Throughput Analysis of a Decentralized RLAN Based on Asynchronous DS/CDMA Using Random Periodic Spreading Sequences

Packet throughput figures are obtained for a decentralized radio local area network (RLAN) which is based on asynchronous direct-sequence code-division multiple-access (DS/CDMA). Packets arrive at the receiver nodes with different power levels. Techniques are developed to derive the probability of packet success for a system employing random periodic spreading sequences. It can be shown, that this system performs far better than a network using random spreading sequences. Based on the packet error probability, throughput figures of slotted DS/CDMA-ALOHA are presented for various scenarios. The effect of applying forward error correction (FEC) is investigated. For finite user environments, additional sources of errors have to be considered. These have a major impact and reduce the overall system performance. Finally, the throughput figures of a system applying the binary exponential backoff algorithm to avoid unstable behavior is investigated. The performance figures of the various systems described in this paper show that DS/CDMA forms a valuable choice for future RLANs.     

The diagnostic significance of clinical signs of right ventricular insufficiency in patients with chronic obstructive bronchitis

A parasitologic investigation, realised between March and November 1993, among 532 pupils 6-15 years old living in N'Djamena's peripheric quarter and in 5 Chari Baguirmi's villages had showed urogenital schistosomiasis infection prevalence is 11.8%.     

Estimation of transportation demand

Conclusion The present analysis of transport demand for manufactured iron and steel products, one of the high-valued commodities, results in price elasticities of demand which are midly elastic with regard to motor carriers and slightly inelastic with regard to railroads. These estimates are sufficiently at variance with the elasticity findings for all manufactured goods together to suggest that there probably exists a rather broad spectrum of transport demand elasticities for most manufactured goods.²² Together with the elasticity estimates obtained, motor carriers have been capturing larger shares of the transport service market over time, more so than would be expected from the price elasticities alone. This is to suggest that nonprice determinants may be crucial in transport desision making, even in the short run.Railroads derive disproportionately large revenue contributions from manufactured goods. Were they to engage in a pricing policy which approximated marginal costs it appears that the rapid growth in the motor carrier share of the manufactured goods market might be halted. Such a pricing policy would not only shift intermodal competition as to commodities handled, but more importantly, it would reintroduce intermodal competition by lengths of haul. Perhaps comparative advantage, and thereby optimal allocation, would be enhanced.     

Development of a high range TLD dosemeter

Global Dosimetry Solutions Inc. has developed a high range TLD dosemeter capable of measuring high-energy photon doses to 1 KGy. Additional correction factors have been established for as many as 10 various X ray and beta sources, allowing for high range monitoring of other sources and energies from 500 to 1000 Gy. The product utilizes TLD-100 and TLD-700 chips, available in three different configurations of very small size, and is offered at an economical price. Data analysis is quick, providing results within 24 h in most cases. This report describes the testing completed to support this product, primarily the determination of the supralinearity corrections necessary for doses up to 1 KGy. The test results are considered preliminary due to minimal data points between 0.5 and 1.0 KGy. Additional irradiations are being conducted to establish a more accurate statistical curve at this high dose level. Due to the high dose residual these dosimeters are considered for single use only.     

Dosimetric properties of new cards with high-sensitivity MCP-N (LiF:Mg,Cu,P) detectors for Harshaw automatic reader

A new configuration for a thermoluminescent dosimetric card has been developed through collaboration between the Institute of Nuclear Physics in Kraków and several commercial dosimetric companies. The card is based on high-sensitivity LiF:Mg,Cu,P circular pellets (MCP-N) welded inside synthetic foils. The basic configuration consists of two pellets of 3.6 mm diameter and thicknesses from 0.25 up to 0.38 mm. The cards can be processed in a standard 6600 or 8800 Harshaw automatic TLD reader. The dosemeters demonstrate very high sensitivity, low background and good stability. This article presents results of the performance tests of the new dosimetric cards in the automatic TLD readers and a comparison of their properties.