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Articles 1 - 16 of 16
Full-Text Articles in Engineering
Analyzing The Non-Functional Requirements In The Desharnais Dataset For Software Effort Estimation, Ali Bou Nassif, Luiz Fernando Capretz, Danny Ho
Analyzing The Non-Functional Requirements In The Desharnais Dataset For Software Effort Estimation, Ali Bou Nassif, Luiz Fernando Capretz, Danny Ho
Electrical and Computer Engineering Publications
Studying the quality requirements (aka Non-Functional Requirements (NFR)) of a system is crucial in Requirements Engineering. Many software projects fail because of neglecting or failing to incorporate the NFR during the software life development cycle. This paper focuses on analyzing the importance of the quality requirements attributes in software effort estimation models based on the Desharnais dataset. The Desharnais dataset is a collection of eighty one software projects of twelve attributes developed by a Canadian software house. The analysis includes studying the influence of each of the quality requirements attributes, as well as the influence of all quality requirements attributes …
Privacy Protection Framework With Defined Policies For Service-Oriented Architecture, David S. Allison, Miriam Am Capretz, Hany F. Elyamany, Shuying Wang
Privacy Protection Framework With Defined Policies For Service-Oriented Architecture, David S. Allison, Miriam Am Capretz, Hany F. Elyamany, Shuying Wang
Electrical and Computer Engineering Publications
Service-Oriented Architecture (SOA) is a computer systems design concept which aims to achieve reusability and integration in a distributed environment through the use of autonomous, loosely coupled, interoperable abstractions known as services. In order to interoperate, communication between services is very important due to their autonomous nature. This communication provides services with their functional strengths, but also creates the opportunity for the loss of privacy. In this paper, a Privacy Protection Framework for Service-Oriented Architecture (PPFSOA) is described. In this framework, a Privacy Service (PS) is used in combination with privacy policies to create privacy contracts that outline what can …
Information Processing With Electron Spins, Supriyo Bandyopadhyay
Information Processing With Electron Spins, Supriyo Bandyopadhyay
Electrical and Computer Engineering Publications
Information processors process information in a variety of ways. The human brain processes information through a highly interconnected system of neurons and synapses, while a digital computer processes information by having a binary switch toggle on and off in response to a stream of binary bits. The “switch” is the most primitive unit of the modern computer. The better it is (faster, more energy efficient, more reliable, etc.), the more advanced is the computer hardware. Energy efficiency, however, is more important than any other attribute, not so much because energy is costly, but because too much energy dissipation prevents increasing …
Metastable State In A Shape-Anisotropic Single-Domain Nanomagnet Subjected To Spin-Transfer-Torque, Kuntal Roy, Supriyo Bandyopadhyay, Jayasimha Atulasimha
Metastable State In A Shape-Anisotropic Single-Domain Nanomagnet Subjected To Spin-Transfer-Torque, Kuntal Roy, Supriyo Bandyopadhyay, Jayasimha Atulasimha
Electrical and Computer Engineering Publications
We predict the existence of a metastable magnetization state in a single-domain nanomagnet with uniaxial shape anisotropy. It emerges when a spin-polarized current, which delivers a spin-transfer-torque possessing a field-like component, is injected into the nanomagnet. At a metastable state, the internal torque due to nanomagnet's shape anisotropy cancels the externally applied spin-transfer-torque and hence the nettorque acting on the magnetization becomes zero. Therefore, it prevents spin-transfer-torque from switching the magnetization from one stable state along the easy axis to the other, even in the presence of room-temperature thermal fluctuations.
Degradation And Phase Noise Of Inaln/Aln/Gan Heterojunction Field Effect Transistors: Implications For Hot Electron/Phonon Effects, C. Y. Zhu, M. Wu, C. Kayis, F. Zhang, X. Li, R. A. Ferreyra, A. Matulionis, Vitaliy Avrutin, Umit Ozgur, Hadis Morkoc
Degradation And Phase Noise Of Inaln/Aln/Gan Heterojunction Field Effect Transistors: Implications For Hot Electron/Phonon Effects, C. Y. Zhu, M. Wu, C. Kayis, F. Zhang, X. Li, R. A. Ferreyra, A. Matulionis, Vitaliy Avrutin, Umit Ozgur, Hadis Morkoc
Electrical and Computer Engineering Publications
In15.7%Al84.3%N/AlN/GaN heterojunctionfield effect transistors have been electrically stressed under four different bias conditions: on-state-low-field stress, reverse-gate-bias stress, off-state-high-field stress, and on-state-high-field stress, in an effort to elaborate on hot electron/phonon and thermal effects. DC current and phase noise have been measured before and after the stress. The possible locations of the failures as well as their influence on the electrical properties have been identified. The reverse-gate-bias stress causes trap generation around the gate area near the surface which has indirect influence on the channel. The off-state-high-field stress and the on-state-high-field stress induce deterioration of the channel, …
Optical And Structural Studies Of Homoepitaxially Grown M-Plane Gan, S. Khromov, B. Monemar, Vitaliy Avrutin, Xing Li, Hadis Morkoç, L. Hultman, G. Pozina
Optical And Structural Studies Of Homoepitaxially Grown M-Plane Gan, S. Khromov, B. Monemar, Vitaliy Avrutin, Xing Li, Hadis Morkoç, L. Hultman, G. Pozina
Electrical and Computer Engineering Publications
Cathodoluminescence(CL) and transmission electron microscopy studies of homoepitaxiallygrownm-plane Mg-doped GaN layers are reported. Layers contain basal plane and prismatic stacking faults (SFs) with ∼106 cm−1 density. Broad emission peaks commonly ascribed to SFs were found to be insignificant in these samples. A set of quite strong, sharp lines were detected in the same spectral region of 3.36–3.42 eV. The observed peaks are tentatively explained as excitons bound to some impurity defects, which can also be related to SFs. Donor-acceptor pair (DAP) recombination involving Si or O and Mg was ruled out by fitting DAP energies and …
Anisotropy Of Free-Carrier Absorption And Diffusivity In M-Plane Gan, P. Ščajev, K. Jarašiūnas, U. Ozgur, Hadis Morkoç, J. Leach, T. Paskova
Anisotropy Of Free-Carrier Absorption And Diffusivity In M-Plane Gan, P. Ščajev, K. Jarašiūnas, U. Ozgur, Hadis Morkoç, J. Leach, T. Paskova
Electrical and Computer Engineering Publications
Polarization-dependent free-carrier absorption (FCA) in bulk m-plane GaN at 1053 nm revealed approximately 6 times stronger hole-related absorption for E⊥c than for E||c probe polarization both at low and high carrier injection levels. In contrast, FCA at 527 nm was found isotropic at low injection levels due to electron resonant transitions between the upper and lower conduction bands, whereas the anisotropic impact of holes was present only at high injection levels by temporarily blocking electron transitions. Carrier transport was also found to be anisotropic under two-photon excitation, with a ratio of 1.17 for diffusivity perpendicular and parallel to the c-axis.
Improved Quantum Efficiency In Ingan Light Emitting Diodes With Multi-Double-Heterostructure Active Regions, X. Li, Serdal Okur, F. Zhang, S. A. Hafiz, Vitaliy Avrutin, Umit Ozgur, Hadis Morkoç, K. Jarašiūnas
Improved Quantum Efficiency In Ingan Light Emitting Diodes With Multi-Double-Heterostructure Active Regions, X. Li, Serdal Okur, F. Zhang, S. A. Hafiz, Vitaliy Avrutin, Umit Ozgur, Hadis Morkoç, K. Jarašiūnas
Electrical and Computer Engineering Publications
InGaN light emitting diodes(LEDs) with multiple thin double-heterostrucutre (DH) active regions separated by thin and low energy barriers were investigated to shed light on processes affecting the quantum efficiency and means to improve it. With increasing number of 3 nm-thick DH active layers up to four, the electroluminescence efficiency scaled nearly linearly with the active region thickness owing to reduced carrier overflow with increasing total thickness, showing almost no discernible efficiency degradation at high injection levels up to the measured current density of 500 A/cm2. Comparison of the resonant excitation dependent photoluminescence measurements at 10 K and room …
Impurity Distribution And Microstructure Of Ga-Doped Zno Films Grown By Molecular Beam Epitaxy, A. V. Kvit, A. B. Yankovich, V. Avrutin, H. Liu, N. Izyumskaya, Ü. H. Özgür, H. Morkoç, P. M. Voyles
Impurity Distribution And Microstructure Of Ga-Doped Zno Films Grown By Molecular Beam Epitaxy, A. V. Kvit, A. B. Yankovich, V. Avrutin, H. Liu, N. Izyumskaya, Ü. H. Özgür, H. Morkoç, P. M. Voyles
Electrical and Computer Engineering Publications
We report microstructural characterization of heavily Ga-doped ZnO (GZO) thin films on GaN and sapphire by aberration-corrected scanning transmission electron microscopy. Growth under oxygen-rich and metal-rich growth conditions leads to changes in the GZO polarity and different extended defects. For GZO layers on sapphire, the primary extended defects are voids, inversion domain boundaries, and low-angle grain boundaries. Ga doping of ZnO grown under metal-rich conditions causes a switch from pure oxygen polarity to mixed oxygen and zinc polarity in small domains. Electron energy loss spectroscopy and energy dispersive spectroscopy spectrum imaging show that Ga is homogeneous, but other residual impurities …
Donor Behavior Of Sb In Zno, H. Y. Liu, N. Izyumskaya, Vitaliy Avrutin, Ü. Özgür, A. B. Yankovich, A. V. Kvit, P. M. Voyles, H. Morkoç
Donor Behavior Of Sb In Zno, H. Y. Liu, N. Izyumskaya, Vitaliy Avrutin, Ü. Özgür, A. B. Yankovich, A. V. Kvit, P. M. Voyles, H. Morkoç
Electrical and Computer Engineering Publications
Electrical behavior of Sb in ZnO:Sb layers doped in a wide concentration range was studied using temperature dependent Hall effect measurements. The layers were grown by plasma-enhanced molecular beam epitaxy, and the Sb concentration was changed by varying the Sb flux, resulting in electron concentrations in the range of 1016 to nearly 1020 cm−3. Upon annealing, the electron concentration increased slightly and more notable was that the electron mobility significantly improved, reaching a room-temperature value of 110 cm2/V s and a low-temperature value of 145 cm2/V s, close to the maximum of …
Energy Dissipation And Switching Delay In Stress-Induced Switching Of Multiferroic Nanomagnets In The Presence Of Thermal Fluctuations, Kuntal Roy, Supriyo Bandyopadhyay, Jayasimha Atulasimha
Energy Dissipation And Switching Delay In Stress-Induced Switching Of Multiferroic Nanomagnets In The Presence Of Thermal Fluctuations, Kuntal Roy, Supriyo Bandyopadhyay, Jayasimha Atulasimha
Electrical and Computer Engineering Publications
Switching the magnetization of a shape-anisotropic 2-phase multiferroic nanomagnet with voltage-generated stress is known to dissipate very little energy (<1 aJ for a switching time of ∼0.5 ns) at 0 K temperature. Here, we show by solving the stochastic Landau-Lifshitz-Gilbert equation that switching can be carried out with ∼100% probability in less than 1 ns while dissipating less than 1.5 aJ at room temperature. This makes nanomagnetic logic and memory systems, predicated on stress-induced magnetic reversal, one of the most energy-efficient computing hardware extant. We also study the dependence of energy dissipation, switching delay, and the critical stress needed to switch, on the rate at which stress on the nanomagnet is ramped up or down.
Impact Of Active Layer Design On Ingan Radiative Recombination Coefficient And Led Performance, X. Li, S. Okur, F. Zhang, V. Avrutin, Ü. Özgür, H. Morkoç, S. M. Hong, S. H. Yen, T. C. Hsu, A. Matulionis
Impact Of Active Layer Design On Ingan Radiative Recombination Coefficient And Led Performance, X. Li, S. Okur, F. Zhang, V. Avrutin, Ü. Özgür, H. Morkoç, S. M. Hong, S. H. Yen, T. C. Hsu, A. Matulionis
Electrical and Computer Engineering Publications
The relative roles of radiative and nonradiative processes and the polarization field on the light emission from blue (∼425 nm) InGaN light emitting diodes (LEDs) have been studied. Single and multiple double heterostructure (DH) designs have been investigated with multiple DH structures showing improved efficiencies. Experimental results supported by numerical simulations of injection dependent electron and hole wavefunction overlap and the corresponding radiative recombination coefficients suggest that increasing the effective active region thickness by employing multiple InGaN DH structures separated by thin and low barriers is promising for LEDs with high efficiency retention at high injection. The use of thin …
Hexagonal-Based Pyramid Void Defects In Gan And Ingan, A. B. Yankovich, A. V. Kvit, X. Li, F. Zhang, V. Avrutin, H. Y. Liu, N. Izyumskaya, Ü. Özgür, H. Morkoç, P. M. Voyles
Hexagonal-Based Pyramid Void Defects In Gan And Ingan, A. B. Yankovich, A. V. Kvit, X. Li, F. Zhang, V. Avrutin, H. Y. Liu, N. Izyumskaya, Ü. Özgür, H. Morkoç, P. M. Voyles
Electrical and Computer Engineering Publications
We report a void defect in gallium nitride (GaN) and InGaN, revealed by aberration-corrected scanning transmission electron microscopy (STEM). The voids are pyramids with symmetric hexagonal {0001} base facets and {101¯1} side facets. Each pyramid void has a dislocation at the peak of the pyramid, which continues up along the [0001] growth direction to the surface. Some of the dislocations are hexagonal open core screw dislocations with {101¯0} side facets, varying lateral widths, and varying degrees of hexagonal symmetry. STEM electron energy loss spectroscopy spectrum imaging showed a large C concentration inside the void and on the void surfaces. There …
Carrier Dynamics In Bulk Gan, Patrick Ščajev, Kęstutis Jarašiūnas, Serdal Okur, Ümit Özgür, Hadis Morkoç
Carrier Dynamics In Bulk Gan, Patrick Ščajev, Kęstutis Jarašiūnas, Serdal Okur, Ümit Özgür, Hadis Morkoç
Electrical and Computer Engineering Publications
Carrier dynamics in hydride vapor phase epitaxy grown bulk GaN with very low density of dislocations, 5–8 × 105 cm−2, have been investigated by time-resolved photoluminescence (PL), free carrier absorption, and light-induced transient grating techniques in the carrier density range of 1015 to ∼1019 cm−3 under single and two photon excitation. For two-photon carrier injection to the bulk (527 nm excitation), diffusivity dependence on the excess carrier density revealed a transfer from minority to ambipolar carrier transport with the ambipolar diffusion coefficient D a saturating at 1.6 cm2/s at room temperature. An …
Electron Scattering Mechanisms In Gzo Films Grown On A-Sapphire Substrates By Plasma-Enhanced Molecular Beam Epitaxy, H. Y. Liu, V. Avrutin, N. Izyumskaya, Ü. Özgür, A. B. Yankovich, A. V. Kvit, P. M. Voyles, H. Morkoç
Electron Scattering Mechanisms In Gzo Films Grown On A-Sapphire Substrates By Plasma-Enhanced Molecular Beam Epitaxy, H. Y. Liu, V. Avrutin, N. Izyumskaya, Ü. Özgür, A. B. Yankovich, A. V. Kvit, P. M. Voyles, H. Morkoç
Electrical and Computer Engineering Publications
We report on the mechanisms governing electron transport using a comprehensive set of ZnO layers heavily doped with Ga (GZO) grown by plasma-enhanced molecular-beam epitaxy on a-plane sapphire substrates with varying oxygen-to-metal ratios and Ga fluxes. The analyses were conducted by temperature dependent Hall measurements which were supported by microstructural investigations as well. Highly degenerate GZO layers with n > 5 × 1020 cm−3 grown under metal-rich conditions (reactive oxygen-to-metal ratio c-direction. For highly conductive GZO layers, ionized-impurity scattering with almost no compensation is the dominant mechanism limiting the mobility in the temperature range from 15 to 330 K …
Structural And Optical Quality Of Gan Grown On Sc2o3/Y2o3/Si(111), L. Tarnawska, P. Zaumseil, M. A. Schubert, S. Okur, U. Ozgur, H. Morkoç, R. Paszkiewicz, P. Storck, T. Schroeder
Structural And Optical Quality Of Gan Grown On Sc2o3/Y2o3/Si(111), L. Tarnawska, P. Zaumseil, M. A. Schubert, S. Okur, U. Ozgur, H. Morkoç, R. Paszkiewicz, P. Storck, T. Schroeder
Electrical and Computer Engineering Publications
Thick (∼900 nm) GaN layers were grown by molecular beam epitaxy on cost-effective Sc2O3/Y2O3/Si(111) substrates and characterized by x-ray diffraction and photoluminescence. Samples grown in Ga-rich condition show superior structural and optical quality with reduced density of cubic GaN inclusions within the hexagonal matrix and a relatively strong photoluminescence emission at 3.45 eV at 10 K. Cubic inclusions are formed in the initial growth stage and their concentration is reduced with increasing film thickness and after rapid thermal annealing.