Scheduling jobs with agreeable processing times and due dates on a single batch processing machine

AbstractIn this paper we study the problems of scheduling jobs with agreeable processing times and due dates on a single batch processing machine to minimize total tardiness, and weighted number of tardy jobs. We prove that the problem of minimizing total tardiness is NP-hard even if the machine capacity is two jobs and we develop a pseudo-polynomial-time algorithm for an NP-hard special case of this problem. We also develop a pseudo-polynomial-time algorithm for the NP-hard problem of minimizing weighted number of tardy jobs, which suggests that this problem cannot be strongly NP-hard unless P=NP

Topcolor-Assisted Supersymmetry

It has been known that the supersymmetric flavor changing neutral current problem can be avoided if the squarks take the following mass pattern, namely the first two generations with the same chirality are degenerate with masses around the weak scale, while the third generation is very heavy. We realize this scenario through the supersymmetric extension of a topcolor model with gauge mediated supersymmetry breaking.Comment: 12 pages, latex, no figure

Processing, Microstructure, and Properties of Multiphase Mo Silicide Alloys

Multiphase Mo silicide alloys containing T2 (Mo{sub 5}SiB{sub 2}), Mo{sub 3}Si and Mo phases where prepared by both melting and casting (M and C) and powder metallurgical (PM) processes. Glassy phases are observed in PM materials but not in M and C materials. Microstructural studies indicate that the primary phase is Mo-rich solid solution in alloys containing {le}(9.4Si+13.8B, at. %) and T2 in alloys with {ge}(9.8Si+14.6B). An eutectic composition is estimated to be close to Mo-9.6Si-14.2B. The mechanical properties of multiphase silicide alloys were determined by hardness, tensile and bending tests at room temperature. The multiphase alloy MSB-18 (Mo-9.4Si-13.8B) possesses a flexure strength distinctly higher than that of MoSi{sub 2} and other Mo{sub 5}Si{sub 3} silicide alloys containing no Mo particles. Also, MSB-18 is tougher than MoSi{sub 2} by a factor of 4

Effect of Small Amounts of B and C Additions on Glass Formation and Mechanical Properties of a Zr-Base Alloy

The effect of B and C additions up to 0.4 at. % on glass formation and mechanical properties of a Zr-base alloy Vitreloy 105 was studied using various techniques. All alloys were prepared by arc melting and drop casting. Boron additions increase the glass forming ability by lowering Tm and increasing Tg. Carbon additions only lower Tm, but do not affect Tg. B and C additions occupy free space and do not harden the glass phase

Oxygen impurities in NiAl: Relaxation effects

We have used a full-potential linear muffin-tin orbital method to calculate the effects of oxygen impurities on the electronic structure of NiAl. Using the supercell method with a 16-atom supercell we have investigated the cases where an oxygen atom is substitutionally placed at either a nickel or an aluminum site. Full relaxation of the atoms within the supercell was allowed. We found that oxygen prefers to occupy a nickel site over an aluminum site with a site selection energy of 138 mRy (21,370 K). An oxygen atom placed at an aluminum site is found to cause a substantial relaxation of its nickel neighbors away from it. In contrast, this steric repulsion is hardly present when the oxygen atom occupies the nickel site and is surrounded by aluminum neighbors. We comment on the possible relation of this effect to the pesting degradation phenomenon (essentially spontaneous disintegration in air) in nickel aluminides.Comment: To appear in Phys. Rev. B (Aug. 15, 2001

Direct fabrication of high-performance high speed steel products enhanced by LaB6

A direct fabrication technology (DFT) without smelting has been developed for fabricating sophisticated high speed steel products with low pollution, near-net shaping and short process. The steel consisting of (wt.%): 6.4W, 5.0Mo, 4.2Cr, 3.1V, 8.5Co and 1.28C, was fabricated as exemplary material. The activated and reactive sintering of green compacts under vacuum with low activation energy, redox reaction enhanced diffusion and the construction of concentration gradient of alloying elements around pores, promotes the nearly full densification (>\ua099.40%). Also, the DFT steels show high purity and superior mechanical properties. Minor strengthening agent LaB (0.1\ua0wt.%), which is easily to be accurately introduced in DFT, obviously increases the hot hardness, temper resistance, bend strength and toughness of DFT M3:2. The strengthening effect of boron atoms and La-rich complexes are proposed to directly result in the high hot hardness and temper resistance of LaB containing steel

Core-shell Co/CoO integrated on 3D nitrogen doped reduced graphene oxide aerogel as an enhanced electrocatalyst for the oxygen reduction reaction

Here, we demonstrate that Cobalt/cobalt oxide core-shell nanoparticles integrated on nitrogen-doped (N-doped) three-dimensional reduced graphene oxide aerogel-based architecture (Co/CoO-NGA) were synthesized through a facile hydrothermal method followed by annealing treatment. The unique endurable porous structure could provide sufficient mass transfer channels and ample active sites on Co/CoO-NGA to facilitate the catalytic reaction. The synthesized Co/CoO-NGA was explored as an electrocatalyst for the oxygen reduction reaction, showing comparable oxygen reduction performance with excellent methanol resistance and better durability compared with Pt/C

Core-shell Co/CoO integrated on 3D nitrogen doped reduced graphene oxide aerogel as an enhanced electrocatalyst for the oxygen reduction reaction

Here, we demonstrate that Cobalt/cobalt oxide core-shell nanoparticles integrated on nitrogen-doped (N-doped) three-dimensional reduced graphene oxide aerogel-based architecture (Co/CoO-NGA) were synthesized through a facile hydrothermal method followed by annealing treatment. The unique endurable porous structure could provide sufficient mass transfer channels and ample active sites on Co/CoO-NGA to facilitate the catalytic reaction. The synthesized Co/CoO-NGA was explored as an electrocatalyst for the oxygen reduction reaction, showing comparable oxygen reduction performance with excellent methanol resistance and better durability compared with Pt/C

Present day challenges in understanding the geomagnetic hazard to national power grids

Power grids and pipeline networks at all latitudes are known to be at risk from the natural hazard of geomagnetically induced currents. At a recent workshop in South Africa, UK and South African scientists and engineers discussed the current understanding of this hazard, as it affects major power systems in Europe and Africa. They also summarised, to better inform the public and industry, what can be said with some certainty about the hazard and what research is yet required to develop useful tools for geomagnetic hazard mitigation