Large Obstacles Research Articles

Оцінка динамічної навантаженості екіпажів моторвагонного поїзда з сис-темою пасивної безпеки при його зіткненні з великим транспортним засо-бом

A topical problem of the home railway transport is motor-car train renewval, speed increase, and safety improvement in accordance with the Ukrainian State Standards DSTU EN 12633 and DSTU EN 15227, which specify the passenger car crashworthiness and passive safety, respectively, in emergency collisions with various obstacles. Relying on the world experience, researchers of the institute of Technical Methanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine developed a passive protection concept for home high-speed passenger trains in emergency collisions according to the DSTU EN 15227 requirements, proposals on the passive propection of a home motor-car train head car, lower- and upper-level honeycomb energy-absorbing devoces (EAD 1 and UL EAD, respectively) for the head car front part, and EAD 2 and EAD 3 low-level devices to be installed in intercar connecteions. The upper- and lower-level protective devices for home motor-car trains were developed based on finite-element simulation results using previous experience in the development of a passive protection device for a high-speed passenger locomotive and the results of a successful crash test of its proptotype. For Scenario 3, which chraracterizes a collision of a reference motor-car train at 110 km/h with a 15 t large road vehicle at a railway crossing, a model of a large deformable obstacle (LDO) was developed in compliance with the DSTU EN 15227 requirements. Finite-element models were developed to determine the force characteristics of interaction between the proposed head car passive protection devices and an LDO. The aim of this paper is to determine dynamic loads on a motor-car train equipped with passive protection devices in its collision with a large road vehicle. Based on a mathematical collision model for identical motor-car trains, a mathematical model was developed for a collision of a reference train with a large road vehicle at a railway crossing (Scenario 3) with account for the determined force characteristics of obstacle ? two EAD 1 low-level devices and obstacle ? two UL EAD upper-level devices interaction and the in-collision work of the head car structure. Dynamic loads on the cars of a reference train with a passive safety system (a head car mass of 80 t and intermediate car masses of 50 t or 64 t) were analyzed for its collision by Scenario 3. Two EAD layouts in the head car front part were studied. It was found that the proposed passive protection of the reference train cars meets the DSTU EN 15227 criteria for Scenario 3 for both EAD layouts and the determined variants of lower- and upper-level EAD use according to the intermediate car masses. The proposed mathematical model of dynamic loads on a passenger train with a passive safety system in its collision with a large road vehicle and the results obtained may be used in designing an up-to-date high-speed motor-car train to the DSTU EN 15227 requirements.

Injectable and Self-Healing Probiotics-Loaded Hydrogel for Promoting Superbacteria-Infected Wound Healing.

Superbacteria-induced skin wound infections are huge health challenges, resulting in significant financial and medical costs due to notable morbidity and mortality worldwide. Probiotics are found in the skin and are effective in treating bacterial infection, moderating the microbial dysbiosis and inflammation induced by pathogens, regulating the immune system, as well as even promoting tissue repair. However, improving their colonization efficiency and viability remains a large obstacle for proper applications. Inspired by probiotic therapy and the natural extracellular matrix structure, hyaluronate-adipic dihydrazide/aldehyde-terminated Pluronic F127/fucoidan hydrogels loaded with Lactobacillus rhamnosus (HPF@L.rha) with unique (bio)physicochemical characteristics were developed through the dynamic Schiff-base reaction for superbacteria-infected trauma management. The developed HPF@L.rha exhibit a shortened gelation time, enhanced mechanical strength, and excellent self-healing and liquid-absorption abilities. Importantly, their anti-superbacteria (Pseudomonas aeruginosa) effect was greatly increased in a dose-dependent fashion. Additionally, in vitro evaluation shows that the prepared HPF@L.rha containing appropriate probiotic concentrations (less than 1 × 107 CFU/mL) possess satisfactory cytocompatibility and blood compatibility. Further, compared to the HPF hydrogel, in vivo the hydrogel combined with probiotics significantly inhibits P. aeruginosa infection and inflammation, promotes the formation of re-epithelialization and collagen, and thus accelerates full-thickness superbacteria-infected wound repair, which is comparable to commercial Prontosan gel formulation. This work suggests that the combination of biomimicking hydrogels and probiotic therapy displays the great potential to manage superbug-infected trauma.

A Minimalistic Stochastic Dynamics Model of Cluttered Obstacle Traversal

Robots are still poor at traversing cluttered large obstacles required for important applications like search and rescue. By contrast, animals are excellent at doing so, often using direct physical interaction with obstacles rather than avoiding them. Here, towards understanding the dynamics of cluttered obstacle traversal, we developed a minimalistic stochastic dynamics simulation inspired by our recent study of insects traversing grass-like beams. The 2-D model system consists of a forward self-propelled circular locomotor translating on a frictionless level plane with a lateral random force and interacting with two adjacent horizontal beams that form a gate. We found that traversal probability increases monotonically with propulsive force, but first increases then decreases with random force magnitude. For asymmetric beams with different stiffness, traversal is more likely towards the side of the less stiff beam. These observations are in accord with those expected from a potential energy landscape approach. Furthermore, we extended the single gate in a lattice configuration to form a large cluttered obstacle field. A Markov chain Monte Carlo method was applied to predict traversal in the large field, using the input-output probability map obtained from single gate simulations. This method achieved high accuracy in predicting the statistical distribution of the final location of the body within the obstacle field, while saving computation time by a factor of <inline-formula><tex-math notation="LaTeX">$10^5$</tex-math></inline-formula> over our dynamic simulation.

Jet-HR2: A Flying Bipedal Robot Based on Thrust Vector Control

Achieving short-distance flight helps improve the efficiency of humanoid robots moving in complex environments (e.g., crossing large obstacles or reaching high places) for rapid emergency missions. This study proposes a design of a flying humanoid robot named Jet-HR2. The robot has 10 joints driven by brushless motors and harmonic drives for locomotion. To overcome the challenge of the stable-attitude takeoff in small thrust-to-weight conditions, the robot was designed based on the concept of thrust vectoring. The propulsion system consists of four ducted fans, that is, two fixed on the waist of the robot and the other two mounted on the feet, for thrust vector control. The thrust vector is controlled by adjusting the attitude of the foot during the flight. A simplified model and control strategies are proposed to solve the problem of attitude instability caused by mass errors and joint position errors during takeoff. The experimental results show that the robot's spin and dive behaviors during takeoff were effectively suppressed by controlling the thrust vector of the ducted fan on the foot. The robot successfully achieved takeoff at a thrust-to-weight ratio of 1.17 (17 kg / 20 kg) and maintained a stable attitude, reaching a takeoff height of over 1000 mm.

High-order shallow water expansions in free surface flows: Application to steady overflow processes

Free surface flow modeling in the natural environment is frequently conducted within a depth-integrated framework using the non-linear shallow water equations or Saint-Venant equations. However, these equations underestimate the discharge in overflow processes over obstacles, such as during the flooding of coastal levees. Alternative models are constructed by expansions in terms of a shallowness parameter σ, with the 2nd-order results being the so-called Serre-Green-Naghdi theory, widely used in ocean research. Higher-order expansions are required in some instances to obtain more accurate results or to set the validity limit of the leading order term of these perturbation results. However, most of the high-order results available apply to water wave problems over horizontal beds, yet not to the overflow over obstacles of generally uneven bathymetry. High-order shallow water expansions for open channel flows over uneven beds are developed in this work by an iterative procedure to generate the corresponding asymptotic expansions up to the high-order O(σ6), resulting in high-order ODEs when the Bernoulli equation at the free surface streamline is invoked to include gravity effects. These new equations are applied to the overflow process, as occurs during the coastal flooding in a levee-protected area. A perturbation solution to this problem is presented up to O(σ6) for the main overflow variables, which are successfully and systematically compared with a new set of experiments conducted in a large scale obstacle model. The novel theoretical solutions presented are further demonstrated to be better than former theories available in the literature.

Strategy optimization of proton exchange membrane fuel cell cold start

<p indent="0mm">Under the background of “carbon peaking and carbon neutrality” goals, the proton exchange membrane fuel cell (PEMFC) vehicle attracts extensive attention due to its high energy conversion efficiency, long range and zero emission. However, the challenge of cold start in low temperature environments becomes a large obstacle to its commercialization and application. The current cold start performance of typical commercial fuel cell vehicles cannot reach the optimal target yet. Several problems such as the lack of complete mechanical systems of water transport and phase change and the absence of simulation models for on-board fuel cells at system level still exist. Thus, researchers have carried out a great number of experiments and simulations to study the mechanism of degradation, water transport, phase change and heat transfer as well as start-up strategy optimization of PEMFC cold start. By measuring the output performance, it is found that the degradation of performance is attributed to the formation of ice which covers the reaction active region, blocks the gas channel and increases the electrical contact resistance. Researchers also believe that the reduction of durability is owing to the volume change of water-ice phase change which leads to the damage of the structure by characterizing the microstructure of the fuel cell. With the help of transparent cells, neutron imaging and simulations of multiphase PEMFC models, the distribution, transport and phase change of water and ice during cold start have been studied. The results indicate that the electrochemical product water first saturates the PEM and the catalyst layer (CL) as membrane water. Then the water remains liquid in the form of supercooled water at low temperatures, and finally flows out of the cell or freezes suddenly. By studying the heat transfer process both in plane and through plane during cold start, researchers find that at central regions of the single cell and in the middle part of the stack, the temperature rises fastest. They also find that the irreversible reaction heat generated by cathodic oxygen reduction reaction (ORR) is the main source of heat generation. Based on the cold start mechanism of PEMFCs, researchers have developed various self-start and auxiliary start strategies. The start-up mode and control strategies have been optimized. The internal structure and materials of each part have been improved. And a series of auxiliary startup strategies such as gas purging, heater heating, reaction heating, gas heating as well as coolant heating have been proposed. A large number of simulations and experiments are carried out to verify the advantages of these strategies. Through these excellent cold start strategies, the commercialization and promotion process of PEMFC vehicles can be accelerated.

Mechanism study on magnitude of mass transfer coefficients in liquid desiccant dehumidification and regeneration

• Mass transfer coefficients of regeneration are much lower than dehumidification. • Lower mass transfer coefficients of regeneration are decided by transfer direction. • Water release has a huge free energy barrier but water absorption has not. • Correlations considering parameters of aqueous solution show higher accuracy. Liquid desiccant systems have attracted extensive attention due to huge energy-saving and environmental potential. Mass transfer coefficients are key parameters for system design and performance evaluation. Contrast experiments between liquid desiccant dehumidification and regeneration were conducted here to investigate the magnitude of mass transfer coefficients by using LiBr aqueous solutions. Mass transfer coefficients of dehumidification were found to be much higher than regeneration even under the condition that the mass transfer driving force and inlet parameters except solution temperatures were kept the same. To obtain microscopic explanation, free energy curves of water transport were simulated by molecular dynamics based on umbrella sampling. Results show that large energy obstacle should be overcome for water moving into air, which is unnecessary for water transported into aqueous solution. Lower mass transfer coefficients of regeneration should be attributed to the mass transfer direction rather than higher solution temperatures of regeneration than dehumidification. Dimensionless correlations of mass transfer coefficients using water diffusivity in LiBr aqueous solution and correlations using surface tensions show better prediction performance than dimensionless correlations using water diffusivity in air. This study discloses changing mechanism of mass transfer coefficients and helps develop correlations with high accuracy.

Self-management of the umbilical of a ROV for underwater exploration

This article focuses on passive self-management of the umbilical of a Remotely Operated Vehicle (ROV) for underwater exploration. The goal is to give a predictable shape to the umbilical, using moving ballasts and buoys to stretch the umbilical and so to avoid entanglement of the cable itself or with surrounding obstacles. The ballasts and buoys move by themselves to maintain the cable taut without a motorized system. A model of the umbilical is proposed. The presence of waves, as well as thecases with and without currents are considered. Three configurations of the umbilical are proposed, each one to be the most adapted to ROV exploration missions: near the surface, sea exploration, and diving in presence of large obstacles.

A ship target dynamic recognition method based on image recognition and VR technology

Effective identification of ship identity is an important means of water traffic management. Aiming at the technical limitations of AIS, radar and other means, a ship automatic recognition method based on machine learning is proposed, and a water traffic visualization system integrating multi-source recognition technology is realized based on VR technology. The test shows that the method and system can solve the technical problems of ship identification caused by data easy to be tampered with, difficult to distinguish massive targets and large obstacles, and provide an effective method for navigation support in key waters.

An experimental study of aerodynamic noise from large obstructions in turbulent boundary layer flows

This paper reports an experimental study on the aerodynamic noise generated by a two-dimensional large obstacle in a turbulent boundary layer. Square and triangular obstacles with varying heights of h/δ=0.48,0.8,1.2,1.6, and 2 (where δ is the boundary layer thickness measured without the obstacle present) are tested at various flow speeds ranging from 20 to 50 m/s. The Reynolds number based on step height and free stream velocity ranged between 7500 and 79 000. A linear microphone array is arranged aside to measure the sound radiation in the spanwise direction. It is suggested that both square and triangular obstructions can lead to a broadband source with a dipole-type directivity. A consistent increase in the noise strength is observed with obstacle height and flow speed. The underlying noise source is revealed by comparing the acoustic spectra of different obstacle geometries. The low-frequency noise is contributed by the turbulence modification due to the flow impingement onto the obstacle, while the high-frequency sound is mainly caused by the diffraction of hydrodynamic pressure by the sharp leading edge.

The Need for and Feasibility of Alternative Ground Robots to Traverse Sandy and Rocky Extraterrestrial Terrain

Robotic spacecrafts have helped expand the reach for many planetary exploration missions. Most ground mobile planetary exploration robots use wheeled or modified wheeled platforms. Although extraordinarily successful at completing intended mission goals, because of the limitations of wheeled locomotion, they have been largely limited to benign, solid terrain and avoided extreme terrain with loose soil/sand and large rocks. Unfortunately, such challenging terrain is often scientifically interesting for planetary geology. Although many animals traverse such terrain at ease, robots have not matched their performance and robustness. This is in major part due to a lack of fundamental understanding of how effective locomotion can be generated from controlled interaction with complex terrain on the same level of flight aerodynamics and underwater vehicle hydrodynamics. Early fundamental understanding of legged and limbless locomotor–ground interaction has already enabled stable and efficient bioinspired robot locomotion on relatively flat ground with small obstacles. Recent progress in the new field of terradynamics of locomotor–terrain interaction begins to reveal the principles of bioinspired locomotion on loose soil/sand and over large obstacles. Multilegged and limbless platforms using terradynamics insights hold the promise for serving as robust alternative platforms for traversing extreme extraterrestrial terrain and expanding the reach in planetary exploration.

Circumferentially rotatable inspection robot with elastic suspensions for bridge cables

PurposePeriodic inspection of bridge cables is essential, and cable-climbing robots can replace human workers to perform risky tasks and improve inspection efficiency. However, cable inspection robots often fail to surmount large obstacles and cable clamps. The purpose of this paper is to develop a practical cable inspection robot with stronger obstacle-surmounting performance and circumferential rotation capability.Design/methodology/approa/chA cable inspection robot with novel elastic suspension mechanisms and circumferential rotation mechanisms is designed and proposed in this study. The supporting force and spring deformation of the elastic suspension are investigated and calculated. Dynamic analysis of obstacle surmounting and circumferential rotation is performed. Experiments are conducted on vertical and inclined cables to test the obstacle-surmounting performance and cable-clamp passing of the robot. The practicality of the robot is then verified in field tests.FindingsWith its elastic suspension mechanisms, the cable inspection robot can carry a 12.4 kg payload and stably climb a vertical cable. The maximum heights of obstacles surmounted by the driving wheels and the passive wheels of the robot are 15 mm and 13 mm, respectively. Equipped with circumferential rotation mechanisms, the robot can flexibly rotate and successfully pass cable clamps.Originality/valueThe novel elastic suspension mechanism and circumferential rotation mechanism improve the performance of the cable inspection robot and solve the problem of surmounting obstacles and cable clamps. Application of the robot can promote the automation of bridge cable inspection.

Research on image stitching method based on improved ORB and stitching line calculation

Image matching is one of the hot issues in recent years. Image matching determines the effect of image mosaic to a large extent. Therefore, a stable, accurate, and fast image matching algorithm is very important for the subsequent processing of image information. Most of the traditional image matching methods have the problems of high-error matching rate and difficulty in to eliminating false matching. To resolve the shortcomings listed here, an improved algorithm was proposed in which a combined measure of Hamming distance. Similarity measurement with Tanimoto similarity measurement was adopted to dispose binary feature vectors. In addition, as an important step in the process of image mosaics, the calculation of the best mosaics can eliminate the ghosting and ghosting that may appear in the mosaics. However, the traditional dynamic planning method is easy to pass through the obstacles and form obvious stitching traces when searching for stitching lines in images with large obstacles. In view of the aforementioned content, we propose a fast and robust method to search the image difference matrix and structure difference matrix of the overlapping area of the input image according to the search strategy to determine the pixel coordinates of the splicing line. Finally, from an optimal splicing line, the experimental results show that our algorithm performs well for eliminating error matching points. Compared with traditional algorithms, matching accuracy is improved by 25%. In terms of calculating the optimal splicing line, the method proposed is faster than the traditional method and has good robustness.

A Low-Cost High-Resolution LiDAR System With Nonrepetitive Scanning

Obstacle visualization and detection are essential parts of autonomous driving. The capability of accurately and rapidly collecting 3D information of the surrounding environment plays a key role in driving decisions of autonomous vehicles. As an active detection device, LiDAR enables high-speed and real-time depth information acquisition by emitting laser pulses and then receiving echoes. However, the frame rate and density of the point cloud generated by conventional LiDARs are limited by the fixing trajectory of the beam-steering unit, which cannot satisfy the requirements of various scenes. This paper presented a novel non-repetitive scanning algorithm and a LiDAR prototype using a galvanometer scanner as the beam-steering unit. The algorithm achieves dynamic scanning between frame rate and lateral resolution by the superposition of multiple raw frames with sparser non-repetitive trajectory. The LiDAR was made of off-the-shelf components to limit the cost less than 450 US dollars and extend its application scenarios. Experimental results demonstrated that the proposed LiDAR achieved dynamic frame rate and lateral resolution. Each raw frame of point cloud has a lateral resolution of 190&#x00D7;16 and four raw frames with different trajectories synthesize a superposition frame with quadruple resolution of 190&#x00D7;64. Complex profiles of targets become clear with the superposition of multiple raw frames. Thus, the novel non-repetitive scanning improves the LiDAR performance of detecting obstacles with small sizes and maintains the detection of large obstacles at higher speed.

Dynamic Walking and Stepping over Large Obstacles of Biped Robots: A Poincaré Map Approach

Dynamic Walking and Stepping over Large Obstacles of Biped Robots: A Poincaré Map Approach

Better together? Treating traumatic brain injury with minocycline plus N-acetylcysteine.

Traumatic brain injury has a complex pathophysiology that produces both rapid and delayed brain damage. Rapid damage initiates immediately after injury. Treatment of traumatic brain injury is typically delayed many hours, thus only delayed damage can be targeted with drugs. Delayed traumatic brain injury includes neuroinflammation, oxidative damage, apoptosis, and glutamate toxicity. Both the speed and complexity of traumatic brain injury pathophysiology present large obstacles to drug development. Repurposing of Food and Drug Administration-approved drugs may be a highly efficient approach to get therapeutics to the clinic. This review examines the preclinical outcomes of minocycline and N-acetylcysteine as individual drugs and compares them to the minocycline plus N-acetylcysteine combination. Both minocycline and N-acetylcysteine are Food and Drug Administration-approved drugs with pleiotropic therapeutic effects. As individual drugs, minocycline and N-acetylcysteine are well tolerated, with known pharmacokinetics, and enter the brain through an intact blood-brain barrier. At concentrations greater than needed for anti-microbial action, minocycline is a potent anti-inflammatory minocycline, also acts as an antioxidant and inhibits multiple enzymes that promote brain injury including metalloproteases, caspases, and polyADP-ribose-polymerase-1. N-acetylcysteine alone is also an antioxidant. It increases brain glutathione, prevents lipid oxidation, and protects mitochondria. N-acetylcysteine also acts as an anti-inflammatory as well as increases extracellular glutamate by activating the Xc cystine-glutamate anti-transporter. These multiple actions of minocycline and N-acetylcysteine have made them attractive candidates to treat traumatic brain injury. When first dosed within the one hour after injury, either minocycline or N-acetylcysteine improves a diverse set of therapeutic outcome measures in multiple traumatic brain injury animal models. A small number of clinical trials for traumatic brain injury have established the safety of minocycline or N-acetylcysteine and suggested that either drug has some efficacy. Preclinical studies have shown that minocycline plus N-acetylcysteine have positive synergy resulting in therapeutic effects and a more prolonged therapeutic time window not seen with the individual drugs. This review compares the actions of minocycline and N-acetylcysteine, individually and in combination. Evidence supports that the combination has greater utility to treat traumatic brain injury than the individual drugs.

Control of Thruster-Assisted, Bipedal Legged Locomotion of the Harpy Robot.

Fast constraint satisfaction, frontal dynamics stabilization, and avoiding fallovers in dynamic, bipedal walkers can be pretty challenging. The challenges include underactuation, vulnerability to external perturbations, and high computational complexity that arise when accounting for the system full-dynamics and environmental interactions. In this work, we study the potential roles of thrusters in addressing some of these locomotion challenges in bipedal robotics. We will introduce a thruster-assisted bipedal robot called Harpy. We will capitalize on Harpy’s unique design to propose an optimization-free approach to satisfy gait feasibility conditions. In this thruster-assisted legged locomotion, the reference trajectories can be manipulated to fulfill constraints brought on by ground contact and those prescribed for states and inputs. Unintended changes to the trajectories, especially those optimized to produce periodic orbits, can adversely affect gait stability and hybrid invariance. We will show our approach can still guarantee stability and hybrid invariance of the gaits by employing the thrusters in Harpy. We will also show that the thrusters can be leveraged to robustify the gaits by dodging fallovers or jumping over large obstacles.

Phytochemicals as an Alternative or Integrative Option, in Conjunction with Conventional Treatments for Hepatocellular Carcinoma.

Simple SummaryHepatocellular carcinoma (HCC) is globally ranked as the sixth most diagnosed cancer, and the second most deadly cancer. To worsen matters, there are only limited therapeutic options currently available; therefore, it is necessary to find a reservoir from which new HCC treatments may be acquired. The field of phytomedicine may be the solution to this problem, as it offers an abundance of plant-derived molecules, which show capabilities of being effective against HCC proliferation, invasion, migration, and metastasis. In our review, we collect and analyze current evidence regarding these promising phytochemical effects on HCC, and delve into their potential as future chemotherapies. Additionally, information on the signaling behind these numerous phytochemicals is provided, in an attempt to understand their mechanisms. This review makes accessible the current body of knowledge pertaining to phytochemicals as HCC treatments, in order to serve as a reference and inspiration for further research into this subject.Hepatocellular carcinoma (HCC) is the most abundant form of liver cancer. It accounts for 75–85% of liver cancer cases and, though it ranks globally as the sixth most common cancer, it ranks second in cancer-related mortality. Deaths from HCC are usually due to metastatic spread of the cancer. Unfortunately, there are many challenges and limitations with the latest HCC therapies and medications, making it difficult for patients to receive life-prolonging care. As there is clearly a high demand for alternative therapy options for HCC, it is prudent to turn to plants for the solution, as their phytochemicals have long been used and revered for their many medicinal purposes. This review explores the promising phytochemical compounds identified from pre-clinical and clinical trials being used either independently or in conjunction with already existing cancer therapy treatments. The phytochemicals discussed in this review were classified into several categories: lipids, polyphenols, alkaloids, polysaccharides, whole extracts, and phytochemical combinations. Almost 80% of the compounds failed to progress into clinical studies due to lack of information regarding the toxicity to normal cells and bioavailability. Although large obstacles remain, phytochemicals can be used either as an alternative or integrative therapy in conjunction with existing HCC chemotherapies. In conclusion, phytochemicals have great potential as treatment options for hepatocellular carcinoma.

The Role of School Administration in Developing Creativity and Its Obstacles as Perceived by School Principals in Government Schools in the Directorate of University District: دور الإدارة المدرسية في تنمية الإبداع ومعيقاته من وجهة نظر مديري ومديرات المدارس الحكومية في مديرية لواء الجامعة

This study aims at identifying the role of school administration in developing creativity and its obstacles as perceived by school principals in government schools in the directorate of University District. This may be attributed to variables of gender, academic qualification, years of experience, and school level. The researcher has used the descriptive analytical method through employing the use of a questionnaire. This questionnaire has been made of 36 sections. 28 sections were designed to identify the role of school administration in developing creativity in the government schools in the directorate of the university district, and 8 to identify the obstacles that face the school’s administration. A sample of 55 male and female principals in government schools in the directorate of the university district have been chosen for the academic year 2019/2020. The results of the study showed that the application of creativity by the school principals in government schools have an overall average of (3.5 out of 5), which is rated as high. For the other two main areas, the administration one resulted with an average of (4.03) with a high rate, and for the obstacles area it resulted with (3.68) and was rated as large obstacles. It also has shown that there were no statistically significant differences in the role of school administration in developing creativity in government schools, which might be attributed to variables of academic qualification, years of experience, and school’s level. However, there was a significant difference attributed to the gender variable, and it was in the favor of females. Based on those results, the researcher suggested a number of recommendations for developing creativity and limiting its obstacles at Jordanian Schools and other Arab countries.

Numerical simulations of gas explosion using Porosity Distributed Resistance approach Part −1: Validation against small-scale experiments

A new model, PDRFOAM, has been developed for the prediction of gas explosions in congested plant. It uses the PDR approach to model the effect of small-scale obstacles, e.g., pipes and vessels on flame propagation and on explosion overpressure. While the effects of large obstacles i.e., that is the large scales are explicitly resolved. The equations for mass, momentum, enthalpy and Favre-averaged regress variable are solved. In addition, porosity modified standard k-ε turbulence model and the transport equations for the flame wrinkling parameter are solved. The model PDRFOAM, is built as a new application in OpenFOAM, suite of models. OpenFOAM is an open-source CFD package of routines for solution of systems of partial differential equations.In addition, to the PDRFOAM model, the CADPDR program was developed which generates various fields (volume blockage, area blockages, surface area, sub-grid drag and turbulence generation parameters) needed by PDRFOAM. CADPDR needs as input obstacle files that list coordinates and dimension of the obstacles e.g. pipes and vessels. The PDRFOAM code solves porosity-modified momentum and continuity equations with sub-grid source terms. The combustion model in PDRFOAM is based on flame area transport. The turbulent burning velocity correlation used is based on Markstein and Karlowitz number. Flame area generation due to the folding of the flame around obstacles is explicitly modelled.This paper presents the formulation of PDRFOAM and validation of the PDRFOAM code against three series of small- and medium-scale experiments i.e., ERGOS, MERGE and Buxton S-Series experiments. A total of more than 150 experiments were used for validation which includes variation in blockage ratio, grid pitch, size of the congested region, equivalence ratio, confinement, partial fill, obstacle diameter, different obstacle shapes and three different fuels. The model is compared against flame position, flame speed as a function of time and maximum overpressure obtained from experiments. Simulations predict the experimental trends of increase in overpressure with increase in blockage ratio, laminar burning velocity, partial fill of the gas cloud, size of the congested region, confinement, grid pitch and obstacle diameter. It also predicts the trends of increase in overpressure with increase in equivalence ratio, variation of maximum overpressure with ignition location, change in obstacle shape and obstacle configuration. The maximum overpressure predicted by simulations (see Fig. 1) is in general within the uncertainty of a factor of two.