bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemically Activated Carbons from Olive Stones — Peculiarities of Pore Structure and Interpretation of Nitrogen Adsorption Data
Authors: Hourieh M.A. , Alaya M.N. , El-Sejariah F. , Youssef A.M.
Published: October 2002

Chemically activated carbons were obtained from olive stones either by carbonization with H3PO4 at 300–600°C or by carbonization with ZnCl2 at 600°C. Nitrogen adsorption at 77 K was determined for all the activated carbons. The adsorption data were interpreted by considering some conventional adsorption models.

Maximum activation with H3PO4 occurred at 450°C. However, the adsorption capacities of the ZnCl2-activated carbons were far higher than those of carbons activated with H3PO4. Carbons activated with H3PO4 or ZnCl2 are mainly microporous with the non-micropores representing a small fraction of the total porosity. Although, the nitrogen isotherms are Langmuirian in shape, application of the Langmuir equation led to large monolayer capacities of uncertain confidence. The surface areas and micropore volumes determined by the application of the t-method of de Boer and the αS-method of Sing were comparable and were slightly higher than those determined by the application of the DR model based on micropore filling. The t-method and the αS-method are complementary to each other and would seem to give confident values because they are based on standard reference non-porous materials. The micropore region may be sub-divided into two sub-regions distinguished by the different filling mechanisms involved.
Characterization and Catalytic Activity of Cr2O3–Al2O3/AlPO4 Catalysts
Authors: Ahmed Farid Sh. , Mostafa Mohamed R. , Kiwan Hala H.
Published: October 2002

Five samples of Al2O3/AlPO4 (Al/P = 1.75) and Cr2O3-loaded Al2O3/AlPO4 (wt% Cr2O3 = 5–25) were prepared. The catalysts were obtained by thermal treatment of the corresponding samples in air at 823 K and were characterized using XRD and DTA techniques. The textural properties (surface area, total pore volume and mean pore radius) were determined from nitrogen adsorption data obtained at 77 K. The acidic properties of all the samples were measured calorimetrically. The catalytic conversion of isopropanol was studied using a microcatalytic pulse technique. No spinel structure was detected by both XRD and DTA techniques and only Cr2O3 was detected for samples containing ≥ 15 wt% chromia. Loading Al2O3/AlPO4 with Cr2O3 led to significant changes in the texture, surface acidity and catalytic activity of the prepared catalysts. Al2O3/AlPO4 catalysts exhibit no dehydrogenation activity, whereas loading with Cr2O3 favoured the dehydrogenation of isopropanol to acetone.
Studies of the Adsorption Thermodynamics of Oxamyl on Fly Ash
Authors: Singh Dhirendra
Published: October 2002

The adsorption thermodynamics of oxamyl on fly ash at 10°C, 25°C and 50°C have been studied via the relevant adsorption isotherms, Freundlich constants (KF and 1/n), distribution coefficient (Kd) and other thermodynamic parameters. The data were well fitted by the Freundlich equation (r2 > 0.98) and yielded S-shaped isotherms at all the temperatures studied. Thermodynamic parameters such as the thermodynamic equilibrium constant (K0), the standard free energy change (ΔG0), the standard enthalpy change (ΔH0) and the standard entropy change (ΔS0) have been calculated as a means of predicting the nature of the adsorption process.
Adsorption of CCl4 from Aqueous Solution on Activated Carbons
Authors: Milchert Eugeniusz , Goc Waldemar , Pelech Robert
Published: October 2002

Investigations of the adsorptivity of selected activated carbons towards aqueous solutions of carbon tetrachloride have been undertaken. The times necessary to achieve adsorption equilibrium and the course of the adsorption isotherms were determined. The isotherms may be described by the Freundlich, Langmuir or Freundlich–Langmuir equations. The adsorptivities and basic parameters for the dynamic adsorption of carbon tetrachloride on DTO activated carbon were calculated.
Physicochemical and Catalytic Properties of Vanadia/Titania Catalysts. I. Structural Properties
Authors: El-Nabarawy Th. , Youssef A.M. , Ahmed S.A. Sayed
Published: October 2002

Titania gels Ta and Tb were precipitated from TiCl4 at pH 3.0 and 9.0, respectively, using ammonia solution. Calcination products were obtained by the thermal treatment of the gels at 300, 400, 600, 750 and 1000°C, respectively. Thermal analysis, X-ray diffraction and FT-IR spectroscopy demonstrated that the anatase → rutile transformation commenced when Ta was calcined at 400°C, with the rutile form predominating when calcination was conducted at 600°C. Calcination at 750°C or 1000°C was associated with complete anatase → rutile conversion. The calcination product of Tb at 400°C was pure anatase, transformation to rutile taking place above this temperature and predominating at 600°C. Rutile was the sole phase present when Tb was calcined at 750°C.

Vanadia/titania catalysts were obtained by impregnating Ta and Tb with an aqueous solution of NH4VO4 of concentration sufficient to obtain samples containing 4.0, 6.0, 8.0 or 12.0 wt% V2O5. The calcination products at 400°C and 600°C were characterized by thermal analysis, X-ray diffraction, FT-IR spectroscopy, electronic spectral analysis and magnetic susceptibility measurements. The presence of vanadium enhanced the anatase → rutile transformation. The measured X-ray diffraction lines and FT-IR peaks indicated the existence of vanadium as a separate oxide, mainly V2O5. However, the electronic spectra and magnetic susceptibility measurements predicted the possible existence of a V4+ species.
Surface and Catalytic Properties of the Co3O4/MgO System Doped with Fe2O3
Authors: El-Shobaky H.G. , Shaheen W.M. , Mokhtar M.
Published: October 2002

The surface and catalytic properties of pure and Fe2O3-doped Co3O4/MgO solids were investigated. The extent of loading was maintained at 38 wt% Co3O4 and the amount of dopant varied between 1.2 wt% and 11.0 wt% Fe2O3. The pure and doped solids were prepared by calcination at 400–1000°C of pure and ferric nitrate-treated magnesium carbonate impregnated with cobalt nitrate solution. The samples thus obtained were examined by TG, DTA and XRD methods, nitrogen adsorption studies at −196°C and the catalysis of H2O2 decomposition at 30–50°C.

The results revealed that Fe2O3 treatment of the Co3O4/MgO system followed by calcination at 400°C resulted in an increase in the particle size of the Co3O4 and MgO phases, whilst the opposite effect was observed when the doped solids were calcined at 600°C. Doping of the Co3O4/MgO system followed by calcination at 400°C effected a measurable decrease in its BET surface area with the reverse effect being observed upon heating at 600°C. An increase in the calcination temperature of pure Co3O4/MgO up to 800°C brought about an abrupt decrease in the intensity of all the diffraction lines associated with the Co3O4 phase. These disappeared completely upon heating the system at 900°C or 1000°C due to dissolution of the cobalt oxide in the MgO lattice to form a solid solution.

A cobalt ferrite phase was detected in the variously doped solids calcined at 800–1000°C even when the initial solids had been treated with 2.4 wt% Fe2O3. This finding suggests that most of the ferrite phase produced was contained in the outermost surface layers of the treated samples.

Treatment of the investigated system with Fe2O3 followed by calcination at 400°C and 800°C led to a progressive decrease in the catalytic activity of the resulting solid due to an increase in the particle size (a decrease in the degree of dispersion) of the catalytically-activeconstituent, i.e. the Co3O4 phase, and due to the conversion of Co3O4 into a CoFe2O4 phase, respectively. In contrast, doping followed by calcination at 600°C led to an increase in the catalytic activity of the resulting solid due to an effective decrease in the particle size of the Co3O4 phase. Calcination of the Fe2O3-doped system at 400–800°C did not modify the mechanism of the catalyzed reaction but changed the concentration of active sites without changing their energetic nature.
Integrated Design System for Lattice Domes
Authors: Lin Suchada P. , Albermani F.
Published: October 2002

In structural design, the preliminary synthesis stage derives judgmental knowledge from engineering heuristic and experience which are usually expressed in symbolic form. On the other hand, detailed design involves extensive numerical processing. An integrated computer-aided design system should be able to handle both symbolic and numerical processings. It must also be able to integrate engineering databases and CAD packages within a single environment. The knowledge-based system approach provides a venue for achieving all these requirements. This paper presents a prototype knowledge-based system for lattice design that can perform several essential tasks including preliminary synthesis, numerical model generation, nonlinear finite element analysis, code compliance checking and member sizing. The system user is guided throughout the design session by interactive graphical user interfaces which facilitate the design process.
Nexorades
Authors: Baverel O. , Nooshin H. , Kuroiwa Y. , Parke G. A. R.
Published: October 2002

The objective of this paper is to discuss the characteristics of a family of space structures that are referred to as ‘nexorades’. Typically, a nexorade is constructed from scaffolding tubes, connected together with swivel couplers. An important application of nexorades is for shelters of various sizes and shapes for temporary or permanent purposes. In such a shelter, the structural skeleton is provided by a nexorade and the cover is provided by a membrane material.
Shape Formation of Some Dome-Like Space Trusses
Authors: Schmidt Lewis C. , Selby Steven
Published: October 2002

This paper presents some results of shaping or forming of dome-like structures comprised of space truss members, starting from an initial planar condition, and being developed to a doubly-curved shape or form. A comparison is made between the dome-like shapes formed from alternative simple square-grid chord modules to form space truss shapes. The elements are either planar squares of chords that are allowed to distort in their planes and twist as defined a priori, thereby forming rhombuses. Alternatively, square modules are used with out-of-plane web members. The out-of-plane web members provide additional constraints that force the square elements of chords to distort out of the plane, as well as allowing distortion in the plane. Additionally, this second type of space truss system allows the possibility of forming or shaping a dome-like structure by a post-tensioning process in a self-forming manner form an initial condition that can be flat or planar.
Form Finding Analysis in Consideration of Cutting Patterns of Membrane Structures
Authors: Ishii Kazuo
Published: October 2002

Methods for shape determination analysis and cutting pattern analysis which have been made so far are summarized, and their features/problems are discussed and a new method is shown. This method is a numerical shape finding method satisfying cutting patterns conditions (geodesic line conditions). The co-ordinates of the nodal points of triangular finite elements are controlled during shape determination analysis to satisfy a geodesic line laid inside the strip. By rearranging triangular finite elements from the obtained shape on the plane surface, cutting patterns can be obtained automatically. Some examples for membrane structures are shown and discussed in the paper.
Cutting Pattern of Fabric Membranes with the Stress Composition Method
Authors: Maurin Bernard , Motro Rene
Published: October 2002

Study of fabric membranes emphasises on numerous difficulties which have to be overcome according to the willingness of reducing errors. We meet hence the first step of form-finding which must be achieved such as it ensures the determination of tensile shapes characterised by the lack of compressive areas. Therefore, it implies the knowledge of both the whole geometry and the prestress tensor at each point of the surface. Nevertheless, these considerations may be regarded as theoretical ones since the designer must then focus on the realisation of the membrane, in other words, on the determination the plane fabric strips which once assembled together and placed into position in space with anchorage points define the required configuration. This paper thus describes a new method devoted to the calculation of the strips with the aim of overcoming the drawbacks of the traditional processes. The used mechanical approaches allow to reduce distortions and errors by taking into account the whole geometrical characteristics of the strip, its stress distribution and the material constitutive laws. The theoretical formulation associates the operations of development and reduction and is based upon an iterative numerical procedure which converges to appropriate plane strips where distortions are minimised by least square methods. Several illustrative applications point out the efficiency of the method.
Multiparametered Formfinding Method: Application to Tensegrity Systems
Authors: Vassart N. , Motro R.
Published: October 2002

A method allowing a multiparametered formfinding for prestressed and selfstressed reticulated systems with tensile and compressive members is presented. Known methods, based on geometric analysis and dynamic (dynamic relaxation) considerations have been developed for these systems but they allow generally the evolution of only one parameter. But, in case of shape finding of non-regular new forms or when the sought-after form is subject to a set of geometrical constraints, it becomes obligatory to elaborate a multiparametered form-finding process.

The proposed numerical method, which is described in this paper, exploits the force density method, already used for form finding of pure tensile structures. However, equilibrium matrix of pure tensile structures as cable nets systems, admits always an inverse, which might be false when tensile and compressive members coexist in the system.

In this paper, different processes allowing to define prestressed (or selfstressed) equilibrium geometry are described. Except for the relational structure which is considered as known at the beginning of the process, two sets of form-finding parameters can be identified for this method: prestress (or selfstress) coefficients of members and coordinates or redundant nodes. The proposed method does not yield a unique geometry but it is very convenient for a multiparametered formfinding, and has produced very interesting results, especially for Tensegrity Systems.

Application of this method of multiparametered formfinding to Tensegrity Systems, provides the designer with an efficient way to achieve interesting new selfstressed geometries, such as the generation of double-layer grids by agglomeration of Tensegrity modules.
Design and Construction of 306m Span Hangar Roof at Capital Airport
Authors: Shutun Liu
Published: October 2002

The 306m-span hangar of Capital Airport is one of the largest hangars in the world, with a span of (153 + 153)m. This roof structure includes tripe-layer pyramidal space grid together with bolted and welded long-span steel space truss. This article describes the type of roof structure, design of joints, quality standard and a safe method for welding and lifting the roof of the hangar.
Long Span Space Frame Hangar Roof with Suspended Docking System and Cranes for Heavy Maintenance of 747-400 Aircraft for Air India at Mumbai, India
Authors: Joglekar S. G. , Khanra K. K. , Navani K. P. , Dadlani N. S.
Published: October 2002

The paper describes the planning, analysis & design of a multi-layered space frame hangar recently built at Mumbai for Air India to service two 747-400 airplanes at a time - one docked in ‘tail-in’ and the other in the ‘nose-in’ position. A unique feature of the hangar is that the docking systems and cranes are suspended from the space frame itself. The design involves a main three-layered pin-jointed space frame strengthened by the addition of two rigid-jointed layers to form a five-layered front girder with a clear span of 129.384m. The front girder is designed to act as a portal along with the two end columns of steel 25m high which are supported on concrete pedestals of 4.5m height. Weighing 65 kg/m2, this long span space frame hangar is believed to be the lightest of its class with suspended docking systems and cranes. The paper also briefly describes the hoisting technique employed to lift the hangar roof weighing 1100 tons, in one piece, using twelve PSC centre hole jacks.
Sustainomics, Sustainable Development and Climate Change
Authors: Munasinghe Mohan
Published: October 2002

This paper examines key issues in the nexus of sustainable development and climate change. It describes sustainomics as ‘a transdisciplinary, integrative, balanced, heuristic and practical meta-framework for making development more sustainable’. The paper seeks to integrate these concepts through two broad approaches involving optimality and durability, and applies these ideas to climate change analysis. Operationally, it plays this bridging role by helping to map the results of environmental and social impact assessments (EIA and SIA) onto the framework of conventional economic analysis of projects. In addition the approach may help to formulate effective sustainable development policies, by linking and articulating these activities explicitly trough the Action Impact Matrix framework.
Wind Energy Directional Spatial Correlation Functions and Application for Prediction
Authors: Sahin Ahmet Duran , Sen Zekai
Published: October 2002

In planning, design, operation and maintenance of wind farms, the spatial variations in wind velocity become significant. Although there are many wind energy studies at a single location, spatial assessment evaluation methods are scanty. Wind velocity maps may provide a common basis for regional assessment and interpretations, but they do not yield means of regional prediction. Hence, the main purpose of this paper is to propose some new concepts and methods that are useful prior to regional wind energy potential calculations. Among these are Directional Point Cumulative Semivariogram (DPCSV) concepts, which provide information concerning local spatial wind velocity and/or elevation changes. It is possible to obtain the radius of wind velocity influence around each station, along desired directions, based on the DPCSV concept. The implementation of the proposed methodology is presented for some wind velocity measurement stations in Turkey. For the application, the sample DPCSVs are first obtained from the available data, and then converted to Local Spatial Dependence Functions (LSDF). These functions are the basic ingredients for the regional wind velocity estimations. The reliability of the methodology is measured through the cross validation procedure and it is observed that the procedure is valid with less than 20% error.
Numerical Simulation of Wind Farm Influence on Wind Flow
Authors: Ivanova Lubov A. , Nadyozhina Ekaterina D.
Published: October 2002

A boundary-layer meso-γ-model was used for calculation of wind and turbulence characteristics inside a wind farm. The study demonstrates the ability of the model to describe wind and turbulence fields in more detail than climatological analysis only. Velocity deficit at the hub height of the wind turbine and standard deviation components inside the wind farm were calculated for various environmental situations which are constructed as combinations of the large scale input parameters of the model with surface and landscape characteristics. The load effects on the wind turbine were parameterised, and the calculated wind profiles inside the wind farm were compared with measurements. The results of 3-dimensional and 2-dimensional versions of the model were compared.
The American Wind Energy Associations Year 2000 Awards
Authors: de Azua Christine Real
Published: October 2002

The AWEA announced several Award winners at the ‘Windpower 2000’ conference in Palm Springs, California. The winners received their awards from outgoing AWEA President Robert Gates.

Walt Musial and Sandy Butterfield, both of the National Wind Technology Center, jointly won the Technical Achievement Award. Musial and the National Wind Technology Center test team were honored “for developing a capability at the National Wind Technology Center to provide blade and drive train structural component testing to the U.S. wind industry”. Butterfield was recognized “for successfully overseeing development of a U.S.-based certification program.”

The National Wind Technology Center (NWTC) is situated in a spectacular setting at the foot of the Rocky Mountains, in the Rocky Flats Environmental Technology Site buffer zone in Golden, Colorado. A few turbines of varying sizes and models can be glimpsed on the open plateau from Route 128 out of Golden. However the small number of turbines belies the importance of this center for the wind power industry. Most of the NWTC's work is carried out indoors, in hangars and computer labs which make it one of the world's unique testing centers.
Wind Energy Status in Bangladesh
Authors: Mahfuz Mohammad Upal
Published: October 2002

Bangladesh is a rural, agricultural country lying in South Asia. Having a vast sea to the south and a long coast line, Bangladesh has a promising prospect for wind energy. For the last few decades all wind energy studies were based on Meteorological Department data that seemed to be insufficient due to inappropriate height for wind power generation. In recent years advanced technologies have been adopted to find the important wind areas of Bangladesh, especially for the study of electric power generation. Different initiatives from the Government and non-government sectors have further strengthened the target through direct involvement in wind velocity measurement and a number of national workshops and international seminars. The revised wind speed data not only show a bright prospect of wind energy in Bangladesh but also bear an important value in rural electrification and irrigation programmes, the two vital sectors of socio-economic development of Bangladesh.
Local and Community Ownership of Renewable Energy Power Production: Examples of Wind Turbine Projects
Authors: Leaney V. , Jenkins D. , Rowlands A. , Gwilliam R. , Smith D.
Published: October 2002

Local and community ownership of renewable energy generation, e.g. grid connected wind turbines, can bring widespread benefits to the local community and economy. Ownership may range from 100% of small projects to minor participation in larger schemes, but the knowledge and experience of local participation is a significant factor. Barriers that have in the past hindered local and community participation have been identified as fair and easy access to information, specialist knowledge, markets and finance. This paper details major advances in community RE projects in the UK over the past two years that have addressed and overcome these barriers. These include the development of a wholly community-led, community-owned wind turbine project in Mid-Wales and the establishment of a Renewable Energy Investment Club to facilitate community investment.
A Blade Element Estimation of the Cut-in Wind Speed of a Small Turbine
Authors: Wood D.H.
Published: October 2002

As the wind speed increases from zero, small turbines will cut-in only when the aerodynamic torque acting on the blades exceeds the resistive torque of the generator and drive system. This Note describes the use of standard blade element theory to calculate the cut-in wind speed, at which rotation commences, using the apparent near-universality of aerofoil lift and drag at high incidence. The starting torque is shown to depend on the “chord-pitch” integral that, in turn, is a function only of the blade geometry. This integral is evaluated for two small blades designed by the author for which the cut-in wind speed has been determined. In both cases, the calculations considerably over-estimate the actual cut-in speed and some possible reasons for this are advanced.
Noise from Traffic in Kuwait and Attitudes of Urban Residents
Authors: Koushki P. A.
Published: October 2002

Findings of a research project funded by the Research Administration of Kuwait University (Report No.: EV02/99) and completed in 1999 provided useful information – for the first time – on the levels of traffic-generated noise pollution and the attitudes of exposed residents concerning this pervasive urban problem. The Research Report presents the levels of noise pollution measured at local, residential and collector streets, arterial roadways and expressways. This information will benefit both the public and responsible urban policy-makers.
Railway Noise Reduction by Controlling Wheel and Rail Roughness
Authors: Dings Pieter
Published: October 2002

Why is wheel and rail roughness important for railway noise? How can roughness best be measured, analysed and presented? Is it the wheel or is it the rail, which of the two has higher roughness levels? Where do wheel and rail roughness come from in the first place and how do they grow? What can be done to reduce roughness, or, what can be done to prevent roughness from growing?
Sheet-Cast Acoustical Foams Outperform Bun Stock
Authors: Castillo Manuel Sánchez
Published: October 2002

Acoustical foams provide one of the easiest, most effective and economical ways to reduce the airborne noise from a mechanical device that is enclosed in a case or cabinet. As a lining for the case, the foam absorbs the sound waves by trapping them within its cells and converting the energy to very low-grade heat. E-A-R engineer Manuel Sánchez recently studied the absorption performance of acoustical foams manufactured by two different methods. Some of his findings are presented here.
Study of the Remaining Life of a Rotary Gear Pump with Bearing Degradation
Authors: Kaplan Robert
Published: October 2002

This study describes vibration levels and patterns generated by a rotory gear pump after the bearings had begun to degrade. The vibration patterns and trends were not unexpected. The machine was operated at significantly increased vibration levels for 15 months. The article includes photographs of component wear. It is hoped that the dats will help the reader evaluate potential remaining life of similar machines with similar faults.
Clean Development Mechanism for Power Infrastructures for China's Sustainable Development
Authors: Deshun Liu , Sugiyama Taishi
Published: October 2002

What is the Clean Development Mechanism (CDM)?

The establishment of Clean Development Mechanism (CDM) is a significant achievement in the political negotiations on the implementation of United Nations Framework Convention on Climate Change (UNFCCC). CDM is stipulated in Article 12 of the Kyoto Protocol (KP), where assisting developing country Parties in achieving sustainable development is explicitly listed as a purpose in parallel with the others. Developed country Parties are to be assisted in achieving compliance with their quantified emission limitation and reduction commitment (QELRC) under Article 3 by acquiring Certified Emission Reductions (CERs) accrued from the CDM. This win-win mechanism reflects two arguments: the responsibility of developed countries for past greenhouse gas emissions, and the legitimate priority needs of developing countries for their social and economic development and poverty eradication. It should be kept in mind, therefore, that when formulating the strategic policy of the CDM, one important principle to be followed is that CDM projects must be compatible with and supportive of national environments and sustainable development priorities and strategies of developing country Parties.
Technical Note: The Contribution of Perlite to the Sound Transmission Loss of Solid Masonry Walls
Authors: Birlik Gülin
Published: October 2002

The sound insulation of solid masonry walls can be improved either by plastering or by changing the constituent materials of the wall blocks. Whilst traditional cement-lime-sand plasters are still in use, plasters containing perlite are preferred, especially in cold climates, due to their high heat insulation characteristics. In this study the contribution of perlite to the sound transmission loss of solid walls is investigated. Two series of measurements were conducted in the laboratory. In the first, perlite was added to the in-laboratory prepared plasters, and in the second perlite was included as an additional constituent to the mixture when casting gypsum blocks. The mean transmission loss of the brick wall was increased by approximately 19 dB when plastered on both sides by plaster containing perlite. When perlite was a constituent of the gypsum wall blocks the average transmission loss was increased by approximately 1 dB.
The Hall Acoustics Computer Model and its Application to the Acoustic Design of a Theater and an Assembly Hall
Authors: Tisseyre A. , Moulinier A.
Published: October 2002

The Hall Acoustics computer model presented here carries out the computation of the acoustic response of rooms and large multipurpose volumes. The model is based on the 3 D representation of the volume. The surfaces are each assigned an absorption coefficient and are subdivided into smaller elements. A matrix of influence coefficients between elements is first calculated. Given a sound source, the energy received by each element is calculated, and from this, the sound level at any point in the volume can be determined, making it possible to calculate a) the attenuation with distance, b) the acoustic illumination on any plane, and c) the reception directivity of the sound energy received at any given point. Echograms at any chosen point in the volume can be calculated, as well as the evolution with time of the reception directivity at the receiver: such a feature enables checking the possible discrepancy between the visual picture and the sound picture. This software makes it possible to modify the shape of the room at will, in order to optimize its acoustic features. Two examples of hall acoustics design are presented (the Théâtre de la Cité in Toulouse, and the Al Shura Main Assembly Hall in Riyadh, Saudi Arabia).
Prediction Models in Building Acoustics
Authors: Gerretsen Eddy , Nightingale Trevor R.T.
Published: October 2002

There is strong interest in being able to predict the apparent sound insulation in completed constructions so that the suitability of the construction details and materials may be assessed at the design stage. Methods do exist that provide estimates of the apparent sound insulation. An example of which is SEA. However, this method is likely too complex to be suitable for most practitioners and consultants as it relies heavily on the user to model the transmission mechanisms from first principles. Thus, from a practitioner's point of view, a model that makes use of commonly available data for the acoustic performance of building products and elements – as measured by standardised laboratory measurement methods ISO 140 – and relates this to the acoustic performance in the completed buildings would be more useful. In response to this, CEN has started to create prediction models for several acoustic aspects in buildings beginning with separate models for the apparent airborne sound insulation and the apparent impact sound insulation. Practical models that allow the prediction of the sound reduction of the individual flanking paths in heavy monolithic constructions are now available (EN 12354–1 for the apparent airborne sound insulation and EN 12354–2 for the apparent impact sound insulation). A new quantity has been introduced in these models to characterise the structure-borne sound transmission at junctions of building elements. Work is now focusing on reliable input data to these models, describing measurement methods to determine the junction quantity, extending application to constructions that are not heavy and monolithic, and verifying the accuracy of the models. Further work is concentrating on models for other aspects such as facade sound transmission from outside to inside and vice-versa and the sound levels caused by mechanical equipment in buildings. This paper provides an overview of prediction models in building acoustics as an introduction to the special session at the Forum Acusticum 1999 in Berlin.
Treatment of Unidentifiability in Structural Model Updating
Authors: Katafygiotis Lambros S. , Lam Heung-Fai , Papadimitriou Costas
Published: October 2002

The present study addresses the issues of non-uniqueness and unidentifiability arising in structural model updating. A Bayesian probabilistic framework is used for model updating which properly handles the uncertainties due to model error and measurement noise associated with model updating. Uncertainties in the model parameters are quantified by probability density functions (PDF) specifying the relative plausibilities of the possible values of the parameters. The Bayesian formulation is well-suited for updating the PDF of the uncertain model parameters taking into account engineering experience and measured dynamic data. Methods are presented for approximating this updated PDF for the general unidentifiable case for which the region of significant probabilities is concentrated in the neighborhood of a manifold of lower dimension than the original parameter space. This PDF is useful for both model updating and structural damage predictions. Asymptotic approximations are also developed for computing the uncertainties in the model response predictions. It is demonstrated that unidentifiable cases are not treatable by existing results valid only for identifiable cases for which the dimension of the manifold is exactly zero. Two examples involving simulated model error and measurement noise are presented to demonstrate the advantages of the new proposed method in effectively addressing unidentifiability issues.
Design of Reinforcement in Prestressed Beams with Openings
Authors: Liu Ronggui , Lu Zhitao , Li Li
Published: October 2002

This paper is concerned with the design of reinforcement in prestressed concrete beams with openings, based on the application of regression analysis to experimental data. The results, verified by tests and the finite element method, show that a new method described in the paper is simple, convenient and reliable, and can be used in engineering design.
Symmetry Reduction of Structures for Large Rotations
Authors: Leung A.Y.T. , Wong C.K.
Published: October 2002

The reduction of the number of unknowns while capturing the essential physical features in a nonlinear analysis of large spatial structures has long been a challenging task for researchers. We approach the problem of large displacement and large rotation analysis of space frame structures by means of group theory and substructuring technique. An accurate nonlinear analysis requires an element that accurately reflects the nonlinear behavior of the structure being modeled. Therefore details of the element formulations and updating procedure for large rotation will be given. The present formulation is capable of modeling a structure (with small to moderate axial force in its members) using one element per member, so that the number of degrees of freedom could be kept to minimum. The present methodology is based on the approach in a paper by Healey and Treacy. Axial deformation only was considered and matrix-iteration was used. We extend their idea to deal with the analysis of symmetry structures under going large displacement and large rotation in bending. Instead of matrix-iteration, we find that the basis vectors required to project the solution space into its symmetry subspace can be easily determined from the projection matrix. Excellent reduction can be obtained using the present method. The reduction efficiency depends on the symmetry of the structures. The higher the degree of symmetry the structure possesses, the greater the reduction will be.
Pounding Response of Adjacent Buildings Subjected to Spatial Earthquake Ground Excitations
Authors: Hao Hong , Liu Xue Yi , Shen Jay
Published: October 2002

Pounding damage is a serious seismic hazard in highly populated areas during major earthquakes. This paper evaluates the effect of earthquake ground motion spatial variations on pounding responses of adjacent structures. Adjacent structures are modeled as two single-degree-of-freedom (SDOF) oscillators with multiple supports. Pounding effects are simulated by spring-dashpot pounding elements. Linear elastic and nonlinear inelastic responses are considered in the analysis. Spatial ground motion input is stochastically simulated. The simulated spatial ground motion time histories are compatible with Newmark and Hall design spectrum individually and with an empirical coherency function between each other. The Newmark method with constant acceleration assumption is employed in step-by-step integration to calculate structural response. Numerical results are presented and discussed in terms of various structural and ground motion parameters.
Local Buckling of Composite Laminated Plate Assemblies Using the Spline Finite Strip Method
Authors: Azhari M. , Abdollahian M. , Bradford M.A.
Published: October 2002

An analysis of the local buckling of composite laminated plates and folded plate assemblies subjected to arbitrary loading is presented. The analysis uses the spline finite strip method, which utilises B3-spline functions for the longitudinal variation of buckling displacements, and an interpolation of Hermitian polynomials for the buckling displacements in the transverse direction. While the spline finite strip method is fairly well-known in buckling analysis, its direct application to the local buckling of composite laminates has been more limited. The method is programmed to study the local buckling of laminated flat plates and L-sections. Examples of the accuracy of the method compared with independent studies, and the influence of increasing the number of lengthwise section knots, are presented for plates of finite length that are subjected to compression, bending and shear.
Design of RC Columns Subjected to Safety Constraint
Authors: Hong H. P. , Wang W.
Published: October 2002

Minimum cost design of reinforced concrete columns subjected to reliability constraints is a multi-level optimization problem because both the analysis of minimum cost design, and the estimation of the reliability are nonlinearly constrained optimization problems. A procedure for reliability constrained optimal design of columns is described in this study. It seems that such a design approach is allowed by the current CSA A23.3–94 design code and will become more relevant for an objective-based design code. This design approach ensures that the designed columns meet specified reliability levels, and that the construction materials having probabilistic characterizations which are different from those used for design code calibrations are used economically. The procedure is demonstrated through example designs of short and slender columns.
A Design Model for Local Web Buckling in Tapered Composite Beams
Authors: Vellasco P. C. G. da S. , Hobbs R. E.
Published: October 2002

Steel-concrete composite flooring systems using steel sections with tapered webs are very attractive from an economical point of view, combining efficient use of steel, wide spans, rapid erection and easy access for services. However, the full economic exploitation of the composite tapered beam solution is inhibited by the limited understanding of certain aspects of its behaviour. One of the most pressing needs is for a better understanding of the local buckling behaviour of the relatively deep slender web at changes of slope in the lower flange. A design formulation has been developed which produces a very simple test of the need for stiffeners. This paper describes the derivation and behaviour of this design model. After that, a calibration of the model against some experiments and a parametric study is presented.
Investigation on Mixed-Mode Cohesive Crack in the Presence of Water Pressure for Interface between Dam and its Foundation
Authors: Shen Xinpu , Chen Lixin
Published: October 2002

Firstly the focus is put on the formulation of an holonomic (in the sense of plastic deformation theory) constitutive model for a mixed-mode cohesive interface crack at the interface of a concrete structure accounting for the influence of water pressure. Secondly, the consequent discretized formulation of piece-wise linear interface laws in terms of generalized variables and its formulation as a linear complementarity problem is presented. At the end of this paper, numerical analysis for mixed-mode cohesive fracture of a concrete-rock interface of a benchmark gravity dam is described.
Range image statistics can explain the anomalous perception of length
Authors: Howe Catherine Q. , Purves Dale
Published: October 2002

A long-standing puzzle in visual perception is that the apparent extent of a spatial interval (e.g., the distance between two points or the length of a line) does not simply accord with the length of the stimulus but varies as a function of orientation in the retinal image. Here, we show that this anomaly can be explained by the statistical relationship between the length of retinal projections and the length of their real-world sources. Using a laser range scanner, we acquired a database of natural images that included the three-dimensional location of every point in the scenes. An analysis of these range images showed that the average length of a physical interval in three-dimensional space changes systematically as a function of the orientation of the corresponding interval in the projected image, the variation being in good agreement with perceived length. This evidence implies that the perception of visual space is determined by the probability distribution of the possible real-world sources of retinal images.
A new class of regulatory genes underlying the cause of pear-shaped tomato fruit
Authors: Liu Jiping , Van Eck Joyce , Cong Bin , Tanksley Steven D.
Published: October 2002

A common, recurring theme in domesticated plants is the occurrence of pear-shaped fruit. A major quantitative trait locus (termed
ovate
) controlling the transition from round to pear-shaped fruit has been cloned from tomato.
OVATE
is expressed early in flower and fruit development and encodes a previously uncharacterized, hydrophilic protein with a putative bipartite nuclear localization signal, Von Willebrand factor type C domains, and an ≈70-aa C-terminal domain conserved in tomato,
Arabidopsis
, and rice. A single mutation, leading to a premature stop codon, causes the transition of tomato fruit from round- to pear-shaped. Moreover, ectopic, transgenic expression of
OVATE
unevenly reduces the size of floral organs and leaflets, suggesting that OVATE represents a previously uncharacterized class of negative regulatory proteins important in plant development.
ENSO and cholera: A nonstationary link related to climate change?
Authors: Rodó Xavier , Pascual Mercedes , Fuchs George , Faruque A. S. G.
Published: October 2002

We present here quantitative evidence for an increased role of interannual climate variability on the temporal dynamics of an infectious disease. The evidence is based on time-series analyses of the relationship between El Niño/Southern Oscillation (ENSO) and cholera prevalence in Bangladesh (formerly Bengal) during two different time periods. A strong and consistent signature of ENSO is apparent in the last two decades (1980–2001), while it is weaker and eventually uncorrelated during the first parts of the last century (1893–1920 and 1920–1940, respectively). Concomitant with these changes, the Southern Oscillation Index (SOI) undergoes shifts in its frequency spectrum. These changes include an intensification of the approximately 4-yr cycle during the recent interval as a response to the well documented Pacific basin regime shift of 1976. This change in remote ENSO modulation alone can only partially serve to substantiate the differences observed in cholera. Regional or basin-wide changes possibly linked to global warming must be invoked that seem to facilitate ENSO transmission. For the recent cholera series and during specific time intervals corresponding to local maxima in ENSO, this climate phenomenon accounts for over 70% of disease variance. This strong association is discontinuous in time and can only be captured with a technique designed to isolate transient couplings.
In vivo
modulation of nonphotochemical exciton quenching (NPQ) by regulation of the chloroplast ATP synthase
Authors: Kanazawa Atsuko , Kramer David M.
Published: October 2002

Nonphotochemical quenching (NPQ) of excitation energy, which protects higher plant photosynthetic machinery from photodamage, is triggered by acidification of the thylakoid lumen as a result of light-induced proton pumping, which also drives the synthesis of ATP. It is clear that the sensitivity of NPQ is modulated in response to changing physiological conditions, but the mechanism for this modulation has remained unclear. Evidence is presented that, in intact tobacco or
Arabidopsis
leaves, NPQ modulation in response to changing CO
2
levels occurs predominantly by alterations in the conductivity of the CF
O
-CF
1
ATP synthase to protons (
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). At a given proton flux, decreasing
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will increase transthylakoid proton motive force (
pmf
), thus lowering lumen pH and contributing to the activation of NPQ. It was found that an ≈5-fold decrease in
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could account for the majority of NPQ modulation as atmospheric CO
2
was decreased from 2,000 ppm to 0 ppm. Data are presented that
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is kinetically controlled, rather than imposed thermodynamically by buildup of ΔG
ATP
. Further results suggest that the redox state of the ATP synthase γ-subunit thiols is not responsible for altering
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. A working model is proposed wherein
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is modulated by stromal metabolite levels, possibly by inorganic phosphate.