In this work, an analysis of land use change was done under two scenarios, 1990 and 2005, to evaluate its effects in Huehuetán watershed runoff by using the same historical storm of the hurricane Stan and the HEC-HMS software; this watershed is located in Chiapas, Mexico. The land use change was made with satellite images interpretation and overlay cartographic operation in the GIS software, ArcView GIS 3.2; the satellite image for 1990 year was LANDSAT TM while 2005 year was SPOT 5. With GeoHMS, an extension for Arc View, was delimitated 25 subbasins and calculated hydrologic parameters to build HMS models, which were constructed in the HEC-HMS 2.2.2 software under synthetic SCS unit hydrograph and with a historical storm during hurricane STAN in October 2005 year. The results show that there were not significant differences in runoff between the two scenarios. In 1990 the flow was 2,566.4 m3·s-1 and 2005 year the flow was 2,544.0 m3·s-1. The runoff decreased 0.87 % in the period of analysis. The results obtained are an expression of good condition of natural resources conservation in the watershed.

For developing the pull force, the tractive elements from the tractor generate slippage due to the adhesion between the tire and the soil. When the tractor moves straight forward, the pull forces and slippages do not change in the rear tires in the 4x2 scheme, neither the rear nor front tires in the 4x4 scheme. As the tractor makes a turn, these parameters change up to generate an instability torque, so that the engine has to develop a torque to overcome it and the driver has to keep forcibly the turn of the tractor toward the indicated side. In this work, were developed the equations to determine the tires pull force and slippage, according to turning radius for tractors having engaged the differential (4x2) and connected the front axle (4x4), considering the sum of the tires slippages, which corresponds to the total pull force developed by the tractor. The results indicated that while the tractor made a turn, as the turning radius decreased, the tire pull force and slip increased in the inner tire (4x2) and rear tire (4x4) and decreased in the outer tire (4x2) and front tire (4x4). For each total pull force needed, there was a limit condition to disengage the differential (4x2) and disconnect the front axle (4x4).

A drying solar tunnel was built with an auxiliary desiccant air recirculation system based on silica gel to adsorb moisture. Onion was cut in slices and dried inside the solar tunnel. Based on empirical data previously obtained, every fifteen minutes per hour, heat regeneration was applied to the auxiliary desiccant system to eliminate the moisture from the silica. Temperature and relative humidity were monitored during the process and drying data were compared with those of a drier that operated without the auxiliary desiccation system. In practical operation without considering initial conditions, the equipment with desiccant system dried the onion slices in 11.1 hours meanwhile the solar tunnel without the auxiliary system required 16.3 hours. A RGB (red green blue) color analysis was carried out for both drying treatments and a better quality was achieved on onions dried with the air-desiccant strategy, as the time exposed to high temperatures under low water quantity was reduced. Onion oxidation was evident when the blue value felt bellow below 100.

SUCROS (a Simple and Universal Crop Growth Simulator) is a mechanistic model, which explains crop growth based on process such as photosynthesis and respiration, under the influence of environmental conditions. The aim of the present research was to investigate to what extend the SUCROS model can predict potential growth and development of a husk tomatoes crop. In order to do that, model predictions of total above-ground dry matter, biomass of leaves, biomass of fruits, biomass of stems of the plants, and leaf area index, were compared against measurements that came from one potential crop growth experiment. In contrast to growth analysis, explanatory models, such as SUCROS, relate crop growth and development with fundamental physiological processes. Afterwards the model calibration was carried out, by adjusting the five model most sensitive parameters, the degree of fit among simulations and measurements was acceptable for almost all calibrated conditions, being (R2>0.92) in case of total above-ground dry matter, (R2>0.95) for biomass of stems, (R2>0.79) for leaves biomass, (R2>0.83) for fruits biomass and (R2>0.58) for the leaf area index.

In the North area of Granma, a Cuban province, the salinity of the soils is an obstacle for the attainment of high yields in the rice. This area is characterized by the scarce precipitation, the shallow phreatic levels (1.5-2.5 m) and strongly mineralized (4.5 g•L-1), that makes indispensable the drainage for the control of the soil salinity. In order to obtain references to introduce the subsurface drainage in these areas, it was carry out during three years, in a pilot lot of 6.5 ha, an experiment with drains spaced at 30 and 100 m in trenches of 1.3 m-depth with filler of shell of rice in the bottom. During the rain season the drains spaced at 30 and 100 m evacuated the 11.2 and 6.0 % of the precipitation, respectively; however, when the phreatic level stayed below the drain, the discharge was almost constant and take values of 0.05 mm•day-1 in the drain of 30 m and of 0.014 in that of 100 m. With the irrigation, the discharges of the drains were similar in both distances and they reached values averages of 1.63 mm•day-1. Under conditions of non-permanent regime, that coincides with the period of no irrigation, the validity of the equation of Glover-Dumm was demonstrated, and the medium value of K obtained from this evaluation ranged between 0.2-0.5 m•day-1. Both spacing were efficiently allow the wash out of the soil salts and to impede that in the fallow time the saline tenors in the soils increased. As the same time, they diminishes the soil salinity from of 11.5 dS•m-1 up to 3 dS•m-1.

The IWA-Anaerobic Digestion Model No. 1 (ADM1) is a structured model that represents complex substrates by their main components; it includes multiple steps to describe biochemical and physicochemical processes involved in anaerobic digestion of complex organic compounds biodegradability. The aim of ADM1 is to create a common framework to develop the simulations of a widely rank of specific processes. Many extensions and modifications of the ADM1 model have been proposed to improve the outputs of the model and to enlarge its capability to handle different substrates exposed to fermentation and not included in the original ADM1. The objective of this review is to provide a general panorama about Anaerobic Digestion Model No. 1 its importance like a common framework to develop a widely specific processes simulations and its development since it was published in 2002. Diverse model applications, original framework modifications and the use of novel methods to increase the predictive capability of the model are discussed. The number of published references about ADM1 has increased in the last years, mainly since 2006. Applications vary from model implementations in wide-plant treatment systems, anaerobic treatment of diverse substrates, kinetic parameters and variables distribution for a more realistic description of the system. The generic model and the relativity easy way to handle the model allow including inhibition phenomena, to consider microbial diversity or an ADM1-ASM coupled, to get key indicators for digester stability and to introduce novel techniques to increase the model performance, quality and advantages.

Round and lanceolated shapeed zapote mamey fruits were axially compressed in order to evaluate the influence of a potential mechanical damage on physical (weight loss and firmness), chemical (total soluble solids and titled tartness) and physiological parameters (ethylene and CO2) during ripeness. Three axial compression distances were evaluated: elastic limit, bioyield point and point of rupture. It was found that lanceolated fruits compressed to the bioyield point had the highest respiration rate and ethylene production. No influence of fruit shape was found in weight loss, firmness, and accumulation of total soluble solids, and titled tartness. In all the cases, compression accelerated the ripeness process.

This research was performed in the Agricultural Department of Mechanical Engineering from the Universidad Autónoma Chapingo in the year 2006. Currently the eradication of plant pathogens is done with chemical fumigants. The widespread use of chemical methods has caused environmental problems, health and sustainability of agricultural soils and substrates. The use of physical methods, mainly in greenhouses, for this purpose appears to be a good alternative as it is intended to eliminate any chemical residue from the application. This study was designed and built a trailer type equipment for disinfection in static agricultural soils with steam-aereated and heated air. For its construction was used stainless steel sheet and PTR, the heat and temperature control was automated. For a sandy loam soil: steam-aereated the time required to increase the temperature of 21 °C C to 71 °C C was 15 minutes and hot air was 3.5 hours. Wiht both procedures keeping the temperature between 71-72 °C indefinitely. With steam-aerated water has a productivity of 487.2 L•h-1, and with hot air from 121.8 L•h-1.