A Thermoelectric generation subsystem model for heat recovery simulations

Thermoelectric devices can convert thermal energy directly into electrical energy, or they can work in reverse and use electrical energy to create a temperature gradient for cooling or heating applications. The absence of moving parts, wide range of operating temperatures, scalability, and modular capabilities makes thermoelectrics attractive for energy generation applications. They have been considered for use with vehicle exhausts, co-generation, and other energy recovery from lost heat in thermodynamic cycles. Thermoelectric devices have relatively low efficiencies but there have been recent advances in thermoelectric materials potentially opening the door to more power applications. As material advancements continue and a wider range of power generation applications will be considered, module and system level modeling becomes critical for the design of the next generation of thermoelectric systems. The overall focus of this thesis is to further develop the current thermoelectric power unit models available, validate the developed model, and implement the model into a simulation environment for feasibility and optimization studies. Current models found in the literature are often based on very specific applications or are too general in nature to truly explore the optimization of a wide range of potential thermoelectric applications. The model developed in this work is highly customizable permitting the optimization of a large number of varying systems. Module mismatch and heat spreading in three dimensions are explored, modeled, and considered for incorporation into the new thermoelectric power unit model to allow for more accurate performance prediction. Mismatch models are developed for thermoelectric modules electrically connected in series and in parallel. Predecessors in the research community believe power output to be hampered due to variation of module specific parameters. Developed models for performance prediction display the extent of the mismatch effect. Experimental validation of the model shows the high level of exactness in prediction. Often, a one dimensional heat transfer assumption is made when analyzing system performance. This is known to cause discrepancies in the thermoelectric power unit model predictions. For thermal resistances with regards to the thermoelectric modules internal to the thermoelectric power unit, a heat spreading effect is observed. This effect requires an analytical method for quantifying the extent of the three dimensional resistance. The analytical model is described and applied to the thermoelectric power unit. Numerical comparison and experimentation are performed to verify the accuracy of the model. The model for heat spreading in three dimensions is incorporated into the new thermoelectric power unit model to allow for more accurate performance prediction. The advanced thermoelectric power unit model is coded in the ThermoElectric Power System Simulator (TEPSS) environment for a project sponsored by New York State Energy Research and Development Authority (NYSERDA). The programmed module will serve as the key component of the software package that will predict the performance of the thermoelectric heat recovery unit used in common thermodynamic cycles. Experimental validation of the advanced model is performed. Data is compared to simulation results from the TEPSS tepowerunit component. The data fits are agreeable when the uncertainty of various system parameters is considered

Sim(2) and SUSY

The proposal of hep-ph/0601236, that the laws of physics in flat spacetime need be invariant only under a SIM(2) subgroup of the Lorentz group, is extended to include supersymmetry. $\mathcal{N}=1$ SUSY gauge theories which include SIM(2) couplings for the fermions in chiral multiplets are formulated. These theories contain two conserved supercharges rather than the usual four.Comment: 10 pages, revtex4. Note added and sign correcte

XMM-Newton Reflection Grating Spectrometer Observations of the Prototypical Starburst Galaxy M82

We present results from XMM-Newton Reflection Grating Spectrometer observations of the prototypical starburst galaxy M82. These high resolution spectra represent the best X-ray spectra to date of a starburst galaxy. A complex array of lines from species over a wide range of temperatures is seen, the most prominent being due to Lyman-alpha emission from abundant low Z elements such as N, O, Ne, Mg and Si. Emission lines from Helium-like charge states of the same elements are also seen in emission, as are strong lines from the entire Fe-L series. Further, the OVII line complex is resolved and is seen to be consistent with gas in collisional ionization equilibrium. Spectral fitting indicates emission from a large mass of gas with a differential emission measure over a range of temperatures (from 0.2 keV to 1.6 keV, peaking at 0.7 keV), and evidence for super-solar abundances of several elements is indicated. Spatial analysis of the data indicates that low energy emission is more extended to the south and east of the nucleus than to the north and west. Higher energy emission is far more centrally concentrated.Comment: 5 pages, 4 figures, MNRAS accepte

The Applicant's Perspective on Urology Residency Interviews: A Qualitative Analysis

ObjectiveTo better understand what urology applicants look for on interview day and what they care about in selecting a residency program through an analysis of anonymous online posts about the urology interview process.MethodsWe collected 3 years (2016-2018) of comments and posts from the Interview Impressions tab of the Urology Match Google Sheet for 133 urology residencies. Qualitative data analysis was performed using grounded theory methodology.ResultsWe identified 6 categories of themes on (1) interview day structure, (2) diverse faculty, (3) program culture, (4) surgical training, (5) research, and (6) program benefits. These themes appeared in comments for 77%-86% of the residency programs except for research which was present for 44% of the programs. The efficiency and structure of interview day are very important. Applicants also care about young and diverse fellowship-trained faculty across a wide breadth of subspecialties. They believe they are able to discern the program culture and collegiality between residents and faculty. Applicants want a balance of surgical and clinical training with a focus on robotics and surgical autonomy. Not all applicants are interested in research but those that are appreciate a strong support system. Finally, additional program benefits and the positives and negatives of the program's location are frequently discussed.ConclusionAnalysis of anonymous social media posts can help improve the interview process for applicants and programs alike. Programs can also identify areas of improvement for residency training. Our findings provide additional insight towards the ultimate goal of improving the match process