Flexible multiply towpreg and method of production therefor

This invention relates to an improved flexible towpreg and a method of production therefor. The improved flexible towpreg comprises a plurality of towpreg plies which comprise reinforcing filaments and matrix forming material; the reinforcing filaments being substantially wetout by the matrix forming material such that the towpreg plies are substantially void-free composite articles, and the towpreg plies having an average thickness less than about 100 microns. The method of production for the improved flexible towpreg comprises the steps of spreading the reinforcing filaments to expose individually substantially all of the reinforcing filaments; coating the reinforcing filaments with the matrix forming material in a manner causing interfacial adhesion of the matrix forming material to the reinforcing filaments; forming the towpreg plies by heating the matrix forming material contacting the reinforcing filaments until the matrix forming material liquefies and coats the reinforcing filaments; and cooling the towpreg plies in a manner such that substantial cohesion between neighboring towpreg plies is prevented until the matrix forming material solidifies

Flexible multiply towpreg

This invention relates to an improved flexible towpreg and a method of production therefor. The improved flexible towpreg comprises a plurality of towpreg plies which comprise reinforcing filaments and matrix forming material; the reinforcing filaments being substantially wetout by the matrix forming material such that the towpreg plies are substantially void-free composite articles, and the towpreg plies having an average thickness less than about 100 microns. The method of production for the improved flexible towpreg comprises the steps of spreading the reinforcing filaments to expose individually substantially all of the reinforcing filaments; coating the reinforcing filaments with the matrix forming material in a manner causing interfacial adhesion of the matrix forming material to the reinforcing filaments; forming the towpreg plies by heating the matrix forming material contacting the reinforcing filaments until the matrix forming material liquifies and coats the reinforcing filaments; and cooling the towpreg plies in a manner such that substantial cohesion between neighboring towpreg plies is prevented until the matrix forming material solidifies

Stress Analysis of a Stepped-Lap Bonded Repair Joint in Composite Laminate under Compressive Loading

With increasing the usage of advanced composite materials in aircraft structures, it is required to have a suitable repair technology for composite airframe. One of the primary requisites of the repair in such structures is that the repaired surface should not affect the aerodynamic contour. Adhesively bonded repair joints are generally preferred over mechanically fastened repair joints to avoid the stress concentration and achieve smooth aerodynamic surface. Significant numbers of research works have been carried on interface stress distributions for lap, butt and scarf adhesive repaired joints under the static tensile loading. However, the behavior of stepped-lap adhesive joints under compressive loading has not been fully understood and there are not many literatures available on this subject. The present work focuses on stress analysis of a laminate that is repaired through a stepped-lap joint repair scheme. The stress analysis has been carried out and stress distributions in the laminate, patch and adhesive were studied. In order to establish and validate the FE approach for analysis of stepped-lap repair joint subjected to compression, an experimental study also has been carried out. The strains from the analysis have been compared with the strains obtained from the test at important locations. Both the results have shown good agreement

Structural Studies of Cu(II) & Ni(II) Complexes with a Chiral Schiff Base

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Criteria for performance evaluation of RC building frames using non-linear time history analysis for performance-based design

Displacement-based design (DBD) is emerging as the new trend for seismic design of buildings. Several displacement-based design procedures have been developed in recent times. The performances of buildings designed using these methods are usually evaluated by conducting non-linear time history analysis (NLTHA). The efficiency of performance assessment depends on proper non-linear material modelling, selection of proper earthquake records and their scaling and appropriate setting up of limit states (acceptance criteria). The present paper discusses the provisions in various seismic guidelines including ATC 63, FEMA P695 (2009) and PEER Centre report No.2010/05 and recent research findings regarding the above parameters. According to FEMA P695, only the far-field record set is required for collapse assessment as there are many unresolved issues concerning the characterization of near-fault hazard and ground motion effects. To verify this, the response spectra are plotted for 10 selected far-field and near-field ground motions and found that there is considerable increase in the response of long period structures when they are subjected to near-field pulses. Time history analysis done on a 15-storeyed frame (which is designed as per DBD) shows an increase in roof displacement of the order of two and inter-storey drift amplification of about 2.7 near the base, when near-field ground motions are used for performance assessment

Gonadotropins for pubertal induction in males with hypogonadotropic hypogonadism: systematic review and meta-analysis.

OBJECTIVE: Hypogonadotropic hypogonadism is characterized by inadequate secretion of pituitary gonadotropins, leading to absent, partial, or arrested puberty. In males, classical treatment with testosterone promotes virilization but not testicular growth or spermatogenesis. To quantify treatment practices and efficacy, we systematically reviewed all studies investigating gonadotropins for the achievement of pubertal outcomes in males with hypogonadotropic hypogonadism. DESIGN: Systematic review and meta-analysis. METHODS: A systematic review of Medline, Embase, Global Health, and PsycINFO databases in December 2022. Risk of Bias 2.0/Risk Of Bias In Non-randomized Studies of Interventions/National Heart, Lung, and Blood Institute tools for quality appraisal. Protocol registered on PROSPERO (CRD42022381713). RESULTS: After screening 3925 abstracts, 103 studies were identified including 5328 patients from 21 countries. The average age of participants was <25 years in 45.6% (n = 47) of studies. Studies utilized human chorionic gonadotropin (hCG) (n = 93, 90.3% of studies), human menopausal gonadotropin (n = 42, 40.8%), follicle-stimulating hormone (FSH) (n = 37, 35.9%), and gonadotropin-releasing hormone (28.2% n = 29). The median reported duration of treatment/follow-up was 18 months (interquartile range 10.5-24 months). Gonadotropins induced significant increases in testicular volume, penile size, and testosterone in over 98% of analyses. Spermatogenesis rates were higher with hCG + FSH (86%, 95% confidence interval [CI] 82%-91%) as compared with hCG alone (40%, 95% CI 25%-56%). However, study heterogeneity and treatment variability were high. CONCLUSIONS: This systematic review provides convincing evidence of the efficacy of gonadotropins for pubertal induction. However, there remains substantial heterogeneity in treatment choice, dose, duration, and outcomes assessed. Formal guidelines and randomized studies are needed

Astrophysical S_{17}(0) factor from a measurement of d(7Be,8B)n reaction at E_{c.m.} = 4.5 MeV

Angular distribution measurements of $^2$H($^7$Be,$^7$Be)$^2$H and $^2$H($^7$Be,$^8$B)$n$ reactions at $E_{c.m.}\sim$~4.5 MeV were performed to extract the astrophysical $S_{17}(0)$ factor using the asymptotic normalization coefficient (ANC) method. For this purpose a pure, low emittance $^7$Be beam was separated from the primary $^7$Li beam by a recoil mass spectrometer operated in a novel mode. A beam stopper at 0$^{\circ}$ allowed the use of a higher $^7$Be beam intensity. Measurement of the elastic scattering in the entrance channel using kinematic coincidence, facilitated the determination of the optical model parameters needed for the analysis of the transfer data. The present measurement significantly reduces errors in the extracted $^7$Be(p,$\gamma$) cross section using the ANC method. We get $S_{17}$~(0)~=~20.7~$\pm$~2.4 eV~b.Comment: 15 pages including 3 eps figures, one figure removed and discussions updated. Version to appear in Physical Review

Statistical classification techniques for photometric supernova typing

Future photometric supernova surveys will produce vastly more candidates than can be followed up spectroscopically, highlighting the need for effective classification methods based on light curves alone. Here we introduce boosting and kernel density estimation techniques which have minimal astrophysical input, and compare their performance on 20 000 simulated Dark Energy Survey light curves. We demonstrate that these methods perform very well provided a representative sample of the full population is used for training. Interestingly, we find that they do not require the redshift of the host galaxy or candidate supernova. However, training on the types of spectroscopic subsamples currently produced by supernova surveys leads to poor performance due to the resulting bias in training, and we recommend that special attention be given to the creation of representative training samples. We show that given a typical non-representative training sample, S, one can expect to pull out a representative subsample of about 10 per cent of the size of S, which is large enough to outperform the methods trained on all of