Clamp Positions Research Articles

Dynamic modeling and stress reduction optimization of parallel pipelines based on pipe-solid element coupling

In aero-engine, spatially parallel pipelines are prone to damage under the harmonic excitation produced by rotors, thus there is an urgent need for vibration reduction research. This paper presents a finite element modeling method for parallel pipelines based on pipe-solid element coupling and performs clamp layout optimization with the objective of reducing the stress response. The modeling idea can be described as follows: the regions of the pipeline with higher stress, such as single and dual clamps and bend sections, are modeled using solid elements, while other regions are modeled using pipe elements, and the different parts are coupled together to complete the overall modeling. An optimization model is created with clamp positions as design variables and the objective function is set as reducing stress response under the resonance condition of the fundamental frequency excitation. The procedure for solving the optimization model is provided based on genetic algorithms. A case study is conducted on a parallel pipeline system with one dual clamp and four single clamps. The rationality of the created spatial parallel pipeline model based on pipe-solid element coupling is demonstrated through a constructed pipeline test system. The model is shown to provide sufficient accuracy while having higher computational efficiency compared with a full 3D solid element model. Furthermore, the stress reduction optimization is performed, and a clamp layout that minimizes the maximum resonant stress of the parallel pipeline system is obtained.

Optimization of fixture locating layout design using comprehensive optimized machine learning

Fixtures are commonly employed in production as work holding devices that keep the workpiece immobilized while machined. The workpiece’s deformation, which affects machining precision, is greatly influenced by the positioning of fixture elements around the workpiece. By positioning the locators and clamps appropriately, the workpiece’s deformation might be decreased. Therefore, it is required to model the fixture–workpiece system’s complicated behavioral relationship. In this study, long short-term memory (LSTM), multilayer perception (MLP), and adaptive neuro-fuzzy inference system (ANFIS) are three machine-learning approaches employed to model the connection between locator and clamp positions and maximum workpiece deformation throughout end milling. The hyperparameters of the developed ANFIS, MLP, and LSTM are chosen using the evolutionary algorithms, including genetic algorithm (GA), particle swarm optimization (PSO), butterfly optimization algorithm (BOA), grey wolf optimization (GWO), and wolf optimization algorithm (WOA). Among developed methods, MLP optimized using BOA (BOA-MLP) reached the highest accuracy among all developed models in predicting the response surface. The developed model had a lower computational load than the final element model in calculating the response surface during the machining process. At the final step, the prementioned five evolutionary algorithms were implemented in the developed BOA-MLP to extract the optimal parameters of the fixture to decrease the deflection of the workpiece throughout the machining. The proposed method was modeled in MATLAB. The outcomes showed that the mentioned model was efficient enough compared with the previous method, such as optimized response surface methodology in the point view of 0.0441 μm lower workpiece deflection.

Cross-clamp location and perioperative outcomes after open infrarenal abdominal aortic aneurysm repair: A Vascular Quality Initiative® review.

By analyzing national Vascular Quality Initiative (VQI) data for patients undergoing open infrarenal abdominal aortic aneurysms (AAA) repair, we sought to better characterize the effects of different suprarenal clamping positions on postoperative outcomes. We performed a retrospective analysis of a prospectively collected national VQI database for all open infrarenal AAA repairs performed between 2003 and 2017. Patients were initially divided into proximal (above 1 renal, above 2 renals, and supraceliac) and infrarenal clamp groups. Patients were then subdivided into those who underwent surgery between 2003-2010 and those who had surgery between 2011-2017. Univariate followed by multivariate analyses were done to compare the baseline characteristics, preoperative, intraoperative, and postoperative outcomes between the two groups. During the study period, 9068 open AAA repairs were recorded in the VQI; of these, 5043 met the inclusion criteria. Aortic clamp level was infrarenal in 59% (N = 2975), above 1 renal in 15% (N = 735), above both renals in 21% (N = 1053), and supraceliac in 5% (N = 280). The average age was 69 years, and males comprised 73% (N = 3701) of the cohort. The overall 30-day mortality for the entire study group was 2.7%. On univariate analysis, patients who underwent proximal clamping had significantly higher 30-day mortality than those undergoing infrarenal clamping (3.7 vs 2.0%, p < 0.001). After adjusting for preoperative and intraoperative variables, this difference became nonsignificant. On multivariate analysis, clamping above both renals or the celiac artery was associated with an increased occurrence of postoperative myocardial infarction (odds ratio = 1.44, p = 0.037 and odds ratio = 1.78, p = 0.023, respectively). All proximal clamp positions were associated with a significant increase in the incidence of AKI and renal failure requiring dialysis. There was no significant difference when looking at overall survival times comparing the suprarenal and infrarenal clamp position groups (p = 0.1). Patients who underwent surgery in the latter half of the study period had longer intraoperative renal ischemia time, increased in estimated blood loss, and longer total procedure time. Suprarenal clamping, at any level, was associated with an increased risk of AKI and renal replacement therapy. Clamping above both renal and celiac arteries was associated with increased cardiac morbidity. Perioperative and long-term mortality was unaffected by clamp level. Patients operating in the latter half of the study had increased estimated blood loss, renal ischemia time, and operative time, which may reflect decreased training in open AAA repair. During open AAA repair, the proximal clamp site should be chosen based on anatomic considerations and not a perceived perioperative mortality benefit. Proximal aortic clamping should always be performed at the safest, distal-most level to reduce cardiac morbidity and the risk of postoperative dialysis.

Fenestrated Endovascular Aneurysm Repair Affords Fewer Renal Complications than Open Surgical Repair for Juxtarenal Abdominal Aortic Aneurysms in Patients with Chronic Renal Insufficiency

ObjectiveAlthough fenestrated endovascular aneurysm repair (FEVAR) has been associated with lower morbidity and mortality than open surgical repair (OSR) in juxtarenal aneurysms (JAAA), there is a paucity of data in the literature comparing outcomes of the approaches specifically in patients with chronic renal insufficiency (CRI). We hypothesized that benefits of FEVAR over OSR observed in the general patient population may be diminished in CRI patients due to their heightened vulnerability to renal dysfunction stemming from contrast-induced nephropathy. This study compares 30-day outcomes between FEVAR and OSR for JAAA in patients with non-dialysis dependent CRI. MethodsAll adults with estimated glomerular filtration rate (eGFR) < 60 mL/min (but not requiring dialysis) undergoing elective, non-ruptured JAAA repairs were identified in the American College of Surgeons – National Surgical Quality Improvement (ACS-NSQIP) Targeted EVAR and AAA databases from 2012–2018. JAAA were identified by recorded proximal aneurysm extent. FEVAR patients were identified in the Targeted EVAR database as those receiving the “Cook Zenith Fenestrated” endograft. OSR cases were defined as those that required proximal clamp positions “above one renal” or “between SMA & renals.” Infra-renal or supra-celiac proximal clamp placement, or cases involving concomitant renal/visceral revascularization were excluded. Thirty-day outcomes including mortality, major adverse cardiovascular events (MACE), pulmonary, and renal complications were compared between FEVAR and OSR groups. ResultsThere were 284 patients with CRI who underwent elective repair of JAAA (FEVAR: 89; OSR: 195). FEVAR patients were significantly older than those undergoing OSR (77.3±7.2 vs. 74.2±7.7, P=0.001) and less likely to be smokers (25.8% vs 42.1%; P = 0.009). Other baseline demographic and pre-operative parameters were comparable between the two groups.Multivariable analysis revealed no significant difference between FEVAR and OSR in 30-day mortality (4.5% vs 4.6%; OR=1.22; 95% CI=0.35 - 4.22; P=0.753) or unplanned re-operation (4.5% vs 5.1%; OR=0.78; 95% CI=0.22 - 2.70; P=0.693). Patients undergoing FEVAR had significantly fewer pulmonary complications (3.4% vs 18.5%; OR=0.12; 95% CI=0.03 - 0.42; P<0.001) and renal dysfunction (3.4% vs 11.8%; OR 0.24 95% CI=0.07 - 0.86; P=0.029) compared to OSR. FEVAR was also associated with significantly shorter ICU and hospital lengths of stay (ICU stay: 0 days vs 3 days, P<0.0001; hospital stay: 3 days vs 8 days, P<0.0001). ConclusionFor patients with chronic renal insufficiency, FEVAR offered improved perioperative renal morbidity compared to OSR without a corresponding mortality benefit. Future studies will be required to determine long term outcomes of this procedure in this vulnerable population.

The Trans-Syndesmotic Axis in Relation to the Distal Anterior Medial Tibial Cortex

Category:AnkleIntroduction/Purpose:Gardner et al. (2006) reported that over 50% of operative syndesmoses are malreduced. The functional consequence of syndesmotic malreduction at two years was reported in 2012. Miller et al. in 2013, found that the 15° and 30°clamp positions caused fibula external rotation and over compression of the syndesmosis joint. The 0° medial clamp position which was in line with the trans-syndesmotic axis (TSA) did not negatively impact fibular reduction as did the other two posterior clamp positions. The purpose of this study is to identify the medial exit point of the TSA on the tibia. We hypothesized that the TSA on the medial side of the ankle would be a constant distance from the medial anterior tibial cortex.Methods:Fifty consecutive CT scans of uninjured ankles were reviewed from our image archive system. On an axial 2- dimensional reformatted image proximal to the ankle joint that included the entire incisura a line was drawn connecting the anterior and posterior limits of the incisura of the tibia. A second line was then drawn at 90 degrees at the midpoint of the first line and extended medially.Results:The average distance of the medial TSA exit point from the anterior edge of the distal medial tibia was 2.9 mm (Range 0- 9 mm, standard deviation 2.03 mm). The average anterior to posterior length of the medial distal tibia was 23.6 mm (Range 16-30, standard deviation 3.01 mm).Conclusion:Syndesmosis reduction clamp placement may first involve identifying the TSA based upon the anterior edge of the distal medial tibia. This region may be used to locate the TSA for optimal medial clamp placement. This study provides a foundation for future clamp placement investigations.

AN INTEGRATED SYSTEM FOR PROCESS-FIXTURE LAYOUT DESIGN OPTIMISATION FOR CUBICAL PARTS

In this article, an integrated computer-assisted process-planning and computer-assisted fixture layout planning system is presented for the automatic generation of process and fixture maps. The part feature model is created using various algorithms and the geometric reasoning approach. The feature-based methodology based on the machining database is then applied for the generation of process maps. The setup scheme algorithm allocates each feature to a definite setup based on its location. The part geometric database and setup plan aids the fixture layout planning process. During fixture layout planning, the standard fixture rules are applied to determine the locating arrangement and feasible datum along with the suitable positions using a fixture database for initial fixture layout planning data. Visual C++ is used to implement the proposed methodology because it interacts with current computer-aided design software. Then a case study is presented to develop an initial fixture layout. Afterwards, the ANSYS parametric design language optimisation tool is applied to automatically optimise locator and clamp positions that yield minimum workpiece deformation. At the end, finite element analysis results depicting deformation magnitudes are presented.

Simultaneous fixturing layout and sequence optimization based on genetic algorithm and finite element method

Dimensional and geometrical precision of industrial parts in the manufacturing process depend heavily on several items such as material, tool, machine tool and fixturing strategy. The workpiece deformation depends on several issues such as workpiece elastic deformation, geometric error of fixcles (we will call locators and clamps as “fixcles” afterwards), fixturing layout, external forces like clamping and machining forces, and variation of contact forces during machining. The optimization of locator and clamp positions, as well as their sequence, are crucial factors in minimizing the deformation error in workpiece machining. This research tries to introduce a new viewpoint toward genetic algorithm (GA) optimization method in order to introduce fixturing regions and fixturing sequence, which minimize the workpiece deformation error in 3-2-1 locating approach. A new concept, namely “Fixturing Clearance (FC)” has been proposed in this study. FC is a criteria which evaluates fixturing layout. All layouts which lead to fewer machining errors than FC have the potential to be accepted in the final fixturing regions. Although GA method originally results in an individual optimum point, the proposed strategy in this study introduces continuous fixturing regions as well as the functional fixturing sequence. An integration between GA and finite element is used to optimize the elastic deformation of the workpiece under clamping and machining loads. The effectiveness of this method has been illustrated on a 2D case study.

Data-driven depth calibration for distributed acoustic sensing

Distributed acoustic sensing (DAS) can make use of an ordinary telecom fiber as a continuous array of acoustic sensors to acquire, for example, downhole seismic. One challenge when using DAS is assigning correct depth to a given part of the DAS data record. Usually, depth is assigned by linear interpolation between reference points in the record for which the depth is known. We present a case where this approach did not work satisfactorily due to a fiber accumulation of unknown length between the reference points in the top and bottom of the well. The data we discuss were acquired using Silixa's iDAS technology retrofitted to previously installed fiber-optic cables. During installation, the cables were clamped to the tubing at each coupling between tubing sections. We found a pattern in the iDAS data that could be related to the clamping points. The pattern is particularly clear for frequencies in the 100–200 Hz band and may be caused by eigenmode vibrations set up by the clamping points. Based on this observation, a method for data-driven depth calibration was developed by matching the observed pattern to the clamp positions known from the tubing-tally information. An algorithm was designed to do the optimization. With regularly spaced clamps, several solutions are output, and some knowledge of the approximate depth is needed to pick the appropriate one. Our data-driven depth calibration was successfully applied to iDAS data from six wells.

Optimization of Fixture Layout and Artificial Neural Network (ANN) Weights of ANN-Finite Element Analysis Based Fixture Layout Model Using Genetic Algorithm

Workpiece elastic deformation in machine manufacturing may cause dimensional errors, which in turn affects the accuracy of the machined parts. Fixturing elements like locators and clamps are used to locate a workpiece with respect to the cutting tool in a given orientation such that the errors caused by workpiece elastic deformation are reduced. The optimization of locator and clamp positions is crucial in minimizing the dimensional errors in machining. In this research paper, a slot milling operation on a rectangular workpiece is considered for which the fixture layout is optimized using a hybrid system of artificial neural network (ANN) and genetic algorithm (GA). The workpiece elastic deformation for different sets of fixture layouts is calculated using finite element method (FEM) and training of ANN is done with the FEM results to develop a numerical model. To enhance the accuracy of learning in lesser time, the weights are optimized for the network using GA before the training phase. The trained ANN recognizes a pattern between the position of fixturing elements and the workpiece elastic deformation. Using the recognized pattern, GA determines the optimal position of locators and clamps to minimize the workpiece elastic deformation and thereby the dimensional errors.

Automated modular fixture planning based on linkage mechanism theory

A new approach to automated modular fixture planning is presented. The approach identifies all the location plan candidates of a workpiece using linkage mechanism theory and excludes the infeasible location plan candidates by evaluating their accessibility and fixturability. The algorithms for analyzing accessibility and fixturability and generating feasible clamp positions of a fixture plan are developed based on several new concepts including IRC triangle, locator visible cone, etc. The approach is capable of handling the workpiece whose side clamping faces consist of planar faces or cylindrical faces. To illustrate the effect of the approach, some test results are described.

Domain:domain interactions within Hop, the Hsp70/Hsp90 organizing protein, are required for protein stability and structure

The major heat shock protein (Hsp) chaperones Hsp70 and Hsp90 both bind the co-chaperone Hop (Hsp70/Hsp90 organizing protein), which coordinates Hsp actions in folding protein substrates. Hop contains three tetratricopeptide repeat (TPR) domains that have binding sites for the conserved EEVD C termini of Hsp70 and Hsp90. Crystallographic studies have shown that EEVD interacts with positively charged amino acids in Hop TPR-binding pockets (called carboxylate clamps), and point mutations of these carboxylate clamp positions can disrupt Hsp binding. In this report, we use circular dichroism to assess the effects of point mutations and Hsp70/Hsp90 peptide binding on Hop conformation. Our results show that Hop global conformation is destabilized by single point mutations in carboxylate clamp positions at pH 5, while the structure of individual TPR domains is unaffected. Binding of peptides corresponding to the C termini of Hsp70 and Hsp90 alters the global conformation of wild-type Hop, whereas peptide binding does not alter conformation of individual TPR domains. These results provide biophysical evidence that Hop-binding pockets are directly involved with domain:domain interactions, both influencing Hop global conformation and Hsp binding, and contributing to proper coordination of Hsp70 and Hsp90 interactions with protein substrates.

Optimal Placement of Fixture Clamps: Minimizing the Maximum Clamping Forces

This paper addresses the problem of synthesizing robust optimal clamping schemes on three-dimensional parts with planar faces, with and without friction. Given a work part with a pre-defined deterministic 3-2-1 location scheme, a set of polygonal convex regions on its faces are defined as areas of admissible clamp positions. A known set of external disturbing wrenches is also given. The frictionless case is considered first, and a new linear program is formulated to provide clamp locations that minimize the maximum clamping force. A transformation of the solution is presented that permits the extraction of both, the optimal positions of the clamps and the magnitude of the corresponding maximum clamping force. Friction is introduced next, and a linear program is presented that minimizes the maximum normal clamping force. We also extend the earlier formulations to support the case of frictionless clamping contacts on cylindrical faces. The result is a nonlinear (but convex) optimization problem that can be easily solved. Finally, we discuss a linear algebraic technique to find the directions, and associated relative motion rates, along which the clamps can be moved while maintaining the clamping forces constant. These lines of constant clamping force, as we name them, identify an equivalence set of clamping schemes (such that the maximum clamping force, given a set of disturbing wrenches, stays invariant).

Comparison of ureteral and cervical descents during vaginal hysterectomy for uterine prolapse

Objective: The study measured ureteral and cervical locations during vaginal hysterectomy for prolapse and the extent of parametrial ligament shortening possible. Study Design: Cervical and ureteral position were measured in 26 women undergoing uterine prolapse correction. Parametrial clamp tip location was also measured. Results: The cervix lay between 0 and –14.5 cm (below) the hymen (mean ± SD –5.35 ± 3.96 cm) and the ureters lay +5.0 to –4.0 cm (mean ± SD +1.89 ± 1.99 cm). Correlation of ureteral with cervical position was 0.69 ( P < .01) and correlation with ipsilateral uterosacral ligament clamp positions was 0.80 ( P < .01). Regression line slope relating cervical descent and cervix to ureter distance was 0.65, indicating that for every 3 cm of cervical descent there was 2 cm widening of the gap between the cervix and ureters and 1 cm descent of the ureter. Conclusion: For every 3 cm of cervical descent the ureters descend 1 cm, thereby widening the ureterocervical gap and permitting ligament shortening during vaginal hysterectomy. (Am J Obstet Gynecol 1998;179:1405-10.)