Effects of Ta Content on Thermodynamic Properties and Transformation Temperatures of Shape Memory NiTi Alloy

Metals and Materials International - In the present work, Ni32-x-Ti-Ta18+x (x?=?0, 2, 3, 4, 5, 6, 7, 8) shape memory alloys, produced by arc-melting method. Then, differential scanning...     

Gas chromatographic-olfactometric characterization of aroma active compounds in sun-dried and vacuum-dried tarhana

The influence of drying methods on the aroma active volatiles of sun-dried tarhana (SDT) and vacuum-dried tarhana (VDT) were compared using headspace SPME, GC-O and GC-MS. Although vacuum drying reduced the total amount of volatiles as compared to SDT (total FID peak area), more aroma active material was retained with VDT (total olfactory peak area). Vacuum drying retained a greater number of aroma active components (41) whereas the sun-dried method retained only 23. Aldehydes were the largest single class of aroma compounds in both types of tarhana: 17 in VDT and 10 in SDT. Other differentiating aroma compounds include alcohols, terpenes, and phenols such as geraniol, terpinolene, and 4-vinylguaiacol among others. A total of 22 aroma active components were present in greater amounts in the VDT versus only four aroma compounds present in greater amounts in the SDT.     

An experimental investigation on the low velocity impact response of composite plates repaired by VARIM and hand lay-up processes

This paper presents results of an experimental investigation on the impact response of repaired and unrepaired glass/epoxy composite plates. Repaired samples were prepared by two different manufacturing methods; vacuum assisted resin infusion process and hand lay-up technique. In order to compare impact response of the repaired and unrepaired samples a number of single impact tests were performed under various impact energies. Damage process of the samples is analyzed from cross-examining load–deflection curves and damaged specimens. From the visual inspection, for the impacted side of the samples, it is noted that the main damage modes for repaired samples are matrix and fiber cracks around point of impact and delaminations while severe matrix cracks expanded through fiber directions are the dominant damage mode for unrepaired samples. At the back surfaces, delaminations and fiber–matrix debonding oriented in the fiber directions are observed for unrepaired samples. However, for repaired samples the fiber fractures through repair line as well as the delaminations become dominant modes. For a reasoning justification in discussing impact test results, interlaminar fracture toughness (Mode I and Mode II) and flexural tests for repaired and non-repaired samples were also conducted.     

Microstructural and wear properties of the Al-B4C composite coating produced by hot-press sintering on AA-2024 alloy

Journal of Mechanical Science and Technology - In this study, the surface of an AA-2024 alloy was covered with reinforced composite coating using hotpress sintering method. Al and B4C powders were...     

The effects of wheat sourdough on glutenin patterns, dough rheology and bread properties

Sourdough was prepared with cellular suspension containing 10⁹ cfu of each strain mL⁻¹ and incubated at 28 °C for 24 h and at 37 °C for 4 h. Two different sourdough levels (20 and 40%) were used in bread dough preparation. The bread doughs were proofed at 30 °C and 85% relative humidity for 60/120/180 min. When glutenin changes that occurred in samples 17, 18, 19, and 20 (40% SD 28) are compared with those that appeared in controls, it is obvious that, the relative intensities of some of the protein bands slightly decreased and a few fainter protein bands appeared (which did not exist in controls). A few fainter protein bands corresponding to the MM ≈ 25 kDa (high-mobility region) and the MM ≈ 66 kDa (low-mobility region) were appeared in the same samples. In the samples prepared with 20% sourdoughs incubated at 28 or 37 °C, the bands were still evident after 180 min of proof. This can be explained that glutenin fractions were not hydrolysed in these applications due to the delay in pH drop. The use of 40% sourdough incubated at 28 °C for 24 h resulted in sticky doughs and breads with lower volume, harder texture, unsatisfactory crumb grain and unpleasant flavour than the rest of the samples. The use of sourdoughs incubated at 37 °C for 4 h caused positive effect on loaf volumes, specific loaf volumes and crumb structure.     

Structural,electrical and optical properties of metal complexes of NNS donor ligand

The temperature dependence of electrical conductivity, optical property and crystal structure (PXRD) of [Ni(Hdammthiol)(CH₃COO)] (1), [Co(Hdammthiol)(CH₃COO)]·H₂O (2) and [Cu(Hdammthiol)(CH₃COO)]·H₂O (3) [where H₂dammthiol is the thiol form of the ligand diacetylmonoxime morpholine N-thiohydrazone (Hdammth)] complexes were investigated. The crystal structures of samples at room temperature were examined by using powder X-ray diffraction (PXRD). The results showed that all the complexes belong to the monoclinic system. Hot probe measurement indicated that these complexes had an n-type electrical conductivity. Optical absorption studies in the wavelength range 190–1100 nm at room temperature showed that the optical band gap E_gd of complexes 1–3 is 2.75 eV, 2.37 eV and 1.58 eV, respectively.     

Geostatistics applied to mine waste characterization at Leadville,Colorado, USA

ABSTRACT

This paper will describe the process of identifying lead contaminated soil areas exceeding a certain threshold at a historical mining district using geostatistical tools. For this purpose, lead concentration samples coming from Leadville County, Colorado were chosen as the data sets to be examined. In order to check integrity of data files, posting of the data values at sample locations is performed on each of the four data sets available. Statistical analysis is used for identifying possible different populations within the study area Based on the statistical results, the data sets were subdivided into four different populations as they relate to residential domains. More detail geostatistical analysis of data set representing the City of Leadville domain (CL) is performed Variogram analysis is used to characterize spatial variability on the data sets within CL limits. Generation of variograms for such data sets and identification of their parameters such as sill, nugget, range, and anisotropy ratios is performed. Once these parameters are identified, variogram modeling is accomplished. A significant spatial correlation is found within CL boundaries and two geostatistical estimation techniques named ordinary kriging and indicator kriging are applied to determine level of contamination at unsampled locations exceeding 3500 PPM threshold. Such techniques are tested by cross validation in order to check possible overestimation bias over 3500 PPM threshold. Indicator Kriging was found to be the best estimator which provided the minimum overestimation bias of areas of contamination exceeding 3500 PPM threshold compared with ordinary kriging.     

The drillability assessment of rocks using the different brittleness values

The brittleness is a fundamental rock property and effective in drilling and rock excavation. Knowing the relations between the drillability and the brittleness will help the rock engineers. For this reason, to investigate the relations between the drilling rate index (DRI) and the different brittleness values, 32 different rock types were tested in the laboratory. Uniaxial compressive strength and tensile strength were determined for the brittleness calculations. The brittleness of B₃ (the ratio of compressive strength minus tensile strength to compressive strength plus tensile strength), and the brittleness of B₈ (the half of the product of compressive strength and tensile strength) were calculated from the test results. In addition, Sievers’ J-miniature drill test and the brittleness test were carried out and DRI values were calculated. Then, B₃ and B₈were correlated with DRI values. A good correlation between DRI and the brittleness of B₃ could not be found. However, a strong exponential relation between DRI and the brittleness of B₈ was found. Comparing the results with the literature showed that there was an agreement between this study and previous studies. It can be concluded that B₈ can be used for the assessment of rock drillability.