Nonequilibrium in a low power arcjet nozzle

Emission spectroscopy measurements were made of the plasma flow inside the nozzle of a 1 kW class arcjet thruster. The thruster propellant was a hydrogen-nitrogen mixture used to simulate fully decomposed hydrazine. The 0.25 mm diameter holes were drilled into the diverging section of the tungsten thruster nozzle to provide optical access to the internal flow. Atomic electron excitation, vibrational, and rotational temperatures were determined for the expanding plasma using relative line intensity techniques. The atomic excitation temperatures decreased from 18,000K at a location 3 mm downstream of the constrictor to 9,000K at a location 9 mm from the constrictor, while the molecular vibrational and rotational temperatures decreased from 6,500K to 2,500K and from 8,000K to 3,000K, respectively, between the same locations. The electron density measured using hydrogen H line Stark broadening decreased from about 10(exp 15) cm(-3) to about 2 times 10(exp 14) cm(-3) during the expansion. The results show that the plasma is highly nonequilibrium throughout the nozzle, with most relaxation times equal or exceeding the particle residence time

Mathematical modeling and simulation of human motion using 3-dimensional, multi-segment coupled pendulum system : derivation of a generalized formula for equations of motion

The use of mathematical models to investigate the dynamics of human movement relies on two approaches: forward dynamics and inverse dynamics. In this investigation a new modeling approach called the Boundary Method is outlined. This method addresses some of the disadvantages of both the forward and the inverse approach. The method yields as output both a set of potential movement solutions to a given motor task and the net muscular impulses required to produce those movements. The input to the boundary method is a finite and adjustable number of critical target body configurations. In each phase of the motion that occurs between two contiguous target configurations the equations of motion are solved in the forward direction as a two point ballistic boundary value problem. In the limit as the number of specified target configurations increases the boundary method approaches a stable algorithm for doing inverse dynamics. A 3-Dimensional, multi-segment coupled pendulum system, that mathematically models human motion, will be presented along with a derivation of a generalized formula that constructs the equations of motion for this model. The suggested model is developed to utilize the boundary method. The model developed in this thesis will lead to a long rang goal, which is the development of a diagnostic tool for any motion analysis laboratory that will answer the question of finding optimal movement patterns, to prevent injury and improve performance in human subjects

Analisis Kesalahan Siswa Dalam Menyelesaikan Soal Persamaan Garis Ditinjau Dari Self Regulated Learning (SRL).

Tujuan penelitian ini adalah untuk mengetahui jenis dan faktor penyebab siswa melakukan kesalahan dalam menyelesaikan soal persamaan garis lurus ditinjau dari self regulated learning (SRL) kelas VIII.2 SMPN 39 Padang. Metode penelitian ini adalah deskriptif kualitatif. Subjek penelitian adalah 32 siswa dari kelas VIII.2 SMPN 39 Padang. Instrumen yang digunakan berupa angket SRL, soal tes dan lembar wawancara. Hasil penelitian  menunjukkan bahwa siswa dengan SRL tinggi tidak melakukan kesalahan, sedangkan siswa dengan SRL sedang melakukan setidaknya satu kesalahan dari ketiga indikator kesalahan, dan siswa SRL rendah dominan melakukan semua kesalahan yakni kesalahan konsep, prinsip dan operasi. Untuk faktor penyebabnya adalah siswa tidak menyerap informasi dengan baik, kurang pengalaman siswa dalam mengerjakan soal, siswa belum memahami materi atau konsep pra syarat secara teliti dan siswa lalai dalam menyelesaikan masalah..Kata Kunci : Analisis Kesalahan, Self Regulated Learning  (SRL), Persamaan Garis Lurus

Bewegungsregelung mobiler Manipulatoren für die Mensch-Roboter-Interaktion mittels kartesischer modellprädiktiver Regelung

Für die Mensch-Roboter-Interaktion wird in dieser Arbeit eine Methode zur Überwachung der komplexen, dynamischen Roboterumgebung vorgestellt. Die Roboterbewegung wird basierend auf dem Konzept der modellprädiktiven Regelung unter Berücksichtigung der detektierten Hindernisse und der stattfindenden Kontakte des Roboters mit seiner Umgebung geregelt, um Kollisionen zu vermeiden und angemessen auf Kontakte zu reagieren. Die Ansätze werden auf einem mobilen Manipulator validiert

The implicit equation of a canal surface

A canal surface is an envelope of a one parameter family of spheres. In this paper we present an efficient algorithm for computing the implicit equation of a canal surface generated by a rational family of spheres. By using Laguerre and Lie geometries, we relate the equation of the canal surface to the equation of a dual variety of a certain curve in 5-dimensional projective space. We define the \mu-basis for arbitrary dimension and give a simple algorithm for its computation. This is then applied to the dual variety, which allows us to deduce the implicit equations of the the dual variety, the canal surface and any offset to the canal surface.Comment: 26 pages, to be published in Journal of Symbolic Computatio