摘要:

AbstractThe research presented in this paper deals with technical and economical evaluations of tunnelling jobs; it has been carried out in collaboration with Scandinava Macchine S.p.A. of Genoa, a company that for 35 years has constructed, sold and serviced tunnelling equipment. By now, the choice of machinery for constructing tunnels is more or less empirically based on the experience gathered over the years. Owing to the high cost of the equipment it is necessary to limit the possibility of making incorrect evaluations as far as machinery choice and foreseeable employment time are concerned. With this objective, the research we have carried out is aimed towards supplying the means for evaluating the technical/economical implications of the possible alternatives whwn constructing tunnells. The research team deemed that the construction of a stochastic, discrete, at-event simulator could fully satisfy the above requirements.Owing to the complexity and vastness of the considered problem, two independent but interfaceable calculation programs have been set up: the first one is represented by the simulator, and supplies the technical characteristics of the tunnel; the second program, utilizing the first one's outputs, exploits the choices taken into consideration. In the experimental phase hierarchic factorial designs have been employed for the economic evaluation of the alternatives, considering characteristic parameters of the subsurface works.

ISSN:0228-6203    

DOI:10.1080/02286203.1994.11760213

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractIn this investigation the use of general purpose multibody computer programs in the dynamic analysis and control of space applications is demonstrated. The dynamics and control of a three-degree of freedom space crane is examined. An inverse-dynamics procedure is used to evaluate the joint torques that produce the desired trajectory of the end effector. The obtained results are verified using existing general purpose multibody computer programs that employ the augmented formulation in which the generalized joint forces are expressed in terms of the constraint Jacobian matrix and Lagrange multipliers. The relationships between the actual driving joint torques of the space crane and the generalized joint forces expressed in terms of Lagrange multipliers are derived and used to develop a general methodology for the control of space mechanisms using general purpose multi body computer codes. Several algorithms for the motion control of the space crane are examined. These algorithms include the open-loop inverse dynamics control, c10s d-loop proportional plus derivative control, and the combination of the two schemes. A parameteric numerical study is performed in order to examine the accuracy, stability and robustness of the proposed control algorithms under different loading conditions, and different sampling rates.

ISSN:0228-6203    

DOI:10.1080/02286203.1994.11760214

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThree recent model reduction techniques developed in the context of balanced representations are evaluated and applied. to the derivation of simplified models of nuclear reactors. Both transIent and steady-state perfonnances are evaluated. Excellent third reduced-order approximations are obtained when applied to an eleventh order nuclear reactor.

ISSN:0228-6203    

DOI:10.1080/02286203.1994.11760215

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractTThe equalizer described in this paper overcomes some of the problems of robustness and numerical efficiency associated with the existing adaptive FIR Kalman equalizers. It is based on the stabilized Fast A posteriori Error sequential Technique (SFAEST), which is a stabilized version of the Fast Kalman Algorithm. Computer simulation studies confirm that the resulting equalizer is relatively fast and robust, and therefore, suitable for real-time applications.

ISSN:0228-6203    

DOI:10.1080/02286203.1994.11760216

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThe introduction of digital technology to audio electronics has become widespread over recent years and it is becoming increasingly desirable to produce a completely digital power amplifier to take over from its analogue counterpart. Class D amplification, which uses the principle of pulse-width modulation (PWM), can be adapted to perform the role of a completely digital power amplifier. The purpose of this paper is to show how distortion is introduced by the PWM sampling process used in the class D amplifier with particular reference to a bass-midrange amplifier with a bandwidth of 6 kHz. A new sampling process is presented which can enhance the performance of the amplifier by introducing lower levels of distortion compared with the usual natural and uniform sampling processes. In addition it is shown that the new sampling process is suitable for implementation in a completely digital system through the use of a digital signal processor.

ISSN:0228-6203    

DOI:10.1080/02286203.1994.11760217

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThe particular problem addressed here is that of regulating the glucose concentration and possibly the insulin concentration in the blood of the human subject. The state equations which relate the concentrations of plasma glucose and insulin in the metabolic system are obtained. Consequently, the associated pulsed transfer function matrix is derived. An efficient algorithm incorporating a three-term (PID) controller is employed to regUlate the system at hand. It Rhould be emphasized that the required continuous measurement of the glucose concentration involves a long time delay that makes the problem qUite complicated. The presented r~alistic simulation results validate the regulation performance of the proposed algorithm.

ISSN:0228-6203    

DOI:10.1080/02286203.1994.11760218

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThis paper is concerned with the use of digital signal processing for monitoring the chest sounds produced by patients suffering from asthma and other related chest disorders. The requirement is to perform spectral estimation on these sounds, to display the results in an informative manner to the medical user and to store these results in compressed form.Spectral estimation may be achieved using Prony's data model as the underlying signal production mechanism. The use of Prony's method allows spectrographs to be presented that are more informative than those produced by the fast Fourier transform (FFT). The method also leads to a data compression technique that allows the data from overnight monitoring to beefficiently stored.

ISSN:0228-6203    

DOI:10.1080/02286203.1994.11760219

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThe paper presents some further developments mechanistic models for the prediction of the dynamics of cutting forces in helical end-milling operations. Since the dynamic cutting force is pro(KjrtionaJ to the chip thickness, a more accurate algorithm for calculation of the chip thickness variation due to tool geometry, run-out, spindle-tool vibration, workpiece material, and the associated cutting parameters is developed. In addition, the nonlinear force due to the process damping is also taken into account. Therefore, the model can be used to predict and analyze the dynamic cutting force accurately in helical end milling operations over a wide range of cutting conditions. A number of machining experiments were performed to verify the predicted cutting force obtained from this model. A good agreement between the predicted and measured cutting forces is demonstrated.

ISSN:0228-6203    

DOI:10.1080/02286203.1994.11760220

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor