Investigation of thermal residual stresses during laser ablation of tantalum carbide coated graphite substrates using micro-Raman spectroscopy and COMSOL multiphysics

Laser ablation of high-temperature ceramic coatings results in thermal residual stresses due to which the coatings fail by cracking and debonding. Hence, the measurement of such residual stresses during laser ablation process holds utmost importance from the view of performance of coatings in extreme conditions. The present research aims at investigating the effect of laser parameters such as laser pulse energy, scanning speed and line spacing on thermal residual stresses induced in tantalum carbide-coated graphite substrates. Residual stresses were measured using micro-Raman spectroscopy and correlated with Raman peak shifts. Transient thermal analysis was performed using COMSOL Multiphysics to model the single ablated track and residual stresses were reported at low, moderate and high pulse energy regimes. The results showed that the initial laser conditions caused higher tensile residual stresses. Moderate pulse energy regime comprised higher compressive residual stresses due to off centre overlapping of the laser pulses. Higher pulse energy (250 μJ), higher scanning speed (1000 mm/s) and moderate line spacing (20 μm) caused accumulation of tensile residual stresses during the final stage of laser ablation. The deviation of experimental residual stresses from COMSOL numerical model was attributed to unaccounted additional stresses induced during thermal spraying process and deformation potentials in the numerical model.     

Design of Dual-Gate P-type IMOS Based Industrial Purpose Pressure Sensor

Silicon - In this treatise, we have proposed a Single Material Gate–Dual Gate Impact Ionization Metal Oxide Semiconductor (SMG DG-IMOS) based Pressure Sensor. The pressure sensor has the most...     

Synthesis and characterization of partially fluorinated hydrophobic–hydrophilic multiblock copolymers containing sulfonate groups for proton exchange membrane

A new hydrophobic–hydrophilic multiblock copolymer has been successfully synthesized based on the careful coupling of a fluorine terminated poly(arylene ether ketone) (6FK) hydrophobic oligomer and a phenoxide terminated disulfonated poly(arylene ether sulfone) (BPSH) hydrophilic oligomer. ¹⁹F and ¹H NMR spectra were used to characterize the oligomers’ molecular weights and multiblock copolymer's structure. The comparison of the multiblock copolymer ¹³C NMR spectrum with that of the random copolymer showed that the transetherification side reaction was minimized in this synthesis. The morphologies of membranes were investigated by tapping mode atomic force microscopy (AFM), which showed that the multiblock membrane acidified by the high temperature method has sharp phase separation. Membrane properties like protonic conductivity, water uptake, and self-diffusion coefficient of water as a function of temperature and relative humidity (RH) were characterized for the multiblock copolymer and compared with ketone type random copolymers at similar ion exchange capacity value and Nafion^® controls. The multiblock copolymers are promising candidates for proton exchange membranes especially for applications at high temperatures and low relative humidity.     

A specification model for context-based collaborative applications

This paper presents a model for building context-based systems in pervasive computing environments from high level specifications. A pervasive computing environment is viewed as a collaboration space consisting of mobile users, system services, and sensors and resources embedded in the physical environment. The approach presented here is developed for building collaborative activities in which users and environment services cooperate towards some shared objectives and tasks. The specification model allows expression of policies related to context-based discovery and secure access of resources, and role-based interactions among users and environmental services. Using several examples we illustrate the capabilities of our specification model for expressing various kinds of context-based requirements for resource access and user interactions.     

The Future Re-Visited

The future of telecommunications is to reach mass population in all regions of the world with services that will benefit humankind leading to the betterment of its and all life in our planet. Telecommunications and its services have to and will become part of life as is breathing to mankind. This future is by far not achieved and for some time to come whatever we develop there is always a next step to it. After all, that keeps our world going.Currently we are again at that stage of work on future generation communications where these words have not yet achieved a consensus. In this paper let us look at the crystal ball and try to materialize at least in words what we see in it [1–20].We first define fourth generation (4G) communication system and beyond 3G (B3G). Then we look at the requirements for future generation communications from the perspective of the users, the operators, and the service providers. Next the technologies that should and are being developed to materialize the future generation are discussed. A dip is also taken into the ongoing standardization or pre-standardization efforts. At first the introduction section tries to raise questions on the “future”.Prof. Dr. Ramjee Prasad, while being a father always there for his children, is also a visionary and a leader in the field of telecommunications. It is with pride and honour that I write in this paper, on the occasion of 60th birthday of my father, my thoughts of the future of telecommunications. I owe to him and my mother the knowledge that I present and the future that I have written of. It is from the spark that they had put in me that this vision of future was created thus the title “the future re-visited”. Disclaimer: This paper reflects opinion of the author not of NTT DoCoMo or DoCoMo Euro-Labs. Anand Raghawa Prasad Senior Member IEEE, project manager network level security model group, DoCoMo Euro-Labs, Munich, Germany was born in Ranchi, India. He received his Ph.D. degree in the field of WLANs: protocols, security and deployment and MSc (Ir.) degree in the field of Self Similarity in ATM Network Traffic from Delft University of Technology, The Netherlands, in 2003 and 1996, respectively. From 1996 to 1998 he worked as research engineer and later project leader in Uniden Corporation, Tokyo, Japan. From 1998 to 2000, he was distinguished member of technical staff and worked as systems architect for IEEE 802.11 based WLANs (WaveLAN and ORiNOCO) in Lucent Technologies, Nieuwegein, The Netherlands. Subsequently, he was technical director at Genista Corporation, Tokyo, Japan, and technical advisor of PCOM:I3, Aalborg, Denmark. He was a voting member of IEEE 802.11 and he is an active participant of 3GPP. In addition to his publications in journals, international conferences and chapters in books, he has 20$+$ patent applications in the field of wireless communications and has co-edited a book titled “WLAN Systems and Wireless IP for Next Generation Communications” and co-authored a book on “Wireless LANs and Wireless IP: Security, Mobility, QoS and Mobile Network Integration” both published by Artech House in 2002 and 2005 respectively. He is writing a book on “Security in Wireless Networks and Mobile Platforms” to be published in August 2006. He has participated in organizing of various International Conferences including VTC, PIMRC and WPMC. He was a guest editor of a special issue on “Security for Next Generation Communications” of the Springer Journal on Wireless Personal Communications and he is a guest editor of a special issue on “Seamless Handover in Next Generation Wireless/Mobile Communications” of Wireless Personal Communications.     

Progression of atypical ductal hyperplasia/carcinoma in situ of the pancreas to invasive adenocarcinoma

Heterochromatin protein 1 (HP1) of Drosophila and its homologs in vertebrates are key components of constitutive heterochromatin. Here we provide cytological evidence for the presence of heterochromatin within a euchromatic chromosome arm by immunolocalization of HP1 to the site of a silenced transgene repeat array. The amount of HP1 associated with arrays in polytene chromosomes is correlated with the array size. Inverted transposons within an array or increased proximity of an array to blocks of naturally occurring heterochromatin may increase transgene silencing without increasing HP1 labeling. Less dense anti-HP1 labeling is found at transposon arrays in which there is no transgene silencing. The results indicate that HP1 targets the chromatin of transposon insertions and binds more densely at a site with repeated sequences susceptible to heterochromatin formation.     

Ideality and noise figure characteristics of r.f. sputtered millimetre GaAs diodes

Refractory Schottky barriers have been incorporated in millimetre GaAs mixer diodes to improve r.f. performance and burnout resistance. It is shown that low power r.f. sputter deposition of TiW and Ti-Mo refractories results in degradation of noise temperature ratio and to a first approximation does not affect d.c. parameters, especially the ideality factor.     

Solar cooling performance predictions via stochastic weather algorithms

System simulations for sizing and performance predictions of various solar systems require some form of weather input to act as a system stimulus. When actual weather data is used, hourly simulations are expensive and require considerable data handling. For many design procedures, however, hourly information is not needed, and simpler methods are desirable. One such method employs a probabilistic approach. This method involves the use of an algorithm that generates a probabilistic matrix, and an analytical formulation which is used to generate synthetic weather data. The approach has been found to be satisfactory. This work uses the stochastic (probablistic) method to produce representative weather for five geographic regions in the U.S. for the summer months. Parallel runs are conducted with real and stochastic weather. A comparison of the results clearly shows that the probabilistic approach can satisfactorily substitute for real weather for long-term system performance.