• Korean Journal of Metals and Materials
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• v.56 no.12
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• pp.915-920
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• 2018

With the development of modern microelectronics technologies, the power density of electronic devices is rapidly increasing, due to the miniaturization or integration of device elements which operate at high frequency, high power conditions. Resulting thermal problems are known to cause power leakage, device failure and deteriorated performance. To relieve heat accumulation at the interface between chips and heat sinks, thermal interface materials (TIMs) must provide efficient heat transport in the through-plane direction. We report on the enhanced thermal conduction of $Al_2O_3-based$ polymer composites, fabricated by the surface wetting and texturing of thermally conductive hexagonal boron nitride(h-BN) nanoplatelets with large anisotropy in morphology and physical properties. The thermally conductive polymer composites were prepared with hybrid fillers of $Al_2O_3$ macro beads and surface modified h-BN nanoplatelets. Hexagonal boron nitride (h-BN) has high thermal conductivity and is one of the most suitable materials for thermally conductive polymer composites, which protect electronic devices by efficient heat dissipation. In this study, we synthesized hexagonal boron nitride nanoparticles by the pyrolysis of cost effective precursors, boric acid and melamine. Through pyrolysis at $900^{\circ}C$ and subsequent annealing at $1500^{\circ}C$, hexagonal boron nitride nanoparticles with diameters of ca. 50nm were synthesized. We demonstrate that the addition of a small amount of calcium fluoride ($CaF_2$) during the preparation of the melamine borate adduct significantly enhanced the crystallinity of the h-BN and assisted the growth of nanoplatelets up to 100nm in diameters. The addition of a small amount of h-BN enhanced the thermal conductivity of the $Al_2O_3-based$ polymer composites, from 1.45W/mK to 2.33 W/mK.

• New Physics: Sae Mulli
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• v.68 no.11
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• pp.1268-1274
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• 2018

Aircraft-warning lights are lights that are used to inform pilots in flight about the presence of buildings or dangerous objects. Currently, the light sources of most aircraft-warning lights have been replaced by light-emitting diodes (LEDs). However, the aircraft-warning lights that are installed do not meet the optical performance standards and may cause airplane collisions. Therefore, the use of such light poses a risk to aviation safety. In order to solve this problem, we designed a Fresnel lens with the same luminous intensity distribution ovef $360^{\circ}$ direction; thus, we collimated the light beam from the LED light source with a narrow beam divergence angle in the form of an array of aspheric pieces. After that, we designed and simulated an aircraft-warning-light optical system with a center luminous intensity of 20,000 cd and a vertical divergence angle of $3^{\circ}$ or more by optimizing the lens' tilt and the distance between the LED and the Fresnel lens.

• Journal of the Institute of Convergence Signal Processing
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• v.21 no.2
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• pp.67-72
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• 2020

AR service using the client-server method and existing physical markers(eg, OR Codes, etc.) causes a delay in the playback time of the contents because the contents download is executed after the marker recognition. In the case of the one-time installation method rather than the client-server method, proactive download of high-capacity contents for playback may cause an inefficiency of the storage space of the device(eg, smartphone, etc.). Therefore, in AR contents playback based on beacon's RSSI to secure the efficiency of the playback device storage space and to quickly play AR contents. The technique for high-speed playback in this study can be applied to various fields such as MICE exhibition using beacon signal.

• Biomedical Science Letters
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• v.27 no.1
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• pp.28-34
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• 2021

The main cause of cervical cancer is a persistent infection with high-risk human papillomavirus (HR-HPV). Cervical cancer is reported as a preventable cancer in more than 80% of cases with early diagnosis and appropriate treatment. Papanicolaou test (Pap test) has been a global strategy to prevent cervical cancer, and recently, HPV test has been reported to be effective against cervical cancer and precancerous lesions. However, pelvic examinations give patients anxiety, discomfort, pain, distress, and psychological stress. HPV test via a urine sample caused less physical and psychological stress and more advantage than the Pap test. Therefore, it is necessary to study the usefulness of the HPV test for easy-to-collect urine samples. A total of 220 samples were collected from a pair of cervical and urine samples from 110 women and only 108 pairs of samples out of 110 were used because 2 cases were not amplified by β-globin. Among 108 pairs of cervical and urine samples, the prevalence of HPV was 37.0% (40/108) in cervical samples, 34.3% (37/108) in urine samples and HR-HPV was 22.2% (24/108) in cervical samples, 18.5% (20/108) in urine samples. In this study, urine samples showed a lower positive rate of HPV than cervical samples. There were many variables that could affect the condition of the urine sample. However, the HR-HPV agreement rate of the cervix and urine samples was 94.44% and the Kappa value was 0.823, which was "almost perfect". Through these results showed the significance of cervical cancer screening using a urine sample. Cervical screening is crucial, as cervical cancer can be prevented in more than 90% of cases. Urine samples collected by non-invasive methods may have the potential advantage of increasing acceptance of cervical cancer screening. Therefore, it is necessary to develop a new cervical cancer screening strategy using urine samples through further study based on the results of this study.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.4
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• pp.171-178
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• 2021

Caravans are easily affected by external physical factors and often cause dangerous situations for passengers. Therefore, in order to secure the stability of the passenger, there is a need to develop a sway reduction device capable of preventing the sway phenomenon in advance. This paper aims to minimize the hitch angle between the tow vehicle and the caravan. Specifically, the initial instability of the caravan is detected through an IMU sensor mounted on each of the tow vehicle and the caravan, and a control value is calculated to reduce errors from the Hitch angle and Hitch yaw rate using a PID controller. Different braking torques are generated, distributed, and controlled on the left and right brakes of the caravan according to the calculated control value. It could be verified through the driving experiment that the hitch angle was decreased compared to the case where the performance of the sway reduction device was not controlled, and the transverse stability improvement rate was improved by 94.49% compared to before control.

• Journal of Korea Water Resources Association
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• v.55 no.7
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• pp.557-563
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• 2022

The rating curve is required to convert measured stage into a discharge and is developed using the measurement. In the development of the rating curve, the segmentation position is determined by considering the hydraulic characteristic and channel shape, and subjective judgment of the Hydrographer may intervene in this process. The segmentation position is so important that it determines the overall form of the rating curve, and the incorrect segmentation can cause errors in the rating curve, especially in extrapolation. In order to develop an accurate rating curve with a small number of measurements, the sections must be divided by considering hydraulic characteristic such as the cross-sectional shape. In this study, hydraulic examination methods such as stage-mean velocity, stage-area, stage-${\sqrt{Q}}$ investigated and supplemented to eliminate subjectivity in segmental positioning. Appropriateness for the segmentation position was verify in consideration of the physical meaning of the rating curve index (c).

• Journal of the Korean Orthopaedic Association
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• v.56 no.3
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• pp.266-271
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• 2021

Osteoporosis associated with pregnancy and lactation is a rare disease that can cause osteoporotic vertebral compression fracture (OVCF). Patients usually complain of severe back pain, which is easily mistaken for pain due to pregnancy, childbirth, and lactation, making a rapid diagnosis and treatment difficult. The authors diagnosed OVCF related to pregnancy and lactation through a physical examination, simple radiography, whole-body bone scan, magnetic resonance image, bone marrow density, and blood tests in a 29-year-old female patient and a 31-year-old female patient who presented with low back pain. This paper reports two cases of symptom improvement through a teriparatide injection, wearing thoracic lumbar sacral orthosis and taking calcium and vitamin D with a review of the literature.

• Journal of architectural history
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• v.31 no.5
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• pp.57-64
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• 2022

Architectural Monuments have to overcome the challenge of time due to physical properties. The fundamental issue must be grounded in an understanding of history and art to overcome this challenge and make themsustainable. Many efforts to preserve the monuments through the 19^th century and at the beginning of the 20^th century to record them in scientific form were successful. To be aware of the meaning of the art and not to be 'barbare' anymore was behind the promotion of these activities. Above all, the 19th-century French architect Viollet-le-Duc contrasted the concept of barbarism with the concept of art and tried to redefine architecture as art. The ritual to escape 'barbare' played an important role in the end. This consciousness was also at work in the propaganda for the preservation of medieval architectural monuments in France, led by intellectuals such as Rodin. Also, the concept of 'barbare' served as an important yardstick whenever the cause of their loss was questioned while important monuments were destroyed in the First World War. From the viewpoint of Germany, Dehio was the pioneer of the preservation movement and documentation of monuments. The principle he advocated was preservation, not restoration. The historian Pevsner, who moved to England, also surveyed monuments in various parts of England and left them in the same format as Dehio. These facts show that architecture as art plays a fundamental role in the history of human life.

• The Korean Journal of Pain
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• v.35 no.4
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• pp.468-474
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• 2022

Background: The new type of corona virus has a wide range of symptoms. Some people who have COVID-19 can experience long-term effects from their infection, known as post-COVID conditions. The authors aimed to investigate prolonged musculoskeletal pain as a symptom of the post-COVID-19 condition. Methods: This is a descriptive study on the patients who were diagnosed with COVID-19 in a university hospital, between March 2020 and March 2021. Patient records and an extensive questionnaire were used to obtain relevant demographic and clinical characteristics, including hospitalization history, comorbidities, smoking history, duration of the pain, the area of pain, and the presence of accompanying neuropathic symptoms. Results: Of the diagnosed patients, 501 agreed to participate in the study. Among the participants, 318 had musculoskeletal pain during COVID-19 infection, and 69 of them reported prolonged pain symptoms as part of their a post-COVID condition which could not be attributed to any other cause. The mean duration of pain was 4.38 ± 1.73 months, and the mean pain level was 7.2 ± 4.3. Neuropathic pain symptoms such as burning sensation (n = 16, 23.2%), numbness (n = 15, 21.7%), tingling (n = 10, 14.5%), stinging (n = 4, 5.8%), freezing (n = 1, 1.4%) were accompanied in patients with prolonged musculoskeletal pain. Conclusions: Patients with COVID-19 may develop prolonged musculoskeletal pain. In some patients, neuropathic pain accompanies it. Awareness of prolonged post-COVID-19 pain is crucial for its early detection and management.

• Journal of Veterinary Clinics
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• v.39 no.5
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• pp.235-239
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• 2022

A 10-year-old neutered male Siberian Husky presented with paraparesis and severe lethargy. On physical examination, the patient was unable to weight-bear and walk and exhibited significant muscle mass loss in both hindlimbs and generalized truncal alopecia with a dull coat of hair. On neurological examination, cranial lumbar vertebral pain, hind limb cross-extensor reflex, delayed hindlimb postural reaction, upper motor neuron bladder dysfunction, and total absence of cutaneous trunci reflex were identified. Computed tomography revealed diffuse idiopathic skeletal hyperostosis and spondylosis deformans of the cervical and thoracolumbar vertebrae. In addition, a generalized decrease in bone mineral density of the vertebrae was identified. Magnetic resonance imaging showed hyperplasia of the epidural fat compressing the spinal cord in the thoracolumbar region and concurrent mild multiple intervertebral disc herniations. No specific findings were observed in cerebrospinal fluid analysis. Blood analysis of thyroid function revealed decreased total T4 and free T4 levels, and increased TSH levels. The patient was tentatively diagnosed with spinal epidural lipomatosis (SEL) secondary to hypothyroidism. The patient was treated with levothyroxine, firocoxib, and gabapentin. Clinical signs gradually improved, and the patient showed normal ambulation 40 days after treatment initiation. SEL is extremely rare in dogs. To the best of our knowledge, this is the first case report of SEL secondary to hypothyroidism that was treated conservatively. Secondary SEL can be sufficiently managed by treating the underlying cause, if possible.