Trifluoromethylsulfonyl-Based Salts of BEDT-TTF: Crystal and Electronic Structures and Physical Properties11

Three 2 : 1 salts of the organic donor molecule bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) with trifluoromethylsulfonyl-based anions N(SO₂CF₃)₂⁻, CH(SO₂CF₃)₂⁻ and C(SO₂CF₃)₃⁻ were prepared by electrocrystallization. These salts were characterized by single-crystal X-ray diffraction, electron spin resonance (ESR) spectroscopy, electrical resistivity measurements and electronic band structure calculations. (ET)₂N(SO₂CF₃)₂ is a two-dimensional (2D) metal, but its ESR spin susceptibility above 150 K shows a weakly semiconducting behavior, presumably because during ESR measurements the sample cooling rate is slow hence allowing the disordered anions to readjust their positions. (ET)₂CH (SO₂CF₃)₂ is a 2D metal and undergoes a metal-to-insulator (MI) transition at 110 K due probably to a geometry change of the donor molecule layers. (ET)₂C(SO₂CF₃)₃ is a one-dimensional (1D) metal and undergoes an MI between 180 and 240 K, which is expected to be of charge density wave type.     

Segmentation of CT brain images using unsupervised clusterings

In this paper, we present non-identical unsupervised clustering techniques for the segmentation of CT brain images. Prior to segmentation, we enhance the visualization of the original image. Generally, for the presence of abnormal regions in the brain images, we partition them into 3 segments, which are the abnormal regions itself, the cerebrospinal fluid (CSF) and the brain matter. However, for the absence of abnormal regions in the brain images, the final segmented regions will consist of CSF and brain matter only. Therefore, our system is divided into two stages of clustering. The initial clustering technique is for the detection of the abnormal regions. The later clustering technique is for the segmentation of the CSF and brain matter. The system has been tested with a number of real CT head images and has achieved satisfactory results.     

Kinetic model of the oxidation of ZrSi<Subscript>2</Subscript> powders

The oxidation kinetics of Zr-disilicide (ZrSi₂) powders up to temperatures of 1550°C were studied in flowing air using non-isothermal and isothermal thermogravimetric (TG) analysis. During the oxidation process two main thermal events were detected. The first stage of the oxidation reaction leads to the formation of elemental silicon as an intermediate reaction product. Upon further temperature increase the newly formed silicon is oxidized. Completely oxidized ZrSi₂ samples consist of ZrSiO₄, amorphous and crystalline SiO₂ as well as some residual ZrO₂. The experimental TG data were analysed with a model-fitting kinetic method. The gas-solid reaction is complex and can best be fitted with a multi-step reaction scheme consisting of branching reactions based on 3D diffusion mechanisms and a fractal order reaction.     

Three‐Dimensional,Time‐Resolved Profiling of Ferroelectric Domain Wall Dynamics by Spectral‐Domain Optical Coherence Tomography

We apply here spectral‐domain optical coherence tomography (SD‐OCT) for the precise detection and temporal tracking of ferroelectric domain walls (DWs) in magnesium‐doped periodically poled lithium niobate (Mg:PPLN). We reproducibly map static DWs at an axial (depth) resolution down to ～ 0.6 μm, being located up to 0.5 mm well inside the single crystalline Mg:PPLN sample. We show that a full 3‐dimensional (3D) reconstruction of the DW geometry is possible from the collected data, when applying a special algorithm that accounts for the nonlinear optical dispersion of the material. Our OCT investigation provides valuable reference information on the DWs’ polarization charge distribution, which is known to be the key to the electrical conductivity of ferroelectric DWs in such systems. Hence, we carefully analyze the SD‐OCT signal dependence both when varying the direction of incident polarization, and when applying electrical fields along the polar axis. Surprisingly, the large backreflection intensities recorded under extraordinary polarization are not affected by any electrical field, at least for field strengths below the switching threshold, while no significant signals above noise floor are detected under ordinary polarization. Finally, we employed the high‐speed SD‐OCT setup for the real‐time DW tracking upon ferroelectric domain switching under high external fields.     

A Model for Continuous Production Control with Warning Signals to Fault Occurrences

The advance of computer, automation and control technology has led to the adoption of continuous control and monitoring of production processes in high technology industries. By monitoring the state of the production process continuously, occurrence of any faults in the production process can be identified with zero or negligible detection delay. As a result, the costs of defective products, loss in yield and restoration are minimized. On the other hand, the sensitivity of the continuous monitoring system could result in very frequent repair and maintenance of the process, causing frequent disruptions of production. This paper addresses the question of the determination of the optimal level at which warning signals should be given of fault occurrences in a production system that is continuously monitored. A model is developed from which the expected total costs per time unit can be derived. A numerical example illustrates the determination of the optimal warning level under this framework.     

ON THE GLOBAL CONVERGENCE OF CONJUGATE GRADIENT METHODS WITH INEXACT LINESEARCH

In this paper we consider the global convergence of any conjugate gradient method of the form d1=-g1,dk+1=-gk+1+βkdk(k≥1)with any βk satisfying sume conditions,and with the strong wolfe line search conditions.Under the convex assumption on the objective function,we preve the descenf property and the global convergence of this method.     

Comparative statics of changes in risk on monotonically and partially responsive kinked payoffs

This paper derives two sets of necessary and sufficient conditions on the comparative statics of changes in risk under kinked payoff functions that are monotonically responsive and partially responsive to the realization of risk, respectively. The former case includes the newsboy problem with backorder; the latter case includes the newsboy problem without backorder and under some restrictions, also includes the optimal deductible insurance problem. Some relatively non-restrictive conditions derived from the necessary and sufficient conditions reveal that the three problems can be quite different, even though they are often viewed in the literature as being congruous. These conditions lead to simple predictions of the direction of change in any risk-averse agent’s optimal choice upon a change in risk, without assuming specific functional forms for the utility function.