Pyramidal Configuration Research Articles

능동 합성개구레이더위성의 다섯 개 반작용휠 운용방법

위성의 자세제어 및 기동을 위해서는 네 개의 반작용휠을 피라미드 형태로 배치하여 사용하는 것이 일반적이다. 하지만 위성의 관성모멘트가 크거나 사용할 수 있는 반작용휠의 용량이 작은 경우에는 다섯 개의 반작용휠을 사용하는 것을 생각해볼 수 있다. 이 경우, 반작용휠 배치부터 운용방법까지 여러 가지 문제를 다시 고려해야 한다. 능동합성개구레이더 위성은 관측 각도 변화를 위해서 롤축 방향으로 빠른 기동이 요구된다. 본 논문에서는 합성개구레이더 위성의 롤축 방향 기동성능 향상을 위하여 다섯 개의 반작용휠을 배치하는 경우, 이를 운용하는 방법을 연구해본다. For satellite attitude control and maneuver, normally four reaction wheels are used through pyramid configuration. However, if satellite's moment of inertia is large or available reaction wheels' capability is small, we can consider using five reaction wheels. In this case, we should think the arrangement of wheels and their operation method. Active SAR satellite requires high agile maneuver about roll axis to achieve looking angle change. In this research, we study the operation method of five reaction wheels configuration for fast roll maneuver.

Synthesis, structure and superoxide dismutase-like activity of two mixed-ligand Cu(II) complexes with N,N′-bis(2-pyridylmethyl)amantadine

Two mixed-ligand Cu(II) complexes, [Cu(L1)(L2)](ClO4)2·H2O (1) and [Cu(L1)(L3)](ClO4)2·H2O·CH3OH (2) (L1=N,N′-bis(2-pyridylmethyl)amantadine, L2=5,5′-dimethy-2,2′-bipyridine, and L3=1,10-phenanthroline), were synthesized and characterized by elemental analysis, UV–Vis, infrared spectra and single crystal X-ray diffraction. Copper ions in 1 and 2 behave the slightly distorted tetragonal pyramid configuration provided by CuN5 coordination set. Both complexes exhibit the quasi-reversible Cu(II)/Cu(I) one-electron redox waves determined by the cyclic voltammetry. Moreover, the frontier molecular orbital energies were obtained by DFT calculations with B3LYP method at LanL2DZ basis. Furthermore, by using NBT assay at pH 7.8, the superoxide dismutase (SOD)-like activity (IC50) of 1 and 2 were measured to be 0.167 and 0.242μM, respectively. The difference in SOD-like activities of two complexes could be ascribed to the rigidity of the auxiliary ligands.

Conformational, NBO, NLO, HOMO-LUMO, NMR, electronic spectral study and molecular docking study of N,N-Dimethyl-3-(10H-phenothiazin-10-yl)-1-propanamine

FT-IR and FT-Raman spectra of N,N-Dimethyl-3-(10H-phenothiazin-10-yl)-1-propanamine were recorded and analyzed. The conformational behaviour is also investigated. The vibrational wave numbers were calculated using density functional quantum chemical calculations. The data obtained from wave number calculations are used to assign vibrational bands obtained experimentally. In the most stable form for N,N-Dimethyl-3-(10H-phenothiazin-10-yl)-1-propanamine, the nitrogen atom of the phenothiazine ring is predicted to adopt an expanded pyramidal configuration with an average CNC angle of 118° while the alkylamine chain points away from the phenothiazine ring. The geometrical parameters are compared with related structures. The stability of the molecule arising from hyper conjugative interaction and charge delocalization has been analyzed using natural bonding orbital analysis. The frontier molecular orbital analysis is used to determine the charge transfer within the molecule. The theoretical NMR spectral analysis, Fukui functions and electronic transition UV–Vis spectral analysis is also reported. The docked title compound forms a stable complex with Plasmodium falciparum and gives a binding affinity value of −6.8 kcal/mol and the results suggest that the compound might exhibit inhibitory activity against Plasmodium falciparum.

1-Alkoxyamino-4-dimethylaminopyridinium salts: synthesis and structure†

N-Alkoxy-N-chlorocarbamates react with 4-dimethyl-aminopyridine yielding 1-alkoxyamino-4-dimethylamino-pyridinium chlorides, new type of O–N–N+ geminal systems. The XRD studies of two representative 1-alkoxyamino-pyridinium chlorides revealed the high pyramidal configuration of the central nitrogen atom in O–N–N+ geminal system.

Monoorgano-gallium and –indium complexes derived from dianionic tridentate ONO Schiff bases: Synthesis, crystal structures and photoluminescence

Reactions of triorgano-gallium and –indium etherates with N′-(2-hydroxybenzylidine)benzohydrazide and N′-(2-hydroxy-3-methoxybenzylidine)benzohydrazide in refluxing benzene afforded complexes of composition [{RM}{–O(C6H3R′-3)CHN–NC(C6H5)O–}] (MGa, In; RMe, Et; R′H, OMe). These complexes have been characterized by elemental analysis, IR, UV-vis, and NMR (1H and 13C{1H}) spectroscopy. The molecular structures of [{MeGa}{–O(C6H4)CHN–NC(C6H5)O–}]2 (1), [{MeGa}{–O(C6H3–OMe)CHN–NC(C6H5)O–}]2 (2) and [{EtGa}{–O(C6H3–OMe)CHN–NC(C6H5)O–}]2 (6) were established by X-ray crystallography. These complexes adopt a dimeric structure with phenolate oxygen bridges with the gallium atom acquiring a distorted square pyramidal configuration. These complexes are emissive in toluene solution at room temperature.

Simplified Transparent Conductive Oxides-Based UltraBroadband Absorber Design

Broadband electromagnetic wave absorbers are of practical importance in many fields. Current absorbers with multilayered configurations at high frequencies suffer from fabrication challenges and design complexity. In this study, we realize a broadband, wide-angle, polarization-independent, perfect infrared absorber with conventional pyramid configuration but only employing one single transparent conductive oxide material without using multilayered design. A transmission line model is introduced to rein the complex frequency responses. Full-wave simulations give consistent results with theoretical predictions. This simplified configuration might relieve the fabrication and design difficulties, exhibiting great potentials in the applications of energy harvesting, IR detection, and imaging systems.

Theoretical insight into electronic structure and optoelectronic properties of heteroleptic Cu(I)-based complexes for dye-sensitized solar cells

A series of heteroleptic Cu(I)-based dyes were investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT). Results showed that Cu(I)-based dyes were inclined to form distorted pseudo-trigonal pyramidal configurations with four-coordinated geometry index τ4 ranging from 0.905 to 0.914. The absorption spectra of Cu(I)-based dyes covered ∼300.0–600.0 nm region, and the lowest excitation states were crucial for efficient electron excitation and separation. Suitable energy levels of Cu(I)-based dyes rendered them thermodynamically favorable for efficient electron injection into semiconductor and regeneration from electrolyte. Relative to π-conjugation, heteroaromatic groups introduced into ancillary ligands could significantly improve the property of Cu(I)-based dyes by decreasing HOMO-LUMO gaps, red-shifting spectral range, strengthening absorption intensity, boosting light-harvesting efficiency, and promoting interfacial electron injection. Specifically, Cu(I)-based dye with dithiole-functionalized group exhibited outstanding optoelectronic property.

A Non-Planar Iodinated Pyrrole Study

ABSTRACTNon-planar iodinated pyrrole structures were found through DFT calculations of geometry optimization, when doping one pyrrole molecule with iodine atoms. This take us to a new mono-iodinated pyrrole structure in which one pyrrole molecule is attacked with one iodine atom in a pyramidal configuration. Then, the pyrrole molecule was attacked with two and until four optimized linear iodine atoms in a pyramidal structure configuration. The corresponding potential energy curves were also constructed in order to know what kind of adsorption (physisorption or chemisorption) is obtained, considering physisorption as lower than ten kcal/mol, and chemisorption greater than twenty kcal/mol according to the literature. Finally, it is known that halogenated pyrrole is a highly conductive material required in several fields.

Molecular dynamics study on the nucleation of Al-Si melts on sheet substrates at the nanoscale.

Molecular dynamics (MD) simulations are performed to study the freezing process of Al-Si melts on heterogeneous Si substrates in detail. We highlight the inherent nanostructure of both the Si primary phase and the Al-Si binary phase. It is found for the first time that the primary Si phase displays a "pyramidal configuration" when the Al-Si melt congeals. Experimental measurements could also verify our simulation results. It can be found that the binary Al-Si phase turns into a "Si-Al-Si sandwich construction" during solidification, regardless of freezing on a single substrate or in the restricted space between substrates. This peculiar phenomenon results from the combined effects of the van der Waals potential well and the interatomic interaction between Al and Si. Furthermore, it is also able to control the thickness of the Si atomic shell of the "sandwich construction", resulting in the silicene-like unilaminar Si nanostructure. Our findings provide novel strategies to fabricate desired shaped nanostructures by means of nanocasting in Al-Si melts at the nanoscale.

From pink to blue and back to pink again: changing the Co(ii) ligation in a two-dimensional coordination network upon desolvation

Heating of a pink two-dimensional Co(II) coordination network {[Co2(μ2-OH2)(bdc)2(S-nia)2(H2O)(dmf)]·2(dmf)·(H2O)}n (1) built from 1,4-benzenedicarboxylic acid (H2bdc) residues and thionicotinamide (S-nia) ligands initiates a single-crystal-to-single-crystal transition accompanied by removal of both coordinated and co-crystallized solvents. In the dry blue form, [Co(bdc)(S-nia)]n (dry_1), the Co(II) centers changed from an octahedral to a square pyramidal configuration.

Two S = 1/2 one-dimensional barium copper phosphates showing antiferromagnetic and ferromagnetic intrachain interactions.

Two barium copper phosphates, BaCu2(PO4)2(H2O) (1) and Ba2Cu(HPO4)(PO4)(OH) (2), were synthesized under mild hydrothermal conditions. The Cu cation in 1 adopts a CuO4(H2O) square pyramidal coordination configuration, forming alternating chains along the b axis through alternative corner and edge sharing, while the geometry of the Cu center in 2 is a CuO4(OH)2 octahedron which further connects each other by edge sharing to constitute uniform chains along the b axis. Magnetic behaviors of both compounds were analyzed by susceptibility, magnetization and heat capacity measurements. The dominant intrachain couplings are antiferromagnetic in 1 with a long-range ordering at 14 K and ferromagnetic in 2 without long-range ordering above 2 K. The first principles calculations indicate that the intrachain ferromagnetic couplings in 2 originate from Cu(1)-O(7)H-Cu(1) dpσ correlation superexchanges. The susceptibility data of compounds 1 and 2 are fitted by using suitable antiferromagnetic chain and ferromagnetic chain models, respectively. In addition, we report the results of the infrared and thermal measurements of both the compounds.

Halide copper(II) complexes of aromatic N-donor containing ligands: Structural, magnetic and reactivity studies

The preparation of four new copper(II) complexes with different N-donor ligands [CuBr2(2-benzylpyridine)2] (1), [CuBr2(2-benzylpyridine)(2,2′-bipyridine)]·H2O (2), [CuBr2(3-methyl-2-phenylpiridine)2] (3), [Cu(picolinate)2]·KI (4) from copper(I) halides as starting material is described. During the preparation of compound 4 a ligand oxidation reaction took place to give the picolinate ligand starting from 2-(2-methylaminoethyl)pyridine. The complexes were characterized by elemental analyses, IR spectroscopy and crystallographic studies. Single crystal X-ray diffraction analysis of the complexes reveals their monomeric penta- and tetracoordinated nature. For all compounds, the copper(II) present a common square planar coordination except for compound 2 which is five coordinated in a quasi-square pyramidal configuration with τ of 0.29. The Cu–N distances for these compounds are in the range of 1.959(4)-2.041(3) A, Cu–O distance was 1.961(3) A and Cu–Br distances were in the range of 2.4052(4)-2.4381(6) A for the square base configuration while for apical distance it was 2.6745(7) A. Magnetic properties have been investigated for all compounds in the temperature range 2-300 K. Compound 1 shows weak antiferromagnetic intermolecular interaction.

Mapping Structural Changes in Electrode Materials: Application of the Hybrid Eigenvector-Following Density Functional Theory (DFT) Method to Layered Li0.5MnO2

The migration mechanism associated with the initial layered-to-spinel transformation of partially delithiated layered LiMnO2 was studied using hybrid eigenvector-following coupled with density functional theory. The initial part of the transformation mechanism of Li0.5MnO2 involves the migration of Li into both octahedral and tetrahedral local minima within the layered structure. The next stage of the transformation process involves the migration of Mn and was found to occur through several local minima, including an intermediate square pyramidal MnO5 configuration and an independent Mn3+ to Mn2+ charge-transfer process. The migration pathways were found to be significantly affected by the size of the supercell used and the inclusion of a Hubbard U parameter in the DFT functional. The transition state searching methodology described should be useful for studying the structural rearrangements that can occur in electrode materials during battery cycling, and more generally, ionic and electronic transport phenomena in a wide range of energy materials.

New Sliding Mode Control Approach for Rapid Attitude Maneuver Using Control Moment Gyros

AbstractA single-gimbal control moment gyro (CMG) is considered to be an ideal torque-generating actuator for rapid attitude maneuvering due to its relatively large output torque. A new attitude control method that is based on the modified Rodrigues parameter (MRP) sliding mode control law for a pyramidal configuration using four CMGs is proposed. Robust inverse steering logic is used to avoid issues of the singularity of the CMGs. The proposed approach is expected to provide rapid and stable attitude maneuvering while avoiding the singularity of the CMGs. In addition, this method is demonstrated on a small satellite, named TSUBAME, designed by the Laboratory of Space Systems at the Tokyo Institute of Technology. The proposed control algorithm is verified through a Monte Carlo simulation and a software-in-the-loop attitude simulator for TSUBAME. The Monte Carlo simulation demonstrated that the new sliding mode control approach successfully tracks a time varying attitude for a nanosatellite model with a ra...

One-pot synthesis, structural characterization, UV–Vis and electrochemical analyses of new Schiff base complexes of Fe(III), Ni(II) and Cu(II)

The complexes [Ni(Pyr2tetam−2H)]·2H2O (1) (Pyr2tetam = (pyridoxyl)2-N1,N4-triethylenetetramine), [Fe(Pyr2tetam−2H)](ClO4)·H2O (2) and [Cu(Pyrtetam−H)](ClO4) (3) (Pyrtetam = pyridoxyl-N1-triethylenetetramine) were obtained through one pot reactions of triethylenetetramine, pyridoxal chloridrate, triethylamine and the metal salts Ni(ClO4)2·6H2O, Fe(ClO4)2·6H2O and Cu(ClO4)2·6H2O. In complexes 1 and 2 the metal centers present a distorted octahedral coordination, while complex 3 shows a square pyramidal configuration. The structures were characterized through X-ray diffractometry, IR and UV–Vis spectra. Cyclic voltammograms of the title compounds are also presented and discussed.

Cobalt and nickel complexes supported by 2,6-bis(imidate)pyridyl ligands: Synthesis, characterization, and 1,3-butadiene polymerization studies

A series of 2,6-bis(imidate)pyridine ligated Co(II) and Ni(II) complexes with general formula of [2,6-(2,6-iPr2C6H3N=COR)2C5H3N]MX2 (R=Me, M=Co, X=Cl (1a); R=Me, M=Ni, X=Br (2a); R=Et, M=Co, X=Cl (1b); R=Et, M=Ni, X=Br (2b); R=iPr, M=Co, X=Cl (1c); R=iPr, M=Ni, X=Br (2c); R=CH2CF3, M=Co, X=Cl (1d); R=CH2CF3, M=Ni, X=Br (2d); R=Ph, M=Co, X=Cl (1e); R=Ph, M=Ni, X=Br (2e); R=CH2Ph, M=Co, X=Cl (1f); R=CH2Ph, M=Ni, X=Br (2f)) were synthesized. Determined by single crystal X-ray analysis, complexes 1e and 2c with NNN tridentate ligands adopted approximate distorted square pyramidal configurations whereas complex 1f with tridentate NNO ligand displayed a distorted square pyramidal configuration. Activated by methylaluminoxane (MAO), these complexes exhibited high cis-1,4 selectivity towards 1,3-butadiene polymerization. The structure of substituent and polymerization conditions significantly influenced the catalytic behaviors of the complexes. The addition of PPh3 to the Co(II)-based systems enhanced the catalytic activity and switched the selectivity from cis-1,4 to 1,2 manner.

First-principles study of amorphousGa4Sb6Te3phase-change alloys

First-principles molecular dynamics simulations within the density functional theory framework were performed to generate amorphous models of the ${\mathrm{Ga}}_{4}{\mathrm{Sb}}_{6}{\mathrm{Te}}_{3}$ phase change alloy by quenching from the melt. We find that Ga-Sb and Ga-Te are the most abundant bonds with only a minor amount of Sb-Te bonds participating to the alloy network. Ga and four-coordinated Sb atoms present a tetrahedral-like geometry, whereas three-coordinated Sb atoms are in a pyramidal configuration. The tetrahedral-like geometries are similar to those of the crystalline phase of the two binary compounds GaTe and GaSb. A sizable fraction of Sb-Sb bonds is also present, indicating a partial nanoscale segregation of Sb. Despite the fact that the composition ${\mathrm{Ga}}_{4}{\mathrm{Sb}}_{6}{\mathrm{Te}}_{3}$ lies on the pseudobinary $\mathrm{Ga}\mathrm{Sb}\ensuremath{-}{\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ tie line, the amorphous network can be seen as a mixture of the two binary compounds GaTe and GaSb with intertwined elemental Sb.

Complexes of Antimony(III)

Lewis acidity of antimony(III) halides and their organo substituted derivatives is well known. The molecules SbX3 are good acceptor and a wide range of neutral complexes have been prepared but it seems antimony trichloride is a weak acceptor as compared to antimony pentachloride. The halide complexes are more interesting because of the part played by the lone pair in determining the stereochemistry where 1:1 complexes have trigonal bipyramidal and 1:2 complexes have square pyramidal configurations. Complexes of antimony trichloride with aromatic hydrocarbon are also known but the presence of organic group in a molecule reduces its capacity to form complexes.DOI: http://dx.doi.org/10.3126/av.v4i0.12357Academic Voices Vol.4 2014: 45-48

Structure and stability of BaTiSi₂O₇.

Due to their optical, photo-luminescence (PL), and afterglow properties, barium titanosilicates are compounds of great interest for functional materials and light-emitting devices. Among them, BaTiSi2O7 (BTS2) is certainly one of the most intriguing; it displays peculiar properties (e.g. PL orange emission) whose exhaustive explanation has been hampered to date by the lack of a structure model. In this work, BTS2 and the related compound BaTiSi4O11 (BTS4) were synthesized through conventional solid-state reaction methods. BTS2 invariably shows complex twinning patterns. Thus, its structure solution and Rietveld structure refinement were attempted using synchrotron powder diffraction. BTS2 was found to be an intergrowth of monoclinic and triclinic crystals. The monoclinic phase has the space group P21/n and unit cell a = 7.9836 (3), b = 10.0084 (4), c = 7.4795 (3) Å, and β = 100.321 (3)°, whereas the triclinic phase has the space group P\bar 1 and unit cell a = 7.99385 (4), b = 10.01017 (5), c = 7.47514 (3) Å, α = 90.084 (8), β = 100.368 (8) and γ = 89.937 (9)°. These lattices can be seen as a distortion of that of tetragonal synthetic β-BaVSi2O7 with Ti in place of V. The structure models obtained from this study confirm the presence of fivefold coordinated Ti atoms in a distorted pyramidal configuration. The proposed solution supports existing theories for the explanation of the PL orange colour in BTS2.

Revisiting pyramid compression to quantify flexoelectricity: A three-dimensional simulation study

Flexoelectricity is a universal property of all dielectrics by which they generate a voltage in response to an inhomogeneous deformation. One of the controversial issues in this field concerns the magnitude of flexoelectric coefficients measured experimentally, which greatly exceed theoretical estimates. Furthermore, there is a broad scatter amongst experimental measurements. The truncated pyramid compression method is one of the common setups to quantify flexoelectricity, the interpretation of which relies on simplified analytical equations to estimate strain gradients. However, the deformation fields in three-dimensional pyramid configurations are highly complex, particularly around its edges. In the present work, using three-dimensional self-consistent simulations of flexoelectricity, we show that the simplified analytical estimations of strain gradients in compressed pyramids significantly overestimate flexoelectric coefficients, thus providing a possible explanation to reconcile different estimates. In fact, the interpretation of pyramid compression experiments is highly nontrivial. We systematically characterize the magnitude of this overestimation, of over one order of magnitude, as a function of the truncated pyramid configuration. These results are important to properly characterize flexoelectricity, and provide design guidelines for effective electromechanical transducers exploiting flexoelectricity.