Modification Coefficient Research Articles

A parametric model for predicting wind-induced pressures on low-rise vertical surfaces in shielded environments

This paper describes the development of a parametric mathematical model to predict wind-induced surface pressures on exterior vertical wall surfaces on a single model block in shielded environments. The first phase of the project focused on the development of a parametric model to determine the average pressure coefficients on exterior building surfaces shielded by a single windward obstruction model block. A pressure modification coefficient was defined to estimate the shielding effect based on the angular relationship between, the shielding block and the surface for which average pressure is to be computed, and the wind direction. The second phase involved expanding the scope of the prediction model to account for the various arrangement possibilities of the shielding blocks relative to the surfaces under investigation. The predicted pressure modification coefficient may be used to estimate average pressure coefficients taking into account the indoor velocity coefficients, surface porosity, window design, and interior partition types. The prediction model considers the effect of multiple shielding blocks, and the gaps between them on a vertical surface relative to wind direction. Wind tunnel verification of the model showed robust estimation of surface pressures in complex urban configurations.

Inelastic performance of cold-formed steel strap braced walls

The inelastic performance of sixteen 2.44 m×2.44 m cold-formed steel strap braced walls was evaluated experimentally. The performance was affected by the holddown detail, which in many cases did not allow the test specimens to reach or maintain a yield capacity and severely diminished the overall system ductility. “Test-based” R d × R o values of 3.65, 2.11 and 1.72 indicate the low ductility levels, which were not adequate to warrant the use of a seismic response modification coefficient of R = 4.0 in design. Capacity design of the SFRS elements must account for the overstrength of the strap material.

RETRACTED ARTICLE: Field testing and capacity-ratings of a short-span bridge superstructures made of advanced composite materials

Recently, there have been many theoretical and experimental studies on advanced composite materials (ACM) bridges in various fields over the world. Compared with a reinforced concrete or steel bridge, an ACM bridge has more advantages in strength, stiffness, transportation, and installation. Many demonstration projects have been carried out in the U.S, and Europe. They are also being developed and tested in South Korea. In South Korea the first of all ACM short-span bridge superstructures was installed on a public highway system in May 2002. Since these composite materials are new to bridge applications, reliable data is not available for their in-service performance. This paper describes in-service performance assessment of all ACM bridge superstructures. To investiga te its in-service performance, field load testing and visual inspections were conducted under an actual service environment. The p aper includes the presentation and discussion for ACM Bridge capacity rating based on the stress modification coefficients obtained from the test results. The test result indicates that the ACM bridge superstructure has no structural problems and is structurally performing well in-service as expected. The results may provide a baseline data for future field ACM bridge capacity rating assessments and also serve as part of a long-term performance of ACM bridge superstructure.

Field testing and capacity-ratings of advanced composite materials short-span bridge superstructures

Recently, there have been many theoretical and experimental studies on advanced composite materials (ACM) bridges in various fields over the world. Compared with a reinforced concrete or steel bridge, an ACM bridge has more advantages in strength, stiffness, transportation, and installation. Many demonstration projects have been carried out in the US, and Europe. They are also being developed and tested in South Korea. In South Korea the first of all ACM short-span bridge superstructure was installed on a public highway system in May 2002. Since these composite materials are new to bridge applications, reliable data is not available for their in-service performance. This paper describes in-service performance assessments of all ACM bridge superstructures. To investigate its in-service performance, field load testing and visual inspections were conducted under an actual service environment. The paper includes the presentation and discussion for the ACM bridge capacity rating based on the stress modification coefficients obtained from the test results. The test result indicates that the ACM bridge superstructure has no structural problems and is structurally performing well in-service as expected. The results may provide a baseline data for future field ACM bridge capacity rating assessments and also serve as part of a long-term performance of ACM bridge superstructure.

FEM modeling method of damage structures for structural damage detection

Many current methods on structural damage identification such as GA algorithms and neural networks technology are often implemented based on a few measured data and a large number of simulation data from structural vibration responses. Therefore, to establish an accurate and efficient dynamics model for a structure with different damage is an important precondition, so that plentiful simulation data of structural vibration response can be acquired using the dynamics model of the structure with damage. There are two problems when directly meshing small structural damage in FEM modeling, i.e., excessive gridding number and unavoidable errors from differently meshing for the same damaged structure. In order to solve these two problems, this paper presents an improved modeling method based on modifying element stiffness matrix at structural damage position using a modification coefficient. The first step of this improved modeling method is to determine modification coefficient of element stiffness matrix based on the coherence of natural frequencies for two kinds of models, and the second step is to verify the coherence of the frequency-response functions. This study also introduces algorithm and calculating results of damaged element stiffness matrix. Influence of structural damage position and constraint conditions on the modification coefficient for small structural damage are also discussed.

Dimensional Variation Analysis and Synthesis for Composite Components and Assemblies

Abstract This paper presents a study on dimensional variations and tolerance analysis and synthesis for polymer matrix fiber-reinforced composite components and assemblies. A composite component dimensional variation model was developed with process simulation based on thermal stress analysis and finite element analysis (FEA). Using the FEA-based dimensional variation model, the deformations of typical composite structures were studied and the regression-based dimensional variation models were developed. The regression-based dimensional variation models can significantly reduce computation time and provide a quick design guide for composite products with reduced dimensional variations. By introducing a material modification coefficient, the comprehensive regression models can handle various fiber and resin types and stacking sequences, which eliminates the complicated, time-consuming finite element meshing and material parameter defining process. A structural tree method (STM) was developed for rapid computation of composite assembly dimensional variations resulting from deformations on individual components, as well as the deformation of composite components with complex shapes. With the STM and the regression-based dimensional variation models, rapid design optimization was conducted to reduce the dimensional variations of composite assemblies. Cost-tolerance functions were developed using a fuzzy multiattribute utility theory based cost-estimation method. Based on the developed dimensional variation and cost-tolerance models, composite assembly tolerance analysis and synthesis were performed in this study. The exploring research work presented in this paper provides a foundation for developing practical and proactive dimensional control techniques for composite products.

Avermectins inhibit multidrug resistance of tumor cells

The modification of the sensitivity of Hep-2 and P388 tumor cells to taxol and vincristine, substrates of multidrug resistance proteins, by naturally occurring avermectins and the effect of avermectins on the accumulation of calcein in cells and the efflux of rhodamine 123 were studied. While avermectins did not affect the sensitivity of tumor cells to hydrogen peroxide and cisplatin, they significantly enhanced the sensitivity of cells of both wild-type and resistant strains to taxol and vincristine. The coefficients of modification for resistant strains were substantially higher. Avermectins suppressed the efflux of rhodamine 123 from cells and increased the accumulation of calcein in cells. The relative inhibitory activity of avermectins depended on the cell type and on the substrate of multidrug resistance proteins whose transport they suppressed (vincristine, taxol, rhodamine 123, calcein acetoxymethyl ester). The least active was avermectin B 1 or ivermectin; the most active avermectins varied depending on the substrate and the cell type. In the case of vincristine transport, the most active avermectin was almost by one order of magnitude more effective than the traditional inhibitor of multidrug resistance cyclosporin A. This property of avermectins can be used in tumor therapy by combining application of avermectins with antitumor preparations, the substrates of multidrug resistance proteins.

Assembly dimensional variation modelling and optimization for the resin transfer moulding process

The increasing demand for composite products to be affordable, net-shaped and efficiently assembled makes tight dimensional tolerance critical. Due to lack of accurate process models, resin transfer moulding (RTM) dimensional analysis and control are often performed using trial-and-error approaches based on engineers' experiences or previous production data. Such approaches are limited to specific geometries and materials and often fail to achieve the required dimensional accuracy in the final products. This paper presents an innovative study on the dimensional variation prediction and control for fibre reinforced polymeric matrix composites. A dimensional variation model was developed for process simulation based on thermal stress analysis and finite element analysis (FEA). This model was validated against experimental data, analytical solutions and data from the literature. Using the FEA-based dimensional variation model, the deformations of typical composite structures were studied, and a regression-based dimensional variation model was developed. By introducing the material modification coefficient, this comprehensive model can account for various fibre/resin types and stacking sequences. The regression-based dimensional variation model can significantly reduce computation time by eliminating the complicated, time-consuming finite element meshing and material parameter defining process and providing a quick design guide for composite products with reduced dimensional variations. The structural tree method (STM) is proposed to compute the assembly deformation from the deformations of individual components as well as the deformation of general shape composite components. The STM enables rapid dimensional variation analysis/synthesis for complex composite assemblies when used along with the regression-based dimensional variation model. The work presented here provides a foundation to develop practical dimensional control techniques for composite products.

Dimension variation prediction for composites with finite element analysis and regression modeling

This paper presents a new method for efficient prediction of dimension variations of polymer matrix fiber reinforced composites. A dimension variation model was developed based on thermal stress prediction with finite element analysis (FEA). This model was validated against experimental data, analytical solutions and the data from literature. Using the FEA-based dimension variation model, deformations of typical composite structures were studied and regression-based dimension variation models were developed. By introducing the material modification coefficient, this comprehensive model can account for various fiber/resin types and stacking sequences. The regression-based dimension variation model can significantly reduce computation time by eliminating the complicated, time-consuming finite element meshing, material parameter defining and evaluation solving process, which provides a quick design guide for composite products with reduced dimension variations. The structural tree method (STM) was developed to compute the assembly dimension variation from the deformations of individual components, as well as the deformation of general shape composite components. The STM enables rapid dimension variation analysis/synthesis for complex composite assemblies with the regression-based dimension variation models. The exploring work presented in this research provides a foundation to develop practical and proactive dimension control techniques for composite products.

The Adoption, Transformation and Institutionalization of the Kaso Concept and Local Allocation Tax

Today, has gained a prominent position as a popular policy concept for less favored problems in the rural areas of Japan. At the same time, many commentators have criticized the concept for its inadequacy as an academic term thus far. Nevertheless, the reason why gained such popularity in both central and local governments so quickly or why a area come to be operationally defined by the municipal depopulation rate has rarely been discussed. The purpose of this paper is to present a thesis that addresses these questions from the viewpoint of local public finance problems, focusing especially on local allocation taxes, a Japanese fiscal equalization scheme.Kaso emerged as an appealing catchphrase to describe rural social problems in the mid 1960s. This term is the opposite of kamitsu which represents the overpopulation problems experienced in metropolitan areas. The opportunity for this term's gaining popularity came after the release of the 1965 census data, which clarified the quantitative realities of depopulation in peripheral areas.Previous studies argued that the release of census data had a strong impact on the populace in regard to the severity of the depopulation problem and this led to the quick permeation of this term. The author believes this to be partly true but thinks that it is insufficient to explain the outcomes. It is argued that this situation has had the most significant impact on national and local government officers since the announcement of the latest census results requires the renewal of statistics used for the fiscal demand calculation of local allocation taxes. According to an estimation using a weighted regression model, given an unchanged local allocation tax system and assuming price constancy, about one third of municipalities with less than 5, 000 inhabitants were anticipated to face more than a 10% decrease of standard fiscal demand. This figure represents the amount of resources ensured by the local allocation tax for each local government as an operationally calculated cost for executing standard administrative activities.This dysfunction of the fiscal equation scheme in severely depopulated municipalities is thought to be the most important factor for the permeation of into central and local governments. The central government quickly established a depopulation modification coefficient (jinkou kyugen hosei) in standard fiscal demand calculations in 1966. In addition, Shimane Prefecture, an area facing this problem, started to develop a Special Area Act for the national government in cooperation with the Prefectures concerned.At the beginning, the area name in the proposed Act is known as a severe depopulation area, not a Kaso area because depopulation is directly connected with the local allocation tax problem. However, the national government started to stress the solving of regional disparities and responded by shifting target areas in resource allocation from metropolitan areas and industrial districts to peripheral areas after the mid 1960s. Following this shift, the Special Area Act movement sought not only to maintain the status quo but also to make the rest of the country catch up, and changed the area name to for its popularity and comprehensiveness.In this change, an operational definition of a area had to be defined. Considering that the starting point of this movement exists in a dysfunctional problem of local allocation tax, it seemed natural to define a area in the proposed Act using the municipal depopulation rate. Finally, the Emergency Area Revitalization Act, which designates its target area by the municipal depopulation rate, came into effect as a members' bill in 1970.

Determination of bearing capacity of shallow foundations without using superposition approximation

The Terzaghi superposition assumption has been widely used to determine the bearing capacity of shallow footings. Although this assumption always errs on the safe side, a rigorous procedure to calculate the bearing capacity is still of engineering value. This paper presents such a procedure that is free from errors as a result of the superposition assumption. It demonstrates that the ultimate bearing capacity can be precisely expressed by the Terzaghi equation, except that the bearing capacity factor Nγis dependent upon the surcharge ratio. A recently developed numerical method, i.e., the critical slip field method, is used to calculate the modification coefficient for modifying Nγ. It is found that this modification coefficient increases with the surcharge ratio at small values of surcharge ratio and then remains constant for large values of surcharge ratio. However, the errors invoked by the superposition assumption do not exceed 10%. On the basis of numerical calculations, a simple closed-form expression of the modification coefficient is proposed that yields the theoretically rigorous ultimate bearing capacity. In the later part of the paper, errors in bearing capacity calculations owing to the use of conventional procedures are analyzed. It is concluded that the continued use of conventional procedures is justified, but the inherent errors should not be neglected in assessing the performance of shallow foundations.Key words: shallow foundation, strip footing, ultimate bearing capacity, critical slip field.

Experimental measurements of the flow resistance and inductance of inertance tubes at high acoustic amplitudes

We measured the flow resistance and flow inductance of inertance tubes at high acoustic amplitudes for four different inner diameters of 0.6, 1.0, 1.5 and 2.0 mm at various tube length ranging from 100 to 1500 mm, at frequencies of 30, 40, 50, 60 and 70 Hz. The experiments were carried out under system mean pressure of 20 bar at room temperature. The experimental data were compared with the explicit solution to the linear momentum equation for small acoustic amplitudes and were fitted with the modification coefficients in terms of the operating frequency and Reynolds numbers characterized by the amplitude of gas velocities.

An efficient method for determining the critical modification coefficient for cylindrical worm gearing in which the worm is generated by a curve

An efficient method for determining the critical modification coefficient for cylindrical worm gearing in which the worm is generated by a curve

An efficient method for determining the critical modification coefficient for cylindrical worm gearing in which the worm is generated by a curve

This paper proposes an efficient method for the determination of the critical modification coefficient (CMC) for the cylindrical worm gearing in which the worm is generated by a curve. The term CMC is defined as the modification coefficient that causes the first boundary points to be just on the boundary of the area of meshing. Solved from a system of five non-linear equations, the CMC not only avoids gear undercutting, but also produces the maximum contact ratio. In developing the system equations, the equation of non-undercutting is derived directly from the curvature information of the generating curve and the parameters of relative motion, without the need to derive any partial derivatives to the equation of the generating surface. By using an equivalent generation mechanism rather than the real one, an explicit form of equation of meshing is created. The equation of meshing created can simplify the form of the equation of non-undercutting, reduce the number of non-linear equations and unknowns in the system equations, increase the speed of convergence and decrease numerical instability. Based on the proposed method, a computer program is created and applied to analyse the CMCs of four commonly used worm gearings: ZA, ZN, ZE and ZC3.

Analytical geometry of straight conical involute gears

Although conical involute gears are frequently used in anti-backlash schemes, no detailed mathematical geometry description of conical involute gear teeth hitherto exists. In this paper we derive the parametric equations for a straight conical involute gear tooth surface and its offset surface. These formulas are then used to create a finite element (FE) model with a specific surface layer. Such a surface layer enables meshing control or modelling of surface properties such as case hardening and surface roughness. In addition, we derive an expression for the minimum value of the inner transverse addendum modification coefficient that avoids undercutting of the whole gear tooth.

Determination of the critical modification coefficient for a cylindrical worm gear drive with the worm generated by a surface of revolution

This paper presents a general method to determine the critical modification coefficient (CMC) for a cylindrical worm gear drive with the worm generated by a surface of revolution. Unlike the existing methods for the determination of the first boundary points, to avoid tedious partial derivatives the curvature information of generating surface and relative motion parameters is directly applied to the worm and the concept of equivalent generation is applied to obtain an explicit form of the equation of meshing; thus it is a very efficient way to determine the first boundary points on the worm gear tooth surface. By solving a system of non-linear equations, the CMC can be obtained and the gear undercutting can be avoided. On the basis of the proposed method, a computer program is created and applied to four commonly used worm gear drives: ZK1, ZK2, F-I and F-II.

創成運動修正機構によるハイポイドギヤの歯面修整に関する研究

This paper analyzes the adjustment of generating motion for hypoid gear with a modified roll, and investigates the effect of this roll on the adjusting result of this gear cutting by tooth contact analysis. By controlling the offset value and the third-order modification coefficient of this roll, the changes in the transmission errors and the bias-in of contact patterns can be adjusted from the toe to heel of tooth surface. If changing its second-order modification coefficient, the maximum of the transmission errors and the H value of V/H can be regulated obviously. In the tooth contact analysis, the instantaneous ellipses of tooth contact are simulated besides that the transmission errors and V/H value are determined. Moreover, the program for drawing the transmission error curve and the contact patterns has been developed. As a result, the detailed state of tooth contact can be demonstrated more clearly.

Some Characteristics of Production of Vidlon Polycaproamide Profiled Twists

The degree of modification of profiled PCA twists is most dependent on the spinneret draw ratio. The modification coefficient of profiled PCA twists approaches the coefficient of the spinnerets used when the molecular weight of the polycaproamide and number of holes in the spinneret increase.

RC系1質点モデルに対する応答制御法の多層構造物への展開

It is very important for performance based design to control the response displacement of the structures for input earthquakes. The previous reports proposed the response displacement control method of S. D. O. F RC structures by changing member sections. This report verified the applicability of previous response control method to multi-story structures. For the verification models, the stiffness and strength of the modified model could be estimated accurately. For the member section modification coefficient, the average of estimation ratio was 1.0 and the standard deviation was 0.1. It was confirmed the previous response control method was effective tool for the multi-story structure.

Centrifugal Lubrication of Spur Gears. 2nd Report, Influence of Cooling Hole on Tooth Fillet Stress.

We have recently proposed a new centrifugal lubrication method in which oil is injected through a hole drilled on the tooth crest of a spur gear. To adapt the method for wide face width spur gears, we set up a cooling hole parallel to the tooth trace on the center line of the tooth profile. The results of numerical analyses have been demonstrated that the recommended setting position of the hole is that where the hole inscribes to the root circle on the center line of the tooth profile; the addendum modification coefficient and rim thickness of the gear should be not less than zero and be not less than five times the module respectively. In such a spur gear, an increase in maximum tensile root fillet stress on the active flank side due to the hole of one module in diameter is less than 10% of the stress of the gear with no hole.