Vessel motion thresholds for maintaining physical and cognitive performance: a study of naval personnel at sea

Methods and results are reported from a study of ships companies' exposure to low-frequency motions on three vessels of the Royal Navy. The aim of the study was to investigate relationships between deck accelerations and the incidence of problems such as difficulties with physical tasks, cognitive activities, motion sickness, and work effort. Ship motions were recorded continuously during sea patrols of 10-14 days. The data collected from the three vessels comprised 105 days of ship motions over 12 patrols, with 779 associated daily diaries from 78 participants. Problems most strongly associated with vessel motions were related to the difficulties with physical tasks. Some cognitive aspects of task performance and motion sickness were associated with vertical acceleration magnitudes, but the correlations were less strong than with physical tasks. Practitioner Summary: Little is known about the severity of ship motions that degrade physical and mental performance. The paper offers preliminary estimates of the motion threshold values below which the performance will not be degraded by motion.     

Analysis of Seidel aberration by use of the discrete wavelet transform

Seidel aberration coefficients can be expressed by Zernike coefficients. The least-squares matrix-inversion method of determining Zernike coefficients from a sampled wave front with measurement noise has been found to be numerically unstable. We present a method of estimating the Seidel aberration coefficients by using a two-dimensional discrete wavelet transform. This method is applied to analyze the wave front of an optical system, and we obtain not only more-accurate Seidel aberration coefficients, but we also speed the computation. Three simulated wave fronts are fitted, and simulation results are shown for spherical aberration, coma, astigmatism, and defocus.     

Using an improvement model to reduce adverse drug events in VA facilities

BACKGROUND: Adverse drug events cause significant morbidity and mortality in health care. Many adverse drug events are due to medication errors and are preventable. In 1999 and 2000 the Patient Safety Center of Inquiry collaborated with the Institute for Healthcare Improvement (IHI) to implement a quality improvement (QI) project designed to reduce medication errors within the Veterans Administration system. METHODS: During a 6- to 9-month period, interdisciplinary teams that want to achieve much higher levels of performance work on a common aim, under the guidance of faculty, and come together for three 2-day educational and planning sessions. Between these sessions, teams implement some of the suggested changes, measure the results of those changes, and report back to the larger group. RESULTS: During the formal project, teams collected allergy information on more than 20,000 veterans and averted 1,833 medication errors that had the potential to cause adverse events. At 6-month follow-up, the majority of teams remained intact, continued to collect data, and maintained their gains, approximately doubling the results obtained during the formal project. Half of the teams expanded their efforts to other settings, and one-third of the teams expanded beyond their original topics. Returns on investment in the QI effort were substantial. CONCLUSIONS: The results suggest that gains made in organized QI efforts can be maintained for 6 months without additional external support or coaching if team structure and leadership support remain intact. Facilitators of QI efforts should focus on teams that are having difficulty learning new techniques. Finally, this effort appeared to generate cost savings.     

High-dynamic-range magnetometry with a single nuclear spin in diamond

Sensors based on the nitrogen-vacancy defect in diamond are being developed to measure weak magnetic and electric fields at the nanoscale. However, such sensors rely on measurements of a shift in the Lamor frequency of the defect, so an accumulation of quantum phase causes the measurement signal to exhibit a periodic modulation. This means that the measurement time is either restricted to half of one oscillation period, which limits accuracy, or that the magnetic field range must be known in advance. Moreover, the precision increases only slowly (as T(-0.5)) with measurement time T (ref.?3). Here, we implement a quantum phase estimation algorithm on a single nuclear spin in diamond to combine both high sensitivity and high dynamic range. By achieving a scaling of the precision with time to T(-0.85), we improve the sensitivity by a factor of 7.4 for an accessible field range of 16?mT, or, alternatively, we improve the dynamic range by a factor of 130 for a sensitivity of 2.5?μT?Hz(-1/2). Quantum phase estimation algorithms have also recently been implemented using a single electron spin in a nitrogen-vacancy centre. These methods are applicable to a variety of field detection schemes, and do not require quantum entanglement.     

Models for the formation of a critical layer in water wave propagation

A theory is presented which provides a model for the appearance of critical layers within the flow below a water wave. The wave propagates over constant depth, with constant (non-zero) vorticity. The mechanism described here involves adjusting the surface-pressure boundary condition; two models are discussed. In the first, the pressure at the surface is controlled (mimicking the movement of a low-pressure region associated with a storm) so that the speed and development of the pressure region ensure the appearance of a critical layer. In the second, the pressure boundary condition is allowed to accommodate the reduction of pressure with altitude, although the effects have to be greatly enhanced for this mechanism to produce a critical layer. These two problems are analysed using formal parameter asymptotics. In the second problem, this leads to a Korteweg-de Vries equation for the surface wave, and then the evolution of appropriate solutions of this equation gives rise to the appearance of a critical layer near the bottom; the corresponding problem at the surface can be formulated but not completely resolved. The appearance of a stagnation point and then a critical layer, either at the surface or the bottom, are discussed; the nature of the flow, and the corresponding streamlines are obtained and some typical flow fields are depicted.     

Highly conductive and porous activated reduced graphene oxide films for high-power supercapacitors

We present a novel method to prepare highly conductive, free-standing, and flexible porous carbon thin films by chemical activation of reduced graphene oxide paper. These flexible carbon thin films possess a very high specific surface area of 2400 m(2) g(-1) with a high in-plane electrical conductivity of 5880 S m(-1). This is the highest specific surface area for a free-standing carbon film reported to date. A two-electrode supercapacitor using these carbon films as electrodes demonstrated an excellent high-frequency response, an extremely low equivalent series resistance on the order of 0.1 ohm, and a high-power delivery of about 500 kW kg(-1). While higher frequency and power values for graphene materials have been reported, these are the highest values achieved while simultaneously maintaining excellent specific capacitances and energy densities of 120 F g(-1) and 26 W h kg(-1), respectively. In addition, these free-standing thin films provide a route to simplify the electrode-manufacturing process by eliminating conducting additives and binders. The synthetic process is also compatible with existing industrial level KOH activation processes and roll-to-roll thin-film fabrication technologies.     

水工隧洞设计和施工

近年来，随着水头高达1000m的不衬砌隧洞的应用，隧洞系统的布置已变得更为灵活，最佳的隧洞设计方案只需考虑不同的施工方法以及其相应的水头损失问题，深入了解和掌握工程地质状况及隧洞支护技术已经成为节省隧洞成本的重要因素。断面仅为相应钻爆隧洞60％的全断面掘进隧洞是一个适当的替代方案，甚至在非常坚硬的岩石中也同样如此，挪威的特色如气垫式调太室、湖泊“水龙头”在某些情况下是替代竖井开挖和大坝建筑的令人关注的方案。     

加拿大沙里文选矿厂处理细粒铅锌矿石的新流程

近来沙里文选厂处理矿山储备矿石中占大多数的细粒矿石的铅锌流程已经发生变化。１９９０年－１９９１年度进行的半工业试验表明，铅磨矿粒度（Ｐ８０）从３８μｍ降到１５μｍ、锌磨矿粒度（Ｐ８０）从４５μｍ降到２４μｍ，精矿品位有实质性的提高。流程改造包括许多新设备的设置，主要是：两台６００ｋＷ维斯特曼斯磨机用于再磨；一台４ｍ直径的浮选柱和一台和于脱水的４ｍ直径的高压过滤机。原有再磨磨矿机另作安排。