Benthic foraminifer stable isotope record from Site 849 (0 - 5 Ma) : local and global climate changes

Benthic foraminifer and δ¹³C data from Site 849, on the west flank of the East Pacific Rise (0°11'N, 110°3l'W; 3851 m), give relatively continuous records of deep Pacific Ocean stable isotope variations between 0 and 5 Ma. The mean sample spacing is 4 k.y. Most analyses are from Cibicides wuellerstorfi> but isotopic offsets relative to Uvigerina peregrina appear roughly constant. Because of its location west of the East Pacific Rise, Site 849 yields a suitable record of mean Pacific Ocean δ¹³C, which approximates a global oceanic signal. The ~lOO-k.y.-period climate cycle, which is prevalent in δ¹⁸O does not dominate the long-term δ¹³C record. For δ¹³C, variations in the -400- and 41-k.y. periods are more important. Phase lags of δ¹³C relative to ice volume in the 41- and 23-k.y. bands are consistent with δ¹³C as a measure of organic biomass. A model-calculated exponential response time of 1-2 k.y. is appropriate for carbon stored in soils and shallow sediments responding to glacial-interglacial climate change. Oceanic δ¹³C leads ice volume slightly in the 100-k.y. band, and this suggests another process such as changes in continental weathering to modulate mean river δ¹³C at long periods. The δ¹³C record from Site 849 diverges from that of Site 677 in the Panama Basin mostly because of decay of ¹³C-depleted organic carbon in the relatively isolated Panama Basin. North Atlantic to Pacific δ¹³C differences calculated using published data from Sites 607 and 849 reveal variations in Pliocene deep water within the range of those of the late Quaternary. Maximum δ¹³C contrast between these sites, which presumably reflects maximum influx of high-δ¹³C northern source water into the deep North Atlantic Ocean, occurred between 1.3 and 2.1 Ma, well after the initiation of Northern Hemisphere glaciation. Export of high-δ¹³C North Atlantic Deep Water from the Atlantic to the circumpolar Antarctic, as recorded by published δ'3C data from Subantarctic Site 704, appears unrelated to the North Atlantic-Pacific δ¹³C contrast. To account for this observation, we suggest that deep-water formation in the North Atlantic reflects northern source characteristics, whereas export of this water into the circumpolar Antarctic reflects Southern Hemisphere wind forcing. Neither process appears directly linked to ice-volume variations

Linear system theory

xv, 581 p.; 23 cm

John Hopkins University: Signals Systems Control

The demonstrations given on this Web site are a collection of Java applets and RealAudio clips that explain many underlying concepts of math and engineering. They were developed at John Hopkins University for a project that attempts to use the technology of the World Wide Web in engineering education. Students, under the supervision of electrical and computer engineering professor Dr. Rugh, have prepared many of the demonstrations. The moving graphics help illustrate such difficult topics as convolution, Fourier Series approximations, and signal sampling -- things that cannot be accomplished through traditional text book learning. A total of nineteen demonstrations are available, and one is still under construction

Weak Decoupling in Linear and Nonlinear Systems

For a large class of nonlinear, time-variable parameter systems, a concept of weak decoupling is introduced. This concept is particularly appropriate for terminal value control problems and as an alternative to decoupling. Some of the rather restrictive assumptions needed in the theory of decoupling are not needed for weak decoupling. Also weak decoupling by state variable feedback is often possible when decoupling cannot be accomplished by state variable feedback. Conditions for the existence of weak decoupling control laws are derived and examples are presented which compare decoupling and weak decoupling

Decoupling in a Class of Nonlinear Systems By State Variable Feedback

For a class of nonlinear systems we derive a necessary and sufficient condition for the existence of a state variable feedback control law which accomplishes decoupling, as well as some conditions which characterize the class of decoupling control laws. Several examples are presented to illustrate the application of these results. For a special subclass which includes the so-called bilinear systems, we give two equivalent forms of the necessary and sufficient condition

Decoupling in Linear Time Variable System Using Output Feedback

For a linear time-variable plant which can be decoupled by state variable feedback, the problem of decoupling by output feedback is discussed. The problem is solved by considering the decoupling problem for a system composed of a compensator in cascade with the plant. The use of the compensator allows decoupling by feedback of the output and its time derivatives. For a special class of compensators, the decoupling can be achieved using only output feedback. Although not of minimal dimension, the compensators used in this paper have the advantage of applicability under very general conditions