Waist Position Research Articles

Measurement of Gaussian laser beam radius using nanosecond-pulse laser etching of titanium film

A method for measuring the Gaussian laser beam radius based on nanosecond-pulse laser etching (NPLE) was proposed. The NPLE method has the advantages of simple operation, low cost and high accuracy. It can be used to directly measure the laser beam size in the range of 0.25 ∼ 6 W without attenuating the laser energy. In the experiments, 1064 nm pulsed laser beam was used to etch titanium film, the size and position of the laser beam waist were measured. The experimental results are consistent with the calibration values of the CCD method, it indicates that the NPLE method is feasible.

A method for calculating fall risk parameters from discrete stride time series regardless of sensor placement

BackgroundTo complement traditional clinical fall risk assessments, research is oriented towards adding real-life gait-related fall risk parameters (FRP) using inertial sensors fixed to a specific body position. While fixing the sensor position can facilitate data processing, it can reduce user compliance. A newly proposed step detection method, Smartstep, has been proven to be robust against sensor position and real-life challenges. Moreover, FRP based on step variability calculated from stride times (Standard deviation (SD), Coefficient of Variance (Cov), fractal exponent, and sample entropy of stride duration) proved to be useful to prospectively predict the fall risk. Research questionsTo evaluate whether Smartstep is convenient for calculating FRP from different sensor placements. Methods29 elderly performed a 6-minute walking test with IMU placed on the waist and the wrist. FRP were computed from step-time estimated from Smartstep and compared to those obtained from foot-mounted inertial sensors: precision and recall of the step detection, Root mean square error (RMSE) and Intraclass Correlation Coefficient (ICC) of stride durations, and limits of agreement of FRP. ResultsThe step detection precision and recall were respectively 99.5% and 95.9% for the waist position, and 99.4% and 95.7% for the wrist position. The ICC and RMSE of stride duration were 0.91 and 54 ms respectively for both the waist and the hand position. The limits of agreement of Cov, SD, fractal exponent, and sample entropy of stride duration are respectively 2.15%, 25 ms, 0.3, 0.5 for the waist and 1.6%, 16 ms, 0.23, 0.4 for the hand. SignificanceRobust against the elderly's gait and different body locations, especially the wrist, this method can open doors toward ambulatory measurements of steps, and calculation of different discrete stride-related falling risk indicators.

Comparison of Two Different Positions for Ultrasound-Guided Intervertebral Distance Evaluation.

During neuraxial anaesthesia, correct patient positioning is key for increased block success and (patient) comfort. The aim of this prospective study was to compare the lateral fetal decubitus (LFD) position with the sitting fetal lotus (SFL) regarding interspinous distance, transverse diameters of paravertebral muscles measured with ultrasonography, and patient comfort. Fifty adult participants who could sit cross-legged and had no lumbar anomalies were included in our prospective study. In both SFL and LFD positions, measurements were performed with ultrasonography; in the axial plane, interspinous distance at the level of L4-L5, in the sagittal plan, with the probe slightly tilted, subcutaneous tissue-spinous process depth, and transverse diameters of paravertebral muscles were measured. Stretcher, waist position, and abdominal comfort were scored on a scale of 1 (very bad) to 7 (perfect) with a verbal numeric satisfaction scale. Interspinous distance was significantly larger in the SFL position than in the LFD position (P < 0.05). There was no significant difference between the two positions (P > 0.05) regarding patient comfort. Paravertebral muscle diameters were significantly broader in the SFL position than in the LFD position. The diameter of the left paravertebral muscle in the SFL position (45.8±8.8 mm) was larger than that in the LFD position (43±7.8 mm; P < 0.001). The diameter of the right paravertebral muscle in the SFL position was (47±9 mm) larger than that in the LFD position (43.4±7.6 mm; P < 0.001). Although there was no difference regarding the comfort between the two positions, the interspinous distance was larger in the SFL position than in the LFD position.

Method for generating spatiotemporal coherency vortices and spatiotemporal dislocation curves.

A simple method for designing spatiotemporal coherency vortices (STCVs) and spatiotemporal dislocation curves (STDCs) is introduced by means of coherent-mode representation and Fourier transforms. A partially coherent pulsed beam is represented by an incoherent superposition of a Gaussian and a Hermite-Gaussian pulsed beam with different waist positions. It well demonstrates that there exist STCVs and STDCs in the space-time plane. The detailed numerical calculations are performed to address the dependence of waist distance of two modes, reference position, beam order, distribution of original spectrum, topological charge and mode weights ratio on the STCVs and STDCs. The physical interpretation behind numerical results is shown. A possible scheme for experimental synthesis of the STCVs is proposed. The obtained results may have potential applications in the fields of light-matter interaction, spatiotemporal spin-orbit angular momentum coupling and STCV-based optical trapping and optical manipulation.

Mechanical response and field measurement analysis of custom-shaped steel sleeves during urban shield tunnel construction

Urban shield tunnel construction is typically affected by limited construction space and the inability to begin from the main line. Conventional lateral initiation solutions result in construction delays and incurs additional construction costs. Hence, based on the Beijing Metro Line 27 project, a novel custom-shaped steel sleeve for lateral initiation is proposed. Numerical simulations are conducted to analyse the stress and deformation characteristics of the steel sleeve during shield initiation. The simulation results, which are validated based on on-site measurements, show that the maximum tensile stress of the shaped steel sleeve structure increases with the shield thrust, and that the average maximum stress occurred at the waist position at the long side of the barrel. However, the stress at the base reduced significantly and a stress concentration occurred at the connection between the sleeve and tunnel portal. The deformation of the sleeve is characterised by a larger long side and a smaller short side owing to the constraint of the tunnel portal. The axial force on the connection bolts below the waist of the sleeve is the highest, whereas the axial force near the tunnel portal is lower. The waist position and the lower section of the sleeve structure are areas where the stress and deformation are weak during the shield initiation of the steel sleeve. Results of engineering test shows that using a shaped steel sleeve for lateral initiation is safe and feasible. However, the waist and bolt connections of the shaped steel sleeve must be scrutinised when used in engineering practice, and standardised construction operations and strengthened monitoring should be implemented.

Single and coupled cavity mode sensing schemes using a diagnostic field.

Precise optical mode matching is of critical importance in experiments using squeezed-vacuum states. Automatic spatial-mode matching schemes have the potential to reduce losses and improve loss stability. However, in quantum-enhanced coupled-cavity experiments, such as gravitational-wave detectors, one must also ensure that the sub-cavities are also mode matched. We propose what we believe to be a new mode sensing scheme, which works for simple and coupled cavities. The scheme requires no moving parts, nor tuning of Gouy phases. Instead a diagnostic field tuned to the HG20/LG10 mode frequency is used. The error signals are derived to be proportional to the difference in waist position, and difference in Rayleigh ranges, between the sub-cavity eigenmodes. The two error signals are separable by 90 degrees of demodulation phase. We demonstrate reasonable error signals for a simplified Einstein Telescope optical design. This work will facilitate routine use of extremely high levels of squeezing in current and future gravitational-wave detectors.

Development of adaptive laser head for compensating error of beam waist position during processing materials using laser beam spot detection method

Development of adaptive laser head for compensating error of beam waist position during processing materials using laser beam spot detection method

Full-Scale Model Test of Subway Contact Channel under Mechanical Construction

The mechanical construction method for a subway contact channel has the advantages of a short construction period and high safety, and is more and more being applied in coastal soft-soil areas. In order to explore the suitability of this method in inland areas, a full-scale model test platform is used to simulate the shield-cutting construction process of the subway contact channel. The convergence deformation of the segments and the strain of the reinforcement and concrete are tested, so as to analyze the internal force and deformation law of the tunnel structure during cutting construction. The influence of the steel ring on the deformation of the subway contact channel is also studied. It is found that the segment convergence at the top is less than that at the waist position, and the convergence deformation of the waist is less than 30 mm; the internal force of the segment redistributes and the axial force mainly decreases during the cutting process; the stress state may change from compression to tension. The segment structure of the main tunnel, the supporting structure in the tunnel, and the stiffness of the steel-ring-lined composite pipe segment have little influence on the cutting force of the contact channel. The research results provide the corresponding technical indexes for the construction of a contact channel by the mechanical method, as well as a reference for the design and optimization of a steel-ring-lined composite pipe segment.

Study on the functional relationship between pressure and displacement with time for waist of elastic legwear using FEM

PurposeThe inward displacement perpendicular to the body surface produced by compression garment is an important index to evaluate pressure comfort and optimal design of tight clothing products. The purpose of this study is to explore the pressure distribution state at waist position of elastic legwear and then to solve the common problem of excessive pressure or easy slippage for waist of elastic legwear.Design/methodology/approachIn this paper, the authors obtained the waist cross-section model of human body using CT scanning and mimics modeling and then simulated the pressure and displacement distribution after wearing sample four elastic legwear using finite element method. The dressing process of elastic legwear was divided into six periods (instantaneous, 1, 2, 4, 8 and 12 h) in this study, and the finite element software ANSYS was used to simulate the displacement and deformation of the waist cross section. The authors finally obtained the functional relationship between pressure/displacement ratio and angle using curve fitting.FindingsIn this paper, the authors obtained the functional relationship between pressure/displacement ratio and angle using curve fitting. Comparison found that the “pressure/displacement–angle” function curve showed an almost consistent trend at any time. That was to say, when the human body was in the state of clothing pressure, the corresponding displacement value of the human body can be calculated by the curve equation under the premise of known pressure value.Originality/valueThis study solves the difficult problem which hard to measure displacement values by conventional methods due to the small deformation of the human body after dressing the compression garment. Conclusions also provide a theoretical reference for evaluating pressure comfort and optimizing clothing structure for the elastic legwear, and this method is also applicable to other types of compression garment.

Fourier Ptychography-Based Measurement of Beam Divergence Angle for Vertical Cavity Surface-Emitting Laser

The Vertical Cavity Surface-Emitting Laser (VCSEL) has led to the rapid development of advanced fields such as communication, optical sensing, smart cars, and more. The accurate testing of VCSEL beam quality is an important prerequisite for its effective application. In this paper, a method for measuring the divergence angle of the VCSEL far field spot based on transmissive Fourier ptychography is proposed. First, a single CCD multi-angle VCSEL far-field spot acquisition system is designed. Second, based on the proposed Fourier ptychographic algorithm with synchronous optimization of embedded optical transfer function, a resolution-enhanced phase image of the spot is reconstructed and the boundary extracted by the Sobel operator of the phase image is defined as the boundary position of the beam waist. In this way, the beam waist radius of the laser beam is calculated. Finally, the divergence angle of the laser beam is measured via the radius of the beam waist. Compared with the traditional Gaussian beam definition method, the method proposed in this paper has higher accuracy in divergence angle measurement. The experimental results show that this method can improve the divergence angle measurement accuracy by up to 9.7%.

Evaluations of nanoparticle capture and transport methods in dielectric bowtie core capillaries.

We propose a flexibly tunable and low-loss optical burette with an all-dielectric bowtie core capillary structure, where nanoparticle arrays can be transported bidirectionally with incident light from one end. Multiple hot spots, acting as optical traps, are periodically distributed at the center of the bowtie cores along the propagation direction because of the mode interference effect of guided lights. By adjusting the beam waist position, the hot spots continuously move across the entire capillary length; thus, trapped nanoparticles also transfer with the hot spots. The bidirectional transfer can be realized simply by changing the beam waist in the forward or backward direction. We confirmed that nanosized polystyrene spheres can be bidirectionally moved along a capillary length of ≈ 20 µm. Furthermore, the magnitude of the optical force can be adjusted using the incident angle and beam waist width, whereas the trapping period can be adjusted using the incident wavelength. These results were evaluated using the finite-difference time-domain method. We believe that this new approach can be extensively used in the field of biochemical and life sciences because of the properties of an all-dielectric structure, bidirectional transportation, and single incident light.

Variational Pose Prediction with Dynamic Sample Selection from Sparse Tracking Signals

AbstractWe propose a learning‐based approach for full‐body pose reconstruction from extremely sparse upper body tracking data, obtained from a virtual reality (VR) device. We leverage a conditional variational autoencoder with gated recurrent units to synthesize plausible and temporally coherent motions from 4‐point tracking (head, hands, and waist positions and orientations). To avoid synthesizing implausible poses, we propose a novel sample selection and interpolation strategy along with an anomaly detection algorithm. Specifically, we monitor the quality of our generated poses using the anomaly detection algorithm and smoothly transition to better samples when the quality falls below a statistically defined threshold. Moreover, we demonstrate that our sample selection and interpolation method can be used for other applications, such as target hitting and collision avoidance, where the generated motions should adhere to the constraints of the virtual environment. Our system is lightweight, operates in real‐time, and is able to produce temporally coherent and realistic motions.

High-power diode-end-pumped 1314 nm laser based on the multi-segmented Nd:YLF crystal.

We demonstrate the first multi-segmented Nd:YLF laser, to the best of our knowledge. The multi-segmented crystal was designed to straightforwardly aim for the minimum thermal stress without sacrificing the overall laser efficiency, with the influence of the pump beam waist position considered in particular. Integrating the enhanced thermo-mechanical resistance of multi-segmented crystal and the alleviated heat load of low quantum defect pumping, this end-pumped 1314 nm Nd:YLF laser system delivered a maximum continuous-wave output power of up to 35.5 W under a pump power of 105 W, corresponding to an optical-to-optical efficiency of 33.8%. Furthermore, by incorporating an acousto-optic modulator, an active Q-switching oscillator was accomplished, yielding a maximum average output power of 22.9 W at a pulse repetition frequency (PRF) of 20 kHz and a largest pulse energy of 13.6 mJ at a PRF of 1 kHz.

Quasi-static test study of tunnel with resistance-limiting shock absorption layer in high-intensity seismic

The Sichuan-Tibet Railway is faced with risks of active faults, unfavorable geological conditions, high in-situ stress levels, and a high potential for Traditional tunnel seismic measures that can no longer guarantee the safety of tunnel structures in high-intensity earthquake areas. The new shock absorption capacity layer with resistance-limiting is proposed in this paper and the resistance-limiting shock absorption principle. To study the safety of the new anti-shock lining structure, a large-scale quasi-static model test was carried out based on the improved static-dynamic coupling shear force. The test analyzes the response rules of strain, structural internal force, and lining failure form of tunnel lining, taking into consideration three influencing factors including layer layout position, layout density, and tunnel buried depth. The results showed that: 1) Under the action of low-cycle reciprocating shear strain, the failure mode of the shallow buried tunnel is mainly the tensile failure of the arch waist and the failure of the arch waist and the side wall, and the failure mode of the deeply buried tunnel is mainly the compression failure of the arch waist; 2) Compared with the case of no shock absorption layer, the lining tensile stress on the inner side of the arch waist position is significantly reduced. Under the high shear strain (0.20%), the increased tensile stress trend was slowed down on the inner side walls; 3) The main working area of the resistance-limiting layer can effectively improve the lining stress distribution underground vibration and protects the tensile damage on the arch waist to the side wall. The width and depth of the crack are weakened and the seismic bearing capacity of the width and depth of the crack is weakened and the seismic bearing capacity of the lining structure is greatly strengthened; 4) The lining cracks without the resistance limiting layer develop violently, and the crack at the arch waist runs The lining structure failure mode of the resistance limiting layer arranged at the arch waist is similar to The lining structure failure mode of the resistance limiting layer.

Effect of annealing process on interface microstructure and mechanical property of the Cu/Al corrugated clad sheet

In this research, annealing treatment was performed on the Cu/Al corrugated clad sheets fabricated by the corrugated cold roll bonding (CCRB) process. Interface microstructure evolution, interface phase development, intermetallic compound (IMC) growth kinetics, interface bonding strength, and electrical resistivity at various positions of the Cu/Al corrugated clad sheet were investigated under different annealing conditions. The IMC layers (CuAl2, Cu9Al4 and CuAl) with uneven thickness were formed at the Cu/Al corrugated interface during the annealing process. Interface defects caused by shear deformation can effectively reduce the growth activation energies of IMC sub-layer at positions I (back waist), III (front waist), and IV (trough). On the contrary, the interface brittle layers and overlayer can slightly increase the activation energy at position II (peak). The sequence of growth activation energies for IMC sub-layer was QCuAl<QCu9Al4<QCuAl2. When Cu/Al corrugated clad sheet was annealed at 350 °C for 30 min, the recrystallization degree of Al plate at position III (front waist) was higher than the position II (peak), which was mainly due to the severe plastic deformation at the front waist position. Meanwhile, the transformation from low angle grain boundaries (LAGBs) to high angle grain boundaries (HAGBs) of the Al plate was more likely to occur at position III (front waist). Interface shear strength presented wavy distribution along the interface when the Cu/Al corrugated clad sheet was annealed at 350 °C for different times. With the increase of annealing time, the average shear strength first increased and then decreased rapidly. When the annealing time was 60 min, the average shear strength reached the maximum value of 45.61 MPa, and the average electrical resistivity reduced to the minimum value of 11.56 × 10−8 Ω m. Considering the double influence of annealing process on bonding strength and electrical resistivity, it was recommended that the Cu/Al corrugated clad sheet be annealed at 350 °C for 60 min.

Circuit-Aided Dummy Design for Human Body-Worn ESD Application

Electrostatic discharge (ESD) is considered for different postures of the body and for different positions of a device under test (DUT). These scenarios lead to large variations in peak discharge currents, and a traditional commercial ESD generator cannot test these satisfactorily. Instead of using actual humans, a full-size dummy has been designed for different body-worn ESD test scenarios, its discharge currents and fields are verified by comparing the measurement results with those taken from volunteers. A wearable DUT on the wrist, elbow, and waist is taken into consideration to compare the characteristics of the dummy to those of the real human body. Furthermore, a circuit model is proposed to aid in understanding the dummy design and the different body-worn scenarios. Finally, the effect of an external connection with different waist positions is analyzed and discussed in a more complex application scenario.

Position effect of laser beam waist in quartz-enhanced photoacoustic spectroscopy

The position effect of laser beam waist with respect to quartz tuning fork (QTF) on the signal of quartz enhanced photoacoustic spectroscopy (QEPAS) was investigated. A laser beam was collimated by a fiber-coupled Grin collimator (FGC) which was assembled to a QEPAS system. The experimental results showed that the maximum signal amplitude occurs at different distances from the FGCs to the QTF. The relationship between the position of the beam waist and the signal amplitude was analyzed. The influence of the beam waist position in the in-plane QEPAS and the on-beam QEPAS is discussed in detail.

Photogrammetric Anthropometry to Determine the Female Waistline.

Background: In this study, we attempted to develop a reference guide to determine the female waistline based on the golden ratio for waist sculpting in females, which may help in waist sculpting by liposuction or non-invasive techniques.Material and methods: To understand the anatomy of the waist, we studied the 60 photographs of females and measured the distances between important anatomical landmarks. The different values and proportions obtained were compared between different groups of heights and two groups of BMI using Statistical Package for the Social Sciences (SPSS) version 23 (IBM Corp., Armonk, NY) through analysis of variance (ANOVA).Results: There is a golden ratio in the distances between xiphoid to waist and waist to the abdominal crease that is close to 1:1.66, and the waist is at the junction of the upper 2/5th and lower 3/5th of the height from xiphoid to abdominal crease. The location of the waist is at one-third of the whole length of the abdomen (the whole length of the abdomen being the length from the xiphoid to the pudendal cleft).Conclusions: We observed in our study that there is a definite mathematical relationship between the length of the abdomen and the waist position, which may be applied for female waist sculpting.

Adjustment of patterns of women’s trousers on the baseof the lower body

This article presents the influence of female lower body characteristics as a waist position to the bottom of thefoot on the design of women’s trousers. First, the author designs patterns for people with straight legs. Second,the product will wear on people with bow legs, X-legs, and people who have big waists and small thighs. Third,the author analyzes the fit of each pattern in every sample and gives directions for pattern correction. Finally,the samples are sewn again until they fit samples and are not wrinkles. The anthropometric theoretical researchmethod is used in the product fit analysis. The theory designs trousers pattern that is used to design patterns forpeople who have straight legs. The experimental research method is used to conduct actual surveys on 40 peoplefrom four groups with different lower body parts through the Likert scale for five evaluation criteria on five levels.The survey results are analyzed on the SPSS software. The results show that Cronbach’s alpha index is over 0.7.Research has made practical contributions in the field of garment product design as well as consulting customerswhen buying and selling clothes.

Determination of the beam waist position for the spin-orbit interaction effect observation

The spin angular momentum and the extrinsic orbital angular momentum of light are associated with the polarization of light and the light propagation trajectory, respectively. Those momenta are interdependent not only in an inhomogeneous or anisotropic medium but even in free space. This interaction is called the spin-orbit interaction of light. The effects of the spin-orbit interaction of light manifest themselves in a small transverse shift of the beam field longitudinal component from the beam propagation axis in the waist region under the circular polarization sign change. They can be observed both for Gaussian beams and for structured beams. The effects of the spin-orbit interaction of light should be taken into account when nanophotonics devices are created, but the detailed investigation of the effect had not been performed yet due to the low intensity noise image of the beam waist. Precise measurements of the focal waist centerline are needed to determine the transverse shift of the beam field longitudinal component of the asymmetric converging beam's waist under the circular polarization sign change. We propose methods for determining the transverse and longitudinal positions of the beam waist. Computer image processing methods made it possible to obtain the value of the beam waist's transverse position with an accuracy of 0.1 mkm. These methods will allow further testing of the shifts' theoretical predictions, the values of which are the order of 1 mkm. The results obtained can also be used for laser processing of materials by polarized light and precise positioning of the beam's focal spot at a surface.