Acoustic characteristics of pulse detonation engine sound propagating in enclosed space

Acoustic characteristics of pulse detonation engine(PDE)sound propagating in enclosed space are numerically and experimentally investigated.The finite element software LS-DYNA is utilized to numerically simulate the PDE sound propagating in enclosed space.Acoustic measurement systems are established for testing the PDE sound in enclosed space,and the time-frequency characteristics of PDE sound in enclosed space are reported in detail.The experimental results show that the sound waveform of PDE sound in enclosed space are quite different from those in open space,and the reflection and superposition of PDE sound on the walls of enclosed space results in the sound pressure oscillating obviously.It is found that the peak sound pressure level(PSPL)and overall sound pressure level(OASPL)of PDE sound in enclosed space are higher than those in open space and their difference increases with the rise of propagation distance.The results of the duration of PDE sound indicate that the A duration of PDE sound in enclosed space is higher than that in open space except at measuring points located at 2-m and 5-m while the B duration is higher at each of all measuring points.Results show that the enclosed space has a great influence on the acoustic characteristic of PDE sound.This research is helpful in performing PDE experiments in enclosed laboratories to prevent the PDE sound from affecting the safety of laboratory environment,equipment,and staffs.

Diagnostic model construction and example analysis of habitat degradation in enclosed bay: II. spatiotemporal variations in habitat degradation in Sansha Bay

The process of habitat degradation varies in habitat type and driving force which shows certain spatial and temporal heterogeneity on regional scales. In the present study, a new diagnostic model for enclosed bay habitat degradation was established, with which the spatial and temporal variation patterns of habitat degradation during 1991–2012 in Sansha Bay, Fujian, China was investigated. The results show that anthropogenic disturbance is the major controlling factor for the habitat degradation in large temporal heterogeneity in the bay. On the other hand, the habitat degradation experienced signifi cant spatial variations among six sub-bays. Under the joint action of temporal and spatial heterogeneity, the degradation trend in growing scale shows a more signifi cant correlation with the distribution of local leading industries along shorelines. Therefore, we quantifi ed the main characters of habitat degradation in Sansha Bay, and have understood the relationship between the status of habitats spatio-temporal variation value and the main controlling factor leading to the changes. However, a defi ciency of this research is the lack of or inaccessible to the detailed data, which shall be better solved in the future study for accessing more data from more sources.

On Characteristics and Cultures of the Hakka's Enclosed Houses in South Jiangxi Province

General situation and distribution of round houses of the Hakka in south Jiangxi were introduced, such architectural styles as enclosed house with a square yard (kouzi wei, in the shape of 口), enclosed house with a yard of three transverse and one longitudinal constructions (guozi wei, in the shape of 国), and enclosed house with a round house in its yard (tao wei) were taken to analyze features of the Hakka's enclosed houses. It was highlighted that the Hakka's enclosed houses in south Jiangxi has diversified architectural styles and outstanding defensive and living functions. Construction art and religious culture shown by the enclosed houses were interpreted, and the branch of Han people with unique dialects, cultures, folk customs and emotional attitudes was proposed as a miniature of the culture in south Jiangxi. Moreover, it was stressed that more attention of the public and more efforts for the protection should be given to the Hakka's cultures in south Jiangxi, carriers of the locals' history over the past thousands of years.

Was the enclosed Qaidam Basin of The Tibetan Plateau Accumulative or Erosive during the Late Quaternary?

A geological feature in the Qaidam Basin known as the"Shell Bar"contains millions of freshwater articulated clam shells buried in-situ.Since the 1980s this feature in the now hyper-arid basin has been interpreted to be lake deposits that provide evidence for a warmer and more humid climate than present during late Marine Isotope Stage 3(MIS 3)(Bowler et al.,1986).However,the global climate during

How the pollution stress acting on the phytoplankton populations ──an observation by the experimental enclosed ecosystem

A marine ended enclosed ecosystem expetiment was conducted by Chinese and Canadian scientists in Xiamen inApril 1985. Pollutants of heavy metals mixed with Cu, Hg, Pb, Zn and Cd and of suspended sediments were added tobags VOlumed about 10 m3. It was showed that dabing 21 days the effects on the plankton populations were evident in thebags due to the contamination, i. e. the growth of diatom population reduced to different levels characterized by the lagappearance of density peaks, low instant growth rate and delay of doulbling time with low biomass. A strong grazing fromthe pollutant affected zooplankton population resulted in heavy stress on the growth of algal population. As a result, thestress transferred to the phytoplankton population through the herbivores.

Numerical Simulation of Residual Circulation due to Bottom Roughness Variability Under Tidal Flows in A Semi-Enclosed Bay

Nowadays there are some chronic serious environmental problems, such as eutrophication, blue tide and so on, in a complicated coastal zone or a semi-enclosed bay, because the water exchanges between an inner bay and an outer sea is weak compared with the supply of contaminant. Under this situation, a method to improve the water quality by 3-dimensional small unsymmetrical structures has been proposed by Komatsu et al. In this paper, several numerical simulations of the tidal current and concentration for various arrangements of bottom roughness in a semi-enclosed model bay are carfled out with a depth-averaged 2-D numerical model. The model is solved by the hybrid finite analytic method with nonstaggered grid. And the SIMPLES algorithm with Rhie and Chow＇ s momentum interpolation technique is used for the simulation. The effect of Komatsu＇ s method for water purification is examined by numerical simulation. The result of numerical experiment indicates that it is possible to generate a new tidal residual current and to activate a tidal exchange by bottom roughness arrangement only.

Enclosed Extent of the Saline Water and its Constraints on the Sedimentary and Salt Forming Characteristics:A Case Study of the Paleogene Playas in Hoh Xil Basin

1 Introduction There is a long period of hot,arid climates in the Jurassic-Neogene,in the eastern of the Neo-Tethys where is been called Western Yunnan—Qiangtang tectonic belt(Zheng et al.,2010).Especially in the Paleogene,under the control of the planetary winds and the north subtropical high pressure belts,a ribbon arid,semi-arid

Evolution Characteristics of Saturated Hydrocarbons of Enclosed Organic Matter in Carbonate Minerals in Tieling Limestone Under High Temperature and High Pressure

The enclosed organic matter chiefly releases lower carbon\|number n\|alkanes under high temperature and high pressure, while the kerogen mainly produces higher carbon\|number n\|alkanes. The residual hydrocarbons generated by both kerogen and enclosed organic matter in the Tieling limestone contain abundant tricyclic terpanes, pentacyclic triterpanes and steranes, but the contents of tetracyclic terpanes and 25\|norhopane are lower. The residual enclosed organic matter shows the same distribution characteristics of n\|alkanes, steranes and terpanes as that of the original bitumen A, i.e., the higher contents of triterpanes and tetracyclic terpanes, the higher ratios of 25\|norhopanes over regular hopanes and markedly degraded steranes. By comparing the residual hydrocarbon, residual enclosed organic matter and original enclosed organic matter, it can be concluded that steranes and terpanes in the residual hydrocarbons are produced mainly by the kerogen and subordinately by the residual enclosed organic matter, the steranes and terpanes do not enter into the residual enclosed organic matter, and the thermal evolution of the residual enclosed organic matter maintains its unique character. Furthermore, pressure retards the pyrolysis of higher carbon\|number alkanes and influences the isomerization ratios of C\-\{29\}\|steranes, making 20S/(20S+20R) lower under the higher pressure than that under lower pressure. Higher pressure retards the thermal evolution of organic matter.

Diagnostic model construction and example analysis of habitat degradation in enclosed bay: I. diagnostic model construction

Presently, research is lacking regarding the diagnosis and evaluation of habitat degradation in enclosed bay systems. We established a diagnostic model for enclosed bay habitat degradation(EBHD model) using a multi-approach integrated diagnostic method in consideration of driving force-pressurestate-infl uence-response. The model optimizes the indicator standardization with annual average change rate of habitat degradation as the basic element, to refl ect accurately the impact of the change and speed of degradation on the diagnostic results, to quantify reasonably the contribution of individual diagnostic indicator to habitat degradation, and to solve the issue regarding the infl uence of subjective factors on the evaluation results during indicator scoring. We then applied the EBHD model for the Sansha Bay in Fujian Province, China, evaluated comprehensively the situation of habitat degradation in the bay, and screened out the major controlling factors in the study area. Results show that the diagnostic results are consistent in overall with the real situation of the study area. Therefore, the EBHD model is advantageous in terms of objectivity and accuracy, making a breakthrough in diagnosis and evaluation for habitat degradation in enclosed bay systems.

Fall detection system in enclosed environments based on single Gaussian model

In this paper,we propose an efficient fall detection system in enclosed environments based on single Gaussian model using the maximum likelihood method.Online video clips are used to extract the features from two cameras.After the model is constructed,a threshold is set,and the probability for an incoming sample under the single Gaussian model is compared with that threshold to make a decision.Experimental results show that if a proper threshold is set,a good recognition rate for fall activities can be achieved.

Relic Oceanic Crust at Sub-arc Depth: an Example from UHP Eclogites Enclosed in Serpentinites from the Southwestern Tianshan Mountains, China

Ultra-high pressure(UHP)eclogites that derive from subducted oceanic crust are rarely found at the Earth’s surface because they need to be enclosed in a buoyant host rock such as serpentinites that facilitate exhumation

Relic Oceanic Crust at Sub-Arc Depth: An Example from UHP Eclogites Enclosed in Serpentinites from the Southwestern Tianshan, China

Ultra-high pressure（UHP）eclogites that derive from subducted oceanic crust are rarely found at the Earth’s surface because they need to be enclosed in a buoyant host rock such as serpentinites that facilitate exhumation（Hermann et al.,2000;Guillot et al.,2001）.Under normal subduction geotherms,serpentinites break down just before UHP conditions are reached and therefore most of the exhumed eclogites representing subducted oceanic crust formed under fore-arc conditions.We investigated eclogite blocks enclosed into serpentinites that occur in the southwestern Tianshan oceanic subduction,China.A previous study proved that the serpentinites derive from altered oceanic crust and experienced UHP metamorphism at low temperatures of 510-530°C（Shen et al.,2015）.Three relatively fresh eclogite samples were studied in detail.Sample 129-7 shows the retrograde mineral assemblage of amphibole+biotite+albite+chlorite+minor titanite and peak metamorphic relics of omphacite+garnet±chlorite.Sample C107-23 is mainly composed of amphibole+albite+chlorite+zoisite+muscovite+minor titanite as a retrograde assemblage and garnet+phengite as the peak metamorphic relics with omphacite only found as inclusions in garnet.Similar to sample C107-23,sample C11066 preserves large-grained euhedral to subhedral garnet relics with omphacite inclusions,and epidote,diopside,amphibole,muscovite,chlorite,albite and biotite are in the matrix belong to the retrograde assemblage.These three retrograde eclogite samples were modelled using thermodynamic calculations in the Mn NCKFMSHO（Mn O-Na;O-Ca O-K;O-FeO-Mg O-Al;O;-SiO;-H;O-Fe;O;）system.Based on the peak assemblage of omphacite+garnet and the crossing of the grossular and pyrope isopleths in garnet,peak P-T conditions of;60-470oC,28-29 kbar（129-7）,450-500oC,28-35 kbar（C107-23）,;75-505oC,26-29 kbar（C11066）were calculated.The retrograde assemblages indicate near isothermal decompression resulting in a clockwise P-T evolution of these eclogites.The peak metamorphic pressures at 500°C are well within UHP conditions（coesite stability field）and are within error the same as peak conditions of the host serpentinites（Shen et al.,2015）.This provides evidence that eclogites and serpentinites shared the same evolution.We infer that the subducted low-density serpentinites were assembled with the high-density eclogites during subdution and helped the latter to exhume back to the surface.The studied eclogites thus represent rare examples of relics of oceanic crust that was subducted to sub-arc depth.

The effects of nutrients and heavy metals on the plankton in marine enclosed ecosystem

Applying marine enclosed ecosystem extensively to study the nutrient variation and its relation to biochemical process by marine ecologists and biogeologists in North America, Europe, Japan and Australia has been lasting for many years. Santschi (1982) reviewed the geochemical recirculation of nutrients systematically. Kremling et al. (1978) described the changes in nutrient in marine enclosed e-

Experimental Study on Seismic Behavior ofSeismic-damaged Lateral Joints in CompositeFrame Consisting of CFSST Columns and SteelBeams Strengthened with Enclosed ReinforcedConcrete

A new composite strengthening method of seismic-damaged lateral joints in composite frame consisting of Concrete-Filled SquareSteel Tubes （CFSST） columns and steel beams strengthened with enclosed Reinforced Concrete （RC） at the ends of columns andwelding steel plates at the ends of beams was presented. Based on the current design specifications, one half scaled models of 4lateral joints in composite frame consisting of CFSST columns and steel beams were designed and manufactured. One model wasoriginal control specimen, one was strengthened by enclosed RC, and the others were strengthened after pre-damage. The destructiontests under lateral cyclic load on the models were carried. The effectiveness of seismic-damaged joints strengthened with enclosedRC and the reinforcement effect on different levels of seismic damage were studied. The test results show that seismic- damagedjoints in composite frame consisting of CFSST columns and steel beams strengthened with enclosed RC meets the strongcolumn-weak beam joints requirement of seismic design, and the failure modes are of all joints are the bending failure of steel beam.The reinforcement with enclosed RC has a significant on increasing the ultimate capacity and the seismic behaviors of joints. Thestudy indicated the rehabilitated joints recover the level of their original seismic performances before seismic damage in a certainextent damage level. Based on the test data, namely the ultimate capacity, limit displacement, ductility, the energy consumptioncoefficient, limit displacementthe strengthening method of seismic-damaged joints by strengthened with enclosed RC is an effectivemethod for seismic strengthening.

Investigation of wave characteristics in a semi-enclosed bay based on SWAN model validated with buoys and ADP-observed currents

In this study, the simulating waves nearshore (SWAN) model with a locally refined curvilinear grid system was constructed to simulate waves in Jervis Bay and the neighbouring ocean of Australia, with the aim of examining the wave characteristics in an area with special topography and practical importance. This model was verified by field observations from buoys and acoustic Doppler profilers (ADPs). The model precisions were validated for both wind-generated waves and open-ocean swells. We present an approach with which to convert ADP-observed current data from near the bottom into the significant wave height. Our approach is deduced from the Fourier transform technique and the linear wave theory. The results illustrate that the location of the bay entrance is important because it allows the swells in the dominant direction to propagate into the bay despite the narrowness of the bay entrance. The wave period T p is also strongly related to the wave direction in the semi-enclosed bay. The Tp is great enough along the entire propagating direction from the bay entrance to the top of the bay, and the largest Tp appears along the north-west coast, which is the end tip of the swells’ propagation.

大型封闭空间中UWB定位基站拓扑的通用设计方法

超宽带(ultra-wide band,UWB)技术是无人装备在巡检具有多障碍物的大型封闭空间时获取定位坐标的主要方法之一。目前主要依赖人工方式设计UWB定位基站拓扑的构型、位置和数量。这种方式存在设计效率低下,设计效果未知,性价比难以确定等问题。为此,本文提出了一套较为科学完善的定位基站拓扑评价体系,并提出了一种在大型封闭空间中自动设计定位基站拓扑的通用方法。该方法以仿真模拟为基础,通过遗传算法结合拓扑评价体系,自动生成贴合实际应用场景的最优拓扑方案,包括最优的基站布设数量以及布设位置信息。实验结果表明:1)经通用设计方法生成的拓扑相比使用基站数量最多的拓扑,综合性能提高了6.2%;相比使用基站数量最少的拓扑,综合性能提高了21.2%。2)经通用设计方法生成的拓扑相比人工设计的锯齿形拓扑,综合性能提高了11.4%,设计效率提高了92.9%。可见,针对具有多障碍物的大型封闭空间场景,本文的方法可以在较短的时间内设计出综合性能较优,性价比较高的定位基站拓扑,为无人装备在此类大型封闭空间中开展全自主定位和巡检奠定了基础。

基于多层融合振动数据分析的GIS设备机械缺陷诊断方法研究

气体绝缘金属封闭开关设备(gas insulated metal enclosed switchgear,GIS)机械缺陷是导致设备故障的重要因素,针对单测点、单证据机械缺陷诊断模型信息缺失和精度不足问题,该文提出一种多层融合振动数据分析的GIS设备机械缺陷诊断方法。首先,基于真型GIS设备振动模拟平台试验研究测点位置与缺陷类型对振动行为的影响特性;然后,联合统计分析、模态分解、尺度变换方法提出机械振动信号整体与局部信息关注的复合参数分析方法,引入主成分分析开展多测点振动信息的特征层融合降维;最后,提出改进放缩权重的Dempster-Shafer(DS)证据理论和Bagging投票机制的强/弱基学习器决策层融合机制,联合构建多层融合振动数据分析的GIS设备机械缺陷诊断模型。结果表明:不同类型机械缺陷信号的响应幅值、特征频点和畸变程度存在显著差异,复合特征参量大小及分散程度各不相同;同时,测点位置对缺陷信号的复合振动特征参量的表现形式及分布区间也具有一定影响;基于多层融合数据分析的诊断模型实现缺陷有效识别,辨识准确率为98.66%,相比单一分类器诊断效果提升5.83%。该文可为GIS设备机械缺陷诊断方法提供有价值的参考。

优质肉鸡不同环境控制下的舍内参数分布规律及性能差异性研究

【目的】明确不同饲养条件下优质肉鸡舍内环境参数变化及与生长发育的内在关联性,为优质肉鸡舍内环境参数控制提供理论依据。【方法】选取0 d龄健康的优质肉鸡L系母鸡480只,随机分成4组,每组120只,6个重复,每个重复20只,Ⅰ、Ⅱ、Ⅲ试验组饲养于3间密闭式环控舱内,根据生长周期分别设计不同的温湿度环境控制模式。对照组Ⅳ育雏期(0~21 d)饲养于环控舱内,后转至半封闭式普通鸡舍,测定各组鸡舍内部环境参数和鸡只体重、体尺变化和性器官发育等生长性能。【结果】(1)处于环控舱内的Ⅳ组鸡温度相对较高,达32℃以上,湿度为55%左右,NH_(3)、PM_(2.5)和PM_(10)浓度始终处于较低的状态,随着转入半封闭式普通鸡舍后与舍外温湿度差逐渐加大,各气体和粉尘浓度变化规律与舍外基本一致,均处于先降后升,O_(2)浓度则始终处于相对稳定的趋势。Ⅰ、Ⅱ、Ⅲ组舍内新鲜空气的交换使温湿度始终维持在预设范围内,NH_(3)、CO_(2)、O_(2)、PM_(2.5)和PM_(10)等环境参数变化趋势基本与舍外一致,略低于普通半封闭式鸡舍。(2)舍外温度与O_(2)、CO_(2)和NH3的相关系数分别为0.7287、-0.7123和-0.6875(P<0.01),舍内温度与O_(2)、CO_(2)和NH_(3)的相关系数分别为0.8071、-8427和-0.7221(P<0.01),都为中等相关或强相关,说明温度对气体浓度的影响较大,相比于舍外,舍内温度与气体浓度的相关性更强。(3)8周龄时Ⅱ组体重显著高于Ⅲ和Ⅳ组(P<0.05,下同),12周龄时各组鸡体况生长发育达到顶峰,Ⅱ组体重比Ⅰ、Ⅲ、Ⅳ组分别高84、144和126 g,此时Ⅱ组体斜长、龙骨长显著高于Ⅰ、Ⅲ和Ⅳ组;16周龄时第Ⅱ组输卵管长度达到23.25 mm,小黄卵泡和卵巢重量分别为6.25个和10.15 g,均显著大于Ⅰ、Ⅲ、Ⅳ组,表明了不同环境参数控制下优质肉鸡生长及性器官发育有明显差异。【结论】不同类型鸡舍环境参数存在一定程度的生长发育和性成熟差异,密闭式环控舱环控模式更适合我国优质肉鸡健康生长及福利养殖的发展需要,优质肉鸡在不同生长周期内对于温湿度的要求不尽相同,其中Ⅱ组环控模式在不同日龄段生长及性器官发育上更具优势,建议加大推广在家禽养殖上的应用。

GIS多频振动信号产生机理及实验研究

当前国内外对气体绝缘金属封闭开关设备(gas insulated metal enclosed switchgear,GIS)的异常振动,尤其是引发振动的激励源、多频振动产生机理等问题缺少实质性研究进展。首先,建立受力模型,研究引发GIS振动的激励源,得到引发分箱型GIS振动的力源值,并指出正常运行状态,三相母线间电动力是主频振动的主要激励源。触头接触不良将导致触头斥力合力增大,地脚螺栓松动将导致系统固有频率的变化,影响非线性振动响应频谱特征;然后,将GIS按照薄壁圆柱壳进行研究,计算GIS壳体多阶固有频率,建立有效的非线性振动方程,首次利用解析方法揭示非线性GIS系统多频振动信号的产生机理;最后,研制成功振动信号采集系统,在550 k VGIS产品上设置典型机械缺陷,经实验验证,系统激发出的振动响应幅值极值点及频率与理论分析结果一致。论文的研究成果可为GIS机械缺陷的检测及诊断提供一定的支持和参考。

组合光透视下小面积室内封闭空间分割方法

为提高室内空间的优化规划设计能力,提出基于点云数据语义分割的组合光透视下小面积室内封闭空间分割方法。构建小面积室内封闭空间的环境三维信息感知模型,采用室内空间点云提取室内封闭空间图像的坐标信息,结合语义组合特征分割方法将融合空间信息映射到高分辨空间异质单元结构中,引入几何约束的子空间投影特征信息,结合组合光透视的高分辨率分割图模型参数融合方法,提取小面积室内封闭的端元,采用点云数据语义分割方法实现空间分割。结果表明,采用该方法有效实现对复杂室内场景的三维重建,空间分割的均方根误差较低为0.808%,峰值信噪比较高42.156 dB,空间分割速度较快,平均为12.83 ms。