Hybrid Spark Research Articles

Accelerating Spark-Based Applications with MPI and OpenACC

The amount of data produced in scientific and commercial fields is growing dramatically. Correspondingly, big data technologies, such as Hadoop and Spark, have emerged to tackle the challenges of collecting, processing, and storing such large-scale data. Unfortunately, big data applications usually have performance issues and do not fully exploit a hardware infrastructure. One reason is that applications are developed using high-level programming languages that do not provide low-level system control in terms of performance of highly parallel programming models like message passing interface (MPI). Moreover, big data is considered a barrier of parallel programming models or accelerators (e.g., CUDA and OpenCL). Therefore, the aim of this study is to investigate how the performance of big data applications can be enhanced without sacrificing the power consumption of a hardware infrastructure. A Hybrid Spark MPI OpenACC (HSMO) system is proposed for integrating Spark as a big data programming model, with MPI and OpenACC as parallel programming models. Such integration brings together the advantages of each programming model and provides greater effectiveness. To enhance performance without sacrificing power consumption, the integration approach needs to exploit the hardware infrastructure in an intelligent manner. For achieving this performance enhancement, a mapping technique is proposed that is built based on the application’s virtual topology as well as the physical topology of the undelaying resources. To the best of our knowledge, there is no existing method in big data applications related to utilizing graphics processing units (GPUs), which are now an essential part of high-performance computing (HPC) as a powerful resource for fast computation.

Evaluation of Wear and Corrosion Behaviour of Hybrid Sintered Ti<sub>6</sub>Al<sub>4</sub>V Alloy

Ti6Al4V alloy was consolidated by hybrid spark plasma sintering at a temperature of 1200 °C, pressure of 50 MPa, holding time of 5 min and heating rate of 100 °C/min. This resulted in the maximum value of sintered density. Microstructural evolutions of the sintered compact were analysed with SEM. Sliding wear test were accomplished at different sliding loads of 5, 8 and 10 N using ball on disc tribometer configuration with stainless steel as the counterface material. Wear debris obtained was found to contain mostly the sintered materials with minute traces of the counterface material. The coefficient of friction reaches the maximum with increase in applied load. Worn surface analyses revealed the wear mechanism was abrasive. The potentiodynamic polarisation of the sintered compact showed the sintered compact in 0.9 wt % NaCl solution exhibited more resistance to corrosion.

Study of the effect of composition on the microstructure and thermophysical properties of niobium-based refractory systems

The structure and thermophysical properties—thermal diffusivity, thermal conductivity, linear thermal expansion coefficient, and specific heat capacity—in a temperature range of 20–1400°C are studied; DSC analysis of Nb–Si composites containing 12–18 and 14 at % Si, which are prepared by hybrid spark plasma sintering and hot pressing, respectively, is conducted. The effect of the composition and temperature on the structure and characteristics of thermophysical properties is estimated.

A comparative study of spark plasma sintering and hybrid spark plasma sintering of 93W–4.9Ni–2.1Fe heavy alloy

Mixed 93W–4.9Ni–2.1Fe powders were sintered via the spark plasma sintering (SPS) and hybrid spark plasma sintering (HSPS) techniques with 30mm and 60mm samples in both conditions. After SPS and HSPS, the 30mm and 60mm alloys (except 60mm-SPS) had a relative density (>99.2%) close to the theoretical density. Phase, microstructure and mechanical properties evolution of W–Ni–Fe alloy during SPS and HSPS were studied. The microstructural evolution of the 60mm alloys varied from the edge of the sample to the core of the sample. Results show that the grain size and the hardness vary considerable from the edge to the core of sintered sample of 60mm sintered using conventional SPS compared to hybrid SPS. Similarly, the hardness also increased from the edge to the core. Furthermore, the 60mm-HSPS alloy exhibited improved bending strength of 1115MPa when compared to that of 60mm-SPS, 920MPa. The intergranular fracture along the W/W grain boundary is the main fracture modes of W–Ni–Fe, however in the 60mm-SPS alloy peeling of the grains was also observed which diminished the properties. The mechanical properties of SPS and HSPS 93W–4.9Ni–2.1Fe heavy alloys are dependent on the microstructural parameters such as tungsten grain size and overall homogeneity.

Joining of silicon carbide ceramic by hybrid spark plasma sintering

The possibility of joining of silicon carbide ceramic by hybrid spark plasma sintering (Hybrid SPS/ FAST) was demonstrated. An increase in the brazing temperature and addition of SiC and B powders into the base braze formulation (C + Si) allowed the seam uniformity to be considerably improved and the thermal cycling resistance of the brazed structure to be enhanced. Introduction of boron into the braze formulation allows the free silicon content to be reduced to zero, which is impossible with boron-free brazes.

Specific features of sintering of HfB2-based refractory ceramic by hybrid spark plasma sintering

Systems based on refractory ZrB2 and HfB2 powders are the most promising for fabrication of newgeneration aircraft parts working under extreme conditions. The complexity of sintering of these powders is overcome by using the spark plasma sintering method (SPS/FAST) with additional inductive heating. The sintering of HfB2-SiC samples separately in the SPS mode or by inductive heating at 100 deg min−1 failed to provide samples with required quality. It was shown that the relative density differential for samples 100 mm in diameter, sintered in the combined-heating mode [simultaneously by inductive and spark plasma sintering (SPS)] does not exceed 2.4%. Oxidation resistance tests of the samples at temperatures T ≥ 1800°C demonstrated that further studies of the HfB2-SiC system as a material for aircraft articles are needed.

Spark ignition to homogeneous charge compression ignition mode transition study: a new modelling approach

A hybrid spark ignition/homogeneous charge compression ignition engine model for simulating the spark ignition to homogeneous charge compression ignition transition in a four-cylinder gasoline engine is presented. This hybrid spark ignition/homogeneous charge compression ignition model has been developed to provide help in understanding the complicated spark ignition to homogeneous charge compression ignition transition process and in tackling the control problems associated with it. The model was built in Matlab/Simulink, coupled with a tabulated stochastic reactor model and a detailed chemical kinetics mechanism. Typical computational times encountered in the simulation using this model were of the order of seconds for one engine cycle. The model was validated in steady-state spark ignition and homogeneous charge compression ignition operation by experimental data, followed by model-based parametric studies in homogeneous charge compression ignition operation. Then, a spark ignition to homogeneous charge compression ignition mode transition was simulated using the model. The results showed good agreement with experimental data, in terms of cylinder pressure, combustion phasing, air/fuel ratio, residual gas fraction and nitrogen oxides. The high computational efficiency and relatively high accuracy of this model enable its good applicability in experimental design and controller development, and potential use in hardware-in-loop applications.

In-cylinder studies of hybrid combustion in a direct injection single-cylinder optical engine

Over the last decade, controlled autoignition (CAI) combustion, or homogeneous charge compression ignition (HCCI), has been the subject of numerous studies and has shown its potential to reduce fuel consumption and NO x emissions simultaneously from gasoline engines. However, there are still some fundamental questions that are yet to be addressed, such as combustion control and underlying physical and chemical processes. In the present study, a single-cylinder optical gasoline engine was operated with negative valve overlap to investigate CAI and hybrid spark ignition (SI)–CAI combustion. The effects of direct fuel injection and spark timings were studied by means of a simultaneous in-cylinder heat release study and high-speed visualization of total chemiluminescence, OH and CHO radicals.

A highly stabilized hybrid spark chamber for β-ray imaging

This paper describes an attempt to improve the stability of the hybrid spark chamber presented in a previous paper. The occurrence of sparks induced in the proportional chamber gap of the hybrid spark chamber is suppressed by the use of a thyratron discharge circuit connected to this gap in parallel, since it reduces the stability of the hybrid spark chamber. Operation and effects of the discharge circuit are described. The present method enables us to realize highly stabilized spark chambers for routine use in radiochromatography.

A hybrid spark chamber for measuring radionuclide distributions

This paper describes the operational characteristics of a hybrid spark chamber designed to improve the instability of self-triggering spark chambers for measuring radionuclide distributions. The chamber consists of a parallel plate spark chamber and a parallel plate proportional chamber in the same gas space. This construction of the chamber enables us to obtain good counting plateaus, that is, good stability, and high spatial resolution for the incidence of minimum ionizing β-rays.