Browsing by Author "Martins, A."
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- An enhanced proposal in neighbor list planning for LTE SON radio access networksPublication . Duarte, D.; Martins, A.; Vieira, Pedro; Rodrigues, A.; Silva, N.Nowadays, a coexistence of 2nd Generation (2G), 3rd Generation (3G) and 4th Generation (4G) networks is being witnessed. Due to this situation, it became evident the need for Self-Organizing Networks (SON), which aims to automate most of the associated radio planning and optimization tasks. Within SON, this paper presents the latest work around an algorithm that optimizes the Neighbor Cell List (NCL) for Long Term Evolution (LTE) evolved NodeBs (eNBs). The algorithm is based on intra-site distance, its antenna orientation (azimuth/elevation), radiation pattern and overlap areas between cells. The research initial steps were already published (Duarte, D.; Vieira, P.; Rodrigues, A.; Martins, A.; Oliveira, N.; Varela, L., “Neighbour List Optimization for Real LTE Radio Networks,” Wireless and Mobile, 2014 IEEE Asia Pacific Conference on, pp.183,187, 28-30 Aug. 2014).
- Crossed sector automatic detection in 4G Radio Access NetworksPublication . Martins, A.; Vieira, Pedro; Franco, C.; Rodrigues, A.; Silva, N.The Long Term Evolution (LTE) is the latest step in the advancing series of mobile telecommunications systems, it is called the fourth Generation (4G). In order to boost performance and deal with the increasing complexity within the operating 3G/4G networks, the Self-Organizing Networks (SON) concept was introduced.
- Desilication of MOR zeolite: Conventional versus microwave assisted heatingPublication . Paixão, V.; Monteiro, R.; Andrade, M.; Fernandes, A.; Rocha, J.; Carvalho, A. P.; Martins, A.MOR zeolites were modified via desilication treatments with NaOH, under conventional and microwave heating. The samples were characterized by powder X-ray diffraction, (27)Al and (29)Si NMR spectroscopy. TEM and N(2) adsorption at -196 degrees C. The acidity of the samples and the space available inside the pores were evaluated through a catalytic model reaction, the isomerization of m-xylene, for which the profiles of the coke thermal decomposition were also analyzed. Powder X-ray diffraction and (29)Si and (27)Al MNR results show that in comparison with conventional heating, microwave irradiation (a less time consuming process) leads to identical amount of Si extraction from the zeolite framework. With this treatment. in addition to the customary mesopores development promoted by conventional heating, a partial conversion of the zeolite microporosity into larger micropores, is observed. The microwave irradiated and conventionally heated samples show different catalytic behavior in the m-xylene isomerization model reaction. It was observed that, by controlling the experimental conditions, it is possible to obtain samples with catalytic properties closer to the parent material, which is also confirmed by the respective coke analysis. (C) 2011 Elsevier B.V. All rights reserved.
- Determinants of malnutrition among under-fives in Bengo province, AngolaPublication . Brito, Miguel; Soares, A.; Fançony, C.; Martins, A.Introduction - Nutrition is capable of maximize health and minimize morbidity and mortality in early childhood. In fact, some nutritional disturbances, if not detected nor treated in the first 1000 days of a child0s life, can have irreversible consequences impairing an individual for his entire life. New interventions to reduce undernutrition should be designed taking into account their determinants. This study aims to identify factors associated with undernutrition (wasting, stunting and underweight) among children under 5 years in Bengo province, Angola. Materials and Methods - Logistic regression analysis was used to examine undernutrition against a set of variables associated with health, water and parental caregiver factors. Children nutritional status was classified as underweight, stunted and wasted if their Z-scores for weight-for-age (WAZ), heightfor- age (HAZ) and weight-for-height (WHZ) were less than 2.0 SD of the WHO (2006) standards. Results - The present study comprised 803 children, of whom 50.8% were males and 43% aged 0–23 months. Concerning to parental practices, 36% of the under-twos were currently breastfeeding, and 89% were breastfeed for more than 12 months. 84% started complementary feedin within <6 months of birth. The caregivers reported that 34% of the children had diarrhea in the last 2 weeks and 53.4% of the mothers did not treat drinking water. The prevalence of wasting was 5.6%, of stunting 30.7% and of underweight 29.0%. The most significant factors for wasting were age of the child (OR 4.5, 2.1–9.3 risk for 0–23 age), being breastfed (OR 4.0, 2.0–7.7) and diarrhea episodes (OR 2.0, 1.0–3.7). The most significant factors for stunting were mother0s education (OR 0.5, 0.2–0.9 for mother with secondary or higher education), age of the child (OR 0.5, 0.4–0.8 risk for 0–23 age), being breastfed (OR 0.4, 0.3–0.6). The most significant factors for underweight were age of the child (OR 1.7, 1.1–2.6 risk for 0–23 age class), being breastfed (OR 1.7, 1.1–2.7) and diarrhea episodes (OR 1.9, 1.3–3.1). Conclusions The study suggests the necessity of different approaches in interventions depending on the age group. Community-based education interventions are needed to reduce preventable morbidity and mortality triggered by undernutrition.
- Efficient cyclohexane oxidation with hydrogen peroxide catalysed by a C-scorpionate iron(II) complex immobilized on desilicated MOR zeolitePublication . Martins, Luisa; Martins, A.; Alegria, Elisabete; Carvalho, A. P.; Pombeiro, ArmandoThe hydrotris(pyrazol-1-yl)methane iron(II) complex [FeCl2{eta(3)-HC(pz)(3)}] (Fe, pz = pyrazol-1-yl) immobilized on commercial (MOR) or desilicated (MOR-D) zeolite, catalyses the oxidation of cyclohexane with hydrogen peroxide to cyclohexanol and cyclohexanone, under mild conditions. MOR-D/Fe (desilicated zeolite supported [FeCl2{eta(3)-HC(pz)(3)}] complex) provides an outstanding catalytic activity (TON up to 2.90 x 10(3)) with the concomitant overall yield of 38%, and can be easy recovered and reused. The MOR or MOR-D supported hydrotris(pyrazol-1-yl)methane iron(II) complex (MOR/Fe and MOR-D/Fe, respectively) was characterized by X-ray powder diffraction, ICP-AES, and TEM studies as well as by IR spectroscopy and N-2 adsorption at -196 degrees C. The catalytic operational conditions (e.g., reaction time, type and amount of oxidant, presence of acid and type of solvent) were optimized. (C) 2013 Elsevier B.V. All rights reserved.
- Energy savings in 3G using dynamic spectrum access and base station sleep modesPublication . Cunha, T.; Rodrigues, A.; Vieira, Pedro; Martins, A.; Silva, N.; Varela, L.The energy consumption and energy efficiency of mobile telecommunication networks are crucial factors for the sustainability of this industry. This paper targets the reduction of the energy consumption at a Base Station (BS) level through the adoption of sleep modes during the off-peak periods of the day and relying in the existence of co-located and overlaid frequency bands to provide the coverage and capacity backup for the switched-off cells. It relies on the Dynamic Spectrum Allocation (DSA) method to opportunely relocate users during the low-load periods while maintaining the service quality of service (QoS). For the input data, real traffic statistics were used. Using this strategy and the proposed algorithm it was possible to achieve savings of about 43% per-site. The results were furthered to the study of a Portuguese mobile operator case and it was concluded that savings of more than 1.25 million euros were easily achieved.
- A hybrid neighbor optimization algorithm for SON based on network topology, Handover counters and RF measurementsPublication . Duarte, D.; Martins, A.; Vieira, Pedro; Rodrigues, A.With the increasing complexity of current wireless networks, it became evident the need for Self-Organizing Networks (SON), which aims to automate most of the associated radio planning and optimization tasks. Within SON, this paper aims to optimize the Neighbor Cell List (NCL) for radio network cells. An algorithm composed by three decision criteria was developed: geographic localization and orientation, according network topology, Radio Frequency (RF) measurements collected by drive-tests or traces and Performance Management (PM) counters from Handover (HO) statistics. The first decision, proposes a new NCL taking into account the Base Station (BS) location and interference tiers, based on the quadrant method. The last two decision criteria consider signal strength and interference level measurements and HO statistics in a time period, respectively. They also define a priority to each cell and added, kept or removed neighbor relation, based on user defined constraints. The algorithms were developed and implemented over new radio network optimization professional tool. Several case studies were produced using real data from a mobile operator.
- Impact of music intervention on psychological and physiological parameters of patients undergoing myocardial perfusion scintigraphyPublication . Vieira, Lina Oliveira; Rotaru, A.; Rodrigues, I.; Martins, A.; Carvalho, C.; Alvernaz, A.; Oliveira, L.; Grilo, Ana; Raminhas Carapinha, Maria JoãoAim/Introduction: Myocardial Perfusion Scintigraphy (MPS), a well-established imaging procedure for diagnosing ischemic heart disease, has multiple phases that can induce patients’ anxiety, discomfort, and dissatisfaction. Several non-pharmacological strategies have been used to alleviate anxiety and improve patient comfort and satisfaction, such as music intervention. This study aimed to evaluate the efficacy of musical intervention in the outcomes of patients undergoing MPS. Materials and Methods: A randomized clinical trial was conducted on patients undergoing an MPS one-day protocol stress-rest, in a Nuclear Medicine Department between January 15, and March 18, 2024. Patients were divided into a control group (CG) and an experimental group (EG). In the EG, a musical intervention was performed during the rest image acquisition, allowing patients to choose from a selection of musical tracks curated by a music lecturer. Anxiety levels were assessed at four different moments in both groups: before and after the stress image acquisition (T1 and T2), and before and after the rest image acquisition (T3 and T4), using physiological parameters at all times and psychological parameters for CG at T1 and T4 and for EG at T1, T3 and T4. Image quality analysis was performed using measures of contrast, noise, number, and amplitude of patients' movements. All studies were reviewed by two researchers and evaluated by three nuclear medicine technologists. Results: The sample comprised 30 participants with an average age of 71±11.02yrs [45-87yrs] with 15 participants enrolled in each group. Patients in EG reduced their anxiety scores from 36±9.44 at T1 to 33±7.07 at T3 and 28±9.11 at T4, while patients in CG reduced their anxiety scores from 39±10.62 at T1 to 33±9.66 at T4. Regarding patient motion, there was a reduction from the CG to EG in movements between 1-2 pixels (CG = 21, EG= 19) and movements higher than 2 pixels (CG =19, EG=6). In some myocardial walls on the three tomographic slices, the correlation between psychological parameters and image noise was lower in T4 for the EG. No significant results were found in image contrast. Conclusion: For the EG, the image noise was ~3% lower than in CG. Anxiety decreased throughout the MPS procedure with lower values at T4 for the EG. Additionally, the musical intervention seems to be effective as the EG showed lower values of patient movement.
- Microwave synthesis of SAPO-11 materials for long chain n-alkanes hydroisomerization: effect of physical parameters and chemical gel compositionPublication . Bertolo, R.; Silva, J.M.; Ribeiro, M.F.; Martins, A.; Fernandes, A.The present work concerns the preparation of SAPO-11 materials using microwave (MW) heating during the crystallization process. Different experimental conditions such as crystallization temperature and time were explored, together with different Si sources. The final materials were fully characterized using chemical analysis, XRD diffraction, pyridine adsorption followed by FTIR, nitrogen sorption and NMR spectroscopy and compared with the respective conventional SAPO-11 materials, synthesized using the same initial chemical composition of the gel but under conventional electric heating. The results showed that SAPO-11 materials can be synthesized in less time (within minutes) and at lower temperature (170 °C) with MW heating than with conventional heating (respectively 24 h and 200 °C). MW heating allows nanosized SAPO-11 materials to be obtained but the nature of the Si source used has a marked influence on the textural properties and, especially, on the acidity of SAPO-11. The catalytic properties of the materials (with 0.5 wt.% Pt) were evaluated in the hydroisomerization of long chain n-alkanes using n-decane as model molecule. Optimized MW samples using colloidal AS-40 Si source showed higher yields in monobranched isomers due to a joint effect of low acidity and suitable textural properties.
- Modifications of MCM-22 zeolite through sequential post-synthesis treatments. Implications on the acidic and catalytic behaviourPublication . Machado, V.; Rocha, J.; Carvalho, A. P.; Martins, A.Desilication and a combination of alkaline followed by acid treatment were applied to MCM-22 zeolite using two different base concentrations. The samples were characterised by powder X-ray diffraction, Al-27 and Si-29 MAS-NMR spectroscopy, SEM, TEM and low temperature N-2 adsorption. The acidity of the samples was study through pyridine adsorption followed by FTIR spectroscopy and by the analyses of the hydroxyl region. The catalytic behaviour, anticipated by the effect of post-synthesis treatments on the acidity and space available inside the two internal pore systems was evaluated by using the model reaction of m-xylene transformation. The generation of mesoporosity was achieved upon alkaline treatment with 0.05 M NaOH solution and practically no additional gain was obtained when the more concentrate solution, 0.1 M, was used. Instead, Al extraction takes place along with Si, as shown by Si-29 and Al-27 MAS-NMR data, followed by Al deposition as extraframework species. Samples submitted to alkaline plus acid treatments present distinct behaviour. When the lowest NaOH solution was used no relevant effect was observed on the textural characteristics. Additionally, when the acid treatment was performed on an already fragilized MCM-22 structure, due to previous desilication with 0.1 M NaOH solution, the extraction of Al from both internal pore systems promotes their interconnection, evolving from a 2-D to a 3-D porous structure. This transformation has a marked effect in the catalytic behaviour, allowing an increase of m-xylene conversion as a consequence of an easier and faster molecular traffic in the 3-D structure. On the other hand, the continuous deposition of extraframework Al species inside the pores leads to a shape selective effect that privileges the formation of the more valuable isomer p-xylene.