Andrés García

Maternal quality and differences in milk production and composition for male and female Iberian red deer calves (Cervus elaphus hispanicus)

Several theories predict a sex-biased investment either through unbalanced sex ratios in offspring or through differences in provisioning. According to them, one would expect an optimisation in indirect fitness, or else a compensation for increased mortality of one sex. In addition, biases in provisioning may also arise as a consequence of weight-dependent non-adaptive nutrient demands by offspring. This study examines milk provisioning and sex biases in offspring sex ratio together with maternal quality variables. Mothers of higher quality (weight and age) showed greater milk provisioning ability (in terms of production) resulting in greater calf weight gain. Mothers of sons produced greater yields of milk, milk protein, fat and lactose than mothers of daughters, and increased percentage of protein after controlling for higher male birth weight. In contrast, mothers of males did not differ from mothers of females in age or any body weight variables related to maternal quality. These results suggest that differences in milk production and composition for sons and daughters are rather a mechanism to optimise indirect fitness than a mechanism to compensate for increased mortality in male calves, or a consequence of greater weight-dependent nutrient demands by heavier male calves. Results also suggest that biases in milk provisioning may occur without biases in offspring sex ratio, and furthermore, in contrast to the prediction that biases should be relative to the mean investment of the population, that milk provisioning biases might not be relative.

Lactation under food constraints in Iberian red deer Cervus elaphus hispanicus

The plane of nutrition in deer may affect body condition and lactation in hinds and calf growth both through long-term density-dependent effects and by shortterm abiotically originated falls in food supply. Our study examines the effect of low nutrient availability after calving on lactation in captive Iberian red deer Cervus elaphus hispanicus. Twelve hinds and their calves were allotted to a food restricted (50–60% daily energy requirements) or a control group just after calving. Hinds in the food-restricted group showed a greater body mass loss, produced less milk and yield of milk fat, protein and lactose, and a different lactation curve shape, which resulted in reduced calf growth. However, the time course of lactation variables appeared to show a compensatory response up to week 4: a greater milk fat content in low-nutrition hinds than in the control group appeared to compensate for lower milk production, as neither calf nor hind mass differed from the control group, and lactation variables in both groups showed a standard lactation pattern. In contrast, as milk fat content fell below that of the control group after week 4, the low nutrition plane overcame a standard lactation pattern and groups differed in most variables (e.g. calf and hind mass and percentage of calf growth). Our results appear to show that deer mobilise body reserves in lactation to maintain offspring growth under temporary reductions in food intake, which may be a strategy of securing investment in current offspring at the expense of reproducing the following season.

Subspecies and Body Size Allometry Affect Milk Production and Composition, and Calf Growth in Red Deer: Comparison of Cervus elaphus hispanicus and Cervus elaphus scoticus

Studies comparing lactation in wild mammals have shown that maternal weight scales with offspring weight, milk production, or its energy. However, no study appears to have scaled milk composition with maternal or offspring weight. Although diet affects milk composition and production, their effects in biological studies have almost never seemed to be controlled. In this study, we compare two subspecies of red deer, Scottish deer, Cervus elaphus scoticus (10 lactations), and Iberian deer, Cervus elaphus hispanicus (14 lactations), kept under the same diet and housing to assess differences in hind and calf weights and their trends, milk production and composition, and their allometric relationships. Scottish hinds were heavier, and calf weight and gains were greater than Iberian ones, with greater milk production and milk protein content, but they did not differ in fat or lactose content. Calf birth weight, milk production, and protein content showed significant allometric relationships with maternal weight, but no relationship was found for fat, lactose, or any of these variables with calf birth weight. Protein content correlated with calf birth weight, and calf weight trend depended on milk protein production rather than on that of fat or lactose. Protein may be the most important milk component to explain growth and milk composition differences between closely related mammals.

Inverse dynamics based control system for a three-degree-of-freedom flexible arm

This article describes a new control scheme designed for a three-degree-of-freedom flexible arm. This arm has been built with light links, has most of its mass concentrated at the tip, and uses a special mechanical configuration to approximately decouple tip motions in spherical coordinates. This configuration facilitates the dynamic modeling and control of the arm. A compliance matrix can be used to model the oscillations of the structure. A consequence of this simple dynamic is that minimum sensing effort is required (only direct motor and tip measurements), and the use of complex observers is avoided because the state of the system can be very easily obtained from these measurements. A two-nested control-loop scheme is used to control the tip position by using joint position and tip acceleration feedbacks. The stability of the controlled system is analytically proven in the case of perfect dynamic modeling. Then, an analysis of stability in the case of modeling errors is carried out, and conditions for local stability are derived. Experimental results are presented for the cases of perturbation control and trajectory tracking. Comparative results between controlled and noncontrolled tip responses are also shown.

Gauge-Based Tip Position Control of a New Three-Degree-of-Freedom Flexible Robot

Flexible robots have given rise to numerous investigations, and their use is easily justified in two main cases: (1) when the weight of the robot has to be minimized and (2) when collisions of the robot with the environment are foreseen, as a flexible lightweight robot delivers less impact energy. Much work has been done by different authors on the position control of flexible robots using feedback of the tip position or tip acceleration. However, the use of these sensing devices is problematic in practical applications of flexible arms: three-dimensional tip position sensing is expensive, and occlusions appear at some arm configurations. Accelerometers cannot be used when contact of the tip with the environment is expected because these sensors cannot stand the high negative accelerations produced at the impact (unless very low speed motions are performed). This paper studies the possibility of carrying out the tip position control of a three-degree-of-freedom flexible arm using sensing devices placed far away from the tip (where contact is expected) in such way that they can easily stand the impact, which will be needed in the development of a position/force control for flexible robots. A control scheme based on motor position sensing plus some strain gauges placed on the arm structure is proposed. Stability of this control scheme is proven and is experimentally verified on a flexible manipulator prototype that was developed in the authors’ laboratory.

Experimental Testing of a Gauge Based Collision Detection Mechanism for a New Three-Degree-of-Freedom Flexible Robot

The use of flexible robots can be easily justified in two main cases: (1) when the weight of the robot has to be minimized and (2) when collisions between the robot and the environment are foreseen, since a flexible, lightweight robot implies less impact energy. The position control of these robots has already been analyzed in previous communications. However, the second of these cases justifying the use of flexible robots requires further consideration, leading to the development of a force controller. Inmost up to date analysis the force control is studied beginning from a known contact point at a given collision time. In a more realistic approach, however, an accurate detection of the collision would be needed prior to dealing with the force control. After developing a reliable position controller for a three-degree-of-freedom flexible robot using strain gauges placed over the robot structure, in this paper we deal with the possibility of carrying out the collision detection for the same prototype. This has been easily achieved by analyzing some estimated signals such as tip position and tip velocity. However, a complete analysis of the information obtained with the sensors has been required to obtain those estimates and a signal processing scheme had to be devised for a previous filtering of the original signals from the sensors (encoders and strain gauges). This work has been carried out as a first step towards the position/force control. Experimental results on a three-degree-of-freedom flexible arm prototype are presented to verify how well this method performs.

Distributed decision support system for airport ground handling management using WSN and MAS

The economic situation in the air transportation industry claims for new business models supported by accurate management processes, which need constant feedback of the real status of the environment. The objective of this work is to achieve an updated/real decision support systems (DSS) to allocate resources in an airport even when disturbances occur by combining artificial intelligent techniques with visibility technologies. This work proposes the combined use of Multi-agent systems (MAS) along with Wireless Sensor Networks (WSN) to provide the required information on the status of the resources and the environment. The MAS is based on a double layer of decision-taking levels and on a Markov reward function whereas the WSN is based on a Zigbee network of Radio Frequency Identification (RFID) readers with active tags as end nodes, which are carried by the physical resources. The proposed distributed DSS has been tested at Ciudad Real Central Airport in Spain.

Analysis of the applicability of RFID & wireless sensors to manufacturing and distribution lines trough a testing multi-platform

The increasing number of product references involved in production and distribution lines, implies an added complexity for the management and control systems of companies. Moreover, customers are increasingly in favour of the use of new technology when placing their orders, such as on-line booking and purchasing, and their requirements are increasingly greater. Customers, as well as companies, are demanding updated information on the condition and location of their ordered products during fabrication and transportation phases. This paper proposes an analysis of the applicability of accessing information in real-time related to a products condition along the manufacturing and supply chain, by means of the integration of RFID systems with sensors and wireless networks. To achieve this purpose a multi-service controller board has been designed into which specific operation modules are plugged. The modules are active or passive RFID readers, modules with sensors or actuators, or modules for data storage. Furthermore, some other communication modules have also been developed offering WLAN, ZigBee or GPRS networks. Using these solutions, companies will have a more reliable and faster access to information in different areas of manufacturing and logistics. Their ease of implantation and reliability makes the use of the systems analysed here, an ideal solution for companies who wish to monitor over their manufacturing and distribution lines more easily. In addition, when all this technology works together, new functions and applications appear with interesting results for the different case studies.

Robustness Comparative Study of Two Control Schemes for 3-DOF Flexible Manipulators

This article describes a comparative study of two control schemes designed for a new three-degree-of-freedom flexible arm. This arm has been built with light links, has most of its mass concentrated on the tip, and its special mechanical configuration uncouples tip motions in spherical coordinates. This special configuration simplifies the dynamic modeling and control of the arm. A compliance matrix is used to model the oscillations of the structure. A consequence of this simple dynamics is that minimum sensing effort is required (only direct motor and tip measurements), and the use of complex observers is avoided because the state of the system can be very easily obtained from these measurements; then its control becomes very simple. Two two-nested control loop schemes are used to control the tip position, by using a joint position and tip acceleration feedback, measured with accelerometers placed at the tip (first control scheme), or tip deflexions feedback, measured with strain gauges placed at the bars of the mechanism near the joints (second control scheme). Both control systems can be considered as equivalents when nominal payload is used for designing them. It can be proved that the use of strain gauges is more robust than the use of accelerometers as tip sensors if the tip mass differs from the nominal one. Simulated results are presented for both control schemes and different payload conditions. Comparative results between the controlled and non-controlled tip responses are also shown.

The impact of auto-ID technology in materials handling systems

Abstract Auto ID lechnology is a very powerful tool that will open the way for new method, and solutions for handling. In general Materials Handling refers to the necessary tasks to be perfomed in order to move load around the factory floor as well as to store and freight it. This paper highlights the impact that the introduction of Auto-ID technology will have in various industrial Materials Handling Systems. Current limitation s in these systems are analyzed and some examples are presented to out line the importance of Auto-ID in solving specific prohlems.