Unsustainable Land-Based Source Pollution in a Climate of Change: A Roadblock to the Conservation and Recovery of Elkhorn Coral <i>Acropora palmata</i>(Lamarck 1816)

Chronic eutrophication and turbidity are critical detrimental factors impacting coral reef ecosystems, adversely affecting their ecological functions, services, benefits, and resilience across multiple spatial scales and over prolonged periods of time. Inadequate land use practices and lack of appropriate sewage treatment can adversely contribute to increase land-based source pollution (LBSP) impacts in coastal waters and to magnify impacts by sea surface warming trends associated to climate change. Fringing coral reefs off Vega Baja, Puerto Rico, support extensive remnant patches of Elkhorn coral Acropora palmata (Lamarck 1816), which was listed in 2006 as a threatened species under the US Endangered Species Act. Chronic impacts by LBSP have significantly affected local downstream fringing reefs. We characterized the spatial extent of a water quality stress gradient across 12 reefs along the Vega Baja coast through monthly measurements of multiple physico-chemical parameters. Most parameters, particularly PO4, , chlorophyll-a, and the concentration of optical brighteners (OABs), showed a statistically significant increase (PERMANOVA, p < 0.05) in waters close to the main pollution sources, but also in waters adjacent to Cibuco River effluents. Dissolved oxygen also declined and turbidity increased on polluted sites. PO4, , and chlorophyll-a, exceeded recommended concentrations for coral reef ecosystems by factors of 7 - 50 times, 600 - 1240 times, and 17 - 83 times, respectively, depending on the source of the effluents and the distance from sewage pollution sources. Also, water turbidity exceeded 4 - 10 times the recommended value for pristine coral reefs. Coral reefs showed significant decline in close proximity to the polluted zone, showing a significantly different benthic community structure (PERMANOVA, p < 0.0001) dominated by non-reef building taxa (i.e., macroalgae, algal turf) and bare substrate. Percent coral cover and abundance of A. palmata, showed a significant increase with distance. Coral species richness, species diversity index, and the variance in taxonomic distinctness were very low on reef patches adjacent to the polluted zone, increased at a moderate distance with increasing coral cover and co-existence of multiple species, and declined far from the pollution source due to dominance exerted by A. palmata. This study suggests that chronic LBSP resulted in a major decline of one of the largest and most dense remnant stands of A. palmata across the northeastern Caribbean and that nutrient and chlorophyll-a concentrations were unsustainable for coral reefs. This situation requires immediate solution to prevent further damage to these unprecedented resources. It further suggests that chronic LBSP may synergistically magnify sea-surface warming impacts driving corals to an increased state of risk in face of forecasted climate change impacts. Actions to mitigate and adapt to climate change impacts on coral reefs must require a priori controls of LBSP to be effective.

Spatial Distribution Assessment and Source Apportionment of Land-Based Pollutant Yield from Qingdao, China

The spatial distribution of chemical oxygen demand(COD) and total nitrogen(TN) yield from Qingdao are studied by comparing pollutant yield amount, densities and spatial aggregation(Getis-Ord indexes) among the land-based pollutant source regions(PSRs) entering the three sub-seas(i.e. the Jiaozhou Bay(JZB), other coastal area in the Yellow Sea(OCAYS) and Laizhou Bay(LZB), respectively). Industrial composition of the loads are also studied by comparing pollutant yield among the sources of agriculture, rural domesticity, industry, urban domesticity and service, and calculation of Gini coefficient. Results show that spatial distribution of COD and TN yield from Qingdao are extremely unbalanced. The JZB, with less than 3% of the total coastal sea area of Qingdao, received 62% COD load and 65% TN yield from Qingdao, while the OCAYS, with more than 97% area, only received 23% COD and 20% TN, which consist with the much worsen water quality of JZB than that of OCAYS. On the other hand, the source apportionment of COD and TN loads in the PSRs entering JZB and the OCAYS was similar. The agricultural and domestic sources with high pollution intensity account for more than 80%, while the industrial and service sources with low pollution intensity account for less than 20%. While Gini coefficients, COD 0.81 and TN 0.84 which are much higher than the ‘imbalance' threshold of 0.4, show the uneven industrial structure of Qingdao. These results may be useful in the determination of land-based pollution total amount control at the PSR level.

外投料式滚筒筛分骨料的效率研究

为了提高外投料式滚筒筛分骨料的效率,对其筛分过程进行研究。以(10~40)mm粒度范围的骨料为研究对象,基于离散元理论,利用EDEM建立筛分模型并结合其筛分过程进行模拟仿真,得到在一定条件时,其转速和进料角度对滚筒筛分效率的影响规律:骨料筛分的最佳转速为15rpm,最佳进料角度为150°;通过正交实验模拟,得到了外投料式滚筒筛的滚筒转速、进料角度、进料量三因素对骨料筛分效率的显著性和最佳取值。仿真研究结果可以为外投料式滚筒筛的结构设计及其工艺参数优化提供借鉴和参考,具有较强的工程应用价值。

Radial mixing and segregation of granular bed bi-dispersed both in particle size and density within horizontal rotating drum

Taking simultaneous variations in both particle volume and density into account, the radial mixing and segregation of binary granular bed in a rotating drum half loaded were investigated by a 3D discrete element method. Then, based on the competition theory of condensation and percolation, radial segregation due to differences in particle volume and/or density was analyzed. The results show that if either percolation effect induced by volume difference or condensation effect induced by density difference dominates in the active layer of moving bed, separation will occur. Controlling the volume ratio or density ratio of the two types of particles can achieve an equilibrium state between percolation and condensation, and then homogenous mixture can be obtained. When the percolation balances with the condensation, the relationship between volume ratioand density ratiopresents nearly a power function. Scaling up a rotating drum will not affect the mixing degree of the granular bed so long as the volume ratio and density ratio are predefined.

模块化滚筒好氧发酵反应器设计与试验

针对现有滚筒式好氧发酵反应器存在腔体容积固定不可调、运行能耗高、尾气余热回用难等问题,基于模块化设计理念,研发了一种模块化滚筒好氧发酵反应器,主要由滚筒、曝气系统、余热回用装置、驱动系统和密封连接件等模块单元组成。对模块化滚筒好氧发酵反应器进行堆肥性能试验,结果表明:高温期持续9 d,发酵持续15 d后种子发芽指数达90%以上,各项指标均满足堆肥腐熟和无害化要求。该设计提高了滚筒好氧发酵反应器加工组装效率,扩大了滚筒好氧发酵反应器适用范围,具有规模可调、分段驱动、分级发酵、精准曝气等优点,可为滚筒好氧发酵反应器堆肥技术发展和应用提供支撑。

带式输送机驱动系统的分析与比较

带式运输机在起停运行时存在着刚性撞击和负载起动等情况,会对带式输送机造成损伤,针对此现象,文中采取在大规模的带式输送机上应用软起动驱动系统解决,软起动驱动系统主要采用永磁直驱滚筒、液黏传动、变频器、可控启动传动系统CST和柔性驱动系统FDS等方案。对5种驱动装置的柔性启动机理进行了较为详尽的阐述;通过比较5种驱动系统,分析其优缺点,并对应用于带式输送机的软起动驱动装置所带来的经济效益进行了分析。

投喂频率对陆基圆桶养殖大口黑鲈生长及水体水质的影响

【目的】研究不同投喂频率对陆基圆桶养殖大口黑鲈(Micropterus salmoides)生长性能、水体水质及其微生物群落结构的影响。【方法】本研究开展了2次/天和3次/天两种投喂频率实验。【结果】3次/天组的终末体质量和特定生长率高于2次/天组。投喂频率对水体中氨氮(TAN)、亚硝酸盐(NO2-N)、悬浮物量(SS)和化学需氧量(COD)等指标的浓度均有显著性影响(P<0.05),且2次/天组高于3次/天组。两组养殖水体的细菌群落结构相似,其优势菌门均为变形菌门(Proteobacteria)和拟杆菌门(Bacte-roidetes),优势菌属均为邻单胞菌属(Plesiomonas)和红细菌属(Rhodobacter);对大口黑鲈养殖过程中常见致病菌丰度进行统计,发现3次/天组豚鼠气单胞菌(Aeromonas caviae)的平均丰度(0.08%)显著低于2次/天组(0.14%)(P<0.05)。环境因子与细菌群落结构关联分析结果显示,氨氮(TAN)、总氮(TN)和总磷(TP)对水体细菌群落结构均有显著性影响(P<0.05)。【结论】大口黑鲈陆基圆桶养殖模式中,3次/天投喂频率较2次/天投喂频率具有生长快、养殖水体关键水质指标水平低以及致病菌丰度低的优势。本研究结果可为陆基圆桶养殖大口黑鲈的科学投喂提供实际支持。

器以载道:铜鼓文化在铸牢中华民族共同体意识中的价值逻辑及实践路径

铸牢中华民族共同体意识是习近平总书记提出的重大原创性论断,是维护各民族根本利益和实现中华民族伟大复兴的必然要求。中华民族共同体意识厚植于中华优秀传统文化之中。具有两千多年历史的中国铜鼓不仅是中华民族历史文化变迁的“见证者”,也是中华民族交往交流交融的“记录者”。中华民族共享的文化符号、共生的历史记忆、共有的价值观念都在铜鼓文化中可见一斑。为全面体现、充分发挥铜鼓文化这一中华优秀传统文化在铸牢中华民族共同体意识中的价值和功能,应积极彰显共享文化符号,维系中华民族情感纽带;增进文化互鉴融通,强化中华民族文化认同;打造铜鼓文旅品牌,推动各民族共同富裕。

高应力大巷底鼓机理及其稳定性控制方法

针对余吾煤业1号回风大巷在高应力扰动下出现的巷道底鼓严重问题,综合运用理论分析、数值计算和现场试验相结合的方法,系统研究了高应力大巷底鼓机理及其稳定性控制方法。理论计算结果表明,高应力巷道底板破坏深度达1.35 m,底板滑移面受到的滑动力达3.11 MPa,超过了底板砂质泥岩极限抗拉强度,导致巷道底板发生底鼓。从高应力巷道底鼓控制角度出发,提出了高应力巷道顶底板加强锚索与巷道两帮锚杆联合支护的巷道底鼓控制技术,数值模拟结果表明巷道底鼓量可降低67%,有效控制底鼓的同时,也可为巷道整体稳定提供支撑。通过现场试验,研究提出的巷道底鼓控制方法可使回风大巷顶板下沉值降低37%,底鼓值降低72%,两帮变形量降低53%,有效保证了回风大巷的稳定。研究结果对于指导深部矿井高应力环境下巷道底鼓控制具有重要实践意义。

双折线卷筒上钢丝绳卷绕状态的力学分析

钢丝绳偏角直接影响钢丝绳在双折线卷筒上的卷绕整齐性。因此本文以双折线卷筒的钢丝绳截面单元微元体为分析对象,建立了双折线卷筒在均速转动条件下钢丝绳卷绕状态的力学模型。通过该力学模型分析表明,卷筒均速转动下钢丝绳后偏时钢丝绳随着钢丝绳偏角增大受到挤压力增大,但“骑绳”现象很难发生;当钢丝绳前偏时钢丝绳偏角超过绳槽螺旋角时“跳绳”现象可能会发生,并且钢丝绳偏角越大“跳绳”越容易发生。其次,通过所建的力学模型对工程实例进行了计算分析;结果表明,平行线绳槽段的钢丝绳偏角是决定“跳绳”发生的关键,同时钢丝绳张力越大越容易发生“跳绳”。本文建立的双折线卷筒力学分析模型可以为提升绞车的参数设计和钢丝绳的选择提供了的理论依据。

广西瑶族长鼓舞文化英译研究

瑶族长鼓舞是中国国家级非物质文化遗产之一,流传于湖南、广东、广西等地。本文以广西瑶族长鼓舞为研究对象,通过实地调查与翻译实践相结合,探讨瑶族长鼓舞的发展现状,以便提高瑶族长鼓舞的知名度,促进其传承和发展。在苏珊·巴斯特内文化翻译观的指导下,译者根据文本特点选择归化与异化的翻译策略,采用、意译、音译、省译、增译等翻译方法,增强国外读者对广西瑶族长鼓舞文化的理解,促进广西瑶族长鼓舞文化的对外宣传。

Kinematics and Path Following Control of an Articulated Drum Roller

Automatic navigation of an articulated drum roller, which is an articulated steering type vehicle widely used in the construction industry, is highly expected for operation cost reduction and improvement of work effi- ciency. In order to achieve the path following control, considering that its steering system is articulated steering and two frames are articulated by an active revolute joint, a kinematic model and an error dynamic state-space equation of an articulated drum roller are proposed. Besides, a state- feedback control law based on Lyapunov stability theory is also designed, which can be proved to achieve the purpose of control by the analysis of stability. What＇s more, to evaluate the performance of the proposed method, simu- lation under the MATLAB/Simulink and experiments using positioning algorithm and errors correction at the uneven construction site are performed, with initial dis- placement error （-1.5 m）, heading error （-0.11 tad） and steering angle （-0.19 rad）. Finally, simulation and exper- imental results show that the errors and steering angle can decrease gradually, and converge to zero with time. Meanwhile, the control input is not saturated. An articu- lated drum roller can lock into a desired path with the proposed method in uneven fields.

Performance of rotating drum biofilter for volatile organic compound removal at high organic loading rates

Uneven distribution of volatile organic compounds （VOCs） and biomass, and excess biomass accumulation in some biofilters hinder the application of biofiltration technology. An innovative multilayer rotating drum biofilter （RDB） was developed to correct these problems. The RDB was operated at an empty bed contact time （EBCT） of 30 s and a rotational rate of 1.0 r/min. Diethyl ether was chosen as the model VOC. Performance of the RDB was evaluated at organic loading rates of 32,1, 64.2, 128, and 256 g ether/（m^3·h） （16.06 g ether/（m^3·h） ≈ 1.0 kg chemical oxygen demand （COD）/（m^3·d））. The EBCT and organic loading rates were recorded on the basis of the medium volume. Results show that the ether removal efficiency decreased with an increased VOC loading rate. Ether removal efficiencies exceeding 99% were achieved without biomass control even at a high VOC loading rate of 128 g ether/（m^3·h）. However, when the VOC loading rate was increased to 256 g ether/（m^3·h）, the average removal efficiency dropped to 43%. Nutrient limitation possibly contributed to the drop in ether removal efficiency. High biomass accumulation rate was also observed in the medium at the two higher ether loading rates, and removal of the excess biomass in the media was necessary to maintain stable performance. This work showed that the RDB is effective in the removal of diethyl ether from waste gas streams even at high organic loading rates. The results might help establish criteria for designing and operating RDBs.

Fatigue behaviour of coke drum materials under thermal-mechanical cyclic loading

Coke drums are vertical pressure vessels used in the delayed coking process in petroleum refineries. Significant temperature variation during the delayed coking process causes damage in cracking. There were some studies on coke drums in the form of bulging and the fatigue life estimation for the coke drums, but most of them were based on strain-fatigue life curves at constant temperatures, which do not consider simultaneous cyclic temperature and mechanical loading conditions. In this study, a fatigue testing system is successfully devel- oped to allow performing thermal-mechanical fatigue （TMF） test similar to the coke drum loading condition. Two commonly used base and one clad materials of coke drums are then experimentally investigated. In addition, a comparative study between isothermal and TMF lives of these materials is conducted. The experimental findings lead to better understanding of the damage mechanisms occurring in coke drums and more accurate prediction of fatigue life of coke drum materials.

Reliability modeling of hydraulic system of drum shearer machine

The hydraulic system plays an important role in supplying power and its transition to other working parts of a coal shearer machine. In this paper, the reliability of the hydraulic system of a drum shearer was analyzed. A case study was done in the Tabas Coal Mine in Iran for failure data collection. The results of the statistical analysis show that the time between failures （TBF） data of this system followed the 3-parameters Weibull distribution. There is about a 54% chance that the hydraulic system of the drum shearer will not fail for the first 50 h of operation. The developed model shows that the reliability of the hydraulic system reduces to a zero value after approximately 1 650 hours of operation. The failure rate of this system decreases when time increases. Therefore, corrective maintenance （run-to-t^ailure） was selected as the best maintenance strategy for it.

Particle breakage of sand subjected to friction and collision in drum tests

This paper presents a laboratory experimental study on particle breakage of sand subjected to friction and collision,by a number of drum tests on granular materials(silica sand No.3 and ceramic balls)to investigate the characteristics of particle breakage and its effect on the characteristics of grain size distribution of sand.Particle breakage increased in up convexity with increasing duration of drum tests,but increased linearly with increasing number of balls.Particle breakage showed an increase,followed by a decrease while increasing the amount of sand.There may be existence of a characteristic amount of sand causing a maximum particle breakage.Friction tests caused much less particle breakage than collision tests did.Friction and collision resulted in different mechanisms of particle breakage,mainly by abrasion for friction and by splitting for collision.The fines content increased with increasing relative breakage.Particle breakage in the friction tests(abrasion)resulted in a sharper increase but with a smaller total amount of fines content in comparison with that in the collision tests(splitting).For the collision tests,the fines content showed a decrease followed by an increase as the amount of sand increased,whereas it increased in up convexity with increasing number of balls.The characteristic grain sizes D_(10) and D_(30) decreased in down convexity with increasing relative breakage,which could be described by a natural exponential function.However,the characteristic grain sizes D50 and D60 decreased linearly while increasing the relative breakage.In addition,the coefficients of uniformity and curvature of sand showed an increase followed by a decrease while increasing the relative breakage.

The Mathematical Simulation of Brush Drums in a Dual Saw Cylinder Chamber Gin for the Purpose of Increasing the Quantity of Captured Cotton Fiber from Saw

An analysis of the efficiency of the ginning of cotton fibers with two saw cylinders has been carried out. In comparison to a one-cylinder machine, the 2 cylinder approach can help to preserve the natural characteristics of cotton fiber and seeds. This technology allows economizing electricity and decreasing damage to fiber and also increases the productivity of the machine.

An inverse method for online stress monitoring and fatigue life analysis of boiler drums

A method based on solution of the inverse heat conduction problem was presented for online stress monitoring and fatigue life analysis of boiler drums. The mathematical model of the drum temperature distribution is based on the assumptions that the difference of temperature along the longitudinal axis of the boiler drum is negligible with changes only in the radial direction and the circumferential direction, and that the outer surface of drum is thermaUy insulated. Combining this model with the control-volume method provides temperatures at different points on a cross-section of the drum. With the temperature data, the stresses and the life expectancy of the boiler drum are derived according to the ASME code. Applying this method to the cold start-up process of a 300 MW boiler demonstrated the absence of errors caused by the boundary condition assumptions on the inner surface of the drum and testified that the method is an applicable technique for the online stress monitoring and fatigue life analysis of boiler drums.

Reliability and maintainability analysis of electrical system of drum shearers

The reliability and maintainability of electrical system of drum shearer at Parvade. 1 Coal Mine in central Iran was analyzed. The maintenance and failure data were collected during 19 months of shearer operation. According to trend and serial correlation tests, the data were independent and identically distributed （iid） and therefore the statistical techniques were used for modeling. The data analysis show that the time between failures （TBF） and time to repair （TTR） data obey the lognormal and Weibull 3 parameters distribution respectively. Reliability-based preventive maintenance time intervals for electrical system of the drum shearer were calculated with regard to reliability plot. The reliability-based maintenance intervals for 90%, 80%, 70% and 50% reliability level are respectively 9.91, 17.96, 27.56 and 56.1 h. Also the calculations show that time to repair （TTR） of this system varies in range 0.17-4 h with 1.002 h as mean time to repair （MTTR）. There is a 80% chance that the electrical system of shearer of Parvade. 1 mine repair will be accomplished within 1.45 h.

Factors affecting thin coal seam shearer drum coal-loading performance by a model test method

To solve the problem of a low coal-loading rate being exhibited by the drum shearer on Chinese thin coal seams,systematic tests and research were performed to study the pivotal factors’influences on drum coal-loading rate using a model test method.The effects of the drum hub diameter,cutting depth,vane helix angle,drum rotation speed and hauling speed on drum coal-loading rate were determined under circumstances of coal-loading with drum ejection and pushing modes,and reasons for these phenomena were analyzed.The results indicate that the influence of the drum cutting depth on the drum coal-loading rate is the most significant.The parameters of hub diameter,drum rotation speed and hauling speed can influence the drum coal-loading rate by cutting the coals’filling rate in the drum.The parameters of vane helix angle and drum rotation speed can influence drum coal-loading rates by influencing the ratio of cutting coals’tangential and axial speed in the drum.The coal-loading rate with drum ejection is clearly higher than that observed with drum pushing.Research in this study can provide support to design the drum structure and select drum operational parameters for a thin coal seam shearer.