Search results for: pupil size
Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 5695

Search results for: pupil size

1705 Elevated Temperature Shot Peening for M50 Steel

Authors: Xinxin Ma, Guangze Tang, Shuxin Yang, Jinguang He, Fan Zhang, Peiling Sun, Ming Liu, Minyu Sun, Liqin Wang

Abstract:

As a traditional surface hardening technique, shot peening is widely used in industry. By using shot peening, a residual compressive stress is formed in the surface which is beneficial for improving the fatigue life of metal materials. At the same time, very fine grains and high density defects are generated in the surface layer which enhances the surface hardness, either. However, most of the processes are carried out at room temperature. For high strength steel, such as M50, the thickness of the strengthen layer is limited. In order to obtain a thick strengthen surface layer, elevated temperature shot peening was carried out in this work by using Φ1mm cast ion balls with a speed of 80m/s. Considering the tempering temperature of M50 steel is about 550 oC, the processing temperature was in the range from 300 to 500 oC. The effect of processing temperature and processing time of shot peening on distribution of residual stress and surface hardness was investigated. As we known, the working temperature of M50 steel can be as high as 315 oC. Because the defects formed by shot peening are unstable when the working temperature goes higher, it is worthy to understand what happens during the shot peening process, and what happens when the strengthen samples were kept at a certain temperature. In our work, the shot peening time was selected from 2 to 10 min. And after the strengthening process, the samples were annealed at various temperatures from 200 to 500 oC up to 60 h. The results show that the maximum residual compressive stress is near 900 MPa. Compared with room temperature shot peening, the strengthening depth of 500 oC shot peening sample is about 2 times deep. The surface hardness increased with the processing temperature, and the saturation peening time decreases. After annealing, the residual compressive stress decreases, however, for 500 oC peening sample, even annealing at 500 oC for 20 h, the residual compressive stress is still over 600 MPa. However, it is clean to see from SEM that the grain size of surface layers is still very small.

Keywords: shot peening, M50 steel, residual compressive stress, elevated temperature

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1704 Laparoscopic Curative Resection for Right-Sided Colonic Tumours: Initial Experience from a Cancer Hospital of a Developing Country

Authors: Awais Naeem, Osama Shakeel, Aamir Ali Syed, Shahid Khattak

Abstract:

Introduction: Laparoscopic right hemicolectomy is an advanced cancer surgery in today's era. The aim of this study was to evaluate the surgical and initial oncological outcomes after curative, laparoscopic resection of right sided colonic tumors. Also to compare our results with those of previous randomized trials. Methods And Procedures: We retrospectively analyzed the medical record files of all the patients who presented to our hospital with the diagnosis of right sided colon carcinoma from January 2012 to December 2017 and underwent laparoscopic right hemicolectomy. Demographics, operative findings and histopathological reports were all recorded on a preformed data sheet. All the analysis was performed on SPSS 20. Results: Total of 48 patients were included. There were 37 male and 11 female patients with mean age of 49.7 (range from 25 – 82). Mean hospital stay was 8.25 ± 3.17 days. Blood loss was 80mls and operative mean time was 240 minutes. Eighteen patients had extended right hemicolectomy. Median length of the specimen retrieved was 31cm (range, 14-59cm). Mean size of tumor was 6.44cm + 2.53. Total number of lymph nodes removed was 20.5 + 8.3. All had R0 resection. Post-operatively 2 patients had pelvic collection and there was no 30 day mortality. In 33 patients there was T3 disease, 5 had T2 and 10 had T4 disease. There was distant recurrence in 4 patients with peritoneal metastasis in 3 and liver metastasis in 1 patient. Forty-six patients are still alive and 44 are disease free. The mean follow-up period was 25.31 (12 to 60) months. Conclusion: Our early experience with Laparascopic Right hemicolectomy as a safe and oncologically feasible surgical option. We attained comparable surgical results with curative intent.

Keywords: right hemicolectomy, right sided colonic tumors, laparoscopic, curative intent

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1703 Generation of Charged Nanoparticles and Their Contribution to the Thin Film and Nanowire Growth during Chemical Vapour Deposition

Authors: Seung-Min Yang, Seong-Han Park, Sang-Hoon Lee, Seung-Wan Yoo, Chan-Soo Kim, Nong-Moon Hwang

Abstract:

The theory of charged nanoparticles suggested that in many Chemical Vapour Depositions (CVD) processes, Charged Nanoparticles (CNPs) are generated in the gas-phase and become a building block of thin films and nanowires. Recently, the nanoparticle-based crystallization has become a big issue since the growth of nanorods or crystals by the building block of nanoparticles was directly observed by transmission electron microscopy observations in the liquid cell. In an effort to confirm charged gas-phase nuclei, that might be generated under conventional processing conditions of thin films and nanowires during CVD, we performed an in-situ measurement using differential mobility analyser and particle beam mass spectrometer. The size distribution and number density of CNPs were affected by process parameters such as precursor flow rate and working temperature. It was shown that many films and nanostructures, which have been believed to grow by individual atoms or molecules, actually grow by the building blocks of such charged nuclei. The electrostatic interaction between CNPs and the growing surface induces the self-assembly into films and nanowires. In addition, the charge-enhanced atomic diffusion makes CNPs liquid-like quasi solid. As a result, CNPs tend to land epitaxial on the growing surface, which results in the growth of single crystalline nanowires with a smooth surface.

Keywords: chemical vapour deposition, charged nanoparticle, electrostatic force, nanostructure evolution, differential mobility analyser, particle beam mass spectrometer

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1702 Crystallinity, Antimicrobial Activity and Dyeing Properties of Chitosan-G-Poly(N-Acryloyl Morpholine) Copolymer

Authors: Fakhreia A. Al Sagheer, Enas I. Ibrahim, Khaled D. Khalil

Abstract:

N-Acryloyl morpholine, NAM, was grafted onto chitosan utilizing homogeneous conditions with 1% acetic acid as the solvent, and potassium persulfate and sodium sulfite as the redox initiator. The effects of various reaction parameters, such as time, temperature, and monomer and initiator concentrations, on the percentage of grafting (G%) and the grafting efficiency (E%) were determined. The graft copolymer showed a remarkably improved crystallinity, as compared to the unmodified chitosan, based on the FESEM, XRD, and DSC results. Chitosan-g-poly(N-acryloyl morpholine) (Cs-PNAM), the copolymer obtained by using this procedure, was characterized by utilizing FTIR, FESEM, TGA, and XRD analysis. As expected, the results of an evaluation of antibacterial and antifungal activities show that the grafted chitosan copolymers exhibit stronger inhibitory effects against both types of microbes than does chitosan. Moreover, the size of the inhibition zone created by the graft copolymer was observed to be proportional to its G% corresponding to its morpholine content. Fortunately, the graft copolymer showed a marked growth inhibition against candidiasis (C.Albicans and C.Kefyr). We conclude that the graft copolymer may be highly effective in the prevention and treatment of candidiasis. In addition, the extent and pH dependence of uptake of different types of dyes (acidic: EBT, and MV; and basic: MB) by grafted chitosan in pH 6.5 aqueous solutions was determined. The results show that, the grafted copolymer exhibited a greater affinity to absorb the acid dyes more than the basic ones especially at relatively low temperature. Thus the modified chitosan can be used, in wastewater treatment, as efficient economic absorbent especially for anionic dyes from the industrial processing effluents.

Keywords: chitosan, N-Acryloyl morpholine, homogeneous grafting, antimicrobial activity, dye uptake

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1701 Deciphering the Action of Neuraminidase in Glioblastoma Models

Authors: Nathalie Baeza-Kallee, Raphaël Bergès, Victoria Hein, Stéphanie Cabaret, Jeremy Garcia, Abigaëlle Gros, Emeline Tabouret, Aurélie Tchoghandjian, Carole Colin, Dominique Figarella-Branger

Abstract:

Glioblastoma (GBM) contains cancer stem cells that are resistant to treatment. GBM cancer stem cell expresses glycolipids recognized by the A2B5 antibody. A2B5, induced by the enzyme ST8 alpha-N-acetyl-neuraminide alpha-2,8-sialyl transferase 3 (ST8Sia3), plays a crucial role in the proliferation, migration, clonogenicity, and tumorigenesis of GBM cancer stem cells. Our aim was to characterize the resulting effects of neuraminidase that remove A2B5 in order to target GBM cancer stem cells. To this end, we set up a GBM organotypic slice model; quantified A2B5 expression by flow cytometry in U87-MG, U87-ST8Sia3, and GBM cancer stem cell lines, treated or not by neuraminidase; performed RNAseq and DNA methylation profiling; and analyzed the ganglioside expression by liquid chromatography-mass spectrometry in these cell lines, treated or not with neuraminidase. Results demonstrated that neuraminidase decreased A2B5 expression, tumor size, and regrowth after surgical removal in the organotypic slice model but did not induce a distinct transcriptomic or epigenetic signature in GBM CSC lines. RNAseq analysis revealed that OLIG2, CHI3L1, TIMP3, TNFAIP2, and TNFAIP6 transcripts were significantly overexpressed in U87-ST8Sia3 compared to U87-MG. RT-qPCR confirmed these results and demonstrated that neuraminidase decreased gene expression in GBM cancer stem cell lines. Moreover, neuraminidase drastically reduced ganglioside expression in GBM cancer stem cell lines. Neuraminidase, by its pleiotropic action, is an attractive local treatment against GBM.

Keywords: cancer stem cell, ganglioside, glioblastoma, targeted treatment

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1700 Experimental Research of Smoke Impact on the Performance of Cylindrical Eight Channel Cyclone

Authors: Pranas Baltrėnas, Dainius Paliulis

Abstract:

Cyclones are widely used for separating particles from gas in energy production objects. Efficiency of normal centrifugal air cleaning devices ranges from 85 to 90%, but weakness of many cyclones is low collection efficiency of particles less than 10 μm in diameter. Many factors have impact on cyclone efficiency – humidity, temperature, gas (air) composition, airflow velocity and etc. Many scientists evaluated only effect of origin and size of PM on cyclone efficiency. Effect of gas (air) composition and temperature on cyclone efficiency still demands contributions. Complex experimental research on efficiency of cylindrical eight-channel system with adjustable half-rings for removing fine dispersive particles (< 20 μm) was carried out. The impact of gaseous smoke components on removal of wood ashes was analyzed. Gaseous components, present in the smoke mixture, with the dynamic viscosity lower than that of same temperature air, decrease the d50 value, simultaneously increasing the overall particulate matter removal efficiency in the cyclone, i.e. this effect is attributed to CO2 and CO, while O2 and NO have the opposite effect. Air temperature influences the d50 value, an increase in air temperature yields an increase in d50 value, i.e. the overall particulate matter removal efficiency declines, the reason for this being an increasing dynamic air viscosity. At 120 °C temperature the d50 value is approximately 11.8 % higher than at air temperature of 20 °C. With an increase in smoke (gas) temperature from 20 °C to 50 °C, the aerodynamic resistance in a 1-tier eight-channel cylindrical cyclone drops from 1605 to 1380 Pa, from 1660 to 1420 Pa in a 2-tier eight-channel cylindrical cyclone, from 1715 to 1450 Pa in a 3-tier eight-channel cylindrical cyclone. The reason for a decline in aerodynamic resistance is the declining gas density. The aim of the paper is to analyze the impact of gaseous smoke components on the eight–channel cyclone with tangential inlet.

Keywords: cyclone, adjustable half-rings, particulate matter, efficiency, gaseous compounds, smoke

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1699 On the Perceived Awareness of Physical Education Teachers on Adoptable ICTs for PE

Authors: Tholokuhle T. Ntshakala, Seraphin D. Eyono Obono

Abstract:

Nations are still finding it quite difficult to win mega sport competitions despite the major contribution of sport to society in terms of social and economic development, personal health, and in education. Even though the world of sports has been transformed into a huge global economy, it is important to note that the first step of sport is usually its introduction to children at school through physical education or PE. In other words, nations who do not win mega sport competitions also suffer from a weak and neglected PE system. This problem of the neglect of PE systems is the main motivation of this research aimed at examining the factors affecting the perceived awareness of physical education teachers on the ICT's that are adoptable for the teaching and learning of physical education. Two types of research objectives will materialize this aim: relevant theories will be identified in relation to the analysis of the perceived ICT awareness of PE teachers and subsequent models will be compiled and designed from existing literature; the empirical testing of such theories and models will also be achieved through the survey of PE teachers from the Camperdown magisterial district of the KwaZulu-Natal province of South Africa. The main hypothesis at the heart of this study is the relationship between the demographics of PE teachers, their behavior both as individuals and as social entities, and their perceived awareness of the ICTs that are adoptable for PE, as postulated by existing literature; except that this study categorizes human behavior under performance expectancy, computer attitude, and social influence. This hypothesis was partially confirmed by the survey conducted by this research in the sense that performance expectancy and teachers’ age, gender, computer usage, and class size were found to be the only factors affecting their awareness of ICT's for physical education.

Keywords: human behavior, ICT Awareness, physical education, teachers

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1698 Investigation of Electrospun Composites Nanofiber of Poly (Lactic Acid)/Hazelnut Shell Powder/Zinc Oxide

Authors: Ibrahim Sengor, Sumeyye Cesur, Ilyas Kartal, Faik Nuzhet Oktar, Nazmi Ekren, Ahmet Talat Inan, Oguzhan Gunduz

Abstract:

In recent years, many researchers focused on nano-size fiber production. Nanofibers have been studied due to their different and superior physical, chemical and mechanical properties. Poly (lactic acid) (PLA), is a type of biodegradable thermoplastic polyester derived from renewable sources used in biomedical owing to its biocompatibility and biodegradability. In addition, zinc oxide is an antibacterial material and hazelnut shell powder is a filling material. In this study, nanofibers were obtained by adding of different ratio Zinc oxide, (ZnO) and hazelnut shell powder at different concentration into Poly (lactic acid) (PLA) by using electrospinning method which is the most common method to obtain nanofibers. After dissolving the granulated polylactic acids in % 1,% 2,% 3 and% 4 with chloroform solvent, they are homogenized by adding tween and hazelnut shell powder at different ratios and then by electrospinning, nanofibers are obtained. Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimeter (DSC) and physical analysis such as density, electrical conductivity, surface tension, viscosity measurement and antimicrobial test were carried out after production process. The resulting structures of the nanofiber possess antimicrobial and antiseptic properties, which are attractive for biomedical applications. The resulting structures of the nanofiber possess antimicrobial, non toxic, self-cleaning and rigid properties, which are attractive for biomedical applications.

Keywords: electrospinning, hazelnut shell powder, nanofibers, poly (lactic acid), zinc oxide

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1697 A Descriptive Study on Micro Living and Its Importance over Large Houses by Understanding Various Scenarios and Case Studies

Authors: Belal Neazi

Abstract:

'Larger Houses Consume More Resources’ – both in construction and during operation. The most important aspect of smaller homes is that it uses less electricity and fuel for construction and maintenance. Here, an urban interpretation of the contemporary minimal existence movement is explained. In an attempt to restrict urban decay and to encourage inner-city renewal, the Tiny House principles are interpreted as alternative ways of dwelling in urban neighbourhoods. These tiny houses are usually pretty different from each other in interior planning, but almost similar in size. The disadvantage of large homes came up when people were asked to vacate as they were not able to pay the massive amount of mortgages. This made them reconsider their housing situation and discover the ideas of minimalism and the general rising inclination in environmental awareness that serve as the basis for the tiny house movement. One of the largest benefits of inhabiting a tiny house is the decrease in carbon footprint. Also, to increase social behaviour and freedom. It’s better for the environmental concern, financial concerns, and desire for more time and freedom. Examples of the tiny house village which are sustaining homeless population and the use of different reclaimed materials for the construction of these tiny houses are explained in the paper. It is proposed in the paper, that these houses will reflect the diversity while proposing an alternative model for the rehabilitation of decaying row-homes and the renewal of fading communities. The core objective is to design small or micro spaces for the economically backward people of the place and increase their social behaviour and freedom. Also, it’s better for the environmental concern, financial concerns, and desire for more time and freedom.

Keywords: city renewal, environmental concern, micro-living, tiny house

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1696 The Security Trade-Offs in Resource Constrained Nodes for IoT Application

Authors: Sultan Alharby, Nick Harris, Alex Weddell, Jeff Reeve

Abstract:

The concept of the Internet of Things (IoT) has received much attention over the last five years. It is predicted that the IoT will influence every aspect of our lifestyles in the near future. Wireless Sensor Networks are one of the key enablers of the operation of IoTs, allowing data to be collected from the surrounding environment. However, due to limited resources, nature of deployment and unattended operation, a WSN is vulnerable to various types of attack. Security is paramount for reliable and safe communication between IoT embedded devices, but it does, however, come at a cost to resources. Nodes are usually equipped with small batteries, which makes energy conservation crucial to IoT devices. Nevertheless, security cost in terms of energy consumption has not been studied sufficiently. Previous research has used a security specification of 802.15.4 for IoT applications, but the energy cost of each security level and the impact on quality of services (QoS) parameters remain unknown. This research focuses on the cost of security at the IoT media access control (MAC) layer. It begins by studying the energy consumption of IEEE 802.15.4 security levels, which is followed by an evaluation for the impact of security on data latency and throughput, and then presents the impact of transmission power on security overhead, and finally shows the effects of security on memory footprint. The results show that security overhead in terms of energy consumption with a payload of 24 bytes fluctuates between 31.5% at minimum level over non-secure packets and 60.4% at the top security level of 802.15.4 security specification. Also, it shows that security cost has less impact at longer packet lengths, and more with smaller packet size. In addition, the results depicts a significant impact on data latency and throughput. Overall, maximum authentication length decreases throughput by almost 53%, and encryption and authentication together by almost 62%.

Keywords: energy consumption, IEEE 802.15.4, IoT security, security cost evaluation

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1695 Innovative Technologies for Aeration and Feeding of Fish in Aquaculture with Minimal Impact on the Environment

Authors: Vasile Caunii, Andreea D. Serban, Mihaela Ivancia

Abstract:

The paper presents a new approach in terms of the circular economy of technologies for feeding and aeration of accumulations and water basins for fish farming and aquaculture. Because fish is and will be one of the main foods on the planet, the use of bio-eco-technologies is a priority for all producers. The technologies proposed in the paper want to reduce by a substantial percentage the costs of operation of ponds and water accumulation, using non-polluting technologies with minimal impact on the environment. The paper proposes two innovative, intelligent systems, fully automated that use a common platform, completely eco-friendly. One system is intended to aerate the water of the fish pond, and the second is intended to feed the fish by dispersing an optimal amount of fodder, depending on population size, age and habits. Both systems use a floating platform, regenerative energy sources, are equipped with intelligent and innovative systems, and in addition to fully automated operation, significantly reduce the costs of aerating water accumulations (natural or artificial) and feeding fish. The intelligent system used for feeding, in addition, to reduce operating costs, optimizes the amount of food, thus preventing water pollution and the development of bacteria, microorganisms. The advantages of the systems are: increasing the yield of fish production, these are green installations, with zero pollutant emissions, can be arranged anywhere on the water surface, depending on the user's needs, can operate autonomously or remotely controlled, if there is a component failure, the system provides the operator with accurate data on the issue, significantly reducing maintenance costs, transmit data about the water physical and chemical parameters.

Keywords: bio-eco-technologies, economy, environment, fish

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1694 Management Effects on Different Sustainable Agricultural with Diverse Topography

Authors: Kusay Wheib, Alexandra Krvchenko

Abstract:

Crop yields are influenced by many factors, including natural ones, such as soil and environmental characteristics of the agricultural land, as well as manmade ones, such as management applications. One of the factors that frequently affect crop yields in undulating Midwest landscapes is topography, which controls the movement of water and nutrients necessary for plant life. The main objective of this study is to examine how field topography influences performance of different management practices in undulated terrain of southwest Michigan. A total of 26 agricultural fields, ranging in size from 1.1 to 7.4 ha, from the Scale-Up at Kellogg Biological Station were included in the study. The two studied factors were crop species with three levels, i.e., corn (Zea mays L.) soybean (Glycine max L.), and wheat (Triticum aestivum L.), and management practice with three levels, i.e., conventional, low input, and organic managements. They were compared under three contrasting topographical settings, namely, summit (includes summits and shoulders), slope (includes backslopes), and depression (includes footslope and toeslope). Yield data of years 2007 through 2012 was processed, cleaned, and filtered, average yield then was calculated for each field, topographic setting, and year. Topography parameters, including terrain, slope, curvature, flow direction and wetness index were computed under ArcGIS environment for each topographic class of each field to seek their effects on yield. Results showed that topographical depressions produced greatest yields in most studied fields, while managements with chemical inputs, both low input and conventional, resulted in higher yields than the organic management.

Keywords: sustainable agriculture, precision agriculture, topography, yield

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1693 Enhanced Wound Healing Efficacy of Cordycepin-Melittin Nanoconjugate in Excised Wounds of Diabetic Rats

Authors: Mohammed Flaih Alotaibi, Rasheed Ahemad Shaik, Mohammed Z. Nasrullah

Abstract:

Diabetic foot ulcers are the foremost global healthcare burden. Hyperglycemia in diabetics is incriminating in impeding wound healing and it can allow for more severe medical issues. The study was intended to establish a nanoconjugate of cordycepin-melittin (COR-MEL) and evaluate its healing effects in wounded diabetic rats. Diabetes induced by injecting streptozotocin intraperitoneally (50 mg/kg, body weight). Therefore, animals were classified into various groups; diabetic untreated, vehicle-treated, COR alone, MEL alone, and COR-MEL nanoconjugate treated, respectively. Animals with diabetes were exposed to excision and treated with Vehicle, COR, MEL, or COR-MEL nanoconjugate topically. After 14 days, the wounded skin was sliced and subjected to histological and biochemical assessments. The formulated nanoconjugate has a particle size of 253.5± 17.4 nm by a polydispersity index of 0.36 ± 0.05, and a zeta potential of 1.72 ± 0.3 mV. The study demonstrated an accelerated wound contraction in COR-MEL-treated diabetic rats, which was further validated by histological analysis. The nanoconjugate further exhibited antioxidant activities by inhibiting the accumulation of malondialdehyde and exhaustion of superoxide dismutase and glutathione peroxidase enzymatic activities. The nanoconjugate further demonstrated an enhanced anti-inflammatory activity by retarding the expression of proinflammatory cytokines (IL-6 and TNF-α). Additionally, the nanoconjugate exhibits a strong expression of growth factors (TGF-β1, VEGF-A, and PDGFR-β), indicating enrichment of proliferation. Likewise, nanoconjugate increased the concentration of hydroxyproline as well as the mRNA expression of collagen, type I, alpha 1. Thus, it is concluded that the nanoconjugate possesses a potent wound-healing activity in diabetic rats via antioxidant, anti-inflammatory, and pro-angiogenetic mechanisms.

Keywords: diabetic wounds, cordycepin, melittin, nanoconjugate, wound healing

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1692 Synthesis of Pd Nanoparticles Confined in Graphene Oxide Framework as Nano Catalyst with Improved Activity and Recyclability in Suzuki-Miyaura Cross-Coupling Reaction

Authors: Thuy Phuong Nhat Tran, Ashutosh Thakur, Toshiaki Taniike

Abstract:

Recently, covalently linked graphene oxide frameworks (GOFs) have attracted considerable attention in gas absorbance and water purification as well-defined microporous materials. In spite of their potential advantages such as a controllable pore dimension, adjustable hydrophobicity, and structural stability, these materials have been scarcely employed in heterogeneous catalysis. Here we demonstrate a novel and facile method to synthesize Pd nanoparticles (NPs) confined in a GOF (Pd@GOF). The GOF with uniform interlayer space was obtained by the intercalation of diboronic acid between graphene oxide layers. It was found that Pd NPs were generated inside the graphitic gallery spaces of the GOF, and thus, formed Pd NPs were well-dispersed with a narrow particle size distribution. The synthesized Pd@GOF emerged as an efficient nanocatalyst based on its superior performance (product yield and recyclability) toward Suzuki-Miyaura cross-coupling reaction in both polar and apolar solvents, which has been hardly observed for previously reported graphene-based Pd nanocatalysts. Furthermore, the rational comparison of the catalytic performance between two kinds of Pd@GOF (Pd NPs encapsulated in a diboronic ester-intercalated GOF and in a monoboronic ester-intercalated GOF) firmly confirmed the essential role of a rigid framework design in the stabilization of Pd NPs. Based on these results, the covalently assembled GOF was proposed as a promising scaffold for hosting noble metal NPs to construct desired metal@GOF nanocatalysts with improved activity and durability.

Keywords: graphene oxide framework, palladium nanocatalyst, pore confinement, Suzuki-Miyaura cross-coupling reaction

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1691 Bio Energy from Metabolic Activity of Bacteria in Plant and Soil Using Novel Microbial Fuel Cells

Authors: B. Samuel Raj, Solomon R. D. Jebakumar

Abstract:

Microbial fuel cells (MFCs) are an emerging and promising method for achieving sustainable energy since they can remove contaminated organic matter and simultaneously generate electricity. Our approach was driven in three different ways like Bacterial fuel cell, Soil Microbial fuel cell (Soil MFC) and Plant Microbial fuel cell (Plant MFC). Bacterial MFC: Sulphate reducing bacteria (SRB) were isolated and identified as the efficient electricigens which is able to produce ±2.5V (689mW/m2) and it has sustainable activity for 120 days. Experimental data with different MFC revealed that high electricity production harvested continuously for 90 days 1.45V (381mW/m2), 1.98V (456mW/m2) respectively. Biofilm formation was confirmed on the surface of the anode by high content screening (HCS) and scanning electron Microscopic analysis (SEM). Soil MFC: Soil MFC was constructed with low cost and standard Mudwatt soil MFC was purchased from keegotech (USA). Vermicompost soil (V1) produce high energy (± 3.5V for ± 400 days) compared to Agricultural soil (A1) (± 2V for ± 150 days). Biofilm formation was confirmed by HCS and SEM analysis. This finding provides a method for extracting energy from organic matter, but also suggests a strategy for promoting the bioremediation of organic contaminants in subsurface environments. Our Soil MFC were able to run successfully a 3.5V fan and three LED continuously for 150 days. Plant MFC: Amaranthus candatus (P1) and Triticum aestivium (P2) were used in Plant MFC to confirm the electricity production from plant associated microbes, four uniform size of Plant MFC were constructed and checked for energy production. P2 produce high energy (± 3.2V for 40 days) with harvesting interval of two times and P1 produces moderate energy without harvesting interval (±1.5V for 24 days). P2 is able run 3.5V fan continuously for 10days whereas P1 needs optimization of growth conditions to produce high energy.

Keywords: microbial fuel cell, biofilm, soil microbial fuel cell, plant microbial fuel cell

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1690 Evaluation of Egg Quality Parameters in the Isa Brown Line in Intensive Production Systems in the Ocaña Region, Norte de Santander

Authors: Meza-Quintero Myriam, Lobo Torrado Katty Andrea, Sanchez Picon Yesenia, Hurtado-Lugo Naudin

Abstract:

The objective of the study was to evaluate the internal and external quality of the egg in the three production housing systems: floor, cage, and grazing of laying birds of the Isa Brown line, in the laying period between weeks 35 to 41; 135 hens distributed in 3 treatments of 45 birds per repetition were used (the replicas were the seven weeks of the trial). The feeding treatment supplied in the floor and cage systems contained 114 g/bird/day; for the grazing system, 14 grams less concentrate was provided. Nine eggs were collected to be studied and analyzed in the animal nutrition laboratory (3 eggs per housing system). The random statistical model was implemented: for the statistical analysis of the data, the statistical software of IBM® Statistical Products and Services Solution (SPSS) version 2.3 was used. The evaluation and follow-up instruments were the vernier caliper for the measurement in millimeters, a YolkFan™16 from Roche DSM for the evaluation of the egg yolk pigmentation, a digital scale for the measurement in grams, a micrometer for the measurement in millimeters and evaluation in the laboratory using dry matter, ashes, and ethereal extract. The results suggested that equivalent to the size of the egg (0.04 ± 3.55) and the thickness of the shell (0.46 ± 3.55), where P-Value> 0.05 was obtained, weight albumen (0.18 ± 3.55), albumen height (0.38 ± 3.55), yolk weight (0.64 ± 3.55), yolk height (0.54 ± 3.55) and for yolk pigmentation (1.23 ± 3.55). It was concluded that the hens in the three production systems, floor, cage, and grazing, did not show significant statistical differences in the internal and external quality of the chicken in the parameters studied egg for the production system.

Keywords: biological, territories, genetic resource, egg

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1689 Investigating the Relationship of Social Capital with Student's Aggressive Behavior: Case Study of Male Students of Middle School in Isfahan

Authors: Mohammadreza Kolaei, Vahid Ghasemi, Ebrahim Ansari

Abstract:

This research was carried out with the aim of investigating the relationship between social capital and aggressive behavior of students (Case study: male students of middle school in Isfahan). In terms of methodology, this research is an applied research which is done by descriptive-analytical method and survey method. The instrument for collecting the data was a questionnaire consisting of: questionnaire for measuring aggressive behavior and social capital questionnaire, which was used after the validity and reliability of this questionnaire. On the other hand, the statistical population of the study consisted of all students in the guidance school of Isfahan in the academic year of 2016. For determining the sample size, the Kerjesy and Morgan tables were used and the sampling method of this multi-stage random sampling was used. After collecting the data, they were analyzed by SPSS software. The findings of the research showed that at 95% confidence level, the student's social capital increases, reducing his aggressiveness. Also, the amount of student aggression is estimated at 4% according to its social capital. Also, with increasing social capital of the school, the student's student aggression is reduced, with the student's student aggression's exposure to her social capital being estimated at 3%. On the other hand, increasing the amount of mother's presence in the home decreases the amount of student aggression. Also, the amount of student aggression is estimated at 1% according to the amount of mother's presence in her home. Ultimately, the amount of student aggression decreases with increasing presence of father at home. Also, the amount of student aggression is estimated at 2% according to the variable of father's presence in his home.

Keywords: investigating, social capital, aggressive behavior, students, middle school, Isfahan

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1688 A Systematic Review and Meta-Analysis of Diabetes Ketoacidosis in Ethiopia

Authors: Addisu Tadesse Sahile, Mussie Wubshet Teka, Solomon Muluken Ayehu

Abstract:

Background: Diabetes is one of the common public health problems of the century that was estimated to affect one in a tenth of the world population by the year 2030, where diabetes ketoacidosis is one of its common acute complications. Objectives: The aim of this review was to assess the magnitude of diabetes ketoacidosis among patients with type 1 diabetes in Ethiopia. Methods: A systematic data search was done across Google Scholar, PubMed, Web of Science, and African Online Journals. Two reviewers carried out the selection, reviewing, screening, and extraction of the data independently by using a Microsoft Excel Spreadsheet. The Joanna Briggs Institute's prevalence critical appraisal tool was used to assess the quality of evidence. All studies conducted in Ethiopia that reported diabetes ketoacidosis rates among type 1 diabetes were included. The extracted data was imported into the comprehensive meta-analysis version 3.0 for further analysis. Heterogeneity was checked by Higgins’s method, whereas the publication bias was checked by using Beggs and Eggers’s tests. A random-effects meta-analysis model with a 95% confidence interval was computed to estimate the pooled prevalence. Furthermore, subgroup analysis based on the study area (Region) and the sample size was carried out. Result and Conclusion: After review made across a total of 51 articles, of which 12 articles fulfilled the inclusion criteria and were included in the meta-analysis. The pooled prevalence of diabetes ketoacidosis among type 1 diabetes in Ethiopia was 53.2% (95%CI: 43.1%-63.1%). The highest prevalence of DKA was reported in the Tigray region of Ethiopia, whereas the lowest was reported in the Southern region of Ethiopia. Concerned bodies were suggested to work on the escalated burden of diabetes ketoacidosis in Ethiopia.

Keywords: DKA, Type 1 diabetes, Ethiopia, systematic review, meta-analysis

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1687 Highly Oriented and Conducting SNO2 Doped Al and SB Layers Grown by Automatic Spray Pyrolysis Method

Authors: A.Boularouk, F. Chouikh, M. Lamri, H. Moualkia, Y. Bouznit

Abstract:

The principal aim of this study is to considerably reduce the resistivity of the SnO2 thin layers. In this order, we have doped tin oxide with aluminum and antimony incorporation with different atomic percentages (0 and 4%). All the pure and doped SnO2 films were grown by simple, flexible and cost-effective Automatic Spray Pyrolysis Method (ASPM) on glass substrates at a temperature of 350 °C. The microstructural, optical, morphological and electrical properties of the films have been studied. The XRD results demonstrate that all films have polycrystalline nature with a tetragonal rutile structure and exhibit the (200) preferential orientation. It has been observed that all the dopants are soluble in the SnO2 matrix without forming secondary phases. However, dopant introduction does not modify the film growth orientation. The crystallite size of the pure SnO2 film is about 36 nm. The films are highly transparent in the visible region with an average transmittance reaching up to 80% and it slightly reduces with increasing doping concentration (Al and Sb). The optical band gap value was evaluated between 3.60 eV and 3.75 eV as a function of doping. The SEM image reveals that all films are nanostructured, densely continuous, with good adhesion to the substrate. We note again that the surface morphology change with the type and concentration dopant. The minimum resistivity is 0.689*10-4, which is observed for SnO2 film doped 4% Al. This film shows better properties and is considered the best among all films. Finally, we concluded that the physical properties of the pure and doped SnO2 films grown on a glass substrate by ASPM strongly depend on the type and concentration dopant (Al and Sb) and have highly desirable optical and electrical properties and are promising materials for several applications.

Keywords: tin oxide, automatic spray, Al and Sb doped, transmittance, MEB, XRD and UV-VIS

Procedia PDF Downloads 51
1686 A Design for Customer Preferences Model by Cluster Analysis of Geometric Features and Customer Preferences

Authors: Yuan-Jye Tseng, Ching-Yen Chen

Abstract:

In the design cycle, a main design task is to determine the external shape of the product. The external shape of a product is one of the key factors that can affect the customers’ preferences linking to the motivation to buy the product, especially in the case of a consumer electronic product such as a mobile phone. The relationship between the external shape and the customer preferences needs to be studied to enhance the customer’s purchase desire and action. In this research, a design for customer preferences model is developed for investigating the relationships between the external shape and the customer preferences of a product. In the first stage, the names of the geometric features are collected and evaluated from the data of the specified internet web pages using the developed text miner. The key geometric features can be determined if the number of occurrence on the web pages is relatively high. For each key geometric feature, the numerical values are explored using the text miner to collect the internet data from the web pages. In the second stage, a cluster analysis model is developed to evaluate the numerical values of the key geometric features to divide the external shapes into several groups. Several design suggestion cases can be proposed, for example, large model, mid-size model, and mini model, for designing a mobile phone. A customer preference index is developed by evaluating the numerical data of each of the key geometric features of the design suggestion cases. The design suggestion case with the top ranking of the customer preference index can be selected as the final design of the product. In this paper, an example product of a notebook computer is illustrated. It shows that the external shape of a product can be used to drive customer preferences. The presented design for customer preferences model is useful for determining a suitable external shape of the product to increase customer preferences.

Keywords: cluster analysis, customer preferences, design evaluation, design for customer preferences, product design

Procedia PDF Downloads 172
1685 Socio-economic Baselining of Selected Icrmp Sites in Southwestern Cebu, Central Philippines

Authors: Rachel Luz P. Vivas-rica, Gloria G. Delan, Christine M. Corrales, Alfonso S. Piquero, Irene A. Monte

Abstract:

ABSTRACT -Selected Integrated Coastal Resource Management Program (ICRMP) sites in Southwestern Cebu were studied employing a stratified proportional sampling method using semi-structured questionnaires. Four hundred sixteen (416) respondents from five barangays with Marine Protected Areas (MPAs) and four barangays without marine sanctuaries were considered in the study. Results showed similarity of socio-economic characteristics in terms of average age, majority were middle aged, and married. Households were male dominated, obtained low education for both MPA and Non-MPA areas. In terms of occupation, majority in both areas engaged in fulltime fishing however part time jobs as carpenter, construction worker, driver or farmer as another income source. Most of the households were nuclear families with average family size of five for both MPA and Non-MPA. Fishing experience ranged from less than 1 year to more than 50 years. Fishing grounds were within the 15 kilometer radius of each considered site. Even if the respondents were totally dependent on fishing as a major source of income, still their income is way below the poverty threshold both in the MPA and Non-MPA areas. This is further explained by the marginality of their fishing implements wherein majority uses gill nets, hook & line, spear and paddle boat in fishing. Their volume of catch from an average of 6 hours fishing expedition ranges from half a kilo to a maximum of 4 kilos. Majority are not members of fishing groups or organizations.

Keywords: integrated coastal resource management program, marine protected areas, socio-economic, poverty threshold

Procedia PDF Downloads 505
1684 Carbon Blacks: A Broad Type of Carbon Materials with Different Electrocatalytic Activity to Produce H₂O₂

Authors: Alvaro Ramírez, Martín Muñoz-Morales, Ester López- Fernández, Javier Llanos, C. Ania

Abstract:

Carbon blacks are value-added materials typically produced through the incomplete combustion or thermal decomposition of hydrocarbons. Traditionally, they have been used as catalysts in many different applications, but in the last decade, their potential in green chemistry has gained significant attention. Among them, the electrochemical production of H₂O₂ has attracted interest because of their properties as high oxidant capacity or their industrial interest as a bleaching agent. Carbon blacks are commonly used in this application in a catalytic ink that is drop-casted on supporting electrodes and acts as catalysts for the electrochemical production of H₂O₂ through oxygen reduction reaction (ORR). However, the different structural and electrochemical behaviors of each type of carbon black influence their applications. In this line, the term ‘carbon black’, has to be considered as a generic name that does not guarantee any physicochemical properties if any further description is mentioned. In fact, different specific surface area (SSA), surface functional groups, porous structure, and electro catalysts effect seem very important for electrochemical applications, and considerable differences were found during the analysis of four types of carbon blacks. Thus, the aim of this work is to evaluate the influence of SSA, porous structure, oxygen functional groups, and structural defects to differentiate among these carbon blacks (e.g. Vulcan XC72, Superior Graphite Co, Printex XE2, and Prolabo) for H₂O₂ production via ORR, using carbon paper as electrode support with improved selectivity and efficiency. Results indicate that the number and size of pores, along with surface functional groups, are key parameters that significantly affect the overall process efficiency.

Keywords: carbon blacks, oxygen reduction reaction, hydrogen peroxide, porosity, surface functional groups

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1683 Impact of an Instructional Design Model in a Mathematics Game for Enhancing Students’ Motivation in Developing Countries

Authors: Shafaq Rubab

Abstract:

One of the biggest reasons of dropouts from schools is lack of motivation and interest among the students, particularly in mathematics. Many developing countries are facing this problem and this issue is lowering the literacy rate in these developing countries. The best solution for increasing motivation level and interest among the students is using tablet game-based learning. However, a pedagogically sound game required a well-planned instructional design model to enhance learner’s attention and confidence otherwise effectiveness of the learning games suffers badly. This research aims to evaluate the impact of the pedagogically sound instructional design model on students’ motivation by using tablet game-based learning. This research was conducted among the out-of-school-students having an age range from 7 to 12 years and the sample size of two hundred students was purposively selected without any gender discrimination. Qualitative research was conducted by using a survey tool named Instructional Material Motivational Survey (IMMS) adapted from Keller Arcs model. A comparison of results from both groups’ i.e. experimental group and control group revealed that motivation level of the students taught by the game was higher than the students instructed by using conventional methodologies. Experimental group’s students were more attentive, confident and satisfied as compared to the control group’s students. This research work not only promoted the trend of digital game-based learning in developing countries but also supported that a pedagogically sound instructional design model utilized in an educational game can increase the motivation level of the students and can make the learning process a totally immersive and interactive fun loving activity.

Keywords: digital game-based learning, student’s motivation, instructional design model, learning process

Procedia PDF Downloads 411
1682 The Role of Sustainable Financing Models for Smallholder Tree Growers in Ghana

Authors: Raymond Awinbilla

Abstract:

The call for tree planting has long been set in motion by the government of Ghana. The Forestry Commission encourages plantation development through numerous interventions including formulating policies and enacting legislations. However, forest policies have failed and that has generated a major concern over the vast gap between the intentions of national policies and the realities established. This study addresses three objectives;1) Assessing the farmers' response and contribution to the tree planting initiative, 2) Identifying socio-economic factors hindering the development of smallholder plantations as a livelihood strategy, and 3) Determining the level of support available for smallholder tree growers and the factors influencing it. The field work was done in 12 farming communities in Ghana. The article illuminates that farmers have responded to the call for tree planting and have planted both exotic and indigenous tree species. Farmers have converted 17.2% (369.48ha) of their total land size into plantations and have no problem with land tenure. Operations and marketing constraints include lack of funds for operations, delay in payment, low price of wood, manipulation of price by buyers, documentation by buyers, and no ready market for harvesting wood products. Environmental institutions encourage tree planting; the only exception is with the Lands Commission. Support availed to farmers includes capacity building in silvicultural practices, organisation of farmers, linkage to markets and finance. Efforts by the Government of Ghana to enhance forest resources in the country could rely on the input of local populations.

Keywords: livelihood strategy, marketing constraints, environmental institutions, silvicultural practices

Procedia PDF Downloads 43
1681 Physicochemical and Thermal Characterization of Starch from Three Different Plantain Cultivars in Puerto Rico

Authors: Carmen E. Pérez-Donado, Fernando Pérez-Muñoz, Rosa N. Chávez-Jáuregui

Abstract:

Plantain contains starch as the majority component and represents a relevant source of this carbohydrate. Starches from different cultivars of plantain and bananas have been studied for industrialization purposes due to their morphological and thermal characteristics and their influence on food products. This study aimed to characterize the physical, chemical, and thermal properties of starch from three different plantains cultivated in Puerto Rico: Maricongo, Maiden, and FHIA 20. Amylose and amylopectin content, color, granular size, morphology, and thermal properties were determined. According to the content of amylose in starches, FHIA 20 starch presented minor content of the three cultivars studied. In terms of color, Maiden and FHIA 20 starch exhibited a significantly higher whiteness index comparing their values with Maricongo starch. The starches of the three cultivars had an elongated-ovoid morphology, with a smooth surface and a non-porous appearance. Regardless of similarities in their morphology, FHIA 20 showed a lower aspect ratio, which meant that their granules tended to be more elongated granules. Comparing the thermal properties of starches, it was found that the initial gelatinization temperature of the starch of the cultivars was similar. However, the final gelatinization temperatures of the starches belonging to the cultivars Maricongo (79.69°C) and Maiden (77.40°C) were similar, whereas FHIA 20 starch presented a noticeably higher final gelatinization temperature (87.95°C) and transition enthalpy. Despite source similarities, starches from plantain cultivars showed differences in their composition and thermal behavior. Therefore, this represents an opportunity to diversify their use in food-related applications.

Keywords: aspect ratio, morphology, Musa spp., starch, thermal properties

Procedia PDF Downloads 243
1680 A Study of Soft Soil Improvement by Using Lime Grit

Authors: Ashim Kanti Dey, Briti Sundar Bhowmik

Abstract:

This paper presents an idea to improve the soft soil by using lime grits which are normally produced as waste product in the paper manufacturing industries. This waste material cannot be used as a construction material because of its light weight, uniform size and poor compaction control. With scarcity in land, effective disposal of lime grit is a major concern of all paper manufacturing industries. Considering its non-plasticity and high permeability characteristics the lime grit may suitably be used as a drainage material for speedy consolidation of cohesive soil. It can also be used to improve the bearing capacity of soft clay. An attempt has been made in this paper to show the usefulness of lime grit in improving the bearing capacity of shallow foundation resting on soft clayey soil. A series of undrained unconsolidated cyclic triaxial tests performed at different area ratios and at three different water contents shows that dynamic shear modulus and damping ratio can be substantially improved with lime grit. Improvement is observed to be more in case of higher area ratio and higher water content. Static triaxial tests were also conducted on lime grit reinforced clayey soil after application of 50 load cycles to determine the effect of lime grit columns on cyclically loaded clayey soils. It is observed that the degradation is less for lime grit stabilized soil. A study of model test with different area ratio of lime column installation is also included to see the field behaviour of lime grit reinforced soil.

Keywords: lime grit column, area ratio, shear modulus, damping ratio, strength ratio, improvement factor, degradation factor

Procedia PDF Downloads 488
1679 On the Monitoring of Structures and Soils by Tromograph

Authors: Magarò Floriana, Zinno Raffaele

Abstract:

Since 2009, with the coming into force of the January 14, 2008 Ministerial Decree "New technical standards for construction", and the explanatory ministerial circular N°.617 of February 2, 2009, the question of seismic hazard and the design of seismic-resistant structures in Italy has acquired increasing importance. One of the most discussed aspects in recent Italian and international scientific literature concerns the dynamic interaction between land and structure, and the effects which dynamic coupling may have on individual buildings. In effect, from systems dynamics, it is well known that resonance can have catastrophic effects on a stimulated system, leading to a response that is not compatible with the previsions in the design phase. The method used in this study to estimate the frequency of oscillation of the structure is as follows: the analysis of HVSR (Horizontal to Vertical Spectral Ratio) relations. This allows for evaluation of very simple oscillation frequencies for land and structures. The tool used for data acquisition is an experimental digital tromograph. This is an engineered development of the experimental Languamply RE 4500 tromograph, equipped with an engineered amplification circuit and improved electronically using extremely small electronic components (size of each individual amplifier 16 x 26 mm). This tromograph is a modular system, completely "free" and "open", designed to interface Windows, Linux, OSX and Android with the outside world. It an amplifier designed to carry out microtremor measurements, yet which will also be useful for seismological and seismic measurements in general. The development of single amplifiers of small dimension allows for a very clean signal since being able to position it a few centimetres from the geophone eliminates cable “antenna” phenomena, which is a necessary characteristic in seeking to have signals which are clean at the very low voltages to be measured.

Keywords: microtremor, HVSR, tromograph, structural engineering

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1678 In a Situation of Great Distress: Cross Border Migration and the Quest for Enduring Security in North-East Nigeria

Authors: Nuhu Bitrus Mailabari

Abstract:

Nigeria is a highly multifarious nation trapped between affluence and affliction. On one hand, the state has vast territorial size, economic strength, relative internal cohesion, and good external linkages. On the other, it is bedeviled with enormous challenges. It is common knowledge that the North-East geo-political zone has suffered colossal destruction for the most part of the last ten years due to the activities of the insurgent group Boko Haram. Several factors (political, economic, religious, socio-cultural) have been credited with the heightened insecurity in the region. Without a doubt, the security crisis in the region has rekindled several discussions critical to Nigeria’s security architecture. However, the debate on finding an enduring solution to the devastation in the North East continually neglects the nexus between cross border migration and national security. Using content analysis, this paper debates two main issues that continue to affect security in the North East. One, the cumulative impact of the Economic Community of West African States (ECOWAS) protocol on the free movement of people and goods. Two, the porous nature of Nigeria’s borders. Theoretically, the paper will rely on the systems theory because of its broad focus on structure, linkage, and process. The work concludes in twofold. First, that cross border migration and poor border management processes further worsened the political and socio-economic conditions of a region that is already in a bad state. Secondly, in addition to the existing strategies, Nigeria must develop a holistic approach including new methods of handling cross border movements in solving the security issues.

Keywords: border, cross border, migration, Nigeria, northeast region, security

Procedia PDF Downloads 146
1677 Faster Pedestrian Recognition Using Deformable Part Models

Authors: Alessandro Preziosi, Antonio Prioletti, Luca Castangia

Abstract:

Deformable part models achieve high precision in pedestrian recognition, but all publicly available implementations are too slow for real-time applications. We implemented a deformable part model algorithm fast enough for real-time use by exploiting information about the camera position and orientation. This implementation is both faster and more precise than alternative DPM implementations. These results are obtained by computing convolutions in the frequency domain and using lookup tables to speed up feature computation. This approach is almost an order of magnitude faster than the reference DPM implementation, with no loss in precision. Knowing the position of the camera with respect to horizon it is also possible prune many hypotheses based on their size and location. The range of acceptable sizes and positions is set by looking at the statistical distribution of bounding boxes in labelled images. With this approach it is not needed to compute the entire feature pyramid: for example higher resolution features are only needed near the horizon. This results in an increase in mean average precision of 5% and an increase in speed by a factor of two. Furthermore, to reduce misdetections involving small pedestrians near the horizon, input images are supersampled near the horizon. Supersampling the image at 1.5 times the original scale, results in an increase in precision of about 4%. The implementation was tested against the public KITTI dataset, obtaining an 8% improvement in mean average precision over the best performing DPM-based method. By allowing for a small loss in precision computational time can be easily brought down to our target of 100ms per image, reaching a solution that is faster and still more precise than all publicly available DPM implementations.

Keywords: autonomous vehicles, deformable part model, dpm, pedestrian detection, real time

Procedia PDF Downloads 261
1676 Competing Interactions, and Magnetization Dynamics in Doped Rare-Earth Manganites Nanostructural System

Authors: Wiqar Hussain Shah

Abstract:

The Structural, magnetic and transport behavior of La1-xCaxMnO3+ (x=0.48, 0.50, 0.52 and 0.55 and =0.015) compositions close to charge ordering, was studied through XRD, resistivity, DC magnetization and AC susceptibility measurements. With time and thermal cycling (T<300 K) there is an irreversible transformation of the low-temperature phase from a partially ferromagnetic and metallic to one that is less ferromagnetic and highly resistive. For instance, an increase of resistivity can be observed by thermal cycling, where no effect is obtained for lower Ca concentration. The time changes in the magnetization are logarithmic in general and activation energies are consistent with those expected for electron transfer between Mn ions. The data suggest that oxygen non-stoichiometry results in mechanical strains in this two-phase system, leading to the development of irreversible metastable states, which relax towards the more stable charge-ordered and antiferromagnetic microdomains at the nano-meter size. This behavior is interpreted in terms of strains induced charge localization at the interface between FM/AFM domains in the antiferromagnetic matrix. Charge, orbital ordering and phase separation play a prominent role in the appearance of such properties, since they can be modified in a spectacular manner by external factor, making the different physical properties metastable. Here we describe two factors that deeply modify those properties, viz. the doping concentration and the thermal cycling. The metastable state is recovered by the high temperature annealing. We also measure the magnetic relaxation in the metastable state and also the revival of the metastable state (in a relaxed sample) due to high temperature (800 ) thermal treatment.

Keywords: Rare-earth maganites, nano-structural materials, doping effects on electrical, magnetic properties, competing interactions

Procedia PDF Downloads 112