Cross-sectional Area Of Shaft Research Articles

Effect of robotic gait training on muscle and bone characteristics in spinal cord transected rats.

Osteoporosis and loss of muscle mass are secondary issues with spinal cord injury. Robotic gait training has provided evidence of increasing bone density and muscle mass, but its effect on bone strength is undetermined. The purpose of this study was to determine the effect of a 6-week robotic locomotion training program on skeletal muscle mass and bone characteristics. Twelve female Sprague-Dawley rats received a mid-thoracic spinal cord transection at 5 days old and at 3 weeks old were assigned to a Control or Trained Group. The Trained Group performed 5-min sessions on the Rat Stepper 5 days a week for 6 weeks with 90% of body weight supported. At the end of the 6 weeks, body mass was obtained and right femurs and four lower extremity muscles were harvested. Femur bone mineral density was measured with DXA and mechanical characteristics of the femur were determined via 3-point bending testing. Independent t-tests, effects sizes and percent differences were computed between the two groups (p < 0.05). The Trained Group had significantly larger normalized femur mass (p = 0.007) and normalized soleus muscle mass (p = 0.033) when compared to the Control Group. There was a medium or large effect size with the Trained Groups' femurs having larger mass, bone mineral density, rupture loads, cortical wall thickness, shaft cross sectional area, soleus mass, normalized gastrocnemius mass, and smaller shaft inner diameters compared to the Control Group. These changes may contribute to decreasing osteoporosis and fracture risk in those with spinal cord injuries.

Evaluation of fire smoke and heat exhaust performance of shafts by natural venting in tunnels

Theoretical analysis and numerical simulations are performed to study the smoke and heat exhaust performance of natural venting system with different shaft forms. Based on the mass conservation for the gas flow in the shaft, equations for estimating the total gas mass flow rate are derived. The methods for determining the smoke and heat exhaust efficiencies are also proposed. A numerical model is built for series of CFD simulations considering different shaft forms (length–width ratio of shaft vent and shape). The results clearly present the details of the natural venting process by displaying the temperature and velocity fields. The boundary layer separation and plug-holing phenomena are also observed. The effects of the shaft shapes on the smoke and heat exhaust efficiencies have been discussed quantitatively. It is highlighted that when the cross-sectional area of shaft is constant, a smaller length–width ratio of the shaft vent leads to higher smoke and heat exhaust efficiencies. Moreover, the smoke and heat exhaust efficiencies of cylindrical shafts are higher than those of cubic ones. The findings of this paper could provide some principles for the design of natural ventilation shaft in urban tunnels. For example, the length–width ratio of shaft vent less than 1:3 is recommended for the design of natural venting system in tunnels.

Bilateral pectoralis major MRI in weightlifters: findings of the non-injured side versus age-matched asymptomatic athletes.

To evaluate magnetic resonance imaging (MRI) features of the contralateral side in weightlifting athletes with pectoralis major (PM) tears. We hypothesized that MRI of the non-injured side may present increased pectoralis major tendon (PMT) length and thickness and greater pectoralis major muscle (PMM) volume and cross-sectional area when compared with the control group. We retrospectively identified MRI cases with unilateral PM injury and reviewed imaging findings of the contralateral side. Also, we evaluated MRI from ten asymptomatic control weightlifting athletes, with PM imaging from both sides. Two musculoskeletal radiologists independently reviewed MRI and measured PMT length, PMT thickness, PMM volume (PMM-vol) and PMM cross-sectional area (PMM-CSA), as well as humeral shaft cross-sectional area (Hum-CSA) and the ratio between PMM-CSA and Hum-CSA (PMM-CSA/Hum-CSA). Data were compared between the non-injured side and controls. The MRI protocol from both groups was the same and included T1 FSE and T2 FATSAT axial, coronal, and sagittal images, one side at a time. We identified 36 male subjects with unilateral PM injury with mean age 35.7 ± 8years and 10 age- and gender-matched controls (p = 0.45). A total of 36 PM MRI with non-injured PM and 20 PM MRI studies were included in this study. PMT length and PMT thickness were significantly higher in contralateral PM injury versus control subjects (both P < 0.001). Also, PM-CSA and Hum-CSA were greater in the contralateral PM injury group (P = 0.032 and P < 0.001, respectively). PMT thickness > 2.95mm had 80.6% sensitivity and 90.0% specificity to differentiate the non-injured PM group from controls. Non-injured side MR imaging of patients with previous contralateral PM lesion demonstrates greater PMT thickness and length as well as PM-CSA and Hum-CSA than controls.

Selection Methodology of Femoral Stems According to the Cross Section and the Maximum Stresses.

The maximum stresses on a femoral stem must be known for selecting the right size and shape of the shaft cross-sectional area for reducing the stress shielding effect generated after the total hip arthroplasty (THA) surgical procedure. The methodology proposed in this study provides the tools to the designers of femoral stems and orthopedic surgeons to select the adequate femoral stem cross section, decreasing the stiffness of the stem, thus reducing the stress shielding effect in the patient bones. The first contribution is the theoretical development of the maximum static stress calculation for 12 different femoral stem models with the beam theory, followed by the comparison with the static finite element analysis (FEA) simulations and finally the experimental corroboration of one femoral stem model measuring the strain with linear strain gages and transform it to stresses, the three different approaches provide comparable results, with a maximum average error of less than 8.5%. The second contribution is the formulation of a new selection methodology based on maximum stresses in the femoral stem and the cross section area for decreasing the stress shielding effect, optimizing the area needed for withstand the loads and decreasing the overall stiffens of the stem.

Failure analysis of PTO shaft of an agricultural tractor

The Power Take-Off (PTO) shaft is an efficient means of transferring mechanical power between farm tractors and attached implements. The PTO shaft of any agricultural tractor is basically a drive shaft engraving with number of splines that converts the primary energy of the tractor to a rotating motion of a nicely connected power shaft. The shaft is usually having external splines and its rotational movement is actually valuable for the operation of various farm implements like pumps, thresher, rotary tiller etc. to do numerous farming operations because it could be coupled at its external end. Because of the movement of the PTO shaft, the attached implements perform the final agricultural operations. During the operations, number of failures usually occurred to the PTO the shaft and the attached implements. They could become very unsafe to the users as it may stopped working of the attached implement/equipment suddenly. In this research, a metallurgical investigation has been carried out to study the root cause of failure in a PTO shaft. It was found out that the failure happened where there is sudden change in the shaft cross sectional area which leads its failure due to torsion and bending effects. The analysis results may be helpful to the end users as far as the cost during various farming operations is concerned.

Theoretical and numerical study on mass flow rates of smoke exhausted from short vertical shafts in naturally ventilated urban road tunnel fires

The study focuses on the mass flow rate of the buoyancy-driven gases exhausted from the shaft in naturally ventilated urban road tunnel fires. Theoretical analyses and numerical simulations are performed. The model to predict the mass flow rate of the incoming smoke exhausted by the nearest shaft is developed by considering that the smoke is exhausted along the four sides of the shaft separately. Based on the heat balance between the incoming smoke exhausted and the total gas flow exhausted, the model to estimate the total mass flow rate exhausted from the shaft (both smoke and entrained air) is also established. Meanwhile, a series of numerical simulation in a naturally ventilated tunnel considering the heat release rate (HRR), the shaft height, shaft length and width, shaft location was carried out. The simulation results show that the shaft height has a limited contribution to the mass flow rate of the incoming smoke exhausted while a larger shaft cross-sectional area shows a favorable performance in exhausting the smoke. Further, the air entrainment into the shaft increases with both the shaft height and shaft cross-sectional area. Comparisons of the mass flow rates of the incoming smoke and the total mass flow rates exhausted between simple calculations and simulations are made, showing that the simple models perform well. Further, it is found that there exist two regimes for the total mass flow rate corresponding to different smoke modes in the shaft (complete plug-holing, plug-holing and without plug-holing), which is caused by the different driven forces in the shaft. The outcomes of this work could provide some guidance for the design of vertical shaft and smoke control in naturally ventilated tunnel in urban area.

Impact of different manufacturers and gauge sizes on the performance of backflush needle

The present study aimed to identify the factors regulating aspiration rate (AR) of backflush needles and to compare those factors across various backflush needles from different manufacturers. The 27-gauge (27G), 25-gauge, and 23-gauge backflush needles from four different manufacturers, Alcon, MedOne, VitreQ, and DORC, were used for this experiment. AR was measured at four different aspiration vacuum levels: 100, 200, 400, and 650 mmHg. AR was significantly increased as the aspiration vacuum level increased when both aspirating balanced salt solution (BSS) and ethylene glycol; however, 27G products from VitreQ and MedOne were unable to aspirate ethylene glycol at the low aspiration vacuum level of 100 mmHg. When aspirating BSS at the high aspiration vacuum level of 650 mmHg, a smaller gauge number generally resulted in a significantly higher AR. AR, inner diameter, and cross-sectional area in Alcon products were significantly larger in any gauge, and the shaft length of Alcon products was significantly shorter than those of other manufacturers’ products in any gauge. Cross-sectional area negatively correlated with the degree of shaft deflection (r2 = 0.21, p = 0.042). These results imply that AR differs significantly among backflush needles and among companies depending on the shaft cross-sectional area.

Factors influencing the airflow rate of kitchens in cooking exhaust shaft system of high-rise residential buildings

Insufficient shaft cross-sectional area of cooking exhaust shaft system in high-rise buildings influences the ventilation capacity of range hoods in kitchens, which cause damage to human health or increase the energy consumption of the building. There are numerous factors that affect ventilation capacity of the exhaust system, such as exhaust shaft cross section, range hood performance, operating rates and distribution of range hoods. The purpose of this research is to conduct a quantitative study on the effects of these parameters on the airflow rate of kitchens. A theoretical model of the cooking exhaust shaft system was established according to the Fluid Network Theory, it was further validated by a full-scale model experiment and used to calculate the airflow rate of kitchens for a 33-storey residential building. The results show that when the exhaust shaft cross section is designed to be 500 mm × 400 mm according to standard, regardless of the performance of the range hood, the airflow rate of kitchens of some users will be either insufficient or excessive, and cannot meet 300~500 m3/h required by Chinese standards. But when the shaft cross section is 750 mm × 600 mm and the standard range hoods are used, the airflow rate of kitchens can reach 300~500 m3/h at any operating rate. The established model can be applied in other countries to study the ventilation effect of the similar cooking exhaust shaft system in residential or other buildings. The research results can be useful for improving the design of the cooking exhaust shaft system in residential buildings.

Race and ethnic variation in proximal femur structure and BMD among older men.

Femoral neck dimensions and vBMD from QCT were compared among 3,305 black, Asian, Hispanic, and white men >or=65 yr of age. All had similar stature-adjusted mean femoral neck volume, but black and Asian men had thicker cortices and higher trabecular vBMD, which may increase bone strength. Hip fracture rates among elderly U.S. black and Asian men are lower than rates among white men. Structural characteristics or volumetric BMD (vBMD), which confer advantages for femoral neck bone strength, may vary by race/ethnicity. However, this topic has not been studied in detail. In a cross-sectional study, dimensions and vBMD in the femoral neck and shaft were obtained from QCT scans among 3,305 men >or=65 yr of age in the Osteoporotic Fractures in Men (MrOS) study. Femoral neck measures were cross-sectional area; integral, cortical, and medullary volumes and integral, cortical, and trabecular vBMD. Shaft measures were cross-sectional, cortical, and medullary areas and cortical vBMD. Self-reported race/ethnicity was classified as black, Asian, Hispanic, or white. We used multivariable linear regression models with adjustment for age, height, and body mass index to compare means of the outcome measures in black, Asian, and Hispanic men to those in whites. All groups had similar femoral neck integral volume. Among black and Asian men, mean cortical volume as a percent of integral volume was 6% greater, integral vBMD was 6-10% greater, and trabecular vBMD was 33-36% greater than means among whites. Shaft cross-sectional area was similar among blacks, but smaller among Asians, compared with whites. However, mean shaft cortical area was greater among blacks but similar among Asians and whites, resulting in mean cortical thickness being 5% greater among black and Asian men. Blacks also had greater mean cortical vBMD in both the femoral neck and shaft. Black and Asian men >or=65 yr of age have features in the proximal femur that may confer advantages for bone strength. Specifically, greater cortical thickness and higher trabecular vBMD among black and Asian men could help explain the lower hip fracture rates in these populations. Discerning the mechanisms underlying these differences could provide advances for the prevention and treatment of osteoporosis.

Everyday activity predicts bone geometry in children: the iowa bone development study.

Bone adapts to changing mechanical loads by altering the structure appropriately. These adaptations should be evident in the bone cross-sectional area (CSA) and section modulus (Z), indices of axial and bending strength, respectively. In this cross-sectional study, we investigated associations between physical activity, CSA, and Z in 467 young children (mean age 5.2 yr). We also examined whether lean tissue mass, which is predominantly muscle, mediates the relationship between physical activity and bone structural measures. Physical activity was assessed using accelerometry and questionnaire. Proximal femur measures of the neck, intertrochanteric, and shaft CSA (cm) and Z (cm) were derived from dual-energy x-ray absorptiometry (DXA) scans using the Hip Structure Analysis program. Total body lean mass (kg) was also measured using DXA. Boys were more physically active than girls. Boys also had greater CSA, Z, and lean mass than girls. At each region, time spent in vigorous activity was positively and consistently associated with CSA and Z in boys and girls (r = 0.19 to 0.32). After adjustment for age, body mass, and height, vigorous activity explained, on average, 6.9% of the variability in CSA and Z. With additional adjustment for lean mass, vigorous activity explained 3.7% of the remaining variability in CSA and Z. This study demonstrates that everyday amounts of physical activity in healthy, normal children are associated with bone geometry and that differences in lean mass explain some, but not all, of this association. This suggests that, even in young, nonathletic children, bone may adapt to physical activity by structurally remodeling.

Parametric study on the impact-echo method using mock-up shafts

In this study, the impact-echo method was employed to evaluate the integrity of shafts, and parametric simulations of the impact-echo method were carried out numerically and experimentally. A one-dimensional finite element study was performed for mock-up shafts that include solid and damaged shafts. The mock-up shaft was made of Monocast, and four types of flaws were considered: (1) axisymmetric voids, (2) non-axisymmetric voids, (3) necks, and (4) bulbs. The reduction in shaft cross-sectional area varied from 30 to 80%. Subsequently, experimental studies were carried out to verify the finite element models using similar mock-up shafts. These experimental studies were carried out in the air and soil, and impact responses were analyzed in both time and frequency domains. It was shown that the results of the experiment were in agreement with those of numerical studies, and the accuracy of the impact-echo method was influenced by the type, size and location of flaws. In addition, it was also revealed that axisymmetric void, non-axisymmetric void, and neck could be detected in the frequency domain when the reduction in shaft cross-sectional area was more than 50%. Alternatively in the time domain, it was possible to identify the flaw reliably when the reduction was 30%. This latter approach provides the better possibility of detecting smaller flaw in shaft.