古代的救荒政策

我国是世界上自然灾害较多的国家。据邓拓《中国救荒史》中的统计,从公元前1766年到公元1937年的3,703年中,共发生自然灾害5,258次。古代抗御灾害的能力是很低的,一遇荒年,就会哀鸿遍野,民不聊生。封建统治者考虑到国家的安危,不得不进行救济,而救荒的根本办法是储粮备荒。《周礼·地官·司徒》记载,周代设有仓人,其任务是:“

Double Symplectic Eigenfunction Expansion Method of Free Vibration of Rectangular Thin Plates

The free vibration problem of rectangular thin plates is rewritten as a new upper triangular matrix differential system. For the associated operator matrix, we find that the two diagonal block operators are Hamiltonian. Moreover, the existence and completeness of normed symplectic orthogonal eigenfunction systems of these two block operators are demonstrated. Based on the completeness, the general solution of the free vibration of rectangular thin plates is given by double symplectie eigenfunction expansion method.

The structure,tensile properties and water resistance of hydrolyzed feather keratin-based bioplastics

Feather, as a by-product of the poultry industry, has long been treated as a solid waste, which causes environ- mental and economic problems. In this work, the hydrolyzed feather keratin （HFK） was extracted from the chicken feather using a cost-effective method of alkali-extraction and acid-precipitation by applying urea and sodium sulfide. The aim was development and characterization of the eco-friendly films based on the HFK with variable glycerol contents by a thermoplastic process. The thermal analysis showed that high temperature and high pres- sure improved the compatibility between the glycerol and the HFI（ molecules. Also it was shown that the addi- tion of water is necessary in the hot-pressing process of films, The FT-IR analysis indicated that the formation of the new hydrogen bonds between HFK and glycerol. By increasing the glycerol content, the film tensile strength （orb ） decreases from 10,5 MPa to 5.7 MPa and the solubility increases from 15.3% to 20.9%, while the elongation at break （εb） achieves the maximum value of 63,8% for the film with 35% glycerol. The swelling was just below 16.9% at 25 ℃ for 24 h, suggesting a good stability of the films in water. The water vapor permeability （WVP） varied between 3.02 x 10 ^10g. m 2. s-1 . pa-1 and 4.11 x 10-10g · m-2 · s-1 · Pa-1 for the films with 20%and 40% glycerol, respectively. The HFK film was uniform, translucent and tough, which could be used in packaging and agricultural field.

Preparation and Characterization of Nano-Particles PZT Ferroelectric Thin Films by RF-Magnetron Sputtering

Pt/Ti bottom electrodes were fabricated on SiO2/Si substrates by magnetron dual-facingtarget sputtering system. Lead zirconate titanate（PZT） thin films were deposited on Pt/Ti/SiO2/Si substrates by radio frequency （RF） magnetron sputtering system. The thickness of PZT thin films which were deposited for 5 h was about 800 nm. XRD spectra show that PZT thin films deposited in Ar ambience and rapid-thermal-annealed for 20 min at 700 ℃ have good crystallization behavior and perovskite structure. AFM micrographs show that mean diameter of crystallites is 70 nm and surface structures of PZT thin films are uniform and dense. Raw mean, root mean square roughness and mean roughness of PZT thin films are 34..357 rim, 2. 479 nm and 1. 954 nm respectively. As test frequency is 1 kHz, dielectric constant of PZT thin films is 327.5. Electric hysteresis loop shows that coercive field strength, residual polarization strength and spontaneous polarization strength of PZT thin films are 50 kV/cm, 10μC/cm^2 and 13μC/cm^2 respectively.

Automatically extracting sheet-metal features from solid model

With the development of modern industry, sheet-metal parts in mass production have been widely applied in mechanical, communication, electronics, and light industries in recent decades; but the advances in sheet-metal part design and manufacturing remain too slow compared with the increasing importance of sheet-metal parts in modern industry. This paper proposes a method for automatically extracting features from an arbitrary solid model of sheet-metal parts; whose characteristics are used for classification and graph-based representation of the sheet-metal features to extract the features embodied in a sheet-metal part. The extracting feature process can be divided for valid checking of the model geometry, feature matching, and feature relationship. Since the extracted features include abundant geometry and engineering information, they will be effective for downstream application such as feature rebuilding and stamping process planning.

Comparative Leaves Anatomical Studies of Bouea, Mangifera and Spondias （Anacardiaceae） in Malaysia

Leaves anatomy of two species of Bouea, 11 species of Mangifera and two species of Spondias were studied in order to see the differences in stomata type, petiole, midrib and lamina anatomy and leaf venation. This study aims to use anatomical characters for species and genus identification. Common characters observed were the absence of trichomes, closed vascular bundles, uniseriate epidermal layers, resin canal in parenchyma cells, anticline wall pattems and druses crystals in leaf lamina transverse sections. All species displayed closed vascular bundles except Mangiferapajang which showed a combination of medullary vascular bundles. Uniseriate epidermal layer was observed in all species. All the species showed straight-wavy anticlinal walls. Druses crystals were found in the parenchyma cells of all the species. Four types of stomata were observed namely anomocytic, anisocytic, staurocytic and diacytic. Anomocytic, anisocytic and staurocytic stomata were observed in Mangifera, diacytic in Bouea and anomocytic in Spondias.

Surface characteristics and structure of oxide films containing Ca and P on Ti substrate

The oxide films were obtained in an electrolyte of calcium glycerphosphate (Ca-GP) and calcium acetate (CA) by microarc oxidation (MAO). The oxide films displayed a porous and rough structure on the film surface, and the roughness tended to increase with increasing voltage of microarc oxidation. The oxide film exhibited a uniform coating and tends to be well boned to the substrate. The thickness of oxide films depended on the final voltage at a constant concentration of electrolyte solution. Ca and P were also incorporated into the oxide film during the microarc oxidation process. It was found that the electrolyte of calcium glycerphosphate (Ca-GP) and calcium acetate (CA) was suitable for microarc oxidation to form oxide film containing Ca and P on Ti substrate. The concentration of Ca and P were 11.6 at% and 6.4 at%, respectively, when microarc oxidation was performed in the electrolyte of 0.06 M Ca-GP and 0.25 M CA at current density 50 A/m^2 and final voltage 350 V. The composition of the Ca, P and Ti changed during depth profiling. The crystalline phases were only anatase when final voltage was below 300 V and rutile was presented when voltage was up to 350 V. The microstructure, phase structure and phase composition were investigated by scanning electron microscopy (SEM), atomic force microscope (AFM), energy dispersive X-ray microanalyser (EDX), and X-ray diffraction (XRD).

Real-Time Characterization of Fibrinogen Interaction with Modified Titanium Dioxide Film by Quartz Crystal Microbalance with Dissipation

The adsorption of fibrinogen can be used as a quick indicator of surface haemocompatibility because of its prominent role in coagulation and platelet adhesion. In this work the molecular interaction between fibrinogen and a modified titanium oxide surface/platelet has been studied by quartz crystal microbalanee with dissipation （QCM-D） in situ. In order to further characterize the conformation of adsorbed fibrinogen, αC and γ-chain antibody were used to check the orientation and denaturation of fibrinogen on solid surface. QCM-D investiga- tions revealed the fibrinogen have the trend to adsorb on hydropllilic surface in a side-on orientation by positively charged αC domains, which would reduce the exposure of platelet bonding site on γ chain and enable less platelet adhesion and be activated. These obser- vations suggest that certain conformations of adsorbed fibrinogen are less platelet adhesive than others, which opens a possibility for creating a non-platelet adhesive substrates.

Minor Morphological Features in Maria Archeological Ruins Using Thin Section Analysis

Maria sites are important historical sites, backing to the Byzantine period. The sites suffer from weathering noted as honeycomb, exfoliation and discoloration with white salt efflorescence at some parts. These are diagnostic features for salt weathering as confirmed by the laboratory investigations using thin section analysis. The salt is found to be from three sources, namely, water spray, chemical alteration of the mortar＇s carbonate content into sulfate salts by acid rain, and wet deposition of air pollutants on the surface of the stones ruins. The cracks noted in the structures of this archeological building are the results of landslides in this area. Knowledge of the archeological sites material examined can be greatly enhanced by understanding the process in their formation of degradation. This paper aims to describe the use of thin sections/micromorphology in the archeological sites. Analysis data of physical sitting, geology, geomorphology, and climate have been done to determine the main nature of hazards in this sites. Dynamic processing problems are existing along Alexandria coast including beach erosion, pollution and manmade. Thin section analysis is used to determine the factor in increasing the hazard level.

Characterization and Drying of Green Mint

Mint is a medicinal and aromatic plant. It is very important for the pharmacopoeia, perfumes, confectionery and liquor industry. Some green mint leaves without rods are used as samples. Physical and mechanical properties of the sample such as the desorption isotherms, the density and volumetric withdrawal are determined. The kinetics of drying, where it follows the changes of the water content of the sample as a function of the drying time for the three temperatures 30, 40 and 50℃, is also presented and discussed.

Investigation of luminescence from SiC nano-granule films on porous glass substrate

SiC granule films were fabricated onto porous glass substrate by RF-magnetron sputtering. Photoluminescence （PL） measurements show that there are light emissions at three different wavelengths. Ultraviolet emission peaked at 360 nm originated from the band-band transmission of SiC nanoparticles with relatively small size. The 370 nm light emission was due to the luminescence of the nano-skeletons of porous glass that was formed during the etching of the glass substrate. The blue emission at about 460 nm was associated with the recombination of the excited electron and O-deficient defects appeared at the interface between SiC nanoparticles and the porous glass. Furthermore, the optimal PL performance was obtained when SiC deposited time was I h and the glass substrate was etched for 20 min in the annealing sample （450 ℃）.

Characteristics of Amorphous Silicon Nitride Films Deposited by LF-PECVD from SiH_4/N_2

Amorphous silicon nitride films were deposited by low-frequency plasma-enhanced chemical vapor deposition（LF-PECVD） using silane and nitrogen as precursors. Characteristics such as deposition rate, surface morphology, and chemical composition were measured by spectroscopic ellipsometry（SE）, atomic force mieroscope（AFM） and x-ray photoelectron spectroscopy（XPS）. It was shown that amorphous silicon nitride film could be prepared by LF-PECVD with good uniformity and even surface. The XPS result indicated that a small quantity of oxygen was involved in the sample, which was discussed in this paper.

Obtaining Thin Film of SnO2/Cu2O and Characterization by X-Ray Diffraction

Thin films of tin and copper oxide forming heterojunction are being studied for applications in photovoltaic systems. The procedure for obtaining such a film was based on the technique of spray pyrolysis with working temperature of 600 ℃. The XRD （X-ray diffraction） showed the formation of tin oxides （SnO2） and copper （Cu2O） and its structural parameters are a, b and c, 4.7534 A^°, 4.7534 A^°, 3.1998 A^° （tetragonal form） and 4.2580 A^°, 4.2580 A^°, 4.2580 A^° （cubic form）, respectively. Highseore Plus program was used for phase identification and DBWSTool2.4 program used for refinement. The grain size was estimated by Williamson-Hall.

《管子》选读

德有六兴……所谓六兴者何？曰：辟田畴,制坛宅,修树艺,劝士民,勉稼穑,修墙屋,此谓厚其生。发伏利,输墆积,修道途,便关市,慎将宿,此谓输之以财。导水潦,利陂沟,决潘渚,溃泥滞,通郁闭,慎津梁,此谓遗之以利。薄征敛,轻征赋,弛刑罚,赦罪戾,宥小过,此谓宽其政。养长老,慈幼孤,恤鳏寡,问疾病,吊祸丧,此谓匡其急。衣冻寒,食饥渴,匡贫窭,振罢露,资乏绝,此谓振其穷。

Characterization of sputtered ZnO films under different sputter-etching time of substrate

Polycrystalline ZnO films are prepared using radio frequency magnetron sputtering on glass substrates which are sputter-etched for different time. Both the size of ZnO grains and the root-mean-square (RMS) roughness decrease, as the sputter-etching time of the substrate increases. More Zn atoms are bound to O atoms in the films, and the defect concentration is decreased with increasing sputter-etching time of substrate. Meanwhile, the crystallinity and c-axis orientation are improved at longer sputter-etching time of the substrate. The Raman peaks at 99 cm-1, 438 cm-1 and 589 cm-1 are identified as E2(low), E2(high) and E1(LO) modes, respectively, and the position of E1(LO) peak blue shifts at longer sputter-etching time. The transmittances of the films, which are deposited on the substrate and etched for 10 min and 20 min, are higher in the visible region than that of the films deposited under longer sputter-etching time of 30 min. The bandgap increases from 3.23 eV to 3.27 eV with the increase of the sputter-etching time of substrate.

Investigation and characterization of an arc-shaped piezoelectric generator

A novel arc-shaped piezoelectric generator based on flexible PVDF thin film is presented and systemically studied.With a periodical external force,the generator can produce peak voltage of 45.6 V and peak power of 30.7μW.The maximum power density reaches 38.4μW/cm3with a 4 cm×2 cm×100μm device,at the optimum load resistance of 33.33 MOhm.The influence of frequency,size dimension and load resistance are investigated through experimental measurements.With this high output arc-shaped generator,capacitors can be effectively charged and three commercial LEDs have been directly lighted without any energy storage unit.

Visualization of Film Wavelike Characteristics and Measurement of Film Thickness in Spray Cooling

An experimental investigation was performed to study the heat transfer in an eight-nozzle spray cooling system with de-ionized water as the working fluid. Visualization of the liquid-solid contact area and the flow near the heated surface was made using a microscopic lens system in conjunction with an advanced high-speed camera. The film thickness and film wavelike characteristics under liquid volume flow rates ranged from 2.78×10 -6 m 3 /s to 1.39×10 -5 m 3 /s and surface temperatures between 22℃ and 78.2℃ were examined respectively. The development process of the liquid film on the heated surface was observed. The local mean film thickness, the film wavelike characteristics and the behavior of the bubbles appeared in the liquid film were captured using an image processing technique. It is discovered that there exists a climax of local mean film thickness during the starting process of spray cooling. When the liquid film reaches the dynamic stable state, the dimensionless mean film thickness decreases with the increase of the liquid volume flow rate, and increases with the increase of surface temperature generally. Besides, the volume flow rate has a more significant impact on the wavelength and amplitude of the liquid film compared to the surface temperature.

Research on structural characteristics of large-scale CdS thin films deposited by CBD under low ammonia condition

Cadmium sulfide(Cd S) buffer layers with the scale of 10 cm×10 cm are deposited by chemical bath deposition(CBD) with different temperatures and thiourea concentrations under low ammonia condition.There are obvious hexagonal phases and cubic phases in Cd S thin films under the conditions of low temperature and high thiourea concentration.The main reason is that the heterogeneous reaction is dominant for homogeneous reaction.At low temperature,Cd S thin films with good uniformity and high transmittance are deposited by adjusting the thiourea concentration,and there is almost no precipitation in reaction solution.In addition,the low temperature is desired in assembly line.The transmittance and the band gap of Cd S thin films are above 80% and about 2.4 e V,respectively.These films are suitable for the buffer layers of large-scale Cu(In,Ga)Se2(CIGS) solar cells.