On a class of branching problems in broadcasting and distribution

We introduce the following network optimization problem: given a directed graph with a cost function on the arcs, demands at the nodes, and a single source s, find the minimum cost connected subgraph from s such that its total demand is no less than lower bound D. We describe applications of this problem to disaster relief and media broadcasting, and show that it generalizes several well-known models including the knapsack problem, the partially ordered knapsack problem, the minimum branching problem, and certain scheduling problems. We prove that our problem is strongly NP-complete and give an integer programming formulation. We also provide five heuristic approaches, illustrate them with a numerical example, and provide a computational study on both small and large sized, randomly generated problems. The heuristics run efficiently on the tested problems and provide solutions that, on average, are fairly close to optimal.     

Semantic-based role matching and dynamic inspection for smart access control

Multimedia Tools and Applications - In this paper, we propose a scheme of semantic-based role matching and dynamic inspection for smart access control. The basic roles are established first, and...     

Development of an articulated mine-detecting manipulator system for mobile robots

This paper presents a servo motor selection technique for a mobile mine detection system which is operated in the field condition. As a first step, mine detection sensor should follow the earth profile while maintaining a constant distance to the earth surface. In order to acquire a reasonable manipulator trajectory and its required torque, a kind of modeling technique is devised to remove the unwanted fluctuations in the earth data. Then, Straete et al.’s normalization method is adopted and is improved to select the adequate actuator for each joint of manipulator. The improvements are as follows: First, an equivalent output power lines are plotted at the same load curve, which gives another selection criterion. Second, a temperature based criterion is proposed for the continuous limit, which estimates the steady state winding temperature of a motor, and can be used to determine a suitable motor and gear ratio. This formulation gives not only the selection of a motor and gear ratio, but also gives the estimated operating temperature. Finally, realized system is verified through the basic performance test.     

Dynamic voltage restoration with minimum energy injection

Voltage sag is one of the most important power quality problems challenging the utility industry. Voltage sags can be compensated for by voltage and power injection into the distribution system. By injecting voltage with a phase advance with respect to the sustained source-side voltage, reactive power can be utilized to help voltage restoration. Hence, the consumption of real power, from the perspective of the energy supply device, can be reduced. This energy-saving voltage injection comes at the expense of an increased voltage injection magnitude, load power swing, phase shift, and discontinuity of voltage wave-shape. For this reason, several proposed compensation strategies are examined, in terms of satisfying custom power while taking into consideration the capacity of the energy-storage device and the voltage injection constraint of dynamic voltage restorer. Numerical examples are included to illustrate the efficacy of the proposed control strategies     

Under excitation limiter and its role in preventing excessivesynchronous generator stator end-core heating

The process of synchronous generator stator end-region (SER) heating in the under-excited condition is investigated using a thermal model based on flux densities consideration. The parameter of the model are identified using the least-square method and from which the SER steady-state and transient thermal responses are determined. A new SER heating limit is derived and used for the design of the under-excitation limiter. The proposed method makes more effective use of the generator capability to absorb reactive power without causing instability, SER overheating, and serious system overvoltage problems     

Effect of Cryoprotectant and Freeze-Drying Process on the Stability of W/O/W Emulsions

In order to protect a hydrophilic drug and to prolong its further delivery, the formulation of multiple emulsions could be worthy. However, the double emulsions are not stable, their structure can change, leading to the formation of a single emulsion as the destruction of the system, and the drug can release easily from the globules in liquid state. The freeze-drying technology could be used to produce dry emulsion, the powder form being much more stable. The aim of this work was to study the influence of a cryoprotectant and a freeze-drying process on the stability of W/O/W emulsions. Samples were frozen at two different freezing rate (ν _f  = 0.55°C/min and 1.25°C/min) and successively dried at two different sublimation temperature (T _s  = ? 10°C and ? 20°C). The particle size distributions were measured by granulometer and UV spectrophotometer was performed to investigate the leakage of internal constituent. The glass transition temperature (T _g ) of the double emulsions was analyzed by DSC. The particle sizes became even smaller after freeze drying, except when κ-carrageenan is used as a cryoprotectant. In that case, the particles became aggregated after freeze drying, whatever the process conditions. The mean size is considerably reduced when the globules are diluted at low concentration in glucose and trehalose solution. When the concentration is increased, the size distribution is not significantly affected. The leakage of the internal aqueous phase to the external one during freeze drying was measured as an indicator of the structure stability. It is affected by the nature of the cryoprotectant and the conditions of the freeze-drying process. The leakage of the internal phase was smaller when cycle III (ν _f  = 1.25°C/min, T _s  = ? 10°C) was processed. From our experiments, we suppose that the water transfer from the inner phase to the outer aqueous phase results in the diminution of the globules size in double emulsion. The T _g of the double emulsions diluted with trehalose and glucose were determined at ? 33.8°C and ? 47.1°C. In contrast, the T _g of double emulsion with κ-carrageenan and HES did not appear.     

Chemical analysis of fuel crud obtained from Korean nuclear power plants

Crud samples were obtained from two different kinds of used fuels in PWRs. The constituent elements were analysed according to the shapes of crud particles by SEM and EPMA. The principal elements of octahedral crystal particles were identified as Ni and Fe, where the ratio (Fe/Ni) was approximately 2. The major element of the observed needle-like structures was determined to be Ni. In addition, Zr composed the main element of particles shaped like broken fragments sized at 10-50 μm in diameter. The round particles less than 20 μm in diameter were identified as Si-containing compounds. We also found the Zn element in a series of fuel crud samples obtained from a plant. Zn was mainly detected in the hard crud, inner layer of crud, but not on the surface of crud. It was observed that there is an inverse relationship between the Ni and Zn contents in the hard crud.     

Geometric parameter design of a cantilever probing needle used in epoxy ring probe card

In wafer probe card fabrication, contact force and forward displacement of needle tip are both important considerations affecting the probing results critically. This study establishes a finite element model of a cantilever probing needle used in epoxy ring probe card, to explore the effects of needle geometric parameters and probing overdrive upon the needle tip situation. Taguchi's methodology is used to derive the optimal parameter selection. Analytical results show that factors of taper length and needle diameter are the most influential in contact force, and the force can be controlled by the horizontal distance of cantilever measured from the needle tip to the epoxy fixed end. As for the forward displacement of the needle tip, both of taper length and cantilever horizontal distance are significant, and the probing displacement of the needle tips could be validly adjusted by the factors of bending angle and insert angle. A real experimental card has been made to verify the analytical results. Related materials can be provided as effective references in probe card design.