Additional results on integrals of beam eigenfunctions

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.New simplest expression beam mode integrals are presented, including further simplifications and corrections of previous results; this type of integrals appear in computational methods in structural dynamics and vibrations of diverse structures and machines, and in aircraft dynamics methods.Revisión por pare

On the conditions for synchronous harmonic free vibrations

All conditions for synchronic harmonic oscillations are presented. These are for discrete and continuous undamped linear systems in free vibration. A vibrations literature review indicates that only one or the basic condition for synchronous harmonic free vibrations is known. This is, initial conditions as an eingenvector (or eigenfunction) for the initial displacements, and no generalized velocities for t=0. Moreover, although assumed or expected for continuous systems, this result appears solely or mainly for discrete systems in the literature

Complete results for free and forced vibrations of inerter-added one-degree-of-freedom systems

A comprehensive study on the influence of an inerter on the response of single-degree-of-freedom systems is presented; therefore, complete and thorough results for free and forced vibrations of linear SDOF systems with inerter are obtained. The free response results are for damped and undamped systems; moreover, the forced response solutions are for harmonic and arbitrary excitations. The classical problems of rotating unbalanced mass and support vibration isolation are solved

Una nueva especie de bagre de caverna, género Trichomycterus (Siluriformes: Trichomycteridae), del sistema río Magdalena, cordillera Oriental, Colombia

A new species of troglomorphic catfish is described from de Gedania Cave, located in the middle Suárez River drainage, Magdalena River system, Colombia. The new species can be distinguished from its congeners by the combination of the following characters: reduction or loss of the cornea, reduction of eyes and skin pigmentation, very long nasal and maxillary barbels (maximum of 160% and 135% of HL, respectively), nine branched pectoral-fin rays, first unbranched ray of the pectoral fin prolonged as a long filament, reaching 80% of pectoral-fin length, anterior cranial fontanel connected with the posterior fontanel through an opening of variable length and width, first dorsal-fin pterygiophore inserted between neural spines of free vertebra 13-14 and free vertebrae 33-34. The presence of troglomorphisms such as regression of the eyes, reduction of skin pigmentation and long barbels suggest the troglobitic status of this species. A comparative analysis with other species of Trichomycterus from epigean and hypogean environments is presented.Una nueva especies de bagre troglomorfo es descrito de la cueva de Gedania, cuenca media del río Suárez, sistema río Magdalena, Colombia. La nueva especie puede distinguirse de sus congéneres por la combinación de los caracteres de reducción o pérdida de la córnea, reducción de ojos y pigmentación de la piel, barbillas nasales y maxilares muy largas (máximo 160 % y 135 % de LC respectivamente), nueve radios ramificados de la aleta pectoral, primer radio simple de la aleta pectoral prolongado como un filamento largo, alcanzando 80 % de la longitud de la aleta pectoral, fontanela craneal anterior conectada con la fontanela posterior por una apertura de amplitud y longitud variable, primer pterigioforo de la aleta dorsal insertado entre la espina neural de la vértebra libre 13-14 y 33-34 vertebras libres. La presencia de características troglomorficas como la regresión de ojos y reducción de la pigmentación, así como barbillas largas sugieren el estatus troglobítico de la especie. Se presenta un análisis comparativo con otras especies de Trichomycterus de ambientes epigeos e hipogeos

Narrowbandness of seismic ground displacement on a broader area of the lithosphere and importance on base motion in isolated structures

Power spectral density of horizontal ground displacement of large and recent events in earthquake-prone Latin America is analyzed. The results confirm -in a larger region of the world- that strong motion horizontal displacement is a narrowband process, which was previously demonstrated solely on a very limited area: the State of California. Nonetheless, those limited and previous results proved to be important in seismic base isolation; particularly, in the solution of the problem of large displacements at the structure base. This is a current problem for which more expensive techniques than passive control are presently being implemented, as active or hybrid control; therefore, it is emphasized that a solution exists within simple base isolation, and it is based on ground displacement narrowbandness

Reliability Improvement Of End Suction Pump In Severe Service Through Engineered Component Upgrade

Case StudyCS1An end suction pump for amine service at an Ammonia plant was successfully upgraded by improvement of its components. Two 290 kW (390 HP) pumps, turbine/motor driven, rated for 262 m^3/hr (1,153 gpm) and 271 m (889 ft), operate in severe service conditions due low NPSHA and part-load operation. The equipment exhibited rough operation with high vibration and an elevated repair frequency by recurrent fatigue failure of shaft, severe wear ring rubs, impeller corrosion/erosion, mechanical seal leakage and bearing damages. After a catastrophic failure, involving pump and electric motor, that caused an emergency plant shutdown, an upgrade for the pumps was engineered. The objective was to overcome design weaknesses and incorporate features to increase reliability. Impeller deficiencies were identified and corrected and its metallurgy improved to endure severe cavitation/recirculation damage. The power end was completely redesigned, incorporating larger shaft and bearing housing stiffness, together with a material upgrade, oversized bearings and lubrication enhancements. As a result, a failure frequency as large as 9 a year has been eliminated since the upgrade and the pump presently accumulates 3 years of continuous operation. An outstanding improvement in reliability was obtained together with considerable savings in investment & maintenance costs

Successful Modification Of Vertical-Turbine Pumps For Capacity And Reliability Improvement

Case StudyA modification of seven 560 hp vertical-turbine pumps was carried out with outstanding results to improve their actual capacity. The installation was limited to 64% of its rated capacity, which was never reached, and the operating demand required to maintain all seven pumps in continuous service. Reliability of the pumps was additionally impaired by severe cavitation damage of impellers. A plant revamp required increased and reliable cooling water flow, with a limited time frame of seven months for full implementation. Original cast iron impellers were reverse engineered and manufactured oversize in 18Cr-16Mn steel. Bowls were modified for the larger impellers. Performance for all pumps was adjusted in a test stand and the efficiency improved not to exceed the rated horsepower of installed electric motors. As a result, the capacity of the installation reached its rated value. Operation was optimized with six pumps in operation and one in standby feeding 33% more water. After 26 months in service, none of the pumps had shown capacity drop or required maintenance beyond repacking. Significant savings were attained compared to the installation of new pumps

Experience With Vertical-Turbine Pumps Rebowl Upgrade

Case StudyCS1Four 580 HP cooling tower feed pumps were upgraded by retrofitting improved bowl assemblies with enclosed stainless-steel impellers. Pumps exhibited capacity limitation up to 50% of rated and cavitation damage in original semi-open cast iron impellers, requiring continuous operation of all installed equipment, including the stand-by pump, to cover plant requirements. Performance of the pumps was optimized by rework of new impellers and stand testing to satisfy guarantee point and improve efficiency to accommodate power limitation of existing drivers. As a result, rated capacity was recovered, allowing one pump in stand-by, with a significant reliability improvement and considerable savings in maintenance costs, together with a lower capital investment compared to the replacement of the complete units

A new species of cave catfish, genus <i>Trichomycterus</i> (Siluriformes: Trichomycteridae), from the Magdalena River system, Cordillera Oriental, Colombia

A new species of troglomorphic catfish is described from de Gedania Cave, located in the middle Suárez River drainage, Magdalena River system, Colombia. The new species can be distinguished from its congeners by the combination of the following characters: reduction or loss of the cornea, reduction of eyes and skin pigmentation, very long nasal and maxillary barbels (maximum of 160% and 135% of HL, respectively), nine branched pectoral-fin rays, first unbranched ray of the pectoral fin prolonged as a long filament, reaching 80% of pectoral-fin length, anterior cranial fontanel connected with the posterior fontanel through an opening of variable length and width, first dorsalfin pterygiophore inserted between neural spines of free vertebra 13-14 and free vertebrae 33-34. The presence of troglomorphisms such as regression of the eyes, reduction of skin pigmentation and long barbels suggest the troglobitic status of this species. A comparative analysis with other species of Trichomycterus from epigean and hypogean environments is presented

LEARNING FOR THE GENERATION OF SHARED VALUE: CHALLENGE OF THE MANAGEMENT PROGRAM OF A PUBLIC UNIVERSITY

Companies as organizations focused on the fulfillment of particular objectives direct and maximizing limited resources in the function of satisfying needs in society, however, motivated by profit and rarely conceived of their investors as sufficient, causing neglect and distancing from the commitment to ethical and responsible management of resources, oriented by market orders, under policies more concerned with their profits than with operational practices that, in addition to improving their competitiveness, help to improve social conditions in a reactivation process after the pandemic experienced, contribute to the quality of life in general in the communities involved in their production processes, in other words, the generation of shared value (SV). The results of a study that sought to identify, through the perception delivered by students and graduates of an administration program of a public university, the level of perception of learning that allows contributing to the culture in the generation of shared value in organizations. It is a population that, due to its formation, challenges them with the transfer of knowledge that contributes to the economic reactivation, as well as to the generation of SV in the organizations. The study is based on Porter's and Kramer's ideas on preconceiving a) products and markets, b) redefining productivity in the value chain, and c) building support clusters. The methodology implemented for the analysis was mixed, using the survey as a data collection instrument. The results show that the students and graduates of the program observed show that there is a medium-low environment in the three concepts evaluated, with a medium level of 40%, a low level of 35% and a high level of only 24%