Combined Operators Opening Closing

An iajection mol ding machine is operated by hydrauHc power and equipped with an electric motor and hydrauHc pump. The maximum hydrauHc oil pressure is ca 14 MPa (2000 psi). A hydrauHc cylinder opens and closes the mold and holds the mold closed duriag iajection another cylinder forces the screw forward, thereby injecting the melt iato the mold. A separate hydrauHc motor turns the screw to plasticate, homogenize, and pressurize the melt. Control of these movements is a combined function of the hydrauHc and electrical systems (35—37). 

Oil shale deposits in Estonia are exploited either in open pits (typically at a depth <30 m) or underground mines (if depth >30 m) in the ratio 47 wt% to 53 wt% (Eesti Polevkivi Ltd. 2003). The largest underground mine, the Estonia mine, reaches depths of 40-70 m the smaller Viru mine is still in operation, whereas the Ahtme mine was closed by 2002 (for locations, see Fig. 3). There are two open pit mines in operation, Narva and Aidu , with a combined production of 5.5 Mt in 2002 (Eesti Polevkivi Ltd. 2003) and yielding shales with calorific values of 8.3-9.0MJ/kg (Koel 1999). 

The solution is introduced into the drum, which is then closed with a lid and set in motion for one or more hours. A side lid is then opened permitting alcohol to evaporate thereby gradually predrying the powder. During the latter operation a small amount of graphite is added so that its total content amounts to 0.25-0.3%. The evaporation of alcohol from the drum may be combined with the recovery of this solvent. For this purpose the lid is not removed but connected with a duct producing a reduced pressure within the drum. The solvent thus drawn off is then recovered either by condensation or adsorption. 

Each spin orbital is a product of a space function fa and a spin function a. or ft. In the closed-shell case the space function or molecular orbitals each appear twice, combined first with the a. spin function and then with the y spin function. For open-shell cases two approaches are possible. In the restricted Hartree-Fock (RHF) approach, as many electrons as possible are placed in molecular orbitals in the same fashion as in the closed-shell case and the remainder are associated with different molecular orbitals. We thus have both doubly occupied and singly occupied orbitals. The alternative approach, the unrestricted Hartree-Fock (UHF) method, uses different sets of molecular orbitals to combine with a and ft spin functions. The UHF function gives a better description of the wavefunction but is not an eigenfunction of the spin operator S.2 The three cases are illustrated by the examples below. 

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