Effects of blood transfusion on left ventricular output in premature babies

Tracheostomy tube insertion is periodically performed when patients with acquired immunodeficiency syndrome (AIDS) require prolonged mechanical ventilation. In this population, bedside percutaneous tracheostomy may be a better technique than conventional operating room tracheostomy because it reduces procedural cost, requires no patient transport, and requires few sharp instruments, thereby potentially decreasing risk to surgical staff. A retrospective review was conducted in the Department of Medical Records at St. Vincents Hospital and Medical Center of New York City. Nine consecutive patients diagnosed with AIDS and undergoing percutaneous tracheostomy from January 1, 1992, to December 31, 1996, were identified. All patients were males (mean age 32.1 +/- 4 years, CD4 count average 145) and were ventilator-dependent for mean of 24 +/- 3 days. The procedure was successful and without complications in all patients. Follow-up was 27 months (range 1-42 months) and in-hospital mortality was 77 per cent. The average length of survival for those patients who died in the hospital was 29 days (range, 3-120). Two patients survived the hospitalization after undergoing decannulation on postoperative days 29 and 52, respectively. Despite the poor prognosis after tracheostomy in patients with AIDS this procedure allows better oral care and may improve patient comfort. Bedside percutaneous tracheostomy can be performed with less risk to surgical personnel and patient when compared to conventional surgery. This minimally invasive procedure safely and efficiently provides prolonged tracheal access in patients with AIDS.     

Position control and repeatability of a pneumatic rodless cylinder system for continuous positioning

Pneumatic cylinder systems have the potential to provide high output power to weight and size ratios at a relatively low cost. However, they are mainly employed in open-loop control applications where positioning repeatability is not of great importance. In this paper the repeatability of a pneumatic rodless cylinder system under closed-loop PD control is examined for its potential use in robotic applications. Our analysis shows that the linearized continuous time dynamics is dependent on the trimmed and operating conditions. This can cause positioning problems when a controller is designed based upon the transfer function obtained at a particular trimmed point. Furthermore, there are uncertainties associated with the dynamics which can lead to precision errors in both transient and steady-state responses. Due to these complexities, a pragmatic gain tuning methodology is proposed to achieve satisfactory nominal transient response characteristics over the range of loading requirements. With this scheme, it is suggested that the performance of the conventional controller be evaluated in terms of its repeatability. The repeatability of the system under different start–stop positions and loading conditions is experimentally found to be less than ±0.3 mm. This repeatability value is within typical industrial requirements.     

A novel microstrip square-loop dual-mode bandpass filter with simultaneous size reduction and spurious response suppression

In this paper, a new capacitively stepped-impedance resonator(CSIR) is proposed to develop the microstrip square-loop dual-mode bandpass filter. Using this new design, simultaneous size reduction and spurious response suppression for the dual-mode bandpass filter can be achieved. An analytical formulation of this novel resonator is given in order to elucidate the spurious frequencies relocation design. Together with this formulation, a generalized dual-mode bandpass filter model is developed so as to ease the analysis of transmission zero and insertion loss. A prototype filter is designed at 900MHz with 1.5% fractional bandwidth. Significant spurious suppressions up to 33 and 35 dB are measured at 1.8 and at 2.7 GHz, respectively. A circuitry size reduction of 54% is achieved when compared with that of the conventional structure. Moreover, the CSIR allows frequency tuning and, thus, a varactor-tuned filter is designed and a measured tunable center frequency between 1.5-1.62GHz is demonstrated. Utilizing the proposed structure, not only size reduction,as well as spurious response suppression, but also center frequency tuning can be achieved.     

The design of school furniture for Hong Kong schoolchildren. An anthropometric case study

Anthropometric data of Hong Kong schoolchildren have been collected and analysed in order to develop recommendations for the design of chairs and tables for use in Hong Kong Government coeducational schools. The anthropometric data for Hong Kong have been compared with data from a Western population (United Kingdom) and another Asian population (Japan). Five sizes of chair and table combinations have been proposed to accommodate six primary and seven secondary forms (pupils aged from 6 to 18 years). The recommended design dimensions, based on the anthropometric characteristics of the Hong Kong target populations, are discussed in relation to recommendations from previous research in this area.     

Multiple time constant modelling of a printed conducting polymer electrode

Constant phase elements (CPE) are routinely used to describe the frequency response of electrochemical systems. However, this approach is often scientifically unsatisfactory because the physical origin of the phase is unclear. Here we observe CPE-like behaviour in a conducting polymer poly(3,4-ethylenedioxythiophene)/poly(styrene-4-sulfonate) (PEDOT:PSS) film that was inkjet printed onto paper to form a flexible electrochemical double layer capacitor electrode. We show that the response of the electrochemically active film can also be described using a physical model with multiple parallel finite RC (resistor–capacitor) transmission lines whose lengths and time constants are determined by the distribution of the measured film thickness. The modeled volumetric capacitance and ionic conductivity match those determined experimentally, suggesting that the physical origin of the constant phase response is a distribution of mass transport limited time constants.     

A parametric study on the fractal finite element method for two‐dimensional crack problems

The Fractal Finite Element Method for calculating 2D stress intensity factors is modified by making the similarity ratio in the construction of the fractal mesh a variable. A parametric study is then carried out to examine the effects of the similarity ratio, the number of transformation terms, reduced integration and the initial crack opening angle on the quality of the numerical solutions. It is concluded that a large similarity ratio should be used to create the fractal mesh, and that reduced integration and a small initial crack opening angle may be used without producing significant errors in the solutions. Copyright © 2003 John Wiley & Sons, Ltd.     

Experiments for first year engineering students using tin-bismuth alloys

Introductory courses, whether at the freshman or junior level, are frequently based on the paradigm that processing affects structure, which affects properties, which, in turn, determine performance, and is the basis for design. Once this is understood by the students, it is possible to have them make design decisions based on experimental data and have them identify alternative materials using the paradigm. This paper describes a series of experiments and demonstrations that can be incorporated into an introductory materials course to help students appreciate how processing changes structure, which leads to a change in properties.     

Opening Up the Future of Open Source: From Open Innovation to the Internet of Things for the Built Environment

The architecture, engineering and construction industry is increasingly operating within the merging of physical and digital that defines our era of connectivity. Meanwhile, new semi-open-source platforms such as WikiHouse and Resilient Modular Systems, together with the prospect of traditional supply chains being replaced by localised digital manufacturing, are challenging notions of design ownership. Guest-Editor Wendy W Fok considers what questions designers should be asking themselves in this climate     

Variable Temperature Blackbodies via Variable Conductance: Thermal Design,Modelling and Testing

This paper presents the overall design for large (\(\sim \)400 mm aperture) reference blackbody cavities currently under development at the Science and Technology Facilities Council Rutherford Appleton Laboratory Space Department (STFC RAL Space), in collaboration with the National Physical Laboratory (NPL). These blackbodies are designed to operate in vacuum over a temperature range from 160 K to 370 K, with an additional capability to operate at \(\sim \)100 K as a point of near-zero radiance. This is a challenging problem for a single blackbody. The novel thermal design presented in this paper enables one target that can physically achieve and operate successfully at both thermal extremes, whilst also meeting stringent temperature gradient requirements. The overall blackbody design is based upon a helium gas-gap heat switch and modified to allow for variable thermal conductance. The blackbody design consists of three main concentric cylinder components—an inner cavity (aluminium alloy), a radiation shield (aluminium) and an outer liquid nitrogen (\(\hbox {LN}_{2}\)) jacket (stainless steel). The internal surface of the cavity is the effective radiating surface. There is a helium gas interspace surrounding the radiation shield and enclosed by the \(\hbox {LN}_{2}\) jacket and the inner cavity. The blackbodies are now at a mature stage of development. In this paper, the overall design, focusing upon the thermal design solution, is detailed. This paper will also concern the full-scale prototype breadboard model, for which results on thermal stability, spatial gradients and other sensitivities will be presented.