Controller Stability and Low-frequency Interaction Analysis of Railway Train-Network Systems

In electrified railways, low-frequency oscillations (LFO) are commonly observed as a result of the widespread implementation of electric trains incorporating power electronic converters. While the impedance method has been employed in current stability studies for train-network systems, there is a requirement to extend stability modeling and analysis studies for the train-network system considering multiple trains having different control strategies. Hence, this paper establishes a unified impedance model in the dq-frame for the aforementioned system. Subsequently, an improved stability criterion, namly the dominant eigenvalue frequency response criterion (DEFRC), is proposed to assess system stability and unveil the mechanism of LFO. Furthermore, the interaction between different trains is clarified by analysis and case studies. Finally, the theoretical analysis is verified for accuracy based on time domain simulations

Localization and discrimination of GG mismatch in duplex DNA by synthetic ligand-enhanced protein nanopore analysis

: Mismatched base pairs in DNA are the basis of single-nucleotide polymorphism, one of the major issues in genetic diseases. However, the changes of physical and chemical properties of DNA caused by single-site mismatches are often influenced by the sequence and the structural flexibility of the whole duplex, resulting in a challenge of direct detection of the types and location of mismatches sensitively. In this work, we proposed a synthetic ligand-enhanced protein nanopore analysis of GG mismatch on DNA fragment, inspired by in silico investigation of the specific binding of naphthyridine dimer (ND) on GG mismatch. We demonstrated that both the importing and unzipping processes of the ligand-bound DNA duplex can be efficiently slowed down in α-hemolysin nanopore. This ligand-binding induced slow-down effect of DNA in nanopore is also sensitive to the relative location of the mismatch on DNA duplex. Especially, the GG mismatch close to the end of a DNA fragment, which is hard to be detected by either routine nanopore analysis or tedious nanopore sequencing, can be well differentiated by our ND-enhanced nanopore experiment. These findings provide a promising strategy to localize and discriminate base mismatches in duplex form directly at the single-molecule level

Some thoughts and suggestions on the practice of water prevention and control in coal mines

According to some hot spots such as exploration before excavation，difficulties like drainage mining under special conditions and contradictory while operating procedures in recent coal mining water prevention projects, confusions brought to production practice and safety supervision are analyzed, some opinions are also put forward. Firstly, the connation of “doubt will be prospected” is discussed in this paper. It is assured that “doubt will be explored” comes after “prediction and forecast”. The “prediction and forecast” are key factors to problems like types of water hazards, water pressure and positions of water, based on what water exploration and release can be designed. From the historical background and realistic conditions, the analysis shows that the exploration before excavation proposed in [2011] No.70 document formulated by Shanxi Province is implemented under specific conditions, with strong pertinence (ancient wells and cellar water). The type of water damage is clear, the space position of water pressure source is roughly known, and the design conditions of drilling hole are available. Therefore, design conditions of water exploration drillings are acquired and “exploration before excavation” is reasonable. However, the scope of “exploration before excavation” cannot be extended infinitely to other fields, otherwise it will be aimless, causing bumps in design, execution and supervision. Secondly, degradation of water on soft rocks is analyzed. Degradations like crumble, rock mud, expansion and floor heave can happen on complicated soft rocks which possess weak cementation, low altitude, high expansion and strong watery, limiting production efficiency. The purpose of pre-dredging weak aquifer under soft rock condition is to improve the production conditions and to increase production efficiency. It is suggested that the regulations should make principles constraints on such drainage holes, so as to facilitate enterprises to formulate construction technical measures in combination with the actual situations. Otherwise, there will be a difference in understanding between government regulators and enterprises. Finally, according to the definition in the procedure, the water-conducting fracture zone does not include the caving zone (above the caving zone); nevertheless, the empirical formula in the procedure and the attached drawings show that the water-conducting fracture zone includes the caving zone, which has inconsistency between the front and the back. For this case, two alternative revision suggestions are advanced. Through the analysis of this paper, some fuzzy concepts are clarified, which is convenient for the production unit to accurately implement the rules and regulations, conducive to the precise supervision of safety supervision department. Besides, dilemma between the supervision department and the enterprise can be avoided

Quantitative Assessment Mechanism of Low Frequency Oscillations in Train-Network Systems

Low frequency oscillations (LFOs) in the electrified train-network system can lead to serious traction blockade accidents. Although impedance models and stability analysis tools have been applied in existing studies to address specific cases, a generalized mechanism to address LFO is still not established so far. This paper proposes a quantitative assessment method to reveal the underlying mechanism of LFOs. Founded on the improved Nyquist criterion, a stability margin indicator is defined to concretely describe system stability, then its corresponding expression is derived by combining the simplified impedance model as the basis for quantitative analysis. To this end, the identified negative resistances in the impedance model are revealed as the root cause of LFOs. Besides, theoretical justification for the impact of parameter tuning on the system stability is provided based on the explicit formula of the stability margin indicator. Finally, the effectiveness and accuracy of the theoretical analysis are verified under simulations and hardware-in-the-loop experimental conditions

Low-frequency oscillation of train–network system considering traction power supply mode

Abstract The low-frequency oscillation (LFO) has occurred in the train–network system due to the introduction of the power electronics of the trains. The modeling and analyzing method in current researches based on electrified railway unilateral power supply system are not suitable for the LFO analysis in a bilateral power supply system, where the trains are supplied by two traction substations. In this work, based on the single-input and single-output impedance model of China CRH5 trains, the node admittance matrices of the train–network system both in unilateral and bilateral power supply modes are established, including three-phase power grid, traction transformers and traction network. Then the modal analysis is used to study the oscillation modes and propagation characteristics of the unilateral and bilateral power supply systems. Moreover, the influence of the equivalent inductance of the power grid, the length of the transmission line, and the length of the traction network are analyzed on the critical oscillation mode of the bilateral power supply system. Finally, the theoretical analysis results are verified by the time-domain simulation model in MATLAB/Simulink

Extralobar pulmonary sequestration: A case report and literature review

Key Clinical Message Pulmonary sequestration is a congenital malformation of lung development in which part of the lung tissue is separated from the normal lung during the embryonic phase and develops separately and receives blood supply from an aberrant systemic artery forming a nonrespiratory mass. In brief, early in embryonic development, certain tissues that should have atrophied and been gradually absorbed are left behind due to impairment of the atrophy process and form anomalous branches of the aorta, which pull parts of the lung tissue, isolating them from normal lung tissue and bronchi, and thus forming separate lung tissue. According to the relationship of the mass to the pleural covering, pulmonary sequestration can be divided into two types, intralobar pulmonary sequestration (ILS) and extralobar pulmonary sequestration (ELS), of which approximately 75% of cases are ILS, but ELS is less common. Symptoms are not obvious in either type, making diagnosis and differential diagnosis more difficult. Here we report a 33‐year‐old patient with only insignificant abdominal distension who was eventually diagnosed with retroperitoneal ELS

The role of leisure-time physical activity in maintaining cervical lordosis after anterior cervical fusion and its impact on the motor function in patients with hirayama disease: a retrospective cohort analysis

Abstract Background Surgical treatment has been increasingly performed in Hirayama disease (HD) patients to limit excessive neck flexion and restore cervical lordosis. However, postoperative recurrence of cervical lordosis loss may restart the progress of HD. Many studies have demonstrated a relationship between neck muscle strength and cervical lordosis, and it is widely accepted that leisure-time physical activity (LTPA) can increase muscle strength. However, there are few reports about the correlation between LTPA and maintenance of postoperative cervical curvature. Objective To quantify the cervical lordosis and motor function before and after operation in HD patients and to analyze the impact of postoperative LTPA levels on the changes in these measurements. Methods C2-7 Cobb were measured in 91 HD patients before, 2–5 days and approximately 2 years after operation. Motor unit number estimation (MUNE) and handgrip strength (HGS) were performed in all patients before and approximately 2 years after operation, and both cross-sectional area and fatty infiltration of posterior cervical muscles were measured in 62 patients. Long-form international Physical Activity Questionnaire and its different domains was administered to all patients at postoperative 2-year assessments. Results The C2-7 Cobb was larger immediately and approximately 2 years after operation than that at preoperative assessment (P < 0.05). The preoperative to postoperative change in C2-7 Cobb was associated with postoperative changes in the symptomatic-side HGS and bilateral MUNE measurements (P < 0.05). Importantly, the patients performing LTPA had greater improvements in C2-7 Cobb from immediate to approximately 2 years after operation and greater C2-7 Cobb at last follow-up than those without LTPA, and postoperative improvements in both symptomatic-side MUNE measurements and symptomatic-side HGS were also greater in the former than in the latter (P < 0.05). Conclusions Postoperative LTPA has a positive effect on recovery/maintenance of cervical lordosis after operation, which may alleviate the motor unit loss of distal upper limbs in HD patients. Therefore, postoperative LTPA may be beneficial for postoperative rehabilitation or early conservative treatment of HD patients

Bisdemethoxycurcumin Attenuated Renal Injury via Activation of Keap1/Nrf2 Pathway in High-Fat Diet-Fed Mice

Bisdemethoxycurcumin (BDMC), a principal and active component of edible turmeric, was previously found to have beneficial effects on metabolic diseases. Chronic kidney disease (CKD) may benefit from its potential therapeutic use. Using a high-fat diet (HFD)-fed mouse model, we examined the effects of BDMC on renal injury and tried to determine how its associated mechanism works. A number of metabolic disorders are significantly improved by BDMC, including obesity, hyperglycemia, hyperinsulinemia, hyperlipidemia and inflammation. Further research on renal histopathology and function showed that BDMC could repair renal pathological changes and enhance renal function. Moreover, decreased serum malondialdehyde (MDA), elevated superoxide dismutase (SOD) activity, and the inhibition of renal reactive oxygen species (ROS) overproduction revealed the alleviation of oxidative stress after BDMC administration. In addition, renal Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2 (Keap1/Nrf2) pathway was activated in BDMC-treated mice. In conclusion, these findings demonstrated BDMC as a potential therapy for HFD-induced CKD via the activation of the Keap1/Nrf2 pathway

Impacts of Climate Change on Runoff in the Heihe River Basin, China

Located in the central part of the arid regions of Northwest China, the Heihe River Basin (HRB) plays an important role in wind prevention, sand fixation, and soil and water conservation as the second largest inland river basin. In the context of the warming and wetting climate observed in Northwest China, the situation of the ecological environment in the HRB is of significant concern. Using the data from meteorological observation stations, grid fusion and hydrological monitoring, this study analyzes the multi-scale climate changes in the HRB and their impacts on runoff. In addition, predictive models for runoff in the upper and middle reaches were developed using machine learning methods. The results indicate that the climate in the HRB has experienced an overall warming and wetting trend over the past 60 years. At the same time, there are clear regional variabilities in the climate changes. Precipitation shows decreasing trends in the northwestern part of the HRB, while it shows increases at rates higher than the regional average in the southeastern part. Moreover, the temperature increases are generally smaller in the upper reaches than those in the middle and lower reaches. Over the past 60 years, there has been a remarkable increase in runoff at the Yingluo Gorge (YL) hydrological station, which exhibits a distinct “single-peak” pattern in the variation of monthly runoff. The annual runoff volume at the YL (ZY) hydrological station is significantly correlated with the precipitation in the upper (middle) reaches, indicating the precipitation is the primary influencing factor determining the annual runoff. Temperature has a significant impact only on the runoff in the upper reaches, while its impact is not significant in the middle reaches. The models trained by the support vector machines and random forest models perform best in predicting the annual runoff and monthly runoff, respectively. This study can provide a scientific basis for environmental protection and sustainable development in the HRB