Modeling of precipitation hardening in Mg-based alloys

This work deals with the development of Mg-based alloys with enhanced properties at elevated temperatures. This is achieved by precipitation of binary phases such as MgZn₂ and Mg₂Sn during the aging of these alloys. The aim of the present work is to develop and calibrate a model for precipitation hardening in Mg-based alloys, as different types of precipitates form simultaneously. The modified Langer-Schwartz approach, while taking into account nucleation, growth and coarsening of the new phase precipitations, was used for the analysis of precipitates’ evolution and precipitation hardening during aging of Mg-based alloys. Two strengthening mechanisms associated with particle-dislocation interaction (shearing and bypassing) were considered to be operating simultaneously due to particle size-distribution. Parameters of the model, R _N i and k _{σ i} , were found by fitting of calculated densities and average sizes of precipitates with ones estimated from experiments. The effective diffusion coefficients of phase formation processes, which determine the strengthening kinetics, were estimated from the hardness maximum positions on the aging curves.     

A new supervised classification algorithm in artificial immune systems with its application to carotid artery Doppler signals to diagnose atherosclerosis

Because of its self-regulating nature, immune system has been an inspiration source for usually unsupervised learning methods in classification applications of Artificial Immune Systems (AIS). But classification with supervision can bring some advantages to AIS like other classification systems. Indeed, there have been some studies, which have obtained reasonable results and include supervision in this branch of AIS. In this study, we have proposed a new supervised AIS named as Supervised Affinity Maturation Algorithm (SAMA) and have presented its performance results through applying it to diagnose atherosclerosis using carotid artery Doppler signals as a real-world medical classification problem. We have employed the maximum envelope of the carotid artery Doppler sonograms derived from Autoregressive (AR) method as an input of proposed classification system and reached a maximum average classification accuracy of 98.93% with 10-fold cross-validation method used in training-test portioning. To evaluate this result, comparison was done with Artificial Neural Networks and Decision Trees. Our system was found to be comparable with those systems, which are used effectively in literature with respect to classification accuracy and classification time. Effects of system's parameters were also analyzed in performance evaluation applications. With this study and other possible contributions to AIS, classification algorithms with effective performances can be developed and potential of AIS in classification can be further revealed.     

Logical diagnosis ofLDL programs

The debuggers of Ref. 11) and most of their derivatives are of themeta-interpreter type. The computation of the debugger tracks the computation of the program to be diagnosed at the level of procedure call. This is adequate if the intuitive understanding of the programmer is in terms of procedure calls; as is indeed the case in Prolog. InLDL however, while the semantics of the language are described in a bottom-up, fixpoint model of computation,⁸⁾ theactual execution of a program is a complex sequence of low-level procedure calls determined (and optimized) by the compiler. Consequently, a trace of these procedure calls is of little use to the programmer. Further, one cannot “execute” anLDL program as if it was a Prolog program; the program may simply not terminate in its Prolog reading and severalLDL constructs have no obvious Prolog counterparts. We identify the origin of a fault in theLDL program by a top-down, query/subquery approach. The basic debugger, implemented in Prolog, is a shell program between the programmer and theLDL program: it poses queries and uses the results to drive the interaction with the user. It closely resembles the one presented in Ref. 11). The core of a more sophisticated debugger is presented as well. Several concepts are introduced in order to quantify debugging abilities. One is that of agenerated interpretation, in which the structureless intended interpretation of Ref. 11) is augmented with causality. Another is the (idealized) concept of areliable oracle. We show that given an incorrect program and a reliable oracle which uses a generated interpretation, a cause for the fault will be found in finitely many steps. This result carries over to the more sophisticated debugger.     

Task Switching After Cerebellar Damage.

The authors of this study investigated task switching following cerebellar damage. The study group consisted of 7 children and adolescents (M age = 13.8 years) who underwent surgical removal of a benign posterior fossa tumor. They were tested at a sufficient interval after surgery (M lag = 6.13 years) for restoration of normal cognitive skills and intelligence. Although all showed normal learning of the task compared with control participants, when rapid behavioral changes were required (short preparation time), they exhibited behavioral rigidity manifested by enhanced switching cost. These results are in line with another study on serial reaction time with the same patients (A. Berger et al., in press). They have important implications for our understanding of the cognitive sequelae of early cerebellar damage as well as the involvement of the cerebellum in task switching. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of gravity on InGaSb crystal growth

The effect of gravity on dissolution of GaSb in InSb melt and growth of InGaSb was experimentally investigated. Experiments were carried out in a GaSb(seed)/InSb/GaSb(feed) sandwich system under an imposed temperature gradient. In the experiments, the GaSb feed crystal dissolved into the InSb melt to supply the required GaSb component for the growth of In_0.1Ga_0.9Sb crystal. Two parameters were considered: (1) the inclination angle (θ) of the sample for gravity as 0° and 53°, and (2) the sample diameter (D) as 9 mm and 5mm. When θ was 0°, the interface was almost flat, indicating that convection was axisymmetric and stable. Whereas the interface was distorted towards gravitational direction when θ was 53°, indicating that solutal convection was dominant. The decrease of growth temperature and sample diameter reduced the distortion of interface and the dissolution amount of GaSb feed. The homogeneous crystals were grown at the initial growth stage by supplying the GaSb component during growth.     

Turned trochoidal disturbance on a liquid jet surface

This paper shows that a turned trochoidal function disturbance may lead to peripheral drops production. The resulting model is used to describe that a turned trochoidal disturbance leads to peripheral drops production on the liquid jet surface without the necessity for superimposed disturbances. The trochoid is a non-unique parametric function. Only non-unique parametric functions disturbances may lead to peripheral drops production. The trochoidal function disturbance is decomposed to Fourier series. Every Fourier element receives an amplification factor in accordance to the Rayleigh inviscid jet model. Peripheral drops are received on the jet surface. The paper shows that all trochoidal disturbance functions, prolate cycloid, cycloid and curtate cycloid have a capability of peripheral drops producing. A limited capability of peripheral drops production is introduced for the trochoidal curtate cycloid. Produced drops size are reduced for increasing the jet velocity and wave number. Smaller drops are also received by transition from the prolate cycloid to curtate cycloid disturbance.     

A modelling study for moisture diffusivities and moisture transfer coefficients in drying of solid objects

This article presents an effective analytical model for determining the moisture diffusivities and moisture transfer coefficients for solid objects (namely, infinite slab, infinite cylinder, sphere; and also for irregularly shaped objects, by using a shape factor) subject to drying applications in a medium. The unsteady-state moisture diffusion analysis is used on the basis of two important criteria: 0·1 <Bi < 100 and Bi > 100. The drying coefficients and lag factors were employed. The analytical models are then verified using available experimental data taken from the literature. The results show that the method presented here can be used to determine the moisture diffusion coefficients and moisture transfer coefficients for such solid objects in a simple and accurate manner for a variety of drying applications.     

Misalignment tolerance analysis of free-space optical interconnects via statistical methods

System-level packaging is one of the critical issues that need to be addressed for free space optical interconnections (FSOI) to become useful in desktop systems. The performance of FSOI, e.g., in terms of system bit-error rate, is greatly affected by misalignments in the optical system. Therefore tolerancing, i.e., the ability to analyze and predict the effects of misalignments in the system, is of prime importance to system designers. We introduce an approach in which we study the effects of optical misalignments and other tolerance factors using statistical methods. We use Monte Carlo simulations, design of the experiments, and regression techniques to fit a polynomial equation that expresses the relationship between the system performance and the tolerance factors. This prediction model can be used for design, cost optimization, and quality control purposes. In addition, we perform a sensitivity analysis to determine those tolerance variables that have the greatest effect on system performance.     

A receptor-based bioassay for quantitative detection of gallium

The detection of gallium in biological samples is required due to its role in the diagnosis of tumor and for possible treatment of malignancies. However, the use of purely instrumental techniques is unsuitable for detection of low levels of gallium in biological matrixes. We have synthesized new protein conjugates based on 4-(2-pyridylazo) ligands. The conjugates were successfully employed for the detection of gallium in biological matrixes using a nonantibody-based sandwich assay format. The recovery level obtained was between 97 and 101.3 with a relative standard deviation of less than 5%. The assay resulted in a detection limit of 5 x 10(-8) M and a remarkable selectivity for gallium(III) relative to other metals investigated. The new method provided adequate accuracy for gallium applicable for animal physiology and clinical toxicology.