Reliable Process Control Research Articles

Cool the Generators: System Reliability and Fault Tree Analysis of Hydrogen Cooling Systems

A comprehensive hydrogen (H2) cooling system (HCS) is presented for the cooling of n # 250-MW generators of fossil-fuel power plants. A novel six stage hot redundant structure (S2HRS)-based HCS clubbed with highly reliable and efficient process control and instrumentation system is proposed for the cooling of large generators in integrated gasification combined cycle power plants (CCPPs). This article provides a comparison between the proposed and the existing systems in terms of system reliability and fault tree analysis (FTA). The effectiveness of real-time featured proposed HCS is validated by computer simulation using RS-View32 Works, a real-time automation platform.

Real-Time Breakthrough Detection for Laser Drilling Based on Coaxial Visual Sensing Technology

As the production demand for laser drilled holes continues to grow, efficient and reliable process monitoring and control techniques are required in order to improve the manufacturing efficiency and reduce manufacturing cost for ensuring quality conformance. A robust, real-time monitoring system for breakthrough and the drilling depth detection in laser drilling is proposed. The system is based on based on coaxial visual sensing technology of the working surface using a CMOS camera, coupled with microcontroller control of the drilling laser operation. The camera is installed adjacent to the entry surface of the workpiece, and the spatial extend of the laser-induced plasma at the working site is monitored as the criterion for breakthrough detection. Therefore, on-line inspection system with low cost is developed to increase productivity. Experimental results show that the proposed system successfully detects when the laser beam has broken through a workpiece, and turns off the laser automatically by feedback control.

Stepwise reduction of the culture redox potential allows the analysis of microaerobic metabolism and photosynthetic membrane synthesis in Rhodospirillum rubrum

Bacterial growth under oxygen-limited (microaerobic) conditions is often accompanied by phenomena of great interest for fundamental research and industrial application. The microaerobic lifestyle of anoxygenic photosynthetic bacteria like Rhodospirillum rubrum harbors such a phenomenon, as it allows the formation of photosynthetic membranes and related interesting products without light. However, due to the technical difficulties in process control of microaerobic cultivations and the limited sensitivity of available oxygen sensors, the analysis of microaerobic growth and physiology is still underrepresented in current research. The main focus of the present study was to establish an experimental set-up for the systematic study of physiological processes, associated with the growth of R. rubrum under microaerobic conditions in the dark. For this purpose, we introduce a robust and reliable microaerobic process control strategy, which applies the culture redox potential (CRP) for assessing different degrees of oxygen limitation in bioreactor cultivations. To describe the microaerobic growth behavior of R. rubrum cultures for each of these defined CRP reduction steps, basic growth parameters were experimentally determined. Flux variability analysis provided an insight into the metabolic activity of the TCA cycle and implied its connection to the respiratory capacity of the cells. In this context, our results suggest that microaerobic growth of R. rubrum can be described as an oxygen-activated cooperative mechanism. The present study thus contributes to the investigation of metabolic and regulatory events responsible for the redox-sensitive formation of photosynthetic membranes in facultative photosynthetic bacteria. Furthermore, the introduced microaerobic cultivation setup should be generally applicable for any microbial system of interest which can be cultivated in common stirred-tank bioreactors.

Precise millisecond annealing for advanced material processing

AbstractFlash lamp annealing (FLA) reduces the thermal budget on the bulk and thus hinders undesired thermal diffusion. For reliable process control, however, a temperature measurement concept is needed that is capable of facing the high radiation background of the flash lamps and the millisecond detection regime at the same time (Reichel et al., Crit. Rev. Solid State Mater. Sci. 36, 102 (2011) [1]). A new concept has been developed for precise in‐situ temperature measurement during flash‐lamp millisecond annealing. There has been taking advantage of FLA for various applications. Implantation and subsequent FLA were used to obtain III‐V semiconductor quantum dots on silicon pillars (Prucnal et al., Nano Lett. 11, 2814 (2011) [2]). The same procedure was applied to achieve superconductivity with conventional silicon technolog (Fiedler et al., Phys. Rev. B 83, 214504 (2011) [3]). FLA was further used for advanced doping of “dirty‐silicon” solar cells. The short annealing cycles allow for successful dopant activation while undesired metal impurities remain electrically inactive (Prucnal et al., Acta Phys. Pol. A 120, 192 (2011) [4]). These examples show that in‐situ process control is required to make sure the major advantage of millisecond annealing is not narrowed by unreliable temperature measurement. In this contribution, a method will be presented that satisfies this issue by in‐situ distinction between thermal and flash lamp radiation (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Dynamic process control and monitoring of novel S3RS based hydrogen cooling system

Hydrogen gas is circulated in a closed loop within the generators to remove heat from its active parts. Then it is cooled by gas-to-water heat exchangers that are part of the stator frame. Faster heat dissipation of generators in power plant call for hydrogen cooling system (HCS) at generating end. Purity in hydrogen (H2) improves its ability to dissipate heat within generators. Therefore, there is an essential requirement of a highly reliable and efficient process control and monitoring system of H2 cooling. This paper presents development and implementation of supervisory control and data acquisition (SCADA) based process control and monitoring system. It proposes a novel six stage standby redundant structured (S3RS) HCS for generators cooling in typical thermal power plant. The entire process control and monitoring of HCS has been developed and simulated on RSViewSE, a real-time industrial automation platform by Allen Bradley–Rockwell Automation. And, the system reliability of proposed S3RS process model is implemented using MATLAB. This process model satisfies the requirement of IEEE Std. C37.1™-2007, the standard for SCADA and Automation Systems. It also follows IEEE Std. 493™-1997, the standard for design of reliable industrial and commercial power systems, and IEC 60034-3, the standard for rotating electrical machines.

SU‐C‐217BCD‐04: Application of Statistical Process Control to Long Term CT Constancy Testing

Purpose: To validate how a reliable Statistical Process Control can be implemented, using routine scanning of a test phantom and automatic QA program, to establish effective long term performance monitoring of CT imaging systems. Methods: A data set of 21474 QA images acquired on 1565 distinct days was collected on a CT system from 2002 until 2011, during a large population based quantitative imaging study with a longitudinal component, using the Catphan® 500 phantom. The image data was processed with the ImageOwl Catphan®QA software. Tolerances for CT imaging quality parameters were selected from IEC‐61223‐3‐5 and other sources. Process capability, Cp, describes the ratio of tolerance range to observed standard deviation. Cpk additionally weighs in closeness to one side of specification limits. A process capability equal to 1 means 99.7% chance of correctly observing a single measurement within specification, i.e. 3 sigma. Results: While slice thickness measurement can be an extremely reliable process (Cp=4.5, 5.1), image uniformity at standard +/−4HU limits, though generally reliable (Cp=2.1), showed relatively high probability of reporting false positive system out of specification (Cpk=0.8), due to measurements being near lower limit. Tube aging is manifested by changes in effective energy, causing changes in readings of sensitometric targets. This is confirmed by an effective energy value reset at tube renewal. Conclusions: By monitoring modern CT scanners with today's test systems using commonly accepted control limits, reliable go/no‐go signals can be generated for most CT QA variables. However, physicists implementing a monitoring system have to pay special attention to low process capability caveats when establishing monitoring action rules. This is especially important when implementing monitoring of large scale clinical or research operations requiring high reliability and cost effective QA solutions. Funding provided by The Phantom Laboratory, Incorporated and Image Owl, Incorporated

Activity Coefficients of di-(2-ethylhexyl) Phosphoric Acid in Select Diluents

This work characterizes the non-ideal behavior of the solvent extraction agent di-(2-ethylhexyl) phosphoric acid (HDEHP), constituting one piece of an effort to develop increasingly accurate models of advanced fuel separation processes such as TALSPEAK. Robust models are particularly important for processing high-level radioactive material in order to minimize the generation of secondary waste and to ensure reliable process control. Here, vapor pressure osmometry (VPO) data on binary solutions of HDEHP in toluene, dodecane, or cyclooctane yields the activity coefficients for each component after analysis. Initially, diluent activity data is obtained using the VPO results and then modeled using Scatchard-Hildebrand theory to provide the activity coefficients for HDEHP.

Correlation of Community Dynamics and Process Parameters As a Tool for the Prediction of the Stability of Wastewater Treatment

Wastewater treatment often suffers from instabilities and the failure of specific functions such as biological phosphorus removal by polyphosphate accumulating organisms. Since most of the microorganisms involved in water clarification are unknown it is challenging to operate the process accounting for the permanent varying abiotic parameters and the complex composition and unrevealed metabolic capacity of a wastewater microbial community. Fulfilling the demands for water quality irrespective of substrate inflow conditions may emit severe problems if the limited management resources of municipal wastewater treatment plants are regarded. We used flow cytometric analyses of cellular DNA and polyphosphate to create patterns mirroring dynamics in community structure. These patterns were resolved in up to 15 subclusters, the presence and abundances of which correlated with abiotic data. The study used biostatistics to determine the kind and strength of the correlation. Samples investigated were obtained from a primary clarifier and two activated sludge basins. The stability of microbial community structure was found to be high in the basins and low in the primary clarifier. Despite major abiotic changes certain subcommunities were dominantly present (up to 80% stability), whereas others emerged only sporadically (down to 3% stability, both according to equivalence testing). Additionally, subcommunities of diagnostic value were detected showing positive correlation with substrate influxes. For instance blackwater (r(s) = 0.5) and brewery inflow (both r(s) = 0.6) were mirrored by increases in cell abundances in subclusters 1 and 6 as well as 4 and 8, respectively. Phosphate accumulation was obviously positively correlated with nitrate (r(s) = 0.4) and the presence of denitrifying organisms (Rhodacyclaceae). Various other correlations between community structure and abiotic parameters were apparent. The bacterial composition of certain subcommunities was determined by cell sorting and phylogenetic tools like T-RFLP. In essence, we developed a monitoring tool which is quick, cheap and causal in its interpretation. It will make laborious PCR based technique less obligatory as it allows reliable process monitoring and control in wastewater treatment plants.

A New Automated and High Speed Machinery System for Filling High Viscous Liquids

The application of automation to industries brings revolution for manufacturing techniques and allows more sophisticated, flexible, reliable, and cost-effective manufacturing process control. Automation is to use control system to reduce human labor intervention during manufacturing processes and production. It plays very important role and puts strong impact in industries. Automation is not only significantly increasing the production speed but also more accurately controlling product quality. The automated manufacturing can maintain consistent quality, shorten lead time, simplify material handling, optimize work flow, and meet the product demand for flexibility and convertibility in production. The current economic globalization requires significant labor cost reduction through industry automation, better machine tools, and efficient production process. This paper is to design and develop a new automated and high speed machinery system for filling high viscous liquids. It includes the design of automated and high speed machinery, computer aided modeling and simulation of automated mechanical system, and prototype testing. The major advantages of this new automated and high speed liquid filling system include reliable function, high volume filling rates, good sealing capacity, and cost-effective manufacturing process. This new automated and high speed manufacturing systems has been analyzed by computer aided modeling and simulation, and verified through prototype testing. Both results indicate that this automated and high speed manufacturing systems can keep high product quantity and reliable product quality.

Fabrication of sub-100-nm metal-oxide-semiconductor field-effect transistors with asymmetrical source/drain using I-line double patterning technique

The authors present a simple double patterning technique with I-line stepper to define nanoscale structures and have successfully fabricated n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with sub-100-nm gate length. With this approach, polycrystalline silicon (poly-Si) gate with linewidth down to 80 nm could be formed with good control, which far exceeds the resolution limit of conventional I-line lithography. Moreover, ineffectiveness of end point detection in the second poly-Si gate definition is also addressed. For reliable process control in the second etching step, appropriate mask design is found to be essential. Finally, sub-100-nm MOSFETs with or without halo implemented symmetrically or asymmetrically are fabricated and characterized.

UT/SRP CO2 capture pilot plant — Operating experience and procedures

Abstract The Separations Research Program (SRP) pilot plant is located at The University of Texas (UT) Pickle Research Campus and has been operated as a carbon capture facility since 2002. The semi-works scale pilot facility uses air and 3–14 mol% CO2 as flue gas as it applies the latest advancements in carbon dioxide recovery technology. The capacity of the pilot plant is approximately 15 m3/min of gas and 130 liters/min of solvent. Past experimental studies include solvent performance characterization using potassium carbonate with piperazine, monoethanolamine, concentrated piperazine and other proprietary solvents. In recent years, the pilot plant has been utilized to determine the mass transfer and hydraulic characteristics of various structured and random packings using amine-based solvents for CO2 absorption. In 2002, the UT/SRP began developing improved measurement techniques and operating procedures to ensure reliable process control and closure of material and energy balances. Past experience and learning with the UT/SRP pilot plant is currently being utilized for the design and operation of several future pilot plants that will process actual coal-fired flue gas. The purpose of the presentation is to provide a brief description of the UT/SRP CO2 capture pilot plant capabilities, innovative operational procedures and instrument accuracies. The objectives of this paper are to discuss SRP pilot plant experience including: process description, operations and control, key equipment, measurement methods including novel techniques, overall process performance, and future work.

Minority carrier lifetime imaging of silicon wafers calibrated by quasi-steady-state photoluminescence

Reliable process control or predictions of solar cell efficiencies from minority carrier lifetimes on silicon wafers require precise lifetime measurements. For inhomogeneous material quality this implies the necessity of adequately averaged spatially resolved lifetime measurements. Materials such as, e.g. multicrystalline upgraded metallurgical grade silicon frequently feature relatively low lifetimes, high trap densities, and several material parameters (charge carrier mobilities and net dopant concentration) that are not straightforwardly predictable or measurable. As this may substantially compromise conventional lifetime measurements, we present a solely luminescence based lifetime imaging technique, which requires virtually no a priori information about material parameters. Our approach is based on a calibration of a wafer's photoluminescence image through a precise lifetime determination of a part of this wafer via quasi-steady-state photoluminescence. Carrier mobilities, net dopant concentration, and surface morphology leave the determination of lifetime virtually unaffected, the injection dependence of lifetime is properly taken into account, and lifetimes down to the timescale of a microsecond can be reliably measured.

Monitoring of magnetron target poisoning by measurement of higher harmonics of discharge voltages

Reactive magnetron sputtering suffers from processing stability problems and the optimal experimental conditions for thin film deposition usually lie very close to an abrupt transition from the metallic to the compound mode. Therefore, a fast feedback method is needed to automatically control either the flow of the reactive gas, or the discharge power to keep the process at the desired operating point. A promising method for this process of monitoring, based on the measurement of amplitudes of higher harmonic frequencies of discharge voltages, is proposed. The measurement of the amplitudes can be performed either by an uncompensated probe in the plasma or on the cable between the RF generator and the sputtered target. The sensitivity of the proposed method is significantly better than measurement of other electrical quantities conventionally used for process control. Physical reasons for the change in amplitudes of higher harmonic frequencies during the mode transition are found. The paper shows that the observed changes in amplitudes of higher harmonics by the transition are not caused either by the pressure change, or by the changes in the composition of the gas in the reactor volume. It is found that the amplitudes of higher harmonics reflect primarily the state of the magnetron target poisoning. The amplitudes thus belong to a group of process parameters representing the target state, which are considered to be the best for reliable process control.

Operating map – tool for plating functional layers

The increasing demand for special functional layers and layer systems requires reliable electroplating process control. The use of operating maps is demonstrated covering all aspects of the layer formation starting from nucleation, crystal growth and structure as a function of electrochemical kinetics as well as hydrodynamics and mass transport. In particular, the ins uence of pulse plating of Zn as an example is demonstrated. Finally, techniques to characterise the deposits such as Xray s uorescence (layer thickness and distribution), X-ray diffraction (texture and grain size) as well as methods to evaluate hardness, Young’s modulus and ductility are applied. The data are used to produce the operating map via a system of neural networks so that the effect of changing electrochemical deposition parameters and resultant deposit characteristics can be determined. This methodology has the advantage of short access time and high reliability.

Design of self-assembling micromirror arrays for light guiding applications

We present the design and the potential of actuable micromirror arrays for light guiding applications on large areas. These micromirror arrays are intended to be implemented into the windows of buildings and to provide functionalities like daylight guiding into rooms, heat regulation, and glare protection. Placed between two panes of a window, these mirrors are maintenance-free and not subject to defilement. The use of micro system technology on large areas requires very low cost processes and materials, a concept with a minimum of process steps, as well as very easy and reliable process control. We present our design approaches and the corresponding technological results.

모꾸메가네 장신구를 위한 은/동 접합 잉곳 소재 개발

Mokumegane is one of the sophisticated metal craft techniques enabling wood grain surface effect. To embody the mokumegane, an ingot of well-bonded stacked metal plates has been required. Traditionally prepared mokumegane ingots were bonded using charcoal which enables reduction atmosphere, but sometimes end up with collapse of bonding interface due to the lack of reliable process control. We proposed a systematic vacuum direct bonding process for ingots. First, we confirmed copper//copper homogeneous plate bonding at by applying uniaxial press of 2.5kg. We observed 80min required to obtain 90%-bonding ratio and the diffusion coefficient would be enhanced up to 100 times due to surface effect. Second, by considering enhanced diffusion behavior, we also obtained optimum bonding condition in copper/silver heterogeneous plates that ensures 90%-bonding ratio at for 10min with apply uniaxial press. A 7-layered copper/silver ingot is prepared successfully, and eventually the prototype mokumegane cases for mobile phone were fabricated with these ingot.

Characterization of interface state densitiesby photocurrent analysis: comparison of results for different insulator layers

In this work, silicon insulator interfaces are characterized by detailed photocurrent analysis. Results obtained for a variety of samples with different insulator layers and layer thicknesses are presented and discussed. The results show the applicability of the technique for a reliable process control and include data on high-k layers for the first time. Comparison of experiment and simulation is used to explain the injection level dependence of the measurements.

Advanced inspection technique for deep-submicron and high-aspect-ratio contact holes

We developed a technique using electron beams for inspecting contact holes immediately after dry etching and detecting incomplete contact failures. Wafers with deep-submicron contact holes that had high aspect ratios of 10 could be detected during practical inspection time by controlling the charging effect on the wafer surfaces. Measurements of the energy distribution in the secondary electrons exhausted from the bottom of the holes indicated that they were accelerated by the charge-up voltage on the wafer surfaces. Our analysis showed that high-density electron beams must be used to charge the surfaces when the aspect ratio is high. The minimum thickness of the residual SiO2 that could be detected at the bottom of the contact holes was 2 nm using an aspect ratio of 8. Applying this mechanism to optimize the dry etching process in semiconductor manufacturing showed that we could achieve reliable process control.

326 Monitoring and Adaptive Control of Cutting Forces Based on Spindle Motor and Servo Motor Currents in Machining Centers

For the intelligent manufacturing by a machining center, the authors have proposed an extension of fixed cycles to end milling processes in our previous works. For the enhancement of machining productivity, the extension of tool life, and the improvement of machining accuracies, we have proposed a scheme to optimize machining parameters within such a fixed cycle based on the regulation of cutting forces by using the initial machining database. In continuous machining, cutting forces gradually increase as the tool wear progresses. Therefore, it is crucial to perform a more reliable process control by continuously monitoring the cutting force. It is, however, unfavorable to install an additional sensor to monitor cutting forces from the viewpoint of the cost, reliability, and maintainability. To address this issue, this paper presents a scheme to estimate cutting forces by monitoring spindle and servo motor currents, along with a kinematic parameter defined by the geometrical interference between a tool and a workpiece.

New chalcogenide glass chemical sensors for S2- and dissolved H2S monitoring

A non-optimised treatment of wastewaters containing organic and biological substances is very often accompanied by an accidental emanation of hydrogen sulphide H2S and therefore leads (i) to an undesirable odour in the vicinity of water treatment plants, and (ii) to a potential hazard for the neighbouring population. Fast, sensitive and reliable monitoring devices hence of significant importance. Chalogenide and chalcohalide glass are new promising membrane material for detection of heavy metal ions and toxic anions and particularly well adapted for continuous in situ monitoring and industrial process control. In the present paper, we will discuss analytical characteristics of new chalcogenide glass chemical sensors for detection of S2- and dissolved H2S, which slow reliable process control to be carried out at natural pH of wastewaters.