Evaluation of simple dynamic models and controllers for hydraulic and nozzle pressure in injection molding

Simple pseudo-steady state relations between the hydraulic and nozzle pressures of an injection molding machine were presented and verified experimentally. A simulation study was performed to evaluate the performance of simple controllers using dynamic models developed for the hydraulic and nozzle pressures. The controllers chosen were the discrete proportional, proportional-integral (PI), and proportional-integral-derivative (PID) types, tuned according to the ITAE criterion. The control of hydraulic pressure simulation showed that the PI controller had the best overall performance, whereas the result of nozzle pressure control loop simulation showed that the PID controller performance was better than that of the PI controller. All the controllers, in both loops, gave responses that were about an order of magnitude more rapid than the open loop response.     

A low-level approach to improve programming learning

Universal Access in the Information Society - Learning to program is becoming a universally desired ability. Discovering better ways to teach programming and improving existing ones is essential to...     

Problems of village electrification based on PV systems in Romania: Individual solar home systems for settlements in the Cerna Valley

The autonomous PV systems cover a wide area of the applications that can be developed in the country, in places far from the national grid and with a low demand of electric power. The electrification of homes and farms in rural areas by using PV systems would contribute to improving the inhabitants' social, economic and cultural standard.In Romania, it is estimated that there are about 10,000 homes, farms and schools located in more than 500 settlements which could be electrified by using PV systems. The individual solar home systems would allow each user to adjust his own electricity consumption according to weather variations. A major problem in the development of these systems is the identification of the optimum technical and economic solutions as well as of the main financing sources. The paper aims to present the technical, economic and social problems involved by the implementation of such a project of PV-based electrification in Romania, presenting the particular case of two settlements (Scarisoara and Prisacina) located in the Cerna Valley - the Banat Mountains.     

Fluorescent solar concentrators. Experimental results

A physical characterization is presented for classes of selected fluorescent substances, with special emphasis on their concentration in the support. The influence of climatic factors was analyzed from two points of view: spectral and structural. Two types of geometrical models of fluorescent solar concentrators have been obtained : plates and cylinders.     

Importance of health education at a secondary school: experience with a course on viral hepatitis

The hepatitis C virus is the main causative agent for sporadic as well as parenteral cases of non-A non-B hepatitis. Alpha interferon is a biologically active protein produced by B lymphocytes and monocytes which can be manufactured by recombinant DNA technology. Treatment of chronic hepatitis C with interferon in adults is associated with a sustained response in 20-25% of treated cases. First studies provide encouraging results for the use of interferon in the treatment of chronic hepatitis C in children, but controlled trials using this drug in a larger population of children are needed.     

Diphtheria antitoxin levels in the 14-30-year age group in Italy

Two patients with diabetes mellitus sustained spontaneous calcaneus fracture after deep heel burns. Both cases had avulsion type fracture of the os calcis. The authors discuss the incidence and possible etiology with literature review.     

Dynamics and control of pressure in the injection molding of thermoplastics

A detailed study was carried out to understand the dynamics of pressure variations at different points in the injection-molding system. Thus, hydraulic, nozzle, and cavity pressures were evaluated, in addition to the pressure gradient in the cavity. Both steps and pseudorandom binary sequences (PRBS) were employed to obtain and compare dynamic models describing these variables. Subsequently, these models were employed to evaluate and select optimal controllers for the different variables.