明、清官式建筑石作技术(三)

第四节台基石活台基的本义包括地下部分和露明部分。地下部分通称"埋深"("埋身")。露明部分为普通台基作法的,通称为"台明"。须弥座作法的,仍称须弥座。这里所说的台基石活实际上系指地面以上的台基露明部分。一。

明清官式建筑石作技术(四)

二、须弥座式的台基须弥座式的台基多用于宫殿建筑中,有时也用于一般大式建筑。除此而外,须弥座还可用于基座类砌体,如:月台、平台、高台、祭坛、佛座乃至陈设座等等。

明清官式石作技术(七)

第七节台阶台阶俗称"阶脚"。台阶可分成踏跺和礓礤((足姜)(足察))两大类。台阶的面阔、进深尺寸及单件尺寸详见表7和表8。一、踏跺(一)踏跺种类(图28)1.垂带踏跺:两侧带垂带的踏哚。2.如意踏跺:不带垂带的踏跺。这种踏跺从三面都可以上人。3.御路踏跺:带御路石的踏跺。

GENETIC OPTIMIZATION OF HOT FILAMENT PARAMETERS IN HFCVD SYSTEM

In HFCVD system the substrate temperature is a key factor which deeply affects the quality of diamond films. Th e magnitude and the variation of the substrate temperature must be limited in a suitable range to deposit diamond films of uniform thickness over large areas. In this paper, the hot filament parameters are investigated on the basi s of GAs to realize a good substrate temperature profile. Computer simulations d emonstrate that on parameters optimized by GAs a uniform substrate temperatur e field can be formed over a relatively large circle area with R s=10 cm.

房地产业呼唤“名牌”

市场经济在运行中必然会出现“明星”企业。它们对行业的发展所产生的影响相当大,有时甚至能起到行业引导作用。而“明星”企业之所以成为“明星”就必须依靠自身的产品,要有“名牌”,没有“名牌”产品的企业很难成为业内的佼佼者,纵然由于幸运一时被推上浪尖亦将很快便消失。 市场经济不能没有竞争,有时还是相当严酷的竞争。

Dislocation of Cz-sapphire substrate for GaN growth by chemical etching method

The diameter of Czochralski (Cz) sapphire crystals is 50 mm. The sapphire substrates were lapped by using diamond powders and polished by chemical mechanical polishing(CMP) method using alkali slurry with SiO2 abrasive. After obtaining the smooth surfaces, the chemical etching experiments were processed by using fused KOH and NaOH etchants at different temperature for different times. The dislocation was observed by means of optical microscope and scanning electron microscope. The clear and stable contrast images of sample etching pits were observed. On the whole, the dislocation density is about 104?105 cm?2. Comparing the results under the conditions of different etchants, temperatures and times during the etching proceeding, it was found that the optimal condition for dislocation displaying is etching 15 min with fused KOH at 290 ℃. At the same time, the formation of the etch pits and the reducing method of dislocation density were also discussed.

Study on the propagation of interface crack of young concrete lining and rock under blasting load

In the construction of water conservancy and hydropower project,young concrete lining structure is often affected by blasting load. Young concrete has a lot of micro-fractures with random distribution,which are easier to propagate and connect under blasting load. This paper focuses on the calculation on dynamic stress intensity factors of bond interface crack of concrete-rock according to concrete age. Result shows that different incidence angles of stress wave lead to different crack propagation mechanisms. Under the normal incidence of impact load,the bonding interface crack propagation of the concrete lining is mainly caused by reflection tensile stress,which forms from the free surface. With horizontal incidence of stress wave,the bond interface crack propagation of concrete lining is affected by concrete age. With the increase of concrete age,the elasticity modulus margin between concrete and rock decreases gradually,and the crack propagation form changes from shear failure to tensile damage.

Effects of substrate and transfer on CVD-grown graphene over sapphire-induced Cu films

We differentiated the effects of Cu films deposited on single crystalline a-,r-,and c-plane sapphire substrates upon graphene films synthesized with atmospheric pressure chemical vapor deposition(CVD).The data illustrate that the realization of high-crystalline Cu film is dependent not only on the crystallinity of underlying substrate,but also on the symmetric match of crystallographic geometry between metal film and substrate.We also systematically investigated the effects of PMMA removal on the Raman ID/IG and IG/I2D values of transferred graphene.The results reveal that different PMMA removal methods do not alter the ID/IG values;instead,the residue of PMMA increases the IG/I2D values and the thermal decomposition of PMMA leads to higher IG/I2D values than the removal of PMMA with acetone.The effects of PMMA removal on variations of the Raman spectra are also discussed.

Study on growing thick AlGaN layer on c-plane sapphire substrate and free-standing GaN substrate

In this study,the thick AlGaN epilayers have been grown on the c-plane sapphire substrate and the free-standing GaN substrate using low-temperature AlN nucleation layers by low-pressure metal-organic chemical vapor deposition(LPMOCVD).High resolution X-ray diffraction(HRXRD),atom force microscopy(AFM),scanning electron microscopy(SEM),photoluminescence(PL) and Raman scattering measurements have been employed to study the crystal quality,threading dislocation density,surface morphology,optical properties and phonon properties of thick AlGaN epifilms.The results indicate that AlGaN epifilms crystal quality can be improved greatly when grown on the free-standing GaN substrate.We calculated the threading dislocation density and found that thick AlGaN epifilm grown on the free-standing GaN substrate is much lower in total threading dislocation density than that grown on the sapphire substrate,although the surface morphology is rougher than that of sapphire substrate.

Ultrawide-bandgap(6.14 eV)(AlGa))_(2)O_(3)/Ga_(2)O_(3)heterostructure designed by lattice matching strategy for highly sensitive vacuum ultraviolet photodetection

One judiciously designed strategy of utilizing an ultrathin but conductive Ga_(2)O_(3):Si nanolayer to prepare(AlGa)_(2)O_(3)crystalline film is demonstrated.Benefiting from the existence of Ga_(2)O_(3):Si nanolayer,a high-quality(Al_(0.68)Ga_(0.32))_(2)O_(3)sesquioxide film with 68 at.%aluminum was epitaxially grown on sapphire substrates,which was characterized by high-resolution transmission electron microscopy,X-ray photoelectron spectroscopy and X-ray diffraction.Its bandgap was broadened to 6.14 eV,and a vacuum ultraviolet(VUV)(AlGa)_(2)O_(3)/Ga_(2)O_(3):Si photodetector was subsequently fabricated.The detector exhibits a pretty high on-off ratio of about 10^(3),an open-circuit voltage of 1.0 V and a responsivity of 8.1 mA W^(-1) at 0 V bias voltage.The performances imply that the proposed strategy is valuable for improving the quality and also adjusting the bandgap of(AlGa)_(2)O_(3)sesquioxides,which is expected to facilitate their application in VUV photodetection.

GaN-based light emitting diodes on nano-hole patterned sapphire substrate prepared by three-beam laser interference lithography

Nano-hole patterned sapphire substrates （NHPSSs） were successfully prepared using a low-cost and high-efficiency approach, which is the laser interference lithography （LIL） combined with reactive ion etching （RIE） and inductively coupled plasma （ICP） techniques. Gallium nitride （GaN）-based light emitting diode （LED） structure was grown on NHPSS by metal organic chemical vapor deposition （MOCVD）. Photoluminescence （PL） measurement was conducted to compare the luminescence efficiency of the GaN-based LED structure grown on NHPSS （＇NHPSS-LED） and that on unpatterned sapphire substrates （UPSS-LED）. Electroluminescence （EL） measurement shows that the output power of NHPSS-LED is 2.3 times as high as that of UPSS-LED with an injection current of 150 mA. Both PL and EL results imply that NHPSS has an advantage in improving the crystalline quality of Gab/epilayer and light extraction efficiency of LEDs at the same time.

Investigation of thermal radiation effect on optical dome of sapphire coated yttrium oxide

Compared to traditional optical domes, domes of sapphire coated with films can effectively reduce emissivity and increase transmittance. The purpose of this work is to investigate the thermal radiation effect on sapphire optical dome coated with yttrium oxide by a radio frequency mag- netron sputtering method. The emissivity of sapphire coated with Y203 films is studied by both numerical and experi- mental methods. The results indicate that the emissivity of sapphire substrate is reduced effectively with increasing the thickness of the Y203 film. In addition, a finite element model is developed to simulate the radiation intensity of the optical dome. The thermal responses indicate that the max- imum temperature is reduced apparently compared with the uncoated sapphire as Y203 film thicknesses increase. The average irradiance distribution at different film thicknesses with time shows that the self-thermal radiation disturbance of sapphire optical dome delays 0.93 s when the thickness of Y203 film is 200μm, which can guarantee the dome works properly and effectively even in a harsh environment.

Synthesis of monoclinic structure gallium oxide film on sapphire substrate by magnetron sputtering

Gallium oxide （Ga203） films were deposited on singlecrystalline sapphire （0001） substrate by radio frequency （RF） magnetron sputtering technique in the temperature range of 300--500 ℃. The microstructure of the fl-Ga203 films were investigated in detail using X-ray diffractometer （XRD） and scanning electron microscope （SEM）. The results show that the film prepared at 500℃ exhibits the best crystallinity with a monoclinic structure （fl-Ga203）. Structure analysis reveals a clear out-of-plane orientation offl-Ga203 （201） II A1203 （0001）. The average transmittance of these films in the visible wavelength range exceeds 90%, and the optical band gap of the films varies from 4.68 eV to 4.94 eV which were measured by an ultraviolet-visible-near infrared （UV-vis-NIR） spectrophotometer. Therefore, it is hopeful that the fl-Ga203 film can be used in the UV optoelectronic devices.

Ultrahigh Density Modulation of Aligned Single-Walled Carbon Nanotube Arrays

Controlling the densities of aligned single-walled carbon nanotube arrays （SWNTs） on ST-cut quartz is a critical step in various applications of these materials. However the growth mechanism for tuning SWNT density using the chemical vapor deposition （CVD） method is still not well understood, preventing the development of efficient ways to obtain the desired results. Here we report a general ＂periodic＂ approach that achieves ultrahigh density modulation of SWNT arrays on ST-cut quartz substrates--with densities increased by up to -60 times compared with conventional methods using the same catalyst densities--by varying the CH4 gas ＂off＂ time. This approach is applicable to a wide range of initial catalyst densities, substrates, catalyst types and growth conditions. We propose a general mechanism for the catalyst size-dependent nucleation of SWNTs associated with different free carbon concentrations, which explains all the observations. Moreover, the validity of the model is supported by systematic experiments involving the variation of key parameters in the ＂periodic＂ CVD approach.

基于馆藏文物的唐代螺钿铜镜科技分析

螺钿镜是主要流行于唐代的一种特种工艺镜,流传下来的实物极为罕见。本文对六枚陕西历史博物馆藏唐代螺钿铜镜的合金组成及制作工艺进行分析研究。结果显示,所分析铜镜合金配比非常适合铸造铜镜,体现了唐代已熟练掌握铜镜合金配方;其样式与日本正仓院保存铜镜相同,但直径较小;其主要工艺特点是蚌片上镶嵌宝石及螺钿片间镶嵌孔雀石等碎石。研究结果可为唐代螺钿铜镜的保护修复提供参考。

Enhanced Raman scattering of graphene on Ag nanoislands

The effect of Ag nanoislands on the Raman of graphene was investigated in this work.Compared with that on the bare silicon wafer,Raman enhancement was observed in the graphene film that covered on Ag/Si surface with nanoscale Ag islands,which would be induced by the localized plasmon resonance in Ag nanostructures.The interaction between the graphene sheet and Ag/Si substrate was further studied.The peak shift and line shape of Raman spectroscopy indicated a nonuniform strain distribution in the Ag/Si supported graphene film.

Formation mechanism of subtrenches on cone-shaped patterned sapphire substrate

In this paper, the cone-shaped patterned sapphire substrates (PSS) were etched by an inductively couple plasma with BCl 3 as the reacting gas. The influence of the operating pressure and the RF bias power on subtrenches of the cone-shaped PSS and the formation mechanism of subtrenches were investigated. The profiles of patterns were characterized by FESEM (field emission scanning electron microscope). It showed that the subtrench size varied with the operating pressure and the RF bias power. As the operating pressure increased from 0.2 Pa to 0.9 Pa, the subtrenches changed from narrow and deep to wide and shallow; then to narrower and shallower. When the RF bias power varied from 200 W to 600 W, the subtrenches gradually became noticeable. The FESEM results also indicated that the subtrenches were formed due to the ion scattering effect which was caused by tapered sidewalls and charges accumulation. It is discovered that the scattering effect is closely related with the operating pressure and RF bias power.

Influence of annealing on the structural,optical and electrical properties of indium oxide films deposited on c-sapphire substrate

Indium oxide(In_2O_3) films were prepared on Al_2O_3(0001) substrates at 700 °C by metal-organic chemical vapor deposition(MOCVD).Then the samples were annealed at 800 °C,900 °C and 1 000 °C,respectively.The X-ray diffraction(XRD) analysis reveals that the samples were polycrystalline films before and after annealing treatment.Triangle or quadrangle grains can be observed,and the corner angle of the grains becomes smooth after annealing.The highest Hall mobility is obtained for the sample annealed at 900 °C with the value about 24.74 cm^2·V^(-1)·s^(-1).The average transmittance for the films in the visible range is over 90%.The optical band gaps of the samples are about 3.73 e V,3.71 e V,3.70 eV and 3.69 eV corresponding to the In_2O_3 films deposited at 700 °C and annealed at 800 °C,900 °C and 1 000 °C,respectively.

The influence of pressure on the growth of a-plane GaN on r-plane sapphire substrates by MOCVD

Nonpolar a-plane （1120） GaN films have been grown on r-plane （1102） sapphire by metal-organic chemical vapor deposition （MOCVD） under different growth pressures. The as-grown films are investigated by optical microscopy, high-resolution X-ray diffraction （HRXRD） and Raman scattering. As growth pressure rises from 100 mbar to 400 mbar, the surface gets rougher, and the in-plane XRD full width at half maximum （FWHM） along the c-axis [0001] increases while that along the m-axis [1100] decreases. Meanwhile, residential stresses are reduced along both the c-axis and the m-axis. The structural anisotropy feature under 400 mbar is inverted with respect to 100 mbar, and the weakened anisotropy is achieved under a moderate pressure of 200 mbar, probably due to the suppressed Ga atomic migration along the c-axis under a larger pressure. We propose that pressure can affect a-plane growth through the V/III ratio.