ANALYSIS OF HOUSEWIVES' GROCERY SHOPPING BEHAVIOR IN TAIWAN: AN APPLICATION OF THE POISSON SWITCHING REGRESSION

The purpose of this study is to empirically investigate Taiwanese married women's grocery shopping behavior in relation to their labor force participation status. In this study, focus is limited to their grocery shopping frequency which is meant to be a proxy for an input to household production, i.e., food at home. A Poisson switching regression model is developed to estimate parameters of married women's shopping behavior. The results show that the labor force participation status does have a great impact on time allocation behavior.Household production, Labor supply rationing, Poisson switching regression, Shopping frequency, Time allocation, Consumer/Household Economics,

Metallic Carbon Nanotubes, Microwave Characterization And Development Of A Terahertz Detector

It is reported that terahertz radiation from 0.69 to 2.54 THz has been sensitively detected in a device consisting of bundles of carbon nanotubes containing single wall metallic carbon nanotubes, quasi-optically coupled through a lithographically fabricated antenna, and a silicon lens. The measured data are consistent with a bolometric detection process in the metallic tubes and the devices show promise for operation well above 4.2 K. Microwave measurements have also been done up to 20GHz. Voltage responsivity got here is comparable to that of the Schottky diode detector. The detection at microwave frequencies are consistent with the diode detection mode. S11 parameters of different devices were measured using microwave probing, and de-embedding process has been done to get the impedances of the SWNTs. A circuit model was fitted based on the measurement data, and different values of the elements of the circuit are extracted. Frequency response from the circuit model is consistent with the experimental data

Integration of Biomolecular Recognition Elements with Solid-State Devices

Continued advances in stand-alone chemical sensors requires the introduction of new materials and transducers, and the seamless integration of the two. Electronic sensors represent one of the most efficient and versatile sensing transducers that offer advantages of high sensitivity, compatibility with multiple types of materials, network connectivity, and capability of miniaturization. With respect to materials to be used on this platform, many classes and subclasses of materials, including polymers, oxides, semiconductors, and composites have been investigated for various sensing environments. Despite numerous commercial products, major challenges remain. These include enhancing materials for selectivity/specificity, and low cost integration/ miniaturization of devices. Breakthroughs in either area would signify a transformative innovation. In this thesis, a combined materials and devices approach has been explored to address the above challenges. Biomolecular recognition elements, exemplified by aptamers, are the most recent addition to the library of tunable materials for specific detection of analytes. At the same time, nanoscale electrical devices based on tunnel junctions offer the potential for simple design, large scale integration, field deployment, network connectivity, and importantly, miniaturization to the molecular scale. To first establish a framework for studying sorption properties of solid oligonucleotides, custom designed aptamers sequences were studied to determine equilibrium partition coefficients. Linear-solvation-energy-relationship (LSER) analysis provides quantifications of non-covalent bonding properties and reveals the dominance of hydrogen bonding basicity in oligonucleotides. We find that DNA-analyte interactions have selective sorption properties similar to synthetic polymers. LSER analysis provides a chemical basis for material-analyte interactions. Oligonucleotide sequences were integrated with gold nanoparticle chemiresistors to transfer the selective sorption properties to microfabricated electrical devices. Responses generated by oligonucleotides under dry conditions were similar to standard organic mediums used as capping agents and suggests that DNA-based chemiresistor sensors operate with a similar mechanism based on sorption induced swelling. The equilibrium mass-sorption behavior of bulk DNA films could be translated to the chemiresistor sensitivity profiles. Our work establishes oligonucleotides, including aptamers, as a class of sorptive materials that can be systematically studied, engineered, and integrated with nanoscale electronic sensor devices. Experiments to investigate secondary structure effects were inconclusive and we conclude that further work should investigate DNA aptamers in buffered, aqueous environments to unequivocally establish the ability of chemiresitors to signal molecular recognition. Concurrent with the above studies, device integration and miniaturization was investigated to combine many sensing materials into a single, compact design. Arrays of nanoscale chemiresistors with critical features on the order of 10 – 100 nm were developed, using dielectrophoretic assembly of gold nanoparticles to control placement of the sensing material with nanometer accuracy. The nanoscale chemiresistors achieved the smallest known gold nanoparticle chemiresistors relying on just 2 – 3 layers of nanoparticles within 50 nm gaps, and were found to be more robust and less dependent on film thickness than previously published designs. Due to shorter diffusion paths, the sensors are also faster in response and recovery. A proof-of-concept, integrated single-chip sensor array was created and it showed similar response patterns as non-integrated sensor arrays. Dielectrophoresis is established as a key enabler for nanoscale, integrated devices. Based on the major findings of the thesis work, additional investigations were initiated to investigate the potential for nanoscale chemiresitor sensors to operate in buffered, aqueous (liquid) flow cells. Preliminary experiments show that chemiresistor sensing is transferable to liquid environments where analyte molecules are observed to partition from the bulk liquid to the sensing materials, leading to a detectable change of the device electrical properties. Comparing micron- and nano-scale devices fabricated using aqueous oligonucleotide-functionalized gold nanoparticles, it was found that nanoscale chemiresistors are more resistant to solvent damage than 5 µm chemiresistors. We conclude that future experiments to investigate aptamer sensing in aqueous solutions is a promising direction. Overall, this thesis is a significant contribution to materials development and device design to attain improved sensor selectivity and higher levels of device integration. First, it offers a scheme for design, selection, and validation of materials that confer analyte-specific interactions. Second, it paves the way for large scale sensor integration and parallel operation on a single chip. Lastly, it offers an approach to combine biomolecular recognition elements with electronic devices into robust, nanoscale detection systems. Based on the major findings of the thesis work, additional investigations were initiated to investigate the potential for nanoscale chemiresitor sensors to operate in buffered, aqueous (liquid) flow cells. Preliminary experiments show that chemiresistor sensing is transferable to liquid environments where analyte molecules are observed to partition from the bulk liquid to the sensing materials, leading to a detectable change of the device electrical properties. Comparing micron- and nano-scale devices fabricated using aqueous oligonucleotide-functionalized gold nanoparticles, it was found that nanoscale chemiresistors are more resistant to solvent damage than 5 µm chemiresistors. We conclude that future experiments to investigate aptamer sensing in aqueous solutions is a promising direction. Overall, this thesis is a significant contribution to materials development and device design to attain improved sensor selectivity and higher levels of device integration. First, it offers a scheme for design, selection, and validation of materials that confer analyte-specific interactions. Second, it paves the way for large scale sensor integration and parallel operation on a single chip. Lastly, it offers an approach to combine biomolecular recognition elements with electronic devices into robust, nanoscale detection systems

A high performance surface acoustic wave visible light sensor using novel materials: Bi2S3 nanobelts

Low dimensional Bi2S3 materials are excellent for use in photodetectors with excellent stability and fast response time. In this work, we developed a visible light sensor with good performance based on surface acoustic wave (SAW) devices using Bi2S3 nanobelts as the sensing materials. The SAW delay-line sensor was fabricated on ST-cut quartz with a designed wavelength of 15.8 microns using conventional photolithography techniques. The measured center frequency was 200.02 MHz. The Bi2S3 nanobelts prepared by a facile hydrothermal process were deposited onto SAW sensors by spin-coating. Under irradiation of 625 nm visible light with a power intensity of 170 μW cm−2, the sensor showed a fast and large response with a frequency upshift of 7 kHz within 1 s. The upshift of the frequency of the SAW device is mainly attributed to the mass loading effect caused by the desorption of oxygen from the Bi2S3 nanobelts under visible light radiation

A high performance surface acoustic wave visible light sensor using novel materials: Bi2S3 nanobelts

Low dimensional Bi2S3 materials are excellent for use in photodetectors with excellent stability and fast response time. In this work, we developed a visible light sensor with good performance based on surface acoustic wave (SAW) devices using Bi2S3 nanobelts as the sensing materials. The SAW delay-line sensor was fabricated on ST-cut quartz with a designed wavelength of 15.8 microns using conventional photolithography techniques. The measured center frequency was 200.02 MHz. The Bi2S3 nanobelts prepared by a facile hydrothermal process were deposited onto SAW sensors by spin-coating. Under irradiation of 625 nm visible light with a power intensity of 170 μW cm−2, the sensor showed a fast and large response with a frequency upshift of 7 kHz within 1 s. The upshift of the frequency of the SAW device is mainly attributed to the mass loading effect caused by the desorption of oxygen from the Bi2S3 nanobelts under visible light radiation

Topography measurements using an airborne Ka-band FMCW Interferometric Synthetic Aperture Radar

Radar interferometry at millimeter-wave frequencies has the ability of topography measurement of different types of terrain, such as water surfaces and tree canopies. A Ka-band interferometric radar was mounted on an airborne platform, and flown over the Connecticut river region in western Massachusetts near Amherst on June 11, 2012. More than 20 Gigabytes of raw data was recorded. This dissertation outline presents the results of the data processing, which includes (1) the estimation and removal of the embedded high frequency phase error in the raw data; (2) the synthetic aperture processing; (3) the interferometric processing. The digital elevation model (DEM) has been generated based on an external DEM from MassGIS. The accuracy of the topography measurement can be affected by many factors, such as the de-correlation between channels and the residual phase error. This dissertation outline proposes to evaluate the accuracy of the topography measurement by quantifying each error source. Specifically, the performance of the phase error estimator and the Doppler centroid estimation will be analyzed, and an algorithm which estimates the attitudes of the airborne platform will be developed

A case study of weather research and forecasting model over the Midwest USA

Chemical Transport Models (CTMs) are important tools for air quality research, and it is of the same importance to provide accurate weather information as input data to CTMs. In this thesis, the Weather Research and Forecast (WRF) model was used as an input to a CTM and a sensitivity analysis of 17 WRF runs was conducted to explore the optimum physics configuration in 6 physics categories for the Midwest USA in May 2011, including cumulus, surface layer, microphysics, land surface model, planetary boundary layer, longwave radiation and shortwave radiation. Two domains were used: the coarse domain (12 km grid size) covering most parts of the North America and the nested domain (4 km grid size) covering the Illinois State and adjacent areas. The model output from the nested domain was evaluated statistically and results were compared with observation data using the Model Evaluation Tools (MET) software package and the National Center for Atmospheric Research Command Language (NCL). Benchmark values of several weather variables from the literature were adopted as a reference when discussing model statistical performance. After the sensitivity analysis was finished, the same optimum physics configuration for May was evaluated for October using measured meteorological data to test the applicability of the WRF model during different weather conditions. Finally, both the coarse domain and the fine domain were evaluated to investigate model sensitivity to the horizontal resolution. Compared with the starting run, the optimum run was found to produce better temperature (0.35 K decrease in hourly mean bias and 0.26 K decrease in hourly root mean square error), pressure (4.3 Pa decrease in hourly mean bias and 3.91 K decrease in hourly root mean square error) and relative humidity (1.44 % decrease in hourly mean bias and 1.76 % decrease in hourly root mean square error) results, while keeping the ability to simulate wind speed and wind direction accurately compared with other studies. In addition, all the statistical measures were within the benchmark value ranges that were available in the literature (Emery et al., 2001). When applying the same optimum physics configuration to October, WRF still produced acceptable results, with only gross error of wind direction out of the benchmark value range in hourly statistics (30.02° compared with 30° from the benchmark value). Comparison between the coarse domain and the fine domain suggested that decreasing horizontal resolution did not necessarily lead to increasing the model simulation skill. The unique contribution of this research is to provide a general method of sensitivity analysis in WRF and obtain the optimum WRF physics configurations for the Midwest USA. These contributions are important because CTMs need accurate weather inputs to produce reliable outputs, and it is not easy to find the optimum WRF outputs given that there are many choices to make when running WRF