Evaluation of network coding techniques for a sniper detection application

This paper experimentally studies the reliability and delay of flooding based multicast protocols for a sniper detection application. In particular using an emulator it studies under which conditions protocols based on network coding deliver performance improvements compared to classic flooding. It then presents an implementation of such protocols on mobile phones

Cardiovascular function and ballistocardiogram: a relationship interpreted via mathematical modeling

Objective: to develop quantitative methods for the clinical interpretation of the ballistocardiogram (BCG). Methods: a closed-loop mathematical model of the cardiovascular system is proposed to theoretically simulate the mechanisms generating the BCG signal, which is then compared with the signal acquired via accelerometry on a suspended bed. Results: simulated arterial pressure waveforms and ventricular functions are in good qualitative and quantitative agreement with those reported in the clinical literature. Simulated BCG signals exhibit the typical I, J, K, L, M and N peaks and show good qualitative and quantitative agreement with experimental measurements. Simulated BCG signals associated with reduced contractility and increased stiffness of the left ventricle exhibit different changes that are characteristic of the specific pathological condition. Conclusion: the proposed closed-loop model captures the predominant features of BCG signals and can predict pathological changes on the basis of fundamental mechanisms in cardiovascular physiology. Significance: this work provides a quantitative framework for the clinical interpretation of BCG signals and the optimization of BCG sensing devices. The present study considers an average human body and can potentially be extended to include variability among individuals

MAC layer functions for SLEF

We develop three functions around the MAC layer: (1) Pseudo broadcast is a technique used to improve throughput of broadcast transmissions in case of congested networks. The mechanism consists in sending a packet in unicast to a station using RTS/CTS. Other stations will receive the packet by capturing all the frames that are transmitted on the network, even if they are not directed to them. (2) The injection rate of packets in the MAC layer has to be controlled. The application must not be allowed to deliver to the MAC layer more packets than the number that can be sent by the network adapter. It is also necessary to know the nominal rate of the network. (3) An indication of activity on the network has to be provided. This function has to detect the activity of other SLEF stations in the neighborhood. The address of the last transmitting station and the time of transmission have to be provided. The implementation is carried out using JAVA and native native code and it is portable across all operating systems and wireless cards

On the friction coefficient of straight-chain aggregates

A methodology to calculate the friction coefficient of an aggregate in the continuum regime is proposed. The friction coefficient and the monomer shielding factors, aggregate-average or individual, are related to the molecule-aggregate collision rate that is obtained from the molecular diffusion equation with an absorbing boundary condition on the aggregate surface. Calculated friction coefficients of straight chains are in very good agreement with previous results, suggesting that the friction coefficients may be accurately calculated from the product of the collision rate and an average momentum transfer,the latter being independent of aggregate morphology. Langevin-dynamics simulations show that the diffusive motion of straight-chain aggregates may be described either by a monomer-dependent or an aggregate-average random force, if the shielding factors are appropriately chosen.Comment: 22 pages, 6 figures, revised version. To appear in the Journal of Colloid and Interface Scienc

ConfErr: A Tool for Assessing Resilience to Human Configuration Errors

We present ConfErr, a tool for testing and quantifying the resilience of software systems to human-induced configuration errors. ConfErr uses human error models rooted in psychology and linguistics to generate realistic configuration mistakes; it then injects these mistakes and measures their effects, producing a resilience profile of the system under test. The resilience profile, capturing succinctly how sensitive the target software is to different classes of configuration errors, can be used for improving the software or to compare systems to each other. ConfErr is highly portable, because all mutations are performed on abstract representations of the configuration files. Using ConfErr, we found several serious flaws in the MySQL and Postgres databases, Apache web server, and BIND and djbdns name servers; we were also able to directly compare the resilience of functionally-equivalent systems, such as MySQL and Postgres

A network coding approach to the shipper detection problem

This paper experimentally studies the reliability and delay of flooding based multicast protocols for a sniper detection application. In particular using an emulator it studies under which conditions protocols based on network coding deliver performance improvements compared to classic flooding. It then presents an implementation of such protocols on mobile phones

Delay with network coding and feedback

We consider the problem of minimizing delay when broadcasting over erasure channels with feedback. A sender wishes to communicate the same set of μ messages to several receivers over separate erasure channels. The sender can broad- cast a single message or a combination (encoding) of messages at each timestep. Receivers provide feedback as to whether the transmission was received. If at some time step a receiver cannot identify a new message, delay is incurred. Our notion of delay is motivated by real-time applications that request progressively refined input, such as the successive refinement of an image encoded using multiple description coding. Our setup is novel because it combines coding techniques with feedback information to the end of minimizing delay. It allows Θ(μ) benefits as compared to previous approaches for offline algorithms, while feedback allows online algorithms to achieve smaller delay than online algorithms without feedback. Our main complexity results are that the offline minimization problem is NP-hard when the sender only schedules single messages and that the general problem remains N P -hard even when coding is allowed. However we show that coding does offer delay and complexity gains over scheduling. We also discuss online heuristics and evaluate their performance through simulations

Real-time Delay with Network Coding and Feedback

We consider the problem of minimizing delay when broadcasting over erasure channels with feedback. A sender wishes to communicate the same set of m messages to several receivers. The sender can broadcast a single message or a combination (encoding) of messages to all receivers at each timestep, through separate erasure channels. Receivers provide feedback as to whether the transmission was received. If, at some time step, a receiver cannot identify a new message, delay is incurred. Our notion of delay is motivated by real-time applications that request progressively refined input, such as the refinements or different parts of an image. Our setup is novel because it combines coding techniques with feedback information to the end of minimizing delay. Uncoded scheduling or use of multiple description (MDS) codes has been well-studied in the literature. We show that our setup allows O( m ) benefits as compared to both previous approaches for offline algorithms, while feedback allows online algorithms to achieve smaller delay compared to online algorithms without feedback. Our main complexity results are that the offline minimization problem is NP-hard when the sender only schedules single messages and that the general problem remains NP-hard even when coding is allowed. However we show that coding does offer complexity gains by exhibiting specific classes of erasure instances that become trivial under coding schemes. We also discuss online heuristics and evaluate their performance through simulations

Nível socioeconômico na primeira infância e oclusopatia em adolescentes e adultos jovens no Uruguai

This study aims to estimate orthodontic treatment need among 15-24 year-old individuals in Montevideo, Uruguay, and the association of occlusal traits with demographic, clinical and socioeconomic factors, considering a life course approach. A cross-sectional study using data from the First National Oral Health Survey in Uruguay was conducted. A two-stage cluster procedure was used to select a sample of 278 individuals in Montevideo. Household interviews and oral examinations were performed by six dentists. Dental Aesthetic (DAI) and Decayed Missing and Filled Teeth Indices (DMFT) were used to assess orthodontic treatment need and dental caries, respectively. Early life and current socioeconomic factors were obtained from the interview. Ordinal logistic regression was used to model the DAI index. Prevalence of definite malocclusion was 20.6%, followed by severe (8.2%) and very severe (7.6%). In the adjusted analysis, individuals with untreated dental caries (OR = 1.11; 95%CI: 1.03-1.20) and those who reported a lower socioeconomic level at 6 years of age (OR = 5.52; 95%CI: 1.06-28.62) had a higher chance of being a worse case of malocclusion. Current socioeconomic position was not associated with orthodontic treatment need. Individuals aged 22-24 years (OR = 1.59; 95%CI: 1.05-2.41) had a lower chance than those aged 14-17. This study shows that orthodontic treatment need is relatively high in Uruguayan adolescents and young adults. There is a potential relationship between early life socioeconomic status and the occurrence of malocclusion in adolescents and young adults under a life course approach.El objetivo de este estudio es estimar el tratamiento de ortodoncia que necesitan jóvenes entre 15 y 24 años en Montevideo, Uruguay, y la asociación de los rasgos oclusores con factores demográficos, clínicos y socioeconómicos, considerando el ciclo vital. Se trata de un estudio transversal que maneja datos de la Primera Encuesta Nacional de Salud Bucal en Uruguay. Se utilizó un procedimiento de análisis de clúster en dos fases para seleccionar una muestra de 278 personas en Montevideo. Se realizaron entrevistas domiciliarias y exámenes bucales por parte de seis dentistas. Se usaron también datos de índices de cirugías estéticas (DAI) y del número de dientes cariados, perdidos y obturados (DCPO), con el fin de evaluar el tratamiento necesario ortodóntico y las caries dentales, respectivamente. La primera infancia y la situación socioeconómica actual fueron factores que se obtuvieron de la entrevista. Se usó una regresión logística ordinaria para modelar el índice DAI. La prevalencia de la maloclusión definitiva fue de un 20,6%, seguida por la severa (8,2%) y la muy severa (7,6%). En el análisis ajustado, las personas que no se habían tratado las caries dentales (OR = 1,11; IC95%: 1,03-1,20), y quienes informaron de un nivel socioeconómico bajo a los 6 años de edad (OR = 5,52; IC95%: 1,06-28,62), tenían una mayor probabilidad de sufrir un caso de maloclusión. La posición socioeconómica actual no se asoció con el tratamiento ortodóntico necesitado. Las personas con 22-24 años (OR = 1,59; IC95%: 1,05-2,41) tenían una probabilidad más baja que aquellos con una edad entre 14-17. Este estudio muestra que el tratamiento ortodóntico necesario es relativamente alto en adolescentes uruguayos y adultos jóvenes. Hay una relación potencial entre el estatus socioeconómico en la primera infancia y la ocurrencia de maloclusión en adolescentes y jóvenes adultos desde una perspectiva del ciclo vital.O estudo teve como objetivo estimar a necessidade de tratamento ortodôntico na faixa etária de 15 a 24 anos em Montevideo, Uruguai, e a associação entre características oclusais e fatores demográficos, clínicos e socioeconômicos, com base na trajetória de vida. Foi realizado um estudo transversal, utilizando dados da 1a Pesquisa Nacional de Saúde Oral do Uruguai. Foi utilizado um procedimento de cluster em dois estágios para selecionar uma amostra de 278 indivíduos em Montevideo. Entrevistas domiciliares e exames odontológicos foram realizados por seis odontólogos. O índice de estética dentária (DAI) e o índice de dentes cariados, perdidos e obturados (DMFT/CPOD) foram usados para avaliar a necessidade de tratamento ortodôntico e de cárie dentária, respectivamente. Foram obtidos dados socioeconômicos da primeira infância e atuais, a partir de entrevistas. Foi utilizada a regressão logística ordinal para modelar o índice de estética dentária. A prevalência de oclusopatia definida era 20,6%, seguida pela forma grave (8,2%) e muito grave (7,6%). Na análise ajustada, indivíduos com cárie dentária não tratada (OR = 1,11; IC95%: 1,03-1,20) e aqueles de nível socioeconômico mais baixo aos 6 anos de idade (OR = 5,52; IC95%: 1,06-28,62) mostravam chances mais altas de apresentar oclusopatia mais grave. O nível socioeconômico atual não mostrou associação com necessidade de tratamento ortodôntico. Os indivíduos na faixa etária de 22-24 anos (OR = 1,59; IC95%: 1,05-2,41) mostraram probabilidade menor de oclusopatia quando comparados com a faixa etária de 14-17 anos. O estudo mostra que a necessidade de tratamento ortodôntico é relativamente alta entre adolescentes e adultos jovens uruguaios. De acordo com a abordagem de trajetória de vida, existe uma relação potencial entre nível socioeconômico na primeira infância e oclusopatia em adolescentes e adultos jovens