Design and research of measuring system of clamping force of hemostats

Reliability of medical instruments such as hemostats is extremely important because these instruments are used in patients who are in critical condition. Clamping force of hemostats, as an important parameter of hemostats, should be detected. However, it could not be tested directly. In order to test it, a testing system has been put forward. The system is comprised of sensor, acquisition card, and three-way tap and so on. This system is controlled by a computer. The testing system has been proved to be effective in testing the clamping force of hemostats.

Effect of an Airbag-selective Portal Vein Blood Arrester on the Liver after Hepatectomy:A New Technique for Selective Clamping of the Portal Vein

Objective:A novel technique was explored using an airbag-selective portal vein blood arrester that circumvents the need for an intraoperative assessment of anatomical variations in patients with complex intrahepatic space-occupying lesions.Methods:Rabbits undergoing hepatectomy were randomly assigned to 4 groups:intermittent portal triad clamping(PTC),intermittent portal vein clamping(PVC),intermittent portal vein blocker with an airbag-selective portal vein blood arrester(APC),and without portal blood occlusion(control).Hepatic ischemia and reperfusion injury were assessed by measuring the 7-day survival rate,blood loss,liver function,hepatic pathology,hepatic inflammatory cytokine infiltration,hepatic malondialdehyde levels,and proliferating cell nuclear antigen levels.Results:Liver damage was substantially reduced in the APC and PVC groups.The APC animals exhibited transaminase levels similar to or less oxidative stress damage and inflammatory hepatocellular injury compared to those exhibited by the PVC animals.Bleeding was significantly higher in the control group than in the other groups.The APC group had less bleeding than the PVC group because of the avoidance of portal vein skeletonization during hepatectomy.Thus,more operative time was saved in the APC group than in the PVC group.Moreover,the total 7-day survival rate in the APC group was higher than that in the PTC group.Conclusion:Airbag-selective portal vein blood arresters may help protect against hepatic ischemia and reperfusion injury in rabbits undergoing partial hepatectomy.This technique may also help prevent liver damage in patients requiring hepatectomy.

The calculation of the Reproducibility Error in the technological system with the clamp on the gas power

The paper deduced a calculation formula by the classic control theory on the Reproducibility Error of parts processing in the technology system,the flexible clamp system, with the clamping device on the gas power,and analyzed its influencing factor with examples,the Reproducibility Error law:\ The larger the diameter of the cylinder,the smaller the error; the slower the tool speed,(k values smaller),the smaller the error.

Experimental Investigation and Optimization Design of Multi-Support Pipeline System

The design of aircraft hydraulic pipeline system is limited by many factors,such as the integrity of aviation structure or narrow installation space,so the limited clamp support position should be considered.This paper studied the frequency adjustment and dynamic responses reduction of the multi-support pipeline system through experiment and numerical simulation.To avoid the resonance of pipeline system,we proposed two different optimization programs,one was to avoid aero-engine working range,and another was to avoid aircraft hydraulic pump pulsation range.An optimization method was introduced in this paper to obtain the optimal clamp position.The experiments were introduced to validate the optimization results,and the theoretical optimization results can agree well with the test.With regard to avoiding the aero-engine vibration frequency,the test results revealed that the first natural frequency was far from the aero-engine vibration frequency.And the dynamic frequency sweep results showed that no resonance occurred on the pipeline in the engine vibration frequency range after optimization.Additionally,with regard to avoiding the pump vibration frequency,the test results revealed that natural frequencies have been adjusted and far from the pump vibration frequency.And the dynamic frequency sweep results showed that pipeline under optimal clamp position cannot lead to resonance.The sensitivity analysis results revealed the changing relationships between different clamp position and natural frequency.This study can provide helpful guidance on the analysis and design of practical aircraft pipeline.

Plastic Mechanism of Multi-pass Double-roller Clamping Spinning for Arc-shaped Surface Flange

Compared with the conventional single-roller spinning process, the double-roller clamping spinning（DRCS） process can effectively prevent the sheet metal surface wrinkling and improve the the production efficiency and the shape precision of final spun part. Based on ABAQUS/Explicit nonlinear finite element software, the finite element model of the multi-pass DRCS for the sheet metal is established, and the material model, the contact definition, the mesh generation, the loading trajectory and other key technical problems are solved. The simulations on the multi-pass DRCS of the ordinary Q235A steel cylindrical part with the arc-shaped surface flange are carried out. The effects of number of spinning passes on the production efficiency, the spinning moment, the shape error of the workpiece, and the wall thickness distribution of the final part are obtained. It is indicated definitely that with the increase of the number of spinning passes the geometrical precision of the spun part increases while the production efficiency reduces. Moreover, the variations of the spinning forces and the distributions of the stresses, strains, wall thickness during the multi-pass DRCS process are revealed. It is indicated that during the DRCS process the radical force is the largest, and the whole deformation area shows the tangential tensile strain and the radial compressive strain, while the thickness strain changes along the generatrix directions from the compressive strain on the outer edge of the flange to the tensile strain on the inner edge of the flange. Based on the G-CNC6135 NC lathe, the three-axis linkage computer-controlled experimental device for DRCS which is driven by the AC servo motor is developed. And then using the experimental device, the Q235A cylindrical parts with the arc-shape surface flange are formed by the DRCS. The simulation results of spun parts have good consistency with the experimental results, which verifies the feasibility of DRCS process and the reliability of the finite element model for DRCS.

Numerical simulation of horizontal transversal displacement under different fixed clamping force of welding fixture for superalloy during TIG welding

A numerical model is established by Abaqus software for superalloy during tungsten inert gas （TIG） welding with welding fixture to simulate the weld temperature filed, stress and strain field, and weld plate＇s horizontal trasnsveral shift. The clamp force perpendicular to the weld plate varying with welding time was analyzed. The maximum clamp force during welding process was calculated. Under the condition of insufficient of clamping force, a half or one third of the maximum clamp force for example, the weld plate＇s horizontal transversal displacement could happen and also be computed.

Plastic Deformation Mechanism in Double-Roller Clamping Spinning of Flanged Thin-Walled Cylinder

Double?roller clamping spinning(DRCS) is a new process for forming a thin?walled cylinder with a complex surface flange. The process requires a small spinning force,and can visibly improve forming quality and production e ciency. However,the deformation mechanism of the process has not been completely understood. Therefore,both a finite element numerical simulation and experimental research on the DRCS process are carried out. The results show that both radial force and axial force dominate the forming process of DRCS. The deformation area elongates along the radial direction and bends along the axial direction under the action of the two forces. Both the outer edge and round corner of the flange show the tangential tensile stress and radial compressive stress. The middle region shows tensile tangential stress and radial stress,while the inner edge shows compressive tangential stress and radial stress. Tan?gential tensile strain causes a wall thickness reduction in the outer edge and middle regions of the flange. The large compressive thickness strain causes material accumulation and thus,an increase in the wall thickness of the round corner. Because of bending deformation,the round corner shows a large radial tensile strain in addition. The inner edge of the flange shows small radial compressive strain and tensile strain in thickness. Thus,the wall thickness on the inner edge of the flange continues to increase,although the increment is small. Furthermore,microstructure analysis and tensile test results show that the flanged thin?walled cylinder formed by DRCS has good mechanical properties. The results provide instructions for the application of the DRCS process.

Minimum Normal Force Principle Based Quantitive Optimization of Clamping Forces for Thin Walled Part

Based on the stability criteria of workpiece-fixture system, quantitative optimization of clamping forces during precise machining process for thin walled part is studied considering the contact condition between wokpiece and locator, the contact mechanical model is achieved, which is further been used to calculate the entire passive forces acting on the statically undetermined workpiece by means of the force screw theory as well as minimum norm force principle. Furthermore, a new methodology to optimize clamping forces is put forward, on the criteria of keeping the stability of workpiece during cutting process. By this way, the intensity of clamping forces is decreased dramatically, which will be most beneficial for improving the machining quality of thin-walled parts. Finally, a case study is used to support and validate the proposed model.

STRENGTH ANALYSIS OF CLAMPING IN MICRO/NANO SCALE EXPERIMENTS

Two kinds of clamping in micro/nano scale experiments are investigated in this paper, one based on electron-beam-induced deposition, and the other on the van der Waals interaction. The clamping strength and mechanism are analyzed both theoretically and experimentally. The influence of relative humidity on the micro/nano clamping and the method of electrostatic clamping are discussed. The clamping strength and performance of different clamping methods are compared considering the size and material of the clamped objects, and the application environments.

Tepid antegrade intermittent blood cardioplegia as an alternative for intermittent crossclamping with Lidoflazine

Background: Blood cardioplegia is a technique with many variations in its use. Intermittent cross clamping with Lidoflazine has proven to deliver good cardioprotection in our center. Question: Is tepid (32°C) antegrade intermittent blood cardioplegia an efficient, safe and easy-to-use alternative to intermittent cross-clamping with Lidoflazine in elective isolated CABG in low-risk patients? Primary outcomes are heart enzymes (cTnI, CK-MB). Secondary outcomes are operation times, length of hospital stay, major complications and in-hospital mortality. Methods: From January 2012 until November 2012, 40 patients with LVEF ≥50%, EuroSCORE

Floating Clamping Mechanism of PT Fuel Injector and Its Dynamic Characteristics Analysis

PT fuel injector is one of the most important parts of modern diesel engine.To satisfy the requirements of the rapid and accurate test of PT fuel injector,the self-adaptive floating clamping mechanism was developed and used in the relevant bench.Its dynamic characteristics directly influence the test efficiency and accuracy.However,due to its special structure and complex oil pressure signal,related documents for evaluating dynamic characteristics of this mechanism are lack and some dynamic characteristics of this mechanism can＇t be extracted and recognized effectively by traditional methods.Aiming at the problem above-mentioned,a new method based on Hilbert-Huang transform（HHT） is presented.Firstly,combining with the actual working process,the dynamic liquid pressure signal of the mechanism is acquired.By analyzing the pressure fluctuation during the whole working process in time domain,oil leakage and hydraulic shock in the clamping chamber are discovered.Secondly,owing to the nonlinearity and nonstationarity of pressure signal,empirical mode decomposition is used,and the signal is decomposed and reconstructed into forced vibration,free vibration and noise.By analyzing forced vibration in the time domain,machining error and installation error of cam are revealed.Finally,free vibration component is analyzed in time-frequency domain with HHT,the traits of free vibration in the time-frequency domain are revealed.Compared with traditional methods,Hilbert spectrum has higher time-frequency resolutions and higher credibility.The improved mechanism based on the above analyses can guarantee the test accuracy of injector injection.This new method based on the analyses of the pressure signal and combined with HHT can provide scientific basis for evaluation,design improvement of the mechanism,and give references for dynamic characteristics analysis of the hydraulic system in the interrelated fields.

Design of a novel high holding voltage LVTSCR with embedded clamping diode

In order to reduce the latch-up risk of the traditional low-voltage-triggered silicon controlled rectifier(LVTSCR), a novel LVTSCR with embedded clamping diode(DC-LVTSCR) is proposed and verified in a 0.18-μm CMOS process. By embedding a p+implant region into the drain of NMOS in the traditional LVTSCR, a reversed Zener diode is formed by the p+implant region and the n+bridge, which helps to improve the holding voltage and decrease the snapback region.The physical mechanisms of the LVTSCR and DC-LVTSCR are investigated in detail by transmission line pulse(TLP)tests and TCAD simulations. The TLP test results show that, compared with the traditional LVTSCR, the DC-LVTSCR exhibits a higher holding voltage of 6.2 V due to the embedded clamping diode. By further optimizing a key parameter of the DC-LVTSCR, the holding voltage can be effectively increased to 8.7 V. Therefore, the DC-LVTSCR is a promising ESD protection device for circuits with the operation voltage of 5.5–7 V.

MODELING, VALIDATION AND OPTIMAL DESIGN OF THE CLAMPING FORCE CONTROL VALVE USED IN CONTINUOUSLY VARIABLE TRANSMISSION

Associated dynamic performance of the clamping force control valve used in continuously variable transmission （CVT） is optimized. Firstly, the structure and working principle of the valve are analyzed, and then a dynamic model is set up by means of mechanism analysis. For the purpose of checking the validity of the modeling method, a prototype workpiece of the valve is manufactured for comparison test, and its simulation result follows the experimental result quite well. An associated performance index is founded considering the response time, overshoot and saving energy, and five structural parameters are selected to adjust for deriving the optimal associated performance index. The optimization problem is solved by the genetic algorithm （GA） with necessary constraints. Finally, the properties of the optimized valve are compared with those of the prototype workpiece, and the results prove that the dynamic performance indexes of the optimized valve are much better than those of the prototype workpiece.

IMPROVE THE KINETIC PERFORMANCE OF THE PUMP CONTROLLED CLAMPING UNIT IN PLASTIC INJECTION MOLDING MACHINE WITH ADAPTIVE CONTROL STRATEGY

The kinetic characteristics of the clamping unit of plastic injection molding machine that is controlled by close loop with newly developed double speed variable pump unit are investigated. Considering the wide variation of the cylinder equivalent mass caused by the transmission ratio of clamping unit and the severe instantaneous impact force acted on the cylinder during the mold closing and opening process, an adaptive control principle of parameter and structure is proposed to improve its kinetic performance. The adaptive correlation between the acceleration feedback gain and the variable mass is derived. The pressure differential feedback is introduced to improve the dynamic performance in the case of small inertia and heavy impact load. The adaptation of sum pressure to load is used to reduce the energy loss of the system. The research results are verified by the simulation and experiment, The investigation method and the conclusions are also suitable for the differential cylinder system controlled by the traditional servo pump unit.

Linear fast shutdown technology based on self-resonant constant voltage clamping

Transient electromagnetic method(TEM)has been widely used in the field of medium and shallow underground detection due to its high detection efficiency and large detection depth.However,due to the long turn-off time of the transmitting current caused by the inductive characteristics of the transmitting coil,the early signals will be overwhelmed by primary field.Since the early signals contain most of shallow geological signals,it is necessary to reduce the long turn-off time to get shallow layer signal.Due to lack of a reliable and effective clamping method for high-power transmission at present,we design a TEM transmitter fast turn-off circuit,combining self-resonant zero-voltage switching technology with the corresponding timing control circuit to solve this problem effectively.A transient electromagnetic transmitter based on self-resonant constant voltage clamping technology was fabricated to charge the clamping capacitor.The rated transmitting current of the transmitter is 20 A,and the turn-off time is continuously adjustable from 550-50μs.Moreover,the current drop process is approximately linear rather than exponential attenuation.Compared with the existing clamping methods,the proposed clamping method solves the problems that transient voltage suppressor(TVS)clamping cannot be used in high-power occasions and has a high failure rate.It also solves the problem of long pre-charge time in traditional capacitor clamping methods due to insufficient inductance of the small size transmitting coil.The proposed method can provide a reference for fast shutdown of large current.

Gradual Clamping Reduced Ischemia-Reperfusion Injury in an Isolated Rat Heart Model

Objectives: We hypothesized that the organisms and their organs or tissues could adapt themselves to the gradual changes of environment for surviving or reducing damage. This study explored whether gradual clamping (GC) could reduce myocardial ischemia-reperfusion (IR) injury in rat heart. Methods: Twelve rats were randomized to IR group and GC group, then the hearts were isolated and perfused with Langendorff apparatus. Before cardioplegia, the perfusion was stopped abruptly in IR group while slowly with 5-minute in GC group. The hearts were subjected to 30-minute ischemia and 60-minute reperfusion. The left ventricular develop pressure (LVDP) and systolic pressure (LVSP), the maximal rate of the increase and decrease of left ventricular pressure (+dp/dtmax, ﹣dp/dtmax) were measured by polygraph system at different time points. The recovery of the variables was expressed as the ratio of these values at individual time point after reperfusion to the baseline respectively. Results: The recovery of LVDP after reperfusion was better than that in IR group (P = 0.034). No significant difference in the recovery of LVSP, +dp/dtmax and ﹣dp/dtmax between groups was observed. Conclusions: Gradual clamping could improve the recovery of LVDP after IR, suggesting that gradual clamping could reduce myocardial IR injury.

Prompt efficiency of energy harvesting by magnetic coupling of an improved bi-stable system

In order to improve the transform efficiency of bi-stable energy harvester（BEH）,this paper proposes an advanced bi-stable energy harvester（ABEH）,which is composed of two bi-stable beams coupling through their magnets.Theoretical analyzes and simulations for the ABEH are carried out.First,the mathematical model is established and its dynamical equations are derived.The formulas of magnetic force in two directions are given.The potential energy barrier of ABEH is reduced and the snap-through is liable to occur between potential wells.To demonstrate the ABEH＇s advantage in harvesting energy,comparisons between the ABEH and the BEH are carried out for both harmonic and stochastic excitations.Our results reveal that the ABEH＇s inter-well response can be elicited by a low-frequency excitation and the harvester can attain frequent jumping between potential wells at fairly weak random excitations.Thus,it can generate a higher output power.The present findings prove that the ABEH is preferable in harvesting energy and can be optimally designed such that it attains the best harvesting performance.

A Micro-coupling for Micro Mechanical Systems

The error motions of micro mechanical systems, such as micro-spindles, increase with the increasing of the rotational speed, which not only decreases the rotational accuracy, but also promotes instability and limits the maximum operational speed. One effective way to deal with it is to use micro-flexible couplings between the drive and driven shafts so as to reduce error motions of the driven shaft. But the conventional couplings, such as diaphragm couplings, elastomeric couplings, bellows couplings, and grooved couplings, etc, cannot be directly used because of their large and complicated structures. This study presents a novel micro-coupling that consists of a flexible coupling and a shape memory alloy（SMA）-based clamp for micro mechanical systems. It is monolithic and can be directly machined from a shaft. The study performs design optimization and provides manufacturing considerations, including thermo-mechanical training of the SMA ring for the desired Two-Way-Shape-Memory effect（TWSMe）. A prototype micro-coupling and a prototype micro-spindle using the proposed coupling are fabricated and tested. The testing results show that the prototype micro-coupling can bear a torque of above 5 N · mm and an axial force of 8.5 N and be fitted with an SMA ring for clamping action at room temperature（15 ℃） and unclamping action below –5 ℃. At the same time, the prototype micro-coupling can work at a rotational speed of above 200 kr/min with the application to a high-speed precision micro-spindle. Moreover, the radial runout error of the artifact, as a substitute for the micro-tool, is less than 3 μm while that of turbine shaft is above 7 μm. It can be concluded that the micro-coupling successfully accommodates misalignment errors of the prototype micro-spindle. This research proposes a micro-coupling which is featured with an SMA ring, and it is designed to clamp two shafts, and has smooth transmission, simple assembly, compact structure, zero-maintenance and balanced motions.

Supraceliac Aortic Clamping for Repair of Ruptured Abdominal Aortic Aneurysm in Patients with Short Aortic Neck Length

Objective: Prompt bleeding control with proximal aortic clamping and subsequent aortic repair are very important for ruptured abdominal aortic aneurysm. However, unsuitable anatomy, such as short aortic neck length, not only disturbs the means to an expeditious repair, but may also increase morbidity and mortality. In the present study, we aimed to evaluate the efficacy of supraceliac aortic clamping for improving surgical outcomes for patients with ruptured abdominal aortic aneurysm, who have a short aortic neck length. Method: Between April 2010 and September 2015, eighteen patients underwent emergent open surgical repair of ruptured abdominal aortic aneurysm. Eight patients with a short aortic neck length underwent supraceliac aortic clamping, and 10 underwent infrarenal aortic clamping. Results: The mean supraceliac aortic clamping time was 30 ± 7 minutes. There was 1 operative death in the infrarenal aortic clamping group due to respiratory failure, and the overall operative mortality was 6%. There were no significant differences between the 2 groups with respect to postoperative complication rates or mortality. Furthermore, there were no significant differences in variables of renal function between the 2 groups, through-out the study period. Conclusion: Supraceliac aortic clamping was associated with minimal mortality and morbidity, but not with harmful effects on postoperative renal function. Thus, supraceliac aortic clamping can be safely applied for ruptured abdominal aortic aneurysm with short aortic neck length.