如何设置定时关机

正当你需要休息或者外出时,这时电脑可能还需要继续运行,比如备份文件、下载文件之类的可以由软件自主完成的任务等等,这时候你就需要通过设置定时关机来管理你的电脑。定时关机除了可以使用系统自带的命令来实现之外,还可以用一些软件来实现,以下一一为大家讲述。     

Solution copolymerization of methyl methacrylate and alkyl methacrylates in a continuous stirred tank reactor(CSTR)

Continuous solution copolymerization of methyl methacrylate with ethyl methacrylate or n-butyl methacrylate was carried out in a continuous stirred tank reactor. Solvent and initiator used were toluene and benzoyl peroxide, respectively. Reaction volume was 1.2 litters, residence time 3 hours and polymerization temperature 80°C. The copolymerization conversions were analyzed by UV spectrophotometry and confirmed by measuring the solid weights of copolymers obtained after evaporating solvent. The copolymerization of methyl methacrylate and alkyl methacrylates followed the second order kinetics. The simulated conversions and copolymerization rates were compared with the experimental results. The average time to reach dynamic steady-state was three and half times of the residence time.     

Single-mode, optical-fiber sensors and tunable wavelength filters based on the resonant excitation of metal-clad modes

The resonant excitation of metal-clad modes, including fundamental and higher-order modes, in a multilayer structure deposited on the polished cladding of a single-mode optical fiber is theoretically analyzed and experimentally demonstrated. The excitation of metal-clad modes is shown as a resonant power transfer from the fiber to the metal-clad mode that takes place for an external refractive-index value such that the effective index of the metal-clad mode reaches the cladding level. The observed attenuation on the TM polarization provides a suitable transducing mechanism for refractive-index sensor devices as well as the principle for developing tunable wavelength-polarized filters with a wide range of optical performance characteristics.     

Effects of oxygen pressure on the growth of pulsed laser deposited ZnO films on Si(0 0 1)

ZnO thin films were prepared on Si(0 0 1) substrates using a pulsed laser deposition (PLD) technique and then their growth and properties were investigated particularly as a function of ambient O₂ pressure during film growth. It was found that the microstructure, crystallinity, orientation and optical properties of the films grown are strongly dependent on the O₂ pressures used. Completely c-axis oriented ZnO films are grown in a low O₂ pressure regime (5×10⁻⁴-5×10⁻² Torr), whereas a randomly oriented film with a much lower crystallinity and a rougher grained-surface is grown at an O₂ pressure of 5×10⁻¹ Torr. This deterioration in film quality may be associated with the kinetics of atomic arrangements during deposition. Our results suggest that ambient O₂ pressure is an important processing parameter and should be optimized in a narrow regime in order to grow a ZnO film of good properties in PLD process.     

地区电网应对各种事故的策略

本文研究各种电网事故发生的原因,提出综合性的应对策略,从地区电网的角度加强继电保护和安全稳定自动装置的优化配置;采用先进可靠的调度自动化系统对电网进行密切监控;保证正常情况下系统的安全稳定运行和事故时能够及时正确地切除故障,防止事故扩大。     

Five New Oxylipins from Chaenomeles sinensis

In the course of our continuing search for bioactive constituents of Korean medicinal plants, we isolated five new oxylipins, chaenomic acid A–E ( 1 – 5 ), and six known ones ( 6 – 11 ) from the twigs of Chaenomeles sinensis. The structures of the new compounds ( 1 – 5 ) were determined by spectroscopic methods, including 1D and 2D NMR (¹H and ¹³C NMR, ¹H–¹H COSY, HMQC, HMBC, and NOESY), olefin cross‐metathesis, and LC/MS analysis. The known compounds ( 6 – 11 ) were identified by comparison of their spectroscopic data and specific optical rotation with the reported data. The isolated compounds ( 1 – 11 ) were tested for their inhibitory effects on nitric oxide production in lipopolysaccharide‐activated murine microglial cells and for their cytotoxic activities against four human cancer cell lines (A549, SK‐OV‐3, A498, and HCT‐15).     

Quantitative assessment of temperature effect on cone resistance

The measurements of a strain gauge type cone penetrometer are influenced by the temperature change during penetration. A real-time temperature compensation technique using a fiber Bragg grating (FBG) sensor is suggested to correct the effect of temperature on cone tip resistance. A 7-mm micro cone penetrometer equipped with FBG sensors and electrical strain gauges was developed to evaluate the suggested technique. Design concepts include the cone configuration, sensor installation and the temperature compensation process. It is shown that the measured cone tip resistance is significantly affected by the temperature; the error increasing with increasing temperature change. The cone tip resistance measured by the FBG sensor is effectively corrected by the real-time compensation method. The q _c profile of the strain gauge indirectly corrected by the re-penetration test is quite similar to the real-time compensated profile. It is concluded that the proposed real-time temperature compensation using the FBG sensor is an effective technique to obtain reliable cone tip resistance profiles.     

Structural and Piezoelectric Properties of (Na1−xKx)NbO3 Platelets and Their Application for Piezoelectric Nanogenerator

(Na_1?xK_x)NbO₃ (NKN) platelets synthesized at 600°C for 12 h have an Amm2 orthorhombic structure. However, the structure of NKN platelets synthesized at 500°C is a mixture of R3m rhombohedral and Amm2 orthorhombic structures. The formation of a rhombohedral structure is attributed to the presence of OH^? and H₂O defects in the NKN platelets. The piezoelectric strain constant (d₃₃) of NKN platelets synthesized at 600°C for 12 h is 100 pmV^?1, whereas that of NKN platelets synthesized at 500°C is lesser (50 pmV^?1) due to the presence of these defects. Piezoelectric nanogenerators (PNGs) are fabricated using composites consisting of NKN platelets and polydimethylsiloxane. A large output voltage of 25 V and output current of 2.7 μA were obtained for the PNG with NKN platelets synthesized at 600°C for 6 h. This PNG shows a high output electrical energy of 3.0 μW at an external load of 5.1 MΩ.     

Cyanidin-3-glucoside ameliorates CCl4-induced liver injury in mice

The protective effect of cyanidin-3-glucoside (C3G) against carbon tetrachloride (CCl₄)-induced liver injury in mice was investigated. Administration of C3G attenuated the levels of serum aspartate aminotransferase, alanine aminotransferase, and liver lipid peroxidation in CCl₄-treated mice. Histopathological examination of mouse livers showed that C3G reduced the incidence of liver lesions induced by CCl₄. Moreover, C3G prevented DNA damage and decreased the protein levels of γ-H2AX in CCl₄-treated mouse livers. C3G also increased the activity of the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase, which were decreased due to CCl₄ administration in CCl₄-treated mouse livers. C3G inhibited the expression levels of IL-6 and iNOS in CCl₄-treated mice. C3G apparently protects the liver from CCl₄-induced hepatic damage through antioxidant and anti-inflammatory mechanisms.