Robust Sliding Control of SEIR Epidemic Models

This paper is aimed at designing a robust vaccination strategy capable of eradicating an infectious disease from a population regardless of the potential uncertainty in the parameters defining the disease. For this purpose, a control theoretic approach based on a sliding-mode control law is used. Initially, the controller is designed assuming certain knowledge of an upper-bound of the uncertainty signal. Afterwards, this condition is removed while an adaptive sliding control system is designed. The closed-loop properties are proved mathematically in the nonadaptive and adaptive cases. Furthermore, the usual sign function appearing in the sliding-mode control is substituted by the saturation function in order to prevent chattering. In addition, the properties achieved by the closed-loop system under this variation are also stated and proved analytically. The closed-loop system is able to attain the control objective regardless of the parametric uncertainties of the model and the lack of a priori knowledge on the system.

Linear Chromatic Adaptation Transform Based on Delaunay Triangulation

Computer vision algorithms that use color information require color constant images to operate correctly. Color constancy of the images is usually achieved in two steps: first the illuminant is detected and then image is transformed with the chromatic adaptation transform ( CAT). Existing CAT methods use a single transformation matrix for all the colors of the input image. The method proposed in this paper requires multiple corresponding color pairs between source and target illuminants given by patches of the Macbeth color checker. It uses Delaunay triangulation to divide the color gamut of the input image into small triangles. Each color of the input image is associated with the triangle containing the color point and transformed with a full linear model associated with the triangle. Full linear model is used because diagonal models are known to be inaccurate if channel color matching functions do not have narrow peaks. Objective evaluation showed that the proposed method outperforms existing CAT methods by more than 21%; that is, it performs statistically significantly better than other existing methods.

Effects of Spring Temperatures on the Strength of Selection on Timing of Reproduction in a Long-Distance Migratory Bird

Climate change has differentially affected the timing of seasonal events for interacting trophic levels, and this has often led to increased selection on seasonal timing. Yet, the environmental variables driving this selection have rarely been identified, limiting our ability to predict future ecological impacts of climate change. Using a dataset spanning 31 years from a natural population of pied flycatchers (Ficedula hypoleuca), we show that directional selection on timing of reproduction intensified in the first two decades (1980-2000) but weakened during the last decade (2001-2010). Against expectation, this pattern could not be explained by the temporal variation in the phenological mismatch with food abundance. We therefore explored an alternative hypothesis that selection on timing was affected by conditions individuals experience when arriving in spring at the breeding grounds: arriving early in cold conditions may reduce survival. First, we show that in female recruits, spring arrival date in the first breeding year correlates positively with hatch date; hence, early-hatched individuals experience colder conditions at arrival than late-hatched individuals. Second, we show that when temperatures at arrival in the recruitment year were high, early-hatched young had a higher recruitment probability than when temperatures were low. We interpret this as a potential cost of arriving early in colder years, and climate warming may have reduced this cost. We thus show that higher temperatures in the arrival year of recruits were associated with stronger selection for early reproduction in the years these birds were born. As arrival temperatures in the beginning of the study increased, but recently declined again, directional selection on timing of reproduction showed a nonlinear change. We demonstrate that environmental conditions with a lag of up to two years can alter selection on phenological traits in natural populations, something that has important implications for our understanding of how climate can alter patterns of selection in natural populations.

Low Effort L-i Nuclear Fusion Plasma Control Using Model Predictive Control Laws

One of the main problems of fusion energy is to achieve longer pulse duration by avoiding the premature reaction decay due to plasma instabilities. The control of the plasma inductance arises as an essential tool for the successful operation of tokamak fusion reactors in order to overcome stability issues as well as the new challenges specific to advanced scenarios operation. In this sense, given that advanced tokamaks will suffer from limited power available from noninductive current drive actuators, the transformer primary coil could assist in reducing the power requirements of the noninductive current drive sources needed for current profile control. Therefore, tokamak operation may benefit from advanced control laws beyond the traditionally used PID schemes by reducing instabilities while guaranteeing the tokamak integrity. In this paper, a novel model predictive control (MPC) scheme has been developed and successfully employed to optimize both current and internal inductance of the plasma, which influences the L-H transition timing, the density peaking, and pedestal pressure. Results show that the internal inductance and current profiles can be adequately controlled while maintaining the minimal control action required in tokamak operation.

Preliminary observation on culture of Penaeus monodon in low-saline waters

The feasibility of semi-intensive culture of Penaeus monodon in low saline environment was investigated by comparing the growth and production in low (0.16-6.52 ppt) and high (4.60-19.42 ppt) saline areas at two stocking densities (10.5 and 16 individuals/m super(2)). After 135 days of culture, yield of shrimp in low and high stocking densities was 1563.37 kg/ha and 2274 kg/ha, respectively, in low saline ponds, and 1173.00 and 1974.00 kg/ha, respectively in high saline ponds. Food conversion ratio (FCR, 1.31-1.58) and specific growth rate (SGR 21.04-21.19%) were higher in low saline ponds as compared to high saline ponds (FCR, 1.35-1.68; SGR, 19.22-19.88%). Growth of shrimp was satisfactory in low saline ponds even when salinity decreased after 60 days of culture to almost freshwater level (0.16 ppt) indicating the variability of semi-intensive culture of P. monodon in low saline environment.

Os sermões de santo Antônio de Lisboa / de Pádua: elementos retóricos, teológicos e contextuais

Santo Antônio de Lisboa / de Pádua viveu entre 1191 e 1231, período conhecido como Baixa Idade Média (século XIII ao XV), estudou nos centros de ensino mais proeminentes de Portugal em sua época, Mosteiro de São Vicente e Mosteiro de Santa Cruz de Coimbra, o que lhe possibilitou assimilar vasto conhecimento que seria usado posteriormente na pregação e no combate aos hereges, sobretudo os cátaros. Em uma época de efervescência religiosa, em que os fiéis exigiam maior participação na vida eclesiástica, e de crescentes críticas, os movimentos mendicantes foram o sustentáculo de Roma: os dominicanos com os estudos e com a pregação, e os franciscanos com a pregação por meio sobretudo da vida exemplar. É também nesse período que tem início o estabelecimento de uma arte de pregar medieval, que possui como referência a própria prédica dos primórdios do Cristianismo, baseando-se principalmente em Jesus Cristo e no apóstolo Paulo; nos Padres da Igreja, sobretudo Santo Agostinho e Gregório Magno; e, enfim, em diversos preceptores do século XIII. Santo Antônio valeu-se de todo o conhecimento adquirido nos mosteiros pelos quais passou e da ars praedicandi do período, mostrando-se bastante familiarizado com as questões de seu tempo. Critica severamente aos sacerdotes iníquos, organiza de forma sistemática a teologia da Trindade e se põe como eco estrondoso do IV Concílio de Latrão. Em seus sermões é possível verificar a presença de vários elementos persuasivos que possuem como objetivo alcançar a benevolência do ouvinte e, assim, atingir o propósito máximo, no dizer de Santo Agostinho: instruir para convencer e comover. Para alcançar tal propósito, fez amplo uso das cláusulas, das Ciências Naturais, dos Pais da Igreja, de escritores pagãos e dos bestiários medievais. Este último foi de vital importância principalmente na pregação contra os hereges cátaros, que negligenciavam a natureza como algo puro e de onde se poderia retirar preceitos espirituais ocultos. São esses os objetos, textuais e contextuais, a serem observados na presente dissertação.

开垦和放牧对内蒙古半干旱草原蒸发散的影响

为了研究开垦和放牧对内蒙古半干旱草原生态系统蒸发散的影响，我们以内蒙古锡林郭勒盟多伦县的草地和农田以及锡林浩特围封草地和退化草地为实验样地，利用涡度协方差技术对四个样地2006-2007年的蒸发散和微气象因子进行连续测定，探讨开垦和放牧对内蒙古半干旱草原生态系统蒸发散的影响及其驱动机制。同时利用稳定同位素技术区分多伦半干旱草原生态系统蒸发散的组分，初步探讨生态系统蒸发散各组分的变化特征及其驱动因子。 在观测的两年里，四个生态系统的年蒸发散接近或超过了年降雨量。在较湿润年份（2006年）的生长季（5-9月），开垦使得半干旱草原的蒸发散降低了15%，而在较干旱年份（2007年）降低了7%。放牧在2006年生长季期间使草原生态系统蒸发散降低了13%，而在2007年生长季里，围封草地和退化草地的蒸发散没有显著性差异。开垦和放牧造成的土壤含水量显著下降是生态系统蒸发散降低的最主要的原因。此外，农田开垦改变了植被的种类和物候特征，缩短了植物的生长期（农作物的生长期主要是6-8月，而草地的生长季一般为5-9月），是造成农田整个生长季的蒸发散比草地低的另一个原因。干旱年份降雨量少、土壤含水量低，限制了植被的生长，降低了冠层导度，从而导致了植物蒸腾的下降。另一方面，在干旱年份，开垦和放牧增加了草原生态系统蒸发散对土壤含水量变化的敏感性，表明未来降雨格局的变化不仅直接通过影响土壤含水量来改变蒸发散，而且会影响蒸发散和土壤含水量之间的相关性。 通过研究生态系统对不同强度和不同时间降雨的响应表明，> 3 mm的降雨会增加内蒙古半干旱草原生态系统的土壤含水量和蒸发散，对内蒙古半干旱草原生态系统关键过程有效。雨后1-2天蒸发散达到峰值，之后下降。多数大的降雨事件后，农田和退化草地蒸发散峰值比相对应的草地高，之后下降的也快，这与植被的生长状况、凋落物的量和地面的裸露程度有关。雨后土壤含水量和蒸发散的变化与降雨事件的大小呈正相关的关系，并且蒸发散的变化与土壤含水量的变化有显著的线性相关性，说明了土壤含水量是影响蒸发散变化的主要因子。土壤含水量初始值和干旱期的长短会影响内蒙古半干旱草原生态系统蒸发散对降雨的响应。土壤含水量初始值低会增强蒸发散对降雨的响应，而土壤含水量初始值高时，蒸发散对降雨的响应会下降。干旱期长会增强蒸发散对降雨的瞬时响应。围封草地由于有凋落物的缓冲和保水作用，未来降雨强度的增加会促进围封草原植被的生长;而退化草地地表裸露，对大的降雨事件缓冲作用小，地表径流和土壤蒸发强烈，不利于保水和植被的生长。因此，未来极端降雨事件频率的增加和干旱期的延长势必会对半干旱草原生态系统产生影响，尤其对退化草地产生不利影响。 为了进一步了解蒸发散组分的变化规律及其驱动因子，我们利用稳定同位素与微气象技术相结合的方法，区分半干旱草原生态系统蒸发散的组分。区分结果表明，在2006年和2007年整个生长季期间，植物蒸腾均为蒸发散的主要形式，在2006年和2007年生长季期间植物蒸腾占蒸发散的比例分别为88%和73%。影响植物蒸腾的因子主要是净辐射、大气相对湿度、土壤含水量和叶面积指数;影响蒸发的因子主要是大气相对湿度、土壤含水量和风速;而影响蒸发散的因子主要是净辐射、大气相对湿度、土壤含水量和风速，说明了这些水分流失过程受到不同环境因子的驱动。此外，我们根据一个简单的模型把同位素方法区分的蒸发散组分外推到整个生长季，结果表明，在2006年和2007年整个生长季蒸腾与蒸发散的比例高，并且蒸腾与降雨量的比例高，由此说明，半干旱草原生态系统植被能够有效地利用水分，雨水利用效率高。生态系统总初级生产力（GPP）与植物蒸腾（T）存在明显的正相关关系，从5-8月，生态系统水分利用效率（GPP/T）逐渐升高。 我们的研究结果表明：人类的活动如开垦和放牧通过改变植被类型、土壤持水能力和蒸发散对土壤含水量的响应，降低了草原生态系统的蒸发散，增加了生态系统蒸发散对降雨响应的敏感性，不利于土壤的保水和植被对水分的利用。半干旱草原生态系统蒸发散组分的稳定同位素技术区分，为进一步从新的角度探讨土地利用方式的改变对草原生态系统蒸发散影响的生理机制提供了可能。