Engineering Commons^™

Direct Displacement‐Based Design: Use Of Inelastic Vs. Elastic Design Spectra, Anil K. Chopra, Rakesh K. Goel

Civil and Environmental Engineering

Direct displacement‐based design requires a simplified procedure to estimate the seismic deformation of an inelastic SDF system, representing the first (elastic) mode of vibration of the structure. This step is usually accomplished by analysis of an “equivalent” linear system using elastic design spectra. In this paper, an equally simple procedure is developed that is based on the well‐known concepts of inelastic design spectra. We demonstrate that the procedure provides the following: (1) accurate values of displacement and ductility demands, and (2) a structural design that satisfies the design criteria for allowable plastic rotation. In contrast, the existing procedure using elastic …

Method And Apparatus For Adaptive Process Control Of Critical Dimensions During Spin Coating Process, Richard N. Savage, Emir Gurer

Materials Engineering

A spin coating process for controlling the mean thickness of photoresist on the surface of a semiconductor wafer. The wafer surface has a central axis normal to the surface. The process comprises the steps of applying the solution to the wafer surface and spinning the wafer about the central axis at a spindle speed until the solution has dried. The spindle speed is a function of the desired mean thickness of the photoresist, the barometric pressure and the relative humidity. The spindle speed is determined from a statistical model described by the equation: MT=A+BxRH+CxBP+D/SS^1/2 wherein: MT is mean thickness …

A Modal Pushover Analysis Procedure To Estimate Seismic Demands For Buildings: Theory And Preliminary Evaluation, Anil K. Chopra, Rakesh K. Goel

Civil and Environmental Engineering

The principal objective of this investigation is to develop a pushover analysis procedure based on structural dynamics theory, which retains the conceptual simplicity and computational attractiveness of current procedures with invariant force distribution, but provides superior accuracy in estimating seismic demands on buildings.

The standard response spectrum analysis (RSA) for elastic buildings is reformulated as a Modal Pushover Analysis (MPA). The peak response of the elastic structure due to its nth vibration mode can be exactly determined by pushover analysis of the structure subjected to lateral forces distributed over the height of the building according to s^*_n = …

Enhanced Biodegradation Of Hydrocarbon Contaminants Using Photocatalytic Pretreatment, Chad E. Green, Anita Stansberry, Jeff Sczechowski, Yarrow Nelson

Civil and Environmental Engineering

Photocatalysis was investigated as a pretreatment for hydrocarbon groundwater contamination at an abandoned oil field in Guadalupe, CA. A laboratory photoreactor, with a UV fluorescent lamp submerged in a suspension of TiO₂ catalyst particles, was used to determine oxidation rates and the increase in biodegradability of the hydrocarbon mixture. Chemical oxidation demand (COD) and 5-day biological oxygen demand (BOD₅) were measured as a function of exposure time using standard methods. During eight-hour photoreactor runs in a nitrogen atmosphere, the COD of diluent solutions in de-ionized water and diluent solutions in simulated groundwater both decreased by approximately 50%, …

Bottom Mounted Doppler Flow Meter For Canals, Stuart W. Styles

BioResource and Agricultural Engineering

Doppler technology, similar to that used by meteorologist to track weather patterns, has been developed and expanded to fill the need for advanced water flow measurement technology that is relatively easy to use, applicable to various hydraulic conditions, and very accurate. This report discusses the operation of doppler units, provides a comparison of the technology, benefits, cost, and use.

Adjustable Magnetic Coupler, Charles M. Burt

BioResource and Agricultural Engineering

Efficiency in terms of power consumption is vital and continues to be increasingly important. The use of adjustable speed pumps can reduce energy consumption and improve controllability of pressure or flows. One such technology, the MagnaDrive coupler, has been developed for service in a variety of applications.

Pumped Storage: Simple Changes, Big Savings, Charles M. Burt

BioResource and Agricultural Engineering

Several California irrigation districts achieved savings on electrical energy charges by implementing various types of pumped storage systems. Pumped storage uses some type of reservoir to store pumped water at a higher elevation than the original water supply. During times of peak statewide electricity demand, pumping is reduced while water is withdrawn from the reservoir which acts as a buffer.

Load Monitoring System, Charles M. Burt

BioResource and Agricultural Engineering

Arvin-Edison Water Storage District received a loan - from the CEC's loan program for the development of new energy conservation technology - in 1995 to develop a program with variable frequency drives. This report discusses the design of the "Load Monitoring System", cost, the need for such a system, initial start-up challenges, configuration options, and benefits.

Evaluation Of Retrievable Drip Tape Irrigation Systems, Charles M. Burt, Jess T. Barreras

BioResource and Agricultural Engineering

California growers of lettuce, broccoli, celery, and cauliflower have long been leaders in drip tape applications. Starting in the early 1990s, large acreages of buried, subsurface drip irrigation (SDI) were installed with the intent of leaving the tape in the ground for up to 10 years (Burt and Styles, 1999). Tape burial depths were typically 20 - 25 cm below the soil surface. Although yields and irrigation efficiencies typically increased, there were numerous challenges with SDI. Since the tape was buried, such issues occurred as gopher damage, problems with root intrusion, soil back-siphonage when the system was shut off, damage …