双乳山水库左岸帷幕灌浆试验成果分析

帷幕灌浆试验是帷幕灌浆施工的重要依据,文中结合双乳山左岸帷幕灌浆试验,介绍了灌浆试验的施工方法,通过10个灌浆孔的透水率、单位注入量和1个检查孔的压水试验对灌浆试验结果进行了分析.     

Integral controller design based on disturbance cancellation: Partial LTR approach for non-minimum phase plants

For non-minimum phase plants, the loop transfer recovery (LTR) design of integral controllers based on the disturbance cancellation is considered. Since the design requires an unstabilizable extended plant, the standard LTR method cannot be applied. A new partial LTR method is proposed to overcome the difficulty. The target of the proposed design is a fictitious controller including a disturbance estimator based on the measurement of the minimum phase state. It is shown that the Riccati equation including the gain matrix of the disturbance estimator in the target can be used to recover the target feedback property in the output feedback controller. A simple design example is presented to show the effectiveness of the proposed method.     

Corrosion Behavior of Epoxy-Coated Rebar with Pinhole Defect in Seawater Concrete

Experiments were carried out to investigate the corrosion behavior of epoxy-coated rebar(ECR) with pinhole defect(diameter in hundreds of microns) immersed in the uncarbonated/carbonated simulated pore solution(SPS) of seawater concrete. Corrosion behavior was analyzed by electrochemical impedance spectroscopy. The composition and morphology of corrosion products were characterized by X-ray diffraction, energy-dispersive spectrometry and scanning electron microscopy. Meanwhile, oxide film produced by preheating before spray coating was investigated by X-ray photoelectron spectroscopy and Mott–Schottky technology. Results indicated that corrosion behavior of ECR with pinhole defect exhibited three stages when immersed in the uncarbonated/carbonated SPS. In the initial stage, steel in defect was passivated when exposed in the uncarbonated SPS and corroded when exposed in the carbonated SPS, due to competitive adsorption between chloride and hydroxyl ions. In the second stage, the oxide film under coating reconstituted(the thickness and defects density decreasing) in the uncarbonated SPS, which was caused by the synergy between high hydroxide and chloride activity, while in the carbonated SPS, crevice corrosion happened under the coating around pinhole,because of the different oxygen concentrations cell at the coating/steel interface. In the third stage, localized corrosion occurred under the coating around the pinhole in the uncarbonated SPS, which was probably induced by ion diffusion at the nano-scale coating/steel interface. The corrosion products adjacent to the defects were re-oxidized from FeCl_2·4H_2O and Fe_2(OH)_3Cl to Fe_2O_3·H_2O, and the corrosion area was expanded outward in the carbonated SPS.     

转fps基因烟草纯合系的获得及其特性分析

携带有外源法呢基焦磷酸合酶（fps）基因和卡那霉素抗性基因（Npt—Ⅱ）的烟草种子在含卡那霉素（300mg／L）的培养基上能够正常地萌发和生长，对照种子虽能萌发，但幼苗形态与对照有着明显的差异。转fps基因植株所具有的卡那霉素抗性和与其抗病性之间密切相关，由此建立了一种鉴定转基因烟草后代纯合度的简易方法，得到4个fps转基因烟草纯合系（K-4、K-6、K-17、K-35），并对其农艺性状、田间抗性、化学成份和品质进行了评估，其中K-4转基因品系的综合性状较原有品种有所提高。     

Pyrolytic transformation of liquid precursors to shaped bulk ceramics

The pyrolysis behavior of polysiloxane liquids in transformation to shaped ceramic bodies has been studied through liquid casting, crosslinking, and pyrolysis. The control of crosslinking temperatures with a second heating allows the self-demolding of crosslinked polysiloxanes from casting molds to form shaped polysiloxane bodies with good bonding quality. Pyrolysis of the polysiloxane bodies at various temperatures yields dense shaped SiOC materials changing in appearances from colorless transparent to dark brown to dark, corresponding to different degrees of pyrolysis. This indicates the homogeneous transformation of the polysiloxane network during organic-to-inorganic transformation. The bulk pyrolysis characteristics including bonding quality, microstructures, densities and shrinkage are studied in association with the effect of pyrolysis temperatures and precursor chemistries. The structural evolution of the polymeric network is analyzed by ²⁹Si NMR, ¹³C NMR and FTIR spectroscopy. Through controlling the crosslinking and optimizing precursors, we have achieved net-shaped bulk SiOC material with a relatively large dimension.     

Zeolite 4A-Incorporated Polymeric Membranes for Pervaporation Separation of Methanol–Methyl Acetate Mixtures

Zeolite 4A-incorporated poly(vinyl alcohol)/poly(vinyl pyrrolidone) (PVA/PVP) membranes were prepared for pervaporation separation of methanol/methyl acetate mixtures. These membranes were characterized by Infrared spectroscopy, X-ray diffraction and Scanning electron microscopy. The results showed that crystallinity of the membrane decreased with the increase of zeolite 4A content. The effect of zeolite loading, feed composition and temperature on the membrane separation performance were discussed in detail. With the increase of zeolite 4A content, permeation flux increased continuously, but separation factor first increased and then decreased. The addition of 2.5 wt% zeolite 4A in the polymer membrane improved the separation factor from 12.9 (for PVA/PVP membrane) to the maximum value of 34.4 for 20 wt% methanol in feed at 45 °C. The separation factor decreased with increasing feed temperature, however, the flux increased with increasing feed temperature. Zeolite 4A-incorporated PVA/PVP membranes provide an effective method for the separation of methanol/methyl acetate azeotropic mixtures.     

基于波动理论的管结构损伤检测方法

针对在役海洋平台的无损检测大都采用超声等主动检测手段,这会受到工况的影响。而声发射等被动检测手段避免了这一问题,实现了对现役海洋平台的在线监测。综述了基于瞬态波、应力波、导波和模态声发射等波动理论进行的管结构声发射检测研究成果。对基于波动理论进行复杂结构检测的前景做了展望。     

多次采样技术在红外推扫系统中的分析与应用

介绍了影响红外推扫系统噪声等效温差(NETD)的参数,证明了多次采样技术可以显著降低系统NETD,提出了在驻留时间一定的情况下选择积分时间和采样次数的原则.通过短波红外相机实验表明多次采样技术可以显著提高图像质量.     

Experimental research on a novel cold storage defrost method based on air bypass circulation and electric heater

Frost accumulation on evaporator decreased cooling capacity and COP (coefficient of performance) of cold storage refrigeration system, so timely and effective defrost was significant to cold storage energy-saving operation. The EHD (electric heat defrosting) method was commonly used in cold storages, however, defrost efficiency of the traditional EHD is rather low, and defrost operation usually caused an unfavorable storage temperature fluctuation, which is harmful to storage quality and shelf-life of stored products. In order to solve the problems existing in the traditional EHD method, a novel defrost method with air bypass circulation and electric heater was proposed for the first time in this paper. Five practical cases of this new method with different defrost heaters and air circulation modes were comparatively studied. The results showed that the case with heater embedded in evaporator fins and air circulating through bypass channel was the optimum implementation way of the new method. Compared with the traditional EHD method, the defrost time of this new method was shortened by 62.1%, defrost energy consumption was reduced by 61.0%, and storage temperature fluctuation was decreased by 70.1%. In addition, the defrost efficiency was up to 77.6%, which was 2.93 times of the traditional EHD method.     

Synthesis of thin alpha alumina platelets with a large aspect ratio

Since α-Al₂O₃ platelets with small thickness and large aspect ratio are needed in various applications, it is of great importance to control their morphology. In the present work, we successfully fabricated α-Al₂O₃ platelets with small average thickness below 100 nm and large average aspect ratio above 100 by molten-salt method, using Al₂(SO₄)₃ as the raw material, eutectic mixtures of Na₂SO₄ and K₂SO₄ as the molten salt as well as TiO₂ and SiO₂ as the co-dopants. The effects of calcination temperature, seeds amount and seeds morphology on the final morphology of α-Al₂O₃ platelets were investigated. The growth mechanism of the α-Al₂O₃ platelets in molten salt was also discussed. A new growth mechanism of α-Al₂O₃ platelets in molten salt has been proposed, which is different from previous mechanism but can explain the two different phenomena caused by seeds with different sizes and quantity.