Method For Calculation Of Resistance Research Articles

Analysis of Losses in Cables and Transformers with Unbalanced Load and Current Harmonics

The power quality problems are more and more serious in the power system. The harmonics and the three-phase imbalance have a greater impact on the line loss of power grid. We focus on the power losses in cables and transformers with unbalanced load in current harmonics basing on the equivalent resistance method. The impact caused by the skin effect is illustrated in order to enhance the accuracy of the theoretical calculation. For this purpose, a mathematical development that takes in account the presence of current harmonic components and unbalanced load in the losses calculation is presented. The reliability of the method is verified in a simulation model. According to the comparative analysis between the simulation and the proposed method, we can conclude that the harmonic resistance calculation method considering skin effect is more accurate than the traditional method. The results show that the additional loss caused by the harmonics has a nonlinear relation with the harmonic currents. At the same time, the additional loss of distribution network under compound disturbance with unbalanced load in current harmonics is studied. Compared with the cases that two phase load are heavy and one phase load is light or one phase load is heavy and other two phase load are light, when one phase load is heavy, one phase load is light and one phase load is the average value of the others, the additional loss of the system is the least one. The additional loss for the case with that two phase load are heavy and one phase load is light is the biggest one.

Multi-objective optimization of trimaran sidehull arrangement via surrogate-based approach for reducing resistance and improving the seakeeping performance

Trimaran hull forms have been very attractive in the past decade. Hydrodynamic performance of trimaran ships is influenced by sidehull arrangement. The present study was intended to construct a surrogate model for better understanding of the hydrodynamic performance of a trimaran ship. Accordingly, seakeeping and resistance of an inverted-bow trimaran were considered as objectives of a simulation-based design (SBD) optimization framework. Different longitudinal, transversal, and vertical position of trimaran’s sidehull were investigated based on an advanced free-surface steady Reynolds-averaged Navier–Stokes (URANS) solver within StarCCM+ for resistance calculation and 3D panel method in Ansys-AQWA for seakeeping analyses. Quality and applicability of metamodeling optimization and its computational time were examined for future trimaran hull design projects. Total resistance for drag reduction, pitch and heave motion, and vertical acceleration at fore perpendicular for seakeeping performance were objectives of the study. The optimization results indicated a 6.9% drag reduction and 4.7% improvement in seakeeping performance, which yield lower longitudinal and large transversal distances of the sidehull. Furthermore, the conducted investigations demonstrated the effectiveness and capability of the proposed optimization platform for other marine industrial projects.

Fire resistance of timber-concrete composite slabs

The paper presents a simplified method for calculation of resistance of a TCC slab in fire conditions.Within the method the tensile and the compressive failure criteria in the outermost fibres of the cross-section are checked. The influence of the fire is applied through one-dimensional charring of the timber part of the cross-section in accordance with current standards on reduction of properties of materials. The concrete-timber connection is assumed to be ideal during the determination of resistant moment of the TCC cross-section. On the other hand, the calculation of the deflection of the TCC slab is conducted with the reduction of the connection’s rigidity. The ineffective zone of the timber as well as the cracked tensile zone of concrete part do not contribute to the effective stiffness of the TCC slab. The method is validated against the results of full sized fire tests of one way spanning TCC slabs form literature. Calculated and experimentally determined midspan deflections and failure times of the TCC slabs are compared and their considerable agreement is observed. Due to its convenience and accuracy, the present simplified method represents a useful tool for designers of TCC structures in fire conditions.

Fuel Oil Consumption Monitoring and Predicting Gas Emission Based on Ship Performance using Automatic Identification System (AISITS) Data

The increasing number of ships has an impact on increasing the amount of fuel consumption and exhaust emissions produced by ships when operating. Analysis of IEA and ICCT shows the amount of emissions and consumption in 2007 to 2015 relatively increased. Ship exhaust emissions become one of the main sources of pollution of the marine environment. Pollutants originating from emissions of ships that have high CO, NOx, HC, SO2 and CO2, even sulphur pollutants can cause the risk of disruption of the human health system. Therefore monitoring technology is used by the user or operator to ensure that the ship operates efficiently. An integrated monitoring system is expected to report information such as fuel consumption, emissions and EEOI generated by the ship. The algorithm developed in this study uses the empirical formulation of the Holtrop Method (for basic resistance calculations) and the Stawave Method (for calculation of wind resistance, waves, draft changes and water properties) written in the PHP script programming. This programming is the basis of development at the interface of a program to bring up fuel monitoring data, EEOI and emissions in real time on each ship.

Modelling and design method for static resistance of a new connection between steel tubular column and flat concrete slab

This paper presents the results of a numerical and analytical investigation into the punching shear behaviour of an innovative simple and effective shear connection between steel tubular column and flat concrete slab using welded shear studs, steel plates and bent-up rebars. The finite element numerical simulation model was validated against two full-scale physical tests carried out by the authors. The validated numerical simulation model was used to perform extensive numerical parametric studies to investigate the effects of changing different design parameters including flat slab depth, concrete grade, bent-up rebar design, shear stud dimensions (length and diameter) and steel tube size, so as to develop thorough understanding of their punching shear behaviour and to provide comprehensive data for development of an analytical method for design. The developed analytical design method can be used to check capacities of shear studs, bent-up rebars and slab punching shear resistance. For this shear connection system, it is easy to prevent shear stud yield failure and bent-up rebar failure so that the system behaves as an enlarged column for calculating punching shear resistance of the slab. For the enlarged column, punching shear resistance calculation method in Eurocode 2 [2] can be used.

Application of wave added resistance calculation method in comprehensive optimization design of ship hull form

Application of wave added resistance calculation method in comprehensive optimization design of ship hull form

Analysis of temperature changes on three-phase synchronous generator using infrared: comparison between balanced and unbalanced load

Synchronous generators are a major tool in an electrical energy generating systems, the load supplied by the generator is unbalanced. This paper discusses the effect of synchronous generator temperature on the condition of balanced load and unbalanced load, which will then be compared with the measurement result of both states of the generator. Unbalanced loads can be caused by various asymmetric disturbances in the power system and the failure of load forecasting studies so that the load distribution in each phase is not the same and causing the excessive heat of the generator. The method used in data collection was by using an infrared thermometer and resistance calculation method. The temperature comparison result between the resistive, inductive and capacitive loads in the highest temperature balance occured when the generator is loaded with a resistive load, where T = 31.9 ° C and t = 65 minutes. While in a state of unbalanced load the highest temperature occured when the generator is loaded with a capacitive load, where T = 40.1 ° C and t = 60 minutes. By understanding this behavior, we can maintain the generator for longer operation life.

Wave resistance calculation method combining Green functions based on Rankine and Kelvin source

Wave resistance calculation method combining Green functions based on Rankine and Kelvin source

Cross‐border transmission line losses calculation using adaptive Monte–Carlo method

This study deals with calculation of transmission line losses. Having in mind that this type of losses, besides the line load and the other external input quantities such as atmospheric conditions, strongly depends on measurement uncertainty as well, the issue can be considered through finding the most convenient approach in calculation of measurement uncertainty. In this respect, two approaches (methods) are the most common: traditional method based on the guide to the expression of uncertainty in measurement (GUM) and the adaptive Monte–Carlo method (AMC). The study reveals the main disadvantages of the GUM, which is so far considered as a most accurate method. The observed drawbacks of the GUM can be successfully overcome by using of the AMC method. The comparison between the methods is performed on 110 kV cross-border transmission line from Croatian Transmission System Operator Ltd. The results show the great difference in the estimated variances, i.e. GUM variances are significantly overestimated what results in incorrect transmission losses allocation procedure with respect to its final financial effect. The study confirms that the AMC method is likely to be more practically suitable method for transmission line resistance and losses calculation.

Research of nano silver alloy pasteto solar cell

From theory and experiment, the method toimprove the performance of silver paste was explored. Through the analysis about the SEM images to the electrode contact section of the crystal silicon solar cell, the different contact modes and resistance calculation methods of the metal paste and silicon were verified. Through the resistance calculation, consideringthe different oxide and silver silicon contact alloy characteristics, two kinds of additive compositions were found that which may have good performance in alloy paste of the solar cell.

Accuracy of borehole thermal resistance calculation methods for grouted single U-tube ground heat exchangers

The borehole thermal resistance – that is, the thermal resistance between the fluid in the U-tube and the borehole wall – is both a key performance characteristic of a closed-loop borehole ground heat exchanger and an important design parameter. Lower borehole thermal resistance leads to better system performance and/or lower total borehole length and possibly lower installation costs. Borehole thermal resistance may be determined using in situ thermal response testing, but for design purposes, it is important to be able to predict the borehole thermal resistance prior to installation. Due to the complexity of calculating it, numerous simplified methods have been proposed. This paper reviews published methods for calculating borehole thermal resistance for grouted boreholes with single U-tubes and compares their results against a rigorous analytical method.Another quantity that is particularly important for deep boreholes is the internal thermal resistance – that is, the thermal resistance between the upward-flowing and downward-flowing fluid paths in the borehole. Short-circuiting between the two legs has the effect of reducing the total heat transfer and can be quantified as an adjustment to the borehole thermal resistance, resulting in an effective borehole thermal resistance. A few simplified methods for calculating internal thermal resistance are compared against a rigorous analytical method.The simplified methods for calculating both borehole thermal resistance and internal thermal resistance are compared in parametric studies spanning the range of borehole diameters, pipe spacing, ground thermal conductivities and grout thermal conductivities found in practice. Many of the simplified methods work well with some combinations of parameters and poorly with others. The first-order multipole expressions are closed-form algebraic expressions that give results within 2% (for borehole thermal resistance) and 6% (for internal thermal resistance) over the entire range of parameters. This represents significantly better accuracy than any of the other simplified methods and, therefore, the first-order multipole algorithm is recommended for single U-tube applications when the tubes are symmetrically placed.

Research on Transformer Winding Deformation and Winding Resistance

In this paper, the influence of transformer winding deformation on the equivalent electrical parameters is studied, and the proximity effect and skin effect caused by AC current in the wire are simulated. It is verified that the current distribution will be affected by the proximity effect and skin effect. This effect will lead to the change of the AC resistance of split conductor. An equivalent area method for the quantitative calculation of the high frequency resistance of windings is presented. It contributes to the analysis and diagnosis of transformer winding faults, especially the diagnosis of transformer winding deformation.

주행저항 산출방법이 차대동력계를 이용한 중대형 차량의 연비평가 결과에 미치는 영향에 관한 연구

The purpose of this study is know the fuel economy of difference tractive resistance calculation methods on light duty low-floor bus. Two tractive resistance calculation methods(coastdown test and JFCM conversion formula) are tested to understand the difference of fuel economy. JFCM was developed for fuel economy regulations of heavy duty vehicle. That show a big difference as a result of the calculation using coastdown test and JFCM conversion formula. The difference of the tractive resistance affects the fuel economy.

An Approximate Method for Calculation of Mean Statistical Value of Ship Service Speed on a Given Shipping Line , Useful in Preliminary Design Stage

Abstract During ship design, its service speed is one of the crucial parameters which decide on future economic effects. As sufficiently exact calculation methods applicable to preliminary design stage are lacking the so called contract speed which a ship reaches in calm water is usually applied. In the paper [11] a parametric method for calculation of total ship resistance in actual weather conditions (wind, waves, sea current), was presented. This paper presents a parametric model of ship propulsion system (screw propeller - propulsion engine) as well as a calculation method, based on both models, of mean statistical value of ship service speed in seasonal weather conditions occurring on shipping lines. The method makes use of only basic design parameters and may be applied in preliminary design stage.

A conformal-mapping method for predicting the thermal properties of U-shaped borehole heat-exchangers

This article investigates the thermal properties of U-shaped borehole heat-exchangers (UBHE), and the effects of related variables on the outlet temperature of UBHE. The conformal-mapping method, a simple and accurate thermal resistance calculation method, is employed to carry out UBHE design. The thermal analysis includes both the outside and the inside of the borehole. Outside the borehole, the finite line-source model calculates the wall temperature of the borehole in a steady state condition. Inside the borehole, the quasi-three-dimensional theory evaluates the temperature distribution of the working fluid. The results show that the conformal-mapping method yields an accurate solution for the outlet temperature of UBHE. The calculated solutions were compared with four cases of experimental data with good accuracy (within 6%). Under conditions of heat dissipation (cooling), the conformal-mapping method predicts results that are more accurate than the Hellström method (within about 1.33%). Sensitivity analysis shows that the heat backflow of UBHE can be reduced by increasing the distance of branch pipes and the liquid flow rate of the U-tube and reducing the depth of well.

An efficient modified flanges only method for plate girder bending resistance calculation

The very popular “Flange Only” method suggested in the BS 5950 for calculation of bending resistance of plate girder with Class 4 slender web is studied and compared with the more complicated effective width method adopted by the EC3. It is shown that within all practical range of web depth to thickness ratio, the flanges only method is conservative but sometime may be inefficient. Based on the study of these two methods, a very simple modification factor, which can be obtained conveniently by hand calculation, is proposed to improve the efficiency of the flanges only method. It is shown that the proposed modified flanges only method, while still always remaining conservative, could be able to estimate the bending resistance of the girder more accurately than the original flanges only method. In most cases, the bending resistances predicted by the proposed method are within the range of 94% to 97% of those predicted by the more complicated effective width method.

Research on Elastic Resistance Calculation Methods of Curved Wall Tunnel

Analyze the role of tunnel lining structure calculation for the elastic resistance, and point out the influence of assuming elastic resistance of Budd-chiarieva method on calculation result and its shortages. Then put forward a new calculation method — Iterative method which can accurately determine elastic resistance distribution law of curved wall tunnel, and introduce basic idea, influencing factor of elastic resistance distribution law, practical method of Iterative method, and the method of improving iterative speed, and the process for calculating internal force of structure is given using Iterative method; contract the calculation results of internal force of structure by Iterative method and Budd-chiari eva method and point out the differences by practical calculation examples. Finally, the application scope of iterative method and necessity for further study are suggested.

Numerical simulation of wave resistance of trimarans by nonlinear wave making theory with sinking and trim being taken into account

Up to now, there are no satisfactory numerical methods for simulating wave resistance of trimarans, mainly due to the difficulty related with the strong nonlinear features of the piece hull wave making and their interference. This article proposes a numerical method for quick and effective calculation of wave resistance of trimarans to be used in engineering applications. Based on Wyatt's work, the nonlinear free surface boundary condition, the time domain concept, and the full nonlinear wave making theory, using the Rankine source Green function, the 3-D surface panel method is expanded to solve the trimaran wave making problems, with high order nonlinear factors being taken into account, such as the influence of the sinking and trim, transom, and ship wave immersed hull surface. And the software is successfully developed to implement the method, which is validated. Several trimaran models, including a practical trimaran with a sonar dome and the transom, are used as numerical calculation samples, their wave making resistance is calculated both by the present method and some other methods such as linear (Dawson) methods. Moreover, sample model resistance tests were carried out to provide data for comparison, validation and analysis. Through the validation by model experiments, it is concluded that present method can well predict the wave making resistance, sinking and trim, and the accuracy of wave making resistance calculation is significantly improved by taking the trim and sinking into account, especially at high speeds.

Measurement of contact resistance of multiwall carbon nanotubes by electrical contact using a focused ion beam

Carbon nanotubes (CNTs) have found many potential applications but using CNTs as building blocks for nanoelectronics is still challenging. Various micro- and nanofabrication techniques including focused ion beam (FIB) are therefore being developed for combining CNTs into a nanodevice or to help assess the electrical properties of integrated CNTs. In this paper, multiwall carbon nanotubes (MWNTs) are assembled between a pair of gold (Au) electrodes by dielectrophoresis (DEP). Contact resistances of MWNT-Au and, in particular, MWNT-MWNT are measured with the help of making electrical connections between a MWNT and electrodes by FIB induced tungsten deposition. A method for resistance calculation is presented which considers the contact length of MWNTs. Under the conditions of this research, measured conducting resistances of MWNTs were from 1–10 kΩ/μm and the contact resistance of MWNTs with Au was around 100 kΩ μm. The contact resistance between MWNTs varied depending on contact configurations and could be as low as 50 KΩ. The effect of FIB parameters on the measurement results is discussed.

Influence of Resistance Calculation Method in Numerical Wave Tank on Wave Force

CADMAS-SURF/3D is a three-dimensional numerical wave tank under development which has recently been applied to some studies of wave-structure interaction. However some problems have been pointed out: for example it is difficult to determine the reasonable drag coefficient and grid dependency of resistance is remarkable. In this study we clarified grid dependency of resistance using a conventional resistance calculation method and examined the influence of drag coefficient on wave force. Next the applicability of the CADMAS-SURF/3D with a Dupuit-Forhhimer method was investigated through the comparison between experimental and numerical results of wave pressures acting on the superstructure of sloping breakwater.