Academic literature on the topic 'Switching function pattern'

The processes of development form a continuum that begins with gametogenesis and ends only with the death of the individual organism. It is therefore artificial to try to define separate phases and stages of these processes, just as it is artificial to try to separate the structural history of the embryo into a series of discrete forms through time with discrete and definable properties (let alone trying to match such artifacts to putative phylogenetic stages). But at the same time, the sequence of mechanisms of development is hierarchically organized. The major early event is the transfer of control over development itself from the purely maternal factors inherited within the egg and particularly in the egg cytoplasm, to the switching on of the zygotic genome and transfer to zygotic control of cell function, interaction and differentiation, morphogenesis and cytodifferentiation. This transfer does not occur at a single instant, nor is it easy to generalize about it even with a single group of organisms. Other landmarks are harder to find, especially ones that can be compared consistently over a range of different organisms. However, one can roughly divide the processes of development, for the purpose of organizing a discussion at least, into two main phases: early and late pattern formation phases. Early pattern formation can be defined as that part of the developmental sequence in which all the major mechanisms that control the shaping of the embryo, both its morphogenesis and cytodifferentiation, are set into place. In a vertebrate, early pattern formation would be everything from gametogenesis up to and including gastrulation, by which time all the essential elements of tissue interaction that will cause the morphogenesis of the embryo have not only been regionally defined and correctly positioned, but have started to function. Late pattern formation comprises the stages of morphogenesis and cytodifferentiation. As we will see, morphogenesis itself can be divided into two stages, early and late: roughly speaking, in the earlier part, morphogenetic pattern-controlling mechanisms are set in place, and in later stages their results are expressed.

Multilevel inverters have seen an increasing popularity in the last few years for medium- and high-voltage applications. The most popular has been the three-level neutral clamped inverter. Multilevel inverters synthesize output voltage from more than two voltage levels. Thus, the output signal spectrum is significantly improved in comparison with the classical two-level converters. This chapter discusses modelling and control of a Neutral Point Clamped (NPC) inverter which operates with the PWM switching pattern using a DSP. The mathematical model of the NPC inverter is carried out using conversion and connection functions for an easier understanding of the system operation. Simulation results using MATLAB program are reported, and it is shown that the performances obtained for driving an asynchronous motor using this inverter are very promising. Finally, analysis of the theoretical and the experimental results is carried out in order to validate the effectiveness of the proposed control solution.

Twinned crystals are normally classified according to twin-laws and morphology, or according to their mode of origin, or according to a structural basis, but there is another classification that deserves wider acceptance, one that is based on the tensor properties of the orientation states. An advantage of such a classification is the logical relationship between free energy and twin structures, for it becomes immediately apparent which forces and fields will be effective in moving twin walls. The domain patterns in ferroelectric and ferromagnetic materials are strongly affected by external fields, but there are many other types of twinned crystals with movable twin walls and hysteresis. These materials are classified as ferroelastic, ferrobielastic, and various other ferroic species. As explained in the next section, each type of switching arises from a particular term in the free energy function. Ferroic crystals possess two or more orientation states or domains, and under a suitably chosen driving force the domain walls move, switching the crystal from one domain state to another. Switching may be accomplished by mechanical stress (X), electric field (E), magnetic field (H), or some combination of the three. Ferroelectric, ferroelastic, and ferromagnetic materials are well known examples of primary ferroic crystals in which the orientation states differ in spontaneous polarization (P(s)), spontaneous strain (x(s)), and spontaneous magnetization (I(s)), respectively. It is not necessary, however, that the orientation states differ in the primary quantities (strain, polarization, or magnetization) for the appropriate field to develop a driving force for domain walls. If, for example, the twinning rules between domains lead to a different orientation of the elastic compliance tensor, a suitably chosen stress can then produce different strains in the two domains. This same stress may act upon the difference in induced strain to produce wall motion and domain reorientation. Aizu suggested the term ferrobielastic to distinguish this type of response from ferroelasticity, and illustrated the effect with Dauphine twinning in quartz. Other types of secondary ferroic crystals are listed in Table 16.1, along with the difference between domain states, and the driving fields required to switch between states.

An individual switching technique for semi-conductor components of power converters presents an individual electrical and thermal output performance. Therefore, understanding the switching patterns or sequence and their effect can significantly improve the overall performance of the power converters. In this paper, a sequence based control methodology for a power converter system to optimize its electrical and thermal performance will be presented, analysed, and discussed. The method includes modelling the converter system with respect to a sequence of switching events, defining and formulating the control objectives into a form of a cost function, and solving the cost function for the optimal electrical performance.

Abstract Focused Ion Beam (FIB) chip circuit editing is a well-established highly specialized laboratory technique for making direct changes to the functionality of integrated circuits. A precisely tuned and placed ion beam in conjunction with process gases selectively uncovers internal circuitry, create functional changes in devices or the copper wiring pattern, and reseals the chip surface. When executed within reasonable limits, the revised circuit logic functions essentially the same as if the changes were instead made to the photomasks used to fabricate the chip. The results of the intended revision, however, can be obtained weeks or months earlier than by a full fabrication run. Evaluating proposed changes through FIB modification rather than proceeding immediately to mask changes has become an integral part of the process for bringing advanced designs to market at many companies. The end product of the FIB process is the very essence of handcrafted prototyping. The efficacy of the FIB technique faces new challenges with every generation of fabrication process node advancement. Ever shrinking geometries and new material sets have always been a given as transistor size decreases and overall packing density increases. The biggest fundamental change in recent years was the introduction of the FinFET as a replacement for the venerable planar transistor. Point to point wiring change methodology has generally followed process scaling, but transistor deletions or modifications with the change to Fins require a somewhat different approach and much more careful control due to the drastic change in height and shape. We also had to take into consideration the importance of the 4th terminal, the body-tie, that is often lost in backside editing. Some designs and FET technology can function acceptably well when individual devices are no longer connected to the bulk substrate or well, while others can suffer from profound shifts in performance. All this presents a challenge given that the primary beam technology improvements of the fully configured chip edit FIB has only evolved incrementally during the same time period. The gallium column system appears to be reaching its maximum potential. Further, as gallium is a p-type metal dopant, there are limitations to its use in close proximity to certain active semiconductor devices. Amorphous material formation and other damage mechanisms that extend beyond what can be seen visually when endpointing must also be taken into account [1]. Device switching performance and even transmission line characteristics of nearby wiring levels can be impacted by material structural changes from implantation cascades. Last year our lab participated in a design validation exercise in which we were asked to modify the drive of a multi-finger FinFET device structure to reduce its switching speed impact on a circuit. The original sized device pulled the next node in the chain too fast, resulting in a timing upset. Deleting whole structures and bridging over/around them is commonly done, but modifications to the physical size of an FET device is a rare request and generally not attempted. It requires a level of precision in beam control and post-edit treatment that can be difficult to execute cleanly. Once again during a complex edit task we considered the use of an alternate ion beam species such as neon, or reducing the beam energy (low kV) on the gallium tool. Unfortunately, we don’t yet have easy access to a versatile viable replacement column technology grafted to a fully configured edit station. And while there should be significantly reduced implant damage and transistor functional change when a gallium column FIB is operated at lower accelerating potential [2], the further loss of visual acuity due to the reduced secondary emission, especially when combined with ultra-low beam currents, made fast and accurate navigation near impossible. We instead chose the somewhat unconventional approach of using an ultra-low voltage electron beam to do much of the navigation and surface marking prior to making the final edits with the gallium ion beam in a dual-beam FIB tool. Once we had resolved how to accurately navigate to the transistors in question and expose half of the structure without disturbing the body-tie, we were able to execute the required cut to trim away 50% of the structure and reduce the effective drive. Several of the FIB modified units functioned per the design parameters of a smaller sized device, giving confidence to proceed with the revised mask set. To our surprise, the gallium beam performed commendably well in this most difficult task. While we still believe that an inert beam of similar characteristics would be preferable, this work indicates that gallium columns are still viable at the 14 nm FinFET node for even the most rigorous of editing requirements. It also showed that careful application of e-beam imaging on the exposed underside of FinFET devices could be performed without degrading or destroying them.

Abstract Via analytical modeling and experimental validation, this study examines the bending stiffness adaptation of bistable origami modules based on generalized Kresling pattern. These modules, which are the building blocks of an octopus-inspired robotic manipulator, can create a reconfigurable articulation via switching between their stable states. In this way, the manipulator can exhibit pseudo-linkage kinematics with lower control requirements and improved motion accuracy compared to completely soft manipulators. A key to achieving this reconfigurable articulation is that the underlying Kresling modules must show a sufficient difference in bending stiffness between their stable states. Therefore, this study aims to use both a nonlinear bar-hinge model and experimental testing to uncover the correlation between the module bending stiffness and the corresponding origami designs. The results show that the Kresling origami module can indeed exhibit a significant change in bending stiffness because of the reorientation of its triangular facets. That is, at one stable state, these facets align close to parallel to the longitudinal axis of the cylindrical-shaped module, so the module bending stiffness is relatively high and dominated by the facet stretching. However, at the other stable states, the triangular facets are orientated close to perpendicular to the longitudinal axis, so the bending stiffness is low and dominated by crease folding. The results of this study will provide the necessary design insights for constructing a fully functional manipulator with the desired articulation behavior.