Viscous damped space structure for reduced jitter

A technique to provide modal vibration damping in high performance space structures was developed which uses less than one once of incompressible fluid. Up to 50 percent damping can be achieved which can reduce the settling times of the lowest structural mode by as much as 50 to 1. This concept allows the designers to reduce the weight of the structure while improving its dynamic performance. Damping by this technique is purely viscous and has been shown by test to be linear over 5 orders of input magnitude. Amplitudes as low as 0.2 microinch were demonstrated. Damping in the system is independent of stiffness and relatively insensitive to temperature

Mechanics of fluid-activated, clustered satellite bellows

AbstractA bellows, or a closed thin-walled elastic tube with corrugated walls, undergoes longitudinal extension when subjected to internal fluid pressure. Investigated herein is the mechanical behavior of several pressurized bellows in clusters, which are designed to bend and twist as well as to extend and compress longitudinally. Bellows in clusters can be employed as robotic limbs, such as manipulator arms and legs for walking machines. For limb bending, analysis shows that there is an optimal geometry for satellite bellows, or a set of identical bellows clustered longitudinally about a central core. For limb torsion, the bellows are clustered in a cylindrical helix whose angle is chosen to produce the desired load–displacement relationships, for instance the highest rotation for a given torque. For both bending and torsional limbs, experimental results are included that exhibit the predicted mechanical behavior

Agro-terrorism and the Grain Handling Systems in Canada and the United States

The grain handling sector in Canada and the United States is vital to agriculture and trade. In a typical year on the Canadian prairies, about 140,000 producers deliver some 20 to 30 mmt of grain for export to primary elevators. In the United States, about 2.1 million producers deliver about 300 mmt of grain to primary elevators. Canadian grain is moved to export position using more than 400,000 hopper cars and marine containers, where about 1,200 ships per year are loaded. In the United States, about 1.08 million rail carloads of grain are originated per year, and about 23 mmt of grain are shipped on barges per year. These U.S. figures are in addition to trucks, which, more so than in Canada, are also used to deliver grain to primary processors and to terminal and export markets. The volume of grain trade gives rise to concern about risks of terrorism in the sector.(1) From a security perspective, the grain, pulse and oilseed supply chain is noteworthy because much of it is characterized by relatively long-term, insecure, bulky storage (particularly on farms) along with numerous modal and inter-modal product transfers. These factors suggest there are many places where chemical or biological contaminants could be introduced into this supply chain. From the perspective of the United States, security throughout the Canadian system as well as the U.S. system is a concern, since cross-border traffic in these products is significant, with an average of about six million tonnes of grain products alone imported into the U.S. each year (USDA-FAS, 2003). Numerous interventions to enhance food safety and mitigate the risk of terrorism have been adopted or are in the process of being developed. Some of these are private initiatives and voluntary, as a component of firm-level security processes. Others are being adopted in response to legislated initiatives. The stakes are large, and there are likely to be substantial differences in costs and effectiveness of different approaches.Agricultural and Food Policy, Food Consumption/Nutrition/Food Safety,

Experiments with sheep

We conducted experiments with sheep during the past winter. The College owns seven breeds of registered sheep. They were wintered in a comfortable barn, where each lot could be controlled in all its relations. Grain, hay, water, and facilities for weighing were all convenient. The sheep were gentle and familiar with the herdsman, who did all the feeding and weighing, and made written reports daily, that were recorded. Every provision that could be made to secure accurate work was at hand. The experiment began Dec. 10th and continued for 90 days, to March 7th. We had in view the amounts of grain and hay necessary to winter each breed, the gain or loss in weight, the cost of the feed, the average feed and weight for the whole flock, the wool clipped from each breed, unscoured and scoured, the comparative value in both conditions, the comparison of the wools of the different breeds under the microscope, the loss in scouring of each breed, and the average value of wool from each breed

Angus and short-horn feeding experiment.

In March 1894 we bought ten head of Aberdeen Angus, and ten head of Short-horn steers, coming two years old that spring. They averaged perhaps, twenty-three months of age when we begun feeding them under exact conditions April 1st of that year. We had in view inquiry into the feeding qualities of the two breeds when selected so that they would be fairly representative animals, as near the same age as possible, and fed as nearly alike as they could be in all respects. We also desired to get further indications with regard to the effect of feeding corn meal on pasture, and its profitableness, and note the effect of changing feed. Six of the Short-horns were purchased from James A. Kelley of Newton, Jasper county, and four head were selected from herds in Story county; the ten head costing four cents a pound live weight. The ten Angus steers were bought from Evans & Son of Mills county, selected from a herd of one hundred head, at a cost of five cents a pound live weight. While these were fairly good cattle, neither lot was as good as we desired. We had difficulty in finding good specimens of both breeds. The Short-horns were fatter than the Angus when they came to the college, as a lot, because half of them had bee:1 more liberally fed on corn during the winter. Both lots were thoroughbreds, or high grades. The experiment will be treated in three periods. The first from April 1st to June 1st; the second period from June 15th to July 16; and the third period, August 1st to February 1st, nine months in all. The fifteen days from June 1st to 15th was the changing period from grain to grass, and the fifteen days from July 16th to August 1st was the changing period from grass back to grain, which periods will be treated separately, as a changing period is always a losing period, if the change is radical

Steer and heifer beef II.

The first investigation of the subject of steer and heifer beef by this station was made in 1893 and reported in Bulletin No. 24. In that experiment fifteen high grade Shorthorn yearlings were used, five of which were steers, five heifers, which were spayed, and five heifers not spayed. These cattle were all purchased from Mr. A. J. Graves, a Shorthorn breeder within a few miles of the college, and were raised alike and sired by the same bull. They were put on feed January 4th, when coming two years old, and fed until the first of the following December, when they were sent to market and sold separately, each lot on its merits. They were fed alike and on the same kind of a ration from first to last, but the amount of feed was regulated to conform to the capacity of each lot

Root crops

This station has experimented during the past season with several root crops, among which were the Long Red Mangel, Medium Red, Golden Tankard, Yellow Swedish Turnip, Rutabagas, and Carrots. These were planted on one acre of August plowed meadow sod ground, disced twice November 1st in order to kill insects. In the spring it was plowed twelve inches deep and thoroughly pulverized by the disc and harrow. The seed was planted in the last days of May and first day of June, in small ridges, two feet apart, with a Planet Jr. seeder. Cultivation the first time was done with a hand cultivator. The few weeds in the rows were pulled by hand. After that, cultivation was done four times with a one horse Planet Jr. cultivator; at the last cultivation the earth was turned toward the rows. At this, time the ground between the rows was entirely shaded with the tops. The few remaining weeds, after the last cultivation, were removed with hand and hoe; comparatively little hand work was done. A good stand was obtained of all roots, except the carrots, which are most difficult to start, being slow of growth when young, and requiring more hand work than most roots

Winter wheats

This Station planted several varieties of winter wheat on September 24th and 25th, 1891. The drouth of the fall o f 1891 prevented planting earlier. The fall growths were light, consequently they did not go into the winter in the best condition. The varieties planted were Turkish Red, Pool, Jones White Fife, Golden Cross, Found in Golden Cross, Hybrid Dattel, Hybrid Lamed, Stewart, Early Red Clawson, Johnson’s, Velvet Chaff, and the Surprise. The ground was clover sod, plowed September 1st, 1891. It was very dry. It was disced three times, rolled twice, harrowed twice, and the seed drilled in