Unsupervised image thresholding: hardware architecture and its usage for FPGA-SoC platform

ABSTRACT

Otsu’s global automatic image thresholding operation is used in various image processing applications. It needs computation of normalized cumulative histogram, mean and cumulative moments that are compute-intensive operations. In this paper, a custom architecture is presented for an efficient computation of Otsu’s algorithm along with its utilization as an intellectual property (IP) core in a field programmable gate array (FPGA) based system-on-chip (SoC) environment for the application of connected component analysis (CCA). A self-normalization technique is employed, where single-cycle, read–modify–write operations are performed with block random access memories (BRAMs) and digital signal processing (DSP)slices. The architecture is designed for 640 × 480 size of images that are captured by a high-resolution analouge camera and buffered in a DDR2 SDRAM of Xilinx ML-507 platform at 25.175 MHz clock frequency. The embedded PowerPC processor core is used to control the frame acquisition process. Experimental results on Virtex-5 xc5vfx70t FPGA device show that the architecture utilizes 1.4% slices, 2.7% BRAMs and 3.9% DSP48E slices. The total power consumption of the design is 1440.59 mW. The proposed architecture as an IP core is able to work in real-time with standard VGA resolution video and requires low computational resources.     

3,4-Dihydro-2H-pyran promoted aerobic oxidative aromatization of 1,3,5-trisubstituted pyrazolines and Hantzsch 1,4-dihydropyridines

An unprecedented facile oxidation of 1,3,5-trisubstituted pyrazolines and Hantzsch 1,4-dihydropyridines (DHPs) to the corresponding pyrazoles and pyridines was observed, mediated by 3,4-dihydro-2H-pyran in air. The reaction showed excellent reactivity, functional group tolerance, and high yield without using any metal and/or halogen based oxidizing agents.     

Kinetics of Stripping Ni(II) from the Ni‐BTMPPA Complex/BTMPPA/Kerosene System by Sulfate‐Acetato Solution

The kinetics of stripping of Ni²⁺ from a Ni‐BTMPPA complex, dissolved in a kerosene solution of BTMPPA (H₂A₂, Cyanex 272), by acidic sulfate‐acetato solution, was studied using the single (falling) drop technique and flux (F) method of data treatment. The empirical flux equation at 303 K is F_b (kmol/m²s) = 10^?4.35 [Ni²⁺] (1+10^?3.42 [H⁺]^?1)^?1 ([H₂A₂]_(o)^0.5+2.50 [H₂A₂]_(o))^?1 (1+6[SO₄^2?]) (1+3.20 [Ac^?]). Activation energy (E_a), entropy change in activation (ΔS^±), and enthalpy change in activation (ΔH^±) were measured under different experimental conditions. Based on the empirical flux equation, E_a and ΔS^±, the mechanism of Ni²⁺ stripping is provided. In a low [H⁺] region, the stripping reaction steps appear as [NiA⁺] → Ni²⁺ + A^? and [Ni(HA₂)₂]_(int) → [NiHA₂]⁺_(int) + HA_2(int)^? in lower and higher concentration regions of free BTMPPA, respectively, provided [SO₄^2?] and [Ac^?] are kept low. However, at higher [H⁺] concentrations, the stripping is under diffusion control. With increasing [SO₄^2?] and [Ac^?], the enhancement of the rate is attributed to the attack of the Ni(II) complex by SO₄^2? or HSO₄^? and Ac^? to form NiSO₄ or NiHSO₄⁺ and NiAc⁺ complexes. Negative ΔS^± values indicate that the rate‐determining stripping reaction steps occur via an substitution nucleophilic, bimolecular (S_N2) mechanism.     

Synthesis and Structural Characterisation of Two Copper(II) Complexes of <Emphasis Type="Italic">N</Emphasis>-(1-acetyl-2-propylidene) (2-pyridylmethyl) amine

Two new complexes [CuBr(C₁₁H₁₃N₂O)] (1) and [Cu(NCO)(C₁₁H₁₃N₂O)] (2) containing the tridentate Schiff base ligand, N-(1-acetyl-2-propylidene)(2-pyridylmethyl) amine which is the 1:1 condensation product of acetylacetone and 2-aminomethylpyridine, have been synthesised and characterised by elemental analysis, IR and electronic spectra, electrochemical study and single crystal X-ray diffraction study. Crystal structures reveal that the copper atom in both the complexes are in square geometry formed by the N₂O donor set of the Schiff base and a bromine atom in 1 and one cyanate ligand in 2. Both bromide and isocyanate ligands act in a terminal monodentate fashion.     

Hydrogen‐Bonded Organic Frameworks (HOFs): A New Class of Porous Crystalline Proton‐Conducting Materials

Two porous hydrogen‐bonded organic frameworks (HOFs) based on arene sulfonates and guanidinium ions are reported. As a result of the presence of ionic backbones appended with protonic source, the compounds exhibit ultra‐high proton conduction values (σ) 0.75× 10^?2 S cm^?1 and 1.8×10^?2 S cm^?1 under humidified conditions. Also, they have very low activation energy values and the highest proton conductivity at ambient conditions (low humidity and at moderate temperature) among porous crystalline materials, such as metal–organic frameworks (MOFs) and covalent organic frameworks (COFs). These values are not only comparable to the conventionally used proton exchange membranes, such as Nafion used in fuel cell technologies, but is also the highest value reported in organic‐based porous architectures. Notably, this report inaugurates the usage of crystalline hydrogen‐bonded porous organic frameworks as solid‐state proton conducting materials.     

Reaction pathway of POCl3-mediated Knoevenagel condensation of bisulfite adducts with 2,4-thiazolidinedione

We investigated the POCl₃-mediated transformation of aromatic bisulfite adducts to the corresponding 5-arylidenethiazolidine-2,4-diones. The in situ transformation of an aromatic bisulfite adduct to the parent aldehyde in a non-aqueous non-polar solvent (toluene) was demonstrated using DoE (Design of experiment), offline ¹H NMR, online ReactIR, HPLC, LC-MS, and GC-MS. By means of these analytical tools, we determined, for the first time, the structure of the intermediate species (aldehyde) prior to the carbon–carbon double-bond formation. The carbon–sulfur bond undergoes a fast cleavage, immediately after the addition of POCl₃, which finally affords the corresponding 5-arylidenethiazolidine-2,4-diones.     

Bimodal Functionality in a Porous Covalent Triazine Framework by Rational Integration of an Electron‐Rich and ‐Deficient Pore Surface

A porous covalent triazine framework (CTF) consisting of both an electron‐deficient central triazine core and electron‐rich aromatic building blocks is reported. Taking advantage of the dual nature of the pore surface, bimodal functionality has been achieved. The electron deficiency in the central core has been utilized to address one of the pertinent problems in chemical industries, namely separation of benzene from its cyclic saturated congener, that is, cyclohexane. Also, by virtue of the electron‐rich aromatic rings with Lewis basic sites, aqueous‐phase chemical sensing of a nitroaromatic compound of highly explosive nature (2,4,6‐trinitrophenol; TNP) has been achieved. The present compound supersedes the performance of previously reported COFs in both the aspects. Notably, this reports the first example of pore‐surface engineering leading to bimodal functionality in CTFs.     

One Novel Cu(II)–Amino Acid Schiff Base Complex Derived from Salicylaldehyde and L-Serine: Identification of Unusual Monodentate 4,4′-Bipyridine

One novel copper(II) complex [Cu(L)(4,4′-bipy)](ClO₄) (1), (where L: tridentate Schiff base derived from salicylaldehyde and L-serine) has been synthesised and characterised by spectroscopic and electrochemical studies. The single-crystal structure of the complex was determined. The crystal structure features the presence of [Cu(L)(4,4′-bipy)]⁺ cations and ClO₄⁻ anions aggregated by hydrogen bonding. Here, 4,4′-bipyridine functions as a monodentate ligand, which appears to be an unusual phenomenon.     

Equilibrium glassy phase in a polydisperse hard-sphere system

The phase diagram of a polydisperse hard-sphere system is examined by numerical minimization of a discretized form of the Ramakrishnan-Yussouff free-energy functional. Crystalline and glassy local minima of the free energy are located and the phase diagram in the density-polydispersity plane is mapped out by comparing the free energies of different local minima. The crystalline phase disappears and the glass becomes the equilibrium phase beyond a "terminal" value of the polydispersity. A crystal-to-glass transition is also observed as the density is increased at high polydispersity. The phase diagram obtained in our study is qualitatively similar to that of hard spheres in a quenched random potential.