Effect of Mining Thickness on Overburden Movement and Underground Pressure Characteristics for Extrathick Coal Seam by Sublevel Caving with High Bottom Cutting Height

Because the coal seam is particularly thick and the mining intensity is large, the mining of extremely thick coal seams often causes a wide range of disturbed fractures, which in turn induces the phenomenon of strong underground pressure such as induced support crushing and water inrush. Through theoretical analysis, laboratory similarity simulation test, and other methods, this paper studies the effect of mining thickness on overburden movement and underground pressure characteristics for extremely thick coal seams by sublevel caving with high bottom cutting height. Some conclusions can be drawn as follows: (i) under the “beam-hinged cantilever beam rocks” structure theory, the rock pillar thickness which needs to be controlled increases linearly as a function of mining thickness is achieved, and the reason of increased of support resistance in full-mechanized caving mining in extremely thick seams is explained in the theory; (ii) based on the results of the theoretical analysis and the lab simulation tests, the law of the abutment pressure peak is inverse to the full-seam mining thickness, and the distance between abutment peak and working face is proportional to the full-seam mining thickness, that is to say that the damage range of overlying strata increased; (iii) there are three working states of loading support in extrathick coal seams, such as normal circumstance, lower main roof pressure, and higher main roof pressure, meanwhile these states keep changing; (iv) under the guarantee of stope safety conditions, due to lower support strength, it will benefit the special thick seam top-coal caving under normal circumstance; (v) increasing the supporting strength can balance the impact loading under the lower main roof pressure, guaranteeing valid support for roof strata; (vi) by releasing high pressure, due to lower production, lower recovery rate of coal and other measures guarantee the stability of the stope support in the case of the higher main roof pressure.

Approximate Analyzing of Labeled Transition Systems

As the most important formal semantic model, labeled transition systems are widely used, which can describe the general concurrent systems or control systems without disturbance. However, under normal circumstance, transition systems are complex and difficult to use due to large amount of calculation and the state space explosion problems. In order to overcome these problems, approximate equivalent labeled transition systems are proposed by means of incomplete low-up matrix decomposition factorization. This technique can reduce the complexity of computation and calculate under the allowing errors. As for continuous-time linear systems, we develop a modeling method of approximated transition system based on the approximate solution of matrix, which provides a facility for approximately formal semantic modeling for linear systems and to effectively analyze errors. An example of application in the context of linear systems without disturbances is studied.

Study on the Purification Effect of Chlorophytum Comosum on Indoor Formaldehyde

In order to investigate the effect of absorption and purification of indoor formaldehyde by chlorophytum comosum under normal circumstance, chlorophytum comosum is used as the test material and formaldehyde concentration of different closure time is measured by indoor formaldehyde velocimeter. Absorptive capacity of chlorophytum comosum on indoor formaldehyde is analyzed by comparing formaldehyde concentration. The results of experiment show that taking closure time of 24h as an example formaldehyde concentration changes from 0.41 mg/m3 to 0.32 mg/m3 and the removal rate is 21.95% in the room of 15 square meters ,and absorption effect of chlorophytum comosum is good for indoor formaldehyde. Combined with the actual situation chlorophytum comosum can be used in the room place and decorative materials with less formaldehyde content are chosen ,and indoor temperature and humidity remain appropriate to purify indoor formaldehyde by combining with the ventilation method.

Reduction-Triggered Breakable Micelles of Amphiphilic Polyamide Amine-g-Polyethylene Glycol for Methotrexate Delivery

Reduction-triggered breakable polymeric micelles incorporated with MTX were prepared using amphiphilic PAA-g-PEG copolymers having S–S bonds in the backbone. The micelles were spherical with diameters less than 70 nm. The micelles could encapsulate the hydrophobic MTX in the hydrophobic core. The drug loading content and drug loading efficiency of the micelles were highly dependent on the copolymer chemical structure, ranging from 2.9 to 7.5% and 31.9 to 82.5%, respectively. Both the drug loading content and drug loading efficiency increased along with more hydrophobic segments in the copolymers. In normal circumstance, these micelles were capable of keeping stable and hold most of the MTX in the core, stabilizing the incorporated MTX through theπ-πstacking with the phenyl groups in the backbone of the copolymers. In reductive environments that mimicked the intracellular compartments, the entire MTX payload could be quickly released due to the reduction-triggered breakage of the micelles. These micelles showed good antiproliferative activity against several cancer cell lines, including KB, 4T-1 and HepG2, especially within the low drug concentration scope.

A New Front-End Anonymity and Back-End Real-Name Mechanism in e-Commerce

In this paper, we propose a new approach using both the Citizen Digital Certificate and anonymous identification to fulfill the back-end real-name and front-end anonymous verification requirements in an online transaction. Anonymous identification is a simple design to establish the link between the real name and the pseudonym (account ID) selected by the user during the registration, in which the reverse-lookup is not allowed so that the anonymous verification is achieved. The back-end real-name mechanism in this model plays an important role which requires total fairness and trust. Thus, we use the government MOICA as the trust back-end platform, which issues the Citizen Digital Certificate and thus will have the user’s real-name. The main purpose of the front-end anonymity mechanism is that, the online shopping store does not know the real identities of its customers but pseudonyms. The customer is able to conduct a transaction anonymously in a normal circumstance, in which his/her privacy is preserved. The back-end real-name mechanism will be activated only when crime events occur. In such cases, anonymity will be removed through legal means to trace the real identity.