An inverse analysis approach to determine fatigue performance of bituminous mixes

In pavement engineering, fatigue resistance is evaluated using different tests protocols and different specimen geometries. The dependency of the specimen shape geometry on fatigue performance does not allow the evolution of intrinsic material properties. This paper deals with the calibration of intrinsic fatigue damage parameters for bituminous materials. A fatigue damage model is implemented. The decrease of stiffness of the specimen during fatigue tests for different laboratory testing conditions is calculated from finite element computations. An inverse optimization technique is used in order to adjust the fatigue damage parameters on bending fatigue tests. A Levenberg-Marquardt algorithm is implemented to fit the finite element specimen global response on experimental results. An application on bending laboratory fatigue tests is presented to illustrate the applicability of the method for pavement engineering.     

A comparative analysis of hotspot identification methods

The identification of crash hotspots is the first step of the highway safety management process. Errors in hotspot identification may result in the inefficient use of resources for safety improvements and may reduce the global effectiveness of the safety management process. Despite the importance of using effective hotspot identification (HSID) methods, only a few researchers have compared the performance of various methods. In this research, seven commonly applied HSID methods were compared against four robust and informative quantitative evaluation criteria. The following HSID methods were compared: crash frequency (CF), equivalent property damage only (EPDO) crash frequency, crash rate (CR), proportion method (P), empirical Bayes estimate of total-crash frequency (EB), empirical Bayes estimate of severe-crash frequency (EBs), and potential for improvement (PFI). The HSID methods were compared using the site consistency test, the method consistency test, the total rank differences test, and the total score test. These tests evaluate each HSID method's performance in a variety of areas, such as efficiency in identifying sites that show consistently poor safety performance, reliability in identifying the same hotspots in subsequent time periods, and ranking consistency. To evaluate the HSID methods, five years of crash data from the Italian motorway A16 were used.The quantitative evaluation tests showed that the EB method performs better than the other HSID methods. Test results highlight that the EB method is the most consistent and reliable method for identifying priority investigation locations. The EB expected frequency of total-crashes (EB) performed better than the EB expected frequency of severe-crashes (EBs), although the results differed only slightly when the number of identified hotspots increased. The CF method performed better than other HSID methods with more appealing theoretical arguments. In particular, the CF method performed better than the CR method. This result is quite alarming, since many agencies use the CR method. The PFI and EPDO methods were largely inconsistent. The proportion method performed worst in all of the tests. Overall, these results are consistent with the results of previous studies.The identification of engineering countermeasures that may reduce crashes was successful in all of the hotspots identified with the EB method; this finding shows that the identified hotspots can also be corrected.The advantages associated with the EB method were based on crash data from one Italian motorway, and the relative performances of HSID methods may change when using other crash data. However, the study results are very significant and are consistent with earlier findings. To further clarify the benefits of the EB method, this study should be replicated in other countries. Nevertheless, the study results, combined with previous research results, strongly suggest that the EB method should be the standard in the identification of hotspots.     

Numerical methods to determine effective elastic properties

Effective elastic properties for heterogeneous materials are widely discussed in the literature. We discuss and review the application range and accuracy of different numerical approaches to determine those effective elastic values from digitized material samples. Recent examples are used for illustration. Whereas the use of most effective-medium theories is restricted to a limited number of geometries the possible application range of numerical methods is much wider. There are two fundamental different numerical methods to extract effective elastic properties from a given microstructure. Both approaches are sensitive to size effects. Static methods can address this problem by applying uniform stress or uniform displacement boundary conditions. For dynamic wave propagation simulations the ratio of the dominant wavelength to the typical inclusion size is the most crucial factor.     

A comparative analysis of methods of measuring reactive power

A comparative analysis of methods of measuring reactive power for ac networks is carried out. Analytic relations for the systematic error as a function of the current and voltage parameters are obtained. For the method based on a Hilbert converter, the complexities of its practical realization are considered. It is shown that for ac networks, the method based on the discrete Fourier transform of the current and voltage is the most accurate.     

On interval methods applied to robot reliability quantification

Interval methods have recently been successfully applied to obtain significantly improved robot reliability estimates via fault trees for the case of uncertain and time-varying input reliability data. These initial studies generated output distributions of failure probabilities by extending standard interval arithmetic with new abstractions called interval grids which can be parameterized to control the complexity and accuracy of the estimation process. In this paper different parameterization strategies are evaluated in order to gain a more complete understanding of the potential benefits of the approach. A canonical example of a robot manipulator system is used to show that an appropriate selection of parameters is a key issue for the successful application of such novel interval-based methodologies.     

Introducing methods of determining metal elemental compositions

A method is presented for determining elemental compositions of metals and alloys by means of an EMAL-2 mass spectrometer within the accreditation framework of the United Kingdom Accreditation Service (UKAS/NAMAS) for a Russian test laboratory. The analysis method has been adapted to meet international standards and rules. Particular attention is given to measurement errors. A new solution is proposed that improves the measurement accuracy considerably. Translated from Izmeritel'naya Tekhnika, No. 2, pp. 52–56, February, 1998.     

New methods to determine the importance measures of initiating and enabling events in fault tree analysis

Components' importance measures play a very important role in system reliability analysis. They are used to identify the weakest parts of the system for design improvement, failure diagnosis and maintenance. This paper deals with the problem of determining the importance measures of basic events in case of unreliability analysis of binary coherent and non-coherent fault trees. This type of analysis is typical of catastrophic top events, characterised by unacceptable consequences. Since the unreliability of systems with repairable components cannot be exactly calculated via fault tree, the Expected Number of Failures - which is obtained by integrating the unconditional failure frequency - is considered as it represents a good upper bound. In these cases it is important to classify events as initiators or enablers since their roles in the system are different, their sequence of occurrence is different and consequently they must be treated differently. New equations based on system failure frequency are described in this paper for determining the exact importance measures of initiating and enabling events. Simple examples are provided to clarify the application of the proposed calculation methods. Compared with the exact methods available in the literature, those proposed in this paper are easier to apply by hand and are simpler to implement in a fault tree analyser.     

Use of biogenic and abiotic elemental selenium nanospheres to sequester elemental mercury released from mercury contaminated museum specimens

Mercuric chloride solutions have historically been used as pesticides to prevent bacterial, fungal and insect degradation of herbarium specimens. The University of Manchester museum herbarium contains over a million specimens from numerous collections, many preserved using HgCl(2) and its transformation to Hg(v)(0) represents a health risk to herbarium staff. Elevated mercury concentrations in work areas (～ 1.7 μg m(-3)) are below advised safe levels (<25 μg m(-3)) but up to 90 μg m(-3) mercury vapour was measured in specimen boxes, representing a risk when accessing the samples. Mercury vapour release correlated strongly with temperature. Mercury salts were observed on botanical specimens at concentrations up to 2.85 wt% (bulk); XPS, SEM-EDS and XANES suggest the presence of residual HgCl(2) as well as cubic HgS and HgO. Bacterially derived, amorphous nanospheres of elemental selenium effectively sequestered the mercury vapour in the specimen boxes (up to 19 wt%), and analysis demonstrated that the Hg(v)(0) was oxidised by the selenium to form stable HgSe on the surface of the nanospheres. Biogenic Se(0) can be used to reduce Hg(v)(0) in long term, slow release environments.     

土壤无机元素测定的前处理方法研究

用等离子体发射光谱仪(ICP)同时测定土壤样本中多元素含量,其前处理方法目前还没有国家统一标准。本文以茶园土壤为样本研究了ICP测定多元素含量的前处理方法。实验结果表明,采用硝酸-高氯酸混合酸湿法消煮土壤样品,全部24种无机元素的检出限为0.31-118.04μg/L。对于As、Cd、Hg、Pb等有害元素和Co、Cr、Cu、Fe、Mn、Ni、V、Zn等人体必需元素有较高的回收率(79.37-118.0%)。该处理方法的样液上机测定信号强度大,灵敏度高,重复性好,可作为今后测定茶园土壤无机元素含量的标准处理方法。     

Use of a ring probe to determine thermal conductivity coefficients

A method for using a constant-power ring probe to determine thermal conductivity coefficients is considered.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 46, No. 3, pp. 451–455, March, 1984.     

Use of recursive methods in fuzzy fault tree analysis: an aid to quantitative risk analysis

This paper demonstrates the use of recursive techniques in quantitative risk analysis when the probability of occurrence of the basic events is uncertain (fuzzy) in nature instead of having a precise value. Cases of both coherent and non-coherent fault trees with replicated events are dealt with. The analyses have been computerized using an IBM compatible personal computer (PC-AT). The source code is in C and uses Turbo-C graphics routines for creating plots. A wide variety of examples with different membership functions have been considered.     

Use of CCTV to determine road accident factors in urban areas

This paper sets out to assess whether there is a potential use for images collected through the increasingly ubiquitous use of CCTV cameras in urban areas as a means of increasing understanding of the causes of road traffic accidents. Information on causation and contributory factors is essential as a means of understanding why accidents occurred and how the occurrence of similar events may be prevented in the future. CCTV records of accidents could provide an independent perspective on an accident and have the potential to increase both the quality and quantity of information available to the safety researcher.

This study focuses on an area of central Leeds in the UK and shows that an existing CCTV camera system used for urban traffic management reasons has the potential to record around a quarter of the accidents which occur in the area, based on patterns of past occurrence. Most city centres in the UK will have similar camera systems set-up. By the introduction of additional strategically placed cameras and replacement of existing cameras with ones dedicated to accident recording, this figure could be increased substantially.

The paper also considers how effective cameras and video records will be as a means of identifying contributory factor information once an accident is recorded. The contributory factor classification used by a recently introduced system in Britain is assessed in terms of how visible each of the factors is likely to be on video and their relative frequency of occurrence. It is concluded that CCTV has a high potential to provide corroborative evidence about many of the most commonly occurring factors, and to throw further light on accident causation.     

Comparative analysis of electrical detection methods of DNA synthesis

The incorporation of a complementary deoxynucleotide (dNTP) into a self-primed single-stranded DNA (ssDNA) attached to the surface of a sensor electrode generates an H+ charge that can be either trapped on the sensor surface or diffused into the surrounding solution. Electrical detection methods of DNA synthesis are based on these H+ kinetic mechanisms. The detection method that uses ISFET, which is related to the surface trapping mechanism, showed a better sensing signal than the induced charge detection method, which is related to the diffusion of H+ into the surrounding solution. The trapping reaction should be well-controlled, however, so that it would be stable under various surface conditions and temperatures. Moreover, the reaction should be reversible, and the reaction parameters should be well-sustained in the subsequent synthesis cycles. For the induced charge method, the AC current level was too small to be detected using an ordinary amplifier circuit with the same sensor size as that of ISFET. Consequently, the sensor operation sustainability and signal-to-noise ratio characteristics should be addressed carefully in the selection of the proper sensor type.     

A comparative study of bibliometric past performance analysis and peer judgement

A comparison is made between two types of research past performance analysis: the results of bibliometric-indicators and the results of peer judgement. This paper focuses on two case studies: the work of Dutch National Survey Committees on Chemistry and on Biology, both compared with our bibliometric results for research groups in these disciplines at the University of Leiden. The comparison reveals a serious lack of agreement between the two types of past performance analysis. This important, science-policy relevant observation is discussed in this paper.     

Use of digital filters to determine the frequency of a sinusoidal signal

An interference-protection-optimum method of measuring the frequency of sinusoidal signals using digital filters, based on the root mean square deviation criterion, is investigated. An algorithm for the digital processing of the input signal is proposed, and a model of a digital filter for achieving this and the principle of the construction of a digital measuring instrument for determining the parameters of a sinusoidal signal are proposed.Translated from Izmeritel'naya Tekhnika, No. 8, pp. 60–63, 1994.     

Use of fused quartz as a reference standard in comparative methods of thermal conductivity measurements

A method has been developed for taking into account radiation when the thermal flux through a quartz-standard specimen is calculated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 23, No. 4, pp. 669–672, October, 1972.     

A comparison of different methods to determine the threshold of fatigue crack propagation

Three different methods for determining the threshold value for fatigue crack growth — the load-shedding technique, the stepwise increase of load amplitude on specimens precracked in cyclic compression, and decrease of stress intensity range at a constant maximum stress intensity — were applied to a high-strength aluminium alloy. The load-shedding technique tended to lead to higher values of the threshold, especially at low R-ratios. The threshold determined with decreasing stress intensity range at a constant maximum stress intensity was larger than the effective threshold determined with stepwise increasing of load amplitude on specimens precracked in cyclic compression.