钢壳沉管自密实混凝土工作性能评价方法的对比试验研究

自密实混凝土目前尚无统一的工作性能评价方法。通过在室内开展500~850 mm扩展度范围的自密实混凝土工作性能指标的对比试验,从填充性、间隙通过性和抗离析性能三个方面对自密实混凝土的性能评价方法进行了讨论。结果表明:采用坍落扩展度U_SF、扩展时间T₅₀₀、L型仪测试通过率H₂/H₁和视觉稳定性指数A_VSI的综合评价指标可对自密实混凝土的工作性能进行较好的表征;U_SF和T₅₀₀对自密实混凝土的填充性可以进行比较好的评价;L型仪或J环试验对自密实混凝土的间隙通过性可以进行较好的评价;对现场混凝土的稳定性可先采用视觉稳定性试验(VSI)初步评价,需要定量评价时,可采用离析率筛析试验(GTM筛析法);对侧墙等竖向构件混凝土的抗离析性评价,除了采用GTM筛析法之外,必要时还需增加压力泌水试验。     

SHAKE: Single HAsh key establishment for resource constrained devices

Pairwise secret key establishment leveraging properties of the wireless channel, is an effective security means in scenarios where no common secret or PKI is available. Related work has shown that secret bit streams can be extracted from, e.g., signal strength ratio measurement between two peers. However, they all require a considerable amount of computing resources by the two parties.In this paper we present SHAKE, a novel algorithm to establish a key using the physical properties of the wireless channel.SHAKE is particularly suitable for scenarios where the two peers have very diverse computational resources. For example, SHAKE can be used to establish a key between a sensor and the sink in a Wireless Sensor Network. We show that a secret key can be established shifting the computational burden on one peer while the other party only require one hash evaluation, what can be afforded by any resource constrained device.We evaluate SHAKE through theoretical analysis and provide validation through real world measurements. According to our experiments, the proposed protocol generates high-entropy bit at remarkable rates and enjoys minimal computational complexity requirements at one of the two parties.     

方格星虫低聚肽的分离、鉴定及其促骨发育作用评价

目的:从方格星虫中分离和筛选可促进骨形成的生物活性低聚肽。方法:通过酶解法和膜分离法制备寡肽,并通过HPLC-MS/MS鉴定肽段序列。通过在线数据库预测药物形成,并通过斑马鱼模型评估促进骨形成的作用。结果:共鉴定出10种低分子量肽,通过斑马鱼骨发育模型获得了两种潜在的候选肽,其氨基酸序列分别为GFAGDDAPR和GLGGLSPEK;分别命名为GSP1和GSP2;其分子量分别为905.04和857.06 Da;与空白对照组相比,1~50 μg/mL GSP1溶液浓度处理的AB斑马鱼幼鱼颅骨积分光密度和绿色荧光的面积均有所增加,GSP1浓度在5 μg/mL时促进骨发育的效果最好（P<0.05）。1~50 μg/mL GSP2溶液浓度处理的AB型斑马鱼幼鱼颅骨积分光密度和绿色荧光的面积均有所增加,且随着浓度的增加而增大,GSP2浓度在50 μg/mL时促进骨发育的效果最好（P<0.05）。结论:小于1000 Da的寡肽有望成为促进骨形成的候选药物。     

水面无人艇远距离通信系统设计与实现

无人艇远距离通信在开展海洋调查作业中具备重要用途,从岸端通信设备和艇载通信设备两方面开展无人艇远距离通信系统设计与设备研制,并在万山和黄海周边海域开展该通信系统的宽带和窄带测试,辅助采用系留无人机对整套系统进行通信增程试验。测试结果表明,岸端通信设备升高129 m时,宽带通信可达45 km;岸端通信设备升高180 m时,窄带通信可达50 km,通信质量稳定可靠,满足无人艇远距离通信需求。     

Passivation coating on titanium powder surface via SnCl4-Ti gas–solid fluidization reaction

Titanium powder is easily oxidized in the forming and sintering process due to its active chemistry. In this study, a passivation coating is formed on Ti powder surface via SnCl₄-Ti gas–solid fluidization reaction using fluidized bed. It is found that at 200–350 ℃, Ti-Sn-Cl-O passivation layer is formed on Ti powder surface on account of the reaction among SnCl₄, oxide film on powder surface, and Ti matrix. Upon further increasing the temperature to above 500℃, deoxygenation reaction occurs accompanied by the formation of gaseous TiCl_m and TiO_xCl_y escaping from Ti powder matrix, resulting in the decreasing of surface oxygen content. Besides, elemental Sn and Ti-Sn compounds are formed on Ti powder surface, and part of Sn is diffused into titanium matrix. The passivation behavior is mainly consisted of oxygen film destruction and oxygen removal with the fluidization temperature increasing. Overall, the suitable temperature is about 350℃ to form a passivation coating on Ti powder surface, which can achieve oxidation isolation and deoxygenation in subsequent forming and sintering process.     

Influence of several irreversible losses on the performance of a ferroelectric Stirling refrigeration-cycle

An irreversible cycle model of the Stirling refrigeration-cycle, using a ferroelectric material as the working substance, is established. Several irreversibilities due to thermal resistances between the working substance and the heat reservoirs, regenerative losses in two regenerative processes, and heat-leak loss between the heat reservoirs are taken into account. The influence of these irreversible losses on the performance of the ferroelectric Stirling refrigeration-cycle is analyzed, based on a general expression of the polarization of ferroelectric materials and a linear heat-transfer law. The cooling rate is optimized for a given power input. Some fundamental optimal relations and general performance characteristic curves of the cycle are obtained. The maximum cooling rate and other relevant performance parameters are determined. Some special cases are discussed in detail. When the regenerative losses are neglected, the results obtained may be directly used to describe the optimal performance of a ferroelectric Carnot refrigeration-cycle. Moreover, it is expounded that the calculated results are very general and also suitable for the ferroelectric Stirling and Carnot refrigeration cycles whose working substances obey the Curie–Weiss law and Curie law.     

Combining fluorescent in situ hybridization (fish) with cultivation and mathematical modeling to study population structure and function of ammonia-oxidizing bacteria in activated sludge

16S rRNA-targeted oligonucleotide probes for phylogenetically defined groups of autotrophic ammonia-oxidizing bacteria were used for analyzing the natural diversity of nitrifiers in an industrial sewage treatment plant receiving sewage with high ammonia concentrations. In this facility discontinuous aeration is used to allow for complete nitrification and denitrification. In situ hybridization revealed a yet undescribed diversity of ammonia oxidizers occurring in the plant. Surprisingly, the majority of the ammonia oxidizers were detected with probe combinations which indicate a close affiliation of these cells with Nitrosococcus mobilis. In addition, low numbers of ammonia-oxidizers related to the Nitrosomonas europaea - Nitrosomonas eutropha cluster were present. Interestingly, we also observed hybridization patterns which suggested the occurrence of a novel population of ammonia oxidizers. Confocal laser scanning microscopy revealed that all specifically stained ammonia oxidizers were clustered in microcolonies formed by rod-shaped bacteria. Combination of FISH and mathematical modeling was used to investigate diffusion limitation of ammonia and O₂ within these aggregates. Model simulations suggest that mass transfer limitations inside the clusters arc not as significant as the substrate limitations due to the activity of surrounding heterotrophic bacteria. To learn more about the ammonia-oxidizers of the industrial plant, we enriched and isolated ammonia-oxidizing bacteria from the activated sludge by combining classical cultivation techniques and FISH. Monitoring the isolates with the nested probe set allowed us to specifically identify those ammonia oxidizers which were found in situ to be numerically dominant. The phylogenetic relationship of these isolates determined by comparative 165 rDNA sequence analysts confirmed the affiliation suggested by FISH.     

The Fe3+ role in decreasing the activity of Nafion-bonded IrO2 catalyst for proton exchange membrane water electrolyser

Fe³⁺ is a common ion contaminant for the proton exchange membrane water electrolyser (PEMWE). In this work, three-electrode-system was employed to study the effect of Fe³⁺ on Nafion-bonded IrO₂ catalyst which is conventional anode catalyst for PEMWE. Study results showed that Fe³⁺ contamination decreased IrO₂ catalytic activity significantly only when the following two conditions were both satisfied: 1) Nafion resin exists in working electrode; 2) working electrode potential was over 1.471 V (vs. NHE) which is around the initial voltage of oxygen evolution reaction (OER). Besides, the contaminated working electrode activity was recovered to about 16% by being immersed into 3 M H₂SO₄ solution, but it was recovered to about 59% by ethanol washing method. These study results revealed that Fe³⁺ plays a role of catalyst for H₂O₂ production during OER process, which leads to Nafion resin decomposition. The degradation products covered working electrode surface, and thus decreased effective active sites of IrO₂. Nafion degradation was further confirmed by analyzing 1) F⁻ content in anode water and 2) FTIR of contaminated Nafion membrane.     

Single-Cell Atlas of Adult Testis in Protogynous Hermaphroditic Orange-Spotted Grouper,Epinephelus coioides

Spermatogenesis is a process of self-renewal and differentiation in spermatogonial stem cells. During this process, germ cells and somatic cells interact intricately to ensure long-term fertility and accurate genome propagation. Spermatogenesis has been intensely investigated in mammals but remains poorly understood with regard to teleosts. Here, we performed single-cell RNA sequencing of ~9500 testicular cells from the male, orange-spotted grouper. In the adult testis, we divided the cells into nine clusters and defined ten cell types, as compared with human testis data, including cell populations with characteristics of male germ cells and somatic cells, each of which expressed specific marker genes. We also identified and profiled the expression patterns of four marker genes (calr, eef1a, s100a1, vasa) in both the ovary and adult testis. Our data provide a blueprint of male germ cells and supporting somatic cells. Moreover, the cell markers are candidates that could be used for further cell identification.