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Transient measurement is expected to be widely required in the future power system. One of the the most cost-effective ways to widely equip the power system with the transient measurements is to upgrade current voltage transformers to be enabled with transient measuring ability. This paper presents a algorithm-based technique involving the non-linear features of VT to enable CVT and PT with a wideband transient voltage measuring ability, including the methods of building the non-linear transient model and inverse calculation method based on the output voltage to recover the input voltage waveform. In this paper, the method of synthesizing the equivalent circuit model for a PT or a CVT is presented in detailed. Meanwhile, the inverse calculation method based on circuit theories and Bergeron equivalence as well as NR equivalence is also presented. The verification experiments were performed on a 110kV CVT and 10kV PT with the lightning impulses as the verification source. The experimental results show a good match to the input waveform recorded by standard divider.

This paper based on density functional theory (DFT) investigate the interaction of C5-PFK molecule with Cu (110) and (100) surfaces, in order to analyze the chemical compatibility of Cu metal in the environment of C5F10O (C5-PFK) insulation gas. The frontier molecular orbital theory implies that the C = O group in the C5-PFK molecule can interact strongly with the Cu surfaces. The results show that both Cu (110) and (100) surfaces have strong interactions with the C5-PFK molecule, showing chemisorption of the molecule, with Ead of -1.17 and -1.03 eV, respectively. Meanwhile, the C5-PFK molecule performs strong electron-accepting behavior in the interactions, which captures 0.262 and 0.204 e from the Cu (110) and (100) surface, respectively. Even though, the geometric and electronic properties of Cu surface are not largely impacted, as supported by the basically unchanged morphologies and DOS curves of Cu surfaces before and after gas adsorption. These findings manifest the favorable stability and compatibility of Cu metal in the C5-PFK environment. Our work uncovers the safe operation of C5-PFK immersed insulation devices with Cu-based generatrix and shell in a long running, which is of great significance to guarantee the safe operation of the power system.

The combination between non-orthogonal multiple access (NOMA) and hybrid automatic repeat request (HARQ) is capable of realizing ultra-reliability, high throughput and many concurrent connections particularly for emerging communication systems. This paper focuses on characterizing the asymptotic scaling law of the outage probability of HARQ-aided NOMA systems with respect to the transmit power, i.e., diversity order. The analysis of diversity order is carried out for three basic types of HARQ-aided downlink NOMA systems, including Type I HARQ, HARQ with chase combining (HARQ-CC) and HARQ with incremental redundancy (HARQ-IR). The diversity orders of three HARQ-aided downlink NOMA systems are derived in closed-form, where an integration domain partition trick is developed to obtain the bounds of the outage probability specially for HARQ-CC and HARQ-IR-aided NOMA systems. The analytical results show that the diversity order is a decreasing step function of transmission rate, and full time diversity can only be achieved under a sufficiently low transmission rate. It is also revealed that HARQ-IR-aided NOMA systems have the largest diversity order, followed by HARQ-CC-aided and then Type I HARQ-aided NOMA systems. Additionally, the users' diversity orders follow a descending order according to their respective average channel gains. Furthermore, we expand discussions on the cases of power-efficient transmissions and imperfect channel state information (CSI). Monte Carlo simulations finally confirm our analysis.

Repeated impulse voltage has long been considered to affect the insulation property of power equipment, which is called accumulative effect. This phenomenon is widely studied on oil paper insulation but rarely on oil polypropylene film insulation, which is widely used in power capacitors and other equipment. Therefore, the accumulative effect of repeated impulse on oil polypropylene insulation is studied in this work. First, a repeated impulse accumulating test platform was set up and the accumulation characteristics of oil polypropylene insulation with repeated impulses were tested and analyzed. Next, the residual breakdown voltage, surface morphology and gas composition dissolved in the oil in different aging levels were tested. The results indicated that the OPF insulation residual breakdown voltage decreased and the film surface roughness increased when subjected to the repeated impulses. The dissolved gas contents changed along with the impulse accumulation aging. Lastly, the possible mechanisms of the accumulative effect in oil polypropylene insulation are discussed based on the test results.

Lightning-induced overvoltage in substations is one of the main causes of insulation damage in transformers. As the complexity of power grids is continuing to increase, the existing lightning overvoltage statistical waveform may no longer meet the requirements of modern power systems. It is therefore necessary to obtain the statistical characteristics of lightning-induced overvoltage on transformers. However, the existing devices in current power systems cannot meet the requirements for monitoring of the lightning-induced overvoltages because of their limited bandwidths and sampling rates. This paper proposes a method for monitoring of lightning-induced overvoltages on substation transformers based on the principle of ZnO lightning arrester block voltage division. Consistency testing was performed on the voltage division ratio of a ZnO lightning arrester block in both the linear and nonlinear regions. The experimental results confirmed the feasibility of the proposed method and field applications using this sensor showed that long-term research will be helpful in obtaining the characteristics of lightning-induced overvoltage.

The unbalance current issue of the high-speed railway is the most prominent power quality of the traction power supply systems. Bullet trains can generate energy feedback when they brake, which should not be neglected. In this study, the effects of energy feedback on the unbalance issue are analysed, under different operating conditions of the trains. A collaborative unbalance compensation method (CUCM) for the high-speed railway is proposed in this work to lower the compensation capacity of the expensive power electronics compensation devices. To ensure that the CUCM works well, a further analysis of the two compensation principles, the railway power conditioner principle and Steinmetz principle, was carried out. The analysis results showed that the two compensation principles have different implementation methods and compensation current expressions, but the compensation essences were the same. According to the principle analysis results, a collaborative strategy was used. A capacity analysis of the CUCM, based on the actual operating situations of the bullet trains, was also completely done in this study. The simulation and experimental results showed that the proposed CUCM could adequately compensate the unbalance current of the high-speed railway power systems well with a low cost, in both traction and energy feedback situations.

Power capacitors suffer multiple impulse voltages during their lifetime. With the multiple impulse voltage aging, the internal insulation, oil-film dielectric may deteriorate and even fail in the early stage, which is called accumulative effect. Hence, the time-domain dielectric response of oil-film dielectric with multiple impulse voltage aging is studied in this paper. At first, the procedure of the preparation of the tested samples were introduced. Secondly, an aging platform, impulse voltage generator was built to test the accumulative effect of capacitor under multiple impulse voltage. Then, a device was used to test the time-domain dielectric response (polarization depolarization current, PDC) of oil-film dielectric in different aging states. And finally, according to the PDC data, extended Debye model and characteristic parameters were obtained by matrix pencil algorithm identification. The results indicated that with the increase of impulse voltage times, the time-domain dielectric response of oil-film dielectric changed accordingly. The polarization current curve moved up gradually, the insulation resistance decreased when subjected to the repeated impulses. In frequency domain, the frequency spectrum of tan δ changed along with the impulse accumulation aging, especially at low frequency. At last, combined with the aging mechanism of oil-film dielectric under multiple impulse voltage, the test results were discussed.

The transient analysis model of grounding systems is an important tool to analyze the lightning characteristics of grounding devices. When lightning enters the soil through the grounding device, there is a centralized discharge channel. The spatial structure of the discharge channel in the soil has a great effect on the accuracy of the transient analysis model of the soil impulse discharge. In this paper, based on the gray information analysis method, the volume of successive impulse discharge channels in the ground under various currents and soil conditions is calculated, and the changing law with time interval is analyzed. According to the experimental results, an analysis method of the model considering the discharge channel structure is proposed, and an example is analyzed. The results show that the time interval has an effect on the volume of the discharge channel. In a certain range, the volume of the channel increases with the time interval of successive impulse discharges. Taking the critical breakdown electric field strength as the judgment condition and the residual resistivity as the variable, the development process of the discharge channel can be simulated. The calculated results of the model are close to the experimental results.

The sensing of bioactive molecules based on photochemical techniques has become one of the fastest-growing scientific fields. Surface-enhanced Raman scattering (SERS) is a highly sensitive technique for the detection of low-concentration molecules, including DNA, microRNA, proteins, blood, and bacteria; single-cell detection and identification; bioimaging; and disease diagnosis, providing abundant structural information for biological analytes. One rapidly developing field of SERS biosensor design is the use of carbon-based nanomaterials as substrate materials, such as zero-dimensional carbon quantum dots, one-dimensional carbon nanotubes, two-dimensional graphene, and graphene oxide (GO) and three-dimensional spatial carbon nanomaterials or carbon-based core-shell nanostructures. In this review, we describe the recent developments in SERS biosensors, in particular carbon-based SERS, for the detection of bioactive molecules. We systematically survey recent developments in carbon nanomaterial-based SERS biosensors, focusing on fundamental principles for carbon-based materials for SERS biosensor design, fabrication, and operation, and provide insights into their rapidly growing future potential in the fields of biomedical and biological engineering, in situ analysis, quantitative analysis, and flexible photoelectric functional materials. As such, this review can play the role of a roadmap to guide researchers toward concepts that can be used in the design of next-generation SERS biosensors while also highlighting current advancements in this field. The various sheets, tubes, and dot-like nanostructures formed by carbon atoms can make a molecular sensing technology safer and more effective. In surface-enhanced Raman spectroscopy (SERS), detection of single molecules is achieved by attaching biological targets to signal-boosting substrates, typically metal nanoparticles. Biao Kong from Fudan University in Shanghai, China, and colleagues review how metal SERS substrates are being replaced by carbon-based nanostructures engineered to produce localized ‘hotspots’ where electric fields are enhanced. These substrates offer improved biocompatibility and customizable device structures. For example, graphene can easily host tumor cells for cancer sensing, while carbon dots can attach to DNA strands to act as ultra-small barcodes. The favorable mechanical properties of carbon also enable production of innovative materials including drug-sensing nanosheets that adhere to the surfaces of banknotes and coins. In this review, recent developments of carbon nanomaterial-based SERS biosensors are systematically summarized, which focus on fundamental principles for carbon-based materials for SERS biosensor design, fabrication methods and operation mechanisms, providing insight into their rapidly growing future potential in the fields of biomedical and biological engineering, in-situ analysis, quantitative analysis and flexible photoelectric functional materials.

C 5 F 10 O/N 2 gas is considered to be a promising substitute for SF6 gas in medium-voltage(MV) grade electrical equipment due to its excellent environmental protection characteristics and high insulation performance. In this paper, the thermal decomposition characteristics of C 5 F 10 O/N 2 /N2 gas mixture in the temperature range of 300-500°C were studied by building a partial overheating fault experimental platform. Studies have shown that the thermal decomposition products of C 5 F 10 O/N 2 /N2 gas mixture at high temperature are C 2 F 4 , CO 2 , C 4 F 10 , C 3 F 6 , C 3 F 7 H, C 3 F 8 , CF 4 , C 2 F 6 , C 4 F 6 O 3 and C 6 F 14 . C 5 F 10 O gas decomposes at 300°C to produce a small amount of C 3 F 6 , and the temperature above 400°C will produce C 4 F 6 O 3 and C 6 F 14 . C 3 F 6 , C 4 F 6 O 3 and C 6 F 14 can be regarded as the characteristic decomposition products of the severity of partial overheating fault of C 5 F 10 O/N 2 /N 2 gas mixture. The concentration of most of the decomposition products will increase with the increase of experimental temperature, but the heating time has almost no effect on the formation of decomposition products. Relevant research results can provide guidance for the development of online monitoring equipment for partial overheating fault of C 5 F 10 O/N 2 /N2 gas mixture insulation equipment.

To assess the insulation condition of oil-paper bushing, an assessment method based on polarization and depolarization currents was proposed in this paper. Firstly, the polarization and depolarization current test principle and equipment were introduced and set up to measure the polarization and depolarization currents at pA level. In order to verify the field test effect, the polarization and depolarization currents tests for field bushings were conducted. Three oilpaper bushing with different insulation condition (new, natural aging and moisture containing) were chosen as the test object. The test results indicated that the polarization and depolarization currents showed different character of different bushing insulation conditions. The dielectric loss at low frequency was highly correlated with aging degree and the moisture containing. The DC conductivity was highly correlated with moisture containing but lowly correlated with aging degree.

The combination between non-orthogonal multiple access (NOMA) and hybrid automatic repeat request (HARQ) is capable of realizing ultra-reliability, high throughput and massive concurrent connections particularly for emerging communication systems. This paper focuses on characterizing the asymptotic scaling law of the outage probability of the HARQ with chase combining (HARQ-CC)-aided downlink NOMA scheme with respect to the transmit power, i.e., diversity order. The diversity order of the two- user HARQ-CC-aided NOMA system is derived in closed-form, where an integration domain partition trick is developed to obtain the upper and lower bounds of the outage probability. The analytical results show that the diversity order is a decreasing step function of transmission rate given the ratio between the transmit powers allocated to the two users. Moreover, full time diversity can only be achieved under a sufficiently low transmission rate. Additionally, the users' diversity orders follow a descending order according to their respective average channel gains. Monte Carlo simulations finally confirm the analysis.

Rapid sensitive sensing in wide fields such as food science and medical science by using Surface-enhanced Raman scattering (SERS) has been a promising technique recently. Inspired by the bionic superhydrophobic surface, we prepared a superhydrophobic Ag nanoparticles (Ag NPs) decorated Cu(OH)2 nanoneedle array SERS substrate by a facile electrochemical method. Different with the traditional SERS detection method, molecules are detected in droplets rapidly on the substrate based on the superhydrophobicity, offering low concentration and recyclable detection. The substrate exhibits excellent Raman signal enhancement by using several probe molecules. The nanoneedle array structure offers simultaneously a 3D scaffold for Ag NPs forming unique electromagnetic field enhancement and a superhydrophobic surface for recyclable using. The recyclability in SERS detection was tested by using crystal violet and rhodamine 6G as the probe molecules alternatively, obtaining at least 6 times reutilization without any cleaning process with little fluctuation of the signal intensity. Practical application in real environment has been investigated by detecting melamine in milk and thiram in apple juice, with the detection limits approximately 0.1 ppm, far lower than the national standard. With the advantages of easy preparing, high sensitivity and recyclability, the prepared substrates are expected owing great potential in rapid detection in food safety, medical testing and environmental monitoring in the future.

An ultrasensitive “turn off” Surface Enhanced Raman Spectroscopy (SERS) sensor was developed for the detection of heparin based on the anti-aggregation of 4-mercaptobenzoic acid stabilized gold nanoparticles. In this paper, protamine, a small protein molecule with positive charges, could induce the aggregation of 4-MBA functionalized gold nanoparticles via surface electrostatic interaction. However, in the presence of heparin, the aggregation of 4-MBA functionalized gold nanoparticles decreased due to the fact that heparin has a strong affinity toward protamine, further causing the loss of the Raman enhanced effect. The normalized SERS intensity of the Raman reporter was proportional to the concentration of added heparin and a good linear detection range was obtained from 0.05 to 20 ng mL−1 (R2 = 0.999) with a calculated detection limit of 0.03 ng mL−1. Moreover, the developed highly selective method is also successfully demonstrated in fetal bovine serum. Our method is specific, simple and cheap, which could be applied to other further research studies of heparin.

Coupled plasmonic assemblies have recently attracted tremendous research interest in the field of Surface Enhanced Raman Scattering (SERS) due to their unique optical and biocompatible properties. Using DNA to connect different parts of assembled plasmonic nanostructures has been a simple but useful method to achieve the expected nanocomposites. This work prepared a satellite SERS substrate based on gold nanorod/gold nanosphere structures, in the hope of providing a novel SERS sensor for biomedicine related applications. A seed growth method was adopted to fabricate gold nanorods, using a region specific method to connect the gold nanorod core with the gold nanosphere satellites. The fabricated nanocomposites were further self-assembled with p-mercaptobenzoic acid (p-MBA) molecule layers as Raman reporters for SERS experiments. The obtained satellite nanostructure could produce “hot spots” between the gold nanorods and gold nanospheres to improve the SERS sensitivity and also to function as a key factor to tune the localized surface plasmon resonance (LSPR) absorption band to the near-infrared region. Finally, the optimized satellite SERS sensor was applied in the detection of Crystal Violet (CV) with a limit of detection as low as 10−11 M, proving that the self-assembled nanocomposite could act as an effective substrate for single molecule detection.

Due to the different overvoltage waveforms and the different distribution of the waveform parameters, the failure characteristics of insulating medium under these overvoltage waveforms are significantly different. However, the failure probability characteristics are closely related to the risk assessment of insulation failure of power system. Meanwhile, the failure probability characteristics of insulating medium under different overvoltage waveforms are not fully understood. Therefore, it is necessary to carry out research on the difference of failure probability characteristics of insulating material under different impulse voltages. In this paper, a double exponential impulse wave (DEIW) and bipolar oscillatory attenuated impulse wave (BOAIW) test platform was set up. Then, we obtained the failure probability of oil-immersed insulation paper (OIP) for transformer under the DEIW and the BOAIW. The differences and commonalities of the failure probability characteristics of OIP under different waveforms were further analyzed. Finally, we realized the prediction of the failure probability characteristics of oil-paper insulation under different impulse voltages.

Taxus cuspidata S. et Z. is an excellent natural source of bioactive polysaccharides and has various biological activities. The objective of this study was to evaluate the effect of antidiabetic and antitumor activities of polysaccharides from Taxus cuspidata branches and leaves (TCBL) and to determine the optimum extraction technology of TCBL using a low-temperature and high-efficiency enzyme and ultrasound-assisted coupled extraction (EUCE) method. Optimal technology parameters were determined as follows: an extraction temperature of 51 &deg, C, an extraction time of 33 min, a ratio of material to liquid of 1:19 (g:mL), and an enzyme concentration of 0.10 mg&middot, mL&minus, 1. Under the optimized conditions, the polysaccharide yield from TCBL obtained by EUCE was 4.78% &plusmn, 0.18%. The four purified polysaccharides (Pe1, Pe2, Pe3, Pe4) from TCBL are mainly composed of arabinose, galactose, glucose, a small amount of xylose, and mannose. This composition was assessed by HPIC analysis. The antidiabetic activity and antitumor activity of polysaccharides from TCBL were assayed in vitro. Among the four purified polysaccharides from TCBL, purified Pe4 had the highest inhibitory capacity against &alpha, glucosidase, and its IC50 value was 123.0 &micro, g&middot, 1. Pe1 had the highest antitumor capacity against MCF7 cells and HepG2 cells, with IC50 values of 169.0 and 132.0 &micro, 1. Pe4 had the highest antitumor effect on human cervical cancer cells (Hela), and its IC50 value was 89.9 &micro, 1. Pe4 polysaccharide demonstrated a good &alpha, glucosidase inhibitory activity and antitumor capacity against Hela cells. Therefore, Pe4 polysaccharide from TCBL is a beneficial source of potential inhibitors of type II diabetes and human cervical cancer activity.

Electrode have an important influence on the breakdown of liquid dielectrics. The interface of electrodes and liquid dielectrics may affect the injection and distribution of space charge in liquid dielectrics, and thereby affecting the breakdown of liquid dielectrics. To find experimental evidence, the Kerr electro-optic method was used to observe the space charge in transformer oil under different electrode materials (Brass, Aluminum). With the use of array photodetector, the space-time evolution of space charge in liquid dielectrics can be directly measured under a single impulse voltage. The results show that when impulse voltage was applied to the electrodes, the Br (+)-Br (-) electrodes injected unipolar positive space charges, the Al (+)-Al (-) electrodes injected unipolar negative space charges, the Br (+)-Al (-) electrodes injected bipolar homo-charges, and the Br (-)-Al (+) didn’t inject significant space charges. The reason of this phenomenon may be the different properties of electric double layer formed by different electrodes and transformer oil. Considering that the homo-charge injection can weaken the electric field near the electrode, the breakdown voltage under Br (+)-Al (-) should be highest, which is consistent with other researchers’ conclusions. This study provides an experimental basis for selecting a suitable electrode combination to strength the breakdown voltage of transformer oil.

Few effective insulation state detection methods for power capacitor can be used in field. In this paper, a power capacitor insulation state detection method based on polarization-depolarization current is proposed. Firstly, the basic principles of the method are discussed. Then, two characterized parameters are conducted based on polarization and depolarization currents, which are DC conductivity and 0.1Hz dielectric loss. A test device based on this method is developed to evaluate the insulation state of power capacitor with different aging conditions. The test results showed that the polarization and depolarization currents increased along with the aging conditions. The DC conductance and 0.1Hz dielectric loss also increased along with the aging conditions. The test indicated the polarization-depolarization current method is suitable for power capacitor insulation state detection.

Traditional Chinese medicines (TCM) have a long history of use because of its potential complementary therapy and fewer adverse effects. However, the toxicity and safety issues of TCM have drawn considerable attention in the past two decades. Metabolomics is an “omics” approach that aims to comprehensively analyze all metabolites in biological samples. In agreement with the holistic concept of TCM, metabolomics has shown great potential in efficacy and toxicity evaluation of TCM. Recently, a large amount of metabolomic researches have been devoted to exploring the mechanism of toxicity induced by TCM, such as hepatotoxicity, nephrotoxicity, and cardiotoxicity. In this paper, the application of metabolomics in toxicity evaluation of bioactive compounds, TCM extracts and TCM prescriptions are reviewed, and the potential problems and further perspectives for application of metabolomics in toxicological studies are also discussed.

With the development of data science, there are more and more ways to dig for patterns hidden in the data. If we can apply the advanced model of data science to the power data, we can mine the potential value of power data. In this paper, the monitoring and inspection data of 110kV main transformers and related basic environmental data are fused to establish conditional inference tree model and AdaBoost algorithm to evaluate whether the 110kV main transformers have defects and faults. The accuracy of the two algorithms is compared. Finally, we select the AdaBoost algorithm with higher accuracy for building the 110kV main transformer fault evaluating model. This paper provides a reference for the automatic detection of power grid faults, and provides new ideas for the application of power grid big data.

The detection and monitoring methods of power equipment are relatively complex. The analysis of a large amount of data obtained from detection and monitoring and the development of data recording methods make it possible to obtain higher-dimensional power data. If we adopt appropriate data analysis method to the data sets, we can better get the potential laws and value of power data. In this paper, we took various basic monitoring data and faults records of the 110kV main transformers into consideration, and the grid-equipment-environment data was fused. Based on the fused data, we used the decision tree and random forest algorithm to evaluate the main transformers’ defects and faults. The evaluation results of the two algorithms were obtained and compared, which proved the effectiveness of the fault evaluation algorithm and selected a more accurate fault evaluation algorithm. This paper provides new ideas for smart fault detection for power grid, and provides a reference for a more in-depth evaluation of power grid equipment.

To solve the power quality problem in a V/V cophase railway power supply system, a hybrid electrical magnetic power quality compensator (HEMPQC) based on magnetic static var compensator (MSVC) and hybrid power quality compensator (HPQC) is proposed in this paper. Compared with conventional HPQC, the proposed HEMPQC could keep the active compensation capacity minimum to any load condition. The output current of MSVC is conducted to make the active compensation capacity minimum. The coupling branch impedance optimum design procedures are deduced. Based on the instantaneous current detecting and reactive current distribution method, the collaboration control strategy is proposed for HEMPQC to achieve the dynamic tracking of the reference signals. Finally, simulation and experimental results have verified the proposed hybrid compensation system and compensation method effectively.

To solve power quality problem in V/V traction power supply system, a novel electrical magnetic hybrid power quality compensation system based on railway power conditioner (RPC) and magnetic static var compensator (MSVC) is proposed in this study. The RPC is only used to transfer active power and suppressing harmonics. The MSVC is used to compensate reactive power and suppress 3rd and 5th harmonic currents. The proposed hybrid compensation system will reduce the capacity as well as the DC-link voltage of RPC. The principle of negative, reactive and harmonic currents compensation is analysed first. And then, a collaborative control strategy is proposed to make the compensation system have a fast respond speed. At last the simulation and experiment results have verified the proposed structure and its control strategy effectively.

In this study, a simple and highly sensitive colorimetric assay of H2O2 using triangular Ag nanoplates has been carried out. In the presence of H2O2, the Ag nanoplates are etched from triangle to round, which leads to the vanishment of the surface plasmon resonance (SPR) absorption at 400 nm and significant decrease the absorbance of the band at 670 nm. The color change of the reaction system from the initial blue to mauve can be observed. This proposed method can determine H2O2 with a dynamic range of 50 nM to 1 μM and a low detection limit of 1.36 nM. The high sensitivity of the triangular nanoplates can be ascribed to highly reactive edges/tips, and strongly tip sharpness and aspect ratio dependent SPR absorption of the triangular nanostructure. This sensing system is further extended to the detection of glucose by H2O2 generated from the enzymatic oxidation of glucose, and thus holds great promises in clinical applications.

In this work, hierarchical flower-like gold microstructures (HFGMs) are synthesized on a flexible PET film substrate by electrochemical deposition method as a SERS sensor without surfactant or directing agent. The effects of deposition current and electrolyte concentration on morphology and SERS performance are discussed to find the optimal preparation conditions. SERS activity of samples with different morphologies was investigated by comparing experiments and the mechanism was discussed. It shows the HFGMs with 3D nanoflakes and nanosheet tips present outstanding SERS activity with ultrasensitive detection limits. The lowest concentration of R6G that can be detected is 10−10 M, and the characteristic signals of thiram can be detected as low as 0.1 ppm. The HFGMs substrate show great potential of application in trace detection by SERS.

Surface enhanced Raman scattering (SERS) has been widely used in detection of food safety due to the nondestructive examination property. Here, we reported a flexible SERS film based on a polymer-immobilized gold nanorod polymer metafilm. Polystyrene–polyisoprene–polystyrene (SIS), a transparent and flexible, along with having excellent elasticity, polymer, was chosen as the main support of gold nanorods. A simple phase transfer progress was adopted to mix the gold nanorods with the polymer, which can further be used in most water-insoluble polymers. The SERS film performed satisfactorily while being tested in a series of standard Raman probes, like crystal violet (CV) and malachite green (MG). Moreover, the excellent reproducibility and elastic properties make the film a promising substrate in practical detection. Hence, the MG detection on the fish surface and trace thiram detection on orange pericarp were inspected with detection results of 1 × 10–10 and 1 × 10–6 M, which were below the demand of the N...

A novel hydrophobic-SERS substrate platform based on silver nanoparticles (AgNPs) functionalized commercially available filter paper was reported. Compared with conventional substrates, not only could this novel SERS substrate meet the requirements of simple and large-scale preparation, but also realized direct droplet-detection with reusable property. In this work, the fabrication, physical characterization, and SERS sensitivity of the substrates to spot-on food determination were studied. The experimental results show the method exhibited high reproducibility with less than 9% spot-to-spot variation in Raman intensity. Furthermore, the method was successfully applied to detect melamine in diluted milk with the instrument detection limit (IDL) down to 1 ppm in a linear correlation (1 ppm–1000 ppm). In addition, this SERS substrate could also be applied successfully in other fields, such as the determination of pesticide (thiram) and dye (malachite green) in real environment.

In order to study the suppression effect of the overvoltage when the Impact capacitor is applied in the neutral bus of the High-voltage Converter station, this paper takes the BIN-JIN HVDC transmission project as the research object and establishes an internal overvoltage calculation model in the PSCAD/EMTDC. The variation of overvoltage amplitude in neutral bus which is in the ground short circuit fault and valve triggering pulse loss fault situation is calculated and analyzed under different impact capacitor configuration schemes. The calculation results showed: installing impact capacitor can significantly reduce the overvoltage level in the neutral Bus of the converter station; and the more the capacity of the impact capacitor increased, the more obvious the suppression effect is; The impact capacitor has a restraining effect on the overvoltage of the neutral bus only when it is on the same side with the bus. To sum up, the impact capacitor could be installed to reduce the level of the inner overvoltage.

Flexible substrates have been proposed for daily-life applications in SERS detection due to the prominent sample collection properties such as they can be wrapped around non-planar object surface. Combining the noble metals with polymers, flexible SERS substrates could be fabricated with advantages of light weight, transparency and high SERS sensitivity. Herein, we prepare a gold nanorods (AuNRs)/poly(methyl methacrylate) (PMMA) film as flexible SERS substrate by self-assembling a uniformly AuNRs array layer on PMMA template. This AuNRs/PMMA film performs excellently on thiram trace detection with the lowest detection concentration of 0.5 ppb. The fabricated substrates were applied for practical detection with cucumber by directly covering the AuNRs/PMMA flexible film on the target surface. Furthermore, the high SERS sensitivity as well as great reproducibility present a wide range of prospections for the further application of non-plane surface.

The high-speed railway load is a single-phase load with high power, which can generate large negative sequence current (NSC). Many compensation methods have been applied to compensate NSC which is a big power quality problem of railway power supply system, and each method has its own characteristics. A hybrid compensation system is proposed in this paper. The system consists of two different compensation methods. One is based on railway power conditioner(RPC) with modular multilevel converter(MMC) structure(MRPC), and the other is based on Steinmetz compensation principle with magnetic static var compensation (MSVC). The MRPC has a fast response speed but expensive price, while the MSVC has a low response speed but much cheaper price. Compared with MRPC-ONLY compensation method, the hybrid compensation system has a lower cost by reducing the compensation capacity of MRPC with MSVC. Firstly, the compensation principles of the hybrid compensation system is analyzed in detail. Then, the collaboration control strategy of compensation system is proposed. Moreover, the cost of the hybrid compensation system and the MRPC-ONLY compensation method are compared. Finally, simulation and experiment results are both presented to verify the effectiveness of the hybrid compensation system and its control method.

Mercury is a major threat to the environment and to human health. It is highly desirable to develop a user-friendly kit for on-site mercury detection. Such a method must be able to detect mercury below the threshold levels (10 nM) for drinking water defined by the U.S. Environmental Protection Agency. Herein, we for the first time reported catalytically active gold amalgam-based reaction between 4-nitrophenol and NaBH4 with colorimetric sensing function. We take advantage of the correlation between the catalytic properties and the surface area of gold amalgam, which is proportional to the amount of the gold nanoparticle (AuNP)-bound Hg(2+). As the concentration of Hg(2+) increases until the saturation of Hg onto the AuNPs, the catalytic performance of the gold amalgam is much stronger due to the formation of gold amalgam and the increase of the nanoparticle surface area, leading to the decrease of the reduction time of 4-nitrophenol for the color change. This sensing system exhibits excellent selectivity and ultrahigh sensitivity up to the 1.45 nM detection limit. The practical use of this system for Hg(2+) determination in tap water samples is also demonstrated successfully.

Herein, a label-free and highly sensitive electrochemical aptasensor for the detection of angiogenin was proposed based on a conformational change of aptamer and amplification by poly(diallyldimethyl ammonium chloride) (PDDA)-functionalized graphene/gold nanoparticles (AuNPs) composites-modified electrode. PDDA-functionalized graphene (P-GR) nanosheets as the building block in the self-assembly of GR nanosheets/AuNPs heterostructure enhanced the electrochemical detection performance. The electrochemical aptasensor has an extraordinarily sensitive response to angiogenin in a linear range from 0.1 pM to 5 nM with a detection limit of 0.064 pM. The developed sensor provides a promising strategy for the cancer diagnosis in medical application in the future.