Numerical study of an exhaust heat recovery system using corrugated tubes and twisted tape inserts

Thesis (M.S.) University of Alaska Fairbanks, 2014Diesel engine generators are the major power source for small communities in cold regions. Diesel generators waste about 1/3 of their fuel energy in the form of heat through exhaust gas. The primary goal of this work is to capture part of the heat from the exhaust and improve the efficiency of the system. A gas to liquid heat transfer performance of a concentric tube heat exchanger with corrugated tubes and twisted tape inserts is investigated by considering its effects on engine performance and economics. This type of heat exchanger is expected to be inexpensive to install and effective in heat transfer, with minimal effect on exhaust emissions of diesel engines. Most previous research has investigated liquid to liquid heat transfer in corrugated tubes at low Reynolds, not gas to liquid heat transfer. The SolidWorks Flow Simulation computer program was used to perform these studies. The program is first validated by comparing simulation results with renowned correlations and field measurements. Simulations are then conducted for a concentric tube heat exchanger with corrugated tubes and twisted tapes of different configurations to determine the optimal design. The maximum enhancement in the rate of heat transfer was found in an annularly corrugated tube heat exchanger with twisted tape inserts. This exchanger transfers about 235.3% and 67.26 % more heat compared to plain tube and annularly corrugated tube heat exchangers without twisted tapes, respectively. Based on optimal results, for a 120 kWe diesel generator, the application of an annularly corrugated tube heat exchanger with twisted tape inserts can save 2,250 gallons of fuel annually (a cost of approximately $11,330) expected payback of initial cost in one month. In addition, saving heating fuel also reduces CO₂ emissions by 23 metric tons per year

Multiple wavelength InGaAs quantum dot lasers using selective area epitaxy

The authors demonstrate multiple wavelength lasers fabricated from InGaAsquantum dots. Selective area epitaxy is used to grow the active region, consisting of five layer stack of InGaAsquantum dots with different band gapenergies in selected regions of the substrate, for fabrication of the lasers. The mechanism responsible for engineering of the band gap of quantum dots is discussed. The performance of the selectively grown lasers is compared to the lasers fabricated from structures grown in a standard, nonselective area growth process.The Australian Research Council is gratefully acknowledged for financial support

Determining the extent and characteristics of overrepresentation of large truck crashes in daytime and nighttime work zones

The growth of vehicle travel in the United States has accelerated wear on the interstate highway system leading to frequent pavement repair and rehabilitation projects. The presence of work zones not only causes traffic congestion and backup but also increases the crash risk. Therefore, the FHWA (Federal Highway Administration) has allotted a significant amount of funds to improve work zone traffic safety and operations. This thesis compares truck and automobile crash characteristics in work zones with those of non-work zones and thus identifies engineering countermeasures to improve work zone truck safety. The researcher used a contingency analysis approach in this study. First, he categorized the North Carolina crash data using different variables. Once categorized, the Breslow-Day test is used to compare the odds of truck and automobile crashes between work zones and non-work zones. Overall, the researcher did not find a significant difference between odds of truck and automobile crashes compared to previous studies. The researcher believes that the difference in results between the present study and the previous studies could either be due to differences in the approach used or better truck management techniques employed by the North Carolina DOT (Department of Transportation). The researcher also identified that the maintenance projects performed during the day had a significantly higher odds of truck crashes relative to that of automobiles in work zones compared to control sections when workers were present, either with a lane closure or without a lane closure. The researcher believes that the results from the day maintenance projects and its subcategories are the key findings of this study. Therefore, these key findings are used to identify the possible reasons and countermeasures for any disproportionate change in truck to automobile crashes. The identified list of countermeasures includes the use of law enforcement, a smart work zone system, a dynamic late merge system, CMS (Changeable Message Signs), speed display signs, and a CB (Citizen Band) Wizard. These countermeasures were checked for cost effectiveness using a benefit cost (B/C) analysis. The researcher found that law enforcement, smart work zones with costs lower than or equal to half a million dollars, CMS, speed display signs, and the CB Wizard have B/C ratios greater than one and seem to be worthwhile for deployment in work zones. Smart work zones with significantly higher costs of 2.5 million dollars, for example, could be deployed using a more detailed analysis of work zone characteristics. Finally, dynamic late merge system could be used if the site conditions indicate a crash reduction potential of at least 10 – 15 percent

Low-Cost Lung Cancer Detection Using Machine Learning on Breath Samples

In recent years, electronic nose devices have become a popular approach for identifying respiratory disorders including lung cancer. Traditional e-nose systems have had very consistent principles and patterns of sensor responses. After coming to the realization that detecting cancer at early stages can save 99 percent of lives, it has become imperative to design a machine that can easily detect for lung cancer(the most common type of cancer) in a cost-effective and accurate way. Designing an Al Nose was a perfect way to counteract the problem. A tiny e-nose system with 14 gas sensors of four types was created and fifty breath samples were analyzed. Five feature extraction techniques and two classifiers were used to test the system's efficiency in recognizing and discriminating lung cancer from other respiratory disorders and healthy controls. Finally, the impact of different sensor types on the capacity of e-nose systems to identify objects was investigated. The sensitivity, specificity, and accuracy of distinguishing lung cancer patients from healthy controls are 91.58 percent, 91.72 percent, and 91.59 percent, respectively, when utilizing the DA fuzzy 5-NIN classification approach. The findings imply that type-specific sensors might improve the diagnostic accuracy of e-nose devices greatly. These findings indicated that the e-nose system described in this work might be used in lung cancer screening with good results. Furthermore, while creating e-nose systems, it is critical to consider type-different sensors. This machine covers all aspects to most effectively develop a machine that can detect lung cancer that is user-friendly and low cost

The Role of Influenza Infection on Cell Metabolism

In this particular study global metabolomics LCMS data was analyzed to determine the effect of influenza infection on host metabolic processes. Specifically, wild-type male and female mouse lung samples from mice infected with PR8 (H1N1) or both PR8 and a reinfection of X31 (H3N2) were analyzed. The LC/MS(liquid chromatography-mass spectrometry) based global metabolomics will be performed on the samples using hydrophilic interaction liquid chromatography to separate polar analytes from the tissues (Dettmer, Aronov, 2007). Metabolites impacted by influenza infection in all samples will be analyzed to compare male and female mice, as well as differences between PR8 infection and X31 reinfection. Bioinformatic analysis will be done using MIDTOD-a software which performs automated, high throughput statistical analysis and identification of metabolites. Information regarding the regulatory and biosynthetic relationships between the metabolites and genes and proteins is also obtained. This metabolite analysis is part of a larger study being done (including genomics and proteomics) to fully characterize the effects of Influenza infection on cellular function

STATIC TYPE CHECKER TOOLS FOR DART

This project presents the static type checkers that I developed for the optional type system of the Dart programming language. Dart is an optionally typed language and as a result has an unsound type system. In this project I have created the static type checker tools for dart. The first static type checker tool ensures mandatory typing of Dart code. This checker can be invoked by giving a new compiler option that I have added to the compiler configuration. This checker will help in catching any type errors early at compile time rather than at run time. The second static type checker improves the Dart’s support for covariant generics. This static checker issues warnings at compile time if the covariant use of generics is followed by a modification of the collection passed covariantly. I have also introduced three annotations that will add more type safety to the Dart programming language. The @notnull annotation is to ensure that null values are not passed as arguments to method parameters. This nullness checker ensures that a running program will never throw a null pointer exception. The @modifies annotation supports the covariance check. The @linear annotation is used to prevent unexpected modification of objects by aliasing. The @linear annotation can be used in conjunction with Dart isolates for concurrent programming

Acid fast cysts in diarrheal stool samples of HIV positive patients

Background: Gastrointestinal infections are very common in patients with HIV infection or AIDS, and diarrhea is a common clinical presentation of these infections. Acid fast protozoans are very commonly responsible for diarrhea in HIV positive patients leading to death in many cases.Methods: The study group included 50 HIV seropositive patients suffering from diarrhea and the control group included 50 HIV seronegative patients suffering from diarrhea. The stool samples collected were concentrated using formol-ether concentration technique and stained using modified Ziehl-Neelsen’s staining procedure.Results: Among the diarrheal stool samples of HIV positive patients (n=50), 17 (34%) were positive for acid fast cysts, and among the HIV negative stool samples (n=50), 2 (4%) were positive for acid fast cysts. Cryptosporidium oocysts were detected in 15 (30%) and Isospora oocysts in 2 (4%) of the samples in the study group. Cryptosporidium oocysts were detected in 2 (4%) of the samples in the control group. There existed a significant difference between the positivity of HIV-positive and HIV-negative diarrheal stool samples.Conclusion: Timely and effective diagnosis could help in delivering appropriate treatment in an already immunocompromised patient.

Neonatal sepsis due to Weeksella virosa

Weeksella virosa was previously included in group II f of CDC. We here present the Microbiological characteristics of the isolate from a case of neonatal sepsis at our center. The organism is a non-fermenter growing only on blood agar and not on Mac Conkey agar, oxidase and catalase positive, and negative for several other bio-chemical tests, except for indole with Ehrlich’s reagent. The isolate in the present case study was sensitive to aminoglycosides and β- lactams, and resistant to quinolones and carbapenems