Average Conversion Efficiency Research Articles

Experimental study on the emission characteristics and performance of PNA coupled aftertreatment system with different catalyst loading

In order to meet the strict emission regulations in the future, passive NOx absorber (PNA) and electrically heated catalyst (EHC) will gradually become the necessary technologies for diesel engines. In this paper, based on a diesel engine with PNA, EHC, diesel oxidation catalyst (DOC), selective catalytic reduction catalyst integrated into diesel particulate filter (SDPF) and selective catalytic reduction catalyst (SCR), the impact of PNA emission characteristics and performance with different catalyst loading were investigated. The results showed that EHC was coupled behind the DOC is more conducive to energy conservation and reducing NOx emissions. Compared with EHC was coupled in front of the DOC, the time for SDPF inlet temperature to reach 180 ℃ was reduced by 123 s, the power consumption of EHC was reduced by 0.25 kWh and nitrogen oxide (NOx) conversion efficiency increased by 16.61% in the cold start phase when EHC was coupled behind the DOC. Meanwhile, PNA has a certain adsorption effect on CO, THC, and NOx. When EHC was coupled behind the DOC, the adsorption amount of carbon monoxide (CO), total hydrocarbon (THC), and NOx increases with the increase of PNA catalyst loading. The maximum adsorption time of PNA for NOx reached 171 s. Similarly, the conversion efficiency of CO, THC, and NOx during the cold start stage also increases with the increase of PNA catalyst loading. The maximum average conversion efficiency of CO, THC, and NOx was 60.58%, 88.60%, and 95.72%, respectively. In cold start phase, the PNA50 has achieved high PNA performance, and the gain brought by higher catalyst loading is not obvious. In medium–high temperature phase, due to the high exhaust temperature, PNA has no effect on the conversion efficiency of CO, THC, and NOx. PN conversion efficiency is more than 99% and is not affected by the PNA type. The findings provide the fundamental insights to promote the application of PNA and EHC in diesel engines and reduce emissions of diesel engines under cold start conditions.

Compost Waste Heat to Power Organic Rankine Cycle Design and Analysis

Abstract This paper presents a feasibility study of a hybrid compost waste heat to power/Concentrating Solar Panel (CSP) green energy Organic Rankine Cycle (ORC). The power plant is baselined to operate with a duty of 24/7 on compost waste heat and utilize solar thermal energy to boost power output during the day. This paper discusses the design of the power plant, the design of a compost driven heat exchanger/boiler, compost pile thermal analysis, CSP analysis, and simulated power plant output analysis The selection of isobutane as ORC working fluid is justified herein. A Levelized Cost of Energy (LCOE) analysis was performed to ensure that the energy produced by this hybrid power plant would come at a reasonable and competitive cost. The results herein show that the hybrid power plant affords an LCOE of 4 ¢/kWh for compost operation alone and an LCOE of 10.7 ¢/kWh for compost and CSP solar energy operation. The hybrid compost/ORC power plant presented herein affords an average energy conversion efficiency of 4.3%. Centric to the operation of the compost waste heat to power plant presented herein is the correct design and selection of the heat exchanger which interfaces the compost waste heat stream to the isobutane ORC. The design and analysis of this heat exchanger as well as commercially off-the-shelf hardware to meet the specifications is given in detail herein

Conversion of wet microalgae to biodiesel with microalgae carbon based magnetic solid acid catalyst

A microalgae carbon based magnetic solid acid catalyst (MCMSA) was prepared using microalgal residue after lipids extraction as carbon source through magnetization, carbonization and sulfonation. The effects of three preparation conditions of pore-forming agent type, carbonization temperature, and sulfonation agent type on the MCMSA were studied. The specific surface area, functional group, acidity and magnetism of MCMSA were studied to determine the optimized catalyst. The MCMSA prepared under the condition that the pore-forming agent is NaCl (1:1 m/m), the carbonization temperature is 800 °C, and the sulfonation agent is H2SO4 (1:10 m/v, 150 °C) has a high specific surface area (124.70 m2/g), high acidity (3.64 mmol/g) and high magnetism (1.042 emu/g), and shows good thermal stability at transesterification temperature of 90 °C with low loss of acid groups. MCMSA showed high conversion efficiency (98.51 %) in the microwave-assisted catalytic transesterification at 90 °C with MCMSA dosage of 5 wt% and methanol to wet microalgae ratio of 6.25:1 (v/m). It could maintain catalytic activity in five consecutive cycles without further treatment, and the average conversion efficiency was approximately 85.5 %. The results showed that the MCMSA could replace the traditional homogeneous acid catalyst for the preparation of microalgae biodiesel.

Dietary supplementation of Ficus hookeri leaves as herbal feed additive affects nutrient utilization and growth performances in growing crossbred calves

The objective of this study was to evaluate the effect of dietary supplementation of Da qing shu (Ficus hookeri) leaf meal as herbal feed additive on nutrients utilization and growth performance of growing crossbred calves. Ten Jersey male cross-bred calves (~ 4 months of age) were divided equally into two groups (G1 and G2) and were fed ad lib. under stall feeding on a paddy straw based mixed ration consisting of 50% paddy straw and 50% concentrate mixture for a duration of 140 days. Two types (C1 and C2) of iso-nitrogenous concentrate mixtures were prepared. Four per cent (w/w) wheat bran in concentrate mixture (C2) of test group (G2) was replaced by sun dried ground Ficus hookeri leaf meal. Experimental calves of test group (G2) were fed Ficus hookeri leaf meal @ 2% of the diet. Daily dry matter intake (g/d) was similar among the calves of two experimental groups. Apparent digestibility of DM, OM, NDF, ADF and cellulose improved in the Ficus hookeri leaf meal fed calves (G2). DCP value of the ration was similar while, TDN value of the ration was higher in the calves of Ficus hookeri leaf meal supplemented group (G2). However, plane of nutrition among the calves of both experimental groups was similar. Average finishing body weight, daily body weight gain, feed conversion efficiency and blood glucose level were higher in Ficus hookeri leaf fed calves (G2). Therefore, it may be concluded from the results of the study that dietary supplementation of Da qing shu (Ficus hookeri) leaf meal as herbal feed additive @ 2% of total mixed diet significantly improved the fibre digestibility, average daily body weight gain and feed conversion efficiency in growing Jersey male crossbred calves.

Synthesis of gallium phosphide quantum dots with high photoluminescence quantum yield and their application as color converters for LEDs

Group III–Ⅴ quantum dots (QDs) are preferred over Group Ⅱ–Ⅵ materials because of their relatively mild toxicity. In this study, a facile synthetic method to obtain gallium phosphide (GaP) QDs with color conversion performance is reported. Colloidal GaP QDs were produced via a hot-injection method using an optimized combination of precursors. The products showed controllable emissions from 400 to 520 nm, depending on the band gap. High photoluminescence (PL) quantum yields of 35–40% with a full width at half maximum (FWHM) of 75 nm were achieved in the green emission region. In addition, the green-emission GaP QDs were applied as a color-conversion material for optical devices with UV and blue LED chips. An average color conversion efficiency of 15% was achieved. This study demonstrates the possibility of using GaP QDs as a competitive color-conversion material.

Customizable and upgradable design triple-band dual circular polarization rectenna for ambient RF energy harvesting

A Customizable and upgradable design of triple-band dual circular polarization (CP) rectenna is presented for ambient RF energy harvesting of available frequency bands (i.e., 1800, 2.15, 2.42) efficiently. A broadband dual CP receiving antenna is proposed with a broadband impedance matching bandwidth of 123% from 1 to 4.2 GHZ and axial-ratio (AR) bandwidth of 75% from 1.45 to 3.06 GHz with a maximum gain of 5.54 dBi to cover the selected frequency bands. Besides, the proposed triple-band rectifier with a multi-stub impedance matching network is feasible for RF harvesting with the new design method, and the non-dependence of the resonance frequencies on the distance between the stubs, the rectifier can be easily adjusted for other frequencies. The proposed rectenna’s measurement results show that the generated average dc output voltage and conversion efficiency are improved to 0.8 V and 60%, respectively, at a low RF input power density of −2 dBm for a load resistance of 1.5 kΩ.

Experimental assessment of a pilot-scale gasification plant fueled with olive pomace pellets for combined power, heat and biochar production

This research work examines the performance of an experimental gasification plant fueled with exhausted olive pomace pellets for the concurrent production of electricity, heat and biochar in the olive oil industry. The gasification plant consists of an air-blown downdraft fixed-bed gasifier that generates a lean fuel gas, termed producer gas, in a self-sustaining autothermal process. After conditioning of the producer gas in a cooling and cleaning unit, a four-stroke spark-ignition engine coupled to an electric generator is eventually used as power generation unit. An extensive experimental assessment of this facility was performed under partial and nominal load operation and was supplemented by a physicochemical analysis of the carbonaceous solid material discharged from the gasifier. The mass and energy balances of the gasification plant were calculated, including the carbon conversion efficiency and diverse energy conversion efficiencies. The results revealed an overall stable operation of the gasification plant in terms of composition and heating value of the producer gas and cogenerative production of electricity and heat in the engine–generator set. Under nominal operating conditions, the net electrical efficiency of the gasification plant was 12%–13%, with an average carbon conversion efficiency of the biomass feedstock into producer gas just above 80% and an average cold gas efficiency close to 70%.

Theoretical investigation of a novel electrochemical electricity generator driven by diurnal temperature variation

Diurnal temperature variation is ubiquitous and abundant, which is an untapped energy source generated by intermittent solar radiation. Tapping into this vast energy with energy-efficient and cost-effective technologies may provide a promising approach for transitioning to an energy-sustainable economy and society. In this study, a novel temperature-induced electrochemical power generator is proposed and investigated to harvest the thermal energy brought by the diurnal temperature variation. The novelty of such a power generator lies in its separate electrochemical and heat exchange processes. The mathematical models are established and functionalized to simulate the performance of the proposed generator in practical application. To investigate and prove the feasibility and effectiveness of the proposed generator, several essential environmental parameters and working condition factors are studied. The results show that the proposed generator is workable for generating electricity empowered by the diurnal temperature variation, which could generate 3.27 kWh of electricity at a standard working condition in one diurnal period. Whereas ambient temperature is marginal to its net energy output, other parameters, i.e., solar radiation, wind velocity, and cells’ area, have significant effects on the performance. The net energy outputs of the proposed generator grow significantly from 0.69 kWh to 7.10 kWh with the solar radiation increasing from 200 W/m2 to 1200 W/m2, which is acceptable to provide electricity for the domestic daily demand, otherwise can be scalable to meet the needs. Furthermore, annual average energy conversion efficiencies of the generator are more than 2% in different typical weather conditions. This paper may enrich the renewable and sustainable power generation technology, as well as guide the design, optimization and application of the novel temperature-induced electrochemical power generator driven by the diurnal temperature variation to expedite the net zero.

350-2500 nm supercontinuum white laser enabled by synergic high-harmonic generation and self-phase modulation

Supercontinuum white laser with large bandwidth and high pulse energy would offer incredible versatility and opportunities for basic science and high technology applications. Here, we report the generation of high-efficiency 2.8-octave-spanning ultraviolet-visible-infrared (UV-Vis-IR) (with 350-2500 nm 25 dB bandwidth) supercontinuum white laser from a single chirped periodically poled lithium niobate (CPPLN) nonlinear crystal via synergic high-harmonic generation (HHG) and self-phase modulation (SPM). The CPPLN exhibits multiple controllable reciprocal-lattice bands to simultaneously support the quasi-phase matching (QPM) for simultaneous broadband 2nd-10th HHG via cascaded three-wave mixing against a broadband fundamental pump laser. Due to the efficient second-order nonlinearity (2nd-NL) up-conversion and significant 3rd-NL SPM effect both in the pump and HHG laser pulses, 350-2500 nm supercontinuum white laser is eventually obtained with 17 μJ per pulse under pump of 45 μJ per pulse mid-infrared femtosecond laser corresponding to an average high conversion efficiency of 37%. Our work opens up a route towards creating UV-Vis-IR all-spectrum white lasers through engineering the synergic action of HHG and SPM effects in nonlinear crystals for applications in ultrafast spectroscopy, single-shot remote sensing, biological imaging, and so on.

Exploration on the emissions and catalytic reactors interactions of a non-road diesel engine through experiment and system level simulation

In this paper, the emission characteristics and catalytic reactors interactions of a non-road diesel engine are investigated under non-road transient cycle (NRTC) by experiment and system level simulation. The results showed that the overall emission conversion efficiency of hydrocarbon (HC), carbon monoxide (CO), nitrogen oxides (NOX) and particulate matter (PM) is 96.68 %, 91.45 %, 97.67 % and 93.33 %, respectively under NRTC in experiment. In addition, the interactions of each catalytic converter for emissions under NRTC have been obtained through simulation. When the diesel oxidation catalytic (DOC) temperature is higher than 600 K, CO and HC emissions basically achieve almost 0 through DOC purification. Furthermore, DOC can convert nitric oxide (NO) into nitrogen dioxide (NO2) which provides strong oxidation for the passive regeneration of diesel particulate filter (DPF). The NO reaction rate is closely related to DOC temperature. And the average conversion efficiency from NO to NO2 in DOC is 40.36 %. Moreover, the DOC inlet pressure has almost no effect on the conversion of HC and CO. When the temperature of selective catalytic reduction (SCR) is higher than 500 K, the averages NOx conversion efficiency of SCR is up to 98.74 %. And ammonia purification catalyst (ASC) can further reduce NO emissions while absorbing slip ammonia. When the inlet temperature of DPF is more than 520 K, it has almost no effect on the oxidation of PM. The PM conversion efficiency of aftertreatment system (ATS) is mainly affected by the PM collection efficiency of DPF. The average PM collection efficiency of DPF is 53.32 %, while the PM conversion efficiency of ATS is 91.54 % by simulation. Although DPF will convert PM to CO, these CO cannot be completely converted into carbon dioxide (CO2). So the CO conversion efficiency of ATS is lower than that of DOC.

Membrane filtration processing of infant milk formula alters protein digestion in young pigs

Reducing heat treatment (HT) during processing of infant milk formula (IMF) is desirable to produce a product that more closely resembles breast milk. By employing membrane filtration (MEM), we produced an IMF (60:40 whey to casein ratio) at pilot scale (250 kg). MEM-IMF had a significantly higher content of native whey (59.9 %) compared to HT-IMF (4.5 %) (p < 0.001). Pigs, at 28 days old, were blocked by sex, weight and litter origin and assigned to one of two treatments (n = 14/treatment): (1) starter diet containing 35 % of HT-IMF powder or (2) starter diet containing 35 % of MEM-IMF powder for 28 days. Body weight and feed intake were recorded weekly. Pigs at day 28 post weaning were sacrificed 180 min after their final feeding, for the collection of gastric, duodenal, jejunum and ileal contents (n = 10/treatment). MEM-IMF diet resulted in more water-soluble proteins and higher levels of protein hydrolysis in the digesta at various gut locations compared to HT-IMF (p < 0.05). In the jejunal digesta, a higher concentration of free amino acids were present post MEM-IMF consumption (247 ± 15 µmol g−1 of protein in digesta) compared to HT-IMF (205 ± 21 µmol g−1 of protein). Overall, average daily weight gain, average dairy feed intake and feed conversion efficiency were similar for pigs fed either MEM-IMF or HT-IMF diets, but differences and trends to difference of these indicators were determined in particular intervention periods. In conclusion, reducing heat treatment during processing of IMF influenced protein digestion and revealed minor effects on growth parameters providing in vivo evidence that babies who are fed with IMF processed by MEM are likely to have different protein digestion kinetics but minimal effect on overall growth trajectories as babies fed IMF processed by traditional thermal processing.

A zero switch and sensorless reconfiguration approach for sustainable operation of roof‐top photovoltaic system during partial shading

AbstractPhotovoltaic (PV) roof‐top systems in real‐time environments are highly susceptible to the commonly occurring scenario of partial shading that occurs due to unavoidable conditions such as the shadow of buildings and trees. The occurrence of partial shading creates a serious mismatch among the modules of PV arrays that results in severe unexpected power losses in PV arrays. The conventional and hybrid configurations used for loss mitigation in PV arrays are sometimes unreliable and incapable of generating higher power during partial shading. Hence, this paper focuses on the development of a simple and effective technique for the reliable operation of PV arrays and loss reduction during the occurrence of partial shading. The technique is applicable to arbitrary array sizes having no dynamic parts and requires no switches and sensors for implementation to enhance the performance and operation of the system. The performance and reliability of the technique have been investigated under MATLAB simulation and real‐time scenarios by comparing it with various configurations under shading. The investigation reveals a higher power output by the proposed technique with an average conversion efficiency of higher than 90% and power enhancement of 19.07% than other configurations.

Economic analysis of crossbred (Landrace × Desi) pig reared under different floor space allowances

Present experiment was conducted to study the relative economics of crossbred (Landrace×Desi) pigs with thirty six crossbred barrows reared under 3 different floor space allowances (n=12 each) having group size of 4 pigs/pen. One group (TIS) was provided floor space as per Indian Standards (0.9, 1.35 and 1.8 m2/pig for weaner, grower and finisher stages, respectively) specifications, while other two groups with 33% (T2/3) and 50% (T1/2) reduced floor space allowances. Only covered floor area was provided for all the groups. Different parameters analyzed during the study involved growth, feed conversion efficiency, requirement of water and labour for floor washing, and some other economic variables. Pigs were reared up to 28 weeks of age. Relative economics of pig rearing for three floor space allocation groups was calculated using partial budget analysis. Major performance traits, i.e. average daily gain (ADG) and feed conversion efficiency (FCE) did not differ significantly among the groups. Although body weights of T2/3 and T1/2 groups were marginally higher than TIS group. In contrary to minor savings of labour, large quantity of water was saved in T1/2 and T2/3 groups (805.4 liters/pig and 400.1 liters/pig, respectively) than TIS group between weaner and finisher stages. Additionally, input costs of ₹` 145 and ` ₹ 96 per pig was saved by providing floor space as per T1/2 and T2/3 groups, respectively than TIS group. It can be concluded that economic gains were maximum in 50% floor space reduction group without adverse effect on performance traits of crossbred pigs.

Real-time nonlinear model predictive control for optimizing the ammonia coverage ratio of an SCR system based on TC-QPSO

SCR systems with complex chemical reaction dynamics are important components of emission aftertreatment systems. Their contradictory emission requirements of higher NOx conversion efficiency and lower NH3 slip can be simultaneously achieved by optimizing the ammonia coverage ratio, which can be accomplished with a nonlinear model predictive control (NMPC) framework. However, how to find a reasonable NMPC approach for optimizing the ammonia coverage ratio and utilize an appropriate method to solve it remain a formidable challenge. In this paper, a two-layer hierarchical control framework for an SCR system is developed to decouple the optimization and tracking control of the ammonia coverage ratio. In the upper layer, an NMPC controller with a long prediction horizon is designed to account for the emission objectives and constraints and generate optimal trajectories for the ammonia coverage ratio. In the lower layer, a robust observing and tracking controller with a short horizon is employed which takes the planned trajectories as the tracking target. Moreover, an improved thermonuclear-initiation and cross-boundary quantum-behaved particle swarm optimization (TC-QPSO) method for optimizing the ammonia coverage ratio based on its dynamic characteristics is proposed to solve the NMPC problem. The simulation results show that the proposed TC-QPSO emission optimization effects of NOx and NH3 are closest to those of the SQP method (the benchmark controller) with a slight computation time penalty. The experimental results under the three transient cycles show that the average NOx conversion efficiency of the proposed two-layer hierarchical control framework with the TC-QPSO algorithm can reach more than 98% with an average NH3 slip of less than 11 ppm, which is able to satisfy emission requirements, and that compared to the traditional QPSO algorithm, the average NH3 slip of the proposed TC-QPSO algorithm is improved by 45.6% with an average NOx conversion efficiency penalty of 1.09% and its emission optimization effects have better robustness for uncertainties in transient cycles.

Four-terminal perovskite/silicon series solar cells with 28% efficiency achieved by suppressing edge recombination

Although the commercial application of solar cells pursues scalable and large-area devices, small-area solar cells on a scale of several centimeters possess many advantages such as low fabrication cost and facile high-throughput screening in the research laboratory. Most emerging photovoltaic technology starts from the studying of small-area devices. Recently, perovskite/silicon tandem solar cells have aroused extensive research interest because they can break through the radiative efficiency limit of single-junction solar cells. However, when commercial large-area silicon cells are cut into small pieces with a few squared centimeters in area for laboratory use, there occurs a significant efficiency loss, limiting the performance of tandem cells. Herein, to eliminate the thermal damage caused by the traditional laser cutting method and also reduce the non-radiative recombination of heterojunction silicon cells after being cut, a cold-manufacturing method of grinding wheel dicing is used to cut heterojunction silicon cells. This method is realized by high-speed mechanical grinding accompanied by liquid washing, which avoids damaging the edge of solar cell caused by heat. Compared with the device cut by laser, the heterojunction silicon cells cut by the cold-manufacturing method exhibit less cross-sectional damage. The measurements by scanning electron microscopy (SEM) and three-dimensional optical profilometer reveal that the morphology of the device edge is smoother than the counterpart cut by laser. Device physics measurements including electrochemical impedance spectrum(EIS), dark current-voltage curves, transient photovoltage (TPV), transient photocurrent (TPC), and the dependence of short-circuit current density and open-circuit voltage on light intensity reveal that the cold-manufacturing method can significantly prevent the heterojunction silicon cells from non-radiatively recombining after being cut. These results indicate that the edge-recombination of the silicon solar cells cut by grinding wheels is reduced compared with that cut by laser. As a result, statistical analysis of the device performance reveals that both the open-circuit voltage and fill factor of the device are improved, and the average photoelectric conversion efficiency increases by an absolute efficiency of ~1%. Stacking the obtained silicon cells with the normal transparent perovskite solar cells, the obtained four-terminal perovskite/silicon tandem solar cells deliver an efficiency of over 28%. This work emphasizes the importance of reducing efficiency loss during manufacturing the heterojunction silicon solar cell in fabricating high-performance silicon-based tandem solar cells.

Energetic and parametric studies of a basic hybrid collector (PV/T-Air) and a photovoltaic (PV) module for building applications: Performance analysis under El Jadida weather conditions

The photovoltaic thermal hybrid collectors represent one of the most used technologies in positive energy buildings, the device allows converting the available solar energy into heat and electricity at the same time. In this study, a comparative analysis is introduced between two different types of solar conversion devices: conventional hybrid solar air collector (PV/T-Air) and photovoltaic (PV) module. Also, a parametric study was performed to know the impact of different parameters related to the performance of both solar systems. A numerical system based on the fourth order Runge–Kutta iteration method, is used in this study, founded on a strong coupling between the heat balance equations and the different electrical and thermal parameters of both configurations that are included in this work. The energy performance evaluation was applied to the climatic conditions of El Jadida city, located in Morocco. The numerical results indicates that the estimated value of the daily average overall energy conversion efficiency attains: 30.22% for the PV module, and 52.14% for the examined hybrid air collector (PV/T-Air). These results are calculated with an air mass flow rate of 0.0215 kg/s, and these values are according to the meteorological data collected on the site of El Jadida city for a sunny day in July.

Over 700 mV IBC Solar Cell by Optimizing Front Surface Field Passivation

In this article, the front surface field (FSF) passivation of n-type interdigitated back contact (IBC) solar cell was studied and a method to improve the FSF passivation performance of n-type IBC solar cell was proposed. We optimized the phosphorus diffusion on the front surface of IBC solar cell to form a field passivation structure with low surface concentration and shallow junction depth. The surface recombination rate was calculated using EDNA2. Solar cell parameters were simulated by Quokka, and finally we did experiment verification. The results showed that when the deposition time and flow rate of POCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> in the phosphorus diffusion process time is 3 min and POCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> flow rate is 80 sccm, the front surface saturation current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) is reduced to 3.71 fA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , corresponding to the front surface recombination rate of 100 cm/s. On solar cells, open-circuit voltage reached 704 mV, the average conversion efficiency of IBC solar cell exceeded 24%, and the highest conversion efficiency reached 24.28%.

Site-Specific Tritium Labeling at the Predefined Internal Position of the Chemically-Modified RNA

In nucleic acid drug discovery, it is extremely important to develop a technology to understand the distribution in target organs and to trace the degradation process in the body in order to optimize the structure and improve the efficiency of the clinical trial process. Since nucleic acid drugs are essentially metabolically degraded into numerous fragments, labeling at the internal position is preferable to that at the terminus. Due to the high molar specific activity of tritium, various approaches for tritium-labeling have been studied for nucleic acid drugs. Nevertheless, a generally-applicable method for tritium labeling of the internal position of a nucleic acid has not been established. In this study, we have demonstrated a new and efficient method for site-specific tritium labeling of the cytosine base at a predefined internal position in nucleic acid drugs. This method was developed by the chemical modification of the cytosine 4-amino group with the pyridinyl vinyl keto group by the functionality-transfer reaction using the reactive oligodeoxynucleotide (ODN), followed by reduction with NaBT4. Applicability to a variety of chemical structures, such as 5-methyl cytosine, 2'-O-methyl, 2'-fluoro ribose derivatives, Locked/Bridged nucleic acid (LNA/BNA) derivatives, as well as phosphorothioate bonds, has been evidenced using nine oligoribonucleic acid (ORN) substrates. It has been clearly demonstrated that this method is an excellent method for tritium-labeling of nucleic acid with an average conversion efficiency of 74%, an average isolated labeling yield of 60%, and an average specific activity of 61 GBq/mmol. This method is expected to contribute to the preclinical absorption, distribution, metabolism, excretion (ADME) studies of nucleic acid drug candidates.

Modeling of a PV system by a back-mounted spray cooling section for performance improvement

The cell temperature is an important factor affecting the operation performance of a photovoltaic (PV) module. In this work, efforts are made to study the possibility of a PV system with spray cooling section formed by different lengths of guide and support plates at the rear surface of the PV module. A 3-D model of heat and mass transfer that integrates photoelectric conversion efficiency varying with the cell temperature under different spray cases was established. The effects of different parameters like nozzle height, the lengths of guide plate and support plate, nozzle installation angle, spray water pressure and ambient conditions on the PV performance were simulated in both spray and non-spray cases. Results show that the optimal configuration of the proposed PV cooling system is obtained at the nozzle height of the bottom scheme where the length of guide plate is 588.9 mm, the length of support plate is 680 mm and the nozzle installation angle is horizontal. Moreover, the average cell temperature and average conversion efficiency at the spray water pressure of 3 bar are 51.90 °C and 17.58%, respectively in the spray case while they are 68.80 °C and 16.06%, respectively in the non-spray case (the solar radiation is kept at 800 W/m2 and the ambient temperature is 35 °C). The PV cooling system leads to an average reduction in the cell temperature of 12.31 °C and an average increment in the conversion efficiency of 1.10% when compared with the non-spray case within the ambient temperature of 31–41 °C at the relative humidity of 45%. There is a slight rise in the average cell temperature as the relative humidity increases in the spray case while the average cell temperature changes a little in the non-spray case within the relative humidity of 15–90% at the ambient temperature of 35 °C. This study proves that the proposed PV cooling system is an effective way to improve the performance of PV module during hot periods.

A hybrid transient CFD-thermoelectric numerical model for automobile thermoelectric generator systems

Dynamic performance prediction of the automobile thermoelectric generator system is one of the research hotspots in the field of thermoelectric technology. In this work, a hybrid transient CFD-thermoelectric numerical model is proposed for the first time to predict the dynamic response characteristics of an automobile thermoelectric generator system. Taking the exhaust gas of a heavy truck under a highway fuel economy test driving cycle as the transient heat source, the transient numerical study on the automobile thermoelectric generator system is carried out. It is found that the dynamic output power of the automobile thermoelectric generator system changes more smoothly than exhaust temperature due to the effect of thermal inertia, while the conversion efficiency fluctuates greatly. The transient output power at t = 467 s and transient conversion efficiency at t = 635 s reach the highest values of 45.16 W and 39.68 %, respectively. Within the period of 765 s, the total power generation and average conversion efficiency of the automobile thermoelectric generator system are 26460 J and 3.29 %, respectively. Through the transient experimental validation, the average error of transient output voltage between experimental and model results is 6.43 %. This work fills the gap in the dynamic performance prediction of thermoelectric devices used for fluid waste heat recovery. The findings are helpful in better understanding the dynamic response characteristics of the automobile thermoelectric generator system.