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THE CURRENT STATUS OF BIOMEDICAL ENGINEERING IN THE USA

  • Webster, John G.
    • Proceedings of the KOSOMBE Conference
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    • v.1992 no.05
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    • pp.27-47
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    • 1992
  • Engineers have developed new instruments that aid in diagnosis and therapy Ultrasonic imaging has provided a nondamaging method of imaging internal organs. A complex transducer emits ultrasonic waves at many angles and reconstructs a map of internal anatomy and also velocities of blood in vessels. Fast computed tomography permits reconstruction of the 3-dimensional anatomy and perfusion of the heart at 20-Hz rates. Positron emission tomography uses certain isotopes that produce positrons that react with electrons to simultaneously emit two gamma rays in opposite directions. It locates the region of origin by using a ring of discrete scintillation detectors, each in electronic coincidence with an opposing detector. In magnetic resonance imaging, the patient is placed in a very strong magnetic field. The precessing of the hydrogen atoms is perturbed by an interrogating field to yield two-dimensional images of soft tissue having exceptional clarity. As an alternative to radiology image processing, film archiving, and retrieval, picture archiving and communication systems (PACS) are being implemented. Images from computed radiography, magnetic resonance imaging (MRI), nuclear medicine, and ultrasound are digitized, transmitted, and stored in computers for retrieval at distributed work stations. In electrical impedance tomography, electrodes are placed around the thorax. 50-kHz current is injected between two electrodes and voltages are measured on all other electrodes. A computer processes the data to yield an image of the resistivity of a 2-dimensional slice of the thorax. During fetal monitoring, a corkscrew electrode is screwed into the fetal scalp to measure the fetal electrocardiogram. Correlations with uterine contractions yield information on the status of the fetus during delivery To measure cardiac output by thermodilution, cold saline is injected into the right atrium. A thermistor in the right pulmonary artery yields temperature measurements, from which we can calculate cardiac output. In impedance cardiography, we measure the changes in electrical impedance as the heart ejects blood into the arteries. Motion artifacts are large, so signal averaging is useful during monitoring. An intraarterial blood gas monitoring system permits monitoring in real time. Light is sent down optical fibers inserted into the radial artery, where it is absorbed by dyes, which reemit the light at a different wavelength. The emitted light travels up optical fibers where an external instrument determines O2, CO2, and pH. Therapeutic devices include the electrosurgical unit. A high-frequency electric arc is drawn between the knife and the tissue. The arc cuts and the heat coagulates, thus preventing blood loss. Hyperthermia has demonstrated antitumor effects in patients in whom all conventional modes of therapy have failed. Methods of raising tumor temperature include focused ultrasound, radio-frequency power through needles, or microwaves. When the heart stops pumping, we use the defibrillator to restore normal pumping. A brief, high-current pulse through the heart synchronizes all cardiac fibers to restore normal rhythm. When the cardiac rhythm is too slow, we implant the cardiac pacemaker. An electrode within the heart stimulates the cardiac muscle to contract at the normal rate. When the cardiac valves are narrowed or leak, we implant an artificial valve. Silicone rubber and Teflon are used for biocompatibility. Artificial hearts powered by pneumatic hoses have been implanted in humans. However, the quality of life gradually degrades, and death ensues. When kidney stones develop, lithotripsy is used. A spark creates a pressure wave, which is focused on the stone and fragments it. The pieces pass out normally. When kidneys fail, the blood is cleansed during hemodialysis. Urea passes through a porous membrane to a dialysate bath to lower its concentration in the blood. The blind are able to read by scanning the Optacon with their fingertips. A camera scans letters and converts them to an array of vibrating pins. The deaf are able to hear using a cochlear implant. A microphone detects sound and divides it into frequency bands. 22 electrodes within the cochlea stimulate the acoustic the acoustic nerve to provide sound patterns. For those who have lost muscle function in the limbs, researchers are implanting electrodes to stimulate the muscle. Sensors in the legs and arms feed back signals to a computer that coordinates the stimulators to provide limb motion. For those with high spinal cord injury, a puff and sip switch can control a computer and permit the disabled person operate the computer and communicate with the outside world.

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Effect of Acupuncture on Nasal Obstruction in Patients with Persistent Allergic Rhinitis: A Randomized Controlled Trial (지속성 알레르기비염의 비폐색에 대한 침치료의 효과: 무작위배정 대조군 연구)

  • Jo, Jeong-Hyo;Hong, Kweon-Eey;Kang, Wee-Chang;Choi, Sun-Mi;Park, Yang-Chun
    • Journal of Acupuncture Research
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    • v.22 no.6
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    • pp.229-239
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    • 2005
  • Objectives : Allergic rhinitis is a prevalent disease. Nasal obstruction is one of the main symptom in allergic rhinitis. It induces sleep disturbances, depression, attention deficit, memory impairments. Acupuncture treatment for rhinitis was mentioned in literature, but there is not enough report that provide evidence by well designed clinical study. The purpose of this research is to examine the effect of acupuncture treatment for nasal obstruction of allergic rhinitis. Methods : In this randomized, single blind, placebo-controlled study, we compared active acupuncture with minimal acupuncture for the treatment of nasal obstruction owing to persistent allergic rhinitis. Acupoints used in active acupuncture group were I120($Y{\hat{o}}nghyang$), GV23($Sangs{\hat{o}}ng$), IL4(Hapkok). Volunteers who satisfied the requirements were enrolled in study. Total nasal volume(NV) and total nasal minimum cross-sectional area(MCA) were measured by acoustic rhinometry before and after treatments(0min, 7.5min, 15min). Results : 101 subjects finished study. There were not difference between two groups on age, sex, weight, height, blood pressure, pulse, respiratory rate, severity of persistent allergic rhinitis, number of positive antigen. After treatment(0min) total NV were significantly increased compared with before treatment in active acupuncture group(p=0.0007) and minimal acupuncture group(p=0.0175). After treatment(15min) total NV of minimal acupuncture group was decreased compared with before treatment(p=0.2560), but total NV of active acupuncture group was maintained increasing in degree of borderline significance(p=0.0871). After treatment(0min) total NV were significantly increased compared with before treatment in active acupuncture group(0.0007) and minimal acupuncture group(p=0.0175). After treatment(Omin) total MCA were significantly increased compared with before treatment in active acupuncture group(p<0.000l) and minimal acupuncture group(p=0.0005). After treatment(15min) total MCA of minimal acupuncture group was decreased compared with before treatment(p=0.6082), but total NV of active acupuncture group was maintained increasing in degree of borderline significance(p=0.0929). Conclusion : Acupuncture treatment reduced nasal obstruction in persistent allergic rhinitis. Further study in the form of long term is needed.

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Effect of Sa-am Acupuncture Method for Chronic Tension-type Headache;A Randomized Controlled Trial (만성 긴장성 두통 환자에 대한 사암침 치료효과의 Pilot 임상연구)

  • Hong, Kwon-Eui;Park, Yang-Chun;Jo, Jeong-Hyo;Jo, Hyun-Gyeong;Jeong, In-Cheol;Kang, Wee-Chang;Lee, Sang-Bong;Choi, Sun-Mi
    • Journal of Acupuncture Research
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    • v.24 no.1
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    • pp.13-28
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    • 2007
  • Objectives : Clinical character of chronic tension-type headache is bilateral, moderate intensity, persistent and chronic, repeating disease and CTTH is a common prevalent disease, but pathophysiology and likely mechanism remain unclear. It impedes subjective quality of life. The purpose of this research is to examine the effect of sa-am acupuncture method for chronic tension-type headache. Methods : In this randomized, single blind, placebo-controlled study, we compared active acupuncture with sham acupuncture for the treatment of chronic tension-type headache. Volunteers who satisfied the requirements were enrolled in study. Evaluation of chronic tension-type headache was measured by VAS and Headache Disability Inventory(HDI), Six point Linkert Scale before and after treatments. Results : 26 subjects finished study. There were not difference between two groups on age, sex, weight, height, blood pressure, pulse, respiratory rate, Byeonjeung, sunrise of treatment. In change of VAS, there were not difference between two groups on before treatment. Before treatment per visit, VAS of 6th and 7th visit were significantly decreased in active acupuncture(each p=0.039, p=0.008) and were not decreased in sham acupuncture. In change of VAS on a withdrawing needling after treatment, VAS of 1st, 2nd, 6th and 7th visit were significantly decreased in active acupuncture (each p=0.001, 0.038, 0.035, 0.008) and VAS of 2nd, 4th and 5th, 6th visit were significantly decreased in sham acupuncture(each p=0.033, 0.032, 0.035, 0.031). In change of VAS on 2hrs after treatment, VAS of 4th and 5th, 6th visit were significantly decreased in active acupuncture(each p=0.014, 0.023, 0.027) and 5th visit were significantly decreased in sham acupuncture(each p=0.004, 0.009). In change of VAS on 4hrs after treatment, VAS of 4th and 5th, 6th visit were significantly decreased in active acupuncture(each p=0.018, 0.011, 0.015) and 5th, 6th visit were significantly decreased in sham acupuncture(each p=0.020, 0.015). In change of VAS on the next day after treatment, VAS of 3th and 4th and 5th, 6th visit were significantly decreased in active acupuncture(each p=0.032, 0.011, 0.005, 0.012) and 4th, 5th visit were significantly decreased in sham acupuncture(each p=0.001, 0.012). In change of VAS according to a current time(before treatment, after a withdrawing needling, 2hrs, 4hrs, the next day), total score of VAS was decreased more active acupuncture group than sham acupuncture group, but there were no statistical significance compared with sham acupuncture group. In change of HDI score, after treatment was decreased than before treatment in two group, but there were no statistical significance compared with two group. In change of Six point Linkert scale score, after treatment was decreased than before treatment in two group on 6th, 7th visit(active acupuncture 6th 7th each p=0.002, 0.003, sham acupuncture 6th 7th each 0.003, 0.009), but there were no statistical significance compared with tow group. Conclusion : Sa-am acupuncture treatment is effective to improve the symptoms and quality of life in patients with chronic tension-type headache.

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Analysis of Experimental Researches in Korea on the Effects of Aromatherapy to Relieve Pain (아로마테라피의 통증 감소 효과에 관한 국내 실험논문 분석)

  • Park, Jeong-Sook;Park, Jeong-Eon;Yang, Jang-Soon;Kwak, Hye-Weon;Han, Jung-An
    • Journal of Hospice and Palliative Care
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    • v.14 no.1
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    • pp.8-19
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    • 2011
  • Purpose: This study identifies research trends and provides fundamental data related to curative power of aromatherapy to relieve pain in Korea. Methods: The study analyzed 44 experimental studies on humans that were published in Korea before the end of December, 2009. The key words used for searching were: aroma, aromatherapy, hyang-yobeob, hyanggi-yobeob, hyanggichilyo, aromatherapy and pain, headache, scapulodynia, omodynia, feeling uncomfortable in the perineal region, sense of pain, labor pains, arm pain, menstrual pain, aches, and dysmenorrheal. Those words were found on websites, including those for Korea Education & Research Information Service, the National Assembly Library, KISS, KoreaMed, and NDSL. Collected data were analyzed using descriptive statistics. Results: The results showed that most of essential oils to relieve pain is composed of three to four kinds of oils, including Lavender, Roman chamomile, Rosemary, and Clarysage. Aromatherapy is applied usually by means of massage (50%), inhalation (13.6%), or a combination of the above two (13.6%). Measuring instruments as a dependent variable include VAS, questionnaire, GRS, blood pressure, pulse, and Algometer. Aromatherapy plays an important role in soothing headaches and arthralgia. However, when it comes to labor and menstrual pain, it doesn't seem to be effective. Conclusion: The study found that different kinds of oil, frequencies, and periods of time are used for the same symptoms. Further research should employ standardized oil blending, application, duration, and measuring instruments, and more systematically analyze the effects of aromatherapy to establish the effects on relieving pain.

Study on Effect of Varience of Physiological Responses in Color Foot Reflexology Using Color Light (컬러광을 활용한 발반사요법이 인체 생리적 반응 변화에 미치는 영향에 관한 연구)

  • Jin, Hye-Ryeon;Yu, Mi;Park, Kyung-Jun;Kim, Nam-Gyun;Chung, Sung-Whan;Kim, Dong-Wook
    • Science of Emotion and Sensibility
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    • v.13 no.1
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    • pp.187-196
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    • 2010
  • Recently, people have been suffering from stress-related fatigue and psychological disorders. Most people depend on medicine for pain relief; many treat pain also through alternative medicine or replacement therapy. However, drug therapy has many side effects, including increased stress after the therapy. In comparison, alternative therapies such as massage and foot reflexology are less damaging to the body, and such therapies can be provided without physical or psychological discomfort. In this regard, the author had previously co-developed color foot reflexology, which combines the merits of color therapy and foot reflexology; color foot reflexology has been shown to have beneficial effects without undue pain. This study investigates the effects of color foot reflexology on the physiological response of the body by comparing the body’s response to the signal with that to the placebo. Healthy adult subjects were selected for the experiment, which was conducted under optimal experimental conditions and design. The results indicated that when stimulated, parasympathetic nerves increased in HRV and that blood pressure, pulse, body heat, peripheral blood flow were dramatically activated. However, the results for the placebo indicated minimal changes or irregular outcomes. The results provide strong evidence for the beneficial effects of the color foot reflexology instrument on the autonomic nervous system and on the physiological response of the body. Future research is warranted to verify the results of the current study by examining patients suffering from diseases and disorders arising from irregular physiological functions in the context of the foot.

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Excessive Daytime Sleepiness Case Confounding with Thyrotoxicosis (과도한 주간 졸림과 탈력발작을 주소로 내원한 환자에서 발견된 갑상선 중독증)

  • Chung, Jae-Kyung;Kim, Eui-Joong
    • Sleep Medicine and Psychophysiology
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    • v.18 no.1
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    • pp.40-44
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    • 2011
  • Narcolepsy is a sleep disorder, which is characterized by excessive daytime sleepiness (EDS) that is typically associated with cataplexy, sleep fragmentation and other REM sleep-related phenomenon such as sleep paralysis and hypnagogic hallucination. Narcoleptic symptoms can be developed from various medical or neurological disorders. A 17-year-old male patient admitted for the evaluation of EDS which started three-month ago. He slept more than 18 hours a day with cataplexy and hypnagogic hallucination. He was obese with body mass index (BMI) of 30.4 kg/$m^2$. After admission he was newly diagnosed to the thyrotoxicosis. T3 391.2 ng/dL (60-181), free T4 4.38 ng/dL (0.89-1.76), TSH <0.01 ${\mu}IU$/mL (0.35-5.5) were measured. His pulse rate ranged 70-90 beats per minute and blood pressure ranged 150/100-120/70 mmHg. Polysomnography revealed many fragmentations in sleep with many positional changes (81 times/h). Sleep onset latency was 33.5 min, sleep efficiency was 47.9%, and REM latency from sleep onset was delayed to 153.6 min. REM sleep percent was increased to 27.1%. Periodic limb movement index was 13.4/h. In the multiple sleep latency test (MSLT), average sleep latency was 0.4 min and there were noted 3 SOREMPs (Sleep Onset REM sleep period) on 5 trials. We couldn't discriminate the obvious sleep-wake pattern in the actigraph and his HLA DQB1 $^*0602$ type was negative. His thyroid function improved following treatment with methimazole and propranolol. Vital sign maintained within normal range. Cataplexy was controlled with venlafaxine 75 mg. Subjective night sleep continuity and PLMS were improved with clonazepam 0.5 mg, but the EDS were partially improved with modafinil 200-400 mg. Thyrotoxicosis might give confounding role when we were evaluating the EDS, though sleep fragmentation was one of the major symptoms of narcolepsy, but enormous amount of it made us think of the influence of thyroid hormone. The loss of sleep-wake cycle, limited improvement of EDS to the stimulant treatmen, and the cataplexy not supported by HLA DQB1 $^*0602$ should be answered further. We still should rule out idiopathic hypersomnia and measuring CSF hypocretin level would be helpful.

Safety and efficacy of the ultra-rush immunotherapy with extracts of Dermatophagoides pteronyssinus in children (집먼지 진드기 항원을 이용한 초급속면역치료의 안전성과 효과)

  • Hyun, Sei Eun;Kim, Hyoung Yun;Kwak, Ji Hee;Shin, Youn Ho;Seo, Ji Yeong;Han, Man Yong
    • Clinical and Experimental Pediatrics
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    • v.51 no.8
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    • pp.868-873
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    • 2008
  • Purpose : Immunotherapy is accepted as the only treatment of allergic disease that can modify the natural course of the disease and ameliorate symptoms. This study aimed to evaluate the safety and efficacy of ultra-rush therapy using Dermatophagoides extracts in children. Methods : Of children older than four years who had visited Bundang CHA Pediatric Allergy Clinic, those showing positive reactions only to Dermatophagoides in the skin prick test and to the nasal provocation test were included. In all, 11 and 12 patients respectively preferred conventional and ultra-rush immunotherapy. We elevated allergen concentrations diluted to 1,000:1 of the end strength by 2-3 times with 30-minute intervals and checked oxygen saturation, pulse rate, blood pressure, and systemic reactions every 15 minutes. Immunotherapy effectiveness was valued by changes in nasal provocation test scores before and after immunotherapy. Results : The average ages of patients in the conventional and ultra-rush immunotherapy groups were $8.3{\pm}2.3$ and $9.2{\pm}2.8years$, respectively. Systemic reactions were observed in six in the ultra-rush group (50%) without anaphylaxis and one (9%) in the conventional group. The average scores in the nasal provocation test before and after treatment in the conventional group were $8.2{\pm}1.5$ and $4.6{\pm}2.1$, respectively (P=0.043). In the ultra-rush immunotherapy group, the scores changed from $6.2{\pm}2.2$ to $3.7{\pm}2.5$ (P=0.017). Conclusion : Ultra-rush immunotherapy using Dermatophagoides in children is effective for treating allergic disease but can induce systemic effects rather than conventional immunotherapy.

Carbon nanotube field emission display

  • Chil, Won-Bong;Kim, Jong-Min
    • Electrical & Electronic Materials
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    • v.12 no.7
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    • pp.7-11
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    • 1999
  • Fully sealed field emission display in size of 4.5 inch has been fabricated using single-wall carbon nanotubes-organic vehicle com-posite. The fabricated display were fully scalable at low temperature below 415$^{\circ}C$ and CNTs were vertically aligned using paste squeeze and surface rubbing techniques. The turn-on fields of 1V/${\mu}{\textrm}{m}$ and field emis-sion current of 1.5mA at 3V/${\mu}{\textrm}{m}$ (J=90${\mu}{\textrm}{m}$/$\textrm{cm}^2$)were observed. Brightness of 1800cd/$m^2$ at 3.7V/${\mu}{\textrm}{m}$ was observed on the entire area of 4.5-inch panel from the green phosphor-ITO glass. The fluctuation of the current was found to be about 7% over a 4.5-inch cath-ode area. This reliable result enables us to produce large area full-color flat panel dis-play in the near future. Carbon nanotubes (CNTs) have attracted much attention because of their unique elec-trical properties and their potential applica-tions [1, 2]. Large aspect ratio of CNTs together with high chemical stability. ther-mal conductivity, and high mechanical strength are advantageous for applications to the field emitter [3]. Several results have been reported on the field emissions from multi-walled nanotubes (MWNTs) and single-walled nanotubes (SWNTs) grown from arc discharge [4, 5]. De Heer et al. have reported the field emission from nan-otubes aligned by the suspension-filtering method. This approach is too difficult to be fully adopted in integration process. Recently, there have been efforts to make applications to field emission devices using nanotubes. Saito et al. demonstrated a car-bon nanotube-based lamp, which was oper-ated at high voltage (10KV) [8]. Aproto-type diode structure was tested by the size of 100mm $\times$ 10mm in vacuum chamber [9]. the difficulties arise from the arrangement of vertically aligned nanotubes after the growth. Recently vertically aligned carbon nanotubes have been synthesized using plasma-enhanced chemical vapor deposition(CVD) [6, 7]. Yet, control of a large area synthesis is still not easily accessible with such approaches. Here we report integra-tion processes of fully sealed 4.5-inch CNT-field emission displays (FEDs). Low turn-on voltage with high brightness, and stabili-ty clearly demonstrate the potential applica-bility of carbon nanotubes to full color dis-plays in near future. For flat panel display in a large area, car-bon nanotubes-based field emitters were fabricated by using nanotubes-organic vehi-cles. The purified SWNTs, which were syn-thesized by dc arc discharge, were dispersed in iso propyl alcohol, and then mixed with on organic binder. The paste of well-dis-persed carbon nanotubes was squeezed onto the metal-patterned sodalime glass throuhg the metal mesh of 20${\mu}{\textrm}{m}$ in size and subse-quently heat-treated in order to remove the organic binder. The insulating spacers in thickness of 200${\mu}{\textrm}{m}$ are inserted between the lower and upper glasses. The Y\ulcornerO\ulcornerS:Eu, ZnS:Cu, Al, and ZnS:Ag, Cl, phosphors are electrically deposited on the upper glass for red, green, and blue colors, respectively. The typical sizes of each phosphor are 2~3 micron. The assembled structure was sealed in an atmosphere of highly purified Ar gas by means of a glass frit. The display plate was evacuated down to the pressure level of 1$\times$10\ulcorner Torr. Three non-evaporable getters of Ti-Zr-V-Fe were activated during the final heat-exhausting procedure. Finally, the active area of 4.5-inch panel with fully sealed carbon nanotubes was pro-duced. Emission currents were character-ized by the DC-mode and pulse-modulating mode at the voltage up to 800 volts. The brightness of field emission was measured by the Luminance calorimeter (BM-7, Topcon).

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The development of conductive 10B thin film for neutron monitoring (중성자 모니터링을 위한 전도성 10B 박막 개발)

  • Lim, Chang Hwy;Kim, Jongyul;Lee, Suhyun;Jung, Yongju;Choi, Young-Hyun;Baek, Cheol-Ha;Moon, Myung-Kook
    • Journal of Radiation Protection and Research
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    • v.39 no.4
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    • pp.199-205
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    • 2014
  • In the field of neutron detections, $^3He$ gas, the so-called "the gold standard," is the most widely used material for neutron detections because of its high efficiency in neutron capturing. However, from variable causes since early 2009, $^3He$ is being depleted, which has maintained an upward pressure on its cost. For this reason, the demands for $^3He$ replacements are rising sharply. Research into neutron converting materials, which has not been used well due to a neutron detection efficiency lower than the efficiency of $^3He$, although it can be chosen for use in a neutron detector, has been highlighted again. $^{10}B$, which is one of the $^3He$ replacements, such as $BF_3$, $^6Li$, $^{10}B$, $Gd_2O_2S$, is being researched by various detector development groups owing to a number of advantages such as easy gamma-ray discrimination, non-toxicity, low cost, etc. One of the possible techniques for the detection is an indirect neutron detection method measuring secondary radiation generated by interactions between neutrons and $^{10}B$. Because of the mean free path of alpha particle from interactions that are very short in a solid material, the thickness of $^{10}B$ should be thin. Therefore, to increase the neutron detection efficiency, it is important to make a $^{10}B$ thin film. In this study, we fabricated a $^{10}B$ thin film that is about 60 um in thickness for neutron detection using well-known technology for the manufacturing of a thin electrode for use in lithium ion batteries. In addition, by performing simple physical tests on the conductivity, dispersion, adhesion, and flexibility, we confirmed that the physical characteristics of the fabricated $^{10}B$ thin film are good. Using the fabricated $^{10}B$ thin film, we made a proportional counter for neutron monitoring and measured the neutron pulse height spectrum at a neutron facility at KAERI. Furthermore, we calculated using the Monte Carlo simulation the change of neutron detection efficiency according to the number of thin film layers. In conclusion, we suggest a fabrication method of a $^{10}B$ thin film using the technology used in making a thin electrode of lithium ion batteries and made the $^{10}B$ thin film for neutron detection using suggested method.

Effect of Noise in Human Body (소음이 인체에 미치는 영향)

  • 이영노
    • Proceedings of the KOR-BRONCHOESO Conference
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    • 1972.03a
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    • pp.7-8
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    • 1972
  • The effects of noise exposure are of two types: Nonauditory effects and auditory effects. Nonauditory effects of noise exposure are interference with communication by speech, sleeping and emotional behavior. The noise will cause the high blood pressure and rapid pulse, also that decrease the salivation and gastric juice. in experimentaly showed that the Corticoid hormon: Gonatotropic hormone were decrease and Thyrotropic hormoone is increase. Auditory effect of noise exposure. when the normal ear is exposed to noise at noise at hamful intensities (above 90㏈) for sufficiently long periods of time, a temoral depression of hearing results, disappearing after minutes or hours of rest. When the exposure longer or intesity greater is reached the Permanent threshold shift called noise-induced hearing loss. Hearing loss resulting from noise exposure presents legal as well as medical problems. The otologist who examines and evaluates the industrial hearing loss cases must be properly informed, not only concerning the otologic but also about the physical and legal aspects of the problems. The measurement of hearing ability is the most important part of a hearing conservation, both preplacement and periodic follow-up tests of hearing. The ideal hearing conservation program would be able to reduce or eliminate the hazardous noise at its source or by acoustic isolation of noisy working area and two ear protections (plugs and muff type) were developed for personal protection.

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