Type II robotic assembly line balancing problem: An evolution strategies algorithm for a multi-objective model

In this paper a different type II robotic assembly line balancing problem (RALB-II) is considered. One of the two main differences with the existing literature is objective function which is a multi-objective one. The aim is to minimize the cycle time, robot setup costs and robot costs. The second difference is on the procedure proposed to solve the problem. In addition, a new mixed-integer linear programming model is developed. Since the problem is NP-hard, three versions of multi-objective evolution strategies (MOES) are employed. Numerical results show that the proposed hybrid MOES is more efficient.     

A control theoretical modelling for velocity tuning of the conveyor belt in a dynamic mixed-model assembly line

This paper proposes a control theoretical modelling to study dynamic behaviour of a mixed-model assembly line. First, an open-loop model is developed for the system, then examined via different conveyor’s velocity values. It is realised that the performance of the system is very sensitive to the velocity; therefore, a closed-loop (CL) model is developed taking feedback from the system. By the use of proportional-integral-derivative (PID) controller and SIMULINK, some interesting results are obtained applying CL model: regardless of the sequence of the products in the line, the total work-overload and idleness always equals to zero. Moreover, less working area within the workstation is required. Based on the statistical analysis, it is found that no significant increase in makespan is imposed by CL model. It is also shown that PID controller is robust not only to the disturbances of the velocity, also to the uncertainties in the assembly operation times. These results are supported by many numerical experiments dealing with different test problems, line configurations and sequences. Finally, using a discrete event simulation model, the proposed approach is applied into a seru production mode. Simulation results show that the feedback PID controller can deal with real-world assembly line problems, successfully.     

The effect of long term use of amiodarone hydrochloride on time and frequency domain parameters of signal averaged electrocardiogram in patients with ischemia heart disease

The aim of this study was to assess the influence of amiodarone hydrochloride on time- and frequency-domain parameters of signal-averaged electrocardiogram (SAECG) in patients with ischaemic heart disease (IHD). The study population consisted of 33 patients (18 female and 15 male), mean age 59.2 +/- 7.7. Amiodarone hydrochloride was orally used in the initial dose 600 mg/day for 10 days, and subsequently 200 mg/days for 6 weeks. Recording of SAECG and ambulatory Holter monitoring were made at baseline and in 10 day and after 6 weeks of therapy. The following time-domain parameters were analyzed: the root mean square voltage of the last 40 and 50 ms of the filtered QRS (RMS40 i RMS50), total time duration of filtered QRS (t-QRS) and duration of low amplitude signals < 40 microV in the terminal part of QRS (LPD). Late potentials (LP) were recognized when at least two from three criteria were fulfilled: 1) RMS40 < 20 microV, 2) t-QRS > 114 ms, 3) LPD > 38 ms. Frequency analysis of SAECG allowed to calculate the following parameters in logarithmic scale: energy spectrum > -60 dB (A) and decibel drop at 40Hz (Dd) and also in linear scale: area ratio 20-50/0-20Hz (Ar) and magnitude ratio (MR1-7). The values of RMS40 and RMS50 did not significantly change during amiodarone therapy. The obtained values of t-QRS were significantly longer after antiarrhythmic therapy, respectively 97.8 +/- 9.1 ms at the baseline, 102.1 +/- 10 ms after 10 days (p < 0.05), and 104.1 +/- 10.4 ms after 6 weeks (p < 0.005). Moreover the values of LPD did not significantly change after amiodarone treatment. At the baseline the presence of LP were observed in 3 (9%), after 10 days were recorded in 8 (24%), and after 6 weeks in 7 (22%) cases. Only in one case the LP were observed during the whole antiarrhythmic therapy. Moreover, amiodarone hydrochloride did not statistically significant change frequency-domain parameters in logarithmic scale and in linear scale.     

Chemical Functionalization of Graphene Oxide by Poly(styrene sulfonate) Using Atom Transfer Radical and Free Radical Polymerization: A Comparative Study

Poly(sodium styrenesulfonate)-functionalized graphene was prepared from graphene oxide, using atom transfer radical polymerization and free radical polymerization. In atom transfer radical polymerization route, the amine-functionalized GO was synthesized through hydroxyl group reaction of GO with 3-amino propyltriethoxysilane. Atom transfer radical polymerization initiator was grafted onto modified GO (GO-NH₂) by reaction of 2-bromo-2-methylpropionyl bromide with amine groups, then styrene sulfonate monomers were polymerized on the surface of GO sheets by in situ atom transfer radical polymerization. In free radical polymerization route, the poly(sodium 4-styrenesulfonate) chains were grafted on GO sheets in presence of Azobis-Isobutyronitrile as an initiator and styrene sulfonate monomer in water medium. The resulting modified GO was characterized using range of techniques. Thermal gravimetric analysis, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy results indicated the successful graft of polymer chains on GO sheets. Thermogravimetric analysis showed that the amount of grafted polymer was 22.5 and 31?wt% in the free radical polymerization and atom transfer radical polymerization methods, respectively. The thickness of polymer grafted on GO sheets was 2.1?nm (free radical polymerization method) and 6?nm (atom transfer radical polymerization method) that was measured by atomic force microscopy analysis. X-ray diffractometer and transmission electron microscopy indicated that after grafting of poly(sodium 4-styrenesulfonate), the modified GO sheets still retained isolated and exfoliated, and also the dispersibility was enhanced.     

Improvements and complications involved with adding an 85-GHzchannel to cloud liquid water radiometers

The improvement in cloud-liquid estimates by a microwave radiometer with the addition of measurements at 85 GHz is quantified. Atmospheric emission is simulated from radiosonde data at frequencies commonly used by ground-based water-vapor radiometers (22.235 and 31.65 GHz) and also at 85.5 GHz. Retrieval algorithms are developed from opacities based on full Mie extinction by cloud droplets and under an assumption that ice effects are not significant for downwelling emission. The algorithms use either three frequencies or only the lower two. The inclusion of 85-GHz information significantly improves liquid-water path estimates at all levels of integrated liquid water. The Rayleigh approximation is shown to be valid for most cloudy conditions. Uncertainty in the calculated opacities due to varying cloud droplet-size distributions and liquid-water content profiles is quantified. The accuracy of a retrieval algorithm trained by Rayleigh approximation opacities and including the additional uncertainty is shown to provide estimates with error levels similar to those from the algorithm trained with full Mie opacities