Progression of mid-tropospheric stable layer over Delhi region during May 1989 –A case study

The paper presents details of the formation and di~sipa1ion of upper air inversions between 500 and 300 hPa from 20 to 28 May 1989 over Delhi and adjoining areas and discusses the associated synoptic features.

Enhancement of Flotation Performance of Oxidized Coal by the Mixture of Laurylamine Dipropylene Diamine and Kerosene

Conventional hydrocarbon oil cannot adhere effectively to oxidized coal, resulting in a low yield of clean coal. In this study, a high-speed homogenizer was used to emulsify LDD (laurylamine dipropylene diamine) and kerosene, which enhanced the flotation efficiency of oxidized coal. The flotation results showed an increase from 4.12% (only kerosene) to 23.33% (emulsified oil). An increase in contact angle indicated that the mixture reagent can increase the hydrophobicity of coal particles, which is attributed to the adsorption of LDD onto the coal particle surface and the decrease of the oil droplet A lower surface tension of LDD allows it to produce a stable layer of froth than the layer generated by kerosene alone.

STUDI FONDASI TIANG BOR UNTUK JEMBATAN DI LAUT

Structurally, the bridge is separated into the upperstructure, and substructure such as foundation. According to its function, the foundation of the bridge supports and transmits the load from the superstructure to a strong and stable layer of soil. The construction of a bridge at sea has a high level of difficulty and risk. There are forces that influence the foundation at sea. The greater the loads that are held by the foundation, the greater the bearing capacity required for the foundation. The foundation used the bored pile casing method. The concept of a bored pile foundation casing method itself uses a steel casing pipe that is installed to a specified depth. This method is used when the borehole is very prone to landslides, so it is very suitable to be applied to soil which is sand below the groundwater level or at sea. In this paper, we will discuss the bearing capacity of the bored pile foundation and the loads that affect the bearing capacity of the foundation. Bearing capacity includes axial and lateral bearing capacity. So the results of this study will show how much effective bearing capacity must be considered when creating a foundation for bridges at sea.Secara struktural jembatan dipisahkan menjadi struktur atas, dan struktur bagian bawah seperti fondasi. Sesuai fungsinya, fondasi jembatan menopang dan meneruskan beban dari bangunan atas jembatan ke lapisan tanah yang kuat dan stabil/solid. Pembangunan jembatan panjang di tengah laut memiliki tingkat kesulitan dan resiko tinggi. Terdapat gaya-gaya yang mempengaruhi fondasi yang dibuat di laut. Semakin besar beban-beban yang ditahan fondasi maka semakin besar pula daya dukung yang dibutuhkan fondasi. Fondasi yang dipakai adalah fondasi tiang bor dengan metode casing. Konsep dari fondasi tiang bor metode casing sendiri menggunakan pipa selubung baja (casing) yang diinstall sampai kedalaman yang ditentukan. Metode ini digunakan bila lubang bor sangat mudah longsor, sehingga sangat cocok untuk diaplikasikan pada tanah yang merupakan pasir di bawah muka air tanah atau di laut. Pada penulisan ini akan dibahas mengenai daya dukung fondasi tiang bor dan beban-beban yang mempengaruhi daya dukung fondasi tersebut. Daya dukung mencakup daya dukung aksial dan lateral. Sehingga hasil studi ini akan menunjukan seberapa besar daya dukung efektif yang harus dipertimbangkan pada saat ingin membuat fondasi untuk jembatan di laut.

Failure Analysis and Control Measures of Deep Roadway with Composite Roof: A Case Study

There is great variation in the lithology and lamination thickness of composite roof in coal-measure strata; thus, the roof is prone to delamination and falling, and it is difficult to control the surrounding rock when developing roadway in such rock strata. In deep mining, the stress environment of surrounding rock is complex, and the mechanical response of the rock mass is different from that of the shallow rock mass. For composite-roof roadway excavated in deep rock mass, the key to safe and efficient production of the mine is ensuring the stability of the roadway. The present paper obtains typical failure characteristics and deformation and failure mechanisms of composite-roof roadway with a buried depth of 650 m at Zhaozhuang Coal Mine (Shanxi Province, China). On the basis of determining a reasonable cross-section shape of the roadway and according to the failure characteristics of the composite roof in different regions, the roof is divided into an unstable layer, metastable layer, and stable layer. The controlled unstable layer and metastable layer are regarded as a small structure while the stable layer is regarded as a large structure. A superimposed coupling support technology of large and small structures with a multi-level prestressed bearing arch formed by strong rock bolts and highly prestressed cable bolts is put forward. The support technology provides good application results in the field. The study thus provides theoretical support and technical guidance for ground control under similar geological conditions.

Dynamic flows create potentially habitable conditions in Antarctic subglacial lakes

Trapped beneath the Antarctic ice sheet lie over 400 subglacial lakes, which are considered to be extreme, isolated, yet viable habitats for microbial life. The physical conditions within subglacial lakes are critical to evaluating how and where life may best exist. Here, we propose that Earth’s geothermal flux provides efficient stirring of Antarctic subglacial lake water. We demonstrate that most lakes are in a regime of vigorous turbulent vertical convection, enabling suspension of spherical particulates with diameters up to 36 micrometers. Thus, dynamic conditions support efficient mixing of nutrient- and oxygen-enriched meltwater derived from the overlying ice, which is essential for biome support within the water column. We caution that accreted ice analysis cannot always be used as a proxy for water sampling of lakes beneath a thin (<3.166 kilometers) ice cover, because a stable layer isolates the well-mixed bulk water from the ice-water interface where freezing may occur.

GRAPHYNE LAYERS FORMED ON THE BASIS OF 5 - 7 GRAPHENE LAYERS

Методом молекулярной механики MM2 рассчитана геометрически оптимизированная структура 43 новых полиморфных разновидностей L графиновых слоев, модельно сформированных на основе слоев 5 - 7 графена. Установлено, что возможно существование 3 полиморфных разновидностей α типа и по 20 разновидностей β и Ɣ типов. Наиболее устойчивым должен быть слой Ɣ1 - L, так как у него минимальный параметр деформации Def = 9,0 °. Новые полиморфы графина могут найти практическое применение в качестве молекулярных сит или адсорбентов водорода. The geometrically optimized structure of 43 new polymorphic varieties of L- graphyne layers modeled on the basis of layers 5 - 7 of graphene has been calculated by the method of MM2 molecular mechanics. It was found that 3 polymorphic varieties of α type and 20 varieties of β and Ɣ types are possible. The Ɣ1 - L is the most stable layer since it has the minimal deformation parameter Def = 9,0 °. Practical applications of new graphyne polymorphs can be used for molecular sieves or hydrogen adsorbents.

Analysis of Back-Building Convection in Simulations with a Strong Low-Level Stable Layer

In a mesoscale convective system (MCS), convection that redevelops over (i.e., back-builds), and/or repeatedly passes over (i.e., trains) a region for an extended period of time can contribute to extreme rainfall and flash flooding. Past studies have indicated that both mesoscale ascent and lifting of the inflow layer by a cold pool or bore are important when this back-building/training convection is displaced from the leading line [sometimes called rearward off-boundary development (ROD)]. However, Plains Elevated Convection At Night (PECAN) field campaign observations suggest that the stability of the nocturnal boundary layer is highly variable and some MCSs with ROD have only a weak surface cold pool. Numerical simulations presented in this study suggest that in an environment with strong boundary layer stability, ROD can be supported by mechanisms other than those mentioned above. Simulations were initialized using a sounding from ahead of a PECAN MCS with a strong stable layer and ROD, and the three-dimensional simulation produced an MCS similar to that observed despite the homogeneous initial conditions. Some of the findings presented herein challenge existing understanding of nocturnal MCSs, and especially how downdrafts interact with a stable boundary layer. Notably, downdrafts can reach the surface, and different regions of the MCS may have different propagation mechanisms and different relevant inflow layers. Unlike previous studies of ROD, parcel lifting may be supported by an intrusion (an elevated layer of downdraft air) modified by the three-dimensional vertical wind shear.

HAFNIUM AND NITROGEN INTERACTION AT Hf/GaN(0001) INTERFACE

The growth and stability of hafnium films on [Formula: see text]-GaN(0001) surface with native oxide was investigated with X-ray and ultraviolet photoelectron spectroscopy (XPS, UPS). It is shown that hafnium creates a continuous and stable layer on GaN substrate. Thermal treatment at [Formula: see text]C of Hf/GaN system causes decomposition of GaN and reaction of hafnium with atomic nitrogen from the substrate. XPS spectra demonstrate the reaction by a strong shift of the N 1s and Hf 4f lines. An attempt for bringing on the same reaction with molecular nitrogen under pressure of [Formula: see text] mbar was not successful. UPS spectra show a metallic character of the hafnium adlayer in such instances.