Co-channel interference in cellular radio systems using frequency hopping code division multiple access (FH-CDMA)

The expected interference power in a digital cellular radio system using frequency hopping code division multiple access is investigated. The up-link only is considered. Using both analytical and numerical methods, a probability density function for this power is derived. This function is used to predict the hop erasure probability of a system, as a function of the tolerable signal to interference ratio and of the system load.Mr. Al-Etaibi is sponsored by Saudi Telecom     

Effect of a cylindrical refracting interface on ultrasoundintensity and the CW Doppler spectrum

The insonation of axisymmetric flow in a tube by an ultrasound beam which is refracted at the tube surface is considered. A three-dimensional (3-D) model for refraction at a cylindrical interface is developed. The incident beam, which is planar but otherwise arbitrary, is refracted at a single acoustic impedance interface between the medium within the tube and the surrounding medium. A ray approximation is used as the ultrasonic wavelength is small compared to the radius of curvature of the tube. A parametric form for the ray paths is obtained and used to derive an expression for the intensity. The intensity depends on the specific position within the tube, as well as the ratio of sound speeds, N, and the Doppler angle &thetas;_D. A diverging (N=1.2, &thetas;_D=45°) and a converging (N=0.8, &thetas;_D=45°) case are presented in detail. The converging interface results in more extreme intensity distortion. The regions of maximum and minimum intensity over a tube slice are immediately adjacent in both diverging and converging cases. Once the intensity distribution across a tube slice is known, the previously reported (Aldis and Thompson, 1992) volume integral method for the calculation of continuous wave (CW) Doppler spectral power density (spd) functions may be used. The effect of refraction of the incident beam on the spd function is shown for both an infinite beam and a circular beam with radius equal to the tube radius. A curved acoustic impedance interface, as may be encountered in vitro in flow phantoms or in vivo in vascular disease, leads to nonuniform insonation and spectral distortion which depends on transducer orientation     

Calculation of Doppler spectral power density functions

A volume integral method for the calculation of Doppler ultrasound spectral power density (spd) functions is described. Axisymmetric flow in a circular tube with a power law velocity profile is assumed. The spd function is regarded as a probability density function for scatterer velocity, and the assumptions under which this is justified are considered. It is shown that the spd function is independent of Doppler angle except in the presence of wall reflection effects. A coordinate system centered on the beam is used and this enables the integrals to be easily formulated for arbitrary beams. Irregularly shaped and nonuniform beams can be treated. For the common flow and beam patterns, which exhibit symmetry, the volume integrals can often be reduced to a single integral and evaluated directly. The method is applied and the spectra are calculated for various different cases. Results are obtained for uniform rectangular and circular insonating beams, and for nonuniform beams with Gaussian, jinc, and sinc profiles. The effects of narrow beams and wall reflection are shown. The method may be readily applied to other beam and flow patterns, and extension to more complicated situations is also discussed.     

Improved diagnostics for determination of minimum explosive concentration,ignition energy and ignition temperature of dusts

We have designed additional instrumentation for some of the standard tests on dust explosibility and flammability. The new instrumentation defines the experimental conditions of the standard tests more precisely. Additional physical parameters that are measured are relative dust concentrations, energy of spark ignition sources, temperature, and timing of events that occur during the course of the tests.Relative dust concentrations are determined by measuring the attenuation of light through the dust cloud. The light source is a light emitting diode (LED) and the light is detected by a phototransistor (PT). Up to four LED—PT pairs used simultaneously and signals are recorded with a dual-beam oscilloscope with dual-trace vertical amplifiers. Time response of the system is the order of 5 ms. The PT signal is also useful for detecting ignition and the passage of flame fronts.The spark energy in the minimum ignition energy tests is measured by recording the voltage across the spark gap and the spark current with the dual beam oscilloscope. The LED—PT probes have been very useful in the minimum ignition energy tests for measuring the time of the spark relative to the arrival time of the dust at the electrode position.Dynamic measurements of temperature were made in the Godbert—Greenwald furnace, using fast-reponse thermocouples. Ignition delays were also studied using the LED—PT probe.     

On the feasibility of a 2-Mb/s bearer service in a future cellularradio system using code-division multiple access

The universal mobile telecommunications system (UMTS) and other third-generation mobile radio systems will be required to support data rates up to 2 Mb/s. This paper examines whether a direct-sequence spread-spectrum air interface can support such a high data rate in an outdoor environment. A mathematical analysis of the operation of a RAKE receiver is presented. Monte-Carlo methods are used to establish the probability that a 2-Mb/s link is possible and the proportion of system capacity such a link would consume. It is concluded that with sufficiently complex RAKE receivers and a high enough chip rate, it is certainly practical for a direct-sequence code-division multiple-access (DS-CDMA) mobile radio system to offer a 2-Mb/s service and that the overall spectrum efficiency will be high provided that the majority of users of the system use much lower data rates     

Hyperleptinemia as a component of a metabolic syndrome of cardiovascular risk

OBJECTIVES: The authors explored the role of casemix adjustment when profiling outcomes of ambulatory care. METHODS: The authors reviewed the medical records of 656 patients with hypertension, diabetes, or chronic obstructive pulmonary disease (COPD) receiving care at one of three Department of Veterans Affairs medical centers. Outcomes included measures of physiological control for hypertension and diabetes, and of exacerbations for COPD. Predictors of poor outcomes, including physical examination findings, symptoms, and comorbidities, were identified and entered into regression models. Observed minus expected performance was described for each site, both before and after casemix adjustment. RESULTS: Risk-adjustment models were developed that were clinically plausible and had good performance properties. Differences existed among the three sites in the severity of the patients being cared for. For example, the percentage of patients expected to have poor blood pressure control were 35% at site 1, 37% at site 2, and 44% at site 3 (P < 0.01). Casemix-adjusted measures of performance were different from unadjusted measures. Sites that were outliers (P < 0.05) with one approach had observed performance no different from expected with another approach. CONCLUSIONS: Casemix adjustment models can be developed for outpatient medical conditions. Sites differ in the severity of patients they treat, and adjusting for these differences can alter judgments of site performance. Casemix adjustment is necessary when profiling outpatient medical conditions.     

Ion induced deformation of soft tissue

In this paper the effects of changing the ion concentration in and around a sample of soft tissue are investigated. The triphasic theory developed by Lai et al. (1990, Biomechanics of Diarthrodial Joints, Vol. 1, Berlin, Springer-Verlag) is reduced to two coupled partial differential equations involving fluid ion concentration and tissue solid deformation. These equations are given in general form for Cartesian, cylindrical and spherical geometries. After solving the two equations quantities such as fluid velocity, fluid pressure, chemical potentials and chemical expansion stress may be easily calculated. In the Cartesian geometry comparison is made with the experimental and theoretical work of Myers et al. (1984, ASME J. biomech. Engng, 106, 151-158). This dealt with changing the ion concentration of a salt shower on a strip of bovine articular cartilage. Results were obtained in both free swelling and isometric tension states, using an empirical formula to account for ion induced deformation. The present theory predicts lower ion concentrations inside the tissue than this earlier work. A spherical sample of tissue subjected to a change in salt bath ion concentration is also considered. Numerical results are obtained for both hypertonic and hypotonic bathing solutions. Of particular interest is the finding that tissue may contract internally before reaching a final swollen equilibrium state or swell internally before finally contracting. By considering the relative magnitude, and also variation throughout the time course of terms in the governing equations, an even simpler system is deduced. As well as being linear the concentration equation in the new system is uncoupled. Results obtained from the linear system compare well with those from the spherical section. Thus, biological swelling situations may be modelled by a simple system of equations with the possibility of approximate analytic solutions in certain cases.     

Mobile phone data statistics as a dynamic proxy indicator in assessing regional economic activity and human commuting patterns

Various studies demonstrate that data on mobile phone use are useful when analysing problems in the fields of human activity or population dynamics, including tourism, transportation planning, public administration, etc. However, one of the biggest challenges is related to the restrictions contained in the General Data Protection Regulation that force the use of statistics about mobile operator client activities instead of allowing the analysis of mobile operator data. Therefore, a data analytics approach that does not involve information on the mobility of particular persons was developed, providing economically relevant data on aggregate mobility while protecting personal data. The activity data aggregation was conducted at 15-min intervals in the area of each cellular base station; “activity” is defined as the number of outgoing and incoming calls and sent and received text messages (short message service or SMS) and, in some instances, as the count of unique users. The case study examines all of Latvia's municipalities, analysing the economic activity level in each municipality in comparison to the mobile phone activity in three periods: 2015–2016, 2017, and 2018. It was concluded that the economic activity in municipalities can be estimated, and positive dynamics of regional development have been detected. Such data and the data analytics method, which provides an understanding of how economic activities evolve in real time in particular locations and economic activity centres, can improve regional development planning and plan implementation. In order to assess which are the centres of economic activity in each municipality and its sphere of influence, the patterns of human commuting and fluctuations of internal activity on workdays and weekends/holidays in 2017–2018 were determined. In general, there is a shortage of reliable data on human commuting within Latvia and its specific regions; therefore, the method described here provides a practical tool for regional governments to keep track of strategy implementation and for strategic gap analysis.     

IgG subclass antibodies to glutamic acid decarboxylase and risk for progression to clinical insulin-dependent diabetes

Pancreatic islet beta cell destruction leading to insulin-dependent diabetes mellitus (IDDM) is believed to be mediated by a T-helper 1 (T(H)1) lymphocyte response to islet antigens. In the mouse, T(H)1 (IL-2, IFN-gamma) and T(H)2 (IL-4, -5, -6, -10) responses are associated with the generation of IgG2a and IgG1 subclasses, respectively. The equivalent human subclasses have not been defined. Because the IgG subclass response to an antigen may be a potentially useful marker of T(H)1/T(H)2 immune balance we measured IgG subclass antibodies to glutamic acid decarboxylase (GAD), a major islet autoantigen in IDDM, in 34 newly-diagnosed IDDM patients and in 28 at-risk, first-degree relatives of people with IDDM. In the newly-diagnosed patients, total IgG antibodies to GAD were detected in 74% (25/34); IgG1 and/or IgG3 were significantly more frequent than IgG4 or IgG4/IgG2 (14/34 versus 5/34, p = 0.01). GAD antibody-negative patients were significantly younger (p = 0.01). In 15 at-risk relatives who had not progressed to clinical diabetes after a median of 4.5 years, 10 had IgG2 and/or IgG4 antibodies compared to only 3/13 progressors (p = 0.02). Total IgG and IgG2 antibodies were higher in non-progressors. Non-progressors were older than progressors (p = 0.01), and relatives with IgG2 and/or IgG4 responses were also older (p = 0.01). These results suggest that IgG subclass antibodies to GAD may contribute to diabetes risk assessment in islet antibody relatives.