Scielo RSS <![CDATA[Journal of applied research and technology]]> vol. 13 num. 3 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>Improving speech intelligibility for binaural voice transmission under disturbing noise and reverberation using virtual speaker lateralization</b>]]> Subjective speech intelligibility tests were carried out in order to investigate strategies to improve speech intelligibility in binaural voice transmission when listening from different azimuth angles under adverse listening conditions. Phonetically balanced bi-syllable meaningful words in Spanish were used as speech material. The speech signal was played back through headphones, undisturbed, and also with the addition of high levels of disturbing noise or reverberation, with a signal to noise ratio of SNR = -10 dB and a reverberation time of T60 = 10 s. Speech samples were contaminated with interaurally uncorrelated noise and interaurally correlated reverberation, which previous studies have shown the more adverse. Results show that, for speech contaminated with interaurally uncorrelated noise, intelligibility scores improve for azimuth angles around ±30° over speech intelligibility at 0°. On the other hand, for interaurally correlated reverberation, binaural speech intelligibility reduces when listening at azimuth angles around ±30°, in comparison with listening at 0° or azimuth angles around ±60°. <![CDATA[<b>The impact of emotions on the helpfulness of movie reviews</b>]]> Online customer reviews have become a significant source of product-related information for consumers. As a result of the growing number of customer reviews, determining which customer reviews are the most helpful is important in reducing information overload. The ways in which reviews can be helpful need to be identified. In this study, we examine the impact of emotional content in online customer reviews on the number of votes those customer reviews receive that indicate they were helpful. We find that content that is more emotional yields more votes. Furthermore, our findings suggest that reviews with positive emotional content have a positive effect on review helpfulness whereas reviews with negative emotional content have no effect on review helpfulness. This study contributes to an understanding of emotional content in word of mouth and has important implications for online retailers and consumers. <![CDATA[<b>Analyzing and forecasting the global CO<sub>2</sub> concentration - a collaborative fuzzy-neural agent network approach</b>]]> In order to effectively analyze and forecast the global CO2 concentration, a collaborative fuzzy-neural agent network is constructed in this study. In the collaborative fuzzy-neural agent network, a group of autonomous agents is used. These agents are programmed to analyze and forecast the global CO2 concentration using the fuzzy back propagation network (FBPN) approach based on their local views. A collaboration mechanism is established to communicate the settings and forecasts of these agents, and to derive a single representative value from these forecasts using a radial basis function network. The real data were used to evaluate the effectiveness of the collaborative fuzzy-neural agent network approach. <![CDATA[<b>Energy based reliable multicast routing protocol for packet forwarding in MANET</b>]]> Mobile Ad hoc Network consists of mobile nodes without any assisting infrastructure. Mobility of nodes causes network partition. This leads to heavy overhead and less packet forwarding ratio. In this research work, Residual Energy based Reliable Multicast Routing Protocol (RERMR) is proposed to attain more network lifetime and increased packet delivery and forwarding rate. A multicast backbone is constructed to achieve more stability based on node familiarity and trustable loop. Reliable path criterion is estimated to choose best reliable path among all available paths. Data packets will be forwarded once the reliable path is chosen. We have also demonstrated that residual energy of paths aids to provide maximum network lifetime. Based on the simulation results, the proposed work achieves better performance than previous protocols in terms of path reliability rate, network stability rate, end to end delay, end to end transmission and communication overhead. <![CDATA[<b>Development of an axial suspended AMB experimental bench for load and disturbance tests</b>]]> This paper provides the development of an axial suspended active magnetic bearing (AMB) experimental bench for load and disturbance tests. This test bench must be capable of levitating a 2 kg steel disc at a stable working distance of 3 mm and a maximum attraction distance of 6 mm. The suspension is accomplished by two electromagnets producing upward and downward attraction forces to support the steel disc. An inductive sensor measures the position of the steel disc and relays this to a PC based controller board (dSPACE® controller). The control system uses this information to regulate the electromagnetic force on the steel disc. The intent is to construct this system using relatively low-cost, low-precision components, and still be able to stably levitate the 2 kg steel disc with high precision. The dSPACE® software (ControlDesk®) was used for data acquisition. In this paper, an overview of the system design is presented, followed by the axial AMB model design, inductive sensor design, actuating unit design and controller development and implementation. The paper concludes with results obtained from the dSPACE® controller and evaluation of the axial suspended AMB experimental bench with load and disturbance tests. <![CDATA[<b>Efficient data transfer in mobile ad-hoc network using OPSM for disaster response applications</b>]]> The nodes in mobile ad-hoc network depend on battery for its power. Therefore, effective utilization of energy is necessary for efficient transfer of data between the persons involved in rescue without connection termination in disaster situation. An Optimal Path Selection Model (OPSM) is proposed to achieve this. First, routes are identified with the links having high power ratio and link duration. The path selection aims at reducing the number of node failures which in turn obtains energy saving. Then, the source will select a node-disjoint path based on energy and hop for data transfer and store the remaining paths in cache. Priority based path maintenance is also proposed for the selection of routes from cache based on remaining energy if the primary selection fails. Path selection and maintenance extend the network lifetime by reducing the energy usage in transmission. Simulation results revealed that OPSM achieves 64% and 50% reduction in energy consumption compared to Dynamic Source Routing (DSR) and Multipath DSR (MDSR). The number of path breakages is also 11 times and 5.5 times lesser than DSR and MDSR. Thus, it can be said that OPSM is a better choice for optimal path selection for performance enhancement by saving energy and improving lifetime. <![CDATA[<b>Hexagonal scale invariant feature transform (H-SIFT) for facial feature extraction</b>]]> Feature transformation and key-point identification is the solution to many local feature descriptors. One among such descriptor is the Scale Invariant Feature Transform (SIFT). A small effort has been made for designing a hexagonal sampled SIFT feature descriptor with its applicability in face recognition tasks. Instead of using SIFT on square image coordinates, the proposed work makes use of hexagonal converted image pixels and processing is applied on hexagonal coordinate system. The reason of using the hexagonal image coordinates is that it gives sharp edge response and highlights low contrast regions on the face. This characteristic allows SIFT descriptor to mark distinctive facial features, which were previously discarded by original SIFT descriptor. Furthermore, Fisher Canonical Correlation Analysis based discriminate procedure is outlined to give a more precise classification results. Experiments performed on renowned datasets revealed better performances in terms of feature extraction in robust conditions. <![CDATA[<b>Comparison among some well known control schemes with different tuning methods</b>]]> This paper presents a comparison between some well-known control schemes such as feedback, feedback plus feed-forward, cascade and cascade plus feed-forward for controlling a third-order process. The controller applied in various control schemes is a PID controller that has been tuned using Ziegler Nichols (ZN) and relay auto-tuning (RA) methods. The comparative analysis is based upon various performance measures such as rise time (t r), settling time (t s), maximum overshoot (Mp), steady-state error (e ss), integral of absolute error (IAE), integral of square error (ISE), integral of time square error (ITSE), and integral of time absolute error (ITAE). Simulation results show that the RA method provides superior performance in case of feedback plus feed-forward and cascade control schemes. On the other hand, the ZN method proves to be better in case of cascade plus feed-forward control scheme. <![CDATA[<b>Reliability optimization of electrical distribution systems using internal loops to minimize energy not-supplied (ENS)</b>]]> The topology of the electrical distribution systems is somehow similar to the topology of leaves as a natural optimal system. The leaves having internal loops (ILs) are more reliable than ones having radial structure. In this paper, a novel approach using ILs is proposed to optimize the distribution systems reliability. As using ILs in electrical distribution system improves the system reliability and requires additional costs, a cost-benefit analysis is necessary. Using a novel way such as ILs to improve the power grid reliability in compare to conventional approaches is one contribution of this paper. Considering the economic effects in addition to technical aspects is another advantage of the proposed method. In this paper, the cost of energy not-supplied (CENS) reduction is used to investigate the benefits of ILs that simplifies and reduces the computations regarding the system CENS without ILs and through using them. The introduced objective function (OF) consists of the saved cost due to reduction of CENS and also the additional investment of using ILs. The method is applied to a realistic 34-bus system of Tehran Regional Electrical Company (TREC). The genetic algorithm (GA) is used to solve the optimization problem. The test results illustrate by reasonable investment for ILs according to an optimum solution, the considerable reliability improvement and economic benefits are achievable. <![CDATA[<b>Discussion on key successful factors of TPM in enterprises</b>]]> It generally takes 2.5 to 3 years for an enterprise to implement TPM in a full swing; however, the actual duration depends on each company's corporate status. Generally speaking, for a company with big staff, it even takes 3 to 5 years, but the major consideration should depend on whether the actual benefit is remarkable or not. This research aims to find out whether total productive maintenance (TPM) was carried out by enterprises, to inspect the enterprises' current performance, and to make comparison with those enterprises that have successfully carried out TPM. Through the findings, we hope to provide reference for enterprise owners when they carry out TPM, so as to reduce the cost for fumble. <![CDATA[<b>A proposed method for design of test cases for economic analysis in power systems</b>]]> Nowadays, in power systems, we still lack the existence of standardized test systems that can be used to benchmark the performance and solution quality of proposed optimization techniques. Several authors report that the electric load pattern is very complex. It is therefore necessary to develop new methods for design of test cases for economic analysis in power systems. Therefore, we compared two methods to generate test systems: time series model and a method simulating stable random variables based on the use of Chambers-Mallows-Stuck. This paper describes a method for simulating stable random variables in the generation of test systems for economic analysis in power systems. A study focused on generating test electrical systems through stable distribution to model for unit commitment problem in electrical power systems. Usually, the instances of test systems in unit commitment are generated using normal distribution, but the behavior of electrical demand does not follow a normal distribution; in this work, simulation data are based on a new method. For empirical analysis, we used three original systems to obtain the demand behavior and thermal production costs. Numerical results illustrate the applicability of the proposed method by solving several unit commitment problems directly and through the Lagrangian relaxation of the original problem. <![CDATA[<b>Script format document authentication scheme based on watermarking techniques</b>]]> In almost all watermarking-based document authentication systems, the documents are considered as binary images and then, the watermark is embedded using some image watermarking algorithm. However actually important documents are saved using document file formats, such as Portable Document Format (PDF) or Open Document Format (ODF), among others, because in general the file size is smaller compared with an image file, and also these are considered as more secure than other types of file format. However, the documents with these formats can also be maliciously modified for illegal purposes, making necessary the development of mechanisms that are able to detect such modifications. Considering the situations mentioned above, this paper proposes a document authentication scheme in which a watermark is directly embedded into the document file format as part of the document itself. The experimental results show a desirable performance of the proposed algorithm.