Abstract. Starting from some theoretical considerations, the article presents some experimental results on the assessment of dry and viscous friction forces that occur in the operation of hydraulic cylinders, the basic elements from the structure of hydraulic drive systems. It also presents some specific aspects regarding the durability of the seals of hydraulic cylinders, in order to increase lifetime of hydraulic cylinders, respectively lifetime of hydraulic drive systems. IntroductionAs it is known, improving energy efficiency of industrial machinery and equipment is a constant direction of activity for researchers and manufacturers of such products. On this line, a couple of theoretical and experimental research activities have been developed in order to find new technical solutions for driving, and also to assess/quantify their effects in terms of energy, with a goal to improve efficiency of various drive systems. Such research activities have also been conducted for hydraulic and pneumatic drive systems (Fluid Power systems), and the results obtained were very good, especially in cases when electronic control and adjustment systems have been comprised in the hydraulic actuators, this meaning also applying information technology in drive processes and developing intelligent hydraulic drive systems. To improve energy efficiency of hydraulic drive systems, an important direction of action was to increase energy efficiency of each individual component, targeting a decrease in fluid flow and pressure losses, in energy losses, generally speaking, and correspondingly targeting increased efficiency rates and prolonged life span of components.One of the most important components of hydraulic drives is represented by hydraulic drive motors, which convert hydrostatic energy into mechanical energy. There are three types of hydraulic motors, namely: linear, rotary and reciprocating hydraulic motors. This paper discusses issues concerning the linear hydraulic motors, also generically known as "hydraulic cylinders" and presents some experimental research activities conducted in the institute INOE 2000-IHP in Bucharest, Romania, aiming to assess the total energy losses in the operation of a hydraulic cylinder and increase the life span of these components. These total energy losses include viscous friction losses occurring on fluid flow [1], friction losses that occur in the hydraulic cylinder rod seal [2], friction losses that occur in the hydraulic cylinder piston seals [3] and [4], and also dry (or Coulomb) friction energy losses in rod and piston guides.An important part in increasing the life span of the hydraulic cylinders is played by durability of sealing systems, which are the first causing decommissioning of hydraulic cylinders.

The article presents a solution for solving the problems of eco-efficient combustion of pelletized or chopped and dried agricultural and forest residual biomass, using the TopLit UpDraft (TLUD) gasification process. By using this solution, thermal energy is produced, and about 10�20% residual charcoal, not transformed into gas, called biochar, too. Biochar is a good amendment for agricultural soils and reduces the concentration of CO2 in the environment by capturing carbon in the soil for long periods. Biochar acts in the soil like a sponge that can absorb up to five times its own weight; it stores water and nutrients and allows microorganisms to settle inside its pores. A bench for testing combustion in TLUD gasifiers, developed in is equipped with a data acquisition program, designed in LabView, with a user-friendly our laboratory, is presented; it graphical interface that displays all acquired parameters and the related graphs in real time for various operating modes and for various types of biomass. The production temperature and the amount of air in the gasifier are the main factors that impinge on the physico-chemical properties of the biochar. The data acquired from two combustion tests carried out with a primary air / secondary air ratio of 1/3 and 1/2, respectively, are presented, from which it turns out that that gasification (in our case, gasification of pellets) with lower speed results in a larger amount of biochar, hence a more eco-efficient combustion, with significant benefits for the environment.

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Some industrial applications like electrical discharge machining involve large currents and voltages that can lead to severe EMC (electro-magnetic compatibility) problems. These environments are susceptible to large surges of electricity which may potentially damage the sensible modules/devices or may modify commands sent over communication lines. One solution to reduce the magnitude of these problems is the galvanic isolation, especially by using optical medium for sensible signals like switching and discharge commands. The paper focuses on practical aspects of implementing galvanic isolation using optocouplers and fiber optics between microcontroller-based control board and power board with switching devices, as well as measuring the delays on the signal chain.

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