Preliminary Feasibility Studies Research Articles

A reliability simulation approach for use in the design process

A simulation model for use in the engineering design process is reported. The simulation model facilities reliability modeling by design engineers and reliability analysts early in the design process. The model applies to preliminary feasibility and design tradeoff studies. The authors describe the model, focus on applications to mission reliability analysis, and give a case study for the voice-communication system of the F-16 fighter aircraft.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A Proposed Dynamic Pressure and Temperature Primary Standard.

Diatomic gas molecules have a fundamental vibrational motion whose frequency is affected by pressure in a simple way. In addition, these molecules have well defined rotational energy levels whose populations provide a reliable measure of the thermodynamic temperature. Since information concerning the frequency of vibration and the relative populations can be determined by laser spectroscopy, the gas molecules themselves can serve as sensors of pressure and temperature. Through measurements under static conditions, the pressure and temperature dependence of the spectra of selected molecules is now understood. As the time required for the spectroscopic measurement can be reduced to nanoseconds, the diatomic gas molecule is an excellent candidate for a dynamic pressure/temperature primary standard. The temporal response in this case will be limited by the equilibration time for the molecules to respond to changes in local thermodynamic variables. Preliminary feasibility studies suggest that by using coherent anti-Stokes Raman spectroscopy we will be able to measure dynamic pressure up to 108 Pa and dynamic temperature up to 1500 K with an uncertainty of 5%.

Structural design of cylindrical railguns

A systematic structural design approach to the development of cylindrical electromagnetic launchers has been formulated, using classical analytical methods in preliminary feasibility studies and finite-element methods to simulate static and dynamic structural response. Three-dimensional stress analysis results indicate that conventional assumptions associated with two-dimensional analysis for design are generally valid. Frequency-domain analysis of the subject structure and associated design loads can be used to estimate the significance of inertial effects under dynamic loading. Results of the study show that significant improvements in system performance are possible despite the limitations of nonconducting structural materials currently available for railgun fabrication.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Recurrence of Exceedence of Threshold Seismic Ground Motion from Earthquake Recurrence, Ground-Motion Attenuation, and Hypocentral-Depth Relations

In evaluating potential sites of major engineered facilities for purposes of preliminary screening, feasibility, or conceptual design it is important to establish the recurrence interval (return period) of critical levels of seismically-induced ground motion. An essential element in estimating this parameter both in regions with and without known seismogenic faults, is the analysis of “random” earthquakes. A useful tool in performing this analysis is the well known earthquake size-to-recurrence equation, log 10 N = a – bM. This paper illustrates how this equation can be used with attenuation relations and hypocentral depths to estimate recurrence of exceedence of threshhold values of seismic ground-motion parameters. Intended for preliminary site screening, feasibility, and conceptual design studies in regions of “random” earthquakes, with or without seismogenic faults, the illustrated method of approach provides reasonable constraints to preliminary evaluation and site selection decisions when recurrence of threshhold ground motion is considered. In a first hypothetical example a site in a region where all earthquakes are “random” is assumed. Using a given threshold acceleration level and a suitable attenuation equation the areas within which epicenters of given-magnitude earthquakes must be located for the earthquakes to produce the threshold site acceleration are calculated. By means of a recurrence equation these areas are converted to an annual frequency and return period of epicenters of events capable of generating the specified ground motion. Finally, estimates of hypocentral depth are used to convert epicentral frequency to frequency of exceedence of the specified acceleration at the given site. In a second hypothetical example an active fault generating a given magnitude earthquake is assumed and a site acceleration derived. The recurrence of exceedence of this value by lower magnitude “random” earthquakes is then calculated and it is shown that recurrence of site acceleration generated by “random” events can be significant even in regions of known seismogenic structures.

Myoventriculoplasty and neoventricle myograft cardiac augmentation to establish pulmonary blood flow: Preliminary observations and feasibility studies

In 10 dogs, a latissimus dorsi muscle (myograft) was neuroelectrically stimulated at 120 cycles/min for as long as 80 days. The higher thresholds and multiple lead penetrations required of direct muscle stimulation for muscle conditioning were avoided. Vascular delay and protective wrapping of the myograft in four dogs resulted in rapid seroma and fibrous sheath formation, which precluded further study. Of the six other myografts that were stimulated, two were used as functional right ventricular myoventriculoplasties and four were employed as neoventricle myografts with inflow and outflow valved conduits that were used to provide total pulmonary blood flow. Myoventriculoplasty produced functional enlargement of the right ventricle with synchronously contractile muscle. Neoventricles provided hemodynamically stable total pulmonary blood flow for as long as 20 hours, until internal chamber thrombus formed. Transpulmonary blood pressure generation by the neoventricle was found to be programmable up to physiologic systemic pressures by modulation of chamber preload and burst stimulation frequency at 50 msec intervals, delivered 120 times per minute. Synchronization capabilities for implantable burst pulse generators would further improve the efficacy of these myograft techniques designed to augment or supplant ventricular function, particularly to provide transpulmonary blood flow at programmable pressures.

Guidance dynamics of mixed-mu levitators for MAGLEV vehicles

Mixed-mu levitation is the principle whereby iron is freely levitated in a magnetic field, being stabilized by the proximity of diamagnetic superconducting screen material [1]. For application to MAGLEV ground transport, superconducting field coils and stabilizing screens are mounted in on-board cryogenic levitator pods of the vehicle to give levitation about a mild steel rail [2]. The system exhibits little natural damping and the guidance damping requirements are particularly severe. Preliminary feasibility studies [3] show that reasonable ride characteristics in guidance are obtained using passive damping screens utilizing a secondary suspension and a primary system employing copper sheets attached to the cryostat walls. This paper fully investigates the damping and both static and dynamic stiffness obtained from the interactions of all mixed-mu lavitator components and, in particular, that occurring between the superconducting screens and the eddy current damper sheets. The superconducting screens are shown to provide a negative damping component whilst the damper sheets provide an enhanced dynamic stiffness. A non-linear time response analysis is presented together with predictions of both dynamic and static forces, the latter showing good agreement with magnetostatic experimental results.

Use of I-131 labeled, murine Fab against a high molecular weight antigen of human melanoma: preliminary experience.

High molecular weight antigen (HMWA) is a tumor-associated proteoglycan of human malignant melanoma. I-131 labeled Fab fragments of these specific antibodies were used for preliminary feasibility studies for radioimmunodetection and therapy of human subjects who had inoperable metastatic melanoma. Ten patients received tracer doses of 5-13 mCi (185-481 MBq) of I-131 (anti-HMWA) Fab. All patients (8/8) who had melanoma lesions greater than 1 cm by correlative diagnostic methods had one or more lesions that had localization to tumor of the radiolabeled Fab. In all, 17 of 23 (74%) documented metastases were seen. There were no false positives in this series. Two patients who had avid uptake received potentially radiotherapeutic doses of 142 mCi (5,254 MBq) (one patient) and 181 mCi (6,697 MBq) and 193 (7,141 MBq) (total: 374 mCi or 13,838 MBq) (one patient). For both of these patients, whole body imaging studies showed that the localization of the high dose I-131 Fab was predominantly in tumor. The patient who received the larger dose showed a greater than 50% reduction in the size of pelvic and pericaval nodes, with stabilization of disease at the smaller nodal size for a period of three months. On whole body images, the anti-Fab HMWA appears to be more tumor selective than Fab preparations that target the p97 antigen for melanoma, and there is less uptake in liver.

ESO 16 Metre Very Large Telescope - Instrument Matching in Spectroscopy and Direct Imaging

Preliminary feasibility studies have been carried out in the framework of the ESO VLT project which have permitted the evaluation of several possible approaches to the instrument matching problem. This paper briefly discusses the detector long term perspective, recalls the main scaling laws and attempt to provide some quantitative analysis of spatial performance of instrumentation in a few typical cases. Field slicing technique is proposed as a potential solution to solve detector matching problems.

Use of Cotton in Accident Dosimetry

Abstract In this paper we present preliminary phenomenological and feasibility studies of accident dosimetry based on absorbed dose by cotton fibres. Cotton fibres are very often the main constituent of clothing. It should thus be possible to estimate the dose received by an individual exposed to ionising radiation and not wearing an individual dosemeter. Cotton fabric was chosen for its well known structure and its suitability for studies by simple techniques such as exoelectron emission from surface defects selected for its high sensitivity.

Preliminaries to the automatic recognition of speech: language identification

The goal of automatically understanding speech usually has been approached by first simplifying the task—by studying the speech of one talker, by restricting vocabulary, by considering only high-quality signals, by analyzing one language, etc. In addition, much experimental work has been characterized by an emphasis on either the speech-analysis or the pattern-recognition/statistical aspects of the problem. A new procedure is described for automatically determining the language of a connected-speech sample. The parameters extracted from the acoustic signal are a small number of gross linguistic categories that seem to be robust and reasonably independent of talker and channel, yet carry enough information to separate languages. Successful preliminary feasibility studies using manually transcribed parameters, as well as the performance of the procedures currently in use for automatic implementation of the scheme, are described. The effects of inaccuracies in labeling on the identification of a language are considered. Implications of these studies for the implementation of schemes for word identification and speech recognition are discussed.

Radio-frequency Techniques for Measuring Water Levels in Narrow-Diameter Piezometers*

AbstractThree radio-frequency techniques for measuring water levels in narrow-diameter piezometers are briefly described. Preliminary feasibility studies indicate that one of these techniques is reasonably satisfactory and could be developed further for measuring water levels of lakes, rivers, dams, water wells, and reservoirs.