The utilization of natural gum polysaccharides as the vehicle for drug delivery systems and other biomedical applications has increased in recent decades. Their biocompatibility, biodegradability, and price are much cheaper than other materials. It is also renewable and available in massive amounts, which are the main reasons for its use in pharmaceutical applications. Gum can be easily functionalized with other natural polymers to enhance their applications. Various aspects of the utilization of natural gums in the forms of polyelectrolyte complexes (PECs) for drug delivery systems are discussed in this review. The application of different mathematical models were used to represent the drug release mechanisms from PECs; these models include a zero-order equation, first-order equation, Higuchi, simplified Higuchi, Korsmeyer−Peppas, and Peppas−Sahlin.

Direct methanol fuel cells (DMFCs) offer high energy density, simple liquid fuel storage, and the ability to operate at ambient temperature. They may be used in a variety of portable mobile power supplies, small civilian power supplies, and automotive power supplies. However, in the process of electrochemical reaction inside a DMFC, because the reactants and products are distributed unevenly, the in-plane concentration of reactants and reaction rate are different; thus, the current density generated in the active area shows a high degree of non-uniformity. The high local current density can easily lead to the acceleration of DMFC aging. As a result, the operating cost of the DMFC is increased and the service life is shortened, which limits the commercial application of DMFCs. In this work, we develop an in-plane gradient loading catalyst. The loading on both the anode and cathode catalysts was lower near the inlet and higher close to the outlet. The experimental results of the single-c... [more]

A rotary desiccant-based air-conditioning system is a heat-driven hybrid system which combines different technologies such as desiccant dehumidification, evaporative cooling, refrigeration, and regeneration. This system has an opportunity to utilize low-grade thermal energy obtained from the sun or other sources. In this paper, the basic principles and recent research developments related to rotary desiccant-based cooling systems are recalled and their applications and importance are summarized. It is shown that with novel system configurations and new desiccant materials, there is great potential for improving the performance and consistency of rotary desiccant systems; at the same time, the use of solar energy for regeneration purposes can minimize the operating cost to a great extent. Some examples are presented to demonstrate how rotary desiccant air conditioning can be a promising solution for replacing traditional vapor-compression air-conditioning systems. Recent advances and on... [more]

To reach Carbon Peak in 2030 and Carbon Neutrality in 2060, China is developing renewable energy at a fast pace. Renewable energy enterprises will participate in the power market in an all-round way as China gradually improves its electricity market. Signing the Power Purchase Agreement (PPA) helps renewable energy companies to avoid market risk and achieve sustainable development. Therefore, a novel PPA pricing model is proposed in our research. Based on the theory of the Levelized Cost of Energy (LCOE), our model considers system operating costs in China’s dual-track electric power sector, which is both government-guided and market-oriented. First of all, key influencing factors of the PPA agreement are analyzed in view of the developments of the renewable energy and electricity markets in China. Next, the design of pricing strategies for renewable energy power plants to cope with market challenges is presented through a photovoltaic project case study. The results show that when the... [more]

In this paper, a new hybrid algorithm based on two meta-heuristic algorithms is presented to improve the optimization capability of original algorithms. This hybrid algorithm is realized by the deep ensemble of two new proposed meta-heuristic methods, i.e., slime mold algorithm (SMA) and arithmetic optimization algorithm (AOA), called DESMAOA. To be specific, a preliminary hybrid method was applied to obtain the improved SMA, called SMAOA. Then, two strategies that were extracted from the SMA and AOA, respectively, were embedded into SMAOA to boost the optimizing speed and accuracy of the solution. The optimization performance of the proposed DESMAOA was analyzed by using 23 classical benchmark functions. Firstly, the impacts of different components are discussed. Then, the exploitation and exploration capabilities, convergence behaviors, and performances are evaluated in detail. Cases at different dimensions also were investigated. Compared with the SMA, AOA, and another five well-kno... [more]

This paper presents a new method for the diagnostics of a hot water storage tank under operating conditions. Depending on the operating point of the tank, the method enables determination of thermal conductivity coefficients of the coil heat exchanger, which allows us to determine the intensity of heat transfer between the transfer medium and water in the tank as well as of tank walls, which consequently enables determination of heat losses to the environment. Furthermore, the dynamic properties of the tank may also be determined by applying this method. The advantage of this method is possibility of analyzing changes in the material constants of the coil heat exchanger, tank walls, and dynamic properties of the tank as a function of mass flow of the medium supplying the coil heat exchanger. The possibility of determining coefficients of thermal conductivity as well as the inertia of tank and exchanger, based on temperature measurements acquired in operating conditions is a novelty in... [more]

Oxy-combustion with high flame temperature, low heat loss, high combustion efficiency, and low NOx emissions is being extensively studied. The thermal radiation from soot particles and gases in oxy-combustion accounts for the vast majority of the total heat transfer. Based on a detailed chemical reaction mechanism coupled with the soot particle dynamics model and optically thin radiation model, the influence of the flame structure and temperature distribution on the thermal radiation in oxygen-enriched counterflow diffusion flames was studied in this paper. The results revealed that reasonable assignment of total recycled flue gas and the degree of dilution of fuel and oxidant were critical, which can be used to adjust the overall radiation situation of the flame. At the same adiabatic flame temperature, as the fuel concentration decreased and the oxidant concentration increased (the stoichiometric mixture ratio is from 0.3 to 0.6), the soot formation decreased, which led to the partic... [more]

The Peukert and Liebenow equations were obtained from experimental studies of lead−acid batteries. Currently, they are used to evaluate capacity released by batteries of other electrochemical systems (alkaline, lithium-ion, etc.), as well. In this paper, it is experimentally proved that for lithium-ion batteries, the Peukert equation can be used in two intervals of the discharge currents. The first interval includes currents from 0.2Cn up to the first inflection point of the experimental function of the battery capacity dependence on the discharge currents C(i). The second interval covers currents from the second inflection point of the experimental function C(i) up to the maximum currents that were used in the experiments. For some lithium-ion batteries, the range of low discharge currents, where the Peukert equation is applicable, is quite large and often completely covers the range of the discharge currents used in practice for these batteries. Therefore, many authors, when estimati... [more]

In this research, the main purpose was to study the applicability of a machining method on microscale medical-equipment manufacturing. The characteristics of wire electrochemical micromachining (WECMM) against NiTi 50-50 wire was investigated. The study utilized a tungsten wire 0.03 mm in diameter as an electrode to cut a fine slot into the nickel−titanium wire. In order to reach a high-precision WECMM finish, an ultrashort pulse power generator was used as a power source to minimize the stray current effect, thus improving the machining accuracy. During the process, various machining parameters were tested for their effects on machining characteristics. In addition, ultrasonic-vibration-aided WECMM was investigated to determine whether it benefited the machining characteristics. The experiment’s results showed that under such an experiment setting, microslots can be successfully manufactured. Furthermore, with the advance adjustment of experimental parameters, the machining accuracy w... [more]

The circular economy and maximization of environmental sustainability are increasingly becoming the vision and mission of companies competing in present-day global markets. In particular, in the energy sector, the transition from fossil fuels to renewable sources of energy has become the widespread mantra. One typical example is the deployment of devices which produce clean energy, such as solar photovoltaic panels and solar thermal panels, wind generators, tidal stream generators, wave power generators, etc. These are undoubtedly generating clean energy, but their manufacture creates hazardous by-products, the disposal of which results in increased environmental pollution. Chemical Vapor Deposition (CVD) is widely used in manufacturing of solar photovoltaic cells. In these processes, typically, crystalline silicon is precipitated from chlorosilanes, iodides, bromides and fluorides. Polluting by-products include deposition of a silicon film, formation of SiO2 powder and formation of to... [more]

In the application of DPFs (diesel particulate filters), temperature prediction and control technology during the regeneration phase has always been a great challenge, which directly affects the safety and performance of diesel vehicles. In this study, based on theoretical analysis and sample gas bench test results, a one-dimensional simulation model is built with GT-POWER software. The effects of soot loading quantity and oxygen concentration on regeneration temperature performance are studied. Simulation results show that, when the soot loading quantity exceeds 46 g (12.7 g/L), the maximum temperature inside DPF during the regeneration phase would be higher than 800 °C, and the risk of burning crack would be high. When the oxygen concentration in the exhaust gas is low (lower than 7%), the fuel injected into exhaust gas fails to give off enough heat, and the exhaust gas temperature fails to reach the target regeneration temperature, hydrocarbon emission could be found from the DPF ou... [more]

Micro-electro-mechanical systems (MEMS) occupy an important position in the national economy and military fields, and have attracted great attention from a large number of scholars. As an important part of the micro-electromechanical system, the micro-combustor has serious heat loss due to its small size, unstable combustion and low combustion efficiency. Aiming at enhancing the heat transfer of the micro-combustor, improving the combustion stability and high-efficiency combustion, this paper embedded porous media in the combustor, and the effects of different parameters on the combustion characteristics were numerically studied. The research results showed that the layout of porous media should be reasonable, and the small and large pore porous media embedded in the inner and outer layers, respectively, can bring better combustion performance. Meanwhile, A: 10−30 has a high and uniform temperature distribution, and its methane conversion rate reached 97.4%. However, the diameter ratio... [more]

This study aims to quantify the climate change impact of pyrochar production from pulp and paper mill sludge and the subsequent utilisation in combined heat and power (CHP) plants for co-generation of heat and electricity using the environmental life cycle assessment (E-LCA) method. In the Pyrochar Scenario, in which the sludge is pyrolyzed into pyrochar, the authors have assumed that pyrochar would replace coal. In the Reference Scenario, sludge is incinerated with a subsequent low rate of energy recovery. A comprehensive sensitivity analysis was performed to determine the conditions in which the sludge pyrochar would offer the greatest climate-effect benefits. The parameters selected for the said analysis are the form of pyrochar (pellet or powder), fuels replaced by it in the CHP plant (solid waste and peat vis-à-vis coal), and the utilisation of the pyrochar fuel in another European country (Germany and Spain vis-à-vis Sweden). The results of this E-LCA clearly show that using pyro... [more]

Biodiesel is a biodegradable, renewable, and carbon-neutral alternative to petroleum diesel that can contribute to the global effort of minimizing the use of fossil fuels and meeting the ever-growing energy demands and stringent environmental constraints. The aim of this work was to (1) review the recent progress in feedstock development, including first, second, third, and fourth-generation feedstocks for biodiesel production; (2) discuss recent progress in lipase research and development as one of the key factors for establishing a cost-competitive biodiesel process in terms of enzyme sources, properties, immobilization, and transesterification efficiency; and (3) provide an update of the current challenges and opportunities for biodiesel commercialization from techno-economic and social perspectives. Related biodiesel producers, markets, challenges, and opportunities for biodiesel commercialization, including environmental considerations, are critically discussed.

The numerical analysis of many geotechnical problems involves a high number of structural elements, leading to extensive modelling and computational effort. Due to its exceptional ability to circumvent these obstacles, the embedded beam element (EB), though originally intended for the modelling of micropiles, has become increasingly popular in computational geotechnics. Recent research effort has paved the way to the embedded beam element with interaction surface (EB-I), an extension of the EB. The EB-I renders soil−structure interaction along an interaction surface rather than the centreline, making it theoretically applicable to any engineering application where beam-type elements interact with solid elements. At present, in-depth knowledge about relative merits, compared to the EB, is still in demand. Subsequently, numerical analysis are carried out using both embedded beam formulations to model deep foundation elements. The credibility of predicted results is assessed based on a co... [more]

One of the quickest ways to influence both the wall temperature and thermal NOx emissions in rotary kilns is to change the air−fuel ratio (AFR). The normalized counterpart of the AFR, the equivalence ratio, is usually associated with premixed flames and studies of its influence on diffusion flames are inconsistent, depending on the application. In this paper, the influence of the AFR is investigated numerically for rotary kilns by conducting steady-state simulations. We first conduct three-dimensional simulations where we encounter statistically unstable flow at high inflow conditions, which may be caused by vortex stretching. As vortex stretching vanishes in two-dimensional flow, the 2D simulations no longer encounter convergence problems. The impact of this simplification is shown to be acceptable for the thermal behaviour. It is shown that both the wall temperature and thermal NOx emissions peak at the fuel-rich and fuel-lean side of the stoichiometric AFR, respectively. If the AFR... [more]

The research of oil/air two-phase flow and heat transfer is the fundamental work of the design of lubrication and heat transfer in aero-engine bearing chamber. The determination of impact state criterion of the moving oil droplets with the wall and the analysis of oil droplet deposition characteristics are important components. In this paper, the numerical analysis model of the impact between the moving oil droplet and the wall is established by using the finite volume method, and the simulation of oil droplet impingement on the wall is carried out. Then the effects of oil droplet diameter, impact velocity, and incident angle on the characteristic parameters of impact state are discussed. The characteristic parameters include the maximum spreading length, the maximum spreading width, and the number of splashing oil droplets. Lastly the calculation results are verified through comparing with the experimental results in the literature. The results show as follows: (1) The maximum spreadi... [more]

CO2 flooding is an important method for improving oil recovery for reservoirs with low permeability. Even though CO2 could be miscible with oil in regions nearby injection wells, the miscibility could be lost in deep reservoirs because of low pressure and the dispersion effect. Reducing the CO2−oil miscibility pressure can enlarge the miscible zone, particularly when the reservoir pressure is less than the needed minimum miscible pressure (MMP). Furthermore, adding intermediate hydrocarbons in the CO2−oil system can also lower the interfacial tension (IFT). In this study, we used dead crude oil from the H Block in the X oilfield to study the IFT and the MMP changes with different hydrocarbon agents. The hydrocarbon agents, including alkanes, alcohols, oil-soluble surfactants, and petroleum ethers, were mixed with the crude oil samples from the H Block, and their performances on reducing CO2−oil IFT and CO2−oil MMP were determined. Experimental results show that the CO2−oil MMP could be... [more]

This paper analyzes the performance of a three-phase converter architecture with a reduced common mode voltage to be used in electric motor drives. Starting from the classical three-phase bridge architecture, two additional switches are inserted in the DC link, in order to decouple the source from the load during the freewheeling intervals. Ad-hoc modulation strategies are introduced and evaluated against the classical three-phase space vector modulation. Three main parameters are analyzed: common mode voltage, efficiency and reliability. Experimental measurements on a converter prototype are used to evaluate the common mode performance. The efficiency in the case of Si-IGBT and SiC-MOSFETs is experimentally evaluated. Reliability analysis performed with a Coffin-Mason model showed that the higher efficiency offered by the SiC devices allows for a marked extension of the lifetime.

In inductive power transfer (IPT) systems, series−series (S-S) and double capacitances and inductances−series (LCCL-S) compensation topologies are widely utilized. In this study, the basic characteristics of S-S and LCCL-S are analyzed and compared in the tuning state. In addition, considering the universality of detuning, and because the two topologies have the same secondary structures, the voltage and current stress on components, input impedances, voltage gains, and output powers of S-S and LCCL-S are mainly analyzed and compared in the detuning state, which is caused by variations in the secondary compensation capacitance. To compare the efficiency of the two topologies and verify the comparative analysis, comparative experiments based on a 2.4-kW IPT experimental prototype are conducted. The comparative result shows that the S-S compensation topology is more sensitive to load variations and less sensitive to secondary compensation capacitance variations than LCCL-S. Both in the t... [more]

Active power filters (APF) aim at solving the harmonic problem originated by the nonlinear load in power systems. However, the high dv/dt and di/dt outputs from power electronic devices in a voltage source converter on APF introduced unwanted conducted electromagnetic interference (EMI) when compensating for the low-frequency harmonic components. Hence, this paper develops a spectrum analysis approach to investigate and quantify the source differential-mode (DM) voltage of a single-phase shunt APF to suppress the DM EMI via periodic carrier frequency modulation (PCFM). In this scheme, the analytical expressions of source DM voltage in the APF using the PCFM scheme are obtained with a double Fourier series. In addition, the influence of PCFM parameters on the source DM voltage spectrum is predicted based on the analytical expression. As a result, the PCFM parameters, which have the best suppression effect on the DM EMI are obtained. The experiment results proved the validity of the sawt... [more]

The half bridge (HB) modular multilevel converter (MMC) technology is considered a breakthrough to mitigate the shortcomings of the conventional voltage source converter (VSC) in high-voltage direct-current (HVDC) grid application. However, interruption of the DC fault is still a challenge due to fast di/dt and extremely high levels of DC fault current. The fault interruption using a DC circuit breaker (DCCB) causes enormous energy dissipation and voltage stress across the DCCB. Therefore, the use of a fault current limiter is essential, and the superconducting fault current limiter (SFCL) is the most promising choice. Past literature has focused on the operating characteristics of DCCB or limiting characteristics of the SFCL. However, there is little understanding about the fault interruption and system recovery characteristics considering both DCCB and SFCL. In this paper, we have presented a comparative study on fault interruption and system recovery characteristics considering thre... [more]

The injection water and formation water in the Mahu oil field have high salinity and poor compatibility, which leads to scaling and blockage in the formation or fracture propping zone during production. In this paper, a scale-inhibiting fracturing fluid system is developed which can prevent the formation of scale in the reservoir and solves the problem of scaling in the fracture propping zone at the Mahu oil field. Firstly, based on scale-inhibition rate, the performances of six commercial scale inhibitors were evaluated, including their acid and alkali resistance and temperature resistance. Then, the optimal scale inhibitors were combined with the fracturing fluid to obtain a scale-inhibiting fracturing fluid system. Its compatibility with other additives and scale-inhibition performance were evaluated. Finally, the system’s drag-reduction ability was tested through the loop friction tester. The results showed that, among the six scale inhibitors, the organic phosphonic acid scale inh... [more]

Increasing demands on mobility and transport, but limited space above ground, lead to new traffic routes being built, even more underground in the form of tunnels. In addition to improving the traffic situation, tunnels offer the possibility of contributing to climate-friendly heating by indirectly serving as geothermal power plants. In this study, the geothermal potential of the future longest railway tunnel in the world, the Brenner Base Tunnel, was evaluated. At the Brenner Base Tunnel, warm water naturally flows from the apex of the tunnel towards the city of Innsbruck, Austria. In order to estimate its geothermal potential, hydrological data of discharge rates and temperatures were investigated and analyzed. The investigations indicated the highest geothermal potential in the summertime, while the lowest occurs during winter. It could be shown that these variations were a result of cooling during discharge through areas of low overburden (mid mountain range), where the tunnel atmo... [more]

The n-butanol/n-octanol fueled reactivity-controlled compression ignition engine was numerically studied based on the KIVA-CHEMKIN code. First, the knocking combustion characteristics were analyzed while functioning with a premixed n-butanol percentage of 20% (B20), since it exhibited the most severe knocking. Ten local regions were monitored to obtain local data, such as pressure and heat release rate. The local pressure oscillation was quantified by a band-pass filter. Second, the premixed n-butanol percentage and the intake valve close (IVC) timing were varied to investigate their effects on the combustion characteristics and emissions formations, as well as their potential for mitigating knocking. The results showed that a strong pressure oscillation was observed for B20 near the cylinder wall, which indicates severe knocking. This consequence is mainly caused by the low-temperature combustion of the n-octanol/n-butanol/air mixture near the cylinder-wall region. Increasing premixed... [more]