Dissertations / Theses on the topic 'Salt attack'

The salt attack of Fired Clay Bricks (FCBs) causes surface damage that is aesthetically displeasing and eventually leads to structural damage. Methods for determining the resistances of FCBs to salt weathering have mainly tried to simulate the process by using accelerating aging tests. Most research in this area has concentrated on the types of salt that can cause damage and the damage that occurs during accelerated aging tests. This approach has lead to the use of accelerated aging tests as standard methods for determining resistance. Recently, it has been acknowledged that are not the most reliable way to determine salt attack resistance for all FCBs in all environments. Few researchers have examined FCBs with the aim of determining which material and mechanical properties make a FCB resistant to salt attack. The aim of this study was to identify the properties that were significant to the resistance of FCBs to salt attack. In doing so, this study aids in the development of a better test method to assess the resistance of FCBs to salt attack. The current Australian Standard accelerated aging test was used to measure the resistance of eight FCBs to salt attack using sodium sulfate and sodium chloride. The results of these tests were compared to the water absorption properties and the total porosity of FCBs. An empirical relationship was developed between the twenty-four-hour water absorption value and the number of cycles to failure from sodium sulfate tests. The volume of sodium chloride solution was found to be proportional to the total porosity of FCBs in this study. A phenomenological discussion of results led to a new mechanism being presented to explain the derivation of stress during salt crystallisation of anhydrous and hydratable salts. The mechanical properties of FCBs were measured using compression tests. FCBs were analysed as cellular materials to find that the elastic modules of FCBs was equivalent for extruded FCBs that had been fired a similar temperatures and time. Two samples were found to have significantly different elastic moduli of the solid microstructure. One of these samples was a pressed brick that was stiffer due to the extra bond that is obtained during sintering a closely packed structure. The other sample was an extruded brick that had more firing temperature and time compared with the other samples in this study. A non-destructive method was used to measure the indentation hardness and indentation stress-strain properties of FCBs. The indentation hardness of FCBs was found to be proportional to the uniaxial compression strength. In addition, the indentation hardness had a better linear correlation to the total porosity of FCBs except for those samples that had different elastic moduli of the solid microstructure. Fractography of exfoliated particles during salt cycle tests and compression tests showed there was a similar pattern of fracture during each failure. The results indicate there were inherent properties of a FCB that determines the size and shape of fractured particles during salt attack. The microstructural variables that determined the fracture properties of FCBs were shown to be important variables to include in future models that attempt to estimate the resistance of FCBs to salt attack.

There are still research gaps regarding the effects of key parameters such as water-to-cementitious materials ratio (w/cm), type of binder and pore structure characteristics on the response of concrete to special forms of sulfate attack: physical salt attack (PSA) and thaumasite sulfate attack (TSA). Hence, this study aims at developing an innovative type of concrete: nano-modified fly ash concrete, incorporating various dosages of nano-silica (NS) or nano-alumina (NA) and fly ash, and explores its efficiency in resisting various forms of sulfate attack.

Cette thèse, menée dans le cadre d'une Convention Industrielle de Formation par la Recherche (CIFRE) avec l'entreprise MENARD, est consacrée à l'étude de la durabilité d'un procédé particulier de renforcement de sol appelé Colonnes à Module Contrôlé (CMC). Cette application consiste en la mise en place d'un réseau d'inclusions verticales semi-rigides dans un sol afin d'améliorer les caractéristiques globales du terrain avant construction. Ces travaux font suite aux travaux de thèse de François Duplan (2011-2014) sur le développement de nouveaux composites cimentaires destinés à cette application. Dans ce but, il avait optimisé des compositions de mortiers incorporant des granulats spéciaux tels que des billes d'argile expansée ou des granulats en caoutchouc issus du broyage de pneus usagés. Les effets de l'introduction de ces granulats dans les composites ont été analysés aussi bien à l'état frais qu'à l'état durci et complètent les précédentes analyses de F. Duplan, notamment en termes d'indicateur de durabilité (perméabilité aux gaz, diffusion aux ions chlorures) et de comportement mécanique à long terme (retrait et fluage). A l'issue d'une analyse environnementale de l'application, trois mécanismes potentiels de dégradation ont été sélectionnés pour des investigations sur la durabilité des CMC : l'attaque acide, l'attaque sulfatique externe et la dégradation par cristallisation de sels. La réalisation d'essais accélérés en laboratoire a permis de mettre en évidence la pertinence du ciment CEM III/C, utilisé actuellement par MENARD, dans la majorité des cas. La faible teneur en C3A de ce liant permet en effet de limiter la production d'éléments expansifs dans le cas d'une attaque sulfatique externe et sa proportion limitée en hydrates du clinker (en particulier en portlandite) ainsi que le faible rapport C/S des C-S-H assurent une meilleure tenue aux attaques acides. La dégradation par remontée capillaire et cristallisation de sels dépendant avant tout des caractéristiques du réseau poreux et des conditions d'évaporation et beaucoup moins du type de ciment, l'utilisation du ciment CEM III/C présente moins d'intérêt. L'incorporation de granulats en caoutchouc ou de billes d'argile expansée dans les composites ne modifie qu'à la marge leur tenue aux mécanismes de dégradations testés. La majorité des phénomènes de dégradation de l'application étant liée à la pénétration d'agents agressifs au cœur des composites cimentaires, la prédiction des propriétés diffusives du matériau est essentielle dans l'estimation des risques encourus par l'application. Un nouveau modèle prédictif est proposé et comporte deux échelles d'homogénéisation : la première au niveau de la pâte de ciment et la deuxième au niveau du mortier. Les résultats obtenus par ce modèle sont fidèles aux résultats expérimentaux avec des erreurs relatives inférieures à 15%. L'estimation du coefficient de diffusion est globalement plus précise pour les composites incorporant des billes d'argile expansée que pour ceux incorporant des granulats en caoutchouc, une conséquence de la forme sphérique de ces billes mieux en accord avec les hypothèses du modèle mis en œuvre
This CIFRE PhD-thesis carried out within the framework of Convention Industrielle de Formation par la REcherche (CIFRE) with the company MENARD, focuses on the durability of a specific soil-reinforcement system called Controlled Modulus Columns (CMC) which consists in a network of semi-rigid vertical inclusions cast into the ground in order to enhance its global characteristics before building. This study comes after the PhD work conducted by François Duplan (2011-2014) on the design of new cementitious composites intended for the CMC application and incorporating innovative aggregates like expanded clay grains or rubber aggregates obtained by grinding end-of-life tyres. The effects of addition of such aggregates into the composites have been studied both at fresh and hardened states and complete Duplan previous findings in particular with regards durability indicators (gas permeability, chloride diffusion) and mechanical long-term behaviour (creep and shrinkage). Three potential degradation mechanisms have been selected for the CMC system after an environmental analysis: acid attack, external sulphate attack and salt crystallisation. Laboratory accelerated tests highlighted that CEM III/C cement, actually used by MENARD, is suitable in most of the cases. The low C3A content of this binder reduces the production of expansive products in the case of external sulphate attack and its limited clinker hydrates proportions (in particular in portlandite), along with the low C/S ratio of the C-S-H enhance the resistance to acid attack. Salt crystallisation through capillary rise primarily depends on the porous network characteristics and less on the cement ones, meaning that CEM III/C cement is less relevant in that specific case. Based on the tested degradation mechanisms, incorporating rubber aggregates or expended clay ones into the cementitious composites does not significantly affect their durability. Most of the application degradation phenomenon being linked to the ingress of aggressive agents into the composites; the prediction of their diffusive properties is crucial to assess the risks involved for the application. A new predictive model is proposed with a dual homogenisation process: the first one at the cement paste level and the second one on the mortar level. Predicted results are in agreement with ones from experimental tests with a relative error less than 15%. Diffusion coefficient estimates are globally better for composites that contain expended clay aggregates than those incorporating rubber aggregates due to spherical shape of the first in accordance with the model hypotheses

El objetivo de esta tesis es discutir los resultados de dos ensayos clínicos (Ensayo 1 e Ensayo 2) desarrollados para que pudiéramos diseñar con mejor calidad metodológica un protocolo para evaluar el papel de la acupuntura en la prevención de las crises de migraña. Posteriormente, un ensayo clínico fase III fue ejecutado haciendo uso de toda esa bases de conocimiento alcanzado después de esos ensayos clínicos referidos. En cada ensayo, los pacientes con migraña han sido asignados de manera aleatoria a dos grupos, el de acupuntura real y otro de acupuntura sham. Dos abordajes terapéuticas con acupuntura real han sido empleadas. En el primero ensayo, ha sido hecho un tratamiento individualizado. En el otro ha sido aplicado un tratamiento semi-estándar. Todos los enfermos han recibido 16 sesiones de acupuntura en 12 semanas. El seguimiento ha sido hecho por 6 meses después del término del tratamiento. Los “primary endpoints” eran: el porcentaje de pacientes con reducción ≥40% (ensayo 1) y ≥50% in la frecuencia de las crisis de migraña (ensayo 1 y 2) y el número de días con migraña (ensayo 2). Diarios de cefalea han sido adoptados para la recogida continua de datos. Todos los diarios han sido comparados con el diario del periodo “baseline”. Mejora con diferencia estadística significante apareció tan solo en el primero estudio. El grupo de acupuntura comparado al sham señalo mejora en el segundo mes de tratamiento cuando ha sido evaluado el porcentaje de pacientes con reducción ≥50% en el número de crisis de migraña (P=0.021). Hubo diferencias estadísticas también en dos variables secundarias: reducción en el número de días con migraña en el segundo mes de tratamiento (P=0.007) y el porcentaje de pacientes con reducción ≥40% de la frecuencia de crisis de migraña disminuyó en el primero (P=0.044) y segundo (P=0.004) mes de tratamiento. El tratamiento con acupuntura individualizado adoptado en el primero estudio parece ser un abordaje más adecuado cuando el objetivo sea el de evaluar cuál sería el efecto de la acupuntura para la profilaxis de la migraña.
The aim of this thesis is to discuss the results reached through two trials (Trial 1 and Trial 2) developed to reach a best methodological design to evaluate the role of acupuncture to prevent migraine attacks. Phase III trial was done using the knowledge background obtained after these referred trials. Subjects with migraine were randomized to the real or sham acupuncture groups in two different trials. Distinctive treatment approaches were tested as being real acupuncture. In the first one, the “individualized” treatment was applied. The “semi-standardized” acupuncture treatment was evaluated in the second trial. All patients were treated with 16 acupuncture sessions during twelve weeks. Post-treatment follow-ups were done during 6-months. The primary endpoints adopted were the percentage of patients with reduction ≥40% (Trial 1) and ≥50% in migraine attacks frequency (Trials 1 and 2) and the total of days with migraine (Trial 2). Headache diaries were used to obtain data in the baseline period and the full time of the study. Data from all diaries were compared with the baseline period. Improvements with statistical significant differences appeared only in Trial 1. Real acupuncture group was superior to sham group in the second month of the treatment, when the percentage of patients with ≥50% reduction in migraine attack frequency was evaluated (P=0.021). The reported differences appeared also in two secondary endpoints: number of days with migraine per month (P=0.007) in the second month of the treatment and in the first (P=0.044) and second (P=0.004) months of the treatment when the percentage of patients with a ≥40% reduction in migraine attack frequency was measured. The “individualized” treatment adopted in Trial 1 seemed to be the best approach to test the acupuncture effects in trials for migraine prophylaxis.

I denna uppsats analyseras tio stycken förstasidor av nyhetstidningarna Dagens Nyheter samt Aftonbladet med syftet att undersöka hur och med vilka visuella uttryck terrorattacken på Drottninggatan 2017 visualiserades. Resultatet av en semiotisk analys av nyhetstidningarna Dagens Nyheter samt Aftonbladets förstasidors visualisering av terrorattacken på Drottninggatan 2017 visar på att journalisterna som rapporterade använde sig gärna av argument som spelade på läsarnas känslor. Stora bilder som gärna väcker känslor präglade förstasidorna dagen efter terrordådet. Bilderna i sig innehöll visuella element som visade på att de förhöll sig till en retorisk strategi vid rapporteringen. Tidigare studier har främst fokuserat på hur nyhetsmedia har ramat in händelsen, med hjälp av den semiotiska analysen kan djupare mening och förståelse nås för hur och på vilket sätt nyhetsmedia visualiserade terrorattacken.
In this essay, 10 front pages of the newspapers Dagens Nyheter and Aftonbladet are analysed with the aim of examining how and with what visual expression the terrorist attack on Drottninggatan 2017 was visualised. The results of a semiotic analysis of the newspapers Dagens Nyheter and Aftonbladet's front page visualisation of the terrorist attack on Drottninggatan 2017 show that the journalists who reported used arguments that alluding to readers' feelings. Large images that like to evoke emotions marked the front pages the day after the terrorist attack. The images themselves contained visual elements that showed that they related to a rhetorical strategy when reporting. Previous studies have mainly focused on how the news media has framed the incident, with the help of the semiotic analysis, a deeper meaning and understanding can be reached for how and in what way the news media visualised the terrorist attack.

Cette thèse s'intéresse à la sécurité des programmes embarqués face aux attaques par injection de fautes. La prolifération des composants embarqués et la simplicité de mise en œuvre des attaques rendent impérieuse l'élaboration de contre-mesures.Un modèle de fautes par l'expérimentation basé sur des attaques par impulsion électromagnétique a été élaboré. Les résultats expérimentaux ont montré que les fautes réalisées étaient dues à la corruption des transferts sur les bus entre la mémoire Flash et le pipeline du processeur. Ces fautes permettent de réaliser des remplacements ou des saut d'instructions ainsi que des modifications de données chargées depuis la mémoire Flash. Le remplacement d'une instruction par une autre bien spécifique est très difficile à contrôler ; par contre, le saut d'une instruction ciblée a été observé fréquemment, est plus facilement réalisable, et permet de nombreuses attaques simples. Une contre-mesure empêchant ces attaques par saut d'instruction, en remplaçant chaque instruction par une séquence d'instructions, a été construite et vérifiée formellement à l'aide d'outils de model-checking. Cette contre-mesure ne protège cependant pas les chargements de données depuis la mémoire Flash. Elle peut néanmoins être combinée avec une autre contre-mesure au niveau assembleur qui réalise une détection de fautes. Plusieurs expérimentations de ces contre-mesures ont été réalisées, sur des instructions isolées et sur des codes complexes issus d'une implémentation de FreeRTOS. La contre-mesure proposée se révèle être un très bon complément pour cette contre-mesure de détection et permet d'en corriger certains défauts
This thesis focuses on the security of embedded programs against fault injection attacks. Due to the spreadings of embedded systems in our common life, development of countermeasures is important.First, a fault model based on practical experiments with a pulsed electromagnetic fault injection technique has been built. The experimental results show that the injected faults were due to the corruption of the bus transfers between the Flash memory and the processor’s pipeline. Such faults enable to perform instruction replacements, instruction skips or to corrupt some data transfers from the Flash memory.Although replacing an instruction with another very specific one is very difficult to control, skipping an instruction seems much easier to perform in practice and has been observed very frequently. Furthermore many simple attacks can carried out with an instruction skip. A countermeasure that prevents such instruction skip attacks has been designed and formally verified with model-checking tool. The countermeasure replaces each instruction by a sequence of instructions. However, this countermeasure does not protect the data loads from the Flash memory. To do this, it can be combined with another assembly-level countermeasure that performs a fault detection. A first experimental test of these two countermeasures has been achieved, both on isolated instructions and complex codes from a FreeRTOS implementation. The proposed countermeasure appears to be a good complement for this detection countermeasure and allows to correct some of its flaws

碩士
國立高雄第一科技大學
營建工程所
96
This research aims at carrying out air-borne salt investigation and realizing the relationship between climate factors and air-borne salt. Within the research, 12 sites of collecting air-borne salt have been set up between Chiagi and Kaohsiung. What have been found that there are obvious dependency between humidity, wind speed, sea wind rate, precipitation and air-borne salt as well as that there seems to be a certain degree of influence on airborne salt caused by the distance to the seashore. After collecting relevant climate and airborne salt data, regression analysis is executed on collected data for finding out some empirical formula related to predicting airborne salt. Then, by applying the technique of Monte-Carlo Simulation (MCS) on Fick’s second diffusion law with the consideration of stochastic behavior of cementitious material as well as the microclimate around the concrete structures like temperature, air-borne salt, etc., one proposal for developing the performance-based design of anticorrosion of RC structures under air-borne salt attack is considered. Through the examples illustrated in this paper, the availability of the proposed performance-based design method can be verified even with different mixing proportion and mixing material for the required service life under various air-borne salt attack environment. Moreover, because considering the convenience and availability of indoor rapid chlorine migration test, this research adopts the method proposed in 「anticorrosion technical specification for expressway concrete structure JTG/T B07-01-2006[12]」 - Rapid Chloride Migration test ( abbreviated as RCM) to determine diffusion coefficient of chloride within concrete. And through comparison of RCM result with other method, the fitness of RCM result for result of natural exposed structure is discussed. What have been found is that the result of RCM indicates its non-steady state of migration, similar to the natural migration mechanism of chlorine ion within concrete structure. Besides, due to the shorter test period of RCM, RCM can be regarded as a kind of rapid chloride migration test in the laboratory with practicability.

碩士
國立交通大學
資訊管理研究所
106
Today internet becomes very scalable and sometimes difficult to manage. However, to the best of our knowledge, wireless communication systems are recognizing as less secure and exposed to numerous attacks. The usage of Wireless Sensor Networks(WSNs) in different fields is possible nowadays due to the ease of their deployment and the reduction of their cost. Wireless Sensor Networks are growing considerably and they are useful to our daily life. Nevertheless, we need to provide a high security to the WSNs because of the sensitivity that the sensor nodes carry out over the network. This study aims to develop an efficient approach to detect the Sybil attack, one of the threatening attack within the WSNs. Most of the researchers on Sybil attack detection used the nodes positions to detect the counterfeits nodes within the network. Therefore, the most used method is the Received Signal Strength (RSSI). It consists to record the observations about the nodes related to their location information. Unfortunately, this method shows its limit when the nodes within the Wireless Sensor Network(WSN) are not fixed. The second weakness of this method is the power consumption, which is the main issue in WSN. This paper proposed an algorithm using IPv6, MAC address and salt number to prevent the Sybil attack within the WSN. The performances analysis show that our approach has better performance on efficiency and effectiveness.

This thesis is unique in that it investigated two completely different forms of concrete deterioration: physical sulfate attack and the alkali-silica reaction (ASR). Research was undertaken to better understand physical sulfate attack in order to provide much needed guidance on how to prevent durable this form of deterioration. A testing regime was designed to evaluate and analyze different concrete mixtures with varying water to cementitious material ratios (w/cm), cement types (Type I and V), and use of supplementary cementing materials (SCMs) in accelerated laboratory exposure and outdoor exposure testing. The accelerated laboratory testing evaluated the performance of concrete cylinder segments fully submerged in 30% (by mass of solution) sodium sulfate solution exposed to a temperature and humidity cycle that would promote cycles of alternative conversion between anhydrous sodium sulfate (thenardite) and decahydrate sodium sulfate (mirabilite). In the outdoor exposure site, two different sized concrete cylinders per mixture proportion were partially submerged in 5% (33,000 ppm) sodium sulfate solution and exposed to alternative wetting and drying conditions, along with, temperature fluctuations that would promote conversion between thenardite (Na2SO4) and mirabilite (Na2SO4∙10H2O). With regard to ASR test methods, it has been shown with past research that it is not possible to evaluate “job mixtures” or determine alkali thresholds using ASTM C 1293 (Concrete Prism Test) with evaluating aggregates and concrete mixture proportions for the susceptibility of ASR when testing job mixtures. The most commonly cited issue with the concrete prism test is excessive leaching of alkalis during the course of the test, which may not be a major issue when using the standard, high-alkali concrete mixtures as per ASTM C 1293 but is clearly an issue when testing lower-alkali concrete mixtures. For low-alkali mixtures, alkali leaching can reduce the internal alkali content below the threshold that triggers expansion for a given aggregate. A comprehensive study was initiated that evaluated various modifications to ASTM C 1293, with the intention of developing a testing regime better suited to testing “job mixes” and/or low-alkali concrete mixtures.
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A comprehensive study was conducted on the effects of de-icer and anti-icer chemicals on cement-based materials. Portland cement mortars and concretes were exposed to over 16 chloride-based and non-chloride-based generic and commercial products and changes in cement-based material properties were measured. Deleterious chemical actions of several types of these products on cement-based materials were observed, departing from the well-known position that attributes the concrete damage from such salts mainly to physical actions under freezing and thawing exposure. Independent of freezing and thawing exposure, mortars and concretes exposed to concentrated calcium chloride and magnesium chloride solutions were found to undergo severe deterioration whereas those exposed to sodium chloride did not. The mechanisms of deterioration are complex with factors such as concentration, temperature, and availability of calcium hydroxide playing important roles. It was found that the formation of calcium oxychloride of the form 3Ca(OH)2.CaCl2.12H2O, and the 3- and 5-form magnesium oxychloride, 3Mg(OH)2.MgCl2.8H2O and 5Mg(OH)2.MgCl2.8H2O, were the main causes for the severe deterioration, and to a lesser extent brucite, gypsum, and magnesium silicate hydrate (M-S-H). The instability of these oxychloride compounds when subjected to conditions normally encountered in sample preparation is suggested as the reason why field investigations have failed to relate distressed concrete to chemical attack by such de-icer and anti-icer chemicals. Concentrated solutions of calcium magnesium acetate were also found to be harmful to cement-based materials by dissolution of calcium hydroxide and formation of calcium acetate hydrate, whereas low concentrated solutions tended to cause slow deterioration by magnesium attack forming brucite, gypsum, and M-S-H. Potassium acetate chemicals did not cause significant deterioration in mortars when these products were diluted (25% by mass), but undiluted products (50% by mass) caused considerable distress in concrete specimens. The combined effect of chemical attack impairing concrete mechanical properties and subsequent salt scaling damage was proposed as the most likely mechanisms of field deterioration.

For repairing concrete transportation infrastructure, such as pavements and bridges, much importance is placed on early-age strength gain as this has a major impact on scheduling and opening to traffic. However, the long-term performance and durability of such repair materials are often not satisfactory, thus resulting in future repairs. This research project focuses on the evaluation of the durability of various rapid-setting cementitious materials. The binders studied in this project include calcium aluminate cement (CAC), calcium sulfoaluminate cement (CSA), Type III portland cement, alkali-activated fly ash (AAFA) , and various prepackaged concrete materials. In addition, selected CAC and CSA mixtures were further modified with the use of a styrene-butadiene latex. The durability aspects studied include freezing-and-thawing damage and the implications of air entrainment in these systems, alkali-silica reaction, sulfate attack, and permeability of the concrete matrix and potential corrosion.
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Recent denial of service attacks are mounted by professionalsusing Botnets of tens of thousands of compromisedmachines. To circumvent detection, attackers areincreasingly moving away from pure bandwidth oods toattacks that mimic the Web browsing behavior of a largenumber of clients, and target expensive higher-layer resourcessuch as CPU, database and disk bandwidth. Theresulting attacks are hard to defend against using standardtechniques as the malicious requests differ from thelegitimate ones in intent but not in content.We present the design and implementation of Kill-Bots, a kernel extension to protect Web servers againstDDoS attacks that masquerade as ash crowds. Kill-Botsprovides authentication using graphical tests but is differentfrom other systems that use graphical tests. First,instead of authenticating clients based on whether theysolve the graphical test, Kill-Bots uses the test to quicklyidentify the IP addresses of the attack machines. Thisallows it to block the malicious requests while allowingaccess to legitimate users who are unable or unwillingto solve graphical tests. Second, Kill-Bots sends a testand checks the client's answer without allowing unauthenticatedclients access to sockets, TCBs, worker processes,etc. This protects the authentication mechanismfrom being DDoSed. Third, Kill-Bots combines authenticationwith admission control. As a result, it improvesperformance, regardless of whether the server overloadis caused by DDoS or a true Flash Crowd. We have implementedKill-Bots in the Linux kernel and evaluated itin the wide-area Internet using PlanetLab.

Mestrado em Ciências da Fisioterapia
O objetivo deste estudo foi caracterizar os parâmetros de esforço de uma sessão de Body Attack™ (BA™) utilizando as opções de baixo impacto e compará-la com os valores de referência na bibliografia para uma sessão de BA™ de alto impacto e as recomendações do American College of Sports Medicine (ACSM). Participaram neste estudo 10 indivíduos saudáveis, 2 do género feminino e 8 do género masculino. Cada sujeito realizou uma prova de esforço máxima com análise de gases e posteriormente uma sessão de BA™ com opções de baixo impacto. Nesta sessão verificou-se que a frequência cardíaca (FC) média atingida foi de 110,8 bat/min (±23,6 bat/min) que corresponde a 63,8% da FC máxima (±11%) e o dispêndio energético total (DE) foi de 469,4 kcal (±170,8 kcal). Dos 60 minutos de duração média da sessão, os indivíduos estiveram cerca de 27,2 minutos a uma intensidade moderada a vigorosa. Verificou-se que o DE total (664,2±108,7 kcal) e a percentagem da FC máxima (73,2±9,7%) é significativamente diferente entre uma sessão de BA™ de baixo impacto e outra de alto impacto. Conclui-se assim que sessões de BA™ de baixo impacto têm intensidade e DE inferior a sessões de BA™ de alto impacto ambas cumprindo as recomendações do ACSM.

The practice of spamming (sending unsolicited electronic communications) has been dubbed “the scourge of the 21st century” affecting different stakeholders. This practice is also credited for not only disrupting electronic communications but also, it overloads electronic systems and creates unnecessary costs for those affected than the ones responsible for sending such communications. In trying to address this issue nations have implemented anti-spam laws to combat the scourge. South Africa not lagging behind, has put in place anti-spam provisions to deal with the scourge. The anti-spam provisions are scattered in pieces of legislation dealing with diverse issues including: consumer protection; direct marketing; credit laws; and electronic transactions and communications. In addition to these provisions, an Amendment Bill to one of these laws and two Bills covering cybercrimes and cyber-security issues have been published. In this thesis, a question is asked on whether the current fragmented anti-spam provisions are adequate in protecting consumers. Whether the overlaps between these pieces of legislation are competent to deal with the ever increasing threats on electronic communications at large. Finally, the question as to whether a multi-faceted approach, which includes a Model Law on spam would be a suitable starting point setting out requirements for the sending of unsolicited electronic communications can be sufficient in protecting consumers. And as spam is not only a national but also a global problem, South Africa needs to look at the option of entering into mutual agreements with other countries and organisations in order to combat spam at a global level.
Mercantile Law
LL. D.