SC-FDMA versus OFDMA: Sensitivity to Large Carrier Frequency and Timing Offsets on the Uplink

In this paper, we present a comparison between the sensitivity of SC-FDMA and OFDMA schemes to large carrier frequency offsets (CFO) and timing offsets (TO) of different users on the uplink. Our study shows the following observations: 1) In the ideal case of zero CFOs and TOs (i.e., perfect synchronization), the uncoded BER performance of SC-FDMA with frequency domain MMSE equalizer is better than that of OFDMA due to the inherent frequency diversity that is possible in SCFDMA. Also, because of inter-symbol interference in SC-FDMA, the performance of SC-FDMA with MMSE equalizer can be further improved by using low-complexity interference cancellation (IC) techniques. 2) In the presence of large CFOs and TOs, significant multiuser interference (MUI) gets introduced, and hence the performance of SC-FDMA with MMSE equalizer can get worse than that of OFDMA. However, the performance advantage of SC-FDMA with MMSE equalizer over OFDMA (due to the potential for frequency diversity benefit in SC-FDMA) can be restored by adopting multistage IC techniques, using the knowledge of CFOs and TOs of different users at the receiver

Contactless conductivity of nanoparticles from electron magnetic resonance lineshape analysis

A contactless method to determine the electrical conductivity of nanoparticles is presented. It is based on the lineshape analysis of electron magnetic resonance signals which are `Dysonian' for conducting samples of sizes larger than the skin depth. The method is validated bymeasurements on a bulk sample of La0.67Sr0.33MnO3 where it gives values close to those obtained from direct measurement of conductivity and is then used to determine the conductivity of nanoparticles of La0.67Sr0.33MnO3 dispersed in polyvinyl alcohol as a function of temperature. (C) 2010 Elsevier Ltd. All rights reserved.

Diesel Engine Driven Stand-Alone Variable Speed Constant Frequency Slip Ring Induction Generator - Theory and Experimental Results

The operation of a stand-alone, as opposed to grid connected generation system, using a slip-ring induction machine as the electrical generator, is considered. In contrast to an alternator, a slip-ring induction machine can run at variable speed and still deliver constant frequency power to loads. This feature enables optimization of the system when the prime mover is inherently variable speed in nature eg. wind turbines, as well as diesel driven systems, where there is scope for economizing on fuel consumption. Experimental results from a system driven by a 44 bhp diesel engine are presented. Operation at subsynchronous as well as super-synchronous speeds is examined. The measurement facilitates the understanding of the system as well as its design.

Electron paramagnetic resonance evidence for Jahn-Teller glasses

Single crystal E.P.R. studies of copper as a dopant in lithium potassium sulphate, lithium ammonium sulphate and lithium sodium sulphate have been carried out from room temperature down to 77K. The three Jahn-Teller (JT) systems behave very similarly to one another. The room temperature dynamic JT spectra with giso = 2·19 ± 0·01 and Aiso = ±(33 ± 4) times 10-4 cm-1 transform around 247 K to spectra characterized by randomly frozen-in axial strains with g‖ = 2·4307 ± 0·0005, g⊥ = 2·083 ± 0·001, A‖ = ±(116 ± 2) times 10-4 cm-1 and A⊥ = ∓(14 ± 4) times 10-4 cm-1. We proposed that the low temperature phase (below 247 K) of each of these systems provides an example of a Jahn-Teller glass.

Stock Option Compensation in Finland: An Analysis of Economic Determinants, Contracting Frequency, and Design

This paper addresses several questions in the compensation literature by examining stock option compensation practices of Finnish firms. First, the results indicate that principal-agent theory succeeds quite well in predicting the use of stock options. Proxies for monitoring costs, growth opportunities, ownership structure, and risk are found to determine the use of incentives consistent with theory. Furthermore, the paper examines whether determinants of stock options targeted to top management differ from determinants of broad-based stock option plans. Some evidence is found that factors driving these two types of incentives differ. Second, the results reveal that systematic risk significantly increases the likelihood that firms adopt stock option plans, whereas total firm risk and unsystematic risk do not seem to affect this decision. Third, the results show that growth opportunities are related to time-dimensional contracting frequency, consistent with the argument that incentive levels deviate more rapidly from optimum in firms with high growth opportunities. Finally, the results suggest that vesting schedules are decreasing in financial leverage, and that contract maturity is decreasing in firm focus. In addition, both vesting schedules and contract maturity tend to be longer in firms involving state ownership.

Impedance‐frequency characteristics of metal‐oxide‐semiconductor structures on polycrystalline silicon

This paper reports the variations in impedance with frequency of metal‐oxide‐semiconductor (MOS) structures on polycrystalline silicon. The origin of these impedance‐frequency characteristics are qualitatively explained. These characteristics indicate that the MOS structure on polycrystalline silicon can be exploited to realize voltage controlled filters.

Magnetic resonance imaging and ultrasonography in brachial plexus birth injury

Brachial plexus birth injury (BPBI) is caused by stretching, tearing or avulsion of the C5-C8 or Th1 nerve roots during delivery. Foetal-maternal disproportion is the main reason for BPBI. The goal of this study was to find out the incidence of posterior subluxation of the humeral head during first year of life in BPBI and optimal timing of the ultrasonographic screening of the glenohumeral joint. The glenohumeral congruity and posterior subluxation of the humeral head associated to muscle atrophy were assessed and surgical treatment of the shoulder girdle as well as muscle changes in elbow flexion contracture were evaluated. The prospective, population based part of the study included all neonates born in Helsinki area during years 2003-2006. Patients with BPBI sent to the Hospital for Children and Adolescents because of decreased external rotation, internal rotation contracture or deformation of the glenohumeral joint as well as patients with elbow flexion contracture were also included in this prospective study. The incidence of BPBI was calculated to be 3.1/1000 newborns in Helsinki area. About 80% of the patients with BPBI recover totally during the follow-up within the first year of life. Permanent plexus injury at the age of one year was noted in 20% of the patients (0.64/1000 newborns). Muscle imbalance resulted in sonographically detected posterior subluxation in one third of the patients with permanent BPBI. If muscle imbalance and posterior subluxation are left untreated bony deformities will develop. All patients with internal rotation contracture of the glenohumeral joint presented muscle atrophy of the rotator cuff muscles. Especially subscapular and infraspinous muscles were affected. A correlation was found particularly between greatest thickness of subscapular muscle and subluxation of the humeral head, degree of glenoid retroversion, as well as amount of internal rotation contracture. Supinator muscle atrophy was evident among all the studied patients with elbow flexion contracture. Brachial muscle pathology seemed to be an important factor for elbow flexion contracture in BPBI. Residual dysfunction of the upper extremity may require operative treatment such as tendon lengthening, tendon transfers, relocation of the humeral head or osteotomy of the humerus. Relocation of the humeral head improved the glenohumeral congruency among patients under 5 years of age. Functional improvement without remodeling of the glenohumeral joint was achieved by other reconstructive procedures. In conclusion: Shoulder screening by US should be done to all patients with permanent BPBI at the age of 3 and 6 months. Especially atrophy of the subscapular muscle correlates with glenohumeral deformity and posterior subluxation of the humeral head, which has not been reported in previous studies. Permanent muscle changes are the main reason for diminished range of motion of the elbow and forearm. Relocation of the humeral head, when needed, should be performed under the age of 5 years.

The elastic manifestation of a spin-glass transition: a low-frequency study

The authors report here the first measurements of low-frequency dynamic elastic properties of a spin glass (Fe59Ni21Cr20) across the transition temperature (Tg approximately=16 K). A minimum in the sound velocity (V) and a maximum in the internal friction (Q-1) were found at temperatures close to but below Tg. The elastic data were compared with the AC susceptibility data taken at similar frequency.

Electron paramagnetic resonance studies of some ternary oxides of copper (II)

The electron paramagnetic resonance (EPR) of ternary oxides of Cu(II) has been studied between 4.2 and 300 K. The systems include those with 180 degrees Cu-O-Cu interactions (such as Ln2CuO4, Sr2CuO2Cl2, Sr2CuO3 and Ca2CuO3) or 90 degrees Cu-O-Cu interactions (such as Y2Cu2O5 or BaCuO2) as well as those in which the Cu2+ ions are isolated (such as Y2BaCuO5, La1.8Ba1.2Cu0.9O4.8 and Bi2CuO4). The change in the EPR susceptibility as a function of temperature is compared with that of the DC magnetic susceptibility. Compounds with extended 180 degrees Cu-O-Cu interactions which have a low susceptibility also do not give EPR signals below room temperature. For compounds such as Ca2CuO3 with one-dimensional 180 degrees Cu-O-Cu interactions a weak EPR signal is found the temperature dependence of which is very different from that of the DC susceptibility. For Y2BaCuO5 as well as for La1.8Ba1.2Cu0.9O4.8 the EPR susceptibility as well as its temperature variation are comparable with those of the static susceptibility near room temperature but very different at low temperatures. Bi2CuO4 also shows a similar behaviour. In contrast, for Y2Cu2O5, in which the copper ions have a very distorted nonsquare-planar configuration, the EPR and the static susceptibility show very similar temperature dependences. In general, compounds in which the copper ions have a square-planar geometry give no EPR signal in the ground state (0 K) while those with a distortion from square-planar geometry do give a signal. The results are analysed in the light of recent MS Xalpha calculations on CuO46- square-planar clusters with various Cu-O distances as well as distortions. It is suggested that in square-planar geometry the ground state has an unpaired electron in anionic orbitals which is EPR inactive. Competing interactions from other cations, an increase in Cu-O distance or distortions from square-planar geometry stabilise another state which has considerably more Cu 3d character. These states are EPR active. Both these states, however, are magnetic. For isolated CuO46- clusters the magnetic interactions seem to involve only the states which have mainly anionic character.

Microscopic expression for frequency and wave vector dependent dielectric constant of a dipolar liquid

A microscopic expression for the frequency and wave vector dependent dielectric constant of a dense dipolar liquid is derived starting from the linear response theory. The new expression properly takes into account the effects of the translational modes in the polarization relaxation. The longitudinal and the transverse components of the dielectric constant show vastly different behavior at the intermediate values of the wave vector k. We find that the microscopic structure of the dense liquid plays an important role at intermediate wave vectors. The continuum model description of the dielectric constant, although appropriate at very small values of wave vector, breaks down completely at the intermediate values of k. Numerical results for the longitudinal and the transverse dielectric constants are obtained by using the direct correlation function from the mean‐spherical approximation for dipolar hard spheres. We show that our results are consistent with all the limiting expressions known for the dielectric function of matter.