• Journal of Pharmaceutical Investigation
• /
• 제20권1호
• /
• pp.35-42
• /
• 1990

A new form of sulfabenzamide was characterized using X-ray diffraction patterns and differential scanning calorimetry. Solubility studies demonstrated that, of the sulfabenzamide polymorphs, the new form was more soluble than form I. Compression of the new form at compression force of 1000 $kg/cm{^2}$ didn't induce polymorphic change in the crystal. Similar patterns were also produced through grinding. The effects of some diluents on the polymorphic transformation from the new form into form I by grinding and compression were also studied. Three diluents, $Avicel^{\circledR}$, lactose and starch showed no influence on the polymorphic transformation. The new form seemed to be more suitable for the pharmaceutical preparation.

• 한국수학사학회지
• /
• 제29권3호
• /
• pp.157-172
• /
• 2016

Sophus Lie's research is regarded as one of the most important mathematical advancements in the $19^{th}$ century. His pioneering research in the field of differential equations resulted in an invaluable consolidation of calculus and group theory. Lie's group theory has been investigated and constantly modified by various mathematicians which resulted in a beautifully abstract yet concrete theory. However Lie's early intentions and ideas are lost in the mists of modern transfiguration. In this paper we explore Lie's early academic years and his object of studies which clarify the ground breaking ideas behind his theory.

• Structural Engineering and Mechanics
• /
• 제24권1호
• /
• pp.51-62
• /
• 2006

Differential transform method (DTM) for free vibration analysis of both ends simply supported beam resting on elastic foundation is suggested. The fourth order partial differential equation for free vibration of the beam resting on elastic foundation subjected to bending moment, shear and axial compressive load is obtained by using Winkler hypothesis and small displacement theory. It is assumed that the material is linear-elastic, and that axial load and modulus of subgrade reaction to be constant. In the analysis, shear and axial load effects are considered. The frequency factors of the beam are calculated by using DTM due to the values of relative stiffness; the results are presented in graphs and tables.

• Smart Structures and Systems
• /
• 제19권3호
• /
• pp.243-257
• /
• 2017

In this paper, free vibration of functionally graded (FG) size-dependent nanobeams is studied within the framework of nonlocal Timoshenko beam model. It is assumed that material properties of the FG nanobeam, vary continuously through the thickness according to a power-law form. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. The non-classical governing differential equations of motion are derived through Hamilton's principle and they are solved utilizing both Navier-based analytical method and an efficient and semi-analytical technique called differential transformation method (DTM). Various types of boundary conditions such as simply-supported, clamped-clamped, clamped-simply and clamped-free are assumed for edge supports. The good agreement between the presented DTM and analytical results of this article and those available in the literature validated the presented approach. It is demonstrated that the DTM has high precision and computational efficiency in the vibration analysis of FG nanobeams. The obtained results show the significance of the material graduation, nonlocal effect, slenderness ratio and boundary conditions on the vibration characteristics of FG nanobeams.

• Structural Engineering and Mechanics
• /
• 제57권1호
• /
• pp.179-200
• /
• 2016

In this paper the differential transformation method (DTM) is utilized for vibration and buckling analysis of nanotubes in thermal environment while considering the coupled surface and nonlocal effects. The Eringen's nonlocal elasticity theory takes into account the effect of small size while the Gurtin-Murdoch model is used to incorporate the surface effects (SE). The derived governing differential equations are solved by DTM which demonstrated to have high precision and computational efficiency in the vibration analysis of nanobeams. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of thermal loading, small scale and surface effects, mode number, thickness ratio and boundary conditions on the normalized natural frequencies and critical buckling loads of the nanobeams in detail. The results show that the surface effects lead to an increase in natural frequency and critical buckling load of nanotubes. It is explicitly shown that the vibration and buckling of a nanotube is significantly influenced by these effects and the influence of thermal loadings and nonlocal effects are minimal.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제13권1호
• /
• pp.435-451
• /
• 2019

Impossible differential cryptanalysis is an essential cryptanalytic technique and its key point is whether there is an impossible differential path. The main factor of influencing impossible differential cryptanalysis is the length of the rounds of the impossible differential trail because the attack will be more close to the real encryption algorithm with the number becoming longer. We provide the upper bound of the longest impossible differential trails of several important block ciphers. We first analyse the national standard of the Russian Federation in 2015, Kuznyechik, which utilizes the 16-byte LFSR to achieve the linear transformation. We conclude that there is no any 3-round impossible differential trail of the Kuznyechik without the consideration of the specific S-boxes. Then we ascertain the longest impossible differential paths of several other important block ciphers by using the matrix method which can be extended to many other block ciphers. As a result, we show that, unless considering the details of the S-boxes, there is no any more than or equal to 5-round, 7-round and 9-round impossible differential paths for KLEIN, Midori64 and MIBS respectively.

• 한국항해항만학회지
• /
• 제28권1호
• /
• pp.23-29
• /
• 2004

본 논문은 EUROFIX 시스템에 적용하기 위한 Reed-Solomon 코딩에 대해서 다룬다. EUROFIX는 최근에 위성시스템의 비상수단으로서 인식되는 LORAN-C 시스템을 이용하여 DGNSS(Differential Global Navigation Satellite Systems) 정보를 전송하는 통합위치결정 시스템으로서, LORAN-C 신호 펄스열들의 펄스 위치 변조에 의한 LORAN-C 전송을 통해서 데이터 통신을 한다. 또한 통신 시스템에서 처리되는 광대한 양의 데이터에 대한 오류론 제어하기 위한 수단으로 오류 정정 부호나 정정 알고리즘이 대두되었으며, 실제로 중요한 적용요소가 되고 있다. 이에 따라 본 논문에서는 EUROFIX 정보전송의 부호화과정에서의 오류정정을 위해서 유한체 푸리에 변환을 이용한 Reed-Solomon 코드의 부호화 및 복호화에 대해서 연구하였다. 시뮬레이션을 통해서, EUROFIX 정보전송의 오류정정에 효과적인 것을 알 수 있었다.

• 전기학회논문지
• /
• 제61권11호
• /
• pp.1601-1605
• /
• 2012

Three-phase voltage and current is applied to the three-phase alternating current motors which are commonly used in industry. Three phase variables of a, b, c are converted into d, q, 0 axis and the AC machines are modeled and analyzed. Basically the coordinate transformation or d-q transformation is used for convenience, a few steps are needed to analyze the motor performances - separating d and q components, establishing each equivalent circuit, and solving the differential equations of the circuits. In this study, a modeling technique of induction motor using complex vector is proposed and it can explain the induction motor physically. This method does not need the separating process of d and q components. With this technique, the model becomes simple, is easy to understand in physical, and can get the same results with those from the other models. These simulation results of the proposed model are compared with them for the conformation of the proposed method.

• 한국안전학회지
• /
• 제29권4호
• /
• pp.28-33
• /
• 2014

Recently, the actuator worked by the driving recovery-force of the thermo elastic martensitic transformation of shape memory alloys(SMA) has been studied. This paper presents a study on the fatigue life of shape memory alloy (SMA) actuators undergoing thermally induced martensitic phase transformation under various stress levels. shape memory recoverable stress and strain of Ti-44.5at.%Ni-8at.%Cu alloys were by means of constant temperature tensile tests. Differential scanning calorimetry (DSC) was employed in order to investigate the transformation characteristics of the alloy before the tests. the results were summarized as follows. The martensite inducing stress incerased with the increasing of the Cu-contents. The fatigue life decreased with the increasing of the test load and the Cu-content. The data acquired will be very useful during the design process of an SMA NiTiCu element as a functional part of an actuator.

• Journal of Microbiology and Biotechnology
• /
• 제16권10호
• /
• pp.1629-1633
• /
• 2006

Ginsenosides have been regarded as the principal components responsible for the pharmacological and biological activities of ginseng. The transformation of ginsenosides with live lactic acid bacteria transformed ginsenosides Rb2 and Rc into Rd, but the reactions were slow. When the crude enzymes obtained from several lactic acid bacteria were used for transformation, those from Bifidobacterium sp. Int57 exhibited the most potent transforming activity of ginsenosides to compound K. In comparison, a relatively higher level of Rh2 was produced by the enzymes from Lactobacillus delbrueckii and Leuconostoc mesenteroides. These results suggest that it is feasible to develop a specific bioconversion process to obtain specific ginsenosides using the appropriate combination of ginsenoside substrates and specific microbial enzymes.