The effect of aggregate gradation on creep and moisture susceptibility performance of warm mix asphalt

It is clear that the purpose of mixture design is to select optimum asphalt content for a desired aggregate structure to meet the prescribed criteria. Aggregate makes up high proportion of volume and mass of mixtures; hence, it is considered as an important constituent of asphalt concrete. This study postulates that the gradation is an important characteristic of the aggregate in adoption of the optimum mixture. One aggregate source, three gradations and different percentages of Sasobit^® was used to manufacture hot mix asphalt and warm mix asphalt. The test results indicated that the aggregate gradation affects the rutting resistance and especially the moisture susceptibility of the introduced mixtures, differently. Rutting resistance was evaluated using the flow number parameter, and in order to determine the moisture sensitivity mechanism, a mechanical and visual inspection tests were carried out. At the end, it is concluded that the optimum aggregate gradation for these two types of mixtures is different.     

Improved method of considering air void and asphalt content changes on long-term performance of asphalt concrete pavements

Mixture properties (aggregate gradation and volumetric quantities), rate of loading and environmental conditions are the most important factors that affect the |E*| values. The main objective of this study was to develop a rational approach to investigate and model the effect of air voids and asphalt content on the |E*| master curves and consequently predict pavement performance. In this study, |E*| tests were conducted on three asphalt concrete mixtures with the same aggregate gradation, but different binder grades. For each of these mixtures, the air void and asphalt contents were varied at three levels. It is found that the developed method provides a more accurate estimate of the effects of volumetric changes in hot mix asphalt. The application of the proposed approach would be most beneficial for quality control/quality assurance purposes, performance-related specifications and for estimating contractors' incentives and penalties, where |E*| is utilised to predict the pavement performance.     

Introducing a simple method to determine aggregate gradation of hot mix asphalt using image processing

The aggregate gradation is one of the most important parameters in the mechanical properties of hot mix asphalt (HMA). Thus, determining the aggregate gradation is a very significant subject in civil engineering. Usually, to estimate the aggregate gradation, it is required to separate the aggregate from the bitumen, and this operation can be time-consuming and even dangerous related to chemical solvents. Moreover, several computer-based methods have been established to model the internal structure of HMA in two- and three-dimensional methods and can be applied to determine the aggregate gradation, but these methods need special and expensive equipment. Therefore, in this study, a simple approach is introduced to quickly and easily determine the aggregate gradation of HMA from the prepared cross-section images of cylindrical samples using numerical and image-processing techniques such as fitting equation and colour space system. The obtained results indicate that the introduced method can detect the aggregate gradation with high accuracy and can be used as a satisfactory alternative to other expensive methods.     

基于ICC阶调调整的陶瓷喷墨印刷颜色校正

目的 为了解决不同批次陶瓷制品的颜色一致性问题,提出一种基于ICC编辑的陶瓷喷墨制品颜色校正方法.方法 根据二分法原理,通过实验测量,找出网点阶调修正的颜色校正模型最佳校正参数a值,计算并绘制各单色通道色彩调整曲线Si.结果 应用经过Si值网点补偿校正后的ICC特性曲线,印刷并输出网点阶调测试色卡,测量得出各通道网点百分比的阶调值与基准值的平均差值减小到0.4％.结论 提出的基于ICC编辑的陶瓷喷墨印刷制品颜色校正方法有效解决了同一印前文件不同批次陶瓷制品颜色不一致的问题.     

Wet packing of blended fine and coarse aggregate

All codified methods for measuring the packing density of aggregate are carried out under dry condition. However, these dry packing methods do not account for the effect of water in the concrete mix. In a previous study, a wet packing method for measuring the packing density of fine aggregate under wet condition has been developed and it was found that the packing density of fine aggregate can be substantially higher under wet condition than dry condition. Nevertheless, many researchers still believe that for coarse aggregate, it does not matter much whether the packing density is measured under dry or wet condition. In this study, the wet packing method was extended to measure the packing density of coarse aggregate and blended fine and coarse aggregate. The results revealed that whilst the packing density of coarse aggregate is only slightly higher under wet condition than dry condition, the packing density of blended fine and coarse aggregate is highly dependent on whether the aggregate is dry or wet. Hence, when measuring the packing density of blended aggregate, the wet packing method should always be used.     

Optimisation of hot mix asphalt performance based on aggregate selection

Researchers over the last four decades have identified and demonstrated the effects of aggregate morphological properties (particularly shape, size distribution, angularity and texture) on the mechanical properties of hot mix asphalt (HMA). Rare studies, however, have clearly established the relationships between the aggregate properties and pavement performance. Therefore, they have not provided methods to optimise aggregate properties at the design stage to improve that performance. This study focuses on understanding the effects of aggregate gradation and type on moisture damage resistance of HMA and on pavement performance as indicated by stiffness and rutting. Results show that basalt aggregate achieves higher moisture susceptibility resistance and stiffness than limestone aggregate. Coarser gradation has the highest permanent deformation, while open gradation 2C provides the lowest moisture damage resistance. Furthermore, dense gradation 4C provides the lowest rutting and the highest stripping resistance. It is indicated that suitable selection of aggregate type and gradation can improve pavement performance and reduce the moisture damage problem of HMA.     

Impact of particle packing mix design method on fracture properties of natural and recycled aggregate concrete

The fracture properties of four types of concrete prepared using natural coarse aggregate and recycled coarse aggregate and conventional and particle packing method (PPM) of mix design approaches are studied. The three‐point bending (TPB) test is performed using three different sizes of single edge notched beam. The fracture energy is calculated from the load‐CMOD curve obtained in the TPB test, and in this process the load‐CMOD curve is curtailed at 2% of the depth of the beam. Based on CTOD_c and w₁ relationship, appropriate softening function is used to estimate the double‐K fracture parameters. The fracture energy and fracture toughness parameters of recycled aggregate concrete (RAC) is inferior to the natural aggregate concrete (NAC). The PPM mix design improves the fracture properties of concrete in comparison to the conventional mix design approach. The fracture properties of PPM mix designed RAC are comparable to that of NAC prepared using conventional method.     

Effect of batch age on potency and dissolution of levothyroxine sodium tablets: impact of BP and USP monograph differences on dissolution results

Controversies surround levothyroxine sodium as a drug and product, and are reflected in compendia (USP vs BP) differences in levothyroxine sodium tablets specifications concerning potency limit and dissolution test conditions, and in lack of consensus on several issues such as whether the drug BCS class I or III. We have recently published a clinical study in patients comparing the efficacy of multisource 100?mcg levothyroxine sodium tablets (three sources, two brands, a total of five batches). Clinical efficacy and dissolution rate data varied among the tablet batches studied and indicated that brand/source interchangeability could not be claimed. The efficacy parameters showed good correlation with dissolution data generated under BP 2014, but not under USP 2014 dissolution test conditions. In the present study, we decided to expand the number of tablet batches studied in vitro to a total of 12, to report potency and content uniformity data missing in the clinical study, and to further examine the discrepancy in dissolution results based on the medium used. The wide range of batch age in the studied samples allowed investigating the effect of batch age on in-vitro tablet performance parameters. Generated potency values indicated the prevalence of super-potent tablet batches. The dissolution data reflected the effect of compendia monograph differences in dissolution medium. The results also indicated an inverse relationship between tablet potency and batch age and, between dissolution and batch age. The possible effect of potency results on the generated dissolution data was discussed. Statistical significance of correlations examined was assessed by linear and non-linear regression analysis. Statistical significance was evident for the relation between batch age and BP 2014 dissolution data, compared to USP 2014 dissolution results.     

An artificial neural network model for virtual Superpave asphalt mixture design

This study presents an artificial neural network (ANN) model to predict the asphalt mixture volumetrics at Superpave gyration levels. The input data-set needed by the algorithm is composed of gradation of the mix, bulk specific gravity of aggregates, low- and high-performance grade of the binder, binder content of the mix and the target number of gyrations (i.e. N_ini, N_des and N_max). The proposed ANN model uses a three-layer scaled conjugate gradient back-propagation (feed-forward) network. The ANN was trained using data obtained from numerous roads with a total of 1817 different mix designs. Results revealed that the ANN was able to predict V_a within V_a (measured) ± 1.0% range 85–93% of the time and within V_a (measured) ± 0.5% range 60–70% of the time. Currently with the developed ANN model, Superpave mix design can take approximately between 1.5 and 4.5 days, which corresponds to 3–6 days of savings.     

Effect of aggregate gradations on properties of porous friction course mixes

This paper presents the study on effect of aggregate gradation on the mix design and performance properties of porous friction course (PFC) mixes. Six aggregate gradations were tested with due consideration to gradations specified for PFC or similar mixes by different agencies around the world. The PFC mixes were characterized for volumetric properties, permeability, unaged and aged abrasion loss, moisture susceptibility, and rutting resistance. The results were statistically analysed to identify the factors that significantly influence the properties of PFC mixes. Findings of the study clearly indicate that the gradations specified by various agencies will have significant effect on the design properties of PFC mixes, thus they are different. It also, helps in framing the Master aggregate gradation band for PFC mixes. Generally, permeability property is considered to be an optional parameter in the design. However, the findings of the present study recommended considering the permeability as one of the prime parameters in the design of PFC mixes.     

The Use of Incomplete Beta Functions for Prior Distributions in Binomial Sampling

Let θ be the proportion of defectives in a batch selected at random from a fixed population of batches. The paper deals with the determination of the prior distribution of θ, using prior knowledge obtained from batches examined in the past. Assuming a beta type prior distribution, the following three situations are investigated: a. Past records provide the numbers r ₁, r ₂, …, r _N of defectives found in N samples of size n from N previously inspected batches;

b. The expected fraction defective in a batch, E(θ), and the probability, P, of a batch exceeding twice the expected fraction defective are approximately known;

c. (c) The probabilities of θ exceeding a certain value θ₁ and of θ falling below another value θ₂ are approximately known.

Methods of estimating the parameters of the prior distribution are given, and charts are provided to facilitate their determination.

The effects of errors in the parameters on the posterior distribution are discussed in relation to sample size and number of defectives found in the sample. The effects of assuming a beta distribution when in fact some other distribution would have been appropriate are found to be negligible in most practical applications.     

Gradation-based framework for asphalt mixture

Aggregates are the major component of asphalt mixtures, greatly influencing the mixtures resistance to failure. The structure that is formed by the aggregates will depend mostly on the size distribution, shape and mineral composition. Coarse aggregate have a strong influence on the resistance to rutting, while fines provide stability to the mixture. In the present study a generalized framework is developed to identify the range of aggregate sizes which form the load carrying structure in hot mix asphalt and determine its quality. The method has been developed as a numerical procedure based on packing theory. Parameters like porosity and coordination number have been used to evaluate the quality of the load carrying structure and relate it to resistance to rutting. The framework has been evaluated on several field and laboratory mixtures and related to their rutting performance. The gradation analysis of the mixtures has compared favorably with the performances reported from the field and laboratory testing. The developed gradation analysis framework has proven to be a tool to identify those mixtures with a poor rutting performance based on the gradation of the aggregates.     

Single machine batch scheduling with sequential job processing

The problem of scheduling n jobs on a single machine in batches to minimize some regular cost functions is studied. Jobs within each batch are processed sequentially so that the processing time of a batch is equal to the sum of the processing times of the jobs contained in it. Jobs in the same batch are completed at the same time when the last job of the batch has finished its processing. A constant set-up time precedes the processing of each batch. The number of jobs in each batch is bounded by some value b. If b < n, then the problem is called bounded. Otherwise, it is unbounded. For both the bounded and unbounded problems, dynamic programming algorithms are presented for minimizing the maximum lateness, the number of late jobs, the total tardiness, the total weighted completion time, and the total weighted tardiness when all due dates are equal, which are polynomial if there is a fixed number of distinct due dates or processing times. More efficient algorithms are derived for some special cases of both the bounded and unbounded problems in which all due dates and/or processing times are equal. Several special cases of the bounded problem are shown to be NP-hard. Thus, a comprehensive classification of the computational complexities of the special cases is provided.     

The burn-in test scheduling problem with batch dependent processing time and sequence dependent setup time

The burn-in test scheduling problem (BTSP) is a variation of the complex batch processing machine scheduling problem, which is also a generalisation of the liquid crystal injection scheduling problem with incompatible product families and classical identical parallel machine problem. In the case we investigated on the BTSP, the jobs are clustered by their product families. The product families can be clustered by different product groups. In the same product group, jobs with different product families can be processed as a batch. The batch processing time is dependent on the longest processing time of those jobs in that batch. Setup times between two consecutive batches of different product groups on the same batch machine are sequentially dependent. In addition, the unequal ready times are considered in the BTSP which involves the decisions of batch formation and batch scheduling in order to minimise the total machine workload without violating due dates and the limited machine capacity restrictions. Since the BTSP involves constraints on unequal ready time, batch dependent processing time, and sequence dependent setup times, it is more difficult to solve than the classical parallel batch processing machine scheduling problem with compatible product families or incompatible product families. These restrictions mean that the existing methods cannot be applied into real-world factories directly. Consequently, this paper proposes a mixed integer programming model to solve the BTSP exactly. In addition, two efficient solution procedures which solve the BTSP are also presented.     

Investigation of asphalt concrete rutting mechanisms by X-ray computed tomography imaging and micromechanical finite element modeling

This paper systematically investigates the changes in asphalt concrete (AC) microstructure caused by full-scale accelerated pavement testing with a heavy vehicle simulator (HVS), using X-ray computed tomography images taken before and after HVS rutting tests. A viscoelastic micromechanical finite element modeling was also used to investigate effects of bitumen mastic and aggregate skeleton properties on shear resistance. The primary purpose was to determine the reasons behind the earlier failure of the rubberized gap graded AC mix used in the test compared to the polymer modified dense graded mix also included in the experiment. Shear related deformation appears to control the long term rutting performance of the test sections while densification was primarily an initial contributor at the very early stages of trafficking. A high concentration of aggregate interlock in the polymer modified mix, as a result of the dense gradation and larger aggregate sizes, appears to have resulted in greater dissipation of shear stresses and therefore greater shear resistance. The lack of this interlocking effect for the rubberized gap graded mix is proposed to have caused the earlier failure on HVS test sections.     

Minimising makespan on parallel batch processing machines with non-identical ready time and arbitrary job sizes

This paper considers the parallel batch processing machine scheduling problem which involves the constraints of unequal ready times, non-identical job sizes, and batch dependent processing times in order to sequence batches on identical parallel batch processing machines with capacity restrictions. This scheduling problem is a practical generalisation of the classical parallel batch processing machine scheduling problem, which has many real-world applications, particularly, in the aging test operation of the module assembly stage in the manufacture of thin film transistor liquid crystal displays (TFT-LCD). The objective of this paper is to seek a schedule with a minimum total completion time for the parallel batch processing machine scheduling problem. A mixed integer linear programming (MILP) model is proposed to optimise the scheduling problem. In addition, to solve the MILP model more efficiently, an effective compound algorithm is proposed to determine the number of batches and to apply this number as one parameter in the MILP model in order to reduce the complexity of the problem. Finally, three efficient heuristic algorithms for solving the large-scale parallel batch processing machine scheduling problem are also provided.     

Discrete deterministic and stochastic blending problems with two quality characteristics: aluminum blending

This research is motivated by the problem of assigning the output of electrolytic cells to oven batches in the production of aluminum, so as to maximize the expected revenue. Cell output cannot be split between batches, and the batch sizes are constrained. Each batch is classified into a revenue category based on the levels of two impurities. The impurity levels differ from cell to cell and additional random quantities of impurities are added during the oven process. We develop optimal and heuristic solution approaches for the deterministic version of the problem (known amount of impurities) and use them as the basis for a heuristic procedure for the stochastic version. Using data from a high-grade aluminum manufacturer, we demonstrate that our approach finds near-optimal solutions to the stochastic problem, with significant gains over solving deterministic versions in which the stochasticity is modeled only approximately.     

The Development of a Blend-Sampling Technique to Assess the Uniformity of a Powder Mixture

This article discusses the challenges overcome during the development of a blendsampling technique and the successful validation of the blending operation for a tablet dosage form containing 2% active ingredient. Content uniformity results are discussed for three pilot-scale (15-kg) and seven commercial-scale (150-kg) batches of tablets. Blend and core content uniformity data from the pilot-scale batches were acceptable. For the initial commercial-scale batches, although the tablet core content uniformity data were acceptable, the blend uniformity results were poor. The blend data for these batches had very high mean values, but acceptable relative standard deviations (RSDs). This suggested that the drug was being preferentially sampled by the thief, but in a consistent, reproducible manner. Extensive testing was performed on a commercial-scale development batch to identify potential causes of sampling error. The results of this testing helped define the blend-sampling technique and strategy used to validate the mixing operation.     

Monte Carlo Optimization,Simulation and Sensitivity of Queueing Networks

The degradation of a drug product over time must be studied carefully to determine the appropriate shelf-life of the product. It is desirable to use data from all batches of the drug product to estimate a common shelf-life. The current Food and Drug Administration Guideline for analyzing data from multiple batches in stability studies emphasizes hypothesis testing for assessing the equality of degradation rates among batches. We propose a definition for a meaningful difference in batch degradation rates. Furthermore, we use simultaneous confidence intervals for estimating differences in batch slopes and for making decisions about pooling data from separate batches. We believe that an estimation procedure based on simultaneous confidence intervals is philosophically and practically a better approach to this problem.     

Diagnosing batch processes with insufficient fault data: generation of pseudo batches

To ensure the safety of a batch process and the quality of its final product, one needs to quickly identify an assignable cause of a fault. Cho and Kim (2003 Cho, HW and Kim, KJ. 2003. A method for predicting future observations in the monitoring of a batch process. J. Qual. Tech, 35: 59–69.  ) recently proposed a diagnosis method for batch processes using Fisher's Discriminant Analysis (FDA), which showed a satisfactory performance on industrial batch processes. However, their method (or any other method based on empirical models) has a major limitation when the fault batches available for building an empirical diagnosis model are insufficient. This is a highly critical issue in practice because sufficient fault batches are likely to be unavailable. In this work, we propose a method to handle the insufficiency of the fault data in diagnosing batch processes. The basic idea is to generate so-called pseudo batches from known fault batches and utilise them as part of the diagnosis model data. The performance of the proposed method is demonstrated using a real data set from a PVC batch process. The proposed method is shown to be capable of handling the data insufficiency problem successfully, and yields a reliable diagnosis performance.