不同成因磷灰石可浮性的研究

对五种不同成因磷灰石的浮选行为与表面,溶解速度,油酸钙沉淀和油酸盐吸附量等之间的关系作了系统研究。实验表明,磷灰石的溶解速度,油酸钙沉淀量及充分浮选所需油酸钾浓度都与磷灰石的比表面积有关。 沉积型磷灰石有较大比表面积,在水溶液中溶下较多量ca~(2+)离子,生成较多油酸钙沉淀,充分浮选时需较高油酸钾浓度。 充分浮选时,捕收剂在五种不同磷灰石表面的复盖率看来是相近的,都有油酸钙沉淀生成,这与ca~(2+)离子从磷灰石表面溶下速度及达到一定复盖率时所需的捕收剂浓度有关。     

An efficient intrusion detection system for MQTT-IoT using enhanced chaotic salp swarm algorithm and LightGBM

International Journal of Information Security - Internet of Things (IoT) networks are becoming increasingly popular for monitoring critical environments of various types. For the communication of...     

Design and implementation of an industrial vector-controlled induction motor drive

Vector-controlled induction motor drives are quite popular in the industry in applications that demand high dynamic performance. This paper describes the implementation of a complete industrial vector-controlled drive for a 30 kW induction motor. The control algorithms for the drive are implemented using a TMS320F28335 Digital Signal Controller (DSC). Various monitoring and protection functions for the drive are implemented using a Cyclone IV FPGA that communicates with the DSC, and acts as the master controller for the drive. The FPGA also communicates with a Human–Machine Interface to provide a simple graphical control interface to the operator.     

Stabilization of a Distorted Conformation of Cyclohexane Adsorbed in the Voids of Silicalite-1

The dimensions and topology of the voids in porous zeolites can influence the conformational geometry of guest molecules confined within it. Here we report an infrared and Raman vibrational spectroscopic study of cyclohexane confined within the voids of a medium-pore zeolite, Silicalite-1. We find that on confinement two conformers of cyclohexane are in thermal equilibrium, one of which lacks a center of inversion and is the preferred conformation at lower temperatures. Molecular modeling supports this observation; in the intersection-voids of Silicalite-1 host–guest dispersive interactions favour a distorted-chair conformer of cyclohexane with symmetry lower than D_3d. The results are compared with those for cyclohexane confined in the comparatively larger voids of Zeolite-Y, where it is known to exist exclusively in the chair conformer.     

Methanol-to-gasoline(MTG)conversion over ZSM-5. A temperature programmed surface reaction study

The conversion of methanol to gasoline over zeolite ZSM-5 has been studied by temperature programmed surface reaction (TPSR). The technique is able to monitor the two steps in the process: the dehydration of methanol to dimethyl ether and the subsequent conversion of dimethyl ether to hydrocarbons. The activation barriers associated with each step were evaluated from the TPSR profiles and are 25.7 and 46.5 kcal/mol respectively. The methanol desorption profile shows considerable change with the amount of methanol molecules adsorbed per Brønsted site of the zeolite. The energy associated with the desorption process, (CH₃OH)_nH_s+-ZSM5 (CH₃OH)_n–1H⁺-ZSM5+CH₅OH, shows a spectrum of values depending onn.     

Compact slotline fed enhanced gain dipole antenna for 5.2 GHz/5.8‐GHz applications

A high‐efficiency and high‐gain slotline fed directive dipole antenna is developed for microwave applications. The antenna offers an average gain of 7.9 dBi with a front to back ratio better than 20 dB and a cross polar level better than ?20 dB. Design equations of the antenna are developed and validated on different substrates. The simulation and experimental results show that the proposed antenna exhibits high gain and robust radiation patterns in the entire frequency band. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

Systematic Welding Process Parameter Optimization in Activated Tungsten Inert Gas (A-TIG) Welding of Inconel 625

Transactions of the Indian Institute of Metals - This article presents the welding process parameter optimization for activated tungsten inert gas welding of a 6.5 mm thick Inconel 625...     

Optimization of the process parameters for the removal of boron from drinking water by electrocoagulation—a clean technology

BACKGROUND: There are a number of articles related to removal of boron by electrocoagulation using aluminium electrodes, but there are fewer articles describing the use of magnesium as the anode material. The main disadvantage of aluminium electrodes is the residual aluminium present in the treated water due to cathodic dissolution, which can create health problems. In the case of magnesium electrodes, there is no such disadvantage. This paper presents the results of studies on the removal of boron using magnesium and stainless steel as anode and cathode, respectively. RESULTS: Results show that a maximum removal efficiency of 86.32% was achieved at a current density of 0.2 A dm^?2 and pH of 7 using magnesium as the anode and stainless steel as the cathode. The adsorption of boron fitted the Langmuir adsorption isotherm, suggesting monolayer coverage of adsorbed molecules. The adsorption process follows second‐order kinetics. Temperature studies showed that adsorption was endothermic and spontaneous in nature. CONCLUSIONS: The magnesium hydroxide generated in the cell remove the boron present in the water and reduced to a permissible level and making it drinkable. The process scale up results was consistent with the results obtained from the laboratory scale, showing the robustness of the process. Copyright © 2010 Society of Chemical Industry     

A Study of Microstructure and Mechanical Properties of Grade 91 Steel A-TIG Weld Joint

In the present study, A-TIG welding was carried out on grade 91 steel plates of size 220 × 110 × 10 mm using the in-house developed activated flux to produce butt-joints. The room-temperature impact toughness of the A-TIG as-welded joint was low due to the presence of untempered martensite matrix despite the low microinclusion density caused by activated flux and also low δ-ferrite (<0.5 %) content. Toughness after postweld heat treatment (PWHT) at 760 °C-2 h was 20 J as against the required value of 47 J as per the specification EN: 1557:1997. However, there was a significant improvement in impact toughness after PWHT at 760 °C for 3 h. The improvement in toughness was attributed to softening of martensite matrix caused by precipitation of carbides due to tempering reactions. The precipitates are of type M₂₃C₆, and they are observed at grain boundary as well as within the grains. The A-TIG-processed grade 91 steel weld joint was found to meet the toughness requirements after PWHT at 760 °C-3 h. Observations of fracture surfaces using SEM revealed that the as-welded joint failed by brittle fracture, whereas post-weld heat-treated weld joints failed by decohesive rupture mode.     

Beneficial effects of O-phase on the hydrogen absorption of Ti–Al–Nb alloys

The beneficial effects of O-phase on hydrogen absorption/desorption were demonstrated in three Ti–Al–Nb alloys with compositions in the vicinity of Ti₂NbAl. The alloys were first quenched from high temperature and then aged for a certain period of time at a lower temperature to get O-phase precipitation in the matrix before pressure–composition (P–C) isotherm measurements. All three alloys absorb hydrogen to β hydride at a very low equilibrium pressure. Further absorption to γ hydride is difficult for the quenched O-phase free specimens. β->γ hydride transformation occurs in all the aged specimens and the reversible absorption/desorption between β and γ hydrides is observed in some aged specimens with relatively high volume fraction of O-phase in the matrix. The hydrogen absorption/desorption abilities of these alloys become poor when the Nb content is decreased. The determined formation heat for β->γ hydride transformation is in the range of −30–45 kJ/mol H₂, which is larger than that of binary Ti₃Al. It is found that the value of formation heat becomes more negative with the increasing amount of O-phase and is relatively independent of the interface between O-phase and matrix. This indicates the beneficial effect is related to the O-phase structure itself.