• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.10
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• pp.1-5
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• 2011

A magnetic resonant coil system for enhancement of wireless power transfer efficiency of NFC devices was proposed. The NFC system consists of resonant coils arrange between source coil and device coil. The effects of resonant coil was measured using a 13.56MHz RFID reader and tag system and simulated by 3D RF simulator. The measurement results from RFID reader and tag show that the maximum distance of signal transmission is increased by 96.72% and received voltage of RFID tag is grew by 17.95% thanks to the magnetic resonant coils.

• The Journal of the Korea Contents Association
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• v.12 no.7
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• pp.247-254
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• 2012

This study presents the assessment results of coil length characteristics according to the volume of cerebral artery among the inpatients that received angiography and coil embolization following intracranial aneurysm from March, 2010 to September 2011. The volume rendering method was applied to the patients that received embolization to their cerebral arteries to obtain volume measurements. After coil embolization, the volume ratios were calculated with the volumes and lengths of coils. The embolic volume ratios were $43.11{\pm}3.11%$, $36.07{\pm}2.03%$, 40.91%, and 38.25% when the aneurysm sizes were 6mm or less, 6~10mm, 10~15mm and 20mm or more, respectively, being similar to the recommended volume ratios. Regardless of the types of aneurysm, the coil length according to volume was 0.65cm per $1mm^3$ of 20~$100mm^3$ when one type of 0.25mm diameter coil was used. They were 0.62cm per $1mm^3$ of 20~$150mm^3$ when one type of coil was used in the aneurysm volume of the saccular type and 0.60cm per $1mm^3$ of 20~$90mm^3$ when one type of coil was used in the aneurysm volume of the multi-lobulated type.

• Korean Journal of Radiology
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• v.20 no.8
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• pp.1285-1292
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• 2019

Objective: To evaluate the safety and efficacy of the coil-protected technique for liquid embolization in neurovascular malformations. Materials and Methods: Twenty-two patients who underwent coil-protected liquid embolization for symptomatic cranial (n = 13) and spinal (n = 9) arteriovenous fistula (AVF) or arteriovenous malformations (AVMs) were identified. A total of 36 target feeder vessels were embolized with N-butyl cyanoacrylate and/or Onyx (Medtronic). This technique was used to promote delivery of a sufficient amount of liquid embolic agent into the target shunt or nidus in cases where tortuous feeding arteries preclude a microcatheter wedging techniqu and/or to prevent reflux of the liquid embolic agent in cases with a short safety margin. The procedure was considered technically successful if the target lesion was sufficiently filled with liquid embolic agent without unintentional reflux. Angiographic and clinical outcomes were retrospectively evaluated. Results: Technical success was achieved for all 36 target feeders. Post-embolization angiographies revealed complete occlusion in 16 patients and near-complete and partial occlusion in three patients each. There were no treatment-related complications. Of the six patients who showed near-complete or partial occlusion, five received additional treatments: two received stereotactic radiosurgery for cerebral AVM, two underwent surgical removal of cerebral AVM, and one underwent additional embolization by direct puncture for a mandibular AVM. Finally, all patients showed complete (n = 19) or near-complete (n = 3) occlusion of the target AVF or AVM on follow-up angiographies. The presenting neurological symptoms improved completely in 15 patients (68.2%) and partially in seven patients (31.8%). Conclusion: The coil-protected technique is a safe and effective method for liquid embolization, especially in patients with various neurovascular shunts or malformations who could not be successfully treated with conventional techniques.

• Journal of Power Electronics
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• v.17 no.3
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• pp.835-847
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• 2017

A transmitting coil with an optimal topology and number of turns can effectively improve the performance of the wireless power transfer (WPT) systems for endoscope robots. This study proposes the evaluation parameters of the transmitting coils related to the performance of the WPT system to standardize the design of the transmitting coils. It considers both the quality factor of transmitting coils and the coupling factor between the two sides. Furthermore, an analytical model of transmitting coils with different topologies is built to exactly estimate the evaluation parameters. Several coils with the specified topologies are wound to verify the analytical model and the feasibility of evaluation parameters. In the case of a constant power received, the related evaluation parameters are proportional to the transfer efficiency of the WPT system. Therefore, the applicable frequency ranges of transmitting coils with different topologies are determined theoretically. Then a transmitting coil with a diameter of 69 cm is re-optimized both theoretically and experimentally. The transfer efficiency of the WPT system is increased from 3.58% to 7.37% with the maximum magnetic field intensity permitted by human tissue. Finally, the standardized design of the transmitting coil is achieved by summing-up and facilitating the optimization of the coils in various situations.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.1064-1069
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• 1994

In order to realize the function of human interface of telecommunications whose objective is to interchange useful information among persons, we developed a bone conduction telephone with which hearing impaired persons with conductive or noise-induced hearing loss and presbycusis can communicate with each other without any other additional devices such as hearing aids. The bone conduction telephone we developed has chatacteristics as follows : (i) a hearing impaired person and a normal hearing person can communicate by bone and air conduction hearings, respectively, using only this telephone set because, as its receiver, it uses a bone conduction vibrator with which we can realize such function with the voice coil and damper of a small speaker unit, the vibrating plate, etc., (ii) it has tone control function compensating hearing losses of hearing impaired persons according to their hearing loss/frequency chatacteristics. Using the tone control function together with a received volume control, it has the received volume range of 20dB in loudness rating; and (iii) it has the function of three emergency calls and a bell lamp as the visual display of a received call.

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.1
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• pp.26-32
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• 2014

Purpose: As PET-MRI which has excellent soft tissue contrast is developed as integration system, many researches about clinical application are being conducted by comparing with existing display equipments. Because PET-MRI is actively used for head and neck cancer diagnosis in our hospital, lymph node metastasis before the patient's surgery was diagnosed and clinical usefulness of head and neck cancer PET-MRI scan was evaluated using pathological opinions and idiopathy surrounding tissue metastasis evaluation method. Materials and Methods: Targeting 100 head and neck cancer patients in SNUH from January to August in 2013. $^{18}F-FDG$ (5.18 MBq/kg) was intravenous injected and after 60 min of rest, torso (body TIM coil, Vibe-Dixon) and dedication (head-neck TIM coil, UTE, Dotarem injection) scans were conducted using $Bio-graph^{TM}$ mMR 3T (SIEMENS, Munich). Data were reorganized using iterative reconstruction and lymph node metastasis was read with Syngo.Via workstation. Subsequently, pathological observations and diagnosis before-and-after surgery were examined with integrated medical information system (EMR, best-care) in SNUH. Patient's diagnostic information was entered in each category of $2{\times}2$ decision matrix and was classified into true positive (TP), true negative (TN), false positive (FP) and false negative (FN). Based on these classified test results, sensitivity, specificity, accuracy, false negative and false positive rate were calculated. Results: In PET-MRI scan results of head and neck cancer patients, positive and negative cases of lymph node metastasis were 49 and 51 cases respectively and positive and negative lymph node metastasis through before-and-after surgery pathological results were 46 and 54 cases respectively. In both tests, TP which received positive lymph node metastasis were analyzed as 34 cases, FP which received positive lymph node metastasis in PET-MRI scan but received negative lymph node metastasis in pathological test were 4 cases, FN which received negative lymph node metastasis but received positive lymph node metastasis in pathological test was 1 case, and TN which received negative lymph node metastasis in both two tests were 50 cases. Based on these data, sensitivity in PET-MRI scan of head and neck cancer patient was identified to be 97.8%, specificity was 92.5%, accuracy was 95%, FN rate was 2.1% and FP rate was 7.00% respectively. Conclusion: PET-MRI which can apply the acquired functional information using high tissue contrast and various sequences was considered to be useful in determining the weapons before-and-after surgery in head and neck cancer diagnosis or in the evaluation of recurrence and remote detection of metastasis and uncertain idiopathy cervical lymph node metastasis. Additionally, clinical usefulness of PET-MRI through pathological test and integrated diagnosis and follow-up scan was considered to be sufficient as a standard diagnosis scan of head and neck cancer, and additional researches about the development of optimum MR sequence and clinical application are required.

• Journal of Korean Dental Science
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• v.16 no.2
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• pp.182-191
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• 2023

Purpose: This study investigated the orthodontic tooth movement after weekly parathyroid hormone (PTH) injection in mongrel dogs and analyzes bone formation activity on the tension and pressure sides of the tooth movement in mongrel dogs. Materials and Methods: Three mongrel dogs were used in this study. The first premolar was extracted and orthodontic force using 150 g of closed coil springs between the canine and second premolar was applied. The low-dose PTH group (PTH_1) and high-dose PTH group (PTH_2) received weekly injections of 1.61 ㎍/kg and 3.23 ㎍/kg of PTH, respectively. The control group received weekly injections of 1 ml of saline. Clinical, histomorphometric analysis were carried out. Result: The orthodontic tooth movement was greatest in the PTH_2 group and the lowest in the control group. Fluorescence staining images showed higher bone remodeling on the tension side of the tooth movement in the PTH_1 and PTH_2 groups. PTH_2 group showed a thicker labeling band than the PTH_1 group. PTH_2 group showed the highest mineral apposition rate and bone formation rate, followed by the PTH_1 group and the control group. Conclusion: Weekly intermittent PTH injection, especially in the short-term and at higher doses with orthodontic force, successfully increased orthodontic tooth movement and bone remodeling in mongrel dogs.

• Journal of Korean Neurosurgical Society
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• v.65 no.5
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• pp.710-718
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• 2022

Objective : Although endovascular treatment for intracranial aneurysms is considered effective and safe, its durability is still debated. Also, few studies have described angiographic follow-up plan after endovascular treatment of intracranial aneurysm, especially in ruptured cases. Hence, we report the long-term results of follow-up angiography protocol. Methods : Radiological records of 639 cases of coil embolization with ruptured aneurysms from March 2003 to December 2016 were retrospectively reviewed. Patients who received treatment of a saccular aneurysm less than 7 mm resulted with near complete occlusion were included. Two hundred thirty-eight aneuryms which received the follow-up angiography at least once were enrolled. We classified four periods of follow-up as follows : post-treatment 1 year (defined as the first period), from 1 to 2 years (the second period), 2 to 5 years (the third period), and over 5 years (long-term). Results : We identified 14 cases (6.4%) of recurrence from 218 aneurysms in follow-up angiography in the first period. Among 143 aneurysms in the second period, five cases (3.5%) of recurrence were identified. There were no findings suspicious of recanalization in 97 patients in the third period. Of the total 238 cases, there were 19 recurrences, for a recurrence rate of 8.0%. Six (31.6%) out of 19 recurrences showed a tendency toward repeat recurrences even after additional treatment. Twenty-eight received long-term follow-up over 5 years and there was no recurrence. Conclusion : Most of the recurrence were found during the first and the second year. We suggest that at least one digital subtraction angiography examination may be necessary around post-treatment 2 years, especially in ruptured cases. If the angiographic results are favorable at 2 years post-treatment, long-term result should be favorable.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.422-427
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• 2008

This study is to illustrate the usefulness of Kriging Dimension Reduction Method(KDRM), which is to construct probability distribution of response function in the presence of the physical uncertainty of input variables. DRM has recently received increased attention due to its sensitivity-free nature and efficiency that considerable accuracy is obtained with only a few number of analyses. However, the DRM has a number of drawbacks such as instability and inaccuracy for functions with increased nonlinearity. As a remedy, Kriging interpolation technique is incorporated which is known as more accurate for nonlinear functions. The KDRM is applied and compared with MCS methods in a compression coil spring design problem. The effectiveness and accuracy of this method is verified.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.11
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• pp.875-881
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• 2003

The received signal of a mobile phone is normally sensed through two independent means which are the sound generation of a speaker and vibration generation of a vibration motor. As an improvement scheme to meet the consumer's demand on weight reduction and miniaturization of a mobile phone, the design and development of an integrated vibration and sound generating device are performed in this research. To this purpose, the optimal shapes of the voice coil. the permanent magnet and the vibration plate are designed, and the excitation force applied to the vibration system of the new device is estimated and verified through theoretical analyses, computer simulation, and experiments using an expanded model. In addition, vibration performance comparison of the device with the existing vibration motor is performed, and from the overall process, therefore, the method and procedure for the vibration performance analysis of the integrated vibration and sound generating device are established.