Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

2010

Discipline
Institution
Keyword
Publication
Publication Type
File Type

Articles 781 - 810 of 6945

Full-Text Articles in Physical Sciences and Mathematics

Current Status And Long-Term Trends In Water Quality And Living Resources In The Virginia Tributaries And Chesapeake Bay Mainstem From 1985 Through 2009, Daniel M. Dauer, Harold G. Marshall, John R. Donat, Michael F. Lane, Suzanne C. Doughten, Frederick A. Hoffman, Raghavendra Kurada Nov 2010

Current Status And Long-Term Trends In Water Quality And Living Resources In The Virginia Tributaries And Chesapeake Bay Mainstem From 1985 Through 2009, Daniel M. Dauer, Harold G. Marshall, John R. Donat, Michael F. Lane, Suzanne C. Doughten, Frederick A. Hoffman, Raghavendra Kurada

Status and Trends for Virginia Chesapeake Bay

The period prior to the implementation of the Chesapeake Bay Monitoring Program was characterized by a marked decline in the water quality of the Chesapeake Bay. The disappearance of submerged aquatic vegetation in certain regions of the Bay, declines in the abundance of some commercially and recreationally important species, increases in the incidence of low dissolved oxygen events, changes in the Bay's food web, and other ecological problems have been related to the deteriorating water quality (e.g. USEPA, 1982,1983;Officer et al.,1984; Orth and Moore, 1984). The results of concentrated research efforts in the late 1970s and early 1980s stimulated the …


The Update, November 2010, University Of Northern Iowa. College Of Humanities, Arts And Sciences. Nov 2010

The Update, November 2010, University Of Northern Iowa. College Of Humanities, Arts And Sciences.

Update

Inside this issue:

-- Working to Recover: Geology Professor, Community Actor Becomes 'Super Volunteer'
-- Department News
-- Graphic Communications Name Change
-- Film Screening: Living Downstream
-- Action is Eloquence
-- Color and Camouflage
-- Regents Award
-- Student Spotlights
-- Get Your Green On
-- WCF Symphony & School of Music Events
-- UNI Art Students Study Abroad in Berlin
-- UNI's Cyber Defense Team
-- Student Spotlights Continued...
-- Students and Faculty Attend Major Graphics Trade Show in Chicago
-- UNI Teacher Wins Prestigious Award

-- WCF Symphony & School of Music Events Continued...
-- UNI Forensics …


Heavy Metal Concentrations In Water And Surface Sediments Of Wilgreen Lake, Madison County, Kentucky, Chad Von Gruenigen, Walter S. Borowski Nov 2010

Heavy Metal Concentrations In Water And Surface Sediments Of Wilgreen Lake, Madison County, Kentucky, Chad Von Gruenigen, Walter S. Borowski

EKU Faculty and Staff Scholarship

Heavy metal pollution remains a problem in natural waters, particularly for localities near plausible anthropogenic sources. We assayed the level of heavy metals in surface waters and within surface sediments of Wilgreen Lake, whose watershed drains industrial, urban, and residential areas near Richmond, Kentucky.

Water samples were treated according to Environmental Protection Agency (EPA) protocols and digested with trace-metal-grade nitric and hydrochloric acids. Sediment samples were collected with a grab sampler and digested using established EPA procedures with hydrogen peroxide and trace-metal-grade nitric acid. Both water samples and sediment samples were sent to Activation Laboratories for analysis, and were measured …


Patterns Of Heavy Metal Concentration In Core Sediments, Wilgreen Lake, Madison County, Kentucky, Clint Mcmaine, Walter S. Borowski Nov 2010

Patterns Of Heavy Metal Concentration In Core Sediments, Wilgreen Lake, Madison County, Kentucky, Clint Mcmaine, Walter S. Borowski

EKU Faculty and Staff Scholarship

Elevated levels of cadmium, copper, lead, and nickel were found within the waters of Wilgreen Lake during a preliminary survey in 2007. Accumulation of heavy metals in freshwater systems is a known problem. Heavy metals enter the lake in the dissolved phase or adsorbed onto sediment particles and may be linked to industries within the lake’s watershed. Under certain geochemical conditions such as anoxia, heavy metals may detach from sediment particles and diffuse into overlying lake waters, causing a renewed influx of heavy metals into the ecosystem. We hypothesize that heavy metals should decrease in concentration upcore as a result …


Powerpack: Energy Profiling And Analysis Of High-Performance Systems And Applications, Rong Ge, Xizhou Feng, Shuaiwen Song, Hung-Ching Chang, Dong Li, Kirk W. Cameron Nov 2010

Powerpack: Energy Profiling And Analysis Of High-Performance Systems And Applications, Rong Ge, Xizhou Feng, Shuaiwen Song, Hung-Ching Chang, Dong Li, Kirk W. Cameron

Mathematics, Statistics and Computer Science Faculty Research and Publications

Energy efficiency is a major concern in modern high-performance computing system design. In the past few years, there has been mounting evidence that power usage limits system scale and computing density, and thus, ultimately system performance. However, despite the impact of power and energy on the computer systems community, few studies provide insight to where and how power is consumed on high-performance systems and applications. In previous work, we designed a framework called PowerPack that was the first tool to isolate the power consumption of devices including disks, memory, NICs, and processors in a high-performance cluster and correlate these measurements …


On Semigroups With Lower Semimodular Lattice Of Subsemigroups, Peter R. Jones Nov 2010

On Semigroups With Lower Semimodular Lattice Of Subsemigroups, Peter R. Jones

Mathematics, Statistics and Computer Science Faculty Research and Publications

The question of which semigroups have lower semimodular lattice of subsemigroups has been open since the early 1960s, when the corresponding question was answered for modularity and for upper semimodularity. We provide a characterization of such semigroups in the language of principal factors. Since it is easily seen (and has long been known) that semigroups for which Green's relation J is trivial have this property, a description in such terms is natural. In the case of periodic semigroups—a case that turns out to include all eventually regular semigroups—the characterization becomes quite explicit and yields interesting consequences. In the general case, …


How To Write A Good Paper In Computer Science And How Will It Be Measured By Isi Web Of Knowledge, Rǎzvan Andonie, Ioan Dzitac Nov 2010

How To Write A Good Paper In Computer Science And How Will It Be Measured By Isi Web Of Knowledge, Rǎzvan Andonie, Ioan Dzitac

All Faculty Scholarship for the College of the Sciences

The academic world has come to place enormous weight on bibliometric measures to assess the value of scientific publications. Our paper has two major goals. First, we discuss the limits of numerical assessment tools as applied to computer science publications. Second, we give guidelines on how to write a good paper, where to submit the manuscript, and how to deal with the reviewing process. We report our experience as editors of International Journal of Computers Communications & Control (IJCCC). We analyze two important aspects of publishing: plagiarism and peer reviewing. As an example, we discuss the promotion assessment criteria used …


Accelerated Erosion Of Saltmarshes Infested By The Non-Native Burrowing Crustacean Sphaeroma Quoianum, Timothy Mathias Davidson, Catherine E. De Rivera Nov 2010

Accelerated Erosion Of Saltmarshes Infested By The Non-Native Burrowing Crustacean Sphaeroma Quoianum, Timothy Mathias Davidson, Catherine E. De Rivera

Environmental Science and Management Faculty Publications and Presentations

Lateral erosion of saltmarshes is affected by many abiotic and biotic factors. While abiotic factors are typically regarded as primary drivers of erosion, biotic influences such as burrowing or bioturbating taxa can also extensively modify the physical structure of this marine habitat. Many estuaries on the Pacific coast of North America have been invaded by populations of the burrowing non-native isopod Sphaeroma quoianum, which are thought to exacerbate the erosion of saltmarshes. We conducted a mensurative experiment to examine the relationship between populations of S. quoianum and lateral erosion rate of saltmarshes in Coos Bay, Oregon, USA. After 1 …


Low Temperature Photo-Oxidation Of Chloroperoxidase Compound Ii, Xinting Yuan, Xin Sheng, John A. Horner, Brian Bennett, Leslie W. -M. Fung, Martin Newcomb Nov 2010

Low Temperature Photo-Oxidation Of Chloroperoxidase Compound Ii, Xinting Yuan, Xin Sheng, John A. Horner, Brian Bennett, Leslie W. -M. Fung, Martin Newcomb

Physics Faculty Research and Publications

Oxidation of the heme-thiolate enzyme chloroperoxidase (CPO) from Caldariomyces fumago with peroxynitrite (PN) gave the Compound II intermediate, which was photo-oxidized with 365 nm light to give a reactive oxidizing species. Cryo-solvents at pH ≈ 6 were employed, and reactions were conducted at temperatures as low as − 50 °C. The activity of CPO as evaluated by the chlorodimedone assay was unaltered by treatment with PN or by production of the oxidizing transient and subsequent reaction with styrene. EPR spectra at 77 K gave the amount of ferric protein at each stage in the reaction sequence. The PN oxidation step …


Effects Of Hurricane Katrina On Freshwater Fish Assemblages In A Small Coastal Tributary Of Lake Pontchartrain, Louisiana, Martin O'Connell Nov 2010

Effects Of Hurricane Katrina On Freshwater Fish Assemblages In A Small Coastal Tributary Of Lake Pontchartrain, Louisiana, Martin O'Connell

Earth and Environmental Sciences Faculty Publications

Hurricane Katrina struck southeastern Louisiana on 29 August 2005 and thereby created an opportunity to examine the effects of a catastrophic storm on fish assemblages in a coastal stream. Bayou Lacombe is a small (46.1 river kilometers), primarily freshwater stream that drains into the northeastern portion of Lake Pontchartrain, a large oligohaline estuary located north of New Orleans. In summer 2005 (prior to the hurricane), three upstream and three downstream reaches of Bayou Lacombe were surveyed by electrofishing. These same six reaches were resurveyed in the summer of 2006 to assess the effects of the hurricane on fish assemblages. There …


Bandwidth Tuning Triggers Interplay Of Charge Order And Superconductivity In Two-Dimensional Organic Materials, S. Kaiser, M. Dressel, Y. Sun, A. Greco, J. A. Schlueter, Gary L. Gard, N. Drichko Nov 2010

Bandwidth Tuning Triggers Interplay Of Charge Order And Superconductivity In Two-Dimensional Organic Materials, S. Kaiser, M. Dressel, Y. Sun, A. Greco, J. A. Schlueter, Gary L. Gard, N. Drichko

Chemistry Faculty Publications and Presentations

We observe charge-order fluctuations in the quasi-two-dimensional organic superconductor β″-(BEDT-TTF)₂SF₅CH₂CF₂SO₃, both by means of vibrational spectroscopy, locally probing the fluctuating charge order, and by investigating the in-plane dynamical response by infrared reflectance spectroscopy. The decrease of the effective electronic interaction in an isostructural metal suppresses both charge-order fluctuations and superconductivity, pointing to their interplay. We compare the results of our experiments with calculations on the extended Hubbard model.


Model Checking Hierarchical Probabilistic Systems, Jun Sun, Songzheng Song, Yang Liu Nov 2010

Model Checking Hierarchical Probabilistic Systems, Jun Sun, Songzheng Song, Yang Liu

Research Collection School Of Computing and Information Systems

Probabilistic modeling is important for random distributed algorithms, bio-systems or decision processes. Probabilistic model checking is a systematic way of analyzing finite-state probabilistic models. Existing probabilistic model checkers have been designed for simple systems without hierarchy. In this paper, we extend the PAT toolkit to support probabilistic model checking of hierarchical complex systems. We propose to use PCSP#, a combination of Hoare’s CSP with data and probability, to model such systems. In addition to temporal logic, we allow complex safety properties to be specified by non-probabilistic PCSP# model. Validity of the properties (with probability) is established by refinement checking. Furthermore, …


Model Checking A Model Checker: A Code Contract Combined Approach, Jun Sun, Yang Liu, Bin Cheng Nov 2010

Model Checking A Model Checker: A Code Contract Combined Approach, Jun Sun, Yang Liu, Bin Cheng

Research Collection School Of Computing and Information Systems

Model checkers, like any complex software, are subject to bugs. Unlike ordinary software, model checkers are often used to verify safety critical systems. Their correctness is thus vital. Verifying model checkers is extremely challenging because they are always complicated in logic and highly optimized. In this work, we propose a code contract combined approach for checking model checkers and apply it to a home-grown model checker PAT. In this approach, we firstly embed programming contracts (i.e., pre/post-conditions and invariants) into its source code, which can capture correctness of model checking algorithms, underlying data structures, consistency between different model checking parameters, …


Efficient Mining Of Multiple Partial Near-Duplicate Alignments By Temporal Network, Hung-Khoon Tan, Chong-Wah Ngo, Tat-Seng Chua Nov 2010

Efficient Mining Of Multiple Partial Near-Duplicate Alignments By Temporal Network, Hung-Khoon Tan, Chong-Wah Ngo, Tat-Seng Chua

Research Collection School Of Computing and Information Systems

This paper considers the mining and localization of near-duplicate segments at arbitrary positions of partial near-duplicate videos in a corpus. Temporal network is proposed to model the visual-temporal consistency between video sequence by embedding temporal constraints as directed edges in the network. Partial alignment is then achieved through network flow programming. To handle multiple alignments, we consider two properties of network structure: conciseness and divisibility, to ensure that the mining is efficient and effective. Frame-level matching is further integrated in the temporal network for alignment verification. This results in an iterative alignment-verification procedure to fine tune the localization of near-duplicate …


Smoothness Of Lipschitz Minimal Intrinsic Graphs In Heisenberg Groups ℍN, N > 1, Luca Capogna, Giovanna Citti, Maria Manfredini Nov 2010

Smoothness Of Lipschitz Minimal Intrinsic Graphs In Heisenberg Groups ℍN, N > 1, Luca Capogna, Giovanna Citti, Maria Manfredini

Mathematics Sciences: Faculty Publications

We prove that Lipschitz intrinsic graphs in the Heisenberg groups ℍn, with n > 1, which are vanishing viscosity solutions of the minimal surface equation, are smooth and satisfy the PDE in a strong sense.


Interactions Of Carbon Nanotubes With Human Lung Epithelial Cells In Vitro, Assessed By Raman Spectroscopy, Peter Knief Nov 2010

Interactions Of Carbon Nanotubes With Human Lung Epithelial Cells In Vitro, Assessed By Raman Spectroscopy, Peter Knief

Doctoral

Current methods for the evaluation of cellular interactions with nanoparticles are non-specific, relatively slow and invasive to the cell. Raman spectroscopy is a non invasive technique whose potential in the biosciences has already been demonstrated and has been used in the investigation of cell interactions with various external agents. The main focus of this study is to employ Raman spectroscopy to investigate the interaction of A549 human lung cells with single walled carbon nanotubes. · Carbon nanotubes have attracted considerable interest not only for their outstanding physical and electronic properties, promising a potentially vast number of applications, but also for …


Development Of Acrylamide Based Photopolymer For Full Colour Display Holography, Chakrapani Meka Nov 2010

Development Of Acrylamide Based Photopolymer For Full Colour Display Holography, Chakrapani Meka

Doctoral

Holography is a firmly established discipline that can be used as a tool for scientific and engineering studies and as a display medium as well. Until now both silver halide photographic emulsions (SHPE) and dichromated gelatine (DCG) have been the most common materials used for high efficiency full colour reflection hologram recording. However, these materials require wet chemical processing for developing the holograms which is laborious and costly from the point of view of commercial applications. Self-developing photopolymers such as acrylamide based photopolymer (ABP) which do not require development are the ideal choice for real-time recording and reconstruction of holograms. …


Solar Radiation Damage To Human Skin Mitochondria, Luciene Zanchetta Nov 2010

Solar Radiation Damage To Human Skin Mitochondria, Luciene Zanchetta

Doctoral

The central objective of this study was to assess solar radiation-induced changes in cellular function, mitochondrial function and mitochondrial DNA to further investigate the role of these energy-dedicated and metabolically essential organelles in the response to the main environmental stressor associated with skin cancer initiation. An in vitro approach was chosen employing the human malignant melanoma (A375) and human amelanotic melanoma (C32) cells and the human spontaneously immortalized keratinocytes (HaCaT). A Q-Sun Solar Simulator was used to expose cells to low-level simulated solar radiation (SSR) as it provides a mimic of solar radiation that is environmentally relevant in the UV …


Book Review: Stars Above, Earth Below: A Guide To Astronomy In The National Parks, T. D. Oswalt Nov 2010

Book Review: Stars Above, Earth Below: A Guide To Astronomy In The National Parks, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Stars Above, Earth Below : a Guide to Astronomy in the National Parks by Tyler Nordgren. Springer/Praxis, 2010 444p, 9781441916488 $29.95.


Visual Salience And Reference Resolution In Situated Dialogues: A Corpus-Based Evaluation., Niels Schütte, John D. Kelleher, Brian Mac Namee Nov 2010

Visual Salience And Reference Resolution In Situated Dialogues: A Corpus-Based Evaluation., Niels Schütte, John D. Kelleher, Brian Mac Namee

Conference papers

Dialogues between humans and robots are necessarily situated and so, often, a shared visual context is present. Exophoric references are very frequent in situated dialogues, and are particularly important in the presence of a shared visual context - for example when a human is verbally guiding a tele-operated mobile robot. We present an approach to automatically resolving exophoric referring expressions in a situated dialogue based on the visual salience of possible referents. We evaluate the effectiveness of this approach and a range of different salience metrics using data from the SCARE corpus which we have augmented with visual information. The …


Impact Investigation Of Reactor Fuel Operating Parameters On Reactivity For Use In Burnup Credit Applications, Tanya N. Sloma Nov 2010

Impact Investigation Of Reactor Fuel Operating Parameters On Reactivity For Use In Burnup Credit Applications, Tanya N. Sloma

UNLV Theses, Dissertations, Professional Papers, and Capstones

When representing the behavior of commercial spent nuclear fuel (SNF), credit is sought for the reduced reactivity associated with the net depletion of fissile isotopes and the creation of neutron-absorbing isotopes, a process that begins when a commercial nuclear reactor is first operated at power. Burnup credit accounts for the reduced reactivity potential of a fuel assembly and varies with the fuel burnup, cooling time, and the initial enrichment of fissile material in the fuel. With regard to long-term SNF disposal and transportation, tremendous benefits, such as increased capacity, flexibility of design and system operations, and reduced overall costs, provide …


Pulsed Laser Deposition Of Graphite Counter Electrodes For Dye-Sensitized Solar Cells, Krishna P. Acharya, Himal Khatri, Sylvain Marsillac, Bruno Ullrich, Pavel Anzenbacher, Mikhail Zamkov Nov 2010

Pulsed Laser Deposition Of Graphite Counter Electrodes For Dye-Sensitized Solar Cells, Krishna P. Acharya, Himal Khatri, Sylvain Marsillac, Bruno Ullrich, Pavel Anzenbacher, Mikhail Zamkov

Electrical & Computer Engineering Faculty Publications

We report on pulsed laser deposition of graphite onto flexible plastic and conductive glass substrates for use as a counter electrode in dye-sensitized solar cells. The efficiency of as-prepared graphite electrodes was tested using CdS-sensitized solar cell architecture resulting in external quantum efficiency comparable to that of conventional platinum counter electrodes. This work highlights the possibility of using pulsed laser deposited graphite as a low-cost alternative to platinum, which could be fabricated both on flexible and rigid substrates.


An Implementation Of Natural Language User Interface In Smart Home System., Ngoi Se Keng Nov 2010

An Implementation Of Natural Language User Interface In Smart Home System., Ngoi Se Keng

Student Works (2010-2019)

Smart Home System has facilitated the control of home appliances through computer system. However, the physical interactions between the user and existing graphical user interface such as pointing and clicking button could be a challenge to elderly, whom are generally having vision and motor impairment. This project specifically focuses on the development of a user interface that does not require physical interaction. In this regard, a prototype smart home system namely Natural Language Instruction Driven System (NLIDS) that employed natural language (speech) based user interface has been developed. The prototype system consists of three modules, which are Input & Response …


Applied Technologies And Prospects Of Conformance Control Treatments In China, Yuzhang Liu, Baojun Bai, Yefei Wang Nov 2010

Applied Technologies And Prospects Of Conformance Control Treatments In China, Yuzhang Liu, Baojun Bai, Yefei Wang

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

China is the largest user of chemical-based conformance control treatments and a series of technologies have been successfully developed and deployed in recent years. This paper first shows the milestones of development and application of conformance control technologies in China. Then integrated conformance control technologies are reviewed followed by the lessons we have learned, and then a few major specific conformance control technologies are addressed, including tracer injection and channels explanation, potentiometric testing to identify areal sweep efficiency, Pressure Index (PI) decisionmaking technology to select well candidate, complementary decision-making technology to select well candidate and design application parameters, and major …


Technology Integration In Secondary Mathematics Classrooms: Effect On Students’ Understanding, Megan Sheehan, Leah Nillas Nov 2010

Technology Integration In Secondary Mathematics Classrooms: Effect On Students’ Understanding, Megan Sheehan, Leah Nillas

Scholarly Publications

Technology use in secondary mathematics courses has the potential to bring about broad changes in learning environment and teaching pedagogy, allowing students to communicate and collaborate in new ways and to conjecture, justify, and generalize findings. However, this potential is only realized when teachers use technology in ways encouraging these outcomes (Galbraith, 2006). The purpose of this study is to examine the integration of technology in secondary mathematics classrooms and to evaluate the effectiveness of its use in relation to students’ learning outcomes. This self study research was conducted in honors geometry and AP calculus classes. Data sources included transcripts …


Note On Gradient Estimates Of Heat Kernel For Schrödinger Operators, Shijun Zheng Nov 2010

Note On Gradient Estimates Of Heat Kernel For Schrödinger Operators, Shijun Zheng

Mathematical Sciences: Faculty Publications

Let H = -Δ+V be a Schrödinger operator on Rn. We show that gradient estimates for the heat kernel of H with upper Gaussian bounds imply polynomial decay for the kernels of certain smooth dyadic spectral operators. The latter decay property has been known to play an important role in the Littlewood-Paley theory for Lp and Sobolev spaces. We are able to establish the result by modifying Hebisch and the author’s recent proofs. We give a counterexample in one dimension to show that there exists V in the Schwartz class such that the long time gradient heat …


Situating Spatial Templates For Human-Robot Interaction, John D. Kelleher, Robert J. Ross, Brian Mac Namee, Colm Sloan Nov 2010

Situating Spatial Templates For Human-Robot Interaction, John D. Kelleher, Robert J. Ross, Brian Mac Namee, Colm Sloan

Conference papers

People often refer to objects by describing the object's spatial location relative to another object. Due to their ubiquity in situated discourse, the ability to use 'locative expressions' is fundamental to human-robot dialogue systems. A key component of this ability are computational models of spatial term semantics. These models bridge the grounding gap between spatial language and sensor data. Within the Artificial Intelligence and Robotics communities, spatial template based accounts, such as the Attention Vector Sum model (Regier and Carlson, 2001), have found considerable application in mediating situated human-machine communication (Gorniak, 2004; Brenner et a., 2007; Kelleher and Costello, 2009). …


Search For Gravitational Waves From Compact Binary Coalescence In Ligo And Virgo Data From S5 And Vsr1, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Nov 2010

Search For Gravitational Waves From Compact Binary Coalescence In Ligo And Virgo Data From S5 And Vsr1, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We report the results of the first search for gravitational waves from compact binary coalescence using data from the Laser Interferometer Gravitational-Wave Observatory and Virgo detectors. Five months of data were collected during the Laser Interferometer Gravitational-Wave Observatory's S5 and Virgo's VSR1 science runs. The search focused on signals from binary mergers with a total mass between 2 and 35M⊙. No gravitational waves are identified. The cumulative 90%-confidence upper limits on the rate of compact binary coalescence are calculated for nonspinning binary neutron stars, black hole-neutron star systems, and binary black holes to be 8.7 x 10- …


Stability And Charge Transfer Levels Of Extrinsic Defects In Linbo₃, Haixuan Xu, Aleksandr V. Chernatynskiy, Donghwa Lee, Susan Sinnott, Venkatraman Gopalan, Volkmar Dierolf, Simon R. Phillpot Nov 2010

Stability And Charge Transfer Levels Of Extrinsic Defects In Linbo₃, Haixuan Xu, Aleksandr V. Chernatynskiy, Donghwa Lee, Susan Sinnott, Venkatraman Gopalan, Volkmar Dierolf, Simon R. Phillpot

Physics Faculty Research & Creative Works

The technologically important incorporation of extrinsic defects (Mg2+, Fe2+, Fe3+, Er3+, and Nd3+) in LiNbO3 is investigated using density-functional theory combined with thermodynamic calculations. Defect energies, the charge compensation mechanisms, and charge transfer levels, are determined for congruent and stoichiometric compositions. In general, under congruent (Nb2O5-rich) conditions impurities occupy lithium sites, compensated by lithium vacancies. Under stoichiometric (Li2O-rich) conditions, impurities occupy both lithium and niobium sites. The effects of the concentration of Mg on the dominant defect and site occupancy are analyzed. In …


Revenue Management Model For On-Demand It Services, Tieming Liu, Chinnatat Methapatara, Laura Wynter Nov 2010

Revenue Management Model For On-Demand It Services, Tieming Liu, Chinnatat Methapatara, Laura Wynter

Research Collection School Of Computing and Information Systems

This paper presents a model for applying revenue management to on-demand IT services. The multinomial logit model is used to describe customer choice over multiple classes with different service-level agreements (SLAs). A nonlinear programming model is provided to determine the optimal price or service level for each class. Through a numerical analysis, we examine the impacts of system capacity and customer waiting incentives on the service provider’s profit and pricing strategies.