Paramétrisation des points algébriques de degré donné sur la courbe d'équation affine y3=x(x−1)(x−2)(x−3)

We give a parameterization of the algebraic points of given degree over $\mathbb{Q}$ on the curve$y^3=x(x?1)(x?2)(x?3)$ This result extends a previous result of E.F. Schaefer who described in Schaefer (1998) [1] the set of algebraic points of degree ?3 over $\mathbb{Q}$.     

Short shots and industrial case studies: Understanding fluid flow and solidification in high pressure die casting

The geometric complexity and high fluid speeds involved in high pressure die casting (HPDC) combine to give strongly three dimensional fluid flow with significant free surface fragmentation and splashing. A simulation method that has proved particularly suited to modelling HPDC is Smoothed Particle Hydrodynamics (SPH). Materials are approximated by particles that are free to move around rather than by fixed grids, enabling more accurate prediction of fluid flows involving complex free surface motion. Three practical industrial case studies of SPH simulated HPDC flows are presented; aluminium casting of a differential cover (automotive), an electronic housing and zinc casting of a door lock plate. These show significant detail in the fragmented fluid free surfaces and allow us to understand the predisposition to create defects such as porosity in the castings. The validation of flow predictions coupled with heat transfer and solidification is an important area for such modelling. One powerful approach is to use short shots, where insufficient metal is used in the casting or the casting shot is halted part way through, to leave the die cavity only partially filled. The frozen partial castings capture significant detail about the order of fill and the flow structures occurring during different stages of filling. Validation can occur by matching experimental and simulated short shots. Here we explore the effect of die temperature, metal super-heat and volume fill on the short shots for the casting of a simple coaster. The bulk features of the final solid castings are found to be in good agreement with the predictions, but the fine details appear to depend on surface behaviour of the solidifying metals. This potentially has significant implications for modelling HPDC.     

A combined DCA: GA for constructing highly nonlinear balanced boolean functions in cryptography

Substitution boxes, aka S-boxes, are a key component of modern crypto-systems. Several studies and developments were carried out on the problem of building high-quality S-boxes in the last few years. Qualities of such boxes, such as nonlinearity and balance, steer the robustness of modern block ciphers. This work is concerned with the construction of highly nonlinear balanced Boolean functions. A deterministic optimization model which is the minimization of a polyhedral convex function on a convex polytope with 0–1 variables is introduced. A local deterministic optimization approach called DCA (Difference of Convex functions Algorithm) is investigated. For finding a good starting point of DCA we propose two versions of a combined DCA–GA (Genetic Algorithm) method. Numerical simulations prove that DCA is a promising approach for this problem. Moreover the combination of DCA–GA improves the efficiency of DCA and outperforms other standard approaches.     

An efficient combined DCA and B&;B using DC/SDP relaxation for globally solving binary quadratic programs

This paper addresses a new continuous approach based on the DC (Difference of Convex functions) programming and DC algorithms (DCA) to Binary quadratic programs (BQP) which play a key role in combinatorial optimization. DCA is completely different from other avalaible methods and featured by generating a convergent finite sequence of feasible binary solutions (obtained by solving linear programs with the same constraint set) with decreasing objective values. DCA is quite simple and inexpensive to handle large-scale problems. In particular DCA is explicit, requiring only matrix-vector products for Unconstrained Binary quadratic programs (UBQP), and can then exploit sparsity in the large-scale setting. To check globality of solutions computed by DCA, we introduce its combination with a customized Branch-and-Bound scheme using DC/SDP relaxation. The combined algorithm allows checking globality of solutions computed by DCA and restarting it if necessary and consequently accelerates the B&B approach. Numerical results on several series test problems provided in OR-Library (Beasley in J Global Optim, 8:429–433, 1996), show the robustness and efficiency of our algorithm with respect to standard methods. In particular DCA provides ϵ-optimal solutions in almost all cases after only one restarting and the combined DCA-B&B-SDP always provides (ϵ−)optimal solutions.     

Bounds of weighted multilinear Hardy-Cesàro operators in <Emphasis Type="Italic">p</Emphasis>-adic functional spaces

We introduce the p-adic weighted multilinear Hardy-Cesàro operator. We also obtain the necessary and sufficient conditions on weight functions to ensure the boundedness of that operator on the product of Lebesgue spaces, Morrey spaces, and central bounded mean oscillation spaces. In each case, we obtain the corresponding operator norms. We also characterize the good weights for the boundedness of the commutator of weighted multilinear Hardy-Cesàro operator on the product of central Morrey spaces with symbols in central bounded mean oscillation spaces.     

Measurement of isomeric-yield ratios for the 197Au(γ,n)196m,gAu reactions induced by bremsstrahlung

We measured isomeric-yield ratios for the ¹⁹⁷Au(γ,n)^196m,gAu reactions with bremsstrahlung energies of 50-, 60-, 70- MeV, and 2.5-GeV at the two different electron linac of the Pohang accelerator laboratory by using the activation method. The photons were produced when a pulsed electron beam hit a thin tungsten target. The well-known photoactivation method was used and hence the induced activities in the irradiated foils were measured with the high-resolution γ-ray spectrometric system consisting of lithium drifted high-purity Germanium detector and a multichannel analyzer. The measured isomeric-yield ratios for the ¹⁹⁷Au(γ,n)^196m,gAu reactions were (4.95 ± 0.51) × 10^?4, (5.72 ± 0.72) × 10^?4, (6.03 ± 0.50) × 10^?4, and (9.27 ± 0.83) × 10^?4 for 50-, 60-, 70-MeV, and 2.5-GeV bremsstrahlung energies, respectively. The present results measured with the bremsstrahlung energy higher than 60-MeV are the first measurement.     

The isomeric ratios in photonuclear reactions of natural strontium induced by bremsstrahlungs in the giant dipole resonance region and by 65 MeV bremsstrahlung

We have determined the isomeric ratio of ^85m,gSr in photonuclear reactions of natural strontium induced by bremsstrahlungs with end-point energies in the giant dipole resonance (GDR) region as well as the isomeric ratios of ^85m,gSr and ^84m,gRb produced at 65 MeV bremsstrahlung. In GDR region the target was irradiated at electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The target irradiation with 65 MeV bremsstrahlung was performed at the linear electron accelerator of the Pohang Neutron Facility, Pohang, South Korea. The gamma spectra of the samples irradiated in both cases were measured with spectroscopic systems consisting of 8192 channel analyzer and high-energy resolution (180 keV at gamma ray 1332 keV of ⁶⁰Co) HP(Ge) semiconductor detector Canberra. The GENIE2000 (Canberra) computer program was used for data processing. The results were discussed and compared with those of other authors.     

Trace analysis of tetracycline antibiotics in human urine using UPLC–QToF mass spectrometry

A rapid, sensitive and specific ultra-performance liquid chromatography–quadrupole time-of-flight mass spectrometry (UPLC–QToF-MS) method has been developed and validated for simultaneous determination of three tetracyclines (TCs) including oxytetracycline, tetracycline, and chlortetracycline in human urine. Human urine sample preparation involves pH adjustment to 4 with hydrochloric acid, pre-concentration, and cleanup by solid phase extraction (SPE) process. The chromatographic separation of all TCs was achieved in less than 5 min using UPLC and ESI-QToF-MS was successfully employed for the identification and quantification. The accurate masses of the product ions were calculated using lock mass correction, and were deviated from the theoretical masses by 0.5–1.9 mDa and 1.1–4.5 ppm, respectively. The developed method was validated in terms of linearity, sensitivity, selectivity, decision limit, detection capability, accuracy, and precision. Limit of detection and limit of quantitation for all TCs were estimated in the range of 0.089–0.138 ng mL^{− 1} and 0.294–0.455 ng mL^{− 1}, respectively. High overall recoveries of greater than 90% were achieved with linear responses over the 0.5–2 ng mL^{− 1} range for all TCs in urine samples.