Remarkable analytic relations among greybody parameters

In this paper we derive and discuss several implications of the analytic form of a modified blackbody, also called greybody, which is widely used in Astrophysics, and in particular in the study of star formation in the far-infrared/sub-millimeter domain. The research in this area has been greatly improved thanks to recent observations taken with the Herschel satellite, so that it became important to clarify the sense of the greybody approximation, to suggest possible further uses, and to delimi its intervals of validity. First, we discuss the position of the greybody peak, making difference between the optically thin and thick regimes. Second, we analyze the behavior of bolometric quantities as a function of the different greybody parameters. The ratio between the bolometric luminosity and the mass of a source, the ratio between the so-called "sub-millimeter luminosity" and the bolometric one, and the bolometric temperature are observables used to characterize the evolutionary stage of a source, and it is of primary importance to have analytic equations describing the dependence of such quantities on the greybody parameters. Here we discuss all these aspects, providing analytic relations, illustrating particular cases and providing graphical examples. Some equations reported here are well-known in Astrophysics, but are often spread over different publications. Some of them, instead, are brand new and represent a novelty in Astrophysics literature. Finally we indicate an alternative way to obtain, under some conditions, the greybody temperature and dust emissivity directly from an observing spectral energy distribution, avoiding a best-fit procedure.Comment: accepted by MNRA

Comparison between different electrical configurations of emergency diesel generators for redundancy and reliability improving

The failure of an emergency diesel generator could cause a blackout with economic or human losses, especially if it occurs in a hospital. The authors performed an up to date statistic on diesel generators fails has been investigated in a hundred of hospitals. Although standard maintenance operation has been correctly performed, it has been found a 6 % of failures for the genset per year. MTBF of generators and main components have been investigated and updated values are reported in this paper. Components reliability is proved to be at its maximum technological value, consequently an innovative solution is here proposed. Often neighboring buildings or different electrical systems have separated emergency generators. Nowadays, in case of genset failure, most of the electrical installations are not designed to be fed from other generators. Several electrical configurations for diesel generators interconnections have been studied, in order to guarantee the mutual succor between them and therefore improving reliability. Two innovative schemes for emergency generators connection are here proposed for a more reliable electrical design

Does the logistics sector gain from manufacturing internationalisation? An empirical investigation on the Italian case

The present paper deals with the impact of manufacturing internationalisation, in the forms of international trade, cooperation agreement and FDI, on the logistics sector. Some descriptive statistics are provided for the Italian macro-areas and the logistics employment and an econometric analysis is carried out at the "regional-industry" level (20 NUTS2 regions and 11 logistics sub-sectors) with reference to the Italian case in the period 1996-2001. Results show that export and FDIs positively affect the logistics employment variation in 1996-2001, while import and cooperation agreements display a negative or not significant impact.logistics, employment, internationalisation, trade, FDI, cooperation agreement.

Fire risk in MTBF evaluation for UPS system

The reliability improvement of no-break redundant electrical systems is the first aim of the proposed strategy. The failure of some UPS (Uninterruptible Power Supply) system may lead to the fire occurrence. The most used electrical configurations are presented and discussed in the paper. The innovation of the proposed method consists of taking into account the fire risk to improve the accuracy of wiring configuration and component’s failure rate. Thorough research on MTBF (Mean Time Between Failure) data has been performed for each wiring component and UPS. The fire risk is taken into account introducing an equivalent fire block in the Reliability Block Diagram scheme; it has an MTBF value calculated form yearly statistics of UPS fire events. The reliability of the most used UPS electrical configurations is evaluated by means of the RBD method. Different electrical systems have been investigated and compared based on MTBF. The importance of fire compartmentation between two or more UPS’ connected in parallel is proved here

The firm-specific determinants of agglomeration: a comparison

This paper deals with the agglomeration of economic activities in Italy. By using the Guimaraes et al. [2004] version of the Ellison & Glaeser [1994] index, we test the hypothesis that the determinants of agglomeration differ in significance, intensity and sign between multinational and national firms. The data concerning the agglomeration of 112 manufacturing and mining industries, computed over the 686 Italian Local Labor Systems (SLL) in the year 2001, show that some agglomeration forces are industry-specific while some others are firm-specific. Indeed, on the one hand the industrial concentration and the inter-industry externalities seem to act as centripetal forces for all types of enterprises, on the other hand the intra-industry spillovers appear to favor the agglomeration of only multinational firms, while acting as centrifugal force both for the clustering of national firms and for the co-agglomeration between foreign and domestic enterprises. This result suggests that the possibility of knowledge transmission between firms belonging to the same industry may discourage the most advanced enterprises to co-locate with the less innovative firms. The main policy implication is that a high Intellectual Property Regime (IPR) is preferred to a low protection of intellectual property, since in the latter case the co-agglomeration does not occur and multinational and national firms do no interact and do not exchange knowledge, while in the former scenario domestic and foreign enterprises co-locate, and even if the high IPR limit the transfer of knowledge, other mechanisms, such as the labor turnover, may occur and promote knowledge spillovers between firms

A Systematic Approach for Evaluating Satellite Communications Systems

The aerospace environment imposes straight opera- tive conditions so every electronic system usually needs to be validated for these. The same way, communica- tion systems need to be evaluated before their intro- duction in aerospace applications. In the paper we present a new methodology for the evaluation of com- munication systems in space applications. The meth- odology aims, by abstraction, at identifying all the critical aspects for the evaluation and at defining a standard and reusable framework in order to be appli- cable to any Communication Systems. The methodol- ogy has been applied for the evaluation of three Data Bus for satellite communications: 1553, 1-Wire and Profibus DP RS 485 based systems have been analyzed and evaluate

Does the transport industry gain from manufacturing internationalization? An empirical investigation on the Italian regions

The present paper deals with the impact of manufacturing internationalisation, in the forms of international trade, cooperation agreements – measured by inward and outward processing trade (IPT and OPT, respectively) - and FDI, on the transport industry employment. Descriptive statistics and econometric analysis are carried out at the “regional-industry” level (20 NUTS2 regions and 8 transport sub-industries) with reference to Italy in the period 1996-2001. Results show that export, FDI and the components of IPT (temporary import and re-export) positively affect the transport employment variation in 1996-2001, while import and the components of OPT (temporary export and re-import) display a negative impact

Review of the Maximum Likelihood Functions for Right Censored Data. A New Elementary Derivation.

Censoring is a well known feature recurrent in the analysis of lifetime data, occurring in the model when exact lifetimes can be collected for only a representative portion of the surveyed individuals. If lifetimes are known only to exceed some given values, it is referred to as right censoring. In this paper we propose a systematization and a new derivation of the likelihood function for right censored sampling schemes; calculations are reported and assumptions are carefully stated. The sampling schemes considered (Type I, II and Random Censoring) give rise to the same ML function. Only the knowledge of elementary probability theory, namely the definitions of the order statistics and the conditional probability distribution function, are required in the proofs. Lastly we give an intuitive interpretation of Type I Censoring as a special case of Random Censoring, so that a global theory holds