Economic News Releases and Financial Markets in South Africa

We examine the impact of economic news releases on returns, volatility and jumps of the stock and foreign exchange markets of South Africa. We also assess the impact of macroeconomic determinants. The dataset range is fifteen years covering the period from January, 2000 to December, 2014. Results are robust to different sub-periods before and after the global financial crisis of 2008. Volatility is estimated with the use of the median realized variance estimator. Jumps are also detected. The impact of the announcements is assessed building using regression techniques. Returns, volatility and jumps of both stock and foreign exchange markets are significantly explained nationally by macroeconomic fundamentals and economic news releases

Low off-state Leakage Currents in AlGaN/GaN High Electron Mobility Transistors By Employing A Highly Stressed SiNx Surface Passivation Layer

In this study, the impact of the stress in SiNx surface passivation layers on off-state drain and gate leakage currents and off-state breakdown voltage in AlGaN/GaN High Electron Mobility Transistors (HEMTs) is assessed. The SiNx films were deposited at room temperature by inductively coupled plasma chemical vapour deposition (ICP-CVD). Compared to unpassivated devices, the off-state drain and gate leakage currents of AlGaN/GaN HEMTs is increased by up to 2 orders of magnitude for a 200 nm thick SiNx passivation layer with 309 MPa compressive stress. The use of a bilayer SiNx passivation scheme comprising 70 nm SiNx with 309 MPa compressive stress followed by 130 nm SiNx with 880 MPa compressive stress resulted in off-state drain and gate leakage currents reduced by up to 1 order of magnitude when compared to unpassivated devices

Nefeli: Hint-Based Execution of Workloads in Clouds

Abstract—Virtualization of computer systems has made feasi-ble the provision of entire distributed infrastructures in the form of services. Such services do not expose the internal operational and physical characteristics of the underlying machinery to either users or applications. In this way, infrastructures including computers in data-centers, clusters of workstations, and networks of machines are shrouded in “clouds”. Mainly through the deployment of virtual machines, such networks of computing nodes become cloud-computing environments. In this paper, we propose Nefeli, a virtual infrastructure gateway that is capable of effectively handling diverse workloads of jobs in cloud environments. By and large, users and their workloads remain agnostic to the internal features of clouds at all times. Exploiting execution patterns as well as logistical constraints, users provide Nefeli with hints for the handling of their jobs. Hints provide no hard requirements for application deployment in terms of pairing virtual-machines to specific physical cloud elements. Nefeli helps avoid bottlenecks within the cloud through the realization of viable virtual machine deployment mappings. As the types of jobs change over time, deployment mappings must follow suit. To this end, Nefeli offers mechanisms to migrate virtual machines as needed to adapt to changing performance needs. Using our prototype system, we show significant improvements in overall time needed and energy consumed for the execution of workloads in both simulated and real cloud computing environments. I

Dual barrier InAlN/AlGaN/GaN-on-silicon high-electron-mobility transistors with Pt and Ni based gate stacks

In this work, we report the performance of 3 μm gate length "dual barrier„ InAlN/AlGaN/GaN HEMTs on Si substrates with gate-drain contact separations in the range 4-26 μm. Devices with Pt and Ni based gates were studied and their leakage characteristics are compared. Maximum drain current IDS of 1 A/mm, maximum extrinsic transconductance gm ~203 mS/mm and on-resistance Ron 4.07 Ω mm for gate to drain distance LGD = 4 μm were achieved. Nearly ideal sub-threshold swing of 65.6 mV/dec was obtained for LGD = 14 μm. The use of Pt based gate metal stacks led to a two to three orders of magnitude gate leakage current decrease compared to Ni based gates. The influence of InAlN layer thickness on the transistor transfer characteristics is also discussed

Low off-state Leakage Currents in AlGaN/GaN High Electron Mobility Transistors By Employing A Highly Stressed SiNx Surface Passivation Layer

In this study, the impact of the stress in SiNx surface passivation layers on off-state drain and gate leakage currents and off-state breakdown voltage in AlGaN/GaN High Electron Mobility Transistors (HEMTs) is assessed. The SiNx films were deposited at room temperature by inductively coupled plasma chemical vapour deposition (ICP-CVD). Compared to unpassivated devices, the off-state drain and gate leakage currents of AlGaN/GaN HEMTs is increased by up to 2 orders of magnitude for a 200 nm thick SiNx passivation layer with 309 MPa compressive stress. The use of a bilayer SiNx passivation scheme comprising 70 nm SiNx with 309 MPa compressive stress followed by 130 nm SiNx with 880 MPa compressive stress resulted in off-state drain and gate leakage currents reduced by up to 1 order of magnitude when compared to unpassivated devices