Search results for: ring compression tests

Authors: M. Ghosh, A. Miroux, L. A. I. Kestens

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At molecular or micrometre scale, practically all materials are neither homogeneous nor isotropic. The concept of texture is used to identify the structural features that cause the properties of a material to be anisotropic. For metallic materials, the anisotropy of the mechanical behaviour originates from the crystallographic nature of plastic deformation, and is therefore controlled by the crystallographic texture. Anisotropy in mechanical properties often constitutes a disadvantage in the application of materials, as it is often illustrated by the earing phenomena during drawing. However, advantages may also be attained when considering other properties (e.g. optimization of magnetic behaviour to a specific direction) by controlling texture through thermo-mechanical processing). Nevertheless, in order to have better control over the final properties it is essential to relate texture with materials processing route and subsequently optimise their performance. However, up to date, few studies have been reported about the evolution of texture in 6061 aluminium alloy during warm processing (from room temperature to 250ºC). In present investigation, recrystallized 6061 aluminium alloy samples were subjected to tensile and plane strain compression (PSC) at room and warm temperatures. The gradual change of texture following both deformation modes were measured and discussed. Tensile tests demonstrate the mechanism at low strain while PSC does the same at high strain and eventually simulate the condition of rolling. Cube dominated texture of the initial rolled and recrystallized AA6061 sheets were replaced by domination of S and R components after PSC at room temperature, warm temperature (250ºC) though did not reflect any noticeable deviation from room temperature observation. It was also noticed that temperature has no significant effect on the evolution of grain morphology during PSC. The band contrast map revealed that after 30% deformation the substructure inside the grain is mainly made of series of parallel bands. A tendency for decrease of Cube and increase of Goss was noticed after tensile deformation compared to as-received material. Like PSC, texture does not change after deformation at warm temperature though. n-fibre was noticed for all the three textures from Goss to Cube.

Keywords: AA 6061, deformation, temperature, tensile, PSC, texture

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Authors: K. Kaouther, D. Hafedh, A. Ben Cheikh Larbi

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Various structures and compositions thin films were deposited on 100C6 (AISI 52100) steel substrate by PVD magnetron sputtering system. The morphological proprieties were evaluated using an atomic force microscopy (AFM). Vickers microindentation tests were performed with a Shimadzu HMV-2000 hardness testing machine. Hardness measurement was carried out using Jonsson and Hogmark model. The results show that the coatings topography was dominated by domes and craters. Mechanical behavior and failure modes under microindentation were depending of coatings structure and composition. TiAlN multilayer showed exception in the microindentation resistance compared to TiN single layer and TiAlN/TiAlN nanolayer. Piled structure provides an increase of failure resistance and a decrease in cracks propagation.

Keywords: PVD thin films, multilayer, microindentation, cracking, damage mechanisms

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Authors: Barun K. De

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Acquired immunodeficiency syndrome (AIDS) is caused by two types of human immunodeficiency viruses, collectively designated HIV. HIV infection is spreading globally particularly in developing countries. Before an individual is diagnosed with HIV, the disease goes through different phases. First there is an acute early phase that is followed by an established or chronic phase. Subsequently, there is a latency period after which the individual becomes immunodeficient. It is in the acute phase that an individual is highly infectious due to a high viral load. Presently, HIV diagnosis involves use of tests that do not detect the acute phase infection during which both the viral RNA and p24 antigen are expressed. Instead, these less sensitive tests detect antibodies to viral antigens which are typically sero-converted later in the disease process following acute infection. These antibodies are detected in both asymptomatic HIV-infected individuals as well as AIDS patients. Studies indicate that early diagnosis and treatment of HIV infection can reduce medical costs, improve survival, and reduce spreading of infection to new uninfected partners. Newer 4th generation combination antigen/antibody tests are highly sensitive and specific for detection of acute and established HIV infection (HIV1 and HIV2) enabling immediate linkage to care. The CDC (Center of Disease Control, USA) recently recommended an algorithm involving three different tests to screen and diagnose acute and established infections of HIV-1 and HIV-2 in a general population. Initially a 4th generation combo test detects a viral antigen p24 and specific antibodies against HIV -1 and HIV-2 envelope proteins. If the test is positive it is followed by a second test known as a differentiation assay which detects antibodies against specific HIV-1 and HIV-2 envelope proteins confirming established infection of HIV-1 or HIV-2. However if it is negative then another test is performed that measures viral load confirming an acute HIV-1 infection. Screening results of a Phoenix area population detected 0.3% new HIV infections among which 32.4% were acute cases. Studies in the U.S. indicate that this algorithm effectively reduces HIV infection through immediate treatment and education following diagnosis.

Keywords: new algorithm, HIV, diagnosis, infection

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Authors: Mohammad R. Jafari, Francois G. Bernardeau

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With its arid climate, Qatar experiences low annual rainfall, intense storms, and high evaporation rates. However, the fast-paced rate of infrastructure development in the capital city of Doha has led to recurring instances of surface water flooding as well as rising groundwater levels. Public Work Authority (PWA/ASHGHAL) has implemented an approach to collect and discharge the flood water into a) positive gravity systems; b) Emergency Flooding Area (EFA) – Evaporation, Infiltration or Storage off-site using tankers; and c) Discharge to deep injection wells. As part of the flood prevention scheme, 21 deep injection wells have been constructed to discharge the collected surface and groundwater table in Doha city. These injection wells function as an alternative in localities that do not possess either positive gravity systems or downstream networks that can accommodate additional loads. These injection wells are 400-m deep and are constructed in a complex karstic subsurface condition with large cavities. The injection well system will discharge collected groundwater and storm surface runoff into the permeable Umm Er Radhuma Formation, which is an aquifer present throughout the Persian Gulf Region. The Umm Er Radhuma formation contains saline water that is not being used for water supply. The injection zone is separated by an impervious gypsum formation which acts as a barrier between upper and lower aquifer. State of the art drilling, grouting, and geophysical techniques have been implemented in construction of the wells to assure that the shallow aquifer would not be contaminated and impacted by injected water. Injection and pumping tests were performed to evaluate injection well functionality (injectability). The results of these tests indicated that majority of the wells can accept injection rate of 200 to 300 m³ /h (56 to 83 l/s) under gravity with average value of 250 m³ /h (70 l/s) compared to design value of 50 l/s. This paper presents design and construction process and issues associated with these injection wells, performing injection/pumping tests to determine capacity and effectiveness of the injection wells, the detailed design of collection system and conveying system into the injection wells, and the operation and maintenance process. This system is completed now and is under operation, and therefore, construction of injection wells is an effective option for flood control.

Keywords: deep injection well, flood prevention scheme, geophysical tests, pumping and injection tests, wellhead assembly

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Authors: Maysam Mard-Soltani, Mohamad Javad Rasaee, Saeed Khalili, Abdol Karim Sheikhi, Mehdi Hedayati

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Production of specific antibody responses against hTSH is a cumbersome process due to the high identity between the hTSH and the other members of the glycoprotein hormone family (FSH, LH and HCG) and the high identity between the human hTSH and host animals for antibody production. Therefore, two polyclonal antibodies were purified against two recombinant proteins. Four possible ELISA tests were designed based on these antibodies. These ELISA tests were checked against hTSH and other glycoprotein hormones, and their sensitivity and specificity were assessed. Bioinformatics tools were used to analyze the immunological properties. After the immunogen region selection from hTSH protein, c terminal of B hTSH was selected and applied. Two recombinant genes, with these cut pieces (first: two repeats of C terminal of B hTSH, second: tetanous toxin+B hTSH C terminal), were designed and sub-cloned into the pET32a expression vector. Standard methods were used for protein expression, purification, and verification. Thereafter, immunizations of the white New Zealand rabbits were performed and the serums of them were used for antibody titration, purification and characterization. Then, four ELISA tests based on two antibodies were employed to assess the hTSH and other glycoprotein hormones. The results of these assessments were compared with standard amounts. The obtained results indicated that the desired antigens were successfully designed, sub-cloned, expressed, confirmed and used for in vivo immunization. The raised antibodies were capable of specific and sensitive hTSH detection, while the cross reactivity with the other members of the glycoprotein hormone family was minimum. Among the four designed tests, the test in which the antibody against first protein was used as capture antibody, and the antibody against second protein was used as detector antibody did not show any hook effect up to 50 miu/l. Both proteins have the ability to induce highly sensitive and specific antibody responses against the hTSH. One of the antibody combinations of these antibodies has the highest sensitivity and specificity in hTSH detection.

Keywords: hTSH, bioinformatics, protein expression, cross reactivity

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Authors: Hyery Kang, Dong-Yeun Koh, Yun-Ho Ahn, Huen Lee

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Determination of the behavior of clathrate hydrate with inhibitor in the THz region will provide useful information about hydrate plug control in the upstream of the oil and gas industry. In this study, terahertz time-domain spectroscopy (THz-TDS) revealed the inhibition of the THF clathrate hydrate system with dosage of polyvinylpyrrolidone (PVP) with three different molecular weights. Distinct footprints of phase transition in the THz region (0.4–2.2 THz) were analyzed and absorption coefficients and real part of refractive indices are obtained in the temperature range of 253 K to 288 K. Along with the optical properties, ring breathing and stretching modes for different molecular weights of PVP in THF hydrate are analyzed by Raman spectroscopy.

Keywords: clathrate hydrate, terahertz spectroscopy, tetrahydrofuran, inhibitor

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Authors: Sy-Wei Lo, Chi-Heng Yu

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A new design of aerostatic thrust bearing is proposed for high static stiffness. The bearing body, which is mead of polymer covered with metallic membrane, is held by a circular ring. Such a support helps form a concave air gap to grasp the air pressure. The polymer body, which can be made rapidly by either injection or molding is able to provide extra damping under dynamic loading. The smooth membrane not only serves as the bearing surface but also protects the polymer body. The restrictor is a capillary inside a silicone tube. It can passively compensate the variation of load by expanding the capillary diameter for more air flux. In the present example, the stiffness soars from 15.85 N/µm of typical bearing to 349.85 N/µm at bearing elevation 9.5 µm; meanwhile the load capacity also enhances from 346.86 N to 704.18 N.

Keywords: aerostatic, bearing, polymer, static stiffness

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Authors: Alessandra Aparecida Vieira França, Adriana de Paula Lacerda Santos, Mauro Lacerda Santos Filho

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The purpose of this research i to study the behavior of precast prestressed hollow core slabs subjected to shear. In order to achieve this goal, shear tests were performed using hollow core slabs 26,5cm thick, with and without a concrete cover of 5 cm, without cores filled, with two cores filled and three cores filled with concrete. The tests were performed according to the procedures recommended by FIP (1992), the EN 1168:2005 and following the method presented in Costa (2009). The ultimate shear strength obtained within the tests was compared with the values of theoretical resistant shear calculated in accordance with the codes, which are being used in Brazil, noted: NBR 6118:2003 and NBR 14861:2011. When calculating the shear resistance through the equations presented in NBR 14861:2011, it was found that provision is much more accurate for the calculation of the shear strength of hollow core slabs than the NBR 6118 code. Due to the large difference between the calculated results, even for slabs without cores filled, the authors consulted the committee that drafted the NBR 14861:2011 and found that there is an error in the text of the standard, because the coefficient that is suggested, actually presents the double value than the needed one! The ABNT, later on, soon issued an amendment of NBR 14861:2011 with the necessary corrections. During the tests for the present study, it was confirmed that the concrete filling the cores contributes to increase the shear strength of hollow core slabs. But in case of slabs 26,5 cm thick, the quantity should be limited to a maximum of two cores filled, because most of the results for slabs with three cores filled were smaller. This confirmed the recommendation of NBR 14861:2011which is consistent with standard practice. After analyzing the configuration of cracking and failure mechanisms of hollow core slabs during the shear tests, strut and tie models were developed representing the forces acting on the slab at the moment of rupture. Through these models the authors were able to calculate the tensile stress acting on the concrete ties (ribs) and scaled the geometry of these ties. The conclusions of the research performed are the experiments results have shown that the mechanism of failure of the hollow-core slabs can be predicted using the strut-and-tie procedure, within a good range of accuracy. In addition, the needed of the correction of the Brazilian standard to review the correction factor σcp duplicated (in NBR14861/2011), and the limitation of the number of cores (Holes) to be filled with concrete, to increase the strength of the slab for the shear resistance. It is also suggested the increasing the amount of test results with 26.5 cm thick, and a larger range of thickness slabs, in order to obtain results of shear tests with cores concreted after the release of prestressing force. Another set of shear tests on slabs must be performed in slabs with cores filled and cover concrete reinforced with welded steel mesh for comparison with results of theoretical values calculated by the new revision of the standard NBR 14861:2011.

Keywords: prestressed hollow core slabs, shear, strut, tie models

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Authors: Jeferson Brito Fernades, Breno Padovezi Rocha, Roger Augusto Rodrigues, Heraldo Luiz Giacheti

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The geotechnical projects demand the appropriate knowledge of soil characteristics and parameters. The determination of geotechnical soil parameters can be done by means of laboratory or in situ tests. In countries with tropical weather, like Brazil, unsaturated soils are very usual. In these soils, the soil suction has been recognized as an important stress state variable, which commands the geo-mechanical behavior. Triaxial and direct shear tests on saturated soils samples allow determine only the minimal soil shear strength, in other words, no suction contribution. This paper briefly describes the triaxial test with controlled suction as well as discusses the influence of suction on the shear strength parameters of a lateritic tropical sandy soil from a Brazilian research site. In this site, a sample pit was excavated to retrieve disturbed and undisturbed soil blocks. The samples extracted from these blocks were tested in laboratory to represent the soil from 1.5, 3.0 and 5.0 m depth. The stress curves and shear strength envelopes determined by triaxial tests varying suction and confining pressure are presented and discussed. The water retention characteristics on this soil complement this analysis. In situ CPT tests were also carried out at this site in different seasons of the year. In this case, the soil suction profile was determined by means of the soil water retention. This extra information allowed assessing how soil suction also affected the CPT data and the shear strength parameters estimative via correlation. The major conclusions of this paper are: the undisturbed soil samples contracted before shearing and the soil shear strength increased hyperbolically with suction; and it was possible to assess how soil suction also influenced CPT test data based on the water content soil profile as well as the water retention curve. This study contributed with a better understanding of the shear strength parameters and the soil variability of a typical unsaturated tropical soil.

Keywords: site characterization, triaxial test, CPT, suction, variability

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Authors: C. S. Paglia, E. Pesenti, A. Krattiger

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Commercially available methacrylate and acrylamide-based acrylic resins for injection in concrete systems have been tested with respect to the sealing performance and the rebar corrosion. Among the different resins, a methacrylate-based type of acrylic resin significantly inhibited the rebar corrosion. This was mainly caused by the relatively high pH of the resin and the resin aqueous solution. This resin also exhibited a relatively high sealing performance, in particular after exposing the resin to durability tests. The corrosion inhibition behaviour and the sealing properties after the exposition to durability tests were maintained up to one year. The other resins either promoted the corrosion of the rebar and/or exhibited relatively low sealing properties.

Keywords: acrylic resin, sealing performance, rebar corrosion, materials

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Authors: S. B. Rathna Kumar, Sandya K. Varudhini, Aparna Ravichandran

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Telugu is a south central Dravidian language spoken in Andhra Pradesh, a southern state of India. The available speech identification tests in Telugu have been developed to determine the communication problems of individuals having a flat frequency hearing loss. These conventional speech audiometric tests would provide redundant information when used on individuals with high-frequency sloping hearing loss because of better hearing sensitivity in the low- and mid-frequency regions. Hence, conventional speech identification tests do not indicate the true nature of the communication problem of individuals with high-frequency sloping hearing loss. It is highly possible that a person with a high-frequency sloping hearing loss may get maximum scores if conventional speech identification tests are used. Hence, there is a need to develop speech identification test materials that are specifically designed to assess the speech identification performance of individuals with high-frequency sloping hearing loss. The present study aimed to develop speech identification test for individuals with high-frequency sloping hearing loss in Telugu. Individuals with high-frequency sloping hearing loss have difficulty in perception of voiceless consonants whose spectral energy is above 1000 Hz. Hence, the word lists constructed with phonemes having mid- and high-frequency spectral energy will estimate speech identification performance better for such individuals. The phonemes /k/, /g/, /c/, /ṭ/ /t/, /p/, /s/, /ś/, /ṣ/ and /h/are preferred for the construction of words as these phonemes have spectral energy distributed in the frequencies above 1000 KHz predominantly. The present study developed two word lists in Telugu (each word list contained 25 words) for evaluating speech identification performance of individuals with high-frequency sloping hearing loss. The performance of individuals with high-frequency sloping hearing loss was evaluated using both conventional and high-frequency word lists under recorded voice condition. The results revealed that the developed word lists were found to be more sensitive in identifying the true nature of the communication problem of individuals with high-frequency sloping hearing loss.

Keywords: speech identification test, high-frequency sloping hearing loss, recorded voice condition, Telugu

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Authors: S. A. Naeini, M. Ghorbani Tochaee

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The aim of this study is to assess the influence of plastic fines content on sand-clay mixtures on maximum shear modulus and liquefaction resistance using a series of resonant column tests. A high plasticity clay called bentonite was added to 161 Firoozkooh sand at the percentages of 10, 15, 20, 25, 30 and 35 by dry weight. The resonant column tests were performed on the remolded specimens at constant confining pressure of 100 KPa and then the values of G_max and liquefaction resistance were investigated. The maximum shear modulus and cyclic resistance ratio (CRR) are examined in terms of fines content. Based on the results, the maximum shear modulus and liquefaction resistance tend to decrease within the increment of fine contents.

Keywords: Gmax, liquefaction, plastic fines, resonant column, sand-clay mixtures, bentonite

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Authors: O. Arikan, C. Kocatepe, G. Ucar, Y. Hacialiefendioglu

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In this paper, influence of harmonics on medium voltage distribution system of Bogazici Electricity Distribution Inc. (BEDAS) which takes place at Istanbul/Turkey is investigated. A ring network consisting of residential loads is taken into account for this study. Real system parameters and measurement results are used for simulations. Also, probable working conditions of the system are analyzed for %50, %75 and %100 loading of transformers with similar harmonic contents. Results of the study are exhibited the influence of nonlinear loads on %THDV, P.F. and technical losses of the medium voltage distribution system.

Keywords: distribution system, harmonic, technical losses, power factor, total harmonic distortion, residential load, medium voltage

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Authors: Gabrielle Peck, Ryan Hayes

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Current large scale fire tests focus on flammability and heat release measurements. Smoke toxicity isn’t considered despite it being a leading cause of death and injury in unwanted fires. A key reason could be that the practical difficulties associated with quantifying individual toxic components present in a fire effluent often require specialist equipment and expertise. Fire effluent contains a mixture of unreactive and reactive gases, water, organic vapours and particulate matter, which interact with each other. This interferes with the operation of the analytical instrumentation and must be removed without changing the concentration of the target analyte. To mitigate the need for expensive equipment and time-consuming analysis, a portable gas analysis system was designed, constructed and tested for use in large-scale fire tests as a simpler and more robust alternative to online FTIR measurements. The novel equipment aimed to be easily portable and able to run on battery or mains electricity; be able to be calibrated at the test site; be capable of quantifying CO, CO2, O2, HCN, HBr, HCl, NOx and SO2 accurately and reliably; be capable of independent data logging; be capable of automated switchover of 7 bubblers; be able to withstand fire effluents; be simple to operate; allow individual bubbler times to be pre-set; be capable of being controlled remotely. To test the analysers functionality, it was used alongside the ISO/TS 19700 Steady State Tube Furnace (SSTF). A series of tests were conducted to assess the validity of the box analyser measurements and the data logging abilities of the apparatus. PMMA and PA 6.6 were used to assess the validity of the box analyser measurements. The data obtained from the bench-scale assessments showed excellent agreement. Following this, the portable analyser was used to monitor gas concentrations during large-scale testing using the ISO 9705 room corner test. The analyser was set up, calibrated and set to record smoke toxicity measurements in the doorway of the test room. The analyser was successful in operating without manual interference and successfully recorded data for 12 of the 12 tests conducted in the ISO room tests. At the end of each test, the analyser created a data file (formatted as .csv) containing the measured gas concentrations throughout the test, which do not require specialist knowledge to interpret. This validated the portable analyser’s ability to monitor fire effluent without operator intervention on both a bench and large-scale. The portable analyser is a validated and significantly more practical alternative to FTIR, proven to work for large-scale fire testing for quantification of smoke toxicity. The analyser is a cheaper, more accessible option to assess smoke toxicity, mitigating the need for expensive equipment and specialist operators.

Keywords: smoke toxicity, large-scale tests, iso 9705, analyser, novel equipment

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Authors: Bashar Tarawneh, Yasser Hakam

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Rapid Impact Compaction (RIC) is a modern dynamic compaction device mainly used to compact sandy soils, where silt and clay contents are low. The device uses the piling hammer technology to increase the bearing capacity of soils through controlled impacts. The RIC device uses "controlled impact compaction" of the ground using a 9-ton hammer dropped from the height between 0.3 m to 1.2 m onto a 1.5 m diameter steel patent foot. The delivered energy is about 26,487 to 105,948 Joules per drop. To evaluate the performance of this technique, three project sites in the United Arab Emirates were improved using RIC. In those sites, a loose to very loose fine to medium sand was encountered at a depth ranging from 1.0m to 4.0m below the ground level. To evaluate the performance of the RIC, Cone Penetration Tests (CPT) were carried out before and after improvement. Also, load tests were carried out post-RIC work to assess the settlements and bearing capacity. The soil was improved to a depth of about 5.0m below the ground level depending on the CPT friction ratio (the ratio between sleeve friction and tip resistance). CPT tip resistance was significantly increased post ground improvement work. Load tests showed enhancement in the soil bearing capacity and reduction in the potential settlements. This study demonstrates the successful application of the RIC for middle-deep improvement and compaction of the ground. Foundation design criteria were achieved in all site post-RIC work.

Keywords: compaction, RIC, ground improvement, CPT

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Authors: Cristina Lavilla, Andreas Heise

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The synthesis of sequence-controlled polymers has received increasing attention in the last years. Well-defined polyacrylates, polyacrylamides and styrene-maleimide copolymers have been synthesized by sequential or kinetic addition of comonomers. However this approach has not yet been introduced to the synthesis of polypeptides, which are in fact polymers developed by nature in a sequence-controlled way. Polypeptides are natural materials that possess the ability to self-assemble into complex and highly ordered structures. Their folding and properties arise from precisely controlled sequences and compositions in their constituent amino acid monomers. So far, solid-phase peptide synthesis is the only technique that allows preparing short peptide sequences with excellent sequence control, but also requires extensive protection/deprotection steps and it is a difficult technique to scale-up. A new strategy towards sequence control in the synthesis of polypeptides is introduced, based on the sequential addition of α-amino acid-N-carboxyanhydrides (NCAs). The living ring-opening process is conducted to full conversion and no purification or deprotection is needed before addition of a new amino acid. The length of every block is predefined by the NCA:initiator ratio in every step. This method yields polypeptides with a specific sequence and controlled molecular weights. A series of polypeptides with varying block sequences have been synthesized with the aim to identify structure-property relationships. All of them are able to adopt secondary structures similar to natural polypeptides, and display properties in the solid state and in solution that are characteristic of the primary structure. By design the prepared polypeptides allow selective modification of individual block sequences, which has been exploited to introduce functionalities in defined positions along the polypeptide chain. Poly(ethylene glycol)(PEG) was the functionality chosen, as it is known to favor hydrophilicity and also yield thermoresponsive materials. After PEGylation, hydrophilicity of the polypeptides is enhanced, and their thermal response in H2O has been studied. Noteworthy differences in the behavior of the polypeptides having different sequences have been found. Circular dichroism measurements confirmed that the α-helical conformation is stable over the examined temperature range (5-90 °C). It is concluded that PEG units are the main responsible of the changes in H-bonding interactions with H2O upon variation of temperature, and the position of these functional units along the backbone is a factor of utmost importance in the resulting properties of the α-helical polypeptides.

Keywords: α-amino acid N-carboxyanhydrides, multiblock copolymers, poly(ethylene glycol), polypeptides, ring-opening polymerization, sequence control

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Authors: Chen Liu, Dawit Negussey

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EPS (Expanded Polystyrene) geofoam as light-weight material in geotechnical applications are made of pre-expanded resin beads that form fused cellular micro-structures. The strength and deformation properties of geofoam blocks are determined by unconfined compression of small test samples between rigid loading plates. Applied loads are presumed to be supported uniformly over the entire mating end areas. Predictions of field performance on the basis of such laboratory tests widely over-estimate actual post-construction settlements and exaggerate predictions of long-term creep deformations. This investigation examined the development of contact pressures at a large number of discrete points at low and large strain levels for different densities of geofoam. Development of pressure patterns for fine and coarse interface material textures as well as for molding skin and hot wire cut geofoam surfaces were examined. The lab testing showed that I-Scan tactile sensors are useful for detailed observation of contact pressures at a large number of discrete points simultaneously. At low strain level (1%), the lower density EPS block presents low variations in localized stress distribution compared to higher density EPS. At high strain level (10%), the dense geofoam reached the sensor cut-off limit. The imprint and pressure patterns for different interface textures can be distinguished with tactile sensing. The pressure sensing system can be used in many fields with real-time pressure detection. The research findings provide a better understanding of EPS geofoam behavior for improvement of design methods and performance prediction of critical infrastructures, which will be anticipated to guide future improvements in design and rapid construction of critical transportation infrastructures with geofoam in geotechnical applications.

Keywords: geofoam, pressure distribution, tactile pressure sensors, interface

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Authors: Yoftahe Nigussie

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This research explores the implementation of a vapor absorption refrigeration system (VARS) in mini-bus cars to enhance air conditioning efficiency. The conventional vapor compression refrigeration system (VCRS) in vehicles relies on mechanical work from the engine, leading to increased fuel consumption. The proposed VARS aims to utilize waste heat and exhaust gas from the internal combustion engine to cool the mini-bus cabin, thereby reducing fuel consumption and atmospheric pollution. The project involves two models: Model 1, a two-fluid vapor absorption system (VAS), and Model 2, a three-fluid VAS. Model 1 uses ammonia (NH₃) and water (H₂O) as refrigerants, where water absorbs ammonia rapidly, producing a cooling effect. The absorption cycle operates on the principle that absorbing ammonia in water decreases vapor pressure. The ammonia-water solution undergoes cycles of desorption, condensation, expansion, and absorption, facilitated by a generator, condenser, expansion valve, and absorber. The objectives of this research include reducing atmospheric pollution, minimizing air conditioning maintenance costs, lowering capital costs, enhancing fuel economy, and eliminating the need for a compressor. The comparison between vapor absorption and compression systems reveals advantages such as smoother operation, fewer moving parts, and the ability to work at lower evaporator pressures without affecting the Coefficient of Performance (COP). The proposed VARS demonstrates potential benefits for mini-bus air conditioning systems, providing a sustainable and energy-efficient alternative. By utilizing waste heat and exhaust gas, this system contributes to environmental preservation while addressing economic considerations for vehicle owners. Further research and development in this area could lead to the widespread adoption of vapor absorption technology in automotive air conditioning systems.

Keywords: room, zone, space, thermal resistance

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Authors: Adam Janásek, Marek Pagáč

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The article is looking for an experimental determination of tool life tests for ceramic cutting inserts. Mentioned experimental determination should provide an added information about cutting process. The mechanism of tool wear, cutting temperature in machining, quality machined surface and machining process itself is the information, which are important for whole manufacturing process. Mainly, the roughness plays very important role in determining how a real object will interact with its environment. The main aim was to determine the number of machined inserts, tool life and micro-geometry, as well. On the basis of previous tests the tool-wear was measured at constant cutting parameter which is more typical for high volume manufacturing processes.

Keywords: ceramic, insert, machining, surface roughness, tool-life, tool-wear

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Authors: Pelin Su Firat, Sohyung Cho

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Biopsy or aspiration procedures are known to be complicated as they involve the penetration of a needle through human tissues, including vital organs. This research presents the design of a force sensor-guided device to be used with syringes and needles for aspiration and biopsy. The development of the device was aimed to help accomplish accurate needle placement and increase the performance of the surgeon in navigating the tool and tracking the target. Specifically, a prototype for a force-sensor embedded syringe has been created using 3D (3-Dimensional) modeling and printing techniques in which two different force sensors were used to provide significant force feedback to users during the operations when needles pernitrate different tissues. From the extensive tests using synthetic tissues, it is shown that the proposed syringe design has accomplished the desired accuracy, efficiency, repeatability, and effectiveness. Further development is desirable through usability tests.

Keywords: biopsy, syringe, force sensors, haptic feedback

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Authors: Aleksandra BužArovska, Gordana Bogoeva Gaceva

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Biodegradable polymers have received significant scientific attention in tissue engineering (TE) application, in particular their composites consisting of inorganic nanoparticles. In the last 15 years, they are subject of intensive research by many groups, aiming to develop polymer scaffolds with defined biodegradability, porosity and adequate mechanical stability. The most important characteristic making these materials attractive for TE is their biodegradability, a process that could be time controlled and long enough to enable generation of a new tissue as a replacement for the degraded polymer scaffold. In this work poly(L-lactic acid) scaffolds, filled with TiO2 nanoparticles functionalized with oleic acid, have been prepared by thermally induced phase separation method (TIPS). The functionalization of TiO2 nanoparticles with oleic acid was performed in order to improve the nanoparticles dispersibility within the polymer matrix and at the same time to inhibit the cytotoxicity of the nanofiller. The oleic acid was chosen as amphiphilic molecule belonging to the fatty acid family because of its non-toxicity and possibility for mediation between the hydrophilic TiO2 nanoparticles and hydrophobic PLA matrix. The produced scaffolds were characterized with thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and mechanical compression measurements. The bioactivity for bone tissue engineering application was tested in supersaturated simulated body fluid. The degradation process was followed by Fourier transform infrared spectroscopy (FTIR). The results showed anisotropic morphology with elongated open pores (100 µm), high porosity (around 92%) and perfectly dispersed nanofiller. The compression moduli up to 10 MPa were identified independent on the nanofiller content. Functionalized TiO2 nanoparticles induced formation of hydroxyapatite clusters as much as unfunctionalized TiO2. The prepared scaffolds showed properties ideal for scaffold vascularization, cell attachment, growth and proliferation.

Keywords: biodegradation, bone tissue engineering, mineralization, PLA scaffolds

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Authors: Sang-Woo Kim, Young-Seon Lee

Abstract:

An important concern in metal forming, even at elevated temperatures, is whether a desired deformation can be accomplished without any failure of the material. A detailed understanding of the critical condition for crack initiation provides not only the workability limit of a material but also a guide-line for process design. This paper describes the utilization of ductile fracture criteria in conjunction with the finite element method (FEM) for predicting the onset of fracture in warm metal working processes of magnesium alloy sheets. Critical damage values for various ductile fracture criteria were determined from uniaxial tensile tests and were expressed as the function of strain rate and temperature. In order to find the best criterion for failure prediction, Erichsen cupping tests under isothermal conditions and FE simulations combined with ductile fracture criteria were carried out. Based on the plastic deformation histories obtained from the FE analyses of the Erichsen cupping tests and the critical damage value curves, the initiation time and location of fracture were predicted under a bi-axial tensile condition. The results were compared with experimental results and the best criterion was recommended. In addition, the proposed methodology was used to predict the onset of fracture in non-isothermal deep drawing processes using an irregular shaped blank, and the results were verified experimentally.

Keywords: magnesium, AZ31 alloy, ductile fracture, FEM, sheet forming, Erichsen cupping test

Procedia PDF Downloads 373

Authors: BoSheng Liu

Abstract:

The research goal is to re-image a locally-sourced waste product as abuilding material. The author aims to contribute to the compressed stabilized earth block (CSEB) by investigating the promising role of dredged material as an alternative building ingredient in the production of bricks and tiles. Dredged material comes from the sediment deposited near the shore or downstream, where the water current velocity decreases. This sediment needs to be dredged to provide water transportation; thus, there are mounds of the dredged material stored at bay. It is the interest of this research to reduce the filtered un-organic soil in the production of CSEB and replace it with locally dredged material from the Atchafalaya River in Morgan City, Louisiana. Technology and mechanical innovations have evolved the traditional adobe production method, which mixes the soil and natural fiber into molded bricks, into chemically stabilized CSEB made by compressing the clay mixture and stabilizer in a compression chamber with particular loads. In the case of dredged material CSEB (DM-CSEB), cement plays an essential role as the bending agent contributing to the unit strength while sustaining the filtered un-organic soil. Each DM-CSEB unit is made in a compression chamber with 580 PSI (i.e., 4 MPa) force. The research studied the cement content from 5% to 10% along with the range of dredged material mixtures, which differed from 20% to 80%. The material mixture content affected the DM-CSEB's strength and workability during and after its compression. Results indicated two optimal workabilities of the mixture: 27% fine clay content and 63% dredged material with 10% cement, or 28% fine clay content, and 67% dredged material with 5% cement. The final product of DM-CSEB emitted between 10 to 13 times fewer carbon emissions compared to the conventional fired masonry structure. DM-CSEB satisfied the strength requirement given by the ASTM C62 and ASTM C34 standards for construction material. One of the final evaluations tested and validated the material performance by designing and constructing an architectural, conical tile-vault prototype that was 28" by 40" by 24." The vault utilized a computational form-finding approach to generate the form's geometry, which optimized the correlation between the vault geometry and structural load distribution. A series of scaffolding was deployed to create the framework for the tile-vault construction. The final tile-vault structure was made from 2 layers of DM-CSEB tiles jointed by mortar, and the construction of the structure used over 110 tiles. The tile-vault prototype was capable of carrying over 400 lbs of live loads, which further demonstrated the dredged material feasibility as a construction material. The presented case study of Dredged Material Compressed Stabilized Earth Block (DM-CSEB) provides the first impression of dredged material in the clayey mixture process, structural performance, and construction practice. Overall, the approach of integrating dredged material in building material can be feasible, regionally sourced, cost-effective, and environment-friendly.

Keywords: dredged material, compressed stabilized earth block, tile-vault, regionally sourced, environment-friendly

Procedia PDF Downloads 115

Authors: Yukinori Taniguchi, Kazuyoshi Kurita, Kohei Mizuta, Keigo Nishitani, Ryuichi Fukuda

Abstract:

Tungsten carbide is widely used as a tool material in metal manufacturing process. Since tungsten is typical rare metal, establishment of recycle process of tungsten carbide tools and restore into cemented carbide material bring great impact to metal manufacturing industry. Recently, recycle process of tungsten carbide has been developed and established gradually. However, the demands for quality of cemented carbide tool are quite severe because hardness, toughness, anti-wear ability, heat resistance, fatigue strength and so on should be guaranteed for precision machining and tool life. Currently, it is hard to restore the recycled tungsten carbide powder entirely as raw material for new processed cemented carbide tool. In this study, to suggest positive use of recycled tungsten carbide powder, we have tried to fabricate a carbon based sintered steel which shows reinforced mechanical properties with recycled tungsten carbide powder. We have made set of newly designed sintered steels. Compression test of sintered specimen in density ratio of 0.85 (which means 15% porosity inside) has been conducted. As results, at least 1.7 times higher in nominal strength in the amount of 7.0 wt.% was shown in recycled WC powder. The strength reached to over 600 MPa for the Fe-WC-Co-Cu sintered alloy. Wear test has been conducted by using ball-on-disk type friction tester using 5 mm diameter ball with normal force of 2 N in the dry conditions. Wear amount after 1,000 m running distance shows that about 1.5 times longer life was shown in designed sintered alloy. Since results of tensile test showed that same tendency in previous testing, it is concluded that designed sintered alloy can be used for several mechanical parts with special strength and anti-wear ability in relatively low cost due to recycled tungsten carbide powder.

Keywords: tungsten carbide, recycle process, compression test, powder metallurgy, anti-wear ability

Procedia PDF Downloads 249

Authors: Hazal Yılmaz, Hale Karakaş

Abstract:

In the scope of the study, it is aimed to investigate and review the performance of denim fabrics that are foam washed. Foam washing was compared as an alternative to stone washing in terms of sustainability and performance parameters. For this purpose, seven different denim fabrics, which are both stone washed and foam washed separately in 3 different washing durations (30-60-90 mins), were compared. In the study, the same fabrics were processed with both foam and stone separately. The washing process steps were reviewed, and their water consumption values were compared. After washing, a total of 42 fabric samples were obtained, and tensile strength, tear strength, abrasion, weight loss after abrasion, rubbing fastness, color fastness tests were carried out on the fabric samples. The obtained test results were reviewed and evaluated. As a result of tests, it has been observed that the performance of foam washed fabrics in terms of tensile, tear strength and rubbing fastness test results are better than stone washed fabrics, and it has been seen that foam washed fabrics' color fastness test results are as stone washed. As a result of all these tests, it can be seen that foam washing is an alternative to stone washing due to its performance parameters and its sustainability performance with less water usage.

Keywords: denim fabrics, denim washing, foam washing, performance properties, stone washing, sustainability

Procedia PDF Downloads 71

Authors: Won-Ho Kim

Abstract:

In this paper, a design of H.263 based wireless video transceiver is presented for wireless camera system. It uses standard WIFI transceiver and the covering area is up to 100m. Furthermore the standard H.263 video encoding technique is used for video compression since wireless video transmitter is unable to transmit high capacity raw data in real time and the implemented system is capable of streaming at speed of less than 1Mbps using NTSC 720x480 video.

Keywords: wireless video transceiver, video surveillance camera, H.263 video encoding digital signal processing

Procedia PDF Downloads 364

Authors: Yelbek B. Utepov, Assel S. Tulebekova, Alizhan B. Kazkeyev

Abstract:

Maturity sensors are used to determine concrete strength by the non-destructive method. The method of placement of the maturity sensors determines their number required for a certain frame of a monolithic building. Previous studies weakly describe this aspect, giving only logical assumptions. This paper proposes a cheap prototype of an embedded wireless sensor for monitoring concrete structures, as well as an alternative strategy for placing sensors based on the transitional boundaries of the temperature distribution of concrete curing, which were determined by building a heat map of the temperature distribution, where unknown values are calculated by the method of inverse distance weighing. The developed prototype can simultaneously measure temperature and relative humidity over a smartphone-controlled time interval. It implements a maturity method to assess the in-situ strength of concrete, which is considered an alternative to the traditional shock impulse and compression testing method used in Kazakhstan. The prototype was tested in laboratory and field conditions. The tests were aimed at studying the effect of internal and external temperature and relative humidity on concrete's strength gain. Based on an experimentally poured concrete slab with randomly integrated maturity sensors, it was determined that the transition boundaries form elliptical forms. Temperature distribution over the largest diameter of the ellipses was plotted, resulting in correct and inverted parabolas. As a result, the distance between the closest opposite crossing points of the parabolas is accepted as the maximum permissible step for setting the maturity sensors. The proposed placement strategy can be applied to sensors that measure various continuous phenomena such as relative humidity. Prototype testing has also revealed Bluetooth inconvenience due to weak signal and inability to access multiple prototypes simultaneously. For this reason, further prototype upgrades are planned in future work.

Keywords: heat map, placement strategy, temperature and relative humidity, wireless embedded sensor

Procedia PDF Downloads 177

Authors: M. E. Turan, H. Zengin, E. Cevik, Y. Sun, Y. Turen, H. Ahlatci

Abstract:

In this study, the effects of B₄C and SiC particle reinforcements on wear properties of magnesium matrix metal composites produced by pressure infiltration method were investigated. AZ91 (9%Al-1%Zn) magnesium alloy was used as a matrix. AZ91 magnesium alloy was melted under an argon atmosphere. The melt was infiltrated to the particles with an appropriate pressure. Wear tests, hardness tests were performed respectively. Microstructure characterizations were examined by light optical (LOM) and scanning electron microscope (SEM). The results showed that uniform particle distributions were achieved in both B₄C and SiC reinforced composites. Wear behaviors of magnesium matrix metal composites changed as a function of type of particles. SiC reinforced composite has better wear performance and higher hardness than B₄C reinforced composite.

Keywords: magnesium matrix composite, pressure infiltration, SEM, wear

Procedia PDF Downloads 360

Authors: K. Abuzayan, H. Alabed

Abstract:

The objectives of this study (baseline study, n = 20) were to implement Matlab procedures for quantifying selected static balance variables, establish baseline data of selected variables which characterize static balance activities in a population of healthy young adult males, and to examine any trial effects on these variables. The results indicated that the implementation of Matlab procedures for quantifying selected static balance variables was practical and enabled baseline data to be established for selected variables. There was no significant trial effect. Recommendations were made for suitable tests to be used in later studies. Specifically it was found that one foot-tiptoes tests either in static balance is too challenging for most participants in normal circumstances. A one foot-flat eyes open test was considered to be representative and challenging for static balance.

Keywords: static balance, base of support, baseline data, young adults

Procedia PDF Downloads 521

Authors: Gurjinder Singh Randhawa, Jonny Garg, Sukhraj Singh, Gurmeet Singh Cheema

Abstract:

A major problem related to the use of rotavator is wear of rotavator blades due to abrasion by soil hard particles, as it seriously affects tillage quality and agricultural production economy. The objective of this study was to increase the wear resistance by covering the rotavator blades with two different hard facing electrodes. These blades are generally produced from low carbon or low alloy steel. During the field work i.e. preparing land for the cultivation these blades are subjected to severe wear conditions. Comparative wear tests on a regular rotavator blade and two kinds of hardfacing with electrodes were conducted in the field. These two different hardfacing electrodes, which are designated HARD ALLOY-400 and HARD ALLOY-650, were used for hardfacing. The wear rate in the field tests was found to be significantly different statistically. When the cost is taken into consideration; HARD ALLOY-650 and HARD ALLOY-400 have been found to be the best hardfacing electrodes.

Keywords: hardfacing, rotavator blades, hard alloy-400, abrasive wear

Procedia PDF Downloads 425