Search

Phase stability and its effect on tensile properties of MAR-M247 alloy have been investigated during thermal exposure at 800–900 °C for up to 10,000 h. Detailed investigations reveal that the larger secondary γ′ phase has no obvious growth, but the smaller tertiary γ′ phase obviously coarsens and the coalescence occurs during thermal exposure at 850 °C and below. γ′ coarsening behavior is consistent with the description of Ostwald ripening theory before γ′ coalescence. Hf-rich blocky MC carbide shows excellent thermal stability, but Ta-rich script-type MC carbide gradually degenerates via reaction, MC + γ → M23C6 + γ′ and finally forms γ׳ film around MC and M23C6 carbides. With increasing thermal exposure time, the tensile strength decreases. The ductility first increases and then decreases during exposure at 800 °C, but it decreases continuously at 900 °C. In addition, the ductility keeps almost constant when the exposure time is longer than 5000 h.

The relationship between the tensile properties and δ (delta) phase precipitation in cast alloy IN625 was investigated in this paper. Although the influences of δ phase on the mechanical properties have been pointed out in our previous work, the relationship is still not directly determined due to the coexistence of γ″ (gamma double prime) and δ precipitates. In order to exclude the effect from γ″ phase, various fractions of δ precipitates with few γ″ precipitates were obtained by a set of experimental alloys aging at 750 °C, and tensile tests were conducted in parallel. The results showed that both yield strength and ultimate tensile strength increased nearly in linear with increasing δ phase fraction, while the elongation was relatively and limitedly affected by δ precipitation when the area fraction of δ phase was above 10%.

Although PtAl2 is a promising high-temperature alloy, the improvement of its strength is still a big challenge. To solve this problem, we apply first-principles calculations to study the influence of alloying elements on the structural stability, elastic properties and brittle-or-ductile behavior of PtAl2. The results show that alloying elements prefer to occupy the Al site in comparison to the Pt site. Importantly, the calculated bulk modulus of doped PtAl2 is much larger than that of the parent PtAl2 due to the formation of TM-Pt and TM-Al bonds. In addition, alloying elements effectively improve the ductility of PtAl2. Finally, our work can provide new information to improve the mechanical properties of Pt-Al high-temperature materials.

Previous 6T SRAMs commonly employ a wordline voltage underdrive (WLUD) scheme to suppress half-select (HS) disturbs in read and write cycles, at the expense of reduced cell read current ( $I_{\mathrm {CELL}}$ ) and degraded write margin (WM). This paper proposes the dual-split-control (DSC) scheme, including split WLs and split cell VSS (CVSS), for 6T SRAM to maintain a compact cell area and improve HS cell stability during the read and write cycles without degrading $I_{\mathrm {CELL}}$ and WM. A segmented CVSS-strapping scheme is developed to suppress the ground bounce on the split-CVSS lines. The CVSS voltage for S6T can be generated by either a constant voltage source or a charge-sharing-based CVSS generation scheme. A 28-nm 256-kb DSC6T SRAM macro was fabricated and achieves a 280-mV lower VDDmin than a conventional 6T SRAM.

Low-power embedded memory and an ARM Cortex-M0 core that operate at 30 MHz were fabricated in combination with a 60-nm c-axis aligned crystalline indium–gallium–zinc oxide FET and a 65-nm Si CMOS. The embedded memory adopted a structure wherein oxide semiconductor-based 1T1C cells are stacked on Si sense amplifiers. This memory achieved a standby power of 3 nW while retaining data and an active power of 11.7 $\mu \text{W}$ /MHz by making each bitline as short as each sense amplifier. The Cortex-M0 core adopted a flip-flop (FF) in which an oxide semiconductor-based 3T1C cell is stacked on the Si scan FF cell without area overhead, and achieved a standby power of 6 nW while retaining data. This combination of embedded memory and Cortex-M0 core can provide high-performance as well as low-power operation, which is essential for Internet of Things devices.

Precise prediction of coal thickness is of the utmost importance in realizing intelligent and unmanned mining. As the channel wave is characterized by an easily recognizable waveform, a long propagation distance, and strong energy, it is widely used for coal thickness inversion. However, most traditional inversion methods are local in nature, and the inversion result is probably not optimal in the global scope. This paper introduces the GA-SIRT hybrid approach, which combines Genetic Algorithms (GA) and Simultaneous Iterative Reconstructive Techniques (SIRT) in order to deal with the above problem and to improve the accuracy of coal thickness inversion. The proposed model takes full advantage of the strong global search capability of GA and of the fast local convergence rate of the SIRT. Moreover, it inhibits the poor local search ability and the local optimal value effect of the GA and the SIRT respectively. The application of the GA-SIRT in the Guoerzhuang coal mine has significantly enhanced its accuracy, stability, and overall computational efficiency. Hence, the introduced novel hybrid model can precisely resolve and identify the coal thickness according to the channel wave. It can also be extended to other geophysical tomographic inversion problems towards the reduction of potential local optimal solutions.

The hydrogeological conditions of coal mines in China are quite complex, and water inrush accidents occur frequently with disastrous consequences during coal extraction. Among them, the risk of coal mining under a river is the highest due to the high water transmissivity and lateral charge capacity of the unconfined aquifer under the river. The danger of mining under a river requires the accurate determination of the developmental mechanisms of the water flowing fractured zone (WFFZ) and the water flow mechanisms influenced by the specific geological conditions of a coal mine. This paper first used the transient electromagnetic (TEM) method to monitor the development of the WFFZ and the water flow mechanisms following the mining of a longwall face under a river. The TEM survey results showed that the middle Jurassic coarse sandstone aquifer and the Klzh unconfined aquifer were the main aquifers of the 8101 longwall panel, and the WFFZ reached the aquifers during the mining process. Due to the limited water reserves in the dry season, the downward flowing water mainly came from the lateral recharge in the aquifer. The water inrush mechanisms of the 8101 longwall panel in Selian No.1 Coal mine were analyzed based on the water flow mechanisms of the aquifer and the numerical simulation results. This provides theoretical and technical guidance to enact safety measures for mining beneath aquifers.

The thermal decomposition kinetics of bezafibrate in a nitrogen atmosphere has been investigated by analyzer DTG-60. The thermal behavior of bezafibrate at the different heating rates 4, 8, 12, 16 and 20 °C min−1 displays two-stage decomposition processes among 500–650 K. The activation energy (E) and pre-exponential factor (A) were calculated to be 128.72 kJ mol−1 and 3.56 × 1010 min−1 by Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, Doyle, Kissinger and Satava–Sestak methods for the second-stage decomposition process. The results show that the non-isothermal thermal decomposition mechanism of bezafibrate is classified as three-dimensional diffusion model, and the integral and differential equations are $$g(\alpha ) = [1 - (1 - \alpha )^{1/3} ]^{2}$$ and $$f(\alpha ) = \frac{3}{2}\left( {1 - \alpha } \right)^{{{\raise0.7ex\hbox{$2$} \!\mathord{\left/ {\vphantom {2 3}}\right.\kern-0pt} \!\lower0.7ex\hbox{$3$}}}} \left[ {1 - \left( {1 - \alpha } \right)^{{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 3}}\right.\kern-0pt} \!\lower0.7ex\hbox{$3$}}}} } \right]^{ - 1}{.}$$ The enthalpy (ΔH ≠), entropy (ΔS ≠) and Gibbs free energy (ΔG ≠) were calculated to be 123.74 kJ mol−1, −91.07 J mol−1 K−1 and 178.29 kJ mol−1, respectively.

Gamma prime (γ′) stability and its influence on tensile behavior of a newly developed wrought superalloy with various Fe contents was studied both experimentally and thermodynamically. The results show that the γ′-solvus temperature is higher and γ–γ′ lattice mismatch is bigger in the alloy with the lower Fe content. During long-term thermal exposure at 650–750 °C, the coarsening behavior of γ′ precipitates follows Ostwald ripening kinetics and the lower Fe content can decrease the coarsening rate of γ′ precipitates due to the increase of the activation energy for γ′ coarsening. Moreover, the lower Fe content can retard the transformation from γ′ to η phase. The tensile properties of the alloys with different Fe contents are almost same after standard heat treatment. However, after thermal exposure, the decrease of tensile strength in the alloy with lower Fe content is less than that of the alloys with higher Fe content due to the improvement of γ′ stability.

The worldwide first 100MHz dynamic oxide semiconductor RAM (DOSRAM) is successfully demonstrated using a new high-mobility crystalline In-Ga-Zn-O (IGZO) material. The new IGZO exhibits around two times carrier mobility of conventional IGZO, while still achieving an extremely low off-state leakage (I off ) at ∼10−21A (zA) level. Attributed to DOSRAM performance improvement, 100MHz normally-off (Noff) CPU is successfully demonstrated with drastically reduced power consumption (∼94% power reduction for ARM Cortex-M0 and ∼70% power reduction for memory), making it a promising candidate for IoT application. In addition, an OS-FPGA is successfully fabricated by integration of 65nm SiFET and 60nm oxide semiconductor FET (OSFET) with an operation frequency of 360MHz. The application of the OSFET in analog circuits will also be discussed in this paper.

An embedded 1 Mbit 2T1C gain-cell memory macro using indium-gallium-zinc oxide semiconductor FETs (OSFETs) with an extremely low off-state current of less than 1 zA (10−21 A) was fabricated. In the 2T1C gain cell, an OSFET for the write operation was stacked over a SiFET for the read operation. The 1 Mbit macro was fabricated using a combination of 60-nm OSFET and 65-nm CMOS processes. It achieves a 140 MHz operation and data retention of more than 1 h. Its static power in the standby state and active power are 31 μW and 64 μW/MHz, respectively. The macro with long-term data retention can reduce the static power by power gating. 2T1C OSFET-based embedded memory is applicable to devices requiring high performance as well as low power.

90 degree optical hybrid is the key part of space coherent optical communication and the high efficient mixing technology is an effective means to achieve great detect sensitivity. Most of optical components in optical hybrid are sensitive to polarization state, therefore, the polarization state of incident light will affect the function of hybrid. Through an theoretical analysis and simulation of the performance of hybrid whose incident light is linearly or elliptically polarized light, the result shows that the heterodyne efficiency of hybrid reaches its maximum when incident light is 45°linearly, and the change of polarization orientation can decrease the optical power entering I branch, making the heterodyne efficiency declines. Degree of polarization will increase phase difference of both branch which is orthometric in hybrid, causing the process of phase locking more difficult. Moreover, the effect of deviation of directivity of wave plate on hybrid performance is studied, for 1/4 wave plate, its deviation will change the power allegation and phase error of IandQ branch, but for 1/2 wave plate, phase error cannot be brought in, but it will change the direct current(DC) component of branch. The above polarization state changes will not bring additional phase error in I branch, ensuring the normal functioning of hybrid. This study gives a theoretical foundation to the design of space optical hybrid.

Low-power embedded memory and an ARM Cortex-M0 core that operate at 30 MHz were fabricated in combination with a 60-nm c-axis aligned crystalline indium-gallium-zinc oxide FET and a 65-nm Si CMOS. The embedded memory adopted a structure in which oxide semiconductor-based 1T1C cells are stacked on Si sense amplifiers. This memory achieved a standby power of 3 nW while retaining data and an active power of 11.7 µW/MHz by making each bitline as short as each sense amplifier. The M0 core adopted the flip-flop in which an oxide semiconductor-based 3T1C cell is stacked on the Si scan flip-flop cell without area overhead and achieved a standby power of 6 nW while retaining data. The combination of the embedded memory and the M0 core provided high-performance, low-power Internet of Things devices operating with a broad range of active standby power ratios.

For the first time, laboratory 60 nm c-axis aligned crystalline In-Ga-Zn-O (CAAC-IGZO) oxide semiconductor FET (OSFET) was successfully integrated with industrial 65 nm Si MOSFET (SiFET). By this hybrid process, OSFET with extremely low off-state leakage level ∼zA (1×10−21A) was fabricated, while traditional Si device can only reach 1×10−12A leakage level. For IoT (Internet of Things) applications, normally-off CPU (Noff CPU) fabricated by this hybrid process achieved 86% reduction of power consumption. The hybrid process can be extended to other applications like eDRAM, image sensor and FPGA.

Cast alloy IN625 is a candidate Ni-base alloy for advanced ultra-supercritical (A-USC) power plants. The aim of this study was to investigate the influences of Nb on δ phase precipitation and the tensile properties in this alloy. The results show that the δ phase is easy to precipitate after long-term aging at 700 °C (the service temperature of A-USC power plants) and it is strongly affected by the content of Nb in the alloy. The strength of alloys after aging at 700 °C for 10,000 h increases with the increasing Nb content and also increases sharply when compared to that of as-heat-treated alloys. The increase in strength is found to be primarily associated with the precipitation of the δ phase.