Seismic Response of Structures with Underground Stories Considering Non-Linear Soil-Structure Interaction

Most of the research conducted for soil-structure interaction analysis of structures are assuming the linear behavior of soil. It is well known that during strong ground excitations the soil adjacent to the structure behaves highly non-linear. The nonlinear soil behavior affects the soil-structure interaction in a complex way especially because of the inadequacy in modeling the unbounded soil medium. In the case where an elastic soil behavior is assumed, the surface motion will be amplified proportionally to the input motion. However, in reality the amplitude and frequency content of the response are modified due to the soil’s stiffness degradation and higher energy dissipation. The present work deals with the influence of soil non-linearity, introduced by hysteretic behavior of near-field soil, on the soil-foundation-structure interaction phenomena. The objective is to reveal the beneficial or detrimental effects of the non-linear SSI concerning both the drift and settlement of structures with underground stories. To examine the effect of non-linear soil-structure interaction a realistic non-linear soil model is incorporated into the finite difference FLAC software. To better understanding the non-linear dynamic SSI, interface elements are also used between the near-field soil and basement walls. For a practical structure throughout a parametric study, some non-linear seismic analyses are performed to demonstrate the effectiveness of the affecting parameters in response of the structure. The results showed much difference on seismic response of structure such as drift, settlement and developing pressure around the basement walls when the non-linear soil-structure interaction is considered

Capacity-achieving Polar-based LDGM Codes

In this paper, we study codes with sparse generator matrices. More specifically, low-density generator matrix (LDGM) codes with a certain constraint on the weight of all the columns in the generator matrix are considered. In this paper, it is first shown that when a binary-input memoryless symmetric (BMS) channel $W$ and a constant $s>0$ are given, there exists a polarization kernel such that the corresponding polar code is capacity-achieving and the column weights of the generator matrices are bounded from above by $N^s$. Then, a general construction based on a concatenation of polar codes and a rate-$1$ code, and a new column-splitting algorithm that guarantees a much sparser generator matrix is given. More specifically, for any BMS channel and any $\epsilon > 2\epsilon^*$, where $\epsilon^* \approx 0.085$, an existence of sequence of capacity-achieving codes with all the column wights of the generator matrix upper bounded by $(\log N)^{1+\epsilon}$ is shown. Furthermore, coding schemes for BEC and BMS channels, based on a second column-splitting algorithm are devised with low-complexity decoding that uses successive-cancellation. The second splitting algorithm allows for the use of a low-complexity decoder by preserving the reliability of the bit-channels observed by the source bits, and by increasing the code block length. In particular, for any BEC and any $\lambda >\lambda^* = 0.5+\epsilon^*$, the existence of a sequence of capacity-achieving codes where all the column wights of the generator matrix are bounded from above by $(\log N)^{2\lambda}$ and with decoding complexity $O(N\log \log N)$ is shown. The existence of similar capacity-achieving LDGM codes with low-complexity decoding is shown for any BMS channel, and for any $\lambda >\lambda^{\dagger} \approx 0.631$.Comment: arXiv admin note: text overlap with arXiv:2001.1198

A universal system for digitization and automatic execution of the chemical synthesis literature

Robotic systems for chemical synthesis are growing in popularity but can be difficult to run and maintain because of the lack of a standard operating system or capacity for direct access to the literature through natural language processing. Here we show an extendable chemical execution architecture that can be populated by automatically reading the literature, leading to a universal autonomous workflow. The robotic synthesis code can be corrected in natural language without any programming knowledge and, because of the standard, is hardware independent. This chemical code can then be combined with a graph describing the hardware modules and compiled into platform-specific, low-level robotic instructions for execution. We showcase automated syntheses of 12 compounds from the literature, including the analgesic lidocaine, the Dess-Martin periodinane oxidation reagent, and the fluorinating agent AlkylFluor

The post-impact response of flax/UP composite laminates under low velocity impact loading

Flax fiber reinforced unsaturated polyester (UP) composite laminates were fabricated by vacuum bagging process and their impact and post-impact responses was investigated through experimental testing and finite element simulations. Samples of 60 mm x 60 mm x 6.2 mm were cut from the composite laminates and were subjected to a low-velocity impact loading to near perforation using hemispherical steel impactor at three different energy levels, 25, 27 and 29 Joules, respectively. Post impact with incident energy of 25 Joules was employed to occure full penetration. The impacted composite plates were modelled with various lay-ups using finite element software LS-DYNA (LS-DYNA User’s Manual 1997) to provide a validated FE model for the future investigations in the field. The effects of impact and post impact on the failure mechanisms were evaluated using scanning electron microphotography (SEM). Parameters measured were load bearing capability, energy absorption and damage modes. The results show a significant reduction in impact strength after post impact events at all energy levels