The dependence of critical temperature on oxygen concentration in YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>6+<Emphasis Type="Italic">x</Emphasis></Subscript> in terms of the fragmented chain model

An extended ASYNNNI model, that beside nearest-neighbour and next-nearest neighbour O-O interactions in the basal plane also includes interactions between the three nearest oxygen atoms, is used to describe the statistics of CuO chain fragmentation and to calculate doping and T _c in YBa₂Cu₃O_6+x . Calculations were made by the Monte Carlo method employing the recently proposed charge transfer model that assumes only chains whose length is equal to, or exceeds, a characteristic (critical) length, l _cr , can provide holes to the layers and contribute to doping p. The obtained p(x) is then combined with a universal T _c versus p relation to yield T _c (x) characteristics that correlate remarkably with those reported in recent experiments. The best coordination between theoretical and experimental T _c (x) characteristics has been achieved for l _cr = 2, implying that only isolated basal plane oxygen atoms (trivial chains) do not contribute holes to CuO₂ layers.     

UMTS RAN Capacity Analysis for Special Events

Special events such as music festivals, sports etc are characterised as “high user density” where user behaviour is determined by the dynamics of the event. This is the reason that it is necessary for a mobile network operator to dimension its network based on maximum expected resource requirements instead on averaged values. Although special events are taking place almost every week, in most cases not enough attention has been paid to the problem of resource dimensioning in the Universal Mobile Telecommunications System networks, and the appropriate cost function to equate the optimal quantities resources has not been developed. It is therefore necessary to be aware that special events networks should be dimensioned with the maximum resource requirements, using distributed antenna system (DAS) where possible, and the consolidated baseband processing resources. Appropriate cost function will be used to describe optimal design that should depend on the number of sectors needed, radio network controller and the overall network capacity. A suitable radio access network (RAN) analysis has been performed and a cost function has been developed in order to create the metrics that can be used for evaluating the cost of dimensioning the RAN in special events. It can be shown based on proposed metrics that 10 % of savings in resources could be achieved by degrading the grade of service less than 1 %.     

Design of the Microprocessor-Based Digital System for DC Motor Speed Control

This paper presents the pole-placement method for the synthesis of the dc motor speed control system. The proposed grapho-analytical procedure, applicable to third-order digital control systems, enables the designer to readily obtain the information about effects of system constants and adjusting system parameters on the accuracy, speed of response, and stability margin. The design of the real motor speed control system is presented to illustrate the proposed technique.     

Turbo Coding with Equalization in WCDMA Downlink

In this paper, the performance of turbo coding in WCDMA downlink is considered in conjunction with receivers using two adaptive channel equalizers. Bit error and frame error rates are compared to the performance of the conventional Rake receiver. Special consideration is given to the cases with two receive antennas, the efficiency of the channel interleaver, the number of iterations in decoding, the performance with various numbers of users, the influence of mobile receiver velocity as well as to the effect of power control. The simulation results show that turbo coding, combined with power control and channel equalizers is a very efficient way to implement reliable data transmissions in WCDMA downlink. The results in the paper also verify that the adaptive channel equalizers is a very promising technique to improve the receiver performance and increase the user capacity.     

Using a nonparametric technique to measure the cost efficiency of postal delivery branches

A multiple-input and multiple-output model for measuring the cost efficiency of postal delivery branches is proposed. We analyze the complete postal network of the Serbian post delivery offices, which includes 1,194 post office branches. To compare the branches that operate under the same or similar conditions, the branches are grouped into 18 clusters by implementing the appropriate clustering algorithm. This enables a three-level analysis: branches–clusters–network. The cost efficiency of the branches is measured using data envelopment analysis. The efficiency of a particular cluster is calculated as an average cost efficiency score of the branches that belong to this cluster, and finally, the efficiency of the postal delivery network is assessed. The distribution of cost efficiency scores per clusters takes values from 15 to 92 %. At the level of the total network, the cost efficiency is 40 %, which indicates that there are possibilities for improvement. To obtain more specific guidelines, that is, the decomposition of cost efficiency into pure technical efficiency, the scale efficiency and allocative efficiency were assessed for each cluster and for the total delivery network. This research is beneficial to policy makers defining the scope of universal service obligation and to company managers who want to optimize the postal network. For example, the results of this study indicate that, at a minimum, 794 delivery branches could improve their efficiency by resource reallocation.     

Phenolic compounds in field horsetail (Equisetum arvense L.) as natural antioxidants

In this paper, the study of antioxidant activity and phenolic composition of three different extracts (EtOAc, n-BuOH and H(2)O) of field horsetail (Equisetum arvense L.) is presented. The antioxidant activity has been evaluated measuring the total reducing power (expressed by Ascorbate Equivalent Antioxidant Capacity - AEAC), inhibition of lipid peroxidation, and free radical scavenging capacity (RSC) towards 2,2-diphenyl-1-picrylhydrazyl (DPPH radical) and nitric oxide (NO), respectively. In addition, the total flavonoid content (TFC) and phenolic constituents of each extract have been determined. The results obtained show that the highest RSC regarding both DPPH and NO radicals is expressed by EtOAc extract (EC(50)=2.37 microg/mL and EC(50)=90.07 microg/mL, respectively), and the lowest by H(2)O extract (EC(50)=37.2 microg/mL and EC(50)>333.33 microg/mL, respectively). n-BuOH extract showed the highest total reducing power (AEAC=13.40 microg/mL). Differences in the phenolic composition of examined extracts are found comparing the HPLC chemical profiles. Although, isoquercitrin is the main flavonoid in both EtOAc and n-BuOH extracts, a considerable amount of di-E-caffeoyl-meso-tartaric acid was presented in the n-BuOH extract. In H(2)O extract high content of phenolic acids and low percentage of flavonoids were detected.     

1D linear-phase band-pass multiplierless FIR Hilbert transformers and filters

An original analytical method, based on modified Christoffel–Darboux formula, is used in the paper in order to synthesise a linear-phase band-pass finite impulse response (FIR) filter function that can have an effect of Hilbert transformer. New structure of the band-pass FIR filter in recursive realisation, together with the corresponding difference equation, is presented providing the efficient filter solution without multipliers. Several examples of filter types for different parity of two real free integer parameters, including a particular solution of Hilbert transformer, are considered in terms of required number of adders and values of cut-off frequencies of the pass and stop bands. A comparison of the proposed band-pass filter characteristics with those of a classical filter solution is provided in the paper.     

Feasibility study for cell electroporation detection and separation by means of dielectrophoresis

Electroporation is a phenomenon during which exposure of a cell to high voltage electric pulses results in a significant increase in its membrane permeability. Aside from the fact that after the electroporation the cell membrane becomes more permeable, the cells' geometrical and electrical properties change considerably. These changes enable use of the force on dielectric particles exposed to non-uniform electric field (dielectrophoresis) for separation of non-electroporated and electroporated cells. This paper reports the results of an attempt to separate non-electroporated and electroporated cells by means of dielectrophoresis. In several experiments we managed to separate the non-electroporated and electroporated cells suspended in a medium with conductivity 0.174 S/m by exposing them to a non-uniform electric field at a frequency of 2 MHz. The behaviour of electroporated cells exposed to dielectrophoresis raises the presumption that in addition to conductivity, considerable changes in membrane permittivity occur after the electroporation.     

Disappearing Polymorphs Revisited

Nearly twenty years ago, Dunitz and Bernstein described a selection of intriguing cases of polymorphs that disappear. The inability to obtain a crystal form that has previously been prepared is indeed a frustrating and potentially serious problem for solid‐state scientists. This Review discusses recent occurrences and examples of disappearing polymorphs (as well as the emergence of elusive crystal forms) to demonstrate the enduring relevance of this troublesome, but always captivating, phenomenon in solid‐state research. A number of these instances have been central issues in patent litigations. This Review, therefore, also highlights the complex relationship between crystal chemistry and the law.