Volume 25, No. 4 (2019)

HYDROGENOTUNGSTATO COMPLEXES WITH TIN HALOGENURES (IV): INFRARED AND MÖSSBAUER STUDIES

DINORA DE BARROS(1), MOUHAMADOU SEMBENE BOYE(*2), LIBASSE DIOP(1)

Six new hydrogenotungstato adducts and complexes have been synthesized and studied by infrared and Mössbauer techniques. The structures are mainly discrete, the anion behaving as a bidentate -one case- or a monodentate ligand in most cases. When extra hydrogen bonds are considered, supramolecular architectures may be obtained.

NEW CHALLENGES IN ABRASIVE WATER JET MACHINING

CATALINA CIOFU(1*), CATALIN TAMPU(1), EUGEN HERGHELEGIU(1), COSMIN ALEXANDRU IANCU(1), GHEORGHE BRABIE(1)

Abrasive water jet machining (AWJM) is one of the most important method used in cutting different types of materials: alloy sheet, marble, glass, rocks. This process is used in the aeronautic, automotive, metallurgy industries and even in some art techniques and textile industry. The method consists in transforming the kinetic energy of a solid particle directed with water jet at a high pressure to remove material through erosion and abrasion. AWJM is low cost equipment compared to other conventional cutting technologies. This paper is an attempt to review the achievements made in AWJM technology for different hardness materials.

STRESS AND DEFORMATIONS IN TOROIDAL SHELLS WITH ELLIPTICAL TRANSVERSAL SECTION

RADU IATAN(*1), GHEORGHIŢA TOMESCU(1), ION DURBACĂ(1)

The article approaches the analysis of stress and deformation states; in the toroidal shell with the elliptical cross section with two specific positions, relative to the axis of symmetry. The internal pressure of a working environment as well as the effect of its temperature are considered external loads. The two effects may overlap taking into account the elastic state of the shell material.

VARIATION OF HARMONICS EMISSION FROM MODERN LAMPS IN A POWER SUPPLY NETWORK

RÓBERT ISTÓK

The objective of this paper is to prove the relationship between the Total Harmonics Disturbance emission of lamps network and the number of lamps. In the lighting field the LED lighting emission diode is the absolutely winner. The low power consumption and the characteristics of LED made it ideally for most of indoor and outdoor applications. The dimmability of the LEDs which is between 0% and 100% made it ideally for intelligent lighting applications. This large dimmability range could be obtained only with incandescent and halogen bulbs, compare to CFL compact fluorescent lamps where the maximum dimmability is around of 60%. One of the prices of this positive characteristics of modern lamps, is the electromagnetic compatibility EMC. It is well known that the modern lamps have a common part, and this is the electronic ballast. And as all electronics circuits, the electronic ballasts are an important source of EMC noise emission. The noise emission of electronic ballast is mainly conducted emission type. Start from construction of electronic ballast which contains an AC/DC converter and a buffer capacitor the emission of half harmonics is presented too. The emission of half harmonics is proportionally with the cost of lamps, because the cost of lamps depends by the methods used for noise emission rejection too. Typically the cheaper lamps have a higher noise emission than the expensive lamps. Known of noise emission lamps separately is not enough for characterization of low noise emission from lighting network. The low frequency noise emission of a lighting network is lower than in case of a single lamp. The variation of temperature determines a variation of low frequency noise emission too.

APPLICATION OF SYSTEM ANALYSIS IN ORDER TO MONITOR GRAIN SILOS

MOHAMED NAJEH LAKHOUA

After a presentation of the management of grain silos, we present the necessity of the system analysis and the identification of information in grain silos based on the OOPP method (Objectives Oriented Project Planning). This kind of analysis enables an efficient management and monitoring of the activities of grain silos. In fact, the OOPP method constitutes a tool of a global system modeling that allows us to analyze a difficult situation by a hierarchically decomposition until attainment a basic level allowing to an operational planning. Then, the aim of this paper is the application of the OOPP method to the analysis of grain silos which enables us to contribute to the development and deployment of an Information System and monitoring of grain storage.

USE OF THE MICROWAVE ENERGY FOR ALUMINUM WASTE FOAMING

LUCIAN PAUNESCU(1*), MARIUS FLORIN DRAGOESCU(2), SORIN MIRCEA AXINTE(2,3), ANA CASANDRA SEBE(4)

The paper presents an aluminum foam experimental technique using the microwave energy. The raw material was recycling aluminum waste processed by ecological melting and gas atomizing to obtain the fine powder required in the foaming process. The powder mixture was completed with dolomite as a foaming agent. The products had a fine and homogeneous porous structure (pore size between 0.4-0.9 mm). The density (1.17-1.19 g/cm3), the compressive strength (6.83-7.01 MPa) and the thermal conductivity (5.71-5.84 W/m·K) had values almost similar to the foams made by conventional methods.