A New Constant Air Volume Flow Regulation Method for Blowers Used in HVAC&R Systems

Accurate constant air volume flow rate regulation is essential in HVAC&R systems to provide comfort and required system performance. In the motor, the torque is regulated to provide the required air volume flow rate by monitoring the motor rotational speed. Various correlations including exponential functions and high order of polynomials used to regulate the torque in terms of motor speed and air volume flow rate are presented in the literature. However, all these formulas have not addressed the issue of inaccuracy of the air volume flow control in high altitudes regions. Therefore, a new 5-coefficient formula is proposed in this paper to maintain the constant air volume flow rate even when the altitude changes significantly

Seasonal Energy Efficiency Rating Improvement Of Residential HVAC Systems Using A Low Power Inverter With A PSC Compressor

Homeowners in the United States can generally choose among three types of air conditioning systems: fixed-speed compressor systems that cycle on and off to deliver an average cooling capacity; fixed-speed / multi-capacity compressor systems with reduced cycling; and variable speed compressor systems that match the cooling load of the household, thereby delivering better temperature and humidity control with higher efficiency and comfort levels. While HVAC systems account for about 45% of the energy consumption in U.S. homes and variable speed compressor systems can achieve significantly higher efficiency, they only account for 10% of the market and systems installed in new buildings mostly remain single speed. This could be explained in part by the initial system cost and the complex electronic circuitry used to vary compressor speed. This paper presents a system solution to improve the Seasonal Energy Efficiency Rating (SEER) of Permanent Split Capacitor (PSC) compressor systems by introducing a low power inverter used only for operation at low capacities. SEER results for 3 tons and 5 tons systems with scroll and rotary compressors are presented. The impact of varying the speed of the PSC outdoor fan on SEER is also discussed

Aeneas: A tool to enable applications to effectively use non-relational databases

Non-relational databases arise as a solution to solve the scalability problems of relational databases when dealing with big data applications. However, they are highly configurable prone to user decisions that can heavily affect their performance. In order to maximize the performance, different data models and queries should be analyzed to choose the best fit. This may involve a wide range of tests and may result in productivity issues. We present Aeneas, a tool to support the design of data management code for applications using non-relational databases. Aeneas provides an easy and fast methodology to support the decision about how to organize and retrieve data in order to improve the performance.Peer ReviewedPostprint (author’s final draft

Clima organizacional en las empresas mineras : el caso Orcopampa

Uno de los aspectos claves para lograr que las inversiones obtengan alta tasa de rentabilidad con un m?nimo riesgo es contar con un clima organizacional propicio que garantice un alto nivel de satisfacci?n de los trabajadores y un elevado nivel de productividad. Por ello es indispensable que las organizaciones eval?an constantemente su clima organizacional para lograr que el personal se sienta motivado e identificado con su lugar de trabajo. La presente investigaci?n tiene como objetivo establecer qu? dimensiones componen el clima organizacional en las empresas mineras en el Per?, para lo cual se toma como modelo la unidad econ?mica administrativa Orcopampa de la Compa??a de Minas Buenaventura SAA. Se busca determinar cu?l es el clima organizacional actual y qu? medidas se deben tomar para obtener un clima organizacional ideal, cu?l es la percepci?n de los actores al respecto y qu? recomendaciones se deberi?n dar para fortalecer un adecuado clima organizacional. La investigaci?n se centra en el diagn?stico y la evaluaci?n del clima organizacional con la finalidad de disminuir la brecha existente entre el clima actual y el ideal. Comprende estilo de liderazgo, manejo y niveles de comunicaci?n, diferentes relaciones laborales entre los trabajadores, rigidez, flexibilidad y adaptabilidad de la organizaci?n. Asimismo, se explican los factores que influyen en la eficacia del personal e intervienen en su grado de identificaci?n, motivaci?n y compromiso

Aplicación de herramientas Lean Manufacturing para incrementar la productividad de la empresa Agroindustria Santa Marina, San José, 2021

La presente investigación tiene como principal objetivo Aplicar las herramientas lean manufacturing para incrementar la productividad en la empresa Agroindustria Santa Marina, San José, 2022. El estudio es de tipo aplicado, de diseño pre experimental donde se evaluó el comportamiento de la variable dependiente Productividad producto de Lean Manufacturing, en el pre test y también en el post test. La población estuvo conformada por los procesos de producción de la empresa, y la muestra fue igual a la población. Los instrumentos empleados para la recolección de datos fueron guía de observación, ficha de registro de productividad, ficha de registro de tiempos de maquinaria tpm y actividades smed, check list de 5S. Los datos fueron analizados mediante el programa SPSS, con un nivel de significancia de 0.000 mediante la prueba de T-Student. Se concluye que las herramientas Lean manufacturing mejoran la productividad en un 11%

Automatic query driven data modelling in Cassandra

Non-relational databases have recently been the preferred choice when it comes to dealing with Big Data challenges, but their performance is very sensitive to the chosen data organisations. We have seen differences of over 70 times in response time for the same query on different models. This brings users the need to be fully conscious of the queries they intend to serve in order to design their data model. The common practice then, is to replicate data into different models designed to fit different query requirements. In this scenario, the user is in charge of the code implementation required to keep consistency between the different data replicas. Manually replicating data in such high layers of the database results in a lot of squandered storage due to the underlying system replication mechanisms that are formerly designed for availability and reliability ends. We propose and design a mechanism and a prototype to provide users with transparent management, where queries are matched with a well-performing model option. Additionally, we propose to do so by transforming the replication mechanism into a heterogeneous replication one, in order to avoid squandering disk space while keeping the availability and reliability features. The result is a system where, regardless of the query or model the user specifies, response time will always be that of an affine query

BCN Rocks: aprendiendo geología urbana a través de una aplicación App interactiva

BCN Rocks is an application (App) for personal mobile devices (Android and iOS versions) suitable for secondary and high school students as well as people without background in Earth Sciences. The main objective of this App is to learn geology using the city facades and pavements of two emblematic spaces of the city of Barcelona, the Passeig de Gràcia and the Barri Gòtic. The application has three main sections (ELEMENTS, EXPLORE, and LABORATORY) that are intended to satisfy the different needs of users. In the first section, Elements, the user will find all the information about rocks forming the selected buildings as well as a brief explanation about the history and architecture of each edifice. The second section, Explore, aims to arise the curiosity of users. In this sense, several routes are proposed according to different criteria including geographic position and age of the edifices. Finally, the third section, Laboratory, allows all users to investigate several geological aspects by means of interactive experiments.Este trabajo se enmarca en un proyecto financiado por la Fundación Española para la Ciencia y la Tecnología, FECYT (ref. 8524) en el que ha participado la Universitat de Barcelona, el Instituto de Ciencias de la Tierra Jaume Almera del Consejo Superior de Investigaciones Científicas (ICTJA-CSIC) y la empresa FUSTA. AG agradece su contrato Ramón y Cajal (RYC-2012-11024).Peer Reviewe

Las pruebas de laboratorio para la identificación de sars-cov-2 en tiempos de pandemia en el Perú: Algunas precisiones acerca del «rendimiento diagnóstico»

Carta al editorRevisión por pare

Titania-doped tantala/silica coatings for gravitational-wave detection

Reducing thermal noise from optical coatings is crucial to reaching the required sensitivity in next generation interferometric gravitational-wave detectors. Here we show that adding TiO2 to Ta2O5 in Ta2O5/SiO2 coatings reduces the internal friction and in addition present data confirming it reduces thermal noise. We also show that TiO2-doped Ta2O5/SiO2 coatings are close to satisfying the optical absorption requirements of second generation gravitational-wave detectors

Vitamin D status and risk of incident tuberculosis disease: A nested case-control study, systematic review, and individual-participant data meta-analysis

Background: Few studies have evaluated the association between preexisting vitamin D deficiency and incident tuberculosis (TB). We assessed the impact of baseline vitamins D levels on TB disease risk.Methods and Findings: We assessed the association between baseline vitamin D and incident TB in a prospective cohort of 6,751 HIV-negative household contacts of TB patients enrolled between September 1, 2009, and August 29, 2012, in Lima, Peru. We screened for TB disease at 2, 6, and 12 months after enrollment. We defined cases as household contacts who developed TB disease at least 15 days after enrollment of the index patient. For each case, we randomly selected four controls from among contacts who did not develop TB disease, matching on gender and year of age. We also conducted a one-stage individual-participant data (IPD) meta-analysis searching PubMed and Embase to identify prospective studies of vitamin D and TB disease until June 8, 2019. We included studies that assessed vitamin D before TB diagnosis. In the primary analysis, we defined vitamin D deficiency as 25-(OH)D \u3c 50 nmol/L, insufficiency as 50-75 nmol/L, and sufficiency as \u3e75nmol/L. We estimated the association between baseline vitamin D status and incident TB using conditional logistic regression in the Lima cohort and generalized linear mixed models in the meta-analysis. We further defined severe vitamin D deficiency as 25-(OH)D \u3c 25 nmol/L and performed stratified analyses by HIV status in the IPD meta-analysis. In the Lima cohort, we analyzed 180 cases and 709 matched controls. The adjusted odds ratio (aOR) for TB risk among participants with baseline vitamin D deficiency compared to sufficient vitamin D was 1.63 (95% CI 0.75-3.52; p = 0.22). We included seven published studies in the meta-analysis and analyzed 3,544 participants. In the pooled analysis, the aOR was 1.48 (95% CI 1.04-2.10; p = 0.03). The aOR for severe vitamin D deficiency was 2.05 (95% CI 0.87-4.87; p trend for decreasing 25-(OH)D levels from sufficient vitamin D to severe deficiency = 0.02). Among 1,576 HIV-positive patients, vitamin D deficiency conferred a 2-fold (aOR 2.18, 95% CI 1.22-3.90; p = 0.01) increased risk of TB, and the aOR for severe vitamin D deficiency compared to sufficient vitamin D was 4.28 (95% CI 0.85-21.45; p = 0.08). Our Lima cohort study is limited by the short duration of follow-up, and the IPD meta-analysis is limited by the number of possible confounding covariates available across all studies.Conclusion: Our findings suggest vitamin D predicts TB disease risk in a dose-dependent manner and that the risk of TB disease is highest among HIV-positive individuals with severe vitamin D deficiency. Randomized control trials are needed to evaluate the possible role of vitamin D supplementation on reducing TB disease risk