Exact Angle Research Articles

Ray and energy-flux velocities at a contact of two viscoelastic anisotropic materials

SUMMARY A g*-Hamiltonian method for tracing real rays was developed that can handle cusps and triplication of quasi-shear wave in a general viscoelastic anisotropic medium. We demonstrate that the g*-Hamiltonian method can produce homogeneous ray-velocity vectors (with parallel real and imaginary parts) and the slowness vectors of reflected and transmitted waves at the interface based on the real Snell's law (RSL), which constrains only the continuity of the real parts of the slowness vectors, or the real slowness direction (RSD) method, which ignores the inhomogeneous component of the slowness vector. These methods are based on the characteristic lines with different Hamiltonians. Our research indicates that these methods are limited to pre-critical incidence ranges. Moreover, we derived a complex energy velocity vector (energy flux velocity) expression, which is always homogenous. We found that directions of corresponding energy velocity calculated with complex Snell's law (CSL) at a contact of two viscoelastic anisotropic materials well match the solutions of the RSL and RSD methods for all R/T waves except post-critical incidence in which the RSL and RSD methods fail to obtain homogenous ray velocities. The RSL and RSD methods result in discrepancies in the ray quality factor, R/T coefficients, and energy ratios, especially for post-critical incidence. However, the exact critical angle determined by the RSD method approximates the ‘critical’ angle for anelastic/inhomogeneous waves, which was a previous challenge. Our calculations suggest that the energy velocity and energy quality factor obtained with the CSL method can be used for real ray tracing at the interface of viscoelastic anisotropic media, and the complex energy flux velocity vector is always exactly homogeneous. For the post-critical incidence, the RSL and RSD methods fail because the ray quality factor drastically changes from the infinite down to near 2, which contradicts homogeneous ray velocity even in elastic anisotropic materials for RSD method. However, the energy flux quality factor for the elastic-anisotropic material is all infinite, even for post-critical incidence, which is correct. We also show that the CSL method has the same efficiency as the RSD method.

Extracting information from the cutting force signal to explain and exploit its discrepancy between up and down slot milling at the same chip thickness

In milling, different cutting forces can occur at the same undeformed chip thickness depending on process kinematics and feed. To clarify and exploit this phenomenon, which has not been reported in the technical literature, the cutting force was recorded during full-width orthogonal milling. The latter process was chosen as the same undeformed chip thickness is developed at certain tool rotation angles and at different feeds, thus allowing the exploration of the effect of these parameters on the cutting force. Using analytical methods to describe the cutting kinematics, the exact rotation angle of the tool corresponding to its engagement with the workpiece was calculated. In addition, the precise relationship between chip thickness and occurring cutting force in up and down slot milling at various feeds was determined. Herein, for increasing the accuracy, the tool path was considered as trochoidal rather than circular. In addition, analytical methods were developed to calculate the cutting force direction, shear angle and chip compression ratio. The measurements of the deformed chip thickness over the deformed chip length verified the assumptions and correctness of the developed analytical procedures. Additionally, based on a FEM simulation of the developed stress fields during material removal, the stress field depth parameter ds was introduced. Using ds and the calculated direction of the cutting force towards the instantaneous workpiece surface, regions of effective material strengthening or weakening were detected within the developing stress field during up and down milling respectively, which change the cutting force. In this way, the discrepancies between the cutting forces occurring in up and down milling at the same undeformed chip thickness and various feeds were clarified and process conditions were proposed to exploit them to reduce cutting loads and energy requirements.

Tripling of the scattering vector range of X-ray reflectivity on liquid surfaces using a double-crystal deflector.

The maximum range of perpendicular momentum transfer (q z) has been tripled for X-ray scattering from liquid surfaces when using a double-crystal deflector setup to tilt the incident X-ray beam. This is achieved by employing a higher-energy X-ray beam to access Miller indices of reflecting crystal atomic planes that are three times higher than usual. The deviation from the exact Bragg angle condition induced by misalignment between the X-ray beam axis and the main rotation axis of the double-crystal deflector is calculated, and a fast and straightforward procedure to align them is deduced. An experimental method of measuring scattering intensity along the q z direction on liquid surfaces up to q z = 7 Å-1 is presented, with liquid copper serving as a reference system for benchmarking purposes.

The Natural (non-invasive) Erection Test: Is it a reliable alternative to the artificial erection test?

To test the accuracy and reliability of the natural erection test (NET) as compared to the artificial erection test in assessing penile curvature in hypospadias. 50 children underwent both natural and artificial erection tests intraoperatively between January 2020 and October 2021. These included 5 glandular, 26 distal, 9 proximal, and 10 perineal hypospadias patients with curvature. The mean follow up period was 20 months (range 16-37). Under anesthesia, the curvature was assessed before degloving, then after degloving using both the natural and the artificial erection test. The NET test was repeated after curvature correction (3 times per patient). The measurements were analyzed using paired t-test. Two fingers of the left hand press just below the symphysis pubis to stop blood drainage from the penis and two fingers of the right hand massage the blood from the perineum distally into the penis until it becomes hard without tourniquet. The standard artificial erection test was performed using saline injected through a butterfly needle into the corporeal bodies without tourniquet. Photos were taken of both tests using the exact angle and angle of curvature was measured using Angle Meter App. There was no statistically significant difference between both erection tests with a P value of 0.705. The Bland-Altman plot also showed that all studied children have a difference in their natural and artificial erection tests within the limits of agreements. Erection is commonly induced using the artificial saline injected erection test first described by Gittes and less commonly using pharmaceutical erection test first described by Perovic. The severity of chordee apparent during artificial erection test varies with the amount of pressure used during injection. Also, it is difficult to place the tourniquet proximal enough to detect chordee at the base of the penis. It may be associated with hematoma formation, oedema, postoperative pain and the need for multiple punctures to assess the curvature before and after repair. Disadvantages of the pharmacological-induced erections in hypospadias include increased blood loss during erection, additional cost, and the need for a reversal agent. The natural erection test mimic the normal erection mechanism and may avoid all these potential disadvantages. The study showed that the natural erection test is easy to perform, non-invasive, non-traumatic and can be repeated several times intraoperatively without the need of repeated puncturing of the corpora cavernosa and avoids the potential risks and complications of the artificial erection test.

Vibration Transmission across Seismically Damaged Beam-to-Column Junctions of Reinforced Concrete Using Statistical Energy Analysis

To detect human survivors trapped in buildings after earthquakes by using structure-borne sound it is necessary to have knowledge of vibration transmission in collapsed and fragmented reinforced-concrete buildings. In this paper, statistical energy analysis (SEA) is considered for modelling vibration transmission in seismically damaged, reinforced concrete, beam-to-column junctions where the connection between the beam and the column is made only via the steel reinforcement. An ensemble of 30 randomly damaged beam-to-column junctions was generated using a Monte Carlo simulation with FEM. Experimental SEA (ESEA) is then considered with two or three subsystems to determine the coupling loss factors (CLFs) between the beam and the column with either bending modes or the combination of all mode types. It is shown that bending modes dominate the dynamic response and that the uncertainty of predicting the CLFs using FEM with ESEA is sufficiently low that it should be feasible to estimate the coupling even when the exact angle between the beam and the column is unknown. In addition, the use of two rather than three subsystems for the junction significantly decreases the number of negative coupling loss factors with ESEA. An initial analysis of the results in this paper was presented at the 50th International Congress and Exposition on Noise Control Engineering.

Fault diagnosis of power converters in a grid connected photovoltaic system using artificial neural networks

Introduction. The widespread use of photovoltaic systems in various applications has spotlighted the pressing requirement for reliability, efficiency and continuity of service. The main impediment to a more effective implementation has been the reliability of the power converters. Indeed, the presence of faults in power converters that can cause malfunctions in the photovoltaic system, which can reduce its performance. Novelty. This paper presents a technique for diagnosing open circuit failures in the switches (IGBTs) of power converters (DC-DC converters and three-phase inverters) in a grid-connected photovoltaic system. Purpose. To ensure supply continuity, a fault-diagnosis process is required throughout all phases of energy production, transfer, and conversion. Methods. The diagnostic approach is based on artificial neural networks and the extraction of features corresponding to the open circuit fault of the IGBT switch. This approach is based on the Clarke transformation of the three-phase currents of the inverter output as well as the calculation of the average value of these currents to determine the exact angle of the open circuit fault. Results. This method is able to effectively identify and localize single or multiple open circuit faults of the DC-DC converter IGBT switch or the three-phase inverter IGBT switches.

Research on polarization characteristics of background light by modified polarization difference imaging method

<sec>The random scattering event of light by water medium is the primary reason for the degradation in underwater imaging. Underwater polarization imaging technology can enhance the signal-to-noise ratio of imaging effectively by utilizing the polarization information difference between background scattered light and target light. However, as scattering events increase in the water body, it is difficult to maintain the polarization characteristics of light, which reduces the effect of removing scattering based on polarization characteristics. In addition, the polarization rule of background scattered light in water is unclear, and there is a lack of quantitative description of the polarization characteristics of scattered light. Therefore, the study of polarization transmission characteristics of underwater scattered light is of great significance in reducing the scattering light of underwater polarization imaging.</sec><sec>In order to clarify the polarization characteristics of underwater background scattered light, especially the polarization angle information, this paper proposes a method for ascertaining polarization angle of background light based on modified polarization difference imaging method. In this method, the coupling relationship between optimal weight coefficient and enhancement measure evaluation (EME) value of the Stokes vector difference result is analyzed, and the background light polarization angle is calculated based on the optimal weight coefficient. Combined with the experimental results, the EME distribution trend of the optimal weight coefficient and the modified polarization difference imaging method results in different turbidity water bodies are determined, the scattering suppression limit is explored, and the trend of background scattered light polarization direction with turbidity of water is analyzed. The results show that the proposed method can obtain the exact polarization angle of background scattered light in different water environments, revealing a trend that the polarization direction of background scattered light becomes orthogonal to the incident light direction as the turbidity of the water increases. This research provides a methodological basis for determining the polarization direction of the background scattered light in underwater imaging.</sec>

Blind detection of circular image rotation angle based on ensemble transfer regression and fused HOG.

Aiming at the problems of low accuracy in estimating the rotation angle after the rotation of circular image data within a wide range (0°-360°) and difficulty in blind detection without a reference image, a method based on ensemble transfer regression network, fused HOG, and Rotate Loss is adopted to solve such problems. The proposed Rotate Loss was combined to solve the angle prediction error, especially the huge error when near 0°. Fused HOG was mainly used to extract directional features. Then, the feature learning was conducted by the ensemble transfer regression model combined with the feature extractor and the ensemble regressors to estimate an exact rotation angle. Based on miniImageNet and Minist, we made the circular random rotation dataset Circular-ImageNet and random rotation dataset Rot-Minist, respectively. Experiments showed that for the proposed evaluation index MSE_Rotate, the best single regressor could be as low as 28.79 on the training set of Circular-ImageNet and 2686.09 on the validation set. For MSE_Rotate, MSE, MAE, and RMSE on the test set were 1,702.4325, 0.0263, 0.0881, and 0.1621, respectively. And under the ensemble transfer regression network, it could continue to decrease by 15%. The mean error rate on Rot-Minist could be just 0.59%, significantly working easier in a wide range than other networks in recent years. Based on the ensemble transfer regression model, we also completed the application of image righting blindly.

End-to-End Moving Target Indication for Airborne Radar Using Deep Learning

Moving target indication (MTI) based on space–time adaptive processing (STAP) has been widely used in airborne radar due to its ability for clutter suppression performance. However, the existing MTI methods suffer from the problems of insufficient training samples and low detection probability in a non-homogeneous clutter environment. To address these issues, this paper proposes a novel deep learning framework to improve target indication capability. First, combined with the problems of target indication caused by the non-homogeneous clutter, the clutter-plus-target training dataset was modeled by simulation, where various non-ideal factors, such as aircraft crabbing, array errors and internal clutter motion (ICM), were considered. The dataset considers various realistic situations, making the proposed method more robust. Then, a five-layer two-dimensional convolutional neural network (D2CNN) was designed and applied to learn the clutter and target characteristics distribution. The proposed D2CNN can predict the target with a high resolution to implement an end-to-end moving target indication (ETE-MTI) with a higher detection accuracy. In this D2CNN, the input was obtained by the clutter-plus-target angle-Doppler spectrum with a low-resolution estimated only by a few samples. The label was given by the target angle-Doppler spectrum with a high-resolution obtained by the target’s exact angle and Doppler. Thirdly, the proposed method used a few samples to improve the target indication and detection probability, which solved the problem of insufficient samples in the non-homogeneous clutter environments. To elaborate, the proposed method directly implements ETE-MTI without the support of the conventional STAP algorithm to suppress the clutter. The results verify the validity and the robustness of the proposed ETE-MTI with a few samples in the non-homogeneous and low signal-to-clutter ratio (SCR) environments.

Buckling analysis of variable stiffness composite plates with elliptical cutouts using an efficient RPIM based on naturally stabilized nodal integration scheme

Buckling resistance of variable stiffness composite (VSC) plates can be significantly improved by designing fiber orientation distributions, which affect structural stiffness and stress distribution. In this paper, a meshless model of VSC plates is developed using a radial basis point interpolation method (RPIM) based on the naturally stabilized nodal integration (NSNI) scheme, and the buckling behavior of the VSC plates with elliptical cutouts is investigated. In this model, a set of nodes is used to discretize the problem domain, which makes the loading response of the VSC plates can be calculated by its exact fiber angle. And the mechanical behavior of the VSC plates with various complex geometries and cutouts can be accurately simulated. This meshless method is verified by comparing with the finite element method (FEM) and semi-analytical solutions. And compared with the traditional RPIM based on the Gaussian integration (GI), NSNI-based RPIM achieves considerable enhancement in computational efficiency while maintaining high accuracy. Employing this efficient meshless method, the buckling behavior of the VSC plates with elliptical cutouts for different boundary conditions is studied. And the effects of size and location of the cutout on the buckling response of the VSC plates are analyzed. The research on the VSC plates with cutouts in this paper has practical implications for the design of cutouts for VSC plates and provides a new method for the numerical research of VSC plates.

Online Instruction to Measure Axial Alignment with the Bonesetter App.

Background and objectives: Alignment of the lower extremity is important when treating congenital deformities, fractures, and joint replacement. During the COVID-19 pandemic, AO North America offered an online course on deformity measurement and planning. The Bonesetter app is a deformity planning tool that is freely available online. The purpose of this study was to see how effective an online course was in teaching axial alignment measurement and to assess that skill using an online digital planning tool, the Bonesetter app. Materials and Methods: An online module on axial alignment was provided during the AONA osteotomy course as well as a tutorial on how to use an online digital planning tool (Bonesetter app). The tools within the Bonesetter app allow users to draw digital lines directly on the CT images and measure the exact angle between two planes. Participants in this study were directed to perform these measurements in four different cases that tested different variations of deformity. Results: The measurements were completed correctly in case 1 = 56%, case 2 = 61%, case 3 = 84%, and case 4 = 76%. The standard deviation of angular digital measurements between individuals was ±4.26 degrees. Measuring the angle directly vs. drawing angles to a horizontal line had smaller standard deviations per case (p < 0.005) and less incidents outside 1 standard deviation for each measurement. Errors in adding and subtracting were the most common errors, particularly in relation to femoral anteversion or retroversion. Conclusions: The online course successfully instructed a group of orthopedic surgeons to measure alignment and malalignment of lower limb axial deformities. The Bonesetter app helped participants to learn this skill and identify errors in measurement. The inability to differentiate between anteversion and retroversion of the femur is a common source of error when it occurs and should be a focus of instruction.

Laboratory Evaluation of the (355, 532) nm Particle Depolarization Ratio of Pure Pollen at 180.0° Lidar Backscattering Angle

While pollen is expected to impact public human health and the Earth’s climate more and more in the coming decades, lidar remote sensing of pollen has become an important developing research field. To differentiate among the pollen taxa, a polarization lidar is an interesting tool since pollen exhibit non-spherical complex shapes. A key attribute is thus the lidar particle depolarization ratio (PDR) of pollen, which is however difficult to quantify as pollen are large and complex-shaped particles, far beyond the reach of light scattering numerical simulations. In this paper, a laboratory π-polarimeter is used to accurately evaluate the PDR of pure pollen, for the first time at the lidar exact backscattering angle of 180.0°. We hence reveal the lidar PDR of pure ragweed, ash, birch, pine, cypress and spruce pollens at 355 and 532 nm lidar wavelengths, as presented at the ELC 2021 conference. A striking result is the spectral dependence of the lidar PDR, highlighting the importance of dual-wavelength (or more) polarization lidars to identify pollen taxa. These spectral and polarimetric fingerprints of pure pollen, as they are accurate, can be used by the lidar community to invert multi-wavelength lidar polarization measurements involving pollen.

Raman imaging of twist angle variations in twisted bilayer graphene at intermediate angles

Van der Waals layered materials with well-defined twist angles between the crystal lattices of individual layers have attracted increasing attention due to the emergence of unexpected material properties. As many properties critically depend on the exact twist angle and its spatial homogeneity, there is a need for a fast and non-invasive characterization technique of the local twist angle, to be applied preferably right after stacking. We demonstrate that confocal Raman spectroscopy can be utilized to spatially map the twist angle in stacked bilayer graphene for angles between 6.5∘ and 8∘ when using a green excitation laser. The twist angles can directly be extracted from the moiré superlattice-activated Raman scattering process of the transverse acoustic (TA) phonon mode. Furthermore, we show that the width of the TA Raman peak contains valuable information on spatial twist angle variations on length scales below the laser spot size of ∼500 nm.

ESKİ BİR FOTOĞRAFIN PEŞİNDE KENTİN OTOETNOGRAFİK İZİNİ SÜRMEK: YENİDEN FOTOĞRAFLANAN ÇUKURÇARŞI’DAN GERİYE KALANLAR

This study, which started with a well-known photograph of the famous Çukurçarşı, one of the vital spots in the history of Eskişehir, seeks to narrate the change and transformation of the city within the subject-space relationship based on personal and social memory with a historical background. In this study, a particular method is proposed with regards to the perspective of visual sociology toward urban space, and a research based on this method is designed and carried out. This research is designed in three phases that initiate with selecting an old photograph of the city and tracing its path. The first phase consists of experiencing the field through an autoethnographic lens and taking notes. In the second phase, the researcher finds the location where the photo was taken and takes a new photo of it from the exact angle and spot using the rephotography technique. In the last phase, which is designed as 'art within the scope of the research', a photo collage is designed by wandering through the depths of the archive and bringing together the images, newspaper clippings, photos taken by local photographers, maps, catalogs and booklets that depict and describe Eskişehir Köprübaşı and Çukurçarşı. The art technique in this phase is reflected through the artistic skills and competencies of the researcher/photographer.

Paper 09: Postage-Stamp Glenoid Fracture after Bankart Repair. How Many Anchors are Safe? - A Biomechanical Analysis

Objectives:Fractures of anterior glenoid rim, aka “Postage-Stamp” fractures, are potential complications of arthroscopic Bankart repairs that occur when a fracture line propagates through previous anchor sites producing a serrated edge. (Fig.1: A and J) Placing multiple anchors adjacent to glenoid rim in attempt to recreate the labral bumper was suggested to reduce the risk of recurrent dislocation after surgery, [Boileau et al 2006] as well as to create a stress riser that may predispose to fracture if another traumatic event may occur.This controlled laboratory study investigated the effect of increased number holes, and different types and sizes of suture anchors on the load necessary to create Postage-Stamp fractures. Our objective was to establish a safe number of anchors that could be inserted in the anterior glenoid rim without incurring in a substantially high risk of fracture.Hypothesis:Increasing the number of holes and anchors and their size would decrease forces necessary to break the anterior glenoid rim.Methods:We tested 46 synthetic scapulae with similar compressive strength and elastic modulus of human glenoid (4th gen. composite scapulae, Sawbones, Pacific Research Laboratories, USA) in a servohydraulic apparatus (Fig.1: B and H) following a previous published biomechanical model. [Farmer et al2014] A guide ensured holes were drilled and anchors were inserted in the same exact angle, depth and location for every specimen. (Fig.1: C to F) A metallic humeral head applied force to the anterior glenoid rim at 1mm/s until fracture occurred. (Fig. 1: G to K) Load-to-fracture of intact glenoid was compared to groups of drilling anchor holes (# 3,4,5,6 and 7) of different diameters (1.6mm and 3mm), and groups with anchors of different sizes and types (1.6mm all-suture and 3mm core anchors).(Fig.1: I to K) One-way ANOVA followed by Turkey post-hoc test compared groups to determine the number of holes necessary to weaken glenoids below 70% of intact value with a p value <0.005.Results:Intact glenoid mean load-to-fracture was 1,238 ± 74N. Drilling 3 to 7 holes of 1.6mm-diameter linearly reduced load to 93%, 89%, 74%, 56% and 52% of intact value respectively, while 3.0mm drill holes reduced load to 87%, 65%, 51%, and 40% respectively.(Fig.2) Directly comparing drill role sizes there were significant differences on the 4, 5 and 7 holes groups (p=0.045, 0.032 and 0.015, respectively), so that a glenoid could safely sustain up to 5 holes of 1.6mm, but no more than 3 holes of 3.0mm-diameter.(Fig.3)Inserting 1.6mm “all-suture” anchors in the 1.6mm-diameter holes did not change the load-to-fracture on the 4 or 5 holes groups (Fig.4A), indicating that the number of drill holes was the main determinant of anterior glenoid rim strength, so that the all-suture anchors did not act as stress risers. Thus, up to 5 “all-suture” 1.6mm anchor could be safely used on a Bankart repair.The 3.0mm “core” anchors increased the load-to-fracture when compared to the group with the same number of holes of the same diameter size. Despite 4 holes of 3.0mm-diameter decreased the load-to-fracture bellow the safety line of 70% of intact value, the group with 4 anchors of 3.0mm-diameter “core” anchors increased load-to-fracture to 85% of intact value (p=0.033).(Fig.4B) This stress shield effect of the 3.0mm core anchor was not noticed on the 5 anchors group, in which the overall strength of the construction was bellow the 70% of intact safety line.Conclusions:Our data call in that up to four 3.0mm “core” anchors or five 1.6mm-diameter “all-suture” anchors could be safely inserted in the anterior glenoid rim without incurring in increased risk of Postage-Stamp fracture. One should prefer small diameter anchors if more than 4 anchors were intended on a Bankart repair.This study contributed to important data about number, size and type of anchors that the anterior glenoid rim could safely sustain in order to avoid postage-stamp fracture in case a new traumatic dislocation episode occur after a Bankart repair, which is of clinical interest in high risk population preoperative planning and selection of implant size, type and number.

Metacarpal fractures — A method to simulate life-like fractures in human cadaveric specimens for surgical education

Metacarpal fractures are a type of fracture which trauma surgeons face frequently. Restoration of hand function is the primary objective. The aim of this study was to investigate whether life-like fractures of human cadaveric metacarpals with intact soft-tissue envelope could be simulated for surgical education. Six fresh-frozen human distal forearm and hand specimens were fractured on a custom-made drop-test bench. This reproducible method is based on a weight falling from a predefined height onto the fixed specimens. All fractures were analyzed by fluoroscopy and CT. In all specimens included in this study, several typical lesions were created, resulting in a total of 19 metacarpal fractures. There were 6 fractures involving the capital region, 5 metaphyseal fractures with partial involvement of the diaphysis and 7 pure diaphyseal fractures. One metacarpal comprised a trifocal lesion consisting of a metaphyseal undisplaced fracture, a diaphyseal wedge fracture and a non-displaced articular base fracture. Human cadaveric metacarpals with intact soft tissue can be successfully fractured by a drop-test bench setup. The resulting fractures resemble realistic fracture patterns. Load and exact load angle seem to be critical. Such fractured specimens can be used in surgical education courses. Courses providing fractured specimens with intact soft-tissue envelope can improve clinical teaching for young surgeons and experts alike.

Cyber Psychological Case Studies of Sextortion for Identifying the Accused in the Offences Committed on Social Media

Human behaviors can never fail to astound society. People behave as they want in their privacy and sometimes it can be weirdest, dark, and taboo. Sex is not a routine and normal topic in the conversation of Indian society. Therefore, people are very secretive about their sexual beliefs, thoughts, and sexuality. Whenever anybody does anything where she/he knows that their act is not going to be known by others people tend to involve in such acts. This is the exact angle that blackmailers in sextortion have identified and they get success too in duping people. They threaten people to viral their videos or chat in the sexual act. But, the Majority of the crimes committed on social media go unreported or untraced. Due to lack of procedural setups to identify the accuses. especially in the cases of sextortion where name and shame in the society are attacked of any individual. The present research paper aims to provide a simple procedural method to identify the accused in the offences committed on social media. The authors of the research paper have chatted with the 11 blackmailers of sextortion on social media and the authors were able to identify the location of the accused. The research paper is attempting to explain the dynamics of crime and victimization of sextortion from a cyber psychological perspective.

“Crack under pressure”—Inducing life-like mandible fractures as a potential benefit to surgical education in oral and maxillofacial surgery

The aim of this study was to investigate whether life-like fractures of human cadaveric mandibles with a focus on the condylar process and the intact soft tissue envelope could be simulated.A total of nine fresh-frozen human head specimens were fractured in a custom-made drop-test bench. This reproducible method is based on a weight falling from a defined height onto the fixed specimens, simulating a direct blow to the symphysis of the mandible. All the fractures were analyzed by fluoroscopy and CT-scans.In all the specimens that were included in this study, several typical lesions could be created, resulting in a total of 27 mandible fractures. Seven condylar head fractures with intracapsular fracture patterns, three high, two low and five subcondylar fractures as well as different corpus fractures occurred. Human cadaveric mandibles as part of a complete head specimen with intact soft tissue can be successfully fractured by means of a drop-test bench setup. The amount of load and the exact angle at which the load is applied seem to be of high relevance. Such fractured specimens can be implemented in surgical education courses to teach and improve osteosynthetic techniques.

Shaping ability of 2Shape and NeoNiTi rotary instruments in preparation of curved canals using micro-computed tomography

BackgroundVarious systems of nickel-titanium (NiTi) instrument have long been commercially available. However, the preparation of narrow and curved root canals has always been challenging. The purpose of this study was to compare the shaping ability of two NiTi systems (2Shape and NeoNiTi) in severely curved root canals with different morphological patterns using micro-computed tomography (Micro-CT).MethodsA total of 22 human extracted permanent teeth of mandibular first molars, with the exact mesial angle of curvature of 25 and 35 degrees, according to Schneider’s technique, were distributed randomly into two groups (group I: 2Shape, group II: NeoNiTi) based on the rotary system used (n = 22). The groups were subdivided into two subgroups corresponding to the angle of canal curvature (25° and 35°) (n = 11). Canals were scanned using Micro-CT pre- and post-preparation to assess the volume of dentin removed; canal transportation; and canal centering ratio at 3, 6, and 9 mm from the apex. The Mann–Whitney U test was utilized to determine any significant differences between the two systems. The level of statistical significance was set at p < 0.05.ResultsThere was no significant difference between the two groups in volume of dentin removed; canal transportation; and centering ability for 25° and 35° canal curvatures at 3, 6, and 9 mm from the apex (coronal, middle, and apical) thirds (p > 0.05). At the middle third, the NeoNiTi group demonstrated a statistically significant increase in volume of dentin removed for 35° canal curvatures compared to the 2Shape group.ConclusionWithin the limitation of our in vitro study, 2Shape and NeoNiTi systems with severely curved canals were confirmed to be relatively safe in preparation and to respect original canal anatomy. Nevertheless, NeoNiTi instruments produced more centered preparation and minimal canal deviation compared to the 2Shape system.

Vibration transmission across fractured beam-to-column junctions of reinforced concrete

To detect human survivors trapped in buildings after earthquakes by using structure-borne sound it is necessary to have knowledge of vibration transmission in collapsed and fragmented reinforced-concrete buildings. In this paper, Statistical Energy Analysis (SEA) is used to model the vibration transmission in seismic damaged reinforced concrete beam-to-column junctions where the connection between the beam and the column is made only via the steel reinforcement. An ensemble of 30 randomly damaged beam-to-column junctions was generated using a Monte Carlo simulation with FEM. Experimental SEA (ESEA) is then considered with two or three subsystems to determine the CLFs between the beam and the column with either bending modes or the combination of all mode types. It is shown that bending modes dominate the dynamic response and that the uncertainty of predicting the CLFs using FEM with ESEA is sufficiently low that it should be feasible to estimate the coupling even when the exact angle between the beam and the column is unknown. In addition, the use of two rather than three subsystems for the junction significantly decreases the number of negative coupling loss factors with ESEA.