Quasi-optimal Design Research Articles

URLLC in UAV-enabled multicasting systems: A dual time and energy minimization problem using UAV speed, altitude and beamwidth

Realizing ultra-high reliability for short packets in sixth-generation (6G) networks is a crucial task for network designers as classical Shannonian capacity bounds become obsolete. Moreover, for multiuser communications, due to distinct aerodynamics, the trajectory design for a fixed-wing unmanned aerial vehicle (UAV) fundamentally differs from rotary-wing UAVs, which poses a challenge for systems designers. This paper addresses these challenges and relies on a fixed-wing UAV-enabled multicasting system to deliver common short blocklength ultra-reliable and low-latency (URLLC) packets to the ground nodes (GNs) using a Snake Traversal trajectory path. To accomplish this task, we consider the fly-and-communicate protocol for the UAV, where the UAV sweeps a large rectangular area to disperse a common file to GNs with obscure positions. In this vein, we investigate the dual time and energy minimization problems by presenting a quasi-optimal design of the UAV’s flying speed, altitude, and antenna beamwidth. Simulation results of numerical search reveal the optimal altitude and half-power beamwidth, which minimize the completion time and energy consumption, respectively. Moreover, for optimized beamwidth, the UAV speed monotonically increases with the altitude, whereas both the completion time and energy consumption monotonically decrease with the altitude. We also analyze the effects of the blocklength and decoding error probability on optimal UAV speed, completion time, and energy consumption. Additionally, simulation results show that for the completion time, the percentage difference between minimum UAV altitude hmin and maximum UAV altitude hmax is 195.252%, whereas for the energy consumption, the percentage difference at hmin and hmax is 196.912%. Similarly, for the completion time, the percentage difference at minimum UAV antenna beamwidth θmin and maximum UAV antenna beamwidth θmax is 181.586%, whereas for the energy consumption the percentage difference at θmin and θmax is 189.269%. This demonstrates the efficacy of the proposed technique is almost two times in reducing the completion time and the energy consumption effectively between the minimum and the maximum values of the UAV altitude and the UAV antenna beamwidth. Lastly, the results show that for both the blocklength and decoding error probability, the UAV speed monotonically increases, while completion time and energy consumption monotonically decrease.

URLLC-Enabled by Laser Powered UAV Relay: A Quasi-Optimal Design of Resource Allocation, Trajectory Planning and Energy Harvesting

Ultra-reliable and low-latency (URLLC) traffic in the upcoming sixth-generation (6G) systems utilize short packets, signalling a distancing from traditional communication systems devised only to support long data packets based on Shannon&#x0027;s capacity formula. This poses a formidable challenge for system designers and network operators. Many URLLC scenarios involve infrastructure-less unmanned aerial vehicle (UAV)-assisted communications. One of the biggest challenges with UAVs is their limited battery capacity, which can cause abrupt disruption of UAV-assisted communications. To overcome these limitations, we consider URLLC-enabled <i>over-the-air</i> charging of UAV relay system using a laser transmitter. Furthermore, we formulate a non-convex optimization problem to minimize the total decoding error rate subject to optimal resource allocation, including blocklength allocation, power control, trajectory planning, and energy harvesting to facilitate URLLC in such systems. In this regard, given its lower complexity, a novel perturbation-based iterative method is proposed to solve the optimization problem. The proposed method yields optimal blocklength allocation and power control for the two transmission phases, i.e., from the source node to the UAV and from the UAV to the robot acting as a ground station. It also maps the UAV trajectory from the initial position to the final position, and the UAV completes the flight using the laser&#x0027;s harvested energy. It is shown that the proposed algorithm and fixed baseline scheme, named fixed blocklength (FB), yield a similar performance as the exhaustive search in terms of UAV energy consumption. In contrast, fixed trajectory (FT) delivers the worst performance. Simultaneously, the proposed method yields the best performance in terms of the lowest average overall decoding error compared to fixed baseline schemes, including FB and FT, showing the efficacy of the proposed technique.

Quasi-optimal design of a parallel-type double-mass dynamic vibration absorber equipped with a damped primary system

This is a follow-up article to a talk given a week ago at the D&D 2022 conference. At that time, we discussed the rate of deterioration of vibration suppression performance of the DVA optimized based on the H∞ criterion that occurs when the two absorber masses of a parallel-type double-mass dynamic vibration absorber (DVA) are set to equal. There are five dimensionless parameters necessary for optimal design of the double-mass DVA. One of them is the mass ratio of two absorbers arranged in parallel. Depending on a given system condition, the optimum mass ratio of the two absorbers becomes as small as 0.75(75%), but even when this mass ratio is set to 100%, the degradation rate of the DVA performance was only 0.43%. Now, in addition to the H∞ criterion, which aims to minimize the height of the resonance point of the primary system, there is the H2 criterion, which minimizes the area (called the H2 norm, which represents the energy of the vibration) under the curve obtained by squaring the frequency response function. In this presentation, we investigate how much the performance of a DVA designed with this H2 criterion deteriorates when the two absorber masses are equal.

Quasi-optimal design of a parallel-type double-mass dynamic vibration absorber equipped with a damped primary system

Multiplexing dynamic vibration absorbers (DVAs) provide better vibration control force compared to that obtained with classical single-mass DVAs. In fact, previous studies have shown that the vibration suppression performance of double-mass DVAs is superior to that of the single-mass DVAs. In the optimal design of a parallel-type double-mass DVA, five dimensionless design parameters must be optimized. One of them is the mass ratio of two DVAs arranged in parallel. However, in many cases, especially in the parallel-type, the mass ratio of two DVAs cannot be set to the optimal value, because existing structures and machine parts are sometimes used as DVAs. In this report, I investigated how the optimal values of other design parameters change when the two DVA masses are set equal, and finally, how bad the vibration suppression performance of DVA becomes.

On a Quasi Optimal Algorithm for Analog Circuits Optimization

An analog circuit design methodology based on applications of control theory is the basis for constructing an optimal or quasi-optimal design algorithm. The main criterion for identifying the required structure of the algorithm is the behavior of the Lyapunov function, which was decisive for the circuit optimization process. The characteristics of the Lyapunov function and its derivative are the basis for finding the optimal structure of the control vector that determines the structure of the algorithm. A block diagram of a quasi-optimal algorithm that implements the main ideas of the methodology is constructed, and the main characteristics of this algorithm are presented in comparison with the traditional approach

A quasi-optimal design formula of a parallel-type double-mass dynamic vibration absorber based on the stability criterion

A quasi-optimal design formula of a parallel-type double-mass dynamic vibration absorber based on the stability criterion

Integration of Ordinal Optimization with Ant Lion Optimization for Solving the Computationally Expensive Simulation Optimization Problems

The optimization of several practical large-scale engineering systems is computationally expensive. The computationally expensive simulation optimization problems (CESOP) are concerned about the limited budget being effectively allocated to meet a stochastic objective function which required running computationally expensive simulation. Although computing devices continue to increase in power, the complexity of evaluating a solution continues to keep pace. Ordinal optimization (OO) is developed as an efficient framework for solving CESOP. In this work, a heuristic algorithm integrating ordinal optimization with ant lion optimization (OALO) is proposed to solve the CESOP within a short period of time. The OALO algorithm comprises three parts: approximation model, global exploration, and local exploitation. Firstly, the multivariate adaptive regression splines (MARS) is adopted as a fitness estimation of a design. Next, a reformed ant lion optimization (RALO) is proposed to find N exceptional designs from the solution space. Finally, a ranking and selection procedure is used to decide a quasi-optimal design from the N exceptional designs. The OALO algorithm is applied to optimal queuing design in a communication system, which is formulated as a CESOP. The OALO algorithm is compared with three competing approaches. Test results reveal that the OALO algorithm identifies solutions with better solution quality and better computing efficiency than three competing algorithms.

Quasi-Optimal Design of the Switched Reluctance Motor

The article deals with issues that arise in the process of designing a high-speed switched reluctance motor electric generator for working together with a steam microtubule. A method of two-stage optimization of the geometric relations of the stator and rotor of a switched reluctance motor is described. The first of them is used to search for geometric relationships without taking into account the losses in the magnetic system and the shape of the current pulse in the windings. At the second stage, rational parameters of the voltage pulse applied to the winding are determined for the selected options, losses in the magnetic system and in the windings of the electric machine under consideration are calculated, and one of the options is selected, which is considered quasi-optimal, providing minimum losses at the maximum developed moment.

A Multi-Level Optimization Method for Elastic Constants Identification of Composite Laminates

A new and effective elastic constants identification technique is presented to extract the elastic constants of a composite laminate subjected to uniaxial tensile testing. The proposed technique consists of a new multi-level optimization method that can solve different types of minimization problems, including the extraction of material constants of composite laminates from given strains. In the identification process, the optimization problem is solved by using a stochastic multi-start dynamic search minimization algorithm at the first level in order to obtain the statistics of the quasi-optimal design variables for a set of randomly generated starting points. The statistics of the quasi-optimal elastic constants obtained at this level are used to determine the reduced feasible region in order to formulate the second-level optimization problem. The second-level optimization problem is then solved using the particle swarm algorithm in order to obtain the statistics of the new quasi-optimal elastic constants. The iteration process between the first and second levels of optimization continues until the standard deviations of the quasi-optimal design variables at any level of optimization are less than the prescribed values. The proposed multi-level optimization method, as well as several existing global optimization algorithms, is used to solve a number of well-known mathematical minimization problems to verify the accuracy of the method. For the adopted numerical examples, it has been shown that the proposed method is more efficient and effective than the adopted global minimization algorithms to produce the exact solutions. The proposed method is then applied to identify four elastic constants of a [0°/±45°]s composite laminate using three strains in 0°, 45°, and 90° directions, respectively, of the composite laminate subjected to uniaxial testing. For comparison purposes, several existing global minimization techniques are also used to solve the elastic constants identification problem. Again, it has been shown that the proposed method is capable of producing more accurate results than the adopted available methods. Finally, experimental data are used to demonstrate the applications of the proposed method.

Exploring the Possibilities for Improving the Performance of the Adapters used for Launching Multiple Small Space Vehicles on a Single Launch Vehicle

Background/Objectives: The research is aimed at determining the ways to improve the effectiveness of reconfigurable and extendable multipurpose adapters for multiple launch of small space vehicles by a launch vehicle. Methods: The structural design method is selected for studying design and constructive shape of the SSV adapters. The structural approach was used to define the principle for optimization of adapters of various constructive schemes, excluding modifications of launch vehicle used for multiple launches and enabling to extend and reduce adapter configuration with respect to a universal basic structure used for all tasks for SSV launch to be solved. Findings: To obtain quasi-optimal design and engineering parameters for the entire target set of tasks solved by the adapter, based on the structural approach we have considered design schemes of multi-purpose adapters for multiple and concurrent launching of SSVs of rod, shell, beam and platform types with side and end attachment configuration, the schemes with shock absorbers mounted in the places of adapters and MCAs installation, and scheme configuration combining adapter + small upper stage. The base and extension structures have been determined to form multi-purpose adapter with flexible and extensible design. As a result of the proposed technical solutions, weight of the adapter is reduced by 30%, configuration density is increased by 30-40 %, the number of the launched SSVs is increased, the fairing length and weight is reduced by 50%, root-mean-square amplitudes of accidental vibration decreased by 2.5-3 times, level of shock loads during SSV separation decreases by 6-10 dB, provision is made for shockless separation of SSV required lateral alignment of LV, cost reduction for ground and flight tests. Application/Improvements: Further improvement of the multi-purpose adapters is connected with the co-design of “Adapter + SSV” system, taking into account the mutual influence of design and engineering parameters of the SSV, adapter and LV used to launch them.

A New Method for Quasi-Optimal Design of Water Distribution Networks

In recent years optimal design of water distribution networks (WDNs) has been a subject of interest to several researchers. In this regard, in the previous researches various optimization techniques such as linear and non-linear programming and also meta-heuristic algorithms have been used for optimal design of WDNs. Among these techniques, meta-heuristic algorithms have shown the best performance. One of the disadvantages of implementing these methods for optimizing of WDNs is their high computational costs which make their usage sometimes impossible for large real life WDNs. In this paper a new method for quasi-optimal design of WDNs is presented. In the proposed method that is based on some hydraulic rules, diameters are selected so that the energy loss per unit length of pipes will be in a specific range. Using this method and without any requirement to available optimization techniques, design of WDNs can be done in a lower time relative to the mentioned techniques, so that the cost of the designed network will be very close to the least cost. Two sample networks have been designed using the proposed new method. Comparison of the obtained results with the available optimization techniques indicates the ability of this method to find the near optimal solutions in the shortest time.

Structure of quasi-optimal time algorithm for analog circuits design

The generalized methodology developed earlier for analog circuits design and based on applying the optimal control theory is the basis for developing an optimal or quasi-optimal design algorithm. In this context the most crucial criterion making it possible to find the required structure of algorithm is the behavior of the Lyapunov function determined for circuit optimization process. Characteristics of the Lyapunov function and its derivative form the basis of search for the optimal structure of control vector which, in turn, determines the algorithm structure. A functional block diagram of the quasi-optimal algorithm implementing the main ideas of the earlier developed methodology has been built, and the main characteristics of this algorithm were determined in comparison with the traditional approach and with quasi-optimal design strategy.

Analysis and Design of a Bidirectional Isolated DC–DC Converter for Fuel Cells and Supercapacitors Hybrid System

Electrical power systems in future uninterruptible power supplies or electrical vehicles may employ hybrid energy sources, such as fuel cells and supercapacitors. It will be necessary to efficiently draw the energy from these two sources as well as recharge the energy storage elements by the dc bus. In this paper, a bidirectional isolated dc-dc converter controlled by phase-shift angle and duty cycle for the fuel-cell hybrid energy system is analyzed and designed. The proposed topology minimizes the number of switches and their associated gate driver components by using two high-frequency transformers that combine a half-bridge circuit and a full-bridge circuit together on the primary side. The voltage doubler circuit is employed on the secondary side. The current-fed input can limit the input current ripple that is favorable for fuel cells. The parasitic capacitance of the switches is used for zero voltage switching (ZVS). Moreover, a phase-shift and duty-cycle modulation method is utilized to control the bidirectional power flow flexibly and it also makes the converter operate under a quasi-optimal condition over a wide input voltage range. This paper describes the operation principle of the proposed converter, the ZVS conditions, and the quasi-optimal design in depth. The design guidelines and considerations regarding the transformers and other key components are given. Finally, a 1-kW 30~50-V-input 400-V-output laboratory prototype operating at 100-kHz switching frequency is built and tested to verify the effectiveness of the presented converter.

Feasibility analysis of isopropanol recovery by hybrid distillation/pervaporation process with the aid of conceptual models

In this contribution, main results of a techno-economic feasibility study to recover spent isopropyl alcohol (IPA) from a pre-treated waste stream composed by IPA (95.64 wt.%) and water (4.36 wt.%) are presented. Based on conceptual models for the unit operations, a quasi-optimal design for a hybrid process combining pervaporation and distillation is found under process specifications given by a pharmaceutical company. The proposed procedure allows a separated design of each unit with the aid of conceptual models. While distillation is evaluated from pinch theory, the conceptual model for pervaporation considers that the maximum driving force (i.e., no liquid temperature drop) is maintained across the membrane unit. A brief performance comparison for different membranes is also performed as part of the assessment to the company. For this purpose, the pervaporation separation index (PSI index) defined as the product of the permeate mass flux and the separation factor was used for membranes for which either literature data or membrane supplier brochures were available. In the case of the membrane PERVAP 2216 from Sulzer, several pervaporation experiments at 80 °C and permeate pressure of 1.52 kPa were carried out. The PSI index was then redefined as the overall separation factor times the inverse of the minimum membrane area required to perform a given separation. The results obtained emphasize the usefulness of conceptual modeling in all steps of process design.

Designing 2-Phase Prevalence Studies in the Absence of a "Gold Standard" Test

A population survey for estimating prevalence is challenging when a disease or condition is difficult to diagnose. If clinical diagnosis is expensive, a 2-phase study, in which less expensive but less accurate tests are administered to all study subjects in the first phase (screening phase) and a more accurate but expensive or time-consuming test is administered to only a subset of the subjects in the second phase, is an attractive approach. Published research has discussed ways of maximizing precision of the prevalence estimate from a 2-phase study with a "gold standard" second-phase test. For many psychiatric disorders, even the best diagnostic tests are not of gold standard quality. In this paper, the authors propose a quasi-optimal design for 2-phase prevalence studies without a gold standard test; random-effects latent class analysis facilitates the estimation of prevalence and appropriately addresses the issue of dependent errors among the diagnostic tests. The authors show that the quasi-optimal design is efficient compared with the balanced and random designs when there is strong inter-test dependence caused by additional factors, apart from disease status, and highlight the importance of collecting data on those subjects testing negative in the first phase.

A forest of principles

I am astonished at Lewis Wolpert's claim that all the big principles in biology are understood — especially in developmental biology. If one knew all the principles then new facts would simply slot into their expected places, as they do in any well understood aspect of physics. But in all areas of biology bewildering new facts are discovered at an increasing rate. I frankly do not believe that Wolpert has a conceptual scheme where each new fact simply evokes an acquiescent nod of the head. Either he is goading us into protest or his ‘principles’ are very different from mine.What can we expect of principles in biology? Consider ‘the principle of quasi-optimal design.’ There are physical limits that dictate the relative sizes of parts of different-sized animals. Thus, a mouse's eye is many times larger than an elephant eye scaled down in proportion to the size of the mouse: the latter would have a minute pupil giving appalling spatial resolution and admitting very little light. Similarly, the elephant's legs would break every time it stood up if they were simply the mouse's legs scaled up in size.These ‘design principles’ are our minds' generalization from particular instances that have been embodied in genomes under the action of natural selection. We have successfully found a few such generalizations, but we emphatically do not understand all the physical limiting factors that have moulded the genomes of all species, and I have not even heard mention of limiting factors in development, although they must surely exist.Now consider a problem in neuroscience. The neocortex of the brain is large in primates and huge in humans; comparative neuroanatomists have told us that it stores knowledge of the world, and if they are right, we can understand the selective advantage it gives us. Neurophysiologists, on the other hand, tell us how the neocortex represents sensory stimuli but say nothing about how this representation is analysed, stored, accessed or used. Only a fool could hold that no new principles might emerge from reconciling these two astonishingly different accounts.I think my examples illustrate the general nature of biological principles. There are not just a few universal ones like the great conservation laws of physics. Instead, they form a forest, and quasi-optimal design is but one tree in it — or perhaps just a branch of the Tree of Adaptation. Wolpert might claim that adaptations are all examples of a single general principle which we already know, but this is unhelpful because we need to know what factor is limiting in each particular case: optics will not help you to understand the elephant's leg bones or neocortical size. If we did understand all the relevant limiting factors, we would be closer to knowing why a species has evolved to a certain average size, why the mass of its neocortex is a particular fraction of its body mass, and so on for many questions that we do not yet even know enough to ask. It is an absolutely safe bet that there are many new principles waiting to be found.Mendel discovered both a whole range of new facts and the principle by which they could be understood, but few are so lucky nowadays. Thus, my request to the good fairy godmother of science would be “Please give me exact references to some facts that require new concepts for their understanding”. I would add “Please pick facts pointing to concepts appropriate for my energies and abilities; I could not handle a tree of Darwinian or Mendelian size, but I would greatly enjoy some of the conceptual fruit still to be found in plenty out among the leafy branches of the Biological Forest of Principles”.

On the selection of measures of distance between probability distributions

A notion of relative strength and weakness is defined for the comparison of measures of distance between probability distributions and is shown to be appropriate for use in the selection of distances as quasioptimal design criteria in problems such as signal selection and detector design when the preferred criteria, probability of error and asymptotic relative efficiency, are intractable. Csiszar's work on the topological properties of ƒ-divergences, a class of distances also investigated by Ali and Silvey, enables one to identify strong distances and provides a justification for the experimental findings of previous investigators.