Engineering Commons^™

Excitation And De-Excitation Mechanisms Of Er-Doped Gaas And Algaas, David W. Elsaesser

Theses and Dissertations

Electrical and optical characterization have been performed on GaAs and Al_xGa_1-xAs samples doped with Er either by ion implantation or during Molecular Beam Epitaxial (MBE) growth. Deep Level Transient Spectroscopy (DLTS) and Temperature-Dependent Hall Effect (TDH) measurements indicated the presence of two hole traps in Er-doped GaAs, at 35 and 360 meV above the valence band maximum. The former (shallower) center was thought to be due to Er substituting for a Ga atom (Er_Ga) and giving rise to an isoelectronic impurity potential. The second center was attributed to an Er atom occupying an interstitial …

Non-Linear Finite Element Analysis Of Reinforced Concrete Beams, Wael Mohamed El-Dessouki

Archived Theses and Dissertations

No abstract provided.

Prediction Of Paper Color: A Process Simulation Approach, Mayank Chaturvedi

Masters Theses

A simulation model was developed for a dye mixing process and for the prediction of the optical properties of the paper. The model was integrated with the MAPPS (Modular Analysis of Pulp and Paper Systems) simulation software package. The model was validated using dyed handsheets made in a laboratory and dyed paper made on a pilot papermachine. Validation comprised of prediction of the optical properties of the handsheets and the machine-made paper which contained various combinations of three non-fluorescent dyes. Sheet reflectances were predicted at 20 nanometer intervals for discrete light wavelength range of 400 to 700 nanometers and verified …

Optimization Of Sodium Carbonate-Sodium Hydroxide Pulping Of Wheat Straw For Corrugating Medium Production, Irmak Yayin

Masters Theses

This study's primary objective was to present sodium carbonate pulping as an alternative to soda or lime pulping of wheat straw for corrugating medium production. If sodium carbonate pulping is comparable with soda pulping in terms of strength properties, it could be the preference of choice because the recovery of sodium carbonate is simpler requiring less capital investment. The two strength properties that were optimized with respect to total chemical charge, cooking time, and sodium hydroxide fraction in the cooking liquor were Concora crush resistance and STFI compressive strength. These are the two most important strength properties for the end …

Materially Nonlinear Finite Element Analyses Of Trusses And Slab-On-Grade Problems, Moayyad Moh'd Al-Nasra

Civil & Environmental Engineering Theses & Dissertations

The overall approach is to employ the finite-element method along with specified material models to account for material nonlinearity. This study includes two different applications: truss structures and slabs-on-grade.

Procedures for materially nonlinear analysis of truss structures, which apply for both determinate and indeterminate cases are proposed. The proposed procedures are simple and can handle a variety of different stress-strain functions, and the applied load does not have to be incremental. Proposed procedures results are verified with the output of NASTRAN.

A finite-element model for slab-on-grade is introduced. The concrete slab is represented by eight-node brick elements, and the joints …

The Multi-Fiber Arrangement In The Loom Of North - South Politics, Meeta Sehgal

Dissertations, Theses, and Masters Projects

No abstract provided.

Development Of An Automated Ultrasonic Inspection Cell For Detecting Subsurface Discontinuities In Cast Iron, John Scott Burningham

Dissertations and Theses @ UNI

Manufacturing of value added products by companies in todays global marketplace requires the vendors to meet certain minimum standards, SAE, ASTM, ISO, etc. In a global economy, as a manufacturer for the year 2000 and beyond, preferred vendors will become ISO 9000 certified to maintain a market share of produced goods.

An automated inspection cell was developed for the inspection of cast iron ports to detect subsurface discontinuities. The cell consists of an ultrasonic flaw detector (UFD), transducer, robot, immersion tank, computer, and software. Normal beam pulse-echo ultrasonic nondestructive testing is performed on each rough casting.

Using test blocks and …

A Wear Analysis Study Of Selected Alternative Foundry Tooling Materials Using Impact Abrasion Testing, L. Fred Vondra

Dissertations and Theses @ UNI

The purpose of this study was to simulate the wear characteristics of foundry tooling using an impact abrasion test apparatus. The wear characteristic was exhibited by non-metallic materials and was measured as a function of percentage weight loss and was benchmarked against Class 30 gray iron. The research question focused on whether or not a non-metallic material exists that exhibits comparable or superior wear characteristics to Class 30 gray iron for possible consideration as tooling materials for foundry applications. The information obtained adds to knowledge and is useful to foundry professionals in making tooling decisions.

The 34 test materials were …