41 research outputs found
Reconstructing William Craig Explanation of Absolute Time Based on Islamic Philosophy
After the advent of the theory of special relativity, the existence of an
absolute time in nature was rejected in physics society. In recent decades,
William Craig has endeavored to offer an interpretation of empirical evidences
corresponding to theory of relativity with the preservation of an absolute
time. His strategy is based on two viewpoints including dynamical theory of
time and the Eminent God's temporal being. After considering and criticizing
these two viewpoints, using the well-known overall substantial motion of nature
in Islamic philosophy and thus the realization of a general time for all the
nature, we have tried to reconstruct Craig argument for an absolute time.
Although Craig has considered some evidences from modern physics reasoning on
an absolute time, the special advantage of the approach considered here is in
this fact that it connects better the existing gap between the metaphysics and
the physics of the argument.Comment: 16 page
fracture and microstructural study of bovine bone under mixed mode i ii loading
Abstract Understanding the fracture behavior and associated crack growth mechanism in bone material is an important issue for biomechanics and biomaterial researches. Fracture of bone often takes place due to complex loading conditions which result in combined tensile-shear (i.e. mixed mode) fracture mechanism. Several parameters such as loading type, applied loading direction relative to the bone axis, loading rate, age and etc., may affect the mixed mode fracture resistance and damage mechanism in such materials. In this research, a number of mixed mode I/II fracture experiments are conducted on bovine femur bone using a sub-sized test configuration called "compact beam bend (CBB)" specimen to investigate the fracture toughness of bone under different mode mixities. The specimen is rectangular beam containing a mid-edge crack that is loaded by a conventional three-point bend fixture. The results showed the dependency of bone fracture toughness on the state of mode mixity. The fracture surfaces of broken CBB specimens under different loading conditions were studied via scanning electron microscopy (SEM) observations. Fracture surface of all investigated cases (i.e. pure mode I, pure mode II and mixed mode I/II) exhibited smooth patterns demonstrating brittle fracture of bovine femur. The higher density of vascular channels and micro-cracks initiated in the weakened area surrounded by secondary osteons were found to be the main cause of the decreased bone resistance against crack growth and brittle fracture
Effect of substituents on thermal behavior of some symmetric double schiff’s bases containing a cardo group
1083-1087Thermal behavior of symmetric double schiff’s bases containing cardo group has been studied by TGA and DSC techniques
at 10°C/min in nitrogen atmosphere. DSC transitions, thermal stability and kinetic parameters are affected by nature and
position of substituents. Schiff’s bases are thermally stable between 173-272°C and followed either a single step or two steps
degradation (fractional or integral order). Different magnitudes of n, E and A suggested different degradation mechanisms. A
large and negative magnitudes of “S* confirmed highly ordered transition state, while positive magnitudes of “S* confirmed less
ordered transition state
A cleaner approach for reduction of some symmetric diimines using NaBH4
438-442Symmetric diimines have been reduced to their corresponding amines by means of NaBH4 using THF as a solvent at room temperature. The reaction time and yield are 3-4 hr and 77-93%, respectively. Reduction process is very effective, inexpensive and clean for the synthesis of symmetric diamines in good yield. The structures of the compounds are supported by FTIR, mass spectrometry, ¹H and ¹³C NMR spectral dat
Ultrasonic speed, density, viscosity and associated acoustical parameters of chloroform solutions of symmetric double Schiff bases at 308.15K
ABSTRACT The density, viscosity and ultrasonic spee