Search for serendipitous TNO occultation in X-rays

To study the population properties of small, remote objects beyond Neptune's orbit in the outer solar system, of kilometer size or smaller, serendipitous occultation search is so far the only way. For hectometer-sized Trans-Neptunian Objects (TNOs), optical shadows actually disappear because of diffraction. Observations at shorter wave lengths are needed. Here we report the effort of TNO occultation search in X-rays using RXTE/PCA data of Sco X-1 taken from June 2007 to October 2011. No definite TNO occultation events were found in the 334 ks data. We investigate the detection efficiency dependence on the TNO size to better define the sensible size range of our approach and suggest upper limits to the TNO size distribution in the size range from 30 m to 300 m. A list of X-ray sources suitable for future larger facilities to observe is proposed.Comment: Accepted to publish in MNRA

TARP: A traffic-aware restructuring protocol for Bluetooth radio networks

[[abstract]]Bluetooth is a low-cost and short-range wireless communication technology. The Bluetooth device randomly searches and connects with other devices using the inquiry/inquiry scan and the page/page scan operations, resulting an uncontrolled scatternet topology. The unpredictable scatternet topology usually raises the problem of redundant traffic and causes inefficient communications. A traffic-aware restructuring protocol (TARP) is presented for partially restructuring a piconet or a pair of two neighboring piconets by applying role switch mechanism. The proposed TARP mainly consists of intra-piconet and inter-piconet restructuring protocols. According to the recent routes and their traffic load information, the intra-piconet restructuring protocol adjusts piconet structure by selecting the proper device to play a master role of a piconet and applies takeover operation to rapidly restructure the piconet topology. The inter-piconet restructuring protocol exchanges devices of two neighboring piconets to reduce the route length and thus improve the power and bandwidth consumptions and the end-to-end transmission delay. Performance results reveal that the proposed restructuring protocols reduce path length of recent routes and save power consumption, thus significantly improve the performance for a given connected scatternet.[[incitationindex]]SCI[[conferencelocation]]Berlin, German

Low-energy electronic recoil in xenon detectors by solar neutrinos

Low-energy electronic recoil caused by solar neutrinos in multi-ton xenon detectors is an important subject not only because it is a source of the irreducible background for direct searches of weakly-interacting massive particles (WIMPs), but also because it provides a viable way to measure the solar $pp$ and $^{7}\textrm{Be}$ neutrinos at the precision level of current standard solar model predictions. In this work we perform $\textit{ab initio}$ many-body calculations for the structure, photoionization, and neutrino-ionization of xenon. It is found that the atomic binding effect yields a sizable suppression to the neutrino-electron scattering cross section at low recoil energies. Compared with the previous calculation based on the free electron picture, our calculated event rate of electronic recoil in the same detector configuration is reduced by about $25\%$. We present in this paper the electronic recoil rate spectrum in the energy window of 100 eV - 30 keV with the standard per ton per year normalization for xenon detectors, and discuss its implication for low energy solar neutrino detection (as the signal) and WIMP search (as a source of background).Comment: 12 pages, 3 figure

Reliability and Aging Analysis on SRAMs Within Microprocessor Systems

The majority of transistors in a modern microprocessor are used to implement static random access memories (SRAM). Therefore, it is important to analyze the reliability of SRAM blocks. During the SRAM design, it is important to build in design margins to achieve an adequate lifetime. The two main wearout mechanisms that increase a transistor’s threshold voltage are bias temperature instability (BTI) and hot carrier injections (HCI). BTI and HCI can degrade transistors’ driving strength and further weaken circuit performance. In a microprocessor, first-level (L1) caches are frequently accessed, which make it especially vulnerable to BTI and HCI. In this chapter, the cache lifetimes due to BTI and HCI are studied for different cache configurations, namely, cache size, associativity, cache line size, and replacement algorithm. To give a case study, the failure probability (reliability) and the hit rate (performance) of the L1 cache in a LEON3 microprocessor are analyzed, while the microprocessor is running a set of benchmarks. Essential insights can be provided from our results to give better performance-reliability tradeoffs for cache designers