The development of a power spectral density processor for C and L band airborne radar scatterometer sensor systems

A real-time signal processor was developed for the NASA/JSC L-and C-band airborne radar scatterometer sensor systems. The purpose of the effort was to reduce ground data processing costs. Conversion of two quadrature channels of data (like and cross polarized) was made to obtain Power Spectral Density (PSD) values. A chirp-z transform (CZT) approach was used to filter the Doppler return signal and improved high frequency and angular resolution was realized. The processors have been tested with record signals and excellent results were obtained. CZT filtering can be readily applied to scatterometers operating at other wavelengths by altering the sample frequency. The design of the hardware and software and the results of the performance tests are described in detail

Advanced development for space robotics with emphasis on fault tolerance

This paper describes the ongoing work in fault tolerance at the University of Texas at Austin. The paper describes the technical goals the group is striving to achieve and includes a brief description of the individual projects focusing on fault tolerance. The ultimate goal is to develop and test technology applicable to all future missions of NASA (lunar base, Mars exploration, planetary surveillance, space station, etc.)

Importance of support and loading conditions in overdenture FEM model investigations

W badaniach modelowych FEM protez overdenture założenie więzów ograniczających ruchomość protezy w sposób zgodny z zasadami ich funkcjonowania pozwala na rozpoznanie obciążeń złączy, przy znacznym uproszczeniu modelu numerycznego. Dla powszechnie dostępnych w sprzedaży typów złączy podczas transmisji sił żucia stwierdzono występowanie znacznych wartości obciążeń bocznych, co stanowi bezpośrednie wyjaśnienie przyczyn niepowodzeń mechanicznych. Założenie pionowych kierunków sił zgryzowych prowadzi do znacznego niedoszacowania obciążeń złączy.In overdenture FEM analysis, assumption of constrains reducing denture movement according to the rules of their functioning allows to determine loads of attachments, at the same time significantly simplifying numerical model. For commonly available types of attachments - during occlusal forces transmission found has been an occurrence of considerable lateral loads, which directly explains the causes of mechanical failures. Assumption of vertical occlusal forces directions leads to remarkable underestimating of attachments loads

Modelling studying as the tool of the identification forces of mandibular systems muscles

W pracy przedstawiono metodykę identyfikacji sił mięśni żwaczowych narządu żucia. W zaproponowanym podejściu przeprowadzono ocenę sił mięśniowych narządu żucia, z uwzględnieniem oddziaływania układu nerwowego. Taki sposób prowadzenia badań modelowych jest alternatywnym ujęciem problemu równowagi biostatycznej narządu żucia, w stosunku do dotychczas stosowanych metod obliczeniowych. Dodatkowo podczas przeprowadzonych obliczeń numerycznych uwzględniono ograniczenia, związane z maksymalną wydolnością poszczególnych mięśni żwaczowych. Wyniki obliczeń numerycznych przedstawiono w postaci przebiegów czasowych sił mięśni narządu żucia oraz charakterystyki odwzorowującej wpływ przyłożenia zewnętrznego obciążenia do łuku zębowego żuchwy.The paper presents a methodology to identify the forces of masticatory muscles. The proposed approach was evaluated masticatory muscle forces, including the impact of the nervous system. This method of research is an alternative model of the problem of balance of masticatory biostatic, with respect to existing methods of calculations. In addition, in carrying out numerical calculations take into account constraints related to the maximum capacity of the individual muscles. The results of numerical calculations are presented in the form of time histories of forces of masticatory muscles and the characteristics of mapping decisions and brokering the impact of application of external load to the arch of the mandible

FEM numerical simulation of contact stresses between driving shaft and hub impeller of fuel pump

Purpose: The aim of the work was to test the contact stresses in the model system of the turbine hub cooperating with the fuel pump drive shaft. The hypothesis of the work was that, by means of FEA, it is possible to assess the contact stresses in the materials of the turbine hub and the fuel pump shaft during torque transmission. Design/methodology/approach: A turbine with fibre-reinforced polyphenylene sulphide (PPS) composite cooperating with a stainless steel shaft (X46Cr13/1.4034) in a commonly used D-flat shape joint was selected for the experimental research. To assess contact stresses, the CAD model (NX, Siemens) of the entire turbine was limited to the hub area. The drive shaft is supported in accordance with the bearing in the fuel pump, and the possibility of rotation about the axis along the length of the torque-producing magnet is taken away. The system was loaded with a torque of 200 Nmm on the turbine. The turbine hub and shaft were calculated, taking into account the phenomenon of contact detachment or slip at the value of the friction coefficient of 0.1. Findings: The pressure transmission area was found in the area at the edge of the flat surface D-flat and on the opposite side of the D-convexity. The contact stresses on the D-flat side reached values close to the composite strength. Research limitations/implications: The studies did not take into account the technological inaccuracies, thermal deformation, local material properties, and wear. The value of the friction coefficient was not measured in realistic conditions with fuel lubrication. Practical implications: FEA has been achieved, which allows to reduce the cost of experimental research. Originality/value: The proposed model allows for further studies of the influence of elasticity of various materials and structures on contact stresses in order to assess wear resistance

Full Contoured Tooth-Implant Supported 3-Pointic All-Ceramic Denture During Occlusal Load Transfer in Lateral Region

Implant and a tooth supported dentures are avoided by dentists because of uneven distribution of occlusal loads between a stiffer implant and a more pliable tooth. The hypothesis was that a 3-point all-ceramic bridge supported on a natural second premolar tooth and a two-pieces typical implant bears safely mastication loads. The finite element analysis showed that the implant splinted by all-ceramic zirconium bridge with the second premolar was safe under lateral mastication load, but there was found an overload at wide zone of bone tissue around the implant under the load of 800 N. The patients can safely masticate, but comminution of hard food should be avoided and they should be instructed that after such an indiscretion they need to contact a dental professional, because, in spite of integrity of the prosthesis, the bone tissue around the implant may fail and there is a hazard of intrusion of the tooth

The analysis of the effect of wrought wire clasps on the conditions of abutment teeth

Laboratory evaluation of spring constants (k) of wrought wire clasps (WWC) separated from removable partial denture (RPD) and the results of tibological tests which represent the dependence of enamel wear with normal force have been presented in the paper. The results of laboratory examinations have been combined with the results of clinical assessment of the level of abutment teeth wear. On the basis of the examinations performed it has been revealed that the following factors have the greatest impact on tribological wear of abutment teeth: the time of using RPD and the normal force exerted by WWC on abutment tooth. Normal force depends to a great extent on the place of contact of WWC with the tooth. It has also been found that abutment teeth featuring higher scale of wear are more loosened. The diameter of wire used for making WWC, total length of the arm and k determined for the total length of the arm did not have any impact upon the scale of wear of abutment teeth