A numerical study of dynamic behaviors of a unitized regenerative fuel cell during gas purging

The gas purging states affect electricity output and energy storage capacity of unitized regenerative fuel cells. In this study, a model of unitized regenerative fuel cell is established. Cell voltages and operating temperatures influences on the dynamic distribution of thermal fluid during purging process and the discharge of residual liquid water in electrolytic cell mode are investigated. The motivation of the present study is better understanding the gas purging characteristics and its effect on reaction behaviors of unitized regenerative fuel cells. Simulation results reveal a significant influence of purging gas temperature on the water flooding and a great effect of operating voltage on the water diffusion. The operating temperature of electrolytic cell model almost has little effect on purging results at different cell temperature and the same purging gas temperature. When the purging gas temperature is changed, higher temperatures of cell and purging gas facilitate liquid water discharging out from the cell regions. In cell water flooding situation, when having large liquid content, the purging gas has little effects on the water expelling process.     

认知双向中继网络在κ-μ衰落信道下的中断性能分析

针对认知双向中继网络在进行数据传输时面临的复杂无线信道场景问题,采用广义κ-μ分布构建认知双向中继网络中的视距和非视距无线传输信道,推导次网络在κ-μ衰落信道下的统一中断概率,并分析次网络在多种单一和混合衰落信道情况下的中断性能。仿真结果表明,无线信道的衰落程度对次网络的中断概率影响显著,依据衰落信道类型合理设置网络参数将有助于提升次网络中断性能。     

Single-Cell Microgels for Diagnostics and Therapeutics

Cell encapsulation within hydrogel droplets is transforming what is feasible in multiple fields of biomedical science such as tissue engineering and regenerative medicine, in vitro modeling, and cell-based therapies. Recent advances have allowed researchers to miniaturize material encapsulation complexes down to single-cell scales, where each complex, termed a single-cell microgel, contains only one cell surrounded by a hydrogel matrix while remaining <100 μm in size. With this achievement, studies requiring single-cell resolution are now possible, similar to those done using liquid droplet encapsulation. Of particular note, applications involving long-term in vitro cultures, modular bioinks, high-throughput screenings, and formation of 3D cellular microenvironments can be tuned independently to suit the needs of individual cells and experimental goals. In this progress report, an overview of established materials and techniques used to fabricate single-cell microgels, as well as insight into potential alternatives is provided. This focused review is concluded by discussing applications that have already benefited from single-cell microgel technologies, as well as prospective applications on the cusp of achieving important new capabilities.     

气体裂变产物88Kr半衰期测量

为准确测定气体裂变产物⁸⁸Kr的半衰期，本工作从辐照铀靶中分离得到3个放化纯的⁸⁸Kr气体测量源。以⁸⁵Kr作内标监督源，¹³⁷Cs或⁵⁷Co作外标监督源，使用多个HPGe探测器分别采用单探测器位置接力法和双探测器位置接力法跟踪测量⁸⁸Kr 196.3 keV能量的特征γ射线，跟踪时间均在8个半衰期以上，以获得其半衰期数据。对3次独立测量数据用多种方法进行处理，最终得到⁸⁸Kr半衰期测定结果为（2.796±0.015） h。     

Two-Phase Bidirectional Dual-Relay Selection Strategy for Wireless Relay Networks

In this article, we introduce a new bi-directional dual-relay selection strategy with its bit error rate (BER) performance analysis. During the first step of the proposed strategy, two relays out of a set of N relay-nodes are selected in a way to optimize the system performance in terms of BER, based on the suggested algorithm which checks if the selected relays using the max-min criterion are the best ones. In the second step, the chosen relay-nodes perform an orthogonal space-time coding scheme using the two-phase relaying protocol to establish a bi-directional communication between the communicating terminals, leading to a significant improvement in the achievable coding and diversity gain. To further improve the overall system performance, the selected relay-nodes apply also a digital network coding scheme. Furthermore, this paper discusses the analytical approximation of the BER performance of the proposed strategy, where we prove that the analytical results match almost perfectly the simulated ones. Finally, our simulation results show that the proposed strategy outperforms the current state-of-the-art ones.     

探究智能变电站的继电保护二次回路故障诊断问题

本文即针对当前智能变电站中的故障诊断问题展开分析,主要以继电保护二次回路故障检测为主,就诊断检测系统进行阐述,总结了能够针对各种故障问题进行检测手段,意在能够借此提升变电站的智能化发展水平。     

Cell-free Stem Cell-Derived Extract Formulation for Regenerative Medicine Applications

Stem cells for regenerative medicine purposes offer therapeutic benefits, but disadvantages are still ill defined. The benefit of stem cells may be attributed to their secretion of growth factors (GFs), cytokines (CKs), and extracellular vesicles (EVs), including exosomes. We present a novel cell-free stem cell-derived extract (CCM), formulated from human progenitor endothelial stem cells (hPESCs), characterized for biologically active factors using ELISA, nanoparticle tracking analysis and single particle interferometric reflectance imaging sensing. The effect on fibroblast proliferation and ability to induce stem cell migration was analyzed using Alamar Blue proliferation and Transwell migration assays, respectively. GFs including IGFBP 1, 2, 3, and 6, insulin, growth hormone, PDGF-AA, TGF-α, TGF-β1, VEGF, and the anti-inflammatory cytokine, IL-1RA were detected. Membrane enclosed particles within exosome size range and expressing exosome tetraspanins CD81 and CD9 were identified. CCM significantly increased cell proliferation and induced stem cell migration. Analysis of CCM revealed presence of GFs, CKs, and EVs, including exosomes. The presence of multiple factors including exosomes within one formulation, the ability to promote cell proliferation and induce stem cell migration may reduce inflammation and pain, and augment tissue repair.     

基于滑模变结构控制的三段式继电保护离线整定的定值性能分析

在传统的三段式继电保护离线整定的定值性能分析过程中，常因定值选择不合理而导致定值计算准确度低。为此，在确定影响分支系数大小的因素的基础上，将分支系数看作为预计算变量，建立故障分析模型，计算三段式继电保护过程后备保护定值；设定三段式继电保护离线整定定值优化约束条件，采用滑膜变结构控制方法设定控制策略，结合惩罚函数的形式将约束条件添加到目标函数中，将定值性能分析问题转化为无约束优化问题，实现基于滑模变结构控制的三段式继电保护离线整定的定值性能分析。实验结果表明，相比于传统方法，该方法的定值准确度更高，定值性能更好。     

Performance of a CO2 sorbent for indoor air cleaning applications: Effects of environmental conditions,sorbent aging,and adsorption of co-occurring formaldehyde

Indoor air cleaning systems that incorporate CO₂ sorbent materials enable HVAC load shifting and efficiency improvements. This study developed a bench-scale experimental system to evaluate the performance of a sorbent under controlled operation conditions. A thermostatic holder containing 3.15 g sorbent was connected to a manifold that delivered CO₂-enriched air at a known temperature and relative humidity (RH). The air stream was also enriched with 0.8-2.1 ppm formaldehyde. The CO₂ concentration was monitored in real-time upstream and downstream of the sorbent, and integrated formaldehyde samples were collected at different times using DNPH-coated silica cartridges. Sorbent regeneration was carried out by circulating clean air in countercurrent. Almost 200 loading/regeneration cycles were performed in the span of 17 months, from which 104 were carried out at reference test conditions defined by loading with air at 25°C, 38% RH, and 1000 ppm CO₂, and regenerating with air at 80°C, 3% RH and 400 ppm CO₂. The working capacity decreased slightly from 43-44 mg CO₂ per g sorbent to 39-40 mg per g over the 17 months. The capacity increased with lower loading temperature (in the range 15-35°C) and higher regeneration temperature, between 40 and 80°C. The CO₂ capacity was not sensitive to the moisture content in the range 6-9 g/m³, and decreased slightly when dry air was used. Loading isothermal breakthrough curves were fitted to three simple adsorption models, verifying that pseudo-first-order kinetics appropriately describes the adsorption process. The model predicted that equilibrium capacities decreased with increasing temperature from 15 to 35°C, while adsorption rate constants slightly increased. The formaldehyde adsorption efficiency was 80%-99% in different cycles, corresponding to an average capacity of 86 ± 36 µg/g. Formaldehyde was not quantitatively released during regeneration, but its accumulation on the sorbent did not affect CO₂ adsorption.     

Nash equilibrium cooperative transmission strategy considering competition

In cooperative communications, employing the idle relay node for forwarding data can effectively improve the transmission rate and performance of the wireless networks. Therefore, various relay node selection algorithms are proposed. However, most of the existing algorithms just focus on the benefit caused by relay nodes, while ignoring the negative effect of the backoff duration time which does not exist in direct transmission, when more than one flow compete for the same relay node. To this end, considering both advantage and adverse impact caused by the relay node, we adopt the game-theoretic approach and propose a cooperative transmission strategy based on the Nash equilibrium, named the Nash Equilibrium Cooperative Transmission Strategy (NECTS). The NECTS can not only guarantee the gain of each flow, but also maximize the system performance, and improve the system throughput effectively. Simulation results show that the NECTS can take the advantage of cooperative communications. Meanwhile, it can avoid the unnecessary competition, and its performance outperforms that of the existing methods.