Linear Compressor Discharge Manifold Design For High Thermal Efficiency

In the design of hermetic compressors for household refrigeration, one important part of the overall efficiency of the machine comes from a good thermal efficiency of the discharge manifold. It is desired that the heat generated during the compression process and accumulated by the gas in the discharge chamber does not return to the compression chamber walls. If not, this heat returns to the pump, reducing volumetric efficiency. Current technologies like on/off and variable velocity compressors, normally make use of metallic parts in the discharge chamber, such parts having high thermal conduction coefficients making them less efficient. Linear compressor technology, together with the non-use of oil allows the improvement of the discharge manifold system, increasing the thermal insulation of the heat from discharge chamber to compression chamber, improving efficiency. This article aims to show the development of this improved discharge system, tests performed, and results obtained

Linear Compressor Suction Valve Optimization

Design of hermetic compressors for household refrigeration follows a common sequence that considers an initial concept, normally based on existing families. Those are then upgraded with new features, aiming improvements in efficiency, sound quality or even cost reduction. Common compressors have a cylinder head that carries discharge and suction valve. In a new and compact designs for linear compressor suction valve is placed on the top of the piston, requiring new shapes in order to make it possible to satisfy, gas flow, fatigue and dynamics requirements. This article aims to present the use of optimization procedure used to develop the suction valve design for a linear compressor, the results obtained with the optimization process, and final results in compressor, in terms of performance and noise

Radar Detection of High Concentrations of Ice Particles - Methodology and Preliminary Flight Test Results

High Ice Water Content (HIWC) has been identified as a primary causal factor in numerous engine events over the past two decades. Previous attempts to develop a remote detection process utilizing modern commercial radars have failed to produce reliable results. This paper discusses the reasons for previous failures and describes a new technique that has shown very encouraging accuracy and range performance without the need for any hardware modifications to industrys current radar designs. The performance of this new process was evaluated during the joint NASA/FAA HIWC RADAR II Flight Campaign in August of 2018. Results from that evaluation are discussed, along with the potential for commercial application, and development of minimum operational performance standards for a future commercial radar product

Male social niche conformance? Effects of manipulated opportunity for extra-pair mating on behavior and hormones of male zebra finches

Success in sperm competition is an important determinant of male fitness in mating systems with female multiplemating. Thus, sperm competition risk represents a key dimension of the male social environment to which in-dividual males are expected to adaptively adjust their reproductive phenotype. Such adaptive phenotypicadjustment we here refer to as male social niche conformance. In this pre-registered study, we investigated howmale zebra finches, Taeniopygia guttata, adjust their behavior to sperm competition risk. We experimentallymanipulated the opportunity for extra-pair mating to create two levels of sperm competition risk: 1) Single-pair,no sperm competition risk; 2) Double-pair, sperm competition risk. We compared male courtship, mate guarding,copulation rates, and aggression between the treatment groups. To identify hormonal correlates of malebehavioral adjustment, we measured plasma testosterone and corticosterone levels before and after the socialtreatment started. Contrary to our pre-registered predictions, males from the Double-pair treatment groupdecreased courtship rates compared to those from the Single-pair group, and Double-pair males responded lessaggressively towards intruders than Single-pair males. Testosterone levels decreased over the breeding cycle, butsocial treatment had no effect on either testosterone or corticosterone levels. Our results indicate that male zebrafinches do not intensify courtship or competitive reproductive behaviors, or upregulate key hormones whenanother breeding pair is present. Although we found no evidence for the predicted adaptive behavioral responsesto sperm competition risk, we show that male zebra finches plastically adjust their behavior to their socialenvironmen

Summary of the High Ice Water Content (HIWC) RADAR Flight Campaigns

NASA and the FAA conducted two flight campaigns to quantify onboard weather radar measurements with in-situ measurements of high concentrations of ice crystals found in deep convective storms. The ultimate goal of this research was to improve the understanding and develop onboard weather radar processing to detect regions of high ice water content ahead of an aircraft and enable tactical avoidance of the potentially hazardous conditions. Both High Ice Water Content (HIWC) RADAR campaigns utilized the NASA DC-8 Airborne Science Laboratory which was equipped with a Honeywell RDR-4000 weather radar and icing instruments to characterize the ice crystal clouds. The purpose of this paper is to summarize how these campaigns were conducted and highlight key results

Evaluation of radar reflectivity factor simulations of ice crystal populations from in situ observations for the retrieval of condensed water content in tropical mesoscale convective systems

This study presents the evaluation of a technique to estimate cloud condensed water content (CWC) in tropical convection from airborne cloud radar reflectivity factors at 94 GHz and in situ measurements of particle size distributions (PSDs) and aspect ratios of ice crystal populations. The approach is to calculate from each 5 s mean PSD and flight-level reflectivity the variability of all possible solutions of m(D) relationships fulfilling the condition that the simulated radar reflectivity factor (T-matrix method) matches the measured radar reflectivity factor. For the reflectivity simulations, ice crystals were approximated as oblate spheroids, without using a priori assumptions on the mass–size relationship of ice crystals. The CWC calculations demonstrate that individual CWC values are in the range ±32 % of the retrieved average CWC value over all CWC solutions for the chosen 5 s time intervals. In addition, during the airborne field campaign performed out of Darwin in 2014, as part of the international High Altitude Ice Crystals/High Ice Water Content (HAIC/HIWC) projects, CWCs were measured independently with the new IKP-2 (isokinetic evaporator probe) instrument along with simultaneous particle imagery and radar reflectivity. Retrieved CWCs from the T-matrix radar reflectivity simulations are on average 16 % higher than the direct CWCIKP measurements. The differences between the CWCIKP and averaged retrieved CWCs are found to be primarily a function of the total number concentration of ice crystals. Consequently, a correction term is applied (as a function of total number concentration) that significantly improves the retrieved CWC. After correction, the retrieved CWCs have a median relative error with respect to measured values of only −1 %. Uncertainties in the measurements of total concentration of hydrometeors are investigated in order to calculate their contribution to the relative error of calculated CWC with respect to measured CWCIKP. It is shown that an overestimation of the concentration by about +50 % increases the relative errors of retrieved CWCs by only +29 %, while possible shattering, which impacts only the concentration of small hydrometeors, increases the relative error by about +4 %. Moreover, all cloud events with encountered graupel particles were studied and compared to events without observed graupel particles. Overall, graupel particles seem to have the largest impact on high crystal number-concentration conditions and show relative errors in retrieved CWCs that are higher than for events without graupel particles

PspF-binding domain PspA1-144 and the PspA·F complex: New insights into the coiled-coil-dependent regulation of AAA+ proteins.

Phage shock protein A (PspA) belongs to the highy conserved PspA/IM30 family and is a key component of the stress inducible Psp system in Escherichia coli. One of its central roles is the regulatory interaction with the transcriptional activator of this system, the σ54 enhancer binding protein PspF, a member of the AAA+ protein family. The PspA/F regulatory system has been intensively studied and serves as a paradigm for AAA+ enzyme regulation by trans-acting factors. However, the molecular mechanism of how exactly PspA controls the activity of PspF and hence σ54-dependent expression of the psp genes is still unclear. To approach this question, we identified the minimal PspF-interacting domain of PspA, solved its structure, determined its affinity to PspF and the dissociation kinetics, identified residues that are potentially important for PspF regulation and analyzed effects of their mutation on PspF in vivo and in vitro. Our data indicate that several characteristics of AAA+ regulation in the PspA·F complex resemble those of the AAA+ unfoldase ClpB, with both proteins being regulated by a structurally highly conserved coiled-coil domain. The convergent evolution of both regulatory domains points to a general mechanism to control AAA+ activity for divergent physiological tasks via coiled-coil domains

Rebels without regret: Documentary artivism in the digital age

This article takes up the implications of the blurring of art and politics in two documentary contexts: Ai Weiwei’s art activism in China, as documented in Alison Klayman’s award-winning film Never Sorry, and the Gezi protests in Turkey, documented and disseminated virally through the Internet. Drawing parallels between the self-proclaimed hooliganism of Ai Weiwei and the Turkish protesters, who co-opted the hooligan label that the government used to incriminate them and turned it into a tool for resistance, the article argues that hooliganism is just another incarnation of unruly documentary artivism, which has become prevalent in an era of digitally mediated, global social justice movements. As an interpretive framework for understanding how documentary hooliganism operates, the article proposes Tony D. Sampson’s theory of virality and its application of Dawkins’s neo-Darwinian memetic thought contagion model to the way ideas and political gestures spread in the twenty-first century. Hooliganism, like viruses or memetic thoughts, has a self-spreading tendency; its anarchic affect is contagious and creates volatile yet powerful social encounters. Therefore, the article claims that the foregrounding of hooliganism, which is itself a phenomenon that describes ‘affective contagious encounters’ among anonymous crowds, in the artivist practices of Ai Weiwei and Turkish protesters point to the potential of unruly forms of documentation to influence and inspire selforganized mobilization

Rethinking media responsibility in the refugee ‘crisis’: a visual typology of European news

In this paper, we analyse how news images of the 2015 Syrian refugee ‘crisis’ visualise refugees and how, in so doing, they mobilise various forms of moral responsibility in ‘our’ mediated public life – various practical dispositions of action towards the misfortunes of migrants and refugees at Europe’s border. On the basis of empirical material from European news (June-December 2015), we construct a typology of visibilities of the ‘crisis’, each of which situates refugees within a different regime of visibility and claim to action: i) visibility as biological life, associated with monitorial action; ii) visibility as empathy associated with charitable action; iii) visibility as threat, associated with state security; iv) visibility as hospitality, associated with political activism; and v) visibility as selfreflexivity, associated with a post-humanitarian engagement with people like ‘us’. In conclusion, we argue that, important as these five categories of visibility are in introducing public dispositions to action towards the vulnerable, they nonetheless ultimately fail to humanise migrants and refugees. This failure to portray them as human beings with lives that are worth sharing should compel us, we urge, to radically re-think how we understand the media’s responsibility towards vulnerable others