Regulator problem for uncertain linear discrete-time systems with constrained control

A necessary and sufficient condition to test the robustness of a regulator of uncertain linear systems with constrained control is given. The candidate regulator for this test is that stabilizing nominal systems. An illustrative example is also given.     

Thermodynamic approach of inflation process of K‐BKZ polymer sheet with respect to thermoforming

The problem of modeling and the dynamic finite element simulation of thermoforming process for viscoelastic sheet are considered. The pressure load used in modeling is thus deduced from the thermodynamic law of ideal gases. The viscoelastic behavior of the K‐BKZ model is considered. The Lagrangian formulation together with the assumption of the membrane theory is used in the finite element implementation. The numerical validation is performed by comparing the theoretical solution for the uniaxial and equibiaxial hencky deformation with numerical results. Moreover, the influence of the K‐BKZ constitutive model, for three linear time distribution of airflow rate loading, on the thickness and on the stress distribution in thermoforming of containers made of HDPE are analyzed. POLYM. ENG. SCI., 45:1319–1335, 2005. © 2005 Society of Plastics Engineers     

Machine assignment and part-families formation using group technology

The conventional way of solving the group technology (GT) problem is to start from an assignment of parts to machines and try to find a partitioning of machine cells and part families. The similarity between parts is measured based on commonality of the machines assigned to them. However, parts are assigned to machines based on their operation requirements and the operation capabilities of machines. Similarity between parts should be based on their required operations. In this paper, the authors attempt to solve or facilitate solving the GT problem at the assignment level. An algorithm for assigning parts to machines is provided which utilizes the types of operations required by parts and applies GT principles in producing the assignment. This leads to better partitioning of machine cells and part-families. Furthermore, operation sequences required by parts in determining the similarity between parts have been considered. An algorithm to form part-families based on the operation sequence similarity coefficient has been developed. The resulting families are then used by the assignment algorithm to produce machine assignments to part-families. The use of the algorithm is demonstrated by examples.     

Dark Current and Signal-to-Noise Ratio in BDJ Image Sensors

In this paper, analytical expressions of dark currents and equivalent noise generators of a CMOS color image sensor are presented, and the signal-to-noise ratio (SNR) at both outputs is evaluated. Static measurements and simulations on Austria Micro Systems 0.35-mum CMOS test structures yield guidelines to increase the SNR of the buried double junction photodetector     

Depollution of atmospheric emissions of wood pyrolysis furnaces

The wood carbonization in Tunisia consists essentially of traditional activity using charcoaling stacks and pits characterized by high atmospheric pollution and poor energy conversion. Indeed, 70% of the initial mass of anhydrous wood are found in the vapor as aerosols, polluting and toxic gases and complex condensable organic compounds that can cause a substantial pollution of air, ground and water. Several processes of treatment and energy valorization of such effluents were proposed, but the incineration remains at present the most promising technique of depollution. The results show that the incineration, at about 1000°C, of wood carbonization smokes allows the destruction of 99% of the mass of pollutants except CO₂ and the reduction of polluting gas emission. The possible valorization of the smoke’s energy in the exit of the incinerator enhances the thermal efficiency of the process.     

A furostanol saponin from fruits of Balanites aegyptiaca

A new furostanol saponin was isolated from the mesocarp of Balanites aegyptiaca fruits and identified as 26-O-beta-D-glucopyranosyl-(25R)-furost-5-ene-3,22,26-triol 3-O-[[alpha-L-rhamnopyranosyl-(1-->2)]-[beta-D-xylopyranosyl-(1-->2)]-be ta- D-xylopyranosyl-(1-->2)]-beta-D-xylopyranoside (balanitesin).     

Recruitment strategies in the women's health trial: feasibility study in minority populations. WHT:FSMP Investigators Group. Women's Health Trial:Feasibility Study in Minority Populations

The Women's Health Trial:Feasibility Study in Minority Populations (WHT:FSMP) examined the feasibility of recruiting postmenopausal women from a broad range of racial and socioeconomic backgrounds into a primary prevention trial requiring marked reductions in dietary fat. Postmenopausal women aged 50-79 yr who had no history of cardiovascular disease or cancer and who consumed 36% or more total energy from fat qualified to participate. We randomized the women into dietary intervention (60%) or control (40%) groups; we aimed to randomize 750 women in 18 months in each of the three clinical centers. All centers achieved goals for randomization based on ethnicity, and two centers exceeded overall recruitment goals. The greatest source of randomized participants was mass mailing, followed by items in the media, referrals, and community outreach. Recruitment yields were generally similar for the ethnic groups but lower for less-educated participants. The experience of WHT:FSMP indicates that postmenopausal women from the African-American, Hispanic, and non-Hispanic white communities can be recruited into dietary intervention studies for the prevention of disease.     

Converting Daily Rainfall Data to Sub-daily—Introducing the MIMD Method

One of the most important analysis in many hydrological and agricultural studies is to convert the daily rainfall data into sub-daily (hourly) because in many rainfall stations, only the daily rainfall data are available and for a comprehensive rainfall analysis, these data should be converted to sub-daily. Many experimental and analytical methods are available for this conversion but one of the simplest yet accurate ones has been proposed by the Indian Meteorological Department (IMD). Since the IMD method has shown low accuracy in some regions, in this study, the IMD method is modified to a single parameter equation, called Modified Indian Meteorological Department (MIMD) in order to improve the accuracy of the conversion. For this reason, the parameter is calibrated so that the maximum correlation between observed and estimated values is achieved. Five stations in different regions with different climatic conditions were selected so that the daily and sub-daily rainfall data were available in each of them. Then, the parameter of the MIMD method was derived for each station. The results were compared with both observed data and IMD method and it was shown that the mean correlation coefficient of MIMD and IMD methods were 0.9 and 0.73 respectively for 12-h rainfall depth which indicated that the accuracy of the MIMD method in estimation of sub-daily rainfall depths was significantly increased. Moreover, the results showed that the accuracy of the MIMD method decreases as rainfall duration decreases.

     

Influence of annealing on properties and structure of alumina

Alumina bodies were prepared from pure alumina powder (98.9% Al₂O₃ consisting of 82% > 53m). The powder was compacted by hot-pressing at 1200° C, Compacted bodies were annealed at 1300, 1400 and 1500° C. Annealing continued at each maximum temperature for 25, 50 and 100 h. Strong bodies were obtained with maximum bulk density of 2.32 g cm^–3 and minimum apparent porosity of 30.21%. The change in sintering parameters with annealing was correlated with developed structure.     

Calcium carbonate and ammonium polyphosphate flame retardant additives formulated to protect ethylene vinyl acetate copolymer against fire: Hydrated or carbonated calcium?

In this study, the effect of the chemical nature of different calcium (Ca)-based minerals as flame retardant additives in combination with ammonium polyphosphate (APP), in 1:1 proportions, on the flame retardancy behavior and performance of ethylene vinyl acetate copolymer was discussed. Combining APP with partly and completely hydrated calcium oxide led to superior flame-retardant function detected in mass loss calorimeter measurements with respect to the corresponding system containing carbonated calcium. This privileged character was attributed to the higher reactivity of hydrated Ca-based fillers toward APP in comparison with Ca carbonate, which induced the formation of an intumescent residue. The difference between reactivity potential of hydrated and dry Ca was demonstrated by the newly formed thermally stable species, and further evidenced by thermogravimetric analysis performed on APP/fillers blends. Moreover, the presence of more crystalline domains in the Ca/phosphorus-based compounds was evidenced by XRD analysis of the mass loss calorimeter test residues. The results of this work highlight the role of blend additive systems on the performance of flame retardancy of polymer materials.