A rounding lemma is presented which has applications in the field of discrete mathematics. The lemma can be used to simplify complex terms and analyse certain recurrence relations.
A rounding lemma is presented which has applications in the field of discrete mathematics. The lemma can be used to simplify complex terms and analyse certain recurrence relations.
A new self-tuning regulator for control of mean arterial blood pressure using sodium nitroprusside is presented. In addition to adapting to various patient response gains and time constants, the controller can accommo...
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A new self-tuning regulator for control of mean arterial blood pressure using sodium nitroprusside is presented. In addition to adapting to various patient response gains and time constants, the controller can accommodate variations in pure time delays, a problem that has not been addressed fully in previously proposed controllers. The control algorithm derivation is based on incorporating a self-tuning controller with an adaptive discrete time delay compensator. The derivation, however, is general and can potentially be applied to other pharmacological agents in addition to sodium nitroprusside. The a priori information required for implementation of the controller is the estimate of the order of the patient response transfer function and the range of the pure time delay. An attractive feature of the controller is its capability to optimize the level of the infused drug during the transient phase of the control without creating an output offset. This feature tends to reduce the overall level of the infused drug. Hence, it may be useful when the cost of a drug or its long-term administration side effects is of concern, such as in the case of sodium nitroprusside.
This article explores a fisheye lens approach to viewing and browsing graphs. A fisheye view of a graph shows an area of interest quite large and with detail and shows other areas successively smaller and in less deta...
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This article explores a fisheye lens approach to viewing and browsing graphs. A fisheye view of a graph shows an area of interest quite large and with detail and shows other areas successively smaller and in less detail. A fisheye lens seems to have all advantages of the other approaches for viewing and browsing a graph without any of drawbacks. Graphs with hundreds of vertices and edges are common in many application areas of computer science, such as network topology, and graph theory. There are literally hundreds of algorithms for positioning nodes to produce an aesthetic and informative display. Displaying all the information associated with the vertices and edges shows the global structure of the graph but has the drawback that details are typically too small to be seen. Alternatively, zooming into a part of the graph and panning to other parts does show local details but loses the overall structure of the graph. Using two or more views, one of the entire graph and the other of a zoomed portion, gives one the advantage of seeing both local detail and overall structure but has drawbacks of requiring extra screen space and forcing the viewer to mentally integrate the views.
This article presents examples of protocol failures in cryptographic operations. In many protocols, the security of the cryptographic portion is progressively weakened as a result of the protocol being exercised, for ...
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This article presents examples of protocol failures in cryptographic operations. In many protocols, the security of the cryptographic portion is progressively weakened as a result of the protocol being exercised, for example, by reducing the size of the key space that one would have to search to identify an active cryptographic key but these are not considered examples of true protocol failures, even though they are clearly examples of potential sources of failure in the intended security function of a protocol. Finding and fixing failures of the latter type is the function of conventional analysis of cryptoalgorithms. An algorithm or protocol can be unconditionally secure, computationally secure, provably secure, or, of course, insecure. A scheme is said to be unconditionally secure if the probability of breaking it is independent of the computing resources and time an opponent is able or willing to spend. A scheme is said to be computationally secure if breaking it requires an attacker to carry out some computation that is possible in principle but for which all known methods of execution require an infeasible amount of computation.
The creation of software agents has generated much recent interest. A variety of approaches and projects use the term 'agents,' ranging from adaptive user interfaces to systems that use planning algorithms to ...
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The creation of software agents has generated much recent interest. A variety of approaches and projects use the term 'agents,' ranging from adaptive user interfaces to systems that use planning algorithms to generate shell scripts. Generally, agents assist users in a range of daily, mundane activities like setting up meetings, sending out papers, locating information in multiple databases, tracking the whereabouts of people, and so on. The objective is to design agents that blend transparently into normal work environments, while relieving users of low-level administrative and clerical tasks. The practical aspects of software agents are taken seriously. Users should be able to assume the agents are reliable and predictable and the human user remains in ultimate control. One of the most difficult aspects of agent design is to define specific tasks that are both feasible using current technology, and are truly useful to the everyday user. Agents must provide solutions to real problems that are important to real users.
During the past five years, encryption technology has become easily available to both individuals and businesses, affording them a level of security formerly available to only military, national security, and law enfo...
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During the past five years, encryption technology has become easily available to both individuals and businesses, affording them a level of security formerly available to only military, national security, and law enforcement agencies. This article analyzes trends in encryption technology. It is divided into four primary sections: technology, market analysis, export controls,and public policy issues. The current trends in encryption technology include increasing miniaturization, increasing use of public and private key cryptography, and the continued development of increasingly secure algorithms. The National Security Agency (NSA) is likely to continue protecting its 'turf' by advocating continued restrictions on encryption technology. It may attempt to expand its domain within the government. Commercial encryption technologies described in the article are Data Encryption Standard, RSA ( named after Rivest, Shamir, and Adelman) algorithms. RSA is a public key algorithm that is widely used for data security.
Measurement of aortic input impedance in the rat is complicated by a high basal heart rate but is possible if appropriate compensation is made for frequency-dependent errors in modulus and phase resulting from analog ...
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Measurement of aortic input impedance in the rat is complicated by a high basal heart rate but is possible if appropriate compensation is made for frequency-dependent errors in modulus and phase resulting from analog filters in the equipment and from nonalignment of pressure and flow sensors. Because input impedance is a complex quantity, accurate values for both phase and modulus are required before meaningful interpretation of the data can be made. We measured aortic pressure and electromagnetic ascending aortic blood flow in mature, ether-anesthetized, open-chest male Wistar rats. Pressure and flow waveforms were averaged in the time domain and converted to Fourier series. Flow moduli were corrected for the measured frequency response of the flowmeter. Phase spectra were corrected by the classic frequency-domain and two new time-domain methods. Compensation for instrumentation errors was assessed at two different flowmeter filter settings in five animals. Reproducibility, variability, and the effects of vasoconstriction were assessed in 43 animals. Three methods of estimating characteristic impedance from the impedance spectra were evaluated and found to produce comparable results at baseline and following pharmacological elevation of blood pressure with graded methexamine infusion. Physiologically equivalent values for phase, as assessed by comparing oscillatory power calculated from the impedance spectra, were obtained with each of the phase-correction techniques. The new time-domain methods facilitate the assessment of aortic input impedance in this small animal model because they do not require measurement of the spatial separation between pressure and flow transducers and pulse wave velocity in the proximal aorta.
An efficient computer implementation of an originally developed spectral representation of multiple-valued input binary functions is presented. In such a representation, the spectrum for each multiple-valued input bin...
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An efficient computer implementation of an originally developed spectral representation of multiple-valued input binary functions is presented. In such a representation, the spectrum for each multiple-valued input binary function is composed of a vector of Walsh transforms, each of them defined for one pair of input variables of the function. By that approach, the number of spectral coefficients describing a given multiple-valued input binary function is a minimal one. The implementation of the algorithm allows for the calculation of the spectra of binary functions having an arbitrary number of literals;each of them can have up to 32 different logical values. The algorithm is interactive so users can manually determine the generation of a partial or whole spectrum.
We consider M (greater-than-or-equal-to 2) transmitting stations sending packets to a single receiver over a slotted time-multiplexed link. For each phase consisting of T consecutive slots, the receiver dynamically al...
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We consider M (greater-than-or-equal-to 2) transmitting stations sending packets to a single receiver over a slotted time-multiplexed link. For each phase consisting of T consecutive slots, the receiver dynamically allocates these slots among the M transmitters. The cost per slot for holding a packet may vary among the transmitters, and may be interpreted in terms of multiple classes of messages. Our objective is to characterize policies that minimize the discounted and long-term average costs due to holding packets at the M stations, based on delayed information on the numbers of packets being held at the respective transmitters. We derive properties of optimal (discounted) policies that reduce the computational complexity of the optimal How control algorithm. For M = 2, we show that the minimal total cost is convex and submodular in the state, and we prove the following properties of optimal policies: 1) when the state at transmitter i increases by unity while the state at the other transmitter j is fixed, the optimal allocation is either unchanged, or increases by one at transmitter i and decreases hy one at transmitter j;and 2) the optimal policy is of the threshold type. We use these properties to show that the optimization reduces to the calculation of optimal allocations for a finite number of states. In addition, for each such state (excluding the origin), property 1) implies a significant reduction in the computation of optimal allocations. As an application, we further characterize optimal policies when the message generation at the transmitter of higher priority is stochastically larger than the message generation at the other. Under additional restrictions on the average arrival rate and the second moment of the number of arrivals per slot, similar results are derived for optimal policies with time-average costs.
A technique is presented for three-dimensional (3-D) reconstruction of the left-ventricular endocardial surface from multiplanar transesophageal echocardiograms, using both commercial software and investigator written...
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A technique is presented for three-dimensional (3-D) reconstruction of the left-ventricular endocardial surface from multiplanar transesophageal echocardiograms, using both commercial software and investigator written Fortran programs for Intel 80286 and 80386 microcomputers. The approach provides quantitative global and regional cardiac performance measures and allows viewing the endocardial surface, at end-diastole and end-systole, from chosen perspectives. Anatomical landmarks are incorporated to aid in orientation. For regional calculation, the surface is divided into equal angular elements with each conceptually connected to the left-ventricular end-diastole centroid, forming a pyramidal volume element. This angular division automatically normalizes for heart size. The fractional change of these elements over the cardiac cycle provides a regional ejection fraction measure which is color-coded on the reconstructed endocardial surface. Composite perspective views, regional ejection fraction histograms and calculations of global end-diastolic, end-systolic, and stroke volumes, are all performed by the method.
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