Conditional Control Charts for Weibull Quantiles Under Type II Censoring

In this article, we propose control charts for the quantiles of the Weibull distribution, for type II censored data, based on the distribution of a pivotal quantity conditioned on ancillary statistics. These control charts must be considered as alternatives to bootstrap type control charts. We derive an analytical form of the conditional distribution function of the monitored statistic and we use this function to propose ARL‐unbiased control limits. We further demonstrate that the proposed conditional chart have a general analytical form for the ARL that can be evaluated numerically without use of simulations and we also show that these charts perform at least as well as the bootstrap type ones. We finally apply the conditional charts to a dataset on the strength of carbon fibers to detect shifts in a specified Weibull quantile. Copyright © 2014 John Wiley & Sons, Ltd.     

Dynamic shear rheological behavior of PP/EPR in‐reactor alloys synthesized by multi‐stage sequential polymerization process

The rheological behavior, morphology, and mechanical properties of in‐reactor alloy of polypropylene (PP)/ethylene propylene rubber (EPR) synthesized by multi‐stage sequential polymerization process are studied in this article. The relationship between polymerization parameters, morphology, and rheological properties are evaluated by scanning electron microscopy (SEM) and small amplitude oscillation rheometry in the linear viscoelastic region. The electron microscopy of samples is showed that by increasing switching frequency in polymerization time, the size of EPR particles decrease. By increasing switching frequency, the curves of complex viscosity against angular frequency of samples are shifted to higher values at low range of shear rates with no significant change at higher frequencies in Power‐law region. The modified Cole‐Cole plots revealed the enhanced melt elasticity by increasing switching frequency up to 230°C. The plot of phase angle versus absolute value of complex modulus G* is used for the evaluation of matrix‐droplets interaction at various temperatures. It is observed two different behaviors before and after 230°C which is the evidence of the change in relaxation mechanism of the blend components because of coarsening the rubber particles in the phase separation process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Investigation of the effect of presulphidation on coke deposition on 25Cr-35Ni alloy during ethane steam cracking

The process of hydrocarbons cracking is carried out in the presence of heat-resistant alloys Fe-Ni-Cr, which HP40 alloy (25Cr-35Ni) has the most applications among olefin plants. Since these alloys naturally tend to form coke, the industry has always tried to reduce the coke formation by reducing the catalytic properties of the coils. In this research, the effect of dimethyl disulphide (DMDS) concentration (200–900 ppm) on the HP40 alloy of industrial coils at the presulphidation stage is evaluated. In the presulphidation stage, the alloy surface is in contact with sulphur in the absence of hydrocarbons, and this affects the amount of coke formation in the cracking process. Also, the surface composition and morphology of coke are identified using EDX and SEM analysis. These results showed that at the 500 ppm concentration of DMDS, coke deposition is minimized. Additionally, our findings indicated that coke morphology has not changed under different presulphidation conditions, and coke is still a filament type, but the size of the filaments has changed. Moreover, the study of HP40 composition in both preoxidized and presulphide stages shows that presulphidation reduces the amount of Fe and Ni in the coke layer significantly.     

A systematic approach for estimating water losses in irrigation canals

In order to determine water losses in irrigation canals, a systematic approach was developed, consisting of two main components: a seepage simulation model and a hydraulic simulation model. The SEEP/W module of the Geo-Studio software was used to simulate the seepage rate, and the Hydrologic Engineering Center-River Analysis System (HEC-RAS) hydrodynamic model was used for hydraulic simulation. Different operation scenarios were designed to investigate all possible situations in daily operation of water distribution and delivery systems. The seepage simulation results show that the seepage losses were higher at the bottom and corners of the canal, because the hydraulic gradient was affected by the hydraulic load. The hydraulic simulation results show that due to physical and management infrastructure (using non-automated and operator-based regulation structures), operational losses accounted for a significant volume of losses compared to seepage losses. In most operation scenarios, the maximum seepage loss was 10%, and the remaining 90% was related to operational losses. It is concluded that any factor (decrease or increase of inflow to the canal) that causes an increase or decrease of operational losses is ultimately a determining factor in reducing or increasing total losses. Therefore, management approaches should be adopted to improve performance of the system and reduce losses, especially operational losses, by improving the operation methods of water level regulation and off-take structures.     

Rapidly destructive hip disease: clinical and imaging abnormalities

The clinical and radiographic records of 23 patients (15 women, eight men) with rapidly destructive hip disease (RDHD) were retrospectively reviewed. Criteria for RDHD included a history of hip pain of 1-6 months duration and the radiographic appearance of a rapidly progressive atrophic form of bone destruction involving both the femoral head and the acetabulum. Radiographs of the remainder of the appendicular skeleton were assessed in 14 patients. The mean patient age was 72 years. The average time from clinical presentation to the appearance of severe hip destruction was 14 months. Five patients demonstrated similar atrophic bone destruction around other articulations. No patients had clinical or laboratory evidence of sepsis or neurologic disease. Although previous reports have suggested that RDHD is degenerative in nature, similar involvement of other articulations suggests that it may represent a focal finding of a more generalized process.     

Tibiofibular syndesmosis: high-resolution MRI using a local gradient coil

The purpose of this study was to validate the accuracy of the assessment of ventricular function by first-pass radionuclide angiography (FPRNA) with 123I myocardial tracers and a multicrystal gamma camera. METHODS: Left ventricular ejection fraction (LVEF) and right ventricular ejection fraction were measured in 69 patients by FPRNA using 123I myocardial tracers (126 +/- 7 MBq) and 99mTc tracers (541 +/- 141 MBq) on a multicrystal gamma camera with a high-sensitivity collimator. For 44 patients, ejection fraction values measured by 123I-FPRNA were compared to those estimated by equilibrium radionuclide angiography (ERNA). Visual wall-motion analysis was also performed to judge clinical acceptability of 123I-FPRNA images for identification of wall-motion abnormality. RESULTS: Mean LVEFs (%) estimated by 123I-FPRNA and by 99mTc-FPRNA were 49.6 +/- 13.6 and 49.1 +/- 14.1, respectively (nonsignificant p value). An excellent correlation was found between LVEFs estimated by 123I-FPRNA and 99mTc-FPRNA (r = 0.96, s.e.e. = 1.9%). Values of LVEF measured by 123I-FPRNA also demonstrated excellent correlation with those measured by ERNA (r = 0.95, s.e.e. = 2.2%). A good correlation was also noted between right ventricular ejection fractions measured by 123I-FPRNA and 99mTc-FPRNA (r = 0.72, s.e.e. = 4.0%). The Spearman rank correlation coefficient between 123I-FPRNA and ERNA wall-motion scores was 0.87 (n = 135, p < 0.001). CONCLUSION: Resting ventricular function can be reliably measured with 123I-FPRNA in combination with a multicrystal gamma camera. This indicates that the assessment of ventricular function is feasible in conjunction with 123I myocardial imaging without an increase in cost or radiation dose to patients.     

Two-Dimensional Inverse Heat Transfer Analysis of Functionally Graded Materials in Estimating Time-Dependent Surface Heat Flux

Two-dimensional transient inverse heat conduction problem (IHCP) of functionally graded materials (FGMs) is studied herein. A combination of the finite element (FE) and differential quadrature (DQ) methods as a simple, accurate, and efficient numerical method for FGMs transient heat transfer analysis is employed for solving the direct problem. In order to estimate the unknown boundary heat flux in solving the inverse problem, conjugate gradient method (CGM) in conjunction with adjoint problem is used. The results obtained show good accuracy for the estimation of boundary heat fluxes. The effects of measurement errors on the inverse solutions are also discussed.     

Improving the Aging Resistance of Bitumen by Reduction

The aging properties of bitumen evaluated by means of Fourier transform Infrared spectroscopy. The effect of sodium borohydride as a reducing agent on the chemical structure of bitumen in aging process was studied. The bitumen was aged by means of the rolling thin film oven test then pressure aging vessel. Reduced modified bitumen were resistant to the formation of carbonyl and sulfoxide groups nearly unchanged, indicating the improvement of aging resistance of bitumen by the reduction process. As well as physical properties tests (penetration and softening point) of bitumen showed the more resistance of reduced modified bitumen against aging.     

Dynamic risk analysis using alarm databases to improve process safety and product quality: Part II—Bayesian analysis

Part II presents step (iii) of the dynamic risk analysis methodology; that is, a novel Bayesian analysis method that utilizes near‐misses from distributed control system (DCS) and emergency shutdown (ESD) system databases—to calculate the failure probabilities of safety, quality, and operability systems (SQOSs) and probabilities of occurrence of incidents. It accounts for the interdependences among the SQOSs using copulas, which occur because of the nonlinear relationships between the variables and behavior‐based factors involving human operators. Two types of copula functions, multivariate normal and Cuadras–Augé copula, are used. To perform Bayesian simulation, the random‐walk, multiple‐block, Metropolis–Hastings algorithm is used. The benefits of copulas in sharing information when data are limited, especially in the cases of rare events such as failures of override controllers, and automatic and manual ESD systems, are presented. In addition, product‐quality data complement safety data to enrich near‐miss information and to yield more reliable results. Step (iii) is applied to a fluidized‐catalytic‐cracking unit (FCCU) to show its performance. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

NONLINEAR FINITE ELEMENT ANALYSIS OF COUPLED HEAT AND MASS TRANSFER PROBLEMS WITH AN APPLICATION TO TIMBER DRYING*

A finite element formulation and solution of a set of nonlinear coupled heat and mass transfer equations for porous capillary media is presented. The model considers temperature and moisture dependent material properties and can accomodate diffusion of moisture as either a liquid or a vapor. Application was made to drying of timber and predicted results agreed well with the experimental data.