On the minimum orbital intersection distance computation: a new effective method

The computation of the Minimum Orbital Intersection Distance (MOID) is an old, but increasingly relevant problem. Fast and precise methods for MOID computation are needed to select potentially hazardous asteroids from a large catalogue. The same applies to debris with respect to spacecraft. An iterative method that strictly meets these two premises is presented.Comment: 13 pages, 10 figures, article accepted for publication in MNRA

Prototipo de sistema integrado de gestión académica para la Institución Educativa Privada Sagrado Corazón de Jesús de Casa Grande utilizando la metodología RUP y el Framework Cake PHP

Este trabajo consiste en el desarrollo de un prototipo de Sistema Integrado de la Gestión Académica para la Institución Educativa Privada “Sagrado Corazón de Jesús” de la ciudad de Casa Grande, el cual consiste es únicamente un prototipo de un sistema de información para controlar y gestionar los procesos académicos básicos de la institución, haciendo que los procesos sean más eficientes reduciendo tiempo y costo para beneficio de todos los usuarios de las distintas áreas. Actualmente, la Institución “Sagrado Corazón de Jesús” carece de un sistema de información que le permita gestionar eficientemente los procesos académicos que realiza, tales como admisión y matriculas, programación de horarios y clases, asistencias, gestión de egresados y promociones, etc realizando mayormente el proceso manualmente y guardando parte de la información en archivos separados como en Excel y Word, los cuales no permiten obtener eficientemente la información para la toma de decisiones La propuesta es un prototipo del sistema de información que podrá solucionar esos problemas, el cual se desarrollará usando la metodología RUP y el framework CakePHP, y se encargará de la gestión de los procesos académicos importantes de la institución. Debido a motivos de tiempo y estudios, el investigador sólo trabajará hasta esa fase, porque no será un sistema funcionando al 100%. Luego de desarrollar el prototipo usando RUP y CakePHP, se obtuvo un prototipo que cumple al menos con la mayoría de expectativas que tienen los clientes (el colegio y sus integrantes administrativos), lo cuales se sienten conformes con ese prototipo, el cual, de convertirse en un sistema completo, sería aún más confortante para ellos. De antemano, pido disculpas por cualquier error que pueda encontrarse en el presente trabajo, puesto a que no ha sido de manera intencional, sino errores propios que cualquier ser humano puede cometer en cualquier situación.This work consists of the development of a prototype of Integrated System of the Academic Management for the Educational Private Institution “Sagrado Corazón de Jesús” from Casa Grande city, which consists it is only a prototype of a system of information to control and to manage the academic basic processes of the institution, doing that the processes are more efficient reducing time and cost for benefit of all the users of the different areas. Currently, the Institution lacks a system of information that allows him to manage efficiently the academic processes that it realizes, such as admission and you register, programming of schedules and classes, assistance, management of gone away and promotions, etc realizing mainly the process manually and keeping part of the information in files separated like in Excel and Word, which do not allow to obtain efficiently the information for the decision making. The proposal is a prototype of the information system that will be able to solve these problems, which will be developed using the methodology RUP and the framework CakePHP, and will be responsible for the management of the processes leading academics of the institution. Due to reasons of time and studies, the researcher will only work up to that stage, because it will not be a system running at 100%. After developing the prototype using RUP and CakePHP, was obtained a prototype that meets the majority of expectations that have clients (the school and its members administrative), they feel they are in conformity with that prototype, which become a complete system, would be even more comforting to them. In advance, I apologize for any errors that may be found in the present work, since it has not been intentional, but errors that any human being can commit in any situation.Tesi

Un Método de Perturbaciones Especiales en la Dinámica de Tethers

En la simulación dinámica de tethers se usan "bead models" que discretizan el cable mediante "cuentas" distribuidas en toda su longitud y cuya evolución temporal se aborda numéricamente. Dependiendo de la precisión deseada, el número de partículas oscila, típicamente, entre 5 y 50. En ocasiones la simulación se extiende sobre tiempos largos (varios años). La complejidad de las interacciones del cable con el medio espacial exige optimizar, en tiempo y precisión, los propagadores que constituyen el núcleo central del proceso. El "método de perturbaciones especiales" objeto de este artículo conjuga sencillez de programación, rapidez y precisión, y permite propagar la órbita de cualquier partícula material. Describe la evolución de ciertos "elementos orbitales", constantes del problema "no perturbado}"que, en el "perturbado", evolucionan en la escala de tiempos impuesta por la perturbación. Puede usarse con cualquier tipo de órbita, está libre de singularidades asociadas a inclinación y/o excentricidad pequeñas, y el uso de parámetros de Euler le confiere robustez

PENGARUH AUDIT INTERNAL DAN KUALITAS SISTEM INFORMASI AKUNTANSI PENJUALAN TERHADAP EFEKTIVITAS PENJUALAN (Studi Pada 3 Perusahaan BUMN Sektor Jasa di Kota Bandung)

Abstrak Penelitian ini bertujuan untuk mengetahui pengaruh audit internal, dan kualitas sistem informasi akuntansi penjualan terhadap efektivitas penjualan secara parsial maupun secara simultan. Penelitian menggunakan pendekatan kuantitatif. Teknik pengumpulan data yang digunakan adalah dengan menggunakan instrument kuesioner. Penelitian ini menggunakan data primer. Subjek penelitian ini adalah tiga (3) Persusahaan BUMN Sektor Jasa di Kota Bandung dan objek penelitiannya yaitu audit internal, kualitas sistem informasi akuntansi penjualan, dan efektivitas penjualan. Teknik pengambilan sampel yang digunakan adalah simple random sampling dengan jumlah responden sebanyak 57 orang. Analisis statistik yang digunakan dalam penelitian ini adalah uji asumsi klasik, analisis regresi, korelasi, analisis koefisien determinasi dan uji hipotesis yang diolah dengan menggunakan program SPSS 23,0 for windows. Hasil penelitian menunjukkan bahwa (1) secara parsial pengaruh audit internal sebesar 25,90% dan kualitas sistem informasi akuntansi sebesar 33% terhadap efektivitas. (2) secara simultan audit internal dan kualitas sistem informasi akuntansi penjualan terhadap efektivitas penjualan sebesar 58,9%, sedangkan sisanya sebesar 41,1% merupakan pengaruh faktor lain di luar variabel independen yang diteliti. Seperti Efektivitas Pengendalian Internal, Pengetahuan Akuntansi, Operasi Penjualan, Sistem Pengendalian Intern Penjualan, Efektivitas Pengendalian Piutang. Kata Kunci: Audit Internal, Kualitas Sistem Informasi Akuntansi Penjualan, Efektivita

Reduction of Saturn Orbit Insertion Impulse using Deep-Space Low Thrust

Orbit insertion at Saturn requires a large impulsive manoeuver due to the velocity difference between the spacecraft and the planet. This paper presents a strategy to reduce dramatically the hyperbolic excess speed at Saturn by means of deep-space electric propulsion. The interplanetary trajectory includes a gravity assist at Jupiter, combined with low-thrust maneuvers. The thrust arc from Earth to Jupiter lowers the launch energy requirement, while an ad hoc steering law applied after the Jupiter flyby reduces the hyperbolic excess speed upon arrival at Saturn. This lowers the orbit insertion impulse to the point where capture is possible even with a gravity assist with Titan. The control-law algorithm, the benefits to the mass budget and the main technological aspects are presented and discussed. The simple steering law is compared with a trajectory optimizer to evaluate the quality of the results and possibilities for improvement

Asymptotic Solution for the Current Profile of Passive Bare Electrodynamic Tethers

A relatively high-accuracy analytical solution for the current and potential profile along a passive bare electrodynamic tether is provided using perturbation theory. An ad hoc nondimensional formulation of the governing local bias and orbital motion limited current collection equations allows one to approach the problem with a perturbation technique in which a parameter, epsilon, quantifies the influence of ohmic effects on the final solution. For the case of small ohmic effects an approximate solution is obtained with a third-order expansion. Conversely, the case of dominant ohmic effects is treated based on an extension of the exact analytical solution available for the particular case of zero load and negligible potential drop at the cathodic end of the tether. After computing the analytical current and potential profile the maximum and average current, the Lorentz force and torque, as well as the optimum load impedance for maximum power generation are obtained. When compared with the exact, numerically-computed solution an accuracy of better than5%is achieved for the computation of the average current across the full parameter space. The error with respect to the generated power becomes negligible when the load impedance is set to the optimum value, while it can grow to a maximum of about 30% for the less relevant case in which the load impedance of the power generation system is badly mismatched. The results, which are valid for a general rectilinear passive electrodynamic tether with constant cross section satisfying orbital motion limited theory and irrespective of the particular orbit configuration, will be of aid in the design and analysis of space missions involving bare electrodynamic tethers

Orbital Injection of the SEDSAT Satellite: Tethered Systems Dynamics and Flight Data Analysis

This report deals with the following topics which are all related to the orbital injection of the SEDSAT satellite: Dynamics and Stability of Tether Oscillations after the First Cut. The dynamics of the tether after the first cut (i.e., without the Shuttle attached to it) is investigated. The tether oscillations with the free end are analyzed in order to assess the stability of the rectilinear configuration in between the two tether cuts; analysis of Unstable Modes. The unstable modes that appear for high libration angles are further investigated in order to determine their occurrences and the possible transition from bound librations to rotations; Orbital Release Strategies for SEDSAT. A parametric analysis of the orbital decay rate of the SEDSAT satellite after the two tether cuts has been carried out as a function of the following free parameters: libration amplitude at the end of deployment, deviation angle from LV at the first cut, and orbital anomaly at the second cut. The values of these parameters that provide a minimum orbital decay rate of the satellite (after the two cuts) have been computed; and Dynamics and Control of SEDSAT. The deployment control law has been modified to cope with the new ejection velocity of the satellite from the Shuttle cargo bay. New reference profiles have been derived as well as new control parameters. Timing errors at the satellite release as a function of the variations of the initial conditions and the tension model parameters have been estimated for the modified control law

The ion beam shepherd: A new concept for asteroid deflection

A novel slow push asteroid deflection strategy has been recently proposed in which an Earth threatening asteroid can be deflected by exploiting the momentum transmitted by a collimated beam of quasi-neutral plasma impinging against the asteroid surface. The beam can be generated with state-of-the art ion engines from a hovering spacecraft with no need for physical attachment or gravitational interaction with the celestial body. The spacecraft, placed at a distance of a few asteroid diameters, would need an ion thruster pointed at the asteroid surface as well as a second propulsion system to compensate for the ion engine reaction and keep the distance between the asteroid and the shepherd satellite constant throughout the deflection phase. A comparison in terms of required spacecraft mass per total imparted deflection impulse shows that the method outperforms the gravity tractor concept by more than one order of magnitude for asteroids up to about 200 m diameter. The two methods would yield comparable performance for asteroids larger than about 2 km

Mobile Personal Healthcare System for Non-Invasive, Pervasive and Continuous Blood Pressure Monitoring: A Feasibility Study

Background: Smartphone-based blood pressure (BP) monitor using photoplethysmogram (PPG) technology has emerged as a promising approach to empower users with self-monitoring for effective diagnosis and control ofhypertension (HT). Objective: This study aimed to develop a mobile personal healthcare system for non-invasive, pervasive, and continuous estimation of BP level and variability to be user-friendly to elderly. Methods: The proposed approach was integrated by a self-designed cuffless, calibration-free, wireless and wearable PPG-only sensor, and a native purposely-designed smartphone application using multilayer perceptron machine learning techniques from raw signals. We performed a pilot study with three elder adults (mean age 61.3 ± 1.5 years; 66% women) to test usability and accuracy of the smartphone-based BP monitor. Results: The employed artificial neural network (ANN) model performed with high accuracy in terms of predicting the reference BP values of our validation sample (n=150). On average, our approach predicted BP measures with accuracy \u3e90% and correlations \u3e0.90 (P \u3c .0001). Bland-Altman plots showed that most of the errors for BP prediction were less than 10 mmHg. Conclusions: With further development and validation, the proposed system could provide a cost-effective strategy to improve the quality and coverage of healthcare, particularly in rural zones, areas lacking physicians, and solitary elderly populations

Evaluation of comparative advantages in the profitability and competitiveness of the small-scale dairy system of Tulancingo Valley, Mexico

This article combines a Policy Analysis Matrix with a sensitivity and poverty line analysis with the objective of evaluating the economic contribution of comparative advantages to the private profitability and competitiveness of small-scale dairy systems. For 1 year, socioeconomic data were collected from 82 farms selected from four strata via statistical sampling. Two scenarios were established to determine the quantitative contribution of comparative advantages: (1) a simulated scenario, which accounted for the cost of purchasing the total food and the opportunity cost of the family labour force (FLF), and (2) an actual production scenario, which accounted for the cost of producing food and eliminating the payment of the FLF and included other incom