Waveform acquisition with resolutions exceeding those of the ADCs employed

This chapter discusses various software/firmware and hardware methods and architectures to improve the fidelity of the acquired waveforms beyond the vertical and horizontal resolutions that are possible with the ADC employed. The applicability of these approaches, and the limits on the enhancements that are achievable, depend upon the nature of the acquired waveform, and they are presented separately for one-shot, repeatable and repetitive waveforms. The possibilities of combining applicable methods in order to simultaneously increase both resolutions are also discussed. The consideration is illustrated by the simulation results and the acquired experimental waveforms relevant to the ultrasonic non-destructive evaluation

Investigating the effect of process parameters on dimensional accuracy and ultimate tensile strength of micro injection moulded micro parts

This thesis presents two models for optimizing and guiding the micro injection moulding process. The models are generated by the use of a mathematical procedure, an understanding of the process, and empirical data obtained from several sets of experiments. Micro injection moulding is a well-known process that is heavily used in the mass production of micro polymer parts. It is a very reliable process and apart from the initial investment required for manufacturing a mould, the process is very low cost. Furthermore, polymer developments have led to the process being suitable for the production of micro parts in equipment used in several industries such as medical, automotive, aerospace and sensing. Due to these important industrial applications, several quality criteria have been the subject of research in recent years. One of the main challenges in micro moulding is the modelling of the process in terms of polymer flow and accuracy. This is because current available models use PVT data (pressure, volume, temperature) that is used for modelling of conventional injection moulding. Furthermore, these models ignore several factors in micro moulding such as the high shear rates and 3D flow of the polymer melt. Moreover, modelling of the mechanical properties of the micro parts based on mathematical systems used for macro parts leads to large errors. This study proposes a new method for modelling the effect of process parameters on the dimensional accuracy and UTS (Ultimate tensile strength) of micro walls. This results in reduction of risk and cost, and optimization of the process. The “accuracy model” relates the dimensional error to four process parameters (polymer melt and mould temperature, and injection velocity and pressure), polymer characteristics (density, specific heat capacity and thermal conductivity) and a characteristic of the machine (plunger diameter). The “mechanical model” relates the part’s UTS to the same parameters as in the accuracy model. In order to develop the “accuracy model” an understanding of the effect of process parameters on dimensional accuracy and the polymers needs to be obtained. Several sets of experiments were conducted to investigate and establish this effect. Two polymers, Polyoxymethylene (POM) and Polypropylene (PP), were used to conduct the study. The results showed that the polymer melt temperature had the highest effect, followed by injection pressure, injection velocity and mould temperature. Amongst these, injection velocity had an adverse effect on dimensional accuracy. Further analysis was done to investigate whether the effect was consistent for several sets of the parameters. Results of the experiments showed that while the effect was not linear, the trends obtained earlier were correct. The same procedure was applied to investigate the effect of process parameters on the UTS of the micro walls. Polymer melt temperature had the highest level of influence, followed by injection velocity, injection pressure and mould temperature. Increase in all parameters resulted in reduction of the UTS, except for the mould temperature. Next, the two models were developed through a method called dimensional analysis. Several dimensionless expressions were developed to form a general relationship between the parameters and the quality criteria. Then, the obtained results and data were used to find the constants and the specific form of the functions. The overall models were validated by a fresh set of selected experiments using an original brass insert. The achieved trends and models were validated experimentally, using a different mould insert with a micro channel with a different dimension. While the values for the dimensional error and UTS were different, the trends obtained before were correct for the new insert. The same trend was observed with the models. Again, predictions for PP parts had better agreement with experimental data compared to those of POM. In addition, the amount of error for the steel insert was higher, due to different thermal conductivity of the insert material and surface roughness of the micro channels

Investigating the effect of process parameters on dimensional accuracy and ultimate tensile strength of micro injection moulded micro parts

This thesis presents two models for optimizing and guiding the micro injection moulding process. The models are generated by the use of a mathematical procedure, an understanding of the process, and empirical data obtained from several sets of experiments. Micro injection moulding is a well-known process that is heavily used in the mass production of micro polymer parts. It is a very reliable process and apart from the initial investment required for manufacturing a mould, the process is very low cost. Furthermore, polymer developments have led to the process being suitable for the production of micro parts in equipment used in several industries such as medical, automotive, aerospace and sensing. Due to these important industrial applications, several quality criteria have been the subject of research in recent years. One of the main challenges in micro moulding is the modelling of the process in terms of polymer flow and accuracy. This is because current available models use PVT data (pressure, volume, temperature) that is used for modelling of conventional injection moulding. Furthermore, these models ignore several factors in micro moulding such as the high shear rates and 3D flow of the polymer melt. Moreover, modelling of the mechanical properties of the micro parts based on mathematical systems used for macro parts leads to large errors. This study proposes a new method for modelling the effect of process parameters on the dimensional accuracy and UTS (Ultimate tensile strength) of micro walls. This results in reduction of risk and cost, and optimization of the process. The “accuracy model” relates the dimensional error to four process parameters (polymer melt and mould temperature, and injection velocity and pressure), polymer characteristics (density, specific heat capacity and thermal conductivity) and a characteristic of the machine (plunger diameter). The “mechanical model” relates the part’s UTS to the same parameters as in the accuracy model. In order to develop the “accuracy model” an understanding of the effect of process parameters on dimensional accuracy and the polymers needs to be obtained. Several sets of experiments were conducted to investigate and establish this effect. Two polymers, Polyoxymethylene (POM) and Polypropylene (PP), were used to conduct the study. The results showed that the polymer melt temperature had the highest effect, followed by injection pressure, injection velocity and mould temperature. Amongst these, injection velocity had an adverse effect on dimensional accuracy. Further analysis was done to investigate whether the effect was consistent for several sets of the parameters. Results of the experiments showed that while the effect was not linear, the trends obtained earlier were correct. The same procedure was applied to investigate the effect of process parameters on the UTS of the micro walls. Polymer melt temperature had the highest level of influence, followed by injection velocity, injection pressure and mould temperature. Increase in all parameters resulted in reduction of the UTS, except for the mould temperature. Next, the two models were developed through a method called dimensional analysis. Several dimensionless expressions were developed to form a general relationship between the parameters and the quality criteria. Then, the obtained results and data were used to find the constants and the specific form of the functions. The overall models were validated by a fresh set of selected experiments using an original brass insert. The achieved trends and models were validated experimentally, using a different mould insert with a micro channel with a different dimension. While the values for the dimensional error and UTS were different, the trends obtained before were correct for the new insert. The same trend was observed with the models. Again, predictions for PP parts had better agreement with experimental data compared to those of POM. In addition, the amount of error for the steel insert was higher, due to different thermal conductivity of the insert material and surface roughness of the micro channels

Ultrasonic instrument for accurate measurements of spatial parameters in blood vessels

The present research is aimed at the development of an ultrasonic medical instrument capable of measuring the intima-media thicknesses (IMT) of artery walls that are considered by medical practitioners as good indicators of the risk of atherosclerosis. This overcomes two notable limitations of the instruments available at present – insufficient axial resolution and lack of synchronisation to the heart cycle that make the measurements difficult to use, e.g., for annual screening of patients and like-for-like comparisons. These limitations were addressed by using a combination of on-the-fly averaging and interleaved sampling for acquiring echo waveforms, and triggering the scans at a particular instant of the heart cycle. The developed electronic instrumentation consisted of a battery powered electrocardiogram (ECG) monitor that transmitted the ECG data using an infrared link to the ECG processor that triggered the scans. Such architecture eliminated any possibility of accidentally connecting the patient to a source of voltage capable of causing serious injury and of causing radio frequency interference to medical equipment located in a close proximity. The algorithm for detecting the R-waves from noisy ECGs was fully verified with simulated and experimental ECG records, and implemented in firmware on board the ECG processor. The rate of R-wave detection of the developed algorithm is 88.24% out of 204 heartbeats recorded. In order to ease the interpretation of the recorded echoes, both mathematical and physical simulations of tubular objects were carried out. The calculated resolution of the system was estimated 2.5um. Spatial resolution of 15um was achieved during the in-vivo experiments. Some of the factors that might have caused this difference have been discussed with suggestions on possible methods of improvements. The set of experimental waveforms recorded in vivo demonstrated the correct operation of the developed instrument, appropriate consistency and some features that were expected and described in the literature. The developed instrument seems ready for application to a broader group of subjects

The Long-term Effects of Percutaneous Laser Disc Decompression (PLDD) Treatment on Lumbar Disc Protrusion: A 2-Year Follow-up

Introduction: Nowadays many physicians have focused their attention on using low invasive methods for the treatment of disc protrusion. Thus, the current study was carried out to evaluate the effect and therapeutic outcomes of clinical percutaneous laser disc decompression (PLDD) in the treatment of chronic low back pain caused by disc protrusion during a two-year follow-up.Methods: This historical cohort study was conducted on 40 patients, who were suffering from chronic low back pain caused by disc protrusion diagnosed, and referred to the pain clinic of Akhtar Hospital from March to August 2016 were treated with PLDD and were followed up for at least two years after performing PLDD (from 2018 to 2019). All the information has been extracted using medical records and patient interviews. The severity of pain was measured by the Numeric Rating Scale (NRS), and the Oswestry disability index (ODI) was measured before and two years after the treatment.Results: The most common sites for two-level PLDD were L4-S1 and L3-L5, and the most common sites for one-level PLDD were L5-S1 and L4-L5. Overall, the levels of pain and functional disability two years after PLDD showed significant improvements (P = 0.0001). The results revealed no statistically significant differences in NRS and ODI scores between the two groups of men and women two years after PLDD (P > 0.05). Furthermore, they indicated no statistically significant differences in NRS and ODI scores between the different disc protrusion levels two years after PLDD (P > 0.05).Conclusion: It seems that the PLDD is a low-invasive, safe, and effective method that can be used in patients with chronic low back pain caused by a disc protrusion. Therefore, it can be considered as a suitable choice in treating patients with chronic low back pain caused by a disc protrusio

Salivary Secretor Status of Blood Group Antigens in Patients with Head and Neck Cancer

BACKGROUND: Head and neck cancers include malignancies of the scalp and neck skin, nasal cavity, paranasal sinuses, oral cavity, salivary glands, pharynx and larynx. The term ABO secretor refers to people who secrete blood group antigens in their body fluids such as saliva, sweat, tears, semen, and serum. Non-secretors refer to those who do not secrete their blood group antigens in their body fluids. The lack of blood type antigens in body discharge increases the susceptibility to certain types of diseases and infection. AIM: Our study aimed to investigate the relationship between the secretion of blood groups in the saliva of patients with head and neck cancers. MATERIAL AND METHODS: This case-control study was performed on 110 people (57 patients with head and neck cancer who were referred to Imam Khomeini Hospital, Tehran and 53 cancer-free controls). Five ml of non-stimulated saliva were collected by the spitting method. By agglutination or lack of agglutination in the test tubes, we determined the patient’s secretor or non-secretor condition. RESULTS: In terms of secretor status, 52.7% of all samples were secretors. In the case group, 19 out of 57 cases (33.3%) were secretors, and 38 were non-secretors (66.7%). In the control group, 39 out of 53 cases (73.6%) were secretors, and 14 cases were non-secretors (26.4%). There was a significant difference in the percentage of non-secretors between the two groups (p = 0.00). CONCLUSION: People with non-secretor status may be more prone to develop head and neck cancer. The presence of these antigens in saliva may have a protective effect

A Miniaturized wide Stopband Low-pass Filter using T and Modified L Shapes Resonators

A new structure of microstrip-based low-pass filter with wide stopband and sharp roll-off is introduced, in this paper. In the proposed topology, resonators with T and modified L Shapes have been used. To improve the suppression factor and relative stopband bandwidth, the second resonator has been added to the first resonator. The designed filter has been fabricated on a 20 mm thickness RO4003 substrate, which has a loss tangent of 0.0021 and a relative dielectric constant equal to 3.38. All parameters including roll of rate, stopband, bandwidth, return loss, insertion loss, and figure of merit have significant coefficients. Simulation has been ran using advanced design system software. The 3dB cutoff frequency is appropriate. The value of the insertion loss parameter is <0.1 dB and the S11 parameter is −22 dB at this point. The stopband is extended from 2.42 up to 24 GHz, which shows an ultra-stopband. The results of the simulation and experiment are almost similar, which indicates a proper performance of the designed structure

The Potential of Amaranthus caudatus as a Phytoremediating Agent for Lead

The potential of Amaranthus caudatus as a phytoremediating agent was studied, using lead spiked soil to grow the plants. The effect of the concentration of lead on plant growth was studied. The main aim of the study was to assess the accumulation of lead (Pb) in different compartments of the plant. The plants were grown in soils treated with solutions corresponding to 25, 50, 75 and 100 ppm of Pb. The plants were than separated into roots, stems and leaves and dried at 600C in a convection oven for 48 hours.The metals from the plant were extracted using wet digestion process. Pearson’s coefficient correlation analysis was used to measure the relationship between Pb concentration in the soil and in plant tissues. The highest concentration was recorded in the roots of plants at 50 ppm concentration. A. Caudatus plants exposed to 25 ppm of Pb showed highest increase in root and stem growth. The lowest root growth was observed in plants exposed to 100 ppm of Pb. There is a negative relationship between the concentration of Pb in the soil and that in the above ground plant tissues. Key Words: Accumulation, Amaranthus, Lead, Phytoremediation

Outcome of three dimensional osteotomy for cubitus varus deformity

Background: Cubitus varus is the most common angular deformity resulting from supracondylar fracture of the humerus in children and adults. There are several options for correcting this deformity, but three dimensional osteotomy is now a popular method for the operative treatment of cubitus varus deformity. Objective of current study was to evaluate clinical and radiological outcome of three dimensional corrective osteotmy for cubitus varus deformity.Methods: This prospective interventional study was conducted in the department of orthopaedic surgery, BSMMU, Shahbag, Dhaka from January 2016 to September 2020. Within this period, total 40 cases of cubitus varus deformity, age ranging from 8-20 years that has the inclusion criteria was enrolled as a study sample with proper consent. All the data were analyzed statistically by using SPSS-22.Results: The results of present study showed significantly improved carrying angle, range of motion, internal rotation angle at the time of final follow-up period of six months or more. The outcome of the subjects was graded as excellent in 16 (40%), good in 18 (45%), fair in 4 (10%) and poor in 2 (5%) patients. Excellent, good and fair results were considered as satisfactory outcome and only poor result was considered as unsatisfactory outcome.Conclusions: After analyzing the results of present study it can be concluded that three dimensional osteotomy is a safe technique with satisfactory outcome in treatment of cubitus varus deformity