THIS RESEARCH STUDIES THE BEHAVIOR OF THE OPTIMAL PARAMETERS AND THE EFFICIENCY OF THE TUNED COMBINED DAMPER (TCD) IN THE CONTROL OF A STRUCTURE SUBJECTED TO SEISMIC EXCITATION, WHEN UNCERTAINTY IS INCORPORATED IN THE MASS RATIO AND THE LENGTH RATIO. THE TCD IS A DEVICE MADE UP OF A TUNED LIQUID COLUMN DAMPER (TLCD), AND A TUNED MASS DAMPER (TMD). SEISMIC EXCITATION IS MODELED AS A STATIONARY TYPE ZERO-MEAN GAUSSIAN STOCHASTIC PROCESS. IT IS CONSIDERED A SEISMIC EXCITATION WITH A HIGH FREQUENCY CONTENT. THE EQUIVALENT STATISTICAL LINEARIZATION METHOD IS USED TO LINEARIZE THE NONLINEAR EQUATION ASSOCIATED WITH THE TUNED FLUID DAMPER. THE SENSITIVITY OF THE OPTIMAL PARAMETERS, THE TUNING RATIO AND THE HEAD LOSS COEFFICIENT OF THE TLCD, AND THE TUNING AND DAMPING RATIO OF THE AMS ARE ANALYZED BY INCLUDING AN UNCERTAINTY IN THE MASS RATIO AND THE LENGTH RATIO. REDUCTION OF DISPLACEMENT OF THE MAIN STRUCTURE IS USED AS OPTIMIZATION CRITERION. THE TCD EFFICIENCY AND ROOT MEAN SQUARE RMS OF THE MAIN SYSTEM DISPLACEMENT ARE OBTAINED. THE RESULTS SHOW THAT THE MOST SENSITIVE PARAMETER IS THE HEAD LOSS COEFFICIENT, WHEN FACED WITH AN UNCERTAINTY IN THE LENGTH RATIO. IT IS CONCLUDED THAT THE EFFICIENCY OF THE TCD AND RMS OF DISPLACEMENT OF THE MAIN STRUCTURE IS INSENSITIVE TO AN UNCERTAINTY OF LESS THAN 10%, BOTH OF THE MASS RATIO AND THE LENGTH RATIO.

THE BEHAVIOR OF THE TUNED LIQUID COLUMN DAMPER (TLCD) IS ANALYZED IN THE CONTROL OF NON-LINEAR STRUCTURES SUBJECTED TO RANDOM SEISMIC EXCITATIONS. THE STRUCTURE IS MODELED AS A SYSTEM OF ONE DEGREE OF FREEDOM WITH INCURSION IN THE NON-LINEAR RANGE. THE BOUC-WEN HYSTERETIC MODEL IS USED TO MODEL THE NON-LINEAR BEHAVIOR OF THE STRUCTURE. A STATIONARY STOCHASTIC ANALYSIS IS PERFORMED IN THE DOMAIN OF THE FREQUENCY. AN EQUIVALENT STATISTICAL LINEARIZATION WAS USED FOR THE ANALYSIS OF THE MAIN SYSTEM AND THE TLCD. THE TLCD PARAMETERS CONSIDERED FOR THE OPTIMIZATION PROCESS WERE THE FREQUENCY AND THE HEAD LOSS COEFFICIENT. TWO TARGET FUNCTIONS WERE CONSIDERED, (I) REDUCTION OF THE MAIN DISPLACEMENT OF THE SYSTEM, (II) REDUCTION OF THE HYSTERETIC ENERGY. TWO RANDOM PROCESSES WERE CONSIDERED AS SEISMIC EXCITATION, FIRST A BROAD BANDWIDTH PROCESS AND SECONDLY A NARROW BANDWIDTH PROCESS. THE RESULTS SHOW THAT FOR A BROAD BANDWIDTH PROCESS, THE TLCD TENDS TO TUNE WITH THE LINEAR EQUIVALENT FREQUENCY OF THE SYSTEM IN THE CASE WITHOUT TLCD, WHILE FOR THE NARROW BANDWIDTH PROCESS, IT TUNES (TLCD) WITH THE DOMINANT FREQUENCY OF THE INPUT. IT IS SEEN THAT THE TLCD BECOMES DETUNED WITH REGARD TO THE FREQUENCY OF THE STRUCTURE AS THE STRUCTURE BECOMES MORE NON-LINEAR. IT IS ALSO SEEN THAT THE OPTIMAL TUNING RATIO OF THE TLCD IS UNSENSITIVE TO THE MASS RATIO OF THE DEVICE AND THE MAIN DAMPING RATIO OF THE SYSTEM. IT IS ALSO CONCLUDED THAT IN CASE OF FLEXIBLE STRUCTURES, THE OPTIMAL HEAD LOSS COEFFICIENT TENDS TO BE LOWER AND INCREASES WITH REGARD TO ITS LENGTH RATIO. IT IS SEEN THAT THE EFFECTIVENESS OF THE TLCD IS GREATER FOR HIGHER MASS RATIOS OF THE DEVICE. IN ADDITION, IT IS FOUND THAT THE OPTIMAL TLCD BECOMES LESS EFFECTIVE AS THE STRUCTURE ENTERS THE NON-LINEAR RANGE, SHOWING LOWER EFFICIENCY THAN WHAT IS SEEN IN THE LITERATURE FOR OPTIMAL TLCDS IN LINEAR STRUCTURES.

THIS PAPER INVESTIGATES THE APPLICATION OF A PROBLEM-BASED LEARNING (PBL) TEACHING METHODOLOGY TO A COURSE ON ENGINEERING PROJECT SCHEDULING, WHICH INTRODUCES THE CRITICAL PATH METHOD (CPM). DURING THIS COURSE, STUDENTS SOLVED REAL-LIFE CIVIL ENGINEERING PROBLEMS USING PBL TO COMPARE PBL WITH TRADITIONAL PROBLEM-SOLVING METHODS. IN THE EXPERIMENTAL DESIGN, THE STUDENTS WERE RANDOMLY DIVIDED INTO TWO GROUPS. TRADITIONAL TEACHING SESSIONS WERE IMPARTED TO THE FIRST GROUP, WHICH WAS DESIGNATED AS THE CONTROL GROUP, WHEREAS THE CPM WAS TAUGHT TO THE SECOND GROUP VIA THE PBL TEACHING METHODOLOGY. AFTER THE CLASSROOM SESSIONS, AN EVALUATION TOOL WAS APPLIED: RESPONSES WERE ANALYZED USING WILCOXON AND FISHER STATISTICS, AND A SET OF OPEN-ENDED QUESTIONS WERE QUALITATIVELY ANALYZED VIA A PATTERN-MATCHING TECHNIQUE. THE RESULTS FOR THE GROUP THAT UTILIZED PBL WERE FAVORABLE; THIS FINDING DEMONSTRATED THE EFFICIENCY OF THIS TOOL FOR TEACHING CPM. IN ADDITION, THE RESULTS FOR THE STUDENTS THAT APPLIED PBL METHODOLOGY DEMONSTRATED A HIGH DEGREE OF ACCEPTANCE OF THE CPM METHODOLOGY, WHICH MOTIVATES ITS IMPLEMENTATION INTO TEACHING OTHER SUBJECTS RELATED TO PROJECT SCHEDULING IN CIVIL ENGINEERING.

IT IS CRUCIAL TO ESTABLISH AN ENTRY PROFILE TO ACHIEVE A UNIVERSITY GRADUATION PROFILE CONSISTENT WITH THE CURRENT SITUATION KNOWN BY THE INSTITUTION OF HIGHER EDUCATION REGARDING THE CHARACTERISTICS OF THE NEWLY ENROLLED STUDENTS. THIS WORK PROPOSES THE DEFINITION OF INCOME PROFILES BASED ON SOCIODEMOGRAPHIC VARIABLES, ADMISSION CONDITIONS, PREVIOUS EDUCATION, MOTIVATION, AND INTERESTS. FOR THIS, DATABASES AND CHARACTERIZATION SURVEYS APPLIED TO FIRST-YEAR STUDENTS FROM FIVE ENGINEERING DEGREES ARE USED. AS A RESULT, COMMON CHARACTERISTICS IN THE STUDIED CAREERS ARE IDENTIFIED, SUCH AS AGE, ENTRYWAY, AND NOT DECLARING THEMSELVES PART OF NATIVE PEOPLES OR IN A DISABILITY SITUATION. OTHER VARIABLES THAT DIFFERENTIATED THE GROUPS, SUCH AS TYPE OF SECONDARY EDUCATION, PERFORMANCE, AND GENDER GAP, WERE ALSO RECOGNIZED. IN ADDITION, THE ESTABLISHED PROFILES ARE RELATED TO THE GENERIC GRADUATION SKILLS. IN THIS WAY, ACTIONS TO STRENGTHEN STUDENTS? CAPACITIES CAN BE GENERATED, AND THEY HAVE THE SUPPORT TOOLS THAT ALLOW FOR IMPROVING ACHIEVEMENT INDICATORS DURING THEIR UNIVERSITY LIFE.

EN ESTA INVESTIGACIÓN SE ESTUDIA EL COMPORTAMIENTO DE UNA ESTRUCTURA DE UN GRADO DE LIBERTAD SOMETIDA A UNA EXCITACIÓN SÍSMICA ESTOCÁSTICA DE ALTO CONTENIDO DE FRECUENCIAS, LA CUAL ES CONTROLADA POR UN AMORTIGUADOR DE COLUMNA DE LÍQUIDO SINTONIZADO (ACLS) ÓPTIMO, CUANDO SE INTRODUCE INCERTIDUMBRE EN ALGUNOS PARÁMETROS DEL SISTEMA. SE ANALIZA LA INFLUENCIA EN EL COMPORTAMIENTO DE LOS PARÁMETROS ÓPTIMOS DEL ACLS, EN LA EFICIENCIA MEDIDA COMO REDUCCIÓN DEL DESPLAZAMIENTO DEL SISTEMA PRINCIPAL Y EN LA RAÍZ CUADRÁTICA MEDIA (RMS) DE DESPLAZAMIENTO DE LA ESTRUCTURA. SE REALIZA UNA LINEALIZACIÓN ESTADÍSTICA EQUIVALENTE PARA INCLUIR LA NATURALEZA NO LINEAL DEL ACLS. LOS PARÁMETROS ÓPTIMOS DE ACLS SON LA RAZÓN DE FRECUENCIAS Y EL COEFICIENTE DE PÉRDIDA DE CARGA. LA OPTIMIZACIÓN DEL ACLS SE REALIZA MINIMIZANDO LA REDUCCIÓN DE LA DESVIACIÓN ESTÁNDAR DEL DESPLAZAMIENTO DE LA ESTRUCTURA PRINCIPAL. LA INCERTIDUMBRE ES INGRESADA EN LA RAZÓN DE MASA, LA RAZÓN DE LONGITUD Y EL COEFICIENTE DE PÉRDIDA DE CARGA. SE ANALIZA EL COMPORTAMIENTO DE LA EFICIENCIA, MEDIDA COMO UNA REDUCCIÓN PORCENTUAL DEL DESPLAZAMIENTO AL INCLUIR UN ACLS ÓPTIMO Y EL RMS DEL DESPLAZAMIENTO, ANTE LA INCLUSIÓN DE INCERTIDUMBRE EN LOS PARÁMETROS ANTES MENCIONADOS. SE ENCUENTRA QUE LA INTRODUCCIÓN DE INCERTIDUMBRE EN EL PERIODO DE LA ESTRUCTURA PRODUCE LA MAYOR SENSIBILIDAD EN LOS PARÁMETROS ÓPTIMOS DEL ACLS, LA EFICIENCIA Y EL RMS DEL DESPLAZAMIENTO DE LA ESTRUCTURA. ESTO SE PRODUCE PRINCIPALMENTE EN ESTRUCTURAS RÍGIDAS Y CON UNA RAZÓN DE MASA PEQUEÑA. POR OTRA PARTE, UNA INCERTIDUMBRE EN LA RAZÓN DE MASA, Y EN LA RAZÓN DE LONGITUD DEL ACLS, NO PRODUCE VARIACIONES EN LA EFICIENCIA NI EN EL RMS DE DESPLAZAMIENTO DE LA ESTRUCTURA.

EN ESTA INVESTIGACIÓN SE ANALIZA EL COMPORTAMIENTO DE UNA ESTRUCTURA LINEAL DE UN GRADO DE LIBERTAD, QUE ES CONTROLADA POR UN AMORTIGUADOR COMBINADO SINTONIZADO (ACS). ÉSTE SE COMPONE DE DOS DISPOSITIVOS, UN AMORTIGUADOR DE MASA SINTONIZADO (AMS) Y UN AMORTIGUADOR DE COLUMNA DE LÍQUIDO SINTONIZADO (ACLS). EL ACS ES SOMETIDO A UNA EXCITACIÓN SÍSMICA ESTOCÁSTICA CON EL OBJETIVO DE ANALIZAR LA INFLUENCIA DEL CONTENIDO DE FRECUENCIAS EN LA EFICIENCIA DEL DISPOSITIVO. COMO MEDIDA DE EFICIENCIA, SE CONSIDERA EL PORCENTAJE DE REDUCCIÓN DE LA DESVIACIÓN ESTÁNDAR DE DESPLAZAMIENTO DEL SISTEMA PRINCIPAL. LOS PARÁMETROS OPTIMIZADOS DE CADA DISPOSITIVO SON LA FRECUENCIA Y AMORTIGUAMIENTO EN EL CASO DEL AMS, ADEMÁS DE FRECUENCIA Y COEFICIENTE DE PÉRDIDA DE CARGA PARA EL ACLS. SE REALIZA UN ANÁLISIS DE SENSIBILIDAD DE LOS PARÁMETROS ÓPTIMOS DEL ACS, CON RESPECTO A LA RAZÓN DE MASA, PERIODO DE LA ESTRUCTURA PRINCIPAL Y CONTENIDO DE FRECUENCIAS DE LA EXCITACIÓN. LAS PRINCIPALES CONCLUSIONES OBTENIDAS, SON QUE LA EFICIENCIA DEL ACS DEPENDE DEL CONTENIDO DE FRECUENCIAS DE LA EXCITACIÓN. ADEMÁS, ESTA AUMENTA A MEDIDA QUE LA RAZÓN DE MASA AUMENTA, INDEPENDIENTE DEL CONTENIDO DE FRECUENCIAS DE LA EXCITACIÓN. POR OTRA PARTE, EL ACS ES MENOS EFICIENTE PARA ESTRUCTURAS MÁS FLEXIBLES.

SEWAGE TREATMENT PLANTS (STPS) SANITIZE WASTEWATER SO THAT IT CAN BE DISCHARGED INTO NATURAL WATERCOURSES. AS A RE-SULT OF THIS TREATMENT, BIOSOLIDS OR SLUDGE ARE GENERATED. SLUDGE DISPOSAL IS A POTENTIAL SOURCE OF SOIL AND WATER POLLUTION, AND ITS MANAGEMENT CAN ACCOUNT FOR UP TO 50% OF THE OPERATION-AL COSTS OF WASTEWATER TREATMENT FACILITIES. ON THE OTHER HAND, THE MANAGEMENT OF OTHER SOURCES OF ORGANIC WASTES SUCH AS FRUIT AND VEGETABLE WASTE (FVW) REPRESENT A CHALLENGE AND AN OPPORTUNITY, DUE TO THEIR HIGH VOLUMES AND POTENTIAL EN-ERGY VALORIZATION THOUGH BIOLOGICAL AND THERMAL PROCESSES. IN THIS ARTICLE, WE REVIEW THE MAIN REPORTS REGARDING ANAEROBIC CO-DIGESTION OF SEWAGE SLUDGE WITH FVW AND SIMILAR RESIDUES. ONLY PILOT AND FULL-SCALE EXPERIENCES WERE INCLUDED IN OUR SEARCH, IN AN ATTEMPT TO PROVIDE A REALISTIC ASSESSMENT OF THE DEGREE OF TECHNOL-OGY ADOPTION IN INDUSTRIAL PLANTS. ADDITIONALLY, WE REVIEW THE CUR-RENT CHILEAN, EUROPEAN AND AMERICAN REGULATIONS REGARDING ?NAL DISPOSAL OR ELIMINATION OF SLUDGE, WITH EMPHASIS ON THOSE THAT INVOLVE WASTE ENERGY VALORIZATION, SUCH AS INCINERATION IN CEMENT PLANTS.

EN ESTA INVESTIGACIÓN SE ANALIZA EL VALOR DE LA EFICIENCIA DEL AMORTIGUADOR DE COLUMNA DE LÍQUIDO SINTONIZADO (ACLS), CALCULADA A TRAVÉS DE LA TEORÍA ESTOCÁSTICA DE VIBRACIONES. SE EMPLEAN TRES CRITERIOS O FUNCIONALES DE OPTIMIZACIÓN. EL MODELO CONSISTE EN UN SISTEMA PRINCIPAL DE UN GRADO DE LIBERTAD, CON COMPORTAMIENTO NO LINEAL, CONTROLADO POR UN ACLS NO LINEAL. EL ANÁLISIS ESTOCÁSTICO SUPONE UN ESTADO ESTACIONARIO Y REALIZA UNA LINEALIZACIÓN ESTADÍSTICA EQUIVALENTE, PARA EL COMPORTAMIENTO NO LINEAL, CON LO QUE SE OBTIENEN REDUCCIONES TEÓRICAS DE DESPLAZAMIENTO Y DE ENERGÍA HISTERÉTICA. LUEGO, ÉSTAS SE COMPARAN CON LAS REDUCCIONES OBTENIDAS CON UNA SIMULACIÓN DE MONTECARLO CON 200, 450, 800, 1250, 1850, 2600 SIMULACIONES. PARA LA SIMULACIÓN SE PLANTEAN LAS ECUACIONES NO LINEALES, QUE SE INTEGRAN DIRECTAMENTE SIN LINEALIZARLAS. LAS SIMULACIONES SE REALIZAN CON SISMOS ARTIFICIALES DE ALTO CONTENIDO DE FRECUENCIAS, COMPATIBLES CON LA NORMA CHILENA NCH2745 (2013). LOS RESULTADOS DE LA SIMULACIÓN DE MONTECARLO SON SENSIBLES AL NÚMERO DE SIMULACIONES CONSIDERADAS. SE PRODUCE UNA CONVERGENCIA PARA DOS CRITERIOS. LOS ERRORES SON MENORES AL 10%, LO QUE SE CONSIDERA ACEPTABLE. LAS REDUCCIONES OBTENIDAS PARA LA ENERGÍA HISTERÉTICA DE UN ANÁLISIS TEÓRICO, SOBRESTIMAN LA EFICIENCIA DEL ACLS, PARA UN CRITERIO CON UN PERIODO DE 2.0 S, Y PARA TODOS LOS CRITERIOS CUANDO SE TIENE UN PERIODO DE 2.5 S.