Apparent stress-strain relationships in experimental equipment where magnetorheological fluids operate under compression mode

Abstract: This paper presents an experimental investigation of two different magnetorheological ( MR) fluids, namely, water-based and hydrocarbon-based MR fluids in compression mode under various applied currents. Finite element method magnetics was used to predict the magnetic field distribution inside the MR fluids generated by a coil. A test rig was constructed where the MR fluid was sandwiched between two flat surfaces. During the compression, the upper surface was moved towards the lower surface in a vertical direction. Stress-strain relationships were obtained for arrangements of equipment where each type of fluid was involved, using compression test equipment. The apparent compressive stress was found to be increased with the increase in magnetic field strength. In addition, the apparent compressive stress of the water-based MR fluid showed a response to the compressive strain of greater magnitude. However, during the compression process, the hydrocarbon-based MR fluid appeared to show a unique behaviour where an abrupt pressure drop was discovered in a region where the apparent compressive stress would be expected to increase steadily. The conclusion is drawn that the apparent compressive stress of MR fluids is influenced strongly by the nature of the carrier fluid and by the magnitude of the applied current

On the biology and bioacoustic characteristic of spotted catfish arius maculatus (Thunberg 1792) from the Malaysian Estuary.

Estuaries of Matang mangrove reserves in Perak provide an ideal habitat for Arius maculatus population. Results of our survey showed that most of the fish species caught were in their sub-adult stages with size ranged between 11 – 21 cm SL as shown in length frequency analysis. The relative growth condition of the fish population was allometrically negative with “b” value < 3.0 (W = 0.040L2.78) respectively. Study on reproductive biology of the species showed that almost half of the specimens caught were comprised of maturing males and female’s gonad development attained stage II – III. Stomach content analysis demonstrated that A. maculatus was an excellent benthic feeder in muddy water environment. Three major food items have been listed and dominated by zoobenthos and benthic crustacean. Meanwhile bioacoustic study showed that the fish produced a distinct sound resulted from stridulation of pectoral fins. The roles played by Matang mangrove systems as an integral breeding and nursery ground for this particular species was also discussed

Evaluation of Trace Metal Levels in Tissues of Two Commercial Fish Species in Kapar and Mersing Coastal Waters, Peninsular Malaysia

This study is focused on evaluating the trace metal levels in water and tissues of two commercial fish species Arius thalassinus and Pennahia anea that were collected from Kapar and Mersing coastal waters. The concentrations of Fe, Zn, Al, As, Cd and Pb in these coastal waters and muscle, liver and gills tissues of the fishes were quantified. The relationship among the metal concentrations and the height and weight of the two species were also examined. Generally, the iron has the highest concentrations in both water and the fish species. However, Cd in both coastal waters showed high levels exceeding the international standards. The metal level concentration in the sample fishes are in the descending order livers > gills > muscles. A positive association between the trace metal concentrations and weight and length of the sample fishes was investigated. Fortunately the level of these metal concentrations in fish has not exceeded the permitted level of Malaysian and international standards

Growth of tiger grouper (Epinephelus fuscoguttatus) juvenile from wild and hatchery at different type of feeds

This study aimed to observe the influence of two sources of juvenile tiger grouper Epinephelus fuscoguttatus (Forsskål, 1775) from the sea and the hatchery by several types of food (pellets, tilapia anchovies). Growing Studies were carried out above 9600 juvenile tiger grouper from two sources namely differing from the sea of 4800 juvenile and 4800 juvenile hatchery from hatching. The design of treament were done by 2x3  with four replications. During the 30 day rearing period, each 5 days is taken  sampling total body length (cm) juvenile tiger grouper. The results showed that during the rearing period the value of marine juvenile grouper only high growth in juvenile ate anchovies and tilapia except on day 5 and 30, and could not adapt to the food from the pellet. While in hatchery juvenile tiger grouper had high growth to consume pellets only and could not adapt well to the food of tilapia and except anchovies on day 15th

The epifaunal marine bivalves and macrophytes in Merambong Shoal, Pulai River Estuary, Straits of Malacca

The study was carried out to investigate the diversity of epifaunal bivalves in Merambong seagrass bed, Pulai River Estuary. The sample collection field trips started from May 2008 to July 2009, 18 transects (from six stations) have been laid perpendicularly along the elongated shoal during lowest low spring tide. A total of 15 species from 10 bivalve families were recorded throughout the study period. Young Anadara gubernaculum attached to Enhalus ecoroides showed the highest abundance throughout the seagrass bed. Veneridae is the most diverse family with four species recorded during the study followed by 2 species each for Mytilidae and Pinnidae. Negative correlation was observed between Circe scripta abundance and Ulva spp. coverage (r 2 =-0.829, P= 0.042). Station 4 (H'=1.2137; 1-D=0.5807; S=10) and Station 6 (H'=1.5279; 1-D=0.6696; S=13) have higher bivalve diversity and species richness, and are more heterogeneous compared to other stations. However, bivalve density was relatively lower in both stations 4 and 6 than the rest of the stations. The result of this study revealed that the coverage of macrophytes plays an important role in determining the density and distribution of epifaunal bivalves

The performance of magnetorheological fluid in squeeze mode

Abstract: In magnetorheological (MR) fluid, the rheological properties can be changed in a controlled way, the changes being reversible and dependent on the strength of the magnetic field. The fluids have potentially beneficial applications when placed in various geometrical arrangements. The squeeze mode is a geometrical arrangement where two flat parallel solid surfaces, facing each other, are pushed towards each other by an external force operating at right angles to the surfaces. The liquid initially in the gap between them is free to move away from this increasingly small gap, and it does so by flowing parallel to the surfaces, and collecting in a region where it is no longer in the gap between them. The performance of an MR fluid in compression ( squeeze) mode has been studied with the magnetic field being generated by a coil carrying different magnitudes of DC electrical current. A test rig was designed to perform this operation with the flat surfaces being horizontal and being pushed together in a vertical direction and the liquid being forced to move in all directions in a horizontal plane. The rig operated by decreasing the size of the gap at a constant rate. For each trial the current in the coil was kept constant and the instantaneous compressive force was recorded. When plotting compressive stress against compressive strain for each trial, the slope of the curve was found to be larger in general when the current was larger. This was an expected result; however, the behaviour is more complicated than this. For a significant range of values of compressive strain, the slope falls to zero, so that the compressive stress shows no increase during this period while the compressive strain continues to increase. The details of this behaviour are strongly dependent on the initial size of the ga

Spitting success and accuracy in archer fishes Toxotes chatareus (Hamilton, 1822) and Toxotes jaculatrix (Pallas, 1767)

Spitting success and accuracy of two congeneric archer fishes Toxotes chatareus and Toxotes jaculatrix were studied to determine whether spitting success and accuracy rate varied with height and/or group size. Overall, individuals of both species exhibited greater spitting success rate when alone than in a group. Greatest spitting success was observed in T. jaculatrix (29.87%) when alone followed by T. chatareus (27.55%), while lowest spitting success (14.88%) was observed for the average of all individuals in a group of two T. chatareus and two T. jaculatrix. Based on spitting accuracy categories right side high (RH), right side low (RL) and left side high (LH) showed no significant differences among the test groups

A budget feasible peer graded mechanism for iot-based crowdsourcing

We develop and extend a line of recent works on the design of mechanisms for heterogeneous tasks assignment problem in ’crowdsourcing’. The budgeted market we consider consists of multiple task requesters and multiple IoT devices as task executers. In this, each task requester is endowed with a single distinct task along with the publicly known budget. Also, each IoT device has valuations as the cost for executing the tasks and quality, which are private. Given such scenario, the objective is to select a subset of IoT devices for each task, such that the total payment made is within the allotted quota of the budget while attaining a threshold quality. For the purpose of determining the unknown quality of the IoT devices we have utilized the concept of peer grading. In this paper, we have carefully crafted a truthful budget feasible mechanism for the problem under investigation that also allows us to have the true information about the quality of the IoT devices. Further, we have extended the set-up considering the case where the tasks are divisible in nature and the IoT devices are working collaboratively, instead of, a single entity for executing each task. We have designed the budget feasible mechanisms for the extended versions. The simulations are performed in order to measure the efficacy of our proposed mechanismPeer ReviewedPostprint (author's final draft

Effect of vitamin E (Tri E®) on antioxidant enzymes and DNA damage in rats following eight weeks exercise

<p>Abstract</p> <p>Background</p> <p>Exercise is beneficial to health, but during exercise the body generates reactive oxygen species (ROS) which are known to result in oxidative stress. The present study analysed the effects of vitamin E (Tri E^®) on antioxidant enzymes; superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (Cat) activity and DNA damage in rats undergoing eight weeks exercise.</p> <p>Methods</p> <p>Twenty four <it>Sprague-Dawley </it>rats (weighing 320-370 gm) were divided into four groups; a control group of sedentary rats which were given a normal diet, second group of sedentary rats with oral supplementation of 30 mg/kg/d of Tri E^®, third group comprised of exercised rats on a normal diet, and the fourth group of exercised rats with oral supplementation of 30 mg/kg/d of Tri E^®. The exercising rats were trained on a treadmill for 30 minutes per day for 8 weeks. Blood samples were taken before and after 8 weeks of the study to determine SOD, GPx, Cat activities and DNA damage.</p> <p>Results</p> <p>SOD activity decreased significantly in all the groups compared to baseline, however both exercised groups showed significant reduction in SOD activity as compared to the sedentary groups. Sedentary control groups showed significantly higher GPx and Cat activity compared to baseline and exercised groups. The supplemented groups, both exercised and non exercised groups, showed significant decrease in Cat activity as compared to their control groups with normal diet. DNA damage was significantly higher in exercising rats as compared to sedentary control. However in exercising groups, the DNA damage in supplemented group is significantly lower as compared to the non-supplemented group.</p> <p>Conclusions</p> <p>In conclusion, antioxidant enzymes activity were generally reduced in rats supplemented with Tri E^®probably due to its synergistic anti-oxidative defence, as evidenced by the decrease in DNA damage in Tri E^®supplemented exercise group.</p