Head Configuration Research Articles

Aerodynamics Analysis of Speed Skating Helmets: Investigation by CFD Simulations

In this work, we investigate the flow field around speed skating helmets and their associated aerodynamic drag by means of computational fluid dynamics (CFD) simulations. An existing helmet frequently used in competition was taken as a baseline. Six additional helmet designs, as well as the bare-head configuration, were analysed. All the numerical simulations were performed via 3D RANS simulations using the SST k-ω turbulence model. The results show that the use of a helmet always reduces the aerodynamic drag with respect to the bare head configuration. Besides, an optimised helmet design enables a reduction of the skaters aerodynamic drag by 5.9%, with respect to the bare-head configuration, and by 1.6% with respect to the use of the baseline Omega helmet.

Case Report: Sapho Syndrome Previously Mistaken for Paget's Disease

SAPHO syndrome is a rare clinical entity, an acronym named for its frequent coincident clinical manifestations, synovitis, acne, pustulosis, hyperostosis, and osteitis. Its clinical phenotype is widely heterogeneous, which coupled with its rarity causes many misdiagnoses. Herein, we present a case of a patient that was previously diagnosed with Paget’s disease. After an MVA, the full extent of his disease was detected via incidental imaging, which demonstrated sclerosis and ankylosis of the lumbar spine, sclerosis of the clavicles, and the pathognomonic bull’s head configuration on bone scan. Upon further questioning, the patient also harbored intermittent palmar pustulosis, psoriasis, sternoclavicular pain and tenderness, and widespread morning joint stiffness that ameliorates with activity. A high index of suspicion, and knowledge of its variable manifestations are paramount to arrive at a SAPHO diagnosis and thereby provide appropriate therapy to the patient.

Investigation of gas-liquid mass transfer and power consumption characteristics in jet-flow high shear mixers

Experimental measurements were performed to systematically investigate the effects of operating conditions and structural configurations of the rotor-stator head on gas-liquid characteristics (volumetric mass transfer coefficient, gas hold-up and bubble dispersion) and power consumption of the jet-flow high shear mixer (HSM). Gas hold-up distribution, bubble dispersion and flow fields under different structural configurations were also analyzed and verified by the computational fluid dynamics (CFD). The results indicated that the gas-liquid mass transfer performance and power consumption in jet-flow HSM were significantly impacted by the structural parameters involving blade angle, blade arc and stator bottom opening. Increasing gas flow rate or reducing surface tension could enhance the gas-liquid mass transfer performance to some extent. In addition, gas hold-up distribution and bubble dispersion in the gas-liquid system were more uniform with the modified configuration of the rotor-stator head. The dimensionless correlations were established based on the experimental data to predict Pog and kLa in gas-liquid operation of the jet-flow HSM: Pog = 0.958⋅(sinθ)1.567(D/(Ds – Db))-0.164 with the standard deviation (σ) of 16%; ShL = 7.92 × 104⋅FlQ0.38Fr0.69Pog0.29 with σ of 17%. This work can provide useful guidance on scaleup design and optimization of the jet-flow HSM to intensify the transfer properties for gas-liquid operation systems.

Compression-hypoxic birth injuries and skull configuration

The fetus has birth traumatic, compression-hypoxic, and hypoxic-ischemic brain lesions during childbirth. There are problems in their differentiation in clinical and anatomopathological practice. It is proposed to divide birth traumatic injuries into two types: 1) obvious traumatic injuries and 2) compression-hypoxic traumatic injuries. Signs of compression-hypoxic birth injuries were found in 24.4% of the examined fetuses and newborns delivered via vacuum extraction and application of obstetric forceps. This allows compression hypoxia to be attributed to birth injury rather than to hypoxic-ischemic encephalopathy. It is proposed to use the concept of compression-hypoxic birth injury. The morphological signs that are characteristic of this type of birth injury are given. It is indicated that the impact of physical forces on the fetal head is mediated by its configuration. The mechanisms of birth traumatic injuries are systematized. The pathological configuration of the fetal head is shown to be of importance in explaining the cause of birth injury.

A contribution to the knowledge of cavernicolous ground beetles from Sichuan Province, southwestern China (Coleoptera, Carabidae, Trechini, Platynini).

Two new genera and four new species of cave-adapted ground beetles are described from Sichuan Province, southwestern China. Uenoaphaenopsgen. nov. is established to place the trechine species Qianotrechus fani Uéno, 2003 occurring in the limestone cave Hua’er Dong, southeastern Sichuan (Luzhou: Gulin). Chu pheggomisetoidesgen. nov. & sp. nov., from the limestone cave Hanwang Dong, northeastern Sichuan (Guangyuan: Chaotian), is somewhat like the European cavernicolous trechine genus Pheggomisetes Knirsch, 1923, from Bulgaria and Serbia, in particular in the configurations of head and pronotum. Boreaphaenops liyuanisp. nov., also from Hanwang Dong, is the second representative of the genus and the first record in Sichuan. Agonotrechus sinotroglophilus Deuve, 1999, a troglophile, is reported from Sichuan for the first time. The other two new species belong to the platynine genus Jujiroa Uéno, 1952: J. uenoisp. nov. from the cave Banche Dong on the northern side of the Dadu River (Leshan: Shawan) and J. wangzhenisp. nov. from the cave Hua’er Dong, which is sympatric with Uenoaphaenops fani (Uéno, 2003) comb. nov. A distribution map for the localities of all abovementioned caves and a key to Jujiroa species known in Sichuan are provided.

Effect of head and PV array configurations on solar water pumping system

Nowadays, the photovoltaic (PV) to power the water pumps is a newly accepted technology with few challenges associated with high initial cost and lower system efficiency. The literature suggests the majorly of commercial pumps at present, underperform, due to poor system design, low efficiency and mismatch of components. In this paper Matlab Simulink model of a solar photovoltaic (PV) water pumping system (SPVWPS) has been created. Such a model; demonstrates the system characteristics under different operating parameters. This model can successfully and completely check the feasibility, size and optimize the system for its complete utilization. The effect of various parameters such as operating head of the pump, radiation, PV array configurations on the performance of the SPVWPS has been discussed and presented in the paper.

An absolute surface encoder with a planar scale grating of variable periods

An absolute surface encoder for measurement of absolute in-plane position with a mode-locked femtosecond laser and a planar scale grating having variable periods along the two orthogonal directions is proposed. In the proposed method, the absolute in-plane position is measured through observing the spectra of the coupled groups of the positive and negative first-order diffracted mode-locked femtosecond laser emanated from a single point on the planar scale grating. Due to the dispersive effect of the planar scale grating having variable periods, each of the diffracted modes has a unique angle of diffraction associated with the absolute position information. Therefore, the absolute in-plane position can be detected by obtaining the peak frequencies in the optical spectra of the coupled positive and negative first-order diffracted beams received by dual detector units. The dual-detector configuration of the optical head also contributes to improving the robustness of the absolute position measurement against the angular error motion of the planar scale grating. Furthermore, interference signals capable of being used for the improvement of the absolute position measurement can be generated under the dual detector configuration. Results of the numerical calculations for the theoretical verification of the proposed method, fabrication of a scale grating having a variable period (VLS grating) with interference lithography, design and development of the optical head, as well as the results of basic experiments by using the developed optical head and the VLS grating, are reported.

Myosin dynamics during relaxation in mouse soleus muscle and modulation by 2'-deoxy-ATP.

Skeletal muscle relaxation has been primarily studied by assessing the kinetics of force decay. Little is known about the resultant dynamics of structural changes in myosin heads during relaxation. The naturally occurring nucleotide 2-deoxy-ATP (dATP) is a myosin activator that enhances cross-bridge binding and kinetics. X-ray diffraction data indicate that with elevated dATP, myosin heads were extended closer to actin in relaxed muscle and myosin heads return to an ordered, resting state after contraction more quickly. Molecular dynamics simulations of post-powerstroke myosin suggest that dATP induces structural changes in myosin heads that increase the surface area of the actin-binding regions promoting myosin interaction with actin, which could explain the observed delays in the onset of relaxation. This study of the dATP-induced changes in myosin may be instructive for determining the structural changes desired for other potential myosin-targeted molecular compounds to treat muscle diseases. Here we used time-resolved small-angle X-ray diffraction coupled with force measurements to study the structural changes in FVB mouse skeletal muscle sarcomeres during relaxation after tetanus contraction. To estimate the rate of myosin deactivation, we followed the rate of the intensity recovery of the first-order myosin layer line (MLL1) and restoration of the resting spacing of the third and sixth order of meridional reflection (SM3 and SM6 ) following tetanic contraction. A transgenic mouse model with elevated skeletal muscle 2-deoxy-ATP (dATP) was used to study how myosin activators may affect soleus muscle relaxation. X-ray diffraction evidence indicates that with elevated dATP, myosin heads were extended closer to actin in resting muscle. Following contraction, there is a slight but significant delay in the decay of force relative to WT muscle while the return of myosin heads to an ordered resting state was initially slower, then became more rapid than in WT muscle. Molecular dynamics simulations of post-powerstroke myosin suggest that dATP induces structural changes in myosin that increase the surface area of the actin-binding regions, promoting myosin interaction with actin. With dATP, myosin heads may remain in an activated state near the thin filaments following relaxation, accounting for the delay in force decay and the initial delay in recovery of resting head configuration, and this could facilitate subsequent contractions.

Aerodynamic interactions of a Reusable Launch Vehicle model with different nose configurations

The Two-Stage-To-Orbit (TSTO) hypersonic vehicle is an example of a Reusable Launch Vehicle (RLVs) configuration, and it has the advantages of small mass and large payload. A TSTO concept aircraft comprising a booster and a cruiser was proposed in this paper. The typical trapezoidal wing configuration was used as the booster and the wing spherical cone was used as the cruiser. Based on the three-dimensional hybrid LES/RANS numerical simulation method, the aerodynamic interference characteristics of different nose configurations in the cruise stage were studied, the pressure and heat flux distributions on the upper and lower surfaces of the cruise stage and the booster stage were calculated and analysed, the characteristics and mechanism of the aerodynamic interference between the two stages were revealed, and the structural changes of the flow field and the characteristics of the aerodynamic interference under different head configurations of the cruise stage were compared. The results show that the shock/shock interaction outside the blunt nose of the cruiser causes serious aerodynamic and thermal problems on the stagnation point. There are complex shock wave/boundary layer interactions and reflected shock trains between the two stages, which results in high-level pressure and heat flux on the surfaces. An alteration of the nose configuration can greatly improve the wall pressure and heat flux on the surface. The Bend cone model provides the greatest reduction in peak pressure and heat flux and is a suitable choice for an RLV cruiser.

A Fabry–Perot Interferometer-Based Fiber Optic Dynamic Displacement Sensor With an Analog in-Phase/Quadrature Generator

In this paper, the design details of a low-cost and high resolution Fiber Optic Dynamic Displacement sensor are discussed. The sensor is designed based on the principle of extrinsic Fiber Optic Fabry-Perot Interferometer (FPI). Higher sensitivity is achieved by using a double pass sensor head configuration. To resolve direction ambiguity, quadrature signals are generated by employing Phase Generated Carrier (PGC) demodulation technique. An Analog In-phase/Quadrature phase (I/Q) generator is designed to perform light intensity compensation, carrier mixing, and filtering operations to obtain the quadrature signals. Arctangent algorithm and phase unwrapping algorithms are used to obtain dynamic displacement from the quadrature signals. The sensor is demonstrated to measure non-contact dynamic displacement at a working distance of 5 cm with an amplitude resolution of 12 nm, a precision of 1.4 nm, and a standard deviation of 2%. The sensor is also able to measure multi-frequency dynamic displacements generated by piezo actuators. Potential applications of the sensor include condition monitoring and predictive maintenance in industries.

A geometrically exact approach for floating slender bodies with finite deformations

Fast prediction of the equilibrium configuration of a static floating rigid body is a challenging problem, especially if the body geometry is complex. To address this problem, a new model is developed to seek quickly the equilibrium configurations (position and orientation) of a continuous slender body with finite deformations relatively to the water surface. The non-linear description of the body geometry relies on the geometrically exact approach, where the orientations of the sections are parametrized by a continuous field of rotation matrices. After introducing the advantages of this approach, a new model giving the exact net wrench of buoyancy forces applied to the so-called Cosserat beam is reported. Then, an optimization method adapted to the Lie group manifold is developed to compute the equilibrium configurations. The numerical results are then compared to experimental data to validate the accuracy of the model. Finally, the inverse problem consisting of finding the relevant body deformation for a desired equilibrium configuration is introduced. After demonstrating that the inverse problem is ill-posed, a method is reported to deform continuously the body with a constant stable head configuration.

Parameters characterizing the posture of preterm children in standing and sitting position.

Systematic observations of fetal posture show that, although for most of the time the fetus does not have a preferred posture, it has a certain repertoire of repeated active postures. The observed postures cannot be considered random configurations of head and limb position: the fetus and the young infant have an active, but variable posture that is relatively unrelated to the orientation of the force of gravity. The study included 101 children, aged 6-7, including 50 preterm children, 48 boys and 53 girls (research group) and 51 full-term children; 22 boys and 53 girls (control group). The photogrammetric method with moire effect on Mora 4G CQ Elektronik was used to examine the body posture. Significant statistical differences in GAMMA (p< 0.001) and KLL (p= 0.020) parameters in preterm children and in control group were noted. Both parameters presented higher value in the control group. The posture of preterm children is characterized by a smaller angle of upper thoracic curvature and smaller angle of lumbar lordosis. The posture of preterm children in sitting position is characterized by a smaller angle of thoracic kyphosis. Preterm birth disturbs the development of proper antigravitational mechanism and causes possible posture dysfunctions at the age of 6.

Numerical simulation of flow distribution in the header of plate-fin heat exchanger

Plate-fin heat exchangers are widely used in industry at present due to their compact structure and high efficiency. However, there is a problem of flow maldistribution, resulting in poor performance of heat exchangers. The influence of the header configuration on fluid flow distribution is studied by using CFD software FLUENT. The numerical results show that the fluid flow inside the header is seriously uneven. The reliability of the numerical simulation is validated against the published results. They are found to be basically consistent within considerable error. The optimal number of the punch baffle is investigated. Various header configuration with different opening ratios have been studied under the same boundary conditions. The gross flow maldistribution parameter (S) is used to evaluate flow nonuniformity, and the flow maldistribution parameters of different schemes under different Reynolds numbers are listed and compared. The optimal header with minimum flow maldistribution parameter is obtained through the performance analysis of headers. It is found that the flow maldistribution of the improved header is significantly smaller compared with the conventional header. Hence, the efficiency of the heat exchanger is effectively enhanced. The conclusion provides a reference for the optimization design of plate-fin heat exchanger.

Enhanced design for microscale distribution of drug heads for transdermal patches

In this study, we propose an enhanced design of transdermal drug patch that offers better pharmacological efficacy and patient compliance than conventional designs that necessitate the entire skin under the patch to be in direct contact with the drug. This new design involves several periodically repeating portions of patched and unpatched areas, which creates a series of high local flux regions around the boundary between these patched and unpatched areas because of increased lateral spread of drug. Using numerical simulations of governing mass transfer equations for blood flow through trans-dermal regions modelled as a porous medium, the proposed design was found to be 100% more effective than the conventional one in terms of average flux from the drug head. A reduction of up to 50%, in the time required to reach steady state was also observed with the new design. Depending upon the effective area ratio chosen, the two superior drug head configurations suggested were found to be able to increase the average flux of the design further by 5% to 40%. The findings of the study provide a new approach by which one can design and fabricate transdermal patches that can accurately deliver any required dose without the use of a rate limiting membrane.

Decoupling the Interacting Head Motif and the Super Relaxed State of Myosin in Reconstituted Cardiac Bipolar Thick Filaments

Like many other classes of myosins, vertebrate cardiac myosin is suggested to exist in possibly two different structural states: an open head configuration in which myosin heads are readily accessible to bind and interact with actin and a closed head configuration where the heads are sequestered by the proximal part of the myosin tail, traditionally known as the Interacting Head Motif (IHM). At the biochemical level, this sequestered state is loosely correlated to the Super Relaxed (SRX) state of myosin, which has ∼10-fold prolonged ATP turnover rate (∼ 0.003 s−1) as compared to that of the open head configuration.

Detecting Bruise Damage and Level of Severity in Apples Using a Contactless NIR Spectrometer

HighlightsIn the Emission Head (EH) configuration differences in apple bruise severity were well captured.A good representation of new samples variability, in calibration, ensured robust quantitative PLS-DA models.EH mode with PLS-DA is an attractive spectroscopic option for inline apple sorting based on bruise damage. Abstract. Bruise damage in apples is very common and undesirable because it hinders consumer satisfaction and greatly contributes to food loss. Fast detection of bruise damage in fruit using spectroscopic systems is still problematic, especially in terms of quantitative and objective assessments of mechanical damage and standardization of bruise measurement method, among other issues. Non-destructive techniques among which is near infrared (NIR) spectroscopy are under development as a potential solution carrier for such issues. A study of bruise damage was conducted on three apple cultivars using Fourier transform (FT) near infrared spectroscopy in two configurations (‘emission head’ of Bruker’s Matrix-F and ‘integrating sphere’ of Bruker’s multipurpose analyzer, MPA). The emission head (EH) allows for contactless large sample (100 mm) exposure that simulates on-line applications, while the MPA (sample size: 22 mm) is commonly used for in-laboratory analysis of inhomogeneous material such as fruit. Bruise damages were mechanically induced in apples, bruise sizes measured physically and destructively. Partial least squares discriminant analysis (PLS-DA) was used to determine the differences captured by the scanning spectrometers in apple fruit tissues. Discriminant analysis revealed that in both sample acquisition modes, distinction between bruised and non-bruised apple fruit tissue was achieved with high (from 78% to 93%) accuracy of classification (ACcl) based solely on spectral data. The classification accuracy improved when individual cultivars were considered and ranged from 94% to 96%. Classification models were tested for robustness and showed that both cultivar and bruise severity had influence on classification models’ performance. The results showed ability of the emission head configuration in detecting bruises and differentiating between severity of bruises in apple fruit, thus making it a good candidate for use in rapid detection and quantitative assessment of bruising in apple on sorting lines. Possibilities for improving the classification model performance and ensuring their robustness for the EH were suggested. Keywords: Apple bruise, Discriminant analysis, Model performance, Model threshold, NIR spectroscopy.

Superficial Fluctuations in Functional Near-Infrared Spectroscopy.

Functional near-infrared spectroscopy (fNIRS) is a non-invasive optical functional neuroimaging that has seen rapid development and increasing use in studying human brain under normal and diseased conditions. Compared with blood-oxygenation-level dependent functional magnetic resonance imaging (BOLD fMRI), fNIRS offers advantages including its low cost, portability and compatibility with implanted medical devices. Thus, fNIRS can be used to monitor brain activity particularly in infants, elders and patients who are unable to undergo routine fMRI scans. However, fNIRS suffers from its susceptibility to scalp and to systemic physiological noises. Fluctuations originated from heartbeat, respiration and low-frequency oscillations lead to contamination of cerebral activity. In order to tap the full potential of fNIRS, it is essential to eliminate these confounding noises from fNIRS measurements. Therefore, the present study aims to understand the underlying relationship between superficial signals and the compound signals respectively measured by short channels and long channels of fNIRS optodes in a whole head configuration. Our results reveal that: 1) 49.56% of total variances in long-channel data are contributed by a global component shared across all long channels; 2) this global component is significantly correlated with the superficial fluctuations extracted from short-channel data. Finally, our findings indicate that compound signals measured by long channels of fNIRS are contaminated by superficial fluctuations and that careful removal of these fluctuations from long-channel data is critical in obtaining accurate images of cerebral activity with fNIRS.

In Silico Analysis of the Effect of Alkyl Tail Length on Antiagglomerant Adsorption to Natural Gas Hydrates in Brine

Antiagglomerant (AA) gas hydrate inhibitors can prevent blockages in oil and gas flowlines and could help enable safe and profitable production from deepwater environments. AAs, which are generally surfactants, often have an ionic head and one or more alkyl tails. Here, we use molecular dynamics simulations to investigate the mechanistic and energetic effects of alkyl tail length on adsorption to an sII methane/propane hydrate for well-known AA molecules (n-alkyl-tri(n-butyl)ammonium salt surfactants) of varying tail length. We consider alkyl tails from 8 to 16 carbon atoms and show that the dodecyl (12-carbon) tail has the highest percentage of the strongest binding configuration (i.e., the simultaneous head and tail binding configuration) and the lowest free energy of binding among the five molecules investigated. This maximum in strongest-configuration binding statistics and minimum in binding free energy at a tail length of 12 carbons may result from the appropriate size of the AA molecule with the dodecyl tail for spanning the most abundant binding sites on the hydrate surface. Furthermore, competition between the enthalpic gain of removing the hydrophobic tail from the aqueous solution and the entropic penalty of binding gives an optimum binding free energy for the dodecyl tail. Notably, experimental work on the same quaternary ammonium cations of varying tail length shows a maximum in performance for the dodecyl tail. This suggests that free energy of binding and more computationally efficient measures such as head-plus-tail binding probability are possible metrics for using molecular simulation to predict experimental and field performance of surfactant-type AAs, a capability which could accelerate the chemical innovation process.

P289SPECT camera head configuration, acquisition time, and resolution recovery processing impact image defect size quantification

P289SPECT camera head configuration, acquisition time, and resolution recovery processing impact image defect size quantification

Evaluation of neutron fluence in the treatment room and along the maze of an 18 MV linear accelerator

Neutron fluence and dose equivalent rate in the treatment room and along the maze of an 18 MV medical linear accelerator was evaluated using Monte Carlo code MCNP5. Scope of the study was to test the hypothesis that a simple accelerator head model can adequately estimate the neutron fluence in the treatment room and along the maze without the requirement of a detailed modeling of the complex accelerator head configuration. The accelerator head was modeled either as a spherical cell source of 10 cm in radius or as a point source in the centre of a spherical cell of 10 cm internal and 20 cm external radious, both made of tungsten. The calculations were compared against measurements performed using gold and indium activation foils. A good agreement between calculated and experimental results was observed in the treatment room. However, the calculations at the maze entrance overestimated the neutron fluence by a factor of 3. The results of the study contribute towards the development of a simple and computationally cost effective methodology for the calculation of neutron dose in the treatment room and the maze of high energy medical accelerators providing a representative simulation of the complex accelerator, bunker and maze configurations that cannot be described by presently used analytical expressions.