Elliptical Head Research Articles

Analysis of remaining life assessment of three-phase gravity separator for oil rectification with the simultaneous usean RBI matrix

The paper presents a detailed description of the oil rectification process used in upstream oil and gas plants, including the significant equipment involved. One such equipment highlighted in the study is a pressure vessel utilized as a separator to separate the liquid and gas phases. This pressure vessel has been in operation for over two decades. A thorough examination of the mentioned pressure equipment was conducted during the process evaluation. It was discovered that the internal side of the vessel, particularly its back elliptical head, had suffered extensive damage due to erosion and corrosion, emerging as the most significant cause of the deterioration. The application of RBI-estimation revealed that the vessel falls under the category of highly risk equipment, and there is a significant risk of both environmental and financial consequences associated with its potential failure (leakage). Such failure is anticipated to occur promptly in the area below the wear plate of the vessel's nozzle.

Experimental and numerical study on mechanical performance of single shear bolted connections with novel elliptical one-sided bolts

One-sided bolts, which typically employed for connecting components with closed cross section, often present complexities in both construction and installation. Addressing the limitations of conventional one-sided bolts, this study introduces a novel variant distinguished by its elliptical head, offering ease of installation without the need for specialized tools. Due to the special shape of the bolt head, the mechanical properties of the bolt need to be studied in depth. To investigate the shear properties of the novel elliptical one-sided bolts, three sets of single lap shear experiments were conducted. Subsequently, finite element numerical analyses were employed to simulate these experiments, facilitating the development of a reliable finite element model. Furthermore, parametric analyses were undertaken to examine the influence of various parameters on the ultimate shearing capacity and displacement of joints. The findings indicate that the shear capacity of the single lap joint employing novel elliptical one-sided bolts closely rivals that of ordinary hexagonal bolts with equivalent diameters. However, an enhancement in slip resistance capacity is observed in the novel elliptical one-sided bolt joints compared to hexagonal bolts. Notably, the parameters of the bolt exert a more pronounced impact on the ultimate shearing capacity and displacement of joints when contrasted with parameters associated with the plates. The recommended torque coefficient for the novel elliptical one-sided bolt is established as 0.2, and it is recommended to use appropriate torque to ensure the slip performance of the joint during practical application.

STensile behaviour of T-stub to hollow section column using elliptical-head one-side bolts

The Elliptical-head one-side bolt (EOB) is a typical representative of the third generation for one-side bolts, relying on its elliptical head and bolt hole to achieve orthogonal anchorage, and the application scenario is mainly the bolted connection of closed-section members. Studies have been reported for the shear performance of EOBs bolted lap connections and the tensile behaviour of concrete-filled steel tubes, but there is still a lack of the tensile performance of EOBs connecting Hollow section columns (HSCs), which is necessary for the application of the component method for the beam-column joints design. Therefore, numerical simulation and theoretical analysis methods were employed in this paper to demonstrate the feasibility of adopting EOBs for this type of connection, including typical failure modes, novel yield line pattern in the HSC wall, comparison with the Conventional high-strength bolt (CHB) connections, analysis of the parameters related to the elliptical bolt head and hole, and the establishment and validation of the methodology for calculating the HSC bearing capacity. The results show that: The novel trapezoidal yield line pattern tended to show in the HSC wall with the smaller bolt pitch distance and larger gauge distance; The yield strength of the EOBs bolted T-stub to HSC connections was reduced by about 15% compared to the CHBs bolted ones; Vertical layout of bolt holes, accuracy of rough assembly, rotation deviation of bolt shank within 20° and avoidance of bolt offsets in bolt hole were recommended for EOB connections; The novel yield line pattern established in this paper predicted the yield strength of the connections, and the accuracy and stability were verified by comparing with finite element modelling (FEM) results.

Shear performance of elliptical head one-sided bolt double-lapped joint with plug-in gasket

One-sided bolts are commonly used for bolted connections between closed section members to address the issue of insufficient space for nut installation. Among them, the elliptical head one-sided bolt uses the difference in length between its long and short axes. This allows the bolt head to be inserted into the elliptical bolt hole and subsequently rotated by 90 degrees, effectively achieving anchoring. But the use of elliptical bolt holes may cause some problems, such as bolt slippage and stress concentration around the bolt holes. In this paper, building upon the elliptical head one-sided bolt concept, a novel structure for one-sided bolted connection is proposed, incorporating a plug-in gasket to improve the mechanical properties of the elliptical one-sided bolted joints. Six sets of steel plate double-lapped joints, connected by elliptical head one-sided bolts and plug-in gaskets, were designed for shear resistance tests. A finite element model was designed using ABAQUS, based on the test specimen parameters. By comparing the simulation results with the experimental findings, the reinforcing effect of the gasket on joint stress was analyzed and validated. The results show that the plug-in gasket effectively resolves the excessive slippage issues and enhances the initial stiffness of the joint. Moreover, when pressure is applied to the bolt hole, the plug-in gasket reduces the stress concentration caused by the extrusion between the bolt hole and the bolt shank, thus preventing local premature failure of the bolt hole.

A free-swimming tadpole model based on immersed boundary-lattice Boltzmann method and its application

A two-dimensional (2D) free-swimming tadpole model is built in this study using the immersed boundary-lattice Boltzmann method. The tadpole is developed by connecting a passive elliptical head with a beating tail. This developed tadpole is capable of controlling the tail swing amplitude to change the swimming speed and achieve the desired swimming direction by attaching an angle offset on the tail axis. The hydrodynamics of the proposed tadpole model in swimming is investigated by regulating the width of the confined space. To be specific, three points are summarized below. First, a lower swimming speed will be produced in a narrower channel under the identical swimming pattern. Second, under the effect of a slight swing strength, a small-scale disturbance is triggered to the surrounding fluid, and a small swimming speed will be generated. Third, a relatively small or excessive swimming speed adversely affects the stability of its swimming. Moreover, a perception-response strategy for the tadpole is further formulated to achieve its autonomous locomotion control. A virtual perceptive field is proposed as the visual range, which is conducive to implementing tadpole motion control based on a set of mechanical response rules. With the above-mentioned improvements, the tadpole can effectively achieve obstacle avoidance in sophisticated obstacle array environments and tracking sine curve routines. Accordingly, this study can provide a valuable reference for the theoretical design of underwater bionic tadpole-like robots.

Contact Mechanics of Elliptical and Spherical Head Implants during Axial Rotation in Anatomic Total Shoulder Arthroplasty: A Biomechanical Comparison.

Elliptical humeral head implants have been proposed to result in more anatomic kinematics following total shoulder arthroplasty (aTSA). The purpose of this study was to compare glenohumeral contact mechanics during axial rotation using spherical and elliptical humeral head implants in the setting of aTSA. Seven fresh-frozen cadaveric shoulders were utilized for biomechanical testing in neutral (NR), internal (IR), and external (ER) rotation at various levels of abduction (0°, 15°, 30°, 45°, 60°) with lines of pull along each of the rotator cuff muscles. Each specimen underwent the following three conditions: (1) native, and TSA using (2) an elliptical and (3) spherical humeral head implant. Glenohumeral contact mechanics, including contact pressure (CP; kPa), peak contact pressure (PCP; kPa), and contact area (CA; mm2), were measured in neutral rotation as well as external and internal rotation using a pressure mapping sensor. Elliptical head implants showed a significantly lower PCP in ER compared to spherical implants at 0° (Δ-712.0 kPa; p = 0.034), 15° (Δ-894.9 kPa; p = 0.004), 30° (Δ-897.7 kPa; p = 0.004), and 45° (Δ-796.9 kPa; p = 0.010) of abduction, while no significant difference was observed in ER at 60° of abduction or at all angles in NR and IR. Both implant designs had similar CA in NR, ER, and IR at all tested angles of abduction (p > 0.05, respectively). In the setting of aTSA, elliptical heads showed significantly lower PCP during ER at 0° to 45° of abduction, when compared to spherical head implants. However, in NR and IR, PCP was similar between implant designs. Both designs showed similar CA during NR, ER, and IR at all abduction angles. basic science; controlled laboratory study.

Analysis of discontinuity stress at shell and elliptical head juncture using theory of beam on elastic foundation

A thin-walled pressure vessels under internal pressure generates higher amount of stresses at shell-head juncture compared to membrane stress. These localized stresses are generated due to change in the shape of the meridian. The change in shape of the meridian is seen at the head and shell junction. The discontinuity in shape changes the direction of resultant stress. To predict the accurate stresses around the discontinuity region, bending of beam on an elastic foundation is used as part of the analytical analysis. Charts have been plotted of various stresses generated near juncture. The method is applied to pressure vessel with cylindrical shell and elliptical head. The theoretical results are then compared to the analytical results obtained from finite element analysis (FEA). In the present work, the discontinuity stresses have been evaluated analytically and the same is also compared with the finite element analysis results. It is found that the results of FE analysis closely agrees with the analytical results maximum percentage variation of 1.19.

Elliptical and spherical heads show similar obligate glenohumeral translation during axial rotation in total shoulder arthroplasty

BackgroundElliptical shape humeral head prostheses have been recently proposed to reflect a more anatomic shoulder replacement. However, its effect on obligate glenohumeral translation during axial rotation compared to a standard spherical head is still not well understood. The purpose of the study was to compare obligate humeral translation during axial rotation using spherical and elliptical shaped humeral head prostheses. It was hypothesized that the spherical head design would show significantly more obligate translation when compared to the elliptical design.MethodsSix fresh-frozen cadaveric shoulders were utilized for biomechanical testing of internal (IR) and external (ER) rotation at various levels of abduction (0°, 30°, 45°, 60°) with lines of pull along each of the rotator cuff muscles. Each specimen underwent the following three conditions: (1) native; total shoulder arthroplasty (TSA) using (2) an elliptical and (3) spherical humeral head implant. Obligate translation during IR and ER was quantified using a 3-dimensional digitizer. The radius of curvature of the superoinferior and anteroposterior dimensions of the implants was calculated across each condition.ResultsPosterior and inferior translation as well as compound motion of spherical and elliptical heads during ER was similar at all abduction angles (P > 0.05, respectively). Compared to the native humeral head, both implants demonstrated significantly decreased posterior translation at 45° (elliptical: P = 0.003; spherical: P = 0.004) and 60° of abduction (elliptical: P < 0.001; spherical: P < 0.001). During internal rotation at 0° abduction, the spherical head showed significantly more compound motion (P = 0.042) compared to the elliptical head. The spherical implant also demonstrated increased anterior translation and compound motion during internal rotation at 60° abduction (P < 0.001) compared to the resting state. This difference was not significant for the native or elliptical head design at this angle (P > 0.05).ConclusionIn the setting of TSA, elliptical and spherical head implants showed similar obligate translation and overall compound motion during axial rotation. A gained understanding of the consequences of implant head shape in TSA may guide future surgical implant choice for better recreation of native shoulder kinematics and potentially improved patient outcomes.Level of evidenceControlled Laboratory Study.

A Novel Freshwater Cyanophage Mae-Yong1326-1 Infecting Bloom-Forming Cyanobacterium Microcystis aeruginosa.

Microcystis aeruginosa is a major harmful cyanobacterium causing water bloom worldwide. Cyanophage has been proposed as a promising tool for cyanobacterial bloom. In this study, M. aeruginosa FACHB-1326 was used as an indicator host to isolate cyanophage from Lake Taihu. The isolated Microcystis cyanophage Mae-Yong1326-1 has an elliptical head of about 47 nm in diameter and a slender flexible tail of about 340 nm in length. Mae-Yong1326-1 could lyse cyanobacterial strains across three orders (Chroococcales, Nostocales, and Oscillatoriales) in the host range experiments. Mae-Yong1326-1 was stable in stability tests, maintaining high titers at 0–40 °C and at a wide pH range of 3–12. Mae-Yong 1326-1 has a burst size of 329 PFU/cell, which is much larger than the reported Microcystis cyanophages so far. The complete genome of Mae-Yong1326-1 is a double-stranded DNA of 48, 822 bp, with a G + C content of 71.80% and long direct terminal repeats (DTR) of 366 bp, containing 57 predicted ORFs. No Mae-Yong1326-1 ORF was found to be associated with virulence factor or antibiotic resistance. PASC scanning illustrated that the highest nucleotide sequence similarity between Mae-Yong1326-1 and all known phages in databases was only 17.75%, less than 70% (the threshold to define a genus), which indicates that Mae-Yong1326-1 belongs to an unknown new genus. In the proteomic tree based on genome-wide sequence similarities, Mae-Yong1326-1 distantly clusters with three unclassified Microcystis cyanophages (MinS1, Mwe-Yong1112-1, and Mwes-Yong2). These four Microcystis cyanophages form a monophyletic clade, which separates at a node from the other clade formed by two independent families (Zierdtviridae and Orlajensenviridae) of Caudoviricetes class. We propose to establish a new family to harbor the Microcystis cyanophages Mae-Yong1326-1, MinS1, Mwe-Yong1112-1, and Mwes-Yong2. This study enriched the understanding of freshwater cyanophages.

Genomic analysis of a novel active prophage of Hafnia paralvei.

Little is known about the prophages in Hafniaceae bacteria. A novel Hafnia phage, yong2, was induced from Hafnia paralvei by treatment with mitomycin C. The phage has an elliptical head with dimensions of approximately 45 × 38nm and a long noncontractile tail of approximately 157 × 4nm. The complete genome of Hafnia phage yong2 is a 39,546-bp double-stranded DNA with a G+C content of 49.9%, containing 59 open reading frames (ORFs) and having at least one fixed terminus (GGGGCAGCGACA). In phylogenetic analysis, Hafnia phage yong2 clustered with four predicted Hafnia prophages and one predicted Enterobacteriaceae prophage. These prophages and members of the family Drexlerviridae together formed two distinct subclades nested within a clade, suggesting the existence of a novel class of prophages with conserved sequences and a unique evolutionary status not yet studied before in Hafniaceae and Enterobacteriaceae bacteria.

A creeping-wave elliptic-head model that explains non-monotonic envelope interaural time differences

Interaural time and level differences (ITDs and ILDs) created by interactions of impinging sound with the head facilitate horizontal-plane sound localization. ILDs are known to be non-monotonic functions of azimuth, resulting in predictable mislocalization of tonal sources at some frequencies, while ITDs are typically construed as monotonic functions of azimuth. However, recent measurements using a binaural mannequin revealed envelope ITDs (ENV-ITDs) that were non-monotonic functions of azimuth, with the extent of nonmonotonicity dependent on carrier frequency. This study proposes that delayed sound traveling around the back of the head causes this phenomenon. ENV-ITDs created by a time-dependent model of incident sound waves propagating around the front and back of an elliptical head were compared to ENV-ITDs computed using publicly available HRTF libraries for a broadband speech excitation signal. Results from the model align with data from the HRTF libraries, with nonmonotonicities in the ENV-ITD-azimuth functions occurring at nearly identical azimuths and frequencies. These data suggest the veracity of this phenomenon and may have implications for spatial hearing abilities. They also suggest that time-independent models of ITDs that only consider frequency and incident angle, such as spherical head or circular arc length models, could be updated to include such time dependence.

Numerical simulation and an innovative design of the inlet gas distributor in an industrial adsorption tower

Gas distributor plays an important role in operation performance of gas-solid and gas-liquid reactions and separation processes. In this work, computational fluid dynamics method was used to simulate the gas distribution of the inlet gas distributor in an industrial pressure swing adsorption tower. The employed model has been validated with available empirical formula. The simulation results show that the industrial perforated plate gas distributor brings a strong flow along the elliptical head wall and large vortexes. It shows bad gas distribution performance. Therefore, a conical shell gas distributor is proposed. Its structural parameters, such as cone angle and hole distribution are optimized. The optimal cone angle is 166°. Furthermore, an imperforated area with a diameter of 290 mm is necessary to decrease the gas velocity at the center area. The optimal distributor can effectively weaken the large vortexes above the distributor and the high gas velocity at axial center. Compared with the industrial distributor, the inhomogeneity index M of the gas distribution is decreased from 5.61 to 2.48, and the pressure drop △P of the distributor is decreased from 59.3 Pa to 46.0 Pa. In addition, the designed distributor is also suitable for towers with larger diameters.

Stress analysis and applicability analysis of the elliptical head

As the main pressure components of pressure vessels, the mechanical performance of cylinders and heads affects the normal operation of pressure vessels. At present, no unified theoretical formula exists for the connection region between an elliptical head and the cylinder. Therefore, the authors consider the standard elliptical head as the research object. First, the theoretical stress calculation formula is deduced according to the deformation continuity equation. Second, the stress is experimentally measured using an internal-pressure thin-walled-vessel stress measurement device, and the theoretical and experimental stress values in the discontinuous region between the elliptical head and cylinder are analysed and compared to verify the accuracy and applicability of the theoretical stress calculation formula. The results show that the theoretical stress calculation formula in the discontinuous region between the elliptical head and cylinder is valid. By comparing and analysing the theoretical and experimental stress values, the accuracy and applicability of the theoretical stress calculation formula in the discontinuous region are verified. The findings can provide guidance for the stress measurement of internal-pressure vessels.

Design and Analysis of Mechanical Microswimmers

The fascinating field in present civilization scenario at the edge of science is micro-swimmers, which is a combination of bio physics with self-propulsion mechanisms involving swimming strategies at low Reynolds number. These micro swimming robots offer many advantages in biomedical applications such as drug delivery to some specific locations in our human body and also conducting some surgical operations like opening of blocked arteries etc. In recent times, blocked arteries become a major case in the medical world. This is can be diagnosed by Angioplasty (is a minimally invasive, endovascular procedure to widen narrowed or obstructed arteries or veins, typically to treat arterial atherosclerosis) method. So this is the main reason to choose the aorta as our domain for analysis purpose. This paper presents a micro-swimmer with three different heads they are spherical head, Capsule type head and Tapered cylindrical or elliptical head and modelled using SOLIDWORKS and analysis in ANSYS FLUENT.

Elliptical heads result in increased glenohumeral translation along with micro-motion of the glenoid component during axial rotation in total shoulder arthroplasty

IntroductionElliptical-shaped humeral head prostheses have recently been proposed to reflect a more anatomic shoulder replacement. However, its subsequent effect on micro-motion of the glenoid component is still not understood.Materials and methodsSix fresh-frozen, cadaveric shoulders (mean age: 62.7 ± 9.2 years) were used for the study. Each specimen underwent total shoulder arthroplasty using an anatomic stemless implant. At 15°, 30°, 45° and 60° of glenohumeral abduction, 50° of internal and external rotations in the axial plane were alternatingly applied to the humerus with both an elliptical and spherical humeral head design. Glenohumeral translation was assessed by means of a 3-dimensional digitizer. Micro-motion of the glenoid component was evaluated using four high-resolution differential variable reluctance transducer strain gauges, placed at the anterior, posterior, superior, and inferior aspect of the glenoid component.ResultsThe elliptical head design showed significantly more micro-motion in total and at the superior aspect of glenoid component during external rotation at 15° (total: P = 0.004; superior: P = 0.004) and 30° (total: P = 0.045; superior: P = 0.033) of abduction when compared to the spherical design. However, during internal rotation, elliptical and spherical heads showed similar amounts of micro-motion at the glenoid component at all tested abduction angles. When looking at glenohumeral translation, elliptical and spherical heads showed similar anteroposterior and superoinferior translation as well as compound motion during external rotation at all tested abduction angles. During internal rotation, the elliptical design resulted in significantly more anteroposterior translation and compound motion at all abduction angles when compared to the spherical design (P < 0.05).ConclusionIn the setting of total shoulder arthroplasty, the elliptical head design demonstrated greater glenohumeral translation and micro-motion at the glenoid component during axial rotation when compared to the spherical design, potentially increasing the risk for glenoid loosening in the long term.Level of evidenceControlled Laboratory Study

Momentless design of variable stiffness composite cylindrical vessels with elliptical heads

Membrane stress state is favorable for pressure vessels to resist internal pressure since the stress through shell thickness is constant. However, bending stresses resulted from bending moments of pressure vessels will destroy the favorable membrane stress state leading to nonuniform stress through shell thickness. Thus, suppressing bending moments in pressure vessels will be an efficient way to achieve improvement of load carrying capacity. A momentless design of variable stiffness composite cylindrical vessels with elliptical heads which are widely used in engineering has been presented in this study. The momentless governing equations concerning both the elliptical head and junction region of the pressure vessels under uniform pressure are derived. Numerical analyses are carried out on the pressure vessel models with different configurations. The variable angles of fiber orientations over these models are explicitly provided. The stress resultants and deformation behaviors together with the curvature changes of these models have been checked and compared. Results show that based on the variable fiber angles over the structure obtained from the presented mathematical design methodology, the bending moments are successfully suppressed in the variable stiffness composite pressure vessels. The momentless design method will ensure the pressure vessels to service in an efficient membrane state.

Radiographic evaluation of humeral head reconstruction with stemmed and stemless spherical implants compared with stemless elliptical head implants.

BackgroundThe purpose of this study was to compare the accuracy of anatomic reconstruction of three different humeral head designs after anatomic total shoulder arthroplasty.MethodsPostoperative radiographs of 117 patients who underwent anatomic total shoulder arthroplasty with three different implant designs (stemmed spherical, stemless spherical, and stemless elliptical) were analyzed for landmarks that represented the prearthritic state and final implant position. We assessed the change in center of rotati7on and humeral head height on the anteroposterior view and the percentage of prosthesis overhang on the axillary lateral view. A modified anatomic reconstruction index, a compound score that rated each of the 3 parameters from 0 to 2, was created to determine the overall accuracy of the reconstruction.ResultsExcellent modified anatomic reconstruction index scores (5 or 6 points) were achieved by 68.1% of the cases in the stemless elliptical group compared with 33.3% of the cases in the stemless spherical group and by 28.3% of the cases in the stemmed spherical group (P = .001).The mean difference in restoration of humeral head height (P < .001) and percentage of prosthesis overhang (P < .001) was superior for the stemless elliptical group compared with the two other spherical head groups. There was no difference between groups for the shift in center of rotation (P = .060).ConclusionsIn this radiographic investigation comparing three different humeral head designs with respect to anatomic restoration parameters, the stemless elliptical implant more closely restored the geometry of the prearthritic humeral head as assessed by humeral head height, prosthesis overhang, and a compound reconstruction score.

Rotational range of motion of elliptical and spherical heads in shoulder arthroplasty: a dynamic biomechanical evaluation

IntroductionElliptical shape humeral head prostheses have been proposed to reflect a more anatomic shoulder replacement. Its effect on the rotational range of motion (ROM) compared to a standard spherical head is still not understood. The purpose was to investigate if there would be a difference in rotational ROM when comparing elliptical and spherical prosthetic heads in a dynamic shoulder model. The authors hypothesized that the use of elliptical heads would result in significantly more rotational ROM compared to the spherical head design.Materials and methodsSix fresh-frozen, cadaveric shoulders were evaluated using a dynamic shoulder model. After being tested in the native condition, each specimen underwent 6 conditions in the hemiarthroplasty state: (1) matched-fit spherical head, (2) oversized spherical head, (3) undersized spherical head, (4) matched-fit elliptical head, (5) oversized elliptical head, and (6) undersized elliptical head. Following conversion to total shoulder arthroplasty (TSA), the 6 prior conditions were rerun. Each condition was tested at 0°, 30° and 60° of glenohumeral abduction. Rotational ROM was quantified using 3-dimensional tracking, while dynamically applying alternating forces for internal and external rotation via the rotator cuff tendons.ResultsElliptical and spherical prosthetic heads showed no significant difference in the degree of the total, internal, and external rotational ROM for both the hemiarthroplasty and TSA state. Conversion from hemiarthroplasty to TSA resulted in less degree of total rotational ROM for both head designs in all abduction positions, without reaching statistical significance. There was a significant decrease in total, internal, and external rotational ROM for both elliptical and spherical heads in every replacement condition, when comparing 0° to 30° and 60° of abduction (P < 0.05, respectively).ConclusionIn a dynamic shoulder model, elliptical and spherical prosthetic head designs showed no significant difference in the degree of the total, internal, and external rotational ROM in both the hemiarthroplasty and TSA state.Level of evidenceControlled laboratory study

Hydrodynamic study of sperm swimming near a wall based on the immersed boundary-lattice Boltzmann method

This paper presents a numerical study on a sperm swimming in a viscous fluid by using an immersed boundary-lattice Boltzmann method (IB-LBM). The sperm is modeled simply by integrating a slender tail and an elliptical head. By applying a tail traveling wave vertical to the wall, a sperm swims near a surface is simulated. Based on which the corresponding swimming velocity, pressure, and shear stress are analyzed, and the mechanisms of accumulation and acceleration in the swimming process are further investigated. It is found when getting close to the wall, the integration of pressure gradient around the sperm increases, and then, the sperm is accelerated. On the other hand, we also observed that the integration of pressure gradient toward the wall tends to raise; this means a more considerable attraction from the wall occurs. These results provide us some new insights to understand the phenomena of the sperm’s wall acceleration and wall accumulation. Moreover, the variations of the pressure and shear stress indices on the sperm suggested that some perceptible mechanical information based on the flow can be formed. Which reminded us that sperm might be able to sense the flow and adjust its motion.

Fast and robust occluded face detection in ATM surveillance

Crimes with respect to ATMs (Automatic Teller Machines) have attracted more and more attention, where criminals deliberately cover their faces in order to avoid being identified. This paper proposes a fast and robust face occlusion detection algorithm for ATM surveillance, which is demonstrated to be effective and efficient to handle arbitrarily occluded faces. In this algorithm, we innovatively propose to make use of the Omega shape formed by the head and shoulder of the person for head localization to tackle severe face occlusion. For this purpose, we first construct a novel energy function for elliptical head contour detection. Then, we develop a fast and robust head tracking algorithm, which utilizes the gradient and shape cues in a Bayesian framework. Lastly, to verify whether a detected head is occluded or not, we propose to fuse information from both skin color and face structure using the AdaBoost algorithm. Experimental results on real world data show that our proposed algorithm can achieve 98.64% accuracy on face detection and 98.56% accuracy on face occlusion detection, even though there are severe occlusions in faces, at a speed of up to 12 frames per second.