162 research outputs found
Load-Settlement Response of Square Footing on Geogrid Reinforced Layered Granular Beds
Experimental studies were carried out to obtain the load-settlement response of a model square footing resting on unreinforced and reinforced granular beds. The response was obtained for two cases: (a) geogrid-reinforced sand layer, and (b) geogrid-reinforced layered system consisting of aggregate layer overlying a sand layer. The parameters considered in the experimental study include the thickness of the aggregate layer, the depth of geogrid reinforcement placed in sand layer and in aggregate layer, width of the reinforcement, and relative density of bed. Plate vibrator was used to compact uniform sand beds to relative densities equal to 50 % and 70 % inside large-size test chamber of dimensions equal to 1 m × 1 m × 1 m (in length, in width, and in depth). Load was applied on square footing using a 100 kN capacity actuator in displacement-controlled mode, and the improvement in the load carrying capacity of the footing resting on reinforced sand layer and layered system was quantified in terms of load improvement factors. In addition, the optimum embedment depth and width of reinforcements were proposed for various cases considered in the study. The optimum depth of reinforcement for the case of aggregate layer overlying sand layer decreased to 0.30 times the width of the footing from 0.45 times the width of the footing for sand only case
Ring-Expansion Induced 1,2-Metalate Rearrangements:Highly Diastereoselective Synthesis of Cyclobutyl Boronic Esters
The broad synthetic utility of organoboron compounds stems from their ready ability to undergo 1,2-migrations. Normally, such shifts are induced by α-leaving groups or by reactions of alkenyl boronates with electrophiles. Herein, we present a new strategy to induce 1,2-metalate rearrangements, via ring expansion of vinylcyclopropyl boronate complexes activated by electrophiles. This leads to a cyclopropane-stabilized carbocation, which triggers ring expansion and concomitant 1,2-metalate rearrangement. This novel process delivers medicinally relevant 1,2-substituted cyclobutyl boronic esters with high levels of diastereoselectivity. A wide range of organolithiums and Grignard reagents, electrophiles, and vinylcyclopropyl boronic esters can be used. The methodology was applied to a short, stereoselective synthesis of (±)-grandisol. Computational studies indicate that the reaction proceeds via a nonclassical carbocation followed by anti-1,2-migration
Physical reflective boundary conditions applied to smoothed particle hydrodynamics (sph) method for solving fluid dynamics problems in 3-d domains
This paper aims to present the physical reflective boundary conditions (RBC) in 3-D domains and applications in fluid dynamics problems. Currently, RBC have been used in meshfree particle methods as an attempt to respect the continuum physical laws at the macroscopic domain, without the application of fictitious/ ghost particles - that improperly mix molecular and continuum mechanics concepts [1]. RBC methodology, validation in 2-D domains and applications in hydrostatics and hydrodynamics cases were presented in [2]. Hydrostatics and hydrodynamics cases with the RBC implementation in 3-D domains are presented in this work. A Newtonian, incompressible, uniform and isothermal fluid inside an immobile reservoir open to the atmosphere and dam break flow have been studied. In the first case, a modified SPH formulation using a modified pressure concept [3] has been used. Dam breaking simulations used the standard SPH formulation. In both cases, the numerical results showed good agreement with the analytical results or literature data
Effect of temperature and chain length of added primary amines on the sphere to rod transition of aqueous ionic micelles
The importance of micelles as templates for nanomaterials is growing day by day. This resulted in an increasing interest for micelles in different sizes and shapes. Addition of n-amines to micellar solutions was found to bring change in the shape of the micelles from sphere to rod in aqueous ionic micellar solutions. The change in shape is qualitatively obtained from sudden change in the slope of pH versus amine concentration plots because the degree or protonation of n-alkylamines depends on the shape of micelles. In the present investigation, pH is measured at different temperatures to elucidate the influence of addition of n-amines on sphere-to-rod transition in aqueous micellar solutions. The surfactants employed in the present investigation are cetyltrimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC), and sodium dodecyl sulphate (SDS).As the amine concentration is increased, the pH increases linearly at certain amine concentration and the slope of the resulting straight line changes on further addition of amine. It is noticed that increasing temperature requires more amine for structural transition of aqueous ionic micelles. It is also observed that the effectiveness of added amines leading to shape transition from sphere to rod is in the order of C8NH2>C7NH2> C6NH2
Synthesis of Nanocrystalline Yttria Stabilized Zirconia for SOFC
Nanocrystalline zirconia powders stabilized
with varying concentration of yttria (YSZ) were
synthesized following urea solution combustion route.
Thermogravimetric analysis combined with differential
scanning calorimetry was carried out for the intermediate
gel for analyzing reaction kinetics. The final products
were characterized by X‐ray diffractometry, transmission
electron microscopy and specific surface area
measurements. Sintering behavior of theses powders
were studied. The powder quality is poor in respect of
surface area and sintered density
An international prospective study of INICC analyzing the incidence and risk factors for catheter-associated urinary tract infections in 235 ICUs across 8 Asian Countries
Background: Identify urinary catheter (UC)-associated urinary tract infections (CAUTI) incidence and risk factors (RF) in 235 ICUs in 8 Asian countries: India, Malaysia, Mongolia, Nepal, Pakistan, the Philippines, Thailand, and Vietnam. Methods: From January 1, 2014, to February 12, 2022, we conducted a prospective cohort study. To estimate CAUTI incidence, the number of UC days was the denominator, and CAUTI was the numerator. To estimate CAUTI RFs, we analyzed 11 variables using multiple logistic regression. Results: 84,920 patients hospitalized for 499,272 patient days acquired 869 CAUTIs. The pooled CAUTI rate per 1,000 UC-days was 3.08; for those using suprapubic-catheters (4.11); indwelling-catheters (2.65); trauma-ICU (10.55), neurologic-ICU (7.17), neurosurgical-ICU (5.28); in lower- middle-income countries (3.05); in upper-middle-income countries (1.71); at public-hospitals (5.98), at private-hospitals (3.09), at teaching-hospitals (2.04). The following variables were identified as CAUTI RFs: Age (adjusted odds ratio [aOR] = 1.01; 95% CI = 1.01-1.02; P < .0001); female sex (aOR = 1.39; 95% CI = 1.21-1.59; P < .0001); using suprapubic-catheter (aOR = 4.72; 95% CI = 1.69-13.21; P < .0001); length of stay before CAUTI acquisition (aOR = 1.04; 95% CI = 1.04-1.05; P < .0001); UC and device utilization-ratio (aOR = 1.07; 95% CI = 1.01-1.13; P = .02); hospitalized at trauma-ICU (aOR = 14.12; 95% CI = 4.68-42.67; P < .0001), neurologic-ICU (aOR = 14.13; 95% CI = 6.63-30.11; P < .0001), neurosurgical-ICU (aOR = 13.79; 95% CI = 6.88-27.64; P < .0001); public-facilities (aOR = 3.23; 95% CI = 2.34-4.46; P < .0001). Discussion: CAUTI rate and risk are higher for older patients, women, hospitalized at trauma-ICU, neurologic-ICU, neurosurgical-ICU, and public facilities. All of them are unlikely to change. Conclusions: It is suggested to focus on reducing the length of stay and the Urinary catheter device utilization ratio, avoiding suprapubic catheters, and implementing evidence-based CAUTI prevention recommendations
Alcohol use and burden for 195 countries and territories, 1990-2016 : a systematic analysis for the Global Burden of Disease Study 2016
Background Alcohol use is a leading risk factor for death and disability, but its overall association with health remains complex given the possible protective effects of moderate alcohol consumption on some conditions. With our comprehensive approach to health accounting within the Global Burden of Diseases, Injuries, and Risk Factors Study 2016, we generated improved estimates of alcohol use and alcohol-attributable deaths and disability-adjusted life-years (DALYs) for 195 locations from 1990 to 2016, for both sexes and for 5-year age groups between the ages of 15 years and 95 years and older. Methods Using 694 data sources of individual and population-level alcohol consumption, along with 592 prospective and retrospective studies on the risk of alcohol use, we produced estimates of the prevalence of current drinking, abstention, the distribution of alcohol consumption among current drinkers in standard drinks daily (defined as 10 g of pure ethyl alcohol), and alcohol-attributable deaths and DALYs. We made several methodological improvements compared with previous estimates: first, we adjusted alcohol sales estimates to take into account tourist and unrecorded consumption; second, we did a new meta-analysis of relative risks for 23 health outcomes associated with alcohol use; and third, we developed a new method to quantify the level of alcohol consumption that minimises the overall risk to individual health. Findings Globally, alcohol use was the seventh leading risk factor for both deaths and DALYs in 2016, accounting for 2.2% (95% uncertainty interval [UI] 1.5-3.0) of age-standardised female deaths and 6.8% (5.8-8.0) of age-standardised male deaths. Among the population aged 15-49 years, alcohol use was the leading risk factor globally in 2016, with 3.8% (95% UI 3.2-4-3) of female deaths and 12.2% (10.8-13-6) of male deaths attributable to alcohol use. For the population aged 15-49 years, female attributable DALYs were 2.3% (95% UI 2.0-2.6) and male attributable DALYs were 8.9% (7.8-9.9). The three leading causes of attributable deaths in this age group were tuberculosis (1.4% [95% UI 1. 0-1. 7] of total deaths), road injuries (1.2% [0.7-1.9]), and self-harm (1.1% [0.6-1.5]). For populations aged 50 years and older, cancers accounted for a large proportion of total alcohol-attributable deaths in 2016, constituting 27.1% (95% UI 21.2-33.3) of total alcohol-attributable female deaths and 18.9% (15.3-22.6) of male deaths. The level of alcohol consumption that minimised harm across health outcomes was zero (95% UI 0.0-0.8) standard drinks per week. Interpretation Alcohol use is a leading risk factor for global disease burden and causes substantial health loss. We found that the risk of all-cause mortality, and of cancers specifically, rises with increasing levels of consumption, and the level of consumption that minimises health loss is zero. These results suggest that alcohol control policies might need to be revised worldwide, refocusing on efforts to lower overall population-level consumption.Peer reviewe
Reconfigurable manufacturing system – a new class of manufacturing system
Today’s manufacturing environment is highly uncertain, and it is continuously changing. It is characterized by shorter life cycles of products and technologies, shorter delivery times, an increased level of customization at the price of a standard product, increased product variety, quality as well as demand variability and intense global competition. Academicians, as well as practitioners, agree that uncertainty will continue to grow in the twenty-first century. To deal with the uncertainties in demand variation and production capacity a manufacturing system is required which can be easily reconfigured when there is a need at low cost. A reconfigurable manufacturing system is such a type of system. In the present work, the concept of the reconfigurable manufacturing system has been discussed and reviewed. It has been compared with dedicated systems and flexible manufacturing systems. Part family formation and barriers of reconfiguration also have been discussed. This work is an attempt to contribute to the conceptual systematization of the reconfigurable manufacturing system and reconfigurability by synthesizing the vast literature available after a systematic review
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