Moment Method Calculations Research Articles

Probability‐Based Finite‐Time Security Control for Switched Stochastic Systems via a Novel Event‐Triggered Mechanism and Its Application

ABSTRACTThis article discusses the finite‐time boundedness (FTB) issue and ‐gain analysis for switched stochastic systems, particularly under the dual influence of DoS attacks and false data injection attacks, by employing a novel event‐triggered mechanism. Different from the moment calculation method, a probability‐based FTB is studied which offers more pertinence. To obtain a less conservative condition of FTB, a switched Lyapunov function is constructed. Additionally, a memory‐based dynamic event‐triggered mechanism is designed to reduce the amounts of triggering and mitigate the state response fluctuations. Based on the incomplete information above, state feedback controllers are devised to satisfy stochastic FTB, ensuring the successful attainment of finite‐time ‐gain. Sufficient conditions are cast into a convex optimization problem by LMIs which can be solved easily. Finally, a compared numerical example and an RLC series circuit are adopted to demonstrate the availability of the theoretical results.

Friction moment calculation method for tapered roller bearings under combined loads

Friction moment calculation method for tapered roller bearings under combined loads

Flexural stiffness of RC beams with high‐strength steel bars after exposure to elevated temperatures

AbstractIn this paper, the flexural stiffness of the reinforced concrete (RC) beams reinforced with high‐strength steel bars after exposure to different elevated temperatures was investigated experimentally and theoretically. The effects of the elevated temperature (room temperature, 200°C, 400°C, 600°C, 800°C, and 1000°C), high‐temperature duration time (0 h, 1 h, and 2 h), and steel bar types (HRB600 and HRB500) on the load–deflection response, load–stiffness response, and crack distribution of tested beams were investigated. The results showed that when the temperature is below 600°C, the effect of high temperature on the stiffness reduction of high‐strength RC beams is not significant, while the beams reduced the stiffness when the exposure temperature reached 800°C and 1000°C, regardless of the type of the steel bars. The elevated temperature accelerated the development of the deflection of RC beams, and the bending stiffness of the RC beams decreased more severely as the increase of duration time. By using appropriate degradation factors, the residual stiffness of the beams was predicted well by the analysis calculation method and the effective inertia moment calculation method, for example, the prediction accuracy is over 91% and 85.8% for the cases under and over 800°C, respectively. However, for the beams at 1000°C, a correction coefficient (0.652) was applied to improve the accuracy of the calculative stiffness of the HRB600 RC beams at the service load stage.

DYC Design for Autonomous Distributed Drive Electric Vehicle Considering Tire Nonlinear Mechanical Characteristics in the PWA Form

This paper presents a novel direct yaw moment control (DYC) strategy for autonomous distributed drive electric vehicle (DDEV) to improve path-following driving stability under critical maneuvers. Due to the fact that the tire mechanical characteristics show highly nonlinear under those critical conditions, the piecewise affine (PWA) identification method is chosen in this work to model the tire nonlinear mechanical characteristics since it shows best model accuracy/simplicity compromise for system control design. On this basis, to properly reflect the coupling behaviors between longitudinal motion and lateral motion, the vehicle dynamics model which considers the tire nonlinear mechanical characteristics in the PWA form is established. By analyzing the phase plane of vehicle nonlinear model, a novel external yaw moment calculation method based on global fast terminal sliding mode (GFTSM) control method is applied to the upper layer of DYC architecture for eliminating the errors of yaw rate and sideslip angle. Then, different weight coefficients are allocated to obtain the final external yaw moment. In the lower controller, the optimal four-wheel torque is distributed according to a concise and accurate algorithm in which adaptive weight coefficients are considered. The simulation results verify the effectiveness of the proposed control strategy in improving the driving stability performance of autonomous DDEV against two other control strategies under three extreme conditions.

Parameter analysis and design on socket CFST column-cap beam joint with UHPC grouted connection

The excellent mechanical properties of concrete-filled steel tube (CFST) make it a competitive alternative to column-cap/foundation cap socket connections in accelerated bridge construction (ABC). To investigate more research parameters and facilitate the seismic design of socket CFST column joints, a detailed numerical analysis model of socket column-cap beam joint was established and verified by experimental data, and the bearing capacity and failure modes of socket joints under the dimensions of the CFST parts and their material properties were investigated as well. It is found that the size of steel tube, the strength of steel tube, the socket depth of CFST, and the type of forming hole have significant effects on the strength and failure modes of column to cap beam socket joints. This study also proposed a moment calculation method for socket joints that can accurately predicts the bearing capacity under different failure modes. Finally, a design process was developed to facilitate the widespread application of this socket CFST column-cap beam joint with Ultra High-Performance Concrete (UHPC) grouted connection.

Improved overturning moment calculation method for large caliber artillery based on dynamics analysis

The effect of launch load on rotating parts is very complicated during firing of large caliber artillery. In the design of artillery firepower system, the traditional method to derive artillery overturning moment by taking the elevating part as the analysis object and using the static equilibrium equation cannot accurately reflect the real state of artillery firing. Therefore, taking the whole gun dynamics simulation as the analysis method and combining with the shooting test data, the force state of the elevating mechanism is obtained. The dynamic simulation results, the calculation results of the traditional formula, the measured results of the shooting test and the attitude change of the gun monitored by high-speed camera are compared and analyzed. The result shows that the turret race shaking is an important factor affecting the accuracy of design and simulation calculation. When the turret race shaking is considered, the simulation results are consistent with the experimental results, but inconsistent with the calculation results of the traditional design formula; The simulation results without considering the turret race shaking are consistent with the results of the traditional design formula, but they are different from the test results. Considering the influence of the angular acceleration of the rotating part given by the turret race shaking, the overturning moment formula is improved, and the force analysis formulas of the rotating part and the elevating part are carried out respectively and the calculation results of the improved formula are in good agreement with the test results. The research complements the calculation method of the overturning moment of the gun, which can be extended to the design of key components such as elevating mechanism and gun carriage.

Study on the Thermodynamic Properties of Thin Film of FCC Interstitial Alloy AuSi at Zero Pressure Using the Statistical Moment Method

We built a model and proposed a theory about the thermodynamic properties of face-centered cubic (FCC) binary interstitial alloy’s thin films based on the statistical moment method and performed numerical calculations for AuSi (gold silicide). First, the statistical moment method (SMM) calculations for the thermodynamic properties of Au are compared with reported experiments and calculations that show a good agreement between the calculations in this paper and earlier studies. Additionally, the SMM calculations for thermodynamic properties of AuSi alloy films are performed, which show that the thermal expansion coefficient, the specific heat at constant volume, and the specific heat at constant pressure increases, while the isothermal elastic modulus decreases with increasing temperature and increasing interstitial atom concentration. Furthermore, when the number of layers reaches 100, the thermodynamic properties of the film are similar to those of the bulk material. The achieved theoretical results for AuSi films are novel and can be useful in designing future experiments.

Sales Forecasting Analysis Using Trend Moment Method: A Study Case of a Fast Moving Consumer Goods Company in Indonesia

The market of Fast-Moving Consumer Goods (FMCG) companies in Indonesia is enormous. Unilever has 400 brands in more than 190 countries, making it a global business that is as influential in the consumer product market as it is in Indonesia. Sales forecasting at this company is very useful for planning expenses and the company's total costs on the business strategy. This study uses trend moment method to forecast the sales and earnings of Unilever Indonesia companies at the end of the year. This article aims to test the performance of the trend moment method calculation on the prediction of net sales and profits in FMCG companies. At the end of the analysis process, it can be concluded that forecasting using trend moment method is going very well. This indicator of success is shown by the error level of MAPE, which is below 10%.

KORELASI KEHADIRAN DENGAN HASIL BELAJAR MAHASISWA TEKNIK MESIN UNIVERSITAS MUHAMMADIYAH TANGERANG DI ERA NEW NORMAL

Correlation can be said to be a fact of the relationship between two or more variables. This study aims to determine the correlation between attendance and learning outcomes of Mechanical Engineering Students at Muhammadiyah University of Tangerang in the new normal era. The research method used is a quantitative method with a correlation of two variables. Analysis of attendance variables with student learning outcomes using the product moment calculation method. The results showed that the correlation between attendance and student learning outcomes had a very small and not close effect, namely 0.38. This shows that 14.8% of learning outcomes are influenced by attendance and 85.2% are influenced by other factors

Revisiting the Schrage Equation for Kinetically Limited Evaporation and Condensation

Abstract The Schrage equation is commonly used in thermofluid engineering to model high-rate liquid–vapor phase change of pure fluids. Although shortcomings of this simple model were pointed out decades ago and more rigorous models have emerged from the kinetic theory community, Schrage's equation continues to be widely used. In this paper, we quantify the accuracy of the Schrage equation for evaporation and condensation of monatomic and polyatomic fluids at the low to moderately high flux operating conditions relevant to thermofluid engineering applications. As a high-accuracy reference, we numerically solve a Bhatnagar, Gross, and Krook (BGK)-like a model equation for polyatomic vapors that have previously been shown to produce accurate solutions to the Boltzmann transport equation. We observe that the Schrage equation overpredicts heat/mass fluxes by ∼15% for fluids with accommodation coefficients close to unity. For fluids with smaller accommodation coefficients, such as water, the Schrage equation yields more accurate flux estimates. We find that the Mott-Smith-like moment methods developed for liquid–vapor phase change are much more accurate than the Schrage equation, achieving heat/mass flux estimates that deviate by less than 1% (evaporation) and 4% (condensation) from the reference solution. In light of these results, we recommend using the moment method equations instead of the Schrage equation. We also provide tables with our high-accuracy numerical data for evaporation of any fluid and condensation of saturated water vapor, engineering equations fit our data, and code for moment method calculations of evaporation and condensation.

Experimental study on seismic performance of prefabricated replaceable beam-column connectors using double-sided angle steel

An innovative performance-reparability beam-column connection was proposed in this paper. Based on quasi-static test of two specimens without replaceable angle steel, five specimens with double-side angle steels and one specimen with one-side replaceable angle steel, the seismic performance of this new type of beam-column connector was analyzed. Through the analyses of destruction form, hysteretic loops, skeleton curves, cumulative dissipated energy, strength and stiffness degradation, residual deformation and re-centering behavior as well as the measured strains results of the beam-column connector, the effects of setting angle steel, initial prestressing, different flange thickness of the connector and replacement of angle steel on the seismic performance of the prefabricated beam-column connectors were examined. The results indicated that the seismic performance of this new type connector shown an excellent seismic behavior. Setting replaceable angle steel and increase the number of angle steel could effectively improve the seismic performance; The seismic performance repair could be achieved quickly by using of thicker angle steel after replacement; Reasonable initial prestress could effectively increase the ultimate load, initial stiffness, re-centering ability and the energy consumption of the specimens; Increasing the flange thickness of the connector could reduce the expansion degree of the flange. The mechanism of "elastic in the minor earthquake, self-centering in the moderate earthquake and replaceable in the major earthquake" could be realized well by rational design, and the repair of structure after earthquake can be solved easily by different very low-cost solutions. Based on the test results, a moment calculation method, which could distinguish the gap opening was proposed, and the calculated results agreed well with the experimental results.

Geometrically Invariant NSCT–GPCET-Based Image Watermarking with Accurate Moment Calculation

Generic polar complex exponential transform (GPCET), as continuous orthogonal moment, has the advantages of computational simplicity, numerical stability, and resistance to geometric transforms, which make it suitable for watermarking. However, errors in kernel function discretization can degrade these advantages. To maximize the GPCET utilization in robust watermarking, this paper proposes a secondary grid-division (SGD)-based moment calculation method that divides each grid corresponding to one pixel into nonoverlapping subgrids and increases the number of sampling points. Using the accurate moment calculation method, a nonsubsampled contourlet transform (NSCT)–GPCET-based watermarking scheme with resistance to image processing and geometrical attacks is proposed. In this scheme, the accurate moment calculation can reduce the numerical error and geometrical error of the traditional methods, which is verified by an image reconstruction comparison. Additionally, NSCT and accurate GPCET are utilized to achieve watermark stability. Subsequent experiments test the proposed watermarking scheme for its invisibility and robustness, and verify that the robustness of the proposed scheme outperforms that of other schemes when its level of invisibility is significantly higher.

Experimental investigation on the seismic behaviour of innovative self-centring precast steel-concrete hybrid frames

An innovative self-centring precast steel-concrete hybrid (SPH) frame was proposed. The proposed SPH frame was assembled with reinforced concrete (RC) columns and prefabricated steel-concrete hybrid (PH) beams using steel end plates and high-strength bolts. The RC columns consisted of a traditional RC section and an unbonded post-tensioned (PT) screw-thread steel (STS) bar, and the PH beam was composed of two steel beam ends, a prefabricated RC beam unit and four unbonded PT strands. The self-centring ability of the structure system was mainly provided by the PT steel reinforcements; the energy dissipation capacity was mainly provided by the bolted web friction devices (WFDs) applied to the beam and the plastic deformation of the steel beam ends. To examine the seismic behaviour of this innovative structural system, cyclic tests were conducted on two SPH frames and one non-prestressed precast steel-concrete hybrid (NPH) frame. By analysing failure modes, hysteretic loops, skeleton curves, energy dissipation, displacement ductility ratios, stiffness degradation and the relative self-centring efficiency (RSE), the effects of the initial prestress, the pretorque of the high-strength bolts at the WFDs and the construction measure at the column base were thoroughly assessed. The test results indicated that the proposed noncontact oil jack prestressing technique used in the PH beams was reliable; during the testing process, gap opening and closing could be clearly observed at the interfaces between the RC beam unit and the steel beam end; the SPH frames exhibited better self-centring and energy consumption capabilities than the NPH frame; and the SPH frame exhibited a typical two-stage cyclic behaviour, namely, a self-centring stage and an energy consumption stage. In the self-centring stage (before the drift ratio of 2.0%), the SPH frame could effectively control residual deformation, and the RSE remained at approximately 85%; in the energy consumption stage (after the drift ratio of 2.0%), the SPH frame could effectively consume the absorbed energy. Based on the test results, a moment calculation method, which could distinguish the gap opening in the PH beam, was proposed, and the calculated results agreed well with the experimental results.

Experimental and Theoretical Conformational Analysis of Tris(4-methylphenyl)phosphine and Its Chalcogenides

Conformational analysis of tris(4-methylphenyl)phosphine and its oxide, sulfide, and selenide has been performed by the dipole moment method and DFT quantum chemical calculations at the B3PW91/ 6-311++G(df,p) level of theory. The title compounds have been found to exist in solution as a single symmetrical conformer with gauche,gauche,gauche orientation of the substituents on the phosphorus atom with respect to the P=X bond (X = LEP, O, S, Se).

Re-adjustments for MOM calculations of microstrip and stripline power dissipation

AbstractMicrostrip and stripline losses in Method of Moments (MOM) calculations have an error arising from the large current density at the strip edges, characterized by an integration limit (W/2-d) in the equation for current density in thin strips (width W), where d is a fitting parameter. It depends primarily on the width of the MOM subsection on the edge of the strip. By comparing with the integration limit (W/2-Δ) for an actual strip with finite thickness, a correction factor is estimated. The equations incorporating d are confirmed by comparing with MOM calculations of isolated stripline, uniformly spaced parallel strips, striplines and microstrips close to ground planes, and with a strip in a uniform, externally applied magnetic field. The results are also consistent with measurements with copper. This makes the accuracy of the loss estimates commensurate with the excellence of the other aspects of MOM simulations.

A time-varying friction moment calculation method of an angular contact ball bearing with the waviness error

Angular contact ball bearings (ACBs) are extensively applied in various mechanical rotational systems. Most of current works are focused on time-invariant calculation methods of the ACBs with and without the waviness. This work proposes a time-varying calculation method for computing the friction moment of an ACB. This method considers the variations of the contact forces between the contact parts of ACB. In this method, the rolling friction moments caused by the elastic material hysteresis, slipping friction moments produced by the differential ones, slipping moment generated by the sliding friction between the cage and ring, and viscous friction moments engendered by the gas–oil mixture are formulated. The friction moments of ACB with the waviness on the single part and all parts are analyzed. The friction moments from the previous time-invariant and proposed time-varying methods are discussed to show the superiorities of proposed method. The effects of the waviness amplitude, shaft velocity, radial force, and waviness order on the time-varying friction moment of the ACB are discussed. The simulation results indicate that the proposed time-varying method can offer a more reasonable and precise approach to study the time-varying friction moments of the ACBs.

Post-Yielding Behavior of Hinge-Supported Wall with Buckling-Restrained Braces in Base

A novel structural wall with hinge support and buckling restrained braces (BRBs) set in the base (HWBB) is studied. HWBB can be applied to precast manufacturing due to its considerable ductility and the separate loading mechanism in HWBB–frame structure. In elastic stage, BRBs play a brace role to make the hinged wall resist horizontal forces like a shear wall. BRBs dissipate seismic energy through plastic and hysteresis effects after yielding and the damage is only concentrated in BRBs. The performance of an HWBB is equivalent to a shear wall structure with excellent ductility and stable energy dissipation capacity. Numerical analysis indicates that the hinged wall body in the HWBB well controls the deformation mode of the structure, avoiding the concentration of story drifts, thereby protecting the remaining parts of the structure. It is revealed that the moments of the wall body will generate significant increments after BRBs yielding, and the Seismic Intensity Superposition Method is proposed to calculate the moments. In this method, nonlinear response of an HWBB can be regarded as the sum of the responses of two elastic corresponding structures excited with two parts of the seismic intensity, respectively. Modes and moments equations of the hinged wall with uniform distribution of stiffness and mass are derived, and calculation results coincide with that of the nonlinear time history analysis (NHA). For a more general case, the white noise scan method is proposed to solve the structure’s natural characteristics and to further calculate the response. Finally, the post-yielding moment calculation method and the process based on design response spectrum are proposed. It is proved that the moments from proposed Seismic Intensity Superposition Method can envelop most of the moments from NHA, and it is a good estimate of the response of HWBB in nonlinear stage.

Efficient metering and surveying sampling designs in longitudinal Measurement and Verification for lighting retrofit

Measurement and Verification (M&V) is often required for energy efficiency or demand side management projects in buildings, to demonstrate that savings were in fact achieved. For projects where sampling has to be done, these costs can be the most significant driver of the overall M&V project cost, especially in multi-year (longitudinal) projects. This study presents a method for calculating efficient combined metering and survey sample designs for longitudinal M&V of retrofit projects. In this paper, a building lighting retrofit case study is considered. A Dynamic Linear Model (DLM) with Bayesian forecasting is used. The Bayesian component of the model determines the sample size-weighted uncertainty bounds on multi-year metering studies, with results from previous years incorporated into the overall calculation to reduce forecast uncertainty. The DLM is compared to previous meter sampling methods, and an investigation into the robustness of efficient sampling plans is also conducted. The Mellin Transform Moment Calculation method is then used to combine the DLM with a Dynamic Generalised Linear Model describing the uncertainty in survey results for the longitudinal monitoring of lamp population decay. A genetic algorithm is employed to optimise the combined sampling design. Besides the reliable uncertainty quantification features of the method, results show a reduction in sampling costs of 40% for simple random sampling, and approximately 26.6% for stratified sampling, as compared to realistic benchmark methods.

Investigation of thermodynamic and mechanical properties of AlyIn1−yP alloys by statistical moment method

The thermodynamic and mechanical properties of III-V zinc-blende AlP, InP semiconductors and their alloys have been studied in detail from statistical moment method taking into account the anharmonicity effects of the lattice vibrations. The nearest neighbor distance, thermal expansion coefficient, bulk moduli, specific heats at the constant volume and constant pressure of the zincblende AlP, InP and AlyIn1−yP alloys are calculated as functions of the temperature. The statistical moment method calculations are performed by using the many-body Stillinger-Weber potential. The concentration dependences of the thermodynamic quantities of zinc-blende AlyIn1−yP crystals have also been discussed and compared with those of the experimental results. Our results are reasonable agreement with earlier density functional theory calculations and can provide useful qualitative information for future experiments. The moment method then can be developed extensively for studying the atomistic structure and thermodynamic properties of nanoscale materials as well.

Modifying and Accelerating the Method of Moments Calculation

This manuscript deals with optimizing the numerical method called the method of moments (MoM). This method is widely utilized for field computation of 3D structures. MoM is exploited in hydraulics as well as in the electromagnetic field theory. Emphasis is put on minimizing calculations necessary for constructing a system of linear equations exploiting symmetry or similarity of elements of geometric structure. The manuscript also contains a comparison of computing times using standard MoM and a proposed modified MoM keeping the same structure of the solved construction.