Application of fuzzy control algorithms for electric vehicle antilock braking/traction control systems

The application of fuzzy-based control strategies has gained enormous recognition as an approach for the rapid development of effective controllers for nonlinear time-variant systems. This paper describes the preliminary research and implementation of a fuzzy logic based controller to control the wheel slip for electric vehicle antilock braking systems (ABSs). As the dynamics of the braking systems are highly nonlinear and time variant, fuzzy control offers potential as an important tool for development of robust traction control. Simulation studies are employed to derive an initial rule base that is then tested on an experimental test facility representing the dynamics of a braking system. The test facility is composed of an induction machine load operating in the generating region. It is shown that the torque-slip characteristics of an induction motor provides a convenient platform for simulating a variety of tire/road /spl mu/-/spl sigma/ driving conditions, negating the initial requirement for skid-pan trials when developing algorithms. The fuzzy membership functions were subsequently refined by analysis of the data acquired from the test facility while simulating operation at a high coefficient of friction. The robustness of the fuzzy-logic slip regulator is further tested by applying the resulting controller over a wide range of operating conditions. The results indicate that ABS/traction control may substantially improve longitudinal performance and offer significant potential for optimal control of driven wheels, especially under icy conditions where classical ABS/traction control schemes are constrained to operate very conservatively.     

Thermal-hydraulic behavior of the NUR nuclear research reactor during a fast loss of flow transient

Nuclear safety analysis remains of crucial importance for both the design and the operation of nuclear reactors. Safety analysis usually entails the simulation of several selected postulated accidents, which can be divided into two main categories, namely reactivity insertion accident (RIA) and loss of flow accident (LOFA). In this paper, thermal-hydraulic simulations of fast LOFA accident were carried out on the new core configuration of the material test research reactor NUR. For this purpose, the nuclear reactor analysis PARET code was used to determine the reactor performance by calculating the reactor power, the reactivity and the temperatures of different components (fuel, clad and coolant) as a function of time. It was observed that during the transient the maximum clad temperature remained well below the critical temperature limit of 110 °C, and the maximum coolant temperature did not exceed the onset of nucleate boiling point of 120 °C. It is concluded that the reactor can be operated at full power level with sufficient safety margins with regard to such kind of transients.     

Static and dynamic light scattering from polystyrene/cyclohexane/toluene solutions

Summary Static and dynamic light scattering data from polystyrene in cyclohexane and toluene mixed solvent are reported. It is found from the Zimm plot analysis of the static data that if the subtraction of solvent signal is made properly then, the results are consistent with those in toluene indicating a preferential adsorption of the good solvent. Contin analysis of the dynamic data yields two modes unlike the dynamics of polystyrene in single solvent solutions which exhibit a single mode at all polymer concentrations covered here. A possible interpretation of the fast and slow modes is given. Keywords: Mixed Solvent; Dilute Polymer Solution; Preferential Adsorption; Static and Dynamic Light Scattering; Relaxation Modes. Received: 28 May 1999/Accepted: 8 September 1999     

Prospects and Challenges of Developing Plant-Derived Snake Antivenin Natural Products: A Focus on West Africa

Snakebite envenomation (SBE) is an important public health issue that is now receiving renewed attention following its reclassification as a Neglected Tropical Disease (NTD). Most incidences occur in rural areas of resource-limited countries, as such, timely and appropriate medical care for SBE is often inaccessible. The administration of anti-snake venom serum (ASV) is the only effective definitive treatment of SBE, but treatment failure to available ASVs is not uncommon. Emerging evidence highlights the potential of small-molecule compounds as inhibitors against toxins of snake venom. This presents an encouraging prospect to develop an alternative therapeutic option for the treatment SBE, that may be amenable for use at the point of care in resource-constraint settings. In view of the pivotal role of natural products in modern drug discovery programmes, there is considerable interest in ethno-pharmacological mining of medicinal plants and plant-derived medicinal compounds toward developing novel snake venom-neutralising therapeutics. In this review, we compile a collection of medicinal plants used in the treatment of SBE in West Africa and highlight their promise as potential botanical drugs or as sources of novel small-molecule compounds for the treatment of SBE. The challenges that must be surmounted to bring this to fruition including the need for (sub) regional collaboration have been discussed.     

Catalytic Asymmetric Allylation of 3‐Aryloxindoles by Merging Palladium Catalysis and Asymmetric H‐Bonding Catalysis

A catalytic asymmetric allylic alkylation reaction of 3‐aryloxindoles was accomplished via a dual catalysis merging palladium catalysis and asymmetric H‐bonding catalysis for the first time. Using this approach, allylated oxindoles bearing chiral all‐carbon quaternary centers were produced in high yields with good enantioselectivities (up to 92 % yield and 96:4 er).

     

Signal strength based link sensing for mobile ad-hoc networks

Mobility causes frequent link failures in ad-hoc networks. This results in a severe degradation of performance specially in case of high mobility of nodes. This is because the routing protocols for ad-hoc networks are not equipped to handle high mobility. In this paper, we have presented a new link management algorithm to locally manage links. This new mechanism is based on signal strength measurements. Researchers over the years have presented approaches which use signal strength measurements but their focus has been on re-active protocols while our algorithm is aimed at pro-active protocols. Pro-active protocols are used since they provide greater flexibility to take advantage of the mesh configuration. We develop the hysteresis mechanism provided by OLSR, based on hello packets, to include signal strength measurements. The mechanism in OLSR uses Hello packets received/lost to decide to establish link or not. The problem with this approach arises when there is high mobility in which case the time to break the link and use a new path becomes significant. To overcome this, we propose to use signal strength to determine if the link-quality is improving or deteriorating. This combination of the two mechanisms, makes the link management more robust and also helps in anticipating link breakages thereby greatly improving performance.     

Synthesis and Physico-Chemical Studies of Ester-Quat Surfactants in the Series of (Dodecanoyloxy)propyl n-Alkyl Dimethyl Ammonium Bromide

Ester-quat surfactants in the series of (dodecanoyl oxy) propyl n-alkyl dimethyl ammonium bromide referred to here as LC₃Cm (where m is the hydrocarbon chain lengths 8, 12 and 14) were synthesized and characterized by the usual spectroscopic methods (NMR, IR, MS…). Their physico-chemical properties were investigated by surface tension and conductimetric measurements. From surface tension measurements, isotherms and thermodynamic adsorption parameters were determined. The critical micelle concentration (CMC), the degree of counter ion dissociation (α) of micelles in the water and the standard Gibbs free energy $( \Updelta G_{\text{m}}^{0}) $ , of micellization were also determined by conductimetric measurements. The results obtained from both methods were compared to the similar surfactants in the series of quaternary ammonium surfactants. Optical microscopy was also used to study the behavior of anhydrous surfactants and the binary water/surfactant system as a function of temperature.     

Reliable Key Management and Data Delivery Method in Multicast Over Wireless IPv6 Networks

Multicast is an efficient way to reduce the required bandwidth of transmitting data simultaneously to a group of users in wireless IPv6 networks. Nevertheless, multicast suffers from two main drawbacks which can be looked from two perspectives, namely security and QoS. With regard to security, the main challenge is to provide security protection to multicast data, which can be achieved by using a secure key management process. Considering a highly dense environment where connection of users to the network is changing frequently due to join or leave operations, key updating approach may burden a network devices with a huge amount of complex encryption/decryption processes. From the QoS perspective, multicast transmission over WLAN offers a tradeoff between the transmission rate and the coverage. The transmission rate of multicast is confined by the user with the lowest data rate in the group which is called fixed base rate problem. To address the above mentioned problems, we propose and implement a lightweight key management and data delivery scheme for multicast over wireless IPv6 networks. The proposed solution is envisaged to reduce the complexity of key updating, while at the same time is able to address the fixed base rate problem. The performance evaluation (by means of analytical and test-bed implementation) of the proposed key management method indicates its efficiency in reducing communication, computation, and storage costs, while maintaining both forward and backward securities. Moreover, the proposed data delivery method is able to improve the throughput and QoS, with low packet loss and transmission delay.     

Combining mass spectrometry and pull-down techniques for the study of receptor heteromerization. Direct epitope-epitope electrostatic interactions between adenosine A2A and dopamine D2 receptors

Previous results from FRET and BRET experiments and computational analysis (docking simulations) have suggested that a portion of the third intracellular loop (I3) of the human dopamine D2 receptor (D2R) and the C-tail from the human adenosine A2A receptor (A2AR) are involved in A2AR-D2R heteromerization. The results of the present studies, using pull-down and mass spectrometry experiments, suggest that A2AR-D2R heteromerization depends on an electrostatic interaction between an Arg-rich epitope from the I3 of the D2R (217RRRRKR222) and two adjacent Asp residues (DD401-402) or a phosphorylated Ser (S374) residue in the C-tail of the A2AR. A GST-fusion protein containing the C-terminal domain of the A2AR (GST-A2ACT) was able to pull down the whole D2R solubilized from D2R-tranfected HEK-293 cells. Second, a peptide corresponding to the Arg-rich I3 region of the D2R (215VLRRRRKRVN224) and bound to Sepharose was able to pull down both GST-A2ACT and the whole A2AR solubilized from A2AR-tranfected HEK-293 cells. Finally, mass spectometry and pull-down data showed that the Arg-rich D2R epitope binds to two different epitopes from the C-terminal part of the A2AR, containing the two adjacent Asp residues or the phosphorylated Ser residue (388HELKGVCPEPPGLDDPLAQDGAVGS412 and 370SAQEpSQGNT378). The present results are the first example of epitope-epitope electrostatic interaction underlying receptor heteromerization, a new, expanding area of protein-protein interactions.     

SiC/MoSi_2复合材料的原位反应热压烧结工艺

从热力学角度研究了Mo-Si-C三元系中所有二元化合物化合反应的吉布斯自由能随温度变化的规律,探索了SiC/MoSi_2复合材料原位反应热压烧结的最佳工艺参数.结果表明,利用Mo、Si、C混合粉末原位反应合成SiC/MoSi_2复合材料在热力学上是完全可行的,反应烧结温度低于1728 K(1455 ℃)是为抑制Mo_2C形成,保证SiC生成的热力学条件.采用原位反应热压烧结工艺能够制备具有优异显微组织的SiC/MoSi_2复合材料.