工业负荷可持续并网太阳能光伏的可行性评价

可再生能源发电因其间歇性而具有多变性,对发展中国家来说,可再生能源发电的成本很高。由于电价定价和机制设计不合理,上网电价和净计量等支持性政策和方案对消费者也没有太大吸引力。屋顶太阳能光伏系统自用技术可以避免这些方案的缺点,因为这种技术比公用电网的发电成本更低。因此,产消者可以以最低价格使用大部分电力,更具吸引力。本文分析了并网工业太阳能光伏发电系统的成本和可行性。结果发现,基于储能并网的光伏系统成本为0.0086$/(kW·h),公用电网将以0.062$/(kW·h)的价格出售给产消者,与使用时间评级模型相比,年能源成本将降低35.23%。此外,所提出的方案可满足96%的年能源需求,保证了供应的安全性,所提出的模型可用于其他发展中国家。

3D direct printing of mechanical and biocompatible hydrogel meta-structures

Direct Ink Writing(DIW)has demonstrated great potential as a versatile method to 3D print multifunctional structures.In this work,we report the implementation of hydrogel meta-structures using DIW at room temperature,which seamlessly integrate large specific surface areas,interconnected porous characteristics,mechanical toughness,biocompatibility,and water absorption and retention capabilities.Robust but hydrophobic polymers and weakly crosslinked nature-origin hydrogels form a balance in the self-supporting ink,allowing us to directly print complex meta-structures without sacrificial materials and heating extrusion.Mechanically,the mixed bending or stretching of symmetrical re-entrant cellular lattices and the unique curvature patterns are combined to provide little lateral expansion and large compressive energy absorbance when external forces are applied on the printed meta-structures.In addition,we have successfully demonstrated ear,aortic valve conduits and hierarchical architectures.We anticipate that the reported 3D meta-structured hydrogel would offer a new strategy to develop functional biomaterials for tissue engineering applications in the future.

4D biofabrication via instantly generated graded hydrogel scaffolds

Formation of graded biomaterials to render shape-morphing scaffolds for 4D biofabrication holds great promise in fabrication of complex structures and the recapitulation of critical dynamics for tissue/organ regeneration.Here we describe a facile generation of an adjustable and robust gradient using a single-or multi-material one-step fabrication strategy for 4D biofabrication.By simply photocrosslinking a mixed solution of a photocrosslinkable polymer macromer,photoinitiator(PI),UV absorber and live cells,a cell-laden gradient hydrogel with pre-programmable deformation can be generated.Gradient formation was demonstrated in various polymers including poly(ethylene glycol)(PEG),alginate,and gelatin derivatives using various UV absorbers that present overlap in UV spectrum with that of the PI UV absorbance spectrum.Moreover,this simple and effective method was used as a universal platform to integrate with other hydrogel-engineering techniques such as photomask-aided microfabrication,photo-patterning,ion-transfer printing,and 3D bioprinting to fabricate more advanced cell-laden scaffold structures.Lastly,proof-of-concept 4D tissue engineering was demonstrated in a study of 4D bone-like tissue formation.The strategy’s simplicity along with its versatility paves a new way in solving the hurdle of achieving temporal shape changes in cell-laden single-component hydrogel scaffolds and may expedite the development of 4D biofabricated constructs for biological applications.

Review of Recent Progress in Robotic Knee Prosthesis Related Techniques:Structure,Actuation and Control

As the essential technology of human-robotics interactive wearable devices,the robotic knee prosthesis can provide above-knee amputations with functional knee compensations to realize their physical and psychological social regression.With the development of mechanical and mechatronic science and technology,the fully active knee prosthesis that can provide subjects with actuating torques has demonstrated a better wearing performance in slope walking and stair ascent when compared with the passive and the semi-active ones.Additionally,with intelligent human-robotics control strategies and algorithms,the wearing effect of the knee prosthesis has been greatly enhanced in terms of stance stability and swing mobility.Therefore,to help readers to obtain an overview of recent progress in robotic knee prosthesis,this paper systematically categorized knee prostheses according to their integrated functions and introduced related research in the past ten years(2010−2020)regarding(1)mechanical design,including uniaxial,four-bar,and multi-bar knee structures,(2)actuating technology,including rigid and elastic actuation,and(3)control method,including mode identification,motion prediction,and automatic control.Quantitative and qualitative analysis and comparison of robotic knee prosthesis-related techniques are conducted.The development trends are concluded as follows:(1)bionic and lightweight structures with better mechanical performance,(2)bionic elastic actuation with energy-saving effect,(3)artificial intelligence-based bionic prosthetic control.Besides,challenges and innovative insights of customized lightweight bionic knee joint structure,highly efficient compact bionic actuation,and personalized daily multi-mode gait adaptation are also discussed in-depth to facilitate the future development of the robotic knee prosthesis.

Scalable fabrication of sub-10 nm polymernanopores for DNA analysis

We present the first fabrication of sub-10 nm nanopores in freestanding polymer membranes via a simple,costeffective,high-throughput but deterministic fabrication method.Nanopores in the range of 10 nm were initially produced via a single-step nanoimprinting process,which was further reduced to sub-10 nm pores via a post-NIL polymer reflow process.The low shrinkage rate of 2.7 nm/min obtained under the conditions used for the reflow process was the key to achieving sub-10 nm pores with a controllable pore size.The fabricated SU-8 nanopore membranes were successfully employed for transient current measurements during the translocation of DNA molecules through the nanopores.

Energetic, economic, and environmental analysis of solid oxide fuel cell-based combined cooling, heating, and power system for cancer care hospital

In this study,energetic,economic,and environmental analysis of solid oxide fuel cell-based combined cooling,heating,and power(SOFC-CCHP)system is proposed for a cancer care hospital building.The energy required for the hospital power,cooling,and heating demands was obtained based on real and detailed field data,which could serve as a reference for future works in the field.These data with a 3D model for the hospital building are constructed and created in eQUEST software to precisely calculate the energy demands of the existing system(baseline case).Then,energetic,economic,and environmental models were developed to compare and assess the performance of the proposed SOFC-CCHP system.The results show that the proposed system can cover about 49% to 77% of the power demand of the hospital with an overall efficiency of 78.3%.Also,the results show that the levelized cost of electricity of the system and its payback period at the designed capacity of the SOFC is 0.087S/kWh and 10 years,respectively.Furthermore,compared to the baseline system of the hospital,the SOFC-CCHP reduces the CO_(2) emission by 89% over the year.The sensitivity analysis showed that a maximum SOFC efficiency of 52%and overall efficiency of 80%are achieved at cell operating temperature of 1027℃ and fuel utilization factor of 0.85.

Thermal conductivity of micro/nano-porous polymers: Prediction models and applications

Micro/nano-porous polymeric material is considered a unique industrial material due to its extremelylow thermal conductivity, low density, and high surface area. Therefore, it is necessary to establishan accurate thermal conductivity prediction model suiting their applicable conditions and provide atheoretical basis for expanding their applications. In this work, the development of the calculationmodel of equivalent thermal conductivity of micro/nano-porous polymeric materials in recent yearsis summarized. Firstly, it reviews the process of establishing the overall equivalent thermal conductivity calculation model for micro/nanoporous polymers. Then, the predicted calculation models ofthermal conductivity are introduced separately according to the conductive and radiative thermalconductivity models. In addition, the thermal conduction part is divided into the gaseous thermalconductivity model, solid thermal conductivity model and gas-solid coupling model. Finally, it isconcluded that, compared with other porous materials, there are few studies on heat transfer of micro/nanoporous polymers, especially on the particular heat transfer mechanisms such as scale effectsat the micro/nanoscale. In particular, the following aspects of porous polymers still need to be furtherstudied: micro scaled thermal radiation, heat transfer characteristics of particular morphologies at thenanoscales, heat transfer mechanism and impact factors of micro/nanoporous polymers. Such studieswould provide a more accurate prediction of thermal conductivity and a broader application in energyconversion and storage systems.

Leakage pressures for gasketless superhydrophobic fluid interconnects for modular lab-on-a-chip systems

Chip-to-chip and world-to-chip fluidic interconnections are paramount to enable the passage of liquids between component chips and to/from microfluidic systems.Unfortunately,most interconnect designs add additional physical constraints to chips with each additional interconnect leading to over-constrained microfluidic systems.The competing constraints provided by multiple interconnects induce strain in the chips,creating indeterminate dead volumes and misalignment between chips that comprise the microfluidic system.A novel,gasketless superhydrophobic fluidic interconnect(GSFI)that uses capillary forces to form a liquid bridge suspended between concentric through-holes and acting as a fluid passage was investigated.The GSFI decouples the alignment between component chips from the interconnect function and the attachment of the meniscus of the liquid bridge to the edges of the holes produces negligible dead volume.This passive seal was created by patterning parallel superhydrophobic surfaces(water contact angle>150°)around concentric microfluidic ports separated by a gap.The relative position of the two polymer chips was determined by passive kinematic constraints,three spherical ball bearings seated in v-grooves.A leakage pressure model derived from the Young-Laplace equation was used to estimate the leakage pressure at failure for the liquid bridge.Injection-molded,Cyclic Olefin Copolymer(COC)chip assemblies with assembly gaps from 3 to 240μm were used to experimentally validate the model.The maximum leakage pressure measured for the GSFI was 21.4 kPa(3.1 psig),which corresponded to a measured mean assembly gap of 3μm,and decreased to 0.5 kPa(0.073 psig)at a mean assembly gap of 240μm.The effect of radial misalignment on the efficacy of the gasketless seals was tested and no significant effect was observed.This may be a function of how the liquid bridges are formed during the priming of the chip,but additional research is required to test that hypothesis.