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Silver, R. H.

Publications and source records attributed to Silver, R. H..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

An overview of dredging operations in the Chesapeake Bay

Maintenance of the Baltimore and the Newport News/Norfolk harbors as well as of the Chesapeake and Delaware Canal is accomplished by different dredging operations which depend on the amount and type of material to be moved, water depth, and location of disposal sites. Methods for determining the physical or chemical-biological interactive effects of these activities on the environment and on the shellfish and finfish industries on the Bay are discussed. The types of dredges used are classed according to their mode of operation.

Silver, R. H.↗
NASA NTRS1976

Accelerated heat-aging studies on fluororubber in various media

Heat-aging studies were conducted on fluororubber (copolymers of vinylidene fluoride and perfluoropropylene) using N,N-dicinnamylidene-1,6-hexanediamine, a Schiff's base of 1,6-hexanediamine, and MgO as acid acceptor. The principal technique employed was chemical stress relaxation for determining network changes brought about in the heat-aged fluororubber. This technique was backed up by swelling measurements, gel permeation chromatography, and IR spectroscopy. Stress relaxation curves are plotted for a wide range of variation in parameters (time, crosslinking density, state of curing, temperature, intermittent and continuous relaxation).

Kalfayan, S. H.↗
NASA NTRS1976

Myocardium wall thickness transducer and measuring method

A miniature transducer for measuring changes of thickness of the myocardium is described. The device is easily implantable without traumatizing the subject, without affecting the normal muscle behavior, and is removable and implantable at a different muscle location. Operating features of the device are described.

Feldstein, C.↗
NASA NTRS1976

Catheter tip force transducer for cardiovascular research

A force transducer for measuring dynamic force activity within the heart of a subject essentially consists of a U-shaped beam of low elastic compliance material. Two lines extend from the beams's legs and a long coil spring is attached to the beam. A strain gauge is coupled to one of the beam's legs to sense deflections thereof. The beam with the tines and most of the spring are surrounded by a flexible tube, defining a catheter, which is insertable into a subject's heart through an appropriate artery. The tines are extractable from the catheter for implantation into the myocardium by pushing on the end of the spring which extends beyond the external end of the catheter.

Feldstein, C.↗
NASA NTRS1976

Myocardial wall-thickness transducer

Device consists of highly compliant circular beam attached to piezoresistive strain gage and barbed needle. Radial deflection of myocardium is measured with minimal disturbance of normal heart functions.

Feldstein, C.↗
NASA NTRS1975

Catheter-tip force transducer for cardiovascular research

Sensor can be installed in left ventricle by means of procedures available for inserting catheter into an artery at body's extremities and manipulating it through vessel and past aortic valve. Metallic tines of device can be used as internal electrode for electrocardiogram.

Feldstein, C.↗
NASA NTRS1975

Subminiature transducers for measuring forces and deformation of heart muscle

Two subminiature transducers, one measuring muscle forces and one measuring muscle displacement, can be inserted into heart muscle without interfering with it. Probe, approximately 1 mm (0.04 in), causes no damage to heart muscle. Probe can be rotated to different positions to measure muscle forces from various directions.

Feldstein, C.↗
NASA NTRS1974

High-temperature gas/liquid stress relaxometers

Two relaxometers allow testing of elastomers in various fluids. First relaxometer uses fork-like loading spacer interposed between loading lever and support ring, so that sample is stretched predetermined amount. In second relaxometer, degree of initial elongation is set by means of adjustable collar, which, when locked in place on piston rod, enables sample to be stretched predetermined length.

Kalfayan, S. H.↗
NASA NTRS1973

Thermally actuated valve

Effective seal in one-shot valve is made by shrink-fitting ball within cylinder; thermal expansion of cylinder, caused by contiguous source of heat, will release ball and open valve. Valve can also be adapted for repeated operation and made capable of being opened without pressurized fluid.

Silver, R. H.↗
NASA NTRS1972

Long Term Aging of Elastomers: Chemorheology of Viton B Fluorocarbon Elastomer

The continuation of a study to ascertain the nature, extent, and the rate of chemical changes that take place in certain selected elastomers is reported. Under discussion is Viton B, regarded as a temperature and fuel resistant fluorocarbon rubber. The kinetic analysis of the chemical stress relaxation, and infrared and gel permeation chromatography analysis results are discussed.

Kalfayan, S. H.↗
NASA NTRS1972

A study of the frictional and stick-slip behavior of magnetic recording tapes

Methods were developed to determine the coefficient of friction and the extent of stick-slip of magnetic recording tapes. After a preliminary phase during which experimental procedures were established and screening of candidate tapes was carried out, the frictional and stick-slip behavior of four selected tapes, using four different kinds of magnetic heads, was studied at various temperatures, under dry and humid conditions, and in various gaseous atmospheres, such as argon, helium, nitrogen and air. The effects of tape speed and outgassing on the drag properties of the tapes were also studied. A rank was assigned to each tape and magnetic head as a result of these tests. This study helped in the selection of a magnetic tape in a flight project, and will be useful in the consideration of tapes and magnetic heads for future spacecraft applications.

Kalfayan, S. H.↗
NASA NTRS1972

Studies on the frictional behavior of magnetic recording tapes

Methods were developed for measuring frictional forces acting on a magnetic tape in motion or at rest, as well as the extent of stick slip. The effects of factors such as temperature, humidity, kind of gaseous atmosphere, and tape speed on the frictional interaction between various tapes and heads were investigated. Results were instrumental in the selection of a tape for the Mariner Mars 1971 spacecraft. Studies are reported on the stick slip behavior of tapes and the performance of a metallic tape, compared with the usual plastic tapes.

Kalfayan, S. H.↗
NASA NTRS1971

Long-term aging of elastomers: Chemical stress relaxation of fluorosilicone rubber and other studies

Aerospace applications of elastomers are considered, including: propellant binders, bladder materials for liquid propellant expulsion systems, and fuel tank sealants for high-speed aircraft. A comprehensive molecular theory for mechanical properties of these materials has been developed but has only been tested experimentally in cases where chemical degradation processes are excluded. Hence, a study is being conducted to ascertain the nature, extent, and rate of chemical changes that take place in some elastomers of interest. Chemical changes that may take place in the fluorosilicone elastomer, LS 420, which is regarded as a fuel and high-temperature-resistant rubber are investigated. The kinetic analysis of the chemical stress relaxation and gel permeation chromatography studies comprise the major portion of the report.

Kalfayan, S. H.↗
NASA NTRS1970

Noncontacting-optical-strain device

Noncontacting-strain-measuring gauge and extensometer remotely measures the mechanical displacement along the entire length of a test specimen. Measurement is accomplished by continuous scanning of a reflected light from reflective bench markings or stripes previously affixed to the specimen.

Silver, R. H.↗
NASA NTRS1967

Miniature stress transducer Patent

Miniature solid state, direction sensitive, stress transducer design with bonded semiconductive piezoresistive element for sensing residual stresses

San Miguel, A.↗