Modeling and simulation of non-isothermal catalytic packed bed membrane reactor for H2S decomposition

The recovery of H₂ from H₂S is an economical alternative to the Claus process in petroleum and minerals processing industries. Previous studies [React. Kinet. Catal. Lett. 62 (1997) 55; Catal. Lett. 37 (1996) 167] have demonstrated that catalytic decomposition of H₂S over bimetallic sulfide can proceed at relatively higher rates than over mono-metallic systems due to chemical synergism although conversions are still thermodynamically limited. In the present study, the performance of a catalytic membrane reactor containing a packed bed of Ru–Mo sulfide catalyst has been investigated with a view to improving H₂ yield beyond the equilibrium ceiling. A system of differential equations describing the non-isothermal reactor model has been solved to examine the effect of important hydrodynamic and transport properties on conversion. The results were obtained using a Pt-coated Nb membrane tube as the catalytic reactor enclosed in a quartz shell cylinder. Reynolds number for shell and tube side (Re^s and Re^t) as well as the modified wall Peclet number, Pe_m, dramatically affect H₂S conversions. Membrane reactor conversion rose monotonically with axial distance exceeding the equilibrium conversion by as much as eight times under some conditions.     

A novel single-phase self-regulated self-excited inductiongenerator using a three-phase machine

This paper presents a steady-state analysis of a novel single-phase self-regulated self-excited induction generator which employs a three-phase machine. Performance equations are derived using the method of symmetrical components, while the pattern search method of Hooke and Jeeves is used for the determination of the machine variables. The advantages of the generator include simple circuit configuration, small voltage regulation, good phase balance, and large power output. With an appropriate choice of the series and shunt capacitances, a nearly balanced operating condition can be obtained for a certain load. The theoretical analysis is validated by experiments performed on a small induction machine     

Effect of refrigerant charge on the performance of air conditioning systems

An air conditioning system operates in an optimal condition if the system is fully charged with a specified amount of refrigerant. Poor field maintenance or refrigerant leakage causes low level of charge resulting in a lower thermal performance and higher operating cost. An experimental investigation was conducted to study the effect of low charge level of R‐22 on the performance of a 3‐ton residential air conditioning system. The experimental results show that if a system is undercharged to 90 per cent then the effect is small: a 3.5 per cent reduction in cooling capacity and a 2 per cent increase in the coefficient of performance (COP). However, the system performance suffers serious degradation if the level of charge drops below 80 per cent. An ice layer formed on the outer surface of the cooling coil impedes the heat transfer between the warm air and cold refrigerant vapour. An economic analysis shows that the cost of properly charging an under‐charged system which is at an 85 per cent charge level, can pay for itself in savings in a short period of 3–4 months. Copyright © 2001 John Wiley & Sons, Ltd.     

On nonparametric local inference for density estimation

Bandwidth selection has been an important topic in nonparametric density estimation. In this paper an effective method for local bandwidth selection is proposed. For local bandwidth selection, due to data sparsity and other reasons, extremely small bandwidths are sometimes selected, which lead to severe undersmoothing. To circumvent this difficulty, the main idea behind the proposed method is to choose the largest bandwidth that still achieves the optimal rate. When coupled with practical bias reduction techniques, the bandwidth selected from this method can be applied simultaneously to conduct both local point and interval estimation. Simulation studies demonstrate the effectiveness of the proposed approach, which compares favorably with other existing approaches.     

Synthesis of a new type poly(vinyl alcohol)/peat/bamboo charcoal/KNO3 composite bead used as biofilter material

A new type poly(vinyl alcohol) (PVA)/peat/bamboo charcoal (BC)/KNO₃ composite bead was prepared, which has a diameter of 2.4–6.0 mm and a density of 1.133 g/cm³ and is a porous spherical particle. The biochemical kinetic behaviors of n‐butyl acetate in PVA/peat/BC/KNO₃ spherical composite bead biofilter (BC biofilter) and PVA/peat/granular activated carbon (GAC)/KNO₃ spherical composite bead biofilter (GAC biofilter) were investigated. The values of half‐saturation constant K_s for BC biofilter and GAC biofilter were 27.89 and 27.95 ppm, respectively. The values of maximum reaction rate V_m for BC biofilter and GAC biofilter were 13.49 and 13.65 ppm/s, respectively. Zero‐order kinetic with the diffusion limitation was regarded as the most adequate biochemical reaction model for the two biofilters. The microbial growth rate and biochemical reaction rate for two biofilters were inhibited at higher inlet concentration, and the degree of inhibitive effect was more pronounced in the inlet concentration range of 100–800 ppm. The biochemical kinetic behaviors of the two biofilters were similar. The maximum elimination capacity of BC biofilter and GAC biofilter were 111.65 and 122.67 g C/h m³ bed volume, respectively. The PVA/peat/BC/KNO₃ composite bead was suitable as a biofilter material. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Evaluation of intermodel agreement using ISO 13655 M0, M1, and M2 measurement modes in commercial spectrophotometers

Spectrophotometers are routinely used for color measurement and color management in many commercial printing and proofing workflows. In the case of media containing optical brightening agents, ultraviolet (UV)‐induced fluorescence has led to poor levels of agreement between models from different manufacturers, and different models from the same manufacturer. A relevant standard, ISO 13655, has been revised and now clearly defines measurement modes and conditions for the UV component in spectrophotometers. ISO 13655:2009—Graphic Technology—Spectral Measurement and Colorimetric Computation for Graphic Arts Images now defines four measurement modes: M0, M1, M2, and M3. The intermodel difference between 10 commercially available spectrophotometers is evaluated for different substrate types in measurement modes (M0, M1, and M2) as allowed by each instrument. In particular, the authors compare devices using M0 legacy mode versus newer instruments that are compliant with the new M1 and M2 (UV‐included and UV‐excluded) measurement modes. A finding with significant practical applications is that there is greatly improved intermodel agreement between the new generation of ISO 13655‐compliant instruments in M1 (D50) mode when compared with the previous generation of hand‐held spectrophotometers. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 27–37, 2017     

On uniform integrability and asymptotically risk-efficient sequential estimation

In the theory of asymptotically risk-efficient sequential estimation, one encounters uniform integrability of both positive and negative powers of stopping rules and moment convergence of randomly stopped statistics. We describe a simple approach to obtain these uniform integrability and moment convergence results, not only in the classical setting of i.i.d. observations but also for much more general stochastic sequences. We also use this approach to establish asymptotic risk efficiency of sequential estimators of means of stochastic sequences and to derive asymptotic approximations for the mean squared errors of ratio estimators.     

Possible Sampling Artifact in Real Time Particle Size Distributions Related to Sampling Rate

The availability of high time-resolution (1 s full spectrum scan) particle sizers permitted atmospheric researchers to scrutinize the characteristics of ultrafine particles in rapidly varying (perhaps, random) high concentration environments such as roadside, on-road, and tunnels. These data also revealed possible artifacts associated with the slower (～ 30 s or more) scanning sizers when used in this kind of environment. This study discusses sampling rate artifact problems based on simulations using 1 s Engine Exhaust Particle Sizer data taken on a mobile platform.     

双水相系统萃取细菌素发酵

以生长速率为标准,筛选出适合菌株乳酸乳球菌乳酸亚种ATCC 11454生长的成相聚合物聚乙二醇(PEG)20000、成相盐MgSO4.以细菌素浓度为筛选标准,优选出适合菌体生长及细菌素积累的双水相系统:PEG 20000 11%-MgSO4 3.5%.菌株细胞在该系统中完全分配在下相,虽然细胞的生长只有单相对照培养基的60%,但产物产量可提高33%.双水相系统系线和相体积比的改变均影响到菌体的生长及目的产物的积累.