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Inconel 718 superalloy was fabricated by selective laser melting (SLM) and subsequently subjected to different heat treatments. Microstructure evolution was examined by X-ray diffraction, optical microscopy, scanning and transmission electron microscopies. In the horizontal section (normal to the building direction) of the as-built sample, columnar and cellular sub-structures formed in the overlapping area, while only cellular sub-structures existed in the central fusion area. Columnar structures were observed in the vertical section (parallel to the building direction). In the as-built condition, austenite γ and Laves phases predominated, almost to the exclusion of all other phases. When treated by the direct double aging (DA) process, δ-Ni3Nb phases precipitated mainly in the interdendritic regions where Nb preferentially segregated. Homogenization plus double aging (HA), and solution plus double aging (SA) treatments significantly eliminated microsegregation and Laves phases owing to the diffusion of Nb and Ti to the γ matrix. The δ phase dissolved in the HA-treated sample but precipitated in the SA-treated sample. The γ′-Ni3(Al,Ti) phase was prone to precipitate when treated by HA, while γ″-Ni3Nb phase tended to precipitate in the SA sample. Due to the precipitation of the higher fraction of the major strengthening γ″ phases, the SA sample showed the highest hardness value among the as-built, DA, HA, and SA samples. The morphology, distribution and crystallography of precipitates and their formation mechanisms are discussed and analyzed.

This research aimed to develop a set of practical and straightforward test methods to evaluate the rolling shear properties of cross-laminated bamboo and timber (CLBT) panels. Meanwhile, firsthand experimental data on the shear performance of panels laminated with unidirectional engineered bamboo panels and balsa wood lumbers were reported. The mechanical test results for balsa wood used in the hybrid CLBT panels were given. The bonding line's shear test between the out-layer bamboo panels and core wood was performed through the oblique compression shear test. The rolling shear tests of CLBT panels were performed with the two-plate planer shear test method and short-span bending shear test method. The full strain fields of specimens near ultimate loading conditions were given based on the two-dimensional Digital Image Correlation (DIC) method. This study showed that the rolling shear performance of core wood is determined by the annual ring geometrical parameters of wood products in the RT plane. The mean rolling shear moduli were 43 MPa and 48 MPa for two-plate specimens measured with dial gauges and strains, which is estimated through the Digital Image Correlation (DIC) method. The mean shear strength was 0.96 MPa obtained through two-plate shear tests and 2.50 MPa through the short-span bending shear test. The force corresponding to first-crack development instead of the maximum load is suggested to be adopted to calculate the shear strength of CLBT and other hybrid cross-laminated panels. Relatively small modulus and strength values were noticed for the hybrid panels due to the limited contribution of bamboo layers; thus, reinforcement at the stress-concentration regions was suggested for further researches on such lightweight hybrid cross-laminated panels.

The effects of annealing temperatures on the electrochemical properties of silicon carbide anode films are investigated for lithium-ion battery applications. The SiC film shows improved electrochemical performance with increasing annealing temperature. The 900 ° C-annealed SiC film exhibits a reversible capacity of 580 mAh g $^{-1}$ over 100 cycles. Moreover, the 900 ° C-annealed film displays better rate performance with less severe degradation $(\sim 12.2$%) than the other two films.

Polyaniline (PANI) with a well-ordered 3D micro array is prepared by using MEMS processes and its electrochromic properties are investigated by comparison with a 2D planar one. The 3D sample has similar response speeds to the 2D one but displays (~1.2×) higher specific capacitance than the latter due to its more PANI content under the same footprint. The 3D micro array is also helpful to enhance the mechanical strength of the PANI film against repeated electrochemical cycling. Moreover, because the 3D array is well-ordered and also its feature size (~4 μm) is comparable to the infrared wavelength, strong interaction occurs between the infrared light and the structure; consequently, the 3D sample shows much larger emissivity modulation (~0.3) than the 2D one (~0.1).

Background Acute lower respiratory tract infections (ALRIs) caused by respiratory syncytial virus (RSV) are a leading cause of hospitalization in infants. Numerous risk factors have been identified in the aetiology of severe RSV-associated ALRI necessitating hospitalisation, including prematurity and congenital heart disease. Down syndrome (DS), a common genetic disorder associated with congenital and dysmorphic features, has recently been identified as an independent risk factor for RSV-associated ALRI requiring hospitalisation; however, the disease burden of RSV-associated ALRI in this population has not yet been established. Similarly, the impact of DS as an independent risk factor has not yet been quantified. We aimed therefore to estimate the incidence of admissions in children with DS, and by comparing this with unaffected children, to quantify the risk of DS independent of other risk factors. Methods A systematic review of the existing literature published between 1995 and March 1, 2017 was performed to quantify the incidence of hospitalisation due to RSV-associated ALRI in children with DS. Meta-analyses were performed on extracted data using STATA statistical software, and hospitalisation rates for children with and without DS under the age of 2 were calculated. Findings 5 articles were ultimately deemed eligible for analyses. Analyses were limited to children under the age of 2 years. We calculated the hospitalisation rate for children with DS in this age group to be 117.6 per 1000 child-years (95% CI 67.4-205.2), vs a rate of 15.2 per 1000 child-years (95% CI 8.3-27.6) in unaffected children. This indicates DS contributes to a 6.8 (95% CI 5.5-8.4) fold increase in the relative risk of hospitalisation for RSV-associated ALRI. Interpretation Though limited by a small number of articles, this review found sufficient evidence to conclude DS was a significant independent risk factor for the development of severe RSV-associated ALRI requiring hospitalisation. Further studies are needed to define the impact of DS in conjunction with other comorbidities on the risk of severe RSV infection. Determining benefits of immunoprophylaxis or future vaccines against RSV in this at-risk population is warranted.

In order to reflect the anisotropic confined situations of quasi-one-dimensional (Q1D) wurtzite nanowires (NWs) in axial and radial directions and wurtzite GaN crystal, a two-parameter variational approach is brought forward and applied to investigate luminous properties of excitonic states in wurtzite NW systems. Numerical calculations on a GaN NW are performed. The quantum size effect on the excitonic binding energies of ground states, the ground state energies as well as the emission spectra is analyzed in detailed. Both the light hole excitons and heavy hole excitons in wurtzite NWs are taken in account. The calculated excitonic binding energies in the wurtzite GaN NWs are far larger than those in cubic GaAs-based quantum wires with the same radius. This is mainly ascribed to the large effective masses of electron and hole and relatively small dielectric constants in GaN material. The excitons emission wavelengths calculated here qualitatively agree with recent experimental results of exciton luminous spectra in Q1D GaN NWs. This confirmed the reasonability and reliability of the present theoretical scheme and numerical results. The numerical results also show that the two-parameter variational approach is reasonable and necessary for the description of excitonic states in Q1D wurtzite GaN NWs.

The transition metal fluorides KMF3 (M = Mn, Co, and Ni) were synthesized through a simple solution route. The crystal structure, morphology and electrical transport property of the resulting products were investigated. The compound KMF3 crystallizes in a cubic perovskite structure with space group Pm-3m (No. 221). A crystal structure of KMF3 was refined by the Rietveld method based on the X-ray powder diffraction data. The unit-cell parameters are 4.189 46(4), 4.075 58(4), and 4.025 70(2) for KMnF3, KCoF3 and KNiF3, respectively. A metal–insulator transition was observed in temperature-dependent electrical transport characterization in the temperature range from 250 to 280 K for these three compounds, which is considered to be related to spin-exchange in this kind of material.

Alpine grassland ecosystem of the headwater area of three rivers, Qinghai-Tibet plateau, has been degraded during past decades due to the intensified human activities and climate change. The severely degraded grassland, named “black-beach” has partly been restored with planting the located quality forage and fertilizing in recent years. In this study, we collected soil samples (0-4 depth) from three grasslands at different cultivated ages (cultivation of 4, 7 and 9 years) and one natural grassland at severely degraded level (served as a control) to explore the effect of pasture cultivation on soil nutrients. In addition, the size and the depth of the bare patches in the severely degraded grassland were investigated to estimate cultivated grasslands‟ capability of fixing the soil substances and recovering the soil nutrients. The results showed that the soil nutrient in the cultivated pasture declined at the early stage of cultivation, increased with cultivated ages, i.e., total N, total C, Ca, and P in soils at 0-4 cm depth increased 10-23% after 9 years of cultivation. Pasture cultivations can be regarded as a good strategy to fix the soil surface and recover the soil nutrients of severely degraded grassland on the Qinghai-Tibetan Plateau of China.

Qinghai-Tibet Plateau, known as the “World's Ridge”, exerts an proud impact carbon pool in sustaining global carbon circulation balance in terms of global climate change. In this study, five sites of alpine grassland at different degradation gradient were surveyed in Guoluo Prefecture of Qinghai Province, China. Soil total organic carbon (TOC) was tested for calculating the density of soil organic carbon, to evaluate the grassland ecosystem function of carbon maintenance. The results showed that the ecosystem function of carbon maintenance for alpine grassland varied along the degradation gradient. The function of both heavily degraded and severely degraded grasslands decreased a lot. However, the function of lightly degraded grassland increased a little compared to the non-degraded grassland. Urgent actions are needed to protect alpine grassland against heavy and severe degradation.

A turret of electro-hydraulic servo system and its implementation mechanism is a set of high speed and high precision dierential servo system to control and drive the launcher, which can recurrent the command radar position and movement rules in two directions of azimuth and height. The core part is a set of valve controlled hydraulic cylinder in height and a set of valve controlled motor in azimuth. The mechanical part is composed of servo valve, servo motor, oil cylinder andthe hydraulic energy system and the electrical control signal coming from the dynamic dierential electrical signal given by the command radar. The principle of valve controlled hydraulic is shown in Figure 1.

A feeding trial A as conducted at the farm of Qinghai Academy of Animal and Veterinary Science, Xining, China during 1996 - 1997 with three dry yak cows (initial body weight 163 - 197 kg, age 5 - 6 years) by using 3 x 3 Latin Square Design to determine the effect of levels of feed intake on digestion, nitrogen balance and purine derivative excretion in urine of yak cows. The animals were fed oat hay (nitrogen 13.5 g/kg dry matter (DM), metabolisable energy 8.3 MJ/kg DM), i.e., 0.3, 0.6 and 0.9 of voluntary intake (VI). Each intake treatment lasted for 17 days and the samples (feeds, faeces and urine) were collected during last 7 days of each period. The results indicate that digestibility of dietary DM, OM, NDF and ash declined when intake levels increased from 0.3 to 0.9 VI [DM, from 66.1% to 59.1% (P < 0.05); OM, from 68.1% to 59.9% (P < 0.05); NDF, from 62.1% to 54.3% (P < 0.05); and ash, from 33.9% to 11.8% (P < 0.05)]. Around 0.10 g N/kg W-0.75 was deficient daily in yak cows at 0.3 VI, and positive N balances were observed at 0.6 and 0.9 VI. Intake levels significantly (P < 0.05) affected total PD excretion in yak urine. The proportion of allantoin increased (P < 0.05) and uric acid decreased (P < 0.05) as intake level of feed increased. (C) 2004 Elsevier B.V. All rights reserved.

The purpose of this study is to examine the relationship between molar intrusion efficiency and bone density in patients with different vertical facial morphology. Thirty-six female patients, with overerupted upper first molars, were divided into two groups according to mandiblular plane angle (FH-MP): hyperdivergent, FH-MP>30° (G1), hypodivergent, FH-MP

It has been demonstrated that inter-site synchronization has the potential to significantly increase capacity in cellular networks based on GSM and EDGE. In combination with frequency reuse and fractional loading, synchronization reduces interference through intelligent allocation of frequency hopping parameters. This paper discusses frequency-planning strategies for synchronized GSM and EDGE networks. In addition, field trial results in a mature GSM market are presented. In particular, FLP 1/1 with synchronization is compared with an optimized ad-hoc plan in terms of voice quality and number of call drops.

Radio resource management becomes more and more challenging as the demand for network capacity increases. This paper describes a local frequency optimization method called manual frequency re-allocation (FRA) to minimize interference level by allocating less disturbed frequencies to individual cells. This paper reports performance results of FRA field trials conducted in three live AMPS/TDMA cellular networks using different optimization approaches.

The performance of transmission control protocol (TCP) over wireless links could degrade due to handoff, high bit error rate and long roundtrip delay on the air interface. Radio link protocol (RLP) uses channel coding and ARQ to mitigate impairment over wireless channels. In this paper, we study the performance of TCP over adaptive RLP. We investigate this problem in the context of the TDMA (IS-136 and IS-130) wireless network, where the wireless data is transmitted through the reliable RLP. The RLP is modified with an adaptive channel coding scheme. First, we analyze the throughput of RLP with combination of ARQ and fixed channel codes. Second, we consider an adaptive channel coding scheme using punctured convolutional codes and ARQ that maximizes the throughput under variable channel conditions. Third, we simulate the effect of radio environment and compare the performance of TCP over RLP with fixed and adaptive channel coding. Our simulation results indicate significant improvement in throughput performance for TCP over adaptive RLP.

A new architecture called the dual-homing hierarchical self-healing ring (DH-HSHR) architecture is proposed to interconnect SONET self-healing rings, and the design of DH-HSHR network is considered. A DH-HSHR survives all single network failures, including single link and single node failures. A link cost model that incorporates both the route mileage and the capacity of the fiber systems is used. Network design is obtained through a heuristic algorithm. Simulated annealing is applied to further reduce the cost of the design. Numerical results are presented on the design of a DH-HSHR network and comparison is made between the heuristic and simulated annealing algorithms for various network sizes and demand patterns.

It is anticipated that future wireless communications systems will need to support multimedia applications with heterogeneous traffic types. To ensure user performance while maintaining network efficiency, it is important to introduce quality of service (QoS) schemes and optimize wireless channel utilization. A mechanism consisting of a user packet scheduling algorithm for QoS provisioning and a load-balancing algorithm is proposed for wireless multimedia communications. The user QoS guarantee is provided by a token bank leaky bucket (TBLB) approach, which keeps track of data service for individual users based on their QoS profile. The proposed scheme extends the leaky bucket mechanism to the scheduling of packet transmission in a multiple-channel system, where radio channel re-assignment is performed to balance the traffic load when necessary. This study further evaluates the performance of the proposed mechanism with respect to a variety of traffic models, such as Web browsing and real-time packetized voice.

A wireless packet data communications system utilizing the General Packet Radio Service (GPRS) is studied. A traffic model that exhibits self-similarity is considered for wireless Internet applications. The radio channel is modeled as a two-state Markov fading channel. The performance of TCP over such a packet radio link is obtained through analysis and simulation. Theoretical bounds are derived for system load and user performance. To gain insight to dimensioning of wireless packet data networks, TCP throughput and delay are studied with respect to the number of users and file size. The impact of radio link retransmission and system load on TCP timeout is also investigated.

Large-volume and uniform atmospheric glow discharges are finding a vast range of processing applications, many of which have been traditionally addressed with the vacuum plasma technology. When excited at kilohertz or above, these atmospheric plasmas operate typically at low current densities below 30mA∕cm2 and often they are perceived to have very similar properties regardless of their operation conditions. Recently a radio-frequency (rf) atmospheric glow discharge was observed at high current density of up to 1A∕cm2, thus suggesting a previously overlooked and potentially different operation regime. Through a computational study of rf atmospheric glow discharges over a wide range of current density, this paper presents evidence of at least two glow modes, namely, the α mode and the γ mode. It is shown that gas ionization in the α mode is volumetric occurring throughout the electrode gap whereas in the γ mode it is dominated by localized events near the boundary between the sheath and the plasma bulk. Se...

Diagnosing the degradation degree of grassland ecosystem is the basis for ecological restoration. However, there is no literature documenting how to quantify the grassland degradation degree by using visible indicators. In this study, an integrated degradation index was developed to assess the grassland condition on the basis of applicability and certainty analysis through a cases study from degraded alpine grassland on Qinghai-Tibetan Plateau of China.