On the false-diffusion problem in the numerical modelling of convection-diffusion processes

This thesis is concerned with the classification and evaluation of various numerical schemes that are available for computing solutions for fluid-flow problems, and secondly, with the development of an improved numerical discretisation scheme of the finite-volume type for solving steady-state differential equations for recirculating flows with and without sources. In an effort to evaluate the performance of the various numerical schemes available, some standard test cases were used. The relative merits of the schemes were assessed by means of one-dimensional laminar flows and two-dimensional laminar and turbulent flows, with and without sources. Furthermore, Taylor series expansion analysis was also utilised to examine the limitations that were present. The outcome of this first part of the work was a set of conclusions, concerning the accuracy of the numerous schemes tests, vis-a-vis their stability, ease of implementation, and computational costs. It is hoped that these conclusions can be used by `computational fluid-dynamics' practitioners in deciding on an optimum choice of scheme for their particular problem. From the understanding gained during the first part of the study, and in an effort to combine the attributes of a successful discretisation scheme, eg positive coefficients. conservation and the elimination of 'false-diffusion', a new flow-oriented finite-volume numerical scheme was devised and applied to several test cases in order to evaluate its performance. The novel approach in formulating the new CUPID* scheme (for Corner UPw^nDing) underlines the idea of focussing attention at the control-volume corners rather than at the control-volume cell-faces. In two-dimensions, this leads to an eight neighbour influence for the central grid point value, depending on the flow-directions at the corners of the control-volume. In the formulation of the new scheme, false-diffusion is considered from a pragmatic perspective, with emphasis on physics rather than on strict mathematical considerations such as the order of discretisation, etc. The accuracy of the UPSTREAM scheme (for JJPwind in STREAMIines) indicates that although it is formally only first-order accurate, it considerably reduces 'false-diffusion'. Scalar transport calculations (without sources) show that the UPSTREAM scheme predicts bounded solutions which are more accurate than the upwind-difference scheme and the unbounded skew-upstream-difference scheme. Furthermore, for laminar and turbulent flow calculations, improved results are obtained when compared with the performances of the other schemes. The advantage of the UPSTREAM-difference scheme is that all the influence coefficients are always positive and thus the coefficient matrices are suitable for iterative solution procedures. Finally, the stability and convergence characteristics are similar to those of the upwind-difference scheme, eg converged solutions are guaranteed. What cannot be guaranteed, however, is the conservatism of the scheme and it is recommended that future work should be directed towards improving that disadvantage

A Hospital-based Observational Study of Type 2 Diabetic Subjects from India

Aim: The aim of this study was to describe the profile of the subjects with type 2 diabetes mellitus (T2DM) to obtain aclear picture from Western India, that would help in management of diabetes. Methods: An observational study wasconducted with newly diagnosed 622 type 2 diabetic subjects attending Dept. of Diabetology, All India Institute ofDiabetes and Research and Yash Diabetes Specialties Centre (Swasthya), Ahmedabad during the period from August 2006 to January 31, 2009. Subjects completed an interviewer-administered comprehensive questionnaire, which included variables such as sociodemographic presenting symptoms, risk profile (hypertension, obesity, dyslipidemia and glycemic status), family history of diabetes, physical activity and behavioral profile. Blood pressure, body mass index (BMI), glycosylated hemoglobin (HbA1c) and fasting lipid profile were measured. Descriptive and bivariate analyses were carried out using SPSS version 11.5. Results: A total of 622 T2DM cases with mean age (years) 47.7 ± 10.9 were studied. Of these, 384 (62%) were male. The majority of T2DM subjects were obese (68%) and 67% had positive family history of diabetes. Renal dysfunctions and vision impairment were found in 10% (62/622) and 9% (57/622), respectively in T2DM subjects. The mean HbA1c level was 9.02% ± 1.67 and good glycemic control (HbA1c level <7%) was achieved only in 7.4% T2DM subjects. The Chi-square (χ2) analysis showed that higher BMI (≥25 kg/m2) is significantly associated with hypertension among T2DM subjects (p < 0.01). There were statistically significant differences between male and female study subjects with respect to mean age, BMI, waist and hip circumference and mean low-density lipoprotein (LDL) level (p < 0.05). Conclusions: The present study revealed that obesity, family history of diabetes, dyslipidemia, uncontrolled glycemic status, sedentary lifestyles and hypertension were more prevalent in T2DM subjects. Hence, the overall risk profile was very poor and needs improvement. The characterization of this risk profile will contribute in defining more effective and specific strategies for screening and controlling T2DM in Western India

A Hospital-based Observational Study of Type 2 Diabetic Subjects from Gujarat, India

The aim of this observational study was to describe the profile of subjects with type 2 diabetes mellitus from Gujarat, India. The study was performed with newly-diagnosed 622 type 2 diabetic subjects who attended the Department of Diabetology, All India Institute of Diabetes and Research and Yash Diabetes Specialties Centre (Swasthya), Ahmedabad, during August 2006–January 2009. The subjects completed an interviewer-administered questionnaire. The questionnaire included variables, such as sociodemographic factors, presenting symptoms, risk profile (hypertension, obesity, dyslipidaemia, and glycaemic status), family history of diabetes, physical activity, and behavioural profile. Blood pressure, body mass index (BMI), glycosylated haemoglobin levels, and fasting lipid profile were measured. Descriptive and bivariate analyses were carried out using the SPSS software (version 11.5). In total, 622 type 2 diabetes mellitus (T2DM) cases with mean age of 47.7±10.9 years were studied. Of the 622 subjects, 384 (62%) were male. The majority (68%) of the T2DM subjects were obese, and 67% had a positive family history of diabetes. Renal dysfunctions and vision impairment were, respectively, found in 10% (n=62) and 9% (n=57) of the 622 T2DM subjects. The mean HbA1c level was 9.02±1.67%, and good glycaemic control (HbA1c level <7%) was achieved only in 7.4% of the T2DM subjects. Results of chi-square analysis showed that higher BMI (≥25 kg/m2) was significantly associated with hypertension among the T2DM subjects (p<0.01). There were significant differences (p<0.05) between male and female subjects with respect to mean age, BMI, waist and hip-circumference, and mean low-density lipoprotein (LDL) level. The results revealed that many factors, such as obesity, fami-ly history of diabetes, dyslipidaemia, uncontrolled glycaemic status, sedentary lifestyles, and hypertension were prevalent among the T2DM subjects. The characterization of this risk profile will contribute to designing more effective and specific strategies for screening and controlling T2DM in Gujarat, India

Study of importance of medial cortex in distal femur comminuted fracture

Background: Distal femur fractures require high energy trauma by means of road traffic accidents. There are various modalities of fixation, involving plating, external fixator and intramedullary nailing. cause of nonunion like smoking, osteoporosis, early weight bearing, improper construction of fixation, improper reduction.Methods: The study was conducted on 20 patients having distal femur fractures operated previously by using a different modality of implant goes in failure like bending of implant, broken of implant, peri implant fracture after second episode of trauma. Patient was preoperatively assessing for rule out occult low grade infection by blood investigation like ESR and CRP. Previous X-ray review to find cause of nonunion.Results: All patients showed a complete union at the fracture site with an average duration of 4-6 months. There was no complaint of infection, joint stiffness or difficulty in weight bearing after treatment with revision fixation and bone grafting. Patients were able to walk without affecting their daily activity of living.  Conclusions: Comminuted medial cortex left unfixed or maligned will go into varus collapse and leads to failure of fixation

Parametrical modeling and design optimization of blood plasma separation device with microchannel mechanism

This paper presents an analysis of biofluid behavior in a T-shaped microchannel device and a design optimization for improved biofluid performance in terms of particle liquid separation. The biofluid is modeled with single phase shear rate non-Newtonian flow with blood property. The separation of red blood cell from plasma is evident based on biofluid distribution in the microchannels against various relevant effects and findings, including Zweifach-Fung bifurcation law, Fahraeus effect, Fahraeus-Lindqvist effect and cell free phenomenon. The modeling with the initial device shows that this T-microchannel device can separate red blood cell from plasma but the separation efficiency among different bifurcations varies largely. In accordance with the imbalanced performance, a design optimization is conducted. This includes implementing a series of simulations to investigate the effect of the lengths of the main and branch channels to biofluid behavior and searching an improved design with optimal separation performance. It is found that changing relative lengths of branch channels is effective to both uniformity of flow rate ratio among bifurcations and reduction of difference of the flow velocities between the branch channels, whereas extending the length of the main channel from bifurcation region is only effective for uniformity of flow rate ratio

A Hospital-based Observational Study of Type 2 Diabetic Subjects from Gujarat, India

The aim of this observational study was to describe the profile of subjects with type 2 diabetes mellitus from Gujarat, India. The study was performed with newly-diagnosed 622 type 2 diabetic subjects who attended the Department of Diabetology, All India Institute of Diabetes and Research and Yash Diabetes Specialties Centre (Swasthya), Ahmedabad, during August 2006 -January 2009. The subjects completed an interviewer-administered questionnaire. The questionnaire included variables, such as sociodemographic factors, presenting symptoms, risk profile (hypertension, obesity, dyslipidaemia, and glycaemic status), family history of diabetes, physical activity, and behavioural profile. Blood pressure, body mass index (BMI), glycosylated haemoglobin levels, and fasting lipid profile were measured. Descriptive and bivariate analyses were carried out using the SPSS software (version 11.5). In total, 622 type 2 diabetes mellitus (T2DM) cases with mean age of 47.7\ub110.9 years were studied. Of the 622 subjects, 384 (62%) were male. The majority (68%) of the T2DM subjects were obese, and 67% had a positive family history of diabetes. Renal dysfunctions and vision impairment were, respectively, found in 10% (n=62) and 9% (n=57) of the 622 T2DM subjects. The mean HbA1c level was 9.02\ub11.67%, and good glycaemic control (HbA1c level &lt;7%) was achieved only in 7.4% of the T2DM subjects. Results of chi-square analysis showed that higher BMI ( 6525 kg/m2) was significantly associated with hypertension among the T2DM subjects (p&lt;0.01). There were significant differences (p&lt;0.05) between male and female subjects with respect to mean age, BMI, waist- and hip-circumference, and mean low-density lipoprotein (LDL) level. The results revealed that many factors, such as obesity, family history of diabetes, dyslipidaemia, uncontrolled glycaemic status, sedentary lifestyles, and hypertension were prevalent among the T2DM subjects. The characterization of this risk profile will contribute to designing more effective and specific strategies for screening and controlling T2DM in Gujarat, India

Factors Associated with Consumption of Diabetic Diet among Type 2 Diabetic Subjects from Ahmedabad, Western India

This cross-sectional study assessed the current situation of and factors associated with consumption of diabetic diet among 399 type 2 diabetes mellitus (T2DM) subjects from Ahmedabad, Western India. The study was performed with diagnosed (at least one year old) diabetic subjects who attended the Department of Diabetology, All India Institute of Diabetes and Research and Yash Diabetes Specialties Centre (Swasthya Hospital), Ahmedabad during July 2010\u2013November 2010. The subjects completed an interviewer- administered questionnaire. The questionnaire included variables, such as sociodemographic factors, family history of diabetes, behavioural profile, risk profile (glycaemic status, hypertension, and obesity), and diet-related history (consumption of diabetic diet, consumption of low fat/skimmed milk, method of cooking, and sources for diet advice). Blood pressure, body mass index, glycosylated haemoglobin (HbA1c) level, and fasting lipid profile were measured. All analyses including multivariate logistic regression were conducted using SPSS, version 11.5. In total, 399 T2DM subjects (65% male, 35% female) with mean age of 53.16\ub17.95 years were studied. Although 73% of T2DM subjects were consuming diabetic diet, the good glycaemic control (HbA1c level &lt;7%) was achieved only in 35% of the subjects. The majority (75%) of the subjects had a positive family history of diabetes, and 52% were obese. In 77%, the main source of dietary advice was doctor. In 36%, the main methods of cooking were: boiling and roasting. The final multivariate model showed that visit to dietician, level of education, intake of low fat, and family history of diabetes were independent predictors for diabetic diet consumption among T2DM subjects. However, longitudinal and cohort studies are required to establish the association between consumption of diabetic diet and glycaemic control

Systematic review and meta-analysis of effectiveness of treatment options against SARS-CoV-2 infection

Treatment options for severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) are limited with no clarity on efficacy and safety profiles. We performed a systematic review and meta-analysis of studies on patients ≥18 years reporting data on therapeutic interventions in SARS-CoV-2. Primary outcome was all-cause mortality and secondary outcomes were rates of mechanical ventilation, viral clearance, adverse events, discharge, and progression to severe disease. Pooled rates and odds ratios (OR) were calculated. Twenty-nine studies with 5207 patients were included. Pooled all-cause mortality in intervention arm was 12.8% (95% confidence interval [CI]: 8.1%-17.4%). Mortality was significantly higher for studies using hydroxychloroquine (HCQ) for intervention (OR: 1.36; 95% CI: 0.97-1.89). Adverse events were also higher in HCQ subgroup (OR: 3.88; 95% CI: 1.60-9.45). There was no difference in other secondary outcomes. There is a need for well-designed randomized clinical trials for further investigation of every therapeutic intervention for further insight into different therapeutic options

Comparative reliability of inkjet-printed electronics packaging

This article compares the thermomechanical behavior of 3-D inkjet-printed microelectronics devices relative to those fabricated from traditional methods. It discusses the benefits and challenges in the adoption of additive manufacturing methods for microelectronics manufacture relative to conventional approaches. The critical issues related to the design and reliability of additively manufactured parts and systems stem from the change in the manufacturing process and the change in materials utilized. This study uses numerical modeling techniques to gain insight into these issues. This article is an extension of the same topic presented at the 2018 IEEE Electronics Packaging Technology Conference. An introduction providing an overview of the area, covering salient academic research activities and discussing progress toward commercialization is presented. The state-of-the-art modular microelectronics fabrication system developed within the EU NextFactory project is introduced. This system has been used to manufacture several test samples, which were assessed both experimentally and numerically. A full series of JEDEC tests showed that the samples were reliable, successfully passing all tests. The numerical model assessing the mechanical behavior of an inkjet-printed structure during layer-by-layer fabrication is presented. This analysis predicts that the stresses induced by the UV cure process are concentrated toward the extremities of the part and, in particular, in the lower layers which are constrained by the print platform. Subsequently, a model of a multilayer microelectronics structure undergoing JEDEC thermal cycling is presented. The model assesses the differences in mechanical properties between a conventional FR4/copper structure and an inkjet-printed acrylic/silver structure. The model identified that the influence of the sintering process on subsequent material properties, behavior of the inject-printed structure, and reliability of the inject-printed structure is significant. Key findings are that while stresses in the conventional and inkjet boards are relatively similar, the inkjet-printed board exhibits significantly greater deformation than the standard board. Furthermore, the mechanical stresses in the inkjet fabricated board are strongly dependent on the elastic modulus of the sintered silver material, which, in turn, is dependent on the sintering process

Fabrication of hollow polymer microstructures using dielectric and capillary forces

Electric Field Assisted Capillarity is a novel one-step process suitable for the fabrication of hollow polymer microstructures. The process, demonstrated to work experimentally on a microscale using Polydimethylsiloxane (PDMS), makes use of both the electrohydrodynamics of polymers subject to an applied voltage and the capillary force on the polymers caused by a low contact angle on a heavily wetted surface. Results of two-dimensional numerical simulations of the process are discussed in this paper for the special case of production of microfluidic channels. The paper investigates the effects of altering key parameters including the contact angle with the top mask, the polymer thickness and air gap, the permittivity of the polymer, the applied voltage and geometrical variations on the final morphology of the microstructure. The results from these simulations demonstrate that the capillary force caused by the contact angle has the greatest effect on the final shape of the polymer microstructures