Lower Peak Force Research Articles

A comparative study on trocar configurations and the use of steerable instruments in totally extraperitoneal inguinal hernia surgery training.

Totally extraperitoneal (TEP) inguinal hernia surgery is a commonly performed but technically challenging procedure with a long learning curve. As TEP can be executed using two different trocar placements: a midline or a triangular configuration, the question remains which one is technically easier to master. In a multicenter crossover-study, medical students were randomised into two groups and executed tasks on a box trainer that measured time, volume and force parameters. Additionally, the study assessed whether the SATA instrument, a steerable laparoscopic instrument that articulates the instrument's tip, would reduce the difficulty of performing the tasks in the midline configuration. After training, all participants executed a first experiment using both trocar configurations, followed by a second experiment executed with steerable and non-steerable instruments in the midline configuration. Subjective and objective performances per condition and learning curves were assessed. Participants were faster and showed lower peak forces in the triangulated configuration. Learning curve analysis showed a positive improvement in time and path length in the midline configuration. Although participants rated ergonomics and intuitiveness similarly between the instruments, they found the task easier with the SATA instruments, ranking the added value of the steering function as 5 out of 5. Objectively, time and path length showed no significant differences while exerted forces were lower when using conventional instruments. Although the midline configuration is preferred in terms of comfort and posture, the findings indicate that, for inexperienced practitioners, performing TEP surgery in midline configuration is both subjectively and objectively more challenging, highlighting the need for extensive training to overcome its difficulties and possibly shorten its learning curve. Although instruments with additional steering functions were preferred over conventional instruments in the more challenging midline configuration, additional steering complexity did not result in better parameter outcomes, showing the need for more extensive training.

A study of energy absorption properties of Heteromorphic TPMS and Multi-morphology TPMS under quasi-static compression

TPMS (Triply periodic minimal surface) has attracted significant attention recently because of its superior energy-absorbing properties. To improve its energy-absorbing performance and designability, a heteromorphic structure for TPMS is proposed. This structure is formed by the fusion of two kinds of TPMS and inherits the structural characteristics of both TPMS. We systematically investigate Heteromorphic TPMS and Multi-morphology TPMS using quasi-static compression tests and finite element simulations. The results showed that the Heteromorphic TPMS with Gyroid and Primitive fusion structure, which inherits the advantageous parts of Gyroid and Primitive, possesses a lower Peak Force. For instance, the SEA (Specific Energy Absorption) value increases by 24.4 %, and the CFE (Crush Force Efficiency) increases by 68.5 %. Heteromorphic TPMS with Gyroid and Diamond fusion can bring more flexible designability. Research on Multi-morphology TPMS showed that compared with a single structure, its energy absorption performance was better, and all structures had greatly improved CFE, making them more secure in practical applications. For Multi-morphology TPMS, the MulD&G (A structure that superimposes Diamond and Gyroid) has the highest energy absorption performance, with 76.3 % improvement in CFE compared to the single structure, and the formation of gradient energy absorption in Multi-morphology TPMS depends on the preferential deformation of the inferior structure.

β-Grain refinement in WAAM Ti-6Al-4 V processed with inter-pass ultrasonic impact peening

As-deposited Wire-Arc Additive Manufactured (WAAM) Ti-6Al-4V parts typically contain large columnar β-grains on a centimetre scale, with a strong 〈001〉 fibre texture, leading to anisotropic mechanical properties and unacceptable scatter in damage tolerance. Inter-pass deformation, introduced by the application of Ultrasonic Impact Peening (UIP) across each added layer, has been shown to be effective in refining the β-grain structure and achieving a weaker texture. The depth of deformation and the grain refinement mechanism induced by UIP have been investigated by combining advanced electron backscatter diffraction (EBSD) characterization with a ‘stop action’ observation technique. UIP facilitates a similar refinement mechanism and nearly the same depth of deformation as conventional machine hammer peening, with the advantages of a much higher strain rate, lower peak force, and two orders of magnitude lower impact energy, making it a faster and more economical process. β recrystallization is seen within the deformation zone during re-heating through the α → β transition. Although new recrystallized β-grains formed in the UIP surface-deformed layer to a shallower depth than that of remelting, recrystallization initiated ahead of the melt pool and the recrystallized grains grew downwards to a greater depth before remelting. These refined grains were thus able to survive and act as nucleation sites at the fusion boundary for epitaxial regrowth during solidification, greatly refining the grain structure.

Curved-crease origami hybrid structures with tailorable buckling and energy absorption

Origami-inspired structures (OIS), renowned for their lightweight design, encounter energy absorption challenges attributed to global buckling. This paper presents a design and hybridization strategy that integrates origami-inspired structures with existing state-of-the-art cellular lattices to create origami-inspired hybrid structures (OIHS), aimed at addressing buckling concerns and customizing the crushing behavior of thin-walled structures. The investigation explores the compressive response of additively-manufactured curved crease OIS and prismatic structures (PS) with diverse cross-sections, including circular origami structure (COS), triangular origami structure (TOS), square origami structure (SOS), and hexagon origami structure (HOS). The experimental results indicate that the COS design offered the highest specific energy absorption (SEA) of 11 kJ/kg, due to controlled deformation associated with the crease lines. The COS hybridized structure, with cellular lattices, exhibited a yielding-dominated behavior, resulting in a lower peak force, a sustained plateau force and a well-controlled deformation response. Furthermore, the COS hybridized with a plate lattice, exceeded the SEA of the auxetic and BCC OIHS structures by 62 % and 71 %, respectively. The circular origami plate hybrid (COPH) design was selected to investigate the effect of varying the top edge angle (α) and the relative density on the mechanical properties and the SEA. It was found that increasing the value of alpha resulted in a higher peak stress and an increased buckling load. Moreover, with its higher relative density, the vertical plate within the OIS contributed to a greater level of structural stability in the plateau region, resulting in an increase in mechanical properties and SEA. These findings advance the understanding of OIS by presenting effective hybridization strategies to mitigate buckling and achieve stable plateau stresses and higher crushing force efficiencies, particularly at lower relative densities, surpassing those reported in the literature. This contributes significantly to the broader field of lightweight structural design.

Crashworthiness design for novel polygonal asymmetric origami tubes

Origami tubes have attracted widespread attention because it is inclined to deform in the complete diamond mode (DM) with a low initial peak force Fmax and high average crushing force Fave. Although conventional origami tubes can improve crashworthiness, there are still many areas that fail to generate traveling plastic hinge lines, and the crashworthiness can be further improved. This paper presents a novel polygonal asymmetric origami tube (PAT) with origami patterns that can trigger more traveling plastic hinge lines compared to those of conventional origami patterns. The theoretical analysis of the deformation mechanism suggests that the PAT can realize hierarchical deformation and avoid stress concentration at sharp corners. The quasi-static experiments and numerical simulations reveal that the novel origami pattern can successfully trigger up to four times more traveling plastic hinge lines than the conventional square box (CSB) under the premise that each plastic hinge line is similar in length. Compared with the CSB, the PAT can deform in DM with a 56.0 % reduction of Fmax and a 59.1 % increase of Fave. Notably, the stableness of load-carrying capacity SLC is 90.2 %, which is 260.8 % higher than the CSB. A series of parametric studies reveal that the dihedral angle ratio α / β and the width-to-thickness ratio c / t of the PAT have a significant effect on crashworthiness. A smaller ratio of α / β and c / t provides the PAT with superior crashworthiness. Comparing the PAT with other types of origami tubes and multi-cell tubes indicates that the PAT also exhibits outstanding crashworthiness. The impact experiments also unveil a significantly enhanced crashworthiness of the PAT. Compared with the CSB, the Fmax decreases by approximately 46.4 %, while the Fave increases by around 92.7 %. The SLC and SEA values for the PAT surpass those of the CSB by about 260.8 % and 93.1 %, respectively. Furthermore, the theoretical analysis for predicting the Fave of the PAT is developed, with a maximum error not exceeding 8.5 %.

Nature-inspired 3D printing-based double-graded aerospace negative Poisson’s ratio metastructure: Design, Fabrication, Investigation, optimization

The advanced metamaterials concept has been widely explored and utilized in many industries, ranging from automotive applications to medicine, and has great potential in the aerospace field. Novel nature-inspired 3D printed double-graded aluminum foam-filled negative Poisson’s ratio metamaterials (DGAT) were designed, fabricated, and investigated. Their mechanical properties were examined by the finite element method and experiments. The geometrical parameters and combination types show different effects on the mechanical properties of DGAT metastructures. Under axial compressive loading, the DGAT structure has a lower peak force and higher specific energy absorption. Then, parametric analysis shows that several design parameters (e.g. m, T, θ, tmin, tmax) have a very strong effects on the mechanical performance. Finally, multi-objective optimization is performed to maximize specific energy absorption while reducing maximum impact force. Optimization results show that the novel graded metamaterials have stronger energy absorption capacity than the ordinary counterparts. Especially, the specific energy absorption can be increased to 80% with 15% peak loading force rising. Due to their unique structural design and excellent mechanical properties, the DGAT metastructures have great potential applications in the fields of transportation protection, military protection engineering, manned spacecraft cushioning and energy-absorbing boxes.

Experimental and numerical investigations on impact response of reinforced concrete beams with a sandwich panel protective layer

This paper investigates the response of reinforced concrete beams protected by an aluminium foam sandwich panel under impact loadings. A series of impact tests were conducted on one reinforced concrete beam and five beams with a protective layer, focusing on their dynamic responses and failure patterns. Test parameters included the type of protective layers (unprotected, aluminium foam and sandwich panel) and impact energy. Test results showed that the aluminium foam and sandwich panel could effectively protect the reinforced concrete beam from severe damage under impact loadings and converted the failure pattern of beams from shear failure to flexure-shear failure. Compared with the unprotected beam, the beams with a protective layer exhibited a lower peak force and developed a smaller mid-span deformation. Besides, the protective effects of the aluminium foam and sandwich panel were found to be nearly the same. Moreover, the peak force, plateau force and deformation of the beams were increased with the increasing impact energy. A numerical model was developed to investigate the energy distribution of beams with a sandwich panel protective layer. Based on the validated model, the effects of longitudinal reinforcement ratio and shear-span ratio on the impact response of beams were further studied. It was found that the deformation of beams increased significantly with the increasing shear-span ratio, whereas an increase in the longitudinal reinforcement ratio led to a decreased deformation. This study provides an important reference for designing reinforced concrete beams with a sandwich panel protective layer to resist impact loads.

Dynamic response of rock sheds to successive rockfall impacts using lightweight expanded clay aggregate (LECA) cushions: An experimental and numerical study

This study investigates the effectiveness of Lightweight Expanded Clay Aggregate (LECA) as a novel cushion material mitigating repeated rockfall impacts on reinforced concrete (RC) slabs in rock sheds. Small-scale impact tests and finite element simulations analyze LECA particle size, cushioning material, block shape, and impact energy level influence on the dynamic response and damage. Results show LECA outperforms sand in attenuating impact forces and transmitted loads under successive impacts, which indicates a better protection effect on the substructure. Smaller LECA particles lead to wider stress distribution angles, longer impact durations, and lower peak forces. Block shape significantly influences impact force, with higher unified nose factors increasing forces. LECA cushions exhibit a dynamic amplification factor less than 1, indicating reduced transmitted loads compared to sand. Under high-impact energy conditions, the LECA cushion limits RC slab deflection within the elastic limit across all block shapes, while sand exceeds the elastic limit, potentially leading to structural failure. LECA mitigates flexural cracking and redistributes loads more uniformly, reducing overall RC slab damage compared to sand. However, localized failure modes require further optimization. This study highlights LECA's potential for enhancing rock shed structural safety and resilience against severe rockfall events, providing insights for optimal mitigation strategies.

Optimizing isometric midthigh pull testing protocols: impact on peak force and rate of force development and their association with jump performance.

Isometric strength testing is widely applied in sports science. However, we hypothesized that traditional testing procedures with a dual focus on both peak force (PF) and rate of force development (RFD) may compromise the true assessment of early RFD measures and lower the associative value towards vertical jump performance. Therefore, PF and RFD were assessed for 47 active participants (24 females, 23 males) with a traditional isometric midthigh pull (IMTP) protocol ("push as hard and fast as possible" over 4 s) and an RFD-specific protocol ("push as fast as possible" over 2 s). IMTP measures were compared to squat (SJ), countermovement (CMJ) and drop-jump (DJ) performance. The RFD-specific protocol provided higher RFD (P<0.05) for time domains up to 100 ms but lower PF (P<0.001). Independent of protocol, SJ and CMJ performance displayed significant, but low-to-moderate correlations with all RFD measures (r=0.30-0.52) as well as PF (r=0.44), whereas DJ did not show any correlation. In conclusion, an RFD-specific protocol appears relevant for the assessment of RFD in the time domain up to 100 ms. However, the observed associations between RFD/PF measures and vertical jump performance remained low-to-moderate independent of the IMTP test protocol.

Comparison of Force Distribution during Laryngoscopy with the C-MAC D-BLADE and Macintosh-Style Blades: A Randomised Controlled Clinical Trial.

Background: The geometry of a laryngoscope's blade determines the forces acting on the pharyngeal structures to a relevant degree. Knowledge about the force distribution along the blade may prospectively allow for the development of less traumatic blades. Therefore, we examined the forces along the blades experienced during laryngoscopy with the C-MAC D-BLADE and blades of the Macintosh style. We hypothesised that lower peak forces are applied to the patient's pharyngeal tissue during videolaryngoscopy with a C-MAC D-BLADE compared to videolaryngoscopy with a C-MAC Macintosh-style blade and direct laryngoscopy with a Macintosh-style blade. Beyond that, we assumed that the distribution of forces along the blade differs depending on the respective blade's geometry. Methods: After ethical approval, videolaryngoscopy with the D-BLADE or the Macintosh blade, or direct laryngoscopy with the Macintosh blade (all KARL STORZ, Tuttlingen, Germany), was performed on 164 randomly assigned patients. Forces were measured at six positions along each blade and compared with regard to mean force, peak force and spatial distribution. Furthermore, the duration of the laryngoscopy was measured. Results: Mean forces (all p < 0.011) and peak forces at each sensor position (all p < 0.019) were the lowest with the D-BLADE, whereas there were no differences between videolaryngoscopy and direct laryngoscopy with the Macintosh blades (all p > 0.128). With the D-BLADE, the forces were highest at the blade's tip. In contrast, the forces were more evenly distributed along the Macintosh blades. Videolaryngoscopy took the longest with the D-BLADE (p = 0.007). Conclusions: Laryngoscopy with the D-BLADE resulted in significantly lower forces acting on pharyngeal and laryngeal tissue compared to Macintosh-style blades. Interestingly, with the Macintosh blades, we found no advantage for videolaryngoscopy in terms of force application.

Impact performance of unconventional trigger holes

Abstract Crash boxes in vehicles are one of the passive safety measures that aim to reduce injury to passengers and damage to the vehicle during a collision. Their function is to absorb the mechanical energy resulting from a collision by deforming plastically. Considering human safety, not only the energy must be damped, but also the forces acting on the passengers must be controlled. This force control can be adjusted to some extent using trigger mechanisms. There is a wide variety of research on hole type triggers, but they concentrated on traditional shapes; unique or hybrid shapes have not been sufficiently tested. This study examined the effects of various hole profiles with equal areas on dynamic mechanical performances of Al 6063-T6 rectangular crash boxes. Four types of trigger shapes were formed: upward keyhole, downward keyhole, U-shaped, and S-shaped. The dynamic performance evaluation was carried out experimentally by testing five types of geometries, the fifth one being the geometry without any trigger. In addition, dynamic Finite element analyses were conducted and validated using the experimental data, with the aim of employing the Finite element models in future geometry improvement studies. The experimental results were interpreted with some common evaluation parameters: peak force, crash force efficiency, mean crash force, and total energy absorption. The downward keyhole profile generally gave the best results, while the lowest peak force was observed in the U-shaped profile.

A comparative study of lower limb strength during vertical jump of male college students in table tennis, badminton and tennis

The objectives of this paper are to explore the correlation of kinetic indices of SJ (squat jump) and CMJ (counter-movement jump) and the differences of lower limb strength mechanics indexes of table tennis, badminton and tennis players under SJ and CMJ. This study included 60 male collegiate athletes, 20 each from table tennis, badminton, and tennis. Subjects performed SJ and CMJ tests on a force platform and the vertical jump data were analyzed. Table tennis, badminton and tennis players demonstrated significant differences in the SJ and CMJ assessments. Badminton players outperformed table tennis players in terms of peak power (PP) (p = 0.005) and peak velocity (PV) (p = 0.017). Badminton players beat table tennis players in PV (p = 0.028), PP (p = 0.022), fast twitch fibers (FTF) (p = 0.033) and pre-stretch effect (EP) (p = 0.0004). Tennis players exhibited lower peak force (PF) (p = 0.006) indicators than badminton players. For athletes in all three sports, the SJ test markers (vertical jump displacement, PF, PP and PV) demonstrated a strong positive correlation. There was a highly significant positive correlation between VJD and PF, PP, PV and FTF among badminton players. Significant positive connections were discovered between PF, PP, PV, FTF and EP, as well as between PP and PV and FTF and EP. PV and FTF had a very strong positive correlation, as did EP, PV and FTF. College badminton players had higher vertical jumps than table tennis and tennis players. In addition to vertical jump height, PP (power production), PV (power velocity) and FTF (force-time factors) are important markers for assessing the success of vertical jumps in athletes’ daily training. These findings can assist coaches and athletes develop better vertical jump training programs.

Augmented reality‐based telepresence in a robotic manipulation task: An experimental evaluation

AbstractA spectrum of control methods in human–robot interaction was investigated, ranging from direct control to telepresence with a virtual representation of the robot arm. A total of 24 participants used a setup that included a Franka Emika Panda robot arm, Varjo XR‐3 head‐mounted display, and Leap Motion Controller. Participants performed a box‐and‐block task using the bare hand (A), and under five gesture‐controlled robotic operation methods: direct sight (B), sight via video‐feedthrough (C), in a 3D telepresence environment with (D) and without (E) virtual representation of the robot arm, and using a 2D video feed (F). The number of grabbing attempts did not differ significantly between conditions, but local operation (B &amp; C) yielded more transferred blocks than teleoperation (D–F). Teleoperation using a 3D presentation was advantageous compared to teleoperation using a 2D video feed, as demonstrated by lower peak forces and smaller range in gripper heights in conditions D and E compared to condition F, a finding supported by analyses of the head movement activity. Finally, the bare hand yielded the best performance and subjective ratings. In summary, teleoperation using a 3D presentation provided a smoother interaction than teleoperation with a 2D video feed. However, direct human interaction remains a benchmark yet to surpass.

On the protectiveness of additively manufactured mouthguards

A mouthguard is a piece of equipment worn in sports worldwide to greatly reduce the chance of orodental injuries. This work uses a newly developed method for testing and analysing mouthguards subjected to high impact energies of up to 100 J. This method allows investigation and comparison between the use of additive manufacturing, and current best mouthguard manufacturing technology of thermoforming with Ethylene-vinyl acetate (EVA). The impact experiments are conducted using a drop tower and high-speed images are captured for the further analysis. Important physical parameters such as peak force, impulse and dissipated energy in the mouthguard are determined. The results revealed that the additively manufactured mouthguards made from Arnitel® ID 2045 lead to a peak force and impulse of impact that is on average 10% and 25% lower, respectively, than that experienced when using the EVA mouthguard. A lower peak force and impulse is preferred as it reduces the chance of an orodental injury occurring. The research shows that previously mouthguards have been tested at impact energies far lower than those experienced in impact prone sports such as field hockey. When using impacts with higher energies, the findings show that additive manufacturing provides a viable technology for manufacturing mouthguards, which offers many new benefits.

Effect of the surface geometry of uncemented acetabular cups on primary stability in a model of uncemented total hip replacement in dogs.

To compare the in vitro stability of acetabular cups with peripherally reinforced fixation in a model of uncemented total hip replacement in dogs. 63 polyurethane foam blocks and 3 acetabular implant designs: hemiellipsoidal (Model A) and 2 models with equatorial peripheral fins (Model B with 1 level and Model C with 2 levels of fins). 2 loading patterns-edge loading and push-out tests-were performed until failure and peak forces were recorded. Implantation behavior was visually assessed and the required seating force was assessed using a force-displacement curve. Model B showed significantly lower peak force than Model A in edge loading tests with standardized impaction. In the push-out test, Model A had a greater maximal force than Models B and C, with mean maximal forces of 213.7 N, 139.4 N, and 138.9 N, respectively. In the seating force test, Models B and C required a higher force for 2-mm deep implantation (362.0 N and 361.6 N, respectively) than Model A (194.4 N), and were associated with dorsal tilting of the components. Our results suggest that cups with a peripheral design (B, C) have less primary stability than hemiellipsoidal cups (A). Furthermore, models with peripheral fins (B, C) appeared to have incomplete seating if a higher force was not used during implantation and, therefore, the risk of malpositioning was increased. These data indicate that hemiellipsoidal cups provide the same or better initial stability and require a lower impaction force.

Group differences and associations between patient-reported outcomes and physical characteristics in chronic low back pain patients and healthy controls

BackgroundPatients with chronic low back pain can exhibit altered slower gait, poor balance, and lower strength/power, and psychological dysfunctions such as pain catastrophizing and fear of movement. Few studies have investigated the relationships between physical and psychological dysfunctions. This study examined associations between patient-reported outcomes (pain interference, physical function, central sensitization, and kinesiophobia) and physical characteristics (gait, balance, and trunk sensorimotor characteristics). MethodsLaboratory testing included a 4-m walk, balance, and trunk sensorimotor testing with 18 patients and 15 controls. Gait and balance were collected with inertial measurement units. Isokinetic dynamometry measured trunk sensorimotor characteristics. Patient-reported outcomes included PROMIS Pain Interference / Physical Function, Central Sensitization Inventory, and Tampa Scale of Kinesiophobia. Independent t-tests or Mann-Whitney U tests were used to compare between groups. Additionally, Spearman's rank correlation coefficient (rs) established associations between physical and psychological domains, and Fisher z-tests compared correlation coefficient values between groups (significance P < 0.05). FindingsThe patient group had worse tandem balance and all patient-reported outcomes (P < 0.05) while no group differences were observed in gait and trunk sensorimotor characteristics. There were significant correlations between worse central sensitization and poor tandem balance (rs = 0.446–0.619, P < 0.05) and lower peak force and rate of force development (rs = −0.429–0.702, P < 0.05). InterpretationObserved group differences in tandem balance agree with previous studies, indicating impaired proprioception. The current findings provide preliminary evidence that balance and trunk sensorimotor characteristics were significantly associated with patient-reported outcomes in patients. Early and period screening could help clinicians further categorize patients and develop objective treatment plans.

Multimodal Robot-Assisted Instrument Interaction for Solo Laparoscopic Sacrocolpopexy

Laparoscopic sacrocolpopexy (LSC) involves at least three clinicians who are required to operate under non-ergonomic postures for long periods of time. Furthermore, LSC is characterized by miscommunication and high vaginal vault manipulation forces which possibly lead to overtensioning of tissue. This work presents a multimodal robotic assistance approach for solo LSC. Multimodality provides a set of instrument interaction modes that allows the surgeon to operate in close vicinity with the patient. It increases situational awareness and avoids miscommunication while ensuring safe vaginal vault exposure. The robotic setup is experimentally validated by ten gynecologists who performed a vaginal mesh fixation task on a box trainer. When compared to manual surgery, it was found that robotic assistance allows the solo surgeon to operate as fast (24.07±1.63 min vs. 23.75±1.54 min, p = 0.49) and with lower peak forces (12.23 ± 3.03N vs. 9.26 ± 1.41N, p = 0.02) applied to the vaginal vault. The results are promising as they show that the multimodal approach allows for robot-assisted solo surgery. This way, it frees clinicians from non-ergonomic tasks while maintaining similar surgery times and quality. Moreover, it reduces the risk of overtensioning of the vaginal tissue.

An Examination of the Impact of Blue Heat Treatment on the Forced Caused by the Vertical Motion of Endodontic Files

Objective: To assess the vertical forces produced during canal shaping by the Reciproc Blue (RB) and Reciproc (R) systems. Place and Duration: In the Operative Dentistry Department, Altamash Institute of Dental Medicine Karachi for one-year duration from January 2022 to December 2022. Methods: A total of 32 maxillary premolar teeth were selected, each with two distinct constricted and straight canals. Every tooth was positioned in a standing position on a platform attached to a force analysing device after access cavity preparation (M5-20 Advanced Digital Force Gauge; Mark-10 Corporation, NY, USA). Until the K file size was up to 15, the glide route was prepared manually. Then, using an R25/RB25 file, all of the groups' canals were completely shaped (0.08 taper, size 25). The canal was shaped with a mild and steady pressure on the file that produced a gradual, 2 mm amplitude "in-and-out" movement. It took three attempts for the file to successfully reach the WL. The canal was irrigated and recapitulated with sodium hypochlorite (1%) solution following each insertion. The Student's t-test was used to analyze the shaping time. The Mann Whitney test was applied to analyse the upward and inward peak forces. With a 95% level of confidence, SPSS software was used for all statistical analyses. Results: A single file was inserted into each root canal successfully three times for shaping till the WL achieved. With each additional file insertion, the overall real-time force increased in each group grew. The R group displayed lower peak forces in comparison to the RB group in the 3 insertions, and both groups inward peak forces varied from 1.76 to 8.64 N. (P&lt;0.05). Complete canal shaping of the RB and R systems took an average of 24.30±3.98 s and 21.91±3.56s, respectively (P&gt;0.05). During canal shaping in this experiment, no file fracture occurred. Conclusion: The forces generated during canal shaping were influenced by the blue heat treatment. Higher inward peak forces were higher in the RB file than the R file. Keywords: Root canal preparation, Endodontics, vertical force and shaping time.

An Insight on Mud Behavior Upon Stepping

In this research we show a characterization of mud behavior under vertical stepping. We showed that mud stiffness can vary 45-fold and the energy spent to generate equivalent impulse can vary 2-fold depending on the mud water content, but also that stepping faster on mud leads to lower peak forces and higher energy consumption. Next, we showed that the peak force generated can be increased by 33% by changing the foot stiffness, but is reduced by 18% if stepping is repeated on the same spot. We then demonstrated how force control can be used to achieve identical force profiles on very different muds. These results will help to design mechanical parts or control strategies for legged robot locomotion on mud.

Comprehensive Crashworthiness Studies of Novel Alternately-Assembled Multi-Frusta Structures for Energy Absorption Applications

In this paper, we propose a new multicellular design of assembled multi-frusta with alternate orientations and varied taper angles for effective energy absorption applications. Extensive crush test experiments, comprehensive finite-element simulations and analytical modeling were carried out to evaluate the energy absorption performance of the newly proposed multicellular assemblies. The performances of these assemblies are calibrated against conventional assembly of uniform tubes. Two aspects of the work were parametrically examined. The first was concerned with the effect of the frusta taper angle, while the second was concerned with the multi-frusta layout on the energy absorption of the proposed multi-frusta assembled structures. The results reveal that the face centered square layout with an appropriately selected taper angle possesses the optimal high specific energy absorption, low peak force, and smooth crushing force curve, which makes it a crashworthy device.