Optimal Frequency and Amplitude of Vertical Viewpoint Oscillation for Improving Vection Strength and Reducing Neural Constrains on Gait

Inducing self-motion illusions referred as vection are critical for improving the sensation of walking in virtual environments (VE). Adding viewpoint oscillations to a constant forward velocity in VE is effective for improving vection strength under static conditions. However, the effects of oscillation frequency and amplitude on vection strength under treadmill walking conditions are still unclear. Besides, due to the visuomotor entrainment mechanism, these visual oscillations would affect gait patterns and be detrimental for achieving natural walking if not properly designed. This study was aimed at determining the optimal frequency and amplitude of vertical viewpoint oscillations for improving vection strength and reducing gait constraints. Seven subjects walked on a treadmill while watching a visual scene. The visual scene presented a constant forward velocity equal to the treadmill velocity with different vertical viewpoint oscillations added. Five oscillation patterns with different combinations of frequency and amplitude were tested. Subjects gave verbal ratings of vection strength. The mediolateral (M-L) center of pressure (CoP) complexity was calculated to indicate gait constraints. After the experiment, subjects were asked to give the best and the worst oscillation pattern based on their walking experience. The oscillation frequency and amplitude had strong positive correlations with vection strength. The M-L CoP complexity was reduced under oscillations with low frequency. The medium oscillation amplitude had greater M-L CoP complexity than the small and large amplitude. Besides, subjects preferred those oscillation patterns with large gait complexity. We suggested that the oscillation amplitude with largest M-L CoP complexity should first be chosen to reduce gait constraints. Then, increasing the oscillation frequency to improve vection strength until individual preference or the boundary of motion sickness. These findings provide important guidelines to promote the sensation of natural walking in VE.     

信息网络环境下智能安防报警系统设计

为了保证学校学生和其他在校人员的学习生活安全,并且可以最大限度的保障内部人员的人身以及财产安全,需要对校园的安防报警系统进行优化。但目前设计方法在智能安防报警系统优化过程中,无法在校内无人的状况下对学校的突发事件智能安防报警系统,存在校园智能安防报警系统性能不高的问题。为此,提出了一种基于MSP430单片机的信息技术环境下校园智能安防报警系统设计方法。该设计方法先将MSP430单片机嵌入至安防报警系统多控制传感器模块中进行实时监测,并且统计关于学校内部人员以及其贵重物品的进出与防火灾安全情况,然后采用C/S(Client/Server)结构根据安全状况设置智能声光报警,使用无线传输技术快速组网,各个采集终端在监控安防报警信息的同时,利用无线方式发送到总控制平台,方便学校的管理人员实时了解学校安防状况。最后在危险情况发生时发送短信快速通知校内安防人员,尽量避免或者降低校内人员的财产损失,保证学生以及校内其他人员的安全。仿真实验证明,所提方法提高了信息网络环境下校园智能安防报警系统的稳定性,增强了校园智能安防报警系统的灵活性和自动性。     

Acoustically-observable properties of adult gait

An approach has been developed for extracting human gait parameters from micro Doppler sonar grams. Key parameters include average speed of walking, torso velocity, walk cycle time, and peak leg velocity. The approach is a modification of a technique previously used in radar data analysis. It has been adapted because of differences between sonar and radar micro Doppler grams. The approach has been applied to an acoustic data set of 16 female and 60 male walkers. Statistics have been tabulated that illustrate the similarities and dissimilarities between female and male gait. Males tend to walk with larger walk cycle times and peak leg velocities than females.     

Perception of acoustic source characteristics: walking sounds.

The current study investigated the ability of subjects to perceive source characteristics (the gender of a human walker) of a naturally occurring auditory event (human walking). A number of acoustic properties were measured and subjected to statistical analyses in order to identify those properties that differentiate male and female walking footsteps. A principal component analysis on the statistical properties of the spectral energy distributions then identified two classes of information that were important in determining subject perception of the gender of a walker: (1) the spectral peak which integrates the information about the spectral central tendency of frequency and shape of the spectral peak; and (2) the contribution of high-frequency spectral components. A follow-up experiment then manipulated these spectral properties to verify their contributions in the perceptual classification of walker gender. Additionally, the effect of shoe on the gender judgement in walking sequences was assessed by having both male and female walkers wear male's shoes.     

Rhythm analysis of orthogonal signals from human walking

In physical terms, periodic movements of a human body resulting from walking produce a pulse sequence with repetition time T(1) (instant cadence frequency, 1/T(1)) and duration time T(2). Footstep forces generate periodic T(1) broadband seismic and sound signals due to the dynamic forces between the foot and the ground/floor with duration time T(2), which is equal to the time interval for a single footstep from heel strike to toe slap and weight transfer. In a human gait study (for normal speeds of walking), T(1) was detected as 0.5-0.69 s and double limb support takes up about 12% of the gait cycle (2T(1)), so T(2) is greater than 0.12-0.17 s. Short range (of about 50 m) signatures for 30 humans were recorded simultaneously by four orthogonal sensor types at two locations. The sensor types were active Doppler sonar/radar and passive seismic/acoustics. Analysis of signals from these four sensors collected for walking humans showed temporal synchronization and stability of the cadence frequencies, and the cadence frequency from each sensor was equivalent. The time delay between signals from these sensors due to the differences in speeds of propagation for seismic, sound, and electromagnetic waves allows calculation of the distance from a walker to the sensor suite.     

A novel remote sensing technique for recognizing human gait based on the measurement of induced electrostatic current

In this paper, we propose an effective non-contact method for the monitoring of human gait including stepping, walking and running by measuring the induced electrostatic signals. Based on the kinematics principles and theories of electrodynamics in the view of capacitance variation, we analyze the characteristics of induced electrostatic current on electrode generated by human body motion without the need to attach electrode on human body to deduce the detection equations of human gait. The experimental results of human body motion recognition match the theoretical analysis well, and the obvious biped motion feature of induced electrostatic signal waveform proves that adopting this method in human body monitoring applications benefits in the low false-alarm rate, which verifies our expectation that the adoption of non-contact electrostatic detection technique will open up a new area of remote biometric measurements which can be applied in the field of human machine interface, health care and security.     

Dynamics of human walking at steady speeds

Biped locomotion is discussed through a Lagrangian formulation for velocity-dependent, body driving forces. An analysis of level walking in humans is given through the known experimental data on the ground-reaction force and the external work without recourse to inverted-pendulum modeling. At a certain speed, rectilinear motion of the center of mass with its backward rotation along a shortened hypocycloid is ensured by double-frequency nonlinear oscillations, whose energy cost is 1% of the external work. With increasing speed, a peculiarity and an instability of the trajectory indicate, respectively, a slow-to-normal gait crossover and the maximal fast walking speed. Key words: integrative biology, biped locomotion, human gaits, muscles.     

Nonlinear time series analysis of normal and pathological human walking

Characterizing locomotor dynamics is essential for understanding the neuromuscular control of locomotion. In particular, quantifying dynamic stability during walking is important for assessing people who have a greater risk of falling. However, traditional biomechanical methods of defining stability have not quantified the resistance of the neuromuscular system to perturbations, suggesting that more precise definitions are required. For the present study, average maximum finite-time Lyapunov exponents were estimated to quantify the local dynamic stability of human walking kinematics. Local scaling exponents, defined as the local slopes of the correlation sum curves, were also calculated to quantify the local scaling structure of each embedded time series. Comparisons were made between overground and motorized treadmill walking in young healthy subjects and between diabetic neuropathic (NP) patients and healthy controls (CO) during overground walking. A modification of the method of surrogate data was developed to examine the stochastic nature of the fluctuations overlying the nominally periodic patterns in these data sets. Results demonstrated that having subjects walk on a motorized treadmill artificially stabilized their natural locomotor kinematics by small but statistically significant amounts. Furthermore, a paradox previously present in the biomechanical literature that resulted from mistakenly equating variability with dynamic stability was resolved. By slowing their self-selected walking speeds, NP patients adopted more locally stable gait patterns, even though they simultaneously exhibited greater kinematic variability than CO subjects. Additionally, the loss of peripheral sensation in NP patients was associated with statistically significant differences in the local scaling structure of their walking kinematics at those length scales where it was anticipated that sensory feedback would play the greatest role. Lastly, stride-to-stride fluctuations in the walking patterns of all three subject groups were clearly distinguishable from linearly autocorrelated Gaussian noise. As a collateral benefit of the methodological approach taken in this study, some of the first steps at characterizing the underlying structure of human locomotor dynamics have been taken. Implications for understanding the neuromuscular control of locomotion are discussed. (c) 2000 American Institute of Physics.     

Effect of Body Weight-supported Walking on Exercise Capacity and Walking Speed in Patients with Knee Osteoarthritis: A Randomized Controlled Trial

Objective: To compare the effect of body-weight-supported treadmill training (BWSTT) and full-body-weight treadmill training (FBWTT) on patients with knee osteoarthritis (OA). Methods: Design was Randomized controlled trial. Patients with knee osteoarthritis (n = 30; mean age, 76.0±7.5 y) were randomly assigned to BWSTT or FBWTT group. All patients performed 20 min walking exercise twice a week for 6 weeks under the supervision of the therapist. Main measures were 10-meter walking test (10MWT), functional reach test (FRT), timed get up and go test (TUG), one-leg standing test, 6-minute walking test (6MWT), the parameters set on the treadmill, MOS Short-Form 36-Item Health Survey (SF36), Japanese Knee Osteoarthritis Measure (JKOM). Results: Twenty-five patients (10 men, 15 women; mean age, 76.5 ± 8.0 y) completed the experiment. Exercise capacity, indicated by the heart rate, was similar in both groups. After 3 weeks of BWSTT, the patients performed significantly better in the 10-m and 6-min walking tests. This was not the case with FBWTT even after 6 weeks training. Pain levels assessed were significantly improved after 3 weeks of BWSTT and 6 weeks of FBWTT. There were no significant improvements in either group assessed by the FRT, one-leg standing time test, TUG, or SF -36 questionnaire. Conclusions: BWSTT enhanced exercise capacity in terms of walking speed and pain reduction after 3 weeks; however, there was no significant improvement in patients'' functional abilities or quality of life.     

Isokinetic trunk and knee muscle strengths and gait performance in walking patients with T-cell lymphotropic virus type 1-associated myelopathy/ tropical spastic paraparesis (HAM/TSP)

The aim of this study was to investigate the isokinetic trunk and knee muscle strengths, and examine the clinical relevance of dynamic muscle strengths and gait performance in walking patients with human T-cell lymphotropic virus type 1-associated myelopathy/ tropical spastic paraparesis (HAM/TSP). Thirteen patients with HAM/TSP (8 females and 5 males, aged 38–76) and 13 sex- and age-matched healthy control subjects participated in the study. We assessed gait speed, stride length, cadence; and maximal isokinetic torque of trunk and knee extensors and flexors at 30°/s, 60°/s and 90°/s using a Biodex System 3 dynamometer. Furthermore, we calculated the isokinetic trunk extensor/flexor (E/F) and hamstrings/quadriceps (H/Q) strength ratios (parameter of the muscle strength balance about the trunk and knee joint). Compared with the age-matched controls, the patients with HAM/TSP had significantly reduced gait speed, stride length and cadence (P < 0.05). Peak torque values related to body weight (PTBW) were significantly reduced, especially for the knee flexors (P < 0.05). For the knee extensors, the PTBW values were significantly reduced at an increased angular velocity (P < 0.05). The PTBW of knee flexors was positively correlated with gait speed and cadence in the patients with HAM/TSP. The H/Q ratio but not E/F ratio was significantly decreased compared with the control. Our results indicated that the isokinetic trunk and knee muscle performance had reduced from the ambulatory stage, and suggested the deterioration in knee muscle performance to be associated with gait disturbance in walking HAM/TSP patients.     

基于异构计算的简单行走模型的吸引区域研究

被动行走机器人由于结构简单、能量利用率高而倍受青睐, 但其很容易跌倒, 因此准确把握最终步态与吸引区域成了关键. 由于面对非光滑系统, 大规模数值计算很难避免, 为此本文先提出基于CPU+GPU异构平台的Poincaré映射算法. 该算法可发挥最新平台计算潜力, 比传统CPU上算法快上百倍. 得益于此, 本文针对双足被动行走的最基本模型, 大规模地选取样点进行计算, 不仅清晰地得出吸引区域的形状轮廓和细节特征, 揭示了其内在分形结构, 还得到系统吸引集和吸引区域随倾角k的变化关系, 发现了新的稳定三周期步态和倍周期分岔混沌现象, 并研究了吸引区域.     

驱动马达定向运动的随机动力学模型

本文在非对称周期势中考虑驱动马达的机械化学耦合,基于布朗马达的工作原理,利用MATLAB数值模拟驱动马达在一定实验条件下的运动特征.我们首先模拟了单个驱动马达的位移和速度随时间变化的图像,然后分别计算了多个驱动马达运动的平均速度,最后计算了不同负载力条件下马达运动速度的系综平均值.模拟结果表明驱动马达在定向运动中存在等待态和行走态,行走步长约为8.2nm,且马达运动具有一定的随机性.通过与实验比较,发现模型计算结果与实验吻合.     

Phonetogram Changes for Trained Singers Over a Nine-Month Period of Vocal Training

Professional vocalists encounter demands requiring voluntary control of phonation, while utilizing a considerable range of frequency and intensity. These quantifiable acoustic events can be measured and represented in a phonetogram. Previous research has compared the phonetograms of trained and untrained voices and found significant differences between these groups. This study was designed to assess the effects of vocal training for singers over a period of nine months. Phonetogram contour changes were examined, with the primary focus on expansion of frequency range and/or intensity control. Twenty-one first-year, master's level, vocal music students, who were engaged in an intensive vocal performance curriculum, participated in this study. Following nine months of vocal training, significant differences were revealed in the subjects' mean frequency range and minimum vocal intensity across frequency levels. There was no significant difference for the mean maximum vocal intensity across frequency levels following vocal training.     

Initiation gait variability is higher in the morning in elderly inpatients

Objective: Although elderly inpatients are known to experience decreased physical activity in the morning, falls occur frequently during this time. Gait variability is an evaluation of gait instability and a risk factor for falls. Gait initiation requires complex processes, and it is important to evaluate gait variability not only during steady-state gait but also during gait initiation. However, the effect of the diurnal pattern on variability in gait characteristics is still unknown. The aim of this study was to investigate the effect of the diurnal pattern on initiation and steady-state gait variability in elderly inpatients. Method: Thirty-seven elderly inpatients (28 women; mean age, 79.7 ± 9.5 years) who could walk without support were sampled in this study. The quantitative measure of gait variability was evaluated using the coefficient of variation (CV) based on four consecutive stride durations determined using triaxial accelerometers. Gait characteristics were evaluated during initiation and steady-state gait and defined as initiation CV and steady-state CV, respectively. This measurement was performed at two time points, morning and daytime. Results: There was no significant difference between initiation and steady-state gait characteristics in the daytime condition. However, in the morning condition, the initiation CV was higher than the steady-state CV. Furthermore, the initiation CV was higher in the morning than during daytime (p < 0.01). Conclusion: Our study revealed that the variability of initiation gait is higher in the morning. It may be important to assess the risk of falls, including initiation gait, in the morning.     

基于改进ViT的红外人体图像步态识别方法研究

针对卷积神经网络在步态识别时准确率易饱和现象,以及Vision Transformer(ViT)对步态数据集拟合效率较低的问题,提出构建一个对称双重注意力机制模型,保留行走姿态的时间顺序,用若干独立特征子空间有针对性地拟合步态图像块;同时,采用对称架构的方式,增强注意力模块在拟合步态特征时的作用,并利用异类迁移学习进一步提升特征拟合效率。将该模型运用在中科院CASIA C红外人体步态库中进行多次仿真实验,平均识别准确率达到96.8%。结果表明,本文模型在稳定性、数据拟合速度以及识别准确率3方面皆优于传统ViT模型和CNN对比模型。     

基于小波变换的人体步态序列提取

将小波变换用于处理人体行走时产生的加速度信号.利用离散小波变换的多尺度、多分辨率特性对原始加速度信号进行尺度分解,在对小波基以及分解尺度进行合理选取后准确地从加速度信号中提取出隐藏的步态节律.与利用阈值法直接对原始加速度信号提取峰值的算法比较后发现：利用小波分解得到与步态节律相关的特征尺度后再进行峰值检测能显著地提高信号峰值的检出率;即使当原始信号存在较严重的噪声干扰时,该方法也能保证所提取出的步态序列的准确性.这对于步态序列的后续分析具有至关重要的意义.研究表明,离散小波变换是一种有效的提取步态节律的方 关键词： 小波变换 步态序列 峰值检测 特征尺度     

Aerodynamic Measurements: Normative Data for Children Ages 6:0 to 10:11 Years

Normative measures of open quotient, speed quotient, maximum flow declination rate (MFDR), and subglottal pressure were determined for 75 children between the ages of 6 years 0 months and 10 years 11 months. The participants produced a sustained /a/ at low, comfort, and high pitches for a minimum of 5 seconds, and five to seven repetitions of /pa/ at low, comfort, and high pitches. No statistically significant differences were found in the mean measures of any aerodynamic variables (open quotient, speed quotient, maximum flow declination rate, subglottal pressure) between the frequency levels (low, comfort, high pitches). Also, no strong evidence (P > .05) exists that age or sex effect differed between the frequency levels (low, comfort, high) for any of the aerodynamic measures. For /a/ response tasks, mean open quotient measures increased slightly from low to comfort frequency and from comfort to high frequency. Mean speed quotient measures showed minimal differences between low and comfort frequency, with decreased mean measures for high frequency. Mean MFDR measures increased from low to comfort frequency and from comfort to high frequency. Mean subglottal pressure measures increased slightly from low to comfort frequency and from comfort to high frequency.     

Effect of Age, Gender, and Repeated Measures on Intraoral Air Pressure in Normal Adults

The effect of age, gender, and repeated measures on intraoral air pressure (P0) was examined. Sixty adults comprised of 10 males and 10 females in each of three age groups (i.e., 20-39, 40-59, and 60-83 years) participated. P0 was assessed during voiceless stop plosive /p/ productions in repeated vowel/consonant syllables. The three medial plosives of a seven-syllable train were averaged to comprise a token. Five tokens were obtained and averaged for each of three trials. Thus each participant contributed 105 syllables and a subsequent three P0s for analyses. There was no statistically significant difference in P0 as a function of age or gender (P > 0.05). These findings support the conception that P0 remains stable throughout adulthood and is not dependent on gender. Differences in repeated measures of P0 attained statistical significance (P = 0.03), however the mean differences between trials (0.23 cm H20) were negligible and deemed to be clinically insignificant. Thus, across a short sampling session, P0 is a relatively stable measurement and does not change as a function of age or gender.     

Gait Stability Measurement by Using Average Entropy

Gait stability has been measured by using many entropy-based methods. However, the relation between the entropy values and gait stability is worth further investigation. A research reported that average entropy (AE), a measure of disorder, could measure the static standing postural stability better than multiscale entropy and entropy of entropy (EoE), two measures of complexity. This study tested the validity of AE in gait stability measurement from the viewpoint of the disorder. For comparison, another five disorders, the EoE, and two traditional metrics methods were, respectively, used to measure the degrees of disorder and complexity of 10 step interval (SPI) and 79 stride interval (SI) time series, individually. As a result, every one of the 10 participants exhibited a relatively high AE value of the SPI when walking with eyes closed and a relatively low AE value when walking with eyes open. Most of the AE values of the SI of the 53 diseased subjects were greater than those of the 26 healthy subjects. A maximal overall accuracy of AE in differentiating the healthy from the diseased was 91.1%. Similar features also exists on those 5 disorder measurements but do not exist on the EoE values. Nevertheless, the EoE versus AE plot of the SI also exhibits an inverted U relation, consistent with the hypothesis for physiologic signals.     

Multimodal Standardization of Voice Among Four Multicultural Populations: Fundamental Frequency and Spectral Characteristics

A stratified random sample of 20 males and 20 females matched for physiological factors and cultural-linguistic markers were examined to determine differences in fundamental frequency and spectral characteristics during prolongation of three vowels: [a], [i], and [u]. The ethnic-gender breakdown included four sets of five male and five female subjects comprised of Caucasian and African-American speakers of standard American English, native Hindi Indian speakers, and native Mandarin Chinese speakers. Acoustic measures were analyzed using the Multidimensional Voice Program (Kay Elemetrics, Lincoln Park, NJ) (Model 4305) from which fundamental frequency and associated acoustic spectra were extracted from a 200-ms sample of each vowel token. Statistically significant group differences for the main effects of culture, race, and gender were found. The acoustic differences found are attributed to biomechanical, physiological, cultural, and linguistic factors.