High sensitive quasi freestanding epitaxial graphene gassensor on 6H-SiC

We have measured the electrical response to NO$_2$, N$_2$, NH$_3$ and CO for epitaxial graphene and quasi freestanding epitaxial graphene on 6H-SiC substrates. Quasi freestanding epitaxial graphene shows a 6 fold increase in NO2 sensitivity compared to epitaxial graphene. Both samples show a sensitivity better than the experimentally limited 1 ppb. The strong increase in sensitivity of quasi freestanding epitaxial graphene can be explained by a Fermi-energy close to the Dirac Point leading to a strongly surface doping dependent sample resistance. Both sensors show a negligible sensitivity to N$_2$, NH$_3$ and CO

Exploring pathways for sustainable water management in river deltas in a changing environment

Exploring adaptation pathways into an uncertain future can support decisionmaking in achieving sustainable water management in a changing environment. Our objective is to develop and test a method to identify such pathways by including dynamics from natural variability and the interaction between the water system and society. Present planning studies on long-term water management often use a few plausible futures for one or two projection years, ignoring the dynamic aspect of adaptation through the interaction between the water system and society. Our approach is to explore pathways using multiple realisations of transient scenarios with an Integrated Assessment Meta Model (IAMM). This paper presents the first application of the method using a hypothetical case study. The case study shows how to explore and evaluate adaptation pathways. With the pathways it is possible to identify opportunities, threats, timing and sequence of policy options, which can be used by policymakers to develop water management roadmaps into the future. By including the dynamics between the water system and society, the influence of uncertainties in both systems becomes clearer. The results show, among others, that climate variability rather than climate change appears to be important for taking decisions in water management

On the Strong Scaling of the Spectral Element Solver Nek5000 on Petascale Systems

The present work is targeted at performing a strong scaling study of the high-order spectral element fluid dynamics solver Nek5000. Prior studies indicated a recommendable metric for strong scalability from a theoretical viewpoint, which we test here extensively on three parallel machines with different performance characteristics and interconnect networks, namely Mira (IBM Blue Gene/Q), Beskow (Cray XC40) and Titan (Cray XK7). The test cases considered for the simulations correspond to a turbulent flow in a straight pipe at four different friction Reynolds numbers $Re_{\tau}$ = 180, 360, 550 and 1000. Considering the linear model for parallel communication we quantify the machine characteristics in order to better assess the scaling behaviors of the code. Subsequently sampling and profiling tools are used to measure the computation and communication times over a large range of compute cores. We also study the effect of the two coarse grid solvers XXT and AMG on the computational time. Super-linear scaling due to a reduction in cache misses is observed on each computer. The strong scaling limit is attained for roughly 5000 - 10,000 degrees of freedom per core on Mira, 30,000 - 50,0000 on Beskow, with only a small impact of the problem size for both machines, and ranges between 10,000 and 220,000 depending on the problem size on Titan. This work aims at being a reference for Nek5000 users and also serves as a basis for potential issues to address as the community heads towards exascale supercomputers.Comment: 10 pages, 9 figures, Proceedings of the Exascale Applications and Software Conference 2016 (EASC '16, Stockholm

Захисні лісові насадження – важливий структурний елемент у формуванні національної екологічної мережі

Описано роль і значення захисних лісових насаджень як важливого структурного елементу при формуванні національної екологічної мережі.Описана роль и значение защитных лесных насаждений как важного структурного элемента при формировании национальной экологической сети.Role and meaning of forest protective stands as an important structural element for national ecological network formation is described

Direct magneto-optical compression of an effusive atomic beam for high-resolution focused ion beam application

An atomic rubidium beam formed in a 70 mm long two-dimensional magneto-optical trap (2D MOT), directly loaded from a collimated Knudsen source, is analyzed using laser-induced fluorescence. The longitudinal velocity distribution, the transverse temperature and the flux of the atomic beam are reported. The equivalent transverse reduced brightness of an ion beam with similar properties as the atomic beam is calculated because the beam is developed to be photoionized and applied in a focused ion beam. In a single two-dimensional magneto-optical trapping step an equivalent transverse reduced brightness of $(1.0\substack{+0.8-0.4})$ $\times 10^6$ A/(m$^2$ sr eV) was achieved with a beam flux equivalent to $(0.6\substack{+0.3-0.2})$ nA. The temperature of the beam is further reduced with an optical molasses after the 2D MOT. This increased the equivalent brightness to $(6\substack{+5-2})$$\times 10^6$ A/(m$^2$ sr eV). For currents below 10 pA, for which disorder-induced heating can be suppressed, this number is also a good estimate of the ion beam brightness that can be expected. Such an ion beam brightness would be a six times improvement over the liquid metal ion source and could improve the resolution in focused ion beam nanofabrication.Comment: 10 pages, 8 figures, 1 tabl

Совершенствование региональных целевых программ – инструмента управления социально-экономическим развитием Одесского региона и его конкурентоспособностью

Розглянуто регіональні цільові програми розвитку Одеського регіону; виявлено недоліки діючого підходу до розробки й оцінки програм на регіональному рівні; подано рекомендації щодо загальних підходів до програмного управління, експертизи проектів; запропоновано експертний метод оцінки ефективності цільових програм із точки зору управління процесом розробки та реалізацією програм, своєчасного прийняття рішень. Ключові слова: регіональні цільові програми, соціально-економічний розвиток, регіон, управління, конкурентоспроможність.Рассмотрены региональные целевые программы развития Одесского региона; выявлены недостатки действующего подхода к разработке и оценке программ на региональном уровне; даны рекомендации по общим подходам к программному управлению, экспертизе проектов; предложен экспертный метод оценки эффективности целевых программ с точки зрения управления процессом разработки и ходом реализации программ, своевременного принятия решений. Ключевые слова: региональные целевые программы, социально-экономическое развитие, регион, управление, конкурентоспособность.The paper considers the regional target programs of Odessa region development. Shortcomings of the present approach to the development and evaluation of programs at the regional level are shown, recommendations on common approaches to program management and project appraisal are given; expert method for evaluating target programs is proposed from the view of managing the process of development and implementation of programs, timely decisions. Keywords: regional target programs, socio-economic development, region, management, competitiveness

Atomic-scale structure of self-assembled In(Ga)As quantum rings in GaAs

We present an atomic-scale analysis of the indium distribution of self-assembled In(Ga)As quantum rings (QRs) which are formed from InAs quantum dots by capping with a thin layer of GaAs and subsequent annealing. We find that the size and shape of QRs as observed by cross-sectional scanning tunneling microscopy (X-STM) deviate substantially from the ring-shaped islands as observed by atomic force microscopy on the surface of uncapped QR structures. We show unambiguously that X-STM images the remaining quantum dot material whereas the AFM images the erupted quantum dot material. The remaining dot material shows an asymmetric indium-rich crater-like shape with a depression rather than an opening at the center and is responsible for the observed electronic properties of QR structures. These quantum craters have an indium concentration of about 55% and a diameter of about 20 nm which is consistent with the observed electronic radius of QR structures.This work was partially supported by the GOA BOF UA 2000, IUAP, FWO-V projects G.0274.01N, G.0435.03, the WOG WO.035.04N (Belgium), the Spanish MCYT under NANOSELF project TIC2002-04096-C03-03 (Spain), the European Commission GROWTH Programme, NANOMAT project, contract No. G5RD-CT-2001-00545, and the European Commission SANDiE Network of Excellence, contract No. NMP4-CT-2004-500101.Peer reviewe

Electrothermal simulation of large-area semiconductor devices

The lateral charge transport in thin-film semiconductor devices is affected by the sheet resistance of the various layers. This may lead to a non-uniform current distribution across a large-area device resulting in inhomogeneous luminance, for example, as observed in organic light-emitting diodes. The resistive loss in electrical energy is converted into thermal energy via Joule heating, which results in a temperature increase inside the device. On the other hand, the charge transport properties of the device materials are also temperature-dependent, such that we are facing a two-way coupled electrothermal problem. It has been demonstrated that adding thermal effects to an electrical model significantly changes the results. We present a mathematical model for the steady-state distribution of the electric potential and of the temperature across one electrode of a large-area semiconductor device, as well as numerical solutions obtained using the finite element method