Showing papers by "Technical University of Madrid published in 1995"

The barley Hooded mutation caused by a duplication in a homeobox gene intron

Abstract: IN barley (Hordeum vulgare L.) the unit of inflorescence is the spikelet, which bears a fertile bract, the lemma, and the floret consisting of palea, two lodicules, three stamens and the pistil1. The Hooded mutation causes the appearance of an extra flower of inverse polarity on the lemma2. This phenotype is governed by the single dominant genetic locus K3. Here we show that the homeobox gene Knox3 represents this locus. Ectopic Knox3 gene expression in the primordium of the extra floret is caused by a 305-base pair duplication in intron 4, and phenocopies of the mutation are obtained in the heterologous tobacco system by Knox3 overexpression. It is concluded that homeotic genes of the Knox gene family are involved in floral evocation. Furthermore, the study of polarity of reproductive organs in K and related mutants can now focus on homeobox genes.

Strict and nonstrict independent and-parallelism in logic programs: Correctness, efficiency, and compile-time conditions

Abstract: This paper presents some fundamental properties of independent and- parallelism and extends its applicability by enlarging the class of goals eligible for parallel execution. A simple model of (independent) and-parallel execution is proposed and issues of correctness and efficiency are discussed in the light of this model. Two conditions, “strict” and “nonstrict” independence, are defined and then proved sufficient to ensure correctness and efficiency of parallel execution: If goals which meet these conditions are executed in parallel, the solutions obtained are the same as those produced by standard sequential execution. Also, in the absence of failure, the parallel proof procedure does not generate any additional work (with respect to standard SLD resolution), while the actual execution time is reduced. Finally, in case of failure of any of the goals, no slowdown will occur. For strict independence, the results are shown to hold independently of whether the parallel goals execute in the same environment or in separate environments. In addition, a formal basis is given for the automatic compile-time generation of independent and-parallelism: Compiletime conditions to efficiently check goal independence at run time are proposed and proved sufficient. Also, rules are given for constructing simpler conditions if information regarding the binding context of the goals to be executed in parallel is available to the compiler.

A high-gain, compact, nonimaging concentrator: RXI

Abstract: The design procedure of a new nonimaging concentrator (called an RXI) is explained. Rays that impinge on the concentrator aperture, within the acceptance angle, are directed to the receiver by means of one refraction, one reflection, and one total internal reflection. The concentrator can be made as a single dielectric piece (in which the receiver is immersed) whose aspect ratio (thickness/aperture diameter) is close to 1/3. Ray-tracing analysis of a rotational symmetric RXI shows total transmissions of greater than 94.5% (no absorption or reflection losses are considered) when the acceptance angle of the incoming rays is small (<3°) and when the receiver area is the smallest possible (maximal concentration.)

Long-term energy use and economic evaluation of three tillage systems for cereal and legume production in central Spain

Abstract: Three different experiments have been carried out in the area to the northeast of Madrid (central Spain) over 10 years with winter wheat (Triticum aestivum L.), winter barley (Hordeum vulgare L.), spring barley and vetch (Vicia sativa L.) grown for hay. In these experiments, three tillage systems were compared: conventional tillage (primary tillage was mouldboard ploughing to 300 mm depth), minimum tillage (primary tillage was spring tine cultivation either with a chisel or a cultivator to 150 mm depth) and zero tillage (direct drilling), in relation to energy consumption, production costs, energy efficiency and productivity, and economic returns. The experiments were performed on a Vertic Haploxeralf of a clay loam texture. The aforementioned variables were calculated considering every input (i.e. fertilisers, seeds, herbicides, machinery and fuel) including all the labour practices performed to harvesting. Post-harvesting activities were not included. The results showed that important energy and production cost savings may be achieved through minimum tillage and zero tillage, compared with conventional tillage. These energy savings ranged from 7 to 11% for cereal crops, whereas for vetch crops the reduction was 10% for minimum tillage and 15% for zero tillage. Production costs for minimum tillage were 13–24% less than for conventional tillage. For zero tillage these reductions ranged from 6 to 17%. For cereal crops, minimum tillage and zero tillage had energy productivities which were 18% and 20%, respectively, greater than that for conventional tillage. In most cases, yields of winter crops were similar, regardless of the tillage system considered. Only spring barley showed lower yields with zero tillage. For winter cereals the profitability with minimum tillage and zero tillage is higher than that with conventional tillage. However, spring barley is less profitable when using zero tillage.

An overall study of the half-bridge complementary-control DC-to-DC converter

Abstract: The half-bridge complementary-control power converter has been recently proposed as a low-output voltage DC-to-DC power converter due to its excellent features (efficiency around 90% at as low an output voltage as 33 volts) A study of the statics and dynamics of this power converter is proposed in this paper Thus, DC voltage conversion ratio both in continuous and discontinuous conduction mode, the boundary between both modes, the DC current level in the transformer and a small-signal average model have all been obtained From the latter, transfer functions between duty cycle and output voltage and between input and output voltages have been also obtained, and some simplifications and design rules have been proposed to facilitate the design of the feedback loop >

Knowledge-based models for adaptive traffic management systems

Abstract: This paper describes a general approach for real time traffic management support using knowledge based models. Recognizing that human intervention is usually required to apply the current automatic traffic control systems, it is argued that there is a need for an additional intelligent layer to help operators to understand traffic problems and to make the best choice of strategic control actions that modify the assumption framework of the existing systems. The need for an open architecture is stated, in order to allow users to modify decision criteria according to their experience, given that no skills are available yet to deal with real time strategy decision making. An architecture of knowledge is described that is oriented towards traffic management strategic advice applied in the TRYS system developed by the authors. This system has been installed for urban motorway control in several Spanish cities. Finally, an example of knowledge-based modeling, using TRYS, is presented in a case study where both the TRYS model and its operation are described. It is concluded that such an approach is feasible, and is compatible with existing state of the art traffic control systems.

An analysis of the influence of reinforcement fracture on the strength of discontinuously-reinforced metal-matrix composites

Abstract: A micromechanical model was developed to study the influence of reinforcement fracture on the tensile strength of discontinuously-reinforced metal-matrix composites. The analyses were carried out within the framework of the shear lag model, which provides simple expressions for the average stresses acting on the reinforcement as a function of the matrix strength and of the reinforcement aspect ratio. The reinforcement strength was assumed to follow the Weibull statistics, and in this way, the fraction of intact and broken reinforcements can be obtained for any combination of matrix and reinforcement properties. The overall composite strength was then calculated by assuming that broken reinforcements do not contribute to the composite strengthening. The model was employed to study the influence of various parameters, such as matrix and reinforcement strength, and reinforcement aspect ratio and size, on the strength of discontinuously-reinforced metal-matrix composites. Finally, the model predictions were compared with experimental results on several high strength Al alloys reinforced with SiC particulates.

Productivity and water use efficiency of sweet sorghum (Sorghum bicolor (L.) Moench) cv. "Keller" in relation to water regime

Abstract: Sweet sorghum (Sorghum bicolor (L.) Moench) has been recognized as an alternative crop for energy purposes. In the central area of the Iberian Peninsula, its main growth period coincides with the dry season and irrigation is needed for reasonable sorghum productivity. Knowledge of irrigation-yield relationships is fundamental, since water is a scarce resource there. Our objectives in this work were to study the effect of water regime on the productivity and water use efficiency (WUE) in a sweet sorghum cultivar “Keller” grown in lysimeters in Madrid. Experiments were carried out during three crop cycles. Three irrigation regimes: H1, H2 and H3, corresponding to a water supply of 5.7, 11.4 and 17.1 dm3 m−2 day−1 were experimented with during the main growth period. Maximum aerial biomass production was 4.0 103g DM m−2 in the H3 regime. WUE was quite similar for every irrigation regime but varied between sorghum seasons. 4.6 g aerial biomass DM dm−3 was obtained as the average for a crop cycle length of approximately 130 days. The water regime did not clearly affect the sugar content in stalk sections. The mean value of sugar content in whole stalks was 41.4% w/w on a dry-weight basis. The ratio of ethanol production to evapotranspired crop water was estimated at 0.63 g dm−3 (mean value).

RX: a nonimaging concentrator

Abstract: A detailed description of the design procedure for a new concentrator, RX, and some examples of it’s use are given. The method of design is basically the same as that used in the design of two other concentrators: the RR and the XR [Appl. Opt. 31, 3051 (1992)]. The RX is ideal in two-dimensional geometry. The performance of the rotational RX is good when the average angular spread of the input bundle is small: up to 95% of the power of the input bundle can be transferred to the output bundle (with the assumption of a constant radiance for the rays of the input bundle).

Products of networks with logarithmic diameter and fixed degree

Abstract: Analyzes some general properties of product networks that are pertinent to parallel architectures and then focuses on three case studies. These are products of complete binary trees, shuffle-exchange and de Bruijn networks. It is shown that all of these are powerful architectures for parallel computation, as evidenced by their ability to efficiently emulate numerous other architectures. In particular, r-dimensional grids and r-dimensional meshes of trees can be embedded efficiently in products of these graphs, i.e. either as a subgraph or with small constant dilation and congestion. In addition, the shuffle-exchange network can be embedded in an r-dimensional product of shuffle-exchange networks with dilation cost 2r and congestion cost 2. Similarly, the de Bruijn network can be embedded in an r-dimensional product of de Bruijn networks with dilation cost r and congestion cost 4. Moreover, it is well known that shuffle-exchange and de Bruijn graphs can emulate the hypercube with a small constant slowdown for "normal" algorithms. This means that their product versions can also emulate these hypercube algorithms with constant slowdown. Conclusions include a discussion of many open research areas. >

A new lossless power MOSFET driver based on simple DC/DC converters

Abstract: A new kind of power-MOSFET driver has appeared: lossless or resonant drivers. Their main goals are the reduction of power consumption and protections against overvoltage in the gate terminal. In this paper, a new lossless driver is presented; its operation is based on the use of DC/DC converters to supply and to recover driving energy with a few components and easy design. >

Germination studies in endemic plant species of the iberian peninsula

Abstract: The germinative behavior of nine plant species of the Iberian Peninsula, four of them catalogued as vulnerable or endangered by the International Union for the Conservation of Nature, was studied under controlled laboratory conditions Most of the species studied germinated better at relatively low temperatures (15 °C and 20 °C) and, in general, high germination rates were also obtained at alternating temperatures (25/15 °C) Coronopus navasii germinated over 60% at 25 °C, the highest temperature used in this study Lavatera oblongifolia did not surpass 20% germination under any of the conditions assayed Seed coat scarification increased germination in Helianthemum squamatum, while seed pretreatments with hot water or sulfuric acid were effective in H polygonoides Less favorable results were obtained in Lavatera oblongifolia, whereas scarification was completely ineffective in Onobrychis peduncularis ssp matritensis

Implementation of multiple specialization in logic programs

Abstract: We study the multiple specialization of logic programs based on abstract interpretation. This involves in general generating several versions of a program predicate for different uses of such predicate, making use of information obtained from global analysis performed by an abstract interpreter, and finally producing a new, "multiply specialized" program. While the topic of multiple specialization of logic programs has received considerable theoretical attention, it has never been actually incorporated in a compiler and its effects quantified. We perform such a study in the context of a parallelizing compiler and show that it is indeed a relevant technique in practice. Also, we propose an implementation technique which has the same power as the strongest of the previously proposed techniques but requires little or no modification of an existing abstract interpreter.

Germination behaviour in seeds of Diplotaxis erucoides and D. virgata

Abstract: Summary The seed germination behaviour of four populations each of Diplotaxis erucoides (L.) DC. and D. virgata (Cav.) DC, two weedy Brassicaceae species widely distributed in the Mediterranean region, was studied under controlled light, temperature and moisture conditions. Germination rates in D. virgata were generally higher at alternating (25/15^C) and low (15^C) temperatures, whereas in D. erucoides optimal germination rates were achieved at higher temperatures (25^C). No correlation between seed weight and germination was found in either species. In D. virgata, the geographic origin of the seed had an important effect on germination percentage. Great germination variability was found among the populations and even among seeds belonging to the same population. In this species, the application of gibberellic acid stimulated germination, especially in the populations with higher dormancy levels. Dormancy was found in mature D. virgata seeds but not in those of D. erucoides. In both species, germination percentages decreased after a certain period of storage at low temperatures. This period varied depending on the species and the population considered.

Asymptotic behaviour and statistical applications of divergence measures in multinomial populations: a unified study*

Abstract: Divergence measures play an important role in statistical theory, especially in large sample theories of estimation and testing. The underlying reason is that they are indices of statistical distance between probability distributions P and Q; the smaller these indices are the harder it is to discriminate between P and Q. Many divergence measures have been proposed since the publication of the paper of Kullback and Leibler (1951). Renyi (1961) gave the first generalization of Kullback-Leibler divergence, Jeffreys (1946) defined the J-divergences, Burbea and Rao (1982) introduced the R-divergences, Sharma and Mittal (1977) the (r,s)-divergences, Csiszar (1967) the ϕ-divergences, Taneja (1989) the generalized J-divergences and the generalized R-divergences and so on. In order to do a unified study of their statistical properties, here we propose a generalized divergence, called (h,ϕ)-divergence, which include as particular cases the above mentioned divergence measures. Under different assumptions, it is shown that the asymptotic distributions of the (h,ϕ)-divergence statistics are either normal or chi square. The chi square and the likelihood ratio test statistics are particular cases of the (h,ϕ)-divergence test statistics considered. From the previous results, asymptotic distributions of entropy statistics are derived too. Applications to testing statistical hypothesis in multinomial populations are given. The Pitman and Bahadur efficiencies of tests of goodness of fit and independence based on these statistics are obtained. To finish, apendices with the asymptotic variances of many well known divergence and entropy statistics are presented.

Distributed concurrent constraint execution in the CIAO system

Abstract: This paper describes the current prototype of the distributed CIAO system. It introduces the concepts of "teams" and "active modules" (or active objects), which conveniently encapsulate different types of functionalities desirable from a distributed system, from parallelism for achieving speedup to client-server applications. It presents the user primitives available and describes their implementation. This implementation uses attributed variables and, as an example of a communication abstraction, a blackboard that follows the Linda model. The functionalities of the system are illustrated through examples, using the implemented primitives. The implementation of most of the primitives is also described in detail.

Mechanical behaviour and failure mechanisms of a binary Mg6%Zn alloy reinforced with SiC particulates

Abstract: The mechanical behaviour in tension and fully reversed cyclic deformation as well as the fracture toughness were measured in an Mg6%Zn alloy reinforced with 20vol.% SiC particulates. The addition of the ceramic reinforcements led to significant improvements in stiffness (up to 62%) and strength, but the ductility and fracture toughness were dramatically reduced. The composite exhibited a strong rsponse to artificial aging, which increased the yield and tensile strength by 120 MPa over that of the as-received material. Cyclic strain hardening was observed in the solution heat treated condition, while the cyclic stress-strain curve was stable after artificial aging at high temperature. In addition, the cyclic yield strength in compression was always lower than in tension owing to the presence of plastic deformation by twinning in compression, which reduced the resistance to plastic flow. The failure mechanisms were very similar in all cases, regardless of the heat treatment and loading condition. Porosity and the inability of the matrix alloy to accommodate the large strain gradients induced by the presence of the SiC particulates were identified as the main causes of the poor ductility and toughness of these composites.

MIX: a general purpose multiagent architecture

Abstract: The MIX multiagent architecture has been conceived as a general purpose distributed framework for the cooperation of multiple heterogeneous agents. This architecture, starting from previous work in our group on multiagent systems, has been redesigned and implemented within a research project investigating a particular class of hybrid systems: those integrated by connectionist and symbolic components. This paper describes in some detail the principal concepts of the architecture: the network model and the agent model. Around these models, a set of languages and tools have been developed. In particular, an Agent Description Language (MIX-ADL) has been designed to specify agents declaratively in a hierarchy of classes.

The hypBFCDE operon from Rhizobium leguminosarum biovar viciae is expressed from an Fnr-type promoter that escapes mutagenesis of the fnrN gene.

Abstract: Pea (Pisum sativum L.) bacteroids produced by Rhizobium leguminosarum bv. viciae UPM791 synthesize a membrane-bound (NiFe) hydrogenase which oxidizes H2 arising from the nitrogen fixation process in root nodules. Synthesis of the active enzyme requires the products of the structural genes hupSL and an array of accessory proteins from at least 15 additional genes, including the gene cluster hypABFCDE, likely involved in nickel metabolism. Unlike the hupSL genes, which are expressed only in symbiosis, the hypBFCDE operon was also activated in vegetative cells in response to low pO2 in the culture medium. In microaerobic cells and in bacteroids, transcription of the hypBFCDE operon occurred from a promoter, P5b, with a transcription initiation site located 190 bp upstream of the ATG start codon of hypB, within the coding sequence of hypA. Transcription start site 5b was preceded by an Fnr box (anaerobox), 59-TTGAgccatgTCAA-39, centered at position -39.5. Expression of the P5b promoter in the heterologous Rhizobium meliloti bacterial host was dependent on the presence of an active fixK gene. A 2.6-kb EcoRI fragment was isolated from an R. leguminosarum bv. viciae UPM791 gene bank by complementing an R. meliloti FixK- mutant. Sequencing of this DNA fragment identified an fnrN gene, and cassette insertion mutagenesis demonstrated that R. leguminosarum bv. viciae fnrN is able to replace the R. meliloti fixK gene for activation of both the R. leguminosarum bv. viciae hypBFCDE operon and the R. meliloti fix genes. However, bacteroids from a genomic FnrN- mutant of R. leguminosarum bv. viciae exhibited wild-type levels of hydrogenase activity. Microaerobic expression of P(5b) was reduced to ca. 50% of the wild-type level in the FnrN(-) mutant. These results indicate that hyp gene expression escapes mutagenesis of the fnrN gene and suggest the existence of a second fnr-like gene in R. leguminosarum by. viciae. Southern blot analysis with an fnrN internal probe revealed the presence of a second genomic region with homology to fnrN.

A PREttier compiler-compiler: generating higher-order parsers in C

Abstract: Top-down (LL) context-sensitive parsers with integrated synthesis and use of attributes are easy to express in functional programming languages, but the elegant functional programming model can also serve as an exact prototype for a more efficient implementation of the technology in ANSI C. The result is a compiler-compiler that takes unlimited lookahead and backtracking, the extended BNF notation, and parameterized grammars with (higher-order) meta-parameters to the world of C programming. This article reports on the utility in question three years after public release. Precc generates standard ANSI C and is ‘plug compatible’ with lex- generated lexical analyzers prepared for the UNIX yacc compiler-compiler. In contrast to yacc, however, the generated code is modular, which allows parts of scripts to be compiled separately and linked together incrementally. The constructed code is relatively efficient, as is demonstrated by the example Occam parser treated in depth here, but the main advantages we claim are ease of use, separation of specification and implementation concerns, and maintainability.

Fuzzy reasoning for multisensor management

Abstract: A multisensor management scheme is proposed in this contribution, intended to be applicable to a generalized suite of several multitask sensors, deployed for multitarget surveillance purposes. The objective of the multisensor management function is to optimize, in a coordinated fashion, the measurement process of each sensor using overall system performance information. The coordination manager will provide each sensor with a list of sensor-level tasks, ranked according to their priorities, which are in turn obtained from the inferred global system-level necessity of fulfilling the task. Each sensor-level task will be also accompanied with an indication of the sensing performance objective desired to achieve with it, expressed in different terms depending on the type of task. The management process will be performed by means of a symbolic reasoning process starting from the output information of the data fusion and situation assessment functions. Fuzzy reasoning strategies and possibility theory concepts, in conjunction with heuristic search techniques, are applied to the processes of system-level task necessity evaluation, sensor-level task priority computation, specification of the sensing performance objectives (desired to guarantee with each task) and sensor(s)-to-task(s) assignment.

Influence of reinforcement fracture on the cyclic stress-strain curve of metal-matrix composites

Abstract: The cyclic stress-strain curve of a 2618 Al alloy reinforced with 15 vol.% SiC particulates was measured through the incremental step method in the naturally aged and peak-aged conditions. The mechanical response was also simulated by means of the finite element analysis of a unit cell to determine the average stresses acting on the matrix and on the reinforcements during cyclic deformation. The stresses on the reinforcements were used to calculate the fraction of broken reinforcements by assuming that the reinforcement strength follows the Weibull statistics. Then the cyclic stress-strain curve, including the influence of reinforcement fracture, was obtained by neglecting the load carried by broken reinforcements. Finally, the predictions of the model (the cyclic stress-strain curve and the fraction of broken reinforcements) were compared with the experimental results.