An active buffer management technique for providing interactive functions in broadcast video-on-demand systems

Multicast delivery is an efficient approach to the provision of a video-on-demand (VoD) service. Interacting with the video stream is a desirable feature for users. However, it is a challenging task to provide the functionality in the multicast environment because a lot of users share multicast delivery channels. In this paper, we propose an active buffer management technique to provide interactive functions in broadcast VoD systems. In our scheme, the client can selectively prefetch segments from broadcast channels based on the observation of the play point in its local buffer. The content of the buffer is adjusted in such a way that the relative position of the play point is kept in the middle part of the buffer. Our simulations show that the active buffer management scheme can implement interactive actions through buffering with a high probability in a wide range of user interaction levels.     

Farm to Consumer: Factors Affecting the Organoleptic Characteristics of Coffee. II: Postharvest Processing Factors

The production and consumption of coffee are increasing despite the roadblocks to its agriculture and global trade. The unique, refreshing, and stimulating final cupping quality of coffee is the only reason for this rising production and consumption. Coffee quality is a multifaceted trait and is inevitably influenced by the way it is successively processed after harvesting. Reportedly, 60% of the quality attributes of coffee are governed by postharvest processing. The current review elaborates and establishes for the first time the relationship between different methods of postharvest processing of coffee and its varying organoleptic and sensory quality attributes. In view of the proven significance of each processing step, this review has been subdivided into three sections, secondary processing, primary processing, and postprocessing variables. Secondary processing addresses the immediate processing steps on the farm after harvest and storage before roasting. The primary processing section adheres specifically to roasting, grinding and brewing/extraction, topics which have been technically addressed more than any others in the literature and by industry. The postprocessing attribute section deals generally with interaction of the consumer with products of different visual appearance. Finally, there are still some bottlenecks which need to be addressed, not only to completely understand the relationship of varying postharvest processing methods with varying in‐cup quality attributes, but also to devise the next generation of coffee processing technologies.     

Energetic and exergetic parametric study of a SOFC-GT hybrid power plant

A parametric study is conducted on a hybrid SOFC-GT cycle as part of a national program aiming to improve the efficiency of the actual gas turbine power plants and to better undertake the future investigations. The proposed power plant is mainly constituted by a Gas Turbine cycle, a SOFC system, and an ammonia water absorption refrigerating system. An external pre-reformer is installed before the SOFC. Heat recovery systems are adopted to valorize the waste heat at the SOFC and GT exhausts. The gas from the SOFC exhaust is also used as additional supply for the combustion chamber. An extraction is performed on the gas Turbine in order to feed the SOFC cycle by thermal heat flux at medium pressure.The equations governing the electrochemical processes, the energy and the exergy balances of the power plant components are established. Numerical simulation using EES software is performed. The influences of key operating parameters, such as humidity, pre-reforming fraction, extraction fraction from the Gas Turbine and fuel utilization on the performances of the SOFC-GT hybrid system are analyzed. Obtained results show that the integration of the SOFC enhances significantly the hybrid overall cycle efficiency. The increase of the ambient temperature and humidity reduces the system efficiencies. The utilization factor has a negative effect on the SOFC temperature and voltage. That leads to a decrease in the power plant performances. While the pre-reforming fraction, has a positive effect on the indicated parameters.     

Abiotic degradation of hexahydro-l,3,5-trinitro-1,3,5-triazine in the presence of hydrogen sulfide and black carbon.

We report that hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) was rapidly destroyed by sulfides in the presence of black carbon, forming nitrite and formaldehyde, rather than toxic nitrosated reduction products. Although traditionally viewed as inactive sorbents, black carbons have been noted to participate in the destruction of certain contaminants, such as azo dyes, via quinonoid groups. However, in our experiments sulfide modification of quinones did not seem to be involved. Although at least 1.2 mM sulfides were needed for the reaction to proceed, abiotic natural attenuation of RDX in marine sediments may occur, because these concentrations are found in certain marine sediments, together with black carbon. In the absence of natural black carbons, synthetic black carbons, such as activated carbon, may be added to sediments. As compared with other in situ techniques, such as bioremediation and zero-valent iron cutoff trenches, which often generate nitrosated byproducts, this in situ, abiotic technique may be an attractive alternative.     

Evanescent magnetic field effects on entropy generation at the onset of natural convection

This paper numerically investigates the effect of an externally evanescent magnetic field on total entropy generation in a fluid enclosed in a square cavity by using a control volume finite element method to solve the conservation equations at Prandtl number of 0·71. The values of relaxation time of the magnetic field are chosen, so that the Lorentz force acts only in the transient state of entropy generation in natural convection. The total entropy generation was calculated for, fixed value of irreversibility distribution ratio, different relaxation time varying from 0 to 1/5 and Grashof number varying from 10⁴ to 10⁵. The effects of the Hartman number and the magnetic field inclination angle on the evolution of total entropy generation throughout the transient regime were investigated. Results show that the application of evanescent magnetic field not only suppresses the fluctuation of the total entropy generation in the transient state, but also reduces the gap for magnetic field relaxation time less than 1/10.     

Non-phosgene synthesis of hexamethylene-1,6-diisocyanate from thermal decomposition of hexamethylene-1,6-dicarbamate over Zn–Co bimetallic supported ZSM-5 catalyst

A non-phosgene route for the synthesis of hexamethylene-1,6-diisocyanate(HDI) was developed via catalytic decomposition of hexamethylene-1,6-dicarbamate(HDC) over Zn–Co bi-metallic supported ZSM-5 catalyst.The catalyst was characterized by FTIR and XRD analyses. Three solvents dioctyl sebacate(DOS), dibutyl sebacate(DBS) and 1-butyl-3-methylimidazolium tetrafluoroborate(BMIMBF_4) were investigated and compared; DOS gave better performance. The catalytic performances for thermal decomposition of HDC to HDI using DOS as solvent were then investigated, and the results showed that, under the optimized reaction conditions, i.e.,10 wt%concentration of HDC in DOS, 250 °C temperature, 60 min reaction time, 83.8% yield of HDI had been achieved over Zn–Co/ZSM-5. Decomposition of the intermediate hexamethylene-1-carbamate-6-isocyanate(HMI) over Zn–Co/ZSM-5 in DOS solvent was further studied and the results indicated that yield of HDI from HMI reached to 69.6%(98.6% HDI selectively) at 270 °C, which further increased the yield of the total HDI(HDI_(tol)) to as high as 95.0%. Recycling of catalyst showed that HDI and HMI yield slightly decreased, and by-product yield increased after the catalyst was reused for 4 times. At last possible reaction mechanism was proposed.     

Spontaneous and anodic oxidation of Tantalum and Zirconium in phosphate solutions

Spontaneous and anodic oxidation of Ta and Zr have been studied in 0.1 M solutions of H₃PO₄, NaH₂PO₄, Na₂HPO₄ and Na₃PO₄. Below 10 A/cm² the dependence of the spontaneous-oxidation rate on potential follows a Tafel relation. Te results indicate that the partial anodic reaction of film formation is balanced by the cathodic reduction of dissolved oxygen. The kinetics of anodic oxidation are discussed on the basis of a one phase oxide file liable to contamination by phosphate anions. Oxide growth follows the high field ionic conduction even below the oxygen evolution potential. The simple exponential relation of Güntherschulze and Betz is valid. This is supported by the linearity obtained between (1) reciprocal capacity and the logarithm of current density i and (2) the potential E and log i for oxide formation at constant charge. Approximate calculations of the effective activation distance show that the degree of contamination by anions is the same in the four equimolar solutions indepent of PH.     

Application of shadow price in capacity expansion of state dependent routing

We develop a capacity expansion method for state dependent routing which utilizes the concept of shadow price. To cope with the computational complexity which is inherent with the capacity expansion process, special forms of fixed point iteration are developed for network blocking evaluation. The proposed capacity expansion method is illustrated through the example of a well known state dependent routing, namely Least Busy Alternate Routing. We verify the method in simulated networks and the resulting network cost is seen to be quite close to the ones derived from the methods with much higher computational complexity. The proposed method also results in a network design that satisfies the prescribed network blocking probability very accurately.     

Comparative study of the geotechnical properties of the coastal Sabkhas of Saudi Arabia and their hazardous effects

Sabkha is composed of sand deposits mixed with silt and clay intercalated with evaporites. Two types of sabkha are present in Saudi Arabia: the inland sabka, which is found in the northern part of the country and coastal sabkha, which is located along the Red Sea and Arabian Gulf. The main geotechnical hazards include settlement, corrosive action, heave due to salt crystallization/recrystallization and flooding due to the low infiltration rates. This comparative study indicates the engineering properties of the coastal sabkha along the Red Sea differ from those of the sabkha along the Arabian Gulf, which is likely to be more costly to develop.