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1.
ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｐｈｙｓｉｃｓｏｆａｖｏｒｔｅｘｌａｔｔｉｃｅ (ＶＬ)ｉｎｔｙｐｅ ＩＩｓｕｐｅｒｃｏｎｄｕｃｔｏｒｓｈａｓｂｅｅｎｔｈｅｆｏｃｕｓｏｆｉｎｔｅｒｅｓｔｓｉｎｃｅｔｈｅｂｅｇｉｎｎｉｎｇｏｆｈｉｇｈ Ｔｃ ｒｅｓｅａｒｃｈ .Ｉｔｉｓｗｅｌｌ ｋｎｏｗｎｔｈａｔ,ａｆｔｅｒｔｈｅｅｘｔｅｒｎａｌｍａｇｎｅｔｉｃｆｉｅｌｄｅｘｃｅｅｄｓｉｔｓｃｒｉｔｉｃａｌｖａｌｕｅＨｃ1 ,ｔｈｅｍａｇｎｅｔｉｃｆｉｅｌｄｃａｎｐｅｎｅｔｒａｔｅａｔｙｐｅ ＩＩｓｕｐｅｒｃｏｎｄｕｃｔｏｒｉｎ…  相似文献   

2.
The properties of a two-dimensional vortex system with random columnar defects were studied by cooling the vortex system to zero temperature. The vortex lattice became more and more disordered with increasing pinning strengthf p. At smallf p, a triangular vortex, lattice away from the pins was observed. The peak of structure factorS(G0) of the vortex lattice decreased with pinning strengthf p, which accorded with the finding that the probability of vortex to be pinned increased withf p. Some of our results agreed with experimental findings. Project supported by the Ministry of Science and Technology of China (NKBRSF-G19990646) and Zhejiang Province Scientific Foundation (199031).  相似文献   

3.
INTRODUCTION Throughout this paper, we shall work with a filtered complete probability space (?,F,(Ft),P) sat-isfying the usual conditions. Let B=(Bt)t≥0 be a stan-dard Brownian motion with B0=0. Denote by ú the set of all non-negative real numbers. Recall that a diffusion process X starting at x≥0 is called the square of a Bessel process of dimension δ>0 if d X t = δd t 2 | X t |d Bt , X 0= x, (1) Clearly, this equation has a unique non-negative strong solution X, i.e., …  相似文献   

4.
Suppose {Xi,i≥1} and {Yi, i≥1} are two independent sequences with distribution functions and , respectively. Zi,n is the combination of Xi and Yi with a probability for each I with 1≤ i≤n. The extreme value distribution GZ(x) of this particular triangular array of the i.i.d. Random variables Z1,n,… Z2,n, Zn,n is discussed. We found a new form of the extreme value distributions i)ΦAα1(x)Φα2 and ii) ψAα(x)ψα2(x)α1<α2), which are not max-stable. It occurs if FX and FY belong to the same MDA(Φ) or MDA(Ψ).  相似文献   

5.
In this paper we study the scaling behavior of nucleotide cluster in 11 chromosomes of Encephalitozoon cuniculi Genome. The statistical distribution of nucleotide clusters for 11 chromosomes is characterized by the scaling behavior of P（S） ∝ e^-αs＇ where S represents nucleotide cluster size. The cluster-size distribution P（S1＋S2） with the total size of sequential C-G cluster and A-T cluster S1＋S2 were also studied. P（S1＋S2） follows exponential decay. There does not exist the case of large C-G cluster following large A-T cluster or large A-T cluster following large C-G cluster. We also discuss the relatively random walk length function L（n） and the local compositional complexity of nucleotide sequences based on a new model. These investigations may provide some insight into nucleotide cluster of DNA sequence.  相似文献   

6.
Exchange coupling and magnetization reversal mechanism in two series of Co_xNi_(1-x)/CoO(30 nm)(x=0.2 and 0.4)bilayers are studied by vector magnetometer.Two components of magnetization are measured parallel and perpendicular to the applied field.At low temperatures,coercivity H_c∝(t_(FM))~(-n),n=1.5 and 1.38 for x=0.2 and 0.4,respectively,in agreement with the random field model.At room temperature,the coercivity is nearly proportional to the inverse FM layer thickness.In addition to the exchange field and the coercivity,the characteristic of the magnetization reversal mechanism was found to change with temperature.At temperatures below 180 K,magnetization reversal process along the unidirectional axis is accompanied only by nucleation and pinning of domain wall while magnetization rotation is also involved at high temperatures.  相似文献   

7.
Xia  Fengshun  Li  Wenpeng  Guo  Junheng  Han  You  Zhang  Minqing  Wang  Baoguo  Li  Wei  Zhang  Jinli 《天津大学学报(英文版)》2021,27(5):409-421

A pore-array intensified tube-in-tube microchannel (PA-TMC), which is characterized by high throughput and low pressure drop, was developed as a gas–liquid contactor. The sulfite oxidation method was used to determine the oxygen efficiency (φ) and volumetric mass transfer coefficient (kLa) of PA-TMC, and the mass transfer amount per unit energy (ε) was calculated by using the pressure drop. The effects of structural and operating parameters were investigated systematically, and the two-phase flow behavior was monitored by using a charge-coupled device imaging system. The results indicated that the gas absorption efficiency and mass transfer performance of the PA-TMC were improved with increasing pore number, flow rate, and number of helical coil turns and decreasing pore size, row number, annular size, annular length, and surface tension. The φ, ε and kLa of PA-TMC could reach 31.3%, 1.73 × 10−4 mol/J, and 7.0 s−1, respectively. The Sherwood number was correlated with the investigated parameters to guide the design of PA-TMC in gas absorption and mass transfer processes.

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8.
The asymptotically distribution free (ADF) method is often used to estimate parameters or test models without a normal distribution assumption on variables, both in covariance structure analysis and in correlation structure analysis. However, little has been done to study the differences in behaviors of the ADF method in covariance versus correlation structure analysis. The behaviors of 3 test statistics frequently used to evaluate structural equation models with nonnormally distributed variables, χ2 test TAGLS and its small-sample variants TYB and TF(AGLS) were compared. Results showed that the ADF method in correlation structure analysis with test statistic TAGLS performs much better at small sample sizes than the corresponding test for covariance structures. In contrast, test statistics TYB and TF(AGLS) under the same conditions generally perform better with covariance structures than with correlation structures. It is proposed that excessively large and variable condition numbers of weight matrices are a cause of poor behavior of ADF test statistics in small samples, and results showed that these condition numbers are systematically increased with substantial increase in variance as sample size decreases. Implications for research and practice are discussed.  相似文献   

9.
A discriminant method for optimizing activity in nuclear medicine studies is validated by comparison with ROC （received operating characteristic）-curves. The method is tested in 21 single photon emission computerized tomography （SPECT）, performed with a cardiac phantom. Three different lesions （Lb L2 and L3） were placed in the myocardium-wall by pairs fbr each SPECT. Three activities （84, 37 or 18.5 MBq） of 99mTc were used as background. Linear discriminant analysis was used to select the parameters that characterize image quality among the measured variables in the images [（Background-to-Lesion （B/Li） and Signal-to-Noise （S/N） ratios）]. Two clusters with different image quality （P=0.021 ） were obtained. The ratios B/Lj, B/L2 and B/L3 are the parameters used to construct the function with 100% of cases correctly classified into the clusters. The value of 37 MBq was the lowest tested activity for which good results for the B/Li ratios were obtained. The result coincides with the applied ROC-analysis （r=0.89）.  相似文献   

10.
Drawing on self‐determination theory, a person‐centered methodology was adopted to identify distinct pupil profiles based on their psychological need satisfaction. A sample of 586 pupils (387 male, 199 female; mean age = 12.6, range 11–15 years old) from three secondary schools reported their psychological need satisfaction, and well‐ and ill‐being, with teachers rating pupil achievement. Hierarchical cluster analysis revealed five distinct profiles. Four profiles indicated synergy existed between the three needs, showing similar in‐group levels of satisfaction across the needs but in varying amounts. Univariate and multivariate analyses, controlling for school and taught subject, revealed the satisfied group displayed the highest classroom performance (F4,540 = 7.03; p < 0.001; ηp2 = 0.05), well‐being (F8,1,136 = 45.63; p < 0.001; Wilk's Λ = 0.57; ηp2 = 0.24) and lowest ill‐being (F8,1,134 = 23.39; p < 0.001; Wilk's Λ = 0.74, ηp2 = 0.14), whereas the dissatisfied group displayed the most adverse outcomes. The findings illustrate that the three psychological needs may operate interdependently and should be considered in combination rather than in isolation. The research offers practical insights into why pupils may function differently in classrooms and could inform targeted initiatives towards pupils with psychological need satisfaction deficits.  相似文献   

11.
In this paper, by using the L p -Brunn-Minkowski theory and its dual theory, L 2-version on the conjectured projection inequality is investigated, the (reverse) inclusive relationship between L 2-projection body and the classical projection body are established, and a constrained minimization problem is solved. Project supported by the National Natural Sciences Foundation of China (Grant Nos.10671117, 10801140)  相似文献   

12.
Hierarchical Bayesian method for estimating the failure probabilityp i under DOOF by taking the quasi-Beta distributionB(p i−1, 1, 1,b) as the prior distribution is proposed in this paper. The weighted Least Squares Estimate method was used to obtain the formula for computing reliability distribution parameters and estimating the reliability characteristic values under DOOF. Taking one type of aerospace electrical connector as an example, the correctness of the above method through statistical analysis of electrical connector accelerated life test data was verified. Project (No. 59975081) supported by the National Natural Science Foundation of China  相似文献   

13.
Most Piagetian formal operational reasoning tasks show horizontal decalage; that is, subjects pass certain tasks and fail others that have the same logical structure. The study reported here analyzes the importance of individual difference variables, as postulated by the neo-Piagetian theory of Pascual-Leone, in explaining subject performance in formal reasoning. A sample of 72 freshman students were administered a test of formal reasoning having 20 items of different types of reasoning, and the tests of the individual difference variables. Results obtained from multiple regression analyses show that Pascual-Leone's structural M-capacity (Ms) is the most consistent predictor of success in the different formal reasoning tasks, followed by Witkin's cognitive style, and to a much lesser degree Raven's progressive matrices, and Pascual-Leone's functional M-capacity (Mf). It was found that in the total score on the 20 items of formal reasoning, Ms accounted for 23.3% of the variance (R = 0.483, F = 6.39, p = 0.014) and Witkin's Group Embedded Figures Test, increased the multiple R significantly (F = 7.77, p = 0.007) and accounted for 7.6% of the variance. Mf and the Raven test did not make a significant contribution to the regression equation. Correlation coefficients among most of the items having the same reasoning pattern but different content are generally low but statistically significant (p < 0.01). Intercorrelations among items having the same formal reasoning pattern and content are fairly high (p < 0.001). These results emphasize the importance of individual difference variables: information-processing capacity (Pascual-Leone) and oversensitivity to potentially misleading information (Witkin). It is suggested that in order to understand student performance in formal reasoning tasks, we should expect horizontal decalages as a rule and not the exception, as Piaget had postulated. Educational implications are drawn.  相似文献   

14.
ABSTRACT

This study investigated the effect of Ethnoscience instruction and moderating effects of school location and parental educational status on students' attitude to science. It employed pretest-posttest, non-equivalent control group quasiexperimental design. Participants were 352 Junior Secondary School 1 (aged 9–12 years) students from two schools, each in urban and rural areas of Ìbàdàn, southwestern Nigeria. Instruments used are: Teachers Instructional Guide on Ethnoscience instruction, Teachers Instructional Guide on Modified Lecture Method and Attitude Toward Science Scale (r?=?0.86). Three null hypotheses were tested at 0.05 level of significance. Data were analyzed using Analysis of Covariance. Significant main effect of treatment on attitude to science (F(1, 347)?=?296, p?<?0.05) was recorded, with Ethnoscience instruction group performing better than the Modified Lecture Method group. Effect size of treatment was strong (η2 p?=?0.46). Also recorded were significant main effects of school location (F(1, 347)?=?10.2, p?<?.05) and parental educational status (F(1, 347?=?3.37), p <?0.05) on students' attitude to science with weak effect sizes (η2 p?=?0.029 and η2 p?=?0.019 respectively). Learners in rural schools performed better than those in urban schools and those from lowly educated parents had better performance than highly educated parents. Ethnoscience instruction promoted learners' attitude to science. Therefore, its use in educational instruction, especially among traditional science learners, should be explored.  相似文献   

15.
Sweetpotato starch thermal properties and its noodle quality were analyzed using a rapid predictive method based on near-infrared spectroscopy （NIRS）. This method was established based on a total of 93 sweetpotato genotypes with diverse genetic background. Starch samples were scanned by NIRS and analyzed for quality properties by reference methods. Results of statistical modelling indicated that NIRS was reasonably accurate in predicting gelatinization onset temperature （To） （standard error of prediction SEP=2.014 ℃, coefficient of determination RSQ=0.85）, gelatinization peak temperature （Tp） （SEP=-1.371 ℃, RSQ=0.89）, gelatinization temperature range （Tr） （SEP=2.234 ℃, RSQ=0.86）, and cooling resistance （CR） （SEP=0.528, RSQ=0.89）. Gelatinization completion temperature （To）, enthalpy of gelatinization （△H）, cooling loss （CL） and swelling degree （SWD）, were modelled less well with RSQ between 0.63 and 0.84. The present results suggested that the NIRS based method was sufficiently accurate and practical for routine analysis of sweetpotato starch and its noodle quality.  相似文献   

16.
In this paper, it is proved that the radial pth mean body RpK（p 〉 0） is homothetic to the difference body DK when K is a simplex, Furthermore, the equality Rp（Rq） = Rq（Rp） is established when p 〉 0 and q 〉 0. It is also proved the Brunn-Minkowski inequality of radial pth mean body of simplex and uniqueness property.  相似文献   

17.
This study investigated demographic characteristics such as type of university attended, course of study and gender as determinants of duration of unemployment among university graduates in Nigeria. Data were collected from 1 451 employed university graduates in 300 firms in Nigeria. Results showed a significant difference between duration of unemployment and course of study (F(6,1444) = 17.84; p < 0.05) with graduates of Engineering and Medicine having the least duration of unemployment. Significant differences also existed between duration of unemployment and the type of university attended (F(2,1448) = 5.50; p < 0.05). Unemployment period was significantly shorter for graduates of private universities compared to those from public universities. However, gender differences did not significantly affect unemployment period (t0.05 = -0.211; p > 0.05). One major policy implication of the findings is that entrepreneurial skills and initiative should become major concerns of higher education institutions to facilitate employability of graduates who will increasingly be called upon not only as successful applicants but also and above all as job creators.  相似文献   

18.
BaFe12O19 powders with nanocrystaUine sizes were produced by sol-gel auto-combustion method. The precursors were prepared under the molar ratios of citric acid to the metal nitrate of 0.5, 1.0 and 1.5. Appropriate ethylene diamine （C2H8N2） was added in order to adjust pH of 7. The ions distribution of citric acid at different pH explains the effect of citric acid in the starting solution. The XRD patterns of the as-burnt powders and annealing powders show different phases for different citric acid content. In addition, the lattice constants （a, c） derived from X-ray diffraction pattern were changed from 0.58881 nm to 0.58997 nm and 2.32057 nm to 2.32296 nm respectively. The data from VSM indicated that the powder with high citric acid content took on good magnetic properties. Pure single BaFe12O19 of the specific maximum magnetization M（1 T）≈ 49.73 Am^2/kg, the specific remanent magnetization Mr ≈ 30.77 Am^2/kg and the coercive force He≈ 467 kA/m was produced when the molar ratios of citric acid to the metal nitrate was 1.5.  相似文献   

19.
The construction of multirate rearrangeable network has long been an interesting problem. Of many results published, all were achieved on 3-stage Clos network. The monotone routing algorithm proposed by Huet al. (2001) was also first applied to 3-stage Clos network. In this work, we adopt this algorithm and apply it to log d (N,m,p) networks. We first analyze the properties of log d (N,m,p) networks. Then we use monotone algorithm in log d (N,0,p) network. Furthermore we extend the result to construct multirate rearrangeable networks based on log d (N,m,p) network (1≤m≤n−1). Project (No. 10371028) supported by the National Natural Science Foundation of China  相似文献   

20.
Congruences for finite triple harmonic sums   总被引：1，自引：0，他引：1  
Zhao (2003a) first established a congruence for any odd prime p>3, S(1,1,1;p)≡-2Bp-3 (mod p), which holds when p=3 evidently. In this paper, we consider finite triple harmonic sum S(α,β,γ;p) (mod p) is considered for all positive integers α,β,γ. We refer to w=α β γ as the weight of the sum, and show that if w is even, S(α,β,γ;p)≡0 (mod p) for p≥w 3; if w is odd, S(α,β,γ;p)≡rBp≥w (mod p) for p≥w, here r is an explicit rational number independent of p. A congruence of Catalan number is obtained as a special case.  相似文献   

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