Critical Performance Parameters Research Articles

Nickel Removal from Waters Using a Surfactant-Enhanced Hybrid Powdered Activated Carbon/Microfiltration Process. II. The Influence of Process Variables

This study focused on the removal of nickel ions from aqueous solution using a surfactant-enhanced (SE) powdered activated carbon (PAC)/microfiltration (MF) hybrid membrane process. The main objective of the research is to investigate the technical performance of the process under the influences of all relevant process variables namely process time, recycling time, pH, temperature, PAC concentration, surfactant concentration, nickel concentration, cross-flow velocity, and transmembrane pressure, thus to reveal its applicability to water problems involved in heavy metal pollution. The concentrations of PAC, surfactant, metal, and H+ ion were determined as significant process stream variables, while transmembrane pressure and temperature came into prominence as significant operating variables. ANOVA calculations indicated that the total influences of these six variables on process performance realized in a range of about 93−98%. Nickel concentration and PAC amount in the feed were established as the most influential variables for nickel rejection, and surfactant rejection and permeate flux, respectively. The increase of PAC from 0.1 to 4 g/L led to a flux decline of about 60%. The most critical parameter for process performance was the mass ratio of PAC to surfactant (PAC/surfactant) per unit mass of metal removed. The process which may be effectively operated in continuous cross-flow filtration mode within a short filtration time of 30 min has crucial advantages compared to high pressure driven membrane processes and offers a promising alternative to remove heavy metal pollutants from drinking waters and metal bearing wastewaters.

Critical Performance and Durability Parameters of an Integrated Aftertreatment System used to Meet 2007 Tier II Emission Standards

Critical Performance and Durability Parameters of an Integrated Aftertreatment System used to Meet 2007 Tier II Emission Standards

Estimation of Autotrophic Maximum Specific Growth Rate Constant—Experience from the Long‐Term Operation of a Laboratory‐Scale Sequencing Batch Reactor System

The autotrophic maximum specific growth rate constant, muA,max, is the critical parameter for design and performance of nitrifying activated sludge systems. In literature reviews (i.e., Henze et al., 1987; Metcalf and Eddy, 1991), a wide range of muA,max values have been reported (0.25 to 3.0 days(-1)); however, recent data from several wastewater treatment plants across North America revealed that the estimated muA,max values remained in the narrow range 0.85 to 1.05 days(-1). In this study, long-term operation of a laboratory-scale sequencing batch reactor system was investigated for estimating this coefficient according to the low food-to-microorganism ratio bioassay and simulation methods, as recommended in the Water Environment Research Foundation (Alexandria, Virginia) report (Melcer et al., 2003). The estimated muA,max values using steady-state model calculations for four operating periods ranged from 0.83 to 0.99 day(-1). The International Water Association (London, United Kingdom) Activated Sludge Model No. 1 (ASM1) dynamic model simulations revealed that a single value of muA,max (1.2 days(-1)) could be used, despite variations in the measured specific nitrification rates. However, the average muA,max was gradually decreasing during the activated sludge chlorination tests, until it reached the value of 0.48 day(-1) at the dose of 5 mg chlorine/(g mixed liquor suspended solids x d). Significant discrepancies between the predicted XA/YA ratios were observed. In some cases, the ASM1 predictions were approximately two times higher than the steady-state model predictions. This implies that estimating this ratio from a complex activated sludge model and using it in simple steady-state model calculations should be accepted with great caution and requires further investigation.

Impact of Negative-Bias Temperature Instability in Nanoscale SRAM Array: Modeling and Analysis

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> One of the major reliability concerns in nanoscale very large-scale integration design is the time-dependent negative-bias-temperature-instability (NBTI) degradation. Due to the higher operating temperature and increasing vertical oxide field, threshold voltage (<formula formulatype="inline"><tex>$V_{t}$</tex></formula>) of PMOS transistors can increase with time under NBTI. In this paper, we examine the impact of NBTI degradation in memory elements of digital circuits, focusing on the conventional 6T-SRAM-array topology. An analytical expression for the time-dependent <formula formulatype="inline"><tex>$V_{t}$</tex></formula> degradation in PMOS transistors based on the empirical reaction-diffusion (RD) framework was employed for our analysis. Using the RD-based <formula formulatype="inline"><tex>$V_{t}$</tex></formula> model, we analytically examine the impact of NBTI degradation in critical performance parameters of SRAM array. These parameters include the following: 1) static noise margin; 2) statistical <emphasis emphasistype="smcaps">read</emphasis> and <emphasis emphasistype="smcaps"> write</emphasis> stability; 3) parametric yield; and 4) standby leakage current <formula formulatype="inline"><tex> $(I_{\rm DDQ})$</tex></formula>. We show that due to NBTI, <emphasis emphasistype="smcaps">read</emphasis> stability of SRAM cell degrades, while <emphasis emphasistype="smcaps">write</emphasis> stability and standby leakage improve with time. Furthermore, by carefully examining the degradation in leakage current due to NBTI, it is possible to characterize and predict the lifetime behavior of NBTI degradation in real circuit operation. </para>

InGaAsP–InP Avalanche Photodiodes for Single Photon Detection

In this paper, we describe the design, characterization, and modeling of InGaAsP/InP avalanche diodes designed for single photon detection at wavelengths of 1.55 and 1.06 mum. Through experimental and theoretical work, we investigate critical performance parameters of these single photon avalanche diodes (SPADs), including dark count rate (DCR), photon detection efficiency (PDE), and afterpulsing. The models developed for the simulation of device performance provide good agreement with experimental results for all parameters studied. For 1.55-mum SPADs, we report the relationship between DCR and PDE for gated mode operation under a variety of operating conditions. We also describe in detail the dependence of afterpulsing effects on numerous operating conditions, and in particular, we demonstrate and explain a universal functional form that describes the dependence of DCR on hold-off time at any temperature. For 1.06-mum SPADs, we present the experimentally determined relationship between DCR and detection efficiency for free-running operation, as well as simulations complementing the experimental data.

Reversed-Phase High-Performance Liquid Chromatographic Prefractionation of Immunodepleted Human Serum Proteins to Enhance Mass Spectrometry Identification of Lower-Abundant Proteins

Serum analysis represents an extreme challenge due to the dynamic range of the proteins of interest, and the high structural complexity of the constituent proteins. In serum, the quantities of proteins and peptides of interest range from those considered "high abundance", present at 2-70% by mass of total protein, to those considered "low abundance", present at 10(-12) M or less. This range of analytical target molecules is outside the realm of available technologies for proteomic analysis. Therefore, in this study, we have developed a workflow toward addressing the complexity of these samples through the application of multidimensional separation techniques. The use of reversed-phase methods for the separation and fractionation of protein samples has been investigated, with the goal of developing an optimized serum separation for application to proteomic analysis. Samples of human serum were depleted of the six most abundant proteins, using an immunoaffinity LC method, then were separated under a variety of reversed-phase (RP) conditions using a macroporous silica C18 surface modified column material. To compare the qualities of the RP separations of this complex protein sample, absorbance chromatograms were compared, and fractions were collected for off-line SDS-PAGE and 2D-LC-MS/MS analysis. The column fractions were further investigated by determination of protein identities using either whole selected fractions, or gel bands excised from SDS-PAGE gels of the fractions. In either case samples underwent tryptic fragmentation and peptide analysis using MALDI-MS or LC-MS/MS. The preferred conditions for RP protein separation exhibited reproducibly high resolution and high protein recoveries (>98%, as determined by protein assay). Using the preferred conditions also permitted high column mass load, with up to 500 microg of protein well tolerated using a 4.6 mm ID x 50 mm column, or up to 1.5 mg on a 9.4 mm ID x 50 mm column. Elevated column temperature (80 degrees C) was observed to be a critical operational parameter, with poorer results observed at lower temperatures. The combination of sample simplification by immunoaffinity depletion combined with a robust and high recovery RP-HPLC fractionation yields samples permitting higher quality protein identifications by coupled LC-MS methods.

Ensuring the operational health of droplet-based microelectrofluidic biosensor systems

Recent events have heightened the need for fast, accurate, and reliable biological/chemical sensor systems for critical locations. As droplet-based microelectrofluidic sensor systems become widespread in these safety-critical biomedical applications, reliability emerges as a critical performance parameter. In order to ensure the operational health of such safety-critical systems, they need to be monitored for defects, not only after manufacturing, but also during in-field operation. In this paper, we present a cost-effective concurrent test methodology for droplet-based microelectrofluidic systems. We present a classification of catastrophic and parametric faults in such systems and show how faults can be detected by electrostatically controlling and tracking droplet motion. We then present a fault simulation approach based on tolerance analysis using Monte-Carlo simulation to characterize the impact of parameter variations on system performance. Finally, we present experimental results on a droplet-based microelectrofluidic system for a real-time polymerase chain reaction application.

Statistical Modelling of MOS Transistor Mismatch for High‐voltage CMOS Processes

AbstractThe random mismatch of semiconductor devices caused by local variations of the production process strongly influences critical performance parameters of analog circuits. In order to estimate the influence of the device mismatch on the circuit yield during the design phase, statistical mismatch models for the individual components must be provided for circuit simulation. Based on extensive statistical measurements of matched pairs using special test structures, an algorithm is presented to extract device mismatch parameters for high‐voltage transistors. Due to the special construction of high‐voltage transistors the mismatch parameters must be determined in two steps taking into account the effect of the drift region at high gate voltages. Therefore, the device mismatch for the threshold voltage, the gain factor and the mobility reduction are extracted from a sensitivity model in saturation, whereas the extraction of the drift‐resistance mismatch uses a modified MOS transistor model in the ohmic region. Based on the mismatch parameters for several device sizes a proper geometric model is extracted allowing the mismatch parameters to be scaled with the device dimensions. The mismatch parameters are implemented as part of circuit simulation model libraries to be used for Monte Carlo simulation. Production control parameters enable the monitoring of device mismatch for high‐voltage CMOS transistors. Copyright © 2005 John Wiley &amp; Sons, Ltd.

KNOW THY PROCESS

THE U.S. FOOD & DRUGADMINIStration has sent the pharmaceutical industry a message with its guidance document supporting process technology (PAT), part of a broader initiative on current Good Manufacturing Practices (cGMP). Quality, the agency asserts, cannot be tested into products; it should be built-in or be there by design. Make it so, the agency concludes, by better understanding and controlling manufacturing processes, and regulatory oversight will come, as it's needed, based on scientific, risk-based assessments. According to FDAs definition, PAT is a system for designing, analyzing, and controlling manufacturing through timely measurements of critical quality and performance parameters. It defines analytical broadly to include chemical, physical, mathematical, and other analyses used in an integrated way Available PAT tools include multivariate data acquisition and analysis, analyzers and other systems to monitor and control processes and production end points, and continuous improveme...

05/00317 Mild combustion: Cavaliere, A. and de Joannon, M. Progress in Energy and Combustion Science, 2004, 30, (3), 329–366

This experimental study investigates the stability and emission characteristics of the nonpremixed MILD combustion from a parallel jet burner firing propane (C3H8) in a cylindrical furnace without preheating and dilution. Forty cases are examined by varying the fuel-air nozzle separation S (= 8 mm–105 mm), global equivalence ratio Φ (= 0.6–1.0) and thermal input Pin (= 10 and 15 kW) to highlight the impact of S. The investigation is carried out based on the measurements of in-furnace temperature and exhaust species concentrations, as well as the visual inspection into the furnace. It is demonstrated that the NO emission (ENO) decreases generally with increasing either S (at S > 8 mm) or Φ (at least for Φ ≤ 1.0). Interestingly, the combustion for S = 8 mm behaves like a premixed counterpart and so is distinct from the other cases: e.g., this combustion is fully flameless or stable in the MILD regime over a wider range of Φ and its ENO has a weaker dependence on the furnace temperature. By contrast, for S = 45 mm, the flameless mode takes place only at Φ = 1.0 due to the small mixing zone under this air-fuel arrangement, which is revealed by aerodynamic analysis. Hence, the corresponding experimental ENO-S relationship appears to have a turning point around S = 45 mm. For the present study, all the measured NO emissions for S = 8–105 mm fall as the overall furnace temperature rises, which seemingly differs from the existing knowledge. To explain this and other results, the numerical analysis from computational fluid dynamics (CFD) is performed. It is found that the variations of NO emissions depends on the maximum temperature within the furnace rather than the average furnace temperature. Finally, the present study approves that the fuel-air jet separation should be taken as a critical operational parameter when designing the parallel multiple jet burner for nonpremixed MILD combustion.

Capillary isoelectric focusing--reproducibility and protein adsorption.

Capillary isoelectric focusing (CIEF) is an important tool for the quality assurance of biotechnologically maintained drugs and for proteome analysis. The critical performance parameters of this technique are the precisions of isoelectric point (pI) values and peak areas. Compared to capillary zone electrophoresis (CZE), where precise results can be obtained (e.g., 0.5% relative standard deviation (RSD) for peak areas, n = 60), only few data are available for CIEF experiments. So far, reproducible data of pI values (RSD = 0.5%) have been acquired, but peak areas show inferior results (about 3-15% RSD). Nonstable capillary coatings and protein adsorption have been discussed as possible reasons. Recent work of Righetti et al. [25, 27] has proven that the use of coated capillaries can reduce the adsorption of proteins by 50% but cannot prevent it. In our CIEF experiments irregular and poorly reproducible peak patterns have been observed. In a long-time experiment of 106 repeated runs, an overall RSD of 10% was obtained for peak areas, RSD of 2% only in series of about 10 consecutive replicates. Especially at higher concentrations the reproducibility deteriorates. This seems to be the result of a self-amplifying process, induced by adsorbed protein molecules, leading to further agglomerations. CZE control experiments in linear polyacrylamide (LPA)-coated capillaries proved a strong pH dependency of these effects within a small range. Compared to bare fused-silica surfaces, adsorption effects are reduced but not inhibited. An enhancement of reproducibility in CIEF experiments can be achieved only by controlling the interactions of proteins and capillary walls.

Numerical simulation of semiconductor optical amplifier assisted Sagnac gate and investigation of its switching characteristics

The switching characteristics of a semiconductor optical amplifier (SOA)-assisted Sagnac gate are analyzed in terms of their critical performance parameters for full duty cycle operation from 10 to 40 GHz. Within this frame, the influence of the control pulse width, as well as of the SOA gain recovery time on the switching energy and the contrast ratio, is examined through numerical simulation. The obtained results show that full switching operation at 40 GHz or higher is feasible either by deploying gain recovery reduction techniques in bulk SOAs, or other alternative technologically advanced optical devices, such as quantum-dot SOAs.

Analysis of a vapour ejector refrigeration system with environment friendly refrigerants

Vapour ejector refrigeration system yields better performance when the ejector operates at choking-mode. A computer code based on existing one dimensional ejector theory has been developed to carry out a study on performance of the system. When operating conditions are changed, the critical performance parameters of the system get shifted to different critical values. The code includes effects of change in specific heat of the working fluid and friction at the constant-area mixing chamber besides internal irreversibility of the ejector. The simulated performance results are compared with the available experimental data from the literature for validation. The effects of operational parameters and ejector configurations of the system on critical performance are studied. Also, comparison of performance of the system with environment friendly refrigerants, R134a, R152a, R290, R600a and R717 is made.

Experimental simulation of impact and sliding wear in the top piston ring groove of a gasoline engine

The influence of normal impact and sliding on wear and surface damage at the lubricated interface between the top piston ring and the piston was investigated using a specially adapted tribometer. Standard production components were tested, the piston rings being nitrocarburized steel with a production lapped finish and the pistons a hypereutectic aluminium-silicon alloy, either tin-plated or hard anodized. Experiments were undertaken at loads, velocities and temperatures comparable with a modern automotive, four-stroke, gasoline engine, either dry or lubricated with a fully formulated SAE 10W30 engine oil. Lubricant starvation was found to be the most critical operational parameter leading to surface damage and wear. An important phenomenon observed was the tendency of piston material to transfer and adhere to the ring surface, so-called ‘microwelding’. Anodizing was shown to be a very effective treatment to resist microwelding, although it is regarded as an expensive solution by the automotive industry. The experimental observations are consistent with fatigue wear of the piston groove, followed by material transfer to the piston ring flank and accelerated wear during sliding.

A Circumferential Slot Virtual Impactor

A virtual impactor aerosol concentrator has been developed that uses circumferential slots for acceleration of aerosol particles and for collection of the coarse fraction. This allows for accurate and economical machining of small slot widths, which leads to low-pressure losses for the separation process. One important application of the device is in the concentration of bioaerosols, especially for military field applications where minimization of power consumption is necessary. A prototype configuration of the circumferential slot virtual impactor (CSVI), which was designed using numerical methods, was constructed and tested. The device has a curvilinear slit nozzle with a diameter of 150.3 mm (5.918 in), which provides a total slot length of 472 mm. Its slot width was 0.499 mm (0.0197 in). According to Loo and Cork, for circular-jet virtual impactors the misalignment between the axis of the acceleration jet and the receiver nozzle will cause an increase in wall losses of about 1.6% for each 1% of misalignment. Measurements were made of the nozzle dimensions in the critical region of the CSVI that showed 1.8% relative misalignment. When this prototype was operated at a flowrate of 122 l/min and a flow fraction (minor air flowrate/total air-flowrate) of 10%, the cutpoint was 2.2 μm aerodynamic diameter and the corresponding cutpoint Stokes number was 0.58. The collection efficiency was greater than 72% for particle sizes larger than twice the cutpoint, up to the largest particle size tested (10 μm aerodynamic diameter). The peak collection efficiency was greater than 95%. For virtual impactors, a critical performance parameter is the loss of particulate matter to the inner walls of the system. For the prototype system, where numerical methods had been used to generate designs that reduced wall losses, the losses at the cutpoint size of 2.2 μm aerodynamic diameter, are approximately 3%. For an operational condition of a total flowrate of 122 l/min and a coarse particle flow fraction of 10%, the pressure drop across the major flow stream (fine particle stream) was 63 Pa (0.25 in of water), with an ideal power consumption of 0.14 watts.

Vitesse wins InP from DARPA

Vitesse has received a $6m DARPA contract to develop InP ICs for military communications, in collaboration with BAE Systems and the University of Illinois Urbana Champaign (UIUC). It will develop advanced manufacturing processes and communication ICs using its sub-micron VIP-2 InP HBT technology. The initial 18-month contract contains option phases, which, if implemented, would bring the total value of the contract to more than $15m. The contract allows Vitesse to enhance the capabilities of its VIP-2 process, selected for its ability to enhance speed, power, performance, circuit reliability and production-worthy manufacturing practices required for the DARPA specification. InP technology allows direct digital synthesis of high-frequency signals, simplifying the system design and reducing the number of discrete components required in advanced satellite, aircraft and terrestrial communication systems. Vitesse will collaborate with BAE Systems on the design of communications circuits; initially, these are for direct digital frequency synthesis (DDFS) for electronic warfare and radar applications. UIUC will focus on research for the next-generation transistor structures meant to further extend circuit performance and applications. A factor of two improvements in critical performance parameters has already been attained in early VIP-2 experiments at 0.45μ. Further scaling is planned, incorporating UIUC’s findings, the ultimate goal to shrink device geometry to 0.25μ. This will result in static flip-flop toggle frequencies of 150GHz. This is a short news story only. Visit www.three-fives.com for the latest advanced semiconductor industry news.

Bolted large seismic steel beam-to-column connections Part 2: numerical nonlinear analysis

A large bolted steel moment-resisting connection was studied by nonlinear numerical analysis. This connection was a single-sided beam-to-column assembly that is representative of exterior beam-to-column connections. It was composed of a W36 × 150 Grade 50 beam and a W14 × 283 Grade 50 column. The T-stubs were cut from W40 × 264 sections of Grade 50 steel. The T-stub stems were welded and prestressed by high-strength bolts to the beam flanges in a fabricating shop. Final beam-to-column assembly required no additional welding: the T-stub flanges were bolted to the column and the column shear tab was bolted to the beam web. During cyclic testing the beam deformation was minimal due to the active participation of the T-stub flanges. A separation was observed between the T-stub flanges and the column flange. The separation occurred due to plastic bending deformation in the T-stub flanges. This phenomenon allowed energy dissipation and prevented severe buckling in the beam flanges and beam web. The tests revealed the importance of the numerical analysis of the connection to obtain a better understanding of the critical performance parameters. A finite element analysis was conducted on a specimen with rectangular- shaped stems. The analysis consisted of two parts: a solid element analysis of the T-stub under tension load in the stem and a shell element modeling with buckling and instability analysis. The solid element analysis was conducted to study the local behavior of the T-stub, whereas the shell model analysis was performed to study the global behavior of the connection.

Lux transfer: Complementary metal oxide semiconductors versus charge-coupled devices

We compare the performance of competing CCD and CMOS imaging sensors including backside-illuminated devices. Comparisons are made through a new performance transfer curve that shows at a glance performance deficiencies for any given pixel architecture ana- lyzed or characterized. Called lux transfer, the curve plots SNR as a function of absolute light intensity for a family of exposure times over the sensor's dynamic range (i.e., read noise to full well). Critical performance parameters on which the curve is based are reviewed and analytically described (e.g., quantum efficiency (QE), pixel nonuniformity, full well, dark current, read noise, modulation transfer function (MTF), etc.). Be- sides SNR, many by-products come from lux transfer including dynamic range, responsivity (e 2 /lux-s), charge capacity, linearity, and Interna- tional Organization for Standards (ISO) rating. Experimental data gener- ated by 4 mm, three transistor (3T) pixel digital video graphics array (DVGA) and a 5.6-mm, 3T pixel digital extended graphics array (DXGA) CMOS sensors are presented that demonstrate lux transfer use. © 2002

Optomechanical model of surface micromachined tunable optoelectronic devices

Linewidth is a critical performance parameter for many optoelectronic devices. We have developed a combined optical and mechanical simulation tool and demonstrate its application to micromachined vertical-cavity tunable optoelectronic devices. The deformation of the mirror surface is calculated from the area moment method. The optical field distribution is calculated by the Fox-Li method, and the diffraction losses are estimated from second-order perturbation theory. By comparison to experimental results, we find that the deformation of the central plate is well predicted by our theory. While deformation can be a major source of linewidth broadening in MEMS tunable optoelectronic devices, it is not the primary source in our devices.

Realistic end-to-end simulation of the optoelectronic links and comparison with the electrical interconnections for system-on-chip applications

A detailed comparison of optoelectronic versus electrical interconnections for system-on-chip applications is performed in terms of signal latency and power consumption. Realistic end-to-end models of both interconnection schemes are employed in order to evaluate critical performance parameters. A variety of electrical and optoelectronic interconnection configurations are implemented and simulated using accurate optical device and electronic circuit models integrated under an integrated circuit (IC) design computer-aided design tool. Two commercial complementary metal-oxide-semiconductor (CMOS) technologies (0.8 /spl mu/m and 0.25 /spl mu/m) are used for the estimation of the signal latency and the power consumption as a function of the interconnection length for the different link configurations. It was found that optoelectronic interconnects outperform their electrical counterparts, under certain conditions, especially for relatively long lines and multichannel data links.