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Induced Hyperfine Field in Doped Chalcopyrite Compounds Cu(In1-xAx)S2 (A = V and Cr) 铜(In1-xAx)S2 (A = V和Cr)掺杂黄铜矿化合物的诱导超细场
Pub Date : 2022-07-04 DOI: 10.3329/dujs.v69i3.60024
M. Shahjahan, Raisul Islam
Hyperfine field and electronic states of doped chalcopyrite compounds Cu(In1-xAx)S2 with A = V and Cr are calculated by Korringa- Kohn-Rostoker Green’s function method, where x denotes the concentration of A atoms. The V and Cr doped compounds are ferromagnetically stable in terms of energy minimization and their electronic states are half metallic. The hyperfine fields in the stable ferromagnetic (FM) state are calculated with their valence and core contributions. In addition, site preference local magnetic moments are calculated for the FM and disordered spin moment (DSM) states. Density of states (DOS) exhibit the spintronic property of half metallicity. The local core and valence field polarizations are found in the doped chalcopyrite systems, where the s-orbital hybridization with the local d-shell is explained in terms of some exchange mechanisms.Dhaka Univ. J. Sci. 69(3): 149-153, 2022 (June)
采用Korringa- Kohn-Rostoker Green函数法计算了A = V和Cr掺杂黄铜矿化合物Cu(In1-xAx)S2的超细场态和电子态,其中x为A原子的浓度。V和Cr掺杂的化合物在能量最小化方面是铁磁稳定的,它们的电子态是半金属的。计算了稳定铁磁(FM)状态下的超精细场,计算了它们的价态和磁心贡献。此外,还计算了调频态和无序自旋态的位置偏好局域磁矩。态密度(DOS)表现出半金属丰度的自旋电子性质。在掺杂的黄铜矿体系中发现了局域核和价场极化,其中s轨道与局域d壳层的杂化可以用一些交换机制来解释。达卡大学学报,69(3):149- 153,2022 (6)
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引用次数: 0
Electrochemical Studies on Interactions of Cu2+, Zn2+ and Cd2+ with Leucine and Isoleucine Cu2+、Zn2+和Cd2+与亮氨酸和异亮氨酸相互作用的电化学研究
Pub Date : 2022-07-04 DOI: 10.3329/dujs.v69i3.60035
M. Hasan, M. Ehsan
The interaction of some divalent metal ions with leucine (leu) and isoleucine (ile) was studied in aqueous solution. Electrochemical techniques like cyclic voltammetry, chronoamperometry and chronocoulometry were used for this study. The electrochemical study demonstrates that the maximum interaction of each metal ion occurs with two deprotonated ligand. The metal ions exchange electrons quasi-reversibly in presence of the ligands and some sort of chemical reaction may be competing with diffusion process at the electrode surface. The current-time and charge-time response accounts for the adsorption of reactant or product or both at the electrode surface.Dhaka Univ. J. Sci. 69(3): 230-237, 2022 (June)
研究了一些二价金属离子在水溶液中与亮氨酸和异亮氨酸的相互作用。本研究采用了循环伏安法、计时安法和计时库容法等电化学技术。电化学研究表明,每种金属离子的最大相互作用发生在两个去质子配体上。金属离子在配体存在下准可逆地交换电子,在电极表面可能发生某种化学反应与扩散过程相竞争。电流时间和电荷时间响应说明了电极表面对反应物或生成物或两者的吸附。达卡大学学报(自然科学版),69(3):230-237,2022 (6)
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引用次数: 0
Numerical Method for 2D Quasi-linear Hyperbolic Equation on an Irrational Domain: Application to Telegraphic Equation 二维拟线性双曲型方程在无理区上的数值解法:在电报方程中的应用
Pub Date : 2021-12-01 DOI: 10.3329/dujs.v69i2.56492
Bishnu Pada Ghosh, N. C. Roy
We develop a novel three-level compact method (implicit) of second order in time and space directions using unequal grid for the numerical solution of 2D quasi-linear hyperbolic partial differential equations on an irrational domain. The stability analysis of the model problem for unequal mesh is discussed and it is revealed that the developed scheme is unconditionally stable for the Telegraphic equation. For linear difference equations on an irrational domain, the alternating direction implicit method is discussed. The projected technique is scrutinized on several physical problems on an irrational domain to exhibitthe accuracy and effectiveness of the suggested method.Dhaka Univ. J. Sci. 69(2): 116-123, 2021 (July)
本文提出了一种在时间和空间方向上使用不等网格的二阶三阶紧致方法(隐式),用于求解非合理域上二维拟线性双曲型偏微分方程的数值解。讨论了不等网格模型问题的稳定性分析,揭示了所开发的格式对于电报方程是无条件稳定的。讨论了非合理域上线性差分方程的交替方向隐式解法。在一个不合理域的物理问题上对投影技术进行了检验,证明了该方法的准确性和有效性。达卡大学学报(自然科学版),69(2):116-123,2021 (7)
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引用次数: 1
Facial Expression Identification using Regularized Supervised Distance Preserving Projection 基于正则化监督距离保持投影的面部表情识别
Pub Date : 2021-12-01 DOI: 10.3329/dujs.v69i2.56485
S. Jahan, Moriyam Akter, Sifta Yeasmin, Farhana Ahmed Simi
Facial expression recognition is one of the most reliable and a key technology of advanced human-computer interaction with the rapid development of computer vision and artificial intelligence. Nowadays, there has been a growing interest in improving expression recognition techniques. In most of the cases, automatic recognition system’s efficiency depends on the represented facial expression feature. Even the best classifier may fail to achieve a good recognition rate if inadequate features are provided. Therefore, feature extraction is a crucial step of the facial expression recognition process. In this paper, we have used Regularized Supervised Distance Preserving Projection for extracting the best features of the images. Numerical experiment shows that the use of this technique outperforms many of state of art approaches in terms of recognition rate.Dhaka Univ. J. Sci. 69(2): 70-75, 2021 (July)
随着计算机视觉和人工智能的迅速发展,面部表情识别是先进人机交互技术中最可靠的关键技术之一。目前,人们对改进表情识别技术的兴趣越来越大。在大多数情况下,自动识别系统的效率取决于所代表的面部表情特征。如果提供的特征不充分,即使是最好的分类器也可能无法达到良好的识别率。因此,特征提取是人脸表情识别过程中至关重要的一步。在本文中,我们使用正则化监督距离保持投影来提取图像的最佳特征。数值实验表明,该方法在识别率方面优于许多现有方法。达卡大学学报(自然科学版),69(2):70-75,2021 (7)
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引用次数: 0
Synthesis and Characterization of Mixed Ligand Complexes of Copper(II) with Adenine and Dicarboxylic Acids 铜(II)与腺嘌呤和二羧酸混合配体配合物的合成与表征
Pub Date : 2021-12-01 DOI: 10.3329/dujs.v69i2.56486
Sumaia Abdullah, M. Rahman, Humaira Yeasmin, A. Shaikh, P. K. Bakshi
Three mixed ligand complexes of copper(II) with adenine and dicarboxylic acids have been synthesized. The resulting complexes were characterized by their melting point, solubility, metal content analysis, FT-IR and UV-visible spectroscopy, magnetic measurement, thermal analysis, cyclic voltammetric measurement and X-ray powder diffraction study. The products are microcrystalline powder, slightly soluble in water and decompose at high temperature. Under experimental condition, the ligands adenine (Ade) behaves as a neutral ligand, whereas oxalic acid (OxH2), succinic acid (SucH2) and tartaric acid (TarH2) are doubly deprotonated to form dianionic ligands that are coordinated to the Cu(II) ion. The Cu(II) content analysis of the complexes confine to their stoichiometry [Cu(Ade)(L)(H2O)] (L = Ox, Suc, or Tar dianion). Electrochemical redox behavior of the complexes in their reaction medium was also examined. They exhibit quasi-reversible one-electron transfer processes.Dhaka Univ. J. Sci. 69(2): 76-81, 2021 (July)
合成了三种铜(II)与腺嘌呤和二羧酸的混合配体配合物。通过熔点、溶解度、金属含量、FT-IR和uv -可见光谱、磁测量、热分析、循环伏安测量和x射线粉末衍射研究对所制配合物进行了表征。产品为微晶状粉末,微溶于水,高温分解。在实验条件下,配体腺嘌呤(Ade)表现为中性配体,而草酸(OxH2)、琥珀酸(SucH2)和酒石酸(TarH2)被双去质子化形成与Cu(II)离子配位的二阴离子配体。配合物的Cu(II)含量分析仅限于它们的化学计量[Cu(Ade)(L)(H2O)] (L = Ox、su或Tar)。研究了配合物在反应介质中的电化学氧化还原行为。它们表现出准可逆的单电子转移过程。达卡大学学报(自然科学版),69(2):76- 81,2021 (7)
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引用次数: 1
Pregnancy Complications in Women with PCOS: A Meta-Analysis 多囊卵巢综合征妇女妊娠并发症:一项荟萃分析
Pub Date : 2021-12-01 DOI: 10.3329/dujs.v69i2.56487
K. Tanvir, Mohammad Lutfor Rahman
Polycystic ovary syndrome (PCOS) is a hormonal disorder which affects women in their reproductive ages. There might have association between maternal and neonatal complications with PCOS. The goal of this study is to look for the association between polycystic ovary syndromes (PCOS) and obstetric complications through meta-analysis on the basis of previously published studies from 2000 to 2019. In the current endeavour 17 studies involving 1975 women with PCOS and 10812 controls were selected for pooling. During pregnancy period women who have PCOS showed a significantly higher risk of developing gestational diabetes mellitus (GDM) (RR 2.51; 95% CI: 1.71-3.65), pregnancy induced hypertension (PIH) (RR 2.76; 95% CI: 2.04-3.72), preeclampsia (RR 2.14; 95% CI: 1.34-3.40), preterm birth (RR 1.41; 95% CI: 1.08-1.85) compared to controls. Neonatal birth weight is significantly lower (SMD -0.18; 95% CI: -0.33 to -0.03) compared to controls. It is concluded that women who have PCOS have greater chance of having pregnancy complications as well as risk of neonatal complications such as having low birth weight.Dhaka Univ. J. Sci. 69(2): 82-87, 2021 (July)
多囊卵巢综合征(PCOS)是一种影响育龄妇女的荷尔蒙失调。多囊卵巢综合征可能与产妇和新生儿并发症有关。本研究的目的是通过荟萃分析,在2000年至2019年之前发表的研究的基础上,寻找多囊卵巢综合征(PCOS)与产科并发症之间的关系。在目前的努力中,17项研究涉及1975名多囊卵巢综合征妇女和10812名对照。妊娠期多囊卵巢综合征患者发生妊娠期糖尿病(GDM)的风险显著增高(RR 2.51;95% CI: 1.71-3.65)、妊高征(PIH) (RR 2.76;95% CI: 2.04-3.72),先兆子痫(RR 2.14;95% CI: 1.34-3.40),早产(RR 1.41;95% CI: 1.08-1.85)。新生儿出生体重显著降低(SMD -0.18;95% CI: -0.33至-0.03)。结论是,患有多囊卵巢综合征的妇女有更大的机会出现妊娠并发症以及新生儿并发症的风险,如低出生体重。达卡大学学报(自然科学版)69(2):82- 87,2021 (7)
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引用次数: 0
Studying the Third Cumulant of the Mixture of Dirichlet-multinomial Distributions dirichlet -多项式混合分布的第三次累积量研究
Pub Date : 2021-12-01 DOI: 10.3329/dujs.v69i2.56489
Farzana Afroz
Traditionally, the overdispersion parameter ϕ is estimated by using Pearson’s lack of fit statistic X2or the Deviance statistic D, which do not perform well in the case of sparse data. This paper particularly focuses on an estimator ϕnew of overdispersion parameter which was proposed for sparse multinomial data. The estimator was derived on the basis of an assumption on the 3rd cumulant of the response variable.When the data comes from the Dirichlet-multinomial distribution ϕnew is known to have the lowest root mean squared error comparing to the other three estimators. In this paper the 1st to 3rd order raw moments of the finite mixture of Dirichlet-multinomial distributions are derived, which results in complicated mathematical expressions. Furthermore, it is found that the 3rd cumulant of this mixture does not satisfy the assumption which is considered in the derivation of ϕnew .Dhaka Univ. J. Sci. 69(2): 96-100, 2021 (July)
传统上,过散参数φ是通过使用Pearson的缺乏拟合统计量x2或偏差统计量D来估计的,这在稀疏数据的情况下表现不佳。本文重点研究了一种用于稀疏多项数据的过色散参数估计器。该估计量是基于对响应变量的第3个累积量的假设而导出的。当数据来自dirichlet多项分布时,与其他三个估计器相比,已知ϕnew具有最低的均方根误差。本文导出了dirichlet -多项式有限混合分布的一阶至三阶原始矩,其数学表达式十分复杂。此外,发现该混合物的第3个累积量不满足在推导中考虑的假设,这是在新的。达卡大学学报.科学69(2):96- 100,2021 (7)
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引用次数: 0
Performance Enhancement of an a-Si:H/μc-Si:H Heterojunction p-i-n Solar Cell by Tuning the Device Parameters a-Si:H/μc-Si:H异质结p-i-n太阳能电池性能的优化研究
Pub Date : 2021-12-01 DOI: 10.3329/dujs.v69i2.56488
Md Nazmul Islam, H. R. Ghosh
In this work, the solar cell design parameters like- layer thickness, bandgap, donor and acceptor concentrations are varied to find optimum structure of a hydrogenated amorphous silicon (a-Si:H) and hydrogenated microcrystalline silicon (μc-Si:H) heterojunction p-i-n solar cell. A thin a-Si:H p-layer of 1 to 5 nm followed by a thick a-Si:H i-layer of thickness 1400 to 1600 nm and then thin n-layer of thickness 1 to 5 nm with acceptor concentration of 102 cm−3 and donor concentration of 1020 cm−3 and the bandgaps of p-, i-, and n- layers with higher bandgaps closer to 2.2 eV for a-Si:H p-layer, 1.85 eV for a-Si:H i-layer, and 1.2 eV for μc-Si:H n-layer have showed better performances. The optimum cell has a JSC of 18.93 mA/cm2, VOC of 1095 mV, Fill factor of 0.7124, and efficiency of 14.77%. The overall external quantum efficiency of the numerically designed cell also remained very high from 85-95 % for wavelengths of 300-650 nm range. This indicates that the device will perform its best under both high and low frequency i.e. ultra-violet, near visible and visible light wavelengths.Dhaka Univ. J. Sci. 69(2): 88-95, 2021 (July)
本文通过改变太阳能电池的设计参数,如-层厚度、带隙、供体和受体浓度等,找到了氢化非晶硅(a- si:H)和氢化微晶硅(μc-Si:H)异质结p-i-n太阳能电池的最佳结构。A - si:H薄层厚度为1 ~ 5 nm,然后是厚度为1400 ~ 1600 nm的A - si:H薄层,然后是厚度为1 ~ 5 nm的n薄层,受体浓度为102 cm−3,施主浓度为1020 cm−3,p-、i-和n-层的带隙较高,A - si:H薄层的带隙接近2.2 eV, A - si:H薄层的带隙接近1.85 eV, μc-Si:H薄层的带隙接近1.2 eV,表现出较好的性能。优化后的电池JSC为18.93 mA/cm2, VOC为1095 mV,填充系数为0.7124,效率为14.77%。在300-650 nm波长范围内,数值设计的电池的整体外量子效率也保持在85- 95%之间。这表明该器件在高频和低频(即紫外线、近可见光和可见光波长)下都能发挥最佳性能。达卡大学学报:自然科学版,69(2):88- 95,2021 (7)
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引用次数: 0
Analyzing Infant Mortality in Rural Bangladesh: A Frailty Modeling Approach 分析孟加拉国农村婴儿死亡率:脆弱性建模方法
Pub Date : 2021-12-01 DOI: 10.3329/dujs.v69i2.56484
B. Pal, Ahsan Rahman Jaamee
In practice, it may happen that data may arise from a hierarchical structure i.e., a cluster is nested within another cluster. In this case, nested frailty model is appropriate to analyze survival data to obtain optimal estimates of the parameters of interest. To identify significant determinants of infant mortality in rural Bangladesh, survival data have been extracted from Bangladesh Demographic and Health Survey (BDHS), 2014. Because of the presence of two-level clustering in data, nested frailty model has been employed for the purpose of analysis. Recommendations have been suggested based on the results obtained from the survival model to reduce the infant mortality in rural Bangladesh to a great extent.Dhaka Univ. J. Sci. 69(2): 63-69, 2021 (July)
在实践中,数据可能来自层次结构,即一个集群嵌套在另一个集群中。在这种情况下,嵌套脆弱性模型适合分析生存数据,以获得感兴趣参数的最佳估计。为了确定孟加拉国农村婴儿死亡率的重要决定因素,从2014年孟加拉国人口与健康调查(BDHS)中提取了生存数据。由于数据中存在两级聚类,因此采用嵌套脆弱性模型进行分析。根据生存模型得出的结果,提出了建议,以便在很大程度上降低孟加拉国农村地区的婴儿死亡率。达卡大学学报(自然科学版),69(2):63- 69,2021 (7)
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引用次数: 1
Track and Landfall Characteristics of Very Severe Cyclonic Storm Fani over the Bay of Bengal using WRF Model 利用WRF模式分析孟加拉湾甚强气旋风暴范尼的路径和登陆特征
Pub Date : 2021-12-01 DOI: 10.3329/dujs.v69i2.56490
Md Shakil Hossain, Md Abdus Samad, Most Razia Sultana, M. Mallik, Md Joshem Uddin
An attempt has been made to assess the capability of the Weather Research and Forecasting (WRF) model in simulating the track and landfall characteristics of Tropical Cyclone (TC) Fani (25th April – 05th May 2019) over the Bay of Bengal (BoB). WRF model has conducted on a single domain of 10 km horizontal resolution using Global Data Assimilation System (GDAS) data (0.250×0.250). The model predicted outcomes show auspicious agreement with the observed datasets of the Bangladesh Meteorological Department (BMD) and India Meteorological Department (IMD). It is found that the diminished lead time of the model run plays a crucial role in delivering good consistency with the minimum forecast uncertainty. A strong correlation between the track and intensity forecast deviations has also been determined. According to the results, the model simulation which captures the minimum deviation in the intensity forecast also ensures better track prediction of the system. The feasibility of the track and landfall forecast by the model even up to 27 hr advance is reasonably well. Finally, it can be decided that the model is capable to predict the cyclonic storm Fani precisely and it can be chosen confidently for future events over the BoB.Dhaka Univ. J. Sci. 69(2): 101-108, 2021 (July)
本文试图评估天气研究与预报(WRF)模式模拟热带气旋(TC) Fani(2019年4月25日至5月5日)在孟加拉湾(BoB)上空的路径和登陆特征的能力。WRF模型使用全球数据同化系统(GDAS)数据在10公里水平分辨率的单一域上进行(0.250×0.250)。该模型预测的结果与孟加拉国气象局(BMD)和印度气象局(IMD)的观测数据集非常吻合。研究发现,模型运行提前期的缩短在提供与最小预测不确定性的良好一致性方面起着至关重要的作用。还确定了轨道和强度预报偏差之间的强相关性。结果表明,模型仿真在捕获强度预测偏差最小的情况下,也保证了系统更好的轨迹预测。该模式预报的路径和登陆提前27小时的可行性较好。最后,可以确定该模型能够准确地预测气旋风暴Fani,并且可以自信地选择它来预测BoB的未来事件。达卡大学学报(自然科学版),69(2):101- 108,2021 (7)
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引用次数: 4
期刊
Dhaka University Journal of Science
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