Microsimulation modelling of driver behaviour towards alternative warning devices at railway level crossings

Level crossings are amongst the most complex of road safety issues, due to the addition of rail infrastructure, trains and train operations. The differences in the operational characteristics of different warning devices together with varying crossing, traffic or/and train characteristics, cause different driver behaviour at crossings. This paper compares driver behaviour towards two novel warning devices (rumble strips and in-vehicle audio warning) with two conventional warning devices (flashing light and stop sign) at railway level crossings using microsimulation modelling. Two safety performance indicators directly related to collision risks, violation and time-to-collision, were adopted. Results indicated the active systems were more effective at reducing likely collisions compared to passive devices. With the combined application of driving simulation and traffic microsimulation modelling, traffic safety performance indicators for a level crossing can be estimated. From these, relative safety comparisons for the different traffic devices are derived, or even for absolute safety evaluation with proper calibration from field investigations.     

Identification of vehicle suspension parameters by design optimization

The design of a vehicle suspension system through simulation requires accurate representation of the design parameters. These parameters are usually difficult to measure or sometimes unavailable. This article proposes an efficient approach to identify the unknown parameters through optimization based on experimental results, where the covariance matrix adaptation–evolutionary strategy (CMA-es) is utilized to improve the simulation and experimental results against the kinematic and compliance tests. This speeds up the design and development cycle by recovering all the unknown data with respect to a set of kinematic measurements through a single optimization process. A case study employing a McPherson strut suspension system is modelled in a multi-body dynamic system. Three kinematic and compliance tests are examined, namely, vertical parallel wheel travel, opposite wheel travel and single wheel travel. The problem is formulated as a multi-objective optimization problem with 40 objectives and 49 design parameters. A hierarchical clustering method based on global sensitivity analysis is used to reduce the number of objectives to 30 by grouping correlated objectives together. Then, a dynamic summation of rank value is used as pseudo-objective functions to reformulate the multi-objective optimization to a single-objective optimization problem. The optimized results show a significant improvement in the correlation between the simulated model and the experimental model. Once accurate representation of the vehicle suspension model is achieved, further analysis, such as ride and handling performances, can be implemented for further optimization.     

Demand patterns of rice imports in Malaysia: Implications for food security

Malaysia is a net importer of rice. More than a quarter of its rice requirement is met by import. Rice imports play a crucial role in determining the country’s food security. Import strategy of the company, which owns the exclusive import right, has a profound impact on an array of economic, political, and societal stabilities. However, domestic agricultural policies and relevant past studies have not addressed the strategic concern in the current food security framework. Therefore, this study analyzes demand patterns of rice imports in Malaysia with an ultimate intention to provide policy implications for its food security. From the Error Correction Model of Almost Ideal Demand System (ECM-AIDS), estimates of demand elasticity suggest that rice imports will be narrowly sourced, largely from Viet Nam with Thailand second in importance. Such an import strategy is similar to the pre-crisis model, which was weak in mitigating negative effects of supply disruption during the Food Price Crisis 2007/08. Instead, the exclusive importer could (1) multi-source rice imports, (2) import paddy (for longer storage life and supporting downstream activities), and/or (3) balance its business orientation with the national food security. In sum, this study provides evidences for the need to consider rice imports in the country’s future food security framework.     

Characteristics of Manchester-Coded FSK

In this paper, the Manchester-coded frequency-shift-keyed (MCFSK) signal is shown to be representable in terms of an in-phase(I)and a quadrature(Q)carrier term. TheI-term carries the bit timing and theQ-term carries the message information. Based on this representation, a simple derivation of the power spectral density for MCFSK is presented. The effect of premodulation pulse shaping on the spectral occupancy of MCFSK is then investigated using trapezoidal, triangular and cosine-squared pulses. Formulas for the power spectral density are derived and curves of fractional in-band power are obtained which will be useful for band occupancy determination. Finally, the bit error rate (BER) performance for MCFSK in an ideal channel is derived and shown to be the same as that for coherent FSK.     

Isolation and Identification of Lactic Acid Bacteria from Fermented Red Dragon Fruit Juices

Abstract: Red dragon fruit or red pitaya is rich in potassium, fiber, and antioxidants. Its nutritional properties and unique flesh color have made it an attractive raw material of various types of food products and beverages including fermented beverages or enzyme drinks. In this study, phenotypic and genotypic methods were used to confirm the identity of lactic acid bacteria (LAB) appeared in fermented red dragon fruit (Hylocereus polyrhizus) beverages. A total of 21 isolates of LAB were isolated and characterized. They belonged to the genus of Enterococcus based on their biochemical characteristics. The isolates can be clustered into two groups by using the randomly amplified polymorphic DNA method. Nucleotide sequencing and restriction fragment length polymorphism of the 16S rRNA region suggested that they were either Enterococcus faecalis or Enterococcus durans. Practical Application: Current research revealed the use of biochemical analyses and molecular approaches to identify the microbial population particularly lactic acid bacteria from fermented red dragon fruit juices.     

A Programmable Impedance Matching Circuit for Voiceband Modems

A line impedance-matching circuit for a voiceband modem is described. The circuit can be programmed to realize four different impedances. A switched-capacitor filter is used to generate the required transfer functions. The impedance-matching concept and circuits are described. Measured results are presented that show that the four impedances are realized with sufficient accuracy for voiceband modems. The circuit was fabricated in a standard 0.35-mum mixed-signal CMOS process.     

Clustering-Based Adaptive Crossover and Mutation Probabilities for Genetic Algorithms

Research into adjusting the probabilities of crossover and mutation p_m in genetic algorithms (GAs) is one of the most significant and promising areas in evolutionary computation. p_x and p_m greatly determine whether the algorithm will find a near-optimum solution or whether it will find a solution efficiently. Instead of using fixed values of p_x and p_m , this paper presents the use of fuzzy logic to adaptively adjust the values of p_x and p_m in GA. By applying the K-means algorithm, distribution of the population in the search space is clustered in each generation. A fuzzy system is used to adjust the values of p_x and p_m. It is based on considering the relative size of the cluster containing the best chromosome and the one containing the worst chromosome. The proposed method has been applied to optimize a buck regulator that requires satisfying several static and dynamic operational requirements. The optimized circuit component values, the regulator's performance, and the convergence rate in the training are favorably compared with the GA using fixed values of p_x and p_m. The effectiveness of the fuzzy-controlled crossover and mutation probabilities is also demonstrated by optimizing eight multidimensional mathematical functions     

Effect of Bcl-2 overexpression on cell cycle and antibody productivity in chemostat cultures of myeloma NS0 cells

Chemostat cultures of NS0 cell lines were carried out at dilution rates ranging from 0.8 d(-1) to 0.2 d(-1). Compared with the control, the viable cell density of the Bcl-2 cell line was approximately 10% higher at 0.8 d(-1) and increased to 55% when the dilution rate was reduced to 0.2 d(-1). As the dilution rate was reduced, the viability of the two cultures diverged reaching a difference of 43% at 0.2 d(-1). The specific growth rate of the control cells was the same as the dilution rate down to a value of 0.6 d(-1). By contrast, the specific growth rate of Bcl-2 cells was parallel to the dilution rate down to a value as low as 0.3 d(-1). For both NS0 cell lines, the G1 cell population decreased, while the S and G2/M cell populations increased as the dilution rate was reduced. The antibody titer of the control cells increased from 7 to 21 microg.ml(-1) as the dilution rate was reduced from 0.8 to 0.2 d(-1). With an initial increase from 2 to 15 microg.ml(-1) as the dilution rate was reduced from 0.8 to 0.4 d(-1), the antibody titer of the Bcl-2 cells remained constant as the dilution rate was further reduced to 0.2 d(-1). A good correlation between specific antibody production rate and the percentage of G2/M cells was observed.     

Unraveling the droplet drying characteristics of crystallization‐prone mannitol – experiments and modeling

Spray‐dried mannitol is a potential lactose replacement in pharmaceutical formulations, yet the drying behavior of individual mannitol droplets within the spray chamber has not been fully understood. This work explored the drying characteristics of mannitol by employing the reaction engineering approach (REA) in data analysis. A glass filament single droplet drying technique was used to monitor the changes in droplet temperature, mass, and diameter. The drying kinetics data obtained clearly demonstrated the droplet “wet‐bulb” period, the crust formation, and the crystallization phenomena. The master activation‐energy curves developed from REA modeling responded sensitively to varying drying temperatures, which could have led to different crystallization events. The deviation of these plots from the expected norms that do not encounter a phase change was used effectively to discern the physics involved. A REA kinetic model was proposed to assist in process optimization of large‐scale spray‐drying operations. © 2017 American Institute of Chemical Engineers AIChE J, 63: 1839–1852, 2017