MRC Laboratory of Molecular Biology
CUED - Cambridge University Engineering DepartmentNot a member yet
45551 research outputs found
Sort by
Curved-crease origami face shields for infection control
No full textThe COVID-19 pandemic has created enormous global demand for personal protective equipment (PPE). Face shields are an important component of PPE for front-line workers in the context of the COVID-19 pandemic, providing protection of the face from splashes and sprays of virus-containing fluids. Existing face shield designs and manufacturing procedures may not allow for production and distribution of face shields in sufficient volume to meet global demand, particularly in Low and Middle-Income countries. This paper presents a simple, fast, and cost-effective curved-crease origami technique for transforming flat sheets of flexible plastic material into face shields for infection control. It is further shown that the design could be produced using a variety of manufacturing methods, ranging from manual techniques to high-volume die-cutting and creasing. This demonstrates the potential for the design to be applied in a variety of contexts depending on available materials, manufacturing capabilities and labour. An easily implemented and flexible physical-digital parametric design methodology for rapidly exploring and refining variations on the design is presented, potentially allowing others to adapt the design to accommodate a wide range of ergonomic and protection requirements
Open-source modelling of aerosol dynamics and computational fluid dynamics: Nodal method for nucleation, coagulation, and surface growth
No full textUnderstanding formation, growth and transport of aerosols is critical to processes ranging from cloud formation to disease transmission. In this work, a numerical algorithm of aerosol dynamics including nucleation, coagulation, and surface growth was coupled with flow and heat transfer equations enabling the solution of three-dimensional multi-physics aerosol processes in an open-source platform. The general dynamic equation was solved by a nodal method where the particle size distribution was represented by a finite number of nodes. The models were verified by comparing four test cases, (1) pure coagulation, (2) nucleation and coagulation, (3) pure surface growth, and (4) a general dynamic equation that includes the three mechanisms provided in literature. A high temperature aerosol flow in a cooled pipe is chosen as a tutorial case of coupled computational aerosol and fluid dynamics. The aerosolGDEFoam code is available at https://openaerosol.sourceforge.io and can be further modified under GNU general public licence. Programme summary: Programme title: aerosolGDEFoam CPC Library link to programme files: http://dx.doi.org/10.17632/3s368jpdx2.1 Developer's repository link: https://openaerosol.sourceforge.io/ Licencing provisions: GNU General Public Licence 3 Programming language: C++ Nature of problem: aerosolGDEFoam solves the general dynamic equation coupled with flow and heat transfer equations enabling the solution of three-dimensional multi-physics aerosol processes using the open-source computational platform, OpenFOAM [1]. The general dynamic equation describes changes in aerosols due to e.g. nucleation, coagulation and evaporation/condensation, processes which depend on local conditions such as temperature and humidity. A zero-dimensional form of the general dynamic equation from Prakash et al. [2] has been implemented and verified with previously published examples. Solution method: aerosolGDEFoam employs an explicit time-stepping for the time-dependent source terms for aerosol dynamics. The solution methods and schemes provided by OpenFOAM 6 are used for spatial derivatives. References: [1] OpenFOAM6, OpenFOAM v6, in The OpenFOAM Foundation, https://openfoam.org/, [2] Prakash, A., A.P. Bapat, and M.R. Zachariah, A Simple Numerical Algorithm and Software for Solution of Nucleation, Surface Growth, and Coagulation Problems. Aerosol Science and Technology, 2003. 37(11): p. 892–898
Calculating the chemical exergy of materials
No full textModern society requires large amounts of materials which lead to emissions of greenhouse gases. Effective climate policy should focus on not just energy efficiency but material efficiency as well. Exergy analysis is a powerful metric used to identify opportunities for efficiency improvement in industrial resource flow systems. Exergy offers a single unified measure of energy and material resources and indicates the real thermodynamic value of these resources, but the method suffers from a lack of comprehensive specific material chemical exergy datasets. The variety of different materials used in the global resource supply chain necessitates a combination of exergy calculation approaches. These approaches are combined into a single exergy calculator tool with over 1400 substances in the dataset. The chemical exergy values computed for key materials typically differ by less than 10% from values estimated in literature. The calculator is used in a case study of the upstream global material supply chain in 2013. The exergy resource map is visualized in a Sankey diagram and is found to be 72% resource efficient with 170 EJ of combined exergy losses and destruction. Further analysis is conducted on the refining, utilities, and industry sectors which are found to be 72%, 44%, and 50% resource efficient, respectively. Their combined losses and destruction are 15, 101, and 54 EJ, respectively. This study and the calculator developed provide a comprehensive dataset of chemical exergy values for a wide range of materials and can be applied in a variety of studies using exergy analysis
Empirical investigation of the applicability of constructability methods to prevent design errors
No full textPurpose: The paper aims to identify the effective constructability methods and tools that should be applied during the early project design stages to prevent specific constructability failures regarding project context. Design/methodology/approach: Seventeen basic constructability problems were defined, 12 constructability implementation methods for investigation were selected, and a general tool representing potential causal connections between the problems and the methods that could prevent them was developed. A comparative case study was conducted through a rigorous investigation of the construction documentation of four major building construction projects. Nearly four hundred constructability problems were identified. The tool developed was used to draw conclusions about the preferred constructability methods, in general, and with respect to specific project contexts. Findings: The managerial approach offers the best methods for preventing constructability problems. The major methods that emerged were (1) assigning a constructability champion, (2) facilitating the involvement of the general contractor early in the design process, and (3) augmenting design quality control. At the other end of the scale, methods such as company procedures and owner involvement were found to be the least effective. Originality/value: The paper offers the ability to relate constructability problems to preventive mechanisms and to identify the appropriate steps to be taken to resolve these problems. The mechanism described here can be used by construction companies that keep failure data within accounting files to check projects in retrospect and draw lessons from them to be implemented in future projects
R&D Management at a time of crisis: what are we learning from the response to the COVID-19 pandemic?
No full textModelling Parallel-Connected, No-Insulation High-T<inf>c</inf>Superconducting Magnets
No full textThe charging/discharging delays in superconducting coils wound without insulation (NI coils) are a major drawback of the technique. While removing the insulation improves safety margins, the increase in the characteristic time constant τc can make a coil unfit for a particular purpose. It is widely accepted for instance that NI coils will not be used in ac applications where τc ∼ 1/f. To decrease τc of the NI coils, the same length of superconductor can be wound/connected in parallel rather than in series - decreasing the inductance L, and hence the time constant τ c, while maintaining the number of amp-turns IopN. Here we investigate the effect of parallel connecting coils in a magnet using a 2D axially symmetric model which captures all the necessary electromagnetic properties of the HTS NI coils. These properties include: critical current anisotropy Jc(B,θ), turn-to-turn conductivity, as well as winding parallelism. Our modeling results show that the parallel connected magnet experiences magnet-wide shielding current effects. Whilst these shielding currents affect field homogeneity - the model enables this effect to be quantified. Furthermore, shielding currents are not an issue when running NI coils in saturated mode. The modeling work presented here provides a simple initial example of how magnet designers may approach designing, optimizing, and operating high current, HTS NI coils
Grounded Theory: A Guide for Exploratory Studies in Management Research
No full textGrounded theory was first introduced more than fifty years ago, but researchers are often still uncertain about how to implement it. This is not surprising, considering that even the two pioneers of this qualitative design, Glaser and Strauss, have different views about its approach, and these are just two of multiple variations found in the literature. While studies using grounded theory in management research are becoming more popular, these are often mixed with the case study approach, or they provide contradictory guidelines on how to use it. The aim of this paper is to provide a clear guide for researchers who wish to use grounded theory in exploratory studies in management research. To support this goal, the methodology’s different terms and variations, as found in the literature, are also discussed. This study can support researchers using this methodology, but it is also useful for reviewers and examiners who wish to understand more about it and the different ways in which researchers have implemented it
Deep learning for hologram generation
No full textThis work exploits deep learning to develop real-time hologram generation. We propose an original concept of introducing hologram modulators to allow the use of generative models to interpret complex-valued frequency data directly. This new mechanism enables the pre-trained learning model to generate frequency samples with variations in the underlying generative features. To achieve an object-based hologram generation, we also develop a new generative model, named the channeled variational autoencoder (CVAE). The pre-trained CVAE can then interpret and learn the hidden structure of input holograms. It is thus able to generate holograms through the learning of the disentangled latent representations, which can allow us to specify each disentangled feature for a specific object. Additionally, we propose a new technique called hologram super-resolution (HSR) to super-resolve a low-resolution hologram input to a super-resolution hologram output. Combining the proposed CVAE and HSR, we successfully develop a new approach to generate super-resolved, complex-amplitude holograms for 3D scenes
Schottky barrier heights of defect-free metal/ZnO, CdO, MgO, and SrO interfaces
No full textThe Schottky barrier heights (SBHs) of defect-free interfaces of ZnO, CdO, MgO, and SrO with various metals and different terminations are investigated by density functional supercell calculations. The oxide bands are corrected for their density functional bandgap error by applying a U-type term to their metal-d and O-p states where necessary. The p-type SBHs are found to decrease linearly with increasing metal work function. The pinning factor S of the non-polar and polar interfaces is similar for each oxide. S is found to be 0.26, 0.56, 0.74, and 0.96 for CdO, ZnO, MgO, and SrO, respectively, with S increasing with increasing oxide ionicity. The calculated pinning factors are generally consistent with the metal-induced gap state model in terms of variation in ionicity and dielectric constant. A significant shift of SBHs from the non-polar to the polar interfaces of 0.4, 1, and 0.5 eV for ZnO, MgO, and SrO, respectively, is found, which can be explained by an interfacial dipole. Our results are also useful to describe Co,Fe|MgO interfaces in magnetic tunnel junctions
Integration of Organic Electrochemical Transistors with Implantable Probes
No full textOrganic electrochemical transistors (OECTs) are widely used as amplifying transducers of biological signals due to their high transconductance and biocompatibility. For implantable applications that penetrate into tissue, OECTs need to be integrated onto narrow probes. The scarcity of real estate necessitates the use of small local gate electrodes and narrow interconnects. This work shows that both of these factors lead to a decrease in the maximum transconductance and an increase in gate voltage required to attain this maximum. This work further shows that coating the gate electrode with a thick conducting polymer improves performance. These findings help guide the development of efficient OECTs on implantable probes