Chinese Journal of Engineering
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Open Access journal
ISSN (Online) 2314-8063
Published by Hindawi [334 journals]
- An Experimental and Numerical Study on Embedded Rebar Diameter in Concrete
Using Ground Penetrating Radar
Abstract: High frequency ground penetrating radar (GPR) has been widely used to detect and locate rebars in concrete. In this paper, a method of estimating the diameter of steel rebars in concrete with GPR is investigated. The relationship between the maximum normalized positive GPR amplitude from embedded rebars and the rebar diameter was established. Concrete samples with rebars of different diameters were cast and the maximum normalized amplitudes were recorded using a 2.6 GHz GPR antenna. Numerical models using GPRMAX software were developed and verified with the experimental data. The numerical models were then used to investigate the effect of dielectric constant of concrete and concrete cover on the maximum normalized amplitude. The results showed that there is an approximate linear relationship between the rebar diameter and the maximum GPR normalized amplitude. The developed models can be conveniently used to estimate the embedded rebar diameters in existing concrete with GPR scanning; if the concrete is homogeneous, the cover depth is known and the concrete dielectric constant is also known. The models will be highly beneficial in forensic investigations of existing concrete structures with unknown rebar sizes and locations.
PubDate: Wed, 17 Aug 2016 07:59:52 +000
- Enabling Technologies for Fifth-Generation Mobile Communications
PubDate: Tue, 26 Apr 2016 13:42:22 +000
- Research on Joint Handoff Algorithm in Vehicles Networks
Abstract: With the communication services evolution from the fourth generation (4G) to the fifth generation (5G), we are going to face diverse challenges from the new network systems. On the one hand, seamless handoff is expected to integrate universal access among various network mechanisms. On the other hand, a variety of 5G technologies will complement each other to provide ubiquitous high speed wireless connectivity. Because the current wireless network cannot support the handoff among Wireless Access for Vehicular Environment (WAVE), WiMAX, and LTE flexibly, the paper provides an advanced handoff algorithm to solve this problem. Firstly, the received signal strength is classified, and the vehicle speed and data rate under different channel conditions are optimized. Then, the optimal network is selected for handoff. Simulation results show that the proposed algorithm can well adapt to high speed environment, guarantee flexible and reasonable vehicles access to a variety of networks, and prevent ping-pong handoff and link access failure effectively.
PubDate: Mon, 18 Apr 2016 15:43:28 +000
- 5G: Vision and Requirements for Mobile Communication System towards Year
Abstract: The forecast for future 10 years’ traffic demand shows an increase in 1000 scales and more than 100 billion connections of Internet of Things, which imposes a big challenge for future mobile communication technology beyond year 2020. The mobile industry is struggling in the challenges of high capacity demand but low cost for future mobile network when it starts to enable a connected mobile world. 5G is targeted to shed light on these contradictory demands towards year 2020. This paper firstly forecasts the vision of mobile communication’s application in the daily life of the society and then figures out the traffic trends and demands for next 10 years from the Mobile Broadband (MBB) service and Internet of Things (IoT) perspective, respectively. The requirements from the specific service and user demands are analyzed, and the specific requirements from typical usage scenarios are calculated by the defined performance indicators. To achieve the target of affordable 5G service, the requirements from network deployment and operation perspective are also captured. Finally, the capabilities and the efficiency requirements of the 5G system are demonstrated as a flower. To realize the vision of 5G, “information a finger away, everything in touch,” 5G will provide the fiber-like access data rate, “zero” latency user experience, and connecting to more than 100 billion devices and deliver a consistent experience across a variety of scenarios with the improved energy and cost efficiency by over a hundred of times.
PubDate: Wed, 06 Apr 2016 14:04:42 +000
- Propagation Channel Comparison between 23.5 and 45 GHz in
Abstract: The characteristics of propagation channel at 23.5 and 45 GHz in an indoor conference room are studied based on hybrid approach. A ray-based simulator which includes the reflection, penetration, diffraction, and diffuse scattering is adopted to generate the massive channel realizations. This platform is well calibrated in path and power delay profile (PDP) levels according to some specified measurements at different frequencies. Subsequently, according to the simulated channel samples, the statistical channel model for both the large and small scale characteristics is established based on the alpha-beta approach and extended Saleh-Valenzuela (S-V) structure, respectively. Results show that the slope of fitted path loss (PL) is less than free space due to the waveguide effect for both 23.5 and 45 GHz in indoor scenario and larger PL is experienced at higher frequency. Additionally, the cluster is more centralized with less spreads and decaying faster in delay domain at 45 GHz.
PubDate: Tue, 15 Mar 2016 08:05:47 +000
- Multiuser Beamforming with Limited Feedback for FDD Massive MIMO Systems
Abstract: This paper discusses the multiuser beamforming in FDD massive MIMO systems. It first introduces the feature of FDD massive MIMO systems to implement multiuser beamforming schemes. After that, considering the realistic implementation of multiuser beamforming scheme in FDD massive MIMO systems, it introduces the knowledge of channel quantization. In the main part of the paper, we introduce two traditional multiuser beamforming schemes and analyse their merits and demerits. Based on these, we propose a novel multiuser beamforming scheme to flexibly combine the merits of the traditional beamforming schemes. In the final part of the paper, we give some simulation results to compare the beamforming schemes mentioned in the paper. These simulation results show the superiority of the proposed beamforming scheme.
PubDate: Mon, 07 Mar 2016 13:59:31 +000
- Investigation of Control Model in a New Series Hybrid Hydraulic/Electric
System for Heavy Vehicles Based on Energy Efficiency
Abstract: An interesting model which was able to recuperate and reuse braking energy was investigated. It was named series hybrid hydraulic/electric system (SHHES). The innovated model was presented for heavy hybrid vehicles to overcome the existing drawbacks of single energy storage sources. The novelty of this paper was investigation of a new series hybrid vehicle with triple sources, combustion engine, electric motor, and hydraulic sources. It was simulated with MATLAB-Simulink and different operational mode of control system was investigated. The aim was to improve the efficiency of the energy-loading components in the power train system and the transmission system independently. The ability to store and reuse the kinetic energy was added to the system to prevent energy wasting while the vehicle was braking. Control models were also investigated to realize suitable control algorithms to offer the best efficiency in system components for different vehicle conditions. The torque control strategy based on fuzzy logic controller was proposed to achieve better vehicle performance while the fuel consumption was minimized. The results implied efficient storage and usage in the transmission system. A small vehicle model experimentally verified the simulation results.
PubDate: Thu, 03 Mar 2016 09:11:56 +000
- Statistical Characteristics of Measured 3-Dimensional MIMO Channel for
Outdoor-to-Indoor Scenario in China and New Zealand
Abstract: The 3-dimensional (3D) channel model gives a better understanding of statistical characteristics for practical channels than the 2-dimensional (2D) channel model, by taking the elevation domain into consideration. As different organizations and researchers have agreed to a standard 3D channel model, we attempt to measure the 3D channel and determine the parameters of the standard model. In this paper, we present the statistical propagation results of the 3D multiple-input and multiple-output (MIMO) channel measurement campaign performed in China and New Zealand (NZ). The measurements are done for an outdoor-to-indoor (O2I) urban scenario. The dense indoor terminals at different floors in a building form a typical 3D propagation environment. The key parameters of the channel are estimated from the measured channel impulse response (CIR) using the spatial-alternating generalized expectation-maximization (SAGE) algorithm. Till now there is abundant research performed on the azimuth domain; this paper mainly considers the statistical characteristics of the elevation domain. A statistical analysis of 3D MIMO channel results for both China and NZ measurements is presented for the following parameters: power delay profile (PDP), root mean square (rms), delay spread (DS), elevation angle-of-arrival (EAoA) distribution, elevation angle-of-departure (EAoD) distribution, elevation angular spread (AS), and cross-polarization discrimination (XPD).
PubDate: Thu, 03 Mar 2016 07:57:43 +000
- Modeling and Experiments of Severe Slugging in a Riser System
Abstract: A transient mathematical model based on continuity equations for liquid and gas phases, with a momentum equation for the mixture, was developed, and numerical solutions and simulations corresponding to severe slugging in pipeline-riser system were presented, and the results were compared with the experimental data to verify the mathematical model. In numerical solutions, backward Euler schemes were adopted as predictors and trapezoidal methods were used as correctors. Variable time steps were employed for higher computational efficiency and accuracy in the integration. Experiments of severe slugging characteristics were performed, and the simulation results of the cycle periods and bottom pressure were compared with experimental values. Finally, the calculation results of detailed characteristics were analyzed thoroughly. The results show that the developed mathematical model can accurately predict the cycle time and the detailed characteristics of severe slugging. Under the experimental conditions, the liquid slug length can reach 1.6 times the height of the riser, and the maximum instantaneous gas velocity of outlet is 50 times the inlet gas velocity, and the maximum instantaneous liquid velocity of outlet is 28 times the inlet liquid velocity, having important implications for the hazard assessment of severe slugging.
PubDate: Mon, 29 Feb 2016 13:06:46 +000
- Combinatorial Bayesian Dynamic Linear Models of Bridge Monitored Data and
Abstract: Considering the uncertainties and randomness of the mass structural health monitored data, the objectives of this paper are to present (a) a procedure for effective incorporation of the monitored data for the reliability prediction of structural components or structures, (b) one transforming method of Bayesian dynamic linear models (BDLMs) based on 1-order polynomial function, (c) model monitoring mechanism used to look for possible abnormal data based on BDLMs, (d) combinatorial Bayesian dynamic linear models based on the multiple BDLMs and their corresponding weights of prediction precision, and (e) an effective way of taking advantage of combinatorial Bayesian dynamic linear models to incorporate the historical data and real-time data in structural time-variant reliability prediction. Finally, a numerical example is provided to illustrate the application and feasibility of the proposed procedures and concepts.
PubDate: Mon, 15 Feb 2016 12:21:53 +000
- Numerical Evaluations of Functionally Graded RC Slabs
Abstract: Nowadays, using fibrous materials is used widely in strengthening applications such as cross-section enlargement and using functionally graded reinforced concrete. Functionally graded reinforced concrete is used as multireinforced concrete layers that can be reinforced by different fiber types. The objective of this research was to address the structural benefits of functionally graded concrete materials by performing analytical simulations. In order to achieve this purpose, in the first stage of this study, three functionally graded reinforced concretes by steel and polypropylene (PP) were experimentally tested under flexural loading. Inverse analysis was applied to obtain the used material properties of reinforced concrete by FEMIX software. After obtaining the material properties, to assess the performance of proposed slabs, some other cases were proposed and numerically evaluated under flexural and shear loading. The results showed that increasing steel fiber in reinforced entire cross section led to achieve better shear and flexural performance while the best performance of reinforced functionally graded slabs was achieved for slab at 1% fiber content. In the second stage, nineteen reinforced functionally graded RC slabs with steel bars were simulated and assessed and some other cases were considered which were not experimentally tested.
PubDate: Wed, 10 Sep 2014 08:12:32 +000
- A New Mathematical Inventory Model with Stochastic and Fuzzy Deterioration
Rate under Inflation
Abstract: This paper develops an inventory model for items with uncertain deterioration rate, time-dependent demand rate with nonincreasing function, and allowable shortage under fuzzy inflationary situation. The goods are not deteriorating upon reception, but the deteriorating starts after elapsing a specified time. The lead time and inflation rate are both uncertain in the model. The resultant effect of inflation and time value of money is assumed to be fuzzy in nature and also we consider lead time as a fuzzy function of order quantity. Furthermore the following different deterioration rates have been considered: for the first case we consider fuzzy deterioration rate and for the second case we assume that the deterioration rate is time dependent and follows Weibull distribution with three known parameters. Since the inflation rate, deterioration rate, and the lead time are fuzzy numbers, the objective function becomes fuzzy. Therefore the estimate of total costs for each case is derived using signed distance technique for defuzzification. The optimal replenishment policy for the model is to minimize the total present value of inventory system costs, derived for both the above mentioned policies. Numerical examples are then presented to illustrate how the proposed model is applied.
PubDate: Thu, 14 Aug 2014 10:03:19 +000
- The Design of an Urban Roadside Automatic Sprinkling System: Mitigation of
PM2.5–10 in Ambient Air in Megacities
Abstract: The objective of this research paper is to describe the system architecture for an urban roadside automatic mist-generating system. Its primary purpose is to mitigate particulate matter especially PM2.5–10. In this paper, four graphs are provided to exhibit the constituent elements of this system. This paper also discusses the functional extensions of this system for alternative uses in civil engineering which include winter road deicing and desnowing with added salt; clean-up of street dust; lowering of temperature of a “hot island” during the summer; the addition of humidity in an arid area; and the suppression of flu virus in the winter season. The structure and function of this system are comprehensively discussed in this paper. This system is compared to existing and other proposed systems in terms of control options, efficiency, and primary functional issues. The unique design of the road automatic sprinkling system renders itself a prominent option. Although there are no data available for this conceptual system, some expected qualitative and quantitative outcomes are provided and justified. The paper concludes with some potential research areas and challenges associated with this system architecture.
PubDate: Wed, 23 Jul 2014 09:48:20 +000
- A Review on the Development of Rotman Lens Antenna
Abstract: Rotman lenses are the beguiling devices used by the beamforming networks (BFNs). These lenses are generally used in the radar surveillance systems to see targets in multiple directions due to its multibeam capability without physically moving the antenna system. Now a days these lenses are being integrated into many radars and electronic warfare systems around the world. The antenna should be capable of producing multiple beams which can be steered without changing the orientation of the antenna. Microwave lenses are the one who support low-phase error, wideband, and wide-angle scanning. They are the true time delay (TTD) devices producing frequency independent beam steering. The emerging printed lenses in recent years have facilitated the advancement of designing high performance but low-profile, light-weight, and small-size and networks (BFNs). This paper will review and analyze various design concepts used over the years to improve the scanning capability of the lens developed by various researchers.
PubDate: Thu, 17 Jul 2014 00:00:00 +000
- Trabecular Bone Image Segmentation Using Wavelet and Marker-Controlled
Abstract: This paper presents a new strategy for the segmentation of trabecular bone image. This kind of image is acquired with microcomputed tomography (micro-CT) to assess bone microarchitecture based chiefly on bone mineral density (BMD) measurements to improve fracture risk prediction. Disease osteoporosis can be predicted from features of CT image where a bone region may consist of several disjoint pieces. It relies on a multiresolution representation of the image by the wavelet transform to compute the multiscale morphological gradient. The coefficients of detail found at the different scales are used to determine the markers and homogeneous regions that are extracted with the watershed algorithm. The method reduces the tendency of the watershed algorithm to oversegment and results in closed homogeneous regions. The performance of the proposed segmentation scheme is presented via experimental results obtained with a broad series of images.
PubDate: Sun, 13 Jul 2014 07:04:46 +000
- A Novel Design of Parasitically Gap Coupled Patches Forming an Elliptical
Patch Antenna for Broadband Performance
Abstract: A novel single layer assembly of gap coupled elements in elliptical shape is proposed in this communication to achieve broadband performance. Among the five patches considered in the present assembly, two pairs of patches having different patch areas are arranged around an edge truncated elliptical patch. The central edge truncated elliptical patch is fed through an inset feed arrangement and the other patches are parasitically gap coupled to the central patch. With such an arrangement, an enhanced impedance bandwidth of 2.45 GHz (or 36.2%) with respect to central frequency 6.1 GHz is achieved. Three resonant modes are excited with this arrangement giving improved bandwidth and gain in comparison to a conventional elliptical patch antenna. The simulated radiation patterns of proposed arrangement of patches suggest that these are identical in shape and direction of maximum radiations is directed normally to assembly of patches.
PubDate: Tue, 01 Jul 2014 09:47:34 +000
- Broadband Semielliptical Patch Antenna with Semicircular Ring Slot for
Abstract: This paper reports the design and analysis of a semielliptical patch antenna modified by cutting semicircular ring slot in patch geometry and obtained results are discussed. The reported antenna is designed on a multilayered substrate material having two glass epoxy FR-4 substrates separated by a thin foam substrate having thickness 1.0 mm. The size of ground plane is 75 m5 mm, whereas the patch dimension along major and minor axes is 23.0 mm and 14.0 mm, respectively. The two modes corresponding to resonance frequencies 3.39 GHz and 3.73 GHz are excited to provide wide impedance bandwidth 21.1% with respect to central frequency with stable radiation patterns. The antenna shows circular polarization with axial ratio bandwidth 5.5% and minimum axial ratio value 1.65 dBi. The radiation patterns of proposed antenna are normal to the surface of patch and are almost identical in shape as required for practical applications. The proposed antenna covers entire median band of WiMax communication systems ranges from 3.40 GHz to 3.6 GHz.
PubDate: Thu, 19 Jun 2014 12:18:50 +000
- Cathodic Protection of Pipeline Using Distributed Control System
Abstract: Distributed control system (DCS) is available in most of the compressor stations of cross-country pipeline systems. Programmable logic controller (PLC) is used in all the intermediate pigging (IP) stations/sectional valve (SV) stations to collect the field data and to control the remote actuated valves. This paper presents how DCS or PLC can be used for cathodic protection of gas pipelines. Virtual instrumentation (VI) software is used here for simulation and real-time implementation purpose. Analog input channels available in DCS/PLC can be used to measure pipe to soil potential (PSP) with the help of half-cell and voltage transducer. Logic blocks available in DCS can be used as low selector switch to select the lowest PSP. Proportional-integral (PI) controller available in DCS/PLC can be used for taking the controlling action. PI controller output varies the firing angle of AC phase controller. Phase controller output is rectified, filtered, and fed to the pipeline as cathodic protection current. Proposed scheme utilizes existing infrastructure to control pipeline corrosion.
PubDate: Mon, 16 Jun 2014 08:10:39 +000
- Team Robot Motion Planning in Dynamics Environments Using a New Hybrid
Algorithm (Honey Bee Mating Optimization-Tabu List)
Abstract: This paper describes a new hybrid algorithm extracted from honey bee mating optimization (HBMO) algorithm (for robot travelling distance minimization) and tabu list technique (for obstacle avoidance) for team robot system. This algorithm was implemented in a C++ programming language on a Pentium computer and simulated on simple cylindrical robots in a simulation software. The environment in this simulation was dynamic with moving obstacles and goals. The results of simulation have shown validity and reliability of new algorithm. The outcomes of simulation have shown better performance than ACO and PSO algorithm (society, nature algorithms) with respect to two well-known metrics included, ATPD (average total path deviation) and AUTD (average uncovered target distance).
PubDate: Thu, 29 May 2014 12:13:06 +000
- Time-Dependant Responses of High-Definition Induction Log and Case Studies
Abstract: The process of drilling mud filtrate invading into a reservoir is time dependant. It causes dynamic invasion profiles of formation parameters such as water saturation, salinity, and formation resistivity. Thus, the responses of a high-definition induction log (HDIL) tool are time dependent. The logging time should be considered as an important parameter during logging interpretation for the purposes of determining true formation resistivity, estimating initial water saturation, and evaluating a reservoir. The time-dependent HDIL responses are helpful for log analysts to understand the invasion process physically. Field examples were illustrated for the application of present method.
PubDate: Mon, 19 May 2014 06:54:59 +000
- Siting and Sizing of DG in Medium Primary Radial Distribution System with
Enhanced Voltage Stability
Abstract: This paper intends to enumerate the impact of distributed generation (DG) on distribution system in terms of active as well as reactive power loss reduction and improved voltage stability. The novelty of the method proposed in this paper is the simple and effective way of sizing and siting of DG in a distribution system by using two-port Z-bus parameters. The validity of the method is verified by comparing the results with already published methods. Comparative study presented has shown that the proposed method leads existing methods in terms of its simplicity, undemanding calculation procedures, and less computational efforts and so does the time. The method is implemented on IEEE 69-bus test radial distribution system and results show significant reduction in distribution power losses with improved voltage profile of the system. Simulation is carried out in MATLAB environment for execution of the proposed algorithm.
PubDate: Tue, 29 Apr 2014 10:18:00 +000
- Optimal Demand Side Bidding with Carbon Emission by Using MRS Strategy
Abstract: A new moderate-random-search strategy (MRPSO) is used for an optimal bidding strategy of a supplier, considering linear bidding curve model with a precise model and emission as constraints, and who delivered electricity to end users in oligopolistic dynamic electricity is studied. Bidding strategy of a supplier is solved by MRPSO, where mean best position () boosts the diversity and the exploration ability of particle. The MRPSO adopts an attractor as the main moving direction of particles, which replaces the velocity update procedure in the particle swarm optimization. The effectiveness of the proposed approach is tested with linear bidding model and the results are compared with the solutions obtained using classical PSO. In this paper, a comparative study has been done by a competitive bidding model tested on IEEE 14- and IEEE 39-bus systems and results motivate the suppliers towards opting green technologies.
PubDate: Tue, 22 Apr 2014 06:41:56 +000
- Transient Thermoelastic Analysis of Pressurized Rotating Disks Subjected
to Arbitrary Boundary and Initial Conditions
Abstract: This paper focuses on exact analytical solution of transient thermoelastic behaviors of rotating pressurized disks subjected to arbitrary boundary and initial conditions. The pressure, inner radius, and outer radius are considered constant. The basic thermoelasticity theory under generalized assumptions is used to solve the thermoelastic problem. Using the method of the separation of variables, the relations of temperature and transient thermal stresses in the radial direction are obtained. In the case study, the disk is considered under heat flux. Some useful discussions and numerical examples are presented. The analytical results were compared with those of the finite element method and good agreement was found. The relations obtained in this paper can be applied to any arbitrary boundary and initial conditions.
PubDate: Thu, 17 Apr 2014 11:38:24 +000
- On a Homotopy Perturbation Treatment of Steady Laminar Forced Convection
Flow over a Nonlinearly Stretching Porous Sheet
Abstract: The steady two-dimensional laminar forced convection boundary layer flow of an incompressible viscous Newtonian fluid over a nonlinearly stretching porous (permeable) sheet with suction is considered. The sheet’s permeability is also considered to be nonlinear. The boundary layer equations are transformed by similarity transformations to a nonlinear ordinary differential equation (ODE). Then the homotopy perturbation method (HPM) is used to solve the resultant nonlinear ODE. The dimensionless entrainment parameter and the dimensionless sheet surface shear stress are obtained for various values of the suction parameter and the nonlinearity factor of sheet stretching and permeability. The results indicate that the dimensionless sheet surface shear stress decreases with the increase of suction parameter. The results of present HPM solution are compared to the values obtained in a previous study by the homotopy analysis method (HAM). The HPM results show that they are in good agreement with the HAM results within 2% error.
PubDate: Tue, 08 Apr 2014 07:07:47 +000
- Assessment of Municipal Solid Waste Management System in a Developing
Abstract: This study represents a few basic steps of municipal solid waste management practiced in the six major cities of Bangladesh, namely, Dhaka, Chittagong, Khulna, Rajshahi, Barisal, and Sylhet. A six-month field study was conducted to identify the solid wastes management steps such as storage at source, separation, on-site storage, collection, transportation, treatment, reuse, recycling, and ultimate disposal. This study addresses the role of the city authority to meet the demand of the city dwellers in solving this emerging socioenvironmental issue and the initiatives taken by some nongovernmental organizations and community based organizations. The problems and constraints of the solid wastes management system are also identified to find a sustainable management concept for the urban areas of Bangladesh.
PubDate: Thu, 27 Mar 2014 09:07:49 +000
- A CAS Approach to Handle the Anisotropic Hooke’s Law for Cancellous
Bone and Wood
Abstract: The present research entirely relies on the Computer Algebric Systems (CAS) to develop techniques for the data analysis of the sets of elastic constant data measurements. In particular, this study deals with the development of some appropriate programming codes that favor the data analysis of known values of elastic constants for cancellous bone, hardwoods, and softwood species. More precisely, a “Mathematica” code, which has an ability to unfold a fourth-order elasticity tensor is discussed. Also, an effort towards the fabrication of an appropriate “MAPLE” code has been exposed, that can calculate not only the eigenvalues and eigenvectors for cancellous bone, hardwoods, and softwood species, but also computes the nominal average of eigenvectors, average eigenvectors, average eigenvalues, and the average elasticity matrices for these materials. Further, using such a MAPLE code, the histograms corresponding to average elasticity matrices of 15 hardwood species have been plotted and the graphs for I, II, III, IV, V, and VI eigenvalues of each hardwood species against their apparent densities are also drawn.
PubDate: Sun, 23 Mar 2014 12:16:33 +000
- Elitist Genetic Algorithm Based Energy Balanced Routing Strategy to
Prolong Lifetime of Wireless Sensor Networks
Abstract: Wireless sensor networks have gained worldwide attention in recent years due to the advances made in wireless communication. Unequal energy dissipation causes the nodes to fail. The factors causing the unequal energy dissipation are, firstly, the distance between the nodes and base station and, secondly, the distance between the nodes themselves. Using traditional methods, it is difficult to obtain the high precision of solution as the problem is NP hard. The routing in wireless networks is a combinatorial optimization problem; hence, genetic algorithms can provide optimized solution to energy efficient shortest path. The proposed algorithm has its inherent advantage that it keeps the elite solutions in the next generation so as to quickly converge towards the global optima also during path selection; it takes into account the energy balance of the network, so that the life time of the network can be prolonged. The results show that the algorithm is efficient for finding the optimal energy constrained route as they can converge faster than other traditional methods used for combinatorial optimization problems.
PubDate: Sun, 16 Mar 2014 07:11:19 +000
- Investigation of Solar Drying of Ginger (Zingiber officinale): Emprical
Modelling, Drying Characteristics, and Quality Study
Abstract: Drying is a simultaneous heat and mass transfer energy intensive operation, widely used as a food preservation technique. In view of improper postharvest methods, energy constraint, and environmental impact of conventional drying methods, solar drying could be a practical, economical, and environmentally reliable alternative. In the present paper applicability of mixed mode solar cabinet dryer was investigated for drying of commercially important and export oriented ginger. Freshly harvested ginger slices were successfully dried from initial moisture content of 621.50 to 12.19% (d.b.) and their drying characteristics, quality parameters, and kinetics were evaluated. The results showed that present solar dryer could be successfully applied for drying of ginger in view of quality, reduced drying time, and zero energy requirement as compared to conventional open sun drying and convective drying techniques, respectively. Drying curves showed that drying occurred in falling rate period and no constant period was observed. The effective moisture diffusivity was determined by using Fick’s second law and found to be m2/s. The drying data was fitted to five thin layer drying models and compared using statistical criteria. Page model was found to be most suitable to describe the drying kinetics of ginger in solar dryer under natural convection among the tested models.
PubDate: Thu, 13 Mar 2014 14:09:52 +000
- Analyzing the Heat Transfer Property of Heat Pipe Influenced by Integrated
Abstract: Heat pipe with discrete heat transfer property is often called thermal superconductor because it has extremely large thermal conductivity. This special heat transfer property is destroyed by integrating cooling apparatus and further reducing the cooling power of a heat pipe cooler. This paper experimentally studied the heat transfer property of heat pipe influenced by integrated cooling apparatus. To simplify the investigating process, a home-made square heat pipe with the dimensions of mm3 was built with two pieces of copper plates and two pieces of glass plates face to face, respectively. The two pieces of copper plates were constructed with inside walls of capillary structure and the two pieces of glasses were with antifog inside walls for observing the inner phenomenon. Moreover, isothermal circulating cooling water was applied outside the heat pipe instead of cooling fin. The results show that heat vapor in the heat pipe is condensed earlier and cannot reach the remote section of condenser. In other words, the heat transfer property of heat pipe is destroyed by integrating cooling water. This phenomenon causes the unfavorable cooling power of the heat pipe cooler.
PubDate: Tue, 11 Mar 2014 09:06:56 +000
- Transient Stability Improvement of a Power System with Parametric
Uncertainties Using a Robust Optimal H2 State Feedback Controller
Abstract: In recent years, improvement of dynamic behavior of power systems has interested many researchers and to achieve it, various control methods are proposed. In this paper, in order to improve transient stability of power system, a robust optimal H2 state feedback is employed. In order to appropriate formulation of the problem, linear matrix inequality (LMI) theory is used. To achieve the best answer, controller parameters are tuned using particle swarm algorithm. The obtained results of the proposed method are compared to conventional power system stabilizer.
PubDate: Tue, 11 Mar 2014 08:03:04 +000