重力作用下尘粒运动的数值解法

提出了重力作用下尘粒运动的数值解法。依据尘粒的重力、浮力及所受到的阻力推出了尘粒自然沉降时的运动方程。当尘粒的运动在斯托克斯领域内时采用理论公式求解其运动轨迹,当尘粒的运动进入非斯托克斯领域内时,提出了修正斯托克斯公式的方法以达到用理论公式来近似模拟该领域内的尘粒自然沉降运动     

Potential of Hemidesmus indicus for phytoextraction of lead from industrially contaminated soils

Many sites in the industrial region of Kattedan near Hyderabad, Andhra Pradesh (AP), India are contaminated with high concentrations of lead. The use of plants to remove toxic metals from soils (phytoremediation) is emerging as a potential strategy for cost-effective and environmentally sound remediation of contaminated soils. We studied remediation of soils contaminated with lead using a lead hyperaccumulating plant, Hemidesmus indicus. The ability of this plant to accumulate lead in shoots and roots was studied with pot experiments. The results showed that accumulation was maximum in roots for the first 1-3 weeks and later for a contact period of three months, the accumulation rate was maximum in shoots. In addition we used various chelating agents such as EDTA, HEDTA, DTPA and CDTA to determine the best chemical modifier for efficient lead removal from contaminated soils. The effect on lead accumulation of plant in the presence of various metal co-ions was also studied. An attempt was made for the decontamination of lead from five different "Real-life" soils of Kattedan using H. indicus.     

Role of climate risks and socio-economic factors in influencing the impact of climatic extremes: a normalisation study in the context of Odisha,India

Economic costs imposed by climatic extremes have been increasing over the years and are expected to follow a similar trend in the coming years as well. Such costs are incurred due to two factors: (1) natural climate variability and anthropogenic climate change and (2) exposure and vulnerability of socio-economic factors. The impact of these factors as identified separately through a ‘normalisation technique’ is analysed in the existing normalisation studies conducted mostly in developed country contexts; these have produced mixed results. However, one needs to enquire about the influence of the above two factors in a developing country context where the anticipated impacts of climate extremes are significant. This study, therefore, makes an attempt to adjust impact data, in terms of the reported population affected and economic damages of three extreme events, namely cyclones, floods and droughts, together for societal changes between 1972 and 2009 in Odisha in eastern India. Further, the second component is analysed in two ways: (1) assuming that exposed socio-economic factors are equally vulnerable similar to the other normalisation studies, i.e. no adaptation and (2) incorporating adaptation in the existing normalisation methods—which has attracted less attention so far in the literature. The results suggest that: (a) both the natural climate variability and the socio-economic factors influence the increasing damages in the recent decades, and (b) when adaptation is introduced in the normalisation model, economic losses have reduced significantly compared to the estimates using the existing normalisation models.     

Performance investigation of a single-stage metal hydride heat transformer

This article presents the performance analysis of a single-stage metal hydride-based heat transformer (SS-MHHT) working with three different alloy pairs, namely LaNi_4.6Al_0.4/MmNi_4.15Fe_0.85, LaNi_4.61Mn_0.26Al_0.13/La_0.6Y_0.4Ni_4.8-Mn_0.2, and Zr_0.9Ti_0.1Cr_0.9Fe_1.1/Zr_0.9Ti_0.1Cr_0.6-Fe_1.4. The performances of the SS-MHHT are predicted by solving the conjugate heat and mass (hydrogen) transfer equations in cylindrical coordinates. The effects of various parameters such as heat output (T_H), heat input (T_M), and heat sink (T_L) temperatures on the coefficient of performance (COP_HT), specific heating power (SHP) and second law efficiency (η_E) are presented. The effects of overall heat transfer coefficient and mass ratio on the coefficient of performance (COP_HT) and specific heating power (SHP) are also presented. Numerical results are compared with the experimental data reported in the literature, and a good agreement is found between them. The maximum COP_HT of 0.436 and SHP of 54 W/kg are obtained for LaNi_4.61Mn_0.26Al_0.13/La_0.6Y_0.4Ni_4.8-Mn_0.2 pair. For a given operating temperatures of T_M = 358 K and T_L = 298 K, the maximum temperature lift of about 50 K is predicted for Zr_0.9Ti_0.1Cr_0.9Fe_1.1 /Zr_0.9Ti_0.1Cr_0.6Fe_1.4 pair.     

Nanofluid heat transfer under mixed convection flow in a tube for solar thermal energy applications

The solar flat plate collector operating under different convective modes has low efficiency for energy conversion. The energy absorbed by the working fluid in the collector system and its heat transfer characteristics vary with solar insolation and mass flow rate. The performance of the system is improved by reducing the losses from the collector. Various passive methods have been devised to aid energy absorption by the working fluid. Also, working fluids are modified using nanoparticles to improve the thermal properties of the fluid. In the present work, simulation and experimental studies are undertaken for pipe flow at constant heat flux boundary condition in the mixed convection mode. The working fluid at low Reynolds number in the mixed laminar flow range is undertaken with water in thermosyphon mode for different inclination angles of the tube. Local and average coefficients are determined experimentally and compared with theoretical values for water-based Al₂O₃ nanofluids. The results show an enhancement in heat transfer in the experimental range with Rayleigh number at higher inclinations of the collector tube for water and nanofluids.     

Ciprofloxacin degradation in photo-Fenton and photo-catalytic processes: Degradation mechanisms and iron chelation

Ciprofloxacin(CIP)is a broad spectrum synthetic antibiotic drug of fluoroquinolones class.CIP can act as a bidentate ligand forming iron complexes during its degradation in the photoFenton process(PFP).This work investigates on PFP for the degradation of CIP to understand the formation mechanism and stability of iron complexes under ultraviolet(UV)-light illumination.A comparison was made with the UV-photocatalysis(UV/TiO_2)process where CIP doesn't form a complex.In PFP,the optimal dose of Fe~(2+)and H_2O_2were found to be 1.25 and10 mmol/L with pH of 3.5.An optimal TiO_2dose of 1.25 g/L was determined in the UV/TiO_2process.Maximum CIP removal and mineralization efficiency of 93.1%and 47.3%were obtained in PFP against 69.7%and 27.6%in the UV/TiO_2process.The mass spectra could identify seventeen intermediate products including iron-CIP complexes in PFP,and only seven intermediate products were found in the UV/TiO_2process with a majority of common products in both the processes.The proposed mechanism supported by the mass spectra bridged the routes of CIP cleavage in the PFP and UV/TiO_2process,and the decomposition pathway of Fe~(3+)-CIP chelate complexes in PFP was also elucidated.Both in PFP and UV/TiO_2processes,the target site of HO~·radical attack was the secondary-N atom present in the piperazine ring of the CIP molecule.The death of Escherichia coli bacteria was 55.7%and 66.8%in comparison to the control media after 45 min of treatment in PFP and UV/TiO_2process,respectively.     

A coordinated control strategy using supercapacitor energy storage and series dynamic resistor for enhancement of fault ride-through of doubly fed induction generator

Power fluctuation and fault-related complication are the two major issues for doubly fed induction generator (DFIG)-based wind energy conversion system (WECS). The occurrence of fault leads to the rotor over current, stator over current, and DC-link overvoltage as well. These uncertainties may damage the rotor circuit, converter circuit and force the disconnection of wind system from the grid. To get rid of these issues, a supercapacitor energy storage element along with a passive series dynamic resistor (SDR) is suggested in this paper. Supercapacitor energy storage system (SCESS) is located across the DC-link, which able to handle the power fluctuation and the SDR is placed in rotor circuit, which will reduce the overcurrent possibility. Simulation is carried for a DFIG-based WECS for three phase to ground fault and two phase to ground fault. During symmetrical fault as well as asymmetrical fault, various operational disorders appeared such as rotor overcurrent, stator overcurrent and DC-Link overvoltage are found to be within their permissible limits. The results reveal the effectiveness of the proposed strategy over the conventional vector control scheme and SCESS as well.     

Primary vegetative growth on an old tailings dam,Zawar mines

Tailings containing toxic qualities of heavy metals are a potential source of pollution. Stabilisation by vegetative methods have been found the most effective. In an attempt to vegetate tailings dams it has been noted that while certain milky latex containing plants can be grown without any preconditioning of the soil, almost any plant can be grown after proper conditioning. However, the plants grown there cannot be consumed by humans or cattle due to their high metal content.     

Toxicological effects on some biochemical parameters of fresh water fish Channa punctatus (Bloch.) under the stress of nickel

Toxicological effects of some biochemical parameters of freshwater fish Channa punctatus (Bloch), under the stress of Nickel (NiSO4. 6H2O), at various concentrations of 10, 20, 30 and 40 ppm for 30 days were observed. Gradual decrease in the levels of liver protein and liver ascorbic acid due to proteolysis and liver glucose breakdown respectively was observed. Contradictorily, high liver cholesterol level, may be due to hepatic disfunctioning and accumulation in brain. There was also gradual decrease in the brain protein level showing significant alterations but the brain ascorbic acid level showed no significant alterations. Decrease in the protein and ascorbic acid level and increase of cholesterol level thus indicates stressful condition of the fish.     

Silver nanoparticles from Tabernaemontana divaricate leaf extract: mechanism of action and bio-application for photo degradation of 4-aminopyridine

Silver nanoparticles (Ag NPs) were synthesised by the reduction of Ag⁺ to Ag⁰ in the presence of enol form of flavonoids present in plant extract of Tabernaemontana divaricate (T. divaricate). Prepared Ag NPs were characterised using UV–Vis, XRD, HR-TEM with EDX and XPS techniques. XPS spectra exhibited peaks at 366 eV and 373 eV, which specified spin orbits for Ag 3d_3/2, and Ag 3d_5/2 that confirmed the formation of Ag NPs. Ag NPs were spherical in shape with an average size of 30 nm as revealed by HR-TEM and FE-SEM techniques. EDX studies verified the high purity of Ag NPs with silver 46.96%, carbon 16.35%, oxygen 16.22%, nitrogen 20.25% and sulphur 0.21%. LC–MS analysis of plant extract confirmed the qualitative presence of alkaloids, tannins, flavonoids, phenols, and carbohydrates. Prepared Ag NPs showed good photocatalytic activity towards degradation of 4-Amniopyridine with 61% degradation efficiency at optimum conditions in 2 h of reaction time under visible light. The ten intermediates were found within the mass number of 0–450. Ag NPs synthesised using bio-extract have also shown good inactivation against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) bacteria due to the availability of free radicals.

Graphical abstract