Zur Modellierung von Sauterdurchmesser und Hold-up beim Einsatz eines konischen Turbinenrührers zum Dispergieren gas-flüssig

By comparing the experimental data of the Sauter-mean-diameter d ₃₂ and the hold up ? with models from literature, there are presented equations for d ₃₂ and ? for the used conical turbine in gas-liquid systems. The necessary adjustment of the proportionality constants of the literature equations will be explained on the basis of fluiddynamical phenomena. It can be established by fluid-dynamical results of a former study carried out with laser-doppler-anemometry. Coalescence phenomena are taken into account in the model using an analogy to bubble columns. The analogy to bubble columns turns out to be suitable. Arguments for the necessity of considering the local fluiddynamics in the modelling of dispersions are presented.     

Laboratory aid and ultrasonography in the diagnosis of appendicitis in children

The purpose of this study was to evaluate the relationship between the number of yolk sacs and amnionicity in monochorionic twin pregnancies scanned early in the first trimester. We retrospectively reviewed images of all monochorionic twins scanned between 6 and 9.5 weeks' gestation and with pathologic or sonographic confirmation of chorionicity-amnionicity. Each film was reviewed for the number of yolk sacs present, as well as for the gestational age at which the amniotic membrane was first visualized. Twenty monochorionic-diamniotic pregnancies and two monochorionic-monoamniotic pregnancies met the criteria for inclusion in the study. In diamniotic pregnancies scanned at less than 8 weeks' gestation, only the yolk sacs were identified; none of the dividing amniotic membranes were detected. Two yolk sacs were identified in all but one case. In this case, although one yolk sac was seen at 6 weeks, follow-up scanning at 8 weeks revealed two yolk sacs. In each of the monochorionic-monoamniotic twin pregnancies, one yolk sac was seen at 9 weeks and a single amnion encircled both embryos. We conclude that the sonographic identification of two yolk scas in monochorionic twins enables us to make the diagnosis of diamniotic twins early in the first trimester, before the amniotic membrane can be imaged. The presence of one yolk sac should prompt a follow-up ultrasonogram to assign amnionicity definitively.     

Suppression of boron penetration in p+ polysilicon gateP-MOSFETs using low-temperature gate-oxide N2O anneal

It has been reported that high-temperature (~1100°C) N₂ O-annealed oxide can block boron penetration from poly-Si gates to the silicon substrate. However, this high-temperature step may be inappropriate for the low thermal budgets required of deep-submicron ULSI MOSFETs. Low-temperature (900~950°C) N₂O-annealed gate oxide is also a good barrier to boron penetration. For the first time, the change in channel doping profile due to compensation of arsenic and boron ionized impurities was resolved using MOS C-V measurement techniques. It was found that the higher the nitrogen concentration incorporated at Si/SiO₂ interface, the more effective is the suppression of boron penetration. The experimental results also suggest that, for 60~110 Å gate oxides, a certain amount of nitrogen (~2.2%) incorporated near the Si/SiO₂ interface is essential to effectively prevent boron diffusing into the underlying silicon substrate     

Short-circuit power driven gate sizing technique for reducing powerdissipation

One major challenge in low-power technology is how to reduce overall power dissipation of a given subsystem without impacting its performance. In this paper we present a technique that can be applied to the nonspeed-critical nets in a circuit in order to reduce overall power dissipation. This technique involves a study of short-circuit power dissipation as a function of input signal slews and output load conditions, to aid in making a judicious choice of drive strengths for various gates in a circuit. The resulting low-power solution does not degrade the original performance and yields a circuit which occupies less silicon area. The technique described here can be incorporated into any power optimization or synthesis tool. Lastly, we present the savings in power and area for a 32-b carry lookahead adder which was designed using the technique described here     

K- and Q-bands CMOS frequency sources with X-band quadrature VCO

Fully integrated 10-, 20-, and 40-GHz frequency sources are presented, which are implemented with a 0.18-/spl mu/m CMOS process. A 10-GHz quadrature voltage-controlled oscillator (QVCO) is designed to have output with a low dc level, which can be effectively followed by a frequency multiplier. The proposed multipliers generate signals of 20 and 40 GHz using the harmonics of the QVCO. To have more harmonic power, a frequency doubler with pinchoff clipping is used without any buffers or dc-level shifters. The QVCO has a low phase noise of -118.67 dBc/Hz at a 1-MHz offset frequency with a 1.8-V power supply. The transistor size effect on phase noise is investigated. The frequency doubler has a low phase noise of -111.67 dBc/Hz at a 1-MHz offset frequency is measured, which is 7 dB higher than a phase noise of the QVCO. The doubler can be tuned between 19.8-22 GHz and the output is -6.83 dBm. A fourth-order frequency multiplier, which is used to obtain 40-GHz outputs, shows a phase noise of -102.0 dBc/Hz at 1-MHz offset frequency with the output power of -18.0 dBm. A large tuning range of 39.3-43.67 GHz (10%) is observed.     

Diagnosis of tapping operations using an AI approach

On-line diagnosis of the machining operations is essential because it can prevent potential problems caused by abnormal conditions. So far, little research has been done for the on-line diagnosis of tapping operations. However, tapping is a very important machining operation. And the on-line diagnosis is essential. In this work, an artificial neural network was utilized for the diagnosis of the tapping operation. The input vector for the neural network is obtained by processing the signals of the thrust, torque, and lateral forces during the tapping operations. A total of ten indices were used in the input layer of the network. The output of the artificial neural network provides the tapping states. Five different tapping states were investigated: normal operation, tap wear, misalignment, oversize hole, and undersize hole. The weights and thresholds of the artificial neural network can be modified by the generalized delta rule. Experimental results showed that diagnosis of tapping operations through an artificial neural network can reach a success rate of over 95%.     

Distributed Multirobot Exploration and Mapping

Efficient exploration of unknown environments is a fundamental problem in mobile robotics. We present an approach to distributed multirobot mapping and exploration. Our system enables teams of robots to efficiently explore environments from different, unknown locations. In order to ensure consistency when combining their data into shared maps, the robots actively seek to verify their relative locations. Using shared maps, they coordinate their exploration strategies to maximize the efficiency of exploration. This system was evaluated under extremely realistic real-world conditions. An outside evaluation team found the system to be highly efficient and robust. The maps generated by our approach are consistently more accurate than those generated by manually measuring the locations and extensions of rooms and objects.     

Reliability of a k-out-of-n: G system with common-mode outages

This paper presents the model of a k-out-of-n: G system with common mode outages. The objective is to analytically derive the mean operating mode between failures for a non-repairable component system. The average system failure time and the system availability are also considered. Then, the model is extended to a system with repairable components and unrestricted repair, in which service times are exponentially distributed.