Approach Angle Research Articles

Mechanistic Insights into Substrate Positioning That Distinguish Non-heme Fe(II)/α-Ketoglutarate-Dependent Halogenases and Hydroxylases

Non-heme iron halogenases and hydroxylases activate inert C–H bonds to selectively catalyze the functionalization of diverse biological products under physiological conditions. To better understand the differences in substrate positioning key to their divergent reactivities, we compiled available crystallographic and spectroscopic data, which revealed that hydroxylases prefer an acute oxo–Fe–H target angle while halogenases prefer a more obtuse angle. With molecular dynamics simulations guided by this experimental information, we simulated the representative hydroxylases TauD and VioC and the halogenases BesD and WelO5 with both acute and obtuse harmonic restraints. We identified key substrate interaction partners that maintain the angle of approach in the respective enzymes, such as Asp94 in TauD and His127 in BesD. Moreover, our simulations reveal that the protein environment in halogenases prevents the sampling of acute angles observed in hydroxylases and vice versa. To validate these classical observations, we optimized the structure with large-scale quantum mechanical (QM) simulations and confirmed that QM-derived substrate–enzyme hydrogen bond strengths were higher in the native configurations. We computed reaction barriers for the rate-limiting hydrogen atom transfer step and found them to be slightly lower from an acute angle regardless of the enzyme–substrate complex. Analysis of the halogenase reaction coordinate reveals the formation of hydrogen bonding networks between the Fe(III)-hydroxyl, monodentate succinate, and a member of the second coordination sphere that may inhibit the hydroxyl rebound.

Digital transport traseology based on Agisoft Metashape and unmanned aerial vehicle

Introduction. A vehicle and trace evidence analysis is one of the most requested types of examinations performed within the framework of criminal cases on road traffic accidents. The main methodical guidelines for traffic and trace evidence analyses were developed in the past century, while nowadays the fourth industrial revolution is on the rise. The industrial revolution is based on computer and information technologies, various software and hardware tools. Hence there is a vital necessity in update of the vehicle and trace evidence analysis methodology in order to conform to current-day realities.Materials and methods. Results of use of the unmanned aerial vehicle and Agisoft Metashape software are presented in the article in the context of specific road traffic accidents. It was made clear that application of this method has the following advantages: firstly, time of fixation of objects of the roadway network, vehicles and their traces on traffic ways is significantly reduced; secondly, fixation accuracy is improved; thirdly, use of the method makes it possible to establish all actual facts needed to perform analysis of the mechanism of a road traffic accident. Digital models obtained using this method could be used for 3D modeling, what offers an opportunity for more accurate determination of a mode and an angle of approach of vehicles before an accident with significant reduction of financial and time expenditures.Results. It was shown that digital models of road traffic accident sites and vehicles could be entered into the case file in general as well as into an expert’s statement in particular. Such entering will improve objectivity and believability of the conducted examination. Digital models of road traffic accident sites (digital twins) could be stored for an indefinitely long time and could contain the entire information on physical accident scene. Therefore such digital models are considered as valuable information while performing additional or repeated examinations.Conclusion. The proposed method for creating a digital model of a vehicle or a site of a traffic accident can be used in digital transport traceology.

Mandibular Fossa Approach to Petroclival and Anterior Pontine Lesions.

Objective To describe the anatomy related to a novel approach to the petroclival region through the mandibular fossa for the treatment of petroclival and anterior pontine lesions. Design Five dry skulls were examined for surgical approach. Three adult cadaveric heads underwent bilateral dissection. One cadaveric head was evaluated with computed tomography after dissection. Setting This study was performed in an academic medical center. Participants Neurosurgical anatomy researchers performed this study using dry skulls and cadaveric heads. Main Outcome Measurements This was a proof-of-concept anatomical study. Results The mandibular fossa approach uses a vertical preauricular incision above the facial nerve branches. Removal of the temporomandibular joint exposes the mandibular fossa. The anterior boundary is the mandibular nerve at the foramen ovale, and the posterior boundary is the jugular foramen. The chorda tympani, eustachian tube, and tensor tympani muscle are sectioned. The carotid artery is transposed out of the petrous canal, and a petrosectomy is performed from Meckel's cave to the foramen magnum and anterior occipital condyle. Dural opening exposes the anterior pons, vertebrobasilar junction, bilateral vertebral arteries, and the ipsilateral anterior and posterior inferior cerebellar arteries. At completion, the temporomandibular joint is reconstructed with a prosthetic joint utilizing a second incision along the mandible. Conclusions The mandibular fossa approach is a new trajectory to the petroclival region and the anterior pons. It combines the more anterior angle of endoscopic approaches along with the enhanced control of open approaches. Further study is necessary before this approach is used clinically.

ILIF ASSISTIDA POR ENDOSCOPIA POR VIA TRANSILÍACA: ESTUDO EM CADÁVER

ABSTRACT Objective: Demonstrate the feasibility of endoscopic assisted L5S1 intraforaminal lumbar interbody fusion (iLIF) through a transiliac approach. Methods: Ten transiliac iLIF and ten supra iliac iLIF were performed bilaterally at L5S1 in five randomly selected fresh-frozen human cadavers. The following measurements were recorded: distances from the transiliac track to the iliac crest, posterior superior iliac spine, and superior gluteal neurovascular bundle; pelvic parameters; approach angles; cage’s lateral and AP center point ratio (CPR); percentage of the cage crossing the midline in the AP and lateral views. Endplate integrity was assessed through endoscopic visualization. In addition, the facet joint, sacroiliac joint, iliolumbar ligament, and exiting and traversing nerve roots were checked for integrity through anatomic dissection. Results: In the transiliac technique, the axial and coronal approach angles were significantly decreased by 13.5º (95% CI -15.5; -11.5; p value<0.001) and 13.2º (95% CI -15.3; -11.1; p value<0.001), respectively, the sagittal approach angle was significantly increased by 5.4º (95% CI 1.8,8.9; p-value = 0.008), and the AP CPR was significantly higher (MD 0.16; 95% CI 0.12,0.20; p value<0.001). The percentage of the cage crossing the AP view’s midline was increased by 31.6% (95% CI 19.8,43.4; p value<0.001). The integrity of endplates, facet joints, sacroiliac joints, iliolumbar ligament, and exiting and traversing nerve roots was maintained. Conclusion: L5S1 transiliac iLIF is a feasible surgical technique. It allows a more centrally placed interbody cage in the coronal plane without compromising the anterior position in the lateral plane. The integrity of the major anatomic structures at risk was preserved. Evidence Level III: A case-control study.

ТОПЫРАҚТЫҢ БЕТКІ ҚАБАТЫН ӨҢДЕУГЕ АРНАЛҒАН БЕЛСЕНДІ ЖЕТЕКГІ БАРАЙНАЛМАЛЫ ЖҰМЫСШЫ БӨЛІКПЕН ҚАРЫҚША ҚАЛЫПТАСУЫН ЗЕРТТЕУ

For the surface tillage, it is common to utilize machines and tools, and their tillage implements are set in motion through contact with the soil and by the tractor's PTO. The furrow produced by the rotating tillage implements is characterized by an uneven bottom that matches the furrow length and aligns with the direction of the movement of the machine-tractor aggregates. However, an analysis of research suggests that this scenario does not fully capture the process of furrow formation by the cutting blade of the concerned tillage implement powered by the tractor's PTO. For the reasons outlined above, determining the tillage implement parameters to achieve the desired quality of surface soil tillage is quite challenging. This article, therefore, delves into the process of furrow formation using the power driven tillage implement.The objective of this study is to develop a methodology for determining the parameters of the furrow formed by the power driven tillage implement’s cutting blade. Experiments were conducted in a soil box filled with sandy soil, considering approach angles ranging from 30 to 90° and kinematic parameters varying between 0.8 and 2.2. The findings reveal that the cutting blade of the rotating implement, designed in an elliptical fashion, generates a furrow that takes on a parallelogram shape when seen from above. At a small approach angle, the implement's cutting blade produces a short, narrow furrow that deviates from the implement's path and remains within the implement's working width.

Hexagonal disc working bodies for working soils subject to wind erosion

Necessary quality of soil cultivation is not always achieved by disk plough-harrows. To solve this problem the improved working unit - flat hexagonal disk was proposed. The aim of the investigation was to determine the dependence of the functional efficiency of the soil tilling implement with flat hexagonal working bodies on its mechanical and technological parameters. The technological process of interaction of the flat hexagonal disk working unit with soil and plant residues was a subject of investigation. To assess the quality of the tillage depending on the approach angle (θ = 15, 25, 35°), machine speed (V = 6, 8, 10 km/h) and processing depth (h = 60, 80, 100 cm) the laboratory tests in the soil channel and field researches at Siberian zonal machine-testing station were carried out. On the surface of the soil channel the stubble cover with weeds was simulated. The ratio of stubble conservation in the soil after the experiment to the weight of stubble used for imitation of the stubble cover served as a criterion of evaluation of the safety of stubble on the surface of the field. The relation of a difference in the weight of mulch, scattered over the soil surface before the test, and that, gathered after the passage of the machine, to the initial weight of mulch was used as a criterion of embedding of vegetative mass in soil. The prototypes of flat hexagonal disc carried out quality tillage with ridgeness no more than 4 cm, the stubble conservation 86…94 %, the chopped straw mass integrity 60 %. Reduction in the presence in soil of erosion-dangerous particles to 1 % allows using flat hexagonal discs in areas exposed to wind erosion

Utilization of pre-hospital emergency medical services: Secondary data analysis of health insurance data from Saxony-Anhalt

Utilization of emergency care is subject to demographic changes. In Germany, there was an increase of 4% to 6% annually between the years 2000 and 2017. Studies revealed that age and regional structures were related to utilization. The aim of this cross-sectional study was to analyze utilization of pre-hospital emergency medical services in Saxony-Anhalt and to identify associated factors. Based on data from the AOK Saxony-Anhalt for 2019, transportation with ground ambulances of insured persons living in Saxony-Anhalt were identified and recorded. Insured time of all AOK insured persons living in Saxony-Anhalt was used to determine incidence rates. For the multivariate analysis of associated factors, a Poisson regression model was adapted. 112,575 transportations of patients were identified; an average of 1.53 events per person or 149.6 per 1,000 person years. Inpatient hospital treatment was provided for 53.2% of emergency patients and outpatient hospital treatment for 37.1%. Frequent users represented 14.6% of the events. The incidence rate was highest for older persons and those with care dependency. In addition, the risk of using emergency services was higher among men and in suburban and urban regions (compared with rural regions), even after adjustment. Utilization is higher in the cohort studied compared to that found in other studies. The high proportion where inpatient hospital treatment is not necessary, as well as the clear association with care dependency and age, offer possible angles of approach for interventions to relieve the burden on emergency services.

Vortex induced vibration for mixed convective flow past a square cylinder

In this work, a comprehensive numerical investigation of the combined effect of buoyancy and flow approach angle (α) on vortex-induced vibration of an elastically mounted square cylinder at a fixed Reynolds number, Re = 100, Prandtl number (Pr = 7.1) and mass ratio (Mred) of 2 is conducted. Extensive numerical experiments were carried out for different flow approach angles (α = 0°-90°) and for various reduced velocities (Ured = 3–25) at Richardson number, Ri = 0, 0.25 and 0.50. The Arbitrary Lagrangian-Euler (ALE) approach models the solid-fluid interaction. The coupled fluid-structure interaction problem in two-degree-of-freedom (2-DOF) was solved using a high-fidelity finite difference-based solver. The Lock-in regime was found to be fixed, between Ured = 5 and 6, for all flow approach angles irrespective of Ri. For all flows other than transverse flow, the reduced frequency is found to be equal in both directions (fx=fy) but in the transverse situation, (α=90°), reduced frequency in the x-direction is twice that of the y-direction for all reduced velocities (Ured). Different vortex shedding modes 2S, 2S*, P + S and 2P are also observed in the study. The average coefficient of drag (C¯D) and Nusselt number (N¯u) was found to peak at α = 45° for all Ured. It was also found that as α is increased, C¯DandN¯u increases due to larger heated surface area exposure to the fluid particles. When Ri increases, C¯DandN¯u increases at a α due to the higher heat transfer rate. Highest value of N¯u is observed for Ured = 6, α = 45° at Ri = 0.5.

Effect of joints on microwave fracturing of the Bukit Timah granite using an open‐ended antenna

AbstractMicrowave fracturing of rocks before mechanical breakage could improve the performance of mechanical excavators and reduce environmental impacts. Previous research focused on the microwave fracturing of intact rock blocks. By using an open‐ended antenna, this paper investigates the effect of pre‐existing joints on the microwave fracturing of the Singapore Bukit Timah granite blocks. The results show that the specimens are weakened in the manners of cracking, spalling, melting, or a combination of them. The crack number and the total crack length produced by microwave treatment of jointed rock blocks are slightly smaller than those in the intact rock blocks. The interaction between joints and microwave‐induced cracks can be summarized into the following four patterns: (1) microwave‐induced cracks become arrested so that the crack propagation is terminated; (2) microwave‐induced cracks penetrate the joints and continue to propagate; (3) microwave‐induced cracks become deflected along the joints; and (4) microwave‐induced cracks propagate forward following the joints. The smaller the approach angle between the microwave‐induced crack and the pre‐existing joint is, the more microwave‐induced cracks tend to be arrested at the joint. Increasing the approach angle between the microwave‐induced crack and the joint can increase the chance of microwave‐induced crack penetrating the joint. The results also show that the smaller the distance is between the microwave radiation point and the joint, the easier it is for microwave‐induced cracks to penetrate the joints; otherwise, the microwave‐induced crack is more likely to be arrested at the pre‐existing joint.

Determination of the Entry Point for Lower Lumbar Intradiscal Procedure Using Transforaminal Technique: Cross-Sectional Study Using Magnetic Resonance Imaging.

Triangular working area otherwise known as the Kambin triangle is designated as a safe place to position the instrument during the operation, with minimal risk to exiting nerves. This study aims to improve understanding and increase the safety of various transforaminal intradiscal procedures at L3/L4, L4/L5, and L5/S1 levels. A cross-sectional analysis involving 102 MRIs that met the inclusion criteria was obtained and analyzed at the L3/L4, L4/L5, and L5/S1 discs level. For each level, the Kambin triangle was measured. By evaluating those measurements, the viability of this method was determined. Safe working zone approach angles were consistently getting wider from L3 to S1 levels. It was statistically significant to be wider for the left side for the mean angle of lateral nucleus trajectory at the L4/L5 level and L5/S1. The entry point is at 32, 45, and 55-60 mm from the midline, and the instrument should be directed at 12°, 20°, and 27° medially for the lateral nucleus at L3/L4, L4/L5, and L5/S1, respectively. The center of the nucleus pulposus entry point is at 64, 77, and 85 mm from the midline with a medial inclination of 40°, 47°, and 52°, respectively, for L3/L4, L4/L5, and L5/S1. For the posterior nucleus pulposus, the skin should be pierced 90, 140, and 180 mm from the midline and directed medially at 53°, 61°, and 68°, respectively, for L3/L4, L4/L5, and L5/S1. The posterior annulus fibrosis entry point is 172, 355, and 450 mm with a medial inclination of 69°, 80°, and 84° at L3/L4, L4/L5, and L5/S1, respectively. The sagittal inclination is 3° cephalad at L3/L4, 10° caudally at L4/L5, and 27° caudally at L5/S1. Preoperative MRI assessment is important to determine the angle of trajectory for the safe entry point for intradiscal procedure via transforaminal approach.

Dispositif thérapeutique et de recherche en psychodrame

ObjectivesThis article is part of a general reflection on psychoanalytical psychodrama, and of a dynamic evaluation of its effects and psychotherapeutic processes, and builds upon what has already been written on the subject. The angle of approach adopted here concerns the contents and the articulation between, on the one hand, the sessions themselves and, on the other hand, the team's reflection on the clinical material outside of the sessions themselves. MethodThe methodology adopted is based on a contemporary and global description of the major stakes of the technique, differentiating its analytical framework from its different variations in terms of setting (according to the institution or the patients received), in order to facilitate the understanding and the grasp of its effects for the reader. Based on an updated literature review and taking into account current research on evaluation and practices, we rely on several key concepts, such as the work of co-construction, group elaboration of transferential issues, the deployment of symbolization processes, and transitional play itself. ResultsIt appears that the work of co-construction during the session, between the therapists and the patient(s), and the work undertaken in intervision and supervision outside of the sessions, are part of an interactive dialectic, functioning in a loop, reciprocally interlocking, and producing effects of potentially therapeutic changes for our patients. These effects are visible and observable both in the content of the psychodrama and the exchanges with the patients, and in the exchanges with the patients and their families, both in and out of the sessions. DiscussionThe investment of the setting by the therapists solicits them during and outside the session, individually and as a group, leading them to engage in a complex, multidimensional work, taking various but complementary forms. Analyzing what is played out, consciously and unconsciously, during these different times and spaces, allows us to promote the understanding of their links, and, moreover, to support these processes of co-construction of psychic life and symbolization processes. Thus, by putting the co-therapists to work – psychoanalytically speaking – regarding their positioning, experiences and elaborations, the practice of psychodrama also has a didactic and formative aim. ConclusionsThe proposals put forward in the article allow for a better understanding of the therapeutic processes that psychoanalytic psychodrama supports, by showing how the group work engaged in by the therapists is indeed carried out on several levels and in several spaces, making the usual understanding of these issues more complex. They invite us to pursue research concerning this type of therapy, highlighting both the group issues and the place afforded to play. We promote the use of psychodrama in our psychiatric and medico-social institutions that serve complex patients, for whom the more classic treatments are not always indicated nor efficient in treating difficult symptomatology, and who often refuse elaboration, or even exchange.

The influence of multi-metal-veins on fractures propagation investigated by the experiment and simulation

Fracture propagation is affected by multi-metal-veins formed by geological diagenesis in shale during the hydraulic fracturing. However, the influence of multi-metal-veins on fractures propagation remains unclear. To solve the problem, based on the semi-circle bending (SCB) test and the extended finite element (XFEM) theory, the interaction between multi-metal-veins and fractures is investigated. The experimental results reveal that the fractures usually deflect at the upper or lower interfaces between metal veins and rocks (e.g. the specimen S-2), which is different from the propagation behavior of fractures in calcite veins. Meanwhile, the fracture toughness of the specimen S-1 is 24.40% higher than that of the specimen S-2, indicating that the increasing of total thickness of multiple metal veins increases the resistance to the fracture vertical propagation. The simulation results show that the increasing of the number, total thickness of veins, the modulus difference between veins and rock, the approach angle and the notch angle all increase the resistance of the fracture passing through metal veins. The maximum deviation distance (Dmax) of the fracture decreases with the number of veins, while thickness combination types of metal veins do not affect Dmax. The reduction of the notch angle leads to the more tortuous fracture propagation path. Finally, we propose a new comprehensive fracture network pattern. Fracture networks are divided into two categories, including orthogonal fracture networks and sub-orthogonal fracture networks, and then divided into six sub-categories further. The research results will provide reference for hydraulic fracturing of shale reservoirs containing multi-metal-veins.

Three-Dimensional Approach Angle Guidance Under Varying Velocity and Field-of-View Limit Without Using Line-of-Sight Rate

In this article, a practical three-dimensional (3-D) guidance is designed to achieve trajectory constrained flight, i.e., arriving at the destination with desired approach angles under limited field-of-view (FOV) and varying velocity. For this goal, the nonlinear engagement model is first transformed to a set of new differential equations in terms of the line-of-sight (LOS) angles. Then, the approach angle constraints are handled by constructing two reference range profiles as cubic polynomials of LOS angles. By solving the unknown coefficients involved in the polynomials, a semianalytical 3-D guidance solution is derived from the second-order range dynamics. To meet the FOV limit and avoid the initial guidance saturation, the achievable approach angle set is determined for capturability analysis by introducing the look angle dynamics with respect to the range profiles. The technique does not involve the model linearization, guidance switching logic, constant velocity assumption, and LOS rate information. Notably, only the LOS angle measurement is required during the guidance process once the initial conditions are provided, which makes it preferable for vehicles equipped with passive angles-only sensors. Extensive numerical simulations and Monte Carlo test are conducted to validate effectiveness and robustness of the proposed technique.

Percutaneous biopsy of musculoskeletal tumors and the potential for needle tract seeding: technical considerations, current controversies, and outcomes.

Multidisciplinary communication and planning between the musculoskeletal radiologist and orthopedic oncologist are essential for proper biopsy planning when a primary musculoskeletal malignancy is suspected. Image-guided percutaneous biopsy allows for real-time visualization of the biopsy needle and surrounding structures, combining high diagnostic accuracy with safety and cost-effectiveness. However, determining a surgically optimal biopsy trajectory for a mass can be technically challenging due to critical surrounding anatomy or challenging needle approach angles. Inappropriately placed biopsies can have serious repercussions on patient function and oncological survival. The potential for needle tract seeding and local recurrence after biopsy of sarcoma has been central to the debate regarding the need for excision of the biopsy tract. This multidisciplinary review highlights current controversies in the field, including the issue of core needle biopsy tracts and their excision, technical considerations and advances in image-guidance in the setting of challenging biopsies, advances in histopathological diagnostics with implications for targeted therapy in sarcoma, as well as surgical and oncological outcomes after needle tract biopsy.

The Sironix ACL Jig: A Solution for Tibial Tunnel Angle and Length

Anterior cruciate ligament (ACL) reconstruction is widely performed arthroscopic procedures amongst sportspersons to prevent worsening of knee joint injury. The Sironix ACL jig is a novel approach to ensure an appropriate angle for accurate placement and drilling of tibial and femoral tunnels, that is a critical step for stronger and stable ACL graft fixation. It is designed as a patented jig with a three-point arm contact system. The three reference points serve as a continuous visual feedback on the angle of approach during surgery and minimize the parallax errors. Sironix ACL jig helps the orthopaedic surgeon in deciding the feasibility of a single bundle or double bundle ACL technique, facilitates varying technique choices for drilling, including inside-out and outside-in, accurately determines the tibial and femoral tunnel positioning in arthroscopic or open ACL reconstruction and therefore increases the procedural convenience.

Morphometric comparison of Fisch type A and endoscopic endonasal far-medial supracondylar approaches to the jugular foramen.

The jugular foramen (JF) is one of the most complex and challenging skull base regions to approach surgically. The extreme medial approach to access the JF provides the approach angle from an anterior direction and does not require dissection and sacrifice of the jugular bulb (JB) to reach the pars nervosa. The authors compared the Fisch type A approach to the extreme medial approach to access the JF and evaluated the usefulness of the extreme medial approach. This study was performed at the Anatomical Laboratory for Visuospatial Innovations in Otolaryngology and Neurosurgery of The Ohio State University. For the comparison of surgical maneuverability and visualization, two angles were measured: 1) the angle of attack (AoA), defined as the widest angle of movement achieved with a straight dissector; and 2) the angle of endoscopic exposure (AoEE), defined as the widest angle of movement in the nasal cavity. The differences in eustachian tube (ET) management, approach angle, surgical maneuverability, and surgical application of the Fisch type A approach to the extreme medial approach were compared. There was no difference between ET mobilization and transection regarding cranial-caudal (CC) or medial-lateral (ML) AoA (p = 0.646). The CC-AoA of the Fisch type A approach was significantly wider than the CC-AoA of the extreme medial approach (p = 0.001), and the CC-AoEE was significantly wider than the CC-AoA of the extreme medial approach (p < 0.001). There was no significant difference between the CC-AoA of the Fisch type A approach and the CC-AoEE. The ML-AoA of the Fisch type A approach was significantly wider than the ML-AoA of the extreme medial approach (p = 0.033), and the ML-AoEE was significantly wider than ML-AoA in the extreme medial approach (p < 0.001). The ML-AoEE was significantly wider than the ML-AoA in the Fisch type A approach (p = 0.033). The surgical maneuverability of the extreme medial approach was not inferior to that of the Fisch type A approach. The extreme medial approach can provide excellent surgical field visualization, while preserving the JB. Select cases of chordomas, chondrosarcomas, and JF schwannomas should be considered for an extreme medial approach. These two approaches are complementary, and a case-by-case detailed analysis should be conducted to decide the best approach.

The structural groups approach and transmission angles limits

Present work makes a synthesis of a papers cycle in which it were shown a new approach to appreciate forces transmission in mechanisms and so, we performed the structural groups procedure. This approach makes forces transmission analysis for each structural group, not for the mechanism taken as a whole. This point of view enables approach of every mechanism used into practice, as we have shown in third section. Besides this, the proposed procedure clarifies some problems, like those regarding mechanisms containing RTR structural group.

Morphologically Adaptive Crash Landing on a Wall: Soft‐Bodied Models of Gliding Geckos with Varying Material Stiffnesses

Bioinspired Robots In article number 2200120, Ardian Jusufi and co-workers present a bio-inspired soft robotic lander inspired from geckos perching on trees. Hard landings are demonstrated for a range of approach angles and speeds, making the soft bodied lander robust to external perturbations resembling those experienced in real-world conditions. The bio-inspired passive perching mechanism can simplify the design and computational effort required to perform rapid landings on walls. Art work: Ella Maru Studio.

Numerical simulation on proppant migration and placement within the rough and complex fractures

Hydraulic fracturing is a key technology for the development of unconventional hydrocarbon resources. The proppant placement morphology determines the fracture conductivity, thus affecting the reservoir stimulation effect. In this paper, the proppant migration and placement within complex fractures was studied by considering the fracture wall roughness through computational fluid mechanics-discrete element method (CFD-DEM) in numerical simulation, which is a key approach to study the proppant migration and placement. The results show that the proppant placement non-uniformity, proppant migration capacity, and proppant volume filled in the far-end and the secondary branched fracture are enhanced within the rough fracture compared with those within smooth fractures. The proppant migration capacity is increased within the fracture at low inclination angles (<60°) and low approach angles (<90°), and the proppant placement area is larger in the inclined fracture than that in the vertical fracture. The rise of injection rate and fracturing fluid viscosity causes more proppants migrate to far-end or secondary fractures, resulting in a non-proppant area within the near-wellbore fracture. An increase by 1.3 times in the injection rate and 3 times in the fracturing fluid viscosity leads to a decrease by 26.6% and 27%, respectively, in the proppant placement area within the near-wellbore fracture. The staged injection with small size proppants followed by large size proppants increases the proppant placement area in the primary fracture by 13%–26%, and that with large size proppants followed by small size proppants increases the proppant placement area by 19%–25%, which is due to that the latter method facilitates filling of the secondary branched fracture. The injection location mainly affects the proppant filling degree within the near-wellbore fractures. Compared with the upper injection, the middle and lower injection is not beneficial to filling of proppants within the near-wellbore fracture.

Modelling surface roughness in finish turning as a function of cutting tool geometry using the response surface method, Gaussian process regression and decision tree regression

In this study, the modelling of arithmetical mean roughness after turning of C45 steel was performed. Four parameters of cutting tool geometry were varied, i.e.: corner radius r, approach angle κ, rake angle γ and inclination angle λ. After turning, the arithmetical mean roughness Ra was measured. The obtained values of Ra ranged from 0.13 μm to 4.39 μm. The results of the experiments showed that surface roughness improves with increasing corner radius, increasing approach angle, increasing rake angle, and decreasing inclination angle. Based on the experimental results, models were developed to predict the distribution of the arithmetical mean roughness using the response surface method (RSM), Gaussian process regression with two kernel functions, the sequential exponential function (GPR-SE) and Mattern (GPR-Mat), and decision tree regression (DTR). The maximum percentage errors of the developed models were 3.898 %, 1.192 %, 1.364 %, and 0.960 % for DTR, GPR-SE, GPR-Mat, and RSM, respectively. In the worst case, the maximum absolute errors were 0.106 μm, 0.017 μm, 0.019 μm, and 0.011 μm for DTR, GPR-SE, GPR-Mat, and RSM, respectively. The results and the obtained errors show that the developed models can be successfully used for surface roughness prediction.