Facing Non-Stationary Conditions with a New Indicator of Entropy Increase: The Cassandra Algorithm

We address the problem of detecting non-stationary effects in time series (in particular fractal time series) by means of the Diffusion Entropy Method (DEM). This means that the experimental sequence under study, of size $N$, is explored with a window of size $L << N$. The DEM makes a wise use of the statistical information available and, consequently, in spite of the modest size of the window used, does succeed in revealing local statistical properties, and it shows how they change upon moving the windows along the experimental sequence. The method is expected to work also to predict catastrophic events before their occurrence.Comment: FRACTAL 2002 (Spain

Acculturation Status and Sexuality Among Female Cuban American College Students

The authors examined relations among different measures of acculturation, and between acculturation and sexual behavior, in a sample of female Cuban American college students (n = 61, M age = 18.4 years) who completed self-report surveys. In the first set of analyses, weak to moderate associations emerged among 4 measures of acculturation (birthplace, childhood language use, current language use, and ethnic identity), suggesting that inconsistent findings from prior research may have resulted from measurement limitations. In multivariate analyses, the authors examined predictors of sexual behavior and found that 1 aspect of acculturation (higher levels of ethnic identity) and background characteristics (being older and less religious) were associated with voluntary sexual intercourse. Moreover, higher levels on a sexual risk composite were associated with being born in the United States, more ethnically identified, older, and less religious. These analyses highlight the need for specificity in assessing acculturation in a college student population and support the need to examine cultural factors directly in sexuality research

Problem Behavior Theory: An Examination of the Behavior Structure System in Latino and non-Latino College Students

Scholars have proposed that diverse problem and conventional behaviors reflect a single underlying factor; however, others suggest that the strength and pattern of interrelations among problem and conventional behaviors are not consistent across different cultural groups. The present study investigated the factor structure of problem and conventional behaviors in Cuban, non-Cuban Latino, and non-Latino college students. Two hundred and sixty-nine college students (70% women; M age=19.0, SD=2.34) reported on their substance use, and involvement in deviant (e.g., fighting, shoplifting, vandalism) and conventional (e.g., school performance, religiosity) behaviors. In support of the behavior system of Problem Behavior Theory (PBT), a single-common factor accounted for the significant interrelations among the different problem behaviors for the entire sample. However, variations in the number of factor structures emerged by ethnic group and gender, suggesting that the behavior system may operate differently across these groups. A discussion of the role of culture on problem and conventional behaviors is presented. Escolares han propuesto que diversos comportamientos problematicos y convencionales reflejan solo un factor subyacente: sin embargo, otros sugieren que la fuerza y el modelo de interrelaciones entre comportamientos problematicos y convencionales no sean constantes a través de diversos grupos culturales. El estudio presente investigó la estrucutra factorial de comportamientos problematicos y convencionales en Cubano, no-Cubano Latino, y no- Latino estudiantes de universidad. Doscientos y sesenta nueve estudiantes de la universidad (mujeres 70%; M edad = 19.0, SD = 2,34 divulgaron sobre su uso de la sustancia y su implicación en comportamientos irregulares (e.g. el luchar, el robar en tiendas, el vandalismo) y convencionales (e.g. funcionamento en la escuela, religiosidad). En sustento del sistema del comportamiento en la Teoría del Comportamiento Problematico (TCP), solo un factor común consideró las interralaciones significativas entre los diversos comportamientos problematicos para la población entera. Sin embargo, las variaciones en el número de las estructuras factoriales emergieron por el grupo étnico y el género, sugiriendo que el sistema del comportamiento puede funcionar diferentemente a través de estos grupos. Una discusión de la función de la cultura en comportamientos problemáticos y convencionales se presenta

Identity and Institutional Change in a Mature Field: The Re-emergence of the Swiss Watchmaking Industry, 1970-2008

Thesis advisor: Mary Ann GlynnThis dissertation examines the decline and re-emergence of the Swiss mechanical watch industry from 1970-2008, exploring how, when, and why market demand for legacy technologies resurrect and reshape a mature field. Extending existing research on technology emergence and death, I reveal the dynamics of technology and field re-emergence. I focus on the mechanisms of identity and institutional change associated with re-emergence, as well as how institutional leaders and guardians serve as agents of change who simultaneously preserve and reframe the values and product conceptions associated with a legacy technology. Additionally, I advance the notion of identity ambidexterity by examining how organizations explore and exploit multiple elements of their identity simultaneously during such periods of instability. Using qualitative and quantitative methods, I analyze a wide range of interview, archival, historical, and observational data at the levels of the industry and the organization. More broadly, I seek to demonstrate how the reclamation of legacy identities reshapes the institutional environment of a mature field, and how incumbent firms re-define their organizational identities after a technological innovation threatens to destroy their dominant market position.Thesis (PhD) — Boston College, 2013.Submitted to: Boston College. Carroll School of Management.Discipline: Management and Organization

Compression and diffusion: a joint approach to detect complexity

The adoption of the Kolmogorov-Sinai (KS) entropy is becoming a popular research tool among physicists, especially when applied to a dynamical system fitting the conditions of validity of the Pesin theorem. The study of time series that are a manifestation of system dynamics whose rules are either unknown or too complex for a mathematical treatment, is still a challenge since the KS entropy is not computable, in general, in that case. Here we present a plan of action based on the joint action of two procedures, both related to the KS entropy, but compatible with computer implementation through fast and efficient programs. The former procedure, called Compression Algorithm Sensitive To Regularity (CASToRe), establishes the amount of order by the numerical evaluation of algorithmic compressibility. The latter, called Complex Analysis of Sequences via Scaling AND Randomness Assessment (CASSANDRA), establishes the complexity degree through the numerical evaluation of the strength of an anomalous effect. This is the departure, of the diffusion process generated by the observed fluctuations, from ordinary Brownian motion. The CASSANDRA algorithm shares with CASToRe a connection with the Kolmogorov complexity. This makes both algorithms especially suitable to study the transition from dynamics to thermodynamics, and the case of non-stationary time series as well. The benefit of the joint action of these two methods is proven by the analysis of artificial sequences with the same main properties as the real time series to which the joint use of these two methods will be applied in future research work.Comment: 27 pages, 9 figure

An automatic machine able to perform variable rate application of flame weeding: design and assembly

This paper describes the design and development of an automatic machine able to perform Variable Rate Application of cross flaming in maize fields. The VRA flaming machine was designed to remove weeds mechanically from the inter-row area and perform selective and targeted cross flaming along the crop rows. The mechanical treatment will be performed in a continuous way, even without weed presence. On the contrary, cross flaming on the maize rows is applied selective and automatically only if weeds are presence. Flame weeding is applied by means of prismatic burners fed by Liquefied Petroleum Gas, able to treat 25 cm wide strips of soil surface including crop rows. Flaming can be used selectively in maize, which can tolerate the heat released from the burners. Mechanism of morphological tolerance is the presence of many layers of the outer leaf tissue protecting the inner growing point. A low or a high LPG dose can be chosen automatically according to the weed cover percentage detected by a weed detection system. The ignition system of the VRA flaming machine is almost instantaneous and the complete flame in the burner is obtained in 0.4 s. The machine is provided with an automatic steering system in order to avoid damaging the maize plants with the rigid tools used for mechanical weed removal. The VRA flaming machine is a new technology for precision agriculture and was designed and built within the “Robot fleets for Highly Effective Agriculture and forestry management” (RHEA) Project, funded by EU, aimed to develop a fleet of heterogeneous autonomous robot units in order to perform site-specific treatments related to crop protection in different agricultural scenarios

The use of different hot foam doses for weed control

Thermal weed control technology plays an important role in managing weeds in synthetic herbicide-free systems, particularly in organic agriculture. The use of hot foam represents an evolution of the hot water weed control thermal method, modified by the addition of biodegradable foaming agents. The aim of this study was to test the weeding eect of dierent five hot foam doses, in two sites of dierent weed composition fields [i.e., Festuca arundinacea (Schreb.), Taraxacum ocinale (Weber) and Plantago lanceolata (L.)], by evaluating the devitalisation of weeds, their regrowth, the weed dry biomass at the end of the experiment and the temperature of hot foam as aected by dierent foam doses. The results showed that the eect of the hot foam doses diered with the dierent infested weed species experiments. In the Festuca arundinacea (Schreb.) infested field, all doses from 3.33 L m2 to 8.33 L m2 led to a 100% weed cover devitalisation and a lower weed dry biomass compared to the dose of 1.67 L m2, whereas the weed regrowth was similar when all doses were applied. In the Taraxacum ocinale (Weber) and Plantago lanceolata (L.) infested fields, doses from 5.00 L m2 to 8.33 L m2 in site I and from 3.33 L m2 to 8.33 L m2 in site II led to 100% of weed cover devitalisation. The highest doses of 6.67 L m2 and 8.33 L m2 led to a slower weed regrowth and a lower weed dry biomass compared to the other doses. The time needed for weeds to again cover 50%, after the 100% devitalisation, was, on average, one month when all doses were applied in the Festuca arundinacea (Schreb.) infested field, whereas in the Taraxacum ocinale (Weber) and Plantago lanceolata (L.) fields, this delay was estimated only when doses of 6.67 L m2 and 8.33 L m2 were used in site I and a dose of 8.33 L m2 in site II. Thus, in the Festuca arundinacea (Schreb.) field experiments hot foam doses from 3.33 L m2 to 8.33 L m2 were eective in controlling weeds, and the use of the lowest dose (i.e., 3.33 L m2) is recommended. However, for Taraxacum ocinale (Weber) and Plantago lanceolata (L.) the highest doses are recommended (i.e., 6.67 L m2 and 8.33 L m2), as these led to 100% weed devitalisation, slower regrowth, and lower weed dry biomass than other doses. A delay in the regrowth of weeds by 30 days can lead to the hypothesis that the future application of hot foam as a desiccant in no-till field bands, before the transplant of high-income vegetable crops, will provide a competitive advantage against weeds

Flaming, glyphosate, hot foam and nonanoic acid for weed control: a comparison.

Synthetic herbicides are commonly used in weed management, however, 70 years of use has led to weed resistance and environmental concerns. These problems have led scientists to consider alternative methods of weed management in order to reduce the inputs and impacts of synthetic herbicides. The aim of this experiment was to test the level of weed control using four weeding methods: glyphosate applied at an ultra-low volume, the organic herbicide nonanoic acid, flaming, and hot foam. The results showed that weed control was eective only when flaming and hot foam were applied (99% and 100% weed control, respectively). Nonanoic acid at a dose of 11 kg a.i. ha1 diluted in 400 L of water did not control developed plants of Cyperus esculentus (L.), Convolvulus arvensis (L.) and Poa annua (L.). Glyphosate at a dose of 1080 g a.i. ha1 (pure product) only controlled P. annua (L.), but had no eect on C. esculentus (L.) and C. arvensis (L.). After the aboveground tissues of weeds had died, regrowth began earlier after flaming compared to hot foam. There was no regrowth of P. annua (L.) only after using hot foam and glyphosate. Hot foam was generally better at damaging the meristems of the weeds. In one of the two experiment sites, significantly more time was needed after the hot foam to recover 10% and 50% of the ground compared to flaming. The time needed to recover 90% of the ground was on average 26–27 days for flaming and hot foam, which is the time that is assumed to be required before repeating the application. A total of 29 days after the treatments, weeds were smaller after flaming, glyphosate and hot foam compared to nonanoic acid and the control, where they had more time to grow

Hot foam and hot water for weed control: a comparison

Thermal weed control plays an important role in managing weeds in synthetic herbicide-free systems, particularly in organic agriculture and in urban areas where synthetic herbicides are prohibited. This study compares the impact on weed control of increased doses of hot water and hot foam (i.e. 0, 0.67, 1.67, 3.33, 5.00, 6.67 and 8.33 kg m–2). The doses were applied using the same machine. The temperatures, weed control effectiveness, weed regrowth after the death of the aboveground vegetative weed tissues, and weed dry biomass 30 days after the treatments were studied in two experimental fields with a different weed composition (i.e. Site I and Site II). The results showed that difficult weeds to control, such as Cynodon dactylon (L.) Pers., Digitaria sanguinalis (L.) Scop. and Taraxacum officinale Weber, like all the other species in the initial weed populations in the two experiments, died after lower doses of hot foam compared to hot water. Adding foam to hot water made it possible to lower the required dose of water by at least 2.5-fold compared to hot water used alone. By insulating the weeds, the foam led to higher peak temperatures and slower temperature decay, thus determining an effective weed control with lower doses compared to hot water. Starting from 11 days and 16 days after treatments (for Site I and Site II, respectively), there were no statistically significant differences in weed regrowth between hot foam and hot water at all the doses applied. There were no differences between the dry biomass of weeds collected 30 days after treatments when the same doses of hot foam and hot water were used

The influence of non-living mulch, mechanical and thermal treatments on weed population and yield of rainfed fresh-market tomato (Solanum lycopersicum L.)

Weed control is often a major limitation for vegetable crops, since compared to arable crops fewer herbicides are available and the crops are more sensitive to weeds. Field experiments were carried out in the province of Pisa (Central Italy) to determine the effect of two different mulches (black biodegradable plastic film and wheat straw) and mechanical and thermal treatments on weed population and yield of rain-fed fresh market tomato (Solanum lycopersicum L.). Rolling harrow, flaming machine and precision hoe for weed control, which were either built, enhanced or modified by the University of Pisa were used separately (mechanical-thermal strategy) or in combination with a straw mulch (mechanical-thermal-straw strategy). These two innovative strategies were compared with the traditional farming system, which uses a biodegradable plastic mulch film. The strategies were compared in terms of machine performance, weed density, total labour requirement, weed dry biomass, and crop fresh yield at harvest. The total operative time for weed control was on average ~25 h ha-1 for the two systems, which included mulching, and over 30 h ha-1 for the mechanical-thermal strategy. The three strategies controlled weeds effectively, with only 30 g m-2 in each treatment. Tomato yield, however, was 35% higher for strategies that included mulching (both biodegradable film and straw)