Community, Boundary and Identity: The House Image in Robert Frost

This dissertation provides a detailed description of the research work completed on fin staged heat exchangers. The effects of staging fin on the frosting performance of heat pump evaporators and the whole heat pump system have been studied experimentally and theoretically. Frost degrades the performance of fin-and-tube outdoor coils as well as the whole heat pump system. The objective of the experimental part of this study was to investigate the effects of the staging fin on the frost/defrost performance of heat pump outdoor coils under different operating conditions. To accomplish this objective, a series of frosting tests was conducted on an off-the-shelf heat pump system with five (three two-row and two three-row) evaporators over a range of outdoor temperatures and humidities and a range of airflow rates typical of those found in residential sized heat pumps. Performances of the heat pump unit with baseline or fin staged outdoor coils at either frosting or steady-state test conditions are compared and analyzed. Experimental data showed that for a given tworow heat pump outdoor coil operating at the standard ANSI/ASHRAE 35 °F (1.7 °C) frosting conditions, fin staging increased cycle time and COP. There was a small decrease in peak capacity at lower initial airflow rates. At a lower temperature of 28 °F (2.2 °C), cycle time continued to be enhanced with fin staging, and cyclic COP was within 5% of the base case when fin staging was used. In the second step of this work, an analytical model to simulate the performance of both the baseline and fin staged heat pump coils under frosting conditions was developed based on fundamental heat and mass transfer principles. The transient performance of the frosted evaporator was analyzed with the quasi-steady state approach. The section-by-section evaluation scheme was combined with the tubeby- tube approach to model the mass transfer process in the frost formation module. The two-dimensional fin surface was divided into a number of parallel non-overlapping sections. Each of the sections was the calculation unit for the mass transfer. Methods for calculating the airside heat transfer coefficient and friction factor were developed and applied to the simulation model of the fin staged coil. To verify the validity of the frosted evaporator model, the frosting performance of three two-row coils at the same test conditions was simulated and compared with experimental data. The frosted evaporator model appeared to provide satisfactory simulation of the fin-and-tube heat exchanger during the frost buildup process. Comparisons with the test data indicated that the model could capture the trends of the coil capacity, pressure drop, airflow and frost growth. The model also provided a variety of other simulation results including frost mass accumulation, air velocity inside coil, air and refrigerant outlet state, and so on. Overall, the numerical results were in reasonable agreement with the test data under different frosting operation conditions.

Texte remanié de: Dissertation--Trier, Allemagne--Universität Trier, 2002. / Bibliogr. p. 142-149.

The four poets in this dissertation--Hester Pulter, Anne Bradstreet, Thomas Hardy, and Robert Frost--write poems that resist domestic confinement. In these poems, houses become prisons from which the poet must enact an escape. Pulter, Bradstreet, Hardy and Frost--writers drawn from two sides of the Atlantic and two different centuries--are nevertheless linked by the urge to create poems that will provide doorways to less confined states of existence. They are also linked by the formal strategies they use for the attainment of such poetic release, and by the scale of their rebellion against enclosing structures. All four poets make claustrophobic domestic spaces the topic of their poetry, but rather than writing their objections into the unbounded space of free verse, they mimic the confinement of small rooms in the restrained dimensions of their poems. Rather than discard the enclosure of poetry, they accept its confinement. Their forms of release, then, are more pointed; they emerge at brief instances, as opposed to making wholesale departures. Instead of using their poems to create boundless spaces, unrestricted by walls and ceilings and floors, they use their poems to create rooms similar to those occupied by their personae. In poems such as these, poetic freedom is less absolute than relative to the extent of confinement, and it is made sweeter by the awareness of inescapable limits. / text

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The economic impact of frost on agriculture remains a global problem. It is a particular concern for the New Zealand wine industry, where the consequences of an unexpected spring frost can be disastrous. Marlborough is located in the north-eastern corner of the South Island and is the largest grape-growing region in New Zealand. The region is surrounded by complex mountainous terrain that gives rise to extremes of climate, particularly large spatial variations of minimum temperature and the frequent occurrence of spring frost. The high spatial variation of near-surface minimum temperature can lead to under-preparedness among grape growers who rely on accurate frost forecasts as part of their frost mitigation systems. Field campaigns of the 1980’s and 90’s extended the understanding of the physical meteorological processes that affect cooling in complex terrain. More recent modelling efforts continue to refine this knowledge, although much less attention is given to the effects of different cooling processes on near-surface temperature. Agricultural developments in areas of complex terrain would benefit from an increased understanding of the meteorological processes that govern near-surface cooling, as this will help with the local prediction of frost. The spatial variation of near-surface minimum temperatures is first explored by identifying relationships with synoptic weather patterns using the Kidson (2000) synoptic classification scheme. Analysis revealed that Kidson types associated with the largest daily variations in near-surface minimum temperature (T, TNW and H) are not always associated with the occurrence of frost. Frost is more likely to occur during the cooler airflows of Kidson type HW, HNW and SW, or during the settled anticyclonic conditions that follow cooler airflows. The relationship between the spatial variation of near-surface minimum temperature and regional airflow patterns is explored using numerical weather prediction (NWP) modelling. Results indicated that a high σ Tmin around the region is a product of interaction between the region’s complex terrain and ambient meteorology, and it could occur in both settled weather and more dynamic synoptic conditions. A high regional σ Tmin during light ridge top winds could occur as a function of a location’s relative susceptibility to ventilation from thermally-induced drainage winds, and it may also occur as a result of the simultaneous ventilation and stagnation of near-surface air layers as synoptic wind interacts with local topography. The influence of the vertical structure of the nocturnal boundary layer (NBL) on nearsurface minimum temperature was investigated with the University of Canterbury Sonic Detection And Ranging (SODAR). Measurements confirmed the formation of low-level jets (LLJ’s) in the Awatere and Wairau Valleys during settled weather conditions, and that shear-induced turbulence beneath the jets was sufficient to mix warmer air to the surface and increase local temperatures. The process is sufficient to reduce frost risk to some of the region’s upper valleys during clear settled weather. In stronger ridge top winds development of the LLJ’s can be suppressed or eliminated and this was found to reduce shear-induced turbulence near the surface, allowing increased near-surface cooling. While results from this study are of greatest value to the prediction of near-surface minimum temperature and frost in Marlborough, the results could be applied to improved prediction of near-surface minimum temperature in complex terrain around the world. Further research could be directed toward the interaction of synoptic winds with thermally-induced airflows, as the transition zone between these wind systems is believed to govern the temporal and spatial evolution of near-surface stagnation, and this is related to episodes of strong near-surface cooling.

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Cold-acclimation-specific (CAS) gene expression was examined by screening a cDNA library prepared from poly(A)$ sp+$ RNA of cold-acclimated seedlings of a freezing-tolerant variety of alfalfa (Medicago falcata cv Anik). Three distinct CAS cDNA clones, pSM784, pSM2201, and pSM2358 were isolated. The genes corresponding to all three clones are coordinately induced by cold. Expression of these genes is not triggered by other stress treatments such as heat shock, water stress, wounding, or treatment with exogenous ABA. A positive correlation was observed between the level of expression of each gene and the degree of freezing tolerance of four alfalfa cultivars. / A full-length cDNA clone for the most abundantly-expressed gene, cas18 was isolated and sequenced. The deduced polypeptide, CAS18, is relatively small (167 amino acids), is highly hydrophillic, rich in glycine and threonine, and contains two distinctive repeat elements. It exhibits homology with members of the LEA/RAB/Dehydrin gene family--proteins which accumulate in response to water stress or abscisic acid (ABA). The cas18 cDNA hybridizes to three transcripts of 1.6, 1.4 and 1.0 kb in cold acclimated seedlings and cell cultures. The clone described here, Acs784, corresponds to the 1.0 kb transcript. / Expression of this gene is 30-fold greater in cold-acclimated cells than in nonacclimated cells after one week of low temperature treatment. Return to room temperature (deacclimation) results in the rapid disappearance of the three transcripts within just 5 hours. Studies of nuclear "run-on" transcription and transcript stability show that low temperature regulates the expression of cas18 at both the transcriptional and post-transcriptional levels.