Digital Commons Network^™

The Role Of The Goal In Solving Hard Computational Problems: Do People Really Optimize?, Sarah Carruthers, Ulrike Stege, Michael E. J. Masson

The Journal of Problem Solving

The role that the mental, or internal, representation plays when people are solving hard computational problems has largely been overlooked to date, despite the reality that this internal representation drives problem solving. In this work we investigate how performance on versions of two hard computational problems differs based on what internal representations can be generated. Our findings suggest that problem solving performance depends not only on the objective difficulty of the problem, and of course the particular problem instance at hand, but also on how feasible it is to encode the goal of the given problem. A further implication of …

Investigating Sociodemographic Disparities In Cancer Risk Using Web-Based Informatics, Hong-Jun Yoon, Georgia Tourassi

Journal of Human Performance in Extreme Environments

Cancer health disparities due to demographic and socioeconomic factors are an area of great interest in the epidemiological community. Adjusting for such factors is important when developing cancer risk models. However, for digital epidemiology studies relying on online sources such information is not readily available. This paper presents a novel method for extracting demographic and socioeconomic information from openly available online obituaries. The method relies on tailored language processing rules and a probabilistic scheme to map subjects’ occupation history to the occupation classification codes and related earnings provided by the U.S. Census Bureau. Using this information, a case-control study is …

Deep Gaze Velocity Analysis During Mammographic Reading For Biometric Identification Of Radiologists, Hong-Jun Yoon, Folami Alamudun, Kathy Hudson, Garnetta Morin-Ducote, Georgia Tourassi

Journal of Human Performance in Extreme Environments

Several studies have confirmed that the gaze velocity of the human eye can be utilized as a behavioral biometric or personalized biomarker. In this study, we leverage the local feature representation capacity of convolutional neural networks (CNNs) for eye gaze velocity analysis as the basis for biometric identification of radiologists performing breast cancer screening. Using gaze data collected from 10 radiologists reading 100 mammograms of various diagnoses, we compared the performance of a CNN-based classification algorithm with two deep learning classifiers, deep neural network and deep belief network, and a previously presented hidden Markov model classifier. The study showed that …

Engaging In Performance Measurement: Introducing Bibliometric Services, Caroline Leiß

Proceedings of the IATUL Conferences

No abstract provided.

Epics: Children's Educational Demonstrations, Aaron P. Kreuter, Ruby A. Wellen, Alexander D. Falkenberg, Jamie M. Arabshahi

Engagement & Service-Learning Summit

No abstract provided.

Utilizing Gis To Locate Endangered Gravel Hill Prairies Of The Wabash River Valley, Ryan W.R. Schroeder

Engagement & Service-Learning Summit

The Gravel Hill Prairies (GHP’s) of the Wabash River Valley are an endangered ecosystem in the state of Indiana and provide optimal growing conditions for a number of state endangered plants. Currently only four remnants are known to exist near Lafayette, IN, found by a previous study conducted in 1980 by Post, Bacone, and Aldrich (Proceedings of the Indiana Academy of Science, 1984, vol. 94: 457-464). These unique ecosystems have been found to occur almost exclusively on soils classified as Rodman Gravelly Loams and Strawn-Rodman complexes which occur predominantly along the outwash terraces of the Wabash River and its tributaries. …

Stochastic Estimation Of Field Management Zones Using Multi-Year Yield Data And A Hidden Markov Random Field, Alex Layton, James V. Krogmeier, Aaron Ault, Dennis Buckmaster

Department of Electrical and Computer Engineering Technical Reports

Modern precision agriculture equipment enables treating different areas of a field differently, i.e., site specific management. This results in the concept of management zones, which are a compromise between treating a field uniformly and treating every plant individually.

This work presents an algorithm for inferring the management zones for a field based on yield data from multiple years. The algorithm uses a hidden Markov random field model (HMRF) to find regions of the field which likely correspond to the same underlying yield distribution (i.e., “management zones”). These regions are assumed to be the same for each year, but their distributions …

The Roles Of Internal Representation And Processing In Problem Solving Involving Insight: A Computational Complexity Perspective, Todd Wareham

The Journal of Problem Solving

In human problem solving, there is a wide variation between individuals in problem solution time and success rate, regardless of whether or not this problem solving involves insight. In this paper, we apply computational and parameterized analysis to a plausible formalization of extended representation change theory (eRCT), an integration of problem solving by problem space search and insight as problem restructuring which proposes that this variation may be explainable by individuals having different problem representations and search heuristic choices. Our analyses establish not only the intractability of eRCT in general, but also sets of restrictions under which eRCT-based problem solving …

Conditional Cash Transfers For Primary Education: Which Children Are Left Out?, Jonathan Bauchet, Eduardo A. Undurraga, Victoria Reyes-García, Jere R. Behrman, Ricardo A. Godoy

Department of Agricultural Economics Faculty Publications

Conditional cash transfer (CCT) programs to increase primary-school enrollment and attendance among low-income households have been shown to benefit children and households, but to date little is known about who joins such programs. We test three hypotheses about predictors of CCT program participation in indigenous societies in Bolivia, focusing on attributes of the household (ethnicity), parents (modern human capital), and children (age, sex). We model whether children receive a transfer from Bolivia’s CCT program (Bono Juancito Pinto), using data from 811 school-age children and nine ethnic groups. Children from the group least exposed to Westerners (Tsimane’) are 18–22 …

Improving The Reliability Of A Domestic Refrigerator Compressor Subjected To Repetitive Loading, Seongwoo Woo, Dennis O'Neal

International Compressor Engineering Conference

As a reliability quantitative specification, parametric accelerated life testing was used to assess the reliability of a newly designed compressor of a commercial refrigerator subjected to repetitive stresses. A generalized life-stress failure model and new sample size equation with a new load concept were derived starting with the basic refrigeration cycle. The sample size equation with the acceleration factor also enabled the parametric accelerated life testing to quickly evaluate the expected lifetime. The design of this testing should help an engineer uncover the design parameters affecting reliability during the design process of the compressor system. Consequently, it should help companies …

Numerical Study On The Internal Characteristics Of Single Screw Expanders Used In Organic Rankine Cycle Systems, Lili Shen, Wei Wang, Yu-Ting Wu, Biao Lei, Ruiping Zhi, Chongfang Ma

International Compressor Engineering Conference

Single screw expanders have been widely studied in middle-low temperature heat recovery power system of organic Rankine cycle, which is significant for the energy-conservation and environment-protection. However, internal irreversible loss including leakage, heat transfer and friction power loss has great influence on the performances of single screw expanders. Although some present researches of single screw expanders have been carried out, few can directly reflect the effect of internal irreversible loss on the performance of expanders. Therefore, it is necessary to research the internal characteristics of the single screw expanders. In this paper, a numerical study of a single screw expander …

Application Of Dynamic Centrifugal Compressor Model For Mechanical Vapor Recompression System Simulation, Le Wang, Guangbin Liu, Chuandong Xie, Jun Xiao, Chenyan Zhang

International Compressor Engineering Conference

In order to reducing energy costs and CO2 foot-print, mechanical vapor recompression system (MVR) is used for thermal separation processes such as evaporation and distillation are energy intensive instead of multiple-effect evaporation system. For medium and high capacities, centrifugal compressor (fan) is the most commonly used type for gas compression with a limited operational range and control of the compressors is crucial for safe and efficient operation. The model based on first principles is developed for dynamic performance, which is determined from the compressor geometry and not from the experimentally determined characteristic performance curves. Impeller losses are studied: incidence, skin …

Unsteady Numerical Simulation Of Scroll Expander Based On Cfd, Bin Peng, Li Yaohong, Shengxian Zhao

International Compressor Engineering Conference

As a key component of organic Rankine cycle system(ORC), the performance analysis of the scroll expander is critical for the whole system, and the force analysis of the orbiting scroll plays an important role in the output performance of the expander. In this study, CFD based 3D unsteady flow numerical simulation is performed on scroll expander, the flow characteristics, mechanical properties, output torque and power of the R134a scroll expander under different speed are analyzed in detail with dynamic mesh technology. The analysis shows that the inlet mass flow rate increases with the raise of shaft speed, the output torque …

Understanding How First-Generation College Students’ Out-Of-School Experiences, Physics And Stem Identities Relate To Engineering Possible Selves And Certainty Of Career Path, Dina Verdín, Allison Godwin, Gerhard Sonnert, Phillip M. Sadler

School of Engineering Education Graduate Student Series

This full, research category study examines how out-of-school experiences in Grades 9-12 predict first-generation college students’ engineering possible selves and certainty of career path. The data for this study came from a large-scale survey on outreach programs which was distributed in first- semester English courses to capture an array of responses from students interested in STEM and non-STEM careers. We used structural equation modeling to examine a set of hypotheses: 1) out-of-school experiences would be mediated by interest and recognition in physics and STEM and no direct effect will be found for out-of-school experiences on physics and STEM identities, 2) …

Design And Implementation Of An Efficient Parallel Feel-The-Way Clustering Algorithm On High Performance Computing Systems, Weijian Zheng, Fengguang Song, Dali Wang

Department of Computer Science Technical Reports

No abstract provided.

A Meta-Analysis Of Gifted And Talented Identification Practices, Jaret Hodges, Juliana Tay, Yukiko Maeda, Marcia Gentry

Department of Education Studies Graduate Student Publications

Researchers consider the underrepresentation of Black, Hispanic, and Native American students is largely due to the use of traditional methods of identification (i.e., IQ and standardized achievement tests). To address this concern, researchers created novel nontraditional identification methods (e.g., nonverbal tests, student portfolios, affective checklists). This meta-analysis of 54 studies, consisting of 85 effect sizes representing 191,287,563 students, provides evidence that nontraditional identification methods, while able to narrow the proportional identification gap between underrepresented (Black, Hispanic, and Native American) and represented (Asian and White American) populations, are still unable to address the issue of education inequity. An overall risk ratio …

Comparison Of Dehumidification Performance Of Counter And Cross-Flow Type Liquid Desiccant Dehumidifiers, Hye-Jin Cho, Jae-Weon Jeong

International Refrigeration and Air Conditioning Conference

In HVAC systems, a liquid desiccant system has attracted research attentions due to its advantages on removing latent loads in a conditioned building with less energy consumption. The dehumidifier is the key component in a liquid desiccant system, whose heat and mass transfer performance directly affects the whole dehumidification performance. The coupled heat and mass transfer performance is affected not only by the properties of packing material and inlet conditions of air and desiccant solution, but also by the flow direction between air and desiccant solution. This paper experimentally investigates the dehumidification performance of the counter-flow type and cross-flow type …

Effects Of Economizer Type And Size To The Gas Injected System Using Zeotropic R32/R1234ze(E) Mixture, Zuo Cheng, Baolong Wang, Wenxing Shi, Xianting Li

International Refrigeration and Air Conditioning Conference

Refrigerant mixtures are commonly regarded as a potential substitute because rare pure refrigerants can totally meet all the requirements of environmental, thermodynamic and safe properties. Meanwhile as an effective means, vapour injection is widely applied to improve the system performance of heat pump under large pressure ratio. However, the difference of using pure refrigerant and refrigerant mixtures, which configuration of vapour injection is more suitable for refrigerant mixtures are still unclear. In this paper, R32/R1234ze(E) mixtures are chosen as refrigerant pairs for its great potential in the future, and the scroll compressor is chosen as well to carry out the …

A Review Of Electronic Expansion Valve Correlations For Air-Conditioning And Heat Pump Systems, Hanlong Wan, Yunho Hwang, Saikee Oh

International Refrigeration and Air Conditioning Conference

Split-type air-conditioning systems with multiple indoor units and variable capacity feature, also known as variable refrigerant flow systems (VRF), are growing in both residential and commercial buildings for its flexibility in configurations and high energy efficiency through zoning control and variable capacity control. The VRF system controls its capacity by the combination of drive frequency of variable speed compressor and opening of electronic expansion valves (EEV). According to fluid dynamics analysis, the mass flow rate is a function of the EEV opening. Therefore, the accurate correlation of mass flow rate through an EEV is important in accurate prediction of the …

Comparison Of Two Object-Oriented Modeling Environments For The Dynamic Simulations Of A Residential Heat Pump, Viren Bhanot, Rohit Dhumane, Andrea Cioncolini, Paolo Petagna, Jiazhen Ling, Vikrant Chandramohan Aute, Reinhard Radermacher

International Refrigeration and Air Conditioning Conference

Object-oriented physical-modelling platforms greatly facilitate the task of the modelling engineer by abstracting away a lot of the complexity associated with sorting the governing equations and also the nuances of the numerical methods used for solving the differential-algebraic equations (DAEs). For this reason, they have been steadily gaining in popularity in the field of thermofluid simulations. In this study, we compare two platforms of this type: Dymola and EcosimPro. Dymola is a physical modelling environment originally developed at Lund University and now being developed by Dassault Systèmes, and is a commercially available implementation of the open-source physical modelling language Modelica. …

Heat Transfer Process Within The R744 Two-Phase Ejector: Numerical And Experimental Study, Michal Haida, Jacek Smolka, Armin Hafner, Mikolaj Mastrowski, Michal Palacz, Kenneth B. Madsen, Andrzej J. Nowak, Krzysztof Banasiak

International Refrigeration and Air Conditioning Conference

The proposed three dimensional CFD model to simulate the influence of the heat transfer on the R744 two-phase ejector performance is presented. The numerical model was developed based on the homogeneous real fluid flow assumption with the enthalpy-based formulation of the energy equation. The R744 two-phase ejector was designed to evaluate the temperature profile within the ejector walls. The prototype R744 ejector for experimental investigation was manufactured by Institute of Thermal Technology and ATM in Poland. The performance measurements were carried out at a R744 test facility at SINTEF/NTNU in Norway. The foregoing ejector was equipped with the thirteen thermocouples …

A Preliminary Experimental Study On The Performance Of A Membrane-Based Air Dehumidifier Using Ionic Liquid, Xiaobing Liu, Joseph Warner, Ming Qu, Xiaoli Liu, Harish Opadrishta, Parmalee William

International Refrigeration and Air Conditioning Conference

Liquid desiccant air dehumidification (LDAD) is a promising alternative to the dehumidification systems that use mechanical cooling. However, its use in the market is still very limited due to its high installation cost, intensive carryover, and maintenance issues associated with the corrosion resulting from conventional liquid desiccants. The research reported in this paper aimed at addressing these challenges by applying membrane technology and ionic liquids in LDAD. This paper introduces a design of a membrane-based ionic liquid desiccant air dehumidification (MILDAD). A small-scale prototype of the MILDAD was built and tested in controlled conditions to characterize its performance. The preliminary …

Uncertainty Analysis Of The Experimental Results Of Air Conditioner Performance Due To The Uncertainty Of The Equation Of State, Howard Cheung, Jérôme Frutiger, Ian Bell, Jens Abildskov, Gürkan Sin, Shengwei Wang

International Refrigeration and Air Conditioning Conference

In previous literature, the uncertainty analyses of experimental results of air conditioners usually ignored the uncertainty due to the equation of state (EoS) of the refrigerants. One possible reason was that the uncertainty reported in the EoS literature was much smaller than the one of the measurement. However, with the advancement of measurement technologies, the impact of measurement uncertainty on the air conditioner performance calculation is lowered and becomes on par with that of the EoS. Simultaneously, new research findings give more comprehensive understanding of the EoS uncertainties, such as that the uncertainty of EoS reported in previous studies was …

Theoretical Study On A Modified Subcooling Vapor-Compression Refrigeration Cycle Using Hydrocarbon Mixture R290/R600a, Qi Chen, Jianlin Yu, Gang Yan, Yunho Hwang

International Refrigeration and Air Conditioning Conference

In this study, a modified subcooling vapor-compression refrigeration cycle (MSVRC) using refrigerant mixture R290/R600a was proposed for applications in refrigerator-freezers. In the MSVRC, A phase separator is utilized to split the refrigerant mixture and obtain two different components after partial condensation in the condenser. Moreover, an internal evaporating subcooler is introduced to enhance the overall system performance. Energetic and exergetic analysis methods are used to theoretically evaluate the system operating performance of MSVRC and compared with the traditional vapor-compression refrigeration cycle (TVRC). The simulation results show that the MSVRC outperforms TVRC in the aspect of coefficient of performance (COP), volumetric …

Thermodynamic Design Of A Mesoscale Vapor Compression Cooling Device, Ricardo Yee, Christian Hermes

International Refrigeration and Air Conditioning Conference

This paper presents a thermodynamic methodology for designing a vapor compression refrigeration system aiming at electronics cooling. A cycle simulation model was developed firstly assuming isentropic compression and isenthalpic expansion, whereas the heat exchangers (condenser and evaporator) were modelled following a distributed approach. Whilst a 3-D heat conduction model calculates the heat leakage from the condenser to the evaporator, 2-D heat conduction models provide the temperature distribution (and the heat transfer rates) at the cold and hot ends. The fluid flow was modelled as 1-D considering both the momentum and the energy conservation equations to design the heat exchangers geometry …

A Design Approach For Liquid Separators Applied To Household Refrigerators, Isabel Janke, Alexsandro Dos Santos Silveira, Joel Boeng

International Refrigeration and Air Conditioning Conference

The objective of this study was to develop a methodology for designing a T-junction liquid-vapor separator for household refrigerators. The influence of the following independent parameters on the separator performance was studied: i) refrigerant mass flow rate, ii) inlet vapor quality, iii) evaporation temperature, iv) critical droplet diameter, v) critical bubble diameter and vi) suction ratio. For modeling purposes, the T-junction was divided into three sub-models: inlet, vapor and liquid branches. The inlet branch sub-model revealed that a proper phase separation occurs with larger diameters as the refrigerant mass flow rate and vapor quality increase. The dimensions of the vapor …

Cfd Simulation Of Vortex Flashing Flows In Convergent-Divergent Nozzles, Jingwei Zhu, Stefan Elbel

International Refrigeration and Air Conditioning Conference

Vortex control is a novel two-phase convergent-divergent nozzle restrictiveness control mechanism by adjustable nozzle inlet vortex. It requires no change to the physical dimensions of the nozzle geometry. A nozzle with inlet vortex was called vortex nozzle (or swirl nozzle). Previous experiments on vortex nozzle with initially subcooled R134a showed that the nozzle becomes more restrictive as the strength of the inlet vortex increases. The maximum vortex control range has been observed to be 42% of maximum choked total mass flow rate through the nozzle. The control range of inlet pressures and mass flow rates that can be achieved by …

Theoretical And Experimental Evaluation Of Microchannel Condensers Applied To Household Refrigerators, Renata Soares Rametta, Joel Boeng, Joel Boeng

International Refrigeration and Air Conditioning Conference

The aim of this work is to study, theoretically and experimentally, the impact of using forced-draft microchannel condensers in a specific model of household refrigerator. To this end, a mathematical model was developed to predict the condenser heat released rate and the air-side pressure drop as a function of geometry and operating conditions. This model was then added to an existing simulation platform of household refrigerators, in an attempt to study the effect of the heat exchanger on the appliance performance. Experiments were carried out in an open-type wind tunnel and in a climate-controlled test chamber, to validate both the …

Performance Analysis Of Active Magnetic Regenerative Refrigeration Cycle Using Transient Modeling, Minwoong Kang, Stefan Elbel

International Refrigeration and Air Conditioning Conference

This paper evaluates the performance of an active magnetic regenerative refrigeration cycle (AMRRC) by using a transient modeling tools. While theoretical COPs of magnetic refrigeration systems are quite promising, parasitic losses inherent to the cycle can substantially reduce the energy efficiency that can be achieved in reality. For solid state refrigeration systems, such as the AMRR cycle, the regenerator undergoes cyclic heating and cooling, making the thermal capacitance of the component a critical parameter during no flow periods. Additional performance reductions are experienced due to additional temperature differences required to convect heat into and out of the magnetic regenerator through …

Modeling And Experimental Study On A Direct Expansion Based Enhanced Dehumidification Air Conditioning System, Wenjing Chen, Ming-Yin Chan, Wen Bing Weng, Shi Ming Deng

International Refrigeration and Air Conditioning Conference

Direct expansion (DX) air conditioning (A/C) systems are widely used for controlling indoor air temperature and humidity in various buildings in hot and humid climates since they are simpler and more energy efficient, and generally cost less to own and maintain. However, it is often problematic for a DX A/C system to provide desired humidity control due to the current system design trends, variable weather conditions and the commonly used control strategies for DX A/C systems. Therefore, a standalone DX based enhanced dehumidification air conditioning (EDAC) system is proposed to provide suitable indoor humidity control at different seasons. There are …