Publications by authors named "Jeongwon Lee"

18 Publications

  • Page 1 of 1

Effect of hyperspectral image-based initial conditions on improving short-term algal simulation of hydrodynamic and water quality models.

J Environ Manage 2021 Sep 12;294:112988. Epub 2021 Jun 12.

School of Civil and Environmental Engineering, Konkuk University, Seoul 05029, Republic of Korea. Electronic address:

Hydrodynamic and water quality modeling have provided valuable simulation results that have enhanced the understanding of the spatial and temporal distribution of algal blooms. Typical model simulations are performed with point-based observational data that are used to configure initial and boundary conditions, and for parameter calibration. However, the application of such conventional modeling approaches is limited due to cost, labor, and time constraints that preclude the retrieval of high-resolution spatial data. Thus, the present study applied fine-resolution algal data to configure the initial conditions of a hydrodynamic and water quality model and compared the accuracy of short-term algal simulations with the results simulated using conventional point-based initial conditions. The environmental fluid dynamics code (EFDC) model was calibrated to simulate Chlorophyll-a (Chl-a) concentrations. Hyperspectral images were used to generate Chl-a maps based on a two-band ratio algorithm for configuring the initial condition of the EFDC model. The model simulation with hyperspectral-based initial conditions returned relatively accurate results for Chl-a, compared to the simulation based on point-based initial conditions. The simulations exhibited percent bias values of 9.93 and 14.23, respectively. Therefore, the results of this study demonstrate how hyperspectral-based initial conditions could improve the reliability of short-term algal bloom simulations in a hydrodynamic model.
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http://dx.doi.org/10.1016/j.jenvman.2021.112988DOI Listing
September 2021

Heuristic machinery for thermodynamic studies of SU(N) fermions with neural networks.

Nat Commun 2021 Mar 31;12(1):2011. Epub 2021 Mar 31.

Department of Physics, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China.

The power of machine learning (ML) provides the possibility of analyzing experimental measurements with a high sensitivity. However, it still remains challenging to probe the subtle effects directly related to physical observables and to understand physics behind from ordinary experimental data using ML. Here, we introduce a heuristic machinery by using machine learning analysis. We use our machinery to guide the thermodynamic studies in the density profile of ultracold fermions interacting within SU(N) spin symmetry prepared in a quantum simulator. Although such spin symmetry should manifest itself in a many-body wavefunction, it is elusive how the momentum distribution of fermions, the most ordinary measurement, reveals the effect of spin symmetry. Using a fully trained convolutional neural network (NN) with a remarkably high accuracy of ~94% for detection of the spin multiplicity, we investigate how the accuracy depends on various less-pronounced effects with filtered experimental images. Guided by our machinery, we directly measure a thermodynamic compressibility from density fluctuations within the single image. Our machine learning framework shows a potential to validate theoretical descriptions of SU(N) Fermi liquids, and to identify less-pronounced effects even for highly complex quantum matter with minimal prior understanding.
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http://dx.doi.org/10.1038/s41467-021-22270-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8012572PMC
March 2021

REDD1 Is Involved in Amyloid β-Induced Synaptic Dysfunction and Memory Impairment.

Int J Mol Sci 2020 Dec 13;21(24). Epub 2020 Dec 13.

Department of Health Sciences, The Graduate School of Dong-A University, Dong-A University, Busan 49315, Korea.

Alzheimer's disease (AD) is a neurodegenerative disease characterized by neurological dysfunction, including memory impairment, attributed to the accumulation of amyloid β (Aβ) in the brain. Although several studies reported possible mechanisms involved in Aβ pathology, much remains unknown. Previous findings suggested that a protein regulated in development and DNA damage response 1 (REDD1), a stress-coping regulator, is an Aβ-responsive gene involved in Aβ cytotoxicity. However, we still do not know how Aβ increases the level of REDD1 and whether REDD1 mediates Aβ-induced synaptic dysfunction. To elucidate this, we examined the effect of Aβ on REDD1-expression using acute hippocampal slices from mice, and the effect of REDD1 short hairpin RNA (shRNA) on Aβ-induced synaptic dysfunction. Lastly, we observed the effect of REDD1 shRNA on memory deficit in an AD-like mouse model. Through the experiments, we found that Aβ-incubated acute hippocampal slices showed increased REDD1 levels. Moreover, Aβ injection into the lateral ventricle increased REDD1 levels in the hippocampus. Anisomycin, but not actinomycin D, blocked Aβ-induced increase in REDD1 levels in the acute hippocampal slices, suggesting that Aβ may increase REDD1 translation rather than transcription. Aβ activated Fyn/ERK/S6 cascade, and inhibitors for Fyn/ERK/S6 or mGluR5 blocked Aβ-induced REDD1 upregulation. REDD1 inducer, a transcriptional activator, and Aβ blocked synaptic plasticity in the acute hippocampal slices. REDD1 inducer inhibited mTOR/Akt signaling. REDD1 shRNA blocked Aβ-induced synaptic deficits. REDD1 shRNA also blocked Aβ-induced memory deficits in passive-avoidance and object-recognition tests. Collectively, these results demonstrate that REDD1 participates in Aβ pathology and could be a target for AD therapy.
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http://dx.doi.org/10.3390/ijms21249482DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7763153PMC
December 2020

Akt and calcium-permeable AMPA receptor are involved in the effect of pinoresinol on amyloid β-induced synaptic plasticity and memory deficits.

Biochem Pharmacol 2021 02 11;184:114366. Epub 2020 Dec 11.

Department of Health Sciences, The Graduate School of Dong-A University, Busan 49315, Republic of Korea; Laboratory of Anti-viral Drug Discovery, Dong-A University, Busan, Republic of Korea; Institute of Convergence Bio-Health, Dong-A University, Busan, Republic of Korea. Electronic address:

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative disorders characterized by memory deficits. Although no drug has given promising results, synaptic dysfunction-modulating agents might be considered potential candidates for alleviating this disorder. Pinoresinol, a lignan found in Forsythia suspensa, is a memory-enhancing agent with excitatory synaptic activation. In the present study, we tested whether pinoresinol reduces learning and memory and excitatory synaptic deficits in an amyloid β (Aβ)-induced AD-like mouse model. Pinoresinol enhanced hippocampal long-term potentiation (LTP) through calcium-permeable AMPA receptor, which was mediated by Akt activation. Moreover, pinoresinol ameliorated LTP deficits in amyloid β (Aβ)-treated hippocampal slices via Akt signaling. Oral administration of pinoresinol ameliorated Aβ-induced memory deficits without sensory dysfunction. Moreover, AD-like pathology, including neuroinflammation and synaptic deficit, were ameliorated by pinoresinol administration. Collectively, pinoresinol may be a good candidate for AD therapy by modulating synaptic functions.
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http://dx.doi.org/10.1016/j.bcp.2020.114366DOI Listing
February 2021

How to Dress Radio-Frequency Photons with Tunable Momentum.

Phys Rev Lett 2019 Jul;123(3):033203

Research Laboratory of Electronics, MIT-Harvard Center for Ultracold Atoms, Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

We demonstrate how the combination of oscillating magnetic forces and radio-frequency (rf) pulses endows rf photons with tunable momentum. We observe velocity-selective spin-flip transitions and the associated Doppler shift. Recoil-dressed photons are a promising tool for measurements and quantum simulations, including the realization of gauge potentials and spin-orbit coupling schemes which do not involve optical transitions.
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http://dx.doi.org/10.1103/PhysRevLett.123.033203DOI Listing
July 2019

Evidence of a turbulent ExB mixing avalanche mechanism of gas breakdown in strongly magnetized systems.

Nat Commun 2018 08 30;9(1):3523. Epub 2018 Aug 30.

Department of Nuclear Engineering, Seoul National University, Seoul, 08826, Republic of Korea.

Although gas breakdown phenomena have been intensively studied over 100 years, the breakdown mechanism in a strongly magnetized system, such as tokamak, has been still obscured due to complex electromagnetic topologies. There has been a widespread misconception that the conventional breakdown model of the unmagnetized system can be directly applied to the strongly magnetized system. However, we found clear evidence that existing theories cannot explain the experimental results. Here, we demonstrate the underlying mechanism of gas breakdown in tokamaks, a turbulent ExB mixing avalanche, which systematically considers multi-dimensional plasma dynamics in the complex electromagnetic topology. This mechanism clearly elucidates the experiments by identifying crucial roles of self-electric fields produced by space-charge that decrease the plasma density growth rate and cause a dominant transport via ExB drifts. A comprehensive understanding of plasma dynamics in complex electromagnetic topology provides general design strategy for robust breakdown scenarios in a tokamak fusion reactor.
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http://dx.doi.org/10.1038/s41467-018-05839-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6117305PMC
August 2018

A high-efficiency regime for gas-phase terahertz lasers.

Proc Natl Acad Sci U S A 2018 06 11;115(26):6614-6619. Epub 2018 Jun 11.

Department of Physics, Duke University, Durham, NC 27708;

We present both an innovative theoretical model and an experimental validation of a molecular gas optically pumped far-infrared (OPFIR) laser at 0.25 THz that exhibits 10× greater efficiency (39% of the Manley-Rowe limit) and 1,000× smaller volume than comparable commercial lasers. Unlike previous OPFIR-laser models involving only a few energy levels that failed even qualitatively to match experiments at high pressures, our ab initio theory matches experiments quantitatively, within experimental uncertainties with no free parameters, by accurately capturing the interplay of millions of degrees of freedom in the laser. We show that previous OPFIR lasers were inefficient simply by being too large and that high powers favor high pressures and small cavities. We believe that these results will revive interest in OPFIR laser as a powerful and compact source of terahertz radiation.
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http://dx.doi.org/10.1073/pnas.1803261115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6042148PMC
June 2018

Physicochemical study of ascorbic acid 2-glucoside loaded hyaluronic acid dissolving microneedles irradiated by electron beam and gamma ray.

Carbohydr Polym 2018 Jan 13;180:297-303. Epub 2017 Oct 13.

Department of Biotechnology, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea; Juvic Inc., Yonsei Engineering Research Park, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea. Electronic address:

A dissolving microneedle (DMN) patch encapsulated with ascorbic acid 2-glucoside (AA2G) in a needle-shaped hyaluronic acid (HA) backbone was fabricated and sterilized by electron beam (e-beam, 5-40kGy) and gamma ray (γ-ray, 5-30kGy). DMN structures maintained their morphologies and fracture force regardless of e-beam and γ-ray irradiation doses. Both e-beam (40kGy) and γ-ray (20 and 30kGy) met the product sterility requirements for cosmetics and vaccines; however, γ-ray irradiation significantly degraded the encapsulated AA2G, while e-beam maintained AA2G activity. Thus, an e-beam dose of 40kGy, which satisfied the sterility requirements without loss of AA2G, is suitable for terminal sterilization of DMNs. Moreover, we confirmed that the optimized irradiation (e-beam, 40kGy) did not affect dissolution rate and drug release profile of DMNs. Further, we confirmed that HA, the backbone polymer of DMNs, could be utilized as a stabilizer that inhibits degradation of encapsulated AA2G by irradiation. This detailed analysis can be developed further to optimize various biological drugs in transdermal drug delivery systems.
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http://dx.doi.org/10.1016/j.carbpol.2017.10.044DOI Listing
January 2018

A stripe phase with supersolid properties in spin-orbit-coupled Bose-Einstein condensates.

Nature 2017 03;543(7643):91-94

1Department of Physics, MIT-Harvard Center for Ultracold Atoms, and Research Laboratory of Electronics, MIT, Cambridge, Massachusetts 02139, USA.

Supersolidity combines superfluid flow with long-range spatial periodicity of solids, two properties that are often mutually exclusive. The original discussion of quantum crystals and supersolidity focused on solid He and triggered extensive experimental efforts that, instead of supersolidity, revealed exotic phenomena including quantum plasticity and mass supertransport. The concept of supersolidity was then generalized from quantum crystals to other superfluid systems that break continuous translational symmetry. Bose-Einstein condensates with spin-orbit coupling are predicted to possess a stripe phase with supersolid properties. Despite several recent studies of the miscibility of the spin components of such a condensate, the presence of stripes has not been detected. Here we observe the predicted density modulation of this stripe phase using Bragg reflection (which provides evidence for spontaneous long-range order in one direction) while maintaining a sharp momentum distribution (the hallmark of superfluid Bose-Einstein condensates). Our work thus establishes a system with continuous symmetry-breaking properties, associated collective excitations and superfluid behaviour.
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http://dx.doi.org/10.1038/nature21431DOI Listing
March 2017

Spin-Orbit Coupling and Spin Textures in Optical Superlattices.

Phys Rev Lett 2016 Oct 27;117(18):185301. Epub 2016 Oct 27.

Research Laboratory of Electronics, MIT-Harvard Center for Ultracold Atoms, Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

We propose and demonstrate a new approach for realizing spin-orbit coupling with ultracold atoms. We use orbital levels in a double-well potential as pseudospin states. Two-photon Raman transitions between left and right wells induce spin-orbit coupling. This scheme does not require near resonant light, features adjustable interactions by shaping the double-well potential, and does not depend on special properties of the atoms. A pseudospinor Bose-Einstein condensate spontaneously acquires an antiferromagnetic pseudospin texture, which breaks the lattice symmetry similar to a supersolid.
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http://dx.doi.org/10.1103/PhysRevLett.117.185301DOI Listing
October 2016

Durable superhydrophilic/phobic surfaces based on green patina with corrosion resistance.

Phys Chem Chem Phys 2015 Mar;17(10):6786-93

Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang, Gyeongbuk 790-784, Republic of Korea.

Special wetting surfaces with superhydrophilicity or superhydrophobicity have attracted great interest because of their potential for practical applications. However, since the special wetting surface may be used in a severe environment, including polluted air and seawater, it is necessary to develop a durable special wetting surface with excellent corrosion-resistance. Here, we report a new strategy for robust superhydrophilic or superhydrophobic green patina surfaces on copper substrates with superior corrosion resistance and adhesion strength, which have great potential for treating marine pollution. The as-prepared surfaces exhibited superhydrophilicity with underwater superoleophobicity or superoleophilicity with under-oil superhydrophobicity, which allowed them to selectively separate oil and water with high efficiency. More importantly, the surface displayed not only good mechanical stability but also chemical stability in corrosive liquids owing to the intrinsic properties of the patina and hydrophobic coating. Furthermore, the surface can be utilized as coating material for the decoration of building exteriors and prevention from surface fouling. We believe that our proposed method would make it possible to develop engineering materials that require robust anti-fouling, anti-frost, and anti-corrosion properties in marine environments.
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http://dx.doi.org/10.1039/c4cp05590jDOI Listing
March 2015

Glioma grading using apparent diffusion coefficient map: application of histogram analysis based on automatic segmentation.

NMR Biomed 2014 Sep 7;27(9):1046-52. Epub 2014 Jul 7.

Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, South Korea; Medical Imaging Research Section, Electronics and Telecommunications Research Institute (ETRI), Daejeon, South Korea.

The accurate diagnosis of glioma subtypes is critical for appropriate treatment, but conventional histopathologic diagnosis often exhibits significant intra-observer variability and sampling error. The aim of this study was to investigate whether histogram analysis using an automatically segmented region of interest (ROI), excluding cystic or necrotic portions, could improve the differentiation between low-grade and high-grade gliomas. Thirty-two patients (nine low-grade and 23 high-grade gliomas) were included in this retrospective investigation. The outer boundaries of the entire tumors were manually drawn in each section of the contrast-enhanced T1 -weighted MR images. We excluded cystic or necrotic portions from the entire tumor volume. The histogram analyses were performed within the ROI on normalized apparent diffusion coefficient (ADC) maps. To evaluate the contribution of the proposed method to glioma grading, we compared the area under the receiver operating characteristic (ROC) curves. We found that an ROI excluding cystic or necrotic portions was more useful for glioma grading than was an entire tumor ROI. In the case of the fifth percentile values of the normalized ADC histogram, the area under the ROC curve for the tumor ROIs excluding cystic or necrotic portions was significantly higher than that for the entire tumor ROIs (p < 0.005). The automatic segmentation of a cystic or necrotic area probably improves the ability to differentiate between high- and low-grade gliomas on an ADC map.
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http://dx.doi.org/10.1002/nbm.3153DOI Listing
September 2014

Fabricating centimeter-scale high quality factor two-dimensional periodic photonic crystal slabs.

Opt Express 2014 Feb;22(3):3724-31

We present a fabrication route for centimeter-scale two-dimensional defect-free photonic crystal slabs with quality factors bigger than 10,000 in the visible, together with a unique way to quantify their quality factors. We fabricate Si(3)N(4) photonic crystal slabs, and perform an angle-resolved reflection measurement. This measurement data is used to retrieve the quality factors of the slabs by fitting it to a model based on temporal coupled-mode theory. The macroscopic nature of the structure and the high quality factors of their resonances could open up new opportunities for realizing efficient macroscale optoelectronic devices such as sensors, lasers, and energy harvesting systems.
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http://dx.doi.org/10.1364/OE.22.003724DOI Listing
February 2014

Enabling enhanced emission and low-threshold lasing of organic molecules using special Fano resonances of macroscopic photonic crystals.

Proc Natl Acad Sci U S A 2013 Aug 5;110(34):13711-6. Epub 2013 Aug 5.

Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

The nature of light interaction with matter can be dramatically altered in optical cavities, often inducing nonclassical behavior. In solid-state systems, excitons need to be spatially incorporated within nanostructured cavities to achieve such behavior. Although fascinating phenomena have been observed with inorganic nanostructures, the incorporation of organic molecules into the typically inorganic cavity is more challenging. Here, we present a unique optofluidic platform comprising organic molecules in solution suspended on a photonic crystal surface, which supports macroscopic Fano resonances and allows strong and tunable interactions with the molecules anywhere along the surface. We develop a theoretical framework of this system and present a rigorous comparison with experimental measurements, showing dramatic spectral and angular enhancement of emission. We then demonstrate that these enhancement mechanisms enable lasing of only a 100-nm thin layer of diluted solution of organic molecules with substantially reduced threshold intensity, which has important implications for organic light-emitting devices and molecular sensing.
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http://dx.doi.org/10.1073/pnas.1311866110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3752230PMC
August 2013

Observation of trapped light within the radiation continuum.

Nature 2013 Jul;499(7457):188-91

Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

The ability to confine light is important both scientifically and technologically. Many light confinement methods exist, but they all achieve confinement with materials or systems that forbid outgoing waves. These systems can be implemented by metallic mirrors, by photonic band-gap materials, by highly disordered media (Anderson localization) and, for a subset of outgoing waves, by translational symmetry (total internal reflection) or by rotational or reflection symmetry. Exceptions to these examples exist only in theoretical proposals. Here we predict and show experimentally that light can be perfectly confined in a patterned dielectric slab, even though outgoing waves are allowed in the surrounding medium. Technically, this is an observation of an 'embedded eigenvalue'--namely, a bound state in a continuum of radiation modes--that is not due to symmetry incompatibility. Such a bound state can exist stably in a general class of geometries in which all of its radiation amplitudes vanish simultaneously as a result of destructive interference. This method to trap electromagnetic waves is also applicable to electronic and mechanical waves.
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http://dx.doi.org/10.1038/nature12289DOI Listing
July 2013

Observation and differentiation of unique high-Q optical resonances near zero wave vector in macroscopic photonic crystal slabs.

Phys Rev Lett 2012 Aug 8;109(6):067401. Epub 2012 Aug 8.

Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

We demonstrate and distinguish experimentally the existence of a special type of Fano resonances at k≈0 in a macroscopic two-dimensional photonic crystal slab. We fabricate a square lattice array of holes in a silicon nitride layer and perform an angular resolved spectral analysis of the various Fano resonances. We elucidate their radiation behavior using temporal coupled-mode theory and symmetry considerations. The unique simplicity of this system whereby an ultralong lifetime delocalized electromagnetic field can exist above the surface and consequently easily interact with added matter, provides exciting new opportunities for the study of light and matter interaction.
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http://dx.doi.org/10.1103/PhysRevLett.109.067401DOI Listing
August 2012

Evaluation of palatal bone density in adults and adolescents for application of skeletal anchorage devices.

Angle Orthod 2012 Jul 11;82(4):625-31. Epub 2011 Nov 11.

Department of Orthodontics, St. Vincent Hospital, The Catholic University of Korea, Seoul, South Korea.

Objectives: To measure the cortical and cancellous bone densities of the palatal area in adolescents and adults and to compare bone quality among placement sites of temporary anchorage devices.

Materials And Methods: One hundred twenty cone beam computerized tomography scans were obtained from 60 adolescents (mean age, 12.2 ± 1.9 years) and 60 adults (24.7 ± 4.9 years). The measurements of palatal bone density were made in Hounsfield units (HU) at 72 sites at the intersections of eight mediolateral and nine anterioposterior reference lines using InVivoDental software. Repeated-measures analysis of variance was used to analyze intragroup and intergroup differences.

Results: The cortical and cancellous bone densities in the adults (816 and 154 HU, respectively) were significantly higher than those in the adolescents (606 and 135 HU; P < .001 and P  =  .032, respectively). However, the anterior portion of the cortical bone in adolescents had similar density values to the posterior portion of the cortical bone in adults. Gender comparison revealed that females had greater cortical bone densities (769 HU) than their male counterparts did (654 HU; P < .001).

Conclusions: Palatal bone densities were significantly higher in adults than in adolescents, and the anterior palatal areas of adolescents were of similar values to those at the posterior palate of adults.
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http://dx.doi.org/10.2319/071311-445.1DOI Listing
July 2012

Three-dimensional visualization of human vocal organ on the web.

J Digit Imaging 2002 20;15 Suppl 1:264-6. Epub 2002 Mar 20.

3D Medical Imaging Laboratory, Clinical Research Institute, Seoul National University Hospital, Korea.

In the field of image technology, three-dimensional (3D) image display can give the intuitive information more efficiently. In medical science, 3D visualization is used for the purpose of education and diagnosis and is becoming increasingly more important. In this article, several structures of the larynx are visualized by 3D image and displayed on the Web to provide users an easy approach to the image. VRML is used on Web3D display because it is popular and easy to manipulate.
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http://dx.doi.org/10.1007/s10278-002-5050-9DOI Listing
August 2002