Study of SENT specimens with a tilted notch to evaluate ductile tearing in spiral welded pipeline applications

There is an increasing interest for the use of spiral welded pipelines in strain based design applications. Environmentally imposed loads are able to plastically deform the pipelines, meaning that their structural response is of the utmost importance. However, since the influence of the spiral weld is not fully grasped, further investigation is necessary. The mechanical response of the pipeline is not only influenced by its material properties, but also by the angular position of the welds. Subsequently, the effect of mixed mode loading is a crucial aspect when assessing the helical welds. To evaluate the ductile tearing of the pipeline material, multiple single edge notched tensile (SENT) tests - each with a tilted notch of 25° with respect to the transverse direction - were executed. The extension of the crack is assessed by means of potential drop measurements and finite element simulations. Resistance curves were realized by combining the crack opening displacement with the associated crack extension. This is an ongoing investigation and in this paper a first set of five tests are evaluated

Coital frequency and condom use in monogamous and concurrent sexual relationships in Cape Town, South Africa

Introduction: A decreased frequency of unprotected sex during episodes of concurrent relationships may dramatically reduce the role of concurrency in accelerating the spread of HIV. Such a decrease could be the result of coital dilution - the reduction in per-partner coital frequency from additional partners - and/or increased condom use during concurrency. To study the effect of concurrency on the frequency of unprotected sex, we examined sexual behaviour data from three communities with high HIV prevalence around Cape Town, South Africa. Methods: We conducted a cross-sectional survey from June 2011 to February 2012 using audio computer-assisted self-interviewing to reconstruct one-year sexual histories, with a focus on coital frequency and condom use. Participants were randomly sampled from a previous TB and HIV prevalence survey. Mixed effects logistic and Poisson regression models were fitted to data from 527 sexually active adults reporting on 1210 relationship episodes to evaluate the effect of concurrency status on consistent condom use and coital frequency. Results: The median of the per-partner weekly average coital frequency was 2 (IQR: 1-3), and consistent condom use was reported for 36% of the relationship episodes. Neither per-partner coital frequency nor consistent condom use changed significantly during episodes of concurrency (aIRR=1.05; 95% confidence interval (CI): 0.99-1.24 and aOR=1.01; 95% CI: 0.38-2.68, respectively). Being male, coloured, having a tertiary education, and having a relationship between 2 weeks and 9 months were associated with higher coital frequencies. Being coloured, and having a relationship lasting for more than 9 months, was associated with inconsistent condom use. Conclusions: We found no evidence for coital dilution or for increased condom use during concurrent relationship episodes in three communities around Cape Town with high HIV prevalence. Given the low levels of self-reported consistent condom use, our findings suggest that if the frequency of unprotected sex with each of the sexual partners is sustained during concurrent relationships, HIV-positive individuals with concurrent partners may disproportionately contribute to onward HIV transmission

Evaluating audio computer assisted self-interviews in urban south African communities: evidence for good suitability and reduced social desirability bias of a cross-sectional survey on sexual behaviour

Background: Efficient HIV prevention requires accurate identification of individuals with risky sexual behaviour. However, self-reported data from sexual behaviour surveys are prone to social desirability bias (SDB). Audio Computer-Assisted Self-Interviewing (ACASI) has been suggested as an alternative to face-to-face interviewing (FTFI), because it may promote interview privacy and reduce SDB. However, little is known about the suitability and accuracy of ACASI in urban communities with high HIV prevalence in South Africa. To test this, we conducted a sexual behaviour survey in Cape Town, South Africa, using ACASI methods. Methods: Participants (n = 878) answered questions about their sexual relationships on a touch screen computer in a private mobile office. We included questions at the end of the ACASI survey that were used to assess participants’ perceived ease of use, privacy, and truthfulness. Univariate logistic regression models, supported by multivariate models, were applied to identify groups of people who had adverse interviewing experiences. Further, we constructed male–female ratios of self-reported sexual behaviours as indicators of SDB. We used these indicators to compare SDB in our survey and in recent FTFI-based Demographic and Health Surveys (DHSs) from Lesotho, Swaziland, and Zimbabwe. Results: Most participants found our methods easy to use (85.9%), perceived privacy (96.3%) and preferred ACASI to other modes of inquiry (82.5%) when reporting on sexual behaviours. Unemployed participants and those in the 40–70 year old age group were the least likely to find our methods easy to use (OR 0.69; 95% CI: 0.47–1.01 and OR 0.37; 95% CI: 0.23–0.58, respectively). In our survey, the male–female ratio for reporting \u3e2 sexual partners in the past year, a concurrent relationship in the past year, and \u3e 2 sexual partners in a lifetime was 3.4, 2.6, and 1.2, respectively— far lower than the ratios observed in the Demographic and Health Surveys. Conclusions: Our analysis suggests that most participants in our survey found the ACASI modality to be acceptable, private, and user-friendly. Moreover, our results indicate lower SDB than in FTFI techniques. Targeting older and unemployed participants for ACASI training prior to taking the survey may help to improve their perception of ease and privacy

Coital frequency and condom use in monogamous and concurrent sexual relationships in Cape Town, South Africa

Introduction: A decreased frequency of unprotected sex during episodes of concurrent relationships may dramatically reduce the role of concurrency in accelerating the spread of HIV. Such a decrease could be the result of coital dilution - the reduction in per-partner coital frequency from additional partners - and/or increased condom use during concurrency. To study the effect of concurrency on the frequency of unprotected sex, we examined sexual behaviour data from three communities with high HIV prevalence around Cape Town, South Africa. Methods: We conducted a cross-sectional survey from June 2011 to February 2012 using audio computer-assisted self-interviewing to reconstruct one-year sexual histories, with a focus on coital frequency and condom use. Participants were randomly sampled from a previous TB and HIV prevalence survey. Mixed effects logistic and Poisson regression models were fitted to data from 527 sexually active adults reporting on 1210 relationship episodes to evaluate the effect of concurrency status on consistent condom use and coital frequency. Results: The median of the per-partner weekly average coital frequency was 2 (IQR: 1 - 3), and consistent condom use was reported for 36% of the relationship episodes. Neither per-partner coital frequency nor consistent condom use changed significantly during episodes of concurrency (aIRR = 1.05; 95% confidence interval (CI): 0.99-1.24 and aOR = 1.01; 95% CI: 0.38-2.68, respectively). Being male, coloured, having a tertiary education, and having a relationship between 2 weeks and 9 months were associated with higher coital frequencies. Being coloured, and having a relationship lasting for more than 9 months, was associated with inconsistent condom use. Conclusions: We found no evidence for coital dilution or for increased condom use during concurrent relationship episodes in three communities around Cape Town with high HIV prevalence. Given the low levels of self- reported consistent condom use, our findings suggest that if the frequency of unprotected sex with each of the sexual partners is sustained during concurrent relationships, HIV-positive individuals with concurrent partners may disproportionately contribute to onward HIV transmission

An externally validated fully automated deep learning algorithm to classify COVID-19 and other pneumonias on chest computed tomography.

peer reviewedPurpose: In this study, we propose an artificial intelligence (AI) framework based on three-dimensional convolutional neural networks to classify computed tomography (CT) scans of patients with coronavirus disease 2019 (COVID-19), influenza/community-acquired pneumonia (CAP), and no infection, after automatic segmentation of the lungs and lung abnormalities. Methods: The AI classification model is based on inflated three-dimensional Inception architecture and was trained and validated on retrospective data of CT images of 667 adult patients (no infection n=188, COVID-19 n=230, influenza/CAP n=249) and 210 adult patients (no infection n=70, COVID-19 n=70, influenza/CAP n=70), respectively. The model's performance was independently evaluated on an internal test set of 273 adult patients (no infection n=55, COVID-19 n= 94, influenza/CAP n=124) and an external validation set from a different centre (305 adult patients: COVID-19 n=169, no infection n=76, influenza/CAP n=60). Results: The model showed excellent performance in the external validation set with area under the curve of 0.90, 0.92 and 0.92 for COVID-19, influenza/CAP and no infection, respectively. The selection of the input slices based on automatic segmentation of the abnormalities in the lung reduces analysis time (56 s per scan) and computational burden of the model. The Transparent Reporting of a Multivariable Prediction Model for Individual Prognosis or Diagnosis (TRIPOD) score of the proposed model is 47% (15 out of 32 TRIPOD items). Conclusion: This AI solution provides rapid and accurate diagnosis in patients suspected of COVID-19 infection and influenza

Next-generation sequencing-based genome diagnostics across clinical genetics centers: Implementation choices and their effects

Implementation of next-generation DNA sequencing (NGS) technology into routine diagnostic genome care requires strategic choices. Instead of theoretical discussions on the consequences of such choices, we compared NGS-based diagnostic practices in eight clinical genetic centers in the Netherlands, based on genetic testing of nine pre-selected patients with cardiomyopathy. We highlight critical implementation choices, including the specific contributions of laboratory and medical specialists, bioinformaticians and researchers to diagnostic genome care, and how these affect interpretation and reporting of variants. Reported pathogenic mutations were consistent for all but one patient. Of the two centers that were inconsistent in their diagnosis, one reported to have found 'no causal variant', thereby underdiagnosing this patient. The other provided an alternative diagnosis, identifying another variant as causal than the other centers. Ethical and legal analysis showed that informed consent procedures in all centers were generally adequate for diagnostic NGS applications that target a limited set of genes, but not for exome- and genome-based diagnosis. We propose changes to further improve and align these procedures, taking into account the blurring boundary between diagnostics and research, and specific counseling options for exome- and genome-based diagnostics. We conclude that alternative diagnoses may infer a certain level of 'greediness' to come to a positive diagnosis in interpreting sequencing results. Moreover, there is an increasing interdependence of clinic, diagnostics and research departments for comprehensive diagnostic genome care. Therefore, we invite clinical geneticists, physicians, researchers, bioinformatics experts and patients to reconsider their role and position in future diagnostic genome care

Energy Efficiency of Induction Machines: A Critical Assessment (Energie efficiëntie van inductiemachines: een kritische beoordeling)

In deze thesis worden enkele fundamentele aspecten met betrekking tot het rendement van inductiemachines behandeld. De normen en de verschillende daarin beschreven methodes voor het bepalen van de energie efficiëntie van inductiemachines worden besproken. Een nauwkeurige vergelijking van de vier meest gekende en recente methodes brengt de verschillen in kaart. Aan de hand van meetresultaten van verschillende machines worden de verschillen tussen en tekortkomingen van bepaalde methodes bevestigd. Daarbij wordt speciale aandacht besteed aan de nieuwe zogenaamde Eh-Y methode. Een beknopt overzicht van belangrijke aandachtspunten voor de optimalisatie van het totaalrendement van motorsystemen en de rol die de (efficiëntie van de) inductiemachine daarin speelt, wordt aangevuld met enkele voorbeelden. Aan de hand van metingen op machines van verschillende bouwgrootte en efficiëntieklasse worden verschillen tussen het rendement in motor- ten opzichte van dat in generatorbedrijf besproken en verklaard. Speciale aandacht wordt besteed aan het gedrag en de prestaties van de inductiemachine gevoed uit een asymmetrisch net. Hierbij wordt specifiek onderzocht of en hoe de susceptibiliteit voor onbalans beïnvloed wordt door materiaalkeuzes, waarbij gefocust wordt op de koper rotor technologie. Daartoe worden eerst de verschillende normen voor het beschrijven en kwantificeren van spanningsonbalans bestudeerd. De theoretische bespreking wordt ondersteund door experimenten op verschillende machines.status: publishe

Electric Motors

The first section of this chapter focuses on the losses in electric motors. First the different loss components are described. Next, the influence of practical operating conditions on efficiency are addressed. The second section is devoted to standards on efficiency testing and classification. In the last section, the technology used in high efficiency motors is discussed briefly by looking at materials, design and manufacturing evolutions.edition: 1ststatus: publishe

2D Finite Element Analysis of a Solid Rotor Sector Motor

A solid rotor sector motor is a type of induction motor with a segmented stator rather than a ring-shaped or linear one. The operating principle and parasitic end effects are similar to those of a linear induction motor (LIM). A 2D finite element method model (2D FEM) including the 3D end effects is developed to calculate the torque and field distribution. A comparison with measurements is given and the simulation results are found to be a good prediction of the actual torque characteristics.status: accepte

Energy related environmental impact reduction opportunities in machine design: case study of a laser cutting machine

Energy consumption is responsible for a substantial part of the environmental impact generated by industrial production (Gutowski et al.,2006). Currently, minimising the energy consumption is hardly a priority for many machine tool designers, since they concentrate primarily on improving functionality, accuracy and safety. Nevertheless, alternative machine tool designs with improved energy consumption are emerging. This paper investigates the case of a laser cutting machine tool as common sheet metal processing machine tool. This paper verifies the potential for energy improvement by means of a case study. The analysis covers both the energy consumption during productive and non-productive time. Energy consumption improvement opportunities are identified. For this purpose a conventional CO2 laser cutting machine tool was investigated and compared with a possible fibre laser based machine tool configuration. The analysis shows that the CO2 laser source and the chiller unit are the largest energy consumers during productive time. During non-productive time, 12% of the yearly energy consumption is required to keep the chiller and other components active. For the alternative machine tool configuration it is assumed that no energy is needed during off-mode. The same scenario saves 16.6 MWh during productive time because of the improved efficiency of a fibre laser source.status: publishe