Luo X.,Sigma Group |
Luo X.,North West University South Africa |
Zhang M.,Florida Institute of Technology |
Potgieter M.,North West University South Africa |
And 2 more authors.
Astrophysical Journal | Year: 2015
Based on a hybrid galactic cosmic-ray transport model, which incorporated MHD global heliospheric data into Parker's cosmic-ray transport equation, we studied the behavior of the transport of galactic cosmic rays and the corresponding gradients in their flux near the heliopause (HP). We found that, (1) by increasing the ratio of the parallel diffusion coefficient to the perpendicular diffusion coefficient in the interstellar magnetic field of the outer heliosheath, the simulated radial flux near the HP increases as well. As the ratio multiplying factor reached 1010, the radial flux experienced a sudden jump near the HP, similar to what Voyager 1 observed in 2012. (2) The effect of changing the diffusion coefficients' ratio on the radial flux variation depends on the energy of the cosmic rays, the lower the energy, the more pronounced the effect is. (3) The magnitude of the diffusion coefficients also affect the radial flux near the HP, the modulation beyond the HP varies by adjusting the magnitude multiplying factor. © 2015. The American Astronomical Society. All rights reserved..
Jiang C.,Sigma Group |
Feng X.,Sigma Group
Solar Physics | Year: 2014
Numerical reconstruction/extrapolation of the coronal nonlinear force-free magnetic field (NLFFF) usually takes the photospheric vector magnetogram as input at the bottom boundary. The magnetic field observed at the photosphere, however, contains a force that is in conflict with the fundamental assumption of the force-free model. It also contains measurement noise, which hinders the practical computation. Wiegelmann, Inhester, and Sakurai (Solar Phys. 233, 215, 2006) have proposed to preprocess the raw magnetogram to remove the force and noise to provide better input for NLFFF modeling. In this paper we develop a new code of magnetogram preprocessing that is consistent with our extrapolation method CESE-MHD-NLFFF (Jiang, Feng, and Xiang in Astrophys. J.755, 62, 2012; Jiang and Feng in Astrophys. J.749, 135, 2012a). Based on the magnetic-splitting rule that a magnetic field can be split into a potential-field part and a non-potential part, we split the magnetogram and dealt with the two parts separately. The preprocessing of the magnetogram's potential part is based on a numerical potential-field model, and the non-potential part is preprocessed using the similar optimization method of Wiegelmann, Inhester, and Sakurai (2006). The code was applied to the SDO/HMI data, and results show that the method can remove the force and noise efficiently and improve the extrapolation quality. © 2013 Springer Science+Business Media Dordrecht.
Song W.B.,Sigma Group
Solar Physics | Year: 2010
Referring to the aerodynamic drag force, we present an analytical model to predict the arrival time of coronal mass ejections (CMEs). All related calculations are based on the expression for the deceleration of fast CMEs in the interplanetary medium (ICMEs), is the solar wind speed. The results can reproduce well the observations of three typical parameters: the initial speed of the CME, the speed of the ICME at 1 AU and the transit time. Our simple model reveals that the drag acceleration should be really the essential feature of the interplanetary motion of CMEs, as suggested by Vršnak and Gopalswamy (J. Geophys. Res. 107, 1019, 2002). © Springer Science+Business Media B.V. 2010.
Chatterjee S.,Sigma Group |
Kishinevsky M.,Intel Corporation |
Ogras U.Y.,Intel Corporation
IEEE Design and Test of Computers | Year: 2012
Although communication fabrics at the microarchitectural level are mainly composed of standard primitives such as queues and arbiters, to get an executable model one has to connect these primitives with glue logic to complete the description. In this paper we identify a richer set of microarchitectural primitives that allows us to describe complete systems by composition alone. This enables us to build models faster (since models are now simply wiring diagrams at an appropriate level of abstraction) and to avoid common modeling errors such as inadvertent loss of data due to incorrect timing assumptions. Our models are formal and they are used for model checking as well as dynamic validation and performance modeling. However, unlike other formalisms this approach leads to a precise yet intuitive graphical notation for microarchitecture that captures timing and functionality in sufficient detail to be useful for reasoning about correctness and for communicating microarchitectural ideas to RTL and circuit designers and validators. © 1984-2011 IEEE.
Jiang C.,Sigma Group |
Feng X.,Sigma Group
Solar Physics | Year: 2012
We present a fast solver for computing potential and linear force-free fields (LFFF) above the full solar disk with a synoptic magnetic map as input. The global potential field and the LFFF are dealt with in a unified way by solving a three-dimensional Helmholtz equation in a spherical shell and a two-dimensional Poisson equation on the solar surface. The solver is based on a combination of the spectral method and the finite-difference scheme. In the longitudinal direction the equation is transformed into the Fourier spectral space, and the resulting two-dimensional equations in the r-θ plane for the Fourier coefficients are solved by finite differencing. The solver shows an extremely fast computing speed, e. g., the computation for a magnetogram with a resolution of 180(θ)×360(φ) is completed in less than 2 s. Even on a high-resolution 600×1200 grid, the solution can be obtained within only about one minute on a single CPU. The solver can potentially be applied directly to the original resolution of observed magnetograms from SDO/HMI for routinely analyzing daily full-disk data. © 2012 Springer Science+Business Media B.V.
Sigma Group | Date: 2014-09-17
Methods, system and devices for wireless transmission of HDMI data streams. Plurality of data multiplex converters are constructed and used in parallel to process one HDMI datastream into plurality of channels of data packets wherein the plurality of channels of data packets are transmitted through Wi-Fi wireless protocols to a destination device. The received plurality of channels of data packets are reassembled into one data stream for display or play.
Sigma Group | Date: 2014-09-17
Methods and systems for a novel multi-media macro-network. A Picon media server is connected with variety of high data rate sources including high definition video and audio connections. Picon media server is configured to process the variety of data streams into lower data rate IP packets and dynamically transmit them wirelessly via plurality of channels and antennas to variety of Picon receivers which are configured to congregate the received data packets into the correct signal formats for specific displays.
Sigma Group | Date: 2016-06-29
Sigma Group | Date: 2015-11-02
Methods and systems for operating a wireless clock system for multimedia datastream transmission and display. Source clock frames are compared with a reference clock frames and the clock difference are transmitted to a wireless clock receiver which also receives the same reference clock frames. Source clock frames are re-constructed using the reference clock frames, clock difference information and the receivers local clock system.
News Article | September 11, 2013
Toto Sugiri is a veteran in the Indonesia technology scene. But not many people know his story and the things he has done over the past three decades as he maintains low profile and shies away from media attention. Some may know him as the founder self-funder of Indonesia’s first tier four data center, DCI; others may know him as a mentor in Founder Institute Jakarta; but fewer may know this 60-year-old entrepreneur is the founder of the 900 man Sigma Group that was acquired by Telkom Indonesia in 2007, or what he went through and his entrepreneurial journey. Toto completed his masters in computer engineering in Germany and returned to Indonesia in 1980. He started as a software engineer at an oil company and also ran his own software development startup before joining the bank his family owned. In the bank, Toto assembled his team and built customized software to help the bank computerize. This made his family’s bank the first few in the country to transact on computers. He was promoted fast. Despite the impact he brought to the bank, he detested the job as there was a lot of unhealthy politics in the hierarchy; it wasn’t a meritocratic organization. In addition to the unhappiness, Toto was pushed away by his desire to be a software provider whose product could help companies. He quit the lucrative bank job in 1989, his sixth year there, and started his own company. It wasn’t a difficult decision as his subordinates and his wife were very supportive. When I quit my job, five of my guys followed me to start this small company. At the start, we only had money enough for ten months of operation. If we didn’t get any money within the ten months, we would have run out of money and needed to find jobs together. Despite the risk, everyone wanted to give it a shot. We started the company, Sigma. In engineering, it means the sum of everyone. We started with a simple goal of being a software company that has a product that is used by more than 10 companies. It was that simple. Getting the first customer is always hard. Toto shared that he was very lucky to secure his first customer- a bank- after just two months in operation. He shared that being in the banking industry for the past six years made him reputable in the banking industry and people know him. This helped. As a new local player, nobody believed in us, but one bank gave us the chance to compete for their project. We discussed with the bank on how we could help integrate the software and train their staff to use it. We also shared that being a startup, we could not afford to buy the servers needed and required the bank to purchase it. At same time, we also negotiated to hold the copyright to the software we built so we could sell it to other banks. Being honest and forthright made the bank trust us and they gave us the project. With this deal, Sigma became profitable in its first year of operation. At end of its first year, Toto gathered his partners: With these goals, Toto framed the paper in front of his desk and took these goals as the compass for every business decision he made. By year three, they achieved every one of the goals and Sigma grew exponentially. At one point, more than 50 banks in Indonesia used Sigma’s software. This made Sigma highly profitable. Besides continuing to scale Sigma to greater heights, Toto is also concerned about the well being of his staff. He encouraged them to be entrepreneurial and Sigma would fund or provide loans for them to start. At its peak, Sigma has 15 subsidiaries that were started by his own staff. From 1989, there was a decade of exponential growth and life was rosy. But by 1998, all that had come to a halt. Political unrest and a financial crisis hit indonesia. That was a chaotic period in Indonesia that saw countrywide demonstrations, racial riots that killed thousands, the Indonesian currency becoming a sixth of its value, people’s savings became worthless, commodity prices shooting up, and many banks closed down. In such times, most businesses would have folded and their owners fled far away. But Toto knew he could not flee as his hundreds of staff needed him here. He relocated his wife and daughter to the U.S. and returned to continue Sigma’s operations in Indonesia. Toto bought houses and built offices on Bali island as that was the safest place in Indonesia then. He got his staff and their families to shift over so as to ensure their safety and started Balicamp- a subsidiary of Sigma that focuses on software development and customization for international companies. This was a successful move and they got many US and international clients. Despite some disturbing events such as the dot com crisis in early 2000 and the Bali bombing in 2002, Sigma Group continued its growth to become a 900 man company. In 2007, the Sigma Group was involved in a high-stakes takeover by sovereign-owned Telkom Indonesia, as the state wanted the technology company to develop the country’s technology infrastructure. Seeing this as a greater purpose for his two decade old startup, Toto part company with his lucrative company. From the early days of Sigma, one could see that Toto’s focus was less on money and more on how each of his staff could become successful and comfortable. Now, Toto has started and self-financed a 200 million dollar tier-four data center, DCI. He leaves the management of this new project to youth and takes up just an advisory role. Besides this, Toto also dedicates some of his time to mentoring young entrepreneurs at Founders Institute Jakarta and doing angel investing.