Browsing by Author "Wang, Jing"

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    Information-driven Data Gathering In Wireless Sensor Networks
    (Computer Science & Engineering, 2010-11-01)
    Since the advance of wireless technology enables the mass production of low-cost, small-sized sensor nodes, sensor nodes can be densely deployed in an area for high tolerance to node failure or to achieve better coverage statistically. The redundancy of sensor nodes results in the temporal and spatial correlation of sensory data, which motivates the information-driven data gathering approaches for wireless sensor networks (WSNs).Since existing approaches target at the sensory data that are already highly correlated with each other, little attention has been paid to the idea of changing the sampling schedules of the sensor nodes to reduce the correlation among sensory data. In this dissertation, sampling strategies and the relevant medium access control (MAC) protocol are presented to demonstrate how the correlation can be reduced through adjusting the sampling time shifts of sensor nodes.The asynchronous lossless data gathering strategy aims at extending the sampling cycle of individual node while guaranteeing the original signal to be fully recovered by the sink. Based on the correlation signal model, details of the collaborative reconstruction of the original signal are presented. An exponential temporal-spatial correlation model is introduced for presenting lossy data gathering strategies. It is justified by real data collected from wireless sensor networks. Regarding lossy data gathering applications, the sensor nodes take samples asynchronously to obtain more informative samples. Furthermore, the entropy of the joint Gaussian random variables is adopted to quantify the improvement on the quality of information obtained from the asynchronous samples. Oppeinhem's inequality is applied to prove the entropy is increased by introducing a non-zero temporal correlation parameter. A recursive algorithm is designed to solve the optimal asynchronous sampling problem with a set of sub-optimal sampling time shifts. Bounds on the performance of the three asynchronous sampling strategies are derived respectively.Motivated by the benefit of asynchronous sampling strategies, an information-driven MAC protocol is proposed to avoid the severe collisions of event reports in the event detection applications. Other than choosing a subset of nodes to report to the sink, the proposed protocol assigns sampling shifts to nodes in order to change the bursty traffic into a streamlined traffic. Consequently, the MAC performance is improved by essentially replacing the collision prone traffic with the streamlined one. An optimal probability model is adopted for selecting nodes' transmission slots that minimize collisions and in turn reduce the correlation among event reports. Through theoretical analysis and simulations, it is shown that the protocol relates the MAC performance with the information quality of event reports, which is quantified by the Cramer-Rao lower bound (CRLB) of parameter estimation. In addition to the benefit of reduced collision probability, the CRLB is lowered by the proposed MAC protocol after the nodes' s sampling time moments are shifted from each other.
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    PI(4)P-Dependent recruitment of Clathrin Adaptors to the trans-Golgi Network
    (2005-04-29) Wang, Jing; Yin, Helen L.
    The Trans Golgi Network (TGN) is the cell's central sorting station, and the complex trafficking patterns are organized by many types of trafficking adaptors. These include the heterotetrameric adaptor protein complexes (APs) and the monomeric Golgi-localized, gamma-ear containing, Arf-binding proteins (GGAs). The fundamental question of how these adaptors are recruited to TGN membrane remains unclear. Previous studies have shown that adaptor recruitment to the TGN is absolutely dependent on the small GTPase ADP ribosylation factor 1 (Arf1), but paradoxically, Arf1 has a broader intracellular distribution than these adaptors. We found that the Golgi is particularly enriched in phosphatidylinositol 4 phosphate [PI(4)P] and that the clathrin adaptor AP-1 binds PI(4)P directly, suggesting that PI(4)P binding may specify the TGN-specific recruitment in conjunction with Arf1. My studies showed that another monomeric clathrin adaptor GGA also binds PI(4)P and Arf1 independently. The C-terminal "triple helix bundle" of the GGA GAT domain is a polyfunctional module that interacts with multiple partners including PI(4)P and ubiquitin, and ubiquitin may provide a recognition signal for GGAs to control protein sorting. We found that PI(4)P increases wild type GAT binding to ubiquitin-conjugated agarose beads, but has no effect on a mutant GAT that does not bind PI(4)P. Therefore, PI(4)P may be an allosteric regulator of GGAs which enhances ubiquitin binding to GGAs. Based on these results, we conclude: (1) PI(4)P defines the TGN organelle identity by recruiting TGN-targeted adaptors; (2) TGN-enriched adaptors are recruited to the Golgi by binding to both PI(4)P and Arf1, and neither alone is sufficient; (3) PI(4)P acts as a scaffold, and may also be an allosteric regulator for GGAs that modulates GGA function with other ligands. We propose that the integration of combinatorial inputs from PI(4)P, Arf1 and ubiquitin may coordinately specify clathrin adaptor TGN recruitment through multiple low-affinity interactions.
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    Power supply noise in delay testing
    (2009-05-15) Wang, Jing
    As technology scales into the Deep Sub-Micron (DSM) regime, circuit designs have become more and more sensitive to power supply noise. Excessive noise can significantly affect the timing performance of DSM designs and cause non-trivial additional delay. In delay test generation, test compaction and test fill techniques can produce excessive power supply noise. This will eventually result in delay test overkill. To reduce this overkill, we propose a low-cost pattern-dependent approach to analyze noise-induced delay variation for each delay test pattern applied to the design. Two noise models have been proposed to address array bond and wire bond power supply networks, and they are experimentally validated and compared. Delay model is then applied to calculate path delay under noise. This analysis approach can be integrated into static test compaction or test fill tools to control supply noise level of delay tests. We also propose an algorithm to predict transition count of a circuit, which can be applied to control switching activity during dynamic compaction. Experiments have been performed on ISCAS89 benchmark circuits. Results show that compacted delay test patterns generated by our compaction tool can meet a moderate noise or delay constraint with only a small increase in compacted test set size. Take the benchmark circuit s38417 for example: a 10% delay increase constraint only results in 1.6% increase in compacted test set size in our experiments. In addition, different test fill techniques have a significant impact on path delay. In our work, a test fill tool with supply noise analysis has been developed to compare several test fill techniques, and results show that the test fill strategy significant affect switching activity, power supply noise and delay. For instance, patterns with minimum transition fill produce less noise-induced delay than random fill. Silicon results also show that test patterns filled in different ways can cause as much as 14% delay variation on target paths. In conclusion, we must take noise into consideration when delay test patterns are generated.
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    Radiation Effects on Low-dimensional Carbon System
    (2013-08-05) Wang, Jing
    Ion irradiation has been known to be an effective tool for structure modification with micro/nano-scale precision. Recently, demonstrations have been made for nano-machining, such as the cutting and welding of carbon nanotubes. Understanding the fundamental effects of ion irradiation on carbon nanotubes is critical for advancing this technique as well as for scientific curiosity. Molecular dynamics modeling was performed to study irradiation stability, structural changes, and corresponding thermal properties. In our study, Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) was used to perform atomic scale simulation. In order to understand size and geometry effects on carbon damage creation, the threshold energy of displacement was calculated as a function of recoiling angles for both single-walled and multi-walled nanotubes. A strong directional dependence was found to exist in different shells of multi-walled carbon nanotubes. We found that carbon atoms on the innermost tube were more susceptible to be displaced toward the center of axis. The calculation matrix was further extended to nanotubes having different diameters for a full-scale understanding of the creation of defects. Besides studies on defects creation, thermal properties of carbon nanotubes were studied via a simplified model of the carbon nanotube network. Thermal conductivity, were found to be increased nearly one order of magnitude in carbon nanotube networks after irradiation and subsequent annealing. All the modeling results were compared with experimental observations either obtained from this project as a parallel study or from previous works, for the purpose of verification and validation. For experimental works, atomic scale characterization was performed by using transmission electron microscopy and the thermal conductivity measurement was characterized by using laser flash technique. Through a combination of modeling and experimentation, we proved that ion beam techniques can be used to enhance thermal conductivity in carbon nanotube bundles by inter-tube defects mediated phonon transport.
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    The role of ascorbate peroxidase-3 in oxidative stress
    (2007-05) Wang, Jing
    The Arabidopsis gene APX3 that encodes a putative peroxisomal membrane-bound ascorbate peroxidase was overexpressed In Escherichia coli and transgenic tobacco plants. APX3 expressing bacterial cells showed high APX activity, whereas no APX activity could be detected in bacterial cells alone. APX3 expressing plants had substantial levels of APX3 mRNA and protein. The H2O2 can be converted to more reactive toxic molecules, e.g. OH, if it is not quickly removed from plant cells. Expression of APX3 in tobacco can protect leaves from oxidative stress damage caused by aminotriazole which inhibits catalase activity that is found mainly in glyoxisomes and peroxisomes and leads to accumulation of H2O2 in those organelles. However, these plants did not show increased protection from oxidative damage caused by paraquat which leads to ROS production in chloroplasts. Therefore, protection provided by expression of APX3 seems to be specific against oxidative stress originating in peroxisomes, not from chloroplasts, which is consistent with the hypothesis that APX3 is a peroxisomal membrane-bound antioxidant enzyme.
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    Using linear mixed model to analyze the longitudinal data
    (Texas Tech University, 2007-05) Wang, Jing; Martin, Clyde F.; Ibragimov, Akif
    The purpose of this research is to analyze longitudinal data using linear mixed model with application to voltage-dependent motility and/ or stiffness changes of the hair bundle of outer hair cells (OHCs). I introduce PROC MIXED procedure in SAS for repeated measurement data. In an addition, I will give an overview of several procedures in the SAS System for statistical modeling.