Transmit permission control on spread ALOHA packets in LEOsatellite systems

A transmit permission control method for improving the throughput characteristics of a low Earth orbit (LEO) satellite communication system employing spread-slotted ALOHA multiple-access scheme is proposed. Both nonfading and fading satellite links are considered. The basic idea of the proposed scheme is to decrease the level of interference at each satellite and, hence, to increase the probability of packet success, by prohibiting the packet transmission from the users with relatively high propagation loss to their connecting satellites. It is shown that the method has the ability to improve the throughput performance in heavy traffic loads and the peak value of the throughput, significantly. It is also shown that the average delay performance of the system employing the proposed scheme is superior to that of the conventional system at heavy traffic loads     

Adopting a policy of reuse

In many firms' experience, reusing elements of proven systems designs and software is best done through a companywide program. Reuse means savings in design, testing, manufacturing and support. The author gives the basic information a company needs to get started. The author discusses the context for reuse, planning and strategy involved in a reuse program     

Gluing of sintered parts made of silicon nitride

Problems of gluing parts made of silicon nitride are considered. The quality of glued joints is estimated. The effects of the composition (the types of binder and filler), the technological parameters (thickness of the joint, roughness of the glued surfaces, porosity of the parts), and the test conditions are considered. The technology for gluing parts made of RBSN and HP parts made of Si₃N₄ and results of tests of glued joints are described.Translated from Ogneupory, No. 4, pp. 18 – 20, April, 1996.     

The As-prepared surfaces of C-axis-oriented Nd1Ba2Cu3Oy thin films characterized using scanning probe microscopes

Recently, superconducting Nd₁Ba₂Cu₃O_y (Ndl23) thin films with high superconducting transition temperature (T _c) have been successfully fabricated at our institute employing the standard laser ablation method. In this paper, we report the results of surface characterization of the Nd123 thin films using an ultrahigh vacuum scanning tunneling microscope/spectroscopy (UHV-STM/STS) and an atomic force microscope (AFM) system operated in air. Clear spiral pattern is observed on the surfaces of Nd123 thin films by STM and AFM, suggesting that films are formed by two-dimensional island growth mode. Contour plots of the spirals show that the step heights of the spirals are not always the integer or half-integer number of thec-axis parameter of the structure. This implies that the surface natural termination layer of the films may not be unique. This result is supported byI-V STS measurements. The surface morphology of the Nd123 thin films is compared with that of thec-axis-oriented Y₁Ba₂Cu₃S_y thin films. Surface atomic images of the as-prepared Nd123 thin films are obtained employing both STM and AFM. STS measurements show that most of the surfaces are semiconductive. The results of STS measurements together with the fact that we are able to see the surface atomic images using scanning probe microscopes suggest that exposure to air does not cause serious degradation to the as-prepared surfaces of Nd123 thin films.     

Cytotoxicity versus antibacterial activity of some antiseptics in vitro

The relationship between endometriosis and infertility is observed frequently. Patients with both conditions require a conservative approach to their management. Since hormonal therapy is one of those approaches, we sought to compare the efficacy of Danazol and Gestrinone in 80 infertile patients (48 and 32, respectively). Therapy lasted 6 months in both treatment groups, and all patients studied had laboratory tests performed and were clinically evaluated and classified through laparoscopy before and after therapy. The improvement of symptoms and favorable follow-up were similar with both treatments. The reestablishment of menstrual patterns and fertility were also nearly alike in both groups. However, Gestrinone was associated with fewer secondary effects and is easier to administer than Danazol. We conclude that Gestrinone is a useful medication in the management of the infertile patient with endometriosis.     

Schedule estimation and uncertainty surrounding the cone of uncertainty

Software development project schedule estimation has long been a difficult problem. The Standish CHAOS Report indicates that only 20 percent of projects finish on time relative to their original plan. Conventional wisdom proposes that estimation gets better as a project progresses. This concept is sometimes called the cone of uncertainty, a term popularized by Steve McConnell (1996). The idea that uncertainty decreases significantly as one obtains new knowledge seems intuitive. Metrics collected from Landmark's projects show that the estimation accuracy of project duration followed a lognormal distribution, and the uncertainty range was nearly identical throughout the project, in conflict with popular interpretation of the "cone of uncertainty".     

Ozone micro-bubble disinfection method for wastewater reuse system.

Reuse of wastewater is regarded as one important way to deal with the world's shortage of potable water. The authors focused on a disinfection system using micro-bubbles and evaluated its capability for wastewater reuse. This paper reports experimental results from examination of the basic characteristics of micro-bubbles and disinfection of secondary effluent by air or ozone micro-bubbles. The results suggest that when micro-bubbles are applied in an ozonation system it is possible to reduce the reactor size, the amount of ozone decomposition equipment needed and the ozone dose rate.     

Preliminary studies using hybrid mediated electrochemical oxidation (HMEO) for the removal of persistent organic pollutants (POPs).

This study investigates the hybrid mediated electrochemical oxidation (HMEO) technology, which is a newly developed non thermal electrochemical oxidation process for organic destruction. A combination of ozone and ultrasonication processes to the mediated electrochemical oxidation (MEO) process is termed as hybrid mediated electrochemical oxidation. The electrochemical cell was developed in this laboratory. In the present study, several organic compounds, such as phenol, benzoquinone and ethylenediaminetetraacetic acid (EDTA), were chosen as the model organic pollutants to be destructed by the hybrid process. The organic destruction was monitored based on the CO2 generation and total organic carbon (TOC) reduction. The HMEO process was found to be extremely effective in the destruction of all the target organics chosen in this study. The information obtained from this study will provide an insight in adopting this technique for dealing with more recalcitrant organics (POPs).