Buffer Structure Research Articles

Mechanical properties of lander bionic buffer structure based on additive manufacturing

In order to meet the energy absorption requirements of the landing buffer, this paper starts with the buffer filling material of the buffer, draws on the Kelvin structure and spiral structure, and applies the engineering bionics principle to design and establish two structural models: a soccerball-like bionic structure and a multi-spiral bionic structure. Considering the energy absorption and reusability requirements of the lander buffer structure, the bionic structure sample is prepared by additive manufacturing technology and NiTi alloy with shape memory effect. The mechanical properties, energy absorption and recoverability of the sample are analyzed and verified by simulation and experiment. The results show that the accuracy of the numerical simulation is verified by comparing the force-displacement curves of the simulation test and the isometric static pressure test; the multi-spiral bionic structure has better mechanical properties, and its maximum energy absorption is 3096.23 J; the recovery rates of the two structures are as high as 98.02%and respectively 97.12%, and the recovery rate of the soccerball-like bionic structure is slightly higher. This study uses additive manufacturing to prepare the leg-type lander buffer bionic structure, which provides a reference for the bionic design of the lander buffer structure.

Epitaxy of >7 μm Thick GaN Drift Layers on 150 mm Si(111) Substrates Realizing Vertical PN Diodes with 1200 V Breakdown Voltage

Metal‐organic chemical vapor deposition growth of vertical GaN PN structures on 6″ Si(111) substrates enabling a 1200 V breakdown voltage is demonstrated. Thanks to an optimized buffer structure utilizing island growth in an AlN/Al0.1Ga0.9N superlattice, the threading dislocation density is drastically reduced, and sufficient compressive stress is incorporated in active GaN layers to compensate for the thermal mismatch. Crack‐free PN structures with drift layer thicknesses up to 7.4 μm are realized with a threading dislocation density of ≈5 × 108 cm−2 and an absolute wafer bow <50 μm. Quasi‐vertical PN diodes reveal a linear increase in the breakdown voltage with the drift layer thickness with an average breakdown field of ≈1.6 MV cm−1. Additionally, the leakage current is shown to decrease monotonically as the drift layer thickness increases. For a 7.4 μm thick drift layer with a net ionized donor concentration of 0.9 × 1016 cm−3, a high breakdown voltage of 1200 V, a low specific on‐resistance of 0.4 mΩ cm−2, and a low leakage current of 10−4 A cm−2 (at a reverse bias of 650 V) are obtained. These results demonstrate the great potential of cost‐effective vertical GaN‐on‐Si power devices operating in the kilovolt range.

A compact quasi-zero stiffness metamaterial for energy absorption and impact protection

A compact mechanical metamaterial for impact protection is proposed in this study. During compression, the unit cell of the metamaterial exhibits quasi-zero stiffness (QZS) and quasi-zero Poisson’s ratio (QZPR) characteristics, along with large densification strain, making it suitable for protection against low-speed impacts. Firstly, the parametric geometric model of the metamaterial is established, with sinusoidal thin-walled structures serving as the primary load-bearing units. The grid structures are employed to connect the thin-walled structures into a unified system. Secondly, to shorten the design cycle, numerical methods for the mechanical properties of the buffer structure are developed. The motion equation of the thin-walled structure are expressed in terms of arc length coordinates and solved using the Runge–Kutta method and the shooting method. The grid structure deformation and the effect of material plastic reinforcement on the structural mechanical response are analyzed, and the energy absorption (EA) of the buffer structure is calculated. Both simulation and experimental results demonstrate the high accuracy of the proposed calculation method. Lastly, drop hammer experiments are conducted to evaluate the impact mitigation performance of the designed buffer structure. The results indicate that the structure exhibits excellent impact mitigation capabilities, highlighting its potential for practical applications.

Enhancement of Cd‐Free All‐Dry‐Processed Cu(In1‐x,Gax)Se2 Thin‐Film Solar Cells by Simultaneous Adoption of an Enlarged Bandgap Absorber and Tunable Bandgap Zn1‐xMgxO Buffer

Attempts to remove environmentally harmful materials in mass production industries are always a major issue and draw attention if the substitution guarantees a chance to lower fabrication cost and to improve device performance, as in a wide bandgap Zn1‐xMgxO (ZMO) to replace the CdS buffer in Cu(In1‐x,Gax)Se2 (CIGSe) thin‐film solar cell structure. ZMO is one of the candidates for the buffer material in CIGSe thin‐film solar cells with a wide and controllable bandgap depending on the Mg content, which can be helpful in attaining a suitable conduction band offset. Hence, compared to the fixed and limited bandgap of a CdS buffer, a ZMO buffer may provide advantages in Voc and Jsc based on its controllable and wide bandgap, even with a relatively wider bandgap CIGSe thin‐film solar cell. In addition, to solve problems with the defect sites at the ZMO/CIGSe junction interface, a few‐nanometer ZnS layer is employed for heterojunction interface passivation, forming a ZMO/ZnS buffer structure by atomic layer deposition (ALD). Finally, a Cd‐free all‐dry‐processed CIGSe solar cell with a wider bandgap (1.25 eV) and ALD‐grown buffer structure exhibited the best power conversion efficiency of 19.1%, which exhibited a higher performance than the CdS counterpart.

Design of High-Reliability Low-Dropout Regulator Combined with Silicon Controlled Rectifier-Based Electrostatic Discharge Protection Circuit Using Dynamic Dual Buffer

Overshoot and undershoot caused by the current load impact the accuracy of the required output voltage and circuit performance. The transient response issue in existing low-dropout (LDO) regulators is a dynamic specification that must be addressed at the design stage. This transient response is influenced by system parameters such as stability and gain. The LDO regulator suggested in this study is designed to minimize the change in output voltage by considerably enhancing the gain using a dynamic dual buffer structure. A dynamic dual buffer is utilized to effectively control undershoot and overshoot. Under the conditions that the input voltage range is from 3.3 to 4.5 V, the maximum load current is 300 mA, the output voltage is 3 V, and the output of the proposed LDO regulator with the dynamic dual buffer structure has undershoot and overshoot voltages of 41 mV and 31 mV, respectively. That is, the output voltage of the proposed LDO regulator effectively provided and discharged an additional current suited for the undershoot/overshoot conditions to enhance the transient response characteristics. Furthermore, the electrostatic discharge (ESD) robustness characteristics of the proposed LDO regulator improved because of the silicon-controlled rectifier underlying the ESD protection device embedded in the output node and power line.

Data-dependent half-select free GSRAM cell with word line write-assist and built-in read buffer schemes for use in PUFs-based IoT devices

In this study, a static-RAM cell using the Gnr-GDI method is proposed as a weak-type physical unclonable function (PUF) circuit to generate a unique and stable binary output for secure IoT devices. Regarding the memory level, a suitable combination of dynamic body bias, stacked networks, and multi-Vth techniques has been used in the architecture of asymmetric cell-structure inverters as a latch section to reduce power consumption and improve hardware efficiency. In addition, the logic styles of virtual ground and power gating based on word and BL data lines and a tri-state buffer structure have been used to extend the write VTC and improve read stability, respectively. From the perspective of PUF performance, the body of the latch section can form skewed VTCs based on the setting of critical parameters in GnrFET technology to achieve an efficient PUF circuit design.At the memory performance level, the Monte Carlo (MC) method-based results confirm the reasonable performance of the proposed structure in terms of static noise margin (SNM) and hardware efficiency, such as 53 % delay and 72 % energy-delay product (EDP) parameters, compared with the 6 T SRAM structure in a similar 16 nm GnrFET technology. In addition, in terms of the performance as a PUF circuit, the simulation results demonstrate the superiority of the proposed cell in terms of energy consumption, BER, response time, uniqueness, and stability under non-technological variation conditions of temperature and supply voltage. The outstanding performance results of the figure of merits (FoMs), CEQM, and UR2, which are composed of variability, energy, reliability, and layout-level factors, indicate the suitability of the proposed memory architecture for use in both the memory and PUF modes.Furthermore, to investigate the application level, memory structure has been used to store fingerprint images as PUF data using a hardware algorithm. The results of the proposed comprehensive FoM, which is based on the simultaneous consideration of circuit level and quality parameters, indicate that the proposed memory scheme in a bit-interleaved architecture-compatible design can be introduced as a high-performance candidate for generating and storing unique binary data in PUF-based IoT platforms.

Design and Analysis of a New Buffer Structure with Negative Stiffness and Poisson’s Ratio

Design and Analysis of a New Buffer Structure with Negative Stiffness and Poisson’s Ratio

Miniaturization study on helmholtz-based photoacoustic cell for PAS-based trace gas detection

In this study, the acoustic behavior and gas flow noise in a Helmholtz photoacoustic cell were simulated and optimized to study the influence of the cell dimensions and buffer structure. Numerical analysis using finite element analysis and experimental validation were performed in this study. A spindle-type photoacoustic cell with a resonator volume of 0.5 mL and buffer volume of 0.4 mL was selected for CH4 detection. Besides its strong photoacoustic enhancement, the spindle-type buffer structure has the best ability to eliminate flow noise compared to the other buffer structures. A linearity of 0.9992 was achieved over a wide concentration range of 0–10000 ppm in the CH4 measurement experiment. The 1σ equivalent detection limit for a response time of 10 s was measured to be 0.49 ppm. Allan deviation analysis indicated that a minimum detection limit of 17.9 ppb can be achieved by extending the integration time to 4760 s.

Optofluidic time-stretch imaging flow cytometry with a real-time storage rate beyond 5.9 GB/s.

Optofluidic time-stretch imaging flow cytometry (OTS-IFC) provides a suitable solution for high-precision cell analysis and high-sensitivity detection of rare cells due to its high-throughput and continuous image acquisition. However, transferring and storing continuous big data streams remains a challenge. In this study, we designed a high-speed streaming storage strategy to store OTS-IFC data in real-time, overcoming the imbalance between the fast generation speed in the data acquisition and processing subsystem and the comparatively slower storage speed in the transmission and storage subsystem. This strategy, utilizing an asynchronous buffer structure built on the producer-consumer model, optimizes memory usage for enhanced data throughput and stability. We evaluated the storage performance of the high-speed streaming storage strategy in ultra-large-scale blood cell imaging on a common commercial device. The experimental results show that it can provide a continuous data throughput of up to 5891 MB/s.

Optimization of Epitaxial Structures on GaN-on-Si(111) HEMTs with Step-Graded AlGaN Buffer Layer and AlGaN Back Barrier

Recently, crack-free GaN-on-Si growth technology has become increasingly important due to the high demand for power semiconductor devices with high performances. In this paper, we have experimentally optimized the buffer structures such as the AlN nucleation layer and step-graded AlGaN layer for AlGaN/GaN HEMTs on Si (111) substrate by varying growth conditions and thickness, which is very crucial for achieving crack-free GaN-on-Si epitaxial growth. Moreover, an AlGaN back barrier was inserted to reduce the buffer trapping effects, resulting in the enhancement of carrier confinement and suppression of current dispersion. Firstly, the AlN nucleation layer was optimized with a thickness of 285 nm, providing the smoothest surface confirmed by SEM image. On the AlN nucleation layer, four step-graded AlGaN layers were sequentially grown by increasing the Al composition from undermost layer to uppermost layer, meaning that the undermost one was close to AlN, and the uppermost was close to GaN, to reduce the stress and strain in the epitaxial layer gradually. It was also verified that the thicker step-graded AlGaN buffer layer is suitable for better crystalline quality and surface morphology and lower buffer leakage current, as expected. On these optimized buffer structures, the AlGaN back barrier was introduced, and the effects of the back barrier were clearly observed in the device characteristics of the AlGaN/GaN HEMTs on Si (111) substrate such as the transfer characteristics, output characteristics and pulsed I-V characteristics.

Finding regulatory modules of chemical reaction systems

Within a cell, numerous chemical reactions form chemical reaction networks (CRNs), which are the origins of cellular functions. We previously developed a theoretical method called structural sensitivity analysis (SSA), which enables us to determine, solely from the network structure, the qualitative changes in the steady-state concentrations of chemicals resulting from the perturbations to a parameter. Notably, if a subnetwork satisfies specific topological conditions, it is referred to as a buffering structure, and the effects of perturbations to the parameter within the subnetwork are localized to the subnetwork (the law of localization). A buffering structure can be the origin of modularity in the regulation of cellular functions generated from CRNs. However, an efficient method to search for buffering structures in a large CRN has not yet been established. In this study, we prove the “inverse theorem” of the law of localization, which states that a certain subnetwork exhibiting a confined response range is always a buffering structure. In other words, we are able to identify buffering structures in terms of confined responses rather than the topological conditions. By leveraging this property, we develop an algorithm to enumerate all buffering structures for a given network by calculating responses. Additionally, we show that the hierarchy of perturbed response patterns corresponds to that of buffering structures, and present a method to illustrate the hierarchy. Our method will be a powerful tool for understanding the regulation of cellular functions generated from CRNs. Published by the American Physical Society 2024

Encapsulating Si particles in multiple carbon shells with pore-rich for constructing free-standing anodes of lithium storage

Silicon based (Si-based) materials are considered to be the most promising anode materials for lithium-ion batteries (LIBs) due to their high specific capacity. However, the issues of poor electrical conductivity and volume expansion during cycling have not been effectively addressed. The optimum remedy is to select specific materials to establish an exceptional conductive and volume buffer structure to assist the Si materials to develop its excellent lithium storage properties. Here, Si particles were encapsulated into porous carbon fibers containing ultrafine Co particles (CP) to obtained Si-x@CP-y film. Among them, the addition of Si particles and the void structure was precisely regulated to achieve a superior electrode with a high specific capacity. Subsequently, the two-dimensional conductive material reduced graphene oxide (rGO) nanosheets were further incorporated to obtain Si-2@CP-2@rGO films with core@multi-shell structure. The final electrode was equipped with one-, two-, and three-dimensional electronic pathways to allow rapid electron transport, and featured with multi-layer buffer structure and reserved pores that could effectively mitigate volume changes. As expected, the free-standing Si-2@CP-2@rGO electrode delivered a high specific capacity of 1221.2 mAh/g after 100 cycles at 0.1 A/g in a half cell, and the assembled full cell showed 249.0 mAh/g after 200 cycles at 0.2 A/g, which fulfilled the lightweight requirement for new energy storage devices.

Spray-Dried Chitosan Hydrogel Particles as a Potential Delivery System for Benzydamine Hydrochloride.

Chitosan, being a biocompatible and mucoadhesive polysaccharide, is one of the most preferred hydrogel-forming materials for drug delivery. The objectives of the present study are to obtain spray-dried microparticles based on low-molecular-weight chitosan and study their potential application as cargo systems for the orally active drug benzydamine hydrochloride. Three types of particles are obtained: raw chitosan particles (at three different concentrations), cross-linked with sodium tripolyphosphate (NaTPP) particles (at three different chitosan:NaTPP ratios), and particles coated with mannitol (at three different chitosan:mannitol ratios), all of them in the size range between 1 and 10 µm. Based on the loading efficiency and the yields of the formulated hydrogel particles, one model of each type is chosen for further investigation of the effect of the cross-linker or the excipient on the properties of the gel structures. The morphology of both empty and benzydamine hydrochloride-loaded chitosan particles was examined by scanning electron microscopy, and it was quite regular and spherical. Interactions and composition in the samples are investigated by Fourier-transformed infrared spectroscopy. The thermal stability and phase state of the drug and drug-containing polymer matrixes were tested by differential scanning calorimetry and X-ray powdered diffraction, revealing that the drug underwent a phase transition. A drug release kinetics study of the chosen gel-based structures in simulated saliva buffer (pH = 6.8) and mathematical modeling of the process were performed, indicating the Weibull model as the most appropriate one.

A TeZla micromixer for interrogating the early and broad folding landscape of G-quadruplex via multistage velocity descending

Biomacromolecular folding kinetics involves fast folding events and broad timescales. Current techniques face limitations in either the required time resolution or the observation window. In this study, we developed the TeZla micromixer, integrating Tesla and Zigzag microstructures with a multistage velocity descending strategy. TeZla achieves a significant short mixing dead time (40 µs) and a wide time window covering four orders of magnitude (up to 300 ms). Using this unique micromixer, we explored the folding landscape of c-Myc G4 and its noncanonical-G4 derivatives with different loop lengths or G-vacancy sites. Our findings revealed that c-Myc can bypass folding intermediates and directly adopt a G4 structure in the cation-deficient buffer. Moreover, we found that the loop length and specific G-vacancy site could affect the folding pathway and significantly slow down the folding rates. These results were also cross-validated with real-time NMR and circular dichroism. In conclusion, TeZla represents a versatile tool for studying biomolecular folding kinetics, and our findings may ultimately contribute to the design of drugs targeting G4 structures.

Boosting the Stability and Performance of SOFCs: A New Approach to Oxygen Storage Capacity Using Lanthanum-Doped Ceria Interlayer Technology

Being carbon neutral is one of the world's most important objectives. More than 65 percent of the countries that emit harmful greenhouse gases have committed to achieving net-zero emissions by the middle of the century.[1] There are numerous essential ways to gather energy for worldwide missions, including fuel cells, solar power, wind power, etc. The growing marketplace of fuel cells is following the trend of green-energy demand. Solid oxide fuel cells (SOFCs) are gaining popularity in the next-generation energy industry due to their high energy conversion efficiency, fuel flexibility, and low emissions.[2]The main challenges for the commercialization of SOCs that need to address are high performance, long-term durability, and effective cost. Stabilized zirconia such as Yttria-stabilized zirconia (YSZ) and Scandia-stabilized zirconia (ScSZ) is commonly used as a self-standing electrolyte support. The inability of zirconia-based electrolytes to react with Sr-rich cathode materials like LSC, LSCF, BSCF, etc. Therefore, the electrodes and the zirconia-based electrolyte must have the best-interlayered buffer structure. Optimizing interlayer microstructures to make them more effective at high-performance ESCs is of great interest. Several Rare-earth doped ceria (RDC) materials, including (Gd, Ce)O2, (Sm, Ce)O2, and (La, Ce)O2, have been used as efficient interlayers to lessen reactivity and preserve ionic conductivity in the interface. However, the difference in the thermal expansion coefficient (TEC) between the GDC and the YSZ poses a significant problem for starting and halting SOCs. In the present work, we focus on the commercial lanthanum-doped ceria (Ce0.6La0.4O1.8 - LDC) as a buffer layer between the YSZ electrolyte and the LSCF cathode because of its higher oxygen storage capacitance. The reactivity of the YSZ/GDC composite was higher than that of the YSZ/LDC composite. And the total conductivity of the LDC/YSZ composite is higher than GDC/YSZ composite even though LDC has lower conductivity than GDC. Moreover, the mismatching of TEC was reduced by replacing the GDC with the LDC bilayer.Consequently, the maximum power density for the electrolyte-supported cell SOFC with LDC interlayer was ~0.55 W.cm−2 at 1073 K. A variety of additives (Co, Mn, and Cu) was added to the LDC buffer layer to examine the sintering properties. The addition of copper not only obtained the highest microstructural density but also improve mechanical stability under cost-effective processes.

Patterns of change in regulatory modules of chemical reaction systems induced by network modification.

Cellular functions are realized through the dynamics of chemical reaction networks formed by thousands of chemical reactions. Numerical studies have empirically demonstrated that small differences in network structures among species or tissues can cause substantial changes in dynamics. However, a general principle for behavior changes in response to network structure modifications is not known. The chemical reaction system possesses substructures called buffering structures, which are characterized by a certain topological index being zero. It was proven that the steady-state response to modulation of reaction parameters inside a buffering structure is localized in the buffering structure. In this study, we developed a method to systematically identify the loss or creation of buffering structures induced by the addition of a single degradation reaction from network structure alone. This makes it possible to predict the qualitative and macroscopic changes in regulation that will be caused by the network modification. This method was applied to two reaction systems: the central metabolic system and the mitogen-activated protein kinases signal transduction system. Our method enables identification of reactions that are important for biological functions in living systems.

Toward Red Light Emitters Based on InGaN-Containing Short-Period Superlattices with InGaN Buffers

In order to shift the light emission of nitride quantum structures towards the red color, the technological problem of low In incorporation in InGaN−based heterostructures has to be solved. To overcome this problem, we consider superlattices grown on InGaN buffers with different In content. Based on the comparison of the calculated ab initio superlattice band gaps with the photoluminescence emission energies obtained from the measurements on the specially designed samples grown by metal-organic vapor phase epitaxy, it is shown that by changing the superlattice parameters and the composition of the buffer structures, the light emission can be shifted to lower energies by about 167 nm (0.72 eV) in comparison to the case of a similar type of superlattices grown on GaN substrate. The importance of using superlattices to achieve red emission and the critical role of the InGaN buffer are demonstrated.

Structural, optical, and electrical characterization and performance comparison of AlGaN/GaN HEMT structures with different buffer layers

AlGaN/GaN high electron mobility transistor (HEMT) structures are promising for high power and high speed electronic applications. The selection of a good buffer structure is crucial for the achievement of high quality HEMT devices. Here, we present a comparative analysis of structural, optical, and electrical properties of AlGaN/GAN HEMT structures with three different buffer configurations: step-graded AlGaN and superlattice-based buffers on Si, and no buffer on SiC substrates. The analysis of structural properties showed that the structure on SiC has better crystal quality. The Analysis also provided an insight of the role superlattice buffer to cut-off the dislocations and enhance the GaN channel crystallinity. Optical and electrical characterizations showed the enhanced 2DEG quality in the superlattice-based structure, due to the better stress management in the top layers. The electronic and optoelectronic quality of the structures were studied by fabricating HEMT and metal-semiconductor-metal photodetector devices. The devices analysis showed that the superlattice based structure outperformed the other two structures with drain current and transconductance of 406.3 mA/mm and 81.5 mS/mm, respectively, as well as photo-to-dark current ratio that is 2–3 orders of magnitude higher than the other two structures, under 325 nm light illumination. The results provide insights into the impact of different buffer configurations on the performance of AlGaN/GaN HEMT structures, suggesting that the superlattice buffer structure is the optimal choice for fabricating high-performance AlGaN/GaN HEMT-based electronics.

Investigation on the Mechanical Properties and Shape Memory Effect of Landing Buffer Structure Based on NiTi Alloy Printing

With the deepening of human research on deep space exploration, our research on the soft landing methods of landers has gradually deepened. Adding a buffer and energy-absorbing structure to the leg structure of the lander has become an effective design solution. Based on the energy-absorbing structure of the leg of the interstellar lander, this paper studies the appearance characteristics of the predatory feet of the Odontodactylus scyllarus. The predatory feet of the Odontodactylus scyllarus can not only hit the prey highly when preying, but also can easily withstand the huge counter-impact force. The predatory feet structure of the Odontodactylus scyllarus, like a symmetrical cone, shows excellent rigidity and energy absorption capacity. Inspired by this discovery, we used SLM technology to design and manufacture two nickel-titanium samples, which respectively show high elasticity, shape memory, and get better energy absorption capacity. This research provides an effective way to design and manufacture high-mechanical energy-absorbing buffer structures using bionic 3D printing technology and nickel-titanium alloys.

Preparation of Buffered Nano-Submicron Hierarchical Structure Hollow SiOx @C Anodes for Lithium-Ion Battery Materials with Carboxymethyl Chitosan.

Silicon-based materials are among the most promising anode materials for next-generation lithium-ion batteries. However, the volume expansion and poor conductivity of silicon-based materials during the charge and discharge process seriously hinder their practical application in the field of anodes. Here, we choose carboxymethyl chitosan (CMCS) as the carbon source coating and binding on the surface of nano silicon and hollow silicon dioxide (H-SiO2 ) to form a hierarchical buffered structure of nano-hollow SiOx @C. The hollow H-SiO2 can alleviate the volume expansion of nano silicon during the lithiation process under continuous cycling. Meanwhile, the carbon layer carbonized by CMCS containing N-doping further regulates the silicon's expansion and improves the conductivity of the active materials. The as- prepared SiOx @C material exhibits an initial discharge capacity of 985.4 mAh g-1 with the decay rate of 0.27 % per cycle in 150 cycles under the current density of 0.2 A g-1 . It is proved that the hierarchical buffer structure nano-hollow SiOx @C anode material has practical application potential.