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Wyniki wyszukiwania dla: heat exchange in heat recovery steam generators (hrsg)
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Superconductivity in the Endohedral Ga Cluster Compound PdGa5
PublikacjaSuperconductivity is observed below Tc = 1.6 K in an endohedral Ga cluster compound PdGa5 using magnetization and heat capacity measurements. Electronic structure calculations show that the density of states (DOS) at the Fermi level is dominated by Ga s and p states and that the overall shape of DOS is similar to what was found in other endohedral Ga cluster superconductors, such as MoxGa5x+1, ReGa5, and T2Ga9 (T = Rh and Ir)....
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Underwater Wet Repair Welding of API 5L X65M Pipeline Steel
PublikacjaThis paper presents results of the research of effect of polymer insulation of pipeline made of API 5L X65M steel as well as underwater wet welding parameters on properties of joints made by covered electrodes. Effect of heat input on structure and hardness of joints during repair of underwater pipeline was analyzed. Welding defects like microcracks, micro-lacks of fusion, slag inclusions, as well as HAZ hardness increase over...
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The influence of stainless steels microstructure evolution on the mechanical properties of pressure installation elements
PublikacjaIn this paper results of FEM analysis performed for pipe and 90o elbow, made of super duplex stainless steel, after precipitation of sigma phase (),were presented. Heat treatment conditions simulate accidental overheating that can occur in nuclear installations after cooling circulation fails. For initial and modified microstructure tensile test was performed and numerical description of work hardening curves was done. Verification...
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The influence of stainless steels microstructure evolution on the mechanical properties of pressure installation elements
PublikacjaIn this paper results of FEM analysis performed for pipe and 90o elbow, made of super duplex stainless steel, after precipitation of sigma phase (s), were presented. Heat treatment conditions simulate accidental overheating that can occur in nuclear installations after cooling circulation fails. For initial and modified microstructure tensile test was performed and numerical description of work hardening curves was done. Verification...
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Thermodynamic Cycles of Air Microturbine Power Plants Working on Biomass Fuels
PublikacjaThe gas turbine engine is modified to work as an air turbine set which consists, in the simplest arrangement, of a compressor, a heat exchanger and a turbine. Air is a working medium for both: the compressor and the turbine. This kind of air turbine set can be applied in power plants working on biomass fuels. In this solution we can burn fuels of varying parameters in the external combustion chamber without any harmful effects...
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„Gdański eksperyment” studentów PG poleci rakietą z Europejską Agencją Kosmiczną
PublikacjaPięcioosobowy zespół studentów Politechniki Gdańskiej, który przyjął nazwę HEDGEHOG (High quality Experiment Dedicated to microGravity Exploration, Heat flow and Oscillation measurement from Gdansk), zakwalifikował się do programu REXUS/BEXUS Student Experiment Programme koordynowanego przez Europejską Agencję Kosmiczną (ESA). W lutym 2018 roku studenci polecą do kosmodromu Esrange nieopodal Kiruny w północnej Szwecji, by poszerzyć...
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Zastosowanie algorytmu regulacji DMC z pomiarem wartości wielkości sterującej do sterowania blokiem wymienników ciepła
PublikacjaW artykule opisano zastosowanie zmodyfikowanego algorytmu regulacji predykcyjnej DMC do sterowania wybranym blokiem wymienników ciepła. Przedstawiono charakterystykę obiektu sterowania, specyficzne zadania stawiane układowi regulacji oraz sposób realizacji regulatora. Omówiono właściwości opracowanego układu regulacji i zaprezentowano wyniki jego działania.A modified DMC control algorithm application for control of heat exchanger...
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Mathematical modeling and prediction of pit to crack transition under cyclic thermal load using artificial neural network
PublikacjaThe formation of pitting is a major problem in most metals, which is caused by extremely localized corrosion that creates small holes in metal and subsequently, it changes into cracks under mechanical load, thermo-mechanical stress, and corrosion process factors. This research aims to study pit to crack transition phenomenon of steel boiler heat tubes under cyclic thermal load, and mathematical modeling...
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Operation evaluation method for marine turbine combustion engines in terms of energetics
PublikacjaAn evaluation proposal (quantitative determination) of an y combustion turbine engine operation has been presented , wherein the impact energy occurs at a given time due to Energy conversion. The fact has been taken into account that in this type of internal combustion engines the energy conversion occurs first in the combustion chambers and in the spaces between the blade of the turbine engine. It was assumed that in the combustion...
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Microwave radiation in the synthesis of urethane prepolymers
PublikacjaThis paper describes the use of microwave radiation in the synthesis of urethane prepolymers in bulk (without solvent). The prepolymers were synthesized using 1,6-hexamethylene diisocyanate (HDI) and poly (ε-caprolactone) diol (PCL) at a molar ratio of 4:1. The reaction was carried out without a catalyst in the reactor with a conventional heating system (oil bath) or in the microwave reactor (MW Reactor NOVA 09) at temperatures...
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Different design aspects of an Organic Rankine Cycle turbine for electricity production using a geothermal binary power plant
PublikacjaIn recent years, pressure has been growing to increase the share of renewable energy sources in electricity generation, which may offer opportunities for the development of geothermal energy in regions that have been so far considered unprofitable in this respect. One such country currently undergoing an energy transition is Poland in which low-temperature geothermal resources are currently used for district heating and recreation...
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The Effect of Surface Treatment with Isocyanate and Aromatic Carbodiimide of Thermally Expanded Vermiculite Used as a Functional Filler for Polylactide-Based Composites
PublikacjaIn this work, thermally expanded vermiculite (TE-VMT) was surface modified and used as a filler for composites with a polylactide (PLA) matrix. Modification of vermiculite was realized by simultaneous ball milling with the presence of two PLA chain extenders, aromatic carbodiimide (KI), and 4,4’-methylenebis(phenyl isocyanate) (MDI). In addition to analyzing the particle size of the filler subjected to processing, the efficiency...
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Improvement of the thrust bearing calculation considering the convectional heating within the space between the pads
PublikacjaA modern thrust bearing calculation tool should consider not only the oil film between pad and rotating collar but also the space between the pads. The oil flow in the space has a significant influence on the oil film inlet temperature, the convectional cooling of pad and collar and should be included in the bearing calculation methods. The authors use a tool developed at Clausthal University of Technology in cooperation with the...
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Thermodynamical approach to quantifying quantum correlations
PublikacjaWe consider the amount of work which can be extracted from a heat bath using a bipartite state ρ shared by two parties. In general it is less then the amount of work extractable when one party is in possession of the entire state. We derive bounds for this “work deficit” and calculate it explicitly for a number of different cases. In particuar, for pure states the work deficit is exactly equal to the distillable entanglement of...
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Environmentally acceptable lubricants (EAL) compared with a reference mineral oil as marine stern tube bearing lubricant – Experimental and theoretical investigations
PublikacjaThe purpose of this research is to indicate the potential differences in bearing characteristics resulting from the application of different lubricant types with the same viscosity grade. The effect of different environmentally acceptable lubricants (EALs) on hydrodynamic journal bearing properties is studied experimentally and compared to the properties obtained after lubrication with a reference mineral oil. The results of the...
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Cold Cracking Of Underwater Wet Welded S355G10+N High Strength Steel
PublikacjaWater as the welding environment determines some essential problems influencing steel weldability. Underwater welding of high strength steel joints causes increase susceptibility to cold cracking, which is an effect of much faster heat transfer from the weld area and presence of diffusible hydrogen causing increased metal fragility. The paper evaluates the susceptibility to cold cracking of the high strength S355G10+N steel used,...
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A prototype femtosecond laser system for MEMS fabrication
Publikacjan this article, the concept of a prototype femtosecond laser micromachining system and a femtosecond solid-state Yb:KYW laser is presented. Ultrashort laser pulses have many advantages over the long pulses in laser micromachining, due to their unique ability to interact with different materials without transferring heat to them. This allows very precise and pure laser-processing, clean cuts and sharp edges. A femtosecond laser...
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A multistage turbine for a micro power plant
PublikacjaThis paper presents results of a design analysis of a multi-stage turbine for the cogeneration micro-power plant working in accordance with Organic Rankine Cycle (ORC). The heat power of the plant is assumed equal to 20 kW and the corresponding available electric output is estimated to be of about 3 kW. Different variants of the radial and axial-flow turbines have been considered, while the detailed results of the calculations...
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Application of gaze tracking technology to quality of experience domain
PublikacjaA new methodological approach to study subjective assessment results employing gaze tracking technology is shown. Notions of Human-Computer Interaction (HCI) and Quality of Experience (QoE) are shortly introduced in the context of their common application. Then, the gaze tracking system developed at the Multimedia Systems Department (MSD) of Gdansk University of Technology (GUT) is presented. A series of audio-visual subjective...
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Impact of thermal loading into the structural performance of ships: A review
PublikacjaThe presented study reviews the recent advances done regarding the impact of thermal loading on the structural performance of ships. Firstly, the studies related to the mechanical and thermal properties of typical materials used in shipbuilding are outlined. Secondly, a brief introduction to the heat transfer analysis, Finite Element modelling and thermal stresses is provided. Finally, the review of papers dealing with the structural...
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A new model of fuel spray shape at early stage of injection in a marine Diesel engine
PublikacjaIn the cylinders of a marine diesel engine, self-ignition occurs in very shortly time after the fuel injection into the combustion chamber. Therefore, the paper present was to develop a model of diesel fuel spray for the early stage of fuel spray for in marine diesel engine. There were taken into consideration the main aspects technical such as nozzle diameter of marine engine injector and backpressure in combustion chamber. In...
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Numerical investigation of multiphase blood flow coupled with lumped parameter model of outflow
PublikacjaPurpose The purpose of this paper is the application of the computational fluid dynamics model simulating the blood flow within the aorta of an eight-year-old patient with Coarctation of Aorta. Design/methodology/approach The numerical model, based on commercial code ANSYS Fluent, was built using the multifluid Euler–Euler approach with the interaction between the phases described by the kinetic theory of granular flow (KTGF). Findings A...
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Calculation method for flow boiling and flow condensation of R134a and R1234yf in conventional and small diameter channels
PublikacjaThe paper presents the results of calculations performed using the authors’ model to predict the heat transfer coefficient during flow boiling for two refrigerants R134a and R1234yf. The experimental data from various past studies have been collected and the calculations have been conducted for the full range of quality variation and a wide range of mass velocity. The aim of the study was to test the sensitivity of the in-house...
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The energy approach to fatigue crack growth of S355 steel welded specimens subjected to bending
PublikacjaThe study presents the results of the research on the rate of fatigue crack growth subjected to bending in the ferritic-pearlitic structure. The studies were carried out at a constant amplitude of the moment and at various values of the load ratios R and at the operating frequency of the machine of 28.4 Hz. Flat specimens made of S355 steel and with fillet welds and with double-sided blunt external notches as well as concave...
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Analog modelling in qualitative analysis of vibration propagation
PublikacjaThe theory of dynamic systems is usually used to model the real systems. The models are based on solving ordinary differential equations, partial or difference, which enable obtaining the relation between input signal and the system response (output signal). The analogy between those models and generalized dynamic systems or control systems can be practically used. Vibration propagation can be described in a similar way as the...
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Temper bead welding of S460N steel in wet welding conditions
PublikacjaWet welding is the most common method of welding in water environment. It is most often used for repairing of underwater parts of offshore structures. However, the water as a welding environment causes an increase of susceptibility of steels to cold cracking. For underwater constructions high strength low alloy (HSLA) steel are widely used. In wet welding condition a HSLA steel is characterized by high susceptibility to cold cracking....
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Ferro- and antiferro-magnetism in (Np, Pu)BC
PublikacjaTwo new transuranium metal boron carbides, NpBC and PuBC, have been synthesized. Rietveld refinements of powder XRD patterns of {Np,Pu} BC confirmed in both cases isotypism with the structure type of UBC. Temperature dependent magnetic susceptibility data reveal antiferromagnetic ordering for PuBC below T-N = 44 K, whereas ferromagnetic ordering was found for NpBC below T-C = 61 K. Heat capacity measurements prove the bulk character...
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Theoretical Organic Rankine Cycle efficiency depending on different thermodynamic work variables.
PublikacjaOne of promising technologies of utilizing low- temperature waste heat is through ORC (Organic Rankine Cycle) system implementation. A primary objective in designing in-stallations based on such systems is to maximize the installation's work efficiency. On the other hand, ecological factors are commonly considered a natural barrier in introducing new, often very expensive technologies. Ecological effect of a potential modernization...
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Cavitation Erosion Resistance Influence of Material Properties
PublikacjaThe cavitation erosion is the phenomena that causes degradation of fluid flow machinery components due to repetitive implosion of cavitation bubbles adjacent to the solid surface. Cavitation erosion is a complex phenomenon, which includes not only hydrodynamic factors of liquid, but also properties of erodible material e.g. microstructure, hardness or Young modulus. In order to reduce the negative impact of erosion on machine components,...
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Evolution of Physical Properties of RE 3 Ni 5 Al 19 Family (RE = Y, Nd, Sm, Gd, Tb, Dy, Ho, and Er)
PublikacjaSingle crystals of RE3Ni5Al19 series (RE = Y, Nd, Sm, Gd, Tb, Dy, Ho, and Er) are grown using the Al self-flux method. The crystal structure is examined by both single crystal and powder X-ray diffraction. Physical properties are studied for the first time for RE3Ni5Al19 (RE = Y, Nd, Gd, Tb, Dy, Ho, and Er) by means of magnetic susceptibility, electrical resistivity, and heat capacity measurements. Complex magnetic behaviors, with...
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Crystal structure, chemical bonding, and physical properties of layered AIrSn2 (A = Sr and Ba)
PublikacjaWe report the experimental and theoretical investigation of structure, chemical bonding interactions, and physical properties of new ternary stannides AIrSn2 (A = Sr and Ba). AIrSn2 (A = Sr and Ba) crystallizes in the orthorhombic Re3B-type structure with the space group Cmcm (No. 64). According to single-crystal X-ray diffraction results, the structure of AIrSn2 (A = Sr and Ba) can be considered as a Zintl-type compound with heterogeneous...
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Generalized regression neural network and fitness dependent optimization: Application to energy harvesting of centralized TEG systems
PublikacjaThe thermoelectric generator (TEG) system has attracted extensive attention because of its applications in centralized solar heat utilization and recoverable heat energy. The operating efficiency of the TEG system is highly affected by operating conditions. In a series-parallel structure, due to diverse temperature differences, the TEG modules show non-linear performance. Due to the non-uniform temperature distribution (NUTD) condition,...
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Molecular Dynamics simulations of thermal conductivity of penta-graphene
PublikacjaThe thermal conductivity of penta-graphene (PG), a new two dimensional carbon allotrope and its dependence on temperature, strain, and direction are studied in this paper. The thermal conductivity of PG is investigated using a non-equilibrium molecular dynamics simulation (NEMD) with the Two Region Method by applying the optimized Tersoff interatomic potential. Our study shows that the thermal conductivity of PG (determined for...
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The Environmental Benefits of Photovoltaic Systems: The Impact on the Environment in the Production of Photovoltaic Systems: With a Focus on Metal Recovery
PublikacjaGreenhouse gases (GHGs) such as carbon dioxide, nitrous oxide and methane, trap heat and energy, thus preventing solar radiation from escaping back into space. As the quantity of greenhouse gases in the atmosphere increases so does the trapped heat and corresponding global temperature. As a result, storms become more violent, droughts more prevalent, glaciers melt, and sea levels rise, to name but a few effects of a rapidly changing...
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Efficiency and proportions of waste tyre pyrolysis products depending on the reactor type—A review
PublikacjaThis article discusses the current use of different pyrolytic reactors, their constructions and operating principles regarding the yields of main products of waste tyre pyrolytic recycling. Whether one makes a larger or smaller profit, or even a loss due to a surcharge being levied on waste tyre recycling, depends on the sale of the pyrolysis products (gas, char, oil), the proportions and market prices of which differ. The cheapest...
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Rozprzestrzenianie się w podtorzu skutków katastrof kolejowych z udziałem materiałów niebezpiecznych
PublikacjaDuża część przewozów materiałów niebezpiecznych prowadzona jest koleją. W związku z tym bezpieczeństwo tych przewozów nabiera coraz większego znaczenia. Każda katastrofa z udziałem materiałów niebezpiecznych ma negatywny wpływ na uczestników tego zdarzenia oraz na otaczające środowisko, bowiem jej zasięg na ogół nie jest lokalny. Z tego wynika, że w przypadku zaistnienia katastrofy należy minimalizować jej skutki oraz w dalszych...
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Analiza sterowania ułamkowego PIλDμ mocą reaktora jądrowego
PublikacjaW artykule przedstawiono syntezę regulatora PIλDμ niecałkowitego rzędu dla potrzeb sterowania mocą reaktora jądrowego lekko wodnego określanego, jako typu PWR (Pressurized Water Reactor). W tym celu wykorzystano nieliniowy model matematyczny reaktora PWR o parametrach skupionych obejmujący procesy generacji i wymiany ciepła oraz termicznych efektów reaktywnościowych. Nastawy regulatora PIλDμ niecałkowitego rzędu dobrano w sposób...
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Experimental research on water lubricated marine stern tube bearings in conditions of improper lubrication and cooling causing rapid bush wear
PublikacjaWater lubricated bearings are popular in sliding bearings of marine propeller shafts, turbines and pump shafts. Such popularity is partly due to their simple construction which also means a relatively affordable price. In practical experience one may also observe cases of rapid wear or even malfunctions of this bearings, some of which may be caused by insufficient flow of lubricant leading to overheating. The conducted...
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The properties of reduced Bi-Ge-O glasses for thermoelectric devices
PublikacjaThe bismuth-germanate glasses have been investigated to examine their applicability for thermoelectric devices. In order to increase their electrical conductivity, the 25Bi2O3–75GeO2 glass samples have been reduced at 340-380°C for 10 hours in hydrogen. It has been shown that such heat treatment in H2 leads to the reduction of metal ions Bi3+ and Ge4+ into neutral atoms and the formation of metal grains both in an amorphous glass...
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Novel Analytic-Numerical Model of Free Convection: with Leading Edge Considered
PublikacjaA novel solution of the free convection boundary problem is represented in analytical form for velocity and temperature for an isothermal vertical plate, as an example. These fields are built as a Taylor Series in the x coordinate with coefficients as functions of the vertical coordinate (y). We restrict ourselves by cubic approximation for both functions. The basic Navier-Stokes and Fourier-Kirchhoff equations and boundary conditions...
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Interaction of Acoustic and Thermal Modes in the Vibrationally Relaxing Gases. Acoustic Cooling
PublikacjaThe dynamic equation which governs an excess temperature associated with the thermal mode in vibrationally relaxing gas is derived. The nonlinear transfer of acoustic energy to the energy of the thermal mode in a relaxing gas causes slow variation of temperature with time. The nal dynamic equation is instantaneous. All types of sound, including aperiodic, may be considered as an acoustic source of corresponding heating or cooling....
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Comparative study of selected fluids for use in supercritical Organic Ranking Cycles
PublikacjaIn view of increasing interest in improving energy efficiency of energy conversion devices, there is an increasing requirement of combined production of heat and electricity as well as demand for increased implementation of renewable energy resources. The micro cogenerative units utilizing the Organic Rankine Cycle are focusing the attention of many research centres around the world. In the present paper calculations of ORC cycles...
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Interaction of Acoustic and Thermal Modes in the Gas with Nonequilibrium Chemical Reactions: Possibilities of Acoustic Cooling
PublikacjaNonlinear generation of thermal mode during propagation of dominative sound in a chemically reacting gas is considered. The dynamic equation of excess temperature associated with the thermal mode is derived. It is instantaneous and includes quadratic nonlinear acoustic source reflecting the nonlinear character of interaction between acoustic and non-acoustic types of gas motion. Both periodic and aperiodic sound may be considered...
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Influence of hydrogen on a nanocrystalline high-entropy oxide with application potential in hydrogen technologies
PublikacjaThe influence of hydrogen on a (Co0⋅2Cu0⋅2Mg0⋅2Ni0⋅2Zn0.2)O HEO with a rock salt structure was studied. Two forms of this HEO (nanopowder and sinter) were prepared via mechanochemical synthesis (MS) and additional heat treatment, respectively. The chemical stability of the synthesized samples in a pure hydrogen atmosphere was investigated using Sievert’s technique. High-pressure hydrogenation at 250 ◦C had no noticeable effect...
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Superconductivity of Ta-Hf and Ta-Zr alloys: Potential alloys for use in superconducting devices
PublikacjaThe electronic properties relevant to superconductivity are reported for bulk Ta-Hf and Ta-Zr body centered cubic alloys, in a large part to determine whether their properties are suitable for potential use in superconducting qbits. The body centered cubic unit cell sizes increase with increasing alloying. The results of magnetic susceptibility, electrical resistivity, and heat capacity characterization are reported. While elemental...
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Prowadzenie ruchu małej elektrociepłowni gazowej według kryterium efektu ekonomicznego
PublikacjaCechą charakterystyczną źródeł gazowych jest ich duża elastyczność ruchowa, w porównaniu do większości źródeł konwencjonalnych i odnawialnych. Cecha ta może i powinna być wykorzystywana do poprawy wskaźników ekonomicznych obiektu. W tym celu należy przeanalizować możliwości jakie daje prowadzenie ruchu źródeł nie w standardzie pracy z wymuszeniem zapotrzebowania na ciepło, ale właśnie maksymalnie wykorzystując elastyczność ruchową...
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Prowadzenie ruchu małego źródła kogeneracji gazowej według kryterium efektu ekonomicznego
PublikacjaCechą charakterystyczną źródeł gazowych jest ich duża elastyczność ruchowa, w porównaniu do większości źródeł konwencjonalnych i odnawialnych. Cecha ta może i powinna być wykorzystywana do poprawy wskaźników ekonomicznych obiektu. W tym celu należy przeanalizować możliwości jakie daje prowadzenie ruchu źródeł nie w standardzie pracy z wymuszeniem zapotrzebowania na ciepło, ale właśnie maksymalnie wykorzystując elastyczność ruchową...
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Koncepcja stanowiska oraz badania możliwości bezpompowego przetłaczania czynnika w rurce ciepła z pętlą obiegową. Część I - Wstęp-charakterystyka obiegu LHP
PublikacjaBezpompowa cyrkulacja czynnika roboczego występuje w rurkach ciepła z pętlą obiegową (LHP, ang. Loop Heat Pipe). Rurki ciepła oparte na pętli, to urządzenia dwufazowe służące do transportu ciepła, wykorzystujące grawitacyjne i kapilarne siły do wzbudzania obiegu czynnika roboczego. LHP stało się bardzo obiecującym urządzeniem, możliwym do wykorzystania w różnego rodzaju zaawansowanych urządzeniach pracujących naziemnie. W pierwszej...
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Detailed studies of superconducting properties of Y2Pd1.25Ge2.75
PublikacjaWe report a successful synthesis of a high-purity intermetallic germanide Y2Pd1.25Ge2.75, crystallizing in the disordered variant of the AlB2-type structure. A single-phase sample was obtained via arc-melting by deliberately tuning the composition out of the ideal 2:1:3 ratio. Specific heat, electrical resistivity and magnetization measurements show that the compound is a weakly-coupled (λ e-p = 0.58) type-II superconductor with...
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Characterization of structural, thermal and mechanical properties of bismuth silicate glasses
Publikacjahe influence of heating and reduction processes on the structural, thermal and mechanical properties of bismuth-silicate glasses has been investigated. Two compositions of glasses: 40Bi2O3–60SiO2 (Bi0.57Si0.43Ox) and 27Bi2O3–73SiO2 (Bi0.43Si0.57Ox) were fabricated by a typical melt quenching technique. Then the reduction in hydrogen at 380 °C for 20, 42 or 67 h was performed. It was found that a 50 μm-thick layer was formed on...