Microstructure and mechanical properties of bamboo in compression

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 34).Bamboo has received much interest recently as a construction material due to its strength, rapid growth, and abundance in developing nations such as China, India, and Brazil. The main obstacle to the widespread use of bamboo as a structural material is the lack of adequate information on the mechanical properties of bamboo. In this work, the microstructure and mechanical properties of Phyllostachis dulcis bamboo are studied to help produce a model for the mechanical properties of bamboo. Specifically, a linear relationship is established between the density of bamboo samples, which is known to vary radially, and their strength in compression. Nanoindentation of vascular bundles in various positions in bamboo samples revealed that the Young's modulus and hardness of the bundles vary in the radial direction but not around the circumference. The compressive strength of bamboo samples was found to vary from 40 to 95 MPa, while nanoindentation results show the Young's modulus of vascular bundles ranges from 15 to 18 GPa and the hardness ranges from 380 to 530 MPa.by Michael R. Gerhardt.S.B

An Empirical Study of Gender and Race in Trademark Prosecution

This Article is the first to empirically examine the extent to which women and minorities succeed in prosecuting trademark applications before the United States Patent and Trademark Office (“USPTO”). Trademark registration is an important measure of entrepreneurial activity and progress in business, education, and the arts. To explore how women and minorities are succeeding in this domain, we compared 1.2 million trademark applications over thirty years with demographic information on race and gender. We analyze whether trademark prosecution reflects systematic underrepresentation of women and minorities similar to those reported in patent and copyright prosecution. We found that trademark data showed significant differences from the other two federal intellectual property (“IP”) regimes. Our analysis reveals that women regularly secure trademark registration at a higher rate than men. Women are underrepresented in the pool of trademark applicants compared to their presence in the population, but not all minority groups are underrepresented. For women and underrepresented minorities, the disparity is decreasing at a rate not seen in other IP registration systems. While recent work has significantly advanced our understanding of trademark prosecution, no published studies consider the race and gender of trademark applicants. By filling that void, this Article substantially contributes to our understanding of minority intellectual property ownership and provides a new foundation for policy shifts and further research to assure that intellectual property ownership paths, theory, law, and reform are grounded in equality

The Gender Gap in Academic Patenting

The gender gap in academia has long been the focus of public discourse regarding the role of universities in promoting social values. In this study, we consider women’s participation in transferring knowledge from the academy to industry. A prominent model for such transfer is reflected in patent registration for inventions developed through scholarly research. And while academic patenting is a significant component of the professional activities of many faculty members, the extent to which women’s scientific discoveries are patented and commercialized has received relatively little attention. The U.S. academy is a leader in science and a pioneer of technology transfer. This study analyzes the extent to which inventions by academic women are protected by university patents. Through analysis of inventors’ names, we ascertain the expected gender of inventors listed on applications filed by U.S. academic institutions. From this data, we report the extent to which a gender gap exists in patent application, grant rates, fields of research, and forward citations. Our study yielded several key findings. First, we found a significant increase in the number of patent applications originating from universities from 2000 to 2015. We identified a similar increase in applications by inventor teams made up of only women, though these applications were granted at a lower rate and were cited less frequently than patents obtained by teams including men. We found differences in team composition, with women being much more likely to work alone than men. We also noted an interesting disparity in subject matter, with drugs and chemistry (especially molecular biology) dominating the technological fields of university applications. The Article concludes that while women increasingly participate in academic patenting, a significant gender gap persists. Our findings may serve as a springboard for further research on the reasons for the failure to achieve gender equality, as women’s representation in the academy continues to increase

Simulated dynamics of optically pumped dilute nitride 1300 nm spin vertical-cavity surface-emitting lasers

The authors report a theoretical analysis of optically pumped 1300 nm dilute nitride spin-polarised vertical-cavity surface-emitting lasers (VCSELs) using the spin-flip model to determine the regions of stability and instability. The dependence of the output polarisation ellipticity on that of the pump is investigated, and the results are presented in twodimensional contour maps of the pump polarisation against the magnitude of the optical pump. Rich dynamics and various forms of oscillatory behaviour causing self-sustained oscillations in the polarisation of the spin-VCSEL subject to continuouswave pumping have been found because of the competition of the spin-flip processes and birefringence. The authors also reveal the importance of considering both the birefringence rate and the linewidth enhancement factor when engineering a device for high-frequency applications. A very good agreement is found with the experimental results reported by the authors' group. © The Institution of Engineering and Technology 2014

Spitzer Observations of Star Formation in the Extreme Outer Disk of M83 (NGC5236)

Spitzer IRAC observations of two fields in the XUV-disk of M83 have been recently obtained,3R_{HII} away from the center of the galaxy (R_{HII)=6.6 kpc).GALEX UV images have shown the two fields to host in-situ recent star formation.The IRAC images are used in conjunction with GALEX data and new HI imaging from THINGS to constrain stellar masses and ages of the UV clumps in the fields,and to relate the local recent star formation to the reservoir of available gas. multi wavelength photometry in the UV and mid-IR bands of 136 UV clumps(spatial resolution >220pc) identified in the two target fields, together with model fitting of the stellar UV-MIR SED,suggest that the clumps cover a range of ages between a few Myr and >1Gyr with a median value around <100Myr,and have masses in the range 10^3-3*10^6M, with a peak ~10^4.7M.The range of observed ages,for which only a small fraction of the mass in stars appears to have formed in the past ~10Myr, agrees with the dearth of Ha emission observed in these outer fiel ds. At the location of our IRAC fields, the HI map shows localized enhancement and clumping of atomic gas. A comparison of the observed star formation with the gas reservoir shows that the UV clumps follow the Schmidt--Kennicutt scaling law of star formation,and that star formation is occurring in regions with gas dens ities at approximately (within a factor of a few) the critical density value de -rived according to the Toomre Q gravitational stability criterion. The signifi cant 8 micron excess in several of the clumps (16% of the total by number accou nting for ~67% of the 8 micron flux)) provides evidence for the existence of dust in these remote fields, in agreement with results for other galaxies. Furt hermore, we observe a relatively small excess of emission at 4.5 micron in the clumps...Comment: Accepted for Publication in the Astronomical Journal,[35 pages, 11 figures], the paper with original size is in http://www.astro.umass.edu/~dongh/M83.pdf comments: add one reference Crosthwaite et al 2002 for picture

The Role of Water in Vapor-fed Proton-Exchange-Membrane Electrolysis

Water-vapor fed electrolysis, a simplified single-phase electrolyzer using a proton exchange membrane electrode assembly, achieved >100 mA/cm2 performance at <1.7 V, the best for water-vapor electrolysis to date, and was tested under various operating conditions (temperature and inlet relative humidity (RH)).To further probe the limitations of the electrolyzer, a mathematical model was used to identify the overpotentials, local water activity, water content values, and temperature within the cell at these various conditions. The major limitations within the water-vapor electrolyzer are caused by a decreased water content within the membrane phase, indicated by increased Ohmic and mass transport losses seen in applied voltage breakdowns. Further investigations show the water content (λ, mole of water/mole of sulfonic acid) can decrease from 13 at low current densities down to 6 at high current densities. Increasing the temperature or decreasing RH exacerbates this dry-out effect. Using our mathematical model, we show how these mass transport limitations can be alleviated by considering the role of water as both a reactant and a hydrating agent. We show that low cathode RH can be tolerated as long as the anode RH remains high, showing equivalent performance as symmetric RH feeds