Properties of the super-alpha composite transistor at high frequencies

The equivalent circuit of the composite transistor, the input impedance and the current gain have been developed by analysing its equivalent circuit, in terms of the various parameters of the individual transistors in the common base and common emitter configuration. It is found that in the C.E. configuration, the short-circuit input impedance hi_e has a negative resistance component over a frequency range in which the current gain in the C.B. configuration h/b is greater than 1.     

Analysis of a 35·6 kb Region on the Right Arm of Saccharomyces cerevisiae Chromosome XV

We report the sequence of a 35 600 bp fragment covering the PET123 region on the right arm of chromosome XV from Saccharomyces cerevisiae. This region contains 19 possible open reading frames (ORFs) of which 16 are non-overlapping ORFs. Eight ORFs correspond to the SPP2, SMP3, RPB2, PDR5, NFI1, PUP1, PET123 and MTR10 loci, described previously. Two ORFs correspond to yeast homologues of genes from other organisms: O3530 is a member of the large ribosomal subunit protein L13 family and O3560 (SME1 gene) is a 94-codon ORF and is a homologue of the mammalian SmE spliceosomal core protein. Three ORFs (O3513, O3521, O3548) present significant similarities to proteins of unknown function and three ORFs (O3510, O3536, O3545) lack homology to sequences within the databases screened. The sequence has been deposited in the GenBank database under Accession Number U55020. © 1997 by John Wiley & Sons, Ltd.     

Robust SVM-direct torque control of induction motor based on sliding mode controller and sliding mode observer

This paper proposes a design of control and estimation strategy for induction motor based on the variable structure approach. It describes a coupling of sliding mode direct torque control (DTC) with sliding mode flux and speed observer. This algorithm uses direct torque control basics and the sliding mode approach. A robust electromagnetic torque and flux controllers are designed to overcome the conventional SVM-DTC drawbacks and to ensure fast response and full reference tracking with desired dynamic behavior and low ripple level. The sliding mode controller is used to generate reference voltages in stationary frame and give them to the controlled motor after modulation by a space vector modulation (SVM) inverter. The second aim of this paper is to design a sliding mode speed/flux observer which can improve the control performances by using a sensorless algorithm to get an accurate estimation, and consequently, increase the reliability of the system and decrease the cost of using sensors. The effectiveness of the whole composed control algorithm is investigated in different robustness tests with simulation using Matlab/Simulink and verified by real time experimental implementation based on dS pace 1104 board.     

RELATIONSHIPS OF SELECTED WHEAT PARAMETERS TO BURGHUL-MAKING QUALITY

Ten Triticum aestivum and eleven Triticum turgidum var. durum varieties were screened for their one thousand kernel weight (1000 KW), particle size index (PSI), sodium-dodecyl-sulfate (SDS) sedimentation volume, flour swelling power, protein content, amylose content and swelling power of starch. The varieties were processed to Burghul (parboiled wheat) and utilized in the preparation of Burghul Mufalfal and Kibbeh. The products were rated sensorially for particle separation and hardness (Burghul Mufalfal) and denseness (Kibbeh). Marked differences were noted between the aestivums and durums as to their 1000 KW, PSI and SDS-sedimentation volumes. Significant correlations were observed between the sensory ratings of the two Burghul-based products and the 1000 KW, PSI and SDS-sedimentation volumes. Cluster analysis, using the chemical/physicochemical parameters as variables, identified two clusters; a “durum” cluster (11 durums, 2 aestivums) and an “aestivum” cluster (8 aestivums). The varieties of the “durum” cluster yielded quality Burghul Mufalfal and Kibbeh; the varieties of the “aestivum” cluster yielded inferior Burghul Mufalfal and less compact Kibbeh. Quality Burghul is best-processed from large size and hard-grained varieties of low SDS-sedimentation volumes (mostly durums) having 1000 KW > 34.5 g, 31.9 < PSI < 45.6 and 13.8 mL < SDS-sedimentation volumes < 30.1 mL.     

THE PERFORMANCE OF A COLLECTOR-STORAGE WALL IN ALEXANDRIA,EGYPT

This investigation presents an analysis of the performance of a collector-storage wall composed of concrete using the weather data of Alexandria, Egypt. An energy balance on the collector-storage wall is used to predict the energy flows into and out of the wall. The numerical model is then incorporated into TRNSYS to determine the thermal performance of the wall. The effect of the wall thickness, the number of glazing, the building capacitance, and the night insulation resistance on the performance of the collector-storage wall in Alexandria, Egypt are studied.     

Remote,surface and laboratory detection of radioactive minerals of Rosetta black-sand beach deposits,Egypt

Abstract

Detailed aerial and ground radiometric surveys were conducted on the coastal plain of the Mediterranean Sea, on both sides of the estuary of the Rosetta branch of the River Nile. Auger samples representing the upper 1 m, were collected and analysed for the two principal radioactive minerals in the black sands, zircon and monazite.

The results obtained by the various methods, particularly aeroradiometry, revealed five main zones of heavy mineral concentration along the beach to the east and west of the Rosetta estuary. The present-day Rosetta branch is responsible for the formation of the first zone of mineral concentration. The second and fifth zones can be related to the ancient extinct estuaries of the Bolbitine and Sebennytic branches mentioned by Ball (1942) (after Herodotus, 450 B.C.). The third and fourth zones are believed to correspond to two ancient extinct estuaries of the River Nile, which were probably not in existence at the time of Herodotus and therefore were not reported by Ball (1942).

The study revealed that there is a general direct correlation between the aerial data and that from ground radiometry and zircon and monazite tenors as in the case of Damietta black-sand beach deposits (Meleik et al. 1978).

It was found that the mean background radioactivity either from the air or from the ground, as well as the correlation coefficients, are generally higher and stronger on the western side of the Rosetta estuary than on its eastern side. Moreover, the mean concentration of zircon on the western side (0·62 per cent) reaches approximately 1·5 times that on the eastern side (0·39 per cent), while that of monazite remains almost the same westwards (0·16 per cent) and eastwards (0·14 percent).     

Improvement of low fat mozzarella cheese properties using denatured whey protein

Mozzarella cheese was made from buffalo milk (6% fat) or from partially skimmed buffalo milk (2 and 4% fat) with 0.5 and 1% denatured whey protein. Adding whey protein to buffalo milk decreased rennet coagulation time and curd tension whereas increased curd synaeresis. Addition of whey protein to cheese milk increased the acidity, total solids, ash, salt, salt in moisture, also some nitrogen fractions. The meltability and oiling‐off values increased but the calcium values of mozzarella cheese decreased. The sensory properties of low fat mozzarella cheese were improved by addition of whey protein to the cheese milk.     

Effect of nanoclay concentration level on the electrical properties of polypropylene under electron irradiation in a SEM

For studying the electrical properties (charge trapping, transport and secondary electron emission) of the polypropylene‐based nanocomposites with different contents of natural clay, the specimens were submitted to electron irradiation of a scanning electron microscope. A device, suitably mounted on the sample holder of the scanning electron microscope, was used to measure two currents (i.e. leakage and displacement currents) induced in the polypropylene‐based nanocomposites (polymer nanocomposites) under electron irradiation. The evolution of trapped charge during irradiation for each type of studied polymer nanocomposites is deduced. The amount of trapped charge at the steady state is also determined by measuring the change of secondary electron image size associated to the electron trajectory simulation. It is found, surprisingly, that not only the leakage current increases as a function of clay loading level but also trapped charge. However, this could be related to the increase of conductivity in one hand and to proliferation of interfaces between nanoparticles and neighbouring materials on the other hand. These two processes play crucial role in controlling the carrier transport (through polymer nanocomposites or/and along its surface) closely related to the charge storage and leakage current. Additional experiment using dielectric spectroscopy were performed to show the effect of clay concentration in changing the dielectric relaxation behaviour and to evidence the existence of interfaces between nanoparticles and polymer. The secondary electron emission during electron irradiation is also studied through the total electron yield that is deduced by correlating the measured leakage and displacement currents.