The large-scale evaluation and gradual optimization (LEGO) model of software development was designed to be capabilities-driven. Although the motivation for its structure was support of research projects, this model i...
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The Stennis Space Center acts as the program office for remote sensing activities on behalf of the NASA Office of Commercial Programs. The Commercial Earth Observations Program (CEOP) is a key, cooperative effort with...
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ISBN:
(纸本)081940604X
The Stennis Space Center acts as the program office for remote sensing activities on behalf of the NASA Office of Commercial Programs. The Commercial Earth Observations Program (CEOP) is a key, cooperative effort with U.S. industry focused on strengthening our nation's economic standing in space-based remote sensing technology. Implementation costs for current remote sensing satellite systems are in the range of $130-300M. Available technology in small launch vehicles and space-qualified subsystem miniaturization could provide a development environment capable of reducing costs, while maintaining performance, Stennis is supplying systems engineering support to determine the technical and economic feasibility of a commercial remote sensing small satellite. Study efforts focus on the systems design of launch vehicle, sensor system, communications, attitude control, power, computational processing, and ground station capabilities. Results reveal that a example small satellite system, with a limited capability remote sensing payload, could be deployed for less than $20M. Technological advances and overall cost reductions in space systems may enable industry to develop new and expanded information service markets.
Prosthetic socket design is the most important aspect of the fit of a lower extremity prosthesis. The comfort and mobility of wearing a prosthetic socket mainly depends on the design of weight bearing characteristics ...
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ISBN:
(纸本)0819407437
Prosthetic socket design is the most important aspect of the fit of a lower extremity prosthesis. The comfort and mobility of wearing a prosthetic socket mainly depends on the design of weight bearing characteristics of the socket. The weight bearing characteristics of a socket are determined by the relative positions among the tissues (such as bones, muscles, and fat) of the residual limb and the wall of the socket. Therefore, socket fitting cannot be guaranteed if the internal structural information of a residual limb is not made available to the prosthetist. current prosthetic socket design and manufacture processes are disadvantaged by the inherent difficulties in determining the weight bearing characteristics of a socket due to the lack of crucial information about the internal structure of the residual limb, such as bone position, and muscle, and fat distribution. This disadvantage can be overcome through the use of an ultrasound imaging system and a computer-aided socket design system. The discussion of the complete system is out of the scope of this paper. An ultrasound imaging algorithm which provides the external shape of the limb, the bone position, and the texture pattern of the soft tissues within the limb is presented in this paper. The algorithm using the Compound B-scan imaging principle combined with geometrical transformation and statistical information faithfully measures and reconstructs with topographical shape and internal structure information of a residual limb.
The current distributions on microstrip lines with finite conductor thickness and finite conductivity are investigated in the TM mode. It is found that the lower surface of the conducting strip carries significantly m...
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The current distributions on microstrip lines with finite conductor thickness and finite conductivity are investigated in the TM mode. It is found that the lower surface of the conducting strip carries significantly more current than the upper surface. The percentage of the current carried by the lower surface increases with increasing dielectric constant of the substrate. Detailed information on current distributions is useful in design of high-T(c) superconductor lines.
Techniques for optically controlling the latching capabilities of the light amplifying optical switch (LAOS) are described. It is shown that the latching can be controlled by reducing either the voltage or the current...
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Techniques for optically controlling the latching capabilities of the light amplifying optical switch (LAOS) are described. It is shown that the latching can be controlled by reducing either the voltage or the current of the latching element. The operation and design of functional blocks that implement set/reset flip flops, gated latches, and inverting logic are discussed.< >
Our Laboratory has demonstrated the feasibility of operating Gate Turnoff Thyristors(GTOs) in series to produce a repetitive opening and closing switch capable of operating at voltages higher than that of a single GTO...
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Our Laboratory has demonstrated the feasibility of operating Gate Turnoff Thyristors(GTOs) in series to produce a repetitive opening and closing switch capable of operating at voltages higher than that of a single GTO. The next task is to produce a practical device capable of continuous operation at voltage levels in the tens of kilovolts. The immediate application is to replace gaseous components in the command charger of a high energy pulser system. Our laboratory is currently designing and building such a device. The design issues of such a device are substantial, with high voltage being the least significant, in the sense that optical triggering and standard isolation and insulation techniques can readily handle the system voltages. Control and instrumentation are critical since, for our design goal of 25 KV system voltage, twelve GTOs must be arrayed in series and synchronized in turning off and on, in repetitive time windows on the order of 100 nanoseconds each. Moreover, it is imperative that the possible failure of one device be anticipated and action taken to shutdown the system during this failure mode, again in a 100 nanosecond window. In failure mode, one component failing places all other components at risk, which can have disastrous consequences. Therefore, our design incorporates a computer actuated data acquisition and control system, capable of monitoring the voltage across each of the twelve GTOs and taking appropriate action to protect the system, automatically, during failure mode, with no intervention required from a human operator. Since the switch will operate nearly continuously, thermal management is a key issue. Liquid cooling is required, due to the high dissipation of GTOs. Water cooling presents problems in that electrical conductivity of the coolant can change and present a shorting path for the high voltage. Insulating oil may be used, but the heat transfer efficiency declines drastically, requiring larger, to the point of unwiedly, he
POHM is applied to the design of the low-profile IFF (identification of friend or foe) airborne antenna whose height is less than 1 in. The basic idea of the POHM is that the physical optics technique is used to exten...
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POHM is applied to the design of the low-profile IFF (identification of friend or foe) airborne antenna whose height is less than 1 in. The basic idea of the POHM is that the physical optics technique is used to extend the application of the method of moments to a larger class of problems. The POHM program is tested with geometrical optics, geometrical theory of diffraction, and measured data. It is seen that the accuracy of the POHM is quite satisfactory for large ground plates. In the angular region, z>or=0, the accuracy of the POHM is very high because the physical optics currents on the body are included. However, the accuracy decreases because the POHM assumes that no currents exist on the shadow area (z<0) of the surface on the body.< >
An original approach is proposed to controlling WDM (wavelength-division multiplexing) passive optical stars, termed queuing arrivals for delayed reception operation (QUADRO). In WDM stars the fundamental problem of r...
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An original approach is proposed to controlling WDM (wavelength-division multiplexing) passive optical stars, termed queuing arrivals for delayed reception operation (QUADRO). In WDM stars the fundamental problem of receiver conflicts leads to severe performance degradation. In current solutions conflicts are prevented by scheduling transmissions or resolved by retransmissions. The proposed approach introduces the concept of resolving reception conflicts by incorporating a delay line receiver design. It thus brings the optical star networks a step closer to all-optical realization. In addition, it allows almost total utilization of the channels, as obtainable until now only by TDM.< >
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