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The analytical capabilities of a funds flow statement are significant and important, but are not used to the full extent. The statement reflects the impact of operating, investment and financial activities of enterprises on the status of its monetary assets and their equivalents during the reporting period of time and allows to explain the reasons of changes during this period. The policy of managing the balances of monetary assets should provide for cost-effective use. The movement of funds from operating activities can be carried out both by direct and indirect methods. The direct method allows to analyze and evaluate the directions of income and expenditure of money, trace the movement of funds as result of operating, investment and financial activities, to carry out analysis of the net cash flow and define its structure. The statement, drawn up indirectly, reflects the reasons for the change in balance of funds and their transformation into various forms of assets, and discloses the relation of profits with changes in circulating assets and current liabilities and reserves. Given the importance of cash, the different analytical value of the statements, compiled directly and indirectly, and with the purpose of an efficient comprehensive analysis of monetary flows for the effective managerial decision-making, it is suggested to compile the statement using both methods.

Indirect bridge health monitoring is conducted by running an instrumented vehicle over a bridge, where the vehicle serves as a source of excitation and as a signal receiver; however, it is also important to investigate the response of the instrumented vehicle while it is in a stationary position while the bridge is excited by other source of excitation. In this paper, a numerical model of a stationary vehicle parked on a bridge excited by another moving vehicle is developed. Both stationary and moving vehicles are modeled as spring–mass single-degree-of-freedom systems. The bridges are simply supported and are modeled as 1D beam elements. It is known that the stationary vehicle response is different from the true bridge response at the same location. This paper investigates the effectiveness of contact-point response in reflecting the true response of the bridge. The stationary vehicle response is obtained from the numerical model, and its contact-point response is calculated by MATLAB. The contact-point response of the stationary vehicle is investigated under various conditions. These conditions include different vehicle frequencies, damped and undamped conditions, different locations of the stationary vehicle, road roughness effects, different moving vehicle speeds and masses, and a longer span for the bridge. In the time domain, the discrepancy of the stationary vehicle response with the true bridge response is clear, while the contact-point response agrees well with the true bridge response. The contact-point response could detect the first, second, and third modes of frequency clearly, unlike the stationary vehicle response spectra. [ABSTRACT FROM AUTHOR]

Reinforcement learning (RL) algorithms have been successfully applied to a range of challenging sequential decision‐making and control tasks. In this paper, we classify RL into direct and indirect RL according to how they seek the optimal policy of the Markov decision process problem. The former solves the optimal policy by directly maximizing an objective function using gradient descent methods, in which the objective function is usually the expectation of accumulative future rewards. The latter indirectly finds the optimal policy by solving the Bellman equation, which is the sufficient and necessary condition from Bellman's principle of optimality. We study policy gradient (PG) forms of direct and indirect RL and show that both of them can derive the actor–critic architecture and can be unified into a PG with the approximate value function and the stationary state distribution, revealing the equivalence of direct and indirect RL. We employ a Gridworld task to verify the influence of different forms of PG, suggesting their differences and relationships experimentally. Finally, we classify current mainstream RL algorithms using the direct and indirect taxonomy, together with other ones, including value‐based and policy‐based, model‐based and model‐free. [ABSTRACT FROM AUTHOR]

The chief aim of this research paper is to discover the notable challenges and deterrents in learning English as a second language (ESL) with special reference to the South Asian languages (Bengali and Nepali) speaking students. It critically describes language learning methods with respect to these two South Asian languages. The research is based on experience and an experimental study. The paper has conducted an experimental study on 150 students learning English through various methods. There is a critical analysis of teaching methods with the help of the experimental study. It discloses the various patterns and features of these prominent South Asian languages of these countries. The paper concludes that the Direct Method is the best of all methods on account of code fixing habit in other methods with special reference to these speakers because these languages have quite different patterns and features. The paper finally gives some recommendations. [ABSTRACT FROM AUTHOR]

This study is aimed at finding the entire points that a manipulator can launch an object onto by an optimal motion. These points are called throw-able workspace, which are located outside the reachable workspace of the robot. From an optimization point of view, some throwing parameters can be found to decrease motion cost. In this paper, by using this concept, the best combination of throwing and trajectory planning is attempted. The proposed method consists of two basic ideas: first, defining the optimal throwing problem as the optimal control problem (OCP) and solving it using the indirect solution approach based on the fundamental lemma of calculus of variations. To achieve the best release angle and speed, the throwing equation of motion is applied as a moving-end boundary condition (BC). Second, based on the obtained optimal throwing, an algorithm is presented to calculate the maximum throw-able workspace. The simulation results demonstrate the effectiveness of the proposed framework for both single link and spatial two-degree-of-freedom throwing robots. [ABSTRACT FROM AUTHOR]

In this paper, we present a new approach for solving a broad class of energy-optimal trajectory problems in relative motion using the recently developed Theory of Functional Connections (TFC). A total of four problem cases are considered and solved, i.e. rendezvous and intercept with fixed and free final time. Each problem is constrained and formulated using an indirect approach which casts the optimal trajectory problem as a system of linear or nonlinear two-point boundary value problems for the fixed and free final time cases, respectively. Using TFC, we convert each two-point boundary value problem into an unconstrained problem by analytically embedding the boundary constraints into a "constrained expression." The latter includes a free-function that is expanded using Chebyshev polynomials with unknown coefficients. Regardless of the values of the unknown coefficients, the boundary constraints are satisfied and simple optimization schemes can be employed to numerically solve the problem (e.g. linear and nonlinear least-square methods). To validate the proposed approach, the TFC solutions are compared with solutions obtained via an analytical based method as well as direct and indirect numerical methods. In general, the proposed technique produces solutions to machine level accuracy. Additionally, for the cases tested, it is reported that computational run-time within the MATLAB implementation is lower than 28 and 300 ms for the fixed and free final time problems respectively. Consequently, the proposed methodology is potentially suitable for on-board generation of optimal trajectories in real-time. • Energy-optimal problems in relative motion are solved via TFC. • Boundary constraints are analytical embedded reducing the search space. • Functional interpolation is performed with linear and non-linear least-squares. • TFC is compared with other state-of-the-art methods. • TFC is shown to solve all problems with a loss accuracy on the order of 10–17 and with a computational runtime between 28 ms (linear problems) and 300 ms (non-linear problems). [ABSTRACT FROM AUTHOR]

The real-time and fuel-optimal powered descent guidance is one of the critical technologies for planetary landing. This work focuses on the powered descent guidance algorithm based on pseudospectral convex optimization and aims to increase the accuracy and adaptability of the algorithm. The entire powered descent process is divided into phases according to the thrust switching times, and the pseudospectral method is adopted to discretize the optimization problem. Convexification process is performed to transform the optimization problem into a convex programming problem, and a successive solving process algorithm is proposed. For the established multi-phase pseudospectral convex optimization formulation, the indirect method is adopted to derive and determine the optimal phase division from switching function, and the adaptive multi-phase pseudospectral convex optimization method is proposed. Numerical examples demonstrate that the proposed method has excellent accuracy and adaptability. • An adaptive powered descent guidance algorithm is proposed. • A multi-phase pseudospectral convex optimization formulation is studied and established. • The optimal phase division is proved to be no more than twice according to switching function. • Accuracy and adaptability of the proposed algorithm is demonstrated by numerical examples. [ABSTRACT FROM AUTHOR]

Multilayered thin films are essential to most microelectro-mechanical systems (MEMSs). The reliability and predictability of the behavior of such systems, especially when intended for usage at high temperatures or in harsh environments, demand the consideration of thermo-mechanical properties of the individual films of the multilayer arrangement during the design stage. This paper introduces a newly derived analytical model for the convenient indirect determination of the temperature-dependent Young's modulus and the thermally induced stress of individual layers within a multilayered thin film system, i.e., a multilayer-adapted Stoney equation. It is based on sample curvature measurement and requires data from only a single experiment. Experimental and numerical investigations of the new models are carried out using a five-layered sample of a RuAl metallization system developed for wireless high-temperature acoustic sensing. The results highlight the usability of the new model in practical MEMS analysis, enabling insights into complex layer stacks by overcoming current experimental limitations.

For geostationary orbit transfers, a long duration is required using electric propulsion and a large propellant mass is needed with chemical propulsion. Hybrid transfers can achieve a balance between the fuel consumption and transfer time. In this paper, a trajectory optimization method is proposed for time-fixed minimum-fuel orbital transfer with combined chemical–electric propulsion. The necessary conditions and transversality conditions related to impulsive burns are derived theoretically with Pontryagin’s maximum principle. The long-duration geostationary orbit transfer is a many-revolution transfer, and is solved with the homotopic approach from the short-duration transfer problem. The variation in fuel consumption with transfer time is nearly linear, and the variation in the magnitude of impulsive burn is exponential. A simple model is presented for the estimation of fuel consumption and magnitude of impulsive burn with given transfer time, specific impulse of propulsion system and low-thrust magnitude.

We propose an indirect method of ASTM D-1200 for measurement of viscosity from 0.1 to 30 stokes (St) using Ford cup 5 (range 2~ 12 St) by developing a statistical relation. General purpose low styrene content polyester resin (without adding initiator, hardener and accelerator) was used for viscosity measurement. In existing ASTM D 1200 standard, ford cups (1-4) are used to measure the viscosity up to 2 St, while fifth cup is used for measurement from 2 to 12 St. Viscosity above 12 St is not estimated using existing ASTM D- 1200 method. In contrast, our method and statistical relation proposed in this paper estimates viscosity in the flexible range of 0.1 to 30 St by using Ford cup 5 only. The estimated values were confirmed by existing ASTM D-1200 (0.1 to 12 St) and by using Ubbelohde viscometer (12 to 30 St). Values estimated above 12 St are from the proposed model are also in good conformance (percentage error ~ 5% or less) with experimental results. The satisfaction level of the estimated values with the experiments suggests that the model has also the potential for application to paints, polymer and oil industry.

In this paper, optimal swing up of a double inverted pendulum (DIP) with two underactuated degrees of freedom (DOFs) is solved using the indirect solution of optimal control problem. Unlike the direct method that leads to an approximate solution, the proposed indirect method results in an exact solution of the optimal control problem, but suffers from its limited convergence domain which makes it difficult to solve. In order to overcome this problem, an inversion-based method is used to obtain the required initial solution for the indirect method. In the proposed methodology, dynamic equations are derived for a general inverted pendulum using Euler-Lagrange formulation. Then the necessary optimality conditions are derived for a DIP on the cart using the Pontryagin’s maximum principle (PMP). The obtained equations establish a two-point boundary value problem (TPBVP) which solution results in optimal trajectories of the cart and pendulums. In order to demonstrate the applicability of the presented method, a simulation study is performed for a DIP. The simulation results confirm the superiority of the proposed method in terms of reduced effort.

In the dynamic manipulation of objects, the aim is to throw an object by a robot to the desired target even outside the reachable workspace. In this paper, the concept of the throw-able workspace or dynamic manipulation workspace is defined as a set of points which the robot is able to throw the object at them. Thus, in order to obtain the maximum dynamic manipulation workspace which means the farthest points that object can be manipulated, it is necessary to solve the optimal throwing problem. To this end, the optimal throwing problem is defined as the optimal control problem solved using the indirect solution method based on the fundamental theorem of the calculus of variations. By applying the throwing equation as a moving boundary condition, the derived optimality conditions construct a two-point boundary value problem which its solution results in the optimal throwing. Finally, an algorithm is presented to calculate the maximum dynamic manipulation workspace. Then, simulation results are presented for a single link robot in order to evaluate the defined concept as well as the effectiveness of the proposed method for problem-solving.

The assessment of drought tolerance of winter soft wheat samples by a direct and an indirect method The article presents the results of assessment of drought tolerance of winter soft wheat samples under stress conditions ‘zasushnik’, as well as the results of study of wheat drought resistance according to the degree of seed germination on osmotic solutions. As a result of the studies, there were identified the samples with the highest degree of resistance to drought. According to drought resistance, the most significant values were found in the samples ‘Asket’ (79.3%), ‘1377/06’ (78.7%), ‘Kazachka’ (77.6%), ‘Krasa Dona’ (75.3%), ‘Shef’ (73.5% %), ‘Bonus’ (73.2%), ‘1232/13’ (73.2%), ‘352/11’ (71.6%), ‘Luchezar’ (71.3%), ‘1237/13’ (70.4%). The highest values of the index of complex stability were established in the samples ‘1377/06’ (255.4 per-unit), ‘Asket’ (253.4 per-unit) ‘Kazachka’ (252.1 per-unit), ‘1232/13’ (245.4 per-unit), ‘Shef’ (245,0 per-unit), ‘Krasa Dona’ (244,3 per-unit), ‘Bonus’ (236,9 per-unit), ‘Luchezar’ (236.2 per-unit), ‘352/11’ (240.0 per-unit). One of the indirect methods is the method of determining the level of resistance to complex drought; the samples ‘Asket’ (43%), ‘1237/13’ (40%), ‘Krasa Dona’ (33.0%), ‘260/09’ (31.0%), ‘Kazachka’ (31.0%), ‘1377/06’ (31.0%) showed the highest degree of resistance. In the conditions of model drought in comparison with the optimal conditions, all the studied samples showed a decrease of the trait ‘1000-kernel weight’. One of the reactions to lack of moisture is the reduction of productive stems from 1 m2. The reduction of productive stems in the experiment in relation to the control variety ranged from 4 to 45%. The kernel weight per main head decreased from 36 to 65% was observed in all studied samples. The varieties ‘Asket’ (226.2 g), ‘Krasa Dona’ (191.8) and ‘Lydia’ (190.4 g) produced high grain yields in strongly arid conditions.

In this paper, a numerical indirect method based on wavelets is proposed for solving the general continuous time-variant linear quadratic optimal control problem. The necessary optimality conditions are applied to convert the main problem into a boundary value problem, as a dynamic system. The new problem, using two discrete schemes, Legendre and Chebyshev wavelets, is changed to a system of algebraic equations. To demonstrate the efficiency of the proposed method two analytical and two numerical examples are given. [ABSTRACT FROM AUTHOR]

Summary: Mode shapes have been playing a vital role in the research and application of bridge structural health monitoring. This paper presents a novel indirect method identifying bridge mode shapes using dynamic responses of a tractor–trailer vehicle model, which consists of one tractor and three instrumented trailers. In an effort to eliminate the road roughness effect, accelerations of adjacent trailers are firstly subtracted. Wavelet analysis is then employed to identify bridge mode shapes from the subtracted accelerations in an iterative manner. Furthermore, wavelet denoising algorithm is adopted to improve the identification accuracy in the presence of measurement noise. Systematic numerical simulations, in which a tractor–trailer model passes over an expressway bridge, are conducted in order to investigate the performance of the proposed method. Sensitivity analysis including vehicle speed, class of road roughness, and noise level are studied in this numerical investigation. Results demonstrate that the proposed method is able to identify bridge modal frequencies and mode shapes with satisfactory resolution, accuracy, and robustness. [ABSTRACT FROM AUTHOR]

Traditionally, fuel-optimal problems for low-thrust spacecraft transfers are connected with energy-optimal problems to increase the convergence possibility of indirect methods. However, for low-thrust many-revolution missions, it is still hard to resolve the energy-optimal problems in a fast and reliable manner due to the strong nonlinearity. To address this issue, a warm-start multihomotopic optimization approach is proposed in this article, wherein the Sundman transformation and multihomotopic techniques are used to connect the energy-optimal problems to linear ones with analytical solutions. This article focuses on the following three contributions. First, the energy-optimal control problems are transformed into true longitude-depended energy-optimal problems based on the homotopy to dynamical model and Sundman transformation, and the equivalence relations of the solutions before and after transformation are obtained analytically. Second, the problems are further connected with time-free energy-optimal problems based on a homotopy to the time constraint. Third, the time-free problems are linearized near a nominal trajectory, and the corresponding analytical solutions are obtained. Starting with the analytical solutions, the algorithm can gradually iterate back to the solutions of the original energy- and fuel-optimal problems. Since the whole transformation process is lossless (optimality is preserved under the transformation process), the developed warm-start multihomotopic algorithm enjoys the advantages on reliable convergence and high computational efficiency. Numerical simulations of Earth-orbit transfer missions from GTO to GEO are conducted by comparing with traditional methods, and the results are given to substantiate the effectiveness of the proposed warm-start multihomotopic method. [ABSTRACT FROM AUTHOR]

This article presents a new and fast indirect method for solving fuel-optimal descent trajectories in the gravitational field of an irregularly-shaped asteroid. The costates associated with a two-impulse descent trajectory are used as approximate costates for the costate initialization of a finite-thrust fuel-optimal trajectory planning problem. The approximate solutions of the initial velocity and mass costates are given in analytical forms. A simple shooting equation is derived to solve the approximate position costates. The two-impulsive descent trajectory is solved by an irregular gravitational Lambert solver. Based on the Lambert solver and approximate costates, an algorithm is proposed for trajectory optimization with varying time of flight. The effectiveness and efficiency of the proposed method are tested through the simulation of landing on the asteroid 433 Eros. Additionally, a computationally efficient approximate model is employed to replace the polyhedral model, which greatly improves the computational speed and enhance the ability to address uncertainties. [ABSTRACT FROM AUTHOR]

In this paper we present a new approach to solve the fuel-efficient powered descent guidance problem on large planetary bodies with no atmosphere (e.g., Moon or Mars) using the recently developed Theory of Functional Connections. The problem is formulated using the indirect method which casts the optimal guidance problem as a system of nonlinear two-point boundary value problems. Using the Theory of Functional Connections, the problem's linear constraints are analytically embedded into a functional, which maintains a free-function that is expanded using orthogonal polynomials with unknown coefficients. The constraints are always analytically satisfied regardless of the values of the unknown coefficients (e.g., the coefficients of the free-function) which converts the two-point boundary value problem into an unconstrained optimization problem. This process reduces the whole solution space into the admissible solution subspace satisfying the constraints and, therefore, simpler, more accurate, and faster numerical techniques can be used to solve it. In this paper a nonlinear least-squares method is used. In addition to the derivation of this technique, the method is validated in two scenarios and the results are compared to those obtained by the general purpose optimal control software, GPOPS-II. In general, the proposed technique produces solutions of O (1 0 − 10) accuracy. Additionally, for the proposed test cases, it is reported that each individual TFC-based inner-loop iteration converges within 6 iterations, each iteration exhibiting a computational time between 72 and 81 milliseconds, with a total execution time of 2.1 to 2.6 seconds using MATLAB. Consequently, the proposed methodology is potentially suitable for real-time computation of optimal trajectories. [ABSTRACT FROM AUTHOR]

A branch of dynamic manipulation is robotic throwing which recently plays a major role in the performance improvement of robotic manipulations. This paper aims at the optimal throwing using a robotic arm. Launching the captured object to a specified target by minimum control effort with the specified final time is the mission of the throwing robot in this study. Taking into account the indirect method based on the fundamental theorem of the calculus of variations, the optimal throwing problem is defined as the optimal control problem (OCP). By employing Pontryagin's Minimum Principle (PMP), the optimality conditions are extracted and then considering the throwing equation as a moving-end boundary condition (BC), the corresponding OCP converts to a two-point boundary value problem (BVP). By applying the moving-end BCs, the best releasing condition is automatically obtained. Next, a simple algorithm is presented to solve the resulting BVP which leads us to the multiple optimal solutions that have been sorted according to the defined cost function values. This multiplicity of solutions allows for the selection of the most practical optimal solution. The feasibility of the derived framework is validated by some simulations and experiments done for a fabricated throwing robot. [ABSTRACT FROM AUTHOR]

• A DNN-based method is developed to deal with low-thrust optimal orbit transfer. • The method is a combination of traditional techniques and DNNs. • The method has advantages on the computational efficiency and reliability. Initial solution guess has a significant impact on the convergence of indirect methods, especially for continuous low-thrust trajectory optimization problems. In this study, an intelligent initial solution supplying approach based on deep neural networks (DNNs) is proposed to help achieve the fast generation of optimal trajectories for low-thrust orbit transfers. Energy-optimal and fuel-optimal trajectories with three different terminal conditions are considered. Based on the training dataset obtained by an indirect method, DNNs are constructed to approximate the solutions corresponding to different flight states. Based on the trained DNNs, an intelligent trajectory optimization method named DNN-based method is developed with the help of the homotopy technique. Numerical simulations are conducted to evaluate the performance of the proposed method on success rates and time consumptions. Simulation results demonstrate that the combination of traditional techniques and the new DNN technology can achieve the fast generation of low-thrust optimal trajectories with advantages on computational efficiency and reliability. [ABSTRACT FROM AUTHOR]

Minimum resolvable temperature difference (MRTD) is considered as the most important parameter of thermal imagers. A new method of MRTD measurement without drawbacks of other methods is presented in this paper. Proposed MRTD measurement method coded as virtual MRTD is based on a three steps measurement concept using semi-automatic objective measurements and computer simulation. First, objective parameters of the tested thermal imager are measured. Second, software simulates this tested thermal imager and generates the image of 4-bar target of specified spatial frequency (size) and contrast (temperature difference). Third, a human observer analyses the images of the 4-bar target generated by the software on the screen of PC set and measures MRTD of the simulated thermal imager at specified set of spatial frequencies. The proposed method offers higher measurement speed, lower cost and typically better accuracy in comparison with the typical MRTD measurement method. [ABSTRACT FROM AUTHOR]

This article focuses on the information content and significance of the cash flow statement. In accordance with IAS 7 Cash Flow Statement, the basic principles for grouping cash flows as such from operating, investing and financing activities are presented. For some specific transactions and events that give rise to discussions in the accounting community, fundamental rules for their classification are set out in the cash flow statement. The conceptual logic and practical applicability of the acceptable methods for accounting for cash flows are analyzеd. [ABSTRACT FROM AUTHOR]

This paper proposes an indirect method to measure absolute acoustic nonlinearity parameters using surface acoustic waves by employing a fully non-contact laser-ultrasonic technique. For this purpose, the relationship between the ratio of relative acoustic nonlinearity parameters measured using the proposed method in two different materials (a test material and a reference material) and the ratio of absolute acoustic nonlinearity parameters in these two materials was theoretically derived. Using this relationship, when the absolute nonlinearity parameter of the reference material is known, the absolute nonlinearity parameter of the test material can be obtained using the ratio of the measured relative parameters of the two materials. For experimental verification, aluminum and copper specimens were used as reference and test materials, respectively. The relative acoustic nonlinearity parameters of the two materials were measured from surface waves generated and received using lasers. Additionally, the absolute parameters of aluminum and copper were measured using a conventional direct measurement method, with the former being used as a reference value and the latter being used for comparison with the estimation result. The absolute parameter of copper estimated by the proposed method showed good agreement with the directly measured result. [ABSTRACT FROM AUTHOR]

Natural ventilation is energy-saving and preferred in livestock buildings under suitable conditions, especially for cattle and sheep. The natural ventilated livestock buildings usually have large-openings which result in the non-uniform distribution of wind speed and pressure at the openings, which makes it difficult to determine the air inlet and outlet and challenging to estimate airflow rate in a natural ventilated livestock buildings. Thermal buoyancy and wind pressure are the driving forces of natural ventilation whose airflow rate can be estimated directly by differential pressure method, wind speed method and CFD method, or indirectly by heat balance, moisture balance, CO² balance and tracer gas method. This review paper investigates the published works on the theory of natural ventilation in livestock buildings and the methods of airflow rate estimation to obtain a better understanding on the state of art for the mechanisms and estimation methods of airflow rate of natural ventilation in livestock buildings. Furthermore, this paper summarizes the key factors affecting natural ventilation and the principles of improving accuracy in the application of estimation methods to guide ventilation measurements better, promote natural ventilation or mixed ventilation in livestock barns, and provide a basis for optimizing environmental control strategies for the environment as a whole. Finally, different estimation methods of airflow rate are compared and the research gaps need to be further improved are concluded in this paper. Up to now, it is short of an accurate and disputable method to measure airflow rate in natural ventilation. The differences among different estimation methods are generally between 10% and 300%, showing a very big variance. The estimation accuracy of different methods is affected by the factors such as the discharge coefficient, the pressure coefficient, the reliability of estimated heat and moisture production from animal, and the measuring position of sensors. Compared with other methods, the CO² balance method is widely used in the field measurements, and the result is relatively stable. However, it is highly needed to standardize the layout of sensors and the usage of the measured gas concentrations from different sensors to appropriately calculate concentration difference between indoor and outdoor, improving the accuracy of assessing CO² production from livestock buildings. The moisture balance method has a potential application in field measurements and practical situations because of its low cost of sensors and relatively good performance in estimation airflow rate. Nevertheless, it is necessary to further establish the estimation models on moisture production from house level and dynamic latent heat production from animals to improve the accuracy of moisture balance method. In addition, it is helpful to assess the reliability of the measured airflow rates and decrease the uncertainty in airflow rate estimation using multiple methods at the same time. Furthermore, the existing methods are more suitable for design assistance rather than regulating the airflow rate in real situation. It is necessary to improve the existing method or establish a new method to guide the regulation of natural ventilation directly and effectively in livestock buildings. [ABSTRACT FROM AUTHOR]

Equipping a spacecraft with multiple solar-powered electric engines (of the same or different types) compounds the task of optimal trajectory design due to presence of both real-valued inputs (power input to each engine in addition to the direction of thrust vector) and discrete variables (number of active engines). Each engine can be switched on/off independently and "optimal" operating power of each engine depends on the available solar power, which depends on the distance from the Sun. Application of the Composite Smooth Control (CSC) framework to a heliocentric fuel-optimal trajectory optimization from the Earth to the comet 67P/Churyumov-Gerasimenko is demonstrated, which presents a new approach to deal with multiple-engine problems. Operation of engine clusters with 4, 6, 10 and even 20 engines of the same type can be optimized. Moreover, engine clusters with different/mixed electric engines are considered with either 2, 3 or 4 different types of engines. Remarkably, the CSC framework allows us 1) to reduce the original multi-point boundary-value problem to a two-point boundary-value problem (TPBVP), and 2) to solve the resulting TPBVPs using a single-shooting solution scheme and with a random initialization of the missing costates. While the approach we present is a continuous neighbor of the discontinuous extremals, we show that the discontinuous necessary conditions are satisfied in the asymptotic limit. We believe this is the first indirect method to accommodate a multi-mode control of this level of complexity with realistic engine performance curves. The results are interesting and promising for dealing with a large family of such challenging multi-mode optimal control problems. • Optimization of low-thrust interplanetary trajectories with multiple engines. • Engine clusters with the same or different/mixed engine types are considered. • Same-type engine cluster with 4, 6, 10 and 20 engines are investigated. • Different-type engine clusters with 2, 3 and 4 engines are investigated. • Fuel-optimal trajectories from Earth to comet 67P/Churyumov-Gerasimenko. [ABSTRACT FROM AUTHOR]

Efficient performance of a number of engineering systems is achieved through different modes of operation - yielding systems described as "hybrid", containing both real-valued and discrete decision variables. Prominent examples of such systems, in space applications, could be spacecraft equipped with 1) a variable- I sp , variable-thrust engine or 2) multiple engines each capable of switching on/off independently. To alleviate the challenges that arise when an indirect optimization method is used, a new framework — Composite Smooth Control (CSC) — is proposed that seeks smoothness over the entire spectrum of distinct control inputs. A salient aftermath of the application of the CSC framework is that the original multi-point boundary-value problem can be treated as a two-point boundary-value problem with smooth, differentiable control inputs; the latter is notably easier to solve, yet can be made to accurately approximate the former hybrid problem. The utility of the CSC framework is demonstrated through a multi-year, multi-revolution heliocentric fuel-optimal trajectory for a spacecraft equipped with a variable- I sp , variable-thrust engine. • Optimization of low-thrust interplanetary trajectories with variable specific impulse, variable thrust engines. • A new framework, called Composite Smooth Control (CSC), is developed to handle various types of state-triggered constraints. • Indirect optimization method is used to formulate fuel-optimal problems. • Complex-based derivative approach is used to construct co-state dynamics numerically. • Multi-revolution, multi-year trajectory optimization is analyzed. [ABSTRACT FROM AUTHOR]

We examine whether the choice of cash flow disclosure under International Accounting Standard 7 has an influence on the cost of capital incurred by Australian listed companies. Results indicate that indirect method companies incur a significantly higher ex‐ante cost of equity than direct method companies using a combined equity model approach. We also demonstrate that using an optimal weighted combination of equity models reduces model variance and bias compared to using a single equity model. Our findings support mandating the direct method and have the potential to induce companies to report the direct method to increase company value. [ABSTRACT FROM AUTHOR]

This paper proposes an indirect visual simultaneous localization and mapping (V-SLAM) for large-scale outdoor environments based on linear models. With the scale-invariant feature transform (SIFT) algorithm, a design combining key-frame insertion and map management is proposed to avoid redundant computation and unreliable landmarks. Then, an iterative linear equation is employed to update landmarks. With the supplement of reliable map data, absolute camera poses can be obtained using a simple linear equation based on a linearity index. In addition, a linear model helps the system to detect candidates of looped frames and discard invalid loops by means of an outlier weight function. If a loop is detected, an improved trajectory bending algorithm is introduced to optimize the estimations of poses and landmarks. To evaluate the effectiveness of the proposed approach, extensive experiments are conducted using various sequences from a well-known public dataset. Experimental results show that the proposed V-SLAM outperforms other existing methods in terms of various metrics. [ABSTRACT FROM AUTHOR]

The surrogate reaction 238U(3He,tf) is used to determine the 237Np(n,f) cross section indirectly over an equivalent neutron energy range from 10 to 20 MeV. A self-supporting ~;;761 mu g/cm2 metallic 238U foil was bombarded with a 42 MeV 3He2+ beam from the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory (LBNL). Outgoing charged particles and fission fragments were identified using the Silicon Telescope Array for Reaction Studies (STARS), consists of two 140 mu m and one 1000 mu m Micron S2 type silicon detectors. The 237Np(n,f) cross sections, determined indirectly, were compared with the 237Np(n,f) cross section data from direct measurements, the Evaluated Nuclear Data File (ENDF/B-VII.0), and the Japanese Evaluated Nuclear Data Library (JENDL 3.3) and found to closely follow those datasets. Use of the (3He,tf) reaction as a surrogate to extract (n,f) cross section in the 10 to 20 MeV equivalent neutron energy is found to be suitable.

This paper proposes a new shape-based method in spherical coordinates to solve three-dimensional rendezvous problems. Compared with the existing shape-based methods, the proposed method does not need parameter optimization. Moreover, it improves the flexibility of orbit fitting, greatly reduces the velocity increment and maximum thrust acceleration, and ensures the orbit safety to a certain extent. The shaping function can provide the initial estimate for numerical trajectory optimization and improve the convergence rate in a certain range when combined with the normalization method. The superiority of the proposed method over the existing methods is demonstrated by two numerical examples. Its effectiveness at initial estimation generation in the indirect optimization of a low-thrust trajectory is demonstrated by the third example.

Indirect bridge health monitoring is conducted by running an instrumented vehicle over a bridge, where the vehicle serves as a source of excitation and as a signal receiver; however, it is also important to investigate the response of the instrumented vehicle while it is in a stationary position while the bridge is excited by other source of excitation. In this paper, a numerical model of a stationary vehicle parked on a bridge excited by another moving vehicle is developed. Both stationary and moving vehicles are modeled as spring–mass single-degree-of-freedom systems. The bridges are simply supported and are modeled as 1D beam elements. It is known that the stationary vehicle response is different from the true bridge response at the same location. This paper investigates the effectiveness of contact-point response in reflecting the true response of the bridge. The stationary vehicle response is obtained from the numerical model, and its contact-point response is calculated by MATLAB. The contact-point response of the stationary vehicle is investigated under various conditions. These conditions include different vehicle frequencies, damped and undamped conditions, different locations of the stationary vehicle, road roughness effects, different moving vehicle speeds and masses, and a longer span for the bridge. In the time domain, the discrepancy of the stationary vehicle response with the true bridge response is clear, while the contact-point response agrees well with the true bridge response. The contact-point response could detect the first, second, and third modes of frequency clearly, unlike the stationary vehicle response spectra.

The present article deals with the measurement methods based on experimental tests and their impact on the resultant volumetric error of CNC machine tools (MT). Volumetric error compensations represent a promising technology to increase the production accuracy of machine tools. This article studies direct and indirect methods to measure the volumetric accuracy on a MT. The assessed parameters are not only the resultant volumetric error of the machine, but also time consumption of measurement, repeatability, and evaluation of individual geometric errors. Finally, recommendations are made to improve the effect of volumetric errors compensation using the above-mentioned methods for three-axis MT. [ABSTRACT FROM AUTHOR]

Background: The serum concentration of thyrotropin (TSH) represents a first-line test in diagnostic algorithms. The estimation of TSH reference intervals (RIs) is still a matter of debate due to the high prevalence of subclinical disease making difficult the definition of truly healthy subjects. The aim of this study was to estimate TSH RIs in healthy subjects and to evaluate the effect of age and gender on TSH concentration. Methods: Forty-four thousand one hundred and fifty-six TSH data were collected between July 2012 and April 2018 at the Department of Laboratory Medicine, University-Hospital, Palermo. Common and sex-specific RIs were estimated by Arzideh's indirect method after exclusion of individuals younger than 15 years, subjects with repeated TSH tests and with abnormal free thyroxine (fT4), free triiodothyronine (fT3) or anti-thyroid-peroxidase antibodies. The combined effect of age and gender on TSH values was evaluated. Results: RIs estimated in the selected individuals (n = 22602) were, respectively, 0.18–3.54 mIU/L (general), 0.19–3.23 mIU/L (men) and 0.18–3.94 mIU/L (women). Women showed significantly higher median TSH than men (1.46 vs. 1.39 mIU/L; p < 0.0001). Both in men and in women, median TSH decreased along with age; however, although up to 60 years in both men and women showed similar values, afterwards women showed constantly higher TSH than men. Accordingly, statistical analysis showed a significant interaction between gender and age (p = 0.001), suggesting that the effect of age on TSH is different between genders. Conclusions: Our findings suggest that the indirect method, with appropriate cleaning of data, could be useful to define TSH RIs. [ABSTRACT FROM AUTHOR]

Background: In order to establish suitable reference intervals (RIs) of serum cytokeratin-19 fragment (Cyfra211) and neuron specific enolase (NSE) for the healthy Chinese population in Chengdu, China, an indirect method was developed using the data from the people presented for routine health check-up. Methods: All results for 4,988 healthy persons serum cytokeratin-19 fragment and 3,293 healthy persons neuron specific enolase were collected in our laboratory information system between January 2016 and December 2018. Outliers were identified and excluded using the stem-and-leaf and box plot methods. Mann-Whitney U test was used to observe the difference between sexes. Spearman's rank correlation analysis was used to evaluate the correlation between serum results and age. The RIs were defined by nonparametric 95th percentile interval. Results: After statistical analysis the indirect RIs were 0.0 - 3.70 ng/mL (Cyfra211) and 0 - 17.26 ng/mL (NSE) in males and 0.0 - 3.35 ng/mL (Cyfra211) and 0.0 - 16.29 ng/mL (NSE) in females. Cyfra211 and NSE levels in males and females had no correlation with age. Therefore, there was no need to establish RIs according to age group. RIs of Cyfra211 and NSE were verified and passed the verification in the end. Conclusions: Using health check-up persons' laboratory data values is a relatively easy and cheap method of establishing laboratory specific references. This method deserves to be promoted and applied by other clinical laboratories. [ABSTRACT FROM AUTHOR]

A main objective of this work is to assess the feasibility of space missions to a new population of near Earth asteroids which temporarily orbit Earth, called temporarily captured orbiter. We design rendezvous missions to a large random sample from a database of over 16,000 simulated temporarily captured orbiters using an indirect method based on the maximum principle. The main contribution of this paper is the development of techniques to overcome the difficulty in initializing the algorithm with the construction of the so-called cloud of extremals. [ABSTRACT FROM AUTHOR]

Abstract An interplanetary trajectory optimization of the multi-asteroid rendezvous is investigated for a solar sail-based spacecraft. The optimal control problem is formulated using the calculus of variations and Pontryagin's maximum principle and the first order necessary conditions for optimality of the problem are derived. To achieve the optimal solution, the indirect method transforms the optimal control problem into a multiple point boundary value problem and solves it via shooting method, and the pseudospectral method discretizes the state and control variables and solves the NLP problem. In this paper, a numerical method combining the global optimization algorithm and a nonlinear equation solver is proposed to get the optimal solution of the indirect method. Additionally, costates are estimated to validate the optimality of the solution obtained via the pseudospectral method. Finally, numerical examples are given to verify the effectiveness of the proposed methods. The results indicate that the optimal solutions to the problems with two and three targets can be solved using the proposed indirect method algorithm. As the number of visiting targets is more than three, the direct method will be more efficient. Highlights • Necessary condition for optimality of multi-asteroid rendezvous problem is derived. • A shooting method is developed to solve the multiple point boundary value problem. • A hybrid method combining the indirect method and the pseudospectral method is developed. [ABSTRACT FROM AUTHOR]

This study describes the use of hair traps as a complementary method to obtain samples for stable isotope analysis from medium- and large-sized mammals. We sampled three protected areas within the Atlantic Forest, Brazil. Traps formed an enclosure of ~16 m2 composed of two barbed-wire strands at different heights, baited with corn, salt, fruits and cinnamon powder. Samples were identified using hair microstructure. We identified 11 species – four globally and six nationally threatened – of which 63.6% were frugivorous. We found high species richness with a small sampling effort, indicating that hair traps can prove useful for isotopic ecology and other applied ecological studies. [ABSTRACT FROM AUTHOR]

This paper proposes an indirect method to measure absolute acoustic nonlinearity parameters using surface acoustic waves by employing a fully non-contact laser-ultrasonic technique. For this purpose, the relationship between the ratio of relative acoustic nonlinearity parameters measured using the proposed method in two different materials (a test material and a reference material) and the ratio of absolute acoustic nonlinearity parameters in these two materials was theoretically derived. Using this relationship, when the absolute nonlinearity parameter of the reference material is known, the absolute nonlinearity parameter of the test material can be obtained using the ratio of the measured relative parameters of the two materials. For experimental verification, aluminum and copper specimens were used as reference and test materials, respectively. The relative acoustic nonlinearity parameters of the two materials were measured from surface waves generated and received using lasers. Additionally, the absolute parameters of aluminum and copper were measured using a conventional direct measurement method, with the former being used as a reference value and the latter being used for comparison with the estimation result. The absolute parameter of copper estimated by the proposed method showed good agreement with the directly measured result.

The article discusses issues related to the use of methods of digital steganography for information security in systems of critical appointment. The advantages of using data embedding in an image container are shown. The main disadvantages of the existing methods of embedding in the image container are given. The issues of JPEG image compression for digital steganography are described. The allocation of stable regions in the attacking effects on the basis of the moving mask is proposed. The mathematical apparatus for masking images by the Sobel method is shown. The indirect steganography method of hiding data in blocks which contain information about the circuit is developed.