The effects of bleached and unbleached rosemary oleoresins on light-sensitized oxidation of soybean oil

Bleached and unbleached forms of a rosemary oleoresin (RO) in stripped and nonstripped soybean oil behave both as antioxidant and prooxidant in a light-induced oxidative system. At 0.02 and 0.05% levels, RO had the greatest antioxidant activity, while at 0.01 and 0.5% levels it had the highest prooxidant activity in both stripped and nonstripped soybean oil. Treatment of both soybean oil systems with tertiary butylhydroquinone controlled light-induced oxidation of the oil better than did the oleoresin treatments. The prooxidant activity of the 0.5% RO level was probably due to an excess of prooxidant components being carried into the oil at that level, whereas the reduced antioxidant activity at 0.01% was probably due to the low initial level of active antioxidant components being added to the oil. Published as Journal Series No. 10072, Nebraska Agricultural Research Division, Department of Food Science and Technology, University of Nebraska, Lincoln, NE 68583-0919.     

秦安县农村户用改进型沼气池建造的关键技术

近年来,随着我县农村户用沼气建设力度的不断加大,为缓解我县能源资源短缺的现状,通过对农村户用沼气池施工技术及工艺的改进,进行技术集成示范,总结出秦安农村户用改进型沼气池的建造技术,为该地区沼气事业的发展提供科学依据.     

Exploring single electrode reactions in polymer electrolyte fuel cells

Utilising a pseudo-reference electrode in polymer electrolyte fuel cells allows for the separation of anodic and cathodic contributions to the entire cell impedance. Modelling the impedance responses by using equivalent circuits inhibits the investigation of kinetic parameters of the basic electrochemical reactions, which take place at single electrode-electrolyte interfaces. Therefore, we evaluate single electrode impedance measurements by a kinetic model, which is based on specific reaction pathways, either for the oxygen reduction reaction (ORR) or the hydrogen oxidation reaction (HOR). As a consequence, it is possible to obtain kinetic parameters for the specific reaction of interest. Furthermore, the information gained from the single electrode impedance measurements and the kinetic model can give insight into single reactions steps. In particular, the ORR has to include a chemical step in the reaction pathway.     

ESTIMATION FOR NONNEGATIVE AUTOREGRESSIVE PROCESSES WITH AN UNKNOWN LOCATION PARAMETER

Abstract. Consider an AR(1) process given by X ^t=γ+ø X _t+ Z _t≥ 1. where 0 ≤γ, 0 ≤ø 1 are unknown parameters and the innovations Z _t, ≥ 1, are independently and identically distributed positive random variables. We propose estimates of (γø) which are obtained as the solution to a linear programming problem and establish their strong consistency. When the Z _ts have the exponential distribution. our estimate becomes the conditional maximum likelihood estimate given X ₀. Under the assumption of regular variation of the innovation distribution at its left and right endpoints (assumed to be 0 and ∝ respectively), we establish asymptotic limit laws for the estimates. Consistent estimators for a class of moving-average processes with heavy-tailed innovation distribution are also presented.     

THE ROLE OF LATTICE OXYGEN IN THE DYNAMIC BEHAVIOR OF OXIDE CATALYSTS

The lattice of an oxide catalyst used for oxidation reactions can act as a reservoir for oxygen, storing and releasing it for reactions at the catalyst surface under appropriate conditions. The implication of this oxygen storage property of an oxide catalyst on its dynamic response characteristics has been investigated through an experimental study of 2-butene oxidation over vanadium oxide as a model reaction. Isothermal reaction rate measurements in a differential reactor and nonisothermal studies in a single pellet reactor have been carried out. Following a step increase in the feed butene concentration, isothermal reaction rate overshoot and pellet temperature overshoot were observed. These observations could be modelled in a qualitatively correct way by a very simple model accounting for the participation of lattice oxygen in the catalytic reactions under dynamic conditions. It is demonstrated through model simulations that the ignition characteristics of a catalyst pellet are significantly affected by the participation of the lattice oxygen, when steady state multiplicity is present.     

On the nature of the active state of silver during catalytic oxidation of methanol

Under the applied high reaction temperatures (900 K) the Ag surface is restructured and a tightly held oxygen species is formed on the surface (O) apart from O atoms dissolved in the bulk (O). Methanol oxidation to formaldehyde proceeds through this O species as demonstrated by application of a variety of spectroscopic techniques.     

甲缩醛空气氧化制甲醛催化剂的研制和工艺条件探讨

考察了铁钼催化剂对甲缩醛空气氧化制甲醛的催化性能。制备了多种不同钼铁比和第三、第四组分的催化剂,进行了活性评价和筛选,探讨了适宜的工艺条件范围。对于所选定的催化剂(钼铁比为1.82～1.88;铬铁比为0.1～0.38)在适宜的工艺条件(甲缩醛进料浓度4.5～5.5％;甲缩醛和氧气进料比1:2.0±0.2;空速12000～22000h~(-1);热点温度370～390℃)下,甲醛收率可达85％左右。     

An analytical tuning approach to multivariable model predictive controllers

Multivariable model predictive control is a widely used advanced process control methodology, where handling delays and constraints are its key features. However, successful implementation of model predictive control requires an appropriate tuning of the controller parameters. This paper proposes an analytical tuning approach to multivariable model predictive controllers. The considered multivariable plants are square and consist of first-order plus dead time transfer functions. Most of the existing model predictive control tuning methods are based on trial and error or numerical approaches. In the case of no active constraints, closed loop transfer function matrices are derived and decoupling conditions are addressed. For control horizon of one, analytical tuning equations and achievable performances are obtained. Finally, simulation results are used to verify the effectiveness of the proposed tuning strategy.     

环十二烷空气催化氧化制环十二醇及酮

研究了以偏硼酸为催化剂的环十二烷常压空气氧化制环十二醇、酮的反应规律,采用鼓泡搅拌釜作为反应器,在间歇操作方式下,通过改变通氧速率、搅拌转速、反应温度、催化剂用量,测定了反应液中烷、醇、酮的浓度随反应时间的变化关系,得到了醇、酮选择性与烷转化率的关系,确定了适宜的工艺操作条件。在连续操作方式下,通过改变烷的进料速度,测得了反应产物中烷、醇、酮的浓度随空时的变化关系,并与间歇操作获得的实验结果进行了比较。     

SC-1型乙烯裂解炉先进控制系统开发与应用

针对SC-1型乙烯气液相裂解炉控制问题,提出了一种鲁棒性较强的先进控制策略,开发了由“DCS控制层”和“上位机控制层”构成的先进控制系统.该系统有效地解决了燃料热值波动对裂解炉裂解气出口温度的影响,减少了裂解气出口温度和裂解炉总加工量的波动,实现了“卡边”控制及生产过程的安全逻辑保护,优化控制器可一键投运和切除,解决了裂解炉控制问题的复杂性.该系统成功应用于兰州石化46万吨／年乙烯装置,大幅度提高了装置的平稳率,提升了双烯收率,降低了装置能耗.