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Rozic B.,Jozef Stefan Institute | Lu S.G.,Pennyslvania State University | Kutnjak Z.,Jozef Stefan Institute | Neese B.,Pennyslvania State University | Zhang Q.M.,Pennyslvania State University
Ferroelectrics | Year: 2011

Electrocaloric effect (ECE), i.e., the heating or cooling of electrocaloric material due to the applied electric field under adiabatic conditions, is very attractive phenomenon for application in cooling and heating devices of new generation in which heating and cooling elements will be made without moving parts and they would be energetically more efficient and friendlier for environment. The first observations of the giant ECE were made by indirect measurements of the electric polarization. In our case we investigated the electrocaloric effect by direct measurements. Here we present results of the temperature change ΔTEC in a relaxor ferroelectric terpolymer P(VDF-TrFE-CFE) near the room temperature. Copyright © Taylor & Francis Group, LLC.


Rozic B.,Jozef Stefan Institute | Malic B.,Jozef Stefan Institute | Malic B.,Jožef Stefan International Postgraduate School | Ursic H.,Jozef Stefan Institute | And 7 more authors.
Ferroelectrics | Year: 2012

The electrocaloric effect (ECE) has recently become very attractive phenomenon due to its various potential applications, for example in heating or cooling devices of new generation which could be more efficient and environmentally friendly. Here a direct measurements of the ECE in thick films of 8/65/35 PLZT ceramics, and in the relaxor ferroelectric polymer composition P(VDF-TrFE-CFE) 0.95-P(VDF-CTFE) 0.05 near room temperature are presented. Our results are consistent with those obtained by indirect measurements. The maximum of the ECE responsivity ΔT EC/E in 8/65/35 PLZT thick films is achieved near the critical point, and in the terpolymer/copolymer blends it is shifted toward higher fields.


Lu Y.,Pennyslvania State University | Luo X.,University of New Mexico | Polgar M.,Pennyslvania State University | Cao Y.,Xi'an Jiaotong University
Journal of Computer Information Systems | Year: 2010

Computer crime hackers have been identified as a primary threat to computer systems, users, and organizations. Much extant research on hackers is conducted from a technical perspective and at an individual level of analysis. This research empirically examines the social organization of a hacker community by analyzing one network called Shadowcrew. The social network structure of this infamous hacker group is established using social networking methods for text mining and network analysis. Analysis of relationships among hackers shows a decentralized network structure. Leaders are identified using four actor centrality measures (degree, betweenness, closeness, and eigenvector) and found to be more involved in thirteen smaller sub-groups. Based on our social network analysis, Shadowcrew exhibits the characteristics of deviant team organization structure.


Weichel R.,Pennyslvania State University | Wang G.,Aura Systems | Mayer J.,Pennyslvania State University | Hofmann H.,University of Michigan
2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings | Year: 2010

LC filters at the input of a DC-DC converter can introduce instability when used with feedback control. Traditional methods of addressing this issue focus on sizing the input filter to avoid instability, introducing passive damping elements, and, most recently, using state feedback to actively stabilize the input filter. This work presents a new method of actively stabilizing the input filter via current-mode control, using a control law that incorporates an additional feedback term for the input capacitor voltage. The stability of a buck converter under such a control law is investigated via root locus, and analysis is verified by experimental results. © 2010 IEEE.


Coder J.G.,Pennyslvania State University | Maughmer M.D.,Pennyslvania State University
53rd AIAA Aerospace Sciences Meeting | Year: 2015

A method is described for applying the linear-stability-based amplification factor transport (AFT) transition model to the popular, two-equation shear stress transport (SST) eddy-viscosity model, yielding the SST-AFT framework. The turbulent kinetic-energy-equation is modified by introducing a new source term that improves its ability to maintain laminar flow without affecting its near-wall behavior in fully turbulent regions. This source term includes a turbulence suppression function that maintains laminar flow until the critical amplification factor is reached. Test cases using the SST-AFT model are presented for a zero-pressure-gradient flat plate and several airfoils, including a multi-element one. Predictions with SST-AFT compare favorably with experiment, confirming the potential capabilities of the new transition/turbulence framework. © 2015 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.


Ortbal K.,Pennyslvania State University | Frazzette N.,Pennyslvania State University | Mehta K.,Pennyslvania State University
Procedia Engineering | Year: 2016

Social entrepreneurship is an increasingly popular model for addressing societal issues in resource-constrained settings. However, like traditional for-profit ventures, social enterprises are dependent on profit generation for success and sustainability. An increasing number of academic and professional institutions are interested in developing curricula to train aspiring social entrepreneurs to build successful ventures. To ensure profitability, aspiring social entrepreneurs must be able to identify their stakeholders and understand the motivations and needs that influence them. However, current methods for collecting and organizing critical data points are often prohibitively expensive in terms of time and money in the early stages of venture development. To empower aspiring social entrepreneurs, programs need tools that take their unique constraints and needs into consideration while delivering positive results. In this article, Constructed Stakeholder Personas (CSPs) are introduced as an adaptation of customer personas, a well-established business development tool, to serve as an alternative to the more cost-prohibitive tools available today. A methodology, which allows educators or experts to create CSPs for use by aspiring social entrepreneurs, is then presented. This dramatically cuts down on the time and cost needed for less experienced entrepreneurs to understand the geographic, demographic, and psychographic details that shape stakeholders' motivations and needs. Finally, a case study is presented that illustrates a potential use case for CSPs. © 2016 The Authors.


Ortbal K.,Pennyslvania State University | Frazzette N.,Pennyslvania State University | Mehta K.,Pennyslvania State University
Procedia Engineering | Year: 2016

While social entrepreneurship is a promising model for addressing social challenges, the success and sustainability of a venture is reliant on an entire stakeholder structure external to the entrepreneurial team. Across academic and professional programs, social entrepreneurship curriculum spends a great deal of time stressing this point; however thoroughly understanding a venture's stakeholder structure is difficult. Especially for novice teams in the early stages of venture development, current methods for collecting critical data points on the identities, needs, and motivations that shape a venture's stakeholder structure can be prohibitively difficult and expensive in terms of time and money. Programs need tools that empower aspiring social entrepreneurs by accounting for their unique needs and constraints without compromising results. In this article, Stakeholder Journey Mapping is presented as an adaptation of current customer journey mapping methods, capable of being an educational tool that lowers barriers and costs for new social entrepreneurs. A methodology for creating Stakeholder Journey Maps is presented in the form of a workshop plan, and is followed by a case study. © 2016 The Authors.


Reed P.M.,Pennyslvania State University | Kasprzyk J.R.,Pennyslvania State University | Kirsch B.R.,University of North Carolina at Chapel Hill | Characklis G.W.,University of North Carolina at Chapel Hill
Modelling for Environment's Sake: Proceedings of the 5th Biennial Conference of the International Environmental Modelling and Software Society, iEMSs 2010 | Year: 2010

There is a growing consensus that non-structural supply management instruments such as water markets have significant potential to reduce the risks and vulnerabilities in complex urban water systems. This paper asks a common question, "What are the tradeoffs for a city using water market supply instruments?". This question emerges quickly in policy and management, but we contend its answer is deceptively difficult to attain using traditional planning tools and management frameworks. This paper demonstrates these issues using visualization and many-objective planning tools demonstrated in the context of a city in the Lower Rio Grande Valley (LRGV) of Texas, USA determining how to use its regional water market to manage population and drought risks.


Liu M.,Dalian University of Technology | Shen Z.,Dalian University of Technology | Guo X.,Dalian University of Technology | Song C.,Dalian University of Technology | Song C.,Pennyslvania State University
Huagong Xuebao/CIESC Journal | Year: 2015

Isopropylation of 4-isopropybiphenyl to 4, 4'-diisopropylbiphenyl was carried out over hierarchical mesoporousmordenite zeolites through alkalis modification of H-mordenite zeolite in a fixed-bed reactor. In order to investigate the effects of the pore structure and the acid sites of the zeolite samples on the catalytic properties, the parent and modified zeolite samples were thoroughly characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), ammonia temperature programmed desorption (NH3-TPD), and N2 physical adsorption-desorption. The results showed that the alkalis treatment adapted the pore structure, and the acid strength and amount without obvious destruction to the MOR topological structure. This adaption was contributed to the improvements of 4-isopropybiphenyl conversion and reaction stability. Modifying the sample with alkalis first and then followed by an acid treatment was in favor of removing the extra-framework alumina from the alkalis treatment and adapting the acid sites on the extra surface of the sample, which can successfully improve the selectivity of 4, 4'-diisopropylbiphenyl. © All right reserved.

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