Communications satellites: orbiting into the 90s

Engineering advances in satellite communications are discussed. These include sophisticated switchboards, narrow beams, source coding for higher capacity, larger networks, and the use of higher and lower frequency bands and lower orbits. One of the most popular new 14/11-14/12 GHz commercial services has been time-division multiplexing of multiple carriers operating at low to medium bit rates. Multiple-carrier, low-burst-rate TDMA (time-division multiple access), in which several TDMA carriers are shared among ground terminals, is widely used with very small-aperture terminals (VSAT) on the customer's premises. NASA's (US National Aeronautic and Space Administration) ACTS and Italy's Italsat both plan to use signal regeneration at 30/20 GHz. Onboard switching and multiplexing will not only minimize noise and boost power, but also trim the cost of the entire satellite network     

Network Control for Multibeam TDMA and SS/TDMA

This paper concentrates on the control of individual burst transmissions of traffic and reference stations in TDMA and SS/ TDMA networks. In a TDMA system, the principal task of a TDMA terminal is to transmit each burst at the proper time to assure that, at the satellite, the burst resides in its assigned location in the TDMA frame. The composite of assigned positions for all bursts in the TDMA frame, or frames if more than one transponder is involved, is called the burst time plan. The paper discusses a specific concept of control used by a station to acquire and synchronize its burst transmission to assigned time slot(s) in the TDMA frame. The concept is applied to single-beam (global or regional) and muitibeam systems. The method used controls the instant of traffic burst transmission by introducing a time delay at each station which causes the round-trip propagation time between the satellite and all earth stations to be equal for burst position control purposes. This time delay is simple to implement in the TDMA terminal's timing circuitry and does not require the storage of traffic to accomplish it. It is also shown that the control method leads to a simple means for accomplishing synchronous burst time plan changes throughout the network. The functions of the reference stations needed to accomplish the burst time plan control are defined and explained. The discussion extends to SS/TDMA, and explains how the satellite switch state time plan change can be synchronized to the overall network burst time plan change.     

Total volatile acids content as a quality index of irradiated hake (Merluccius merluccius hubbsii) fillets

Irradiation of hake (Merluccius merluccius hubbsii) fillets with 500 krad (5 k Gy) of Co⁶⁰ gamma rays caused a delay in the formation of volatile acids during storage under refrigeration at 4–5°C. Loss in organoleptic acceptability could be correlated with the increase in volatile acids both in the unirradiated and irradiated fish stored at 4–5°C, suggesting that the volatile acids number (VAN) can be a useful tool for the quality evaluation of hake fillets.     

In vivo incorporation of3H arachidonic acid and14C linoleic acid into liver lipids from essential fatty acid-deficient rats

Essential fatty acid (EFA)-deficient rats were injected intraportally with a labeled solution containing³H arachidonic acid and¹⁴C-linoleic acid during a 1 min period. Livers were quickly frozen, pulverized, and the lipids extracted and fractioned by thin layer chromatography. The incorporation of³H and¹⁴C into liver lipids was measured, and the per cent distribution of radioactivity into the different lipid fractions determined and compared with those previously obtained from normal rats. In contrast with normal rats, ca. 70% of the³H arachidonic acid and¹⁴C-linoleic acid incorporated into total lipids from EFA-deficient rats was recovered in the phospholipid fraction. From the results of this experiment, it is suggested that a more active deacylation-reacylation cycle in EFA-deficiency could be responsible for this increase.     

Walsh-Hadamard analysis applied to the study of light propagation in a tapered gradient-index medium

The analysis of light propagation in a tapered gradient-index (GRIN) medium when the input signal is a binary function is considered with the Walsh-Hadamard analysis. The study of the evolution of the sequency spectrum through the GRIN medium by the Walsh-Hadamard transform confirms the self-imaging effect.     

High‐quality instant sorghum porridge flours for the West African market using continuous processor cooking

The overall goal of this study was to develop high quality, pregelatinised sorghum flours for instant thin and thick porridges, foods that are commonly consumed in the West Africa Sahel. Use of a continuous processor, a high shear/low pressure mixer, with feed sorghum flour moisture content of 30% to 35% and a screw temperature fixed at 168 °C gave instant sorghum flours with stable and creamy thin and thick porridge textures. Water activity of 0.22–0.35 for instant flours was within an acceptable range for dried commercial cereal foods. Molecular weight distributions of starch molecules showed significant fragmentation in instant flours that likely contributed to their smoother and creamy texture, and rheometry showed stronger gels and lower viscosity for the instant thick and thin porridges, respectively. In sensory testing performed in Niger at four locations, instant flour thin and thick porridges scored better than the control prepared locally from the same flour.     

Green Cloud Meta-Scheduling

This article aims to evaluate the flexibility of GreenMACC (Metascheduling Green Architecture to Provide Quality of Service in Cloud Computing). The GreenMACC has a module called LRAM (Local Resource Allocation Manager) to automate the execution of all scheduling policies implemented in the architecture. This module enables the Meta-scheduler automatically adjust for each type of service requested by the user of a private cloud. Due to this function, can be ensure the most appropriate behavior to the principles of GreenIT while worrying about the quality of service. In this paper is shown the importance of the LRAM on GreenMACC. This article is also shown how to include a new policy in GreenMACC in a way that identifies the LRAM and automatically use. Through the performance evaluation of the new policy included it could be concluded that the GreenMACC is a flexible, reliable architecture and the LRAM module enables the automation of choosing the best scheduling mechanism in a private cloud.     

Calculation of the total lethality of conductive heat in cylindrical cans sterilization using linear and non linear survival kinetic models

There is growing evidence suggesting that inactivation of bacterial spores may follow the Weibullian model, of which the log linear relationship between survival ratio and time is just a special case. Where true, the time and not only the temperature dependence of the rate must be taken into account. Also, it is of interest to estimate spores survival not only at the coldest point but also throughout the whole container's volume.Numerical calculation on changing survival ratios was performed by combining the conductive heat transfer model with that of the nonlinear inactivation kinetics. Results are based on published linear and non linear inactivation parameters of Clostridium botulinum spores, typical thermal properties of solid foods and realistic thermal processing conditions. Results could be used to quantify the efficacy of thermal processes of solid products in terms of spores' residual survival ratio at the coldest point and in the container as a whole.