Minimum-time trajectory generation for constrained linear systems using flatness and B-splines

In this article, we discuss minimum-time trajectory generation for input-and-state constrained continuous-time LTI systems in the light of the notion of flatness and B-splines parametrisation. Flat systems have the useful property that the input and the state trajectories can be completely characterised by the (so-called) flat output. We propose a splines parametrisation for the flat output, and the corresponding parametrisations for the performance output, the states and the inputs. Using this parametrisation the problem of minimum-time constrained trajectory planning is cast into a feasibility-search problem in the splines control-point space, in which the constraint region is characterised by a polytope. A close approximation of the minimum-time trajectory is obtained by systematically searching the end-time that makes the constraint polytope to be minimally feasible.     

Long-lived neutron-induced radioisotopes in OKTAVIAN facility concrete wall after 38 year-operation

An intense 14 MeV neutron source facility named OKTAVIAN was installed in the A15 building,Osaka University in 1981.Along the operation period,new radioisotopes with various half-life have been produced as neutron activation products in its concrete wall shield.In this work,we investigated the concrete wall in the heavy irradiation room of OKTAVIAN using gamma spectrometry method to discover the presence of radioisotope having large half-life value (long-lived radioisotope) as neutron activation products.Computational simulations were performed prior to measurement to predict the presence of long-lived radioisotopes by employing MCNP5 and FISPACT codes.A pre-calibrated Germanium detector with high energy resolution was employed to measure the concrete.Several long-lived activation products have been observed such as ¹⁵²Eu,⁵⁴Mn,⁶⁵Zn,²²Na and ⁶⁰Co.The activity of each radioisotope was derived after estimating the detector efficiency using MCNP5.As a result of the measurement and analysis,the followings are concluded:(1) Though presence of activation products represents radiological risk to everyone who performs an experimental activity in the irradiation room of the OKTAVIAN facility,the present result shows that past experiments were carried out safely without any significant additional exposure dose coming from the wall for the last 38 years.(2) The approximated total fluence of D-T neutrons to the wall was successfully estimated from the produced radioisotope,¹⁵²Eu,because it has the longest half-life of 13.5 years among the observed radioisotopes.(3) From the results of (1) and (2),it could be possible to estimate the total activity of the concrete wall in the OKTAVIAN facility,which is very essential and important information,because this would be very valuable for decommissioning or disposal of the facility in the future.     

Numerical assessment on improving multistage centrifugal impeller performance by changing inlet skew angle at impeller inlet

Multistage centrifugal impellers with four different skew angles were investigated by using computational fluid dynamics. The purpose of this work is to investigate the influences of lean angle at the blade tip of the impeller inlet. Four variations of lean angles, that is, 8°, 10°, 15° and 20°, were made at first stage impeller. Reynolds Average Navier Stokes equation was used in simulation together with a shear-stress transport (SST) k-w turbulence model and mixing-plane approach, respectively. Three dimensional fluid flows were simplified using periodic model to reduce the computational cost and time required. A good performance was expected that the secondary flow can be effectively reduced in the flow passage of the impeller without excessive increase in manufacturing cost caused by the secondary flow. The results show that secondary flow affects the main flow intricately to form vortices or having non-uniform velocity in the flow passage, which in turn results in substantial fluid energy loss not only in the impeller but also in the guide vane downstream of impeller. The numerical solutions were performed and allowed the optimum design and operating conditions to be obtained.     

User consent modeling for ensuring transparency and compliance in smart cities

Smart city infrastructures such as transportation and energy networks are evolving into so-called cyber physical social systems (CPSSs), which collect and     

Study of microcellular foaming of polystyrene aided with 45 kHz of ultrasound waves energy

ABSTRACT

In the microcellular foam plastic processing, cellular formation stage was being an essential stage since the nucleation and growth of the cell take place within. Based on classical nucleation theory, diminution of the free energy for nucleation, exponentially lead to an increase in the nucleation rate. This can be done by increasing the super-saturation level which achieved by heating the gas-saturated polymer. Hence, the advance is taken out by utilizing the ultrasound wave simultaneously with heating for foaming Polystyrene-scCO₂, which, not only to keep the super-saturation degree but also reduce the nucleation barrier. In this work, foaming was conducted under 45 kHz of ultrasound and varying the foaming temperature after saturating polystyrene with scCO₂. The results demonstrate, that foaming under ultrasound, the expansion ratio attained up to 1.5 fold, increase along with the heating temperature. Higher cell densities obtained with ultrasound applied at 50°C, however only slight difference can be seen, which about 10¹⁰–10¹¹ cell/cm³. From the cell size distribution results, cell distributed around 0.5–3.5 µm, with or without ultrasound applied for 60 and 70°C, Meanwhile at 50°C of foaming, the lowest cell size obtained with the aid of ultrasound in the range of 0.3–2.4 µm.     

Optimization of microwave-assisted extraction with saponification (MAES) for the determination of polybrominated flame retardants in aquaculture samples

The efficiency of microwave-assisted extraction with saponification (MAES) for the determination of seven polybrominated flame retardants (polybrominated biphenyls, PBBs; and polybrominated diphenyl ethers, PBDEs) in aquaculture samples is described and compared with microwave-assisted extraction (MAE). Chemometric techniques based on experimental designs and desirability functions were used for simultaneous optimization of the operational parameters used in both MAES and MAE processes. Application of MAES to this group of contaminants in aquaculture samples, which had not been previously applied to this type of analytes, was shown to be superior to MAE in terms of extraction efficiency, extraction time and lipid content extracted from complex matrices (0.7% as against 18.0% for MAE extracts). PBBs and PBDEs were determined by gas chromatography with micro-electron capture detection (GC-μECD). The quantification limits for the analytes were 40–750 pg g^?1 (except for BB-15, which was 1.43 ng g^?1). Precision for MAES-GC-μECD (%RSD?<?11%) was significantly better than for MAE-GC-μECD (%RSD?<?20%). The accuracy of both optimized methods was satisfactorily demonstrated by analysis of appropriate certified reference material (CRM), WMF-01.     

Study on low pressure evaporation of fresh water generation system model

A low pressure evaporation fresh water generation system is designed for converting brackish water or seawater into fresh water by distillation in low pressure and temperature. Distillation through evaporation of feed water and subsequent vapor condensation as evaporation produced fresh water were studied; tap water was employed as feed water. The system uses the ejector as a vacuum creator of the evaporator, which is one of the most important parts in the distillation process. Hence liquid can be evaporated at a lower temperature than at normal or atmospheric conditions. Various operating conditions, i.e. temperature of feed water and different orifice diameters, were applied in the experiment to investigate the characteristics of the system. It was found that these parameters have a significant effect on the performance of fresh water generation systems with low pressure evaporation.     

Textile-based microfluidics: modulated wetting,mixing, sorting,and energy harvesting

Microfluidics technology allows us to perform rapid and massively parallel manipulation and characterization of fluid samples with biomedical and environmental importance. In the attempt to achieve resource-efficient fabrication and operation of the microfluidic devices, paper-based and thread-based microfluidics have been previously demonstrated by other researchers. We propose to develop textile-based microfluidics, formed by three-dimensional networks of individual threads, to further advance the ability of paper-based and thread-based microfluidics. This paper describes four different phenomena that we investigate in textile-based microfluidic systems: modulated wetting, liquid mixing, liquid sorting, and energy harvesting. Our results indicate the feasibility of textiles as a new platform to develop low-cost microfluidic technology.     

Effects of intensive urbanization on the intrusion of shallow groundwater into deep groundwater: examples from Bangkok and Jakarta

Asian megacities have severe pollution problems in both coastal and urban areas. In addition, the groundwater potential has decreased and land subsidence has occurred because of intensive groundwater pumping in urban areas. To prevent the adverse effects of urbanization on groundwater quality, it is necessary to confirm the changes in groundwater flow and contaminant transport caused by urbanization. We examined the effects of urbanization on contaminant transport in groundwater. The research areas were located around Bangkok, Thailand, and Jakarta, Indonesia, cities with populations of approximately 8 and 12 million, respectively. Each metropolitan city is located on a river delta and is adjacent to a bay. We measured the water level and collected water samples at boreholes at multiple depths (100 to 200 m) in 2004 and 2006 in Bangkok and Jakarta, respectively. The current hydraulic potential is below sea level in both cities because of prior excess abstraction of groundwater. As a result, the direction of groundwater flow is now downward in the coastal area. The Cl(-) concentration and delta(18)O distributions in groundwater suggest that the decline in hydraulic potential has caused the intrusion of seawater and shallow groundwater into deep groundwater. Concentrations of Mn and NO3(-)-N in groundwater suggest the intrusion of these contaminants from shallow to deep aquifers with downward groundwater flow and implies an accumulation of contaminants in deep aquifers. Therefore, it is important to recognize the possibility of future contaminant transport with the discharge of deep groundwater into the sea after the recovery of groundwater potential in the coastal areas.