The railgun force in the presence of secondary arcs

A model of the railgun forces in the presence of a secondary arc has been developed. The model approximates the railgun rails as parallel, circular, cross-sectional wires, and the armature and secondary arc as filaments. The classical railgun force equation has been generalized, and its correspondence to an equivalent electrical circuit has been identified. It is shown that the forces tend to drive the primary and secondary arcs together or apart, depending on their separation and the magnitude of the currents flowing in the primary and secondary arcs     

Numerical and experimental investigation of preform design in non-axisymmetric warm forming

This paper describes a numerical and experimental investigation of preform design in non-axisymmetric warm forming in order to achieve a large reduction in the volume of flash. A titanium TA2 watch-case-like component was used as an example. Sixteen different shapes of hollow preforms were specially designed for finite-element simulation. Their diameters of the center-holes were designed based on the values of the diameters of end-face configurations of punches and ejectors. The corresponding thicknesses of the preforms were determined by the assumption of constant volume. Under the same processing conditions, the diameter of center-hole of the preform should be the inner diameter of ejector such that its volume of flash was able to be greatly reduced to 6% of the volume of the formed component whereas the volume of flash was approximately 25% in the conventional implementation. Experiments were subsequently performed to verify the simulation results. This study rationally demonstrates the success of the preform design for warm forming of non-axisymmetric components, and provides great improvement in the utilization of material in the bulk forming process. Thus, the achievement is a tremendous saving in materials, more than a fourfold, particularly for these rare and expensive alloys.     

A monolithic current-mode CMOS DC-DC converter with on-chip current-sensing technique

A monolithic current-mode CMOS DC-DC converter with integrated power switches and a novel on-chip current sensor for feedback control is presented in this paper. With the proposed accurate on-chip current sensor, the sensed inductor current, combined with the internal ramp signal, can be used for current-mode DC-DC converter feedback control. In addition, no external components and no extra I/O pins are needed for the current-mode controller. The DC-DC converter has been fabricated with a standard 0.6-/spl mu/m CMOS process. The measured absolute error between the sensed signal and the inductor current is less than 4%. Experimental results show that this converter with on-chip current sensor can operate from 300 kHz to 1 MHz with supply voltage from 3 to 5.2 V, which is suitable for single-cell lithium-ion battery supply applications. The output ripple voltage is about 20 mV with a 10-/spl mu/F off-chip capacitor and 4.7-/spl mu/H off-chip inductor. The power efficiency is over 80% for load current from 50 to 450 mA.     

A surrogate model to assess the whole body SAR induced by multiple plane waves at 2.4?GHz

The assessment of the exposure to electromagnetic waves is nowadays a key question. Dealing with the relationship between exposure and incident field, most of previous investigations have been performed with a single plane wave. Realistic exposure in the far field can be modeled as multiple plane waves with random direction of arrival, random amplitude, and random phase. This paper, based on numerical investigations, studies the whole body specific absorption rate (SAR) linked to the exposure induced by five random plane waves having uniformly distributed angles of arrival in the horizontal plane, log-normal distributed amplitudes, and uniformly distributed phases. A first result shows that this random heterogeneous exposure generates maximal variations of ??25% for the whole body specific absorption. An important observation is that the exposure to a single plane wave arriving face to the body, used for the guidelines, does not constitute the worst case. We propose a surrogate model to assess the distribution of the whole body SAR in the case of an exposure to multiple plane waves. For a sample of 30 values of whole body SAR induced by five plane waves at 2.4?GHz, this simple approach, considering the resulting SAR as the sum of the SAR induced by each isolated plane wave, leads to an estimated distribution of whole body SAR following the real distribution with a p value of 76% according to the Kolmogorov statistical test.     

Copper deposition onto silicon by galvanic displacement: Effect of Cu complex formation in NH4F solutions

Copper was deposited onto rotating Si substrates by galvanic displacement in 6.0 M NH₄F to determine the effects of Cu complex formation on deposition rates. Deposition rates decreased with increasing rotation speed, indicating that Cu(I) intermediates, stabilized by NH₃, diffuse away from the Cu surface before they reduce to Cu(0). UV-visible spectra of contacting solutions and direct measurements of mass changes resulting from Cu deposition and Si removal confirmed this proposal. These findings contrast those reported previously for deposition from HF solutions, in which Cu(I) species are unstable and reduce rapidly to Cu(0). These data and mixed-potential theory were used to develop a reaction-transport model that accurately describes the effects of mass transfer and electrochemical reaction rates on Cu deposition dynamics and open-circuit potential (OCP) values. The effects of ascorbic acid and tartrate additives on film properties and formation rates were also examined. Cu reduction kinetics decreased significantly when ascorbic acid (0.01 M) was present. Adhesion of Cu films was improved when ascorbic acid was used, but internal stresses caused films to distort when their thicknesses exceeded 100 nm. Adding potassium sodium tartrate to solutions containing ascorbic acid decreased film stresses and led to robust films with excellent adhesion.     

Flavor reversion in soybean oil

Summary A simulated soybean oil has been synthesized from purified fatty acids. The flavor characteristics of the oil after heat and light treatment are described and compared to those of soybean and cottonseed oils. The generous financial assistance of the National Association of Margarine Manufactures is gratefully acknowledged. Contribution No. 613 from the Department of Chemistry, University of Pittsburgh.     

Effect of cellulose-derivatives and emulsifiers on creep-recovery and crumb properties of gluten-free bread prepared from sorghum and gelatinised cassava starch

The effect of cellulose-derivatives and emulsifiers on the creep-recovery behaviour of gluten-free dough prepared from gelatinised cassava starch and sorghum was studied. Cellulose treated doughs, except the treatment with 2.4% w/w fwb CMC, had lower resistances to deformation (range 10–33%) than emulsifier-treated doughs (range 3–13%). The higher elastic recovery of emulsifier-treated doughs corresponded to lower compliances and higher zero shear viscosities than for doughs treated with cellulose-derivatives. Addition of egg white powder (6.7% w/w fwb) eliminated several textural defects associated with gluten-free bread. Cellulose-derivatives did not decrease crumb firmness or staling rate when compared to the control. Though increasing emulsifier concentration (from 0.4% to 2.4% w/w fwb) decreased crumb firmness, crumbs treated with 2.4% w/w fwb emulsifiers, except diacetyl tartaric acid esters of mono- and diglycerides, were weak and difficult to handle after slicing. Nevertheless, all gluten-free breads treated with 2.4% w/w fwb emulsifiers staled at a slower rate than the control.     

The effect of resin finish on the dimensional stability of cotton knitted fabric

In this article, the effect of resin finish on the degree of set is discussed. Furthermore, the relationship of the degree of set and dimensional stability is analyzed. After relaxation treatments, the yarns in a fabric would be set at a certain level. As the fabric is subjected to prolonged relaxation treatments, the yarn will become more set until the shape of the unraveled yarn is similar to the shape of the loop in the fabric. The yarn that is removed from a knitted fabric has a curvature value close to zero, and the curvature is exactly as the corresponding position at the knitted loop. From previous research, it is known that the degree of set affects the dimensional properties in a plain knitted fabric. In this article, the degree of set increases with resin level. It explains why the resin finish can stabilize the dimensional properties indirectly.