Selected mapping technique for reducing PAPR of single‐carrier signals

Single‐carrier transmission with frequency‐domain equalization (SC‐FDE) is widely known as a promising transmission technique providing low error probability with low peak‐to‐average power ratio (PAPR) of transmit signal. However, the low‐PAPR property of SC‐FDE cannot be maintained if multi‐level data modulation is introduced. The low‐PAPR property of SC‐FDE can be maintained by applying transmit filtering with roll‐off factor at the expense of spectrum efficiency. In this paper, we propose two types of selected mapping (SLM) to reduce the PAPR of SC‐FDE transmit signal. The first SLM technique is conducted in the frequency domain, where the phase rotation is applied to subcarriers similar to the SLM technique for orthogonal frequency division multiplexing transmission. The second SLM technique is conducted in the time domain, where the phase rotation is applied directly to data‐modulated symbol sequence. Computer simulation confirms that both SLM techniques are able to reduce the PAPR of SC‐FDE signal without significant degradation of bit‐error rate performance and spectrum efficiency. Copyright © 2016 John Wiley & Sons, Ltd.     

Robust Statistical Methods for Empirical Software Engineering

There have been many changes in statistical theory in the past 30 years, including increased evidence that non-robust methods may fail to detect important results. The statistical advice available to software engineering researchers needs to be updated to address these issues. This paper aims both to explain the new results in the area of robust analysis methods and to provide a large-scale worked example of the new methods. We summarise the results of analyses of the Type 1 error efficiency and power of standard parametric and non-parametric statistical tests when applied to non-normal data sets. We identify parametric and non-parametric methods that are robust to non-normality. We present an analysis of a large-scale software engineering experiment to illustrate their use. We illustrate the use of kernel density plots, and parametric and non-parametric methods using four different software engineering data sets. We explain why the methods are necessary and the rationale for selecting a specific analysis. We suggest using kernel density plots rather than box plots to visualise data distributions. For parametric analysis, we recommend trimmed means, which can support reliable tests of the differences between the central location of two or more samples. When the distribution of the data differs among groups, or we have ordinal scale data, we recommend non-parametric methods such as Cliff’s δ or a robust rank-based ANOVA-like method.     

Turbulent forced convection in a heat exchanger square channel with wavy-ribs vortex generator☆

Turbulent forced convective heat transfer and flow configurations in a square channel with wavy-ribs inserted diagonally are examined numerical y. The influences of the 30° and 45° flow attack angles for wavy-ribs, blockage ratio, RB=b/H=0.05–0.25 with single pitch ratio, RP=P/H=1 are investigated for the Reynolds number based on the hydraulic diameter of the square channel, Re=3000–20000. The use of the wavy-ribs, which inserted diagonal in the square channel, is aimed to help to improve the thermal performance in heat exchange systems. The finite volume method and SIMPLE algorithm are applied to the present numerical simulation. The results are presented on the periodic flow and heat transfer profiles, flow configurations, heat transfer characteristics and the performance evaluations. The mathematical results reveal that the use of wavy-ribs leads to a higher heat transfer rate and friction loss over the smooth channel. The heat transfer enhancements are around 1.97–5.14 and 2.04–5.27 times over the smooth channel for 30° and 45° attack angles, respectively. However, the corre-sponding friction loss values for 30° and 45° are around 4.26–86.55 and 5.03–97.98 times higher than the smooth square channel, respectively. The optimum thermal enhancement factor on both cases is found at RB=0.10 and the lowest Reynolds number, Re=3000, to be about 1.47 and 1.52, respectively, for 30° and 45° wavy-ribs.     

Methodology for design and analysis of reactive distillation involving multielement systems

A new methodology for design and analysis of reactive distillation has been developed. In this work, the element-based approach, coupled with a driving force diagram, has been extended and applied to the design of a reactive distillation column involving multielement (multicomponent) systems. The transformation of ordinary systems to element-based ones and the aggregation of non-key elements allow the important design parameters, such as the number of stages, feed stage and minimum reflux ratio, to be determined by using simple diagrams similar to those regularly employed for non-reactive systems consisting of two components. Based on this methodology, an optimal design configuration is identified using the equivalent binary-element-driving force diagram. Two case studies of methyl acetate (MeOAc) synthesis and methyl-tert-butyl ether (MTBE) synthesis have been considered to demonstrate the successful applications of the methodology. Moreover, energy requirements for various column configurations corresponding to different feed locations are determined to verify whether the optimal design can be identified by following the proposed methodology.     

Flow topology,heat transfer characteristic and thermal performance in a circular tube heat exchanger inserted with punched delta winglet vortex generators

To improve the heat transfer rate and thermal performance, the punched delta winglet vortex generators, DWVGs, were inserted in the middle of the circular tube heat exchanger. The effects of the flow attack angles and the flow directions were investigated numerically for the Reynolds number Re = 100–2000. The finite volume method and the SIMPLE algorithm were used to study. The results are reported in terms of the flow structure, heat transfer behavior and thermal performance evaluation and also compared with the smooth tube with no vortex generators. As the numerical results, the use of the DWVGs in the tube can improve the heat transfer rate and thermal performance by creating the vortex flow through the tested section. The rise of the flow attack angle results in the increasing strength of the vortex flows. The flow attack angle of 25° performs the highest heat transfer rate and thermal performance, while the flow attack angle of 0o gives the reversed results. The computational results reveal that the optimum thermal enhancement factor is around 2.80 at Re = 2000, α = 25°, with the winglet tip pointing downstream. The correlations on both the Nusselt number ratio and friction factor ratio for the DWVG in the tube heat exchanger are presented.     

Distribution and residue depletion of oxytetracycline in giant freshwater prawn (Macrobrachium rosenbergii)

Distribution and residue depletion patterns of oxytetracycline were examined in giant freshwater prawns, Macrobrachium rosenbergii, after medicated-feed treatment at the feeding level of 4 g/kg of feed for 5 consecutive days. The concentration of oxytetracycline in prawn muscle tissues was measured using high-performance liquid chromatography equipped with a fluorescence detector. The limit of detection was 0.1 microg/g. In the medicated-feed-treated group, oxytetracycline was detectable 8 days posttreatment at the feeding level of 4 g/kg of feed for 5 consecutive days. The depletion half-life and mean residence time of oxytetracycline were 30.96 and 100.3 h, respectively. The dose of 4 g/kg of feed for 5 consecutive days can be recommended for therapeutic dosage regimen in giant freshwater prawn aquaculture. The minimal withdrawal period of M. rosenbergii muscle tissue should be 8 days postcessation of medicated feed.     

Influences of the wavy surface inserted in the middle of a circular tube heat exchanger on thermal performance

Numerical investigations on flow topology, heat transfer behavior and performance evaluation in a circular tube inserted with various configurations of wavy surfaces, Inclined wavy surface (IWS), V-downstream wavy surface (VDWS), V-Upstream wavy surface (VUWS) are presented. The effects of the flow attack angles; 20°, 30°, 45° and 60° are studied for the Reynolds numbers, Re = 100-2000. The numerical results are compared with the smooth circular tube with no wavy surface and the previous works. It is found that the IWS, VDWS and VUWS can produce longitudinal vortex flow and impinging jet of the fluid flow like inclined baffle, V-downstream baffle and V-Upstream baffle, respectively, but give lower friction loss. The flow phenomena created by the wavy surfaces help to augment the heat transfer rate and thermal performance in the test tube. In the range studied, the order of enhancement for heat transfer rate is around 1.40-3.75, 1.60-6.25 and 1.30-5.80 times higher than the smooth tube for IWS, VDWS and VUWS, respectively. Moreover, the maximum thermal performance, presented in terms of the Thermal enhancement factor (TEF), is found to be about 1.60, 2.40 and 2.10, respectively, for IWS, VUWS and VDWS.     

Drying characteristics of peppercorns in a rectangular fluidized-bed with triangular wavy walls

An experimental study on drying kinetics of peppercorns has been conducted in two different drying fluidized-bed configurations: rectangular fluidized-bed (RFB) and rectangular fluidized-bed with wavy walls (RFBW). In the RFBW, two opposite triangular wavy walls with three blockage ratios (e/H) are formed to produce vortex/swirl flows leading to stronger turbulence and longer residence time of the flow in the bed. For each bed, three inlet hot airs (T_in) at 60 °C, 80 °C and 100 °C and two superficial air velocity, U* of 1.2 and 2.0 (U* = U/U_mf) are introduced. The experimental results reveal that the air temperature and air velocity show significant effects on the drying rate of both beds, especially at T_in = 100 °C and U* = 2.0. The RFBW performs much better than the RFB due to shorter drying time. The average drying time of the RFBW with e/H = 0.3125, 0.3750 and 0.4375 is, respectively, around 29%, 36% and 43% less than that of the RFB. In addition, three mathematical drying models are offered for both the beds and the effect of the air temperature and velocity on the drying model constants was determined by fitting the experimental data using regression analysis techniques. The three models satisfactorily described the drying characteristics of peppercorns especially for the Henderson and Pabis model. The RFBW with e/H = 0.4375 is preferable in the study.     

Effects of Electrode Configuration on Electrokinetic Stabilization for Caisson Anchors in Calcareous Sand

The study is on the electrokinetic strengthening of caisson anchors embedded in offshore calcareous sand. The effects of electrode configuration on the effectiveness of electrokinetic treatment are investigated based on electric field analysis and are verified by results from a series of large scale laboratory tests on caisson models of 200?mm diam and 400?mm height, embedded in calcareous sand submerged under seawater. The electrokinetic treatment generates cementation of soil solids as well as bonding between soil and caisson shafts, which leads to increases in the side resistance and overall pullout resistance. The effectiveness of electrokinetic treatment is directly related to the electric field intensity. A linear relationship is observed between the increase in the side resistance and energy consumption. The study shows that the effectiveness of electrokinetic treatments can be maximized by the optimization of the electric field distribution through the electrode configuration.     

Detection of deoxynivalenol contamination in wheat products in Thailand

A total of ninety samples in three kinds of wheat products (30 noodle, 30 bread, and 30 cereal samples) were collected from the supermarkets in Bangkok, Thailand, from February to April 2007. The occurrence of deoxynivalenol (DON) contamination in wheat products was investigated using high-performance liquid chromatography equipped with a UV light detector. The extraction method was performed using a multifunctional cleanup column. The limit of quantification was 0.10 microg x g(-1) from the range obtained in a linear calibration. The survey found almost 94% of the DON-contaminated samples below 1 microg x g(-1), which corresponds to the U.S. Food and Drug Administration advisory level. DON was detected in 18.9% (17 of 90) of all samples, in 6.67% (2 of 30) and 16.67% (5 of 30) of noodle and bread samples at levels from 0.17 to 0.35 and 0.14 to 1.13 microg x g(-1), respectively, while it was in 33.33% (10 of 30) of cereal samples at levels from 0.13 to 0.39 microg x g(-1). The results suggest that the exposure to DON from the consumption of wheat products, especially noodles, bread, and cereal, is at a very low risk level.