Behaviour of S 355JO steel subjected to uniaxial stress at lowered and elevated temperatures and creep

This paper considers main mechanical properties of structural-high strength low alloy (HSLA) S 355JO (ASTM A709 Gr50) steel subjected to uniaxial tensile tests at lowered and elevated temperatures. The engineering stress vs strain diagrams as well as curve’s dependence of ultimate and yield strengths vs both lowered and elevated temperatures are presented. The focus is also on specimen elongations vs temperature at elevated temperatures. Short-time creep tests for selected constant stresses at selected temperatures were curried out. Uniaxial creep behaviour for selected creep test was modeled by the rheological model. The creep curve determined by modeling procedure was compared with experimentally obtained one. Also, notch impact energy test, using Charpy pendulum impact machine was performed and according to the proposed formula, fracture toughness is calculated. All of experimental tests were performed using modern computer directed experimental systems.     

Modification of the forced-choice method as a criterion of job proficiency.

Attempted to verify the value of classical and modified forced-choice rating systems. A double modification was performed: (a) only items of a general nature, i.e., those concerning all jobs in a large group of jobs were used; and (b) only items of neutral attractiveness were used. The lists of classical and modified forced-choice items were constructed separately for 250 blue-collar workers, 110 white-collar workers, and 97 supervisors. The modified forced-choice system was superior for the blue- and white-collar workers. The comparison of the mean ratings of each group also indicated superiority separation using the modified forced-choice system. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sustainability of energy,water, and environmental systems: a view of recent advances

Clean Technologies and Environmental Policy -     

Associations of perceived indoor environmental quality with stress in the workplace

Indoor environmental quality (IEQ) is a general indicator of the quality of conditions inside a building. We investigated associations of perceived IEQ including air quality, thermal comfort, noise, and light quality with stress at work and the extent to which workplace location modifies these associations. We recruited 464 full-time workers from four companies in Singapore. Data on socio-demographic characteristics, lifestyle/health-related factors, and workplace factors were collected through self-administered questionnaires. Perceived IEQ satisfaction scores of all four factors were collected using the validated OFFICAIR questionnaire. We fitted a logistic regression model to assess associations between each perceived IEQ score and stress at work, adjusting for potential confounders. The odds ratio for stress at work associated with a 1-unit increase in perceived air quality score was 0.88 (0.82-0.94), 0.89 (0.82-0.97) for thermal comfort, 0.93 (0.87-0.98) for noise, and 0.88 (0.82-0.94) for light quality. Significant associations were found in office and control rooms for all four perceived IEQ, except for thermal comfort in office rooms. Higher satisfaction levels of perceived air quality, thermal comfort, noise, and lighting, were significantly associated with a reduction in stress at work. Our findings could potentially provide a useful tool for environmental health impact assessment for buildings.     

Quantitation of Multiple Sphingolipid Classes Using Normal and Reversed-Phase LC–ESI–MS/MS: Comparative Profiling of Two Cell Lines

Sphingolipids are an important class of compounds that regulate signal transduction and other vital cellular processes. Herein, we report sensitive normal and reversed phase LC–MS/MS methods for quantitation of multiple sphingolipid classes. In the normal-phase ESI/MS/MS method, a high content of organic solvents was utilized, which, although it included hexane, ethyl acetate, acetonitrile containing 2% methanol, 1–2% acetic acid, and 5 mM ammonium acetate, resulted in a very efficient electrospray ionization of the ceramides (Cers) and hexosylceramides (MHCers). Three normal-phase LC–MS/MS methods using segmented phases were developed to specifically target Cers, MHCers, or sphingomyelins (SMs). This segmentation scheme increases the number of data points acquired for a given analyte and enhances the sensitivity and specificity of the measurements. Nine separate reversed phase chromatography methods were developed for the three classes of compounds. These assays were used for comparing the levels of Cers, SMs, and MHCers from mouse embryonic fibroblast (pMEF) and human embryonic kidney (HEK293) cells. These findings were then compared with the reported data from RAW264.7 mouse macrophage cells, BHK21 hamster cells, and human plasma and serum samples. The analysis of cell lines, using both normal and reversed phase chromatography, revealed discrimination based on the type of chromatography chosen, while sphingolipid assays of samples containing different amounts of protein showed different results, even after normalizing for protein content. Also, LC/MS/MS profiles were provided for the classes and individual compounds so that they could be used as “molecular profiles” for class or individual sample analysis.     

Controllable and SDA-free synthesis of sub-micrometer sized zeolite ZSM-5. Part 2: Influence of sodium ions and ageing of the reaction mixture on the chemical composition, crystallinity and particulate properties of the products

In this work, the influences of excess amount of sodium ions and the way/duration of ageing of the reaction mixture (hydrogel) on structural, particulate, morphological and chemical properties of the crystalline end products obtained by hydrothermal treatment (heating at 483 K for 2 h) of the TPA-free reaction mixture: 1.0Al₂O₃/100SiO₂/xNa₂O/4000H₂O/yNa₂SO₄ (0.4 ? (x + y) ? 100) seeded by silicalite-1 nanocrystals (260 nm, 4 wt.% of silica in gel mixture), was investigated by different characterization methods such as, powder X-ray diffraction (XRD), scanning-electron microscopy (SEM), particle size distribution (PSD) measuring by laser light scattering (LLS) and X-ray fluorescence (XRF). The obtained results showed that addition of sodium sulfate in low-alkaline reaction mixture enhances the aggregation of the particles of colloidal silica and formation of gel by the action of sulfate oxy-anions while in high-alkaline reaction mixtures the condensation process takes place on the surface of the crystalline end products. Excess amount of sodium ions do not increase the crystallization rate thus showing that the rate-determining factor is concentration of “free” low-molecular weight silicate species, determined by the alkalinity of system. On the other hand, addition of sodium sulfate considerably reduces the formation of crystal aggregates, by combined chemical and electrical interactions. Ageing of the reaction mixture (hydrogel) mainly influences the particle size distribution of the crystalline end products, which is explained by the change in the relative rates of crystal growth and crystal aggregation with the time of ageing. However, hydrogel ageing does not affect the size and number of crystals in the crystalline end product, showing that the growth precursor particles form during hydrothermal treatment of the reaction mixture and not during its room-temperature ageing.     

A beam model for large displacement analysis of flexibly connected thin-walled beam-type structures

This paper presents a beam formulation for large displacement analysis of beam-type structures with flexible connections. Within the framework of updated Lagrangian incremental formulation and the nonlinear displacement field of thin-walled cross-sections, which accounts for restrained warping and the second-order displacement terms due to large rotations, the equilibrium equations of a straight beam element are firstly developed. Due to the nonlinear displacement field, the geometric potential of semitangential moment is obtained for both the internal torsion and bending moments, respectively. Material nonlinearity is introduced for an elastic-perfectly plastic material through the plastic hinge formation at finite element ends. To account for the flexible connection behaviour, a special transformation procedure is developed. The numerical algorithm is implemented in a computer programme and its reliability is validated trough several test examples.