Optimal Configuration Algorithm for Mechanical Products Based on the Constraint of Carbon Footprint

Transcription

1 312 The Open Mechancal Engneerng Journal, 2015, 9, Send Orders for Reprnts to Open Access Optmal Confguraton Algorthm for Mechancal Products Based on the Constrant of Carbon Footprnt We Bo *,1, L Renwang 2, Zheng Hu 1 and Zong Xanlang 1 1 College of Mechancal Engneerng, Tanjn Unversty of Scence and Technology, Tanjn, , P.R. Chna 2 Faculty of Mechancal Engneerng and Automaton, Zhejang Sc-Tech Unversty, Hangzhou, , P.R. Chna Abstract: The concept of carbon footprnt controllable product s put forward frstly whch means to prepose the controllng for carbon footprnt to the stage of product development and confguraton, dfferent from the postcontrol tradtonally. Thus the control objectves can be more quantfed and easy realzed. Product characterstcs (ndcators, ncludng carbon footprnt have no certan relaton between each others. In order to obtan the optmal product confguraton scheme based on the constrant of carbon footprnt, three-stage theory s proposed whch ncludes the functonal confguraton, the carbon footprnt complance evaluaton, and the optmal comprehensve evaluaton. After above-mentoned stages, functon feasble soluton set, CFP conformng set and the optmal scheme are generated respectvely. Grey relaton analyss s verfed effectve on comprehensve beneft evaluaton by an example of small reducer. Keywords: Carbon footprnt, mult-objectve decson-mang, product confguraton. 1. INTRODUCTION As a bg concept, Carbon footprnt (CFP can be subdvded nto four nds of natonal carbon footprnt, enterprse carbon footprnt, personal carbon footprnt and product carbon footprnt. And now, more and more concern and attenton s pad to the last. Carbon footprnt label s the manfestaton of product carbon footprnt. It shows the amount of greenhouse gas emssons n the all processes whch ncludes producton, transportaton, sales stage (some products carbon footprnt also nclude use stage and fnal dsposal stage. One of the purposes of carbon footprnt label s to mae enterprses better communcate nformaton about the products wth consumers: to ntroduce consumers about enterprse s contrbuton n energy conservaton and carbon emssons reducton, and provde nformaton about carbon footprnt to consumers so that they can compare the products from dfferent manufacturers. In recent years, low carbon product standards developed rapdly, and the trend has the potental to evolve nto a wde range of green trade barrers, ratonalty n surface, legalty n form, wdespread n content, concealment n mplement. The concept of Carbon Footprnt Controlled Products s put forward not only to meet the external demands such as carbon tarffs and other nternatonal trade barrers, consumer preference and government control, but also to help enterprses themselves to ncrease use effcency of energy and resources, mprove producton process, reduce cost etc., wth the prces of energy and raw materals rsng qucly. Because carbon footprnt has great effect on the greenhouse, more and more partners worldwde ncludng manufacturers, consumers, governments and envronmental groups attach great mportance on carbon footprnt of products. Many scholars have done a lot of research n related felds. The man progresses focus on: Low carbon manufacturng and desgn technology. Some people thn that Rapd Manufacturng (RM s the low carbon manufacturng technology of the future [1]. A method can dentfy the man process of the lfe cycle whch mpact clmate change n enterprse producton and supply s proposed [2]. A method of manufacturng effcency evaluaton provdes a general conceptual and computatonal framewor for the effcency evaluaton of the manufacturng processes [3]. A future vson s proposed toward developng a method for reducng carbon footprnt through smultaneous consderaton of manufacturng processes and supply chan actvtes [4]. Some people establsh a multconstraned objectve optmzaton model of lowcarbon desgn mprovement of ey modular unt wth a target of the most reducton of carbon emsson whch s caused by the mprovement of low-carbon desgn parameters [5]. Low carbon supply chan. To brng the carbon management nto supply chan, the balance between cost, servce, qualty and carbon can be acheved by the coordnaton of supply chan n product, process, nformaton and captal [6]. A mult-objectve mxed nteger programmng model s used to ntegrate carbon emssons and the total cost of logstcs supply chan nto the desgn process, the effects of carbon tradng rght to supply chan desgn also be taen nto X/ Bentham Open

2 Optmal Confguraton Algorthm for Mechancal Products The Open Mechancal Engneerng Journal, 2015, Volume account [7]. Applyng EPC to the enterprse product supply chan, tracng and montorng the products carbon emssons from producton, storage, dstrbuton, transport and consumpton, carbon footprnt data can be acqured [8]. The verfcaton of product carbon footprnt. A large number of scholars have research the carbon footprnt calculaton method and the carbon footprnt verfcaton of specfc products n the many felds such as plastc, wood, hotel etc. [9-12]. In fact, carbon footprnt over the lfe cycle only represent one feature attrbutes to a product. Only after enterprses have taen all aspects nto consderaton ncludng cost, qualty and many other factors whle mang product desgn and confguraton can they mae the rght decson. Especally, decreased carbon footprnt may mean the deteroraton of other ndcators of cost etc. wth uncertan relatonshp between these factors. Hence obvously, from the overall pont of vew the carbon footprnt of products s not as lttle as possble. For core enterprse, t should try to match reasonable carbon footprnt and other related ndcators, and control the carbon footprnt at an deal level, such product can be sad carbon footprnt controllable products. Therefore, product carbon footprnt plannng should be a mult-objectve decson problem based on the constrant of carbon footprnt. 2. CONFIGURATION STRATEGY AND ALGORI- THM OF CFP CONTROLLABLE PRODUCT For tradtonal product confguraton, the functonal requrements of customers are consdered only, namely the realzaton of the product functon module. Based on the constrant of carbon footprnt, the confguraton scheme s carbon footprnt must be n control. Due to carbon footprnt controllable product requres quantfcaton n the desgn stage accordng to a certan standard, thus a more accurately carbon footprnt can be securely realzed after product moldng. Certanly, t s very necessary to balance cost, qualty, delvery tme and other factors meanwhle Collaboratve R&D Framewor of CFP Controllable Product In vew of Lfe Cycle Assessment (LCA, t manly ncludes supply chan mported carbon footprnt (raw materals and components, carbon footprnt from the core manufacturng enterprse, logstcs carbon footprnt, carbon footprnt resultng from consumers usng and carbon footprnt of EOL (End of Lfe, etc. Fg. (1 llustrates collaboratve research and development framewor of CFP controllable product. In the whole lfe cycle of a product, carbon footprnts from transportaton, usng, EOL are nfluenced by many Fg. (1. The collaboratve research and development framewor of CFP controllable product.

3 314 The Open Mechancal Engneerng Journal, 2015, Volume 9 Bo et al. factors, and the overall stable data base related to them s not gettable easly and accurately. Thus, for core enterprse, the most valuable ln to control carbon footprnt les n the choce of parts supplers and enterprse manufacturng. Therefore, confguraton algorthm s a ey for the carbon footprnt controllable product development. Fg. (1 llustrates that: the confguraton process needs to go through three stages: functon confguraton, carbon footprnt complance evaluaton and comprehensve beneft evaluaton. And functon feasble soluton set, carbon footprnt conformng set and the optmal scheme are generated respectvely after above-mentoned stages. How to determne the target of a product s carbon footprnt? If clent has requrements for carbon footprnt, t should be satsfed as far as possble. Under the condton that the clents haven t come up wth specfc requrements, the ndustry standard should to be met as far as possble. Otherwse, the core enterprses can also set a compettve carbon footprnt standard by method of top-down or bottom-up to embody ther socal responsblty and have the preferences of envronmental conscous customers. Why s t emphaszed that the above processes are on a collaboratve development platform? The next research of ths paper s based on a premse, that the core enterprse can obtan suppler s nformaton real-tme such as prce, qualty, delvery tme, carbon footprnt ndexes etc. through convenent means for nstance Internet. Combned wth ratng ndex to suppler, the core enterprse can consttute an ndex database of product components and parts. Ths database s vtal for subsequent evaluaton for scheme. Therefore, n the vew of ths pont, the product development process of core enterprse s a collaboratve development process actually accompaned by nformaton exchangng wth supplers contnuously Confguraton Algorthm Grey Relatonshp Analyss (GRA ams at analyzng the relatonshps n behavor, posture, boundary. Dfferencng from the tradtonal mathematcal analyss, GRA provdes a smple scheme to analyze the seres relatonshps or the system behavor, even f the gven nformaton s few. In fact, t mght be reconed as a contrastng way, n wholeness, equpped wth reference for contrastng [13]. In the early stage of product desgn and development, product s attrbute data nclude carbon footprnt s fuzzy. Therefore a satsfactory result can be drawn by usng the method of GRA. Defnton 1: Product characterstcs (ndcator seres. Characterstcs nformaton of an object part can be expressed as : x ' = (x ' (1, x ' (2,, x ' ( therefore, as commonly used ndcators for mechancal product suppler evaluaton, cost (C, qualty (Q, on-tme delvery rate (T, purchase cost savng rate (H, credt (M, plus the carbon footprnt, a seres to descrbe the parts characterstcs (ndcator of suppler s: x ' = ((CFP,C,Q,T, H, M, Defnton 2: Schemes-characterstcs (ndcator matrx. The matrx whch descrbes all characterstcs ((ndcators of a product s functons confguraton for a schemes s: (CFP 1 (CFP 2 (CFP 3 C 2 C n Q 1 Q 2 Q n T 1 T 2 T n H 1 H 2 H n M 1 M 2 M n In the above matrx, each row represents a characterstc (ndcator, and each column represents a product s characterstc ((ndcator set for the confguraton scheme For functon confguraton and carbon footprnt complance evaluaton and comprehensve beneft evaluaton. Because the suppler s equvalent n parts functon, the stage of product functon confguraton can be approxmated to a problem of permutaton and combnaton. Usng exhaustve method or related computer software and procedures, an deal result can be obtaned. For comprehensve beneft evaluaton. As Fg. (1 llustrates, at ths stage, secondary apprasal targets should to be comprehensve evaluated except carbon footprnt. The man steps are as follows: Accordng to schemes-characterstc (ndcator matrx, we can form the scheme pattern seres: x And s scheme number. To form the characterstc(ndcator pattern seres x (, and s the number of product s characterstcs(ndcators. Here s 5. For nstance, cost seres x (1 = (,C 2,C 3,C 4,C 5,C 6, qualty seres x (2 = (Q 1,Q 2,Q 3,Q 4,Q 5,Q 6. Intalzng the characterstc (ndcator pattern seres x ( For cost seres x (1, Therefore, the characterstc (ndcator pattern seres of scheme 1 s x 1 = (1,1,1,1,1, and the others are: = (C,Q,T, H, M ( = 1,2,,n INIT x'( = x( x(1 = (, C 2, C 3, C 4, C 5, C 6 x = ( C, Q Q 1, T T 1, H H 1, M M 1 ( = 2,3,,n The nflux of ndcator s polartes s as follows: Q(2,T (3, H (4, M (5 P OL (max ( P OL (mn

4 Optmal Confguraton Algorthm for Mechancal Products The Open Mechancal Engneerng Journal, 2015, Volume The ndcator s domnatng data and ther ntalzed values are shown as Table 1. Table 1. Domnatng data and ther ntalzed values. Domnatng Data Intalzed Values C(1 C mn={, C 2,, C 6} C mn/ Q(1 Q max={q 1, Q 2,, Q 6} Q max/ Q 1 T(1 T max={t 1, T 2,, T 6} T max/ T 1 H(1 H max={h 1, H 2,, H 6} H max/ H 1 M(1 M max={m 1, M 2,, M 6} M max/ M 1, x = 1 n The grey correlaton grade s a comparatve measure between the seres. To determne the scheme s based on the grey correlaton grade, and the maxmum value scheme s the best. 3. INSTANTIATION 5 =1 (, x ( A small reducer enterprse, adopts the above mechancal products optmal confguraton algorthm based on the constrant of carbon footprnt to verfy the effectveness. The assembly BOM s shown n Fg. (2. Accordng to the polartes of seres and by means of Domnatng Prncple n grey theory, the reference seres s obtaned. x 0 x 0 = (C(1,Q(2,T (3, H (4, M (5 = ( C mn, Q max Q 1, T max T 1, H max, M max H 1 M 1 By tang dfference as Δ 0 ( = x 0 ( x (, we thus have the followng dfference seres Δ ( = 1,2,3,,n : Calculatng all schemes grey relatonal coeffcent and grade. Defnton 3: Grey relatonal coeffcent s a comparatve measure between ponts. (, x ( = x(mn +ζ x(max Δ 0 ( +ζ x(max where x(mn = mn mn Δ 0 ( s lower envronment parameter n, and x(max = max max Δ 0 ( s supper envronment parameter n. ζ [0,1], dstngushng coeffcent, usually accordng to the prncple of mnmum nformaton, ζ =0.5. Set x(mn = a x(max = b Δ = ( C mn C Δ(mn = mn then, grey relatonal coeffcent (,x ( = C, Q max Q Δ(max = max LY gr Q, T max T mn Δ 0 ( Δ 0 ( max LY gr T, H max H a b Δ 0 ( b = ( H, M max M M Defnton 4: By focusng the (, x ( at utter ponts the algorthm on grey relatonal grade s as follows: Fg. (2. BOM of the reducer. Among the parts, F s manufactured by the enterprse, and E, G, H, I are matched by external supplers. The matchng numbers of supplers for them are 3, 2, 3, 2 respectvely. The ndex sequence lsts of dfferent supplers are shown n Table 2. Table 2. The ndex sequence lsts of dfferent supplers. Parts Num Suppler Index Sequence E 3 S3000-E (126,240,0.990, S3001-E (115,260,0.990, S3002-E (130,138,0.990, F 2 Manufactured (65, 85, 0.990, G 3 H 4 I 4 S4000-G (217,355,0.995,0.960 S4001-G (204,370,0.995,0.965 S1000-H (78, 65, 0.990, S1001-H (70, 68, 0.980, S1002-H (73, 66, 0.990, S2000-I (43, 50, 0.990, S2001-I (38, 55, 0.995,0.980 The stage of functon confguraton. Because dfferent supplers parts are standard n functon and nterface, there aren t constrant conflcts. Theoretcally, t s a problem of permutaton and combnaton. Obvously, there are =36 functon feasble

5 316 The Open Mechancal Engneerng Journal, 2015, Volume 9 Bo et al. Fg. (3. The combnaton of the supplers. schemes. Fg. (3 llustrates the combnaton between the supplers. The stage of complance evaluaton for carbon footprnt. To fnd the schemes whch reach the carbon footprnt level from the functon feasble scheme set (namely the schemes whose total CFP satsfy CFP p Descrpton of the problem: The assembly BOM has four varables, a, b, c, and d, representng four alternatve carbon footprnt value repectvely. It s nown that a has three optons, b has two optons, c has three optons, and d has two optons. Accordng to the requrement, the carbon footprnt of the products can t be more than 1555 g, and the carbon footprnt of F (2 s 130 g ( So the total carbon footprnt of the other four parts can t be more than 1425 g, a+b+c+d p, and p s 1425 g. For smplcty, CFP, C, Q, T are consdered frstly. { } a = 78,70,73 b = { 43,38} s.t c = 126,115,130 d = { 217,204} a+ b+ c+ d p; { } Fg. (4 shows partal results screenshot by software calculatng. Accordng to the above result calculated, there are 6 schemes conformng to carbon footprnt constrant. they are [280,152,345,612], [292,152,345,612], [280,172,345,612], [312,152,345,612], [292,172,345,612], [280,172,378,612]. Usng [280,152,345,612] as an example, whch corresponds to Scheme 1, explaned as follows: the Scheme s confgured by S1001-H(70,68,0.980,0.960, S2001-I(38,55,0.995,0.980, S3001-E(115,260,0.990,0.960, S4001-G(204,370,0.995,0.965, and manufactured part F(65,85,0.990, where a=70, b=38, c=115, d=204. So, for Scheme 1, Total CFP : =1519 g Total cost: =2552 yuan Total qualfed rato: = Total On-Tme Delvery Rate (ODR: = To use the same method to calculate the remanng data of other fve schemes, addng the purchase cost savng rate (H and credt (M, the ndex lst of carbon footprnt conformed set as shown n Table 3. And now, carbon footprnt as constrant have been met, therefore no longer nvolved n the comprehensve evaluaton subsequently. Table 3. Index lst of CFP conformed set. X1 X2 X3 X4 X5 X6 C( Q( T( H( M( The phase of optmal comprehensve evaluaton. From Table 3, we can form the scheme pattern seres: Scheme 1: x 1 = (,Q 1,T 1, H 1, M 1 = (2552, , , 0.17, 0.89 Scheme 2: x 2 = (C 2,Q 2,T 2, H 2, M 2 = (2544, , , 0.12, 0.92 Scheme 3: x 3 = (C 3,Q 3,T 3, H 3, M 3 = (2532, , , 0.19, 0.83

6 Optmal Confguraton Algorthm for Mechancal Products The Open Mechancal Engneerng Journal, 2015, Volume Fg. (4. Partal results screenshot by software. Scheme 4: x '4 = (C 4,Q 4,T 4,H 4,M 4 = (2540,0.8820,0.8280,0.21,0.87 Scheme 5: x 5 = (C 5,Q 5,T 5, H 5, M 5 = (2524, , , 0.14, 0.81 Scheme 6: x 6 = (C 6,Q 6,T 6, H 6, M 6 = (2480, , , 0.16, 0.80 Characterstc(ndcator pattern seres: Cost seres: x (1 = (,C 2,C 3,C 4,C 5,C 6 = (2552, 2544, 2532, 2540, 2524, 2480 Qualty seres: x (2 = (Q 1,Q 2,Q 3,Q 4,Q 5,Q 6 = (0.8469, , , , , ODR seres: x (3 = (T 1,T 2,T 3,T 4,T 5,T 6 = (0.8367, , , , , Purchase cost savngs rate seres: x (4 = (H 1, H 2, H 3, H 4, H 5, H 6 = (0.17, 0.12, 0.19, 0.21, 0.14, 0.16 Credt seres: x (5 = (M 1, M 2, M 3, M 4, M 5, M 6 = (0.89, 0.92, 0.83, 0.87, 0.81, 0.80 Intalzng the characterstc (ndcator pattern seres x (, therefore x(1 = (1,0.9969,0.9921,0.9953,0.9890, x(2 = (1,1.0489,0.8865,1.0489,1.0280, x(3 = (1,1.0205,0.9898,0.9896,0.9795, x(4 = (1,0.706,1.118,1.235,0.824,0.941 x(5 = (1,1.034,0.933,0.978,0.910,0.899

7 318 The Open Mechancal Engneerng Journal, 2015, Volume 9 Bo et al. Thus, the characterstc (ndcator pattern seres of scheme 1 s x 1 = (1,1,1,1,1, and the others are: The nflux of ndcator s polartes are as follows: The ndcator s domnatng data and ther ntalzed values are as shown n Table 4. Table 4. Domnatng data and ntalzed values. Domnatng Data Intalzed Values C( Q( T( H( M( Accordng to the polartes of seres and by means of Domnatng Prncple n grey theory, the reference seres s obtaned. By tang dfference as Δ 0 ( = x 0 ( x (, we x 2 = (0.9969,1.0489,1.0205,0.706,1.034 x 3 = (0.9921,0.8865,0.9898,1.118,0.933 x 4 = (0.9953,1.0489,0.9896,1.235,0.978 x 5 = (0.9890,1.0280,0.9795,0.824,0.910 x 6 = (0.9718,0.9870,0.9795,0.941,0.899 Q(2,T (3, H (4, M (5 P OL (max C(1 P OL (mn x 0 x 0 = (C(1,Q(2,T (3, H (4, M (5 thus have the followng dfference seres Δ ( = 1,2,3,,n : Calculatng all schemes grey relatonal coeffcent and grade. The grey relatonal coeffcent (,x ( = = ( , , ,1.235,1.034 Δ 1 = ( , , ,0.235,0.034 Δ 2 = ( ,0,0,0.529,0.006 Δ 3 = ( , , ,0.117,0.101 Δ 4 = ( ,0, ,0,0.056 Δ 5 = ( , , ,0.411,0.124 Δ 6 = (0, , ,0.294,0.135 Δ(mn = mn mn Δ 0 ( = 0 Δ(max = max where a=0, b= max 0 ( = a b Δ 0 (+0.5 b = ( 1 = ( , , , , = ( , 0.5, 0.5, 0.25, = ( , , , , = ( , 0.5, , 0.5, = ( , , , , = (1, , , , The grey correlaton grade, x = 1 n That s to say: Accordng to the value of grey correlaton grade, the ranng of schemes from good to bad s: Scheme6, Scheme5, Scheme4, Scheme1, Scheme2, Scheme3 Therefore, based on the constrant of carbon footprnt, the optmal confguraton scheme s scheme6 [280,172,378,612], that means the proper supplers are: S1001-H(70,68,0.980,0.960, S2000-I(43,50,0.990,0.970, S3000-E(126,240,0.990,0.950, S4001-(204,370,0.995, CONCLUSION n =1 (, x ( 1, x 1 = , x 2 = , x 3 = , x 4 = , x 5 = , x 6 = , x 6 >, x 5 >, x 4 >, x 1 >, x 2 >, x Through the comprehensve evaluaton of the carbon footprnt of product, enterprses can reasonably plan the product carbon footprnt under the premse of carbon footprnt constrants external, connectng wth ther actual technology and management level. The carbon footprnt controllable product means preposng the controllng acton for carbon footprnt to the stage of product development and confguraton, dfferent from the postcontrol tradtonally. Thus the control objectves can be more quantfed and easy realzed. Some conclusons of ths study are summarzed.

8 Optmal Confguraton Algorthm for Mechancal Products The Open Mechancal Engneerng Journal, 2015, Volume The collaboratve research and development framewor of CFP controllable product s proposed based on LCA. The phase of product confguraton s the most valuable ln n lfe cycle for a product carbon footprnt. The three-phase theory under the constrant of carbon footprnt s beng ntroduced. Grey correlaton analyss s verfed to have a better effect n terms of comprehensve beneft evaluaton for a carbon footprnt controllable product. CONFLICT OF INTEREST The author confrms that ths artcle content has no conflct of nterest. ACKNOWLEDGEMENTS The wor was fnancally supported by the Natonal Natural Scence Foundaton of Chna (Grant No and the Scence Research Foundaton of Tanjn Unversty of Scence and Technology (Grant No REFERENCES [1] G. Hague, ATKINS: Manufacturng a Low Carbon Footprnt. Southborough Unversty, UK, [2] A. Scpon, M Mastrobuono, A Mazz, A. Mazz, A. Manzardo, Voluntary GHG management usng a lfe cycle approach: A case study, Journal of Cleaner Producton, vol. 18, pp , [3] S. Rahmfard, Y. Seow, T. Chlds, Mnmzng emboded product energy to support energy effcent manufacturng, CIRP Annals- Manufacturng Technology, vol. 59, pp , 2010 [4] A.J. Alsaffar, K.R. Haapala, K. Km, G.E. Oudan Kremer, A process-based approach for cradle-to-gate energy and carbon footprnt reducton n product desgn, In: ASME 2012 Internatonal Manufacturng Scence and Engneerng Conference Notre Dame, Indana, USA, June 4-8, 2012, pp [5] H. Bao, G. Lu, J. Wang, Optmal desgn of products wth lowcarbon based on carbon footprnt analyss, Journal of Computer- Aded Desgn and Computer Graphcs, vol. 25, pp , [6] B. Karen, G. Detmar, H. Jeffrey, Masterng Carbon Management Balancng Trade - offs to Optmze Supply Chan Effcences, IBM Global Busness Servces, [7] T. Abdallah, A. Dabat, D. Smch-Lev, Sustanable supply chan desgn: A closed-loop formulaton and senstvty analyss, Producton Plannng and Control, vol. 23, pp , [8] D.L. Ingram, Lfe cycle assessment to study the carbon footprnt of system components for Colorado blue spruce feld producton and use, Journal of the Amercan Socety for Hortcultural Scence, vol. 138, pp. 3-11, [9] P. L, J.H. Huang, Y.F. Mo, G.H. Yang, Carbon footprnt calculaton and analyss of accommodaton servces n four-star hotels of Kunmng, Toursm Trbune, vol. 25, no. 3, pp , [10] J. Cong, X. Lu, X. Zhao, Demarcaton problems and the correspondng measurement methods of the urban carbon accountng, Chna Populaton Resources and Envronment, vol. 24, no. 4, pp , [11] S. Chen, Y. L, L. Cao, Data qualty analyss wth combnaton uncertanty and senstvty for carbon footprnt assessment of products, Chna Envronment Scence, vol. 34, pp , [12] A. Dormer, D.P. Fnn, P. Ward, J. Cullen, Carbon footprnt analyss n plastcs manufacturng, Journal of Cleaner Producton, vol. 51, pp , July, [13] J. Deng, The Prmary Methods of Grey System Theory, Wuhan, Hube provnce: Huazhong Unversty of Scence and Technology Press, 2005, pp Receved: January 8, 2015 Revsed: January 15, 2015 Accepted: January 16, 2015 Bo et al.; Lcensee Bentham Open. Ths s an open access artcle lcensed under the terms of the Creatve Commons Attrbuton Non-Commercal Lcense ( whch permts unrestrcted, non-commercal use, dstrbuton and reproducton n any medum, provded the wor s properly cted.