小直径长距离泥水盾构滚刀失效分析以及改进措施

以某输气管道越江工程盾构施工过程中的盘形滚刀失效为例,对盘形滚刀在破岩过程中所受到的破岩载荷进行分析。基于滚刀所受到的破岩载荷联系实际工程中的滚刀失效情况,分别对滚刀轴承散架、刀圈失效、刀圈断口的SEM图进行分析,利用所得到的滚刀失效原因对现场施工提出了提高刀盘转速以降低刀盘推力的方案。经过掘进后发现,滚刀损坏情况减缓,节约了施工成本。此类盾构施工具有更多的推广价值。

起床真有趣

'丁零零……'小闹钟又响了,妈妈起床了,开始施展她的第一法术——响音术。妈妈首先把音乐打开,声音调到最高。我被音乐声吵醒了,只好把脑袋硬躲在被子下面。睡不着,还是快快出来认输吧.我只好起床了。妈妈又开始了训斥模式。我现在只好快速地穿上衣服和裤子。哎呀.裤子穿反了,屁股搬家啦.我像一个快要散架的骨头人,懒洋洋地走进了洗手间。

喝水的感觉,真好

今天我照例去学羽毛球,同学们一到齐,便开始训练了。跑步、高远球、后场击球步伐……二十来个回合下来,我们一个个张大了嘴巴,热得汗流浃背、气喘吁吁。老师看到我们都筋疲力尽,终于喊了一声'停'。

A Simplified Expression for a Diffusion-Dissolution Con-trolled Release of Drug from Matrix in TDDS

Chandrasekran-paul (1982) made an equation of drug release from matrix system as follows:In this paper a simplified expression has been deduced from it within ordinary range of experimental time and with appropriate values of K. The cumulative amount of drug release may vary in directproportion to the square root of time with an intercept,that is,The release behaviour of both nifedipine patch and propranolol patch has fit the expression with good correlation coefficient.The re0lease data of hydrocortisone creams (Shah,1989)also can be described by the same expression.Compared with Higuchi’s equation,the presence of the intercept,A〃,may be relative to drug dissolution characteristics

A Generalized Limit Equilibrium Method for the Solution of Active Earth Pressure on a Retaining Wall

In this paper, a generalized limit equilibrium method of solving the active earth pressure problem behind a retaining wall is proposed.Differing from other limit equilibrium methods, an arbitrary slip surface shape without any assumptions of pre-defined shapes is needed in the current framework, which is verified to find the most probable failure slip surface. Based on the current computational framework, numerical comparisons with experiment, discrete element method and other methods are carried out. In addition, the influences of the inclination of the wall, the soil cohesion, the angle of the internal friction of the soil, the slope inclination of the backfill soil on the critical pressure coefficient of the soil, the point of application of the resultant earth pressure and the shape of the slip surface are also carefully investigated. The results demonstrate that limit equilibrium solution from predefined slip plane assumption, including Coulomb solution, is a special case of current computational framework. It is well illustrated that the current method is feasible to evaluate the characteristics of earth pressure problem.

Pickering interfacial biocatalysis with enhanced diffusion processes for CO_(2) mineralization

Utilization of carbon dioxide(CO_(2))has become a crucial and anticipated solution to address environmental and ecological issues.Enzymes such as carbonic anhydrase(CA)can efficiently convert CO_(2) into various platform chemicals under ambient conditions,which offers a promising way for CO_(2) utilization.Herein,we constructed a Pickering interfacial biocatalytic system(PIBS)stabilized by CA‐embedded MOFs(ZIF‐8 and ZIF‐L)for CO_(2) mineralization.Through structure engineering of MOFs and incorporation of Pickering emulsion,the internal and external diffusion processes of CO_(2) during the enzymatic mineralization were greatly intensified.When CO_(2) was ventilated at a flow rate of 50 mL min^(–1) for 1 h,the pH value of PIBS dropped from~8.00 to~6.50,while the average pH value of free system only dropped to~7.15,indicating that the initial reaction rate of CO_(2) mineralization of PIBS is nearly twice that of the free system.After the 8^(th) cycle reaction,PIBS can still produce more than 9.8 mg of CaCO_(3) in 5 min,realizing efficient and continuous mineralization of CO_(2).

Detection of Tetracycline Antibiotics in Water by Dispersive Micro-solid Phase Extraction using Fe_(3)O_(4)@[Cu_(3)(btc)_(2)]Magnetic Composite Combined with Liquid Chromatography-Tandem Mass Spectrometry

Residues of tetracycline antibiotics(TCs) in environments may be harmful to human.Due to their high polarities,it is extremely challenging to efficiently enrich TCs with low concentrations in natural waters for analysis.In this work,a magnetic metal-organic framework Fe_(3)O_(4)@[Cu_(3)(btc)_(2)]was synthesized and applied as a dispersive micro-solid phase extraction adsorbent for TCs enrichment.Effects of dispersive micro-solid phase extraction conditions including extraction time,solution p H,and elution solvent on the extraction efficiencies of TCs were investigated.Results show that TCs could be enriched efficiently by Fe_(3)O_(4)@[Cu_(3)(btc)_(2)],and electrostatic interaction between TCs and Fe_(3)O_(4)@[Cu_(3)(btc)_(2)]dominated this process.Combined with liquid chromatography-tandem mass spectrometry,four TCs residues (oxytetracycline,tetracycline,chlortetracycline,and doxycycline) in natural waters were determined.The detection limits (LOD,S/N=3) of the four antibiotics were 0.01-0.02μg/L,and the limits of quantitation (LOQ,S/N=10)were 0.04-0.07μg/L.The recoveries obtained from river water and aquaculture water spiked with three TCs concentration levels ranged from 70.3%to 96.5%with relative standard deviations of 3.8%-12.8%.Results indicate that the magnetic metal-organic framework based dispersive micro-solid phase extraction is simple,rapid and high-loading for antibiotics enrichment from water,which further expand the practical application of metal-organic frameworks in sample pretreatment for environmental pollutant analysis.

Design of Dissipative Braces for an Existing Strategic Building with a Pushover Based Procedure

The research presented in this paper deals with the seismic protection of existing frame structures by means of passive energy dissipation. An iterative displacement-based procedure, based on capacity spectrum, to design dissipative bracings for seismic retrofitting of the frame structures is described, and some applications are discussed. The procedure can be used with any typology of dissipative device and for different performance targets. In this work, the procedure has been applied, with both traditional pushover （load profile proportional to first mode） and multimodal pushover, to an existing RC （reinforced concrete） frame building. In the application, the buckling restrained braces have been used in order to prevent damages to both the structure and non structural elements. The use of multimodal pushover proves to be more effective than pushover based on single mode in case of medium rise RC frame building （higher than 30 m） but, once this building is retrofitted, and therefore regularized, with a bracing system, the difference between using monomodal or multimodal pushover becomes insignificant.

Effect of the Molecular Structure of Polymer Dispersants on Limestone Suspension Properties in Fine Grinding

Polymer dispersants are widely used as grinding aids to reduce the viscosity of mineral particle suspensions and to improve energy efficiency during fine grinding. The authors studied here the effects of polymer dispersants of different molecular structure on limestone suspension properties in wet stirred media milling. The polymers differed in their molecular weight and PDI （polydispersity index）. Two traditionally fractionated polymer dispersants having a high PDI （over 2） and one made by controlled radical polymerization having a low PDI （1.2） were tested. It was noticed that these dispersants worked as electrosteric stabilizers and prevented the agglomeration of ground limestone particles. Their addition allowed increased solids concentrations to be used in the grinding experiments and at the same time lowered the particle size and specific energy consumption. The particle sizes obtained were about 1 μm regardless of the dispersant or its dose. The dispersant with a low PDI reduced the viscosity more than did the high PDI dispersants. The results indicate that higher solids concentrations can be used at the same dispersant dose when a low PDI dispersant is used, leading to energy savings via increased throughput. Alternatively, a lower dose of low PDI polymer dispersant than of a high PDI polymer dispersant can be used at the same solids concentration.

Advances in numerical simulation of demolition blasting

The applications of numerical simulation in demolition blasting were reviewed.Several methods of numerical simulation in demolition blasting were introduced.The strength and weakness of the numerical methods mentioned in this paper were also indicated,respectively.Furthermore,the solid lattice model in the frame of discrete element method(DEM),which was developed by the author and his team,was detailedly described.The existed problems in the current numerical simulation methods of demolition blasting were presented and the future trend of the numerical simulation is finally prospected.

天嚣

名作介绍:《天嚣》这是一篇歌颂科考队员群体以及蒙古族普通百姓的优秀小说,歌颂了队员们不畏艰难困苦,直面恶劣天气,保护科研资料的大无畏英雄气概,也歌颂了蒙古族人们关心科考队员、善良奉献的精神。风,像浪一样,梗着头向钢架房冲撞。钢架房,便发疟疾般地一阵阵战栗、摇晃,像是随时都要散架。(开篇运用比喻修辞手法,表现风凶猛的特点。)

尽职的老衣架

'咔嚓——'天上闪过一道刺眼的闪电,照亮了一栋门窗紧闭的房子,仔细一看,阳台上还挂着一个衣架,正在瑟瑟发抖。这个衣架的表面已不再光滑,假如你靠近它仔细听,还会听到几声微弱的咳嗽声。第二天,雨过天晴。主人打开紧闭的门窗,想要透透气。这时飞来了一只小鸟,它看见了那年老的衣架,劝说道':你已经奉献了青春,可以光荣退役了。'小猫听了也说:'你随时都会散架,还不如早点儿退役,对主人对你都好。'

笑笑笑话

变相加班老乖一般不会让大家加班,只会星期五给布置个任务,然后叮嘱你周末好好休息,东西不急,星期一上班前给她看就行。散架了出奇买了个魔方,他研究了大半天,一点儿头绪都没有。得意不屑地看了他一眼,接过魔方说:'笨死了,看我的.'然后,双手如电般旋转……看得出奇眼花缭乱。突然……得意把魔方扭散架了.!

Estimates on the amplitude of the first Dirichlet eigenvector in discrete frameworks

Consider a finite absorbing Markov generator, irreducible on the non-absorbing states. PerronFrobenius theory ensures the existence of a corresponding positive eigenvector ψ. The goal of the paper is to give bounds on the amplitude max ψ/ min ψ. Two approaches are proposed: One using a path method and the other one, restricted to the reversible situation, based on spectral estimates. The latter approach is extended to denumerable birth and death processes absorbing at 0 for which infinity is an entrance boundary. The interest of estimating the ratio is the reduction of the quantitative study of convergence to quasi-stationarity to the convergence to equilibrium of related ergodic processes, as seen by Diaconis and Miclo(2014).

Multi-window Gabor frames and oblique Gabor duals on discrete periodic sets

Given L, N, M ∈ N and an NZ-periodic set S in Z, let l2(S) be the closed subspace of l2(Z) consisting of sequences vanishing outside S. For f = { fl : 0≤l≤L-1 }l2(Z), we denote by G(f, N, M) the Gabor system generated by f, and by L(f, N, M) the closed linear subspace generated by G(f, N, M). This paper addresses density results, frame conditions for a Gabor system G(g, N, M) in l2(S), and Gabor duals of the form G(a, N, M) in some L(h, N, M) for a frame G(g, N, M) in l2(S) (so-called oblique duals). We obtain a density theorem for a Gabor system G(g, N, M) in l2(S), and show that such condition is suficient for theexistence of g={XE1:0≤l≤L-1} with G(g,N,m) We characterize g with G(g,N,m) being respectively a frame for L(g,N,m) being a tight frame for l2(S).and G(h, N, M ) in L(h, N, M ), we establish a criterion for the existence of an oblique Gabor dual of g in L(h, N, M), study the uniqueness of oblique Gabor dual, and derive an explicit expression of a class of oblique Gabor duals (among which the one with the smallest norm is obtained). Some examples are also provided.

A novel de novo mutation of ACTG1 in two sporadic non-syndromic hearing loss cases

Dear Editor,Actins are a family of essential cytoskeletal proteins involved in nearly all cellular processes（Lambrechts et al.,2004）.Of the six human genes that encode actins,only ACTG1and ACTB are ubiquitously expressed.ACTG1（OMIM#604717）,which is linked to the DFNA20/26 locus,wasidentified in autosomal dominant, non-syndromic hearing loss （NSHL） cases （Baek et al., 2012; Liu et al., 2008; Park et al., 2013; Yuan et al., 2016）. In addition, some ACTG1 （OMIM #614583） mutations are associated with Baraitser-Winter syndrome, which is characterized by developmental delay, facial dysmorphologies, brain malformations, colobomas, and variable hearing loss （Riviere et al., 2012）.