Optimal design of a heat exchanger network composed of parallel tubes

Networks of tubes for heat and mass transport abound both in nature and in engineered systems. In this paper we study the optimal design of heat exchanging flow networks composed of parallel tubes. The impact of the network size-limiting constrains (surface area, tubes diameter), fluid flow regime, as well as the fluid pumping power requirements is addressed in this paper for the cases when Biot number is smaller than 0.1

The co-production of value in digital, university–industry R&D collaborative projects

In the context of R&D collaborations between universities and industry, this study investigates the co-production process and the contextual elements that shape it. We develop a conceptual framework that builds on the service-dominant logic perspective that value propositions emerge from the interaction between co-producing parties and the integration of resources. Specifically, the framework explicates how individual, organizational, and external factors shape the type of interactions and the platforms used, the availability and use of operand and operant resources, and the organizational and individual outcomes sought in R&D collaborative projects. We investigate the interplay among these factors through group interviews with UK industry practitioners and university researchers in the context of digital research projects. The types of interaction, resources, and outcomes sought that characterize successful R&D collaboration are revealed, and the contextual aspects that enable, facilitate, block, or create barriers to successful R&D collaborations are identified. Finally, we propose five practical principles for the successful development of collaborative R&D projects within the university–industry context

The Arena: An indoor mixed reality space

ln this paper, we introduce the Arena, an indoor space for mobile mixed reality interaction. The Arena includes a new user tracking system appropriate for AR/MR applications and a new Too/kit oriented to the augmented and mixed reality applications developer, the MX Too/kit. This too/kit is defined at a somewhat higher abstraction levei, by hiding from the programmer low-level implementation details and facilitating ARJMR object-oriented programming. The system handles, uniformly, video input, video output (for headsets and monitors), sound aurelisation and Multimodal Human-Computer Interaction in ARJMR, including, tangible interfaces, speech recognition and gesture recognition.info:eu-repo/semantics/publishedVersio

Um Caso Único de Hemorragia Digestiva Alta Recorrente Causada por Duas Lesões de Dieulafoy Metácronas: a Importância da Avaliação por Ecoendoscopia

Introduction: Dieulafoy's lesion (DL) is a rare but important cause of acute, severe, life-threatening, and recurrent upper gastrointestinal bleeding (UGIB). It is frequently difficult to diagnose DL with upper GI endoscopy (UGIE), and endoscopic ultrasonography (EUS) may be valuable. There are only 2 reported bleeding cases caused by two synchronous DL but no reported cases of two metachronous DL. Case report: A 28-year-old healthy male presented with acute severe UGIB. UGIE was inconclusive. Systematic EUS mapping identified a gastric DL. After several attempts of EUS-guided hemostasis, DL was marked using a through-the-scope clip and the patient underwent successful transcatheter arterial embolization (TAE). Three years later, a new severe UGIB episode was caused by a second gastric DL in a different location, which was identified and marked by EUS and further successfully treated through TAE. The patient maintained follow-up without evidence of further bleeding. Discussion/conclusion: The authors report a unique case of severe, recurrent UGIB caused by two metachronous gastric DL lesions. The importance of systematic EUS scanning for diagnosis, treatment, and follow-up of DL is emphasized, as well as the potential influence in the outcome of other techniques like angiographic embolization.info:eu-repo/semantics/publishedVersio

Design of a high power production target for the Beam Dump Facility at CERN

The Beam Dump Facility (BDF) project is a proposed general-purpose facility at CERN, dedicated to beam dump and fixed target experiments. In its initial phase, the facility is foreseen to be exploited by the Search for Hidden Particles (SHiP) experiment. Physics requirements call for a pulsed 400 GeV/c proton beam as well as the highest possible number of protons on target (POT) each year of operation, in order to search for feebly interacting particles. The target/dump assembly lies at the heart of the facility, with the aim of safely absorbing the full high intensity Super Proton Synchrotron (SPS) beam, while maximizing the production of charmed and beauty mesons. High-Z materials are required for the target/dump, in order to have the shortest possible absorber and reduce muon background for the downstream experiment. The high average power deposited on target (305 kW) creates a challenge for heat removal. During the BDF facility Comprehensive Design Study (CDS), launched by CERN in 2016, extensive studies have been carried out in order to define and assess the target assembly design. These studies are described in the present contribution, which details the proposed design of the BDF production target, as well as the material selection process and the optimization of the target configuration and beam dilution. One of the specific challenges and novelty of this work is the need to consider new target materials, such as a molybdenum alloy (TZM) as core absorbing material and Ta2.5W as cladding. Thermo-structural and fluid dynamics calculations have been performed to evaluate the reliability of the target and its cooling system under beam operation. In the framework of the target comprehensive design, a preliminary mechanical design of the full target assembly has also been carried out, assessing the feasibility of the whole target system.Comment: 17 pages, 18 figure

Terapêutica intravesical com bacilo de Calmette-Guérin no tratamento do carcinoma da bexiga / o que sabemos até agora

AbstractIntroductionThe use of intravesical Bacillus Calmette-Guérin is a valid option in the treatment of non-muscle invasive bladder tumors, making it the main subject of a lot of publications. The aim of the present study is to review and consolidate the data available about this subject.MethodsA review of the data available was made on PubMed with the keywords: “intravesical BCG” and “non-muscle invasive bladder cancer”. Original and review articles written in English or Portuguese were selected. We present the discussion alongside the results for structural purposes.Results and discussionScientific evidence strongly advises in favor of BCG use on intermediate and high risk tumors, due to its impact on the recurrence and possibly on the progression rates. It is important to be watchful for possible local and systemic side effects, that when detected call for a rightful therapeutically decision alongside the recommended schemes.ConclusionThe use of intravesical BCG with therapeutically purposes has strong evidence on the non-muscle invasive bladder tumors. More studies are needed in order to better understand the best administration scheme and its mechanism of action

Reciprocal stream-riparian fluxes: effects of distinct exposure patterns on litter decomposition

Resource fluxes at the stream–riparian interface are a vital contributor to both systems’ energy budgets. The effect of distinct litter exposure patterns—direction of the riparia–stream movement and duration of exposure at each habitat—however, remains to be elucidated. In this field experiment, oak leaves in fine and coarse mesh bags were either exposed to a stream-to-riparia or riparia-to-stream movement sequence for distinct periods (2:6, 4:4, or 6:2 weeks). After 8 weeks, ash-free mass loss, microbial activity, and fungal biomass were compared in leaves undergoing inverse movement sequences (e.g., 2-week exposure to the riparian area at the beginning vs. end of the colonization period). Mass loss in coarse mesh bags was negatively affected when leaves were previously exposed to a short (2 weeks) terrestrial pre-conditioning period, despite higher microbial activity and fungal biomass, when compared to the inverse movement. This effect on mass loss was neutralized by longer terrestrial exposures that likely allowed for a more thorough conditioning of the leaves, through extended leaching and terrestrial microbial colonization. Our results suggest that terrestrial pre-conditioning periods of < 2 weeks lead to litter-quality legacy effects in tough leaves, to which aquatic communities respond through lower substrate degradation efficiency, hindering stream decomposition. Contrastingly, oak aquatic pre-conditioning, regardless of duration, provides riparian communities with a high-quality resource, promoting litter processing through grazing behavior. As climate-induced hydrological shifts may result in altered provision/quality of detritus subsidies at the stream–riparia interface, we suggest that assessments of decomposition dynamics should consider the entire litter conditioning history

Probabilistic model for the representation of the reservoir water level of concrete dams during normal operation periods

The dam’s reservoir water level varies over the year according to the water inflow and outflow, as a function of environmental events but also of dam exploitation management policy and human decisions. In the Portuguese dam safety regulation (RSB 2007), the normal water level (NWL) is considered as the optimum exploitation level. However, as proved by the continuous monitoring over the lifetime of a set of dams, the NWL is occasionally exceeded for non-negligible time periods. The reservoir water level, to which the water pressure on the upstream face is related, is a fundamental parameter for the safety and reliability analysis of concrete dams. When water-induced actions are considering the leading loads, only the maximum reservoir water level, usually associated with a high-return-period flood, is relevant. However, for other combinations, in particular, earthquake scenarios, the consideration of the variability of the water level over time is crucial. In reliability analysis of concrete dams, the reservoir water level has been considered either as a deterministic variable, once the loading scenario analyzed assume water-induced actions as leading loads (Westberg 2010), or as a random variable defined using hydrological site information of a specific study case (Altarejos et al. Structural Safety 36-37:1–13 2012). This work proposes a probabilistic model of the reservoir water level of any new dam based only on its geometrical properties, which provides a low-cost alternative to in-depth hydrological analysis. The proposed model can be useful in two stages of the lifecycle of dams: (i) initial design and feasibility stages, and (ii) routine safety assessment of existing structures, as in both stages the costs of a complete hydrological analysis is too high for the level of detail required. For that, the recorded reservoir water level of 27 Portuguese large concrete dams is used. A normalized sinusoidal model, with annual period, is adjusted to the reservoir water level annual history of those dams by beta regression. Generally, a good agreement between observations and the proposed model, for most of the annual adjustments, was achieved. The distribution parameters of the random variables were estimated through the maximum likelihood estimation (MLE) method. The physical, model and statistical uncertainties were quantified and can now be included in a reliability analysis procedur

Shape optimization for the generalized Graetz problem

We apply shape optimization tools to the generalized Graetz problem which is a convection-diffusion equation. The problem boils down to the optimization of generalized eigen values on a two phases domain. Shape sensitivity analysis is performed with respect to the evolution of the interface between the fluid and solid phase. In particular physical settings, counterexamples where there is no optimal domains are exhibited. Numerical examples of optimal domains with different physical parameters and constraints are presented. Two different numerical methods (level-set and mesh-morphing) are show-cased and compared

Plant genotype influences aquatic-terrestrial ecosystem linkages through timing and composition of insect emergence

Terrestrial leaf litter provides aquatic insects with an energy source and habitat structure,and species differences in litter can influence aquatic insect emergence. Emerging insects also provide energy to riparian predators. We hypothesized that plant genetics would influence the composition and timing of emerging insect communities among individual genotypes of Populus angustifolia varying in litter traits. We also compared the composition and timing of emerging insect communities on litter from mixed genotypes of three cross types of a hybridizing cottonwood complex: P. angustifolia, P. fremontii, and their F1 hybrids. Using litter harvested from an experimental common garden, we measured emerging insect community composition, abundance, and production for 12 weeks in large litter packs affixed with emergence traps. Five major findings emerged. (1) In support of the genetic similarity hypothesis, we found that, among P. angustifolia tree genotypes, litter from more closely related genotypes had more similar litter thickness, nitrogen concentrations, decomposition rates, and emerging insect communities. (2) Genetic similarity was not correlated with other litter traits, although the litter fungal community was a strong predictor of emerging insect communities. (3) Litter decomposition rate, which was the strongest predictor of emerging aquatic insect communities, was influenced by litter thickness, litter N, and the litter fungal community. (4) In contrast to strong community composition differences among P. angustifolia genotypes, differences in community composition between P. fremontii and P. angustifolia were only marginally significant, and communities on F1 hybrids were indistinguishable from P. angustifolia despite genetic and litter trait differences. (5) Mixed litter packs muted the genetic effects observed in litter packs con- sisting of single genotypes. These results demonstrate that the genetic structure of riparian forests can affect the composition and timing of aquatic insect emergence. Because many riparian trees are clonal, including P. angustifolia, large clone size is likely to result in patches of genetically structured leaf litter that may influence the timing and composition of insect emergence within watersheds. Riparian restoration efforts incorporating different tree genotypes could also influence the biodiversity of emerging aquatic insects. Our work illustrates the importance of plant genes for community and ecosystem processes in riparian corridors