Speed Control of DC Motor with MRPID Controller in the Presence of Noise

Speed control of a DC motor has always been a challenge because of its variable torque. But it becomes more challenging when noise enters the system at its input. Therefore, there is a need of more advanced controllers. In this paper, a multi-resolution proportional integral derivative (MRPID) controller has been proposed to be utilized to control the speed of a DC motor. It works well even in the presence of noise as compared to the conventional PID controller. Also, performance of a PID controller deteriorates when nonlinearity or uncertainty arises in the system. This degraded performance can be improved by utilizing the multi-resolution property of wavelets, which decomposes the error signal into various frequency components. Further, wavelet coefficients of these decompositions are used to generate the control signal for controlling speed of a DC motor. In this paper, performances of a MRPID, a fractional order PID (FOPID) and a conventional PID controllers are compared in the presence of noise for speed control of a DC motor. The results obtained using a MRPID controller are observed to be better in terms of improved transient characteristics and disturbance rejection for a DC motor as compared to those obtained with PID and FOPID controllers.

     

Determination of silver in rocks by a stoichiometric radioreagent radioisotope dilution technique

A rapid procedure for the routine determination of nanogram amounts of silver in rocks is described. After dissolution of the sample with a hydrofluoric-nitric-perchloric acid mixture in the presence of ¹¹⁰Ag tracer, the silver is separated by extraction as the dithizonate into xylene and back-extracted into dilute hydrochloric acid. After evaporation and removal of the hydrochloric acid, the silver is taken up in an acetic acid-sodium tartrate buffer solution and reacted with a constant amount of radioactively labelled iodide. The silver iodide formed is isolated by extraction into amyl alcohol and silver is determined by the ratio of the counting rate of the iodide to that of the silver in the silver iodide complex. Results of the analyses of several U.S. Geological Survey standard rocks are given.     

Eine1H- und13C-{1H}-NMR-Spektren von Stereocopolymeren von Lactid

Ohne Zusammenfassung     

Three-dimensional modelling of discrete particles by superellipsoids

Discrete Elements are used for the simulation of granular materials (sand, ballast) as well as for molecular assemblies. Circles (2D) and spheres (3D) are often used in literature on the Discrete Element Method (DEM) however they represent a strong idealisation of the real geometry. Superellipsoids provide the opportunity to generate a wide variety of three-dimensional geometrical shapes (e.g. sphere, cube, cylinder). The motion of each particle is described by means of rigid body dynamics. Suitable numerical integration methods are necessary which are able to conserve the essential physical quantities like momentum energy etc.. Possible choices are e.g. the explicit Verlet-Leapfrog method for the translation and the explicit fourth order Runge-Kutta method for the rotation. The implemented contact formulation takes damping as well as friction into account. Efficient implementation of the contact search is the main aim of this part of the work. It is subdivided into the neighbourhood search and the local search. A bisection algorithm is used to calculate the gap between two superellipsoids within the search. For the neighbourhood search two binning algorithms were implemented and compared for several packages of particles. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Implementing the Science Teaching Standards Through Complex Instruction: A Case Study of Two Teacher-Researchers

In this case study, an “interpretive collaborative” methodology is applied. The experiences of two elementary teacher-researchers are described, as they explore science teaching and learning in their two nongraded primary classrooms through the process of complex instruction. This study involves three strands: the theoretical base of complex instruction, the on-going collaboration between two experienced teachers, and the Science Teaching Standards in relation to complex instruction. Findings suggest that, because the teacher's role in conducting complex instruction activities is multifaceted and complex, successful implementation of complex instruction and the National Science Education Standards required ongoing collaboration and support among teachers. The teacher-researchers reported that it was their collegial relationship that encouraged them to explore, prepare, and implement inquiry activities or tasks for their students.     

Lysozyme purification from tobacco extract by polyelectrolyte precipitation

Tobacco is widely used as a model plant for feasibility studies of recombinant protein production from transgenic plants. However, dealing with large quantities of biomass to recover recombinant proteins is a challenge for down-stream processing. In this study, the effect of isoelectric precipitation on native tobacco protein was first studied. Among the three acids studied, hydrochloric acid is shown to be more effective than acetic or citric acid, and at pH 4, 60% of native tobacco protein was precipitated by HCl. Egg white lysozyme was used as the model protein to test the feasibility of polyelectrolyte precipitation in protein recovery from tobacco extract. Precipitation of lysozyme at pH 7 was shown ineffective probably because of the interference of polyphenolic acids. However, after isoelectric precipitation at pH 5 poly(acrylic) acid (PAA) was shown to precipitate 85% of the soluble lysozyme when the polymer dosage was increased to 1.5 mg polymer/mg lysozyme, while negligible amounts of native tobacco protein was co-precipitated. Lysozyme precipitation by PAA in tobacco extract obtained at pH 5 was also studied, and lysozyme yield was significant improved.     

Electron photoejection from sodium salts of perylenide (Pe⨪,Na+) and its dianion (Pe2–,2Na+) in tetrahydrofuran. A new transient involving the ejected electron and its nature

Polarization effects in two-photon spectroscopy are here demonstrated to depend critically on the rotational branch being observed, and not just on the vibrational symmetry. This has been experimentally verified for benzene in the gas phase. Ignoring this rotational two-photon effect can and has in the literature lead to misassignments.