Catalytic Ignition and Upstream Reaction Propagation in Monolith Reactors

Using numerical simulations, this work demonstrates a concept called back-end ignition for lighting-off and pre-heating a catalytic monolith in a power generation system. In this concept, a downstream heat source (e.g. a flame) or resistive heating in the downstream portion of the monolith initiates a localized catalytic reaction which subsequently propagates upstream and heats the entire monolith. The simulations used a transient numerical model of a single catalytic channel which characterizes the behavior of the entire monolith. The model treats both the gas and solid phases and includes detailed homogeneous and heterogeneous reactions. An important parameter in the model for back-end ignition is upstream heat conduction along the solid. The simulations used both dry and wet CO chemistry as a model fuel for the proof-of-concept calculations; the presence of water vapor can trigger homogenous reactions, provided that gas-phase temperatures are adequately high and there is sufficient fuel remaining after surface reactions. With sufficiently high inlet equivalence ratio, back-end ignition occurs using the thermophysical properties of both a ceramic and metal monolith (coated with platinum in both cases), with the heat-up times significantly faster for the metal monolith. For lower equivalence ratios, back-end ignition occurs without upstream propagation. Once light-off and propagation occur, the inlet equivalence ratio could be reduced significantly while still maintaining an ignited monolith as demonstrated by calculations using complete monolith heating

Transient Catalytic Combustor Model With Detailed Gas and Surface Chemistry

In this work, we numerically investigate the transient combustion of a premixed gas mixture in a narrow, perfectly-insulated, catalytic channel which can represent an interior channel of a catalytic monolith. The model assumes a quasi-steady gas-phase and a transient, thermally thin solid phase. The gas phase is one-dimensional, but it does account for heat and mass transfer in a direction perpendicular to the flow via appropriate heat and mass transfer coefficients. The model neglects axial conduction in both the gas and in the solid. The model includes both detailed gas-phase reactions and catalytic surface reactions. The reactants modeled so far include lean mixtures of dry CO and CO/H2 mixtures, with pure oxygen as the oxidizer. The results include transient computations of light-off and system response to inlet condition variations. In some cases, the model predicts two different steady-state solutions depending on whether the channel is initially hot or cold. Additionally, the model suggests that the catalytic ignition of CO/O2 mixtures is extremely sensitive to small variations of inlet equivalence ratios and parts per million levels of H2

Simulation of Fluid Flow and Collection Efficiency for an SEA Multi-element Probe

Numerical simulations of fluid flow and collection efficiency for a Science Engineering Associates (SEA) multi-element probe are presented. Simulation of the flow field was produced using the Glenn-HT Navier-Stokes solver. Three dimensional unsteady results were produced and then time averaged for the collection efficiency results. Three grid densities were investigated to enable an assessment of grid dependence. Collection efficiencies were generated for three spherical particle sizes, 100, 20, and 5 micron in diameter, using the codes LEWICE3D and LEWICE2D. The free stream Mach number was 0.27, representing a velocity of approximately 86 ms. It was observed that a reduction in velocity of about 15-20 occurred as the flow entered the shroud of the probe.Collection efficiency results indicate a reduction in collection efficiency as particle size is reduced. The reduction with particle size is expected, however, the results tended to be lower than previous results generated for isolated two-dimensional elements. The deviation from the two-dimensional results is more pronounced for the smaller particles and is likely due to the effect of the protective shroud

Intravascular Ultrasound in the Detection of Bridging Stent Graft Instability During Fenestrated and Branched Endovascular Aneurysm Repair Procedures: A Multicentre Study on 274 Target Vessels

Objective: The use of intravascular ultrasound (IVUS) reduces contrast medium use and radiation exposure during conventional endovascular aneurysm repair (EVAR). The aim of this study was to evaluate the safety and efficacy of IVUS in detecting bridging stent graft (bSG) instability during fenestrated and branched EVAR (F/B-EVAR). Methods: This was a prospective observational multicentre study. The following outcomes were evaluated: (1) technical success of the IVUS in each bSG, (2) IVUS findings compared with intra-operative angiography, (3) incidence of post-operative computed tomography angiography (CTA) findings not detected with IVUS, and (4) absence of IVUS related adverse events. Target visceral vessel (TVV) instability was defined as any branch or fenestration issues requiring an additional manoeuvre or re-intervention. Any IVUS assessment that detected stenosis, kinking, or any geometric TVV issue was considered to be branch instability. All procedures were performed in ad hoc hybrid rooms. Results: Eighty patients (69% males; median age 72 years; interquartile range 59, 77 years) from four aortic centres treated with F/B-EVAR between January 2019 and September 2021 were included: 70 BEVAR (21 off the shelf; 49 custom made), eight FEVAR (custom made), and two F/B-EVAR (custom made), for a total of 300 potential TVVs. Two TVVs (0.7%) were left unstented and excluded from the analysis. The TVVs could not be accessed with the IVUS catheter in seven cases (2.3%). Furthermore, 17 (5.7%) TVVs could not be examined due to a malfunction of the IVUS catheter. The technical success of the IVUS assessment was 91.9% (274/298), with no IVUS related adverse events. Seven TVVs (2.5%) showed signs of bSG instability by means of IVUS, leading to immediate revisions. The first post-operative CTA at least 30 days after the index procedure was available in 268 of the 274 TVVs originally assessed by IVUS. In seven of the 268 TVVs (2.6%) a re-intervention became necessary due to bSG instability. Conclusion: This study suggests that IVUS is a safe and potentially valuable adjunctive imaging technology for intra-operative detection of TVV instability. Further long term investigations on larger cohorts are required to validate these promising results and to compare IVUS with alternative technologies in terms of efficiency, radiation exposure, procedure time, and costs

The controlled-drift detector,”

Abstract A new position-sensing X-ray detector is presented. The novel device is called Controlled-Drift Detector (CDD). The detector is fully depleted and is operated by switching between integration and drift modes. The relevant details of the detector design are discussed. A complete experimental characterization of the fast readout of the integrated signal charges achievable with static drift "elds in the range 100}400 V/cm has been carried out. Preliminary measurements to evaluate the charge-handling capacity are also shown. The CDD can provide unambiguous two-dimensional position measurement, high-resolution X-ray spectroscopy and time resolution below 1 ms

Portable Unit for Metabolic Analysis

The Portable Unit for Metabolic Analysis measures human metabolic function. The compact invention attaches to the face of a subject and it is able to record highly time-resolved measurements of air temperature and pressure, flow rates during inhalation and exhalation, and oxygen and carbon dioxide partial pressure. The device is capable of `breath-by-breath` analysis and `within-breath` analysis at high temporal resolution

Silicon pixel detector for the TTF-FEL beam trajectory monitor

Abstract In order to achieve the high brightness promised by the single-pass Free Electron Laser (FEL) at the TESLA Test Facility (TTF) at DESY, the electron beam position must be controlled better than 10 m over a distance of 15 m. The design of a monitor system with this accuracy is described. The silicon pixel detector, which is critical to this monitor, must have a position resolution of 1 m and an excellent sensitivity for soft X-rays above 150 eV. The silicon pixel detector and its readout electronics are also described

Lunar Surface Systems Supportability Technology Development Roadmap

The Lunar Surface Systems Supportability Technology Development Roadmap is a guide for developing the technologies needed to enable the supportable, sustainable, and affordable exploration of the Moon and other destinations beyond Earth. Supportability is defined in terms of space maintenance, repair, and related logistics. This report considers the supportability lessons learned from NASA and the Department of Defense. Lunar Outpost supportability needs are summarized, and a supportability technology strategy is established to make the transition from high logistics dependence to logistics independence. This strategy will enable flight crews to act effectively to respond to problems and exploit opportunities in an environment of extreme resource scarcity and isolation. The supportability roadmap defines the general technology selection criteria. Technologies are organized into three categories: diagnostics, test, and verification; maintenance and repair; and scavenge and recycle. Furthermore, "embedded technologies" and "process technologies" are used to designate distinct technology types with different development cycles. The roadmap examines the current technology readiness level and lays out a four-phase incremental development schedule with selection decision gates. The supportability technology roadmap is intended to develop technologies with the widest possible capability and utility while minimizing the impact on crew time and training and remaining within the time and cost constraints of the program

Эффективность учебно-диспансерной работы в сельских районах и ее роль в подготовке врача-стоматолога

Важнейшими предпосылками дальнейшего усовершенствования подготовки специалистов является укрепление связи учебного процесса с учебно-диспансерной и лечебной работой студентов в сельской местности, приближение будущего врача к предстоящей практической деятельности в условиях сельской больницы. Успешное ее решение, по нашему опыту, способствует достаточно высокий исходный уровень теоретических знаний у студентов, умение использовать их на практике, овладение необходимыми мануальными навыками. Кроме того, большое значение имеет консультации профессора, доцентов, опытных ассистентов. В современной стратегии профилактической деятельности важное место принадлежит всеобщей диспансеризации населения, которая предполагает ежегодное медицинское обследование каждого жителя с целью выявления лиц с ранними проявлениями заболеваний челюстно-лицевой системы. В 1987/88 г.г. в районах Полтавской области осмотрено 17157 человек. Наряду с диспансерным осмотром организованных групп (механизаторов, животноводов, ветеранов войны и труда) осмотрено 7 635 детей в детских садах, школах, ПТУ. Из числа осмотренных 11 215 нуждались в санации полости рта. Санировано 3 741 человек. Причем вся эта работа проводилась с учетом режима занятий и занятости учащихся на осенних сельхозработах; The most important prerequisites for further improvement of the training of specialists are to strengthen the connection between the educational process and the educational and clinical work of students in rural areas, the approach of the future doctor to the forthcoming practical activities in a rural hospital. Its successful solution, in our experience, contributes to a sufficiently high initial level of theoretical knowledge among students, the ability to use them in practice, mastering the necessary manual skills. In addition, the importance of consulting the professor, associate professors, experienced assistants. In the current strategy of preventive activities, an important place belongs to the universal medical examination of the population, which involves an annual medical examination of each resident in order to identify those with early manifestations of diseases of the maxillofacial system. In 1987/88. in the Poltava region, 17157 people were examined. Along with the dispensary examination of organized groups (machine operators, livestock breeders, veterans of war and labor) 7,635 children were examined in kindergartens, schools, vocational schools. Among those examined, 1115 were in need of sanitation of the oral cavity. 3 741 people were sanitized. And all this work was carried out taking into account the mode of employment and employment of students in the autumn agricultural work; Найважливішими передумовами подальшого удосконалення підготовки фахівців є зміцнення зв'язку навчального процесу з навчально-диспансерної і лікувальною роботою студентів в сільській місцевості, наближення майбутнього лікаря до майбутньої практичної діяльності в умовах сільської лікарні. Успішне її рішення, за нашим досвідом, сприяє досить високий вихідний рівень теоретичних знань у студентів, вміння використовувати їх на практиці, оволодіння необхідними чуттєвими навичками. Крім того, велике значення має консультації професора, доцентів, досвідчених асистентів. У сучасній стратегії профілактичної діяльності важливе місце належить загальної диспансеризації населення, яка передбачає щорічне медичне обстеження кожного жителя з метою виявлення осіб з ранніми проявами захворювань щелепно-лицьової системи. У 1987/88 р.р. в районах Полтавської області оглянуто 17157 осіб. Поряд з диспансерним оглядом організованих груп (механізаторів, тваринників, ветеранів війни та праці) оглянуто 7 635 дітей в дитячих садах, школах, ПТУ. З числа оглянутих 11 215 потребували санації порожнини рота. Санувати 3 741 осіб. Причому вся ця робота проводилася з урахуванням режиму занять і зайнятості учнів на осінніх сільськогосподарських роботах