A Multimedia World Wide Web Based Conference Minute System for Group Collaboration

In this paper, we propose a World Wide Web based conference minute system which preserves important information in the conference as web documents and maintains hyperlinks to related minutes to accelerate the progress of the project. This system, based on our Java application sharing framework, provides capabilities to record and replay the audio/video data of the video conference and operations of the shared applications used in the meeting in a synchronous manner. Through the hyperlinks, people can quickly understand the logic flow of every meeting held in the project duration and select any part in a meeting for replay to know what has actually happened. Furthermore, when a new meeting is held, a minute template is generated by the system to inherit the hyperlinks from its predecessors. Other related minutes and the execution status of the resolutions in the project can be easily accessed through the hyperlinks between them. Through the help of the system, execution of the project and management of its organizational memory could be easily achieved to increase the productivity of the collaborative groups with geographically dispersed members.     

Effects of alloying elements on the mechanical properties and corrosion behaviors of 2205 duplex stainless steels

The effects of alloying elements on the microstructure, mechanical properties, and corrosion behaviors of duplex stainless steels (DSSs) have been investigated in this study. Experimental alloys were prepared by varying the concentrations of the constituent elements in DSSs. Hot ductility test, tensile test, charpy impact test, and corrosion test were performed to evaluate the properties of the experimental alloys. The results showed that the extent of edge cracking of DSSs increased with the increasing value of the crack sensitivity index (CSI). The higher the hot ductility index (HDI) was, the better the hot ductility of DSSs achieved. Austenite (γ) stabilizer generally caused a decrease in the strength and an increase in the charpy impact absorbed energy of the stainless steel. On the contrary, ferrite (α) former exerted its beneficial effect on the strength but became detrimental to the toughness of DSSs. The presences of sulfur and boron also caused a decrease in the impact energy, but nitrogen and carbon hardly affected the toughness within the concentration range tested in this study. The value of pitting nucleation potential (E _np ) of different nitrogen contents in 3.5 wt.% NaCl solution at room temperature was almost the same, but the value of pitting protection potential (E _pp ) among these alloys was increased with increasing the content of nitrogen. The susceptibility to stress corrosion cracking (SCC) of DSSs was high when tested in boiling 45 wt.% MgCl₂ solution. On the other hand, the time to failure of the experimental steels in 40 wt.% CaCl₂ solution at 100 °C was longer than that in MgCl₂ solution. Nitrogen could affect the SCC behavior of DSSs in CaCl₂ solution through the combinative effects by varying the pitting resistance and the slip step dissolution. An optimum nitrogen (N) content of 0.15 wt.% was found where the highest SCC resistance could be obtained. Although γ phase exhibited better resistance to SCC, cracks were found to penetrate through α and γ grains or to propagate along the α/γ interface. As a result, a mixed transgranular plus intergranular mode of fracture surface was observed.     

Effects of cooling time and alloying elements on the microstructure of the gleeble-simulated heat-affected zone of 22% Cr duplex stainless steels

The effects of austenite stabilizers, such as nitrogen, nickel, and manganese, and cooling time on the microstructure of the Gleeble simulated heat-affected zone (HAZ) of 22% Cr duplex stainless steels were investigated. The submerged are welding was performed for comparison purposes. Optical microscopy (OM) and transmission electron microscopy (TEM) were used for microscopic studies. The amount of Cr₂N precipitates in the simulated HAZ was determined using the potentiostatic electrolysis method. The experimental results indicate that an increase in the nitrogen and nickel contents raised the δ to transformation temperature and also markedly increased the amount of austenite in the HAZ. The lengthened cooling time promotes the reformation of austenite. An increase in the austenite content reduces the supersaturation of nitrogen in ferrite matrix as well as the precipitation tendency of Cr₂N. The optimum cooling time from 800 to 500 °C (Δt _8/5) obtained from the Gleeble simulation is between 30 and 60 s, which ensures the austenite content in HAZ not falling below 25% and superior pitting and stress corrosion cracking resistance for the steels. The effect of manganese on the formation of austenite can be negligible.     

有机硅改性环氧树脂

有机硅改性环氧树脂是近年来发展起来的既能降低环氧树脂内应力 ,又能增加环氧树脂韧性、耐高温性等性能的有效途径。二者相容性是有机硅改性环氧树脂的关键。本文综述了有机硅改性环氧树脂的各种改性方法、机理及研究进展     

FEEDBACK LINEARIZATION DESIGNS FOR UNCERTAIN NONLINEAR TIME-DELAY PROCESSES: A COMPARATIVE STUDY

This work concerns the phenomena in which the feedback linearization control is applied to uncertain nonlinear time-delay processes. Under the I/O linearization algorithm, both nonlinear controllers are used to stabilize the closed-loop system with transformed delay inputs. When the effect of input perturbations can converge to zero or asymptotically vanish, these nonlinear feedback designs with only an adjustable parameter can directly improve the tracking performance. The simple linearizing controller can directly regulate the system output at unstable operating point. Combined with deadtime compensation the nonlinear predictive controller with the aid of appropriate state prediction is valid for the real process in the presence of large time delay. Finally, via computer simulation and test of control ability of both feedback control designs the useful comparative results are presented.     

Effect of Heating Rate on the Dielectric Properties of the PMN-PT Relaxor Ceramics

The effect of heating rate (2 to 30°C/min) during sintering on the perovskite phase content, density, microstructure, and dielectric properties of 0.9PbMg_1/3Nb_2/3O₃–0.1PbTiO₃ relaxor ferroelectric ceramics has been studied. Increasing the heating rate reduced the level of PbO evaporation and resulted in high perovskite content and dense ceramics. With slow heating rate (2–10°C/min), excess MgO segregated as isolated submicrometer particles in the perovskite grains; these precipitates were absent in ceramics sintered with a heating rate of 30°C/min. The maximum dielectric constant was optimized with a heating rate of 10°C/min. The temperature of maximum dielectric constant shifted downward as the heating rate was increased.     

Calculating double-exponential diode model parameters frompreviously extracted single-exponential model parameters

A procedure is proposed to calculate both pre-exponential reverse currents of the double-exponential model of a diode's current-voltage experimental characteristics from previously extracted reverse current and diode quality factor of the diode's single-exponential model. The procedure is illustrated by modelling the drain-body junction of a MOSFET including its parasitic series resistance     

A simple device for detecting impact time in impact-echo testing of concrete

The objective of this paper is to describe a simple device for detecting the time of an impact and to demonstrate its efficiency in measuring the depth of surface-opening cracks in concrete. Surface-opening cracks in concrete are relatively deep so that a mechanical impact instead of an ultrasonic transmitter is used to generate stress waves with enough energy for successful evaluation. A technique called the time-of-flight diffraction technique with impact-generated stress waves is an efficient method for detection of surface-opening cracks in concrete. Because the initial time of the impact is unavailable in a mechanical impact device, two receivers are employed in the test. One of the receivers is used to determine the time of the impact indirectly. The present study developed a simple device to record the time of impact initiation. The device comprises a conductive impact device, a sensing film, and an auxiliary circuit. With the device, stress waves are generated and the time of impact is detected so that the evaluation work needs only a single receiver. Laboratory studies were carried out on concrete specimens containing cracks with depths of 0.158 and 0.90 m. Field studies were performed on a dam damaged by an earthquake. Experimental results show that the new device can be used to accurately determine the crack depth in concrete. Using the device, the cost and effort for evaluation and signal analysis are reduced, which largely enhances the evaluation efficiency.     

The accuracy of ultrasonography and 201Tl-99mTc subtraction scan in localization of parathyroid lesions

Pulsed xenon chloride excimer and holmium laser-tissue interaction is primarily based on tissue water vaporization. Consequently, each ablative laser pulse produces a rapidly expanding and imploding vapour bubble in blood or the target tissue. In experimental studies, explosive water vaporization is the major mechanical cause of observed tissue dissections. By reduction of the induced bubble volume, a reduction in experimentally and clinically observed dissections after coronary excimer laser angioplasty is to be expected. This reduction of mechanical damage, however, in combination with efficient and substantial plaque debulking is the major challenge in the development of laser angioplasty.