Choice of Metrics used in Collaborative Filtering and their Impact on Recommender Systems

The capacity of recommender systems to make correct predictions is essentially determined by the quality and suitability of the collaborative filtering that implements them. The common memory-based metrics are Pearson correlation and cosine, however, their use is not always the most appropriate or sufficiently justified. In this paper, we analyze these two metrics together with the less common mean squared difference (MSD) to discover their advantages and drawbacks in very important aspects such as the impact when introducing different values of k-neighborhoods, minimization of the MAE error, capacity to carry out a sufficient number of predictions, percentage of correct and incorrect predictions and behavior when attempting to recommend the n-best items. The paper lists the results and practical conclusions that have been obtained after carrying out a comparative study of the metrics based on 135 experiments on the MovieLens database of 100,000 ratios

Influencia del comportamiento del Sistema Bancario frente al desarrollo de las MYPES del sector servicios de la ciudad de Moquegua en el período 2012-2015

La investigación realizada buscó comprobar la influencia del comportamiento del sistema bancario en el desarrollo de las mypes del sector servicios de la ciudad de Moquegua en el período 2012-2015, siendo el objetivo general determinar tal nivel de influencia. Nuestra hipótesis apuntaba que existía una influencia directa del comportamiento del sistema bancario sobre el desarrollo de las mypes, es decir, que a medida que este comportamiento fuese más positivo, habría un mayor crecimiento. Se tomó como muestra a 356 de un estimado de 4860 micro y pequeñas empresas del sector servicios de la ciudad de Moquegua. Se optó por una metodología inferencia, dada la dificultad de obtener información cuantificable de cada empresa. Los resultados contradijeron los supuestos, pues, al parecer, existen factores mucho más relevantes que explican el desarrollo de las mypes, como la falta de una cultura crediticia, a la vez que los bancos no han logrado un acercamiento con el sector microempresarial.Tesi

Centro de residencia y rehabilitación como respuesta a la inadecuada atención del paciente de la tercera edad en Chiclayo

La presente investigación, “Centro de Residencia y Rehabilitación como respuesta a la inadecuada atención del paciente de la tercera edad en Chiclayo”, tiene como objetivo principal proponer un proyecto arquitectónico que brinde servicios de atención médica, rehabilitación, residencia y recreación; para mejorar la atención y calidad de vida en los pacientes de la tercera edad de la ciudad de Chiclayo. El adulto mayor en la actualidad, ha experimentado un notorio aumento de su población, sin embargo, la consideración y el apoyo que reciben estas personas es muy escaso. Se les considera poco productivos, se les da mínima importancia en el tema de inserción social y laboral, se ven excluidos en servicios de salud, residencia, recreación entre otros, a menudo el adulto mayor se ve cada vez más segregado de la sociedad y siendo esta una población que va en constante y fuerte crecimiento, no existen centros que brinden un adecuado servicio. Por ello; el presente proyecto, tiene como finalidad crear un centro de atención para las personas de la tercera edad, ofreciéndoles espacios agradables y óptimos, que permitan mejorar su calidad de vida, redefiniendo la tradicional percepción que se tiene los centros de salud, asilos o residencias; en su mayoría solitarios, tenebrosos, e inmersos en el caos la ciudad. Lo que se busca entonces y mediante este proyecto en cambio es que el paciente interactúe más con la naturaleza, mediante espacios abiertos y con actividades al aire libre, en donde también puedan interactuar con su familia y demás grupos de edad, generando un ambiente intergeneracional que les permita llevar su envejecimiento de manera más activa y saludable, puedan potenciar sus habilidades y destrezas y con esto reinsertarse de manera efectiva a la sociedad. El lugar escogido, está ubicado al noreste del Distrito de Monsefú, por contar con un clima sub tropical, predominio de vegetación y zonas agrícolas, ideales para que las personas de la tercera edad disfruten del área libre y el contacto directo con la naturaleza

A framework for collaborative filtering recommender systems

As the use of recommender systems becomes more consolidated on the Net, an increasing need arises to develop some kind of evaluation framework for collaborative filtering measures and methods which is capable of not only testing the prediction and recommendation results, but also of other purposes which until now were considered secondary, such as novelty in the recommendations and the users? trust in these. This paper provides: (a) measures to evaluate the novelty of the users? recommendations and trust in their neighborhoods, (b) equations that formalize and unify the collaborative filtering process and its evaluation, (c) a framework based on the above-mentioned elements that enables the evaluation of the quality results of any collaborative filtering applied to the desired recommender systems, using four graphs: quality of the predictions, the recommendations, the novelty and the trust

A Balanced Memory-Based Collaborative Filtering Similarity Measure.

Collaborative filtering recommender systems contribute to alleviating the problem of information overload that exists on the Internet as a result of the mass use of Web 2.0 applications. The use of an adequate similarity measure becomes a determining factor in the quality of the prediction and recommendation results of the recommender system, as well as in its performance. In this paper, we present a memory-based collaborative filtering similarity measure that provides extremely high-quality and balanced results; these results are complemented with a low processing time (high performance), similar to the one required to execute traditional similarity metrics. The experiments have been carried out on the MovieLens and Netflix databases, using a representative set of information retrieval quality measures

Hierarchical graph maps for visualization of collaborative recommender systems

In this paper we provide a method that allows the visualization of similarity relationships present between items of collaborative filtering recommender systems, as well as the relative importance of each of these. The objective is to offer visual representations of the recommender system?s set of items and of their relationships; these graphs show us where the most representative information can be found and which items are rated in a more similar way by the recommender system?s community of users. The visual representations achieved take the shape of phylogenetic trees, displaying the numerical similarity and the reliability between each pair of items considered to be similar. As a case study we provide the results obtained using the public database Movielens 1M, which contains 3900 movies

A collaborative filtering approach to mitigate the new user cold start problem.

The new user cold start issue represents a serious problem in recommender systems as it can lead to the loss of new users who decide to stop using the system due to the lack of accuracy in the recommenda- tions received in that first stage in which they have not yet cast a significant number of votes with which to feed the recommender system?s collaborative filtering core. For this reason it is particularly important to design new similarity metrics which provide greater precision in the results offered to users who have cast few votes. This paper presents a new similarity measure perfected using optimization based on neu- ral learning, which exceeds the best results obtained with current metrics. The metric has been tested on the Netflix and Movielens databases, obtaining important improvements in the measures of accuracy, precision and recall when applied to new user cold start situations. The paper includes the mathematical formalization describing how to obtain the main quality measures of a recommender system using leave- one-out cross validation

Causal representation of multi-loop Feynman integrands within the loop-tree duality

The numerical evaluation of multi-loop scattering amplitudes in the Feynman representation usually requires to deal with both physical (causal) and unphysical (non-causal) singularities. The loop-tree duality (LTD) offers a powerful framework to easily characterise and distinguish these two types of singularities, and then simplify analytically the underling expressions. In this paper, we work explicitly on the dual representation of multi-loop Feynman integrals generated from three parent topologies, which we refer to as Maximal, Next-to-Maximal and Next-to-Next-to-Maximal loop topologies. In particular, we aim at expressing these dual contributions, independently of the number of loops and internal configurations, in terms of causal propagators only. Thus, providing very compact and causal integrand representations to all orders. In order to do so, we reconstruct their analytic expressions from numerical evaluation over finite fields. This procedure implicitly cancels out all unphysical singularities. We also interpret the result in terms of entangled causal thresholds. In view of the simple structure of the dual expressions, we integrate them numerically up to four loops in integer space-time dimensions, taking advantage of their smooth behaviour at integrand level.Comment: 24 pages, 8 figures. v2: references added; matches published versio

Cálculo del costo de producción de heno de alfalfa y avena en el NO de Chubut

La producción de heno en los valles del NO de la Provincia de Chubut tiene una tradición importante. Este forraje se utiliza diferido en invierno en los mismos establecimientos o para atender la demanda de muchos de los campos ganaderos extensivos del área árida que no tienen posibilidad de hacer reservas. En el presente trabajo se analizaron los costos para la campaña 2022/2023 de la producción de heno de alfalfa y avena bajo dos esquemas distintos: labranza tradicional y siembra directa, y de rollos de alfalfa con labranza tradicional y siembra directa. Para su cálculo se consideró que las labores de labranza, siembra, fertilización, aplicación de herbicida, cosecha y acopiado se contratan, se aplica riego complementario, con control químico de malezas, se hace una fertilización de base con fosfato diamónico y con aplicaciones de urea durante el cultivo de avena. En el caso de la avena, se imputa un 33% de la cuota anual de amortización e interés del equipo de riego en función de los meses que ocupan anualmente los cultivos. Para el alfalfar se estimó una vida útil de diez años, algo habitual en la zona. Con respecto a los rindes de producción en alfalfa se lo estimó 12.500 kg de ms/ha, lo que permitiría obtener en 500 fardos de 25 kg en tres cortes anuales o 25 rollos de 500 kg. En avena se estimó una producción de 8000 kg ms/ha, dando 350 fardos de 23 kg. Se consideró que los trabajos de corte, enfardado/enrollado y acopio se hace con maquinaria contratada. Finalmente se presenta la incidencia por rubro y por etapa para cada caso.EEA EsquelFil: Bottaro, Hugo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agroforestal Esquel; ArgentinaFil: Bobadilla, Segundo Evaristo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agroforestal Esquel; ArgentinaFil: Lexow, Guillermo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agroforestal Esquel; ArgentinaFil: Garcia, Marcos Jesus. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agroforestal Esquel; Argentin

Short-term functional outcomes in patients undergoing primary total knee arthroplasty according to their body mass index

Background: The impact of an increased body mass index (BMI) in patients with ostheoarthritis who undergo total knee arthroplasty (TKA) remains a controversial variable in terms of risks and benefits. This study aimed to evaluate the influence of BMI in the functional outcomes of patients with ostheoarthritis who underwent TKA. Methods: We followed a cohort of patients who underwent total knee arthroplasty with a primary diagnosis of osteoarthritis. Patients were stratified into 3 groups according to the World Health Organization classification of BMI. We assessed the association between BMI group and functional scores using the Western Ontario and McMaster osteoarthritis index (WOMAC) over the time intervals of pre– and postoperatively at 1 month, 3 months and 1 year. Results: The difference in means between pre-surgical WOMAC and WOMAC at first follow-up according to each BMI group was divided as follows: normal 10.9 (p=0.195), overweight 15.7 (p≤0.001) and obese 20.6 (p≤0.001). Study participants with a higher BMI had worse preoperative WOMAC scores and had greater improvement from baseline to 1 month. After one year of follow-up, participants in all BMI groups had similar WOMAC scores. Conclusions: Patients with obesity who underwent TKA showed greater functional improvement one month after surgery compared to the other BMI groups. Subsequently, it was observed at the end of the 12-month follow-up that all patients, regardless of BMI, had improved functional outcomes, and the magnitude of improvement was similar in all BMI groups.