Engineering Commons^™

Simulated Effects Of Reflective Mulch On Energy And Water Conservation In Semi-Arid Central California Greenhouses, T. Mehlitz, Ilhami Yildiz, S. Rahman, C. Hardin

BioResource and Agricultural Engineering

In addition to the labor, energy and water consumption are the two main cost drivers in current greenhouse systems. Consequently, considerable effort is expended to conserve energy and water, and look for alternative energy sources. Greenhouses in hot and arid regions also require large quantities of water for irrigation. Proper environmental management systems can significantly change the energy and moisture dynamics of greenhouse production systems. This study aims to focus on reducing energy and water consumption in semi-arid California greenhouses. Influences of mulch (having different reflectivities) on energy and water conservation were investigated. The reflectivity of mulch used as a …

Design And Evaluation Of A Greenhouse Interface For Climate Control Programming And Networking, G. Diaz, S. F. Kelly, Ilhami Yildiz

BioResource and Agricultural Engineering

At Cal Poly the motto is “Learn by Doing”. In the College of Agriculture, this is especially true and many of the labs provide an opportunity for students to implement this philosophy. Updated climate controls were installed in a series of greenhouses on the top floor of the Agricultural Science building that are used for student and faculty research projects. A Programmable Logic Controller (PLC) was installed to actuate the various vents, shading, heating, cooling and irrigation. A control program was developed to control and log temperatures and other operating parameters to monitor the greenhouse. An easy to use computer …

Simulated Effects Of Various Environmental Management Practices On Energy Consumption In Open And Confined Greenhouse Systems, Ilhami Yildiz, D. P. Stombaugh

BioResource and Agricultural Engineering

The objective of this study was to evaluate the effects of relative humidity, light management levels, minimum ventilation rates, CO₂ enrichment and canopy size on energy consumption in three different greenhouse systems (conventional, open-loop heat pump, and confined heat pump) in winter, spring, and summer months. No difference was observed in energy consumption with relative humidity set point levels in winter due to the already low relative humidity levels. Some differences were observed in spring and summer due to extra dehumidification required to maintain the inside relative humidity at lower levels. Energy consumption in summer was reduced up to …

Irrigation District Energy Survey, Charles M. Burt, Daniel J. Howes

BioResource and Agricultural Engineering

This survey was completed by ITRC on behalf of the California Energy Commission Public Interest Energy Research (PIER) Program. The purpose of the survey was to establish a benchmark for the present status of the pumping systems used by agricultural water districts in California and to determine the districts' needs. The needs discussed involve technical assistance, research grant and low-interest loan funding, and district-related policy issues. Thirty agricultural water districts were selected for the survey. These districts were selected based on energy use per acre of irrigated area, size, geographic location, and distribution infrastructure.

Engineering Research 2008, College Of Engineering, Michigan Technological University

Michigan Tech Engineering Magazine

Table of Contents

• Energy
• Air & Water
• Engineered Materials
• Sensing & Imaging
• Research Centers & Institutes
• People
• Innovation & Technology Transfer

Lectures On Computational Numerical Analysis Of Partial Differential Equations, James M. Mcdonough

Mechanical Engineering Textbook Gallery

From Chapter 1:

The purpose of these lectures is to present a set of straightforward numerical methods with applicability to essentially any problem associated with a partial differential equation (PDE) or system of PDEs independent of type, spatial dimension or form of nonlinearity.

Acuta Enews January 2008, Vol. 37, No. 1

ACUTA Newsletters

ln This lssue

From ACUTA Headquarters.................. Jeri A. Semer, CAE, ACUTA Executive Director

Board Report.............Riny Ledgerwood, San Diego State Univ., ACUTA Sec./Treasurer

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Thanks to 2007 Journal Advertisers

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Welcome New Members

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Rotor Position And Vibration Control For Aerospace Flywheel Energy Storage Devices And Other Vibration Based Devices, B. X. S. Alexander

ETD Archive

Flywheel energy storage has distinct advantages over conventional energy storage methods such as electrochemical batteries. Because the energy density of a flywheel rotor increases quadratically with its speed, the foremost goal in flywheel design is to achieve sustainable high speeds of the rotor. Many issues exist with the flywheel rotor operation at high and varying speeds. A prominent problem is synchronous rotor vibration, which can drastically limit the sustainable rotor speed. In a set of projects, the novel Active Disturbance Rejection Control (ADRC) is applied to various problems of flywheel rotor operation. These applications include rotor levitation, steady state rotation …

The Development Of An In Vivo Spinal Fusion Monitor Using Microelectromechanical (Mems) Technology To Create Implantable Microsensors, Lisa Anne Ferrara

ETD Archive

Surgical fusion of the spine is a conventional approach, and often last alternative, to the correction of a degenerative painful spinal segment. The procedure involves the surgical removal of the intervertebral disc at the problematic site, and the placement of a bone graft that is commonly harvested from the patients iliac crest and placed within the discectomized space. The surrounding bone is expected to incorporate and remodel into the bone graft to eventually provide an immobilized site. Spinal instrumentation often accompanies the bone graft to provide further immobility to the targeted site, thus augmenting the fusion process. However, the status …

Relationship Between Arch Height And Midfoot Joint Pressures During Gait, Dong Gil Lee

ETD Archive

A foot arch is a multi-segmented curved structure which acts as a spring during locomotion. It is well known that ligaments are important components contributing to this spring-like property of the arch. In addition, intrinsic and extrinsic foot muscles contribute to arch support. According to the windlass foot model, arch height and midfoot joint orientation change during gait. However, it is not known whether altered joint configurations result in increased joint stress during gait. If so, it is possible for there to be a "vicious cycle" in which joint stress increases as the arch height diminishes, which may then lead …

Broader Use Of Steel Slag Aggregates In Concrete, Jigar P. Patel

ETD Archive

Steel slag is an industrial byproduct obtained from the steel manufacturing industry. It is produced in large quantities during the steel-making operations which utilize Electric Arc Furnaces (EAF). Steel slag can also be produced by smelting iron ore in the Basic Oxygen Furnace (BOF). Steel slag can be used in the construction industry as aggregates in concrete by replacing natural aggregates. Natural aggregates are becoming increasingly scarce and their production and shipment is becoming more difficult. Steel slag is currently used as aggregate in hot mix asphalt surface applications, but there is a need for some additional work to determine …

High Intensity Laser Power Beaming For Wireless Power Transmission, Daniel Edward Raible

ETD Archive

This paper describes work supporting the development of a high intensity laser power beaming (HILPB) system for the purpose of wireless power transmission. The main contribution of this research is utilizing high intensity lasers to illuminate vertical multi-junction (VMJ) solar cells developed by NASA-GRC. Several HILPB receivers are designed, constructed and evaluated with various lasers to assess the performance of the VMJ cells and the receiver under a variety of conditions. Several matters such as parallel cell back-feeding, optimal receiver geometry, laser wavelength, non-uniform illumination and thermal effects at high intensities are investigated. Substantial power densities are achieved, and suggestions …

Damage Detection Of Rotors Using Magnetic Force Actuator: Analysis And Experimental Verification, Alexander Hans Pesch

ETD Archive

The ability to monitor the structural health of rotordynamic systems is becoming increasingly important as critical components continue to be used despite aging and the associated potential for damage accumulation. The aim of this thesis is to investigate a novel structural health monitoring approach for the detection of damage in rotating shafts, which utilizes a magnetic force actuator for applying multiple types of force inputs on to a rotating structure for analysis of resulting outputs. The magnetic actuator will be used in conjunction with conventional support bearings and also be applied to rotor under full magnetic levitation. The results of …

Lattices In Finite Real Reflection Groups, Colum Watt, Thomas Brady

Articles

For a finite real reflection group, $W$, with Coxeter element $\gamma$ we give a uniform proof that the closed interval, $[I, \gamma]$ forms a lattice in the partial order on $W$ induced by reflection length. The proof involves the construction of a simplicial complex which can be embedded in the type W simplicial generalised associahedron.

A Study Of Sip Based Instant Messaging Focusing On The Effects Of Network Traffic Generated Due To Presence, Finnian Mckeon

Conference Papers

The increasing usage of Instant Messaging(IM) applications worldwide continues to grow year on year. However, larger numbers of users creates problems with greater network traffic, interoperability and proprietary protocol dependence. Network traffic due to presence information being exchanged between users and servers needs to be considered, but is it possible to estimate or measure this traffic? There have been very few studies performed on the impact of presence traffic. The purpose of this research is to implement a SIP/SIMPLE network environment that will allow the evaluation of key metrics such as the latency and throughput of the network under a …

Throughput Enhancement Through Combined Fragmentation And Rate Method In Ieee 802.11b Wlans, Marek Bykowski, Karol Kowalik, Brian Keegan, Mark Davis

Conference papers

IEEE 802.11 allows for fragmentation tuning and rate selection. Their combined usage is referred sometimes to link adaptation. However, the algorithms of link adaptation are beyond the 802.11 standards. In this paper we investigate the benefits arising from proper use of link adaptation. Particularly, we develop a mathematical model describing the fragmented transmission in 802.11b. We examine potential benefits of it over AWGN and fading channels. More significantly we combine fragmentation tuning with bit-rate selection to yield the highest achievable throughput performance for any given channel conditions. Finally, we propose an algorithm that performs the optimal link adaptation.

Electrokinetic Separation Of Co-Solutes Into Bimodal Fibers By Electrospinning, Chunya Wu, Shinobu Nagata, Gary C. Tepper, James T. Mcleskey Jr.

Mechanical and Nuclear Engineering Publications

Composite and chemically/physically distinct fibers of sodium poly[2-(3-thienyl)-ethoxy-4-butylsulfonate] (PTEBS) and polyethylene oxide (PEO) were formed by electrospinning from a homogeneous aqueous solution containing PTEBS and PEO co-solutes. Composite nanofibers of diameter of ∼60nm were electrospun from an aqueous solution. The addition of ammonium hydroxide (NH4OH) to the water solution resulted in “bimodal” electrospun fibers consisting of distinct large diameter white PEO fiber segments and small diameter black PTEBS fiber segments. The optical absorptionspectrum of the composite PTEBS/PEO nanofibers did not exhibit the characteristic peak around 460nm, which is present in the bulk spectrum.

Cellular Automata Simulation Of Topological Effects On The Dynamics Of Feed-Forward Motifs, Advait Apte, John W. Cain, Danail Bonchev, Stephen S. Fong

Chemical and Life Science Engineering Publications

Background

Feed-forward motifs are important functional modules in biological and other complex networks. The functionality of feed-forward motifs and other network motifs is largely dictated by the connectivity of the individual network components. While studies on the dynamics of motifs and networks are usually devoted to the temporal or spatial description of processes, this study focuses on the relationship between the specific architecture and the overall rate of the processes of the feed-forward family of motifs, including double and triple feed-forward loops. The search for the most efficient network architecture could be of particular interest for regulatory or signaling pathways …

Field Emission From Self-Assembled Arrays Of Lanthanum Monosulfide Nanoprotrusions, V. Semet, Vu Thien Binh, M. Cahay, K. Garre, S. Fairchild, L. Grazulis, J. W. Fraser, D. J. Lockwood, S. Pramanik, B. Kanchibotla, Supriyo Bandyopadhyay

Electrical and Computer Engineering Publications

The field emission properties of LaS nanoprotrusions called nanodomes, formed by pulsed laser deposition on porous anodic alumina films, have been analyzed with scanning anode field emission microscopy. The voltage necessary to produce a given field emission current is 3.5 times less for nanodomes than for thin films. Assuming the same work function for LaS thin films and nanoprotrusions, that is, 1 eV, a field enhancement factor of 5.8 is extracted for the nanodome emitters from Fowler-Nordheim plots of the field emission data. This correlates well with the aspect ratio of the tallest nanodomes observed in atomic force micrograph measurements.

Reduction Of Efficiency Droop In Ingan Light Emitting Diodes By Coupled Quantum Wells, Xianfeng Ni, Qian Fan, Ryoko Shimada, Ü. Özgür, Hadis Morkoç

Electrical and Computer Engineering Publications

Light emitting diodes(LEDs) based on InGaN suffer from efficiency droop at current injection levels as low as 50 A cm−2. We investigated multiple quantum wellInGaNLEDs with varying InGaN barrier thicknesses (3–12 nm) emitting at ∼400–410 nm to investigate the effect of hole mass and also to find out possible solutions to prevent the efficiency droop. In LEDs with electron blocking layers, when we reduced the InGaN barriers from 12 to 3 nm, the current density for the peak or saturation of external quantum efficiency increased from 200 to 1100 A cm−2 under pulsed injection conditions, which eliminates the heating effects …

Large Pyroelectric Effect In Undoped Epitaxial Pb(Zr,Ti)O3 Thin Films On Srtio3 Substrates, Bo Xiao, Vitaliy Avrutin, Huiyong Liu, Ü. Özgür, Hadis Morkoç, Changzhi Lu

Electrical and Computer Engineering Publications

We have studied pyroelectric and ferroelectric properties of Pb(Zr,Ti)O3thin filmsgrown epitaxially on SrTiO3(001) substrates by rf magnetron sputtering. The pyroelectric coefficient was measured in the temperature range from 280 to 370 K using the Byer–Roundy method. Values as high as 48 nC/cm2 K have been obtained at 300 K. The PZTthin films exhibited a remanent polarization of 45–58 μC/cm2. The improved pyroelectric coefficient was attributed to a high crystalline quality of the films, as revealed by x-ray diffraction that showed only (001)-oriented perovskitePZT phase and a ω-rocking curve full width at half maximum value as low as 4.2 arc min …

On The Efficiency Droop In Ingan Multiple Quantum Well Blue Light Emitting Diodes And Its Reduction With P-Doped Quantum Well Barriers, Jinqiao Xie, Xianfeng Ni, Qian Fan, Ryoko Shimada, Ü. Özgür, Hadis Morkoç

Electrical and Computer Engineering Publications

Multiple quantum well(MQW) InGaN light emitting diodes with and without electron blocking layers, with relatively small and large barriers, with and without p-type doping in the MQW region emitting at ∼420nm were used to determine the genesis of efficiency droop observed at injection levels of approximately ⩾50A/cm2. Pulsed electroluminescence measurements, to avoid heating effects, revealed that the efficiency peak occurs at ∼900A/cm2current density for the Mg-doped barrier, near 550A/cm2 for the lightly dopedn-GaN injection layer, meant to bring the electron injection level closer to that of holes, and below 220A/cm2 for the undoped InGaN barrier cases. For samples with GaN …

Cavity Polaritons In Zno-Based Hybrid Microcavities, R. Shimada, J. Xie, Vitaliy Avrutin, Ü. Özgür, Hadis Morkoç

Electrical and Computer Engineering Publications

Among wide-bandgap semiconductors, ZnO is a very attractive candidate for blue-ultraviolet lasers operating at room temperature owing to its large exciton binding energy and oscillator strength. Especially, ZnO-based microcavity structures are most conducive for polariton lasing at room temperature. We report the observation of cavitypolaritons in bulk ZnO-based hybrid microcavities at room temperature. The bulk ZnO-based hybrid microcavities are composed of 29 pairs of Al0.5Ga0.5N∕GaNdistributed Bragg reflector (DBR) at the bottom of the λ-thick cavity layer and eight pairs of SiO2∕Si3N4 DBR as the top mirror, which provided cavityQvalues of ∼100. Anticrossing behavior between the lower and upper polariton branches …

Self-Assembled Deoxyguanosine Based Molecular Electronic Device On Gan Substrates, H. Liddar, J. Li, A. Neogi, P. B. Neogi, A. Sarkar, S. Cho, Hadis Morkoç

Electrical and Computer Engineering Publications

Nanoscale hybrid molecular organic photodetectors based on self-assembled guanosine molecules conjugated to wide-bandgap GaNsemiconductors has been realized in the ultraviolet wavelength regime. Metal-semiconductor-metal based photodetector is fabricated using ordering of modified guanosine based semiconductor nanowires which exhibit I-Vcharacteristics with high current response and higher rectification ratio compared to Si based hybrid photodetectors. Photocurrent response of a two-terminal device shows the typical characteristics of a semiconductorphotodiode with a cutoff wavelength at ∼325nm. The I-Vcharacteristics have been elucidated using the induced polarization properties of self-assembled guanosine semiconductor.

Transverse Spin Relaxation Time In Organic Molecules, B. Kanchibotla, S. Pramanik, S. Bandyopadhyay, M. Cahay

Electrical and Computer Engineering Publications

We report a measurement of the ensemble-averaged transverse spin relaxation time (T∗2) in bulk and few molecules of the organic semiconductor tris-(8-hydroxyquinolinolato aluminum) or Alq3. This system exhibits two characteristic T∗2 times: the longer of which is temperature independent and the shorter is temperature dependent, indicating that the latter is most likely limited by spin-phonon interaction. Based on the measured data, we infer that the single-particle T2 time is probably long enough to meet Knill’s criterion for fault-tolerant quantum computing even at room temperature. Alq3 is also an optically active organic, and we propose a simple …

Magnetic Field Effects On Spin Texturing In A Quantum Wire With Rashba Spin-Orbit Interaction, P. Upadhyaya, S. Pramanik, S. Bandyopadhyay, M. Cahay

Electrical and Computer Engineering Publications

A quantum wire with strong Rashba spin-orbit interaction is known to exhibit spatial modulation of spin density along its width owing to coupling between subbands caused by the Rashba interaction. This is known as spin texturing. Here, we show that a transverse external magnetic field introduces additional complex features in spin texturing, some of which reflect the intricate details of the underlying energy dispersion relations of the spin-split subbands. One particularly intriguing feature is a 90° phase shift between the spatial modulations of two orthogonal components of the spin density, which is observed at moderate field strengths and when only …

Optical Transitions In A Quantum Wire With Spin-Orbit Interaction And Its Applications In Terahertz Electronics: Beyond Zeroth-Order Theory, P. Upadhyaya, S. Pramanik, S. Bandyopadhyay

Electrical and Computer Engineering Publications

We calculate the terahertz absorption spectra associated with intersubband transitions in a semiconductor quantum wire in the presence of spin-orbit interaction and a transverse magnetic field. The frequencies and intensities of the absorption peaks are found to depend strongly on the spin-orbit coupling strength, which can be varied with an external electric field. This feature can be exploited to realize reconfigurable multispectral terahertz detectors and amplitude and/or frequency modulators. We also show that electric dipole transitions between spin-split levels in the same subband (which are normally deemed forbidden) become allowed because of spin texturing effects. The absorption associated with these …

The Inequality Of Charge And Spin Diffusion Coefficients, Sandipan Pramanik, Supriyo Bandyopadhyay, Marc Cahay

Electrical and Computer Engineering Publications

Since spin and charge are both carried by electrons (or holes) in a solid, it is natural to assume that charge and spin diffusion coefficients will be the same. Drift-diffusion models of spin transport typically assume so. Here, we show analytically that the two diffusion coefficients can be vastly different in quantum wires. Although we do not consider quantum wells or bulk systems, it is likely that the two coefficients will be different in those systems as well. Thus, it is important to distinguish between them in transportmodels, particularly those applied to quantum wire based devices.

Current Versus Voltage Characteristics Of Gan/Algan/Gan Double Heterostructures With Varying Algan Thickness And Composition Under Hydrostatic Pressure, I. P. Steinke, P. P. Ruden, X. Ni, H. Morkoç, K.-A. Son

Electrical and Computer Engineering Publications

We have studied current versus voltage characteristics of n-GaN∕u-AlGaN∕n-GaN double heterostructure devices under hydrostatic pressure up to 500MPa. Devices were grown on c-plane sapphire substrates by organometallic vapor phase epitaxy using epitaxial layer overgrowth. The effect of AlGaN layer thickness and composition on the pressure sensitivity was investigated. For a fixed applied bias, we found that the current decreases approximately linearly in magnitude with increasing hydrostatic pressure over the range of voltages and pressures applied. The decrease in current magnitude can be attributed to piezoelectric effects and is consistent with model calculations. The polarizationcharge densities at the GaN∕AlGaN interfaces change …

Wanted: Trained Security Specialists', Brent Wilson, Jim Aman, Josée Bourget

Faculty Publications - Department of Electrical Engineering and Computer Science

This paper looks at security concerns within the IT industry and how to increase student interest in this field of study. One specific activity is presented as a way to expose students to security concerns they are likely to encounter as a system administrator.