• Prediction of Ignition Regimes in DME/Air Mixtures with Temperature and Concentration Fluctuations

      Luong, Minh Bau; Hernandez Perez, Francisco E.; Sow, Aliou; Im, Hong G. (American Institute of Aeronautics and Astronautics, 2019-01-07)
      The objective of the present study is to establish a theoretical prediction of the autoignition behavior of a reactant mixture for a given initial bulk mixture condition. The ignition regime criterion proposed by Im and coworkers based on the Sankaran number (Sa), which is a ratio of the laminar flame speed to the spontaneous ignition front speed, is extended to account for both temperature and equivalence ratio fluctuations. The extended ignition criterion is then applied to predict the autoignition characteristics of dimethyl ether (DME)/air mixtures and validated by two-dimensional direct numerical simulations (DNS). The response of the ignition mode of DME/air mixtures to three initial mean temperatures of 770, 900 K, and 1045 K lying within/outside the NTC regime, two levels of temperature and concentration fluctuations at a pressure of 30 atm and equivalence ratio of 0.5 is systematically investigated. The statistical analysis is performed, and a newly developed criterion –the volumetric fraction of Sa < 1.0, FSa,S, is proposed as a deterministic criterion to quantify the fraction of heat release attributed to strong ignition. It is found that the strong and weak ignition modes are well captured by the predicted Sa number and FSa,S regardless of different initial mean temperatures and the levels of mixture fluctuations and correlations. Sap and FSa,S demonstrated under a wide range of initial conditions as a reliable criterion in determining a priori the ignition modes and the combustion intensity.
    • Linear kernel tests via emperical likelihood for high dimensional data

      Ding, L.; Liu, Z.; Li, Y.; Liao, S.; Liu, Y.; Yang, P.; Yu, G.; Shao, L.; Gao, Xin (2019-01)
    • Approximate kernel selection with strong approximate consistency

      Ding, L.; Liao, S.; Liu, Y.; Yang, P.; Li, Y.; Pan, Y.; Huang, C.; Shao, L.; Gao, Xin (2019-01)
    • Second order online multitask learning

      Yang, P.; Zhao, P.; Zhou, J.; Gao, Xin (2019-01)
    • Development of Printed Sensors for Shoe Sensing Applications

      Nag, Anindya; Feng, Shilun; Mukhopadhyay, Subhas; Kosel, Jürgen (IEEE, 2018-12-14)
      The paper presents the design and implementation of a low-cost shoe sensing system using laser-induced graphene sensors. Commercial polymer films were laser-induced to photo-thermally form graphene, which was then used as electrodes on Kapton tapes to form sensor patches. Experiments were then conducted with these sensor prototypes to validate its functionality as pressure sensors to be used in shoe sensing system. Different weights were tested with the developed system to ensure the capability of these sensor patches to be used as pressure sensing. The results look promising to be a system for monitoring the movement of a person wearing a shoe containing these low-cost pressure sensors.
    • Development of Novel Gold/PDMS Sensors for Medical Applications

      Nag, Anindya; Feng, Shilun; Afsarimanesh, Nasrin; Mukhopadhyay, Subhas; Kosel, Jürgen (IEEE, 2018-12-14)
      The paper presents the design and fabrication of novel gold/PDMS sensors using the sputtering method to use them for biomedical applications. The electrodes on the sensor patches were formed by placing a masked template containing the design over the PDMS. The sensor patches were flexible in nature with interdigitated electrodes formed on them. CTx-I, being one of the significant bone turnover biomarkers to determine the condition of the bones was tested at different concentrations to validate the functionality of the patches for this purpose. The results look promising to upgrade this idea into a fully-functionalized system for medical applications.
    • A robust monitoring technique for fault detection in grid-connected PV plants

      Harrou, Fouzi; Taghezouit, Bilal; Sun, Ying (IEEE, 2018-12-13)
      Monitoring the operation condition of photovoltaic (PV) systems is crucial to improving their efficiency. In this paper, an effective method to supervise the DC part of PV plants under noisy environment is provided. In fact, noisy measurements make the supervision more challenging as the feature extraction of the fault is more difficult. The designed approach merges the desirable proprieties of the discrete wavelet transform and the exponentially weighted moving average scheme to appropriately detect faults in PV system. Specifically, this approach is employed to check the residuals generated by a simulation model based on a single-diode modeling for fault detection. We evaluated the efficiency of the proposed approach on a real PV system in Algeria. Results indicated that the proposed approach has good capacity in supervising the DC part of PV plants.
    • Mechanical Computing Using Multifrequency Excited NEMS Resonator

      Kazmi, Syed N.R.; Ilyas, Saad; Costa, Pedro M.F. J.; Younis, Mohammad I. (IEEE, 2018-12-13)
      A silicon based nanoelectromechanical resonator is fabricated and is actively tuned through electrostatic actuation. We present multifrequency excitation of a NEMS resonator to dynamically perform all the fundamental logic operations (NOT, NOR, XNOR, NAND, OR, AND, and XOR). The multifrequency excitation allows to uniquely define resonant and non-resonant states as high and low logic outputs for all fundamental logic gates. The performance of this logic device is examined in terms of its speed of operation, energy consumption, and integration density. This work paves the way towards energy efficient nano-elements-based mechanical computing.
    • Stretchability of Archimedean-Spiral Interconnects Design

      Alcheikh, Nouha; Hussain, Muhammad. M. (IEEE, 2018-12-13)
      The island-interconnects design represents one of the categories which is widely used in stretchable electronics. Recently, Archimedean spiral interconnects are proposed as one of the best solutions for achieving a high level of stretchability. According to existing studies, their shape designs need to be investigated. Hence, this paper aims to examine the effect of the shape and the geometrical parameters of the Archimedean spiral on their stretchability. Due to the complex geometry, we use finite element method (FEM) to calculate the maximum stress and strain under axial deformation. The results conclude that with a narrow width and larger height, the Archimedean spiral shows highly stretchability more than 277% and 440% under maximum tensile strain εmax=1% and εmax=1.7%, respectively which correspond to the critical intrinsic strain of silicon. These results can be promising to fabricate high stretchable Archimedean spiral interconnects.
    • In-Plane Air Damping of NEMS and MEMS Resonators

      Alcheikh, Nouha; Kosuru, Lakshmoji; Kazmi, Syed N. R.; Younis, Mohammad I. (IEEE, 2018-12-13)
      This paper presents a study of the quality factor dependence on the geometrical parameters of in-plane clamped-clamped micro- and nano-beams capacitive structures at low-to-high pressure range. We found that smaller length and larger beam thickness maximize the quality factor. To minimize squeeze film damping, the structures have been fabricated with large capacitive air gaps. Despite the high ratio of the gap/thickness, we report significant effect of the gap width on the quality factor. It is found that, for micro-beams, this effect is limited at low pressure while for nano-beams, it continues until high pressure range. The geometry and the air gap effects on the damping of beams resonators have been examined experimentally. A finite-element study of the effect of the capacitive gap for in-plane resonators of one and two-side electrodes is presented. It is found that the presence of the double electrodes for in-plane resonators can cause significant drop of the quality factor compared to the single-sided beam resonator.
    • Memristor Based Programmable Current Reference Generator

      Bahloul, Mohamed A.; Bouraoui, Mariem; Barraj, Imen; Fouda, Mohammed E.; Masmoudi, Mohamed (IEEE, 2018-12-13)
      Current reference circuits are widely used in analog integrated circuit design. However, due to PVT and aging variations, the reference currents are mostly affected which requires reprogramming the reference circuit. Recently, memristors are investigated in many analog applications due to the programmability and non-volatility. In this paper, we introduce a simple programmable memristor-based circuit that can be used in current reference generators. The circuit is based on one memristor and one CMOS transistor to tune the resistance of the memristor. VTEAM memristor model is used to study the proposed circuit programmability. The necessary tuning conditions for the circuit are discussed. Then, the proposed circuit have been used in the well-known Beta-Multiplier current reference to generate a programmable current reference. The designed circuit has a reasonable current tuning range due to the limited range of the used memristor model. Different circuit simulations are provided using ST 65nm CMOS Technology.
    • Ordered Sequence Detection and Robust Design for Pulse Interval Modulation

      Guo, Shuaishuai; Park, Ki-Hong; Alouini, Mohamed-Slim (IEEE, 2018-12-09)
      This paper proposes an ordered sequence detection (OSD) for digital pulse interval modulation (DPIM) applied in optical wireless communications (OWC). To detect a packet consisting of $L$-chips, the computational complexity of OSD is of the order $\mathcal{O}(L\log_2L)$. Moreover, this paper also proposes a robust pulse interval modulation (RPIM) scheme based on OSD. In RPIM, the last of every $K$ symbols is with more power to transmit information and simultaneously to provide a built-in barrier signal. In this way, error propagation is bounded in a slot of $K$ symbols. Together with interleaver and forward error correction (FEC) codes, the bit error rate (BER) can be greatly reduced. We derive the approximate uncoded BER performance of conventional DPIM with OSD and the newly proposed RPIM with OSD based on order statistic theory. Simulations are conducted to collaborate on theoretical analysis and show that RPIM with OSD considerably outperforms existing DPIM with optimal threshold detection in either uncoded or coded systems over various channels.
    • Robust 3-D Location Estimation in the Presence of Anchor Placement and Range Errors

      Suliman, Mohamed Abdalla Elhag; Ballal, Tarig; AlSharif, Mohammed H.; Saad, Mohamed; Al-Naffouri, Tareq Y. (IEEE, 2018-12-04)
      This paper addresses the problem of 3-D location estimation from perturbed range information and uncertain anchor positions. The 3-D location estimation problem is formulated as a min-max convex optimization problem with a set of second-order cone constraints. Robust optimization tools are applied to convert these cone constrains to semi-definite programming constraints and achieve robust location estimation without prior knowledge of the statistical distributions of the errors. Simulation results demonstrate the superiority of the proposed approach over other benchmark algorithms in a wide range of measurement error scenarios.
    • Parallel Approximation of the Maximum Likelihood Estimation for the Prediction of Large-Scale Geostatistics Simulations

      Abdulah, Sameh; Ltaief, Hatem; Sun, Ying; Genton, Marc G.; Keyes, David E. (IEEE, 2018-11-26)
      Maximum likelihood estimation is an important statistical technique for estimating missing data, for example in climate and environmental applications, which are usually large and feature data points that are irregularly spaced. In particular, the Gaussian log-likelihood function is the de facto model, which operates on the resulting sizable dense covariance matrix. The advent of high performance systems with advanced computing power and memory capacity have enabled full simulations only for rather small dimensional climate problems, solved at the machine precision accuracy. The challenge for high dimensional problems lies in the computation requirements of the log-likelihood function, which necessitates O(n2) storage and O(n3) operations, where n represents the number of given spatial locations. This prohibitive computational cost may be reduced by using approximation techniques that not only enable large-scale simulations otherwise intractable, but also maintain the accuracy and the fidelity of the spatial statistics model. In this paper, we extend the Exascale GeoStatistics software framework (i.e., ExaGeoStat1) to support the Tile Low-Rank (TLR) approximation technique, which exploits the data sparsity of the dense covariance matrix by compressing the off-diagonal tiles up to a user-defined accuracy threshold. The underlying linear algebra operations may then be carried out on this data compression format, which may ultimately reduce the arithmetic complexity of the maximum likelihood estimation and the corresponding memory footprint. Performance results of TLR-based computations on shared and distributed-memory systems attain up to 13X and 5X speedups, respectively, compared to full accuracy simulations using synthetic and real datasets (up to 2M), while ensuring adequate prediction accuracy.
    • Evolution of Junction Temperature and Heating Effects in UV AlGaN Nanowires LEDs

      Priante, Davide; Elafandy, Rami T.; Prabaswara, Aditya; Janjua, Bilal; Zhao, Chao; Tangi, Malleswararao; Alias, Mohd Sharizal; Alaskar, Yazeed; Albadri, Abdulrahman M.; Alyamani, Ahmed Y.; Ng, Tien Khee; Ooi, Boon S. (OSA, 2018-11-20)
      We show reduced junction temperature and heat dissipation in AlGaN nanowires LEDs on a metal substrate compared to devices on a silicon substrate by employing the forward-voltage and peak-shift methods.
    • Inkjet Printed RF Sensor Array For Lung Disease Detection

      Tayyab, M.; Sharawi, M.S.; Shamim, Atif (Institution of Engineering and Technology, 2018-11-20)
      We propose an RF sensor array for lung disease detection. The size of the sensor array is 4cm*89.4cm. The sensor consists of 38 electrodes and 37 ports. The first two electrodes are optimized to operate at 60 MHz and act as a signal exciter. The remaining 36 electrodes receive the radiated field. The transmission coefficients Si1 at each passive port are calculated using HFSS software. An equation was designed for dielectric constant estimation using the Least Squares (LS) method. The sensor is fabricated using Inkjet printing. The experiments of the fabricated sensor were conducted on an average adult human chest elliptical model.
    • All-Dielectric Terahertz Half-Wave Plate with Antireflection Layer

      Zi, Jianchen; Xu, Quan; Wang, Qiu; Tian, Chunxiu; Li, Yanfeng; Zhang, Xixiang; Han, Jiaguang; Zhang, Weili (OSA, 2018-11-20)
      We present an all-dielectric terahertz half-wave plate with an antireflection layer. The device is made of pure silicon, and can realize cross polarization conversion with almost 100% conversion rate and 90% of transmission at the operating frequency.
    • A New ROI-Based performance evaluation method for image denoising using the Squared Eigenfunctions of the Schrödinger Operator

      Chahid, Abderrazak; Serrai, Hacene; Achten, Eric; Laleg-Kirati, Taous-Meriem (IEEE, 2018-11-16)
      In this paper a new Region Of Interest (ROI) characterization for image denoising performance evaluation is proposed. This technique consists of balancing the contrast between the dark and bright ROIs, in Magnetic Resonance (MR) images, to track the noise removal. It achieves an optimal compromise between removal of noise and preservation of image details. The ROI technique has been tested using synthetic MRI images from the BrainWeb database. Moreover, it has been applied to a recently developed denoising method called Semi-Classical Signal Analysis (SCSA). The SCSA decomposes the image into the squared eigenfunctions of the Schrödinger operator where a soft threshold h is used to remove the noise. The results obtained using real MRI data suggest that this method is suitable for real medical image processing evaluation where the noise-free image is not available.
    • From Terahertz Surface Waves to Spoof Surface Plasmon Polaritons

      Xu, Yuehong; Zhang, Ying; Xu, Quan; Zhang, Xueqian; Li, Yanfeng; Gu, Jianqiang; Tian, Zhen; Ouyang, Chunmei; Zhang, Xixiang; Zhang, Weili; Han, Jiaguang (IEEE, 2018-11-16)
      Surface plasmon polaritons (SPPs) promise versatile potential applications in many aspects and thus have been a subject of enormous interest. However, in the terahertz regime, due to perfect conductivity of most metals, it is hard to realize a strong confinement of SPPs although a propagation loss could be sufficiently low. Here we introduce the recent work from terahertz surface waves to spoof SPPs based on metasurfaces.
    • Real-Time Distributed Motion Planning with Submodular Minimization

      Jaleel, Hassan; Abdelkader, Mohamed; Shamma, Jeff S. (IEEE, 2018-11-16)
      We present a real-time implementation of a distributed motion planning framework that is based on model predictive control with one step prediction horizon and submodular function minimization. In particular, our focus is to evaluate the real-time performance of this distributed motion coordination framework. For performance evaluation, we develop a realistic simulation environment for the challenging setup of capture the flag game, which is played between two teams. We consider a scenario in which each team has four quadcopters and the game is played in an arena with multiple obstacles. We develop the simulation setup primarily in Gazebo with software in the loop. The software in the loop is the autopilot software, which is used to stabilize and control the motion of each quadcopter. The motion plan for the defense team is computed by minimizing submodular potential functions using the distributed and online algorithm presented in our previous work. Based on extensive simulations under various conditions, we verify that the proposed approach can be used effectively for real-time distributed control of multiagent systems over discrete input space.