Analysis of the Stability of Floating Ice Blocks

Determining the conditions under which an approaching ice floe becomes entrained under an intact ice cover is a fundamental component of any numerical model that attempts to successfully predict ice-jam formation or ice-jam release events. Current stability theory is based on empirical relationships that attempt to characterize stability on the basis of Froude number. This paper seeks to evaluate the stability of floating ice blocks though a force-moment analysis, building on previously published experimental results that measured the dynamic pressures beneath a floating ice block under various thickness-to-depth ratios and flow velocities. The experimental results were extended to measure the dynamic pressures beneath a block that had rotated about its downstream corner until the top upstream corner was at the water surface elevation, giving an indication of how the submerging force and underturning moment changes as the block begins to rotate. The force-moment analyses developed in this paper were compared with previously published observations of block entrainment and were found to match those observations well.     

Wizard of Oz support throughout an iterative design process

The Wizard of Oz prototyping approach, widely used in human-computer interaction research, is particularly useful in exploring user interfaces for pervasive, ubiquitous, or mixed-reality systems that combine complex sensing and intelligent control logic. The vast design space for such nontraditional interfaces provides many possibilities for user interaction through one or more modalities and often requires challenging hardware and software implementations. The WOz method helps designers avoid getting locked into a particular design or working under an incorrect set of assumptions about user preferences, because it lets them explore and evaluate designs before investing the considerable development time needed to build a complete prototype.     

High-Temperature Superconductivity: The Hole-Pairing Is s-Wave, and the Holes Are on the SrO, BaO, or Interstitial Oxygen

Muon spectroscopy experiments (⁺SR) on YBa₂Cu₃O₇ have shown since 1987 that the hole-pairing is s-wave rather than d-wave (as claimed in 1994 by Sonier et al.). New data taken for a high-quality crystal in a large applied field of 60 kOe show that the claims of d-wave pairing are invalid and based on a misinterpretation of what is actually fluxon-reordering. Several experiments have shown that the holes of high-T _c superconducting oxides reside in the SrO, BaO, or interstitial oxygen regions, and not in the cuprate-planes. These include: (i) successful predictions that PrBa₂Cu₃O₇ and three other compounds would superconduct, because the superconductivity is in the BaO or SrO layers (not in the cuprate-planes); (ii) successful demonstration that a Pr-on-a-Ba-site defect (above a cuprateplane) is a magnetic pair-breaker that kills superconductivity, but that Pron-a-Pr site (below the plane) does not destroy superconductivity, although the two sites are virtually the same distance from the cuprate-plane; (iii) evidence that cuprate-plane free Sr₂YRuO₆ has an onset of superconductivity at 49 K when doped with Cu on Ru sites, which nearly coincides with the onset temperatures of R_2–z Ce _z Sr₂Cu₂RuO₁₀ (for R=Eu or Gd) and GdSr₂Cu₂RuO₈, presumably because the SrO layers, not the CuO₂ planes, superconduct in all three types of compounds; (iv) data indicating that all high-temperature oxide superconductors are p-type and have electronically paired holes; and (v) evidence that the pairing is similar for the cuprates and the ruthenates, and for some organics where sulfur carries the holes.     

High-power, high-repetition rate pulser for photo-impulse ionized lasers

The design and operational parameters of a high-power pulser suitable for a photo-impulse ionized laser are presented. The relatively compact device utilizes a ceramic thyratron in a triggered resonant charging circuit. Efficient operation at repetition rates up to 40 kHz, with pulsed powers in excess of 2 MW and average powers of several kilowatts has been achieved.     

Modified application of describing functions in the determination of limit cycles for relay systems

A modified method for the study of limit cycles in relay systems using a describing-function approach is presented. Results of applying the method in three systems are quoted. The method is appropriate for situations in which the normal describing function approach fails to predict a limit cycle.     

Effects of supporting electrolytes on copper electroplating for filling through-hole

The filling of micron through-holes (THs) in a printed circuit board (PCB) by copper electroplating was investigated in this study. The role of supporting electrolytes, such as H₂SO₄, Na₂SO₄ and K₂SO₄, was explored using practical TH filling plating and linear-sweep voltammetry (LSV) analysis of plating solutions. The copper could selectively fill THs using one organic additive, namely, tetranitroblue tetrazolium chloride (TNBT), as an inhibitor. The inhibiting strength of TNBT depended on the supporting electrolytes. Although H₂SO₄ could enhance the inhibiting strength of TNBT, it also decreased the filling capability of the copper plating solution; Na₂SO₄ and K₂SO₄ did not enhance the inhibiting strength of TNBT but they increased the filling capability of the copper plating solution. Additionally, the protons could chemically interact with TNBT to form precipitate, whereas sodium and potassium ions did not easily interact with TNBT. The filling capability of the copper plating solution using Na₂SO₄ and K₂SO₄ as supporting electrolytes could be greatly improved by adding a small amount of bis(3-sulfopropyl)-disulfide (SPS) and poly(ethylene glycol) (PEG) with a molecular weight of 600.