Detection of Delayed Neutrons from Fissionable Samples: Monte Carlo Modelling and Physical Assumptions for a Design of the DET-12 Device

An activation of fissionable materials with neutrons has been considered as a possible neutron diagnostic of D–D and D–T fusion plasma. Fission reaction caused by fusion neutrons leads up to emission of secondary neutrons: prompt and delayed. Physical assumptions have been outlined to design a new device (DET-12) for measurements of delayed neutrons emitted from samples of fissionable materials activated with neutrons at big fusion-plasma devices. The aim is to support a classic neutron activation method used as one of plasma diagnostics at tokamaks or stellarators. An interpretation of the time decay of delayed neutrons enables an assessment of the primary neutron flux which induced fission reaction. Monte Carlo calculations have been carried out in order to elaborate the method considered. Nuclides like: pure ²³⁵U, ²³⁸U and ²³²Th, have been selected as possible materials to be irradiated. Physical fundamentals of generation of the delayed neutrons are mentioned and a resulting concept of the DET-12 device, built in the Institute of Nuclear Physics, Poland, is presented. A general size and dimensions of particular constituent material layers, and a number and placement of neutron detectors are optimized by means of Monte Carlo modelling. Recommendations for a technical design of the measuring chamber were formulated. Detection efficiency of DET-12 has been also estimated.     

A time‐efficient shrinkage algorithm for the Fourier‐based prediction enabling proactive optimisation in software‐defined networks

This paper focuses on the problem of time‐efficient traffic prediction. The prediction enables the proactive and globally scoped optimisation in software‐defined networks (SDNs). We propose the shrinkage and selection heuristic method for the trigonometric Fourier‐based traffic models in SDNs. The proposed solution allows us to optimise the network for an upcoming time window by installing flow entries in SDN nodes before the first packet of a new flow arrives. As the mechanism is designed to be a part of a sophisticated routing‐support system, several critical constraints are considered and taken into account. Specifically, the system is traffic‐ and topology‐agnostic, thus the prediction mechanism must be applicable to the networks with highly variable traffic loads (e.g., observed inside intra‐DCNs: datacentre networks). Furthermore, the system must effectively optimise routing in large‐scale SDNs comprised of numerous nodes and handling millions of flows of a dynamic nature. Therefore, the prediction must be simultaneously accurate as well as being time efficient and scalable. These requirements are met by our Fourier‐based solution, which subtracts consecutive harmonics from the original signal and compares the result with an adaptive threshold adjusted to the signal's standard deviation. The evaluation is performed by comparing the proposed heuristic with the well‐known Lasso method of proven accuracy. The results show that our solution is able to retain prediction accuracy at a comparable level. Moreover, in accordance with our main aim, we operate in a manner which is always significantly faster. In some cases, computation times are reduced by as much as 50 times.     

Wind and Fire Coupled Modelling—Part II: Good Practice Guidelines

The requirement to model wind is inherently connected with the modelling of many fire-related phenomena. With its defining influence on fire behaviour, spread and smoke transport, the solution of a problem with and without wind exposure will lead to substantially different results. As wind and fire are phenomena that often require different scales of analysis and approaches to modelling, their coupling is not a trivial task. This paper is the second part of a two-paper review of the coupling between fire safety engineering and computational wind engineering (CWE). Part I contained a review of historical interactions between these disciplines, sorted into six distinct areas: flames, indoor flows, natural ventilators, tunnels, wildfires and urban smoke dispersion. This part of the review contains practical information related to wind modelling in fire analysis, based on various available CWE best practice guidelines. As the authors conclude, the most relevant of these are guidelines related to urban physics and natural ventilation; however, many more are discussed and presented, together with the results of other essential wind engineering experiments and computations. Introduction of wind as a boundary condition is explained in details, both based on wind statistics, or meso/micro scale coupled modelling. The guidelines for wind/fire coupled analyses are subdivided into recommendations for: building the digital domain, spatial and temporal discretisation, the consequences of the choice of a turbulent flow model, and the procedure for optimising CFD analysis of both wind and fire phenomena.     

13C n.m.r. spectra of polymers made by ring-opening polymerization of (±)- and (+)-exo-5-methylbicyclo [2.2.1] hept-2-ene using metathesis catalysts

A range of olefin metathesis catalysts has been used to prepare ring-opened polymers of (±)- and (+)-exo-5-methylbicyclo [2.2.1] hept-2-ene, (l), having cis double bond contents of 11–100%. The ¹³C n.m.r. spectra of these polymers are interpreted in terms of TH, TT, HH, HT and tt, tc, ct, cc structures (T = tail, H = head, referring to methyl groups; t = trans, c = cis, referring to double bonds). The all-cis polymer has a fully-syndiotactic ring sequence, but polymers with less than 55% cis double bonds have an atactic ring sequence. The substitution shift parameters indicate that the cyclopentane rings in the polymer chain adopt the puckered conformation which minimizes non-bonded repulsion between the cis-1,3-olefinic substituents.     

Data Fusion Algorithm for the Altitude and Vertical Speed Estimation of the VTOL Platform

An approach to the autonomous of the realization VTOL platform take-off and landing significantly simplifies the operator labor to control such device. At the same time, implementation of these control scenarios allows to perform these tasks under failure conditions (for example communication breakdowns). One condition of proper operation of the vertical movement control system is the ability to provide reliable information about the altitude of the controlled platform. In this paper one of the solutions for obtaining estimate of the altitude based on sensor data fusion is presented. Proposed scheme uses information obtained from pressure sensor, inertial measurement unit, ultrasonic sensor and GPS, all of these instruments are nowadays very often mounted on VTOL platforms.     

The influence of silver on the properties of cryptomelane type manganese oxides in N2O decomposition reaction

The cryptomelane type oxides were prepared by the redox precipitation technique using Mn(CH₃COO)₂ and KMnO₄ precursors. Nitrogen sorption, XRD, TEM and TPD of oxygen studies showed changes of the surface, structural and redox properties of the samples upon silver introduction. Samples were investigated in the N₂O decomposition reaction. Direct introduction of silver to the synthesis mixture caused partial distortion of regular channel-like structure of the oxides, leading to the decrease of Mn–O bonds strength. As results samples showed slightly better catalytic activity at low temperatures, but were less stable at high temperatures. An introduction of silver by the impregnation method caused the decrease of the surface area of the samples, increase of surface oxygen mobility, leading to the small changes of activity.     

Application of linear discriminant analysis in prostate cancer research by synchrotron radiation-induced X-ray emission

The ability to visualize an object of interest is one of the cornerstones of advancement in science. For this reason, synchrotron radiation-induced X-ray emission (micro-SRIXE) holds special promise as a imaging technique in structural biology, biochemistry, and medicine. It gives the possibility to image concentration of most of the elements in a sample at high space resolution. Statistical analysis of data obtained for samples of prostate tissues in an experiment at L-beam line HASYLAB (Hamburg, Germany) is presented in this paper. The regions for the measurements were selected according to the histological view of the sample. By histological examination, samples were divided into five groups (from healthy to Gleason4, most advanced stage of cancerogenesis). Data obtained in micro-SRIXE experiments on prostate cancer samples provide information about concentrations of certain elements in these groups. The rising problem is to find out concentrations of which elements allow the researcher to discriminate between different (early mentioned) groups. Linear discriminant analysis, a basic technique for feature extraction, was used in statistical analysis of the data. Our results indicate that the use of synchrotron radiation and discriminant analysis in the study of prostate cancer tissues provide information that can be key to better understanding of biomolecular functions.     

Thermal diffusivity characterization of europium zirconate,cerate and hafnate

The following paper presents study on synthesis and thermal diffusivity of europium zirconate, cerate and hafnate as a new types of materials with pyrochlore or fluorite type of lattice, dedicated to replacement of conventional 8YSZ (yttria stabilized zirconia) in TBC (thermal barrier coatings) systems for aircraft gas turbines.All materials were synthesized via solid-state reaction (SSR) preceded preparation of powder mixtures (mechanical milling in ethanol). The feedstock powders were characterized by analysis of crystallite size, particle size distribution and phase composition. On the base of DSC measurements, the parameters of high temperature sintering were selected (1350?°C/2?h/15?MPa). Structural characterization of obtained materials inclusive analysis of morphology, chemical and phase composition of sinters was performed. Thermal diffusivity was measured in temperature range 25÷1400?°C by laser flash analysis (LFA). The obtained materials with pyrochlore and fluorite type of lattice exhibit lower thermal diffusivity compared to that of yttria-stabilized zirconia at high temperatures. In particular, the most promising material in view of insulating properties is Eu₂Ce₂O₇, which exhibit much lower thermal diffusivity than Eu₂Zr₂O₇ and Eu₂Hf₂O₇, especially at temperature higher than 1000?°C. However, in temperature range 25–700?°C, europium hafnate and zirconate exhibit lower thermal diffusivity compared to that of europium cerate and 8YSZ.