@article{bilbro_trew_2015, title={A Five-Parameter Model of the AlGaN/GaN HFET}, volume={62}, ISSN={["1557-9646"]}, DOI={10.1109/ted.2015.2394376}, abstractNote={We introduce an analytic expression for the drain current Id(Vgs, Vds) of an AlGaN/GaN heterojunction field-effect transistor (HFET) as a function of its gate and drain voltages. We derive the function from a compact physical model of conduction current in the HFET. The proposed expression for the current is configured by five parameters, which can be expressed in terms of the geometry and materials of a device. We extend the model to small-signal RF operation by embedding it in a 12-parameter RLC network that represents terminal feed impedances and device parasitics. We adjust the parameters of the extended model to simultaneously fit dc and RF measurements of an industrial transistor.}, number={4}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Bilbro, Griff L. and Trew, Robert J.}, year={2015}, month={Apr}, pages={1157–1162} }
 @article{goswami_trew_bilbro_2014, title={Modeling of the Gate Leakage Current in AlGaN/GaN HFETs}, volume={61}, ISSN={["1557-9646"]}, DOI={10.1109/ted.2014.2302797}, abstractNote={A new physics-based model of the gate leakage current in AlGaN/GaN heterojunction field effect transistors (HFETs) is demonstrated. The model predicts accurately the gate-leakage current for a wide range of gate-drain voltage. The model is based on the formulation of tunneling and space charge limited (SCL) current flow. The gate leakage current is shown to flow through two paths: 1) the surface of the device establishes the primary path and the current transport mechanism is modeled using SCL transport in the presence of shallow traps and 2) the traps in the AlGaN layer assist in the tunneling of electrons from the gate to the 2-D electron gas, which flows to the drain electrode constituting the second path for the leakage current. The trap levels extracted from the model are consistent with the reports presented in the literature. The model appropriately explains the gate leakage current of the AlGaN/GaN HFETs for drain voltages up to 170 V and is verified by comparing the model results with the measured gate leakage data of industrial devices.}, number={4}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Goswami, Arunesh and Trew, Robert J. and Bilbro, Griff L.}, year={2014}, month={Apr}, pages={1014–1021} }
 @article{goswami_trew_bilbro_2014, title={Physics of gate leakage current in N-polar InAlN/GaN heterojunction field effect transistors}, volume={116}, ISSN={["1089-7550"]}, DOI={10.1063/1.4900581}, abstractNote={A physics based model of the gate leakage current in N-polar InAlN/GaN heterojunction field effect transistors is demonstrated. The model is based on the space charge limited current flow dominated by the effects of deep traps in the InAlN surface layer. The model predicts accurately the gate-leakage measurement data of the N-polar InAlN/GaN device with InAlN cap layer. In the pinch-off state, the gate leakage current conduction through the surface of the device in the drain access region dominates the current flow through the two dimensional electron gas channel. One deep trap level and two levels of shallow traps are extracted by fitting the model results with measurement data.}, number={16}, journal={JOURNAL OF APPLIED PHYSICS}, author={Goswami, Arunesh and Trew, Robert J. and Bilbro, Griff L.}, year={2014}, month={Oct} }
 @article{hou_bilbro_trew_2013, title={A Compact Physical AlGaN/GaN HFET Model}, volume={60}, ISSN={["1557-9646"]}, DOI={10.1109/ted.2012.2227323}, abstractNote={We introduce a physics-based compact model for AlGaN/GaN heterojunction field-effect transistors (HFETs) that is suitable for both RF microwave and switched-mode power supply (SMPS) applications, so that RF techniques can help determine HFET performance in SMPS applications. Such simulations can predict the on-resistance, slew rate, and breakdown voltage from the physical design of the transistor. Starting from an expression for the drain-source conduction current, charge distribution and displacement current are determined. The new model was implemented in Verilog-A and implemented in AWRDE, the design environment from Applied Wave Research. The HFET model was validated by comparison with Silvaco simulations and with data from an AlGaN/GaN HFET S-band amplifier. The new model accurately predicts device performance for dc, small-signal, and large-signal operations.}, number={2}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Hou, Danqiong and Bilbro, Griff L. and Trew, Robert J.}, year={2013}, month={Feb}, pages={639–645} }
 @article{goswami_trew_bilbro_2013, title={Physics based modeling of gate leakage current due to traps in AlGaN/GaN HFETs}, volume={80}, ISSN={["1879-2405"]}, DOI={10.1016/j.sse.2012.10.005}, abstractNote={Abstract A new model for the gate leakage current in AlGaN/GaN HFETs is demonstrated. The model is completely physical and is based on the formulation of space charge limited current flow. Two levels of shallow traps in the AlGaN surface layer are considered to evaluate the model. The depth of the traps is consistent with the reports presented in the literature. The model adequately explains the measured gate leakage current and for the first time, predicts accurately the experimentally observed change in slope of the gate leakage current versus the gate to drain voltage.}, journal={SOLID-STATE ELECTRONICS}, author={Goswami, A. and Trew, R. J. and Bilbro, G. L.}, year={2013}, month={Feb}, pages={23–27} }
 @article{schimizzi_trew_bilbro_2012, title={A Simplified Physical Model of RF Channel Breakdown in AlGaN/GaN HFETs}, volume={59}, ISSN={["1557-9646"]}, DOI={10.1109/ted.2012.2211360}, abstractNote={A temperature-dependent impact-ionization-initiated RF breakdown model in the 2DEG channel of AlGaN/GaN HFETs is reported. When operating these devices in RF power amplifier circuits, impact ionization in the channel has a significant effect upon gain saturation, power-added efficiency, and output power. An analytical physics-based model of channel breakdown is formulated based on TCAD investigations of the internal device behavior. This model is integrated with an existing physics-based HFET compact model and accurately predicts large-signal device performance. Values of thermal resistance and the breakdown temperature coefficient were extracted from simulations of an industrial HFET and are in agreement with the literature, thus validating that the model captures the dominant breakdown mechanism.}, number={11}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Schimizzi, Ryan D. and Trew, Robert J. and Bilbro, Griff L.}, year={2012}, month={Nov}, pages={2973–2978} }
 @inproceedings{trew_hou_schimizzi_goswami_bilbro_2012, title={Large-signal FET Models and a New AlGaN/GaN HFET model for power amplifier design}, DOI={10.1109/icwits.2012.6417696}, abstractNote={A historical review of large-signal compact FET models is presented. Device models used in circuit design typically are based upon equivalent circuit techniques. However, it is possible to develop physics-based compact models. In this work, a new physics-based model for AlGaN/GaN HFETs that can be integrated into the commercial simulators is described. The new model has demonstrated good agreement between measured and simulated data for communications band power amplifiers.}, booktitle={2012 IEEE International Conference on Wireless Information Technology and Systems (ICWITS)}, author={Trew, R. J. and Hou, D. and Schimizzi, R. and Goswami, A. and Bilbro, G. L.}, year={2012} }
 @article{bilbro_hou_yin_trew_2009, title={Predicting the performance of a power amplifier using large-signal circuit simulations of an AlGaN/GaN HFET model}, volume={7216}, ISSN={["1996-756X"]}, DOI={10.1117/12.803348}, abstractNote={We have quantitatively modeled the conduction current and charge storage of an HFET in terms its physical dimensions and material properties. For DC or small-signal RF operation, no adjustable parameters are necessary to predict the terminal characteristics of the device. Linear performance measures such as small-signal gain and input admittance can be predicted directly from the geometric structure and material properties assumed for the device design. We have validated our model at low-frequency against experimental I-V measurements and against two-dimensional device simulations. We discuss our recent extension of our model to include a larger class of electron velocity-field curves. We also discuss the recent reformulation of our model to facilitate its implementation in commercial large-signal high-frequency circuit simulators. Large signal RF operation is more complex. First, the highest CW microwave power is fundamentally bounded by a brief, reversible channel breakdown in each RF cycle. Second, the highest experimental measurements of efficiency, power, or linearity always require harmonic load pull and possibly also harmonic source pull. Presently, our model accounts for these facts with an adjustable breakdown voltage and with adjustable load impedances and source impedances for the fundamental frequency and its harmonics. This has allowed us to validate our model for large signal RF conditions by simultaneously fitting experimental measurements of output power, gain, and power added efficiency of real devices. We show that the resulting model can be used to compare alternative device designs in terms of their large signal performance, such as their output power at 1dB gain compression or their third order intercept points. In addition, the model provides insight into new device physics features enabled by the unprecedented current and voltage levels of AlGaN/GaN HFETs, including non-ohmic resistance in the source access regions and partial depletion of the 2DEG in the drain access region.}, journal={GALLIUM NITRIDE MATERIALS AND DEVICES IV}, author={Bilbro, Griff L. and Hou, Danqiong and Yin, Hong and Trew, Robert J.}, year={2009} }
 @article{smith_bilbro_nemanich_2009, title={Theory of space charge limited regime of thermionic energy converter with negative electron affinity emitter}, volume={27}, ISSN={["1071-1023"]}, DOI={10.1116/1.3125282}, abstractNote={A theory of the space charge limited output current regime of a vacuum thermionic energy conversion device (TEC) employing a negative electron affinity (NEA) diamond emitter electrode is derived. The theory is developed by assuming that the electrons behave as a collisionless gas and self-consistently solving Vlaslov’s equation and Poisson’s equation. Special cases of the theory are addressed. Calculations are performed to model a TEC with a nitrogen doped diamond emitter material under various conditions. It is shown that the NEA material outperforms a similar positive electron affinity material in terms of output power and efficiency because the NEA lowers the electrostatic boundary condition at the emitter and therefore mitigates the negative space charge effect.}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Smith, Joshua Ryan and Bilbro, Griff L. and Nemanich, Robert J.}, year={2009}, month={May}, pages={1132–1141} }
 @article{smith_bilbro_nemanich_2007, title={Considerations for a high-performance thermionic energy conversion device based on a negative electron affinity emitter}, volume={76}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.76.245327}, abstractNote={A theory is developed to model the effect a negative electron affinity (NEA) emitter electrode has on the negative space charge effect of a vacuum thermionic energy conversion device (TEC). The theory is derived by treating the electrons in the interelectrode space as a collisionless gas and self-consistently solving the Boltzmann transport equation and Poisson equation. The theory determines the point on the voltage-current characteristic such that the maximum motive due to space charge is at the same level as the conduction band minimum. It is shown that emitter electrodes with an NEA significantly mitigate the negative space charge effect; therefore a TEC employing such an electrode will outperfrom a similar TEC with conventional electrodes in terms of output power. Additionally, it is shown that a TEC with an NEA emitter electrode can have a greater interelectrode spacing than a TEC with conventional electrodes operating under similar conditions where the outputs of both TEC's are comparable.}, number={24}, journal={PHYSICAL REVIEW B}, author={Smith, Joshua Ryan and Bilbro, Griff L. and Nemanich, Robert J.}, year={2007}, month={Dec} }
 @article{bilbro_nemanich_2006, title={Localized emission from flat diamond cathodes}, volume={15}, ISSN={["1879-0062"]}, DOI={10.1016/j.diamond.2005.10.045}, abstractNote={We analyze steady-state field emission from an n-type semiconductor under the assumption that its surface presents no barrier for electron emission from the conduction band into the vacuum. We construct a classical Lagrangian field theory for the coupled electric and quasi-fermi potentials and use it to show that uniform emission is unstable against laterally nonuniform perturbations. We use a two-parameter model of normal emission current to show that the Lagrangian of the linearized system is minimal when all electrons are emitted from a single site. In addition to this intensely localized emission, we show the normal electric field at the surface is moderately enhanced at the solitary emission site even though the surface itself is planar. We use the result to explain the isolated emission sites observed in nanocrystalline n-type diamond films.}, number={9}, journal={DIAMOND AND RELATED MATERIALS}, author={Bilbro, Griff L. and Nemanich, Robert J.}, year={2006}, month={Sep}, pages={1418–1423} }
 @article{trew_liu_bilbro_kuang_vetury_shealy_2006, title={Nonlinear source resistance in high-voltage microwave AlGaN/GaN HFETs}, volume={54}, ISSN={["0018-9480"]}, DOI={10.1109/TMTT.2006.873627}, abstractNote={Wide bandgap semiconductors are used to fabricate field-effect transistors with significantly improved RF output power compared to GaAs- and InP-based devices. Nitride-based heterostructure field-effect transistors can be biased at high drain voltages, up to and exceeding 100 V, which results in high RF output power. However, the operation of these devices at high drain bias introduces physical phenomena within the device that affect both dc and RF performance. In this study, the existence of a nonlinear source resistance due to space-charge limited current conditions is demonstrated and verified. Inclusion of the nonlinear source resistance in a physics-based device simulator produces excellent agreement between simulated and measured data. The nonlinear source resistance degrades RF performance and limits amplifier linearity.}, number={5}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Trew, RJ and Liu, YY and Bilbro, GL and Kuang, WW and Vetury, R and Shealy, JB}, year={2006}, month={May}, pages={2061–2067} }
 @article{bilbro_trew_2006, title={RF knee walkout and source access region of unpassivated HFETs}, volume={42}, DOI={10.1049/el:20062113}, abstractNote={A simple circuit model is used for the source access region of an AlGaN/GaN HFET in a microwave power amplifier to show that the interaction between gate-to-source surface current and 2DEG conductivity by itself can produce RF knee walkout.}, number={24}, journal={Electronics Letters}, author={Bilbro, G. L. and Trew, R. J.}, year={2006}, pages={1425–1427} }
 @article{smith_nemanich_bilbro_2006, title={The effect of Schottky barrier lowering and nonplanar emitter geometry on the performance of a thermionic energy converter}, volume={15}, ISSN={["1879-0062"]}, DOI={10.1016/j.diamond.2005.12.057}, abstractNote={An extension of the classical model of thermionic emission was developed to include the effects of nonplanar emitter surfaces and Schottky barrier lowering (SBL) on the output of a thermionic energy converter (TEC). Nonplanar emitter geometries along with Schottky barrier lowering may be useful in increasing both the maximum output power and output current of a thermionic energy converter. The finite element method was used to calculate the enhanced normal electric field at the surface of an emitter coated with an ultra-nanocrystalline diamond (UNCD) film and patterned with field enhancing tips. The result was used to determine the local enhanced output current and power. For the geometries considered the increased surface area of the emitter plays a significant role in increasing the output power and output current. Moreover, a calculation of the single electron time of flight shows that electrons traveling through a field enhanced region of the interelectrode space might spend half as long in transit, thus helping to mitigate the negative space charge effect that degrades the performance of vacuum TECs.}, number={4-8}, journal={DIAMOND AND RELATED MATERIALS}, author={Smith, J. R. and Nemanich, R. J. and Bilbro, G. L.}, year={2006}, pages={870–874} }
 @article{smith_bilbro_nemanich_2006, title={Using negative electron affinity diamond emitters to mitigate space charge in vacuum thermionic energy conversion device}, volume={15}, ISSN={["0925-9635"]}, DOI={10.1016/j.diamond.2006.09.011}, abstractNote={A negative electron affinity (NEA) diamond surface is employed as an emitter electrode in a vacuum thermionic energy conversion device in order to mitigate the negative space charge effect. The motive diagram of an NEA device operating at the virtual saturation point is compared to a similar device with a conventional emitter material operating in the space charge limited regime in order to understand how NEA mitigates space charge. Output current characteristics are calculated for various NEA values, and the results are compared to an ideal (no space charge) model. Increasing the value of the NEA causes the output current characteristic to approach that of the ideal model. Motive diagrams for various values of NEA are calculated and used to explain this phenomenon. It is shown that an NEA device can achieve a maximum output power density equal to the maximum output power density of a similar ideal device.}, number={11-12}, journal={DIAMOND AND RELATED MATERIALS}, author={Smith, J. R. and Bilbro, G. L. and Nemanich, R. J.}, year={2006}, pages={2082–2085} }
 @article{rying_ozturk_bilbro_lu_2005, title={In situ selectivity and thickness monitoring during selective silicon epitaxy using quadrupole mass spectrometry and wavelets}, volume={18}, ISSN={["1558-2345"]}, DOI={10.1109/TSM.2004.836660}, abstractNote={This work reports on a novel in situ sensing technique for monitoring the thickness of selectively grown Si epitaxial layers. The technique can be extended to detect selectivity loss when Si nuclei begin to appear on the insulator surface. In this technique, a quadruple mass spectrometer (QMS) monitors the ionized molecular hydrogen (H/sub 2//sup +/) signal, which is a by-product of the chemical-vapor deposition process. The thickness of the epitaxial layer is determined by evaluating the area under the hydrogen signal. We have deliberately used silane (SiH/sub 4/) without HCl or Cl/sub 2/ to achieve both nonselective and selective depositions. We also show that the amount of hydrogen produced by the deposition process is a strong function of the exposed Si area on the wafer and the effect can be accurately monitored by QMS. This finding was exploited to develop an in situ sensing method to detect the selectivity loss. When selectivity is lost, Si nuclei begin to form on the insulator surface increasing the effective Si area on the wafer. Consequently, the rate of hydrogen production increases rapidly as nuclei coalesce, resulting in a distinct change in the functional form of the hydrogen signal. The hydrogen signal was analyzed using an automatic edge detection procedure based on the wavelet transform modulus maxima representation. The technique facilitated the determination of selective film thickness from the time-integrated hydrogen (H/sub 2//sup +/) signal. To the authors' knowledge, This work represents one of the first applications of wavelets to in situ process monitoring and fault detection in semiconductor manufacturing. The authors expect the methodology presented in This work to be readily transferable to other selective deposition processes, including those that utilize dichlorosilane and disilane since hydrogen is a by-product of those processes as well.}, number={1}, journal={IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING}, author={Rying, EA and Ozturk, MC and Bilbro, GL and Lu, JC}, year={2005}, month={Feb}, pages={112–121} }
 @article{trew_bilbro_kuang_liu_yin_2005, title={Microwave AlGaN/GaN HFEVs}, volume={6}, ISSN={["1527-3342"]}, DOI={10.1109/MMW.2005.1417998}, abstractNote={This article presents the operating physics, performance potential, and status of device development of microwave AlGaN/GaN heterostructure field-effect transistors. AlGaN/GaN HFETs show potential for use in improved RF performance microwave amplifier applications. Development progress has been rapid, and prototype devices have demonstrated RF output power density as high as 30 W/mm. Microwave amplifier output power is rapidly approaching 100 W for single-chip operation, and these devices may soon find application for cellular base station transmitter applications. Devices are being developed for use in X-band radars, and RF performance is rapidly improving. The HFET devices experience several physical effects that can limit performance. These effects consist of nonlinearities introduced during the high-current and high-voltage portions of the RF cycle. High-current phenomena involve the operation of the conducting channel above the critical current density for initiation of space-charge effects. The source resistance is modulated in magnitude by the channel current, and high source resistance results. High voltage effects include reverse leakage of the gate electrode and subsequent charge trapping effects on the semiconductor surface, and RF breakdown in the conducting channel. These effects can produce premature saturation effects. Also, under certain conditions, high voltage operation of the device can initiate an IMPATT mode of operation. When this occurs, the channel current increases and RF gain is increased. This phenomenon enhances the RF output power of the device. The physical limiting effects can be controlled with proper design, and the outlook for use of these devices in practical applications is excellent.}, number={1}, journal={IEEE MICROWAVE MAGAZINE}, author={Trew, RJ and Bilbro, GL and Kuang, W and Liu, Y and Yin, H}, year={2005}, month={Mar}, pages={56–66} }
 @article{thompson_bilbro_2005, title={Sample-sort simulated annealing}, volume={35}, ISSN={["1941-0492"]}, DOI={10.1109/TSMCB.2005.843972}, abstractNote={A simulated annealing (SA) algorithm called Sample-Sort that is artificially extended across an array of samplers is proposed. The sequence of temperatures for a serial SA algorithm is replaced with an array of samplers operating at static temperatures and the single stochastic sampler is replaced with a set of samplers. The set of samplers uses a biased generator to sample the same distribution of a serial SA algorithm to maintain the same convergence property. Sample-Sort was compared to SA by applying both to a set of global optimization problems and found to be comparable if the number of iterations per sampler was sufficient. If the evaluation phase dominates the computational requirements, Sample-Sort could take advantage of parallel processing.}, number={3}, journal={IEEE TRANSACTIONS ON SYSTEMS MAN AND CYBERNETICS PART B-CYBERNETICS}, author={Thompson, DR and Bilbro, GL}, year={2005}, month={Jun}, pages={625–632} }
 @article{ramanath_snyder_bilbro_sander_2002, title={Demosaicking methods for Bayer color arrays}, volume={11}, ISSN={["1560-229X"]}, DOI={10.1117/1.1484495}, abstractNote={Digital Still Color Cameras sample the color spectrum using a monolithic array of color filters overlaid on a charge coupled device array such that each pixel samples only one color band. The resulting mosaic of color samples is processed to produce a high resolution color image such that the values of the color bands not sampled at a certain location are estimated from its neighbors. This process is often referred to as demosaicking. This paper introduces and compares a few commonly used demosaicking methods using error metrics like mean squared error in the RGB color space and perceived error in the CIELAB color space. © 2002 SPIE and IS&T.}, number={3}, journal={JOURNAL OF ELECTRONIC IMAGING}, author={Ramanath, R and Snyder, WE and Bilbro, GL and Sander, WA}, year={2002}, month={Jul}, pages={306–315} }
 @article{rying_bilbro_lu_2002, title={Focused local learning with wavelet neural networks}, volume={13}, ISSN={["1045-9227"]}, DOI={10.1109/72.991417}, abstractNote={A novel objective function is presented that incorporates both local and global errors as well as model parsimony in the construction of wavelet neural networks. Two methods are presented to assist in the minimization of this objective function, especially the local error term. First, during network initialization, a locally adaptive grid is utilized to include candidate wavelet basis functions whose local support addresses the local error of the local feature set. This set can be either user-defined or determined using information derived from the wavelet transform modulus maxima representation. Next, during the network construction, a new selection procedure based on a subspace projection operator is presented to help focus the selection of wavelet basis functions to reduce the local error. Simulation results demonstrate the effectiveness of these methodologies in minimizing local and global error while maintaining model parsimony and incurring a minimal increase on computational complexity.}, number={2}, journal={IEEE TRANSACTIONS ON NEURAL NETWORKS}, author={Rying, EA and Bilbro, GL and Lu, JC}, year={2002}, month={Mar}, pages={304–319} }
 @article{bilbro_2002, title={Theory of electrodeposition of diamond nanoparticles}, volume={11}, ISSN={["0925-9635"]}, DOI={10.1016/S0925-9635(02)00104-8}, abstractNote={We theoretically investigate the electrophoretic agglomeration of uncharged, possibly aggregated, nanodiamond (ND) particles, from liquid suspension onto a sharpened anode. We propose that the shape of such a ND agglomeration can be understood in terms of surface tension and Maxwell stress.}, number={8}, journal={DIAMOND AND RELATED MATERIALS}, author={Bilbro, GL}, year={2002}, month={Aug}, pages={1572–1577} }
 @article{bilbro_2002, title={Theory of nanotip formation}, volume={20}, number={3}, journal={Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures}, author={Bilbro, G. L.}, year={2002}, pages={757–761} }
 @article{thompson_bilbro_2000, title={Comparison of a genetic algorithm with a simulated annealing algorithm for the design of an ATM network}, volume={4}, ISSN={["1089-7798"]}, DOI={10.1109/4234.864190}, abstractNote={The genetic algorithm (GA) and simulated annealing algorithm (SA) are empirically compared for the problem of optimizing the topological design of a network. In addition to the usual problem of optimizing only the placement of links, in this paper the number and placement of concentrators are also decision variables for a class of problems using a real set of concentrators, links, and traffic. The average GA solution cost less than the average SA solution.}, number={8}, journal={IEEE COMMUNICATIONS LETTERS}, author={Thompson, DR and Bilbro, GL}, year={2000}, month={Aug}, pages={267–269} }
 @misc{hall_clements_liu_bilbro_2000, title={Integrated circuits having cooperative ring oscillator clock circuits therein to minimize clock skew}, volume={6,104,253}, number={2000 Aug. 15}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Hall, L. C. and Clements, S. M. and Liu, W.-T. and Bilbro, G. L.}, year={2000} }
 @article{bilbro_nemanich_2000, title={Nongeometric field enhancement in semiconducting cold cathodes and in metal-insulator-semiconductor structures}, volume={76}, ISSN={["0003-6951"]}, DOI={10.1063/1.125620}, abstractNote={We extend the usual one-dimensional equilibrium theory of the surface space charge region that screens a semiconductor from an external electric field in order to admit perturbations in three dimensions and time. We identify a class of perturbations of the one-dimensional equilibrium that grow exponentially in time at least until our first-order perturbation theory fails. The resulting spontaneous field enhancement may explain enhancement factors observed in electron emission from semiconducting cathodes and may similarly contribute to gate leakage in metal–oxide–semiconductor field effect transistors.}, number={7}, journal={APPLIED PHYSICS LETTERS}, author={Bilbro, GL and Nemanich, RJ}, year={2000}, month={Feb}, pages={891–893} }
 @misc{bilbro_snyder_zilic_2000, title={Systems and methods for using diffraction patterns to determine radiation intensity values for areas between and along adjacent sensors of compound sensor arrays}, volume={6,021,241}, number={2000 Feb. 1}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Bilbro, G. L. and Snyder, W. E. and Zilic, A.}, year={2000} }
 @misc{bilbro_snyder_zilic_1999, title={Compound image sensor array having staggered array of tapered optical fiber bundles}, volume={5,974,215}, number={1999 Oct. 26}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Bilbro, G. L. and Snyder, W. E. and Zilic, A.}, year={1999} }
 @article{bilbro_hall_clements_liu_1999, title={Convolution, deconvolution, and mean field annealing suitable for analog VLSI}, volume={46}, ISSN={["1057-7130"]}, DOI={10.1109/82.752912}, abstractNote={We formulate several standard digital image processing operations as circuits suitable for implementation in real-time analog VLSI, including nonlinear piecewise-constant image restoration using mean field annealing as a global optimization technique. We report test results from an imaging chip that performs user-controlled convolution of the image. We use simulated results for mean field annealing (MFA) in SPICE to show that deconvolution could be implemented by rearranging the subcircuits that perform the corresponding convolution. We report the results of realizing deconvolution in this way on a printed circuit board.}, number={2}, journal={IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS II-ANALOG AND DIGITAL SIGNAL PROCESSING}, author={Bilbro, GL and Hall, LC and Clements, M and Liu, WT}, year={1999}, month={Feb}, pages={120–128} }
 @article{zhu_bilbro_chow_1999, title={Phase balancing using simulated annealing}, volume={14}, ISSN={["0885-8950"]}, DOI={10.1109/59.801943}, abstractNote={Deregulation eliminates the boundary of the territory of the monopoly power industry. Competition forces utilities to improve power quality as well as to reduce investment and operation costs. Feeder imbalance describes a situation in which the voltages of a three-phase voltage source are not identical in magnitude, or the phase differences between them are not 120 electrical degrees, or both. It affects motors and other devices that depend upon a well-balanced three-phase voltage source. Phase balancing is to make the voltages balanced at each load point of the feeder. Phase swapping is a direct approach for phase balancing with the minimum cost. Phase balancing can enhance utilities' competitive capability by improving reliability, quality, and reducing costs. Therefore, phase balancing optimization is nowadays receiving more attention in the power industry, especially in today's deregulating environments. The nonlinear effects, such as, voltage drops and energy losses, make the problem difficult to solve. This paper introduces simulated annealing as an effective method to solve a power distribution phase balancing problem with its nonlinear effects.}, number={4}, journal={IEEE TRANSACTIONS ON POWER SYSTEMS}, author={Zhu, JX and Bilbro, G and Chow, MY}, year={1999}, month={Nov}, pages={1508–1513} }
 @article{hatfield_bilbro_1999, title={Simulation of room temperature thermionic emission from AlxGa1- xN negative electron affinity cathodes}, volume={17}, number={2}, journal={Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures}, author={Hatfield, C. W. and Bilbro, G. L.}, year={1999}, pages={552–556} }
 @article{hatfield_bilbro_1999, title={Simulation of thermionic emission from aluminum gallium nitride cathodes at elevated temperatures}, volume={17}, number={5}, journal={Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures}, author={Hatfield, C. W. and Bilbro, G. L.}, year={1999}, pages={1987–1992} }
 @article{lo_makrucki_bilbro_elmaghraby_1998, title={Call admission control schemes and ATM network topological design}, volume={111}, ISSN={["0377-2217"]}, DOI={10.1016/S0377-2217(97)00320-2}, abstractNote={Call admission control criteria are not only important for call admission control itself, but also can be an important input to network topological design. In this paper, we show the difference in terms of network cost incurred by adopting different call admission control schemes in network topological design. We compare two call admission control schemes. Scheme 1 uses equivalent bandwidth as its call admission control criterion and Scheme 2 is based on modeling the volatility of call traffic using Reflected Brownian Motion. Though Scheme 2 increases the complexity of network topological design, it can give lower network costs. Our experimental results show that for the same traffic mix, the network cost can be as little as 10% and as much as 35% lower when Scheme 2 is used instead of Scheme 1. The differences between the pair of resulting networks suggests that network topological design can be used as one of the criteria for choosing the call admission control scheme.}, number={2}, journal={EUROPEAN JOURNAL OF OPERATIONAL RESEARCH}, author={Lo, SZ and Makrucki, BA and Bilbro, GL and Elmaghraby, SE}, year={1998}, month={Dec}, pages={393–404} }
 @article{hatfield_bilbro_allen_palmour_1998, title={DC I-V characteristics and RF performance of a 4H-SiC JFET at 773 K}, volume={45}, ISSN={["0018-9383"]}, DOI={10.1109/16.711376}, abstractNote={The dc I-V characteristics of a 4H-SiC JFET at 773 K were predicted with SPISCES. These characteristics were used to estimate the RF performance of the JFET in a class A power amplifier. The results indicate that A/sub c/=4.29, P/sub 1-dB/=0.953 W/mm, and PAE=13.3% at low frequency, and that f/sub T/=6.1 GHz.}, number={9}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Hatfield, CW and Bilbro, GL and Allen, ST and Palmour, JW}, year={1998}, month={Sep}, pages={2072–2074} }
 @article{han_snyder_bilbro_1998, title={Discontinuity-preserving vector smoothing of multivariate MR images using vector mean field annealing}, volume={9}, ISSN={["0924-9907"]}, DOI={10.1023/A:1026415719566}, number={3}, journal={JOURNAL OF MATHEMATICAL IMAGING AND VISION}, author={Han, YS and Snyder, WE and Bilbro, GL}, year={1998}, month={Nov}, pages={199–212} }
 @article{dai_snyder_bilbro_williams_cowan_1998, title={Left-ventricle boundary detection from nuclear medicine images}, volume={11}, ISSN={["0897-1889"]}, DOI={10.1007/BF03168721}, abstractNote={We present here a new algorithm for segmentation of nuclear medicine images to detect the left-ventricle (LV) boundary. In this article, other image segmentation techniques, such as edge detection and region growing, are also compared and evaluated. In the edge detection approach, we explored the relationship between the LV boundary characteristics in nuclear medicine images and their radial orientations: we observed that no single brightness function (eg, maximum of first or second derivative) is sufficient to identify the boundary in every direction. In the region growing approach, several criteria, including intensity change, gradient magnitude change, gradient direction change, and running mean differences, were tested. We found that none of these criteria alone was sufficient to successfully detect the LV boundary. Then we proposed a simple but successful region growing method—Contour-Modified Region Growing (CMRG). CMRG is an easy-to-use, robust, and rapid image segmentation procedure. Based on our experiments, this method seems to perform quite well in comparison to other automated methods that we have tested because of its ability to handle the problems of both low signal-to-noise ratios (SNR) as well as low image contrast without any assumptions about the shape of the left ventricle.}, number={1}, journal={JOURNAL OF DIGITAL IMAGING}, author={Dai, XL and Snyder, WE and Bilbro, GL and Williams, R and Cowan, R}, year={1998}, month={Feb}, pages={10–20} }
 @article{wang_snyder_bilbro_santago_1998, title={Performance evaluation of filtered backprojection reconstruction and iterative reconstruction methods for PET images}, volume={28}, ISSN={["0010-4825"]}, DOI={10.1016/S0010-4825(97)00031-0}, abstractNote={The filtered backprojection (FBP) algorithm and statistical model based iterative algorithms such as the maximum likelihood (ML) reconstruction or the maximum a posteriori (MAP) reconstruction are the two major classes of tomographic reconstruction methods. The FBP method is widely used in clinical setting while iterative methods have attracted research interests in the past decade. In this paper we studied the performance of the FBP, the ML and the MAP methods using simulated projection data. The experiment showed that the MAP algorithm generated superior image quality in terms of the bias, the variance, and the average mean squared error (MSE) measures.}, number={1}, journal={COMPUTERS IN BIOLOGY AND MEDICINE}, author={Wang, CX and Snyder, WE and Bilbro, G and Santago, P}, year={1998}, month={Jan}, pages={13–25} }
 @article{kolenchery_townsend_bilbro_1997, title={Performance of local power control in peer-to-peer impulse radio networks with bursty traffic}, number={5}, journal={TR (Center for Advanced Computing and Communication)}, author={Kolenchery, S. S. and Townsend, J. K. and Bilbro, G. L.}, year={1997} }