Auto-tuning of Digitally Controlled Single-Phase Low Harmonic Rectifiers and Inverters

Effective power transfer has been one of the main issues in power electronics. In particular, low-harmonic alternating current (AC) shaping is required by various regulations at the interface between AC power grid and direct current (DC) loads or sources,. In order to meet rapidly evolving efficiency standards and environmental concerns, intelligent AC current shaping strategies are required. In the power converter stage, however, inherent uncertainties caused by passive component tolerances and changes in operating conditions may impair the control loop stability, while mis-detection of operating modes over wide load range aggravates the situation further. This thesis introduces an auto-tuning technique in digitally controlled single-phase AC-DC rectifiers and DC-AC inverters. The approach is capable of precise on-line estimation of the power stage passive component values. The control loop compensator parameters are modified adaptively to maintain the nominal stability margins and control loop bandwidth based on the estimated component values. Furthermore, accurate continuous conduction mode (CCM) and discontinuous conduction mode (DCM) boundary detection is achieved as a result of the tuning process, without the need for additional circuitry. Implementation of the tuning approach is relatively simple. The proposed tuning approach is verified on experimental AC-DC and DC-AC prototypes

Virtual graphic representation of construction equipment for developing a 3D earthwork BIM

BIM provides a visualization of the construction design that allows a construction manager to review the construction process and the information that is associated with the progress. BIM is usually applied to modeling struc­tural objects with parametric geometry where the sequence of process can be predefined. However, BIM technology can also be applied to objects with irregular shape where parametric modeling is not possible such as earthwork topography based on TIN (Triangular Irregular Network).The objective of this research is to develop a 3D earthwork BIM method­ology and provide a graphic simulation that is capable of assisting construction equipment operators during excavation work. The 3D earthwork BIM presents a modeling technique that involves integrating hardware and software technolo­gies. This combination of technologies is used to represent the actual excavator configuration in a 3D virtual environ­ment. When it is applied to actual excavation work, it was proved that the 3D earthwork BIM could synchronize the virtual excavator configuration with the actual excavator configuration during excavation work in real time

Prototyping a remotely-controlled machine for concrete surface grinding operations

The surface of concrete pavement needs to be flattened for the smoothness and comfortability of highways. Surface grinding can provide flatness in the hardened concrete surface, and improve adhesion between the existing con­crete surface and the subsequent layer. The surface grinding process, however, is executed under hazardous work condi­tions and the outcome is affected by a machine operator’s skill. Automation of this process can provide a hazard-free work environment and increase the quality of the ground surface. This paper presents an application of an automated concrete surface grinding machine that an operator can remotely control with computer assistance. A combination of hardware and software technologies was applied to prototype automated functions of the machine. Field tests demon­strated that remote control of concrete surface grinding is feasible and can be utilized as a semi-automated scheme on actual construction sites. First published online: 23 Jun 201

Robotic Bridge Paint Removal: Field Testing and Evaluation of Promising Technologies

1993 Grant AgreementPeriodic paint removal and re-application is necessary to protect steel girder bridges against corrosion. The paint removal operation for bridge maintenance, however, is hazardous to the workers involved in the process and the natural environment. A particular problem is that certain types of paint used on bridges in the past contain toxic lead. The Robotic Bridge Paint Removal (RBPR) project was initiated under a grant agreement with Federal Highway Administration (FHWA) to study the important factors related to the robotic paint removal process. During the design and development, the unique shape of the bridge beam and the requirement for dust and debris containment caused many problems. These problems, in turn, provided challenges to produce innovative solutions. The robotic paradigm was identified as an especially effective approach for spot cleaning corroded paint on bridge structures. A vision-based computer control architecture was developed that provides the adaptive remote control capabilities for the spot cleaning process. Field tests were conducted throughout the project to evaluate design concepts, identify areas that could be improved, and demonstrate the final working prototype. The results of these demonstrations indicate the application of the robotic paradigm to bridge paint removal has real potential to: 1) improve workers' safety, 2) protect the natural environment during the paint removal process, and 3) minimize the risks to the general public. This project would not have been possible without the close partnership between the North Carolina State University Construction Automation and Robotics Laboratory (CARL) and the North Carolina Department of Transportation (NCDOT). The NCDOT not only loaned many of the key hardware components to the project, they also participated in reconfiguring, upgrading and field testing the new system

Effect of rapid influenza diagnostic tests on patient management in an emergency department

Objective We evaluated the effect of rapid influenza diagnostic tests (RIDTs) on patient management in an emergency department for 3 years after 2009, and also identified factors associated with the choice of treatment for patients with influenza-like illnesses. Methods The study period consisted of three influenza epidemic seasons. Patients older than 15 years who underwent RIDTs in the emergency department and were then discharged without admission were included. Results A total of 453 patients were enrolled, 114 of whom had positive RIDT results and 339 had negative results. Antiviral medication was prescribed to 103 patients (90.4%) who had positive RIDT results, while 1 patient (0.3%) who tested negative was treated with antivirals (P<0.001). Conservative care was administered to 11 RIDT-positive patients (9.6%) and 244 RIDT-negative patients (72.0%) (P<0.001). Symptom onset in less than 48 hours, being older than 65 years, and the presence of comorbidities were not associated with the administration of antiviral therapy. Conclusion RIDT results had a critical effect on physician decision-making regarding antiviral treatment for patients with influenza-like illnesses in the emergency department. However, symptom onset in less than 48 hours, old age, and comorbidities, which are all indications for antiviral therapy, were not found to influence the administration of antiviral treatment

Learning curve and period of experience required for the competent diagnosis of acute appendicitis using abdominal computed tomography: a prospective observational study

Objective To assess the learning curve of novice residents in diagnosing acute appendicitis using abdominal computed tomography (CT) scans. Methods This prospective observational study was conducted within a 4-month period from March 1 to June 30, 2015. After CT scans for right lower quadrant pain or similar acute abdomen were evaluated, postgraduate year 1 (PGY-1) residents completed an interpretation checklist. The primary outcome was evaluation of the learning curve for competent CT scan interpretation under suspicion of acute appendicitis. Secondary outcomes were cumulative numbers of accurate abdominal CT interpretations regardless of initial clinical impression and training period. Results PGY-1 residents recorded a total of 230 interpretation checklists. There were 53, 51, 46, 44, and 36 checklists recorded by individual residents and 92, 92, 91, 91, and 61 respective training days in the emergency department, excluding rotation periods in other departments. After 16 to 20 interpretations of abdominal CT scans performed under suspicion of acute appendicitis, the residents could diagnose acute appendicitis with more than 95% accuracy. Overall, the sensitivity and specificity for diagnosing acute appendicitis were 97% (95% confidence interval, 94 to 100) and 83% (95% confidence interval, 80 to 87), respectively. After 61 to 80 abdominal CT interpretations regardless of suspicion of acute appendicitis and after 41 to 50 days in training, PGY-1 emergency department residents could diagnose acute appendicitis with more than 95% accuracy. Conclusion PGY-1 residents require 16 to 20 checklist interpretations to acquire acceptable abdominal CT interpretation. After performing 61 to 80 CT scans regardless of suspicion of acute appendicitis, they could diagnose acute appendicitis with acceptable accuracy

Effect of transported hospital resources on neurologic outcome after out-of-hospital cardiac arrest

Objective. Appropriate regional transport protocol for out-of-hospital cardiac arrest (OHCA) patients is important for achieving favorable outcomes in a certain community. This study aimed to investigate the effect of transported hospital resources on the neurologic outcome after OHCA. Methods. We categorized cardiac receiving centers (CRC) in our community into two levels (primary [P-CRC] and definite CRC [D-CRC]) according to the hospital resources that were identified by the Hospital Assessment Survey in 2015. OHCA patients with presumed cardiac etiology resuscitated by emergency medical service providers between 2012 and 2014, were enrolled in the study. The main exposure was the level of CRC. The primary endpoint was discharge with good neurologic outcomes. We compared outcomes between CRCs after adjusting for potential confounders. Results. Among the 9,912 patients, 5,876 were transported to P-CRC and 4,036 to D-CRC from 2012 to 2014. Patients admitted to D-CRC showed better neurologic outcome than those admitted to P-CRC (6.2% vs 1.5%, p<0.001). With regard to patients who survived to admission, the neurologic outcome of patients in D-CRC was better than those in P-CRC (11.3% vs 3.3%, p<0.001). In the multivariable logistic model, the adjusted odds ratio for all OHCA patients was 2.10 (95% confidence interval, 1.51–2.95). Conclusion. Transportation of OHCA patients to the D-CRC resulted in significantly good neurologic outcome than those transported to P-CRC. Further research is needed to establish a regional OHCA transport protocol

Integrated computational-experimental soil behavior characterization from direct simple shear tests on Boston Blue Clay

A constitutive model that represents soil behavior under a wide range of loading conditions is necessary for the simulation of complex boundary value problems. However, most laboratory tests are interpreted with an assumption of uniform stresses and strains within the tested soil specimen even when the specimen is known to experience non-uniform stress-strain distribution as in the Direct Simple Shear (DSS) test. Numerous tests are often needed to fully characterize a soil’s nonlinear and anisotropic and time-dependent behavior and to develop an appropriate soil model. This study utilizes an evolutionary inverse analysis approach to directly extract non-uniform stresses and strains within an undrained DSS test specimen, and which is subsequently to K0 consolidated-undrained direct simple shear (CK0UDSS) tests on Boston Blue Clay (BBC). The extracted soil behavior is consistent with known behavior of BBC including anisotropic stress-strain response and small strain nonlinearity obtained under complex laboratory loading conditions. The developed material models from DSS tests on Boston Blue Clay (BBC) are directly applied to deep excavation case histories. The analysis results show that the global responses, such as lateral wall deflections and vertical ground surface settlements, can be successfully reproduced. The proposed approach represents a major shift in our ability to efficiently bridge numerical modeling and laboratory testing and change the way we approach soil characterization and constitutive model development. We can use very few laboratory tests to directly develop versatile material models that can be used in the solution of geotechnical field problems without the need for complex formulations or long development periods or calibration process. This is something that we have been unable to do before

Colorful graphene-based wearable e-textiles prepared by co-dyeing cotton fabrics with natural dyes and reduced graphene oxide

Abstract In addition to the functionality of electronic textiles (e-textiles), their aesthetic properties should be considered to expand their marketability. In this study, premordanted cotton fabrics were co-dyed with reduced graphene oxide (rGO) and natural dyes to develop ecofriendly and colorful graphene-based wearable e-textiles. The color attributes of the textiles were analyzed in terms of the dyeing conditions, namely, rGO loading, mordant type, and natural dye type. The lightness of the dyed samples increased in the order of cochineal < gardenia blue < rhubarb. Regardless of the natural dye and rGO loading, the lightness of the fabrics mordanted with Fe was lower than that with Al and Cu. Moreover, the rhubarb- and gardenia blue-dyed fabrics exhibited broad chroma and hue dispersions, indicating the strong impact of the dyeing conditions. With increasing rGO loading, the chroma of the rhubarb-dyed fabrics substantially decreased, resulting in decreased color saturation. The initial greenish-blue color of the gardenia blue-dyed fabrics gradually changed to yellowish-green and then yellow. Regardless of the natural dye, drastic overall color changes were observed, with average values of 7.60, 11.14, 12.68, and 13.56 ΔE CMC(2:1) at increasing rGO loadings of 1, 3, 5, and 7% owb, respectively