Nonlocal acoustic metasurface absorber for ultra-broadband sound absorption

Classical designs of acoustic meta-absorber usually have a trade-off between bandwidth, efficiency and thickness. Here, we introduce the concept of nonlocal acoustic metasurface absorber by using a bridge structure connecting resonating unit cells to improve the performances of the meta-absorber. By utilizing the coupling effect between the adjacent unit cells, ultra-broadband sound absorption is achieved with deep-wavelength thickness. The physical mechanism of the nonlocal acoustic metasurface absorber is investigated by developing analytical models. We theoretically and numerically study the nonlocal metasurface with connecting bridge and the traditional metasurface without bridge. The nonlocality can introduce three specific effects: 1. Optimizing of effective acoustic impedances. 2. Shift of Fabry-Perot resonant frequencies. 3. Strengthening of the coupling effects between adjacent unit cells. These effects help to improve the bandwidth and the efficiency of the acoustic meta-absorber. We numerically and experimentally achieve an averaged absorption coefficient larger than 0.9 within the ultra-broadband bandwidth from about 600 Hz to 2600 Hz, with a sample thickness of 6.8 cm, , /9 for the lowest frequency. Our finding demonstrates the advantage of non-local acoustic metasurface to conceive subwavelength sound meta-absorber.

Quantifying air leakage through party walls in Toronto semidetached and row-home dwellings

This study contributes to the development of quantifying and understanding building air tightness as it relates to Toronto semi-detached and row homes, particularly party walls. While infiltration characteristics of single family detached homes have been widely developed and understood, the isolation of semi-detached and row home single family dwelling units is relatively unexplored. When quantifying air leakage in a building attached to an adjacent dwelling unit, air is drawn through the exterior envelope as well as the party wall (i.e. shared common wall). The purpose of the proposed testing method, guarded blower door testing, is to isolate air leakage through the party wall from the envelope. Currently the party wall is considered a fire-rated assembly but is not part of the air barrier system. Issues associated with party wall air leakage include spread of fire, indoor air quality, transfer of tobacco smoke between dwellings, and heat loss through the party to attic detail. Data collected on buildings constructed between 1890 and 1920 (Century buildings) has been compared to the data collected on buildings constructed between 2012 to 2017 (new buildings). Air leakage has been collected on twenty-six of Century semi-detached homes with solid masonry construction and twenty-one new semi-detached/row homes of lightweight wood frame construction. Each unit was tested independently and simultaneously, or “guarded”, with the adjacent unit, to pressure neutralize allowing for quantification of envelope and party wall air leakage. Party wall leakage was found to be similar to leakage through the exterior walls. The leakage accounted for 22% of the total infiltration in Century old buildings and 38% in Modern dwellings.

Quantifying air leakage through party walls in Toronto semidetached and row-home dwellings

This study contributes to the development of quantifying and understanding building air tightness as it relates to Toronto semi-detached and row homes, particularly party walls. While infiltration characteristics of single family detached homes have been widely developed and understood, the isolation of semi-detached and row home single family dwelling units is relatively unexplored. When quantifying air leakage in a building attached to an adjacent dwelling unit, air is drawn through the exterior envelope as well as the party wall (i.e. shared common wall). The purpose of the proposed testing method, guarded blower door testing, is to isolate air leakage through the party wall from the envelope. Currently the party wall is considered a fire-rated assembly but is not part of the air barrier system. Issues associated with party wall air leakage include spread of fire, indoor air quality, transfer of tobacco smoke between dwellings, and heat loss through the party to attic detail. Data collected on buildings constructed between 1890 and 1920 (Century buildings) has been compared to the data collected on buildings constructed between 2012 to 2017 (new buildings). Air leakage has been collected on twenty-six of Century semi-detached homes with solid masonry construction and twenty-one new semi-detached/row homes of lightweight wood frame construction. Each unit was tested independently and simultaneously, or “guarded”, with the adjacent unit, to pressure neutralize allowing for quantification of envelope and party wall air leakage. Party wall leakage was found to be similar to leakage through the exterior walls. The leakage accounted for 22% of the total infiltration in Century old buildings and 38% in Modern dwellings.

Crosstalk Reduction on Delay Line with Rectangular-Patches (RPs) Design

In this paper, a novel helix delay line with RPs structures is proposed to investigate the performance of crosstalk reduction. In the past, conventional delay lines consist of equal-length parallel unit lines which are closely packed to minimize the fabricated cost and routing area. All spacing between the adjacent parallel unit lines of delay lines should be smaller. When the operating signal frequency ups to the GHz level, the electromagnetic noise has become a dominant issue coupling from adjacent lines. It is called as a crosstalk source. The crosstalk may affect system-level timing. Besides, it causes error switching of logic gates that will reduce the signal quality. The feature of proposed helix delay line is that the far-end crosstalk (FEXT) is a dominated noise that accumulates at the receiving end. RPs structures are added and aligned at the center of the two parallel adjacent unit lines of the proposed helix delay line, which are used to reduce the difference between inductive and capacitive coupling coefficient ratios, and to reduce FEXT that maintains the signal integrity (SI) quality on receiving end.

Discretization of the parking problem

The present work consider a natural discretization of R´enyi’s so-called “parking problem”. Let l, n, i be integers satisfying l ≥ 2, n ≥ 0 and 0 ≤ i ≤ n − l. We place an open interval (i, i + l) in the segment [0, n] with i being a random variable taking values 0, 1, 2, . . . , n − l with equal probability for all n ≥ l. If n < l we say that the interval does not fit. After placing the first interval two free segments [0, i] and [i + l, n] are formed and independently filled with the intervals of length l according to the same rule, etc. At the end of the filling process the distance between any two adjacent unit intervals is at most l−1. Let ξn,l denote the cumulative length of the intervals placed. The asymptotics behavior of expectations of the aforementioned random sequence have already been studied. This contribution has an aim to continue this investigation and establish the behavior of variances of the same sequence.

1228. Risk Factors for Contamination with Carbapenemase-Producing Enterobacteriales (CPE) in Exposed Hospital Drains in Ontario, Canada

Background Hospital drains may be a source of CPE in patients. We determined prevalence of and risk factors for CPE contamination of hospital drains exposed to patients with CPE colonization/infection. Methods We cultured hand hygiene and patient use sink as well as tub/shower drains exposed to 310 inpatients colonized/infected with CPE in 10 Ontario hospitals. A multi-level logistic regression model was fitted to determine whether type of drain/room/unit was associated with CPE drain contamination. Drain and room occupant CPE isolates underwent Illumina whole-genome and MinION sequencing. Single nucleotide variant (SNV) phlogenomic analyses and plasmid characterization were performed. Results 53/ Of the 1,209 drains, 53 (4%) at 7 (70%) hospitals yielded CPE. Patient room shower drains were significantly more likely to yield CPE than hand hygiene sink (OR 3.35, 95% CI 1.61–6.97) and patient use sink (OR 10.89, 95% CI 3.62–32.80) drains. Hand hygiene sink drains were significantly more likely to yield CPE than patient use sink drains (OR 3.26, 95% CI 1.05–10.13). 8 (15%) drain isolates matched the room occupant CPE gene/species; 24 (44%) matched the gene but not species, and 23 (42%) matched neither gene nor species. Among 13 drain/11 room occupant pairs with molecular comparisons to date, only 1/13 (8%) drain isolates matched the respective room occupant carbapenemase allele and replicon harboring the carbapenemase gene (IncN replicon harboring blaKPC-3). In addition, one drain isolate had a plasmid highly related to plasmids of 2 isolates from a patient occupying a room in an adjacent unit (IncN3 replicons harboring blaKPC-2). At another hospital, all 6 drain isolates were located on one unit and had an IncHI2A/HI2/TrfA replicon harboring blaNDM-1; 5 of these were E. cloacae ST66, with 0–3 SNV differences observed between isolates. Conclusion Different drain types have different risks of CPE contamination. In our setting, most drain contamination was not caused by recognized room occupants. Further investigation is needed to understand the sources of hospital drain CPE contamination. Disclosures All authors: No reported disclosures.

Investigation on the Loading Characteristics in Proof Units

Blast-proof units are used in explosive production applications to isolate the adjacent unit from damaging shockwave effects in the event of an accidental explosion. The damage is mainly caused by the transmission wave through the wall and the diffraction wave over the upper edge. Investigation on the blast flow field in blast-proof units subjected to internal blast loading is studied by numerical simulation in the current paper. The influence of the height of the proof unit is analyzed and on the cap situation is studied. The result shows that increasing the height of blast-proof units may not have a positive effect on reducing the diffraction wave, because it may enhance the reflection wave, which might have a greater effect than the diffraction wave. We can reduce the shock wave in the next unit by adding a cap, which is very effective. The study may contribute to further understanding on the experiment results and the design of blast-proof units.

Machine Slideway Wear to the Precision of the Whole Machine Impact

This paper studies the influence of machine slideway precision on the overall accuracy of machine tools, and puts forward the root causes of the decline in accuracy of machine tool guide is rail wear, the decline of rail accuracy will impact on the adjacent unit cell, thus decline the accuracy of the machined parts; Finally takes floor-type milling & boring machine as research object, bases on geometric error models of the theory of multi-body system to describe the spindle box rail wear trends and establish relationship between the spindle box rail wear and the machine precision.

The Pragmatics of "Unruly" Dative Absolutes in Early Slavic

This chapter examines some uses of the dative absolute in Old Church Slavonic and in early recensional Slavonic texts that depart from notions of how Indo-European absolute constructions should behave, either because they have subjects coreferential with the (putative) main-clause subjects or because they function as if they were main clauses in their own right. Such "noncanonical" absolutes have generally been written off as mechanistic translations or as mistakes by scribes who did not understand the proper uses of the construction. In reality, the problem is not with literalistic translators or incompetent scribes but with the definition of the construction itself; it is quite possible to redefine the Early Slavic dative absolute in a way that accounts for the supposedly deviant cases. While the absolute is generally dependent semantically on an adjacent unit of discourse, it should not always be regarded as subordinated syntactically. There are good grounds for viewing some absolutes not as dependent clauses but as independent sentences whose collateral character is an issue not of syntax but of the pragmatics of discourse.