Local Clamping Research Articles

Impact of Clamping Force Distribution on Loss Processes in a Segmented PEMFC

The operation of large-scale polymer electrolyte membrane fuel cells (PEMFC) inevitably leads to significant spatial gradients along the gas channels. Depending on the local operating conditions, the physicochemical processes and thus also the resistances in the cell vary, which in turn determine the local performance. In addition, design parameters such as the spatial clamping force distribution have a significant influence on the ohmic contact resistance and the compression of the porous layers and thus the diffusion resistance. Thereby, the influences of these factors on the corresponding resistances are opposite to each other, resulting in conflicting objectives.To enable an optimization of the operating strategy and the component design, a quantification of the local resistances and their dependencies is essential.This requires a measurement setup that allows the precise adjustment of the operating conditions and contact pressure along the gas channel, as well as a measurement and analysis method that identifies and quantifies the locally occurring processes.For this purpose, we are applying electrochemical impedance spectroscopy (EIS) on a segmented cell. In this cell the local clamping force is individually adjusted and continuously measured for each segment enabling measurements at constant clamping force as well as selectable clamping force distributions. The local performance limiting loss processes within the cell are separated by the distribution of relaxation times (DRT) and quantified by a physico-chemical meaningful transmission line model (TLM) as a function of local operating conditions and clamping force [1, 2, 3].In this contribution an experimental analysis of the ohmic, charge transfer and diffusion resistances will be presented. The impact of contact pressure distribution and operating conditions on resistances and their distribution along the gas channels will be discussed. Furthermore, it is demonstrated how the performance can be optimized by adjusting the contact pressure distribution along the gas channel.1. H. Schichlein et al., J. Appl. Electrochem. 32, pp. 875-882 (2002).2. E. Ivers-Tiffée et al., J. Ceram. Soc. Japan 125, pp. 193-201 (2017).3. M. Heinzmann et al., J. Power Sources 558, 232540 (2023).

Automatic Prediction of Ischemia-Reperfusion Injury of Small Intestine Using Convolutional Neural Networks: A Pilot Study.

Acute intestinal ischemia is a life-threatening condition. The current gold standard, with evaluation based on visual and tactile sensation, has low specificity. In this study, we explore the feasibility of using machine learning models on images of the intestine, to assess small intestinal viability. A digital microscope was used to acquire images of the jejunum in 10 pigs. Ischemic segments were created by local clamping (approximately 30 cm in width) of small arteries and veins in the mesentery and reperfusion was initiated by releasing the clamps. A series of images were acquired once an hour on the surface of each of the segments. The convolutional neural network (CNN) has previously been used to classify medical images, while knowledge is lacking whether CNNs have potential to classify ischemia-reperfusion injury on the small intestine. We compared how different deep learning models perform for this task. Moreover, the Shapley additive explanations (SHAP) method within explainable artificial intelligence (AI) was used to identify features that the model utilizes as important in classification of different ischemic injury degrees. To be able to assess to what extent we can trust our deep learning model decisions is critical in a clinical setting. A probabilistic model Bayesian CNN was implemented to estimate the model uncertainty which provides a confidence measure of our model decisions.

Damage mechanisms under static and fatigue loading at locally compacted regions in a high pressure resin transfer molded carbon fiber non-crimp fabric

Manufacturing defects are an issue of composite manufacturing processes. Local clamping is proposed to prevent fiber washout during high pressure resin transfer molding of non-crimp fabrics. At the clamping regions the material is compacted by through-the-thickness compression. The current work investigates the mechanical performance of such regions under static and fatigue loading. Two typical manufacturing defects are intrinsic to the compacted regions: fiber undulation and resin starved/dry spots. In component tests the thereby generated damage is monitored using 3D digital image correlation and the complete processes of damage initiation and propagation are analyzed. Static and low cycle fatigue failure are dominated by fiber undulation at the edges of the compacted region, triggering matrix damage and delaminations. High cycle fatigue is dominated by decreasing fiber matrix adhesion within the compacted region, leading to longitudinal splitting and progressive fiber failure. Identification of damage initiation is supported by numerical finite element simulations.

Analysis on clinical characteristics of 13 extremely severe burn patients complicated with severe inhalation injury in August 2nd Kunshan factory aluminum dust explosion accident

Objective: To investigate the clinical characteristics of extremely severe burn patients complicated with severe inhalation injury caused by dust explosion. Methods: The medical records of 13 extremely severe burn patients complicated with severe inhalation injury in August 2nd Kunshan factory aluminum dust explosion accident, who were admitted to the First Affiliated Hospital of Soochow University on August 2nd, 2014, were retrospectively analyzed. The following indicators were collected: (1) Acute Physiology and Chronic Health Evaluation Ⅱ (APACHE Ⅱ) score and Sequential Organ Failure Assessment (SOFA) score at post admission hour (PAH) 24. (2) Prognosis, death time, causes of death, and the mortality of patients with different sexes. (3) The number of times of airway electronic bronchoscopy, airway characteristics, and the corresponding onset time. (4) The number and result of microorganism culture of lesion tissue during the leukoplakia formation stage. Detection of Pseudomonas aeruginosa in patients with and without leukoplakia in airway mucosa. Fisher's exact probability test was used to detect the mortality of patients with different sexes. Kappa test was used to detect the relevancy between leukoplakia and Pseudomonas aeruginosa. Results: (1) The APACHE Ⅱ score of patients of this group at PAH 24 was (19±3) points, and the SOFA score was (12±3) points. (2) Eight patients survived, while 5 patients died, and the time of death was 19-46 (34±10) d after injury. The main cause of death was multiple organ dysfunction syndrome, which was secondary to severe infection. One of the 7 male patients and 4 of the 6 female patients died, but there was no significantly statistical difference in mortality between patients of the two sexes (P>0.05). (3) Airway electronic bronchoscopy was performed 4-25 (10±5) times among patients of this group. Hyperemia and edema were found in the airway mucosa of all the 13 patients 2-3 weeks after injury; ulcer was found in the airway mucosa of 5 patients 2-4 weeks after injury; leukoplakia was found in the airway mucosa of 7 patients 4-14 weeks after injury; granulation formed in the airway mucosa of 7 patients 10-15 weeks after injury, and airway patency was affected, which was solved after local clamping or replacement of lengthened tracheal cannula. (4) During the leukoplakia formation stage, 19 cases of microorganism culture were performed basing on airway lesion tissue, and the results were 15 cases of Pseudomonas aeruginosa, 5 cases of Acinetobacter baumannii, 2 cases of Serratia marcescens, as well as 1 case of Stenotrophomonas maltophilia, Burkholderia cepacia, and Proteus mirabilis each. Among 7 patients with airway mucosa leukoplakia, 6 patients were detected with Pseudomonas aeruginosa. Among 6 patients without airway mucosa leukoplakia, 1 patient was detected with Pseudomonas aeruginosa. The appearance of leukoplakia was consistent with the detection of Pseudomonas aeruginosa (Kappa=0.69, P<0.05). Conclusions: Most of these extremely severe burn patients complicated with severe inhalation injury caused by dust explosion survived, and there was no significant gender difference in mortality. Electronic bronchoscopy showed that the early manifestations of airway mucosa were hyperemia and edema, followed by varying degrees of erosion, ulcer, leukoplakia, and granulation formation, etc. Leukoplakia may be relevant to Pseudomonas aeruginosa infection.

A Temporary Local Rigid Clamping Structure to Improve Antibuckling Ability of the Thin-Walled Cylinder Under External Pressure

Although the inner container of the cryogenic liquid semitrailer works under inner pressure, it needs to be vacuumed during the helium leak detection. Furthermore, the inner container usually cannot meet the stability requirements during the evacuation, though equipped with stiffening structures such as supporting rings for baffles inside the container. Therefore, a kind of temporary local rigid clamping structure was proposed to improve the antibuckling ability of the inner container during the helium leak detection. “Lulu” can was taken as the thin-walled cylindrical shell specimen under external pressure and was clamped with the temporary local rigid ring on the outside surface. The critical pressures were experimentally and numerically studied for the specimen with local clamping rings of different sizes, in which eigenvalue buckling analysis and nonlinear analysis were employed with the aid of ANSYS. It indicates that the critical pressure of the specimen with the local clamping ring is higher than that without the clamping ring. Finally, the optimal clamping scheme including size and location of clamping rings for the inner container of DC18 type cryogenic liquid semitrailer was studied with the finite element method, which aimed to improve the antibuckling capacity of the inner container during the helium leak detection.

Vortex switching in ferroelectric nanodots and its feasibility by a homogeneous electric field: Effects of substrate, dislocations and local clamping force

Taking into account the effects of asymmetric mechanical fields (e.g., caused by substrate, dislocations and local clamping force), we conduct phase-field simulations to investigate the evolution of vortex domain structure in ferroelectric nanodots. For nanodots under different mechanical constraints, their characteristics of the domain evolution, e.g., the hysteresis loop, the domain patterns and the evolution paths, have been revealed and compared comprehensively. Our calculations show that substrate, dislocations and local clamping force significantly affect the domain evolution of the nanodots, leading to distinct behaviors from those of the free-standing ones. For such systems, as the asymmetric mechanical field breaks the symmetry of vortex domain nucleation and growth, the evolution of the vortex domain structure is dominated by a specific region of dipoles, which we name “dominant dipoles”. As a result, the nanodots exhibit distinct evolution paths, and the coercive field of vortex switching by a curled electric field is reduced compared with the free-standing ones. More importantly, for such systems, it is possible to realize single-vortex switching by a homogeneous electric field through controlling the flowing direction of the dominant dipoles. Our study provides useful information on the practical control of the vortex domain structure in ferroelectric nanostructures by conventional electrostatic fields.

Gate-controlled field-effect diodes and silicon-controlled rectifier for charged-device model ESD protection in advanced SOI technology

Silicon-controlled rectifier (SCR) devices are used as local clamping ESD devices. However, conventional designs suffer from slow turn-on, which causes problems in sub 10 ns charged-device model (CDM) protection, especially in deeply scaled technologies. In this paper, a double-well field-effect diode (DWFED) and an improved field-effect diode (FED) are designed to address this challenge. They are fabricated and characterized in 45 nm silicon-on-insulator (SOI) technology and experimentally demonstrated to be suitable for pad-based local clamping under a normal supply voltage ( V dd) range (at or below 1 V) in high-speed applications. ESD protection capabilities are investigated using very fast transmission line pulse (VF-TLP) tests to predict the device performance in CDM events. FED’s advantages in improving transient turn-on behavior and reducing DC leakage current are analyzed and compared with the regular SCR and the DWFED. Technology CAD (TCAD) simulations are used to interpret turn-on behavior and guide design. The improved devices may be implemented in a local clamping scheme that expands the ESD design window for advanced technology nodes.

Mechanisms of the blockade of glutamate channel receptors: Significance for structural and physiological investigations

The mechanism of the blocking action of phenylcyclohexyl derivative IEM-1925 on ionotropic NMDA and AMPA glutamate receptors was studied. Experiments on isolated rat brain neurons (hippocampal pyramidal cells and striatal cholinergic interneurons) were performed using local voltage clamping in the "whole cell" configuration. In equilibrium conditions at a membrane potential of -80 mV, there was no selectivity in the action of IEM-1925 on the open channels of either type of glutamate receptor. However, data were obtained showing significant differences in the mechanisms of the blocking actions. Although IEM-1925 was unable to penetrate into closed channels of either receptor type, molecules were able to leave closed AMPA receptor channels but not closed NMDA receptor channels. In hyperpolarization, the departure of the blocker from open NMDA receptor channels was slowed, while departure from open and closed AMPA receptor channels was accelerated. The blocker thus appeared able to penetrate AMPA receptor channels to enter cells, the gating mechanism of these channels being located above the blocker binding site. The actions of IEM-1925 on NMDA and AMPA receptors were compared with its ability to suppress tremor in mice induced with s.c. doses of arecoline. The results indicated that both types of receptors have a role in producing tremor. The differences in the mechanisms of action on AMPA and NMDA receptors may explain the ambiguous nature of the effects of the glutamate channel blocker in experimental therapy.

Internal stress effects on fatigue crack initiation at notches

In this paper the effects of the internal stresses on crack initiation at notches is investigated. Internal stresses are induced by applying two pre-loading cycles at a given load ratio, R = S MIN/ S MAX, to the ‘virgin’ notched specimen. After pre-loading, blocks of 10 6 cycles with a constant nominal stress range, Δ S, slightly larger than the nominal threshold stress range, Δ S th, are applied with increasing minimum stress, S MIN, in each subsequent block until a crack initiates. The lowest S MIN above which a crack initiates is recorded as S IN. The process is repeated for a wide range of positive and negative load ratios in order to obtain S IN/ S MAX vs. load ratio curve. This curve for positive load ratios surprisingly resembles the K PR/ K MAX plot reported in the literature for a cracked specimen. The results are explained in terms of compressive internal stress and the associated local clamping action at the notch cyclic plastic zone. Both the analytical and finite element calculations show a fairly good agreement with the experimental results.

Thickness profiles through fatigued bulk ceramic lead zirconate titanate

Wedge-cut samples of fatigued ferroelectric lead zirconate titanate ceramics were investigated using piezoresponse force microscopy in conjunction with conventional electrical hysteresis measurements. The local clamping of domains is monitored at different depths in the sample. The coercive fields in grains near the electrodes differ for different materials and preparation methods of the electrodes. For silver, fatigue consistently generates a space charge in the depth of the sample. For platinum electrodes, the fatigue behavior scatters strongly. Microscopically, it either occurs directly underneath the electrodes or resembles the behavior of the silver electrodes in other samples.

174. High Efficiency HDAd-Mediated Hepatic Transduction Can Be Achieved by Delivery into the Surgically Isolated Liver of Nonhuman Primates

Type 1 diabetes results from autoimmune destruction of pancreatic β cells. This process might be reverted by genetically engineering endocrine pancreas in vivo to express factors that induce β-cell replication and neogenesis and counteract the immune response. However, the pancreas is difficult to manipulate and pancreatitis is a serious concern, which has made effective gene transfer to this organ elusive. Thus, new approaches for gene delivery to pancreas in vivo are required. Here we show that mouse pancreatic β-cells were efficiently transduced, and they expressed β-galactosidase after systemic injection of adenovirus with clamped hepatic circulation. Seven days after vector administration about 70% of pancreatic islets showed β-gal expression. In these islets, about 20% of the β-cells were transduced by the adenoviruses. Furthermore, scattered acinar cells expressing β-gal were also observed. In addition to mouse, we also examined the ability of adenovirus to transduce dog pancreas. We have observed that acinar, ductal and endocrine pancreatic cells were transduced after injection of adenovirus in dogs underwent local clamping of pancreatic circulation. Thus, these approaches may be used to transfer genes of interest to pancreas for both the study of islet biology and the gene therapy of diabetes and other pancreatic disorders.

Primary Venorrhaphy for Traumatic Inferior Vena Cava Injuries

Primary venorrhaphy for traumatic inferior vena cava (IVC) injury has been criticized because of the potential for stenosis, thrombosis, and embolism. A retrospective study was performed to evaluate the morbidity and outcome of this method. Thirty-eight patients at our institution had traumatic injuries to the IVC between 1994 and 1999. Thirty (79%) were from firearms, five (13%) from stab wounds, and three (8%) from blunt trauma. Six patients died in the emergency department. The remaining 32 patients underwent exploratory celiotomy with 23 survivors and nine intraoperative deaths for a mortality rate of 28 per cent (nine of 32). Vascular control was achieved by manual compression in 44 per cent and by local clamping directly above and below the injury in 38 per cent. All repairs were by primary venorrhaphy, and no patient was treated with patch angioplasty or venous reconstruction. Three patients had caval ligation. Follow-up IVC imaging in 11 patients revealed that the IVC was patent in eight, narrowed in two, and thrombosed below the renal veins in one. One patient developed a pulmonary embolus. The vast majority of traumatic injuries to the IVC can be managed by direct compression or local clamping and primary venorrhaphy. Direct repairs are associated with a low thrombosis and embolic complication rate.

Localized saturation of loss grating in complex-coupled DFB laser diodes

The longitudinal dependence of the standing-wave envelope in a complex-coupled DFB InGaAsP MQW laser is experimentally investigated. We have observed localized clamping of the luminescence for unstable operating conditions. This local clamping is a consequence of the absorber saturation with increasing injection current and of the short period of the standing-wave envelope that is characteristic for multimode emission. The period can be used as a criterion to distinguish between regions of multimode emission and optical instabilities.

Lattice vibrations and specific heat of a small particle

By using an elastic body approximation, lattice vibrations of a small particle are discussed. Consideration of both vector fields and a scalar field yields the proper vibrational modes. Eigenfrequencies of the elastic vibrations are derived by considering circumstances surrounding a small particle: matrix effect, surface relaxation effect, local clamping effect and shape effect. Among these, the surface relaxation effect and the local clamping effect are shown to be responsible for the specific heat of a small particle observed by Novotony and Meincke (1973).