A discrete method of optimal control based upon the cell state space concept

A discrete method of optimal control is proposed in this paper. The continuum state space of a system is discretized into a cell state space, and the cost function is discretized in a similar manner. Assuming intervalwise constant controls and using a finite set of admissible control levels (u) and a finite set of admissible time intervals (), the motion of the system under all possible interval controls (u, ) can then be expressed in terms of a family of cell-to-cell mappings. The proposed method extracts the optimal control results from these mappings by a systematic search, culminating in the construction of a discrete optimal control table.The possibility of expressing the optimal control results in the form of a control table seems to give this method a means to make systems real-time controllable.Dedicated to G. LeitmannThe material is based upon work supported by the National Science Foundation under Grant No. MEA-82-17471. The author is also indebted to Professor G. Leitmann for his many helpful comments.     

药用缓释辅料——羟丙基甲基纤维素的合成及其缓释性能的研究

本文研究了药物缓释材料HPMC的合成方法,探讨了碱纤维素制备,醚化剂浓度,混合醚化剂配经以及产品后处理对高粘度HPMC的影响。本文还初步对KCl,氨茶碱,硝酸异山梨醇酯等药物采用合成的HPMC作辅料,进行了缓释制剂的研究,结果表明合成的HPMC具有满意的缓释性能。     

Some non conventional devices with temperature control design and application

The development of a temperature control system based on semiconductor thermobatteries has been used in a set of devices for studying the martensitic transformation. The devices range from a simple stage for an optical microscope to a more elaborated system as a differential scanning calorimeter [1]. Here the attention is placed in this last system. The general problems of the temperature scanning calorimetry are reviewed from the signal theory point of view and the solutions applied to our system discussed. Some measurements are shown as an example of its application.     

ALLOSTERIC REGULATION OF THE STATE OF ADENYLYLATION OF GLUTAMINE SYNTHETASE IN PERMEABILIZED CELL PREPARATIONS OF Rhoaopseudomonas sphaeroides

Following a freeze-thaw cycle, and the treatment of Rhodopseudomonas sphaeroides withthe nonionic detergent Lubrol PX, the permeabilized cell suspensions can be assayed directlyboth for the intracellular levels of glutamine synthetase and the state of adenylylation(i.e. the average number n of adenylylated subunits/dodecameric molecules). It seems that all components of the bicycle system are retained if cells grown with lowconcentrations of a?monia as the sole nitrogen source are used. The value of n was depend-ent upon the concentration of substrates (ATP, Pi) and allosteric effectors (ATP, gluta-mine and α-ketoglutarate) of adenylyltransferase. The value of n affected by UTP, thespecific substrate of the uridylyltransferase shows first the evidence that the bicycle cascadecontrol system studied in Escherichia coli may exist in this phototrophic bacterium.     

An overview of laboratory performance studies conducted by the IAEA for marine pollution studies of metals and organic contaminants

Aspects of the International Atomic Energy Agency (IAEA) Analytical Quality Control Services (AQCS) for marine environmental studies are discussed, focusing on recent laboratory performance studies (LPS) and the production of reference materials for trace metals and organic compounds in various marine matrices. The IAEA has organized seventeen global interlaboratory studies for a range of organic contaminants. Of note has been the inclusion of numerous polychlorinated biphenyl congeners (PCBs) and some sterols of anthropogenic origin. Concurrently, there have been eleven worldwide intercomparison exercises for trace metals in the marine environment, most of which included methylmercury. Although such interlaboratory studies can help improve performance in individual laboratories and regional laboratory networks, the results reveal that problems remain in the determination of some metals and many organic contaminants.     

Anion control of isomerism, crystal packing and binding properties in a mononuclear zinc complex

The coordination chemistry of the tetradentate pyridyl N-donor ligand cis-3,5-bis-[2-pyridinyleneamin]-trans-hydroxycyclohexane (DDOP) has been investigated with zinc(II) nitrate and triflate. The resulting complexes, [Zn(DDOP)(H₂O)(NO₃)](NO₃) (1), and [Zn(DDOP)(H₂O)(OTf)](OTf) (2) differ not only in their counterions, but also the arrangement of the axial ligands and their solid state hydrogen bonded networks. Isothermal titration calorimetry was used to assess the difference in binding properties exhibited by the two zinc complexes at physiological pH in an aqueous environment. A series of coordinating amino acids were found to preferentially bind to the mononuclear zinc triflate (1) complex over the corresponding nitrate (2) assembly, with histidine exhibiting a two centre binding mode.     

Kinetic modelling of the thermal oxidation of polyisoprene elastomers. Part 2: Effect of sulfur vulcanization on mass changes and thickness distribution of oxidation products during thermal oxidation

Thermal oxidation of sulfur vulcanized polyisoprene samples was studied by gravimetry and IR mapping of carbonyl groups (to determine the oxidized layer thickness (TOL)) at temperatures ranging from 60 to 150 °C in air. Oxidation appears noticeably lower than that for the starting non-vulcanized polyisoprene, revealing a stabilizing effect of sulfur-containing species. After a short period where mass loss presumably due to water evaporation predominates, the sample mass increases until a plateau corresponding to 6.3% (at 60 °C) to 0.5% (at 140 °C) mass gain. Practically no weight gain (∼0.1%) was observed at 150 °C. The mass uptake is due to oxygen grafting to the chains. TOL varies from about 4.6 mm (70 °C) to about 1 mm (150 °C).A kinetic model, derived from a mechanistic scheme of radical chain oxidation including stabilizing events due to hydroperoxide reduction by sulfur-containing groups and taking into account the diffusion-reaction coupling, was established and numerically resolved. The model predictions for mass changes and TOL values are in good agreement with experimental data.     

Steric control over hydrogen bonding in crystalline organic solids: a structural study of N,N'-dialkylthioureas

Hydrogen bonding in crystalline N,N'-dialkylthioureas was examined with the help of single-crystal X-ray diffraction, DFT calculations, and Cambridge Structural Database (CSD) analysis. A CSD survey indicated that unlike the related urea derivatives, which persistently self-assemble into one-dimensional hydrogen-bonded chains, the analogous thioureas can form two different hydrogen-bonding motifs in the solid state: chains, structurally similar with those found in ureas, and dimers, that further associate into hydrogen-bonded layers. The formation of one motif or another can be manipulated by the bulkiness of the organic substituents on the thiourea group, which provides a clear example of steric control over the hydrogen bonding arrangement in crystalline organic solids.     

Optimal dynamic advertising policies for hereditary processes

In this paper, the Nerlove-Arrow model of optimal dynamic advertising policies is generalized by assuming a general probability distribution of the forgetting time, rather than the exponential one. A control problem with integrodifferential equations of motion is defined for which the transitory and steady-state properties of the optimal advertising policy are examined. The effects of assumptions like IHR-distributions and DHR-distributions, the existence of an upper bound for the forgetting time, etc., are explained. It is shown that there are two (in the case of an exponential distribution even three) different current-value adjoint functions associated with the problem, and relations between the two (three) are established. Also provided is a sensitivity analysis.Thanks are due to G. Feichtinger and S. Jorgensen for useful discussions.     

On the minimal time function for distributed control systems in Banach spaces

In this paper, it is shown that the minimal time function is locally Lipschitz continuous for the control systemx=Ax+u in a Banach spadeE, under either of two conditions:A is linear and generates aC ₀-semigroup of bounded linear operators; orA is nonlinear, possibly multivalued, and dissipative. The main tool used for the nonlinear case is a result of Barbu concerning the null controllability of the system.