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Objective: To investigate the dominant metabolic enzymes of six effective components (astragaloside IV, glycyrrhizic acid, calycosin-glucuronide, formononetin, ononin, calycosin-7-O-β-D- glucoside) of Huangqi Liuyi decoction extract (HQD).Methods: Mouse liver microsomes were prepared. The effects of specific inhibitors of CYP450 enzymes on the metabolism of six effective components of HQD were studied using liver microsomal incubation in vitro.Results: The chemical inhibitors of CYP2C37 inhibit the metabolism of glycyrrhizic acid and astragaloside IV. Formononetin and astragaloside IV metabolism is inhibited by the chemical inhibitors of CYP2C11. The chemical inhibitors of CYP2E1 and CYP1A2 inhibit the metabolism of calycosin-glucuronide. Chemical CYP3A11 inhibitors prevent formononetin and glycyrrhizic acid from being metabolized. However, no inhibitor significantly affected the metabolism of ononin and calycosin-7-O-β-D-glucoside.Conclusion: CYP2C37 may be involved in the metabolism of astragaloside IV and glycyrrhizic acid, the metabolism of astragaloside IV and formononetin may be related to CYP2C11, the metabolism of calycosin-glucuronide may be related to CYP1A2 and CYP2E1, and CYP3A11 may be involved in the metabolism of glycyrrhizic acid and formononetin. This research provides an experimental basis for exploring the pharmacokinetic differences caused by metabolic enzymes.

Purpose: To investigate the safety and effectiveness of semen strychni total alkaloid microcapsules (SSTAM), compared with semen strychni total alkaloids (SSTA). Methods: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was employed to assess pharmacokinetics of brucine and strychnine in rats. Acute toxicity was investigated in pre-test and formal experiments in mice. The pharmacodynamics of SSTAM and SSTA were evaluated by their analgesic and anti-inflammatory activities. Results: With respect to brucine, the half-life of SSTA group (1.6 mg/kg), low-dose SSTAM group (6 mg/kg) and high-dose SSTAM group (10 mg/kg) was 5.723, 9.321 and 9.025 h, respectively. With respect to strychnine, the half-life of SSTA group, low-dose SSTAM group and high-dose SSTAM group was 4.065, 8.819 and 8.654 h, respectively. The LD50 values of SSTAM group and SSTA group were 236.59 and 30.27 mg/kg, respectively. The pain inhibition rates of SSTAM groups (25 and 50 mg/kg) were higher than that of SSTA group (p < 0.05) while the pain threshold values of the SSTAM groups (25 and 50 mg/kg) were higher than that of blank control (p < 0.01) and SSTA groups (p < 0.01) at 60 min and 120 min. The inhibition rates of the SSTAM groups (25 and 50 mg/kg) were higher than that of SSTA group based on ear swelling and cotton ball granulation tests. Compared with blank control and SSTA groups, the absorbance values of SSTAM groups (25 and 50 mg/kg) were lower (p < 0.01). Conclusion: SSTAM increases the dosage of administration but reducea the toxicity of the alkaloids in rats, and is thus a potentially safe and effective drug delivery system.

Additional file 1.

Additional file 3: Table S3. Degree of linkage disequilibrium of MTHFR genetic polymorphisms between VSD group and control group.

Additional file 2: Table S2. Degree of linkage disequilibrium of MTHFR genetic polymorphisms between ASD group and control group.

Additional file 4: Table S4. Degree of linkage disequilibrium of MTHFR genetic polymorphisms between PDA group and control group.

Additional file 3: Table S3. Degree of linkage disequilibrium of MTHFR genetic polymorphisms between VSD group and control group.

Additional file 4: Table S4. Degree of linkage disequilibrium of MTHFR genetic polymorphisms between PDA group and control group.

Additional file 1: Table S1. Degree of linkage disequilibrium of MTHFR genetic polymorphisms between total CHD group and control group.

Additional file 2: Table S2. Degree of linkage disequilibrium of MTHFR genetic polymorphisms between ASD group and control group.

There are many receiving-end provincial grids in North China-Central China synchronous power grid. They get power through UHVDC transmission channel and interprovincial HVAC transmission channel. This paper analyzes two important instability risks faced by this type of provincial power grid, including power angle instability after DC blocking fault and voltage instability after AC system fault. The typical engineering control measures for the instability risk are given, and their applicable conditions, characteristics and application strategies are analyzed. Finally, the application prospect of battery energy storage technology to improve the safety and stability of power grid is discussed.

Based on the actual inspection requirements, this paper fully studies the application scenarios of UAV and robot inspection, and develops an intelligent UAV line inspection robot composite system based on UAV, robot, edge computing, machine vision, artificial intelligence and other technologies, which plays a significant role in promoting the application practice of UAV and robot inspection technology.

This study aims to define an optimal dosage and to investigate the therapeutic effects of brucine dissolving microneedles (Bru-DMNs) on rheumatoid arthritis (RA). Composite PVP K30 and CS were selected as needle tip materials, single PVA as a backing material, and brucine (Bru) as the drug of this model. Bru-DMNs were successfully fabricated by a two-step centrifugation method. The DMNs produced satisfactory mechanical strength and biocompatibility, and the needle body was completely dissolved in approximately 10 min. After microneedle (MN) administration, the skin recovered to its original state within 6 h free of irritation. The transdermal test in vitro revealed that the skin transmittance of Bru could be significantly improved by MN administration. Drug load in the MN was released after 6 h, with cumulative permeability at 94.84%. To define the optimal dosage of Bru-DMNs for RA, the present study established an RA rat model and administered different concentrations of Bru solution or suspension. The optimal dosage of MN production (approximately 124.50 g/patch) was determined when Bru concentration was at 16 mg/mL. Further pharmacodynamics exploration revealed that drug loading MN effectively inhibited toe swelling of RA rats, reduced synovial hyperplasia due to articular cartilage erosion, and diminished swelling in the thymus and spleen. Network pharmacological analysis demonstrated that Bru might play a role in the RA treatment by regulating TNF-ɑ, IL-17and IL-1β. This regulation pathway was verified by ELISA and western blot assays.

A novel biological material named activated carbon fibers-sodium alginate@Sphingopyxis sp. YF1 (ACF-SA@YF1) was synthesized for microcystin-RR (MC-RR) and nutrient pollutant degradation in eutrophic water. The synthesized biomaterial was characterized by scanning electron microscopy (SEM). Box-Behnken design and response surface methodology (RSM) were utilized for the optimization of conditions during the MC-RR degradation. The degradation of MC-RR and nutrient pollutants was dynamically detected. The results revealed that the optimal conditions were temperature 32.51 °C, pH 6.860, and inoculum 14.97%. The removal efficiency of MC-RR, nitrogen, phosphorus, and chemical oxygen demand were 0.76 μg/mL/h, 32.45%, 94.57%, and 64.07%, respectively. In addition, ACF-SA@YF1 also performed satisfactory cyclic stability, while the MC-RR removal efficiency was 70.38% after seven cycles and 78.54% of initial activity after 20 days of storage. Therefore, it is reasonable to believe that ACF-SA@YF1 is an effective material which has a great prospect in removing MC-RR and nutrients from freshwater ecosystems.

With the wide application of power electronic technologies in power system, such as HVDC, new energy power stations and FACTS, the dynamic characteristics of the interconnected power grid have changed dramatically, and the traditional quasi steady model based electromechanical transient program cannot simulate the fast switching process of the power electronic components and its non-fundamental frequency or asymmetry characteristic, which is important to the accuracy of HVDC and FACTS models. Because of the limitation of calculation load and computing speed, traditional electromagnetic transient program cannot replace electromechanical transient program in large-scale power system stability analysis. FEMTP should be redesigned for transient stability analysis of large-scale electronic power system. Then the generator and transmission line’s electromagnetic models are discussed in this paper, and the discussion and simulation shows the adequation of their electromechanical transient model in FEMTP. Afterwards, the implementation of FEMTP was discussed in detail, and the example of China East power grid shows the appropriation of simplified electromechanical models and proposed technologies.

Power grids in China are in the stage of rapid development of UHV AC and DC. Cascading failures with timing and propagation characteristics become the main threat to power grid security. Based on the EMS and WAMS information and according to the principle of practicality, a practicable scheme for cascading failure prediction and analysis is proposed. And the related analysis system has been developed. In line with the timing development characteristics of cascading failures, the overall system layered architecture and key technologies are proposed. The access relationship of the main sub-function modules of the system is explained. Firstly, the EMS and WAMS multiple source data integration technologies are described. Furthermore, comprehensively considering the variation of power grid structure and state changes, the vulnerability component set identification is realized. Thirdly, on the basis of the set of vulnerability elements, the full dynamic process simulation program is used to select and check progressive cascading fault sets automatically, which can consider the effects of relay protection and security control equipment. Finally, in view of the possible serious faults, aiming at the weak section in the fault propagation path, the corresponding power flow auxiliary adjustment strategy is presented.

The construction of Jiangsu UPFC project has put forward higher requirements for the simulation and modeling of large-scale power electronics equipment. In order to deeply analyze the dynamic response of unified power flow controller based on modular multilevel converter(MMC-UPFC). The study of this paper is based on the MMC-UPFC operation principle and control strategy. We established the electromagnetic transient model framework and conducted a research of IEEE 39 case and South Jiangsu 500kV UPFC project in electromagnetic transient and electromechanical transient hybrid simulation program. Besides, a basic model framework of UPFC is also development in independent designed large-scale power system analysis software package called PSD-PSModel hybrid simulation platform and the MMC-UPFC hybrid simulation capabilities is realized. At the same time, the basic functions of the model are verified by simulation results. The achievement can provide strong technical support for further MMC-UPFC project and educational theory.

As the development and building of 220kV and 500kV Unified Power Flow Controller (UPFC) in Jiangsu grid of China, a higher requirement is put forward by power grid analysis on the accuracy of modelling and simulation. UPFC has different characteristics under different control strategies, and Modular Multilevel Converters (MMC) simulation is a difficult task. In order to study its dynamic characteristics, an electromagnetic model of UPFC based on MMC was proposed, which could simulate its different control strategies and relative dynamic characteristics. The proposed model was realized in PSD-PSModel program and verified using IEEE39 case. The simulation results show that the proposed UPFC model could provide effective tool for analysing the UPFC's dynamic characteristics.

The time-domain simulation plays an important role in planning, designing and operation of the power system, but mismatches between its results and the actual system response show that the credibility evaluation of dynamic models is critical in all the above aspects of power systems. This paper discusses the technologies of credibility evaluation, including hybrid dynamic simulation with PMU measurements, error analysis and the calculated indices. Moreover, a phase shift method is presented to implement hybrid dynamic simulation in PSD-FDS. Then the paper proposes a credibility evaluation scheme to provide solution for the evaluation. At last, one sample is used to validate the implementation of hybrid dynamic simulation, while the other sample illustrates the effectiveness of the credibility evaluation approach.

A large number of blackouts have happened in power system recently, and most of them are cascading outages. Because of their severe consequences, a variety of methods are proposed to study the mechanism of cascading outages. These methods can be divided into four categories: self-organized critical theory, complex network theory, operational reliability theory, and power system simulation theory. This article reviewed the researches on cascading outages, and pointed out some important research achievements and their drawbacks.

Risk assessment theory is paid more and more attention to consider the random characteristics of power system, but traditional method could not consider the operating factors as frequency response of generators and loads, various emergency control measures. In this paper, a dynamic contingency analysis method base on dynamic load flow is proposed considering the above factors. The dynamic contingency analysis is a less time-consuming approach, but could simulate as well the detailed load shedding relay model, and the time-varying reliability model. So the proposed dynamic contingency analysis gives a good tool for cascading failure simulation.

Special protection systems (SPSs) are very important for the safety and stability of large-scale power systems. A more accurate assessment of system security can be achieved if SPS models are constructed to conform to the actual situation of power grids. However, it is difficult to realistically simulate the performance of SPSs for a large-scale power system. Based on virtual relays and ladder diagrams, this paper proposes a general modelling method for SPSs that conforms to their actual characteristics. Moreover, the full dynamic calculations including these models can be realized using this approach. The modelling process is significantly simplified and the computing work is considerably reduced using the new method. The results show that the simulation program, including the SPS models, can more accurately represent the dynamic performance of a power system after a disturbance, especially during cascading outages caused by power flow transfers. The method can be a useful tool for accurately analyzing the dynamic stability of power systems.

VSC-HVDC (Voltage Source Converter High Voltage Direct Current) transmission system is a recent HVDC technology. The paper presents a new way of VSC-HVDC electromechanical transient modeling and simulation, which is based on the theory of equivalent sources. This method uses equivalent sources to substitute for voltage source converter, in addition, there are no simulation of IGBTs or PWM trigger modular, so it is more appropriate for electromechanical transient modeling and simulation. By this way, the detailed dynamic model for VSC-HVCD is developed. This model includes four parts, i.e. the normal ac system, the VSC-HVDC inner dc system, the interface between ac and dc system and the VSC-HVDC control system. Then a case of VSC-HVDC transmission system is established in PSCAD, the results show that by using this method for VSC-HVDC electromechanical transient modeling and simulation, not only the steady-state power flow can be controlled, but the system can achieve ideal dynamic response.

To solve the problem of lacking of accurate protection relay models in power system dynamic simulation, a general modeling method of protection relay based on “virtual relay” is proposed. A “virtual relay” is a kind of simulation for real relay and defined with rules of logic operation. With hierarchical structure and object-oriented modeling strategy, this method has the advantages of clean logic and convenient modeling, and it's easy for the users to correct models and expand functions. An open and transparent protective relay model library is developed and dynamic simulation calculation including protection relay models is realized. The simulation results revealed that the dynamic simulation program including protection relay models can represent the dynamic performance of electric power system after disturbance more actually. It can be used to analyze cascading failures caused by incorrect operation of protective relays, replay the accident in a long time after a disturbance in power system, study the essence cause of accident and find the correct fault prevention measures.

This paper discusses a new mixed numerical integral algorithm for unified dynamic simulations of power systems in which the electro-mechanical transient, medium-term and long-term dynamic phenomena are united. The main problems were analyzed using the existing Gear integral algorithm for the dynamic simulation of power systems. The new mixed integral algorithm integrates the advantages of the implicit trapezoidal integration algorithm with a fixed time step and the Gear algorithm with a variable time step. The proposed algorithm was found to achieve a great computational efficiency in the transient stability stage of unified dynamic simulation and can easily deal with discontinuous equations in control system models. The simulation results of two actual large-scale power systems show that the proposed algorithm is effective and feasible.

This paper proposes a method to perform electromechanical and electromagnetic transient hybrid simulation, including the interface location, the mutual equivalence solution of the electromechanical system and the electromagnetic system, which can perform excellently when the positive and negative sequence parameters of the equivalent circuit are different. The least square method is adopted to obtain the fundamental frequency current as the equivalent solution of the electromagnetic system. The method was demonstrated to be effective and feasible through two cases. It solves hybrid simulation problems when variable faults (including asymmetric faults) occur in an electromechanical network.

With the rapid development of large-scale interconnected power systems, inter-area low frequency oscillation phenomena occasionally occur; thus, the small signal stability problem has become a serious issue affecting power system stability. When analyzing the small signal stability of a large-scale power grid (in particular, on-line dynamic security early warning systems), given the high rank of the differential algebra equations (DAEs), the serial eigenvalue algorithm cannot meet the requirements of computation speed. In recent years, the development of multi-core CPU technology has been very rapid. By fully using the hardware resources of multi-core CPU computers, the small signal stability calculation speed problem can be effectively solved in parallel computing technology. In this paper, a frequency-domain parallel eigenvalue search algorithm of power systems based on multi-processing is described, with the algorithm realized in the PSD-SSAP system, which is widely used in China. The calculation is accurate, the realization of the algorithm is simple, and the parallel computing efficiency is very high. Numerical simulation results of actual large-scale power systems show that the proposed algorithm is correct and efficient.

Fault simulation is one of the main components of dynamic electric power system simulation programs. In this work, a fault-branch based admittance matrix was used to simulate a variety of multiple symmetrical or asymmetrical faults in unified dynamic power system simulation software. Admittance matrix contraction was employed to process multiple faults and random faults. An important feature of this method is its ability to process any faults in a branch without the addition of new branches or nodes, which improves the calculation efficiency and the usability of the software.

A new fuzzy theory based principle for distinguishing unstable swing from stable swing in complicated power systems is presented in this paper. In terms of the behavior of electrical quantities, the distinction between stable and unstable swing conditions isn't clear and certain because of the affection of various system parameters in the power system. To solve the problem, the new principle uses the so-called fuzzy comprehensive evaluation to detect out-of-step conditions. Based on the several criteria characterized by fuzzy membership functions, it has many advantages over a conventional principle using a single criterion, such as improved performance and convenience of relay setting etc. Finally, the results of digital simulations are also provided in this paper.