1,598 research outputs found
Improving Prediction Quality in Collaborative Filtering Based on Clustering
In this paper we present the recommender systems that use the k-means clustering method in order to solve the problems associated with neighbor selection. The first method is to solve the problem in which customers belong to different clusters due to the distance-based characteristics despite the fact that they are similar customers, by properly converting data before performing clustering. The second method explains the k-prototype algorithm performing clus-tering by expanding not only the numeric data but also the categorical data. The experimental results show that better prediction quality can be obtained when both methods are used together. 1
3D Teeth Reconstruction from Panoramic Radiographs using Neural Implicit Functions
Panoramic radiography is a widely used imaging modality in dental practice
and research. However, it only provides flattened 2D images, which limits the
detailed assessment of dental structures. In this paper, we propose Occudent, a
framework for 3D teeth reconstruction from panoramic radiographs using neural
implicit functions, which, to the best of our knowledge, is the first work to
do so. For a given point in 3D space, the implicit function estimates whether
the point is occupied by a tooth, and thus implicitly determines the boundaries
of 3D tooth shapes. Firstly, Occudent applies multi-label segmentation to the
input panoramic radiograph. Next, tooth shape embeddings as well as tooth class
embeddings are generated from the segmentation outputs, which are fed to the
reconstruction network. A novel module called Conditional eXcitation (CX) is
proposed in order to effectively incorporate the combined shape and class
embeddings into the implicit function. The performance of Occudent is evaluated
using both quantitative and qualitative measures. Importantly, Occudent is
trained and validated with actual panoramic radiographs as input, distinct from
recent works which used synthesized images. Experiments demonstrate the
superiority of Occudent over state-of-the-art methods.Comment: 12 pages, 2 figures, accepted to International Conference on Medical
Image Computing and Computer-Assisted Intervention MICCAI 202
Irreversible extinction of ferroelectric polarization in P(VDF-TrFE) thin films upon melting and recrystallization
We observed the irreversible extinction of ferroelectric polarization in spun coated poly(vinylidene fluoride-co-trifluoroethylene) thin films upon melting and recrystallization. We investigate the alteration of the ferroelectric properties correlated with the preferred polymer crystal orientation with respect to the electrodes using grazing incident scattering, spectroscopy, and electron microscopes. Heat treatment above melting point gave rise to the significant reduction of the ferroelectric performance mainly caused by the modification of molecular orientation of polymer crystals whose c and b axes are perpendicular and parallel to the electrode surface, respectively, leading to almost zero effective electric field. (c) 2006 American Institute of Physicsopen464
Phenylalanine ammonia-lyase expression and pyranocoumarin accumulation in Angelica gigas plantlets exposed to light-emitting diodes
Angelica gigas (Dang Gui) is an important medicinal plant. In this study, we examined the accumulation of pyranocoumarin (decursin and decursinol angelate) and the expression of phenylalanine ammonia-lyase (PAL) in Korean angelica plantlet grown under different light-emitting diodes (LEDs) (red, orange, green, blue, and white). Three weeks after LED exposure (WAE), the transcript levels of phenylalanine ammonia-lyase mRNA in seedlings grown under orange LEDs were 4-, 18-, and 7-fold higher than those in seedlings grown under green, blue, and white LEDs, respectively. The decursinol angelate content was almost double than the decursin content. The highest levels of decursin (3.2 mg/g dry weight) and decursinol angelate (6 mg/g dry weight) were detected in plants grown under orange LEDs, at 2 WAE. Therefore, we suggest that orange LEDs may affect decursin and decursinol angelate accumulation. The findings of this study could help to determine an effective strategy for producing secondary metabolites in A. gigas using LED technology
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Fabrication of Complex 3D Micro-Scale Scaffolds and Drug Delivery Devices using Dynamic Mask Projection Microstereolithography
Microstereolithography (μSL) technology can fabricate three-dimensional (3D) tissue
engineered scaffolds with controlled biochemical and mechanical micro-architectures. A
μSL system for tissue engineering was developed using a Digital Micromirror Device
(DMDTM) for dynamic pattern generation and an ultraviolet (UV) lamp filtered at 365 nm for
crosslinking the photoreactive polymer solution. The μSL system was designed with x-y
resolution of ~2 μm and a vertical (z) resolution of ~1 μm. To demonstrate the use of μSL in
tissue engineering, poly(propylene fumarate) (PPF) was synthesized with a molecular weight
of ~1200 Da. The viscosity of the PPF was reduced to ~150 cP (at 50 o
C) by mixing with
diethyl fumarate (DEF) in the ratio of 7:3 (w/w). Finally, ~2 % (w/w) of (bis(2,4,6-
trimethylbenzoyl) phenylphosphine oxide (BAPO) was added to the solution to serve as a
photoinitiator. Cure depth experiments were performed to determine the curing
characteristics of the synthesized PPF, and the resulting system and photopolymer were used
to construct a variety of 3D porous scaffolds with interconnected pores between 100 and 150
μm and a micro-needle array with height of ~800 μm and individual tip diameters of ~20 μm.
SEM and microscope images of the micro-architectures illustrate that the developed μSL
system is a promising technology for producing biodegradable and biocompatible
microstructures.Mechanical Engineerin
Improvement of Mechanical Properties of UV-curable Resin for High-aspect Ratio Microstructures Fabricated in Microstereolithography
Recently, microstructures fabricated using microstereolithography technology have been used in the biological, medical and mechanical fields. Microstereolithography can fabricate real 3D microstructures with fine features, although there is presently a limited number of materials available for use in the process. Deformation of the fine features on a fabricated microstructure remains a critical issue for successful part fabrication, and part deformation can occur during rinsing or during fabrication as a result of fluid flow forces that occur during movement of mechanical parts of the system. Deformation can result in failure to fabricate a particular feature by breaking the feature completely, spatial deflection of the feature, or attaching the feature to neighboring microstructures. To improve mechanical strength of fabricated microstructures, a clay nanocomposite can be used. In particular, a high-aspect ratio microstructure can be fabricated without distortion using photocurable liquid resin containing a clay nanocomposite. In this paper, a clay nanocomposite was blended with a photocurable liquid resin to solve the deformation problem that occurs during fabrication and rinsing. An optimal mixture ratio of a clay nanocomposite was found through tensile testing and the minimal allowable distance between microstructures was found through fabrication experimentation. Finally, using these results, high-aspect ratio microstructures were fabricated using a clay nanocomposite resin without distortion
Total Gastrectomy in Gastric Conduit Cancer
We report a very rare case of surgery on gastric conduit cancer. A 67-year-old male patient underwent esophagectomy and intrathoracic esophagogastrostomy for squamous cell carcinoma of the lower thoracic esophagus 27 months ago. Upon follow-up, a gastric carcinoma at the intra-abdominal part of the gastric conduit was found on an esophagogastroduodenoscopy. We performed total gastrectomy and esophagocolonojejunostomy in the manner of Roux-en-Y anastomosis. The postoperative course was not eventful and an esophagogram on the 10th postoperative day showed no leakage or stenosis of the passage. The patient was discharged on the 17th day with no complications
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