1,721,395 research outputs found
A comparison study on the high-rate co-digestion of sewage sludge and food waste using a temperature-phased anaerobic sequencing batch reactor system
No full textdAssessing contemporary anaerobic biotechnologies requires proofs on reliable performance in terms of renewable bioenergy recovery such as methane (CH(4)) production rate, CH4 yield while removing volatile solid (VS) effectively. This study, therefore, aims to evaluate temperature-phased anaerobic sequencing batch reactor (TPASBR) system that is a promising approach for the sustainable treatment of organic fraction of municipal solid wastes (OFMSW). TPASBR system is compared with a conventional system, mesophilic two-stage anaerobic sequencing batch reactor system, which differs in operating temperature of 1st-stage. Results demonstrate that TPASBR system can obtain 44% VS removal from co-substrate of sewage sludge and food waste while producing 1.2 m(3)CH(4)/m(system)(3)/d (0.2 m(3)CH(4)/kgVS(added)) at organic loading rate of 6.1 gVS/L/d through the synergy of sequencing-batch operation, co-digestion, and temperature-phasing. Consequently, the rapid and balanced anaerobic metabolism at thermophilic stage makes TPASBR system to afford high organic loading rate showing superior performance on OFMSW stabilization. (C) 2011 Elsevier Ltd. All rights reserved
Contrast ratio and switching of zigzag defect-free surface stabilized FLCD by photoinduced alignment
No full textThe contrast ratio and electro-optical switching behaviours of surface stabilized ferroelectric liquid crystal cells with alignment layers of a photodegradable polyimide prepared by polarized ultraviolet light irradiation have been investigated. The higher contrast ratio was obtained for a zigzag defect-free sample obtained by the photo-induced alignment method than by the rubbing method. The switching behaviours of the FLC, such as spontaneous polarization and response time, were measured. Higher spontaneous polarization and faster response times were obtained with cells prepared by the photoinduced alignment method. In addition, response times of the order of microseconds, which are fast enough to realize high quality moving images with video-frame rate, were obtained
Zigzag defect-free alignment of surface stabilized ferroelectric liquid crystal cells with a polyimide irradiated by polarized UV light
No full textZigzag defect-free surface stabilized ferroelectric liquid crystal (SSFLC) cells were prepared using a photodegradable polyimide (PI) having a cyclobutane ring in the backbone. The PI layers were irradiated by polarized ultraviolet light (PUVL) at normal incidence to the surface, and characterized by UV and FTIR spectroscopy. The anisotropy originates from preferential cleavage of PI chains oriented parallel to the polarization direction of the irradiating PUVL. After the polarized UV light irradiation, the PI surface was much flatter than that after rubbing, but it induced a similar order parameter of dye-doped nematic LC molecules to that for a rubbed cell. Alignment of both the FLC molecules and the layer structure is important in SSFLC. After 40 min irradiation, the FLC molecules were well aligned homogeneously, and the FLC cells showed a uniform texture without zigzag defects which also indicates a well aligned layer structure. Zigzag defect-free alignment may result from the flatter surface, the much smaller and more constant pretilt angles, and the bigger cone angle than those achieved by rubbing
Switching behaviors of ferroelectric liquid crystal cells with a polyimide alignment layer
No full textThe spontaneous polarizations, response and decay times, and light transmittances of ferroelectric liquid crystal cells were observed. When a field was applied, the spontaneous polarization of ferroelectric liquid crystal by a rubbing method was higher than that was by a LB technique. In the cases of response and decay times, the FLC cell treated by the rubbing method at once was faster than that by the LB method. Especially, the response time of a ferroelectric liquid crystal cell of having an alignment layer treated by the LB 1 layer after rubbing, was similar to that by rubbing, but decay time fell in between the cells of a rubbed surface and of a LB film. (C) 2001 Elsevier Science B.V. All rights reserved
The optimisation of food waste addition as a co-substrate in anaerobic digestion of sewage sludge
No full textFood waste has been regarded as the main source of various environmental pollution in Korea due to the high volatile solids (VS) and moisture content caused by the features of dietary habits. The feasibility of food waste as a co-substrate in anaerobic digestion of sewage sludge was investigated in mesophilic and thermophilic conditions using batch tests. Cumulative methane production, dissolved organic carbon (DOC) and volatile fatty acids (VFA) were monitored to find the optimal mixing ratios of food waste and sewage sludge for the enhanced performance of co-digestion. It was observed that adequately mixed food waste led to the enhanced methane production both at mesophilic and thermophilic conditions. However, a conventional linear regression conducted for the optimisation of co-substrate mixing ratios was not accurate in describing exact methane production trends of co-digestion because of the different biodegradability of substrates. Therefore, a remodified Gompertz equation showing nonlinear relationship between variables was developed to find exact information with the same experimental data obtained at 29 VS/l generally used in biochemical methane potential (BMP) tests. Based on an influential parameter, methane production rate (MPR), the optimal mixing ratios of food waste were 39.3% and 50.1% in mesophilic and thermophilic conditions, respectively. To confirm the application of the remodified Gompertz equation, secondary batch tests were conducted with the Substrate concentrations of 1-4g VS/l. In overall range tested, the confident mixing ratios of food waste was adjusted to 30-40% and 40% in mesophilic and thermophilic conditions, respectively. The most significant factor for enhanced performance was the improved organic carbon content provided by additional food waste
Image-based visual servoing using position and angle of image features
No full textA new image-based visual servoing, using position and angle bf image features, is presented. The proposed method can manipulate the three-dimensional trajectory of a robot by using only the error defined in the two-dimensional, image plane. Experimental results show that the proposed method has a linear trajectory for the selected one point in the gripper, and so avoids collision with the work table or ether objects
Parametric study on the impact-echo method using mock-up shafts
No full textIn this study, the impact-echo method was employed to evaluate the integrity of shafts, and parametric simulations of the impact-echo method were carried out numerically and experimentally. A one-dimensional finite element study was performed for mock-up shafts that include solid and damaged shafts. The mock-up shaft was made of Monocast, and four types of flaws were considered: (1) axisymmetric voids, (2) non-axisymmetric voids, (3) necks, and (4) bulbs. The reduction in shaft cross-sectional area varied from 30 to 80%. Subsequently, experimental studies were carried out to verify the finite element models using similar mock-up shafts. These experimental studies were carried out in the air and soil, and impact responses were analyzed in both time and frequency domains. It was shown that the results of the experiment were in agreement with those of numerical studies, and the accuracy of the impact-echo method was influenced by the type, size and location of flaws. In addition, it was also revealed that axisymmetric void, non-axisymmetric void, and neck could be detected in the frequency domain when the reduction in shaft cross-sectional area was more than 50%. Alternatively in the time domain, it was possible to identify the flaw reliably when the reduction was 30%. This latter approach provides the better possibility of detecting smaller flaw in shaft. (C) 2002 Elsevier Science Ltd. All rights reserved
Ammonia inhibition and microbial adaptation in continuous single-chamber microbial fuel cells
No full textHere, we report that a continuous single-chamber microbial fuel cell (MFC) is applicable to wastewaters containing a high nitrogen concentration using a process of adaptation. Continuous experiments are conducted to investigate the inhibitory effect of total ammonia nitrogen (TAN) on the MFC using influents with various concentrations of TAN ranged from 84 to 10,000 mg N L(-1). As the TAN concentration increases up to 3500 mg N L(-1). the maximum power density remains at 6.1W m(-3). However, as the concentration further increases. TAN significantly inhibits the maximum power density, which is reduced at saturation to 1.4W m(-3) at 10,000 mg N L(-1). We confirm that the adapted electrical performance of a continuous MFC can generate approximately 44% higher power density than the conductivity control. A comparative study reveals that the power densities obtained from a continuous MFC can sustain 7-fold higher TAN concentration than that of previous batch MFCs. TAN removal efficiencies are limited to less than 10%, whereas acetate removal efficiencies remain as high as 93-99%. The increased threshold TAN of the continuous MFC suggests that microbial acclimation in a continuous MFC can allow the electrochemical functioning of the anode-attached bacteria to resist ammonia inhibition. (C) 2011 Elsevier B.V. All rights reserved
Characteristics of carbon nano-dots fabricated by the thermo-electrical pulse induced evaporation
No full text- …
