[en] This paper presents a brief review of studies on cross flow induced vortices in downside of tubes which leads to vibration. Two types of vibrations have been studied for tubes in cross flow: first vibration of the tube due to vortex shedding which is important primarily in cross flow but this vibration disappears in slug flow or froth flow regions which are important in numerous heat exchangers, secondly fluid elastic excitation which is most dangerous mechanism in heat exchanger tube bundles. The paper also presents the other parameters such as temperature variation on tube, pressure effect, lift and drag generation and their influence on heat exchanger tubes, different models comparison and tube size effect of tubes for vortices. (author)

[en] Groundwater recharge is complex phenomenon to understand and describe because it cannot be seen with open eyes. We have to depend some theoretical assumptions to understand this complicated hidden natural underground water movement process. There are many factors affecting and controlling the water movement in soil profile. Groundwater use in district chakwal is of a fundamental importance to meet the rapidly expanding drinking and agricultural water requirements. The man factors contributing to groundwater recharge in chakwal are rainfall, evapotranspiration and geology. due to the semi arid climatic conditions of the area, this resource is almost the only key to economic development. There are a number of dug wells in the area where water is getting stored during rainy season. source and processes of recharge in humid areas are different compared with semi-arid areas. Due to the main resource of available water in the area, the potential groundwater recharge estimation could be good exercise to visulize the amount of rainwater entering the ground. For groundwater recharge estimation there are a number of simple and advanced techniques available. In the present study simple methods were used to estimate potential recharge due to available limited resources. Rainfall runoff, gravimetric and water table fluctuation methods were used to quantify rainfall recharge during the monsoon season. The average potential recharge estimated was 60% of the rainfall of 148 mm. Rainfall runoff and gravimetric methods were found to be comparable for short period potential recharge estimation while water table fluctuation method gives actual recharge and require longer period data. Potential recharge values were higher for area having grassland type vegetation and low for area covering shrubs and tick vegetation. (author)

[en] Tungsten Inert Gas (TIG) welding is the most common practice in aluminum alloys. It is necessary to devise a fail-safe design against fatigue failure of welded structures. Under the presence of cyclic load fatigue life is usually predicted by endurance limit of working material. In this research paper a comprehensive effort is made to investigate the endurance limit of aluminum alloy AA2219-T87. A four point rotating and bending fatigue testing machine is used to test the fatigue life estimation of the said alloy. Results obtained through experimentations are verified through numerical simulation by using software package ANSYS Workbench 14. 0. A brief microstructural study is also performed using metallurgical microscope. A gigantic contrast in grain structure is observed in different zones, formed due to TIG welding. Variation in material strength due to grains shifting from unwelded base metal (BM) to weld nugget zone (WZN) is studied in this research. (author)

[en] In microwave electronic distance measurement (EDM) sensors, the accuracy of results depends on the resolution of the measurements. This paper deals with the effects of calibrating frequency span on the resolution of microwave measurements. The isolated parameter is reflection coefficient (SdB) of wide band horn antenna and the reflecting materials selected are copper and water because of the higher reflectivity. A number of reflections measurements have been performed between horn and copper plate and when the same antenna is placed in front of water in PVC pipes for different range of calibrating frequency spans. The results show that the resolution of measurements improves with the enhancement of calibrating frequency span. (author)

[en] Response of three 150x150x450mm short reinforced concrete (RC) columns confined with different types of confining steel was investigated. Standard stirrups, strips and stapled strips, each having same cross-sectional area, were employed as confining steel around four comer column bars. Experimental work was aimed at probing into the affect of stapled strip confinement on post elastic behavior and ductility level under cyclic axial load. Ductility ratios, strength enhancement factor and core concrete strengths were compared to study the affect of confinement. Results indicate that strength enhancement in RC columns due to strip and stapled strip confinement was not remarkable as compared to stirrup confined column. It was found that as compared to stirrup confined column, stapled strip confinement enhanced the ductility of RC column by 183% and observed axial capacity of stapled strip confined columns was 41 % higher than the strip confined columns. (author)

[en] This paper parametrically optimizes the laser marking process for marking stainless steel AISI 316L for marking's quality and time using Taguchi method wherein the rationale is to ensure the compatibility of the process with material being processed. Four parameters namely laser frequency, number of layers removed, laser power and scanning speed are investigated herein. Main effect for means and signal to noise ratio have been done to study and optimize the effects of variables on stated performance measures respectively. The process is mathematically formulated via linear regression model. It is found that among the factors studied herein, major contributing factor for marking time is number of layers removed whereas scanning speed effects surface roughness the most. Optimum levels for minimizing marking time are determined to be: level 1 for laser frequency and number of layers removed, level 2 for laser power and level 3 for scanning speed. On the other hand, for minimization of surface roughness, optimum levels are found to be: level for laser frequency, number of layers removed and laser power and level 3 for scanning speed. The mathematical model developed herein is found to be statistically significant at 95% confidence level with contributions of model terms to be. 98.92% for marking time and 96.84% for surface roughness. The developed models are validated by the confirmatory run wherein good agreement between predicted and experimental values is obtained. (author)

[en] Recently vanous software have been invented in order to make the job of image manipulation more comfortable and effective. Using software images are merged in such a way that ocular review cannot differentiate the resulting forgeries from authentic images. This paper proposes a model for the identification of such merged images. Proposed methodology for identification is the connection of two stages feature extraction using principle component analysis and the use of classifier based on the evolutionary artificial neural network (EANN). The behavioral aspects of EANN phenotype was evaluated under changing parameters. The results obtained after experimentation were promising. (author)

[en] In order to attain supreme energy from wind turbine economically, blade profile enactment must be acquired. For extracting extreme power from wind, it is necessary to develop rotor models of wind turbine which have high rotation rates and power coefficients. Maximum power can also be haul out by using suitable airfoils at root and tip sections of wind turbine blades. In this research four different S-series airfoils have been selected to study their behavior for maximum power extraction from wind. The wind conditions during the research were scertained from the wind speeds over Kallar Kahar Pakistan. In order to study the wind turbine operation, the extremely important parameters are lift and drag forces. Therefore an endeavor to study lift force and drag force at various sections of wind turbine blade is shown in current research. In order to acquire the utmost power from wind turbine, highest value of sliding ratio is prerequisite. At various wind speeds, performance of several blade profiles was analyzed and for every wind speed, the appropriate blade profile is ascertained grounded on the utmost sliding ratio. For every airfoil, prime angle of attack is resolute at numerous wind speeds. (author)

[en] The energy absorbing characteristics of a vibrating system is termed as damping. The phenomena is very important for structures subjected to earthquake and other dynamic loading conditions where small duration are involved. Damping characteristics of a material play an important role in overall stability of a structure. The higher is the damping value, the shorter will be the time to disappear the vibrations. However, damping requirement at the cost of strength of a given material is not justified in any case. This paper describes that the damping of material can be calculated from the time history curve as well as resonance frequency curve. Both these curves are available in new testing arrangements of Impulse Load Test (I. L.T.) and therefore were utilized for damping evaluation of concrete [i). In this paper, the author is describing the I. L.T test either on cement concrete or asphalt concrete by considering relevant ASTM specifications. There are certainly different variables taken into account with respect to cement concrete or asphalt concrete. After the experiment, the conclusions are drawn in different ways depending upon either the specimen is of cement concrete or asphalt and by considering their relevant variables. (author)

[en] Multiple-Input Multiple-Output antennas in conjunction with Orthogonal Frequency-Division Multiplexing is a dominant air interface for 4G and 5G cellular communication systems. Additionally, MIMO- OFDM based air interface is the foundation for latest wireless Local Area Networks, wireless Personal Area Networks, and digital multimedia broadcasting. Whether it is a single antenna or a multi-antenna OFDM system, accurate channel estimation is required for coherent reception. Training-based channel estimation methods require multiple pilot symbols and therefore waste a significant portion of channel bandwidth. This paper describes a virtually blind spectrum efficient channel estimation scheme for MIMO-OFDM systems which operates well below the Nyquist criterion. (author)