Amit Kumar Mondal

Densely Packed Lanthanide Cubane Based 3D Metal–Organic Frameworks for Efficient Magnetic Refrigeration and Slow Magnetic Relaxation

Two isostructural densely packed squarato-bridged lanthanide-based 3D metal-organic frameworks (MOFs) [Ln5(μ3-OH)5(μ3-O)(CO3)2(HCO2)2(C4O4)(H2O)2] [Ln = Gd (1) and Dy (2)] show giant cryogenic magnetic refrigeration (for 1) and slow magnetic relaxation (for 2). The structural analyses reveal the presence of a self-assembled crown-shaped building unit with a cubane-based rectangular moiety that leads to a special array of metal centers in 3D space in the complexes. Magnetic investigations confirm that complex 1 exhibits one of the largest cryogenic magnetocaloric effects among the molecular magnetic refrigerant materials reported so far (-ΔSm = 64.0 J kg(-1) K(-1) for ΔH = 9 T at 3 K). The cryogenic cooling effect (of 1) is also quite comparable with that of the commercially used magnetic refrigerant gadolinium-gallium garnet, whereas for complex 2, slow relaxation of magnetization was observed below 10 K.

Lanthanide-Directed Fabrication of Four Tetranuclear Quadruple Stranded Helicates Showing Magnetic Refrigeration and Slow Magnetic Relaxation

A rare class of four tetranuclear lanthanide based quadruple stranded helicates namely, [Ln4L4(OH)2](OAc)2·xH2O (Ln = Gd(III)(1), Dy(III)(2) and x = 4, 5 respectively), [Er4L4(OH)2](NO3)2·9H2O (3), and [Dy4L4(NO3)](NO3)2·2CH3OH·H2O (4) were synthesized by employing succinohydrazone derived bis-tridentate ligand (H2L) and characterized. Structures of 1-3 are similar to each other except the nature of counterions and number of lattice water molecules. In 4, a distorted nitrate ion was arranged in a hexagonal manner holding four dysprosium centers in a slightly twisted manner. Because of the symmetrical nature of each complex, the C4 axis crosses the center of helicate resulting a pseudo-D4 coordination environment. Each ligand coordinates to lanthanide centers in helical manner forming mixture of left (Λ) and right (Δ) handed discrete units. Complex 1 exhibits antiferromagnetic exchange interaction between nearby Gd(III) centers and shows magnetic refrigeration (-ΔSm = 24.4 J kg(-1) K(-1) for ΔH = 7 T at 3 K). AC magnetic susceptibility measurements of 2 and 4 demonstrate slow relaxation behavior, with Ueff (effective energy barrier) of 20.5 and 4.6 K, respectively. As per our knowledge, complexes 1, 2, and 4 represent the first examples of aesthetically pleasing quadruple stranded helicates showing potential magnetocaloric effect and single-molecule-magnet-like behavior.

Probing the Effects of Ligand Field and Coordination Geometry on Magnetic Anisotropy of Pentacoordinate Cobalt(II) Single-Ion Magnets

In this work, the effects of ligand field strength as well as the metal coordination geometry on magnetic anisotropy of pentacoordinated CoII complexes have been investigated using a combined experimental and theoretical approach. For that, a strategic design and synthesis of three pentacoordinate CoII complexes [Co(bbp)Cl2]·(MeOH) (1), [Co(bbp)Br2]·(MeOH) (2), and [Co(bbp)(NCS)2] (3) has been achieved by using the tridentate coordination environment of the ligand in conjunction with the accommodating terminal ligands (i.e., chloride, bromide, and thiocyanate). Detailed magnetic studies disclose the occurrence of slow magnetic relaxation behavior of CoII centers with an easy-plane magnetic anisotropy. A quantitative estimation of ZFS parameters has been successfully performed by density functional theory (DFT) calculations. Both the sign and magnitude of ZFS parameters are prophesied well by this DFT method. The theoretical results also reveal that the α → β (SOMO-SOMO) excitation contributes almost entirely to the total ZFS values for all complexes. It is worth noting that the excitation pertaining to the most positive contribution to the ZFS parameter is the dxy → dx2-y2 excitation for complexes 1 and 2, whereas for complex 3 it is the dz2 → dx2-y2 excitation.

A brief history and future aspects in automatic cleaning systems for solar photovoltaic panels

The energy or efficiency produced by solar photovoltaic modules is related with the Sun’s available irradiance and spectral content, as well as other factors like environmental, climatic, component performance and inherent system. These dust, dirt and bird droppings are the major reasons for the solar photovoltaic system underperformance. This paper discusses a comprehensive overview of dust problem and the recent developments made on automated cleaning system for solar photovoltaic modules which give brief overview on techniques like electrical, mechanical, chemical and electrostatic. The main objective of the study is to review the literature on solar photovoltaic module automated cleaning techniques for identifying research gaps in the automated cleaning systems.

HAAR like Feature-Based Car Key Detection Using Cascade Classifier

The paper reports effective real-time implementation for specific object detection in an image or sequence of images. For the present work, car key has been taken as an object under consideration. The classifier is developed using OpenCV-Python. The procedure encompasses training and detection. A wide variety of object images are used for training purpose. The developed xml classifier is then tested on separate test images. The classifier has a good success rate with minimal false object detection rate.

Quantitative Estimation of Ising-type Magnetic Anisotropy in a Family of C3 Symmetric CoII Complexes

In this paper, the influence of the structural and chemical effects on the Ising-type magnetic anisotropy of pentacoordinate CoII complexes has been investigated by using a combined experimental and theoretical approach. For this, a deliberate design and synthesis of four pentacoordinate CoII complexes [Co(tpa)Cl]⋅ClO4 (1), [Co(tpa)Br]⋅ClO4 (2), [Co(tbta)Cl]⋅(ClO4 )⋅(MeCN)2 ⋅(H2 O) (3) and [Co(tbta)Br]⋅ClO4 (4) by using the tripodal ligands tris(2-methylpyridyl)amine (tpa) and tris[(1-benzyl-1 H-1,2,3-triazole-4-yl)methyl]amine) (tbta) have been carried out. Detailed dc and ac measurements show the existence of field-induced slow magnetic relaxation behavior of CoII centers with Ising-type magnetic anisotropy. A quantitative estimation of the zero-field splitting (ZFS) parameters has been effectively achieved by using detailed ab initio theory calculations. Computational studies reveal that the wavefunction of all the studied complexes has a very strong multiconfigurational character that stabilizes the largest ms =±3/2 components of the quartet state and hence produce a large negative contribution to the ZFS parameters. The difference in the magnitudes of the Ising-type anisotropy can be explained through ligand field theory considerations, that is, D is larger and negative in the case of weak equatorial σ-donating and strong apical π-donating ligands. To elucidate the role of intermolecular interactions in the magnetic relaxation behavior between adjacent CoII centers, a diamagnetic isostructural ZnII analog (5) was synthesized and the magnetic dilution experiment was performed.

Development of position tracking and guidance system for Unmanned Powered Parafoil Aerial Vehicle

An experimental Unmanned Powered Parafoil Aerial Vehicle (UPPAV) was developed to gather aerial data. Certain characteristics like low-speed, low-cost, and high stability makes the powered Parafoil a versatile and promising platform for surveillance and imaging applications. UPPAVs are easy to operate, robust and safe and have high flight duration. The developed UPPAV has a chassis fitted with a high torque Brushless DC motor, Servo motor and a Parafoil wing. This paper describes development of the position tracking and guidance system using the GPS unit placed on the chassis. It focuses on the extraction and transmission of the specific GPS values like longitude, Latitude and Altitude from the bulk values obtained. The GPS navigation system will provide continuous position of the system. These obtained values can be used by the pilot to maneuver the system to the desired location. The developed system mounted on the chassis consists of Microcontrollers, GPS, and 433 MHz transreceivers.

Performance analysis of a powered parafoil unmanned aerial vehicle using open loop flight test results and analytical results

This paper presents an approach to design and develop an Unmanned Powered Parafoil Aerial Vehicle (UPPAV) to surveillance an area. The paper discusses in detail about the relation between Parafoil size and payload weight. Analytical calculations are done to understand the UPPAV performance. The performance results are then compared with open loop flight test results.

Development of a Damper Control System for Combined Cycle Thermal Gas Power Plant

This paper addresses a technique to solve the problem of heat dissipation in solenoid coil of the solenoid valve which is controlling the hydraulic damper by using pulse width modulation (PWM) switching technique with low frequency. In addition to this damper controlling is achieved via wireless controlling. By using PWM based low frequency switching technique the gas turbine trip will be protected. PWM is achieved by microcontroller and wireless control is done by ZigBee.© 2014 ASME

Determinants of vision function related quality of life of patients undergoing unilateral cataract surgical services in charitable hospitals in India: a multicentre prospective cohort study

Based on the World Health Organization‟s (WHO) definition of health, quality of life is an integral part of health and well-being and the WHO recommended that vision related quality of life (VRQoL) form part of assessments and evaluations of interventions in eye health. Cataract surgery has a multiplier effect as it not only improves the Quality of Life (QoL) but also prolonging life as people who can see better post-surgery are more likely to get exercise, take their medications and avoid falls. The age-standardised global prevalence of blindness was reported at 0.48% in 2015 as against 0.75% in 1990. Though this decline is encouraging, cataract continues to remain the main cause of blindness with the vast majority of cataract blind living in low and ABSTRACT