Thermal Dissipation Performance of a Heat Sink/Vapor Chamber Prepared by Metal Injection Molding Process

Chena Bor-Yuan,Hwang Kuen-Shyang 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1

In this study, copper vapor chambers with built-in cooling fins, which eliminated the soldered or brazed joints in the conventional vapor chamber, were fabricated using the metal injection molding process. The results show that with optimized molding parameters, fins with an aspect ratio up to 18 could be produced. After sintering, the densities of the fin and chamber reached 96%. With only 32 cooling fins and a small fan installed, the thermal resistance of the heat sink was 1.156 ℃/W, and the power dissipation was 40W when the junction temperature was 70℃. When copper powder was sintered onto the chamber to make a vapor chamber, the thermal resistance decreased to 1.046℃/W.

Synthesis of T2-weighted images from proton density images using a generative adversarial network in a temporomandibular joint magnetic resonance imaging protocol

Chena, Lee,Eun-Gyu, Ha,Yoon Joo, Choi,Kug Jin, Jeon,Sang-Sun, Han Korean Academy of Oral and Maxillofacial Radiology 2022 Imaging Science in Dentistry Vol.52 No.-

Purpose: This study proposed a generative adversarial network (GAN) model for T2-weighted image (WI) synthesis from proton density (PD)-WI in a temporomandibular joint(TMJ) magnetic resonance imaging (MRI) protocol. Materials and Methods: From January to November 2019, MRI scans for TMJ were reviewed and 308 imaging sets were collected. For training, 277 pairs of PD- and T2-WI sagittal TMJ images were used. Transfer learning of the pix2pix GAN model was utilized to generate T2-WI from PD-WI. Model performance was evaluated with the structural similarity index map (SSIM) and peak signal-to-noise ratio (PSNR) indices for 31 predicted T2-WI (pT2). The disc position was clinically diagnosed as anterior disc displacement with or without reduction, and joint effusion as present or absent. The true T2-WI-based diagnosis was regarded as the gold standard, to which pT2-based diagnoses were compared using Cohen's ĸ coefficient. Results: The mean SSIM and PSNR values were 0.4781(±0.0522) and 21.30(±1.51) dB, respectively. The pT2 protocol showed almost perfect agreement(ĸ=0.81) with the gold standard for disc position. The number of discordant cases was higher for normal disc position (17%) than for anterior displacement with reduction (2%) or without reduction (10%). The effusion diagnosis also showed almost perfect agreement(ĸ=0.88), with higher concordance for the presence (85%) than for the absence (77%) of effusion. Conclusion: The application of pT2 images for a TMJ MRI protocol useful for diagnosis, although the image quality of pT2 was not fully satisfactory. Further research is expected to enhance pT2 quality.

Synthesis of T2-weighted images from proton density images using a generative adversarial network in a temporomandibular joint magnetic resonance imaging protocol

Lee Chena,Ha Eun-Gyu,Choi Yoon Joo,Jeon Kug Jin,Han Sang-Sun 대한영상치의학회 2022 Imaging Science in Dentistry Vol.52 No.4

Purpose: This study proposed a generative adversarial network (GAN) model for T2-weighted image (WI) synthesis from proton density (PD)-WI in a temporomandibular joint (TMJ) magnetic resonance imaging (MRI) protocol. Materials and Methods: From January to November 2019, MRI scans for TMJ were reviewed and 308 imaging sets were collected. For training, 277 pairs of PD- and T2-WI sagittal TMJ images were used. Transfer learning of the pix2pix GAN model was utilized to generate T2-WI from PD-WI. Model performance was evaluated with the structural similarity index map (SSIM) and peak signal-to-noise ratio (PSNR) indices for 31 predicted T2-WI (pT2). The disc position was clinically diagnosed as anterior disc displacement with or without reduction, and joint effusion as present or absent. The true T2-WI-based diagnosis was regarded as the gold standard, to which pT2-based diagnoses were compared using Cohen’s ĸ coefficient. Results: The mean SSIM and PSNR values were 0.4781(±0.0522) and 21.30(±1.51) dB, respectively. The pT2 protocol showed almost perfect agreement (ĸ = 0.81) with the gold standard for disc position. The number of discordant cases was higher for normal disc position (17%) than for anterior displacement with reduction (2%) or without reduction (10%). The effusion diagnosis also showed almost perfect agreement (ĸ = 0.88), with higher concordance for the presence (85%) than for the absence (77%) of effusion. Conclusion: The application of pT2 images for a TMJ MRI protocol useful for diagnosis, although the image quality of pT2 was not fully satisfactory. Further research is expected to enhance pT2 quality.

Organized hematoma of temporomandibular joint

Lee, Chena,Yook, Jong In,Han, Sang-Sun Korean Academy of Oral and Maxillofacial Radiology 2018 Imaging Science in Dentistry Vol.48 No.1

Organized hematoma is a pseudo-tumorous lesion mostly occurs at sinonasal cavity and often confused with malignant neoplasm. The initiation of this lesion is blood accumulation, probably due to trauma, and this hematoma develops into organized hematoma as it encapsulated with fibrous band and neo-vascularized. Since it is uninformed at temporomandibular joint (TMJ) region, imaging diagnosis might be challenging. Also, delayed detection of mass involving TMJ is not uncommon due to confusion with joint disorder. Thus, this report introduced the rare pathology, organized hematoma on TMJ with advanced imaging features. Also, diagnostic point for early detection was described for the TMJ tumors and pseudo-tumors considering complexity of surgical intervention in this region.

A dose monitoring system for dental radiography

Lee, Chena,Lee, Sam-Sun,Kim, Jo-Eun,Symkhampha, Khanthaly,Lee, Woo-Jin,Huh, Kyung-Hoe,Yi, Won-Jin,Heo, Min-Suk,Choi, Soon-Chul,Yeom, Heon-Young Korean Academy of Oral and Maxillofacial Radiology 2016 Imaging Science in Dentistry Vol.46 No.2

Purpose: The current study investigates the feasibility of a platform for a nationwide dose monitoring system for dental radiography. The essential elements for an unerring system are also assessed. Materials and Methods: An intraoral radiographic machine with 14 X-ray generators and five sensors, 45 panoramic radiographic machines, and 23 cone-beam computed tomography (CBCT) models used in Korean dental clinics were surveyed to investigate the type of dose report. A main server for storing the dose data from each radiographic machine was prepared. The dose report transfer pathways from the radiographic machine to the main sever were constructed. An effective dose calculation method was created based on the machine specifications and the exposure parameters of three intraoral radiographic machines, five panoramic radiographic machines, and four CBCTs. A viewing system was developed for both dentists and patients to view the calculated effective dose. Each procedure and the main server were integrated into one system. Results: The dose data from each type of radiographic machine was successfully transferred to the main server and converted into an effective dose. The effective dose stored in the main server is automatically connected to a viewing program for dentist and patient access. Conclusion: A patient radiation dose monitoring system is feasible for dental clinics. Future research in cooperation with clinicians, industry, and radiologists is needed to ensure format convertibility for an efficient dose monitoring system to monitor unexpected radiation dose.

Efficacy of corticosteroid ductal irrigation in acute salivary gland inflammation induced in a rat model

Lee Chena,Lee Ari,Kim Hak-Sun,Choi Yoon Joo,Jeon Kug Jin,Han Sang-Sun 대한영상치의학회 2022 Imaging Science in Dentistry Vol.52 No.1

Purpose: This study aimed to compare the therapeutic effects of corticosteroid irrigations and normal saline irrigations in the early inflammatory state of the salivary gland. Materials and Methods: Adult male Wistar rats were divided into experimental (n= 6) and control (n= 3) groups. Inflammation was induced in the experimental subjects on both sides of the submandibular gland with ligation. After 14 days, both sides of the glands were de-ligated and retroductal irrigation using saline (n = 3) and a corticosteroid (n = 3) was performed on the left sides only. The controls (n = 3) were used to normalize the gland state for the effects of diet and aging. Magnetic resonance imaging was performed to confirm inflammation and post-irrigation gland recovery by measuring relative signal intensity (SI). The glands were excised for histological examination. Results: All experimental animals showed inflamed glands with increased SI and subsequent recovery of the gland with decreased SI to varying degrees. The SI of the controls showed no significant changes during the overall period. The mean SI change of the irrigated gland was higher than that of the non-irrigated side, without a significant difference. The corticosteroid-irrigated glands showed a greater change in SI than that of the saline-irrigated glands. Histology revealed that inflammation was not observed in most of the irrigated glands, while mild to moderate quantities inflammatory cells were found in non-irrigated glands. Conclusion: Corticosteroid irrigation mitigated the early stages of salivary gland inflammation more effectively than normal saline.

An Investigation of the Cross-border E-commerce Export Trade of Agricultural Products in Shandong Province

Xi Chena 한국무역연구원 2019 무역연구 Vol.15 No.1

This paper focuses on the cross-border e-commerce export trade of China’s agricultural products, and analyzes the current situation and problems of cross-border e-commerce export trade of agricultural products in the Shandong Province of China. It was found that there are some problems in the cross-border e-commerce export trade of agricultural products in Shandong Province, such as lagging construction of a cross-border e-commerce platform, high cost of cross-border logistics, shortage of compound cross-border e-commerce talents, quality certification, standardization issues of cross-border e-commerce agricultural products, and related service supervision of cross-border e-commerce of agricultural products. Countermeasures are put forward to promote the integration and development of cross-border e-commerce and traditional industries, establish an international logistics system adapted to the development of cross-border e-commerce, train and introduce high-end talents of cross-border e-commerce, strengthen the quality standardization and brand building of cross-border e-commerce agricultural products, and improve the mechanism of tax supervision, and rights and interests protection related to cross-border e-commerce agricultural products. This will provide a theoretical basis for future research on related topics, provide a theoretical basis for the export form of cross-border e-commerce of agricultural products in Shandong Province, and also provide a basis for cross-border e-commerce of agricultural products in other provinces of China.

Therapeutic effect of intraductal irrigation of the salivary gland: A technical report

Lee, Chena,Kim, Jo-Eun,Huh, Kyoung-Hoe,Yi, Won-Jin,Heo, Min-Suk,Lee, Sam-Sun,Choi, Soon-Chul Korean Academy of Oral and Maxillofacial Radiology 2017 Imaging Science in Dentistry Vol.47 No.2

Purpose: Obstructive and inflammatory disease often occurs in the major salivary glands, and no predictive treatment has yet been developed for this condition. The aim of this report was to introduce an intraductal irrigation procedure and to illustrate its application to practical patient cases. Materials and Methods: Two patients complaining of pain and swelling in the parotid gland during meals who underwent sialography were diagnosed as having sialodochitis with sialadenitis. Intraductal irrigation was then performed on the parotid gland on the side of the complaint. The irrigation procedure was conducted in the same manner as the sialography procedure, except that saline was used as the filling solution. Symptom severity was evaluated with a numerical rating scale (NRS) at the initial visit and a month after the irrigation. Results: The initial NRS value of patient 1 was 10. The value decreased to 6 and then to 0 after 2 irrigation procedures. The NRS value of patient 2 regarding the symptoms involving the left parotid gland decreased from 4-5 to 1 after 4 irrigation procedures performed at 1-month intervals. Conclusion: Intraductal irrigation of the salivary gland may be a simple, safe, and effective treatment option for patients with obstructive and inflammatory disease of the salivary gland that is capable of resolving their symptoms.

Efficacy of corticosteroid ductal irrigation in acute salivary gland inflammation induced in a rat model

Lee, Chena,Lee, Ari,Kim, Hak-Sun,Choi, Yoon Joo,Jeon, Kug Jin,Han, Sang-Sun Korean Academy of Oral and Maxillofacial Radiology 2021 Imaging Science in Dentistry Vol.51 No.-

Purpose: This study aimed to compare the therapeutic effects of corticosteroid irrigations and normal saline irrigations in the early inflammatory state of the salivary gland. Materials and Methods: Adult male Wistar rats were divided into experimental (n=6) and control (n=3) groups. Inflammation was induced in the experimental subjects on both sides of the submandibular gland with ligation. After 14 days, both sides of the glands were de-ligated and retroductal irrigation using saline (n=3) and a corticosteroid (n=3) was performed on the left sides only. The controls (n=3) were used to normalize the gland state for the effects of diet and aging. Magnetic resonance imaging was performed to confirm inflammation and post-irrigation gland recovery by measuring relative signal intensity (SI). The glands were excised for histological examination. Results: All experimental animals showed inflamed glands with increased SI and subsequent recovery of the gland with decreased SI to varying degrees. The SI of the controls showed no significant changes during the overall period. The mean SI change of the irrigated gland was higher than that of the non-irrigated side, without a significant difference. The corticosteroid-irrigated glands showed a greater change in SI than that of the saline-irrigated glands. Histology revealed that inflammation was not observed in most of the irrigated glands, while mild to moderate quantities inflammatory cells were found in non-irrigated glands. Conclusion: Corticosteroid irrigation mitigated the early stages of salivary gland inflammation more effectively than normal saline.

레일리 페이딩 채널에서 대표적인 3차원 신호성상도의 성능

진진흥(Zhenxing Chena),최재철(Chae Cheol Choe),강석근(Seog Geun Kang) 한국방송·미디어공학회 2011 방송공학회논문지 Vol.16 No.4