Design and Implementation of a Multi-port Solid State Transformer for Flexible Der Integration

Conventional power system includes four major sections, bulk generation, transmission network, distribution network, and loads. The main converter in the conventional electric grid is the low-frequency passive transformer providing galvanic isolation and voltage regulation for various voltage zones. In this configuration, small-scale renewable energy resources are generally connected to the power system at low voltage zones or inside microgrids. Recent developments in the design of power electronic elements with higher voltage and power ratings and medium/high frequency enable making use of solid state transformer at different voltage levels in the distribution system and microgrid design. In this work, the concept of a Multi-Port Solid State Transformer (MPSST) for distribution network application is introduced. MPSST provides a compact, integrated and galvanically isolated multi-port node for microgrid and distribution applications and reduces the number and size of the converters in the concept of efficient smart distribution systems. A new architecture for distribution systems integrating distributed generation (DG) at different voltage zones using MPSST is proposed, studied and simulated. The developed concept interconnects different voltage types and levels using one compact converter with a centralized control logic. In addition, a general method is developed and mathematically analyzed to provide active and reactive power support using the local alternative power sources through MPSST. MPSST is a combination of high-frequency power electronic converters and a multi-winding high-frequency transformer. The total size of the MPSST is dramatically smaller than the conventional transformers with the same voltage and power rating. MPSST also enables online measurement and data collection and active control of the parameters at all connected ports. A two-layer control technique, which is a combination of duty cycle control and a modified phase shift control is used to regulate the voltage and power flow of the different ports. Since the converter has several independent and dependent variables, a transfer matrix between variables of the converter is calculated and used in system control. Finally, the implementation process of the converter including, component selection, modeling, software development, and transformer design is presented and the first prototype of the MPSST is developed and tested in the lab. Chapter five includes the hardware test results and the discussion and comparison of the results with the design expectations

Application of computer vision for roller operation management

Compaction is the last and possibly the most important phase in construction of asphalt concrete (AC) pavements. Compaction densifies the loose (AC) mat, producing a stable surface with low permeability. The process strongly affects the AC performance properties. Too much compaction may cause aggregate degradation and low air void content facilitating bleeding and rutting. On the other hand too little compaction may result in higher air void content facilitating oxidation and water permeability issues, rutting due to further densification by traffic and reduced fatigue life. Therefore, compaction is a critical issue in AC pavement construction.;The common practice for compacting a mat is to establish a roller pattern that determines the number of passes and coverages needed to achieve the desired density. Once the pattern is established, the roller\u27s operator must maintain the roller pattern uniformly over the entire mat.;Despite the importance of uniform compaction to achieve the expected durability and performance of AC pavements, having the roller operator as the only mean to manage the operation can involve human errors.;With the advancement of technology in recent years, the concept of intelligent compaction (IC) was developed to assist the roller operators and improve the construction quality. Commercial IC packages for construction rollers are available from different manufacturers. They can provide precise mapping of a roller\u27s location and provide the roller operator with feedback during the compaction process.;Although, the IC packages are able to track the roller passes with impressive results, there are also major hindrances. The high cost of acquisition and potential negative impact on productivity has inhibited implementation of IC.;This study applied computer vision technology to build a versatile and affordable system to count and map roller passes. An infrared camera is mounted on top of the roller to capture the operator view. Then, in a near real-time process, image features were extracted and tracked to estimate the incremental rotation and translation of the roller. Image featured are categorized into near and distant features based on the user defined horizon. The optical flow is estimated for near features located in the region below the horizon. The change in roller\u27s heading is constantly estimated from the distant features located in the sky region. Using the roller\u27s rotation angle, the incremental translation between two frames will be calculated from the optical flow. The roller\u27s incremental rotation and translation will put together to develop a tracking map.;During system development, it was noted that in environments with thermal uniformity, the background of the IR images exhibit less featured as compared to images captured with optical cameras which are insensitive to temperature. This issue is more significant overnight, since nature elements are not able to reflect the heat energy from sun. Therefore to improve roller\u27s heading estimation where less features are available in the sky region a unique methodology that allows heading detection based on the asphalt mat edges was developed for this research. The heading measurements based on the slope of the asphalt hot edges will be added to the pool of the headings measured from sky region. The median of all heading measurements will be used as the incremental roller\u27s rotation for the tracking analysis.;The record of tracking data is used for QC/QA purposes and verifying the proper implementation of the roller pattern throughout a job constructed under the roller pass specifications.;The system developed during this research was successful in mapping roller location for few projects tested. However the system should be independently validated

Atomic White-Out: Enabling Atomic Circuitry Through Mechanically Induced Bonding of Single Hydrogen Atoms to a Silicon Surface

We report the mechanically induced formation of a silicon-hydrogen covalent bond and its application in engineering nanoelectronic devices. We show that using the tip of a non-contact atomic force microscope (NC-AFM), a single hydrogen atom could be vertically manipulated. When applying a localized electronic excitation, a single hydrogen atom is desorbed from the hydrogen passivated surface and can be transferred to the tip apex as evidenced from a unique signature in frequency shift curves. In the absence of tunnel electrons and electric field in the scanning probe microscope junction at 0 V, the hydrogen atom at the tip apex is brought very close to a silicon dangling bond, inducing the mechanical formation of a silicon-hydrogen covalent bond and the passivation of the dangling bond. The functionalized tip was used to characterize silicon dangling bonds on the hydrogen-silicon surface, was shown to enhance the scanning tunneling microscope (STM) contrast, and allowed NC-AFM imaging with atomic and chemical bond contrasts. Through examples, we show the importance of this atomic scale mechanical manipulation technique in the engineering of the emerging technology of on-surface dangling bond based nanoelectronic devices.Comment: 9 pages (including references and Supplementary Section), 8 figures (5 in the main text, 3 in Supplementary

Quantitative study of the structural requirements of phthalazine/quinazoline derivatives for interaction with human liver aldehyde oxidase

Aldehyde oxidase is a molybdenum-containing enzyme distributed throughout the animal kingdom. Although this enzyme is capable of metabolizing a wide range of aldehydes and N-heterocyclic compounds, there is no reported detailed study of physicochemical requirements of the enzyme-substrate interactions. The aim of this study, therefore, was to investigate quantitatively the relationships between the kinetic constants of aldehyde oxidase-catalyzed oxidation of some phthalazine and quinazoline derivatives (as substrates) and their structural parameters. Multiple regression and stepwise regression analyses showed that polarity of phthalazines (expressed as dipole moment μ, cohesive energy density δT and an indicator variable for hydrogen-bond acceptor ability of R1 substituent, HBA) had a negative effect on the enzyme activity (leading to the reduction of Vmax and increase of Km). Electron withdrawing substituents in the quinazoline series are favorable for interaction with the enzyme. This finding and also the relationships of 1/Km of phthalazines with the energy of the lowest unoccupied molecular orbital and log Vmax/logKm of phthalazines with degree of bonding of the two nitrogen atoms in the molecules are consistent with the mechanism of action. The reaction involves a nucleophilic attack on an electron-deficient sp2-hybridized carbon atom and formation of an epoxide intermediate following the disruption of the aromatic structure

Pre-registration nursing students’ experiences of stress

This research study aimed to explore stress among pre-registration nursing students in the United Kingdom. The specific objectives of the study were: To explore the experience of stress among pre-registration nursing students; to determine the type of stress and sources of stress in pre-registration nursing field; to investigate the perceptions of pre-registration nursing students on stress and anxiety in pre-registration nursing programme; and to identify suitable measures that can be implemented to help the pre-registration nursing students to cope with stress. Qualitative research method and phenomenological approach was used in this study and the data was collected with the help of face-to-face semi-structured interviews. The setting for the current study was a higher education institution (HEI) that delivers pre-registration nurse education in the UK. The study sample was six pre-registration nursing students from the East Midlands who were in the first, second, and in final year of the study program leading to BSc (Hons) Nursing with NMC Registration. A thematic analysis of the data was conducted which led to four emergent themes: Pre-registration nursing students’ experiences of stress; re-registration nursing students’ perceptions of stress and anxiety; sources of stress in the nursing field; and measures for coping with stress. The findings revealed that the pre-registration nursing students in this study perceived stress as a problem associated with human health that basically is caused by academic pressure presented by either theoretical assignments, projects, and examinations and placement demands such as while caring for patients. Moreover, stress among pre-registration nursing students was found to be a problem embedded in their lifestyle that impacts their wellbeing. Further findings showed that the study participants perceived that stress and anxiety are interrelated; anxiety takes place in response to stress resulting from academic and clinical placement pressure; and anxiety has a strong relationship with stress and is a contributor to depression too. The study participants also perceived that the major causes of stress include social distress, financial problems, academic pressure, demands of clinical placement, and family expectations. Academic pressure was found to be the most common cause of stress among the pre-registration nursing students in this study. Lastly, the findings revealed that the coping strategies that can help pre-registration nursing students to manage stress are adopting social support mechanisms, encouraging physical activities, and spiritual support. Keywords: Pre-registration nursing students, Stress, Coping. DOI: 10.7176/JHMN/85-14 Publication date: January 31st 202

CONSUMER INNOVATIVENESS LEADING TO INNOVATION ADOPTION

Innovation is the key to success, therefore innovators need to be influenced for innovation adoption; through market analysis for consumers possess the necessary traits to understand the value of innovation in their lifestyles. This research study has analyzed the mobile phone consumer market empirically for the traits that are necessary for the adoption of innovation and has identified the market segments that are more motivated to embrace innovativeness. A consumer survey is conducted by using an adopted scale from 404 respondents. The data is analyzed by factor analysis, and 2 SLS regression method. The results reveal that consumer innovativeness is strongly influenced by personality traits such as intelligence, rationality, self-efficacy, interconnectedness, cosmopolites, and subjective norm. The study further provides the insight that consumers are ready to adopt the innovation and possess the necessary innovativeness trait to intellectually and rationally evaluate the innovative offering available in the marke