Digital Commons Network^™

Electron Transport In Gaas Quantum Wells: Effect Of Interface Roughness Scatterin, Rita Gupta

Turkish Journal of Physics

The importance of interface roughness (IFR) scattering of electrons and LO-phonons for electron transport in semiconductor quantum wells is discussed. Modulation doping of quantum wells minimizes the effect of impurity scattering on the low-field electron mobility so that IFR scattering of electrons in the well becomes the major limiting factor. A model calculation of IFR scattering of electrons in quantum wells is presented and it is shown that (both)\Lambda and \Delta, the parameters defining IFR, can be estimated by comparing the theoretical and experimental electron mobilities. The application of high electric field leads to a distribution of hot electrons which …

Feasibility Of The Gainp/Ingaas/Gaas System For Modulation Doped Field-Effect Transistors, C. Besi̇kci̇, Y. Ci̇van

Turkish Journal of Physics

Si-doped single Ga_{0.51}In_{0.49}P layers and GaInP/InGaAs/GaAs modulation doped field-effect transistor structures grown by gas source molecular beam epitaxy were characterized in detail through Hall-Effect and Deep Level Transient Spectroscopy techniques. Electrical characterization of the undoped and moderately Si-doped (N_D = 3 x 10^{17} cm^{-3}) GaInP layers yielded an electron trap with an activation energy of 0.75 eV and a temperature dependent capture cross section with a capture barrier of 0.593 eV showing DX center properties. The trap was not detected in highly Si doped (N_D = 4 x 10^{18} cm^{-3}) as grown layers suggesting that it is a defect complex …

Silicon-Based Optoelectronics: Progress And Challenges, Tamim P. Sidiki, Clivia M. Sotomayor Torres

Turkish Journal of Physics

We review the status of silicon-based optoelectronics with emphasis on light emitting diodes. Erbium-doped Si, por-Si and silicon-based superlattices and nanostructures are discussed. The origin behind light emission in silicon with feature sizes below about 60 nm still remains poorly understood.

3 \Mu M Intersubband Quantum Well Photodetector (Qwip), Rita Gupta, A. L. Y. Wong, S. K. Haywood

Turkish Journal of Physics

In recent years photodetectors operating in the mid- to far infrared region of 3-15 \mu m have been designed based on electron and hole intersubband transitions in multiple quantum wells and superlattices. In general, QWIPs based on electron transitions show greater detectivity compared to the hole-based photodetectors. However, selection rules for electron intersubband transitions usually forbid the TE mode operation, associated with normal light incidence; Therefore, special coupling structures/geometries have been employed to couple light into the device. The spectral region 3-5 \mu m is of interest for a variety of applications such as environmental gas sensing, thermal imaging etc. …

Hellish-Vcsel: A Hot Electron Laser, A. Obrien-Davies, N. Balkan, A. Boland-Thoms, M. J. Adams, J. Roberts

Turkish Journal of Physics

Hot Electron Light emission and Lasing In Semiconductor Heterostructures (HEL-LISH-1) is a novel hot electron surface emitter consisting of a GaAs QW on the n side of an Ga_{1-x}Al_xAs p-n junction. It utilises hot electron transport parallel to the junction plane. The injection of hot electron hole pairs into the QW is achieved via tunnelling and thermionic emission processes. Recently this structure has been modified by the incorporation of an upper and lower DBR defining a VCSEL (HELLISH-VCSEL). This has been shown to lase at room temperature with a Full Width at Half Maximum (FWHM) of 1.5 nm. In this …

The Effect Of Non-Equilibrium Acoustic Phonons On The Tunnel Current In Gaas/Alas Superlattices, S. A. Cavill, F. F. Ouali, L. J. Challis, A. J. Kent, M. Henini, A. V. Akimov

Turkish Journal of Physics

We present the first study of the effect of ballistic acoustic phonons generated by a heated metal film on the tunnel current in GaAs/AlAs superlattices. The phonon-induced increase of the tunnel current as a function of applied voltage has a maximum at a voltage that varies linearly with heater temperature both in zero and applied magnetic field. The behaviour is consistent with phonon-assisted tunnelling by stimulated phonon emission. The system acts as a phonon spectrometer in the < 1THz frequency region with a resolution of approximately 200 GHz.

Carrier Transport And Band Offsets In Two Dimensional Heterostructures, Hi̇lmi̇ Ünlü

Turkish Journal of Physics

Advances in the low dimensional heterojunction device technology cannot be complete without adequate and reliable analytic model for determining interface properties such as band offsets needed to study the carrier transport and to evaluate the device performance at high temperatures and pressures. In this article, using the extended universal tight binding model of semiconductors, a new way of determining the band offsets in heterostructures is presented. In this model the band offsets are first determined by aligning the vacuum level, defined relative to valence band maximum which is screened by optical dielectric constant of semiconductors, at the interface at absolute …

Cover And Contents

Turkish Journal of Physics

No abstract provided.

Cover And Contents

Turkish Journal of Physics

No abstract provided.

Influence Of Electrical Field On Pulsed Laser Beam Welding Of Stainless Steel (304), Salah A. H. Fawzi̇, Raz N. Ari̇f

Turkish Journal of Physics

Pulsed laser beam welding experiment were carried out on stainless steel (SUS 304), using vertical and horizontal electric fields of different intensities to study its effectiveness on the welding process, regarding depth and weld quality. Pulsed Nd: YAG laser emitting 10 ms pulses in the TEM_{00} mode at 1.06 \mu m wave length was employed, microstructure of welded zone and defect were investigated using optical and scanning electron microscopes. Tensile test and microhardness measurements were carried out to evaluate the weld quality. Welding by this method increased the efficiency tremendously and a depth increase of 85% was achieved.

Cover And Contents

Turkish Journal of Physics

No abstract provided.

Cover And Contents

Turkish Journal of Physics

No abstract provided.

Gathering To Nauvoo: Mormon Immigration 1840-46, Fred E. Woods

Faculty Publications

The gathering of the Mormon pioneers to Utah (commencing in 1847) has received extensive attention; however, the earlier LDS immigration to Nauvoo has not been adequately treated. This paper is the inspiring story of the British Saints who traveled to Nauvoo between June 1840 and February 1846. The international call to gather was received by the Prophet Joseph Smith during the second presentation of the Restored Church, less than six months after its organization in 1830.

Performance Surface Prediction For Wan-Based Clusters, Mark J. Clement, J. Kelly Flanagan, Glenn M. Judd, Bryan S. Morse, Joy L. Peterson

Faculty Publications

The last five years have been a period of exponential growth in the number of machines connected to the Internet and the speed at which these machines communicate. The infrastructure is now in place to consider a nationwide cluster of workstations as a viable parallel processing platform. In order to achieve acceptable performance on this kind of a machine, performance prediction tools must provide information on where to place computational objects. Incorrect object placement can result in poor performance and congestion in the network. This research develops a new paradigm for predicting performance in the Wide Area Network (WAN) based …

More Precious Than Gold: The Journey To And Through Zion In 1849-50, Fred E. Woods

Faculty Publications

The California gold rush, the first international gold rush in history, turned the world upside down, reaching its zenith in the years 1849-50. As a result of the rush during these two climactic years, the population swelled our nation's Pacific coast, entitling California to receive statehood in the fall of 1850. During these catalytic years, Latter-day Saints were journeying to the American West for a different kind of treasure. They gathered from afar to their Mormon mecca nestled in the Salt Lake Valley to fulfill their dreams of establishing Zion. Yet the California gold rush had a significant impact on …

Of Governments And Governance, A. Michael Froomkin

Articles

The Magaziner Report focuses on achieving short-term goals without giving sufficient consideration to long-term consequences affecting the structure of Internet governance and democracy in general. This overly pragmatic approach creates a paradoxical climate: overly-friendly to government intervention (in e-commerce regulation) while also overly willing to defer to privatized governance structures (in other areas). As the recent World Intellectual Property Organization ("WIPO") domain name/trademark process demonstrates, certain Internet governance processes raise several questions, not least discerning whether such processes include adequate notice and consultation. More traditional democratic processes, such as legislation and regulation, have routinized means of giving affected parties notice …

Finding Internet Sites On Elder Issues: Health And Human Services, Robin Schard

Articles

No abstract provided.

Search Tools: Skills And Strategies, Robin Schard

Articles

No abstract provided.

Affirmative Action And Discrimination, Girardeau A. Spann

Georgetown Law Faculty Publications and Other Works

The contemporary debate about race in the United States is perplexing. Each side seems genuinely to feel distressed at the demands being made by the other. Racial minorities point to Dred Scott's insistence on racial castes, Plessy's endorsement of official segregation, and Brown's reluctance to remedy unlawful discrimination as evidence that the white majority is inevitably inclined to advance its own interests at minority expense. Minority group members, therefore, tend to argue that the only way to arrest this majoritarian inclination is through the use of race-conscious remedial programs that will ensure an equitable distribution of resources. Most members of …

Ten Commandments Of Tractor Safety, Jill Webster

All Current Publications

Know your tractor. Most farmers know their machines well, but what about new farm help, or a neighbor’s tractor? Always look at the operators manual before operating an unfamiliar machine. Know the location of each control. Locations of important items, PTO levers for example, vary from one manufacturer to another.

The Warren Court And The Concept Of A Right, David Luban

Georgetown Law Faculty Publications and Other Works

The Warren Court is dead. None of its Justices remain on the benchindeed, only Justice White survives-and the recent history of the Supreme Court has been in large part a history of repudiating controversial Warren Court doctrines. Public opinion likewise repudiates Warren-style judicial activism, and constitutional scholarship-which as recently as the mid- 1980s consisted in considerable measure of theoretical defenses for Warren Court-inspired methods of interpreting the Bill of Rights-has grown increasingly skeptical of expansive interpretive strategies. It is quite possible that future constitutional historians will regard the Warren era as an aberration. The Warren Court, after all, was not …

Taking Problem Solving Pedagogy Seriously: A Response To The Attorney General, Carrie Menkel-Meadow

Georgetown Law Faculty Publications and Other Works

Attorney General Janet Reno has taken seriously the notion that lawyers should make the world better than they find it, that problems should be prevented, where possible, before they occur, and that law should serve the needs of the people and deliver long-term justice. I want to suggest some concrete ways in which we can take her challenges seriously.

Interaction Between Karst, Water And Agriculture Over The Climatic Gradient Of Israel, Amos Frumkin

International Journal of Speleology

The dry climate of Israel and the karstic nature of its rocks have always imposed human innovation for utilisation of water resources and agriculture. Large perennial karst springs are available only in the lowlands, but sophisticated water supply systems were built both in the lowland and highland regions. Marl layers interbedded within carbonates give rise to local perched springs and allow terrace construction. Deforestation has taken place for some 4000 years, causing intense soil erosion, but terraces have reduced this impact.

Bs News

Building Services Engineering

No abstract provided.

Camera Trackers, Matthew Cutts

Link Foundation Modeling, Simulation and Training Fellowship Reports

Tracking an object's location with inertial sensors works well over short time periods, but sensor drift and errors in integration cause errors to accumulate exponentially. Images, in contrast, work very well to determine a camera's location provided that the camera moves slowly. I received fellowship funding to work on a hybrid image and inertial tracker. The idea was to use data from the image sensors to correct errors and drift in the inertial sensors. The computer vision community has expended a great deal of energy in pursuing motion tracking from images. This area of research is also related to compositing …

Vortex Generated Rotor Wake Model For Real-Time Simulation, Kenneth S. Graham

Link Foundation Modeling, Simulation and Training Fellowship Reports

The University of Alabama Flight Dynamics Laboratory (UA FDL) has been simulating helicopters since 1981. The real-time, man-in-the-loop, simulator was developed locally and is continuously being upgraded. The hardware, software, architecture and math models are all developed in-house by a team of faculty and graduate students. Since 1994, the UA rotor model has been Bladehelo [2] - a true blade model that numerically integrates the flapping motion of individual blades and the shaft rotation. The approach is physically based. Discrepancies are studied until they are understood. Bladehelo played a key role in the discovery of residual bending [3], [4]. Bladehe!o …

Spatially Augmented Reality, Ramesh Raskar

Link Foundation Modeling, Simulation and Training Fellowship Reports

To create an effective illusion of virtual objects coexisting with the real world, see-through HMD-based Augmented Reality techniques supple1nent the user's view with images of virtual objects. We introduce here a new paradigm, Spatially Augmented Reality (SAR), where virtual objects are rendered directly within or on the user's physical space. A key benefit of SAR is that the user does not need to wear a head-mounted display. Instead, with the use of spatial displays, wide field of view and possibly high-resolution images of virtual objects can be integrated directly into the environ1nent. For example, the virtual objects can be realized …

(Er)Race-Ing An Ethic Of Justice, Anthony V. Alfieri

Articles

No abstract provided.

Prosecuting Race, Anthony V. Alfieri

Articles

Theoreticians and practitioners in the American criminal justice system increasingly debate the role of racial identity, racialized narratives, and race-neutral representation in law, lawyering, and ethics.

This debate holds special bearing on the growing prosecution and defense of acts of racially motivated violence. In this continuing investigation of the prosecution and defense of such violence, Professor Alfieri examines the recent federal prosecution of five white New York City police officers charged with assaulting Abner Louima, a young male Haitian immigrant, in 1997. Professor Alfieri presents a race conscious, community-oriented model of prosecutorial discretion guided by constitutional precepts, citizenship ideals, professionalism …

Elder Law-Related Organizations On The Internet, Robin Schard

Articles

No abstract provided.