Heat transfer and performance characteristics of axial cooling fans with downstream guide vanes

This study examines experimentally the effect of stators on the performance and heat transfer characteristics of small axial cooling fans. A single fan impeller, followed by nine stator blades in the case of a complete stage, was used for all the experimental configurations. Performance measurements were carried out in a constant speed stage performance test rig while the transient liquid crystal technique was used for the heat transfer measurements. Full surface heat transfer coefficient distributions were obtained by recording the temperature history of liquid crystals on a target plate. The experimental data indicated that the results are highly affected by the flow conditions at the fan outlet. Stators can be beneficial in terms of pressure drop and efficiency, and thus more economical operation, as well as, in the local heat transfer distribution at the wake of the stator blades if the fan is installed very close to the cooling object. However, as the separation distance increases, enhanced heat transfer rate in the order of 25% is observed in the case of the fan impelle

Representation of Semantic Similarity in the Left Intraparietal Sulcus: Functional Magnetic Resonance Imaging Evidence

According to a recent study, semantic similarity between concrete entities correlates with the similarity of activity patterns in left middle IPS during category naming. We examined the replicability of this effect under passive viewing conditions, the potential role of visuoperceptual similarity, where the effect is situated compared to regions that have been previously implicated in visuospatial attention, and how it compares to effects of object identity and location. Forty-six subjects participated. Subjects passively viewed pictures from two categories, musical instruments and vehicles. Semantic similarity between entities was estimated based on a concept-feature matrix obtained in more than 1,000 subjects. Visuoperceptual similarity was modeled based on the HMAX model, the AlexNet deep convolutional learning model, and thirdly, based on subjective visuoperceptual similarity ratings. Among the IPS regions examined, only left middle IPS showed a semantic similarity effect. The effect was significant in hIP1, hIP2, and hIP3. Visuoperceptual similarity did not correlate with similarity of activity patterns in left middle IPS. The semantic similarity effect in left middle IPS was significantly stronger than in the right middle IPS and also stronger than in the left or right posterior IPS. The semantic similarity effect was similar to that seen in the angular gyrus. Object identity effects were much more widespread across nearly all parietal areas examined. Location effects were relatively specific for posterior IPS and area 7 bilaterally. To conclude, the current findings replicate the semantic similarity effect in left middle IPS under passive viewing conditions, and demonstrate its anatomical specificity within a cytoarchitectonic reference frame. We propose that the semantic similarity effect in left middle IPS reflects the transient uploading of semantic representations in working memory

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Dynamics of Cortical Networks Segregated into Layers and Columns

The neocortex covers 90% of the human cerebral cortex [41] and is responsible for higher cognitive function and socio-cognitive skills in all mammals. It is known to be structured in layers and in some species or cortical areas, in columns. A balanced network model was built, which incorporated these structural organizations and in particular, the layers, minicolumns and hypercolumns. The dynamics of eight different network models were studied, based on combinations of structural organizations that they have. The eigenvalue spectra of their matrices was calculated showing that layered networks have eigenvalues outside their bulk distribution in contrast to networks with columns and no layers. It was demonstrated, through simulations, that networks with layers are unstable and have a lower threshold to synchronization, thus, making them more susceptible to switch to synchronous and regular activity regimes [10]. Moreover, introduction of minicolumns to these networks was observed to partially counterbalance synchrony and regularity, in the network and neuron activity, respectively. Layered networks, principally the ones without minicolumns, also have higher degree correlations and a reduced size of potential pre- and post- connections, which induces correlations in the neuronal activity and oscillations

Representations of regular and irregular shapes by deep Convolutional Neural Networks, monkey inferotemporal neurons and human judgments.

Recent studies suggest that deep Convolutional Neural Network (CNN) models show higher representational similarity, compared to any other existing object recognition models, with macaque inferior temporal (IT) cortical responses, human ventral stream fMRI activations and human object recognition. These studies employed natural images of objects. A long research tradition employed abstract shapes to probe the selectivity of IT neurons. If CNN models provide a realistic model of IT responses, then they should capture the IT selectivity for such shapes. Here, we compare the activations of CNN units to a stimulus set of 2D regular and irregular shapes with the response selectivity of macaque IT neurons and with human similarity judgements. The shape set consisted of regular shapes that differed in nonaccidental properties, and irregular, asymmetrical shapes with curved or straight boundaries. We found that deep CNNs (Alexnet, VGG-16 and VGG-19) that were trained to classify natural images show response modulations to these shapes that were similar to those of IT neurons. Untrained CNNs with the same architecture than trained CNNs, but with random weights, demonstrated a poorer similarity than CNNs trained in classification. The difference between the trained and untrained CNNs emerged at the deep convolutional layers, where the similarity between the shape-related response modulations of IT neurons and the trained CNNs was high. Unlike IT neurons, human similarity judgements of the same shapes correlated best with the last layers of the trained CNNs. In particular, these deepest layers showed an enhanced sensitivity for straight versus curved irregular shapes, similar to that shown in human shape judgments. In conclusion, the representations of abstract shape similarity are highly comparable between macaque IT neurons and deep convolutional layers of CNNs that were trained to classify natural images, while human shape similarity judgments correlate better with the deepest layers

Πολυκριτηριακή Μεθοδολογία Χωροθέτησης και Περιβαλλοντικής Αξιολόγησης Οικολογικών Εμπορικών Λιμένων

Μέσω της παρούσας διπλωματικής εργασίας γίνεται μια προσπάθεια να παρουσιαστεί και να προσεγγιστεί, με ένα ολοκληρωμένο τρόπο, το πλαίσιο των περιβαλλοντικών – πράσινων εμπορικών λιμένων και να αξιολογηθεί η συμβολή της πολυκριτηριακής μεθόδου ανάλυσης (Multi Criteria Decision Analysis, MCDA) ως εργαλείου χωροθέτησης και οικολογικής αξιολόγησης αυτών. Περιγράφονται τα περιβαλλοντικά προβλήματα των εμπορικών λιμένων και αναλύονται οι περιβαλλοντικοί δείκτες. Αναφέρονται οι πλέον διαδεδομένες μέθοδοι πολυκριτηριακών αναλύσεων (MCDA) καθώς επίσης τα λογισμικά λήψης αποφάσεων (Decision Making Software, DMS) που υποστηρίζουν τις μεθόδους αυτές. Παρουσιάζεται συγκριτικός πίνακας με τα κριτήρια αξιολόγησης των DMS για την επιλογή του καταλληλότερου λογισμικού. Για την παρούσα μελέτη επιλέχθηκε το λογισμικού λήψεως αποφάσεων «MindDecider». Η μελέτη ολοκληρώνεται με την εφαρμογή της πολυκριτηριακής μεθόδου χωροθέτησης- αξιολόγησης οικολογικού εμπορικού λιμένα με τη χρήση του λογισμικού που προαναφέρθηκε για έξι υποθετικούς λιμένες. Ακολουθούν συμπεράσματα και προτάσεις για περεταίρω μελέτη του θέματος.This thesis is an effort to demonstrate in an integrated way, the framework of eco ports and to assess the contribution of the Multi Criteria Decision Analysis, (MCDA) method, as a tool for choosing the most environmentally appropriate place for the construction of a port and also to environmentally evaluate existing ports using ecological indicators. A general description for the environmental problems of ports is provided. Also an analysis of the environmental indicators that evaluate an eco port is presented The most common methods of MCDA are presented, as well as the Decision Making Software, (DMS) that supports the implementation of these methods. In this thesis there is also presented a comparison table for various DMS software based on five criteria, in order to evaluate and choose the most suitable software for the case. According to this table the «MindDecider» was found as the most appropriate and user friendly software. This thesis is completed with the implementation of the multi criteria method of placement or evaluating commercial ports using the pre chosen software for six commercial port scenarios. At the end of the thesis conclusions and suggestions are presented for further study.Δημήτριος-Ιωάννης Π. Κάλφα

Effect of Stators on the Performance and the Thermal Capabilities of Small Axial Cooling Fans

This investigation examines experimentally the effect of stators on the performance curves and the heat transfer capabilities of small axial cooling fans. The experimental data indicated that the results are highly affected by the flow conditions at the fan outlet. Downstream guide vanes can be beneficial in terms of pressure drop and efficiency, and thus more economical operation, as well as,in the local heat transfer distribution at the wake of the stator blades especially when the fan is installed very close to the cooling object. However, the more jet spreading and mixing with the surroundings achieved due to the absence of stators at higher separation distances results in increased turbulent levels improving the average heat transfer rate in the stagnation region. The increase heat transfer rate, in the case of a single fan impeller (swirling jet),can be25% higher compared with the case of a typical fan stage (non-swirling jet)showing a similarity with the general trends of swirling and non-swirling impingement jets

Heat Transfer and Performance Characteristics of Axial Cooling Fans with Downstream Guide Vanes

This study examines experimentally the effect of stators on the performance and heat transfer characteristics of small axial cooling fans. A single fan impeller, followed by nine stator blades in the case of a complete stage, was used for all the experimental configurations. Performance measurements were carried out in a constant speed stage performance test rig while the transient liquid crystal technique was used for the heat transfer measurements. Full surface heat transfer coefficient distributions were obtained by recording the temperature history of liquid crystals on a target plate. The experimental data indicated that the results are highly affected by the flow conditions at the fan outlet. Stators can be beneficial in terms of pressure drop and efficiency, and thus more economical operation, as well as, in the local heat transfer distribution at the wake of the stator blades if the fan is installed very close to the cooling object. However, as the separation distance increases, enhanced heat transfer rate in the order of 25% is observed in the case of the fan impeller