AN EXPERIMENT IN CONTINGENT VALUATION AND SOCIAL DESIRABILITY

Social desirability (SD) represents the problem of subjects responding with social norms rather than individual values. This paper briefly surveys the SD literature and considers its relevance for contingent valuation (CV) studies. In an empirical study, undergraduate students were administered the Marlowe-Crowne Social Desirability Scale, as well as CV questions. High SD scores were hypothesized to imply a greater likelihood of offering a protest reason for a zero bid and to increase bids for socially desirable commodities. While all hypotheses were not supported, the empirical results suggest that SD can influence CV responses and should not be dismissed prematurely.Research Methods/ Statistical Methods,

Mobile Heat Pump Exploration Using R445A and R744

The increased usage of hybrid and electric vehicles where waste heat availability is limited has spurred research and development of mobile heat pump systems. Many options exist for heat pump system architectures and refrigerants to be used. Currently R134a use is prevalent in vehicle air conditioning systems but offers poor heat pump performance at low ambient temperatures. Two refrigerants will be explored in this paper, R744 and R445A. Both of these refrigerants are getting attention in vehicle A/C systems because of their relatively low GWP but each offers benefits over R134a in heat pump systems as well. Both refrigerants operate at higher pressures which improves the performance at low ambient temperatures in part due to higher compressor inlet refrigerant densities. R134a (and R445A to a lesser extent) also suffer from the drawback of going into sub-atmospheric pressure operation at temperatures commonly seen in vehicles. Data will be shown for multiple system architectures comparing these refrigerants to R134a. Advantages and disadvantages of each refrigerant will be shown. System control and optimization is important to get the maximum performance from each refrigerant and system. Control exploration will be presented for each alternative refrigerant

Internal Heat Exchanger Performance Quantification and Comparison Testing Methods Including Exploration of the Effects of Location of Measurements and Oil in Circulation

The Internal Heat Exchanger (IHX) is widely known for its potential to improve the performance of air conditioning systems.  The adoption of alternative, more environmentally friendly, refrigerants such as R744 has brought elevated attention to IHX development due to relatively large performance increases from IHX usage compared to conventional refrigerants. In addition, the increasing need for even small incremental improvements in systems using conventional refrigerants has driven the expanded development and implementation of IHXs. The focus of this study is the quantification and comparison of the performance of internal heat exchangers and the effects of location of measurements and oil in circulation rates on the measurement accuracy and actual IHX performance. Typical IHX performance measurements yield the heat exchanger capacity, effectiveness, and the refrigerant pressure drop across each side of the heat exchanger. Existing test standards vary widely on the required test conditions, allowable oil in circulation rates, and instrument locations. The goal of comparison testing is of course to accurately quantify performance while also achieving repeatable results which allow for a fair and useful comparison between IHXs. Test conditions and temperature measurement location can have a large effect on both the accuracy and repeatability of measurements. Conditions close to the saturation dome, i.e. low subcooling or superheat, can make it difficult to accurately determine and control the state point. Thermal stratification across the cross section of the IHX tubes can also lead to measurement difficulty depending on the temperature probe placement. Oil in circulation rates directly factor into the heat exchanger capacity calculations but also can affect the actual heat exchanged as well as the measurements themselves. This paper will discuss these effects and their implications on standard development and test facility design

Continuum model of strong light-matter coupling for molecular polaritons

Strong coupling between light and matter generates hybrid polaritons. We present a continuum model that describes the polaritons by light and matter densities of states (DOS) that only depend on the refractive index of the material. This model is applied to molecular polaritons derived from molecules with broad spectral absorption. While the photonic DOS has a complex spectral distribution, the matter DOS is largely unmodified by strong coupling. We argue that bright states cannot be partitioned from dark states, and instead the photonic DOS is shared over a vast number of matter states

Energy Transfer Based Test Method Development and Evaluation of Horizontal Air Flow Re-Circulatory Air Curtain Efficiencies

Air curtains are often used to reduce the energy transfer across high traffic doorways of cold storage facilities and cold food sections of warehouse type supermarkets. A test method and facility were developed to quantify and visualize the performance of air curtains covering a doorway between a simulated cold storage building and the simulated surrounding ambient conditions. This method was used to determine the effectiveness of horizontal air flow recirculatory air curtains compared to an open doorway. Tracer gas methods have been used in the past to determine losses but this method is designed to measure the actual energy flow through the doorway. Two environmental calorimeters were configured side-by-side with a 2.1m by 2.1m doorway separating high temperature and low temperature spaces. The higher temperature calorimeter contained PID controlled heaters and steam generators to maintain temperature and humidity conditions. The power input to these and all other electrical devices as well as the power loss through the calorimeter walls were measured. The difference at steady state between these values yields the energy transfer through the doorway. The lower temperature side contained a cooling coil located in a wind tunnel and PID controlled trim heaters to finely control the temperature. The coolant flow rate and temperature difference across the coil were measured along with the power consumption of all electrical devices and heat transfer through the walls. The difference between these values yields the heat transfer through the doorway which was used as a check for the calculation from the higher temperature calorimeter. The heat transfer was first measured through the open doorway with no air curtain with the warm side controlled to 24ºC and 60% relative humidity and the cold side controlled to 4ºC. The horizontal air flow, recirculatory air curtain was then installed, optimized, and tested at the same ambient conditions. The air curtain reduced the heat transfer between the calorimeters from 35.7kW to 10.3kW yielding an effectiveness of 71%. There is clear visual evidence that was measured by air thermocouple grids and shown in temperature gradient plots which exemplifies the effectiveness of the air curtain at creating a barrier between the warm and cold sides. The flow of warm air through the top of the doorway and the return flow of cold air through the bottom of the doorway with no air curtain was clearly visible and the temperature gradients became diagonal to horizontal. Upon air curtain activation, the temperature gradients became vertical showing that there was little energy transfer from side to side. In addition to energy savings, there is a comparable benefit in the reduction of humidity transfer which helps to prevent icing and condensation on products and on the floor. The reduction in humidity transfer also helps to prevent frosting of the cooling coils which results in fewer defrost cycles being necessary. Reduced frosting of cooling coils improves performance and further reduces energy consumption

Tunable Hydrophobicity in DNA Micelles:Design, Synthesis, and Characterization of a New Family of DNA Amphiphiles

This work describes the synthesis and characterization of a new family of DNA amphiphiles containing modified nucleobases. The hydrophobicity was imparted by the introduction of a dodec-1-yne chain at the 5-position of the uracil base, which allowed precise and simple tuning of the hydrophobic properties through solid-phase DNA synthesis. The micelles formed from these modified DNA sequences were characterized by atomic force microscopy, dynamic light scattering, and polyacrylamide gel electrophoresis. These experiments revealed the role of the quantity and location of the hydrophobic units in determining the morphology and stability of the micelles. The effects of hybridization on the physical characteristics of the DNA micelles were also studied; these results showed potential for the sequence-specific noncovalent functionalization of the self-assembled aggregates

Controlling the Manifold of Polariton States Through Molecular Disorder

Exciton polaritons, arising from the interaction of electronic transitions with confined electromagnetic fields, have emerged as a powerful tool to manipulate the properties of organic materials. However, standard experimental and theoretical approaches overlook the significant energetic disorder present in most materials now studied. Using the conjugated polymer P3HT as a model platform, we systematically tune the degree of energetic disorder and observe a corresponding redistribution of photonic character within the polariton manifold. Based on these subtle spectral features, we develop a more generalized approach to describe strong light-matter coupling in disordered systems that captures the key spectroscopic observables and provides a description of the rich manifold of states intermediate between bright and dark. Applied to a wide range of organic systems, our method challenges prevailing notions about ultrastrong coupling and whether it can be achieved with broad, disordered absorbers

Efficient Singlet Fission and Triplet-Pair Emission in a Family of Zethrene Diradicaloids.

Singlet fission offers the potential to overcome thermodynamic limits in solar cells by converting the energy of a single absorbed photon into two distinct triplet excitons. However, progress is limited by the small family of suitable materials, and new chromophore design principles are needed. Here, we experimentally vindicate the design concept of diradical stabilization in a tunable family of functionalized zethrenes. All molecules in the series exhibit rapid formation of a bound, spin-entangled triplet-pair state TT. It can be dissociated by thermally activated triplet hopping and exhibits surprisingly strong emission for an optically "dark" state, further enhanced with increasing diradical character. We find that the TT excited-state absorption spectral shape correlates with the binding energy between constituent triplets, providing a new tool to understand this unusual state. Our results reveal a versatile new family of tunable materials with excellent optical and photochemical properties for exploitation in singlet fission devices