The Open Biotechnology Journal, 2015, 9, Experimental and Numerical Analysis of Drip Tape Layout for Irrigation of Sugarcane in Latosol

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1 Send Ode fo Repint to The Open Biotechnology Jounal, 215, 9, Open Acce Expeimental and Numeical Analyi of Dip Tape Layout fo Iigation of Sugacane in Latool Kai Huang 1,2,*, Deuo Cai 1, Jinchuang Guo 2 and Wei Pan 2 1 College of Civil Engineeing and Achitectue, Guangxi Univeity, Nanning 534, China; 2 Guangxi Intitute of Hydaulic Reeach, Nanning 5323, China Abtact: A laboatoy oil column expeiment wa fit conducted to analyze wate movement in latool of ugacane field unde dip iigation fom ingle-point ouce at diffeent emitte dichage ate. Next, a mathematical model of oil wate movement unde dip iigation fom ingle-point ouce wa built uing Hydu-3D, which could accuately imulate the hape of the wetted oil volume and the ditibution of volumetic wate content in the expeiment. Futhe, a Hydu-3D model of oil wate movement unde dip iigation fom double-point ouce wa built and then ued to analyze the effect of citical paamete on iigation unifomity. Reult howed that emitte pacing affected iigation unifomity geatly, but emitte dichage ate did not. Accoding to the iigation unifomity, poject cot and opeational management patten, appopiate dip tape paamete fo iigation of ugacane in latool wee detemined: emitte dichage ate 1.38 L/h, emitte pacing 3 cm, and ingle-emitte iigation volume 9. L. Keywod: Dip tape, hydu-3d, latool, ugacane field. 1. INTRODUCTION Dip iigation i a wate-aving iigation technique that ue emitte to diectly delive wate o a mixtue of wate and fetilize to the cop oot in a unifom and accuate way [1, 2]. The benefit of dip iigation and the efficiency of wate ue ae diectly affected by the chaacteitic of the wetted oil volume, while the wetted oil volume i contolled by a vaiety of facto uch a oil type, initial oil wate content, emitte dichage ate, emitte pacing and iigation volume [3, 4]. Thu fa, elevant expeimental [5-7] and numeical tudie [8-1] have been conducted extenively, which povide impotant efeence fo appopiate deign of dip iigation ytem. Latool i one of the majo oil type in ugacane field of Guangxi Povince and widely occu in the coatal aea of outhen Guangxi, China. No tudie have invetigated the election of dip tape layout paamete fo appopiate iigation of ugacane in latool. Thi ituation lead to ome degee of abitaine in the deign of dip iigation ytem and negatively affect the benefit of dip iigation poject in Guangxi. Theefoe, to find out the effect of dip tape layout paamete on the wetted oil volume in latool unde ugacane ha geat implication fo the deign of ugacane iigation poject in the vat egion of Guangxi. In thi tudy, a epeentative oil wa elected to pefom oil column expeiment of dip iigation fom inglepoint ouce. Soil wate movement wa analyzed unde dip iigation at thee emitte dichage ate accoding to the *Adde coepondence to thi autho at the Guangxi Univeity, Nanning 534, China; Tel: ; Fax: ; gxhuangkai@126.com emitte dichage level in common ue. A mathematical model of oil wate movement unde dip iigation fom double-point ouce wa built uing Hydu-3D and then ued to ytematically analyze the effect of citical paamete on wate ditibution unifomity of the wetted oil volume. Appopiate emitte pacing and dichage ate of dip tape wee elected fo iigation of ugacane in latool. Futhe, pefeed iigation volume and time wee detemined fo dip iigation of ugacane at diffeent gowth tage in accodance with the patten of ugacane copping, oot ditibution and poject management. 2. MATERIAL AND METHODS 2.1. Expeimental Soil The expeimental oil wa collected fom a ugacane field in the pilot demontation bae fo efficient wateaving iigation technology in Wulangjiang Village of Xichang Town in Hepu County, outhweten Guangxi Povince, China. Eight ton of oil wa taken fom the plow laye of 1 4 cm. The oil wa ai-died, cuhed and paed though a 2-mm ieve befoe ue. When pepaing fo the expeiment, the oil wa loaded into boxe by laye (5-cm thick each) and compacted with a flat plate to enue the unifomity. The contact uface between laye wa oughened to pevent tatification. The initial volumetic oil wate content and dy denity wee meaued immediately afte the oil wa filled into the boxe. The phyical popetie of the tet oil wee hown in Table Expeimental Device The expeimental ytem wa compied of a wate upply, a oil box and a oil-wate monito. The wate upply / Bentham Open

2 266 The Open Biotechnology Jounal, 215, Volume 9 Huang et al. Table 1. Phyical popetie of expeimental oil. Soil Claification Mechanical Compoition/% <.2 mm.2.5 mm >.5 mm Wate Content/ (cm 3 cm -3 ) Dy Denity/ (g cm -3 ) Latool wa a peitaltic pumpcapable of adjuting the flow ate to imulate diffeent emitte dichage ate. The oil box wa a ectangula plexigla box (1 cm long 6 cm wide 85 cm high). An emitte wa fixed to the middle of the long ide of the gla box and kept 2 cm away fom the gla wall to avoid the impact of wall. Fou pobe of an AZS-2 oil wate eno wee buied at diffeent depth (5, 15, 25 and 35 cm, epectively), with 15 cm hoizontal ditance fom the emitte. Data wee ecoded by the pobe evey 1 min. When pepaing fo the expeiment, the oil wa loaded into boxe by laye (5-cm thick each) and compacted with a flat plate to enue the unifomity. The contact uface between laye wa oughened to pevent tatification Expeimental Deign A laboatoy oil column expeiment of wate movement unde uface dip iigation wa conducted in common cenaio of emitte dichage ate (1.38, 2.2 and 2.8 L/h). The iigation volume wa et to 18 L. Each expeiment wa epeated thee time and the eult wee expeed a the mean value. Duing the expeiment, the oil uface wa coveed with a platic film to pevent evapoation. Data wee ecoded evey 3 min, including the uface ponding adiu, the wetted uface adiu and the vetical wetted depth. At the end of iigation, oil ample wee taken at 5-cm inteval by meh-tatified ampling and ued dying method fo meauing oil moitue. 3. NUMERICAL MODEL BUILDING 3.1. Pinciple It i aumed that the oil i an iotopic and homogeneou medium. Then oil wate movement can be decibed uing Richad equation a follow: t = x K(h)h x + h K (h) + h K (h) K (h) y y z z + z (1) Whee i volumetic oil wate content (cm 3 /cm 3 ) ; h i negative hydaulic head (cm); t i time (min); and K(h) i unatuated hydaulic conductivity (cm/min). The paamete of oil wate movement wee detemined uing pedo-tanfe function [11]. The van Genuchten model wa ued to decibe Hydu-3D a follow: + n ( h) = [1 + h ], h l K Se[1 (1 S K( h) = K, h m, h < 1/ m e m 2 ) ], h < (2) (3) in which S e = (4) m = 11/ n, n > 1 (5) whee S e i effective oil wate atuation (cm 3 /cm 3 ); i atuated wate content (cm 3 /cm 3 ); i eidual wate content (cm 3 /cm 3 ); K i atuated hydaulic conductivity (cm/min); l i poe connectivity facto (l =.5); m and n ae hape facto; and i ai intake facto (cm -1 ) Simulation Aea Fo imulating oil wate movement unde dip iigation fom ingle-point ouce, the coodinate oigin wa et at the emitte and the length of 4, 4 and 5 cm wee taken along the hoizontal x-, hoizontal y- and vetical z-diection. Fo imulating oil wate movement unde dip iigation fom double-point ouce, the length of emitte pacing wa taken along the hoizontal x-diection, with one emitte located at the coodinate oigin and the othe at the end of the length along x-diection; the length of 4 and 5 cm wee taken along the hoizontal y- and vetical z-diection Bounday Condition Duing the expeiment, the ponding aea at the oil uface changed ove time, which could be egaded a a dynamic-head bounday. Since Hydu-3D can not imulate the dynamic-head bounday, thi condition wa egaded a a contant-head bounday accoding to peviou tudie [12, 13]. Additionally, the contant-head adiu R wa et a the ponding adiu when uface ponding geneally tabilized in the laboatoy oil column expeiment. Then the above bounday can be decibed a follow: 2 2 h = x + y R, z =, t T (6) The othe boundaie wee et a confining boundaie Initial Condition The initial oil wate content meaued befoe the tat of the expeiment wa taken a the initial condition of wate movement. Thi condition can be decibed a follow: ( x, y, z,) = x X, 3.5. Model Paamete Detemination y Y, Z z, t = (7) Pedo-tanfe function wee ued to geneate the hydaulic paamete of the van Genuchten model and obtain the peliminay paamete of the model. Then the baic paamete of the model wee obtained by epeated calibation in accodance with expeimental ecod wee hown in Table

3 Expeimental and Numeical Analyi of Dip Tape Layout The Open Biotechnology Jounal, 215, Volume Table 2. v-g model paamete of the expeimental oil. Soil Claification / (cm 3 /cm 3 ) / (cm 3 /cm 3 ) / (1/cm) n K / (cm/min) Latool Accoding to the expeimental obevation, the infiltation adiu wee 6.5 cm, 8 cm, 9 cm at the emitte dichage ate of 1.38, 2.2 and 2.8 L/h, epectively. 4. RESULTS 4.1. Expeimental Data Analyi Fig. (1) illutated the elationhip between wetting font migation and iigation time unde dip iigation at the emitte dichage ate of 1.38, 2.2 and 2.8 L/h (iigation volume 18 L). Clealy, emitte dichage ate affected the wetted depth geatly, but had little effect on the wetted adiu. Duing the ame iigation time, the wetted depth inceaed with inceaing emitte dichage ate to a geate degee than did wetted adiu. Unde iigation of the ame volume, emitte with a geate dichage ate eulted in lightly hote wetted adiu and depth than did emitte with a lightly malle dichage ate immediately afte the completion of iigation. Howeve, the diffeence wee not ignificant ince the total iigation time wa hote fo emitte with a geate dichage ate. Duing the ame iigation time, the wetted depth wa fold the wetted adiu, indicating moe ignificant infiltation in the vetical diection. The wetted adiu and depth exhibited a powe function elationhip with iigation time. a. Wetted adiu b. Wetted depth Fig. (1). Exponent elationhip between wetting font migation and dip iigation time at diffeent emitte dichage ate (L/h) Model Accuacy Analyi Fit, we compaed wetting font migation between the imulated and meaued eult. Fig. (2). peented the meaued and imulated ditance of oil wetting font fom the point ouce at diffeent iigation time (dichage ate 1.38 L/h, volume 18 L). Thee wa clealy a gap between the meaued and imulated value of the wetting font at the initial tage of iigation. The imulated wetting font moved fate than the meaued one at 3, 9 min. Epecially, the imulated value of the wetted adiu wee 2 3 cm geate than the meaued value at the ame iigation time. At the late tage of iigation, the gap between the meaued and imulated value wa gadually diminihed with inceaing iigation time and almot diappeaed at the iigation time of 15 min. The model oveetimated wetting font migation mainly becaue Hydu-3D could not imulate the moving-head bounday condition and thu egaded it a a contant-head bounday condition in the imulation. Additionally, the infiltation adiu wa et a the ponding adiu when uface ponding geneally tabilized in the laboatoy oil column expeiment. A a matte of fact, the ponding adiu gadually changed befoe eaching the table tate, and the actual ponding adiu wa malle than the imulated value befoe the table tate. Theefoe, the meaued value of the wetting font wee malle than the imulated value at the initial tage of iigation, which accounted fo the hote ditance of wetting font migation in the meauement than in the imulation. A the time elaped, the diffeence between the meaued and imulated value wa gadually diminihed and almot diappeaed. Theefoe, the imulated eult of wetting font migation could bette eflect the actual ituation at the iigation time moe than 15 min Fig. (2). Meaued (olid) and imulated (dahed) hape of the wetting font at diffeent iigation time (min).

4 268 The Open Biotechnology Jounal, 215, Volume 9 Huang et al. Next, we compaed the imulated and actual iigation volume and examined the diffeence in oil wate content at fou monitoing point between the imulated and meaued eult. Accoding to tatitic, the iigation volume duing model calculation wa 4.48 L. Since the imulation aea accounted fo 1/4 of the wetted oil volume, the imulated ingle-emitte iigation volume wa L. The expeimental iigation volume wa 9. L. Since the expeimental aea accounted fo 1/2 of the wetted oil volume, the actual ingle-emitte iigation volume wa 18. L. Thee wa a mino diffeence of.44% between the imulated actual iigation volume, which met the accuacy equiement. Fig. (3) howed the change in the monitoed and imulated oil wate content ove time at 5, 15, 25 and 35 cm depth with 15 cm hoizontal ditance fom the emitte (ingle-emitte iigation volume 18 L). On balance, the monitoed and imulated value of oil wate content followed imila tend at the fou monitoing point. Howeve, the time of the tating point of the change howed diffeence between the monitoed and imulated value. Such diffeence wa gadually diminihed with inceaing depth of the monitoing point. With 15 cm hoizontal ditance fom the emitte, the aival time of the imulated wetting font wa ealie than the than the monitoed eult by 1 h at 5 cm depth wee hown in Fig. (3a), by.5 h at 15 cm depth wee hown in Fig. (3b) and by.17 h at 25 cm depth wee hown in Fig. (3c); the aival time of the imulated wetting font wa geneally conitent with the monitoed eult at 35 cm depth wee hown in Fig. (3d). A mentioned ealie, the dynamic-head bounday condition wa egaded a a contant-head bounday condition in model imulation. Thu, the imulated value of wetting font migation wee geate than the meaued value at the initial tage of iigation. The imulated wetting font aived ealie than the monitoed wetting font at the point cloe to the emitte, but thi time diffeence wa diminihed gadually with inceaing iigation time. Once oil wate content a. Pobe buied at 5 cm depth b. Pobe buied at 15 cm depth c. Pobe buied at 25 cm depth d. Pobe buied at 35 cm depth Fig. (3). Monitoed and imulated wate content of the wetted oil volume at diffeent iigation time (h). enteed a table tate, the eo between the imulated and meaued eult wee 1.7% at 5 cm depth, 2.6% at 15 cm depth,.5 % at 25 cm depth and 3.% at 35 cm depth. The accuacy of the model imulation completely met the equiement of iigation deciion, and the imulated eult of oil wate content could exactly eflect the change in the actual oil wate content. In ummay, the imulation eult of the popoed model could accuately eflect the actual ituation of wetting font migation and oil wate content change when dip iigation lated moe than 27 min. Additionally, ugacane i a cop chaacteized by dill owing, hallow oot, and cloe-planting. The copping patten of wide-naow ow (wide ow pacing m; naow ow pacing.4.5 m) i commonly ued in ugacane field with dip iigation. It ha been epoted that ugacane oot ae mainly ditibuted in the 2 cm (62%) and 2 4 cm oil laye (23.4%); the optimal iigation depth and width fo ugacane of the vigoou gowth tage ae appoximately 3 and 4 cm, epectively Effect of Emitte Spacing on Iigation Unifomity Emitte pacing i an impotant paamete of dip iigation ytem deign. We ued Hydu-3D to build a model of wate movement unde dip iigation fom double-point ouce. The iigation condition wee a follow: emitte dichage ate 1.38 L/h, ingle-emitte iigation volume 5.5 L, and emitte pacing 3, 4 and 5 cm. Fig. (4). howed a imulated wate content ditibution in the wetted oil volume at diffeent emitte pacing by the end of iigation. The eult howed that emitte pacing wa an impotant facto affecting iigation unifomity fo dip iigation in latool of ugacane field. At the emitte pacing of 3 cm, the wetted depth wa 33.5 cm and the iigation unifomity appeaed good; the wetted oil volume fomed a wetting zone with conitent wetted depth and unifom wate diti-

5 Expeimental and Numeical Analyi of Dip Tape Layout The Open Biotechnology Jounal, 215, Volume bution wee hown in Fig. (4a). At the emitte pacing of 4 cm, the wetted depth diectly below the emitte wa 31.5 cm, while that diectly below the midpoint of two emitte wa 25 cm, with a 6.5 cm diffeence; the change in the hape of the wetting font wa 2.6%, indicating the poo iigation unifomity wee hown in Fig. (4b). At the emitte pacing of 5 cm, the wetted depth diectly below the emitte wa 31.5 cm, while that diectly below the midpoint of two emitte wa only 1 cm, with a 21.5 cm diffeence and 68.3% change in the hape of the wetting font; wate content in the coe aea of the wetted oil volume diectly below the midpoint of two emitte wa.153, ignificantly lowe than that diectly below the emitte which wa.332; thee eult wee indicative of the woe iigation unifomity wee hown in Fig. (4c). Since the copping patten of ugacane (dill owing and cloe planting) ha highe demand fo iigation unifomity, we ecommend the emitte pacing of 3 cm fo dip iigation at the emitte dichage ate of 1.38 L/h in latool of ugacane field Effect of Emitte Dichage Rate on Iigation Unifomity Emitte dichage ate i anothe impotant paamete of dip iigation ytem deign. We ued Hydu-3D to build a a. 3 cm emitte pacing b. 4 cm emitte pacing c. 5 cm emitte pacing Fig. (4). Simulated wate content ditibution in the wetted oil volume unde dip iigation at diffeent emitte pacing. model of wate movement unde double-point ouce of dip iigation with the following paamete: emitte pacing 4 cm, ingle-emitte iigation volume 9 L, and emitte dichage ate 1.38, 2.2 and 2.8 L/h. Fig. (5). Showed a imulated wate content ditibution in the wetted oil volume at diffeent emitte dichage ate by the end of iigation. The eult howed that emitte dichage ate had little effect on iigation unifomity in latool of ugacane field. Unde iigation of the ame volume, emitte with a geate dichage ate had a hote iigation time and thu eulted in a malle wetted volume, lightly inceaing the iigation unifomity. At the emitte dichage ate of 1.38 L/h, the wetted depth diectly below the emitte wa 31.5 cm, while that below the midpoint of two emitte wa 25 cm; the 6.5 cm diffeence accounted fo 2.6% change in the hape of the wetting font wee hown in Fig. (5a). At the emitte dichage ate of 2.2 L/h, the wetted depth diectly below the emitte wa 31. cm, while that below the midpoint of two emitte wa 24 cm; the 6. cm diffeence accounted fo 19.4% change in the hape of the wetting font wee hown in Fig. (5b). At the emitte dichage ate of 2.8 L/h, the wetted depth diectly below the emitte wa 29. cm, while that below the midpoint of two emitte wa 23.5 cm; the 5.5 cm diffeence accounted fo 19.% change in the hape of

6 27 The Open Biotechnology Jounal, 215, Volume 9 Huang et al the wetting font wee hown in Fig. (5c). Theefoe, it i infeaible to impove iigation unifomity by a geate emitte dichage ate in latool of ugacane field. Fom the pepective of poject cot, uing a malle emitte dichage ate at the ame emitte pacing can ignificantly educe poject invetment. Howeve, the iigation time will need to be inceaed to obtain the ame iigation volume. Hence, both the poject cot and opeational management hould be taken into conideation in ode to elect the appopiate emitte dichage ate Reaonable Paamete Analyi of Dip Tape in Latool of Sugacane Field Baed on the above analyi, thee combination of emitte dichage ate and pacing (1.38, 2.2 o 2.8 L/h and 3 cm) enable common dip tape to meet the equiement of iigation unifomity in latool of ugacane field in Guangxi. The combination of lowe emitte dichage ate (1.38 L/h) and 3 cm emitte pacing i mot cot effective, while the combination of highe emitte dichage ate (2.8 L/h) and 3 cm emitte pacing i mot expenive and time efficient, and thu i the eaiet to manage. Given that the ingle-emitte iigation volume deied fo ugacane of the a L/h emitte dichage ate b. 2.2 L/h emitte dichage ate c. 2.8 L/h emitte dichage ate Fig. (5). Simulated wate content ditibution in the wetted oil volume unde dip iigation at diffeent emitte dichage ate. gowing peiod i 9 L in latool, then one otational iigation goup need the iigation time of 6.5 h at the emitte dichage ate of 1.38 L/h, 4.1 h at the emitte dichage ate of 2.2 L/h, and 3.2 h at the emitte dichage ate of 2.8 L/h. Accoding to the exiting management ytem fo ugacane field, two otational iigation goup ae completed in one day. The opeato need to manually contol the valve in the field fo the changing ove between otational iigation goup, and the pe-et contol time i at leat.5 h. Hence, the election of emitte dichage ate at 1.38, 2.2 o 2.8 L/h leave enough time fo field contol of the valve by the opeato. The coeponding 1-d cumulative unning time wa 13, 8.2 and 6.4 h. Since ainfall i abundant in Guangxi, ugacane field ae geneally iigated at a elatively low fequency (1 12 time a yea). If uing the emitte dichage ate of 1.38 L/h, the 1-d cumulative unning time of the iigation ytem i etimated to be 13 h. Thi tategy can be ecommended a the pefeential option a it not only complie with the egulatoy equiement but alo fit the wok chedule of ugacane fame and meet geneal equiement of iigation management. Fo ugacane field with pecial equiement fo 1-d cumulative unning time of

7 Expeimental and Numeical Analyi of Dip Tape Layout The Open Biotechnology Jounal, 215, Volume the iigation ytem, the appopiate emitte dichage ate hould be detemined in accodance with the ingle-emitte iigation volume and unning time. Taking into conideation the poject cot and opeational management patten, we ecommend the following eaonable deign paamete of common dip tape fo ue in latool of ugacane field in Guangxi: emitte dichage ate 1.38 L/h, emitte pacing 3 cm, and ingle-emitte iigation volume 9 L. CONCLUSION Emitte pacing tongly affected iigation unifomity in latool of ugacane field. An emitte pacing of 3 cm enued iigation unifomity, while the emitte pacing of 4 o 5 cm eulted in poo iigation unifomity in the expeimental oil. Hence, dip tape with 3-cm emitte pacing ae ecommended fo iigation of ugacane copped in the dill owing and cloe planting patten. Emitte dichage ate had little effect on iigation unifomity in latool of ugacane field. The appopiate emitte dichage ate hould be elected by taking into conideation the poject cot and opeational management equiement. In accodance with the poject cot, opeational management patten, and wate demand of ugacane, the appopiate deign paamete of dip tape fo iigation of latool unde ugacane wee detemined: emitte dichage ate 1.38 L/h, emitte pacing 3 cm, and ingle-emitte iigation volume 9 L. CONFLICT OF INTEREST The autho confim that thi aticle content ha no conflict of inteet. ACKNOWLEDGEMENTS Thi wok i uppoted by the Agicultual Sci-Tech Achievement Tanfomation Fund of Guangxi, China (No ), the Non-pofit Induty Financial Pogam of Minity of Wate Reouce, China (No ). REFERENCES [1] Chale MB. Rapid field evaluation of dip and mico pay ditibution unifomity. Iigat Dainage Syt 24; 18: [2] Baagn J, Balt V, Wu IP. Aement of emiion unifomity fo mico-iigation deign. Bioyt Eng 26; 93: [3] Sun H, Li MS, Ding H, Wang YX, Cui WM. Expeiment on effect of dippe dichage on cotton-oot ditibution. Tanact Chin Soci Agicult Eng 29; 25: [4] Subbaiah R. A eview of model fo pedicting oil wate dynamic duing tickle iigation. Iigat Sci 213; 31: [5] Wang ZR, Wang WY, Wang QJ, Zhang JF. Expeimental tudy on oil wate movement fom a point ouce. J Hydaul Eng 2; 6: [6] Cote CM, Bitow KL, Chalewoth PB, Cook FJ, Thobun PJ. Analyi of oil wetting and olute tanpot in ubuface tickle iigation. Iigat Sci 23; 22: [7] Bhatnaga PR, Chauhan HS. Soil wate movement unde a ingle uface tickle ouce. Agicult Wate Manag 28; 95: [8] Povenzano G. Uing HYDRUS-2D imulation model to evaluate wetted oil volume in ubuface dip iigation ytem. J Iigat Dainage Eng 27; 133: [9] Mazia M, Kandelou, Jii Simunek. Compaion of numeical, analytical, and empiical model to etimate wetting patten fo uface and ubuface dip iigation. Iigat Sci 21; 28: [1] Dabach S, Lazaovitch N, imnek J, Shani U. Numeical invetigation of iigation cheduling baed on oil wate tatu. Iigat Sci 213; 31: [11] Liu JL, Xu SH, Liu H. A eview of development in etimating oil wate etention chaacteitic fom oil data. J Hydaul Eng 24; 2: [12] Li MS, Kang SZ, Sun HY. Relationhip between dippe dichage and oil wetting patten fo dip iigation. Tanact Chin Soci A- gicult Eng 26; 22: 32. [13] Zhao Y, Li MS. Analyi of oil uface ponding adiu movement model unde point ouce dip iigation. Wate Saving Iigat 214; 12: Received: May 26, 215 Revied: July 14, 215 Accepted: Augut 1, 215 Huang et al.; Licenee Bentham Open. Thi i an open acce aticle licened unde the tem of the ( which pemit uneticted, noncommecial ue, ditibution and epoduction in any medium, povided the wok i popely cited.