Bayrakci M.,Pennslyvania State University |
Choi Y.,Pukyong National University |
Brownson J.R.S.,Pennslyvania State University
Energy Procedia | Year: 2014
Photovoltaic (PV) systems in the USA are often perceived as useful only in warm and sunny climate regions. However, PV systems can be installed and operated in cold regions as well, including places that get snow. Sunlight is the source of electricity, and thermal heat is not required to generate electricity in PV systems. Given similar irradiation conditions, lower PV-cell temperatures can lead to increases in efficiency, which leads to an increase in power generation, thus allowing the user to benefit more from the PV technology. This study focuses on the relationship between the level of energy production and varying temperatures. Two models have been developed to show temperature effect on photovoltaic systems, using transient systems simulation (TRNSYS), a FORTRAN-based modular program to assess solar conversion and heat transfer. The first model (Model A) ignores temperature and the other (Model B) takes it into consideration. In Model A, the efficiency was assumed to be constant through the year. In Model B, the temperature and the resulting efficiency change of the PV cells are defined according to deviations from the nominal operating cell temperature (NOCT), using equations from the literature. These two models were executed for 236 cities across the USA by using second-generation Typical Meteorological Year (TMY) data. These two models calculate discrete outputs of power density, given irradiance and temperature conditions. Comparative analyses were made between these two models. The power output differences for 236 cities across the USA were used to generate contour maps indicating a continuous surface of differences between these two models. Comparing Model B relative to Model A power outputs increase during the months of November to February for the Northeast and the Midwest regions of the USA (16% -20 %), whereas they decrease slightly in May to August (-4%). On the other hand, power outputs decrease considerably from May to August for the South and Southwest of the USA (- 12% - 15%), whereas they increase slightly from December to February (5%). Geospatial trends show two different behaviours in winter time and in summer time due to ambient temperature. © 2014 The Authors. Published by Elsevier Ltd.
Wang L.,Baylor University |
Law S.,University of California at San Diego |
Fraker C.,Ohio State University |
Vela R.,Pennslyvania State University |
And 3 more authors.
National Aerospace and Electronics Conference, Proceedings of the IEEE | Year: 2011
A new software-defined S-band radar (SDSR) has recently been developed at the Air Force Research Laboratory. The system is built upon individual off-the-shelf components, devices, and instruments, and the center of the architecture is an Arbitrary Waveform Generator (AWG). The AWG can be programmed to generate various kinds of radar waveforms, which are mixed with a carrier to create S-band radar signals. The AWG can be interfaced with a computer which runs on MatLab or LabView for software definition of radar waveforms. Furthermore, the computer can be connected to the Internet for receiving data from remote users. As a result, the new SDSR can be used to support studies of radar waveforms in a large area by remote users. The characteristics of the radar system are studied and the performance of the system is optimized by selecting the parameters of the building components. The newly developed SDSR is used to test the wavelet-based radar waveforms, which verifies the theoretical results produced earlier. © 2011 IEEE.
Aguirre M.E.,Pennslyvania State University |
Frecker M.,Pennslyvania State University
ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2010 | Year: 2010
This work describes a design and optimization method for developing hybrid, multi-material, compliant instruments which are expected to be useful in mini-laparoscopy and natural orifice translumenal endoscopic surgery. These two-material devices are designed specifically for Penn State's lost mold rapid infiltration process, which is capable of fabricating hundreds of freestanding meso-scale parts in parallel. New narrow-gauge surgical procedures impose severe geometric constraints that challenge traditional compliant mechanism design methods. Since narrow-gauge constraints leave geometry optimization ineffective, new design methods are explored to improve the performance of a 1 mm diameter contact-aided compliant forceps. By considering hybrid designs, new design possibilities are enabled through material variation. The hybrid forceps has desired regions of flexibility and stiffness that can be isolated to improve tool performance. For instance, a hybrid forceps can be designed with greater flexibility in some regions to provide larger jaw openings while maintaining high stiffness in other regions to obtain large grasping forces, both vital features in a surgical forceps. Using ANSYS to model large deformation and contact, an optimization problem is formulated to maximize tool performance and to determine optimal segregation of hybrid materials considering a range of modulus ratios. Materials under consideration include nanoparticulate 3 mol% yttria partially stabilized zirconia (3YSZ) and austenitic (300 series) stainless steel. All results are compared to previously optimized homogeneous designs. Copyright © 2010 by ASME.
Saffer D.M.,Pennslyvania State University |
Lockner D.A.,U.S. Geological Survey |
McKiernan A.,Pennslyvania State University
Geophysical Research Letters | Year: 2012
At subduction zones, earthquake nucleation and coseismic slip occur only within a limited depth range, known as the "seismogenic zone". One leading hypothesis for the upper aseismic-seismic transition is that transformation of smectite to illite at ∼100-150°C triggers a change from rate-strengthening frictional behavior that allows only stable sliding, to rate weakening behavior considered a prerequisite for unstable slip. Previous studies on powdered gouges have shown that changes in clay mineralogy alone are unlikely to control this transition, but associated fabric and cementation developed during diagenesis remain possible candidates. We conducted shearing experiments designed specifically to evaluate this hypothesis, by using intact wafers of mudstone from Ocean Drilling Program Site 1174, offshore SW Japan, which have undergone progressive smectite transformation in situ. We sheared specimens along a sawcut in a triaxial configuration, oriented parallel to bedding, at normal stresses of ∼20-150MPa and a pore pressure of 1MPa. During shearing, we conducted velocity-stepping tests to measure the friction rate parameter (a-b). Friction coefficient ranges from 0.28-0.40 and values of (a-b) are uniformly positive; both are independent of clay transformation progress. Our work represents the most direct and comprehensive test of the clay transformation hypothesis to date, and suggests that neither illitization, nor accompanying fabric development and cementation, trigger a transition to unstable frictional behavior. We suggest that strain localization, in combination with precipitation of calcite and quartz, is a viable alternative that is consistent with both field observations and recent conceptual models of a heterogeneous seismogenic zone. © 2012. American Geophysical Union. All Rights Reserved.
Bennett A.,Pennslyvania State University |
Ivanov K.,Pennslyvania State University |
Avramova M.,Pennslyvania State University
Mathematics and Computations, Supercomputing in Nuclear Applications and Monte Carlo International Conference, M and C+SNA+MC 2015 | Year: 2015
There has been a recent trend towards Monte Carlo based multi-physics codes to get high accuracy reactor core solutions. These high accuracy solutions can be used as reference solutions to validate deterministic codes. To obtain this high accuracy solution, a high fidelity coupled code was created. The coupling is done with a Monte Carlo code and a thermal-hydraulic subchannel code. The use of a Monte Carlo code allows exact geometry modeling, as well as the use of continuous energy cross sections. Coupling with a thermal-hydraulic code allows the feedback effects to be accurately modeled. The coupling is done with MCNP6, which is a general purpose Monte Carlo transport code, and CTF, which is a subchannel code. The coupling was preformed using an internal coupling method for each pin and axial level. The On-The-Fly cross sections were used to decrease the complexity of the coupling and to decrease the memory requirement. The coupled MCNP6/CTF code was tested on a 3X3 PWR mini assembly test problem that included a guide tube as well as a single BWR fuel pin test problem with a very bottom peaked axial power profile. The results of these test problems were compared with similar coupled Monte Carlo/thermal-hydraulic subchannel codes and there was good agreement in the results. In this paper, the foundation of the coupled code is given, and it shows that the coupling was accurately implemented. © Copyright (2015) by the American Nuclear Society.
Datta S.,Pennslyvania State University |
Liu H.,Pennslyvania State University |
Narayanan V.,Pennslyvania State University
Microelectronics Reliability | Year: 2014
Tunneling-field-effect-transistor (TFET) has emerged as an alternative for conventional CMOS by enabling the supply voltage (VDD) scaling in ultra-low power, energy efficient computing, due to its sub-60 mV/decade sub-threshold slope (SS). Given its unique device characteristics such as the asymmetrical source/drain design induced uni-directional conduction, enhanced on-state Miller capacitance effect and steep switching at low voltages, TFET based circuit design requires strong interactions between the device-level and the circuit-level to explore the performance benefits, with certain modifications of the conventional CMOS circuits to achieve the functionality and optimal energy efficiency. Because TFET operates at low supply voltage range (VDD<0.5V) to outperform CMOS, reliability issues can have profound impact on the circuit design from the practical application perspective. In this review paper, we present recent development on Tunnel FET device design, and modeling technique for circuit implementation and performance benchmarking. We focus on the reliability issues such as soft-error, electrical noise and process variation, and their impact on TFET based circuit performance compared to sub-threshold CMOS. Analytical models of electrical noise and process variation are also discussed for circuit-level simulation. © 2014 Published by Elsevier Ltd.