Further considerations of a 1‐subcycle parallel thinning algorithm

Abstract

In this paper, we present two improved versions of a pseudo 1‐subcycle parallel thinning algorithm which we proposed earlier [1] and describe a two‐stage structure to realize the 1‐subcycle parallel algorithm.

The purpose of the first improved algorithm is to produce the P8ET (perfect 8‐curve excluding T‐junction)‐type thin line which is well‐defined in general. This algorithm involves local branches containing T‐junctions or quasi T‐junctions. The second improved algorithm obtains an isotropic skeleton of an L‐shape pattern, such that the visual quality of a skeleton is more satisfactory. In this algorithm, another set of thinning conditions especially designed is also involved.

We also describe a two‐stage structure which consists of a thinning table and a control unit. The thinning table is used to provide the attributes of an input 3×3 local pattern. The control unit is used to check the removal of the center “1” pixel of this local pattern. The inputs of the control unit also comprise the outputs of other neighboring thinning tables. This structure can exactly implement the original 1‐subcycle parallel algorithm. The above‐mentioned algorithms have been implemented on this realized structure in this paper.

Several experiments confirm that the improved algorithms can produce the desired effective thin line, and also show that the realized structure is feasible and practicable.     

Optimal short‐term scheduling of shunt compensators via a decomposition algorithm

Abstract

The short term (one day) scheduling of VAr controllers involves the setting of shunt compensators, EHV taps and generator voltages. A decomposition approach is presented to solve the problem of optimal short‐term scheduling of shunt compensators in this paper. The entire problem is decomposed into two levels: the master and the slave levels. The master level deals with minimization of the depreciation cost of compensators in order to reduce the control actions for compensators while satisfying operating constraints. The slave level treats minimization of capitalized MW losses while satisfying system security constraints by adjusting generator voltages and taps. These two levels interact through linear constraints in the iteration process. The IEEE 30‐bus and a practical 265‐bus systems, namely Taiwan Power System, are used to serve as samples to show the applicability of the presented approach.     

Quality improvement of paper‐sheets by radiation‐induced graftcopolymerization of vinyl monomers onto paper‐cellulose

Abstract

Gamma radiation‐induced graftcopolymerization of serveral vinyl monomers onto paper‐cellulose has been investigated by using four kinds of domestic paper‐sheets. Among the vinyl monomers the ethyleneglycol dimethacrylate‐acryl amide (EGDMA‐A.Amide) system was found to give the best flexibility and the strongest tensile‐strength.

The in situ copolymerization‐rate and the grafting‐rate of the monomer system of EGDMA‐A.Amide were found to be proportional to the 0.46th power and 1.0–1.2th power of the gamma does‐rate respectively. The grafted copolymer‐chains of the EGDMA‐A.Amide System were confirmed by the infrared absorption spectra in which the characteristic absorption bonds of 5.8μ (ester group) and 6.06μ (amide group) were displayed.

The tensile strength of the EGDMA—A.Amide copolymer grafted papers prepared through the gamma dose up to 1.29 Mrad was found to be 1–2.83 times (dry state) and 1.16–3 times (wet state) the sizes of the corresponding original papers under the same state of testing.     

Application of genetic algorithm to the observer‐based controller design for neutral systems

Abstract

In this paper, the dynamic observer‐based controller design for a class of neutral systems with known and uncertain time delays is considered. Delay‐dependent and delay‐independent stabilizability criteria are proposed to guarantee the stability for the feedback control systems. Linear matrix inequality (LMI) and genetic algorithm (GA) are used to design the observer‐based control. Design procedure for the observer‐based control is provided. A numerical example is given to illustrate our results.     

Control of an Error of a Finite‐Difference Solution of the Heat‐Conduction Equation by the Conjugate Equation

The results of the calculation of temperature by the finitedifference method can be verified and the value of the remaining error can be estimated by the conjugate problem with a moderate expenditure of computer resources.     

Elasto‐plastic deformation of upsetting by boundary element method

Abstract

This paper presents the utilization of boundary element method (BEM) to analyze the elasto‐plastic deformation of upsetting problems. Method of successive elastic solutions is used in the nonlinear analysis; both the linear strain hardening and the power law relation are used as constitutive equations of the material. For the later model the slope of strain hardening at each step is modified to a more correct prediction to make the deformation step larger and to obtain better convergence. The result may verify the stress‐strain curve as it does, and verify the similar pattern of the plastic zone propagation as Roll's result by finite element method. It is shown that various frictional conditions and width‐height ratios of the workpiece also influence the propagation behavior of plastic zones.     

A correction on “further considerations of a 1‐subcycle parallel thinning algorithm”

Abstract

A disconnectedness problem which appeared in the 1‐subcycle parallel thinning algorithm [1] is shown and a correct condition is presented to overcome this problem. As a result, to preserve the connectivity of a P8ET‐type thin line, the removal of a (quasi) T‐junction should be guaranteed by its neighbors that do not belong to any one of the commonly used subwindows, mutually opposite subwindows, and T‐junction cases.     

A branch and bound algorithm for scheduling problem of a robot‐centered manufacturing cell

Abstract

An alternative formulation of the scheduling problem in a robot‐centered manufacturing cell has been described here, which was originally formulated by Lin et al. [7] as a mixed integer programming problem. An efficient procedure based on the branch and bound technique has been proposed. In order to reduce the complexity of the branching procedure, several sequencing rules [4] have been imbedded into the proposed procedure and an integrated algorithm has then been presented. The computational results have indicated the proposed algorithm to be efficient. Finally, conclusions and some suggestions are given.     

Analysis of Crystallization of a Supercooled Melt by the Integral‐Balance Method

Using the integralbalance method, the Stefan problem is solved for simply shaped crystals (a prism, a cylinder, and a sphere) grown in a supercooled melt. It is shown that the rate of crystal growth increases with the surfacetovolume ratio (in passage from a prism to a cylinder and a sphere). For all the three shapes of crystals studied the dependence of the speed of motion of the crystallization front on the supercooling is nonlinear and is characterized by a progressive increase.     

Kinetics of Carbon Multi‐wall Nanotube Synthesis by Catalytic Pyrolysis of Methane

Abstract

By method of isothermal gravimetry at 600–700°C, CH₄ concentration 32–100% in Ar and 91–100% in H₂ under atmospheric pressure the kinetics of CH₄ pyrolysis under Ni/La₂O₃ catalysts is studied. Estimated apparent activation energy of reaction is 73 kJ/mol for fresh catalyst and 71 kJ/mol for aged one. The reaction order on CH₄ changes from 1.05 at 600°C to 1.3 at 700°C. The influence of H₂ concentration on the reaction rate is more complicated. On the basis of kinetics measurements continuously working laboratory‐scale reactor with gas and catalyst counter‐flow is constructed and tested.     

Experimental Investigation of the Method of Layer‐by‐Layer Lifting Buildup of Ice in a Bath and in Cellular Cans

A new more rapid method of freezing to obtain ice in baths and cans is set forth, and the results of its experimental testing in a bath and in cellular cans of a thermoelectric ice generator are presented. The choice of the type of cooling system is justified, and the experimental rig and the features of the experimental procedure are described. It is shown that dividing the total thickness of the ice block into 3–4 layers allows attaining a maximum effect in increasing the capacity of the ice generator within 15%. The main factors that determine the efficiency of the layerbylayer lifting buildup of ice were determined and analyzed qualitatively.     

Scattering of electromagnetic pulse from a moving and vibrating perfect plane using characteristic‐based algorithm

Abstract

One‐dimensional numerical simulation results of plane Gaussian electromagnetic pulses reflected from constantly moving and vibrating perfect conductors are provided in this paper. The computational data were obtained using the characteristic‐based algorithm with the aid of relativistic boundary conditions and characteristic variable boundary conditions. Since the perfect conductor can travel and vibrate simultaneously, the size of the grid cell immediately next to the boundary and the corresponding numerical time‐step are time‐dependent. The present numerical method has been shown to accurately handle such problems. In this paper both the reflected electric field intensities and the corresponding spectra are illustrated. The calculated Doppler shifts are found to have good agreement with the theoretical values.     

A design of fast‐locking without overshoot frequency‐locked servo system by fuzzy control technique

Abstract

In this paper, a Fuzzy Pulse Pump Controller (FPPC) is proposed to realize a Fuzzy‐Controlled Frequency‐Locked Servo system (FC‐FLS) for getting a fast locking response without overshoot. A prototype FC‐FLS is designed and built to assess the system performance. In comparison with the Frequency Pump Controller‐based FLS (FPC‐FLS) and Variable Slope Pulse Pump Controller‐based FLS (VSPPC‐FLS), the acquisition times of the FC‐FLS are improved over 40%. In particular, there is no overshoot in the FC‐FLS for any servo distance. This means that a fast‐locking FLS, without overshoot, has been successfully implemented as theoretical prediction.     

Deadlock avoidance algorithm for flexible manufacturing systems by calculating effective free space of circuits†

Modern flexible manufacturing systems (FMS) are highly automated and flexible in which raw parts of various types are processed concurrently. Deadlock issue arises easily in these systems due to shared equipment usage and high production flexibility. It was indicated in Wysk et al . (Wysk, R., Yang, N. and Joshi, S., Detection of deadlocks in flexible manufacturing cells. IEEE Trans. Rob. Auto., 1991, 7, 853–859.) that when a manufacturing system is modelled by a digraph, existence of circuits in such a graph is a necessary condition for deadlock. Deadlock avoidance for systems with free choice in part routing has been well studied in the Petri net formalism, however, we have not found that it has been studied systematically in the digraph formalism. Because of choices introduced, part flow dynamics become much more complex. Based on our previous work Zhang et al . (Zhang, W., Judd, R.P. and Paul P., Evaluating order of circuits for deadlock avoidance in a flexible manufacturing system. Int. J. Prod. Res., 2006, 44, 5247–5259.), this paper presents a deadlock avoidance algorithm for FMS, which allows free choices in part routing by calculation of effective free space of circuits of the digraph model. The algorithm is highly permissive since the effective free space calculation captures more parts flow dynamics, especially when there exist multiple knots in the digraph model. And it runs in polynomial time once the set of circuits of the digraph is computed offline. Simulation results on selected examples are given.     

3‐D spatiotemporal subband decomposition of image sequences by mathematical morphology

Abstract

An efficient 3‐D spatiotemporal image sequence decomposition method using mathematical morphology is described in this paper. The method can be used to decompose the spectrum of the input signal into 8 and 4 spatiotemporal subband images. It does this using two different sets of structuring elements. After decomposition, each band image can be decimated and coded for data transmission. This subband pyramid scheme preserves the number of pixels which existed in the original image, has an efficient hierarchical data structure, and allows parallel implementation. Therefore, this scheme has great potential for High Definition Television (HDTV) coding, multimedium video compression, etc. As regards filtering, the unique advantages of morphology over the linear filtering approach are: 1) it utilizes direct geometric interpretations; and 2) it is simple and efficient when used in conjunction with parallel/pipelining hardware. Some image sequence examples are given to show the effectiveness of this approach.     

Nighttime maintenance of the equatorial ionization by F‐region polarization field

Abstract

The east‐west plasma drift produced by the F‐region dynamo which has been proposed by Rishbeth(16) is included in the continuity equation of electron density, together with other transport and photo‐chemical processes. The numerical solution of the equation reveals that the inclusion of zonal drift has an effect of increasing the maximum electron density N_m during the night, especially just before sunrise. The height h_m of N_m is also increased but at earlier hours. The reasons for these effects are discussed briefly.     

Registration of ground‐based LiDAR point clouds by means of 3D line features

Abstract

Techniques for extracting data from LiDAR point clouds can be refined for increased accuracy. In this paper, the authors elaborate on an innovative approach for registering ground‐based LiDAR point clouds using overlapping scans based on 3D line features. The proposed working scheme consists of three major kernels: a 3D line feature extractor, a 3D line feature matching mechanism, and a mathematical model for simultaneously registering ground‐based LiDAR point clouds of multi‐scans on a 3D line feature basis. All processing chains in this study are featured efficiently and come close to meeting the needs of practical usage. Experiments conducted show the proposed method of employing 3D line features to be a useful alternative or complement to point, surface and other features for LiDAR (Light Detection And Ranging) point clouds registration. It is especially effective in areas rich in man‐made structures.     

Mathematical Model of Oil Displacement by Water with the Use of Polymer‐Disperse Systems

A mathematical model describing the process of displacement of oil by water with the use of polymerdisperse systems is proposed. The point of the technology consists of pumping sequentially water, a lowconcentration polymer solution, and water with disperse particles. The porous medium is given in the form of two interpenetrating continua, one of which is associated with mobile phases and the other — with immobile phases. The corresponding expressions for dynamic porosity and the residual resistance factor have been obtained. In describing the mass transfer between the continua, an ideal model of a porous medium in the form of a bundle of capillaries of different radii and the pore and particlesize distribution functions have been used.