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Optical analysis of low concentration evacuated tube solar collector
Teles, Mavd R.,Carvalho, Raquel,Ismail, Kamal A.R. Techno-Press 2017 Advances in energy research Vol.5 No.3
The continuous increase of emission rates of green house gases and the effects on global warming added a new dimension to the problem of substituting the petroleum and its derivatives by environment friendly and sustainable energy sources for the world. Solar and wind energy appear at the top of the list of renewable of high potential, widely available, of dominated technology and well accepted. Brazil is one of the few countries in the world that receives number hours of sunshine exceeding 3,000 hours per year with a daily average of 4.5 to 6 kWh. However, this potential is largely unexplored and poorly tapped. The number of renewable systems implanted in Brazil has grown in recent years, but still insignificant when compared, for example, with Germany and Spain among others. This paper presents the results of an optical study on small concentration solar collector with evacuated tube enveloping the absorber and internal reflective surface fixed on the bottom part of the evacuated tube. The designed collector has a 2D geometrical concentration ratio between 2.455 and 4.91. The orientation of the solar collector, the ratio of the radius of the receiver to the radius of the absorber, the incidence angle for each period of the year, the collector inclination angle, the aperture angle of the reflective surface, concentration and optical efficiency were determined. The ray traces and flux distribution on the absorber of the evacuated tube solar collector were determined by using the program Ray Optics Simulation. The optical efficiency varies during the year according to the solar declination. For the periods were the solar declination is close to zero the efficiencies are maximum, and the variation during the day is around 25.88% and 99.9%. For the periods were the solar declination is maximum the efficiencies are minimum, and the variation during the day is around 23.78% and 91.79%.
A new formulation of cracking in concrete structures based on lumped damage mechanics
Daniel V.C. Teles,Rafael N. Cunha,Ricardo A. Picón,David L.N.F. Amorim,Yongtao Bai,Sergio P.B. Proença,Julio Flórez-López 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.88 No.5
Lumped Damage Mechanics (LDM) is a theory proposed in the late eighties, which assumes that structural collapse may be analyzed as a two-phase phenomenon. In the first (pre-localization) stage, energy dissipation is a continuous process and it may be modelled by means of the classic versions of the theory of plasticity or Continuum Damage Mechanics (CDM). The second, post-localization, phase can be modelled assuming that energy dissipation is lumped in zones of zero volume: inelastic hinges, hinge lines or localization surfaces. This paper proposes a new LDM formulation for cracking in concrete structures in tension. It also describes its numerical implementation in conventional finite element programs. The results of three numerical simulations of experimental tests reported in the literature are presented. They correspond to plain and fiber-reinforced concrete specimens. A fourth simulation describes also the experimental results of a new test using the digital image correlation technique. These numerical simulations are also compared with the ones obtained using conventional Cohesive Fracture Mechanics (CFM). It is then shown that LDM conserves the advantages of both, CDM and CFM, while overcoming their drawbacks.
Energy equivalent lumped damage model for reinforced concrete structures
Renério Pereira Neto,Daniel V.C. Teles,Camila S. Vieira,David L.N.F. Amorim 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.2
Lumped damage mechanics (LDM) is a recent nonlinear theory with several applications to civil engineering structures, such as reinforced concrete and steel buildings. LDM apply key concepts of classic fracture and damage mechanics on plastic hinges. Therefore, the lumped damage models are quite successful in reproduce actual structural behaviour using concepts well-known by engineers in practice, such as ultimate moment and first cracking moment of reinforced concrete elements. So far, lumped damage models are based in the strain energy equivalence hypothesis, which is one of the fictitious states where the intact material behaviour depends on a damage variable. However, there are other possibilities, such as the energy equivalence hypothesis. Such possibilities should be explored, in order to pursue unique advantages as well as extend the LDM framework. Therewith, a lumped damage model based on the energy equivalence hypothesis is proposed in this paper. The proposed model was idealised for reinforced concrete structures, where a damage variable accounts for concrete cracking and the plastic rotation represents reinforcement yielding. The obtained results show that the proposed model is quite accurate compared to experimental responses.
Gustavo Batista de Castro Souza,Flávio Henrique Teles Vieira,Cláudio Ribeiro Lima,Getúlio Antero de Deus Júnior,Marcelo Stehling de Castro,Sérgio Granato de Araujo,Thiago Lara Vasques 한국전자통신연구원 2016 ETRI Journal Vol.38 No.1
Smart metering systems have become widespread around the world. RF mesh communication systems have contributed to the creation of smarter and more reliable power systems. This paper presents an algorithm for positioning GPRS concentrators to attain delay constraints for a ZigBee-based mesh network. The proposed algorithm determines the number and placement of concentrators using integer linear programming and a queueing model for the given mesh network. The solutions given by the proposed algorithm are validated by verifying the communication network performance through simulations.
권오영 ( Oh Young Kwon ),서효석 ( Hyo Seok Seo ),구스타보텔레스 ( Gustavo Teles ) 한국실천공학교육학회 2011 실천공학교육논문지 Vol.3 No.1
가상 환경에서의 학습 시스템은 기존 E-Learning 시스템에서 부족했던 몰입감을 주고 사용자의 흥미 유발을 촉진할 수 있고 위험하거나 비용이 많이 드는 교육 컨텐츠를 제공할 수 있다. 본 논문에서 학습 유형을 실시간강의, 상시 학습, 실습 교육, 그리고 스터디 그룹 활동으로 구분하였다. 혼합 현실을 제공하는 가상 세계인 Second Life를 이용하여 이들 학습 유형을 지원하는 온라인 강의 시스템을 구축하였다. 구축된 온라인 강의 시스템을 운영함으로써 가상 학습 환경을 제공하였다. Learning system on virtual environment gives the immersive feeling that lacks in existing E-Learning system, excites user`s interest, and offers dangerous and expensive education contents. In this paper, we classified the learning categories into four classes: realtime lecture, anytime study, practice education, and the activity of study group. We built the on-line lecture system using Second Life that supports 3D virtual world and mixed reality. We provided virtual learning environment as running developed virtual world on-line lecture system.
Claudio Andre Barbosa de Lira,Ricardo Borges Viana,Kaylla Priscilla Mesquista,Douglas de Assis Teles Santos,Mário Hebling Campos,Marília Santos Andrade,Rodrigo Luiz Vancini 대한장연구학회 2019 Intestinal Research Vol.17 No.4
Background/Aims: Despite the evidence of a modest to high prevalence of gastrointestinal (GI) symptoms in recreational runners and endurance athletes, the frequency and intensity of GI symptoms in exercisers, but nonathletes, individuals from different modalities have been less investigated. Therefore, the present study aimed to assess the prevalence of GI symptoms in individuals that practice moderate or vigorous physical exercise, at rest and during physical exercise training session. Methods: The sample consisted of 142 exercisers individuals (64 women and 78 men with mean age of 32.9±10.7 years). Out of the 142 participants, 71 reported to perform moderate physical exercise and 71 reported to perform vigorous physical exercise. Participants were assessed by an internet-based questionnaire designed to assess the frequency and intensity (at rest and during physical exercise training session) of 18 GI symptoms. Results: The GI symptoms most frequently reported by the respondents (during rest and physical exercise training session, respectively) were flatulence (90.8% and 69.7%), abdominal noise (77.5% and 41.5%), and eructation (73.9% and 52.1%). Overall, the frequency and intensity of symptoms were higher (P<0.050) during rest than physical exercise training session for who perform moderate and vigorous physical exercise. Conclusions: It can be concluded that GI symptoms in exercisers, but nonathletes, individuals are more prevalent during rest than during physical exercise training session, suggesting that moderate and vigorous physical exercise may act as a regulator of the GI tract.
Vitamin D Is Required for IFN- -Mediated Antimicrobial Activity of Human Macrophages
Fabri, M.,Stenger, S.,Shin, D.-M.,Yuk, J.-M.,Liu, P. T.,Realegeno, S.,Lee, H.-M.,Krutzik, S. R.,Schenk, M.,Sieling, P. A.,Teles, R.,Montoya, D.,Iyer, S. S.,Bruns, H.,Lewinsohn, D. M.,Hollis, B. W.,Hew American Association for the Advancement of Scienc 2011 Science translational medicine Vol.3 No.104
<P>Control of tuberculosis worldwide depends on our understanding of human immune mechanisms, which combat the infection. Acquired T cell responses are critical for host defense against microbial pathogens, yet the mechanisms by which they act in humans remain unclear. We report that T cells, by the release of interferon-γ (IFN-γ), induce autophagy, phagosomal maturation, the production of antimicrobial peptides such as cathelicidin, and antimicrobial activity against Mycobacterium tuberculosis in human macrophages via a vitamin D-dependent pathway. IFN-γ induced the antimicrobial pathway in human macrophages cultured in vitamin D-sufficient sera, but not in sera from African-Americans that have lower amounts of vitamin D and who are more susceptible to tuberculosis. In vitro supplementation of vitamin D-deficient serum with 25-hydroxyvitamin D3 restored IFN-γ-induced antimicrobial peptide expression, autophagy, phagosome-lysosome fusion, and antimicrobial activity. These results suggest a mechanism in which vitamin D is required for acquired immunity to overcome the ability of intracellular pathogens to evade macrophage-mediated antimicrobial responses. The present findings underscore the importance of adequate amounts of vitamin D in all human populations for sustaining both innate and acquired immunity against infection.</P>