Ensuring cost-effective heat exchanger network design for non-continuous processes

The variation in stream conditions over time inevitably adds significant complexity to the task of integrating non-continuous processes. The Time Averaging Method (TAM), where stream conditions are simply averaged across the entire time cycle, leads to unrealistic energy targets for direct heat recovery and consequently to Heat Exchanger Network (HEN) designs that are in fact suboptimal. This realisation led to the development of the Time Slice Method (TSM) that instead considers each time interval separately, and can be used to reach accurate targets and to design the appropriate HEN to maximise heat recovery. However, in practise the HENs often require excessive exchanger surface area, which renders them unfeasible when capital costs are taken in to account. An extension of the TSM that reduces the required overall exchanger surface area and systematically distributes it across the stream matches is proposed. The methodology is summarised with the help of a simple case study and further improvement opportunities are discusse

Carbon Emissions Pinch Analysis (CEPA) for emissions reduction in the New Zealand electricity sector

Carbon Emissions Pinch Analysis (CEPA) is a recent extension of traditional thermal and mass pinch analysis to the area of emissions targeting and planning on a macro-scale (i.e. economy wide). This paper presents an extension to the current methodology that accounts for increased demand and a carbon pinch analysis of the New Zealand electricity industry while illustrating some of the issues with realising meaningful emissions reductions. The current large proportion of renewable generation (67% in 2007) complicates extensive reduction of carbon emissions from electricity generation. The largest growth in renewable generation is expected to come from geothermal generation followed by wind and hydro. A four fold increase in geothermal generation capacity is needed in addition to large amounts of new wind generation to reduce emissions to around 1990 levels and also meet projected demand. The expected expansion of geothermal generation in New Zealand raises issues of GHG emissions from the geothermal fields. The emissions factors between fields can vary by almost two orders of magnitude making predictions of total emissions highly site specific

Stability of Extemporaneously Prepared Sodium Benzoate Oral Suspension

The stability of extemporaneously prepared sodium benzoate oral suspension in cherry syrup and Ora-Sweet was studied. Oral solutions of 250-mg/mL sodium benzoate were prepared in either cherry syrup or Ora-Sweet. To a beaker, 50 grams of Sodium Benzoate Powder USP was dissolved and filtered, the solution was divided equally into two parts, and each aliquot was added into two separate calibrated 100-mL amber vials. In the first vial, cherry syrup was added to make a final volume of 100 mL. In the second vial, Ora-Sweet was added to give a final volume of 100 mL. This process was repeated to prepare three solutions of each kind and all were stored at room temperature. A 250-µL sample was withdrawn immediately after preparation and again at 7, 14, 28, 60, and 90 days for each sample. At each time point, further dilution was made to an expected concentration of 0.25 mg/mL with sample diluent, and the samples were assayed in triplicate by stability-indicating high-performance liquid chromatography. Stability was defined as the retention of at least 90% of the initial concentration. At least 92% of the initial concentration of sodium benzoate in cherry syrup and at least 96% of the sodium benzoate in Ora-Sweet remained throughout the 90-day study period. There were no detectable changes in color and no visible microbial growth in any sample. Extemporaneously compounded suspensions of sodium benzoate in cherry syrup or Ora-Sweet were stable for at least 90 days when stored in a 4-oz amber plastic bottle at room temperature in reduced lighting

WinGEMS modelling and pinch analysis of a paper machine for utility reduction

A multi-ply paper machine process model was developed using WinGEMS and the stream data produced was used to conduct a pinch analysis. The product stream was excluded from the analysis and the composite curves display the enthalpy contained only in the inputs and outputs to the various sections of the paper machine. The pinch point for the overall paper machine was 55.9 C while the minimum hot utility target was 170 MW. Occurrences of cross pinch heat transfer were identified and discussed. Heat recovery options for heating of the fresh water showers, using waste heat streams were investigated. Steam savings of over 14 MW could be achieved by recovering heat from two waste streams that currently go directly to drain with no heat recovery taking place. The use of pinch analysis for utilities targeting under non-continuous conditions was examined. Finally, the feasibility of integrating non-conventional technologies, such as heat storage, is discussed

Highly-tunable formation of nitrogen-vacancy centers via ion implantation

We demonstrate highly-tunable formation of nitrogen-vacancy (NV) centers using 20 keV 15N+ ion implantation through arrays of high-resolution apertures fabricated with electron beam lithography. By varying the aperture diameters from 80 to 240 nm, as well as the average ion fluences from 5 x 10^10 to 2 x 10^11 ions/cm^2, we can control the number of ions per aperture. We analyze the photoluminescence on multiple sites with different implantation parameters and obtain ion-to-NV conversion yields of 6 to 7%, consistent across all ion fluences. The implanted NV centers have spin dephasing times T2* ~ 3 microseconds, comparable to naturally occurring NV centers in high purity diamond with natural abundance 13C. With this technique, we can deterministically control the population distribution of NV centers in each aperture, allowing for the study of single or coupled NV centers and their integration into photonic structures.Comment: Related papers at http://pettagroup.princeton.ed

Predicting the Risk of Obstructive Sleep Apnea and Difficult Endotracheal Intubation in a Surgical Population in a Rural Community Hospital Setting

Purpose: The purpose of this paper is to provide a theoretical framework with practical application for facilitating patient flow through the operative process using the Lean philosophy to minimized delays and cancellations. Theoretical orientation: Efficient, quality patient care has always been the hallmark of Nurse Anesthetist practice. Lean healthcare introduces continuous quality improvement (CQI) processes used in Lean manufacturing to the healthcare system. The principal aspect of Lean healthcare is the concept of a value stream where work is standardized, work flow is streamlined and waste is eliminated, thus creating value. Nature of Review: In the surgical suite waits, delays and cancellation are endemic. Lean healthcare views these as waste in the system. They must be eliminated to provide value to the patient, who is the ultimate customer. Managing the flow of the patient successfully through this process will increase the quality of patient care ( value ), increase patient and provider satisfaction, increase operating room efficiency and reduce cost. Nurse Anesthetists are uniquely positioned in the operative arena to accomplish this. The greatest opportunity to reduce delays and cancellations is seen with smoothing the inter-daily workload. Successful interventions to accomplish this include: 1) maximizing the preoperative anesthesia assessment, 2) standardizing and streamlining work during the perioperative phase to minimize turn over time, and 3) adequate staffing levels to optimize postoperatively care

Assessment of flagellate diversity at deep-sea hydrothermal vents using the combined approach of culture-dependent and culture-independent methods

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 2000Eighteen strains of flagellated protists representing 9 species were isolated and cultured from four deep-sea hydrothermal vents in the Eastern Pacific Ocean: Juan de Fuca Ridge, Guaymas Basin, and both 21°N and 9°N on the East Pacific Rise (EPR). The hydrothermal vent flagellates belonged to six different taxonomic orders: the Ancyromonadida, Bicosoecida, Cercomonadida, Choanoflagellida, Chrysomonadida, and Kinetoplastida. Molecular and ultrastructural evidence point to one of the isolates, Ancyromonas, as a plausible candidate for the closest relative to the common ancestor of Metazoans, Fungi, and Choanoflagellates (the Opisthokonta). Using l8S rDNA sequences from most of the major eukaryotic lineages, maximum likelihood, minimum evolution and maximum parsimony analyses yielded congruent phylogenies supporting this hypothesis. Deep-sea vent samples were both cultured to select for kinetoplastid flagellates and analyzed without culturing by denaturing gradient gel electrophoresis (DGGE) using PCR primers specific to the kinetoplastid clade. By comparing these two different methods of analysis, my goal was to decrease the biases and/or errors inherent in either method alone and to improve our ability to assess flagellate diversity and distribution in samples from remote vent environments. PCR and DGGE were used to specifically isolate and amplify target DNA's from all cultured kinetoplastid species in matching vent samples, thus corroborating the findings of culturing. Molecular methods had the additional ability to detect species presence where culturing did not, thereby providing a better indication of the distribution of these species. Many of the vent isolates were ubiquitous members of marine, freshwater, and terrestrial ecosystems worldwide, suggesting a global distribution of these flagellate species. This discovery advanced the hypothesis that ubiquity in distribution patterns among heterotrophic flagellates implies high tolerance and/or adaptability to a wide range of environmental conditions. Experiments under vent conditions of high pressure and high concentrations of metals and sulfide showed that some of these species are very tolerant to extreme environmental conditions.WHOI Education Office, National Science Foundation, Rhinehart Coastal Research Center, PADI Foundatio

An economical analysis of farming in Overton county, Tennessee

This farm analysis was based on an economic analysis of fifty representative farms in Overton County. The material from this analysis was supplemented by United States Census reports, Climatological records, soil survey reports, and other data that would aid in a complete economic analysis of agricultural conditions and enable definite recommendations to be made for the improvement of agricultural conditions in this area. The objects of this economic study were: (1) To determine the factors that affect farm profits in that area. (2) To discover the most profitable and the least profitable farms, and to study their organization and management to determine the reasons for their success or failure. (3) To use these facts in making recommendations for changes in the organization and management of the farms in this county and of those counties on the northeast Highland Rim, having similar conditions

Carbon emissions pinch analysis (CEPA) for emissions reduction in the New Zealand electricity sector

Carbon Emissions Pinch Analysis (CEPA) is a recent extension of traditional thermal and mass pinch analysis to the area of emissions targeting and planning on a macroscale (i.e. economy wide). This paper presents a carbon pinch analysis of the New Zealand electricity industry and illustrates some of the issues with realising meaningful emissions reductions. The current large proportion of renewable generation sources (~67% in 2007) complicates wholesale emissions reductions. The biggest growth in renewable generation is expected to come from geothermal energy followed by wind and hydro. A four fold increase in geothermal generation capacity is needed in addition to large amounts of new wind generation to reduce emissions to around 1990 levels and also meet projected demand. The expected expansion of geothermal generation in New Zealand raises issues of GHG emissions from the geothermal fields. The emissions factors between fields can vary by almost two orders of magnitude making predictions of total emissions highly site specific