Origami Solar-Tracking Concentrators

The field of solar cells has conventionally been dominated by crystalline silicon, owing to its low cost. Alternative semiconductor materials are typically prohibitively priced, but recent developments are slowly improving their feasibility. This project explores one such option, by incorporating compound parabolic reflective concentrators into solar cell design. Different 2D designs were constructed, and their light collection simulated, using Matlab. The concentrators were optimized for power output. Future research will convert high-performing 2D designs to 3D ones, to better understand the real-world performance of the concentrators.http://deepblue.lib.umich.edu/bitstream/2027.42/169572/1/Chen_Tainon_FinalReport.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/169572/2/Chen_Tainon_ExpoPresentation.pd

An experimental and theoretical study of structural damping in compliant foil bearings

This paper describes an experimental investigation into the dynamic characteristics of corrugated foil (bump foil) strips used in compliant surface foil bearings. This study provided and opportunity to quantify the structural damping of bump foil strips. The experimental data were compared to results obtained by a theoretical model developed earlier. The effects of bearing design parameters, such as static loads, dynamic displacement amplitudes, bump configurations, pivot locations, surface coatings, and lubricant were also evaluated. An understanding of the dynamic characteristics of bump foil strips resulting from this work offers designers a means for enhancing the design of high-performance compliant foil bearings

Fabrication of site‐controlled InGaN quantum dots using reactive‐ion etching

We adopted the simple top‐down etching to fabricate site‐ and dimension‐controlled InGaN quantum dots. Each quantum dot is disk shaped and embedded in a nanoscale pillar. Arrays of nanopillars with varying densities and nanopillar diameters were fabricated from an InGaN/GaN single quantum well using inductively‐coupled plasma reactive‐ion etching. Micro‐photoluminescence (µ‐PL) was used to characterize the emission properties of individual and ensemble of nanopillars. Strong and distinct PL signal of a single nanopillar was observed even at the room temperature. The emission was found to exhibit characteristics from a discrete energy state that is homogeneously broadened. The ensemble of nanopillars exhibited a similar emission linewidth as the single nanopillar, indicating a well controlled quantum dot dimensions and uniformity. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90543/1/609_ftp.pd

Semiconductor nanoring lasers

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98671/1/ApplPhysLett_98_201105.pd

Lasing in a metal-clad microring resonator

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98661/1/ApplPhysLett_98_131107.pd

PERLAKSANAAN DAN KEBERKESANAN KAEDAH LATTICE DALAM PENGAJARAN KEMAHIRAN MATEMATIK: SATU KAJIAN KES DI SEKOLAH RENDAH

Dalam pendidikan matematik, penguasaan pendaraban nombor merupakan salah satu kemahiran penting untuk matapelajaran matematik di sekolah rendah. Seandainya murid-murid tidak dapat menguasai kemahiran ini pada peringkat awal pembelajaran matematik, mereka bakal menghadapi pelbagai masalah dan cabaran dalam penguasaan kemahiran seterusnya yang memerlukan kemahiran pendaraban sebagai asas. Oleh yang demikian, satu kajian telah dijalankan untuk menilai sejauh manakah keberkesanan perlaksanaan kaedah Lattice dalam membantu meningkatkan kemahiran asas pendaraban, yang melibatkan pendaraban nombor dua dan tiga digit. Rekabentuk kajian yang digunakan ialah kajian kuasi-experimental yang melibatkan sampel murid sebanyak 15 orang murid darjah empat di Sekolah Jenis Kebangsaan Cina Chung Cheng, Batu Pahat, Johor. Ujian Pra dan Pos telah dilakukan bagi membandingkan tahap pencapaian sampel kajian sebelum dan selepas rawatan menerusi empat sesi intervensi. Secara keseluruhannya, hasil kajian telah mendapati peningkatan purata skor sebanyak 42.67 peratus selepas rawatan dengan penggunaan kaedah Lattice. Kesimpulannya, kaedah Lattice merupakan kaedah yang berkesan dalam meningkatkan pemahaman dan kemahiran responden dalam topik pendaraban

Rabi oscillations of a qubit coupled to a two-level system

The problem of Rabi oscillations in a qubit coupled to a fluctuator and in contact with a heath bath is considered. A scheme is developed for taking into account both phase and energy relaxation in a phenomenological way, while taking full account of the quantum dynamics of the four-level system subject to a driving AC field. Significant suppression of the Rabi oscillations is found when the qubit and fluctuator are close to resonance. The effect of the fluctuator state on the read-out signal is discussed. This effect is shown to modify the observed signal significantly. This may be relevant to recent experiments by Simmonds et al. [Phys. Rev. Lett. 93, 077003 (2004)].Comment: 4 pages, 4 figure

TOPICAL REVIEW: Slow light in semiconductor heterostructures

This paper presents an overview of slow light in semiconductor heterostructures. The focus of this paper is to provide a unified framework to summarize and compare various physical mechanisms of slow light proposed and demonstrated in the past few years. We expand and generalize the discussions on fundamental limitation of slow light and the delay–bandwidth product trade-off to include gain systems and other mechanisms such as injection locking. We derive the maximum fractional delay and compare the differences between material dispersion and waveguide dispersion based devices. The delay–bandwidth product is proportional to the square root of the device length for a material dispersion based device but has a linear relationship for a waveguide dispersion based device. Possible scenarios to overcome the delay–bandwidth product limitation are discussed. The prospects of slow light in various applications are also investigated.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58125/2/d7_5_R01.pd

High-temperature phase transitions in SrBi_2Ta_2O_9 film: a study by THz spectroscopy

Time-domain THz transmission experiment was performed on a $\rm SrBi_2Ta_2O_9$ film deposited on sapphire substrate. Temperatures between 300 and 923 K were investigated and complex permittivity spectra of the film were determined. The lowest frequency optic phonon near 28 cm$^{-1}$ reveals a slow monotonic decrease in frequency on heating with no significant anomaly near the phase transitions. We show that the dielectric anomaly near the ferroelectric phase transition can be explained by slowing down of a relaxational mode, observed in the THz spectra. A second harmonic generation signal observed in a single crystal confirms a loss of center of symmetry in the ferroelectric phase and a presence of polar clusters in the intermediate ferroelastic phase.Comment: subm. to J. Phys.: Condens. Matte