A nonlinear seat suspension with high-static low-dynamic stiffness based on negative stiffness structure for helicopter

One of the most important issues for the helicopter pilots is the health risk due to the vibration transmitted to the pilot through the seat. In this article, a seat suspension based on negative stiffness structure is presented to decrease the vibration transmitted to the pilot in both vertical and lateral directions without losing the loading capacity of the system. Here, an integrated model of the suspension–cushion–occupant is derived. To generalize the results of system analysis and its usability in other applications, the impact of parameters on the system performance is studied in dimensionless form. Despite coupling between the lateral and vertical directions, the design parameters of the seat suspension are determined in such a way that the system responds simultaneously as a negative stiffness structure in both directions. The system efficiency in vibration damping is assessed by seat effective amplitude transmissibility and transmissibility criteria. In addition, the whole body vibration and impact of the vibration on the pilot body are evaluated using ISO-2631. To verify the system efficiency in more realistic situation, the simulations are performed using the measured vibration data of a Bell-412 helicopter. The results indicate that the vibration amplitude is decreased by about 45% and 48% in the lateral and vertical directions, respectively. The frequency spectrum comparison of the seat and cabin floor reveals 80% reduction of amplitude in fundamental frequency in the vertical direction, whereas it is about 93% in the lateral direction. Furthermore, the level of pilot’s comfort and perception is improved that demonstrates better riding quality and reduced vibration environment.

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Improvement of Comfort in Suspension Seats with a Pneumatic Negative Stiffness System

Actuators ◽

10.3390/act9040126 ◽

2020 ◽

Vol 9 (4) ◽

pp. 126

Author(s):

Eduardo Palomares ◽

Angel L. Morales ◽

Antonio J. Nieto ◽

Jose M. Chicharro ◽

Publio Pintado

Keyword(s):

Vibration Isolation ◽

Dynamic Stiffness ◽

Nonlinear Dynamic System ◽

Negative Stiffness ◽

Vehicle Model ◽

Seat Suspension ◽

Highly Nonlinear ◽

Linear Actuators ◽

Static Conditions

This paper presents a Negative Stiffness System (NSS) for vibration isolation and comfort improvement of vehicle seats, which enhances the performance of optimized traditional passive seat suspensions. The NSS is based on a set of two Pneumatic Linear Actuators (PLAs) added to a seat supported by a pneumatic spring. One end of each PLA is joined to the seat while the other end is joined to the vehicle frame. In static conditions, the PLAs remain horizontal, whereas in dynamic conditions, their vertical forces work against the pneumatic spring, reducing the overall dynamic stiffness and improving passenger comfort. The paper presents a stability analysis of the highly nonlinear dynamic system, as well as the numerical determination of the optimum PLA pressure for a given passenger mass that maximises comfort without instabilities. Finally, the performance of the proposed NSS is compared to that of a traditionally optimized passive seat suspension via simulations of an eight-degree-of-freedom vehicle model traversing several road profiles and speed bumps. Comfort improvements between 10% and 35% are found in all tests considered.

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The impact of a patient trolley's intra-hospital speed and position on the quality of ventilation performed by a self-inflating bag.

10.21203/rs.3.rs-411850/v1 ◽

2021 ◽

Author(s):

Tomasz Sanak ◽

Monika Bednarek Chaluda ◽

Magdalena Kromka Szydek ◽

Anna Zadlo ◽

Dorota Konieczna ◽

...

Keyword(s):

Video Recording ◽

Vertical Direction ◽

Subjective Assessment ◽

Qualitative Assessment ◽

Whole Body ◽

Movement Direction ◽

Patient Transport ◽

Resonance Frequencies ◽

Rescue Procedures ◽

The Impact

Abstract Purpose: The aim of the study is to make a quantitative and qualitative assessment of selected parameters connected with a patient's ventilation using a self-inflating bag during simulated 'head-first' or ‘legs-first' directions of patient transport. Methods: Seventeen people participated in the conducted study. Their task included conducting alternative ventilation during the transport of the patient (Airway Management Simulator BT Inc.) by using the head or the legs technique: in the transport trolley's movement direction. At all times during the transport, video recording was carried out non–stop, and the spectrum of generated vibrations was recorded using the SVAN 958 vibration spectrum analyser, with a three-direction SVANTEK SV 39A disc for measuring whole body vibrations. Additionally, a survey was carried out. The task of the research participants was to indicate the degree of performer comfort related to the ventilation and the transport process. The assessment of the results was then subjected to statistical analysis. Results: The duration of the patient transport by using the legs-first technique was shorter (57.5 s on average) in comparison with the head-first one (62.5 s on average). The subjective assessment of performer comfort on the transport and ventilation process with the legs-first technique was perceived as higher compared to the head-first one. During the patient transport, the highest a RMS acceleration values in the vertical direction were obtained for frequencies 8-25 [Hz], corresponding to the resonance frequencies of the head (17-25 Hz), trachea and bronchi (12-16 Hz), lungs (4-11 Hz) and the spine (8-12 Hz). According to other authors, vibrations with a frequency of 8-10 Hz lead to a decrease in blood pressure, bradycardia and bradypnoe; vibrations at a frequency of 11-12 Hz cause increased heart rate, peripheral vasoconstriction, fatigue, abnormal temperature, nausea, abdominal and chest pain, while vibrations above 12 Hz cause dangerous arrhythmia, muscle tremors, pain and bleeding. Conclusions: The recommended position of intra-hospital patient transport is the legs-first technique. At the stage of preparation for transport, it is necessary to keep in mind the ergonomic aspects of carrying out possible rescue procedures, e.g. artificial ventilation, the effectiveness of which depends on the height of the patient’s trolley, the elbow-shoulder angle of the paramedic, and their back inclination in the thoracolumbar section. The training of medical staff should include conducting high fidelity simulation of activities connected with e.g. transport, enabling future paramedics to acquaint themselves with the working conditions in terms of the effectiveness of actions and ensuring adequate work ergonomics.

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Theoretical Modeling and Vibration Isolation Performance Analysis of a Seat Suspension System Based on a Negative Stiffness Structure

Applied Sciences ◽

10.3390/app11156928 ◽

2021 ◽

Vol 11 (15) ◽

pp. 6928

Author(s):

Xin Liao ◽

Ning Zhang ◽

Xiaofei Du ◽

Wanjie Zhang

Keyword(s):

Vibration Isolation ◽

Vibration Suppression ◽

Ride Comfort ◽

Dynamic Stiffness ◽

Suspension System ◽

Negative Stiffness ◽

Nonlinear Dynamic Model ◽

Seat Suspension ◽

Vibration Isolation Performance ◽

Isolation Performance

In this study, to improve the vibration isolation performance of a cab seat and the ride comfort of the driver, we propose a mathematical model for a seat suspension system of a construction machinery cab based on a negative stiffness structure (NSS). First, a static analysis of a seat suspension system is conducted and the different parameters and their influences on the dynamic stiffness are discussed. Thereby, the ideal configuration parameter range of the suspension system is obtained. Moreover, the nonlinear dynamic model of the designed seat suspension system is established. The frequency response and the stability are analyzed by using the HBM method and numerical simulation. The vibration transmissibility characteristics and vibration suppression effects of the seat suspension system are presented in detail. The results show that, as compared with a quasi-zero-stiffness system, the QZS-IE system has higher vibration suppression advantages under large excitation and small damping, as well as lower transmissibility and a wider vibration isolation frequency range. In addition, an inerter element with a larger mass ratio and relatively shorter distance ratio is better for vibration isolation performance of the QZS-IE system in a practical engineering application. The results of this study provide a scientific basis for the design and improvement of a seat suspension system.

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An Ultra-Low Frequency Two DOFs’ Vibration Isolator Using Positive and Negative Stiffness in Parallel

Mathematical Problems in Engineering ◽

10.1155/2016/3728397 ◽

2016 ◽

Vol 2016 ◽

pp. 1-15 ◽

Cited By ~ 3

Author(s):

Min Wang ◽

Xuedong Chen ◽

Xiaoqing Li

Keyword(s):

Natural Frequency ◽

Vibration Isolation ◽

Dynamic Stiffness ◽

Low Frequency ◽

Vertical Direction ◽

Negative Stiffness ◽

Effective Bandwidth ◽

Vibration Isolator ◽

Analysis System ◽

The Stability

With the improvement of performance in the ultra-precision manufacturing engineering, the requirements for vibration isolation have become increasingly stringent. In order to get wider effective bandwidth and higher performance of vibration isolation in multiple DOFs system, an ultra-low frequency two DOFs’ vibration isolator with positive and negative stiffness in parallel (PNSP) is proposed. The two DOFs’ isolator which combines a positive stiffness (PS) air spring with a negative stiffness (NS) magnetic spring in parallel and combines a PS flat spring with an NS inverted pendulum in parallel is designed to reduce the natural frequency and broaden the effective bandwidth in horizontal and vertical direction. Based on this structure, stiffness models of different components in different directions are established. Compared with a PS isolator, it possesses the characteristic of high-static-low-dynamic stiffness. The simulation curves also provide strong evidence. Last, a real-time active control system and a spectrum testing and analysis system are used for the contrast experiment between the mentioned PNSP structure and PS only. The experimental results demonstrate that the isolator with PNSP can obviously reduce the natural frequency to 1 Hz and simultaneously maintain the stability of the system and consequently verify the validity and superiority of the mentioned structure.

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Automated unit for magnetic pulse processing of strawberries

E3S Web of Conferences ◽

10.1051/e3sconf/202128507024 ◽

2021 ◽

Vol 285 ◽

pp. 07024

Author(s):

Dmitriy Khort ◽

Alexey Kutyrev ◽

Rostislav Filippov

Keyword(s):

Magnetic Induction ◽

Pulse Repetition Frequency ◽

Vertical Direction ◽

Control Unit ◽

Field Studies ◽

Design Parameters ◽

Magnetic Pulse ◽

Pulse Processing ◽

Working Bodies ◽

The Impact

The article presents the developed automated unit for magnetic pulse processing of strawberries. To maintain the required magnetic induction value in the impact zone, the unit design provides for the possibility of changing the position of the working bodies in the vertical and horizontal planes in an automated mode. The unit includes a device for magnetic pulse treatment of plants, magnetic inductors, a control unit for the system of adaptation of working bodies and a program for controlling operating modes. As a result of field studies, it was found that in order to obtain the required value of magnetic induction in the processing zone at a pulse repetition frequency from 1 to 64 Hz and a magnetic induction of 0.3-15 MT, it is necessary to ensure a distance between the working organs and plants from 10 to 250 mm. The required design parameters of the unit that allow for magnetic pulse processing on strawberry plantings with a row spacing of 0.3-1.5 m are determined: the width of the gripper, adjustable 1.6-3.6 m, the tilt adjustment of the working bodies in the vertical direction from 0 to 90.

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The Impact of Training With Whole Body-EMS

Case Medical Research ◽

10.31525/ct1-nct04288154 ◽

2020 ◽

Author(s):

Keyword(s):

Whole Body ◽

The Impact

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A Melanocortin-4 Receptor Agonist Induces Skin and Hair Pigmentation in Patients with Monogenic Mutations in the Leptin-Melanocortin Pathway

Skin Pharmacology and Physiology ◽

10.1159/000516282 ◽

2021 ◽

pp. 1-10

Author(s):

Varvara Kanti ◽

Lia Puder ◽

Irina Jahnke ◽

Philipp Maximilian Krabusch ◽

Jan Kottner ◽

...

Keyword(s):

Leptin Receptor ◽

Skin Pigmentation ◽

Gene Mutations ◽

Continuous Treatment ◽

Whole Body ◽

Hair Color ◽

Phase 2 ◽

Loss Of Function ◽

The Impact ◽

Over Time

Background and Objectives: Gene mutations within the leptin-melanocortin signaling pathway lead to severe early-onset obesity. Recently, a phase 2 trial evaluated new pharmacological treatment options with the MC4R agonist setmelanotide in patients with mutations in the genes encoding proopiomelanocortin (POMC) and leptin receptor (LEPR). During treatment with setmelanotide, changes in skin pigmentation were observed, probably due to off-target effects on the closely related melanocortin 1 receptor (MC1R). Here, we describe in detail the findings of dermatological examinations and measurements of skin pigmentation during this treatment over time and discuss the impact of these changes on patient safety. Methods: In an investigator-initiated, phase 2, open-label pilot study, 2 patients with loss-of-function POMC gene mutations and 3 patients with loss-of-function variants in LEPR were treated with the MC4R agonist setmelanotide. Dermatological examination, dermoscopy, whole body photographic documentation, and spectrophotometric measurements were performed at screening visit and approximately every 3 months during the course of the study. Results: We report the results of a maximum treatment duration of 46 months. Skin pigmentation increased in all treated patients, as confirmed by spectrophotometry. During continuous treatment, the current results indicate that elevated tanning intensity levels may stabilize over time. Lips and nevi also darkened. In red-haired study participants, hair color changed to brown after initiation of setmelanotide treatment. Discussion: Setmelanotide treatment leads to skin tanning and occasionally hair color darkening in both POMC- and LEPR-deficient patients. No malignant skin changes were observed in the patients of this study. However, the results highlight the importance of regular skin examinations before and during MC4R agonist treatment.

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The Impact of Nordic Walking on Bone Properties in Postmenopausal Women with Pre-Diabetes and Non-Alcohol Fatty Liver Disease

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18147570 ◽

2021 ◽

Vol 18 (14) ◽

pp. 7570

Author(s):

Xiaming Du ◽

Chao Zhang ◽

Xiangqi Zhang ◽

Zhen Qi ◽

Sulin Cheng ◽

...

Keyword(s):

Liver Disease ◽

Fatty Liver ◽

Postmenopausal Women ◽

Fatty Liver Disease ◽

Whole Body ◽

Nordic Walking ◽

Significant Group ◽

Time Interaction ◽

Bone Properties ◽

The Impact

This study investigated the impact of Nordic walking on bone properties in postmenopausal women with pre-diabetes and non-alcohol fatty liver disease (NAFLD). A total of 63 eligible women randomly participated in the Nordic walking training (AEx, n = 33), or maintained their daily lifestyle (Con, n = 30) during intervention. Bone mineral content (BMC) and density (BMD) of whole body (WB), total femur (TF), femoral neck (FN), and lumbar spine (L2-4) were assessed by dual-energy X-ray absorptiometry. Serum osteocalcin, pentosidine, receptor activator of nuclear factor kappa-B ligand (RANKL) levels were analyzed by ELISA assay. After an 8.6-month intervention, the AEx group maintained their BMCTF, BMDTF, BMCL2−4, and BMDL2−4, and increased their BMCFN (p = 0.016), while the Con group decreased their BMCTF (p = 0.008), BMDTF (p = 0.001), and BMDL2−4 (p = 0.002). However, no significant group × time interaction was observed, except for BMDL2−4 (p = 0.013). Decreased pentosidine was correlated with increased BMCWB(r = −0.352, p = 0.019). The intervention has no significant effect on osteocalcin and RANKL. Changing of bone mass was associated with changing of pentosidine, but not with osteocalcin and RANKL. Our results suggest that Nordic walking is effective in preventing bone loss among postmenopausal women with pre-diabetes and NAFLD.

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The Effect of Repeated Whole-Body Cryotherapy on Sirt1 and Sirt3 Concentrations and Oxidative Status in Older and Young Men Performing Different Levels of Physical Activity

Antioxidants ◽

10.3390/antiox10010037 ◽

2020 ◽

Vol 10 (1) ◽

pp. 37

Author(s):

Gabriela Wojciak ◽

Jadwiga Szymura ◽

Zbigniew Szygula ◽

Joanna Gradek ◽

Magdalena Wiecek

Keyword(s):

Physical Activity ◽

Young Men ◽

Oxidative Status ◽

Whole Body ◽

Stress Index ◽

Blood Levels ◽

Long Distance ◽

Antioxidant Defence ◽

Whole Body Cryotherapy ◽

The Impact

Background: The activity of antioxidant enzymes and sirtuins (Sirt) decreases along with age, which is counteracted by aerobic training. Sirtuins increase antioxidant defence. Whole-body cryotherapy (WBC) increases total antioxidant capacity (TAC) in young men. The aim of our study was to assess the impact of 24 WBC treatments on the blood concentration of selected sirtuins and the level of antioxidant defence as well as oxidative stress index of training and non-training men depending on age. Methods: The study involved 40 males. In each group, there were 10 non-training older and young men (60 NTR and 20 NTR), and 10 older and young long-distance runners (60 TR, 20 TR). During an 8-week period, participants underwent 24 WBC treatments (3 min −130 °C), which were performed three times a week (Monday, Wednesday, Friday). The concentrations of Sirt1, Sirt3, TAC, total oxidative status and the activity of superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) in the blood were determined before 1 WBC and after 1 WBC, 12 WBC and 24 WBC. Results: After 1 WBC, the activity of GPx and the concentration of Sirt1 and TAC in 60 TR and TAC in 60 NTR increased. After 12 WBC, the level of Sirt1 in 20 NTR and SOD in 20 TR increased. After 24 WBC, the level of Sirt1 increased in 60 TR and in 20 NTR, Sirt3 in 60 TR and SOD in 20 TR. Conclusions: Cryogenic temperatures increase blood levels of Sirt1 and Sirt3 and systemic antioxidant defence in men, but the effect is dependent on age, level of performed physical activity and the number of applied treatments.

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Weight Status and Visceral Adiposity Mediate the Relationship between Exclusive Breastfeeding Duration and Skin Carotenoids in Later Childhood

Current Developments in Nutrition ◽

10.1093/cdn/nzab010 ◽

2021 ◽

Author(s):

Ruyu Liu ◽

Caitlyn G Edwards ◽

Corinne N Cannavale ◽

Isabel R Flemming ◽

Morgan R Chojnacki ◽

...

Keyword(s):

Adipose Tissue ◽

Exclusive Breastfeeding ◽

Weight Status ◽

Mediating Effect ◽

Physical Growth ◽

Breastfeeding Duration ◽

Whole Body ◽

Controlled Clinical Trial ◽

The Impact ◽

The Relationship

Abstract Background Breastfeeding is associated with healthier weight and nutrient status in early life. However, the impact of breastfeeding on carotenoid status beyond infancy, and the influence of adiposity, is unknown. Objective The aim of the study was to retrospectively investigate the relationship between breastfeeding and carotenoid status, and the mediating effect of weight status and adiposity on this relationship among school-aged children. Methods This was a secondary analysis of baseline data collected from a randomized-controlled clinical trial. (ClinicalTrials.gov Identifier: NCT03521349). 7–12-year-old (n = 81) children were recruited from East-Central Illinois. Dual-energy x-ray absorptiometry (DXA) was used to assess visceral adipose tissue (VAT) and whole-body adiposity (%Fat). Weight was obtained to calculated body mass index percentile (BMI %ile). Skin carotenoids were assessed via reflection spectroscopy. Macular carotenoids were assessed as macular pigment optical density (MPOD). Dietary, birth, and breastfeeding information was self-reported by parents. Results Skin carotenoids were inversely related to %Fat (P < 0.01), VAT (P < 0.01) and BMI %ile (P < 0.01). VAT and BMI %ile significantly mediated this relationship between exclusive breastfeeding duration and skin carotenoids, following adjustment for dietary carotenoids, energy intake, and mother education. Conclusions Weight status and adipose tissue distribution mediate the positive correlation between exclusive breastfeeding duration and skin carotenoids among children aged 7–12 years. The results indicate the need to support breastfeeding and healthy physical growth in childhood for optimal carotenoid status.

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