Analysis of Fractal and Energy Consumption Characteristics of Concrete under Impact Loading

In order to study the compressive deformation and energy evolution characteristics of concrete under dynamic loading, impact compression tests with impact velocities of 5, 6, and 7 m/s were carried out on concrete samples with aggregate volume ratios of 0, 32%, 37%, and 42%, respectively, using a split Hopkinson pressure bar test apparatus. The broken concrete pieces after destruction were collected and arranged. The fractal characteristics of fragmentation distribution of concrete specimens with different aggregate rates under impact were discussed, and the roughness of the fragment surface was characterized by the fractal dimension of the broken fragment and the crack surface energy was calculated. In addition, the analytical equation of the fractal dimension of the broken fragment and the crack surface energy was established. The relationship between the specimen energy absorption and the crack surface energy was compared and analyzed. The results show that the concrete specimens are mainly tensile split failure modes under different impact speeds. The fractal dimension, absorption energy, and crack surface energy all increase with the increase in impact speed and decrease with the increase in the aggregate rate. When the aggregate rate is different, the effective utilization rate of the absorbed energy is the largest when the aggregate content is 37%. The surface energy of the crack can be used to estimate the concrete dynamic intensity.

Reducing unnecessary testing in the emergency department: The case for INR and aPTT

ABSTRACTObjectiveRoutine coagulation testing is rarely indicated in the emergency department. Our goal is to determine the combined effects of uncoupling routine coagulation testing (i.e., international normalized ratio [INR]; activated partial thromboplastin time [aPTT]), disseminating an educational module, and implementing a clinical decision support system (CDSS) on coagulation testing rates in two academic emergency departments.MethodsA prospective pre-post study of INR-aPTT uncoupling, educational module distribution, and CDSS implementation in two academic emergency departments. All patients ages 18 years and older undergoing evaluation and treatment during the period of August 1, 2015, to November 30, 2017, were included. Primary outcome was coagulation testing utilization during the emergency department encounter. Secondary outcomes included associated costs, frequency of downstream testing, and frequency of blood transfusions.ResultsUncoupling INR-aPTT testing combined with educational module distribution and CDSS implementation resulted in significantly decreased coupled INR-aPTT testing, with significantly increased selective INR and aPTT testing. Overall, the aggregate rate of coagulation testing declined for both INR and aPTT testing (48 tests/100 patients/day to 26 tests/100 patients/day). There was a significant decrease in associated daily costs (median cost per day: $1048.32 v. $601.68), realizing estimated annual savings of $163,023 Canadian dollars (CAD). There was no signal of increased downstream testing or patient blood product requirements.ConclusionCompared to baseline practice patterns, our multimodal initiative significantly decreased coagulation testing, with meaningful cost savings and without evidence of patient harm. Clinicians and administrators now have a growing toolkit to target the plethora of low-value tests and treatments in emergency medicine.

Quantitative analysis of concrete on the basis of fuzzy set and computerised tomography number

In this study, the portable power loading device and medical Marconi M8000 spiral CT scanner are used to conduct the uniaxial compression CT scanning test of the concrete. The concrete porosity, hardened cement rate, and aggregate rate are defined, and the variation law of the concrete is analyzed in the uniaxial compression CT test. The proposed method is considered to utilize the value of each CT number, to realize the quantitative partition of the various components of concrete, and to quantitatively evaluate the damage evolution law of the concrete and strain localization during stress. It is shown that damage at the middle section increased from inside to the outside in the uniaxial compression CT test of the concrete.

Photooxidants from brown carbon and other chromophores in illuminated particle extracts

While photooxidants are important in atmospheric condensed phases, there are very few measurements in particulate matter (PM). Here we measure light absorption and the concentrations of three photooxidants – hydroxyl radical (⚫OH), singlet molecular oxygen (1O2*), and oxidizing triplet excited states of organic matter (3C*) – in illuminated aqueous extracts of wintertime particles from Davis, California. 1O2* and 3C*, which are formed from photoexcitation of brown carbon (BrC), have not been previously measured in PM. In the extracts, mass absorption coefficients for dissolved organic compounds (MACDOC) at 300 nm range between 13 000 and 30 000 cm2 (g C)−1 are approximately twice as high as previous values in Davis fogs. The average (±1σ)⚫OH steady-state concentration in particle extracts is 4.4(±2.3)×10-16 M, which is very similar to previous values in fog, cloud, and rain: although our particle extracts are more concentrated, the resulting enhancement in the rate of ⚫OH photoproduction is essentially canceled out by a corresponding enhancement in concentrations of natural sinks for ⚫OH. In contrast, concentrations of the two oxidants formed primarily from brown carbon (i.e., 1O2* and 3C*) are both enhanced in the particle extracts compared to Davis fogs, a result of higher concentrations of dissolved organic carbon and faster rates of light absorption in the extracts. The average 1O2* concentration in the PM extracts is 1.6(±0.5)×10-12 M, 7 times higher than past fog measurements, while the average concentration of oxidizing triplets is 1.0(±0.4)×10-13 M, nearly double the average Davis fog value. Additionally, the rates of 1O2* and 3C* photoproduction are both well correlated with the rate of sunlight absorption. Since we cannot experimentally measure photooxidants under ambient particle water conditions, we measured the effect of PM dilution on oxidant concentrations and then extrapolated to ambient particle conditions. As the particle mass concentration in the extracts increases, measured concentrations of ⚫OH remain relatively unchanged, 1O2* increases linearly, and 3C* concentrations increase less than linearly, likely due to quenching by dissolved organics. Based on our measurements, and accounting for additional sources and sinks that should be important under PM conditions, we estimate that [⚫OH] in particles is somewhat lower than in dilute cloud/fog drops, while [3C*] is 30 to 2000 times higher in PM than in drops, and [1O2*] is enhanced by a factor of roughly 2400 in PM compared to drops. Because of these enhancements in 1O2* and 3C* concentrations, the lifetimes of some highly soluble organics appear to be much shorter in particle liquid water than under foggy/cloudy conditions. Based on extrapolating our measured rates of formation in PM extracts, BrC-derived singlet molecular oxygen and triplet excited states are overall the dominant sinks for organic compounds in particle liquid water, with an aggregate rate of reaction for each oxidant that is approximately 200–300 times higher than the aggregate rate of reactions for organics with ⚫OH. For individual, highly soluble reactive organic compounds it appears that 1O2* is often the major sink in particle water, which is a new finding. Triplet excited states are likely also important in the fate of individual particulate organics, but assessing this requires additional measurements of triplet interactions with dissolved organic carbon in natural samples.

Photooxidants from Brown Carbon and Other Chromophores in Illuminated Particle Extracts

While photooxidants are important in atmospheric condensed phases, there are very few measurements in particulate matter (PM). Here we measure light absorption and the concentrations of three photooxidants – hydroxyl radical (•OH), singlet molecular oxygen (1O2*) and oxidizing triplet excited states of organic matter (3C*) – in illuminated aqueous extracts of wintertime particles from Davis, California. 1O2* and 3C*, which are formed from photoexcitation of brown carbon (BrC), have not been previously measured in PM. In the extracts, mass absorption coefficients for dissolved organic compounds (MACDOC) at 300 nm range between 13,000–30,000 cm2 g–C–1 and are approximately twice as high as previous values in Davis fogs. The average (± 1σ) •OH steady-state concentration in particle extracts is 4.7 (± 1.9) × 10−16 M, which is very similar to previous values in fog, cloud and rain: although our particle extracts are more concentrated, the resulting enhancement in the rate of •OH photoproduction is essentially cancelled out by a corresponding enhancement in concentrations of natural sinks for •OH. In contrast, concentrations of the two oxidants formed primarily from brown carbon (i.e., 1O2* and 3C*) are both enhanced in the particle extracts compared to Davis fogs, a result of higher concentrations of dissolved organic carbon and faster rates of light absorption in the extracts. The average 1O2* concentration in the PM extracts is 1.6 (± 0.5) × 10−12 M, seven times higher than past fog measurements, while the average concentration of oxidizing triplets is 1.0 (± 0.4) × 10−13 M, nearly double the average Davis fog value. Additionally, the rates of 1O2* and 3C* photoproduction are both well correlated with the rate of sunlight absorption. While concentrations of 1O2* and 3C* are higher in our PM extracts compared to fog, the extracts are approximately 1000 times more dilute than water-containing ambient PM. Since we cannot experimentally measure photooxidants under these ambient conditions, we measured the effect of PM dilution on oxidant concentrations and then extrapolated to ambient particle conditions. As the particle mass concentration in the extracts increases, measured concentrations of •OH remain relatively unchanged, 1O2* increases linearly, and 3C* concentrations increase less than linearly, likely due to quenching by dissolved organics. Based on our measurements, and accounting for additional sources and sinks that should be important under PM conditions, we estimate that [•OH] in particles is essentially the same as in fog waters, [3C*] is higher in PM by nearly a factor of 3, and [1O2*] is enhanced by a factor of roughly 600. Because of these enhancements in 1O2* and 3C* concentrations, the lifetimes of some highly soluble organics appear to be much shorter in particle liquid water than under foggy/cloudy conditions. Based on our extrapolated rates of formation, BrC-derived singlet molecular oxygen and triplet excited states are the dominant sinks for organic compounds in particle liquid water, with an aggregate rate of reaction for each oxidant that is approximately 200–300 times higher than the aggregate rate of reactions for organics with •OH. For individual, highly soluble reactive organic compounds it appears that 1O2* is the major sink in particle water. Triplet excited states are likely also important in the fate of individual particulate organics, but assessing this requires additional measurements of triplet interactions with dissolved organic carbon in natural samples.

Mechanical thrombectomy in pediatric acute ischemic stroke: Clinical outcomes and literature review

There are limited data on outcomes of mechanical thrombectomy for pediatric stroke using modern devices. In this study, we report two cases of pediatric acute ischemic stroke treated with mechanical thrombectomy, both with good angiographic result (TICI 3) and clinical outcome (no neurological deficits at 90 days). In addition, we conducted a literature review of all previously reported cases describing the use of modern thrombectomy devices. Including our two cases, the aggregate rate of partial or complete vessel recanalization was 100% (22/22), and the aggregate rate of favorable clinical outcome was 91% (20/22). This preliminary evidence suggests that mechanical thrombectomy with modern devices may be a safe and effective treatment option in pediatric patients with acute ischemic stroke.

Leverage, Risk & Choice Of Capital Structure: An Empirical Case From India

The present empirical paper studies the leverage, risk and choice of capital structure in India through a case of MRF Ltd. from tyres & tubes industry of the Indian corporate sector which covers a time period of ten years (effective nine years) extending from the year 1982-83 to 1991-92 where the company is lying in the top of tyres & tubes industry of the Indian corporate sector on the basis of sales for the year 1991-92 for the purpose of our study. The study reveals that that debt-equity ratio2 and leverage ratio2 have been varying from 53.01 percent in the 1982-83 to 68.25 percent in the year 1985-86, each, with rising trend during the period under study, whereas, aggregate debt-equity ratio2 and leverage ratio2 of the company are worked out 63.71 percent, each, during the period under study. It is found that cost of debt on before and after tax basis (Kdbt & Kdat) has been declining over the period under study, whereas, aggregate cost of debt on before and after tax basis (Kdbt & Kdat) of the company is worked out 17.91 percent and 10.21 percent, respectively, during the period under study. It is observed that rate of return on net assets on before and after tax basis (ROIbt2 & ROIat2) and rate of return on total networth on before and after tax basis (RONbt & RONat) have been rising during the period under study. On aggregate basis, aggregate rate of return on net assets on before and after tax basis (ROIbt2 & ROIat2) is worked out 25.18 percent 14.35 percent, whereas, aggregate rate of return on total networth on before and after tax basis (RONbt & RONat) is worked out 38.42 percent and 21.90 percent, respectively, during the study period. Thus, it is concluded that the company is enjoying favourable leverage with regard to use of debt during seven out of nine years under study. Consequently, rate of return on total networth (RONbt & RONat) is higher than cost of debt (Kdbt & Kdat) and rate of return on net assets (ROIbt2 & ROIat2) on before and after tax basis in the above said seven years under study. It means that use of debt in the capital structure of the company has positive impact on the profitability of the company during seven out of nine years under study which consequently is contributing to the total networth of the company which ultimately is benefitting to the equity shareholders of the company. Leverage created through debt by the company is not generating risk for the company in the above said seven years under study because MRF Ltd. is able to cover the cost of debt (Kdbt & Kdat) on before and after tax basis from the rate of return on net assets (ROIbt2 & ROIat2) on before and after tax basis in the above said seven years under study. However, on aggregate basis, the company has also been experiencing favourable leverage with regard to use of debt on before and after tax basis during the period under study which further means that debt is behaving favourably during the period under study. It is also found that spread and net gain are positive when leverage impact is positive and vice-versa during the period under study. It is also found that effective tax rate born by the company is high, i.e. 43 percent, during the period under study.

Preparation Test Study on High Strength Lightweight Concrete in Engineering Materials

Low and easy brittle characteristics of lightweight aggregate concrete tensile strength, shear strength, combined with high strength lightweight concrete requirements in the selection select strength Lytag, silica fume, superplasticizer material, preparationhigh strength lightweight aggregate concrete. Experimental study on the water-cement ratio, coarse aggregate rate ratio factors on the strength of lightweight aggregate concrete.