ATM switching and CPE adaptation in the North Carolina InformationHighway

This article describes the approach which has been used to implement a sector of the information highway throughout the state of North Carolina, with specific attention focused on the functionality of the equipment that comprises the North Carolina Information Highway (NCIH). This implementation of this information highway is based on ATM technology, used in both the switching systems of the network and the customer premises equipment (CPE). The large ATM switching systems provide the extensive number of connections that are predicted for the information highway. Multiple services can also be supported on the ATM switches. The information streams for these different services can all be converted into ATM format using the appropriate ATM adaptation layer for transport through the ATM network. By being able to support multiple services, and transport them across common ATM facilities, the ATM switches offer the NCIH great flexibility in the applications that can be provided to the customers. Use of the ATM technology allows the NCIH to provide the backbone for various services. To provide the distance learning service application and other applications on the NCIH, ATM capabilities are also being provided in CPE on a service multiplexer     

Spread-spectrum communication techniques

Spread-spectrum modulation can be used in a radio system to reduce the likelihood of intercept, as well as providing some protection against jamming and interference. These antijam, anti-interference and low-probability-of-intercept properties are highly desirable in secured communication systems. In addition, spread-spectrum techniques have been proposed to combat spectral congestion by improving the efficiency of spectrum utilisation. Spread-spectrum techniques are also widely used in ranging systems and in local-area networks (LANs) or other multiple-access systems. In the present article, the three main spread-spectrum techniques are outlined and then applications of frequency-hopping systems and some of the techniques used are described     

Phase II study of vinorelbine (Navelbine) in previously treated small cell lung cancer patients. EORTC Lung Cancer Cooperative Group

26 previously treated patients with progressive recurrent small cell lung cancer (SCLC) were given vinorelbine (Navelbine), 30 mg/m2 weekly. All patients had responded to first-line chemotherapy and were off therapy for at least 3 months. Partial response was observed in 4 out of 25 eligible patients (16%; 95% confidence interval 4-36%), stable disease in 7 patients and progression in 12 patients. The limiting toxicity was a non-cumulative leucopenia (80%, 32% WHO grade 3-4). Reaction at the site of injection was observed in 5 patients, causing treatment discontinuation in 2 cases. Other non-haematological toxicities were moderate. These results suggest acceptable toxicity and some antitumour activity of vinorelbine in pretreated SCLC patients.     

Voluntarism: is it a useful concept for health education in the accident and emergency department?

As the year 2000 looms closer, the emphasis on health education as a means of attaining the 38 targets for 'Health for All' increases. Despite various initiatives, little, if any, progress has been made in narrowing the health divide. Currently, terms such as 'self-care', 'individual responsibility' and 'community empowerment' are often used with emphasis on individual freedom to choose. The author contends that to assume all individuals have that freedom and act voluntarily, is to deny the impact of social structure on health. Health education and the concept of voluntarism will be critically examined from the perspective of nursing in an accident and emergency department.     

THE INFLUENCE OF LOAD MISALIGNMENT DURING UNIAXIAL LOW-CYCLE FATIGUE TESTING—II: APPLICATIONS

Abstract— Models for predicting scatter bands due to bending have been applied to four alloys, namely AISI 316L, Nimonic 101, 9 Cr-1 Mo, and IN 718. The alloys were tested extensively by 26 laboratories in an international round robin exercise sponsored by the Community Bureau of Reference (BCR) of the EC. After initially selecting data for analysis on the basis of their confirmed conformance to the ASTM bending criterion, it has been shown that in all four materials a major fraction of the data scatter could be attributed to bending. Furthermore, at the lowest strain range the predicted bending component represents the highest proportion of the experimental interlaboratory scatter. Many laboratories did not report any measure of bending and so could not be used in the initial analysis. However, a further interesting deduction from the models is that the entire BCR data-set can be encompassed within a scatter band based upon a bending criterion that is twice the allowable ASTM limit. Differences in the extent of scatter between materials at a given total strain range can be attributed to the gradient of the logarithmic plot of total strain range as a function of lifetime.     

Microstructure study of Sm,Mn-modified PbTiO3 piezoelectric ceramics by XRD profile-fitting technique

By using the X-ray diffraction profile-fitting technique, the microstructures of Sm, Mn-modified PbTiO₃ piezoelectric ceramic discs, including ferroelectric domain sizes, microstrains, and their variations with the poling strength have been quantitatively investigated. The results manifest that the modified PbTiO₃ ceramics contain a high density of domain walls due to the presence of finely-divided coherent domain structures (tens of nanometres in dimension). The poling treament can evidently influence the domain-size distribution, with a more homogeneous microstructure being developed; however, it simultaneously causes high anisotropic microstrains within the structure which, together with the high density of domain walls, is expected to be responsible for the unusual high electromechanical coupling properties possessed by this material.     

Development of an octocalcium phosphate cement

From previous studies it is known that alpha-tertiary calcium phosphate and dicalcium phosphate form a cement upon mixing with water. In this study this cement was optimized in terms of the milling of the constituents, their molar ratio, the amount of hydroxyapatite added and the water/powder ratio. The optimum Ca/P molar ratio of the cement mixture was 1.36±0.03. X-ray diffraction showed the reaction product to be octocalcium phosphate. Addition of precipitated hydroxypatite of over 3% diminished the final strength of the cement significantly. However, admixtures of only 2% of precipitated hydroxyapatite (a) kept the final compressive strength at 30±5 MPa after soaking in Ringers solution at 37°C, (b) diminished the initial setting time from 27.5 to 10 min and the final setting time from 65 to 40 min, (c) diminished the time in which the final strength was reached from 36 to less than 14 h. The tensile strength of this cement is 19±1% of its compressive strength. The optimum water/powder ratio as found in this study was 0.30 g/g.     

Comparison of two current modulation strategies for matrixconverters under unbalanced input voltage conditions

In this paper, the input current performance of matrix converters is analyzed, especially with reference to the operating conditions determined by unbalanced supply voltages. The space-vector modulation (SVM) technique is utilized to calculate the duty cycles of the active voltage vectors that must be applied, in each switching cycle period, in order to satisfy the input and output requirements. A detailed theoretical analysis of the input current harmonic content under unbalanced input voltage conditions is presented for two different current modulation strategies. On the basis of numerical simulations as well as measurements on a laboratory prototype setup, the strategies' performance are compared and the validity of the theoretical investigation confirmed. It is concluded that, when the input voltages are unbalanced to a significant extent, a dynamic input current modulation strategy has to be preferred, since a lower harmonic line current distortion will appear