Among multilevel inverters (MLIs), two-level inverters are the most common. However, this inverter type cannot maintain total harmonic distortion (THD) due to its limited number of levels. Reductions in THD are inversely proportional to the number of levels where increased output occurs in diverse ways, and the use of fewer components with low harmonic distortion is necessary for such reductions. This work proposes a seven-level (7L) MLI design with a small number of components and low harmonic distortion. The proposed MLI is combined with switched capacitor (SC) cells to promote output levels and at the same time to boost the input voltage. The connections between the capacitor and the source are based on the series to parallel topology, where the charging and discharging of the SC cells are caused by fluctuations in their connection. The output of the SC cell is combined with an H-bridge inverter controlled by a proposed PWM controller. The simulation result of the SC 7L inverter was... [more]

Non-wood biomass is particularly attractive as a cellulose source because of the lower lignin content. However, optimal cellulose extraction conditions are required as lignin content varies between plant sources. Further, the use of organic acids in place of harsh mineral acids is of interest in “greening” the cellulose production process. This study sought to establish optimum parameters for the extraction of cellulose microfibers (CMFs) from hemp (Cannabis sativa) biomass, using maleic and formic acids. Hemp fibers were pre-treated in NaOH (4 wt%) and aqueous chlorite in acetate buffer before ultrasonic treatment to break down bundles. The CMFs produced were compared with those generated from sulfuric acid hydrolysis. Response surface methodology (RSM) was used to determine combinations of three processing conditions, including acid concentration (45−64%), hydrolysis time (30−90 min), and temperature (45−65 °C). A central composite design (RSM-CCD) model with 21 experimental runs was... [more]

Risk assessment plays an important role in process safety. The result of the assessment is used to determine risk priorities and then develop preventions to reduce risks. A hazard may have multidimensional consequences, including loss of health and safety, asset loss, and environmental damage. Traditionally, these multidimensional consequences are often measured disjointedly. A comprehensive risk assessment would be conducted by many professionals from multiple areas. Each of these professionals uses different indicators to evaluate risks. The poor integration among risk indicators further confuses managers in the risk resilience and prevention development. In addition, this lacks a solid method for assessing the risk of hazards that with multidimensional consequences. The aim of the work is to develop a risk-measuring instrument using a newly proposed approach, the Risk Assessment for Hazards with Multidimensional Consequences (RAMC), which is developed based on the theory of quality... [more]

In this study, the coupling process of flocculation and membrane separation was used to treat tannery chromium removal wastewater, and the experimental results of the different process operating conditions were investigated to optimize the entire process design. First, the wastewater was pretreated by flocculation ultrafiltration (UF), and the produced water could directly enter nanofiltration (NF) for concentration treatment. The removal rates of turbidity, chroma, and chemical oxygen demand (COD) of the pretreated wastewater were 96.5%, 53.7%, and 45.8%, respectively. Then, NF multistage treatment was used to control the freshwater recovery rate to 90%, where the salt content of the primary freshwater was 200−500 mg·L−1, and the salt content of the secondary freshwater was 800−1000 mg·L−1, which all met the reuse standards of the factory. The total dissolved solids (TDS) and COD of the concentrated wastewater were 44,000−46,000 mg·L−1 and 10,000−13,000 mg·L−1, respectively. Finally,... [more]

In the recent literature of process monitoring, homogeneously weighted moving average (HWMA) type control charts have become quite popular. These charts are quite efficient for early detection of shifts, especially of smaller magnitudes, in process parameters such as location and dispersion. A recent study pointed out a few concerns related to HWMA charts that mainly relate to its steady-state performance. It needs to be highlighted that the initial studies on HWMA focused only on the zero-state performance of the chart relative to other well-known memory charts. This study reinvestigates the performance of the HWMA chart under zero and steady states at various shifts. Using the Monte Carlo simulation method, a detailed comparative analysis of the HWMA chart is carried out relative to the exponentially weighted moving average (EWMA) chart with time-varying limits. For several values of design parameters, the in-control and out-of-control performance of these charts is evaluated in term... [more]

Microalgae have a lot of potential as a source of several compounds of interest to various industries. However, developing a sustainable and efficient harvesting process on a large scale is still a major challenge. This is particularly a problem when the production of low-value products is intended. Chemical flocculation, followed by sedimentation, is seen as an alternative method to improve the energetic and economic balance of the harvesting step. In this study, inorganic (aluminum sulfate, ferric sulfate, ferric chloride) and organic (Zetag 8185, chitosan, Tanfloc SG) flocculants were tested to harvest Chlorella vulgaris in batch mode. Preliminary assays were conducted to determine the minimum dosages of each flocculant that generates primary flocs at different pH. Except for chitosan, the organic flocculants required small dosages to initiate floc formation. Additional studies were performed for the flocculants with a better performance in the preliminary assays. Zetag 8185 had the... [more]

Cell-free synthetic biology is advancing with unprecedented control and design. The development of cell-free biosynthesis involves both pure enzyme and crude enzyme systems. The relatively cheap crude enzyme system is more suitable for the scientific research needs of ordinary laboratories. The key factor in giving full play to the advantages of the system is to obtain high-quality cell crude extract and its energy regeneration system, but there is no systematic report on the development history of these two aspects. Therefore, in this paper, the development history of the process of obtaining crude extract from cell-free biosynthesis was carried out based on Escherichia coli, which is widely used at present, and the energy regeneration system was briefly introduced. Finally, the challenges of current cell-free synthetic systems are discussed.

The iterative design process of mechanical products has evolved towards a more sustainable direction driven by the concept of sustainable development. Modular design emphasizes the realization of user requirements under the condition of high efficiency and low cost, which is conducive to the diversification of product design. The sustainable innovative design methods are considered in modular design processes, which can improve the design capabilities of enterprises and enhance competitiveness. However, although the existing methods used in the iterative design of a product scheme contributes to satisfy the user requirements and generate the innovative scheme of the product, the sustainable design concepts such as the impact on the utilization of resources and environment during the iteration of the conceptual scheme and sustainability evaluation of product schemes have not been given sufficient attention. To resolve this, in this work, an iterative conceptual design process is propose... [more]

Thymoquinone (THY) is a bioactive compound present in the seed powder of Nigella sativa (NS). This research aims to precisely and accurately estimate THY using high-performance liquid chromatography (HPLC) with a Quality by Design (QbD) application. Box-Behnken design (BBD) was employed to optimize the chromatographic conditions for HPLC method development, taking mobile phase flow rate, pH of the buffer, and λmax as independent variables and retention time and tailing factor as the measured responses. The mobile phase composition was methanol: acetonitrile: buffer (2.2 mM ammonium formate) at the ratio of 35:50:15 v/v/v on a Symmetry® C18 (5 μm, 3.9 × 150 mm) column. In isocratic mode, it had a flow rate 0.9 mL min−1 and eluted analyte was detected at 249 nm. Validation parameters followed the International Council for Harmonization (ICH) guidelines for the new HPLC method. The method was linear over the range 6.25−100 µg mL−1 with a coefficient of determination (r2) of 0.9957. The li... [more]

The main problem in current energy management is the ability of practical application. To address the problem, this paper proposes a reinforcement learning (RL)-based energy management by combining Tubule Q-learning and Pontryagin’s Minimum Principle (PMP) algorithms for a plug-in hybrid electric bus (PHEB). The main innovation distinguished from the existing energy management strategies is that a dynamic SOC design zone plan method is proposed. It is characterized by two aspects: ① a series of fixed locations are defined in the city bus route and a linear SOC reference trajectory is re-planned at fixed locations; ② a triangle zone will be re-planned based on the linear SOC reference trajectory. Additionally, a one-dimensional state space is also designed to ensure the real-time control. The off-line trainings demonstrate that the agent of the RL-based energy management can be well trained and has good generalization performance. The results of hardware in loop simulation (HIL) demonst... [more]

Robots and robotic systems have become an inevitable part of modern industrial settings. Robotics systems are being introduced for various household services as well. As the interactions between the workspace of robots and humans increases, there is an increased likelihood of unintended harm being caused by the robots to humans due to collisions or abrupt contact. To mitigate this, active and passive compliant mechanisms must be introduced in these systems. In this study, a design optimization case study is carried out for the optimization of a passive compliance mechanism achieved with variable stiffness joints realized by the use of permanent magnets. Three design parameters of the systems, namely, inner stator width, outer stator width, and magnet height, are considered. The objective is to minimize the weight and maximize the maximum torque. A nature-inspired metaheuristic hybridized with a multi-criteria decision-making method is introduced to achieve this. The Non-dominated Sorti... [more]

The objective of this study was to determine the density of anaerobic granules on different heights of a full-scale Upflow Anaerobic Sludge Bed reactor. The density was defined through the settling velocities of anaerobic granules, measured in a full-scale Upflow Anaerobic Sludge Bed reactor. In this study, granular density was calculated with the measured settling velocities and developed mathematical model. The developed mathematical model is based on the Stokes model. In the experiment, granules were taken from different heights of an Upflow Anaerobic Sludge Bed reactor, from 0.6 to 7.6 m. The granules’ diameters varied between 1 and 5 mm. The granules were taken from six different heights through the reactor. The settling velocity of the active granules (with gas in the granule pore and on the surface of the granule) was measured first. After the active granules’ settling velocity measurement, the granules were placed in a vortex to obtain degassed granules (granules without any ga... [more]

A critical review on the improvement of penetration theory is presented in this work. The volumetric liquid-phase mass transfer coefficients kLa in seven different liquids (1-butanol, 2-propanol, anilin, decalin, nitrobenzene, tetralin, and ethylene glycol) aerated with air in a small bubble column (BC) (inner diameter: 0.095 m) were measured at ambient conditions and further analyzed. It was found that the kLa values can be predicted satisfactorily on the basis of the classical Higbie’s penetration model. The gas−liquid contact time was defined as the ratio of the Sauter-mean bubble diameter to bubble rise velocity. Moreover, the experimental kLa values were well predicted, not only in the homogeneous regime, but also in the transition and heterogeneous regimes. This is a new finding, since to date, it was considered that the penetration theory needs a correction factor for a successful application to any liquid, even in the homogeneous regime. The predictions of the mass transfer coe... [more]

The desilication of sodium aluminate solutions prior to precipitation of aluminum tri-hydroxides is an essential step in the production of high purity alumina for aluminum production. This study evaluates the desilication of sodium aluminate solutions derived from the leaching of calcium-aluminate slags with sodium carbonate, using CaO, Ca(OH)2, and MgO fine particles. The influence of the amount of CaO used, temperature, and comparisons with Ca(OH)2 and MgO were explored. Laboratory scale test work showed that the optimal conditions for this process were using 6 g/L of CaO at 90 °C for 90 min. This resulted in 92% of the Si being removed with as little as 7% co-precipitation of Al. The other desilicating agents, namely Ca(OH)2 and MgO, also proved effective in removing Si but at slower rates and higher amounts of Al co-precipitated. The characteristics of solid residue obtained after the process indicated that the desilication is via the formation of hydrogarnet, Grossular, and hydrot... [more]

In this study, three 1.2-L aerobic granular sludge sequencing batch reactors (AGS-SBRs) were used to cultivate nitrifying and nitrifying-denitrifying granules (w/supplemental carbon) and investigate sidestream treatment of synthetic-centrate and real-centrate samples from Ashbridges Bay Treatment Plant (ABTP) in Toronto, Ontario, Canada. Results showed that although the cultivation of distinct granules was not observed in the nitrifying reactors, sludge volume index (SVI30) values achieved while treating real and synthetic centrate were 72 ± 12 mL/g and 59 ± 11 mL/g (after day 14), respectively. Ammonia-nitrogen (NH3-N) removal in the nitrifying SBRs were 93 ± 19% and 94 ± 16% for real and synthetic centrate, respectively. Granules with a distinct round structure were successfully formed in the nitrifying-denitrifying SBR, resulting in an SVI30 of 52 ± 23 mL/g. NH3-N, chemical oxygen demand (COD) and phosphorus (P) removal in the nitrifying-denitrifying SBR were 92 ± 9%, 94 ± 5%, and 8... [more]

Psoriasis is a chronic inflammatory disease. Within psoriatic lesions, microvascular dysfunction and numerous, tortuous blood vessels occurs. The Nd:YAG laser causes the selective destruction of dilated capillaries, which contributes to the inhibition of leukocyte transport within psoriatic lesions and may be an effective method of psoriasis therapy. This preliminary study was designed to assess the effectiveness of the Nd:YAG laser in reducing psoriatic lesions. Twenty volunteers suffering from psoriasis met the inclusion criteria and were qualified for the study. The non-lesional skin areas and areas with psoriatic lesions were imaged using a DUB SkinScanner high-frequency ultrasound, and skin parameters, including the stratum corneum hydration, melanin and hemoglobin level, were evaluated. The thickness of the epidermis and the SLEB layer, as well as the density of the dermis, were assessed before and after the therapy. The Nd:YAG laser, with a wavelength of 1064 nm and a 650-micros... [more]

Aerobic granular sludge (AGS) is known for high phosphorus removal from wastewaters, and phosphorus can be recovered from high phosphorus-containing waste sludge granules. This study aimed at determining the feeding strategy that provides the best performance in terms of the proliferation of polyphosphate-accumulating organisms (PAOs) and phosphorus removal. Using three AGS bioreactors, this study compared phosphorus removal and the proliferation dynamics of PAOs under three different feeding strategies: anaerobic slow feeding (R1), pulse feeding + anaerobic mixing (R2), and pulse feeding (R3). Results indicate that R1 and R2 achieved significantly higher phosphorus removal (97.6 ± 3% for R1 and 98.3 ± 1% for R2) than R3 (55 ± 11%). The anaerobic slow feeding procedure (R1) achieved the highest specific phosphorus release rate (SPRR) and specific phosphorus uptake rate (SPUR) as compared to the other two feeding conditions. 16S ribosomal ribonucleic acid (rRNA) gene sequencing assay of... [more]

The construction of 1500 m depth shaft in Xincheng Gold Mine, China, faces complex stress conditions such as high geostress (>50 MPa), high ground temperature (>50 °C), high water-pressure (>9 MPa), and highly corrosive. Traditional deep shafts excavated by the sinking and lining method cannot adapt to high geostress problems, such as rock bursts and large deformations, etc., in the deep shaft construction process. To avoid and adjust the high geostress induced the rockburst and large deformations, the mechanism of the advanced sequential geopressure release (ASGR) has been proposed for the ground control in deep shaft construction. In this paper, the safe distance between the concrete lining and the shaft excavation face is determined based on the ASGR mechanism, which can provide the space for geopressure release, and primary support based on rock mass quality and numerical simulation was employed to control the geopressure and deformation. A new support scheme for the deep shaft is... [more]

Service network design problems arise at airlines, trucking companies, and railroads wherever there is a need to determine cost-minimizing routes and schedules, given resource availability and service constraints. In recent years, the application of consolidation-based service network design in the express service has attracted lots of academic attention due to the rapid growth of the express industry. This paper studies the consolidation-based service network design problem, which jointly determines the commodity flow, vehicle dispatching, and fleet sizing. We propose a mixed-integer optimization model to address the problem and design an efficient iterative backbone algorithm to solve large-scale real-world problems. The numerical results of large-scale instances confirmed that the solution obtained by our proposed algorithm is better than that of the primal model, and the running time taken is less than half that of the general solution approach. The computational study confirmed th... [more]

Since only uni-direction motion is produced by traditional abrasive flow machining (AFM), so the polishing effects of the inner hole is not easy to achieve uniform roughness of the whole surface after polishing. Therefore, in this study, a rotating device with a DC servo motor was set up in the AFM to increase the tangential forces on the machining surface, and therefore, improve the uniform surface roughness and polishing efficiency. The rotating device was designed by a group of transmission gear set and a DC servo motor to create a rotational finishing path for the abrasive medium. The rotational motion of an abrasive can create different tangential forces on the working surface, inducing a more complex polishing path than that of traditional AFM. In addition to rotational speed, a servo motor can also change rotation directions in one working process, causing an abrasive medium to create many irregular finishing paths in the AFM. The experimental results showed that the surface rou... [more]

The aim of this paper is to design a fuzzy motion control algorithm for a developed monocular vision system based on a cooperative transportation system of two humanoid robots. The control strategies of the cooperation transportation system contain three stages, including object searching, walking toward the transported object, and cooperatively moving the transported object. To have different moving speeds, the gait step size was pre-planned as two different modes, i.e., one of the gaits is selected to let the HR have large variations of motion and another gait is to make the HR with small variations. The fuzzy motion control algorithm is utilized to select the appropriate mode of gait. Both humanoid robots can actively search and move to the front of the target object, then cooperatively lift the target and carry it to the platform. The task of synchronous movement is controlled with fuzzy techniques through the control terminal. From the experimental results, it can be seen that bot... [more]

Kecombrang flowers have bioactive components that can be used as food additives. The development of the kecombrang functional food industry for the production of food additives requires information on production parameters. The extraction process for kecombrang to obtain bioactive components, especially phenols and flavonoids, requires maximum temperature treatment and extraction time. This study aims to determine the standard for the kecombrang flower extraction process, create a machine learning model to estimate the quality parameters of the extraction results (phenol, flavonoid, pH, color, and viscosity), and design a strategy for controlling the extraction machine work to maintain the quality of the extraction, especially of phenols and flavonoids. This research was conducted at extraction temperatures of 60 °C, 65 °C, 70 °C, and 75 °C. During the extraction process, the quality of the material was checked by measuring phenol and flavonoid contents, as well as color, pH, and visco... [more]

Liquid fertilizers are mainly applied by spraying liquid fertilizer on the surface of crop leaves and by deep openings between rows. The first causes considerable environmental pollution, and the second can easily cause to damage the root system of crops. In this study, corn crops were taken as the study object and an efficient deep-hole application method for liquid fertilizer based on alternate drilling was proposed. The needle body is driven by the spur gear wheel system in a caving mechanism to puncture holes alternately in a vertical posture and high-speed punctures are implemented with less disturbance to the soil. The cylindrical hollow cam of the mechanism is controlled so that the fertilizer needle sprays fertilizer when injected into soil and stops injecting when pulled out of the soil. Based on the bench test, fertilizer injecting performance and energy saving performance of the differential two-way fertilizer supply distribution device were analyzed and the head loss for en... [more]

Multiphase pumps are used as an important tool for natural gas hydrate extraction owing to their excellent gas−liquid mixing and transport properties. This paper proposes an adaptive response surface-based integrated optimization design method. A model pump is designed based on the axial flow pump design theory. The model pump is numerically simulated and analyzed to obtain its performance parameters. Then the structural and performance parameters of the pump are parameterized to establish a closed-loop input−output system. Based on this closed-loop system, a sensitivity analysis is performed on the structural parameters of the impeller and guide vane, and the parameters that affect the performance of the gas−liquid hybrid pump the most are derived. The Sparse Grid method was introduced to design the experiment and construct the approximate model. The structural parameters of the impeller and guide vane are used as design variables to optimize the pressure increment and efficiency of t... [more]

In a conventional seed drill, the flow of seeds into the planting bed is usually disrupted and irregular, which contributes to poor seed spacing uniformity. The seed tube of the seed drill may be one of the reasons for disrupted and irregular seed flow. A seed drill, in principle, has to deposit seeds into the ground at a uniform spacing to avoid nutrient competition for optimum yield. This study was inspired to develop a novel helicoidal seed tube that regulates the flow of seeds in a seed tube while being dispensed by the seed drill into the ground. The helicoidal tube was designed to fit the end of a conventional delivery tube of a seed drill. It works by allowing the falling seeds to move through the helix causing a frictional reaction, thereby regulating the velocity of the falling seeds. The developed helicoidal seed tube was tested under laboratory conditions at three heights of the helix (100, 150, and 200 mm) and four pitch sizes (28, 32, 36, and 40 mm). As a result of the lab... [more]