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Abstract

The potential applications of loop heat pipes (LHPs) are the nuclear power space systems, fuel cell thermal management systems, waste heat recovery systems, medium temperature electronic systems, medium temperature military systems, among others. Such applications usually operate in temperature ranges between 500–700 K, hence it is necessary to develop an LHP system that will meet this requirement. Such a thermal management device require to meet various technical problems and challenges currently existing in the development of LHP working in medium temperatures, including: (1) selection of appropriate working fluid; (2) selection of appropriate LHP construction material; (3) construction of suitable test rig capable of testing at elevated temperatures; (4) development of new testing methods. Currently, there are no proven working fluids that can be used in LHPs in medium temperature ranges. Water can be applicable only at temperatures up to 570 K. Caesium can be applicable at temperatures above 670 K. Organic fluids usually tend to generate non-condensable gasses and/or decompose at elevated temperatures and their viscosity dramatically increases. For halides, most of them are very reactive or toxic and their full property data are not available or the majority of the physical properties are predicted, also live tests and their environmental impact data are not adequate. As for casing/LHP construction material, there are no full chemical compatibility tables with most of the medium temperature working fluids and the reactivity of fluids significantly limits the potential materials. Also, testing such an LHP is an endeavour as the reactivity of medium temperature fluids and the use of obscure metals create new challenges. Altogether creates multiple challenges in the development, testing, handling and operating of LHP in the medium temperature range.
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Bibliography

[1] Zohuri B.: Heat Pipe Design and Technology. Modern Applications for Practical Thermal Management (2nd Edn.). Springer, 2016.
[2] Zhang Y. (Ed.): Heat Pipes: Design, Applications and Technology. Nova, 2018.
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[11] Blauciak K., Szymanski P., Mikielewicz D.: The influence of loop heat pipe evaporator porous structure parameters and charge on its effectiveness for ethanol and water as working fluids. Materials 14(2021), 7029.
[12] Nikitkin M.N., Bienert W.B., Goncharov K.A.: Non condensable gases and loop heat pipe operation. SAE Tech. Pap. 981584. In: Proc. 28th Int. Conf. on Environmental Systems, 1998.
[13] Wrenn K.R., Wolf D., Kroliczek E.J.: Effect of non-condensible gas and evaporator mass on loop heat pipe performance. SAE Tech. Pap. 2000-01-2409. In: Proc. 30th Int. Conf. on Environmental Systems, 603–614, 2000.
[14] Ishikawa H., Ogushi T., Nomura T., Noda H., Kawasaki H., Yabe T.: Heat transfer characteristics of a reservoir embedded loop heat pipe (2nd report, influence of noncondensable gas on heat transfer characteristics). Heat Transf. Asian Res. 36(2007), 8, 459–473.
[15] Singh R., Akbarzadeh A., Mochizuki M.: Operational characteristics of the miniature loop heat pipe with non-condensable gases. Int. J. Heat Mass Tran. 53(2010), 17–18, 3471–3482.
[16] He J., Lin G., Bai L., Miao J., Zhang H.: Effect of non-condensable gas on the operation of a loop heat pipe. Int. J. Heat Mass Tran. 70(2014), 449–462.
[17] Prado-Montes P.: Development of an elevated temperature loop heat pipe for space applications and investigation of non-condensable gas impact on its performance. PhD thesis, Polytechnic University of Madrid, Madrid 2014.
[18] Devarakonda A., Xiong D., Beach E.D.: Intermediate temperature water heat pipe tests. AIP Conf. Proc. 746(2005), 158.
[19] Mishkinis D., Prado P., Sanz R., Radkov A., Torres A., Tjiptajardja T.: Loop heat pipe working fluids for intermediate temperature range: from –40°C to +125°C. In: Proc. 1st. Int. Conf. on Heat Pipes for Space Applications, Moscow, Sept. 2009.
[20] Mikielewicz D, Błauciak K.: Investigation of the influence of capilary effect on operation of the loop heat pipe. Arch. Thermodyn. 35(2014), 3, 59–80.
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Authors and Affiliations

Paweł Szymański
1
Dariusz Mikielewicz
1

  1. Gdansk University of Technology, Faculty of Mechanical Engineering and Ship Technology, Narutowicza 11/12,80-233 Gdansk, Poland
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Abstract

Indoor noise can greatly affect the health and comfort of users, so the significance of the right assessment of the compliance with the requirements is obvious. But noise level testing is carried out using different methods, which may not ensure consistency in assessments.
The paper presents the influence of test methods on measurement results determined based on an analysis of inter-laboratory comparative studies. The analyses presented in the paper apply to an equivalent sound pressure level determined for a permanent source of sound – an air-conditioning device. The test methods were characterised according to their precision. In order to compare them, their compatibility was analysed based on the methodology described in the literature, alongside a single-factor analysis of variance. It was determined that there were no grounds for rejecting the hypothesis about lack of statistical differences between the results obtained via different methods. Each of the methods is characterised by different precision, so consequently the same result obtained with each method carries a different risk in regards to noise assessment.
The reason for taking up this kind of research was the decision of the Polish Technical Committee in 2018 about introducing new acoustic requirements in Poland concerning the admissible indoor sound pressure levels. It was decided to implement new international methods of testing indoor sound pressure levels emanating from the service equipment in the building. It was necessary to show the differences between the current method and its new counterparts.
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Bibliography

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Authors and Affiliations

Elżbieta Nowicka
1
Ewa Szewczak
1

  1. Building Research Institute, Warsaw, Poland
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Abstract

Signal attenuation caused by the propagation path between the compromising emanation source (the location of secured IT equipment) and the location of the antenna of the potential infiltrating system has a direct influence on the electromagnetic safety of IT equipment. The article presents original analytical relationships necessary to estimate the attenuation values introduced by the propagation path of the potential compromising emanation signal, which correspond to the most probable locations of IT equipment in relation to the location of the potential infiltrating system. The author of the article analyzes various location scenarios for IT equipment – a potential source of compromising emanations – with a potential infiltrating system located either within or outside the boundaries of a building, in which said IT equipment is located. The aforementioned scenarios are characterized by the lowest propagation path attenuation of potential compromising emanation generated by the secured IT equipment and provide for location masking of the potential infiltrating system. Example design of protective solutions for IT equipment elaborated by article author in the form of a shielding enclosure is presented in the article as well.

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Authors and Affiliations

Leszek Nowosielski
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Abstract

Finite mixture and Markov-switching models generalize and, therefore, nest specifications featuring only one component. While specifying priors in the general (mixture) model and its special (single-component) case, it may be desirable to ensure that the prior assumptions introduced into both structures are compatible in the sense that the prior distribution in the nested model amounts to the conditional prior in the mixture model under relevant parametric restriction. The study provides the rudiments of setting compatible priors in Bayesian univariate finite mixture and Markov-switching models. Once some primary results are delivered, we derive specific conditions for compatibility in the case of three types of continuous priors commonly engaged in Bayesian modeling: the normal, inverse gamma, and gamma distributions. Further, we study the consequences of introducing additional constraints into the mixture model’s prior on the conditions. Finally, the methodology is illustrated through a discussion of setting compatible priors for Markov-switching AR(2) models.

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Authors and Affiliations

Łukasz Kwiatkowski
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Abstract

Machine learning (ML) methods facilitate automated data mining. The authors compare the effectiveness of selected ML methods (RBF networks, Kohonen networks, and random forest) as modelling tools supporting the selection of materials in ecodesign. Applied in the design process, ML methods help benefit from the knowledge, experience and creativity of designers stored in historical data in databases. Implemented into a decision support system, the knowledge can be utilized – in the case under analysis – in the process of design of environmentally friendly products. The study was initiated with an analysis of input data for the selection of materials. The input data, specified in cooperation with designers, include both technological and environmental parameters which guarantee the desired compatibility of materials. Next, models were developed using selected ML methods. The models were assessed and implemented into an expert system. The authors show which models best fit their purpose and why. Models supporting the selection of materials, connections and disassembly methods help boost the recycling properties of designed products.

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Authors and Affiliations

I. Rojek
E. Dostatni
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Abstract

Most automotive electronic components can cause electromagnetic interference, that can cause power electronic circuits to become unstable. As per electromagnetic compatibility (EMC) standards, these electronic circuits should meet the specifications which are not achieved under some conditions. In this paper, the conducted emissions (CEs) are generated due to the switching of a buck converter, which often occurs in automotive electronics. The noise source was found to be due to the presence of common mode currents which largely affects the performance of EMC. Two types of filtering techniques were analysed and designed, and the results were compared to find an effective filtering solution to mitigate the effects of CE due to a common mode noise for the frequency range from 150 kHz to 108 MHz according to the International Special Committee on Radio Interference (CISPR25) standard. The capacitive and parasitic impedance were calculated and then used in the simulation. Finally, the simulated and measured results are presented. The noise level can be minimized by as much as 50 dB, which is an efficient noise reduction value.
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Authors and Affiliations

G. V. Aswini
1
ORCID: ORCID
S. Chenthurpandian
1

  1. Department of Electronics and Communication Engineering, SNS College of Technology, Coimbatore-641035, India
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Abstract

This paper presents that the effect of single aperture size of metallic enclosure on electrical shielding effectiveness (ESE) at 0 – 1 GHz frequency range has been investigated by using both Robinson’s analytical formulation and artificial neural networks (ANN) methods that are multilayer perceptron (MLP) networks and a radial basis function neural network (RBFNN). All results including measurement have been compared each other in terms of aperture geometry of metallic enclosure. The geometry of single aperture varies from square to rectangular shape while the open area of aperture is fixed. It has been observed that network structure of MLP 3-40-1 in modeling with ANN modeled with fewer neurons in the sense of overlapping of faults and data and modeled accordingly. In contrast, the RBFNN 3-150-1 is the other detection that the network structure is modeled with more neurons and more. It can be seen from the same network-structured MLP and RBFNN that the MLP modeled better. In this paper, the impact of dimension of rectangular aperture on shielding performance by using RBFNN and MLP network model with ANN has been studied, as a novelty.

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Authors and Affiliations

Ibrahim Bahadir Basyigit
Habib Dogan
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Abstract

Studies on food preference of herbivores include no-choice test and test with choice or multiple choice. Conclusions from statistic analyses of these tests are compared descriptively. The definition of compatibility index and consumption growth index has enabled us to use nonparametric test for verification of hypotheses about homogeneity of the consumption growths of selected plant species under no-choice and multiple choice conditions. The studies were conducted on food preference of the slug Deroceras reticulatum. It has been found that Chamaenerion angustifolium, Geraniumpusillum and Potentilla anserina can be used to reduce this slug feeding on cultivated plants. It has been also found that seedlings of Polygonum aviculare can be used as alternative food for slugs.

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Authors and Affiliations

Maria Kozłowska
Jan Kozłowski
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Abstract

At the National Institute of Metrological Research (INRIM) an evaluation of a commercial dual source high resistance bridge has been performed. Its two main measurement modes (single measurements and multiple measurements) have been investigated. The best settle time of a 10:1 measurement of high resistance ratio has been estimated to be about three times the time constant of the circuit involving the resistors. This constant, in turn, depends on the highest value resistor. By means of mathematical estimators, suitable numbers of the readings of the detector have been established in order to minimize noises. A compatibility test at 100 TΩ has shown that the best precision of the commercial bridge is achieved utilizing the multiple measurements mode with the auto update function. This mode also allows the characterization of a resistor as a function of the settle time. This characterization can be useful for the owner of the resistor who can request the laboratory to perform the calibration of the resistor with the settle time which is necessary for him.
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Authors and Affiliations

Iulian Mihai
1
Pier Paolo Capra
1
Flavio Galliana
1

  1. National Institute of Metrological Research, Applied Metrology and Engineering Department, Str. delle Cacce 91, 10135 Turin, Italy
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Abstract

Pavements are layered systems from both the geometrical and physical points of view. Flexible pavements most often include a sequence of asphalt layers, typically composed of the wearing course, binder course and base course. So far, there is no definite analytical solution of such a layered system in relation to the temperature distribution that would consider different thermal properties of the respective layers and follow the physical laws of the thermal wave nature of heat propagation. This being so, we are unable to assess the effect of the thermal properties of the respective pavement courses on the overall temperature distribution in the asphalt portion. In multi-layer pavement systems also important are the phenomena taking place at the interfaces between the pavement courses which have a bearing on the service life of pavement. This article presents a newanalytical solution to the problem of heat conduction and refraction in a multi-layer pavement. The solution was used to investigate and determine the effect of wave mode of heat propagation on the vertical temperature distribution, this considering that the pavement system is a sequence of layers comprising the soil subgrade, the base course and the wearing course. Moreover, the classical heat conduction equation is compared with the wave mode equation for a multi-layer pavement system and the temperature distribution in a layered system is compared with the temperature distribution in its homogenized equivalent. The solution of the heat conduction problem in a layered system showed a considerable effect of the thermal compatibility coefficients introduced by the authors and of the thermal refraction of the respective layers on the temperature distribution throughout the multi-layer pavement system. The output of this research includes prediction of the vertical temperature distribution in the pavement and definition of guidelines for reducing the effect of changing climatic conditions on the operation of layered flexible road and airfield pavements. In addition, the research results expand the toolkit for assessing the thermal effect on the actual pavements.
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Authors and Affiliations

Mirosław Graczyk
1
ORCID: ORCID
Józef Rafa
2
ORCID: ORCID
Adam Zofka
1
ORCID: ORCID
Leszek Rafalski
1
ORCID: ORCID

  1. Road and Bridge Research Institute, Instytutowa 1, 03-302 Warsaw, Poland
  2. Institute of Mathematics and Cryptology, Cybernetics Faculty, Military University of Technology, S. Kaliskiego 2, 00-908 Warsaw, Poland

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