Delta Head Research Articles

Wear of ceramic‐on‐carbon fiber‐reinforced poly‐ether ether ketone hip replacements

Total hip replacement has been a successful surgical intervention for over 50 years, with the majority of bearings using a polyethylene cup. Long-term failure due to osteolysis and loosening has been widely documented and alternative bearings have been sought. A novel carbon fiber-reinforced poly-ether ether ketone (CFR-PEEK) cup was investigated through experimental friction and wear studies. Friction studies demonstrated the bearings operated in a boundary lubrication condition, with friction factors higher than those for other hip replacement bearings. The wear study was conducted with 36 mm diameter bearings tested against Biolox Delta heads for a period of 10 million cycles. The mean volumetric wear rate was 0.3 mm(3)/Mc, indicating the ceramic-on-CFR-PEEK bearing to be a very low wearing option for total hip replacement.

Development of Flood Forecasting System Using Statistical and ANN Techniques in the Downstream Catchment of Mahanadi Basin, India

The floods in river Mahanadi delta are due to either dam release of Hirakud or due to contribution of intercepted catchment between Hirakud dam and delta. It is seen from post-Hirakud periods (1958) that out of 19 floods 14 are due to intercepted catchment contribution. The existing flood forecasting systems are mostly for upstream catchment, forecasting the inflow to reservoir, whereas the downstream catchment is devoid of a sound flood forecasting system. Therefore, in this study an attempt has been made to develop a workable forecasting system for downstream catchment. Instead of taking the flow time series concurrent flood peaks of 12 years of base and forecasting stations with its corresponding travel time are considered for analysis. Both statistical method and ANN based approach are considered for finding the peak to reach at delta head with its corresponding travel time. The travel time has been finalized adopting clustering techniques, there by differentiating high, medium and low peaks. The method is simple and it does not take into consideration the rainfall and other factors in the intercepted catchment. A comparison between both methods are tested and it is found that the ANN methods are better beyond the calibration range over statistical method and the efficiency of either methods reduces as the prediction reach is extended. However, it is able to give the peak discharge at delta head before 24 hour to 37 hour for high to low peaks.

Optimal Reservoir Operation for Flood Control Using Folded Dynamic Programming

Folded Dynamic Programming (FDP) is adopted for developing optimal reservoir operation policies for flood control. It is applied to a case study of Hirakud Reservoir in Mahanadi basin, India with the objective of deriving optimal policy for flood control. The river flows down to Naraj, the head of delta where a major city is located and finally joins the Bay of Bengal. As Hirakud reservoir is on the upstream side of delta area in the basin, it plays an important role in alleviating the severity of the flood for this area. Data of 68 floods such as peaks of inflow hydrograph, peak of outflow from reservoir during each flood, peak of flow hydrograph at Naraj and d/s catchment contribution are utilized. The combinations of 51, 54, 57 thousand cumecs as peak inflow into reservoir and 25.5, 20, 14 thousand cumecs respectively as peak d/s catchment contribution form the critical combinations for flood situation. It is observed that the combination of 57 thousand cumecs of inflow into reservoir and 14 thousand cumecs for d/s catchment contribution is the most critical among the critical combinations of flow series. The method proposed can be extended to similar situations for deriving reservoir operating policies for flood control.

Discharge and suspended sediment transport in the Ayeyarwady River, Myanmar: centennial and decadal changes

AbstractAmong the large rivers rising on the Tibetan Plateau and adjacent high mountains, the discharge and suspended sediment load of the Ayeyarwady (Irrawaddy) River are the least well known. Data collected between 1969 and 1996 at Pyay (Prome) are analysed to provide the best available modern estimate of discharge (379 ± 47 × 109 m3/year) and suspended sediment load (325 ± 57 × 106 t/year) for the river upstream of the delta head. A statistical comparison with data collected in the nineteenth century (1871 to 1879) shows discharge has significantly decreased in the last ∼100 years. Regression and correlation analyses between discharge in the modern period and indices of El Niño–Southern Oscillation (ENSO) show a relationship. Copyright © 2009 John Wiley & Sons, Ltd.

Cord Blood Leptin and IGF-I in Relation to Birth Weight Differences and Head Circumference in Monozygotic Twins

To investigate a potential role of leptin and insulin-like growth factor (IGF)-I on fetal growth and metabolic function we determined plasma leptin and IGF-I concentrations in twins in relation to discordant fetal growth. In studying monochorionic twins with inter-twin birth weight difference, we investigated the relative contribution of genetic (fetus) versus environmental (maternal/placental) factors on growth. Thirty-six sets of twins (14 with discordant growth, birth weight difference >15%) who had been treated for severe twin-to-twin transfusion syndrome (TTTS) by laser coagulation were studied. Cord blood samples were collected at birth and analyzed for IGF-I and leptin. Inter-twin differences (delta) of birth weight and head circumference were correlated to delta hormone levels. An inter-twin correlation for leptin (r = 0.69; p <0.0001) and delta IGF-I (r = 0.49; p <0.0001) was found. delta birth weight correlated significantly with delta IGF-I (r = 0.67; p <0.0001) but not with delta leptin (r = 0.23; p = 0.19). delta IGF-I concentrations did not correlate with delta leptin (r = 0.18). delta head circumference correlated significantly with delta leptin (r = 0.47; p <0.01) and with delta IGF-I (r = 0.46; p <0.01). Using a multiple regression model with head circumference as dependent variable, adjusted for gestational age, head circumference remained significantly associated with higher leptin concentrations in all patients (p = 0.03). IGF-I is a good indicator for fetal growth and brain development. Leptin seems to be mainly genetically determined but may play a role in fetal brain development and is not only an index for fetal fat mass.

Natural and Human-Induced Variations in Water and Sediment Runoff in the Danube River Mouth

Long-term natural and human-induced variations in water and sediment runoff in the Danube Delta head were studied on the basis of analysis of an extremely long series of observations (1840–2002). A considerable reduction of sediment runoff in the second half of the 20th century related to sediment accumulation in reservoirs was revealed. It was found that human activities had an insignificant impact on the water runoff variations and the period of 1961–2002 turned out to be abnormally water-abundant.

Analysis of Hydrological and Fluviomorphological Regimes of the Ob River Delta

Data on water discharges and levels, morphometry of river branches, elevation base, runoff, and granulometric composition of sediments in the Ob Delta over the period of instrumental measurements were analyzed and summarized. The obtained results served as a basis for the delta parameterization. Detailed characteristics of the hydrological regime and quantitative characteristics of reversible fluviomorphological deformations averaged for the deltaic water streams were defined at different water levels in the channel. A many-year trend of these deformations was revealed. It was found that in the period between two cycles of field studies of the Ob Delta, no noticeable changes occured in the distribution of water discharges by the main branches at the delta head. Some secondary water streams in the delta lower reaches, where field observations were carried out over the mentioned period of time, featured a certain decrease in the flow discharged by these water streams along with a simultaneous increase in the water turbidity. The area of possible application of the obtained results was outlined.

Riverine sediment balance of the Mackenzie Delta, Northwest Territories, Canada

Data acquisition by Environment Canada and others over the last 20 years now allows the first comprehensive synthesis of the riverine sediment balance of the Mackenzie Delta. The data presented here are: sediment inputs from the Mackenzie and Peel rivers at the delta head and river sediment transfers from the Upper Delta to the Outer Delta (1974–1994); in-channel and overbank sedimentation, including lakes (post-1963); and in-channel erosion along Delta channels (1950–1981). These data indicate that the mean annual sediment input to the Delta is about 128 Mt, and the corresponding loss to offshore is about 85 Mt. The net sedimentation of 43 Mt is divided almost equally between the Upper Delta (mostly on levees and lake beds) and the Outer Delta (mostly on lake shores). Gross sedimentation within the Delta, about 50% of which is on point bars, is much higher, estimated at about 103 Mt annually: the difference is the large amount of sediment reentrainment within the Delta, through bank erosion, primarily along Middle Channel. How much of this pointbar deposition is from settling of sediment delivered by the Mackenzie and Peel rivers (as distinct from local sediment derived from bank scour within the Delta) is not known. Such within-Delta sediment exchange (which could be as high as 50 Mt) might be important in determining the quality of sediment (nutrients, contaminants, etc) that it is being delivered offshore: it would be naïve to assume that all of this sediment is from the present-day input of the Mackenzie and Peel rivers. Copyright © 1999 John Wiley & Sons, Ltd.

HYDRAULIC MODEL STUDIES FOR IMPROVEMENT OF FLOW CONDITIONS AT SAMAL BARRAGE

ABSTRACT The river Brahmani is the second largest river of Orissa with a catchment of 36,260 km2 at head of delta (Jenapur) and 25,250 km2 at Rengali dam site. The river has its origin in the state of Bihar flowing into the Bay of Bengal. Under Rengali multi-purpose Project—Stage- I, a gravity masonry dam was constructed in 1985 at Rengali across the river Brahmani for purpose of flood control and power generation. Under stage-II of the project it was planned to construct a barrage across the river at Samal, utilising the regulated water released from the Rengali Power House Tail Race. The flow conditions upstream of the Samal barrage were adverse which would not fulfill all the requirements of left canal. Therefore, hydraulic model studies were carried out for the Samal Barrage. Suitable solution for efficient working of the canals was obtained based on the physical model studies carried out in 1983–86. Hydraulic flow conditions, operation of gate, function of divide walls/excluders, etc., have been discussed in this paper.

Physicostatistical Approach to River Delta Hydrology

River deltas are characterized by a very complicated and unsteady water regime. They are affected by changes in the river regime at the upper boundary of the delta, changes in the sea level at its lower boundary, and by hydrological and morphological processes within the delta itself. The most significant indicators of all processes affecting the water regime in the delta are changes in water discharges and water levels at various points of the delta hydrographic network as a function of water discharge in the delta head. These dependences are taken as a basis for hydrologic calculations in river deltas. This paper presents a physicostatistical method for plotting, assessing accuracy, and establishing the dynamics of water discharges and water levels in delta streams as a function of water discharge in the delta head. The automated technique allows for an operative solution of hydrologic tasks in river mouths. Recommendations to optimize hydrometric works in river deltas are suggested, which would take into account time-specific changes in delta hydromorphology and delta monitoring tasks.

High resolution computed tomography of the orbit withthe Ohio Nuclear Delta head scanner

The orbit is an ideal structure to examine by CT because of large differences between absorption values of retroorbital fat and other structures such as muscle, optic nerve, and ophthalmic artery. Spatial resolution in CT is dependent upon the volume of each pixel (individual picture element). Whereas the pixel volume of the original EMI scanner was 117 mm, that of the Ohio Nuclear Delta head scanner employed in this paper is only 5 mm. Ovver 200 patients have been examined using this scanning instrument, including 32 patients in whom the orbits were specifically examined with a scan plane parallel to Reid's baseline. Representative abnormalities are discussed and illustrated. Orbital tumors such as hemangiomas, lymphomas, meningiomas, and inflammatory pseudotumors can be accurately localized while still very small.