Search results for: GSM signal strength

Authors: Rania M. Abdallah, Ahmed A. S. Dessouki, Moustafa H. Aly

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This paper has presented a new simple small signal model for a resonant tunnelling diode device. The resonant tunnelling diode equivalent circuit elements were calculated and the results led to good agreement between the calculated equivalent circuit elements and the measurement results.

Keywords: resonant tunnelling diode, small signal model, negative differential conductance, electronic engineering

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Authors: Phinyo Mueangmeesap

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This paper describes about pure sinusoidal inverter simulation and implementation from high voltage DC (156 Vdc). This simulation is to study and improve the efficiency of the inverter. By reducing the loss of power from boost converter in current inverter. The simulation is done by using the H-bridge circuit with pulse width modulate (PWM) signal and low-pass filter circuit. To convert the DC into AC. This paper used the PSCad for simulation. The result of simulation can be used to create prototype inverter by converting 156 Vdc to 110Vac. The inverter gives the output signal similar to the output from a simulation.

Keywords: inverter simulation, PWM signal, single-phase inverter, sinusoidal inverter

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Authors: Negar Riazifar, Nigel G. Stocks

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This paper proposes strategies in level crossing (LC) sampling and reconstruction that provide high fidelity signal reconstruction for speech signals; these strategies circumvent the problem of exponentially increasing number of samples as the bit-depth is increased and hence are highly efficient. Specifically, the results indicate that the distribution of the intervals between samples is one of the key factors in the quality of signal reconstruction; including samples with short intervals do not improve the accuracy of the signal reconstruction, whilst samples with large intervals lead to numerical instability. The proposed sampling method, termed reduced conventional level crossing (RCLC) sampling, exploits redundancy between samples to improve the efficiency of the sampling without compromising performance. A reconstruction technique is also proposed that enhances the numerical stability through linear interpolation of samples separated by large intervals. Interpolation is demonstrated to improve the accuracy of the signal reconstruction in addition to the numerical stability. We further demonstrate that the RCLC and interpolation methods can give useful levels of signal recovery even if the average sampling rate is less than the Nyquist rate.

Keywords: level crossing sampling, numerical stability, speech processing, trigonometric polynomial

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Authors: K. Ravi, Sabu Subhash

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Densely compacted bentonite or bentonite–sand mixture has been identified as a suitable buffer in the deep geological repository (DGR) for the safe disposal of high-level nuclear waste (HLW) due to its favourable physicochemical and hydro-mechanical properties. The addition of sand to the bentonite enhances the thermal conductivity and compaction properties and reduces the drying shrinkage of the buffer material. The buffer material may undergo cyclic wetting and drying upon ingress of groundwater from the surrounding rock mass and from evaporation due to high temperature (50–210 °C) derived from the waste canister. The cycles of changes in temperature may result in thermal history, and the hydro-mechanical properties of the buffer material may be affected. This paper examines the influence of thermal history on the undrained shear strength of bentonite and bentonite-sand mixture. Bentonite from Rajasthan state and sand from the Assam state of India are used in this study. The undrained shear strength values are obtained by conducting unconfined compressive strength (UCS) tests on cylindrical specimens (dry densities 1.30 and 1.5 Mg/m3) of bentonite and bentonite-sand mixture consisting of 30 % bentonite+ 70 % sand. The specimens are preheated at temperatures varying from 50-150 °C for one, two and four hours in hot air oven. The results indicate that the undrained shear strength is increased by the thermal history of the buffer material. The specimens of bentonite-sand mixture exhibited more increase in strength compared to the pure bentonite specimens. This indicates that the sand content of the mixture plays a vital role in taking the thermal stresses of the bentonite buffer in DGR conditions.

Keywords: bentonite, deep geological repository, thermal history, undrained shear strength

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Authors: Linyue Jia, Wenbo Du, Zhaohui Wang, Ke Liu, Shubo Li

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Due to the great potential for weight reduction in aerospace and automotive industries, magnesium-rare earth (Mg-RE) based alloys with outstanding mechanical performance have been widely investigated for decades. However, magnesium alloys are still restricted in engineering applications because of their lower strength and ductility. Hence, there are large spaces and challenges in achieving high-performance Mg alloys. This work reports an Mg-Gd-Er-Zn-Zr alloy with ultrahigh strength and good ductility developed via hot extrusion, pre-deformation, and two-stage aging. The extruded alloy comprises fine dynamically recrystallized (DRXed) grains and coarse worked grains with a large aspect ratio. Pre-deformation has little effect on the microstructure and macro-texture and serves primarily to introduce a large number of dislocations, resulting in strain hardening and higher precipitation strengthening during subsequent aging due to more nucleation sites. As a result, the alloy exhibits a yield strength (YS) of 506 MPa, an ultimate tensile strength (UTS) of 549 MPa, and elongation (EL) of 8.2% at room temperature, showing superior strength-ductility balance than the other wrought Mg-RE alloys previously reported. The current study proposes a combination of pre-deformation and two-stage aging to further improve the mechanical properties of wrought Mg alloys for engineering applications.

Keywords: magnesium alloys, mechanical properties, microstructure, pre-deformation, two-stage aging

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Authors: Hina Gul Rajpoot, Wazeer Hussain Solangi

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Experimental Design (DOE) economically maximizes information; we deliberately change one or more process variables (looms) in order to observe the effect the changes have on one or more response fabric properties. In DOE obtained data can be analyzed to yield valid and objective conclusions. An Experimental Design is lying out of a detailed experimental plan in advance and maximizes the amount of "information" that can be obtained for a given amount of experimental. Fabric of 36 inches having following weaves was used. 3/1 twill, warp cotton (10.5 den), weft Lycra (16 spandex * 70 den) Ends per inch86, Picks per inch 52 and washes process includes Stone wash, Rinse wash, Bleaching and Enzyme wash. Once the samples were ready, they were subjected to tensile and tear strength tests, for these two kinds of samples were considered. One washed fabric samples of warp direction type and other type of the samples was weft direction. Then five samples from each were considered for tensile and teat strength tests separately then takes the mean value. The results found that the lowest strength damaged in the weft direction observed by tensile strength test & Enzyme wash. Maximum breaking load of the enzyme washed fabric sample was 42 kg.

Keywords: twill, indigo dye, tear strength, loom, ball warp, denier or den, seam, waist band, pilling, selvage

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Authors: Bouzidi Yassine

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This experimental work was aimed to characterize the porosity of the concrete cover zone using the capillary absorption test, and establish the links between open porosity characterized by the initial absorption, the compressive strength and carbonation depth. Eight formulations of workability similar made from ordinary Portland cement (CEM I 42.5) and a compound cement (CEM II/B 42.5) four of each type are studied. The results allow us to highlight the effect of the cement type. Indeed, concretes-based cement CEM II/B 42.5 carbonatent approximately faster than concretes-based cement CEM I 42.5. This effect is attributed in part to the lower content of portlandite Ca(OH)2 of concretes-based cement CEM II/B 42.5, but also the impact of the cement type on the open porosity of the cover concrete. The open porosity of concretes-based cement CEM I 42.5 is lower than that of concretes-based cement CEM II/B 42.5. The carbonation depth is a decreasing function of the compressive strength at 28 days and increases with the initial absorption. Through the results obtained, correlations between the quantity of water absorbed in 1 h, the carbonation depth at 180 days and the compressive strength at 28 days were performed in an acceptable manner.

Keywords: initial absorption, cover concrete, compressive strength, carbonation depth

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Authors: Moosa Mazloom, Morteza Mehrvand

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The goal of this study was to investigate the effects of silica fume and super plasticizer dosages on compressive and torsional properties of SCC. This work concentrated on concrete mixes having water/binder ratios of 0.45 and 0.35, which contained constant total binder contents of 400 kg/m3 and 500 kg/m3, respectively. The percentages of silica fume that replaced cement were 0 % and 10 %. The super plasticizer dosages utilized in the mixtures were 0.4%, 0.8%, 1.2 % and 1.6 % of the weight of cement. Prism dimensions used in this test were 10 × 10 × 40 cm3. The results of this research indicated that torsional strength of SCC prisms can be calculated using the equations presented in Canadian and American concrete building codes.

Keywords: self-compacting concrete, rectangular prism, torsional strength

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Authors: Wern-Yarng Shieh, Chao Qian, Bingnan Pei

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A design of communication area for infrared electronic-toll-collection systems to provide an extended communication interval in the vehicle traveling direction and regular boundary between contiguous traffic lanes is proposed. By utilizing two typical low-cost commercial infrared LEDs with different half-intensity angles Φ1/2 = 22° and 10°, the radiation pattern of the emitter is designed to properly adjust the spatial distribution of the signal power. The aforementioned purpose can be achieved with an LED array in a three-piece structure with appropriate mounting angles. With this emitter, the influence of the mounting parameters, including the mounting height and mounting angles of the on-board unit and road-side unit, on the system performance in terms of the received signal strength and communication area are investigated. The results reveal that, for our emitter proposed in this paper, the ideal "long-and-narrow" characteristic of the communication area is very little affected by these mounting parameters. An optimum mounting configuration is also suggested.

Keywords: dedicated short-range communication (DSRC), electronic toll collection (ETC), infrared communication, intelligent transportation system (ITS), multilane free flow

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Authors: Viviana Letelier, Ester Tarela, Giacomo Moriconi

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The cement industry is responsible for around a 5% of the CO2 emissions worldwide and considering that concrete is one of the most used materials in construction its total effect is important. An alternative to reduce the environmental impact of concrete production is to incorporate certain amount of residuals in the dosing, limiting the replacement percentages to avoid significant losses in the mechanical properties of the final material. This study analyses the variation in the mechanical properties of structural concretes with recycled aggregates and volcanic ash as cement replacement to test the effect of the simultaneous use of different residuals in the same material. Analyzed concretes are dosed for a compressive strength of 30MPa. The recycled aggregates are obtained from prefabricated pipe debris with a compressive strength of 20MPa. The volcanic ash was obtained from the Ensenada (Chile) area after the Calbuco eruption in April 2015. The percentages of natural course aggregates that are replaced by recycled aggregates are of 0% and 30% and the percentages of cement replaced by volcanic ash are of 0%, 5%, 10% and 15%. The combined effect of both residuals in the mechanical properties of the concrete is evaluated through compressive strength tests after, 28 curing days, flexural strength tests after 28 days, and the elasticity modulus after 28 curing days. Results show that increasing the amount of volcanic ash used increases the losses in compressive strength. However, the use of up to a 5% of volcanic ash allows obtaining concretes with similar compressive strength to the control concrete, whether recycled aggregates are used or not. Furthermore, the pozzolanic reaction that occurs between the amorphous silica and the calcium hydroxide (Ca(OH)2) provokes an increase of a 10% in the compressive strength when a 5% of volcanic ash is combined with a 30% of recycled aggregates. Flexural strength does not show significant changes with neither of the residues. On the other hand, decreases between a 14% and a 25% in the elasticity modulus have been found. Concretes with up to a 30% of recycled aggregates and a 5% of volcanic ash as cement replacement can be produced without significant losses in their mechanical properties, reducing considerably the environmental impact of the final material.

Keywords: compressive strength of recycled concrete, mechanical properties of recycled concrete, recycled aggregates, volcanic ash as cement replacement

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Authors: Murat Yucel, Murat Yucel, Nail Ferhat Ozturk, Halim Haldun Goktas, Cemal Gemci, Fatih Vehbi Celebi

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In this study, Brillouin gain spectrum (BGS) is experimentally analyzed in the Brillouin optical time domain reflectometry (BOTDR) and Brillouin optical time domain analyzer (BOTDA). For this purpose, the signal level of the microwave generator is varied and the effects of BGS are investigated. In the setups, 20 km conventional single mode fiber is used to both setups and laser wavelengths are selected around 1550 nm. To achieve best results, it can be used between 5 dBm to 15 dBm signal level of microwave generator for BOTDA and BOTDR setups.

Keywords: microwave signal level, Brillouin gain spectrum, BOTDA, BOTDR

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Authors: Mohammad Obeidat, Ayman Mansour

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In this paper a unique issue rising from feedback control of Atrial Fibrillation monitoring system with embedded communication channels has been investigated. One of the important factors to measure the performance of the feedback control closed loop system is disturbance and noise attenuation factor. It is important that the feedback system can attenuate such disturbances on the atrial fibrillation heart rate signals. Communication channels depend on network traffic conditions and deliver different throughput, implying that the sampling intervals may change. Since signal estimation is updated on the arrival of new data, its dynamics actually change with the sampling interval. Consequently, interaction among sampling, signal estimation, and the controller will introduce new issues in remotely controlled Atrial Fibrillation system. This paper treats a remotely controlled atrial fibrillation system with one communication channel which connects between the heart rate and rhythm measurements to the remote controller. Typical and optimal signal estimation schemes is represented by a signal averaging filter with its time constant derived from the step size of the signal estimation algorithm.

Keywords: atrial fibrillation, communication channels, closed loop, estimation

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Authors: Siavash Eftekharifar, Tohid Yousefi Rezaii, Mahdi Shamsi

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The purpose of this paper is to exploit compressed sensing (CS) method in order to model and compress the electrocardiogram (ECG) signals at a high compression ratio. In order to obtain a sparse representation of the ECG signals, first a suitable basis matrix with Gaussian kernels, which are shown to nicely fit the ECG signals, is constructed. Then the sparse model is extracted by applying some optimization technique. Finally, the CS theory is utilized to obtain a compressed version of the sparse signal. Reconstruction of the ECG signal from the compressed version is also done to prove the reliability of the algorithm. At this stage, a greedy optimization technique is used to reconstruct the ECG signal and the Mean Square Error (MSE) is calculated to evaluate the precision of the proposed compression method.

Keywords: compressed sensing, ECG compression, Gaussian kernel, sparse representation

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Authors: B. Ramakrishna, S. Sivamurthy Reddy

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The various types of aggregates such as granite, dolerite, Quartzite, dolomitic limestone, limestone and river gravel were used to produce the concrete with 28-day target compressive strength of 35, 60, and 80 Mpa. The compressive strength of concrete, as well as aggregates, was measured to study the effect of rupture probability of aggregate on the fracture surface of the concrete. Also, the petrographic studies were carried out to study the texture, type of minerals present and their relative proportions in various types of aggregates. The concrete of various grades produced with the same aggregate has shown a rise in RPCA with strength. However, the above relationship has ceased to exist in the concretes of the same grade, made of different types of aggregates. The carbonate aggregates namely Limestone and Dolomitic limestone have produced concrete with higher RPCA irrespective of the strength of concrete. The mode of origin, texture and mineralogical composition of aggregates have a significant impact on their pulse velocity and thereby the pulse velocity of concrete.

Keywords: RPCA, DL, G, LS, RG

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Authors: Vatsal Patel, Niraj Shah

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The aim of the research reported in this paper is to assess the Strength and durability performance of High Performance Concrete containing different percentages of waste marble powder produced from marble industry. Concrete mixes possessing a target mean compressive strength of 70MPa were prepared with 0%,5%,10%,15% and 20% cement replacement by waste marble powder with W/B =0.33. More specifically, the compressive strength, flexural strength, chloride penetration, sorptivity and accelerated corrosion were determined. Concrete containing 10% waste marble powder proved to have best Mechanical and durability properties than other mixtures made with binary blends. However, poorer performance was noticeable when replacement percentage was higher. The replacement of Waste Marble Powder will have major environmental benefits.

Keywords: durability, high performance concrete, marble waste powder, sorptivity, accelerated corrosion

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Authors: Siavash Mirahmadizoghi, Steven Bell, David Simpson

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In this work a new independent component analysis (ICA) based method for noise reduction in evoked potentials is evaluated on for auditory late responses (ALR) captured with a 63-channel electroencephalogram (EEG) from 10 normal-hearing subjects. The performance of the new method is compared with a single channel alternative in terms of signal to noise ratio (SNR), the number of channels with an SNR above an empirically derived statistical critical value and an estimate of the effect of attention on the major components in the ALR waveform. The results show that the multichannel signal processing method can significantly enhance the quality of the ALR signal and also detect the effect of the attention on the ALR better than the single channel alternative.

Keywords: auditory late response (ALR), attention, EEG, independent component analysis (ICA), multichannel signal processing

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Authors: Emmanuel Kamal Aziz Saba, Gihan Abd El-Lateif Younis El-Tantawi, Mohammed Hamdy Zahran, Ibrahim Khalil Ibrahim, Mohammed Abd El-Salam Shehata, Hussein Al-Moghazy Sultan, Medhat Mohamed Anwar

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Examination of the external anal sphincter muscle strength of voluntary contraction is essential in initial assessment and assessment of efficacy of rehabilitation of patients with faecal incontinence (FI) and obstructed defecation (OD). The present study was conducted to evaluate the digital assessment of the external anal sphincter muscle strength of voluntary contraction by using Modified Oxford Scale (MOS) in comparison to anal manometry squeeze pressure. The present cross-sectional study included 65 patients. There were 40 patients (61.5 %) with FI and 25 patients (38.5 %) with OD. All patients were subjected to history taking, clinical examination including assessment of the external anal sphincter muscle strength of voluntary contraction by using MOS and anal manometry (mean squeeze pressure and maximal squeeze pressure). There was a statistically significant positive correlation between MOS and anal manometry squeeze pressures including mean squeeze pressure and maximal squeeze pressure among FI group and OD group. In conclusion, assessment of the external anal sphincter muscle strength of voluntary contraction by using MOS is a valid method and can substitute anal manometry assessment.

Keywords: anal manometry, external anal sphincter muscle, Modified Oxford Scale, muscle strength

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Authors: J. E. Oti, J. M. Kinuthia, R. Robinson, P. Davies

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In this study, The Compressive strength of concretes made with Ground Granulated Blast furnace Slag (GGBS), pulverised Fuel Ash (PFA), rice Husk Ash (RHA) and Waste Glass Powder (WGP) after they were exposed 7800C (exposure duration of around 60 minutes) and then allowed to cool down gradually in the furnace for about 280 minutes at water binder ratio of 0.50 was investigated. GGBS, PFA, RHA and WGP were used to replace up to 20% Portland cement in the control concrete. Test for the determination of workability, compressive strength and tensile splitting strength of the concretes were carried out and the results were compared with control concrete. The test results showed that the compressive strength decreased by an average of around 30% after the concretes were exposed to the heating and cooling scenario.

Keywords: concrete, heating, cooling, pulverised fuel ash, rice husk ash, waste glass powder, GGBS, workability

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Authors: Mahmut Yildirim

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This paper proposed the bidirectional long short-term memory (Bi-LSTM) network-aided deep learning (DL)-based signal detection for Orthogonal frequency division multiplexing with all index modulation (OFDM-AIM), namely Bi-DeepAIM. OFDM-AIM is developed to increase the spectral efficiency of OFDM with index modulation (OFDM-IM), a promising multi-carrier technique for communication systems beyond 5G. In this paper, due to its strong classification ability, Bi-LSTM is considered an alternative to the maximum likelihood (ML) algorithm, which is used for signal detection in the classical OFDM-AIM scheme. The performance of the Bi-DeepAIM is compared with LSTM network-aided DL-based OFDM-AIM (DeepAIM) and classic OFDM-AIM that uses (ML)-based signal detection via BER performance and computational time criteria. Simulation results show that Bi-DeepAIM obtains better bit error rate (BER) performance than DeepAIM and lower computation time in signal detection than ML-AIM.

Keywords: bidirectional long short-term memory, deep learning, maximum likelihood, OFDM with all index modulation, signal detection

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Authors: Reza Keihani, Ali Bahadori-Jahromi, Timothy James Clacy

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Plastic as an environmental burden is a well-rehearsed topic in the research area. This is due to its global demand and destructive impacts on the environment, which has been a significant concern to the governments. Typically, the use of plastic in the construction industry is seen across low-density, non-structural applications due to its diverse range of benefits including high strength-to-weight ratios, manipulability and durability. It can be said that with the level of plastic consumption experienced in the construction industry, an ongoing responsibility is shown for this sector to continually innovate alternatives for application of recycled plastic waste such as using plastic made replacement from polyethylene, polystyrene, polyvinyl and polypropylene in the concrete mix design. In this study, the impact of partially replaced fine aggregate with polypropylene in the concrete mix design was investigated to evaluate the concrete’s compressive strength by conducting an experimental work which comprises of six concrete mix batches with polypropylene replacements ranging from 0.5 to 3.0%. The results demonstrated a typical decline in the compressive strength with the addition of plastic aggregate, despite this reduction generally mitigated as the level of plastic in the concrete mix increased. Furthermore, two of the six plastic-containing concrete mixes tested in the current study exceeded the ST5 standardised prescribed concrete mix compressive strength requirement at 28-days containing 1.50% and 2.50% plastic aggregates, which demonstrated the potential for use of recycled polypropylene in structural applications, as a partial by mass, fine aggregate replacement in the concrete mix.

Keywords: compressive strength, concrete, polypropylene, sustainability

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Authors: Ayman Othman, Tallat Ali

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The successive increase of generated waste materials like glass has led to many environmental problems. Using crushed waste glass in hot mix asphalt paving has been though as an alternative to landfill disposal and recycling. This paper discusses the possibility of utilizing crushed waste glass, as a part of fine aggregate in hot mix asphalt in Egypt. This is done through evaluation of the mechanical properties of asphalt concrete mixtures mixed with waste glass and determining the appropriate glass content that can be adapted in asphalt pavement. Four asphalt concrete mixtures with various glass contents, namely; 0%, 4%, 8% and 12% by weight of total mixture were studied. Evaluation of the mechanical properties includes performing Marshall stability, indirect tensile strength, fracture energy and unconfined compressive strength tests. Laboratory testing had revealed the enhancement in both compressive strength and Marshall stability test parameters when the crushed glass was added to asphalt concrete mixtures. This enhancement was accompanied with a very slight reduction in both indirect tensile strength and fracture energy when glass content up to 8% was used. Adding more than 8% of glass causes a sharp reduction in both indirect tensile strength and fracture energy. Testing results had also shown a reduction in the optimum asphalt content when the waste glass was used. Measurements of the heat loss rate of asphalt concrete mixtures mixed with glass revealed their ability to hold heat longer than conventional mixtures. This can have useful application in asphalt paving during cold whether or when a long period of post-mix transportation is needed.

Keywords: waste glass, hot mix asphalt, mechanical performance, indirect tensile strength, fracture energy, compressive strength

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Authors: H. Alamri

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Natural fiber reinforced composites have attracted researchers for their desirable properties of toughness, high modulus, low density, recyclability, and renewability. In fact, the use of natural fibers in polymer composites has the potential to produce materials with higher specific strength and specific modulus due of their low density. Likewise, polymer-nano-filler composites have been widely investigated for their unique and significant improvement in strength, modulus, impact strength, barrier properties, heat resistance and thermal stability. In this paper, The addition of halloysite nanotubes (HNTs) with three different weight percentages (1%, 3% and 5%) on enhancing barrier and flexural strength and modulus of cellulose-fiber (CF) /epoxy composites after water treatment for six months was studied. Results indicated that water uptake decreased as HNT content increased. The presence of HNT improved flexural strength and flexural modulus of CF/epoxy composites. SEM results showed damages in fiber-matrix interfacial bonding due to water absorption. The addition of HNTs was found to enhance to adhesion between fibers and matrix.

Keywords: mechanical properties, epoxy, nanocomposites, halloysite nanotubes

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Authors: Dhara Shah, Chandrakant Shah

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As everyone knows, fly ash is a residual material we get upon energy production using coal. It has found numerous advantages for use in the concrete industry like improved workability, increased ultimate strength, reduced bleeding, reduced permeability, better finish and reduced heat of hydration. Types of fly ash depend on the type of coal and the coal combustion process. It is a pozzolanic material and has mainly two classes, F and C, based on the chemical composition. The fly ash used for this experimental work contains significant amount of lime and would be categorized as type F fly ash. Generally all types of fly ash have particle size less than 0.075mm. The fineness and lime content of fly ash are very important as they will affect the air content and water demand of the concrete, thereby affecting the durability and strength of the concrete. The present work has been done to optimize the use of fly ash to produce concrete with improved results and added benefits. A series of tests are carried out, analyzed and compared with concrete manufactured using only Portland cement as a binder. The present study is carried out for concrete mix with replacement of cement with different proportions of fly ash. Two concrete mixes M25 and M30 were studied with six replacements of cement with fly ash i.e. 40%, 45%, 50%, 55%, 60% and 65% for 7-day, 14-day, 28-day, 56-day and 90-day. Study focused on compressive strength, split tensile strength, modulus of elasticity and modulus of rupture of concrete. Study clearly revealed that cement replacement by any proportion of fly ash failed to achieve early strength. Replacement of 40% and 45% succeeded in achieving required flexural strength for M25 and M30 grade of concrete.

Keywords: processed fly ash, engineering properties of concrete, pozzolanic, lime content

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Authors: Neeraj Malhotra, Ramya Shenoy

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Objective: To assess the effect of clinical parameters (bonding agent, preparation design & storage media) on the strength of reattached anterior tooth fragment. Methodology: This is a systematic review and meta-analysis for articles referred from MEDLINE, PUBMED, and GOOGLE SCHOLAR. The articles on tooth reattachment and clinical factors affecting fracture strength/bond strength/fracture resistance of the reattached tooth fragment in anterior teeth and published in English from 1999 to 2016 were included for final review. Results: Out of 120 shortlisted articles, 28 articles were included for the systematic review and meta-analysis based on 3 clinical parameters i.e. bonding agent, tooth preparation design & storage media. Forest plot & funnel plots were generated based on individual clinical parameter and their effect on strength of reattached anterior tooth fragment. Results based on analysis suggest combination of both conclusive evidence favoring the experimental group as well as in-conclusive evidence for individual parameter. Conclusion: There is limited evidence as there are fewer articles supporting each parameter in human teeth. Bonding agent had showed better outcome in selected studies.

Keywords: bonding agent, bond strength, fracture strength, preparation design, reattachment, storage media

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Authors: K. Bala Subramanian, A. Siva, S. Swaminathan, Arul. M. G. Ajin

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Concrete is an essential building material which is widely used in construction industry all over the world due to its compressible strength. Curing of concrete plays a vital role in durability and other performance necessities. Improper curing can affect the concrete performance and durability easily. When areas like scarcity of water, structures is not accessible by humans external curing cannot be performed, so we opt for internal curing. Internal curing (or) self-curing plays a major role in developing the concrete pore structure and microstructure. The concept of internal curing is to enhance the hydration process to maintain the temperature uniformly. The evaporation of water in the concrete is reduced by self-curing agent (Super Absorbing Polymer – SAP) thereby increasing the water retention capacity of the concrete. The research work was carried out to reduce water, which is prime material used for concrete in the construction industry. Concrete curing plays a major role in developing hydration process. Concept of self-curing will reduce the evaporation of water from concrete. Self-curing will increase water retention capacity as compared to the conventional concrete. Proper self-curing (or) internal curing increases the strength, durability and performance of concrete. Super absorbing Polymer (SAP) used as internal curing agent. In this study 0.2% to 0.4% of SAP was varied in different grade of high strength concrete. In the experiment replacement of cement by silica fumes with 5%, 10% and 15% are studied. It is found that replacement of silica fumes by 10 % gives more strength and durability when compared to others

Keywords: compressive strength, high strength concrete rapid chloride permeability, super absorbing polymer

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Authors: Ammar Neshati, Elham Hamidi Shishavan

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Statement of Problem: The increase in the use of metal-ceramic restorations and a high prevalence of porcelain chipping entails introducing an alloy which is more compatible with porcelain and which causes a stronger bond between the two. This study is to compare shear bond strength of three base-metal alloys and one noble alloy with the common VMK Master Porcelain. Materials and Method: Three different groups of base-metal alloys (Ni-cr-T3, Super Cast, Verabond) and one group of noble alloy (x-33) were selected. The number of alloys in each group was 15. All the groups went through the casting process and change from wax pattern into metal disks. Then, VMK Master Porcelain was fired on each group. All the specimens were put in the UTM and a shear force was loaded until a fracture occurred. The fracture force was then recorded by the machine. The data was subjected to SPSS Version 16 and One-Way ANOVA was run to compare shear strength between the groups. Furthermore, the groups were compared two by two through running Tukey test. Results: The findings of this study revealed that shear bond strength of Ni-Cr-T3 alloy was higher than the three other alloys (94 Mpa or 330 N). Super Cast alloy had the second greatest shear bond strength (80. 87 Mpa or 283.87 N). Both Verabond (69.66 Mpa or 245 N) and x-33 alloys (66.53 Mpa or 234 N) took the third place. Conclusion: Ni-Cr-T3 with VMK Master Porcelain has the greatest shear bond strength. Therefore, the use of this low-cost alloy is recommended in metal-ceramic restorations.

Keywords: shear bond, base-metal alloy, noble alloy, porcelain

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Authors: Patricia N. Baguio, Angel Amy M. Bunag, Paul Bryan E. Ornopia, John Paul C. Suel

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This research investigates the viability and efficiency of employing ceramic tile additives derived from horn snail shell material, specifically calcium carbonate (CaCO₃). The study aims to evaluate the mechanical properties of ceramic tiles with Calcium Carbonate with varying amounts of CaCO₃, focusing on breaking and flexural strength. The research employs a comprehensive methodology, including material collection, slurry forming, shaping, drying, firing, and statistical analysis using paired sample T-tests. The result indicates a positive correlation between calcium carbonate (CaCO₃) application and ceramic tile strength, revealing increased breaking strength from 29.41 N (non-calcium Carbonate) to 46.02 N (70g CaCO3) and a substantial enhancement to 82.61 N with 150g CaCO₃. Comparative analyses show higher breaking and flexural strength in tiles with Calcium Carbonate with 150g CaCO₃ analysis (p = 0.011), indicating its feasibility for ceramic tile manufacturing, while 70g CaCO₃ shows no significant difference from non-calcium Carbonate tiles (p = 0.135). The addition of horn snail shells shows potential for improving ceramic tile quality and contributes positively to waste management in standard tile production processes.

Keywords: Horn snail shell, calcium carbonate, breaking strength, flexural strength

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Authors: Emre Ozaslan, Bulent Acar, Mehmet Ali Guler

Abstract:

Unidirectional composites are very popular structural materials used in aerospace, marine, energy and automotive industries thanks to their superior material properties. However, the mechanical behavior of composite materials is more complicated than isotropic materials because of their anisotropic nature. Also, a stress concentration availability on the structure, like a hole, makes the problem further complicated. Therefore, enormous number of tests require to understand the mechanical behavior and strength of composites which contain stress concentration. Accurate finite element analysis and analytical models enable to understand mechanical behavior and predict the strength of composites without enormous number of tests which cost serious time and money. In this study, unidirectional Carbon/Epoxy composite specimens with central circular hole were investigated in terms of stress concentration factor and strength prediction. The composite specimens which had different specimen wide (W) to hole diameter (D) ratio were tested to investigate the effect of hole size on the stress concentration and strength. Also, specimens which had same specimen wide to hole diameter ratio, but varied sizes were tested to investigate the size effect. Finite element analysis was performed to determine stress concentration factor for all specimen configurations. For quasi-isotropic laminate, it was found that the stress concentration factor increased approximately %15 with decreasing of W/D ratio from 6 to 3. Point stress criteria (PSC), inherent flaw method and progressive failure analysis were compared in terms of predicting the strength of specimens. All methods could predict the strength of specimens with maximum %8 error. PSC was better than other methods for high values of W/D ratio, however, inherent flaw method was successful for low values of W/D. Also, it is seen that increasing by 4 times of the W/D ratio rises the failure strength of composite specimen as %62.4. For constant W/D ratio specimens, all the strength prediction methods were more successful for smaller size specimens than larger ones. Increasing the specimen width and hole diameter together by 2 times reduces the specimen failure strength as %13.2.

Keywords: failure, strength, stress concentration, unidirectional composites

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Authors: Hung Chih Hsieh, Cheng Hao Chang, Yun Hsiang Chang, Yu Lin Chang

Abstract:

In the applications of the spectrometer, the stray light that comes from the environment affects the measurement results a lot. Hence, environment and instrument quality control for the stray reduction is critical for the spectral reflectance measurement. In this paper, a simple and practical method has been developed to correct a spectrometer's response for measurement errors arising from the environment's and instrument's stray light. A sinusoidal modulated light intensity signal was incident on a tested sample, and then the reflected light was collected by the spectrometer. Since a sinusoidal signal modulated the incident light, the reflected light also had a modulated frequency which was the same as the incident signal. Using the three-parameter sine curve fitting algorithm, we can extract the primary reflectance signal from the total measured signal, which contained the primary reflectance signal and the stray light from the environment. The spectra similarity between the extracted spectra by this proposed method with extreme environment stray light is 99.98% similar to the spectra without the environment's stray light. This result shows that we can measure the reflectance spectra without the affection of the environment's stray light.

Keywords: spectrometer, stray light, three-parameter sine curve fitting, spectra extraction

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Authors: Dong Xie, Leah Howard, Yiming Weng

Abstract:

The objective of this study was to synthesize and characterize 5-acryloyloxy-3,4-dichlorocrotonolactone (a furanone derivative), use this derivative to modify a dental restorative, and study the effect of the derivative on the antibacterial activity and compressive strength of the formed restorative. In this study, a furanone derivative was synthesized, characterized, and used to formulate a dental restorative. Compressive strength (CS) and S. mutans viability were used to evaluate the mechanical strength and antibacterial activity of the formed restorative. The fabricated restorative specimens were photocured and conditioned in distilled water at 37oC for 24 h, followed by direct testing for CS or/and incubating with S. mutans for 48 h for antibacterial testing. The results show that the modified dental restorative showed a significant antibacterial activity without substantially decreasing the mechanical strengths. With addition of the antibacterial derivative up to 30%, the restorative kept its original CS nearly unchanged but showed a significant antibacterial activity with 68% reduction in the S. mutans viability. Furthermore, the antibacterial function of the modified restorative was not affected by human saliva. The aging study also indicates that the modified restorative may have a long-lasting antibacterial function. It is concluded that this experimental antibacterial restorative may potentially be developed into a clinically attractive dental filling restorative due to its high mechanical strength and antibacterial function.

Keywords: antibacterial, dental restorative, compressive strength, S. mutans viability

Procedia PDF Downloads 300