Laboratory study of the temporal evolution of the current-voltage characteristic of a probe in the wake of an object immersed in a pulsed flowing plasma

Measurements of the current-voltage characteristics of a Langmuir probe in the near wake of a disk immersed in a pulsed flowing plasma were made. A 1 cm diameter biasable sphere was placed in the ion-free near wake region of a 10 cm diameter disk immersed in a Mach 8 pulsed flowing plasma. The current-voltage characteristic of the sphere was observed as a function of time as the sphere bias was scanned from -5000 V to +1000 V. The collected current is found to be monotonically increasing with increasing positive bias voltage but exhibits a threshold voltage for current collection as the bias voltage becomes more negative. Potential measurements in the wake region were made for a sphere bias voltages below, at, and above the current collection threshold for a number of times during the wake formation period. The time evolution of the potential profile is shown to change as the sheath around the biased sphere is established. Predictions from the particle trajectory code SIMION are compared with data, showing excellent agreement in the prediction of the current collection threshold

Microwave induced elastic deformation of a metallic thin film

The microwave induced elastic deformation of a metallic thin film is computed numerically and we found that the deformation can be significantly enhanced at resonance. We show that an analytical transmission line model can reproduce the numerical results almost quantitatively and at the same time reveal the underlying physics.Comment: 8 pages,3 figure

On site challenges for the construction of 16-storey condominium: as observed by a young civil engineering technologist

The difference between an engineer and an engineering technologist is that, an engineer would mainly focus and produce structural designs based on engineering calculations, while the job of an engineering technologist is to execute the design in the real working environment by adopting flexible and critical technical ideas on-site. The challenges can be divided into two categories, namely design challenges faced by an engineer and the construction challenges faced by an engineering technologist. Thus, the job scope of an engineering technologist is relatively wider when compared to that of an engineer, as the engineering technologist would be dealing with the consultant, contractors and suppliers on site, while handling the in situ construction challenges. This requires basic understanding of engineering principles and technology, critical thinking and problem-solving skills, modern tools competency in software applications, designs and construction calculations, as well as communication and leadership skills all rolled into one. I have recorded my experience as a junior civil engineering technologist engaged in the construction works of a 16-storey condominium at Langkawi, Kedah. Included in the descriptions are in situ technical problems encountered, potentially unsafe working conditions, foundations, scheduling and housekeeping on site, among others. I hope that the information shared in this entry would make a good introduction and induction for juniors entering the work site, where my personal undertakings could serve as a guide and reminder for them

Fidelity Assessment in Community Programs: An Approach to Validating Simplified Methodology.

Fidelity to intervention protocol is linked to best outcomes for individuals with autism spectrum disorder (ASD; see Boyd & Corley [Autism 5(4):430-441, 2001]; Pellecchia et al. [J Autism Dev Disord 45(9):2917-2927, 2015]); however, fidelity measurement tools that are both accurate and feasible for community use are often not available. In this paper we explore methods for validated simplification of fidelity assessment procedures toward the goal of increased use in clinical practice. Video recordings (n = 36) of therapists working with children with ASD were coded using three variations of fidelity assessment methodology (trial-by-trial, 5-point Likert Scale, and 3-point Likert Scale), and the results were compared for exact agreement, mastery criterion agreement, and overall reliability. The results indicated overall a very high percentage of exact agreement (mean 99.44%, range 94.4-100%) and excellent reliability (mean Krippendorff's alpha [Kα] 1.0) between the trial-by-trial and 5-point Likert Scale across all components; however, the 3-point method may be viewed as being the more feasible strategy within community programs

Statistics Of The Burst Model At Super-critical Phase

We investigate the statistics of a model of type-I X-ray burst [Phys. Rev. E, {\bf 51}, 3045 (1995)] in its super-critical phase. The time evolution of the burnable clusters, places where fire can pass through, is studied using simple statistical arguments. We offer a simple picture for the time evolution of the percentage of space covered by burnable clusters. A relation between the time-average and the peak percentage of space covered by burnable clusters is also derived.Comment: 11 Pages in Revtex 3.0. Two figures available by sending request to [email protected]

Adsorbate Electric Fields on a Cryogenic Atom Chip

We investigate the behaviour of electric fields originating from adsorbates deposited on a cryogenic atom chip as it is cooled from room temperature to cryogenic temperature. Using Rydberg electromagnetically induced transparency we measure the field strength versus distance from a 1 mm square of YBCO patterned onto a YSZ chip substrate. We find a localized and stable dipole field at room temperature and attribute it to a saturated layer of chemically adsorbed rubidium atoms on the YBCO. As the chip is cooled towards 83 K we observe a change in sign of the electric field as well as a transition from a localized to a delocalized dipole density. We relate these changes to the onset of physisorption on the chip surface when the van der Waals attraction overcomes the thermal desorption mechanisms. Our findings suggest that, through careful selection of substrate materials, it may be possible to reduce the electric fields caused by atomic adsorption on chips, opening up experiments to controlled Rydberg-surface coupling schemes.Comment: 5 pages, 4 figure