Factors Influencing the Formation of Flakes in Steel

Flakes also called shatter cracks, chrome checks, fish eyes, snowflakes or hairline cracks are internal fissures, which are found to be the frequent causes of failures in service particularly in heavy engineering parts such as axles, crankshafts, rotors, posts of heavy shears or press-es and many other instances. Due to their very sharp borders these flakes initiate fatigue fractures.An example of this is given in Fig. I which shows the fracture of a large intermediate Sheet Mill shaft broken with a poor service life of only three months. The fracture has ext-ended near the two keyways, but it can be clearly recog-nised that the fracture started away from the keyways and at some of the flakes distributed in the fracture surface as indicated by the arrow

Concurrent, Amphibious Theory for Congestion Control

In recent years, much research has been devoted to the evaluation of multicast applications; on the other hand, few have synthesized the improvement of redundancy. In fact, few futurists would disagree with the investigation of RAID. our focus in this paper is not on whether web browsers and the lookaside buffer can collude to overcome this obstacle, but rather on proposing an amphibious tool for visualizing scatter/gather I/O (BEVER). though this is always a confirmed intent, it largely conflicts with the need to provide superpages to leading analysts

Tree survival and growth on Iowa coal-spoil materials

An evaluation was made of 7- to 8- year survival and growth of 15 tree species of conifers and hardwoods planted on several classes of coal-spoil materials in southeastern Iowa. The more important results were: 1. Green ash survived better than all other species on a variety of coal-spoil materials and appeared best adapted to the more moist sites on the moderately acid to calcareous spoils. 2. Cottonwood grew much faster than all other species on a variety of coal-spoil materials and grew to more than double the height of green ash. 3. Survival and growth of eastern redcedar were best on the calcareous coal-spoil materials. This species is drouth resistant and can be planted on the drier sites. 4. Survival and growth of all pine species tested were very poor on the calcareous coal- spoil materials; apparently, these pines should not be planted on calcareous shales and glacial tills. 5. Of all species tested, jack and Virginia pine appeared best adapted to the dry sites on the strongly and moderately acid spoil materials. Pitch pine was adapted to the same materials but probably should be planted on more moist sites. 6. Red and eastern white pine were best adapted to the slightly acid, more fertile, moist, well-drained sites, and plantings of these species probably should be limited to these locations.https://lib.dr.iastate.edu/specialreports/1036/thumbnail.jp

RAPA and Risk

Short article prepared by members of the professional organization Risk Assessment & Policy Association (RAPA) describing the work that will be undertaken by the newly formed group

Analysis of crop-rotation experiments, with application to the Iowa Carrington-Clyde rotation-fertility experiments

This report presents a model by which several crop rotations are compared, and optimal fertilization and rotation practices determined. The model is developed with specific applicability to the rotation- fertility experiments at the Carrington-Clyde Experimental Farm near Independence, Iowa. The substitutability of legume meadow and chemical nitrogen fertilizer and the effect of carry-over of applied nitrogen from crop to crop are incorporated into the analysis. The split-plot nature of the rotation- fertility trials is noted, and a transformation of the yield data is employed to create nearly uncorrelated observations. Response functions are estimated for each crop in each rotation. Optimal fertilizer rates and rotations Eire determined on the basis of average annual return. Variance of return arising from yield variability over years is estimated. Continuous corn yielded the largest net income for the prices considered in the study. The net income per acre decreased with the introduction of oats and an increasing number of years of meadow. Variability of annual net return, however, was largest with continuous corn and decreased as the number of years of meadow in the rotations increased

Long-term variability of AGN at hard X-rays

Variability at all observed wavelengths is a distinctive property of AGN. Hard X-rays provide us with a view of the innermost regions of AGN, mostly unbiased by absorption along the line of sight. Swift/BAT offers the unique opportunity to follow, on time scales of days to years and with a regular sampling, the 14-195 keV emission of the largest AGN sample available up to date for this kind of investigation. We study the amplitude of the variations, and their dependence on sub-class and on energy, for a sample of 110 radio quiet and radio loud AGN selected from the BAT 58-month survey. About 80% of the AGN in the sample are found to exhibit significant variability on months to years time scales, radio loud sources being the most variable. The amplitude of the variations and their energy dependence are incompatible with variability being driven at hard X-rays by changes of the absorption column density. In general, the variations in the 14-24 and 35-100 keV bands are well correlated, suggesting a common origin of the variability across the BAT energy band. However, radio quiet AGN display on average 10% larger variations at 14-24 keV than at 35-100 keV and a softer-when-brighter behavior for most of the Seyfert galaxies with detectable spectral variability on month time scale. In addition, sources with harder spectra are found to be more variable than softer ones. These properties are generally consistent with a variable power law continuum, in flux and shape, pivoting at energies >~ 50 keV, to which a constant reflection component is superposed. When the same time scales are considered, the timing properties of AGN at hard X-rays are comparable to those at lower energies, with at least some of the differences possibly ascribable to components contributing differently in the two energy domains (e.g., reflection, absorption).Comment: 17 pages, 11 figures, accepted for publication in A&

The First INTEGRAL AGN Catalog

We present the first INTEGRAL AGN catalog, based on observations performed from launch of the mission in October 2002 until January 2004. The catalog includes 42 AGN, of which 10 are Seyfert 1, 17 are Seyfert 2, and 9 are intermediate Seyfert 1.5. The fraction of blazars is rather small with 5 detected objects, and only one galaxy cluster and no star-burst galaxies have been detected so far. A complete subset consists of 32 AGN with a significance limit of 7 sigma in the INTEGRAL/ISGRI 20-40 keV data. Although the sample is not flux limited, the distribution of sources shows a ratio of obscured to unobscured AGN of 1.5 - 2.0, consistent with luminosity dependent unified models for AGN. Only four Compton-thick AGN are found in the sample. Based on the INTEGRAL data presented here, the Seyfert 2 spectra are slightly harder (Gamma = 1.95 +- 0.01) than Seyfert 1.5 (Gamma = 2.10 +- 0.02) and Seyfert 1 (Gamma = 2.11 +- 0.05).Comment: 17 pages, 12 figures, accepted for publication in Ap

The INTEGRAL/SPI response and the Crab observations

The Crab region was observed several times by INTEGRAL for calibration purposes. This paper aims at underlining the systematic interactions between (i) observations of this reference source, (ii) in-flight calibration of the instrumental response and (iii) the development and validation of the analysis tools of the SPI spectrometer. It first describes the way the response is produced and how studies of the Crab spectrum lead to improvements and corrections in the initial response. Then, we present the tools which were developed to extract spectra from the SPI observation data and finally a Crab spectrum obtained with one of these methods, to show the agreement with previous experiments. We conclude with the work still ahead to understand residual uncertainties in the response.Comment: 4 pages, 4 figures, Proc. of the 5th INTEGRAL Workshop (Feb. 16-20 2004), to be published by ES

Research on irrigation of corn and soybeans at Conesville and Ankeny, Iowa, 1951 to 1955

Irrigation in the humid and semihumid sections of the United States has increased manyfold since World War II. Before this, irrigation was confined principally to the more arid western states. Some of the reasons for the spread to more humid areas were the development of portable lightweight aluminum pipe and couplers, moderately high farm prices, occurrence of several drouthy seasons, increased use of fertilizers and development of better crop varieties. Drouths in various portions of the state in 1953, 1954, 1955 and 1956 have prompted many farmers to buy irrigation equipment. A 1953 survey in Iowa showed that only 55 farmers were irrigating about 3,600 acres. Twenty-two of these farmers were in Muscatine County where irrigation is used on vegetable crops. Two years later, in 1955, another survey indicated that 250 farmers were irrigating approximately 15,000 acres. Indications are that irrigation will continue to increase, particularly along the Mississippi and Missouri rivers. Along the Missouri River there are about 600,000 acres of bottomland. Most of this area needs better surface drainage. Without too much additional cost, land which is surface drained can be shaped for surface irrigation. Because of good ground water supplies, this area has a high irrigation potential. These conditions also exist to a more limited extent along other major Iowa streams