Exact analytical solution to ultrasonic interfacial reflection enabling optimal oil film thickness measurement

The ultrasonic reflection from a lubricated interface has been widely analyzed to measure fluid film thickness, with different algorithms being applied to overcome measurement accuracy and resolution issues. Existing algorithms use either the amplitude or the phase angle of the ultrasonic interfacial reflection. In this paper, a new algorithm (named the “exact model – complex”) that simultaneously utilizes both the amplitude and the phase of the complex ultrasonic reflection coefficient is proposed and mathematically derived. General procedures for theoretical analysis in terms of measurement accuracy and uncertainty are proposed and applied to the new algorithm, the beneficial features of which (as compared to other existing algorithms) can be summarized as: 1) a direct calculation, instead of an iterative approximation, 2) guaranteed maximum measurement accuracy, and 3) acceptable measurement uncertainty. None of the existing methods have showed this combination of benefits. Moreover, two groups of raw data from previous experimental studies are utilized to further validate the practical feasibility of the new algorithm. Overall, the proposed “exact model – complex” algorithm fully exploits the potential of ultrasonic reflection for oil film thickness measurement, with an accurate and a convenient calculation suited to practical implementation

The major achievements of grain storage in P. R. China

During the past several decades, China has made great progress in grain storage research, which greatly improved and promoted grain storage techniques and facilities. Especially in the 1990s, modern grain storage depots were constructed, in which four new technologies of grain inspection automation, machinery aeration, grain cooling, and phosphine recirculating fumigation were popularized. The main technologies to phase out methyl bromide in national depots are under-film phosphine recirculation fumigation and mixing fumigation of phosphine and carbon dioxide. In grain storage scientific research, research programs from applied to molecular fields have been implemented in institutes and universities. The 4th national survey of stored grain insects showed 270 species including 44 natural enemies were recorded. Among these stored grain insect pests the psocid, Liposcelis bostrychophila is generally more prevalent in stored grain with high moisture content. Hence, bionomics, ecologies, control measures, and molecular biology have being conducted since 1990s, and many achievements have been obtained. Efficacy of new grain protectants such as diatomaceous earth and spinosad against the main stored grain insects were evaluated. Researches on effective concentration of phosphine, application technique, recirculation fumigation, combination phosphine with carbon dioxide, and phosphine resistance mechanism were executed. Other fumigants tested included ethyl formate, carbon disulfide, and sulfuryl fluoride against stored grain insects were evaluated, or reevaluated. The fumigation activities and mechanisms of ethyl formate to the main stored product insects were systemically studied and the results showed ethyl formate controlled Sitophilus oryzae, Tribolium castaneum, Rhyzopertha dominica and Liposcelis bostrychophila effectively in a very short time, and the fumigation efficacy at relatively low temperature was better than that at relatively higher temperature. With the rapid progress of technology and scientific research, the objectives of high quality, high nutrition, high benefit, low waste, low pollution, and low cost in grain storage will be achieved, even during prolonged storage.Keywords: Review, Grain storage, Insect pest control, Fumigants, Psocid

Fumigation activities of ethyl formate on different strains of Liposcelis bostrychophila

The psocid, Liposcelis bostrychophila is a prevalent insect pest in large grain depots in P.R. China. Our previous research proved that ethyl formate killed psocid adults of susceptible strain within 24 h, and the fumigation efficacy at relatively low temperature was better than that at relatively high temperature. In this paper, fumigation activities of ethyl formate on DDVP and PH3 resistant strains of L. bostrychophila were studied by the sealed jar fumigation method under different ethyl formate concentrations, fumigation times, and temperatures. Results showed that treatment time and concentration significantly affected fumigation effectiveness of ethyl formate against L . bostrychophila adults at 30oC. The 50% lethal concentrations (LC50) of ethyl formate against two resistant strains increased as the temperature increased from 20o to 30oC. At 27±0.5oC and 24 h fumigation, the LC50 were significantly lower for DDVP and PH3 resistant strains than that of the susceptible strains and the LC50 of DDVP resistant strains were significantly lower than that of PH3 resistant strains. Keywords: Fumigation activity, Ethyl formate, Liposcelis bostrychophila, Resistant strai

Microstructure and superconducting properties of hot isostatically pressed MgB2

Bulk samples of MgB2 have been formed by hot isostatic pressing (HIPping) of commercial powder at 100MPa and 950=B0C. The resulting material is 100% dense with a sharp superconducting transition at 37.5K. Microstructural studies have indicated the presence of small amounts of second phases within the material, namely MgO and B rich compositions, probably MgB4. Magnetisation measurements performed at 20K have revealed values of Jc=1.3 x 106A/cm2 at zero field, and 9.3 x 105A/cm2 at 1T. Magneto optical (MO) studies have shown direct evidence for the superconducting homogeneity and strong intergranular current flow in the material.Comment: 3 pages, 6 figures, text updated, new references included and discussed. Submitted to Superconductor Science and Technolog

Enhancement of Critical Current Density in low level Al-doped MgB2

Two sets of MgB2 samples doped with up to 5 at. % of Al were prepared in different laboratories using different procedures. Decreases in the a and c lattice parameters were observed with Al doping confirming Al substitution onto the Mg site. The critical temperature (Tc) remained largely unchanged with Al doping. For 1 - 2.5 at.% doping, at 20K the in-field critical current densities (Jc's) were enhanced, particularly at lower fields. At 5K, in-field Jc was markedly improved, e.g. at 5T Jc was enhanced by a factor of 20 for a doping level of 1 at.% Al. The improved Jcs correlate with increased sample resistivity indicative of an increase in the upper critical field, Hc2, through alloying.Comment: 17 pages, 4 figures, to be published in Superconductor Science and Technolog

On the Ultraviolet Behaviour of Newton's constant

We clarify a point concerning the ultraviolet behaviour of the Quantum Field Theory of gravity, under the assumption of the existence of an ultraviolet Fixed Point. We explain why Newton's constant should to scale like the inverse of the square of the cutoff, even though it is technically inessential. As a consequence of this behaviour, the existence of an UV Fixed Point would seem to imply that gravity has a built-in UV cutoff when described in Planck units, but not necessarily in other units.Comment: 8 pages; CQG class; minor changes and rearrangement

Intense vortex pinning enhanced by semicrystalline defect traps in self-aligned nanostructured MgB2

In this work, we report the discovery of a vortex pinning source: semicrystalline defect wells in self-aligned nanostructured MgB2. It is demonstrated that these aperiodic regions trap numerous crystal defects migrating along nanodomain boundaries during self-alignment and act as intense vortex pinning centers that significantly enhance the high-field performance of MgB2. This suggests that the density of trapped defects in the wells is much greater than that found in other vortex pinning sources