Introduction: Analog vs. Digital

The NRC recognizes that a more complete technical basis for understanding and regulating advanced digital technologies in commercial nuclear power plants is needed. A concern is that the introduction of digital safety systems may have an impact on risk. There is currently no standard methodology for measuring digital system reliability. A tool currently used to evaluate NPP risk in analog systems is the probabilistic risk assessment (PRA). The use of this tool to evaluate the digital system risk was considered to be a potential methodology for determining the risk. To test this hypothesis, it was decided to perform a limited PRA on a single dominant accident sequence. However, a review of existing human reliability analysis (HRA) methods showed that they were inadequate to analyze systems utilizing digital technology. A four step process was used to adapt existing HRA methodologies to digital environments and to develop new techniques. The HRA methods were then used to analyze an NPP that had undergone a backfit to digital technology in order to determine, as a first step, whether the methods were effective. The very small-break loss of coolant accident sequence was analyzed to determine whether the upgrade to the Eagle-21 process protection system had an effect on risk. The analysis of the very small-break LOCA documented in the Sequoyah PRA was used as the basis of the analysis. The analysis of the results of the HRA showed that the mean human error probabilities for the Eagle-21 PPS were slightly less than those for the analog system it replaced. One important observation from the analysis is that the operators have increased confidence steming from the better level of control provided by the digital system. The analysis of the PRA results, which included the human error component and the Eagle-21 PPS, disclosed that the reactor protection system had a higher failure rate than the analog system, although the difference was not statistically significant.

A digital wide-band system for damping ring instabilities in an accelerator is presented. With increased beam intensity, the losses of an accumulator ring tend to increase due to the onset of various instabilities in the beam. An analog feedback damper system has been implemented at Los Alamos National Laboratory. This analog system, while functional, has certain limitations and a lack of programmability, which can be overcome by a digital solution. A digital feedback damper system is being designed through a collaborative effort by researchers at Oakridge National Laboratory, Los Alamos National Laboratory, and the University of Wisconsin. This system, which includes analog-to-digital converters, field programmable gate arrays and digital-to-analog converters can equalize errors inherent to analog systems, such as dispersion due to amplifiers/cables, gain mismatches, and timing adjustments. The digital system features programmable gains and delays, and programmable equalizers that are implemented using digital FIR and comb filters. The flexibility of the digital system allows it to be customized to implement different configurations and extended to address other diagnostic problems.

Digital systems are pervasive in modern society. We use computers for bookkeeping, engineering, publishing, and entertainment. Digital communications systems handle our telephone calls and enable our Web browsing sessions. Other uses of digital systems are less visible. Most consumer electronics products are largely digital and becoming more so. Music today is distributed digitally on compact optical disks, and video production is rapidly becoming a digital process. A typical appliance is controlled digitally by a microcomputer. As many as ten microcomputers can be found in the average car for controlling functions ranging from the sound system to the antilock brakes.

2 - Digital Voice Fundamentals

Verification of either analog or digital systems is known to be difficult. Verifying modern mixed-signal systems increases the complexity further. This paper presents a range based approach to verify mixed-signal systems including parameter variation by a single simulation run. Analog systems are simulated by a SPICE-like simulator which uses a special range arithmetic, called affine arithmetic. The simulation of digital systems is extended to include the earliest and latest possible arrival times for every signal. Special converters transform the signals between each domain. The speed-up of this framework compared to traditional Monte-Carlo simulations was up to 500.

The Indonesian government's initiative to transform digital radio broadcasting has commenced, facilitating the transition from analogue to digital radio transmission via a simulcast system. Comprehensive implementation of these technological changes has the potential to yield optimal digital radio broadcasting ecosystems. A distinguishing attribute of this simulcast system is its capacity to transmit analogue and digital frequencies concurrently. Despite its considerable practical relevance, there is a paucity of systematic knowledge regarding the reasons why analogue and digital radio broadcast simulcast systems must be implemented to maintain pace with the development of broadcasting technology in this digital age. This research contributes to the future of radio broadcasting by exploring the ecosystem factors of a multiplatform simulcast broadcast model. This analysis is grounded in a qualitative examination of the simulcast system (both analogue and digital) within the Internet sector of the broadcast industry. The research identifies several factors: first, terrestrial analogue radio; second, terrestrial digital radio; third, Internet radio and human resources; fourth, analogue and digital simulcast systems; and fourth, Internet multi-social media platforms.

Frequency stabilization for external cavity diode laser has played an important role in physics research. Many laser frequency locking solutions have been proposed by researchers. Traditionally, the locking process was accomplished by analog system, which has fast feedback control response speed. However, analog system is susceptible to the effects of environment. In order to improve the automation level and reliability of the frequency stabilization system, we take a grating-feedback external cavity diode laser as the laser source and set up a digital frequency stabilization system based on National Instrument’s FPGA (NI FPGA). The system consists of a saturated absorption frequency stabilization of beam path, a differential photoelectric detector, a NI FPGA board and a host computer. Many functions, such as piezoelectric transducer (PZT) sweeping, atomic saturation absorption signal acquisition, signal peak identification, error signal obtaining and laser PZT voltage feedback controlling, are totally completed by LabVIEW FPGA program. Compared with the analog system, the system built by the logic gate circuits, performs stable and reliable. User interface programmed by LabVIEW is friendly. Besides, benefited from the characteristics of reconfiguration, the LabVIEW program is good at transplanting in other NI FPGA boards. Most of all, the system periodically checks the error signal. Once the abnormal error signal is detected, FPGA will restart frequency stabilization process without manual control. Through detecting the fluctuation of error signal of the atomic saturation absorption spectrum line in the frequency locking state, we can infer that the laser frequency stability can reach 1MHz.

While low loss and large bandwidth have allowed optical fibers to become essential in a large amount of telecommunication systems, this has not yet been true for video distribution systems where the cost per subscriber must be as low as possible. First optical video distribution systems have been developped using 1.3 pm distributed-feedback (DFB) lasers. Up to now, the modulation format used in such systems is analog amplitude-modulation vestigial-sideband (AM-VSB) scheme since it provides direct compatibility with cable TV industry and present television sets. However, this modulation scheme requires a very high signal-to-noise ratio on the receiver side so that it is necessary to detect large optical powers (above -10 dBm) to ensure good picture quality. This means that the power budget (budget one can afford for optical fibers and splitters losses) for 1.3 im systems, even with powerful optical sources, is not very important; in turn, this means that it seems difficult to cut the cost per subscriber with this technology. With optical Erbium-Doped Fiber Amplifier (EDFA) breakthrough, many suppliers of cable TV transmission systems moved to 1.5 .tm technology. Whereas this new component is revolutionizing most of the telecommunication systems as optical fiber did 20 years ago, the use of optical amplifiers for analog systems is not so impressive as for robust digital transmission systems. This is due to the fragility of analog signal in respect with noise and distortion. Because of the noise generated by an optical amplifier, it is not possible to cascade a large number of them while reaching a realistic signalto-noise ratio at the network termination. Optical amplifiers may also distort the analog signal when the transmitter consists of a directly-modulated semiconductor laser, suffering from chirp (unwanted wavelength modulation when power modulation is achieved through current modulation). Moreover, shifting from 1 .3 .tm to 1 .5 pm wavelength brings new problems : 1 .5 tm DFB lasers are not yet as linear as 1.3 im DFB lasers and analog system designers have to cope with chromatic dispersion at 1 .5 .tm in standard fibers (i.e. non dispersion-shifted fibers). It is clear that many of the technical issues for 1.5 im analog systems are far from being resolved. In this paper, we investigate the way, and to what extent, erbium-doped fiber amplifiers may improve analog systems power budget. The organization of the paper is as follows. In Section 2, we discuss what is the relevant noise parameter for optical amplifiers to predict the signal-to-noise degradation they cause. We also show that the same overall noise performance can be reached with amplifiers featuring different noise parameter and output power combinations. This section is completed with experimental measurements. Linearity definitions and requirements for AM-VSB systems are presented in Section 3. Included is a discussion of some specific factors that degrade the signal linearity within an optical amplifier in respect with optical source characteristics. Finally, the still opened technical matters and potential evolution for 1.5 jim analog systems are briefly summarized in Section 4

A system of scholarly monograph publishing, primarily under the auspices of university presses, coalesced only 50 years ago as part of the final stage of the professionalization of US institutions of higher education. The resulting analogue publishing system supplied the authorized print monographs that academic institutions newly required for faculty tenure and promotion. That publishing system – as each of its components – was bounded, stable, identifiable, well ordered, and well policed. As successive financial shocks battered both the country in general and scholarly publishing in particular, just a decade after its final formation, the analogue system went into extended decline. Finally, it is now giving way to a digital scholarly publishing system whose configuration and components are still obscure and in flux, but whose epistemological bases differ from the analogue system in almost all important respects: it will be relatively unbounded and stochastic, composed of units that are inherently amorphous and shape shifting, and marked by contested authorization of diverse content. This digitally driven, epistemic system shift in scholarly publishing may well be an extended work in progress, since the doomed analogue system is still fiscally dominant with respect to monographs, and the nascent digital system has not yet coalesced around a multitude of emerging digital affordances.

The addition operation is required by any digital, analogue, or control system. The speed and accuracy with which the digital system operates is dependent on the functioning of adders. Adders are utilised in a variety of logical and arithmetic procedures. The goal of VLSI system design research is to improve the performance of digital systems, hence there is a strong incentive to examine and analyse adder architectures. The purpose here is to understand the family of faster adders available, such as the Ripple Carry Adder, Carry Look Ahead Adder, Carry Select Adder, and so on. This paper is about the Kogge Stone Adder in the 18nm FinFET model's technology node. It has a high PDP because it operates at a faster rate than its competitors. The adder is designed and built for bit lengths of 4 and 8, with random input data simulations used to evaluate its operations. Criteria such as power, performance, area, gate count, and PDP are used to construct a comparison. Every block used to construct the adder is inspected, and the results are graphically shown. In order to properly examine the parameters, the acquired data is tabulated.

Begun in 2001 with a total budget of around $100M, the Expanded Very Large Array (EVLA) project is the only major upgrade to the VLA undertaken since the interferometer was dedicated in 1980. The goal of this 11-year long project is to improve all the observational capabilities of the original VLA - except for collecting area and spatial resolution - by at least an order of magnitude. To achieve this, the 28 VLA antennas have been modernized with new digital data transmission systems that link to a new, wideband, fiber optic digital LO/IF system, and eight new sets of cooled receivers are under construction that will offer full frequency coverage from 1 to 50 GHz, with instantaneous bandwidths up to 8 GHz provided by two independent dual polarization frequency pairs. The new WIDAR correlator provided by NRAO's Canadian EVLA partner replaced the old VLA correlator in early 2010 and is currently undergoing commissioning. The long duration of the EVLA construction project coupled with the need to maintain the scientific productivity and user base of the telescope obviously precluded shutting down the old array while new infrastructure was built and commissioned. Consequently, the construction plan was based on the fundamental assumption that the old VLA would continue to operate as new EVLA capabilities gradually came online; in some cases, additional complexity had to be designed into new hardware in order to maintain transitional interoperability between the old analog and new digital systems as the latter were installed and commissioned. As construction has advanced, operations has increasingly had to coexist side by side with EVLA commissioning and verification. Current commissioning plans attempt to balance making new EVLA capabilities available to the user community as soon as they have been installed and verified, and maintaining a stable and robust end-to-end data acquisition and delivery process for the user community.

A series of structural vibration control experiments and related theory are developed to check the effectiveness of analog and digital control system with piezoelectric material sensors and actuators. Velocity feedback analog control has been tried for the cantilever beam with PZT (lead-zirconate-titanate) wafer sensors and actuators. To improve the control system, steady- state quadratic optimal control algorithm using a digital micro-computer has been used. To apply optimal control algorithms, signals sensed by partially distributed sensors were converted to point concept signals like those from conventional displacement or velocity sensors. Actuating voltage signals were then synthesized from point force output signals. This paper presents excellent results for structural vibration control using both analog and digital systems.

The analogue and digital notational systems for documenting choreographic movement provide alternative strategies for spatial design. These strategies overlap architectural design and dance choreography to explore reciprocal exchanges regarding the body, geometry and methods of spatial notation. Analogue and digital notational systems are compared to illustrate a change where the notation is fed back to the performer and used as inspiration for further iterative performances. Whilst the use of analogue notation systems supports the criterion of fundamental design, they have limitations which are overcome with the use of flexible digital systems that more readily adapt to change and interrelate to a dancer’s intentions for movement creation. Performance-driven fabrication explores the practical application of this process. Two stages of ‘Performance-driven design’ and ‘Data-driven fabrication’ are combined, resulting in a spatial design and construction system that incorporates interactivity between human and robotic performers.

Cellular nonlinear/neural networks (CNN's) are one of the analog systems that is hard to emulate or simulate on digital systems. It is known that CNN systems are linear for Gabor-type spatial filters. Although it is possible to represent the state equations of the discrete CNN in matrix notation, it is almost impossible to implement the huge state matrix on a digital system without optimization. In this paper some well known linear equation solving methods are optimized for CNN and required computational powers and memories are compared.

Sidelobe cancellation is an effective beamforming method of interference suppression. In this paper, an analog and digital mixed system for sidelobe cancellation is introduced firstly. Then, a closed-loop sidelobe cancellation method based on iteration is proposed by using the previous system. The working principles of this method are derived and the working processes of this method are given in detail. This new method is proved to be available, and it has some advantages over the old ones.