Monitoring of low plutinium activities in air

The possible methods of monitoring low plutonium activities of the order of 0.1-0.001 MPC (10-0.1 mBq/m³) in the inner and outer atmosphere are analysed and compared. Integral and spectrometric, continuous and discontinuous mode operating monitoring systems are described. Monitors based on gross alpha counting are not sensitive enough to detect reliably plutonium activities below 1 MPC. Surface barrier detectors allow to detect at one hour sampling (and counting) time plutonium activities of the order of 0.1 MPC. A spectrometric, discontinuously operating monitor, using a large area gridded ionisation chamber and a 10 cm diameter membrane filter is described, which allows to detect, at one hour sampling and one hour counting time, plutonium activities below 0.01 MPC.     

连铸的控制冷却

冷却是连铸技术的一个重要部分,气雾冷却喷嘴可以在很大范围内调控水和空气压力,从而控制冷却温度.本文介绍了气雾喷嘴传热系数的测量方法,实验参数与工厂参数一致,变化参数为压力、拉速等.实验测量了传热系数和热流在钢表面的分布.冷却参数对于连铸的设计以及冷却曲线的选择很有用,本文发现在高温区和低温区,冷却强度是有区别的.     

PID controller design of TITO system based on ideal decoupler

The proposed method for designing multivariable controller is based on ideal decoupler D(s) and PID controller optimization under constraints on the robustness and sensitivity to measurement noise. The high closed-loop system performance and robustness are obtained using the same controller in all loops. The method is effective despite the values and positions of the right half plane zeros and dead-times in the process transfer function matrix G_p(s). The validity of the proposed multivariable control system design and tuning method is confirmed using a test batch consisting of Two-Input Two-Output (TITO) stable, integrating and unstable processes, and one Three-Input Three-Output (TITO) stable process.     

Photon-detectors — report on the history and activities of the IMEKO technical committee on photon-detectors (TC-2)

The paper reviews the developments of the technology of photon-detectors as reflected in the work of the relevant IMEKO Technical Committee.     

Remaining load carrying capacity of gas pipelines damaged by surface corrosion

The influence of surface corrosive defects on the remaining working ability of transit gas pipelines of big diameters is discussed. An analytical and a FEM-numerical approach to the problem are presented. Finally a comparison of some of the authors' experimental results (to verify the theoretical solutions) with ANSI/ASME Code recommendations is given.     

Evaluation of correlations between absorbance at 254 nm and COD of river waters

Correlations between the absorbance module at 254 nm (A_{254 nm}^{1 cm}) and COD by the permanganate and dichromate methods in rivers in the lower part of the Odra river basin are given. For the purpose of the conducted study a clean reach of the river, two short reaches with medium and high pollution, especially with lignin and humic substances and phenolic wastes below industrial waste outfalls have been selected. Investigation results from 1973 to 1978 have been evaluated mathematico-statistically: regression equations and empirical relations with average conversion factors and variation coefficient are presented. Relationships between absorbance and COD are also given graphically. Close relations have been found and the absorbance module at 254 nm has been recommended to be used as indicator of organic pollution in selected reaches of the river. The method is suitable for laboratory work as well as automatic monitoring of concentration changes in dissolved organic matter. This work is in relation with the results of many authors who carried out investigations in various localities.     

Adaptive control of PDEs

This paper presents several recently developed techniques for adaptive control of PDE systems. Three different design methods are employed—the Lyapunov design, the passivity-based design, and the swapping design. The basic ideas for each design are introduced through benchmark plants with constant unknown coefficients. It is then shown how to extend the designs to reaction-advection-diffusion PDEs in 2D. Finally, the PDEs with unknown spatially varying coefficients and with boundary sensing are considered, making the adaptive designs applicable to PDE systems with an infinite relative degree, infinitely many unknown parameters, and open loop unstable.     

Cyclotrimerization of isocyanate groups. I. Catalyzed reactions of phenyl isocyanate

Cyclotrimerization of phenyl isocyanate in the presence of various catalysts was studied. All reactions were carried out in 1,4-dioxane at 30–50°C. Reaction products were determined by reverse-phase liquid chromatography. 1,3,5-Triphenyl isocyanurate was formed and also traces of 1,3-diphenylurea and 1,3,5-triphenylbiuret were found. The catalytic activity decreased in the following series: quaternary ammonium salt > organic acid salt ? tertiary amine. Apparent rate constants of cyclotrimerization were calculated and the overall reaction order is discussed. © 1994 John Wiley & Sons, Inc.     

Decentralized and adaptive control of nonlinear fluid flow networks

In this paper we solve a decentralized nonlinear control problem where actuator valves and flow rate sensors are collocated in individual branches and do not exchange information. This is in contrast to our previous paper where a centralized controller required measurements from all the branches of the network. We solve both regulation (constant references) and tracking (time varying reference signals) problems. To eliminate conservativeness in choosing the gains of the controllers, we employ adaptation. We illustrate the results with an example reminiscent of a blood flow network.     

An application of the self-organizing map in the non-Euclidean Traveling Salesman Problem

An application of the self-organizing map (SOM) to the Traveling Salesman Problem (TSP) has been reported by many researchers, however these approaches are mainly focused on the Euclidean TSP variant. We consider the TSP as a problem formulation for the multi-goal path planning problem in which paths among obstacles have to be found. We apply a simple approximation of the shortest path that seems to be suitable for the SOM adaptation procedure. The approximation is based on a geometrical interpretation of SOM, where weights of neurons represent nodes that are placed in the polygonal domain. The approximation is verified in a set of real problems and experimental results show feasibility of the proposed approach for the SOM based solution of the non-Euclidean TSP.