Flow Analysis Method Research Articles

Improvement of Power Flow Capability By Using An Alternative Power Flow Controller

An improved version of power flow-controller (PFC) which is based on multi-winding transformer (MWT) is presented in this paper. The objective of this article is to control the power flow in a power-line to alleviate overload in a heavily loaded system and increase power flow of an under loaded line. The novelty of multi-winding transformer based power-flow controller is the use of unequal voltage ratio in the tap-changer windings of MWT with bi-directional switches to provide a compensating voltage required to achieve the desired power flow. This new model drastically increases the number of compensating points to make it more compact with higher flexibility. It aims to utilize the full potential of a line (bound by its thermal limits) to contribute in power flow by providing several times higher resolution with limited number of switches and reduced amount of copper and iron volume compared to existing state-of-the-art technology. The proposed MWT model has been included in Newton Raphson Load Flow (NRLF) method for power flow analysis. The feasibility of the model has been realized using a standard 5 bus test system and a modified IEEE 57 bus system. Operation of the PFC has been demonstrated using a hardware laboratory prototype for generating nearest compensating points (voltage vectors) corresponding to the obtained compensating voltages after load flow solution. The results obtained are verified by simulating the controller in MATLAB/Simulink.

Research on Detection and Fault Diagnosis Technology of Electric Vehicle Charging Facilities

This paper uses waveform analysis method and data flow analysis method to study fault diagnosis and elimination. Based on the experimental results, the data flow analysis method and waveform analysis method of the vehicle were analyzed in depth. Apply fault diagnosis to find a fast fault diagnosis scheme to determine the hidden dangers of charging pile failure. The advantages and disadvantages of various fault diagnosis methods in maintenance practice are obtained.

High-speed Railway Passenger Flow Analysis Method and Platform Design Based on the Concept of One-Day-One-Plan

Based on the concept of One-Day-One-Plan, passenger demand should be considered different every day while timetable should also be adjusted according to passenger flow fluctuation. The analysis of passenger flow provides basis of line planning problem and train timetabling problem. This paper uses cluster analysis to integrate the characteristic of passenger flow data, designs and subdivides the service level of each OD. A data analysis platform connecting with Line Planning Section and Train Timetabling Section is developed to achieve the quick response of the real-time passenger flow fluctuation, ensure the supply-demand match and improve service level.

Applications of unmanned aerial vehicle (UAV) in road safety, traffic and highway infrastructure management: Recent advances and challenges.

For next-generation smart cities, small UAVs (also known as drones) are vital to incorporate in airspace for advancing the transportation systems. This paper presents a review of recent developments in relation to the application of UAVs in three major domains of transportation, namely; road safety, traffic monitoring and highway infrastructure management. Advances in computer vision algorithms to extract key features from UAV acquired videos and images are discussed along with the discussion on improvements made in traffic flow analysis methods, risk assessment and assistance in accident investigation and damage assessments for bridges and pavements. Additionally, barriers associated with the wide-scale deployment of UAVs technology are identified and countermeasures to overcome these barriers are discussed, along with their implications.

Improved sequential injection method for phosphate quantification within a wide dynamic range with in-line pre-concentration to monitor soil leachates

Phosphate is a well-known contaminant and its content is an indicator of water quality, so it is important to have an efficient monitoring of the soil leaching process.In this work, an automatic, low cost flow analysis method, capable of real-time monitoring of the soil leaching processes using spectrophotometric detection, based on the molybdenum blue reaction, was developed. The developed methodology for phosphate determination was based on the molybdenum blue reaction and includes an on-line solid phase extraction (SPE) step, involving an AG1-X8 anionic exchange sorbent.The described SI method enabled phosphate determination within a wide range, 1–80 µM, with a detection limit of 0.52 µM. It was successfully applied to leachates from laboratory scale soil columns (LSSC) and one sample analysis was carried out in triplicate, in less than 10 minutes.

Space\u2013Time Variational Multiscale Isogeometric Analysis of a tsunami-shelter vertical-axis wind turbine

We present computational flow analysis of a vertical-axis wind turbine (VAWT) that has been proposed to also serve as a tsunami shelter. In addition to the three-blade rotor, the turbine has four support columns at the periphery. The columns support the turbine rotor and the shelter. Computational challenges encountered in flow analysis of wind turbines in general include accurate representation of the turbine geometry, multiscale unsteady flow, and moving-boundary flow associated with the rotor motion. The tsunami-shelter VAWT, because of its rather high geometric complexity, poses the additional challenge of reaching high accuracy in turbine-geometry representation and flow solution when the geometry is so complex. We address the challenges with a space–time (ST) computational method that integrates three special ST methods around the core, ST Variational Multiscale (ST-VMS) method, and mesh generation and improvement methods. The three special methods are the ST Slip Interface (ST-SI) method, ST Isogeometric Analysis (ST-IGA), and the ST/NURBS Mesh Update Method (STNMUM). The ST-discretization feature of the integrated method provides higher-order accuracy compared to standard discretization methods. The VMS feature addresses the computational challenges associated with the multiscale nature of the unsteady flow. The moving-mesh feature of the ST framework enables high-resolution computation near the blades. The ST-SI enables moving-mesh computation of the spinning rotor. The mesh covering the rotor spins with it, and the SI between the spinning mesh and the rest of the mesh accurately connects the two sides of the solution. The ST-IGA enables more accurate representation of the blade and other turbine geometries and increased accuracy in the flow solution. The STNMUM enables exact representation of the mesh rotation. A general-purpose NURBS mesh generation method makes it easier to deal with the complex turbine geometry. The quality of the mesh generated with this method is improved with a mesh relaxation method based on fiber-reinforced hyperelasticity and optimized zero-stress state. We present computations for the 2D and 3D cases. The computations show the effectiveness of our ST and mesh generation and relaxation methods in flow analysis of the tsunami-shelter VAWT.

A Scientometrics Review on Farmland Abandonment Research

Using the Web of Science database, 1498 research articles published between 1900 and 2019 on the subject of farmland abandonment were retrieved. With the help of the SciMAT tool, a theme strategic diagram, overlay map and evolution map represented by keywords were constructed, and the strategic coordinate analysis and data flow analysis methods were used to analyze the research themes, evolutionary states and paths of farmland abandonment in different research time periods. The results show the following: (1) Research on farmland abandonment has rapidly grown in the past ten years, the development of studies on farmland abandonment has become more mature, and the research topics and content have tended to solidify; (2) The research topics of studies on farmland abandonment are mostly centered on forests, patterns, landscapes, land use changes, climate change, etc. The research topics have had strong continuity and few new research hotspots; (3) The study of the ecological environment effect of farmland abandonment is the basic research direction in the field of farmland abandonment and will continue to become a research hotspot; (4) Farmland abandonment has become an important part of the research on land use change and ecosystem processes; (5) The driving force of farmland abandonment includes natural, social and economic factors, among which the socioeconomic factors are the most important driving force, and will continue to be a research hotspot. Finally, this study concludes that the research directions on farmland abandonment in future should strengthen the quantitative assessment of environmental effects of farmland abandonment, information extraction and multiscale simulation monitoring, trend prediction and risk assessment.

Vibrational Energy Flow Model for a High Damping Beam with Constant Axial Force

The energy flow analysis (EFA) method is developed to predict the energy density of a high damping beam with constant axial force in the high-frequency range. The energy density and intensity of the beam are associated with high structural damping loss factor and axial force and introduced to derive the energy transmission equation. For high damping situation, the energy loss equation is derived by considering the relationship between potential energy and total energy. Then, the energy density governing equation is obtained. Finally, the feasibility of the EFA approach is validated by comparing the EFA results with the modal solutions for various frequencies and structural damping loss factors. The effects of structural damping loss factor and axial force on the energy density distribution are also discussed in detail.

Fate of nanoplastics in the environment: Implication of the cigarette butts.

Fate, transport and accumulation of nanoplastics have attracted considerable attention in the past few years. While actual researches have been focused on nanoplastics dispersed or aggregated in different environmental system, no study have been focused on the possibility that nanoplastics are co-transported with other natural or anthropogenic materials. Therefore, the large quantity of debris released in the environment, such as cigarette butts (CGB), could be part of the nanoplastics fate and behavior. Here we show the considerable sorption capacities of cigarette filters for nanoplastics. To address this topic, we chose polystyrene-based nanoplastics with similar state of charge (according to the physico-chemical characteristic of the zeta potential-45 to-40 mV) but with different sizes (50-800nm) and morphologies. A kinetic approach to sorption in fresh water (pH=8.05; 179.5μScm-1) at room temperature was carried out by means of the flow field flow analysis method (AF4) to determine the partition coefficients and water sampling rates between nanoplastics and cigarette butts. Using different models of, more or less environmentally relevant, nanoplastics (NPTs) and adequate analytical strategies, we found partition coefficients between the NPTs and CGBs ranged from 102 to 104 in freshwater conditions. We demonstrated that the physical features of the NPTs (size and morphology) have an influence on the sorption behaviour. Asymmetrical shaped NPTs with broader size distribution seems to be mostly retained in the CGBs after longer equilibration time. This result shows the importance of the NPTs features on the mechanisms governing their transfer and fate in the environment through environmental matrices, especially when other materials are involved. We anticipate our work to be a starting point for investigating the co-transport of NPTs with other materials present in the environment (natural and anthropogenic).

Towards an integrated nutrient management in crop species to improve nitrogen and phosphorus use efficiencies of Chaohu Watershed

Low nitrogen use efficiency (NUE) and phosphorus use efficiency (PUE) of crop farming has been causing serious environmental consequences. Here, we established a NUECF (nutrient use efficiency of crop farming) model with substance flow analysis (SFA) method to examine NUE and PUE of cultivating nine main crops in Chaohu Watershed in 2015. We collected data mainly from questionnaires, interview, literature, and governmental statistical yearbooks. We found that the total NUE and the total PUE were low, bellowing 12.3% and 5.2%, respectively. The nutrient inputs especially large-scale livestock manure, domestic livestock manure, and chemical fertilizers far exceeded the crop products. Different crops also showed the various patterns of nutrient use efficiencies. Rice consumed the largest nutrient inputs (807 kg N ha−1 and 367 kg P ha−1) and contributed the lowest nutrient use efficiencies (NUE: 5.8%, PUE: 2.7%). This was mainly resulted from its large fertilizer application intensity and the largest cultivated area. Rapeseed, vegetable, and wheat also contributed the great nutrient inputs and low nutrient use efficiencies, due to the similar reasons. Concerning the various patterns of fertilizer-application and cultivated areas of these crops, we analyzed six scenarios focusing on rice, wheat, rapeseed, and vegetable for 2030 and 2050 to explore an efficient nutrient management. We selected the four key factors including application intensity of chemical fertilizer, application rate of domestic livestock manure, application rate of large-scale livestock manure, and cultivated area to design the scenarios. The scenario results showed that though current policy of controlling chemical fertilizer application is a good start to manage nutrient, we have to enhance an integrated nutrient management, including reducing chemical fertilizers on specific crops, enlarging livestock manure, and controlling cultivated areas of specific crops. With the integrated nutrient management, we can expect the nutrient inputs to reduced by 26% and hence improve the nutrient use efficiencies efficiently from 2015 to 2050. The study managed the nutrients from examining nutrient use efficiencies among different crops, and could provide an effective way to mitigate the environmental problems from crop farming.

Distribution network operational risk assessment and early warning considering multi‐risk factors

Under the impact of various uncertainties, the potential operation risk of the distribution network is gradually gaining more and more attention in both security and economy. To comprehensively determine the risk level, an operational risk assessment method considering multiple risk factors is proposed. Firstly, probabilistic models are established including temporal distributions of electric vehicles and uncertainties of renewable energy. Secondly, a time-sequential security risk assessment method with several security indicators including overvoltage risk, undervoltage risk, line-overload risk and load-loss risk is established using probabilistic load flow and dynamical sensitivity weight analysis method. Thirdly, conditional value at risk model is presented for time-varying economic risk considering line-loss risk and operational profit or loss risk of distributed generations. Finally, a risk early warning standard is proposed to realise the visualisation of risk warning by defining the risk level and risk area. Simulations of different scenarios are conducted on the modified IEEE 34-bus radial test system and the results reveal that the proposed strategy is effective and practical.

Influence of frequency‐dependent anisotropy on seismic amplitude‐versus‐offset signatures for fractured poroelastic rocks

ABSTRACTFrequency‐dependent amplitude variation with offset offers an effective method for hydrocarbon detections and analysis of fluid flow during production of oil and natural gas within a fractured reservoir. An appropriate representation for the frequency dependency of seismic amplitude variation with offset signatures should incorporate influences of dispersive and attenuating properties of a reservoir and the layered structure for either isotropic or anisotropic dispersion analysis. In this study, we use an equivalent medium permeated with aligned fractures that simulates frequency‐dependent anisotropy, which is sensitive to the filled fluid of fractures. The model, where pores and fractures are filled with two different fluids, considers velocity dispersion and attenuation due to mesoscopic wave‐induced fluid flow. We have introduced an improved scheme seamlessly linking rock physics modelling and calculations for frequency‐dependent reflection coefficients based on the propagator matrix technique. The modelling scheme is performed in the frequency‐slowness domain and can properly incorporate effects of both bedded structure of the reservoir and velocity dispersion quantified with frequency‐dependent stiffness. Therefore, for a dispersive and attenuated layered model, seismic signatures represent a combined contribution of impedance contrast, layer thickness, anisotropic dispersion of the fractured media and tuning and interference of thin layers, which has been avoided by current conventional methods. Frequency‐dependent amplitude variation with offset responses was studied via considering the influences of fracture fills, layer thicknesses and fracture weaknesses for three classes amplitude variation with offset reservoirs. Modelling results show the applicability of the introduced procedure for interpretations of frequency‐dependent seismic anomalies associated with both layered structure and velocity dispersion of an equivalent anisotropic medium. The implications indicate that anisotropic velocity dispersion should be incorporated accurately to obtain enhanced amplitude variation with offset interpretations. The presented frequency‐dependent amplitude variation with offset modelling procedure offers a useful tool for fracture fluid detections in an anisotropic dispersive reservoir with layered structures.

«YAMAL LNG» PROJECT IN THE СONTEXT ОF THE NORTHERN SEA ROUTE DEVELOPMENT

The research paper focuses on identifying the conditions in which Yamal LNG can effectively finance construction work through private investment. The Case study of the Yamal LNG liquefied natural gas production complex, the ratio of the shares of public and private investment in the project for the construction of the Utrenniy terminal is considered. The authors analyze possible ways of financing construction works: using Yamal LNG's own funds, Bank lending, and a loan from NOVATEK PJSC, as the main shareholder of the project. Calculations are made and the expediency of issuing and receiving a loan from PJSC «NOVATEK» for the construction of the terminal «Untrenniy» in the port of Sabetta is proved. Regression analysis confirms the possibility of repayment of the loan from the main Yamal LNG activities is proved. As a result of the study, methods of analysis of solvency, liquidity, autonomy, cash flow analysis, forecasting and generalization methods are used. This analysis allows to take into account the scale of activity of one of the largest operators for the supply of liquefied natural gas in Russia.

APPLICATION OF PASSENGER FLOW ANALYSIS METHODS TO RESTRUCTURING THE PASSENGER TRANSPORT SYSTEM OF THE LEVOBEREZHNY DISTRICT OF MOSCOW

One of the key problems when ensuring the quality of life of residents of large cities of the world is to raise the transport services standards. Among the main aspects of solving this problem is the search for the optimal distribution of flows of personal and ground public municipal passenger transport. In this regard the planning, design, and localization of multifunctional transport interchange hubs (hereinafter – TIH) take on great significance. The experience of their arrangement has received wide acceptance in many countries of the world. In recent years Moscow has also been actively working on the design and construction of TIH; large-scale projects of transport infrastructure facilities construction are being developed. The TIH system should be capable of flexible response to changing transport needs of the population and to their realistic transformation to effectively ensure transport mobility of the population.The objective of the study is to test the passenger flow analysis methods and their application for simulation of the organization and planning of the transport interchange hub in a large district of the city, planning of the route network of municipal passenger transport.The route network of suburban and intercity transport of Northern Administrative District of Moscow has been reviewed. The passenger traffic within the TIHs Rechnoy vokzal and Khovrino has been analyzed.Based on the study, the authors propose to change the route network of ground urban passenger transport. The implementation of route network changing proposals can shorten the time spent on passenger travel and transfer. It is the authors’ opinion that the developed route network is more effective than the existing one and meets the design standards and requirements approved by local city regulations.

Buffer Overflow Vulnerability Detection Based on Unsafe Function Invocation

Buffer overflow vulnerabilities are widespread in software programs and pose a serious security threat. In order to effectively mitigate buffer vulnerabilities, we proposed a buffer overflow vulnerability detection technique based on unsafe function invocation. By extracting the typical characteristics of the insecure function call operation, a vulnerability code characteristic model is constructed, and the model is used as a guide to use the data flow analysis method for vulnerability detection. Experimental results show that our method can effectively detect buffer overflow problems caused by unsafe function invocation in programs.

Mitigating Nitrogen Emissions From Dairy Farming Systems in China

Dairy farming intensification results from the increasing demand for dairy products being met by increasing livestock populations, which places huge pressure on resources and the environment due to poor manure management. In this study, we first quantify the nitrogen (N) flows of two typical dairy manure management systems: “Ganqingfen” system and slurry-based system, based on a substance (N) flow analysis method. Second, the effects of ammonia (NH3) abatement technologies on N recycling efficiency (NRE) and N losses are evaluated for the two systems through a scenario analysis. Furthermore, we explore the mitigation potential of integrated crop and dairy production systems using a scenario analysis of a concatenation of mitigation techniques. The results indicate that the ratio of returned manure N in the “Ganqingfen” and slurry-based manure systems are 32% and 34% of feed N, respectively. N losses from manure management are 56.8–59.5% of total N excretion, of which approximately 50% is emitted as NH3. The scenario analysis indicates that implementation of single or combined NH3 abatement measures can reduce NH3 emissions by 2–56%, whereas nitrous oxide emissions (N2O) can increase depending on the specific measures. Total losses can be reduced from 80.4-83.5 kg N·head-1 to 49.2-55.7 kg N·head-1. Regarding integrated crop and dairy production systems, as the level of scenario optimization improves, resource use (e.g. land use and chemical fertilizer use) and N losses (particularly NH3 emissions) are decreased, while the NRE improves. The results of this study provide insights into the N flow and losses of typical dairy manure management systems in China, as well as effective measures towards the sustainable development of integrated crop and livestock production systems.

A multivariate statistical method for susceptibility analysis of debris flow in southwestern China

Abstract. Southwestern China is characterized by many steep mountains and deep valleys due to the uplift activity of the Tibetan Plateau. The 2008 Wenchuan earthquake left large amounts of loose materials in this area, making it a severe disaster zone in terms of debris flow. Susceptibility is a significant factor of debris flows for evaluating their formation and impact. Therefore, there is an urgent need to analyze the susceptibility to debris flows of this area. To quantitatively predict the susceptibility of the area to debris flows, this study evaluates 70 typical debris flow gullies, which are distributed along the Brahmaputra River, Nujiang River, Yalong River, Dadu River, and Ming River, as statistical samples. Nine indexes are chosen to construct a factor index system and then to evaluate the susceptibility to debris flow. They are the catchment area, longitudinal gradient, average gradient of the slope on both sides of the gully, catchment morphology, valley orientation, loose material reserves, location of the main loose material, antecedent precipitation, and rainfall intensity. Following this, an empirical model based on the Type I quantification theory is established for susceptibility prediction for debris flows in southwestern China. Finally, 10 debris flow gullies upstream of the Dadu River are analyzed to verify the reliability of the proposed model. The results show that the accuracy of the statistical model is 90 %.

Agricultural nitrogen flow in a reservoir watershed and its implications for water pollution mitigation

Miyun Reservoir plays a fundamental role in providing drinking water for Beijing Municipality. In this study, agricultural nitrogen (N) flow was analysed for water pollution mitigation in Miyun Reservoir watershed. A partial substance flow analysis (SFA) method was applied to evaluate the historic changes in N flow from 2001 to 2017. Based on this method, N flow, N losses, N accumulation, and nitrogen use efficiency (NUE) over 17 years were identified and quantified. The results showed that N input, N output, and N stock gradually decreased in this period. The decline of N input mostly resulted from the considerable decrease in chemical fertilizer use and livestock excrement application. With decreasing N input, the N stock also decreased over these years. The N losses generally decreased, except for 2009–2012, as a result of the substantial increase in harvested grains which generated even more straw for feeding or burning. In addition, the average NUE was as low as approximately 15% which may due to the huge straw storage and N losses. It is indicated that there was a great potential to decrease N input especially chemical fertilizer for mitigation of water pollution through analysis. Therefore, combined technology innovation with policy impact was proposed in Miyun County. Reducing chemical fertilizer, improving waste cycling, reducing ammonia volatilization, preventing erosion and runoff and improving peasant awareness of environmental protection were proposed as recommendations. The historic analysis of N flow could be helpful to understand the challenges of N pollution. The integrated policy and technology measures will be effective to achieve water quality control. Both will provide a reference for other countries or regions with the similar issues.

Modeling nitrogen flow in a coastal city—A case study of Xiamen in 2015

Coastal cities, most of them experiencing growing population and rapid urbanization, are facing reactive nitrogen (Nr) pollution crisis and are considered as Nr hotspots worldwide. Increased human activities generate drastic effects on the nitrogen (N) flows of coastal cities. Nevertheless, the N flows of coastal cities are not clearly understood, and the existing city-scale N flow models cannot depict the detailed N flows in coastal cities. Here, we developed a NItrogen MOdel for COastal ciTy (NIMOCOT) which includes four processes and 14 subsystems and used the Material Flow Analysis (MFA) method to model detailed N flows by taking Xiamen as a case study. The results showed that total N inputs to and outputs from Xiamen in 2015 were 403.8 and 201.7 Gg respectively, with half of total N inputs accumulated in the city. The top two N inputs were N embodied in nonfood goods consumption by households and fossil fuel combustion, accounting for 48.5% and 38.5% of total N inputs to Xiamen respectively. After city internal consumption, 109.5 Gg NOx were emitted mainly from energy and industrial subsystems, accounting for 93.2% of total gaseous Nr emissions to the atmosphere. In the typical coastal city, shipping contributed to 34.0% of the total gaseous Nr emissions to the atmosphere in the transportation sector, ranked after highway (58.0%). Moreover, the largest Nr contributor to the hydrosphere came from riparian import (56.0%) which has a significant impact on the hydrosphere of Xiamen. Our results indicated that enhancing the remove ratio of NOx emissions during fossil fuel consumption, and strengthening watershed managements to low riparian N imports from upstream will be useful for reducing N contaminants in environment of Xiamen, and NIMOCOT model is suitable for tracking the key N pollutant sources and could help to make decisions on cutting associate pollutants in coastal cities.

Comparison of intra-aneurysmal flow modification using optical flow imaging to evaluate the performance of Evolve and Pipeline flow diverting stents

BackgroundFlow diverting stent (FDS) devices have revolutionized the treatment of large and complex brain aneurysms, but there is still room for improvement, particularly on the flow diversion properties and technical...