An investigation of an adsorption cogeneration system for power and cooling using low grade heat

PhD ThesisCogeneration is a hot topic in the efforts to reduce dependence on fossil fuel usage and to reduce greenhouse gas emissions by replacing the primary energy source with a low-grade heat source. Cogeneration simultaneously produces power and cooling using a low-grade heat source (e.g. solar energy, geothermal energy or waste heat), which ideally provides a renewable carbon-free solution for implementation in domestic, industrial as well as isolated areas. This research thesis describes for the first time the development and construction of the Low Heat cogeneration chemisorption system, explores its potential and makes suggestions for its future development based on the experience gained during the experiments. The design uses two adsorption cycles operating out of phase and alternatively connected to a scroll expander in order to reach 3kW of cooling and 1kW of electricity. Each adsorption cycle consists of a reactor, a condenser and an evaporator. Each reactor contains a composite mixture of CaCl2 and activated carbon at a ratio of 4:1 by mass. The system was experimentally investigated for its cooling as well as for its cogeneration performance. Experimental investigations were performed for different heating and cooling temperatures, cycle times and the optimum overall ammonia for the system. The maximum refrigeration coefficient of the performance (COPref) of the machine was found to be 0.26 when the refrigeration power was 3.52kW. At the same time, the specific cooling power (SCP) per side was 201.14W/kg (402.28W/kg per cycle) and the cooling capacity 168.96kJ/kg (337.92kJ/kg per cycle). During the cogeneration experiments it was found that the expander affected the pressure and temperature; the refrigerant flow rate and the pressure across the expander were important for the system’s power production. The maximum power recorded was 486W which provides a power coefficient of performance (COPW) of 0.048. A model to describe the desorption power generation as well as the evaporation refrigeration process was developed using the ECLIPSE software. The cooling model was validated from the experimental results and later the power model was used for ii further investigation of the system power performance. The optimisation of the machine completes the study by using both experimental and simulation data

A clinical evaluation of the performance of five commercial artificial intelligence contouring systems for radiotherapy

Purpose/objective(s)Auto-segmentation with artificial intelligence (AI) offers an opportunity to reduce inter- and intra-observer variability in contouring, to improve the quality of contours, as well as to reduce the time taken to conduct this manual task. In this work we benchmark the AI auto-segmentation contours produced by five commercial vendors against a common dataset.Methods and materialsThe organ at risk (OAR) contours generated by five commercial AI auto-segmentation solutions (Mirada (Mir), MVision (MV), Radformation (Rad), RayStation (Ray) and TheraPanacea (Ther)) were compared to manually-drawn expert contours from 20 breast, 20 head and neck, 20 lung and 20 prostate patients. Comparisons were made using geometric similarity metrics including volumetric and surface Dice similarity coefficient (vDSC and sDSC), Hausdorff distance (HD) and Added Path Length (APL). To assess the time saved, the time taken to manually draw the expert contours, as well as the time to correct the AI contours, were recorded.ResultsThere are differences in the number of CT contours offered by each AI auto-segmentation solution at the time of the study (Mir 99; MV 143; Rad 83; Ray 67; Ther 86), with all offering contours of some lymph node levels as well as OARs. Averaged across all structures, the median vDSCs were good for all systems and compared favorably with existing literature: Mir 0.82; MV 0.88; Rad 0.86; Ray 0.87; Ther 0.88. All systems offer substantial time savings, ranging between: breast 14-20 mins; head and neck 74-93 mins; lung 20-26 mins; prostate 35-42 mins. The time saved, averaged across all structures, was similar for all systems: Mir 39.8 mins; MV 43.6 mins; Rad 36.6 min; Ray 43.2 mins; Ther 45.2 mins.ConclusionsAll five commercial AI auto-segmentation solutions evaluated in this work offer high quality contours in significantly reduced time compared to manual contouring, and could be used to render the radiotherapy workflow more efficient and standardized

Seismic constraints from a Mars impact experiment using InSight and Perseverance

NASA’s InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission has operated a sophisticated suite of seismology and geophysics instruments on the surface of Mars since its arrival in 2018. On 18 February 2021, we attempted to detect the seismic and acoustic waves produced by the entry, descent and landing of the Perseverance rover using the sensors onboard the InSight lander. Similar observations have been made on Earth using data from both crewed1,2 and uncrewed3,4 spacecraft, and on the Moon during the Apollo era5, but never before on Mars or another planet. This was the only seismic event to occur on Mars since InSight began operations that had an a priori known and independently constrained timing and location. It therefore had the potential to be used as a calibration for other marsquakes recorded by InSight. Here we report that no signal from Perseverance’s entry, descent and landing is identifiable in the InSight data. Nonetheless, measurements made during the landing window enable us to place constraints on the distance–amplitude relationships used to predict the amplitude of seismic waves produced by planetary impacts and place in situ constraints on Martian impact seismic efficiency (the fraction of the impactor kinetic energy converted into seismic energy)

Seismic constraints from a Mars impact experiment using InSight and Perseverance

NASA’s InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission has operated a sophisticated suite of seismology and geophysics instruments on the surface of Mars since its arrival in 2018. On 18 February 2021, we attempted to detect the seismic and acoustic waves produced by the entry, descent and landing of the Perseverance rover using the sensors onboard the InSight lander. Similar observations have been made on Earth using data from both crewed1,2 and uncrewed3,4 spacecraft, and on the Moon during the Apollo era5, but never before on Mars or another planet. This was the only seismic event to occur on Mars since InSight began operations that had an a priori known and independently constrained timing and location. It therefore had the potential to be used as a calibration for other marsquakes recorded by InSight. Here we report that no signal from Perseverance’s entry, descent and landing is identifiable in the InSight data. Nonetheless, measurements made during the landing window enable us to place constraints on the distance–amplitude relationships used to predict the amplitude of seismic waves produced by planetary impacts and place in situ constraints on Martian impact seismic efficiency (the fraction of the impactor kinetic energy converted into seismic energy)

A Pre-Landing Assessment of Regolith Properties at the InSight Landing Site

This article discusses relevant physical properties of the regolith at the Mars InSight landing site as understood prior to landing of the spacecraft. InSight will land in the northern lowland plains of Mars, close to the equator, where the regolith is estimated to be ≥3--5 m thick. These investigations of physical properties have relied on data collected from Mars orbital measurements, previously collected lander and rover data, results of studies of data and samples from Apollo lunar missions, laboratory measurements on regolith simulants, and theoretical studies. The investigations include changes in properties with depth and temperature. Mechanical properties investigated include density, grain-size distribution, cohesion, and angle of internal friction. Thermophysical properties include thermal inertia, surface emissivity and albedo, thermal conductivity and diffusivity, and specific heat. Regolith elastic properties not only include parameters that control seismic wave velocities in the immediate vicinity of the Insight lander but also coupling of the lander and other potential noise sources to the InSight broadband seismometer. The related properties include Poisson’s ratio, P- and S-wave velocities, Young’s modulus, and seismic attenuation. Finally, mass diffusivity was investigated to estimate gas movements in the regolith driven by atmospheric pressure changes. Physical properties presented here are all to some degree speculative. However, they form a basis for interpretation of the early data to be returned from the InSight mission.Additional co-authors: Nick Teanby and Sharon Keda

On the evolution of particle fragmentation with applications to planetary surfaces

Fragmentation is a complex phenomenon seen ubiquitously in nature, with the elucidation of its complexity being one of the most popular subjects of the last century. It arises across at a vast multitude of scales in a diverse range of fields such as geophysics and materials, mineral processing, meteorological processes, astrophysics and nuclei impacts - only to be limited by the fundamental units of matter itself. This thesis establishes a new statistical basis for the evolution of particle fragmentation and the resulting product population at all scales. It is informed by the underlying physical processes and builds on the existing disconnected models of fragmentation, mainly the time-continuous grinding and the universality of critical scaleinvariant systems arising in geophysical systems. By extending fractal theory into a temporal context and lifting the various limitations posed by fractals, it provides a solution to the fragmentation problem via a statistical approach which is verified and developed based on terrestrial data from both artificial and natural fragmentation processes. It is then applied to model observations from around the solar system as both an explanatory and predictive approach to the evaluation of planetary surfaces, one of the major areas of study in planetary sciences. Furthermore, a stochastic model for drilling in a planetary regolith is developed both mathematically and through the synthesis of digital soil.Open Acces

Economic repercussions of Olympic Games and data mining techniques: attempts of exporting results and conclusions

178 σ.Στο παρούσα διπλωματική εργασία επιχειρείται η αξιολόγηση του οικονομικού αντίκτυπου των Ολυμπιακών Αγωνών, μέσω των τεχνικών εξόρυξης δεδομένων. Αρχικά, το κεφάλαιο 2 παρουσιάζει συνοπτικά τα σύγχρονα ολυμπιακά γεγονότα, που στρέφονται στον αντίκτυπο που έφερε, πριν, κατά και μετά τα παιχνίδια, στην οικονομία κάθε χώρας και δίνεται μια γενική περιγραφή του γεγονότος «Αθήνα 2004», καθώς επίσης και στοιχεία της ελληνικής οικονομίας. Κατόπιν, το κεφάλαιο 3 δίνει μια γενική περιγραφή του προγράμματος (OGGI) και των δεικτών ανάλυσης. Έπειτα, σκιαγραφούνται θεωρητικά - κεφάλαιο 4 - οι διάφορες τεχνικές εξόρυξης πληροφοριών. Οι πληροφορίες δίνονται - κεφάλαιο 5 - σύμφωνα με το λογισμικό που χρησιμοποιείται, το WEKA. Κατόπιν, αναλύουμε τα στάδια της μεθοδολογίας που ακολουθήθηκαν, έτσι ώστε να εξάγουμε διάφορους κανόνες από το σύνολο των στοιχείων που χρησιμοποιήθηκαν (κεφάλαιο 6). Τελικά, όλα τα αποτελέσματα αυτών των κανόνων παρουσιάζονται αναλυτικά στο κεφάλαιο 7. Εάν η Ελλάδα επηρεάστηκε θετικά ή αρνητικά στον τομέα της οικονομίας, από τους Ολυμπιακούς Αγώνες Αθήνα 2004 δεν είναι μια ερώτηση η οποία μπορεί να απαντηθεί αντικειμενικά.In the present thesis is attempted the assessment of economic repercussions of Olympic Games, via techniques of data mining. Initially, chapter 2 presents concisely the modern Olympic events, focusing in the repercussions that brought, before, through and afterwards the Games, in the economy of each country that hosts the Games and is given a general description of event "Athens 2004", as well as Greek economy. Then, chapter 3 gives an overall description of the program "Olympic Games Global Impact" (OGGI) and indexes for analysis. Next, they are sketched out theoretically - capital 4 - the various techniques of excavation of information through data (data mining) that they are used. Information is given - capital 5 - according to the software that is used, the WEKA. Then, we analyze the stages of methodology that were followed, so that we export the various rules of result from the total of data that enjoyed treatment data mining (chapter 6). Final, all the results of this rules is presented analytically in chapter 7. The present work aims in the creation of small aid, that would function as a type of dynamic material for students. If Greece was influenced positively or negatively in the sector of Economy, from the Games is not a question that anyone can answer for sure.Κωνσταντίνος Α. Χαραλάμπου

Economic repercussions of Olympic Games and data mining techniques: attempts of exporting results and conclusions

178 σ.Στο παρούσα διπλωματική εργασία επιχειρείται η αξιολόγηση του οικονομικού αντίκτυπου των Ολυμπιακών Αγωνών, μέσω των τεχνικών εξόρυξης δεδομένων. Αρχικά, το κεφάλαιο 2 παρουσιάζει συνοπτικά τα σύγχρονα ολυμπιακά γεγονότα, που στρέφονται στον αντίκτυπο που έφερε, πριν, κατά και μετά τα παιχνίδια, στην οικονομία κάθε χώρας και δίνεται μια γενική περιγραφή του γεγονότος «Αθήνα 2004», καθώς επίσης και στοιχεία της ελληνικής οικονομίας. Κατόπιν, το κεφάλαιο 3 δίνει μια γενική περιγραφή του προγράμματος (OGGI) και των δεικτών ανάλυσης. Έπειτα, σκιαγραφούνται θεωρητικά - κεφάλαιο 4 - οι διάφορες τεχνικές εξόρυξης πληροφοριών. Οι πληροφορίες δίνονται - κεφάλαιο 5 - σύμφωνα με το λογισμικό που χρησιμοποιείται, το WEKA. Κατόπιν, αναλύουμε τα στάδια της μεθοδολογίας που ακολουθήθηκαν, έτσι ώστε να εξάγουμε διάφορους κανόνες από το σύνολο των στοιχείων που χρησιμοποιήθηκαν (κεφάλαιο 6). Τελικά, όλα τα αποτελέσματα αυτών των κανόνων παρουσιάζονται αναλυτικά στο κεφάλαιο 7. Εάν η Ελλάδα επηρεάστηκε θετικά ή αρνητικά στον τομέα της οικονομίας, από τους Ολυμπιακούς Αγώνες Αθήνα 2004 δεν είναι μια ερώτηση η οποία μπορεί να απαντηθεί αντικειμενικά.In the present thesis is attempted the assessment of economic repercussions of Olympic Games, via techniques of data mining. Initially, chapter 2 presents concisely the modern Olympic events, focusing in the repercussions that brought, before, through and afterwards the Games, in the economy of each country that hosts the Games and is given a general description of event "Athens 2004", as well as Greek economy. Then, chapter 3 gives an overall description of the program "Olympic Games Global Impact" (OGGI) and indexes for analysis. Next, they are sketched out theoretically - capital 4 - the various techniques of excavation of information through data (data mining) that they are used. Information is given - capital 5 - according to the software that is used, the WEKA. Then, we analyze the stages of methodology that were followed, so that we export the various rules of result from the total of data that enjoyed treatment data mining (chapter 6). Final, all the results of this rules is presented analytically in chapter 7. The present work aims in the creation of small aid, that would function as a type of dynamic material for students. If Greece was influenced positively or negatively in the sector of Economy, from the Games is not a question that anyone can answer for sure.Κωνσταντίνος Α. Χαραλάμπου

Surface-active organic matter induces salt morphology transitions during new atmospheric particle formation and growth

.The creation of new atmospheric particles via nucleation is an important source of the particles from which Cloud Condensation Nuclei (CCN) are formed. The new particle formation (NPF) process can significantly alter the atmospheric aerosol size distribution and thus CCN activation. CCN are associated with boundary layer evolution, cloud formation, and cloud properties like albedo, or the lifetime. Water vapor condenses upon atmospheric particulates that grow in size to form cloud droplets. Despite its importance, NPF is poorly understood at the atomic level and the ns time scale especially when organic matter (OM) effects are included. Here we employ molecular dynamics simulations on ammonium chloride wet aerosol models. Salt within the aerosol is found to transition between different morphologies-brine and crystalline-depending on the presence of OM on the surface of the occurring particle. Particle number, size and growth dynamics are associated with this variant salt morphology. Our findings elucidate the dynamics of NPF and particle growth in the presence of OM

The Inhibitory Effect of Free Nitrous Acid and Free Ammonia on the Anoxic Phosphorus Uptake Rate of Polyphosphate-Accumulating Organisms

The purpose of this study is to investigate the effect of free nitrous acid (FNA) and free ammonia (FA) on the anoxic phosphorus uptake rate (PUR) of polyphosphate-accumulating organisms (PAOs) via the utilization of nitrite. With this goal, upon developing a PAO-enriched culture in a sequential batch reactor, a series of batch experiments were conducted to examine the effects of nitrite and ammonium on the anoxic phosphorus uptake rate at different pH levels. According to the results, both free nitrous acid and free ammonia were found to inhibit anoxic PUR to a degree similar to their respective effects on aerobic PUR reported in previous studies, suggesting that phosphorus removal via the anoxic pathway may be just as susceptible as that via the aerobic pathway. The effect of FNA on anoxic PUR is optimally described by a non-competitive inhibition model with a KiFNA value of 1.6 μg N L−1, while the Levenspiel model with an SFA* value of 37 mg N L−1 provided the best fit for the FA effect on PAOs anoxic activities. The results of this study provide new insights regarding the viability of EBPR under high nitrogen loading conditions