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Asymptomatic SARS-CoV-2 infections are responsible for potentially significant transmission of COVID-19. Worldwide, a number of studies were conducted to estimate the magnitude of asymptomatic COVID-19 cases. However, there is a need for more robust and well-designed studies to have a relevant public health intervention. Synthesis of the available studies significantly strengthens the quality of evidences for public health practice. Thus, this systematic review and meta-analysis aimed to determine the overall magnitude of asymptomatic COVID-19 cases throughout the course of infection using available evidences. We followed the PRISMA checklist to present this study. Two experienced review authors (MA and DBK) were systematically searched international electronic databases for studies. We performed meta-analysis using R statistical software. The overall weighted proportion of asymptomatic COVID-19 cases throughout the course infection was computed. The pooled estimates with 95% confidence intervals were presented using forest plot. Egger's tests were used to assess publication bias, and primary estimates were pooled using a random effects model. Furthermore, a sensitivity analysis was conducted to assure the robustness of the result. A total of 28 studies that satisfied the eligibility criteria were included in this systematic review and meta-analysis. Consequently, in the meta-analysis, a total of 6,071 COVID-19 cases were included. The proportion of asymptomatic infections among the included studies ranged from 1.4% to 78.3%. The findings of this meta-analysis showed that the weighted pooled proportion of asymptomatic COVID-19 cases throughout the course of infection was 25% (95%CI: 16-38). The leave-one out result also revealed that the weighted pooled average of asymptomatic SARS-CoV-2 infection was between 28% and 31.4%. In conclusion, one-fourth of SARS-CoV-2 infections are remained asymptomatic throughout the course infection. Scale-up of testing, which targeting high risk populations is recommended to tackle the pandemic.

This book presents the computational methods for solving the solid mechanic problems in the oil well perforator design. Both Lagrangian and Eulerian methods are used to solve the pertinent stress-strain equations and the shock wave running through the materials. Seven good performance oil well perforators and two conical shaped charges for defeating the reactive armor are included in this book as references. The computer programs written in Fortran for the calculation of high explosive burn time and burn distance, shear modulus and yield strength for many materials, as well as MATLAB plotting programs for many perforators are available online as supplementary materials for the book-- Provided by publisher.

Due to their high optical transparency and electrical conductivity, indium tin oxide thin films are a promising material for photonic circuit design and applications. However, their weak optical nonlinearity has been a substantial barrier to nonlinear signal processing applications. In this study, we show that an atomically thin (~1.5 nm) indium tin oxide film in the form of an air/indium tin oxide/SiO 2 quantum well exhibits a second-order susceptibility χ 2 of ~1,800 pm V –1 . First-principles calculations and quantum electrostatic modelling point to an electronic interband transition resonance in the asymmetric potential energy of the quantum well as the reason for this large χ 2 value. As the χ 2 value is more than 20 times higher than that of the traditional nonlinear LiNbO 3 crystal, our indium tin oxide quantum well design can be an important step towards nonlinear photonic circuit applications. An atomically thin indium tin oxide film in the form of a quantum well exhibits a χ 2 of ~1,800 pm V –1 . Theoretical calculations point to an asymmetric electronic interband transition resonance as the reason for this large χ 2 value.

The current well planning process for operators is capital-intensive that takes time and has a lot of discrete, disconnected steps. Well planners and engineers dedicate a significant amount of time and effort to analyze sub-surface and offset well data for trajectory planning, casing policy selection, casing design, torque & drag, hydraulics, time & cost analysis etc. For development wells and unconventional wells, it is a common scenario for drilling engineers to have a very clear understanding of how the well design shall look like as the oil & gas field is extremely well familiar. As an initial step towards standardization, a review and study of several well design processes were performed by interviewing several engineers, all around the globe. The study revealed that even though every engineer had their own way of working, there was an inherent workflow that could be standardized. This standardized workflow was then outlined with user experience development techniques to cater to the generic steps that well planners, engineers and managers had described. With implementation of this standardized workflow and UI/UX supported process, the next step was to build a cloud native solution which supports micro-services-based engineering calculations in the backend. This allowed to implement speed and scalability in the solution which can cater to various personas in a team. The next step was to automate the process for a development field. This was achieved by applying checkpoints in the workflow to identify an exploratory well vs. a development well, before calling a microservice. For a development field, the microservice architecture identifies the design aspects of an existing well and incorporates similar well trajectory turn points, casing policy, casing design, BHA, fluids, operational parameters etc. while honoring the surface hole location, targets, and datum reference of the new wells to be planned. This technique helped to not only automate the engineering calculations but also speed up the entire process of designing each well in under a minute. Apart from engineering calculations, a planning workflow is never complete without team governance, approvals from peers and supervisors, testing various scenarios and creating reports. As these tasks are an inherent part of the planning cycle, they were also incorporated in the workflow. The UX design process techniques ensured that these supplementary tasks were a part of the main workflow and did not interfere with the calculations. The solution has shown a tremendous increase in the work efficiency of user by reducing the planning efforts from days to minutes. The users can now focus on wells using management by exception as the entire design process can be automated. This also eliminates any unnecessary data entry and avoids errors.

Today drilling wells is one of the biggest capital expenditures and is employed starting from exploration, delineation, initial wells for production, and fresh production incorporation when existing wells production have declined. The estimated cost for drilling new wells in Ayatsil field is around 25 MM$, which requires a high level of decision to achieve production goals without exceeding the budget assigned. Therefore, to make the right decision requires an integration of multidisciplinary group of specialists (geologists, geomechanics, reservoir, production and drilling engineers) from well design to execution phases.

Over the last 30 years, group-IV semiconductors have been intensely investigated in the quest for a fundamental direct bandgap semiconductor that could yield the last missing piece of the Si Photonics toolbox: a continuous-wave Si-based laser. Along this path, it has been demonstrated that the electronic band structure of the GeSn/SiGeSn heterostructures can be tuned into a direct bandgap quantum structure providing optical gain for lasing. In this paper, we present a versatile electrically pumped, continuous-wave laser emitting at a near-infrared wavelength of 2.32 µm with a low threshold current of 4 mA. It is based on a 6-periods SiGeSn/GeSn multiple quantum-well heterostructure. Operation of the micro-disk laser at liquid nitrogen temperature is possible by changing to pulsed operation and reducing the heat load. The demonstration of a continuous-wave, electrically pumped, all-group-IV laser is a major breakthrough towards a complete group-IV photonics technology platform. The authors demonstrate electrically pumped continuous-wave operation of a SiGeSn/GeSn lasers. The devices are based on a multi-quantum-well design in a small footprint micro-disk cavity resulting in driving parameters compatible with on-chip operation.

While research on wellbeing within Human-Computer Interaction (HCI) is an active space, a gap between research and practice persists. To tackle this, we sought to identify the practical needs of designers in taking wellbeing research into practice. We report on 15 semi-structured interviews with designers from four continents, yielding insights into design tool use generally and requirements for wellbeing design tools specifically. We then present five resulting design tool concepts, two of which were further developed into prototypes and tested in a workshop with 34 interaction design and HCI professionals. Findings include seven desirable features and three desirable characteristics for wellbeing-supportive design tools, including that these tools should satisfy the need for proof, buy-in, and tangibility. We also provide clarity around the notion of design for wellbeing and why it must be distinguished from design for positive emotions.

Well integrity is of high importance during the entire well life span especially when renewable energy resources such as geothermal are designed to cover the increasing world energy demand. Many studies have documented the importance of the casing–cement interfacial bonding to ensure critical well integrity achievements; however, laboratory experiments and field data are not always aligned. Furthermore, Finite Element Analysis shows relatively high discrepancies compared with the results of various scholarly published works. The limitations in the FEA are most probably generated by the casing–cement interaction modeling parameters. Typically, the contact between casing and cement is modeled using the so-called CZM method, which includes the shear debonding process into the FEA. Several setups have been used in the past to determine the interfacial casing–cement bonding shear strength. Some of these setups are briefly summarized herein. The novelty of this paper consists in the combination of a relatively simple experimental setup with the finite element modeling of the experiment itself to demonstrate that it is important to acquire accurate laboratory data for debonding simulations and, thus, to improve the well integrity prediction. The aim of this paper is to better understand the limitations of the finite element method when modeling shear bonding of the cement and, in the same, to verify that the proposed experimental setup can be modelled using numerical approaches. The successful numerical simulation can later be used for upscaled models. The results confirm the experimental push down setup and aid engineers to further understand and validate CZM models and optimize the well design to achieve maximum well integrity potential. Our results are within 1% error from the average field data.

The key well design issues considered in this paper are the length of the intake section; the hydraulic efficiency of the well; the length of grouted upper casing for wells in fractured rock aquifers and the potential trade-off between well yield and security against pollution; and the economics of well design. For wells in thick, relatively uniform unconsolidated aquifers, the well depth and screen length can be estimated using a simple discharge-drawdown relationship. This approach can help avoid constructing unnecessarily deep wells if alternative guidance to screen the bottom third of the aquifer was followed in such situations. Hydraulic efficiency is an important consideration in well design: the paper highlights that whereas screen entrance velocity has been a topic of much discussion in the literature, well upflow velocity has received less attention, but can be an important contributor to well losses in small diameter screens. In fractured hard rock aquifers, there may be a compromise required in well design between maximising well yield by exploiting shallow fracture zones whilst also providing adequate sanitary protection to the well by installing an upper grouted casing. Recent data from Ireland on the distribution of hydraulic conductivity with depth in poorly productive fractured rock aquifers are used to calculate the reduction in well yield that would result from increasing the length of the grouted upper well casing. Economic aspects of well design are especially important where there are a large number of wells to be drilled and/or where wells are required in poor rural communities in developing countries. The principles of cost-effective boreholes for developing countries are summarised, noting the opportunities for small-diameter shallow wells constructed with inexpensive manual or lightweight mechanical drilling rigs.