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Chương Trần

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Papers by Chương Trần

Một số kinh nghiệm trong ứng dụng trình quản lý lớp học trực tuyến moodle cho các khoá đào tạo, bồi dưỡng ngắn hạn (qua thực tiễn Trường Đại học Quy Nhơn)

Dong Thap University Journal of Science

Bài viết phản ánh thực tiễn ứng dụng trình quản lý lớp học trực tuyến Moodle trong các khoá đào t... more Bài viết phản ánh thực tiễn ứng dụng trình quản lý lớp học trực tuyến Moodle trong các khoá đào tạo, bồi dưỡng thuộc Đề án Ngoại ngữ Quốc gia 2020 tại Trường Đại học Quy Nhơn. Qua thực tế, chúng tôi nhận thấy Moodle với các tính năng tối ưu cho hình thức đào tạo, bồi dưỡng trực tuyến hoặc tích hợp cho thấy tính hiệu quả cả về truyền đạt nội dung, tiết kiệm thời gian, kinh phí và tính kết nối cộng đồng nghề nghiệp sau khoá học. Tuy nhiên, đơn vị đào tạo cần đầu tư cho cơ sở hạ tầng công nghệ và bồi dưỡng đội ngũ quản trị viên, giảng viên trực tiếp giảng dạy để đạt hiệu quả tích hợp cao nhất.

Proposing to improve the Heuristic Algorithms to Solve a Steiner-minimal-tree Problem in Large Size Sparse Graphs

Research and Development on Information and Communication Technology

Steiner Minimal Tree (SMT) is a combinatorial optimization problem that has many important applic... more Steiner Minimal Tree (SMT) is a combinatorial optimization problem that has many important applications in science and engineering; this is an NP-hard class problem. In recent decades, there have been a series of scientific papers published for solving the SMT problem based on the approaches of exact solutions (such as dynamic programming, branch and bound) and approximate solutions (such as heuristic algorithm, metaheuristic algorithm). This paper proposes an improvement for two heuristic algorithms PD-Steiner and SPT-Steiner to solve a SMT problem in large size sparse graphs with edge weight not exceeding 10 and verify this proposal on large-size sparse graphs up to 100000 vertices. These experimental results are useful information for further research on the SMT problem.

Solution of a paradox related to the rigid bar pull-out problem in standard elasticity

Mechanics Research Communications

International Conference on Nonlinear Solid Mechanics 2019: General Topics and Review of Plenary Lectures

Developments and Novel Approaches in Nonlinear Solid Body Mechanics, 2020

The International Conference on Nonlinear Solid Mechanics (ICoN-SoM) 2019, held in Rome from June... more The International Conference on Nonlinear Solid Mechanics (ICoN-SoM) 2019, held in Rome from June 16th through 19th of 2019, had as its main goal to gather together researchers in the field of nonlinear Solid Mechanics in a stimulating research environment. This work accounts for the plenary lectures held during the conference. It is mainly aimed at providing interested researchers with a track of the contents discussed during the conference and with the relevant bibliography of the plenary lectures. Additional information, such as the abstracts of all the talks, can be found on the official web-site of the conference: http://www.memocsevents.eu/iconsom2019.

Symmetric-in-Plane Compression of Polyamide Pantographic Fabrics—Modelling, Experiments and Numerical Exploration

Symmetry, 2020

Symmetric in-plane compression of a pantographic lattice structure is modelled and simulated, and... more Symmetric in-plane compression of a pantographic lattice structure is modelled and simulated, and the results are compared to previously available experimental data. Said experimental results had shown a peculiar behaviour: depending on the fiber density, the deformed shape could present either one or two swellings under compression. The present article is a preliminary modelling attempt aiming at capturing that behaviour numerically.

Optical and structural properties of metalorganic-vapor-phase-epitaxy-grown InAs quantum wells and quantum dots in InP

Physical Review B, 1993

Origin of sharp lines in photoluminescence emission from submonolayers of InAs in GaAs

Physical Review B, 1997

Very sharp and intense low-temperature photoluminescence ͑PL͒ emission is reported from submonola... more Very sharp and intense low-temperature photoluminescence ͑PL͒ emission is reported from submonolayers of InAs in GaAs grown by flow modulation epitaxy at 50 Torr using trimethylindium and tertiarybutylarsine. InAs coverages from 0.25 to 1.0 monolayers were systematically studied using low temperature PL, and photoluminescence excitation spectroscopy and temperature-dependent, time-resolved PL. The observed PL linewidths and energies are satisfactorily explained within a two-dimensional ͑2D͒ quantum well picture over all coverages. In these ultrathin structures we see confirmation of existing models which predict a smooth transition of the PL linewidth to zero in the limit of extremely thin wells. The possibility of weak 0D localization of excitons by thickness variations in the submonolayer samples is discussed. ͓S0163-1829͑97͒06407-2͔

Phase separation in bulk InGaN and quantum wells grown by low pressure MOCVD

1997 Digest of the IEEE/LEOS Summer Topical Meeting: Vertical-Cavity Lasers/Technologies for a Global Information Infrastructure/WDM Components Technology/Advanced Semiconductor Lasers and Applications/Gallium Nitride Materials, Processing, and Devices (C

We have grown high quality InGaN layers and InGaN/GaN multiple quantum wells for blue LED applica... more We have grown high quality InGaN layers and InGaN/GaN multiple quantum wells for blue LED applications. The degree of phase segregation of InGaN in bulk InGaN layers depends on the TMI and TMG flow rates as well as the growth temperature. Even for films without indium droplets on the surface, X-ray diffraction (XRD) reveals the coexistence of different indium compositions

An Investigation of Breakdown Mechanisms in Al(GaN) MSM Photodetectors

Materials Science Forum, 1998

Optical Properties of GaN Films Grown on SiC/Si

Materials Science Forum, 1998

Effective heat dissipation and higher light extraction efficiency of GaN vertical light emitting diodes for solid state lighting applications

physica status solidi c, 2009

Vertical sapphire‐free GaN based LEDs (VLEDs) on metal have shown much better performance and pro... more Vertical sapphire‐free GaN based LEDs (VLEDs) on metal have shown much better performance and prove to deliver an efficiency much higher than most conventional light source. In this paper we show that in addition to many advantages of VLEDs over conventional LEDs in terms of better current spreading, low operation voltage, higher drive current density, faster heat dissipation, VLEDs also enables top surface engineering for efficient light extraction to further light output. High power white LED having efficiency of 110 lumen/watt was achieved through a combination of surface engineering and optimization of the n‐GaN layer thickness underneath the corrugated pyramids surface. The low operation junction temperature of VLEDs demonstrates excellent heat dissipation capabilities. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Slow Spin Relaxation Observed in InGaN/GaN Multiple Quantum Wells

physica status solidi (b), 1999

... B., Scalbert, D., Tran, C., Karlicek, R. and Lascaray, J.-P. (1999), Slow Spin Relaxation Obs... more

Mass Production of High Brightness Blue and Green LEDs by MOCVD

physica status solidi (a), 1999

As more advances are made in the performance of GaN-based devices, a trend toward the use of larg... more As more advances are made in the performance of GaN-based devices, a trend toward the use of large-scale MOCVD reactors for epitaxial growth of GaN-based device structures is clear. In this paper we describe the use of Emcore's SpectraBlue TM reactor for large-scale manufacturing of blue and green LEDs. The high throughput growth of GaN-based LEDs is demonstrated without compromising LED uniformity or overall performance. In-situ control of key parameters critical to the production of high quality LEDs, such as buffer layer growth is now feasible using in-situ reflectance spectroscopy. Film properties as well as LED device performance are discussed.

GaN and AlGaN metal–semiconductor–metal photodetectors

Materials Science and Engineering: B, 1997

GaN based interdigital metal-semiconductor-metal (MSM) photodetectors have been successfully fabr... more GaN based interdigital metal-semiconductor-metal (MSM) photodetectors have been successfully fabricated. The MSM structures were patterned on highly resistive GaN and the ternary compound, AlGaN. For the highly resistive GaN detector, the lowest dark current is 0.1 nA and the UV responsivity of the device was about 460 A W − 1 at a DC bias of 5 V. The AlGaN with 24% Al exhibited larger gains of up to 10 6 A W − 1 at 20 V, but at a very high dark current, 1 mA, and very long detector responses, greater than 60 s. The high gain in this device is not well understood. The preliminary measurements indicate that tunneling occurs at high electric fields since a negative temperature coefficient for the breakdown voltage was observed.

Time-resolved laser spectroscopy of nitride semiconductors

Materials Science and Engineering: B, 1999

We present time-resolved photoluminescence measurements of InGaN MQWs, films, and LEDs.

Reproducibility of GaN and InGaN films grown in a multi-wafer rotating-disc reactor

Materials Science and Engineering: B, 1997

Photoluminescence and raman scattering characterization of silicon-doped In0.52Al0.48As grown on InP (100) substrates by molecular beam epitaxy

Journal of Electronic Materials, 1996

Growth of In0.52Al0.48As epilayers on InP (100) substrates by molecular beam epitaxy at different... more Growth of In0.52Al0.48As epilayers on InP (100) substrates by molecular beam epitaxy at different silicon doping levels is carried out. The doped samples show an inverted S-shaped dependence of the PL peak energy variation with the temperature which weakens at high doping levels due to a possible reduction in the donor binding energy. There is a reduction in both the

Atomic layer epitaxy of InAs using tertiarybutylarsine

Journal of Electronic Materials, 1995

Characterization of very high purity InAs grown using trimethylindium and tertiarybutylarsine

Journal of Electronic Materials, 1995

Structural properties of GaN grown by MOVPE turbodisc mass-production reactor

Journal of Crystal Growth, 1997

The structural properties of GaN films grown on sapphire in a turbodisc multiwafer reactor have b... more The structural properties of GaN films grown on sapphire in a turbodisc multiwafer reactor have been investigated using high-resolution X-ray diffraction and transmission electron microscopy. We found that the line shape of the (0 0 2) rocking curve can be fitted with two peaks. Therefore, we suggest that the GaN films consist of two layers: one related to extended structural

Một số kinh nghiệm trong ứng dụng trình quản lý lớp học trực tuyến moodle cho các khoá đào tạo, bồi dưỡng ngắn hạn (qua thực tiễn Trường Đại học Quy Nhơn)

Dong Thap University Journal of Science

Bài viết phản ánh thực tiễn ứng dụng trình quản lý lớp học trực tuyến Moodle trong các khoá đào t... more Bài viết phản ánh thực tiễn ứng dụng trình quản lý lớp học trực tuyến Moodle trong các khoá đào tạo, bồi dưỡng thuộc Đề án Ngoại ngữ Quốc gia 2020 tại Trường Đại học Quy Nhơn. Qua thực tế, chúng tôi nhận thấy Moodle với các tính năng tối ưu cho hình thức đào tạo, bồi dưỡng trực tuyến hoặc tích hợp cho thấy tính hiệu quả cả về truyền đạt nội dung, tiết kiệm thời gian, kinh phí và tính kết nối cộng đồng nghề nghiệp sau khoá học. Tuy nhiên, đơn vị đào tạo cần đầu tư cho cơ sở hạ tầng công nghệ và bồi dưỡng đội ngũ quản trị viên, giảng viên trực tiếp giảng dạy để đạt hiệu quả tích hợp cao nhất.

Proposing to improve the Heuristic Algorithms to Solve a Steiner-minimal-tree Problem in Large Size Sparse Graphs

Research and Development on Information and Communication Technology

Steiner Minimal Tree (SMT) is a combinatorial optimization problem that has many important applic... more Steiner Minimal Tree (SMT) is a combinatorial optimization problem that has many important applications in science and engineering; this is an NP-hard class problem. In recent decades, there have been a series of scientific papers published for solving the SMT problem based on the approaches of exact solutions (such as dynamic programming, branch and bound) and approximate solutions (such as heuristic algorithm, metaheuristic algorithm). This paper proposes an improvement for two heuristic algorithms PD-Steiner and SPT-Steiner to solve a SMT problem in large size sparse graphs with edge weight not exceeding 10 and verify this proposal on large-size sparse graphs up to 100000 vertices. These experimental results are useful information for further research on the SMT problem.

Solution of a paradox related to the rigid bar pull-out problem in standard elasticity

Mechanics Research Communications

International Conference on Nonlinear Solid Mechanics 2019: General Topics and Review of Plenary Lectures

Developments and Novel Approaches in Nonlinear Solid Body Mechanics, 2020

The International Conference on Nonlinear Solid Mechanics (ICoN-SoM) 2019, held in Rome from June... more The International Conference on Nonlinear Solid Mechanics (ICoN-SoM) 2019, held in Rome from June 16th through 19th of 2019, had as its main goal to gather together researchers in the field of nonlinear Solid Mechanics in a stimulating research environment. This work accounts for the plenary lectures held during the conference. It is mainly aimed at providing interested researchers with a track of the contents discussed during the conference and with the relevant bibliography of the plenary lectures. Additional information, such as the abstracts of all the talks, can be found on the official web-site of the conference: http://www.memocsevents.eu/iconsom2019.

Symmetric-in-Plane Compression of Polyamide Pantographic Fabrics—Modelling, Experiments and Numerical Exploration

Symmetry, 2020

Symmetric in-plane compression of a pantographic lattice structure is modelled and simulated, and... more Symmetric in-plane compression of a pantographic lattice structure is modelled and simulated, and the results are compared to previously available experimental data. Said experimental results had shown a peculiar behaviour: depending on the fiber density, the deformed shape could present either one or two swellings under compression. The present article is a preliminary modelling attempt aiming at capturing that behaviour numerically.

Optical and structural properties of metalorganic-vapor-phase-epitaxy-grown InAs quantum wells and quantum dots in InP

Physical Review B, 1993

Origin of sharp lines in photoluminescence emission from submonolayers of InAs in GaAs

Physical Review B, 1997

Very sharp and intense low-temperature photoluminescence ͑PL͒ emission is reported from submonola... more Very sharp and intense low-temperature photoluminescence ͑PL͒ emission is reported from submonolayers of InAs in GaAs grown by flow modulation epitaxy at 50 Torr using trimethylindium and tertiarybutylarsine. InAs coverages from 0.25 to 1.0 monolayers were systematically studied using low temperature PL, and photoluminescence excitation spectroscopy and temperature-dependent, time-resolved PL. The observed PL linewidths and energies are satisfactorily explained within a two-dimensional ͑2D͒ quantum well picture over all coverages. In these ultrathin structures we see confirmation of existing models which predict a smooth transition of the PL linewidth to zero in the limit of extremely thin wells. The possibility of weak 0D localization of excitons by thickness variations in the submonolayer samples is discussed. ͓S0163-1829͑97͒06407-2͔

Phase separation in bulk InGaN and quantum wells grown by low pressure MOCVD

1997 Digest of the IEEE/LEOS Summer Topical Meeting: Vertical-Cavity Lasers/Technologies for a Global Information Infrastructure/WDM Components Technology/Advanced Semiconductor Lasers and Applications/Gallium Nitride Materials, Processing, and Devices (C

We have grown high quality InGaN layers and InGaN/GaN multiple quantum wells for blue LED applica... more We have grown high quality InGaN layers and InGaN/GaN multiple quantum wells for blue LED applications. The degree of phase segregation of InGaN in bulk InGaN layers depends on the TMI and TMG flow rates as well as the growth temperature. Even for films without indium droplets on the surface, X-ray diffraction (XRD) reveals the coexistence of different indium compositions

An Investigation of Breakdown Mechanisms in Al(GaN) MSM Photodetectors

Materials Science Forum, 1998

Optical Properties of GaN Films Grown on SiC/Si

Materials Science Forum, 1998

Effective heat dissipation and higher light extraction efficiency of GaN vertical light emitting diodes for solid state lighting applications

physica status solidi c, 2009

Vertical sapphire‐free GaN based LEDs (VLEDs) on metal have shown much better performance and pro... more Vertical sapphire‐free GaN based LEDs (VLEDs) on metal have shown much better performance and prove to deliver an efficiency much higher than most conventional light source. In this paper we show that in addition to many advantages of VLEDs over conventional LEDs in terms of better current spreading, low operation voltage, higher drive current density, faster heat dissipation, VLEDs also enables top surface engineering for efficient light extraction to further light output. High power white LED having efficiency of 110 lumen/watt was achieved through a combination of surface engineering and optimization of the n‐GaN layer thickness underneath the corrugated pyramids surface. The low operation junction temperature of VLEDs demonstrates excellent heat dissipation capabilities. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Slow Spin Relaxation Observed in InGaN/GaN Multiple Quantum Wells

physica status solidi (b), 1999

... B., Scalbert, D., Tran, C., Karlicek, R. and Lascaray, J.-P. (1999), Slow Spin Relaxation Obs... more

Mass Production of High Brightness Blue and Green LEDs by MOCVD

physica status solidi (a), 1999

As more advances are made in the performance of GaN-based devices, a trend toward the use of larg... more As more advances are made in the performance of GaN-based devices, a trend toward the use of large-scale MOCVD reactors for epitaxial growth of GaN-based device structures is clear. In this paper we describe the use of Emcore's SpectraBlue TM reactor for large-scale manufacturing of blue and green LEDs. The high throughput growth of GaN-based LEDs is demonstrated without compromising LED uniformity or overall performance. In-situ control of key parameters critical to the production of high quality LEDs, such as buffer layer growth is now feasible using in-situ reflectance spectroscopy. Film properties as well as LED device performance are discussed.

GaN and AlGaN metal–semiconductor–metal photodetectors

Materials Science and Engineering: B, 1997

GaN based interdigital metal-semiconductor-metal (MSM) photodetectors have been successfully fabr... more GaN based interdigital metal-semiconductor-metal (MSM) photodetectors have been successfully fabricated. The MSM structures were patterned on highly resistive GaN and the ternary compound, AlGaN. For the highly resistive GaN detector, the lowest dark current is 0.1 nA and the UV responsivity of the device was about 460 A W − 1 at a DC bias of 5 V. The AlGaN with 24% Al exhibited larger gains of up to 10 6 A W − 1 at 20 V, but at a very high dark current, 1 mA, and very long detector responses, greater than 60 s. The high gain in this device is not well understood. The preliminary measurements indicate that tunneling occurs at high electric fields since a negative temperature coefficient for the breakdown voltage was observed.

Time-resolved laser spectroscopy of nitride semiconductors

Materials Science and Engineering: B, 1999

We present time-resolved photoluminescence measurements of InGaN MQWs, films, and LEDs.

Reproducibility of GaN and InGaN films grown in a multi-wafer rotating-disc reactor

Materials Science and Engineering: B, 1997

Photoluminescence and raman scattering characterization of silicon-doped In0.52Al0.48As grown on InP (100) substrates by molecular beam epitaxy

Journal of Electronic Materials, 1996

Growth of In0.52Al0.48As epilayers on InP (100) substrates by molecular beam epitaxy at different... more Growth of In0.52Al0.48As epilayers on InP (100) substrates by molecular beam epitaxy at different silicon doping levels is carried out. The doped samples show an inverted S-shaped dependence of the PL peak energy variation with the temperature which weakens at high doping levels due to a possible reduction in the donor binding energy. There is a reduction in both the

Atomic layer epitaxy of InAs using tertiarybutylarsine

Journal of Electronic Materials, 1995

Characterization of very high purity InAs grown using trimethylindium and tertiarybutylarsine

Journal of Electronic Materials, 1995

Structural properties of GaN grown by MOVPE turbodisc mass-production reactor

Journal of Crystal Growth, 1997

The structural properties of GaN films grown on sapphire in a turbodisc multiwafer reactor have b... more The structural properties of GaN films grown on sapphire in a turbodisc multiwafer reactor have been investigated using high-resolution X-ray diffraction and transmission electron microscopy. We found that the line shape of the (0 0 2) rocking curve can be fitted with two peaks. Therefore, we suggest that the GaN films consist of two layers: one related to extended structural