Rock excavation using surface miners: An overview of some design and operational aspects

Surface miner, a continuous mining machine, is being manufactured in India and abroad owing to enhanced demand of production in various mining industries like coal, limestone, gypsum, bauxite etc. Different types of surface miners are manufactured today based on cutting drum placement and design specifications. Selective mining without drilling and blasting, high production and small size products are some of the prominent attractive features obtained with these moving marvels. This machine can be used with good efficiency in soft to medium hard rock (100-120 MPa). This paper synthesizes the different applications, equipment models, features offered, operating methods, cutting performance assessment models as well as typical production performance of surface miner in coal and limestone mines of India. Engine hour metre reading, diesel and pick consumptions are linearly influenced by production. The emphasis for future research is also brought out.

The Features and Patterns of Revision Process in English Learners＇ Writing

Revision is an important part of writing process but it often baffles the researchers due to the difficulties in recording the revision process of students. Based on a self-made questionnaire and the online record of the revision process, this study describes the English learners＇ revision behaviors and process in their second semester of a two-year writing course. The analysis indicates that the English learners hold a positive attitude towards revision and but passive in resorting to outside sources for help. The source of the feedback has a great influence on their motivation of revision. On the other hand, although they use all types of revision operations, they concentrate on surface changes and simple operations.

Sensing Thermal Underground Transients of Buried Wired Structures

Mathematical investigations of the dynamic response of buried systems to thermal and/or electromagnetic stimulation continues to be of great importance. The size of such systems can range from the microelectronic scale to large underground structures. Stimulation can occur from unwanted electromagnetic signals entering the buried system, and for assessing the operating state of a buried system that is not usually physically accessible. In both cases detecting damage or status can be accomplished by examining the time dependence of the resultant surface temperature. This study shows how to determine surface temperature for a hypothetical thermal-plus-systems using a combination of Fourier-space and Laplace-time transform techniques. The hypothetical model can be generalized from scaling the relevant relationships.

Effect of thermal storage performance of concrete radiant cooling room on indoor temperature

A building model with radiant cooling system was established and the cooling load, indoor temperature, surface temperature of the wails and other parameters in non-cooling and radiant cooling room were calculated by TRNSYS. The comparative analysis of the characteristics of attenuation and delay proves that the operation of radiant cooling system increases the degree of temperature attenuation of the room and reduces the inner surface temperature of the wall significantly, but has little effect on the attenuation coefficient and delay time of wall heat transfer. The simulation results also show that the inner surface temperature of the walls in the radiant cooling room is much lower than that in non-cooling room in the day with the maximum cooling load, which reduces the indoor operation temperature largely, and improves the thermal comfort. Finally, according to the analysis of indoor temperature of the rooms with different operation schedules of cooling system, it can be derived that the indoor mean temperature changes with the working time of radiant cooling system, and the operation schedule can be adjusted in practice according to the actual indoor temperature to achieve the integration of energy efficiency and thermal comfort.

管45°药芯焊丝CO2气体保护焊焊接技术

本文通过对全国焊工比赛项目药芯焊丝CO2气体保护焊操作技术的摸索和实践,采用一定的操作手法,在保证焊道内部质量的前提下获得了满意的表面成形。

一种改进的动态格子算法在Au团簇基态结构预测中的应用

借助计算机强大的计算能力通过数学的方法预测团簇的最低能量结构,是本文的主要思想和工作.针对Au团簇的结构优化问题,本文提出了一种改进的动态格子搜索算法.将该算法用于Gupta势能建模的Au团簇对其进行优化求解,在若干国际已知算例上,找到了它们其中许多新的最低能量结构.为了用Gupta势能描述Au团簇原子之间的相互作用,本文采用了两组不同的参数.利用参数一(A=0.11844,B=1,p=10.15,q=4.13),优化了原子数N=38?100的Au团簇.其中,对于原子数N=38,55这两个算例,本文算法的结果优于此前文献中的最好结果.另外,利用参数二(A=0.2061,B=1.79,p=10.229,q=4.036),优化了原子数N=100?200的Au团簇,其中对于原子数N=100,110,120,130,140,150,160,170,180,190,200的Au团簇,本文算法所达到的势能均优于此前文献中的最好结果.结果表明了本文算法对于团簇结构优化问题求解的高效性.

连接CAD与CAM的桥梁──SIGRAPH－NC系统

连接ＣＡＤ与ＣＡＭ的桥梁──ＳＩＧＲＡＰＨ－ＮＣ系统ＳＩＧＲＡＰＨ—ＮＣ是西门子利多富公司开发的可供数据机床实现江经的编程软件，是连接ＣＡＤ与ＣＡＭ的桥梁．１９ｏｐＡＰＨ—ＣＡＤ—ＺＤＳＩＧＲＡＰＨ的二维ＣＡＤ具有ＳｌｏｐＡＰＨ—ＣＡＤ—Ａ这样的编制...

Existence of solutions to a class of Kazdan-Warner equations on compact Riemannian surface

Let （∑, g） be a compact Riemannian surface without boundary and λ1（∑） be the first eigenvalue of the Laplace-Beltrami operator △g. Let h be a positive smooth function on ∑. Define a functional （Jα,β（u）=1/2∫∑（｜ gu｜2）dvg-βlog∫heudvg）on a function spaceH={u∈W1,2（∈）：∫∑UDVG=0}.Ifα〈λ1（∑）and Jα,8π has no minimizer on H, then we calculate the infimum of Jα,8π on H by using the method of blow-up analysis. As a consequence, we give a sufficient condition under which a Kazdan-Warner equation has a solution. If α≥ λ1（E）, then infu∈Hα,8π（u）=-∞.Ifβ〉8π ,then for any α ∈ R, there holds infu∈HJα,8π（u）=-∞. Moreover, we consider the same problem in the case that α is large, where higher order eigenvalues are involved.

Coupling Distant Spins of Surface-State Electrons by Manipulating Their Collective Vibrations

The system of electrons on liquid helium is an interesting candidate to implement quantum computation, due to the long coherence times of the qubits encoded by the electronic spins. In order to implement the quantum logic operations between the spins, we propose here a configuration, similarly to the cooled ions in a trap, to couple the distant electrons via manipulating their center of mass （CM） vibrations. First, we show that the electrons could be confined in a common harmonic oscillator potential by using an electrostatic field. Then, with a single current pulse （applied on the micro-electrode below the liquid helium） the distant electronic spins can be coupled simultaneously to the CM mode. Finally, by adiabatically eliminating the CM mode, effective interaction between the distant spins is induced for implementing the desired quantum computing.

On region crossing change and incidence matrix

In a recent work of Ayaka Shimizu, she studied an operation named region crossing change on link diagrams, which was proposed by Kishimoto, and showed that a region crossing change is an unknotting operation for knot diagrams. In this paper, we prove that the region crossing change on a 2-component link diagram is an unknotting operation if and only if the linking number of the diagram is even. Besides, we define an incidence matrix of a link diagram via its signed planar graph and its dual graph. By studying the relation between region crossing change and incidence matrix, we prove that a signed planar graph represents an n-component link diagram if and only if the rank of the associated incidence matrix equals c n + 1, where c denotes the size of the graph.

Towards the manipulation of topological states of matter： a perspective from electron transport

The introduction of topological invariants, ranging from insulators to metals, has provided new insights into the traditional classification of electronic states in condensed matter physics. A sudden change in the topological invariant at the boundaw of a topological nontrivial system leads to the formation of exotic surface states that are dramatically different from its bulk. In recent years, significant advancements in the exploration of the physical properties of these topological systems and regarding device research related to spintronics and quantum computation have been made. Here, we review the progress of the characterization and manipulation of topological phases from the electron transport perspective and also the intriguing chiral/Majorana states that stem from them. We then discuss the future directions of research into these topological states and their potential applications.

Realization approach of Pd-only three-way catalysts with high catalytic performance and thermal stability

Pd-only three-way catalyst （TWC）, Pd supported on washcoating （the mixture of alumina and Ce-Zr solid solution）/cordierite, was prepared and its catalytic performance and the operation window （2-value） at 450 ℃ were evaluated with the simulated automotive exhaust feed gas. Surfactants such as Tween-80 and Span-20 were added in the process of preparing the catalyst in order to improve the thermal stability and catalytic performance of Pd-only TWC. The fresh and aged catalysts at 1000 ℃ for 4 h were characterized by low-temperature N2 adsorption, XRD, XPS, and H2-TPR techniques. The results show that the presence of surfactants in the synthesis slurry could influence the physicochemical properties of the final Pd-only TWC. The FTS catalyst prepared with the mixed surfactant of Tween-80 and Span-20 exhibited excellent three-way catalytic performance. After being aged at 1000℃ for 4 h, the catalytic performances of Pd-only TWCs slightly decreased, but the FTS catalyst still demonstrated higher catalytic performance and better thermal stability compared with the Pd-only catalysts prepared with single surfactant or without any surfactant. And the FTS catalyst has a wider 2 value （operation window） than other catalysts, even after being aged at 1000℃.