Search results for: series resistance effect

Authors: Leyla Sattarzadeh, Maghsoud Peeri, Mohammadali Azarbaijani, Hasan Matin Homaee

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Inflammation by various mechanisms may cause atherosclerosis. Systemic circulating inflammatory markers such as C-reactive protein (CRP), pro-inflammatory cytokines such as Interleukin-6 (IL-6) and adhesion molecules like Intracellular Adhesion Molecule-1 (ICAM-1) are the predictors of cardiovascular diseases. Regarding the conflicting results about the effect of resistance exercise training on these inflammatory markers, the present study aimed to examine the effect of eight week different patterns of resistance exercise training on CRP, IL-6 and ICAM-1 levels in healthy untrained women. 40 volunteered and healthy untrained female university students (aged: 21+ 3 yr., Body Mass Index: 21.5+ 3.5 kg/m2) were selected purposefully and divided into three groups. At the end of training protocol and after subjects drop during the protocol in upper body exercise training (n=11), lower body (n=12) completed the eight week of training period although the control group (n=7) did anything. Blood samples gathered pre and post experimental period and CRP, IL-6 and ICAM-1 levels were evaluated using special laboratory kits, then the difference of pre and post values of each indices analyzed using one way Analysis of Variance (α < 0.05). The results of one way ANOVA for difference of pre and post values of CRP and ICAM-1 showed no significant changes due to the exercise training. But there were significant differences between groups about IL-6. Tukey post- hoc test indicated that there is significant difference between the differences of pre and post values of IL-6 between lower body exercise training group and control group, and eight weeks of lower body exercise training lead to significant changes in IL-6 values. There were no changes in anthropometric indices. The findings show that the different patterns of upper and lower body exercise training by involving the different amount of muscles altered the IL-6 values in lower body exercise training group probably because of engaging the bigger amount of muscles, but showed any significant changes about CRP and ICAM-1 probably due to intensity and duration of exercise or the lower levels of these markers at baseline of healthy people.

Keywords: C-reactive protein, interleukin-6, intracellular adhesion molecule-1, resistance training

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Authors: Tzu-Hsuan Lei, Shu-Chien Wu, Kuang-Che Lo, Shu-Chi Liu, Yu-Cheng Liu

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The focus of this study was on the effects of air propagation associated with vented holes on acoustic resistance properties. A cylindrical hole with diameter and depth of 0.7 mm and 1.0 mm, respectively, was the research target. By constructing a finite element analytical model of its sound field properties, the acoustic-specific airflow resistance relationships were obtained for the differences in sound pressure and flow velocity at the two ends of this vented hole. In addition, the acoustic properties of this vented hole were included in the in-ear earphone simulation model to complete the sound pressure curve simulation analysis of the in-ear earphone system with a vented hole of corresponding size. Then, the simulation results were compared with actual measurements obtained from the standard system. Based on the results, when the in-ear earphone vented hole simulation model considered the simulated specific airflow resistance values of this cylindrical hole, the overall simulated sound pressure performance was highly consistent with that of measured values. The difference in the first peak values of sound pressure at mid-to-low frequencies was reduced from 5.64% when the simulation model did not consider the specific airflow resistance of the cylindrical hole to 1.18%, and the accuracy of the overall simulation was around 70%. This indicates the importance of the acoustic resistance properties of vented holes. Moreover, as specific airflow resistance values were able to be further quantified, the accuracy of the entire in-ear earphone simulation was ultimately and effectively elevated.

Keywords: specific airflow resistance, vented holes, in-ear earphone, finite element method

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Authors: Kianoosh Samimi, Siham Kamali-Bernard, Ali Akbar Maghsoudi

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This paper aims to contribute to the characterization and the understanding of fresh state, compressive strength and chloride penetration tendency of high strength self-compacting concretes (HSSCCs) where Portland cement type II is partially substituted by 10% and 15% of natural pumice and zeolite. First, five concrete mixtures with a control mixture without any pozzolan are prepared and tested in both fresh and hardened states. Then, resistance to chloride penetration for all formulation is investigated in non-steady state and steady state by measurement of chloride penetration and diffusion coefficient. In non-steady state, the correlation between initial current and chloride penetration with diffusion coefficient is studied. Moreover, the relationship between diffusion coefficient in non-steady state and electrical resistivity is determined. The concentration of free chloride ions is also measured in steady state. Finally, chloride penetration for all formulation is studied in immersion and tidal condition. The result shows that, the resistance to chloride penetration for HSSCC in immersion and tidal condition increases by incorporating pumice and zeolite. However, concrete with zeolite displays a better resistance. This paper shows that the HSSCC with 15% pumice and 10% zeolite is suitable in fresh, hardened, and durability characteristics.

Keywords: Chloride penetration, immersion, pumice, HSSCC, tidal, zeolite

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Authors: Sergey M. Karabanov, Dmitry V. Suvorov

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Magnetically controlled microelectromechanical system (MCMEMS) switches is one of the directions in the field of micropower switching technology. MCMEMS switches are a promising alternative to Hall sensors and reed switches. The most important parameter for MCMEMS is the contact resistance, which should have a minimum value and is to be stable for the entire duration of service life. The value and stability of the contact resistance is mainly determined by the contact coating material. This paper presents the research results of a contact coating based on nanoscale ruthenium films obtained by electrolytic deposition. As a result of the performed investigations, the deposition modes of ruthenium films are chosen, the regularities of the contact resistance change depending on the number of contact switching, and the coating roughness are established. It is shown that changing the coating roughness makes it possible to minimize the contact resistance.

Keywords: contact resistance, electrode coating, electrolytic deposition, magnetically controlled MEMS

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Authors: A. Mohammed, R. Lewis, M. Marshall

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Commonly used coatings to protect tools in die casting were used. A heat treatment and then surface coating can have a large effect on erosion damage. Samples have been tested to evaluate their resistances to erosive wear and to assess how this compares with behaviour seen for untreated material. Five commercial (PN + TiN), (PN + TiAlCN), (TiN X 2), (TiN), and (TiAlCN) coatings have been evaluated for their wear resistance. The objective was to permit an optimized selection of coatings to be used to give good resistance to erosive wear. A test-Rig has been developed to study the erosive wear in aluminium die casting and provide an environment similar to industrial operation that is more practical than using actual machines. These surfaces were analysed using a Scanning Electron Microscope (SEM) and Optical Microscopes each with a different level of resolution. Examination of coating materials revealed an important parameter associated with the failure of the coating materials.This was adhesion of the coating material to the substrate surface. A well-adhered coating withstands wear much better compared to the poorest-adhering coating.

Keywords: solid particle erosion, PVD-coatings, steel, erosion testing

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Authors: Rosetta Moshirian Farahi, Ahya Abdi Ali, Sara Gharavi

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The major mechanism of Pseudomonas aeruginosa resistance to fluoroquinolones is the alteration of target enzymes, type II and IV topoisomerases due to mutations in the quinolone resistance-determining regions (QRDR) of the gyrA and parC genes coding A subunits of these enzymes. 37 isolates from patients with burn wounds and 20 isolates from blood, urine and sputum specimen were selected to evaluate mutations involved in antibiotic resistance and were subsequently verified for their resistance to ciprofloxacin. QRDRs regions of gyrA and parC were amplified by polymerase chain reaction (PCR) and were subsequently sequenced. 90% of isolates with MIC≥8 µg/ml to ciprofloxacin had a mutation in gyrA gene in which threonine at position 83 changed to isoleucine. 87.5% of isolates had mutation in parC, Serine 87 changed. 75% had Ser87Leu and 12.5% possessed Serin87Trp. Various silent mutations were also detected such as Val103Val, Ala118Ala, Ala136Ala, His132His in gyrA and Ala115Ala in parC. The data indicates that the common mutation in gyrA is Thr83Ile and in parC is Ser87Leu/Trp. No individual parC mutation was observed while mutations in gyrA and parC occurred simultaneously and appears to be the main reason of high-level resistance to fluoroquinolones in patients with burn wounds and urine infection. The vast majority of P.aeruginosa isolates had mutation in parC which can play a crucial role in increased resistance of these isolates. This is a report of parC mutations from resistant P. aeruginosa isolates from Iran, Tehran.

Keywords: P. aeruginosa, fluoroquinolones, gyrA, parC, antibiotic resistance

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Authors: Vinit Srivastava, Abhay Singh Thakur, Shivam Dubey, Rahul Vaish, Bharat Singh Rajpurohit

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This study examines the problem of students' poor comprehension of the thermal dependence of resistance by investigating this idea using an evidence-based inquiry approach. It suggests a practical exercise to improve secondary school students' comprehension of how materials' resistance to temperature changes. The suggested exercise uses an Arduino and Peltier device to test the resistance of aluminum and graphite at various temperatures. The study attempts to close the knowledge gap between the theoretical and practical facets of the subject, which students frequently find difficult to grasp. With the help of a variety of resistors made of various materials and pencils of varying grades, the Arduino experiment investigates the resistance of a metallic conductor (aluminum) and a semiconductor (graphite) at various temperatures. The purpose of the research is to clarify for students the relationship between temperature and resistance and to emphasize the importance of resistor material choice and measurement methods in obtaining precise and stable resistance values over dynamic temperature variations. The findings show that while the resistance of graphite decreases with temperature, the resistance of metallic conductors rises with temperature. The results also show that as softer lead pencils or pencils of a lower quality are used, the resistance values of the resistors drop. In addition, resistors showed greater stability at lower temperatures when their temperature coefficients of resistance (TCR) were smaller. Overall, the results of this article show that the suggested experiment is a useful and practical method for teaching students about resistance's relationship to temperature. It emphasizes how crucial it is to take into account the resistor material selection and the resistance measurement technique when designing and picking out resistors for various uses. The results of the study are anticipated to guide the creation of more efficient teaching methods to close the gap between science education's theoretical and practical components.

Keywords: electrical resistance, temperature dependence, science education, inquiry-based activity, resistor stability

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Authors: Viera Zatkalíková, Lenka Markovičová, Aneta Tor-Swiatek

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The effect of molybdate addition to chloride environment on resistance of AISI 316Ti stainless steel to pitting corrosion was studied. Potentiodynamic polarisation tests were performed in 1 M and 0.1 M chloride acidified solutions with various additions of sodium molybdate at room temperature. The presented results compare the effect of molybdate anions on quality of passive film (expressed by the pitting potential) in both chloride solutions. The pitting potential increases with the increase inhibitor concentration. The inhibitive effect of molybdate ions is stronger in chloride solution of lower aggressiveness (0.1M).

Keywords: AISI 316Ti steel, molybdate inhibitor, pitting corrosion, pitting potential, potentiodynamic polarisation

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Authors: Naresh Radaliyagoda, Nigel M. Jennett, Rong Lan, David Parfitt

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A series of length scale engineered multilayer material with temperature robust mechanical properties has been suggested. A range of polycrystalline copper sub-layers with the thickness varying from 1 to 25μm and buried in between two nickel layers was produced using electrodeposition dual bath technique. The structure of the multilayers was characterized using Electron Backscatter Diffraction and Scanning Electron Microscope. The interface effect on the hardness and elastic modulus was tested using Nano-indentation. Results of the grain size and layer thickness measurements, and indentation hardness have been compared. It is found that there is a combined length scale effect that improves mechanical properties in Ni/Cu multilayer structures.

Keywords: nano-indentation, size effect, multilayers, electrodeposition

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Authors: Sumit Sen, Sohan Khedekar, Umang Shinde, Shivam Bhargava

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This study has been undertaken to investigate whether the deep learning models are able to predict the future stock prices by training the model with the historical stock price data. Since this work required time series analysis, various models are present today to perform time series analysis such as Recurrent Neural Network LSTM, ARIMA and Facebook Prophet. Applying these models the movement of stock price of stocks are predicted and also tried to provide the future prediction of the stock price of a stock. Final product will be a stock price prediction web application that is developed for providing the user the ease of analysis of the stocks and will also provide the predicted stock price for the next seven days.

Keywords: Autoregressive Integrated Moving Average, Deep Learning, Long Short Term Memory, Time-series

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Authors: A. Khodadadi, Hasani, Salehi

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The advantages of using modified asphalt binders are widely recognized—primarily, improved rutting resistance, reduced fatigue cracking and less cold-temperature cracking. Nanoclays are known to enhance the properties of many polymers. Nanoclays are used to improve modulus and tensile strength, flame resistance and thermal and structural properties of many materials. This paper intends to investigate the application and development of nano-technological concepts for bituminous materials and asphalt pavements. The application of nano clay on the fatigue life of asphalt pavement have not been yet thoroughly understood. In this research, two type of highway asphalt materials, dense Marshall specimens, with 2% nano clay and without nano clay, were employed for the fatigue behavior of the asphalt pavement.The effect of nano additive on the performance of flexible pavements has been investigated through the indirect tensile test for the samples prepared with 2% nano clay and without nano clay in four stress levels from 200–500 kPa. The primary results indicated samples with 2% nano clay have almost double or even more fatigue life in most of stress levels.

Keywords: Nano clay, Asphalt, fatigue life, pavement

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Authors: Muhammad Imran, Iqra Basit, Mobushir Riaz Khan, Sajid Rasheed Ahmad

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The present study investigates the space-time impact of climate change on the rice crop calendar in tropical Gujranwala, Pakistan. The climate change impact was quantified through the climatic variables, whereas the existing calendar of the rice crop was compared with the phonological stages of the crop, depicted through the time series of the Normalized Difference Vegetation Index (NDVI) derived from Landsat data for the decade 2005-2015. Local maxima were applied on the time series of NDVI to compute the rice phonological stages. Panel models with fixed and cross-section fixed effects were used to establish the relation between the climatic parameters and the time-series of NDVI across villages and across rice growing periods. Results show that the climatic parameters have significant impact on the rice crop calendar. Moreover, the fixed effect model is a significant improvement over cross-sectional fixed effect models (R-squared equal to 0.673 vs. 0.0338). We conclude that high inter-annual variability of climatic variables cause high variability of NDVI, and thus, a shift in the rice crop calendar. Moreover, inter-annual (temporal) variability of the rice crop calendar is high compared to the inter-village (spatial) variability. We suggest the local rice farmers to adapt this change in the rice crop calendar.

Keywords: Landsat NDVI, panel models, temperature, rainfall

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Authors: Tushnik Sarkar, Mofazzal H. Khondekar, Subrata Banerjee

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This paper investigates the nature of the fluctuation of the daily average Solar wind speed time series collected over a period of 2492 days, from 1^st January, 1997 to 28^th October, 2003. The degree of self-similarity and scalability of the Solar Wind Speed signal has been explored to characterise the signal fluctuation. Multi-fractal Detrended Fluctuation Analysis (MFDFA) method has been implemented on the signal which is under investigation to perform this task. Furthermore, the singularity spectra of the signals have been also obtained to gauge the extent of the multifractality of the time series signal.

Keywords: detrended fluctuation analysis, generalized hurst exponent, holder exponents, multifractal exponent, multifractal spectrum, singularity spectrum, time series analysis

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Authors: WooYoung Jung, V. Sim

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This paper presents numerical analysis in terms of buckling resistance strength of polymer matrix composite (PMC) infill panels system under the influence of temperature on the foam core. Failure mode under in-plane compression is investigated by means of numerical analysis with ABAQUS platform. Parameters considered in this study are contact length and both the type of foam for core and the variation of its Young's Modulus under the thermal influence. Variation of temperature is considered in static cases and only applied to core. Indeed, it is shown that the effect of temperature on the panel system mechanical properties is significance. Moreover, the variations of temperature result in the decrements of the system strength. This is due to the polymeric nature of this material. Additionally, the contact length also displays the effect on performance of infill panel. Their significance factors are based on type of polymer for core. Hence, by comparing difference type of core material, the variation can be reducing.

Keywords: buckling, contact length, foam core, temperature dependent

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Authors: Ibetombi Soibam

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Li-Zn-Ni ferrite having the compositional formula Li0.4-0.5xZn0.2NixFe2.4-0.5xO4 where x = 0.02 ≤ x ≤0.1 in steps of 0.02 was fabricated by the citrate precursor method. In this method, metal nitrates and citric acid was used to prepare the gel which exhibit self-propagating combustion behavior giving the required ferrite sample. The ferrite sample was given a pre-firing at 650°C in a programmable conventional furnace for 3 hours with a heating rate of 5°C/min. A series of the sample was finally given conventional sintering (CS) at 1040°C after the pre-firing process. Another series was given microwave sintering (MS) at 1040°C in a programmable microwave furnace which uses a single magnetron operating at 2.45 GHz frequency. X- ray diffraction pattern confirmed the spinel phase structure for both the series. The theoretical and experimental density was calculated. It was observed that densification increases with the increase in Ni concentration in both the series. However, samples sintered by microwave technique was found to be denser. The microstructure of the two series of the sample was examined using scanning electron microscopy (SEM). Dielectric properties have been investigated as a function of frequency and composition for both series of samples sintered by CS and MS technique. The variation of dielectric constant with frequency show dispersion for both the series. It was explained in terms of Koop’s two layer model. From the analysis of dielectric measurement, it was observed that the value of room temperature dielectric constant decreases with the increase in Ni concentration for both the series. The microwave sintered samples show a lower dielectric constant making microwave sintering suitable for high-frequency applications. The possible mechanisms contributing to all the above behavior is being discussed.

Keywords: citrate precursor, dielectric constant, ferrites, microwave sintering

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Authors: Bernice V. Y. Wong, Kong Fah Tee

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Cross-laminated timber is increasingly being used in the construction of high-rise buildings due to its simple manufacturing system. In term of fire resistance, cross-laminated timber panels are promoted as having excellent fire resistance, comparable to that of non-combustible materials and to heavy timber construction, due to the ability of thick wood assemblies to char slowly at a predictable rate while maintaining most of their strength during the fire exposure. This paper presents an overview of fire performance of cross-laminated timber and evaluation of its resistance to elevated temperature in comparison to homogeneous timber panels. Charring rates for cross-laminated timber panels of those obtained experimentally were compared with those provided by Eurocode simplified calculation methods.

Keywords: timber structure, cross-laminated timber, charring rate, timber fire resistance

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Authors: M. J. Kim, D. B. Lee

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Centrifugal casting is a metal casting method that uses forces make by centripetal acceleration to distribute molten material in mold. Centrifugal cast parts manufactured in industry contain gas pipes and water supply lines, moreover rings, turbocharger, bushings, brake drums. Turbochargers were exposed to exhaust temperatures of 900-1050°C require a material for the corrosion resistance that will withstand such high component temperatures during the entire service life of the vehicle. Hence, the study of corrosion resistance for turbocharger is important for practical application. DIN1.4091 steels were used widely. The DIN1.4091 steels whose compositions were Fe-34.4Cr-14.5Ni-2.5Mo-0.4W-0.4Mn-0.5Si-(0.009 or 0.35)S (wt.%) were centrifugally cast, and oxidized at 900°C for 50-200 h in order to find the effect of sulfur on the high-temperature oxidation of Fe-34.4Cr-14.5Ni-2.5Mo-0.4W-0.4Mn-0.5Si-(0.009 or 0.35)S (wt.%) alloys. These alloys formed oxide scales that consisted primarily of Cr₂O₃ as the major oxide and Cr₂MnO₄ as the minor one through preferential oxidation of Cr and Mn. Cr formed a thin CrOx oxide film on the surface to prevent further oxidation, and when it is added more than 20%, the sulphide decreased corrosion rate. The high affinity of Mn with S, led to the formation of scattered MnS inclusions, particularly in the 0.35S-containing cast alloy. Sulfur was harmful to the oxidation resistance because it deteriorated the scale/alloy adherence so as to accelerate the adherence and compactness of the formed scales. Acknowledgement: This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2016R1A2B1013169).

Keywords: centrifugal casting, turbocharger, sulfur, oxidation, Fe-34.4Cr-14.5Ni alloy

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Authors: Lule Basha, Eralda Gjika

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The exchange rate is one of the most important economic variables, especially for a small, open economy such as Albania. Its effect is noticeable in one country's competitiveness, trade and current account, inflation, wages, domestic economic activity, and bank stability. This study investigates the fluctuation of Albania’s exchange rates using monthly average foreign currency, Euro (Eur) to Albanian Lek (ALL) exchange rate with a time span from January 2008 to June 2021, and the macroeconomic factors that have a significant effect on the exchange rate. Initially, the Random Forest Regression algorithm is constructed to understand the impact of economic variables on the behavior of monthly average foreign currencies exchange rates. Then the forecast of macro-economic indicators for 12 months was performed using time series models. The predicted values received are placed in the random forest model in order to obtain the average monthly forecast of the Euro to Albanian Lek (ALL) exchange rate for the period July 2021 to June 2022.

Keywords: exchange rate, random forest, time series, machine learning, prediction

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Authors: Lur N. Dreier

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Spontaneous transformation in Ursus maritimus is generally considered to be seldom, albeit not, to this author's best knowledge, previously unpublished in the medical literature. However, no case series has to date described transformative spontaneous processes to filios hominum species. Norwegian public hospital system, is, however, especially the grounds of the specific climate in the Northern hemisphere, and because of a high suited to observe such transformations, both on income level. Hence, this paper describes, to our knowledge, the first case series of 25 patients undergoing treatment for spontaneous transformation in four Norwegian hospitals. The methodology was to include patients on a consecutive basis, identifying clinically and laboratory the typology in each of the four hospitals. The major findings were that the archetypes were heterogeneous, with coercive laboratory findings, with a high degree of redundancy of the process. This might potentially lead to many advances in the diagnostics.

Keywords: case series, transformation, hominum species, maritimus species

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Authors: F. Gheldane, S. Bouras

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Crack propagation behaviour of alumina mullite zirconia ceramic is investigated under monotonic and cyclic loading by means SENB bending method. This material show R-curve effects, i.e. an increase in crack growth resistance with increasing crack depth. The morphological study showed that the resistance of the crack propagation is mainly connected to the crack bridging. The value of bridging stress is in good agreement with the literature. Furthermore, cyclic-loading fatigue is caused by a decrease in the stress-shielding effect, due to degradation of bridging sites under cyclic loading.

Keywords: alumina mullite zirconia, R-curve, bridging, toughening, crack

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Authors: Jonardan Koner

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The study attempts to find out the impact of infrastructural investment on state economic growth in India. It further tries to determine the magnitude of the impact of infrastructural investment on economic indicator, i.e., per-capita income (PCI) in Indian States. The study uses panel regression technique to measure the impact of infrastructural investment on per-capita income (PCI) in Indian States. Panel regression technique helps incorporate both the cross-section and time-series aspects of the dataset. In order to analyze the difference in impact of the explanatory variables on the explained variables across states, the study uses Fixed Effect Panel Regression Model. The conclusions of the study are that infrastructural investment has a desirable impact on economic development and that the impact is different for different states in India. We analyze time series data (annual frequency) ranging from 1991 to 2010. The study reveals that the infrastructural investment significantly explains the variation of economic indicators.

Keywords: infrastructural investment, multiple regression, panel regression techniques, economic development, fixed effect dummy variable model

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Authors: Milad Alizadeh Galdiani, Jabbar Ali Zakeri

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Lateral movement of CWR ballasted track occurs in sharp curves because of the lack of adequate lateral resistance. Several strategies have been proposed and used for increase the lateral resistance of ballasted tracks, but still there are some problems in tracks with small radius curves. In this paper, a new method has been presented for increase the lateral resistance. This method is using the lateral supports as numerical and field studies. In this paper, the field and laboratory tests have been conducted by using the single tie pressure test (STPT) and track panel loading test (LTPT). Then, their results were compared with the numerical results. The results of numerical and field tests showed that the lateral stiffness of ballasted tracks significantly increased when there were lateral supports in ballasted tracks. Also, the track structure had a bilinear behavior.

Keywords: ballasted railway, Lateral resistance, railway buckling, field and numerical studies

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Authors: Sharon Lopez

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Much of critical thought dismisses the notion of subaltern women engaging in resistance because of her complex colonial identity. She is seen in postcolonial theory as being "doubly effaced" and removed from exercising control to speak up and taking part in defiance. This line of reasoning suggests a critical area in which engaging with issues unavoidably excludes subaltern women from the emerging resistance discourse. A position like this also suggests a closed-minded view of human experience and a desire to maintain subalternity. The argument here is that subaltern women might be understood as achieving agency when they engage in resistance and speak out about their circumstances, whether aloud or in silence. Using deductions from Mahasweta Devi's literary narratives such as Imaginary Maps and Breast Stories, the study investigates the tactics Devi employs to engage marginalised women into resistance and establishes that the 'body' emerges in her stories not just as a site of oppression but also as an important motif of power and resistance.

Keywords: subaltern woman, reproductive docy, breast giver, devi

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Authors: Sadaf Ilyas, Saba Riaz

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The extensive use of antibiotics has led to increases emergence of antibiotic-resistant organisms. Pseudomonas is a notorious opportunistic pathogen involoved in nosocomial infections and exhibit innate resistance to many antibiotics. The present study was conducted to assess the prevalence, levels of antimicrobial susceptibility and resistance mechanisms of Pseudomonas. A total of thirty clinical strains of Pseudomonas were isolated from different clinical sites of infection. All clinical specimens were collected from Chughtais Lahore Lab. Jail road, during 8-07-2010 to 11-01-2011. Biochemical characterization was done using routine biochemical tests. Antimicrobial susceptibility was determined by Kirby-Baeur method. The plasmids were isolated from all the strains and digested with restriction enzyme PstI and EcoRI. Transfer of Multi-resistance plasmid was checked via transformation and conjugation to confirm the plasmid mediated resistance to antibiotics. The prevalence of Pseudomonas in clinical specimens was found out to be 14% of all bacterial infections. IPM has shown to be the most effective drug against Pseudomonas followed by CES, PTB and meropenem, wheareas most of the Pseudomonas strains have developed significant resistance against Penicillins and some Cephalasporins. Antibiotic resistance determinants were carried by plasmids, as they conferred resistance to transformed K1 strains. The isolates readily undergo conjugation, transferring the resistant genes to other strains, illustrating the high rates of cross infection and nosocomial infection in the immunocompromised patients.

Keywords: pseudomonas, antibiotics, drug resistance, horizontal gene transfer

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Authors: Eyal Rosen

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This study is aimed to report a possible effect of the presence of dental implants on the development of crown or root fractures in adjacent natural teeth. A series of 26 cases of teeth diagnosed with crown or root fractures following the placement of adjacent dental implants is presented. In addition, a comprehensive systematic review of the literature was performed to detect other studies that evaluated this possible complication. The case series analysis revealed that all crown-fractured teeth were non-endodontically treated teeth (n=18), and all root fractured teeth were endodontically treated teeth (n=8). The time from implant loading to the diagnosis of a fracture in an adjacent tooth was longer than 1 year in 78% of cases. The majority of crown or root fractures occurred in female patients, over 50 years of age, with an average age of 59 in the crown fractures group, and 54 in the root fractures group. Most of the patients received 2 or more implants. Nine (50%) of the teeth with crown fracture were molars, 7 (39%) were mandibular premolars, and 2 (11%) were incisor teeth. The majority of teeth with root fracture were premolar or mandibular molar teeth (6 (75%)). The systematic review of the literature did not reveal additional studies that reported on this possible complication. To the best of the author’s knowledge this case series, although limited in its extent, is the first clinical report of a possible serious complication of implants, associated fractures in adjacent endodontically and non-endodontically treated natural teeth. The most common patient profile found in this series was a woman over 50 years of age, having a fractured premolar tooth, which was diagnosed more than 1 year after reconstruction that was based on multiple adjacent implants. Additional clinical studies are required in order to shed light on this potential serious complication.

Keywords: complications, dental implants, endodontics, fractured teeth

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Authors: Valeria Bondarenko

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In this paper, we propose two problems related to fractal Brownian motion. First problem is simultaneous estimation of two parameters, Hurst exponent and the volatility, that describe this random process. Numerical tests for the simulated fBm provided an efficient method. Second problem is approximation of the increments of the observed time series by a power function by increments from the fractional Brownian motion. Approximation and estimation are shown on the example of real data, daily deposit interest rates.

Keywords: fractional Brownian motion, Gausssian processes, approximation, time series, estimation of properties of the model

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Authors: N. Ben Si Ali, N. Benalia, N. Zarzouri

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Speed sensorless systems are intensively studied during recent years; this is mainly due to their economical benefit and fragility of mechanical sensors and also the difficulty of installing this type of sensor in many applications. These systems suffer from instability problems and sensitivity to parameter mismatch at low speed operation. In this paper an analysis of adaptive observer stability with stator resistance estimation is given.

Keywords: motor drive, sensorless control, adaptive observer, stator resistance estimation

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Authors: Hesham A. Elkaranshawy, Amr M. Abdelrazek, Hosam M. Ezzat

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The system of ordinary nonlinear differential equations describing sliding velocity during impact with friction for a three-dimensional rigid-multibody system is developed. No analytical solutions have been obtained before for this highly nonlinear system. Hence, a power series solution is proposed. Since the validity of this solution is limited to its convergence zone, a suitable time step is chosen and at the end of it a new series solution is constructed. For a case study, the trajectory of the sliding velocity using the proposed method is built using 6 time steps, which coincides with a Runge-Kutta solution using 38 time steps.

Keywords: impact with friction, nonlinear ordinary differential equations, power series solutions, rough collision

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Authors: Armin Ardekani, Mohammad Akbari

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We present a method of generating series solutions to large classes of nonlinear differential equations. The method is well suited to be adapted in mathematical software and unlike the available commercial solvers, we are capable of generating solutions to boundary value ODEs and PDEs. Many of the generated solutions converge to closed form solutions. Our method can also be applied to systems of ODEs or PDEs, providing all the solutions efficiently. As examples, we present results to many difficult differential equations in engineering fields.

Keywords: computational mathematics, differential equations, engineering, series

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Authors: S. H. Abo Sabah, A. B. H. Kueh, M. A. Megat Johari, T. A. Majid

Abstract:

In a recent study, a new bio-inspired honeycomb sandwich beam (BHSB) mimicking the head configuration of the woodpecker was developed. The beam consists of two carbon/epoxy composite face sheets, aluminum honeycomb core, and rubber core to enhance the repeated low-velocity impact resistance of sandwich structures. This paper aims to numerically enhance the repeated low-velocity impact resistance of the BHSB via optimizing the aluminum honeycomb core thickness. The beam was investigated employing three core thicknesses: 20 mm, 25 mm, and 30 mm at three impact energy levels (13.5 J, 15.55 J, 21.43 J). The results revealed that increasing the thickness of the aluminum honeycomb core to a certain level enhances the sandwich beam stiffness. The beam with the 25 mm honeycomb core thickness was the only beam that can sustain five repeated impacts achieving the highest impact resistance efficiency index, especially at high energy levels. Furthermore, the bottom face sheet of this beam developed the lowest stresses indicating that this thickness has a relatively better performance during impact events since it allowed minimal stress to reach the bottom face sheet. Overall, increasing the aluminum core thickness will increase the height of its cells subjecting it to buckling phenomenon. Therefore, this study suggests that the optimal thickness of the aluminum honeycomb core should be 65 % of the overall thickness of the sandwich beam to have the best impact resistance.

Keywords: sandwich beams, core thickness, impact behavior, finite element analysis, modeling

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