A hybrid homogeneously weighted moving average control chart for process monitoring: Discussion

The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) $\overline{X}$ scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA $\overline{X}$ scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA $\overline{X}$ scheme.     

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.     

Effects of Daniella oliveri Wood Flour Characteristics on the Processing and Functional Properties of Wood Polymer Composites

The effects of particle sizes/distribution and contents on the processing, changes in microstructure and functional properties of wood polymer composites (WPCs) prepared from virgin high-density polyethylene (vHDPE) and sodium hydroxide (NaOH) treated Daniella oliveri wood flour via compression molding have been explored. Findings from this study suggested that an appropriate choice of wood flour characteristics could improve the interactions between the wood flour and the vHDPE matrix by eliminating incomplete wetting, segregation, and agglomeration of wood flour particles during processing while enhancing mechanical and thermal properties of the composites. Properties of the WPCs were optimized when wood flour of particle sizes/distribution and contents of +210–300 µm and 35 wt%, respectively, were blended with vHDPE matrix.     

Conceptual Design Framework for Setting Up Aluminum Alloy Powder Production System for Selective Laser Melting (SLM) Process

JOM - Documentation on the correct process and component requirements for setting up efficient aluminum powder production systems capable of manufacturing powder that meets the requirements for the...     

Coconut husk extract: antibacterial properties and its application for shelf-life extension of Asian sea bass slices

Antibacterial properties of ethanolic coconut husk extracts (ECHE) prepared using varying ethanol concentrations as the extracting media against Pseudomonas aeruginosa, Escherichia coli, Vibrio parahaemolyticus, Listeria monocytogenes and Staphylococcus aureus was studied. ECHE60, prepared using 60% ethanol, had similar minimum inhibitory concentration and minimum bactericidal concentration to those extracted using 80% and 100% ethanol (P ˂ 0.05). When Asian sea bass (Lates calcarifer) slices were treated with ECHE60 at 200 and 400 ppm, the quality changes were monitored in comparison with the control (without treatment) during 12 days of refrigerated storage (4 °C). The shelf life of sea bass treated with 400 ppm ECHE60 was extended to 9 days, whereas the control had a shelf life of 3 days. Lipid oxidation was lowered in ECHE60 treated samples than the control during storage. Therefore, ECHE60 could inhibit both spoilage and pathogenic bacteria and also extended the shelf life of sea bass slices.     

Ethanolic Noni (Morinda citrifolia L.) leaf extract dechlorophyllised using sedimentation process: Antioxidant,antibacterial properties and efficacy in extending the shelf-life of striped catfish slices

Antioxidant and antimicrobial activities of ethanolic noni leaf extract (ENLE) without and with chlorophyll removal by sedimentation method were comparatively investigated. Total chlorophyll content was reduced by 82% in the top fraction (CR-ENLE) collected after 24 h at 4 °C as compared to that of ENLE. Antioxidant and antimicrobial activities were lower in the bottom fraction rich in chlorophyll (Chlo-ENLE) than others (P < 0.05). Based on the microbiological limit, the shelf-life of striped catfish slices pre-treated with 400 mg kg⁻¹ C-R-ENLE was extended to 9 days as compared to the 3 days recorded for the control (without pre-treatment). Slices treated with CR-ENLE had lower lipid oxidation than those treated with ENLE during refrigerated storage (P < 0.05). The sedimentation process was therefore a potential green method for producing ENLE having improved antioxidant and antimicrobial activities without green colour. It can be used as a natural additive for shelf-life extension of fish slices.     

Impact of rewetting and drying of rough rice on predicted moisture content profiles during in-bin drying and storage

Accurate prediction of moisture content (MC) is vital for effective control of on-farm, in-bin drying and storage of rough rice, especially for systems using recently introduced technology to automate fan run time. The study used simulations, laboratory, and field experiments to investigate the extent to which rewetting and drying, during in-bin drying and storage, affect accuracy of predicted MC—a critical parameter for automated fan control. Vapor sorption analysis (VSA) was used to generate MC prediction models for rough rice. Simulations of in-bin drying and storage, using in-field weather data, were performed while segregating effects resulting from rewetting and drying of the rough rice and the type of fan control strategy used. Predicted MC profiles of rough rice and drying durations were compared with those resulting from using standard constants in the literature for modeling. The root mean square error associated with predicting the MC by model constants developed using the VSA was 0.54% MC and 1.32% MC dry basis (d.b.), for desorption and adsorption, respectively. Deviation in MC logged by in-bin built, field sensors and that simulated by taking into account the influence of rewetting and drying were generally within 1.5% point difference. Therefore, rewetting and drying did not affect drying duration. However, drying duration was significantly influenced by fan control strategy (p?相似文献   

Control Chart Limits for Monitoring Process Mean Based on Downton's Estimator

Control charts are important tools in statistical process control used to monitor shift in process mean and variance. This paper proposes a control chart for monitoring the process mean using the Downton estimator and provides table of constant factors for computing the control limits for sample size (n ≤ 10). The derived control limits for process mean were compared with control limits based on range statistic. The performance of the proposed control charts was evaluated using the average run length for normal and non‐normal process situations. The obtained results showed that the control chart, using the Downton statistic, performed better than Shewhart chart using range statistic for detection of small shift in the process mean when the process is non‐normal and compares favourably well with Shewhart chart that is normally distributed. Copyright © 2015 John Wiley & Sons, Ltd.     

Influence of stabilising agents on the properties of liposomal encapsulated ethanolic coconut husk extract

Characteristics of liposomal encapsulated ethanolic coconut husk extract (LE-ECHE) as influenced by different stabilising agents (SA) were investigated. LE-ECHE was prepared using four liposome formulations including soy phosphatidylcholine (SPC) alone and SPC mixed with cholesterol (CHL), tween 80 (TWE) or glycerol (GLY) at a ratio of 4 : 1 as lipid phase (LP) at a concentration of 60 µmol mL⁻¹. Particle size, zeta potential, poly-dispersity index, encapsulation efficiency (EE) and suspension stability (SS) of LE-ECHE samples were markedly influenced by SA (P < 0.05). Antioxidant activity of ECHE was retained after entrapment in liposome, regardless of SA used. However, SA affected the antioxidant activities of LE-ECHE differently. Antibacterial properties of ECHE were enhanced after encapsulation in liposome, irrespective of SA. Therefore, liposome with glycerol or cholesterol could serve as a delivery based system for improving the antibacterial properties with high stability, while lowering the undesirable colour of ECHE.