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LoRa Device의 이동성을 고려한 GRU 기반 적응형 데이터 전송 속도 제어 알고리즘
정현호,유성은 제어·로봇·시스템학회 2022 제어·로봇·시스템학회 논문지 Vol.28 No.6
Long Range Wide Area Network (LoRaWAN), a representative technology of Low Power Wide Area Network (LPWAN), is a networking technology for the long-range Internet of Things. It features low power, a long distance, and low speed, and each device in LoRaWAN supports adaptive data rate (ADR) technology to save transmission power. For implementing ADR in LoRaWAN, a network server uses algorithms to reduce power consumption by minimizing the time LoRa Radio packets stay in the air and sends a medium access control (MAC) command frame to increase the data rate or adjust transmission power by referring to signal-to-noise ratio (SNR) values. However, because the existing ADR algorithm for the network server sets the appropriate data rate and transmission power based on the maximum SNR value of the recent 20 packets, it does not support mobile devices because the SNR values of the mobile devices vary over time depending on their speeds. This paper introduces an improved ADR, GRU-ADR, that infers the future SNR values using the deep-learning gated recurrent unit (GRU) model to set appropriate data rates and transmission power using the ADR function even in mobile devices. The simulation study based on the OMNeT++ simulator and the Framework for LoRa (FLoRa) shows that GRU-ADR outperforms the existing ADR in packet delivery ratio (PDR) and energy consumption. .
정현호,지영석,성미선,김경근,윤경철 전남대학교 의과학연구소 2015 전남의대학술지 Vol.51 No.1
This retrospective study was performed to analyze the long-term outcome of topicalcorticosteroid treatment for severe dry eye associated with Sjögren’s syndrome (SS). Patients who had severe dry eye associated with SS were topically treated with loteprednoletabonate 0.5% (group A, n=66) or fluorometholone 0.1% (group B, n=67) twicedaily and were followed up for 2 years. Visual acuity (VA), intraocular pressure (IOP),Schirmer test, tear film breakup time (BUT), keratoepitheliopathy, and symptomscores were measured at baseline and 6, 12, 18, and 24 months after treatment. VAand IOP were not changed significantly during follow-up in either group. Schirmer testresults, keratoepitheliopathy, and symptom scores at 6, 12, 18, and 24 months (p<0.05)and tear film BUT at 12, 18, and 24 months (p<0.05) significantly improved after treatmentcompared with baseline in both groups. No significant differences between thegroups were found in any parameter during follow-up. At 24 months, the number ofpatients with IOP elevation of more than 2 mmHg compared with baseline was 4 ingroup A (6.1%) and 9 in group B (13.4%). The mean IOP in these patients was lowerin group A than in group B (15.00±0.82 mmHg versus 16.50±1.12 mmHg; p=0.04). Long-term application of low-dose topical corticosteroids is effective for controllingsigns and symptoms of chronic, severe dry eye associated with SS. Loteprednol etabonate0.5% may have a lower risk for IOP elevation than fluorometholone 0.1%.
스테이터의 형태에 따른 Cross형 초음파 회전모터의 구동특성
정현호,박태곤 대한전기학회 2005 전기학회논문지C Vol.54 No.10-C
This paper studied Rotary type ultrasonic motor which has cross type stator. The stator consists of hollowed cross type metal which has four piezoelectric ceramics on the ends of cross bars. When two harmonic voltages which have 90o phase difference given to ceramics, the elliptical motion was generated in the inside tips. Inside tips are contact with rotor and these elliptical motions are rotate the rotor. The finite element analysis was used to optimize the dimension and displacement of the stator. And the analyzed results were compared with the experimental results of the motor. As results, the speed and the torque of motor was increased by increasing width of the cross bar. And the speed and torque of motor was not influenced to length of cross bar. The speed and torque was linearly increased by increasing voltage. The maximum torque was generated when the motor fabricated length of cross bar and width of ceramics in the ratio of 1:2.
스테이터의 재질에 따른 Cross형 초음파 회전모터의 구동특성
정현호,박태곤,Chong, Hyon-Ho,Park, Tae-Gone 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.10
Novel structure ultrasonic motors which have cross type stator were designed and fabricated. Driving characteristics of the motors were analyzed and measured by changing the materials of the stator. This ultrasonic motor has stator with hollowed cross bar and the stator rotate the rotor using elliptical displacement of the inside tips. This motion is generated by lateral vibration mode of cross bars. This stator was analyzed by finite element analysis depandent on stator's materials. And the cross type ultrasonic motors were made by analyzed results. The larger displacements were obtained, when the density of material was decreased. But the stress was increased when the stator's material has large density and Young's modulus. The fabricated one has high speed and torque in large stress on contact point between rotor and stator. The stress was more effected on speed and torque than the displacement.
소량의 자발성 뇌내출혈에서 재출혈에 의한 혈종 성장에 미치는 인자
정현호,김세윤,황금,조성민,변진수,허철,홍순기,Jung, Hyun Ho,Kim, Sei Yoon,Whang, Kum,Cho, Sung Min,Pyen, Jhin Soo,Hu, Chul,Hong, Soon Ki 대한신경외과학회 2001 Journal of Korean neurosurgical society Vol.30 No.2
Objectives : Spontaneous intracerebral hemorrhage(S-ICH) is generally considered to be a mon-ophasic event. But some patients with ICH continued to bleed even after hospitalization. In order to evaluate the rebleeding and growth factor of hematoma in small volume S-ICH, 125 cases of S-ICH were reviewed retrospectively. Methods : We assesed age, sex, initial mental state, location of hemorrhage, systolic and diastolic blood pressure, blood pressure patterns, hematologic profile, trauma and stroke history, alcohol consumption and smoking history. Two subgroups-rebleeding groups versus no rebleeding groups-were compared, in terms of data analysis, with student T-test and chi-square test. Results : Substantial growth in the volume of S-ICH occurred in 21 cases(16.8%)-putamen(7 cases), thalamus(6 cases), subcortex(5 cases), cerebellum(2 cases), pons(1 case)-of the 125 patients. There was no significant difference in any of the parameters except initial systolic blood pressure(p=0.037) when patients with and without rebleeding were compared. Conclusion : The rebleeding and growth of the small volume S-ICH was related to the markedly elevated initial systolic blood pressure(${\geq}180mmHg$) and labile pattern of blood pressure.
내경동맥에 발생한 외상성 가성동맥류에 대한 혈관내 스텐트 치료
정현호,김헌주,이명섭,황금,조성민,허철,변진수,홍순기,Jung, Hyun Ho,Kim, Hun Joo,Lee, Myeung Sub,Whang, Kum,Cho, Sung Min,Hu, Chul,Pyen, Jhin Soo,Hong, Soon Ki 대한신경외과학회 2001 Journal of Korean neurosurgical society Vol.30 No.2
This 18-year-old male patient had a massive epistaxis after motorcycle traffic accident on 1st day of admission. There were no other significant brain parenchymal lesion on initial brain CT exam, except multiple pneumocephalus and basal skull fracture lines. We treated epistaxis conservatively till vital signs were corrected, and then conventional cerebral angiogram was followed. On angiogram, there was traumatic pseudoaneurysm on C5 portion(by Fischer) of ICA, so we treated it only by endovascular stenting. For the purpose of sparing parent arterial patency, endovascular stenting on pseudoaneurysm may play a role with safety and good results.