Use of dry yeast cells as a cheap nitrogen source for lactic acid production by thermophilic Bacillus coagulans WCP10-4? ?

Dry yeast cells (DYC) were used as a cheap nitrogen source to replace expensive yeast extract (YE) for L-lactic acid production by thermophilic Bacillus coagulans. Cassava starch (200 g·L⁻¹) was converted to L-lactic acid by simultaneous saccharification and fermentation using Bacillus coagulans WCP10-4 at 50 °C in the presence of 20 g·L⁻¹ of DYC, giving 148.1 g·L⁻¹ of L-lactic acid at 27 h with a productivity of 5.5 g·L⁻¹·h⁻¹ and a yield of 92%. In contrast, 154.4 g·L⁻¹ of lactic acid was produced at 24 h with a productivity of 6.4 g·L⁻¹·h⁻¹ and a yield of 96% when equal amount of YE was used under the same conditions. Use of pre-autolyzed DYC at 50 °C for overnight slightly improved the lactic acid titer (154.5 g·L⁻¹) and productivity (7.7 g·L⁻¹·h⁻¹) but gave the same yield (96%).     

在电子测试技术工程教育中,使用NI LabVIEW和NI ELVIS进行IC参数测试

1引言 将NILabVIEW、NI教学实验室虚拟仪器套件II（NIELVISII）与易于使用、自定义的即插即用IC测试板结合,创建了一个用户界面友好且可编程配置的IC直流参数测试平台,为高等教育提供了测试中小规模集成电路芯片直流参数的动手实践平台。     

The radial basis integral equation method for solving the Helmholtz equation

A meshless method for the solution of Helmholtz equation has been developed by using the radial basis integral equation method (RBIEM). The derivation of the integral equation used in the RBIEM is based on the fundamental solution of the Helmholtz equation, therefore domain integrals are not encountered in the method. The method exploits the advantage of placing the source points always in the centre of circular sub-domains in order to avoid singular or near-singular integrals. Three equations for two-dimensional (2D) or four for three-dimensional (3D) potential problems are required at each node. The first equation is the integral equation arising from the application of the Green’s identities and the remaining equations are the derivatives of the first equation with respect to space coordinates. Radial basis function (RBF) interpolation is applied in order to obtain the values of the field variable and partial derivatives at the boundary of the circular sub-domains, providing this way the boundary conditions for solution of the integral equations at the nodes (centres of circles). The accuracy and robustness of the method has been tested on some analytical solutions of the problem. Two different RBFs have been used, namely augmented thin plate spline (ATPS) in 2D and f(R)=⁴Rln(R) augmented by a second order polynomial. The latter has been found to produce more accurate results.     

The effect of charcoal combustion on iron-ore sintering performance and emission of persistent organic pollutants

A study was carried out into the use of hardwood charcoal as a supplementary fuel in the iron-ore sintering process. The primary fuel was coke breeze with 0%, 20%, 50% and 100% replacement of the energy input with charcoal to produce raw blends with the same heat output as 4.0 wt.% coke breeze. Experimental results indicate that fuel blends where 20% of the heat input was provided by charcoal may improve both the sinter yield and sintering productivity by up to 8%, under normal sintering conditions. In addition, the 20% replacement of coke energy with charcoal would mean that part of the carbon dioxide emitted from the process would be from a renewable source and could be used to offset carbon dioxide emissions from non-renewable fossil fuels. At higher rates of coke breeze energy substitution with charcoal, the lower sintering performance observed was mainly attributed to the lower fixed carbon content and higher volatile matter content of the fuel mix.At the optimum rate of 20% substitution of coke breeze energy input with charcoal, the emission of dioxins were similar to those observed with coke breeze alone as the fuel. However, sintering with 20% energy input from charcoal resulted in a slight increase in middle molecular weight and lower molecular weight PAHs, contributing to a minor increase in B[a]P-eq from 0.15 μg/m³ to 0.17 μg/m³. Overall the results from the laboratory scale tests suggest that it is feasible to substitute 20% of the coke breeze energy input with an equivalent amount of energy from charcoal in the iron-ore sintering process.     

A transparent and flexible organic bistable memory device using parylene with embedded gold nanoparticles

In this work, we demonstrate the fabrication of a transparent and flexible memory device in the simple structure of metal/dielectric/metal (MIM). Here, the MIM structure consists of gold electrode/200 nm Parylene-C/20 nm gold nanoparticles/100 nm Parylene-C/indium-tin-oxide (ITO) coated polyethylene terephthalate (PET). The use of parylene as the dielectric layer is important to ensure that there is no thermal stress induced on the flexible ITO/PET substrate compare to other reported works using various organic dielectrics that require high temperature curing. In addition, parylene deposition does not disturb the drop-casted gold nanoparticles. Hence, the use of parylene will be the right step forward in the fabrication of mechanically flexible and optically transparent devices. Current versus voltage (I–V) plot shows the presence of hysteresis suggesting the charge storage capability as a memory device. In the I–V plot, three distinct regions based on the slope have been identified and the transport mechanisms are discussed and explained. The fabricated device shows similar behavior as write-once-read-many memory device and can be programmed with either positive or negative bias voltage. However, the memory device shows unstable current state when being bent under different curvature diameters.     

SnO2 nanorod arrays: low temperature growth, surface modification and field emission properties

SnO(2) nanorod arrays have been deposited on 4 inch SiO(2)/Si and Si wafers and stainless steel substrates by plasma-enhanced chemical vapor deposition without any high temperature treatment or additional catalysis. The SnO(2) nanorods grow up from seed nanocrystals along the [110] preferential direction by a self-catalyzed vapor-solid growth mechanism. The surface of the SnO(2) nanorods was modified by ZnO, Pt and Ni nanocrystals. After surface modification, the field emission properties of the SnO(2) nanorod arrays are improved. The Ni nanocrystal with sharp tips and edges act as additional field emission sites to SnO(2) nanorods and thus the Ni/SnO(2)/SiO(2)/Si outperforms other samples due to the synergistic effects of good conductivity and hierarchical sharp apexes. The field enhancement factor of the Ni/SnO(2)/SiO(2)/Si increased around 3 times while the turn-on field of 8.0 V μm(-1) is about one third of the SnO(2)/SiO(2)/Si device.     

Modal and stress analysis of gear train design in portal axle using finite element modeling and simulation

The portal axle is a gearbox that is specially designed for off-road driving conditions. It is installed between the wheel and the axle shaft to give higher ground clearance to the vehicle. The modeling and simulation of spur gears in portal axle is important to predict the actual motion behavior. However, gear train design in portal axle is difficult to study comprehensively due to their relatively low cost and short product life cycle. In this study, modal analysis of portal axle is simulated using finite element method (FEM). Modal analysis is simulated on three different combinations of gear train system commonly designed for portal axle. The three gear trains being analyzed are gear train without idler gear, one idler gear and two idler gears. FEM static stress analysis is also simulated on three different gear trains to study the gear teeth bending stress and contact stress behavior of the gear trains in different angular positions from 0° to 18°. The single and double pair gear teeth contact are also considered. This methodology serves as a novel approach for gear train design evaluation, and the study of gear stress behavior in gear train which is needed in the small workshop scale industries.     

Antioxidant activity of phenolics–saponins rich fraction prepared from defatted kenaf seed meal

The current study is aimed to determine the antioxidant properties of crude ethanolic extract (CEE) of defatted kenaf seed meal (DKSM) and its derived n-butanol (BF) and aqueous (AqF) fractions. Spectrophotometric assays showed that BF contained the highest amount of phenolic compounds and saponins, followed by CEE and AqF (p < 0.05). Similarly, HPLC-DAD analysis revealed that level of all the detected predominant phenolic compounds was significantly higher in BF (p < 0.05). Through multiple antioxidant assays, BF exhibited higher antioxidant activity than CEE and AqF, except for iron chelating activity (p < 0.05). Antioxidant activity of CEE and fractions were strongly correlated to their phenolic and saponin contents. This study showed that phenolic compounds and saponins could be extracted and partially purified simultaneously from DKSM by employing a simple alcoholic extraction–fractionation procedure. High antioxidative phenolics–saponins rich fraction from DKSM is a potential active ingredient that could be applied in nutraceuticals, functional foods as well as natural food preservatives.     

Benchmark tests for verifying discrete element modelling codes at particle impact level

Over the past 30 years, the Discrete Element Method (DEM) has rapidly gained popularity as a tool for modelling the behaviour of granular assemblies and is being used extensively in both scientific and industrial applications. However, it is far from clear from reviewing the literature whether the large number of DEM codes have been verified and checked against fundamental benchmark problems. DEM simulates the dynamics of each particle in an assembly by calculating the acceleration resulting from all the contact forces and body forces. It is clearly necessary that such a model be validated or verified by comparing with experimental results, analytical solutions or other numerical results (e.g. Finite Element Analysis (FEA) results) at particle impact level. There appears to be no standard benchmark tests against which DEM codes can be verified. It is thus essential and useful to establish a set of standard benchmark tests to confirm that these DEM codes are modelling the particle dynamics as intended. This paper proposes a set of benchmark tests to verify DEM codes at particle impact level for spherical particles. The analytical solutions derived from elasticity theory for elastic normal collision of two spheres or a sphere with a rigid plane are first reviewed. These analytical solutions apply only to the elastic regime for normal impact. Secondly, the analytical solutions of frictional oblique impact between two spheres or a sphere with a rigid plane are scrutinized and derived. These analytical solutions originate from the dynamics principles and should be satisfied for any DEM contact force model with prescribed friction and restitution coefficients. A set of eight benchmark tests are designed and performed using commercial DEM codes. Test 1 and Test 2 consider the elastic normal impact of two spheres or a sphere with a rigid plane, whereas the other tests (Test 3–Test 8) investigate the energy dissipation due to the collision. These benchmark tests also involve different types of material. The DEM results were compared with the analytical solutions, experimental or FEA results found in the literature. All benchmark tests showed good to excellent match, providing a quantitative verification for the codes used in this study. These benchmark tests not only verify DEM codes but also enhance the understanding of fundamental impact phenomena for modelling a large number of particles.     

Planning of carbon capture and storage with pinch analysis techniques

Carbon capture and storage (CCS) is a means for reducing carbon dioxide (CO₂) emissions from fossil fuel combustion in power generation and industrial processes. It involves the capture of CO₂ for subsequent storage in various geological formations. The selection and matching of the power plants and storage sites are often an issue of optimisation due to various constraints, i.e., time of availability, injection rate, and storage capacity limits. In this work, a novel graphical targeting tool based on pinch analysis is proposed to address the planning problem of the storage of captured CO₂ from power generating plants into corresponding reservoirs. The main consideration for the problem is the time of availability of the latter, since reservoirs need to be developed prior to CO₂ storage. The time limitation is addressed by the graphical technique where time is taken as the governing element in solving the problem. Hypothetical examples are used to elucidate the proposed approach.