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The present study envisaged the effects of leaching solution on the mechanical properties of stope surrounding rock in in situ blasting leaching of sandstone type uranium deposit. Experiments were performed using uniaxial compression tests and SEM observation of sandstone samples after soaking in the H2SO4 solution with pH 1, 2, 3 and 4 for 5, 10, 20, 30 and 40 days. The results showed that at pH 1, the solution levels increased slowly and steadily all the time, and for other pH solutions the levels increased rapidly in the first 5 days with a slow subsequent increase. The pH 2 solution showed reddish brown coloration in varying degrees, since it provided good conditions for Fe(OH)3 precipitation. It is suggested that the pH value of leaching solution should be controlled within 1.5–2.0 during the regular leaching period of ore pile, and then adjusted to 2.0–2.5 after the leaching process based on the forming conditions and uranium-adsorbing characteristic of the Fe(OH)3 colloid. Furthermore, with the increase in the solution pH, the mass change rate of the sandstone sample decreased. The uniaxial compressive strength and elasticity modulus of sandstone samples decreased with an increase in the soaking time and a decrease in the pH. After soaking in acid solution (pH

This paper researched the distribution and the characteristics of residual coal resources for their adaptability into underground coal gasification (UCG) technology to promote a potential green technology for the development of residual coal resources in China. The results reflected that the average recovery rate of resources for coal mines was only 37.67% in China, and the residual coal reserves reached 148.53 gigatons (Gt), of which 52.51% occurred in North China. Furthermore, these resources are mainly distributed in the buried depth shallower than 800 m, accounting for 87.15%. And residual coal types were primarily bituminite with a percentage of 72.89%. We established a multi-level model with membership functions that included an analytic hierarchy and a fuzzy comprehensive evaluation with variable weight theory. As a result, a varying weight fuzzy hierarchical evaluation model for the resource conditions feasibility of residual coal with UCG technology was established. Finally, the model was applied to the resource condition feasibility evaluation of UCG industrial tests at Zhongliangshan, Huating, and Shanjiaoshu Mines. The industrial tests showed that the evaluation model constructed in this paper could comprehensively, objectively, and intuitively reflect the adaptability of residual coal resources to UCG technology, providing a scientific reference for UCG project decision-making.

In this study, underground coal gasification (UCG) technology with the strip mining method was recommended to avoid the instability of surrounding rock in the UCG cavity and possible groundwater pollution, in which mechanical performance and reasonable size of the strip pillar play the crucial role. The respective innovative calculation method considering the thermo-mechanical coupling effect was proposed and applied to size designs of pillars in the UCG projects of the Shanjiaoshu Mine and Mazino coal deposit . The proposed method feasibility was experimentally validated and yielded the following predictions of the coal pillar mechanical performance evolution during the UCG process . Heat-affected zones in the coal pillar and immediate roof gradually increased with the following decline. High temperatures above 250 °C affected the coal and rock masses only at a distance not exceeding 2 m from the surface, but their effect continued even after the UCG termination. High temperatures reduced the load-bearing capacity in the area near the coal pillar surface and induced long-term thermal stresses in coal pillars, which alternatively played a dominant role in affecting the ultimate strength of the coal pillar at different stages. The plastic zone width xp in the pillar is varied and will remain unchanged once it reaches its peak value. The width of strip pillars Wp is greatly influenced by high temperatures; it exhibits a W-shaped variation pattern during the UCG process and slowly drops after gasification. The strip pillar width of UCG can be determined using the maximum value of function Wp(t) considering a certain safety factor. While the wide pillar's total strength and size are slightly affected by the temperature, its width can be obtained from Wp(0) with a safety factor. This study can be used for predicting the mechanical performance evolution and size determination of pillars in the UCG process.

To optimize the gasification process and improve the underground coal gasification (UCG) technology for power generation, a pilot project of UCG integrated with the power generation was built in the abandoned mine “Ankou”. The UCG industrial tests with different oxygen concentrations of oxidant along with the pulsed injection method, and power generation experiments using UCG syngas were conducted. The results indicate that a decrease in the rate of air blowing for a short time exhibited a limited influence on syngas production, but a change in the amount of oxygen injection presented an obvious effect. With the increase in the oxygen concentration in the agent, the H2 content, combustible components and calorific value of syngas, flow ratio, and the consumption of coal, steam and oxygen increased, along with a rise in the gasification efficiency after an initial drop. The oxygen-enriched gasification trials showed higher air consumption, lower consumption of coal, steam and oxygen, and a low combustible components and calorific value of syngas compared to the gasification tests of the oxygen-enriched steam. The evaporation of ground water and coal moisture in the UCG panel provided steam for the oxygen-enriched gasification process, and its utilization rate was about 6–32 wt%. From the characteristics of UCG syngas, the technical transformations such as exhaust gas booster combustion control, high energy ignition, low pressure intake, expansion of the air, and gas inlet pipe diameter were carried out on the existing gas generator sets. The effectiveness of the measures was verified by the power generation experiments.

A novel molecularly imprinted sensor based on photocurrent was fabricated to detect Ni2+. CdTe quantum dots (QDs) were selected as photoelectric material and modified on an indium-tin oxide (ITO) electrode, then the nickel-1-(2-pyridylazo)-2-naphthol molecularly imprinted film was formed on the QDs layer by photopolymerization. While 365 nm ultraviolet light was used as the excitation light, an electron-hole pair could be generated by the QDs. The electron receptor ascorbic acid would form a photocurrent under the excitation of the electron as detection signals. Ni2+ was determined according to “gate-effect”. The complex was characterized by Fourier transform infrared spectrum and the CdTe QDs were characterized by ultraviolet absorption spectrum and fluorescence emission spectrum. The time for elution and rebinding, as well as the concentration of ascorbic acid, were also optimized. The experimental results indicated that there was a liner relationship between the photocurrent and the concentrations of Ni2+ in the range of 5 × 10−11 − 5 × 10−8 M, with a detection limit of 8.31 × 10−12 M. The sensor had good selectivity, and was applied in real water samples analysis.

The capability to spatiotemporally regulate polymerization kinetics in response to dual external stimuli of light and magnetism offers exciting pathways to precisely manipulate polymer composition and sequence. Herein, we report a strategy that adopts snowman-shaped Fe3O4@aSiO2-click-ZnPTPP Janus nanocomposites with a high magnetization value (12.9 emu g−1) and stably confined but accessible catalytic metalloporphyrin moieties as the nanocatalysts for photo-induced electron transfer reversible addition–fragmentation chain transfer (PET-RAFT) polymerization. This method enables the synthesis of diverse polymeric structures from a large range of monomers using ultralow concentrations of nanocatalysts (less than 10 ppm) with simple modulation of light and magnetism. In addition, the nanocatalysts are found to be oxygen-tolerant, and they exhibit non-agglomeration during polymerization. Finally, repeated regeneration of the used nanocatalysts by magnetic extraction or facile centrifugation effectively reduces or even eliminates the contamination and/or decomposition on the final polymer products.

Three new coordination compounds, namely, [(HL)2M(H2O)4] (M = Co, (1); M = Mn, (2); M = Ni, (3), H2L = 5-(pyridin-2-ylmethoxy) isophthalic acid), have been hydrothermally synthesized and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. The structures of complexes 1–3 are strikingly similar and the three complexes are mononuclear compounds. In complexes 1–3, the H2L ligand is partially deprotonated. In addition, the photoluminescent behavior of 2 and the H2L ligand has been investigated in detail.

An integrated ramp generator is presented in this paper. For traditional implementations, the amplitude clamp is realized with zener diode to limit the output voltage to ±VZ, while the zener diode is not available for standard CMOS process. The transmission gate is utilized to make the output voltage in the determined range. The reference voltage is provided by a bandgap voltage reference with temperature compensation, which guarantees the temperature stabilization of the frequency of the ramp generator. The ramp generator was fabricated in a commercial CMOS process. The frequency of 44kHz is achieved under the power supply of 3.5V, and the frequency variation of 41kH to 46kHz with the power supply of 3.3V to 5V.

A multiplexer with split devices for high channel isolation was proposed in this paper. The multiplexer is the most essential circuitry for multi-channel video signal acquisition systems. In the multi-channel applications, high isolation performance is required basically for the efficient signal processing. The noise propagation between channels is unexpected. The split devices technique is employed in the design work. Redundant transistors are inserted between the split cells to realize the noise grounded. This multiplexer is simulated and verified in the commercial CMOS process, and the isolation of more than 70dB was achieved. It has been embedded in a multi-channel analog signal processing system.

In order to study temperature field distribution in burnt surrounding rock and to determine ranges of burnt surrounding rock, coal-wall coking cycle and heat influence in the underground coal gasification (UCG) stope, based on the Laplace transform and inversion formula, we studied the temperature analytical solution of one-dimensional unsteady heat conduction for multi-layer overlying strata under the first and the forth kinds of boundary conditions, and we also carried out a numerical simulation of two-dimensional unsteady heat conduction by the COMSOL multiphysics. The results show that when the boundary temperature of surrounding rock has a linear decrease because of a directional movement of heat source in the UCG flame working face, the temperature in surrounding rock increases first and then decreases with time, the peak of temperature curve decreases gradually and its position moves inside surrounding rock from the boundary. In the surrounding rock of UCG stope, there is an envelope curve of temperature curve clusters. We analyzed the influence of thermophysical parameters on envelope curves and put forward to take envelope curve as the calculation basis for ranges of burnt surrounding rock, coal-wall coking cycle and heat influence. Finally, the concrete numerical values are given by determining those judgement standards and temperature thresholds, which basically tally with the field geophysical prospecting results. Keywords: Underground coal gasification (UCG), Temperature distribution, Laplace transform, Envelope curve, Burnt surrounding rock, Coking cycle

In this paper, a kind of 120 kHz PLL signal source system is presented. Its based on the principle that changes in feedback voltage at a constant surge frequency which is related to reference voltage. At the same time, combine an actual test circumstance; the abnormity of signal lock is analyzed. Based the conclusion and the mode of interior parts, we take a simple adjust measure. The abnormity of the signal source is avoided availably.

This paper presents a low-voltage differential operational transconductance amplifier (OTA) with enhanced DC gain and slew-rate. Based on the current mirror OTA topology, the optimization techniques are discussed in this work. The proposed structure achieves enhanced DC gain, unit gain frequency (UGF) and slew-rate (SR) with adding four devices. The design of the OTA is described with theory analysis. The OTA operates at the power supply of 1.8V. Simulation results for 0.18μm standard CMOS technology show that the DC gain increases from 60.6dB to 65dB, the UGF is optimized from 2.5MHz to 4.3MHz, the SR is enhanced from 0.88 V/μs to 4.8 V/μs with close power consumption dramatically.

A fully integrated CMOS receiver front-end with digital output for optical signal processing system is presented. This circuit is composed of trans-impedance amplifier (TIA) for weak optical current detection, post-amplifier for both a linear and limiting amplification, control circuits and the digital output interface. Measured with photodiode which is driven by pulse voltage source, a sensitivity of 0.7μA was achieved. The current model methodology is employed to optimize the noise performance. The front-end consumes the current of 1.5mA with the power supply of 3.3V. The design was done in a low-cost standard CMOS process with 0.6μm featured size, taking area of 600μm×150μm excluding the bonding pads.

A monolithic MEMS accelerometer process was established. This process successfully combines our standard BiCMOS technology and MEMS surface micromachining technique. The acceleration sensing element is a kind of comb-finger structure which is built by polysilicon surface micromachining technique. The polysilicon structure is designed to form two capacitors for acceleration sensing. The external acceleration will cause the value of two capacitors to vary in different direction. That means one reduces if the other increases. It was integrated with the signal conditioning circuit. In a single die, the active devices including vertical NPN, lateral PNP, PMOS and passive devices such as capacitors, resistors were fabricated which was followed by the steps to form the acceleration sensing structure. The experiment indicates that the fabricated circuit has the function of sensing capacitive variation and with a scale factor of 100mV/g.

To optimize the technological parameter of underground coal gasification (UCG), the experimental results of air gasification, air-steam gasification, oxygen-enrichment steam gasification, pure oxygen steam gasification and two-stage gasification were studied contrastively based on field trial at the Huating UCG project. The results indicate that the average low heat value of gas from air experiment is the lowest (4.1 MJ/Nm3) and the water gas from two-stage gasification experiment is the highest (10.72 MJ/Nm3). The gas productivity of air gasification is the highest and the pure oxygen steam gasification is the lowest. The gasification efficiency of air gasification, air-steam gasification, oxygen-enriched steam gasification, pure oxygen steam gasification and two-stage gasification is listed in ascending order, ranging from 69.88% to 84.81%. Described a contract study on results of a field test using steam and various levels of oxygen enrichment of 21%, 32%, 42% and 100%. The results show that, with the increasing of O2 content in gasifying agents, the gas caloricity rises, and the optimal O2 concentration range to increase the gas caloricity is 30%∼40%. Meanwhile, the consumption of O2 and steam increase, and the air consumption and steam decomposition efficiency fall.

With the practical experience in the UCG power generation test in Huating Coal Group of China, nine ways of enhancement of efficiency of Underground Coal Gasification -Integrated Gasification Combined Cycle (UCG-IGCC) Power Plants are put forward which include selection of proper gasification agent flow rate, proper steam concentration in gasification agent, proper O 2 concentration in gasification agent, the appropriate oxygen making process, appropriate overall rate of air separation system, increase in temperature of gasifiers, control of the length of the reduction zone, increase in the inlet temperature of gas turbines, utilizing the sensible heat of the coal gas.