Showing papers by "Istanbul Technical University published in 1985"

A general model for interface-trap charge-pumping effects in MOS devices

Abstract: Interface-trap charge-pumping effect is analysed on the basis of Shockley-Read-Hall theory of trapping, and a model describing the effect for any trapezoidal gate waveform and any reverse biasing source voltage is derived. A simplified version of the model which is valid for identical rise and fall times is also presented and experimentally verified. Experimental results indicate that the spatial variation of surface potential and the modulation of effective gate area by source voltage may strongly influence the charge-pumping current. It is also shown that the effect of gate-area modulation can be characterized directly from charge-pumping measurements.

Polymerization of styrene and methyl methacrylate by 2,5-dimethyl-2,5-dihydroperoxyhexane, 1. Bulk polymerization

Abstract: A new polymerization initiator 2,5-dimethyl-2,5-dihydroperoxyhexane is used as an initiator for the polymerization of styrene and methyl methacrylate at 80°C. It is found that the rates of initiation for this initiator lie in-between those of di-tert-butyl peroxide and benzoyl peroxide for both monomers. The kinetic results show good agreement between dilatometric and gravimetric measurements for the polymerization of styrene. However, mostly oligomers were obtained at high initiator concentrations with methyl methacrylate. A narrow molecular weight distribution is observed from stress-relaxation measurements for the polystyrene samples obtained at high conversions.

Size, technology and aspects of structure in contractor firms in Turkey

Abstract: The present paper treats the relationships between dimensions of size, technology and selected aspects of organizational structure in contractor firms operating in Turkey. It is proposed that the larger the organization, and the more advanced the technology employed, the higher the level of formalization, the higher the level of standardization, the higher the level of functional specialization and the lower the level of centralization. The data collected supported these propositions, except for the proposition about centralization.

Comparative mechanical properties of human bones

Abstract: In this work, three human bones, femur, tibia and fibula provided from amputation were studied under compressive loads. Tests have been done, shortly and several months after amputation, using a a hard metallic block connected to an Instron Machine. Three bones belonging to the same person showed different compressive strengths for both cases, immediately and longer times after amputation. It is seen that tibia is stronger than the other bones are and fibula is the weakest. Experiments also showed that there is large change in mechanical properties depending on the directions. Using classical metallographic technigues an attempt has been made to correlate the dependence of mechanical behavior of thes three bones on the size and density of the havers canals.

Resonant non-linear waves—IV. continuous and discontinuous solutions and an assessment of modal analyses

Abstract: Modal decomposition for the solution of partial differential equations is a quite commonly used procedure. For the class of problems of resonant systems, this procedure reduces the original partial differential equation to a system of ordinary differential equations describing an ensemble of coupled non-linear oscillators. Again, a common approximation is the single mode analysis, which truncates the infinite series at its first term. This paper indicates that near resonances many non-linear systems develop discontinuous solutions and discusses the range of applicability of the single mode analysis. The discussion is based on the construction of an exact solution to a non-linear integro-differential equation derived by a method due to Collins expanding on a procedure by Keller and applied to various problems in the preceding articles by these authors.

Thermal polymerization of N‐tert‐butylacrylamide in 1,4‐dioxane

Abstract: The kinetics of the thermal polymerization of N-tert-butylacrylamide were investigated in 1,4-dioxane as solvent, in the 65–80°C temperature range. It was found that the overall rate of polymerization which was determined by a gravimetric method is proportional to the 1.9 power of monomer concentration at 70°C. The rate of initiation was determined by ESR spectroscopy using DPPH as an inhibitor, and it was found that the order of initiation rate is 1.8 with respect to monomer concentration at 70°C. The overall activation energy for the thermal polymerization of N-tert-butylacrylamide was found to be 64 ± 9 kJ mol−1 in the 65–80°C temperature range. The activation energy for the rate of initiation was also determined and it was found to be 90 ± 23 kJ mol-1.

Running penny-shaped crack in an infinite elastic solid under torsion

Abstract: This paper is concerned with the problem of a running penny-shaped crack in an infinite elastic solid under torsion A basic formulation for an arbitrary velocity crack is given As an illustrative example, the penny-shaped crack is assummed to expand at a constant velocity For a constant-speed crack, the crack shape is explicitly obtained in exact expression easily comparable to the associated static solution

Resonant non-linear waves—III. Elastic continuum with quadratic non-linearity

Abstract: The paper derives the relevant non-linear integro-differential evolution equation by the method due to Collins expanding on a procedure by Keller. The quadratically non-linear case is not a trivial variation over the cubically non-linear case that was presented in preceding papers. As expected a different scaling and ordering of terms is needed and the first order perturbation solution provides no information on resonance. Nevertheless, although obtained by much longer calculations, the final equation for the present case is of identical form, with differences only in numerical coefficients, with the cubic case that was presented and solved earlier.

Diffraction coefficients related to cylindrically curved soft-hard surfaces

Abstract: An asymptotic solution to the problem of the diffraction of high-frequency waves by the edge of a cylindrically curved surface whose convex and concave faces present soft and hard boundary conditions is obtained. The results permit us to define new diffraction coefficients related to this kind of mixed boundary conditions. When the radius of the curvature becomes infinitely large, the edgediffraction coefficient reduces to this known for the softhard half-plane.

Comparative Mechanical Properties of Human Bones

Abstract: In this work, three human bones, femur, tibia and fibula provided from amputation were studied under compressive loads. Tests have been done, shortly and several months after amputation, using a a hard metallic block connected to an Instron Machine. Three bones belonging to the same person showed different compressive strengths for both cases, immediately and longer times after amputation. It is seen that tibia is stronger than the other bones are and fibula is the weakest. Experiments also showed that there is large change in mechanical properties depending on the directions. Using classical metallographic technigues an attempt has been made to correlate the dependence of mechanical behavior of thes three bones on the size and density of the havers canals.

Thermodynamics of Compatibility in Binary Polymeric Mixtures

Abstract: According to the conventional Flory-Huggins theory, the change in chemical potential of the solvent in solution is given by,