Bearing damage characteristics of fibre-reinforced countersunk composite bolted joints subjected to quasi-static shear loading

This paper studies the progression of damage in carbon fibre-reinforced polymer (CFRP) countersunk composite bolted joints (CBJs) with neat-fit clearance, subjected to quasi-static loading. Damage mechanisms, comprising of fibre buckling and breakage, matrix damage, shear damage and inter-laminar delamination within the CFRP composite parts of the joints have been studied. Load-displacement curves, X-ray and optical microscopic images in single- and three-bolt CBJs were used to investigate damage and deformation characteristics. The observations were then employed to further investigate the type of failure and the extent of damage. The evolution of damage within the composite parts was correlated to the failure characteristics of the joints: It was found that the type and extension of damage is strongly correlated with the ultimate failure load point of the joint in single-bolt CBJs. A combined inter/intra-laminar damage consisting of fibre cluster breakage, extensive fibre buckling, debonding and delamination was observed at the ultimate failure load. This study was then extended to three-bolt CBJ where damage surrounding each bolt and its corresponding failure load was strongly correlated: The final study showed that the ultimate failure point in single-bolt CBJ and the first-bolt-failure point in three-bolt CBJ correspond to the composite plies undergoing intra-laminar damage with the size reaching to the edge of the countersunk head. This damage developed extensively through the thickness of the composite parts underneath the countersink, and in the direction opposite to the loading direction. Outside the countersunk head, debonding and delamination were found to be the dominant damage driving mechanisms. Finally, a new design rule has been proposed to predict the response of multi-bolt joints (damage area and failure load) by using the response in single-bolt CBJ as an initial baseline

Secrecy Sum-Rates for Multi-User MIMO Regularized Channel Inversion Precoding

In this paper, we propose a linear precoder for the downlink of a multi-user MIMO system with multiple users that potentially act as eavesdroppers. The proposed precoder is based on regularized channel inversion (RCI) with a regularization parameter $\alpha$ and power allocation vector chosen in such a way that the achievable secrecy sum-rate is maximized. We consider the worst-case scenario for the multi-user MIMO system, where the transmitter assumes users cooperate to eavesdrop on other users. We derive the achievable secrecy sum-rate and obtain the closed-form expression for the optimal regularization parameter $\alpha_{\mathrm{LS}}$ of the precoder using large-system analysis. We show that the RCI precoder with $\alpha_{\mathrm{LS}}$ outperforms several other linear precoding schemes, and it achieves a secrecy sum-rate that has same scaling factor as the sum-rate achieved by the optimum RCI precoder without secrecy requirements. We propose a power allocation algorithm to maximize the secrecy sum-rate for fixed $\alpha$. We then extend our algorithm to maximize the secrecy sum-rate by jointly optimizing $\alpha$ and the power allocation vector. The jointly optimized precoder outperforms RCI with $\alpha_{\mathrm{LS}}$ and equal power allocation by up to 20 percent at practical values of the signal-to-noise ratio and for 4 users and 4 transmit antennas.Comment: IEEE Transactions on Communications, accepted for publicatio

Implementing literature circles in a fourth grade classroom

This action research project looked at the effects on twenty-one fourth grade students\u27 levels of comprehension, engagement, and writing when literature circles were implemented while reading the novel Jacob\u27s Rescue, by Malka Drucker and Michael Halperin. The participants, twelve female and nine male, live in a lower-middle class suburban community. While reading this novel about a Jewish boy growing up during the Holocaust, students performed literature circles in combination with a balanced literacy program. The effects on students were examined through student work samples, including role sheets, comprehension questions, subject integration and writer\u27s workshop worksheets, self-evaluations and observational notes taken during instruction. The data was analyzed using codes that examined the degree of difficulty a student had completing the task, the effort he/she showed, and the level of accuracy he/she demonstrated, and then counting the occurrences of each code. My findings support the research on literature circles, that implementation does positively impact the level of student comprehension. I did determine that the most difficult to determine effect was student engagement, so I would not consider my results conclusive. In the area of least research, as it relates to literature circles, I found that the students\u27 writing had the most significant and apparent positive growth

Burnout in female counsellor/therapists of the NCS

A series of three studies was conducted to investigate burnout in counsellor/therapists working with the National Counselling Service (NSC) in Ireland. The NCS was established specifically to meet the needs of adult survivors of institutional abuse. and providing a service for such clients may be very challenging. In Study I, which included 26 NCS counsellor/therapists over a period of a year, mean levels of depersonalisation, but not emotional exhaustion or personal accomplishment, increased significantly. Only 12% were in the high or clinical range for depersonalisation on the Maslach Burnout Inventory at Time 1, but 34.6% were in the high range a year later at Time II. There was a significant increase over a one year period in the number of therapists reporting that work was having a negative effect on their personal lives. The most stressful aspects of therapeutic work were the content of therapy sessions; feeling isolated and lacking support; and working with highly traumatized clients. The main negative effects of therapeutic work on therapists' lives were emotional exhaustion, sadness, and mood spillover. The main positive effects were admiring the resilience of clients and developing increased humility. In Study II, which involved 35 NCS counsellor/therapists, the impact of therapist, client, organisational, and extra-organisational factors on burnout was examined. The use of image distorting defenses was found to be associated with emotional exhaustion and depersonalisation. The percentage of cases improved was also negatively correlated with depersonalisation. On the positive side, therapist empathy for clients was associated with increased experience of personal accomplishment. Study III was a qualitative focus group investigation involving 8 NCS therapist/counsellors. A thematic content analysis identified three factors associated with spillover. These were the stigma associated to working with survivors of child abuse/neglect; the power of a client's narrative; and challenges to the boundaries of the therapeutic relationship. Three themes were identified concerning methods for managing spillover. These were separating from a client; developing and using personal energy renewal routines; and channelling of work intrusions when at home. Implications for the results of the series of three studies for an ecological model of therapist burnout, and for NCS therapist/counsellor support and supervision were discussed

You\u27re Breaking My Heart With Good-Bye

https://digitalcommons.library.umaine.edu/mmb-vp/3784/thumbnail.jp

ERTS-1 Virgin Islands experiment 589: Determine boundaries of ERTS and aircraft data within which useful water quality information can be obtained

The author has identified the following significant results. The boundaries of application of ERTS-1 and aircraft data are established for St. Thomas harbor within which useful water quality information can be obtained. In situ physical, chemical, and biological water quality and benthic data were collected. Moored current meters were employed. Optical measurements of solar irradiance, color test panel radiance and water absorption were taken. Procedures for correlating in situ optical, biological, and chemical data with underflight aircraft I2S data and ERTS-1 MSS scanner data are presented. Comparison of bulk and precision CCT computer printout data for this application is made, and a simple method for geometrically locating bulk data individual pixels based on land-water interface is described. ERTS spacecraft data and I2S aircraft imagery are correlated with optical in situ measurements of the harbor water, with the aircraft green photographic and ERTS-1 MSS-4 bands being the most useful. The biological pigments correlate inversely with the optical data for inshore areas and directly further seaward. Automated computer data processing facilitated analysis

Till We Meet Again

[Verse 1] There’s a song in the land of the lily Each sweetheart has heard with a sigh Over high garden walls This sweet echo falls As a solider boy whispers goodbye [Chorus] Smile the while you kiss me a sad adieu When the clouds roll by I’ll come to you Then the skies will seems more blue Down in lovers lane my dearie Wedding bells will ring so merrily Ev’ry tear will be a memory So wait and pray each night for me Till we meet again [Verse 2] Tho’ goodbye means the birth of a tear drop Hello means the birth of a smile And the smile will erase The tear blighting trace When we meet in the after-a-while [Chorus