Hydrogen storage in a layered flexible [Ni2(btc)(en)2]n coordination polymer

[Ni2(btc)(en)2]n coordination polymer exhibits a layered two-dimensional structure with weak interaction between the layers. Correlation of experimental measurements, DFT calculations and molecular simulations demonstrated that its structural features, primarily the inherent flexibility of the layered polymeric structure, lead to improved hydrogen storage performance at room temperature, due to significant enhancement in isosteric heats of hydrogen adsorption. Volumetric measurements of hydrogen adsorption at room temperature show up to 0.3 wt.% hydrogen absorbed at 303 K and 2.63 bar of hydrogen pressure, with isosteric heats of adsorption of about 12.5 kJ mol−1. Predicted performance at room temperature is 1.8 wt.% at 48 bar and 3.5 wt.% at 100 bar, better than both MOF-5 and NU-100, with calculated values of isosteric heats for adsorption of hydrogen in 8–13 kJ mol−1 range at both 77 K and 303 K. Grand canonical Monte Carlo calculations show that this material, at 77 K, exhibits gravimetric hydrogen densities of more than 10 wt.% (up to 8.3 wt.% excess) with the corresponding volumetric density of at least 66 gL−1, which is comparable to MOF-5, but achieved with considerably smaller surface area of about 2500 m2 g−1. This study shows that layered two-dimensional MOFs could be a step towards MOF systems with significantly higher isosteric heats of adsorption, which could provide better room temperature hydrogen storage capabilities.This is the peer reviewed version of the following article: Blagojević, V.A., Lukić, V., Begović, N.N., Maričić, A.M., Minić, D.M., 2016, “Hydrogen storage in a layered flexible [Ni2(btc)(en)2]n coordination polymer”, International Journal of Hydrogen Energy, http://dx.doi.org/10.1016/j.ijhydene.2016.08.20

PRAVO NA BESPLATNO OSNOVNO OBRAZOVANJE – OD IDEALA DO STVARNOSTI

The paper analyses international conventions, case-law of international and national courts and quasi-judicial bodies, as well as the practice of states regarding the right to primary education. In order to enable equal access to compulsory primary education, it is necessary that it is available free to all, which is prescribed by international legal norms. However, results of this research indicate that the meaning of the term free is interpreted quite differently, hence leads to uneven practice between different countries, even within the same region. The former Yugoslav republics are certainly an illustrative example. Thus, part of the paper is devoted to the analysis of the normative framework and practice of the Republic of Serbia, which still does not provide free textbooks for children in primary school.U radu su analizirani međunarodnopravni akti, sudske odluke međunarodnih i nacionalnih sudova i kvazisudskih tela, kao i praksa država u pogledu prava na osnovno obrazovanje. Za omogućavanje jednakog pristupa obaveznom osnovnom obrazovanju neophodno je da ono bude besplatno, što je i propisano međunarodnopravnim aktima. Međutim, rezultati istraživanja su pokazali da se ovaj standard različito tumači, a to dovodi do neujednačene prakse u državama. Ilustrativni primer su svakako bivše jugoslovenske republike, te će poseban deo rada biti posvećen analizi normativnog okvira i prakse Republike Srbije, koja i dalјe ne obezbeđuje besplatne udžbenike za osnovnu školu

On Ability of Troubleshooting by Observing Some Physical Layer Parameters of xDSL Transceivers

This article presents a review of the investigation of the possibility of increasing the efficiency of existing line test solutions for troubleshooting testing for IPTV over xDSL, by the results of experimental research on real system under commercial exploitation. At the beginning of this article the main weaknesses of the existing troubleshooting testing are described. In the continuation of the article the physical layer parameters of xDSL transceiver are listed. This article also provides a few specific examples of xDSL lines with their physical layer parameters of xDSL transceivers followed by analysis how they can be used for the purposes of more efficient measurement of parameters of copper pairs

Thermal stability and degradation of binuclear hexaaqua-bis(ethylenediamine)-(μ 2-pyromellitato)dinickel(II) tetrahydrate

Thermal degradation of ternary transition metal complex containing tetraanion of pyromellitic acid, pyr, and ethylenediamine, en, [Ni2(en)2(H2O)6(pyr)]·4H2O, 1, was investigated under non-isothermal conditions. The mechanism of thermal degradation, which occurs in three steps, was clarified by TG/DSC measurements in conjunction with FT-IR spectroscopy and XRPD analysis. The complexity of all degradation steps has been revealed using isoconversional methods. Dehydration comprises the loss of ten water molecules in a relatively narrow temperature interval, resulting in a very complicated reaction mechanism. In addition, density functional theory calculations have been applied for better understanding of dehydration. The second degradation step, related to loss of en, was separated into two single-step processes with Fraser–Suzuki function. The obtained individual steps were described by Johnson–Mehl–Avrami A2 model and Šesták–Berggren model, respectively. Validation of the proposed kinetic triplets for individual steps was performed using master plot and Pérez-Maqueda criteria. The third degradation step is related to the fragmentation of pyr ion most likely followed with the release of a number of gaseous products

Isokinetic parameters of thermal degradation of powder of [Cd(N-Boc-gly)2(H2O)2]n

The coordination polymer [Cd(N-Boc-gly)2(H2O)2]n undergoes thermally induced degradation in temperature region between 60 and 900oC. Kinetic parameters were determined for dehydration (63-123oC) and further degradation processes (123-461°C) using different isoconversional and non-isoconversional methods. Due to appearance of kinetic “compensation effect”, isokinetic temperatures were determined for individual degradation processes and correlated with resonant vibrational frequencies ascribed to Cd-OH2 coordination bond, Cd-O (O from N-Boc-glyH ligand) coordination bond and C-O covalent bond. [Projekat Ministarstva nauke Republike Srbije, br. 172015

Hydrogen storage in a layered flexible [Ni<inf>2</inf>(btc)(en)<inf>2</inf>]<inf>n</inf> coordination polymer

© 2016 Hydrogen Energy Publications LLC [Ni2(btc)(en)2]n coordination polymer exhibits a layered two-dimensional structure with weak interaction between the layers. Correlation of experimental measurements, DFT calculations and molecular simulations demonstrated that its structural features, primarily the inherent flexibility of the layered polymeric structure, lead to improved hydrogen storage performance at room temperature, due to significant enhancement in isosteric heats of hydrogen adsorption. Volumetric measurements of hydrogen adsorption at room temperature show up to 0.3 wt.% hydrogen absorbed at 303 K and 2.63 bar of hydrogen pressure, with isosteric heats of adsorption of about 12.5 kJ mol−1. Predicted performance at room temperature is 1.8 wt.% at 48 bar and 3.5 wt.% at 100 bar, better than both MOF-5 and NU-100, with calculated values of isosteric heats for adsorption of hydrogen in 8–13 kJ mol−1 range at both 77 K and 303 K. Grand canonical Monte Carlo calculations show that this material, at 77 K, exhibits gravimetric hydrogen densities of more than 10 wt.% (up to 8.3 wt.% excess) with the corresponding volumetric density of at least 66 gL−1, which is comparable to MOF-5, but achieved with considerably smaller surface area of about 2500 m2 g−1. This study shows that layered two-dimensional MOFs could be a step towards MOF systems with significantly higher isosteric heats of adsorption, which could provide better room temperature hydrogen storage capabilities

Influence of Given Parameter Errors on Accuracy of Tunnel Breakthrough by Height

There are two types of geodetic 2D and 1D networks for tunnel construction: overhead and underground. The purpose of these networks is to perform tunnel stake out with allowable deviation in transverse, longitudinal and height terms. Overhead network is developed before a tunnel is built and it connects entry and exit portal into a unique system. Underground network expands during tunnel construction. When evaluating the coordinates of newly assigned underground network points, previously established points are considered as given points. In order to realistically estimate the accuracy of underground network, it is necessary to include all previous measured quantities in the adjustment, and to define a minimum trace at all points. With this approach, estimated coordinates of network points would change each time when network is extended. To avoid this problem, when estimating new points, errors of given parameters must be taken into account. In the example of the Tunnel Vežešnik in Montenegro, when designing a 1D underground network, a case was reviewed when previously established points were taken as given and when their error was considered. To validate this procedure, an accuracy calculation was applied only when the overhead network points were defined as given. The network quality criteria were compared for all cases and it was shown that errors of the given parameters must be taken into account