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62.
Li Li Xiaopeng Fan Kecheng Wu Zhuanglei Zou Yongyan Zhou Dianhai Zhang Ziyan Ren Yanli Zhang 《声与振动》2019,53(6):251-262
In the current paper, which deals with the noise pollution excited by
distribution transformers in the living area, a comprehensive treatment scheme
is put forward for the purpose of reducing the sound pressure level emitting into
the environment. In accordance with the associated test standard, the sound pressure levels of distribution transformer and surrounding environment are not only
tested but analyzed as well. The measurements were carried out with the frequency analysis of the 1/3 octave resolution, with the center frequencies at
125 Hz, 250 Hz, 400 Hz, and 500 Hz. As illustrated, on the basis of the measurement results, the frequency of noise at 500 Hz of distribution transformer causes
the major noise pollution in the surrounding environment. This measurement
result is in line with the noise frequency characteristics of distribution transformer.
There are two transmission routes of noise: i) the noise excited by distribution
transformer transmits by means of the wall of distribution room, and ii) part of
noise spreads through the ground of distribution room. Accordingly, acoustic
shield and vibration isolation device are applied for the reduction of the low frequency noise emitted through the above two paths. Aimed at applying the appropriate acoustic material and vibration mounting, the evaluation of the noise
reduction and vibration absorption is carried out in accordance with the sound
and vibration insulation theory. Following the noise treatment, the transformer
and environment noise are measured again. The corresponding findings shed light
on the fact that the sound level satisfied the requirement of limits of the ordinance.
The proposed noise treatment scheme can be applied to the existing power distribution facilities for controlling the sound levels that reach a point where it is comparatively more unobjectionable. 相似文献
63.
The nonsymmetric semidefinite least squares problem (NSDLS) is to find a nonsymmetric semidefinite matrix which is closest
to a given matrix in Frobenius norm. It is an extension of the semidefinite least squares problem (SDLS) and has important
application in the area of robotics and automation. In this note, by developing the minimal representation of the underlying
cone with the linear constraints, we obtain a regularized strong duality with low-dimensional projection for NSDLS. Further,
we study the generalized differential properties and nonsingularity of the first order optimality system about the dual problem.
These theoretical results demonstrate that we can solve NSDLS as good as the current Lagrangian dual approaches to SDLS. 相似文献
64.
65.
Ziyan Zhang Prof. Vladimir Gevorgyan 《Angewandte Chemie (International ed. in English)》2023,62(47):e202311848
Palladium hydrides are traditionally employed in hydrofunctionalization (i.e. monofunctionalization) of conjugated dienes and enynes, owning to its facile protic hydropalladation of electron-rich (or neutral) unsaturated bonds. Herein, we report a mild PdH-catalyzed difunctionalization of conjugated dienes and enynes. This protocol is enabled by the chemoselectivity switch of the initial hydropalladation step achieved by visible light enhancement of hydricity of PdH species. This method allows for cascade annulation of dienes and enynes with various easily available and abundant substrates, such as acrylic acids, acrylic amides, and Baylis–Hillman adducts, toward a wide range of alkenyl or alkynyl lactones, lactams, and tetrahydrofurans. This protocol also provides an easy access to complex spiro-fused tricyclic frameworks. 相似文献
66.
Jeffrey S. Moore Jinshan Zhang Ziyan Wu Dhandapani Venkataraman Stephen Lee 《Macromolecular Symposia》1994,77(1):295-301
This research aims to develop schemes for the programmed assembly of molecular materials. The underlying premise guiding this work is that structural information stored in the molecular constituents dictates their condensed phase organization (i.e. through the sum of all non-covalent interactions). The challenge then is to design molecular building blocks that encode this information in a decipherable manner. Our approach has relied on the use of organic nanoarchitectures, which we believe will serve as “modular units” for programmed assembly. Large molecules of well defined constitution and geometry offer the advantage that a high level of information can be incorporated into a single unit. The design and synthesis of nanoscale macrocyclics and macrobicyclics for this purpose has been achieved. Studies on the solution aggregation of the macrocyclics have provided a unique opportunity to glimpse some of the interactions which may influence solid state ordering. These building blocks are being used for the rational design of novel materials such as porous organic crystals and tubular mesophases. 相似文献