GLRT-based adaptive detection algorithms for range-spread targets

We address adaptive detection of a range-spread target or targets embedded in Gaussian noise with unknown covariance matrix. To this end, we assume that cells (referred to in the following as secondary data) that are free of signal components are available. Those secondary data are supposed to possess either the same covariance matrix or the same structure of the covariance matrix of the cells under test. In this context, we design detectors relying on the generalized likelihood ratio test (GLRT) and on a two-step GLRT-based design procedure. Remarkably, both criteria lead to receivers ensuring the constant false alarm rate (CFAR) property with respect to the unknown quantities. A thorough performance assessment of the proposed detection strategies, together with the evaluation of their processing cost, highlights that the two-step design procedure is to be preferred with respect to the plain GLRT. In fact, the former leads to detectors that achieve satisfactory performance under several situations of practical interest and are simpler to implement than those designed resorting to the latter     

影响聚丙烯β晶型形成的外部因素

简单介绍形成β晶型聚丙烯的几种常见途径及影响β晶型的各种因素，重点介绍了温度、应力、填料、成核剂及工艺条件等外部因素对β晶型形成的影响。     

Thermodynamic Properties of He@C60

Contributions to thermodynamic properties of the endohedral He@C₆₀, resulting from motion of He inside the cage, are calculated. The contribution to C_v shows a maximum at low temperatures. The maxima for ³He@C₆₀ and ⁴He@C₆₀ are at about 41 K and 30 K, respectively.     

Comparative investigation of the nitrogenation mechanisms of bulk intermetallic Sm2(Fe,Co)17 by two processes

The nitrogenation mechanisms of the Sm₂(Fe_0.5Co_0.5)₁₇ compound were investigated on bulk samples using X-ray diffraction and chemical analysis. Two nitrogenation processes (fluidized bed nitrogenation (FBN) and gaseous nitrogenation (GN)) were used in order to compare the different steps occurring during the treatment. The fluidized bed process leads to a constant nitrogen surface concentration after one hour treatment while the concentration increases continuously with the gaseous process. The overall bulk nitrogenation kinetics is parabolic for the fluidized bed, whereas the gaseous nitrogenation exhibits first an incubation period followed by an accelerated rate. Two different mechanisms, bulk diffusion for the FBN process and an interface reaction for the GN process, govern the nitrogenation kinetics.     

Elaboration of platinum-modified NiAl coatings by combustion synthesis: Simultaneous repairing and coating of Ni-based superalloys

The “SHS build-up process” under high gas pressure was previously reported in literature by the authors in order to repair damaged turbine blades. In this process, a brazing foil is inserted between a substrate of Ni-based superalloy and a reactant compact made of the 50 at % Ni-50 at % Al mixture. The heat released during the combustion synthesis of the Ni + Al compact gives rise to interdiffusion of the elements and consequently to joining at the interface. This study reports the effect of Pt addition to the Ni + Al compact on the SHS build-up process. Indeed, the turbine blades need to be coated after repairing to protect them against corrosion. The aim of this investigation was to show the feasibility of this process for simultaneous repairing and coating. Good results were obtained: the joint quality was found to be good and even with a content of 18 at % Pt, the Pt-aluminide coatings retained the β-NiAl structure without PtAl₂ precipitates. Moreover, these coatings are free of porosity and after 100 h of air treatment, a homogenous oxide layer free of porosity was formed.      

An Improved ADC-Error-Correction Scheme Based on a Bayesian Approach

The paper presents an improved method for analog-to-digital-converter (ADC) nonlinearity correction based on a Bayesian-filtering approach. In particular, the dependence of a previous method version on the statistical characterization of the input signal has been removed. Now, the method can work on whatever stimulus signal is used without a priori knowledge about it. The proposed improvement has been validated by a numerical simulation using behavioral models provided by an ADC manufacturer and by an experiment in real ADCs.     

Natural circulation in a liquid metal one-dimensional loop

A wide use of pure lead, as well as its alloys (such as lead-bismuth, lead-lithium), is foreseen in several nuclear-related fields: it is studied as coolant in critical and sub-critical nuclear reactors, as spallation target for neutron generation in several applications and for tritium generation in fusion systems. In this framework, a new facility named NAtural CIrculation Experiment (NACIE), has been designed at ENEA-Brasimone Research Centre. NACIE is a rectangular loop, made by stainless steel pipes. It consists mainly of a cold and hot leg and an expansion tank installed on the top of the loop. A fuel bundle simulator, made by three electrical heaters placed in a triangular lattice, is located in the lower part of the cold leg, while a tube in tube heat exchanger is installed in the upper part of the hot leg. The adopted secondary fluid is THT oil, while the foreseen primary fluid for the tests is lead-bismuth in eutectic composition (LBE). The aim of the facility is to carry out experimental tests of natural circulation and collect data on the heat transfer coefficient (HTC) for heavy liquid metal flowing through rod bundles. The paper is focused on the preliminary estimation of the LBE flow rate along the loop. An analytical methodology has been applied, solving the continuity, momentum and energy transport equations under appropriate hypothesis. Moreover numerical simulations have been performed. The FLUENT 6.2 CFD code has been utilized for the numerical simulations. The main results carried out from the pre-tests simulations are illustrated in the paper, and a comparison with the theoretical estimations is done.     

Contribution of staling compounds to the aged flavour of lager beer by studying their flavour thresholds

The effect of 26 staling compounds on the aged flavour of a Belgian lager beer was studied. Strikingly, thresholds were regularly found to be substantially lower than those previously reported, and it appeared important to consider threshold values as indicative rather than absolute because of very large variations in sensitivity of individuals. In addition, a masking effect of isoamyl acetate and various interactions were observed between flavour compounds, which can considerably influence their flavour activity, even at sub-threshold concentrations. Cardboard flavour was essentially caused by (E)-2-nonenal. Additionally, methional, 3-methylbutanal, 2-furfuryl ethyl ether, β-damascenone and acetaldehyde were confirmed as key contributors to the aged flavour and to a lesser extent, (E,E)-2,4-decadienal, phenylacetaldehyde, 2-methylpropanal, diacetyl and 5-hydroxymethyfurfural. Finally, the addition of a selection of compounds could fairly well reproduce the flavour of aged lager beer, indicating that these compounds account for the major part of this flavour.