only 156 wavebands from the whole 700 wavebands. Meanwhile, OPLS method was considered to be more suitable for the analyzing than PLS in most of our situations.
EN
Intermittent irrigation has attracted much attention as a water-saving technology in arid and semi-arid regions. For understanding the effect of intermittent irrigation on water and solute storage varied from irrigation amount per time (IRA), irrigation application frequency (IRAF), irrigation intervals (IRI) and even soil texture (ST), intermittent irrigation experiment was carried out in 33 micro-plots in Inner Mongolia, China. The experiment results were used for the calibration and validation of HYDRUS-1D software. Then 3 ST (silty clay loam, silty loam, and silty clay), 5 IRA (2, 4, 6, 8, and 10 cm), 4 IRAF (2, 3, 4, and 5 times) and 4 IRI (1, 2, 3, and 4 days) were combined and total 240 scenarios were simulated by HYDRUS-1D. Analysis of variance (ANVOA) of simulated results indicated that ST, IRA, and IRAF had significant effect on salt and nitrate nitrogen (NO3−-N) storage of 0-40 cm depth soil in intermittent irrigation while only ST affected soil water storage obviously. Furthermore, salt leaching percentage (SLP) and water use efficiency (WUE) of 0-40 cm depth were calculated and statistical prediction models for SLP were established based on the ANOVA using multiple regression analysis in each soil texture. Then constraint conditions of soil water storage (around field capacity), salt storage (smaller than 168 mg·cm−2), WUE (as large as possible) in 0-40 cm depth and total irrigation water amount (less than 25 cm) were proposed to find out the optimal intermittent irrigation strategies. Before sowing, the optimal irrigation strategy for silty clay loam soil was 6 cm IRA, 3 times IRAF, and 2 days IRI respectively. For silty loam and silty clay soils, IRA, IRAF, and IRI were 8 cm, 3 times, and 2 days respectively.
PL
Nawadnianie przerywane zwraca uwagę jako technologia oszczędnego użycia wody w regionach suchych i półpustynnych. Dla zrozumienia wpływu parametrów nawadniania przerywanego, takich jak czas (IRA), częstotliwości stosowania nawadniania (IRAF), odstępy czasu nawadniania (IRI), a także struktury gleby (ST) na magazynowanie wody i substancji rozpuszczonych, przeprowadzono eksperyment przerywanego nawadniania na 33 mikropoletkach w Mongolii Wewnętrznej, w Chinach. Wyniki doświadczeń użyto do kalibracji i walidacji oprogramowania HYDRUS-1D. Następnie 3 ST (mulisty piasek gliniasty, muliste iły i gliny pylaste), 5 IRA (2, 4, 6, 8 i 10 cm), 4 IRAF (2, 3, 4 i 5 razy) i 4 IRI (1, 2, 3 i 4 dni) połączono ogółem w 240 scenariuszy symulowanych przez HYDRUS-1D. Analiza wariancji (ANVOA) symulowanych wyników wykazała, że ST, IRA i IRAF miały znaczący wpływ na sól i azot azotanowy (NO3–-N), składowane na głębokości 0-40 cm gleby w nawadnianiu przerywanym, podczas gdy ST wpływał tylko na magazynowanie wody w glebie. Ponadto, procentowe ługowanie soli (SLP) i efektywność wykorzystania wody (WUE) zostały obliczone dla głębokości 0-40 cm i statystyczne modele predykcyjne dla SLP zostały ustalone na podstawie analizy wariancji i za pomocą analizy regresji wielokrotnej w każdej strukturze gleby. Aby określić optymalną strategię sporadycznego nawadniania, zaproponowano ograniczenie warunków magazynowania wody w glebie (około pojemności polowej), magazynowania soli (mniejsze niż 168 mg · cm–2), WUE (jak największa) w 0-40 cm głębokości i całkowitej ilości wody do nawadniania (mniej niż 25 cm). Przed siewem optymalna strategia nawadniania gleb mulistych gliniastych zakładała odpowiednio 6 cm IRA, 3 razy IRAF i 2 dni IRI. Dla gliny pylastej i ilastych gleb gliniastych założono IRA, IRAF i IRI odpowiednio 8 cm, 3 razy i 2 dni.
8
EN
The representation and processing of uncertainty information is one of the key basic issues of the intelligent information processing in the face of growing vast information, especially in the era of network. There have been many theories, such as probability statistics, evidence theory, fuzzy set, rough set, cloud model, etc., to deal with uncertainty information from different perspectives, and they have been applied into obtaining the rules and knowledge from amount of data, for example, data mining, knowledge discovery, machine learning, expert system, etc. Simply, This is a cognitive transformation process from data to knowledge (FDtoK). However, the cognitive transformation process from knowledge to data (FKtoD) is what often happens in human brain, but it is lack of research. As an effective cognition model, cloud model provides a cognitive transformation way to realize both processes of FDtoK and FKtoD via forward cloud transformation (FCT) and backward cloud transformation (BCT). In this paper, the authors introduce the FCT and BCT firstly, and make a depth analysis for the two existing single-step BCT algorithms. We find that these two BCT algorithms lack stability and sometimes are invalid. For this reason we propose a new multi-step backward cloud transformation algorithm based on sampling with replacement (MBCT-SR) which is more precise than the existing methods. Furthermore, the effectiveness and convergence of new method is analyzed in detail, and how to set the parameters m, r appeared in MBCT-SR is also analyzed. Finally, we have error analysis and comparison to demonstrate the efficiency of the proposed backward cloud transformation algorithm for some simulation experiments.
9
Content available remote Ultrasonic fields and inspection of composites
EN
Composites are widely used in aerospace, shipbuilding, automobile industry and other fields. Reliability and effectiveness of composites whose primary structural components are fiber-reinforced material need a significant demand for nondestructive testing. Mathematical modeling has evolved as an important tool to providing an aided analysis and optimize experimental setups. Modeling will help to reveal the quantitative features relationship in ultrasonic physical phenomena and to accelerate the development of new NDT techniques. Gaussian beam superposition technique has been developed for homogeneous anisotropic materials and extended to simulate in inhomogeneous structures. Modeling the transducer generated sound beam in composites is very difficult, especially when the geometry structure and the material component are complex. However, methods based on the paraxial approximations that model the transducer wave field with a superposition of Gaussian beams are computationally efficient and well behaved. In this paper, the multi-Gaussian beam model for calculating ultrasonic acoustic field in anisotropic material is introduced and developed to calculate the propagation and penetration of Gaussian beams in composite materials. It is presented that numerical simulations and experimental results of transmitted ultrasonic field for composites with different thickness are effective. Accuracy of the proposed model is verified by comparing model-based predictions with experimental results. Automated ultrasonic scanning technology by means of immersion tank and squirter has been extensively applied in composite quality inspection. But the reliability and repeatability of inspection results are strongly depend on the understanding of ultrasonic propagation model in composites.
PL
W pracy przedstawiono wyniki symulacji komputerowej i wyniki pomiarów rozkładu ciśnienia akustycznego fal przechodzących przez płyty kompozytowe o różnych grubościach. Symulacje wykonano dla głowicy ogniskującej pracującej w zanurzeniu. Wpływ kompozytu na kształt wiązki przejawia się głównie w skróceniu długości ogniskowej. W badaniach eksperymentalnych zastosowano głowic o częstotliwości 1 MHz pracujące w zanurzeniu, a badaniu podlegały rozkłady pola akustycznego po przejściu fal przez zbrojone włóknem węglowym próbki kompozytowe o grubościach od 10 do 25 mm. W drugiej części przedstawione są wyniki badania zakrzywionych próbek kompozytowych zawierających wady sztuczne. Badania wykonano metodą przepuszczania głowicami ze sprzężeniem strumieniem wody. Głowice prowadzone były przez dwa współpracujące roboty.
10
Content available remote Robust Cepstrum Radio Frequency Fingerprint Transformed from BPSK Signal
EN
Identifying wireless devices based on Radio Frequency fingerprint (RFF) is a promising physical layer security methodology. One practical issue is the robustness of RFF affected by wireless multi-path channels, etc. Proposed is a kind of RFF with robustness for identifying digital BPSK transmitters. The cepstrum of the received BPSK signal is obtained and then low-pass filtered, the result signal is mainly determined by device impulse response, and thus is robust. The proposed fingerprint can be used in the fusion identification of BPSK wireless transmitters.
PL
W artykule opisano sposób radiowej identyfikacji urządzeń bezprzewodowych, o bezpiecznej identyfikacji cyfrowych nadajników BPSK. Uzyskane cepstrum odebranego sygnału BPSK, poddawane jest filtracji dolno-przepustowej, co w efekcie daje sygnał wyznaczony przez odpowiedź impulsową urządzenia. Opracowany algorytm można wykorzystać w rozpoznaniu łączenia się nadajników BPSK.
EN
In multi-beam synthetic aperture sonar (SAS), the smaller the transmit sensor array’s physics aperture is, the larger its synthetic aperture length is, and then the better its along-track resolution will be. But when the physics aperture is small, the mapping speed should be limited to avoid the azimuth ambiguity. In order to overcome this problem, a scheme of multi-beam SAS with multi-frequency in azimuth is proposed in this paper based on the sensor array configuration and basic principle of multi-beam SAS. A correlated math model is presented and the dot-by-dot imaging algorithm is simulated according to the new scheme. Compared with the primary multi-beam SAS scheme proposed before, the new scheme can improve the along-track resolution and increase the mapping speed. Computer simulation results are given to test the correctness and efficiency of the new scheme.
PL
W artykule przedstawiono nową strukturę wielowiązkowego sensora SAS, pozwalającą na eliminację problemów związanych z dwuznacznością azymutu. Proponowane rozwiązanie bazuje na podstawowych zasadach działania SAS oraz odpowiedniej konfiguracji tablicy czujników. Zbudowano także model matematyczny oraz opracowano algorytm pozwalający na obrazowanie działania punkt po punkcie. Dokonano weryfikacji symulacyjnej proponowanej struktury.
12
Content available remote Research on Coverage Performance of GNSS
EN
The theory of Ground Coverage Performance (GCP) and Space Coverage Performance (SCP) of GNSS constellations is analysed. These performances are influenced by restriction of both the signal’s beam angle and the mask angle which is used by the receivers of users. Then the judgment methods and simulation results are acquired. In practical application, relevant constellations should be selected according to different tasks which are based on the simulation results to ensure the maximum number of visible satellites at the same time.
PL
Przeanalizowano teoretycznie obszary zasięgu naziemne (GCP) i w przestrzeni około-ziemskiej (SCP) dla konstelacji nadajników satelitarnych systemów nawigacji (GNSS). Sprawność zasięgu jest ograniczona zarówno przez kąt promieniowania nadajnika, jak i przez kąt zasięgu odbiorników użytkownika. Przedstawiono metody oceny i wyniki symulacji. W praktycznych zastosowaniach, w zależności od różnych zadań i wyników symulacji, konstelacja satelitów musi być dobrana tak, aby była widoczna maksymalna ich ilość w tym samym czasie. Badania dotyczą systemów: GPS, GLONASS, GALILEO i chińskiego BD2.
13
EN
In this paper, we build a family of chameleon hash functions and strongly unforgeable one-time signature schemes based on the intractability assumption of the discrete logarithm problem (DLP) over inner automorphism groups. Since the DLP assumption over inner automorphism groups does not admit sub-exponential attacks, thus the sizes of the working parameters used in our constructions are shorten significantly. This leads to remarkable gains for our proposals both in running time and in storage space. In addition, as far as we know, this is the first time to build CHF and OTS based on noncommutative groups.
14
Content available remote Effect of Salinity on Soil Respiration and Nitrogen Dynamics
EN
A facility of BaPS (Barometric Process Separation) and indoor incubation experiments were used to determine the effect of soil salinity on soil respiration and nitrogen transformation. The rates of soil respiration, gross nitrification, denitrification, ammonium and nitrate nitrogen concentrations and relevant soil parameters were measured. Results showed that soil respiration and nitrification and denitrification rates were all affected by soil salinity. Furthermore, the effect of soil salinity level on nitrification and denitrification rates had a threshold value (EC1:5 = 1.13 dS/m). When soil salinity level was smaller to this threshold value, the rates of nitrification and denitrification increased with soil salinity while they were reduced when soil salinity level was larger than the threshold value. Moreover, the changing law of soil respiration rate with soil salinity was similar with the nitrification and denitrification rates while the variation tendency was opposite. In addition, the transformation form urea to ammonium and nitrate nitrogen was also reduced with the increase of soil salinity and the reduced effect could be expressed by exponential functions.
PL
Proces BaPS (Ciśnieniowy Proces Separacji) oraz inkubacja pokojowa zostały wykorzystane do określenia wpływu zasolenia gleby na jej oddychanie i transformację azotu. Mierzono szybkości: respiracji gleby, całkowitej nitryfikacji i denitryfikacji, a także stężenie azotu amonowego i azotanowego oraz wartości odpowiednich parametrów gleby. Wyniki wykazały, że respiracja glebowa oraz szybkości nitryfikacji i denitryfikacji były uzależnione od zasolenia gleby. Ponadto stwierdzono, że wpływ poziomu zasolenia gleby na szybkość nitryfikacji i denitryfikacji miał wartość progową (EC1:5 = 1,13 dS/m). Gdy poziom zasolenia gleby był mniejszy od tej wartości progowej, szybkości nitryfikacji i denitryfikacji rosły wraz ze wzrostem zasolenia gleby. Jeżeli zasolenie gleby był większe od progowego, to szybkości te malały. Co więcej, zmiany charakteru zależności szybkości respiracji gleby od jej zasolenia były porównywalne z szybkością nitryfikacji i denitryfikacji, podczas gdy tendencja zmian była odwrotna. Ponadto, transformacja mocznika do amoniaku i azotu azotanowego również zmniejszała się przy wzroście zasolenia gleby, a efekt takiego zmniejszania może być wyrażony funkcją wykładniczą.
15
Content available remote The study on pH gradient control in solution for driving bacteria
EN
Medical applications are the most impactful areas of microrobotics, such as targeting tumoral lesions for therapeutic purposes, minimally invasive surgery (MIS) and highly localized drug delivery. However, miniaturization of the power source with an effective on board controllable propulsion system has prevented the implementation of such mobile robots. Flagellated chemotactic bacteria can be used as an effective integrated propulsion system for microrobots. In this paper, we study the pH gradients control in solution for driving bacteria. The swimming property of flagellar bacteria and mechanism of forming the pH gradient field in solution are discussed. By experiments, we found that the pH gradient field distribution in solution is mainly related to the electrode shape. And the input voltage value can control the stable time of the pH gradient field, while it has no effect on the distribution of the field. The electric potential distribution is analyzed by simulation with COMSOL Multiphysics. The simulation results are consistent with the experiment results, which indicate that the bacteria movement can be controlled by the electrodes' shape and the input voltage.
EN
Radix Isatidis has widely useful activities including anti-virus, anti-bacterial. Tryptanthrin, indigo, and indirubin are active ingredients in R. Isatidis. Response surface methodology (RSM)-optimized infrared-assisted extraction (IRAE) was developed and combined with HPLC for simultaneous determination of tryptanthrin, indigo, and indirubin from R. Isatidis. IRAE were investigated through extraction yields of the three components and optimized by RSM. The optimum conditions were as follows: infrared power of 129 W, solid/liquid ratio of 1:40 g/mL, and irradiation time of 22.5 min. IRAE conditions obtained by RSM were not only accurate, but also had practical value reflecting the expected optimization. Subsequently, this novel IRAE method was evaluated by extraction yield of the components of R. Isatidis samples from different regions. Compared with common extraction methods including maceration extraction (ME), reflux extraction (RE), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE), IRAE showed higher yield with advantages of no limitation of solvent selection, low cost, convenience under optimum extraction conditions. These results suggested the potential of RSM-optimized IRAE for extraction and analysis of the water-/fat-soluble compositions of Chinese herbal medicine. A simple chromatographic separation for simultaneous determination of tryptanthrin, indigo, and indirubin from Chinese herbal medicine R. Isatidis was performed on a C18 column (Diamonsil 150 mm × 4.6 mm i.d., 5 μm) with a mobile phase isocratic consisting of methanol and water at a flow-rate of 0.8 mL min -1. The retention times of tryptanthrin, indigo, and indirubin were 15.4, 31.9, and 58.6 min, respectively. The linear equations were obtained as follows: y = −3094.5744 + 21208.792x for tryptanthrin (R = 0.9998, 0.9–18.0 μg mL -1), y = 4730.0448 + 30180.567x for indigo (R = 0.9997, 0.5–10.0 μg mL−1) and y = −6582.9045 + 67069.312x for indirubin (R = 0.9997, 0.4–8.0 μg mL -1). The result showed that RSM-optimized IRAE was a simple, efficient pretreatment method for the analysis of complex matrix.
17
Content available remote Control of different-rating battery energy storage system interface to a microgrid
EN
This paper focuses on different-rating battery energy storage system (BESS) integrated into a microgrid. To improve the power quality and satisfy the requirements of power system, it is necessary to integrate different-rating BESS composed battery modules (BM) and power conditioning system (PCS) into the microgrid. The BESSs can supply suddenly changed loads, especially for sensitive loads that must have uninterruptible power supply. A new control strategy included slack mode control and load mode control is presented to enable the BESSs operate in two operation mode: the free-slack operation mode and the load-sharing operation mode. In the load sharing operation mode,the controller enable various load proportionally shared by two different-rating BESS parallelly operating without communication between them In the free-slack mode operation, the BESSs acting as a free-slack can adequately balance the active and reactive power of the microgrid to maintain the voltage and frequency at point of common coupling (PCC) to a desired level. The advantage of the proposed control method is that the unified controller is employed for the two operation mode without swithing between different controllers. Details of modeling of the BM and PCS and the corresponding control strategy are described. The effectiveness of the BESSs and proposed control method is verified through simulations and experiments.
PL
W artykule omówiono bateryjny system gromadzenia energii BESS zintegrowany w mikrosiecią. W celu poprawy jakości energii łączy się systemy BESS z układami kondycjonowania PCS. System BESS działający jako układ zabezpieczający przed chwilowymi zanikami energii musi cechować się niezawodnością. Zaprezentowano nowa strategię sterowania łączącą tryb łagodny i tryb kontroli obciążenia. Zaletą metody jest że do sterowania stosowany jest zunifikowany kontroler bez potrzeby przełączania między różnymi kontrolerami. Skuteczność c metody potwierdziły symulacje i eksperymenty.
18
Content available remote Synthesis and characterization of jar-like ZnO structures
EN
A new jar-like ZnO structure was synthesized by heating a mixture of Zn and InI3 powder with a weight ratio of 4:1 dispersed on Si wafer at 450 °C in air. The diameter of the jar was of the order of 15 ?m and the length of 20 ?m. The formation of a molten InI3 drop, coating the drop with Zn powders, oxidation of these Zn grains, decomposition of InI3 to In and I vapors and the subsequent release of these vapors from the structure are considered important steps in the formation of the observed structures. The necessary elements in forming such structures are analyzed, which can be used as a guide in the design of experiments to synthesize similar structures for different purposes. Such structures are predicted to be able to soak large amount of liquid and release it at low rate, which is a desired property in some applications.
EN
In this paper, a two-species Lotka-Volterra predator-prey model with two delays is considered. By analyzing the associated characteristic transcendental equation, the linear stability of the positive equilibrium is investigated and Hopf bifurcation is demonstrated. Some explicit formulae for determining the stability and direction of Hopf bifurcation periodic solutions bifurcating from Hopf bifurcations are obtained by using normal form theory and center manifold theory. Some numerical simulations for supporting the theoretical results are also included.
EN
Magnetite (Fe3O4) nanoparticles were successfully synthesized via a simple solvothermal process and characterized by X-ray diffraction, field emission scanning electron microscopy, and physical property measurement system (PPMS). It was found that the diameters of as-synthesized Fe3O4 nanoparticles became larger as the reaction temperature increased, and the magnetic properties of these nanoparticles could change from ferrimagnetic to superparamagnetic with the decrease in particle size. A possible mechanism for the formation of Fe3O4 nanoparticles has also been proposed.
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