EXPERIMENTAL STUDY TO DETERMINE THE LOCAL CONDENSATION HEAT TRANSFER COEFFICIENTE FOR R134A FLOWING THROUGH A 4.8 MM INTERNAL DIAMETER SMOOTH HORIZONTAL TUBE

Refrigerant fluid R134a is commonly one of the most utilised invapour compression cycles wordlide, wheter in dommestic HVAC orautomotive regrigeration systems. This paper’s goal is toexperimetnally determine the fluid local condensation Heat TransferCoefficient (HTC), in several flor regimes. In this work, the mass fluxwas equal to 200, 250 and 300 kg/(m2s) and the fluid flowedthrough a smooth, horizontal 4.8 mm internal diameter aluminiumpipe, during which its vapour quality varied along the entire qualityrange. A purpose built test rig was developed, in which fluidconditions were constantly monitored and controlled. Throughmeasurements in temperature and pressure, an energy balance wasused to calculate experimentally the local heat transfer coeeficient.Average results for the unit quality range equalled to 3781 , 3459 and3944 W/m2K for saturation temperature equal to 30 C and theaforementioned mass velocities. Likewise, at 35C the averages HTCfound were 2903, 3141 and 3898 W/m2K at the same mass fluxrates. Later on, the experimental results were compared to tencommonly used HTC correlation found in relevant references,with Chato’s correlation returning the best fitting

EXPERIMENTAL STUDY OF THE PRESSURE DROP OF THE ECOFLUID R1234YF COMPARED TO THE FLUID R134A IN SMOOTH TUBES WITH 4.8MM INTERNAL DIAMMETER

The refrigerant fluid R1234yf is a hydrofluorefine with zero potential for degradation of the ozone layer and low potential for global warming. It is one of the potential substitutes for the currently used R134a in automotive systems. In this work, the pressure drop suffered by the fluids R134a and R1234yf when flowing in a test section through a pipe with a 4.8 mm internal diameter was measured. The pressure drop was plotted as a function of the void fraction at the exit of the test section and the values were compared concerning the change in mass flux, change in saturation temperature, and comparatively between R1234yf and R134a. A significant increase in pressure drop was observed by the increases of the mass flux, showing an increment of 155.46% of the pressure loss from 200 to 300 kg·m-2·s-1 for R1234yf at 35ºC and 161.07% for R134a in the same conditions. Despite being high, those values are expected since increasing mass flux also increases the friction between both phases. On the other hand, by increasing the saturation temperature, the pressure drop is slightly lower once the differences between the densities of the liquid and vapor phases are reduced. Compared with R134a, the R1234yf ecofluid presents less pressure drop, showing a reduction of 24% for 300 kg·m-2·s-1

In-network processing of nearest neigbor queries for wireless sensor networks

Abstract. Wireless sensor networks have been widely used for civilian and military applications, such as environmental monitoring and vehicle tracking. The sensor nodes in the network have the abilities to sense, store, compute and communicate. To enable object tracking applications, spatial queries such as nearest neighbor queries are to be supported in these networks. The queries can be injected by the user at any sensor node. Due to the limited power supply for sensor nodes, energy efficiency is the major concern in query processing. Centralized data storage and query processing schemes do not favor energy efficiency. In this paper, we propose a distributed scheme called DNN for in-network processing of nearest neighbor queries. A cost model is built to analyze the performance of DNN. Experimental results show that DNN outperforms the centralized scheme significantly in terms of energy consumption and network lifetime.

NEAT-FT: the European fiber link collaboration

The development of clocks based on optical transitions during the past three decades culminates in the availability of optical clocks with unprecedented stability and uncertainty . Simultaneously, increasing requirements for accurate time and frequency signals, e.g. for tests of fundamental physics or novel applications in relativistic geodesy, put forward new challenges. Typically, such applications rely on the comparison of two remote clocks. Thus, major challenges are how to synchronize these clocks over long distances or how to get the time or frequency signal of a clock to the location where it is required. It is generally agreed that optical fiber links are an excellent alternative to established satellite based distant clock comparison and synchronization techniques. A European joint research project called Network for European Accurate Time and Frequency Transfer (NEAT-FT) has been initiated in 2011 to lay the foundations for a novel approach to disseminate high-precision timing and ultrastable frequency signals by using existing fiber infrastructure. Since Europe has a large number of modern ultra-precise clocks, special emphasis is put on the development of new techniques for time transfer and phase-coherent comparison of remotely located optical clocks and the feasibility of a European fibre network connecting optical clocks in Europe. This talk highlights recent achievements and discusses some applications and prospects

Homicide in Canada and the crime drop

In contrast to the Canadian crime drop of the 1990s, homicide appeared as an anomaly with a peak in the 1970s. Yet previous studies tend to refer only to completed homicides, and here we also include attempts. The resulting trend is remarkably similar to that in Canadian property crime for five decades. This seems unlikely to be a coincidence and we speculate about a causal link

A clock network for geodesy and fundamental science

Leveraging the unrivaled performance of optical clocks in applications in fundamental physics beyond the standard model, in geo-sciences, and in astronomy requires comparing the frequency of distant optical clocks truthfully. Meeting this requirement, we report on the first comparison and agreement of fully independent optical clocks separated by 700 km being only limited by the uncertainties of the clocks themselves. This is achieved by a phase-coherent optical frequency transfer via a 1415 km long telecom fiber link that enables substantially better precision than classical means of frequency transfer. The fractional precision in comparing the optical clocks of three parts in $10^{17}$ was reached after only 1000 s averaging time, which is already 10 times better and more than four orders of magnitude faster than with any other existing frequency transfer method. The capability of performing high resolution international clock comparisons paves the way for a redefinition of the unit of time and an all-optical dissemination of the SI-second.Comment: 14 pages, 3 figures, 1 tabl

Family coordination in families who have a child with autism spectrum disorder

Little is known about the interactions of families where there is a child with autism spectrum disorder (ASD). The present study applies the Lausanne Trilogue Play (LTP) to explore both its applicability to this population as well as to assess resources and areas of deficit in these families. The sample consisted of 68 families with a child with ASD, and 43 families with a typically developing (TD) child. With respect to the global score for family coordination there were several negative correlations: the more severe the symptoms (based on the child’s ADOS score), the more family coordination was dysfunctional. This correlation was particularly high when parents had to play together with the child. In the parts in which only one of the parents played actively with the child, while the other was simply present, some families did achieve scores in the functional range, despite the child’s symptom severity. The outcomes are discussed in terms of their clinical implications both for assessment and for interventio

When is a randomised controlled trial health equity relevant? Development and validation of a conceptual framework

Background Randomised controlled trials can provide evidence relevant to assessing the equity impact of an intervention, but such information is often poorly reported. We describe a conceptual framework to identify health equity-relevant randomised trials with the aim of improving the design and reporting of such trials.Methods An interdisciplinary and international research team engaged in an iterative consensus building process to develop and refine the conceptual framework via face-to-face meetings, teleconferences and email correspondence, including findings from a validation exercise whereby two independent reviewers used the emerging framework to classify a sample of randomised trials.Results A randomised trial can usefully be classified as 'health equity relevant' if it assesses the effects of an intervention on the health or its determinants of either individuals or a population who experience ill health due to disadvantage defined across one or more social determinants of health. Health equity-relevant randomised trials can either exclusively focus on a single population or collect data potentially useful for assessing differential effects of the intervention across multiple populations experiencing different levels or types of social disadvantage. Trials that are not classified as 'health equity relevant' may nevertheless provide information that is indirectly relevant to assessing equity impact, including information about individual level variation unrelated to social disadvantage and potentially useful in secondary modelling studies.Conclusion The conceptual framework may be used to design and report randomised trials. The framework could also be used for other study designs to contribute to the evidence base for improved health equity