多脉冲固体火箭发动机长尾喷管多层热防护结构传热烧蚀特性

针对多脉冲固体火箭发动机长尾喷管热防护结构的传热烧蚀问题,提出了由C/C抗烧蚀层、碳/酚醛相变吸热层和钢壳体结构组成的多层热防护结构,建立了基于热物性参数随时间和温度变化的传热烧蚀数学模型,采用有限差分隐式格式进行求解。在验证了多层防热结构传热烧蚀计算框架准确性的基础上,开展了长尾喷管多层热防护结构传热烧蚀响应过程仿真研究,分析了脉冲间隔时间对多层热防护结构传热烧蚀响应的影响规律。研究结果表明:与传统固体火箭发动机相比,多脉冲发动机工作时碳/酚醛层内热物性参数与热解反应变化较大,导致多层结构内能量分布更加均匀,使得钢壳体外表面温度显著升高,同时C/C抗烧蚀层表面烧蚀量显著下降;随着脉冲间隔时长的增加,C/C抗烧蚀层烧蚀量逐渐下降,碳/酚醛层内热解程度逐渐降低,钢壳体外表面温度先升高后下降,脉冲间隔时长60 s时钢外壳表面温度达到最大值。

基于环形燃料的月球基地用长寿期核电源堆芯物理方案研究

空间核反应堆电源具有结构紧凑、比功率大、寿命长、不依赖光照以及环境适应性强等优点,是月球基地最理想的能源解决方案。以美国FSP方案为参考,确定净输出电功率40 kW、寿期10 a为核电源的基本参数指标。对于月球基地用空间核反应堆电源,热中子反应堆方案相比快中子反应堆方案在减轻屏蔽体质量和节省核燃料方面更加具有竞争力。在对比分析了空间堆上几种常用的金属氢化物后,以长寿命为原则,选择YH_(1.8)作慢化剂。环形燃料作为一种革新性的燃料形式,具有双边慢化和双边冷却的特点,可以减小固体慢化剂的正温度效应并显著提高反应堆的热工安全裕量,是未来高性能反应堆的首选燃料形式。通过借鉴前苏联TOPAZ-Ⅱ空间堆的堆芯结构,在此基础上整合美国FSP方案的系统结构,最终设计出此堆芯方案。通过采用环形燃料元件并对栅格参数进行优化设计,解决了固体慢化剂带来的全堆正温度效应问题;通过引入安全棒设计,解决了特殊临界安全要求问题;通过采用YH_(1.8)慢化剂,解决了慢化剂的氢泄漏问题。以MCNP程序为计算工具,完成了.堆芯物理方案的设计与优化。与FSP方案相比,堆芯(含反射层)尺寸参数相当,没有因为使用慢化剂而使堆芯体积变大,并且^(235)U装量仅需18.463 kg,只有FSP方案的1/4。

瑞敏系列和TURE TEST系列斑贴试剂检测结果比较

目的分析瑞敏系列(R)和TURE TEST系列(T)斑贴试剂检测结果及一致性。方法分别用这两个系列斑贴试剂检测196例慢性湿疹和接触性皮炎患者,对其检测结果进行比较。结果瑞敏系列和TURE TEST系列斑贴试剂对各变应原检测阳性率不完全相同,它们检测常见变应原种类均与国内已有报道类似;两个系列中相同的16种变应原的检测反应强度一致性较好,检测的阳性率差异无统计学意义(P>0.05)。结论两个系列斑贴试剂的一致性较好,临床上可根据患者情况选择应用。

从图灵测试到ChatGPT——AI成为认知主体的可能

从图灵测试到ChatGPT的演进过程彰显了AI认知能力与认知方式的不断拓展与提升,凸显了人机关系或人技关系的认识论问题。图灵测试为AI成为认知主体提供了可能性判据,但此观点受到塞尔、德雷福斯等诸多学者的质疑。就两者论争的问题本身而言,其核心论题可归结为AI与人类认知本质之间的辩证关系;就论争的认识论的维度而言,AI的演进不可避免地影响到认识论的理论建构,反之,认识论也将为AI的发展提供理论指导;就AI的演进过程而言,这种理论论争为其进一步发展厘清了问题、指明了方向。

The Model of Poverty Alleviation and Income Growth by Developing Plateau-characterized Agriculture and Its Achievements Analysis in Yunnan Province——a Case Study in Midu County, Dali Bai Autonomous Prefecture

The policy of taking the targeted poverty alleviation measures has been the mission of the age in propelling the 13th Five-year Plan and building moderately prosperous society. A good poverty alleviation model is of significance for the goal. The research introduced a poverty-stricken county-Midu County, Dali Bai Au- tonomous Prefecture, analyzed the basic approaches and the main achievements of ＂the model of poverty alleviation and income growth by developing plateau-charac- terized agriculture＂, and proposed some suggestions to promoting and applying this model. The research provides references for plateau-characterized agricultural devel- opment and targeted poverty alleviation strategy.

基于红外热像的瓷绝缘子劣化诊断技术研究

瓷绝缘子的劣化给输电线路的安全稳定运行带来了严重威胁,因此及时有效地诊断劣化瓷绝缘子成为电力行业待解决的技术难题之一。基于绝缘子等效电路模型以及温升计算方程,通过仿真分析绝缘子温升规律,分区域对绝缘子进行温度离散程度计算并设定温度阈值,以实现对劣化绝缘子的高效诊断。仿真和试验结果表明:不同区域绝缘子温度离散程度不同;串中任意一片绝缘子的温升随着其内阻的减小呈现先升高后降低的趋势;劣化发生在两端引起的温升较中压端大。依据劣化绝缘子阻值变化所引起的自身温度变化以及相邻绝缘子温度变化情况,能有效识别出劣化绝缘子。

微小多孔介质燃烧器内富氢甲烷全预混燃烧与热性能特性

提出一种可作为微小热源的填充多孔介质的带有瑞士卷预热通道的微小燃烧器,探究了不同燃烧室高度下燃烧器内60%氢气-40%甲烷-空气全预混火焰吹熄极限等燃烧特性.结果表明不同燃烧室高度下的火焰吹熄极限差别不大.同一燃烧室高度下,吹熄极限随雷诺数的减小而变宽,这主要是因为雷诺数较小时的火焰拉伸作用较小.大部分工况下火焰呈现规则的圆形.当雷诺数较大时,燃烧器上壁面外表面温度的最大值和平均值随当量比的增大均增大,同一当量比下增大雷诺数也是类似的结果.当雷诺数较小时,当量比对上述外壁面温度分布特性影响较小.可为实现清洁高效燃烧的全预混燃烧技术的工程应用提供理论基础.

Developmental Threshold Temperature and Effective Accumulative Tem- perature of Pupae and Eggs of Holcocerus hippophaecolus

In order to understand the occurrence and the developmental regularity of seabuckthorn carpenterworm (Holcocerus hippophaecolus) and predict its population density, the developmental threshold temperature (C) and effective accumulative tem- perature (K) of the carpenterworm pupae and eggs were analyzed under the conditions of constant and variable temperatures. The results show that the values of C and K of the carpenterworm pupae are (12.1 ± 0.2) °C and (295.2 ± 4.1) day-degrees at constant temperatures, and (15.5 ± 0.4) °C and (202.4 ± 13.1) day-degrees at variable temperatures. However, the values of C and K of the eggs at variable temperatures are (16.7 ± 0.8) °C and (101.5 ± 12.6) day-degrees. The differences of developmental threshold and effective accumulative temperature under the conditions of constant and variable temperatures of the carpenterworm pupae accord with the developmental regularity of most insects in nature. By comparing five different constant temperatures, the conclusion is that the optimum developmental temperature of the pupae is 21 °C when both the pupation of the mature larvae and the eclosion of the pupae are very accordant. Moreover, the percentage of eclosion is over 90%. The average developmental durations of the carpenter- worm pupae and eggs are 31 and 16 d at variable temperatures.

Effects of Rare Earth and Hot Pressing Sintering Temperature on the Transverse Rupture Strength of Fe-based Diamond Composites

Effects of sintering temperature in hot pressing, t yp es, states and amounts of rare earth as well as TiH 2 on the transverse rupture strength (TRS) of Fe-based composites are studied by means of orthogonal test and variance analysis in this paper. It is found that sintering temperature has a significant effect on the TRS of Fe-based diamond composites. The optimal sin tering temperature is 780～860 ℃. On the contrary, the effects of RE additi v es on values of TRS of the diamond composites have on distinct difference no mat ter the RE is in the state of mixture or compound or oxidization. Experimental r esults demonstrate that Fe-based diamond composites with RE additives exhibit h igher TRS, which results in an increase in diamond retention capacity. The degre e of increment of TRS is different at different sintering temperatures. The opti mal amount of rare earth was found to be about 1% in weight. The effect of RE is more significant at lower sintering temperature. The experimental results also reveal that TiH 2 additive has a negative effect on the TRS of Fe-based compos ites. Microscope observations demonstrate that specimen without TiH 2 additives , shows fewer pores and denser structures in the base metal. It can also be seen from the SEM observation of the resulting fracturing surface of bending test sp ecimens that the bonding of the diamond-matrix interface is better in the speci men without TiH 2 than in the specimen with TiH 2. Also the fracture surface o f the specimen without TiH 2 reveals ductile cup and cone behavior.

Responses of Grassland and Forest to Temperature and Precipitation Changes in Northeast China

Using the Normalized Difference Vegetation Index （NDVI） as an indicator of vegetation growth, we explored the characteristics and differences in the response to drought of five vegetation biomes in Northeast China, including typical steppe, desert steppe, meadow steppe, deciduous coniferous forest and deciduous broad-leaved forest during the period 1982 2009. The results indicate that growing season precipitation may be the primary vegetation growth-limiting factor in grasslands. More than 70% of the temporal variations in NDVI can be explained by the amount of precipitation during the growing season in typical and desert steppes. During the same period, the mean temperature in the growing season could explain nearly 43% of the variations in the mean growing season NDVI and is therefore a dominant growth-limiting factor for forest ecosystems. Therefore, the NDVI trends differ largely due to differences in the vegetation growth-limiting factors of the different vegetation biomes. The NDVI responses to droughts vary in magnitude and direction and depend on the drought-affected areas of the five vegetation types. Specifically, the changes in NDVI are consistent with the variations in precipitation for grassland ecosystems. A lack of precipitation resulted in decreases in NDVI, thereby reducing vegetation growth in these regions. Conversely, increasing precipitation decreased the NDVI of forest ecosystems. The results also suggest that grasslands under arid and semi-arid environments may be more sensitive to drought than forests under humid environments. Among grassland ecosystems, desert steppe was most sensitive to drought, followed by typical steppe; meadow steppe was the least sensitive.

A new generalized fractional Dirac soliton hierarchy and its fractional Hamiltonian structure

Based on the differential forms and exterior derivatives of fractional orders, Wu first presented the generalized Tu formula to construct the generalized Hamiltonian structure of the fractional soliton equation. We apply the generalized Tu formula to calculate the fractional Dirac soliton equation hierarchy and its Hamiltonian structure. The method can be generalized to the other fractional soliton hierarchy.

Intelligent Intercommunicating Multiscale Engineering: The Engineering of the Future

1.Introduction Despite being widely known and investigated as a computer science discipline,artificial intelligence(AI)has attracted incomparable interest from researchers in diversified areas[1].In 1950,Alan Turing raised the classic question that has inspired numerous researchers to date:“Can machines think?”[2].The ultimate benchmark of AI was set by Turing’s revised“imitation game.”

Healing time of incision infection after hepatobiliary surgery treated by needle-free incision suture closure

AIM: To compare the effectiveness of needle-free incision suture closure with butterfly tape and traditional secondary suturing techniques in treating incision infection. METHODS: Two hundred and twenty-three patients with incision infection following hepatobiliary surgery at a tertiary hospital were randomly divided into three groups: 90 patients were closed by needle-free incision suture closure, which gradually closed the incision wound when drainage from incision infection was visibly decreased and healthy granulation tissues had grown; 79 patients were closed by butterfly bandage; another 54 patients were closed by traditional secondary suturing technique. Healing time of incision infection was calculated from the beginning of dressing change to the healing of the incision. RESULTS: Healing time in the needle-free incision suture closure group (24.2 +/- 7.2 d) was significantly shorter than that in the butterfly bandage group (33.3 +/- 11.2 d) and the traditional secondary suturing group (36.2 +/- 15.3 d) (P < 0.05). Healing time in the butterfly bandage group appeared to be slightly shorter than that in the secondary suture group, but the difference was not statistically significant (P > 0.05). CONCLUSION: Needle-free incision suture closure could gradually close the infection wound at the same time of drainage and dressing change, thereby shortening the healing time. (C) 2014 Baishideng Publishing Group Inc. All rights reserved.

Interesting rendezvous location in a liver transplantation patient with anastomosis stricture

An endoscopic or radiologic percutaneous approach may be an initial minimally invasive method for treating biliary strictures after living donor liver transplantation; however, cannulation of biliary strictures is sometimes difficult due to the presence of a sharp or twisted angle within the stricture or a complete stricture. When an angulated or twisted biliary stricture interrupts passage of a guidewire over the stricture, it is difficult to replace the percutaneous biliary drainage catheter with inside stents by endoscopic retrograde cholangiopancreatography. The rendezvous technique can be used to overcome this difficulty. In addition to the classical rendezvous method, in cases with complete transection of the common bile duct a modified technique involving the insertion of a snare into the subhepatic space has been successfully performed. Herein, we report a modified rendezvous technique in the duodenal bulb as an extraordinary location for a patient with duct-to-duct anastomotic complete stricture after liver transplantation.

Plant diversity, population structure, and regeneration status in disturbed tropical forests in Assam, northeast India

We investigated the plant population structure and the phy- tosociological and regeneration status in two disturbed tropical forests in Assam Province, the Hojai Reserve Forest and Kumorakata Reserve Forest. A total of 166 species （80 trees, 20 shrubs and 66 herbs） of 136 genera and 63 families were recorded in both study sites. The disturbance index at the two sites, Kumorakata Reserve Forest and Hojai Reserve Forest, were recorded at 11.4% and 3.70% respectively. Reverse J-shaped population curve and exploitation of tree species in higher girth classes were recorded at both study sites. In the girth classes （10-30 cm, 30-60 cm, 60-90 cm and 90-120 cm in size） the percentage of cut stump density was higher than the percentage of individual living trees. The 18% （Kumorakata Reserve Forest） and 7% （Hojai Reserve Forest） spe- cies were recorded as not regenerating. Illegal felling and over-exploitation of forest resources may lead to species-specific changes in the population structure and can alter the future structure and composi- tion of the forests.

Virtual 5G Network Embedding in a Heterogeneous and Multi-Domain Network Infrastructure

The pursuit of the higher performance mobile communications forces the emergence of the fifth generation mobile communication(5G). 5G network, integrating wireless and wired domain, can be qualified for the complex virtual network work oriented to the cross-domain requirement. In this paper, we focus on the multi-domain virtual network embedding in a heterogeneous 5G network infrastructure, which facilitates the resource sharing for diverse-function demands from fixed/mobile end users. We proposed the mathematical ILP model for this problem.And based on the layered-substrate-resource auxiliary graph and an effective six-quadrant service-type-judgment method, 5G embedding demands can be classified accurately to match different user access densities. A collection of novel heuristic algorithms of virtual 5G network embedding are proposed. A great deal of numerical simulation results testified that our algorithm performed better in terms of average blocking rate, routing latency and wireless/wired resource utilization, compared with the benchmark.

Influence of Hydrogen on Dislocation Structure in a Duplex Stainless Steel

The dislocation structure of specimens of a duplex stainless steel with precharged hydrogen has been investigated by transmission electron microscopy.The result showed the hydrogen acti- vated dislocation source on phase boundaries of ferrite/austenite and makes certain dislocations in austenite grains move.The dislocation appearances in each phase in specimens uncharged with hydrogen have been given for comparison.

Local Geometric Proof of Riemann Conjecture

Riemann hypothesis (RH) is a difficult problem. So far one doesn’t know how to go about it. Studying ζ and using analysis method likely are two incor-rect guides. Actually, a unique hope may study Riemann function , , by geometric analysis, which has the symmetry: v=0 if β=0, and basic expression . We show that |u| is single peak in each root-interval of u for fixed β ∈(0,1/2]. Using the slope ut, we prove that v has opposite signs at two end-points of Ij. There surely exists an inner point such that , so {|u|,|v|/β} form a local peak-valley structure, and have positive lower bound in Ij. Because each t must lie in some Ij, then ||ξ|| > 0 is valid for any t (i.e. RH is true). Using the positivity of Lagarias (1999), we show the strict monotone for β > β0 ≥ 0 , and the peak-valley structure is equiva-lent to RH, which may be the geometric model expected by Bombieri (2000). This research follows Liuhui’s methodology: “Computing can detect the un-known and method”.

Analysing the structure of the optical path length of a supersonic mixing layer by using wavelet methods

The nano-particle-based planar laser scattering （NPLS） technique is used to measure the density distribution in the supersonic mixing layer of the convective Mach number 0.12, and the optical path difference （OPL）, which is quite crucial for the study of aero-optics, is obtained by post processing. Based on the high spatiotemporal resolutions of the NPLS, the structure of the OPL is ana]ysed using wavelet methods. The coherent structures of the OPL are extracted using three methods, including the methods of thresholding the coefficients of the orthogonal wavelet transform and the wavelet packet transform, and preserving a number of wavelet packet coefficients with the largest amplitudes determined by the entropy dimension. Their performances are compared, and the method using the wavelet packet is the best. Based on the viewpoint of multifractals, we study the OPL by the wavelet transform maxima method （WTMM）, and the result indicates that its scaling behaviour is evident.

Study on Microcrystaline Structure and Luminescence of ZnS Thin Film Devices

The Electroluminescence thin films of zinc sulfide do ped with erbium, fabricated by thermal evaporation with two boats, are analyzed by the technology of X-ray diffraction (XRD) and X-ray photoelectron spectrosc opy (XPS). The relationship between electroluminescence brightness and microst ructure of the thin films is obtained. The analysis results of XRD indicate th at the fabricated zinc sulfide thin films belong to the blende structure and hav e a trend of preferential orientation. The XPS measurements reveal the surface m icrostructure states formed mainly by oxygen absorption and carbon absorption th at effect on the EL excitation and relaxation luminescence process. The maximum photoelectron peak corresponding to the doped erbium is detected at a depth of 1 35nm to 350nm that formed the activation layer in the films. Analysis shows that the high brightness of the film devices is attributed to the crystalline planes of growth orientated in the (311), (400). In explanation of this phenomenon, th e status of the substitute energy for Er 3+ replacing Zn 2+ in the hos t lattice of zinc sulfide is discussed. All results of describing above are referable in researching of the electroluminescence excitation machnism of the t hin film devices and in favor of fabricating the thin film devices with high qua lity.