This study proposes a processing framework based on Mutual Information Entropy (MIE) and an improved probability hypothesis density filter to address the key challenges—high clutter density and low detection probability—in Passive Bistatic Radar (PBR) target tracking. First, statistical differences in the correlation between target and clutter points, as well as between reference models, are quantified as mutual information entropy values, which are then used to eliminate clutter points. Second, the classical probability hypothesis density filter is improved through dynamic weight compensation, mitigating particle weight degeneration and reducing the deletion of false targets. This approach effectively resolves issues such as track fragmentation and target loss caused by discontinuous measurements with random intervals under low detection probability. The effectiveness of the proposed framework was verified through simulation experiments, and field test data demonstrated that the proposed method achieves good target-tracking performance in practical applications.
Abstract This paper illustrates a single antenna structure that simultaneously satisfies the antenna requirement for 5G cellular and global navigation satellite systems (GNSS). The antenna has a linearly polarised omnidirectional radiation for the newly defined 5G sub‐6 GHz cellular bands in the 617–5000 MHz frequency range. In contrast, a right‐hand circular polarisation (RHCP) with a hemispherical radiation pattern at the GNSS L1 has a frequency range of 1559–1606 MHz. This multi‐function antenna would provide a simplified product design and better space utilisation, particularly suitable for flat antenna modules and automotive. The primary concept involves employing a planar inverted F antenna structure to generate radiation modes for cellular bands and incorporate U‐slot on the top plate to generate the GNSS radiation modes. The design methodology utilises the characteristic mode analysis tool to tune the desired radiation characteristic mode at the intended frequency range for each function. The antenna was fabricated, and the performance was evaluated on a 1‐m ground plane. The GNSS RHCP gain measures 5 dBc at boresight, with an axial ratio below 2 dB across the L1 bands, while the cellular gain maintains an excellent return loss and omnidirectional radiation pattern performance across the cellular bands.
High and low pressure bypass combined heating supply and low-pressure cylinder zero output technology are two important flexibility transformation technologies, which can effectively improve thermal power units’ peak regulation capacity and heating capacity. In this paper, for the two same model 350 MW supercritical units of North China power grid, a therma lsystem simulating software named Ebsilon is used to build the high and low pressure bypass combined heating supply and low-pressure cylinder zero output model, whose reliability are demonstrated by actual field performance tests. The models’ full operation interval calculation results show that：the high and low pressure bypass combined heating supply model has better thermoelectric decoupling capacity because of it's maximum heating load capacity is 57.27 MW more and minimum electrical load capacity is 141.04 MW less than the low-pressure cylinder zero output model; The low-pressure cylinder zero-output model has a higher energy utilization rate because of its’ electrical load is 61.012 MW higher than high and low pressure bypass combined heating supply model when they have the same main steam and heating steam. Under the existing peak regulation revenue mechanism of North China Power Grid, the low-pressure cylinder zero-output heating can obtain a higher maximum comprehensive income when the main steam flow is less than 505 t/h; the two technologies can obtain the same max comprehensive benefit when the main steam flow is 505 t/h; the high and low pressure bypass combined heating supply model can obtain higher maximum comprehensive revenue when the main steam flow rate is greater than 505 t/h.
Electricity, Production of electric energy or power. Powerplants. Central stations
Abstract Gas‐filled internal crack might appear in thermoset materials like epoxy resin during the equipment manufacturing, which would become a vulnerable local region to initiate the electrical tree, thus prone to cause insulation failure. The withstand voltage test was carried on epoxy samples with artificial cracks based on a rod‐plane electrode arrangement. Simultaneously, surface state variation and tree evolution with crack were observed by an optical microscope in conjunction with a charge‐coupled device camera. The changes in morphology and chemical status of the crack surface were characterized by scanning electron microscopy, laser Raman spectrometer and energy dispersive spectrometer, respectively. It was found that the erosion and tree started from the borderline of crack under a relatively low electric field strength; however, the area near the electrode had relatively little damage. The breaking of epoxy molecular chains coarsens the crack surface and further forms deep channels on a micro‐level, which is the forerunner of the electrical tree inception. Based on these, the initiation mechanisms of the crack‐induced electrical tree and the reasons for the erosion near the borderline have been revealed. This study provides a train thought for the polymer degradation opening up into the initial tree channel during tree evolution processes.
Power grid outage decision-making for maintenance significantly affects the power supply reliability and customer’s satisfactions. The actual maintenance schedule for power grid is subjected to the subjective experience decision-making which is suitable for single maintenance outage plan. However, this method is difficult to achieve the optimal decision-making for multiple outage events, and the existing scheme only considers reducing the amount of outage power, instead of the interests of both the maintenance side and the user side. Therefore, we propose an optimal decision-making method for multiple outage events with consideration of the comprehensive supply-demand factors. Firstly, an outage decision-making model is established for optimal power grid maintenance scheduling with consideration of multiple outage events. In this model, the multi-objective function is constructed with minimized power outage (at grid side), minimized disappointment degree of user’s power consumption (user side) and maximized difference degree of equipment outage time (maintenance side), and the constraints of outage power and special events are used as constraint functions. Secondly, in order to improve the optimization efficiency, a single-objective function optimization model is constructed for optimal power grid outage decision-making based on the proportional coefficient method. Thirdly, a fitness optimization model is constructed based on the penalty function, and the genetic algorithm is used to solve the optimal outage decision-making problem. Finally, a real power grid case is used for simulation analysis, which has verified the correctness and effectiveness of the proposed model and algorithm.
Electricity, Production of electric energy or power. Powerplants. Central stations
<p>Recent research on fold-switching metamorphic proteins has revealed some notable exceptions to Anfinsen's hypothesis of protein folding. We have previously described how a single point mutation can enable a well-folded protein domain, one of the two PAS (Per-ARNT-Sim) domains of the human ARNT (aryl hydrocarbon receptor nuclear translocator) protein, to interconvert between two conformers related by a slip of an internal <span class="inline-formula"><i>β</i></span> strand. Using this protein as a test case, we advance the concept of a “fragile fold”, a protein fold that can reversibly rearrange into another fold that differs by a substantial number of hydrogen bonds, entailing reorganization of single secondary structure elements to more drastic changes seen in metamorphic proteins. Here we use a battery of biophysical tests to examine several factors affecting the equilibrium between the two conformations of the switching ARNT PAS-B Y456T protein. Of note is that we find that factors which impact the HI loop preceding the shifted I<span class="inline-formula"><i>β</i></span> strand affect both the equilibrium levels of the two conformers and the denatured state which links them in the interconversion process. Finally, we describe small molecules that selectively bind to and stabilize the wild-type conformation of ARNT PAS-B. These studies form a toolkit for studying fragile protein folds and could enable ways to modulate the biological functions of such fragile folds, both in natural and engineered proteins.</p>
The tautomerism of organic molecules is widely observed in solution. While for solid organic chemicals, molecules often exist in the most stable tautomeric form. 2-Picolinic acid (PCA) is a very rare case which contains both the neutral molecules and zwitterions in the same crystal structure. Chemical shift assignment for PCA by experimental approach, e.g., 2D NMR methods, is extremely time consuming because the 1H spin-lattice relaxation time (T1) is too long. Density functional theory (DFT) calculation, especially using a periodic model, is an alternative protocol to fix this issue. However, the original crystal structure of PCA cannot be submitted directly for the calculation task due to the proton positional disorder. In this contribution, a virtual structure was constructed via crystallography approach. Theoretical 13C chemical shifts were obtained basing on this virtual model, which are consistent with the experimental values. Also, both neutral PCA and zwitterion demonstrated their featured chemical shifts, such information can be utilized to analyze the molecular states of PCA in its crystalline complexes.
Current lifetime evaluation methods are often ineffective for power electronic devices which have high reliability, long life, and multi-fault mode competition. Accordingly, a lifetime evaluation method based on performance degradation data is proposed. Such data is used to construct performance degradation and lifetime distribution models. Then, the model parameter estimation, model goodness-of-fit checking, and model optimization methods are derived. By considering the trends in the degradation of multiple performance parameters, a competitive failure model is constructed to achieve a fast evaluation for the lifetime of power electronic devices with high reliability, long life, and multi-fault mode competition. As an example, lifetime evaluation is carried out for an insulated gate bipolar transistor. The difference between the evaluation results and measured test results is small, which verifies that the proposed method is quite accurate and effective.
Electricity, Production of electric energy or power. Powerplants. Central stations
The Very Low Frequency (VLF) signal of 10 kHz has strong penetrability of ground objects. Because of the antenna size, its application is limited. Therefore, it is important to study the VLF signal generation method based on appropriately sized high frequency radar antennas. The concept of generating VLF signal with high frequency array antenna is proposed in this paper. The waveform of the emission signal, staggered array structure design, and array parameter selection methods are presented and discussed. The pulse width of the composite signal is increased by using periodic pulse signals as radiation element signals. The resting period of the pulse signals is filled with the pulse width expansion generated by the array and the VLF signal with continuous time is composed in the target area. The performance of the composite VLF signal and the energy utilization of the emission signal are evaluated using Peak SideLobe Ratio (PSLR), Integrated SideLobe Ratio (ISLR) and through the spectrum comparison between the emission signal and the composite signal. With the 10 kHz VLF signal composed by 100 MHz radiant element signals, the hundred meter array is simulated. When the staggered array is constituted by nine arrays and the pulse width of the radiation element is set to 0.115 μs, PSLR and ISLR of the composite signal spectrum are –13.34 dB and –9.44 dB respectively, and the energy proportion of 10 kHz low-frequency signal in the composite signal is 89.79%. The effects of radiation element spacing error, time error, phase error and amplitude error of the radiation element signal and the target’s deviation are analyzed. It is found that the proposed method is an effective one and the simulation results have illustrated the effectiveness.
As an active microwave imaging sensor, Synthetic Aperture Radar (SAR) has become one of the main means of Earth observation owing to its unique technical advantages of all-day, all-weather operation and long working distance. As such, it plays a very important role in military and civilian fields. With the development of SAR remote-sensing technology, high-resolution, high-quality SAR images are produced continuously. However, manual detection and recognition of targets of interest is time-consuming and laborious, so the development of Automatic Target Recognition (ATR) technology is a matter of urgency. The typical SAR ATR system primarily comprises three stages: detection, discrimination, and classification/recognition. The detection and discrimination stages are the basis of the SAR ATR system, and research on SAR applications in the radar field has been conducted by researchers around the world. For single-channel SAR images, target detection and discrimination from simple scenes yield good results. However, in complex scenes, the clutter scattering intensity is relatively high, the clutter background is heterogenous, the target scattering intensity is relatively weak, and the target distribution is dense. These factors continue to make accurate SAR target detection and discrimination difficult. In this paper, we summarize the recent research progress on singlechannel SAR target detection and discrimination methods for complex scenes, analyze the characteristics and problems associated with various methods, and consider the future development trend of single-channel SAR target detection and discrimination methods for complex scenes.
A software package, MRISim, for virtual magnetic resonance imaging (MRI) data acquisition and image reconstruction was developed based on numerical simulation techniques. Virtual MRI data acquisition could be achieved through physical-mathematical modeling of the equipment and samples (i.e., phantom or human body). Image reconstruction of the virtual data was performed in the same manner as that in a real desktop MRI scanner. The software could also be applied for visualization of the features and causes of a variety of MRI artifacts, with the acquisition and processing parameters in the real experiments. MRISim was demonstrated as an efficient and reliable tool to conduct virtual MRI experiments, avoiding high expense of MRI training on real instruments.
With the shift toward the study of systems in operando and with increasing sensitivity, in operando nuclear magnetic resonance (NMR) is becoming more and more widely used in the field of polymer materials. In operando liquid state NMR provide mechanistic and kinetic information on polymerization reactions with the needless for stable labeling isotope, fast analysis, wide application range and maintaining intact samples. In addition, using the hyphenation of other characterization methods with in operando NMR spectroscopy is one of the most powerful methods for the separation and structural elucidation of unknown compounds and molecular compositions of mixtures by designing a suitable probe. In operando NMR spectroscopy will remain an indispensable and versatility tool in macromolecular science for years to come.
Majority of diterpenoid alkaloids are C19-diterpenoid alkaloids found in the plants from the genera Aconitum, Delphinium and Consolida (Ranunculaceae). C19-diterpenoid alkaloids have attached lots of research interests due to their complex structures and remarkable pharmacological activities. This paper reviewed the structural features of natural C19-diterpenoid alkaloids reported in literature from 2010 to 2018, focusing on the NMR spectral characteristics of different subtypes of C19-diterpenoid alkaloids and how their structures could be elucidated from the NMR data. The work may provide a reference for the further research and development of C19-diterpenoid alkaloids.
RESALT technology which is developed based on the Electric dialysis (ED) technology can effectively separate calcium ions from sulfate ions such that the scaling of CaSO4 is inhibited while the wastewater condensation process can be accomplished at the same time. The experiments were conducted in Huadian Laizhou power company with the inlet flow of the FGD wastewater about 3-4 m3/h. The RESALT equipments were tested to treat three kinds of flue gas desulfurization (FGD) wastewater. The results show that sulfate ions could be efficiently separated from calcium ions and the high salt contained wastewater could also be concentrated at the same time. Since there is no additional chemical agents required for the wastewater pre-treatment, electricity consumption is the main component of the cost during the wastewater treatment process, which will rise as the salt concentration of the wastewater goes up. For example, with the concentrations of 6 480 mg/L of SO42–, 1 820 mg/L of Ca2+, 2 462 mg/L of Mg2+, 20 680 mg/L of Cl– and 10 465 mg/L of Na+ in the FGD wastewater, the overall electricity consumption rate is 49.5 kW·h per ton and the direct treatment cost is about 22.6 RMB/ton.
Electricity, Production of electric energy or power. Powerplants. Central stations
Keyvan Firuzi, Mehdi Vakilian, B. Toan Phung
et al.
Power transformer partial discharge signal measurement using Radio Frequency method has advantages over IEC 60270 ‘apparent charge’ measurement method for online monitoring due to greater immunity against external interference. However, the lack of a well-defined calibration relationship between the two methods is main disadvantage of RF method. Simultaneous measurements, using these two methods, carried out on various transformer PD source models, in laboratory, to investigate main parameters that affect the relationship of results of these two methods. In this paper, factors that influence this relationship are classified into three groups: (i) type of PD sources, (ii) transformer windings as PD signal transmitter, and (iii) the inner structure of the transformer. Firstly, the relationship between these two methods has been investigated for some simple types of PD sources. Subsequently, by adding the winding structure model to the void, which is the PD source, its impact on each measurement method and the relationship between them have been studied. The impact of inner structure on the relation between the two methods is compensated through a formula which is proposed as a means for calibration of the RF partial discharge measurement setup. However to compensate for internal insulating system effects more research is required.
The GMD method (geometric mean distance) to calculate inductance offers undoubted advantages over other methods. But so far it seemed to be limited to the case where the current is uniformly distributed over the cross section of the conductor, i.e. to DC (direct current). In this paper, the definition of the GMD is extended to include cases of nonuniform distribution observed at higher frequencies as the result of skin effect. An exact relation between the GMD and the internal inductance per unit length for infinitely long conductors of circularly symmetric cross section is derived. It enables much simpler derivations of Maxwell’s analytical expressions for the GMD of circular and annular disks than were known before. Its salient application, however, is the derivation of exact expressions for the GMD of infinitely long round wires and tubular conductors with skin effect. These expressions are then used to verify the consistency of the extended definition of the GMD. Further, approximate formulae for the GMD of round wires with skin effect based on elementary functions are discussed. Total inductances calculated with the help of the derived formulae for the GMD with and without skin effect are compared to measurement results from the literature. For conductors of square cross section, an analytical approximation for the GMD with skin effect based on elementary functions is presented. It is shown that it allows to calculate the total inductance of such conductors for frequencies from DC up to 25 GHz to a precision of better than 1 %.