Digital Availability of Product Information for Collaborative Engineering of Spacecraft

In this paper, we introduce a system to collect product information from manufacturers and make it available in tools that are used for concurrent design of spacecraft. The planning of a spacecraft needs experts from different disciplines, like propulsion, power, and thermal. Since these different disciplines rely on each other there is a high need for communication between them, which is often realized by a Model-Based Systems Engineering (MBSE) process and corresponding tools. We show by comparison that the product information provided by manufacturers often does not match the information needed by MBSE tools on a syntactic or semantic level. The information from manufacturers is also currently not available in machine-readable formats. Afterwards, we present a prototype of a system that makes product information from manufacturers directly available in MBSE tools, in a machine-readable way.Comment: accepted at CDVE201

A Simple Design Approach of Two-Phase Ejectors for CO2 Transcritical Heat Pumps

Integrating a two-phase ejector in mechanical vapor compression heat pumps is a practical and low-cost solution for improving performance and reducing energy consumption. Typically, using an ejector to recover part of the important pressure expansion losses in CO2 systems may improve the operating conditions of the compressor. One of the prerequisites for the success of such an application is the proper design of the ejector. This study is mainly dedicated to developing a simple approach for CO2 ejector design. The advantage of using the ejector as an expander in a transcritical CO2 heat pump is first introduced. Compressor operation is particularly improved. The development of an ejector design model for CO2 expanding from transcritical to two-phase conditions is presented. Validation of the thermodynamic model with experimental results from the literature shows the predictions to be within an acceptable range of discrepancy. The primary nozzle throat diameter calculations do not exceed ±8% of error for transcritical conditions. The error of the predicted pressure at the outlet of the ejector is in the limit of -15% to +3%. A practical design example for estimating the transcritical CO2 ejectors geometry integrated in a heat pump is presented. The results show the important decrease of primary nozzle diameters with the drop of Tevap, especially for the throat. A decrease of Dmix also occurs with Tevap and an optimal diameter is obtained for each condition considered. The design of the diffuser is based on a compromise between the outlet velocity and the length of the diffuser. The detailed design procedure with the proposed model, complemented with data from the literature, is a valuable tool for rapidly generating useful results and obtaining preliminary designs transcritical CO2 ejector

On bulk singularities in the random normal matrix model

We extend the method of rescaled Ward identities of Ameur-Kang-Makarov to study the distribution of eigenvalues close to a bulk singularity, i.e. a point in the interior of the droplet where the density of the classical equilibrium measure vanishes. We prove results to the effect that a certain "dominant part" of the Taylor expansion determines the microscopic properties near a bulk singularity. A description of the distribution is given in terms of a special entire function, which depends on the nature of the singularity (a Mittag-Leffler function in the case of a rotationally symmetric singularity).Comment: This version clarifies on the proof of Theorem

Nozzle Displacement Effects on Two-Phase Ejector Performance: An Experimental Study

Experimental results of two-phase ejector operation with refrigerant R134a as working fluid are presented in this paper. The tests carried out allowed evaluating the influence of the primary nozzle position in the mixing chamber and of operating conditions such as the thermodynamic state of the fluid at the inlet and outlet of the ejector. Various positions of the primary nozzle were tested and the operating conditions ranges were: primary inlet pressure 8.8-14.9 bars, subcooling 0.2-5 °C and ejector outlet pressure 3.7-4.7 bars. The tests have shown an optimal position of the primary nozzle (NXP=38.1 mm) in the ejector but this position was not very sensitive to operational conditions. The performance of the ejector dropped sharply when the nozzle was placed right at the inlet of the constant-area section in the mixing chamber. Pressures at the primary inlet and outlet had a limited impact on the entrainment ratio (<10%), but it was found that the level of subcooling at the inlet of the primary flow had an important influence on the entrainment ratio with a variations of about 66%. Pressure monitoring inside the ejector showed a strong relation between NXP and pressure variations in the mixing section and the diffuser

Pseudotumoral Malacoplakia of the Bladder

Malacoplakia is a rare inflammatory condition most often affecting the genitourinary system. We report the case of a 24-year-old man who presented with gross hematuria, nocturia, frequency, dysuria and considerable weight loss during the preceding three months. Digital rectal examinationshowed a solid pelvic mass. Ultrasonography and computed tomography showed calyceal dilatation on the right side and a solid bladder mass 10 cm in diameter suspicious of bladder cancer. Transurethral resection of the tumor was incomplete, due to the large volume of the bladder mass. Histological examination of the resected specimen revealed malacoplakia of the bladder. The patient was treated with fluoroquinolone and vitamin C. Follow-up at 3 months showed marked regression of the bladder mass and complete resolution of the calyceal dilatation

Towards a Lagrange-Newton approach for PDE constrained shape optimization

The novel Riemannian view on shape optimization developed in [Schulz, FoCM, 2014] is extended to a Lagrange-Newton approach for PDE constrained shape optimization problems. The extension is based on optimization on Riemannian vector space bundles and exemplified for a simple numerical example.Comment: 16 pages, 4 figures, 1 tabl

Gluten-free diet and gut microbiome

As the only effective therapy against diagnosed celiac disease (CD), the gluten-free diet (GFD) has inevitable repercussion on the gut microbiome composition and functionality. Being the cause or the consequence of the disease, an altered homeostasis of the gut microbiome usually affects CD patients at diagnosis. After describing the main features of this altered physiological condition, this review defines the main nutritional aspects of the GFD and elucidates how this diet regimen does not fully restore the optimal gut microbiome composition and functionality. Unbalanced ratios between beneficial and potentially harmful bacteria are frequently present in fecal materials, biopsy specimens and saliva, used as ecological model systems to observe CD. Metabolome analyses also show how an altered microbiome synthesize different metabolite with respect to healthy conditions. The review concludes illustrating the current supplementations (biotics family), which fortify the GFD with the aim of restoring the homeostasis of the gut microbiome

Fast Indirect GMPPT Method for PV Systems under Uniform and Partial Shading Conditions

Under Partial Shading Conditions (PSCs), conventional MPPT techniques fail to locate the Global Maximum Power Point (GMPP) for PV generators, and when PSCs change suddenly and repetitively, several GMPP tracking techniques takes time to find or miss the target. To overcome these shortcomings, this paper proposes a new and fast technique that can identify and catch very quickly the GMPP. Due to the use of a PID controller, the PV system is improved in terms of response time and becomes very fast. On the other hand, the proposed algorithm is developed upon other known algorithms and enhanced in order to identify the occurrence of PSCs and to find the GMPP. The measured points during identification and searching process are reduced which increases the power efficiency of the PV system. The time required for the algorithm to catch the GMPP is minimized by 25% compared with other works. To examine the performance of the system a hard scenario, that contains several uniform and partial shading conditions, is used. The simulation is implemented in Matlab/Simulink. The obtained results show clearly the advantage of the proposed technique over others