IMS-Based Centralized Service Continuity

The IP Multimedia Subsystem (IMS) has been selected as a telecommunication industrial standard for the signal processing in the heterogeneous access networks. It is also brought up to handle the mobility management. However, the mobility of the user equipment (UE) may disrupt or even intermittently disconnect an ongoing real-time session, which heavily affects the satisfaction of the users. Therefore, how to reduce the service disruption time gets more and more important. This paper first proposes a centralized service continuity scheme, abbreviated as CSC, in IMS-based networks. The CSC treats handover as a service in the IMS network. Its architecture and operation are based on service invocation. The service continuity procedure is performed by an application server called CSC AS. The CSC AS can carry out the third-party call control for fast session re-establishment by initiating two INVITE requests concurrently. In addition, a variant of the CSC, denoted by CSC*, is derived by adopting the E-IMS AKA with one-pass authentication for achieving the acceleration of IMS registration during the handover. Analytical results show that both schemes could shorten the handover latency significantly, as compared with the standard IMS-based service continuity.     

On the meromorphic solutions of an equation of Hayman

The behavior of meromorphic solutions of differential equations has been the subject of much study. Research has concentrated on the value distribution of meromorphic solutions and their rates of growth. The purpose of the present paper is to show that a thorough search will yield a list of all meromorphic solutions of a multi-parameter ordinary differential equation introduced by Hayman. This equation does not appear to be integrable for generic choices of the parameters so we do not find all solutions—only those that are meromorphic. This is achieved by combining Wiman-Valiron theory and local series analysis. Hayman conjectured that all entire solutions of this equation are of finite order. All meromorphic solutions of this equation are shown to be either polynomials or entire functions of order one.     

Absorption of H and D Ly-α radiation by O2 molecules at high temperatures

Absorption cross sections of molecular oxygen were measured at the H and D Ly-α wavelengths (1215.67 and 1215.34 Å) between 800 and 1700°K, the cross sections being given by the equation σ (cm²) = 4.2E-18 exp(-3070/T) (4.2E-18 = 4.2 × 10^-18). The absorption cross section for v = 1 is (9±2)E-19 cm² and that for v = 2 is (7±3)E-18 cm², compared to 1.E-20 cm² for v = 0. Vibrational relaxation times were found to be in agreement with literature data over the range of common temperatures.     

Photoemission from physisorbed Co on clean and Xe-covered Al(111)

Molecular-orbital energy shifts are observed in photoemission from weakly physisorbed CO on clean and Xe-covered Al(111) surfaces. These shifts in ionization potentials are mainly due to final-state relaxation effects, which can be described approximately by a point-charge image-potential model. Differential distance- and orbital-dependent energy shifts suggest that CO molecules lie flat on the substrates. CO is adsorbed on Al(111) with a heat of formation of 0.21 eV/molecule.     

Reliability analysis and design for the fine-pitch flip chip BGA packaging

The geometry of solder joints in the flip chip technologies is primarily determined by the associated solder volume and die/substrate-side pad size. In this study, the effect of these parameters on the solder joint reliability of a fine-pitched flip chip ball grid array (FCBGA) package is extensively investigated through finite element (FE) modeling and experimental testing. To facilitate thermal cycling (TC) testing, a simplified FCBGA test vehicle with a very high pin counts (i.e., 2499 FC solder joints) is designed and fabricated. By the vehicle, three different structural designs of flip chip solder joints, each of which consists of a different combination of these design parameters, are involved in the investigation. Furthermore, the associated FE models are constructed based on the predicted geometry of solder joints using a force-balanced analytical approach. By way of the predicted solder joint geometry, a simple design rule is created for readily and qualitatively assessing the reliability performance of solder joints during the initial design stage. The validity of the FE modeling is extensively demonstrated through typical accelerated thermal cycling (ATC) testing. To facilitate the testing, a daisy chain circuit is designed, and fabricated in the package for electrical resistance measurement. Finally, based on the validated FE modeling, parametric design of solder joint reliability is performed associated with a variety of die-side pad sizes. The results show that both the die/substrate-side pad size and underfill do play a significant role in solder joint reliability. The derived results demonstrate the applicability and validity of the proposed simple design rule. It is more surprising to find that the effect of the contact angle in flip chip solder joint reliability is less significant as compared to that of the standoff height when the underfill is included in the package.     

Noble Metal-Free Surface-Enhanced Raman Scattering Enhancement from Bandgap-Controlled Graphene Quantum Dots

Graphene quantum dot (GQD) represents an emerging noble metal-free surface-enhanced Raman scattering (SERS)-active nanomaterials for applications such as optoelectronics, chemical sensing, and biomedical imaging and therapy. However, it lacks a scalable method to synthesize GQD with selective structures and the fundamental understanding of their SERS enhancement through charge transfer between GQD and probe molecules. Here a bottom–up liquid-phase synthesis of colloidal GQDs with selective bandgaps using atmospheric-pressure microplasmas is reported. Electron microscopic and optical spectroscopic characterizations suggest that highly crystalline GQDs with nanographene structures can be synthesized with ambient conditions using microplasmas. Moreover, the bandgaps of GQDs are tuned from 2.8 to 3.18 eV by controlling the size of organosulfate micelles. Raman spectroscopic study demonstrates that the as-synthesized GQDs exhibit a unique quantum dot bandgap-dependent SERS enhancement property with an improved charge transfer between the GQD and probe molecules. This study provides an insight into the fundamental of semiconductor-enhanced Raman scattering of GQDs and scalable production of structure-controlled GQDs using plasma-activated chemistry.     

Crystallization and annealing effects of sputtered tin alloy films on electromagnetic interference shielding

Sn, Al and Cu not only possess electromagnetic interference (EMI) shield efficiency, but also have acceptable costs. In this study, sputtered Sn-Al thin films and Sn-Cu thin films were used to investigate the effect of the crystallization mechanism and film thickness on the electromagnetic interference (EMI) characteristics. The results show that Sn-xAl film increased the electromagnetic interference (EMI) shielding after annealing. For as-sputtered Sn-xCu films with higher Cu atomic concentration, the low frequency EMI shielding could not be improved. After annealing, the Sn-Cu thin film with lower Cu content possessed excellent EMI shielding at lower frequencies, but had an inverse tendency at higher frequencies. For both the Sn-xAl and Sn-xCu thin films after crystallization treatment, the sputtered films had higher electrical conductivity, however the EMI shielding was not enhanced significantly.     

Optimal and Heuristic Procedures for Row Layout Problems in Automated Manufacturing Systems

In many automated manufacturing environments, particularly flowlines and flexible manufacturing systems (FMSs), machines are arranged along a straight material handling track with a material handling device moving jobs from one machine to aother. These layouts are referred to as row machine layouts. In this paper we study the Row Layout Problem (RLP) under the design objective of minimizing the total backtracking distance of the material handling device, which is a NP-complete problem. We propose the use of a dynamic programming algorithm for its solution. Special cases of the problem, usually encountered in flexible manufacturing cells and which can be solved with polynomial procedures, are also discussed. For the equidistant case (i.e., successive candidate locations are in equal distances), we formulate the problem as an integer linear program. The use of standard mathematical programming codes can efficiently solve this formulation. Two effective heuristic procedures, which explore simple ideas based on local optimality conditions, are also presented. Extensive computational results demonstrate the effectiveness of such heuristics.     

Bionic soft crystalline lens materials for MEMs applications based on self-assembling amphiphilic block copolymer/nanoparticle hybrids

In this study, a biomimetic crystalline lens with properties that combine the softness of a hydrogel comparable to that of a human lens for adjustable focus and the property for image aberration correction with gradient refractive index (GRIN) was developed by the self-organization of an amphiphilic block copolymer blended with high refractive index titanium nanoparticles (TiO₂). The hydrogel lens was prepared by using a thermally responsive poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PPO-PEO-PPO) triblock copolymer (Poloxamer 407) with the lower-critical solution temperature (LCST) property that can be injectable into the eye capsule as a liquid below its LCST and solidifies as a soft gel above the LCST at the human body temperature. By chemical modification of the triblock copolymer with double bonds on its chain-ends (Poloxamer 407A), the soft lens network can be made by using UV crosslinking of the hydrogel. To further increase the refractive index (RI) of the hydrogel lens network and to match its RI to that of the human lens (=1.41), highly visible-light transparent titanium dioxide (TiO₂) nanoparticles were introduced into the hydrogel lens network. To create a biomimetic GRIN lens as in the human’s eyes, an electric field method was also used to induce an axial diffusion of TiO₂ nanoparticles from the center of the lens where TiO₂ nanoparticles were first injected to the edge. The above method demonstrates the potential to use the hydrogel/nanoparticle hybrid as an injectable replacement for a soft optical lens system with an adjustable focus for future MEMs application.     

Plasma flow in MST: Effects of edge biasing and momentum transport from nonlinear magnetic torques

Edge biasing in MST plasmas decreases electrostatic turbulent particle transport and increases the global particle confinement time. New Langmuir probe measurements in the edge identify decreased electric field fluctuations and increased anti-correlation of density and potential fluctuations to be responsible. Fast loss of momentum in the core of MST during sawtooth crash events can be explained as a result of nonlinear magnetic torques which allow viscous coupling over relatively distant regions of the plasma. Flow modifications resulting from biasing, plus other experiments, help reveal the nonlinear nature of this process, most directly measured by the triple product bispectral correlation between the nonlinearly interacting modes. Presented at the Workshop on the Role of Electric Fields in Plasma Confinement and Exhaust, Budapest, 18–19 June, 2000.