Operational Degrees Of Freedom Research Articles

An Accordion-Folding Series-Fed Patch Array With Finite Thickness: A folding technique for CubeSat arrays

Combining antenna arrays with physical reconfigurability (i.e., origami) allows for additional degrees of freedom in operation and enables larger structures to be folded into smaller volumes. The packaging ability of origami antennas is of great interest for CubeSat applications in particular. However, traditional origami is based on the manipulation of thin sheets, making physical reconfigurability with thick substrates very difficult. In this article, we present a foldable series-fed patch array designed on a strictly rigid printed circuit board (PCB). Notably, the array does not require any external mechanical folding appendages (i.e., brackets, tapes, or offsets), and it can be manufactured using commercially available PCBs and equipment. The PCB itself is strategically cut to form lamina emergent torsion (LET) joints. When fully deployed, the array operates at 5.7 GHz. A significant shift is not seen in the operational frequency until the folding exceeds 60° (5.7–5.61 GHz). This shows that the array, even in a state of near extreme faulty deployment, will operate as intended. An 8 × 6 prototype array was fabricated using a Rogers DiClad 880. When fully deployed, the array is extended in a surface area of 280 × 198 × 1.524 mm and can be folded into a 35.5 × 198 × 12.5-mm compartment. The array held its integrity well after 100 cycles. (One cycle starts at a state of full deployment, moves to a state of being fully packaged, and goes back to a state of full deployment.) Measurements show that the active reflection coefficients are in good agreement with the finite array simulations. The measured realized gains at 5.7 GHz for 0° and 30° folds were 22.4 and 21.4 dBi, respectively. At the 60° fold, a realized gain of 20.6 dBi was achieved at the frequency of 5.61 GHz.

Leaky-wave metasurfaces for integrated photonics.

Metasurfaces have been rapidly advancing our command over the many degrees of freedom of light; however, so far, they have been mostly limited to manipulating light in free space. Metasurfaces integrated on top of guided-wave photonic systems have been explored to control the scattering of light off-chip with enhanced functionalities-namely, the point-by-point manipulation of amplitude, phase or polarization. However, these efforts have so far been limited to controlling one or two optical degrees of freedom at best, as well as device configurations much more complex compared with conventional grating couplers. Here we introduce leaky-wave metasurfaces, which are based on symmetry-broken photonic crystal slabs that support quasi-bound states in the continuum. This platform has a compact form factor equivalent to the one of grating couplers, but it provides full command over the amplitude, phase and polarization (four optical degrees of freedom) across large apertures. We present devices for phase and amplitude control at a fixed polarization state, and devices controlling all the four optical degrees of freedom for operation at a wavelength of 1.55 μm. Merging the fields of guided and free-space optics through the hybrid nature of quasi-bound states in the continuum, our leaky-wave metasurfaces may find applications in imaging, communications, augmented reality, quantum optics, LIDAR and integrated photonic systems.

A method of character input for the user interface with a low degree of freedom

In recent times, smart devices equipped with small touch panels have become very popular. Many such smart devices use a software keyboard for character input. Unfortunately, software keyboards have a limitation: the number of buttons and the input degrees of freedom remain the same, because a button and an input value correspond one-to-one. Thus, if we reduce the screen size while the button size remains the same, the number of buttons must decrease. Alternatively, if we maintain the number of buttons and reduce the screen size, the size of the button decreases, making input increasingly difficult. In this study, we investigate a new character input method that is specifically adapted for use on small screens. The proposed input interface has 4 × 2 operational degrees of freedom and consists of four buttons and two actions. By handling two operations as one input, 64 input options are secured. Additionally, we experimentally evaluate the proposed character input user interface deployed on a smart device. The proposed method enables an input of approximately 25 characters per minute, and it shows robust input performance on a small screen compared to previous software methods. Thus, the proposed method is better suited to small screens than were previous methods.

Optimal Operation and Control of Four-Product Dividing-Wall (Kaibel) Distillation Column

Due to globalization and increased market competition, the process industry is seeking to maximize productivity at minimal operational cost. Distillation operation alone accounts for a significant amount of the world’s energy consumption. This consumption can be greatly reduced by using a complex distillation column configuration, such as a fully thermally coupled distillation column or divided-wall distillation column, over conventional arrangements. The divided-wall column offers potential energy and capital investment savings. In this study, it was shown that energy savings of up to 25% can be achieved by using a four-product divided-wall distillation column (Kaibel) compared with conventional column arrangements. The reported capital investment associated with a four-product divided-wall column is approximately 30%. However, design and operation remain a challenge due to the large number of design and operational degrees of freedom. Divided-wall columns can be used for multicomponent separation as well. This research demonstrated the steady-state and dynamic behavior of a Kaibel distillation column using commercial simulation software, i.e., Aspen HYSYS. A self-optimizing control scheme was implemented to reject disturbances during operation and to meet the required product specifications for a Kaibel distillation column.

Continuous production of CO from CO2 by RWGS chemical looping in fixed and fluidized bed reactors

A fixed bed and a fluidized bed reactor design for the reverse water-gas shift chemical looping (RWGS-CL) process with 80 wt% Fe2O3-Ce0.5Zr0.5O2 as oxygen storage material (OSM) are analyzed and compared by process simulation. The influence of gas inlet flow velocity on the reaction regime is investigated and feasible regions of operation for continuous CO production are identified. Two performance indicators are defined for the process: (1) the average CO concentration and (2) the OSM utilization. Optimization problems are solved to maximize the performance indicators and analyze their mutual dependency. The results are discussed in a Pareto plot. It is shown that a fixed bed reactor design is advantageous for the RWGS-CL process because of more degrees of freedom for operation compared to the fluidized bed reactor design. A quasi-continuous production of CO is demonstrated for both reactor designs. A steady CO production with an average CO mole fraction of x¯CO=0.64 and an OSM utilization of 83.9% can be realized with two fixed bed reactors. The fluidized bed reactor configuration can potentially minimize problems associated with material sintering but the average CO concentration and OSM utilization are significantly lower compared to the fixed bed due to the limited operational freedom. The results indicate the importance of dynamic simulations for understanding and exploiting the kinetic and thermodynamic aspects of inherently dynamic processes like RGWS-CL to maximize process performance.

Steady-state operational degrees of freedom in absorption chillers and heat pumps: Methodology and case study

The main purpose of modelling and analysing absorption chillers and heat pumps in operation is to reproduce the system performance using operational data. To perform this analysis, the first two important issues are finding the number of degrees of freedom of the system model and identifying which set of operational process variables are appropriate to reduce the available degrees of freedom to zero. Applying the conventional method of finding degrees of freedom for advanced cyclic processes is a complex, confusing and time consuming process. This paper proposes a simple and straight forward systematic method for determining the degrees of freedom and a way of selecting the appropriate set of process variables to close the mathematical models developed for absorption chillers and heat pumps in operation. The method is applied to different examples of absorption cycles ranging from simple to advanced (complex) configurations. It is also applied to a small scale ammonia-water absorption chiller in a pilot plant to demonstrate the systematic selection of operational process variables for developing a well-posted model for absorption chillers and heat pumps in operation.

Multiagent Strategic Interaction Based on a Game Theoretical Approach to Polarization Reversal in Ferroelectric Capacitors

Ferroelectric materials are currently integrated in nonvolatile memory devices, whose principle is to allocate 0 and 1 logic bits to opposite orientations of the spontaneous polarization vector that are permitted by crystal symmetry. Typically made of randomly oriented grains, ferroelectrics tend to split into domains, according to the experienced sequence of electric fields, thermal treatments and any structural imperfections. On this background, we attempt to formulate new principles of exploiting such structural and operational degrees of freedom for unconventional applications of ferroelectrics. In this paper, we envision a new paradigm of ferroelectrics as processors of multiagent strategic interactions, employing unconventional mathematical tools (normally used for optimizing the decision-making process of rational human subjects) for analyzing ferroelectric capacitors’ response to combinatorial pulses. Specifically, we quantify the way microscopic assembly laws of the ferroelectric material mediate the amount of polarization reversed by two electrical pulses using the mathematical theory of games, applied to a strategic interaction between two hypothetical players impersonated by the two pulses. Such socially meaningful implementations of applied mathematics concepts onto an oxide material substrate are worth to consider in view of artificial intelligence applications, adding ferroelectrics to the class of media able to perform unconventional computations.

J0207-2-2 関節鏡総合トレーニングシステムに関する研究([J0207-2]医療・福祉工学のための3次元造形)

Arthroscopic surgery has become increasingly common in recent years. In this surgical technique, the visual field is extremely limited and the degrees of freedom in operation are lower than that in open surgery. An immature surgical technique could run the risk of damaging articular cartilage and causing other complications, and there only a few reported systems for the objective evaluation of surgical skills in arthroscopic surgery training programs. We propose a training system for arthroscopic surgery using a newly developed box trainer, which is believed to provide more efficient training for surgeons. The box trainer has ten kinds of training exercises. Each task is aimed at training specific skills required for arthroscopic surgery, using simple geometrical shapes or realistic anatomical shapes. The box trainer is controlled by a microcomputer and is able to inform trainees of score, working time and the number of errors. Trainees are notified with a beep alarm when errors are performed. Knee models are fabricated for these tasks using anatomical information from a magnetic resonance imaging knee data set and a 3D reconstruction algorithm with computer-aided manufacturing .

Towards the systematic design of actuation for process systems

Currently systematic design of actuation (operational degrees of freedom) for process systems is not possible because (i) the required domain knowledge has not been identified and (ii) it is unclear how to explore the relation between actuation and operational improvement. This paper proposes geometry and flux equations as the required domain knowledge. It is explained that the relation between actuation and operational improvement should be explored in an optimal control setting. By means of an example (distillation) it is illustrated that a spatial actuation extension may result in considerable operational improvement.

Design and optimization of a hybrid distillation/melt crystallization process

AbstractHybrid distillation/melt crystallization processes are widely used for the separation of isomer mixtures. The design of a hybrid separation processes is not a trivial task because of several structural and operational degrees of freedom. In this article, a new three‐step design approach is proposed to address the above mentioned challenges. In the first step, process alternatives are generated by heuristic rules. In the second step, the generated process alternatives are optimized with respect to their energy consumption by using shortcut methods. In the third step, the most promising alternatives are rigorously optimized with respect to their total annualized costs, whereas the resulting mixed‐integer nonlinear programming (MINLP) problem is solved using a modified generalized benders decomposition (GBD) algorithm to take the nonconvexities into account. The feasibility of this design approach is demonstrated by design of a hybrid distillation/melt crystallization process for separation of a ternary isomer mixture. © 2008 American Institute of Chemical Engineers AIChE J, 2008

Significance of kinetic degrees of freedom in operation of the actomyosin motor

The actomyosin motor as a principal functional component of cell motility is highly coordinated in regulating the participating molecular components. At the same time, it has to be flexible and plastic enough to accommodate itself to a wide variety of operational conditions. We prepared two different types of actomyosin systems. One is a natural intact actomyosin system with no artificial constraint on the kinetic degrees of freedom of the actin filaments, and the other is a regulated one with actin filaments supplemented by intra- and intermolecular crosslinking to suppress the kinetic degrees of freedom to a certain extent. Crosslinked actomyosin systems were found to remain almost insensitive to calcium regulation even when intact troponin–tropomyosin regulatory component was incorporated. Both the ATPase and the motile activities of the actin filaments sliding on myosin molecules were markedly lowered by the crosslinking. In contrast, once the crosslinking was cleaved, both properties returned to the normal as with intact actomyosin systems.

Pollution prevention targets through integrated design and operation

Pollution prevention is one of most pressing objectives for the process industries. In order to set realistic targets for reducing industrial wastes, it is necessary to establish targets for most achievable extent of pollution prevention. In this paper we present a mass-integrated systematic procedure for identifying pollution prevention. In this paper we present a mass-integrated systematic procedure for identifying pollution prevention targets of a process. These targets account for the plant data and anticipated disturbances. A combination of design and operational degrees of freedom are employed to prevent pollution. Species propagation and process performance are tracked via path equations. Mass integration tools along with inclusion isotonicity of interval arithmetic are employed to establish the targets. Several classes of problems are addressed. These include instantaneous and averaged targets for pollution prevention with sink/generator manipulation and targets for material utilities and feedstocks with recycle and interception. The identified targets are global regardless of the non-linearity and non-convexity characteristics of the system.

Optimization of the operation of a gas terminal

Optimal operation of complex process plants requires the assistance of computer systems for day to day operation. The application of computers in plant operation comprises: 1. optimization systems to define the global plant set points such as product purities keeping in mind the physical limits of plant equipment and the boundary conditions of the market for feed and products; and 2. advanced process control systems which help the operator to keep the plant as close to these global set points as possible. This paper deals with the various aspects of an optimization system, which was developed for the gas terminal at Karstø, Norway. It will be shown that, due to the complex process sequence of this plant, the wide range of feedstock quality and the numerous degrees of freedom for operation, the use of the optimization system is essential to ensure plant operation close to its physical limits at minimum operating cost. The optimization system is designed for off-line usage, but can be extended later for on-line use.