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Mechanical Properties of Polymer Modified Mortar

Mechanical Properties of Polymer Modified Mortar

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Date: August 2002
Creator: Palos, Artemio
Description: The mechanical properties of the polymer-modified mortar are markedly improved over conventional cement mortar. We utilized recycled ABS in powder form and a polymer latex emulsion, polymer percentage ranges from 0 to 25 percent by polymer/cement ratio were investigated. The mechanical properties investigated were compression strength and adhesion strength. Compression strength effects did not have an impact on adhesion strength. Adhesion strength was calculated with pullout testing apparatus designed by the author. Results indicate that recycled ABS had a lower adhesive strength than the acrylic latex emulsion and the base mortar, but did increase in adhesive strength when mixed with maleic-anhydride. The adhesive strength was investigated for a Fiber Reinforced Polymer (FRP) made of an "E" glass fiber that is a continuous strand roving oriented and pre-tensioned longitudinally in an isopthalic polyester matrix material. The FRP rebar was compared to standard steel rebars, and found that the standard steel corrugated rebar had a higher adhesive strength, due to mechanical interlocking. This was clarified by measurements using a smooth steel rebar. Characterization of the polymer-modified mortar was conducted by pore analysis and scanning electron microscopy. Scanning Electron Microscopy was implemented to view the polymer particles, the cement fibrils formed by the ...
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Mechanics and Mechanisms of Creep and Ductile Fracture

Mechanics and Mechanisms of Creep and Ductile Fracture

Date: August 2013
Creator: Srivastava, Ankit
Description: The main aim of this dissertation is to relate measurable and hopefully controllable features of a material's microstructure to its observed failure modes to provide a basis for designing better materials. The understanding of creep in materials used at high temperatures is of prime engineering importance. Single crystal Ni-based superalloys used in turbine aerofoils of jet engines are exposed to long dwell times at very high temperatures. In contrast to current theories, creep tests on Ni-based superalloy specimens have shown size dependent creep response termed as the thickness debit effect. To investigate the mechanism of the thickness debit effect, isothermal creep tests were performed on uncoated Ni-based single crystal superalloy sheet specimens with two thicknesses and under two test conditions: a low temperature high stress condition and a high temperature low stress condition. At the high temperature, surface oxidation induced microstructural changes near the free surface forming a layered microstructure. Finite element calculations showed that this layered microstructure gave rise to local changes in the stress state. The specimens also contained nonuniform distribution of initial voids formed during the solidification and homogenization processes. The experiments showed that porosity evolution could play a significant role in the thickness debit effect. This ...
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Mechanism and the Effect of Microwave-Carbon Nanotube Interaction

Mechanism and the Effect of Microwave-Carbon Nanotube Interaction

Date: December 2005
Creator: Ye, Zhou
Description: A series of experimental results about unusual heating of carbon nanotubes by microwaves is analyzed in this dissertation. Two of vibration types, cantilever type (one end is fixed and the other one end is free), the second type is both ends are fixed, have been studied by other people. A third type of forced vibration of carbon nanotubes under an alternating electromagnetic field is examined in this paper. Heating of carbon nanotubes (CNTs) by microwaves is described in terms of nonlinear dynamics of a vibrating nanotube. Results from the model provide a way to understand several observations that have been made. It is shown that transverse vibrations of CNTs during microwave irradiation can be attributed to transverse parametric resonance, as occurs in the analysis of Melde's experiment on forced longitudinal vibrations of a stretched elastic string. For many kinds of carbon nanotubes (SWNT, DWNT, MWNT, ropes and strands) the resonant parameters are found to be located in an unstable region of the parameter space of Mathieu's equation. Third order wave equations are used to qualitatively describe the effects of phonon-phonon interactions and energy transfer from microwaves to CNTs. This result provides another way to input energy from microwaves to carbon ...
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A mechanism for richer representation of videos for children: Calibrating calculated entropy to perceived entropy

A mechanism for richer representation of videos for children: Calibrating calculated entropy to perceived entropy

Date: August 2001
Creator: Kearns, Jodi
Description: This study explores the use of the information theory entropy equation in representations of videos for children. The calculated rates of information in the videos are calibrated to the corresponding perceived rates of information as elicited from the twelve 7 to 10 year old girls who were shown video documents. Entropy measures are calculated for several video elements: set time, set incidence, verbal time, verbal incidence, set constraint, nonverbal dependence, and character appearance. As hypothesized, mechanically calculated entropy measure (CEM) was found to be sufficiently similar to perceived entropy measure (PEM) made by children so that they can be used as useful and predictive elements of representations of children’s videos. The relationships between the CEM and the PEM show that CEM could stand for PEM in order to enrich representations for video documents for this age group. Speculations on transferring the CEM to PEM calibration to different age groups and different document types are made, as well as further implications for the field of information science.
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The Mechanism of Action of Immune Guinea Pig Serum in Staphylococcus Infection in Mice

The Mechanism of Action of Immune Guinea Pig Serum in Staphylococcus Infection in Mice

Date: August 1958
Creator: Moore, James Walter
Description: It is the aim of this work to study the role, if any, of C'4 in the immune response against Staphylococcus aureus infections.
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Mechanisms Affecting Bench Press Throw Performance while Using a Counter-Balanced Smith Machine

Mechanisms Affecting Bench Press Throw Performance while Using a Counter-Balanced Smith Machine

Date: May 2011
Creator: Buddhadev, Harsh
Description: The use of a counter-balance weight system of a Smith machine affects measures of bench press throw performance. Twenty-four men performed bench press throws at 30% of their one-repetition maximum under four different conditions: 1) counter-balance and rebound movement (RC), 2) no counter-balance and rebound movement (RNC), 3) counter-balance and concentric only movement (CC), and 4) no counter-balance and concentric only movement (CNC). Peak power, force, and concentric and eccentric velocities were measured using a linear accelerometer; and peak ground reaction force (GRF) was measured using a forceplate. Peak measures for concentric and eccentric velocities showed that NCB> CB and RBT > CBT. Peak GRF measures showed CB > NCB and RBT > CBT. The lower performance measures for CB were likely due to an increase in the net external load when the barbell accelerates faster than the gravitational constant causing the counter-balance weight becomes ineffective.
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Mechanisms of Methoxide Ion Substitution and Acid- Catalyzed Z/E Isomerization of N-Methoxyimines

Mechanisms of Methoxide Ion Substitution and Acid- Catalyzed Z/E Isomerization of N-Methoxyimines

Access: Use of this item is restricted to the UNT Community.
Date: December 2001
Creator: Dolliver, Debra D.
Description: The second order rate constants for nucleophilic substitution by methoxide of (Z)- and (E)-O-methylbenzohydroximoyl fluorides [C6H4C(F)=NOCH3] with various substituents on the phenyl ring [p-OCH3 (1h, 2h), p-CH3 (1g, 2g), p-Cl (1f, 2f), p-H (1e, 2e), (3,5)-bis-CF3 (1i, 2i)] in 90:10 DMSO:MeOH have been measured. A Hammett plot of these rate constants vs σ values gave positive ρ values of 2.95 (Z isomer) and 3.29 (E isomer). Comparison of these rates with methoxide substitution rates for Omethylbenzohydroximoyl bromide [C6H4C(Br)=NOCH3] and Omethylbenzohydroximoyl chloride [C6H4C(Cl)=NOCH3] reveal an element effect for the Z isomers of Br:Cl:F(1e) = 2.21:1.00:79.7 and for the E isomers of Cl:F(2e) = 1.00:18.3. With the p-OCH3-imidoyl halides the following element effects are found: Br:Cl:F(1h) = 2.78:1.00:73.1 for the Z isomer and Br:Cl:F(2h) = 1.97:1.00:12.1 for the E isomer. Measurement of activation parameters revealed ∆S≠ = -17 eu for 1e and ∆S≠ = -9.9 eu for 2e. Ab initio calculations (HF/6-31+G*, MP2/6-31+G*//HF/6-31+G*, B3LYP/6- 31+G*//HF/6-31+G*, HF-SCIPCM/6-31+G*//HF/6-31+G*) were performed to define the reaction surface. These calculations demonstrate a relatively large barrier for nucleophilic attack in relation to halogen loss and support the experimental findings that this reaction proceeds by an addition-elimination mechanism (AN# + DN). The imidoyl fluorides have been used to synthesize ...
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Mechanisms of Ordered Gamma Prime Precipitation in Nickel Base Superalloys

Mechanisms of Ordered Gamma Prime Precipitation in Nickel Base Superalloys

Date: May 2011
Creator: Singh, Antariksh Rao Pratap
Description: Commercial superalloys like Rene88DT are used in high temperature applications like turbine disk in aircraft jet engines due to their excellent high temperature properties, including strength, ductility, improved fracture toughness, fatigue resistance, enhanced creep and oxidation resistance. Typically this alloy's microstructure has L12-ordered precipitates dispersed in disordered face-centered cubic γ matrix. A typical industrially relevant heat-treatment often leads to the formation of multiple size ranges of γ¢ precipitates presumably arising from multiple nucleation bursts during the continuous cooling process. The morphology and distribution of these γ′ precipitates inside γ matrix influences the mechanical properties of these materials. Therefore, the study of thermodynamic and kinetic factors influencing the evolution of these precipitates and subsequent effects is both relevant for commercial applications as well as for a fundamental understanding of the underlying phase transformations. The present research is primarily focused on understanding the mechanism of formation of different generations of γ′ precipitates during continuous cooling by coupling scanning electron microscopy (SEM), energy filtered TEM and atom probe tomography (APT). In addition, the phase transformations leading to nucleation of γ′ phase has been a topic of controversy for decades. The present work, for the first time, gives a novel insight into the mechanism ...
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Mechanisms of rapid receptive field reorganization in rat spinal cord

Mechanisms of rapid receptive field reorganization in rat spinal cord

Date: August 2002
Creator: Vu, Hung
Description: Rapid receptive field (RF) reorganization of somatosensory neurons in the rat dorsal horn was examined using extracellular single unit recording. Subcutaneous injection of lidocaine into RFs of dorsal horn neurons results in expansion of their RFs within minutes. The expanded RFs appear adjacent to or/and proximal to original RFs. Out of 63 neurons tested, 36 (58%) show RF reorganization. The data suggest that dorsal horn of spinal cord is one of the initial sites for RF reorganization. The neural mechanisms of this effect are not well understood. We propose that changes in biophysical properties (membrane conductance, length constant) of the neurons resulting from lidocaine injection contribute to RF reorganization. Iontophoretic application of glutamate onto dorsal horn neurons that show lidocaine induced RF's expansion were used to test the model. Application of glutamate produced reduction of reorganized RFs in 9 of 20 (45%) tested cells. Application of NBQX produced no effect on either original or expanded RFs indicate that RF shrinkage effects of glutamate involve NMDA receptors. The results are consistent with the prediction of the proposed model. Subcutaneous injection of capsaicin into tactile RFs of low threshold mechanoreceptive dorsal horn neurons produced no effect on the RF sizes that are ...
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Mechanization of Aircraft Performance

Mechanization of Aircraft Performance

Date: 1956
Creator: Cotten, Frances Patterson
Description: The purpose of this paper is to describe the mechanization of the basic equations of motion for the performance and maneuver characteristics of an airplane with some simplifications which render solutions more practicable. The results of a study made to program these equations for calculation by the IBM MODEL 650 digital computer are presented as well as the steps to be taken in using this method of calculation.
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