Effect of single and double strap backpacks on lung function

Carrying heavy and moderate military loads in backpacks or as body armour compresses the chest, causing a change in lung function that is typical of a restrictive ventilatory impairment. It is not known if a lighter backpack load of only 6?kg, such as is typical of loads carried by students, will have a similar effect on lung function. There have been no studies examining whether backpacks of different strapping styles have an effect on lung function. Several designs of student backpack have recently been introduced to the market. One of the most popular is a single-strap backpack. This study examined Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV₁), FEV₁.FVC^???1% and Peak Expiratory Flow (PEF) in 13 participants (4 males, 9 females) wearing each of two 6?kg backpacks, one with two shoulder straps (a Double Strap Backpack (DSB)) and the other with a single strap (a Single Strap Backpack (SSB)) worn across the shoulder and chest. In comparison with the control of no pack (N), SSB significantly reduced FVC (by 3.94%, p?=?0.006) but there were no significant differences in FEV₁, FEV₁. FVC^???1% and PEF. The DSB also significantly reduced FVC (by 1.97%, p?=?0.034) but no significant differences were found in FEV₁, FEV₁. FVC^???1% and PEF measures. In comparison with DSB, the SSB was associated with a significantly lower FVC (by 2.05%, p?=?0.049) and FEV₁ (by 1.88%, p?=?0.029) but there were no significant changes in FEV₁. FVC^???1% and PEF. It is concluded that a backpack load of 6?kg could produce a mild restrictive type of ventilatory impairment in lung function. This effect was greater for a single cross-chest strap than for a more conventional double strap harness.     

Effect of backpack fit on lung function

Carrying loads close to the trunk with a backpack causes a restrictive type of change in lung function in which Forced Vital Capacity (FVC) and Forced Expiratory Volume in 1 s (FEV1) are reduced without a corresponding decrement in the FEV1.FVC( - 1) %. It is not known whether this is due to the weight of the load acting on the chest or to the tightness of fit of the shoulder and chest straps and waist belt of the pack harness. This study examined FVC, FEV1, FEV1.FVC( - 1) %, peak expiratory flow (PEF), forced expiratory flow between 0.2 and 1.2 s (FEF0.2 - 1.2) after the start of expiration and between 25 and 75% of each FVC (FEF25 - 75%) in 12 healthy males wearing a 15 kg backpack in which the shoulder and chest straps and hip belt were loosened by 3 cm from a 'comfort fit' to achieve a 'loose pack' fit (LPF) and tightened by 3 cm from CF to achieve a 'tight pack' fit (TPF). In comparison with the control condition of no pack, a loose pack fit significantly reduced FVC (by 3.6%, p < 0.01), FEV1 (by 4.3%, p < 0.01) and FEF25 - 75% (by 8.4%, p < 0.01). A tight pack fit significantly reduced FVC (by 8.1%, p < 0.01) and FEV1 (by 9.1%, p < 0.001). It also significantly reduced FEF0.2 - 1.2 (by 7.3%, p < 0.05) and FEF25 - 75% (by 21%, p < 0.01). In comparison with a loose pack fit, the tight pack fit was associated with a significantly lower FVC (by 4.6%, p < 0.01), FEV1 (by 5.0%, p < 0.01), FEF25 - 75% (by 13.8%, p < 0.01) and a fall in FEF0.2 - 1.2 (by 5.5%). The latter was approaching significance (p = 0.077). There were no significant changes in FEV1.FVC( - 1)% and PEF. It is concluded that tightening the fit of a backpack significantly affects lung function in a manner that is typical of a restrictive change in lung function and is very similar in pattern to that of wearing a loosely fitted loaded backpack. The effect of tightness of fit is additional to that due to the weight of the load alone and may also reduce expiratory flow at low lung volumes.     

Effect of backpack fit on lung function

Carrying loads close to the trunk with a backpack causes a restrictive type of change in lung function in which Forced Vital Capacity (FVC) and Forced Expiratory Volume in 1?s (FEV₁) are reduced without a corresponding decrement in the FEV₁.FVC^???1 %. It is not known whether this is due to the weight of the load acting on the chest or to the tightness of fit of the shoulder and chest straps and waist belt of the pack harness. This study examined FVC, FEV₁, FEV₁.FVC^???1 %, peak expiratory flow (PEF), forced expiratory flow between 0.2 and 1.2?s (FEF_0.2?–?1.2) after the start of expiration and between 25 and 75% of each FVC (FEF_25?–?75%) in 12 healthy males wearing a 15?kg backpack in which the shoulder and chest straps and hip belt were loosened by 3?cm from a ‘comfort fit’ to achieve a ‘loose pack’ fit (LPF) and tightened by 3?cm from CF to achieve a ‘tight pack’ fit (TPF). In comparison with the control condition of no pack, a loose pack fit significantly reduced FVC (by 3.6%, p?<?0.01), FEV₁ (by 4.3%, p?<?0.01) and FEF_25?–?75% (by 8.4%, p?<?0.01). A tight pack fit significantly reduced FVC (by 8.1%, p?<?0.01) and FEV₁ (by 9.1%, p?<?0.001). It also significantly reduced FEF_0.2?–?1.2 (by 7.3%, p?<?0.05) and FEF_25?–?75% (by 21%, p?<?0.01). In comparison with a loose pack fit, the tight pack fit was associated with a significantly lower FVC (by 4.6%, p?<?0.01), FEV₁ (by 5.0%, p?<?0.01), FEF_25?–?75% (by 13.8%, p?<?0.01) and a fall in FEF_0.2?–?1.2 (by 5.5%). The latter was approaching significance (p?=?0.077). There were no significant changes in FEV₁.FVC^???1% and PEF. It is concluded that tightening the fit of a backpack significantly affects lung function in a manner that is typical of a restrictive change in lung function and is very similar in pattern to that of wearing a loosely fitted loaded backpack. The effect of tightness of fit is additional to that due to the weight of the load alone and may also reduce expiratory flow at low lung volumes.     

Effect of cement dust on lung function in Libyans

Forced vital capacity (FVC, forced expiratory volume in one second (FEV₁), forced expiratory ratio (FEV₁%), forced expiratory flow between 0.2 and 1.21 (FEF_200-1200) and forced mid-expiratory flow (FMF 25-75%) were measured in 100 non-exposed subjects (control) and 110 exposed subjects (mean age 38.0± 8.4 years) exposed to cement dust in a Benghazi cement plant. The exposed group had a significantly lower mean FEV₁% (p<0.001), FEF (p<0.05) and FMF (p<0.01) than the control group. The mean FVC and FEV₁ values in the exposed and the control groups were not significantly different. However, the reduction in lung function in the exposed group was not linked to the period of exposure.     

基于单片机实现对二级倒立摆的控制

本文简要说明了二级倒立摆系统及其建模。并分析了这个系统的特点。着重于建立一个单片机系统，在状态反馈的基础上实现对倒立摆的控制。     

Simulation of maglev vehicles riding over single and double span guideways

A magnetically levitated high speed vehicle on an elevated periodically supported guideway is approximated by a single-mass vehicle on a flexible single and double span beam with rigid piers. To describe the distributed parameter system of the flexible guideway, modal analysis technique is used. Because of the coupling of the moving vehicle and the guideway the system is characterized by an ordinary vector differential equation with periodically time varying coefficients and jumping states at the piers. To compensate the static instability the suspension magnets are actively controlled by a suboptimal time invariant control system. For the single span guideway an analog simulation is shown, whereas for the double span guideway a digital simulation is presented. Examples are given comparing the solutions for dynamic displacements of the system when a direct state feedback controller is used an when the vehicle is modelled as a moving mass or a moving force.     

Convergence and comparison theorems for single and double decompositions of rectangular matrices

Different convergence and comparison theorems for proper regular splittings and proper weak regular splittings are discussed. The notion of double splitting is also extended to rectangular matrices. Finally, convergence and comparison theorems using this notion are presented.     

一种基于传感器温度补偿的双指数函数拟合算法

温度漂移是影响传感器可靠性、精度和使用效能的关键因素,是制约加速度计精度提高的瓶颈。提出一种基于传感器温度补偿的双指数函数拟合算法,一方面采用双指数函数对非线性的温度系数曲线进行补偿,另一方面在双指数函数拟合的算法中,提出一种具有高精度初值的交替迭代法。该方法首先利用四组数据点计算出高精度的初值,再使用交替迭代法优化计算结果,明显改善了传统交替迭代法拟合在初值选取不当时造成的迭代不收敛、精度较低、迭代次数较多的问题。此外双指数函数模型可以采用CORDIC算法集成到硬件中,因此具有工程实用价值。     

单纤双向传输技术在电视跟踪系统中的应用

介绍采用光纤通信实现多路PAL制式模拟视频、多路数据的点对点单纤双向传输,阐述了系统的原理以及具体的实现方法.整个系统主要包括三个大的部分,即模拟视频的数字化以及与数据的同步复用部分、单纤双向传输的实现和光万向连接器部分.     

单纤双向传输技术在电视跟踪系统中的应用

介绍采用光纤通信实现多路PAL制式模拟视频、多路数据的点对点单纤双向传输,阐述了系统的原理以及具体的实现方法。整个系统主要包括三个大的部分,即模拟视频的数字化以及与数据的同步复用部分、单纤双向传输的实现和光万向连接器部分。     

基于CAN和WSNs的井下皮带机打滑保护监测系统研究

针对目前井下皮带机监控系统的现状,设计了一种基于CAN总线和无线传感器网络(WSNs)技术的皮带机打滑保护监测系统,该系统以CC2430芯片为核心设计传感器节点,以CC2430和MCP2515设计Sink节点,并对网络通信协议进行了分析,给出了系统的硬件设计和软件流程.通过在煤矿井下皮带大巷实验,测得了2.4 GHz频...     

Investigation of the influence of design parameters on the flow performance of single and double disk viscous micropumps

This paper investigates the effect of radius ratio, and channel aspect ratio on the flow performance of newly introduced single and double disk viscous micropumps. A lubrication solution for the flow field, which accounts for both radius and channel aspect ratios either in single or double disk micropumps was developed and compared with available experimental data and with an approximate solution which estimates for the flow rate only in single disk pump and neglects channel aspect ratio. Additionally, a number of 3D numerical models for single and double disk micropumps were built and analyzed using the finite volume method. Pressure and drag shape factors were introduced to describe the effects of radius and channel aspect ratios on the flow rate. The values of these factors for the whole range of studied parameters are found analytically and numerically. The error in estimating the flow rate was found to be less than 10% for r ₁ /r ₂ > 0.2, and less than 7% for the studied range of h/w. Also, the lubrication solution was found to be in good agreement with the numerical and experimental results.     

Impact of backpack type on respiratory muscle strength and lung function in children

We examine the influence of backpack type on lung function and respiratory muscle strength in children. Thirty-seven children were assessed for lung function and inspiratory and expiratory muscle strength under four randomly determined conditions: unloaded erect standing and three conditions carrying 15% of the child's body weight. In these three conditions, children carried the weight on a backpack with bilateral shoulder straps carried over both shoulders, on a backpack with bilateral shoulder straps carried over one shoulder and on a backpack with a mono shoulder strap. Significantly lower forced vital capacity, forced expiratory volume in one second and maximal expiratory pressure were observed when children carried a backpack with a mono shoulder strap compared to the unloaded standing position. In conclusion, the restrictive effect and the decrease in expiratory muscle strength were more pronounced for the backpack with a mono shoulder strap, suggesting that a double strap backpack is preferable to a mono shoulder strap backpack.

Practitioner summary: There is little known about the effect of schoolbags on respiratory muscle function. We investigated the influence of backpack type on lung function and respiratory muscle strength. A backpack with a mono shoulder strap created a restrictive effect and a decrease in strength, suggesting that a double strap backpack is preferable to a mono shoulder strap backpack.     

A computer program for time series forecasting using single and double exponential smoothing techniques

This paper presents a microcomputer program for time series forecasting. The program has been developed in GW-BASIC for Zenith 150 microcomputers which are IBM PC compatible. It utilizes Single exponential smoothing, Adaptive-response-rate single exponential smoothing, and Brown's double exponential smoothing methods to forecast the future values of a given time series. The program produces plots of the original time series and forecasted series as well as forecasting errors. It computes 90% and 95% confidence intervals for forecasted values and calculates the following statistics: Mean squared error, Mean absolute percentage error, Mean absolute error, Durbin-Watson statistic, and Theil's U statistic.     

Effect of temperature on electrical characteristics of single electron transistor

Microsystem Technologies - Static and transfer characteristics of single electron transistor are analytically calculated as a function of operating temperature under suitable biasing conditions....     

Effects of the single and double (overlap) scanned excimer laser annealing on solid phase crystallized silicon films

Thin amorphous silicon (a-Si) films were crystallized into polycrystalline silicon (poly-Si) by combining solid phase crystallization (SPC) and subsequent excimer laser annealing (ELA). Then thin film transistors (TFTs) were fabricated by using the poly-Si formed in the single and double excimer laser scanned area. The device performance of the TFTs fabricated with the excimer laser energy density of 230 mJ/cm² is almost equal for the single and double scanned area. This observation indicates that the overlapping laser irradiation with the laser energy density below 230 mJ/cm² does not change the characteristics of TFTs. Based on this result, we discuss the correlation between performance of active matrix organic light emitting display (AMOLED) panels and excimer laser energy density during ELA for SPC treated and non-treated poly-Si films.     

The effect of simulated school load carriage configurations on shoulder strap tension forces and shoulder interface pressure

Recently, several studies have addressed the physical demands of school student's load carriage, in particular the load weight carried, using physical demands indicators such as oxygen consumption, gait, and posture. The objective of this study was to determine the effects of different load carriage configurations on shoulder strap tension forces and shoulder interface pressure during simulated school student's load carriage. A load carriage simulator was used to compare shoulder strap forces and shoulder pressure for 32 combinations of gait speed, backpack weight, load distribution, shoulder strap length and use of a hip-belt. The results showed that the manipulation of backpack weight, hip-belt use and shoulder strap length had a strong effect on shoulder strap tension and shoulder pressure. Backpack weight had the greatest influence on shoulder strap tension and shoulder pressure, whereas hip-belt use and then shoulder strap adjustment had the next greatest effects, respectively. While it is clear that researchers and practitioners are justified in focusing on load magnitude in backpack studies as it has the greatest effect on shoulder forces, hip-belt use and shoulder strap adjustment should also be examined further as they too may have significant effects on the demands placed on backpack users. Based on the present findings, school students should wear their backpacks with the least weight possible, use the hip-belt if present, allow a reasonable amount of looseness in the shoulder straps and should position the heaviest items closest to their back. However, more detailed work using human participants needs to be undertaken before these recommendations can be confirmed.     

肺功能仪数据采集与数据处理系统研究

本文用理论计算公式和实际曲线拟合两种方法对肺功能仪数据采集与数据处理进行研究。虽然两者都还有误差，但是实际曲线拟合效果好于理论公式计算，对于实际曲线拟合还有待于进一步改进。     

交直流两用仪表不对应性误差分析

从电磁式仪表工作原理出发，分析了其测交直流电流的原理及其引起交直流测量时指示不对应性的现象和原因。