An electrochemical impedance spectroscopy and scanning electron microscopy study of the influence of positive plate compression on the electrochemical behaviour of lead-acid batteries

This study has developed an electrochemical impedance spectroscopy (EIS) method for the in situ investigation of the influence of positive plate compression on the electrochemical behaviour of lead-acid batteries during charge/discharge cycling. The EIS data for a fully charged and fully discharged battery are internally consistent with the expected kinetics of a battery in the opposite states of charge, and demonstrate that EIS measurements may be recorded with a high level of reproducibility. Furthermore, this study has necessitated the development of a special cell incorporating horizontally orientated battery plates that can be subjected to elevated pressure through the stacking of lead bricks on top of the cell, as well as a physically robust reference electrode system that can withstand the application of pressure. For this purpose, a platinum-wire pseudo-reference electrode has been developed, and has been shown to exhibit sufficient electrode stability over the period of an EIS recording, enabling the measurement of reproducible and meaningful EIS data. Additionally, the influence of positive plate compression on the behaviour of the lead-acid battery has been investigated by using scanning electron microscopy (SEM). Clearly, the experimental data show that plate compression enhances significantly the kinetics and concomitant performance of the lead-acid battery, and this is related to the enhanced reactivity of the active material, as rationalized by using the agglomeration-of-spheres (AOS) model.     

Efficient Host-Guest Complexation of a Bisporphyrin Host with Electron Deficient Guests: Synthesis,Structure, and Photoinduced Electron Transfer

The encapsulation of 1,8-naphthalic anhydride (NAN), 9-dicyanomethylenefluorene (9-DCF), acenaphthenequinone (ANQ), and 4-chloro-7-nitrobenzofurazan (NBD-Cl) by diethylpyrrole-bridged bisporphyrin (H₄DEP) and its dizinc(II) analogue (Zn₂DEP) are employed to investigate the structural and spectroscopic changes within the bisporphyrin cavity upon substrate binding. Synthesis and X-ray structures of all four encapsulated host-guest complexes (H₄DEP⋅NAN, H₄DEP⋅9-DCF, Zn₂DEP⋅ANQ, and Zn₂DEP⋅NBD-Cl) are reported here. The binding constant calculations show strong 1 : 1 binding between the hosts (H₄DEP and Zn₂DEP) and the guests (NAN/9-DCF/ANQ/NBD-Cl). ¹H-NMR spectra also support the retention of the host-guest assemblies in solution. Negative and positive shifts of the reduction and oxidation potentials, respectively, indicate that it is difficult to reduce/oxidize the encapsulated complexes. The emission intensities of the bisporphyrins (H₄DEP and Zn₂DEP) are substantially quenched in all the complexes, owing to photoinduced electron transfer from the excited state of the bisporphyrins to guest molecules. All the experimental evidence is further substantiated by DFT calculations. Such an efficient electron transfer is only possible when the donor and the acceptor moieties are in close propinquity to each other, which eventually lowers the reorganization energy.     

Investigation of Nd3+ incorporation in Ce-rhabdophane: Insight from structural flexibility and occupation mechanism

LnPO₄ · 0.667H₂O rhabdophane has been considered as a potential material for the precipitation of actinides from radioactive waste liquid, owing to its outstanding characteristics of high actinide bearing and easy synthesis in acid solutions. However, a comprehensive understanding of the actinide occupation and the precipitation response of rhabdophane to remove actinides has yet to be established. In this study, the effect of ions concentration and pH values on the detailed precipitation reaction of Ce_xNd_1-xPO₄ · 0.667H₂O rhabdophane in acid solutions are systematically investigated. Some specific issues such as structural distortion and flexibility, and occupation mechanism are discussed by combining with experiments and density functional theory (DFT) calculation. The results reveal that ions concentration and pH values have a significant impact on the crystallization nucleation step before 12 h. The obtained removal rate of Nd³⁺ is more than 99% in pH 1–5 solutions with the ions concentration of 0.05–0.1 mol/L. Moreover, incorporating Nd in CePO₄ · 0.667H₂O rhabdophane will easily result in the lattice distortion in b-axis. DFT calculation and X-ray photoelectron spectroscopy (XPS) results reveal that Nd is preferentially incorporated in nonhydrated site to form a weaker binding energy of NdO₈ polyhedron.     

Automatic determination of parting directions,parting lines and surfaces for two-piece permanent molds

Minimization of surface area/volume of undercuts, flatness of parting surface and minimization of draw depth play a major role to determine the best pair of parting directions for two-piece permanent molds. In most of the earlier attempts a combined effect of the three factors was not considered. Moreover with the increasing complexity of molded product geometry, heuristic and feature-based approaches may prove inefficient. In this paper the combined affect of minimized surface area of undercut, flatness of parting surface and minimized draw depth is considered for the determination of best parting direction, parting line and surface for a two-piece permanent molded component. Tessellated geometry of the component is used as input.     

Synthesis and characterization of olivine LiNiPO4 for aqueous rechargeable battery

LiNiPO₄ belongs to a family of olivine type compounds, with members LiMPO₄ where M = Fe, Mn, Co or Ni are transition metals. The lithium nickel phosphate was prepared and characterized in order to evaluate a new potential cathode material for our ongoing research in aqueous rechargeable batteries. Annealing the final product is critical in obtaining the stoichiometric LiNiPO₄ pure phase; conventional cooling to a room temperature leads to an indication of Li₃PO₄ and NiO secondary phases as impurities. The synchrotron infrared radiation (SR-IR) as a source for IR spectroscopy pins down the differences in the chemical bonding for annealed and conventional cooled LiNiPO₄ samples. The cyclic voltammetric and galvanostatic studies showed annealed LiNiPO₄ is electrochemically active from which lithium ions can be de-intercalated during oxidation process leading to an amorphous NiPO₄ and a minor product of nickel(II) hydroxide (β-NiOOH). During subsequent reduction, lithium ions are not fully intercalated, however, the structure is reversible and adequate for multiple cycles. The high potential in LiNiPO₄ looks to be very attractive in terms of high energy density, given the efficiency is improved.     

Comparison of lantadenes content and toxicity of different taxa of the lantana plant

Three taxa of the lantana plant (Lantana camara var.Aculeata) I (white-pink), II (yellow-pink), and III (yellow-red)-differed in the content of lantadenes and compounds X, Y, and Z. Lantadene A, lantadene B, and lantadene C were the major lantadenes of taxon III. It contained small amounts of lantadene D. Taxa I and II contained very small amounts of lantadene A and lantadene B. Compounds X, Y, and Z were the major constituents of taxa I and II, and they constituted 59% and 92% of the total constituents in these taxa, respectively. Ingestion of lantana leaf powder of taxon III by male guinea pigs caused severe hepatotoxicity. Taxon I elicited mild hepatotoxicity in one out of six animals while taxon II was nontoxic. The biological and ecological significance of the presence of high amounts of compounds X, Y, and Z in taxa I and n is not known.     

Compositional changes and biosynthesis of lipids in the developing kernels of almond (Prunus amygdalus batsch)

Fruit and kernel weights of developing almond kernels increased with age. The kernel contents had a translucent and jelly-like appearance in the initial developmental stages, but solidified prior to the accumulation of dry matter, mainly oil, from 50 days after fertilisation (DAF). During kernel development the oil content displayed a double sigmoid pattern. Oleic and linoleic acids accumulated to similar levels, but the linolenic acid content decreased during development. Oil-filling ([1-¹⁴C]acetate incorporation) commenced at 50 DAF, and reached a maximum level at 70 DAF. The total polar lipid content was highest at 10 DAF, as determined by radioactive labelling, but from 30 DAF onwards a de-novo synthesis was noted. Diphosphatidyl glycerol (Cardiolipin) acted as a temporary reservoir for the synthesis of phospholipids from 70 DAF, and thereafter the synthesis of phosphatidyl choline was enhanced. In the initial stages, the rate of synthesis of monogalactosyl diglycerides was greater than that of digalactosyl diglycerides, and a de-novo synthesis of both was observed from 30 DAF. The synthesis of triacylglycerols corresponded well with the pattern of oil-filling. The level of ¹⁴C radioactivity recorded in sterol esters was greater at the initial stages, but declined from 50 DAF, possibly because of the effect of dilution, as envisaged in the case of the triacylglycerols.     

Channel allocation and medium access control for wireless sensor networks

Recent developments in sensor technology, as seen in Berkeley’s Mica2 Mote, Rockwell’s WINS nodes and the IEEE 802.15.4 Zigbee, have enabled support for single-transceiver, multi-channel communication. The task of channel assignment with minimum interference, also named as the 2-hop coloring problem, allows repetition of colors occurs only if the nodes are separated by more than 2 hops. Being NP complete, development of efficient heuristics for this coloring problem is an open research area and this paper proposes the Dynamic Channel Allocation (DCA) algorithm as a novel solution. Once channels are assigned, a Medium Access Control protocol must be devised so that channel selection, arbitration and scheduling occur with maximum energy savings and reduced message overhead, both critical considerations for sensor networks. The contribution of this paper is twofold: (1) development and analysis of the DCA algorithm that assigns optimally minimum channels in a distributed manner in order to make subsequent communication free from both primary and secondary interference and (2) proposing CMAC, a fully desynchronized multi-channel MAC protocol with minimum hardware requirements. CMAC takes into account the fundamental energy constraint in sensor nodes by placing them in a default sleep mode as far as possible, enables spatial channel re-use and ensures nearly collision free communication. Simulation results reveal that the DCA consumes significantly less energy while giving a legal distributed coloring. CMAC, our MAC protocol that leverages this coloring, has been thoroughly evaluated with various modes in SMAC, a recent protocol that achieves energy savings through coordinated sleeping. Results show that CMAC obtains nearly 200% reduction in energy consumption, significantly improved throughput, and end-to-end delay values that are 50–150% better than SMAC for our simulated topologies.     

Assessment of relative impacts of various geo-mining factors on methane dispersion for safety in gassy underground coal mines: an artificial neural networks approach

Neural Computing and Applications - Dispersing methane to a safer level is crucial for mines safety as methane has been the greatest contributor of explosion hazard in underground coal mines...