On Weighted Low-Rank Approximation

Our main interest is the low-rank approximation of a matrix in R^m.n under a weighted Frobenius norm. This norm associates a weight to each of the (m x n) matrix entries. We conjecture that the number of approximations is at most min(m, n). We also investigate how the approximations depend on the weight-values.Comment: 13 page

Deconstructing the myths: housing development versus school costs

William Ray of the New Hampshire Housing Finance Authority analyzes the connection between housing development and accelerating public school spending in the Granite State.Housing - Prices - New Hampshire ; Economic conditions - New Hampshire ; Education - New Hampshire

Towards a scalability model for wireless mesh networks

Zenzeleni mesh network is a wireless ad-hoc mesh network that provides voice services using public analogue telephones to the Mankosi community in the Eastern Cape Province. We would like to improve on the network infrastructure by upgrading the mesh routers and introducing low-end smartphones onto the network; and offer both data and voice over Internet protocol services. However, before deploying resources, it is imperative to identify the maximum number of mesh nodes, clients and simultaneous voice over internet protocol calls that can be supported by the mesh network while maintaining acceptable quality of service levels. Absence of such data might lead to financial risk and time depletion when setting up an optimal network. Bolstering the claim are investigations that report drop in quality levels as network density and hop count escalate. As current investigations mostly yield capacity models to predict per-node throughput with increasing hop count, we propose experiments to devise a scalability model to quantify scalability of mesh networks in this paper. We recommend experimental implementations at simulation level in Network Simulator-3 moving on to testbeds built using WiBed, and then finally take results to the field.Telkom, Cisco, Aria Technologies, THRIP, CONFINEDepartment of HE and Training approved lis

Una propuesta de clase con GeoGebra: el dominio, rango y la transformación de funciones construyendo animaciones

Este documento presenta algunos resultados obtenidos en estudiantes para profesor de educación básica con énfasis en matemáticas, en el curso de Didáctica de la Geometría, guiados por el estudio de movimientos rígidos como translaciones y reflexiones, y transformaciones de compresión en representaciones gráficas de un sistema de coordenadas cartesiano en un plano real, haciendo énfasis en el estudio de los comportamientos del dominio y rango de las funciones. La propuesta se desarrolla dentro de la aplicación de una actividad cuyo propósito es hacer uso del software de geometría dinámica “GeoGebra” y sus herramientas, para construir animaciones visualmente atractivas, donde se hiciera evidente el manejo de las transformaciones mencionadas, pretendiendo una reflexión sobre su comportamiento

El dominio, rango y la transformación de funciones construyendo animaciones en GeoGebra

La comunicación expone los resultados del trabajo de investigación “Construcción del concepto de fracción con estudiantes de Licenciatura en Educación Básica”. Caso: una universidad en Bucaramanga, realizado con la integración de los métodos cuantitativo y cualitativo. En una primera etapa se indagan e identifican los diferentes significados de fracción que tienen los estudiantes, a través de una prueba diagnóstica, apoyados en dos lineamientos teóricos: la didáctica de las matemáticas y la formación de maestros; posteriormente, se diseñan e implementan tres unidades didácticas utilizando las herramientas juego Partimundo, bloques lógicos de Dienes y regletas de Cuisenaire para construir los significados de fracción: parte-todo, razón y operador, lo que permite una observación directa del docente-investigador con el grupo objeto. Finalmente se aplica una prueba final que se contrasta con la prueba diagnóstica y el análisis de las observaciones realizadas en la implementación de la estrategia. El impacto de esta investigación genera en la Educación Superior la transformación de procesos de enseñanza a través de experiencias de aprendizaje significativas en los docentes en formación

Models for biomass estimation in native forest tree plantations and secondary forests in the Costa Rican Caribbean Region

The use of forest ecosystems as carbon sinks is now more accepted. However, credible information about its growth in terms of\ud biomass and its capacity to capture and store CO2 is still insufficient in order to suggest ways by which forest owners should be\ud compensated. The objective for this study was to construct models that allow us to determine tree biomass for native tree plantations\ud of Hieronyma alchorneoides Allemào, Vochysia guatemalensis Donn and a group of 35 species of secondary forests in the\ud Costa Rican Caribbean region. In each plantation the tree with the mean diameter at breast height (d) was harvested; in secondary\ud forests the harvested tree corresponded to the mean d tree with the highest Importance Value Index (IVI) for each diametric class.\ud Destructive sampling was used, separating each tree component and collecting a field sample in order to determine dry matter\ud content (MS). All selected models had R2aj values above 82.6%. Tree species from secondary forests showed the lowest R2aj\ud values. Stem, roots and total biomass had R2aj values above 91.3%, while leaves and branches had values between 82.6 and 94.1%.\ud Biomass expansion factor (BEF) in secondary forest was 1.44 and in forest tree plantations it was 1.56. The radical biomass (Bra)\ud relationship to total aboveground biomass (Bat) and stem biomass (Bf) in secondary forests was 0.25 and 0.37, respectively, 0.26\ud and 0.39 for V. guatemalensis and 0.3 and 0.52 for H. alchorneoides.El uso de los ecosistemas forestales como sumideros y reservorios de carbono es cada día más aceptado. Aún así, la información\ud fidedigna sobre su crecimiento en biomasa y la capacidad de captura y de almacenamiento de CO2 es insuficiente para proponer\ud formas de compensación a los propietarios de bosques. El objetivo de este trabajo fue construir modelos para estimar la biomasa\ud del árbol en plantaciones de Hieronyma alchorneoides, Vochysia guatemalensis y para un grupo de 35 especies en bosque secundario,\ud en la zona Caribe de Costa Rica. En cada plantación se extrajo un árbol de diámetro promedio a la altura del pecho (d) y en\ud bosque secundario un árbol de d promedio de la especie de mayor índice de valor de importancia por clase diamétrica. Se utilizó\ud un muestreo destructivo, separando cada componente del árbol y tomando una muestra de campo para determinar la materia seca.\ud Todos los modelos seleccionados tuvieron un R2aj superior al 82,6%. Las especies arbóreas de bosque secundario mostraron R2aj\ud inferiores. El fuste, raíz y biomasa total del árbol mostraron R2aj > 91,3%, y las hojas y ramas, entre 82,6 y 94,1%. El factor de\ud expansión de biomasa en bosque secundario fue de 1,44 y en plantaciones de 1,56. Se estimó que la relación de biomasa radical\ud respecto a biomasa aérea total y biomasa del fuste fue 0,25 y 0,37, respectivamente, en bosques secundarios; 0,26 y 0,39 en V.\ud guatemalensis, y 0,3 y 0,52 en H. alchorneoides.Este trabajo ha sido financiado por la Universidad\ud Nacional Autónoma de Costa Rica, el Ministerio de Ciencia\ud y Tecnología de Costa Rica y gracias al apoyo de la empresa\ud privada. El primer autor se benefició de una beca del\ud Programa Miguel de Cervantes para realizar su tesis doctoral\ud en la Universidad de Alcalá de Henares, España

Clustered Multi-layer Multi-protocol Wireless Mesh Networks

Wireless Mesh Networks (WMNs) have emerged as an alternative option to the wired networks in areas where wired deployment is unfeasible and/or costly. They have been widely adopted in community networks as these networks are mostly built within “not for profit” projects and do not require enterprise class investment which can lead to inefficient network architectures and routing protocol designs. B.A.T.M.A.N-ADV has been designed as a simple routing protocol that adheres to lightweight equipment requirements of wireless mesh deployment in the rural areas of the developing countries. However, it is built around a flat WMN topology which is challenged with scalability, security and implementation issues; which can limit WMN growth and services expansion. This paper proposes and evaluates the performance of a new multi-layer, multi-protocol WMN architecture that addresses B.A.T.M.A.N-ADV scalability issues by borrowing from wired networks their clustering model and building around the B.A.T.M.A.N Experimental (BMX6) protocol to introduce layer2 tunnelling through a cloud of layer3 routers.Telkom, Cisco, Aria Technologies, THRIPDepartment of HE and Training approved lis

A participatory design for a billing system: A South African case study of a community based telephony system

This paper describes the role participatory design can play in developing and implementing an information and communication technology for development project in a rural area. It shows how the process of co-designing an artifact can reflect and shape social development. A case study was conducted in the Mankosi Community in the Eastern Cape with the aim of designing and implementing a billing system for an existing community-owned telephony system, by accommodating the community’s requirements. Relevant criteria had to be considered for this telephony system based on voice over Internet Protocol with the possibility of ‘break-out’ calls to external networks. Different payment modalities were explored that would allow for a transparent method of both collecting money and applying the collected funds to achieve the project’s sustainability. A participative methodology with future users and operators of the network—using scenarios and prototypes to illustrate the implementation—informed the design of the billing system. Data was collected by means of unstructured interviews and focus group discussions. Qualitative data was analyzed using a qualitative content analysis tool. The community indicated that a billing system, based on both vouchers and prepaid service, would satisfy their needs.Telkom, Cisco, Aria Technologies, THRIPDepartment of HE and Training approved lis