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This paper aims to resolve the cavitation problem encountered in cone throttle valves concerning fluid flow performance and pitting from cavitation luminescence, the…
This paper aims to resolve the cavitation problem encountered in cone throttle valves concerning fluid flow performance and pitting from cavitation luminescence, the author studied the flow field within a cone throttle valve set with various valve openings, inlet pressures and outlet back pressures.
The flow and cavitation distribution in the valve under different pressure conditions were obtained in simulations. To confirm these results experimentally, a hydraulic cavitation platform was constructed. The valve was made of polymethyl methacrylate material with high transparency to observe the cavitation directly, as well as cavitation luminescence. The flow characteristics of this valve were measured under various working conditions.
With increasing cavitation strength, a reduction in cavitation on the throttle capacity was more evident. Increasing the back pressure and reducing the working pressure of the valve appropriately improves the flow capacity of the valve, which subsequently improves the performance of the valve. The cavitation luminescence is also linearly related to cavitation intensity. That is, the stronger the flow capacity of the valve, the less likely the luminescence is produced. Moreover, a stronger luminescence intensity worsens the flow performance of the valve.
Owing to the limitation of experimental means and lack of research on bubble shape, the subsequent research will complement this aspect.
With a view to providing theoretical and experimental support, cavitation luminescence is also studied to gain a deeper understanding of the cavitation mechanism in hydraulic valves.
The innovation of this paper is to study the cavitation luminescence in the hydraulic system.
Discusses the efficiency of a cybernetic approach to non‐oscillatory luminescence processes, generated by perturbed biosystems, and applies it to oscillatory luminescence…
Discusses the efficiency of a cybernetic approach to non‐oscillatory luminescence processes, generated by perturbed biosystems, and applies it to oscillatory luminescence processes. Constructs multiplicative stochastic models of oscillatory bio‐ and chemiluminescence processes, generated by some perturbed/stimulated biosystems (a temperature‐stimulated soybean root system, light‐stimulated microporocytes of larch, antiviral drug‐treated vero cells infected by Herpes simplex virus). Determines a correlation structure for these models by analysing their transfer functions. Uses the memory function approach to compare and contrast the oscillatory processes with their non‐oscillatory analogs. Formulates a hypothesis about the dependence between the persistence and the oscillatory behaviour of biosystems and proposes stochastic perturbation measures founded on those multiplicative models.
In general, lighting application, white light emitting diode (LED) usually exposed to an extreme operating temperature of above 90°C. It is well-known that luminous…
In general, lighting application, white light emitting diode (LED) usually exposed to an extreme operating temperature of above 90°C. It is well-known that luminous efficacy and spectral characteristic of white LED are dependent on the temperature, causing thermal effects on luminous efficacy and color shift of white LED become a critical application checkpoint to be addressed by white LED manufactures. Thus, the purpose of this paper is to minimize the thermal stability issue affecting white LED luminescence during operation by introducing phosphor sedimentation process.
The LED samples were assembled and sent for centrifugation with 0, 5 and 10 revolutions per second (rps), respectively, during phosphor sedimentation process. Luminescence properties of these LED samples were then characterized at a varying temperature to investigate the effect of phosphor sedimentation on the luminescence stability of LED samples. The LED samples were also cross-sectioned and analyzed to understand the phosphor sedimentation mechanism. Computational fluid dynamics (CFD) was applied to study the temperature distribution of the non-phosphor sediment (NPS) and phosphor sediment (PS) LED during operation to validate the hypotheses based on experimental data.
Experimental results show that the luminous intensity of PS LED samples degrades less significant at high temperature. The experimental results also show that the color coordinate for PS LED samples is more stable and is less blue-shifted than NPS LED samples as the temperature increased. These are because the heat generated by phosphor particles during operation can be dissipated effectively throughout a high thermal conductivity substrate after phosphor sedimentation. Thus, the phosphor temperature of PS LED is lower than NPS LED during operation as validated with the thermal simulation.
The study of this paper is applicable as a reference for industries who intend to resolve the thermal stability of white LED during operation. The luminescence properties changes as a function of the temperature study in this paper can be used to predict the application performances of white LED accurately. Apart from that, the analysis method of temperature distribution using CFD simulations can be extended by other CFD users in the future.
Implementation of phosphor sedimentation to reduce thermal instability issue of white LED has yet to be reported on previous studies. Most literature just studied the thermal instability issue of either assembled LED or raw material, without suggesting any solution to tackle the issue.
Long afterglow Sr2MgSi2O7 (SMS) phosphor was prepared by Douby's methods at high temperature and reductive atmosphere. The excitation and emission spectra of this phosphor…
Long afterglow Sr2MgSi2O7 (SMS) phosphor was prepared by Douby's methods at high temperature and reductive atmosphere. The excitation and emission spectra of this phosphor showed that both had broad bands and that the main emission peak at 469 nm was due to 4f‐5d transitions of Eu+2 and implied that the luminescence centres Eu+2 occupied the Sr+2 sites in the Sr2MgSi2O7 host. The phosphor doped only with Eu ions did not demonstrate the long afterglow phenomenon, but when co‐doped with Dy+3 ions in the SMS matrix, significant long afterglow was observed.
A kinetic model for the biphasic modulation of phagocytosis, fulfilling the requirements of biochemistry of ligand‐binding reactions, was constructed on the basis of a…
A kinetic model for the biphasic modulation of phagocytosis, fulfilling the requirements of biochemistry of ligand‐binding reactions, was constructed on the basis of a biocybernetic notion of the feedback loop‐containing (autocalytic) process. Using boundary conditions for parameters of possible kinetic models, a single model was selected, in which the biphasic modulatory effect exerted on a phagocytic activity of human neutrophils by the peptide preparation Immax A1 was described as a result of mutual counteraction of two antagonistic compounds (stimulator and inhibitor of phagocytosis) competing for bacterial chemotactic peptide receptors on neutrophils. This model, in which the integrated luminescence‐based normalised measure of inhibition of phagocytosis stands for the reaction rate, was found to have a form of a 2:3 rational function of the peptide preparation concentration. A corresponding stoichiometric scheme, describing the binding both of the inhibitor and of the stimulator to neutrophils, was constructed on the assumption that inhibition was not total when connected with the generation of three‐component complexes, stimulator‐neutrophil‐inhibitor.
The synergistic effect of sodium salt of ethyl phosphonic acid (EPA) and Zn2+ on the inhibition of corrosion of mild steel in neutral aqueous environment containing 60 ppm…
The synergistic effect of sodium salt of ethyl phosphonic acid (EPA) and Zn2+ on the inhibition of corrosion of mild steel in neutral aqueous environment containing 60 ppm Cl‐ has been evaluated by the weight‐loss method. The formulation consisting of 300 ppm EPA and 300 ppm Zn2+ has 88 per cent inhibition efficiency. The nature of the protective film formed on the metal surface has been analysed by x‐ray diffraction, FTIR, uv‐visible and luminescence spectra. The protective film is found to be luminescent and to consist of Fe2+ ‐EPA complex, Zn (OH)2 and a very thin film of oxides of iron.
ZnS:Cu phosphors were prepared by co‐precipitating Cu along with ZnS using H2S and thiourea. Phosphors giving luminescence at around 530 nm were prepared. The difference…
ZnS:Cu phosphors were prepared by co‐precipitating Cu along with ZnS using H2S and thiourea. Phosphors giving luminescence at around 530 nm were prepared. The difference in the characteristic properties among the samples prepared appeared to be due to the formation of nanoparticles during the preparation of the samples by different methods.
Traditional ceramic industries (ceramic tiles, frits, glazes and pigments) generate solid wastes, wastewater and gas emissions that have different characteristics depending on the type of product made. The present study was undertaken to define a series of test methodologies for characterising each type of waste. The approach involved defining the elements to be analysed in each kind of sample, subsequently carrying out the respective test methods for the determinations in terms of type of parameter and sample. In gas emissions, the study addressed fluorine compound analysis. In liquid samples, AAS and ICP‐OES techniques were compared, validating the methods by using reference materials and participating in CALITAX and AQUACHECK intercomparison rounds on wastewater analysis. In solid samples, ICP‐OES and XRF techniques were compared, validating the methods by participating in International Proficiency Tests of Analytical Geochemistry Laboratories (GEOPT‐7, GEOPT‐8 and GEOPT‐9). The selective electrode determination of fluorine in gas emissions yields good results. The study shows that toxicity can be determined in liquid and solid samples by the bioluminescence assay. In liquid samples, good results were found for metal elements analysis by AAS and ICP‐OES, the latter being better. Finally, in solid wastes the ICP‐OES technique has advantages in analysing minor elements compared with XRF, whereas XRF is more suitable for analysing major elements, as it is a faster, more reproducible technique.
The formulation consisting of 300ppm 1‐hydroxyethane‐1, 1‐diphosphonic acid (HEDP), 50ppm polyacrylamide (PAA) and 50 ppm Zn2+ offered 99 per cent corrosion inhibition and…
The formulation consisting of 300ppm 1‐hydroxyethane‐1, 1‐diphosphonic acid (HEDP), 50ppm polyacrylamide (PAA) and 50 ppm Zn2+ offered 99 per cent corrosion inhibition and 99 to 99.9 per cent biocidal inhibition to mild steel in neutral aqueous environment containing 60ppm Cl‐ , a situation commonly encountered in cooling water systems. The nature of the protective film formed on the metal surface was analysed using X‐ray diffraction, UV‐visible reflectance, FTIR and luminescence spectra. The film was found to be luminescent and to consist of Fe2+ ‐HEDP complex, Fe2+ ‐PAA complex and Zn(OH)2.