Nondestructive and Laboratory Evaluation of Damage Gradients in Concrete Structure Exposed to Cryogenic Temperatures

This paper discusses the use of pulse velocity, dynamic Young’s modulus of elasticity, and air permeability of concrete to evaluate the extent of damage and damage gradients to a concrete structure exposed to thermal shock and subsequent cryogenic temperatures. Liquefied natural gas (LNG) is maintained in liquid form at cryogenic temperatures typically below ?160°C (?260°F). The elevated concrete pedestal and precast concrete piles supporting a LNG storage tank were exposed to cryogenic temperatures following a leak of the LNG. The engineering assessment of the concrete structure consisted of a nondestructive evaluation phase using ultrasonic pulse velocity and a subsequent laboratory phase based on concrete cores. Dynamic Young’s modulus of elasticity and air permeability index of 25?mm (1?in.) thick disks sawed from the cores were determined. Analyzing concrete disks at 25?mm (1?in.) increments permitted assessment of changes in these properties with depth and enabled evaluation of depth of damage and damage gradients. The laboratory study confirmed that the distressed zone was limited to a near-surface area of concrete as suggested by the results of pulse velocity testing.     

ENZYMATIC HYDROLYSIS OF STARCH BY USING A SONIFIER

In the present study, the ultrasonication method was used to investigate the effect of ultrasonic energy on the hydrolysis of corn, rice, and wheat starch by using the alpha-amylase enzymes produced by Bacillus species and Bacillus licheniformis. The effects of sonifier operation variables such as duty cycle and acoustic power rate on the stability of alpha-amylase enzymes and hydrolysis degrees of three types of starches were investigated at a temperature of 40°C and pH 6.5. To determine the effect of temperature with sonication on the hydrolysis process, wheat starch hydrolysis experiments were also carried out at a temperature of 50°C. Then, the relation between duty cycle and enzyme stability during hydrolysis for each enzyme at 50°C was expressed by a zero-order inactivation model.     

Effects of hue,saturation, and brightness on preference

A study was done to investigate preference responses for foreground–background color relationships. To do this, 123 university undergraduates in Ankara, Turkey, were asked to view eight background colors selected from HSB color space on which color squares of differing hues, saturations, and brightnesses were presented. Subjects were asked to show the color square they preferred on the presented background color. Findings showed that colors having maximum saturation and brightness were most preferred. Blue was the most preferred hue regardless of background. The findings for preferences for foreground–background color relationships are also included in this article. © 2002 Wiley Periodicals, Inc. Col Res Appl, 27, 199–207, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10051     

Synthesis of polymer supported Ni (II)-Schiff Base complex and its usage as a catalyst in sodium borohydride hydrolysis

Influence of using as catalysis, Ni-Schiff Base complex which we previously synthesized [1] used to support with amberzyme oxirane resin (A.O.R.) polymer for increasing the catalytic activity in NaBH₄ hydrolysis reaction, to hydrogen generation was studied. The prepared catalyst was characterized by using SEM, XRD, BET, FT-IR analyze technique. Polymer supported Ni-Schiff Base complex catalyzed NaBH₄ hydrolysis reaction was investigated depending on concentration of NaBH₄, concentration of NaOH, temperature, percentage of Ni complex in total polymer supported Ni-Schiff Base complex and amount of catalyst factors. The maximum hydrogen production rate from hydrolysis of sodium borohydride with nickel-based complex catalyst compared to the pure nickel catalyst is increased from 772 mL H₂·g^?1 cat.·min^?1 to 2240 mL H₂ g^?1 cat.·min^?1 [1], and with supported amberzyme oxirane resin polymer this nickel based complex catalyst was increased to 13000 mL H₂·g^?1 cat.·min^?1 at 30 °C. The activation energy of complex catalyzed NaBH₄ hydrolysis reaction was found as 25.377 kJ/mol. This work also includes kinetic information for the hydrolysis of NaBH₄.     

Effect of heat treatment on the creep behavior of α/β SiAlON sintered with multication oxide sintering additives

SiAlONs are important materials for high-temperature applications and creep properties of SiAlONs are largely controlled by the amount and type of sintering additives. It has been established that heat treatment can reduce the amount of amorphous intergranular phase through crystallization. However, there is no study on the creep behavior of heat-treated SiAlON ceramics containing multication sintering additives. Therefore, the aim of the study was to investigate the effect of heat treatment on the creep properties of multication containing (Y-Sm-Ca oxides) α/β-SiAlON ceramics. The heat treatments of the sintered samples were carried out at 1600°C for 2 hours. The creep tests were carried out in the range 1300-1400°C under different loads (50-150 MPa). The existing phases and the microstructures of samples before and after creep were investigated using XRD and SEM techniques. It was found that heat treatment resulted in a better creep performance compared to as-sintered samples. The activation energy and stress exponent for heat-treated SiAlONs were also calculated as 708 ± 45 kJ/mol and 1.4, respectively. Compared to the sintered sample values, the results suggested that the acting creep mechanism of grain-boundary sliding and cavitation was reduced with the heat treatment.     

A Measurement and Structural Model for Usability Evaluation of Shared Workspace Groupware

This study presents the development process of a set of questionnaire items to establish a measurement model for the usability of shared workspace groupware systems, which is suggested as a usability scale called SWUS, the Shared Workspace Usability Scale. Manifest variables and latent variables are based on the various dimensions of teamwork collated through the literature. A structural model was built on the measurement model. Models were evaluated through PLS-SEM methods. Data acquired on candidate questionnaire items from 398 international respondents who are users of five different online collaborative word processors was used for the model analysis. Of 37 candidate manifest variables, 22 were retained, which were measuring seven latent constructs: “3C Mechanisms,” “Grounding,” “Team Integration,” “Communication,” “Shared Access,” “Awareness,” and “Usability.” The data provided empirical evidence for the structural model based on these latent variables. The responses of the participants were not sensitive to differences between users in terms of gender and native language but showed sensitivity to age, experience with the evaluated software, and different shared workspace groupware evaluated in the study. Our structural model attempts to integrate several frameworks and models of usability for CSCW environments and provides empirical evidence for its reliability and validity based on subjective responses from users of shared workspace groupware.     

Effect of dextran polymers on the stability of soluble Escherichia coli penicillin G acylase

The stabilisation of Escherichia coli penicillin G acylase (PGA) by dextran polymers (of molecular weight 11.5, 37.7 and 71 kDa) was studied. The inactivation of both the native and dextran‐containing enzyme preparations obeyed first‐order kinetics at the temperature and pH values studied. The optimal concentrations of dextran polymers of molecular weight 11.5, 37.7 and 71 kDa stabilising PGA against inactivation were 50, 20 and 7.5 mmol dm⁻³ respectively. Dextran 11500 (11.5 kDa) gave 100‐fold protection of PGA against thermal inactivation of enzyme above 50 °C. The kinetic constants of the enzyme were slightly altered, but temperature and pH profiles were not altered by the dextrans. © 1999 Society of Chemical Industry