Fixed Reference Point Research Articles

Magnetically coupled tooth arrangement for an implant-supported fixed complete denture: A dental technique

Magnets have been used to help position dental components, including magnetic mounting plates for articulators and magnetic attachments for implant surgical guides. A magnetically coupled tooth arrangement technique used the fixed reference point of integrated implants to determine maxillomandibular relations and the tooth arrangement, thus improving the efficiency of the clinical appointment. The magnetic framework was screwed into the implants only once for the duration of a clinical appointment. The base was used to complete the tooth arrangement and determine the maxillomandibular jaw relationship.

Static Stability of Elbow Interposition Arthroplasty Stabilized With Novel Ligament Reconstruction.

Outcomes of interposition arthroplasty for treatment of elbow arthritis are highly dependent on elbow stability. The purpose of this study was to determine whether interposition arthroplasty with a novel bidirectional ligament reconstruction technique could adequately restore the static stability of the native elbow. Static varus and valgus elbow stability was tested in 7 cadaver elbows with intact ligaments and capsule at 5 flexion angles (0°, 30°, 60°, 90°, and 120°). At each angle, the distance between fixed reference points across the elbow was measured both medially and laterally. The elbows were then destabilized and an interposition arthroplasty with ligament reconstruction was performed. Static elbow stability was reassessed by comparing postoperative deflection measurements with those of the native state. Graft slippage or loosening was visually assessed following testing. Interposition arthroplasty was performed in 7 cadaver specimens. Following ligament reconstruction, specimens reproduced the flexion angle-dependent static stability of native elbows to both varus and valgus stress. The greatest deflection changes between native elbows and elbows after interposition arthroplasty were 2.7% (P = .13) medially and 2.3% (P = .42) laterally, which were not significant. There was no loosening or slippage of either the interposition graft or the ligament reconstruction grafts. Cadaveric elbow specimens underwent interposition arthroplasty with a novel technique for bidirectional ligament reconstruction. Static stability was maintained at varying degrees of elbow flexion, comparable to that of the native elbow. Interposition and ligament reconstruction grafts maintained secure fixation following static biomechanical testing.

Reference‐Dependent Risk‐Taking in the NBA

ABSTRACTThis paper examines whether risk preferences in the NBA are reference‐dependent and attempts to identify the reference point. Using data from 10 NBA seasons (12,890 games), I find that teams are more likely to attempt a riskier three‐point shot (vs. a less risky two‐point shot) when below the reference point than above it, consistent with Prospect Theory. The results further show that teams are not influenced by a single fixed reference point, but instead, their choices depend on the score difference, most recent score change, and pregame expectations. Additionally, the weight given to the reference point changes over the course of the game. Teams show a breakeven effect, such that they are more likely to attempt a three‐point shot when doing so can tie the game. They also show behavior consistent with mental accounting, as the reference point carries more weight at the end of a quarter than at the beginning. These results provide further real‐world evidence for reference‐dependent risk preferences while highlighting the challenge of applying reference‐dependent models to real‐world settings.

A preliminary investigation of the inverse Finite Element Method applied to bridge structures

Deflection monitoring plays a key role in bridge Structural Health Monitoring, as deflection data may offer valuable insights into potential structural issues, such as cracks and corrosion. However, monitoring bridge deflections under operative loads presents challenges, particularly in scenarios where establishing a fixed reference point for displacement sensors is impractical, such as when a bridge spans a waterway or the sensors may be vulnerable to vandalism. In recent years, the inverse Finite Element Method (iFEM) has emerged as a possible solution. This method provides a load- and material-independent means of computing structural displacements from strain measurements, in real time at a minimal computational cost. Additionally, the iFEM can serve as a virtual sensing approach to monitor strains at locations lacking sensors, enabling the assessment of the fatigue life consumption at virtually any point in the structure. Despite its potential, applications of the iFEM in the civil engineering field are very limited, with no validation on full scale bridges has been performed to date. This study addresses this gap by investingating the application of the iFEM for bridge deflection monitoring through distributed strain measurements. The proposed approach is tested on experimental case studies, involving cross-validatiion of reference-free deflections inferred by the iFEM with those obtained from displacement sensors. This work contributes to the advancements of structural health monitoring methodologies in civil engineering, demonstrating the practicality and reliability of iFEM in bridge applications.

Hafele and Keating revisited: A novel interpretation of the results of the Hafele‐Keating experiment

The Hafele‐Keating experiment showed the occurrence of time dilation in clocks placed on two airplanes, one moving eastward and one moving westward relative to the Earth’s rotation. However, the application of the special theory of relativity failed to account for the significant differences in the data. This problem is solved by a novel approach that focuses on the absolute velocities of the clocks with reference to the Earth’s rotation and uses space as a fixed reference point. The basic idea here is that time dilatation is an experimental fact and, therefore, independent from the theory behind it, so it is independent from relativism. Time dilatation also can occur under absolute conditions. Up until now, it is not clear if the concept of relativism is correct or not. The existence of time dilatation cannot be proofs for relativism as time dilatation also can occur under absolute conditions. Here, it is established that the eastbound plane had a higher absolute velocity than its westbound counterpart, resulting in time dilation figures of 50 and 140 ns, respectively.

A Reappraisal of the Accuracy of the Tactile Method for the Detection of the Subgingival Cementoenamel Junction: An In Vivo Study.

This article reappraises the accuracy and factors associated with the detection of the cementoenamel junction (CEJ) using the tactile method. A total of 111 tooth sites of 7 patients scheduled for flap surgery were selected for the study. The CEJ was detected in a blind manner using the conventional tactile method with a standard periodontal probe by a single, trained examiner. A custom-made stent was prepared to standardize the measurements and the distance from a fixed reference point on the stent to the CEJ was measured before (apparent CEJ) and after (real CEJ) opening a gingival flap. To evaluate the effect of local anesthesia (LA) on the measurement error, assessment with and without LA given prior to the measurement was also evaluated. The bone crest-CEJ distance at each site was also recorded in all sites. The measurement error of apparent versus real distance, if any, was compared using Cohen's weighted kappa coefficient (WKC) (± 1 mm). A weak WKC (WKC = 0.539) was found between the apparent and real CEJ distance. Higher WKCs were noted at posterior and proximal sites than the anterior and buccal/lingual sites, respectively (0.840 and 0.545 vs. 0.475 and 0.488). A higher confluence of the agreements was noted when CEJ distance was measured in anesthetized sites (WKC = 0.703). Sites without bone loss showed more coronal deviation of CEJ detection, as opposed to apical deviation seen at sites with bone loss. The conventional CEJ detection using the tactile method was relatively imprecise depending on the anatomical location of the tooth and the bone loss at the site of measurement. However, the detection accuracy improved when the sites were anesthetized. In clinical terms, our data, reported here for the first time imply that, in the absence of visual cues, posterior tooth site measurements of periodontal attachment loss were more reliable in comparison to the other sites. The bone crest level also impacted the measurement deviation to some extent, implying that, possible overestimate of clinical attachment loss may occur at sites without bone loss.

Validation and Safety Profile of a Novel, Noninvasive Fiducial Attachment for Stereotactic Robotic-Guided Stereoelectroencephalography: A Case Series.

We developed, tested, and validated a novel, noninvasive, Leksell G frame-based fiducial attachment, for use in stereotactic registration for stereoelectroencephalography (sEEG). Use of the device increased the number of fixed reference points available for registration, while obviating the need for additional scalp incisions. We report here on our experience and safety profile of using the device. We collected registration data using the fiducial device across 25 adult and pediatric patients with epilepsy consecutively undergoing robotic-guided sEEG for invasive epilepsy monitoring, treated between May 2022 and July 2023. ROSA One Brain was used for trajectory planning and electrode implantation. Postoperative clinical and radiographic data were computed and quantified, including mean registration error for all patients. Entry point, target point (TP), and angular errors were measured. Descriptive statistics and correlation coefficients for error were calculated. Twenty-five patients underwent robotic-guided sEEG implantation (11 patients, bilateral; 10 patients, left unilateral; 4 patients, right). The mean number of electrodes per patient was 18 ± 3. The average mean registration error was 0.77 ± 0.11 mm. All patients were implanted with Ad-Tech depth electrodes. No clinically relevant complications were reported. Analysis of trajectory error was performed on 446 electrodes. The median entry point error was 1.03 mm (IQR 0.69-1.54). The median TP error was 2.26 mm (IQR 1.63-2.93). The mean angular error was 0.03 radians (IQR 0.02-0.05). There was no significant correlation between root mean square error and lead error. Root mean square error did not appreciably change over time, nor were there any significant changes in average angular, entry point, or TP error metrics. A novel, noninvasive, Leksell G frame-based fiducial attachment was developed, tested, and validated, facilitating O-arm-based stereotactic registration for sEEG. This simple innovation maintained an excellent accuracy and safety profile for sEEG procedures in epilepsy patients, with the added advantages of providing additional reference points for stereotactic registration, without requiring additional scalp incisions.

A polynomial algorithm for some instances of NP-complete problems

In this paper, given a fixed reference point and a fixed intersection of finitely many equal radii balls, we consider the problem of finding a point in the said set which is the most distant, under Euclidean distance, to the said reference point. This proble is NP-complete in the general setting. We give sufficient conditions for the existence of an algorithm of polynomial complexity which can solve the problem, in a particular setting. Our algorithm requires that any point in the said intersection to be no closer to the given reference point than the radius of the intersecting balls. Checking this requirement is a convex optimization problem hence one can decide if running the proposed algorithm enjoys the presented theoretical guarantees. We also consider the problem where a fixed initial reference point and a fixed polytope are given and we want to find the farthest point in the polytope to the given reference point. For this problem we give sufficient conditions in which the solution can be found by solving a linear program. Both these problems are known to be NP-complete in the general setup, i.e. the existence of an algorithm which solves any of the above problems without restrictions on the given reference point and search set is undecided so far. Mathematics Subject Classification (2010): 90-08. Received 21 December 2021; Accepted 01 August 2023

Investigation of circular aluminium tube expansion by rigid die as energy absorbers using digital image correlation technology

This paper investigates the expansion of circular aluminium tubes using a rigid die under quasi-static loading conditions through experiments and finite element simulations. This study primarily focuses on the expansion of thin-walled tubes with a thickness ranging from 3.95 to 5 mm, and the finite element model is in good agreement with the experimental results. Additionally, the study emphasizes the impact of the coefficient of friction, energy dissipation properties and the diameter-to-thickness ratio on the energy expenditure associated with the expansion process of aluminium tubes using a rigid die. This study use Digital Image Correlation (DIC) technology to evaluate pictures obtained during experimental procedures, enabling accurate quantification of displacements, stresses, and rotations of major planes. The findings indicate that the energy absorption resulting from friction plays a significant role, with the coefficient of friction serving as a important parameter throughout the expansion process. The energy absorbed by the friction between tube-die contact surfaces was significantly higher than that absorbed by the plastic bending of the aluminium tube. For specimen AT-5.0-1, the energy absorbed by friction and bending is 3352 and 570 J, respectively. Result shows that a notable increase in the ultimate load, rising from 46.03 to 61.54 kN, is required for expanding the aluminium tube with a thickness of 3.95 to 5.0 mm. The local strain patterns seen on the surface of the tube offer useful insights, therefore enhancing researchers’ ability to examine particular points on the specimen’s surface without the need for fixed reference points prior to conducting experiments.

Rapid assessment of the dependence of flexural elastic modulus on temperature through in‐situ image analysis

AbstractThis study aimed to develop a method for rapid and precise measurement of the elastic modulus at high temperatures. High‐temperature in‐situ microscopy was used in conjunction with a testing apparatus to measure the deformation of a specimen in three‐point bending test. The bending deflection was determined in situ by measuring the relative change between the test point on the specimen and a fixed reference point. The deflection was correlated with the elastic modulus to obtain the dependence of the elastic modulus on temperature. The ratio between high‐ and room‐temperature deflection of the bending beam was measured using the relative method and image analysis, with an identical scene and focal length for each photograph and a resolution of less than 1 µm. The deflection ratio was then converted into the ratio between high‐ and room‐temperature elastic modulus, enabling the high‐temperature modulus to be quickly derived. The experiments were performed on a sample made of silicon carbide fiber braided layered composite. The results showed that the elastic modulus changed little within 1100°C, remaining between 80 and 84 GPa. Contrarily, constant‐load tests indicated that the creep of this material was noticeable, making it difficult to obtain reliable elastic modulus.

Enhancing Georeferencing and Mosaicking Techniques over Water Surfaces with High-Resolution Unmanned Aerial Vehicle (UAV) Imagery

Aquatic ecosystems are crucial in preserving biodiversity, regulating biogeochemical cycles, and sustaining human life; however, their resilience against climate change and anthropogenic stressors remains poorly understood. Recently, unmanned aerial vehicles (UAVs) have become a vital monitoring tool, bridging the gap between satellite imagery and ground-based observations in coastal and marine environments with high spatial resolution. The dynamic nature of water surfaces poses a challenge for photogrammetric techniques due to the absence of fixed reference points. Addressing these issues, this study introduces an innovative, efficient, and accurate workflow for georeferencing and mosaicking that overcomes previous limitations. Using open-source Python libraries, this workflow employs direct georeferencing to produce a georeferenced orthomosaic that integrates multiple UAV captures, and this has been tested in multiple locations worldwide with optical RGB, thermal, and multispectral imagery. The best case achieved a Root Mean Square Error of 4.52 m and a standard deviation of 2.51 m for georeferencing accuracy, thus preserving the UAV’s centimeter-scale spatial resolution. This open-source workflow represents a significant advancement in the monitoring of marine and coastal processes, resolving a major limitation facing UAV technology in the remote observation of local-scale phenomena over water surfaces.

Estimation of Sea Surface Topography Using Jason-3 Satellite Altimetry Across the Eastern Indonesian Seas in a period of 2016 to 2021

The measurement of sea level height relative to a fixed reference point, such as the geoid or mean sea level, is known as sea surface topography. There are a number of factors that affect it, such as undulation, sea surface height, and tides. Measurement of sea surface topography is very important to understand ocean dynamics. One of the factors that influences the dynamics of the sea is the flow across Indonesia. The Indonesian traffic flow is the mass flow of water from the Pacific Ocean to the Indian Ocean. The difference in pressure between the two oceans is what causes the flow. The purpose of this study is to provide precise information about the sea surface topography in the East Indonesian Sea region during the 2016–2021 period, which is required for various marine applications. This approach involves processing and analysing Jason-3 altimetry satellite data, which provides precise sea level elevation measurements. The data is then used to determine the value of the sea surface topography, which shows the spatial and temporal variations in sea level height in the region. The average sea surface topography value every month from 2016 to 2021 ranges from 1.05m to 1.30m, with the highest value occurring in January 2021 at 1.2542m and the lowest value occurring in February 2016 at 1.0498m. For the accuracy of processing results, data for 2016–2021 is used as training data for model estimation and 2021 as test data. The root mean square error value is 0.0762m. Changes in sea surface topography values tend to increase every year, except for 2019. The decline that occurred in 2019 was caused by the ENSO phenomenon, which had an effect of -0.807 on sea surface topography with an inverse correlation. The findings of this study provide important details about sea surface topography in Eastern Indonesian waters, which can be applied to enhance our understanding of ocean dynamics.

Adsorbate motors for unidirectional translation and transport.

Artificial molecular motors are designed to transform external energy into useful work in the form of unidirectional motion1. They have been studied mainly in solution2-4, but also on solid surfaces5,6, which provide fixed reference points, allowing for tracking of their movement. However, these molecules require sophisticated design and synthesis, because the motor function must be imprinted into the chemical structure, and show reduced functionality on surfaces compared with in solution5-8. DNA walkers9,10,on the other hand, impart high directionality as they include the surface as part of the motor function, but they require chemical surface patterning and sequential solvent modification for motor activation. Here we show how efficient motors can operate at much smaller length scales on a homogeneous metal surface without any liquid. This is realized by combining a surface with a simple molecule, which, by itself, does not contain any motor unit. The motion, which is tracked at the single-molecule level, is triggered by intramolecular proton transfer with a corresponding modulation of the potential energy surface. Each molecule moves with 100 percent unidirectionality along an atomically defined straight line. Proof of the motor performing meaningful work is shown by controlled transport of single carbon monoxide molecules. This simplistic concept could form the basis for the controlled bottom-up assembly of nanostructures at the atomic scale.

Effect of splinting scan bodies on the trueness of complete arch digital implant scans with 5 different intraoral scanners

Statement of problemThe absence of fixed reference points can affect the trueness of complete arch intraoral digital implant scans. The effect of splinting intraoral scan bodies (ISBs) or the inclusion of artificial landmarks (AL) on the trueness of complete arch digital implant scans is still unclear. PurposeThe purpose of this study was to analyze the effect of splinting ISBs or the inclusion of AL on the trueness of complete arch digital implant scans with 5 intraoral scanners (IOSs). Material and methodsSix tissue-level dental implants (Straumann Tissue Level) were placed in an edentulous patient, and the correspondent definitive cast was digitized with a desktop scanner (IScan4D LS3i) to obtain the reference digital cast. Digital scans (n=10) were performed with 5 IOSs: TRIOS 4, Virtuo Vivo, Medit i700, iTero Element 5D, and Cerec Primescan. Three different scanning techniques were evaluated: conventional (cIOSs), splinted (sIOSs), and AL (AL-IOSs). The scan data obtained were imported into a metrology software program and superimposed to the reference digital cast by using a best-fit algorithm. The overall deviations of the positions of the ISBs were evaluated by using the root-mean-square (RMS) error (α=.05). ResultsThe mean ±standard deviation trueness values for the cIOSs, sIOSs, and AL-IOSs groups were 48 ±8 µm, 53 ±7 µm, and 49 ±11 µm, respectively, with no statistically significant differences (P=.06). Significant differences were found for the IOSs used with each technique (P<.001). Primescan (27 ±4 µm cIOSs; 28 ±3 µm sIOSs; 31 ±3 µm AL-IOSs) showed significantly higher trueness than iTero 5D (47 ±5 µm cIOSs; 47 ±4 µm sIOSs; 50 ±6 µm AL-IOSs) (P=.002) and TRIOS 4 (93 ±18 µm cIOSs; 76 ±18 µm sIOSs; 107 ±13 µm AL-IOSs) (P=.001) for all techniques. In addition, no significant differences were found between the techniques by using iTero 5D or Primescan (P=.348 and P=.059, respectively). ConclusionsThe cIOSs, sIOSs, and AL-IOSs techniques showed similar trueness. The IOS used influenced the trueness of complete arch digital implant scans.

Multi-strategy multi-objective differential evolutionary algorithm with reinforcement learning

Multiobjective evolutionary algorithms (MOEAs) have gained much attention due to their high effectiveness and efficiency in solving multiobjective optimization problems (MOPs). However, when solving MOPs, it is important but difficult to maintain a good balance of exploration and exploitation. In addition, some reference point based MOEAs with fixed reference points perform poorly on MOPs with irregular frontiers. Therefore, this paper proposes a new multistrategy multiobjective differential evolutionary (DE) algorithm, named RLMMDE. In RLMMDE, a multistrategy and multicrossover DE optimizer is utilized to alleviate the exploration and exploitation dilemma. An adaptive reference point activation mechanism based on RL is proposed to activate the adaptive adjustment of reference points. Moreover, a reference point adaptation method is proposed to improve the performance of RLMMDE on irregular frontier problems. Experimental results of RLMMDE tested on some benchmark test suites (i.e., ZDT, DTLZ, UF, WFG, and LSMOP) and two practical mixed-variable optimization problems show that the algorithm outperforms some advanced MOEAs.

Comparison between Measurements of Clinical Attachment Level and Transgingival Probing with Alveolar Bone Crest Level in Chronic Periodontitis Patients

Background: Periodontitis is an inflammatory disease of the supporting tissues of the teeth that leads to crucial changes in the bony architecture. Early detection is of great practical significance so that treatment may be administered before irreversible destruction could occur. Differences exist between different diagnostic methodology concerning the relationship between the measurements and the level of the lesion. The aim of this study was to assess relationship between clinical attachment level (CAL) and alveolar bone crest level (ABCL), reliability of transgingival bone probing level (TBL) for ABCL measurement, and clinical biologic width (CBW) measurement in chronic periodontitis patients. Methods: An analytical cross-sectional study was conducted on 238 periodontal sites in 25 chronic periodontitis patients, aged 20–60 years who were planned for periodontal flap on residual pocket depth of 5-8mm after four weeks of non-surgical therapy. Stent was used for coronal fixed reference point. The relative attachment level (RAL), relative transgingival bone probing level (RTBL), relative alveolar bone crest level (RABCL), and CBW were measured at six sites per tooth excluding third molars. Descriptive and inferential statistical analysis was done. Probability of significance (p-value) was set at 5%. Results: Overall RAL, RTBL and RABCL (mean ± SD) were 8.08 ± 1.23, 10.82 ± 1.1, and 11.15 ± 1.36 mm respectively. Overall CBW (mean ± SD) was 3.06 ± 0.634 mm. Conclusions: There was a significant positive correlation of CAL and TBL with ABCL. Also, the CBW was greater than that of standard histologic BW.

Landmark selection and path planning for unmanned vehicles with position error corrections

Unmanned vehicles have been widely used for sensing, surveillance, surveying, communication, transportation, and many other purposes. Navigation is always an essential operational function in the course of their movements. In the case of the absence of Global Positioning System (GPS) signals, the positioning need of an unmanned vehicle is generally empowered by its onboard Inertial Navigation System (INS). An inherent deficiency of INS, however, is that position errors inevitably occur and will gradually accumulate over time. A feasible approach to correcting errors is to use the fixed reference points with known coordinates in the cruising environment, which we call landmarks, to calibrate the vehicle’s position when it passes by. The vehicle must choose a path along which a sufficient number of landmarks can serve the position calibration requirement. In such a context, this paper introduces a joint landmark selection and path planning problem for unmanned vehicles navigating in two-dimensional (2D) and three-dimensional (3D) environments, in which the vehicles’ position drifting errors need to be rectified through communicating with preset landmarks. To characterize and tackle the problem, a set of new types of subpaths are defined and a bi-objective integer programming model using this building block is formulated for simultaneously minimizing the landmark deployment cost and the vehicle cruise distance. An efficient dynamic programming algorithm, which features a multi-criterion label-correcting form, is developed for searching for the Pareto-optimal solution set of landmark and path selections. Numerical and computational analyses are conducted in both 2D and 3D scenarios, in which a pair of origin and destination places are typically hundreds of kilometers apart and 4 datasets of different scales including 500, 1,000, 1,500, and 2,000 candidate landmarks are randomly generated. A sensitivity analysis reveals the impact of different position drifting increments caused by external environment interferences, varying correction abilities, and heterogeneous landmark deployment costs on the solution behavior. The influence of the number of candidate landmarks, position error limit, and error increment rate on computing time is also evaluated. All these test results conclude that the algorithm is capable of finding in seconds the entire set of Pareto-optimal landmarks and paths in real-world applications.

Impact of preoperative computed tomography image slice thickness on the planning of deep brain stimulation surgery: A phantom study

BackgroundPreoperative Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) coregistration is often applied to perform deep brain stimulation (DBS) surgeries. Thin sliced (high dose) CT is used and recommended because of the high reported accuracy but there are no comparative studies. Thin sliced CT could lead to a higher radiation exposure for the patient in contrast to thicker sliced CT (low dose) due to a longer scanning time. In this study we investigated if the preoperative CT slice thickness had an effect on the registration accuracy in a preoperative simulated DBS setting. Material and methodsAn implanted phantom, a Citrullus lanatus (watermelon), was used to acquire an MRI data set (2 millimeter (mm) T2) with a fixed reference point. Two observers targeted the reference point independently and they recorded and compared the coordinates, ring, and arc angles from all coregistered series with different CT slice thicknesses of 0.5 mm, 1 mm, 1.5 mm, 2 mm, 3 mm, 4 mm, and 5 mm. Separately, both MRI and CT were used as reference series for coregistration and analysis. Lastly, inter-observer reliability was calculated with Kendall’s coefficient of concordance (W). With W> 0.9 defined as very good. ResultsOur results show no relevant effect on the preoperative registration accuracies for the different CT’s with all absolute differences in mm for the stereotactic coordinates< 0.5 and angles in degrees< 0.4. Additionally, the inter-observer reliability was high (W 0.991). ConclusionWe found no relevant effect of increased slice thickness of preoperative CT on the preoperative registration accuracy in a simulated DBS setting.

Pengaruh Gerak Pemakanan (Feeding) Terhadap Hasil Kekasaran Permukaan Baja Karbon S45C Pada Proses Mesin CNC Turning SKT 160A

CNC machine is a machine tool whose entire operation is controlled using a computer by inputting N and G codes. There are 2 types of programming for CNC lathes, namely incremental (the starting point of the program can change or the program endpoint becomes the beginning point of the next program), absolute (the starting point becomes the fixed reference point of the program. The study aimed to determine the low surface roughness value of S45C carbon steel with feeding motion variations of 0.15 mm, 0.25 mm, and 0.35 mm with a cutting depth of 0.4 mm and a constant spindle rotation speed. The insert used is branded iscar with a radius of 0.8 mm.. The lowest roughness value at feeding motion of 0.15 mm belongs to the roughness class, namely N7. The intermediate roughness value at feeding motion of 0.25 mm belongs to the roughness class N7. While the highest roughness value in feeding motion (feeding) 0.35 mm is included in the roughness class, namely N8. The average value results are obtained from the testing process using a roughness test tool (stylus).. The effect of feeding motion on the results of the surface roughness of S45C carbon steel in the CNC process is that the smaller the feeding value, the lower the roughness value produced, while the greater the feeding value, the higher the roughness value produced.

Relationship of Pelvic Positional Change with Leg Length and Offset Measurement in Experimental Total Hip Arthroplasty

During total hip arthroplasty (THA), both pelvic and femur positions affect leg length (LL) and offset (OS) measurements because LL and OS calipers depend on the fixed reference points on the pelvis and femur, respectively. However, LL and OS measurement errors because of pelvic positional changes have not been described. This study aimed to clarify the effects of pelvic positional changes on LL and OS measurements in relation to the pelvic reference using a THA simulator. We developed an experimental THA simulator using Sawbones models of the hemipelvis and femur that facilitated modification of the obliquity, tilt, and rotation of the pelvis. Using an LL and OS caliper, LL and OS measurement errors due to pelvic positional changes were determined with the femoral position fixed. Measurements were performed from two pelvic reference positions: the iliac tubercle (P1) and the top of the iliac crest intersecting the line of the femoral long axis (P2). Concerning pelvic obliquity, the total error of LL was 25.0 mm in P1 and 26.5 mm in P2, while the total error of OS was 13.0 mm in P1 and 10.9 mm in P2. For pelvic tilt, the total error of LL was 9.0 mm in P1 and 3.8 mm in P2, while the total error of OS was 0.5 mm in P1 and 1.0 mm in P2. Regarding pelvic rotation, the total error of LL was 13.8 mm in P1 and 3.2 mm in P2, while the total error of OS was 3.8 mm in P1 and 4.0 mm in P2. Pelvic positional changes alter LL and OS measurements. The acceptable range (error <2 mm) on LL and OS measurement errors of pelvic obliquity was only 2°, regardless of the pelvic reference position. The pelvic reference position should be at the top of the iliac crest intersecting the line of the long axis of the femur because of a small LL measurement error with pelvic tilt and rotation.