Advances in data processing for open-path Fourier transform infrared spectrometry of greenhouse gases

The automated quantification of three greenhouse gases, ammonia, methane, and nitrous oxide, in the vicinity of a large dairy farm by open-path Fourier transform infrared (OP/FT-IR) spectrometry at intervals of 5 min is demonstrated. Spectral pretreatment, including the automated detection and correction of the effect of interrupting the infrared beam, is by a moving object, and the automated correction for the nonlinear detector response is applied to the measured interferograms. Two ways of obtaining quantitative data from OP/FT-IR data are described. The first, which is installed in a recently acquired commercial OP/FT-IR spectrometer, is based on classical least-squares (CLS) regression, and the second is based on partial least-squares (PLS) regression. It is shown that CLS regression only gives accurate results if the absorption features of the analytes are located in very short spectral intervals where lines due to atmospheric water vapor are absent or very weak; of the three analytes examined, only ammonia fell into this category. On the other hand, PLS regression works allowed what appeared to be accurate results to be obtained for all three analytes.     

Real-time monitoring of high-temperature corrosion in stainless steels by open-path laser-induced plasma spectrometry

Open-path laser-induced plasma spectrometry (OP-LIPS) represents an appealing alternative for the real-time monitoring of high-temperature processes due to its inherent non-invasive and remote capabilities. In this work, stainless steel samples have been analyzed at 10 meters from the laser source. The effect of the high-temperature conditions to the protective anti-corrosion layer have been analyzed, as well as additional factors such as the type of steel and the exposure time. The number of pulses required to ablate the alteration layer has been found to follow a linear relationship with the square root of the exposure time, in excellent agreement with the off-line thermogravimetric measurements described in the literature.     

Design considerations for refrigeration cycles

The Carnot COP, which assumes a thermodynamically ideal cycle in which no irreversibilities exist, is often considered to be a design goal for actual cycles. However, the Carnot COP does not consider heat transfer mechanisms. Heat transfer at a finite rate is necessarily an irreversible process and unavoidable in a refrigeration cycle. The lack of consideration of rate processes reduces the usefulness of the Carnot COP as a realistic design goal. In this paper, the limitations of both thermodynamics and heat transfer are considered to identify a more realistic design goal for the COP of refrigeration cycles. The consideration of heat transfer limitations leads to a design rule for the optimum distribution of heat exchange area between the low- and high-temperature heat exchangers.     

Design and performance of an atmospheric pressure inlet system for lithium ion attachment mass spectrometry

We designed a simple and efficient inlet system to act as an interface between samples at atmospheric pressure and the high vacuum inside a mass spectrometer. The newly designed stainless steel orifice leak sample inlet system is simple and rugged and fulfills all the basic requirements. With this inlet system coupled with a lithium ion attachment mass spectrometer, it is possible to detect any chemical species at atmospheric pressure, including radical intermediates, on a real-time basis. For illustrative purposes, the sampling efficiency of the inlet probe coupled with a lithium ion attachment mass spectrometer is discussed for laboratory air and polyethylene pyrolysis.     

Polarization properties of corner-cube retroreflectors: theory and experiment

Polarization properties of the corner-cube retroreflector are discussed theoretically by use of ray tracing and analytical geometry. The Jones matrices and eigenpolarizations of the six propagation trips of the corner-cube retroreflector are derived. An experiment is also set up for the determination of the linear eigenpolarizations and the output states of polarization for incident linearly polarized light. The experimental results are consistent with theoretical expectations.     

Design considerations for STJ x-ray detectors

The geometrical shape and layer thicknesses of superconducting tunnel junctions (STJ) influence their suitability as x-ray detectors. Examples relating to field biasing are discussed. Two related energy loss mechanisms are also modeled.     

Theoretical and practical consideration of the construction of a zero-geometric-loss multiple-pass cell based on the use of monolithic multiple-face retroreflectors

The theory of the multiple-pass cell based on the use of retroreflectors is presented. As a result of this study, it is shown that it is possible to construct an enhanced White cell with zero geometric loss. Starting from theoretical considerations of the design of a new monolithic multiple-face retroreflector, a multiple-pass cell is proposed. Ray-tracing simulations indicate that this cell is easy to align and has zero geometric loss over a very long optical path.     

Materials considerations of implantable neuroengineering devices for clinical use

Implantable devices for recording and stimulation of the human nervous system offer promise for the treatment of disorders including spinal cord injury, stroke, traumatic brain injury, sensory and motor deficits, chronic pain, epilepsy, Parkinson’s disease and amputation. While advances in neuroengineering devices have been impressive, often the expectations and desires for a chronically implantable device remain unrealized. In the face of engineering approaches which perform well on the bench or in acute implantations is an immune response which is well-tuned to recognize foreign bodies, including the materials chosen for our innovations. Recent years have demonstrated a co-evolution of engineering solutions for neural disorders and knowledge of underlying biological hurdles. This review describes the state-of-the-art for implantable neuroengineering devices used for electrical recording and stimulation, the tissue response to these devices, and emerging technologies and materials to mitigate the tissue response. The test methods for candidate materials and paths to the commercial market are briefly described.     

Design considerations for a highly segmented mirror

Design issues for a 30-m highly segmented mirror are explored, with emphasis on parametric models of simple, inexpensive segments. A mirror with many small segments offers cost savings through quantity production and permits high-order active and adaptive wave-front corrections. For a 30-m f/1.5 paraboloidal mirror made of spherical, hexagonal glass segments, with simple warping harnesses and three-point supports, the maximum segment diameter is approximately 100 mm, and the minimum segment thickness is approximately 5 mm. Large-amplitude, low-order gravitational deformations in the mirror cell can be compensated if the segments are mounted on a plate floating on astatic supports. Because gravitational deformations in the plate are small, the segment actuators require a stroke of only a few tens of micrometers, and the segment positions can be measured by a wave-front sensor.     

Design considerations for piezoelectric polymer ultrasound transducers

Much work has been published on the design of ultrasound transducers using piezoelectric ceramics, but a great deal of this work does not apply when using the piezoelectric polymers because of their unique electrical and mechanical properties. The purpose of this paper is to review and present new insight into seven important considerations for the design of active piezoelectric polymer ultrasound transducers: piezoelectric polymer materials selection, transducer construction and packaging requirements, materials characterization and modeling, film thickness and active area design, electroding selection, backing material design, and front protection/matching layer design. Besides reviewing these design considerations, this paper also presents new insight into the design of active piezoelectric polymer ultrasonic transducers. The design and fabrication of an immersible ultrasonic transducer, which has no adhesive layer between the active element and backing layer, is included. The transducer features direct deposition of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer onto an insulated aluminum backing substrate. Pulse-echo tests indicated a minimum insertion loss of 37 dB and -6 dB bandwidth of 9.8 to 22 MHz (71%). The use of polymer wear-protection/quarter-wave matching layers is also discussed. Test results on a P(VDF-TrFE) transducer showed that a Mylar/sup TM/ front layer provided a slight increase in pulse-echo amplitude of 15% (or 1.2 dB) and an increase in -6 dB pulse-echo fractional bandwidth from 86 to 95%. Theoretical derivations are reported for optimizing the active area of the piezoelectric polymer element for maximum power transfer at resonance. These derivations are extended to the special case for a low profile (i.e., thin) shielded transducer. A method for modeling the non-linear loading effects of a commercial pulser-receiver is also included.     

Design considerations and algorithms for partitioning optoelectronic multichip modules

There is considerable interest in the development of optical interconnects for multichip modules (MCM's) to improve their performance. For effective utilization of the optical and electronic technologies, a methodology for partitioning the system is required. The key question to be answered is which technology should be used for each interconnect in a given netlist: optical or electronic. We introduce the computer-aided design approach for partitioning optoelectronic systems into optoelectronic MCM's. We first discuss the design trade-off issues in an optoelectronic system design, including speed, power dissipation, area, and diffraction limits for free-space optics. We then define a formulation for optoelectronic MCM partitioning and describe new algorithms for optimizing this partitioning based on the minimization of the power dissipation. The models for the algorithms are discussed in detail, and an example of a multistage interconnect network is given. Different results, with the number and size of chips being variable, are presented in which improvement for the system packaging has been observed when the partitioning algorithms are applied.     

Design and performance of a throughput-matched, zero-geometric-loss, modified three objective multipass matrix system for FTIR spectrometry

The design of and initial results obtained from a multipass matrix system (MMS) for mid-infrared spectroscopy that operates in the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC) recently constructed in the School of Chemistry at the University of Leeds, is described. HIRAC is an evacuable, temperature variable, photochemical atmospheric reaction chamber. The MMS design is a modified Chernin cell, utilizing three objective mirrors and two field mirrors. In addition to providing the paraxial equations required for design of a throughput matched multipass cell and throughput matched transfer optics, advanced ray tracing simulations have been performed for the Chernin design described herein. The simulations indicate that, for this MMS, which features small off-axis angles and preserves perfectly the focal properties of the original White design, the paraxial equations are nearly exact, throughput losses due to astigmatism are insignificant, and the system has zero theoretical geometric loss. Measurements of the signal incident on the detector at different matrix arrangements confirm the ray trace results, suggesting that geometric loss in this system is insignificant. The MMS described herein provides adequate stability to permit measurements while the chamber mixing fans are on, gives very good detection limits for some representative species, and is easy to align.     

Development and characterization of piezoelectrically actuated corner cube retroreflectors for applications in free-space optical sensor network

In this paper, we report the development of an optical sensor network (OSN) based on piezoelectrically actuated corner cube retroreflectors (PA-CCRs). PA-CCRs were fabricated by microelectromechanical systems processes and assembled by aligning horizontally actuated mirrors and vertical side walls in a holder, which allows mass production. Fabricated PA-CCRs showed a tilting angle by more than 1.5 deg at 5 V bias voltage. A 3 dB cutoff frequency was measured to be in the range of 3.5 kHz. To show the feasilbility, an OSN was established based on fabricated PA-CCRs for on-off keying passive transmission links. The results demonstrated data transmission at a rate up to 5 kb/s.     

Design for electrospray ionization-ion mobility spectrometry

In this study, a new design for electrospray ionization ion mobility spectrometry (ESI-IMS) was developed. This design has two important differences in comparison to the present ESI-IMS systems. First, a few centimeters of the cell comprising the electrospray needle was located outside of the oven used for heating the IMS cell. This modification prevents prespray solvent evaporation problems such as needle clogging and disturbance of the electrospray process. Second, in addition to the drift gas, a counterflow of a heated gas (desolvation gas) was used between the counter electrode and the ion gate to speed up the desolvation process (Hill, H. H., Jr. Anal. Chem. 1998, 70, 4929-4938). This modification increased the solvent evaporation and resulted in decreasing the drift time, increasing the peak intensity and increasing the resolving power (RP) or enhancing the resolution for separation of two adjacent ion peaks. In this work, the ion mobility spectra of different compounds including ethion, malathion, metalaxyl, fenamifos, methylamine, triethylamine, tributhylamine, codeine, and morphine were obtained to confirm enhancing of the resolving power of the ion peaks by using the desolvation gas. Furthermore, the method has also been applied to obtain the figures of merit for ethion as a test compound. The linear dynamic range for ethion was in the range 50-1000 microg/L with a limit of quantification of the 50 microg/L.     

Design considerations for the DASTEK 4830 disk drive

The DASTEK 4830 Disk Drive is designed to provide minicomputer original equipment manufacturers (OEM) with direct access storage having the performance, reliability, and cost/MB characteristics of drives attached to large mainframe computers. This was accomplished by utilizing state-of-the -art technologies in the areas of read/write heads, media, data encoding/decoding, and read/write head positioning as well as packaging improvements and microprocessor based electronics.     

Design of ultrasonic array elements for acoustic power considerations

In sound-transmitting applications such as therapeutic ultrasound, the acoustic power at a particular operating frequency is a critical figure of merit for transducer/array design. A design methodology for enhancing the acoustic power radiated from fluid-loaded piezoelectric array elements at a fixed frequency is developed in this paper. A gradient-based optimization algorithm is integrated within the finite element framework to guide the determination of the two design variables, the piezoelectric element thickness and the matching layer thickness, to optimize the acoustic power output. A method for avoiding explicit remeshing in the optimization iteration is presented. Optimized designs are determined numerically, and the effectiveness of the design method is confirmed by experimental measurements. The validated numerical analysis also shows that conventional design strategies using one-dimensional transducer analysis and rule-of-thumb matching layer or protection layer sizing rules may not give the best design for array elements in acoustic power applications     

Effective use of mass spectrometry for glycan and glycopeptide structural analysis

Most proteins are glycosylated. Mass spectrometry methods are used for mapping glycoprotein glycosylation and detailed glycan structural determination. This technology enables precise characterization of recombinant glycoproteins in the pharmaceutical industry and academic biomedicine.     

Basic considerations in the use of coded excitation for color flow imaging applications

Coded excitation is now a well-established technique in medical ultrasound for B-mode imaging applications. It enables a gain in depth of penetration, without sacrificing the spatial resolution and maintaining an acceptable peak intensity for patient safety. The rationale of this technique for velocity estimation applications still has to be formulated in more precise terms. In particular, differences in the situation that arise in color flow imaging (CFI) applications from typical B-mode imaging conditions, such as signal-to-noise ratio conditions, pulsing strategy, and safety requirements, need to be specifically addressed to assess more quantitatively the potential of this technique. This paper discusses the potential improvement in sensitivity, resolution, and statistical performance provided by coded excitation for CFI applications from theoretical considerations and simulations.