Evolving IT management frameworks towards a sustainable future

Information Technology (IT) Management Frameworks are a fundamental tool used by IT professionals to efficiently manage IT resources and are globally applied to IT service delivery and management. Sustainability is a recent notion that describes the need for economic, environmental and social development with- out compromising the ability of future generations to meet their own needs; this applies to businesses as well as society in general. Unfortunately, IT Management Frameworks do not take sustainability into account. To the practitioner this paper demonstrates sustainability integration thereby allowing CIOs and IT managers to improve the sustainability of their organisation. To the researcher this paper argues that sustainability concerns need to be provided to IT Management through its integration into the mainstream of IT Management Frameworks. This is demonstrated through the high-level integration of sustainability in Six Sigma, C OBI T, ITIL and PRINCE2

Image restoration by selective short space spectral subtraction

Image restoration by short space spectral subtraction has been applied recursively to a photographic system in an attempt to increase the signal to noise ratio proportionally to the amount of optical density present. The image is smoothed in the frequency domain a small space at a time based on the power spectrum at a given density level. The method is a variable filter that is a function of photographic density

Oxygen vacancies in tungsten oxide and their influence on tungsten oxide silicon heterojunction solar cells

Tungsten oxide WOx can be incorporated into amorphous crystalline silicon heterojunction solar cells as hole contact and for interface modification between p type amorphous silicon and indium tin oxide. This paper aims at understanding the influence of tungsten oxides properties on silicon heterojunction solar cells. Using in system photoelectron spectroscopy on thermally evaporated WOx layers, it was verified that WOx with a stoichiometry close to WO3 features a work function close to 6 eV and is therefore suitable as hole contact on silicon. Additionally the oxygen vacancy concentration in WOx was measured using photoelectron spectroscopy. High oxygen vacancy concentrations in WOx lead to a low band bending in the WOx silicon junction. Furthermore solar cells were fabricated using the same WOx, and the band bending in these cells is correlated with their fill factors FF and open circuit voltages VOC VOC . Combining these results, the following picture arises positively charged oxygen vacancies raise the Fermi level in WOx and reduce the band bending at the WOx silicon junction. This, in turn, leads to reduced VOCVOC and FF. Thus, when incorporating WOx into silicon solar cells it is important to minimize the oxygen vacancy density in WOx. Therefore deposition methods, enabling adjustment of the WOx stoichiometry are preferabl

Sputtered Tungsten Oxide as Hole Contact for Silicon Heterojunction Solar Cells

Reactively sputtered tungsten oxide WOx was investigated as hole contact on n type crystalline silicon. Varying the oxygen gas flow during sputtering enables variation of the WOx conductivity from 0.01 to 1000 amp; 937; cm, while the band bending at the interface and the implied fill factor FF change by 70 meV and 1.5 . SputteredWOx shows higher resistivity and higher absorption in the visible range compared with indium tin oxide ITO . Therefore, stacks of WOx and ITO are used in solar cells. It was found that at least 20 nm thick WOx is needed to prevent detrimental effects of the ITO work function on the band bending at the junction, the implied FF, and the real FF of solar cells. WOx hole contacts of different thicknesses and conductivity were applied in solar cells and it was found that the highest FF is achieved using about 20 nm thick interlayers of WOx with the highest possible conductivity. It was found that sputtering enables a drastic improvement of WOx silicon solar cells compared with thermal evaporation, due to the precise control of the WOx conductivity. Unfortunately, the resistivity of the sputteredWOx is still limiting the FF of these device

Valence band alignment and hole transport in amorphous crystalline silicon heterojunction solar cells

To investigate the hole transport across amorphous crystalline silicon heterojunctions, solar cells with varying band offsets were fabricated using amorphous silicon suboxide films. The suboxides enable good passivation if covered by a doped amorphous silicon layer. Increasing valence band offsets yield rising hole transport barriers and reduced device effciencies. Carrier transport by thermal emission is reduced and tunnel hopping through valence band tail states increases for larger barriers. Nevertheless, stacks of films with different band gaps, forming a band offset staircase at the heterojunction could allow the application of these layers in silicon heterojunction solar cell

Amorphous crystalline silicon heterojunction solar cells with black silicon texture

Excellent passivation of black silicon surfaces by thin amorphous silicon layers deposited with plasma enhanced chemical vapor deposition is demonstrated. Minority charge carrier lifetimes of 1.3 milliseconds, enabling an implied open circuit voltage of 714 mV, were achieved. The influence of amorphous silicon parasitic epitaxial growth and thickness, as well as of the texture depth is investigated. Furthermore quantum efficiency gains for wavelenghts above 600 ,nm, as compared to random textured solar cells, are demonstrated in 17.2 efficient amorphous crystalline silicon heterojunction solar cells with black silicon textur

Electronic structure of indium tungsten oxide alloys and their energy band alignment at the heterojunction to crystalline silicon

The electronic structure of thermally co evaporated indium tungsten oxide films is investigated. The stoichiometry is varied from pure tungsten oxide to pure indium oxide and the band alignment at the indium tungsten oxide crystalline silicon heterointerface is monitored. Using in system photoelectron spectroscopy, optical spectroscopy and surface photovoltage measurements we show that the work function of indium tungsten oxide continuously decreases from 6.3 eV for tungsten oxide to 4.3 eV for indium oxide, with a concomitant decrease of the band bending at the hetero interface to crystalline silicon than indium oxid

Buyback Problem - Approximate matroid intersection with cancellation costs

In the buyback problem, an algorithm observes a sequence of bids and must decide whether to accept each bid at the moment it arrives, subject to some constraints on the set of accepted bids. Decisions to reject bids are irrevocable, whereas decisions to accept bids may be canceled at a cost that is a fixed fraction of the bid value. Previous to our work, deterministic and randomized algorithms were known when the constraint is a matroid constraint. We extend this and give a deterministic algorithm for the case when the constraint is an intersection of $k$ matroid constraints. We further prove a matching lower bound on the competitive ratio for this problem and extend our results to arbitrary downward closed set systems. This problem has applications to banner advertisement, semi-streaming, routing, load balancing and other problems where preemption or cancellation of previous allocations is allowed