Transconductor and integrator circuits for integrated bipolar video frequency filters

A description is presented of novel transconductor and integrator circuits which can be used in integrated video frequency filters in bipolar technology. The transconductor consists of a parallel connection of a passive nominal transconductance and an active variable transconductance, resulting in good high-frequency performance up to 70 MHz and less than 1% linearity error for input signals up to 2V pp. The integrator incorporates an operation transconductance amplifier circuit which provides a tunable integrator phase. Simulation results for all circuits and for a fifth-order elliptic low-pass filter with a nominal cutoff frequency of 5 MHz are presente

Practical formulation of the relation between filter specifications and the requirements for integrator circuits

The design of integrated, high-frequency, continuous-time filters has made considerable progress in the past few years. As the signal frequencies increase the design of the integrator circuits used in most of these filters becomes more critical. To give direction to the circuit design, minimum specifications for the gain and phase of the integrator circuits would be helpful. A practical method for obtaining these integrator specifications from the filter specifications is developed. The method is applied to a sixth-order Chebyshev band-pass filter, and the result is verified by computer simulatio

Accurate automatic tuning circuit for bipolar integrated filters

An accurate automatic tuning circuit for tuning the cutoff frequency and Q-factor of high-frequency bipolar filters is presented. The circuit is based on a voltage controlled quadrature oscillator (VCO). The frequency and the RMS (root mean square) amplitude of the oscillator output signal are locked to the frequency and the RMS amplitude of a reference signal, respectively. Special attention is paid to the actual Q-factor in the oscillator. Experimental results for a breadboard circuit operating from 136 to 317 kHz are presente

The use of data models for assessing standard logistics software

The traditional method of selecting standard (logistics) software is very much based on the use of large functional checklists. This paper first describes the limitations of the traditional method and how these limitations are normally resolved. Then the advantages of the use of data models in the area of software selection are argued. Based on these advantages a method is described to compare the data models of different software packages by using a Reference Data Model (RDM). Apparently the results of assessing software systems very much depend on the quality of this RDM. The design of this RDM is therefore a major part of the research. Up to now the use of this data-oriented approach appears very promising, provided that it is seen as an addition to the current method of software selection

Modeling and prediction of surgical procedure times

Accurate prediction of medical operation times is of crucial importance for cost efficient operation room planning in hospitals. This paper investigates the possible dependence of procedure times on surgeon factors like age, experience, gender, and team composition. The effect of these factors is estimated for over 30 different types of medical operations in two hospitals, by means of ANOVA models for logarithmic case durations. The estimation data set contains about 30,000 observations from 2005 till 2008. The relevance of surgeon factors depends on the type of operation. The factors found most often to be significant are team composition, experience, and daytime. Contrary to widespread opinions among surgeons, gender has nearly never a significant effect. By incorporating surgeon factors, the accuracy of out-of-sample prediction of case durations of about 1,250 surgical operations in 2009 is improved by up to more than 15 percent as compared to current planning procedures.planning;ANOVA model;European hospital;current procedure terminology (CPT);health care management;lognormal distribution;operation room;surgeon factors

The WSRT wide-field HI survey: II. Local Group features

We have used the WSRT to carry out an unbiased wide-field survey of HI emission features, achieving an RMS sensitivity of about 18 mJy/Beam at a velocity resolution of 17 km/s over 1800 deg^2. In this paper we present our HI detections at negative velocities which could be distinguished from the Galactic foreground. Fully 29% of the entire survey area has high velocity HI emission with N_HI exceeding our 3 sigma limit of about 1.5x10^17cm^-2 over 30 km/s. A faint population of discrete HVCs is detected in the immediate vicinity of M31 which spans a large fraction of the M31 rotation velocity. This class of features is confined to about 12 deg (160 kpc) projected radius of M31 and appears to be physically associated. We detect a diffuse northern extension of the Magellanic Stream (MS) from at least Dec=+20 to +40 deg., which then loops back toward the south. Recent numerical simulations had predicted just such an MS extension corresponding to the apo-galacticon portion of the LMC/SMC orbit at a distance of 125 kpc. A faint bridge of HI emission appears to join the systemic velocities of M31 with that of M33 and continues beyond M31 to the north-west. This may be the first detection of HI associated with the warm-hot intergalactic medium (WHIM). The distribution of peculiar velocity HI associated with M31 can be described by a projected exponential of 25 kpc scale-length and 5x10^17cm^-2 peak column density. We present the distribution function of N_HI in the extended M31 environment, which agrees well with the low red-shift QSO absorption line data over the range log(N_HI)=17.2 to 21.9. Our data extend this comparison about two orders of magnitude lower than previously possible and provide the first image of the Lyman limit absorption system associated with an L* galaxy. (abridged)Comment: 16 pages, 12 figures, accepted for publication in A&

Night temperature and number of nodes and flowering of the main stem of glasshouse cucumber (Cucumis sativus L.).

Plants of the cucumber cv. Farbio (all-female) were planted on 13 or 27 December, 10 or 24 January and grown at 3 minimum night temperatures, 12, 16 or 20 deg C from planting until 1 April. Node number/stem increased as the night temperature fell. Internodes were longer with later planting and on plants on inner rather than outer rows; these responses could not be related to light intensity alone. The number of flowers/stem was determined by the number of nodes bearing flowers and the number of flowers/node. More flowers/node occurred towards the top of the plant and late planting increased flowering at all nodes; the night temperature had little effect on numbers but these were highest at 16 deg . Earliness to flower of the first flowers/axil and the intensity of flowering both rose with temperature. Flowering was delayed only slightly by later planting. (Abstract retrieved from CAB Abstracts by CABI’s permission

Night temperature and flower abortion of glasshouse cucumber (Cucumis sativus L.).

Plants of the gynaecious cucumber cv. Farbio were planted under glass, about 30 days after sowing, on 13 and 27 December and on 10 and 24 January. Night temperatures of 12, 16 and 20 deg C were compared until 1 April, the day temperature being 21-27 deg . Only 835 of 3600 flowers aborted shortly after opening. The later planted crops showed less abortion than earlier planted ones and the lower the night temperature the higher was the level of abortion. Abortion of the second and third flowers in an axil accounted for 60% of the total, regardless of night temperature. Fruits were picked every 5 days; those with the longest hanging time (i.e. slowest growth) were found primarily in axils just below axils in which all flowers had aborted. Such fruits are known to have a reduced shelf life [see HcA 50, 7105] and quality could thus be controlled to some extent by selective thinning of fruit in these axils. (Abstract retrieved from CAB Abstracts by CABI’s permission