Performance of Transport Protocols for Multimedia Communications in Wireless Sensor Networks

Many wireless sensor network (WSN) applications require efficient multimedia communication capabilities. However, the existing communication protocols in the literature mainly aim to achieve energy efficiency and reliability objectives and do not address multimedia communication challenges in WSN. In this paper, comprehensive performance evaluation of the existing transport protocols is performed for multimedia communication in WSN. Performance metrics such as packet delivery rate, end-to-end packet delay, bandwidth and energy efficiency, frame peak signal-to-noise ratio (PSNR), delay-bounded frame PSNR, frame delivery probability, frame end-to-end delay and jitter are investigated. The results clearly show that the existing transport protocols are far from satisfying the requirements of multimedia communication in WSN and hence there is a need for new effective multimedia delivery protocols for WSN.     

Terahertz emission from CdHgTe/HgTe quantum wells with an inverted band structure

The terahertz electroluminescence from Cd_0.7Hg_0.3Te/HgTe quantum wells with an inverted band structure in lateral electric fields is experimentally detected and studied. The emission-spectrum maximum for wells 6.5 and 7 nm wide is near 6 meV which corresponds to interband optical transitions. The emission is explained by state depletion in the valence band and conduction band filling due to Zener tunneling, which is confirmed by power-law current–voltage characteristics.     

On the problem of internal optical loss and current leakage in laser heterostructures based on AlGaInAs/InP solid solutions

Semiconductor lasers based on MOCVD-grown AlGaInAs/InP separate-confinement heterostructures are studied. It is shown that raising only the energy-gap width of AlGaInAs-waveguides without the introduction of additional barriers results in more pronounced current leakage into the cladding layers. It is found that the introduction of additional barrier layers at the waveguide–cladding-layer interface blocks current leakage into the cladding layers, but results in an increase in the internal optical loss with increasing pump current. It is experimentally demonstrated that the introduction of blocking layers makes it possible to obtain maximum values of the internal quantum efficiency of stimulated emission (92%) and continuouswave output optical power (3.2 W) in semiconductor lasers in the eye-safe wavelength range (1400–1600 nm).     

GaSb laser-power (λ = 1550 nm) converters: Fabrication method and characteristics

Photovoltaic converters of laser light with a wavelength of λ = 1550 nm are developed using liquidphase epitaxy (LPE), metal-organic chemical-vapor deposition (MOCVD), and diffusion from the gas phase into the n-GaSb substrate. Photocells with an area of S of 4, 12.2, and 100 mm² are fabricated and tested. The characteristics of the samples produced by different methods are compared. The monochromatic efficiency is found to be 38.7% for the best converters (with S = 12.2 mm²) at a laser power of 1.4 W.     

The storage life of chilled pork packaged under carbon dioxide

Pork cuts of longissimus dorsi muscle with overlaying fat and skin were packed under vacuum in film of low oxygen transmission rate, or under CO₂ in gas impermeable aluminium foil laminate. Cuts were stored at +3 or −1·5°C. Vacuum packaged cuts were grossly spoiled by Brochothrix thermosphacta after 2 weeks' storage at 3°C and after 5 weeks at −1·5°C. Cuts packaged under CO₂ were grossly spoiled by B. thermosphacta after 5·5 weeks' storage at 3°C. Growth of B. thermosphacta was suppressed when CO₂ packaged cuts were stored at −1·5°C. At that temperature, slow growth of enterobacteria was detected after a lag of about 18 weeks. The enterobacteria caused gross spoilage of an increasing proportion of cuts between 18 and 26 weeks. Muscle tissue with pale, soft, exudative (PSE) characteristics tended to lose colour after long storage periods, apparently because of loss of myogglobin with exudate. Until spoilage, the eating qualities of pork appeared little affected by prolonged storage.     

Compositional evaluation of some cowpea varieties and some under-utilized edible legumes in Nigeria

The nutritive potentials of some cowpea varieties such as Ife Brown, Ife Bimpe, IT84E-124, K59 and TVX716 and some under-utilized edible legumes grown in Nigeria such as pigeon pea (Cajanus cajan), lima bean (Phaseolus lunatus), lablab bean (Dolichos lablab), mucuna bean (Mucuna sp.) and Sphenostilis sternocarpa have been evaluated with respect to their proximate chemical composition, mineral content and some endogenous toxic constituents. The cowpea varieties contained on the average 22.5 g crude protein (CP), 2.60 g crude fibre (CF), 5.89 g either extract (EE) and 3.36 g ash/100 g DM while the under-utilized legumes contained 21.7, 6.10, 2.86, and 3.56 g/100 g DM for CP, CF, EE and ash respectively. Distinct varietal differences were observed for EE values as indicated by the coefficients of variation (CV) of 102% for cowpea and 60.8% for the under-utilized legumes. The CF content of the under-utilized legumes were generally higher than those of the cowpea varieties. Potassium was the most abundant mineral in both the cowpea varieties and the under-utilized legumes with mean values of 1.45 and 1.66% respectively, while P was the least abundant with 13.1 and 8.50 ppm, respectively. There were marked intra-varietal differences in the P content as shown by the high CV of 84.0 and 73.9% for the cowpea varieties and the other legumes. The cowpea varieties generally had higher levels of thioglucosides, trypsin inhibitor activity (TIA) and lower haemagglutinating activity (mean values of thioglucosides: 3.86%, of TIA: 13.9 mg/g protein and of haemagglutinating activity: 13.0 HU/mg N respectively), than the under-utilized legumes with mean respective values of 1.22%, 9.84 mg/g protein and 22.7 HU/mg N. The nutritional implications of these anti-nutritional components were discussed and some reasons adduced for the under-utilization of some of these legumes inspite of their apparent similarity in nutritional quality to the more commonly consumed grain legumes.     

Body composition, energy, protein and iron intake of Nigerian female nursing students

100 apparently healthy female nursing students (aged 20-30 years) were studied. A 24 hours dietary recall was recorded. Additionally a questionnaire was elaborated to collect dietary parameters for 3 days. From the mean daily food intake the energy, protein and iron intake was calculated. A series of anthropometric measurements, i.e. body weight, body height and skinfold thickness (triceps, breast, scapula, abdomen) were used to determine total body fat, lean body mass, optimum weight, and relation weight. The mean total body fat of the 100 subjects was (21.3 +/- 5.1) % and (12.7 +/- 4.4) kg, respectively, the optimum weight (56.6 +/- 6.3) kg and the mean relative weight (101 +/- 12.4) %. 11% of the 100 subjects studied was underweight, 73% showed normal weight, 10% was overweight and 6% obese. All the age groups met their energy and protein requirements as well as the iron intake.     

Changes in differently processed soya bean (Glycine max.) and lima bean (Phaseolus lunatus) with particular reference to their chemical composition and their mineral and some inherent anti-nutritional constituents

The effects of 3 processing techniques: cooking, roasting and autoclaving on the proximate chemical composition, the mineral content and some inherent toxic factors of soya and lima beans were investigated. The processing techniques generally reduced the crude fibre levels and enhanced the extractable fat in the soya and lima beans. The coefficients of variability for crude fibre and ether extract due to the processing techniques of soya and lima beans were 20.9%, 16.0% and 22.3%, 38.1%, respectively. In parallel with decreased ash content in the cooked bean samples, there was a decrease in the K, Mg, Na and P levels relative to the raw bean and also relative to the other processing techniques. Mineral contents of the autoclaved bean samples were generally similar to those of the raw (unprocessed) samples. Under the processing conditions, roasting caused the highest reduction in thioglucoside content (59%) in soya bean while cooking caused the highest reduction in lima bean (78%). Trypsin inhibitor activity (TIA) ranged between 0.59 mg/g sample in the cooked soya bean and 11.6 mg/g sample in the raw bean while the corresponding values for lima bean ranged between 0.59 and 6.3 mg/g sample. Cooking and roasting caused over 90% reduction of TIA, while autoclaving caused 64-69% reduction in both bean samples. Under the assay conditions, haemagglutinating activity was not detected in the cooked and autoclaved soya and lima beans. The need to prevent both functional and nutritional damage to food proteins and other nutrients, resulting from excessive heating, was discussed.     

Optimization of culinary recipes according to amino acid composition

A computation method is suggested, enabling one to optimize the amino acid composition of protein mixtures proceeding from the real content of amino acids and protein assimilation ratios. The method is based on the adequate use of essential amino acids and an amino acid that limits the biological value of proteins. The difference between the real content of essential amino acids and the portions utilized constitutes a non-utilized part of protein. The optimization may be reduced to the computation of its minimal values. The problem can be solved graphically, by exhaustive search of the products ratios with the use of computer or by optimization methods. According to the method designed there have been found optimal ratios of protein mixtures in animal and vegetable products contained by culinary dishes and products. The biological methods permitted one to determine the biological value and protein effectiveness ratio and to establish that they are closely related with the computed characteristics of the non-utilized part of protein and protein utilization ratio. The correlation ratio was found to amount to 0.76-0.89 (p less than 0.05).     

Genetic effects on dairy calf growth

Objectives were to establish growth patterns for weight and height in dairy calves from birth to 90 d and to estimate appropriate genetic parameters. Measurements were 7943 body weights and 7005 wither heights of 752 calves. Represented over 12 yr were three breeds, 348 dams, and 115 sires; data resulted from designed calf nutrition experiments. Sources of variation considered in various least squares analyses of variance were breed, sire in breed, calf in sire in breed, sex of calf, treatment-year category, and several interactions. Repeatabilities of weights and heights between birth and 90 d were .64 and .88; heritabilities were .22 and .30; genetic and phenotypic correlations were .53 and .73. A regression equation was estimated for each calf. From these 752 equations, heritabilities of initial weight, initial height, and rates of growth in weight and height were .53, .50, .44, and .19. Genetic correlations were .81; -.07; -.05; .26; .14; .84. Selection schemes for these traits in dairy cattle should consider that although weights and heights at birth and thereafter are highly and positively correlated genetically, as are gains, birth measurements and gains to 90 d may be uncorrelated.