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Journal articles on the topic 'L2-Halo'

Author: Grafiati

Published: 4 June 2021

Last updated: 12 February 2022

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1

Chupin, Maxime, Thomas Haberkorn, and Emmanuel Trélat. "Low-thrust Lyapunov to Lyapunov and Halo to Halo missions with L2-minimization." ESAIM: Mathematical Modelling and Numerical Analysis 51, no. 3 (April 14, 2017): 965–96. http://dx.doi.org/10.1051/m2an/2016044.

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In this work, we develop a new method to design energy minimum low-thrust missions (L2-minimization). In the Circular Restricted Three Body Problem, the knowledge of invariant manifolds helps us initialize an indirect method solving a transfer mission between periodic Lyapunov orbits. Indeed, using the PMP, the optimal control problem is solved using Newton-like algorithms finding the zero of a shooting function. To compute a Lyapunov to Lyapunov mission, we first compute an admissible trajectory using a heteroclinic orbit between the two periodic orbits. It is then used to initialize a multiple shooting method in order to release the constraint. We finally optimize the terminal points on the periodic orbits. Moreover, we use continuation methods on position and on thrust, in order to gain robustness. A more general Halo to Halo mission, with different energies, is computed in the last section without heteroclinic orbits but using invariant manifolds to initialize shooting methods with a similar approach.

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2

Farquhar, Robert W., and David W. Dunham. "Use of Libration-Point Orbits for Space Observatories." International Astronomical Union Colloquium 123 (1990): 391–95. http://dx.doi.org/10.1017/s0252921100077332.

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AbstractThe Sun-Earth libration points, L1 and L2, are located 1.5 million kilometers from the Earth towards and away from the Sun. Halo orbits about these points have significant advantages for space observatories in terms of viewing geometry, thermal and radiation environment, and delta-V expediture.

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3

Dietrich, Ann, Kathryn Davis, and Jeffrey Parker. "Ascent trajectories from the lunar far-side to Earth–Moon L2 halo orbits." Advances in Space Research 56, no. 11 (December 2015): 2595–611. http://dx.doi.org/10.1016/j.asr.2015.09.030.

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4

Bhattacharjee, Rita. "Synthesis and Characterization of Palladium(II) Complexes with Substituted Dihydrobenzoimidazoquinazoline Derivatives." Mapana - Journal of Sciences 15, no. 2 (November 25, 2016): 17–32. http://dx.doi.org/10.12723/mjs.37.2.

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A series of palladium(II) halo complexes of the types[PdX2L2].nH2O {n = 0, X = Cl, L = L4and L6; X = Br, L = L3,L4, L5 and L6; n = 2, X = Cl, L = L3and L7, X = Br, L = L1};Pd2X4L2 {X = Cl, Br, L = L2 and L8} and Pd2X4L3 [X = Cl, L= L1; X = Br, L = L7] were prepared where L is 6-R-5,6-dihydrobenzoimidazo quinazoline (R-Diq; where R =phenyl: L1/furyl: L2/thiophenyl: L3/o- or phydroxyphenyl: L4, L5/o- or p-chlorophenyl: L6,L7/dimethylaminophenyl: L8and characterized byelemental analyses, molar conductivity measurements,TGA, infrared, electronic, NMR and mass spectraltechniques. Based on these studies, monomeric/dimericstructure with a square planar geometry around the metalion was proposed for these complexes. Anti-microbialactivity for some of the synthesized complexes wereinvestigated.Keywords: dihydrobenzoimidazoquinazoline, palladium(II),thermal analysis, mass spectra, biological activity.

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5

Shirobokov, M. G., and S. P. Trofimov. "Low-Thrust Transfers to Lunar Orbits from Halo Orbits Around Lunar Libration Points L1 and L2." Cosmic Research 58, no. 3 (May 2020): 181–91. http://dx.doi.org/10.1134/s0010952520030065.

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6

Pushparaj, Nishanth, and Ram Krishan Sharma. "Oblateness Effect of Saturn on Halo Orbits of L1 and L2 in Saturn-Satellites Restricted Three-Body Problem." International Journal of Astronomy and Astrophysics 06, no. 04 (2016): 347–77. http://dx.doi.org/10.4236/ijaa.2016.64029.

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7

Lee, Sang-Cherl, Hae-Dong Kim, Do-Chul Yang, Dong-Hyun Cho, Jeong-Heum Im, Tae-Soo No, Seungkeun Kim, and Jinyoung Suk. "Comparison of Global Optimization Methods for Insertion Maneuver into Earth-Moon L2 Quasi-Halo Orbit Considering Collision Avoidance." International Journal of Aeronautical and Space Sciences 15, no. 3 (September 30, 2014): 267–80. http://dx.doi.org/10.5139/ijass.2014.15.3.267.

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8

Noronha, Henrique Gomes, Olavo Biraghi Letaif, Ivan Dias da Rocha, Alexandre Sadao Iutaka, Alexandre Fogaça Cristante, Reginaldo Perilo de Oliveira, and Tarcísio Eloy Pessoa de Barros Filho. "Fraturas do côndilo occipital: atualização da experiência em nosso serviço e revisão da literatura." Coluna/Columna 12, no. 2 (2013): 157–59. http://dx.doi.org/10.1590/s1808-18512013000200014.

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Apresentamos neste trabalho a casuística de fraturas de côndilo occipital diagnosticada e tratada em nosso serviço nos últimos 10 anos. O presente estudo dá continuidade ao levantamento epidemiológico já realizado no período de 1993 a 2000. No período de 2001 a 2011, foram diagnosticados seis casos de fraturas de côndilo occipital e todos eles foram tratados de forma conservadora, exceto um, no qual se colocou um halo craniano inicialmente. Nos cinco casos tratados de modo conservador, observaram-se bons resultados, com estabilidade do segmento nas radiografias funcionais, ausência de limitação de movimento e ausência de dor. O paciente que foi tratado com halo apresentava tetraplegia parcial FRANKEL C e fraturas associadas (C5, C6, L1 e L2) e não apresentou melhora do quadro neurológico, verificando-se limitação do movimento cervical. Destacamos ainda a importância da investigação ativa de lesões na transição occipitocervical, principalmente nos casos decorrentes de trauma de alta energia, pois além das implicações clínicas da detecção precoce da fratura, o melhor emprego dos exames subsidiários tem sido um fator relevante para o aumento da incidência de fraturas do côndilo occipital. Como é historicamente relatado, o tratamento conservador ainda é eficaz e com baixo índice de complicações, e o tratamento cirúrgico deve ser indicado em casos com instabilidade definida.

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9

Buzzoni, Alberto, Giuseppe Altavilla, and Silvia Galleti. "Optical tracking of deep-space spacecraft in Halo L2 orbits and beyond: The Gaia mission as a pilot case." Advances in Space Research 57, no. 7 (April 2016): 1515–27. http://dx.doi.org/10.1016/j.asr.2016.01.003.

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10

Kafafy, R., and Y. Cao. "Modelling ion propulsion plume interactions with spacecraft in formation flight." Aeronautical Journal 114, no. 1157 (July 2010): 417–26. http://dx.doi.org/10.1017/s0001924000003894.

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Abstract This paper presents a simulation study of ion thruster plume effects on formation flying spacecraft. Two formation flight applications using micro-ion propulsion are considered: an L2-Halo orbit interferometer formation and a LEO micro-satellite formation. Worst case scenarios in both missions have been investigated. We focus our study on thruster configurations resulting in possible indirect plume impingement on satellites outside of the direct impingement zone. Indirect impingement which cannot be predicted except through plasma simulation or in-flight measurements might expose critical spacecraft elements such as optical sensors to a harsh contamination environment. A high-fidelity electrostatic plasma simulation code for parallel computing platforms was used in the study. In our study, we found that using miniature scale ion propulsion in both formation missions creates a very low charge-exchange plasma environment which results in tolerable contamination environment for other spacecraft in the formation.

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11

Han, Xiao, Weixiang Sun, Yong Qiu, Leilei Xu, Shifu Sha, Benlong Shi, Huang Yan, Zhen Liu, and Zezhang Zhu. "Halo Gravity Traction Is Associated with Reduced Bone Mineral Density of Patients with Severe Kyphoscoliosis." BioMed Research International 2016 (2016): 1–7. http://dx.doi.org/10.1155/2016/8056273.

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Background. Halo gravity traction (HGT) is one of the most commonly used perioperative techniques for the treatment of severe kyphoscoliosis. This study was to explore the influence of HGT on the BMD of these patients.Methods. Patients with severe kyphoscoliosis treated by preoperative HGT for at least 2 months were included. Patients’ BMD were assessed by dual-energy X-ray absorptiometry at lumbar spine (LS, L2–L4) and femur neck (FN) of the nondominant side. The weight and duration of traction, as well as baseline characteristics, were recorded.Results. Twenty patients were recruited. The average traction duration was77.9±13.0days while the mean traction weight was39.9%±11.1% of total body weight. Remarkable decrease of BMD was observed at LS of 17 (85%) patients and at FN of 18 (90%) patients. After HGT, 75% of patients were found to have osteoporosis, the incidence of which was significantly higher than that before HGT (35%). The correlation analysis revealed BMD reduction was only significantly correlated with the traction duration.Conclusions. The current study showed that preoperative HGT can have obvious impact on the BMD. The BMD reduction is associated with traction duration, suggesting that long traction duration may bring more bone mineral loss.

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12

Shaykhutdinov, A. R., and V. I. Kostenko. "Prospects for Using the Halo-Orbit in the Vicinity of the L2 Libration Point of the Sun–Earth System for the Ground-Space Millimetron Radio Interferometer." Cosmic Research 58, no. 5 (September 2020): 393–401. http://dx.doi.org/10.1134/s0010952520050093.

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13

Grando, Caroline Pietroski, Yasmin Carla Bianchini, Neiva Aparecida Grazziotin, Pauline Mastella Lang, Simone Tuchtenhagen, and Bruno Emmanuelli. "Efeito in vitro da laserterapia e da terapia fotodinâmica na redução de bactérias presentes em canais radiculares." Revista da Faculdade de Odontologia - UPF 25, no. 2 (June 1, 2021): 184–90. http://dx.doi.org/10.5335/rfo.v25i2.10645.

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Este estudo tem por objetivo verificar in vitro o efeito bactericida da laserterapia e da terapia fotodinâmica com laser de baixa potência (660 nm e 808 nm) em bactérias presentes nos canais radiculares. Métodos: foram preparadas 60 placas de Petri com bactérias: 20 placas com Enterococcus faecalis, 20 placas com Staphylococcus aureus e 20 com Pseudomonas aeruginosa. Aleatoriamente, dividiu-se cada grupo em 10 subgrupos (duas placas cada): três subgrupos tratados com laserterapia 660 nm em doses de 150, 225 e 300J/ cm², três subgrupos tratados com terapia fotodinâmica (azul de metileno 0,2% e laser 660 nm) em doses de 150, 225 e 300J/cm²; um subgrupo tratado com laserterapia 808 nm na dose de 225J/cm², um subgrupo com terapia fotodinâmica e laser 808 nm, em dose 225J/cm²; um subgrupo tratado apenas com fotossensibilizante (FS), e um não tratado (controle). Os tratados com laserterapia e terapia fotodinâmica foram irradiados uma única vez e incubados por 24 horas. Os últimos dois não receberam irradiação. As culturas foram analisadas visualmente para verificação do halo de inibição. Nos grupos submetidos somente à laserterapia, para o grupo FS e para o grupo controle, não foram observados halos de inibição, já onde houve aplicação da TFD, tanto com L1 quanto com L2, observaram-se halos de inibição em todas as espécies bacterianas estudadas. Conclui-se que a laserterapia, não produziu efeitos bactericidas e/ou bacteriostáticos, enquanto a terapia fotodinâmica nos dois comprimentos de onda produziu halos significativos de inibição de crescimento nas três bactérias do estudo.

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14

Vargas, Luis C., Karoline M. Gilbert, Marla Geha, Erik J. Tollerud, Evan N. Kirby, and Puragra Guhathakurta. "[α/Fe] ABUNDANCES OF FOUR OUTER M31 HALO STARS." Astrophysical Journal 797, no. 1 (November 20, 2014): L2. http://dx.doi.org/10.1088/2041-8205/797/1/l2.

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15

Rejkuba, M., W. E. Harris, L. Greggio, G. L. H. Harris, H. Jerjen, and O. A. Gonzalez. "TRACING THE OUTER HALO IN A GIANT ELLIPTICAL TO 25 R eff." Astrophysical Journal 791, no. 1 (July 22, 2014): L2. http://dx.doi.org/10.1088/2041-8205/791/1/l2.

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16

Bucchioni, Giordana, and Mario Innocenti. "Rendezvous in Cis-Lunar Space near Rectilinear Halo Orbit: Dynamics and Control Issues." Aerospace 8, no. 3 (March 8, 2021): 68. http://dx.doi.org/10.3390/aerospace8030068.

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The paper presents the development of a fully-safe, automatic rendezvous strategy between a passive vehicle and an active one orbiting around the Earth–Moon L2 Lagrangian point. This is one of the critical phases of future missions to permanently return to the Moon, which are of interest to the majority of space organizations. The first step in the study is the derivation of a suitable full 6-DOF relative motion model in the Local Vertical Local Horizontal reference frame, most suitable for the design of the guidance. The main dynamic model is approximated using both the elliptic and circular three-body motion, due to the contribution of Earth and Moon gravity. A rather detailed set of sensors and actuator dynamics was also implemented in order to ensure the reliability of the guidance algorithms. The selection of guidance and control is presented, and evaluated using a sample scenario as described by ESA’s HERACLES program. The safety, in particular the passive safety, concept is introduced and different techniques to guarantee it are discussed that exploit the ideas of stable and unstable manifolds to intrinsically guarantee some properties at each hold-point, in which the rendezvous trajectory is divided. Finally, the rendezvous dynamics are validated using available Ephemeris models in order to verify the validity of the results and their limitations for future more detailed design.

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17

Kim, Hyunwoo. "Effects of rating criteria order on the halo effect in L2 writing assessment: a many-facet Rasch measurement analysis." Language Testing in Asia 10, no. 1 (November 10, 2020). http://dx.doi.org/10.1186/s40468-020-00115-0.

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Abstract The halo effect is raters’ undesirable tendency to assign more similar ratings across rating criteria than they should. The impacts of the halo effect on ratings have been studied in rater-mediated L2 writing assessment. Little is known, however, about the extent to which rating criteria order in analytic rating scales is associated with the magnitude of the group- and individual-level halo effects. Thus, this study attempts to examine the extent to which the magnitude of the halo effect is associated with rating criteria order in analytic rating scales. To select essays untainted by the effects of rating criteria order, a balanced Latin square design was implemented along with the employment of four expert raters. Next, 11 trained novice Korean raters rated the 30 screened essays with respect to the four rating criteria in three different rating orders: standard-, reverse-, and random-order. A three-facet rating scale model (L2 writer ability, rater severity, criterion difficulty) was fitted to estimate the group- and individual-level halo effects. The overall results of this study showed that the similar magnitude of the group-level halo effect was detected in the standard- and reverse-order rating rubrics while the random presentation of rating criteria decreased the group-level halo effect. A theoretical implication of the study is the necessity of considering rating criteria order as a source of construct-irrelevant easiness or difficulty when developing analytic rating scales.

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18

Marsola, Thiago César Lousada, Sandro da Silva Fernandes, and José Manoel Balthazar. "Stationkeeping controllers for Earth–Moon L1 and L2 libration points halo orbits." Journal of the Brazilian Society of Mechanical Sciences and Engineering 43, no. 7 (June 15, 2021). http://dx.doi.org/10.1007/s40430-021-03071-9.

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19

Pushparaj, Nishanth, and Ram Krishan Sharma. "Halo Orbits at Sun-Mars L1, L2 in the Photogravitational Restricted Three-Body Problem with Oblateness." Advances in Astrophysics 2, no. 1 (February 1, 2017). http://dx.doi.org/10.22606/adap.2017.21005.

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20

Rui, Zhou. "Method for calculating the perturbed trajectoryof a two-impulse flight between the halo orbit in the vicinity of the L2 point of the Sun — Earth systemand the near-lunar orbit." Engineering Journal: Science and Innovation, no. 11 (107) (November 2020). http://dx.doi.org/10.18698/2308-6033-2020-11-2033.

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The paper introduces a new method for solving the problem of calculating the perturbed trajectory of a two-impulse flight between a near-lunar orbit and a halo orbit in the vicinity of the L2 point of the Sun — Earth system. Unlike traditional numerical methods, this method has better convergence. Accelerations from the gravitational forces of the Earth, the Moon and the Sun as point masses and acceleration from the second zonal harmonic of the geopotential are taken into account at all sections of the trajectory. The calculation of the flight path is reduced to solving a two-point boundary value problem for a system of ordinary differential equations. The developed method is based on the parameter continuation method and does not require the choice of an initial approximation for solving the boundary value problem. The last section of the paper provides examples and results of the analysis based on this method.

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21

"Using Generalizability Theory in the Evaluation of L2 Writing 一般化可能性理論を用いた高校生の自由英作文評価の検討." JALT Journal 27, no. 2 (November 1, 2005): 169. http://dx.doi.org/10.37546/jaltjj27.2-2.

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This paper aims to investigate the characteristics of the evaluation of L2 writing—particularly free English compositions by Japanese high school students—using Generalizability Theory (G theory). Although usually considered to be a difficult topic to examine, the evaluation of free compositions can be thoroughly investigated by using G theory. It enables researchers to provide sufficient information regarding the main effects and the interactions of complicated factors within an evaluation by examining its measurement errors. I focused on two factors (more specifically, facets) in order to obtain the data on the evaluation of free compositions. These facets were: (a) the raters—10 high school teachers (expert raters) teaching English at a national high school and two public high schools, and six university students (novice raters) studying English language education at a national university; and (b) the rating scales, which were Jacobs, Zinkgraf, Wormuth, Hartfiel, and Hughey’s (1981) ESL Composition Profile, and a modified version of Kantenbetsu Hyoka of the National Institute for Educational Policy Research (2002). Using these scales, the raters (expert and novice raters) evaluated free compositions written by 20 high school students studying at a national high school in the Chugoku region of Japan. The type of G theory design used in this paper is termed a two-facet crossed design (all the raters evaluate all the compositions using all the items of the rating scales). Studies using G theory are usually comprised of two substudies: a Generalizability Study (G study) and a Decision Study (D study). A G study investigates the manner in which the facets and their interactions (termed as sources of variance) affected the evaluation results by estimating the magnitude of variance components. A D study investigates the degree of reliability of the evaluation by examining generalizability coefficients, which correspond to classical test theory’s reliability coefficients, using simulations that vary the number of raters or items of the rating scales. The G study in this paper dealt with seven sources of variance—persons (p), raters (r), rating scale items (i), and their interactions (p x r, p x i, r x i, and p x r x i). The D study in this paper particularly focused on varying the number of raters for simulations. Several observations resulting from both the G study and the D study were as follows: (a) there was a halo effect tendency in the evaluations by the expert raters because the estimated variance components of the interactions of the sources of variance p x r and r x i were large; (b) the novice raters’ rating experience was insufficient to perform reliable evaluations because the generalizability coefficients of both of the rating scales were low, while the estimated variance component of the interaction of the sources of variance p x r x i, which is regarded as unmeasured error, was large; and (c) the ESL Composition Profile was a more reliable rating scale than the Kantenbetsu Hyoka as shown by the D study simulation results. This paper presentsseveral pedagogical implications based on the results with reference to improvement in the evaluation of free compositions. In particular, I have presented possible methods of diagnostically utilizing the results of G theory to develop and modify the rating scales, and to train the raters.

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