Modelling and Optimisation of Single Junction Strain Balanced Quantum Well Solar Cells

In an attempt to find the optimum number of wells for maximum conversion efficiency a pair of otherwise identical strain balanced samples, one containing 50 wells and the other 65 wells have been characterised. The 65 well sample is found to possess a lower predicted efficiency than the 50 well sample, suggesting that the optimum well number lies between these values. Devices grown using tertiary butyl arsine (TBAs) are found to possess comparable conversion efficiencies to the control cells grown using arsine and slightly superior dark IV characteristics, indicating that TBAs may be substituted for arsine without loss of device efficiency and may even be beneficial to cell performance. Several fundamental refinements to the existing quantum efficiency model of are explored. Firstly, expressions for the strained band gaps are derived. A value for the conduction band offset is . determined using the difference in energy between the heavy and light hole exciton peaks in low temperature photo current scans and found to be 0.55??0.03. The magnitude of the el-hhl exciton binding energy is also estimated from these scans and found to be in excellent agreement with the value obtained from a simple, parameterized expression for the exciton binding energy. Finally, an absolute calculation for the absorption coefficient is incorporated into the quantum efficiency model and values for the heavy and light hole in-planes masses are obtained. The model is found to underestimate the level of absorption in the intrinsic region by an amount consistent with estimates of the magnitude of the reflection from the back surface. The conversion efficiency of a sample predicted using SOL is compared to an independently obtained value. Good agreement is observed between the two results (25.3% and 25.7% for 317 suns AM1.5D). Additionally, an optimum structure for illumination by the AM1.5D spectrum was found to be a 120A well ofIno.lGaAs.Imperial Users onl

Benefits and costs of introducing tariff choice in uncontested markets – A Report for Ofwat

1. Theoretical models indicate that allowing a regulated company to introduce optional (or self selecting) tariffs can make individual consumers (and consumers on average) better off and be profitable for the company, as long as the original (regulated) tariff remains available to all consumers. 2. The models contain some restrictive assumptions and limitations and may be difficult to apply in practice. 3. One particular assumption crucial to the benefits is that consumers choose the best tariff for themselves. More recent research on consumer behaviour in general and in utilities in particular show that this may not be the case. Much of the market literature has been concerned with the telecoms and energy markets. 4. There may be distributional concerns if some consumer groups are less likely to choose well, particularly if there are likely to be long term effects on the ‘base’ tariff. Such concerns are reflected in the current British energy regulator’s consultation on reducing tariff choice for both suppliers and consumers as a response to perceived failure of competition. This experience raises questions about the intrinsic value of choice for consumers. 5. Experience of optional metering in England and Wales provides some evidence of how residential water consumers have responded to that particular tariff choice. Other evidence on water consumer perceptions indicates that the assumptions made in theoretical models of tariff choice may not be applicable to this market. This may affect the applicability of welfare assessments made in the models. 6. We conclude by identifying some questions about the circumstances in which allowing optional tariffs (alongside a regulated base) is likely to be beneficial

Don\u27t Bring a CAD File to a Gun Fight: A Technological Solution to the Legal and Practical Challenges of Enforcing ITAR on the Internet

This Essay begins by outlining Cody Wilson’s motivation to found his organization, Defense Distributed, and the organization’s progress toward its goals. Then, Part II provides a brief overview of the protracted legal battle between Wilson and the State Department over the right to publish Computer-Aided Design (CAD) files on the internet that enable the 3D printing of guns and lower receivers. Part III.A takes a brief look at whether these CAD files are rightly considered speech at all and, if so, what level of protection they might receive. Part III.B then addresses the problem of even asking whether the files are speech subject to regulation. Part III.B also highlights the similarities between regulating internet speech and regulating public-order crimes, focusing on the impact that enforcement problems in both areas can have on government credibility. It ultimately questions whether these legal battles provide any utility to society. In Part IV, this Essay argues that the State Department is utilizing old and incongruent regulations to enforce practically unenforceable laws to little or no effect, ultimately hurting the credibility of the State and martyring people like Wilson. This Essay advocates for a solution that focuses on 3D printer manufacturers as a control point for gun manufacturing. This solution avoids First Amendment issues and makes import and export control a physical reality, rather than an unbounded problem relegated to an open internet. This Essay looks beyond a judicial solution to practical solutions that stem the growth of in-house manufacturing of weapons

Fast Food Failure: How CEO-to-Worker Pay Disparity Undermines the Industry and the Overall Economy

The link between income inequality and economic instability has drawn renewed attention from economists, policy makers, global financial institutions, media, and investors. From Davos to Wall Street to Main Street, there is a growing consensus that inequality slows economic recovery and dampens consumer demand.Yet the gap between the highest and lowest earners in the US economy continues to grow, with consequences for the economy and firm performance. New analysis of the CEO-to-worker compensation ratio across industries shows that Accommodation and Food Services is the most unequal sector in the economy, and that this extreme pay disparity is primarily driven by one of the sector's component industries: fast food. The fast food industry is also one of the highest growth employers in the nation.Over the past year, frustrated front-line fast food workers, striking for higher pay and union representation, have increased public scrutiny of low wages and poor conditions. Workers' nationwide protests, among other factors, spurred industry leader McDonald's to identify several consequences of inequality as a threat to its long-term performance.Fast food income inequality has serious repercussions for the entire industry -- not just McDonald's -- and across the economy as a whole. Fast food companies and other firms will need to address their imbalanced pay practices in order to mitigate the damaging effects of income inequality

Other forms of evidence – and how to use them?

This module covers inclusive approaches to policy-making and other forms of evidence and the ways to use them. While quantitative sources of data are useful in producing some forms of evidence, qualitative sources play an important role, including helping to produce policies that work in practice.Inclusive and “ joined up” approaches to policy-making can play an important role in helping policymakers devise more appropriate policies and achieve more effective policy outcomes

Media, crime and punishment in the digital age

No abstract available