PHÂN BAN TOÁN - CƠ -VẬT LÝ KỸ THUẬT 2007

HI NGH KHOA HC V CễNG NGH LN TH 10 TRNG I HC BCH KHOA HQG TP.HCM PHN BAN TON - C -VT Lí K THUT 2007 TểM TT CC BO CO HI NGH Khoa Khoa hc ng dng TP H Chớ Minh 2007 HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 LI M U Tham d Hi ngh Khoa hc v Cụng ngh ln th 10 ca trng i Hc Bỏch Khoa i hc Quc gia Tp H Chớ Minh, v cng nhõn dp cho mng s kin trng i hc Bỏch khoa TP.HCM va c phong tng danh hiu Anh hựng lao ng thi k i mi 2005, khoa Khoa hc ng dng tin hnh t chc phõn ban hi ngh: phõn ban Toỏn C Vt lý K thut v phõn ban Quang chõm laser bỏn dn Phõn ban Toỏn C Vt lý K thut c t chc nhm cụng b mt s kt qu cụng trỡnh liờn quan n hot ng nghiờn cu khoa hc ca cỏc b mụn Toỏn ng dng, C K thut v Vt lý K thut thi gian gn õy õy l nhng b mụn cú hot ng o to tng i u khp t lnh vc c bn n chuyờn ngnh nờn hot ng NCKH l mt b phn hu c khụng th tỏch ri v h tr c lc cho cụng tỏc o to ca Khoa Phõn ban ó nhn c s hng ng tớch cc ca cỏc cỏn b nghiờn cu ngoi trng, cỏc hc viờn cao hc v cỏc sinh viờn tt nghip cỏc khoỏ u tiờn chuyờn ngnh Toỏn ng dng, C k thut v Vt lý K thut So vi Hi ngh Khoa hc v Cụng ngh ln th 9, ni dung hi ngh ln ny cú nhng im sc v nh hỡnh mt s hng rừ nột phng hng nghiờn cu v o to: phỏt trin cụng ngh tớnh toỏn nhiu lnh vc vi s kt hp mụ hỡnh toỏn hc v ng dng thc tin (x lý tớn hiu, hỡnh nh y sinh, mụ phng c hc, c sinh hc, o lng kim nh vv), c bit nhúm tớnh toỏn mụ phng cỏc lnh vc khoa hc vt liu t c nhng kt qu ni bt mang tm quc t Nhng kt qu trờn ó khng nh mt bc tin vng chc n lc y mnh cụng tỏc nghiờn cu khoa hc ca Khoa Phõn ban ó nhn c 42 bỏo cỏo ca cỏc tỏc gi v cỏc nhúm nghiờn cu hot ng lnh vc Toỏn hc, C K thut v Vt lý k thut Sau phn bin v thi gian hn ch, ban t chc chn 15 bỏo cỏo trỡnh by ti hi ngh, ton nhng bi cũn li s trỡnh by dng poster v ng k yu hi ngh ca phõn ban Ban t chc phõn ban xin chõn thnh cỏm n Ban giỏm hiu v cỏc Phũng Ban ca trng i hc Bỏch khoa TP.HCM ó h tr mi mt t chc hi ngh Do thi gian gp rỳt, phn t chc hi ngh v biờn khụng trỏnh nhng khim khuyt Rt mong s gúp ý xõy dng hon thin hn cỏc hi ngh ti Ban t chc phõn ban Toỏn C Vt lý K thut HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 C QUAN NG T CHC TRNG I HC BCH KHOA TP H CH MINH KHOA KHOA HC NG DNG BAN T CHC GS.TS NGễ KIU NHI Trng Phõn ban TS HUNH QUANG LINH TS NGUYN èNH HUY TS TRNG TCH THIN BAN TH Kí V BIấN TP TS NGUYN TNG LONG TS HUNH QUANG LINH KS TRN DUY LINH HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 A TON NG DNG TNH TON Mễ PHNG LAN TRUYN CHT S DNG PHN MM ANSYS Phm Ngc Dng, Bựi Tỏ Long Vin Mụi trng v Ti nguyờn TểM TT Hin nay, cỏc tớnh toỏn quỏ trỡnh truyn cỏc cht hũa tan cú ý ngha ln i vi vic lp k hoch v phỏt trin h thng bo v nc Tuy nhiờn, vic tớnh toỏn chớnh xỏc cỏc quỏ trỡnh khụng gian v thi gian phn ln trng hp l khụng th c vỡ tớnh phc cng knh v thiu cỏc nghim gii tớch ca phng trỡnh m nú mụ t s phõn b nng cỏc thnh phn trờn kờnh sụng Hn na s lng tham s v phng trỡnh mụ t rt ln khin vic tỡm kim li gii gp nhiu khú khn Bờn cnh ú rt nhiu cụng c mnh cho phộp t ng hoỏ tớnh toỏn ó c nghiờn cu trờn th gii õy l iu kin thun li cho nghiờn cu ng dng gii quyt nhiu bi toỏn thc tin v lan truyn cht Trong bi bỏo ny trỡnh by mt s kt qu bc u ng dng phn mm ANSYS mụ phng lan truyn cht ho tan kờnh sụng ly sụng Hng lm i tng nghiờn cu N NH VNG CA H DNG TUYN TNH Cể CHM TRONG Lp([h, 0];X) Bựi Th Anh(1), Dng ng Xuõn Thnh(2) Khoa Toỏn Tin, trng i Hc S phm Tp HCM (2) Khoa Toỏn-tin, trng i Hc Tụn c Thng, Tp HCM (1) TểM TT Trong bi bỏo ny, chỳng tụi nghiờn cu tớnh n nh vng ca h dng tuyn tớnh cú chm thụng qua khỏi nim bỏn kớnh n nh di tỏc ng ca mt s loi nhiu Kt qu ny bao gm mt s kt qu ó cú ABSTRACT In this paper we study how the uniformly boundness of an operator associated with delay equation changes under affine perturbations Characterizations of the stability radius of it with respect to this type of disturbances are established The results obtained are extensions of the recent published CC TNH CHT NH TNH CA BAO HM THC TCH PHN NGU NHIấN TRONG KHễNG GIAN BANACH Nguyn ỡnh Huy B mụn Toỏn ng dng, trng i hc Bỏch khoa HQG TP.HCM TểM TT Bi bỏo nghiờn cu mt lp phng trỡnh dng bao hm tớch phõn ngu nhiờn khụng gian Banach dng : x ( , t ) a ( , s, t ) + t T0 ( ) G ( , s, t ) F ( , s, x ( , s ) )ds Tỏc gi ó chng minh c s tn ti nghim liờn tc mnh ca phng trỡnh ú trng hp hm di du tớch phõn thoó cỏc gi thit Filippov HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 IU KHIN TI U H NG LC inh Vinh Hin (1), Nguyn Bỏ Thi (2) (1) Cụng ty CP Phn mm Khang Thnh (2) B mụn Toỏn ng dng - Trng i hc Bỏch Khoa HQG TP.HCM (1) nguyenbthi@hcmut.edu.vn, (2) ktvnco@yahoo.com TểM TT i tng nghiờn cu ca bi bỏo ny l bi toỏn iu khin ti u h ng lc vi hm mc tiờu phi tuyn v cú rng buc v thi im t xung Trong thc t thỡ vic t cỏc xung iu khin lờn cỏc h ng lc khụng phi c thc hin mt cỏch t m phi tuõn th nhng rng buc nht nh, ú l khong thi gian gia hai thi im t xung phi ln hn hay bng mt hng s no ú Hn ch ny xut phỏt t bn thõn cỏc thit b iu khin m ú, sau mi tỏc ng xung cn phi cú mt khong thi gian ti thiu thu xp cho tỏc ng tip theo Trong trng hp ny, vic dch chuyn mt xung cú th s kộo theo vic dch chuyn c mt chựm xung Song song vi vic gii quyt nhng rng buc ú, bi bỏo ny cũn cp n mt khớa cnh khỏc ca bi toỏn, ú l vic nghiờn cu cỏc hm mc tiờu phi tuyn thay cho hm tuyn tớnh Vic nghiờn cu nhng bi toỏn nh vy thng rt cú ý ngha c v phng din lý thuyt ln thc tin Da trờn phng phỏp bin i thớch nghi, cụng thc Cauchy v nh lý iu kin cn ca ti u, cỏc tỏc gi ó xõy dng mụ hỡnh toỏn hc v thut toỏn gii bi toỏn Sau cựng l phn minh thut toỏn núi trờn bng chng trỡnh c vit bng Matlab ABSTRACT Object of study in this article is optimal control problem of dynamic systems with nonlinear objective function and constraint of the time when pulses are set In fact, the setting of pulses on the dynamic systems cannot be done freely, it has to follow some specific constraints, i.e the period between the setting time of the two pulses has to be more than or equal a certain constant This limitation is originated from the control equipments in which there must be a minimum time to arrange the next pulse effect after the previous one In this case, a move of a pulse can bring about a move of a bunch of pulse Besides solving those constraints, this article also mentions another aspect of the problem, i.e the study of nonlinear objective function in stead of linear function This study of such a problem is meaningful in both theory and reality aspects Based on the adaptive method, Cauchy formula and theorem of necessary condition of optimal control, the authors constructed a mathematical model and an algorithm to solve the problem Finally, the algorithm mentioned above is illustrated by the program written in Matlab KHOA HC TNH TON TRONG NGHIấN CU BNH DCH COMPUTATIONAL SCIENCES IN STUDYING EPIDEMIC OUTBREAKS Nguyn Vn Minh Mn Khoa Cụng ngh Thụng tin - Trng i hc Bỏch Khoa HQG TP.HCM mnguyen@cse.hcmut.edu.vn TểM TT Dch t hc bn v s lõy lan cỏc bnh truyn nhim v khoa hc tớnh toỏn bn v cỏc phng phỏp toỏn hc, tớnh toỏn v mụ phng cú liờn quan mt thit vi nhau, ớt nht l t th k 18 Tiờu biu l Daniele Bernoulli, nh toỏn hc ngi Thy S ó nghiờn cu v hiu qu ca s tiờm chng u bũ (cowpox) trờn s lõy lan bnh u ngi (smallpox) vo nm 1760 Ngy nay, cỏc bnh rt nguy him nh SARS, cỳm gia cm, bnh AIDS ang lan trn khp cỏc chõu lc Vn ny thu hỳt s quan tõm ca cỏc bỏc s, chuyờn gia sinh thỏi, mụi trng v khoa hc s sng, cỏc nh kinh t, hoch nh chớnh sỏch cng nh cỏc nh toỏn hc v chuyờn gia khoa hc tớnh toỏn Mc tiờu chớnh ca bi vit ny l nhm a quan im rng mt s hp tỏc gia cỏc khoa hc liờn ngnh cn c lu ý xõy dng, u t cú chiu sõu; cỏc nh hoch nh chớnh sỏch khụng ch nờn a cỏc quyt nh phũng nga, ngn chn hay dp tt bnh dch da trờn cỏc biu hin trc quan, cm tớnh Cỏc quyt nh ú phi c da trờn cỏc quan sỏt v tớnh toỏn khoa hc mang tớnh d bỏo Chỳng tụi s trỡnh by HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 di gúc nhỡn mụ hỡnh hoỏ toỏn hc, nhm din t s lõy lan bng cỏc mụ hỡnh toỏn hc, thng kờ v khoa hc mỏy tớnh nhm lng hoỏ cỏc tham s chớnh ca cỏc mụ hỡnh toỏn ABSTRACT Epidemiological science discusses the spreading of infectious diseases and Computational science (investigating mathematical methods, computing and simulations) have an intimate relationship, at least from 18th century Specifically, Daniele Bernoulli, a Swiss mathematician researched the effects of cowpox vaccination on human being's smallpox spreading in 1760 Nowadays, fatal diseases as SARS (severe acute respiratory syndrome) and H5N1 flu, a subtype of the Highly Pathogenic Avian Influenza (HPAI), together with AIDS are spreading on every continents of the globe The problem is one of the major concerns of physicians, environmental and ecological scientists as well as mathematicians and computer scientists The main aim of this writing is to raise a concern that a decent collaboration among related multidisciplinary sciences should have been built up with much care, employing resources effectively; policy makers would not provide prevention measures or controlling actions that are based on simple indicators only The decisions must be made on scientific observations and computations in a cautiously forecasting manner We will discuss the problem under the mathematical modeling view, aimed at describing epidemic spreading by mathematical, statistical models and computing science techniques, from which we are able to quantitatively evaluate major parameters of mathematically epidemic models V mt phng trỡnh súng phi tuyn vi mt iu kin memory ti biờn: S tn ti v khai trin tim cn ca nghim (1) Lờ Xuõn Trng(1) , Nguyn Thnh Long(2) B mụn Toỏn, Khoa Khoa hc C bn, i hc S phm K thut Tp H Chớ Minh E-mail: lxuantruong@gmail.com (2) Khoa Toỏn- tin hc, i hc Khoa hc T nhiờn Tp H Chớ Minh E-mail: longnt@hcmc.netnam.vn, longnt2@gmail.com TểM TT Trong bỏo cỏo ny, chỳng tụi xột bi toỏn biờn v ban u cho phng trỡnh súng phi tuyn cho bi ( ( x, t )u x ) + K u p u + ut q ut = f ( x, t ), < x < 1, < t < T , x u (0, t ) = 0, (1, t )u x (1, t ) = Q(t ), utt u ( x,0) = u0 ( x), ut ( x,0) = u1 ( x), ú p 2, q 2, K , l cỏc hng s cho trc v u , u1 , f , l cỏc hm cho trc n hm u ( x, t ) v giỏ tr biờn cha bit Q (t ) tha phng trỡnh tớch phõn tuyn tớnh t Q(t ) = K1 (t ) u (1, t ) + (t ) u t (1, t ) g (t ) k (t s )u (1, s)ds, ú K1 , , g , k l cỏc hm cho trc tha mt s tớnh cht c phỏt biu phn sau Bi bỏo gm hai phn chớnh Trong phn 1, chỳng tụi chng minh s tn ti v nht nghim mt khụng gian hm thớch hp Trong phn 2, chỳng tụi tỡm khai trin tim cn theo K , , K1 ca nghim n cp N + Chi tit chng minh ca cỏc kt qu ny cú th tỡm thy bi bỏo ca chỳng tụi [2] ABSTRACT In this report, we consider the initial-boundary value problem for a nonlinear wave equation given by HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 p q2 utt x ( ( x, t )u x ) + K u u + ut ut = f ( x, t ), < x < 1, < t < T , u (0, t ) = 0, (1, t )u x (1, t ) = Q(t ), u ( x,0) = u0 ( x), ut ( x,0) = u1 ( x), where p 2, q 2, K , are given constants and u , u1 , f , are given functions The unknown function u ( x, t ) and the unknown boundary value Q (t ) satisfy the linear integral equation t Q(t ) = K1 (t ) u (1, t ) + (t ) u t (1, t ) g (t ) k (t s )u (1, s)ds, where K1 , , g , k are given functions satisfying some properties stated in the next section This paper consists of two main parts In Part 1, we prove the existence and uniqueness for the solutions in a suitable function space In Part 2, we find the asymptotic expansion in K , , K1 of the solutions, up to order N + References: [1] Nguyen Thanh Long, Le Xuan Truong, Existence and asymptotic expansion for a viscoelastic problem with a mixed nonhomogeneous condition, Nonlinear Analysis, Theory, Methods & Applications, Series A: Theory and Methods, 67 (3) (2007), 842-864 [ http://dx.doi.org/10.1016/j.na.2006.06.044 ] [2] Nguyen Thanh Long, Le Xuan Truong, Existence and asymptotic expansion of solutions to a nonlinear wave equation with a memory condition at the boundary, Electron J Diff Eqns., Vol 2007(2007), No 48, pp 1-19 Phng trỡnh súng phi tuyn liờn kt vi iu kin biờn phi tuyn: S tn ti v khai trin tim cn ca nghim (1) Vo Giang Giai (1), Nguyen Thanh Long(2) Cng tỏc viờn ca Khoa Toỏn- tin hc, i hc Khoa hc T nhiờn Tp H Chớ Minh (2) Khoa Toỏn- tin hc, i hc Khoa hc T nhiờn Tp H Chớ Minh E-mail: longnt@hcmc.netnam.vn, longnt2@gmail.com TểM TT Trong bỏo cỏo ny, chỳng tụi xột bi toỏn biờn v ban u cho phng trỡnh súng phi tuyn (1) utt u xx + K u p2 u + ut q2 ut = F ( x, t ), < x < 1, < t < T , u x (0, t ) = P(t ), u x (1, t ) = u (1, t ) p1 u (1, t ) + ut (1, t ) q1 ut (1, t ), u ( x,0) = u0 ( x), ut ( x,0) = u1 ( x), ú p, p1 , q1 2, q > 1, K , l cỏc hng s cho trc v u0 , u1 , F l cỏc hm cho trc, v n hm u ( x, t ) v giỏ tr biờn cha bit P (t ) tha phng trỡnh tớch phõn phi tuyn (2) P(t ) = g (t ) + K u (0, t ) p0 u (0, t ) + ut (0, t ) q0 t ut (0, t ) k (t s)u (1, s )ds, ú p0 , q0 2, K l cỏc hng s cho trc v g, k l cỏc hm cho trc Bi bỏo gm ba phn chớnh Trong phn 1, di cỏc iu kin (u0 , u1 ) H (0,1) ì L2 (0,1), / F L2 ((0,1) ì (0, T )), k W 1,1 (0, T ), g Lq0 (0, T ), = 1, K , K 0, p, p0 , q0 , p1 , q1 2, q > 1, HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 q0/ = q0 , chỳng tụi chng minh s tn ti v nht ca mt nghim yu (u , P ) ca bi toỏn (1), q0 (2) Chỳng minh da vo phng phỏp Faedo-Galerkin v phng phỏp compact yu liờn kt vi toỏn t n iu Vi trng hp q0 = q1 = 2, p, q, p0 , p1 2, phn chỳng tụi chng minh rng (L (0,T ; H nghim nht (u , P ) thuc vo ut L (0, T ; H ), utt L (0, T ; L2 ), ) ) C (0, T ; H ) C1 (0, T ; L2 ) ì H (0, T ), vi u (0,), u (1,) H (0, T ), nu ta gi thit rng (u0 , u1 ) H (0,1) ì H (0,1) v mt s iu kin khỏc Cui cựng, phn chỳng tụi thu c khai trin tim cn ca nghim (u , P ) ca bi toỏn (1), (2) n cp N + theo ba tham s K , , K Chi tit chng minh ca cỏc kt qu ny cú th tỡm thy bi bỏo ca chỳng tụi [1] ABSTRACT In this report, we consider the initial-boundary value problem for the nonlinear wave equation (1) utt u xx + K u p2 u + ut q2 ut = F ( x, t ), < x < 1, < t < T , u x (0, t ) = P(t ), u x (1, t ) = u (1, t ) p1 u (1, t ) + ut (1, t ) q1 ut (1, t ), u ( x,0) = u0 ( x), ut ( x,0) = u1 ( x), where p, p1 , q1 2, q > 1, K , are given constants and u0 , u1 , F are given functions, and the unknown function u ( x, t ) and the unknown boundary value P (t ) satisfy the following nonlinear integral equation (2) P(t ) = g (t ) + K u (0, t ) p0 u (0, t ) + ut (0, t ) q0 t ut (0, t ) k (t s)u (1, s)ds, where p0 , q0 2, K are given constants and g, k are given functions In this paper, we consider three main parts In Part 1, under conditions q 0/ g L (0, T ), F L ((0,1) ì (0, T )), k W (0, T ), = 1, q K , K 0, p, p0 , q0 , p1 , q1 2, q > 1, q0/ = , we prove a theorem of existence and uniqueness q0 of a weak solution (u , P ) of problem (1) and (2) The proof is based on the Faedo-Galerkin method and (u0 , u1 ) H (0,1) ì L (0,1), the weak compact method 1,1 associated with a monotone operator For the case of q0 = q1 = 2, p, q, p0 , p1 2, in Part we prove that the unique solution (u , P ) belongs to (L (0,T ; H ) ) C (0, T ; H ) C1 (0, T ; L2 ) ì H (0, T ), with ut L (0, T ; H ), utt L (0, T ; L2 ), u (0,), u (1,) H (0, T ), if we make the assumption that (u0 , u1 ) H (0,1) ì H (0,1) and some others Finally, in Part we obtain an asymptotic expansion of the solution (u , P ) of the problem (1) and (2) up to order N + in three small parameters K , , K References: [1] Nguyen Thanh Long, Vo Giang Giai, A nonlinear wave equation associated with nonlinear boundary conditions: Existence and asymptotic expansion of solutions, Nonlinear Analysis, Theory, Methods & Applications, Series A: Theory and Methods, 66 (12) (2007), 2852 - 2880 [ http://dx.doi.org/10.1016/j.na.2006.04.013 ] Tớnh cht Hukuhara-Kneser cho mt phng trỡnh tớch phõn phi tuyn Lờ Th Phng Ngc(1), Nguyn Thnh Long(2) HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 (1) Trng Cao ng S phm Nha Trang E-mail: ngoc1966@gmail.com, phuongngoccdsp@dng.vnn.vn (2) Khoa Toỏn-tin hc, i hc Khoa hc T nhiờn E-mail: longnt@hcmc.netnam.vn, longnt2@gmail.com TểM TT p dng nh lý cu trỳc Krasnoselskii-Perov, chỳng tụi chng minh rng cỏc nghim ca mt phng trỡnh tớch phõn phi tuyn tho tớnh cht Hukuhara-Kneser Chi tit chng minh ca cỏc kt qu ny cú th tỡm thy bi bỏo ca chỳng tụi [3] ABSTRACT Applying a structure theorem of Krasnoselskii and Perov, we show that the solution set of a nonlinear integral equation satisfies the classical Hukuhara-Kneser property References: [1] Nguyen Thanh Long, Le Thi Phuong Ngoc, A wave equation associated with mixed nonhomogeneous conditions: The connectivity and compactness of weak solution set, Abstract and Applied Analysis, Volume 2007, Article ID 20295, 17 pages doi:10.1155/2007/20295 [ http://www.hindawi.com/GetArticle.aspx?doi=10.1155/2007/20295 ] [2] Le Thi Phuong Ngoc, Nguyen Thanh Long, On a fixed point theorem of Krasnosel'skii type and application to integral equations, Fixed Point Theory and Applications, Volume 2006 (2006), Article ID 30847, 24 pages doi:10.1155/FPTA/2006/30847 [ http://www.hindawi.com/GetArticle.aspx?doi=10.1155/FPTA/2006/30847 ] [3] Le Thi Phuong Ngoc, Nguyen Thanh Long, The Hukuhara-Kneser Property for a nonlinear integral equation, (Submitted) Phng trỡnh súng Kirchhoff phi tuyn ( ) utt + B ( u x (t ) ) u xx = f ( x, t , u , u , u x , ut , u x (t ) ) liờn kt vi iu kin biờn hn hp thun nht Trn Ngc Dim(1) , Bựi Tin Dng(2) B mụn Toỏn, Khoa Khoa hc ng dng, i hc Bỏch khoa Tp H Chớ Minh Email: minhducfactory@yahoo.com (2) B mụn Toỏn, Khoa Khoa hc C bn, i hc Kin trỳc Tp H Chớ Minh Email: tiendungbuidhkt@gmail.com (1) TểM TT Dựng thut gii qui np, chỳng tụi chỳng minh s tn ti v nht nghim mt nghim yu a phng ca bi toỏn sau: ( ) utt + B( u x (t ) ) u xx = f ( x, t , u, u, u x , ut , u x (t ) ), < x < 1, < t < T , u x (0, t ) hu (0, t ) = u (1, t ) = 0, u ( x,0) = u0 ( x), ut ( x,0) = u1 ( x), u (t ) = u ( y, t ) dy, x x ú h 0, > l cỏc hng s cho trc v B, f , u , u1 l cỏc hm s cho trc Sau ú, chỳng tụi cng nghiờn cu dỏng iu tim cn ca nghim u ( x, t ) ph thuc vo + ABSTRACT HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 Using a recurrent scheme, we prove the existence of a unique local weak solution to the following problem: ( utt + B( u x (t ) ) ) u xx = f ( x, t , u, u, u x , ut , u x (t ) ), < x < 1, < t < T , u x (0, t ) hu (0, t ) = u (1, t ) = 0, u ( x,0) = u0 ( x), ut ( x,0) = u1 ( x), u x (t ) = u x ( y, t ) dy, where h 0, > are given constants and B, f , u , u1 are given functions Afterwards, we also study the asymptotic behavior of the solution u ( x, t ) depending on as + Xp x tuyn tớnh v khai trin tim cn liờn kt vi h phng trỡnh hm phi tuyn (1) Hunh Th Hong Dung(1), Phm Hng Danh(2) B mụn Toỏn, Khoa Khoa hc C bn, i hc Kin trỳc Tp H Chớ Minh Email: dunghth1980@gmail.com (2) Khoa Thng kờ Toỏn tin hc, i hc Kinh t Tp H Chớ Minh Email: hongdanh282@yahoo.com.vn TểM TT Chỳng tụi xột h phng trỡnh hm phi tuyn sau õy X ijk ( x ) m n (1) f i ( x) = aijk x, f j ( Rijk ( x)), f j (t )dt + bijk f j ( Sijk ( x)) + gi ( x), k =1 j =1 k =1 j =1 vi mi x = [ b, b ], i = 1, , n, ú l mt tham s bộ, aijk , bijk l cỏc hng s thc cho m n trc vi m i =1 k =1 n max bijk < 1, Rijk , Sijk , X ijk : , g i : IR, v : ì IR IR l cỏc j n hm s liờn tc cho trc v f i : IR l cỏc n hm Dựng nh lý im bt ng Banach, chỳng tụi chng minh rng h (1) cú nghim nht Trong trng hp C ( ì IR ; IR), chỳng tụi cng thu c s hi t bc hai ca h (1) Nu C N ( ì IR ; IR), thỡ mt khai trin tim cn nghim ca h (1) n cp N + theo thu c, vi nh ABSTRACT We consider the following system of functional equations X ijk ( x ) m n (1) f i ( x) = aijk x, f j ( Rijk ( x)), f j (t )dt + bijk f j ( Sijk ( x)) + gi ( x), k =1 j =1 k =1 j =1 for all x = [ b, b ], i = 1, , n, where is a small parameter, aijk , bijk are the given real constants m n with m i =1 k =1 n max bijk < 1, Rijk , Sijk , X ijk : , g i : IR, and j n : ì IR IR are the given continuous functions and f i : IR are unknown functions By using the Banach fixed point theorem, we prove the system (1) has a unique solution In the case of C ( ì IR ; IR), we also obtain the quadratic convergence of the system (1) If C N ( ì IR ; IR), then an asymptotic HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 C1 ( x,0) = C10 ( x), x 1, where > is given constant and q1 , C10 , , are given functions (3) In this paper, we consider three main parts In Part 1, under conditions C10 L2 (), q1 C (QT ), L2 (QT ), L2 (0, T ), > 0, we prove a theorem of existence and uniqueness of a weak solution C1 of problem (1)-(3) The proof is based on the Faedo-Galerkin method and the weak compact method For the case of q1 C (QT ), , 1/ L2 (QT ), H (0, T ), > 0, in Part we prove that the unique solution C1 belongs to C1 L (0, T ; H ) L2 (0, T ; H ) C ([0, T ]; H ) H (QT ), with C1/ L2 (QT ), if we make the assumption that C10 H (), and some others Finally, in Part we obtain a non-negative solution C1 of the problem (1)-(3) if we make the assumption that C10 L2 (), C10 0, a.e x V MT H ELLIPTIC p- LAPLACE TRONG KHễNG GIAN SOBOLEV Cể TRNG Lờ Khỏnh Lun(1), Trn Minh Thuyt(1), Vừ Giang Giai(2) (1) Trng i hc Kinh t TP HCM E-mail: tmt@euh.edu.vn, luanle@ueh.edu.vn (2) Cng tỏc viờn B mụn Toỏn Cao cp, Khoa Toỏn-tin hc, i hc Khoa hc T nhiờn Tp H Chớ Minh E-mail: khanhduygiai@yahoo.com TểM TT Chỳng tụi nghiờn cu bi toỏn biờn phi tuyn sau p / p d r / r dr r u i (r ) u i (r ) + u i (r ) u i (r ) = f i (r , u1 (r ), u (r ) ), < r < 1, p / / (*) u1 (1) = 0, u (1) u (1) + hu (1) = g , lim r r / p u i/ (r ) < +, (i = 1, 2), r 0+ ú = N 1, p 2, h > 0, g l cỏc hng s cho trc v f1 , f l cỏc hm cho trc Trong bi ny, chỳng tụi dựng phng phỏp Galerkin v compact cỏc khụng gian Sobolev cú trng thớch hp chng minh s tn ti v nht nghim (u1 , u ) ca bi toỏn (*).Sau ú, chỳng tụi cng nghiờn cu dỏng iu tim cn ca nghim (u1 (h), u (h) ) ph thuc vo h h + ABSTRACT We study the following nonlinear boundary value problem (*) p2 / d r / p2 r u ( r ) u i (r ) + u i (r ) u i (r ) = f i (r , u1 (r ), u (r ) ), < r < 1, i r dr u1/ (1) p2 u1/ (1) + hu1 (1) = g , u (1) = 0, lim r r / p u i/ (r ) < +, (i = 1, 2), r + HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 where = N 1, p 2, h > 0, g are given constants, f1 , f are given functions In this paper, we use the Galerkin and compactness method in appropriate Sobolev spaces with weight to prove the existence of a unique weak solution (u1 , u ) of the problem (*) Afterwards, we also study the asymptotic behavior of the solution (u1 (h), u (h) ) depending on h as h + T NG HểA GII BI TON QUI HOCH TUYN TNH NGUYấN V NG DNG Nguyn Phỳ Vinh Khoa Khoa hc C Bn, Trng i hc Cụng nghip Tp HCM Email: vinh1957@yahoo.com TểM TT Trong bi ny u tiờn trỡnh by túm tt thut toỏn Dantzig p dng thut toỏn ny vit chng trỡnh gii bi toỏn qui hoch tuyn tớnh Kt xut lit kờ bng n hỡnh chi tit nh ta gii tay, c bit cỏc thao tỏc tớnh toỏn u l phõn s, sau ú xõy dng thut toỏn Dantzig nguyờn da trờn c s thut toỏn nguyờn thu Dantzig Cui cựng ng dng gii bi toỏn thc t phi thựng cho cỏc n hng may xut khu m tỏc gi ó cú dp kho sỏt Hai chng trỡnh c ci t bng ngụn ng C hng i tng ABSTRACT In this paper, first we show abstractly the Dantzig algorism, we apply this algorism in order to write a program for linear programming problem The output which gives table from this progam is same as table when being solved by hands Any operation in this problems is fractional Next we constitute the integer Dantzig algorism Afterwards we apply this program for distributing cans according to exported T.shirt orders These two programs is installed by object-oriented C programming language V mt bi toỏn elliptic cha s hng Kirchhoff Nguyn Anh Trit (1), Nguyn Thnh Long(2) Khoa Toỏn- tin hc, i hc Khoa hc T nhiờn Tp H Chớ Minh (1) Email: nguyenanhtriet@gmail.com (2) Email: longnt@hcmc.netnam.vn, longnt2@gmail.com TểM TT Túm tt Chỳng tụi nghiờn cu s tn ti nghim ca bi toỏn bin phõn sau M (a(u, u ))a(u, v) = F , v v V , u V , ú * a (,) : V ì V IR l mt dng song tuyn tớnh liờn tc, cng bc trờn mt khụng gian Hilbert V , * F V / , F 0, ký hiu , ch cp tớch i ngu gia V / v V , * M C ( IR+ \ {1}; IR), lim M (t ) = +, v lim tM (t ) = + t t + Cụng c chớnh ca chỳng tụi l phng phỏp Galerkin Chỳng tụi cng cho mt ỏp dng vo mt bi toỏn elliptic cha s hng Kirchhoff ABSTRACT We study the existence of solutions to the following variational problem HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 M (a(u, u ))a(u, v) = F , v v V , u V , where * a (,) : V ì V IR is a bounded coercive bilinear functional on a Hilbert space V , * F V / , F 0, denote , is pair of dual product of V / and V * M C ( IR+ \ {1}; IR), lim M (t ) = +, and lim tM (t ) = + t t + Our main tool is the Galerkin method We also give a application to an elliptic problem involving term Kirchhoff MT PHUNG PHP PHNG TRèNH TCH PHN CHO BI TON NGC PHI TUYN ng c Trng(1), Trn V Khanh(2), Nguyn Huy Tun(3) Khoa Toỏn Tin , trng i Hc Khoa Hc T Nhiờn TP.HCM (2) Khoa Toỏn, trng i Hc Padova, Italy (3) Khoa Toỏn-tin, trng i Hc Tụn c Thng, TP.HCM (1) TểM TT Trong bi bỏo ny, chỳng tụi nghiờn cu mt bi toỏn nguc cho phng trỡnh phi tuyn parabolic cú dng u(t)+Au(t) = f(t,u(t)), u(T) = g, ú A l toỏn t khụng b chn, dng, t liờn hp v f l ỏnh x Lipschitz ton cc Nh ta ó bit, õy l bi toỏn khụng chnh Dựng phng phỏp phng trỡnh tớch phõn, chỳng ta chnh hoỏ nghim ph thuc h s nhiu Chỳng tụi chng minh bi toỏn xp x l chnh v nghim ca nú s hi t v nghim chớnh xỏc u(t) trờn [0,T] tin v Sai s ca bi toỏn c ỏnh giỏ ABSTRACT In this paper, we consider an inverse time problem for a nonlinear parabolic equation in the form u(t)+Au(t) = f(t,u(t)), u(T) = g, where A is a positive self-adjoint unbounded operator and f is a Lipschitz function As known, it is ill-posed Using a method of integral equations, we shall construct regularization solutions depended on a small parameter We show that the regularized problem are well-posed and that their solution u (t ) converges on [0,T] to the exact solution u(t) when tend to zero Error estimate is given HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 B VT Lí K THUT 3D MEDICAL IMAGE RECONSTRUCTION Vu Cong, Huynh Quang Linh Biomedical Engineering Department Faculty of Applied Science, University of Technology, NU-HCM ABSTRACT 3D image reconstruction is an attractive field generally in digital image processing techniques, especially in biomedical imaging It has been strongly developed and practically implemented in almost every modern tomographical modalities but there are many problems which still remain unresolved or can be improved A project in such area has been alternatively developed in order to master mentioned technology and to develop domestic products partially taken place of very expensive imported facilities and softwares This paper introduces first step results of mentioned project: implementing fundamental problems in 3D medical image reconstruction for medical imaging such as algorithms, usual rendering technique, etc and designing a software for reconstructing 3D image from a set of CT images, which was built on VTK (Visualization Toolkit) and Visual C++ ROBUST FACE DETECTION UNDER CHALLENGES OF ROTATION, POSE AND OCCLUSION Phuong-Trinh Pham-Ngoc, Quang-Linh Huynh Department of Biomedical Engineering, Faculty of Applied Science, University of Technology, NU-HCM ABSTRACT Face detection has been a typical active research domain for decades because it can be applied in many fields such as human machine interaction, surveillance, commercial application and health care In this paper, we propose an automatic face detection system which bases on human skin detection, natural properties of faces and the classification strength of Local Binary Patterns (LBPs) and embedded Hidden Markov Models (eHMMs) We create a developed skin color model that reduces effectively similar skin colors causing noise to receive better skin detection for different human races With detected skin regions, natural properties of faces are used to discard non-face objects to retain most reasonable face candidates A flexible classification combining LBP histogram matching and embedded Hidden Markov Models (eHMMs) is used to determine whether detected candidates are faces or not The advantages of this classification is reducing effectively the impact of face rotation, pose and occlusion The experiments show that our system is robust to detect human faces in both video sequences and still images with 93% correct detection among the variety of facial test databases forming from different sources MT XUT THAY I KCH THC BC THCH NGHI CA THUT TON LMS CHO LP BI TON LC NHIU TRONG THU NHN TN HIU Y SINH Hong Mnh H Trng Cao ng K thut Thit b Y t - H ni TểM TT Trong thu nhn tớn hiu y sinh, mụi trng nhiu luụn thay i gii quyt bi toỏn lc nhiu ny, mụ hỡnh lc nhiu thớch nghi v thut toỏn trung bỡnh bỡnh phng ti thiu (LMS) c la chn vỡ tớnh n gin v hiu sut ca thut toỏn ci t Tuy nhiờn cng nh cỏc thut toỏn thớch nghi khỏc HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 Vic chn kớch thc bc thớch nghi nu tho yờu cu n nh cho thut toỏn s lm cho thi gian hi t khụng ỏp ng c cỏc yờu cu hin v ngc li Do vy rt khú khn phi chn giỏ tr kớch thc bc thớch nghi cho thut toỏn ỏp ng c cỏc yờu cu ngy cng cao v tớnh n nh cao, tc hi t nhanh, nhng yờu cu n gin v phn cng Bi vit ny xut mt hng gii quyt yờu cu trờn, vi kớch thc bc thớch nghi ca thut toỏn thay i theo ln ca Gradient, v kt qu mt s th nghim trờn Matlab cho tớn hiu in tõm O KHONG CCH V XC NH V TR VT TH BNG PHNG PHP SIấU M (1) Trn Th Thy (1), Nguyn Quang Thng (1), inh Sn Thch (3) Khoa Khoa hc ng dng, trng i hc Bỏch khoa HQG TP.HCM (2) Phũng thớ nghim Cụng ngh Nano, HQG TP.HCM TểM TT Siờu õm l dng súng õm c ng dng rng rói vic o khong cỏch v nh v vt th Bỏo cỏo gii thiu mt phng phỏp o khong cỏch v xỏc nh v trớ vt th bng súng siờu õm vi s kt hp phng phỏp xỏc sut Bayes x lý tớn hiu Phng phỏp s dng cụng thc xỏc sut ton phn Bayes ỏnh giỏ kh nng khụng gian b chim bi vt th, v t l chim gia cỏc ụ li trờn bn nhm xỏc nh v trớ xỏc sut cao nht cú vt th MEDICAL IMAGE REGISTRATION IN MATLAB Tran Duy Linh, Huynh Quang Linh Department of Biomedical Engineering Faculty of Applied Science University of Technology, NU-HCM tdlinh@hcmut.edu.vn; huynhqlinh@hcmut.edu.vn ABSTRACT Biomedical imaging based on different physical principles has played a more and more important role in medical diagnosis Multiform methods of image diagnosis provide doctors and clinicians with various anatomical and functional information to carry out exact diagnosis and effective treatment Image registration is the process of combination the different sets of data of the same object, which come from different modalities (CT, MRI, SPECT, PET etc.) Pre-processing algorithms improve image quality and image registration algorithms transform the object of images into one coordinate system As a result, registered image would be more informative than original images At the present time, many registration problems still remain unresolved or not optimal This paper introduces some improvements and illustrated implementation in MATLAB SOME TREATMENT RESULTS OF GYNAECOPATHY BY USING LOW POWER SEMICONDUCTOR LASER Bựi Phng Anh, Trn Minh Thỏi, Cn Vn Bộ, Trn Trung Ngha Laser Technology Laboratory Faculty of Applied Science University of Technology, NU-HCM ABSTRACT According to the annual statistic of Ministry of Health, the number of patients increases from 15% to 27% every year: 20% of women over 30 years old having ovarian cyst, over 20% of women over 35 years old having uterine fibroma Taking care of gynaecological health for women is extremely important Popular treatment methods have many blemishes such as: hysterectomy, oophorectomy, vaginectomy etc These methods lead infertility or affect sexual activity of women Laser Technology HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 Laboratory has carried out a project of research into the application of low power semiconductor laser with multi wavelengths in treatment some gynaecopathy and are successfully manufactured an equipment for treatment of some gynaecopathy basing on the combination both traditional oriental acupuncture and modern medicine This equipment was applied by some medical centers in clinical treatment and had success results in some diseases, such as: gynaecological inflammations, benign tumours, child enuresis FABRICATION OF MICHELSON INTERFEROMETER FOR PHASESHIFTING METHOD Dinh Son Thach, Le Dinh Tuan, Nguyen Tang Vu, Nguyen Minh Chau, Tran Thanh Nam Faculty of Applied Science, University of Technology NU-HCM dinhsonthach@gmail.com ABSTRACT Displacement measurement can be performed with high accuracy using phase-shifting method In phase-shifting method, it is often used four steps of phase-shifting for one cycle In conventional method, to measure the displacement of an object by interferometer, the phase of reference beam should be shifted by every /2 in four-step phase-shifting Therefore, the error of this measurement is depended upon the phase-shifting angle In this paper, we propose a new fabrication of Michelson interferometer There are several changes in this fabrication to easily adjust the interferometer with a higher accuracy This article show a simple interferometer with the reference of two light waves These references are quite sensitive to the phase-shifting, each of them is different to the others when changing a very small phase (less than 1àm for visible light, with a very short time (T 2.10-15s)) The important improvement of fabrication is using a piezoelectric actuator to prevent the vibration and to get the high accuracy in phase-shifting Besides, the piezoelectric actuator also help us test the accuracy of the fabrication of Michelson interferometer THIT K V CH TO Mễ HèNH ẩN CHIU TR BNH VNG DA DNH CHO TR S SINH Hunh Th Hong Khoa Khoa hc ng dng, trng i hc Bỏch khoa HQG TP.HCM Email: hoangche2003@yahoo.com TểM TT Thit b ốn chiu vng da dnh cho tr s sinh l mt thit b quang tr liu, thng thy cỏc bnh vin nhi, l mt thit b h tr tt vic iu tr bnh vng da tr s sinh Nguyờn nhõn gõy vng da l s gia tng Bilirubine mỏu v nu khụng c iu tr kp thi cú th gõy tn thng nóo v gõy t vong Mt mụ hỡnh ốn chiu vng da vi h thng LED mu xanh siờu sỏng v cụng sut chiu c iu chnh t ng phự hp c thit k nhm thay th cỏc thit b cỏc thit b ngoi nhp OPTIMIZING THE DESIGN OF THE THREE DEGREE OF FREEDOM PIEZORESISTIVE ACCELERATION SENSOR Tran Duc Tan (a), Nguyen Thang Long (a), Nguyen Phu Thuy (b) (a) Faculty of Electronics and Telecommunication, College of Technology (COLTECH) Vietnam National University Hanoi (b) International Training Institute for Materials Science (ITIMS) tantd@vnu.edu.vn ABSTRACT HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 In this paper, we propose a synthesis and optimization process in order to design a specific MEMSbased acceleration sensor The design synthesis can utilize the fast and accurate simulation of the SUGAR tool along with the fully simulation of ANSYS This design has combined the modified nodal analysis method and the finite element one in optimizing this structure In this structure, the piezoresistance effect was employed in sensing the acceleration in three dimensions CC Mễ HèNH TON HC TAI GIA TRONG BNH VIấM TAI GIA MN TNH Lờ Cao ng, Hunh Quang Linh B mụn Vt lý K thut Y sinh, Khoa Khoa hc ng dng, trng i hc Bỏch khoa HQG TP.HCM TểM TT Bnh viờm tai gia chim khong 3,4% dõn s Vit Nam v lm suy gim thớnh lc n 30dB Cỏc mụ hỡnh toỏn hc cu trỳc tai gia c xõy dng nhm kho sỏt mc gim thớnh lc tai gia cú mng nh b thng, tai gia cú mng nh b rỳt vo so vi tai gia bỡnh thng Kt qu cho thy nhng thay i v cu trỳc ca tai gia ch lm gim sc nghe ti a 15dB, phn gim õm lng cũn li l s thay i chc nng sinh lý ca cỏc thnh phn trỡ s n nh ỏp sut hũm nh THIT K CH TO MY LC MU Nguyn Trung Tớn (1), Mai Hu Xuõn (2) (1) Khoa Khoa hc ng dng, trng i hc Bỏch khoa HQG TP.HCM (2) Cụng ty trang thit b y t XUN TRNG ttinsam@gmail.com TểM TT Mỏy lc mỏu l mt dng thit b rt cn thit quỏ trỡnh ly v lu tr mỏu nhm bo qun tt mỏu thi gian di ngn cn hin tng ụng mỏu mỏu tip xỳc vi mụi trng ngoi Mt mụ hỡnh mỏy lc mỏu cú kh nng iu chnh bng vi x lý c thit k nhm úng gúi mỏu theo nhng tiờu chun nht nh v m bo cht lng lu tr mỏu, cú th trin khai thc t hoc m rng cho cỏc nhu cu v huyt hc khỏc THIT K Mễ HèNH H THNG O VN TC DềNG CHY BNG LASER S DNG HIU NG DOPPLER Lờ Huy Hip, Lng Phỳc Hu Khoa Khoa hc ng dng, trng i hc Bỏch khoa HQG TP.HCM Dinhduyla@yahoo.com TểM TT K thut o tc bng hiu ng doppler laser (LDV) l mt phng phỏp giao hũa gia vic o c t xa v khụng xõm ln mt thnh phn vector tc ti mt im c xỏc nh chớnh xỏc khụng gian ng dng rng rói nht ca k thut ny l lnh vc o dũng chy lu cht mt hay nhiu h thng quang hc kt hp vi to mt h thng o c ng thi c thnh phn vector tc chớnh xỏc cao giỳp cho k thut LDV cú th c ng dng c th vo cỏc lnh vc o c dũng chy ri, c bit ng dng y sinh Mt mụ hỡnh h thng o tc dũng chy bng hiu ng doppler laser c thit k phũng thớ nghim nhm mc ớch o to v nghiờn cu HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 GII THIU NHểM Mễ PHNG TRONG NGHIấN CU VT LIU MI TI B MễN VT Lí K THUT Nguyn Ngc Lnh, Vừ Vn Hong B mụn Cụng ngh Quang t, Khoa Khoa hc ng dng, i hc Bỏch khoa, i hc Quc gia Thnh ph H Chớ Minh TểM TT ỏp ng nhng ũi hi cp thit ca xó hi thi gian gn õy v nghiờn cu v o to lc lng cỏc nh khoa hc tr cng nh cỏc k s chuyờn ngnh Ngoi vai trũ cụng tỏc ging dy nhúm nghiờn cu Vt lý cht rn, Vt lý vt liu v Vt lý tớnh toỏn ó tham gia tớch cc nhim v nghiờn cu khoa hc, hng dn NCS v nm qua ó cụng b hn 25 cụng trỡnh nghiờn cu lờn cỏc Quc t, xut bn quyn sỏch chuyờn kho ú cú 03 quyn ng tỏc gi xut bn M a tng s bi bỏo khoa hc ó c cụng b ca nhúm lờn hn 70 bi ú hn 60 bi l cụng b nc ngoi Cỏc hng nghiờn cu c m rng gm: nghiờn cu cu trỳc v cỏc tớnh cht vt lý ca kim loi lng v vụ nh hỡnh, cỏc oxide kim loi v oxide bỏn dn, vt liu cú kớch thc nano, quasicrystals v quasicrystalline nanoparticles, h vt liu v cú kớch thc nano cha cỏc icosahedra Ngoi ra, vi vic tng bc b sung i ng cỏn b khoa hc tr c o to nc ngoi cú kh nng tin hnh nhng nghiờn cu khoa hc t trỡnh quc t, cng nh vic m rng hp tỏc quc t o to v nghiờn cu khoa hc ca nhúm ó cho thy nhng thnh cụng ỏng k thi gian qua COOLING RATE EFFECTS IN MONATOMIC AMORPHOUS NANOPARTICLES Vo Van Hoang1, T Odagaki2 and M Engel3 Dept of Physics, Institute of Technology, National Univ of HochiMinh City, 268 Ly Thuong Kiet Str., Distr 10, HochiMinh City, Vietnam Email: vvhoang2002@yahoo.com Dept of Physics, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan Institute for Theoritical and Applied Physics, University of Stuttgart, Stuttgart, Germany ABSTRACT Cooling rate effects in monatomic amorphous nanoparticles were studied in a spherical model containing 2469 atoms using Molecular Dynamics (MD) method under non-periodic boundary conditions We use the pair double-well interaction potential developed by Engel et al The good initial equilibrium models at a high temperature (i.e in liquid state) are cooling down by three different cooling rates in order to observe the cooling rate effects We find that cooling rate effects on thermodynamic quantities such as potential energy, surface energy and glass transition temperature ( T g ) are more pronounced than those for static quantities In that, the potential energy and surface energy of the nanoparticles decrease with decreasing cooling rate indicating the forming of more stable configurations with lower cooling rates In contrast, no systematic changes have been found for T g although it has a tendency to decrease with decreasing cooling rate Microstructure of amorphous nanoparticles is analyzed via radial distribution function (RDF), coordination number and bond-angle distributions Relatively weak cooling rate effects on such quantities are found Microstructure of surface and core of amorphous nanoparticles are analyzed In addition, evolution of structure of nanoparticles upon cooling from the melt is discussed Cooling rate effects in such short-range interaction system are discussed and compared with those observed in long-range interaction systems HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 FINITE SIZE EFFECTS ON STATIC AND DYNAMIC PROPERTIES OF NON-PERIODIC BOUNDARY CONDITION SUPERCOOLED LIQUIDS Vo Van Hoang and Nguyen Ngoc Linh Dept of Physics, Institute of Technology, National University of HochiMinh City, 268 Ly Thuong Kiet Str., Distr 10, HochiMinh City-Vietnam Email: vvhoang2002@yahoo.com ABSTRACT Finite size effects on static and dynamic properties of Al2O3.2SiO2 spherical models with different diameters of 2nm, 3nm, 4nm and 5nm have been studied via molecular dynamics (MD) simulation under non-periodic boundary conditions (NPBC) Models have been obtained by cooling from the melts at constant density of 2.60 g/cm3 We found strong finite size effects on both static and dynamic properties of the system Static properties have been studied via partial radial distribution function (PRDF), mean atomic distances and coordination number distributions Dynamic properties of the system with different sizes have been found and discussed via the mean-squared displacement (MSD) of atoms and temperature dependence of diffusion constant Moreover, size dependence of glass transition temperature has been found and discussed GLASS TRANSITION AND THERMODYNAMICS OF LIQUID AND AMORPHOUS TIO2 NANOPARTICLES Vo Van Hoang Dept of Physics, Institute of Technology, National Univ of HochiMinh City, 268 Ly Thuong Kiet Str., Distr 10, HochiMinh City, Vietnam Email: vvhoang2002@yahoo.com ABSTRACT Glass transition and thermodynamics of liquid TiO2 spherical nanoparticles have been studied in a model with different sizes ranged from nm to nm under non-periodic boundary conditions We use the pairwise interatomic potentials proposed by Matsui and Akaogi Models have been obtained by cooling from the melt via molecular dynamics (MD) simulation Structural properties of liquid nanoparticles at 3500 K have been analyzed in details through the partial radial distribution functions (PRDFs), coordination number distributions, bond-angle distributions and interatomic distances Moreover, we also show the radial density profile in nanoparticles Calculations show that size effects on structure of a model are significant and that liquid TiO2 nanoparticles have a distorted pentahedral network structure with the mean coordination number Z Ti O 5.0 and Z O Ti 2.5 while amorphous TiO2 nanoparticles have an octahedral network structure Temperature dependence of surface structure and surface energy of nanoparticles has been obtained and presented In addition, size dependence of glass transition temperature and temperature dependence of diffusion constant of atomic species have been found and discussed CC C IM CU TRC CA HT NANO TiO2 PHA LNG V Vễ NH HèNH Vừ Vn Hong, Ngụ Hunh Bu Trng B mụn Cụng ngh Quang t, Khoa Khoa Hc ng Dng Trng i Hc Bỏch Khoa HQG P.HCM Email: buutrong85@yahoo.com TểM TT Cỏc c im cu trỳc ca ht nano TiO2 chỳng tn ti trng thỏi phi tinh th c kho sỏt thụng qua mụ hỡnh dng cu ng kớnh ln lt l 2nm, 3nm, 4nm, 5nm Bng cỏch ỏp dng iu kin biờn HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 khụng tun hon cựng th tng tỏc Matsui-Akaogi xut (th MA), cỏc c im cu trỳc ca h c ỏnh giỏ thụng qua hm phõn b xuyờn tõm, phõn b phi v, phõn b gúc liờn kt Mt khỏc bng cỏch quan sỏt s thay i ca cỏc i lng trờn ti nhng nhit khỏc tin hnh lm lnh h t nhit cao, ta cú th nghiờn cu c s bin i cu trỳc bờn cỏc ht nano sut quỏ trỡnh lm lnh nhanh Quỏ trỡnh lm lnh c tin hnh t 7000 K vi tc h nhit t l tuyn tớnh theo thi gian thụng qua biu thc T = T t , ú = 4.2945 10 13 K s Ngoi cu trỳc b mt cng nh cỏc i lng nhit ng ca ht cng c phõn tớch thy rừ nh hng ca quỏ trỡnh lm lnh i vi ht nano TiO2 PRESSURE-INDUCED STRUCTURAL TRANSITION IN AMORPHOUS TIO2 NANOPARTICLES AND IN THE BULK Vo Van Hoang Dept of Physics, Institute of Technology, National Univ of HochiMinh City, 268 Ly Thuong Kiet Str., Distr 10, HochiMinh City, Vietnam Email: vvhoang2002@yahoo.com ABSTRACT Pressure-induced structural transition in amorphous TiO2 spherical nanoparticles has been studied in a spherical model of different diameters of nm, nm and nm under non-periodic boundary conditions We use the pairwise interatomic potentials proposed by Matsui and Akaogi Models have been compressed from 3.8 g/cm3 up to very high density (i.e high pressure) in order to investigate the pressure-induced structural changes And we found the change from low-density amorphous (lda) form with to high-density amorphous (hda) one with like those observed in practice We found that the transition pressure is nanoparticle size dependent due to the surface effects In order to compare and to highlight the feature of such transition in nanoparticles, we also present the results of the same transition in the bulk amorphous TiO2 models containing 3000 atoms Structural properties of nanoparticles at 700 K have been analyzed in details through the partial radial distribution functions (PRDFs), interatomic distances, coordination number and bond-angle distributions Moreover, we also show the radial density profile in nanoparticles STRUCTURAL PROPERTIES OF AMORPHOUS SiO2 NANOPARTICLES Nguyen Thi Xuan Huynh1, Vo Van Hoang2, and Hoang Zung1 Computational Physics Lab, College of Natural Sciences of HochiMinh City-Vietnam, 227 Nguyen Van Cu Str., Distr 5, HochiMinh City-Vietnam Email: huynhqn@gmail.com Dept of Physics, Polytechnic Institute of HochiMinh City-Vietnam ABSTRACT Structural properties of amorphous SiO2 nanoparticles have been investigated via Molecular Dynamics (MD) simulations with the interatomic potentials which have weak Coulomb interaction and Morse type short-range interaction under non-periodic boundary conditions Structural properties of SiO2 spherical nanoparticles with different sizes of 2nm, 4nm and 6nm have been studied through partial radial distribution functions (PRDFs), coordination number and bond-angle distributions compared with those observed in the bulk The core structure and surface structure have been studied in details We found significant size effects on structure of nanoparticles Moreover, temperature dependence of structural defects in nanoparticles upon cooling from the melt has been found and presented HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 C C K THUT FINITE ELEMENT SIMULATION OF DENTAL IMPLANTATION PROCESS Rudi van Staden 1, Hong Guan 1, Yew-Chaye Loo 1, Newell Johnson , Neil Meredith Griffith School of Engineering, Griffith University Gold Coast Campus, Australia School of Dentistry and Oral Health, Griffith University Gold Coast Campus, Australia Neoss Pty Ltd, Harrogate, United Kingdom Email contact: Y.Loo@griffith.edu.au ABSTRACT Using the finite element procedure, the insertion process of a dental implant into a section of the mandible is analysed Elevated stress concentrations in both cancellous and cortical bone are examined during implantation An implant of length 11mm is inserted at 1mm increments into the mandible The torque applied to the implant top ranges from to 450Nmm for a total time period of 36 seconds The complex geometrical and material properties of the implant and mandible are modelled using three dimensional (3D) brick elements Nonlinear material properties are assigned for both cancellous and cortical bone The assumptions made in the analysis include: (a) simulating and replicating the implantation process as a step-wise instead of a continuous process; (b) parallel threaded implant is used and the implant does not rotate during insertion into the mandible The optimum insertion torque and the set time periods for each level of torque applied are found to be the controlling factors that would help produce ideal stresses within the jawbone throughout the entire implantation process COLLISION ACCIDENT BETWEEN SHIP AND JETTY Tuong Long Nguyen, Cong Hoa Vu, Quoc Thai Nguyen, The Ky Nguyen Huu Huy Nguyen *, Duy Nguyen* Department of Engineering Mechanics, Ho Chi Minh University of Technology, Vietnam *Ho Chi Minh University of Transports, Vietnam ABSTRACT This paper simulated the impaction of the vessel into the jetty with input data collected from an actual event that happened on the Thi Vai flow on 02/07/2005-Phu My port group This paper is used finite element method and applied ANSYS/LS-DYNA software to simulate and compute Based on information of water police from impact, this paper carried out a solution to solve impact problem in statics using ANSYS10 and simulation of 3D model by LS-DYNA in dynamics with angle between ship and jetty 150 From simulation of 3D impact problem together with failure results derived from tests of waterway police, the angle between ship and jetty 300, so this paper also carried out a solution to solve impact problem in statics using ANSYS10 and simulation of 3D model in dynamics using LS-DYNA This paper found that simulation in 3D will help problem more reality and thence derived results will persuade concerned units (Ship, Jetty, Assessment) Mụ Phng Khp Gi Ngi Bng Phng Phỏp Phn T Hu Hn Nghiờm Xuõn V, Nguyn Vn Lóm, Hunh ng Trng*, Nguyn Tng Long* B Mụn Vt Lý K thut Y Sinh, i Hc Bỏch Khoa, Tp H Chớ Minh, Vit nam *B Mụn C K Thut, i Hc Bỏch Khoa, Tp H Chớ Minh, Vit nam HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 TểM TT Trong bi bỏo ny, mụ hỡnh 3D khp gi ngi c thit lp v tớnh toỏn bng phng phỏp phn t hu hn: trc tiờn, mụ hỡnh hỡnh hc c xõy dng t chng trỡnh Solidworks Tip theo, mụ hỡnh c chuyn tip sang ANSYS, tớnh toỏn trng ng sut, bin dng khp gi Cui cựng, mụ hỡnh c chuyn tip sang ADAMS, tỡm cỏc dng chuyn ng, tc, gia tc ca c h Thụng qua mụ hỡnh tớnh toỏn, bi bỏo s m hng thớ nghim o cho h liờn kt khp-xng ngi INTERACTION BETWEEN PILE- SOIL UNDER DYNAMIC LOAD USING FINITE ELEMENT METHOD Huu Huy Nguyen, Duy Nguyen Tuong Long Nguyen*, Cong Hoa Vu*, Quoc Thai Nguyen*, The Ky Nguyen* Ho Chi Minh University of Transports, Vietnam *Department of Engineering Mechanics, Ho Chi Minh University of Technology, Vietnam ABSTRACT In this paper, pile and soil is simulated by Solid-3D element, contact surface between pile and soil is imitated by contact element in ANSYS/ LS-DYNA software Analysis results of this three-dimensional model were compared with another mathematics model of previous authors: Brinch Hansen, Broms, Reese and Matlock, Poulos, K.X Zavriev VA CHM PH HU KT CU KHUNG SN KHễNG GIAN BNG LS-DYNA Nguyn Quc Thỏi, H Tn Phỏt, Nguyn Th K, V Cụng Hũa, Nguyn Tng Long B Mụn C K Thut, i Hc Bỏch Khoa, Tp H Chớ Minh, Vit nam TểM TT Trong bi bỏo ny, kt cu khung sn khụng gian c mụ hỡnh, tớnh toỏn, mụ phng chng trỡnh LS-DYNA, bng phng phỏp phn t hu hn Kt qu thu c l cỏc trng chuyn v, ng sut, bin dng thay ó i theo thi gian, cho n trng thỏi phỏ hy kt cu khụng gian 3D Mụ hỡnh thớ nghim o trờn mỏy tớnh ny, s giỳp cho nh thit k d oỏn c kh nng phỏt sinh s c qua trỡnh thi cụng cỏc cụng trỡnh quan trng, iu kin an ton NGHIấN CU TRNG NG LC CA CC DềNG HI LU DI TC NG CA CC H O CC Bễ DI Y BIN Nguyn Th K, Nguyn Quc Thỏi, V Cụng Hũa, Nguyn Tng Long Nguyn Hu Huy*, Nguyn Duy* B Mụn C K Thut, i Hc Bỏch Khoa, Tp H Chớ Minh, Vit nam * i hc Giao Thụng Vn Ti Tp H Chớ Minh, Vit nam TểM TT Bỏo cỏo trỡnh by s nh hng ca súng bin lờn s bi lng v xúi mũn bói bin trc v sau khai thỏc cỏt, ng thi tỡm biờn dng khai thỏc cỏt ti u nht Cỏc cụng vic thc hin: u tiờn l thit lp b mt ỏy bin da trờn bỡnh , th hai l tớnh toỏn s nh hng ca dũng chy lờn mt ỏy bin khu vc nghiờn cu, sau ú tớnh toỏn s nh hng ca vic khai thỏc cỏt lờn s bi lng v xi mũn nhng khu vc lõn cn Thụng qua kt qu mụ phng, s tỡm mụ hỡnh khai thỏc cỏt hp lý HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 EFFECT OF SINTERING PROCESS ON FABRICATION OF POROUS Si3N4/SiC NANOCOMPOSITE Vu Cong Hoa Department of Engineering Mechanics, Faculty of Applied Science University of Technology, NU-HCM Email: vuconghoa@hcmut.edu.vn ABSTRACT Porous SiC/Si3N4 composites were fabricated by reaction between Si3N4 and C powder in 0.5 MPa nitrogen atmosphere at 1700oC, 1800oC and 1900oC for 0.5h, 1h and 2h, respectively The characteristics of in situ porous Si3N4/SiC composites were further investigated by X-ray diffraction (XRD) and scanning electronic microscopy (SEM) Results show that the SiC particles are very fine And the transformation from -Si3N4 to -Si3N4 is obvious at 1800oC for 2h and at 1900oC Otherwise, at 1700oC, the formation of rod-like -Si3N4 is inhibited The compressive test was conducted at a crosshead speed of 0.5 mm/min to get the basic mechanical performance of the porous ceramics The highest value of strength of these composites was obtained when sintered at 1800oC for 1h MT S Mễ HèNH TNH TON NG LC HC LU CHT S DNG PHN MM FLUENT & GAMBIT Trn Ngc Phong, Tng Duy Tõn, V Cụng Hũa B Mụn C K Thut, i Hc Bỏch Khoa, Tp H Chớ Minh, Vit nam Email: ngocphong85@gmail.com, tongduytan@gmail.com, vuconghoa@hcmut.edu.vn TểM TT ng lc hc lu cht i vi lu cht chy ng trũn l bi toỏn ph bin k thut Bi bỏo cỏo cp n vic mụ phng v tớnh toỏn ng lc hc i vi dũng lu cht chy mụ hỡnh 3D ng r nhỏnh v gin ti nc Bng b phn mm thng mi FLUENT & GAMBIT, ta kho sỏt c trng ỏp sut, tc ca dũng chy ti tng v trớ mụ hỡnh Mụ hỡnh c chia thnh li phn t t din bng GAMBIT vi cụng c chia li thụng minh TGrid, s dng mụ hỡnh ri k epsilon tiờu chun v dựng phng phỏp phn t sai phõn hu hn gii gn ỳng iu kin biờn l tc u vo cho trc Cỏc th th hin c quan h gia tc, ỏp sut, ng nng ri theo cỏc phng khỏc SOLVING ELASTO-PLASTIC PROBLEM IN PLANE STRESS CASE BY MESHLESS METHOD Trng Tớch Thin, Nguyn Ngc Minh, H Long Võn Department of Engineering Mechanics, Faculty of Applied Science University of Technology, NU-HCM ABSTRACT In this paper, the Element Free Galerkin method (EFGM) has been extended to solve elastoplastic problem in plane stress case To this, the incremental relations of plastic deformation is used to derive a system of elastoplastic EFGM equations; and Return-Mapping algorithm is employed to perform iterative computation For implementation, a MATLAB program has been developed Some plane stress problems have been analyzed using this program to verify the accuracy of the proposed meshless method The results have also been compared with those obtained by ANSYS đ, a popular commercial program employing Finite Element Method (FEM) HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 FLUID DYNAMIC SIMULATION FOR PROPELLER Tich Thien TRUONG, Eng Duy Khuong NGUYEN, Eng Thanh Nha NGUYEN Department of Engineering Mechanics, Faculty of Applied Science University of Technology, NU-HCM Email: tttruong@hcmut.edu.vn, khuongndk@sime.com.vn, thanhnhanguyen@sime.com.vn ABSTRACT A turbomachine is a device in which energy transfer occurs between a flowing fluid and a rotating element due to dynamic action, and results in a change in pressure and momentum of the fluid Mechanical energy transfer occurs inside or outside of the turbomachine, usually in a steady-flow process Turbomachines include all those machines that produce power, such as turbines, as well as those types that produce a head or pressure, such as centrifugal pumps and compressors The turbomachine extracts energy from or imparts energy to a continuously moving stream of fluid However in a positive displacement machine, it is intermittent The turbomachine as described above covers a wide range of machines, such as gas turbines, steam turbines, centrifugal pumps, centrifugal and axial flow compressors, windmills, water wheels, and hydraulic turbines In this text, we shall deal with incompressible and compressible fluid flow machines In turbomachine problems (that its part rotates with high velocity in fluid domain), pressure, force values of fluid flow on blades are so important for design When designers have a model of turbine blade, they want to know how it will work, specially the moment and propulsive force values supplied by it in fluid environment More, they also want to learn the behaviour of these turbine blades in fluid for their optimal design Normally, engineers often many experiments with some blade models for testing Nowadays, with the development of numerical methods and digital computer, we can simulate this kind of problem so fast and comfortably NHN DNG KHUYT TT CA CU Mễ HèNH BNG MNG NEURO-FUZZY Lờ Minh Cnh, Trng Cao ng in Lc TP.HCM, lmcanh@yahoo.com Nguyn S Dng, Trng i hc Cụng nghip TP HCM, nsidung@yahoo.com Ngụ Kiu Nhi, Trng i hc Bỏch khoa TP HCM ngokieunhi@yahoo.com TểM TT Bi bỏo trỡnh by mt phng phỏp nhn dng khuyt tt ca cu mụ hỡnh s dng mng neurofuzzy v phng phỏp phn t hu hn Trong ú, cu trỳc mng neuro-fuzzy c xõy dng da trờn c s ng dng phng phỏp tng hp mng ANFIS ca [1][2] Gii phỏp c thc hin theo hai bc Th nht, xỏc nh v trớ h hng da trờn cỏc h s h hng c xỏc lp cho tng phn t c phỏt trin t [7] Th hai, xỏc nh mc h hng ca cu ti cỏc v trớ ó c xỏc nh bc th nht trờn c s s dng mng neuro-fuzzy Rt nhiu thớ nghim ó c thc hin cho c hai ni dung trờn Kt qu thớ nghim cho thy phng phỏp xut cú hiu qu tt xỏc nh v trớ v ỏnh giỏ mc h hng ca cu mụ hỡnh ng thi, vỡ giỏ tr cỏc i lng vt lý ó c s dng kho sỏt mụ hỡnh cú th xỏc nh c iu kin o c trờn thc t; vic xõy dng cỏc mu d liu phn ỏnh trng thỏi ng x ca cu thụng qua quan h d liu input-output khụng ph thuc nhiu vo tn s kớch thớch v tn s riờng ca cu; v hn na phng phỏp m bo tin cy s liu o cú sai s, ú phng phỏp hon ton cú th ỏp dng chn oỏn khuyt tt trờn cu thc NGHIấN CU LP T H THNG THU NHN T XA TN HIU O BIN DNG, DAO NG CU Ngụ Kiu Nhi, ng Anh Tun, Lờ Thanh Tựng, Phan Chỏnh Vinh Phũng thớ nghim C ng dng, i Hc Bỏch Khoa, Tp H Chớ Minh HINGHKHOAHCVCễNGNGHLNTH10TRNGHBKHQGTP.HCM PHNBANTONCVTLíKTHUT2007 Email: ngokieunhi@yahoo.com; datuan@dee.hcmut.edu.vn; letung1404@yahoo.com; phanvinh@yahoo.com TểM TT Bi bỏo ny gii thiu cỏc kt qu thu c ban u ca vic nghiờn cu lp t h thng thu nhn tớn hiu dao ng, bin dng t xa ca cu Mc tiờu lp t h thng : 1) Phỏt hin cỏc giỏ tr ng sut bin dng vt quỏ giỏ tr cho phộp 2) chn oỏn v nhng v trớ h hng ca cu v d bỏo v tui th ca cu S h hng kt cu õy c hiu ú l s suy gim v cng ca nú Trong nghiờn cu ny thỡ chỳng tụi quan tõm ch yu cng chng un ca cu