U.Porto Journal of Engineering

Analysis of Liquid Flow and Mixing in an Oscillatory Flow Reactor Provided with 2D Smooth Periodic Constrictions

F. Almeida — 2018-10-31

In this research paper the residence time distribution (RTD) was monitored for a range of fluid oscillation, frequency, amplitude and flow rate in two oscillatory flow reactors (OFR) provided with 2D smooth periodic constrictions (2D-SPC) with different designs. It was studied the axial liquid dispersion using axial dispersion model and the mixing efficiency using tank-in-series model for continuous mode. Two cases, with and without fluid oscillation, were studied and determined the optimum conditions to ensure a close plug flow, an efficient mixing and a low axial liquid dispersion. The optimum operation conditions for the two 2D-SPC designs were found. Moreover, the effect of open cross-sectional area (a) on mixing and axial dispersion was also investigated. For low cross-sectional area values the mixing is higher. It was observed that fluid oscillation increases the mixing intensity even at lower flow rates, and the axial dispersion increases as the flow rate increases.

Multivariate Statistical Analysis Approach to Cluster Construction Workers based on Labor Productivity Performance

Diego Calvetti N. — 2018-10-31

In the construction industry, the direct workforce is one of the most important drivers of the work process. Identifying and quantifying labor productivity impact factors allows the diagnosis of recurring problems during the construction phase. Understanding how these factors influence the productive and the nonproductive states according to the characteristics of workers or group of workers is an essential tool to boost productivity. This paper introduces a multivariate statistical analysis approach to cluster workers based on the characteristics of the actions that are performed during the daily construction tasks. This study analyzed the data from a field experiment based on human observation of actions of 10 welders during a week in a pipe-shop. The case study conducted step by step presented in this work indicates retention of 50% and 40% of the total sample in segmented workers clusters.

Design and Construction of Monocopter and its Nonlinear Control Using Photo Diode Array

Ahmad Safaee — 2018-10-31

Monocopter is a single-wing rotary flight system which has the capability of hovering. This flyer includes two dynamic parts in which more efficiency can be expected rather than other Micro UAVs due to the extended area of wing compared to its frame. Low capital cost and simple mechanism rather than other systems such as helicopter are the most important specifications of this flight system. In this paper, a model of monocopter flight system has been designed and implemented. Then, a new method of monocopter control and the related hardware has been designed and constructed using photo diode array in order to define position angle of flight system. Designers and constructors have to build a digital compass with the related advantages and disadvantages for this purpose. In the next stage, the optimized flight sample was redesigned and reconstructed and the dynamic parameters of flying were set due to existed hardware restrictions. Then, different experimental tests have been carried out after hardware installation of the control system. So, the controllable flying has been implemented using this control system.

A Form of List Viterbi Algorithm for Decoding Convolutional Codes

Shamsuddeen Hassan Muhammad — 2018-10-31

Viterbi algorithm is a maximum likelihood decoding algorithm. It is used to decode convolutional code in several wireless communication systems, including Wi-Fi. The standard Viterbi algorithm gives just one decoded output, which may be correct or incorrect. Incorrect packets are normally discarded thereby necessitating retransmission and hence resulting in considerable energy loss and delay. Some real-time applications such as Voice over Internet Protocol (VoIP) telephony do not tolerate excessive delay. This makes the conventional Viterbi decoding strategy sub-optimal. In this regard, a modified approach, which involves a form of List Viterbi for decoding the convolutional code is investigated. The technique employed combines the bit-error correction capabilities of both the Viterbi algorithm and the Cyclic Redundancy Check (CRC) procedures. It first uses a form of ‘List Viterbi Algorithm’ (LVA), which generates a list of possible decoded output candidates after the trellis search. The CRC check is then used to determine the presence of correct outcome. Results of experiments conducted using simulation shows considerable improvement in bit-error performance when compared to classical approach.

Agile Methodology to Performance Measure and Identification of Impact Factors in the Labour Productivity of Industrial Workers

Diego Calvetti N. — 2018-10-31

The objective of this work is to adapt and test an agile methodology based on human observation that waives the data collection based on the timing of time in activity. Aiming to evaluate the productivity and non-productivity of workers in a factory during the pipe welding process for use in the construction of industrial plants. Through human observation the data was gathered by registering punctually the activities of the welders during a week. The results obtained by the Monte Carlo simulation were validated by comparing the results obtained by the probability and statistically analysis of the complete sample. After the simulation validation the Sensibility Analysis test was conducted in order to evaluate the variables of higher impact in the performance of the welders. The average of Labour Rating Factor and Idleness Rating Factor obtained by Monte Carlo simulation were respectively, 0.5529 and 0.4549 and by the sampling chart Labour Rating Factor 0.5552 and Idleness Rating Factor 0.4448. The methodology identified 9(nine) actions in the productive state, where the welding activity presents the greatest impact on the output of the mean of the Labour Rating Factor. In addition, 8(eight) actions were considered non-productive, where displacements and human conditions activities have the greatest impact on the Idleness Rating Factor. Furthermore, the results were compared with the work of other Authors. The research results shows the feasibility for industry to use this proposal of an agile methodology for evaluating the workforce performance, spending less resource compared with traditional ones.