Search

Impact velocity (v0), target strength (fc) and target thickness (hc) are important factors affecting opening damage ( D ¯ ) of PELE penetration into RC target. In this paper, based on the three influence factors of v0, fc and hc, experimental and numerical simulation studies on PELE penetration into RC target were carried out. The study results show that: (1) Since interaction force (or penetration resistance) between projectile and target is positively correlated with v0 and fc, with the increase of v0 and fc, deformation mode of jacket is changed from small bending deformation to large bending deformation and then to curling deformation. Therefore, the variation of jacket deformation mode causes opening diameter of RC target to increase first and then to decrease. It is found that the two factors approximately satisfy a quadratic function relationship, respectively. (2) For PELE projectile penetrating RC targets with thickness of 80–400 mm, the opening diameter of six sets of RC targets grows from 240 to 500 mm, and hc with D ¯ approximately satisfy a linear relationship. (3) Based on the above study results, the relationship between two dimensionless parameters ( I = m v 0 2 d 1 3 f c and H = h c l ) and dimensionless opening diameter ( D ¯ / d 1 ) was determined. Combined with the results of previous research, a dimensionless opening diameter model D ¯ d 1 = f 1 ( Q , G , I ) f 2 ( H ) was established. By tests verified, the test results are all within ±10% error of the theoretical model, which verifies the accuracy of the model.

The UV/optical variation, likely driven by accretion disc turbulence, is a defining characteristic of type 1 active galactic nuclei (AGNs) and quasars. In this work we investigate an interesting consequence of such turbulence using quasars in SDSS Stripe 82 for which the measurements of the UV/optical variability amplitude are available from $\sim$ 10 years long light curves. We discover positive correlations between UV/optical variability amplitude $\sigma_{rms}$ and equivalent widths of CIV, Mg II and [OIII]5007 emission lines. Such correlations remain statistically robust through partial correlation analyses, i.e., after controlling the effects of other variables including bolometric luminosity, central supermassive black hole mass, Eddington ratio and redshift. This, for the first time, indicates a causal link between disc turbulence and emission line production. We propose two potential underlying mechanisms both of which may be involved: 1) quasars with stronger disc turbulence have on average bluer/harder broadband SED, an expected effect of the disc thermal fluctuation model; 2) stronger disc turbulence could lead to launch of emission line regions with larger covering factors., Comment: 12 pages, 7 figures, 5 tables, accepted by ApJ

A penetrator with enhanced lateral effects (PELE), which is a particular thin-walled structure, is characterized by a low-density filling material surrounded by a high-density jacket material. When the PELE projectile penetrates a concrete target, the target is destroyed by its thin-walled jacket to a large opening. An analytical model describing deformation mode of the jacket during the penetration process is presented. Due to opening diameter of target plate is larger than projectile diameter under condition of a thin concrete target, a relationship between opening diameter of target plate and projectile diameter, based on existing experimental results of ridge projectile penetrating thin concrete target, is formulated. The relationship combined with the analytical model is used to predict opening diameter of concrete target. A quantitative comparison between the jacket deformation mode obtained from analytical results and experimental results is made to validate the accuracy of the analytical model proposed. As a result, the analytical results exhibit good correlation with experimental observations in terms of the opening diameter of target plate and the deformation mode of projectile jacket. In addition, the influence mechanism of three factors (jacket strength, impact velocity, and target thickness) on the opening diameter is analyzed. The jacket strength affects the opening diameter by changing the plastic limit bending moment of the jacket. Even though the impact velocity affects the opening diameter by changing the interaction force between the jacket and the target, it is equivalent to indirectly changing the jacket strength. However, the target thickness affects the opening diameter by changing the penetration time.

Aligning protein sequences using a score matrix has became a routine but valuable method in modern biological research. However, alignment in the 'twilight zone' remains an open issue. It is feasible and necessary to construct a new score matrix as more protein structures are resolved. Three structural class-specific score matrices (all-alpha, all-beta and alpha/beta) were constructed based on the structure alignment of low identity proteins of the corresponding structural classes. The class-specific score matrices were significantly better than a structure-derived matrix (HSDM) and three other generalized matrices (BLOSUM30, BLOSUM60 and Gonnet250) in alignment performance tests. The optimized gap penalties presented here also promote alignment performance. The results indicate that different protein classes have distinct amino acid substitution patterns, and an amino acid score matrix should be constructed based on different structural classes. The class-specific score matrices could also be used in profile construction to improve homology detection.

Aligning protein sequences using a score matrix has became a routine but valuable method in modern biological research. However, alignment in "Twilight Zone" is still a challenging issue. New score matrices such as Position Specific Score Matrix and structural context-based matrix have been issued to deal with it, whereas generalized matrices are still useful in pairwise alignment and/or some steps of generating profiles. Family-specific matrices have been proved effective in improving alignment, whereas the generalization of them is reduced. ALPHASUM, a score matrix based on structure alignment of low identity all-alpha proteins is constructed. Performance comparison suggests substitution pattern difference between all-alpha proteins and all proteins and indicates that alignment of all-alpha proteins in "Twilight Zone" can be improved by using alpha class-specific matrix and gap penalties. The implication between structure-derived matrix and influence of amino acid substitution to structure is also suggested.

Sequence alignment has been a most commonly used method in modern biological research. However, sequence alignment in "Twilight Zone" is still a challenging issue. Three protein class-specific matrices are constructed to investigate whether alignment in "Twilight Zone" can be improved by using class-specific matrices and gap penalties. The substitution pattern differences between different protein classes do improve the performances of the three class-specific matrices. Analyzing amino acids substitution pattern based on different matrices also suggests important information for protein sequence design.