Physical Sciences and Mathematics Commons^™

Chemistry Of Surface Waters: Distinguishing Fine-Scale Differences In Sea Grass Habitats Of Chesapeake Bay, Emmanis Dorval, Cynthia M. Jones

OES Faculty Publications

We tested the hypothesis that the physical and chemical processes acting in sea grass habitats of the lower Chesapeake Bay are spatially structured and that dissolved elemental chemistry of sea grass-habitat surface waters have their own unique identity. We sampled surface waters from July to September 2001 in five sea grass habitats of the lower bay: Potomac, Rappahannock, York, Island (Tangier-Bloodsworth), and Eastern Shore. Dissolved Mg, Mn, Sr, and Ba concentrations were measured by sector field inductively coupled plasma-mass spectrometry. As expected, Mg, Sr, and Ba exhibited conservative behavior, but Mn exhibited nonconservative behavior along the salinity gradient. Spatial differences …

Dirac Sextic Oscillator In The Constant Magnetic Field, Ramazan Koç, Mehmet Koca

Turkish Journal of Physics

We introduce a Dirac equation which reproduces the usual radial sextic oscillator potential in the non-relativistic limit. We determine its energy spectrum in the presence of the magnetic field. It is shown that the equation is solved in the context of quasi-exactly-solvable problems. The equation possesses hidden sl_2-algebra and the destroyed symmetry of the equation can be recovered for specific values of the magnetic field which leads to exact determination of the eigenvalues.

Features Of Daily Variation In Cosmic Ray Intensity During High/Low Amplitude Events, Rajesh K. Mishra, Rekha Agarwal Mishra

Turkish Journal of Physics

A detailed study has been conducted on the long-term changes in the diurnal, semi-diurnal and tri-diurnal anisotropy of cosmic rays in terms of the high/low amplitude anisotropic wave train events (HAE/LAE) during the period 1981--94 using the neutron monitor data from the Deep River neutron monitoring station. In all, 38 HAE and 28 LAE cases have been studied. An inter-comparison of the first three harmonics during these events has been made so as to understand the basic reason causing the occurrence of these types of events. It has been observed that the phase of diurnal anisotropy shifts towards earlier hours …

Standard Ubv Observations At The Çanakkale University Observatory (Çuo), Hi̇cran Bakiş, Volkan Bakiş, Osman Demi̇rcan, Edwin Budding

Turkish Journal of Physics

By using standard and comparison star observations carried out at different times of the year, at Çanakkale Onsekiz Mart University Observatory, we obtained the atmospheric extinction coefficients at the observatory. We also obtained transformation coefficients and zero-point constants for the transformation to the standard Johnson UBV system, of observations in the local system carried out with the SSP5A photometer and T40 telescope. The transmission curves and the mean wavelengths of the UBV filters as measured in the laboratory appear not much different from those of the standard Johnson system and found inside the transmission curve of the standard mean atmosphere.

Some Physical Properties Of \Gamma Irradiated Ge_X(As_2te_3)_{100 - X} Chalcogenide System, Afaf Abdel-Aal, Bahiga Abdel-Hameed Mansour, Hoda Mohamed Eissa

Turkish Journal of Physics

The effect of \gamma -radiation on the electrical conductivity, switching, and optical properties of the chalcogenide amorphous system Ge_x(As_2Te_3)_{100 - x} (where x = 0,1,5,10 atm %) have been studied. The results show that the radiation causes a shift of the optical gap,as well as a change in the electrical activation energy and the threshold voltage. As the \gamma -doses increase, the values of the allowed indirect optical energy gap E_{opt} for the different compositions decreases and the tail energy width increases.

Photoconductivity Of Selenium And Sulphur Doped A-Si:H Thin Films, Sanjeev Kumar Sharma, Himanshu Gupta, Rajendra Kumar, Ram Mohan Mehra

Turkish Journal of Physics

This paper presents a study of photoconductivity of S- and Se-doped a-Si:H as a function of composition and temperature. Temperature dependence of photoconductivity of the films was measured under the illumination of white light at 100~mW/cm^2. The room temperature photoconductivity for the same doping concentration of 10^{-4} (to develop H_2Se/SiH_4 and H_2S/SiH_4) is found to be higher in Se-doped -- than S-doped -- a-Si:H film due to a low defect density. From the measurement of intensity dependence of photoconductivity, it is found that the addition of Se and S changes the recombination mechanism from monomolecular, for low-doped films, to bimolecular …

Air Moisture Sensing Properties Of Zncr_2o_4--K_2cro_4 Composites, Neşe Kavasoğlu, Murat Bayhan

Turkish Journal of Physics

Crystalline structure, surface morphology and the response to air moisture of ceramic system of composition ZnCr_2O_4 - K_rCrO_4 formed by solid state reaction at elevated temperatures were investigated. The fired ceramic body, which proved to be mainly constructed from about 1 \mu m sized ZnCr_2O_4 spinel grains, was found to be porous. The humidity sensing behaviour of the sensors reveals that the electrical conduction is protonic and is controlled through the thin layers of water adsorbed on the surface of the grains, with charge transfer to the electrodes. Only the material containing 20\% K_2CrO_4 in ZnCr_2O_4 exhibited an exponential behaviour …

Physical Properties Of Holmium Promoted Superconductivity In Nd-Doped Ybco Ht_C-Superconductors, Morsy Abou Sekkina, Abdul Raouf Tawfik, Osama Hemeda, Mohamad Ahmad Taher Dawoud, Samy El-Attar

Turkish Journal of Physics

Samples of the nominal composition (Y_{0.5}Nd_{0.5-x}Ho_x) Ba_2Cu_3O_{7- \delta} , 0 \le x \le 0.5, have been prepared using the conventional solid state reaction. The effect of holmium and neodymium substitution on electrical resistivity, transition temperature T_c, lattice parameters, size of crystallite and grain size has been investigated. X-ray diffraction, electron micro-probe, scanning electron microscope and IR spectra, have been used in our investigation. The results show that the transition temperature T_c, electron-hole jump rate and lattice parameters (a, b) have minimum values at x = 0.2, while c increases to maximum at x = 0.2. The size of crystallite, the …

Study Of Density Of Localized States In A-Se_{100 - X}Sb_X Films By Space Charge Limited Conduction Measurements, V. S. Kushwaha, Santosh Kumar, A. Kumar

Turkish Journal of Physics

The present paper reports dc conductivity measurements at high electric fields in vacuum evaporated a-Se_{1 - x}Sb_x (x = 0, 0.02, 0.04, 0.06) thin films. At high fields (~ 10^4 V .cm^{-1}), current can be modelled by the theory of space charge-limited conduction in the case of uniform distribution of localised states in the mobility gap of these materials. The addition of Sb in Se results in an increase in the density of localised states.

Dielectric Properties Of Industrial Polymer Composite Materials, Muhammad Akram, Athar Javed, Tasneem Zahra Rizvi

Turkish Journal of Physics

Frequency and temperature dependence of dielectric constant \varepsilon' and dielectric loss \varepsilon" in pure polyester resin and polymer composites with various types of glass fiber are studied in the frequency range 330 Hz-3 MHz and in the temperature range 25-150 °C. The experimental results show that \varepsilon' and \varepsilon'' increased with the addition of glass fiber in polyester resin. The value of \varepsilon' decreased with increasing frequency, which indicates that the major contribution to the polarization comes from orientation polarization. Dielectric loss peaks were also observed in the composite materials at high temperature due to T_g of polyester. The value …

The Effect Of Preparation Conditions On The Growth Rate Of Films, The Yield Of Precipitated Powder And The Dc Conductivity Of Polypyrrole, S. A. Saafan, M. M. Ayad, E. H. El-Ghazzawy

Turkish Journal of Physics

Polypyrrole (PPy) was prepared by a chemical method by using oxidizing agents ferric chloride and potassium persulphate, both as films and pellets. The effect of various variables-such as aging of the films, film thickness, ratios of the reactants and type of the sample (film or disc)-on DC conductivity were investigated. The results from samples prepared with ferric chloride exhibited an increase in conductivity with increasing concentration of oxidizing agent to a certain ratio, above which a slight decrease occurs. Whereas in the case of using potassium persulphate as the oxidizing agent, a decrease in conductivity occurs with increasing its concentration. …

Origins Of Reverse Bias Currents In A Typical Bpw34 Photodiode, Habi̇be Bayhan, Şadan Özden

Turkish Journal of Physics

Measurements of the dark reverse current in a typical BPW34 silicon photodiode have been made in the temperature range 100-300 K at various reverse bias voltages ranging from 0 to 60 V. Various transport models have been applied to analyze the temperature dependence of the reverse current-voltage data. We suggest that Bardeen's model for a modified Schottky-like interfacial junction, that takes into account the effect of interfacial localized states, can be satisfactorily applied to describe the reverse current-voltage characteristics at bias voltages below 50 V.

Unsteady Couette Flow With Heat Transfer Considering Ion-Slip, Hazem Ali Attia

Turkish Journal of Physics

The unsteady Couette flow of an electrically conducting, viscous, incompressible fluid bounded by two parallel non-conducting porous plates is studied with heat transfer taking ion-slip into consideration. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to a constant pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of ion-slip an uniform suction and injection on both the velocity and temperature distributions is examined.

Pre-Computation Approach To Nonlinear Simulations Of Deformable Objects, Jernej Barbic

Link Foundation Modeling, Simulation and Training Fellowship Reports

My research area involves building real-time interactive simulations of solid deformable objects. For example, liver tissue should defo1m realistically during a vi1tual surgery simulation. A virtual assembly simulation can catch airplane construction design flaws early on during the manufacturing process. Deformable objects are also useful in computer games, for example to model the motion of trees in the wind. Researchers in computational physics, mechanics, and applied mathematics have been developing algorithms for simulations of deformable objects for the past 40 years. However, the partial differential equations of solid continuum mechanics that govern deformations of physical objects are very involved and …

Applying Scenario-Based Design And Claim Analysis To The Design Of A Digital Library Of Geography Examination Resources, Yin-Leng Theng, Dion Hoe-Lian Goh, Ee Peng Lim, Zehua Liu, Ming Yin, Natalie Lee-San Pang, Patricia Bao-Bao Wong

Research Collection School Of Computing and Information Systems

This paper describes the application of Carroll’s scenario-based design and claims analysis as a means of refinement to the initial design of a digital library of geographical resources (GeogDL) to prepare Singapore students to take a national examination in geography. GeogDL is built on top of G-Portal, a digital library providing services over geospatial and georeferenced Web content. Beyond improving the initial design of GeogDL, a main contribution of the paper is making explicit the use of Carroll’s strong theory-based but undercapitalized scenario-based design and claims analysis that inspired recommendations for the refinement of GeogDL. The paper concludes with an …

A Multi-Agent Approach For Solving Optimization Problems Involving Expensive Resources, Hoong Chuin Lau, H. Wang

Research Collection School Of Computing and Information Systems

In this paper, we propose a multi-agent approach for solving a class of optimization problems involving expensive resources, where monolithic local search schemes perform miserably. More specifically, we study the class of bin-packing problems. Under our proposed Fine-Grained Agent System scheme, rational agents work both collaboratively and selfishly based on local search and mimic physics-motivated systems. We apply our approach to a generalization of bin-packing - the Inventory Routing Problem with Time Windows - which is an important logistics problem, and demonstrate the efficiency and effectiveness of our approach.

Neural Network-Based Control Of Nonlinear Discrete-Time Systems In Non-Strict Form, Jagannathan Sarangapani, Zheng Chen, Pingan He

Electrical and Computer Engineering Faculty Research & Creative Works

A novel reinforcement learning-based adaptive neural network (NN) controller, also referred as the adaptive-critic NN controller, is developed to deliver a desired tracking performance for a class of non-strict feedback nonlinear discrete-time systems in the presence of bounded and unknown disturbances. The adaptive critic NN controller architecture includes a critic NN and two action NNs. The critic NN approximates certain strategic utility function whereas the action neural networks are used to minimize both the strategic utility function and the unknown dynamics estimation errors. The NN weights are tuned online so as to minimize certain performance index. By using gradient descent-based …

Deuterium Nmr Studies Of Segmental Dynamics Of Anopore-Adsorbed Poly(Methyl Acrylate), Macduff O. Okuom, Frank D. Blum

Chemistry Faculty Research & Creative Works

Studies of segmental dynamics of polymers at interfaces provide a basis for understanding the properties of composite materials. Interfacial phenomena in multi-phase systems need to be understood as devices made from multi-phase polymeric systems become smaller. Various techniques have been used to investigate interfacial polymers at the air-polymer-solid interface; for example, ellipsometry,1 X-ray,2 and neutron reflectometry.3 These techniques typically characterize the structure (often the thickness) of the polymer layer and are normally used to determine the glass-transition temperature (Tg) through a break in the thicknesstemperature curve. There have been a few reports where the dynamics of polymers at the surface-air …

The Inns President's Welcome, Donald C. Wunsch

Electrical and Computer Engineering Faculty Research & Creative Works

No abstract provided.

A Brief History Of Bioperl, Colin Crossman, Arti K. Rai

Faculty Scholarship

Large-scale open-source projects face a litany of pitfalls and difficulties. Problems of contribution quality, credit for contributions, project coordination, funding, and mission-creep are ever-present. Of these, long-term funding and project coordination can interact to form a particularly difficult problem for open-source projects in an academic environment.

BioPerl was chosen as an example of a successful academic open-source project. Several of the roadblocks and hurdles encountered and overcome in the development of BioPerl are examined through the telling of the history of the project. Along the way, key points of open-source law are explained, such as license choice and copyright.

The …

Finding And Maintaining Rigid Components, Audrey Lee, Ileana Streinu, Louis Theran

Computer Science: Faculty Publications

We give the first complete analysis that the complexity of finding and maintaining rigid components of planar bar-and-joint frameworks and arbitrary d-dimensional body-and-bar frameworks, using a family of algorithms called pebble games, is O(n2). To this end, we intro- duce a new data structure problem called union pair- find, which maintains disjoint edge sets and supports pair-find queries of whether two vertices are spanned by a set. We present solutions that apply to generalizations of the pebble game algorithms, beyond the original rigidity motivation.

Pseudo-Triangulations, Rigidity And Motion Planning, Ileana Streinu

Computer Science: Faculty Publications

This paper proposes a combinatorial approach to planning non-colliding trajectories for a polygonal bar-and-joint framework with n vertices. It is based on a new class of simple motions induced by expansive one-degree-of-freedom mechanisms, which guarantee noncollisions by moving all points away from each other. Their combinatorial structure is captured by pointed pseudo-triangulations, a class of embedded planar graphs for which we give several equivalent characterizations and exhibit rich rigidity theoretic properties. The main application is an efficient algorithm for the Carpenter's Rule Problem: convexify a simple bar-and-joint planar polygonal linkage using only non-self-intersecting planar motions. A step of the algorithm …

Splitting Of Vector Bundles On Punctured Spectrum Of Regular Local Rings, Mahdi Majidi-Zolbanin

Dissertations, Theses, and Capstone Projects

In this dissertation we study splitting of vector bundles of small rank on punctured spectrum of regular local rings. We give a splitting criterion for vector bundles of small rank in terms of vanishing of their intermediate cohomology modules Hⁱ(U, E)_{2_i_n−3}, where n is the dimension of the regular local ring. This is the local analog of a result by N. Mohan Kumar, C. Peterson, and A. Prabhakar Rao for splitting of vector bundles of small rank on projective spaces.

As an application we give a positive answer (in a special case) to a conjecture …

The Correlation Between Internal & External Markers For Abdominal Tumors: Implications For Respiratory Gating, David P. Gierga, Johanna Brewer, Gregory C. Sharp, Margrit Betke, Christopher G. Willett, George T.Y. Chen

Computer Science: Faculty Publications

Purpose: The correlation of the respiratory motion of external patient markers and abdominal tumors was examined. Data of this type are important for image-guided therapy techniques, such as respiratory gating, that monitor the movement of external fiducials.

Methods and Materials: Fluoroscopy sessions for 4 patients with internal, radiopaque tumor fiducial clips were analyzed by computer vision techniques. The motion of the internal clips and the external markers placed on the patient’s abdominal skin surface were quantified and correlated.

Results: In general, the motion of the tumor and external markers were well correlated. The maximum amount of peak-to-peak craniocaudal tumor motion …

Agricultural Pollution Of Ground Water Near Gilbertville, Iowa, Paula Frost Even

Dissertations and Theses @ UNI

The transport of nutrients and contaminants from farm fields to the aquifer surrounding Gilbertville, Iowa, was monitored over a six-month period. The Gilbertville city water supply is obtained from the Silurian-Devonian aquifer, which has been determined to be highly susceptible to contamination because of the hydraulic characteristics of the aquifer and the overlying materials that allow contaminants to move to the aquifer fairly quickly. Monthly water samples were collected from April through September of 2004 from 26 private wells and 8 surface water sites within the source water protection area of the town's three wells. Each sample was tested for …

Locality, Network Control And Anomaly Detection, Jim Binkley

Computer Science Faculty Publications and Presentations

Ourmon is a near real-time network monitoring and anomaly detection system that captures packets using port-mirroring on Ethernet switches. It primarily displays data via web graphics using either RRDTOOL stripcharts or via histograms for top talker style graphs. We have developed a theory that network scanning launched primarily by worm programs including TCP and UDP scanners may be caught by monitoring network control data including TCP control packets (SYNS, FINS, RESETS) and ICMP errors, or by monitoring certain carefully chosen metadata such as the flow count itself. In this paper we concentrate on TCP and present a ”flow tuple” focused …

Systems Analysis And Design: Should We Be Researching What We Teach?, A. Bajaj, D. Batra, A. Hevner, J. Parsons, Keng Siau

Research Collection School Of Computing and Information Systems

A guiding premise of academic scholarship is that knowledge gained from first-hand research experience is disseminated to students via the classroom. However, that valuable connection is lost when professors are not researching what they teach. In this paper, we explore issues of mismatch between teaching and research in the Information Systems (IS) discipline. Specifically, while systems analysis and design (SA&D) is an integral topic in IS curricula, this topic is the research specialty of few IS professors. This situation is reflected by the low number of research publications in this area; particularly in the leading mainstream IS journals. We characterize …

Robust Temporal Constraint Networks, Hoong Chuin Lau, Thomas Ou, Melvyn Sim

Research Collection School Of Computing and Information Systems

In this paper, we propose the Robust Temporal Constraint Network (RTCN) model for simple temporal constraint networks where activity durations are bounded by random variables. The problem is to determine whether such temporal network can be executed with failure probability less than a given 0 ≤ E ≤ 1 for each possible instantiation of the random variables, and if so. how one might find a feasible schedule with each given instantiation. The advantage of our model is that one can vary the value of ∊ to control the level of conservativeness of the solution. We present a computationally tractable and …

Exploring Bit-Difference For Approximate Knn Search In High-Dimensional Databases, Bin Cui, Heng Tao Shen, Jialie Shen, Kian-Lee Tan

Research Collection School Of Computing and Information Systems

In this paper, we develop a novel index structure to support effcient approximate k-nearest neighbor (KNN) query in high-dimensional databases. In high-dimensional spaces, the computational cost of the distance (e.g., Euclidean distance) between two points contributes a dominant portion of the overall query response time for memory processing. To reduce the distance computation, we first propose a structure (BID) using BIt-Difference to answer approximate KNN query. The BID employs one bit to represent each feature vector of point and the number of bit-difference is used to prune the further points. To facilitate real dataset which is typically skewed, we enhance …

Security Of An Ill-Posed Operator Based Scheme For Image Authentication, Yongdong Wu, Robert H. Deng

Research Collection School Of Computing and Information Systems

This letter analyzes the security of an image authentication scheme which exploits the instability of an ill-posed operator. Since the ill-posed operator produces only a limited number of authentic images regardless of the number of watermarks, an attacker can impersonate an image owner to generate authentic images at a high probability. Our experiments demonstrate that our attack is both practical and effective.