Increase In Coefficient Of Variation Research Articles

Evaluating Lean Combustion Cycle Stability and Emissions in Spark Ignition Engines with Gasoline, Ethanol, and Methanol Blends

Abstract Fuels for vehicles account for a large portion of the world’s total energy demand, which in turn leads to increased carbon emissions. Ethanol and methanol are a fuel with a simple carbon chain and OH- bonds. It has similar properties to gasoline, and ethanol can be made from the fermentation of plant carbohydrates, called bioethanol. The advantage of using bioethanol is that it contributes to carbon neutrality. This paper will investigate the use of three manually blended gasoline ethanol and methanol (GEM) fuels in a spark ignition engine to address cycle-to-cycle variation (CCV), knock potential, and emissions with lean blend conditions. In the experiments conducted, the air-fuel ratio was conditioned lean by utilizing an electronic control unit to adjust the injector spray duration. This experiment provides results that there is a potential for mild knocking on the use of alcohol fuel with lean fuel mixture conditions at engine speed 4000 RPM, while at engine speed 6000 RPM and 8000 RPM the use of GEM tends to be stable, but in the CCV results the increase in COV (coefficient of variation) value using GEM fuel tends to be more sloping, especially with the addition of more methanol. Emission results from the use of GEM produce top emission CO2 value obtained by the E5M15 mixture at λ=1.2 and an engine speed of 8000 RPM, with a value of 13.75% and then peak CO2 emissions at a value of λ = 1.2 whereas in the use of pure gasoline peak CO2 is at a value of λ = 1.1.

Characterization of the genesis and spatial variability in tectonic fractures in the Gaosong ore field (South China).

This study examines fractures in the Gaosong ore field to determine the main factors affecting the spatial variability in the fracture structure. The attributes of fractures, including the fracture orientation, intensity and intersection density, in the Wuzishan anticline and near the Lotus mountain fault in the Gaosong ore field in the GeJiu ore district were extracted by using a modified circular scanning line method. The fracture intensity and intersection density were analyzed based on the semivariance geostatistics function by using the volume of variation and the amount of relative variability. These parameters quantitatively describe the spatial variability in the fracture structure. The mean and standard variance of fracture intensity and intersection density in the ore field decrease with distance from the Lotus mountain fault, while the coefficient of variation increases. The spatial anisotropy is closely related to the axial direction of the Wuzishan anticline and the orientation of the Lotus mountain fault. The main factors affecting the spatial variability in the fault structure can be determined with the semivariance geostatistics function, and the results are useful for studying the geology of the mining area and can help to construct an accurate structural model to serve the needs of mine production.

Serum Glucose Variability Increases the Risk of Complications Following Aseptic Revision Hip and Knee Arthroplasty.

Increased serum glucose variability has been proposed as a risk factor for perioperative morbidity and mortality. Given the greater surgical complexity and complication risk of revision total joint arthroplasty (TJA), previous findings may not be generalizable to the revision population. The purpose of this study was to investigate the association between glucose variability and postoperative complications following aseptic revision TJA. We identified 1,983 patients who underwent an aseptic revision TJA (636 total knee arthroplasties [TKAs] and 1,347 total hip arthroplasties [THAs]) from 2001 to 2019. Patients with ≥2 postoperative glucose values per day or ≥3 values during hospitalization were included in this study. Glucose variability was assessed using the coefficient of variation (COV). Outcomes included length of hospital stay, 90-day complications, mortality, and periprosthetic joint infection (PJI) as defined by the 2018 International Consensus Meeting criteria. Multivariate regression was used to determine the association between glucose variability and each end point, using COV as continuous and categorical variables (that is, COV tertiles). Patients with high glycemic variability were at 1.7 times greater risk for 90-day complications (odds ratio [OR], 1.664 [95% confidence interval (CI), 1.266 to 2.188]; p < 0.001) and 2 times greater risk for PJI at a minimum 1-year follow-up (OR, 1.984 [95% CI, 1.270 to 3.100]; p = 0.003). The risk of 90-day complications increased by 2.2% (OR, 1.022 [95% CI, 1.012 to 1.032]; p < 0.001) and the risk of PJI increased by 1.8% (OR, 1.018 [95% CI, 1.003 to 1.034]; p = 0.013) for every percentage-point increase in COV. Patients with higher glucose variability also had a longer length of stay (beta, 1.028 days [95% CI, 0.590 to 1.466 days]; p < 0.001). These associations were independent of age, sex, body mass index, Charlson Comorbidity Index, involved joint, operative time, history of diabetes, and mean glucose levels. Higher glucose variability was associated with an increased risk of medical complications and PJI following aseptic revision TJA. Patients undergoing these complex procedures should have glucose levels monitored closely in the perioperative period. Future studies should evaluate the utility of continuous glucose monitoring in this high-risk population. Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Compensating Positron Range Effects of Ga-68 in Preclinical PET Imaging by Using Convolutional Neural Network: A Monte Carlo Simulation Study.

This study aimed to investigate the feasibility of positron range correction based on three different convolutional neural network (CNN) models in preclinical PET imaging of Ga-68. The first model (CNN1) was originally designed for super-resolution recovery, while the second model (CNN2) and the third model (CNN3) were originally designed for pseudo CT synthesis from MRI. A preclinical PET scanner and 30 phantom configurations were modeled in Monte Carlo simulations, where each phantom configuration was simulated twice, once for Ga-68 (CNN input images) and once for back-to-back 511-keV gamma rays (CNN output images) with a 20 min emission scan duration. The Euclidean distance was used as the loss function to minimize the difference between CNN input and output images. According to our results, CNN3 outperformed CNN1 and CNN2 qualitatively and quantitatively. With regard to qualitative observation, it was found that boundaries in Ga-68 images became sharper after correction. As for quantitative analysis, the recovery coefficient (RC) and spill-over ratio (SOR) were increased after correction, while no substantial increase in coefficient of variation of RC (CVRC) or coefficient of variation of SOR (CVSOR) was observed. Overall, CNN3 should be a good candidate architecture for positron range correction in Ga-68 preclinical PET imaging.

Repeatability and reproducibility of apparent diffusion coefficient and fat fraction measurement of focal myeloma lesions on whole body magnetic resonance imaging.

Objective:To assess intra- and inter-reader variability of apparent diffusion coefficient (ADC) and fat fraction (FF) measurement in focal myeloma bone lesions and the influence of lesion size.Methods:22 myeloma patients with focal active disease on whole body MRI were included. Two readers outlined a small (5–10 mm) and large lesion (>10 mm) in each subject on derived ADC and FF maps; one reader performed this twice. Intra- and inter-reader agreement for small and large lesion groups were calculated for derived statistics from each map using within-subject standard deviation, coefficient of variation, interclass correlation coefficient measures, and visualized with Bland–Altman plots.Results:For mean ADC, intra- and inter-reader repeatability demonstrated equivalently low coefficient of variation (3.0–3.6%) and excellent interclass correlation coefficient (0.975–0.982) for both small and large lesions. For mean FF, intra- and inter-reader repeatability was significantly poorer for small lesions compared to large lesions (intra-reader within-subject standard variation estimate is 2.7 times higher for small lesions than large lesions (p = 0.0071), and for inter-reader variations is 3.8 times higher (p = 0.0070)).Conclusion:There is excellent intra- and inter-reader agreement for mean ADC estimates, even for lesions as small as 5 mm. For FF measurements, there is a significant increase in coefficient of variation for smaller lesions, suggesting lesions >10 mm should be selected for lesion FF measurement.Advances in knowledge:ADC measurements of focal myeloma have excellent intra- and inter-reader agreement. FF measurements are more susceptible to lesion size as intra- and inter-reader agreement is significantly impaired in lesions less than 10 mm.

Evaluation of changes in corneal endothelium in chronic kidney disease

Purpose:Chronic kidney disease (CKD) is an emerging health problem worldwide. In CKD corneal endothelial changes also occur probably due to accumulation of inflammatory cytokines and increased multiple toxic products. The aim of this study was to analyze the effect of CKD on corneal endothelium and correlate the findings with severity of disease with help of noninvasive technique.Methods:The study comprised 75 eyes of 75 cases divided into three groups with group A comprising of CKD cases on dialysis, group B of nondialysis CKD cases, and group C of controls. Each group had 25 cases each of either sex and between 15–80 age groups. All patients were investigated for blood urea, serum creatinine, and blood sugar and underwent complete ophthalmic examination of both eyes along with wide-field specular microscopy examination.Results:The majority of patients (33.3%) belonged to age range of 61–70 years with male predominance and the most common cause of CKD was found to be diabetes with 17 (34%) cases. We found normal corneal endothelial cell density (ECD) with the mean ECD of 2364.52 ± 397.72 mm2 in the dialysis group, 2467.8 ± 352.88 mm2 in nondialysis group, and 2521.68 ± 250.26 mm2 in the control group of patients. However, we found significant increase in coefficient of variation (CV) with 36 ± 5.8% in dialysis group, 37 ± 4.5% in nondialysis group and 32 ± 0.8% in controls (P = 0.001) and decreased hexagonality (Hx) with 47 ± 7.3% in dialysis group, 46 ± 4.7% in nondialysis group and 51 ± 6.7% in the controls (P = 0.031). This showed increased tendency of pleomorphism and polymegathism in corneal endothelial cells in CKD cases. No correlation was found between blood urea or serum creatinine levels with endothelial parameters in any group.Conclusion:CKD causes morphological changes like polymegathism and pleomorphism in corneal endothelium and hence these cases are more vulnerable and special care should be taken before any intraocular surgical procedure.

Quantitative assessment of offshore wind speed variability using fractal analysis

Proper understanding of offshore wind speed variability is of essential importance in practice, which provides useful information to a wide range of coastal and marine activities. In this paper, long-term wind speed data recorded at various offshore stations are analyzed in the framework of fractal dimension analysis. Fractal analysis is a well-established data analysis tool, which is particularly suitable to determine the complexity in time series from a quantitative point of view. The fractal dimension is estimated using the conventional box-counting method. The results suggest that the wind speed data are generally fractals, which are likely to exhibit a persistent nature. The mean fractal dimension varies from 1.31 at an offshore weather station to 1.43 at an urban station, which is mainly associated with surface roughness condition. Monthly variability of fractal dimension at offshore stations is well-defined, which often possess larger values during hotter months and lower values during winter. This is partly attributed to the effect of thermal instability. In addition, with an increase in measurement interval, the mean and minimum fractal dimension decrease, whereas the maximum and coefficient of variation increase in parallel.

Quantitative assessment of offshore wind speed variability using fractal analysis

Proper understanding of offshore wind speed variability is of essential importance in practice, which provides useful information to a wide range of coastal and marine activities. In this paper, long-term wind speed data recorded at various offshore stations are analyzed in the framework of fractal dimension analysis. Fractal analysis is a well-established data analysis tool, which is particularly suitable to determine the complexity in time series from a quantitative point of view. The fractal dimension is estimated using the conventional box-counting method. The results suggest that the wind speed data are generally fractals, which are likely to exhibit a persistent nature. The mean fractal dimension varies from 1.31 at an offshore weather station to 1.43 at an urban station, which is mainly associated with surface roughness condition. Monthly variability of fractal dimension at offshore stations is well-defined, which often possess larger values during hotter months and lower values during winter. This is partly attributed to the effect of thermal instability. In addition, with an increase in measurement interval, the mean and minimum fractal dimension decrease, whereas the maximum and coefficient of variation increase in parallel.

3D bearing capacity probabilistic analyses of footings on spatially variable c\u2013\u03c6 soil

The paper examines three-dimensional (3D) analyses of the load bearing capacity of square and strip footings on a spatially variable cohesive–frictional (c–φ) soil. Embedded, rigid and smooth footings are considered. Cohesion and friction angle are modelled using random fields. The vertical scale of fluctuation (SOF) is based on earlier studies of natural soils. For the square footing problem, the horizontal SOF is the subject of a parametric study. For the strip footing, only one value of the horizontal SOF is assumed, and the parametric study concerns the modelled length of the foundation. To generate the fields of strength parameters, the Fourier series method is employed. For both problems analyzed, the influence of the parameters on the probabilistic characteristics of the bearing capacity of the soil is investigated. For the square footing problem, both the mean value of bearing capacity and its coefficient of variation increase with an increasing horizontal fluctuation scale, but they stabilize at higher values of SOF. For the strip footing problem, it appears that 2D modelling is a very conservative approach, and for the precise assessment of the probability of foundation failure, the footing should be modelled in 3D.

Corneal Endothelial Cell Changes in Type 2 Diabetic Patients

Background: Diabetic eye disease is an end-organ response to the effects of the condition on the human system. The cornea is a transparent structure protecting the anterior one-sixth of the eye. Chronic hyperglycemia can affect the corneal layers shape and functions that responsible for corneal transparency. Objectives: Comparison of the changes in corneal endothelium namely, cell density (CD), percentage polymegathism, cell volume (CV) and pleomorphism (6A) along with central corneal thickness (CCT) in patients of type 2 diabetes mellitus with normal age and sex- matched subjects. Patients and methods: A case-control study in Sayed Galal University Hospital. 20 eyes of type 2 diabetic patients and 20 eyes of age and sex matched controls were included in the study. Age, gender, other demographic data, and relevant diabetic history were obtained. Full evaluation of both cases and controls including both anterior and posterior segment complete evaluation was done. Non- contact specular microscopy was used to study the corneal endothelial cells. Results: The mean endothelial cell density (ECD) was non-significantly lower in type 2 diabetics compared to controls (p value = 0.751.). There was a highly significant reduction in hexagonally in the cases compared to controls and highly significant increase in coefficient of variation in the cases compared to controls Conclusion: This study acknowledged that type 2 diabetes causes a significant decrease of hexagonality and increase CV (polymegathism). However, non-significant reduction of ECD was documented

Model I cohesive zone models of different rank coals

The present work develops cohesive zone models (CZM), i.e. cohesion-separation laws, for mode I fractures in different rank coals, including weakly caking coals, gas coals, fat coals, meager-lean coals and anthracite, through disk-shaped compact tension tests. Firstly, the experiments show that with the coal rank rising, the critical crack separation displacements and the degrees of the nonlinearity of the softening function decline gradually. By fitting the experimental data with the four commonly used cohesive zone models including the power law, the exponential law, the bilinear law and the linear law, the best-fitted model for each rank of coals was identified and the corresponding parameters were found. Secondly, to arrive at a general CZM formulation for the different rank coals, Karihaloo’s polynomial law was employed, which also gave better fit to the experimental data compared with the aforementioned four CZMs. After obtaining the CZM for coals, fracture energy was evaluated which is equal to the area under the softening curve. With the increase of the coal rank, the fracture energy reduces but its coefficient of variation increases. Thirdly, the geometric characteristics of fractures in different rank coals are studied. The lower rank coals have more tortuous crack propagation paths and larger roughness coefficients, whereas the higher rank coals possess wider average fracture apertures. Lastly, in order to further test the applicability of the obtained cohesion-separation laws, we implemented the Karihaloo’s polynomial CZM and the bilinear CZM into the cohesive elements of ABAQUS® using the user-subroutine VUMAT, and thereby simulated the crack propagation in single-edge notched beams made of weakly caking coals, fat coals, and meager-lean coals, respectively. It is found that the numerical results based on Karihaloo’s polynomial CZM have a better agreement with the experimental data than the bilinear CZM.

Shear strength of self-compacting concrete and recycled aggregate concrete beams: an appraisal of design codes

Provisions are given in design codes for the calculation of shear strength of conventional concrete (CC) beams. In this paper, a database is generated for self-compacting concrete (SCC) and recycled aggregate concrete (RAC) slender beams with and without shear reinforcement which were investigated for shear strength. Shear capacities of 103 SCC beams and 109 RAC beams with and without shear reinforcement are calculated using the provisions of ACI 318-14, JSCE-2007, NZS 3101-2006 and AS 3600-2009. Calculated nominal shear strengths (Vn) are compared with the experimental shear strengths (Vexp) and statistical parameters are obtained for each code. It was found that all the four codes yielded unconservative estimates of the shear capacities for SCC and RAC beams without shear reinforcement having longitudinal reinforcement less than 1% and depth greater than 450 mm. All the four codes produced reasonable and conservative estimates of the shear capacities of SCC and RAC beams with shear reinforcement. AS 3600-2009 produced minimum average of Vexp/Vn with least scatter but at the same time it yielded maximum unconservative results. A modification in the depth factor of AS 3600-2009 reduced the percentage of unconservative results from 18.67 to 7.8% for SCC beams and 24.67 to 8% for RAC beams without any increase in coefficient of variation (COV).

Speed synchronization, physical workload and match-to-match performance variation of elite football players.

This study aimed to: (i) examine whether the speed synchronization and physical performance of an elite football team changed between the first and the second half, using match time blocks of 15-min, and (ii) explore the match-to-match variation of players’ speed synchronization performance. Twenty-eight outfield elite footballers participated in 51 official matches. Positional data were gathered and used to calculate the total distance covered as a physical workload indicator. For all the outfield teammate dyad combinations (45 pairs), it was processed the percentage of time that players’ speed was synchronized during walking, jogging and running using relative phase (Hilbert Transform). Also, the match-to-match variation of the players’ speed synchronization, expressed in coefficient of variation was computed. The differences in the total distance covered from all players within the different match’s time block periods revealed a moderate decrease in the distance covered in the last 15-min of the match compared to the first 15-min (-6.5; ±1.07%, most likely: change in means with 95% confidence limits). However, when compared the last minutes from both halves a small increase was observed (2.7; ±1.2%, likely) from first to second half. The synchronization of the players’ speed displacements revealed small to moderate decreases in the % of synchronization in the second half periods for the jogging and running speed, while the opposite was found for the walking speed (~13 to 24% more, most likely). The playing position analysis for the walking zone showed similar trends between the groups, with small to moderate higher values in the second half, with the exception of [30’-45’] vs [75’-90’] in the midfielder’s dyads and in [15’-30’] vs [60’-75’] match periods for forwards. Similar trend was found during the running speed, in which small to moderate higher synchronization was found during the first half periods, with the exception of [15’-30’] vs [60’-75’] and [30’-45’] vs [75’-90’] in midfielder’s dyads. Regarding to the match-to-match variation of the players’ speed synchronization, overall results showed small to moderate increases in coefficient of variation during jogging and running displacements from the beginning to the end of the match (32.1; ±13.2% increase in jogging and 26.2; ±10.5% in running, both comparisons most likely). The higher distance covered during most of the first half periods and the higher dyadic synchronization at high speeds might have limited players’ performance in the second half. In addition, the decrease trend in speed synchronization during the second half periods might have resulted from accumulated muscular and mental fatigue towards the match. Within, the match-to-match variation in tactical-related variables increased across the match duration, with especial focus in the midfielder dyads. Dyadic speed synchronization might provide relevant information concerning the individual and collective performance.

EVALUATING THE PERFORMANCE OF THE POP- UP SPRINKLER

This investigation was carried out at Faculty of Agriculture , Menoufia University, Egypt, on the Pop-Up sprinkler at operating pressures of 1.5 , 2 and 3bar, sprinkler emission angles of 45o , 90 o ,135 o, 180 o ,225 o, 270 o , 315 o and 360o and riser heights of 0.15 ,0.75 and 1.25 m . Discharge, uniformity distribution, coefficient of variation and water losses percent of the sprinkler due to evaporation and water drift were determined . Results indicated that, when pressure decreases, discharge and coefficient of uniformity decrease . The percentage of the average decreasing for discharge were 28 and 42% and decreasing of coefficient of uniformity were 12.05 and 23.77% when using the operating pressures of 2 and 1.5 bar compering with 3 bar resp. But increase coefficient of variation and water loss percent due to evaporation and water drift .Moreover, increasing the riser height at the sprinkler emission angles the discharge and the coefficient of uniformity decrease . When angle increase from 45o to 360o the discharge and coefficient of variation increase from o.115 to 0.362 m3 /h and from 14.54 to 30.98 % resp. ,while coefficient of uniformity and water loss percent .decrease from 80.46 to 74.38 % and from 17.85to 11.21 % resp. Due to interaction between the operating pressure 3 bar and height riser of 0.15 m at emission angle of 360o gave the highest value of the discharge , while at the angle of 45 o gave the highest value of coefficient of uniformity.

Partitioning Evapotranspiration into Green and Blue Water Sources in the Conterminous United States

In this study, we combined two 1 km actual evapotranspiration datasets (ET), one obtained from a root zone water balance model and another from an energy balance model, to partition annual ET into green (rainfall-based) and blue (surface water/groundwater) sources. Time series maps of green water ET (GWET) and blue water ET (BWET) are produced for the conterminous United States (CONUS) over 2001–2015. Our results indicate that average green and blue water for all land cover types in CONUS accounts for nearly 70% and 30% of the total ET, respectively. The ET in the eastern US arises mostly from GWET, and in the western US, it is mostly BWET. Analysis of the BWET in the 16 irrigated areas in CONUS revealed interesting results. While the magnitude of the BWET gradually showed a decline from west to east, the increase in coefficient of variation from west to east confirmed greater use of supplemental irrigation in the central and eastern US. We also established relationships between different hydro-climatology zones and their blue water requirements. This study provides insights on the relative contributions and the spatiotemporal dynamics of GWET and BWET, which could lead to improved water resources management.

Cavalier King Charles Spaniels with Chiari-like malformation and Syringomyelia have increased variability of spatio-temporal gait characteristics

BackgroundChiari-like malformation in the Cavalier King Charles Spaniel is a herniation of the cerebellum and brainstem into or through the foramen magnum. This condition predisposes to Syringomyelia; fluid filled syrinxes within the spinal cord. The resulting pathology in spinal cord and cerebellum create neuropathic pain and changes in gait. This study aims to quantify the changes in gait for Cavalier King Charles Spaniel with Chiari-like malformation and Syringomyelia.MethodsWe compared Cavalier King Charles Spaniel with Chiari-like malformation with (n = 9) and without (n = 8) Syringomyelia to Border Terriers (n = 8). Two video cameras and manual tracking was used to quantify gait parameters.Results and conclusionsWe found a significant increase in coefficient of variation for the spatio-temporal characteristics and ipsilateral distance between paws and a wider base of support in the thoracic limbs but not in the pelvic limbs for Cavalier King Charles Spaniels compared with the border terrier.

Effect of travel speed on seed spacing uniformity of corn seed meter

Both seeding performance of seed metering unit and travel speed of seed planter have significant effects on seeding quality, thereby affecting crop growth and yields. In order to determine the effects of different travel speeds on seed spacing uniformity, four different types of seed meters were evaluated at five different travel speeds on seed meter test bench and in field. The tested seed meters included a finger pickup seed meter, a scoop-wheel seed meter, an air-pressure type seed meter and an air-blowing type seed meter. The seeding performance of the horizontal distribution of seeds within a row was described by using the coefficient of variation, the quality of feed index, the multiple index and the miss-seeding index. Experiments were performed in laboratory and field, respectively. Results indicated that different travel speeds have statistically significant effects on seed spacing uniformity. The four types of seed meters performed better on the seed meter test bench than in the field. Coefficient of variation increases and quality of feed index decreases as the travel speed of seed planter increases. The best seed spacing uniformity was obtained with the air-pressure type seed meter, followed with the air-blowing type seed meter, the finger pickup seed meter and the scoop-wheel seed meter. There were considerable differences between the performances of the scoop-wheel seed meter in the bench test and field test; the seeding qualities were much better in the bench test than in the field test. The scoop-wheel seed meter is more sensitive to vibration than the other types of seed meters. Keywords: corn seed meter, travel speed, seed spacing uniformity, precision corn planter, field test, test bench DOI: 10.25165/j.ijabe.20171004.2675 Citation: Liu Q W, He X T, Yang L, Zhang D X, Cui T, Qu Z, et al. Effect of travel speed on seed spacing uniformity of corn seed meter. Int J Agric & Biol Eng, 2017; 10(4): 98–106.

Sleep pressure and time perception in university students

Here we aimed to investigate the association between poor quality of sleep, sleep debt during weekdays and the performance on an interval timing task, using the method of production of time and consisting on five sessions a day for nine days. The sleep of our volunteers was particularly restricted on weekdays. Moreover, later chronotype was associated with the need for compensation on weekends. Regarding the production of time, produced durations were consistently over-produced and there was an evident increase in the mean coefficient of variation (CV) from the wake-up morning to afternoon sessions, followed by a sharp decrease in the evening sessions. Importantly, CV was mainly determined by the interaction between MSFdiff, sleep duration on weekdays and age. In conclusion, our results indicate that when university students are under the effects of social jet lag and reduced sleep duration during weekdays, their performance in interval timing tasks may be compromised.

Reliability Analysis for Flexural Capacity of Recycled Aggregate Concrete Beams

Concrete made of recycled coarse aggregate (RCA) derived from multiple sources can have relative variation in mechanical properties compared with natural aggregate concrete (NAC), resulting in a lower reliability of a recycled aggregate concrete (RAC) beam than that of NAC beam. In this paper, a method is proposed to improve the reliability of beams made with RAC by increasing the reinforcement ratio. According to the equilibrium equations of beams subjected to bending moment, the increase in reinforcement ratio can be achieved by decreasing the RAC design strength. Same mean compressive strengths are assumed for RAC and NAC and four factors are considered including concrete grade, reinforcement grade, reinforcement ratio and the ratio of external loads in reliability analysis. Using NAC beams as a reference and keeping the target reliability index the same as that of RAC beams, the analysis results show that RAC design strength decreases with increase in coefficient of variation (CoV) of RAC compressive strength. When the CoV of RAC compressive strength is 20%, the RAC design strengths are 0.93 and 0.90 times of the NAC design strength with a 95% confidence level for grade C30 and C40 concrete, respectively.

Antihypertensive Drug Use, Blood Pressure Variability, and Incident Stroke Risk in Older Adults: Three-City Cohort Study.

The aim was to determine the association between antihypertensive drug class and incident stroke controlling for long-term blood pressure (BP) variability (BPV) in people aged ≥65 years. The sample included 5951 participants (median age 74 years, 60% women) taking at least 1 drug for hypertension (3727/5951) or with systolic BP >140 mm Hg or diastolic BP >90 mm Hg. Participants were evaluated for incident fatal and nonfatal stroke to 12 years follow-up. BPV was calculated with the coefficient of variation method and regressed against 9 antihypertensive drug classes (BPVreg). Hazard models were used to determine hazard ratios for incident stroke risk attributable to drug class, adjusted for BP, BPVreg, covariates, and delayed entry bias. There were 273 incident strokes over a median of 9.1 years (interquartile range 6.4-10.4). Stroke risk was generally not reduced by BP-lowering drugs. Angiotensin receptor blockers (hazard ratio 1.56; 95% confidence interval 1.06-2.28; P=0.02) and β-blockers (hazard ratio 1.41; 95% confidence interval 1.03-1.92; P=0.03) were associated with an increased total stroke risk. Angiotensin receptor blockers and β-blockers were also associated with ischemic strokes after adjustment for systolic BPV. Diastolic BPV was associated with stroke risk in analyses stratified by systolic BP 140 to 160 mm Hg (per 0.10 increase in coefficient of variation, hazard ratio 1.59; 95% confidence interval 1.05-2.40; P=0.03). The angiotensin receptor blocker and β-blocker drug classes were associated with incident stroke and ischemic stroke in older adults. BPV was generally not associated with incident stroke.