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Efficient Techniques and Algorithms for Improving Indoor Localization Precision on WLAN Networks Applications  [PDF]
Antonio del CORTE-VALIENTE, Jose Manuel GóMEZ-PULIDO, Oscar GUTIéRREZ-BLANCO
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2009, DOI: 10.4236/ijcns.2009.27073
Abstract: This paper proposes efficient techniques that allow the deploying of high precision location applications for indoor scenarios over Wireless Local Area Networks (WLAN). Firstly, we compare the use of radio frequency (RF) power levels and relative time delays based on ray-tracing as detection methods to estimate the localization of a set of mobile station using the fingerprint technique. Detection method play an important role in applications of high frequencies techniques for locations systems based on current and emerging standards such as Wi-Fi (802.11x) and Wi-Max (802.16x). The localization algorithm computes the Eucli- dean distance between the samples of signals received from each unknown position and each fingerprint stored in the database or radio-map obtained using the FASPRI simulation tool. Experimental results show that more precision can be obtained in the localization process by means of relative delay instead of RF power detection method. Secondly, the Euclidean distance has been compared with others similarity distance measures. Finally, an interpolation algorithm between the fingerprinting weighing based on the distances has been implemented in order to eliminate those fingerprints that do not contribute to the improvement in the accuracy. These techniques allow obtaining more precision in the localization of indoor mobile devices over WLAN networks.
Estrategia de Ense?anza Basada en el Cambio Conceptual para la Transformación de Ideas Previas en el Aprendizaje de las Ciencias
Mahmud,Mirna C; Gutiérrez,Oscar A;
Formación universitaria , 2010, DOI: 10.4067/S0718-50062010000100003
Abstract: the objective of this research is to determine the effect of the didactic strategies based on conceptual changes for the transformation of misconceptions about heat and temperature in college students of careers related to science. the design consisted of applying an initial test on previous ideas related to the concepts of heat and temperature. then, a learning experience with instructional activities based on conceptual change model was done to then apply a new test to assess to evalúate the new learning. the descriptive statistical analysis of the items before and after treatment revealed that there were slight changes on misconceptions. moreover, the results of applying the t-student statistic suggest that the strategy based on conceptual changes is effective for the better comprehension of the concepts of heat and temperature.
Accuracy of the Small Field Dosimetry Using the Acuros XB Dose Calculation Algorithm within and beyond Heterogeneous Media for 6 MV Photon Beams  [PDF]
Sotirios Stathakis, Carlos Esquivel, Luis Vazquez Quino, Pamela Myers, Oscar Calvo, Panayiotis Mavroidis, Alonso N. Gutiérrez, Niko Papanikolaou
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2012, DOI: 10.4236/ijmpcero.2012.13011
Abstract: Purpose: The dosimetric accuracy of the recently released Acuros XB advanced dose calculation algorithm (Varian Medical Systems, Palo Alto, CA) is investigated for single radiation fields incident on homogeneous and heterogeneous geometries, as well as for two arc (VMAT) cases and compared against the analytical anisotropic algorithm (AAA), the collapsed cone convolution superposition algorithm (CCCS) and Monte Carlo (MC) calculations for the same geometries. Methods and Materials: Small open fields ranging from 1 × 1 cm2 to 5 × 5 cm2 were used for part of this study. The fields were incident on phantoms containing lung, air, and bone inhomogeneities. The dosimetric accuracy of Acuros XB, AAA and CCCS in the presence of the inhomogeneities was compared against BEAMnrc/DOSXYZnrc calculations that were considered as the benchmark. Furthermore, two clinical cases of arc deliveries were used to test the accuracy of the dose calculation algorithms against MC. Results: Open field tests in a homogeneous phantom showed good agreement between all dose calculation algorithms and MC. The dose agreement was +/?1.5% for all field sizes and energies. Dose calculation in heterogenous phantoms showed that the agreement between Acuros XB and CCCS was within 2% in the case of lung and bone. AAA calculations showed deviation of approximately 5%. In the case of the air heterogeneity, the differences were larger for all calculations algorithms. The calculation in the patient CT for a lung and bone (paraspinal targets) showed that all dose calculation algorithms predicted the dose in the middle of the target accurately; however, small differences (2% - 5%) were observed at the low dose region. Overall, when compared to MC, the Acuros XB and CCCS had better agreement than AAA. Conclusions: The Acuros XB calculation algorithm in the newest version of the Eclipse treatment planning system is an improvement over the existing AAA algorithm. The results are comparable to CCCS and MC calculations especially for both stylized and clinical cases. Dose discrepancies were observed for extreme cases in the presence of air inhomogeneities.
Study of Electromagnetic Compatibility in Hospital Environments  [PDF]
Oscar Gutiérrez, Miguel ángel Navarro, Francisco Saez de Adana, Adolfo Escobar, María E. Moncada, Claudio Marcelo Mu?oz
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2014, DOI: 10.4236/jemaa.2014.67014
Abstract:

This paper presents a study on the effects of radiation from electronic equipment in hospitals. This study was performed in Argentinean, Colombian and Spanish hospitals. The work consists of two parts: a survey to determine the hospital personnel’s knowledge of the problem and a technical part consisting of a measurements campaign to determine the levels of radiated electrical and magnetic fields in several hospitals due to the presence of electromagnetic interferences, such as the use of mobile phones. The study of this problem has been of special interest in countries such as the USA and Canada, and this paper attempts to convey the necessity of creating regulations that can be applied to the hospitals of the countries analyzed. More than fifty hospitals were studied in these three countries, considering the following aspects: the hospital personnel’s awareness of the problem, whether the hospitals have performed previous studies of this type, the appearance of problems in medical equipment due to this interference, the origin of the interference, and the failures that have appeared in computers due to electromagnetic interference. The results show that, most hospitals have a lack of knowledge regarding this issue and that field levels above those allowed by international regulations are present. Therefore, a regulation must be established to avoid the problem.

Ideas para innovar: La evalulación figuroanalógica
Blanco Gutiérrez,Oscar; Arias Lara,Sergio Alejandro;
Educere , 2008,
Abstract: knowledge evaluation, as prominent activity of educational processes for its decisive pedagogical action, forces constantly to reflect about and debate on its practice. this leads to worrying questionings: how is it supposed to evaluate? are the techniques and tools used appropriate? does the way we evaluate make sense? potentially, the teacher finds the answers investigating his or her own action in the classrooms. the following article is part of the results obtained by the authors in their research on alternatives to evaluate knowledge, among several options the figure-analogy evaluation is posed, since it offers important ideas and favorable alignments to be applied in the first stages of primary education.
Simple route for the synthesis of copper hydroxy salts
Aguirre, Jhon Mauricio;Gutiérrez, Adamo;Giraldo, Oscar;
Journal of the Brazilian Chemical Society , 2011, DOI: 10.1590/S0103-50532011000300019
Abstract: the current work introduces a new and rapid synthetic route for the in-laboratory preparation of copper hydroxy nitrate, through the reaction of magnesium hydroxide and copper nitrate aqueous solution. the material with the formula cu2(oh)3no3 and monoclinic phase was characterized by x-ray diffraction, atomic absorption, fourier transform infrared and raman spectroscopy, scanning electron microscopy with edx, and thermal analysis.
El perfil del sinclinal del Rincón Blanco (noroeste de La Rioja): el límite Carbonífero-Pérmico en el noroeste argentino
Gutiérrez,Pedro Raúl; Limarino,Carlos Oscar;
Ameghiniana , 2006,
Abstract: the finding of palynological associations in the río del pe?ón formation (late carboniferous-early permian) is addressed. the fossiliferous section is located in the northern precordillera, more precisely at the río blanco area, situated to the west of jagüe town. the río del pe?ón formation (1,270 m thick) is composed of three members, the lower (729 m thick) bears 21 fossilifeous levels, whereas both the middle (161 m thick) and upper members contain only 2. the lower 16 fossiliferous levels contain palynological associations referred to the raistrickia densa-convolutispora muriornata biozone (dm, c sub-biozone?). the rest of the palynological levels are here included in the pakhapites fusus-vittatina subsaccata biozone (fs). moreover, in this paper the stratigraphic relationship among the palynological associations, the megafloristic nbg biozone and the marine invertebrates assemblages described by previous authors (tivertonia jachalensis- streptorhynchus inaequioenatus biozone) are also identified. the palynological information here presented and previous radiometric ages reported not only by the underlying punta del agua formation (287 and 295 ma) but also by a riodacitic sill intercalated in the lowermost part of the río del pe?ón formation (287,8±0,7 ma) allow to assign the río del pe?ón formation to the uppermost part of the upper carboniferous-lower permian. moreover, the ages of the nbg and dm biozones are constrained to the beginning of the permian. finally the rincón blanco section is proposed as a potential stratotype for the boundary between the dm and fs biozones and thus for the carboniferous-permian boundary.
Efecto diurético de la especie Salvia scutellarioidesen ratas
Ramírez,Jorge Hernán; Palacios,Mauricio; Gutiérrez,Oscar;
Biomédica , 2006,
Abstract: introduction. in the colombian traditional medicine, an infusion made of the entire plant salvia scutellarioides (known locally as mastranto or oreja de perro (dog?s ear)) is used for its antihypertensive and diuretic effects. however, experimental studies have never been done to validate the reported effects. objective. in the current study, a rat model was used to determine the effect of s. scutellarioides on rat diuresis and urinary electrolytes concentration. materials and methods. twenty-four male sprague-dawley rats were distributed in four groups: group 1-normal saline solution, group 2-furosemide (10mg/kg), groups 3 and 4 with s. scutellarioides infusion, 1g/kg and 2g/kg respectively. all treatments were administered in a volume of 25ml/kg of rat weight. after treatment, the rats were placed in a metabolic cage for 6 hours. during this period, urinary excretion was monitored and quantified. at the end of 6 hours, the urinary electrolyte concentrations were measured. results. the administration of s. scutellarioides at doses of 1 and 2 g/kg produced a significant increase in diuresis when compared to the control group (p<0.01). the administration of s. scutellarioides at these doses also increased the urinary excretion of potassium and chloride. conclusions. these results corroborate the apparent diuretic activity of s. scutellarioides described by traditional herbalists and possibly explains its reported antihypertensive effect. further studies are required to determine the pharmacological and toxicological profile of the plant.
Implementación de la técnica en órgano aislado vascular como herramienta para la validación de plantas medicinales: Estudio del efecto vasodilatador de la Salvia scutellarioides
Ramírez,Jorge Hernán; Palacios,Mauricio; Gutiérrez,Oscar;
Colombia Médica , 2007,
Abstract: introduction: salvia scutellarioides is a plant with antihypertensive and diuretic properties. in this study, its vasodilator effect is evaluated using the isolated organ technique. objectives: to standardize the isolated vascular organ, and to study the effect of s. scutellarioides in vasoconstriction by alfa 1 receptors stimulation. methodology: rat aortic rings were placed in an organ bath equipment (biopac?), at 37o c temperature and constant carbogen gas bubbling. tension changes were registered with an isometric tension transducer and data acquisition equipment. during the standardization, six curves of concentration-tension with phenylephrine at 1, 3 and 5 hours were registered, in order to determine maximum tension (tm), and the effective concentration 50 (ec50). finally, three concentration-tension curves were obtained for phenylephrine with s. scutellarioides at a concentration of 10 mg/dl and 20 mg/dl. results: during the technique standardization, no statistically significant differences were found in tm for phenylephrine at 1, 3 and 5 hours. the administration of s. scutellarioides produced a tm dose dependent reduction with no ec50 changes. discussion: the implemented isolated organ technique is viable up to 5 hours, and does not produce alfa 1 receptors desensibilization. the tm diminution by s. scutellarioides is explained by a non competitive alfa 1 antagonism effect. studies to isolate active principles for allowing the initiation of phase i human clinical trials are required.
Estudio del efecto antihipertensivo de la Salvia scutellarioides en un modelo de ratas hipertensas
Ramírez,Jorge; Palacios,Mauricio; Gutiérrez,Oscar;
Colombia Médica , 2006,
Abstract: introduction: an infusion of stems and leaves of the plant salvia scutellarioides (common name: mastranto) is used in the colombian traditional medicine due to its antihypertensive and diuretic effects. up to date, no experimental studies have been done to validate the reported effects. objective: to determine the effect of s. scutellarioides in blood pressure using a model of hypertensive rats. methods: a total of thirty male rats were randomly distributed in five homogeneous randomly distributed groups: group 1. normal saline solution (5 ml/kg p.o.) and normal saline solution (1 ml/kg i.p.); group 2. s. scutellarioides (1 g/kg p.o.) and l-name (40 mg/kg i.p.); group 3. s. scutellarioides (2 g/kg p.o.) and l-name (40 mg/kg i.p.); group 4. enalapril (25 mg/kg p.o.) and l-name (40 mg/kg i.p.); group 5. normal saline solution (5 ml/kg p.o.) and l-name (40 mg/kg i.p.). the treatments were administered daily during four weeks. blood pressure measurements (systolic, median and diastolic) were performed in a non invasive form using a tail pressure meter with a piezo electric sensor; furthermore, renal and cardiac histopathology were performed to all animals. results: the administration of s. scutellarioides 2 g/kg produced a statistically significant reduction of median blood pressure (mbp) and diastolic blood pressure (dbp) in comparison with the group that received l-name and normal saline solution. the mbp and dbp reduction produced by s. scutellarioides was comparable to that of the group that received enalapril 25 mg/kg. reductions in mbp and dbp were obtained during the first week (p<0.001), second week (p<0.01), and fourth week (p<0.05) of treatment. the administration of s. scutellarioides 1 g/kg had no effect on the blood pressure. both doses of s. scutellarioides used did not prevent damage to target organs in this model of hypertension. conclusions: the results of this study do coincide with the apparent antihypertensive activity of s. scutellarioides reported
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