Experimental Performance Evaluation of Cloud-Based Analytics-as-a-Service

An increasing number of Analytics-as-a-Service solutions has recently seen the light, in the landscape of cloud-based services. These services allow flexible composition of compute and storage components, that create powerful data ingestion and processing pipelines. This work is a first attempt at an experimental evaluation of analytic application performance executed using a wide range of storage service configurations. We present an intuitive notion of data locality, that we use as a proxy to rank different service compositions in terms of expected performance. Through an empirical analysis, we dissect the performance achieved by analytic workloads and unveil problems due to the impedance mismatch that arise in some configurations. Our work paves the way to a better understanding of modern cloud-based analytic services and their performance, both for its end-users and their providers.Comment: Longer version of the paper in Submission at IEEE CLOUD'1

A low-cost indoor real time locating system based on TDOA estimation of UWB pulse sequences

One of the most popular technologies adopted for indoor localization is ultrawideband impulse radio (IR-UWB). Due to its peculiar characteristics, it is able to overcome the multipath effect that severely reduces the capability of receivers (sensors) to estimate the position of transmitters (tags) in complex environments. In this article, we introduce a new low-cost real-time locating system (RTLS) that does not require time synchronization among sensors and uses a one-way communication scheme to reduce the cost and complexity of tags. The system is able to evaluate the position of a large number of tags by computing the time difference of arrival (TDOA) of UWB pulse sequences received by at least three sensors. In the presented system, the tags transmit sequences of 2-ns UWB pulses with a carrier frequency of 7.25 GHz. Each sensor processes the received sequences with a two-step correlation analysis performed first on a field-programmable gate array (FPGA) chip and successively on an on-board processor. The result of the analysis is the time of arrival (TOA) of the tag sequence at each sensor and the ID of the associated tag. The results are sent to a host PC implementing trilateration algorithm based on the TDOA computed among sensors. We will describe the characteristics of the custom hardware that has been designed for this project (tag and sensor) as well as the processing steps implemented that allowed us to achieve an optimum localization accuracy of 10 cm

Modal analysis of the fields in the ITER ICRF antenna port plug cavity

The cavity that is formed between the ITER ICRF antenna plug and its port can exhibit resonances at specific fre-quencies, some of them in the relevant range of frequencies for IC heating. These resonances related to eigenmodes of the coaxial cavity, can substantially increase the level of electric fields inside the cavity and the level of RF losses in the B4C neutron shielding tiles at the back of the port-plug cavity can also be significant. For instance, in MWS simulations of a simplified geometry of the antenna in front of a dielectric mimicking the plasma loading, the level of RF losses in the B4C can reach tens of kW in 00ππ toroidal phasing and even larger values in monopole. RF probes will be installed to monitor the RF fields in the port plug cavity and additional simulations are required to properly assess the integration (position, orientation) and their effectiveness. A model with a very detailed geometry of the antenna was also used in Ansys HFSS and TOPICA simulations. On the one hand it is observed that the resistivity of the B4C neutron shielding material located at the back of the cavity has a marked effect on the excitation of the resonances and that for certain ranges of resistivity the numerical computation fails exhausting computer memory requirements (Ansys/HFSS) when trying to solve the total antenna and cavity problem as a single model. On the other hand lossy materials such as the B4C tiles cannot be represented in TOPICA models while a realistic plasma gyrotropic load can not be simulated in HFSS/MWS. Therefore, we introduced a modal analysis in the cavity to decouple solving the computationally intensive plasma-facing front of the launcher from the cavity. The fields computed by TOPICA for various loading conditions and frequencies are evaluated on a set of vertical planes in the cavity and expanded in a series of modal eigenmodes for a given mode of operation. This provides the necessary input for an accurate evaluation of the RF fields in the cavity in an independent model not including the antenna front-face. It will also contribute to the understanding of the impact of the relative toroidal phasing of the strap currents on the excitation of the cavity modes and to simulate accurately the response of the cavity RF probes

Design of an harmonic radar for the tracking of the Asian yellow-legged hornet

The yellow-legged Asian hornet is an invasive species of wasps, indigenous to the Southeast Asia but recently spreading in Southern Europe. Because of its exponential diffusion and its serious threat to the local honeybee colonies (and to humans as well), restraint measures are currently under investigation. We developed and tested an harmonic radar capable of tracking the flying trajectory of these insects, once equipped with a small transponder, in their natural environment. Several hornets were captured close to a small cluster of honeybee hives, tagged with different transponders and then released in order to follow the flight toward their nest. On-field testing proved an initial maximum detection range of about 125 m in a hilly and woody area. A number of detections were clearly recorded, and preferential directions of flight were identified. The system herein described is intended as a first low-cost harmonic radar; it proved the capability to track the hornets while flying and it permitted to test the tagging techniques. Several upgrades of the system have been identified during this work and are extensively described in the last chapter. The designed system has three major advantages over conventional harmonic radars. First and most importantly, it adopts advanced processing techniques to suppress clutter and to improve target detection. Second, it allows radar operations in complex environments, generally hilly and rich in vegetation. Finally, it can continuously track tagged insects (24/7) and in any meteorological condition, providing an effective tool in order to locate the nests of the yellow-legged Asian hornet

Recent upgrades of the harmonic radar for the tracking of the Asian yellow-legged hornet

The yellow-legged Asian hornet is an invasive species of wasps, indigenous of the South-East Asia but quickly spreading in Southern Europe. Because of its exponential diffusion and its serious threat to the local honey bee colonies and to humans as well, restraint measures are under investigation. Among them, the harmonic radar described in (Ecology and Evolution, 6, 2016 and 2170) already proved to be a quite effective way to follow the hornets to their nests; it is in fact capable of tracking the flying trajectory of these insects, once equipped with a small transponder, in their natural environment. The aforementioned harmonic radar was upgraded after a period of intense experimentation; the capture of the hornets was enhanced as well, and other improvements were adopted in the mounting procedure of the transponder. Thanks to these upgrades, the flying capabilities of the hornets were not reduced and a huge collection of data was recorded. The main upgrade to the radar was the adoption of the vertical polarization of the radiated field, with the consequent redesign and manufacturing of the antennas and the different mounting of the transceiver on the insect. The installation of the radar on a telescopic tower drastically improved the maneuverability of the system and the capability to follow the insects’ preferential flying directions. Eventually, the system was able to produce much more continuous traces with a clear indication of the most probable position of the nest. The maximum range of detection was also increased to 150 m

Efficient full wave code for the coupling of large multirow multijunction LH grills

The full wave code OLGA, for determining the coupling of a single row lower hybrid launcher (waveguide grills) to the plasma, is extended to handle multirow multijunction active passive structures (like the C3 and C4 launchers on TORE SUPRA) by implementing the scattering matrix formalism. The extended code is still computationally fast because of the use of (i) 2D splines of the plasma surface admittance in the accessibility region of the k-space, (ii) high order Gaussian quadrature rules for the integration of the coupling elements and (iii) utilizing the symmetries of the coupling elements in the multiperiodic structures. The extended OLGA code is benchmarked against the ALOHA-1D, ALOHA-2D and TOPLHA codes for the coupling of the C3 and C4 TORE SUPRA launchers for several plasma configurations derived from reflectometry and interferometery. Unlike nearly all codes (except the ALOHA-1D code), OLGA does not require large computational resources and can be used for everyday usage in planning experimental runs. In particular, it is shown that the OLGA code correctly handles the coupling of the C3 and C4 launchers over a very wide range of plasma densities in front of the grill

Development of pre-conceptual ITER-type ICRF antenna design for DEMO

ICRF antenna development for DEMO for the pre-conceptual phase is carried out by merging the existing knowledge about multi-strap ITER, JET and ASDEX Upgrade antennas. Many aspects are taken over and adapted to DEMO, including the mechanical design and RF performance optimization strategies. The minimization of ICRF-specific plasma-wall interactions is aimed at by optimizing the feeding power balance, a technique already proven in practice. Technological limits elaborated for the components of ITER ICRF system serve as a guideline in the current design process. Several distinctive aspects, like antenna mounting, integration with the neighbouring components or adaptation for neutron environment, are tackled individually for DEMO

Electromagnetic simulations of JET ICRF ITER-like antenna with TOPICA and SSWICH asymptotic codes

Multi-megawatt Ion Cyclotron Range of Frequencies (ICRF) heating is routinely used in the JET tokamak. To increase the ICRF heating power available from the A2 antennas, the ICRF ITER-Like Antenna (ILA) was reinstalled for the 2015 JET ITER-like wall experimental campaign. The application of high levels of ICRF power typically results in increased plasma wall interaction which leads to the observation of enhanced influx of metallic impurities in the plasma edge. It is assumed that the impurity production is mainly driven by the parallel component of the Radio-Frequency (RF) antenna electric near-field, E// (parallel to the confinement magnetic field of the tokamak), that is rectified in a thin boundary layer (RF sheath). Torino Polytechnic Ion Cyclotron Antenna (TOPICA) code was used to compute E// field maps in front of the ILA and between its poloidal limiters in the presence of plasma using measured density profiles and various antenna feedings. E// field maps calculated between the poloidal limiters were used to estimate the poloidal distribution of RF-sheath Direct Current (DC) potential in this private region of the ILA and make relative comparison of various antenna electrical settings. For this purpose we used the asymptotic version of the Self-consistent Sheaths and Waves for Ion Cyclotron Heating Slow-Wave (SSWICH-SW) code. These estimations can help to study the formation of RF sheaths around the antenna and even at distant locations (∼3m away)

Multi-strap in-port ICRF antenna modeling and development in support of ITER and EU-DEMO

Full-size 3D model of ITER ICRF antenna with 1D plasma electron density (ne) and 3D ne (from EMC3-Eirene) was simulated using the RAPLICASOL (COMSOL-based) code. Impedance matrices and coupled power agree well with TOPICA with 1D ne. Cases with 3D ne show port-to-port differences compared to 1D ne, as well as a lower (about 10%) coupled power. Efficient minimization of ITER antenna near-fields (to reduce RF sheaths by optimizing feeding) calculated by TOPICA and RAPLICASOL is possible with [0;π;π;0] (about balanced strap powers) and is even lower with [0;π;0;π] toroidal phasing (with dominant power from central straps). Lowest near-fields are with [0;π] poloidal phasing, but [0;-π/2] will be used in a load resilience setup with 3dB splitters. Under EUROfusion prospective research and development, in-port ICRF antenna concept for EU-DEMO with 8 quadruplets (4x toroidal by 2x poloidal) is considered to deliver 16.7 MW (3 antennas yielding 50 MW). Areas around the equatorial port and cut-ins in breeding blankets are used, with emphasis on [0;π;π;0] optimization. High-resolution RAPLICASOL calculations with full ne profile (without imposing a minimum ne value) shed light on field distribution with propagative slow wave in detailed antenna geometry

Characterization of 3-strap antennas in ASDEX Upgrade

The response of the local RF current measured at limiters of 3-strap ICRF antenna to variations of power balance and phasing at fICRF=30MHz agrees qualitatively well with EM calculations by TOPICA and RAPLICASOL codes. Measurements of tungsten sputtering yield and DC current at the limiters correlate strongly with the local RF current. In contrast to findings for the 2-strap antennas, values of DC current are predominantly positive, and negative only for some locations and feeding parameters. Explanations can involve more physical mechanisms than only parallel sheath dynamics