5,216 research outputs found
Textured back reflectors for thin-film silicon solar cells
No full textThe low conversion efficiency of thin-film silicon solar cells currently prevents them from competing, commercially, with the dominant crystalline silicon technology. The small thickness of the photo-active layer in thin-film silicon solar cells is an advantage for reducing raw material consumption and increasing industrial throughput, but results in poor light absorption at long wavelengths. A textured back reflector is used to increase the absorption of light that would otherwise escape the solar cell. The aim of this project is to fabricate a high-performing back reflector by analysing the influence of its surface texture on the light scattered by it. A structure, called the optical stack, was fabricated on a wide range of random textures to compare the light absorption in a hydrogenated nanocrystalline silicon (nc-Si:H) absorber. The plasmonic absorption at the silver back reflector in the optical stack was observed by 3-D optical modelling, for different surface textures. A qualitative analysis of the absorption in the optical stack and the plasmonic absorption in the back reflector, identified textures that are promising for increasing the light absorption in a nc-Si:H solar cell. Better light scattering and increased short-circuit current density (Jsc), compared to the reference back reflector, was demonstrated using the selected back reflectors.Sustainable Energy TechnologyElectrical Sustainable EnergyElectrical Engineering, Mathematics and Computer Scienc
Collaborative Proposal: DUSEL R&D at the Kimballton Underground Facility (ICP-MS Confirmation, Material Assay, and Radon Reduction)
No full textExperiments measuring rare events, such as neutrinoless double beta (0{nu}{beta}{beta}) decay, and those searching for, or measuring very weakly interacting particles, such as low energy solar neutrino experiments or direct dark matter searches, require ever lower backgrounds; particularly those from radioactive contamination of detector materials. The underground physics community strives to identify and develop materials with radioactive contamination at permissible levels, and to remove radioactive contaminants from materials, but each such material represents a separate dedicated research and development effort. This project attempted to help these research communities by expanding the capabilities in the United States, for indentifying low levels of radioactive contamination in detector materials through gamma ray spectroscopy. Additionally the project tried to make a cross comparison between well established gamma ray spectroscopy techniques for identifying radioactive contaminations and Inductively Coupled Plasma Mass Spectroscopy, which is a relatively new method for searching for uranium and thorium in materials. The project also studied the removal of radioactive radon gas for laboratory air, which showed that an inexpensive technologically simple radon scrubber can potentially be used for homes or businesses with high radon levels even after the employment of other mitigation techniques
Evaluation of physiotherapy intervention for non-specific sub-acute and chronic low back pain
No full textThis thesis investigates routine physiotherapy management of patients with subacute
and chronic non specific low back pain.
In a pragmatic multi-centre trial patients were randomised to receive a course of
physiotherapy treatment or advice following a bio-psychosocial model. Disease
specific, patient specific and generic measures were used to assess outcome.
The 286 patients recruited in the trial had, on average, minimal to moderate low
back pain disability. Patients reported enhanced perceptions of benefit in the
physiotherapy group but there was no evidence of a long term effect in any other
outcomes. There were no differences between the groups in NHS costs although
patients in the physiotherapy group incurred significantly higher out of pocket
expenses. Further analysis of the outcome data confirmed that the primary outcome
measure (Oswestry Disability Index) was the most responsive instrument because it
was able to detect deterioration as well as improvement.
As the trial demonstrated no additional benefit of physiotherapy over brief advice, it
was important to investigate the effectiveness of the latter. A systematic review
found limited evidence that brief bio-psychosocial advice was more effective in
reducing fear avoidance and improving back beliefs in patients with acute and subacute
low back pain compared with traditional medical advice. There was no direct
evidence to support the use of brief bio-psychosocial advice (2 sessions or less) for
reducing pain or disability.
This thesis describes research that has contributed to European guidelines for the
management of chronic low back pain and reviews extensively the literature that
seeks to evaluate physiotherapy practice. The clinical implication of this research is
that for patients with non specific low back pain of mild severity, brief advice is
likely to be as effective as prolonged physiotherapy intervention. The extent to
which a single session of advice is more effective than no intervention needs further
assessment
Current evidence for a modulation of low back pain by human genetic variants
No full textThe manifestation of chronic back pain depends on structural, psychosocial, occupational and genetic influences. Heritability estimates for back pain range from 30% to 45%. Genetic influences are caused by genes affecting intervertebral disc degeneration or the immune response and genes involved in pain perception, signalling and psychological processing. This inter-individual variability which is partly due to genetic differences would require an individualized pain management to prevent the transition from acute to chronic back pain or improve the outcome. The genetic profile may help to define patients at high risk for chronic pain. We summarize genetic factors that (i) impact on intervertebral disc stability, namely Collagen IX, COL9A3, COL11A1, COL11A2, COL1A1, aggrecan (AGAN), cartilage intermediate layer protein, vitamin D receptor, metalloproteinsase-3 (MMP3), MMP9, and thrombospondin-2, (ii) modify inflammation, namely interleukin-1 (IL-1) locus genes and IL-6 and (iii) and pain signalling namely guanine triphosphate (GTP) cyclohydrolase 1, catechol-O-methyltransferase, μ opioid receptor (OPMR1), melanocortin 1 receptor (MC1R), transient receptor potential channel A1 and fatty acid amide hydrolase and analgesic drug metabolism (cytochrome P450 [CYP]2D6, CYP2C9)
Avatar's 'Development' Predicament
No full textThe globally-acclaimed film looks back to the past from a futuristic standpoint to simulate an archetypal moral tale of developmental inequality. Is that a good thing
Optimization of plasmonic white paint back reflector for flat poly-SiOx passivated silicon solar cells
No full textCrystalline silicon (c-Si) has low absorption coefficient in the near infra-red spectrum(NIR), which results in transmission losses in this region. This means there is a need for a back reflector in c-Si solar cells to capture the NIR light. One of the easiest ways of capturing NIR light is by using a reflective metal layer deposited onto a surface texture. However, in some cases surface texture cannot be applied. Having a flat metal reflector does not accomplish effective absorption of the NIR light. To enable effective absorption of NIR light, Lambertian reflectors are needed, which have a reflectance (rback ) of 1 (100% reflectivity) and a diffuse angle (θd ) of 60°. Lambertian scattering can be accomplished to an extent by using a combination of plasmonic nanoparticles and white paint as back reflectors. There have been many investigations where plasmonic back reflectors (PBR), white paint back reflectors (WPBR) and even plasmonic white paint back reflectors (PWPBR) have been used for enhancing absorption in thin-film solar cell technology. But there are not many instances where these reflectors are utilized in c-Si solar cells. Therefore, in this work plasmonic white paint back reflectors are optimized for poly-SiOx passivated c-Si solar cells. To accomplish this, first a detailed optical study was carried out to analyze various rback and θd combinations that can be obtained with different back reflectors. Then the back reflector combination that gave a decent rback and θd combination where then chosen for solar cell simulations. With the help of simulations, external quantum efficiency (EQE) and implied photo-current gain was quantified for combinations with high rback and θd in comparison with normal silver metal back reflectors. The solar cell stack that generated substantial optical gain with the help of simulations were then fabricated and measured. Measurements revealed significant EQE gain with all PBR, WPBR and PWPBR in comparison with Ag metal BR. Form this research work it was inferred that for poly-SiOx passivated flat c-Si solar cells, PWPBR gives highest EQE in the NIR. However, this is only the case when as thin as possible spacer layers are used.Electrical Engineering | Sustainable Energy Technolog
Structuring Interdigitated Back Contact Solar Cells Using the Enhanced Oxidation Characteristics Under Laser-Doped Back Surface Field Regions
No full textInterdigitated back contact (IBC) architecture can yield among the highest silicon wafer-based solar cell conversion efficiencies. Since both polarities are realized on the rear side, there is a definite need for a patterning step. Some of the common patterning techniques involve photolithography, inkjet patterning, and laser ablation. This work introduces a novel patterning technique for structuring the rear side of IBC solar cells using the enhanced oxidation characteristics under the locally laser-doped n++ back surface field (BSF) regions with high-phosphorous surface concentrations. Phosphosilicate glass layers deposited via POCl3 diffusion serve as a precursor layer for the formation of local heavily laser-doped n++ BSF regions. The laser-doped n++ BSF regions exhibit a 2.6-fold increase in oxide thickness compared to the nonlaser-doped n+ BSF regions after undergoing high-temperature wet thermal oxidation. The utilization of oxide thickness selectivity under laser-doped and nonlaser-doped regions serves two purposes in the context of the IBC solar cell, first patterning rear side and second acting as a masking layer for the subsequent boron diffusion. Proof-of-concept solar cells are fabricated using this novel patterning technique with a mean conversion efficiency of 20.41%.Photovoltaic Materials and Device
Draft Article with suggested Edits "The People Versus Frank Smiley: Investigating an 1894 Sodomy Crime in Territorial Utah"
No full textText document "The People Versus Frank Smiley: Investigating an 1894 Sodomy Crime in Territorial Utah" article written by Randell Hoffman, proof read and edit suggestions by Connell "Rocky" O\u27Donovan. gives back grounds of Frank Smiley\u27s arrest and detention for "Buggary" for his relations with Willis Clark. LGBTQ History through arrest records.Converted from .docx to .pdf for compatibilit
Representative time use data and new harmonised calibration of the American Heritage Time Use Data (AHTUD) 1965-1999
No full textRepresentative and reliable individual time use data, in connection with a proper set of socio-economic back-ground variables, are essential elements for the empirical foundation and evaluation of existing and new theories in general and in particular for time use analyses. Within the international project Assessing Time Use Survey Datasets several potentially useful individual US time use heritage datasets have been identified for use in de-veloping an historical series of non-market accounts. In order to evaluate the series of American Heritage Time Use Data (AHTUD) (1965, 1975, 1985, 1992-94, 1998-99) this paper analyses the representativeness of this data when using given weights and provides a new harmonised calibration of the AHTUD for sound time use analyses. Our calibration procedure with its ADJUST program package is theoretically founded on information theory, consistent with a simultaneous weighting including hierarchical data, ensures desired positive weights, and is well-suited and available for any time use data calibration of interest. We present the calibration approach and provide new harmonised weights for all AHTUD surveys based on a substantially driven calibration frame-work. To illustrate the various application possibilities of a calibration, we finally disentangle demographic vs. time use behavioural changes and developments by re-calibrating all five AHTUD surveys using 1965 popula-tion totals as a benchmark.Representative time use data, calibration (adjustment re-weighting) of microdata, information theory, minimum information loss principle, American Heritage Time Use Data (AHTUD), ADJUST program package
Decoupled front/back dielectric textures for flat ultra-thin c-Si solar cells
No full textThe optical analysis of optically-textured and electrically-flat ultra-thin crystalline silicon (c-Si) slabs is presented. These slabs were endowed with decoupled front titanium-dioxide (TiO2) / back silicon-dioxide (SiO2) dielectric textures and were studied as function of two types of back reflectors: standard silver (Ag) and dielectric modulated distributed Bragg reflector (MDBR). The optical performance of such systems was compared to that of state-of-the-art flat c-Si slabs endowed with so-called front Mie resonators and to those of similar optical systems still endowed with the same back reflectors and decoupled front/back texturing but based on textured c-Si and dielectric coatings (front TiO2 and back SiO2). Our optimized front dielectric textured design on 2-µm thick flat c-Si slab with MDBR resulted in more photo-generated current density in c-Si with respect to the same optical system but featuring state-of-the-art Mie resonators ( + 6.4%), mainly due to an improved light in-coupling between 400 and 700 nm and light scattering between 700 and 1050 nm. On the other hand, the adoption of textured dielectric layers resulted in less photo-generated current density in c-Si up to −20.6% with respect to textured c-Si, depending on the type of back reflector taken into account
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