Researchers who lead the trends

Xuan-Hung Doan, Phuong-Tram T. Nguyen, Viet-Phuong La, Hong-Kong T. Nguyen (2019). Chapter 5. Researchers who lead the trends. In Quan-Hoang Vuong, Trung Tran (Eds.), The Vietnamese Social Sciences at a Fork in the Road (pp. 98–120). Warsaw, Poland: De Gruyter. DOI:10.2478/9783110686081-010 Online ISBN: 9783110686081 © 2019 Sciend

Phase diagram of solution of oppositely charged polyelectrolytes

We study a solution of long polyanions (PA) with shorter polycations (PC) and focus on the role of Coulomb interaction. A good example is solutions of DNA and PC which are widely studied for gene therapy. In the solution, each PA attracts many PCs to form a complex. When the ratio of total charges of PA and PC in the solution, $x$, equals to 1, complexes are neutral and they condense in a macroscopic drop. When $x$ is far away from 1, complexes are strongly charged. The Coulomb repulsion is large and free complexes are stable. As $x$ approaches to 1, PCs attached to PA disproportionate themselves in two competing ways. One way is inter-complex disproportionation, in which PCs make some complexes neutral and therefore condensed in a macroscopic drop while other complexes become even stronger charged and stay free. The other way is intra-complex disproportionation, in which PCs make one end of a complex neutral and condensed in a small droplet while the rest of the complex forms a strongly charged tail. Thus each complex becomes a "tadpole". These two ways can also combine together to give even lower free energy. We get a phase diagram of PA-PC solution in a plane of $x$ and inverse screening radius of the monovalent salt, which includes phases or phase coexistence with both kinds of disproportionation.Comment: 29 pages, 10 figures. Major change in results and tex

Bounded Distributed Flocking Control of Nonholonomic Mobile Robots

There have been numerous studies on the problem of flocking control for multiagent systems whose simplified models are presented in terms of point-mass elements. Meanwhile, full dynamic models pose some challenging problems in addressing the flocking control problem of mobile robots due to their nonholonomic dynamic properties. Taking practical constraints into consideration, we propose a novel approach to distributed flocking control of nonholonomic mobile robots by bounded feedback. The flocking control objectives consist of velocity consensus, collision avoidance, and cohesion maintenance among mobile robots. A flocking control protocol which is based on the information of neighbor mobile robots is constructed. The theoretical analysis is conducted with the help of a Lyapunov-like function and graph theory. Simulation results are shown to demonstrate the efficacy of the proposed distributed flocking control scheme

Capturing natural-colour 3D models of insects for species discovery

Collections of biological specimens are fundamental to scientific understanding and characterization of natural diversity. This paper presents a system for liberating useful information from physical collections by bringing specimens into the digital domain so they can be more readily shared, analyzed, annotated and compared. It focuses on insects and is strongly motivated by the desire to accelerate and augment current practices in insect taxonomy which predominantly use text, 2D diagrams and images to describe and characterize species. While these traditional kinds of descriptions are informative and useful, they cannot cover insect specimens "from all angles" and precious specimens are still exchanged between researchers and collections for this reason. Furthermore, insects can be complex in structure and pose many challenges to computer vision systems. We present a new prototype for a practical, cost-effective system of off-the-shelf components to acquire natural-colour 3D models of insects from around 3mm to 30mm in length. Colour images are captured from different angles and focal depths using a digital single lens reflex (DSLR) camera rig and two-axis turntable. These 2D images are processed into 3D reconstructions using software based on a visual hull algorithm. The resulting models are compact (around 10 megabytes), afford excellent optical resolution, and can be readily embedded into documents and web pages, as well as viewed on mobile devices. The system is portable, safe, relatively affordable, and complements the sort of volumetric data that can be acquired by computed tomography. This system provides a new way to augment the description and documentation of insect species holotypes, reducing the need to handle or ship specimens. It opens up new opportunities to collect data for research, education, art, entertainment, biodiversity assessment and biosecurity control.Comment: 24 pages, 17 figures, PLOS ONE journa

Research and Apply ABC Accounting Method in Practice: The Case of Manufacturing Company in Vietnam

The study was conducted for the purpose of giving some recommendation for the businesses that want to apply ABC accounting method in practice. Data were collected from managers at 162 manufacturing companies in VietNam. Basing on quantitative research method, the study determines the capability of successfully apply the ABC accounting method is influenced by six factors: business strategy of the business; Financial resources of the business; Human resource level; Business characteristics of the business; Organization and management characteristics of the enterprise; Corporate culture. Through findings, some recommendations are given for improving the ability to successfully apply the ABC accounting method in the future, helping VietNamese Firms to enhance their competitive advantage in the integration period. Keywords: Accounting, cost management, manufacturing Vietna

Production analysis of oil production from unconventional reservoirs using bottom hole pressures entirely in the Laplace space

textLaplace transforms are a powerful mathematical tool to solve many problems that describe fluid flow in unconventional reservoirs. However, for the solutions to be useful in applications, for instance history matching, they must be converted from the Laplace space into the real-time domain. A common practice is to numerically invert the transformed Laplace solution. However, we find substantial benefits if the data sets are handled entirely in the Laplace domain, and fitted to models presented in Laplace space rather than in the time domain. The data set used in this work is oil production rate and bottom hole pressure (BHP) from a liquid-rich shale play in North America, which we study to understand the decline of production from a tight formation produced by a fractured horizontal well. Since the BHP is relatively constant in the long run, a constant BHP solution is appropriate to analyze inflow performance analysis for most wells. However in some cases, as a result of operational changes to some wells, mainly periodic shut-ins, the production rate experiences isolated pressure build-ups. Both the production rate and BHP are transformed into the Laplace domain and accounted for in the model. Ours is the first analysis that combines rate and BHP entirely in the Laplace domain. There is no need for a Laplace transform inversion. Two models whose Laplace solutions are readily available are studied side-by-side, a single-compartment model versus a dual-compartment model. We fit the transformed production data of hundreds of wells to the Laplace models. The algorithm to transform data is fairly simple and computationally inexpensive. Since Laplace transformation smoothes the data, the fits are consistently good. Both models yield realistic and similar estimates of ultimate recovery. In most cases the effect of the second compartment in the dual-compartment model can be ignored, i.e., neglecting the fracture-well interaction. The single-compartment model seems adequate for modeling unconventional reservoirs performance. The knowledge of the reservoir model parameters provides estimation of the drainage volume and forecast future production. One of the main advantages of this novel history matching method is its ability to eliminating noise from data scatter without losing important information. As a result, we can match data more easily. Moreover, real-time solutions to many fluid flow problems in porous media often cannot be obtained analytically but rather via numerical computation. Our current method eliminates the need of inverting to real-time solutions. Additionally, these solutions often assume simple closed forms in Laplace domain even for very complex geometry (higher number of compartments), facilitating the task of history matching.Petroleum and Geosystems Engineerin