Showing papers in "Journal of Engineering Science and Technology Review in 2019"

Numerical Investigations of Transient Flow Characteristic in Axial Flow Pump and Pressure Fluctuation Analysis Based on the CFD Technique

Abstract: The technique of Computational fluid dynamics was applied to investigate flow field analysis including static pressure, axial, radial and tangintial velocities vectors as well as fluctuations of pressure analyses in axial pump. Pressure fluctuations are the core causes increase noise level and vibration. For studying pressure mechanism fluctuation in pump changed monitoring rotating points are stalled at an impeller blade. Standard kepsilon turbulence model and sliding mesh technique are adopted by using CFD. The numerical investagation found that pressure in an axial flow pump rises near inlet impeller region to outer part. Higher value of pressure was take place at impeller outlet region. Also, the computational analysis noted that the when a pump functions in larger mass flow, the area of high-pressure in impeller outlet decreases. Moreover, under low flow rate (5 l/min) in middle surface the high-speed area appears near or closed blade and blade tip region for all velocities under investigations. Furthermore. fluctuations of pressure for different point under different flows has four valleys and peaks the similar number of axial impeller passages blades. The results foun that there are two imprtant regions the first one ispositive and second one is negative pressures, this happends owing to this negative pressure area has lower pressure value. Therefore, due to the decline in the water pressure in this area may cause cavitation.

Fractional - order system modeling and its applications

Abstract: In order to control or operate any system in a closed-loop, it is important to know its behavior in the form of mathematical models. In the last two decades, a fractional-order model has received more attention in system identification instead of classical integer-order model transfer function. Literature shows recently that some techniques on fractional calculus and fractional-order models have been presenting valuable contributions to real-world processes and achieved better results. Such new developments have impelled research into extensions of the classical identification techniques to advanced fields of science and engineering. This article surveys the recent methods in the field and other related challenges to implement the fractional-order derivatives and miss-matching with conventional science. The comprehensive discussion on available literature would help the readers to grasp the concept of fractional-order modeling and can facilitate future investigations. One can anticipate manifesting recent advances in fractional-order modeling in this paper and unlocking more opportunities for research.

Traffic Offloading in 5G Heterogeneous Networks using Rank based Network Selection

Abstract: The exponential growth of mobile data traffic and a limited number of spectrum resources has been a big challenge for cellular network providers, henceforth traffic offloading has become one of the most critical issues especially in 5G Heterogeneous Networks (HetNets). Further, network selection plays a vital role for traffic offloading in a cellular network to maintain Quality of Service (QoS), increasing offloading efficiency and throughput. In order to efficiently utilize spectral resources, a Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) algorithm is proposed to be used for ranking a candidate network. The proposed algorithm helps in alleviating the spectrum shortage by offloading the data traffic over Wi-Fi network using unlicensed spectrum. In this work, analysis of the performance of the proposed system model through simulation of an analytical framework has been made. The results have been accumulated in terms of cumulative handover, throughput, the extent of equilibrium & offloading efficiency with respect to residence time and the number of Wi-Fi Access Points (AP’s). Analysis proves that the proposed algorithm improves the equilibrium extent and throughput as compared to traditional Load balancing (LB) and SDN based LB mechanisms. It also shows that offloading efficiency is highly improved over Wi-Fi density and residence time.

Review on Methods of Fault Diagnosis in Photovoltaic System Applications

Abstract: Recently, detection and identification of faults in photovoltaic (PV) system applications have been attracting researchers worldwide. Some of them have investigated the causes of potential faults, have worked on how to monitor and identify the faults through fault diagnosis, and have elaborated on how to develop problem-solving methods for the early detection of faults in PV system operations. This paper attempts to provide information comprehensively from the previous research. It summarizes types of faults, methods used in early fault identification and monitoring, and PV fault prevention and protection systems. The paper also investigates future trends in PV system fault diagnosis which include real-time implementation. The paper is expected to bring new perspective about the literature associate with fault studies in PV systems. This survey will be beneficial for the future discussion on how to provide comprehensive solutions for PV system fault problems. It will help avoid research repetition on similar topics and focus on the improvement and performance development of PV fault diagnosis methods.

Design of Wheatstone Bridge Based Thermistor Signal Conditioning Circuit for Temperature Measurement

Abstract: Thermistors are widely used in temperature measurement due to their fast response, high accuracy, and low cost. However, due to the nonlinear resistance-temperature relationship, there is a need for linearisation in order to design a signal conditioning circuit for accurate temperature measurement. Thus, this paper presents the design of a thermistor signal conditioning circuit based on Wheatstone Bridge. An experiment was conducted on an NTC thermistor to acquire the resistance response to temperature change between 25 oC to 65o C which was in turn used for the model linearization. The obtained parameters from the linearized model are used to design the Wheatstone bridge signal conditioning circuit. The designed measurement system performance evaluation demonstrated a high degree of accuracy with only 1.1 % non-linearity within the specified temperature range.

Survey of Periocular Recognition Techniques

Abstract: Periocular recognition has evolved over the years and has been shown to possess discriminative features for personal identification either as a stand-alone trait or when fused with other modalities such as face and iris, especially in unconstrained scenarios. It has a number of advantages, first being the region could be easily cropped from existing face images. Secondly, unlike the iris, its capturing process is less intrusive. This area of the face is easily captured with ease from the subject, for example by surveillance cameras. Thirdly, in crime scenes where masks hide the face or in cases where the subject's face is covered due to religious or cultural beliefs, the periocular region could still be captured providing useful details, that is, it is robust to face occlusion and is least affected by expression change. This survey relates the various techniques employed for periocular recognition at different stages: segmentation approaches, image preprocessing methods, feature extraction and matching algorithms. This survey is meant to facilitate a quick grasp of the development in this area for interested students, researchers as well as enthusiasts in the field of biometrics or any related application area. Information about the various databases used for performance evaluation of these techniques as well as the performance indicators is also provided.

Appraisal of Road Pavement Evaluation Methods

Abstract: Road pavement evaluation methods are based either on simple index of a surface characteristic, such as International Roughness Index (IRI) for roughness, Rut Depth (RD) for rutting, Sideway Force Coefficient (SFC) for skid-resistance; or, otherwise, on a complex index such as Pavement Condition Index (PCI), related with an overall consideration of the surface condition. Complex indices are commonly used in the frame of Pavement Management Systems (PMS) by road authorities worldwide, in order to assess the pavement condition and to program maintenance and rehabilitation activities along with keeping their road network up to a safe level for the users. Nowadays, these complex indices are considered to be more reliable and suitable to evaluate pavement condition and prioritize future rehabilitation actions. The first-line question is: is it really so? Meaning that, are indices like Present Serviceability Index (PSI) capable of revealing the real condition without misunderstanding or hidden issues? Can they be implemented in all cases and if so, are they enough accurate to lead road authorities to a safe conclusion and subsequently to the right and effective maintenance activities without misleads and useless costs? In the frame of the present paper, some of the most commonly used evaluation methods are enlightened, so as to dig up their advantages and their deficiencies and finally to assess their degree of efficiency. In terms of appraising pavement evaluation methods using complex indicators, the most common methods used are hereafter examined in an attempt to determine the best one for each case. Although the Australian method seems to be the most complete and reliable one, there is no absolute answer for all the cases, meaning that the best one in terms of mitigated implementation cost is suitable for cases with serious financial constraints, whilst in case of evaluations regardless of budget, the most accurate method is the appropriate one.

A Systematic Review on Privacy Preserving Data Publishing Techniques

Abstract: : What is Privacy? According to the definition from Cambridge dictionary, “Someone's right to keep their personal matters and relationships secret”. The term privacy is defined as an action where the data is kept hidden from either anonymous user, server to avoid use of malpractice of the data. Healthcare data is considered as a most significant but sensitive data in the world, since it has all private information about patient such as diseases, treatment, prescription, name, address etc. The volume of the data generated in healthcare industry is rapidly growing. In this patient centric world, to get effective results, we need to increase healthcare data utility. With increasing data utility , the privacy of the same data is compromised which is the another important challenge that users and healthcare data publishers are facing, Since there is no monitory control on data which is published on internet. Hiding sensitive healthcare data from either untrusted users or third party data publishers is an important concern today. Healthcare Data Publishing is the process where certain transformation (such as anonymization, generalization, suppression etc.) can be applied before publishing healthcare data online. From the available research, it is seen that such transformations are not susceptible to certain attacks like background knowledge, homogeneity etc. This review paper studies all existing Privacy Preserving Data Publishing (PPDP) schemes using data generalization. The literature review also touches recent researches on ARX tool – which is an open source data de-identification tool for analysing risk and utility factor of healthcare data. The paper finally concludes with feasible research gaps from available literature survey.

Feasibility of Balcony Wall-Mounted Solar Water Heating System in High-Rise Residential Buildings

Abstract: The application of a solar water heating system is severely restricted by the limited roof area of high-rise buildings in urban areas. Therefore, the installation of a balcony wall-mounted solar water heating system (BWSWHS) on the facades of buildings has become an alternative solution. Annual conventional energy consumption and dynamic cost of three types of water heating systems were compared to prove the technical and economic feasibility of the BWSWHSs. First, the field measurement of the BWSWHS was conducted. Then, according to the principle of maximizing sunshine duration, the azimuth angle (AZ) of the building, suitable facade for installation, and optimal inclination angle of the collector were determined through sunshine simulation. Next, the annual heat gain and conventional energy consumption of the BWSWHSs were obtained from simulation using a verified model. Finally, annual energy consumption and dynamic cost of three types of water heating systems, namely, BWSWHS, electric and natural gas water heating systems, were compared. Results show that the optimal AZ of the building is 30° south by east, the suitable façade for installation is south, and the optimal inclination angle of the collector is 70°. In this case, the thermal efficiency of the collector is 44% and the solar fraction is 41%. Annual conventional energy consumption and dynamic cost are lower than that of the two other systems. The present study provides a basis for the promotion of the BWSWHS in residential high-rise buildings.

Theoretical Back Analysis of Internal Forces of Primary Support in Deep Tunnels

Abstract: The internal forces of primary support obtained by theoretical analysis and numerical simulation often differ significantly from actual data due to the uncertainty of parameters of the surrounding rock and the field construction conditions in tunnels. This study proposed a novel back-analysis method to accurately evaluate the internal forces of the primary support on the basis of radial displacement and contact stress. According to the geometric characteristics and mechanical properties of the primary support in deep tunnels, a mechanical model was established based on theory of circular curved beam. The analytical solutions of these internal forces were then deduced. A case study was conducted to analyze the internal forces of the primary support obtained using the proposed method. Results demonstrate that the internal forces of the primary support of symmetrically loaded tunnels can be directly evaluated by radial displacement and contact stress. The peak-values of internal forces appear in vault, arch springing and the section with a θ angle of 60°. This study provides reference for the dynamic design and optimization of construction for the primary support in tunnels.

Robustness and Disturbance Rejection of PD/H-∞ Integrated Controller for Flexible Link Manipulator System

Abstract: Due to the significant advantages of flexible link manipulators (FLMs) and the high demand for developing a robust controller in order to perform fast and accurate operations, this research proposes the PD/H-∞ integrated controller for the purpose of position tracking and vibration suppression of a FLM system and verifies its robustness by utilizing longer lengths and test the proposed controller under a disturbance. The PD/H-∞ integrated controller was compared with the Linear quadratic regulator (LQR) controller in terms of position tracking and vibration suppression for the lengths of 50 cm, 75 cm and 100 cm, then the controllers were assessed under a disturbance for the three lengths of the FLM system. The PD/H-∞ integrated controller has shown higher capability to control longer lengths and to reject a disturbance than the LQR controller which has been verified via simulation using MATLAB/Simulink software.

Water-Rock Simulation During Limestone Dissolution

Abstract: Limestone reservoir plays a vital role in global oil and gas distribution. Many studies on limestone dissolution have been reported, which mainly emphasize on the main controlling factors of limestone dissolution and reservoir formation mechanism. However, few studies have been conducted on limestone dissolution laws, and a general understanding of limestone dissolution under supergene and burial conditions is lacking. A water–rock simulation experiment was conducted by using five typical Lower Paleozoic limestones in Zhuanghai area of Jiyang depression of China to study limestone dissolution laws under supergene and burial conditions. Sample characteristics were observed by scanning electron microscopy, and limestone dissolution was investigated by inductively coupled plasma optical emission spectrometer (ICP-OES). Results show that the erosion rate of limestone is higher than that of dolomite under supergene condition (22 °C and 1.0 MPa). Limestone has selective corrosion in structure and components. Calcite is generally manifested as a “corroded crystalline cone,” and dolomite generally presents “honeycomb-shaped” corrosion. Under burial conditions, the erosion rate of limestone first increases, decreases, and finally increases in the range of [80 °C, 18 MPa–160 °C, 42 MPa]. In the range of [120 °C, 30 MPa–160 °C, 42 MPa], the erosion rate of dolomite gradually becomes higher than that of calcite, and the erosion of dolomite dominates. Dolomite easily forms secondary pores and high-quality reservoirs than limestone. In this study, the general laws of limestone dissolution were investigated, and conclusions provide references to evaluate high-quality limestone reservoirs.

Self-Attentive Neural Network for Hashtag Recommendation

Abstract: A hashtag is a type of metadata tag used on social networks and can help people search for specific topics or content. To capture the interactive information between words and understand the content of microblog posts deeply, this study proposed a neural network model based on a word-level self-attention mechanism. Given a microblog post, the weight of each word was calculated through a self-attention mechanism, and then the representation of a microblog post was obtained through the weighted summation of words. Finally, a multi-layer perceptron was adopted on the representation of a microblog post to perform the classification. The effectiveness of the proposed model was verified through experiments of large-scale datasets. Results show that: (1) introducing word-level self-attention mechanism into hashtag recommendation is effective. (2) In comparison with the baseline methods used in previous studies, such as convolutional neural network or long short-term memory network, the proposed self-attentive neural networks can provide a more accurate representation of a microblog post and significantly improve the F-score of hashtag recommendation on the same dataset. This study provides references for the methods and evaluation of short-text hashtag recommendations, such as microblogs.

Bearing only Target Tracking using Single and Multisensor: A Review

Abstract: The brief review of methods used for estimating the target state in single and multi-sensor bearing only tracking (BOT) is presented in this paper. It deals with the target state estimation using bearing only measurements. BOT is difficult because of its poor observability in target state and nonlinearity in measurements. The complete survey is done on existing techniques, involved to overcome the difficulties caused by BOT. Here, the target tracking scenarios are divided into three different categories based on the nature of target motion and the number of target and sensors involved. The existing techniques involved are reviewed in detail. Finally the future trends for BOT are also discussed.

Effect of Residual Chlorine on Copper Pipes in Drinking Water Systems

Abstract: Copper pipes corrosion that transport potable water can deteriorate water quality within a distribution system, releasing high copper amounts, exceeding the maximum concentration copper for potable water standards. This study examines the influence of free chlorine on the leaching of copper in the pipes used for the distribution of drinking water. A series of tests was carried out using corrosion test coupons extractable constructed of copper material. The coupons were installed in units containing filtered water (without chlorine, 0 mg/L) and water treated with an average residual chlorine concentration of 0.85 mg/L in the water treatment plant in Azogues city, Ecuador. A corrosion test rack was also installed in a house with an average residual chlorine concentration of 0.37 mg/L. Coupons in these sites were exposed in duplicate for one, two, three and six months. The corrosion coupons were then extracted and weighed to establish the corrosion rate by gravimetric technique. Additional tests were performed in static immersion laboratory tests using drinking water with chlorine concentrations ranging from 0.25 to 5 mg/L for one month. The weight loss tests indicated that an increase in free chlorine concentration, the greater release of copper and therefore a higher corrosion rate.

Internal Model Control of Discrete Non-Minimum Phase Over-Actuated Systems with Multiple Time Delays and Uncertain Parameters

Abstract: : Internal model control (IMC) is an established technique in continuous time linear control, but it is less used for discrete-time systems. Most of the existing solutions do not cover all the situations and, in any case, they lead to complex procedures to design the controller. In this paper, a IMC technique able to control over-actuated systems is used to deal with a discrete-time Non-Minimum-Phase (NMP) process with multiple time delays and uncertain parameters. The proposed IMC control scheme is based on the system augmentation with a suitable number of virtual outputs to the model matrix, in order to create a square matrix, so that the realization of an approximate inverse of the model plant is possible. Robust stability analysis is provided via combination of the value set concept and the zero exclusion conditions. Internal stability is verified using Linear Matrix Inequalities (LMI). Simulations are reported to demonstrate the suitability of the proposed design, as regards robust stability, performance, parametric uncertainties and load disturbances.

Safety Assessment Model of Earth-Rock Dam Based on Ideal Point-Cloud Theory

Abstract: Uncertainty is inevitable in the safety monitoring and evaluation process of earth-rock dam. Such uncertainty makes the accurate reflection of the running status of earth-rock dams of traditional safety assessment results impossible. Thus, this study proposed a safety assessment model of earth-rock dams based on the combination weighting method of ideal point and the cloud theory model. The proposed model was used to scientifically solve the uncertainty during the safety assessment of earth-rock dams. Real and reliable weights of indexes were determined using the combination weighting method based on the ideal point. Then, the safety evaluation grade ranges of each evaluation index were divided on the basis of the measured data. These grade ranges were “softened” by combining cloud theory. The proposed safety assessment model was applied to an earth-rock dam in the reservoir of a pumped storage station in Tai’an City, Shandong Province, China. Results demonstrate that: (1) the proposed model can effectively solve fuzzy and random problems during the safety assessment of earth-rock dams, and (2) the results show that the safety of the investigated earth-rock dam is in a normal running state. This outcome reflects the actual conditions of the earth-rock dam. The proposed model provides references in the diagnosis and decision making in the earth-rock dam management department.

Study on gas emission prediction of steeply inclined coal seam applied horizontal slice mining

Abstract: Calculation of emission quantities from different gas emission sources is important to predict gas emission quantity on the horizontally layered working face of a steep seam. However, existing gas emission prediction model has many problems, such as complicated calculation links, poor accuracy and non-applicability to the steep seam. In this study, a model applicable to predict gas emission from horizontal mining layer of steep seam was constructed based on the different-source prediction method. This model was applied to the west wing working face in the 45# seam of WuDong Mine in Xinjiang Autonomous Region in China. Prediction results of this model were compared with existing standard data of the different-source prediction method. According to analysis results, existing different-source prediction model is optimized specifically and the proposed model adds predictions of pressure relief gas emission in coal mass below the mining seam and gas emission in top goaf. The calculated gas emission in the working face presents an error of +8.63% with actual gas emission. This error conforms to the practical situation of horizontal layered mining of steep seam and verified the reliability of the proposed model. Conclusions obtained in this study serve as theoretical references to gas emission prediction in horizontal mining layer of steep seam.

Methodology for Technical Feasibility Analysis in the Installation of Microgrids

Abstract: The proposal of a methodology for the analysis of the technical feasibility in the installation of Microgrids (MG's) is realized, which shows in several steps the necessary parameters to analyze and determine the viability of a Microgrid (MG) project in a determined area, with a specific demand and objectives. The methodology is based on a critical review of the different cases of MG’s implemented around the world and different techno-economic feasibility study of MG systems.

Thickness Identification of Tunnel Lining Structure by Time–Energy Density Analysis based on Wavelet Transform

Abstract: The concrete thickness of the tunnel lining structure and cover depth is insufficient. Such condition seriously affects the safety and stability of the lining structure. The lining structure thickness is difficult to identify using radar profile horizon tracing method because of the strong interference of steel bars to electromagnetic wave propagation. To explore the reflection characteristics of electromagnetic wave signals at the interface between deep concrete and surrounding rock, a time–energy density analysis based on wavelet transform (TEDAWT) was proposed in this study. Ground–penetrating radar (GPR) forward modelling of the lining structure with different thicknesses of plain and reinforced concrete was carried out by using different central frequencies, namely, 1600 and 900 MHz, respectively. On this basis, the GPR detection signals for the plain and reinforced concrete lining structures were analyzed by employing the TEDAWT method. The feasibility of the TEDAWT method in GPR quantitative identification was verified using physical experiment. Results demonstrate that the identification accuracy of different thicknesses of plain and reinforced concrete structure is high regardless of the method used in either forward modelling or physical experiment, and the relative error is less than 5%. In the identification of concrete cover depth, the resolution of a 1600 MHz antenna is higher than that of a 900 MHz antenna, and the relative error is also less than 5%. The results indicate the application potential of the proposed method for quantitative identification of tunnel lining thickness by non–destructive testing. The proposed method provides not only the thickness distribution of the plain concrete structure but also the distribution of the reinforced concrete structure and concrete cover depth compared with traditional radar profile horizon tracing method.

Bottom Tracking Method Based on LOG/Canny and the Threshold Method for Side-scan Sonar

Abstract: The detection of sea bottom lines is affected by the noise in the water column between the towfish and the seabed. Under these circumstances, using one edge detection technology to detect the bottom line accurately is difficult. A fusion method based on LOG/Canny operator and the threshold approach was proposed in this study to determine sea bottom lines in sonar images accurately. With this method, images filtered by the LOG function and sharpened by a convolution template were utilized as the input images of the Canny detection algorithm to implement bottom tracking. The tracking result was fused with that of the threshold method to obtain merged submarine lines. Interpolation and filtration were subsequently implemented to eliminate outliers. The result was then used to accurately detect sea bottom lines. The measured height and depth were compared using a single-beam depthometer. Results demonstrate that the bottom line is difficult to accurately detect by using only edge detection technologies, such as LOG and Canny, or the threshold method under complex situations in the water column. By contrast, the proposed fusion method can perform detection accurately. Take Mirs Bay of the Shenzhen city as an example, the mean square error of tracking accuracy is determined to be ±0.192 m, which verifies the feasibility of the proposed method. This study provides a reference for the accurate detection of submarine lines in complex conditions wherein large amounts of noise exist in the water column.

Integer Encoding Genetic Algorithm for Optimizing Redundancy Allocation of Series-parallel Systems

Abstract: Reliability redundancy allocation is a combinatorial optimization problem, and numerous intelligent evolutionary algorithms (e.g., genetic algorithm and ant colony optimization) have been proposed to solve it. However, various shortcomings, such as problem specificity and high complexity, hinder their applications. An integer encoding genetic algorithm, namely, integer matrix chromosome encoding scheme, was proposed to improve the effectiveness and computational efficiency of redundancy allocation for series-parallel systems and represent the component mixing in subsystems with integers. The related crossover with a binary window and mutation using a matrix with random float numbers was developed to perform combinatorial evolution. The adjusting operator was designed to guarantee the feasibility of chromosomes, combined with the non-dominated sorting genetic algorithm (NSGA-II) in which a constraint Pareto dominance was introduced to handle design constraints without external coefficients. Numerical and engineering examples of an agricultural Internet of Things for greenhouse planting were provided to illustrate the effectiveness of the proposed algorithm. Results show that the proposed novel algorithm can solve a typical model for reliability redundancy allocation, i.e., a non-maintained bi-state series-parallel system with active redundancy and component mixing strategy. The constraint Pareto dominance is introduced on the basis of the traditional NSGA-II to avoid the complexity and instability of penalty function approaches. The constructed three-objective redundancy allocation problem model can measure the trade-off relationship among three objectives, namely, system reliability, cost, and weight. The improved NSGA-II has the best stability when the optimized value for crossover probability is 0.98 and the mutation probability is set to a small value. Advantages of the presented model and method include its convenience and suitability for different genetic evolutionary platforms.

Solenoid from Experimental HTS tape for Magnetic Refrigeration

Abstract: The project of superconducting magnetic system (SMS) for the magnetic refrigerator machine is proposed. The second-generation high-temperature superconducting tapes for SMS are developed, fabricated and tested in NRC Kurchatov Institute. The magnet consists of 12 non-insulated double pancake coils. The SMS is installed in the vacuum chamber and cooled by a cryo refrigerator.

FR-4 Substrate Based Modified Ultawideband Antenna with Gain Enhancement for Wireless Applications

Abstract: A new circular shape patch ultrawideband (UWB) single feed microstrip antenna is described in this paper. The radiated patch of the proposed UWB antenna is embedded with slots to improve the radiation characteristics ensuring a wide impedance bandwidth. In the ground plane, two rectangular rings slots are etched to provide proper impedance matching over a wide frequency range. The proposed single layer UWB with overall dimensions of 55 mm by 56 mm is fabricated using low cost 4.3 relative permittivity FR-4 substrate. From results obtained, the antenna can provide an impedance bandwidth ranging from 2.2 GHz to more than 12 GHz (138%) that is wider than the standard UWB band. In addition, the modified UWB antenna can enhance the gain to more than 6.6 dB, which is higher than that achieved by the ordinary UWB antenna by more than 16%. Comparison of the modified UWB antenna simulated and measured results shows a close agreement, which enable it to be a promising solution for many wireless applications such as UWB applications, X-band (8-12GHz) satellite communication, portable wireless devices, medical applications, positioning systems cognitive radio and WiMAX 5.4 GHz band application.

Direction Estimation using Patterns of User Movement

Abstract: This study mainly aims to find accurate directions in indoor environments by combining smartphone acceleration readings with WiFi received signal strength (RSS) readings. Patterns of user movement serve as the basis of this approach. These patterns are effectively utilized to detect user direction on the basis of the correlation between the RSS and acceleration values. A series of experiments was conducted to test the proposed approach. The proposed approach achieves 95% accuracy and thus shows great potential as a practical solution for estimating directions in indoor environments.

Analysis on Moisture Migration Law in Loess Fill Subgrade

Abstract: With the development of the highway construction industry in loess areas, exploring the causes of damage in loess fill subgrade has become an important topic that people have been widely concerned about. Specifically, the law of moisture migration inside the loess fill subgrade is the key to solve various loess road damage due to its special water sensitivity. Existing research has mainly focused on the influence of temperature potential and other factors on moisture migration in subgrade. However, the influence of the nature of the loess fill subgrade on the moisture migration law still lacks systematic research. In this study, a series of experiments on moisture migration in loess fill subgrade under different degrees of compaction were performed using a self-made moisture migration test device, which revealed moisture migration law in the fill subgrade. Experimental results show that water migration rate is negatively correlated with a number of wetting-drying cycle, degree of compaction, and initial water content. The final volume moisture content decreases with the increase of migration height after moisture migration is stabilized. Spaces among soil particles are small, and the soil particles are close when the degree of compaction is high. Accordingly, energy consumption for moisture migration is high, and the moisture migration decelerates. Under the same dry density condition, as the initial water content increases, the time to reach the equilibrium of water migration is shorter, and the migration rate is faster. This result also reveals that the key for controlling subgrade quality is to strictly control the degree of compaction, waterproof property, and drainage. This study can provide theoretical references to prevent damage in loess fill subgrade and waterproof the design and construction of subgrade.