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15 November 2006, Volume 27 Issue 11 Previous Issue    Next Issue
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Application of genetic algorithm in economic dispatch of power systems He, Da-Kuo (1); Wang, Fu-Li (1); Jia, Ming-Xing (1); Sang, Hai-Feng (1) 2006, 27 (11):  1181-1184.  DOI: - Abstract ( 282 )   HTML   PDF (1035KB) ( 961 )   The economic dispatch problem (EDP) of power systems is approximated and converted into a differentiate one by way of maximum entropy in accordance to its characteristics. The different advantages and characteristics of conventional optimization methods and genetic algorithm are analyzed, then they are integrated together with a local searching operator introduced into implement rapid searching. An improved genetic algorithm is thus presented to solve EDP of power systems, of which the searching speed and local searching capability are improved by BFGS operator. At the same time, the uniform multiple individuals crossover operator is applied to improve global convergence and lead the population to the global optimum. Two examples are given to verify the validity of the algorithm. References | Related Articles | Metrics

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Target detection method based on wavelet multi-scale extended fractal feature Wei, Ying (1); Wang, Xiao-Zhe (1); Shi, Ze-Lin (2); Xu, Xin-He (1) 2006, 27 (11):  1185-1188.  DOI: - Abstract ( 259 )   HTML   PDF (627KB) ( 456 )   Investigates detection of small targets in complex natural background by way of improving Kaplan's extended fractal feature to adapt itself to target dimensions to a certain extent. In view of the natural background and both the horizontal and vertical directionalities of the speckled man-made targets, a multi-scale extended fractal feature via wavelet analysis is proposed utilizing the directionalities which are well decomposed by wavelet to combine the horizontal and vertical wavelet decomposition of their mutual energy respectively, thus intensifying effectively the target image both horizontally and vertically with background disturbance suppressed. Experimental results showed that the target detection based on such a feature is stable and adaptable to infrared/TV images on either complex ground or sea surface and available to locate quickly the small target from single-frame images. References | Related Articles | Metrics

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H∞ controller design for fractional order system Zhao, Chun-Na (1); Pan, Feng (1); Xue, Ding-Yu (1) 2006, 27 (11):  1189-1192.  DOI: - Abstract ( 225 )   HTML   PDF (1222KB) ( 949 )   Because the characteristic equation of fractional order system is a pseudo-polynomial function with exponential-type fractional orders of complex variable, the control of integer orders cannot be directly applied to it. A robust H∞ controller is therefore designed for fractional order system to which the filter approximation proposed is applied with a weighting function selected properly to meet the requirements for designing the H∞ controller. Simulation results indicate that the performance of the system thus controlled is significantly improved with dynamic behavior satisfactorily obtained. The effectiveness of the method proposed is verified through tests. References | Related Articles | Metrics

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Design of multi-item double auction mechanism Huang, Hai-Xin (1); Xue, Shi-Tong (1); Wang, Ding-Wei (1) 2006, 27 (11):  1193-1195.  DOI: - Abstract ( 350 )   HTML   PDF (150KB) ( 1361 )   The multi-item double auction involves multiple buyers and sellers in making offer for various articles. The mechanism of such an auction is studied and designed with two rules set up and proved. Then, a concise and applicable model is developed to determine the clearing price and match well the buyers and sellers for various articles. The arithmetic provided from the mechanism designed is extended to fit the four classic auctions, and it is very simple for auctioneer to operate. Furthermore, it can be applied to decision optimization models. References | Related Articles | Metrics

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Fuzzy decision-making in competitive bidding and products' discrepancy Wang, Ke (1); Gao, Li-Qun (1); Li, Yang (1) 2006, 27 (11):  1196-1199.  DOI: - Abstract ( 226 )   HTML   PDF (146KB) ( 776 )   Analyzes the bidding behavior on the basis of the theory of static game on which the information is incomplete and that of products' discrepancy, according to the typical static characteristics of game in the competitive bidding activities for a certain project. A gaming model is thus developed on the basis of Hotelling's location model of line segments, taking account of the discrepancy between products which are to be contracted by different bidders and the favoritism of bid inviter with the intention of expressing the bidding process more actual. Then, the way to design the bidding strategy for a bidder is given in case the information is either complete or incomplete, with a numerical example given to explain the algorithm and verify its validity. References | Related Articles | Metrics

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Worm propagation model based on selective-random scan Zhang, Xiang-De (1); Ding, Chun-Yan (1); Zhu, He-Gui (1) 2006, 27 (11):  1200-1203.  DOI: - Abstract ( 260 )   HTML   PDF (803KB) ( 1195 )   Based on the analysis of worms propagation in a close computer group, a new discrete worms propagation model is presented and compared with the real propagation data collected by CAIDA, it is found that the model reflects properly the active role of worms propagation. By extending further the model, the behavior of worms which propagate in the form of selective-random scan is considered and it is concluded that in a close computer group the greater the number of vulnerable computers varies in each and every small network, the quicker the worms propagate. References | Related Articles | Metrics

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TCP-friendly real-time streaming media congestion control based on RTCP feedback Geng, Fu-Quan (1); Fang, Min (1); Zhao, Lin-Liang (1); Wang, Guang-Xing (1) 2006, 27 (11):  1204-1207.  DOI: - Abstract ( 252 )   HTML   PDF (190KB) ( 1541 )   An end-to-end congestion control mechanism, i.e., a-TFRC (ameliorated TFRC), is presented, which is TCP-friendly and based on RTCP feedback. In view of that the real-time streaming media need short delay and short-term jitter, the slow start-up phase of a TFRC is improved to enable the initial sending rate of TFRC flow not to be so low that the delay and jitter begin to lengthen at receiving end. Simulation result shows that the proposed mechanism improves the streaming media throughput and QoS so as to ensure the amicability of TCP flow. References | Related Articles | Metrics

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Research on the robustness based on the internet standard entropy Xu, Feng (1); Zhao, Hai (1); Ha, Tie-Jun (1); Zhang, Yong-Qing (1) 2006, 27 (11):  1208-1211.  DOI: - Abstract ( 247 )   HTML   PDF (601KB) ( 543 )   Internet topology is highly orderly at its router level. According to the basic theory of Shanon's informational entropy, the Internet structure entropy and Internet standard structure entropy were computed using the Internet data provided by CAIDA skitter project. Furthermore, by simulating experiment, the changes in service efficiency, mean shortest path and standard structure entropy were also computed in the circumstance where the Internet is attacked either maliciously or randomly, thus revealing that the scale-free Internet topology is just the main influencing factor on the robustness of Internet. It is seen from the experimental result that Internet is robust to random attack but frail to vicious attack because it has a scale-free effect. References | Related Articles | Metrics

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Solution on the complex network router of the Jing-Luo Ha, Tie-Jun (1); Zhao, Hai (1); Su, Wei-Ji (1) 2006, 27 (11):  1212-1215.  DOI: - Abstract ( 279 )   HTML   PDF (199KB) ( 1390 )   The Jing-Luo is the very important integral parts of the theory of Chinese traditional medicine, which forms complex networks in combination with immunity, nerve and endocrine. Based on the definition of complex networks, modeling and relevant algorithm and theory, what role the acupoint play in message transfer in the networks of Jing-Luo is investigated through testing and verification, as well as the interactive conditions, routes and their high electric conductivity. A route model of the complex networks of Jing-Luo is therefore developed to prove the existence of the complex networks and reveal that the informative substances are propagated along the routes of Jing-Luo in definite direction and at definite speed. It is certain that the basic functions of Jing-Luo are transferring and controlling the informative substances for life keeping. References | Related Articles | Metrics

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Internet validity and its physical properties characteristic quantity Zhao, Hai (1); Xu, Ye (1); Su, Wei-Ji (1); Li, Chao (1) 2006, 27 (11):  1216-1219.  DOI: - Abstract ( 305 )   HTML   PDF (166KB) ( 559 )   As a hot topic in the field of complex networks, the problem of Internet validity is studied. General definitions of Internet space validity and time validity are given, then their physical characteristic parameters, i.e., networks density and Internet traveling diameter, are formally defined with quantitative analysis. Based on the mathematical relationship between the two parameters, which is derived from a series of known formulae, the definition of Internet validity factor is put forward as a parameter to connect Internet space validity with time validity so as to judge comprehensively the Internet validity. A mathematical model of validity factor based on time-evolvement analysis is thus given, which makes it possible to forecast and estimate the development of Internet in the future. References | Related Articles | Metrics

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DOA matrix method and its performance analysis Liu, Fu-Lai (1); Wang, Jin-Kuan (1); Du, Rui-Yan (2); Yu, Ge (1) 2006, 27 (11):  1220-1223.  DOI: - Abstract ( 337 )   HTML   PDF (1355KB) ( 758 )   Using three uniform linear arrays (ULAs), a high-resolution DOA matrix method is proposed for the two-dimensional (2-D) direction-of-arrival (DOA) estimation of multipath narrow-band coherent sources impinging on the far field of an antenna array. With the same eigenvector of the DOA matrix used to estimate the 2-D DOA, the method can automatically implement the pairing of estimated parameters and solve the angle overlapping problem of incident beams. The mean square error (MSE) of the 2-D DOA estimation is discussed. By simulations using Matlab software, the theoretical and experimental MSE curves are compared in relation to CRB, and the results show the proposed method has very high resolution with smaller error and it is applicable to multipath environment. References | Related Articles | Metrics

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Application of integral mean value theorem to inner-product of strain rate vector during disk forging Zhao, De-Wen (1); Du, Hai-Jun (1); Liu, Xiang-Hua (1); Wang, Guo-Dong (1) 2006, 27 (11):  1224-1227.  DOI: - Abstract ( 265 )   HTML   PDF (1623KB) ( 565 )   A new integration method proposed, i.e., the integral mean value theorem, is applied to simplifying the inner product of strain rate vector. The equivalent strain rate during barrel-shaped disk forging is expressed in terms of two-dimensional strain rate vector, then the strain rate ratio function and direction cosine of this vector are determined according to the integral mean value theorem, and its inner-product is integrated term by term. The integration results are summed up to obtain the formula of relevant barreling parameter b and analytical solution of the stress influence factor. A compression test was done to compare the values of the stress influence factor and total pressure thus calculated with those calculated according to Avitzur's approximate solution and the measured values given by the test. The comparison results show that the values thus calculated conform basically to Avitzur s upper bound approximation but are higher than measured ones, among which the relative error of pass reduction from 10% to 33% is 1.9%-9%. References | Related Articles | Metrics

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Research on the corner stress of dog-bone shaped workpiece during flat-spread rolling Yu, Hai-Liang (1); Liu, Xiang-Hua (1); Li, Chang-Sheng (1); Wang, Guo-Dong (1) 2006, 27 (11):  1228-1231.  DOI: - Abstract ( 222 )   HTML   PDF (1017KB) ( 536 )   FEM simulation was done for the deformation behavior of a dog-bone shaped workpiece during flat-spread rolling. The effects of the apical position and maximum height of the workpiece and pass reductions on its corner tensile stress in rolling process were analyzed. The results showed that the change in apical position affects greatly the corner tensile stress which can be increased by 66.7%, and the changes in maximum height and pass reduction affect the corner tensile stress rather smaller. The comer tensile stress increases with the positional distance of the workpiece. The conclusion drawn from the simulation is of significance to improving productivity especially the rate of finished products. References | Related Articles | Metrics

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Cavitation-abrasion behavior of martensitic stainless steel used for hydraulic turbine blades Zhang, Xiao-Bin (1); Liu, Chang-Sheng (1); Zhu, Jie (1); Zheng, Yu-Gui (2) 2006, 27 (11):  1232-1235.  DOI: - Abstract ( 201 )   HTML   PDF (479KB) ( 732 )   Cavitation-abrasion behavior of 0Crl3Ni5Mo steel and its refined alloy in multiphase flow was investigated with a rotary disc tester in distilled water and simulated Yangtze river water, and the results were in contrast with those from 13-4 stainless steel. The microstructures and the eroded surfaces observed by SEM and electro-microscope showed that in the refined 0Crl3Ni5Mo steel the ferrite grain size is smaller and the resistance to abrasion or cavitation-abrasion is obviously higher than the original steel and 13-4 stainless steel. Their accumulative mass losses due to abrasion or cavitation-abrasion all exhibit linearly time-dependent, and the integrated cavitation-abrasion action did more serious damage to the material used than single cavitation erosion or abrasion. References | Related Articles | Metrics

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Effects of microalloying elements on hall-petch relations of 304L austenitic stainless steel Wang, Li-Jun (1); Wang, Kai (1); Ren, Hai-Peng (1); Liu, Chun-Ming (1) 2006, 27 (11):  1236-1239.  DOI: - Abstract ( 330 )   HTML   PDF (372KB) ( 691 )   Four experimental specimens were prepared from molten 304 L austenitic stainless steel, with different trace elements added in it. After cold rolling and recrystallization annealing at different temperatures to cause grain size distribution change to a certain extent, those specimens were annealed again for homogeneity at different temperatures to eliminate the different grain boundary segregation resulting from different annealing temperatures. Then, their mechanical properties were tested with their microstructures observed for grain size statistics, thus getting the Hall-Petch relation through data processing. The effects of such microalloying elements as Nb, B, C and N on Hall-Petch relation were investigated by comparing the results of different specimens and heat-treatments. Conclusions are therefore drawn that: without Nb addition, the trace elements C, N and B have little influence on σ0 in Hall-Petch relation, but N or B can increase grain refinement strengthening coefficient ky. Once Nb is added in the austenitic stainless steel, it compounds with the elements C and N to form the carbonitride of Nb, which has no obvious influence on σ0 but increases ky when reannealing the specimens for homogeneity at 700°C. However, it decreases σ0 but increases ky at 500°C. References | Related Articles | Metrics

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Numerical simulation of ablation of Cflake-SiC-B4C composites plate Yu, Liang (1); Ru, Hong-Qiang (1); Xue, Xiang-Xin (1); Zuo, Liang (1) 2006, 27 (11):  1240-1243.  DOI: - Abstract ( 226 )   HTML   PDF (440KB) ( 811 )   FEM was used to study the ablation behavior of Cflake-SiC-B4C composite plate with different Cflake, contents and degrees of orderliness of Cflake, under aerodynamic heating conditions. The results showed that the transient temperature field distribution in the composite plate is affected obviously by ambient temperature, material's composition, relative density and Cflake with different degrees of orderliness. When the mass fraction of Cflake is 65% in the composite and the mass ratio of SiC to B4C is 5:1 in composite matrix, the composite offers high resistance to oxidation, if the basic structured elements of Cflake are arranged orderly and lots of Cflake grow continuously to form parallel big-area C layers which are piled up to form arched structure of the composite. At that time, the composite offers high resistance to oxidation, just like the testing results. References | Related Articles | Metrics

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Development and application of carbon-free precast block for ladle lining Chen, Min (1); Wang, Nan (1); Yu, Jing-Kun (1); Liu, Wei (2) 2006, 27 (11):  1244-1246.  DOI: - Abstract ( 227 )   HTML   PDF (161KB) ( 1077 )   A carbon free precast block was developed by using fused high-Al corundum as aggregate and electro-melting magnesia and ultra-fine Al2O3 and SiO2 powders as matrix materials. A small linear shrinkage of the precast block was found through the volume expansion due to the spinel which was produced from the reaction of MgO with Al2O3 in matrix. The precast block shows lower apparent porosity and higher hot modulus of rupture and slag corrosion resistance in comparison to conventional Al2O3-MgO-C brick. Practical applications revealed that bonding the precast blocks together as ladle lining can provide better thermal insulation which will effectively reduce the temperature drop of molten steel in refining process and prevent molten steel from carburization. The carbon-free precast block is thus regarded as a new type of ladle lining material that is beneficial to the production of low-carbon and ultra-low-carbon steel. References | Related Articles | Metrics

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Study on transfer process in porous media with chemical reaction in cylindrical coordinates Li, Ming-Chun (1); Tian, Yan-Wen (1); Zhai, Yu-Chun (1) 2006, 27 (11):  1247-1250.  DOI: - Abstract ( 255 )   HTML   PDF (965KB) ( 671 )   The chemical reactions between fluid and porous matrix and the fluid transfer process are proceeding simultaneously and interactively with each other in a porous reactor. A nonlinear mathematical model is developed for the convection/diffusion in cylindrical coordinates through Ergun-Forchheimer-Brinkman equation to express the fluid flow within the porous medium, which is solved discretely and numerically by an ADI (alternate dimension implicit) method. Taking the indirect reduction of iron ore in fixed bed as example, the profiles of the reactive gas concentration field and fractional conversion distribution of solid reactants are given by changing relevant parameters. The results show that the seepage flowrate and particle size are the important parameters affecting significantly the reactive characteristics of the porous reactor. An increase in convection velocity results in both increasing concentration fields of reactive gas and solid fractional conversion which also increases with decreasing particle size in the region near reactor entrance. But, when the region where the chemical reaction takes place deepens gradually, the solid fractional conversion distribution varies reversely, i.e., the solid fractional conversion decreases with particle size. References | Related Articles | Metrics

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Preparation of low Na/K highly purified LiCl by alcohol extraction Jin, Zhe-Nan (1); Li, Xi-Meng (1); Lan, Wei-Jun (1); Liu, Xiu-Ru (1) 2006, 27 (11):  1251-1254.  DOI: - Abstract ( 268 )   HTML   PDF (185KB) ( 2092 )   Based on the different of solubilities of alkali metal chlorides in alcohol, the highly purified lithium chloride with low sodium/potassium contents was prepared for the first time by alcohol extraction process. The results showed that calcium content in mass fraction can be controlled lower than (10-15) × 10-6 after decalcification by adding 0.6% lithium oxalate, meanwhile, the sodium and potassium contents can be lower than 40 × 10-6 and 5 × 10-6, respectively, when filtering the solution 2 times and the liquid to solid ratio 8.5. Such a result means that the alcohol extraction is an effective way to remove sodium and potassium in preparing highly purified lithium chloride. References | Related Articles | Metrics

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Study and its implementation on the CAPP system for middle small-scale machine-building manufacturers Xu, Zhi-Wei (1); Liu, Yong-Xian (1); Tang, Liang (1); Guo, Li-Xin (2) 2006, 27 (11):  1255-1258.  DOI: - Abstract ( 252 )   HTML   PDF (170KB) ( 667 )   Analyzing the characteristics of middle small-scale manufacturers on the basis of actual investigation a CAPP system is designed to adapt to machine-building manufacturers. Finds out the features of technological documents, and the IDEF0 modeling process is introduced to determine the functions required for CAPP, including process planning, management, integration, etc., thus the make up of the CAPP system. Then, the CAPP system architecture and its main modules are designed and implemented to fit in with the requirements of middle small-scale machine-building manufacturers. Some key techniques are discussed, including the data exchange between CAPP and PDM, realization of products structure trees and denotation of special symbols. Describes the way to implement the CAPP system which has been deployed by Shenyang Valve Manufacture Co., Ltd and with very good effect obtained in application. References | Related Articles | Metrics

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Analysis of pressure fluctuation signal in submerged circulative impinging stream reactor with wavelets transform Sun, Huai-Yu (1); Xu, Cheng-Hai (1); Wu, Yuan (2) 2006, 27 (11):  1259-1262.  DOI: - Abstract ( 201 )   HTML   PDF (339KB) ( 591 )   To reveal the frequency character of pressure fluctuation in reactor and what causes it, the wavelet transform is used to analyze the pressure fluctuation signals tested in Submerged Circulative Impinging Stream Reactor (SCISR), where the signals are extracted on different scales to calculate fluctuation energy and the distribution of pressure fluctuation in frequency domain is discussed. The results show that the fluctuation energy concentrates mainly in range below 1 kHz. The energy distribution in space shows that the strong pressure fluctuation region is symmetrical about the impinging plane and approximately symmetrical about the axis. The fluctuation frequency is thus divided into three ranges according to different spatial locations, and the causation of each and every range is analyzed. In response to the change in propeller revolution, the fluctuation energy on every scale increases simultaneously with some changes found in frequency distribution. The volume integral for total fluctuation intensity shows that the fluctuation energy arising from the vortex of major fluid in SCISR is predominant. References | Related Articles | Metrics

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Experimental investigation on relationship between steel bar's compressive stress and induction EMF Chen, Geng-Ye (1); Li, Yan-Feng (1); Tian, Jun (1); Yao, Guang-Ren (2) 2006, 27 (11):  1263-1266.  DOI: - Abstract ( 234 )   HTML   PDF (1576KB) ( 712 )   A compression test was done in combination with induction EMF (electromotive force) to investigate the relationship between the EMF variable e and compressive stress σ, taking the D25 mm HPB 235 and HRB 335 steel bars as specimens. The specimens were passing through an AC induction coil and a tiny EMF was produced axially in the steel bar. Then the specimens were compressed by a hydraulic press. Testing results showed that the EMF e decreases with the increasing stress σ, but a increases with the increasing EMF increment Ae, and the relationship between the two variables, i.e., Ε and σ, or σ and ΔΕ, can be expressed respectively by a linear fitting equation. The stress obtained from the induction EMF measured was compared to that obtained from the strain measured one by one, from which the relative mean error was 2.94%. According to the Biot and Savart Law, the reason why the axial current component Ih in the induction coil winding obliquely around a specimen forms a traverse magnetic field Bx was explored. References | Related Articles | Metrics

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Blasting mechanism of fan-patterned holes and its application in sublevel caving Ren, Feng-Yu (1); Wang, Wen-Jie (1); Han, Zhi-Yong (1) 2006, 27 (11):  1267-1270.  DOI: - Abstract ( 351 )   HTML   PDF (344KB) ( 896 )   Experiments were conducted to investigate the effects of material strength and hole burden on the blast performance of fan-patterned holes in sublevel caving, and to analyze the factors affecting the effective area of blasting. Two important revelations were made in this study: (1) blasts with fan drilling exhibit a strong directionality, and (2) better fragmentation occurs in the hole-bottom region of the fan-patterned holes, where the hole spacing is larger, than in the collar region, where the spacing is smaller. The second phenomenon can be explained by the sequential effect of breakage, that is, between-hole breakage occurs first in the collar region where the spacing between holes is small. Based on the experiment results and conclusions drawn, the effective range of hole density coefficient and the application condition of hole-bottom detonation are discussed. The experimental results were applied to improve the load structure of charges and the sequence of detonation in Beiminghe iron mine. The percentage of oversized lumps of the blasted ore in the mine was lowered to 1.8% from 3.0% and the occurrence of partition wall was successfully eliminated. References | Related Articles | Metrics

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Parameter optimization of soil-nailed wall of deep foundation pit Liu, Jian-Ping (1); Zhu, Fu-Sheng (1); Wang, Hong-Wei (1) 2006, 27 (11):  1271-1274.  DOI: - Abstract ( 238 )   HTML   PDF (1339KB) ( 527 )   To reduce the cost of soil-nailed wall of deep foundation pit and ensure its safety, a model was developed for its parameter optimization, including the number of lines of nails, their horizontal/vertical space, diameter and length. Traditional methods are apt to get locally optimization solution when used for complex optimum design problems like the parameters of soil-nailed wall. In this respect the genetic algorithm (GA) is a method available to get global optimum, but it often has such shortcomings as premature convergence and oscillation in iterative process. Therefor, a forward-and-backward searching algorithm is proposed in combination with GA and some measures for improvement, thus forming an improved hybrid genetic algorithm (IHGA) which, as proved by an engineering example, offers an optimum design that not only provides the stability for deep foundation pit but also reduces the cost of engineering materials. References | Related Articles | Metrics

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Numerical stability analysis of surrounding rock mass layered by structural planes with different obliquities Jia, Peng (1); Tang, Chun-An (1); Yang, Tian-Hong (1); Wang, Shu-Hong (1) 2006, 27 (11):  1275-1278.  DOI: - Abstract ( 295 )   HTML   PDF (1129KB) ( 918 )   The RFPA (realistic failure process analysis) software is used to analyze the deformation/failure of a tunnel passing through the rock mass with incompetent laminar structural planes at different obliquities and the displacement of the key points around the tunnel, with microdimensional elements introduced in combination with the elementary constitution model based on damage mechanics and statistics. The results show that the degree of obliquities of laminar structural plane affects obviously the destabilization/failure mode of surrounding rock. The peripheral stress distribution around tunnel is asymmetrized gradually with the increasing obliquity and, eventually, the asymmetry of failure mode takes place. So, the increase in obliquity is disadvantageous to side wall. It is theoretically and practically of importance to understanding further the destabilization/failure mechanism of the tunnel passing through incompetent structural planes of rock mass and the effective measures to be taken for reinforcement. References | Related Articles | Metrics

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Theoretical and experimental study on anti-fatigue rod Xing, Jun (1); Zhong, Yong (1); Song, Shou-Zhi (1) 2006, 27 (11):  1279-1282.  DOI: - Abstract ( 292 )   HTML   PDF (250KB) ( 681 )   Based on the principle of finite life design, the influencing factors on the fracture resistance and fatigue life of drill rod are analyzed according to wave mechanics and dynamics of percussive drilling. A thin-wall tubular drill rod is thus suggested to improve its fracture resistance by low stress distribution. With the purpose of no extra consumption of drill steel but improving the fracture resistance of drill rod by reducing its cyclic stress, the outer diameter of drill rod is remarkably increased. The fatigue life of the newly developed drill rod is also predicted according to the S-N curve of drill steel and its theoretical loading spectrum. Industrial test indicates that the fatigue life of the thin-wall tubular rod is up to 1200 m, near 70% higher than that of domestic conventional products. References | Related Articles | Metrics

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Multi-period inventory optimization model for stochastic replenishment intervals Ji, Shou-Feng (1); Cao, Chu (1); Huang, Xiao-Yuan (1) 2006, 27 (11):  1283-1286.  DOI: - Abstract ( 348 )   HTML   PDF (200KB) ( 901 )   Studies the problem that a supplier is relatively in an advantageous position but retailers have to decide the quantities to replenish their inventories with various factors taken into account. Assuming that both the allowable stock-out and replenishment intervals are stochastic (independent identically distributed) variables, we give the expected profit function that the replenishment intervals comply with general distribution and the inventory can be controlled effectively by optimizing the replenishment quantity. Then, two particular distribution cases are discussed for replenishment intervals and, by sensitivity analysis, how the replenishment intervals affect retailer s profit is expounded. References | Related Articles | Metrics

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Evaluation based on evidential theory for knowledge sharing risk in organization You, Tian-Hui (1); Fan, Zhi-Ping (1); Yu, Zhu-Chao (1) 2006, 27 (11):  1287-1290.  DOI: - Abstract ( 265 )   HTML   PDF (154KB) ( 802 )   How to analyze and assess the knowledge sharing risks in an organization is studied. The main factors which form knowledge sharing risks are found out through analyzing earlier works in combination with questionnaire/statistics, thus building dimensionally an evaluation index system for such risks. The system includes the risks arising from organization/structure, organizational culture, key personnel and knowledge/technology, etc., the four dimensions. According to the index system and the uncertain information on evaluation indices, a method based on evidential theory is proposed to assess knowledge sharing risk with an example given to show its application. References | Related Articles | Metrics

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Model of order allocation for JIT purchasing and its simulative application Zhang, Cui-Hua (1); Zhu, Hong (1); Ma, Lin (1) 2006, 27 (11):  1291-1294.  DOI: - Abstract ( 302 )   HTML   PDF (1228KB) ( 761 )   JIT (just in time) is an effective mode of optimized purchasing management for supply chain. To implement JIT purchasing, its basic idea and the difference between it and traditional purchasing under the supply chain management are described. Then, a minimization model of total purchasing cost of producer is proposed for JIT purchasing order allocation among multiple suppliers, which shall satisfy a specified percentage of on-time delivery and conform with specific purchasing strategies. Based on the minimum purchasing cost calculated via simulation, a numerical example is given to illustrate the scheme of best order allocation. The sensitivity of purchasing cost to the percentage of on-time delivery is analyzed, and how to study further the problem is predicted. References | Related Articles | Metrics

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Size/temperature effect of Cu-nanoclusters in coalescence process: A molecular dynamics simulation Zhao, Xing (1); Zhang, Cai-Bei (1) 2006, 27 (11):  1295-1298.  DOI: - Abstract ( 243 )   HTML   PDF (313KB) ( 512 )   The coalescence processes of Cu-nanoclusters with different sizes and initial temperatures were studied by molecular dynamics simulation within the framework of embedded atomic potential. How the size/temperature effect of the nanoclusters changes in coalescence process was recorded by snapshots to calculate the geometry parameters of configuration of the system and reveal the temperature changes in the process. The simulation results showed that a nanoclusters coalesces with other ones to a greater degree and the temperature changes greater with the decreasing cluster size at constant initial temperature. However, for the clusters of same nanosize, they coalesce together to a greater degree with increasing initial temperature. Moreover, the nanoclusters in liquid state coalesce together much easier than those in solid state. References | Related Articles | Metrics