Wave attenuation and focusing performance of parallel twin parabolic arc floating breakwaters

The hybrid system consisting of floating breakwater and point absorber wave energy converters provides a promising solution for shoreline protection and wave power generation. In the hybrid system, the breakwater plays an important role in protecting the sheltered area on the lee side and focusing high waves for better energy harvesting on the weather side. To improve the wave attenuation and focusing performance, a twin-breakwater consisting of a pair of parallel parabolic pontoons is proposed. Based on the potential flow theory of linear waves, the influences of gap width and connection method applied between the two pontoons are studied in the frequency domain, with an emphasis on the so-called critical mode around which both wave attenuation and focusing could be improved. Results show that the rigidly connected twin-breakwater is superior to the unconnected twin-breakwater with the same configuration in both wave attenuation and focusing. A second critical mode with lower frequency is also found under particular gap width, providing a potential for the defense of long waves. An optimal attenuation could be obtained by applying a proper gap width

Harmonic Analyses of Hydrodynamic Characteristics for Gap Resonance Between Fixed Box and Vertical Wall

Two marine structures arranged side by side with a narrow gap may suffer from violent free-surface resonance, which would cause green water on deck, dramatically raise hydrodynamic loads on structures and seriously threaten the operation safety. The CFD-based open-sourced software, OpenFOAM®, is employed to simulate the two-dimensional fluid resonance inside a narrow gap between a fixed box and a vertical wall induced by regular waves with different wave heights. The topographies with various plane slopes are placed in front of the wall. The focus of this article is on the influences of the incident wave height and the topographic slope on the nonlinear characteristics of various hydrodynamic parameters (including the wave height in the gap, the vertical wave force, and the horizontal wave force on the box) during gap resonance. The ratios of their high-order to the corresponding 1st-order components under different sets of the incident wave height and the topographic slope are analyzed. It is found that the relative importance of all the high-order components increases gradually with the incident wave height for all the three parameters. The topographic influence on them closely depends on the type of the parameters and the incident wave height. In addition, the occurrence of the 2nd-order gap resonance phenomenon can cause the 2nd-order wave height and horizontal force to be significantly larger than the corresponding 1st-order components.</p

新上市公司會計師聲譽與盈餘管理關係之研究

本研究旨在探討新上市公司會計師事務所聲譽與承銷價格、上市價差及盈餘管理間之關係。上市價差或上市初期超額報酬率在台灣為一既存之事實，通常新股上市後有「蜜月期」之現象，蜜月期之形成乃因上市承銷價格的訂定與投資人的共同想法不一致所致，為何會產生蜜月期和上市價差，其理論及形成原因尚有待國內深入研究。美國有一支研究係在探討會計師事務所聲譽資產與上市價差之關係，本研究爰用該研究之理論以檢視會計師事務所聲譽與上市價差之關係。其次，上市承銷價格的訂定，其主要變數皆與會計資訊有關，因此新上市公司上市前具有動機透過應計項目之管理以操縱財務報表上的數字，俾增高其承銷價格，提高原發行者之財富。一般而言，會計師事務所之規模愈大，愈願意維持其聲譽資產，簽證功能之發揮較有效，審計品質愈好，因此會計師事務所聲譽較高者，其簽證公司之上市承銷價格將較高，而減少上市價差及超額報酬率。另一方面，會計師所執行之審計工作，對會計資訊而言，具有監督制衡的功能，故會計師事務所聲譽較高者，其簽證公司於上市前採行應計項目之管理以操縱損益俾提高承銷價格之程度將較是以本研究設立三項研究假設(一)聲譽較高會計師事者所簽證的公司，其承銷價格比聲譽較低會計師事務所簽證的公司為高: (二)聲譽較高會計師事務所簽證的公司，其超額報酬率比聲譽較低會計師事務所簽證的公司為低(三)聲譽較高會計師事務所簽證的公司，其採行增加盈餘之應計項目變動的程度比聲譽較低會計師事務所簽證的公司為低。實證研究結果顯示(一)聲譽較高與聲譽較低會計師事務所簽證的公司之間，承銷價格無顯著差異(二)聲譽較高與聲譽較低會計師事務所簽證的公司之間，超額報酬率無顯著差異(三)聲譽較高與聲譽較低會計師事務所簽證的公司之間，應計項目之管理亦無顯著差異。亦即無法自本研究的理論於國內得到顯著結果之結論

On the hydrodynamic performance of a vertical pile-restrained WEC-type floating breakwater

This paper presents a numerical study on the hydrodynamic performance of a vertical pile-restrained wave energy converter type floating breakwater. The aims are to further understand the characteristics of such integrated system in terms of both wave energy extraction and wave attenuation, and to provide guidance for optimising the shape of the floating breakwater for more energy absorption and less wave transmission at the same time. The numerical model solves the incompressible Navier-Stokes equations for free-surface flows using the particle-in-cell method and incorporates a Cartesian cut cell based strong coupling algorithm for fluid-structure interaction. The numerical model is first validated against an existing experiment, consisting of a rectangular box as the floating breakwater and a power take-off system installed above the breakwater, for the computation of the capture width ratio and wave transmission coefficients. Following that, an optimisation study based on the numerical model is conducted focusing on modifying the shape of the floating breakwater used in the experiment. The results indicate that by changing only the seaward side straight corner of the rectangular box to a small curve corner, the integrated system achieves significantly more wave energy extraction at the cost of only a slight increase in wave transmission

Research status and application of phase change humidity storage composite materials

Currently, the utilization efficiency of energy still remains at low level, although the depletion of fossil fuel is approaching. Therefore, while vigorously developing new energy, it is of great significance to develop new materials with "passive self-adjustment ability". Phase change humidity storage composite materials is a kind of composite material with phase change and temperature controlling property and humidity storage and humidity controlling property, which are very promising in the field of building wall material. In this paper, the action principle of phase change humidity storage composite materials, packaging technique of phase change material, classification and selection of humidity-controlling material were introduced briefly in the first section. And then the application of phase change humidity storage composite materials in building wall material were reviewed and analyzed in detail. In the third part, characteristics of double-shell phase change micro-nano capsules, polyfatty acid/SiO2 phase change and humidity storage composite materials and decanoic acid-palmitic acid @ Ce-La/TiO2 composites were pointed out. Main problems and research status of phase change humidity storage composite materials were pointed. Finally, it was pointed out the optimized durability of phase change humidity storage composite materials, developing multi-functional phase change humidity storage composite materials are the main development directions of phase change humidity storage composite materials