Rubber Ball Research Articles

A Simple Semi-Analytic Contact Mechanical Model for Tangential and Torsional Fretting Wear of Axisymmetric Contacts

Fretting wear of axisymmetric contacts is considered within the framework of the Hertz–Mindlin approximation and the Archard law for the linear wear. If the characteristic time scale for the wear is much larger than the duration of a single fretting oscillation, the profile change due to wear during one fretting cycle can be neglected for the contact problem as a zero-order approximation. This allows to give an exact contact solution during each fretting cycle, depending on the current worn profile, and thus for the explicit statement of an ordinary integro-differential equation system for the time-evolution of the fretting profile, which can be easily solved numerically. The proposed method gives the same results as a known, contact mechanically more rigorous simulation procedure that also operates within the framework of the Hertz–Mindlin approximation, but works significantly faster than the latter one. Tangential and torsional fretting wear are considered in detail. A comparison of the numerical prediction for the evolution of the worn profile in partial slip torsional fretting of a rubber ball on abrasive paper shows good agreement with experimental results from the literature.

A Simple Semi-Analytic Contact Mechanical Model for Tangential and Torsional Fretting Wear of Axisymmetric Contacts

Fretting wear of axisymmetric contacts is considered within the framework of the Hertz–Mindlin approximation and the Archard law for the linear wear. If the characteristic time scale for the wear is much larger than the duration of a single fretting oscillation, the profile change due to wear during one fretting cycle can be neglected for the contact problem as a zero-order approximation. This allows to give an exact contact solution during each fretting cycle, depending on the current worn profile, and thus for the explicit statement of an ordinary integro-differential equation system for the time-evolution of the fretting profile, which can be easily solved numerically. The proposed method gives the same results as a known, contact mechanically more rigorous simulation procedure that also operates within the framework of the Hertz–Mindlin approximation, but works significantly faster than the latter one. Tangential and torsional fretting wear are considered in detail. A comparison of the numerical prediction for the evolution of the worn profile in partial slip torsional fretting of a rubber ball on abrasive paper shows good agreement with experimental results from the literature.

An intersectional gender analysis of familial and socio-cultural drivers of inequitable scientific career progression of researchers in Sub-Saharan Africa

BackgroundSub-Saharan Africa (SSA) suffers from a dearth of concrete information on the causes of women’s under-representation in scientific research workforce particularly at higher levels compared with the wealth of information that exists in the global north. The goal of this study was to illuminate familial and socio-cultural drivers that contribute to intersectional gender inequities in scientific career progression in SSA to inform strategies that could promote career equity for African scientific researchers.MethodsThis study was nested within the context of ‘Developing Excellence in Leadership, Training and Science in Africa’ (DELTAS Africa)—a health-based scientific research capacity strengthening initiative. It adopted an exploratory qualitative cross-sectional study design. In-depth interviews were conducted among 58 (32 Female and 26 Male) trainees/research fellows at various career stages, affiliated to three purposively selected African Research Consortia. The interviews were conducted between May and December 2018 in English. The data were analysed inductively based on emergent themes.ResultsThe study participants were nationals of thirteen SSA countries. More female than male participants had young children. Four themes were identified. They illustrate women’s and men’s characterisation of the normative career pathway and progression requirements which calls for significant ‘time’ commitments (theme 1), and how social power relations of gender within the family and wider society shapes their participation in scientific research activities (theme 2). This culminates in researchers'' differential experiences of navigating between the ‘two different lives’—family and career, and the resultant implications for their career progression and personal well-being (theme 3). Women researchers made different and conscious trade-offs for navigating the ‘two different lives’ by utilising various metaphors such as the ‘biological clock and career clock’, the ‘glass ball and rubber ball’, and the concept of ‘sacrifice’ (theme 4).ConclusionsThis study is the first of its kind to demonstrate how intersectional gender analysis through use of qualitative research methods may provide novel insights into the hidden familial and socio-cultural drivers of gender inequitable scientific research career progression. It offers important policy and practice measures and approaches for fostering career equity for women and men scientists within research capacity strengthening initiatives in SSA.

Osseoperception in transcutaneous osseointegrated prosthetic systems (TOPS) after transfemoral amputation: a prospective study.

Endo-exo prosthetics (EEP), which belongs to the transcutaneous osseointegrated prosthetic systems (TOPS), provides an alternative bone-anchored rehabilitation method for transfemoral amputees. It led to the question of whether transmitted forces from prosthetic feet are perceptible by osseoperception resulting in proprioceptive feedback of ground conditions. The following hypotheses emerged for our trial with the null hypothesis: EEP fitting after transfemoral amputation does not influence osseoperception. Alternative hypothesis 1: EEP patients achieve better osseoperception results than transfemoral amputees fitted with socket prosthesis. Alternative hypothesis 2: EEP carriers achieve comparable results with regards to their osseoperception as non-amputees. N = 25 patients with EEP (mean age = 50,6 ± 9,4, male/female = 15/10) N = 25 patients with socket prostheses (mean age = 52,6 ± 13,1, male/female = 19/6) and N = 25 healthy volunteers were included in the experimental case-control study. In three blinded test modules (V1, V2, V3), the participants had to identify different degrees of shore hardness (c) of different materials (rubber balls (shore = 5-25c), foam cushions (shore = 5-30c), foam mats (shore = 5-30c) with their prosthetic foot (or a personally defined foot in healthy volunteers) without footwear and had to rank them into the correct order according to their tactile sensation and the degree of hardness. A maximum of 10 points could be scored per run. This experimental observational study included N = 75 participants. The mean age for the entire cohort was 42.8 ± 16.6years and the BMI was 26.0 ± 4.8. Our results show a significant level of differences in tactile osseoperception between all groups (p < 0.001). A correlation between the mean values of V1-3 and the PMQ2.0 as well as the mean values of K-Level and the prosthesis wearing time per day showed for PMQ (r = 0.387, p = 0.006) and K-level (r = 0.448, p = 0.001) which is a moderate effect according to Cohen. Our study results suggest that the EEP treatment can lead to an improvement in tactile sensory perception via the bone-anchored implant, which can lead to an increase in quality of life and improved gait safety.

Subjective responses between real impact sound and rubber ball im-pact sound

By the recent COVID-19 situation, people stay more time in their home and abatements on noise between neighbouring units are increasing. Heavy/soft impact sound is one of the major noise sources in high-rise apartment buildings. Standardized heavy/soft impact source is known for having the most similar physical and subjective characteristics with real impact sound such as a child running, jumping and an adult walking. The single number quantity on the rubber ball was standardized. A classification scheme for rubber ball impact sound needs to be standardized. Several studies on subjective responses were conducted on rubber ball impact sound in various situations. In this study, subjective responses on the rubber impact sound and real impact sound were compared. The subjective experiment was conducted in the listening chamber which is furnished similarly to the typical living room of Korean apartment buildings. In the experiment, rubber ball impact sounds recorded in the real apartment building and real impact sound recorded in the mock-up building were presented through a sub-woofer and multi-channel loudspeaker system. Subjective responses were collected with an 11 points SD scale.

Subjective and objective evaluation of the impact and airborne sound insulation of multi-unit residential buildings

Multi-unit residential building (MURB) occupants often express dissatisfaction with their suites' acoustic conditions despite existing building acoustic standards and regulations as well as growing research on noise control and building acoustics. Reasons for this include the lack of proper characterization of acoustic comfort in MURBs and lack of comprehensive and stringent regulations. To better understand factors that impact acoustic comfort and explore strategies to improve the acoustic performance of MURBs, investigations of acoustic conditions were carried out. This work presents the results of the investigations which include subjective and objective evaluations of acoustic conditions in two MURBs. Impact sound insulation measurements using both a tapping machine and a rubber ball as well as 24-hour indoor noise monitoring were carried out in unoccupied suites. An online survey was then used to collect subjective assessments of the noise conditions in the buildings and the effects on occupants' comfort post occupancy. Results of the data analysis suggest that occupants are more sensitive to low-frequency impact sounds than mid- and high-frequency impact noise.

Background Noise, Noise Sensitivity, and Attitudes towards Neighbours, and a Subjective Experiment Using a Rubber Ball Impact Sound.

When children run and jump or adults walk indoors, the impact sounds conveyed to neighbouring households have relatively high energy in low-frequency bands. The experience of and response to low-frequency floor impact sounds can differ depending on factors such as the duration of exposure, the listener’s noise sensitivity, and the level of background noise in housing complexes. In order to study responses to actual floor impact sounds, it is necessary to investigate how the response is affected by changes in the background noise and differences in the response when focusing on other tasks. In this study, the author presented subjects with a rubber ball impact sound recorded from different apartment buildings and housings and investigated the subjects’ responses to varying levels of background noise and when they were assigned tasks to change their level of attention on the presented sound. The subjects’ noise sensitivity and response to their neighbours were also compared. The results of the subjective experiment showed differences in the subjective responses depending on the level of background noise, and high intensity rubber ball impact sounds were associated with larger subjective responses. In addition, when subjects were performing a task like browsing the internet, they attended less to the rubber ball impact sound, showing a less sensitive response to the same intensity of impact sound. The responses of the group with high noise sensitivity showed an even steeper response curve with the same change in impact sound intensity. The group with less positive opinions of their neighbours showed larger changes in their subjective response, resulting in the expression of stronger opinions even to the same change in loudness of the impact sound. It was found that subjective responses were different when subjects were performing activities of daily living, such as reading or watching TV in the evening, and when they were focused on floor impact sounds in the middle of the night.

Fish-shaped anterior capsular rupture with anterior subcapsular cataract following blunt trauma in a young man

A 20-year-old man presented with a history of blunt trauma by a rubber ball to his right eye. His visual acuity in the affected eye was 20/120 for distance and N36 for near. The lens showed anterior capsule tear with anterior subcapsular cataract, which did not progress to maturation even after 1 month. Following initial conservative management, phacoemulsification with a three-piece monofocal intraocular lens (IOL) implantation was performed and best-corrected visual acuity (BCVA) of 20/20 was achieved. This represents one of the few cases of blunt trauma presenting as an isolated anterior capsule rupture and anterior subcapsular cataract without mature cataract formation.

Cardboard and rubber objects as means of environmental enrichment for rabbits

Environmental enrichment improves rabbit welfare in rabbitries. Various toys for cats and dogs are commercially available, which are made of materials that could be safely used for rabbits as well. The objectives of this study were to evaluate whether cardboard and rubber materials could be used for environmental enrichment for rabbits. The study involved 42 adult New Zealand white rabbits (20 females and 22 males), randomly assigned to seven treatment groups: “C”, without object (control); “RB”, a solid rubber ball; “FT”, a fillable teether filled with hay; “CH”, a cardboard hole; “CS”, a piece of a cat scratcher; “CSC”, a piece of a cat scratcher with catnip; “CF”, an articulated cardboard fish. The behaviour of the rabbits and the percentage of destruction of the objects were recorded for 28 d. The normal behaviours of locomotion, rearing, stretching, stereotypies and sitting were not influenced by the treatments. Lying down was observed more frequently than the full stretched out position for resting. The FT-treatment group presented most behaviours of interaction (biting and sniffing) (&lt;em&gt;P&lt;/em&gt;&amp;lt;0.05) as compared to RB, CSC, and CF-treatment groups. All the objects showed some level of destruction; the mean rates of destruction for CH, CS, CSC and CF were up to 40%, whereas those for FT and RB were under 30%. Taken together, the results suggest that cardboard and rubber materials can be used as means of environmental enrichment for rabbits.

Two cases of rectal foreign body treated by endoscopic transanal removal

We report two cases of rectal foreign bodies inserted for sexual stimulation, one requiring hospitalization and the other only a minimally invasive extraction procedure as an outpatient. Case 1 involved a 43-year-old man who had inserted a rubber ball into his anus for sexual stimulation the previous night. He was unable to remove the ball and was taken to the emergency room because of abdominal pain. Transanal foreign body extraction was performed under general anesthesia by grasping the rubber ball with Kochel endoscopically. Case 2 involved a 27-year-old man. He visited our emergency department after inserting a rubber ball into his anus for sexual stimulation, but was unable to remove it. Under emergency colonoscopy, we pierced the rubber ball with a 25-G needle tip catheter and sucked air out of the ball with a 20-ml syringe connected to the catheter. We extracted the collapsed ball using foreign-body forceps. No complications were encountered.

The Influence of Floor Layering on Airborne Sound Insulation and Impact Noise Reduction: A Study on Cross Laminated Timber (CLT) Structures

The use of timber constructions recently increased. In particular, Cross Laminated Timber floors are often used in multi-story buildings. The development of standardization processes, product testing, design of details and joints, the speed of construction, and the advantages of eco-sustainability are the main reasons why these structures play a paramount role on the international building scene. However, for further developments, it is essential to investigate sound insulation properties, in order to meet the requirements of indoor comfort and comply with current building regulations. This work presents the results obtained by in field measurements developed using different sound sources (tapping machine, impact rubber ball, and airborne dodecahedral speaker) on Cross Laminated Timber floors, changing different sound insulation layering (suspended ceiling and floating floors). Results clearly show that the influence on noise reduction caused by different layering stimulated by diverse noise source is not constant and furthermore that no available analytical model is able to correctly predict Cross Laminated Timber floors acoustic performances.

고무공 충격음의 최소인지한계

Rubber balls are used to measure the low-frequency impact sound on reinforced concrete and wooden structured apartment buildings. Previous studies on rubber ball impact sound showed that the physical properties of a rubber ball cause its impact sound to be similar to real impacts such as jumping and running of children. The rubber ball was standardized in ISO 10140-5 and ISO 16283-2, and studies on the SNQ of rubber ball were conducted. In addition, a classification on rubber ball impact sound is needed for the evaluation and labelling of low-frequency impact sounds. In this study, a subjective evaluation on the just noticeable difference (JND) of rubber ball impact sound was conducted. The presented rubber ball impact sound was recorded from wooden and reinforced concrete structures in apartment buildings. The JND of rubber ball impact sound, in which 75 % of the subjects can distinguish the loudness difference of two kinds of presented sound, was 4.65 dB for the wooden structure and 4.67 dB for the reinforced structure. On average, the JND of the rubber ball impact sound was 4.66 dB. For considering the harmonization with the classification scheme of other noise sources such as service equipment and airborne sound insulation in ISO/PRF TS 19488, a difference of 4 dB between classes is reasonable.

Validation of the elastic angle for quantitative and visible evaluation of skin elasticity in vivo.

BackgroundReduction in skin elasticity due to aging causes skin sagging and wrinkles. Although there are various objective and reliable techniques for measuring skin elasticity, it is difficult to obtain a visual representation of skin elasticity with them. Therefore, we developed a novel device, the Swing anglemeter, and analyzed its effectiveness for measuring skin elasticity of the cheek.Materials and MethodsForty‐five healthy Korean women (age, 23‐60 years) participated. The Swing anglemeter works by dropping a rubber ball on a subject's cheek, which draws a curve as it collides with the cheek. After recording the movement of the ball using the slow‐motion function on a mobile phone, we defined the maximum angle at which the ball bounces off the skin as the elastic angle, using frame‐by‐frame video analysis. Changes in the elastic angle were assessed according to age, and correlation with the Ballistometer® results (Dia‐stron Ltd., Andover, UK) was analyzed for validation.ResultsElastic angles differed significantly (P < .001) according to age. A negative correlation was found between the elastic angle and age (r = −.799, P < .001). Compared with the Ballistometer® measurements, the elastic angle was negatively correlated with alpha (r = −.570, P < .001); it was positively correlated with the mean coefficient of restitution and area (r = .602, P < .001 and r = .535, P < .001, respectively).ConclusionThe elastic angle is a useful parameter for reflecting skin elasticity, both quantitatively and visually. Our method can help subjects understand their skin elasticity status. Therefore, we expect the device will be utilized in various fields within the cosmetic industry.

Development of multi-layered sewer pipe plug — 2nd report: Tensile strength of protective sheet bonded by seams

Since Japanese sewer system is becoming obsolete, it is necessary to reinforce and repair the system without stopping sewer functions. In this study, a multi-layered sewer pipe plug consisting of a protective sheet and inner and outer rubber balls is focused to be installed and removed conveniently at the construction site. In this paper, a suitable testing method and the strength of the protective sheet are discussed experimentally by changing the specimen geometry providing slit and seams. It is found that the slit specimen is most desirable to obtain the standard tensile strength of UHMWPE cloth named Izanas cloth. It is found that the seamed strength is [Formula: see text] MPa, which is about 17% of the standard tensile strength [Formula: see text] MPa.

Development of multi-layered sewer pipe plug — 1st report: Ruptured test and stress analysis of protective sheet

In recent years, the sewer system in Japan is becoming obsolete. It is, therefore, necessary to reinforce or repair without stopping sewer functions by applying a suitable water stopping method. In this study, a multi-layered sewer pipe plug consisting of a protective sheet and inner and outer rubber balls is focused since it can be installed and removed at the construction site in a short time conveniently. This sewer pipe plug has several advantages dealing with various diameters compared to the conventional type. In this study, the rupture test is conducted to improve the water stopping performance. The fractured position of the protective sheet of the sewer pipe plug is investigated experimentally. It is clarified that the maximum stress around the flange portion can be reduced by decreasing the flange inner diameter.

Development of multi-layered sewer pipe plug — 3rd report: Tensile strength of protective sheet bonded by adhesive

Since the sewer system in Japan is becoming obsolete, it is, therefore necessary to reinforce or repair without stopping sewer functions by applying a suitable water stopping method. In this study, a multi-layered sewer pipe plug consisting of a protective sheet and inner and outer rubber balls is focused since it can be installed and removed at the construction site in a short time conveniently. Four types of adhesively bonded structures are investigated experimentally by changing bonding processes and adhesives. It is found that the main and base adhesive joint is the most suitable since the pressurized adhesive strength [Formula: see text] MPa is 30% of the standard tensile strength of the protective sheet [Formula: see text] MPa.

HAND EXERCISE USING A RUBBER BALL INCREASES GRIP STRENGTH IN PATIENTS WITH NON-HAEMORRHAGIC STROKE

Stroke can cause various degrees of disturbance, such as decreased muscle tone, loss of sensibility in some parts of the body, limits the ability to move the affected limbs and incapacity in certain activities. This study aimed to identify the effect of hand exercises using a rubber ball on muscle strength in patients with non-haemorrhagic stroke. we measure handgrip strengths of the respondents as it reflects the muscle strength and integrity functions of the upper limbs. The sample in this study was 40 patients with one-sided upper extremity paresis causing by ischaemic stroke. A pre-experimental method with one group pre-post-test design was used in this study. The respondents were given hand exercise using a ragged rubber ball for seven days twice a day. Handgrip strength of were measured by a handgrip dynamometer before and after the interventions. The Wilcoxon signed-rank test was performed with p-value of 0.000 (ά &lt; 0, 05) which means that hand exercises using a rubber ball does increase the muscle strengths of the upper extremity. We suggest that hand therapy using a ragged rubber ball can be used as an alternative for motor exercise in post-stroke patients.

Numerical analysis on temperature variation of rubber ball subjected to cyclic compression

Numerical analysis on temperature variation of rubber ball subjected to cyclic compression

Can maximal handgrip strength and endurance be improved by an 8-week specialized strength training program in older women? A randomized controlled study

Maximal handgrip strength and endurance are important indicators of upper limb function in older adults. Up to now, there is insufficient information regarding the efficacy of specialized strength training programs for improving handgrip strength. The purpose of this study was to investigate the effectiveness of an 8-week specialized handgrip strength training program on maximal handgrip strength and endurance in healthy older women. A randomized controlled trial was performed. Thirty-six healthy older women (>65 years) were randomly divided into a training group (TG) (n = 18) and a control group (CG) (n = 18). The TG participated in an 8-week specialized handgrip strength training program using rubber balls and hand grippers (2 training sessions/week, 10−15 min, 8–15 repetitions/set, 4–6 total sets/session). Prior to and after the completion of the program, maximal handgrip strength and dynamic endurance (indices: repeated maximal repetitions and percentage change in handgrip strength between first and last 6 repetitions) were assessed in both hands. Repeated measures MANOVA results indicated that maximal handgrip strength (+9.3%–10.4%) and strength values during repeated maximal repetitions (+14% to 27%) significantly increased in TG (p < 0.001), while the percentage change in handgrip strength between the first and last 6 repetitions decreased significantly (−6%) (p < 0.05), irrespective of the tested hand. The results of this study showed that an 8-week specialized handgrip strength training program can be used effectively by athletic trainers, physical and hand therapists to counteract the detrimental effects of the aging process on maximal handgrip strength and endurance in older adults.

Design of framework of Hybrid RMS for Ball Manufacturing Industry

This paper discusses the possibility of implementation of a reconfigurable manufacturing system to aid a manufacturing organization to manufacture tennis and rubber balls simultaneously or exclusively with minimum changeover time. The tennis balls and rubber balls come under a single part family, that is, Ball. They constitute 8 types of products in total. The proposed manufacturing system consists of three individual and parallel manufacturing lines that are capable of manufacturing both tennis and rubber balls. As per the change in demand, the line can be reconfigured to manufacture any product within the part family.