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The Global ETD Search service is a free service for researchers
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Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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Showing 11 to 18 of 18 (0.114 seconds)Spelling suggestions: "subject:"other engineering cience anda matematerials"" "subject:"other engineering cience anda datenmaterials""
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HIGH PERFORMANCE SILVER DIFFUSIVE MEMRISTORS FOR FUTURE COMPUTINGMidya, Rivu 24 March 2017 (has links)
Sneak path current is a significant remaining obstacle to the utilization of large crossbar arrays for non-volatile memories and other applications of memristors. A two-terminal selector device with an extremely large current-voltage nonlinearity and low leakage current could solve this problem. We present here a Ag/oxide-based threshold switching (TS) device with attractive features such as high current-voltage nonlinearity (~1010), steep turn-on slope (less than 1 mV/dec), low OFF-state leakage current (~10-14 A), fast turn ON/OFF speeds (<75/250 ns), and good endurance (>108 cycles). The feasibility of using this selector with a typical memristor has been demonstrated by physically integrating them into a multilayered 1S1R cell. Structural analysis of the nanoscale crosspoint device suggests that elongation of a Ag nanoparticle under voltage bias followed by spontaneous reformation of a more spherical shape after power off is responsible for the observed threshold switching of the device. Such mechanism has been quantitatively verified by the Ag nanoparticle dynamics simulation based on thermal diffusion assisted by bipolar electrode effect and interfacial energy minimization.
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Engineering of Earth-Abundant Electrochemical CatalystsRodene, Dylan D 01 January 2019 (has links)
Alternative energy research into hydrogen production via water electrolysis addresses environmental and sustainability concerns associated with fossil fuel use. Renewable-powered electrolyzers are foreseen to produce hydrogen if energy and cost requirements are achieved. Electrocatalysts reduce the energy requirements of operating electrolyzers by lowering the reaction kinetics at the electrodes. Platinum group metals (PGMs) tend to be utilized as electrocatalysts but are not readily available and are expensive. Ni1-xMox alloys, as low-cost and earth-abundant transition metal nanoparticles (NPs), are emerging as promising electrocatalyst candidates to replace expensive PGM catalysts in alkaline media. Pure-phase cubic and hexagonal Ni1-xMox alloy NPs with increasing Mo content (0–11.4%) were synthesized as electrocatalysts for the hydrogen evolution reaction (HER). In general, an increase in HER activity was observed with increasing Mo content. The cubic alloys were found to exhibit significantly higher HER activity in comparison to the hexagonal alloys, attributed to the higher Mo content in the cubic alloys. However, the compositions with similar Mo content still favored the cubic phase for higher activity. To produce a current density of -10 mA/cm2, the cubic and hexagonal alloy NPs require over-potentials ranging from -62 to -177 mV and -162 to -242 mV, respectively. The cubic alloys exhibited over-potentials that rival commercial Pt-based electrocatalysts (-68 to -129 mV at -10 mA/cm2). The cubic Ni0.934Mo0.066 alloy NPs showed the highest alkaline HER activity of the electrocatalysts studied and therefore a patent application was submitted.
Bulk Ni–Mo phases have been known as electrocatalysts for the HER for decades, while recently transition metal phosphides (TMPs) have emerged as stable and efficient PGM alternatives. Specifically, Ni2P has demonstrated good HER activity and improved stability for both alkaline and acidic media. However, Ni2P electrocatalysts are a compromise between earth-abundance, performance (lower than Ni–Mo and PGMs) and stability. For the first time Ni–Mo–P electrocatalysts were synthesized with varying atomic ratios of Mo as electrocatalysts for alkaline HER. Specific phases, compositions and morphologies were studied to understand the intrinsic properties of TMPs leading to high HER activity. The Ni1.87Mo0.13P and Ni10.83Mo1.17P5 NPs were shown to be stable for 10 h at –10 mA cm-2 with over-potentials of –96 and –82 mV in alkaline media, respectively. The Ni1.87Mo0.13P and Ni10.83Mo1.17P5 NPs exhibited an improved performance over the synthesized Ni2P sample (–126 mV at –10 mA cm-2), likely a result of the overall phosphorous content and hetero-structured morphologies. A strong correlation between phase dependence and the influence of Mo on HER activity needs to be further investigated.
Furthermore, understanding the intrinsic properties of electrocatalysts leading to high water splitting performance and stability can apply electrocatalysts in other research applications, such as photoelectrochemical (PEC) water splitting, water remediation and sustainable chemical processing applications. Contributions to photocatalytic water remediation and electrochemical chlorinated generation to halogenate pyridone-based molecules are reported. Electrochemical techniques were developed and reported herein to aid in understanding electrochemical performance, chemical mechanisms and the stability of electrocatalysts at the electrode-electrolyte interfaces.
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A STUDY TO EVALUATE NON-UNIFORM PHASE MAPS IN SHAPE MEMORY ALLOYS USING FINITE ELEMENT METHODMotte, Naren 01 January 2015 (has links)
The unique thermo-mechanical behavior of Shape Memory Alloys (SMAs), such as their ability to recover the original shape upon heating or being able to tolerate large deformations without undergoing plastic transformations, makes them a good choice for actuators.
This work studies their application in the aerospace and defense industries where SMA components can serve as release mechanisms for gates of enclosures that have to be deployed remotely. This work provides a novel approach in evaluating the stress and heat induced change of phase in a SMA, in terms of the transformation strain tensor. In particular, the FEA tool
ANSYS has been used to perform a 2-D analysis of a Cu-Al-Zn-Mn SMA specimen undergoing a nontraditional loading path in two steps with stress and heating loads. In the first load step, tensile displacement is applied, followed by the second load step in which the specimen is heated while the end displacements are held constant.
A number of geometric configurations are examined under the two step loading path. Strain results are used to calculate transformation strain which provides a quantitative measure of phase at a material point; when transformation strain is zero, the material point is either twinned martensite, or austenite depending on the temperature. Transformation strain value of unity corresponds to detwinned martensite. A value between zero and one indicates mixed phase.
In this study, through two step loading in conjunction with transformation strain calculations, a method for mapping transient non-uniform distribution of phases in an SMA is introduced.
Ability to obtain drastically different phase distributions under same loading path by modifying the geometry is demonstrated. The failure behavior of SMAs can be designed such that the load level the crack initiates and the path it propagates can be customized.
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EFFECT OF MOISTURE ABSORPTION ON THE SINTER QUALITY OF CENTRAL SOLENOID (CS) COIL PACKMohammed, Zeshaan Sher 01 December 2010 (has links)
Fusion energy has been said to be the solution to all the world’s energy problems. The International Thermonuclear Experimental Reactor (ITER) is the flagship project to demonstrate the feasibility of fusion energy. The Central Solenoid (CS), an important component of the reactor, is needed to induce plasma current, initiate, ramp-up, ramp-down, and sustain plasma in a very controlled manner. In order to achieve this, the CS coil packs must be manufactured under controlled conditions. The CS conductor is an advanced cable-in-conduit Nb3Sn superconductor. The CS cable will be made in long continuous sections but with thousands of meter of cable needed, splices will have to be made in the field during construction of the ITER reactor. With the ends of the CS cable being exposed to the environment for an unspecified amount of time, concern has been expressed about the effect of the cable exposure on the quality of the splice. As a result an experimental program was devised to replicate and expedite the environmental damage the cable may see while in the field.
The CS cable samples were exposed to 100% humidity at 60, 80, and 100oC for periods ranging from one week to four weeks. Once the samples were soaked for a period of time they were then sintered as would be done in the field. After sintering the mechanical tests were done to determine the load required to push the sintered strands out of the copper sleeve. Initial results obtained with samples having the sleeve thickness of 1.25mm (0.05in) were inconclusive due to the presence of a fold in the copper sleeve formed during the compaction of the sleeve around the cable. To prevent the fold formation, another set of samples were prepared with thicker copper sleeve of 5mm (0.20in).
Results from these samples yielded data that was more conclusive and showed a possible correlation between aging temperature and sintering strength. The experimental data suggests that the thin oxide layer formed during the elevated temperature soak at 100% humidity may even be beneficial to the sinter quality.
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Integrating steel slag aggregates into asphalt paving by harmonizing availability, quality, economics, and the environmentMurphy, Timothy R. 12 May 2023 (has links) (PDF)
This thesis provides guidance on how to balance matters related to the environmental stewardship, market sources, origin and uses, material properties, performance, and economic impact of using slag materials in pavements. The literature on this topic provides numerous references on the use of slag materials for specific applications, and this thesis aims to make use of those references along with other data from the author to describe slag materials from a holistic perspective and provide some suggestions for balancing several factors that impact optimal use of this resource within pavement structures. Discussion is given to the increased importance of recycling of other materials into the infrastructure and benchmarking those materials against recycling of steel slag. Ensuring adequate performance of pavements while increasing the use of recycled materials and maintaining safety is a successful measure relative to green initiatives and occurs only with careful planning, cooperation, and field validations.
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Mode I Fracture Toughness of Eight-Harness-Satin Carbon Cloth Weaves for Co-cured and Post-bonded LaminatesSmith, Josh E 01 December 2013 (has links) (PDF)
Mode I interlaminar fracture of 3k 8-Harness-Satin Carbon cloth, with identical fill and weft yarns, pre-impregnated with Newport 307 resin was investigated through the DCB test (ASTM D5528). Crack propagations along both the fill and weft yarns were considered for both post-bonded (co-bonded) and co-cured laminates. A patent-pending delamination insertion method was compared to the standard Teflon film option to assess its applicability to mode I fracture testing. The Modified Beam Theory, Compliance Calibration method, and Modified Compliance Calibration method were used for comparative purposes for these investigations and to evaluate the validity of the proposed Equivalent Stiffness (EQS) method. Crack propagation, in all specimens, proceeded in a run-arrest manner for both delamination directions. Energy dissipation in the form of transverse yarn debonding, matrix deformation, and out of plane crack growth was witnessed for specimens with delaminations along weft yarns. A complete comparison between post-bonded and co-cured laminates was not achieved. The patent pending delamination insertion method was found to cause fewer instances of non-linear crack initiation behavior than the Teflon insert and, when non-linear behavior did occur, it was less prevalent. The EQS method was found to achieve fracture toughness values within 5% of the other three data reduction methods for 63% of the propagation values and achieved conservative values for over 33% of the propagations. Suggestions for future studies aimed at completing the comparisons above are provided in Chapter 5.
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BBT Acoustic Alternative Top Bracing CADD Data Set-NoRev-2022Jun28Hemphill, Bill 22 July 2022 (has links)
This electronic document file set consists of an overview presentation (PDF-formatted) file and companion video (MP4) and CADD files (DWG & DXF) for laser cutting the ETSU-developed alternate top bracing designs and marking templates for the STEM Guitar Project’s BBT (OM-sized) standard acoustic guitar kit. The three (3) alternative BBT top bracing designs in this release are (a) a one-piece base for the standard kit's (Martin-style) bracing, (b) 277 Ladder-style bracing, and (c) an X-braced fan-style bracing similar to traditional European or so-called 'classical' acoustic guitars.
The CADD data set for each of the three (3) top bracing designs includes (a) a nominal 24" x 18" x 3mm (0.118") Baltic birch plywood laser layout of (1) the one-piece base with slots, (2) pre-radiused and pre-scalloped vertical braces with tabs to ensure proper orientation and alignment, and (3) various gages and jigs and (b) a nominal 15" x 20" marking template.
The 'provided as is" CADD data is formatted for use on a Universal Laser Systems (ULS) laser cutter digital (CNC) device. Each CADD drawing is also provided in two (2) formats: Autodesk AutoCAD 2007 .DWG and .DXF R12. Users should modify and adapt the CADD data as required to fit their equipment. This CADD data set is released and distributed under a Creative Commons license; users are also encouraged to make changes o the data and share (with attribution) their designs with the worldwide acoustic guitar building community.
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BBT Acoustic Alternative Top Bracing CADD Data Set-NoRev-2022Jun28Hemphill, Bill 22 July 2022 (has links)
This electronic document file set consists of an overview presentation (PDF-formatted) file and companion video (MP4) and CADD files (DWG & DXF) for laser cutting the ETSU-developed alternate top bracing designs and marking templates for the STEM Guitar Project’s BBT (OM-sized) standard acoustic guitar kit. The three (3) alternative BBT top bracing designs in this release are (a) a one-piece base for the standard kit's (Martin-style) bracing, (b) 277 Ladder-style bracing, and (c) an X-braced fan-style bracing similar to traditional European or so-called 'classical' acoustic guitars.
The CADD data set for each of the three (3) top bracing designs includes (a) a nominal 24" x 18" x 3mm (0.118") Baltic birch plywood laser layout of (1) the one-piece base with slots, (2) pre-radiused and pre-scalloped vertical braces with tabs to ensure proper orientation and alignment, and (3) various gages and jigs and (b) a nominal 15" x 20" marking template.
The 'provided as is" CADD data is formatted for use on a Universal Laser Systems (ULS) laser cutter digital (CNC) device. Each CADD drawing is also provided in two (2) formats: Autodesk AutoCAD 2007 .DWG and .DXF R12. Users should modify and adapt the CADD data as required to fit their equipment. This CADD data set is released and distributed under a Creative Commons license; users are also encouraged to make changes o the data and share (with attribution) their designs with the worldwide acoustic guitar building community.
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