Destructive and non-destructive evaluation of concrete for optimum sand to aggregate volume ratio

Aggregates are the biggest contributor to concrete volume and are a crucial parameter in dictating its mechanical properties. As such, a detailed experimental investigation was carried out to evaluate the effect of sand-to-aggregate volume ratio (s/a) on the mechanical properties of concrete utilizing both destructive and non-destructive testing (employing UPV (ultrasonic pulse velocity) measurements). For investigation, standard cylindrical concrete samples were made with different s/a (0.36, 0.40, 0.44, 0.48, 0.52, and 0.56), cement content (340 and 450 kg/m³), water-to-cement ratio (0.45 and 0.50), and maximum aggregate size (12 and 19 mm). The effect of these design parameters on the 7, 14, and 28 d compressive strength, tensile strength, elastic modulus, and UPV of concrete were assessed. The careful analysis demonstrates that aggregate proportions and size need to be optimized for formulating mix designs; optimum ratios of s/a were found to be 0.40 and 0.44 for the maximum aggregate size of 12 and 19 mm, respectively, irrespective of the W/C (water-to-cement) and cement content.     

STORAGE TEMPERATURE EFFECTS ON THE PROTEOLYTIC ACTIVITY OF RADIATION-SURVIVING BACTERIA IN OYSTERS

ABSTRACT— The activity of 2 radiation-surviving and strongly proteolytic strains of Pseudomonas and Achromobacter were compared to the activity of 2 lesser active strains of Neisseria and Bacillus in fresh oysters during iced (32°F) and refrigerated (40°F) storage for 15 days. Radiation doses used for the oysters were 100 and 800 krad. The activity of the former bacteria was higher than that of the latter 2 at both temperatures and radiation doses. Neither the nonirradiated nor the irradiated uninoculated oysters displayed significant increases in proteolytic activity when they were ice-stored for 15 days, but storage at 40°F for the same period resulted in significant activity increases in the nonirradiated. This emphasizes irradiation and storage temperature as related factors. A slight decrease in pH at 15 days in both nonirradiated and 100 krad-irradiated oysters corresponded to the increase in bacterial numbers.     

Effects of Microwave Heating and Gamma Irradiation on Phytate and Phospholipid Contents of Soybean (Glycine max. L.)

The effect of microwave heating and gamma irradiation treatments on phosphorus compounds of soybean seeds were studied. Inorganic phosphorus was significantly (P < 0.05) increased while, phytate and phospholipids were significantly decreased when soybean seeds were microwave-heated for 9 min or more. Furthermore, gamma-irradiation treatments of 20 KGy or more significantly increased inorganic phosphorus and decreased phytate and phospholipids of the beans. Two dimensional thin-layer chromatography was employed to study the phospholipid pattern. Gamma-irradiation at doses from 40 to 100 KGy produced lysophosphatidylcholine and phosphatidic acid. The data of this study showed that, the increase of inorganic phosphorus was mainly due to the decomposition of phytic acids and phosphates of inositol.     

铁对粉末冶金法制备铝基复合材料微观组织和力学性能及磁学性能的影响(英文)

研究铁对粉末冶金法制备铝基复合材料微观组织、力学性能及磁学性能的影响。利用机械混合制备含0,5%,10%和15%Fe(质量分数)的铝基复合材料。Al-Fe混合粉末经压制后在真空炉中600°C烧结1 h。XRD结果表明:在含有5%和10%Fe的试样中只有Fe和Al的衍射峰,而含有15%Fe的试样中则存在Al和Al13Fe4的衍射峰。实验结果表明:随着Fe含量的增加,材料的致密度和导热性变差。复合材料中的Fe可以提高其强度和硬度。材料的强化机制包括基体的晶粒细化,Fe颗粒的均匀分布以及Al13Fe4金属间化合物的形成。含有5%Fe试样的磁化强度为0.3816×10-3A·m2/g,对于含有10%Fe的试样,其磁化强度增加至0.6597×10-3A·m2/g,而对于含有15%Fe试样,其磁化强度降低至0.0702×10-3A·m2/g。这是由于在高铁试样中形成了反磁性的Al13Fe4金属间化合物导致磁化强度降低。     

POSTHARVEST RETARDATION OF SENESCENCE IN SHADO BENNI (ERYNGIUM FOETIDUM, L.) PLANTS

Leaves of shado benni plants (Eryngium foetidum, L.) are used extensively as a seasoning and herbal medicine. However, the very short shelf-life of 3–4 days of harvested plants is a major drawback to wider use. Plants were harvested with roots intact, dipped in gibberellic acid (GA₃) and stored in perforated and nonperforated LDPE bags up to 22 days at 20–22C and 28–30C. Samples were examined for changes in appearance, color, fresh weight and flavor (loss of pungency and off-flavor development). GA₃ effectively retarded plant senescence up to 22 days at both temperatures when stored in nonperforated LDPE bags. Despite the external maintenance of marketable quality, flavor life was 17 days since development of off-flavors and reduction in pungency occurred after this period. Thus, the combination of polyethylene packaging, GA₃ dip treatment and reduced temperature storage extended the shelf-life of shado benni plants in a fresh, turgid and decay-free condition for in excess of two weeks.     

The effect of concentration of chymosin on the yield and sensory properties of camel cheese and on its microbiological quality

The transformation of camel milk into soft cheese by using chymosin and yoghurt starter culture (Streptococcus thermophilus and Lactobacillus bulgaricus) was investigated. The cheese yield and sensory properties were related to the concentration of chymosin. A yield of 16.74 g/100 mL of milk was obtained with a chymosin concentration of 1.7 mL/L of milk. The cheeses obtained with concentrations ranging between 1.0 mL and 2.9 mL of chymosin/L of milk scored highly regarding their sensory properties and had an acceptable microbiological quality. This study demonstrated that cheesemaking from camel milk can be made successfully providing that the appropriate chymosin concentration is used; and that 1.7 mL of chymosin/L of milk was optimal.     

VAPOR OPERATED SOLAR PUMP

The choice of a water pumping system in remote areas depends on the type of energy available for power generation. In most of these areas where electricity and other sources of energy are not available or expensive to obtain, solar energy offers a cheap source of energy which can be utilized for operating water pumping systems. This paper describes a simple low technology vapor operated solar pump having minimum number of moving parts. The system is easy to manufacture and requires low maintenance. The performance of the system is experimentally investigated and the results obtained are presented and discussed.     

Thermal characteristics and corrosion behaviour of Mg–xZn alloys for biomedical applications

The thermal parameters of Mg–xZn cast alloys with 0·5–9 wt% Zn were evaluated by using computer aided cooling curve thermal analysis (CA–CCTA), whereas the corrosion behaviour was investigated by potentiodynamic polarization and immersion tests. Thermal analysis results revealed that the dendrite coherency temperature (T _DCP ) decreased from 642·2 to 600 °C with the addition of Zn from 0·5 to 9 wt%. The liquid fraction at coherency point ( ${f}_{ L}^{ DCP}$ ) increased by 72% when Zn was increased up to 9 wt%. MgZn intermetallic phase was observed in samples with <3 wt% Zn. At higher percentages of Zn, the Mg ₅₁Zn ₂₀ intermetallic phase was also detected in addition to α-Mg and MgZn by first derivative cooling curves under non-equilibrium solidification. All these phases were observed along the grain boundary when Zn was rejected from the solid/liquid interface and enriched in the triple conjunction of grain boundary. The grain size decreased from 185·2 to 71·5 μm when Zn content was increased. The addition of Zn content had a significant effect on the corrosion rate and the corresponding mechanisms. The corrosion rate decreased from 2·1 to 1·81 mmpy as Zn content increased from 0·5 to 3 wt%; afterwards, however, this value increased with further increase of Zn. Mg–3Zn also had the lowest degradation rate and highest corrosion resistance which can be fully utilized for biodegradable orthopedic applications.     

Antioxidative Activity of Maillard Reaction Products in Cooked Ground Beef, Sensory and TBA Values

Maillard reaction products (MRPs) obtained by autoclaving egg albumin acid hydrolysate and glucose for 1 hr were added to ground beef which was cooked and stored at 4°C for 8 days. The antioxidative activity of MRPs was investigated by a trained sensory panel and the TBA test. The panel evaluated samples for loss of desirable cooked beef notes and generation of off-flavors, such as cardboard and painty. With added 1% MRPs, painty aroma and flavor scores were low and did not (p > 0.05) change over time. The coefficients of determination were high (r²= 0.92 to 0.77, p < 0.0001) between aroma and flavor scores for any two similar attributes. The TBA values decreased by 17% with the addition of 0.5% MRP and by 39% with 1% MRP over time.