Optimizing the handover call blocking probability in cellularnetworks with high speed moving terminals

This letter presents a two-layer cellular architecture which optimizes the handoff blocking probability performance of high-speed moving terminals (HSMT) in a congested urban area. The lower layer of the proposed architecture is based on a microcellular solution, for absorbing the traffic loads of both the low-speed moving terminals (LSMT) and the new calls of HSMT. The higher layer is based on a macrocell umbrella solution, for absorbing the traffic load of the existed handoff calls of the HSMT. The results show that using the optimum number of channels in each layer, the handoff call blocking probability of the HSMT is optimized having the minimum effect on the call blocking probability of the microcellular layer     

Optimization of SIMOX for VLSI by electrical characterization

A comprehensive electrical characterization study which was conducted to optimize the fabrication of SIMOX substrates for VLSI is discussed. The oxygen implantation was carried out using medium-current and high-current implanters. The wafers were annealed at 1275°C and 1300°C to produce high-quality, precipitate-free material. The effect of dose, the effect of multiple implantation (by sequentially implanting and annealing), and the effect of the anneal ambient gas and the capping layer during annealing were studied. MOSFETs of various geometries with a gate oxide of ~20 nm were fabricated by a CMOS process incorporating the addition of a thin epitaxial Si layer. A general evaluation of each transistor was conducted by studying its static characteristics. The interface states, bulk traps, and carrier generation phenomena were studied. Good-quality interfaces were obtained. Better implantation control reduced contamination and suppressed deep traps below the detection limit. Multiple implantation resulted in superior material quality. as evidenced by very long generation lifetime values (> 100 μs)     

Reduced-order performance of parallel and series-parallel identifiers with weakly observable parasitics

The stability properties of discrete-time parallel and series-parallel identifiers with respect to a specific model-plant order mismatch are analyzed. While in a deterministic environment with no modeling error the two schemes give identical results, when used in a deterministic environment with modeling error their performance is different. We assume a singularly perturbed state representation for the plant where the modeling error consists of fast parasitics which are weakly observable in the plant output. Detailed bounds on parameter and output estimate errors are established and the robustness of the adaptive identifiers is established by showing that the error bound goes to zero as the modeling error goes to zero, i.e. as the parasitics become infinitely fast. The dependence of this residual identification error on the input signal, the neglected parasitics, and the initial error conditions is shown to be crucial. The bounds indicate possibilities for reducing the error by a proper choice of the input signal.     

Total selenium concentration in tap and bottled drinking water and coastal waters of Greece

The total selenium concentration in various waters from all over Greece was determined fluorimetrically. The concentration in most of the drinking water, either from the tap or bottled, was within the range 100-200 ng l-1 and showed no great seasonal fluctuations. Most Greeks receive 0.2-0.4 micrograms selenium per day from drinking water. Coastal surface water contains 100-250 ng Se l-1, while higher concentrations are found at locations regarded as polluted.     

Theory of constraints-based methodology for effective ERP implementations

The benefits as well as the turmoil that the implementation of enterprise resource planning (ERP) systems creates for multinational companies are well known. Several reports and evidence through case studies underline both the difficulties and the resulting benefits of ERPs. This paper addresses the reasoning behind long implementation times and organizational thunderstorms that tantalise the deployment of ERP systems. It focuses on two aspects of most implementation projects that generate the majority of technical and functional problems and constitute the projects’ bottleneck, i.e. code development within ERP systems due to key and unique requirements in a business environment, and localization and reporting needs that companies must adhere to or want to achieve. The approach proposes the classification of functional requirements into business critical and legally necessary, and the distribution of code development for system not fully supported processes among these two classes is discussed. Subsequently, the implementation times and deployment inefficiencies are coupled with the level of code development, and the difficulty of avoiding this for the two requirements’ classes, mainly due to user inflexibility and local environment peculiarities, is discussed. Using the Theory of Constraints, a coherent methodology for handling bottlenecks and effectively planning the code development effort is proposed, and trade-offs are derived between successful and on-time ERP implementations with managerial enforcement of best practices fully functional within major ERP systems. The approach is verified through field data from an actual SAP R/3 implementation at the largest manufacturer of packaging products and equipment in Europe.     

Effect of pulsed electric current treatment on corrosion of structural metals

Results of corrosion tests of structural metals previously treated using pulsed electric current of high density are presented. According to the data obtained, the treatment substantially affects corrosion of metals. In cases of HSLA steel and 5182 aluminum alloy, an increase of corrosion resistance occurs, whereas the same treatment causes a dramatic reduction of corrosion resistance of 5754 aluminum alloy. Translated from Problemy Prochnosti, No. 4, pp. 62–68, July–August, 2009.     

A switching adaptive controller for feedback linearizable systems

One of the main open problems in the area of adaptive control of linear-in-the-parameters feedback linearizable systems is the computation of the feedback control law when the identification model becomes uncontrollable. The authors propose a switching adaptive control strategy that overcomes this problem. The proposed strategy is applied to nth-order feedback linearizable systems in canonical form. The closed-loop system is proved to be globally stable in the sense that all the closed-loop signals are bounded and the tracking error converges arbitrarily close to zero. No assumptions are made about the type of nonlinearities of the system, except that such nonlinearities are smooth. However, the proposed controller requires knowledge of the sign and lower bound of the input vector field     

The effect of post-implantation annealing temperature on the deep states present in SIMOX MOSFET’s as observed using enhancement mode current DLTS

The effect of various post-implantation annealing temperatures on the deep states present in SIMOX transistors is studied using enhancement mode current DLTS. Two electron traps were detected at 0.45 eV and 0.33 eV below the conduction band edge; both were removed by post-implantation annealing at a temperature of 1275° C. The ability to anneal these states suggests that they are due to the presence of defect structures which are themselves removed during this annealing. Hole traps were also detected at 0.47 eV and 0.38 eV above the valence band edge; however these traps were not removed by high temperature annealing. It is believed that these hole traps are related to the presence of iron contamination.     

Instability analysis and improvement of robustness of adaptive control

The effects of unmodeled high frequency dynamics and bounded disturbances on stability and performance of adaptive control schemes are analyzed. Five possible types of instability mechanisms—parameter drift, ‘linear’ instability, ‘fast adaptation’ instability, ‘high frequency’ instability, and ‘throughput’ instability—are analyzed using simple examples. A procedure is used to construct Lyapunov-like functions for a modified adaptive controller applied to a dominant plant of relative degree one, in the presence of parasitics and disturbances, and obtain sufficient conditions under which none of the five types of instability can occur. The modified scheme is robust in the sense that it guarantees the existence of a large region of attraction from which all the trajectories remain bounded and the state errors converge exponentially to a much smaller residual set. The size of the region of attraction depends on the speed of parasitics in such a way that as the parasitics become infinitely fast, the region of attraction becomes the whole space.     

Branch Network and Modular Service Optimization for Community Banking

In the information society, what is clearly changing is the role and image of bank branches in order to satsify in a more efficient way customers' needs. This paper develops an integrated approach to assist the bank's management in reconfiguring a branch network according to the dictates of the market. We are seeking the optimum number of branches and the optimum mix of services that each branch should offer in order to maximize the revenue–generating measures of the branches within a community. The problem is modeled using a linear program that accounts for community performance as a function of performance variables that are explained by a set of external and internal factors, which reflect community characteristics and modular branch banking parameters, respectively. The relationships between factor and performance variables are identified using regression analysis. An iterative algorithm allows convergence to a solution that provides the best configuration of branches after all possible branch mergers and modular branch adjustments are accomplished.