bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Investigation on Boundary Layer Flow Control with Vortex Generators
Authors: Liu Guang Yuan , Wang Rui Bo , Zhang Chang Rong , Chen Feng , Xie Jiang Yu , Ma Shang
Published: September 2013

The numerical simulation method was adopted to analyze the effect on boundary layer thickness reduction of various vortex generator parameters. Results show that vortex generators are capable of reducing boundary layer thickness for about 66 percent, and the influence on centerline Mach number distributions is neglectable. Practicable vortex generators for 2.4m transonic wind tunnel half-model test section side wall are founded. Research results can be used for further applications of vortex generator in wind tunnel tests.
High Voltage Triggered Spark Gap with Repeatable Gas Filling Structure
Authors: Tian Zuo Xi
Published: September 2013

To resolve the problems of short working life and narrow operating voltage range of the spark gap with one-offin gas filling structure, a spark gap with repeatable gas filling structure was designed. The spark gap was composed of three electrodes and two gaps as well as gas filling devices. Electrodes structures adopted the form of field aberration three-electrode gas spark switch forming two discharge gaps between three electrodes of anode, cathode and triggering electrode. Gas filling devices were composed of fast connector, gas pipe, barometer and air valve, by which the gaps could be repeatedly charged and deflated from a hole at the center of anode. Working life is lengthened by exchanging gas, and operating voltage range is widened by changing gas pressure in a certain range. The spark gap was manufactured and applied successfully in a TEA CO2 laser with pulse energy 170J. The results prove the designs feasible.
Effect of Ball Milling Rotate Speed on the Properties of Quartz Sand Powder Materials
Authors: Wang Zhi Wen , Qiu Zhi Wen , Feng Yan Ping , Xie Ting Ting , Chen Jin Yun , He Qin Qin , Zhao Lei , Zhou Jian Feng , Wan Xiao Bin , Chen Xin Chao , Li Qiang , Ma Xiao Dong , Song Jie Guang , Fu Wei
Published: September 2013

In order to lay raw materials foundation for increasing the performance of insulating brick with the low grade quartz sand along the Yangtze River, the effect of ball milling time on the properties of quartz sand powder was researched via the ball milling method in this paper. The results show the grain diameter of quartz sand powder is gradually decreased, the grain fineness distribution is tapered narrowing. The liquidity of quartz sand powders is became poor with an increaseding the ball milling rotate speed, howerver, the tendency of variation is gradually relaxative. The vibration compaction density is decreased with an increaseding the ball milling rotate speed, but the fall amplitude difference is gradually shrinked. The ball milling rotate speed for 250r/min is better through the whole cost performance analysis.
The Angular Distribution of Scattering Intensity and Polarization for Nano-Graphite Aggregates
Authors: Wang Hong Xia , Sun Hong Hui , Liu Dai Zhi , Song Zi Biao
Published: September 2013

The light scattering characteristics of nanographite aggregates are analyzed in this paper. Three dimensional fractal structures of aggregates were simulated based on the diffusion-limited aggregation model (DLA). For the incident wave of different wavelength, the method of discrete dipole approximation (DDA) was used to compute the light scattering intensity of nanographite aggregates and the changes of polarization along with the scattering angles, and the light scattering characteristics of nanographite aggregates were compared with the equal volume spherical nanographite particles. The computing results show that the non-spherical complex shape of nanographite aggregates has great effect on the scattering characteristics in the visible and near-infrared, and the angle distribution of scattering intensity and polarization have many complex changes. The forward scattering intensity of nanographite aggregates is obviously stronger than the equal volume spherical nanographite particles.
Experimental Study on the Ultra-Precision Polishing for the Quartz Substrates
Authors: Sun Lei , Guo Wei Gang , Yuan Ju Long , Deng Qian Fa , Feng Ming , Zhou Wen Hua
Published: September 2013

The Quartz substrates are widely used in various fields, and the requirement for the surface quality of quartz substrate is higher than ever before. This paper focuses on the ultra-precision polishing technology for the quartz substrates, and the material removal mechanism in the process of ultra-precision polishing is discussed. The results showed that an extremely smooth surface of quartz substrate was obtained in the ultra-precision polishing process, and the best surface roughness reached Ra 0.82nm. Meanwhile, the thickness can be controlled very well.
Study on the Effect of Standoff Distance on Processing Performance of Alumina Ceramics in Two Modes of Abrasive Waterjet Turning Patterns
Authors: Liu Dun , Huang Chuan Zhen , Wang Jun , Zhu Hong Tao , Yao Peng , Liu Zeng Wen
Published: September 2013

Abrasive waterjet (AWJ) turning is an emerging technology, which plays an important role in machining cylindrical parts with the distinct advantages of negligible thermal effects and extremely low cutting force. This paper presents an experimental study of abrasive waterjet turning (AWJT) of Al2O3ceramics. The machining process and performance in terms of the depth of penetration (DOP), surface roughness (Ra) and actual impact angle (β) are discussed to understand the effect of standoff distance (SOD) on the processing performance at two different turning modes. Based on the results of these investigations, there is a significant change ofDOPandRaat differentSODin radial mode turning and the optimalSODof gaining maximumDOPand the minimumRais about 5.5mm.However, theDOPis nearly independent on theSODin offset mode turning. SmallerRaandDOPcan be obtained in offset mode. Furthermore, the results indicate that the roundness error of cylinder parts is probably improved with the properSODinterval in radial mode turning and it is suitable for machining cylinder part with considerably different radial size. The offset mode turning as the next operation after radial mode turning is recommended to process workpiece with excellent roundness. In this way, by understanding the effect ofSODon processing alumina ceramics, the paper establishes a good basis for developing strategies for optimizing processing parameters in order to generate the desired part geometry and achieve better surface quality.
An Experimental Study on Radial-Mode Abrasive Waterjet Turning of Alumina Ceramics
Authors: Yue Zhong Bo , Huang Chuan Zhen , Zhu Hong Tao , Wang Jun , Yao Peng , Liu Zeng Wen
Published: September 2013

A study on the radial-mode abrasive waterjet turning (AWJT) process is presented and discussed. An experimental investigation is carried out to explore the influence of process parameters on the depth of turning and material removal rate (MRR) when turning 96% alumina ceramics. The experiment is designed by the multifactor orthogonal experiment methods. The effect of feed speed, water pressure, abrasive mass flow rate, nozzle tilted angle and surface speed are investigated by the range analysis and variance analysis. The results show that the feed speed is the most significant variables affecting the depth of turning. Based on the test conditions, it is found that the most efficient conditions to maximize depth of turning are at a jet angle of 105 degree, a water pressure of 310MPa, an abrasive mass flow rate of 11.5 g/s, a surface speed of 5.5m/s and a feed speed of 0.05mm/s. At last, the effect mechanism of process variables on the depth of turning is analyzed qualitatively.
Investigation of Surface Roughness for Grinding Silicon Wafer of the Micro Pellet Diamond Tool
Authors: Luo Shenq Yih , Yu Tsung Han
Published: September 2013

The purpose of this paper was to investigate the silicon wafer surface roughness ground by the micro pellet grinding tool and the electroplated disc grinding tool with diamond grit size of 4-6 μm and 10-20μm under the spindle rotation speed of 500-2500 rpm and the feed rate of 1-5 μm/min. The results showed that the micro pellet grinding tool can get a better surface roughness of the silicon wafer than the electroplated disc tool. When the tools containing a larger diamond grit were employed, selecting a higher spindle rotation speed and a lower feed rate can obtain a better wafer roughness. However, when the tools of a smaller diamond grit were used, the spindle rotaion speed operates properly at a optimal value to obtain a best wafer surface roughness, which achieves Ra = 0.03-0.06 μm for the micro pellet tool. Besides, the material removal mechanism during the grinding silicon wafer for these two tools displayed mainly ductile grinding behavior.
Development of an Innovative Water Machining System Employing the Electric Rust Preventive Method - Precise Evaluation of Purity of the Refined Water with a Laser Turbidity Meter
Authors: Nishikawa Naohiro , Sawa Takekazu , Hagihara Yoshihiro , Yoshihara Nobuhito , Okawai Hiroaki , Iyama Toshirou , Mizuno Masahiro , Tsukamoto Shinya
Published: September 2013

Green manufacturing is important subject. In order to reduce waste disposal cost and environmental load, decreasing machining fluid that contains several chemicals such as oil, extreme pressure agent etc. is demanded. In this investigation, the electric rust preventive machining method system that uses only water as machining fluid have been developed. This paper mentioned about evaluation of recycled water quality. The refined water that is purified with developed water recycle system which is installed reverse osmosis membrane (RO) is too clean to evaluate by normal method till now. Using laser turbidity meter, precise water purification is evaluated precisely. Therefore, it is clarified that RO refined water turbidity (RO1=0.0006, RO2=0.0003) is very low compared with clean tap water (0.1207). So, water recycle system can remove contaminating fine particle from water. It is expected that scratch less ultra precision machining with water is enabled to conduct with high filtration ability.
Optimization of Hybrid Laser-Waterjet Micromachining of Silicon
Authors: Tangwarodomnukun Viboon , Wang Jun
Published: September 2013

Micro/nanofabrication with less damage has been raised as a challenging issue in advanced micro/nanomanufacturing industries. Recently, a new hybrid laser-waterjet machining technology has been developed, in which material is removed by laser heating and softening and waterjet cooling and expelling with negligible thermal damage to the workpiece. An optimization of the process parameters, such as laser pulse energy, laser pulse overlap, focal plane position, and waterjet offset distance, in the machining of silicon using this hybrid technology is presented in this study. Grey relational analysis based on an orthogonal array is employed to optimize the multi-performance characteristics, where the groove width and heat-affected zone are minimized while the groove depth is maximized.
Effectiveness of Ultrasonic Vibration on Press Forming
Authors: Ashida Yutaka , Aoyama Hideki
Published: September 2013

In press forming, it is most important to prevent wrinkling and cracking. A small clearance between the upper and lower dies is effective for preventing wrinkle generation. However, the small clearance increases sliding resistance between sheet material and dies and causes cracking of sheet material. On the other hand, large deformation of sheet material requires multi-step press working which involves incremental small deformations in order to avoid wrinkling and cracking. But this method requires a number of dies so that it increases cost and development time. In press forming, lubricant to reduce sliding resistance of sheet material is used for preventing wrinkling and cracks. However, the use of lubricant such as chlorofluorocarbon and trichloroethane has been restricted due to environmental concerns. The development of new press working techniques that do not use lubricant is thus desired. Since wrinkling and cracking are mainly caused by friction between sheet material and dies, forming techniques which can decrease the friction without lubricant are needed.
Research on Grain Impacting Load in Abrasive Flow Machining
Authors: Ding Jin Fu , Zhang Ke Hua , Xu Yong Chao
Published: September 2013

In order to grasp the microcosmic mechanism of abrasive flow machining (AFM), find out the real law of grain cutting workpiece surface, make out a reasonable process parameters and improve the abrasive flow processing efficiency. The process of grain (near to workpiece surface, called as active grains) cutting workpieces material has been analyzed and the cutting force model has been established in present work. Firstly, at the beginning of the present work, the general process of grain cutting, wearing or deburring workpiece surface has been researched. Theoretical analysis shows that the cutting force not only derives from static force, such as abrasive medium viscoelasticity and grain squeezing, but also dynamic force, such as grain impacting load on the workpiece surface. In ordering to prove the dynamic force exists, one or two main dynamic process parameters (such as abrasive viscosity, extrusion pressure, piston velocity) are chosen, dynamic force is most sensitive to the variation of which, meantime, static force is not, and then the effects of main dynamic process parameters on cutting force value have been compared with the effects of others process parameters by several experiments in the present work. The experimental results show that with the same proportion of variation of process parameters, the change in cutting force (mainly axial cutting force) consists with theoretical results very well in some degree.
CVD Micron Diamond Powders
Authors: Zhang T. , Sun F.H. , Shen Bin , Zhang Z.M.
Published: September 2013

The conventional diamond powders (< 10 μm) are generally produced from crushing the large-sized diamonds synthesized by high-pressure and high-temperature (HPHT) technique, whereas they have many morphological imperfections. In the present work, the hot filament chemical vapour deposition (HFCVD) technique is employed for synthesizing such diamond powders. A great many of micron diamonds are grown simultaneously but independently onto a large-area substrate. First, the seeds with an appropriate density approximately 1.3×1010 m-2 are dispersed evenly onto a mirror-polished silicon wafer by using a spin coater machine. Afterwards, the regrowth mechanism of seeds is mainly discussed. The results demonstrate that the unwanted spontaneous and secondary nucleation play a determinant role in keeping well in the morphology of crystals and inhibiting the poly-crystals growth.
Development of a Measuring Equipment for Silicon Wafer Warp
Authors: Liu Hai Jun , Kang Ren Ke , Gao Shang , Zhou Ping , Tong Yu , Guo Dong Ming
Published: September 2013

Larger diameter wafers are used to decrease the cost of IC manufacturing and the wafer thickness is decreasing for form factor and thermal power dissipation considerations. The larger wafer requires a large scanning area to inspect the warp, and warp measurement of large and thin silicon wafers is greatly affected by the gravity-induced deflection. In this paper the gravity-induced deflection was calculated using finite element method by supporting the wafer horizontally with three steel balls. A laser displacement sensor based on triangulation principle was used to measure the warp and an air bearing stage was developed to achieve high straightness. The shape of the wafer was obtained using the silicon wafer warp measuring equipment.
A Study of Mechanical Properties and Material Removal of Polycrystalline Tungsten via Nanoindentation and Nanoscratch
Authors: Kang Cheng Wei , Huang Han
Published: September 2013

Tungsten based products are extensively used in engineering practices. However, there exist some controversies in deformation behaviour between polycrystalline tungsten and its bulk counterpart. In this work, elastic modulus, hardness and removal characteristics of polycrystalline tungsten (poly-W) were investigated by use of nanoindentation and nanoscratch. Atomic Force microscopy (AFM) and Scanning Electron Microscopy (SEM) were employed to characterize the surfaces prior to and after indenting/scratching. The elastic modulus and hardness of the poly-W obtained were 323.6 and 7.1 GPa, respectively. Elastic recovery was barely observed in poly-W after indenting and scratching, indicating that the material was dominantly deformed in plastic regime. The plastic deformation of the poly-W was found to be somehow different from the bulk W, but similar to that of single crystal W nanowhiskers. In multi-scratch test, the pitch distance and scratching speed demonstrated to affect the roughness of the scratched surfaces.
On the Influence to Social Life of the Artistic Features in the Reuse of Materials
Authors: Li Zi Yuan , Hu Wei Ping , Liu Yan , Li Jie , Wang Tian Feng
Published: September 2013

Looking through the history of materials, people have been using them to process and produce our articles for daily uses all the time, therefore discovered the booming of the combination in artistic aesthetics and reused materials. The reuse of materials including the use of green materials which are environmental friendly and the recycle of old materials. The essay below will discuss the effect on the social life of the artistic features in the reuse of materials.
Localized Surface Plasmon Resonance of Single Silver Nano-Hemisphere
Authors: Li Rui , Liu Kun , Pan Shi , Ding Jian Hua
Published: September 2013

In this work, we use 3D finite difference time domain (3D-FDTD) to calculate the plasmon resonance effect for a single silver hemisphere in which the palsmon line shape have distinct peaks when the particles are located on a glass substrate. The dependence of the resonance on hemisphere size and the ratio of height over radius are characterized, and it is found that the surface interface effect played an important role on the plasman resonace effect for a single silver hemisphere.
Analysis of Stress in Half-Space Using Jacobian of Transformation and Gauss Numerical Integration
Authors: Čajka Radim
Published: September 2013

Stress strain analysis of elastic halfspace by means of Gauss numerical integration and Jacobean of transformation is presented. The arbitrary shape and general course of the loaded area in nodal points is allowed by use of 4-and 8-node isoparametric elements, numerical integration and Jacobean transformation. Results of numerical examples are compared with other solutions.
Research on Voltage Oriented Control Strategy of Grid-Connected Inverter of Wind Power Generation
Authors: Yang Yong , Lan Guang Ming , Sun Zhi Qi , Guo Jian , Zhang Zhong Qiang
Published: September 2013

Based on the dynamic mathematical model of three-phase grid-connected inverter, two kinds of control strategies are compared, one is double closed loop control based on grid voltage orientation theory, the other is direct power control. According to the mathematical model of two-phase rotating coordinates of the inverter, in double closed loop control theory, the purpose of control of the inverter by decoupling control and PI control is achieved. From the point of energy on direct power control system, the active, inactive power of output AC of inverter are calculated ,and suitable space voltage vector was selected after comparing with the given values to realize the direct control of the power set point. The basic theory of two control strategies and implementation method are included, and the simulation model was established based on MATLAB/Simulink. And their simulation results, characteristics of two kinds of control methods were compared through simulation data analysis. On the basic of results, the direct power control is better than the double closed loop control.
Intelligent Fault Diagnosis of Gear Box Based on BSS and SVM
Authors: Ma Wei Jin , Yu Rui Xiang , Wang Jun Yuan , Wan Xiao Fei
Published: September 2013

The vibration signal of gear box shows the information of its running state. The thesis explains the basic model and its algorithm of blind source separation, simulates the common fault of gear box in the condition of laboratory, disposing the fault signals of gear box by blind source separation and intelligently identifying the faulty condition of gear box by the method of support vector machine (SVM) after extracting eigenvector, which achieves success.
Solving Secure Problems for Wireless Sensor Networks Using Clustering and OKS
Authors: Zhang Yu Quan
Published: September 2013

A secure scheme for wireless sensor network is presented through dividing sensing area into clusters and using the overlap key sharing (OKS) concept in this paper. The two-dimensional sensing square is divided into a number of small squares called cells, four of which consist of a cluster called logical group. The overlap key sharing protocol creates long bit clusters as the key cluster pools and distributes a sub-group to store every sensor as the key cluster. Analysis and comparison demonstrate this scheme enhances the WSN security, realizes the flexile secure grades for WSNs, and has good network connectivity.
Predicting the Characteristics of Biofouling Mass Based on RBF Network
Authors: Wen Xiao Qiang
Published: September 2013

A new prediction model of material chemical character effects on biofouling mass was built based on RBF network, in which there were four input vectors, which were carbon content, hydrogen content and oxygen content of the solid materials and flow rate, and one output vectors, which was the average amount of biofouling formed on the solid surface. Firstly, creating the sample database and normalizing all samples. Secondly, training the model based on the training samples to obtain the optimal prediction model, then, predicting the training samples. Comparing with experimental results, the accuracy of the RBF model is 95.5%. Besides, the model was tested by poly (ethylene terephthalate), and the predicted and actual results are consistent. Thus, the construction of the predictive model is reasonable and feasible.
The Influence of Sulfurization Time and H2S Concentration on the Properties of Cu2ZnSnS4 Thin Films
Authors: Xie Min , Zhuang Da Ming , Zhao Ming , Li Bo Jian , Song Jun
Published: September 2013

CZTS thin films were fabricated through sulfurization of sputtered alloy precursors. The properties of CZTS films obtained at sulfurization time of less than 2 hours and at H2S concentrations of higher than 15% were investigated. Sulfurization time of 30 min, 60 min and 90 min and H2S concentrations of 20%, 40% and 60% have been chosen for the sulfurization process. It has been found that Cu poor and slightly Zn rich CZTS films can be obtained at all of those sulfurization time and H2S concentrations. Changing the sulfurization time or H2S concentrations wont change the compositions of sulfurized films. Minor SnS coexist with the dominate CZTS although the films are Zn rich and the distributions of Sn and S along the depth of the films are uniform. The films sulfurized at H2S concentration of 20% have the biggest grain size of exceeding 2 μm and obvious columnar CZTS grains can be observed across the whole cross-section.
Research of Superplasticity Deformation Behavior about Coarse-Grain Ti-22Al-25Nb Alloy
Authors: Li Yu Zhi , Yao Ze Kun , Zhou Wei , Qin Chun , Guo Hong Zhen , Liang Xiao Bo
Published: September 2013

This study investigates the superplastic deformation mechanism of coarse-grain materials .Superplasticity deformation behavior of Ti-22Al-25Nb alloy with 200~410μm coarse grain has been investigated through tensile test at 940~990°C and 3.3× (10-2~10-4) s-1 strain rate. Results prove coarse-grain Ti-22Al-25Nb alloy primary depends on slipping of crystal planes between two phases to achieve superplasticity. Transformation from lath O phase to ring equiaxed O phase occurs as temperature rises and its volume percent falls, but percentage of recrystallized B2 phase increases. Dislocation can move round ring equiaxed O phase. Good plasticity can be preserved because O phase can flow as solid particle in semisolid slurry in B2 grain.
Effect of Compactive Efforts on the Strength Properties of Groundnut Shell Ash Stabilized Reclaimed Asphalt Pavement
Authors: Edeh Joseph E. , Eberemu Adrian O. , Aburabul James Mzuaor
Published: September 2013

Large quantities of groundnut shell ash (GSA) are generated from the combustion of groundnut shell, disposed in large quantities on production sites while large volume of reclaimed asphalt pavements (RAP) aggregates are also generated during pavement rehabilitation and reconstruction and disposed along road alignments. This paper presents results of the laboratory evaluation of the effect of compactive efforts on the strength properties of GSA stabilized RAP with a view to determining its suitability as highway pavement material in pavement constructions. The RAP-GSA mixtures were subjected to Reduced British Standard light, RBSL (reduced Proctor); British Standard light, BSL (standard Proctor); West African Standard, WAS and British Standard heavy, BSH (modified Proctor) compactive efforts to determine the compaction characteristics, California bearing ratio (CBR), durability and water absorption characteristics. Test results show that the properties of RAP improved with GSA treatment. The particle grading improved from 99.13 % coarse aggregate and 0.87 % fines, with AASHTO classification of A-1-b for 100 % RAP, and 9.08 % coarse aggregate and 90.92 % fines, with AASHTO classification of A-4 for 100 % GSA to 15.6691.72 % coarse aggregate and 8.2884.32 % fines, with AASHTO classification in the range A-4 (silty soil) to A-1-a (granular materials), for the various RAP-GSA mixes. Maximum dry density (MDD) decreased while the optimum moisture content (OMC) increased with higher GSA content in the RAP + GSA mixes and with decreased compactive effort from BSH to RBSL. Optimum CBR values of 35.1% (unsoaked) and 44.1% (soaked) recorded for 90% RAP + 10% GSA mix achieved with BSH compactive effort, satisfied the durability requirements with insignificant expansion and water absorption and can be used as subbase material in flexible pavements construction. This research provides the results of evaluation of the effect of compactive efforts on the strength properties of GSA stabilized RAP as highway construction material, as it is based on CBR determination. Further work may be encouraged to assess resilient modulus of this material under cyclic load.
Analysis of the Effect of Environmental Factors on Outage Rates of Overhead Distribution Feeders: A Case Study of Zaria Distribution Network
Authors: Jimoh Boyi , Adegboye Juliet N. , Adegboye Babatunde A.
Published: September 2013

The paper is aimed at analysing the environmental factors on the outage rates of the overhead distribution feeders. This was facilitated using daily outage data on the six 33kV feeders of the Zaria distribution system collected from the Zaria Transmission substation of the Power Holding Company of Nigeria (PHCN) for twelve months. Outage models were developed from where power losses due to the feeder outages were obtained. Frequent and delayed forced outages occur during the rainy season, the peak being in August and during harmattan, especially in October. There were relatively high outage rates during the hot season, the maximum occurring in May. Feeders 2, 3 and 6 were most frequently on forced outages. The causes of the high outage rates are attributable to damages done to the overhead lines due to heavy winds, thunder strikes and other disturbances associated with rain. Other reasons include animal-caused outages, increase in the simultaneous use of weather sensitive devices, trees and vehicular accidents. As a result, energy loss was found to be 2947.62GWh, which translates to high revenue loss if the entire nation is considered. The forced outage rates are mapped to external environmental factors while the scheduled outages are due to the intrinsic factors. The paper proposes recommendations for minimizing the outage rates and hence improving the performance of the feeders.
Frequency Characterization of a Polarized UWB MIMO Channel at 3.5 GHz in an Indoor Environment
Authors: Muhehe J.D. , Muia L.M. , Ogola W.O.
Published: September 2013

In this paper, frequency characterization of a UWB indoor MIMO channel is presented. Measurements were conducted on a 4×4 MIMO channel within the frequency range of 2 to 5 GHz with a fixed SNR of 30dB. The impact of antenna polarization on the mutual information was also analyzed with antennas interelement spacing fixed at 2λ. Channel capacity was analyzed both in NLOS and LOS scenarios. It is realized that the spectral efficiency of the channel is a function of the operating frequency and the channel bandwidth.
Reliability Assessment of an Electronic System: A Case Study of Nokia N1650 Mobile Phone Charger in Zaria, Nigeria
Authors: Akinsanmi Olaitan , Ekundayo K.R. , Okorie Patrick U.
Published: September 2013

This paper assesses the reliability of a Nokia N1650 mobile phone charger used in Zaria, Nigeria. The Part Stress Method was employed to assess the reliability of the system. Data on the failure rate of the system components were used, with special considerations given to factors like environment of use, quality of power supply and service personnel. A comparative assessment was made on the system, when operated within the Zaria environment and when operated within the country for which it was designed for (China).The result shows that a lower reliability level is associated with the use of the system in Zaria, Nigeria as compared with the reliability level when in use in the country for which it was designed for. The Mean-Time to Failure of the system which is the time it is expected to function without failure (MTTF) in Nigeria is 1 years as against 10 years in China. The ratio is 10:1 in favour of the designed country. The ratio of the failure rate of the system is also 10:1 in favour of the designed country, meaning it fails ten times faster in Zaria environment as compared to the country for which the system was designed for. These are accounted for by higher variation in the environmental factors such as temperature, poor power quality, and poor maintenance culture in the applied environment.
Computer Immunity Using an Intrusion Detection System (IDS)
Authors: Konyeha Susan , Onibere Emmanuel A.
Published: September 2013

Computers are involved in every aspect of modern society and have become an essential part of our lives, but their vulnerability is of increasing concern to us. Security flaws are inherent in the operation of computers Most flaws are caused by errors in the process of software engineering or unforeseen mishaps and it is difficult to solve these problems by conventional methods. A radical way of constantly monitoring the system for newly disclosed vulnerabilities is required. In order to devise such a system, this work draws an analogy between computer immune systems and the human immune system. The computer immune system is the equivalent of the human immune system. The primary objective of this paper is to use an intrusion detection system in the design and implementation of a computer immune system that would be built on the framework of the human immune system. This objective is successfully realized and in addition a prevention mechanism using the windows IP Firewall feature has been incorporated. Hence the system is able to perform intrusion detection and prevention. Data was collected about events occurring in a computer network that violate predefined security policy, such as attempts to affect the confidentiality, integrity or its availability using Snort rules for known attacks and adaptive detection for the unknown attacks. The system was tested using real-time data and Intrusion Detection evaluation (IDEVAL) Department of Defense Advanced Research Projects Agency (DARPA) data set. The results were quite encouraging as few false positive were recorded.
Manufacturing Work Study and System Analysis of the NIFOR Digester Screw Press
Authors: Abikoye B.O. , Amiolemhen P.E.
Published: September 2013

It is generally assumed that the probability of the customer placing an order is always one, implying that customers will place orders regardless of producer quoted lead times and customer lead time expectations. As the job shops increasingly compete on the basis of the delivery speed and reputation, the relative performance of quoted versus actual realized lead times will have a strong effect on whether the customer will place future orders or not. A work study and manufacturing system analysis was conducted on the NIFOR digester screw press to study the techniques of job shop scheduling. Incessant delay in manufacturing process, job tardiness and unsatisfactory customers feedback had led to this research work. The work involves critical examination of all the resources and factors which affect the efficiency of the job shop. Machines set up times and run times were collected at each machine centre for all the components produced during the period of evaluation. The data collected were used as input data for the Gantt chart to evaluate the total actual times spent in performing each task. The work provides useful information for the development of an improved method of job scheduling for effective machine utilization so as to minimize the total time required for completion of all manufacturing tasks and reduce job tardiness.
Improved Design and Fabrication of a Cassava Chipping Machine
Authors: Mogaji P.B. , Adejuyigbe Samuel B.
Published: September 2013

The short shelf-life and bulkiness of cassava roots pose a great problem in transporting these roots from the farm to the market or factory sites. To overcome this difficulty in the marketing and utilization of cassava and to avoid heavy post-harvest losses, the roots need to be processed into some form of dried product with longer shelf life. The simplest and most common mode of processing cassava is the conversion of the roots into dry chips. Cassava processing into chips by traditional methods which involve the use of knife is labour-intensive but the application of improved processing technology has reduced processing time and labour and encouraged further production. An improved cassava chipping machine, with chip thickness between 3-6mm was designed to enhance the processing of cassava into chips to catalyze its drying period and preserve its nutritional value. The chipping machine consists of a hopper, a cutter plate and a power transmission system powered by a 1 hp electric motor. Computer Aided Design software was used in the design and appropriate material selection was considered for its fabrication. The cassava chipping machine was also simulated for stress analysis and behaviour of the machine was studied when loaded virtually. Chipping efficiency is 94.75%, machine capacity is 0.04kg/sec, chipping rate is 0.034kg/sec which is a function of the force applied.
Modeling of Some Related Parameters for Cracking Palm Nut in a Centrifugal Cracker
Authors: Antia Orua O. , Obahigbon Kessington , Aluyor Emmanuel , Ebunilo Patrick
Published: September 2013

In this study, the principles underlying the energy involved during cracking in a vertical centrifugal nut cracker was analyzed. This will help to elucidate the relationship between various parameters that are relevant to the design and operation of the centrifugal nut cracker for the Tenera and Dura varieties. Experimental analysis was then carried out for each of the two varieties. Each variety was classified into size ranges based on their geometric mean diameter (GMD). Technical analysis revealed that the revolution per minute required by the rotor disc of a centrifugal nut for effective nut cracking is influenced by rotor disc radius (r) and nut dimensions (d1, d2, d3).The modeled equation developed could be used for predicting nut translational kinetic energy required to crack dried nut of the Dura and Tenera varieties to release high percentage of whole kernel.
Enhancement of Microstructural and Hardness Properties of Commercially Pure Titanium (Ti-0.5Zn) by Thermomechanical Processing
Authors: Johnson Temidayo Oluwagbenga , Awopetu Olayinka O. , Dahunsi Olurotimi A.
Published: September 2013

Titanium alloys are widely used in the aerospace, biotechnology, automotive, energy, marine industrial constructions and components due to their high strength-to-density ratio, excellent fatigue/crack propagation behaviour and corrosion resistance. This study investigates the αβ phase transformation which Ti-0.5Zn alloy undergoes on being subjected to heat treatment with the aim of improving its properties and to enhance its industrial application. The β phase, with Widmatansttäten type growth was produced by heat treatment of the alloy in the temperature range of 800°C to 1000°C. The resultant microstructure and hardness of the alloy was also investigated. The result showed improved morphology evidenced by transformation from the equiaxed grains to more lamellar structures in the samples. Hardness property improved by 20% too.
Groundnut Shell Ash Stabilized Reclaimed Asphalt Pavement, as Pavement Material
Authors: Edeh Joseph E. , Joel Manasseh , Aburabul James Mzuaor
Published: September 2013

Large volume of reclaimed asphalt pavements (RAP) aggregates are generated during pavement rehabilitation and reconstruction and disposed along road alignment while large quantities of groundnut shell ash (GSA) are generated from the combustion of groundnut shell and also disposed in large quantities on production sites. This paper presents results of the laboratory evaluation of the characteristics of GSA stabilized RAP with a view to determining its suitability for use as highway pavement material in flexible pavements construction. The RAP-GSA mixtures were subjected to British standard light (BSL) (standard Proctor) compactive effort to determine the compaction characteristics and California bearing ratio (CBR). Test results show that the properties of RAP improved with GSA treatment. The particle grading improved from 99.13% coarse aggregate and 0.87% fines, with AASHTO classification of A-1-b for 100% RAP and 9.08% coarse aggregate and 90.92% fines, with AASHTO classification of A-4 for 100% GSA to 15.6691.72% coarse aggregate and 8.2884.32% fines, with AASHTO classification in the range A-4 (silty soil) to A-1-a [granular material, for the various RAP-GSA mixes. Maximum dry density (MDD) decreased while the optimum moisture content (OMC) increased with higher GSA content in the RAP + GSA mixes. Optimum CBR values of 22.2% (unsoaked) and 18.3% (soaked) were recorded for 80% RAP + 20% GSA and 90% RAP + 10% GSA mixes, respectively. This optimum mixes satisfied durability requirement with insignificant water absorption and can be used as subgrade material in flexible pavements. This research provides the results to the evaluation of GSA stabilized RAP as highway construction material, as it is based on CBR determination. Further work may be encouraged to assess resilient modulus of this material under cyclic load.
Analysis of Property Changes of Ductile Iron in Different Environments
Authors: Oke P.K. , Ukoba O.K.
Published: September 2013

The problem of engineering materials failing in structures like bridges, pipelines, refinery and automobile equipments is becoming a source of concern to the people of the developing nations especially Nigerians. This sometimes might be attributed to the environments in which the materials are being used or stored and the source of the materials. There is a need therefore, to evaluate the effects of these environments on the final property, especially the mechanical properties of the materials. Based on the peculiarity of ductile iron (DI) having its application in most engineering works in different environments, the material was subjected to four different environments namely alkaline (NaOH), brackish (NaCl), air conditioning (A/C), and outside environment, coinciding with the environments of application. The material was later subjected to series of mechanical tests and the behavioural changes (especially the mechanical property) of the materials in these environments were monitored for the period. It was observed that the ductile iron placed outside had the highest elastic properties and hardness of 1341.72Hv while alkaline environment had the highest strength of 3321.75MPa. The alkaline environment gives the highest performance as it had a quality index of 4,038,837, followed by outside environment while salty environment had the least.
Effects of Steelmaking Ladle Holding Period on Continuous Casting Yield
Authors: Edafeadhe Godspower O. , Godwin Harold C.
Published: September 2013

The study was undertaken to ascertain the effects of holding time during secondary steel making, casting duration, strand loss per heat, and tonnage of steel returned per heat on continuous casting yield (%). A total of 1910 heats, spanning a period of seven years (41 production months) were used for the study. Monthly tonnage of liquid steel produced and cast and the corresponding yield were computed from the casting reports. Also extracted from the casting reports are the average monthly holding time (mins) during secondary steel making, monthly average heat casting duration (minutes), average strand loss per heat and monthly average tonnage of steel returned per heat. A statistical package for social sciences (SPSS) was used to analyse the data obtained. The yield was found to be negatively correlated to steel holding time during secondary steel making (-0.257 mins), strand loss per heat (-0.753 tons), and tonnage of heat returned per heat (-0.944 tons), but positively correlated to casting duration (0.371 mins). The result showed that increase in holding time during secondary steel making, strand loss per heat and tonnage of steel returned per heat decrease the yield of continuous casting process. The model formulated was able to explain 93.4% of the total variation in the observed yield. Efforts should therefore be made to monitor and reduce these parameters that decrease the yield through proper process control, regular checks of the continuous casting machines, replacement of worn out moulds, and in-house training and retraining of casters for optimum process performance.
Evaluation of Solar Water Heating Systems in Botswana
Authors: Oladiran M.T. , Ossenburg E.
Published: September 2013

This paper presents results of an assessment of several solar water units to determine causes of their malfunctioning. A survey of solar water heater (SWH) installations in the Gaborone area, Botswana was carried out to obtain performance characteristics of SWH in the local market. Extensive inspections were performed on both in-service and non-functioning units, problems were diagnosed and pragmatic solutions were proffered. The paper presents some of the discoveries made during the investigation, namely, several units did not last up to the payback period of say 10 to 15 years. The results obtained could provide guidance in selecting operating criteria and suitable system design for solar water heating applications.
Development of a Production Planning Method for the NIFOR Digester Screw Press
Authors: Abikoye B.O. , Amiolemhen P.E.
Published: September 2013

In most production environments, the problem of efficiently scheduling production jobs on several machines is an important consideration when attempting to design a work plan that makes effective use of the available resources because job scheduling in manufacturing is at the crux of production planning because of its impact on revenues. This work examined the production planning and scheduling of jobs at the Nigerian Institute for Oil Palm Research (NIFOR) with the aim of developing an effective production planning method for the production of one of its products the Digester Screw Press (DSP). The material flow pattern and current manufacturing practice were observed and production data was collected on machine set up and run times. The data collected was used to estimate the actual average run times for all the machines and the total processing times for each of the three components that make up the Digester Screw Press. The Microsoft Project 2003 was used as a tool in producing an improved job schedule based on the shortest processing time rule. The technique has reduced the general processing time for the production of DSP from 157hours to 99hours. It provides low machine waiting time, high machine utilization and reduced job tardiness across the shop floor.
Application of Multi-Parameter Transformation in Deformation of Dam
Authors: Ehiorobo J.O. , Ehigiator R. Irughe
Published: September 2013

Objects and engineering structures are subject to displacements resulting from numerous internal and external factors. Determination of the magnitude of these displacements is possible on the basis of cyclic measurements of changes in position of points determining the geometrical shape of the studied object. Processing the measurement results is aimed at determining the characteristics of the changes and assessment of possible hazards. The paper proposes a methodology for processing repeated GPS data from two-measurement epoch 2010 and 2011 using a model that utilizes multi-parameter transformation, relating original and repeated observations. The mathematical model was applied to original and repeated Global positioning system (GPS) station observations made to target points at Ikpoba Dam in Benin City. The transformation consisted of a parameter similarity transformation at the reference station (translations in the X-, Yand Z-directions at the instrument station, and rotations about the X-, Y-and Z-axes), plus a scale factor relating original and repeated instrument-target. Using MATLAB programme, three control points were transformed and the coordinates of all other monitoring and reference stations were obtained with reference to the transformed control points.Points displacement between the measurement epoch were then computed from the transformed coordinates. The results obtained showed a maximum error of 1mm on the X coordinate, 2mm on the Y coordinate and 7mm in elevation.
Application of Markov Chain Model to Corporate Manpower Planning: A Nigeria Local Government Hub Example
Authors: Igboanugo A.C.
Published: September 2013

A corporate manpower planning study, seeking to gain insight into, and hence, attempt tounwrapthe wider meanings of a long-run manpower practice inherent in a set of data obtained from one of the 774 Local Government Organizations in Nigeria, was conducted. The data which spanned over a period of twenty years, relate to six states recruitment, staff stock, training, interdiction, wastage, and retirement and, in particular were found to possess Markov properties, especially stochastic regularity, and therefore had absorbing Markov Chain model fitted into the set. Our results suggest that staff habituate substantial number of times (47) among non-absorbing states before subsequent absorption into any of the two absorbing states. And, again, 52% of the workforce gracefully attain retirement while 48% regrettably get wasted. Agreeably, it seemed that the absorbing Markov Chain model employed has established a definite pattern of manpower flow in the organization as a sure-thing principle rather than a chance mechanism.