Analysis of the Flow About Delta Wings with Leading Edge Separation at Supersonic Speeds

A research program was conducted to develop an improved theoretical flow model for the flow about sharp edge delta wings with leading-edge separation at supersonic speeds. The flow model incorporates a representation of the secondary separation region which occurs just inboard of the leading edge on such wings and is based on a slender-wing theory whereby the full three-dimensional problem is reduced to a quasi two-dimensional problem in the cross-flow plane. The secondary separation region was modeled by a surface distribution of singularities or a linearized type of cavity representation. The primary vortex and separation were modeled by a concentrated vortex and cut in the cross-flow potential which represents its feeding sheet. The cross-flow solutions for the cavity model were obtained, but these solutions have physical significance only in a very restricted range of angle of attack. The reasons for the failure of the flow model are discussed. The analysis is presented so that other interested researchers may critically review the work

Generalized pairwise z-complementary codes

An approach to generate generalized pairwise Z-complementary (GPZ) codes, which works in pairs in order to offer a zero correlation zone (ZCZ) in the vicinity of zero phase shift and fit extremely well in power efficient quadrature carrier modems, is introduced in this letter. Each GPZ code has MK sequences, each of length 4NK, whereMis the number of Z-complementary mates, K is a factor to perform Walsh–Hadamard expansions, and N is the sequence length of the Z-complementary code. The proposed GPZ codes include the generalized pairwise complementary (GPC)codes as special cases

The Spin--Symmetry of the Quark Model

Corrections to the exact heavy--quark symmetry results are expected to follow the $1/m_{Q}$ mass effect of the heavy--quark. We show, by an explicit calculation, that there is something other than the mass effect that suppresses the breaking of the spin symmetry

Experimental studies of equilibrium vortex properties in a Bose-condensed gas

We characterize several equilibrium vortex effects in a rotating Bose-Einstein condensate. Specifically we attempt precision measurements of vortex lattice spacing and the vortex core size over a range of condensate densities and rotation rates. These measurements are supplemented by numerical simulations, and both experimental and numerical data are compared to theory predictions of Sheehy and Radzihovsky [17] (cond-mat/0402637) and Baym and Pethick [25] (cond-mat/0308325). Finally, we study the effect of the centrifugal weakening of the trapping spring constants on the critical temperature for quantum degeneracy and the effects of finite temperature on vortex contrast.Comment: Fixed minor notational inconsistencies in figures. 12 pages, 8 figure

W-band waveguide-packaged InP HEMT reflection grid amplifier

This letter presents a 79-GHz broadband reflection-type grid amplifier using spatial power combining to combine the power of 64 unit cells. Each unit cell uses a two-stage cascade configuration with InP HEMTs arranged as a differential pair. A broadband orthogonal mode transducer (OMT) separates two orthogonally polarized input and output signals over a 75 to 85GHz range. In conjunction with the OMT, a mode converter with quadruple-ridged apertures was designed to enhance the field uniformity over the active grid. Measurements show 5-dB small signal gain at 79GHz and an 800-MHz 3-dB bandwidth. The amplifier generates an output power of 264mW with little evidence of saturation

Sand and silty-sand soil stabilization using bacterial enzyme induced carbonate precipitation (BEICP)

The concept of bio-geotechnics represents an innovative, new technical merger between three traditional disciplines: geotechnical, material, and environmental engineering. As originally conceived decades ago, biogeotechnology mechanism uses live micro-organisms to improve and stabilize soils, by which their suitability for construction realizes engineering, environmental, and economical benefits. More recently, though, this concept has been broadened to include a suite of possible strategies, including: 1) using whole-cell microorganisms to secure ‘Microbial Induced CaCO3 Precipitation’ (MICP), 2) using cell-free, free-‘Enzyme Induced CaCO3 Precipitation’ (EICP), and 3) using ‘Microbial Induced Desaturation and Precipitation’ (MIDP). Although none of these biogeotechnical methods have yet reached a pragmatic level of commercial application, promising results have been achieved within laboratory, and in limited instances of large-scale and field-scale evaluation. This dissertation documents the outcomes achieved during an investigation of a novel modification of the latter ‘EICP’ method which could be similarly employed to secure bio-mediated soil improvement. In this case, however, the operative catalytic enzyme (i.e., urease) was extracted from a bacterial source and then used in its free-enzyme form to secure a so-called ‘Bacterial Enzyme Induced Carbonate Precipitation’ (BEICP). A sonication method was applied to lyse living cells of S. pasteurii to obtain the desired urease solution. The urease activity rate of this bacterial extracted enzyme was higher, at an approximate 2X magnification, even though the volume of the sonicated solution had only been reduced one-fourth as compared to that of the original bacterial solution. Furthermore, extending beyond this benefit realized with producing an even higher rate of enzymatic activity, the performance results obtained when using BEICP soil processing demonstrated several additional performance-based benefits. This dissertation consequently documents the engineering properties achieved with BEICP-treated sand processing, as well as comparing these findings against that of traditional MICP treatment. These lab-level research results offer positive evidence for two possible benefits with the BEICP method: 1) mechanical stabilization of sands, and even including that of loose sandy soil materials, and 2) an ability to retain post-treatment permeability of the bio-cemented sands (i.e., as compared to MICP’s typically higher reduction in treated soil permeability). The advantage of BEICP’s free-enzyme processing approach stems from its nano-sized (water-soluble) catalyst dimension, where these nano-enzymes are far more easily able to penetrate the small pore space of a silty sand matrix. In turn, this BEICP method was successfully applicable to the solidification of silty-sand soil. The measurement of unconfined compression strength of BEICP-treated samples ranged from 0.4 to 1.1 MPa, and from 0.23 to 0.84 MPa with silt-sand mixtures at silt levels of 10 and 20 %, respectively. These results accordingly validated the biological treatment process BEICP as a prospectively applicable means of successfully solidifying natural sand and silty-sand soil systems. As previous mentioned, BEICP treated is a new bio-based method, and this dissertation’s accompanying research has further evaluated a variety of processing factors which might impact the resultant engineering properties of bio-cemented sand. Notably, a series of test-tube experiments was conducted to investigate the effects between the bacterial cell and urease in the chemical conversion ratio. The results showed that the precipitation ratio reduced when the concentration of chemical agents increased. These experiments also characterized the urease activity of biological sources and chemical concentration for sand column tests. Two types of sand, including both coarse- and fine-grained sands, were examined in order to evaluate how these size factors impacts product strength and permeability with BIECP treatment. These findings correlated with previous studies on MICP and EICP, where the size of particle and the CaCO3 content played a vital contributing factor relative to both strength increase and permeability reduction. However, more engineering factors, such as injection flow, temperature, chemical concentration, etc., needs to be studied in order to optimize the BEICP-treatment process. Another significant aspect of BEICP-treated soil is that of the durability of the biocemented soil under the freeze-thaw cycling. Sandy soil and silty-sand soils which were originally packed in a loose condition were treated with BEICP processing as well as with commercial Portland cement and fly ash additions. The strength reduction following freeze-thaw cycling was examined on treated samples. This investigation revealed that the BEICP-treated samples retained higher strengths than that in Portland and fly ash cemented samples after freeze-thaw cycling. This approach suggests that this method may have beneficial use when applied to stabilize sub-grade and sub-base materials underlying pavement layers within cold regions. This research effort subsequently started with the development of a sonication technique to lyse viable S. pasteurii bacteria cells in order to release their intracellular urease materials. A particular advantage of using this new method is that it produces distinctly higher levels of urease activity. The extracted enzyme was then used to treat a group of test columns bearing different percentages of coarse- and fine-grained soils by weight. The engineering properties of BEICP-treated soil were evaluated via a series of lab tests. Another clear advantage for BEICP processing is that this method can form calcium-bearing crystals as bridges between fine (silt) and coarse (sand) soil grains, which then increases the overall strength of our silty-sand columns, while at the same time not unduly decreasing matrix permeability

APMEC: An Automated Provisioning Framework for Multi-access Edge Computing

Novel use cases and verticals such as connected cars and human-robot cooperation in the areas of 5G and Tactile Internet can significantly benefit from the flexibility and reduced latency provided by Network Function Virtualization (NFV) and Multi-Access Edge Computing (MEC). Existing frameworks managing and orchestrating MEC and NFV are either tightly coupled or completely separated. The former design is inflexible and increases the complexity of one framework. Whereas, the latter leads to inefficient use of computation resources because information are not shared. We introduce APMEC, a dedicated framework for MEC while enabling the collaboration with the management and orchestration (MANO) frameworks for NFV. The new design allows to reuse allocated network services, thus maximizing resource utilization. Measurement results have shown that APMEC can allocate up to 60% more number of network services. Being developed on top of OpenStack, APMEC is an open source project, available for collaboration and facilitating further research activities

Using Machine Learning for Handover Optimization in Vehicular Fog Computing

Smart mobility management would be an important prerequisite for future fog computing systems. In this research, we propose a learning-based handover optimization for the Internet of Vehicles that would assist the smooth transition of device connections and offloaded tasks between fog nodes. To accomplish this, we make use of machine learning algorithms to learn from vehicle interactions with fog nodes. Our approach uses a three-layer feed-forward neural network to predict the correct fog node at a given location and time with 99.2 % accuracy on a test set. We also implement a dual stacked recurrent neural network (RNN) with long short-term memory (LSTM) cells capable of learning the latency, or cost, associated with these service requests. We create a simulation in JAMScript using a dataset of real-world vehicle movements to create a dataset to train these networks. We further propose the use of this predictive system in a smarter request routing mechanism to minimize the service interruption during handovers between fog nodes and to anticipate areas of low coverage through a series of experiments and test the models' performance on a test set