Even shorter proofs without new variables

Proof formats for SAT solvers have diversified over the last decade, enabling new features such as extended resolution-like capabilities, very general extension-free rules, inclusion of proof hints, and pseudo-boolean reasoning. Interference-based methods have been proven effective, and some theoretical work has been undertaken to better explain their limits and semantics. In this work, we combine the subsumption redundancy notion from (Buss, Thapen 2019) and the overwrite logic framework from (Rebola-Pardo, Suda 2018). Natural generalizations then become apparent, enabling even shorter proofs of the pigeonhole principle (compared to those from (Heule, Kiesl, Biere 2017)) and smaller unsatisfiable core generation.Comment: 21 page

Estudo sobre a produção de pasta kraft de eucalipto para novas aplicações

Most of the fluff pulp produced worldwide is used in the manufacture of absorbents, disposable diaper, intimate and non-woven products. Pre-requisites for fluff pulp are quite different from pulps produced for papermaking. Absorption capacity, absorbency rate, high specific volume (bulk), fibre length, curl and network strength are the most important properties of fluff pulp. Generally, fluff pulp is made from Bleached Softwood Kraft Pulp (BSKP) and Chemi-Thermo Mechanical Pulp (CTMP). However, the potential of Eucalyptus globulus bleached kraft pulp for such kind of applications is still uncertain. In this study, Bleached Eucalypt Kraft Pulp (BEKP) from E. globulus wood was evaluated for the fluff pulp applications and compared with properties of commercial fluff BSKP. A series of six industrial BEKPs produced from predominantly Eucalyptus globulus under variable process conditions were dry-defibrated on a pilot scale hammermill at 3500 rpm and the nonwoven air-laid fabrics evaluated for their specific volume, absorption capacity/absorption rate and the fibre network strength. The effect of non-defibrated fibre agglomerates (knots) on the former properties was evaluated. Processual variations in pulping and bleaching conditions revealed variability within 15% in the absorption capacity of fluff pulps and within 25% in the network strength of the air-laid formulations. These variations were attributed to changes in the chemical composition of BEKPs and fibre morphology. The importance of pulp bleaching sequence on the quality of BEKPs for fluff applications was highlighted. BEKPs having a high residual xylan content with a greater amount of uronic/hexenuronic moieties and coarser/deformed fibres revealed the best performance in fluff applications. The coarseness was considered a critical morphological parameter of the fibres, strongly affecting the porosity of air-laid formulations, which determined the absorption capacity and the network strength. The absorption capacity of fluffed BEKP was comparable to that of commercial softwood bleached softwood kraft pulp (BSKP), although the latter showed almost triple the network strength of air-laid formulations produced with BEKP. BSKP proved to be much more vulnerable to dry-defibration conditions than BEKP and suffered a pronounced cut of fibres, producing larger amounts of fines (dust) and stronger undesirable peeling and straightening of fibres. The same industrial Eucalyptus bleached kraft pulps (fluff pulps) were studied for the absorption properties employing dynamic water vapour sorption and contact angles measurements. The results showed that the accessibility of the fibre surface is related to the reduction of the contact angles, but, simultaneously, to the longer absorption time and less absorption capacity of the fibre network. Therefore, the absorption properties of the pulps are not necessarily directly related to their surface properties. Indeed, absorptivity is related to the surface chemical composition, fibre morphology, and fibre network structure. Thus, surface carboxylic groups promote total water uptake, resulting in better absorption capacity. Greater fibre coarseness and deformations (curl and kink) provide a less wettable surface, but a more porous network with higher specific volume, resulting in more absorbent air-laid formulations. Since multiple variables of the industrial process did not allow to unequivocally trace the relationships between the procedural conditions and the properties of the fluff cellulose, laboratory tests under controlled conditions were carried out to be better understand such relationships. Accordingly, a series of Eucalyptus globulus wood chips were cooked under the same conditions (160°C, 2h) using different active alkali charges (AA) of 13%, 15%, 17% and 18%. All pulps were further oxygen delignified (100°C, 1h) and bleached using the elemental chlorine free (ECF) and the totally chlorine free (TCF) sequences. Lab handsheets (approx. 600 g/m2) were prepared from the never dried bleached pulp and dry-defibrated in a pilot scale hammermill at different intensities (rpm) and analysed for the knots content, absorption capacity and the air-laid fibre network strength. Being dry-defibrated, pulps cooked at an increased AA revealed the reduction in knots and ECF pulps showed better defibration ability than TCF pulps. The fibre network strength was sensible to the conditions of pulping and bleaching and always increased with the increase in cooking AA. The network strength of TCF fluff pulps was from 20 to 70% greater than ECF fluff pulps. Regarding the absorption properties, BEKP fluff pulps showed good absorption capacity improved by the presence of carboxylic acid groups and the hemicelluloses removal. To enhance the absorption properties, network strength and defibration energy in fluff pulps, several chemical and physical modification were performed. For pulp modification, two commercial surfactant debonders and an antimicrobial agent (PHMB) were applied. The use of chemical additives slightly improved the water absorption capacity of pulps, being more pronounced with the application of PHMB, which increased the absorption capacity. Commercial surfactants did not promote much absorption capacity, but significantly reduced the knots contents in fluff pulps, acting essentially as debonders. These additives promoted an increase in the resistance of the fibre network and didn’t affect the morphology of cellulosic fibres. The physical modifications to promote the absorption properties were hyperbaric pressure and accelerated hornification process. Hyperbaric pressure improved not only the rate and absorption capacity of pulps, but also its specific volume and the fibre network strength. The laboratory hornified pulp showed a higher degree of hornification and a reduction in the absorption capacity than the industrially dried pulp, but the industrial hornified pulp (paper-grade) showed improvements in the absorption capacity when compared to the control pulp. The physical modifications to which the cellulose pulp was subjected improved dry defibrillation, decreasing its knot content. This reduction is more accentuated in hornified pulps than in pulps modified by hyperbaric pressure, since the removal of tightly bound water causes the fibres collapse and have less bonding capacity between the fibres. BEKPs can be considered a promising raw material for fluff applications, whose basic properties can be adjusted according to the needs by varying conditions in the pulping, bleaching and posterior treatments employing physical treatments and auxiliary chemical additives. This brings the BEKPs closer to the main properties of BSKPs..A maior parte de pasta fluff produzida mundialmente é utilizada na produção de absorventes, fraldas descartáveis, produtos íntimos e não-tecidos. Os pré requisitos para pasta fluff são bem diferentes das pastas para produção de pasta de papel. As propriedades mais importantes da pasta fluff são a capacidade e velocidade de absorção, elevado volume específico, comprimento de fibra, índice de encaracolamento e resistência de rede. Geralmente, a pasta fluff é produzida com pasta branqueada de madeira resinosa (BSKP) e pasta quimiotermomecânica (CTMP). No entanto, o potencial da madeira de Eucalyptus globulus para a produção deste tipo de pasta é incerto. Neste estudo, a pasta kraft branqueada de madeira de E. globulus (BEKP) foi avaliada para produção de pasta fluff e a pasta obtida foi comparada com as propriedades da pasta fluff (BSKP) comercial. Uma série de seis pastas industriais branqueadas predominantemente de eucalipto (BEKPs), produzidas sob condições extremas foram desfibradas, a seco, num moinho de martelos, em escala piloto, avaliadas as suas características básicas de pasta fluff, nomeadamente o seu volume específico, capacidade de absorção e velocidade de absorção e a estabilidade de rede. Foi avaliado o efeito de aglomerados de fibras não desfibrados (knots) presentes nas pastas. As variações processuais do cozimento e branqueamento revelaram uma variabilidade de 15% na capacidade de absorção das pastas fluff e cerca de 25% na estabilidade de rede. Estas variações são atribuídas às alterações na composição química e morfologia de fibras de BEKPs. Foi evidenciada a importância da sequência de branqueamento das pastas BEKPs para aplicações fluff. As BEKPs com elevado teor de xilana residual, maior quantidade de frações urónicas/hexenurónicas e fibras encaracoladas/deformadas revelaram uma melhor performance para aplicações fluff. O parâmetro coarseness foi considerado um parâmetro morfológico crítico das fibras, afetando fortemente a porosidade das formulações fluff, determinante para a capacidade de absorção e estabilidade de rede. A capacidade de absorção da pasta fluff BEKP, em comparação com a pasta comercial branqueada de fibra longa (BSKP), foi quase o dobro, embora a pasta comercial tenha apresentado cerca do triplo do resultado de estabilidade de rede determinado na formulação ao ar de pasta fluff. As pastas BSKP são mais vulneráveis às condições de desfibramento a seco em comparação com as pastas BEKP e as suas fibras sofreram um pronunciado corte, produzindo uma elevada quantidade de finos (dust) e um indesejável peeling e endireitamento de fibras. As mesmas pastas industriais kraft branqueadas de eucalipto (pastas fluff) foram estudadas para as propriedades de absorção aplicando a sorção dinâmica de vapor e medição de ângulos de contacto. Os resultados mostraram que a acessibilidade da superfície da fibra está relacionada com a redução de ângulos de contacto, mas simultaneamente ao maior tempo de absorção e menor capacidade de absorção da rede de fibra. Portanto, as propriedades de absorção das pastas não estão necessariamente relacionadas com as propriedades da superfície. De facto, a absortividade está relacionada com a composição química da superfície, morfologia da fibra e estrutura da rede de fibra. Deste modo, os grupos carboxílicos de superfície promovem a absorção total de água, resultando numa melhor capacidade de absorção. O maior coarseness e deformações da fibra (curl e kink) promovem uma superfície menos molhável, mas uma rede mais porosa, com maior volume específico, resultando em formulações mais absorventes. Tendo em consideração que as múltiplas variáveis do processo industrial não permitiram traçar de modo inequívoco as relações entre as condições processuais e as propriedades da pasta fluff, foram realizados diversos ensaios laboratoriais, em condições controladas, de forma a compreender estas relações. Deste modo, uma série de aparas de madeira ibérica E. globulus foram digeridas sob as mesmas condições (160°C, 2h), mas com diferentes cargas álcali ativo (AA) de 13%, 15%, 17% e 18%. As pastas cruas foram, posteriormente, deslenhificadas com oxigénio (100°C, 1h) e branqueadas com uma sequência de elemental chlorine free (ECF) e totally chlorine free (TCF). As folhas laboratoriais (com uma gramagem aprox. 600 g/m2) foram preparadas a partir da pasta branqueada, desfibradas a seco num moinho de martelos, a diferentes velocidades de rotação (rpm) e analisadas no teor em knots, capacidade de absorção e estabilidade de rede. Após desfibração a seco, as pastas digeridas com maior carga AA evidenciaram a redução de knots e as pastas ECF demonstraram melhor performance de desfibração em comparação com as pastas TCF. A estabilidade de rede de fibra é sensível às condições de cozimento e branqueamento e aumentam sempre com o aumento de AA. A estabilidade de rede das pastas TCF é superior em cerca de 20 a 70% em comparação com as pastas fluff ECF. As propriedades de absorção das pastas foram significativamente melhoradas pela presença dos ácidos carboxílicos e remoção de hemiceluloses. Com o objetivo de promover as propriedades de absorção, estabilidade de rede e energia de desfibração das pastas fluff foram estudadas modificações químicas e físicas. Para a modificação química foram aplicados dois surfactantes desligantes comerciais e um agente antimicrobiano (PHMB). O uso de aditivos químicos melhorou, ligeiramente, a capacidade de absorção de água das pastas,sendo mais acentuada com a aplicação do PHMB. Os surfactantes comerciais não influenciaram significativamente a capacidade de absorção, mas reduziram significativamente o teor de knots nas pastas fluff, atuando, essencialmente, como agentes desligantes no processo de desfibração a seco. Estes aditivos promoveram a estabilidade de rede e não afetaram a morfologia das fibras celulósicas. As modificações físicas avaliadas para a promoção das propriedades de absorção consistiram na pressão hiperbárica e o processo de hornificação acelerada. A pressão hiperbárica melhorou não apenas a velocidade e a capacidade de absorção das pastas, mas também o volume específico e a estabilidade de rede da fibra. A pasta hornificada laboratorialmente apresentou um maior grau de hornificação em comparação com a pasta acabada industrial, e uma redução na capacidade de absorção, contudo a pasta hornificada industrialmente (pasta acabada) apresentou melhor capacidade de absorção em comparação com a pasta de controlo (ensaio em branco). As modificações físicas a que as pastas foram submetidas facilitaram a desfibração a seco, diminuindo o teor em feixes de fibras (knots). Esta redução é mais acentuada nas pastas hornificadas do que nas pastas modificadas por pressão hiperbárica, uma vez que a remoção de água fortemente ligada provoca o colapso das fibras e tenham menor capacidade de ligação entre elas. As pastas de eucalipto BEKPs podem ser consideradas uma promissora matéria-prima para aplicações fluff, cujas propriedades básicas podem ser ajustadas de acordo com as necessidades, variando as condições dos estágios de cozimento, branqueamento e tratamentos posteriores através de modificações físicas e com aditivos químicos. Estas modificações aproximam as pastas BEKP das propriedades principais das pastas BSKP.Programa Doutoral em Engenharia Químic

Assessing the quality of transmission of lightpaths in multiband C+L networks through Gaussian noise models

In an optical network scenario, wavelength division-multiplexing (WDM) channels are constantly being added and dropped, leading to dynamic traffic variations in the lightpaths. In this work, the impact of the network traffic load and spectral occupancy on the quality of transmission, namely on the normalized nonlinear interference (NLI) power, power transfer due to stimulated Raman scattering (SRS) and optical signal-to-noise ratio (OSNR) of the lightpaths in a C+L multiband optical network is assessed using the recently proposed closed-form interchannel SRS Gaussian noise model (ISRS GN-model). We show that, due to the dynamic traffic behavior, the normalized NLI power can oscillate up to 2 dB in the highest frequency channels due to NLI variations when the tested channels have unequal spacing along the spectrum. For the optimum channel launch power and by increasing the network traffic load, the power transfer between the outer channels can increase up to 5.1 dB due to the SRS effect. With 201 WDM channels, high traffic load and for the optimum channel power, we obtained a maximum OSNR variation along the channel frequencies of only about 0.7 dB. A comparison between the OSNR predictions of the closed-form ISRS GN-model and a closed-form Gaussian noise (GN) model that does not take into account the SRS effect is also performed. In all results obtained, the maximum difference between the OSNR predictions of GN (without SRS) and ISRS GN models is below 0.7 dB at optimum OSNR and maximum C+L band occupancy. For channel launch powers higher than the optimum, the OSNR differences increase up to 3 dB.info:eu-repo/semantics/publishedVersio

On the use of thermal properties for characterizing dimension stones from Portugal

It has been usual practice to measure physical and mechanical properties of dimension stones; however, the same is not true for thermal properties, such as thermal conductivity, thermal diffusivity, specific heat capacity, and heat production which are particularly important when processes related with heating and cooling of buildings must be considered. Thermal conductivity, thermal diffusivity, and specific heat capacity are related with the way thermal energy is transmitted and accumulated in stones; heat production is related with the amount of radioactive elements on the rocks. Several rock samples from several quarries were collected in Mainland Portugal for measuring their thermal conductivities, thermal diffusivities, specific heat capacities, and heat productions. The rock set consists of granites, limestones, and marbles used in architecture and civil engineering. The results of the study indicate that the collected granites have thermal conductivities, thermal diffusivities, and specific heat capacity that vary from 2.98 ± 0.09 to 3.24 ± 0.21 W/m.K, 1.32 ± 0.03 to 1.55 ± 0.12 (x10-6) m2/s, 2.10 ± 0.04 to 2.26 ± 0.04 J/m3.K, respectively; the collected limestones have thermal conductivities, thermal diffusivities, and specific heat capacity that vary from 2.77 ± 0.02 to 3.07 ± 0.03 W/m.K, 1.26 ± 0.01 to 1.42 ± 0.03 (x10-6) m2/s, 2.16 ± 0.05 to 2.32 ± 0.04 J/m3.K, respectively. The average thermal conductivity, thermal diffusivity, and specific heat capacity for marbles is 2.90 ± 0.03 W/m.K, 1.31 ± 0.03 (x10-6) m2/s, 2.22 ± 0.07 J/m3.K. The average heat production per unit volume for the granites is 2.75 (0.25) mW/m3

Performance analysis of a graph coloring algorithm for wavelength assignment in dynamic optical networks

In the near future (5 to 10 years), dynamic optical networks will be crucial in global optical communications in order to respond to the fast growing of on-demand services. Routing and wavelength assignment (RWA) planning tools must be developed to effectively deal with the dynamic scenarios requirements. In this work, a simulation tool for RWA in dynamic optical networks was developed and wavelength assignment (WA) was implemented, through a recently proposed graph coloring algorithm, named Small-Buckets algorithm, that allows recolorings to occur. Several fiber based networks have been studied and it has been concluded that the Small-Buckets algorithm originates lower blocking probabilities than the ones obtained with the First fit algorithm. However, to reach this improved performance, the Small-Bucket algorithm requires a larger number of wavelengths and recolorings.info:eu-repo/semantics/acceptedVersio

Performance evaluation of direct-detection OFDM optical receivers with RF down-conversion

A new method based on the moment generating function is proposed to assess the performance of a direct-detection OFDM optical communication system with radio-frequency I/Q demodulation and its accuracy is validated by Monte Carlo simulation.info:eu-repo/semantics/acceptedVersio

Graph coloring heuristics for optical networks planning

This work focuses on the study of wavelength assignment algorithms based on Graph Coloring techniques. We analyze the performance of the Greedy heuristic, a well-known Graph Coloring heuristic, as well as the Degree of Saturation (DSATUR) and the Recursive Largest First (RLF) heuristics, for planning optical networks. These last two heuristics, to the best of our knowledge, have not yet been applied in the context of optical networks. Extensive simulations have been performed, using real network topologies under a static traffic scenario and we have concluded that the DSATUR and RLF heuristics can outperform the Greedy heuristic in network scenarios where there are several network clusters interconnected by only one or two links. In these cases, the RLF and DSATUR heuristics can provide less 9 and 5 wavelengths, respectively, than the Greedy heuristic, in networks with 34 nodes.info:eu-repo/semantics/acceptedVersio

Deep learning for BER prediction in optical connections impaired by inter-core crosstalk

Four-level pulse amplitude modulation (PAM4) signals transmission in short-haul intensity modulation-direct detection datacenters connections supported by homogeneous weakly-coupled multicore fibers is seen as a promising technology to meet the future challenge of providing enough bandwidth and achieve high data capacity in datacenter links. However, in multicore fibers, inter-core crosstalk (ICXT) limits significantly the performance of such short-reach connections by causing large bit error rate (BER) fluctuations. In this work, a convolutional neural network (CNN) is proposed for eye-pattern analysis and BER prediction in PAM4 inter-datacenter optical connections impaired by ICXT, with the aim of optical performance monitoring. The performance of the CNN is assessed by estimation of the root mean square error (RMSE) using a synthetic dataset created with Monte Carlo simulation. Considering PAM4 interdatacenter connections with one interfering core and for different skew-symbol rate products, extinction ratios and crosstalk levels, the obtained results show that the implemented CNN is able to predict the BER without surpassing a RMSE limit of 0.1.info:eu-repo/semantics/acceptedVersio

Impact of traffic load and spectral occupancy on Gaussian noise models performance for multiband networks

In a network scenario, wavelength division multiplexing channels are added and dropped leading to fluctuations on the network traffic loads along the optical path. In this work, a comparison between the optical signal-to-noise ratio (OSNR) predictions of the recently proposed closed-form generalized Gaussian noise (GGN) model and a closed-form Gaussian noise (GN) model that does not take into account the stimulated Raman scattering (SRS) is performed, for different network traffic loads and spectral occupancy over the entire C+L band. In all results obtained, the maximum difference between the OSNR predictions of GN (without SRS) and GGN models closed forms is below 0.7 dB at optimum OSNR and maximum C+L band occupancy, indicating that the GN-model can also be used in C+L band transmission. For channel launch powers higher than the optimum, the OSNR differences increase up to 3 dB, being the GN-model (without SRS) unsuitable to assess the network performance in such situations.info:eu-repo/semantics/acceptedVersio