Reconsidering Ford’s Highland Park assembly line: new data vs. old ideas

Ford’s Assembly Line at Highland Park is one of the most influential production system conceptualizations. Anecdotal commentary and a limited set of annual data have provided the foundation for popular opinion about Ford and past research on his factory and its management. New data is used to explore Ford’s development of the assembly line. This confirms and strengthens research on line’s effect on labor productivity, but raises several significant incongruities vis-à-vis its modern stereotype. These are important for they show Ford’s assembly line was used differently than modern ones and their production systems were more flexible than previously recognized

Henry Ford vs. assembly line balancing

Ford’s Assembly Line at Highland Park is one of the most influential conceptualizations of a production system. New data reveal Ford’s operations were adaptable to strongly increasing and highly variable demand. These analyses show Ford’s assembly line was used differently than modern ones and their production systems were more flexible than previously recognized. Assembly line balancing theory largely ignores earlier practice. It will be shown that Ford used multiple lines flexibly to cope with large monthly variations in sales. Although a line may be optimized to yield lowest cost production, systems composed of several parallel lines may yield low cost production along with output and product flexibility. Recent research on multiple parallel lines has focussed on cost effectiveness without appreciating the flexibility such systems may allow. Given the current strategic importance of flexibility it should be included in such analyses as an explicit objective

A thin rivulet of perfectly wetting fluid subject to a longitudinal surface shear stress

The lubrication approximation is used to obtain a complete description of the steady unidirectional flow of a thin rivulet of perfectly wetting fluid on an inclined substrate subject to a prescribed uniform longitudinal surface shear stress. The quasi-steady stability of such a rivulet is analysed, and the conditions under which it is energetically favourable for such a rivulet to split into one or more subrivulets are determined

Air-blown rivulet flow of a perfectly wetting fluid on an inclined substrate

Thin-film flows occur in a variety of physical contexts including, for example, industry, biology and nature, and have been the subject of considerable theoretical research. (See, for example, the review by Oron, Davis and Bankoff [4].) In particular, there are several practically important situations in which an external airflow has a significant effect on the behaviour of a film of fluid, and consequently there has been considerable theoretical and numerical work done to try to understand better the various flows that can occur. (See, for example, the studies by King and Tuck [2] and Villegas-Díaz, Power and Riley [6].) The flow of a rivulet on a planar substrate subject to a shear stress at its free surface has been investigated by several authors, notably Myers, Liang and Wetton [3], Saber and El-Genk [5], and Wilson and Duffy [9]. All of these works concern a non-perfectly wetting fluid; the flow of a rivulet of a perfectly wetting fluid in the absence of a shear stress at its free surface has been treated by Alekseenko, Geshev and Kuibin [1], and by Wilson and Duffy [7,8]. In the present short paper we use the lubrication approximation to obtain a complete description of the steady unidirectional flow of a thin rivulet of a perfectly wetting fluid on an inclined substrate subject to a prescribed uniform longitudinal shear stress at its free surface

Root architecture of provenances, seedlings and cuttings of Melia volkensii: implications for crop yield in dryland agroforestry

Melia volkensii (Gürke) is being increasingly promoted as an on-farm tree in Kenya. Researchers’ and farmers’ views on its competitiveness with crops differ; research station studies have found it to be highly competitive whereas farmers do not consider it to be so. Because of difficulties in seed germination, it is probable that dissemination programmes will rely upon plants produced from root and stem cuttings, rather than on seedlings. This study evaluates differences in root system architecture of plants raised from seed (of four provenances), stem or root cuttings and the relationships between the competitivity index (CI) and crop yield. Cuttings were more shallowly rooting than seedlings, and had higher competitivity indices, and there was a negative relationship between CI and crop yield. No differences in root architecture between provenances were found. Therefore, to reduce tree-crop competition, the use of seedlings rather than cuttings should be recommended when promoting the use of this species on dryland farms. If cuttings are used to circumvent the problems of seed germination, alternative methods of controlling competition, such as root pruning, need to be considered

Acoustically controlled enhancement of molecular sensing to assess oxidative stress in cells

We demonstrate a microfluidic platform for the controlled aggregation of colloidal silver nanoparticles using surface acoustic waves (SAWs), enabling surface enhanced Raman scattering (SERS) analysis of a cell based model for oxidative damage. We show that by varying the frequency and the power of the acoustic energy, it is possible to modulate the aggregation of the colloid within the sample and hence to optimise the SERS analysis

Numerical simulation of rivulet evolution on a horizontal cable subject to an external aerodynamic field

On wet and windy days, the inclined cables of cable-stayed bridges may experience a large amplitude oscillation known as rain-wind-induced vibration (RWIV). It has previously been shown by in situ and wind-tunnel studies that the formation of rain-water accumulations or ‘rivulets’ at approximately the separation points of the external aerodynamic flow field and the resulting effect that these rivulets have on this field may be one of the primary mechanisms for RWIV. A numerical method has been developed to undertake simulations of certain aspects of RWIV, in particular, rivulet formation and evolution. Specifically a two-dimensional model for the evolution of a thin film of water on the outer surface of a horizontal circular cylinder subject to the pressure and shear forces that result from the external flow field is presented. Numerical simulations of the resulting evolution equation using a bespoke pseudo-spectral solver capture the formation of two-dimensional rivulets, the geometry, location and growth rate of which are all in good agreement with previous studies. Examinations of how the distribution and magnitude of aerodynamic loading and the Reynolds number influence the rivulet temporal evolution are undertaken, the results of which indicate that while all three affect the temporal evolution, the distribution of the loading has the greatest effect

New developments in rain–wind-induced vibrations of cables

On wet and windy days, the inclined cables of cable stayed bridges can experience large amplitude, potentially damaging oscillations known as rain-wind-induced vibration (RWIV). RWIV is believed to be the result of a complicated non-linear interaction between rivulets of rain water that run down the cables and the wind loading on the cables from the unsteady aerodynamics; however, despite a considerable international research effort, the underlying physical mechanism that governs this oscillation is still not satisfactorily understood. An international workshop on RWIV was held in April 2008, hosted at the University of Strathclyde. The main outcomes of this workshop are summarised in the paper. A numerical method to investigate aspects of the RWIV phenomenon has recently been developed by the authors, which couples an unsteady aerodynamic solver to a thin-film model based on lubrication theory for the flow of the rain water to ascertain the motion of the rivulets owing to the unsteady aerodynamic field. This novel numerical technique, which is still in the relatively early stages of development, has already provided useful information on the coupling between the external aerodynamic flow and the rivulet, and a summary of some of the key results to date is presented

Elite male Flat jockeys display lower bone density and lower resting metabolic rate than their female counterparts: implications for athlete welfare

To test the hypothesis that daily weight-making is more problematic to health in male compared with female jockeys, we compared the bone-density and resting metabolic rate (RMR) in weight-matched male and female Flat-jockeys. RMR (kcal.kg-1 lean mass) was lower in males compared with females as well as lower bone-density Z-scores at the hip and lumbar spine. Data suggest the lifestyle of male jockeys’ compromise health more severely than females, possibly due to making-weight more frequently

Relativistic dust disks and the Wilson-Mathews approach

Treating problems in full general relativity is highly complex and frequently approximate methods are employed to simplify the solution. We present comparative solutions of a infinitesimally thin relativistic, stationary, rigidly rotating disk obtained using the full equations and the approximate approach suggested by Wilson & Mathews. We find that the Wilson-Mathews method has about the same accuracy as the first post-Newtonian approximation.Comment: 4 Pages, 5 eps-figures, uses revtex.sty. Submitted to PR