Optical penetration-based silkworm pupa gender sensor structure

This paper proposes and experimentally demonstrates for what is believed to be the first time a highly sought-after optical structure for highly-accurate identification of the silkworm pupa gender. The key idea is to exploit a long wavelength optical beam in the red or near infrared spectrum that can effectively and safely penetrate the body of a silkworm pupa. Later on, simple image processing operations via image thresholding, blob filtering, and image inversion processes are applied in order to eliminate the unwanted image noises and at the same time highlight the gender gland. Experimental proof of concept using three 636 nm wavelength light emitting diodes, a two-dimensional web camera, an 8 bit microcontroller board, and a notebook computer shows a very high 95.6% total accuracy in identifying the gender of 45 silkworm pupae with a measured fast identification time of 96.6 ms. Other key features include low cost, low component counts, and ease of implementation and control.     

Steady-State and Transient Behavior of Two Heat Exchangers Coupled by a Circulating Flowstream

Systems consisting of two heat exchangers coupled by a circulating flowstream are studied. The systems differ in the flow configurations of the single heat exchangers. For steady-state operation, there exists a heat capacity rate of the circulating flowstream that maximizes the temperature changes of the external flowstreams. Until now, this optimum has been calculated assuming that the overall heat transfer coefficients of the heat exchangers do not depend on the mass flow rate of the circulating flowstream. In this paper, the dependence of the overall heat transfer coefficient on the mass flow rate of the circulating flowstream is taken into account. For transient operating conditions, the system response to perturbations of inlet temperatures and mass flow rates is calculated by the method of Laplace Transforms and an explicit finite difference method. The most significant features of the coupled system become apparent by considering outlet temperature transients induced by perturbations of the mass flow rate of the circulating flowstream.     

Consideration of maldistribution in heat exchangers using the hyperbolic dispersion model

Axial temperature profiles in a shell and tube heat exchanger are numerically calculated for given maldistributions on the tube side. For comparison the same maldistributions are handled with the parabolic and hyperbolic dispersion model with fitted values for the axial dispersion coefficient and third sound wave velocity. The analytical results clearly demonstrate that the hyperbolic model is better suited to describe the steady state axial temperature profiles.     

Application of Danckwerts-type boundary conditions to the modeling of the thermal behavior of metal hydride reactors

The paper presents a model-based investigation of a metal hydride reactor applied as a solid state hydrogen storage device. The elements of a metal hydride reactor are hydrogen supply duct, internal hydrogen distribution, hydride bed, reactor shell and the flow domain of the heat transfer fluid. Internal hydrogen distribution and hydride bed are porous media. Therefore, hydrogen flows through non-porous and porous regions during its reversible exothermic absorption and endothermic desorption, respectively. The interface between porous and non-porous regions is a discontinuity with respect to energy transport mechanisms. Hence, Danckwerts-type boundary conditions for the energy balance equation are introduced. Application of the first and second law of thermodynamics to the interface reveals that temperature jumps may occur at the hydrogen inlet but are not allowed at the hydrogen outlet. Exemplarily the loading behavior of a metal hydride storage tank based on sodium alanate is analyzed. It is demonstrated and experimentally validated that only Danckwerts-type boundary conditions predict the important cooling effect of the inlet hydrogen on the exothermic absorption process correctly.     

Removal of contaminated organic acids from simulated succinic acid fermentation broth by reactive extraction process: Single- and mixed-solute solution

This work aims to study how to remove the organic acid by-products from simulated fermentation broth containing succinic acid by reactive extraction. Model solutions including single-, binary-, ternary-, and quaternary-solute solutions were used. The broths were reactively extracted using 0.25 mol TOA/kg 1-octanol under pH of 2.45-6.0. The extracted broths were then distillated under vacuum -0.017 MPa with operating temperature between 45 and 65°C. Finally, the distilled broths were crystallized at 4°C and pH of 2.0. The results showed that the purity and yield of succinic acid of 99.10% and 30.25%, respectively, were obtained.     

Optimization of key factors affecting hydrogen production from food waste by anaerobic mixed cultures

Key factors (inoculums concentration, substrate concentration and citrate buffer concentration) affecting hydrogen yield (HY) and specific hydrogen production rate (SHPR) from food waste in batch fermentation by anaerobic mixed cultures were optimized using Response Surface Methodology with Central Composite Design. The experiments were conducted in 120 ml serum bottles with a working volume of 70 mL. Under the optimal condition of 2.30 g-VSS/L of inoculums concentration, 2.54 g-VS/L of substrate concentration, and 0.11 M of citrate buffer concentration, the predicted maximum HY and SHPR of 104.79 mL H₂/g-VS_added and 16.90 mL H₂/g-VSS.h, respectively, were obtained. Concentrations of inoculums, substrate and citrate buffer all had an individual effect on HY and SHPR (P < 0.05). The substrate concentration and citrate buffer concentration had the greatest interactive effect on SHPR (P = 0.0075) while their effects on HY (P = 0.0131) were profound. These results were reproduced in confirmation experiments under optimal conditions and generated an HY of 104.58 mL H₂/g-VS_added and an SHPR of 16.86 mL H₂/g-VSS.h. This was only 0.20% and 0.24%, respectively, different from the predicted values. Microbial community analysis by PCR-DGGE indicated that Clostridium was the pre-dominant hydrogen producer at the optimum and worst conditions. The presence of Lactobacillus sp. and Enterococcus sp. might be responsible for the low HY and SHPR at the worst condition.     

Optimization of hydrogen storage tubular tanks based on light weight hydrides

Design of hydrogen storage systems aims at minimal weight and volume while fulfilling performance criteria. In this paper, the tubular tank configuration for hydrogen storage based on light weight hydrides is optimized towards its total weight using the predictions of a newly developed simulation model. Sodium alanate is taken as model material. A clear definition of the optimization is presented, stating a new optimization criterion: a defined total mass of hydrogen has to be charged in a given time, instead of prescribing percentages of the total hydrogen storage capacity. This yields a wider space of possible solutions. The effects of material compaction, addition of expanded graphite and different tubular tank diameters were evaluated. It was found that compaction of the material is the most influential factor to optimize the storage system. In order to obtain lighter storage systems one should concentrate on improving the ratio mass of hydride bed to mass of tank wall by screening lighter materials for the tank wall and developing hydrogen storage materials exhibiting both higher gravimetric and volumetric storage capacities.