Damage evolution in polymer due to exposure to high-pressure hydrogen gas

The use of hydrogen as a fuel is increasing exponentially, and the most economical way to store and transport hydrogen for fuel use is as a high-pressure gas. Polymers are widely used for hydrogen distribution and storage systems because they are chemically inert towards hydrogen. However, when exposed to high-pressure hydrogen, some hydrogen diffuses through polymers and occupies the preexisting cavities inside the material. Upon depressurization, the hydrogen trapped inside polymer cavities can cause blistering or cracking by expanding these cavities. A continuum mechanics–based deformation model was deployed to predict the stress distribution and damage propagation while the polymer undergoes depressurization after high-pressure hydrogen exposure. The effects of cavity size, cavity location, and pressure inside the cavity on damage initiation and evolution inside the polymer were studied. The stress and damage evolution in the presence of multiple cavities was also studied, because interaction among cavities alters the damage and stress field. It was found that all these factors significantly change the stress state in the polymer, resulting in different paths for damage propagation. The effect of adding carbon black filler particles and plasticizer on the damage was also studied. It was found that damage tolerance of the polymer increases drastically with the addition of carbon black fillers, but decreases with the addition of the plasticizer.     

A System for Measurement of Isokinetic Strength for Estimation of Load Handling Capacity

This note describes a method for measurement of isokinetic strength for prediction of manual materials handling capacity of individuals. The apparatus used in this methodology and measurement technique are illustrated in detail.     

Improvement of oxygen mass transfer estimation from oxygen concentration measurements in bubble column reactors

An original procedure has been established for estimating the overall volumetric mass transfer coefficient using the oxygen concentration curves resulting from the usual gassing-in and gassing-out method. This procedure was applied to experimental data obtained in a small scale bubble column using both tap water and a coalescence-inhibiting liquid mixture that represents the coalescence behavior of biological media. It is based on the analysis of the characteristics times of the system, including those of the hydrodynamics of the two phases, the sensor dynamics and the system inertia when the gas composition is modified. A numerical procedure was developed to estimate the characteristic time of the system inertia t_i, using the assumption that this inertia is nearly independent of superficial gas velocity U_G. The calculations confirmed that the optimized t_i value was nearly independent of U_G and of the coalescence behavior of the liquid phase. Additionally, the resulting K_La_L values for tap water were closer to the correlation of Shah et al. [1982. Design parameters estimations for bubble column reactors. A.I.Ch.E. Journal 28, 353-379] than those of other conventional models. Finally, the original procedure was also reported to reduce significantly the square sum deviation between the predicted and the measured oxygen response curves.     

Ergonomic job design in frequent manual lifting tasks: A microcomputer-based model

The main objective of this paper is to generate ergonomic software that can be used in the design and evaluation of manual materials handling tasks so as to minimize the risk of injury. Specifically, this study is aimed at developing a microcomputer-based model for the design of frequent manual lifting tasks based ont he concept of job saverity index. The microcomputer-based software package is intended to be used by non-experts in the field of MMH. Possible engineering and administrative controls are implemented in the software in case if human lifting abilities are exceeded. The software was written in AutoLISP for the IBM personal computer. The knowledge base of the software is built upon a set of two models which were developed in the present study. The models were based on 2,736 observations.     

Simultaneous measurement of gas hold-up and mass transfer coefficient by tracer dynamic technique in “Emulsair” reactor with an emulsion-venturi distributor

Hydrodynamics and gas-liquid mass transfer have been investigated in an “Emulsair” reactor with cocurrent downflow of gas and liquid. This consists of a cylindrical tank with conical bottom topped by an emulsion-venturi as the gas-liquid distributor in which the gas is self-aspired by action of the kinetic energy of the liquid recirculation. An original tracer dynamic technique using the CO₂-N₂/water system that enables the simultaneous measurement of overall gas hold-up and overall volumetric mass transfer coefficient has been developed and validated using conventional techniques, such as volume expansion for gas hold-up and dynamic oxygenation for mass transfer. It has been shown that gas hold-up and K_La_L can be deduced from the moments of experimental response curves using a CO₂ pulse in the gas feed. Experimental results have proved that hydrodynamics and mass transfer in the Emulsair reactor are strongly influenced by the flow regime in the divergent. Two different regimes have been observed depending on the liquid recirculation flow rate: annular and homogeneous bubbling flows. In both regimes, self-aspired gas flow rate, gas hold-up and K_La_L have been reported to increase with the liquid flow rate. The operation effectiveness, estimated from the gas-to-liquid flow rate ratio, has been shown to pass through a maximum around 0.59 as a function of liquid recirculation. A comparison with the literature proved that this maximum is higher than those observed for other kinds of gas-liquid reactors equipped with a venturi. Correlations for mass transfer estimation have been derived and are in agreement with the literature.     

Study of Hydrodynamics,Mixing and Gas‐Liquid Mass Transfer in a Split‐Rectangular Airlift Reactor

Global hydrodynamic characteristics, liquid mixing and gas‐liquid mass transfer for a 63 L split‐rectangular airlift reactor were studied. Correlations for gas holdup and overall liquid circulation velocity were derived for the air‐water system as a function of the specific power input; these were compared to data and correlations for reactor volumes between 4.7 L and 4600 L. A partial recirculation of small bubbles in the riser was observed when U_gr > 0.03 m/s, which was attributed to the use of a single‐orifice nozzle as the gas phase distributor. The dimensionless mixing time and the overall axial dispersion coefficient were nearly constant for the range of gas flow rates studied. However, values of K_L/d_B were greater than those reported in previous studies and this is caused by the partial recirculation of the gas phase in the riser. While scale effects remain slight, the use of a gas distributor favouring this partial recirculation seems adequate for mass transfer in split‐rectangular airlift reactors.     

IESK-ArDB: a database for handwritten Arabic and an optimized topological segmentation approach

Even though a lot of researches have been conducted in order to solve the problem of unconstrained handwriting recognition, an effective solution is still a serious challenge. In this article, we address two Arabic handwriting recognition-related issues. Firstly, we present IESK-arDB, a new multi-propose off-line Arabic handwritten database. It is publicly available and contains more than 4,000 word images, each equipped with binary version, thinned version as well as a ground truth information stored in separate XML file. Additionally, it contains around 6,000 character images segmented from the database. A letter frequency analysis showed that the database exhibits letter frequencies similar to that of large corpora of digital text, which proof the database usefulness. Secondly, we proposed a multi-phase segmentation approach that starts by detecting and resolving sub-word overlaps, then hypothesizing a large number of segmentation points that are later reduced by a set of heuristic rules. The proposed approach has been successfully tested on IESK-arDB. The results were very promising, indicating the efficiency of the suggested approach.     

Patient safety in outpatient surgery: the viewpoint of the healthcare providers

The objective of this study is to understand the viewpoint of healthcare providers with regard to patient safety in outpatient surgery settings. Two methods were used to gather data from the healthcare providers: (1) questionnaire with open-ended questions about six predefined stages of the patient care process; (2) survey with closed questions. With the first method, the main quality and safety of care issues concerned communication to patients, coordination of reports and forms, patient and staff time pressures and standards of care. The first two stages of the outpatient surgery process, i.e. patient work-up prior to day of surgery and patient admission and preparation on the day of surgery, yielded many more comments than the other four stages. The results of the structured questionnaire show that, overall, the healthcare providers report high quality of care provided by themselves (98%) and their surgery centre (96%). With regard to patient safety (i.e. cancellations of surgeries, patient safety problems and serious mistakes), there was a clear difference in perceptions reported by the physicians vs. the nurses and other staff. Nurses and other staff were more likely to report patient safety problems than physicians. The combination of qualitative data from the initial questionnaire and the quantitative data from the structured questionnaire provides a rather complete view of the outpatient surgery staff perceptions of quality and safety of care. This research highlights the importance of getting input from the healthcare providers regarding the quality and safety of care rather than relying only on traditional measures about patient outcomes.     

Bidirectional HMM-based Arabic POS tagging

In this work, we will present a new concept of POS tagging that will be implemented for the Arabic language. Indeed, we will see that in Arabic there are a numerous cases where the determination of the morpho-syntactic state of a word depends on the states of the subsequent words, which represents the theoretical foundation of the approach: how to consider, in addition of the past elements, the future ones. We will then demonstrate how the POS tagging in its statistical application: the HMM, is based mainly on the past elements, and how to combine both direct and reverse taggers to tag the same sequence of words in both senses. Thus, we will propose a hypothesis for the result selecting. In the practical part, we will present, in general, the used resource and the changes made on it. Then we will explain the experiment steps and the parameters collected and presented on graphics, that we will discuss later to lead to the final conclusion.     

Use of polymeric materials as a solid phase for radioimmunoassay and immunoradiometric assay techniques

Poly(acrylamide-acrylic acid-acrylonitrile)-ferrous sulfate, p(AM-AA-AN)-FeSO₄·7H₂O, resin was used as a solid phase for estimation of thyroid stimulating hormone (TSH) by radioimmunoassay (RIA) and immunoradiometric assay (IRMA) techniques. Comparison with cellulose particles as a known polymer solid phase was made. The tracers for RIA and IRMA were prepared by radioiodination of TSH antigen and TSH monoclonal antibody, respectively, using Iodogen as oxidizing agent. The tracers were purified by gel chromatography on Sephadex G-25 column. The polyclonal anti-TSH antibody was prepared via immunization of three white New Zealand rabbits with highly purified TSH antigen. The polymer was prepared by addition of aqueous solution of comonomer (AA-AN) and FeSO₄ as cross-linker to polyacrylamide p(AM) and irradiation of the mixture at ambient temperature in a ⁶⁰Co γ-cell. The polymer prepared and cellulose particles were activated using 1,1-carbonyldiimidazole, and these activated particles were coupled with the polyclonal TSH antibody. Optimization and validation of the RIA and IRMA techniques were made.