Continuous Conversion Research Articles

Fully-integrated electrochemical system that captures CO2from flue gas to produce value-added chemicals at ambient conditions

Fully integrated electrochemical system for continuous CO2capture and conversion.

Nonoxidative coupling of ethane with gold loaded photocatalysts

Direct and continuous conversion of ethane to yield n-butane and hydrogen at near room temperature (ca. 320 K) was examined with gold loaded gallium oxide and titanium dioxide photocatalysts without the aid of any oxidant in a flow reactor.

Temperature-Dependant Active Sites for Methane Continuous Conversion to Methanol Over Cu-Zeolite Catalysts Using Water as the Oxidant

Temperature-Dependant Active Sites for Methane Continuous Conversion to Methanol Over Cu-Zeolite Catalysts Using Water as the Oxidant

TINJAUAN HISTORIS TEKNOLOGI VARIETAS UNGGUL DAN PROGRAM INTENSIFIKASI DALAM PENINGKATAN PRODUKTIVITAS PADI BERKELANJUTAN

<p class="A04-abstrak2">The Indonesian Agency for Agricultural Research and Development (IAARD) has created various technology packages, significantly superior rice varieties with high yields and resistance to various pests and diseases. Since 1943 hundreds of superior varieties of rice have been released. However, domestic rice production has yet to be able to meet the national rice needs. One of the main problems is the decrease in fertile land due to continuous land conversion. Hence, the mainstay in increasing rice production is to escalate productivity through technological improvements. Therefore, IAARD continues to create new high-yielding rice varieties through plant breeding. More than 200 high-yielding varieties of rice have been produced to meet the challenge of increasing productivity. This paper aims to examine the historical profile of the creation of superior rice varieties in line with intensification programs and their role in increasing national rice production. The study was conducted using a desk study approach by examining secondary data and literature from various publications. The study results showed that creating high-yielding varieties accompanied by various intensification programs had increased rice productivity sustainably. The challenge for IAARD is the creation of new high-yielding varieties with higher yields than those currently available.</p>

Modeling and numerical study of SO2-depolarized electrolysis for hydrogen production in the hybrid sulfur cycle

The SO2-depolarized electrolysis (SDE) is one of the main processes in the hybrid sulfur cycle for hydrogen production, the microscopic characteristics of which are still not clear. In this work, a numerical analysis of SDE was conducted. The steady-state, laminar and incompressible 2D model of the electrolytic cell (EC) for carrying out SDE was first developed and verified. Physical field characterization indicated that the velocity was almost uniformly distributed in the flow channel, but higher pressure drops and pumping power consumption existed in the anode channel than in the cathode channel. Meanwhile, the continuous conversion of SO2 to H2SO4 at anode and generation of H2 at cathode along the channel length were determined. Further exploring the impacts of three main operating parameters implied that an appropriate higher electrolytic potential, lower inlet flow rate (not less than 0.005 m/s) and operating temperature were favorable for improving the SDE. After comprehensive consideration of SDE performance and energy consumption, a feasible operating condition of 0.8 V, 303 K, and 0.005 m/s was proposed for SDE process. The developed model and microscopic characterization of SDE will favor the design and optimization of EC for SDE process.

An Ultrasmall Fe3 O4 -Decorated Polydopamine Hybrid Nanozyme Enables Continuous Conversion of Oxygen into Toxic Hydroxyl Radical via GSH-Depleted Cascade Redox Reactions for Intensive Wound Disinfection.

Nanozyme-based chemodynamic therapy (CDT) for fighting bacterial infections faces several major obstacles including low hydrogen peroxide (H2 O2 ) level, over-expressed glutathione (GSH) in infected sites, and inevitable damage to healthy tissue with abundant nonlocalized nanozymes. Herein, a smart ultrasmall Fe3 O4 -decorated polydopamine (PDA/Fe3 O4 ) hybrid nanozyme is demonstrated that continuously converts oxygen into highly toxic hydroxyl radical (•OH) via GSH-depleted cascade redox reactions for CDT-mediated bacterial elimination and intensive wound disinfection. In this system, photonic hyperthermia of PDA/Fe3 O4 nanozymes can not only directly damage bacteria, but also improve the horseradish peroxidase-like activity of Fe3 O4 decorated for CDT. Surprisingly, through photothermal-enhanced cascade catalytic reactions, PDA/Fe3 O4 nanozymes can consume endogenous GSH for disrupting cellular redox homeostasis and simultaneously provide abundant H2 O2 for improving •OH generation, ultimately enhancing the antibacterial performance of CDT. Such PDA/Fe3 O4 can bind with bacterial cells, and reveals excellent antibacterial property against both Staphylococcus aureus and Escherichia coli. Most interestingly, PDA/Fe3 O4 nanozymes can be strongly retained in infected sites by an external magnet for localized long-term in vivo CDT and show minimal toxicity to healthy tissues and organs. This work presents an effective strategy to magnetically retain the therapeutic nanozymes in infected sites for highly efficient CDT with good biosafety.

Design and development of a low-cost system to convert solar thermal energy into electricity for households in South Africa using solar concentrators

South Africa is, due its specific latitude location in the southern hemisphere, exposed to high solar irradiation levels. Black thermal absorbers have a high absorbance for solar incident radiation, while commercial photovoltaic technology only converts about 10% of energy available in the solar spectrum. In this article, low-cost Peltier conversion cells, that are normally used for cooling purposes, and that are freely available in supply stores in South Africa, were identified as suitable conversion cells for converting thermal energy into electricity. Two prototypes of thermal-to-electricity energy conversion systems were subsequently designed and developed. Particularly, advanced pulse mode DC- to- DC conversion technology, a special electronic control system, was developed, that could extract high amounts of electrical energy from the cells and could store the energy in standard storage batteries. A 3 W and a 30 W output continuous conversion capacity system were developed. A power conversion of up to 2 W capacity per individual cell was achieved. The systems used no movable parts, and the lifespan of the systems is projected to be at least twenty years. Cost and viability analyses of the systems were performed and the results were compared to existing solar photovoltaic energy conversion systems. Combining the 30 W capacity system with a black body and reflector plate absorber system revealed a cost structure of only ZAR 0.8 per kWh, as compared with a derived ZAR 3 per kWh for a combined photovoltaic and solar geyser combination, as calculated for a ten-year term. The technology as developed is suitable to be incorporated in South African households and rural Africa applications.

FPGA Design of a High- Resolution FIR Band-Pass Filter by Using LabVIEW Environment

Designers regularly use Finite Impulse Response (FIR) filters to fulfil the need for current electronic design applications such as signal or image processing and digital communications because of the remarkable selectivity computational efficiency. Fast and efficient information processing requires a dedicated microprocessor or a digital signal processor that may not always be available or provide enough performance. In such scenarios, designers can configure FPGAs for processing digitized signals. One of the most popular signal processing applications is filtering. Unlike the Infinite Impulse Response (IIR) filters, FIR filters do not have analog equivalent circuits. For this purpose, continuous time-discrete time conversion is not possible with the help of transforms. Because analog filters cannot have a finite impulse response, the design methods of FIR filters can be made as windowing method, pulse response truncation, and optimal filter design method. Considering this information, it aims to digitally separate two signals with different frequencies (2.4 kHz and 4.2 kHz), which are given to the input as analog, to obtain the desired information signal and suppress other signals. We preferred to use LabVIEW graphical programming language to get the digital FIR filter coefficients. We selected rectangular windowing, set the digital filter's sampling frequency as 18720 Hz, and determined the filter's coefficient with high-frequency resolution as 24. Using filter coefficients in the real-time FPGA-VHDL environment, we showed the performance and resource consumption. LabVIEW is used for simulation as well as obtaining filter coefficients. In addition, we compared both simulation and real-time FPGA-VHDL application output waveforms and examined both platforms' advantages and disadvantages.

Electrified Conversion of Contaminated Water to Value: Selective Conversion of Aqueous Nitrate to Ammonia in a Polymer Electrolyte Membrane Cell

The application of a polymer electrolyte membrane (PEM) electrolytic cell for continuous conversion of nitrate, one of the contaminants in water, to ammonia at the cathode was explored in the present work. Among carbon‐supported metal (Cu, Ru, Rh and Pd) electrocatalysts, the Ru‐based catalyst showed the best performance. By suppressing the competing hydrogen evolution reaction at the cathode, it was possible to reach 94 % faradaic efficiency for nitrate reduction towards ammonium. It was important to match the rate of the anodic reaction with the cathodic reaction to achieve high faradaic efficiency. By recirculating the effluent stream, 93 % nitrate conversion was achieved in 8 h of constant current electrolysis at 10 mA cm−2 current density. The presented approach offers a promising path towards precious NH3 production from nitrate‐containing water that needs purification or can be obtained after capture of gaseous NO x pollutants into water, leading to waste‐to‐value conversion.

How Diverse are State Medical Boards?

How Diverse are State Medical Boards?

Study on continuous cooling process coupled with ortho-para hydrogen conversion in plate-fin heat exchanger filled with catalyst

A mathematical model of the plate-fin heat exchanger filled with catalyst (CFPFHX) is established to investigate the continuous cooling process coupled with ortho-para hydrogen conversion at 42–70 K. The flow and heat transfer performance and the efficiency of ortho-para hydrogen conversion in the CFPFHX are quantitatively evaluated, and the effects of the structural parameters on the flow and heat transfer coupled with ortho-para hydrogen conversion are analyzed. The results show that the Elovich model is the best existing kinetic models of ortho-para hydrogen conversion with an average relative deviation of 1.8%. The Colburn heat transfer factor (j factor) of the hot side of the CFPFHX is 4.3 times that of the plate-fin heat exchanger (PFHX), and the thermal enhancement factor (TEF) of the hot side is 37.7% of that of the PFHX. Meanwhile, for the CFPFHX, the j factor and the TEF of the hot side under different structural parameters are always about 8–10 times and 68%–93% of that of the cold side respectively. Therefore, the CFPFHX can ensure the flow and heat transfer performance and realize the ortho-para hydrogen continuous conversion. And a fin with the larger flow area (high fin height, wide fin spacing and small fin thickness) has a better flow and heat transfer performance and ortho-para hydrogen conversion. The outlet para-hydrogen ratio youtp-H2 and the mass space velocity vm in the CFPFHX have an approximate linear trend. When mass space velocity vm ≤ 0.6589 kg/(m3·s), the outlet para-hydrogen ratio youtp-H2 can meet the requirement at 42–70 K. Above all, the mechanism of flow and heat transfer coupled with ortho-para hydrogen conversion is revealed for the first time in this study, which can provide a theoretical guidance for the application of the integrated technology in large scale hydrogen liquefaction process.

Continuous aqueous-phase cascade conversion of trioses to lactic acid over Nb2O5 catalysts

Continuous aqueous-phase cascade conversion of trioses to lactic acid over Nb2O5 catalysts

Has the growth of cities in Ghana anything to do with reduction in farm size and food production in peri-urban areas? A study of Bolgatanga Municipality

Growth and expansion of urban areas often result in dramatic transformation of land use in cities in Ghana with implications for farming and food production, which is a major livelihood activity for some of the inhabitants. This study assessed the implications of urban growth on farming and food crop production in Bolgatanga Municipality using a mixed method research design. Household interview schedule and key informant interviews were employed in the collection of primary data. In addition, multi-temporal satellite data was used to analyze land use and land cover change in the Municipality. The findings revealed that urban growth, resulting from increase in population, residential and commercial developments, seem to engulf agricultural activities. There has been a dramatic expansion of built-up areas in the Municipality with adverse implications for farming and food production in the future. The study concludes that continuous unguided conversion of farmlands, woodland and shrubs into built-up areas in the Municipality is detrimental to farming and food production. The formulation and implementation of an urban planning policy, by the Municipal Assembly in conjunction with the Land Use and Spatial Planning Department and the Municipal Department of Agriculture, that incorporates zoning of fertile lands for farming purposes and encourages best farming practices is recommended.

Modeling and control strategy analysis of a hydraulic energy-storage wave energy conversion system

Worldwide increasing energy demands promote development of environment-friendly energy sources. As consequences, ocean wave is exploited as an ideal energy source to mitigate greenhouse gas emissions. In this paper, a hydraulic energy-storage wave energy conversion system is constructed, and a mathematical model of main components is built for analysis. Control strategies of generator-side and grid-side are defined for the system, where a Vienna rectifier is applied to converter of generator-side. A two-level space vector plane simplified modulation method for Vienna rectifier is designed for the three-level system and a modulation algorithm is detailed, which has lower complexity compared with traditional three-level space vector pulse width modulation (SVPWM) algorithm. An improved adjusting factor method is proposed to solve the potential imbalance of neutral point caused by uneven charging to the upper and lower capacitors in the three-level structure, which optimizes sector division and inhibits the neutral-point potential offset and fluctuation effectively. Using Matlab/Simulink, the intermittent and continuous power conversion modes of the system under different wave conditions are simulated. The results indicate stable operation of the system, feasible topology scheme, modulation algorithm and control strategy, and effective suppression of AC-side harmonics.

Mitigating the Effect of COVID Lockdown Period on Channel and Bandwidth Utilization in Mobile Communication Network in North Western Rajasthan (India)

The COVID-19 lockdown has led all the citizens (mobile subscribers) of India to stay at home and rather work from home. The people have started consuming more channel utilization (in mobile communication) through a continuous long duration conversations and more internet data through more streaming content as well as logging on to work from home. It was also reflected in how data demand from residential areas rose as compared to commercial areas. Consequently the bandwidth and channel saturation has evolved out to be a severe problem thereby affecting the work performance of all online offices and multi-national companies. This research paper proposes the simulation based experimental study of DITMC technique for mitigating this effect with a special concern in North Western Rajasthan part of India. The simulation results show that significant enhancement of 60.52% in channel utilization and bandwidth optimization is possible with negligible overhead of 0.23%. This technique also enables the telecom operators to ponder research in this field that will promisingly lead to manage augmented number of mobile subscribers (independent of any lockdown period) in limited bandwidth thereby using the spectrum efficiently.

Production of d-tagatose in packed bed reactor containing an immobilized l-arabinose isomerase on alginate support

In this study, l-arabinose isomerase (L-AI, E.C. 5.3.1.4) was immobilized on alginate beads and packed in a reactor for continuous synthesis of d-tagatose from d-galactose of whey. The developed L-AI entrapped on alginate bead ([email protected]) was characterized by scanning electron microscopy, confocal laser scanning microscopy, fourier transform infrared spectroscopy and thermogravimetric analyzer. The effect of pH and temperature on free L-AI vis-a-vis immobilized L-AI was studied. For both types, optimum pH was 6.0 and temperature was 50 °C. The packed bed reactor was also designed for continuous conversion of d-galactose to d-tagatose. d-Galactose derived from whey was used as substrate for the synthesis of d-tagatose by free and immobilized L-AI. The free as well as immobilized L-AI in the reactor achieved the equilibrium conversion of 50% at standard conditions. In addition, the L-AI in packed bed reactor showed conversion of d-galactose into d-tagatose for multiple cycles.

Regulating the Li2S deposition by grain boundaries in metal nitrides for stable lithium-sulfur batteries

Catalysis is a fundamental solution in suppressing the shuttling of lithium polysulfides (LiPSs), which is essential to the practical applications of lithium-sulfur batteries with high energy density. However, the uncontrollable deposition of electronic and ionic insulative Li2S always passivates the catalyst surface for the continuous LiPS conversion. Herein, we propose an effective method to regulate Li2S deposition to avoid the catalyst surface passivation by introducing grain boundaries (GBs) in the catalyst. Hollow microspheres composed of MoN-Mo2N heterostructure with abundant and highly accessible GBs were prepared as the models. The results show GBs act as the two-dimensional nucleation sites, guiding the fast nucleation and three-dimensional deposition of Li2S around them, avoiding the formation of dense Li2S coating on their surface. Thus, the high capacity Li2S deposition with enhanced conversion kinetics was achieved. The interlayer composed of the above catalyst and carbon nanotube effectively suppresses the shuttling of LiPSs and promotes their fast conversion, leading to a low capacity decay of 0.049% per cycle at 1 C for 800 cycles for the assembled battery. With a higher sulfur loading of 4.7 mg cm−2 under 0.5 C, high capacity retention of 77.2% after 200 cycles could also be achieved.

Achieving reversible precipitation-decomposition of reactive Li2S towards high-areal-capacity lithium-sulfur batteries with a wide-temperature range

Facilitating polysulfide conversion by electrocatalysis is a promising strategy to suppress shuttle effect in lithium-sulfur (Li-S) batteries, yet the active sites in electrocatalysts are gradually passivated by continuous formation of Li2S passivation layer over cycling, making it challenging to achieve steady conversion of sulfur species. Herein, a strategy of reactive Li2S collaborated with dual-directional Fe3C electrocatalyst is proposed to achieve fast and continuous conversion of sulfur species for drastically boosting the performance of Li-S batteries. During the reduction process, reactive Li2S with unique three-dimensional porous structure is precipitated on Fe3C surface, which not only shortens ion/electron diffusion path but also exposes and retains more active sites in Fe3C. While for the following oxidation process, Fe3C also promotes the decomposition of reactive Li2S to refresh electrocatalyst surface. Therefore, the high catalytic activity of Fe3C is well retained during the entire electrochemical process, as verified by comprehensive experimental and theoretical calculation results. Eventually, Fe3C enables stable operation of high-areal-capacity Li-S batteries (> 6.0 mAh cm−2) under a wide-temperature range (-10 to 40 °C). Our strategy of coupling reactive Li2S with a bidirectional electrocatalyst provides a new avenue for developing high-energy and wide-temperature Li-S batteries.

Designof a tunable turnstile mode converter for high-power microwave applications.

This study investigates the frequency tunability of a coaxial transverse electromagnetic mode (TEM)-linear-polarized TE11 mode tunable turnstile mode converter (TTMC) for high-power microwave applications using a combination of simulation and experiment. In the proposed structure, the sliding folded waveguide can be moved radially to meet the requirement of linear polarization, and the matching structure is designed to eliminate the undesired reflection. The simulation shows that the conversion efficiency of the TTMC can reach over 99% in the frequency range of 1.45-2.35GHz, corresponding to a frequency tuning bandwidth of about 47.4%. Moreover, the TTMC can maintain a continuous high conversion efficiency at different frequency points by changing the tuning mechanism. The experimental investigation shows that the TTMC can convert the coaxial TEM mode into a circular waveguide TE11 mode with a conversion efficiency of above 95% in the frequency range of 1.55-2.35GHz. The experimental measurements agree well with the simulation results, implying feasibility of the TTMC designand its superior performance.

Polynomial, Neural Network, and Spline Wavelet Models for Continuous Wavelet Transform of Signals.

In this paper a modified wavelet synthesis algorithm for continuous wavelet transform is proposed, allowing one to obtain a guaranteed approximation of the maternal wavelet to the sample of the analyzed signal (overlap match) and, at the same time, a formalized representation of the wavelet. What distinguishes this method from similar ones? During the procedure of wavelets’ synthesis for continuous wavelet transform it is proposed to use splines and artificial neural networks. The paper also suggests a comparative analysis of polynomial, neural network, and wavelet spline models. It also deals with feasibility of using these models in the synthesis of wavelets during such studies like fine structure of signals, as well as in analysis of large parts of signals whose shape is variable. A number of studies have shown that during the wavelets’ synthesis, the use of artificial neural networks (based on radial basis functions) and cubic splines enables the possibility of obtaining guaranteed accuracy in approaching the maternal wavelet to the signal’s sample (with no approximation error). It also allows for its formalized representation, which is especially important during software implementation of the algorithm for calculating the continuous conversions at digital signal processors and microcontrollers. This paper demonstrates the possibility of using synthesized wavelet, obtained based on polynomial, neural network, and spline models, during the performance of an inverse continuous wavelet transform.