Sound Insulation Performance of Composite Double Sandwich Panels with Periodic Arrays of Shunted Piezoelectric Patches

The existing sandwich structure of the aircraft cabin demonstrates a good sound insulation effect in medium and high frequency bands, but poor in the low frequency band. Therefore, we propose an infinite new lightweight broadband noise control structure and study its sound transmission loss (STL). The structure is an orthogonally rib-stiffened honeycomb double sandwich structure with periodic arrays of shunted piezoelectric patches, and demonstrates lighter mass and better strength than the existing sandwich structure. The structure is equivalent according to Hoff’s equal stiffness theory and the effective medium (EM) method. Using the virtual work principle for a periodic element, two infinite sets of coupled equations are obtained. They are solved by truncating them in a finite range until the solution converges. The correctness and validity of the model are verified by using simulation results and theoretical predictions. Eventually, a further study is performed on the factors influencing the STL. All the results demonstrate that the STL in low-frequency can be improved by the structure, and the sound insulation bandwidth is significantly broadened by adding shunted piezoelectric patches. The structure can provide a new idea for the design of broadband sound insulation.

Difference in Response to Feedback and Gender in Three Therapeutic Community Units

Therapeutic communities (TCs) for substance abuse incorporate a system of peer feedback through written affirmations and corrections. Previous research has found that TC residents show a response to affirmations that is detectable for roughly 8 weeks, with response to corrections being of shorter duration and weaker overall. It is not clear whether and to what extent response to feedback in TCs varies between men and women. Previous research in other settings suggests that women should be more responsive to feedback than men. In order to test this hypothesis we draw on a large dataset of affirmations and corrections sent and received in three 80 bed TC units, two of which house men and one of which houses women. The analysis uses a multilevel negative binomial model, treating affirmations and corrections that TC residents receive as predictors of affirmations that they send over a 9 week period (week 0, the week during which affirmations and corrections are actually sent, and eight subsequent weeks). The model controls for gender, age, race, unit and scores on the Level of Service Inventory-Revised (LSI-R). The relationship between affirmations received and those sent is stronger for women during the initial week and on lags 1-2 and 5-8. The relationship between corrections received and affirmations sent is stronger for women on lags 2 and 8. Graphs suggest that response to affirmations falls off in an exponential curve, while that to corrections appears to include a periodic element. These results indicate that both men and women respond to feedback, but that the strength of the women's response is somewhat greater. These results suggest that any difference in suitability by gender to the feedback approach that characterizes TCs may favor women.

EFEKTIVITAS METODE TOKEN KIMIA TERHADAP HASIL DAN RETENSI BELAJAR SISWA PADA MATERI SISTEM PERIODIK UNSUR DI KELAS X MAN 3 PONTIANAK

Student learning results and retention is still low on periodic system learning elements caused by a lack of motivation students in the periodic table system memorize elements and lack of reward when students are already able to memorize the table Periodic system of such elements. So it requires a learning method that can motivate students in deleting periodic table system elements. The study aims to determine the difference in outcomes and retention of learning between students taught with and without using the chemical token method on the periodic element system material, knowing the great effectiveness of the chemical token method of the results and Student learning retention on periodic element system materials in class X MAN 3 Pontianak. This research uses the type of experimental Quasi research with the design of control group design. The sampling technique uses saturated sampling with the X-class of MIA as the experimental class and X-grade IIS 2 as the control class. Data collection techniques using measurement, observation and interview techniques, while the data collection tools are test results and learning retention, interpreters and observation sheets. Analysis Data Using Test-T shows that there are differences in learning outcomes while learning retention differences are known through the Mann-Whitney U test with the result that there is a difference in learning retention between students taught with and without Using a chemical token method. Learning with the chemical token method affects student learning outcomes by 22.91% by medium category, and 10-day student study retention of 36.86% with high category.

Analyses of multi-bandgap property of a locally resonant plate composed of periodic resonant subsystems

A locally resonant (LR) plate made up of a thin plate attached with different types of resonators is analyzed in this paper. Each periodic element may consist of one or more spring-mass resonators attached onto one and the same surface of the plate lattice. The correctness of theoretical plane wave expansion (PWE) method adopted in this paper is validated through the comparisons with the classical theory and finite element method (FEM). When composing the LR plate system with two types of periodic resonant subsystems, there will appear two complete bandgaps, while other additional resonators may cause mainly directional gaps, calculated theoretically and numerically. From the comparisons of band-structure curves between a two-resonator-per-unit-element (TR-UE) system and both corresponding one-resonator-per-unit-element (OR-UE) systems, the bandgap width of the TR-UE system are not stacking effects of two OR-UE systems due to resonance interaction of different types of resonators. Moreover, via the deformation contours by FEM, the correspondence between the vibration modes of subsystems and the bandgap frequencies is demonstrated. The finite plate with limited resonators of two periodic types of parameters is modeled to show visually how flexural waves propagate within/without the bandgaps. Further, by adjusting the damping characteristic of both types of resonators, vibration attenuation band can be broadened widely.

Compact Dual Band Antenna Design for Ku / Ka Band Applications

This communication proposes a compact 16 GHz / 30 GHz dual band antenna design for Ku / Ka band applications. The antenna consists of two layers with lower layer having the fed patch and the upper layer having non-periodic element array. The antenna has been designed to operate at two different frequencies with compact dimensions of (8mm x 8mm) using Rogers RT 5880. The compact size of this proposed antenna also makes it suitable for integration with the microwave and millimeter wave circuits. The proposed antenna provides high radiation efficiency and a peak gain of about 8 dB at the resonant frequencies with reduced side lobe levels.

MAPPING CLASS GROUPS OF HEEGAARD SPLITTINGS

The mapping class group of a Heegaard splitting is the group of connected components in the set of automorphisms of the ambient manifold that map the Heegaard surface onto itself. We find examples of elements of the mapping class group that are periodic, reducible and pseudo-Anosov on the Heegaard surface, but are isotopy trivial in the ambient manifold. We prove structural theorems about the first two classes, in particular showing that if a periodic element is trivial in the mapping class group of the ambient manifold, then the manifold is not hyperbolic.

PERIODIC ELEMENTS OF THE FREE IDEMPOTENT GENERATED SEMIGROUP ON A BIORDERED SET

We show that every periodic element of the free idempotent generated semigroup on an arbitrary biordered set belongs to a subgroup of the semigroup.

Elastohydrodynamic Lubrication of Multiple Periodic Ridges

The lubrication of rolling contacts in which one surface has a roughness consisting of periodic transverse or longitudinal ridges has been widely investigated, both theoretically, by, for example, Venner, Lubrecht, Greenwood, Snidle and Evans [1–4] and by means of experiments [5–7]. The problem is relevant to the lubrication of machined surfaces which have a strong periodic element of roughness.