Evaluation of Cyclic Deformation Behavior of Laser-welded Shape Memory NiTi Alloys at Different Working Temperatures

Post-weld heat-treatment (PWHT) has been established as one of the cost-effective ways to improve the functional properties, namely shape memory and super-elastic effects (SME and SE), of laser-welded NiTi alloys. However, the functional performance of the laser-welded joint at different working temperatures has not been explored yet. The purpose of this study is to investigate the effect of different working temperatures on the functional properties of the laser-welded NiTi alloys before and after PWHT by applying cyclic deformation tests. Two laser-welded samples: as-welded and heat-treated sample (after PWHT at 350 oC or 623 K) were tested in this work at room temperature, 50 oC (or 323 K) and 75 oC (or 348 K) respectively. The samples were cyclically loaded and unloaded for 10 cycles up to 4 % strain. The critical stress to induce the martensitic transformation and the residual strain after the cyclic tests were recorded. The results indicate that the heat-treated sample exhibited better functional properties than the as-welded sample at room temperature and 50 oC (or 323 K). However, both the as-welded and heat-treated samples failed in the cyclic tests at 75 oC (or 348 K). These findings are important to determine the feasible working temperature range for the laser-welded NiTi components to exhibit desirable functional properties in engineering applications involving cyclic loading.

Unloading or not unloading? Sheep welfare implication of rest stop at control post after a 29h transport

In Europe, maximum journey time for transported sheep is set at 29. h (EC Regulation 1/2005), after which animals must be unloaded, fed and watered in control posts stopping for 24. h, as all other species, before continuing their journey. The industry considers these resting times too general, not taking into account the peculiar differences between species or age classes. Also, loading and unloading have been reported to be detrimental for the animals. Therefore, the industry pushes to reduce the times at control post and avoid unloading the animals from the truck. Since there is little information concerning the effect of resting in a stationary truck after long journeys, the present study aims to evaluate the effect of an 8. h rest stop on the truck for transported ewes compared to being unloaded for resting in a control post for the same amount of time, considering physiological and behavioural measures. Two groups of ewes were transported for 29. h, after which one was unloaded and housed in a pen (P) at the control post while the other was left inside the truck (T). After 8. h stop, a further 6. h travel was headed to the farm of origin. A third group (C) stayed at the farm as control. During the stop, standing, resting, moving and eating behaviour of all groups was recorded. Blood parameters, salivary and faecal cortisol were assessed at different stages. The behaviour of P animals during the resting period was more similar to C than to T ones, where feeding and lying behaviours were restricted by the limited space allowance on the truck. After returning to the farm of origin, both T and P animals showed different parameters' levels as compared to C. P ewes showed a mean loss weight of 2. kg not recorded in group T and showed higher signs of muscular damage compared to C group. It was concluded that, with so short resting times as 8. h, there is no clear advantages in terms of animal welfare for avoiding the unloading and loading of the animals in the control post after long journeys.

Heat Activated Prestressing of Shape Memory Alloys for Active Confinement of Concrete Sections

This paper presents the results from the experimental investigation on heat activated prestressing of Shape Memory Alloy (SMA) wires for active confinement of concrete sections. Active confinement of concrete is found to be much more effective than passive confinement which becomes effective only when the concrete starts to dilate. Active confinement achieved using conventional prestressing techniques often faces many obstacles due to practical limitations. A class of smart materials that has recently drawn attention in civil engineering is the super elastic SMA which has the ability to undergo reversible hysteretic shape change known as the shape memory effect. The shape memory effect of SMAs can be utilized to develop a convenient prestressing technique for active confinement of concrete sections.
In this study a series of experimental tests are conducted to study Heat Activated Prestress (HAP) in SMAs. Three different types of tests are conducted with different loading protocol to determine parameters such as HAP, residual strain after heating and range of strain that can be used for effective active confinement after HAP. Test results show a maximum HAP of about 500 MPa can be achieved after heating and approximately 450MPa is retained at 25oC in specimens pre-strained by 6%. A substantial amount of strain recovery upon unloading and after heating the SMA wires is recorded. About 2.5% elastic strain recovery upon unloading from 6% strain level is observed. In the specimen pre-strained by 6%, a total of 4% strain is recovered when unloaded after heating. A strain range of 3% is found available for effective confinement after HAP. Test results demonstrate that SMAs have unique features that can be intelligently employed in many civil engineering applications including active confinement of concrete sections.

Locust bean gum-based microparticles for pulmonary delivery of antibiotics

Dissertação de Mestrado, Ciências Biomédicas, Departamento de Ciências Biomédicas e Medicina, Universidade do Algarve, 2016

Ground reaction forces and plantar pressure distribution during occasional loaded gait

This study compared the ground reaction forces (GRF) and plantar pressures between unloaded and occasional loaded gait. The GRF and plantar pressures of 60 participants were recorded during unloaded gait and occasional loaded gait (wearing a backpack that raised their body mass index to 30); this load criterion was adopted because is considered potentially harmful in permanent loaded gait (obese people). The results indicate an overall increase (absolute values) of GRF and plantar pressures during occasional loaded gait (p < 0.05); also, higher normalized (by total weight) values in the medial midfoot and toes, and lower values in the lateral rearfoot region were observed. During loaded gait the magnitude of the vertical GRF (impact and thrust maximum) decreased and the shear forces increased more than did the proportion of the load (normalized values). These data suggest a different pattern of GRF and plantar pressure distribution during occasional loaded compared to unloaded gait.

Projecto de execução do centro comercial Mercado da Praia: Cidade da Praia: Cabo Verde

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Civil

The influence of gait cadence on the ground reaction forces and plantar pressures during load carriage of young adults

Biomechanical gait parameters—ground reaction forces (GRFs) and plantar pressures—during load carriage of young adults were compared at a low gait cadence and a high gait cadence. Differences between load carriage and normal walking during both gait cadences were also assessed. A force plate and an in-shoe plantar pressure system were used to assess 60 adults while they were walking either normally (unloaded condition) or wearing a backpack (loaded condition) at low (70 steps per minute) and high gait cadences (120 steps per minute). GRF and plantar pressure peaks were scaled to body weight (or body weight plus backpack weight). With medium to high effect sizes we found greater anterior-posterior and vertical GRFs and greater plantar pressure peaks in the rearfoot, forefoot and hallux when the participants walked carrying a backpack at high gait cadences compared to walking at low gait cadences. Differences between loaded and unloaded conditions in both gait cadences were also observed.

Transfer of ultrasmall iron oxide nanoparticles from human brain-derived endothelial cells to human glioblastoma cells.

Nanoparticles (NPs) are being used or explored for the development of biomedical applications in diagnosis and therapy, including imaging and drug delivery. Therefore, reliable tools are needed to study the behavior of NPs in biological environment, in particular the transport of NPs across biological barriers, including the blood-brain tumor barrier (BBTB), a challenging question. Previous studies have addressed the translocation of NPs of various compositions across cell layers, mostly using only one type of cells. Using a coculture model of the human BBTB, consisting in human cerebral endothelial cells preloaded with ultrasmall superparamagnetic iron oxide nanoparticles (USPIO NPs) and unloaded human glioblastoma cells grown on each side of newly developed ultrathin permeable silicon nitride supports as a model of the human BBTB, we demonstrate for the first time the transfer of USPIO NPs from human brain-derived endothelial cells to glioblastoma cells. The reduced thickness of the permeable mechanical support compares better than commercially available polymeric supports to the thickness of the basement membrane of the cerebral vascular system. These results are the first report supporting the possibility that USPIO NPs could be directly transferred from endothelial cells to glioblastoma cells across a BBTB. Thus, the use of such ultrathin porous supports provides a new in vitro approach to study the delivery of nanotherapeutics to brain cancers. Our results also suggest a novel possibility for nanoparticles to deliver therapeutics to the brain using endothelial to neural cells transfer.

Astringency and other oral sensations : biological sources of individual variation and association with food and beverage behaviour

Orosensory perception strongly influences liking and consumption of foods and beverages. This thesis examines the influence of biological sources of individual variation on the perception of prototypical orosensory stimuli, food liking, self-reported alcohol liking and consumption, and indices of health. Two orosensory indices were examined: propylthiouracil (PROP) responsiveness, a genetically-mediated index of individual variation associated with enhanced responsiveness to orosensory stimuli often expressed as PROP taster status (PTS); and thermal taster status (TTS), a recently reported index of orosensory responsiveness. Taster status in PTS and/or TTS confers greater responsiveness to most orosensory stimuli. Gender, age, ethnicity, and fungiform papillae (FP) density were not associated with orosensory responsiveness to tastants, an astringent, and a flavour. Unlike PROP responsiveness, FP density was not associated with TTS. Both PROP responsiveness and TTS were associated with increased responsiveness to orosensory stimuli, including temperature and astringency. For PROP, this association did not hold when stimuli were presented at cold or warm temperatures, which are ecologically valid since most foods and beverages are not consumed at ambient temperature. Thermal tasters (TTs), who perceive 'phantom' taste sensations with lingual thermal stimulation, were more responsive to stimuli at both temperatures than thermal non-tasters (TnTs). While PTS, TIS, and gender affected self-reported liking and consumption of some alcoholic beverages, gender associated with the greatest number of beverage types and consumption parameters, with males generally liking and consuming alcoholic beverages more than females. Age and gender were the best predictors of alcoholic beverageAiking and consumption. As expected, .. liking of bitter and fatty foods and cream was inversely related to PROP responsiveness. TTS did not associate with body mass index or waist circumference, and contrary to previous studies, neither did PROP responsiveness. Taken together, TnTs' greater liking of cooked fruits and vegetables and high alcohol, and astringent alcoholic beverages than TTs suggests differences between TTS groups may be driven by perceived temperature and texture. Neither an interaction between PTS and TTS nor a TTS effect on PROP responsiveness was observed, suggesting these two indices of individual variation exert their influences on orosensory perception independently.

High Permittivity and Low Ceramics in the Bao-SrO-Nb2O5 System

A new group of compounds with composition (Ba5-xSrx) Nb4015, having high permittivity and low loss have been prepared and characterized in the microwave frequency region . X-ray diffraction studies showed that monophase compound existed for all values of x from 0 to 5. Microwave dielectric properties such as and c f showed smooth variation with x , while the unloaded quality factor (Qu) showed remarkable improvement with x

Tailoring the Microwave Dielectric Properties of GdTiNb 1 _-xTa,O6 and Sm 1 _X Y,TiTa06 Ceramics

Microwave dielectric ceramics based on GdTiNb,-,.Ta,O6 and Sml _.,Y,TiTa06 have been prepared by conventional solid state method . The GdTiTaO6 and SmTiTaO6 have aeschenite structure with positive rr and GdTiNbO6 and YTiTaO6 have euxenite structure with negative rr. The rr of the ceramics has been tuned by preparing solid solution phases between the aeschynites and euxenites for a possible zero rr material . It is observed that GdTiNbt_YTa.,O6 undergoes a phase transition from aeschynite to euxenite when x=0.75 and in Sml-,YxTiTa06 for x= 0.73. The microwave dielectric properties change abruptly near the transition region . The rr value approaches zero near the phase transition region while the samples have poor sinterability and poor quality factor . The unloaded quality factor, dielectric constant and the sign of rr of the solid solution phases are found to depend on the average ionic radius of the rare earth ion in RE ,-5RE',TiTaO6. The boundary of the euxenite-aeschynite phase transition occurs at an average ( RE) ionic radius of 0.915 A in Sm,_, Y,.TiTaO6 solid solution phases

Temperature Stable Low Loss Ceramic Dielectrics in (1-x)ZnAI2O4-xTiO2 System for Microwave Substrate Applications

The microwave dielectric properties of ZnAl2O4 spinels were investigated and their properties were tailored by adding different mole fractions of Ti02. The samples were synthesized using the mixed oxide rout.e. The phase purity and crystal structure were identified using X-ray diffraction technique. The sintered specimens were characterized in the microwave frequency range (3-13 GHz). The ZnA12O4 ceramics exhibited interesting dielectric properties (dielectric constant (e,.) = 8.5, unloaded quality factor (Q.) = 4590 at 12.27 GHz and temperature coefficient of resonant frequency (Tf) = -79 ppm/°C). Addition of Ti02 into the spinel improved its properties and the Tf approached zero for 0.83ZnAl2O4- 0.17TiO2• This temperature compensated composition has excellent microwave dielectric properties (Cr _ 12.67, Q, = 9950 at 10.075 GHz) which can be exploited for microwave substrate applications

Microwave Dielectric Properties of BaO -2CeO2-nTiO2 Ceramics

The BaO-2CeO2-nTiO2 ceramics with n = 3, 4 and 5 have been prepared with CeO2 as starting material . The ceramics have been characterized using scanning electron microscopy , X-ray diffraction , Raman and X-ray photoelectron spectroscopy techniques. The microwave dielectric properties have been measured using standard dielectric resonator techniques . BaO-2CeO2-3TiO2 (123), BaO-2CeO2-4TiO2 ( 124) and BaO-2CeO2-5TiO2 ( 125) ceramics showed dielectric constants of 38, 27 and 32, respectively . All the ceramics showed fairly good unloaded Q - factors . 124 and 125 compounds exhibited low tf values, while 123 showed a high rf value

The Effect of Glass Additives on the Microwave Dielectric Properties of Ba(Mg 1 /3Ta2/3)03 Ceramics

The effect of glass additives on the densification , phase evolution, microstructure and microwave dielectric properties of Ba(Mg1;3 Ta2i3)03 (BMT) was investigated . Different weight percentages of quenched glass such as B203 , Si02, B203-SiO2, ZnO-B203, 5ZnO-2B2O3, Al203-SiO2, Na20-2B203.10H20, BaO-B203-SiO2, MgO-B203-SiO2, PbO-B203-SiO2 , ZnO-B203-SiO2 and 2MgO-Al203-5SiO2 were added to calcined BMT precursor . The sintering temperature of the glass -added BMT samples were lowered down to 1300 °C compared to solid-state sintering where the temperature was 1650 °C. The formation of high temperature satellite phases such as Ba5Ta4O15 and Ba7Ta6O22 were found to be suppressed by the glass addition . Addition of glass systems such as B203, ZnO-B203, 5ZnO-2B203 and ZnO-B203-SiO2 improved the densification and microwave dielectric properties. Other glasses were found to react with BMT to form low-Q phases which prevented densification . The microwave dielectric properties of undoped BMT with a densification of 93 . 1 % of the theoretical density were Cr = 24 . 8, Tr = 8 ppm/°C and Q„ x f= 80,000 GHz. The BMT doped with 1.0 wt% of B203 has Q„ x f = 124,700GHz, Cr = 24.2, and T f = -1.3 ppm /°C. The unloaded Q factor of 0.2 wt% ZnO-B203-doped BMT was 136,500 GHz while that of 1.0 wt% of 5ZnO-2B203 added ceramic was Q„ x f= 141,800 GHz . The best microwave quality factor was observed for ZnO -B203-SiO2 (ZBS) glass-added ceramics which can act as a perfect liquid-phase medium for the sintering of BMT. The microwave dielectric properties of 0.2wt% ZBS-added BMT dielectric was Q„ x f= 152,800 GHz, F,= 25.5, and Tr = - 1.5 ppm/°C

Discrete Time Inventory Models with/without Positive Service Time

In everyday life different flows of customers to avail some service facility or other at some service station are experienced. In some of these situations, congestion of items arriving for service, because an item cannot be serviced Immediately on arrival, is unavoidable. A queuing system can be described as customers arriving for service, waiting for service if it is not immediate, and if having waited for service, leaving the system after being served. Examples Include shoppers waiting in front of checkout stands in a supermarket, Programs waiting to be processed by a digital computer, ships in the harbor Waiting to be unloaded, persons waiting at railway booking office etc. A queuing system is specified completely by the following characteristics: input or arrival pattern, service pattern, number of service channels, System capacity, queue discipline and number of service stages. The ultimate objective of solving queuing models is to determine the characteristics that measure the performance of the system