We present an active method for mixing fluid streams in microchannels at low Reynolds number with no dead volume. To overcome diffusion limited mixing in microchannels, surface acoustic wave streaming offers an extremely effective approach to rapidly homogenize fluids. This is a pivotal improvement over mixers based on complex 3D microchannels which have significant dead volume resulting in trapping or loss of sample. Our micromixer is integrable and highly adaptable for use within existing microfluidic devices. Surface acoustic wave devices fabricated on 128° YX LiNbO3 permitted rapid mixing of flow streams as evidenced by fluorescence microscopy. Longitudinal waves created at the solid-liquid interface were capable of inducing strong nonlinear gradients within the bulk fluid. In the highly laminar regime (Re = 2), devices achieved over 93% mixing efficacy in less than a second. Micro-particle imaging velicometry was used to determine the mixing behavior in the microchannels and indicated that the liquid velocity can be controlled by varying the input power. Fluid velocities in excess of 3 cm•s-1 were measured in the main excitation region at low power levels (2.8mW). We believe that this technology will be pivotal in the development and advancement of microfluidic devices and applications.
This report describes a methodology for estimating the power and energy capacities for electricity energy storage systems that can be used to defer costly upgrades to fully overloaded, or nearly overloaded, transmission and distribution (T&D) nodes. This ''sizing'' methodology may be used to estimate the amount of storage needed so that T&D upgrades may be deferred for one year. The same methodology can also be used to estimate the characteristics of storage needed for subsequent years of deferral.
The MATLAB language has become a standard for rapid prototyping throughout all disciplines of engineering because the environment is easy to understand and use. Many of the basic functions included in MATLAB are those operations that are necessary to carry out larger algorithms such as the chirp z-transform spectral zoom. These functions include, but are not limited to mathematical operators, logical operators, array indexing, and the Fast Fourier Transform (FFT). However, despite its ease of use, MATLAB's technical computing language is interpreted and thus is not always capable of the memory management and performance of a compiled language. There are however, several optimizations that can be made within the chirp z-transform spectral zoom algorithm itself, and also to the MATLAB implementation in order to take full advantage of the computing environment and lower processing time and improve memory usage. To that end, this document's purpose is two-fold. The first demonstrates how to perform a chirp z-transform spectral zoom as well as an optimization within the algorithm that improves performance and memory usage. The second demonstrates a minor MATLAB language usage technique that can reduce overhead memory costs and improve performance.
This report describes the research accomplishments achieved under the LDRD Project ''Leaky-mode VCSELs for photonic logic circuits''. Leaky-mode vertical-cavity surface-emitting lasers (VCSELs) offer new possibilities for integration of microcavity lasers to create optical microsystems. A leaky-mode VCSEL output-couples light laterally, in the plane of the semiconductor wafer, which allows the light to interact with adjacent lasers, modulators, and detectors on the same wafer. The fabrication of leaky-mode VCSELs based on effective index modification was proposed and demonstrated at Sandia in 1999 but was not adequately developed for use in applications. The aim of this LDRD has been to advance the design and fabrication of leaky-mode VCSELs to the point where initial applications can be attempted. In the first and second years of this LDRD we concentrated on overcoming previous difficulties in the epitaxial growth and fabrication of these advanced VCSELs. In the third year, we focused on applications of leaky-mode VCSELs, such as all-optical processing circuits based on gain quenching.
With the increasing reliance on cyber technology to operate and control physical security system components, there is a need for methods to assess and model the interactions between the cyber system and the physical security system to understand the effects of cyber technology on overall security system effectiveness. This paper evaluates two methodologies for their applicability to the combined cyber and physical security problem. The comparison metrics include probabilities of detection (P{sub D}), interruption (P{sub I}), and neutralization (P{sub N}), which contribute to calculating the probability of system effectiveness (P{sub E}), the probability that the system can thwart an adversary attack. P{sub E} is well understood in practical applications of physical security but when the cyber security component is added, system behavior becomes more complex and difficult to model. This paper examines two approaches (Bounding Analysis Approach (BAA) and Expected Value Approach (EVA)) to determine their applicability to the combined physical and cyber security issue. These methods were assessed for a variety of security system characteristics to determine whether reasonable security decisions could be made based on their results. The assessments provided insight on an adversary's behavior depending on what part of the physical security system is cyber-controlled. Analysis showed that the BAA is more suited to facility analyses than the EVA because it has the ability to identify and model an adversary's most desirable attack path.
In order to optically vary the magnification of an imaging system, continuous mechanical zoom lenses require multiple optical elements and use fine mechanical motion to precisely adjust the separations between individual or groups of lenses. By incorporating active elements into the optical design, we have designed and demonstrated imaging systems that are capable of variable optical magnification with no macroscopic moving parts. Changing the effective focal length and magnification of an imaging system can be accomplished by adeptly positioning two or more active optics in the optical design and appropriately adjusting the optical power of those elements. In this application, the active optics (e.g. liquid crystal spatial light modulators or deformable mirrors) serve as variable focal-length lenses. Unfortunately, the range over which currently available devices can operate (i.e. their dynamic range) is relatively small. Therefore, the key to this concept is to create large changes in the effective focal length of the system with very small changes in the focal lengths of individual elements by leveraging the optical power of conventional optical elements surrounding the active optics. By appropriately designing the optical system, these variable focal-length lenses can provide the flexibility necessary to change the overall system focal length, and therefore magnification, that is normally accomplished with mechanical motion in conventional zoom lenses.
The SNL/CA Cultural Resources Management Plan satisfies the site's Environmental Management System requirement to promote long-term stewardship of cultural resources. The plan summarizes the cultural and historical setting of the site, identifies existing procedures and processes that support protection and preservation of resources, and outlines actions that would be initiated if cultural resources were discovered onsite in the future.3
We present the results of a one year LDRD program that has focused on evaluating the use of newly developed deep ultraviolet LEDs in water purification. We describe our development efforts that have produced an LED-based water exposure set-up and enumerate the advances that have been made in deep UV LED performance throughout the project. The results of E. coli inactivation with 270-295 nm LEDs are presented along with an assessment of the potential for applying deep ultraviolet LED-based water purification to mobile point-of-use applications as well as to rural and international environments where the benefits of photovoltaic-powered systems can be realized.
This report describes an investigation of the piezoelectric field in strained bulk GaAs. The bound charge distribution is calculated and suitable electrode configurations are proposed for (1) uniaxial and (2) biaxial strain. The screening of the piezoelectric field is studied for different impurity concentrations and sample lengths. Electric current due to the piezoelectric field is calculated for the cases of (1) fixed strain and (2) strain varying in time at a constant rate.