Shear Lag Effect on Bolted C-shaped Cold-formed Steel Tension Members

This study is concentrated on the investigation of the shear lag effect on cold-formed steel tension members. C-shaped sections with different dimensions tested by using bolted connections were discussed in this study. The comparisons were made between the test results and predictions computed based on several specifications. In order to study the stress distribution at the various locations of the cross section of specimen, the finite-element software ANSYS was also utilized in this research. Based on the experimental results, it was found that the tension strengths of test specimens predicted by the AISC-Code (1999), which takes account of the shear lag effect, provide good agreement with the test values. The predictions according to AISI-Code (1996) and AS/NZS 4600 Code (1996) seem to be overestimated as comparing to the test results. It is also noted that there is quite a discrepancy between the test results and the values predicted by British Standard (1998)

Application of Mass Transfer Models in Environmental Engineering

Generally, unit operation processes that are used in environmental engineering are involved in interfacial reaction where mass transfer is an extremely essential component for system optimization. The purposes of this chapter were intended to provide the information of both theoretical model development and engineering practice for mass transfer of important processes in environmental engineering. Those processes include, but are not limited to, (1) ozonation (gas–liquid process), (2) ion exchange (liquid–solid process), (3) biological activated carbon (liquid–solid process), (4) chlorination (gas–liquid process), and (5) carbonation (gas–liquid–solid process)

Adsorption of Nonylphenol to Multi-Walled Carbon Nanotubes: Kinetics and Isotherm Study

We explored the occurrence and distribution of nonylphenol (NP) in 13 Taiwanese source waters. From all the surveyed waters, NP was detected at a high concentration, which could be attributed to contamination by wastewater discharges. In this study, we applied modified multi-walled carbon nanotubes (MWCNTs) for removing NP from aqueous solution. The impact of a few experimental factors, i.e., pH, contact time, MWCNTs dose, and temperature on the NP removal efficiency of modified MWCNTs was studied. The maximum adsorption capacity of the MWCNTs was observed to be 1040 mg NP/g when the initial NP concentration was 2.5 mg/L, and the solution pH was 4. The adsorption process followed the Elovich kinetics and the Elovich isotherm, indicating it is multilayer adsorption. The thermodynamic analysis demonstrated the NP adsorption by MWCNTs was thermodynamically satisfactory and, for the most part, endothermic as in the case of phenol adsorption. The result of the current study demonstrated the significance of free binding sites and the pore size of MWCNTs in the NP adsorption. This paper will help to better comprehend the adsorption behavior and mechanism of alkyl phenolic compounds onto MWCNTs

The persistent shadow of the supermassive black hole of M 87

In April 2019, the Event Horizon Telescope (EHT) Collaboration reported the first-ever event-horizon-scale images of a black hole, resolving the central compact radio source in the giant elliptical galaxy M 87. These images reveal a ring with a southerly brightness distribution and a diameter of ∼42 μas, consistent with the predicted size and shape of a shadow produced by the gravitationally lensed emission around a supermassive black hole. These results were obtained as part of the April 2017 EHT observation campaign, using a global very long baseline interferometric radio array operating at a wavelength of 1.3 mm. Here, we present results based on the second EHT observing campaign, taking place in April 2018 with an improved array, wider frequency coverage, and increased bandwidth. In particular, the additional baselines provided by the Greenland telescope improved the coverage of the array. Multiyear EHT observations provide independent snapshots of the horizon-scale emission, allowing us to confirm the persistence, size, and shape of the black hole shadow, and constrain the intrinsic structural variability of the accretion flow. We have confirmed the presence of an asymmetric ring structure, brighter in the southwest, with a median diameter of 43.3−3.1+1.5 μas. The diameter of the 2018 ring is remarkably consistent with the diameter obtained from the previous 2017 observations. On the other hand, the position angle of the brightness asymmetry in 2018 is shifted by about 30° relative to 2017. The perennial persistence of the ring and its diameter robustly support the interpretation that the ring is formed by lensed emission surrounding a Kerr black hole with a mass ∼6.5 × 109 M⊙. The significant change in the ring brightness asymmetry implies a spin axis that is more consistent with the position angle of the large-scale jet

First Sagittarius A* Event Horizon Telescope results. II. EHT and multiwavelength observations, data processing, and calibration

We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5–11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of ∼50 μas, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*'s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior.http://iopscience.iop.org/2041-8205Physic

First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multiwavelength Observations, Data Processing, and Calibration

We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5–11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of ∼50 μas, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*’s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior

DEIONIZATION OF WATER WITH A RECOVERABLE REGENERANT

A methodology for choosing the most suitable pair of cation and anion exchangers, a UF membrane, and an organic regenerant was developed to achieve the objective of these investigations, i.e. deionization of water with a recoverable regenerant. Based on the results of preliminary investigations, single resin ion exchange column studies, and mixed-bed resin column tests, it was thus concluded that the operation of a mixed-bed resin (Amb-200/IRA-900) DI system in conjunction with a recoverable organic regenerant (sodium gluconate), via ultrafiltration membrane (Sepa-97 CA) process, was technically feasible. The proposed process would have three advantages compared with the conventional mixed-bed deionization process. First, all the cations (Ca(\u27++) and Mg(\u27++)) and anions (SO(,4)(\u27=), Cl(\u27-), and HCO(,3)(\u27-)) retained in the exhausted mixed-bed resin column would be replaced by introducing one organic regenerant, (Sodium Gluconate) to the column. Secondly, the process would not require separation of the resins in a mixed-bed resin column before regeneration. Thirdly, the organic regenerant (Sodium Gluconate) discharged from the column, during the service cycle, can be recoverable and recyclable through use of a UF process. For a service cycle feed solution containing 392 mg/l Ca(\u27++), 98 mg/l Mg(\u27++), 390 mg/l SO(,4)(\u27=), and 760 mg/l Cl(\u27-), it would produce an effluent Sodium Gluconate concentration of 1500-6000 mg/l and column utilization ratio for Amb-200 and IRA-900 resin of approximately 51.3% and 88.6%, respectively. Additional studies utilized Purdue Cold Tap Water as a service cycle feed and resulted in a column effluent with 875-7250 mg/l of Sodium Gluconate and column utilization for Amb-200 and IRA-900 resin of 30% and 56.7%, respectively. In these investigations, the most effective regeneration results (97.3% to 99.8%) were achieved while feeding 8% sodium Gluconate to the mixed-bed resin column at 0.5 gpm/ft(\u272) down-flow rate. The UF/RO Sepa-97 CA membrane was found to be successful for recovery (97%) of an organic regenerant, i.e. Sodium Gluconate, discharging from the column during the service cycle