High performance mobility without agent infrastructure for connection oriented service

Currently it is very difficult for connection oriented applications to use a mobile environment. One reason is that Mobile IP requires intermediate software agents to be deployed in the Internet. This infrastructure based mobility scheme offers connectivity to itinerant hosts but incurs significant handoff and tunneling delays along with deployment costs. These delays are particularly harmful for connection oriented applications. In this paper we investigate an alternate mobility scheme which does not require any such infrastructure but only uses an end-point technique and interestingly provides much faster loss-free handoff for connection oriented applications. This End-to-End scheme named Interactive Protocol for Mobile Networks (IPMN) intelligently performs handoff based on information provided by MAC Layer. The network address change is handled by renewing the existing connections by manipulating the TCP/IP stack at the end-points. Also, unlike several other recently proposed end-to-end techniques which require extensive modification of end-protocols, the proposed scheme does not require any functional change in the TCP/IP protocol software. Besides the difference in deployment scenarios, the IPMN offers blazingly fast event based handoff and much faster and simplified transport (no tunneling delay) than MIP. We have implemented IPMN over FreeBSD. In this paper we show the performance advantage of IPMN over MIP with real deployment for three interesting real-time traffic types — www, voice streaming and, steerable/interactive time critical video.     

Synthesis of HgI2 Nanoparticles and Nanorods by Laser Ablation in Liquid for Photodetector Applications: Effect of Laser Fluence

In this study, mercury iodide (HgI₂) nanoparticles (NPs) were synthesized by pulsed laser ablation in ethanol at laser fluences of 22.9, 33.1, and 43.3 J/cm². The effect of laser fluence on the structural and optical properties of HgI₂ NPs was studied. X-ray diffraction findings reveal that all synthesized HgI₂ samples were polycrystalline in nature with orthorhombic structure. Absorption peak was appeared at 474 nm and the optical energy gap of HgI₂ NPs decreases from 2.13 to 2.05 eV as laser fluence increased from 22.9 to 43.3 J/cm². Zeta potential (ZP) results confirm that the nanoparticles synthesized at 22.9 and 33.1 J/cm² have high degree of stability. Fluorescence measurements show the presence of several emission bands. Raman spectra of HgI₂ NPs show the presence of six vibration modes centered at 15, 29, 37, 44, 51, and 70 cm^?1. Fourier transform infrared (FT-IR) results show the presence of two bonds, namely, C–O and Hg-I. Transmission Electron Microscope (TEM) results showed that the formation of spherical nanoparticles for sample prepared at 22.9 J/cm², 25–75 nm in size. While the nanoparticles synthesized with 33.1 and 43.3 J/cm² exhibit nanorods and nanotubes morphologies, respectively. The dark I–V characteristics of β-HgI₂ NPs/Si heterojunction photodetectors show rectification properties and the junction quality depends on the laser fluence and the best junction characteristics was obtained for heterojunction prepared at 33.1 J/cm². The white light photosensitivity of the HgI₂/p-Si photodetectors was measured at reverse bias under different intensities. The maximum responsivity reached was 3.39A/W at 450 nm for photodetector prepared at 33.1 J/cm².

     

Preparation of colloidal cadmium selenide nanoparticles by pulsed laser ablation in methanol and toluene

Colloidal spherical nanoparticles (NPs) of cadmium selenide (CdSe) have been prepared by laser ablation of cadmium target in methanol and toluene solutions. The properties of CdSe nanoparticles ablated in methanol and toluene were investigated and compared. The morphology and structure of synthesised CdSe NPs were analyzed by X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscope (TEM). XRD investigation revealed that the nanoparticles are crystalline and have hexagonal structure. Optical absorption showed that the value of optical energy gap of ablated CdSe nanoparticles depends on the solution type. TEM measurements showed that CdSe NPs with diameters ranging from 25 to 35 nm were synthesised in methanol while, the nanoparticles ablated in toluene have diameters in the range of (40–50) nm.     

Optoelectronic properties n:CdS:In/p-Si heterojunction photodetector

Optoelectronic properties of CdS:In/Si anisotype heterojunction photodetector fabricated by depositing of polycrystalline CdS and indium doped CdS films used thermal resistive technique on clean monocrystalline p-type silicon substrates are presented. The effect of In diffusion temperature(T _d)in CdS layer on the optoelectronic characteristics of these devices has been studied. Two peaks situated at 650 and 800 nm with values of 0.32 and 0.43 A/W, respectively, were observed in the responsivity plot. Other optoelectronics properties such as detectivity, photovoltaic, and response time are also presented.     

Effect of Laser Fluence on the Structural,Morphological and Optical Properties of 2H-PbI<Subscript>2</Subscript> Nanoparticles Prepared by Laser Ablation in Ethanol

The effect of laser fluence on the optical, structural and morphological properties of PbI₂ nanoparticles NPs synthesized by pulsed laser ablation in ethanol was studied. The direct optical energy gap of PbI₂ NPs prepared at various laser fluences was in the range of (3–3.3 eV) at room temperature. Three absorption peaks related to surface plasmon resonance at 337, 435 and 507 nm are observed. XRD results show that all the grown PbI₂ NPs are polycrystalline in nature and the formation of hexagonal structure 2H-polytype was observed at laser fluence of 3.6 J/cm². The surface morphology of PbI₂ NPs investigated by SEM revealed formation of hexagonal, platelet-like and spherical NPs morphologies. TEM images showed formation of spherical particles with size varied from 10 to 75 nm depending on the laser fluence. PL measurement shows emission of broad peak centered at 350 nm and increasing the laser fluence results in red shift. The Raman spectra of PbI₂ NPs revealed existence of five vibration modes situated at 74, 96,106, 169 and 213 per cm. FT-IR investigation showed a broad band at 3383 per cm indexed to symmetric stretching vibration of Pb–I clusters and band at 725 per cm related to bending mode of O–H.     

Characterization of nanostructured hydroxyapatite prepared by Nd:YAG laser deposition

Pulsed laser deposition, under dry and water vapor conditions, was employed to synthesize nanostructured hydroxyapatite films by pulsed laser deposition (PLD) of chlorapatite target for the purpose of coating metallic bone implants by this material. A pulsed Nd:YAG laser operating at a wavelength of 1064 nm and emitting 9 ns pulses was used for deposition. AFM microscopy, FTIR spectroscopy, optical microscopy, adhesion and microhardness measurements were conducted to characterize the films. The in vitro test for the synthesized hydroxyapatite was performed using simulated body fluid (SBF). The results showed a successful transformation of the chlorapatite to hydroxyapatite films characterized by all the HAp peaks with 60 nm root mean square roughness, (80–327) nm grain size, and a microhardness of 512 HV.     

Overview of Steel Bridges Containing High Strength Steel

The use of high strength steel has the potential to reduce the amount of steel used in bridges and thereby, facilitate a more sustainable construction. A survey of existing bridges built using high strength steel is presented in this paper with emphasis on the Swedish bridge stock. The survey aimed at identifying the steel grades that were used and where in the cross-section they have been used. A case study on the influence of fatigue shows that today’s regulations make it more difficult to use high strength steel in comparison to previous regulations.