bluuebunny/crossref_metadata_2025 huggingface dataset:
Denial-of-Service (DoS) Attack and Botnet
Authors: Arora Arushi , Yadav Sumit Kumar , Sharma Kavita
Published: February 2018

This chapter describes how the consequence and hazards showcased by Denial of Service attacks have resulted in the surge of research studies, commercial software and innovative cogitations. Of the DoS attacks, the incursion of its variant DDoS can be quite severe. A botnet, on the other hand, is a group of hijacked devices that are connected by internet. These botnet servers are used to perform DDoS attacks effectively. In this chapter, the authors attempt to provide an insight into DoS attacks and botnets, focusing on their analysis and mitigation. They also propose a defense mechanism to mitigate our system from botnet DDoS attacks. This is achieved by using a through access list based configuration. The artful engineering of malware is a weapon used for online crime and the ideas behind it are profit-motivated. The last section of the chapter provides an understanding of the WannaCry Ransomware Attack which locked computers in more than 150 countries.
Audio Watermarking With Reduced Number of Random Samples
Authors: Anand Rohit , Shrivastava Gulshan , Gupta Sachin , Peng Sheng-Lung , Sindhwani Nidhi
Published: February 2018

Digital signal watermarking is an indiscernible and safe transmission of freehold data through host signal that includes immersing into and extrication from the actual host. Some algorithms have been investigated for the strong and secure embedding and extraction of watermarks within the host audio files but they do not yet yield good results in compression and re-sampling. In this chapter, an excellent method is suggested for the compressed wave files that uses random carrier to immerse the watermark in the sequence of an audio signal. The watermark is embedded lucently in audio stream after adaptive differential pulse code modulation (ADPCM) before quantization. The proposed scheme has been implemented and its parameters are compared with the finest auditory watermarking method known. A tool has been used to measure the parameters to produce the results and tabular values. The larger PSNR and smaller BER prove that the suggested scheme is robust.
Intelligent Techniques Inspired by Nature and Used in Biomedical Engineering
Authors: Deperlioglu Omer
Published: March 2018

Managing medical information and knowledge is becoming an increasing problem for healthcare professionals. Medical science that contains ever-increasing amounts of knowledge, such as the medical history of a patient, medical data about diseases, diagnosis and treatment methods, should be necessarily a science of information. The real problem faced by patients and healthcare providers is finding and using relevant knowledge at the right time. In this context, in the middle of 1950s, intelligent computer systems, called clinical decision support systems (CDSS), were introduced as a new concept. CDSS is defined as an active intelligent system that can help medical experts to make decisions by taking specific recommendations. Also, it provides decisions based on resolving patient-specific information and related medical truths. The objective of this chapter is to focus on these systems and explain relations with the field of artificial intelligence methods, approaches, or techniques in this manner.
On the Transformation of Social Movements
Authors: Köroğlu Cemile Zehra Zehra , Köroğlu Muhammet Ali
Published: February 2018

As social entities, people could come together and create regular relations and institutions. Concepts such as group, community, society, social movement, etc. are about the social dimension of man. However, according to the conditions of the social, political, religious, and physical environment in which the person lives, their needs and problems can change. As a natural consequence of this, social characteristics of social movements can change. It is inevitable to value new social movements in this respect. Because new social movements in the West are born from a critical intellectual atmosphere against modernity. This situation has developed in an economic system based on the service sector rather than economic-order-based on heavy industry. On the other hand, the Eastern world, especially the Islamic world, has a repertoire of social movements that brings different problems to the agenda because it has different conditions. In this respect, new observations and analyses of Turkey and its surrounding will provide important contributions to the theory of social movements.
Harmful Effects of Ecosystem Impairment on Human Health
Authors: Singh Suruchi , Agrawal Shashi Bhushan , Agrawal Madhoolika
Published: February 2018

Growing global population has caused environment degradation through ecosystem impairment and over exploitation. Although, people have made great moves for improving life style, and enjoy a drastically improved quality of life but such improvements have been made at the cost of environment degradation. Climate change will force humans to adjust with changing environment and find ways to deal with short term protection and long term health consequences. The range of potential threats to human health caused by climate change is increasing and at the same time is not clear. So, owing to the potential magnitude and universality of such an issue, we have a moral obligation for developing proper tools and make informed choices that ultimately result in better lives for the humans.
Airborne Particulate Matter
Authors: Dubey Bhawna , Pal Asim Kumar , Singh Gurdeep
Published: February 2018

Airborne particulate matter is considered to be most challenging environmental issues in the world today due to its impact on various atmospheric processes like regional and global climate change, ecosystem, agriculture and most importantly on human health in recent times. Analysis reveals that particulate matter contains various inorganic and organic compounds and biological entities and their secretions and toxic trace metals. The main regions affected are urban centers due to an increasing population, number of diverse industries, fossil fuel driven vehicles and various construction activities. The present chapter deals with the scenario of particulate matter, their sources of generation, size and their impact on human health and environment mainly in urban dwellings.
Improving Sustainability of the Environment in a Changing Climate
Authors: Arhin Albert
Published: February 2018

The mechanism of Reducing Emissions from Deforestation and Degradation plus conservation, sustainable forest management and enhancement of carbon stocks is emerging as one of the current efforts and actions being developed by the international climate change community to mitigate climate change. This chapter highlights the potentials as well as the challenges of this mechanism to reduce forest loss and improve the health and sustainability of the environment. Main potentials include its resolve to make trees worth more standing than cut, the transfer of funds to support conservation efforts and a focus on delivering social benefits. The main challenges include the less attention on unclear tenure and benefit-sharing framework; weak institutions and the complex historical, political and structural interests which have allowed powerful groups to expropriate the forest resources and trade-offs that may arise during implementation. It then outlines four broad areas where researchers can make contributions in national and local level policy-making and interventions related to REDD+.
Climate Change Impact on the Water Resources of the Limpopo Basin
Authors: Alemaw Berhanu F. , Chaoka Thebeyame Ronald
Published: February 2018

This chapter aims to evaluate the impacts of climate change on both hydrologic regimes and water resources of the Limpopo River Basin in southern Africa. Water resources availability in the basin, in terms of, seasonal and annual runoff (R), soil moisture (S) and actual evapotranspiration (Ea) is simulated and evaluated using the hydrological model, HATWAB. These water balances were computed from precipitation (P), potential evapotranspiration (Ep) and other variables that govern the soil-water-vegetation-atmospheric processes at 9.2km latitude/ longitude gird cells covering the basin. The 1961-90 simulated mean annual runoff reveals mixed patterns of high and low runoff across the region. Although relatively small changes in runoff simulations are prevalent among the three climate change scenarios, generally the OSU simulated relatively high runoff compared to the UKTR and HADCM2 GCMs.
Fraud Track on Secure Electronic Check System
Authors: Zhang Ping , He Yijun , Chow Kam-Pui
Published: February 2018

The Electronic Check (eCheck) is designed to substitute paper checks to enhance the bank service with new ecommerce features in today's global economy, especially meeting the great upsurge of Internet and mobile banking services. The eCheck inherits all features of paper checks in an electronic format with some inherent advantages, as well as some new problems, which will be discussed in this article. Although the concept of eCheck has been put forward for more than two decades, the security of the eCheck system is still the key concern of the whole scheme, as well as the forensic trace of eCheck fraud. In this article, one implementation of a secure eCheck system is introduced which can defend most kinds of eCheck fraud and this article novelly analyzes how to trace back the fraud from a forensic perspective.
Discovering Process Horizontal Boundaries to Facilitate Process Comprehension
Authors: Delias Pavlos , Lakiotaki Kleanthi
Published: February 2018

Automated discovery of a process model is a major task of Process Mining that means to produce a process model from an event log, without any a-priori information. However, when an event log contains a large number of distinct activities, process discovery can be real challenging. The goal of this article is to facilitate process discovery in such cases when a process is expected to contain a large set of unique activities. To this end, this article proposes a clustering approach that recommends horizontal boundaries for the process. The proposed approach ultimately partitions the event log in a way that human interpretation efforts are decomposed. In addition, it makes automated discovery more efficient as well as effective by simultaneously considering two quality criteria: informativeness and robustness of the derived groups of activities. The authors conducted several experiments to test the behavior of the algorithm under different settings, and to compare it against other techniques. Finally, they provide a set of recommendations that may help process analysts during the process discovery endeavor.
Minimal-Disturbance Arm Damper Retrofitting: Evaluation of Retrofit Effect Using Multi-Span Steel Frame Specimens
Authors: Marzano Giuseppe , Zhang Lei , Sasaki Yuga , Kurata Masahiro
Published: February 2018

In steel moment-resisting frames, concrete floor slab attached to steel beams contributes a larger stiffness and moment strength under positive bending. The composite action shifts up the section neutral axis and increases the risk of fracture at the bottom flanges of beam ends. A retrofit technique, named minimal disturbance arm damper (MDAD), is proposed as a solution to restrain the local deformation at beam ends and reduce the frame responses with moderate increase in stiffness, strength and damping. MDAD can retrofit steel frames rapidly by only using the bolt connections and preserve the open space of the frames. In this paper, the effectiveness of MDAD in improving the seismic performance of the steel frame was experimentally and numerically examined through the application to half-scaled multi-span specimens. The test and numerical results both showed significant benefits of MDAD in reducing the positive bending moment at beam ends, delaying the fractures at the bottom flange of beam ends and providing alternative load–carrying paths after fracture to prevent strength reduction.
Seismic Assessment of Existing Eccentrically Braced Frames According to NBCC and ASCE 41-13 Evaluation Procedures
Authors: Koboevic Sanda , Porthier de Bellefeuille Guillaume , Maheu Pierre Etienne
Published: February 2018

The seismic performance of an existing 8-storey EBF with shear-critical links located in Victoria, BC, is assessed. The frame is designed according to 1995 NBCC and the CSA S16-94 steel design standard. Seismic assessment is first performed in accordance with recommendations of the User’s Guide to NBCC 2015 using equivalent static force procedure, response spectrum analysis and linear time history analysis. A Tier 3 systematic evaluation according to ASCE 41-13 is then carried out using a linear static and dynamic procedure. Even though the original frame design was based on capacity design principles, both procedure revealed an inadequate strength of the frame members and the need for strengthening. Although the ASCE 41 procedure resulted in a less severe assessment, failures were predicted for most of the columns and for some outer beams. Considering bending as deformation-controlled action alleviated outer beam response.
Effect of Beam-Column Connection Fixity on Collapse Performance of a Six-Storey Special Concentrically Braced Frame
Authors: Mohsenzadeh Vahid , Wiebe Lydell D.A.
Published: February 2018

Concentrically braced frames are one of the most common seismic force resisting systems because of their high strength and stiffness. In current practice, the gusset plates that connect the brace to the adjacent beams and columns can increase the strength and stiffness of the connection significantly. This strength and stiffness can provide a reserve of lateral force resisting capacity during a large earthquake, which may play a role in the seismic collapse behaviour of the braced frame. An alternative connection has recently been proposed as a means of ensuring that brace buckling occurs only in-plane, that no field welding is required, and that all damage is confined to a replaceable brace module. However, the proposed connection does not include a gusset plate that can provide a similar stiffness and reserve capacity. In order to investigate the potential influence of the range of possible beam-column-gusset plate designs, this paper assesses the effect of the fixity of these connections on the behavior of a six-storey special concentrically braced frame. Nonlinear dynamic analyses have been conducted to determine the seismic performance of the frame with this connection modelled using three different assumptions (pinned, shear tab and fixed), and the collapse risk is assessed using the FEMA P695 methodology. The results show that when the gravity framing is not modelled, the fixity of the beam-column connections is important in avoiding the formation of a soft storey under extreme earthquakes, thereby reducing the probability of collapse of the building.
Seismic Behavior and Design of Innovative Modular Steel Floor System
Authors: Yang Tony Y. , Zhuo Si Rou , Li Yuan Jie
Published: February 2018

With increasing demands in high-rise constructions worldwide, developing a thinner steel floor system is becoming a crucial criterion in maximizing the useable and saleable spaces within a high-rise construction. This research aims to overcome the past drawbacks and develop an innovative and economical steel floor system that can be modularized and used within a modular construction. The proposed modular steel floor system can be fabricated offsite, shipped and assembled on site. This saves the construction time and fabrication cost. In this paper, the specially designed modular floor system was optimized for both gravity and lateral loads. The seismic performances of the proposed floor system are used in a 3-story prototype building. The results show that the proposed system is highly efficient in transferring the gravity and lateral loads which can be used effectively and efficiently for modular constructions worldwide.
Seismic Ratchetting of Single-Degree-of-Freedom Steel Bridge Columns
Authors: Saif Khaled , Lee Chin Long , Yeow Trevor , MacRae Gregory A.
Published: February 2018

Nonlinear time history analyses of SDOF bridge columns with elasto-plastic flexural behaviour which are subject to eccentric gravity loading are conducted to quantify the effect of ratchetting. Peak and residual displacements were used as indicators of the degree of ratchetting. The effects of member axial loads and design force reduction factors were also investigated. It was shown that displacement demands increased with increasing eccentric moment. For eccentric moment of 30% of the yield moment, the average maximum and residual displacements increase by 4.2 and 3.8 times the maximum displacement, respectively, which the engineers calculate using static methods without considering ratchetting effect. Design curves for estimating the displacement demands for different eccentric moments are also developed. The current NZ1170.5 (2016) provisions were found to be inadequate in estimating the maximum displacement for steel structures, and hence, new provisions for steel structures should be presented.
Shake Table Tests of Structures with CFS Strap-Braced Stud Walls
Authors: Terracciano Maria Teresa , Bucciero Bianca , Pali Tatiana , Macillo Vincenzo , Fiorino Luigi , Landolfo Raffaele
Published: February 2018

The unconventionality of the cold-formed steel (CFS) structures raised, in recent times, a lot of interest from many national and international companies resulting in the promotion of experimental activity with the main aim of investigating the seismic behaviour of these systems. In this perspective, a research project carried out at the University of Naples “Federico II” and funded by Lamieredil S.p.A. company started in the last years. The study included an extended experimental campaign, involving shake table tests on two three-storey prototypes in reduced scale (1:3). The investigated lateral load resisting systems were CFS strap-braced stud walls, designed as low dissipative seismic structures. The present paper illustrates case study, prototypes, test program and main shake table tests results.
Equilibrium Analysis of Pin-Jointed Steel Structures under Large Variations of Configuration
Authors: Corbi Ileana , Corbi Ottavia , Tropeano Francesca
Published: February 2018

In the paper an equilibrium analysis of pin-jointed steel structures is described. The attention is focused on the non-linearity problem that characterizes this type of steel structures under large displacements. A matrix method is developed, starting from a balanced and congruent configuration. Firstly, the analysis is conducted on the single bar; the, the behaviour of the global structure is analysed through the re-assembling and the final non-linear relationships between the variation of loads and the configuration are identified in order to proceed to the iterative solution path.
Strip Model Analysis for Steel Plate Shear Walls in Earthquake Resistant Structures
Authors: Totter Eduardo , Formisano Antonio , Mazzolani Federico M. , Crisafulli Francisco
Published: February 2018

Unstiffened Steel Plate Shear Walls (SPSWs) are very effective structural systems designed to resist lateral forces. SPSW systems consist of thin web plates infilled within frames of steel horizontal and vertical boundary elements. The thin unstiffened web plates are expected to buckle in shear and to develop diagonal tension field after buckling under the action of horizontal loads. For unstiffened steel plates, buckling in shear occurs in the elastic range at low stress levels. This behaviour provides strength, stiffness and ductility and allows to have an appropriate level of energy dissipation through tension yielding of the web plates. This paper assesses the inelastic structural response and behaviour of Steel Plate Shear Wall systems using both a modified strip model approach and a new simplified strip model for only beam connected SPSWs. Both models are developed with plasticity concentrated elements and the performed analyses include the nonlinear behaviour of strips, also considering the compressive forces effects over the strip model elements. This research indicates fundamental aspects of the seismic performance of Steel Plate Shear Wall systems, such as energy dissipation capacity, panel ductility demand, seismic inter-story drift and design load demands in Vertical Boundary Elements (VBE) and Horizontal Boundary Elements (HBE) of the frame. The results obtained from the use of these models are compared with selected experimental and numerical results to enrich the research conclusions.
Composite Frames with Dissipative Beam Splices: Numerical Analyses and Design Guidelines
Authors: Calado Luís , Proença Jorge M. , Sio João F.A.
Published: February 2018

Interest in designing structures that cost less to repair after they have been subjected to strong earthquakes has been increasing in the recent years, which led to the development of innovative repairable welded FUSEIS beam splices serving as dissipative beam-to-column connections in moment resisting composite steel and concrete frames. Upon a review on the individual characteristics of the beam splices obtained from an extensive experimental campaign, retrieving the necessary information to perform their modelling and validation in numerical analyses, the beam splices were applied on 3 case study building configurations comprising of 2, 4 and 8 stories to evaluate their global performance under seismic action. Numerical analyses were performed, in which the buildings were designed and safety checked through a Eurocode 8 based procedure that had been proposed herein, including Linear Response Spectrum and Non-linear Static Pushover analyses. Comparison to equivalent traditional moment-resisting frame structures was conducted as well. The outcomes of these numerical analyses were satisfactory: (i) the system exhibited good behavior under seismic action, proving to be relatively strong and stiff with large capacity of energy absorption and (ii) inelastic deformations were strictly limited to the beam splices, avoiding the spread of plasticity to the rest of the structural elements.
Experimental Behavior of Square Tubed-Reinforced-Concrete Column to RC Beam Joints with Internal Diaphragms under Cyclic Loading
Authors: Gan Dan , Zhou Zheng , Zhou Xu Hong
Published: February 2018

This paper describes experimental investigation on three square tubed-reinforced-concrete (TRC) column to reinforced concrete (RC) beam joints with internal diaphragms subjected to cyclic loading, where width-to-thickness ratios of the steel tube in the panel zone and levels of axial load were selected as test parameters. Two failure modes, namely, joint shear failure and beam failure + bond failure were observed in the current test. Test results showed that the proposed composite joints exhibited favorable seismic performance.
Analytical Methodology to Predict the Beam Overstrength Considering the Composite Slab Effects
Authors: Chaudhari Tushar , MacRae Gregory A. , Bull Des , Clifton George Charles , Hicks Stephen
Published: February 2018

The design strength of moment resisting steel frames in seismic regions around the world is generally calculated without considering strength enhancement caused by the slab. For column and panel zone design in New Zealand, the beam overstrength including the slab effect is considered. If the slab could be detailed to provide reliable lateral force resistance, then considering it directly in design would result in smaller beam sizes and more economical steel frames. In this paper, a simple analytical model (considering all key modes of failures) to predict the variation in strength due to the presence of the slab is proposed and validated with the experimental data. The proposed model to develop dependable slab contributions may change the design of steel moment frames around the world.
Seismic Response of Composite Eccentrically Braced Frames with Short Dissipative Element
Authors: Vătăman Adina , Ciutina Adrian , Grecea Daniel
Published: February 2018

Eccentrically braced frames (EBF) in steel and composite solution are very well suited structural assemblies for buildings in areas with high seismicity. Due to their good energy dissipation capacity, they can undergo important lateral deformations by plastic hinge formation in the dissipative element (link element) without impacting the structural integrity of the system. The dissipative link elements can be short, medium or long (according to modern design norms, such as Eurocode 8), based on the ratio between shear force and bending moment. If the dissipative element length is smaller than 1.6(Mpl/Vpl) [mm], it is considered to be a short element and is predominantly subjected to shear. The links can be realized on steel solutions or composite with the concrete slab. However, the steel behavior is assumed for composite link. The current article presents the results of extensive numerical testing based on experimental results on the behavior of composite EBF with short link elements subjected to seismic-like lateral loads. The results will present the main differences in strength, stiffness and ductility between the responses of steel and composite EBFs. Finally, a parametrical study will show the influence of link length, influence of number of stiffeners and of the web slenderness.
Finite Element Modelling of Buckling Restrained Braces under Combined In-Plane and Out-of-Plane Loading
Authors: Cui Jian , Lee Chin Long , MacRae Gregory A.
Published: February 2018

During earthquakes, buckling restrained braces (BRBs) are likely subjected to both in-plane (INP) and out-of-plane (OOP) loadings simultaneously, therefore, BRBs are required to act robustly under combined INP and OOP loading. It is believed that the OOP loading will reduce the energy dissipation ability of BRBs. The intent of this study is to numerically investigate the performance of BRBs under combined INP and OOP loading with a finite element model of BRB with circular cross-section. Restraining concrete within the BRB is modeled as connector elements in the model and is proven to be an effective way. Simulation results show that the performance of BRBs under combined INP and OOP loading is not as good as that under the INP loading only and the energy dissipation ability is decreased by about 15% when the magnitude of OOP loading is equal to that of INP loading. Furthermore, the results give a deeper insight into the behaviour of BRBs under different combined OOP and INP loading histories.
Footfall Induced Vibration Response of a Base-Isolated Steel Building
Authors: Malhotra Raunaq , Ndarowa Caleb , MacRae Gregory A. , Palermo Alessandro , Broglio Sara
Published: February 2018

Footfall induced vibrations can occur in elevated walking surfaces in structures due to normal human activities such as walking and running. If the vibrations are too high, they can cause occupant discomfort. Being able to reliably estimate the dynamic properties of the supporting structural system is a key part of designing a structure to limit such vibrations. However, currently, methods to assess the floor vibration response in realistic structures is not well known. This paper describes walking tests at an office building in the Christchurch CBD designed for earthquake both before and after fitout to determine properties and response. Sensitivity of floors to vibration response parameters such as the individual’s weight, the walking frequency and the presence of non-structural elements is considered. The results are then compared to numerical analyses which were conducted using OASYS, a commercial footfall analysis package, and SeismoStruct, a frame analysis software package. It was found from experimental tests dimensionless response factors (R-values) were generally less than 5 even for pre fit-out indicating that the floor considered is likely to be comfortable for occupants. The effect of fit-out tended to decrease the R-value by a factor of 1.2, but there was considerable scatter. The numerical OASYS and SeismoStruct models had similar stiffness and damping. However, they tended to estimate R-values greater about 1.0 larger than that found from walking field tests, which could be due to the fact that a larger damping value of the actual floor were calculated. These were 7 % and 10 % for pre fit-out and post fit-out respectively. In addition, in the field walking tests, the frequency range of 1.8-2.2 Hz had a negligible effect on the response. There was generally positive correlation between walker mass and R-value.
Effect of Abrasive Particle Size on Lapping of Sapphire Wafer by Fixed Abrasive Pad
Authors: Wang Jian Bin , Li Zhen , Zhu Yong Wei , Jiang Ben Chi , Shi Pei Cheng
Published: February 2018

The choice of abrasive particle size is crucial to improve the lapping efficiency and surface quality in lapping of sapphire wafer by fixed abrasive (FA) pad. A model for the penetration depth of a single abrasive is developed with fixed abrasive pad. A serious of lapping tests were carried out using FA pads embedded with different size of diamond particles to verify the validity of the developed model. Results show that the penetration depth of abrasive is related not only to the particle size, but to the hardness ratio of the work-piece to the pad as well. The material removal rate of sapphire is proportional to the square of abrasive particle size, while the average surface roughness is proportional to the abrasive particle size.
Study on Preparation and Modification of Oil-Soluble Nano-MMT
Authors: Cao Yang , Li Guang Yao , Nie Hua Wei , Zhang Ji Li , Lin Bei Sen
Published: February 2018

We discuss two methods of preparation and modification on nanoMMT, one is called “one-step method”, and another is called “two-steps method”. And then we use the IR, TEM, XRD, granulometer and sedimentation to test the effect of modification. The result shows that two methods can also modify nanoMMT, but the nanoMMT made by “one-step method” in lubricate oil is more stable and dispersed than another’s. Average grain diameter of nanoMMT made by “one-step method” in lubricate oil is 46nm, while another’s is 69.75nm. Also, it’s layer distance has expanded from 1.52nm to 2.10nm.
Effect of Ultrasonic Vibration Assisted Grinding Process on Surface Topography and Properties of C/SiC Composite
Authors: Wang Yan , Lin Bin , Ding Yan Yu , Fu Zhi Qiang , Zhang Xiao Feng , Dong Ying Huai
Published: February 2018

This paper study on the influence of ultrasonic vibration assisted grinding (UAG) process on surface topography and properties of C/SiC composites. Through the surface quality experiments of common grinding (CG) and UAG, the height distribution parameters and function parameters are obtained and used to analyze the characteristics of the material surface topography. The relationship between grinding process and the composites surface quality is pointed out by experimental research. The orthogonal design is employed to optimize ultrasonic parameters and grinding parameters. The optimized condition is carried out to modify the surface quality. The results show that ultrasonic vibration has a great influence on height and surface bearing properties; the surface roughness is improved by the small vibration amplitude and low frequency. The grinding depth is the key factor on surface topography modification and the feed rate is the second. According to the research, an important technical support is carried out to improve the surface performance of C/SiC composites.
Study on Two-Step Aging Technology of 6082 Aluminum Bumper
Authors: Zhao Bei Ming , Hu Miao , Zhu Jun , Han Zhen Yu , Sun Hou Qing , Ji Yu Ling
Published: February 2018

The influence of four parameters of two-step aging on the mechanical properties of 6082 aluminum alloy bumper was studied by orthogonal test. The results show that compared with the single stage aging, the two-step aging process can reduce the aging time and improve the production efficiency under the premise of the mechanical properties of the bumper meet the requirements. Among the four aging process parameters, the second stage aging temperature and holding time are the main factors that affect the final results, while the first stage aging temperature and holding time are secondary factors. The most suitable aging process parameters for the 6082 aluminum alloy bumper is (150 °C, 2 h) + (190 °C, 2.5 h). After two-step aging, the grain of the aluminum bumper is small and evenly distributed, leading to good mechanical properties. The generalized experiment shows that the application of the two-step aging process still has some limitations and needs to be further optimized and perfected.
Cutting Performance of Reaming Alloy Gray Cast Iron HT250 Using Carbide, Cermet and CBN Reamers
Authors: Yang X.K. , Wang Y.G. , Ge W.L. , Chen L. , Ge H.
Published: February 2018

Cutting performance of reaming alloy gray cast iron HT250 using carbide, cermet and CBN reamers was studied. Experiments were conducted under constant cutting parameters and cooling strategy. Tool life, hole diameter, spindle power, surface roughness and tool wear were analyzed. The hole diameter and spindle power would keep steady when reaming with carbide reamer after 400 holes to the tool life of 1050 holes. But holes diameter reduced and spindle power increased with the number of machined holes increasing during the whole tool life when using cermet or CBN reamer. The surface roughness Rz of the holes reamed by carbide reamer was within the tolerance, although it was worse than that reamed by cermet and CBN reamer. It can be summarized that the carbide was the most suitable material for reaming alloy gray cast iron because of the longest tool life, steady hole diameter and spindle power, qualified surface roughness. After machining, crater wear and clearance wear were produced on the cermet and CBN reamer, which were caused by abrasive wear. In addition, flaking and breakages appeared on the edge of cermet reamer, which were not found on CBN reamer. However, the clearance wear of carbide reamer was smaller than that of CBN reamer, and built up edge was found along the cutting edge.
Melt Mold Casting Process Optimization of Train Coupler Based on ProCAST
Authors: Wang Cheng Jun , Chen Jin Yan , Shen Yu Zhe
Published: February 2018

In order to solve production defects such as shrinkage and porosity inside a certain train coupler casting in Anhui Xinhong Machinery Co.,Ltd., the main reasons of defects are found through the process of CAE simulation analysis and physical X ray detection to determine the location and morphology of casting defects and to reflect the actual situation of coupler filling and solidification process. The main reasons are found as follows: uneven thickness of casting structure, insufficient original gating and feeding system and etc. Through the process optimization and apply multidimensional vibration, then test validation, the train coupler casting which meets the technical requirements has been successfully produced, ensuring the smooth mass production of the company. ProCAST numerical simulation results have confirmed the rationality of the proposed work in optimization process measures in reducing and eliminating the shrinkage defects.
Parametric Programming of Multi-Type Holes Using the Improved Genetic Algorithm
Authors: Zhang Yong Bin , Wang Tai Yong , Ding Yan Yu , Shen Teng Yue , Dong Jia Jia , Gao Shan
Published: February 2018

For path planning and program generation of multi-type holes, this paper presents a method of the path planning, by using the improved genetic algorithm based on chaos algorithm, and develops an interactive programming system for multi-type holes. Users can choose regular holes, and input the parameters and the necessary information, according to their needs. Then the system will combine holes automatically, and calculate the position coordinates of each hole. After that the path planning is carried out by using the improved genetic algorithm. Finally, the system carries out the simulation experiment of the path planning, and outputs NC program. Experiment shows the system can realize the path planning of multi-type holes by a combination of regular holes and generate the NC code after path planning. The optimization of path is better and the operation is more convenient than UG and other professional CAM software.
Investigating the Carbonation and Mechanical Performance of Reactive MgO Cement Based Concrete Mixes
Authors: Unluer Cise
Published: February 2018

Carbonation governs the microstructure and the overall mechanical performance of mixes involving MgO cements as the main binder. Aggregate grading has a significant influence on the carbonation process due to the different particle arrangements that determine the porosity and permeability of the resulting formulations. This work investigates the effect of aggregate particle size distribution on the carbonation of blocks containing reactive MgO. Samples containing four different aggregate profiles were subjected to accelerated carbonation at 20% CO2 concentration for up to 28 days. While the influence of gap grading on strength development was not very pronounced, mixes with the lowest initial porosity indicated the greatest increase in density at the end of 28 days. This also translated into the highest strength results obtained due to the formation of hydrated magnesium carbonates, reaching 10 MPa only after 1 day of carbonation. The porosity values measured before carbonation were inversely correlated with the corresponding densities and final strengths of each mix. An inverse correlation between porosity and permeability values before carbonation led to the conclusion that the connectivity of pores rather than the total pore volume controls the carbonation reaction. Mixes with higher initial permeabilities achieved the highest strengths, proving that the extent of CO2 diffusivity is mainly dependent on pore connectivity.
Thermoelectric Properties of Nickel and Boron Co-Substituted NaCo2O4 Prepared by Electrospinning Technique
Authors: Erdal Mehmet Okan , Koyuncu Mustafa , Aksu Mehmet Levent , Uslu Ibrahim , Koçyiğit Serhat
Published: February 2018

In this study nickel and boron doped sodium cobalt oxide NaCo2-xNixByO4 (0≤x≤0.3, 0≤y≤0.1) nanocrystalline thermoelectric ceramic powders were synthesized using electrospinning techniques and then consolidated into bulk ceramics. The differences in the microstructure and thermoelectric properties of the samples as a result of doping effect have been investigated. The crystalline structures of the powders and nanofibers were characterized using X-ray diffraction and scanning electron microscopy and BET Analysis before and after the calcination process at different temperatures. Nanofibers prepared by the use of electrospinning technique, have a diameter of approximately 300 nm, and the diameter of the grains of calcined powders was observed to range between 150 to 500 nanometers. Thermoelectric properties of the bulk ceramics were measured by physical properties measurement system (Lot-Oriel PPMS) in a temperature range of 15–300 K. The calculated values of dimensionless figure of merit at 300 K are 4.25×10-5, 5.3×10-6, 8.6×10-5 and 9×10-6 for sintered powders from undoped, Ni and B doped powders, respectively.
IL-15 Promotes Polyfunctional NK Cell Responses to Influenza by Boosting IL-12 Production
Authors: Wagstaffe Helen R. , Nielsen Carolyn M. , Riley Eleanor M. , Goodier Martin R.
Published: February 2018

IL-15 is a key regulator of NK cell maintenance and proliferation and synergizes with other myeloid cell–derived cytokines to enhance NK cell effector function. At low concentrations, trans-presentation of IL-15 by dendritic cells can activate NK cells, whereas at higher concentrations it can act directly on NK cells, independently of accessory cells. In this study, we investigate the potential for IL-15 to boost responses to influenza virus by promoting accessory cell function. We find that coculture of human PBMCs with inactivated whole influenza virus (A/Victoria/361/2011) in the presence of very low concentrations of IL-15 results in increased production of myeloid cell–derived cytokines, including IL-12, IFN-α2, GM-CSF, and IL-1β, and an increased frequency of polyfunctional NK cells (defined by the expression of two or more of CD107a, IFN-γ, and CD25). Neutralization experiments demonstrate that IL-15–mediated enhancement of NK cell responses is primarily dependent on IL-12 and partially dependent on IFN-αβR1 signaling. Critically, IL-15 boosted the production of IL-12 in influenza-stimulated blood myeloid dendritic cells. IL-15 costimulation also restored the ability of less-differentiated NK cells from human CMV-seropositive individuals to respond to influenza virus. These data suggest that very low concentrations of IL-15 play an important role in boosting accessory cell function to support NK cell effector functions.
HYACINTHACEAE
Authors: Dold A. P. , Hammer S. A.
Published: February 2018

A NEW SPECIES OF ORNITHOGALUM FROM EASTERN CAPE. SOUTH AFRICA
Multiple measures of refractive state of a test eye making use of a Nidek ARK-10000 OPD-scan
Authors: Gillan W.D.H.
Published: February 2018

Introduction: It is important for the users of automated instruments that measure refractive state to know that the results obtained from such instruments  are  accurate  and  repeatable.  This study was conducted to investigate the repeat-ability of multiple measures of refractive state using a Nidek ARK-10000 OPD-scan.Method:  150  measurements  of  refractive state of a test eye were obtained using an OPD- scan.  The  method  of  focusing  and  triggering the instrument was varied for three sets of 50 measurements.Results:  The  results  of  this  study  suggest that the OPD-scan gives reliable and accurate measures of refractive state when taking mul-tiple measurements. Although the means of the various sets of measurements were significantly different, clinically the differences are probably insignificant.
From h e Editor ’ s Desk
Authors: Office Editorial
Published: February 2018

no abstract available
Perceptions, expectations, apprehensions and realities of graduating South African optometry students (PEAR study, 2006)
Authors: Oduntan A. O. , Louw A. , Moodley V. R.
Published: February 2018

The objective of this study was to establish the perceptions, expectations, apprehensions and realities of South Africa optometry students completing their undergraduate studies in 2006. Copies of a questionnaire containing relevant information were distributed to all graduating students at the four Universities offering Optometry. The responses were coded and analyzed. The respondents (N=143), representing 77% of the graduating students included 27.3% males and 72.7% females, aged 20 to 37 years (mean = 23.34 ± 2.75). About a third (32.9%) of the respondents considered opening their own practice as the best way of entering into practice. Also, this mode of practice was considered as providing the greatest fulfilment for their personal (60.8%) and professional (53.8%) goals as well as offering long  term financial security (43.7%). Many (56.6%) have secured employment before graduation. Upon graduation, 43.4% would like to join a franchise.  Many (79.7%) felt that Government was not offering sufficient opportunities for optometrists. The majority, (70.6%) felt that the South African optometry profession is fastly becoming saturated and this was of great concern to many (31.5%). About half, (50.3%) have plans to go overseas to practice and the most common destinations were the UK (36.1%) and Australia (15%).  The mean minimum monthly salary expected as new graduates was between R9 500 and R11 500 in the public and private sectors respectively. On a response scale, the future of optometry in South Africa was scored as 6.59 ± 1.92. Findings in this study may be useful to all stake holders in optometric education in South Africa, as they may reflect the future of the optometry profession in the country.
The covenantal trinitarian alternative to the scholastic dilemma
Authors: Ive Jeremy G.A.
Published: March 2018

This article sets out what it calls the ‘scholastic dilemma’ about whether God’s relation to the world is necessary or contingent – the former is based on a view of God primarily as intellect and the latter on a view of God primarily as will. In his dictum, Deus legibus solutus est sed non exlex, John Calvin rejects both these positions. The trinitarian basis for this dictum was spelt out more fully by later Calvinistic thinkers, including Abraham Kuyper and Cornelius van Til. Implicitly for Calvin and explicitly for Kuyper and Van Til, the love of the Persons of the Trinity for one another is the basis for God’s covenantal trustworthiness in his dealings with the world. Recognising this trinitarian basis allows us to conceive of God as at once faithful in his dealing with the world, and yet not dependent on the world for his existence. This has profound and far-reaching implications for our understanding of society, including the universal and institutional church and a recognition of the priority of relationships, both theoretically and practically.
Integrating different forms of knowledge in the teaching qualification Diploma in Grade R Teaching
Authors: Rousseau Nici
Published: February 2018

From a view of multiple types of knowledge for a blend in teacher education, the paperdiscusses the need for epistemological diversity in the types of knowledge for grade Rteacher education. I claim in this article that for epistemological diversity, innovativemixes of knowledge are required and that they have to be explicated. The argument of thearticle is that the decisions made by teacher educators when constructing a curriculumfor a new grade R qualification are especially challenging because of the narrow purposeof the qualification. The paper offers an analysis of various models of knowledge typesand mixes, outlining each one’s purpose. Finally, the paper provides an epistemologicaldistillation in a conceptual framework which can guide the process of curriculum making,offering all participants a chance to contribute to the layers underneath the patina of thepainting that offers life to the curriculum.
Continuous assessment and matriculation examination marks – An empirical examination
Authors: Shepherd Debra , Van der Berg Servaas
Published: February 2018

This study analyses information and feedback from matriculation level continuous assessment in the South African education system. Continuous assessment (CASS) at the time carried a 25% weight in the final matriculation (Grade 12) mark, and it provides feedback that affects examination preparation and effort. Weak assessment in schools sends wrong signals to students that may have important consequences for the way they approach the final examination. Moreover, similarly wrong signals earlier in their school careers may also have affected their subject choice and career planning.This study compares CASS data to the externally assessed matric exam marks for a number of subjects. There are two signalling dimensions to inaccurate assessments: (i) Inflated CASS marks can give students a false sense of security and lead to diminished exam effort. (ii) A weak correlation between CASS and the exam marks could mean poor signalling in another dimension: Relatively good students may get relatively low CASS marks. Such low correlations indicate poor assessment reliability, as the examination and continuous assessment should both be testing mastery of the same national curriculum. The paper analyses the extent of each of these dimensions of weak signalling in South African schools and draws disturbing conclusions for a large part of the school system.