Escargot

The nonlinear optical characteristics of semiconductors are studied near the two-photon biexciton resonance. Optical bistability is shown to happen below this resonance at very low light intensities

ON THE DELICATE PROPERTIES OF EXCITONIC SURFACE STATES IN MULTILAYER MOLECULAR CRYSTALS

ABSTRACT The Hiirfa.cc KJ.a.l.es of Erenkel exdt.oiiK in senninfinite KysLenis of TmiHiUiyer molecula

Quantum Walks in Quasi-Periodic Photonics Lattices

We present construction rules for a new class of quasiperiodic photonics lattices (QPL) to realize localized quantum walks (LQWs) deterministically. The new quasiperiodic structures are constructed symmetrically with Fibonacci, Thue-Morse, and other quasiperiodic sequences. Our construction rules allow us to build the symmetrical quasiperiodic photonics lattices. As a result, LQWs with symmetrical probability distributions can be realized in these QPLs. Furthermore, the proposed QPLs are composed with different waveguides providing both on- and off-diagonal deterministic disorders. We show LQWs in the proposed QPLs are highly programmable and controllable

The Effects of Collaborative Learning on Young ESL Learners’ L2 Anxiety and Speaking Performance

Foreign Language Anxiety (FLA) is one of the issues of interest attracting researchers in recent decades. However, while collaborative learning introduced a prospective tool for FLA, it has not been much researched in the L2 classroom context, particularly in Vietnam. This paper focuses on using collaborative learning to reduce foreign language anxiety and enhance the L2 speaking performance of young learners at an English center in Ho Chi Minh City. A combination of tools, including Aydin et al.’s (2017) Children Foreign Language Anxiety Scale (CFLAS) for the pre-tests and post-tests, the teacher’s diary, and follow-up interviews, was used to measure the changes in learner’ FLA level and speaking performance. After five-week implementations, these learners’ FLA was slightly alleviated, and their speaking performance was improved using a collaborative learning approach. Moreover, learners were found to have positive attitudes and experience with learning in the new approach. These findings implied that collaborative learning could be a potential treatment to help L2 learners uncover their anxious selves and find more confidence in using the target languag

ỨNG DỤNG CÔNG NGHỆ VIỄN THÁM VÀ GIS NGHIÊN CỨU QUÁ TRÌNH DỊCH CHUYỂN ĐƯỜNG BỜ VÀ ĐÓNG/MỞ CỬA ĐẦM Ô LOAN (PHÚ YÊN) GIAI ĐOẠN 1965 - 2014

Application of remote sensing and GIS (Geographic Information System) technologies found that: Fluctuation process of shoreline in O Loan lagoon became evident, through which a general picture of the shoreline development in a long time from 1965 - 2014 has been launched. The process of erosion - accretion evolutions occurred time by time. In which, the period from 1965 - 1995 was the process of erosion - accretion and gradual northward movement of O Loan lagoon inlet, with erosion area greater than deposition area. The period after 1995 was the process of erosion and An Hai inlet opening during rainy season, coincident with northeast monsoon and typhoon activity; and the process of accretion and An Hai inlet closing during dry season, coincident with southwest monsoon.Trên cơ sở ứng dụng công nghệ viễn thám và GIS (hệ thông tin địa lý) cho thấy: Quá trình biến động của đường bờ biển khu vực đầm Ô Loan được thể hiện rõ rệt, qua đó đã đưa ra bức tranh tổng quát về quá trình phát triển của đường bờ, trong một thời gian dài từ năm 1965 - 2014. Các quá trình xói lở - bồi tụ diễn biến theo thời gian. Trong đó, thời kỳ từ năm 1965 - 1995 là các quá trình xói lở - bồi tụ và dịch chuyển cửa biển đầm Ô Loan dần lên phía bắc, với diện tích bị xói lở lớn hơn diện tích được bồi tụ. Thời kỳ từ sau năm 1995 đến nay là quá trình xói lở và mở cửa biển An Hải chủ yếu xảy ra vào mùa mưa, trùng với thời kỳ gió mùa Đông Bắc và bão hoạt động, còn bồi lấp cửa biển xảy ra vào mùa khô, trùng với thời kỳ gió mùa Tây Nam

On the Performance of Cognitive Underlay SIMO Networks over Equally Correlated Rayleigh Fading Channels

The performance of single-input multiple-output (SIMO) cognitive spectrum sharing networks with the presence of equally correlated Rayleigh fading channels is investigated. In particular, based on the truncated infinitive series of cumulative distribution function (CDF) and probability density function (PDF) of the end-to-end signal-to-noise ratios (SNRs), close-form expressions are provided for the system outage performance, bit error rate and ergodic capacity. It is shown that the system performance merely depends on the correlation coefficient between antennas. Monte-Carlo simulations are also contributed to confirm the accuracy of our analysis

ĐẶC ĐIỂM BIẾN ĐỔI HÌNH THÁI ĐỊA HÌNH BÃI BIỂN NHA TRANG, KHÁNH HÒA

This paper has focused on analyzing morphological change features of Nha Trang Beach based on the comparison of different beach profiles which were measured from July 2008 to September 2016 corresponding to the Northeast and Southwest monsoons. Additionally, the sediment transport balance was estimated by the method of equity value curve. Studied results show that the beach profiles were accreted and eroded during Southwest and Northeast monsoons respectively, but due to the shortage of materials supply, the beach has the narrowing trend. In this paper, some effects of the existing works in Nha Trang Beach such as Vinpearl, Navy Port, and hydro-dams in upstream area of Cai river have been also analyzed for estimating sedimentary supply to beach segments.Bài báo phân tích đặc điểm biến đổi hình thái địa hình bãi biển Nha Trang trên cơ sở so sánh các trắc diện địa hình bãi biển, với số liệu đo đạc từ tháng 7/2008 đến tháng 9/2016, cụ thể vào các thời kỳ gió mùa Đông Bắc và gió mùa Tây Nam tại các vị trí cố định. Đồng thời, cán cân trầm tích được tính toán và phân tích bằng phương pháp đường cong đẳng giá trị. Kết quả cho thấy, bãi biển được bồi tụ vào mùa gió Tây Nam và bị xói lở vào mùa gió Đông Bắc. Tuy nhiên, do thiếu hụt bồi tích nên bãi biển có xu thế thu hẹp. Bài báo còn phân tích một số ảnh hưởng của các công trình hiện diện tại bãi biển Nha Trang, như cầu cảng Vinpearl, cảng Hải Quân và các đập chắn trên lưu vực sông Cái khi xét đến nguồn cung cấp vật liệu bồi tích

Tunable particle separation in a hybrid dielectrophoresis (DEP)- inertial microfluidic device

Particle separation is indispensable in many microfluidic systems and holds a broad range of biomedical applications. Inertial microfluidic devices that work solely on intrinsic hydrodynamic forces and inertial effects can offer label-free, high throughput and high efficiency separation performance. However, the working range of the current inertial microfluidic systems is obtained by tailoring the inertial lift forces and secondary flow drag through flow speed. Each channel design is normally effective for specific target particles, which inevitably lacks the flexibility for various particle mixtures. Redesigning the structure and dimension of microchannels for new sets of particle mixtures is often time-consuming and expensive. In this work, by introducing an external dielectrophoretic force field and coupling it with inertial forces, we proposed here an innovative hybrid DEP-inertial microfluidic platform for particle tunable separation. The working principle of the device was explained and its functionality was validated by experiments. In addition, the dimension of target particle mixture can be varied by adjusting the electrical voltage without redesigning the channel structure or dimensions. It is expected that the proposed DEP-inertial concept can work as a flexible platform for a wide range of biomedical applications

COPPER HEXACYANOFERRATE (II): SYNTHESIS, CHARACTERIZATION, AND CESIUM, STRONTIUM ADSORBENT APPLICATION

Low-cost nanoscale copper hexacyanoferrate (CuHF), a good selective adsorbent for cesium (Cs+) removal, was prepared using the chemical co-precipitation method. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and high-resolution transmission electron microscopy (HR-TEM) were conducted to determine the CuHF morphology. Copper hexacyanoferrate, Cu13[Fe(CN)6]14.(2K).10H2O, has a cubic structure (space group F-43m) in the range of 10-30 nm and a Brunauer-Emmett-Teller (BET) surface area of 462.42 m2/g. The removal of Cs+ and Sr2+ is dependent on pH; the maximum adsorption capacity (qmax) of CuHF is achieved at a pH = 6. From the Langmuir model, qmax = 143.95 mg/g for Cs+ and 79.26 mg/g for Sr2+, respectively. At high concentrations, Na+, Ca2+, and K+ ions have very little effect on Cs+ removal, and Na+ and K+ ions have a higher affinity for removing Sr2+ than Ca2+ at all concentrations. CuHF has a high affinity for alkaline cations in the order: Cs+ > K+ > Na+ > Ca2+ > Sr2+, as proposed and discussed

Sand Spit Morphology at an Inlet on Phu Quoc Island, Vietnam

Tidal inlets with attached sand spits are a very common coastal landform. Since the evolution of sand spits along coastlines influence the social-economic development of local coastal areas, sand spits have become the objects of numerous studies. However, previous studies have mainly focused on sand spits that are usually in the scale of hundreds of meters in width, whilst knowledge about the evolution of smaller-scale sand spits still remains limited. Therefore, in this study, the morphological change of a small and unexplored sand spit in front of Song Tranh Inlet on the west coast of Phu Quoc Island, Vietnam is investigated. Satellite images are first used to observe the morphological change of the sand spit and calculate the longshore sediment transport rates (LSTR) along the sand spit. Waves and beach sediments are collected at the study site to calculate the longshore sediment transport rate using the CERC formula. It is found that there is a seasonal variation in the evolution of the sand spit at Song Tranh Inlet. The longshore sediment transport rates along the spit calculated by image analysis are 39,000 m$^3$/year, 66,000 m$^3$/year, and 40,000 m$^3$/year, whilst the longshore sediment transport rate calculated by the CERC formula is 72,000 m$^3$/year. This study aims to contribute to the methodology for investigating the evolutions of small sand spits and, specifically, sustainable coastal management for Phu Quoc Island, which is well-known as the Pearl Island of Vietnam