Optimization and visualization of rapid prototyping process parameters.

The optimal selection of rapid prototyping (RP) process parameters is a great concern to RP designers. When dealing with this problem, different build objectives have to be taken into consideration. Using virtual rapid prototyping (VRP) systems as a visualization tool to verify the optimally selected process parameters will assist designers in taking critical decisions regarding modeling of prototypes. This will lead to substantial improvements in part accuracy using minimal number of iterations, and no physical fabrication until confident enough to do so. The purpose of this thesis is to demonstrate that virtual validation of optimally selected process parameters can significantly reduce time and effort spent on traditional RP experimentation. To achieve the goal of this thesis, a multi-objective optimization technique is proposed and a model is generated taking into consideration different build objectives, which are surface roughness, support structure volume, build time and dimensional accuracy. The multi-objective method used is the weighted sum method, where a single utility function has been formulated, which combines all the objective functions together. The orders of magnitudes have been normalized, and finally weights have been assigned for each objective function in order to create the general formulation. (Abstract shortened by UMI.)Dept. of Industrial and Manufacturing Systems Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2004 .E47. Source: Masters Abstracts International, Volume: 43-03, page: 0959. Adviser: Waguih ElMaraghy. Thesis (M.A.Sc.)--University of Windsor (Canada), 2004

Exergy-based Index for the assessment of building sustainability

ABSTRACT Exergy-based Index for the assessment of building sustainability Ahmed El shenawy, Ph.D. Concordia University, 2013 The declining state of the environment, combined with the increasing scarcity of natural resources and economic recession, presents us with the need to discover building practices that are capable of producing sustainable buildings. Building promoters are racing to certify the sustainability of their projects, aware that building sustainability assessment will delineate the features of current and future building practice. A sustainable building implies that resource depletion and waste emissions are considered during its whole life cycle. This research project proposes a new methodology and Exergy-based Index to assess building sustainability and to assist decision makers comparing building alternatives, since the wrong decisions can lead to serious consequences and even precipitate crises. The proposed methodology uses the SBTool that has been utilized for defining the criteria for analysing and ranking the environmental performance of buildings. Over the past decade, significant efforts have been made in developing Sustainable Building (SB) assessment tools that allow all stakeholders/actors to be aware of the consequences of various choices and to assess building performance. These SB tools, approaches, rating systems, indices and methods of assessment have already been utilized in the market (e.g., Multi-Criteria Assessment (MCA) methods, such as LEED and SBTool, Life Cycle Analysis (LCA) systems, like ATHENA, and the Single Index (SI) approach (Ecological footprint)). However, are existing SB assessment tools actually capable of considering the regional issues? Is it possible to use them to assess all types of buildings? Are they objective, easy to customize? Is it easy to interpret their final assessment results and are those results transparent to the end users? Despite the usefulness of the current assessment methods in contributing towards a more sustainable building industry, some of the limitations and critiques of these assessment methods indicate that the tools should evolve toward a genuinely generic and scientifically global SB assessment tool. After discussing and summarizing the limitations of the existing definitions, indices and rating systems for building sustainability assessment, a definition of a sustainable building in terms of thermodynamics is proposed, mainly based on the exergy concept. This proposal is supported by a general mathematical calculation for the exergy-based index of building sustainability. The index uses the comparison between the available solar exergy (considered to be the only renewable energy source) and the exergy lost due to a building’s construction and operation to measure the a building’s sustainability. Moreover, the selection and transfer of data from the SBTool, and the assumptions and additional calculations required for the assessment of the exergy-based index of sustainability are presented and quantified. A rating scale is also presented along with the index of building sustainability. Finally, case studies of residential and commercial buildings are used to demonstrate the framework’s reliability. The contribution of the proposed Exergy-based index is evaluated by comparing its similarities and differences with a selection of the available building assessment tools and methods

Motion Control of Holonomic Wheeled Mobile Robot with Modular Actuation

This thesis proposes a control scheme for a new holonomic wheeled mobile robot. The platform, which is called C3P (Caster 3 wheels Platform), is designed and built by the Automation Lab., University of Heidelberg. The platform has three driven caster wheels, which are used because of their simple construction and easy maintenance. The C3P has modular actuators and sensors configurations. The robot’s actuation scheme produces singularity difficulties for some wheel steering configuration, described as the following: When all wheels yield the same steering angle value, the C3P cannot be actuated in the direction perpendicular to the wheel velocity vector. The C3P has a modular sensing scheme defined by sensing the steering angle and the wheel angular velocity of each caster wheel. This work has four main contributions 1- developing a controller based on an inverse kinematics solution to handle motion commands in the singular configurations; 2- modeling the C3P’s forward dynamics of the C3P for the simulation purpose; 3- developing a motion controller based on an inverse dynamics solution; and 4- comparing the C3P with other standard holonomic WMRs. In order to escape singularity condition, the actuated inverse kinematics solution is developed based on the idea of coupling any two wheel velocities to virtually actuate the steering angular velocity of the third wheel. The solution is termed as the Wheel Coupling Equation (WCE). The C3P velocity controller consists of two parts: a) the WCE regulator to avoid singularities and adjust the steering angles to the desired value, and b) the regular PID controller to maintain the reference robot velocities with respect to the floor frame of coordinates. The solution reaches acceptable performance in the simulation examples and in the practical experiments. However, it generates relatively large displacement errors only during the steering angles adjustment period. The Euler-Lagrangian method is used for obtaining the forward dynamic and the inverse dynamic models. The forward dynamic model consists of two equations of motion: the WTD (Wheel Torque Dynamics) to calculate the wheel angular velocities with respect to the actuated wheels’ torques, and the DSE (Dynamic Steering Estimator) for calculating the steering angles and steering angular velocities corresponding to the angular wheels’ velocities and accelerations. The inverse dynamics solution defines the forces and torques acting on each actuator and joint. The solution is used in the development of the C3P velocity and position controllers. In comparison to the proposed inverse kinematics solution, the inverse dynamics solution yields less displacement errors. Lyapunov stability analysis is carried out to investigate the system stability for different steering angles’ combinations. The steering angles’ values are considered as the disturbances affecting the platform. Finally, a comparison is made between the C3P and three other holonomic wheeled mobile robots configurations. The comparison is based on the simulation results in relation to the following aspects: a) mobility, b) total energy consumed by each robot in a finite interval of time and c) hardware complexity. The C3P platform shows its advantage in the aspects “b” and “c”

Helicobacter pylori Western cagA genotype in Egyptian patients with upper gastrointestinal disease

Background: Infection with Helicobacter pylori (H. pylori) causes persistent gastritis that may progress to fatal gastric cancer. The cytotoxin-associated gene A protein (CagA), encoded by the cytotoxin-associated gene A (cagA) is the main virulence factor associated with more severe clinical outcomes. It is further divided into Western-type CagA and East Asian-type CagA. The East Asian-type CagA induces more cytoskeleton changes and is more likely to be associated with gastric cancer.Aim of the study: In the current study we aimed to identify the most prevalent H. pylori cagA genotype among Egyptian patients suffering from dyspepsia and to examine its possible correlation with the associated clinical condition.Patients and methods: Four biopsies were obtained from the antrum and angularis from each of 113 adult patients, who underwent upper endoscopy at the Endoscopy Unit, Theodor Bilharz Research Institute (TBRI) Hospital for the analysis of H. pylori by rapid urease test and detection of 16S rRNA. Nested PCR assay was used to determine cagA genotype.Results: Sixty (53.1%) dyspeptic patients were found infected with H. pylori. Although Egypt has a high prevalence of H. pylori infection, low prevalence of cagA was detected (26.5%). Western type cagA is the predominant type (62.5%) while East Asian type was not detected and others (37.5%) remain uncharacterized. Western-genotype cagA genotype was found in 80% of patients with peptic ulcer disease and 40% of patients with gastritis.Conclusion: Absence of the more virulent East Asian cagA genotype, which is the strongest risk factor for gastric carcinogenesis, may explain the very low gastric cancer rate among Egyptian population compared to other parts of the world. This finding demands further molecular studies using whole genome sequencing and more samples to determine the exact uncharacterized cagA genotype to identify the actual risk in developing gastroduodenal diseases in Egypt.Keywords: Helicobacter pylori, Endoscopic findings, Western type cagA, East-Asian cagA, Peptic ulcer, Gastriti

Detection of antimicrobial resistance genes of Helicobacter pylori strains to clarithromycin, metronidazole, amoxicillin and tetracycline among Egyptian patients

Background: Antibiotic resistance of Helicobacter pylori (H. pylori) treatment is on the rise, and is affecting the efficacy of current used therapeutic regimens.Aim: We aimed to enhance the understanding of antimicrobial resistance rates of H. pylori strains recovered from patients at Theodor Bilharz Research Institute Hospital in Egypt, as a mandatory step before starting treatment.Subjects and methods: Mutant genes conferring metronidazole, amoxicillin, clarithromycin, and tetracycline resistance were detected in 60 H. pylori strains recovered from patients who underwent upper endoscopic examination. Patients were considered to be infected with H. pylori when rapid urease test and detection of 16S rRNA in gastric biopsies recorded positive. Molecular detection of resistant genes to metronidazole (rdx gene) and amoxicillin (pbp1A gene) was carried out by conventional PCR followed by sequencing of PCR products. While detection of 23S rRNA gene conferring clarithromycin resistance and detection of 16S rRNA mutation gene conferring tetracycline resistance were carried out by realtime PCR.Results:  H. pylori resistance rates to metronidazole, and amoxicillin were 25% and 18.3% respectively. While for clarithromycin and tetracycline, point mutations in 23S rRNA types A2142G and A2143G and in 16S rRNA of H. pylori were assessed by real time PCR assay respectively. Resistance mutant genes were found to be 6.7% of clarithromycin and 1.7% of tetracycline. Combined resistance rates to metronidazole and amoxicillin was (11.6%) followed by metronidazole and clarithromycin (5%), while patterns of clarithromycin and amoxicillin (1.6%), metronidazole, clarithromycin and amoxicillin (1.6%) were revealed.Conclusion: Data concerning antimicrobial resistance genes play an important role in empiric treatment of H. pylori infection. According to our results, H. pylori resistance to metronidazole and amoxicillin was relatively high. Clarithromycin is still a good option for first line anti-H. pylori treatment. Combined resistant strains are emerging and may have an effect on the combination therapy.Keywords: H. pylori, Antimicrobial resistance, Gene mutations, Rdx gene, Clarithromycin resistance, Tetracycline resistanc

Flow behavior and mechanical properties of multi-pass thermomechanically processed 7075 Al-alloy

Research on multi-pass hot processing of 7075 Al-alloy was rarely discussed. This study aims to design and evaluate different thermomechanical processing strategies (TMPS) to produce 3 mm-thick sheets of 7075 Al-alloy. A physical simulation was performed using the hot compression test of a Gleeble 3500 to study flow mechanisms and microstructural evolution, while an experimental investigation was carried out using a rolling mill to examine the effect of TMPS on the mechanical properties. Four hot forming strategies were designed and tested at a constant strain rate of 0.1 s−1 over a temperature range of 200–450 °C. These strategies involved applying a constant amount of deformation of 65–70% in single (SP), double (DP), triple (TP), and quadruple (QP) passes of thermomechanical processing to study the influence of multi-pass thermomechanical processing on the final mechanical properties and industrial feasibility. The microstructure analysis showed a significant refinement and more uniform distribution of precipitates with an increasing number of passes, as observed through optical micrographs and the full width at half maximum (FWHM)-position relationship of XRD data. The results indicate that QP is the optimum strategy for producing the best mechanical properties in the shortest production time

Detection of Helicobacter pylori vacA, cagA and iceA1 virulence genes associated with gastric diseases in Egyptian patients

Background: Helicobactor pylori (H. pylori) virulence markers would be useful to predict peptic ulcer disease (PUD) or gastric cancer.Aim: In Egypt, since inadequate data are present regarding H. pylori virulence–related genes in different age group patients with gastro-duodenal diseases, it becomes crucial to study the clinical status of cagA, vacA and iceA1 genotypes of H. pylori strains recovered from patients with dyspepsia.Subjects and methods: The study included 113 dyspeptic patients who were exposed to upper gastrointestinal endoscopic examination. Four antral biopsies were obtained from each patient for the analysis of H. pylori infection by rapid urease test and detection of 16S rRNA.Results: Sixty (53.1%) patients were confirmed to be infected with H. pylori. Upon endoscopy, gastritis was revealed in 27 patients (45%) and10 patients (16.7%) had PUD. Of the 60 H. pylori strains, 39 (65%) had at least one virulence gene. Six different genotypic forms were recognized; vacA (9/60), iceA1 (1/60), vacA/cagA (7/60), vacA/iceA1 (13/60), vacA/cagA/iceA1 (8/60) only one of cagA/iceA type and we could not detect cagA. The overall vacA, iceA1and cagA genes identified were 61.6%, 38.8%, 26.6% respectively, by PCR-based molecular testing. The vacA gene status was highly significant related to gastritis patient (P 0.036). The vacA s1m1 and s2m2 alleles were significantly found in 50% of H. pylori infected patients with PUD and with gastritis 57.1% respectively (P 0.01).Conclusion: In conclusion, the main genotype combinations in the studied Egyptian patients were; vacAs2m2/iceA1, vacAs1m1/cagA, mostly associated with gastritis, and vacAs1/cagA/icA, mainly in PUD. The less virulent (s2, s2m2) H. pylori genotypes were found in patients aged over 43 years

Phenotypic and Molecular Detection of Antiseptic Resistance Genes among Clinical Staphylococcus aureus Isolates During COVID-19 Pandemic

The coronavirus disease (COVID-19) pandemic has expanded the use of chlorhexidine digluconate, a biocide frequently used in hospitals, to inhibit the spread of infection. Genes responsible for resistance against the quaternary ammonium compound qac in Staphylococcus aureus isolates have been shown to confer tolerance to a number of biocidal chemicals, including chlorhexidine. The aim of this study was to determine the occurrence of antiseptic resistance genes (qacA/B and qacC) in clinical isolates of methicillin-susceptible (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA). The study also aimed to investigate the association between the presence of the mecA, qacA/B, and qacC genes in MRSA isolates and the susceptibility of the isolates to chlorhexidine to evaluate its future use in the Theodor Bilharz Research Institute (TBRI) hospital, following the Centers for Disease Control and Prevention recommendations for patients with MRSA. S. aureus isolates (n = 100) were collected from inpatients and outpatients at TBRI. A minimal inhibitory concentration of chlorhexidine was also detected. Polymerase chain reaction was used to detect the mecA, qacA/B, and qacC genes. The results revealed that 84% of S. aureus isolates were MRSA. MRSA (61.9%) and MSSA (68.8%) isolates were susceptible to chlorhexidine. The qacA/B gene was more dominant, being detected in 34%, while qacC was detected in only 5% of S. aureus isolates. All S. aureus isolates with reduced susceptibility to chlorhexidine harbored either the qacA/B or qacC genes. The clinical use of chlorhexidine may continue to increase, emphasizing the significance of continuous caution underlining the emergence of new clones with reduced susceptibility and avoiding antiseptic misuse

Treatment of Gingival Hyperpigmentation by Diode Laser for Esthetical Purposes

BACKGROUND: Gingival hyperpigmentation is a common esthetical concern in patients with gummy smile or excessive gingival display. Laser ablation has been recognized recently as the most effective, pleasant and reliable technique. It has the advantage of easy handling, short treatment time, hemostasis, decontamination, and sterilization effect.AIM: In the present study we wanted to explore the efficacy of a 980 nm wavelength diode laser in gingival depigmentation clinically by using both VAS and digital imaging method as means of assessment.METHODS: Diode laser ablation was done for 15 patients who requested cosmetic therapy for melanin pigmented gums. The laser beam delivered by fiberoptic with a diameter of 320 µm, the diode laser system has 980 nm wave lengths and 3 W irradiation powers, in a continuous contact mode in all cases, the entire surface of each pigmented maxillary and mandibular gingiva that required treatment was irradiated in a single session. Clinical examination and digital image analysis were done and the patients were followed up for 3 successive months.RESULTS: There was a statistically significant change in prevalence of bleeding after treatment, as none of the cases showed any signs of bleeding 1 week, 1 month and 3 months after ablation. No statistically significant change was observed in the prevalence of swelling after treatment The VAS evaluation demonstrated that only 4 patients complained of mild pain immediately after the procedure. No pain was perceived from the patients in the rest of the follow up period. There was no statistically significant change in prevalence of pain immediately after treatment compared to pain during treatment. There was a decrease in cases with mild pain after 1 week, 1 month as well as 3 months compared to pain during treatment and immediately after treatment.CONCLUSION: Within the limitations of this study, the use of diode laser was shown to be a safe and effective treatment modality that provides optimal aesthetics with minimal discomfort in patients with gingival hyperpigmentation