Heavy Flow Research Articles

Effects analysis of reward functions on reinforcement learning for traffic signal control.

The increasing traffic demand in urban areas frequently causes traffic congestion, which can be managed only through intelligent traffic signal controls. Although many recent studies have focused on reinforcement learning for traffic signal control (RL-TSC), most have focused on improving performance from an intersection perspective, targeting virtual simulation. The performance indexes from intersection perspectives are averaged by the weighted traffic flow; therefore, if the balance of each movement is not considered, the green time may be overly concentrated on the movements of heavy flow rates. Furthermore, as the ultimate purpose of traffic signal control research is to apply these controls to the real-world intersections, it is necessary to consider the real-world constraints. Hence, this study aims to design RL-TSC considering real-world applicability and confirm the appropriate design of the reward function. The limitations of the detector in the real world and the dual-ring traffic signal system are taken into account in the model design to facilitate real-world application. To design the reward for balancing traffic movements, we define the average delay weighted by traffic volume per lane and entropy of delay in the reward function. Model training is performed at the prototype intersection for ensuring scalability to multiple intersections. The model after prototype pre-training is evaluated by applying it to a network with two intersections without additional training. As a result, the reward function considering the equality of traffic movements shows the best performance. The proposed model reduces the average delay by more than 7.4% and 15.0% compared to the existing real-time adaptive signal control at two intersections, respectively.

Deep Reinforcement Learning for Traffic Light Timing Optimization

Existing inflexible and ineffective traffic light control at a key intersection can often lead to traffic congestion due to the complexity of traffic dynamics, how to find the optimal traffic light timing strategy is a significant challenge. This paper proposes a traffic light timing optimization method based on double dueling deep Q-network, MaxPressure, and Self-organizing traffic lights (SOTL), namely EP-D3QN, which controls traffic flows by dynamically adjusting the duration of traffic lights in a cycle, whether the phase is switched based on the rules we set in advance and the pressure of the lane. In EP-D3QN, each intersection corresponds to an agent, and the road entering the intersection is divided into grids, each grid stores the speed and position of a car, thus forming the vehicle information matrix, and as the state of the agent. The action of the agent is a set of traffic light phase in a signal cycle, which has four values. The effective duration of the traffic lights is 0–60 s, and the traffic light phases switching depends on its press and the rules we set. The reward of the agent is the difference between the sum of the accumulated waiting time of all vehicles in two consecutive signal cycles. The SUMO is used to simulate two traffic scenarios. We selected two types of evaluation indicators and compared four methods to verify the effectiveness of EP-D3QN. The experimental results show that EP-D3QN has superior performance in light and heavy traffic flow scenarios, which can reduce the waiting time and travel time of vehicles, and improve the traffic efficiency of an intersection.

Study on the stability of oil-water annular flow under different amplitude

Compared with the traditional transportation of high-viscosity crude oil, water annular transportation has the advantages of low energy consumption and no change in crude oil composition. With the continuous development of marine heavy oil transportation, submarine oil pipelines are inevitably subjected to vibration and impact, affecting the annular flow in the pipeline. In this paper, the VOF model in Fluent software is used to simulate the stability of oil-water annular flow in a horizontal pipeline under different amplitudes and the interface characteristic parameters of annular flow. In addition, the influence of vibration on oil-water annular flow in the horizontal pipeline under different marine environments is studied. The results showed that the vibration parameters have an influence on the flow of oil-water annular flow in the horizontal pipeline. Under the condition of constant inlet velocity, the eccentricity degree of oil core is analyzed to reveal the law that the stability of annular flow decreases with the increase of amplitude. The relationship between the eccentricity of oil core and the vibrational parameters of pipes are explored in this paper. At the same time, the unit pressure drop under the condition of pipe vibration and its mechanism are studied. These results could provide references for parameters optimization of heavy oil-water annular flow transportation under vibration conditions.

Interaction predictors of self-perception menstrual symptoms and influence of the menstrual cycle on physical performance of physically active women.

To analyze the physical performance, self-perception menstrual symptoms, of physically active eumenorrheic women with endogenous ovarian cycle in two phases of the menstrual cycle. Twenty-six women participated in the study (age 25.8 ± 3.9years; height 1.64 ± 0.58m; mass 64 ± 12.32kg; menarche 11.69 ± 1.28years). Assessments were performed in two phases of the menstrual cycle (MC), Early-Follicular Phase (FP) and Mid-Luteal Phase (LP), performance was assessed through total time to exhaustion (TTE), complete stages (CE), and final speed (FE), through a graded exercise test (GXT). Information on the participants' menstrual symptoms and their perceptions of the influence of MC on their performance were also collected. Data normality was assessed using the Shapiro-Wilk test. Paired analyses were conducted (t test or Wilcoxon) to examine the responses between the menstrual phases. The interaction analysis of symptom predictors was performed by multiple linear regression, with a significance level of p ≤ 0.05. There was no significant difference in physical performance between the phases during the GXT in TTE (mean difference 8.50; 95% CI - 11.99 to 42; p = 0.36). During FP, women with heavy flow had shorter performance in the GXT (t = - 2.5; p = 0.01), demonstrating an r2 = 0.32. In LP, for the women who reported not having the perception of the influence of the menstrual cycle on exercise, the total test time was longer (t = 2.55; p = 0.01), with an r2 = 0.45. There was no difference in physical performance between FP and LP. However, menstrual flow intensity and perception of cycle interference demonstrated a decrease in TTE.

Analysis of air ingress scenario in GEMINI+ plant

The work presented in this paper was performed within the Euratom Horizon 2020 GEMINI+ project. The GEMINI+ reactor is a prismatic block-type High-Temperature Gas-Cooled Reactor (HTGR). Within tasks devoted to safety, an analysis of air ingress scenario was performed by NRG with the thermal–hydraulic system code SPECTRA, while UJV and NCBJ worked with the integral system code MELCOR. Two air ingress scenarios were analyzed:Design Basis Accident (DBA) scenario. The air ingress scenario selected as DBA is a 65 mm break of a Helium purification line on top of the Steam Generator,Large air ingress scenario. The air ingress scenario selected is guillotine break of the coaxial gas duct.The DBA scenario is characterized by a very long period with practically stagnant gas in the primary system after the initial depressurization. However, very small gas flows through the break due to counter flow and diffusion in the break region (gas velocities of 10–2 m/s) are difficult to model with system codes. Therefore the break models in the system code were calibrated by performing CFD simulations. Furthermore, a model of gas mixing by diffusion was introduced in the NRG analysis for the practically stationary gas in the primary system (gas velocities of 10–4 m/s). The large air ingress scenario, with relatively large flow through the break, is easier to model from this standpoint.The NRG SPECTRA results showed that the amount of air that can reach the core is extremely small in the DBA accident (0.5 kg of graphite consumed after 100 h). The maximum depth of oxidation was 2 µm. In the large air ingress scenario the air ingress is significantly larger. At 100 h, approximately 105 kg of graphite was consumed. Even then, the maximum depth of oxidation was very small, approximately 0.2 mm. MELCOR results, performed at NCBJ and UJV, basically confirmed that the amount of air ingress is very small. The numbers were somewhat higher, mainly due to heavy flow oscillations in the break that could not be mitigated in MELCOR calculations.

Impact of Sediment Deposition on Flood Carrying Capacity of an Alluvial Channel: A Case Study of the Lower Indus Basin

Impacts of climate change and human-made interventions have altered the fluvial regime of most rivers. The increasingly uncertain floods would further threaten the flow delivery system in regions such as Pakistan. In this study, an alluvial reach of the Indus River below Kotri barrage was investigated for the geomorphologic effects of sediments deposited over the floodplain as well as the influences on the downstream flood-carrying capacity. The hydrodynamic modeling suite HEC-RAS in combination with ground and remotely sensed data were used to undertake this analysis. Results suggest that the morphology of the river reach has degraded due to depleted flows over a long period and hydrological extremes that have led to excessive sediment deposition over the floodplain and an enhancement in flood water extension possibility over the banks. A deposition of 4.3 billion cubic meters (BCM) of sediment increased the elevation of the channel bed which in turn reduced a 17.75% flood-carrying capacity of the river reach. Moreover, the excessive deposition of sediments and the persistence of low flows have caused a loss of 48.34% bank-full discharges over the past 24 years. Consequently, the river’s active reach has been flattened, with a live threat of left levee failure and the inundation of the populous city of Hyderabad. The study would gain insights into characterizing the impacts associated with a reduction in the flood-carrying capacity of the alluvial channel on account of the inadequate sediment transport capacity after heavy flow regulations.

Statistical Modeling for Traffic Noise: The Case of Kirkuk City

The auditory system can suffer from exposure to loud noise and human health can be affected. Traffic noise is a primary contributor to noise pollution. To measure the noise levels, 3 variables were examined at 25 locations. It was found that the main factors that determine the increase in noise level are traffic volume, vehicle speed, and road functional class. The data have been taken during three different periods per day so that they represent and cover the traffic noise of the city during heavy traffic flow conditions. Analysis of traffic noise prediction was conducted using a simple linear regression model to accurately predict the equivalent continuous sound level. The difference between the predicted and the measured noise shows that the model's accuracy is 93.93%. The results show the effectiveness of the suggested method and confirm its applicability in developing mitigation plans for both existing and future roadways. To test the effectiveness of the suggested method, the selected location of different road functional classifications of Kirkuk city in Iraq was studied. It was noticed that in all the selected sites, the noise level was observed to be above the permissible noise standard of the World Health Organization (WHO).

Durability Assessment Method of Hollow Thin-Walled Bridge Piers under Rockfall Impact Based on Damage Response Surface

Continuous rigid-frame bridges across valleys are often at risk of rockfalls caused by heavy rainfalls, earthquakes, and debris flow in a mountainous environment. Hollow thin-walled bridge piers (HTWBP) in valleys are exposed to the threat of impact from accidental rockfalls. In the current research, ANSYS/LS-DYNA is used to establish a high-precision rockfall-HTWBP model. The rockfall-HTWBP model is verified against a scaled impact test performed in previously published research. A mesh independence test is also performed to obtain an appropriate mesh size. Based on the rockfall-HTWBP model, the impact force, damage, and dynamic response characteristics of HTWBP under a rockfall impact are studied. In addition, a damage assessment criterion is proposed, based on the response surface model, combined with the central composite design method and Box–Behnken design method. The main conclusions are as follows: (1) the impact force of the rockfall has a substantial impulse characteristic, and the duration of the impulse load is approximately 0.01 s. (2) The impacted surface of the pier is dominated by the final elliptic damage, with conical and strip damage areas as the symmetry axis. The cross-sectional damage mode is from compression failure in the impact area and shear failure at the corner. (3) The maximum displacement occurs in the middle height of the pier. The maximum displacement increases with impact height, impact velocity, and rockfall diameter and decreases with the uniaxial compressive strength of the concrete. (4) The initial impact velocity and diameter of the rockfall are the most significant parameters affecting the damage indices. In addition, a damage assessment method, with a damage zoning diagram based on the response surface method, is established for the fast assessment of the damage level of impacted HTWBP.

Flow characteristics of heavy oil-water flow during high water-content cold transportation

As the water content in heavy oil gathering systems increases to 70–90% and large-scale popularization of cold transportation. Understanding the characteristics of heavy oil-water flow during high water-content cold transportation has greatly gained in importance. Here, a comprehensive flow loop experiment and microscopic observation was employed to investigate the flow characteristics of oil-water flow at low temperatures. The flow patterns of cold transportation were studied experimentally. The flow pattern maps were also created in detail, taking into account the temperatures (60–20 °C), mixture velocities (0.1–1.0 m/s), and water contents (70–90%). The relevant influencing factors of the pressure gradient were then investigated. The lubrication coefficient and viscosity models were used to modify the pressure gradient models, and average relative deviations were within ±25%. Moreover, the distinction between the oil-sticking layer and wax deposition formation mechanisms was highlighted. According to microscopic observation, the major elements impacting the strength of the oil-sticking layer were asphaltene aggregation and water droplet distribution. Finally, an evaluation method for predicting the minimum heavy oil-gathering temperature during high water-content cold transportation was presented. The findings of this study greatly contribute to understanding the mechanisms of cold transportation.

Numerical simulation of electromagnetic heating of heavy oil reservoir based on multi-physical fields coupling model

ABSTRACT Electromagnetic (EM) heating is an advanced technology that can improve the oil recovery rate. Previous studies usually focus on the coupling of EM and thermal reservoir models, with little attention to multi-phase flow in EM heating. In order to accurately analyze the heat and mass transfer in the reservoir under EM heating, this work developed an advanced model coupling the EM-temperature-seepage fields, in which the variation of the physical properties of heavy oil reservoirs has been considered. In addition, the influence of the EM heating factors is also analyzed. The results show a significant saturation partitioning in the heat and mass transfer in heavy oil reservoirs under EM heating, and heavy oil flows more rapidly in areas of high oil saturation. Increasing the EM frequency and power can extend the heating range of the reservoir, but it can cause a dramatic rise in the temperature of the antenna. When the temperature of the production well induces heavy oil flow, increasing the production pressure can significantly improve output. The average flow rate of heavy oil at the producing well increased by 17.61% when the bottom flow pressure decreased from 19 MPa to 17 MPa. The study of the distance between the production well and the antenna finds that the average temperature of the production well is only 463.06 K when the antenna spacing is 15 m. Compared with other situations, 10 m is the most suitable for efficient and continuous exploitation of heavy oil.

Development of drift-flux correlations for vertical forward bubble column-type gas-liquid lead-bismuth two-phase flow

Bubble columns represent an extreme case of gas-liquid two-phase flow, where net liquid velocity is zero and the gas simply bubbles up through the liquid. The bubble column-type gas-liquid metal two-phase flow always appears in an accident scenario for pool-type lead-bismuth eutectic cooled fast breeder reactors. To accurately predict the void fraction for the accident evaluation and design of a reactor system, nine existing drift-flux type constitutive correlations are evaluated with a nitrogen-liquid heavy metal two-phase flow test. Few correlations give a relatively good prediction and the basic assumption in the distribution parameter calculation is not applicable for a bubble column. To solve this problem, analysis based on Clark’s theoretical model is carried out. The results show that the distribution parameter assumes very high values at a low Re number. As the Froude number increases, the distribution parameter tends to decrease. At lower void factions, the distribution parameter is also assumed to be at high values. This indicates that the pipe size, flow rate, and void fraction can all influence the distribution parameter. Considering the quantitative laws of these influence factors obtained by theoretical analysis and fitting the data of Ariyoshi’s test, a new correlation for a bubble column-type gas-LBE two-phase flow is developed and evaluated. The results of the statistical analysis show that the new correlation gives the best prediction for gas-LBE two-phase flow in the void fraction range of 0.018–0.313.

Upaya Pengendalian Banjir Kawasan Sub-Das Celeng Pra Pembangunan Embung Imogiri

Flood on March 17 in the Celeng River, Wukirsari Village, D.I. Yogyakarta became the biggest flood that ever happened on the Bog River. Floods are caused by heavy flow of water from the hills in the Imogiri and Dlingo areas. The Celeng River overflowed and submerged four hamlets in Wukirsari Village, Imogiri District. This study aims to determine flood control efforts in the Celeng sub-watershed area. The research location is in the Kali Celeng sub-watershed, Wukirsari, Imogiri, D.I. Yogyakarta with the control point located in the lower reaches of the Celeng River right at the confluence of the Celeng River and the Oyo River. The hydrological analysis was calculated using the Gamma 1 unit hydrograph method with a return period of 10 years. The maximum flood discharges for each of the Celeng sub-watersheds are 75.73 m3/s, 38.22 m3/s, 37.20 m3/s, 18.54 m3/s, and 21.57 m3/s, and 26.29 m3/s, while the 10-year return flood discharges for the Oyo watershed is 959.60 m3/s. The hydraulic analysis was carried out by modeling the 13.35 km long Celeng River channel with HEC-RAS 4.1 software. The flow simulation is carried out steadily. The simulation results show that during the simulation of the existing state there are several points of the section of the Celeng River that overflow. The overflowing sections are then normalized with certain groove dimensions that are adjusted to the location of the flood point. The results of the flow simulation after normalization show that most of the Celeng River channel can accommodate the flood discharge that occurred. The sections that still overflow after normalization are then given embankments with an average height of 0.75 m.

CFD Simulation of the Hydrodynamics of Core-Annular Flow of Oil, Gas and Water in Elliptic-Cylindrical Duct

Heavy oils, due to their high viscosity, have greater viscous resistance to flow, requiring high pumping power for transport and increasing operating cost. As an alternative to minimize this problem, the core-flow technique emerged, which consists of injecting water simultaneously with the oil flow, causing the heavy oil to be surrounded by a layer of water and flowing in the center of the duct without touching the pipe wall, consequently reducing the friction pressure gradient. Thus, this work aims to numerically study the core-annular flow of oil, water and gas in a cylindrical duct with an elliptical cross-section, considering a three-dimensional, isothermal and incompressible flow. For the numerical solution of the governing equations, the software Ansys FLUENT 15.0 was used. It was found that the lubrication provided by the water on the duct wall reduced the pressure variation by 7.20 times compared to the heavy oil single-phase flow, proving the good efficiency of the core-flow technique.

ENVIRONMENTAL INSECURITY IN PAKISTAN: CONTEMPORARY CHALLENGES AND RESPONSES

This study investigates the contemporary environmental risks of air pollution and heat waves, their causes, and their impacts in Pakistan. The research aims to find out the reasons behind the response challenges despite introducing policy programs such as National Climate Change Policy Framework and initiatives like The Billion Tree Tsunami. This study has used a qualitative research approach by adding a case study analysis and an environmental expert’s opinion. The key findings have revealed that compared to the past, the nature of causes behind rising air pollution and intense heat waves has changed. Heavy traffic flow, stop-and-go traffic phenomenon, uncontrolled emissions, and rapid shifts in rainfall are the principal factors that harm Pakistan’s environment. From the expert’s point of view, the study also reveals that the response mechanism is facing hurdles due to institutional dissonance and lack of capacity building. Further, the findings suggest that a multi-layered approach involving policymakers, experts, academicians, and individuals through a community-driven approach can offer practical solutions. As the study has included the example of an individual-level digital response to current environmental threats, this research would provide a platform to make similar budget-friendly and technology-oriented approaches in the future.

EVALUASI SIMPANG TAK BERSINYAL DI SIMPANG LIMAU BUKITTINGGI

Simpang Limau is one of the Three Unsignalized Intersections on the Bukittinggi-Payakumbuh Cross Road, which has a fairly heavy traffic flow. The purpose of this study was to analyze the performance of an unsignaled intersection using MKJI 1997. The data needed in this study were primary data and secondary data. The primary data is in the form of data on traffic flow conditions, geometric intersections and environmental conditions. Secondary data includes population growth and road network maps. Traffic data collection is carried out by conducting a direct survey to the location for three days, namely Saturday, Sunday, and Monday from 07.00 to 18.00. This data was processed using Microsoft Excel based on the 1997 MKJI and the results obtained were made in the form of tables and graphs. From these tables and graphs it can be seen that the traffic volume, traffic composition, and peak hours that occur at the intersection. The results of calculations at peak hours with the highest flow, namely on Sundays at 17.00-18.00, the traffic volume at this intersection is 1,484 (pcu/hour). The traffic delay at the intersection is 3,066 (sec/pcu). The value of the degree of saturation in the existing condition of 0.74 does not exceed the MKJI determination of 0.75. The value of the intersection delay is 2.693 (sec/pcu) and the probability of the intersection queue is 22.32% to 71.68%.Key words : Unsignalized Intersection, Capacity (C), Degree of Saturation (DS), Delay (D), Probability of Queuing (QP%).

DoSMit: A Novel Way for the Mitigation of Denial of Service Attacks in Software Defined Networking

Abstract: Software Defined Networking (SDN) is a rapidly evolving technology in the field of networking. It allows the computer networks to be managed via software instead of hardware devices. It gives the benefit of simplicity in management and easiness to apply new features in the network. Thus scalability, performance and maintainability become more sophisticated compared to the legacy hardware driven networks. But the SDN has more chances of being attacked by hackers, thus compromising the entire network. One common such threat is Denial of Service (DoS). Apart from such attacks in the legacy networks, the DoS attacks can be aimed at the SDN controller, Openflow switch and the controller-switch link by exhausting their resources. This paper proposes a novel and simple method to detect and mitigate such attacks through a Heavy Packet-in Flow Mitigation feature. Also it introduces an add-on feature ARP Flood Rule to reduce the number of ARP packets during the network initial boot up time. With both the features enabled, the network can reduce the packet-in flows to the controller and rescue the controller from overwhelming with huge packet-in message processing.

MOBILITY AND PROXIMITY COEFFICIENT TO HIGHTRAFFIC VOLUME IN DAILY SCHOOL OPERATIONS

Heavy traffic volume especially in peak time led to bigger issue during daily school operating time. Drivers’ behaviours are often seen as the central cause to the increased number of road accidents around school, particularly during morning hours when accompanying adults are in a rush to office. Good accessibility and connectivity are the main consent in a school planning guideline. However, the proximity to major roads results in a higher level of traffic around the school. The research hypothesis is to investigate whether the proximity distance playing a significant role in determining mobility choice to school. The Geographical Information System software was used to analyse the safety measures such as distance, coverage area and routes to school, while the mobility analysis is done using the SPSS. 553 samples of questionnaires have been distributed at six identified schools in Johor Bahru. The result from analysis shows 79.39% of children use motorised vehicle thus, contributing to poor traffic flow during peak hour. While in comparing the coverage of each school to the guidelines, 99.45% of children’s houses are within the accepted radius distance. The findings of this study will highlight to some poor driving habits among parents, which are a major contributor to the heavy traffic flow surrounding schools.

Tree sketch: An accurate and memory-efficient sketch for network-wide measurement

Traffic measurement provides essential information for bandwidth management and Quality of Service (QoS), which is an enabler of network status discovery. However, with the explosive growth of network traffic, traditional network measurement methods face challenges in terms of memory, computation, accuracy, especially in the high-speed networks. Network devices have no enough CPU or memory resources for collecting, counting and analyzing data streams, which makes measurement results inaccurate and unreliable. To address the problem, we design an accurate and memory-efficient Tree sketch. It consists of three different structures for heavy flow detection, Distributed Denial-of-Service (DDoS) attack detection, super-spreaders detection, respectively. The proposed heavy cuckoo algorithm stores the flows in categories according to their flow sizes reducing hash collisions in the sketch. Besides, Tree sketch employs the Single Instruction Multiple Data (SIMD) instructions to speed up packet processing. Experimental results show that F1 score of Tree sketch is 0.997 with 30 KB memory usage in heavy hitter detection, which is 0.019–0.137 higher than the state-of-the-art sketch algorithms. It is an efficient tool of traffic measurement in the backbone network and provides a good trade-off among accuracy, speed and memory usage.

Direct helium recovery from natural gas by dual reflux pressure swing adsorption cascade

Low-cost helium recovery processes optimised for unconventional sources e.g. small-scale natural gas (NG) reservoirs, offer a new approach to meeting growing demand. We investigated a two-stage dual reflux pressure swing adsorption (DR PSA) cascade for the recovery and purification of dilute helium from various natural gas source analogues comprising of CH4 + N2 + He. First, adsorption isotherms of a binderless zeolite 13X with high methane and nitrogen uptake were measured at 283 to 323 K and pressures up to 10 bar. This material was then used in a laboratory-scale DR PSA apparatus to identify key parameters affecting the separation performance, namely feed step time and location, as well as heavy product and light reflux flow rate. The experiments agreed well with the results of a non-isothermal numerical DR PSA model with an average deviation of 1 mol% between simulated and experimental product purities. Then, the model was extended to consider a two-stage DR PSA cascade with waste recycle. Axial composition profiles within the beds of each stage were obtained numerically and analysed to explain the impact of key process parameters on the separation performance. Tuning these parameters accordingly led to a helium-rich product with over 99 mol% He purity, which could be produced from various natural gas feeds containing from 0.1 to 1 mol% He at 90 to 98% recovery, respectively. The separation performance was compared to other helium recovery processes based on cryogenic distillation, membranes, pressure swing adsorption, and combinations thereof. Compared to these other systems, the DR PSA cascade process delivered a 99 mol% purity product from a 0.1 mol% helium in natural gas feed with 8% higher helium recovery.

Bedload and Concentration Effects on Turbulent Suspension Properties in Heavy Particle Sheet Flows

Bedload and Concentration Effects on Turbulent Suspension Properties in Heavy Particle Sheet Flows