Our Research Projects

Project runs from 01/03/2017 to 09/30/2019

Functionalities will be added for online monitoring of the Power devices including:
• Online monitoring of VDS for device health assessment. This will be done by modifying the existing gate driver circuitry.
• Online estimation of the device junction temperature by measuring the base plate temperatures and feeding the data to a detailed thermal model of the designed converter.
• Active modulation of the gate resistance during the switching transients to control the voltage and current overshoots of the power devices. The static characterization of the XHV-6 modules will be done to figure out the variability among the different modules. Furthermore, several protection features will be added including AC and DC short circuit protection, AC and DC over voltage and over current protection. We will attempt to create a user interface to be implemented for the end users which will show real time date of the MUSE SST system.

Project runs from 01/31/2017 to 01/30/2020

In many existing and emerging large-scale networks, an important application is to spread the information quickly and efficiently over the network. Over the past decade, this topic has received great research interest, and is relatively well studied for static networks. In contrast, our knowledge is far from complete when the network structures change over time, which is typical due to various reasons including environment changes, device and user mobility, variation of social relationship, and growth of the networks. There have been extensive studies on protocol and algorithm development in the area of mobile wireless networks, but many of them resort to simulation and
experimentation with synthetic and real-world mobility traces; a general analytical framework is lacking. In this project, built on our promising preliminary results, we intend to work towards a unified analytical framework for mobile networks that can address various types of mobility patterns and handle both connected and delay-tolerant networks. We also plan to extend our study to mobile social networks, which possess some unique features for information spreading that deserve separate and in-depth considerations. As emerging networks are complex and exhibiting unpredictable dynamics, random-walk based
algorithms become an appealing architectural solution for them. A pertinent question is whether we can further improve the efficiency of these algorithms while maintain their simplicity and robustness. Our preliminary results indicate that, by exploiting some additional information which may readily be available, a speedup by an order of magnitude is potentially achievable. Underlying our efficient algorithms is a design framework based on non-reversible Markov chains. In the second research thrust, we plan to deepen our study on this design framework, and further extend its underlying principle to the study in mobile social networks. The proposed research will be assessed through a comprehensive evaluation plan.

Project runs from 09/01/2016 to 08/31/2020

This proposal aims at solving a long-standing problem in the field of prosthetics –lack of inner-socket sensor technology. Due to this limitation, monitoring the inner socket environment (such as socket pressure, moisture, and temperature) is impossible. The proposed textile based multimodal sensor interface will be evaluated in real-time inner socket environment monitoring to enable self-management.

Project runs from 08/01/2016 to 07/31/2019

This project investigates novel ways to enable efficient preemption and effective latency hiding in single-instruction multiple-thread (SIMT) processors such as graphics processing units (GPUs). With the advent of the big data era, there is an increasing demand for data processing. Given their high computational throughput and high memory access bandwidth, GPUs have been widely used, ranging from smartphones, cloud servers, to supercomputers. Although virtualization has been introduced to enable GPUs as shared resource, significant hurdles remain. First, due to the high number of concurrent threads, GPUs have a large context size. Consequently, state-of-art GPUs resort to techniques like draining to complete the actively running threads before context switching. This may incur significant delay and fail the required quality of service (QoS). Second, it is very common that applications fail to fully utilize the computational resource and achieve the peak performance. There are two fundamental reasons. (a) Each thread requires a non-trivial amount of resource. Therefore, only a limited number of threads can run concurrently even if applications themselves have abundant thread-level parallelism. Without a sufficiently high number of threads, the latency hiding capability of fine-grain multithreading is severely impaired. (b) Long latency operations, off-chip memory accesses in particular, need a very high number of concurrent threads to hide their latency. The on-chip resources, however, cannot accommodate such large numbers of concurrent threads.

Project runs from 07/01/2016 to 06/30/2020

mm/sub-mm wave compressive sensing on diffraction limiting affects.

Project runs from 08/15/2016 to 12/31/2019

Myo-inositol phosphates (InsPs) are signaling molecules that are critically important in a number of developmental, metabolic and signaling processes in eukaryotes. The fully phosphorylated form, inositol hexakisphosphate or InsP6, plays important roles in many eukaryotes. A new frontier for InsP signaling is the study of unique signaling roles for a novel group of InsPs containing diphospho- or triphospho- moieties (PPx) at one or more positions on the Ins ring. In some ways, these PPx-InsPs are analogous to ATP in that they contain high-energy pyrophosphate bonds, and in addition, have been linked to communicating the energy status of the cell in other organisms. In this collaborative project, we previously developed analytical methods to detect and quantify PPx-InsPs in plant tissues, identified and cloned genes encoding the VIP kinases that are responsible for inositol pyrophosphate production in plants, and developed genetic resources to examine function of the Vip genes. Our preliminary data using mutants lacking both Vip genes reveal these genes are key in signaling the energy status of the plant cell. Further, we have identified a possible mechanistic link between inositol pyrophosphate signaling and a major regulator of eukaryotic metabolism, the Sucrose non-fermenting related kinase 1 (SnRK1). Given the immediate need to understand and manipulate plant bioenergy, the long-term goal of this project is to understand how InsP6, InsP7 and InsP8 convey signaling information within the cell. We focus on these molecules in plants, but point out that our model and findings are applicable to understanding the InsP6 signaling hub in other eukaryotes. During the proposed project, we plan to address several unresolved questions pertaining to PPx-InsPs and energy by first adding to a preliminary kinetic model of this signaling pathway.

Project runs from 08/01/2016 to 07/31/2021

The purpose of this request is to request an REU Supplement to our IUCRC Award.

Project runs from 08/09/2016 to 11/08/2019

As part of the UCLA led team, we propose to explore the nontrivial spin textures and dynamics in strongly spin-orbit coupled materials and their heterostructures, particularly with topological insulators (TIs) and emergent two-dimensional transition-metal dichalcogenides (TMDs). The specific research objectives include: (1) spin textures, spin-orbit torque, and THz spin-dynamics in the TIs and the related material combinations, and (2) strong spin-orbit coupling and the resulting spin-valley textures in the TMD based structures. In the first task, novel spin correlated phenomena and innovative applications will be examined primarily in the TI/magnet systems to take advantage of the spin-momentum entwinement in the TIs and the strong exchange interaction with the neighboring magnetic materials. The focus will be on the microscopic modeling of antiferromagnet dynamics, spin wave generation in the THz, and the domain wall motion (including the skyrmions) through electrical control of spin-orbit torque. In the study of the TMD based structures, the unique properties of this system enabled by the spin-valley interlock will be examined from three different aspects to broadly exploit the possibilities they offer; i.e., magneto-optic effect including coherent THz radiation, electrical control of spin-valley polarization, and spin/charge density wave generation. The physical phenomena as well as their applications originating from the nonlinear dynamics and textures will be examined theoretically based on multiscale treatments including the micro-magnetic simulations and first principles calculations. The latter, ab initio method based on the density functional theory formalism will be needed to accurately characterize emergent material properties under such conditions as doping, strain, or chemical functionalization. The analytical effort will be pursued in strong collaboration with the concurrent experimental investigation.

Project runs from 06/01/2016 to 05/31/2020

The Modular Multilevel Converter (MMC) has become established in high voltage and power applications due to its ability to split the system voltage into lower module voltages, its high efficiency, and its unmatched output power quality. Despite these advantages, however, the MMC has not made significant inroads in low and medium power applications. The key reasons are the complex monitoring required to ensure module balancing and the inefficient utilization of modules at voltages below the system maximum. Both of these disadvantages stem from the limitation that MMC modules can only be connected in series or bypassed. Addressing this limitation, we have recently proposed and demonstrated a new family of converters that extend the MMC to provide parallel connectivity of modules. Compared to the MMC, the novel modular multilevel series parallel converter (MMSPC) increases efficiency for the same total silicon and allows charge transfer between modules, akin to switched-capacitor topologies, thus drastically simplifying module balancing. This added functionality could open an entirely new space of low, medium, and high voltage applications of multilevel converters.

Project runs from 08/01/2016 to 07/31/2020

The proposed research will extend the applicability of wide bandgap semiconductors beyond the traditional limits imposed by the unipolar (Baliga’s) figure of merit by demonstrating a path to superjunction structures based on novel doping and defect control processes. This will lead to a new generation of devices that take advantage of the expected capabilities of III-nitrides but are not limited by doping or implantation technology. Superjunction device structures based on AlGaN are proposed where they exploit the doping selectivity observed in different III-nitride polar domains and the lateral polar patterning technology developed at the WideBandgaps Laboratory at NCSU. In addition, further control of point defects will be realized through the use of Fermi level control schemes based on engineered illumination by the use of UV (blue) lasers surface selective during the growth of the device structure. Such structures will eventually allow for significant breakdown voltages exceeding 5 kV and significant low on-resistance, beyond the expected rated BFOM. This research will provide for a transformative and disruptive technology for power electronics and also provide a breakthrough technology for other applications such as efficient deep UV emitters for water purification. The successful demonstration of such disruptive technology would revolutionize energy switching and transmission, energy storage, and related applications in electrical motor drives and other power intensive applications within the US. As such, the White House has recognized the need to build America’s leadership in this technology as part of the manufacturing innovation institutes. In general, this research will directly lead to materials that will be used for applications that deal with the preservation and extension of natural resources by: (1) allowing for the efficient 
use and transmission of electrical energy, (2) availability of clean potable water through 
disinfection by the use of UV, and (3) the detection of pollutants and other effluents. This 
program will provide the opportunity to educate a Ph.D. student with support from an undergraduate student on the growth and characterization of wide bandgap materials while participating with the group’s international collaborators network.

Project runs from 03/01/2017 to 02/29/2020

The project described here is a supplement request to augment the REU Site: From the body to the grid: Joint ERC REU explores energy from nano-scale harvesting to smart grid technology. The supplement is for 2 RET participants to augment the REU site proposal.

Project runs from 09/08/2015 to 09/07/2019

The assignee will be responsible for long-range planning and budget development for the areas of science represented by the program; for
managing an effective, timely merit review, award and declination process, and post-award management process; for communicating effectively the promise of the program and in so doing, advising the community of current and future funding opportunities; for coordinating and collaborating with other Programs in NSF, other Federal agencies and organizations; for advising and assisting the Division Director in the development of long­ range plans that ensure the Directorate’s investments are targeted to challenges and opportunities in the directorate’s research and education fields; for collaboratively overseeing and managing the merit review process for assigned research, education or infrastructure proposals to ensure that investments are made in a diverse, rich mix of bold, cutting-edge projects that promise to advance the frontier and contribute to the attainment of NSF’s strategic goals.

Project runs from 09/01/2015 to 08/31/2019

The project aims to develop a framework for collecting and pre-processing data from wearable sensing devices in the lab and real-world scenarios. We will aim to characterize their signal quality. We will make use of a system which allows users to wear various devices for weeks at the time, stream the data to an aggregator and then to the cloud. The ASSIST HET device will be integrated in this pipeline, and we will aim to integrate all data into a database that can be used by the center. The database will provide a frontend for collaborators and partners to access ASSIST data. Signal descriptors will be computed in order to characterize the quality of the signals and the presence of artifacts. We will focus our analysis on heart rate (HR) and heart rate variability (HRV). We will perform the analyzes on the data captured by the IRB protocol from Dr. Lobaton’s team using multiple wearable devices including the HET, as well as the data from Dr. Michelle Hernandez’s protocols.

Project runs from 09/01/2015 to 08/31/2019

This project encompasses the plan to develop a variable node for epidermal biosensors, in which the node has an interchangeable recognition/transduction element that can be modified to act as a biological, chemical, or electrophysiological sensor. The objective in Year 6 is to continue the development of the patch for multiplexed, epidermal biochemical sensing. The patch, as currently designed, incorporates two bio-recognition elements, glucose oxidase for glucose sensing and lactate oxidase for lactate detection. A temperature sensor, a pH sensor and an optical sensor will be included for calibration of enzymatic activity and measurement of relative deoxygenated hemoglobin amount in blood, respectively. The project aims to further validate the operation of the patch in vitro with the intended goal to be approaching the integration with the HET testbed and the design of pre-clinical human subject trials (≈10 individuals) towards the close of Year 6.

Project runs from 06/15/2016 to 12/14/2020

Agriculture is the primary economic activity undergirding human survival and quality of life and global economic development. To grow agricultural productivity we will establish an interdisciplinary graduate training program to address Plant Production within the Targeted Expertise Shortage Area (TESA) of Food Production. The goals of this program are: 1) comprehensively train three PhD fellows, each in a core discipline within plant production with cross-training in complementary areas; 2) provide experiential training within a technology rich, multidisciplinary research and Extension platform; and 3) graduate students proficient at integrating computational, environmental, biological and physical data into decision tools for increased yield and economic sustainability. This will be achieved through: recruitment of top tier, diverse Fellows; intensive advising and mentoring by exemplary faculty; outstanding academic, international, and industry-based research opportunities; leadership and professional development training, and internships with local Agbiotech companies. Fellows’ research will be grounded in the innovative research platform (AMPLIFY), a strategic industry-academia- producer partnership conducting interdisciplinary multi-scale systems research to advance high- yield sustainable agriculture to meet our world’s growing food requirements. Success will be measured by: 1) diversity of recruits; 2) presentations at professional conferences and publication in refereed journals; 3) timely degree completion; and 4) successful placements in industry, academia, or government appropriate to TESA. This NNF is relevant to the USDA/NIFA Challenge Area, Plant Production. Measurable impacts on TESAs include a more diverse scientific workforce trained in skills necessary to address complex challenges facing agriculture.

Project runs from 02/15/2016 to 01/31/2021

The goal of this project is to develop novel biophotonic devices and systems for studying global hemodynamic parameters in small animals. Such a system would respond to the critical need for small, wireless, minimally invasive systems for recording key physiological parameters during daily living activities in both laboratory environments and natural habitats without disturbing natural behavior and requiring a surgical implantation.

Project runs from 04/01/2016 to 03/31/2021

The objective of this proposal is to develop a computational framework that integrates statistical and computational geometric data analysis techniques for the processing, analysis and representation of patterns in order to unleash the potential of physiological and environmental multi-modal wearable sensing health systems for continuous monitoring and tracking of human wellness and physiological state. To accomplish this objective, this proposal will: (1) develop algorithms for the concurrent modeling of physiological, kinematics and environmental states for inference purposes; (2) develop techniques to transform models between different sensing systems in order to make information sharing compatible across platforms; and (3) develop techniques to maximize the impact on the behavior of individuals by elaborating on schemes for data representation. These techniques will empower users and medical practitioners to understanding, analyze, and make decisions based on patterns present in the data.

Project runs from 04/04/2016 to 07/03/2019

The goal of the Resilient Information Architecture Platform for the Smart Grid (RIAPS) project is to design, prototype, document, and evaluate via concrete applications a software platform for use in various networked computing nodes attached to the Smart Grid.
The Smart Grid will run on software that depends on a software platform. Just as a revolution in Smartphones was started by Android that enabled all sorts of software ‘apps’ to run on a wide variety of devices, our vision is that the same principle applies to the development of the Smart Grid, and the design, specification and prototyping of such an open software platform is essential for the growth and proliferation of the system.

Project runs from 09/15/2015 to 08/31/2020

The objective of this 3-year NSF-CPS proposal is to address three fundamental research challenges required for transcending wide-area communication and control of the North American power grid from a mere optimistic vision to a sustainable reality. Following the US Northeast blackout of 2003 and the subsequent advancement of Synchrophasor technology over the past decade utility owners have gradually started to look beyond the traditional myopic approach of local output feedback and instead use wide-area measurement feedback. However, currently a huge gap exists between implementing such controls using of realistic communication networks in a reliable and economic way. Majority of the ongoing NASPI-net activities are devoted to the hardware architectural planning of aspects of wide-area communication with very little attention to how complicated MIMO control loops, when implemented on top of this communication, may perform under various operating conditions. The vision of this project is to underline the necessity of constructing such an integrated, robust and economically sustainable wide-area communication and control infrastructure by addressing three critical research challenges that stand in its way – namely, (1) understanding how distributed multi-input multi-output (MIMO) controllers dictate and depend on the operational rules of underlying communication systems, and how the two should be co-designed in sync with each other, (2) investigating how wide-area communication can be made economically feasible and sustainable via joint decision-making processes between participating utility companies, and testing how controls can play a potential role in facilitating such economics, and finally (3) exploiting new design ideas of software-defined networks (SDN) so that wide-area communication is not merely a data-transporter but also facilitates the closed-loop dynamic performance of the grid.

Project runs from 05/18/2016 to 09/30/2019

Reverse power flows and variable outputs of solar generation resources could cause temporal and spatial voltage variations in the power network. Such variations can lead to exceedance of voltage limits set by NERC voltage and reactive control standard VAR-001-4 at the sub-transmission level and ANSI
standards at the distribution level. Voltage regulation devices deployed today are operated to cope mainly with system load changes. Their settings are usually determined on a seasonal basis. The location, capacity, and operation of these devices are not designed and coordinated for managing the real-time
variations caused by distributed solar photovoltaics (PVs). As a result, over- or under- voltage problems can happen more frequently, especially in light load seasons such as spring and fall. Those phenomena have already been observed in high solar penetration areas, such as Hawaii and Southern California. PNNL will partner with North Carolina State University (NCSU), GE Global Research, One-Cycle Control Inc. (OCC) and Duke Energy to develop a Coordinated Real-time Sub-Transmission Volt-Var Control Tool (CReST-VCT) to optimize the use of reactive power control devices to stabilize voltage
fluctuations caused by intermittent PV outputs. In order to capture the full value of the Volt-Var optimization, we propose to couple this tool to an Optimal Future Sub-Transmission Volt-Var Planning Tool (OFuST-VPT) for short- and long-term planning. Together, the real-time control and planning tools
will remove a major roadblock in the increased use of distributed PV.