A global approach for using kinematic redundancy to minimize base reactions of manipulators

An important consideration in the use of manipulators in microgravity environments is the minimization of the base reactions, i.e. the magnitude of the force and the moment exerted by the manipulator on its base as it performs its tasks. One approach which was proposed and implemented is to use the redundant degree of freedom in a kinematically redundant manipulator to plan manipulator trajectories to minimize base reactions. A global approach was developed for minimizing the magnitude of the base reactions for kinematically redundant manipulators which integrates the Partitioned Jacobian method of redundancy resolution, a 4-3-4 joint-trajectory representation and the minimization of a cost function which is the time-integral of the magnitude of the base reactions. The global approach was also compared with a local approach developed earlier for the case of point-to-point motion of a three degree-of-freedom planar manipulator with one redundant degree-of-freedom. The results show that the global approach is more effective in reducing and smoothing the base force while the local approach is superior in reducing the base moment

A Theoretical Study on the use of Passive Soil Resistance in Winch Anchor Design

This paper describes work being carried out to determine the length and depth of a cutting blade required to support a rescue vehicle fitted with a winch. Analytical work described relates mostly to the suitability of blade used. The design was confined to the case of the wide cutting blade moving in a direction perpendicular to the breadth of the blade because of its two dimensional simplicity. The approach adopted was based on a method already presented for the rapid calculation of passive soil resistance on a plane wide structure extending to the soil surface and having any rake angle as well as a wide range of directions of interface motion

The Development of Photosystem II-Herbicide Detection Method Using Microalgae as a Biosensor

Herbicides have been found to be significant pollutants of water bodies. In order to control and monitor the pollution, a convenient, sensitive and reliable method is needed. The main objective of this study is to develop a new method to measure the fluorescence yield of microalgae in order to detect photosystem II (PSII) specific herbicides in polluted water. The system was based on a simple mixing of microalgae with PSII specific herbicides. The measured signal was in the form of fluorescence intensity. The study involved the screening of test organisms, determining the best condition of the culture and obtaining a standard curve for each of the PSII herbicides. Only three herbicides were studied; atrazine, simazine and diuron. Chlorella vulgaris was found as the most suitable test organism compared with Chlorococcum sp., Scenedesmus quadriqauda and Selenastrum sp .. Nutrient replacement culturing method was selected as the best condition to grow C. vulgaris. A standard curve was determined for each of the herbicides. C. vulgaris was able to signal atrazine's concentration above 0.04µM according to the standard curve equation. Simazine can be signalled at above 0.05µM from its equation, while diuron can be signalled at above than O.09µM. However, -this basic study needs more infonnation and improvement to be done in the future, so that its full potential can be realised

The Donation-based Approach to Solving Critical Social Issues: An Examination of the Food Waste Recovery Approach to Solving Hunger in the United States

As the issue of hunger continues to plague the lives of nearly 1 billion people around the world, we need to find real, lasting and empowering solutions. This is an interdisciplinary research study into the donation-based approach to solving critical social issues in the United States by examining the food waste recovery and hunger debate. Social, public and private sectors advocate that hunger can be solved through food waste recovery and redistribution methods. From a systems perspective, such thinking is not only problematic for the people facing hunger, but raises concern of achieving overall social justice and change. Using qualitative methods, including interviews, a survey, focus groups, and literature review, this study attempted to understand the systematic nature of food waste, hunger, and the role of the donation system in the United States. Participants were primarily representative of the San Francisco Bay Area, with a small representation from the Eastern United States. An interdisciplinary approach, along with triangulation of primary data, was used to develop a greater understanding into the intricate nature of the issues. This study will show how the rise of capitalism has attributed to the need for food assistance programs in the United States, how donations and aid are treating the symptoms of hunger, and how in many cases the people working to address social issues are benefiting from their very existence; and are therefore less motivated to find long term solutions

Rate of water absorption by soil clods under confined and unconfined conditions

Experiments were conducted to study the rate of water absorption by clod of different sizes and initial moisture content using the capillarity method. Clods were prepared by molding wet clay soil into cubes for easy contact with the wet surface of a water-conducting material. Prepared samples ex-posed to wetting were examined by cutting 5-mm thick slices, starting the base. For confined conditions, a measured load was applied on every clod tested. The results of the clod-wetting experiments show that the rate of water absorption by capillarity was greatest when clods were initially very dry and that smaller clods tended to absorb water faster than bigger cloths confined. However, confining had no significant effect on absorption when the initial condition was very wet

Immobilisation and characterisation of chlorella vulgaris as potential bio-indicator for selected herbicides

Herbicides are one of the major contributing pollutants in water bodies. Several detection methods have been developed to monitor herbicide pollution including the use of bio-indicators. The competency of a bio-indicator in herbicide detection must comply with the sensitivity and efficiency of the method. In this study, Chlorella vulgaris as a bioindicator was immobilised in alginate and compared with the free cell to determine its ability as a bio-indicator. There were two immobilised conditions; immobilised cells of recommended cell concentration (2x10⁴cells/ml) and immobilised cells based upon suitability test. In the suitability test, four bead concentrations were tested; 0.1%w/w, 0.2%w/w, 0.4%w/w and 0.8%w/w. 0.1%w/w was selected as test bead based on stability and water and 26 days in calcium chloride. The other bead concentrations were stable for less than 20 days. The 0.1%w/w bead had constant growth rate and exponential rate pattern of oxygen production for 7 days, compared with the other beads. Free cells and two immobilised conditions were compared using two methods; oxygen production rate inhibition test and 96 hour's toxicity test. Four herbicides were used in this study; Atrazine, Simazine, Diuron and Paraquat. The first three are photosystem II inhibitor and Paraquat is a photosystem I inhibitor. Immobilised microalgae was dark incubated in herbicide for 30 minutes before measuring the oxygen production rate. 30 minutes was chosen as incubation time due to significant inhibition of oxygen production rate by herbicide at this period. Light and temperature values during detection were previously examined and selected for suitability. The selected light intensity was 90µmol/sec/m2 and 28°C for sample chamber's temperature due to the production of oxygen at exponential rate. Cells were incubated for 96 hours in herbicide with 12: 12h light cycle for 96 hour's toxicity test. Cells were enumerated and compare to reference. For immobilised cells, cells were counted after dissolving the beads with trisodium citrate. There were three significant findings in this study. First, the ability to immobilise Chlorella vulgaris as a 2mm bead, which can survive for more than three months. Second, immobilisation of the recommended cell number was the better choice as bio-indicator using oxygen production rate change compared to free cells or test bead. There was 50% inhibition using this condition at 0.12µM Atrazine, 5.8µM Simazine, 0.4µM Diuron and calculated value at 3.913 mM for Paraquat, while the other cell conditions needed higher concentration than 1000µM for 50% inhibition or could not exhibit 50% inhibition. Third, for toxicity testing, free cells is recommended compared to the immobilised cells. Toxicity of free cells at 1000µM was higher in Simazine > Atrazine > Diuron > Paraquat, while at 0.01µM: Diuron > Paraquat > Atrazine> Simazine. For the immobilised conditions, no 50% inhibition of cell number was observed, suggesting the cells were protected by alginate. In conclusion, immobilised cells are potential useful bio-indicator for herbicide or other pollutant that interfere with photosynthesis in water body. However, further research should be done to improve and simplify the method

Puddling Efficiency for Rice Root Growth in a Cohesive Soil

A laboratory study was conducted to determine the influence of water-soil ratio on the ease of puddling air-dried aggregates. Soil puddling was carried out using a rotary stirrer simulating the ratio)' motion of a rotary cultivator commonly used in wetland preparation. The stirrer was driven by an electric motor at a speed of 2000 rev/min. Four water-soil ratios were tested at three different stirring times. The results obtained showed that the fastest dispersion of particles resulting in a minimum wet bulk density of 1.23 Mg/m3 , was achieved at a water-soil ratio of 1.2. Increasing the water-soil ratio above this value did not change the wet bulk density value for all stirring times. Increasing the water-soil ratio above 1.0 did not increase the percentage of aggregate breakdown significantly for aggregates below 0.5 mm diameter. The effect of stirring time on the percentage of aggregate breakdown for aggregates below 0.5 mm diameter, however, was significant at all water-soil ratios when the input energy was 0.084 and 0.168 watt-hours

A width of cut analysis on the performance of a rotary strip tiller

This paper describes a soil bin study on the effect of blade widths upon rotary tiller performance which forms part of the research undertaken by the author on rotary tillage. Blades used were designed and tested at several forward and rotor speed combinations using a single rotor flange. Results obtained for each combination of forward and rotor speed show significant increase in power consumption as cutting width increased. In terms of specific power, however, the wider the cutting widths the lower the specific power values. The highest degree of soil pulverization was caused by the smallest width at the smallest bite length