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141.
142.
This article represents the result of experimental research on transient heat transfer in a multilayered (heterogeneous) wall. Our non-steady thermal transmission simulation is based on a finite-difference calculation method. The value of a Fourier number shows the similarity of thermal variation in conditional layers of an enclosure. Most scientists recommend using no more than a value of 0.5 for the Fourier number when performing calculations on dynamic (transient) heat transfer. The value of the Fourier number is determined in order to acquire reliable calculation results with optimal accuracy. To compare the results of simulation with experimental research, a transient heat transfer calculation spreadsheet was created. Our research has shown that a Fourier number of around 0.5 or even 0.32 is not sufficient (\({\approx }17\,\%\) of oscillation amplitude) for calculations of transient heat transfer in a multilayered wall. The least distorted calculation results were obtained when the multilayered enclosure was divided into conditional layers with almost equal Fourier number values and when the value of the Fourier number was around 1/6, i.e., approximately 0.17. Statistical deviation analysis using the Statistical Analysis System was applied to assess the accuracy of the spreadsheet calculation and was developed on the basis of our established methodology. The mean and median absolute error as well as their confidence intervals has been estimated by the two methods with optimal accuracy (\({F}_{\mathrm{oMDF}}= 0.177\) and \(F_{\mathrm{oEPS}}= 0.1633\) values). 相似文献
143.
The paper presents an improved e-learner model that supports monitoring of user behavior related to information security. The model is built upon standardized IMS specification, according to literature research and survey conducted among e-learners. It is positioned as key part of an extended LTSA architecture in which the learner data is used to improve learner security position by continuous delivery of important information and adapting security mechanisms. The implementation is considered in Moodle LMS. 相似文献
144.
Miodrag Čolić Sergej Tomić Rebeka Rudolf Evgenija Marković Ivana Šćepan 《Journal of materials science. Materials in medicine》2016,27(8):128
Superelastic (SE) and thermo-activated (TA) nickel–titanium (NiTi) archwires are used in everyday orthodontic practice, based on their acceptable biocompatibility and well-defined shape memory properties. However, the differences in their surface microstructure and cytotoxicity have not been clearly defined, and the standard cytotoxicity tests are too robust to detect small differences in the cytotoxicity of these alloys, all of which can lead to unexpected adverse reactions in some patients. Therefore, we tested the hypothesis that the differences in manufacture and microstructure of commercially available SE and TA archwires may influence their biocompatibility. The archwires were studied as-received and after conditioning for 24 h or 35 days in a cell culture medium under static conditions. All of the tested archwires, including their conditioned medium (CM), were non-cytotoxic for L929 cells, but Rematitan SE (both as received and conditioned) induced the apoptosis of rat thymocytes in a direct contact. In contrast, TruFlex SE and Equire TA increased the proliferation of thymocytes. The cytotoxic effect of Rematitan SE correlated with the higher release of Ni ions in CM, higher concentration of surface Ni and an increased oxygen layer thickness after the conditioning. In conclusion, the apoptosis assay on rat thymocytes, in contrast to the less sensitive standard assay on L929 cells, revealed that Rematitan SE was less cytocompatible compared to other archwires and the effect was most probably associated with a higher exposition of the cells to Ni on the surface of the archwire, due to the formation of unstable oxide layer. 相似文献
145.
Various diseases are diagnosed using medical imaging used for analysing internal anatomical structures. However, medical images are susceptible to noise introduced in both acquisition and transmission processes. We propose an adaptive data-driven image denoising algorithm based on an improvement of the intersection of confidence intervals (ICI), called relative ICI (RICI) algorithm. The 2D mask of the adaptive size and shape is calculated for each image pixel independently, and utilized in the design of the 2D local polynomial approximation (LPA) filters. Denoising performances, in terms of the PSNR, are compared to the original ICI-based method, as well as to the fixed sized filtering. The proposed adaptive RICI-based denoising outperformed the original ICI-based method by up to 1.32 dB, and the fixed size filtering by up to 6.48 dB. Furthermore, since the denoising of each image pixel is done locally and independently, the method is easy to parallelize. 相似文献
146.
Sandra Križić Roban 《Photographies》2018,11(2-3):215-234
Post-war experimental and conceptual photography in former Yugoslavia has only rarely been the subject of detailed study and interpretation. In considering this period, it is necessary to take into account several factors, including the absence of permanent exhibition spaces for photography, the lack of magazines in which photographic themes were presented and discussed, the impossibility of studying the field of photography and, finally, the inadequate knowledge and application of contemporary criticism and theories of photography. Nevertheless, from the mid-1950s onwards it is possible to note a variety of innovations in the field, in terms of both form and subject-matter. This article considers rare instances of institutional support for progressive photography-related events and unique, intellectual-poetic works. After the break-up of Yugoslavia, there is a dominant tendency to nationalize art created in the former state, thus ignoring the specific Yugoslav cultural field as well as the European context. Based on a methodology which surpasses the national (but still acknowledges it) and searches for meaning within the broader socio-political space to which art is referring, the research aims to change the paradigm of the peripheral position and general ignorance of the circumstances under which this innovative practice emerges. 相似文献
147.
Nano Research - The widespread and increasing interest in enhancing biosensing technologies by increasing their sensitivities and lowering their costs has led to the exploration and application of... 相似文献
148.
Contents A high accuracy instrument for reactive power and reactive energy measurements in a single phase power network is described in the paper. The measurement principle is in accordance with IEC recommendation. Test results show that in the range of 1 to 100% of the input current the accuracy of the meter is better than 100 ppm for frequency variations of ±5% around the nominal frequency. The instrument could be used as a single-phase reactive power and reactive energy standard. A three phase version of the instrument could be used as a standard or as a revenue meter because of its high accuracy, simple design and anticipated low cost.
Institute for National Measurement Standards, National Research Council 相似文献
Ein Meßgerät höher Präzision zur Blindleistungs- und Blindverbrauchsmessung
Übersicht In diesem Artikel wird ein Meßgerätu zur Blindleistungs- und Blindenergiemessung in Einphasen-Wechselstromnetzen beschrieben. Das Meßprinzip stimmt mit der Vorschrift der IEC überein. Die Meßergebnisse zeigen, daß im Bereich von 1 bis 100% des Eingangsstroms bei Frequenzvariationen von ±5% von der Nennfrequenz die Meßfehler des Gerätes kleiner als 0.01% sind. Das Meßgerät könnte als ein Normal für Blindleistungs- und Blindenergievergleichsmessungen in Einphasensystemen verwendet werden. Eine Dreiphasenversion dieses Meßgerätes könnte wegen seiner hohen Genauigkeit und des einfachen und preiswerten Aufbaus als ein Normal oder als Verbrauchsmeßgerät für die Kostenberechnung benutzt werden.
Institute for National Measurement Standards, National Research Council 相似文献
149.
M. Calović A. Sarić M. Djukanović 《Electrical Engineering (Archiv fur Elektrotechnik)》1996,79(6):479-488
Contents In this paper, a new optimal procedure of the general compensation problem is proposed, by minimizing the performance criterion depending on both active power and energy losses, and by taking into account cost of shunt capacitor banks and system voltage constraints. The new solution method represents a combinatorial searching procedure, with non-differentiable optimization criterion, by using the multi-stage optimization based on dynamic programming. The applications of the method to three different test system have shown important improvements in the sense of speed and effectiveness of calculations, when compared to previously advertised solution methods.
Mehrstufige Optimierung der Parallelkondensatoren in radialen Verteilungsnetzen mittels dynamisch Programmierung
Übersicht In diesem Artikel wird ein neues Verfahren für die allgemeine Blindleistungkompensation vrgestellt. Das Verfahren basiert auf der Minimierung der Optimalitätsbedingung, die Funktion der Wirkleistung und der Energieverluste ist. Die Kosten der Kondensatorbänke und die Betriebsgrenzen der Netzspannungen werden auch berücksichtigt. Die neue Methode stellt ein kombinatorisches Suchverfahren mit nicht-diffenzierbarer Optimalitätsbedingung dar. Dabei wird die mehrstufige Optimierung verwendet die auf der dynamischen Programmierung basiert. Die Bewertung der Methode mittels dreier Testnetze zeigt wichtige Verbesserungen bezüglich Schnelligkeit und Güte der Berechnung, im Vergleich zur früher veröffentlichten Methoden.相似文献
150.