No abstract

Computer systems in the near future are expected to have Non-Volatile Main Memory (NVMM), enabled by a new generation of Non-Volatile Memory (NVM) technologies, such as Phase Change Memory (PCM), STT-MRAM, and Memristor. The non-volatility property has the promise to persist in-memory data structures for instantaneous failure recovery. However, realizing such promise requires a careful design to ensure that in-memory data structures are in known consistent states after failures. This paper studies persistent in-memory B +-Trees as B +-Trees are widely used in database and data-intensive systems. While traditional techniques, such as undo-redo logging and shadowing, support persistent B +-Trees, we find that they incur drastic performance overhead because of extensive NVM writes and CPU cache flush operations. PCM-friendly B +-Trees with unsorted leaf nodes help mediate this issue, but the remaining overhead is still large. In this paper, we propose write atomic B +-Trees (wB +-Trees), a new type of main-memory B +-Trees, that aim to reduce such overhead as much as possible. wB +-Tree nodes employ a small indirect slot array and/or a bitmap so that most insertions and deletions do not require the movement of index entries. In this way, wB +-Trees can achieve node consistency either through atomic writes in the nodes or by redo-only logging. We model fast NVM using DRAM on a real machine and model PCM using a cycle-accurate simulator. Experimental results show that compared with previous persistent B +-Tree solutions, wB +-Trees achieve up to 8.8x speedups on DRAM-like fast NVM and up to 27.1x speedups on PCM for insertions and deletions while maintaining good search performance. Moreover, we replaced Memcached's internal hash index with tree indices. Our real machine Memcached experiments show that wB +-Trees achieve up to 3.8X improvements over previous persistent tree structures with undo-redo logging or shadowing.

No abstract

No abstract

In this paper we study robust speaker recognition in farfield microphone situations such as meeting scenarios. By applying reverberation compensation and feature warping we achieved significant improvements under mismatched training-testing conditions. To capture useful information from multiple distant microphones, two approaches for multiple channel combination are investigated. This leads to 84.1% and 78.1% relative improvements on the Distant Microphone database. Furthermore, we tested the resulting system on the ICSI Meeting Corpus. The improvements are also very high on this task, which indicates that our system is robust to changing conditions in a remote microphone setting.

Recently, 1/f and random telegraph noise (RTN) studies have been used to infer information about bulk dielectric defects' spatial and energetic distributions. These analyses rely on a noise framework which involves charge exchange between the inversion layer and the bulk dielectric defects via elastic tunneling. In this study, we extracted the characteristic capture and emission time constants from RTN in highly scaled nMOSFETs and showed that they are inconsistent with the elastic tunneling picture dictated by the physical thickness of the gate dielectric (1.4 nm). Consequently, our results suggest that an alternative model is required and that a large body of the recent RTN and 1/f noise defect profiling literature very likely needs to be re-interpreted.

No abstract

(V600E)B-RAF kinase is the most frequent onco-genic protein kinase mutation in melanoma and is a promising target to treat malignant melanoma. In this work, a molecular modeling study combining QM-polarized ligand docking, molecular dynamics, free energy calculation, and three-dimensional quantitative structure-activity relationships (3D-QSAR) was performed on a series of pyridoimidazolone compounds as the inhibitors of (V600E)B-RAF kinase to understand the binding mode between the inhibitors and (V600E)B-RAF kinase and the structural requirement for the inhibiting activity. 3D-QSAR models, including CoMFA and CoMSIA, were developed from the conformations obtained by QM-polarized ligand docking strategy. The obtained models have a good predictive ability in both internal and external validation. Furthermore, molecular dynamics simulation and free energy calculations were employed to determine the detailed binding process and to compare the binding mode of the inhibitors with different activities. The binding free energies calculated by MM/PBSA gave a good correlation with the experimental biological activity. The decomposition of free energies by MM/GBSA indicates the van der Waals interaction is the major driving force for the interaction between the inhibitors and (V600E)B-RAF kinase. The hydrogen bond interactions between the inhibitors with Glu501 and Asp594 of the (V600E)B-RAF kinase help to stabilize the DFG-out conformation. The results from this study can provide some insights into the development of novel potent (V600E)B-RAF kinase inhibitors.