Heat transfer from a flat plate in inhomogeneous regions of grid-generated turbulence

Experiments on the convective heat transfer from a flat plate, vertically mounted and parallel to the flow in a wind tunnel, were carried out via Infra-Red thermography and hot-wire anemometry. The Reynolds number based on the inflow velocity and on the length of the plate was about 5×1055×105. A step near the leading edge of the plate was used to promote transition to turbulence, with tripping effects on the heat transfer coefficients shown to be negligible for more than 90% of the plate’s length. Different types of grids, all with same blockage ratio σg=28%σg=28%, were placed upstream of the plate to investigate their potential to enhance the turbulent heat transfer. These grids were of three classes: regular square-mesh grids (RGs), single-square grids (SSGs) and multi-scale inhomogeneous grids (MIGs). The heat transfer coefficients at the mid-length of the plate were correlated with the mean velocity and the turbulence intensity of the flow at a distance from the plate at which the ratio of the standard deviations of the streamwise and wall-normal velocity fluctuations began to increase. However, the heat transfer was shown to be insensitive to the turbulence intensity of the incoming flow in close proximity of the tripping step. Furthermore, the integral length scale of the streamwise turbulent fluctuations was found not to affect the heat transfer results, both near the tripping step and in the well-developed region on the plate. For the smallest plate-to-grid distance, the strongest heat transfer enhancement (by roughly 30%) with respect to the no-grid case was achieved with one of the SSGs. For the largest plate-to-grid distance, the only grid producing an appreciable increase (by approximately 10%) of the heat transfer was one of the MIGs. The present results demonstrate that MIG design can be optimised to maximise the overall heat transfer from the plate. A MIG that produces a uniform transverse mean shear, which is approximately preserved over significant downstream distances from the grid and with a velocity decreasing with distance from the plate, allows a sustained heat transfer enhancement, in contrast to all other grid designs tested here. The most efficient configuration for a MIG is one for which the section of the grid that has lower blockage and thicker bars is adjacent to the plate

Experimental Research Using of MQL in Metal Cutting

In this paper an effect of using of minimal quantity lubrication (MQL) technique in turning operations is presented. Experimental research was performed on carbon steel C45E. Technological parameters: depth of cut, feed rate and cutting speed were adjusted to semi-machining and roughing. Higher values ​​of feed and cutting speed were used, than recommended from literature and different types of cooling and lubrication in turning conditions were applied. As a conventional procedure and technology, lubrication with flooding was applied. As special lubrication the MQL technique was used. During research, monitoring of the cutting force, chip shape, tool wear and surface roughness was performed. Relations between parameters, material machinability and economy of process were analyzed

How Physicality Enables Trust: A New Era of Trust-Centered Cyberphysical Systems

Multi-agent cyberphysical systems enable new capabilities in efficiency, resilience, and security. The unique characteristics of these systems prompt a reevaluation of their security concepts, including their vulnerabilities, and mechanisms to mitigate these vulnerabilities. This survey paper examines how advancement in wireless networking, coupled with the sensing and computing in cyberphysical systems, can foster novel security capabilities. This study delves into three main themes related to securing multi-agent cyberphysical systems. First, we discuss the threats that are particularly relevant to multi-agent cyberphysical systems given the potential lack of trust between agents. Second, we present prospects for sensing, contextual awareness, and authentication, enabling the inference and measurement of ``inter-agent trust" for these systems. Third, we elaborate on the application of quantifiable trust notions to enable ``resilient coordination," where ``resilient" signifies sustained functionality amid attacks on multiagent cyberphysical systems. We refer to the capability of cyberphysical systems to self-organize, and coordinate to achieve a task as autonomy. This survey unveils the cyberphysical character of future interconnected systems as a pivotal catalyst for realizing robust, trust-centered autonomy in tomorrow's world

Possibility of achieving an acceptable response rate of gas-filled surge arresters by substitution of alpha radiation sources by selection of electrode material and the electrode surface topography

The possibility of substituting the usage of a radioactive a-source to improve the characteristics of the gas surge arrester is considered in this paper. The solution to this problem is sought in the engineering of the characteristics by applying different electrode materials and varying electrode surface topography. Materials that differ in the output work value were examined. The electrode surface topographies were either polished, or with engraved regular spikes, or with polished cavities. The paper is mostly experimental in nature. The experiments were performed under well-controlled laboratory conditions. The measurement uncertainty of the experimental procedure was satisfactory. Experimental results were processed by sophisticated statistical methods of low statistical unreliability. The obtained results show that it is possible to avoid the installation of a radioactive source in the gas surge arresters and how it should be done. In this way, a possible contamination of the natural environment with extremely dangerous alpha - radioactive sources would be avoided

Information Leakage Games

We consider a game-theoretic setting to model the interplay between attacker and defender in the context of information flow, and to reason about their optimal strategies. In contrast with standard game theory, in our games the utility of a mixed strategy is a convex function of the distribution on the defender's pure actions, rather than the expected value of their utilities. Nevertheless, the important properties of game theory, notably the existence of a Nash equilibrium, still hold for our (zero-sum) leakage games, and we provide algorithms to compute the corresponding optimal strategies. As typical in (simultaneous) game theory, the optimal strategy is usually mixed, i.e., probabilistic, for both the attacker and the defender. From the point of view of information flow, this was to be expected in the case of the defender, since it is well known that randomization at the level of the system design may help to reduce information leaks. Regarding the attacker, however, this seems the first work (w.r.t. the literature in information flow) proving formally that in certain cases the optimal attack strategy is necessarily probabilistic

Incremental proximal methods for large scale convex optimization

Laboratory for Information and Decision Systems Report LIDS-P-2847We consider the minimization of a sum∑m [over]i=1 fi (x) consisting of a large number of convex component functions fi . For this problem, incremental methods consisting of gradient or subgradient iterations applied to single components have proved very effective. We propose new incremental methods, consisting of proximal iterations applied to single components, as well as combinations of gradient, subgradient, and proximal iterations. We provide a convergence and rate of convergence analysis of a variety of such methods, including some that involve randomization in the selection of components.We also discuss applications in a few contexts, including signal processing and inference/machine learning.United States. Air Force Office of Scientific Research (grant FA9550-10-1-0412

The hurdles of academic publishing from the perspective of journal editors: a case study

In this paper, we provide insight into the editorial process as seen from the perspective of journal editors. We study a dataset obtained from the Journal of the Serbian Chemical Society, which contains information about submitted and rejected manuscripts, in order to find differences between local (Serbian) and external (non-Serbian) submissions. We show that external submissions (mainly from India, Iran and China) constitute the majority of all submissions, while local submissions are in the minority. Most of submissions are rejected for technical reasons (e.g. wrong manuscript formatting or problems with images) and many users resubmit the same paper without making necessary corrections. Manuscripts with just one author are less likely to pass the technical check, which can be attributed to missing metadata. Articles from local authors are better prepared and require fewer resubmissions on average before they are accepted for peer review. The peer review process for local submissions takes less time than for external papers and local submissions are more likely to be accepted for publication. Also, while there are more men than women among external users, this trend is reversed for local users. In the combined group of local and external users, articles submitted by women are more likely to be published than articles submitted by men

PREGLED BAKTERIJSKIH I VIRUSNIH OBOLJENJA SVINJA U EKSTENZIVNOM I INTENZIVNOM NAČINU DRŽANJA

U ovom radu je dat pregled oboljenja svinja bakterijske i virusne etiologije kojamogu da budu prisutna u ekstenzivnom i intenzivnom načinu držanja. Dobrozdravlje svinja je uslov dobre reprodukcije, odnosno rentabilne proizvodnje. Zdravljezavisi od uslova držanja, nege, ishrane, kontrole i zdravstvene zaštite. Veliki brojbolesti koje su prisutne na farmama svinja industrijskog tipa, moguće je primenomprofilaktičkih i terapeutskih mera, kao i pojačanom kontrolom stručnih službi držatipod kontrolom. Odgovarajućom saradnjom vlasnika farmi sa stručnim službama, uzpoštovanje i sprovođenje stručnih saznanja, te primenom niza biotehničkih mera istavljanjem akcenta na preveniranje bolesti svinja, a u cilju promocije dobrog zdravljasvinja, moguće je unaprediti proizvodnju. U ovom preglednom radu dali smo presekoboljenja bakterijske i virusne etilogije koje se srecu na komercijalnim farmama i uekstenzivnom načinu držanja