Changes In Process Variables Research Articles

Melt spinning of continuous fibers by cold air attenuation I: experimental studies

Traditionally ultrafine continuous fibers below 1 dpf are produced by extrusion followed by mechanical drawing. In this study, a modified melt spinning apparatus with a high-speed air nozzle was designed and fabricated to produce continuous polypropylene (PP) fibers by cold air drawing only. With this setup, the fiber is quenched and simultaneously attenuated by a symmetric cold air jet. Since the formation of the fiber structure is highly dependent on the processing conditions, the new process provides a unique operation window to study fiber attenuation and structural formation under high-speed cold air drawing. A parametric study was carried out under different process conditions which included processing temperature, air velocity and polymer volume flow rate. Effects of changes in processing variables on the fiber diameter, molecular orientation, tensile strength and other properties were studied. Findings from this study could lead to new processing technologies for producing innovative fiber products.

Monitoring variability of multivariate processes

The paper focuses on determining changes in process variability of multivariate processes. The problem is compounded by the fact that any of the elements in the variance-covariance matrix of variables could change, leading to a change in the process variability. While it may not be feasible to maintain individual control charts for each element of the variance-covariance matrix, some aggregate measure of the variability criteria could be monitored to initially determine if a change has occurred in the process variability. A couple of aggregate measures are proposed and the performance of these suggested measures is explored through a simulation procedure. Compared to the traditional method, which monitors the determinant of the variance-covariance matrix, these alternatives perform well. The performance measure used is the mean time to first detection of a change in the process variability.

In situ diagnostics of the SiC nanostructures growth process

Combustion synthesis (SHS, self-sustainable high-temperature synthesis), carried out in a modified calorimetric bomb, is a fast, efficient, self-sustainable, and one-step production method of new nanomaterials. Among them, SiC nanowires and their bundles are one of the most interesting due to their properties and a variety of possible applications. However, as the growth process occurs probably partially under non-equilibrium conditions, its control and monitoring are rather difficult. Furthermore, the synthesis is very sensitive to any change of process variables, so that the growth mechanism knowledge is essential for the optimization of the synthesis. To overcome those drawbacks, the in-situ diagnostics of combustion is proposed. It is based on the photo-registration of an optical signal (light emitted and observed via polycarbonate observation port). From full HD 25frames/s with resolution 1920×1080, one may calculate the relative signal intensity, its time evolution and find the reaction fingerprint. The validation of experimental protocol consisted in confirmation of results reproducibility, crucial in case of the nonlinear process, within different calculation algorithms and registration conditions.

The Applicability of Statistical Process Control to Systems Involving People Processes and Business Rhythms

ABSTRACTThe operation and maintenance (O&M) activities of systems can account for 75% of total lifecycle cost. To effectively manage cost, optimize system “on” time, and mitigate defects/failures during the O&M phase of a system's lifecycle, the application of systems monitoring and control is encouraged. Statistical process control (SPC) in general, the control chart specifically, is the most common monitoring approach. The control chart provides alerts with respect to the behavior of systems and processes, as well as changes in process variability. Data applied to control charts is assumed to adhere to a normal distribution, a constraint often satisfied in manufacturing and similar industries where the natural variation in the process or system follows the Gaussian distribution. Systems involving people processes and business rhythms can compromise the normality assumption, reducing the reliability of SPC. Through the application of SPC, this paper proposes a novel approach to monitoring operational systems in the systems engineering O&M phase for the express purpose of reducing high costs by mitigating system discrepancies and uncovering inefficiencies. This paper focuses on processes that require 100% system data sampling due to the operational nature of the system.

A Motivational Physical Activity Intervention for Improving Mobility in Older Korean Americans

There has been limited empirical support for interventions designed to promote physical activity targeting mobility in racially diverse older adults. This study aims to examine the effects of a Motivational Physical Activity Intervention (MPAI) on social resource, behavioral change process, physical activity, and mobility variables in sedentary older Korean Americans. A quasi-experimental, repeated-measure, pre- and post-tests design was used. Sixty-four community-dwelling, sedentary older Korean Americans (n = 33 for MPAI group, n = 31 for Attention Control group) participated in the study. There were significant improvements in social resources, including social support from family and friends; behavioral change process variables, including self-efficacy; motivational appraisal; and self-regulation for physical activity. There were significant intervention effects on physical activity, walking endurance, and flexibility. The MPAI is supported as improving mobility and physical activity, as well as increasing motivation for physical activity in older Korean Americans.

The process of cognitive behaviour therapy for chronic fatigue syndrome: Which changes in perpetuating cognitions and behaviour are related to a reduction in fatigue?

ObjectiveCognitive behaviour therapy (CBT) can significantly reduce fatigue in chronic fatigue syndrome (CFS), but little is known about the process of change taking place during CBT. Based on a recent treatment model (Wiborg et al. J Psych Res 2012), we examined how (changes in) cognitions and behaviour are related to the decrease in fatigue. MethodsWe included 183 patients meeting the US Centers for Disease Control criteria for CFS, aged 18 to 65years, starting CBT. We measured fatigue and possible process variables before treatment; after 6, 12 and 18weeks; and after treatment. Possible process variables were sense of control over fatigue, focusing on symptoms, self-reported physical functioning, perceived physical activity and objective (actigraphic) physical activity. We built multiple regression models, explaining levels of fatigue during therapy by (changes in) proposed process variables. ResultsWe observed large individual variation in the patterns of change in fatigue and process variables during CBT for CFS. Increases in the sense of control over fatigue, perceived activity and self-reported physical functioning, and decreases in focusing on symptoms explained 20 to 46% of the variance in fatigue. An increase in objective activity was not a process variable. ConclusionA change in cognitive factors seems to be related to the decrease in fatigue during CBT for CFS. The pattern of change varies considerably between patients, but changes in process variables and fatigue occur mostly in the same period.

Process predictors of the outcome of group drug counseling.

This study examined the relation of process variables to the outcome of group drug counseling, a commonly used community treatment, for cocaine dependence. Videotaped group drug counseling sessions from 440 adult patients (23% female, 41% minority) were rated for member alliance, group cohesion, participation, self-disclosure, as well as positive and non-positive feedback and advice during the 6-month treatment of cocaine dependence. Average, session-level, and slopes of process scores were evaluated. Primary outcomes were monthly cocaine use (days using out of 30), next session cocaine use, and duration of sustained abstinence from cocaine. Secondary outcomes were endorsement of 12-step philosophy and beliefs about substance abuse. More positive alliances (with counselor) were associated with reductions in days using cocaine per month and next-session cocaine use and increases in endorsement of 12-step philosophy. Patient self-disclosure about the past and degree of participation in the group were generally not predictive of group drug counseling outcomes. More advice from counselor and other group members were consistently associated with poorer outcomes in all categories. Individual differences in changes in process variables over time (linear slopes) were generally not predictive of treatment outcomes. Some group behaviors widely believed to be associated with outcome, such as self-disclosure and participation, were not generally predictive of outcomes of group drug counseling, but alliance with the group counselor was positively associated, and advice giving was negatively associated, with the outcome of treatments for cocaine dependence.

A Novel Technique for Monitoring Hydrate Safety Margin

Summary A novel technique has been developed for optimizing hydrate-inhibitor dose rates by monitoring the actual hydrate safety margin. The technique is based on measuring acoustic velocity and electrical conductivity in an aqueous sample taken from the pipeline/separator. The developed system then determines salt and organic inhibitor concentration (e.g., methanol, monoethylene glycol, and kinetic hydrate inhibitors). In the case of thermodynamic inhibitors, the information is then fed to a thermodynamic model determining the hydrate stability zone (HSZ). Superimposing the pipeline operating conditions (e.g., pressure and temperature profile), the developed system can determine the hydrate safety margin. The system can provide warning if the operating conditions are inside the HSZ or if too much inhibitor is being injected. The technique can be used in optimizing inhibitor-injection rates, reducing the impact on the environment and operational costs. It can also improve production-system reliability by constant monitoring the hydrate safety margin and protecting the system against pump malfunction and/or changes in process variables (e.g., water cut). This technique has been developed through a joint-industry project, and its performance has been intensively evaluated using synthetic samples and real produced-water samples by the authors and the project sponsors in field trials. The results demonstrate that this system can be used for different inhibitor systems, including methanol (MeOH)/NaCl, monoethylene glycol (MEG)/NaCl, and kinetic-hydrate-inhibitor/salt systems, with good accuracy. The developed system can have a major impact on reducing the inhibitor-injection rates and environmental impact and improving the reliability of production systems against risks associated with hydrate formation. The developed system can be laboratory-based, a mobile unit, or online, with near-real-time samples taken from live pipelines/separators.

Polishing and local planarization of plastic spherical capsules using tumble finishing

A new method (a variant of tumble finishing) for polishing and achieving local planarization on precision spherical, plastic capsules is described. Such capsules have niche applications, such as ablators used in high-peak-power laser targets for fusion energy research. The as-manufactured ablators contain many shallow domes (many 100's of nm high and a few 10's of μm wide) on the outer surface which are undesirable due to contributions to instabilities during implosion. These capsules were polished (i.e., tumble finished) by rotating a cylindrical vial containing the capsule, many borosilicate glass or zirconia media, and an aqueous-based colloidal silica polishing slurry. During tumble finishing, the relative media/capsule motions cause multiple, random sliding spherical–spherical Hertzian contacts, resulting in material removal, and possibly plastic deformation, on the capsule. As a result, the domes were observed to locally planarize (i.e., converge to lower heights). Utilizing the correct kinematics (i.e., the characteristics of the media/capsule motions), as controlled by the vial rotation rate and the fill fraction of media and slurry, the high velocity downward circumferential media motions were avoided, preventing fracturing of the fragile capsules. Also, the resulting post-polished surface roughness on the capsule was found to scale with the initial media surface roughness. Hence, pre-polishing the media greatly reduced the roughness of the media and thus the roughness of the polished capsule. A material removal model is described based on the Preston model and spherical–spherical Hertzian contacts which shows reasonable agreement with measured average removal rates of 35±15nm/day and which serves as a valuable tool to scale the polishing behavior with changes in process variables. Narrow domes were observed to planarize more rapidly than wider domes. A local planarization convergence model is also described, based on the concept of workpiece–lap mismatch where the local pressure, and hence removal, varies with the gap at the interface contact. The calculated rate and shape evolution of various size isolated domes compares well with the experimental data.

Enhancing the performance of CUSUM scale chart

Control charts act as the most important statistical process monitoring tool, widely used for the purpose of identifying unusual variations in process parameters. Researchers have implemented different rules to increase the sensitivity of Shewhart, CUSUM and EWMA control charts for the detection of small shifts in process location. However, for the monitoring of process scale, the use of such rules has been limited to Shewhart charts. This study proposes the implementation of sensitizing rules in CUSUM scale charts to enhance their ability to detect smaller changes in process variability. The performance of the proposed schemes is evaluated and compared with the simple scale CUSUM scheme, the EWMS chart, the M-EWMS chart and the COMB chart, in terms of run length characteristics such as average run length (ARL) and standard deviation of the run length distribution (SDRL). Control chart coefficients to set the ARL at the desired level are also provided. Two numerical examples are given to illustrate the application of the proposed schemes on practical data sets.

A density-based statistical process control scheme for high-dimensional and mixed-type observations

Statistical Process Control (SPC) techniques are useful tools for detecting changes in process variables. The structure of process variables has become increasingly complex as a result of increasingly complex technologies. The number of variables is usually large and categorical variables may appear alongside continuous variables. Such observations are considered to be high-dimensional and mixed-type observations. Conventional SPC techniques may lose their accuracy and efficiency in detecting changes in a process with high-dimensional and mixed-type observations. This article presents a density-based SPC approach, which is derived from a Local Outlier Factor (LOF) scheme, as a solution to this problem. The parameters in an LOF scheme are investigated and a procedure to design a corresponding control chart is presented. The good performance of the proposed control scheme is demonstrated via numerical simulation.

Theoretical and Experimental Research on the Features of Cutting Force in Rotary Ultrasonic Face Milling of K9 Glass

This study introduces rotary ultrasonic face milling (RUFM) process into flat surface machining of K9 glass. The effective cutting velocity, and cutting length of single diamond particle were presented in RUFM. The model of material removal for RUFM was developed through examining indentation fracture mechanics theory and material removal characteristics of brittle materials, and analyzing kinematics properties of diamond grits in RUFM. With a view of comparative researches, the cutting force of RUFM and diamond milling of K9 glass are compared. The experimental results tell that the relationship between the cutting depth (dc) and the ultrasonic amplitude (A) of the cutter has remarkable effects on cutting force, which was also discussed in the kinematic characteristics analysis section. The results also show that RUFM process can significantly reduce cutting force and the effects of process variable changes on cutting force in RUFM are weaker as dc is smaller than A. However, the reduction trends of the cutting forces in RUFM are very small and even increased in some process conditions, as dc is larger than A. It suggests that the cutting depth should be smaller than the ultrasonic amplitude of the cutter with RUFM process to obtain better processing performance.

A robust method for coupling detection among process variables

Investigating complex interaction patterns among multiple process variables (PVs) is an important task. This paper demonstrates a robust method to estimate direction and strength of interactions among process variables. The method captures rapid changes in process variables through wavelet analysis. It uses single degree of freedom (SDOF) modelling to approximate a non-linear system in terms of linear damped forced oscillators. Phase interaction theory then extracts coupling direction and strength among process variables. The robustness of the proposed technique is verified on simulated Van der Pol oscillators with known directionality and coupling strength with varying signal to noise ratio (SNR). The effectiveness and feasibility of the proposed method have also been demonstrated on simulated data emanating from Canada Deuterium Uranium (CANDU) nuclear power plant steam generator level control mechanism. The extracted patterns of interaction structure among PVs aid to uncover the polishing mechanisms and provide more insights to investigate fault propagation scenarios.

Stoichiometric conversion of biodiesel derived crude glycerol to hydrogen: Response surface methodology study of the effects of light intensity and crude glycerol and glutamate concentration

Photofermentation by the photosynthetic bacterium Rhodopseudomonas palustris has been used to convert the crude glycerol fraction from biodiesel production to hydrogen as a means of converting this large resource to useful energy. In the present study response surface methodology was applied to investigate the interactive effects among several important process parameters; light intensity, and the concentrations of crude glycerol and glutamate, on the stoichiometric conversion of crude glycerol to hydrogen. Under optimal conditions, a light intensity of 175 W/m 2, 30 mM glycerol, and 4.5 mM glutamate, 6.69 mol hydrogen/mole of crude glycerol were obtained, a yield 96% of theoretical. Determination of nitrogenase activity and expression levels showed that there was relatively little variation in levels of nitrogenase protein with changes in process variables whereas nitrogenase activity varied considerably, with maximal nitrogenase activity (228 nmol of C 2H 4/ml/min) at the optimal central point.

Improved design of quantile-based control charts

In a manufacturing process, deterioration in quality may be represented by changes in process variables’ distributions rather than shifts in their means or variances. In this case, when means or variances cannot reflect the real process conditions, we need to monitor whether a sample conforms to an in-control distribution. Quantile-based control charts are suitable tools which can do the monitoring. However, there are no specific procedures for the users to follow to construct such a chart. In this article, we propose a new criterion for the construction of the quantile-based control chart. With this criterion, appropriate quantiles are selected to maximize the test power of the charted statistic. We study most commonly used distributions and specify guidelines for the construction of the quantile-based control charts. Simulation results demonstrate the high efficiency of the proposed method.

“Ready, willing, and (not) able” to change: Young adults’ response to residential treatment

Background: Young adulthood represents a key developmental period for the onset of substance use disorder (SUD). While the number of young adults entering treatment has increased, little is known about the mechanisms of change and early recovery processes in this important clinical population. This study investigated during-treatment change in key therapeutic processes (psychological distress, motivation, self-efficacy, coping skills, and commitment to AA/NA), and tested their relation to outcome at 3 months post-treatment. Methods: Young adults undergoing residential treatment (N=303; age 18–24; 26% female; 95% Caucasian) were enrolled in a naturalistic prospective study and assessed at intake, mid-treatment, discharge, and 3 months following discharge. Repeated-measures and regression analyses modeled during-treatment change in process variables and impact on outcome. Results: Statistically significant medium to large effect sizes were observed for changes in most processes during treatment, with the exception of motivation, which was high at treatment intake and underwent smaller, but still significant, change. In turn, these during-treatment changes all individually predicted 3-month abstinence to varying degrees, with self-efficacy emerging as the sole predictor in a simultaneous regression. Conclusions: Findings help to clarify the mechanisms through which treatment confers recovery-related benefit among young adults. At treatment intake, high levels of abstinence motivation but lower coping, self-efficacy, and commitment to AA/NA, suggests many entering treatment may be “ready and willing” to change, but “unable” to do so without help. Treatment appears to work, in part, by helping to maintain motivation while conferring greater ability and confidence to enact such change.

A Method for Conducting Intensive Psychological Studies with Early-onset Chronically Depressed Patients

An intensive empirical methodology is introduced to evaluate the efficacy of Cognitive Behavioral Analysis System of Psychotherapy (CBASP) treatment for outpatients with early onset chronic depression. The patient with chronic illness presents a unique measurement challenge to psychotherapists. One of the most prominent reasons is the refractory nature of the disorder. In order to measure the change process, the authors have found it helpful to use an acquisition-learning methodology to answer three questions: (1) What are we trying to teach the patient? (2) How much has the patient learned throughout the course of therapy? And, (3) how does the extent of patient learning impact the change indices at the end of treatment and during the follow-up period? Answering questions 2 and 3 allows us to superimpose the change process variables over the performance learning variables on a graph. These combined variables also allow us to test the hypothesis: By learning what psychotherapy teaches, the chronic psychological disorder may be resolved.

On concept of process signature in analysis of multistage surface formation

In this work, an attempt is made to develop a novel approach based on the concept of process signatures to investigate the correlation of the quality of manufactured surface and the process of its generation which is independent to manufacturing conditions. The process signature is the multiscale modifications of surface topography, which depicts the essential changes of the surface state produced on the original surface after abrasive machining. An advanced signal processing technique, the continuous wavelets transform is used to identify the multiscale transfer function of the process which represents the amount of surface modifications. The applicability of this methodology is demonstrated by several practical examples. It is shown that the signature is strongly influenced by abrasive dispersity and granulometry, process induced modes of deformation. The work demonstrates also that the process signatures respond in a predictable fashion to changes in process variables and combinations of stage.

Influence of Wire Feeding Speed, Welding Speed and Preheating Temperature on Hardness and Microstructure of Weld in RQT 701-british Steel Produced by FCAW

FCAW (flux-cored arc welding) is an arc welding process widely used in different industries to join the metals and alloys. The present study focuses on the effect of FCAW-G process parameters on the hardness and microstructure of weld in RQT 701-British steel having 5 mm thickness. In this study, effects of wire feeding speed, welding speed and preheating temperature were investigated. Different samples were produced by employing wire feeding speed of 4.5, 6 and 7.5 m/min, welding speed of 30, 45 and 60 cm/min and preheating temperature of 200, 300 and 400°C. After welding process, brinel hardness (HB) test was performed on weld metal and the micro-structural evolution of weld was analyzed by optical observations of the weld cross sections. Results were clearly illustrated that change in process variables has significant effect on hardness, grain size and phases transformations in weld metal.

Logging on for Better Sleep: RCT of the Effectiveness of Online Treatment for Insomnia

Despite effective cognitive behavioral treatments for chronic insomnia, such treatments are underutilized. This study evaluated the impact of a 5-week, online treatment for insomnia. This was a randomized controlled trial with online treatment and waiting list control conditions. Participants were 118 adults with chronic insomnia. Participants received online treatment from their homes. Online treatment consisted of psychoeducation, sleep hygiene, and stimulus control instruction, sleep restriction treatment, relaxation training, cognitive therapy, and help with medication tapering. From pre- to post-treatment, there was a 33% attrition rate, and attrition was related to referral status (i.e., dropouts were more likely to have been referred for treatment rather than recruited from the community). Using a mixed model analysis of variance procedure (ANOVA), results showed that online treatment produced statistically significant improvements in the primary end points of sleep quality, insomnia severity, and daytime fatigue. Online treatment also produced significant changes in process variables of pre-sleep cognitive arousal and dysfunctional beliefs about sleep. Implications of these findings are that identification of who most benefits from online treatment is a worthy area of future study.