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

Understanding the Chondrogenic Potential of Articular Chondrocytes

Articular cartilage is a smooth, visco-elastic, aneural, avascular tissue made of water, an exquisitely organized framework of proteoglycans, glycosaminoglycans, and collagen fibrils and articular chondrocytes. It’s beautiful organization and composition provide it with the flexibility and strength to cover, protect and lubricate the ends of long bones in a diarthrodial joint. Cartilage homeostasis relies on articular chondrocytes to translate the mechanical forces of daily activity into efficient remodeling of the extracellular matrix. Age, joint injury, or other insulting factors can progressively incapacitate articular chondrocytes, resulting in cartilage lesions that devolve to degenerative joint disease. Therefore, the central idea explored in this dissertation is the changing chondrogenic potential of articular chondrocytes. In the first study, we asked if chondrogenic potential affects how primary articular chondrocytes respond to dynamic Ca2+ signaling, the primary signaling mediator of mechanotransduction during extracellular matrix remodeling. In the second study, we explored how age and culture conditions that alter chondrogenic potential influence the transcriptional profile of primary articular chondrocytes using in-depth RNA-sequencing technology. These studies highlight that the chondrogenic potential of articular chondrocytes, which is affected by age and the gradual changes in matrix composition, can be understood through dynamic signaling and transcriptional networks and enhanced through tissue engineering principles to improve upon the long-term efficacies of cartilage resurfacing procedures

A Novel, Facile Method for the Synthesis of pH-Modulating Inorganic Carbonate Nonparticles

From the Washington University Office of Undergraduate Research Digest (WUURD), Vol. 12, 05-01-2017. Published by the Office of Undergraduate Research. Joy Zalis Kiefer, Director of Undergraduate Research and Associate Dean in the College of Arts & Sciences; Lindsey Paunovich, Editor; Helen Human, Programs Manager and Assistant Dean in the College of Arts and Sciences Mentor: Samuel Achilef

Gold nanoparticles for sensing Mn2+ in water

Abstract: Gold nanoparticles coated with polymers like chitosan, polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP) and poly acrylic acid (PAA) can effectively be used to detect the presence of Mn2+ ions in water. A shift in the optical absorbance peak of the Au colloid is observed in the presence of Mn2+ ions. The shift in the absorbance peak wavelength is directly proportional to the concentration of Mn2+ ions in water. Chitosan capping was found to give the maximum shift and as such was selected for the development of a sensor for detecting Mn2+ ions in water. The variation in photo-energy of the photons after passing through the colloidal dispersion of chitosan coated Au nanoparticles varies the conductivity of the detector and this can be related to the concentration of the Mn2+ ions in water. Two different detectors were tested, a nanosensor and a light dependent resistor, with the latter demonstrating better response.

Truncated Microstrip Patch Antenna with DGS Based on Double Looped CSRR Arrays for Enhancement of Bandwidth

This paper presents a novel method for the design of truncated microstrip patch antenna with DGS based on Double Looped CSRR arrays for enhancement of bandwidth. The proposed antenna is suitable for WLAN/Wi-Fi, RFID applications. A truncated microstrip patch antenna without DGS was initially designed for a resonant frequency of 2.86GHz having a bandwidth of 95.6MHz. By integrating a new Double Looped CSRR array (DLCSRR) structure on the ground plane, resonant frequency of the antenna is shifted to 2.47GHz and also the bandwidth is enhanced to 202.5MHz. By implementing DLCSRR array structure on the ground plane size reduction and bandwidth enhancement of 52.79% is achieved. The performance of truncated microstrip patch antenna with DGS based on Double Looped CSRR array structure was also compared by replacing conventional proximity fed microstrip patch antenna with the same physical size. The conventional proximity coupled microstrip patch antenna is designed for a resonant frequency of 2.26GHz with a lower bandwidth of 23.3MHz.The antennas were designed using CST simulation software. The measurement  result shows a good agreement with simulated results

Observed changes in ocean acidity and carbon dioxide exchange in the coastal Bay of Bengal – a link to air pollution

Variations in surface water hydrographic properties and Dissolved Inorganic Carbon (DIC) were evaluated in the coastal Bay of Bengal using observations carried out during March–April 1991 and 2011, including 8 yr monthly time-series observations during 2005 and 2013. The coastal Bay of Bengal is characterised by relatively fresher, more basic and lower pCO2 in 1991 compared to 2011. The rates of decrease in pH, increase in DIC and pCO2 per decade were consistent with global trends in the Southwestern (SW) coastal Bay of Bengal, whereas rates in the Northwestern (NW) coastal Bay of Bengal were observed to be 3–5 times higher. The associated recent increase in sulphate and nitrogen aerosol loadings over NW Bay of Bengal from the Indo-Gangetic Plain and Southeast Asia during winter and spring may be mainly responsible for the increased acidity in recent years. Thus, this region, which was previously considered to be a significant sink for atmospheric CO2, now seems to have become a source of CO2 to the atmosphere

Two substitutable perishable product disaster inventory systems

A disaster inventory system is considered in which two substitutable items are stored for disaster management. In the event of disaster management, a particular product may become stock-out and the situation warrants that a demand for the particular product during its stock-out period may be substituted with another available similar product in the inventory. From the utility point of view, continuous review inventory models are quite appro-priate in disaster inventory management. In this paper, a continuous review two substitutable perishable product disaster inventory model is proposed and analyzed. Since the inventory is maintained for disaster management, an adjustable joint reordering policy for replenishment is adopted. There is no lead time and the replenishment is instantaneous. For this model, some measures of system performance are obtained. The stationary behavior of the model is also considered. Numerical examples are also provided to illustrate the results obtained.http://link.springer.com/journal/10479hb2016Industrial and Systems Engineerin

Red Panda: A Novel Method for Detecting Variants in Single-Cell RNA Sequencing

BACKGROUND: Single-cell sequencing enables us to better understand genetic diseases, such as cancer or autoimmune disorders, which are often affected by changes in rare cells. Currently, no existing software is aimed at identifying single nucleotide variations or micro (1-50 bp) insertions and deletions in single-cell RNA sequencing (scRNA-seq) data. Generating high-quality variant data is vital to the study of the aforementioned diseases, among others. RESULTS: In this study, we report the design and implementation of Red Panda, a novel method to accurately identify variants in scRNA-seq data. Variants were called on scRNA-seq data from human articular chondrocytes, mouse embryonic fibroblasts (MEFs), and simulated data stemming from the MEF alignments. Red Panda had the highest Positive Predictive Value at 45.0%, while other tools-FreeBayes, GATK HaplotypeCaller, GATK UnifiedGenotyper, Monovar, and Platypus-ranged from 5.8-41.53%. From the simulated data, Red Panda had the highest sensitivity at 72.44%. CONCLUSIONS: We show that our method provides a novel and improved mechanism to identify variants in scRNA-seq as compared to currently existing software. However, methods for identification of genomic variants using scRNA-seq data can be still improved

An investigation into factors impacting financial exclusion at the bottom of the pyramid in South Africa

Financial exclusion has been shown to have negative socioeconomic effects on citizens, especially at the bottom of the economic pyramid. South Africa suffers from high levels of financial exclusion, disproportionately at the bottom of the pyramid. This study investigates nine factors identified from the literature as being positively associated with financial exclusion using a logistic regression model. The findings show that the most significant factors associated with being financially excluded at the bottom of the pyramid in South Africa were educational level, primary source of income, age, home language and number of dependents. The study further found that gender, relationship status and home ownership were not associated with being financially excluded. An interesting finding was that living in a rural area as opposed to an urban area was not significantly associated with being excluded. The findings and their implications for expanding financial inclusion at the bottom of the pyramid are discussedhttp://www.tandfonline.com/loi/cdsa202017-08-31hb2017Gordon Institute of Business Science (GIBS)Industrial and Systems Engineerin