Improved Design Method Research Articles

Local buckling behaviour and design of profiled sandwich panels

Fully profiled sandwich panels are commonly used in building structures, but are susceptible to local buckling failures. Current European design standard recommends the use of a modified effective width approach to include such local buckling effects in the design. Recent research has shown that this design method predicts unconservative strengths for panels with slender plates (high b/t ratios). The use of sandwich panels with high b/t ratios is very common in practice due to the increasing use of thinner and high strength steel plates. Therefore, a research project was conducted to investigate the local buckling behaviour of foam supported steel plate elements as used in fully profiled sandwich panels with a large range ofb/t ratios (50 to 500) using experiments and finite element analyses (FEA). Both experimental and FEA results revealed the inadequacy of the current design rule for sandwich panels with slender plate elements. An improved design method was therefore developed based on the large amount of data obtained from validated FEA studies. Finally full-scale tests of fully profiled sandwich panels were undertaken to confirm the accuracy of the new design method. This paper presents an overview of these experimental and finite element analysis studies and design rule development followed by the results of the full-scale tests.

Structure variations of pumpkin balloon

A lobed pumpkin balloon by 3-D gore design concept is recognized as a basic form for a super-pressure balloon. This paper deals with extensions of this design concept for other large pressurized membrane structures, such as a stratospheric airship and a balloon of which volume is controllable. The structural modifications are performed by means of additional ropes, belts or a strut. When the original pumpkin shape is modified by these systems, the superior characteristics of the 3-D gore design, incorporating large bulges with a small local radius and unidirectional film tension, should be maintained. Improved design methods which are adequate for the above subjects will be discussed in detail. Application for ground structures are also mentioned.

Controller Design Method for Robustness Improvement of Power-Assist Control

Power-assist system technology and its applications to manufacturing systems, constructing systems, rehabilitation and welfare services have attracted special interest recently. For example, automobile assembly processes utilizing power-assist systems exist. However, the effect of such uncertainties as Coulomb friction on the power-assist systems has not been fully addressed. This study proposes a controller design method for the robustness improvement of power-assist control. Especially, we pay attention to the influence of uncertain Coulomb friction and design the servo control system consisting of two parts. The first part is an on-line impedance control simulator which works as the reference generator. The other one is a sliding mode controller to suppress the errors between the references and corresponding responses. By applying the method to the positioning problem of a cart, the effectiveness of the method is verified by experiments.

A design method for improvement of λg/4 coupled‐line narrow bandpass filter response

AbstractThis paper discusses various changes made in classical coupled‐line narrow bandpass filters to somehow improve frequency response. First, the resonator's strip width was broadened to improve the lines' unloaded Q factor. Second, the in/out coupled‐line sections were replaced by tapped‐line feeding. Finally, a transmission zero was added via a geometrical modification that favors nonadjacent resonator coupling. The theoretical and experimental results obtained with these microstrip filters are compared. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 121–125, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11145

Superconductors and cryotechnology for space communications

In commercial satellite applications, superconductive devices offer the advantage of a reduction in mass and volume, combined with improved high-frequency performance. The Bosch space experiment clearly demonstrates these benefits, and it also shows the applicability of the technology with respect to space qualification procedure. Furthermore, this article describes improved design methods for planar superconducting filters, combining high Q-values with complex designs.

Microirrigation Submain Unit with Pressure Reducing Pipes

A pressure reducing pipe (PRP), used at the inlet of a lateral in microirrigation systems to improve water application uniformity, is developed. It is composed of an internal spiral and a sleeve pipe and is made of molded polyethylene plastic. It functions to dissipate a pressure head that exceeds the required pressure head of a lateral inlet by directing water flow through the spiral grooved path and creating a certain head loss. An improved design method for submain units using the pressure reducing pipes is based on the hydraulics of the submain unit and the characteristics of the head loss in the PRP. The effects of the PRP on water application uniformity in a submain unit are analyzed by computer simulation. The submain unit with the PRP has higher uniformity than that of the commonly used method. After choosing the PRP, the permissible range of pressure variation in a submain will not need to be considered for the submain length in a layout.

Improved design method for optimum gain pyramidal horns

A technique, simple and easy to use, is presented to design the optimum gain pyramidal horn. The optimum gain pyramidal horn design equation available in the literature is improved. Design parameters are computed from the simple and explicit analytical formulas. The pyramidal horn gain is determined with no path length error approximation. Several design examples are given to show the performance of the improved design technique. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 188–193, 2001.

QFT design for uncertain non-minimum phase and unstable plants revisited

Design method for uncertain non-minimum phase and unstable plants in the quantitative feedback theory (QFT) developed by Horowitz and Sidi is revisited in this paper. It is illustrated that the existing method may not work since some design rules have not been clearly specified by several examples including non-minimum phase plants and unstable plants. Then stability of a new nominal plant is carefully examined and analysed, and an improved design method is presented. The result in this paper provides mathematical justification of the QFT design procedure for nonminimum phase and unstable plants in Horowitz and Sidi (1978) and Horowitz (1992).

Design of interference fits via finite element method

Studies of interference fits in ring gear-wheel connections show that the traditional design method based on thick-wall cylinder theory has some limitations. Application of the finite element method (FEM) for the three-dimensional stress analysis of interference fitted connections gives more complete and accurate results than the traditional method. An improved design method utilizes two safety factors, λ s and λ p , providing a new approach for evaluating the quality of interference fits. A tolerancing method utilizing the I max and I min curves provides a quantitative guideline for interference fit design. The selective assembly method combined with the FEM-based method for interference fit design provides an effective approach to achieve more reliable interference-fitted connections and more precise assembly with lower manufacturing cost.

Digital Terrain Modelling of Drainage Channel Erosion

Drainage channels constructed on highly erodible soils in some areas of Southern Navarre during 1988 have undergone severe erosion, including bed and bank degradation. This erosion triggered lateral gully development that affected adjacent cultivated fields. These processes are similar to those observed in permanent gullies in the area. One severely eroded channel representative of the area was selected for further examination. The amount of erosion was determined by comparing the initial size of the drainage channel with its present condition using digital terrain models and a terrain representation system. Results show that average soil losses along the eroded reach are 3·62 m3/m, highlighting the necessity of using improved design methods. Current simulation models can aid in determining such design criteria. If drainage channels are to be constructed in areas of highly erodible soils, they should be shorter and restricted to the lower regions of the watersheds with gentler slopes. Sudden changes in bed slope should be avoided, and adequate erosion control techniques within the channel should be considered. The measurement method used provides detailed information on channel erosion processes with a reasonable effort.

Improved design method for acousto-optic light deflectors

The purpose of this work is to find a reliable approach for one- and two-dimensional acousto-optic deflector design. The design method is based on an improved theoretical model of anisotropic acousto-optic interaction. The new feature of this model is the application of new approximations together with the inclusion of effects that were previously neglected, such as optical beam divergence, second order diffraction and optical activity. Configurations for maximum efficiency and maximum resolution are shown. Optimization of the two-dimensional deflector design is presented. The reliability of the model is demonstrated at wavelengths of 633 and 1064 nm through experimental results with devices designed based on the new model for TeO 2 deflectors.

Accelerated life testing and thermomechanical simulation in power electronic device development

Product development in the power electronic industry is characterized by the short time-to-market and high-reliability requirements. Improved design methods and advanced modelling techniques are therefore required to support package design selection and to arrive at lifetime prediction algorithms for failure prevention. In this work, experimental and computational activities aimed at supporting the development of a press-pack insulated gate bipolar transistor (IGBT) is reported. A testing rig for accelerated testing of single IGBT chips under controlled contact pressure conditions is presented. Then, thermomechanical simulations of accelerated tests by the finite element method provided stress-strain evolution in the device and insight into the sources of local degradation.

Design for optimum gasket assembly stress and leak rate control in bolted gasketed joints

The behavioural factors affecting the design of a bolted gasketed joint for a prescribed leak rate are described. The traditional approach is now known to be ill founded while the proposed alternative has disadvantages. These approaches are outlined and their problems described. An improved design method is presented, on the basis of a design chart. In this the optimum gasket assembly stress to achieve a given level of leak tightness is plotted against the known gasket stress change as the fluid pressure is applied, giving curves for a series of leak-tightness values. The design chart can be derived graphically from a Pressure Vessel Research Council (PVRC) ‘ROTT’ test-data plot or by calculation from the PVRC gasket coefficients Gb, a and Gs; the procedures are described. The approach presented has the advantages of simplicity and accuracy. Examples of the new design chart are given for ten types of gasket and the effects of varying individual PVRC gasket coefficients are demonstrated.

Problem of monitoring the reliability and safety of operating water-development works

1. The monitoring of the condition of water-development works, which is carried out using field observations and investigations will make it possible not only to evaluate the condition of the structures in various stages of construction and service, but also to verify the correctness of the design solutions adopted with respect to the layout of the structures, their construction, and the building technology employed. As practice has demonstrated, design solutions do not always correspond to requirements set forth for the operational reliability of the structures. 2. Results of multiyear field observations and investigations have contributed to improvement of design methods and found reflection in corresponding regulatory-methodical literature. At the same time, there has, up to now, not even been a sufficiently developed procedure with which to determine criteria of the reliable and safe operation of structures. The establishment of these criteria and determination of limiting allowable values of the parameters being monitored should be carried out with allowance for both standard computational requirements, and results of multiyear field observations on the structure. 3. Results of revision to operational-monitoring systems, which can be conducted during scheduled inspections of water-development works, suggest that in the majority of cases, the effectiveness of these systems is inadequate. Unsatisfactory representativeness of field data and a lack of indicators of the condition of the entity being monitored, which are substantiated by proper means—monitoring criteria—are usually basic causes of inadequate effectiveness of operational-monitoring systems. 4. Inadequate representativeness of field data can be explained by both errors in the design of the monitoring system at a given entity, and defects in its implementation, and also by exposure of new monitoring problems during operation, which could not be predicted in the stage of design formulation. That situation where in many cases, the design of monitoring systems is oriented toward the need to confirm only the results of calculations performed under field conditions, and not the models adopted for these calculations also frequently contributes to a reduction in the representativeness of the field data. Support of adequate representativeness of field data where the structure has been in service for an extended time and especially in those cases when the entity was not equipped with embedded monitoring-measuring apparatus that could be restored after failing is a difficult, but very urgent problem,

Seismic and vibration mitigation for the A-type offshore template platform system

In this study an improved design method for the traditional A-type(or V-type) offshore template platform system was proposed to mitigate the vibration induced by the marine environmental loadings and the strong ground motions of earthquakes. A newly developed material model was combined into the structural system and then a nonlinear dynamic analysis in the time domain was carried out. The analysis was focused on the displacement and rotation induced by the input wave forces and ground motions, and the mitigation effect for these responses was evaluated when the viscoelastic damping devices were applied. The wave forces exerted on the offshore structures are based on Stokes fifth-order wave theory and Morison equation for small body. A step by step integration method was modified and used in the nonlinear analysis. It was found that the new design approach enhanced with viscoelastic dampers was efficient on the vibration mitigation for the structural system subjected to both the wave motion and the strong ground motion.

Dispersion control over 150 THz with chirped dielectric mirrors

Ultrabroad-band chirped multilayer dielectric mirrors providing nearly constant negative group delay dispersion over the wavelength range of 640-950 nm and high reflectance between 590 and 970 nm are demonstrated. A key to this performance has been an improved design method, which also substantially reduces the computing time needed for ultimate optimization. The presented devices constitute an enabling technology for producing high-quality terawatt pulses in the sub-10-fs regime. The generation of 5-fs 0.1-TW pulses by using exclusively these mirrors as negative delay line demonstrates this potential.

Predictability of high‐performance spindles using a complete thermo‐elastohydrodynamic lubrication (TEHD) solution

AbstractSpindles experience problems related to increased power and velocity, and can have very high power consumption. The work reported here is aimed at improving design methods for high‐performance spindles and machine‐tool bearings, and is aimed at determining the influence, of the oil quantity supplying the contact, on power consumption and on contact temperature. A finite element program, TACT, can efficiently predict power loss and the thermal state of machine‐tool bearings, and the remaining unknown in these thermo‐piezo‐viscous‐elastic (TPVE) calculations is inlet oil film height. The authors address this problem and, within the context of this work, develop a high‐speed ISO 50 spindle which has a thin‐wall bearing housing, and is ‚thermally tuned‚, so avoiding thermal instability, while the preload stays constant. Its experimentally determined power consumption values agree well with the TPVE prediction for an assumed inlet film height of 0.5 μm.

Comments on corrections to "An improved design method of Rotman lens antennas"

For original paper by Katagi, Mano, and Sato see ibid., vol.32, no.5, p.524 (1984). Corrections to this paper were suggested by Leonakis (see ibid., vol.34, no.8, p.1067, 1986) and by Singhal and Sharma (see ibid., vol.42, no.7, p.1037, 1994). Katagi et al. here comment on the corrections to their paper. Singhal and Sharma reply to the comments. >

フレデリック・ロゥ・オームステッドとヘンリー・ボブソン・リチャードソンの協働

Landscape architect F. L. Olmsted and architect H. H. Richardson collaborated on a number of schemes through 1860s into 1880s. The present paper pointed out thus attributed projects to the number of twenty three, as shown in Figure 1, and identified respective role in ten major conjoint works. Olmsted acted as an environmental mentor to Richardson, and led this most congenial architectural collaborator to cultivate the following framework of his professional career. 1) Pursuit for distinct architectural forms, corresponding to then uprising social forces - commercial core and outlining rural zones, 2) Search for the geological imagery, expressive of an American identity, and 3) Improvement of design methods in the use of bold rockwork. The resulting creative integration of two different design practices is to be ascribed to their mutual notion of effect of organic expression, which derived from the Picturesque tradition, and of a new art form or natural architecture based upon strictly American sources of inspiration ・ the land, as well as recognition of the new social environment.

Draught risk from cold vertical surfaces

Cold, natural convective flows from glazed facades are in winter time often the cause of thermal discomfort and there is a need for research to improve design methods. The objective of the research is to develop expressions for the air flow beyond the floor area, which influences the thermal comfort in the occupied zone. Expressions for the rate of decrement of the maximum velocity with distance from the surface and for the maximum temperature difference between the cold air flow along the floor and the rest of the occupied zone have been developed. The percentage of dissatisfied persons in the occupied zone, due to cold downdraught from a vertical surface, has been estimated.