878 research outputs found
Comparing the Performance of Different Machine Learning Models in the Evaluation of Solder Joint Fatigue Life Under Thermal Cycling
Predicting the reliability of board-level solder joints is a challenging process for the designer because the fatigue life of solder is influenced by a large variety of design parameters and many nonlinear, coupled phenomena. Machine learning has shown promise as a way of predicting the fatigue life of board-level solder joints. In the present work, the performance of various machine learning models to predict the fatigue life of board-level solder joints is discussed. Experimental data from many different solder joint thermal fatigue tests are used to train the different machine learning models. A web-based database for storing, sharing, and uploading data related to the performance of electronics materials, the Electronics Packaging Materials Database (EPMD), has been developed and used to store and serve the training data for the present work. Data regression is performed using artificial neural networks, random forests, gradient boosting, extreme gradient boosting (XGBoost), and adaptive boosting with neural networks (AdaBoost). While previous works have studied artificial neural networks as a way to predict the fatigue life of board-level solder joints, the results in this paper suggest that machine learning techniques based on regression trees may also be useful in predicting the fatigue life of board-level solder joints. This paper also demonstrates the need for a large collection of curated data related to board-level solder joint reliability, and presents the Electronics Packaging Materials Database to meet that need
Population pulsation resonances of excitons in monolayer MoSe2 with sub 1 {\mu}eV linewidth
Monolayer transition metal dichalcogenides, a new class of atomically thin
semiconductors, possess optically coupled 2D valley excitons. The nature of
exciton relaxation in these systems is currently poorly understood. Here, we
investigate exciton relaxation in monolayer MoSe2 using polarization-resolved
coherent nonlinear optical spectroscopy with high spectral resolution. We
report strikingly narrow population pulsation resonances with two different
characteristic linewidths of 1 {\mu}eV and <0.2 {\mu}eV at low-temperature.
These linewidths are more than three orders of magnitude narrower than the
photoluminescence and absorption linewidth, and indicate that a component of
the exciton relaxation dynamics occurs on timescales longer than 1 ns. The
ultra-narrow resonance (<0.2 {\mu}eV) emerges with increasing excitation
intensity, and implies the existence of a long-lived state whose lifetime
exceeds 6 ns.Comment: (PRL, in press
Neuromotor Changes in Participants with a Concussion History can be Detected with a Custom Smartphone App
Neuromotor dysfunction after a concussion is common, but balance tests used to assess neuromotor dysfunction are typically subjective. Current objective balance tests are either cost- or space-prohibitive, or utilize a static balance protocol, which may mask neuromotor dysfunction due to the simplicity of the task. To address this gap, our team developed an Android-based smartphone app (portable and cost-effective) that uses the sensors in the device (objective) to record movement profiles during a stepping-in-place task (dynamic movement). The purpose of this study was to examine the extent to which our custom smartphone app and protocol could discriminate neuromotor behavior between concussed and non-concussed participants. Data were collected at two university laboratories and two military sites. Participants included civilians and Service Members (N = 216) with and without a clinically diagnosed concussion. Kinematic and variability metrics were derived from a thigh angle time series while the participants completed a series of stepping-in-place tasks in three conditions: eyes open, eyes closed, and head shake. We observed that the standard deviation of the mean maximum angular velocity of the thigh was higher in the participants with a concussion history in the eyes closed and head shake conditions of the stepping-in-place task. Consistent with the optimal movement variability hypothesis, we showed that increased movement variability occurs in participants with a concussion history, for which our smartphone app and protocol were sensitive enough to capture
Molecular Hydrogen in the FUSE Translucent Lines of Sight: The Full Sample
We report total abundances and related parameters for the full sample of the
FUSE survey of molecular hydrogen in 38 translucent lines of sight. New results
are presented for the "second half" of the survey involving 15 lines of sight
to supplement data for the first 23 lines of sight already published. We assess
the correlations between molecular hydrogen and various extinction parameters
in the full sample, which covers a broader range of conditions than the initial
sample. In particular, we are now able to confirm that many, but not all, lines
of sight with shallow far-UV extinction curves and large values of the
total-to-selective extinction ratio, = / -- characteristic
of larger than average dust grains -- are associated with particularly low
hydrogen molecular fractions (). In the lines of sight with large
, there is in fact a wide range in molecular fractions, despite the
expectation that the larger grains should lead to less H formation.
However, we see specific evidence that the molecular fractions in this
sub-sample are inversely related to the estimated strength of the UV radiation
field and thus the latter factor is more important in this regime. We have
provided an update to previous values of the gas-to-dust ratio, (H)/, based on direct measurements of (H) and (H I).
Although our value is nearly identical to that found with Copernicus data, it
extends the relationship by a factor of 2 in reddening. Finally, as the new
lines of sight generally show low to moderate molecular fractions, we still
find little evidence for single monolithic "translucent clouds" with 1.Comment: 35 pages, 5 tables, 7 figures, accepted for publication in The
Astrophysical Journal Supplements Serie
Neuromotor Changes in Participants With a Concussion History Can Be Detected With a Custom Smartphone App
Neuromotor dysfunction after a concussion is common, but balance tests used to assess neuromotor dysfunction are typically subjective. Current objective balance tests are either cost- or space-prohibitive, or utilize a static balance protocol, which may mask neuromotor dysfunction due to the simplicity of the task. To address this gap, our team developed an Android-based smartphone app (portable and cost-effective) that uses the sensors in the device (objective) to record movement profiles during a stepping-in-place task (dynamic movement). The purpose of this study was to examine the extent to which our custom smartphone app and protocol could discriminate neuromotor behavior between concussed and non-concussed participants. Data were collected at two university laboratories and two military sites. Participants included civilians and Service Members (N = 216) with and without a clinically diagnosed concussion. Kinematic and variability metrics were derived from a thigh angle time series while the participants completed a series of stepping-in-place tasks in three conditions: eyes open, eyes closed, and head shake. We observed that the standard deviation of the mean maximum angular velocity of the thigh was higher in the participants with a concussion history in the eyes closed and head shake conditions of the stepping-in-place task. Consistent with the optimal movement variability hypothesis, we showed that increased movement variability occurs in participants with a concussion history, for which our smartphone app and protocol were sensitive enough to capture
The role of interpersonal personality traits and reassurance seeking in eating disorder symptoms and depressive symptoms among women with bulimia nervosa
The role of interpersonal factors has been proposed in various models of eating disorder (ED) psychopathology and treatment. We examined the independent and interactive contributions of two interpersonal-focused personality traits (i.e., social avoidance and insecure attachment) and reassurance seeking in relation to global ED psychopathology and depressive symptoms among women with bulimia nervosa (BN)
A decade of stability for wMel Wolbachia in natural Aedes aegypti populations
Mosquitoes carrying Wolbachia endosymbionts are being released in many countries for arbovirus control. The wMel strain of Wolbachia blocks Aedes-borne virus transmission and can spread throughout mosquito populations by inducing cytoplasmic incompatibility. Aedes aegypti mosquitoes carrying wMel were first released into the field in Cairns, Australia, over a decade ago, and with wider releases have resulted in the near elimination of local dengue transmission. The long-term stability of Wolbachia effects is critical for ongoing disease suppression, requiring tracking of phenotypic and genomic changes in Wolbachia infections following releases. We used a combination of field surveys, phenotypic assessments, and Wolbachia genome sequencing to show that wMel has remained stable in its effects for up to a decade in Australian Ae. aegypti populations. Phenotypic comparisons of wMel-infected and uninfected mosquitoes from near-field and long-term laboratory populations suggest limited changes in the effects of wMel on mosquito fitness. Treating mosquitoes with antibiotics used to cure the wMel infection had limited effects on fitness in the next generation, supporting the use of tetracycline for generating uninfected mosquitoes without off-target effects. wMel has a temporally stable within-host density and continues to induce complete cytoplasmic incompatibility. A comparison of wMel genomes from pre-release (2010) and nine years post-release (2020) populations show few genomic differences and little divergence between release locations, consistent with the lack of phenotypic changes. These results indicate that releases of Wolbachia-infected mosquitoes for population replacement are likely to be effective for many years, but ongoing monitoring remains important to track potential evolutionary changes
KELT-7b: A hot Jupiter transiting a bright V=8.54 rapidly rotating F-star
We report the discovery of KELT-7b, a transiting hot Jupiter with a mass of
MJ, radius of RJ, and an orbital
period of days. The bright host star (HD33643;
KELT-7) is an F-star with , Teff K, [Fe/H]
, and . It has a mass of
Msun, a radius of Rsun, and
is the fifth most massive, fifth hottest, and the ninth brightest star known to
host a transiting planet. It is also the brightest star around which KELT has
discovered a transiting planet. Thus, KELT-7b is an ideal target for detailed
characterization given its relatively low surface gravity, high equilibrium
temperature, and bright host star. The rapid rotation of the star (
km/s) results in a Rossiter-McLaughlin effect with an unusually large amplitude
of several hundred m/s. We find that the orbit normal of the planet is likely
to be well-aligned with the stellar spin axis, with a projected spin-orbit
alignment of degrees. This is currently the second most
rapidly rotating star to have a reflex signal (and thus mass determination) due
to a planetary companion measured.Comment: Accepted to The Astronomical Journa
Externalities from Alcohol Consumption in the 2005 US National Alcohol Survey: Implications for Policy
A subsample (n = 2,550) of the 2005 US National Alcohol Survey of adults was used to estimate prevalence and correlates of six externalities from alcohol abuse––family problems, assaults, accompanying intoxicated driver, vehicular accident, financial problems and vandalized property––all from another’s drinking. On a lifetime basis, 60% reported externalities, with a lower 12-month rate (9%). Women reported more family/marital and financial impacts and men more assaults, accompanying drunk drivers, and accidents. Being unmarried, older, white and ever having monthly heavy drinking or alcohol problems was associated with more alcohol externalities. Publicizing external costs of drinking could elevate political will for effective alcohol controls
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