Engineering Commons^™

Crystallization In Nano-Confinement Seeded By A Nanocrystal -- A Molecular Dynamics Study, Heng Pan, Costas Grigoropoulos

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Seeded crystallization and solidification in nanoscale confinement volumes have become an important and complex topic. Due to the complexity and limitations in observing nanoscale crystallization, computer simulation can provide valuable details for supporting and interpreting experimental observations. In this article, seeded crystallization from nano-confined liquid, as represented by the crystallization of a suspended gold nano-droplet seeded by a pre-existing gold nanocrystal seed, was investigated using molecular dynamics simulations in canonical (NVT) ensemble. We found that the crystallization temperature depends on nano-confinement volume, crystal orientation, and seed size as explained by classical two-sphere model and Gibbs-Thomson effect.

Multibit Retention Registers For Power Gated Designs: Concept, Design, And Deployment, Yu Guang Chen, Hui Geng, Kuan Yu Lai, Yiyu Shi, Shih Chieh Chang

Electrical and Computer Engineering Faculty Research & Creative Works

Retention registers have been widely used in power gated designs to store data during sleep mode. However, their excessive area and leakage power render it imperative to minimize the total retention storage size. The current industry practice replaces all registers with single bit retention ones, which significantly limits the design freedom and yields suboptimal designs. Toward this, for the first time in the literature, we propose the concept and the design of multibit retention registers, with which only selected registers need to be replaced. The technique can significantly reduce the number of bits that need to be stored and thus …

Yield And Timing Constrained Spare Tsv Assignment For Three-Dimensional Integrated Circuits, Yu Guang Chen, Kuan Yu Lai, Ming Chao Lee, Yiyu Shi, Wing Kai Hon

Electrical and Computer Engineering Faculty Research & Creative Works

Through Silicon Via (TSV) is a critical enabling technique in three-dimensional integrated circuits (3D ICs). However, it may suffer from many reliability issues. Various fault-tolerance mechanisms have been proposed in literature to improve yield, at the cost of significant area overhead. In this paper, we focus on the structure that uses one spare TSV for a group of original TSVs and study the optimal assignment of spare TSVs under yield and timing constraints to minimize the total area overhead. We show that such problem can be modeled through constrained graph decomposition. An efficient heuristic is further developed to address this …

Monolithic Three-Dimensional Integrated Circuits: Process And Design Implications, Hui Geng, Luke Maresca, Brian Cronquist, Zvi Or-Bach, Yiyu Shi

Electrical and Computer Engineering Faculty Research & Creative Works

Conventional three-dimensional integrated circuits (3D ICs) stack multiple dies vertically for higher integration density, shorter wirelength, smaller footprint, faster speed and lower power consumption. However, the through-silicon-vias (TSVs) in die stacking based 3D ICs are large in size (>1um) and reduce the benefits that can be attained by the technology. In this paper, we will introduce a new fabrication process that facilitates monolithic 3D die integration and yields much smaller TSVs (~50 nm). We will also discuss various design benefits brought by the monolithic 3D IC technology.

Linear Mimo Precoding In Jointly-Correlated Fading Multiple Access Channels With Finite Alphabet Signaling, Yongpeng Wu, Chao Kai Wen, Chengshan Xiao, Xiqi Gao, Robert Schober

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, we investigate the design of linear precoders for multiple-input multiple-output (MIMO) multiple access channels (MAC). We assume that statistical channel state information (CSI) is available at the transmitters and consider the problem under the practical finite alphabet input assumption. First, we derive an asymptotic (in the large-system limit) weighted sum rate (WSR) expression for the MIMO MAC with finite alphabet inputs and general jointly correlated fading. Subsequently, we obtain necessary conditions for linear precoders maximizing the asymptotic WSR and propose an iterative algorithm for determining the precoders of all users. In the proposed algorithm, the search space …

Near Optimal Boundary Control Of Distributed Parameter Systems Modeled As Parabolic Pdes By Using Finite Difference Neural Network Approximation, Behzad Talaei, Hao Xu, S. Jagannathan

Electrical and Computer Engineering Faculty Research & Creative Works

This paper develops a novel neural network (NN) based near optimal boundary control scheme for distributed parameter systems (DPS) governed by semi linear parabolic partial differential equations (PDE) in the presence of control constraints and unknown system dynamics. First, finite difference method (FDM) is utilized to develop a reduced order system which represents the discretized dynamics of PDE system. Subsequently, a near optimal control scheme is proposed for the discretized system by using NN based approximate dynamic programming (ADP). To relax the requirement of system dynamics, a NN identifier is utilized. Moreover, a second NN is proposed to estimate a …

Extremum-Seeking For Nonlinear Discrete-Time Systems With Application To Hcci Engines, H. Zargarzadeh, S. Jagannathan, J. A. Drallmeier

Electrical and Computer Engineering Faculty Research & Creative Works

For many control applications, identifying an optimal operating point by maximizing/minimizing a performance function is important. This paper applies the extremum-seeking method to nonaffine, nonlinear discrete-time systems stabilized by an optimal adaptive controller. First, a novel averaging method is used for the nonlinear discrete-time systems to show that their output unique extrema are stable equilibrium points. Then, a singular perturbation method in discrete time is employed to show that the overall closed loop system will dynamically converge to the extremum. The applicability of this scheme is numerically verified on a Homogeneous Charge Compression Ignition (HCCI) model validated experimentally and expressed …

A Model-Based Fault Detection And Prognostics Scheme For Takagi-Sugeno Fuzzy Systems, Balaje T. Thumati, Miles A. Feinstein, S. Jagannathan

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, a novel model-based fault detection (FD) and prediction scheme is developed for a class of Takagi-Sugeno (T-S) fuzzy systems. Unlike other FD schemes, in the proposed design, an FD observer with online fault learning capability is utilized to generate a residual which is obtained by comparing the system output with respect to the observer output. A fault is declared active if the generated residual exceeds an a priori chosen threshold. Subsequently, the fault magnitude is estimated online by using a suitable parameter update law. Upon detection, the online estimate of the fault magnitude is used in a …

Ambiguity Group Based Location Recognition For Multiple Power Line Outages In Smart Grids, Jie Wu, Jinjun Xiong, Yiyu Shi

Electrical and Computer Engineering Faculty Research & Creative Works

The efficient location recognition of multiple outage lines is critical to not only cascading failure elimination but also repair cost reduction. Most of existing methods, however, fail to handle location recognition well. This failure typically occurs because the methods cannot overcome three challenges: the very limited number of Phasor Measurement Units (PMUs), the high computational complexity, and the possibility of concurrent multiple outage lines. This paper presents an efficient algorithm inspired by the ambiguity group theory to recognize the most likely outage line locations with limited PMUs. Using IEEE 14-, 57-, and 118-bus system, the experimental study demonstrates that the …

Soft-Decision Feedback Turbo Equalization For Ldpc-Coded Mimo Underwater Acoustic Communications, Amirhossein Rafati, Huang Lou, Chengshan Xiao

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, a low-complexity turbo-detection scheme is proposed for single-carrier multiple-input-multiple-output (MIMO) underwater acoustic (UWA) communication systems that employ low-density parity-check (LDPC) channel coding. The proposed iterative soft-decision feedback equalization (SDFE) algorithm offers a novel approach to combat error propagation by utilizing the past soft decisions to mitigate InterSymbol interference. In addition, we utilize an iterative data detection and channel estimation scheme to reduce the pilot overhead used in the data communication system. Performance of the proposed detection scheme is demonstrated through extensive communication data from two undersea experiments. The results show that the proposed SDFE algorithm provides robust …

Low Complexity Detection Algorithm For Under-Determined Mimo Systems, Chen Qian, Jingxian Wu, Yahong Rosa Zheng, Zhaocheng Wang

Electrical and Computer Engineering Faculty Research & Creative Works

A low complexity detection algorithm based on list sphere decoding (LSD) is proposed for under-determined multiple-input multiple-output (UD-MIMO) systems with N transmit antennas and M < N receive antennas. The proposed algorithm utilizes the unique structure of UD-MIMO systems by dividing the N detection layers into two groups. Group 1 contains layers 1 to M that have similar structures as a symmetric MIMO system; while Group 2 contains layers M + 1 to N that contribute to the rank deficiency of the channel Gram matrix. Tree search algorithms are used for both groups, but with different search radii. A new method is proposed to adaptively adjust the tree search radius of Group 2 based on the statistical properties of the received signals. The employment of the adaptive tree search can significantly reduce the computational complexity. Simulation results show that the proposed algorithm can reduce the complexity by one orders of magnitude with less than 0.01 dB degradation in the Bit-Error-Rate (BER) performance. © 2014 IEEE.

Neural Network-Based Finite-Horizon Approximately Optimal Control Of Uncertain Affine Nonlinear Continuous-Time Systems, Hao Xu, Qiming Zhao, Travis Dierks, S. Jagannathan

Electrical and Computer Engineering Faculty Research & Creative Works

This paper develops a novel neural network (NN) based finite-horizon approximate optimal control of nonlinear continuous-time systems in affine form when the system dynamics are complete unknown. First an online NN identifier is proposed to learn the dynamics of the nonlinear continuous-time system. Subsequently, a second NN is utilized to learn the time-varying solution, or referred to as value function, of the Hamilton-Jacobi-Bellman (HJB) equation in an online and forward in time manner. Then, by using the estimated time-varying value function from the second NN and control coefficient matrix from the NN identifier, an approximate optimal control input is computed. …

Investigating The Effect Of Sio2-Tio2-Cao-Na 2o-Zno Bioactive Glass Doped Hydroxyapatite: Characterisation And Structural Evaluation, Chokchai Yatongchai, Anthony W. Wren, Declan J. Curran, Stuart Hampshire, Mark R. Towler

Chemical and Biochemical Engineering Faculty Research & Creative Works

The effects of increasing bioactive glass additions,

SiO₂-TiO₂-CaO-Na₂O-ZnO up to 25 wt% in increments of 5 wt%, on the physical and mechanical properties of hydroxyapatite (HA) sintered at 900, 1000, 1100 and 1200°C for 2 h was investigated. Increasing both the glass content and the temperature resulted in increased HA decomposition. This resulted in the formation of a number of bioactive phases. However the presence of the liquidus glass phase did not result in increased densification levels. At 1000 and 1100°C the additions of 5 wt% glass resulted in a decrease in density which …

Degradable Borate Glass Polyalkenoate Cements, L. Shen, A. Coughlan, Mark R. Towler, M. Hall

Chemical and Biochemical Engineering Faculty Research & Creative Works

Glass polyalkenoate cements (GPCs) containing aluminum-free borate glasses having the general composition Ag₂O-Na₂O-CaO-SrO-ZnO- TiO₂-B₂O₃ were evaluated in this work. An initial screening study of sixteen compositions was used to identify regions of glass formation and cement compositions with promising rheological properties. The results of the screening study were used to develop four model borate glass compositions for further study. A second round of rheological experiments was used to identify a preferred GPC formulation for each model glass composition. The model borate glasses containing higher levels of TiO₂ (7.5 mol %) …

Stereoselective Transformations Of Α-Trifluoromethylated Ketoximes To Optically Active Amines By Enzyme-Nanometal Cocatalysis: Synthesis Of (S)-Inhibitor Of Phenylethanolamine N-Methyltransferase, Guilin Cheng, Qi Wu, Zeyu Shang, Xinhua Liang, Xianfu Lin

Chemical and Biochemical Engineering Faculty Research & Creative Works

One-pot cascade synthesis of optically active α-trifluoro methylated amines directly from ketoximes was accomplished with the use of Candida antarctica lipase B and catalysts prepared by atomic layer deposition (ALD). Compared to the commercial palladium catalyst, the ALD-prepared catalysts showed much higher activity and afforded various α-trifluoro methylated amides in good yields and with high enantioselectivity. One of the enantiopure amides was further hydrolyzed into the corresponding amine, which was treated as a crucial starting material for total synthesis of (S)-inhibitor of phenyl ethanolamine N-methyltransferase without loss of chiral information. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Protocol For Rheological Characterization Of Hydrogels For Tissue Engineering Strategies, Jonathan M. Zuidema, Christopher J. Rivet, Ryan J. Gilbert, Faith A. Morrison

Chemical and Biochemical Engineering Faculty Research & Creative Works

Hydrogels are studied extensively for many tissue engineering applications, and their mechanical properties influence both cellular and tissue compatibility. However, it is difficult to compare the mechanical properties of hydrogels between studies due to a lack of continuity between rheological protocols. This study outlines a straightforward protocol to accurately determine hydrogel equilibrium modulus and gelation time using a series of rheological tests. These protocols are applied to several hydrogel systems used within tissue engineering applications: agarose, collagen, fibrin, Matrigel™, and methylcellulose. The protocol is outlined in four steps: (1) Time sweeps to determine the gelation time of the hydrogel. (2) …

Effect Of Magnetic Nanoparticle Heating On Cortical Neuron Viability, Christopher J. Rivet, Yuan Yuan, Ryan J. Gilbert, Diana Andra Borca-Tasciuc

Chemical and Biochemical Engineering Faculty Research & Creative Works

Purpose: Superparamagnetic iron oxide nanoparticles are currently approved for use as an adjunctive treatment to glioblastoma multiforme radiotherapy. Radio frequency stimulation of the nanoparticles generates localized hyperthermia, which sensitizes the tumor to the effects of radiotherapy. Clinical trials reported thus far are promising, with an increase in patient survival rate; however, what are left unaddressed are the implications of this technology on the surrounding healthy tissue. Methods and materials: Amino silane-coated iron oxide nanoparticles suspended in culture medium were applied to chick embryonic cortical neuron cultures. Cultures were heated to 37 °C or 45 °C by an induction coil system …

Spatial And Temporal Modeling Of Radar Rainfall Uncertainties, Gabriele Villarini, Bong Chul Seo, Francesco Serinaldi, Witold F. Krajewski

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

It is widely acknowledged that radar-based estimates of rainfall are affected by uncertainties (e.g., mis-calibration, beam blockage, anomalous propagation, and ground clutter) which are both systematic and random in nature. Improving the characterization of these errors would yield better understanding and interpretations of results from studies in which these estimates are used as inputs (e.g., hydrologic modeling) or initial conditions (e.g., rainfall forecasting). Building on earlier efforts, the authors apply a data-driven multiplicative model in which the relationship between true rainfall and radar rainfall can be described in terms of the product of a systematic and random component. The systematic …

File Detection On Network Traffic Using Approximate Matching, Frank Breitinger, Ibrahim Baggili

Electrical & Computer Engineering and Computer Science Faculty Publications

In recent years, Internet technologies changed enormously and allow faster Internet connections, higher data rates and mobile usage. Hence, it is possible to send huge amounts of data / files easily which is often used by insiders or attackers to steal intellectual property. As a consequence, data leakage prevention systems (DLPS) have been developed which analyze network traffic and alert in case of a data leak. Although the overall concepts of the detection techniques are known, the systems are mostly closed and commercial. Within this paper we present a new technique for network traffic analysis based on approximate matching (a.k.a …

Quantifying Relevance Of Mobile Digital Evidence As They Relate To Case Types: A Survey And A Guide For Best Practices, Shahzad Saleem, Ibrahim Baggili, Oliver Popov

Electrical & Computer Engineering and Computer Science Faculty Publications

In this work, a survey was conducted to help quantify the relevance of nineteen types of evidence (such as SMS) to seven types of digital investigations associated with mobile devices (MD) (such as child pornography). 97 % of the respondents agreed that every type of digital evidence has a different level of relevance to further or solve a particular investigation. From 55 serious participants, a data set of 5,772 responses regarding the relevance of nineteen types of digital evidence for all the seven types of digital investigations was obtained. The results showed that (i) SMS belongs to the most relevant …

Thermomechanical Properties And Stress Analysis Of 3-D Textile Composites By Asymptotic Expansion Homogenization Method, Muhammad Ridlo Erdata Nasution, Naoyuki Watanabe, Atsushi Kondo, Arief Yudhanto

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper formulates asymptotic expansion homogenization method for the analysis of 3-D composites whereby thermomechanical effects are considered. The equivalent thermomechanical properties, viz. elastic constants and coefficient of thermal expansion, of 3-D orthogonal interlock composites are obtained based on a unit-cell derived from the optical microscopy observation. The Young's modulus and Poisson's ratio obtained from the analysis are compared with those obtained by experiments. The results show a good agreement especially for the Young's modulus. Localization analysis based on the present formulation is also presented to assess the stresses within the constituents of 3-D composites (fiber tows and resin region) …

Active-Passive Networked Multiagent Systems, Tansel Yucelen, John Daniel Peterson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper introduces an active-passive networked multiagent system framework, which consists of agents subject to exogenous inputs (active agents) and agents without any inputs (passive agents) and analyze its convergence using Lyapunov stability. Apart from the existing relevant literature, where either none of the agents are subject to exogenous inputs (i.e., average consensus problem) or all agents are subject to these inputs (i.e., dynamic average consensus problem), the key feature of our approach is that the states of all agents converge to the average of the exogenous inputs applied only to the active agents, where these inputs may or may …

Thermomechanical Modeling Of Cone Sample Of Zrb2-Sic Ceramic Under Arc-Jet Conditions, Lokeswarappa R. Dharani, Jun Wei

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The effects of oxidation on mechanical behavior of a cone sample of ZrB2-SiC ceramic under arc-jet test conditions is studied by a finite element (FE) model. First a steady-state heat transfer FE method was employed to conduct the thermal analysis and obtain the temperature distribution in the inner body of the cone. Then, resulting temperature distribution is applied to the thermomechanical finite element analysis to calculate the thermal stress distribution in the cone body. Due to the mismatch of material properties between the bulk ZrB2-SiC and its new products after oxidation, the outer oxide layers constrain the thermal deformation of …

Proper Orthogonal Decomposition Technique For Sub-Optimal Control Of Flexible Aircraft Wings Using Discrete Actuators, M. Kumar, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Distributed parameter systems are, generally, described by a set of partial differential equations. Control design of these systems is a very complex task as compared to that of the lumped parameter systems that are defined by a set of ordinary differential equations. In this paper, we present a stabilizing state-feedback control design approach for a class of second order system, where the system can be controlled by discrete actuators in the spatial domain. The control methodology is developed by combining the technique of 'Proper Orthogonal Decomposition' and Approximate Dynamic Programming. The Proper Orthogonal Decomposition technique is utilized to obtain a …

Adaptive Control Of Uncertain Systems With Gain Scheduled Reference Models And Constrained Control Inputs, Mehrdad Pakmehr, Tansel Yucelen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper develops a new state feedback model reference adaptive control approach for uncertain systems with gain scheduled reference models in a multi-input multi-output (MIMO) setting with constrained control inputs. A single Lyapunov matrix is computed for multiple linearization of the nonlinear closed loop gain scheduled reference system, using convex optimization tools. This approach guarantees stability of the closed loop gain scheduled reference model. Adaptive state feedback control architecture is then developed, and its stability is proven for the case with constrained control inputs. The resulting closed-loop system is shown to have bounded solutions with bounded tracking error, with the …

Decentralized Adaptive Control Of Uncertain Systems With Gain Scheduled Reference Models, Mehrdad Pakmehr, Tansel Yucelen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Control theoretic concepts for decentralized adaptive control of uncertain systems with gain scheduled reference model is developed. For each subsystem a single Lyapunov matrix is computed, using convex optimization tools, for multiple linearization near equilibrium and non-equilibrium points of the nonlinear closed loop gain scheduled reference subsystem. This approach guarantees stability of the closed loop gain scheduled reference model. Then, decentralized adaptive state feedback control architecture is developed and its stability is proved. Specifically, the resulting closed-loop system is shown to have bounded solutions with bounded tracking error for all the subsystems. Simulation results for two different models of a …

Resilient Networked Multiagent Systems: A Distributed Adaptive Control Approachy, Gerardo De La Torre, Tansel Yucelen, John Daniel Peterson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Control algorithms of networked multiagent systems are generally computed distributivity without having a centralized entity monitoring the activity of agents; and therefore, adverse events such as attacks to the communication network and/or failure of agent-wise components can easily result in system instability and prohibit the accomplishment of system-level objectives. This paper studies resilient coordination of networked multiagent systems in the presence of misbehaving agents, i.e., agents that are subject to such adverse events. In particular, we consider a class of adverse conditions consisting of exogenous disturbances and interagent uncertainties and present a distributed adaptive control architecture to retrieve the nominal …

Decomposition Of Ionic Liquid Ferrofluids For Multi-Mode Spacecraft Propulsion, Steven P. Berg, Brynne Coleman, Joshua L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Ionic liquid ferrofluids based on mixtures of [Emim][EtSO4] and [Bmim][NO3] fuels and hydroxylammonium nitrate oxidizer were synthesized by adding iron oxide nanoparticles. The resulting propellants were then tested for decomposition capability. Spot plate testing indicated that the temperature required to initiate rapid decomposition dropped from 115 °C to 75 °C with a 30% by weight addition of iron oxide for the [Bmim][NO3] propellant. Adding more iron oxide resulted in an increase in onset temperature. The [Emim][EtSO4] propellant had a much lower decrease in onset temperature, bottoming out at 90 °C. Batch reactor tests under vacuum showed that 10% addition of …

Reference Control Architecture In The Presence Of Measurement Noise And Actuator Dynamics, Gerardo De La Torre, Tansel Yucelen, Eric Johnson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper the command governor-based model reference control architecture is developed and analyzed for uncertain dynamical systems in the presence measurement noise and actuator dynamics. Specifically, the command governor is a dynamical system that adjusts the trajectory of a given command in order to enable an uncertain system to be able to follow an ideal reference system capturing a desired closed-loop dynamical system behavior both in transient-time and steady-state. In this paper, we present modifications to the original command governor approach in order to increase its robustness properties against measurement noise and actuator dynamics. In particular, the modified architecture …

Control-Oriented Modeling For Open-Cathode Fuel Cell Systems, Joseph Ishaku, Nima Lotfi, Hesam Zomorodi, Robert G. Landers

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Due to numerous advantages of Polymer Electrolyte Fuel Cells (PEMFCs), they are becoming the mainstream fuel cell of choice for different applications. Open-cathode PEMFCs, in particular, are gaining increased popularity in low to medium power applications due to their simple structure and low parasitic losses. However, in order to achieve safe operation, increased durability and optimal performance, advanced control algorithms, which typically require control-oriented models, need to be implemented on open-cathode fuel cell systems. The open-cathode fuel cell system includes the fuel cell stack and all of the auxiliary components that are vital for its operation. In this paper, control-oriented …