Practical Design Considerations Research Articles

Creating multiple time-shared laser traps with simultaneous displacement detection using digital signal processing hardware

We present a design for implementing multiple laser traps for single-molecule studies through time-sharing using commercially available digital signal processing hardware in a computer running a standard multitasking operating system. This design enables four to six independent laser traps with a visitation frequency of 10,000 s −1 trap −1 and a timing jitter of ±0.5 μs to be created. The design also achieves nanometer-resolution detection of displacement in all of the traps simultaneously via back focal-plane interferometry and only a single quadrant photodiode detector. Practical design considerations and limitations together with the use of fiberlasers in laser traps are discussed. Using this device, the mechanokinetics of multiple molecular motors or adhesion proteins may be measured simultaneously. We present the example biological application of two kinesin-coated beads in separate traps moving on different portions of a microtubule.

Dynamic treatment regimes: practical design considerations

Clinical management of chronic disease requires a dynamic treatment regime (DTR): rules for choosing the new treatment based on the history of response to past treatments. Estimating and comparing the effects of DTRs from a sample of observed trajectories of treatment and outcome depends on the untestable assumption that new treatments are assigned independently of potential future responses to treatment, conditional on the history of treatments and response to date ("sequential ignorability"). In longitudinal observational studies, sequential ignorability must be assumed, while randomization of dynamic regimes can guarantee it. Using several clinical examples, we describe the simplest randomized experimental designs for comparing DTRs. We begin by considering an initial treatment A and a second treatment B, and discuss how a dynamic treatment regime that starts with A and leads (sometimes) to B, might be compared to either fixed treatment A or B. We also illustrate the problem of finding the optimal sequence of treatments in a DTR, when there are several choices. We describe and contrast two ways of incorporating randomization into studies to compare such regimes: baseline randomization among DTRs versus randomization at the decision points (sequentially randomized designs). We discuss estimation and inference from both baseline randomized and sequentially randomized designs and conclude with a discussion of the differences between the experimental and observational approaches to optimizing and comparing dynamic treatment regimes.

High-frequency flyback-type soft-switching PWM DC-DC power converter with energy recovery transformer and auxiliary passive lossless snubbers

A two-switch high-frequency flyback-type zero voltage soft-switching PWM DC-DC power converter for use in auxilary power supplies is proposed. Its basic building block is composed of two active power switches and a flyback high frequency transformer. In addition, two passive lossless snubbers with power regeneration loops for energy recovery that consist of a three-turn auxiliary high frequency transformer, auxiliary capacitors and diodes, are introduced to achieve zero voltage soft switching in the full range of light to full load conditions. The power converter has the advantages of a low cost circuit configuration, a simple control scheme and a high efficiency.The converter's operating principle is described and to in order determine circuit parameters, some practical design considerations are discussed. The effectiveness of the proposed power converter is evaluated and is compared to a hard-switching PWM DC-DC converter. The comparative electromagnetic conductive noise characteristics of both DC-DC power converter circuits are also investigated.

Pulse Current Regenerative Resonant Snubber-Assisted Two-Switch Flyback Type ZVS PWM DC-DC Converter

In this paper, a two-switch high frequency flyback transformer type zero voltage soft switching PWM DC-DC converter using IGBTs is proposed. Effective applications for this power converter can be found in auxiliary power supplies of rolling stock transportation and electric vehicles. This power converter is basically composed of two active power switches and a flyback high frequency transformer. In addition to these, two passive lossless snubbers with power regeneration loops for energy recovery, consisting of a three winding auxiliary high frequency transformer, auxiliary capacitors and diodes are introduced to achieve zero voltage soft switching from light to full load conditions. Furthermore, this power converter has some advantages such as low cost circuit configuration, simple control scheme and high efficiency. Its operating principle is described and to determine circuit parameters, some practical design considerations are discussed. The effectiveness of the proposed power converter is evaluated and compared with the hard switching PWM DC-DC converter from an experimental point of view and the comparative electromagnetic conduction and radiation noise characteristics of both DC-DC power converter circuits are also depicted.

Shock Wave Propagation and Gas-Debris Transport into a Vacuum: A Novel Computational Model - TEXAS-NCV

Pulsed power experiments for basic physics investigations as well as inertial confinement fusion designs have developed Z-pinch technologies that produce terawatt level power using multiwire arrays. The energy released from such pulsed power tests results in fragmentation and vaporization of structures at the central wire array as well as shock wave propagation to the chamber boundaries. Practical design and safety considerations require that tracking of this shock front and the associated gas-debris field be done for a variety of experimental configurations to predict the arrival time of hazardous or radioactive debris at fast closure valve locations. A novel computational model has been developed to handle gas expansion into vacuum using a computer model (TEXAS) operating on a Eulerian mesh. Upon expansion of a high-pressure gas into a region of hard vacuum where free molecular transport dominates, the transport model switches between a traditional Eulerian continuum mechanics model and a free molecular transport model across the interface between the two regions. The interface location then propagates along the mesh as the gas expands. This new quasi-one-dimensional model (TEXAS-NCV) has been implemented and tested for two benchmark cases. Such a model can be useful in the design of inertial fusion systems.

A Practical Design Consideration for Coupled-Resonator Laminated Band Elimination Filter Fabricated with LTCC of High Dielectric Constant.

A practical design procedure of coupled-resonator band elimination filter (BEF) is studied. A small-sized BEF is fabricated with Low Temperature Co-fired Ceramics (LTCC) having high dielectric constant. Deterioration of band elimination characteristic due to approach of the constituent resonators is recovered with the proposed design procedure. But, in a practical fabrication process, additional physical restrictions are placed on this structure, e.g., the length and the impedance of inter-stage transmission line make another problem for its realization. They are overcome by adjustment based on computer simulation, and a fabricated LTCC BEF shows a good performance in an experiment carried out at the 2GHz-band.

Equipment design considerations for large scale cell culture.

Equipment design is frequently recognized as a key component in the success of GMP biologics manufacturing, but is not always implemented with full appreciation of the processing implications. In the case of mammalian cell culture, there are some recognized issues and risks that develop when transitioning to a large scale of operation. The developing demand for cell culture production capacity in the biopharmaceutical industry has led to a progressive increase in the scale of operation in the last decade. This review will provide a high level summary of the documented process difficulties unique to serum-free large scale (LS) cell culture, analyze the engineering constraints typical of these processes, and suggest some practical equipment design considerations to enhance the productivity, reliability and operability of such systems under GMP manufacturing conditions. A systems approach will be used to establish a good LS bioreactor design practice, providing a discussion on gas distribution, agitation, vessel design, SIP/CIP and control issues.

Structural Behaviour of Surfacings on Steel Orthotropic Decks and Considerations for Practical Design

Surfacings on steel orthotropic decks act compositely with the steel deck plate and must be regarded as an integral part of the structural deck system. Surfacing materials are generally visco-elastic to plastic and behave elastically only at low temperatures. Elastic moduli of most surfacings strongly depend on temperature. In semi-plastic condition flexural strain distribution through the surfacing thickness becomes non-linear. With a soft bonding layer, shear slip occurs at the interface. Surfacings contribute substantially to deck rigidity and are subject to considerable stresses due to local bending of the steel deck plate. Locations and causes of critical deck plate stresses affecting surfacing performance are discussed. Characteristic properties of the two basic surfacing categories, the bituminous and the polymer materials, are presented with examples of their applications on orthotropic decks. It is suggested that satisfactory performance of surfacings should be achieved by more stringent limitations of the local deck flexibility.

Conversion of pulverized coal-fired boilers to ones with solid slag removal

The purpose of the present investigation is to explore the feasibility of applying the micromix combustion principle (MCP) to design low NOx burners using 100% H2 as fuel for domestic and industrial boilers. Previous investigations studying the MCP on stationary and aero gas turbine applications, showed low NOx emissions without flashback risk, which represent the two main issues when burning 100% H2. Since boiler burner operating conditions differ from gas turbine combustors, the present paper studies the MCP through CFD calculations under re-defined conditions for domestic and industrial burners, adapting the energy densities, air-fuel equivalence ratios and pre-heated air temperatures. A reference geometry was built to validate the selected numerical models with experimental results from literature. Afterwards, burners were re-dimensioned following an existing geometry-scaling methodology. The obtained results evidenced that MCP characteristics were still maintained for the defined cases, keeping low NOx values between 4 and 14 ppm. The numerical results were also validated through experimental NOx measurements in a laboratory scale micromix burner prototype. In order to assess the benefits of using hydrogen micromix burners in domestic and industrial boilers, the present work includes a final discussion with practical design considerations. The present study lays the groundwork for complementary experimental research work, which is being carried out in laboratory-scale prototypes.

Explosive compaction: design, implementation and effectiveness

Although used for over 70 years, Explosive Compaction (EC) has not attained widespread acceptance despite the attraction of low cost and ease of treating large depths. Lack of familiarity with the method, and an empirical design approach unrelated to theory, appear the primary cause for reticence in adopting EC. To alleviate these concerns, practical design considerations for EC based on detailed experience from nine applications and trials are presented here to illustrate the predictable and repeatable effectiveness of EC. Design is based on cavity expansion theory. EC readily gives volume changes 2–3 times larger than might occur under large earthquake motions, with final average relative densities often greater than 70%. Further, environmental and vibration control issues do not constrain the use of EC provided that appropriate explosives and delayed detonation sequences are used. As pronounced post-blast time effects are evident in penetration testing, evaluation of the effectiveness of EC should be based on a combination of pre- and post-blast penetration testing and volume change measurements.

Practical Design Considerations for Signal Conditioning Unit Interfaced with Multi-point Snow Temperature Recording System

Multi-point Temperature Measurement has always been very important aspect of physical instrumentation mainly in environmental and Industrial application. A multi-point temperature measurement system has been developed to measure temperature at different points simultaneously. This multi-channel system is designed specifically for measuring snow temperature at 28 different points In snow layers and this multi-point data is used in modeling of snow cover. The interfacing of such multi-channel system to Data acquisition system is one of the most critical design aspects, which affect the overall performance of the system. The temperature sensor system and Data Acquisition System may be working satisfactorily when operated independently but total system integrity is absolutely important when these two sub-systems are interfaced together. Further operating conditions in snow causes many performance and reliability issues to be tackled through proper design. This paper discusses the design aspects involved in the interfacing of the multi-channel temperature measurement system with the Data Acquisition System specifically for Snow hydrological applications.

PRACTICAL CONSIDERATIONS FOR DESIGN OF A STEP-FEED BIOLOGICAL NUTRIENT REMOVAL SYSTEM

PRACTICAL CONSIDERATIONS FOR DESIGN OF A STEP-FEED BIOLOGICAL NUTRIENT REMOVAL SYSTEMAs the need to retrofit secondary treatment plants for biological nutrient removal (BNR) has become widespread, process variations such as step-feed BNR have been developed to adapt existing treatment facilities to meet effluent requirements. Since there are relatively few full-scale installations of step-feed BNR, the process and retrofit design concepts are still under development. Although...Author(s)Luis CarrioFred StreettKieth MahoneyChristine deBarbadilloJames AndersonKen AbrahamNicholas PassarelliSourceProceedings of the Water Environment FederationSubjectSession 39 - Municipal Wastewater Treatment Symposium: Nitrogen and Phosphorus RemovalDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2000ISSN1938-6478SICI1938-6478(20000101)2000:11L.803;1-DOI10.2175/193864700784544334Volume / Issue2000 / 11Content sourceWEFTECFirst / last page(s)803 - 823Copyright2000Word count142

Lorenz-based chaotic cryptosystem: a monolithic implementation

A monolithic implementation of a cryptosystem based on the Corron and Hahs (1997) scheme is hereby presented. The baseband chaotic encryption/decryption system has been designed at the transistor level and fabricated using AMI 1.2 /spl mu/m CMOS technology available through the MOSIS foundry. While the mathematical model of the Lorenz system is straightforward, its silicon implementation is not. Typical circuit design considerations need to be considered such as the system's dynamic range, internal signal processing mode and basic building blocks all with the intent to provide an optimal design. This work addresses in detail: (1) practical design considerations of the cryptosystem and (2) actual measurement results that verify theoretical findings.

Complete characterization of transmission losses in generalized nonradiative dielectric (NRD) waveguide

In this paper, transmission losses of the generalized nonradiative dielectric (NRD) waveguide are modeled and presented by our closed-form equations for the design of hybrid and monolithic millimeter-wave integrated circuits. This generalized structure includes our recently proposed channelized NRD-guide. Parametric effects are studied with respect to complex propagation constant and characteristic impedance, and some useful guidelines are generated for practical design considerations. Calculated results are discussed separately for the conductor and dielectric losses for the two fundamental longitudinal section electric (LSE) and longitudinal section magnetic (LSM) modes. It is found that the LSE mode may have losses, in some cases, comparable or even smaller than those of its LSM counterpart, contradicting what has usually been perceived for the conventional NRD-guide design.

Active structural subsystem of the OISI interferometry testbed

An adaptive truss structure has been realized for active vibration damping within a laboratory testbed for future spaceborne optical and infra-red interferometers. The active elements are based on piezoelectric sensors and actuators. The paper first surveys configuration scenarios for space interferometers that aim at nanometre accuracy of optical pathlengths. It then focuses on the function of active structural control. For the laboratory truss, practical design considerations as well as analytical approaches for modelling and system identification, placement of active elements and design of active damping control are discussed in detail. Experimental results of the active damping performance achieved with integral feedback of strut force signals are compared with analytical predictions. The combined effects of active damping and passive vibration isolation are presented, and conclusions are drawn regarding further activities towards nanometre stabilization of optical pathlengths.

Three dimensional stability analysis of high-temperature superconductors using the finite element method

As the properties of high-temperature superconducting tapes improve, practical design considerations require more detailed analysis to prevent quenching. An important issue for high-temperature superconductors is stability; i.e. the ability to maintain or recover superconductivity in the event of a thermal disturbance or flux jump. As a result of the broad range of temperature during a transition and the strong temperature dependence and anisotropy of the material properties, the finite element method (FEM) is used to solve the three-dimensional heat conduction equation. The minimum quench energy for several sources is determined. The different cases considered include: convective boundary condition, source in BSCCO or Ag, increased anisotropy of thermal conductivity of BSCCO, increased critical current density and a constant source in Ag Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O-Ag.

Orchestra shells: Acoustical and practical design considerations

A hall or an outdoor facility is rarely used for a single type of artistic program. Often, it is necessary to design an orchestra shell that transforms theoretically a theatre or an opera house into a concert hall. The acoustical criteria for opera or concerts are quite different; the design of an orchestra shell that would create proper acoustical conditions on stage for the musicians and in the hall for the audience can be quite complex. The larger the hall and the proscenium opening, the harder it is to come up with an adequate solution. The major problems are the following: architecture and aesthetics, acoustical efficiency, ensemble conditions, acoustic response, diffusion, size, weight, transformation time, and storage. Some progress has been made over the last few years, but the problem remains complex. This paper will attempt to explain the design and construction process and will provide recent examples of small and large shells: Ravinia, Lille concert hall, Gradignan, Porto Teatro S. João, Opera Garnier in Paris, Staatsoper in Munich, and Serralves auditorium in Porto.

Population pharmacokinetics. A regulatory perspective.

The application of population approaches to drug development is recommended in several US Food and Drug Administration (FDA) guidance documents. Population pharmacokinetic (and pharmacodynamic) techniques enable identification of the sources of inter- and intra-individual variability that impinge upon drug safety and efficacy. This article briefly discusses the 2-stage approach to the estimation of population pharmacokinetic parameters, which requires serial multiple measurements on each participant, and comprehensively reviews the nonlinear mixed-effects modelling approach, which can be applied in situations where extensive sampling is not done on all or any of the participants. Certain preliminary information, such as the compartment model used in describing the pharmacokinetics of the drug, is required for a population pharmacokinetic study. The practical design considerations of the location of sampling times, number of samples/participants and the need to sample an individual more than once should be borne in mind. Simulation may be useful for choosing the study design that will best meet study objectives. The objectives of the population pharmacokinetic study can be secondary to the objectives of the primary clinical study (in which case an add-on population pharmacokinetic protocol may be needed) or primary (when a stand-alone protocol is required). Having protocols for population pharmacokinetic studies is an integral part of 'good pharmacometric practice'. Real-time data assembly and analysis permit an ongoing evaluation of site compliance with the study protocol and provide the opportunity to correct violations of study procedures. Adequate policies and procedures should be in place for study blind maintenance. Real-time data assembly creates the opportunity for detecting and correcting errors in concentration-time data, drug administration history and covariate data. Population pharmacokinetic analyses may be undertaken in 3 interwoven steps: exploratory data analysis, model development and model validation (i.e. predictive performance). Documentation for regulatory purposes should include a complete inventory of key runs in the analyses undertaken (with flow diagrams if possible), accompanied by articulation of objectives, assumptions and hypotheses. Use of diagnostic analyses of goodness of fit as evidence of reliability of results is advised. Finally, the use of stability testing or model validation may be warranted to support label claims. The opinions expressed in this article were revised by incorporating comments from various sources and published by the FDA as 'Guidance for Industry: Population Pharmacokinetics' (see the FDA home page http:/(/)www.fda.gov for further information).

Active filter used as a controlled reactance to prevent harmonic resonance in interconnected offshore power systems

Harmonic resonance is of particular concern in the design and operation of interconnected offshore power systems. This paper shows that it is possible to attenuate such resonance using an active filter. A new control method is proposed which can assess the system condition from a harmonic point of view and take into account the relative distribution of exciting frequencies and system resonant modes. Measured system busbar voltage is the only feedback required by the filter controller and the power system condition is initially unknown and variable. A series of time domain simulation results are presented to illustrate the effectiveness and limitations of the 'active harmonic damper' while some practical design considerations are highlighted.

Quantitative RT-PCR: pitfalls and potential.

Reverse transcription PCR (RT-PCR) represents a sensitive and powerful tool for analyzing RNA. While it has tremendous potential for quantitative applications, a comprehensive knowledge of its technical aspects is required. Successful quantitative RT-PCR involves correction for experimental variations in individual RT and PCR efficiencies. This review addresses the mathematics of RT-PCR, choice of RNA standards (internal vs. external) and quantification strategies (competitive, noncompetitive and kinetic [real-time] amplification). Finally, the discussion turns to practical considerations in experimental design. It is hoped that this review will be appropriate for those undertaking these experiments for the first time or wishing to improve (or validate) a technique in what is frequently a confusing and contradictory field.