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Vor dem Hintergrund sich weiter verscharfender Verbrauchs- und Emissionsnormen stellen sich neue Herausforderungen an die Kraftstoffzumessgenauigkeit von Einspritzsystemen. Fur Ottomotoren mit Benzin-Direkteinspritzung sind Einspritzventile mit Solenoidantrieb wegen ihrer kostengunstigen Fertigungsweise weit verbreitet. Fur diesen Injektortyp werden neue Regel- und Diagnosekonzepte auf Basis des Raildrucksignals untersucht, welche die Zumessung der eingespritzten Kraftstoffmasse verbessern.

Ziel ist es, ein Konzept für das Risikomanagement mit dem Fokus Entwicklungsprojekte / Innovationsprojekte zu entwickeln. Da die Ziele dieser Projekte auf verschiedenen Szenarien basieren und sich ständig ändern können, sollte man ein dynamisches Risikomanagement durchführen. Bei diesem Artikel wird ein Konzept für ein dynamisches Risikomanagement entwickelt, bei dem die dynamischen Aspekte des Risikomanagements erforscht werden. Darauf aufbauend wird eine Methode für die Berechnung der Gesamtprojektrisiko-Zahl vorgestellt, um das Gesamtprojektrisiko während des Projektlebenszyklus dynamisch monitoren und steuern zu können.

Simple Summary Radiotherapy (RT) with higher single doses is capable of creating a beneficial immunological tumor microenvironment for additional immune therapies to trigger systemic anti-tumor immune responses. Here, we aimed to boost RT-induced immune responses with inactivated whole tumor cell vaccines generated with high hydrostatic pressure (HHP) and to break immunosuppression by inhibition of suppressive immune checkpoint molecules, such as PD-1. Our results highlight that HHP vaccines act systemically to retard tumor growth, but only of previously irradiated tumors. In contrast, abscopal anti-tumor immune responses, namely those to non-irradiated tumors, are triggered by a combination of RT of not too many fractions plus anti-PD-1, being characterized by the induction of distinct immune alterations in the primary and abscopal tumor, respectively. This emphasizes that future multimodal radioimmunotherapy approaches need to be carefully optimized regarding RT fractionation and the interaction of different immunotherapies with each other. Abstract Radiotherapy (RT) is known to have immune-modulatory properties. We hypothesized that RT and inactivated whole tumor cell vaccines generated with high hydrostatic pressure (HHP) synergize to retard the tumor growth which can be additionally improved with anti-PD-1 treatment. In abscopal tumor models, we injected mice with B16-F10 melanoma or TS/A mammary tumors. To evaluate the efficiency of RT in combination with HHP vaccines, we locally irradiated only one tumor with 2 × 8 Gy or 3 × 8 Gy. HHP vaccines further retarded the growth of locally irradiated (2 × 8 Gy) tumors. However, HHP vaccination combined with RT failed to induce abscopal anti-tumor immune responses, namely those to non-irradiated tumors, and even partly abrogated those which were induced with RT plus anti-PD-1. In the latter group, the abscopal effects were accompanied by an elevated infiltration of CD8+ T cells, monocytes/macrophages, and dendritic cells. 3 × 8 Gy failed to induce abscopal effects in association with increased expression of immunosuppressive checkpoint molecules compared to 2 × 8 Gy. We conclude that HHP vaccines induce anti-tumor effects, but only if the tumor microenvironment was previously modulated by hypofractionated RT with not too many fractions, but failed to improve RT plus anti-PD-induced abscopal responses that are characterized by distinct immune alterations.

In this paper, we present the energy-saving potential of using optimized control for centrifugal pump–driven water storages. For this purpose, a Simulink pump-pipe-storage model is used. The equations and transfer function for steady-state and transient system behavior are presented and verified. Two different control strategies—optimum constant flow rate and level guided speed control—are compared to an allegedly optimal-driven pump with constant rotational speed. Twelve centrifugal pumps between 1 and 120 kW nominal power are evaluated to analyze the influence of different system parameters. The system characteristics, which are the static head, dynamic head factor, and maximum filling head, are varied 25 times for each pump in consideration of the pump’s best efficiency point. Thus, 300 different systems are optimized for each control strategy and compared to the constant speed control. The results are analyzed and the relevant system’s parameters, which have the most significant impact on energy savings, are shown. This theoretical energy–saving potential is verified with measurements, which show the high impact of the part load losses of the frequency converter and the electric motor. A law for identifying and estimation potential energy savings is developed using this information. Four use cases are analyzed with this law. It is shown that for a cost-minimal operation, not only the savings potential but also the operating time is decisive.

Due to the thick-walled autoclaves, the ammonothermal system has long been regarded as a black box and the crystal quality was only improved through systematic, time-consuming experiments [1]. One of the main goals therefore was to bring “light into the dark” with new window design for the extreme process parameters of larger than 650 °C and simultaneously 300 MPa.

In addition to the high pressure and temperature, process equipment for ammonothermal syntheses has to withstand ammonothermal reaction media: an aggressive mixture of supercritical ammonia with basic or acidic additives. Severe corrosive attack of process equipment can occur under ammonothermal conditions but needs to be minimized for two reasons. Firstly, corrosive attack can lead to safety issues that must not be neglected. Secondly, corrosion products represent a major source of impurities, which represents a critical issue especially for the synthesis of semiconductors. Consequently, measures for minimizing corrosion are of utmost importance for the adequate design of ammonothermal equipment. In this chapter, materials suitable for ammonothermal applications, for pressure bearing parts as well as for internal setups and corrosion protection, and recent investigations on their corrosion behavior will be reviewed with suggestions for suitable applications and protection systems.

As the ammonothermal method often requires technically challenging conditions such as high temperature, high pressure and reaction media that are rather corrosive towards most metals (see Chap. 11), the further development of ammonothermal process equipment is of vital importance for tapping the full potential of the ammonothermal method. Suitable high-pressure/high-temperature autoclaves are therefore the basic requirement for a successful process. Ammonothermal syntheses are conventionally carried out in autoclaves, which do not allow monitoring of the physical and chemical processes during the experiments. Therefore, in situ measurement techniques at process conditions are crucial for obtaining a holistic understanding of ammonothermal processes. The following chapter presents optical cells for in situ monitoring enabling UV/Vis and Raman spectroscopy, X-ray imaging and X-ray diffraction as well as ultrasonic measurements. Additionally, special equipment like a rotatable feedthrough and a ceramic-crucible-based systems for minimization of corrosion and contamination are described.

The following chapter is mainly aimed at simulators and crystal growers, as viscosity has an influence on the flow behaviour in the reactor and the diffusion coefficient in the crystal’s vicinity. So, the chapter gives an overview of influencing factors to viscosity in ammonothermal media, which are the pressure and temperature as well as the concentration of used mineralizers. Therefore, different possible viscometers are described and discussed in detail for its potential use in ammonothermal media. Hereby two promising options are presented in detail: a modified rolling ball viscometer as well as an adaptation of the ultrasonic pulse-echo method for viscosity measurement for ammonothermal systems. While the last is mostly based on literature research and only some general prove of principle are carried out, the first one is fully described and analysed during operation. This means for the adaptation of this principle four critical aspects have to be overcome. As a result, the viscosity of ammonia in the range above 400 °C up to 600 °C at maximum pressure of 252 MPa is shown. Additionally, some measurements of ammonia-ammonium-fluoride-mixtures are compared with pure ammonia, whereas the viscosity is about 1.4 times lager with ammonium fluoride then without.

The challenges of ammonothermal reactor design are manifold. High-pressure and temperature require the use of high-performance alloys with sufficient strength at elevated temperature and excellent creep resistance: highly alloyed Ni-base and Co-base alloys and a Mo-base alloy have been in use in ammonothermal reactor design. Furthermore, the dimensioning rules have to be strictly followed to minimize stress concentration. Repeated loading cycles and degradation over time have to be considered. Finally yet importantly, good handling of the equipment not only minimizes the workload but also reduces the risk of crucial operating errors. The chapter Technological challenges of autoclave design discusses design options for high-pressure at high-temperature equipment with regard to their mechanic and thermal stability. Materials suitable for ammonothermal pressure vessels will be reviewed and some basic safety advice is given at the end of this chapter.

Formation and transport of Ga-containing intermediates are essential for ammonothermal bulk growth of GaN. In this work, in situ X-ray transmission measurements are established as a tool for monitoring face-selective dissolution of GaN crystals as well as the Ga-concentration in the fluid. The accuracy of concentration determination by X-ray transmission measurements is evaluated and the detection limit for dissolved species is estimated. The detection limit is given both as a gallium concentration and as an attenuation coefficient, thus, it can easily be transferred to other materials of interest. Face-selective ammonothermal etching is investigated for both ammonoacidic and ammonobasic mineralizers. Time- and space-resolved monitoring of the concentration of Ga-containing intermediates is demonstrated using NH4F mineralizer. The results are discussed with respect to the formation of Ga-containing intermediates and mechanisms of mass transport. Based on molecular dynamics simulations, the experimentally observed, unexpectedly low diffusion coefficient for the Ga-transporting species is ascribed at least partially to the diffusion of larger [GaxFy]3x−y aggregates.

White etching cracks (WECs) have been found to form in rolling element bearings as early as 6-24 months into operation, especially in large wind turbine gearboxes. Despite the number of investigations conducted in both industrial and academic research over the past two to three decades, WEC formation and initiation mechanisms are still not well understood. This is due to the complexity of the factors that influence WEC formation, such as speed, load (mechanical and electrical) and lubrication, as well as a lack of effective monitoring techniques that can detect WECs prior to severe bearing failures, such as spalls on the bearing surface. Recent research has suggested that WECs can form in rolling element bearings under the influence of electrical load (potential or current). To investigate the feasibility of WEC detection using the electrostatic (ES) sensing technique, an ES wear site sensor was installed on a bearing test-rig where WECs had been created under the influence of electrical load. The ES responses were compared with those from an acoustic emission (AE) sensor that had been shown to detect WEC failures in a previous study. The physical findings related to WEC failures in the bearings and basic analysis of the sensor signals have been reported in a parallel paper by Zuercher et al. This paper focuses on the analysis of ES and AE signals using a time-frequency method, where correlations between the electrostatic charge signals and AE measurements are found. The results suggest that electrostatic sensors have the potential to detect WEC formation in rolling element bearings.

Machinery such as pumps used for the commercial production of fermented milk products cause vibrations that can spread to the fermentation tanks. During fermentation, such vibrations can disturb the gelation of milk proteins by causing texture defects including lumpiness and syneresis. To study the effect of vibrations on yogurt structure systematically, an experimental setup was developed consisting of a vibration exciter to generate defined vibrational states and accelerometers for monitoring. During the fermentation of skim milk, vibrations (frequency sweep: 25 to 1,005 Hz) were introduced at different pH (5.7 to 5.1, step width 0.1 units) for 200 s. Physical properties of set gels (syneresis, firmness) and resultant stirred yogurts (visible particles, rheology, laser diffraction) were analyzed. Vibrational treatments at pH 5.5 to 5.2 increased syneresis, gel firmness, and the number of large particles (d > 0.9 mm); hence, this period was considered critical. The particle number increased from 34 ± 5 to 242 ± 16 particles per 100 g of yogurt due to vibrations at pH 5.4. In further experiments, yogurts were excited with fixed frequencies (30, 300, and 1,000 Hz). All treatments increased syneresis, firmness, and particle formation. As the strongest effect was observed by applying 30 Hz, the amplitude was set to vibration accelerations of a = 5, 10, 15, 20, and 25 m/s2 in the final experiments. The number of large particles was increased due to each treatment and a positive correlation with the amplitude was found. We concluded that vibrations during gelation increase the collision probability of aggregating milk proteins, resulting in a compressed set gel with syneresis. Resultant stirred yogurts exhibit large particles with a compact structure leading to a reduced water-holding capacity and product viscosity.

InN crystals with hexagonal shapes were grown from InCl3 and KNH2 in supercritical ammonia at around 280 MPa. For a successful crystal growth a molar ratio of the chloride to the amide of 1:3 was applied, thus providing an essentially ammononeutral milieu. The obtained InN crystals vary in size and aspect ratio depending on the applied furnace temperature: at 663 K hexagonal platelets up to 2 mm in diameter, as well as rods with lengths of 4 mm and diameters of 1 mm were obtained; at 773 K rods grew up to 2.5 mm in length. By combining both temperature programs, with a 10 h annealing step at both temperatures, we were able to increase the crystal size up to 5.2 mm in length and 0.4 mm in diameter.

Bearings in electrical environments have been the subject of many publications. These bearings tend to be the victims of early failure in many different applications. In some cases, insulating or grounding the bearings can prevent the failure, but in other cases, especially in combination with the failure mechanism of white etching cracks, no definitive final answer has yet been proposed. In this work, a test-rig that can create white etching cracks in combination with an electric load is used to test a newly developed electrostatic sensor and to further investigate the root causes of the mechanisms of white etching crack formation for early failure detection.

Pump systems around the world account for a high percentage of electrical energy consumption. The energy efficiency of these systems can be improved using control algorithms to determine appropriate operating points. The problem that arises is that computed operating points deviate from real operating points. This is due to deviations of the affinity laws, inaccurate information about pump characteristics, and plant behavior. In order to address this problem, we will present model-free optimization methods that can optimize various pump systems during ongoing operation. First, we will classify different pump systems. Based on this categorization, we will then analyze characteristic systems with regard to their energetic optimum. The resulting findings will enable us to identify suitable optimization algorithms. These model-free optimization algorithms take the form of an extremum seeking control in combination with a Kalman filter, the Nelder Mead algorithm, and a dynamic optimization method. After describing these algorithms, we will optimize and validate three sample classes of pump systems using the respective appropriate optimization strategy. The three classes represent a single-pump system, a multiple parallel pump system and a pump storage system. We can see that all optimization strategies achieve the energetic optimum. We can identify savings of between 7.9% and 50%, depending on the system in question. Finally, we will present a best-fit model-free optimization strategy for each class, and system operators can employ this strategy to ensure energy-optimized operation of their specific system.

Solubility and dissolution kinetics of GaN are investigated, as they represent essential parameters for ammonothermal crystal growth of GaN. In situ X-ray imaging is applied to monitor the dissolving crystal. Both ammonoacidic and ammonobasic conditions are investigated. Compared to NH4F, the dissolution is generally much slower using NaN3 mineralizer, leading to a much longer time needed to establish a saturated solution. The solubility of GaN at 540 °C and 260 MPa in supercritical ammonia with a molar concentration of NaN3 of 0.72 mmol/ml is determined to be 0.15 ± 0.01 mol%. This suggest a severe refinement of raw gravimetric literature data also for alkali metal based mineralizers, as we reported previously for ammonium halide mineralizers. The order of magnitude is in good agreement with refined gravimetric solubility data (Griffiths et al., 2016). The apparent discrepancy between the literature and this work regarding the temperature range in which retrograde solubility occurs is discussed. A possible reason for the occurrence of retrograde solubility at high temperatures is described. The paper is complemented by a section pointing out and partially quantifying potential, reactor-material-dependent sources of errors.

Reactions of Ga or GaN with RbNH2 or CsNH2 under ammonothermal conditions result in liquids representing intermediate compounds in the ammonobasic GaN crystal growth. These liquids are fully miscible with liquid ammonia at room temperature and under autogenous pressure, and may eventually solidify to amorphous solids. The Cs-containing liquid initially contains an equilibrium mixture of tetraamidogallate ions [Ga(NH2)4]− and a dinuclear complex [(H2N)3Ga(μNH)Ga(NH2)3]2–. Oxygen impurities induce the formation of a μ-O-bridged dinuclear complex [(H2N)3GaOGa(NH2)3]2–. Mononuclear tetraamidogallate ions are the dominating species directly after synthesis, but the equilibrium shifts gradually toward the imido complex when ammonia is removed, and eventually a second condensation step to [(H2N)2Ga(μ-NH)2Ga(NH2)2]2– occurs. Addition of excess liquid ammonia under ambient conditions causes quantitative conversion of the dinuclear species to [Ga(NH2)4]−. The [Ga(NH2)4]− ions are also the only observable gallium-co...

Liquid Organic Hydrogen Carriers (LOHCs) are able to store hydrogen in a dense and safe form at ambient conditions. While storage of electrical energy in these carrier systems is one possible and attractive application, the dynamics of the load profile has been believed to represent a major challenge for this storage technology. Conversely, we report here that storage systems based on the LOHC technology are indeed able to deal with significant variations in power demand. This is due to the significant free volume in the LOHC release unit offering the opportunity to handle dynamic behavior by pressure changes. While pressure changes allow quick adaption of the power release on demand, changes in the reactor temperature lead to slow modification of the power output, as demonstrated in this work for hydrogen release from perhydro-dibenzyltoluene (H18-DBT).

High hydrostatic pressure (HHP) is a promising method for the inactivation of cells and enzymes in many applications (e.g. food industry, pharmaceutical industry, chemistry). The effects of various high-hydrostatic pressures (20 MPa, 50 MPa, 55 MPa, 60 MPa, 75 MPa, 100 MPa, 150 MPa, 200 MPa, 400 MPa) on the unicellular flagellate Euglena gracilis were determined: (a) life/dead staining with ethidium bromide (EtBr), (b) loss of flagellum, (c) movement behavior, (d) recovery after 7 d, (e) photosystem II quantum yield (Y(PSII)). Pressure was applied for 300 s at room temperature (pressure increment and decrement: 10 MPa s −1 ). The EC 50 value of vitality (EtBr-positive cells) directly after pressure application was 109 MPa. Cell vitality was not impaired below 100 MPa. No recovery of cells after 7 d-cultivation in fresh medium was observed after pressure treatment above 100 MPa. Flagellum-based free swimming of cells was already impaired at pressures above 50 MPa, where some cells started metabolic movement behavior. From 75 MPa to 100 MPa all cells moved metabolically, while at higher-pressure all cells became immotile. In the pressure range between 75 MPa and 200 MPa, cells lost their flagellum. Interestingly, cells pressurized with 400 MPa retained their flagella. Directly after HHP-treatment EC 50 of Y(PSII)-inhibition was about 101 MPa, after 6 h about 102 MPa. The use of fluorescence-based methods is considerably fast, easy and reliable. Because of the different easily recordable parameters, we believe that Euglena gracilis is a promising test organism to determine HHP-effects on eukaryotes. The effects on photosynthesis indicate impacts on intracellular membrane and protein complexes.

The first gallium-containing nitridosilicate CaGa-SiN3 was synthesized in newly developed high-pressure autoclaves using supercritical ammonia as solvent and nitriding agent. The reaction was conducted in an ammonobasic environment starting from intermetallic CaGaSi with NaN3 as a mineralizer. At 770 K, intermediate compounds were obtained, which were subsequently converted to the crystalline nitride at temperatures up to 1070K (70-150 MPa). The impact of other mineralizers (e. g., LiN3, KN3, and CsN3) on the product formation was investigated as well. The crystal structure of CaGaSiN3 was analyzed by powder X-ray diffraction and refined by the Rietveld method. The structural results were further corroborated by transmission electron mi-croscopy, 29SiMAS-NMR, and first-principle DFT calculations. CaGaSiN3 crystallizes in the orthorhombic space group Cmc21 (no. 36) with lattice parameters a= 9.8855(11), b= 5.6595(1), c= 5.0810(1) a, (Z= 4, Rwp= 0.0326), and is isostructural with CaAlSiN3 (CASN). Eu2+ doped samples exhibit red luminescence with an emission maximum of 620 nm and FWHM of 90 nm. Thus, CaGaSiN3: Eu2+ also represents an interesting candidate as a red-emitting material in phosphor-converted light-emitting diodes (pc-LEDs). In addition to the already known substitution of alkaline-earth metals in (Ca, Sr) AlSiN3: Eu2+, inclusion of Ga is a further and promising perspective for luminescence tuning of widely used redemitting CASN type materials.

Thermal performance of oil-immersed power transformer requires comprehensive solutions for the complex conjugate thermal-hydraulic problem which determines the thermal behavior of the oil and winding set. However, development of a thermal model without consideration of test procedures and limitations can led to inaccurate results during factory acceptance test (FAT). In the current study, we present improvements in modelling and testing based on an effective data exchange between both. Accurate loss calculation in transformer components and better investigation of oil behavior as well as development of more reliable rules to analyze heat-run results with consideration of new effective factors lead to a more accurate calculation of the thermal characteristics. This will increase the level of certainty in meeting the specified temperature rises during FAT, and therefore, accurate prediction of the transformer lifetime. Furthermore, minimum deviation between calculated and measured temperatures will allow optimization of the cooling system resulting in a more economical transformer design.

The steady growing demand of further storage capacity for the compensation of the daily fluctuations of renewable energies in national energy grids requires the development of new scalable energy storages. Pumped Thermal Energy Storages (PTES) like reversible heat pump - organic Rankine cycle systems are a possible candidate for this. In this work, the complete process from initial cycle design and fluid selection to the component selection and CAD work of the demonstrator is shown. For the simulation of the cycles, a stationary Matlab model was used. A screening of various suitable fluids was performed and four promising fluids were selected for further investigation. Out of these four fluids, R1233zd(E) was selected as final candidate for the demonstrator. The simulated power-to-power efficiency ( η P 2 P ) of the system reaches up to 59% for the design case. With the simulated data, the apparatus selection was performed and a CAD model was developed to build the demonstrator as a laboratory scale plant with 14.7 kW electrical compressor power.

Vibrations during the fermentation of yogurt and related milk products have recently been reported to disturb the gelation and result in quality defects such as particle formation, graininess, and syneresis. However, primary research on this topic was focused on experiments performed on a laboratory and pilot-plant scale. In this study, three large dairy factories were visited, and yogurt samples were directly taken out of various fermentation tanks, showing great differences in terms of graininess and particle content. Thereupon, vibration measurements were conducted at three industrial yogurt plants. Particularly, pumps and their influence on the vibrational excitation of the fermentation tanks were examined. The major structural and mechanical differences of these plants, such as distances between the vibration source and the tank or the types of pumps used, led to varying vibrational states at the fermentation tanks. We concluded that the vibrational excitation of each plant must be evaluated individually in order to estimate the potential for vibration-induced texture defects.

Vibrations during yogurt fermentation have been reported to disturb the gelation by inducing large, visible particles. Such vibrations are generated by the machinery used for the industrial manufacture and can cause structural excitation of the fermentation tanks. To study the effect of vibrations on yogurt structure, an experimental setup was constructed consisting of a cylindrical tank (height: 600 mm). The bottom of the tank was excited by a shaker, resulting in a vertical vibration propagation. Skim milk was vibrated during fermentation at 30 Hz and different amplitudes. Vibrated gels showed syneresis up to ∼5%. Samples were taken at different height positions of the fermenter, processed into stirred yogurt, and analyzed. The number of large particles was primarily related to the set vibration amplitude, however, particle formation was more pronounced in the lower and upper area. Yogurts with a high particle number exhibited a reduced water-holding capacity and apparent viscosity. Moreover, the fluid dynamic effects of vibrations were investigated by particle image velocimetry. Vibrations led to uniform to-and-fro motions, whereas chaotic flow was observed at the surface. Finally, the impact of vibrations on the gelation mechanism is discussed.

Copper based fungicides are plant protection products prevalently used in organic agriculture to control several plant diseases. Since copper can have various negative effects on the environment, the amount used should be reduced to the minimum necessary. However, this reduction should not lead to a loss of efficacy, as otherwise the quality and quantity of the yield would be at risk. During this study, a copper sulfate/copper hydroxide mixture was combined with an agent for better adhesion to grapevines. This was achieved by microencapsulation of the active agents into a fat matrix which resulted in the so called CuCaps. Laboratory analysis of dispersibility and particle size proved that CuCaps form an applicable powder, suitable for use in commercial crop protection sprayers. Field experiments demonstrated that CuCaps have an equivalent effect compared to a commercially available copper-based fungicide (CCF). Both, CuCaps and CCF were able to significantly (p

Cs2[Zn(NH2)4] was synthesized under ammonothermal conditions (sc-NH3, 523 K, 155 MPa) from CsNH2 and Zn. Growth of cm-sized crystals succeeded upon application of a temperature gradient. The crystal structure is based on the motif of a hexagonal closed packing of [Zn(NH2)4]2– ions with occurrence of no significant hydrogen bridges according to distances and vibrational spectroscopy. Cs+ ions are located within octahedral and tetrahedral holes of the packing.

In terms of reducing power losses and ensuring optimal lubrication, a high viscosity index is crucial for lubricants exposed to changing load or temperature conditions. Several studies suggest that an enormous improvement of the viscosity-temperature characteristics could be achieved by the application of dissolved CO2 on various base oils. The direct link between the applied pressure and the lubricant viscosity offers the possibility of adjustable and thus tunable lubricants. The practical implementation of dissolved CO2 as a viscosity index improver is investigated on a roller bearing test rig. The results indicate a significant reduction of power losses and show that it is possible to influence the friction condition in the rolling contact through viscosity adaptation.

Combining a heat pump cycle (HP) and an organic Rankine cycle (ORC) in one reversible cycle and adding a thermal storage enables an innovative and reversible energy storage concept. This paper describes preliminary considerations, design methods and the development of a HP-ORC-pilot-plant. The storage temperatures are critical factors, as they determine the storage capacity and influence the power-to-power-efficiency. Methods of multicriteria decision-making, such as Pareto optimization, identify favorable combinations. On this basis a pilot plant is designed for 90°C lower and 120°C upper storage temperature aiming at a power-to-power-efficiency of 59% and an electrical storage capacity of 3,6 kWh/t. The selection of the working fluid has also a strong impact on the reversible process, as apparatus properties alter, in some cases effecting significant increase in costs. In the considered case the refrigerant R1233zd(E) shows the best combination of performance, costs and safety. The realization of the compressor of the heat pump and the expander of the organic Rankine cycle in one single machine is another complex task to be considered. Especially the lubrication system has to fulfill the demands of both modes, thus innovative designs of the oil supply and separation are shown, like parallel and serial layouts.

It is demonstrated that hexagonal GaN can be obtained under ammonothermal conditions (125 MPa and 723 K) using Ba(NH2)2 as mineralizer. The hexagonal wurtzite-type GaN crystallites are several µm in diameter, as examined by scanning electron microscopy. This is to our knowledge the first successful ammonothermal GaN synthesis using an alkaline-earth metal as mineralizer. Ba[Ga(NH2)4]2 was identified as intermediate species in the ammonothermal synthesis process. The formation of h-GaN using Sr(NH2)2 as mineralizer was indicated only at higher temperatures above 1000 K.

In the current study, we present an accurate approach for matching the calculated thermal performance of power transformers with measurements. It is done by adapting some well-known and used assumptions for building a theoretical thermal model based on special measurements for the objective of minimum deviation $(\pm 3\mathrm {K})$. This can guarantee to meet specified temperature rises while providing an optimized high economical cooling system. The theoretical model calculated oil temperature distribution in medium power transformers. The model handles different winding designs and arrangements and solves for multilayer top-oil temperatures in a matrix form. It also calculates the temperature distribution in radiators, which can easily be validated during temperature rise test. First, the winding temperature is calculated, then the measured data from cooling-curves of a set of different transformer designs is inserted in the model. This implies correcting the calculated gradient and recalculating the top-oil temperatures. The model however is under development and in validation with a set of new manufactured transformers in parallel.

A high viscosity index (VI) is crucial for lubricants in industrial gearboxes exposed to changing load or weather conditions. Especially in the field of wind turbine oil, viscosity indices of 150 or higher are demanded to reduce power losses and ensure reliability at the same time. In this context, the use of dissolved CO2 to improve viscosity–temperature behavior has been investigated for task-specific, halogen-free ionic liquids and benchmarked against poly(α-olefins). By measuring the viscosity and density of the lubricants with dissolved CO2, it was proven that the VI can be increased significantly, even at moderate pressures. In addition, measurements and simulation on CO2 solubility and studies on corrosion and tribology under CO2 pressure are presented.

Quantitative data on the solubility of GaN in supercritical ammonia using NH 4 F as mineralizer are reported. The solubility is determined by in situ x-ray imaging of the dissolution of GaN single crystals. First, solubility values obtained by this method with NH 4 Cl as mineralizer are presented and discussed with respect to existing literature data. Monitoring the dissolution process in situ reveals the time when the solubility limit is reached. Thus, it allows to distinguish the saturation of the solution from dissolution based on mass transport and deposition. This is a key advantage of solubility measurements by in situ x-ray imaging compared to gravimetric methods. Our results indicate that the solubility limit is reached much faster than usually assumed in gravimetric solubility studies and the solubility of GaN in ammonothermal media is significantly lower than reported so far.