Measurements of Heat Treatment Effects on Bovine Cortical Bones by Nanoindentation and Compression Testing

Heat treatment of bone is one of the reliable and simple sterilization methods to overcome the risk of rejection and disease transfer from allograft and xenograft, in particular for the prevention of human immunodeficiency virus (HIV) infection. However, the mechanical property of the micro-structural level after heat treatment is not well characterized. To address this issue, this study was carried out to compare the localized mechanical properties of micro-structural tissue with those at the global structural level. Nanoindentation technique has been well accepted as an accurate technique to measure mechanical property of small and heterogeneous specimen nondestructively, as well as the complex bio-material of micro-structural level, often with a resolution of better than 1 μm. In this study, nanoindentation was conducted to measure the localised elastic modulus and hardness values of bones at temperature of 23°C (room temperature – non-heated sample), 90°C and 150°C, respectively. All experiments were conducted at room temperature (~23°C). The elastic modulus (E) and nanoindentation hardenss (H) values in the longitudinal direction of bones heated at 150°C were recorded as 23.43 GPa and 0.73 GPa, respectively;as in transverse direction, the E and H values were 12.77 GPa and 0.54 GPa, respectively. It showed significant increases of 44% and 43% in the longitudinal direction as compared to those of the non heat-treated bones. In addition, E and H values in transverse direction also showed increases of 23% and 38%, respectively as compared to those of the non heat-treated bones. Furthermore, heat-treated bones at 90°C in longitudinal direction also appeared to have significant increases of 18% and 31% in E and H values, respectively. However, the E and H values in transverse direction increase only by 0.4% and 12.8%, respectively. In addition, compressive test is employed to measure the global stiffness (E) of the bone samples. When heated at 150°C, the bone specimen showed an increase of 60% in stiffness (E) and an increase of 26% in yield stress. On the other hand, when heated at 90°C, a slight increase of 11.4% in stiffness (E) and 21.5% in yield stress were recorded respectively. Furthermore, energy dispersive X-ray spectroscopy (EDX) which integrated with Backscattered Electron (BSE) imaging was conducted to examine the relationship between mineral content and mechanical strength within the nanoindentation regions. The data demonstrated that the non heat-treated bones obtained the highest calcium wt% amongst the three groups;as temperature increased, there was a slight decrease in calcium wt%;however, the changes were not severe in this study.

Machinability of Polymeric Composites and Future Reinforcements—A Review

This paper reviews the machinability and mechanical properties of natural fiber-reinforced composites. Coupling agents, operating parameters, as well as chemical treatment effects on natural fiber-reinforced composites’ machinability are also reviewed. Moreover, the impacts of fibers’ physical properties on the machinability of the composite are mentioned. Fiber volume fraction (Vf), fiber orientation as well as chemical treatment effects on mechanical properties are also defined. Conclusively, the effect of fibers’ physical properties as well as mechanical properties is described. It was discovered that chemical treatment of natural fibers improved their compatibility with the matrix by removing their surface tissues, increasing the roughness average (Ra), and reducing moisture absorption. Also, the Orientation of the fiber plays an important role in controlling the mechanical properties of the composite. Moreover, some physical properties of the fibers, including quality of fiber distributed in the matrix;fiber size, length, and diameter;moisture absorption;porosity and the way fibers break during compounding with the matrix, were found to affect the mechanical properties of the composites formed.

Fly Ash-based Geopolymers:Effect of Slag Addition on Efflorescence

Blended fly ash/blast-furnace slag geopolymers are focused on due to their excellent mechanical and chemical resistant properties. We investigated the effect of slag partial substitution for fly ash on the efflorescence of the resulting geopolymers. The efflorescence of geopolymer binders was inspected and evaluated through leaching tests. The efflorescence deposits on surface of the geopolymer binders were analyzed using XRD and SEM-EDS. The results showed that sodium and calcium cations leached from geopolymer binders reacted with the atmospheric CO2 and formed the crystal deposits, gaylussite and calcite, in the forms of granular and angular crystal particles. The slag addition led to a refinement of the pore structure of fly ash-based geopolymers, but an increment in the concentration of alkali leaching. The crystal deposits gradually developed in the pore volume of the binders, and finally exceeded the capacity of pore volume. The extent of efflorescence on the surface of specimens increased with the slag substitution. The visible efflorescence is therefore a result of available alkalis and pore sizes and volumes. Higher concentration of available alkalis and smaller pores （and volume） will lead to more intensive efflorescence.

基于中继的OFDMA网络中可扩展编码视频流传输的权衡优化(英文)

To achieve an optimal trade-off between video quality and energy efficiency in the uplink streaming of multi-user Scalable Video Coding (SVC) videos in relay-based Orthogonal Frequency Division Multiple Access (OFDMA) cellular networks, a cross-layer design framework that jointly selects the Transmission Policy (TP) for SVC video frames, assigns OFDMA subcarriers, and allocates power for each subcarrier is proposed. We apply the dual decomposition method to the problem, and obtain a TP selection subproblem for each SVC video adaptation and a resource allocation subproblem of Joint Subcarrier, Relay and Power Allocation (JSRPA). A second level of dual decomposition is used to divide the JSRPA problem into independent subcarrier subproblems. The proposed Crosslayer Trade-off Optimization (CTO) algorithm is sub-distributed with significantly low complexity. A performance evaluation with typical SVC video traces demonstrates that the proposed algorithm is able to converge and efficiently achieve the optimal trade-off between the video quality and energy consumption at the MSs for uplink SVC streaming.

High Performance Micro CO Sensors Based on ZnO-SnO_(2) Composite Nanofibers with Anti-Humidity Characteristics

ZnO-SnO_(2) composite nanofibers are synthesized via an electrospinning method and characterized by x-ray diffraction,scanning electron microscopy,and transmission electron microscopy.Micro sensors are fabricated by spinning the nanofibers on Si substrates with Pt signal and heater electrodes.The sensors with small areas(600μm×200μm)can detect CO down to 1 ppm at 360℃.The corresponding sensitivity,response time,and recovery time are 3.2,6 s,and 11 s,respectively.Importantly,the sensors can operate at high humidity conditions.The sensitivity only decreases to 2.3 when the sensors are exposed to 1 ppm CO at 95%relative humidity.These excellent sensing properties are due to combining the benefits of one-dimensional nanomaterials and the ZnO-SnO_(2) grain boundary in the nanofibers.

Smart Grid Demand Side Response Model to Mitigate Peak Demands on Electrical Networks

The work presents a demand side response（DSR） model,which assists electricity consumers to proactively mitigate peak demand on electrical networks in Eastern and Southern Australia. A low-cost technical arrangement,which is made of Internet relay,a router,solid state switches,and the suitable software,is used to control electricity demand at user＇s premises. The model allows shifting loads from peak to off-peak periods in order to reduce peaks,which helps to moderate the national electrical demand. The model can be concurrently used to accommodate the utilization of renewable energy sources and the introduction of electric vehicles. The results present possible savings on the electrical energy consumption in the designated regions.

Real-Time Modelling and Optimisation for Water and Energy Efficient Surface Irrigation

The viability and sustainability of crop production is currently threatened by increasing water scarcity. Water scarcity problems can be addressed through improved water productivity and the options usually presumed in this context are efficient water use and conversion of surface irrigation to pressurised systems. By replacing furrow irrigation with drip or centre pivot systems, the water efficiency can be improved by up to 30% to 45%. However, the installation and application of pumps and pipes, and the associated fuels needed for these alternatives increase energy consumption. A balance between the improvement in water use and the potential increase in energy consumption is required. When surface water is used, pressurised irrigation systems increase energy consumption substantially, by between 65% to 75%, and produce greenhouse gas emissions around 1.75 times higher than that of gravity based irrigation systems so their use should be carefully planned keeping in view adverse impact of carbon emissions on the environment and threat of increasing energy prices. With gravity-fed surface irrigation methods, the energy consumption is assumed to be negligible. This study has shown that a novel real-time infiltration model REIP has enabled implementation of real-time optimisation and gravity fed surface irrigation with real-time optimisation has potential to bring significant improvements in irrigation performance along with substantial water savings of 2.92 ML/ha which is equivalent to that given by pressurised systems. The real-time optimisation and control thus offers a modern, environment friendly and water efficient system with close to zero increase in energy consumption and minimal greenhouse gas emissions.

基于结构拓扑随机变异的水平集优化方法

基于结构拓扑导数的水平集优化方法,利用结构拓扑导数信息和通过不断减少结构体积的方式来确定需开孔的结构位置,需选用最大设计区域结构作为初始优化结构.该方法不适合求解结构体积等式约束的优化问题.为了解决上述问题和克服水平集方法不能在结构内产生新孔洞的困难,提出了一种基于结构拓扑随机变异的水平集优化方法.引进了以小概率随机方式进行结构拓扑变异的结构优化方案.设计了变异算子,讨论了提出方法的收敛性情况.最后,结合考虑结构最大设计区域限制的结构拓扑优化的水平集方法,建立了一套新的涉及结构柔顺度作为目标函数,体积作约束条件的水平集演化算法.给出的算例验证了该方法的正确性和有效性.

空间调制系统的遍历容量分析(英文)

Spatial Modulation(SM) is a newlyintroduced wireless transmission scheme,andSpace Shift Keying(SSK) is its simplifiedversion.Their capacity performance has notbeen well examined to date.Starting frombasic definitions of information theory,through theoretical analyses and numericalcalculations,this paper evaluates the capacityof SM systems in various channels.Our conclusion is that under Rayleigh fading channels,the capacity of the SSK system is limited bythe Signal-to-Noise Ratio(SNR) or the number of transmit antennas,whichever one issmaller.From the capacity point of view,theSM system is better than the Single-Input andSingle-Output(SISO) system,but worse thanthe Multiple-Input and Single-Output(MISO)system.The correlation between transmit antennas will degrade the performance of theSSK system.Line-of-Sight(LOS) may causeperformance degradation for SSK,but capacity increases for SM.

Preliminary laboratory test on navigation accuracy of an autonomous robot for measuring air quality in livestock buildings

Air quality in many poultry buildings is less than desirable.However,the measurement of concentrations of airborne pollutants in livestock buildings is generally quite difficult.To counter this,the development of an autonomous robot that could collect key environmental data continuously in livestock buildings was initiated.This research presents a specific part of the larger study that focused on the preliminary laboratory test for evaluating the navigation precision of the robot being developed under the different ground surface conditions and different localization algorithm according internal sensors.The construction of the robot was such that each wheel of the robot was driven by an independent DC motor with four odometers fixed on each motor.The inertial measurement unit(IMU)was rigidly fixed on the robot vehicle platform.The research focused on using the internal sensors to calculate the robot position(x,y,θ)through three different methods.The first method relied only on odometer dead reckoning(ODR),the second method was the combination of odometer and gyroscope data dead reckoning(OGDR)and the last method was based on Kalman filter data fusion algorithm(KFDF).A series of tests were completed to generate the robot’s trajectory and analyse the localisation accuracy.These tests were conducted on different types of surfaces and path profiles.The results proved that the ODR calculation of the position of the robot is inaccurate due to the cumulative errors and the large deviation of the heading angle estimate.However,improved use of the gyroscope data of the IMU sensor improved the accuracy of the robot heading angle estimate.The KFDF calculation resulted in a better heading angle estimate than the ODR or OGDR calculations.The ground type was also found to be an influencing factor of localisation errors.

An intelligent system for egg quality classification based on visible-infrared transmittance spectroscopy

The potential of the visible infrared(Vis–IR)(400–1100 nm)transmittance method to assess the internal quality(freshness)of intact chicken egg during storage at a temperature of 30±7C and 25±4%relative humidity was investigated.Two hundred chicken egg samples were used for measuring freshness and spectra collection during egg storage(up to 25 days).Two correlation models,firstly between Haugh unit(HU)and storage time,and secondly between the yolk coefficient(YC)and storage time,were developed and yielded correlation coefficients(R^2)of 0.86 and 0.96,respectively.These models spanned the period for which egg quality decreased dramatically and are statistically significant(P<0.05).In addition,to reduce the dimensionality of the spectra and extract effective wavelengths,two methods were developed based on principal component analysis(PCA)and a genetic algorithm(GA).The output of PCA and GA were also used comparatively to design an egg quality intelligent system.The result of the analyses indicated that identification ratio of GAwith fast Fourier transform(FFT)preprocessing was superior to other methods,and that the quality classification rates of this method for one-day-old eggs are 100%.This study shows that identification of an egg’s freshness using NIR spectroscopy with GA and artificial neural network(ANN)is reliable.

Research on uplink coordinated transmission schemes in LTE-advanced systems

The investigation of inter-cell interference mitigation techniques is a key area in wireless communications.Coordinated multiple points（CoMP） transmission/reception is a candidate technique for interference cancellation in 3GPP LTE-Advanced system.However,the coordination scheme in CoMP remains a key research problem to be solved,which will have a strong influence on the performance of CoMP.In this paper,a novel coordinated transmission scheme is proposed for the uplink LTE-Advanced system.In our scheme,several base transceiver stations（BTS） and users are selected as coordination partners which form a CoMP cluster.Joint processing is used at the receiver to mitigate interference.From the perspective of coordinated partner selection,our scheme can be divided into static and dynamic coordination which are both considered to fully exploit the throughput gain of CoMP.The proposed schemes are evaluated by system level simulation and compared with the conventional LTE system based upon single cell processing.Our simulation results demonstrate that the proposed schemes attain superior performance as opposed to the conventional system in terms of cell average and cell edge throughput.

Approximate inter-cell interference modeling for cellular network

In this paper, we develop and analyze several inter-cell interference modeling methods for cellular network. The models can analyze multiple interfering signals under different fading scenarios. Incoherent addition of summing multiple interfering signals is assumed. We propose an approximate method that uses the generalized Gram-Charlier series to analyze the error of the reference model. The approximate method is not only simple but also with neglectable errors. The methods proposed could be very useful in practical system design and analysis.

Biocomposites:Their multifunctionality

During the last decade,tissue engineering has shown a considerable promise in providing more viable alternatives to surgical procedures for harvested tissues,implants and prostheses.Due to the fast development on nano-and biomaterial technologies,it is now possible for doctors to use patients’cells to repair orthopaedic defects such as focal articular cartilage lesions.In order to support the three-dimensional tissue formation,scaffolds made by biocompatible and bioresorbable polymers and composite materials,for providing temporary support of damaged body and cell structures,have been developed recently.Although ceramic and metallic materials have been widely accepted for the development of implants,their non-resorbability and necessity of second surgical operation(like for bone repair),which induce extra pain for the patients,limit their wide applications.The development of different types of biocomposites for biomedical engineering applications is described.These biocomposites include(i)basic biomaterials;(ii)natural fiber-reinforced biocomposites and(iii)nanoparticle-reinforced biocomposites.Their multifunctionality is discussed in terms of the control of mechanical properties,biodegradability and bioresorbability.