Assessing the Impact of Chlorine Residual on Trihalomethane and Haloacetonitrile Formation Under Chlorination and Chloramination Disinfection Regimes

A disinfection byproduct (DBP) formation potential (FP) test can be used to indirectly measure the concentration of DBP precursors in natural waters, permitting assessment of various DBP-related treatment processes and control strategies. While these tests require a 7-day chlorine residual (CR) between 3-5 mg L-1 as Cl2, it is not well known if this recommended residual corresponds to the true DBPFP (i.e., the maximum concentrations) for trihalomethanes (THMs) and haloacetonitriles (HANs). In this study, THMs and HANs were quantified as a function of CR under three common disinfection regimes: (1) free chlorine at pH 7.0 (FC7), (2) monochloramine at pH 7.0 (MC7), and (3) monochloramine at pH 8.3 (MC8). Three source waters were collected, one from a drinking water source (LW) and two from the effluent of a wastewater treatment plant (WW1 and WW2), and used to generate a total of 90 sample waters for the DBPFP experiments. Trichloromethane (TCM) was the predominant THM formed in the sample waters, and, for MC8, achieved its maximum value of ~40 µg L-1 at a CR of 30 mg L-1 as Cl2 (referred to as CRMAX), and in excess of the 3-5 mg L-1 as Cl2 target residual. For the FC7 and MC7 disinfection regimes, TCM concentrations continued to increase beyond the maximum CR achieved in this study (73.6- and 17.1 mg L-1 as Cl2, respectively), indicating its true FP was not reached. CRMAX values for the bromine-substituted THMs and HANs varied by disinfectant type and pH, however none were between the 3-5 mg L-1 as Cl2 recommended residual, and were limited by the low bromide concentrations in the source waters (\u3c 0.24 mg L-1). For dichloroacetonitrile, the predominant HAN formed, the CRMAX was 1.5-1.7 mg L-1 as Cl2 for FC7 and in excess of 15 mg L-1 as Cl2 for MC7 and MC8. The results of this study demonstrate the impact of CR on the formation of THMs and HANs, and can be leveraged to help assess various DBP-precursor removal processes and be used to guide development of more a more robust DBPFP test

Study on model for cutting force when milling SCM440 steel

This article presents empirical study results when milling SCM440 steel. The cutting insert to be used was a TiN coated cutting insert with tool tip radius of 0.5 mm. Experimental process was carried out with 18 experiments according to Box-Behnken matrix, in which cutting speed, feed rate and cutting depth were selected as the input parameters of each experiment. In addition, cutting force was selected as the output parameter. Analysis of experimental results has determined the influence of the input parameters as well as the interaction between them on the output parameters. From the experimental results, a regression model showing the relationship between cutting force and input parameters was built. Box-Cox and Johnson data transformations were applied to construct two other models of cutting force. These three regression models were used to predict cutting force and compare with experimental results. Using parameters including coefficient of determination (R-Sq), adjusted coefficient of determination (R-Sq(adj)) and percentage mean absolute error (% MAE) between the results predicted by the models and the experimental results are the criteria to compare the accuracy of the cutting force models. The results have determined that the two models using two data transformations have higher accuracy than model not using two data transformations. A comparison of the model using the Box-Cox transformation and the model using the Johnson transformation was made with a t-test. The results confirmed that these two models have equal accuracy. Finally, the development direction for the next study is mentioned in this articl

Systems and processes for early detection of biological ammonia oxidation in water using fluorometry

This invention relates generally to a system and process for early detection of biological ammonia oxidation in water utilizing a fluorescence-based sensor and process. Various embodiments are configured to read increases in a fluorescence excitation-emission wavelength pair that is responsive to a period of time (days to weeks or even longer) prior to the onset of biological ammonia oxidation, which is considered to be a nitrification event. Fluorescence excitation/emission pairs that have proven to be reliable include a fluorescence excitation wavelength of about 230 nm and an emission wavelength of about 345 nm and an excitation wavelength of 325 and an emission wavelength of 470. The system and process enable drinking water utilities to improve management of its distribution systems and facilitate earlier corrective actions, resulting is less loss of treated water through flushing and other tangible benefits

On sum-rate maximization in downlink UAV-aided RSMA systems

The synergy of uncrewed aerial vehicles (UAVs) and the rate-splitting multiple access (RSMA) technique has thrived as a crucial enabler for multi-user broadband sixth-generation networks. This paper investigates a UAV-aided RSMA downlink communication system considering user mobility and the uniform rectangular array antenna design. In particular, the sum-rate maximization problem is formulated where the UAV beamforming matrix, common rate allocation, and UAV trajectory design are jointly optimized. The deep deterministic policy gradient (DDPG) approach has been proposed to address the nonconcave objective function. In addition, the safe action shaping technique is incorporated into the algorithm to satisfy the variable constraints of the problem statement. The numerical simulation results demonstrated that the proposed approach outperformed other benchmark schemes in various settings of transmit powers and fading environment levels

Multi-objective optimization of the cylindrical grinding process of SCM440 steel using preference selection index method

This paper presents a study to ensure the minimum values of Ra and Rz, and the maximum value of MRR when external cylindrical grinding by the PSI method. The experiments were performed according to the orthogonal Taguchi L9 matrix with the input parameters including workpiece speed, feed rate, and depth of cut in the conventional grinding machine. Analysis of experimental results by Pareto chart showed that the feed rate and the depth of cut most influence on Ra and Rz, respectively. Feed rate and depth of cut all have a great influence on MRR. Meanwhile, the workpiece speed has a negligible effect on all three output parameters. The research results showed that to obtain the minimum values of Ra and Rz, and maximum of MRR, the workpiece speed, feed rate, and depth of cut were 400 rev/min 37.7 mm/min, 0.09 mm/rev, and 0.02 mm, respectively

Compounds from the ethyl acetate extract of <i>Pteris multifida</i> Poir. collected in Nam Dinh province, Vietnam

Pteris multifida Poir. is an evergreen herbaceous fern that is distributed in temperate and tropical regions of East Asia and cultivated in many other countries. It is an ethnomedicinal plant used for detoxicating, cooling, reducing pain, and as a treatment for many diseases like dysentery, typhoid, cholecystitis, diarrhoea, enteritis, jaundice, and eczema among others. Several compounds including flavonoids, sesquiterpenoids, diterpenoids, coumarins, lignans, and sterols with anti-spasmodic, anti-bacterial, anti-hyperlipidemic, anti-oxidative, and cytotoxic activities have been isolated from this plant. In the present study, three sesquiterpenoids, (2S,3S)-pretosin Q (1), (2R,3S)-pterosin C (2), (2S,3S)-pterosin C (3); two lignans, pinoresinol (4); lariciresinol 9-O-β-glucopyranoside (5), three flavonoids, naringenin (6), apigenin (7), and luteolin (8) were obtained from the ethyl acetate extract of the whole of P. multifida collected in Nam Dinh province, Vietnam. The chemical structures were elucidated by various spectroscopic means including one- and two-dimensional (1D, 2D)-NMR, mass spectrometry, and comparison with published data. Compounds 4-6 were isolated from P. multifida for the first time

Tracking Control for an Electro-Hydraulic Rotary Actuator Using Fractional Order Fuzzy PID Controller

This paper presents a strategy for a fractional order fuzzy proportional integral derivative controller (FOFPID) controller for trajectory-tracking control of an electro-hydraulic rotary actuator (EHRA) under variant working requirements. The proposed controller is based on a combination of a fractional order PID (FOPID) controller and a fuzzy logic system. In detail, the FOPID with extension from the integer order to non-integer order of integral and derivative functions helps to improve tracking, robustness and stability of the control system. A fuzzy logic control system is designed to adjust the FOPID parameters according to time-variant working conditions. To evaluate the proposed controller, co-simulations (using AMESim and MATLAB) and real-time experiments have been conducted. The results show the effectiveness of the proposed approach compared to other typical controllers

A study on surface roughness of workpiece when grinding SKD11 and SUJ2 steels using Al

This paper presents a study on surface roughness of workpiece when grinding SKD11, SUJ2 steels using Al2O3 and CBN grinding wheels. The method on modeling and predicting of surface roughness of workpiece in the grinding theoretical research was applied. However, when applying this method, it is necessary to identify the value of the roughness adjust factor in practical case. In this paper, this factor was found by experimental process when surface grinding SKD11 and SUJ2 steels by Al2O3 and CBN wheels. It helps values of calculating surface roughness to be similar to experimental datas

Free-floating magnetic microstructures by mask photolithography

International audienc

Green Synthesis of Selenium Nanoparticles Using <i>Cleistocalyx operculatus</i> Leaf Extract and Their Acute Oral Toxicity Study

Green synthesis has recently attracted extensive attention from scientists all over the world for the production of metal nanoparticles. Selenium nanoparticles (Se NPs) have been demonstrated as a suitable supplement nutrient for the replacement of selenium ions in terms of safety and efficiency. This work presented a friendly and facile approach to synthesize the Se NPs using polyphenols content in the Cleistocalyx operculatus (CO) leaves extract. The synthesizing conditions were optimized to obtain the Se NPs with uniform distribution and shape. The prepared Se NPs were well-characterized using scanning electron microscopy, X-ray diffraction, energy diffractive spectroscopy, and Fourier-transform infrared spectroscopy. The resultant Se NPs were in spherical shape with the particle size in a range from 50–200 nm. The antimicrobial properties of Se NPs were investigated against Echerichia coli and Staphylococcus aureus, which showed reasonable activity. The acute oral toxicity of Se NPs in mice was also studied. The result indicated that Se NPs exhibited lower toxicity than that of SeO2 with the lethal concentration (50% death of mice) of 7.75 mg kg−1.</sub