A reliable, delay bounded and less complex communication protocol for multicluster FANETs

Recently, Flying Ad-hoc Networks （FANETs）, enabling ad-hoc networking between Unmanned Aerial Vehicles （UAVs） is gaining importance in several military and civilian applications. The sensitivity of the applications requires adaptive; efficient; delay bounded and scalable communication network among UAVs for data transmission. Due to communication protocol complexity; rigidity; cost of commercial-off-the-shelf （COT） components; limited radio bandwidth; high mobility and computational resources; maintaining the desired level of Quality of Service （QoS） becomes a daunting task. For the first time in this research we propose multicluster FANETs for efficient network management; the proposed scheme considerably reduces commu- nication cost and optimizes network performance as well as exploit low power; less complex and low cost IEEE 802.15.4 （MAC） protocol for intercluster and intracluster communication. In this research both beacon enabled mode and beaconless modes have been investigated with Guaranteed Time Slots （GTS） and virtual Time Division Multiple Access （TDMA） respectively. The methodology plays a key role towards reserving bandwidth for latency critical applications; eliminate collisions and medium access delays. Moreover analysis ad-hoc routing protocols including two proactive （OLSR, DSDV） and one reactive （AODV） is also presented. The results shows that the proposed scheme guarantees high packet delivery ratios while maintaining acceptable levels of latency requirements comparable with more complex and dedieatedly designed protocols in literature.

Queue Waiting Time Aware Dynamic Workflow Scheduling in Multicluster Environments

Workflows are prevailing in scientific computation. sources, benefiting workflows but also challenging the traditional Multicluster environments emerge and provide more reworkftow scheduling heuristics. In a multicluster environment, each cluster has its own independent workload management system. Jobs are queued up before getting executed, they experience different resource availability and wait time if dispatched to different clusters. However, existing scheduling heuristics neither consider the queue wait time nor balance the performance gain with data movement cost. The proposed algorithm leverages the advancement of queue wait time prediction techniques and empirically studies if the tunability of resource requirements helps scheduling. The extensive experiment with both real workload traces and test bench shows that the queue wait time aware algorithm improves workflow performance by 3 to 10 times in terms of average makespan with relatively very low cost of data movement.

A Comparison of Shale Gas Fracturing Based on Deep and Shallow Shale Reservoirs in the United States and China

China began to build its national shale gas demonstration area in 2012.The central exploration,drilling,and development technologies for medium and shallow marine shale reservoirs with less than 3,500m of buried depth in Changning-Weiyuan,Zhaotong,and other regions had matured.In this study,we macroscopically investigated the development history of shale gas in the United States and China and compared the physical and mechanical conditions of deep and shallow reservoirs.The comparative results revealed that themain reasons for the order-ofmagnitude difference between China’s annual shale gas output and the United States could be attributed to three aspects:reservoir buried depth,reservoir physical and mechanical properties,and engineering technology level.The current engineering technology level of China could not meet the requirements of increasing production and reducing costs for deep shale gas reservoirs;they had reached the beneficial threshold development stage and lacked the capacity for large-scale commercial production.We identified several physical and mechanical reasons for this threshold development stage.Deep shale reservoirs were affected by the bedding fracture,low brittleness index,low clay mineral content,and significant areal differences,as well as by the transformation from elasticity to plasticity,difficulty in sanding,and high mechanical and strength parameters.Simultaneously,they were accompanied by six high values of formation temperature,horizontal principal stress difference,pore pressure,fracture pressure,extension pressure,and closure pressure.The key to deep shale gas horizontal well fracturing was to improve the complexity of the hydraulic fracture network,formadequate proppant support of fracture surface,and increase the practical stimulated reservoir volume(SRV),which accompanied visual hydraulic discrete network monitoring.On this basis,we proposed several ideas to improve China’s deep shale gas development involving advanced technology systems,developing tools,and supporting technologies in shale gas exploration and development in the United States.These ideas primarily involved stimulation technologies,such as vertically integrated dessert identification and optimization,horizontal well multistage/multicluster fracturing,staged tools development for horizontal wells,fractures network morphology monitoring by microseismic and distributed optical fiber,shale hydration expansion,soak well,and fracturing fluid flow back.China initially developed the critical technology of horizontal well large-scale and high-strength volume fracturing with a core of“staged fracturing with dense cutting+shorter cluster spacing+fracture reorientation by pitching+forced-sand addition+increasing diameter perforating+proppant combination by high strength and small particle size particles”.We concluded that China should continue to conduct critical research on theories and technical methods of horizontal well fracturing,suitable for domestic deep and ultra-deep marine and marine-continental sedimentary shale,to support and promote the efficient development of shale gas in China in the future.It is essential to balance the relationship between the overall utilization degree of the gas reservoir and associated economic benefits and to localize some essential tools and supporting technologies.These findings can contribute to the flourishing developments of China’s deep shale gas.