Predictors of summertime heat index levels in New York City apartments

During heat waves, fatal overexposure to heat most often occurs at home. It is not known how factors such as building size, floor level, and different types of air conditioning (AC) contribute to excess indoor heat. We monitored indoor temperature and humidity in 36 apartments in New York City during summers 2014 and 2015 and used these values to calculate the indoor heat index (HI). We investigated the role of AC type and building‐level factors on indoor HI using multilevel regression models. Thirty‐four of 36 homes had AC. Central and ductless AC types were associated with the coolest indoor conditions; homes with window and portable AC were significantly warmer. Apartments on the top floor of a building were significantly hotter during heat advisory periods than other apartments regardless of the presence of AC. High indoor HI levels persisted in some homes for approximately 1 day following the end of the two heat advisory periods. We provide concrete evidence of higher heat levels in top floor apartments and in homes with certain types of AC. High heat levels that persist indoors after outdoor heat has subsided may present an underappreciated public health risk.     

Detectability of corrosion damage with circumferential guided waves in reflection and transmission

There is an increasing interest in high frequency short range guided waves to screen or monitor for corrosion. This contrasts with long range guided waves (LRGWs) which screen pipes for large patches of corrosion and have been successfully used in corrosion management for the past twenty years. The fundamental setup described in this paper uses circumferential guided waves, which are excited at a single location on a pipe and travel around the pipe wall and are detected at the same location. The study uses a finite element model assisted method to evaluate the detection capability of two short range circumferential guided wave setups which use both the reflected and transmitted signals. The setups themselves consist of either an axial array of transducers, for monitoring, or a single transducer which axially scans a pipe. Both setups have an array or scan pitch between either adjacent transducers or measurements. The detection capability of the fundamental Lamb wave modes (A0 and S0) in both reflection and transmission have been compared, as well as a hybrid shear horizontal wave setup, which uses the SH0 mode in reflection and the SH1 mode in transmission. A sensitivity analysis was conducted using two separate methods to determine the probability of detection (POD) for either the reflection or transmission signals. Both methods determine a POD for a specific defect, noise level, and array or scan pitch. Probability images are produced which map the POD for a range of defect sizes. For the parameters investigated in this study, it was found that in transmission large diameter defects have a higher detectability, whereas deep, narrow diameter defects are more detectable in reflection. A generalised overview of the sensitivity of short range guided waves is presented by combining both the reflection and transmission PODs. The data fused sensitivity of the S0 and SH hybrid modes are given as 0.6% and 0.75% cross sectional area (CSA) respectively, allowing for the comparison with LRGWs. The A0 mode was excluded from the POD analysis because it was much less sensitive than the other two modes.     

Determining elastic properties of skin by measuring surface waves from an impulse mechanical stimulus using phase-sensitive optical coherence tomography

The mechanical properties of skin are important tissue parameters that are useful for understanding skin patho-physiology, which can aid disease diagnosis and treatment. This paper presents an innovative method that employs phase-sensitive spectral-domain optical coherence tomography (PhS-OCT) to characterize the biomechanical properties of skin by measuring surface waves induced by short impulses from a home-made shaker. Experiments are carried out on single and double-layer agar–agar phantoms, of different concentrations and thickness, and on in vivo human skin, at the forearm and the palm. For each experiment, the surface wave phase-velocity dispersion curves were calculated, from which the elasticity of each layer of the sample was determined. It is demonstrated that the experimental results agree well with previous work. This study provides a novel combination of PhS-OCT technology with a simple and an inexpensive mechanical impulse surface wave stimulation that can be used to non-invasively evaluate the mechanical properties of skin in vivo, and may offer potential use in clinical situations.     

Thermoacoustic Emission from Carbon Nanotubes Imaged by Atomic Force Microscopy

The thermoacoustic effect of isolated single‐wall carbon nanotubes aligned between electrodes is experimentally observed for the first time by imaging the emitted acoustic wave using an atomic force microscopy‐based technique specifically developed for the task. The capability of such a technique for single‐point thermoacoustic measurements is first verified on carbon nanotubes layers with two electrodes for injecting alternate electric current. The technique is then demonstrated to allow the acquisition, simultaneously with the topography, of images reflecting the pressure of the acoustic wave at fixed distance from the sample. Such a capability is used to collect images reflecting the amplitude of acoustic waves generated by isolated nanotubes and nanotube bundles by the thermoacoustic effect.     

Food safety management system performance in the lamb chain

This study describes a performance measurement of implemented food safety management system (FSMS) along the lamb chain using an FSMS-diagnostic instrument (FSMS-DI) and a Microbiological Assessment Scheme (MAS). Three slaughterhouses, 1 processing plant and 5 butcher shops were evaluated. All the actors along the lamb chain achieved a moderate risky contextual situation, operating in a basic-average FSMS, which was not enough to obtain a good food safety output. Different suggestions are advised for each actor along the lamb chain for improvements towards higher FSMS activity levels or lower risk levels in context characteristics. The combined assessment is a useful tool to identify the possible causes of poor food safety performance in the lamb chain using few sampling locations, saving time and money.     

Laser ultrasonic characterisation of branched surface-breaking defects

Surface-breaking defects often have a geometry which is more complicated than the ‘normal slot’ used in many calibration tests, and this geometry will affect the reflection and transmission of ultrasonic surface waves incident on the defect. We present here measurements on defects with varied branched geometries, designed to simulate stress corrosion cracking (SCC) type defects, characterising the geometry using laser-based ultrasonic generation and detection of Rayleigh waves. We show the behaviour of the near-field enhancement and the far-field reflection as a function of branch position and length, and signal analysis which can be used to gain further information for characterising the defect geometry. The experimental results and finite element method (FEM) models presented in this paper highlight the potential of this technique to test components prone to developing SCC, in order to identify and characterise surface-breaking defects.     

块系覆岩中摆型波传播对巷道支护动力响应影响

为研究支护体自身的动力响应规律,通过理论和计算分析岩体中的非线性摆型波传播对巷道支护动力响应的影响,根据摆型波在非连续自应力块系上覆岩体中传播时的支护动力响应模型,研究上覆岩块间的黏弹性性质及岩块破坏对支护动力响应的影响。通过计算分析得出,上覆岩块间弹性下降时,支护的动态受拉和受压幅值随之下降且周期变大;上覆岩块间阻尼增大时,支护的受拉和受压周期不变,但周期内的微扰动逐渐消失且幅值略有下降;上覆岩块沿垂直冲击方向破裂成两个子块时,支护的受拉和受压次数增加。     

Application of soft-thresholding on the decomposed Lamb wave signals for damage detection of plate-like structures

Effective application of the Lamb waves for structural health monitoring and damage identification intensively relies on the accurate damage-related feature extraction in the received signals. Most of existing signal processing methods extract the damage-related features from the time–frequency joint spectrum which requires a quite amount of effort. In this paper, the soft-thresholding process, based on different signal decomposition methods, is introduced to damage identification so that the damage-related signal features can be manifested more distinctively. By applying two popular signal decomposition methods (i.e., the discrete wavelet transform (DWT) and the empirical mode decomposition (EMD)), the signal of interest can be represented by a series of components with different frequencies. Since most noises exist in the high frequency range, it is feasible to alleviate noise by restricting the energy of high-frequency components. Finally, a denoised signal is synthesized using the corresponding reconstruction method. As an application, the soft-thresholding process is performed to detect a small crack on an isotropic aluminum plate under the white Gaussian noise contamination. The results, from both the numerical finite element simulation and experimental test, indicate that the soft-thresholding process is capable of effectively reducing the effect of noise, convincingly improving the sensitivity of damage identification, and discriminating relatively small damage.     

Effect of plasma absorption on dust lattice waves in hexagonal dust crystals

In the present paper, the effect of plasma absorption on lattice waves in 2D hexagonal dust crystals is investigated. The dispersion relations with the effect of plasma absorption are derived.It is found that the temperature effect(electron-to-ion temperature ratio τ) enhances the frequency of the dust lattice waves, while the spatial effect(dimensionless Debye shielding parameter k) weakens the frequency of the dust lattice waves. In addition, the system stabilities under the conditions of plasma absorption are studied. It is found that the temperature effect narrows the range of instability, while the spatial effect extends this range. And the range of instability is calculated, i.e. the system will always in the stable state regardless of the value of k when τ??3.5. However, the system will be unstable when τ?=?1 and k 4.1.     

Quasi-linear modeling of gyroresonance between different MLT chorus and geostationary orbit electrons

The contributions of dayside and nightside gyroresonance of chorus waves to electron radiation belt evolution at L = 6.6 are detailedly differentiated via fully solving the two-dimensional Fokker-Plank equation.The numerical results show that the chorus waves at different regions play signiffcantly different roles.The dayside chorus waves can cause obvious loss of energetic electrons at lower pitch angles and weak energization at larger pitch angles.The nightside chorus waves can yield significant energization at larger pitch angles,but cannot efficiently resonate with the energetic electrons at lower pitch angle.Due to the numerical difficulty in fully solving Fokker-Planck equation,the cross diffusion terms are often ignored in the previous work.Here the effect of cross diffiusion at different regions is further analyzed.On the dayside,ignoring cross diffusion overestimates the electron phase space density by several orders of magnitude at lower pitch angles,and consequently the dayside chorus waves are incorrectly regarded as an effective energization mechanism.On the nightside,ignoring cross diffusion overestimates the electron phase space density(PSD) by about one order of magnitude at larger pitch angles.These numerical results suggest that cross diffusion terms can significantly affect gyroresonance of chorus waves on both the dayside and nightside,which should be included in the future radiation belt models.