Influence of specific speed on hydraulic performances and pressure fluctuations in mixed-flow pumps

A series of steady and unsteady numerical calculations of the internal flow in mixed-flow pumps with three different specific speeds were carried out based on the N-S equation coupled with the standard k-εturbulence model under different operating conditions to investigate the relationship between the impeller specific speed and the pump performance as well as pressure pulsations.Meanwhile,the pump performance and pressure pulsations inside the mixed-flow pump with three different specific speeds were also analyzed and compared with the corresponding test data.From the results,the averaged deviations between the predicted and tested head among different impellers are below 5%,and with respect to the equivalent impeller specific speeds of 280 and 260,the values are 4.30%and 3.69%,respectively.For all the impeller schemes,the best efficiency point of the mixed-flow pump is found at the flow rate of 1.2 Q_(d) and the higher head deviation occurs at lower flow rates.Especially,it can be found that the specific speed has a slight effect on the pressure fluctuation in the impellers.Eventually,it is determined that the pump performance curves calculated by numerical simu-lations have good agreement with the relevant experimental results,which verifies that the numerical methods used in the present study are accurate to a certain extent.Furthermore,the results also provide some references to the pressure pulsation analysis and the performance improvement of the mixed-flow pump design.

Assessment of Main Parameters of Extreme Earthquakes in Red Sea, West Coast of Saudi Arabia

The negative effects of natural disasters on human life exist from the foot and did not occur at a specific time but found since the creation of mankind. Humans coexist with extreme events all the time, only when the intensity of the event becomes greater than a certain level there is a resulting disaster. Small earthquakes occur all of the time with no adverse effects. Only large earthquakes cause disasters. Statistical analysis reveals that larger events occur less frequently than small events. Through the large number of seismic events, we find that at the end of the year may have a series of seismic events with different values depending on the strength of activity whether it is high or low on Richter scale and the assessment is only for the greatest value in a year even if recurring this value and the volume of dangerous increases and the frequency of their occurrence according to an ongoing activity, major disasters result from a small number of events and sustained results in a large and devastating event, and can be represented by these results and amounts On a log-scale which points are almost on a straight line and a clear indication of the evaluation event. Through previous data analysis we can understand the following events behavior for coordination and guidance on the development of evacuation plans on the expected future and use a Weibull equation to estimate the frequency of the event and the return again as a percentage for each event and the probability of the occurrence of a particular earthquake to some degree on the Richter scale in the sea during any period. Past records of earthquakes at the West Coast of the Kingdom of Saudi Arabia (Red Sea) for years 1913-2016 are used to predict future conditions concerning the annual frequency, the return period, the percentage probability for each event, and the probability of a certain-magnitude earthquake occurring in the region during any period.

Applying Artificial Intelligence(AI)to improve fire response activities

This research discusses how to use a real-time Artificial Intelligence(AI)object detection model to improve on-site incident command and personal accountability in fire response.We utilized images of firegrounds obtained from an online resource and a local fire department to train the AI object detector,YOLOv4.Consequently,the real-time AI object detector can reach more than ninety percent accuracy when counting the number of fire trucks and firefighters on the ground utilizing images from local fire departments.Our initial results indicate AI provides an innovative method to maintain fireground personnel accountability at the scenes of fires.By connecting cameras to additional emergency management equipment(e.g.,cameras in fire trucks and ambulances or drones),this research highlights how this technology can be broadly applied to various scenarios of disaster response,thus improving on-site incident fire command and enhancing personnel accountability on the fireground.

Effect of Opening Size on the Development of Ventilation-limited Fire

There are many factors,that affect the development of indoor fire,such as the size of the fire source,the opening or space of the room,and the nature of the combustible materials.Among them,the space of the room,has a significant impact on the development of a ventilation-limited fire.In this paper,the Fire Dynamics Simulator(FDS)software is used to analyze,the risk of fire initiation in the restricted ventilated compartment,when the size of vertical ventilation space is different.Through,a combination of experimental design,numerical simulation,and theoretical analysis,the changes in the level of carbon monoxide,visibility,temperature,Heat Release Rate(HRR)and,the smoke exhaust efficiency of natural smoke at different opening sizes are observed.It is observed that,when the ratio of inlet and outlet area reaches 2:1,the natural smoke exhaust effect is the best,however,the increasing in the opening size has little significance on the smoke exhaust effect.The research on the influence of smoke outlet size,will helps in the development of the law regarding fire prevention,smoke exhaust design,and fire rescue work of a building.

Earthquake Disaster Management Approach: The Case of Al-Ais, Medina Area in Saudi Arabia

The research tackles earthquakes as one of the most dangerous natural disasters. It defines disasters in general, which in turn include earthquakes, how to manage them, stages of their evolution, and their classification among other kinds of disasters such as hurricanes, floods, drought, desertification, etc. Afterwards, it tackles the impacts of disasters on man, buildings and infrastructure. It defines also the codes and laws existing in the Kingdom of Saudi Arabia to confront and treat the impacts of earthquakes in their different stages (before, during and after) and the authorities involved in managing them. Then, it moves to study the case of Al-Ais Earthquake, and identifies the points of deficiency in dealing with such a disaster. Moreover, the research tackles some global experiences in how to handle the situation, reaching to the presentation of a conceptual approach to confront disasters of earthquakes in their various stages.

A multiple flame-retardant,early fire-warning,and highly sensitive thread-shaped all-fabric-based piezoresistive sensor

In the artificial intelligence age,multifunctional and intelligent fireproof fabric-based electronics are urgently needed.Herein,a novel thread-shaped all-fabric-based piezoresistive sensor(denoted as TAFPS)with properties such as flame retardancy,firewarning,and piezoresistivity is proposed,which is composed of an inner nickel-plated fabric electrode,a multifunctional double helix fabric,and an external flame-retardant encapsulation fabric.Owing to the multiple flame-retardant properties of glass fiber tubular fabric,aminated carbon nanotubes(ACNTs),and ammonium polyphosphate,the char residue of the TAFPS reaches40.3 wt%at 800℃.In addition,the heat-sensitive effect of ACNTs during combustion causes a rapid decrease in the TAFPS resistance,triggering the fire alarm system within 2 s.Additionally,benefiting from the force-sensitive behavior of the double helix layer and tightly wrapped pattern of the external heat-shrinkable tubular fabric,TAFPS demonstrated a high sensitivity of4.40 kPa^(-1)(0–5.81 k Pa)and good stability for 10000 s.Considering its excellent flame resistance,high sensitivity,and agreeable stability,the developed TAFPS can be integrated into fire suits to monitor the exercise training process and the external fire environment.This work offers a novel approach for fabricating all-fabric-based piezoresistive sensors in the future for fire prevention and fire alarms,with promising applications in fire protection,the Internet of Things,and smart apparel.