scholarly journals Assessing the Impact of the Lead/Lag Times on the Project Duration Estimates in Highway Construction

2021 ◽  
Vol 4 (3) ◽  
Author(s):  
Mohamed Abdel Raheem ◽  
Jennifer Reyes ◽  
Xiaohui Wang ◽  
Grecia Silva Sanchez ◽  
Alyssa Marie Garza
Keyword(s):  
Highway Construction ◽  
Total Duration ◽  
Lag Time ◽  
Soil Conditions ◽  
Sensitivity Index ◽  
Highway Projects ◽  
Project Duration ◽  
Time Sensitivity ◽  
Lag Times ◽  
The Impact

The literature mentions multiple factors that can affect the accuracy of estimating the project duration in highway construction, such as weather, location, and soil conditions. However, there are other factors that have not been explored, yet they can have significant impact on the accuracy of the project time estimate. Recently, TxDOT raised a concern regarding the importance of the proper estimating of the lead/lag times in project schedules. These lead/lag times are often determined based on the engineer’s experience. However, inaccurate estimates of the lead/lag time can result in unrealistic project durations. In order to investigate this claim, the study utilizes four time sensitivity measures (TSM), namely the Criticality Index (CI), Significance Index (SI), Cruciality Index (CRI), and the Schedule Sensitivity Index (SSI) to statistically analyze and draw conclusions regarding the impact of the lead/lag time estimates on the total duration in highway projects. An Excel-based scheduling software was developed with Monte Carlo simulation capabilities to calculate these TSM. The results from this paper show that the variability of some lead/lag times can significantly impact the accuracy of the estimated total project duration. It was concluded that the current practices used for estimating the lead/lag times are insufficient. As such, it is recommended to utilize more robust methods, such as the time sensitivity measures, to accurately estimate the lead/lad times in the projects scheduled.

Effect of change orders on rework in highway projects in Palestine

2017 ◽  
Vol 22 (1) ◽  
pp. 62-76 ◽  
Author(s):  
Ibrahim Mahamid
Keyword(s):  
Construction Projects ◽  
West Bank ◽  
Highway Construction ◽  
The West ◽  
Highway Projects ◽  
Change Orders ◽  
Content Type ◽  
Design Changes ◽  
Common Causes ◽  
The Impact

Purpose This study aims at identifying the main causes of change orders in highway construction projects, determining the factors that affect rework in highway construction projects, examining the relationship between change orders and rework and at developing a predictive model that will determine the impact of change orders on rework in highway construction projects in Palestine. Design/methodology/approach A questionnaire survey was used to identify the main change order causes and rework causes from the perspectives of contractors and consultants. The questionnaire contained 16 causes of change orders and 19 causes of rework which had been identified from the literature reviewed. The study also identifies the impact of change orders on rework based on data comprising 22 highway construction projects implemented in Palestine. Both descriptive and inferential statistics were used in analyzing the data. Findings The study concluded that the five most common causes of change orders can be identified as: change of project scope by owner (additional – enhancement), lack of coordination between construction parties; owner’s financial difficulties, change in materials, and errors and omissions in design. The study has also established that among the various factors that causes rework, non-conformance with specification requirements, scope changes, late design changes, lack of labor experience, lack of labor skills and improper subcontractor selection top the list. Using regression analysis, the results reveal a significant relationship between change orders and rework cost in highway construction projects in Palestine. Practical implications By ranking the various change orders causes and rework causes from the perspectives of consultants and contractors, the study provides a fresh perspective on an old chronic problem in the construction sector. This study has provided evidence on the most significant change orders causes and rework causes in the Palestinian highway construction, as well as the impact of change orders or rework on constructions sites. Finally, although this study is specific to the country of Palestine, its results can be applicable to other developing countries facing similar problems in their public construction sectors. Originality/value The results address the common causes of change orders and reworks in highway construction projects in Palestine. The results also address the relation between change orders and rework cost based on data collected from highway construction projects implemented in the West Bank in Palestine. This study is the first study conducted in the West Bank in Palestine to identify the change orders and reworks causes in highway construction projects.

scholarly journals The CGI121 gene from Saccharomyces cerevisiae demonstrates genetic linkage to increased lag time under enological conditions

2020 ◽  
Author(s):  
Runze Li ◽  
Rebecca C. Deed
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Low Temperatures ◽  
Genetic Linkage ◽  
Lag Time ◽  
Lag Phase ◽  
Phenotypic Traits ◽  
Phase Duration ◽  
Fermentation Kinetics ◽  
Lag Times ◽  
The Impact

Abstract Background In winemaking, it is standard practice to ferment white wines at low temperatures (10–18 ºC). However, low temperatures increase the fermentation duration and risk of problem ferments, which can lead to significant costs. The length of the lag period at fermentation initiation is one parameter that is heavily impacted by low temperatures. Therefore, the identification of Saccharomyces cerevisiae genes with an impact on fermentation kinetics, such as lag time, is of interest for winemaking. Results We selected a set of 28 S. cerevisiae BY4743 single deletants based on a prior list of candidate open reading frames (ORFs) mapped to quantitative trait loci (QTLs) on chromosomes VII and XIII influencing the duration of fermentative lag time by bulk segregant analysis. Five out of 28 BY4743 deletants, Δapt1, Δcgi121, Δclb6, Δrps17a, and Δvma21, differed significantly in their fermentative lag phase duration compared to BY4743 in synthetic grape medium (SGM) at 15 ºC, over 72 h. Fermentation at 12.5 ºC for 528 h, to show a greater resolution of the lag times, identified the inability of BY4743 Δapt1 to initiate fermentation and confirmed the significantly longer lag times of the BY4743 Δcgi121, Δrps17a, and Δvma21 deletants. The three candidate ORFs were deleted in S. cerevisiae RM11-1a and S288C to perform single reciprocal hemizygosity analysis (RHA). RHA hybrids and single deletants of RM11-1a and S288C were fermented at 12.5 ºC in SGM. Lag time measurements confirmed genetic linkage of CGI121 on chromosome XIII, encoding a component of the EKC/KEOPS complex, to fermentative lag phase. Nucleotide sequences of RM11-1a and S288C CGI121 alleles differed by only one synonymous nucleotide suggesting that codon bias or positional effects might be responsible for the impact of this gene on lag phase duration. Conclusion This research demonstrates a new role of CGI121 in fermentative lag time in S. cerevisiae during fermentation and highlights the applicability of QTL analysis for investigating complex phenotypic traits in yeast, such as fermentation kinetics.

scholarly journals Influence of Stress on Single-Cell Lag Time and Growth Probability for Listeria monocytogenes in Half Fraser Broth

2009 ◽  
Vol 75 (10) ◽  
pp. 3069-3076 ◽  
Author(s):  
Claire Dupont ◽  
Jean-Christophe Augustin
Keyword(s):  
Listeria Monocytogenes ◽  
Single Cell ◽  
Physiological State ◽  
False Negative ◽  
Lag Time ◽  
Enrichment Broth ◽  
A Cell ◽  
Lag Times ◽  
The Impact ◽  
Growth Probability

ABSTRACT The impacts of 12 common food industry stresses on the single-cell growth probability and single-cell lag time distribution of Listeria monocytogenes were determined in half Fraser broth, the primary enrichment broth of the International Organization for Standardization detection method. First, it was determined that the ability of a cell to multiply in half Fraser broth is conditioned by its history (the probability for a cell to multiply can be decreased to 0.05), meaning that, depending on the stress in question, the risk of false-negative samples can be very high. Second, it was established that when cells are injured, the single-cell lag times increase in mean and in variability and that this increase represents a true risk of not reaching the detection threshold of the method in the enrichment broth. No relationship was observed between the impact on single-cell lag times and that on growth probabilities. These results emphasize the importance of taking into account the physiological state of the cells when evaluating the performance of methods to detect pathogens in food.

The methodological approach for the determination of the pressure of artificial raindrops as a question of the theory of splash soil erosion

2020 ◽  
pp. 24-28
Author(s):  
Mihail Zver'kov
Keyword(s):  
Block Diagram ◽  
Methodological Approach ◽  
Control Measures ◽  
Soil Conditions ◽  
Effective Pressure ◽  
Long Distance ◽  
Splash Erosion ◽  
Rain Drops ◽  
Artificial Rain ◽  
The Impact

To the article the results of the theoretical and experimental researches are given on questions of estimates of the dynamic rate effect of raindrop impact on soil. The aim of this work was to analyze the current methods to determine the rate of artificial rain pressure on the soil for the assessment of splash erosion. There are the developed author’s method for calculation the pressure of artificial rain on the soil and the assessment of splash erosion. The study aims to the justification of evaluation methods and the obtaining of quantitative characteristics, prevention and elimination of accelerated (anthropogenic) erosion, the creation and the realization of the required erosion control measures. The paper considers the question of determining the pressure of artificial rain on the soil. At the moment of raindrops impact, there is the tension in the soil, which is called vertical effective pressure. It is noted that the impact of rain drops in the soil there are stresses called vertical effective pressure. The equation for calculation of vertical effective pressure is proposed in this study using the known spectrum of raindrops. Effective pressure was 1.4 Pa for the artificial rain by sprinkler machine «Fregat» and 5.9 Pa for long distance sprinkler DD-30. The article deals with a block diagram of the sequence for determining the effective pressure of rain drops on the soil. This diagram was created by the author’s method of calculation of the effective pressure of rain drops on the soil. The need for an integrated approach to the description of the artificial rain impact on the soil is noted. Various parameters characterizing drop erosion are considered. There are data about the mass of splashed soil in the irrigation of various irrigation machinery and installations. For example, the rate (mass) of splashed soil was 0.28…0.78 t/ha under irrigation sprinkler apparatus RACO 4260–55/701C in the conditions of the Ryazan region. The method allows examining the environmental impact of sprinkler techniques for analyzes of the pressure, caused by raindrops, on the soil. It can also be useful in determining the irrigation rate before the runoff for different types of sprinkler equipment and soil conditions.

Studies on Related ms Magnitude Rate Models in Triangular Wave Unloading Section of Calcium Medium-Fine Sandstone

2010 ◽  
Vol 152-153 ◽  
pp. 164-170
Author(s):  
Jie Liu ◽  
Jian Lin Li ◽  
Ying Xia Li ◽  
Shan Shan Yang ◽  
Ji Fang Zhou ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Strain Curve ◽  
Experimental System ◽  
Constant Term ◽  
Lag Time ◽  
Vertical Force ◽  
Time Segment ◽  
Triangular Wave ◽  
Apparent Modulus ◽  
The Impact

Specific to the improvement in the present research of mechanical response under cyclic loading, this paper, taking the calcareous middle- coarse sandstone as the research subject and the RMT-150C experimental system in which data is recoded by ms magnitude as the platform, develops several related models concerning the unloading rate of triangle waves. The unloading process is divided into lag time segment and non-lag time segment, with criterions and related parameters provided as well. The term apparent elastic modulus is defined. The test data analysis shows that there exist a linear relationship between the apparent modulus and instant vertical force before load damage in non-lag time segment. On the preceding basis, a rate-dependent model of triangular wave un-installation section in non-lag time segment is established. Due to the inability of the loading equipment to accurately input the triangle wave, the average loading rate is amended and a constant term is added into it. The model is proved to be reliable, as the predicted value of the deformation rate and the stress strain curve coincides with measured value. At the same time, the impact of the lag time is pointed out quantitatively and a predication model of lag time segment is set up.

scholarly journals Reciprocal hemizygosity analysis reveals that the Saccharomyces cerevisiae CGI121 gene affects lag time duration in synthetic grape must

2021 ◽  
Author(s):  
Runze Li ◽  
Rebecca C Deed
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Low Temperatures ◽  
Lag Time ◽  
Lag Phase ◽  
Phenotypic Traits ◽  
Time Duration ◽  
Phase Duration ◽  
Grape Must ◽  
The Impact ◽  
Reciprocal Hemizygosity Analysis

Abstract It is standard practice to ferment white wines at low temperatures (10-18 °C). However, low temperatures increase fermentation duration and risk of problem ferments, leading to significant costs. The lag duration at fermentation initiation is heavily impacted by temperature; therefore, identification of Saccharomyces cerevisiae genes influencing fermentation kinetics is of interest for winemaking. We selected 28 S. cerevisiae BY4743 single deletants, from a prior list of open reading frames (ORFs) mapped to quantitative trait loci (QTLs) on chromosomes VII and XIII, influencing the duration of fermentative lag time. Five BY4743 deletants, Δapt1, Δcgi121, Δclb6, Δrps17a, and Δvma21, differed significantly in their fermentative lag duration compared to BY4743 in synthetic grape must (SGM) at 15 °C, over 72 h. Fermentation at 12.5 °C for 528 h confirmed the longer lag times of BY4743 Δcgi121, Δrps17a, and Δvma21. These three candidate ORFs were deleted in S. cerevisiae RM11-1a and S288C to perform single reciprocal hemizygosity analysis (RHA). RHA hybrids and single deletants of RM11-1a and S288C were fermented at 12.5 °C in SGM and lag time measurements confirmed that the S288C allele of CGI121 on chromosome XIII, encoding a component of the EKC/KEOPS complex, increased fermentative lag phase duration. Nucleotide sequences of RM11-1a and S288C CGI121 alleles differed by only one synonymous nucleotide, suggesting that intron splicing, codon bias, or positional effects might be responsible for the impact on lag phase duration. This research demonstrates a new role of CGI121 and highlights the applicability of QTL analysis for investigating complex phenotypic traits in yeast.

scholarly journals The implications of lag times between nitrate leaching losses and riverine loads for water quality policy

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. W. McDowell ◽  
Z. P. Simpson ◽  
A. G. Ausseil ◽  
Z. Etheridge ◽  
R. Law
Keyword(s):  
Water Quality ◽  
Mean Transit Time ◽  
Lag Time ◽  
Practice Change ◽  
N Leaching ◽  
N Losses ◽  
Leaching Losses ◽  
Nitrate N ◽  
The Mean ◽  
Lag Times

AbstractUnderstanding the lag time between land management and impacts on riverine nitrate–nitrogen (N) loads is critical to understand when action to mitigate nitrate–N leaching losses from the soil profile may start improving water quality. These lags occur due to leaching of nitrate–N through the subsurface (soil and groundwater). Actions to mitigate nitrate–N losses have been mandated in New Zealand policy to start showing improvements in water quality within five years. We estimated annual rates of nitrate–N leaching and annual nitrate–N loads for 77 river catchments from 1990 to 2018. Lag times between these losses and riverine loads were determined for 34 catchments but could not be determined in other catchments because they exhibited little change in nitrate–N leaching losses or loads. Lag times varied from 1 to 12 years according to factors like catchment size (Strahler stream order and altitude) and slope. For eight catchments where additional isotope and modelling data were available, the mean transit time for surface water at baseflow to pass through the catchment was on average 2.1 years less than, and never greater than, the mean lag time for nitrate–N, inferring our lag time estimates were robust. The median lag time for nitrate–N across the 34 catchments was 4.5 years, meaning that nearly half of these catchments wouldn’t exhibit decreases in nitrate–N because of practice change within the five years outlined in policy.

scholarly journals Imaging NAD(H) Redox Alterations in Cryopreserved Alveolar Macrophages from Ozone-Exposed Mice and the Impact of Nutrient Starvation during Long Lag Times

Antioxidants ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 767
Author(s):  
He N. Xu ◽  
Joanna Floros ◽  
Lin Z. Li ◽  
Shaili Amatya
Keyword(s):  
Oxidative Stress ◽  
Alveolar Macrophages ◽  
Redox State ◽  
Redox Status ◽  
Nutrient Starvation ◽  
Ozone Exposure ◽  
Reduced Form ◽  
Time Period ◽  
Lag Times ◽  
The Impact

Employing the optical redox imaging technique, we previously identified a significant redox shift of nicotinamide adenine dinucleotide (NAD and the reduced form NADH) in freshly isolated alveolar macrophages (AM) from ozone-exposed mice. The goal here was twofold: (a) to determine the NAD(H) redox shift in cryopreserved AM isolated from ozone-exposed mice and (b) to investigate whether there is a difference in the redox status between cryopreserved and freshly isolated AM. We found: (i) AM from ozone-exposed mice were in a more oxidized redox state compared to that from filtered air (FA)-exposed mice, consistent with the results obtained from freshly isolated mouse AM; (ii) under FA exposure, there was no significant NAD(H) redox difference between fresh AM that had been placed on ice for 2.5 h and cryopreserved AM; however, under ozone exposure, fresh AM were more oxidized than cryopreserved AM; (iii) via the use of nutrient starvation and replenishment and H2O2-induced oxidative stress of an AM cell line, we showed that this redox difference between cryopreserved and freshly isolated AM is likely the result of the double “hit”, i.e., the ozone-induced oxidative stress plus nutrient starvation that prevented freshly isolated AM from a full recovery after being on ice for a prolonged time period. The cryopreservation technique we developed eliminates/minimizes the effects of oxidative stress and nutrient starvation on cells. This method can be adopted to preserve lung macrophages from animal models or clinical patients for further investigations.

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