bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efficient Replacement of Centrifugal With Absorption Chillers Upgrading the Heat Transfer of the Cooling Tower
Authors: Rogdakis E. D. , Papaefthimiou V. D. 
Published: November 2021

Abstract
It is a general trend today, the old centrifugal machines to be replaced by new absorption machines. The mass flow rate of the cooling water in the centrifugal machines is normally 30% less than that in the two-stage absorption chiller for the same refrigerating capacity. Some absorption chillers manufacturers have updated and improved the double-effect technology increasing the cooling water temperature difference from the typical value of 5.5°C to 7.4°C and reducing the cooling water flow rate by about 30%.
Using such a modern double effect absorption unit to replace a centrifugal chiller the same cooling water circuit can be used and the total cost of the retrofit is minimized. In this case a new flow pattern of the cooling tower is developed, and in this paper the design of a new tower fill is predicted taking into account the new factors characterizing the operating conditions and the required performance of the tower. As an example, the operational curves of a modified cooling tower (1500 KW cooling power) used by a 240 RT double-effect absorption chiller are presented.
Design of a Micro Direct Methanol Fuel Cell (μDMFC)
Authors: Mench M. M. , Wang Z. H. , Bhatia K. , Wang C. Y. 
Published: November 2021

Abstract
Recently, there has been increased interest in the development of a small-sized direct methanol fuel cell (DMFC) for low-power applications. In this paper, the design of a self-activated DMFC stack is presented. Gravitational and capillary forces feed the anode side liquid methanol solution. On the cathode side, air is supplied by thermal and solutal buoyancy forces. Based upon experimental results for a larger test cell, and calculated flow velocities for the small-cell design, the fuel and oxidizer supply rates should be adequate for acceptable performance. The entire DMFC is therefore a pump-less operation and self-activated by electrochemical reactions. At 1 cm3 total volume, the DMFC is expected to provide a power density around 1 W/cm3, with a range of output of 10V, 0.1A to 1 V, 1A depending on the arrangement of individual cell connections.
A 3-D Model for Magntic Damping of G-Jitter Induced Convection and Solutal Transport in a Simplified Bridgman Configuration
Authors: Handa J. , Zhang X. , Li B. Q. , de Groh H. C. 
Published: November 2021

Abstract
A 3-D transient finite element model is developed to represent the oscillating thermal convection induced in a simplified Bridgman configuration filled with a Ga-doped germanium melt in microgravity under the influence of an external magnetic field. The model development is based on the penalty-finite element solution of the equations describing the transport of momentum, heat and solution and also the electromagnetic field distribution in the melt pool. Automatic time step control is applied to help speed up the calculations. Numerical performance of finite element simulations for this class of problems is discussed. In particular, various types of finite element formulations were studied to minimize the global matrix size and to investigate the computational efficiency. Numerical simulations are conducted to study the convection and magnetic damping effects as a function of frequency, directions and amplitudes of g-jitter and also the direction and magnitudes of the applied magnetic fields. The results show that the g-jitter driven flow is time dependent and complex convection pattern can develop in a 3-D configuration even when the thermal conditions are symmetric and that the convection can be suppressed with an applied magnetic field.
Perspectives in Modelling Film-Cooling of Turbine Blades by Transcending Conventional Two-Equation Turbulence Models
Authors: Azzi A. , Lakehal D. 
Published: November 2021

Abstract
The paper exposes some recent new trends in modelling jets-in-crossflow with relevance to film-cooling of turbine blades. The aim is to compare two classes of turbulence models with respect to their predictive performance in reproducing flow physics. The study focuses on anisotropic eddyviscosity/diffusivity models and explicit algebraic stress models, up to cubic fragments of strain and vorticity tensors. The first class of models are DNS-based two-layer approaches transcending the conventional k–ε model by means of a non-isotropic representation of the turbulent transport coefficients; this is employed in connection with a near-wall one-equation model resolving the semi-viscous sublayer. The aspects of this new strategy are based on known DNS statistics of channel flows and boundary layers. The other class of models are quadratic and cubic explicit algebraic stress formulations rigorously derived from second-moment closures. The stress-strain relations are solved in the context of a two-layer strategy resolving the near-wall region by means of a non-linear one-equation model; the outer core flow is treated by use of the two-equation model. The models are tested for the film cooling of a flat plate, and are then extended to film cooling of a symmetrical turbine blade by a row of laterally injected jets. Comparison of the calculated and measured wall-temperature distributions shows that only the anisotropic eddy viscosity/diffusivity model can correctly predict the spanwise spreading of the temperature field and reduces the strength of the secondary vortices. The non-linear algebraic stress models were of a mixed quality in film cooling calculations.
Removal of Contaminants by Induced Air Flow Inside Structures
Authors: Ziskind G. , Dubovsky V. , Letan R. 
Published: November 2021

Abstract
The present paper discusses the continuous removal of contaminants from enclosed spaces by means of induced air flow. The air flow is caused by natural convection in a heated horizontal or vertical duct. The heating of the duct can be achieved by absorption of solar irradiation or any other means. As a result, a steady air flow can be induced inside the duct and the enclosed space, as has been shown by the authors for a small scale laboratory model.
Three dimensional numerical simulations are performed for various kinds of real-size structures, including one-story detached buildings and underground enclosed spaces. The k-epsilon turbulence model is used in the simulations.
The results yield detailed flow field inside the enclosures at various configurations of the openings. Rate of air change is calculated both for the whole enclosure and for the layers above the floor where the contaminants tend to accumulate. Optimal design of the systems is discussed.
Prediction of Thermal Performance of Flip-Chip-Plastic Ball Grid Array (FC-PBGA) Packages: Effect of Die Size
Authors: Ramakrishna K. , Lee T.-Y. 
Published: November 2021

Abstract
Package level thermal performance of flip-chip plastic ball grid array (FC-PBGA) packages has been predicted using experimentally validated mechanistic methodologies. The resulting conjugate heat transfer models have been solved using methods of computational fluid dynamics under natural and forced convection for freestream velocities up to 2 m/s. Overall junction to ambient, Θja, junction-to-board, Ψjb, and junction to case Ψjτ thermal resistances (here after referred to as thermal parameters) have been derived from the results of these computations. Using these models and methodologies, which are previously validated against experimental data, a parametric study of effect of die size on the package thermal parameters has been carried out for die sizes in the range 2 to 20 mm (area of 4–400 mm2) under natural and forced convection with freestream velocities in the range of 0.5 to 2 m/s. The predictions in this study are expected to be ±10% of the measured data. Based on this work the following conclusions have been drawn:
1. The junction to ambient, Θja, and junction to board, Ψjb, thermal resistances decrease with increase in freestream velocity, U, and junction to case thermal resistance, Ψjτ, increases with U. Ψjb shows a weaker dependence on U than Θja does.
2. For a fixed substrate size, package thermal resistances, Θja and Ψjb, decrease as the die size increases from 2 mm (4 mm2) to 20 mm (400 mm2). However, these resistances reach asymptotic values for die sizes above 50 mm2. The change in these resistances is in the range 20% to 35% and the effect of freestream velocity on the percentage changes is small.
3. An extensive database of experimentally validated FC-PBGA package thermal parameters have been generated for a wide range of die sizes.
Three-Dimensional Flow and Heat Transfer Calculations in Micro-Channel Heat Exchangers
Authors: Saha A. K. , Acharya Sumanta 
Published: November 2021

Abstract
A three-dimensional numerical study has been carried out to analyze the unsteady flow and heat transfer in a micro-channel with an array of periodically mounted square cylinders. The current geometry represents a micro-heat exchanger and has potential applications in the cooling of turbine blades and electronic cooling. The cylinder dimensions are of the order of few microns. The three-dimensional unsteady Navier-Stokes and energy equations are solved using higher order temporal and spatial discretizations. The simulations have been carried out for a range of Reynolds number based on cylinder width (180–600) and a Prandtl number of 6.99. Conjugate heat transfer calculations have been employed to account for the conduction in the solid cylinder and convection in the fluid. The flow is found to become unsteady at a critical Reynolds number that falls between 250 and 400. The flow shows quasi-periodic behavior with multiple frequencies at a Reynolds number of 400. The heat transfer enhancement compared to a plane channel is marginal (1.1–1.4 times) for the steady flow cases whereas it is significant (12–15 times) when the flow is unsteady. The friction factor was found to decrease with Reynolds number in both the steady and unsteady regimes. However, the friction factor increases at the critical Reynolds number where it becomes unsteady in nature.
Effect of Condenser Location and Tubing Length on the Performance of a Compact Two-Phase Thermosyphon
Authors: Yuan Lang , Joshi Yogendra K. , Nakayama Wataru 
Published: November 2021

Abstract
This study investigates the issues involved in the design of compact two-phase thermosyphon systems for high power chip cooling. In such systems, the locations of the evaporator and condenser need to be given a high degree of freedom. The key components used in the experiment are: an evaporator enclosure (20 mm × 20 mm × 20 mm internal volume), a simulated chip (20 mm × 20 mm) with an enhancement structure (10 mm × 10 mm × 6.8 mm) and a cartridge heater embedded in a copper rod (11.9 mm × 11.9 mm cross-section). A dielectric coolant (PF-5060, boiling point 56 °C @ 1 atm) is used as the working fluid. Also included in the loop are a natural convection cooled condenser of dimensions 58 mm × 60 mm × 432 mm and connecting tubing. The relative height between the evaporator and the condenser, the tubing length, and the heat input were systematically varied. In this study, the heat flux ranged from 0 to 40 W/cm2; the pressure within the system ranged from −68.9 kPa to +34.5 kPa; and the relative height of the condenser over the evaporator ranged from 15 cm to 45 cm. These ranges represent actual conditions for electronics applications. Experimental studies show that these parameters affect the evaporator thermal resistance from the chip to the boiling pool, and the overall thermal resistance from the chip to the ambient air in a complex way. However, close examination of the data suggests that there could be an optimum point in the parametric domain.
Can the ‘Learn in peace, educate without violence’ intervention in Cote d’Ivoire reduce teacher violence? Development of a theory of change and formative evaluation results
Authors: Devries Karen , Balliet Manuela , Thornhill Kerrie , Knight Louise , Procureur Fanny , N’Djoré Yah Ariane Bernadette , N’Guessan Dedou Gruzshca Ferrand , Merrill Katherine G , Dally Mustapha , Allen Elizabeth , Hossain Mazeda , Cislaghi Beniamino , Tanton Clare , Quintero Lucia 
Published: November 2021

ObjectivesTo gather evidence on whether a brief intervention (Apprendre en paix et éduquer sans violence, developed by the Ivorian Ministry of Education and Graines de Paix) to promote peace in primary schools by reducing teacher violence perpetration and improving pedagogical techniques was acceptable to teachers and affected change in intermediate outcomes.DesignMixed-methods formative research.SettingPrimary schools in Tonkpi region, Cote d’Ivoire.Participants160 teachers participating in the peace training, surveyed three times during implementation; qualitative in-depth interviews with 19 teachers and teacher-counsellors.InterventionsLearn in peace, educate without violence–a brief intervention with primary school teachers designed to promote peace in primary schools.OutcomesFor survey data, we generated composite measures of intermediate outcomes (teachers’ awareness of consequences of violence, self-efficacy in applying positive classroom management methods, acceptance of physical discipline practices in school) and used random intercept linear mixed-effects models to compare responses over time. Qualitative research included open-ended questions about acceptability and perceived need for such an intervention. A framework analysis was undertaken.ResultsFour-months post-training (vs pretraining), teachers had higher self-efficacy in applying positive classroom management methods (pre-mean=26.1; post-mean=27.5; p<0.001) and borderline lower acceptance of physical discipline practices (premean=4.2; postmean=3.6; p=0.10). We found no change in teacher awareness of the consequences of violence. Qualitatively, teachers found the intervention acceptable and understandable, perceiving it as useful because it provided methods for non-violent discipline. Teachers had mixed views about whether the techniques improved classroom dynamics.ConclusionsData suggest that the intervention is acceptable and leads to change in intermediate outcomes for teachers. Further evaluation in a randomised controlled trial is warranted.
Association between surgeon grade and implant survival following hip and knee replacement: a systematic review and meta-analysis
Authors: Fowler Timothy J , Aquilina Alex L , Blom Ashley W , Sayers Adrian , Whitehouse Michael R 
Published: November 2021

ObjectiveTo investigate the association between surgeon grade (trainee vs consultant) and implant survival following primary hip and knee replacement.DesignA systematic review and meta-analysis of observational studies.Data sourcesMEDLINE and Embase from inception to 6 October 2021.SettingUnits performing primary hip and/or knee replacements since 1990.ParticipantsAdult patients undergoing either a primary hip or knee replacement, predominantly for osteoarthritis.InterventionWhether the surgeon recorded as performing the procedure was a trainee or not.Primary and secondary outcome measuresThe primary outcome was net implant survival reported as a Kaplan-Meier survival estimate. The secondary outcome was crude revision rate. Both outcomes were reported according to surgeon grade.ResultsNine cohort studies capturing 4066 total hip replacements (THRs), 936 total knee replacements (TKRs) and 1357 unicompartmental knee replacements (UKRs) were included (5 THR studies, 2 TKR studies and 2 UKR studies). The pooled net implant survival estimates for THRs at 5 years were 97.9% (95% CI 96.6% to 99.2%) for trainees and 98.1% (95% CI 97.1% to 99.2%) for consultants. The relative risk of revision of THRs at 5 and 10 years was 0.88 (95% CI 0.46 to 1.70) and 0.68 (95% CI 0.37 to 1.26), respectively. For TKRs, the net implant survival estimates at 10 years were 96.2% (95% CI 94.0% to 98.4%) for trainees and 95.1% (95% CI 93.0% to 97.2%) for consultants. We report a narrative summary of UKR outcomes.ConclusionsThere is no strong evidence in the existing literature that trainee surgeons have worse outcomes compared with consultants, in terms of the net survival or crude revision rate of hip and knee replacements at 5–10 years follow-up. These findings are limited by the quality of the existing published data and are applicable to countries with established orthopaedic training programmes.PROSPERO registration numberCRD42019150494.
Use of inhalational anaesthetic agents in paediatric and adult patients for status asthmaticus, status epilepticus and difficult sedation scenarios: a protocol for a systematic review
Authors: Gorsky Kevin , Cuninghame Sean , Chen Jennifer , Jayaraj Kesikan , Withington Davinia , Francoeur Conall , Slessarev Marat , Jerath Angela 
Published: November 2021

IntroductionInhaled volatile anaesthetics have a long tradition of use as hypnotic agents in operating rooms and are gaining traction as sedatives in intensive care units (ICUs). However, uptake is impeded by low familiarity with volatiles, unique equipment and education needs. Inhaled anaesthetics are often reserved in ICUs as therapies for refractory and life threatening status asthmaticus, status epilepticus, high and difficult sedation need scenarios given they possess unique pharmacological properties to manage these medical conditions while providing sedation to acutely ill patients. The objective of this systematic review is to collate evidence regarding the efficacy, safety and feasibility of volatile anaesthetics in adult and paediatric ICU patients for these three emergency conditions.Methods and analysisWe will conduct a systematic review of the primary studies in adult and paediatric ICU patients with status asthmaticus, status epilepticus and high/difficult sedation needs. We will include observational and interventional studies published from 1970 to 2021 in English or French investigating patients who have received a volatile inhalational agent for the above indications. We will evaluate the efficacy, safety, feasibility and implementation barriers for the volatile anaesthetics for each of three specified indications. Included studies will not be limited by necessity of a comparator arm. We will also evaluate clinical characteristics, patient demographics and provider attitudes towards volatile anaesthetic administration in defined critical care scenarios. Data will be extracted and analysed across these domains. The databases MEDLINE, EMBASE, the Science Citation Index as well as the Cochrane Central Controlled Trials Register will be queried with our search strategy.Descriptive and statistical analysis will be employed where appropriate. Data extraction and quality assessment will be performed in duplicate using a standardised tool. A narrative approach and statistical analyses will be used to describe patient characteristics, volatile efficacy, safety concerns, technical administration, attitudes towards administration and other implementation barriers.Ethics and disseminationNo ethics board approval will be necessary for this systematic review. This research is independently funded. Results will be disseminated in a peer-reviewed journal and conference presentation.PROSPERO numberCRD42021233083.
Associations between regular GP contact, diabetes monitoring and glucose control: an observational study using general practice data
Authors: Youens David , Robinson Suzanne , Doust Jenny , Harris Mark N , Moorin Rachael 
Published: November 2021

ObjectiveContinuity and regularity of general practitioner (GP) contacts are associated with reduced hospitalisation in type 2 diabetes (T2DM). We assessed associations of these GP contact patterns with intermediate outcomes reflecting patient monitoring and health.DesignObservational longitudinal cohort study using general practice data 2011–2017.Setting193 Australian general practices in Western Australia and New South Wales participating in the MedicineInsight programme run by NPS MedicineWise.Participants22 791 patients aged 18 and above with T2DM.InterventionsRegularity was assessed based on variation in the number of days between GP visits, with more regular contacts assumed to indicate planned, proactive care. Informational continuity (claims for care planning incentives) and relational continuity (usual provider of care index) were assessed separately.Outcome measuresProcess of care indicators were glycosylated haemoglobin (HbA1c) test underuse (8 months without test), estimated glomerular filtration rate (eGFR) underuse (14 months) and HbA1c overuse (two tests within 80 days). The clinical indicator was T2DM control (HbA1c 6.5% (47.5 mmol/mol)–7.5% (58.5 mmol/mol)).ResultsThe quintile with most regular contact had reduced odds of HbA1c and eGFR underuse (OR 0.74, 95% CI 0.67 to 0.81 and OR 0.78, 95% CI 0.70 to 0.86, respectively), but increased odds of HbA1c overuse (OR 1.20, 95% CI 1.05 to 1.38). Informational continuity was associated with reduced odds of HbA1c underuse (OR 0.53, 95% CI 0.49 to 0.56), reduced eGFR underuse (OR 0.62, 95% CI 0.58 to 0.67) and higher odds of HbA1c overuse (OR 1.48, 95% CI 1.34 to 1.64). Neither had significant associations with HbA1c level. Results for relational continuity differed.ConclusionsThis study provides evidence that regularity and continuity influence processes of care in the management of patients with diabetes, though this did not result in the recording of HbA1c within target range. Research should capture these intermediate outcomes to better understand how GP contact patterns may influence health rather than solely assessing associations with hospitalisation outcomes.
Potential impact of a novel pathway for suspected myocardial infarction utilising a new high-sensitivity cardiac troponin I assay
Authors: Meek Rob , Cullen Louise , Lu Zhong Xian , Nasis Arthur , Kuhn Lisa , Sorace Laurence 
Published: November 2021

BackgroundHigh-sensitivity cardiac troponin I (hs-cTnI) assays promise high diagnostic accuracy for myocardial infarction (MI). In an ED where conventional cTnI was in use, we evaluated an assessment pathway using the new Access hsTnI assay.MethodsThis retrospective analysis recruited ED patients with suspected MI between June and September 2019. All patients received routine care with a conventional cTnI assay (AccuTnI +3: limit of detection (LoD) 10 ng/L, 99th centile upper reference limit (URL) 40 ng/L, abnormal elevation cut-point 80 ng/L). Arrival, then 90-minute or 360-minute cTnI levels for low and non-low risk patients, respectively (ED Assessment of Chest pain score) guided diagnosis and disposition which was at treating physician discretion. The same patients had arrival and 90-minute or 180-minute samples drawn for hs-cTnI levels (Access hsTnI: LoD 2 ng/L, 99th centile URL 10 ng/L (females) and 20 ng/L (males); abnormal elevation above the URL and delta >30%). Treating physicians were blinded to the hs-cTnI results. Using the hs-cTnI values, investigators retrospectively assigned likely diagnosis, disposition and likelihood of a 30-day major adverse cardiac event (MACE). Admission was recommended for significantly rising hs-cTnI elevations. The primary objective was to demonstrate an acceptable unexpected 30-day post-discharge MACE rate of <1%. cTnI elevation rates, diagnostic outcomes and ED disposition were also compared between pathways.ResultsFor the 935 patients, unexpected 30-day post-discharge MACE rates were 0/935 (0%, 95% CI 0% to 0.4%) with the conventional or novel pathway. For the high-sensitivity and conventional assays, respectively, abnormal elevation rates were 29% (95% CI 26% to 32%) and 19% (95% CI 17% to 22%), for MI were 9% (95% CI 8% to 11%) and 8% (95% CI 6% to 10%), and for hospital admission were 42% (95% CI 39% to 45%) and 43% (95% CI 40% to 47%).ConclusionThe novel pathway using the Access hsTnI assay has an acceptably low 30-day MACE rate.