Quaternion methods and models of regular celestial mechanics and astrodynamics

This paper is a review, which focuses on our work, while including an analysis of many works of other researchers in the field of quaternionic regularization. The regular quaternion models of celestial mechanics and astrodynamics in the Kustaanheimo-Stiefel (KS) variables and Euler (Rodrigues-Hamilton) parameters are analyzed. These models are derived by the quaternion methods of mechanics and are based on the differential equations of the perturbed spatial two-body problem and the perturbed spatial central motion of a point particle. This paper also covers some applications of these models. Stiefel and Scheifele are known to have doubted that quaternions and quaternion matrices can be used efficiently to regularize the equations of celestial mechanics. However, the author of this paper and other researchers refuted this point of view and showed that the quaternion approach actually leads to efficient solutions for regularizing the equations of celestial mechanics and astrodynamics.This paper presents convenient geometric and kinematic interpretations of the KS transformation and the KS bilinear relation proposed by the present author. More general (compared with the KS equations) quaternion regular equations of the perturbed spatial two-body problem in the KS variables are presented. These equations are derived with the assumption that the KS bilinear relation was not satisfied. The main stages of the quaternion theory of regularizing the vector differential equation of the perturbed central motion of a point particle are presented, together with regular equations in the KS variables and Euler parameters, derived by the aforementioned theory. We also present the derivation of regular quaternion equations of the perturbed spatial two-body problem in the Levi-Civita variables and the Euler parameters, developed by the ideal rectangular Hansen coordinates and the orientation quaternion of the ideal coordinate frame.This paper also gives new results using quaternionic methods in the perturbed spatial restricted three-body problem.

The impact of lead users on innovation success

Purpose The purpose of this paper is to study the impact of lead users (LUs) on innovation success by proposing and validating an integrative model that links LUs, innovation success and knowledge sharing (KS) variables. Design/methodology/approach The authors research is quantitative in nature and data were collected through a survey conducted among 30 information technology Tunisian companies. The authors preliminary analysis was explored using the “SPSS” software and processed through exploratory factor analysis and regression analysis methods. Findings Results showed that LUs who possess advanced skills and valuable knowledge can contribute to enhance new successful innovations, and hence, enable companies to gain short and long-term profits. Besides, the authors confirmed that the impact of LUs on innovation success is mediated by the “KS” behavior. Practical implications An integrative framework that links LUs, innovation success and a third variable called KS is presented to see beyond the intended importance of this type of user regarding the development of new innovations. Originality/value The paper offers new insights to the topic of LUs by emphasizing the role of “KS” variable in strengthening the LUs – innovation success relationship.

Khorana risk score: Is the body mass index a predictable factor for thromboembolism in European countries? A retrospective analysis.

e19612 Background: Five variables (site of cancer, platelet count, haemoglobin level, leukocyte count, and body mass index-BMI) define the Khorana risk score (KS), predicting the high (≥ 3), the moderate (1-2) and the low (0) risk of thromboembolic events (TEs) in cancer outpatients. Nadroparin has been demonstrated to reduce the incidence of TEs by about 50% in cancer outpatients receiving chemotherapy (PROTECHT study) and patients receiving chemotherapy including gemcitabine, platinum analogues or their combination are at higher risk of TEs. Methods: 378 patients enrolled in the PROTECHT study didn’t receive thromboprophylaxis (placebo group) and were evaluable for the KS. The aim of this retrospective analysis was to assess the distribution of the five KS variables and if the replacing of BMI variable, in the KS, with a chemotherapy variable (administration of platinum compound or gemcitabine added 1point and their association 2points) in a PROTECHT score (PrS) could better predict high risk patients. A receiver operating characteristic (ROC) curve has been used to assess the accuracy of both scores. Results: Among patients the five KS variables were distributed as follow: 15% of stomach/pancreas cancer (2points), 33% with lung/gynecologic cancer (1point), 24% with platelet count of ≥350x10^9/L, 7.9% hemoglobin <10g/dL , 14.3% leukocyte count >11x10^9/L (1point each variable) and only 1.3% with BMI ≥ 35 (1point). 15 TEs occurred in the 378 pts, below the TEs distribution according to KS and PrS (see table). The area under the ROC curve was larger with PrS in comparison with KS (0.70 and 0.65 respectively). Conclusions: BMI ≥ 35 seems not to be a predictable factor for TEs in European cancer patients and the use of a chemotherapy variable could be more useful to identify patient at high risk of TE. A formal study is needed to evaluate which score could have a higher predictability to identify high risk patients for TEs. [Table: see text]

Effects of radiation pressure and earth’s oblatness on high altitude artificial satellite orbit

This paper is devoted to study the effects of radiation pressure together with tesseral and zonal harmonics on the high altitude artificial satellites orbits. The equations of motion were regularized by using the KS variables and the problem was solved numerically using the fourth order of Runge Kutta method. A numerical testing was performed on Lageos-1 satellite in order to analyze its orbital changes due to effects of both radiation pressure and Earth's oblateness.

Effects of radiation pressure and earth’s oblatness on high altitude artificial satellite orbit

This paper is devoted to study the effects of radiation pressure together with tesseral and zonal harmonics on the high altitude artificial satellites orbits. The equations of motion were regularized by using the KS variables and the problem was solved numerically using the fourth order of Runge Kutta method. A numerical testing was performed on Lageos-1 satellite in order to analyze its orbital changes due to effects of both radiation pressure and Earth's oblateness.

Effects of radiation pressure and earth’s oblatness on high altitude artificial satellite orbit

This paper is devoted to study the effects of radiation pressure together with tesseral and zonal harmonics on the high altitude artificial satellites orbits. The equations of motion were regularized by using the KS variables and the problem was solved numerically using the fourth order of Runge Kutta method. A numerical testing was performed on Lageos-1 satellite in order to analyze its orbital changes due to effects of both radiation pressure and Earth's oblateness.