Clamp Type Research Articles

Wooden Spatial Structures Assembled with Disassembly Possible Simple Joints

The authors propose a new clamped joint system that can easily join wooden members together and a wooden spatial structure that utilizes this system. The proposed system can clamp wood members without the need for special joint machining. Two types of clamps have been developed: orthogonal clamps and rotational clamps. A frame system is developed using this joint system, which is a hemispherical dome with a diameter of 5.4 m and its membrane is tensioned using struts. A preliminary framework structural analysis and membrane stress analysis are conducted to confirm the safety of the frame. Full-scale mock-up was constructed to validate the frame model analysis and verify construction procedures. As a combinable structure, a small-scale spatial structure assembled using orthogonal clamps is also described. It is the cube-shaped structure 2.8 m wide consisting of wall and ceiling planes. Single clamp loading tests are conducted to understand the load-deformation relationship of the proposed clamped joint system and full-scale horizontal loading tests have been conducted.

Experimental Study on Flexural Performance of lap-spliced and mechanical-spliced (clamp type) rebars in RC Beams

Various methods can be employed to splice reinforcement bars, including lap splicing, welding, and mechanical splicing. Lap splicing is the most used method among these techniques. However, this study primarily focuses on evaluating the potential of mechanical splicing to replace the lap splice method. The investigation involved assessing the flexural performance of six RC beams in a series of laboratory experiments. These beams represented a control beam, an RC beam with lap-spliced rebars, and an RC beam with clamp-type mechanical spliced rebars. The laboratory testing results indicated that the RC beam with lap-spliced rebars had the highest load-bearing capacity, resulting in the highest nominal flexural moment (Mn). In contrast, the control beam demonstrated the highest deflection, signifying a greater level of ductility. However, RC beams with mechanical splices (clamp type), while not achieving the highest flexural moment and ductilities, are still competitive, as the experiment revealed that the difference is not significant. Consequently, it can be concluded that mechanical splicing has the potential to compete with or replace lap splicing in RC beams.

棉秆对夹拉拔试验台设计与试验

In order to explore the relationship between displacement-pulling force and the change of clamping force during the clamping and pulling process of cotton stalks in the field by different types of clamps, a test bench for cotton stalks clamping and pulling was designed. Based on the combination of virtual instrument technology and external hardware, the device is programmed by Gx Works2 and LabVIEW programming software to complete the operation of the test bench clamping and pulling device and the measurement and acquisition of information. From the mapping of the collected information, the average value of the maximum uplift force on the cotton stalks was 500 N, corresponding to an upward movement of 12 mm at the root of the cotton stalks. Through the collected information the effect of two types of clamps on cotton stalks clamping and pulling was analyzed, rigid splints with the clamping force of 750 N and a linear speed of 0.18m/s having the best effect on the cotton stalks clamping and pulling. Rubber splints have the best effect on cotton stalks clamping and pulling when the clamping force is 500 N and the linear speed is 0.36 m/s. Among them, the striped rubber splint has the best effect. The collected information was subjected to analysis of variance (ANOVA), and the results showed that the coefficient of friction of the clamping plate showed a high influence on both the pull-up force and the reduction of clamping force. Based on the obtained results, it can provide a reference for the design of clamping type cotton stalk harvesting machinery.

A unified mixed finite element method for fourth-order time-dependent problems using biorthogonal systems

This article introduces a unified mixed finite element framework based on a saddle-point formulation that applies to time-dependent fourth order linear and nonlinear problems with clamped, simply supported, and Cahn-Hilliard type boundary conditions. The classical mixed formulations lead to large matrix systems that demand huge storage and computational time making the schemes expensive, especially for the time-dependent problems. The proposed scheme circumvents this by employing biorthogonal basis functions that lead to sparse and positive-definite systems. The article discusses a mixed finite element method for the biharmonic problem and the time-dependent linear and nonlinear versions of the extended Fisher-Kolmogorov equations equipped with the aforementioned boundary conditions. The wellposedness of the scheme is discussed and a priori error estimates are presented for the semi-discrete and fully discrete finite element schemes. The numerical experiments validate the theoretical estimates derived in the paper.

Structural basis for intra- and intermolecular interactions on RAD9 subunit of 9-1-1 checkpoint clamp implies functional 9-1-1 regulation by RHINO

Eukaryotic DNA clamp is a trimeric protein featuring a toroidal ring structure that binds DNA on the inside of the ring and multiple proteins involved in DNA transactions on the outside. Eukaryotes have two types of DNA clamps: the replication clamp PCNA and the checkpoint clamp RAD9-RAD1-HUS1 (9-1-1). 9-1-1 activates the ATR-CHK1 pathway in DNA damage checkpoint, regulating cell cycle progression. Structure of 9-1-1 consists of two moieties: a hetero-trimeric ring formed by PCNA-like domains of three subunits and an intrinsically disordered C-terminal region of the RAD9 subunit, called RAD9 C-tail. The RAD9 C-tail interacts with the 9-1-1 ring and disrupts the interaction between 9-1-1 and DNA, suggesting a negative regulatory role for this intramolecular interaction. In contrast, RHINO, a 9-1-1 binding protein, interacts with both RAD1 and RAD9 subunits, positively regulating checkpoint activation by 9-1-1. This study presents a biochemical and structural analysis of intra- and inter-molecular interactions on the 9-1-1 ring. Biochemical analysis indicates that RAD9 C-tail binds to the hydrophobic pocket on the PCNA-like domain of RAD9, implying that the pocket is involved in multiple protein-protein interactions. The crystal structure of the 9-1-1 ring in complex with a RHINO peptide reveals that RHINO binds to the hydrophobic pocket of RAD9, shedding light on the RAD9-binding motif. Additionally, the study proposes a structural model of the 9-1-1-RHINO quaternary complex. Together, these findings provide functional insights into the intra- and inter-molecular interactions on the front side of RAD9, elucidating the roles of RAD9 C-tail and RHINO in checkpoint activation.

Experimental Study and Bearing Capacity Analysis of Retrofitted Built-Up Steel Angle Members under Axial Compression

Against the update of load design standards and requirement of long-term service, many latticed towers using steel angles subjected to gradual performance degradation must be retrofitted for bearing further social functions, e.g., electric power transmission and fifth-generation mobile communication. Therefore, this paper proposed a non-destructive reinforcement method for steel angles by avoiding unnecessary new construction or complex reinforcement procedure. The non-destructive reinforcement of a steel angle is composed of a steel angle, reinforcement plate, and fixture. Standardized fixtures are used to connect the reinforcement plate and steel angle to achieve steel angle reinforcement. In retrofitting tests, built-up steel angle members were loaded under axial compression, in which the failure mode and reinforcement effect of key parameters (e.g., clamp type, slenderness ratio, and clamp distance) were analyzed and compared, where a significant reinforcement effect was obtained with the capacity increment within 39~174%; the clamp types and clamp distance had a slight effect on bearing capacity; and the proposed reinforcement method was more effective for slender members. Based on the mechanical mechanism analysis and failure mode, the accuracy of the design method for calculating the bearing capacity of those built-up steel angle members was suggested and verified, in which a simplified mechanical model for the flexural-buckling mode was developed. The design method based on AISC360-16 agreed well with the test result and could be effectively used for calculating the flexural–torsional bearing capacity of those built-up steel angles. This study can provide a valuable reference for the design and application of non-destructive reinforcement of angle steel towers.

Efficacy of endotracheal tube clamping to prevent positive airways pressure loss and pressure behavior after reconnection: a bench study

BackgroundEndotracheal tube (ETT) clamping before disconnecting the patient from the mechanical ventilator is routinely performed in patients with acute respiratory distress syndrome (ARDS) to minimize alveolar de-recruitment. Clinical data on the effects of ETT clamping are lacking, and bench data are sparse. We aimed to evaluate the effects of three different types of clamps applied to ETTs of different sizes at different clamping moments during the respiratory cycle and in addition to assess pressure behavior following reconnection to the ventilator after a clamping maneuver.MethodsA mechanical ventilator was connected to an ASL 5000 lung simulator using an ARDS simulated condition. Airway pressures and lung volumes were measured at three time points (5 s, 15 s and 30 s) after disconnection from the ventilator with different clamps (Klemmer, Chest-Tube and ECMO) on different ETT sizes (internal diameter of 6, 7 and 8 mm) at different clamping moments (end-expiration, end-inspiration and end-inspiration with tidal volume halved). In addition, we recorded airway pressures after reconnection to the ventilator. Pressures and volumes were compared among different clamps, different ETT-sizes and the different moments of clamp during the respiratory cycle.ResultsThe efficacy of clamping depended on the type of clamp, the duration of clamping, the size of the ETT and the clamping moment. With an ETT ID 6 mm all clamps showed similar pressure and volume results. With an ETT ID 7 and 8 mm only the ECMO clamp was effective in maintaining stable pressure and volume in the respiratory system during disconnection at all observation times. Clamping with Klemmer and Chest-Tube at end inspiration and at end inspiration with halved tidal volume was more efficient than clamping at end expiration (p < 0.03). After reconnection to the mechanical ventilator, end-inspiratory clamping generated higher alveolar pressures as compared with end-inspiratory clamping with halved tidal volume (p < 0.001).ConclusionsECMO was the most effective in preventing significant airway pressure and volume loss independently from tube size and clamp duration. Our findings support the use of ECMO clamp and clamping at end-expiration. ETT clamping at end-inspiration with tidal volume halved could minimize the risk of generating high alveolar pressures following reconnection to the ventilator and loss of airway pressure under PEEP.

Method for determining the locations of power cable damage

Problem. Existing methods for remotely detecting cable damage locations, except in the case of cable breakage, have a common drawback. They are unable to accurately separate the cable core resistance from the transient resistance at the short-circuit location, leading to low accuracy in fault detection. The posterior transient resistance at the short-circuit location can vary widely, depending on when the repair crew arrives. Goal. The goal of this study is to propose a method for identifying the location of "floating breakdown" cable damage. Methodology. The method involves using short-circuit indicators to determine the type and area(s) of the short circuit. The UNI-TUT255A device, a current clamp type, is then installed on the damaged cable core. The Imax option with memory is set, and the cable is switched on at the rated voltage. By comparing the recorded shock current value with the values obtained from a short-circuit model of the cable in MATLAB, the location of the damage along the length of the cable is determined. The point where the shock current value of the model matches the recorded value corresponds to the location of the short circuit. Originality. The proposed method addresses the challenge of locating faults in power cables, specifically those of the "floating breakdown" type. This type of cable damage, which occurs when the cable is accidentally disconnected during a short circuit, poses difficulties in detection, as traditional methods may show normal readings. The method presented in this study overcomes these limitations and provides a practical solution for identifying "floating breakdown" faults. Practical value. The results obtained from this method allow for the accurate detection of faults at the nominal voltage, without the need for burning the cable. This reduces the probability of additional damage caused by overvoltage. Furthermore, the method requires only one operator to carry the necessary equipment, eliminating the need for transport with powerful burning installations typically used in traditional methods.

Development and Experiment of Clamp Type Submarine Cable Inspection Robot

Relying on the research and development project of an auxiliary device for a submarine cable to cross a steel pipeline, with regard to a long-distance submarine cable crossing a pipeline, combined with a pipe-climbing robot and the laying of the submarine cable, this paper developed a detection robot that walks along the outer wall of the cable inside the submarine casing. The non-enclosed four-bar linkage mechanism is adopted, a stepper motor is used to drive a roller to walk on the submarine cable, the diameter change of the submarine cable is recorded in real-time, the damage of the submarine cable is detected when it is moved along the submarine cable, and the walking experiment is carried out. The submarine cable diameter measurement verification experiment showed that the outer wall detection robot of the submarine cable could stably travel on the submarine cable, and at the same time, could measure the real-time diameter of the submarine cable and record the actual condition of the submarine cable through video.

Investigation of Unwanted Oscillations of Electrically Modulated Magnetoelectric Cantilever Sensors.

Magnetoelectric thin-film cantilevers consisting of strain-coupled magnetostrictive and piezoelectric layers are promising candidates for magnetic field measurements in biomedical applications. In this study, we investigate magnetoelectric cantilevers that are electrically excited and operated in a special mechanical mode with resonance frequencies above 500 kHz. In this particular mode, the cantilever bends in the short axis, forming a distinctive U-shape and exhibiting high-quality factors and a promising limit of detection of 70pT/Hz1/2 at 10 Hz. Despite this U mode, the sensors show a superimposed mechanical oscillation along the long axis. The induced local mechanical strain in the magnetostrictive layer results in magnetic domain activity. Due to this, the mechanical oscillation may cause additional magnetic noise, deteriorating the limit of detection of such sensors. We compare finite element method simulations with measurements of magnetoelectric cantilevers in order to understand the presence of oscillations. From this, we identify strategies for eliminating the external effects that affect sensor operation. Furthermore, we investigate the influence of different design parameters, in particular the cantilever length, material parameters and the type of clamping, on the amplitude of the undesired superimposed oscillations. We propose design guidelines to minimize the unwanted oscillations.

Removable, Reconfigurable, and Sustainable Steel Structures: A State-of-the-Art Review of Clamp-Based Steel Connections

In this review paper, first of all, an analysis of the circular economy and its application to steel structures is carried out. It highlights the need to apply the philosophy of Design for Deconstruction or Design for Disassembly (DfD) from the conception of the structure so that it can be truly reconfigurable. Then, a brief review of the different types of connections for steel structures is conducted, comparing the level of research and development of each of them and the degree of reconfiguration that is possible to obtain. Subsequently, the article focuses on the type of connection using clamps, a key point of this work and on which, to date, there are no state-of-the-art studies. It describes the types of clamps, their principle of operation, the types of connections developed with them, and the results of the different investigations that allow for calculating these types of connections. A summary is also given of how these connection types work according to the geometrical characteristics of the clamp and the bolt so that this review work can serve as a driver for the widespread use of clamp-based connections by researchers and engineers in the design and manufacturing of demountable and reconfigurable steel structures. Finally, some conclusions are given, indicating the advantages and disadvantages of this connection system and future lines of research.

Study and Validation of a Novel Grouting Clamp Type Deepwater Oilfield Pipeline Repair Method Based on Computational Fluid Dynamics

In order to handle the corrosion of underwater production pipe sinks in deepwater oil fields, a non-solid phase silicone plugging agent, an external clamp, and an underwater injection tool are combined in this paper’s innovative pipeline repair technique proposal. The optimal main agent to curing the agent ratio for non-solid phase silicone plugging agents was found to be 100:25, which was achieved through an experimental examination of the curing process. The compressive and cementing strength changes in the curd plugging agent were disclosed by testing and evaluating the mechanical behavior of the plugging agent. In addition, the limits of the compressive and cementing strength were found to be 143 MPa and 11.6 MPa, respectively. Based on this, a computational-fluid-dynamics(CFD)-based analytical approach of the complicated flow field in a deep sea environment on the eroding impact of a plugging agent was developed. Through numerical simulation testing, the mathematical relationship between the plugging agent’s maximum pressure and the flow field’s velocity was established. The limits of saltwater and petroleum oil on the erosion of the plugging agent were found to be 4.19 MPa and 3.29 MPa, respectively, which are values that are far below their strength limits. In this way, the viability and efficacy of this novel pipeline repair technique were confirmed. The study presented in this paper sets the groundwork for an in-depth analysis and optimization of novel corrosion control solutions for deepwater oil field subsea process pipes.

Effect of Suspension Clamp Types on the Dynamic Bending Stress of All Aluminium Alloy 1120 Overhead Conductors

Determination of the bending stress is one of the important factors for the design or fatigue assessment of transmission power lines. Researchers and designers calculate the bending stress of overhead conductors by using the Poffenberger–Swart (P-S) formula, which was established for the conductor/metal suspension clamp system. This publication presents experimental work on the effect of different configurations of suspension clamps on the dynamic bending stress that causes fatigue in the conductor. For each type of clamp configuration, specific points of the conductors were instrumented with strain gauges for the measurement of bending strain. The prediction of bending stress by the P-S formula presented errors of up to 140% for clamp different from the one established during the formulation. A better correlation with experimental data was obtained by adjusting considering an effective length of the lever arm for elastomeric clamps.

Open-Circuit Fault-Tolerant Control of a Six-Phase Asymmetric Permanent Magnet Synchronous Motor Drive System

One innovative composite fault-tolerant control tactic is presented for the reliable operation of a power transmission system, which consists of both an asymmetric six-phase permanent magnet synchronous motor (PMSM) and a T-type mid-point clamp type (T-NPC) three-level inverter. First, in order to inherit the better harmonic property of simplified space vector modulation (SVM) and the rapid dynamic capability of direct torque control (DTC), the SVM-DTC control scheme was determined, and the harmonic electric current suppression unit was added to the basic control scheme to obtain good harmonic electric current suppression. In addition, a strategy for open-circuit fault-tolerant control under the SVM-DTC scheme was designed by analyzing the mutual influence between the stator flux linkage and the stator voltage of each phase under an open-circuit fault. Finally, the PMSM drive system principle prototype was tested. By comparing the waveforms of output torque and current of each phase before and after fault tolerance, it shows that the large torque fluctuation (±5%) before fault tolerance was suppressed to ±2% and smoothed out, verifying the effectiveness of fault tolerance control.

Clinical evaluation of winged versus wingless rubber dam clamps in single tooth isolation - A randomized clinical study.

Retention of the rubber dam is done with metallic or nonmetallic clamps for isolation. The two types of metallic clamps most frequently used are winged and wingless. The clinical efficacy of both clamps is needed to be compared. The aim of the study was to evaluate and compare the postoperative pain and clinical efficacy of winged clamps and wingless metallic clamps in rubber dam isolation of permanent molars in class I restoration. After obtaining ethical approval and CTRI registration, a total of 60 patients with mild-to-moderate deep class I caries were included after obtaining informed consent and randomly allocated into two assigned groups: Group A - winged clamp and Group B - wingless clamp, with n = 30 per group. Local anesthesia was administered and the tooth was isolated using a rubber dam as per the standardized protocol. The postoperative evaluation was done for pain using the Verbal Rating Scale (VRS) at 6 and 12 h; trauma to the gingival tissues, sealing ability of the clamp, and slippage of the clamp were evaluated using criteria for clinical evaluation of rubber dam isolation. Independent t-test and Chi-square test were used to compare VRS and clinical parameters, respectively, with P < 0.05. Gingival trauma (P = 0.006) and postoperative pain were statistically significantly more in the wingless group at 6 h (P = 0.016) and 12 h (0.01). Statistically significant lower seepage of fluid (P = 0.017) was observed in the wingless group. Slippage was observed more with the winged group but was statistically insignificant. Both clamps showed acceptable clinical performance. Their use should be planned as per the requisite of the case and the position of the tooth.

Airflow ejection-wrapped clamping type seedling picking method and parameter optimization.

Since the current clamp-type and push-out-type seedling picking method brought damage to seedlings, this study aimed to proposed an airflow ejection-wrapped clamping type seedling picking method, which used airflow to eject out seedling and the seedlings were wrapped clamped to reduce the damage of seedlings during seedling picking process. The parameter model was established through theoretical design, then the parameters were optimized through coupling simulation analysis, and the validity of these parameters was verified through experiments. We found that the diameter of the airflow nozzle was selected as 3.5mm to match with the drainage outlet of the plug tray, and the airflow pressure which could eject out seedlings was calculated as 0.146 Mpa~0.315 Mpa on the basis of gas jet dynamic. The fluid-solid coupling simulation of airflow ejection in Comsol proposed that the seedlings could be ejected out under the airflow pressure was equal to or greater than 0.4 Mpa, and the airflow should be maintained for about 0.3 s to ensure the posture of the seedlings ejected out for better seedling clamping. The further fluid-discrete body simulation of airflow ejection by using Fluent-Edem coupling method indicated that the seedling was damaged under airflow pressure of 0.5 MPa, so the airflow pressure should be set as 0.4 MPa during seedling ejection process. Besides, a wrapped clamping type effector which clamped the seedlings from all sides in the form of flexible package was also designed to match with the airflow ejection method, and the RecurDyn-Edem coupling simulation showed that the end-effector could tightly clamp the seedling without damage when the angle between the clamping slices and the vertical direction was 8.5°. Finally, the airflow ejection-wrapped clamping type seedling picking device was manufactured, and the verification tests verified the simulation results. This research can provide some references for the automatic seedling picking technology.

Viscoelasticity of single folded proteins using dynamic atomic force microscopy.

The advent of atomic force microscopy, along with optical tweezers, ushered in a new field of single molecule force spectroscopy, wherein the response of a single protein or a macromolecule to external mechanical perturbations is measured. Controlled forces ranging from pN to nN are applied to measure the unfolding force distribution of a single protein domain. In a clamp type experiment, the folded protein is subjected to a constant force to measure the unfolding time distribution. Simultaneously, there were efforts to measure the elastic and viscous response of a single domain by applying sinusoidal forces and measuring the resulting deformations produced in a bid to quantify its viscoelasticity. The deformation's phase lag with respect to the applied force provides the elastic and viscous response of the protein, akin to oscillatory rheology. Despite numerous technical advances in AFM, an artefact-free measurement of a folded protein's viscoelasticity largely remains a challenge. In this perspective, we review efforts to measure the viscoelasticity of proteins using dynamic AFM, identifying pitfalls that make these measurements elusive. Finally, we discuss a new promising method, which reported viscoelasticity of a folded protein and its implications for our understanding of protein dynamics and structural flexibility.

Research on the Coordination Suppression Strategy of Neutral Point Potential and Common Mode Voltage for NPC Three-Level Inverter

A Neutral Point Clamped (NPC) type three-level inverter has the advantages of a low switch voltage and a high-quality output waveform. However, there are inherent problems, such as neutral point potential asymmetry and common mode interferences, which easily affect the symmetry of the three-phase output voltage and the safe operation of the inverter. Firstly, according to the different modulation degrees, the fluctuation of midpoint potential can be suppressed by adding an action time correction factor to the traditional space vector pulse-width (SVPWM) modulation strategy and virtual space vector pulse-width (VSVPWM) modulation strategy, respectively. Secondly, considering the suppression of common mode voltage, a new virtual space vector pulse-width (NVSVPWM) modulation strategy is proposed, which uses a set of new vector synthesis methods. Finally, the simulation and experiment prove that the NVSVPWM strategy with an action time correction factor can suppress the fluctuation of the neutral point potential and common mode voltage at the same time, and the effect is significant.

Cervical bleeding with cervical stabilization during IUD placement: allis clamp versus single-tooth tenaculum, a randomized control trial.

To evaluate whether the use of an atraumatic Allis clamp will result in less bleeding than the standard single-tooth tenaculum for cervical stabilization during intrauterine device (IUD) placement. A single-blinded randomized controlled trial was conducted during insertions of IUDs between March 2017 and March 2018. University of Kentucky Institutional Review Board (IRB 16-1110-P3K) approval was obtained. Physicians were randomized to use either an Allis clamp or a single-tooth tenaculum for cervical stabilization. A post-procedure questionnaire was used to collect outcome measures as well as demographic and obstetric-related factors. Of the ninety-five participants, there was no difference in age, self-identified race/ethnicity, or the evaluated obstetric factors between the groups. Bleeding was present after clamp removal in 3 (6.3%) insertions using an Allis clamp and 26 (55.3%) insertions using a single-tooth tenaculum (RR = 0.113, CI = [0.037, 0.3481], p < 0.0001). There was no difference in IUD insertion success rates between the two clamps. There was no difference in the number of interventions needed to obtain hemostasis including indirect pressure, silver nitrate, monsel's solution, or stitch for hemostasis. Pain scores did not differ based on clamp type or age of patient, but were significantly different based on parity (p < 0.001) and IUD type (p < 0.003). Decreased incidence of bleeding from cervical stabilization device, with unchanged insertion success using the Allis clamp can be an alternative to the single tooth tenaculum in the procedure of IUD insertion. The trial was retrospectively registered on 1/11/22 (trial registration number NCT05187078).

Defects recognition of strain clamps based on attentional enhancement mechanism

The crimping quality of tension clamp in overhead transmission line is directly related to the safe and stable operation of transmission line. existing detection methods are low efficiency or availability and developing a timely and effective defect detecting method for strain clamp is a top priority. An X-ray image classification algorithm based on the attentional enhancement mechanism is proposed to identify the defects of different types of strain clamps. DenseNet structure is used as the backbone network to multiplex the X-ray image features, SENet channel is used to enhance the attention to the defect site, and PSANet is used to replace the 3×3 convolution layer in DenseBlock in DenseNet to highlight the features of defects at different scales. Research shows that the average recognition accuracy of the proposed algorithm is 88.1%, which is better than the existing methods.