Approaching the Lambertian limit in randomly textured thin-film solar cells

The Lambertian limit for solar cells is a benchmark for evaluating their efficiency. It has been shown that the performance of either extremely thick or extremely thin solar cells can be driven close to this limit by using an appropriate photon management. Here we show that this is likewise possible for realistic, practically relevant thin-film solar cells based on amorphous silicon. Most importantly, we achieve this goal by relying on random textures already incorporated into state-of-the-art superstrates; with the only subtlety that their topology has to be downscaled to typical feature sizes of about 100 nm

「問題導向學習」教案之品質改善：香港大學醫學院一年級生之經驗與回饋

To improve the quality of paper cases used for problem-based learning in the medical curriculum of the University of Hong Kong, Year 1 students were asked at the end of the year to fill in a questionnaire which addresses specific issues related to problem based learning. In addition, for each of the 6 new cases of PBL which were introduced into the first year, tutorials groups were asked to rate which of the learning objectives as specified in the cased were covered under the 4 themes: Biology of Health and Disease (Knowledge Component); Doctors and Patients (Clinical and communication Skills); Medicine and the Community (Societal and Population Medicine) and Professional Development (Medical Ethics and Law). Over eighty percent of the students found the PBL process to facilitate self directed learning and contributed to their learning. Over forty percent found there was unequal representation of the 4 themes with the issue of Professional Development to be the most inadequately covered. Various factors can be identified for the under representation and inadequate coverage of professional development issues. Possible solutions may include case modifications to ensure a fairer balance of 4 themes, alternative formats of enhancing the discussion of professional development issues, tutor training and coaching the students to address professional development issues

Cosmology in the Solar System: Pioneer effect is not cosmological

Does the Solar System and, more generally, a gravitationally bound system follow the cosmic expansion law ? Is there a cosmological influence on the dynamics or optics in such systems ? The general relativity theory provides an unique and unambiguous answer, as a solution of Einstein equations with a local source in addition to the cosmic fluid, and obeying the correct (cosmological) limiting conditions. This solution has no analytic expression. A Taylor development of its metric allows a complete treatment of dynamics and optics in gravitationally bound systems, up to the size of galaxy clusters, taking into account both local and cosmological effects. In the solar System, this provides an estimation of the (non zero) cosmological influence on the Pioneer probe: it fails to account for the " Pioneer effect " by about 10 orders of magnitude. We criticize contradictory claims on this topic

Rugate filter for light-trapping in solar cells

We suggest a design for a coating that could be applied on top of any solar cell having at least one diffusing surface. This coating acts as an angle and wavelength selective filter, which increases the average path length and absorptance at long wavelengths without altering the solar cell performance at short wavelengths. The filter design is based on a continuous variation of the refractive index in order to minimize undesired reflection losses. Numerical procedures are used to optimize the filter for a 10 μm thick monocrystalline silicon solar cell, which lifts the efficiency above the Auger limit for unconcentrated illumination. The feasibility to fabricate such filters is also discussed, considering a finite available refractive index range

Metric Expansion from Microscopic Dynamics in an Inhomogeneous Universe

Theories with ingredients like the Higgs mechanism, gravitons, and inflaton fields rejuvenate the idea that relativistic kinematics is dynamically emergent. Eternal inflation treats the Hubble constant H as depending on location. Microscopic dynamics implies that H is over much smaller lengths than pocket universes to be understood as a local space reproduction rate. We illustrate this via discussing that even exponential inflation in TeV-gravity is slow on the relevant time scale. In our on small scales inhomogeneous cosmos, a reproduction rate H depends on position. We therefore discuss Einstein-Straus vacuoles and a Lindquist-Wheeler like lattice to connect the local rate properly with the scaling of an expanding cosmos. Consistency allows H to locally depend on Weyl curvature similar to vacuum polarization. We derive a proportionality constant known from Kepler's third law and discuss the implications for the finiteness of the cosmological constant.Comment: 23 pages, no figure

Diffractive beam splitter characterization via a power-recycled interferometer

We used the high-precision laser interferometer technique of power recycling to characterize the optical loss of an all-reflective grating beam splitter. This beam splitter was used to set up a Michelson interferometer with a power-recycling resonator with a finesse of 883. Analyzing the results obtained, we determined the beam splitter's total optical loss to be (0.193+/-0.019)%. Low loss all-reflective beam splitters might find application in future high-power laser interferometers for the detection of gravitational waves

Power-recycled michelson interferometer with a 50/50 grating beam splitter

We designed and fabricated an all-reflective 50/50 beam splitter based on a dielectric grating. This beam splitter was used to set up a power-recycled Michelson interferometer with a finesse of about FPR ≈ 880. Aspects of the diffractive beam splitter as well as of the interferometer design are discussed.DFG/SFB/TR

Laws for the Right to Work of Disabled People: The Italian Experience

This scholarly handbook covers all aspects of people with disabilities entering the workplace, including the legal aspects, transitions, types, and levels of employments, the impact of different disabilities, and the consideration of the intersection of disability with other identities such as gender and ethnicity. Comprehensive in scope, chapters look beyond organizational strategies that accommodate an employee’s disability and use case studies to highlight important issues and the individual’s perspective. The handbook concludes with a reflection on the work included in the book, what was not included and why, and makes recommendations for future disability research. Marking a major contribution to the study of workplace diversity and bringing together academics from various disciplines and global regions, this handbook covers a truly broad and diverse mix of approaches, theories, and models

Consequences of a Change in the Galactic Environment of the Sun

The interaction of the heliosphere with interstellar clouds has attracted interest since the late 1920's, both with a view to explaining apparent quasi-periodic climate "catastrophes" as well as periodic mass extinctions. Until recently, however, models describing the solar wind - local interstellar medium (LISM) interaction self-consistently had not been developed. Here, we describe the results of a two-dimensional (2D) simulation of the interaction between the heliosphere and an interstellar cloud with the same properties as currently, except that the neutral H density is increased from the present value of n(H) ~ 0.2 cm^-3 to 10 cm^-3. The mutual interaction of interstellar neutral hydrogen and plasma is included. The heliospheric cavity is reduced considerably in size (approximately 10 - 14 AU to the termination shock in the upstream direction) and is highly dynamical. The interplanetary environment at the orbit of the Earth changes markedly, with the density of interstellar H increasing to ~2 cm^-3. The termination shock itself experiences periods where it disappears, reforms and disappears again. Considerable mixing of the shocked solar wind and LISM occurs due to Rayleigh-Taylor-like instabilities at the nose, driven by ion-neutral friction. Implications for two anomalously high concentrations of 10Be found in Antarctic ice cores 33 kya and 60 kya, and the absence of prior similar events, are discussed in terms of density enhancements in the surrounding interstellar cloud. The calculation presented here supports past speculation that the galactic environment of the Sun moderates the interplanetary environment at the orbit of the Earth, and possibly also the terrestrial climate.Comment: 23 pages, 2 color plates (jpg), 3 figures (eps