Delay Hierarchy Propagation Model

Construction projects are always exposed to delay. Research has shown that most projects encounter delays and this problem is a global one. Previous research related to delays in construction projects have been dedicated to measuring and ranking the direct delays that have occurred. These types of delay are past delays and have already affected many aspects of the project's performance. This type of research is of the reactive type and handles delays after they have happened. The objective of this research is to model the construction project delays that can be used to predict the level of delays that the project could face during its future life. The proposed Delay Hierarchy Propagation Model (DHPM) is the first attempt to model delays in the construction project. This model is an innovative predictive approach to anticipate the future encountered delays before they become real. The model assumes that the direct delay is generated from earlier events or aspects that are found before the direct delay occurs; these events are called the root delay causes. These root delay causes need to be analysed, measured and managed in order to prevent or mitigate the effect of a later direct delay in the project life. The direct delays were analysed by a cause-effect technique to extract a set of root delay causes. The model assumes that the root delay causes will influence the project resources supply rate. The resource shortage then leads to activity delay and, hence possible delay to the whole project. The DHPM consists of two interrelated models: a Resource Shortage Possibility (RSP) model and the Predicting Project Delay model (PPD) model. The RSP model objective is to predict the possibility of resource shortage, whilst the PPD model objectives are to predict the project finish time and to define the critical areas for the project to delay using the output of the RSP model as input. The RSP model was verified through interview questionnaires with a number of selected personnel from the construction industry. The Delphi method was used to enhance the questionnaire results. The RSP model calculations used a combination of fuzzy logic, analytical hierarchy process (AHP) and multi-attribute theory to obtain the model output. A prototype computer program was introduced. The prototype computer program was then tested on a real construction project. The application of the RSP model showed that it is viable. The PPD model used probabilistic networking to predict the finish time of the project. The model introduced two new terms that can be used to define the most critical activities and the possible resource influence to delay. The comparison between PPD and the classical critical path method (CPM), programme evaluation and review technique (PERT) and Monte Carlo simulation revealed that the proposed model provides new information required to enhance delay management by project management staff

Mode I stress intensity factor with various crack types

Presence of cracks in mechanical components needs much attention, where the stress field is affected by cracks and the propagation of cracks may be occurred causing the damage. The objective of this paper is to present an investigation of crack type effect on crack severity in a finite plate. Three cases of cracked plate with three different types of cracks are assumed in this work, i.e., single edge crack, center crack and double edge crack. 2D numerical models of cases of cracked plate are established in finite element analysis (FEA), ANSYS software by adopting PLANE 183 element. Values of FEA mode I stress intensity factor SIF and Von-Mises stress at crack apex are determined for cases of cracked plate under tensile stress with different values. To identify the crack severity, the comparison of FEA results for different cracked cases is made. The comparison showed that, single edge cracked plate (SECP) has the maximum values of mode I SIF and Von-Mises stress at crack apex, i.e. the greatest crack severity is considered. Also, values of FEA Von-Mises stress at crack apex for center cracked plate (CCP) are moderate and for double edge cracked plate (DECP) are the minimum. Besides, in case of high crack lengths, it is found that, FEA results of mode I SIF in case of (CCP) are higher than those of in case of (DECP). Consequently, crack severity is considered as moderate in case of (CCP) and the minimum in case of (DECP). Empirical formulas are used to approximately estimate mode I SIF for all the case studies of cracked plate in this study and the results are compared to those of FEA. A good agreement between analytical and FEA results has been showed by this comparison

Damage severity for cracked simply supported beams

This paper investigated the static and dynamic behaviors of isotropic cracked simply supported beam using finite element analysis (FEA), ANSYS software. Modal and harmonic vibration analysis of intact and damaged beam were performed in order to extract mode shapes of bending vibration, natural frequencies and obtain frequency response diagram. Static finite element analysis of undamaged and damaged simply supported beam was carried out to determine zero frequency deflection, then stiffness of intact and cracked beam was computed using conventional formula. Crack damage severity of damaged beam was calculated and it is noticed that as crack position is increased from left hand support of beam up to central point and crack depth is increased, then crack damage severity increases. The effect of mode shape pattern is investigated and it is found that the amount of decreasing of natural frequency is proportional to the normalized mode shape at position of crack. The exhibited correlation between results for damaged beam revealed that crack damage severity is proportional to zero frequency deflection and inversely proportional to first mode frequency

BIM Based Facility Condition Assessment

Current practices of using traditional methods of managing data using spreadsheets or hard paper copies for various building data, are commonly being used during building inspection and condition assessment. Building Information Modelling (BIM) can immensely help in solving problems of facility inspection by generating and managing digital representation of the physical and functional characteristics of a facility. This paper describes a model, which is developed to integrate the physical and environmental conditions of a facility on a BIM platform. In this study, factors influencing physical condition and environment condition of the building were identified. Building defects which causes physical deterioration of the building component reduces the ability to perform its intended designed function while environmental condition influences the comfort and health of occupants or users of the building. It is imperative to understand that physical and environment condition of the building are both of vital importance for safety, health and comfort of building users. Factors affecting physical and environment of building were used to develop proposed condition assessment model. Using this proposed model periodic general condition assessment can be performed and correspondingly deterioration graph can be generated for the facility over period of time. Based on inspection data and condition assessment models, building performance can be analyzed for future preventive maintenance

Co-presentation of Posterior Reversible Encephalopathy Syndrome in a patient with Post Dural Puncture Headache

INTRODUCTION: Post Dural Puncture Headache (PDPH) is a well-known complication of neuraxial anesthesia, however the occurrence of seizures and vision loss within few days after dural puncture could be alarming. Posterior Reversible Encephalopathy Syndrome (PRES) is associated with reversible edema and leukoencephalopathy in the posterior parieto-occipital cortex. We report the co-presentation of PRES and PDPH after labor epidural analgesia. CASE PRESENTATION: 25-year-old multiparous African-American woman was admitted for evaluation of new onset seizures and headache in the postpartum period. She had a recent history of multiple needle insertion attempts and inadvertent dural puncture during epidural analgesia for delivery. Soon after delivery, she was diagnosed with PDPH and was treated with epidural blood patch, with no relief of symptoms. Six days later, she developed sudden onset transient blindness, seizures and altered sensorium and magnetic resonance imaging (MRI) of the brain revealed white matter changes suggestive of PRES. CONCLUSION: PRES is an uncommon complication of cerebrospinal fluid (CSF) leak and intracranial hypotension. We report the occurrence of PRES in a patient with no known risk factors, except a traumatic dural tap. Is it important to expand the differentials for headache after dural puncture to encompass PRES as a possibility, especially in patients with a delayed presentation of seizures and cortical blindness

Harmonic Distortion Reduction of Transformer-Less Grid-Connected Converters by Ellipsoidal-Based Robust Control

A photovoltaic generator connected to a large network and supplying a nonlinear load (source of harmonics) injects distorted current into the grid. This manuscript presents an invariant-ellipsoid set design of a robust controlled active power filter to inject current into the large grid with minimum total harmonic distortion (THD). The nonlinear load current is considered an external disturbance to minimize its effect on the injected grid current. Moreover, the large grid is modeled as a fixed voltage source in a series with a Thevenin impedance whose value changes within an interval. Using the invariant-ellipsoid technique, the problem is cast as a robust disturbance-rejection tracking control. The volume of the ellipsoid is minimized, which results in minimizing the effect of disturbance on system performance and keeping the trajectories as close as possible to the origin. The design is cast into a set of nonlinear matrix inequalities that are linearized by fixing a scalar. The resulting convex optimization is solved iteratively by linear matrix inequalities (LMIs). The simulation and experimental findings show that the proposed design is successful in reducing THD injected into the grid when grid impedance is uncertain and variable loads are applied (balanced and unbalanced cases)

Mechanical Characterization of Cryomilled Al Powder Consolidated by High-Frequency Induction Heat Sintering

In the present investigation, an aluminum powder of 99.7% purity with particle size of ~45 µm was cryomilled for 7 hours. The produced powder as characterized by scanning, transmission electron microscopy, and X-ray diffraction gave a particle size of ~1 µm and grain (crystallite) size of 23±6 nm. This powder, after degassing process, was consolidated using high-frequency induction heat sintering (HFIHS) at various temperatures for short periods of time of 1 to 3 minutes. The present sintering conditions resulted in solid compact with nanoscale grain size (<100 nm) and high compact density. The mechanical properties of a sample sintered at 773 K for 3 minutes gave a compressive yield and ultimate strength of 270 and 390 MPa, respectively. The thermal stability of grain size nanostructured compacts is in agreement with the kinetics models based on the thermodynamics effects

May Coronary Artery Bypass Grafting Affect Native Coronary Atherosclerosis progression?

Background: Coronary artery bypass grafting (CABG) continues to be the best standard in the management of severe coronary artery disease (CAD), providing good symptom management and life extension. Although CABG was first performed by reversed saphenous veins (SVGs), surgeons have increasingly adopted arterial conduits because of their longer-term patency and resistance to atherosclerosis. CABG's efficacy may potentially be affected by the extension of atherosclerosis in the native coronary arteries. Few researches have investigated the long-term angiographic disease progression of native coronary arteries after surgical revascularization, or the variables that may impact this progression. Proximal native disease progression was presented to be two to six times more common than distal disease progression, with greater rates of progression in coronaries bypassed by SVGs than arterial grafts. The goal of this research was to determine influence of CABG on the extension of native coronaries atherosclerosis. Methods: This prospective study was established on 25 patients who were diagnosed to have ischemic heart disease in cardiothoracic surgery department in Faculty of Medicine Menoufia University. Results: The study showed that according to the risk factors among the studied cases, smoking was (60%), Dyslipidemia was (32%), HTN was (32%) and Diabetes was (32). According to grafts in proximal lesions, there was progression of atherosclerosis up to total occlusion, but in Distal lesions, there was significant regression of atherosclerosis. As result, there was statistically significant difference between proximal with distal lesions. Also, study showed that there was a significant difference between left system (LAD, D, OM) in comparison with right system (PDA) regarding distal lesion. Our results showed that univariate logistic regression analysis for progression in distal lesion regarding Dyslipidemia and Diabetes. Conclusion: Progression of disease is more evident in coronary segment proximal to anastomosis, while regression of disease is more evident in coronary segment distal to anastomosis with statistically significant difference between them, also the risk of disease progression post CABG was found to be multifactorial, as certain risk factors can affect progression of the disease as Diabetes mellitus and dyslipidemia that were of statistically significance

Haematological abnormalities and risk of covid-19 infection in adult patients attending primary healthcare settings

Centres for Disease Control and prevention (CDC) reports that there are limited data and information about the impact of underlying medical conditions and the risk of infection. To date, there are no studies that report on the risk of infection among patients with haematological diseases or abnormalities. This cross-sectional study reports on the baseline complete blood count in patients attending publicly funded primary care settings with a diagnosis of suspected COVID-19 infections in the state of Qatar. The study will report on the descriptive characteristics of the population, including gender, age and prior abnormalities to their blood test results. We will compare the results of those with positive and negative PCR test results, where appropriate. Nine hundred sixty-two adult patients attended publicly funded primary health care settings in the state of Qatar between February the 10th and April the 30th 2020 with a diagnosis of suspected COVID-19 infections had prior recorded blood investigations in the last six months and were included in this study. The population was young, mean of age is 38.8±11.6. (Median: 36 [Min: 19-Max: 85]). Complete blood count of the sample had minimal missing data points. Females were more presented in our samples, Female (n=560, 58.21%) and Male (n=402, 41.79%). Most of our sample had a documented PCR test result, negative (n=831, 86.38%); positive (n=123, 12.79%) and missing (n=8, 0.83%). Low haemoglobin values (n=265, 27.5%) and low red blood cell count (n =170, 17.7%) were the most prevalent complete blood count abnormality in the population. Leukopenia was less common (n=50, 8.2%). Most of the population had normal platelet count (n=895, 93%). Gender was the most influential factor in our sample to increase the odds of having a positive PCR test Non-results; males were more likely to be affected (P<0.001, Chi-square test) (OR 2.56, 95% CI 1.73-3.77). Categories for haematological abnormalities were not associated with increased risk of having a positive PCT test result. In a population attending primary healthcare settings with early presentation of symptoms of COVID-19 infection, the risk of infection among our cohort was not affected by the prior haematological values of those patients. Gender was the most influential parameter in the risk of infection in our population. Analysis of the results using gender-specific categories for different haematological parameters suggested that patients with abnormal haematological values were not at increased risk of having a positive COVID-19 infection

The Cleveland Clinic Experience with Supraclavicular and Popliteal Ambulatory Nerve Catheters

Continuous peripheral nerve blocks (CPNB) are commonly used for intraoperative and postoperative analgesia. Our study aimed at describing our experience with ambulatory peripheral nerve catheters. After Institutional Review Board approval, records for all patients discharged with supraclavicular or popliteal catheters between January 1, 2009 and December 31, 2011 were reviewed. A licensed practitioner provided verbal and written instructions to the patients prior to discharge. Daily follow-up phone calls were conducted. Patients either removed their catheters at home with real-time simultaneous telephone guidance by a member of the Acute Pain Service or had them removed by the surgeon during a regular office visit. The primary outcome of this analysis was the incidence of complications, categorized as pharmacologic, infectious, or other. The secondary outcome measure was the average daily pain score. Our study included a total of 1059 patients with ambulatory catheters (769 supraclavicular, 290 popliteal). The median infusion duration was 5 days for both groups. Forty-two possible complications were identified: 13 infectious, 23 pharmacologic, and 6 labeled as other. Two patients had retained catheters, 2 had catheter leakage, and 2 had shortness of breath. Our study showed that prolonged use of ambulatory catheters for a median period of 5 days did not lead to an increased incidence of complications