Design of concatenated space-time block codes using signal space diversity and the Alamouti scheme

New full-rate space-time block codes achieving full diversity for quadrature amplitude modulation (QAM) using an even number of transmit antennas over quasi-static Rayleigh fading channels are proposed. The proposed codes are constructed by serially concatenating unitary rotating precoders with the Alamouti code. The coding advantage of the proposed code for a codeword pair corresponding to any distinct input pair is shown to be greater than or equal to that of the ST-CR code.     

Experimental and Numerical Studies in a Vortex Tube

The present investigation deals with the study of the internal flow phenomena of the counter flow type vortex tube using experimental testing and numerical simulation. Visualization was carried out using the surface tracing method, injecting dye on the vortex tube wall using a needle. Vortex tube is made of acrylic to visualize the surface particle tracing and the input air pressure was varied from 0.1 MPa to 0.3 MPa. The experimentally visualized results on the tube show that there is an apparent sudden changing of the trajectory on the vortex tube wall which was observed in every experimental test case. This may indicate the stagnation position of the vortex flow. The visualized stagnation position moves towards the vortex generator with increase in cold flow ratio and input pressure. Three-dimensional computational study is also conducted to obtain more detailed flow information in the vortex tube. Calculated total pressure, static pressure and total temperature distributions in the vortex tube were in good agreement with the experimental data. The computational particle trace on the vortex tube wall is very similar to that observed in experiments.     

An oversampled digital PWM linearization technique for digital-to-analog conversion

An algorithmic-based linearization process for uniformly sampled digital pulsewidth modulation (PWM) is described. It is shown that linearization of the intrinsic distortion resulting in uniformly sampled PWM can be achieved by using a fractional delay digital filter embedded within a noise shaping re-quantizer. A technique termed direct PWM mapping is proposed as a pre-compensation filter scheme for applications in high-resolution digital-to-analog conversion.     

Scheduling algorithm for real-time imprecise computations tominimise maximum weighted errors using the linear programmingmethod

An optimal scheduling algorithm for imprecise systems is presented. The proposed algorithm aims at minimising the maximum weighted errors. A novel property of the algorithm is that the errors are evenly distributed among scheduled tasks. The complexity of the proposed algorithm is O(N³) in the worst case, where N is the number of tasks     

Effects of spin inaccuracy on PMD reduction in spun fibers

Spinning a fiber is the most viable and used technique to reduce polarization mode dispersion (PMD). Many papers have shown that by properly tuning the spin parameters, the differential group delay (DGD) of spun fibers can be greatly reduced. However, the precision with which these optimal profiles are practically implemented may be a problem. In this paper, we perform a statistical analysis of the effects that spin inaccuracy may have on fiber PMD, quantifying how the random uncertainty on spin parameters impairs the DGD. Some preliminary experimental results about spin-induced PMD reduction are also reported.     

Thermosonic bonding of lead-free solder with metal bump for flip-chip bonding

While extensive research on the lead-free solder has been conducted, the high melting temperature of the lead-free solder has detrimental effects on the packages. Thermosonic bonding between metal bumps and lead-free solder using the longitudinal ultrasonic is investigated through numerical analysis and experiments for low-temperature soldering. The results of numerical calculation and measured viscoelastic properties show that a substantial amount of heat is generated in the solder bump due to viscoelastic heating. When the Au bump is thermosonically bonded to the lead-free solder bump (Sn-3%Ag-0.5%Cu), the entire Au bump is dissolved rapidly into the solder within 1 sec, which is caused by the scrubbing action of the ultrasonic. More reliable solder joints are obtained using the Cu/Ni/Au bump, which can be applied to flip-chip bonding.     

The rapid thermal processing chemical vapor deposition of silicon epitaxial films

The future of ultralarge-scale integration technology is tending toward reduced thermal processing to realize devices with higher integration densities and better performance. Rapid thermal processing chemical vapor deposition (RTPCVD) is a promising technology that can preserve the advantages of high-temperature processing without degrading the fidelity of junction profiles. Defect free, thin silicon epilayers with extremely abrupt dopant-transition profiles can be re-producibly grown by RTPCVD. Very high quality n-type and p-type heavily doped epilayers, using boron, arsenic, and phosphorus as dopants, have been grown by RTPCVD. Through superior process control and reduced thermal exposure, RTPCVD is expected to play an important part in the next generation of fabrication technology and in the development of novel silicon-based materials.     

A model for computerized procedures based on flowcharts and success logic trees

A model for plant operating procedure based on flowchart and success logic tree has been developed. The tasks in procedures are classified into orthogonal actions and checks, which play the role of building units of the flowchart as well as an execution unit of procedures. Arrows relate actions and checks to indicate proper workflow. An action or a check is further decomposed into basic instructions considering function allocation between man and computer, characteristics of tasks, etc. N-out-of-M operator combines the instructions within a success logic tree. The flowchart and the tree are comprehensible, transparent, and dynamic. Computers support operators to execute the instructions. The effort to make the tree in allowable states is the driving force for an action or check to be executed successfully. This model improves understandings of procedures, minimizes context switching, and maximizes the usage of computers. Finally a computer based procedure complying with the model was implemented and evaluated with procedures after reactor trip.