Moving Walkways, Escalators, and Elevators

We study a simple geometric model of transportation facility that consists of two points between which the travel speed is high. This elementary definition can model shuttle services, tunnels, bridges, teleportation devices, escalators or moving walkways. The travel time between a pair of points is defined as a time distance, in such a way that a customer uses the transportation facility only if it is helpful. We give algorithms for finding the optimal location of such a transportation facility, where optimality is defined with respect to the maximum travel time between two points in a given set.Comment: 16 pages. Presented at XII Encuentros de Geometria Computacional, Valladolid, Spai

Transforming triangulations on non planar-surfaces

We consider whether any two triangulations of a polygon or a point set on a non-planar surface with a given metric can be transformed into each other by a sequence of edge flips. The answer is negative in general with some remarkable exceptions, such as polygons on the cylinder, and on the flat torus, and certain configurations of points on the cylinder.Comment: 19 pages, 17 figures. This version has been accepted in the SIAM Journal on Discrete Mathematics. Keywords: Graph of triangulations, triangulations on surfaces, triangulations of polygons, edge fli

Bistability patterns and nonlinear switching with very high contrast ratio in a 1550 nm quantum dash semiconductor laser

We report on the experimental observation of optical bistability (OB) and nonlinear switching (NS) in a nanostructure laser; specifically a 1550 nm quantum dash Fabry-Perot laser subject to external optical injection and operated in reflection. Different shapes of optical bistability and nonlinear switching, anticlockwise and clockwise, with very high on-off contrast ratio (up to 180:1) between output states were experimentally measured. These results added to the potential of nanostructure lasers for enhanced performance offer promise for use in fast all-optical signal processing applications in optical networks. © 2012 American Institute of Physics

Tunable microwave signal generator with an optically-injected 1310nm QD-DFB laser

Tunable microwave signal generation with frequencies ranging from below 1 GHz to values over 40 GHz is demonstrated experimentally with a 1310nm Quantum Dot (QD) Distributed-Feedback (DFB) laser. Microwave signal generation is achieved using the period 1 dynamics induced in the QD DFB under optical injection. Continuous tuning in the positive detuning frequency range of the quantum dot's unique stability map is demonstrated. The simplicity of the experimental configuration offers promise for novel uses of these nanostructure lasers in Radio-over-Fiber (RoF) applications and future mobile networks. © 2013 Optical Society of America

Fluctuations of the heat flux of a one-dimensional hard particle gas

Momentum-conserving one-dimensional models are known to exhibit anomalous Fourier's law, with a thermal conductivity varying as a power law of the system size. Here we measure, by numerical simulations, several cumulants of the heat flux of a one-dimensional hard particle gas. We find that the cumulants, like the conductivity, vary as power laws of the system size. Our results also indicate that cumulants higher than the second follow different power laws when one compares the ring geometry at equilibrium and the linear case in contact with two heat baths (at equal or unequal temperatures). keywords: current fluctuations, anomalous Fourier law, hard particle gasComment: 5 figure

Gold substrate-induced single-mode lasing of GaN nanowires

We demonstrate a method for mode-selection by coupling a GaN nanowire laser to an underlying gold substrate. Multimode lasing of GaN nanowires is converted to single-mode behavior following placement onto a gold film. A mode-dependent loss is generated by the absorbing substrate to suppress multiple transverse-mode operation with a concomitant increase in lasing threshold of only ∼13%. This method provides greater flexibility in realizing practical single-mode nanowire lasers and offers insight into the design of metal-contacted nanoscale optoelectronics

Super-Planckian far-field radiative heat transfer

We present here a theoretical analysis that demonstrates that the far-field radiative heat transfer between objects with dimensions smaller than the thermal wavelength can overcome the Planckian limit by orders of magnitude. To guide the search for super-Planckian far-field radiative heat transfer, we make use of the theory of fluctuational electrodynamics and derive a relation between the far-field radiative heat transfer and the directional absorption efficiency of the objects involved. Guided by this relation, and making use of state-of-the-art numerical simulations, we show that the far-field radiative heat transfer between highly anisotropic objects can largely overcome the black-body limit when some of their dimensions are smaller than the thermal wavelength. In particular, we illustrate this phenomenon in the case of suspended pads made of polar dielectrics like SiN or SiO2. These structures are widely used to measure the thermal transport through nanowires and low-dimensional systems and can be employed to test our predictions. Our work illustrates the dramatic failure of the classical theory to predict the far-field radiative heat transfer between micro- and nanodevicesWe acknowledge funding from the Spanish MINECO (FIS2015-64951-R, MAT2014-53432- C5-5-R, FIS2014-53488-P, FIS2017-84057-P), the Comunidad de Madrid (S2013/MIT-2740), the European Union Seventh Framework Programme (FP7-PEOPLE-2013-CIG- 630996, FP7-PEOPLE-2013-CIG-618229), and the European Research Council (ERC-2011-AdG-290981 and ERC-2016- STG-714870). V.F.-H. acknowledges support from “la Caixa” Foundation and J.C.C. thanks the DFG and SFB767 for sponsoring his stay at the University of Konstanz as Mercator Fello

LEAN Production Management Model based on Organizational Culture to Improve Cutting Process Efficiency in a Textile and Clothing SME in Peru

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.In recent years, homegrown SMEs have had low production levels when compared with Chinese garment imports, losing their competitive advantage in the domestic market. SMEs represent 96% of garment companies in Peru and have a positive impact on the creation of jobs. The search for a technique to improve SME output was conducted in various studies; however, the efforts did not bear fruit over time. Thus, this article seeks to improve the low production efficiency in textile and clothing SMEs. Therefore, we proposed a model and validated it in the production area of a denim clothing manufacturing company in Peru. We conducted business diagnostics and found a production efficiency problem. Later, we adapted the Lean production management model to the prevailing organizational culture. The main result was that the company's production efficiency increased from 68% to 71%. Finally, employee commitment, along with the combination of the Lean model and organizational culture, allowed the improvements to stand the test of time after their implementation

Áreas homogêneas e teor de água disponível de um Latossolo Vermelho Amarelo.

O entendimento da variabilidade do solo e a amostragem sistemática do horizonte diagnóstico podem ser úteis na definição de estratégias de manejo. Neste contexto, uma abordagem multivariada dos atributos do horizonte diagnóstico do solo pode ser mais eficiente do que a simples caracterização da variabilidade espacial na superfície. O objetivo deste trabalho foi determinar áreas homogêneas do talhão com base na caracterização do horizonte diagnóstico, utilizando técnicas de análise multivariada, promovendo uma abordagem quantitativa do teor de água disponível. Em uma área de Latossolo Vermelho Amarelo, foram coletadas 97 amostras da camada 0,80-1,00 m, dispostas em malha regular de 175 m. Com base na metodologia proposta, foi possível determinar três áreas homogêneas. Uma destas, caracterizada pelos maiores teores de argila, caulinita e carbono orgânico e menor densidade do solo, apresentou maior umidade gravimétrica em equilíbrio com todos os potenciais estudados; porém, essa maior umidade não resultou em maiores teores de água disponível, que foram menores que 0,15 m3.m?3. As outras duas áreas, caracterizadas pelo maior teor de areia fina, apresentaram teores de água disponível maiores que 0,15 m3.m?3, considerado como satisfatório para o adequado desenvolvimento das plantas

Variabilidade e correlação espacial entre atributos e a umidade gravimétrica de um Latossolo Vermelho Amarelo.

O conhecimento das relações entre os atributos da paisagem, físico-hídricos e carbono orgânico de Latossolos deve ser aprimorado. Os objetivos deste trabalho foram: i) avaliar a variabilidade espacial dos atributos físicos da paisagem, do carbono orgânico e da umidade; e, ii) verificar a ocorrência de correlação espacial entre estes atributos e a umidade gravimétrica. Em uma área de Latossolo Vermelho Amarelo, foram coletadas 97 amostras da camada 0,80- 1,00 m, dispostas em malha regular de 175 m. Foram determinados oito atributos do solo, dois da paisagem e a umidade gravimétrica θ?0,001 MPa, θ?0,003 MPa, θ?0,006 MPa, θ?0,100 MPa, θ?1,000 MPa e θ?1,500 MPa. A variabilidade espacial foi analisada por meio de ajustes dos semivariogramas simples, e as correlações espaciais pelos semivariogramas cruzados. O teor de argila, areia fina e declividade apresentou correlação espacial e foi o atributo chave no arranjo espacial da umidade abaixo de θ?0,100 Mpa. O carbono orgânico também apresentou correlação espacial e foi o atributo chave para umidades acima dessa umidade. A variabilidade espacial dos teores de argila, densidade do solo e carbono orgânico, associada à declividade do terreno, pode ser eficaz na determinação de áreas homogêneas e auxiliar no manejo da água em sistemas agrícolas