Labelling 2-D geometric primitives using probabilistic relaxation:reducing the computational requirements

In previous work, an algorithm for matching geometric features was developed. Although the method worked well, it was demanding in computational resources when applied to large problems. The authors now present methods for reducing the computational requirements, without significantly affecting the reliability of the algorithm     

Temperature and modulation characteristics of resonant-cavitylight-emitting diodes

Resonant-cavity light-emitting diodes (RCLED) are novel, high-efficiency light-emitting diodes which employ optical microcavities. These diodes have higher intensities and higher spectral purity as compared to conventional LEDs. Analytical formulas are derived for the enhancement of the spontaneous emission along the optical axis of the cavity. The design rules for high-efficiency operation of RCLEDs are established. The temperature dependence of the emission intensity is analyzed in the range 20-80° and it is described by an exponential dependence with a characteristic temperature of 112 K. The modulation characteristics of RCLEDs exhibit 3 dB frequencies of 580 MHz. Eye diagrams at transmission rates of 622 Mb/s are wide open indicating the suitability of RCLEDs for high-speed data transmission     

Soft-decision Viterbi decoding with diversity combining formulti-beam mobile satellite communication systems

Diversity combining methods for mobile satellite communication systems employing convolutional encoding and soft-decision Viterbi decoding are evaluated. Computer simulation clarifies that the pre-Viterbi-decoding maximal ratio combining method has better performance than other methods in Rician fading channels. The simulation results agree with the Pe (bit error probability) performance derived from the numerical analysis for slow fading using the approximate Pe performance of Viterbi decoding in AWGN (additive white Gaussian noise) channels and the probability density function of Rician fading. Applying this diversity method to the multi-beam mobile satellite communication systems, a satellite beam diversity reception scheme is proposed. A computer simulation result shows that the proposed scheme decreases the packet error rate of the control signals to less than 1/100 around the satellite beam boundary     

Pressure release of containments during severe accidents in Switzerland

As required by the Swiss Federal Nuclear Safety Inspectorate (HSK) all Switzerland's five nuclear power plants have to install a containment filtered venting system. The integrity of the containment (the last barrier for radioactive releases to the environment) can be threatened by overpressure due to inadequate heat removal. Design requirements have been provided for a specific class of severe accident scenarios. In general the capacity of the system is considered sufficient if it is able to vent the steam production corresponding to a decay heat level of 1% of the thermal reactor power. The mitigation capacity for the reduction of released radioactive material is specified by a retention factor of 1000 for aerosols to prevent or limit a long term ground contamination and a factor of 100 for elementary iodine for prevention or limiting of thyroid doses and to avoid short term evacuation. Besides existing requirements for design, maintenance and operation, additional claims such as passivity and operability at any pressure conditions inside the containment have to be met. Passivity implies that the system can be initiated after a severe accident without any operator action. The system also has to allow early manual venting. Various filtered venting systems are presently available. The nuclear power plants of Beznau, Gosgen, Leibstadt and Muhleberg have already selected such systems and already implemented them or are going to install them step by step. Beznau selected the Sulzer-EWI system which is using a water pool with nozzles-baffle plates and mixing elements to achieve the required filtration of the aerosols. In both Beznau units, the systems are installed and in standby mode. Gosgen, a pressurized water reactor as well as Beznau, is going to implement a filter system developed by Siemens-KWU, known as sliding pressure venting process, combining a venturi scrubber in a water pool and a mesh filter. The boiling water reactor of Leibstadt also selected the same system as Beznau while Müheberg choose the ABB system but not in the common design. The venturi pipes are thereby integrated in the water pool of the outer torus. The system in all five nuclear power plants is fully operable and in standby mode since December 1993.     

Electrical properties of UV photochemically treated CdTe

Single crystal CdTe was grown using the vapour phase technique. The dice were etched using a photochemical method in which the samples were illuminated during the etching process. Laser pulses of various intensities were used as an illumination source during the etching of the CdTe substrate. A pulse excimer laser capable of producing 17 ns pulses of 308 nm wavelength with varuing intensities between 0–35 mW cm⁻² was used. Schottky barriers were made by vacuum evaporation of gold onto the CdTe single crystal substrate. The behaviour of the Au---CdTe devices was studied as a function of the intensity of the laser beam used during the etching of CdTe substrate by principle electrical methods such as capacitance-voltage and current-voltage analysis. The photochemical technique was found to produce a significant change in the electrical properties, such as the barrier height, carrier concentration, ideality factor, and forward-bias threshold of the Au---CdTe Schottky diode.     

Lead acid battery storage configurations for improved availablecapacity

Battery storage is a crucial element in alternative energy and electric vehicle systems. Three battery storage configurations: a conventional; a parallel; and a dual, were analyzed for both shallow cycle and deep cycle lead-acid batteries to determine if capacity improvement is achievable. Daily profiles for the weekly irradiance, daily loads, and ambient temperature are simulated. Cycle tests were performed monthly to determine the effect each configuration had on the available battery capacity. Results for each battery type differ. Available capacity was improved using the parallel configuration with shallow cycle batteries and the dual configuration with deep cycle batteries     

Soft X-ray image storage in poly (methylmethacrylate)

Images stored in resist for soft X-ray lithography or microradiography were found to show a background noise which limits the resolution. This is due to the statistically variable spatial distribution of the photons incident on the resist surface. An estimate of the fundamental noise-limited resolution has been made from the experimental measurement of photon flux incident on the surface and the accurate development rate curves. Monochromatic radiation from a synchrotron source was used.     

A.c. conductivity studies on the silver molybdo-arsenate glassy system

A new quaternary fast-ion conducting silver molybdo-arsenate [Agl-Ag₂O-(MoO₃ + As₂O₅)] (SMA) glassy system has been prepared using the melt-quenching technique for various dopant salt (Agl) concentrations by fixing the formers (MoO₃ + As₂O₅) composition and the modifier (Ag₂O) to formers (M/F) ratio. The prepared compounds were characterized by X-ray diffraction. The impedance measurements were made on different Agl compositions of the SMA glasses as a function of frequency (6.5 Hz–65 kHz) and temperature (303–343 K), using the Solatron frequency-response analyser (model 1250). The bulk conductivity and the appropriate physical model (equivalent circuit) of the SMA glass were obtained from the impedance analysis. The a.c. conductivity was calculated for different Agl compositions of SMA glasses at various temperatures and the obtained a.c. conductivity results were analysed using Jonscher's Universal Law. The conduction mechanism for the highest conducting SMA glassy compound has been explained using the diffusion path model.