Continuous Operation Mode Research Articles

A Novel Approach for Adaptive Partial Sliding Mode Controller Design and Tuning in Non-Minimum Phase Switch-Mode Power Supplies

In this article, a novel systematic approach is proposed for a partial sliding mode controller (SMC) design and tuning in non-minimum phase switch-mode power supplies (SMPS). To achieve a more simplified controller in comparison with the conventional SMCs, the partial SMC (PSMC) is introduced in this article, which just requires a part of the sliding surface for controller formulation. The accuracy of the developed PSMC is proved mathematically within the entire range of operation. Since the control parameters of the PSMC are not selected by trial and error, it can maintain the stability and robustness of the closed-loop system in a broad operational range. In this regard, and to develop a systematic approach for robust control of SMPS, a constant frequency equivalent SMC is designed using the converter nominal parameters. Then, the extracted controller is combined with an adaptive component to ensure asymptotical stability against load and line changes. Considering the Lyapunov stability criteria for nonlinear systems, it is proved that the presented SPMC can be used for output voltage regulation in both discontinuous and continuous operating modes with zero steady state error. To avoid the trial and error method during the controller tuning and parameters selection, the system characteristic equation is extracted using the Jacobian approach. Considering the roots of the characteristic equation and the stable range of the closed-loop system, the controller parameters are tuned. Furthermore, in addition to simulation, the developed approach is evaluated practically using the TMS3220F2810 digital signal processor. It is shown that the dynamic response of the proposed approach is faster than the standard double-loop SMC during load and line changes. Additionally, it is seen that the developed controller is robust against model changes in both continuous and discontinuous operations.

UVC-Assisted Tertiary Treatments for the Removal of Pollutants of Emerging Concern in Real WWTP Matrices

The aim of this work is to investigate the enhancement of UVC-based tertiary treatments; for this purpose, real wastewater treatment plant (WWTP) effluent was spiked with a model pollutant, namely acetaminophen. UVC irradiation resulted in some photodegradation of the acetaminophen, which was enhanced upon the addition of hydrogen peroxide (11 mM), but higher amounts of this oxidizing agent resulted in no significant acceleration of the process. An experimental design methodology based on Doehlert matrices showed the significance of hydrogen peroxide concentration and the flow rate for the reactor operating in continuous mode. The addition of low amounts of iron had a positive influence on the process, most probably due to a photo-Fenton-like process using the complexing ability of organic matter. For effluents with higher turbidity, a strategy combining coagulation-flocculation with UVC irradiation was tested: this approach was meaningful as flocculation-coagulation decreased water turbidity and resulted in a more efficient acetaminophen removal. However, under those conditions, the presence of iron did not show a positive role, most probably because of the absence of organic matter, which makes the UVC/H2O2 process more efficient and, on the other hand, humic-like substances available to complex iron to drive a neutral photo-Fenton process.

Carbon nitride – PVDF photocatalytic membranes for visible-light degradation of venlafaxine as emerging water micropollutant

Metal-free carbon nitride-based membranes were prepared by embedding bulk or exfoliated graphitic carbon nitride (g-C3N4) photocatalysts in a polyvinylidene fluoride (PVDF) matrix. Supported membranes were also fabricated by immobilising these photocatalysts on a polytetrafluoroethylene (PTFE) substrate. The membranes were tested for venlafaxine (VFX) degradation at a feed concentration of 250 µg L−1 under continuous flow mode operation and using a visible-light emitting diode (LED) as energy source. The reduction of the (002) diffraction peak and the increased intensity of the infrared absorption bands confirmed that the exfoliation process decreased the number of aligned g-C3N4 layers, with a more ordered packing of tri-s-triazine units. Additionally, the small particle size (around 745 and 257 nm for bulk and exfoliated g-C3N4, respectively) and the presence of terminal amino groups in the catalysts allowed for homogeneous dispersion in the PVDF matrix. Despite their different surface roughness and cross-sectional microstructure, all the fabricated membranes exhibited similar photocatalytic filtration performance for VFX degradation, resulting in conversions above 95% after 5 h of irradiation (418 nm with an irradiance of 11.2 W m−2) and keeping the VFX concentration in the effluent negligible up to 48 h of continuous operation (mass removal rate of about 6 mg m−2 h−1). In a more complex water matrix (i.e., surface water), the photocatalytic filtration process led to 50% VFX removal (or 3 mg m−2 h−1) at the steady state. Moreover, the permeate flux remained at about 25 L m−2 h−1 throughout the continuous operation, suggesting that fouling did not occur at these conditions.

Electrodialysis with Bipolar Membranes for the Sustainable Production of Chemicals from Seawater Brines at Pilot Plant Scale.

Environmental concerns regarding the disposal of seawater reverse osmosis brines require the development of new valorization strategies. Electrodialysis with bipolar membrane (EDBM) technology enables the production of acid and base from a salty waste stream. In this study, an EDBM pilot plant with a membrane area of 19.2 m2 was tested. This total membrane area results much larger (i.e., more than 16 times larger) than those reported in the literature so far for the production of HCl and NaOH aqueous solutions, starting from NaCl brines. The pilot unit was tested both in continuous and discontinuous operation modes, at different current densities (200-500 A m-2). Particularly, three different process configurations were evaluated, namely, closed-loop, feed and bleed, and fed-batch. At lower applied current density (200 A m-2), the closed-loop had a lower specific energy consumption (SEC) (1.4 kWh kg-1) and a higher current efficiency (CE) (80%). When the current density was increased (300-500 A m-2), the feed and bleed mode was more appropriate due to its low values of SEC (1.9-2.6 kWh kg-1) as well as high values of specific production (SP) (0.82-1.3 ton year-1 m-2) and current efficiency (63-67%). These results showed the effect of various process configurations on the performance of the EDBM, thereby guiding the selection of the most suitable process configuration when varying the operating conditions and representing a first important step toward the implementation of this technology at industrial scale.

Research Progress on the Typical Variants of Simulated Moving Bed: From the Established Processes to the Advanced Technologies

Simulated moving bed (SMB) chromatography is a highly efficient adsorption-based separation technology with various industrial applications. At present, its application has been successfully extended to the biochemical and pharmaceutical industrial sectors. SMB possesses the advantages of high product purity and yield, large feed treatment capacity, and simple process control due to the continuous operation mode and the efficient separation mechanism, particularly for difficult separation. Moreover, SMB performs well, particularly for multi-component separation or complicated systems’ purification processes in which each component exhibits similar properties and low resolution. With the development of the economy and technology, SMB technology needs to be improved and optimized to enhance its performance and deal with more complex separation tasks. This paper summarizes the typical variants or modifications of the SMB process through three aspects: zone variant, gradient variant, and feed or operation variant. The corresponding modification principles, operating modes, advantages, limitations, and practical application areas of each variant were comprehensively investigated. Finally, the application prospect and development direction were summarized, which could provide valuable recommendations and guidance for future research in the SMB area.

On Fractioning the Tire Pyrolysis Oil in a Pilot-Scale Distillation Plant under Industrially Relevant Conditions.

Tire pyrolysis oil (TPO) is one of the most interesting products derived from the pyrolysis of end-of-life tires. Among others, it contains valuable chemicals, such as benzene, toluene, ethylbenzene, and xylene (BTEX), as well as limonene. In order to recover these chemicals, a pilot-scale distillation plant has been designed, erected, and operated using TPO derived from an industrial-scale pyrolysis plant. The distillation facility consists of a packed column (20 kg/h) and is within the fifth technological readiness level. This work describes for the first time the fractioning of the TPO in a continuous operational mode under industrially relevant conditions. For this purpose, different reboiler temperatures (250-290 °C) and reflux ratios (up to 2.4) were preliminarily assessed on the yields and properties of the resulting products: light fraction (LF) and heavy fraction (HF). Thus, the distillation plant is capable of producing 27.0-36.7 and 63.3-73.0 wt % of LF and HF, respectively. The highest BTEX concentration in the LF (55.2 wt %) was found using a reboiler temperature of 250 °C and a reflux ratio of 2.4. Contrarily, the highest limonene concentration (4.9 wt %) in the LF was obtained at 290 °C in the reboiler without reflux. In this sense, the lower the reboiler temperature, the higher the BTEX, and the lower the limonene concentration in the LF. The main results herein obtained serve to gain key insights to operate packed distillation columns using complex and promising hydrocarbons as TPO in order to recover valuable products. In addition, this work provides significant information for optimizing the recovery efficiencies of both BTEX and limonene, as well as their potential applications including that for the resulting HF.

A technological approach using a metal-free immobilized photocatalyst for the removal of pharmaceutical substances from urban wastewaters

The presence of micropollutants (MPs) in aquatic compartments poses a great risk to the ecosystems and human health. Advanced oxidation processes (AOPs), such as light-induced systems employing a variety of powder optical semiconductors, have been widely investigated to remove MPs from water and wastewater. In this work, a metal-free photocatalyst (GCN-T) immobilized in the form of a film (GCN-T/PVDF) was activated by visible light (λexc = 417 nm) and successfully tested in both batch and continuous flow mode reactors for the degradation of two pharmaceutical model compounds (metoprolol and venlafaxine) spiked in ultrapure water (UP) and urban wastewater (WW) samples. A total removal of MPs was reached after 3 h reaction using GCN-T/PVDF film in a batch reactor. Under continuous mode operation, a steady state was attained after 2 h, with ca. 64 % removal for both MPs being obtained. The photocatalytic system was also examined using a non-spiked WW sample to study its performance to remove trace concentrations of these and other MPs in this type of complex matrix. MPs, such as bezafibrate, carbamazepine, diclofenac, isoproturon, and tramadol, were detected and efficiently degraded using the GCN-T/PVDF film. Finally, the ecotoxicity of the WW samples was also investigated using the aquatic invertebrate microcrustacean Daphnia magna. The results showed that the toxicity of WW samples decreases with the photocatalytic treatment.

Column adsorption of biological oxygen demand, chemical oxygen demand and total organic carbon from wastewater by magnetite nanoparticles-zeolite A composite

Herein, magnetite nanoparticles (NPs), zeolite A and magnetite-zeolite A (MAGZA) composite was developed by green methods. The produced nanomaterials were characterized and the effect of process parameters such as flow rate, adsorbent bed height and adsorbate inlet concentration was evaluated for the removal of biological oxygen demand (BOD), chemical oxygen demand (COD) and total organic carbon (TOC) in a column. The characterization results demonstrated the successful synthesis of magnetite NPs, zeolite A and MAGZA composite. The performance of the MAGZA composite in the fixed-bed column was superior to zeolite A and magnetite NPs. The parametric influence indicates that an increase in bed height and a decrease in the flow rate and inlet adsorbate concentration improved the performance of the adsorption column. The adsorption column demonstrated maximum performance at a flow rate (4 mL/min), bed height (5 cm) and inlet adsorbate concentration (10 mg/L). Under these conditions, the highest percent removal of BOD, COD and TOC were 99.96, 99.88 and 99.87%. Thomas and Yoon-Nelson's model suitably fitted the breakthrough curves. After five reusability cycles, the MAGZA composite demonstrated removal percent of BOD (76.5%), COD (55.5%) and TOC (64.2%). The produced MAGZA composite effectively removed BOD, COD and TOC from textile wastewater in a continuous operating mode.

High efficient separation of H2/CH4 using ZIF-8/glycol-water slurry: Process modelling and multi-objective optimization

Hydrogen (H2) is expected to play a vital role in future global energy system. The efficient and low-energy consumption process for H2/CH4 separation from hydrogen rich industrial off-gas is still a key challenge. The absorption-adsorption process for H2/CH4 separation using ZIF-8/glycol-water slurry is a promising alternative technique due to its high separation efficiency, mild operation conditions and continuous operation mode. We proposed two process configurations: a decompression desorption process A to obtain 99.5 mol% H2; and a process B combined with decompression and H2 stripping desorption to attain 99.99 mol% H2. The detailed process modelling and multiple objective optimizations for two processes are conducted to determine optimal operation conditions, stream characteristics, and unit energy requirements. Results show that the H2 recovery ratio and total unit energy consumption reaches 99.70% and 0.3876 kW·h/Nm3 for Process A; 99.47% and 0.4608 kW·h/Nm3 for Process B, respectively. It indicates the novel process can simultaneously achieve high purity and high H2 recovery with low energy consumption.

Comparison of pulse-modulated and continuous operation modes of a radio-frequency inductive ion source

The paper describes an experimental study of the characteristics of a pulse-modulated radio-frequency (RF) discharge sustained at low pressures, typical of the operating modes of RF gridded ion sources. The motivation for the study is the question of whether the RF pulse-modulated mode can increase the efficiency of the ion source. The ion current values extracted from an RF inductive ion source operating in continuous and pulse-modulated modes were compared. The experimental data were also compared with the parameter calculations based on a 0D numerical model of the discharge. The measurements showed that the pulse-modulated operation mode of the RF ion source had a noticeable advantage when the power of the RF generator was 140 W or lower. However, as the generator power increased, the advantage was lost because the pulse-modulated operation mode, having a higher RF power instant value, entered the region of existence sooner than the continuous mode, where the ion production cost begins to grow with RF power.

Online DC-Link Capacitance Monitoring for Digital-Controlled Boost PFC Converters Without Additional Sampling Devices

Aluminum electrolytic capacitors (Al-Caps) are widely used in the dc link of ac/dc applications; however, they are one of the weakest components in power electronic converters. With the degradation of Al-Cap, its capacitance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> ) decreases, and the equivalent series resistance increases. Based on this, many efforts have been made to realize condition monitoring (CM) of Al-Caps. Unfortunately, additional hardware (including current sensors and sampling circuits) and/or powerful data processing tools are usually required, which increases the cost and would bring new reliability risks. Considering this issue, this article presents a transient-based CM scheme for dc-link capacitors in digital-controlled boost power factor correction (PFC) converters, which does not need additional sampling devices. By analyzing the relationship between large-signal transient voltage profile and dc-link capacitance, a calculation model is established. Based on the sampled voltage and current signals used for digital control, the dc-link capacitance can be online estimated. Its feasibility is validated in simulation with a boost PFC operating in continuous conduction mode (CCM) and discontinuous conduction mode. Furthermore, taking a 1-kW boost PFC operating in CCM as a case study, experimental results illustrate that the estimation errors of the dc-link capacitance are less than 3.5% (error of a single test) and 1.5% (average error of multiple tests).

Design, implementation and performance evaluation of different digital control techniques for current controlled DC-DC Buck converter

The paper presents modelling, control architecture, analysis and design of digital compensators for single feedback-loop voltage mode control as well as two feedback-loop average current mode control and peak current mode control of current controlled DC-DC Buck converter operating in continuous conduction mode with output current as control variable. The compensators are derived using digital redesign approach, simulated on MATLAB, implemented as control algorithms on Texas Instruments' 32-bit TMS320F28069M microcontroller platform, and experimentally validated by testing with a laboratory prototype of current controlled Buck converter. Simulation and experimental results are discussed, compared and evaluated for converter output current performance in tracking reference current signal as well as in regulation against input voltage and load disturbances. Salient features of each control technique are identified and described to determine its suitability in applications of DC-DC converters requiring controlled output current.

Chaos Elimination for a Buck Converter Using the Multi-Objective Grey Wolf Optimiser

Abstract A wide variety of nonlinear phenomena, such as bifurcation and chaos, have been observed in power electronics converters. Much research has been conducted on these behaviours in different converter topologies. The buck converter is known to exhibit chaotic behaviour in a wide parameter range, giving rise to unstable behaviours depending on the circuit parameters values. This paper investigates this bifurcation behaviour by varying the parameters of a voltage PI (Proportional Integral) controlled buck converter operating in continuous conduction mode, using a continuous-time model and constant frequency control signal. Furthermore, a novel and improved version of the PI compensation technique, designed using the multi-objective grey wolf optimiser (MOGWO), is proposed to stabilise the buck converter from chaotic state to periodic orbit.

MODELING AND CHARACTERISTIC ANALYSIS OF FRACTIONAL-ORDER BOOST CONVERTER BASED ON THE CAPUTO–FABRIZIO FRACTIONAL DERIVATIVES

This paper presents a novel approach for modeling Boost converters using the Caputo–Fabrizio (C-F) definition-based fractional-order model to address singular characteristics in fractional-order definitions and enhance model accuracy. A small signal modeling method is proposed to improve the accuracy of circuit parameter design and to derive state-averaged models, state-space equations, and transfer functions. The influence of capacitor and inductor orders on steady-state characteristics is analyzed and the influence of fractional-order on ripple characteristics is investigated through simulation. When the fractional-order approaches 1, the output voltage increases and the inductance current decreases, with waveform jitter mitigation. Moreover, boundary conditions for continuous conduction mode operation are established based on ripple characteristics. The numerical and circuit-oriented simulations verify the correctness of the proposed model. Finally, the orders and accurate parameters of capacitors and inductors based on the C-F definition are determined and the experiments are conducted. The comparison between the experimental and simulation results demonstrates that the proposed model can accurately describe the steady-state characteristics of the practical circuit systems, which further validates the accuracy of the proposed method.

Improving structure design of active region of InAs quantum dots by using InAs/GaAs digital alloy superlattice

A 1.3-μm InAs quantum dot laser has been successfully fabricated on a GaAs(100) substrate by molecular beam epitaxy (MBE) technique through using InAs/GaAs digital alloy superlattices instead of the conventional InGaAs layer. The samples grown by conventional growth method and the digital alloy superlattice growth method are characterized by atomic force microscope (AFM) and photoluminescence (PL) spectroscopy. It is found that 8-period sample possesses a low quantum dot density and poor luminescence performance. With the increase of the number of growth periods, the quantum dot density of the sample increases and the luminous performance improves. This indicates that the quality of the grown sample improves with the increase of InAs/GaAs period of the InGaAs layer. When the total InAs/GaAs period is 32, the quantum dot density of the sample is high and the luminescence performance is good. After the experimental measurement, the sample DAL-0 fabricated by conventional growth method and the sample DAL-32 (32-periods InAs/GaAs digital alloy superlattices) are utilized to fabricate quantum dot laser by standard process. The performances of two types of quantum dot lasers obtained with different growth methods are characterized. It is found that the InAs quantum dot lasers fabricated by the sample grown by digital alloy superlattice method have good performances. Under continuous wave operation mode, the threshold current is 24 mA corresponding to a threshold current density of 75 A/cm&lt;sup&gt;2&lt;/sup&gt;. The highest operation-temperature reaches 120 ℃. In addition, InAs quantum dot laser using digital alloy superlattice has good temperature stability. Its characteristic temperature is 55.4 K. Compared with the traditional laser, the InAs quantum dot laser grown by InAs/GaAs digital alloy superlattice has good performance in terms of threshold current density, output power and temperature stability, which indicates that high-quality laser can be obtained by this growth method. Using the InAs/GaAs digital alloy superlattice growth method, the InGaAs composition can be changed without changing the temperature of the source oven. Thus InAs quantum dot lasers with different luminescence wavelengths can be obtained through this growth method. The InAs/GaAs digital alloy superlattice structure can be used to realize different averaging of In content in the growth structure. The method provides a new idea for designing and growing the active region of quantum dot laser.

SCIENTIFIC AND TECHNICAL BASIS FOR THE DEVELOPMENT OF INSTALLATIONS WITH MICROWAVE POWER SUPPLY FOR PROCESSING RAW MATERIALS AT AGRICULTURAL ENTERPRISES

The developed methodology of designing installations with microwave power supply for heat treatment of raw materials of agricultural enterprises is described. The scientific problem is the low energy efficiency of installations designed for heat treatment of raw materials with steam-water mixture, convective heat supply, the absence of continuous-flow installations for farms that ensure the preservation of consumer properties of the heat-treated product at reduced operating costs. (Research purpose) The research purpose is developing the scientific and technical foundations of installations with microwave power supply for processing raw materials at agricultural enterprises. (Materials and methods) Carried out three-dimensional modeling of the structural design of the installations in the Compass 20 program, determined the electrodynamic parameters of the “generator-resonator” system in the CST Microwave Studio program. (Results and discussion) Resonators of different structural designs have been developed for different types of raw materials, in which electromagnetic safety is ensured by forbidden waveguides, decelerating systems in the form of a chain of connected resonators, comb, cylindrical spiral, rod ring, counter pins. In resonators with curved surfaces, several magnetrons of the same frequency or operating at close frequencies with dissectors were used to change the frequency of the generator and increase the number of types of vibrations, and mixing, transporting mechanisms that allow maintaining the well of the technological process less than 0.5 and observing the dimensions of the raw materials in accordance with the depth of penetration of the wave. It was found that when using several magnetrons, the concentration of the electromagnetic field energy in the resonator volume and the reduction of radiation losses are achieved using ceramic reflectors. The values of the intrinsic Q-values of the resonators were determined to evaluate the thermal efficiency coefficient. (Conclusions) Using the examples of an animal colostrum defroster, instant milk pasteurizer and a three-section hop dryer with air-cooled magnetrons, the implementation of the scientific and technical fundamentals of designing microwave equipment for processing raw materials of agricultural enterprises was shown. It was revealed that they provide ways to achieve a continuous mode of operation of the equipment in compliance with electromagnetic safety without a shielding housing by implementing metal-dielectric resonators with decelerating systems and ceramic reflectors with an optimal arrangement of waveguides with air-cooled magnetrons on the curved surfaces of the resonators.

STRESS ANALYSIS IN A CONVEYOR BELT FOR THE MAXWELL MODEL OF ELASTIC ELEMENT

The mechanism of propagation of longitudinal dynamic stresses in a conveyor belt, the material of which corresponds to the Maxwell model of an elastic element, is considered. The features of the occurrence of longitudinal vibrations in the material of the conveyor belt for the section of the transport system equipped with asynchronous motors are considered. It is shown that the acceleration of the conveyor belt occurs as a result of an abrupt change in the traction moment of the asynchronous electric motor when the power consumption of the conveyor section changes. The process of acceleration/deceleration of the conveyor belt is periodic and is determined by the uneven distribution of material along the transport route. This imposes additional restrictions on the synthesis of algorithms for optimal control of the conveyor belt speed. Accounting for uneven distribution of material along the transport route is based on an analytical PiKh-model of the conveyor section. To analyze the longitudinal vibrations in the conveyor belt section of the transport system, the wave equation is written and the boundary conditions are substantiated. An estimate of the propagation velocity of longitudinal vibrations in the conveyor belt is given. A solution of the wave equation based on the method of successive approximations is obtained, which determines the dynamics of the propagation of dynamic stresses along the conveyor belt. An estimate of the value of the characteristic acceleration time of the belt, which determines the continuous mode of operation of the transport conveyor section, is given. The scientific novelty of the results obtained lies in the improvement of the control systems for the flow parameters of the transport system in the presence of restrictions associated with the occurrence of longitudinal vibrations in the conveyor belt. The practical significance of the results obtained lies in the construction of a methodology for calculating the limitations of the acceleration/deceleration mode of a conveyor belt unevenly loaded with material along the transport route.

Rational design of a miniaturized mechanical frequency regulator for the sustained triboelectric generation

Mechanical design offers an effective way to improve triboelectric performance. However, mechanical components can increase the system volume for an installation. In this work, the miniaturized mechanical frequency regulator-based triboelectric nanogenerator (MMFR-TENG) was investigated to utilize irregular mechanical energies and enhance the applicability of mechanically designed TENGs. Based on the wind-up mechanism and the noncontact freestanding mode, the mechanical components and structure were designed and integrated. Based on the rotational energy analysis and root mean square (RMS) outputs, the effects of mechanical component parameters, such as the moment of inertia of rotators, mainspring stiffness, and switch structure, on triboelectric performance and characteristics were assessed, and optimized mechanical conditions were determined. In addition, two different operation modes of the MMFR-TENG, frequency regulation and continuous operation modes, were demonstrated. Our MMFR-TENG can provide an RMS power of 17.9 μW under irregular mechanical energy inflow in the frequency regulation mode. A handheld MMFR-TENG and its capability to charge capacitors were demonstrated. Our MMFR-TENG provides an effective technique to improve the applicability of mechanically designed TENGs in real life.

Ammonia Removal by Simultaneous Nitrification and Denitrification in a Single Dual-Chamber Microbial Electrolysis Cell

Ammonia removal from wastewater was successfully achieved by simultaneous nitrification and denitrification (SND) in a double-chamber microbial electrolysis cell (MEC). The MEC operations at different applied voltages (0.7 to 1.5 V) and initial ammonia concentrations (30 to 150 mg/L) were conducted in order to evaluate their effects on MEC performance in batch mode. The maximum nitrification efficiency of 96.8% was obtained in the anode at 1.5 V, followed by 94.11% at 1.0 V and 87.05% at 0.7. At 1.5 V, the initial ammonia concentration considerably affected the nitrification rate, and the highest nitrification rate constant of 0.1601/h was determined from a first-order linear regression at 30 mg/L ammonium nitrogen. The overall total nitrogen removal efficiency was noted to be 85% via the SND in the MEC operated at an initial ammonium concentration of 50 mg/L and an applied cell voltage of 1.5 V. The MEC operation in continuous mode could remove ammonia (50 mg/L) in a series of anode and cathode chambers at the nitrogen removal rate of 170 g-N/m3.d at an HRT of 15. This study suggests that a standalone dual-chamber MEC can efficiently remove ammonia via the SND process without needing additional organic substrate and aeration, which makes this system viable for field applications.

A Sparse Sampling Sensor Front-end IC for Low Power Continuous SpO 2 & HR Monitoring.

Photoplethysmography (PPG) is an attractive method to acquire vital signs such as heart rate and blood oxygenation and is frequently used in clinical and at-home settings. Continuous operation of health monitoring devices demands a low power sensor that does not restrict the device battery life. Silicon photodiodes (PD) and LEDs are commonly used as interface devices in PPG sensors; however, using of flexible organic devices can enhance the sensor conformality and reduce the cost of fabrication. In most PPG sensors, most of system power consumption is concentrated in powering LEDs, traditionally consuming mWs. Using organic devices further increases this power demand since these devices exhibit larger parasitic capacitances and typically need higher drive voltages. This work presents a sensor IC for continuous SpO 2 and HR monitoring that features an on-chip reconstruction-free sparse sampling algorithm to reduce the overall system power consumption by ∼70% while maintaining the accuracy of the output information. The designed frontend is compatible with a wide range of devices from silicon PDs to organic PDs with parasitic capacitances up to 10 nF. Implemented in a 40 nm HV CMOS process, the chip occupies 2.43 mm 2 and consumes 49.7 μW and 15.2 μW of power in continuous and sparse sampling modes respectively. The performance of the sensor IC has been verified in vivo with both types of devices and the results are compared against a clinical grade reference. Less than 1 bpm and 1% mean absolute errors were achieved in both continuous and sparse modes of operation.