Adjustment Coefficient Research Articles

Design and validation of a novel adaptive motion control for a pendulum spherical robot

AbstractSpherical robots (SRs) have the characteristics of nonholonomic constraints, underactuation, nonchain, and strong coupling, which increase the difficulty of modeling and motion control compared with traditional robots. In this study, we develop an adaptive motion control scheme for a nonholonomic SR, in which an omnidirectional dynamic model is carried out by using the Euler–Lagrange method to describe the omnidirectional motion of the SR more accurately. Furthermore, to facilitate the design of the motion controller, the dynamic model is simplified to obtain the state space expression of the SR. Aiming at the problem of poor control effect caused by the change of system model parameters which are influenced by dynamic model reduction, an adaptive motion control law of SR is designed based on MRAC. And the coefficient adjustment of the controller is obtained by the Lyapunov method, with the guaranteed stability of the closed-loop system. Finally, the controller designed in this thesis is compared with four controllers including linear quadratic regulator, Fuzzy PID, PSO-ADRC, and hierarchical SMC. The experimental comparison proves that the control scheme proposed in this study still has good control ability when the motion parameters are disturbed.

Thermodynamic Properties of Ethanol + Pyridine, Ethanol + Benzene, and Pyridine + Benzene Mixtures at Temperature 298.15 K and Under Atmospheric Pressure

Experimental densities, viscosities, refractive indices, and sound speeds at temperature 298.15 K and atmospheric pressure are reported for the binary liquid mixtures of ethanol + benzene, ethanol + pyridine, and benzene + pyridine. From these experimental data, various thermodynamic excess and deviation properties were calculated and fitted by the Redlich-Kister polynomial to determine the adjustable coefficients and the standard deviations. The number of Redlich-Kister coefficients for significantly representing each thermodynamic property was optimized by applying the F-test. The variation of thermodynamic excess and deviation properties with composition has been interpreted in terms of molecular interactions between components of the mixture and structural effects. Furthermore, several theoretical and semi-empirical models were used to predict the refractive indices and sound speeds of the investigated mixtures. The predicting ability of each model was ascertained in terms of mean absolute percentage deviation between experimental and calculated data.

Adaptive Starting Control Strategy for Hybrid Electric Vehicles Equipped with a Wet Dual-Clutch Transmission

To improve the starting performance of the P2.5 plug-in hybrid electric vehicles with a wet dual-clutch transmission, an adaptive starting control strategy is presented in this paper, which controls the two clutches simultaneously involved in the starting process. A fuzzy controller is designed to identify the starting intention and determine the target torque under different working conditions. The starting process is divided into five periods, and linear quadratic optimal control is adopted to obtain the reference torque trajectory for the third period, while the others are determined by adaptive control by changing the adjustment coefficients according to the starting conditions. The combined pressure feedback controller based on the PID algorithm is proposed to control the wet clutch torque to follow the reference torque trajectory. The MATLAB/Simulink software platform is used to simulate the control strategy. The results show that the proposed strategy can shorten the starting time and reduce the level of jerk. Moreover, with the first-gear starting, the friction work of the whole process and clutch C1 is, respectively, reduced by 1.68% and 4.62% for slowly starting and 23.37% and 23.6% for quickly starting, which can significantly prolong the service lifetime of the clutch compared with the traditional single-clutch starting strategy.

Optimal Reinsurance to Minimize the Probability of Drawdown under the Mean-Variance Premium Principle: Asymptotic Analysis

In this paper, we consider an optimal reinsurance problem to minimize the probability of drawdown for the scaled Cramér–Lundberg risk model when the reinsurance premium is computed according to the mean-variance premium principle. We extend the work of Liang, Liang, and Young [Insurance Math. Econom., 92 (2020), pp. 128–146] to the case of minimizing the probability of drawdown. By using the comparison method and the tool of adjustment coefficients, we show that the minimum probability of drawdown for the scaled classical risk model converges to the minimum probability for its diffusion approximation, and the rate of convergence is of order . We further show that using the optimal strategy from the diffusion approximation in the scaled classical risk model is -optimal.

Analysis of Price Adjustment Payments for RCC T-Beam and Pre-stressed Bridges Construction Contracts

Purpose: Let’s compare and analyze the price adjustment payments for RCC T-beam and Pre-stressed bridges construction contracts for evaluation of the cost effectiveness of price adjustment payment. Design/Methodology/Approach: Based on Questionnaire survey and Official documents, comparison and analysis were done for RCC T-beam and Pre-stressed bridges construction contracts of price adjustment payment. Findings/Result: The weightage of price adjustment payment is 9% of total payment. This assessment was done to show the importance of price adjustment and its study in bridge construction contracts. As per GCC & SCC clause 53.7 of Standard Bidding Document, price adjustment is limited to 25%. Comparison of payments for price adjustments was done for different T-girder and pre-stressed bridges. Price adjustment payments for the computed price adjustment coefficients were calculated and compared with that of the actual payment made. Originality/Value: This research was mainly dedicated to deriving logical price adjustment coefficient ranges in making the price adjustment process for RCC T-girder and prestressed construction contracts economical. Paper Type: Research paper

Evaluation of Price Adjustment Coefficient for Construction Contracts

Purpose: There are many bridges being constructed in Nepal. Brides of different types like Bailey truss, cable stayed, RCC Arch, pre-stressed, RCC Slab, RCC T-Beam, Steel truss, RCC Box, Stone masonry arch, suspension, and suspended bridges are being tendered and constructed at present in Nepal. Most of the bridges being constructed are of RCC T-beam and Prestressed bridges. It has been found the need to carry out research to develop logical price adjustment coefficient ranges for RCC T-beam and Prestressed bridges contracts to make the price adjustment provision more uniform. Design/Methodology/Approach: Primary data was collected by office visits, constituting focus group discussions and interviews of the beneficiaries (clients & contractors) and the secondary data was collected through the Interim payment certificates and contract documents of the selected bridge. Price adjustment calculation was done and price adjustment coefficient ranges for RCC T-girder and prestressed concrete bridges were fixed. Findings/Result: Price adjustment coefficients (Labour coefficient, Material coefficient & Equipment coefficient) were found significantly different since their corresponding weightage in bridge construction are different. Thus, different ranges are to be adopted as per their weightage which is justified by this ANOVA Test. If price adjustment coefficient ranges are not provided in the bidding document, it was seen that the contractor tried to manipulate price adjustment provision to his/her benefit. Originality/Value: The necessary ranges have been developed for coefficients of price adjustments to provide a guideline to the contractor in bidding price adjustment coefficients Paper Type: Research paper

Evaluation of Price Adjustment Coefficient for Construction Contracts

Evaluation of Price Adjustment Coefficient for Construction Contracts

Epitaxial Grown VO2 with Suppressed Hysteresis and Low Room Temperature Resistivity for High-Performance Thermal Sensor Applications

The ability of VO2 to undergo semiconductor-to-metal phase transition (SMT) upon heating makes it a very attractive material for uncooled bolometers. The SMT of VO2 represents a large temperature coefficient of resistance, which is an important parameter for the development of highly responsive microbolometers. However, other characteristics of the SMT of VO2 such as its high transition temperature (341.2 K), the sharpness of the transition, its hysteresis, and the high room temperature resistivity limit the performance of this material in microbolometers. In this work, we grow a high-quality epitaxial ultrathin film VO2 on c-plane Al2O3 by pulsed laser deposition. The low deposition temperature and tuning the oxygen partial pressure during the growth process enable control over the grain size and oxygen vacancy concentration. This allowed controlling the SMT parameters of the samples. In particular, we show that the high density of grain boundaries associated with nanosized grains suppresses the thermal hysteresis of the SMT. Simultaneous control over the density of oxygen vacancies and the size of grains enables the adjustment of the temperature coefficient of resistance, room temperature resistivity, SMT temperature, sharpness, and thermal hysteresis toward suitable values for the fabrication of efficient VO2-based uncooled bolometers. Compared with other VO2 fabrication methods, this approach can be viewed as a simpler alternative for VO2 fabrication with favorable properties for practical bolometer applications.

On the nonlinear dynamics of a piezoresistive based mass switch based on catastrophic bifurcation

This research investigates the feasibility of mass sensing in piezoresistive MEMS devices based on catastrophic bifurcation and sensitivity enhancement due to the orientation adjustment of the device with respect to the crystallographic orientation of the silicon wafer. The model studied is a cantilever microbeam at the end of which an electrostatically actuated tip mass is attached. The piezoresistive layers are bonded to the vicinity of the clamped end of the cantilever and the device is set to operate in the resonance regime by means of harmonic electrostatic excitation. The nonlinearities due to curvature, shortening and electrostatic excitation have been considered in the modelling process. It is shown that once the mass is deposited on the tip mass, the system undergoes a cyclic fold bifurcation in the frequency domain, which yields a sudden jump in the output voltage of the piezoresistive layers; this bifurcation is attributed to the nonlinearities governing the dynamics of the response. The partial differential equations of the motion are derived and discretized to give a finite degree of freedom model based on the Galerkin method, and the limit cycles are captured in the frequency domain by using the shooting method. The effect of the orientation of the device with respect to the crystallographic coordinates of the silicon and the effect of the orientation of the piezoresistive layers with respect to the microbeam length on the sensitivity of the device is also investigated. Thanks to the nonlinearity and the orientation adjustment of the device and piezoresistive layers, a twofold sensitivity enhancement due to the added mass was achieved. This achievement is due to the combined amplification of the sensitivity in the vicinity of the bifurcation point, which is attributed to the nonlinearity and maximizing the sensitivity by orientation adjustment of the anisotropic piezoresistive coefficients.

Reconfigurable Architecture for Noise Cancellation in Acoustic Environment Using Single Multiply Accumulate Adaline Filter

The creation of multiple applications with a higher level of complexity has been made possible by the usage of artificial neural networks (ANNs). In this research, an efficient flexible finite impulse response (FIR) filter structure called ADALINE (adaptive linear element) that makes use of a MAC (multiply accumulate) core is proposed. The least mean square (LMS) and recursive least square (RLS) algorithms are the most often used methods for maximizing filter coefficients. Despite outperforming the LMS, the RLS approach has not been favored for real-time applications due to its higher design arithmetic complexity. To achieve less computation, the fundamental filter has utilized an LMS-based tapping delay line filter, which is practically a workable option for an adaptive filtering algorithm. To discover the undiscovered system, the adjustable coefficient filters have been developed in the suggested work utilizing an optimal LMS approach. The 10-tap filter being considered here has been analyzed and synthesized utilizing field programmable gate array (FPGA) devices and programming in hardware description language. In terms of how well the resources were used, the placement and postrouting design performed well. If the implemented filter architecture is compared with the existing filter architecture, it reveals a 25% decrease in resources from the existing one and an increase in clock frequency of roughly 20%.

Height to diameter ratio model of Larix gmelinii in Daxing'anling Mountains, China

Based on data from 56 plots of natural Larix gmelinii forest in Cuigang Forest Farm of Daxing'anling Mountains, we constructed the height to diameter ratio (HDR) model of L. gmelinii with exponential decay function as the base model. We used the tree classification as dummy variables and the method of reparameterization. The aim was to provide scientific evidence for evaluating the stability of different grades of L. gmelinii trees and stands in Daxing'anling Mountains. The results showed that except for diameter at breast height, the dominant height, dominant diameter, individual tree competition index all had significant correlations with the HDR. The involvement of these variables significantly improved the fitted accuracy of the generalized HDR model, with the adjustment coefficients, root mean square error and mean absolute error being 0.5130, 0.1703 m·cm-1 and 0.1281 m·cm-1, respectively. When the tree classification as a dummy variable was added to parameters 0 and 2 of the generalized model, the fitting effect of the model was further improved. The three above-mentioned statistics were 0.5171, 0.1696 m·cm-1 and 0.1277 m·cm-1, respectively. Through comparative analysis, the generalized HDR model with tree classification as dummy variable had the best fitting effect, which was superior to the basic model, and had higher prediction precision and adaptability.

Axial compressive behavior of GFRP-timber-reinforced concrete composite columns

This paper investigated the compressive behavior of a novel glass fiber reinforced polymer (GFRP)-timber-reinforced concrete composite column (GTRC column), which consisted of reinforced concrete with an outer GFRP laminate and a paulownia timber core. The axial compression tests were performed on 13 specimens to validate the effects of various timber core diameters, slenderness ratios, and GFRP laminate layers/angles on the mechanical behaviors. Test results indicated that with the increase in the timber core diameter, the ductility and energy dissipation ability of the composite column increased by 52.6% and 21.6%, respectively, whereas the ultimate load-bearing capacity and initial stiffness showed a slight decrease. In addition, the GFRP laminate considerably improved the ultimate load-bearing capacity, stiffness, ductility and energy dissipation capability by 212.1%, 26.6%, 64.3% and 3820%, accordingly. Moreover, considering the influence of timber core diameter, an ultimate load-bearing capacity adjustment coefficient was proposed. Finally, a formula was established based on the force equilibrium and superposition for predicting the axial bearing capacity of the GTRC columns.

Economic policy uncertainty, geopolitical risk and cash holdings: evidence from Saudi Arabia

PurposeThis study aims to investigate the influence of economic policy uncertainty (EPU) and geopolitical risk (GPR) on corporate cash holding level and speed of adjustment (SOA) in one of the most important emerging markets in the Middle East and North Africa, Saudi Arabia. It also investigates whether Shariah-compliance as well as financial constraints affect the relationship between both EPU and GPR and corporate cash holdings.Design/methodology/approachThe study employs GMM regression considering a sample of 140 nonfinancial firms drawn from the Saudi stock market over the period 2002 to 2019.FindingsThe authors find evidence in support of the precautionary motive hypothesis. Facing costly external financing induced by economic policy-related uncertainty and geopolitical tension, Saudi firms tend to accumulate cash as a buffer against negative shocks to their cash flows. The results also show that the positive impact of EPU and GPR on the level of cash holding is less pronounced in Shariah-compliant firms, whereas it is more pronounced in more financially constrained firms. Evidence also reveals that the estimated adjustment coefficients show that Saudi firms adjust more quickly toward their target cash ratio in periods of high economic instability and geopolitical risks.Practical implicationsThis study has important implications for managers, policymakers and regulators. For managers, the study is an important reference to understand and design cash management policies by considering factors measured at the country level. More specifically, managers should pay more attention to periods of heightened uncertainties and geopolitical tensions in which the availability of funds is reduced. For policymakers and regulators, this study may be useful in assessing the effect of economic instability on firm’s cash holding decision. Therefore, in an effort to increase the supply of external financing available to firms, policymakers may devise investment friendly environment by controlling country-specific factors.Originality/valueThis paper shows how EPU and GPR as institutional environment factors affect cash holding decision in an oil-rich country.

Look-ahead prediction of spindle thermal errors with on-machine measurement and the cubic exponential smoothing-unscented Kalman filtering-based temperature prediction model of the machine tools

Reducing the thermal equilibrium time is one effective way to improving the efficiency and utilization and ensuring the accuracy of machine tools. This paper proposed the look-ahead prediction of spindle thermal errors based on CES-UKF temperature prediction model using on-machine measurement. It can predict the thermal errors during the warm-up stage just with the measured temperature data in the required on-machine measurement time (ROMT). With the thermal error compensation function, the machine tool only needs warm-up for ROMT to improve the efficiency and ensuring the accuracy of machine tools. The look-ahead temperature prediction is realized combining UKF and CES including real-time adjustment of exponential smoothing coefficients and ROMT calculation. Temperature-sensitive point selection based on self-attention mechanism is established. Gate recurrent unit (GRU)-based thermal error model is proposed considering the thermal hysteresis effects. Verifications and cutting experiments are carried out to testify the effectiveness and robustness of the method.

Theoretical and experimental study on performance of compound-driven MR valve-controlled damper

A compound-driven magnetorheological (MR) valve is designed to cope with the low reliability and high energy consumption of traditional MR valves. The operating magnetic field of the valve is applied by both the excitation coil and ring magnet, maintaining excellent pressure drop performance even at zero current. To analyze the performance and obtain the variation law of the magnetic flux density and pressure drop, a pressure drop mathematical model and a magnetic field simulation model are established. The key parameters of the MR valve are also optimized using non-dominated sorting genetic algorithms-II. A dynamic performance test system is built, and the influence of the load on the pressure drop and hysteresis characteristics of the MR valve is studied. The results show that the optimized pressure drop and adjustable coefficient are improved by 4.7% and 8.6% respectively. The pressure drop grows nonlinearly with the electric current and reaches saturation at a current of 1.5 A, and a pressure drop of 1485 kPa is still generated at zero current. The output damping force of the compound-driven MR valve-controlled damper can be continuously adjustable, indicating that the dynamic performance of the damper can be controlled by adjusting the input current.

Strain Energy Dissipation Characteristics and Neural Network Model during Uniaxial Cyclic Loading and Unloading of Dry and Saturated Sandstone

The energy dissipation characteristics are important features of rock damage and failure during loading. However, the quantitative relationship between energy dissipation and rock failure is not clear. In this work, acoustic emission monitoring tests during uniaxial cyclic loading and unloading were conducted on sandstones in two conditions, namely dry and saturated, to investigate the energy evolution characteristics. Then, an index of the absolute energy ratio and a dynamic adjustment coefficient were put forward to represent rock damage and failure. A recurrent neural network was employed to predict the dynamic adjustment coefficient of dissipative strain energy. The results showed that (1) water saturation promoted the increased rate of dissipative strain energy during the last loading and unloading, but suppressed the sudden drop in elastic strain energy. (2) In the early and middle stages of cyclic loading–unloading, the absolute acoustic emission energy of dry and saturated rock samples was mainly generated by the historical maximum stress, while the absolute acoustic emission energy was mainly generated by cycle loading–unloading in the final cyclic stages. (3) The absolute energy ratio of both dry and saturated rock samples showed a sudden increase at the last cyclic loading–unloading, and this phenomenon can be taken as a precursor of rock damage of cycle loading–unloading. (4) The recurrent neural network for the prediction of the dynamic adjustment coefficient shows good agreement for rock failure related to dissipative strain energy. The results can provide experimental and prediction models for the monitoring and warning of rock engineering disasters in slopes, hydraulic fractures, tunnels, and coal mines.

Design and experimental research of stepped bypass magnetorheological damper

In order to meet the damper performance requirements of heavy vehicles, a stepped-bypass magnetorheological damper is proposed. The mathematical model of damping force is deduced, and its mechanical properties are numerically simulated. Then the damper is manufactured, and the mechanical properties of the stepped bypass magnetorheological damper are experimentally studied. The simulation are consistent with the experimental results. The damper is optimized by orthogonal optimization design test. Finally, it is concluded that the maximum output damping force of the stepped bypass magnetorheological damper is about 4500 N, and the adjustable coefficient K is about 5.4. After optimization, the damping force of the stepped bypass magnetorheological damper is increased by at least 5.3%, and the adjustable coefficient K is at least 1.37 times that before optimization, which is 13% wider than that before optimization.

Multi-Objective Optimization of Magnetorheological Mount Considering Optimal Damping Force and Maximum Adjustable Coefficient

To address the problem of multiple working conditions and complex requirements in magnetorheological fluid (MRF) mounts, a high-precision damping characteristic optimization method is explored. Based on the parallel plate model, the equation of fluid motion in the inertial channel was established according to the Navier–Stokes equation, and the MRF mount damping characteristics were analyzed. Considering the fluid model to be suitable in the steady-state, the model was experimentally verified, and the extended equation was fitted. Multi-objective optimization design was carried out by considering the large damping force and adjustable coefficient as the optimization goal and external geometric dimensions as variables. According to results, under the radial-channel MRF mount structure, the magnet core depth has the least influence on the damping force; furthermore, the damping performance can be quickly improved by changing the height of the inertial channel. The addition of the extended equations further improved the accuracy of the fluid model. The multi-objective optimization design can improve the strength and uniformity of the flux density of the MRF mount damping gap. After optimization, the damping force is increased by 44.64%; moreover, when the current is increased from 1.5 to 1.8 A, the controllable force increases by only 2.26%, and the damping performance is fully exerted.

Food price and Inflation Adjustments in Nigeria: Evidence from Threshold Cointegration

This paper investigates two stages of transmission through which inflation stabilization policy affects headline inflation by estimating a threshold cointegration model. The paper finds that asymmetric monetary shocks passing-through food prices exerts inflationary pressure on consumer prices, and is characterized by deep asymmetric movement, large degree of stickiness in adjusting downward, while exhibiting upward momentum in correcting food price fall. In addition, asymmetries were found in consumer price adjustment as food price shock transmits substantial inflationary pressure to consumer prices, while disinflationary effect originating from a fall in food price is inconsequential. The coefficients of adjustment were found to be robust in the sub-sample. This paper concludes that an unconventional monetary policy intervention that aims at stabilizing headline inflation by means of stimulating food supply could unavoidably inflate food prices more than it could deflate it especially if the elasticity of domestic food output to money supply growth is less compared to response of food price to money supply. Hence, caution must be taken on the size differential of output response to the net rise in money supply and price adjustment to the expansion in money supply.

Astigmatism Profile in a Large Series of Brazilian Patients.

To assess anterior, posterior, and total corneal astigmatism in a large sample of Brazilian patients. In this retrospective cross-sectional study, all patients whose corneas were imaged with the Galilei G6 (Ziemer Ophthalmology) between January 2017 and February 2019 at HOPE Eye Hospital, in Recife, Brazil, were eligible to participate. Anterior, posterior, and total corneal astigmatism values were collected and analyzed. The study included 3,253 eyes of 1,919 patients. The mean magnitude of the anterior, posterior, and total corneal astigmatism was 1.50 ± 1.11, 0.34 ± 0.15, and 1.29 ± 0.98 diopters (D), respectively. Corneal astigmatism was greater than 0.50 D in the anterior cornea of 86.3% of eyes (2,807 eyes) and in the posterior cornea of 13.2% of eyes (429 eyes). Vertical alignment of the steepest corneal meridian was observed in the anterior cornea of 74.5% of eyes (2,423 eyes) and in the posterior cornea of 93.1% of eyes (3,029 eyes). The correlation between the astigmatism magnitude of the anterior and posterior cornea was strong when the steep anterior meridian was aligned vertically (r = 0.720; P < .001), and absent when it was aligned horizontally (r = 0.102; P = .036). Corneal astigmatism values in the Brazilian population were similar to those found in other ethnicities, suggesting that toric calculators, nomograms, coefficients of adjustment, and formulas that were developed based on astigmatism values of other populations may be used in Brazilian patients with comparable accuracy. [J Refract Surg. 2023;39(1):56-60.].