Time series forecasting by neural networks: A knee point-based multiobjective evolutionary algorithm approach

In this paper, we investigate the problem of time series forecasting using single hidden layer feedforward neural networks (SLFNs), which is optimized via multiobjective evolutionary algorithms. By utilizing the adaptive differential evolution (JADE) and the knee point strategy, a nondominated sorting adaptive differential evolution (NSJADE) and its improved version knee point-based NSJADE (KP-NSJADE) are developed for optimizing SLFNs. JADE aiming at refining the search area is introduced in nondominated sorting genetic algorithm II (NSGA-II). The presented NSJADE shows superiority on multimodal problems when compared with NSGA-II. Then NSJADE is applied to train SLFNs for time series forecasting. It is revealed that individuals with better forecasting performance in the whole population gather around the knee point. Therefore, KP-NSJADE is proposed to explore the neighborhood of the knee point in the objective space. And the simulation results of eight popular time series databases illustrate the effectiveness of our proposed algorithm in comparison with several popular algorithms.     

Unpowered Knee Exoskeleton Reduces Quadriceps Activity during Cycling

Cycling is an eco-friendly method of transport and recreation. With the intent of reducing the energy cost of cycling without providing an additional energy source, we have proposed the use of a torsion spring for knee-extension support. We developed an exoskeleton prototype using a crossing four-bar mechanism as a knee joint with an embedded torsion spring. This study evaluates the passive knee exoskeleton using constant-power cycling tests performed by eight healthy male participants. We recorded the surface electromyography over the rectus femoris muscles of both legs, while the participants cycled at 200 and 225 W on a trainer with the developed wheel-accelerating system. We then analyzed these data in time–frequency via a continuous wavelet transform. At the same cycling speed and leg cadence, the median power spectral frequency of the electromyography increases with cycling load. At the same cycling load, the median power spectral frequency decreases when cycling with the exoskeleton. Quadriceps activity can be relieved despite the exoskeleton consuming no electrical energy and not delivering net-positive mechanical work. This fundamental can be applied to the further development of wearable devices for cycling assistance.     

Musculoskeletal complaints among nurses related to patient handling tasks and psychosocial factors--based on logbook registrations

The aims were to evaluate the inter-method reliability of a registration sheet for patient handling tasks, to study the day-to-day variation of musculoskeletal complaints (MSC) and to examine whether patient handling tasks and psychosocial factors were associated with MSC.Nurses (n = 148) fulfilled logbooks for three consecutive working days followed by a day off. Low back pain (LBP), neck/shoulder pain (NSP), knee pain (KP), psychosocial factors (time pressure, stress, conscience of the quality of work) and patient transfers and care tasks were reported.The logbook was reliable for both transfer and care tasks. The numbers of nurses reporting MSC and the level of pain increased significantly during the three working days (15%-30% and 17%-37%, respectively) and decreased on the day off. Stress and transfer task were associated with LPB and transfer tasks were associated with KP.Our results confirm a relationship between work factors and MSC and indicate that logs could be one way to obtain a better understanding of the complex interaction of various nursing working conditions in relation to MSC.     

Validity of self-reporting and video-recording for measuring knee-straining work postures

The aim of this study was to compare the validity of self-reporting and video-recording as methods of measuring the duration of knee-straining work postures, and to evaluate the reproducibility of timings of the video-recordings. Thirty-nine carpenters and 33 floorlayers were video-filmed while working, and were asked immediately afterwards to quantify the amount of time spent in knee-straining positions. The investigators recorded the periods of knee-straining work with a stopwatch during playback of the video-film, and the agreement between the two investigators' measurements was studied in 13 pairs of measurements. The video observation method was very effective for timing knee-strain work. Furthermore, Spearman's correlation coefficient (0.88) indicated a good association between observed and self-reported knee-straining work. Estimation of self-reported kneestraining work collected by interview showed good correlation with measurements of video-recordings. When judging the repeatability of timings of kneestraining work from the video-recordings, a high level of agreement was seen between the two observers in the 13 dual measurements of time spent in knee-straining work positions.     

Biomechanical comparison of carpet-stretching devices

Peak impact forces, measured from seven male carpetlayers using a knee-kicker over 39 trials were 2933?N (SD 397), taking 9·5?ms (SD ± 1·1) to reach peak. The knee-kicking cycle involved high knee decelerations of 880?m.s^?2 (SD ±271). Angles at peak force for the knee (63° SD ± 10°) and hip (80° SD ± 35°) showed considerable variation between individuals. Kneeling forces on the non-kicking leg during the kick cycle were 894?N: comparative forces were 368?N and 476?N measured during use of the power stretcher and crab re-stretcher, respectively. Under dynamic conditions the effective mechanical advantage of the knee-kicker was less than 1·0. In comparison, the mechanical advantage of the power stretcher was approximately 14 times greater over the stretch action. When tested with a crab re-stretcher, the breaking strength of the smooth-edge to which the carpet attaches averaged 2384?N (SD ± 245). Design guidelines for an improved carpet stretching device are provided.     

New method for simultaneous anatomical and functional studies of articular joints and its application to the human knee

In this paper a new methodology is described for the acquisition and computer elaboration of joint anatomy and motion data and the study of their correlation. The method uses a particular commercial electrogoniometer never used before for biomechanic investigations and software developed by the author for numerical interpolations and interactive display of the anatomical structures during joint motion. The original data acquisition protocol and computer elaboration software are described in detail, the theoretical and experimental accuracy of the method is reported and the original features and potential benefits of this approach in the field of joint biomechanics are discussed. Finally an experimental application for geometrical and functional analysis of the knee is presented as a practical example.     

MR imaging of baker cysts—prevalence and relation to internal derangements of the knee

Rationale and objectives: To evaluate the prevalence of popliteal cysts in patients studied with magnetic resonance (MR) imaging. Cyst presence and volume will be related to other internal derangement of the knee.Materials and methods: Three hundred and eighty-two consecutive patients with a MR study of the knee were included. Images were obtained in the three spatial orthogonal planes and evaluated through consensus. Four categories were established for the Baker cyst and synovial fluid (absence, minimum, moderate and massive), and the presence of meniscal, cruciate ligaments and cartilage lesions were recorded. Statistical analysis was carried out with bivariate analysis (χ² of Pearson and Gamma tests).Results: From the 382 patients, 145 had Baker cysts (38.0%). Cyst content was minimum in 99, moderate in 34 and massive in 12. Joint effusion was observed in 269 patients (70.4%), being minimal in 140 patients, moderate in 119 and massive in ten. Meniscal lesions were observed in 195 patients (51%), while 58 patients (15%) had a cruciate ligament lesion. Baker cyst has a statistically significant direct relationship with the presence and quantity of synovial fluid (P=0.002) and with the presence and type of meniscal lesion (P=0.01) but not with cruciate ligaments or cartilage lesions.Conclusions: The prevalence of Baker cysts in MR studies of the knee is high. Its presence and volume are related to the quantity of synovial fluid, and to the presence and severity of meniscal lesions.     

Reliability-based multiobjective optimization for automotive crashworthiness and occupant safety

This paper presents a methodology for reliability-based multiobjective optimization of large-scale engineering systems. This methodology is applied to the vehicle crashworthiness design optimization for side impact, considering both structural crashworthiness and occupant safety, with structural weight and front door velocity under side impact as objectives. Uncertainty quantification is performed using two first order reliability method-based techniques: approximate moment approach and reliability index approach. Genetic algorithm-based multiobjective optimization software GDOT, developed in-house, is used to come up with an optimal pareto front in all cases. The technique employed in this study treats multiple objective functions separately without combining them in any form. It shows that the vehicle weight can be reduced significantly from the baseline design and at the same time reduce the door velocity. The obtained pareto front brings out useful inferences about optimal design regions. A decision-making criterion is subsequently invoked to select the “best” subset of solutions from the obtained nondominated pareto optimal solutions. The reliability, thus computed, is also checked with Monte Carlo simulations. The optimal solution indicated by knee point on the optimal pareto front is verified with LS-DYNA simulation results.     

Comparisons of tibial accelerations when walking on a wood composite vs. a concrete mezzanine surface

Mezzanine surfaces can be made from concrete, bar grate, or composite materials. Anecdotal data indicate that mezzanines in distribution centers made from composite materials, due to their increased compliance, may be a more comfortable working surface. Prior research suggested that a measure of tibial shock, peak tibial acceleration, could potentially discriminate the biomechanical differences between these surfaces. The objective of this study was to quantify differences in tibial accelerations as 27 people walked on mezzanines constructed from concrete and a wood composite material. Accelerometers were attached bilaterally to the shins of volunteers, and data were collected as they walked 30.5 m on each surface at their normal walking speed, a faster-than-normal walking speed, and a slower-than-normal walking speed. Peak acceleration values obtained from the leg with the highest values were compared. On average, the peak acceleration values were 5% higher on the concrete mezzanine as compared with the wood composite mezzanine (p = .036). These findings suggest that individuals working on mezzanines in distribution centers constructed from composite surfaces would potentially experience less discomfort associated with long exposure periods on these surfaces.     

膝关节内侧副韧带损伤的超声诊断价值

目的探讨超声对膝关节内侧副韧带(MCL)损伤的诊断价值。方法回顾性分析19例内侧副韧带不同类型损伤的声像图表现,并与手术及临床结果对照比较。结果11例内侧副韧带完全或部分撕裂伤的超声诊断与手术结果相符,8例挫伤经临床保守治疗前后超声对比观察证实超声检查与临床诊断相符。结论超声是诊断膝关节内侧副韧带损伤的一种可靠方法。