Probability Collectives: A multi-agent approach for solving combinatorial optimization problems

Complex systems generally have many components. It is not possible to understand such complex systems only by knowing the individual components and their behavior. This is because any move by a component affects the further decisions/moves by other components and so on. In a complex system, as the number of components grows, complexity also grows exponentially, making the entire system to be seen as a collection of subsystems or a Multi-Agent System (MAS). The major challenge is to make these agents work in a coordinated way, optimizing their local utilities and contributing the maximum towards optimization of the global objective. This paper discusses the theory of Collective Intelligence (COIN) using the modified version of Probability Collectives (PC) to achieve the global goal. The paper successfully demonstrated this approach by optimizing the Rosenbrock function in which the coupled variables are seen as autonomous agents working collectively to achieve the function optimum. To demonstrate the PC approach on combinatorial optimization problems, two test cases of the Multi-Depot Multiple Traveling Salesmen Problem (MDMTSP) with 3 depots, 3 vehicles and 15 nodes are solved. In these cases, the vehicles are considered as autonomous agents collectively searching the minimum cost path. PC is successfully accompanied with insertion, elimination and swapping heuristic techniques. The optimum results to the Rosenbrock function and both the MDMTSP test cases are obtained at reasonable computational costs.     

Effect of Postweld Heat Treatment on Microstructure, Hardness, and Tensile Properties of Laser-Welded Ti-6Al-4V

The effects of postweld heat treatment (PWHT) on 3.2-mm- and 5.1-mm-thick Ti-6Al-4V butt joints welded using a continuous wave (CW) 4-kW Nd:YAG laser welding machine were investigated in terms of microstructural transformations, welding defects, and hardness, as well as global and local tensile properties. Two postweld heat treatments, i.e., stress-relief annealing (SRA) and solution heat treatment followed by aging (STA), were performed and the weld qualities were compared with the as-welded condition. A digital image correlation technique was used to determine the global tensile behavior for the transverse welding samples. The local tensile properties including yield strength and maximum strain were determined, for the first time, for the laser-welded Ti-6Al-4V. The mechanical properties, including hardness and the global and local tensile properties, were correlated to the microstructure and defects in the as-welded, SRA, and STA conditions.     

Vapor Phase Beckmann Rearrangement of Cyclohexanone Oxime over Different Ferrierite Zeolite Catalysts

Ferrierite zeolite catalysts prepared using different procedures have been tested for their activity for vapor phase Beckmann rearrangement of cyclohexanone oxime to -caprolactam. We report here the results of a study seeking the influence of temperature, nitrogen feed rate, oxime concentration and solvents on the catalyst performance. At low concentration of oxime (2.5 wt%), using acetonitrile as solvent the maximum in the conversion of oxime and selectivity to -caprolactam has been obtained. The presence of weak, medium and strong acid sites as indicated by temperature-programmed desorption of NH₃ corroborates well with the catalytic activities of various ferrierites shown here. Solvent polarity is found to significantly affect the conversion of cyclohexanone oxime.     

Determination of bacterial activity by use of an evanescent-wave fiber-optic sensor

A novel technique based on fiber-optic evanescent-wave spectroscopy is proposed for the detection of bacterial activity in human saliva. The sensor determines th e specific concentration of Streptococcus mutans in saliva, which is a major causative factor in dental caries. In this design, one prepares the fiber-optic bacterial sensor by replacing a portion of the cladding region of a multimode fiber with a dye-encapsulated xerogel, using the solgel technique. The exponential decay of the evanescent wave at the core-cladding interface of a multimode fiber is utilized for the determination of bacterial activity in saliva. The acidogenic profile of Streptococcus mutans is estimated by use of evanescent-waveabsorption spectra at various levels of bacterial activity.     

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.     

Processing, physical and thermal properties of BlackglasTM matrix composites reinforced with NextelTM fabric

The cure and pyrolysis behavior of a BlackglasTM resin and NextelTM 440 impregnated with BlackglasTM resin were studied. Cure of the BlackglasTM resin is an exothermic process and DSC studies indicate that with an increase of catalyst content from 0.1 to 1.0%, the onset and peak temperature of cure are decreased coupled with an increase in the enthalpy of cure indicating a greater extent of cross linking. However, pyrolysis char yield of the pyrolyzate is relatively insensitive to cure conditions.Cure pressure and pyrolysis environment are variables in the processing of BlackglasTM matrix composite reinforced with NextelTM 440 Plain weave fabric. Variations in cure pressure from 30 to 80 psi had no discernible effect on the chemistry of the pryrolyzate. However, the higher cure pressure resulted in top and bottom ply damage. Pyrolysis in an Ar environment resulted in incorporationj of up to 12 wt % C of which 8 wt % as graphitic in nature in the ceramic matrix. Pyrolysis in NH3 resulted in 3.9 wt % nitrogen and 1.5 wt % carbon in the matrix, with all the nitrogen and carbon bonded to Si. The cured panels have to be pyrolyzed/densified between 6–7 times to achieve required density and porosity content. Oxidation behavior of the composites at 1000°C indicate that the argon pyrolyzed CMC's lose more weight due to decomposition of the pyrolytic carbon, whereas, NH3 pyrolyzed CMC's are stable as both the N and C are bonded to Si in the matrix. Dielectric constants K and K measured at 1 GHz in the as-processed condition are high in the argon pyrolyzed CMC, (K = 11–28) due to the presence of pyrolytic carbon. On the other hand NH3 pyrolyzed CMC exhibit low dielectric constant (K = 4). On oxidation, the dielectric constant in both the Ar and NH3 pyrolyzed panels is approximately 4.0.     

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.     

Morphological studies of late-stage spinodal decomposition in polystyrene–cyclohexanol system

We studied the late-stage spinodal decomposition of the polystyrene–cyclohexanol system in relation to membrane formation. Phase separation was effected by the removal of thermal energy from the homogeneous polymer solution. The ultimate morphology of the phase-separated systems has been studied using electron microscopy and has been found to be strongly affected by the quenching time. A shift from a highly interconnected open-cell structure to a closed-cell structure has been observed, indicating the transition of the spinodal decomposition from early to late stages. The cell growth in the late stage has been quantitatively analyzed and a power-law relationship between the cell size and quenching time has been found. The resulting exponent of 0.61 is consistent with literature values from light-scattering measurements, as well as from theoretical derivations. © 1995 John Wiley & Sons, Inc.     

The effects of perioperative blood salvage and autologous blood donation on transfusion requirements in scoliosis surgery

Fifty consecutive cases of surgical instrumentation and fusion for adolescent idiopathic scoliosis were prospectively studied to test the hypothesis that the use of predonated autologous blood combined with judicious perioperative blood salvage could decrease the amount of homologous blood needed. All cases had posterior instrumentation and fusion. Nineteen patients had their rib prominence resected with an average of 4.8 ribs per patient. Our protocol called for perioperative blood salvage with the cell saver and reinfusion of postoperative drained blood if more than 300 ml were drained in 4 hours. Two units of predonated autologous blood was made available. Hypotensive anesthesia and meticulous hemostasis kept the blood loss to a minimum. The average total blood loss was 1,055 ml. Blood loss per segment was 91 ml with an average of 11 segments fused per patient. Patients with rib resection had a blood loss of 1,105 ml, while those without had a blood loss of 955 ml. The cell saver blood returned per case was 391 ml with the hematocrit of the product averaging 46%. Twelve patients were reinfused an average of 300 ml of the postoperative drained blood. The predonated autologous blood was used as part of the intraoperative fluid management. In no patient was homologous blood needed. The average starting hematocrit was 35.6%, with the hematocrit at discharge (seventh day) being 32.4%. There were no complications or blood transfusion reactions. Our results suggest that judicious perioperative blood management may decrease the need for homologous blood transfusion in selected posterior idiopathic scoliosis surgery.