A hybrid homogeneously weighted moving average control chart for process monitoring

Several modifications and enhancements to control charts in increasing the performance of small and moderate process shifts have been introduced in the quality control charting techniques. In this paper, a new hybrid control chart for monitoring process location is proposed by combining two homogeneously weighted moving average (HWMA) control charts. The hybrid homogeneously weighted moving average (HHWMA) statistic is derived using two smoothing constants λ₁ and λ₂ . The average run length (ARL) and the standard deviation of the run length (SDRL) values of the HHWMA control chart are obtained and compared with some existing control charts for monitoring small and moderate shifts in the process location. The results of study show that the HHWMA control chart outperforms the existing control charts in many situations. The application of the HHWMA chart is demonstrated using a simulated data.     

DESIGN AND IMPLEMENTATION OF STATE OBSERVERS IN REACTIVE DISTILLATION

This study demonstrates that state observers can be developed and applied to infer the composition profiles of reactive distillation columns from noise-contaminated temperature measurements. The design and implementation of a Kalman filter (KF) and a Luenberger observer (LO) are carried out, and their performances are quantitatively assessed. The reliability, accuracy, and robustness of the two designs method are examined and compared quantitatively. The design and implementation of a Luenberger observer are simpler and easier to carry out than those of a Kalman filter. On the other hand, a Kalman filter is found to be more robust to a noisy measurements, erroneous initial estimates, and model uncertainties. A Luenberger observer could be used for composition estimation of reactive distillation when an ideal model of the system can reasonably approximate the real system; otherwise, a Kalman filter is recommended to be applied in more practical situations.     

Impact of asthma,exposure period,and filters on human responses during exposures to ozone and its initiated chemistry products

The impact of asthma, exposure period, and filter condition downstream of the mixing box of air‐conditioning system on building occupants' perceptual response, work performance, and salivary α‐amylase secretion during exposures to ozone and its initiated chemistry products is studied. The experiments were conducted in a field environmental chamber (FEC) (240 m³) simulating an office environment. Experiments were conducted during periods when the air‐handling system operated with new or used pleated panel filters at constant recirculation (7/h) and ventilation (1/h) rates. Average ozone and secondary organic aerosols (ozone‐initiated chemistry products) measured during non‐asthmatic and asthmatic subjects' 3‐h exposures in the FEC were in the ranges approximately 20–37 ppb and approximately 1.6–3 μg/m³, respectively. Asthmatic subjects' perceived odor intensity and sensory (eye, nose, and throat) irritation ratings were generally lower than those of non‐asthmatic subjects, possibly explaining why asthmatic subjects accept perceived air quality more than non‐asthmatic subjects. However, asthmatic subjects' perceived physiological‐like symptom ratings (flu, chest tightness, and headache) and concentrations of secreted salivary α‐amylase were generally higher than those of non‐asthmatic subjects. Asthmatic subjects had significantly lower accuracy than non‐asthmatic subjects in a task that required higher concentration although they had higher work speed. Filter condition did not make any significant difference for subjects' responses.     

A Study of Premature Failure of Crusher Jaws

In this article, we report the outcome of an investigation made to uncover the premature fracture of crusher jaws produced in a local foundry. A crusher jaw that had failed while in service was studied through metallographic techniques to determine the cause of the failure. Our investigation revealed that the reason for the fracture was the presence of large carbides at the grain boundaries and in the grain matrix. This led to the formation of microcracks that propagated along the grain boundaries under in-service working forces. It is also believed that the precipitation of carbides at the grain boundaries may have occurred because of improper heat treatment, but not because of a deficiency in composition.     

Online composition estimation and experiment validation of distillation processes with switching dynamics

This study explores both the theoretical and experimental investigations of applying a continuum and noncontinuum state estimator to composition estimation in a distillation process with switching dynamics. In a hybrid distillation modeling, the column compositions are considered as continuum states while the operating modes are modeled as noncontinuum states. A moving horizon estimator (MHE), which has the capability to handle process constraints is developed for composition estimation in a distillation process under known switching mode criteria using the available temperature measurements. The performance of a MHE is shown to be better than that of EKF in handling process and measurement noise under switching dynamics. For some situations where the system operating mode transition is unknown, a new approach to state estimation under unknown switching functions is investigated. The proposed method combines a MHE for composition estimation with a mode change detector to detect a change in the system operating mode and an operating mode estimator to identify the functioning mode. In the presence of both the measurement noise and plant-model mismatch, the developed estimator is shown to be effective in estimating both the column composition and the system operating mode accurately.     

Tri-metallic quantum dot under the influence of solvent additive for improved performance of polymer solar cells

CdTeSe colloidal quantum dot (QD) was used to enhance photon capture in thin film polymer solar cells (TFPSC). The QDs were synthesized in aqueous media from two different precursors. Bulk heterojunction (BHJ) polymer blends composed of P3HT and PCBM were used as an absorber layer of the solar cell to investigate the effect of QDs. Different concentrations of QDs were used in the polymer matrix, which significantly impacted the power conversion efficiency (PCE) of the doped devices. More device performance growth was recorded by employing a small amount of solvent additives to disperse the QDs and increase the polymer's crystallinity in the medium. Hence, the addition of 1, Chloronaphthalene (CN) solvent additive in the QD-doped bulk heterojunction film further enhanced the overall performance of the TFPSC due to improved film morphology that has significantly influenced the charge transport processes. Consequently, the PCE of the solar cell increased by nearly 50% compared to the pristine TFPSC due to the effect of solvent additives.     

Computer Aided Model for Casting Aluminium Using Die-Casting

Computer aided casting of aluminum using die-casting was developed. A piston, which is an automobile part and very important in internal combination engine, was chosen for the research. Pistons are made of aluminum alloy. Models of the products were developed to aid the casting process. Mathematical models that show the dimensions of the casting were also developed. Since the project is about using computer to aid casting process, a program using visual basic （VB） Language was developed. The program was used to incorporate die-casting process into computer system. The written program was tested and the model of the casting product （piston） was displayed. The result shows that computer which is faster with accurate result can be used as an aid in the production of aluminum piston using die-casting process, for accurate planning in the manufacture of the product.     

Estimator-based control of reactive distillation system: Application of an extended Kalman filtering

This paper demonstrates that a state estimator can be successfully designed and implemented in a feedback control system of reactive distillation. The work of the state estimator is to provide the state compositions that are required to be used in the controller for necessary action. The control performance of a system that relies on the state estimator is examined and compared to a system that takes direct measurement from the process assuming the availability of a perfect online analyzer. It is found that the estimator-based system is robust against a moderate measurement errors and erroneous initial conditions. If the state estimator is designed from a highly erroneous process model, noisy measurements and approximate initial conditions, the use of estimator together with an online analyzer (for easily measured states) is recommended to achieve an effective control of a reactive distillation system.     

Sensory pollution from bag-type fiberglass ventilation filters: Conventional filter compared with filters containing various amounts of activated carbon

As ventilation filters accumulate particles removed from the airstream, they become emitters of sensory pollutants that degrade indoor air quality. Previously we demonstrated that an F7 bag-type filter that incorporates activated carbon (a “combination filter”) reduces this adverse effect compared to an equivalent filter without carbon. The aim of the present study was to examine how the amount of activated carbon (AC) used in combination filters affects their ability to remove both sensory offending pollutants and ozone. A panel evaluated the air downstream of four different filters after each had continuously filtered outdoor suburban air over a period of 6 months. Interim assessments (mid-term evaluation) were performed after 3 months. During both assessments, four unused filters, identical in type to the loaded filters, were also evaluated. The evaluated filters included a conventional F7 fiberglass filter and three modifications of a bag-type fiberglass combination filter: the “Heavy” corresponded to a commercially available filter containing 400 g of carbon per square meter of filter area, the “Medium” contained half as much carbon (200 g/m²), and the “Light” contained a quarter as much carbon (100 g/m²). Each filter was weighed at the beginning of the soiling period and after 3 and 6 months of service. Additionally, up- and down-stream ozone concentrations and filter pressure drops were measured monthly. Following 6 months of service, the air downstream of each of the combination filters was judged to be significantly better than the air downstream of the 6-month-old F7 filter, and was comparable to that from an unused F7 filter. Additionally, the combination filters removed more ozone from the air than the F7 filter, with their respective fractional removal efficiencies roughly scaling with their carbon content.     

Development of a simultaneous continuum and noncontinuum state estimator with application on a distillation process

This study focuses on the development and application of a hybrid moving horizon estimator (HMHE) to achieve simultaneous estimation of both continuum and noncontinuum states in a constrained switching dynamic system. One of the major issues in a moving horizon estimation approach is the development of an arrival cost to summarize the effect of past and a prior information. In this work, we have developed a generalized arrival cost, which accounts for both continuum and noncontinuum states. A generalized hybrid state estimator, which can be used as a stand‐alone continuum state estimator, or as a simultaneous continuum and noncontinuum state estimator, is developed. The effects of constraints, process, and measurement noise levels, as well as a moving horizon length on the simultaneous estimation of both the continuum and noncontinuum states are analyzed. The effectiveness of the HMHE is demonstrated through simulation studies, while its practical reliability is tested by conducting experimental studies on a distillation column. © 2011 American Institute of Chemical Engineers AIChE J, 2012