Solid state extrusion of polytetrafluoroethylene fibers

Polytetrafluoroethylene (PTFE) was solid state extruded to fiber form at temperatures between 250 and 300°C and at pressures between 7000 and 15,000 psi. The PTFE fibers had a diameter of 0.0502 inches and the reduction ratio for extrusion was 55.8. The fibers were tested for mechanical strength, and examined with a scanning electron microscope, which revealed a fibrous structure at high magnifications. The melting point of the fibers was 342°C by differential scanning calorimetry. The tensile properties were enhanced with an increase in processing temperature and pressure, the highest properties resulting from an extrusion temperature of 300°C and pressures greater than 10,000 psi. A tensile strength of 5500 psi and a secant modulus of 250,000 psi were obtained.     

Optimum Filters for Estimating Evoked Potential Waveforms

The design of time-invariant and time-varying minimum mean square error filters for processing event related brain potentials is considered. A model for taking into account the randomness associated with the signal as well as that of the noise is described. Results using simulated data show the perfonnance of the time-varying filter to be greatly superior to that of the time-invariant filter. Results of processing measured visual evoked potentials are presented.     

3D failure analysis in depth profiles of sequentially made FIB cuts

A new method of investigating structures below a surface in a dual beam microscope is presented. It comprises electrical measurements in depth profiles of sequential focused ion beam (FIB) cuts by the use of two or more nanomanipulators with plugged in probe needles. The sample is oriented such that the structures are observed with the electron beam while they are cut free with the FIB. The nanomanipulators are moved to contact the structures for examination. The FIB cut is extended step by step, and after each cut the nanomanipulators are repositioned and measurements of the new structures that appear in the FIB cut are made. The measurement series provide a three dimensional electrical characterization of the examined sample volume.     

Bandwidth determined transmoding through fuzzy logic in mobile intelligent multimedia presentation systems

Mobile intelligent multimedia presentation systems are subject to various resource constraints including mobile network characteristics, mobile device capabilities and user preferences. Those presentation systems which incorporate remote multimedia content accessed across HTTP (Hyper Text Transfer Protocol) or RTP (Real Time Transfer Protocol) protocols are particularly reliant on the capabilities of the connecting mobile network (i.e. minimum, average and maximum bandwidth) and in particular on the real-time constraints (i.e. currently available bandwidth, packet loss, bit error rate, latency) which prevail during actual content transmission. One approach to address this is to scale content, thus reducing its datarate requirement, although this technique is inherently limited by the lowest acceptable quality of that media element. Alternatively, content can be converted from one modality to another with a lower resource requirement. TeleMorph, a cross-modality adaptation control platform is detailed here. Initially a brief introduction to Intelligent Multimedia and to Mobile Intelligent Multimedia is given, and key systems discussed. The main premise of TeleMorph is that cross-modality adaptations in mobile presentation systems must be controlled in a manner which gives primary consideration to bandwidth fluctuations as well as the constraints listed above. The current prototype of TeleMorph, which uses a fuzzy inference system to control cross-modality adaptations between video and audio, is described. Particular focus is given to the fuzzy inputs, fuzzy control rules and fuzzy outputs which have been utilised in decision making. TeleTuras, a tourist information application which has been implemented as a testbed for TeleMorph, gives promising evaluation results based on multimedia and bandwidth specific test scenarios. TeleMorph is related to other approaches in the area of Mobile Intelligent Multimedia Presentation Systems. TeleMorph differs from other approaches in that it focuses specifically on the challenges posed by controlling bandwidth determined cross-modality adaptations in a mobile network environment. Future work on TeleMorph’s output presentation composition will incorporate images and text also, thus allowing for extended adaptation between video, audio, images and text, as well as multimodal combinations of these media elements.     

提高柴油机燃料经济性和延长换油期

对车队而言,最关心的是如何降低车辆的运行费用,即在保证发动机使用性能的前提下,最大程度地提高燃料经济性和延长换油期。本研究结果表明,在1995年Caterpillar 3406E和1996年Detriot 60系列柴油发动机上使用由合成油调制的SAE 5W／40和由APIⅡ类基础油调制的SAE 15W／40,不论是燃料经济性还是发动机磨损,两之间不存在统计意义上的差别。     

Comparison of retrospective and contemporary indoor radon measurements in a high-radon area of Serbia

In Niska Banja, Serbia, which is a high-radon area, a comparison was made between two retrospective radon measuring methods and contemporary radon measurements. The two retrospective methods derive the radon concentrations that occurred in dwellings over longer periods in the past, based on the amount of trapped (210)Po on the surface of glass objects (surface traps, ST) or in the bulk of porous materials (volume traps, VT). Both surface implanted (210)Po in glass objects and contemporary radon in air were measured in 46 rooms, distributed in 32 houses of this radon spa-town, using a dual alpha track detector configuration (CR-39 and LR115) and CR-39 track etched detectors, respectively. In addition to the use of surface trap measurements, in 18 rooms (distributed in 15 houses) VT samples of suitable material were also collected, allowing to compare ST and VT retrospective radon concentration estimates. For each room, contemporary annual radon concentrations (CONT) were measured or estimated using seasonal correction factors. The distribution of the radon concentration in all data sets was found to be close to lognormal (Chi-square test>0.05). Geometric means (GM) are similar, ranging from 1040 to 1380 Bq m(-3), whereas geometric standard deviations (GSD) for both the retrospective methods are greater than for the CONT method, showing reasonable agreement between VT, ST and CONT measurements. A regression analysis, with respect to the lognormal distribution of each data set, shows that for VT-ST the correlation coefficient r is 0.85, for VT-CONT r is 0.82 and for ST-CONT r is 0.73. Comparison of retrospective and contemporary radon concentrations with regard to supposed long-term indoor radon changes further supports the principal agreement between the retrospective and conventional methods.     

Performance and deployment evaluation of a parallel application on a private Cloud

In this paper we present the case study of an application of a parallel simulation optimization deployed on a private Cloud. The compute‐intensive application uses a Master/Worker model, supporting communication over both Java RMI and Globus Grid Services between the nodes. The Master deploys Workers over a Eucalyptus Cloud using the Nimbus Context Broker for just‐in‐time configuration and runtime Worker discovery. The computational performance of the Workers under different communication mechanisms and deployment scenarios is presented in an attempt to evaluate the use of Virtual Machines in a Cloud as a tool to achieve application scaling. The deployment of this particular application was crafted to support on‐the‐fly addition of working nodes. The case study suggests a deployment pattern that shapes some requirements and considerations of a scalable Globus‐driven Platform as a Service Cloud. Copyright © 2011 John Wiley & Sons, Ltd.     

Intervalley scattering in GaAs/AlGaAs quantum wells and quantum cascade lasers

The results of simulations of Γ−X scattering in GaAs/AlGaAs quantum wells are presented, discussing the importance of the mole fraction, doping density, and lattice and electron temperatures in determining the scattering rates. A systematic study of Γ−X scattering in GaAs/Al_xGa_1−xAs heterostructures, using a single quantum well to determine the importance of well width, molar concentration x, lattice temperature, and doping density, has been performed. After this we consider a double quantum well to determine the role of intervalley scattering in the transport through single-layer heterostructures, i.e. Γ−X−Γ scattering compared with Γ−Γ scattering. Finally, we estimate the relative importance of intervalley scattering in a GaAs-based quantum-cascade laser device and compare it with other relevant scattering mechanisms important to describe carrier dynamics in the structure. Our simulations suggest that Γ−X scattering can be significant at room temperature but falls off rapidly at lower temperatures.     

A secure and improved self-embedding algorithm to combat digital document forgery

The recent digital revolution has facilitated communication, data portability and on-the-fly manipulation. Unfortunately, this has brought along some critical security vulnerabilities that put digital documents at risk. The problem is in the security mechanism adopted to secure these documents by means of encrypted passwords; however, this security shield does not actually protect the documents which are stored intact. We propose here a solution to this real world problem through a 1D hash algorithm coupled with 2D iFFT (irreversible Fast Fourier Transform) to encrypt digital documents in the 2D spatial domain. Further by applying an imperceptible information hiding technique we can add another security layer which is resistant to noise and to a certain extent JPEG compression. We support this assertion by showing a practical example which is drawn from our set of experiments. This work exploits Jarvis’ kernel to generate the error diffusion signal and the Wavelet-based Inverse Halftoning via De-convolution (WInHD) to recover the approximation of the original signal. Our method not only points out forgery but also allows legal or forensics expert gain access to the original document despite being manipulated. This would undoubtedly be very useful in cases of disputes or claims.