Single Tower Crane Allocation Models Using Ant Colony Optimization

The construction industry greatly benefits from the utilization of heavy machines and equipment to accomplish successful projects. Tower cranes, in specific, have a crucial role in the transportation of material loads across the site. Because these machines are fixed to the ground, it is essential for planners and managers to position them in a location that provides the most efficient transfer of materials possible. This is commonly known as the tower crane allocation problem, and many researchers have attempted to optimize the tower crane location using mathematical, artificial intelligence, and simulation approaches. However, many works from the literature contain critical errors which make the models infeasible. This research presents the application of ant colony optimization (ACO) and an ACO variation to tower crane allocation models. Results show that the approaches presented in this work are up to par with even the most powerful methodologies used to solve the problem

Effects of the chaotic behavior of a superposition of waves in the flux across a channel

S.M., Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1999Includes bibliographical references (p. 59).Several numerical experiments were carried out to study the effects of chaotic behavior on the net tracer flux across a channel. The flow is given by a superposition of two propagating waves. The domain was set up so that a mode-I wave would fit on it, and the perturbation was a mode-4 wave. The experiments were carried out using a grid model with a second-order upwind differencing scheme. Simple Newtonian diffusion was used, and the velocities were calculated from a stream-function satisfying no normal flow boundary conditions. The experiments showed a small increase in the flux does appear due to the chaotic behavior, but this effect is only around 5% when the flux is compared to the one obtained from a pure 1-mode wave system. In contrast there is a difference of around 20% when the pure mode- 1 wave is compared to the pure mode-4 wave, the first one being more transportive. The chaotic behavior of the system is described in detail and a Lagrangian experiment was carried out as well to examine the motion of the particles and to explore a different approach to describing the dispersion of a tracer.by Carlos H. Trevino Lozano.S.M

Thermal Dose Inactivation of Escherichia coli by Magnetic Induced Hyperthermia

Background: Apoptosis of mutated cells via magnetic hyperthermia has gained advocacy as technology capable of being used in lieu of chemotherapy for targeting cancer tumors. Progress of nanotechnology offers effective remote heating of magnetic fluid via hyperthermia. The heating and specific power absorption of these nanoparticles use in the magnetic fluid are dependent on particle properties and treatment locations. Methods: Nanoparticles were fabricated using microfluidic system by interaction of two solutions containing 2Fe(NO3)3+FeSO4 and NaOH+2%Dextran to create nanostructured media with a biocompatible dextran coating and a Fe3O4 core. The nanoparticles, of a concentration of 5mg/ml, were placed in a vile containing Luria-Bertani (LB) media with approximately 2.0x108 cells. The vile was inserted into a DM100 Series Magnetic Hyperthermia Device that provides an alternating magnetic field of 300 Gauss with a frequency of 604KHz. Results: Magnetite produced via the microfluidic systems at flow rate of 0.04mL/s showed uniform particle size distribution with average size 10nm and saturation magnetization up to 60emu/g as well as pure-phase of Fe3O4 with high crystallinity. Zero-Field-Cooled and Field-Cooled measurements indicated a superparamagnetic nature of as synthesized particles with a low blocking temperature that varies by the amount of dextran introduced in the mixture. Conclusions: The superparamagnetic nanoparticles were heated up to 60°C, inciting a heat shock effect that led to the destruction of the E.coli bacteria. The specific power absorption value obtained was 130 W/g, showing that magnetite–dextran nanostructured fluid appears to be a promising active media for the local magnetic hyperthermia for cancer therapy

The Application of Electrosprayed Minocycline-Loaded PLGA For The Treatment Of Glioblastoma

Background: Glioblastoma multiforme (GBM) is one of the most common and aggressive forms of cancer with unfavorable prognosis due to high levels of reoccurrence with around 10,000 patients in the U.S. diagnosed each year. Despite treatment with surgery, radiotherapy, and chemotherapy, survival rate for this disease is around 21 months after diagnosis. Minocycline, a tetracycline-derivative used as an antibiotic, has also demonstrated the ability to inhibit angiogenesis or tumor growth and, presents a possible treatment option for GBM. Methods: Microparticles were fabricated by electrospraying by varying solvent type, distance, flow rate, voltage, and polymer concentration as parameters. The cytotoxicity of endothelial and glioblastoma cells was determined by an MTT assay by determining the absorbance using a spectrophotometer at a wavelength of 350 nm. Scanning electron microscopy (SEM) imaging was used to image the samples to determine microparticle surface morphology and size via an electron beam due to microparticles being sputter coated with gold to generate an electrical conduction. Results: The electrospraying process consists of numerous parameters which directly affect the creation of microparticles. The use of the solvent methanol aids in dissolving minocycline, while the use of DCM is important for the process of electrospraying, due to its higher vapor pressure and ability to dissolve PLGA. Conclusion: In conclusion, electrospraying is a promising method to fabricate drug loaded PLGA microparticles. However, optimization is needed whenever there is a new drug of interest as it can modify the properties of the electrospray solution and result in different effects on the fabrication parameters and particles produced

Influence of Laser Modulation Frequency on the Performance of Terahertz Photoconductive Switches on Semi-Insulating GaAs Exhibiting Negative Differential Conductance

[EN]In typical terahertz time-domain spectroscopy systems, the use of the lock-in technique is necessary because of the low current induced at the receiver so that the laser pump beam must be modulated (chopped) at a frequency much lower than the laser repetition rate. This work shows that, in the case of semi-insulating GaAs (SI-GaAs) antennas, this modulation has an important effect on the antenna current and consequently, on the radiated electromagnetic pulse. There exists a threshold bias (whose value depends on the chopping frequency) where an abrupt increase in the current and consequently, in the terahertz emission takes place. The calculated energy of the pulse below and above the threshold shows that the energy doubles. The exact bias voltage at which this occurs changes with the laser modulation frequency when this is below 350 Hz, but at higher frequencies, the threshold remains almost constant. The experiments show that the responsibility for this behavior is the S-shape negative differential conductance exhibited by SI-GaAs originated by a slow field-enhanced charge trapping mechanism, which is also an important source of noise at the receiver of the system.SpanishMINECO and FEDER under Project TEC2017-83910-R and in Junta de Castilla y León and FEDER under Project SA254P1

Carbon combustion synthesis of Janus-like particles of magnetoelectric cobalt ferrite and barium titanate

Carbon combustion synthesis of oxides was applied for quick and energy efficient production of multiferroic composite of cobalt ferrite and barium titanate to form Janus-like particles matrix structure. The exothermic oxidation of carbon nanoparticles with an average size of 5 nm and a specific surface area of 110 m2/g generates a self-propagating thermal wave with peak temperature of up to 1000 °C. The thermal front rapidly propagates through the mixture of solid reactants (magnetic- CoFe2O4 and ferroelectric-BaTiO3) and results in localized hot-spot sintering of magneto-electric phases to form a nanocomposite structure. Carbon is not incorporated in the product and is emitted as a gaseous CO2. Existence of discrete CoFe2O4 and BaTiO3phases in the composites nanostructures was confirmed using X-ray powder diffraction along with SEM and TEM analysis. We estimated the activation energy for the combustion synthesis of Janus-like particles to be 112 ± 3.3 kJ/mol, indicating that the barium titanate and cobalt ferrite presence decrease the activation energy barrier of carbon oxidation and facilitate the ignition process of the combustion synthesis. We observe that the as-synthesized samples show magnetoelectric coupling on multiferroic cobalt ferrite–barium titanate ceramic composites

Effect of Printing Parameters on the Internal Geometry of Products Manufactured by Fused Filament Fabrication (FFF)

The internal geometry of a 3D-printed product determines its mechanical properties. In Fused Filament Fabrication (FFF) the filaments that build up the internal geometry suffer from variations that have not been sufficiently studied. This research focused on identifying the parameters that most affect the filaments and finding the optimum values to reduce their variations. A fractional factorial design of experiments was used to detect the printing parameters of FFF that most affect the width of extruded filaments, these results were also statistically analyzed. A response optimization was done to obtain the values of the printing parameters that will give the closest width of extruded filaments to the nozzle of the 3D printer used. Results showed layer height has the largest impact on filament width variation.Mechanical Engineerin

In-beam tests of the AMS RICH prototype with 20 A GeV/c secondary ions

Abstract A prototype of the AMS Cherenkov imager (RICH) has been tested by means of a low intensity 20 GeV /c per nucleon ion beam coming from the fragmentation of a primary beam of Pb ions. Data have been collected for charges