苦荞挂面中芦丁含量测定方法研究

建立HPLC方法测定苦荞挂面中芦丁的含量。采用Kromasil C18色谱柱(4.6mm×250mm,5μm),流动相:甲醇-0.2%磷酸溶液(55∶45),流速为1.0mL·min-1。芦丁在1-20μg.mL-1范围内有良好的线性关系(r=0.9996),平均回收率(n=6)为99.0%。该方法快速、准确、重复性好,为苦荞挂面的品质评价提供了一种快速准确的检测方法。     

Ultrasound-assisted leaching of rare earths from the weathered crust elution-deposited ore using magnesium sulfate without ammonia-nitrogen pollution

The in situ leaching process of China's unique ion-adsorption rare earth ores has caused severe environmental damages due to the use of (NH₄)₂SO₄ solution. This study reports that magnesium sulfate (MgSO₄) as a leaching agent would replace (NH₄)₂SO₄ by ultrasonically assisted leaching to deal with the ammonia-nitrogen pollution problem and enhance leaching process. At leaching conditions of 3 wt% MgSO₄ concentration, 3:1 L/S ratio and 30 min, the total rare earth leaching efficiency reaches 75.5%. Ultrasound-assisted leaching experiments show that the leaching efficiency of rare earths is substantially increased by introducing ultrasound, and nearly completely leached out after two stage leaching process. Thus, ultrasonic-assisted leaching process with MgSO₄ is not only effective but also environmentally friendly, and beneficial to leach rare earths at laboratory scale.     

Sequencing and due-date determination in the stochastic single machine problem with earliness and tardiness costs

This paper studies the problem of simultaneous due-date determination and sequencing of a set of n jobs on a single machine where processing times are random variables and job earliness and tardiness costs are distinct. The objective is to determine the optimal sequence and the optimal due-dates which jointly minimize the expected total earliness and tardiness cost. We present an analytical approach to determine optimal due-dates, and propose two efficient heuristics of order O(n log n) to find candidates for the optimal sequence. It is demonstrated that variations in processing times increase cost and affect sequencing and due-date determination decisions. Our illustrative examples as well as computational results show that the proposed model produces optimal sequences and optimal due-dates that are significantly different from those provided by the classical deterministic single machine models. Furthermore, our computational experiments reveal that the proposed heuristics perform well in providing either optimal sequences or good candidates with low overcosts.     

Ca2+ induced Fe(CN)63−/4− electron transfer at Pt supported BLM electrode

The effect of Ca²⁺ on the electron transfer of Fe(CN)₆^3−/4− couple at Pt supported lecithin (PC)/cholesterol (CH) bilayer lipid membrane (BLM) electrode has been studied by voltammetry and ac impedance spectroscopy. Experimental results suggest that the interaction of Ca²⁺ with the BLM can open some kind of channel for Fe(CN)₆^3−/4− ions, allowing increased access of the redox couple to the electrode surface. This phenomenon may be related to the Ca²⁺ regulation or activation effect of ion channel in some biomembranes.     

Finite element analysis of temperature field with phase transformation and non-linear surface heat-transfer coefficient during quenching

I.IntroductionItiswell-knownthatthemechanicalpropertiescanbeimprovedbyquenchingtechnique.Thetemperaturefieldofworkpiecehasagreatinfluenceupontheresiduals'ressesandmicrostructureafterquenching.Thus,thecalculationoftemperaturefieldduringquenchinghasbeenthesubjectofmanyinvestigations.Inthepastresearches,thesurfaceheat-transfercoefficientshavebeenusuallytreatedasconstantitmayleadtotheerrorofcalculationintheanalysisoftemperature.Infact,thesurfaceheat-transfercoefficientsarethenonlinearfunctionofte…     

The stability in neural networks with interneuronal transmission delays

1.IntroductionInthispaper,westudythefollowingmodelofaneuralwithnunits:inwhichfi(t)correspondstothemembranepotentialofthei-thunitattimet;h(xj)denotestheconversionofthemembranepotentialofthe.l-thunitsintoitsfiringrate:coildellotesthestrengthofthej-thunit;accorrespondStothetransmissiondelayalongtheaxonofthe.j-thunit;theConstantpid,enotestheexternalbiasorclampedinputfi-omoutsidethenetworktothei-thunit:hirepresentstheratewithwhichtheI-thLlnltwillresetitspotentialtotherestingstateinisolationwhendis…     

Inégalité entropique pour un solveur conservatif du système de la dynamique des gaz en coordonnées de Lagrange

We show that a conservative scheme for the one dimensional Lagrangian formulation of the system of gas dynamics is entropic. The proof relies only on the first principle of thermodynamics, the concavity of the entropy, and a property of the scheme.     

On minimizing resource consumption with constraints on the makespan and the total completion time

We investigate a single machine scheduling problem where the resource consumed depends on the release times of jobs. The objective is to minimize the total consumption subject to a constraint on the makespan or the total completion time. Results by Li are extended to the case where the consumption function is convex decreasing. A further extension to multiple consumption functions is shown. Conditions for feasibility are developed in each case.     

A micro-investigation on water bridge effects for unsaturated granular materials with constant water content by discrete element method

The most common state of surface soil is unsaturated. Changes in water content will substantially impact its strength, leading to geological and engineering catastrophes. This paper used LIGGGHTS software to simulate the water bridge effect of unsaturated granular materials with constant water content and verify the rationality of the simplification of the stress-force-fabric (SFF) relationship. The results showed that the capillary force was not isotropic, which was different from the previous study, thus it cannot be overlooked in the simplification of the SFF relationship. Moreover, the influence of water content on the macroscopic mechanical behavior of unsaturated granular materials was interpreted through the evolutions of coordination number, interparticle force, fabric and force anisotropy, and other microscopic parameters. Compared to the literature, we found that different water bridge models would not change the characteristics of the solid skeleton.     

Optimal design of gas distributor in fluidized bed for synthesis of silicone monomer

The structure of the gas distributor is closely related to the production efficiency of organosilicon monomers. To improve the production efficiency of organosilicon monomers, this study uses Eulerian-Eulerian two fluid model and proposes a design formula for the gas distributor to optimize the gas distributor. It is proposed that the pressure drop of the gas distributor, the velocity nonuniformity coefficient, the relative standard deviation of the solid holdup, and the solid particle dispersion coefficient are used to evaluate the performance of the gas distributor. The results show that the performance of the gas distributor is significantly improved when the opening ratio Φ = 0.53% is optimized to Φ = 0.18%, in which the relative standard deviation of the solid holdup is reduced by 22%, and the solid particle dispersion coefficient is reduced by 40%. On this basis, this article studies the influence of different arrangements of vent holes on gas-solid fluidization characteristics. The results show that the circular arrangement of vent holes is helpful to the mixing of gas and solid.