國民學校 敎師 自然 및 算數科 再敎育의 分析的 硏究 : Based on the Choong Buk Province

黃秉德,梁仁煥,崔炳文,趙璇衡,朴根生 淸州大學校 科學敎育硏究所 1977 淸州大學校 科學敎育硏究所 Vol.1 No.-

Our college has retrained many primary school teachers during 5 years is science, and during 4 years in case of mathematics. Many problems are found out in the process of retraining them in our school. This study is aimed to research the actual condition of the retraining and to find out the way to improvement from the problems. However, Our study will have some limitation as follows: (1) For our study, only 300 teachers are chosen from the total 1,869 attended at our college(Cheong Ju Teachers College) in 1976. (2) The administrational and financial affairs are analyzed only according to the Ministry of Education with UNICEF funds from 1972 to 1976, and (3) We didn't take any consideration of Ministry of Education Project in Suggesting the way of improvement. Following are some problems found in our study: 1) Throughout the nation, only 23% of primary school teachers were taught in science and mathematice reservice work during the 5 years, and it can be said that it takes about 20 years to retrained all the teachers without consideration of natural increase of teachers. 2) The proportion of selecting primary school teachers in all the country for this reservice training is extreme, for example, Jeju Province is 57.9%, Seoul 17.7%. 3) The proportion of woman teachers selected in Choong Buk primary school is only 3.5% of total woman teachers, who takes 32% of total Choong Buk primary teachers during 5 years. Therefore, it is said that the number is very little. 4) Some teachers have been reselected in the reservice training. In case of the Choong Buk Board of Education. the 6% of teachers selected once were reselected for 5 years. 5) When the test are enforced on attendants to get data before the reservice training. We could find that they didn't understand the basic concept of science except a grade under their charge. 6) In the process of inquiry study, they didn't know even the scientific terms of expectation and reasoning. 7) After 60 hours of reservice training course. We tested them about understanding of the contents of text, and their marks are from 10 to 100. the marks show large individual difference among them. 8) Some teachers may have neither teaching ability nor knowledge of the basic concept, that is 11.3% of total attendants are less than 30 marks in mathematics test. 9) It is too very large work to study reservice text during the 60 hours. 10) There are many difficult signs in the mathematics reservice text having no connection with the actual primary school mathematics text book. 11) In the reservice text of science, there are omitted the method of teaching materials production, the model of inquiry learning, and the evaluation method. 12) From the analysis of questionary response for finding the actual condition of administration of teaching materials, We could find out 15% of primary schools in Choong Buk Province do almost not prepare teaching materials, and 15% of its never put them to practical use. Therefore, We could say that total 30% of them have been teaching without teaching materials. 13) The 42% of attendants in mathematics class answer that they do not understand the new mathematical signs, and 42% of them answer the shortage of hours (60 hours) to understand their reservice text book. 14) The 25% of them answer that they teach children with cramming education, and almost of them want good teachers guide books. As mentioned above, there are found many problems to be solved for reservice training of science education in our country. Some of them will be solved in our study. So We find out its and We suggest the ways solving the problems as follows: A. On the administration of reservice training. 1) The reservice training work for primary school teachers is very significant and will have to be continued. 2) It will be done in not only summer vacation but also winter one for finishing immediatly all over the country. 3) The 60 hours of science reservice training course work are very short, and the classmember of attendants will be regulated. 4) The funds for reservice operation and travelling expenses for attendants will be realized. B. On selecting the attendants 1) When the attendants are selected, there will be consideration of age, rank, term of their service, sex and academic background. 2) as far as possible, it will be selected as homogeous groups, and it will be effective to teach them with division between class teacher and nonclass teacher. 3) When select attendants are it will be taken consideration of balance between city and province for the diffusion effect and parallel development in reservice training work. 4) It must give a chance to woman as same as to man teacher according to a rule of equal select chance. 5) The principal, instructor and school inspector will be reeducated for fixing of science curriculum. C. On reservice training text book 1) The text book must reedit moderatly for 60 hours, or the time of retraining for the text book finished will be extented. In our opinion, it is to be desired that the time have to be added. 2) The difficult signs must be omitted, taking into account for the mathematics knowledge and time of education period. 3) In the science reservice training text book, it must supplement the tack for framming of inquiry teaching plan, the method for making teaching materials, and the skill for replacing of teaching materials. D. For the curriculum management of science. 1) The Governmental Company must settle the shortage of science teaching materials in primary school. 2) For the charge of the old state of teaching method, the teachers must devote themselves to teach children without miscellaneous duties. 3) The authorities concerned (for example, Ministry of Education, Teachers College, etc.) must make guide books for science teachers, and supply them to primary school teachers. 4) It must be given the chance of long period reeducation to the incompetent primary school teachers, and problem will have to be studied under the situation of educational administration.

‘로자리오 비얀코’(Vitis vitisvinifera)와 ‘캠벨’( Vitis labrusca) 포도과실의 유황패드 처리에 따른 저장성 향상

임병선(Byung-Seon Lim),이신희(Shin Hee Lee),조미애(Mi-Ae Jo),황정환(Jung Hwan Hwang),황용수(Yong Su Hwang2) 한국원예학회 2010 한국원예학회 학술발표요지 Vol.2010 No.10

The effect of combined Rehmannia glutinosa Libosch and Eleutherococcus senticosus Max(OPB) extracts on bone mineral density in ovariectomized rats.

Kim,Jung-Keun 대한구강생물학회 2007 International Journal of Oral Biology Vol.32 No.4

This study was conducted to investigate the preventingeffects of OPB (Rehmannia glutinosa Libosch and Eleuth-erococcus senticosus Max extracts) and combined OPB/Calcium therapy on bone loss in ovariectomized rats. SixtySprague Dawley rats of 12-week-old were divided into eightgroups: OVX (ovariectomized), OPBL (OPB 50mg/kg),OPBM (OPB100mg/kg), OPBH (OPB 200mg/kg), OPBL/CAL(OPBL+CAL), OPBM/CAL (OPBM+CAL), OPBH/CAL (OPBH+CAL) and CAL (Calcium citrate 88.33mg/kg+1α, 25-dihydroxy-vitamin D3 33.33IU/kg). Bone mineraldensity (BMD), bone mineral content (BMC), bone strengthindices and cortical thickness were analyzed by peripheralquantitative computerized tomography (pQCT). pQCTscanning showed that OVX induced a significant decreasein trabecular bone mineral density and bone mineralcontent in the proximal tibia (-36.4±2.4%, -21.8±12.7%).These decreases were significantly prevented by theadministration of OPBM and OPBM/CAL. Cortical BMDand BMC of tibia were slightly enhanced by OPB and OPB/CAL. However there was no significant difference betweenOVX and OPB, OPB/CAL treated group. Bone strengthindices and cortical thickness were not significantly different.Our results suggest that OPB and combined OPB/Calciumtherapy are effective in preventing the development of boneloss induced by ovariectomy in rats.

Network Traffic Grouping Approach based on Statistic Signature and Support Vector Machine

Hwang Seon Hwan,Baek Young Mi,Yun Jeong Bae,Han Ki Jun 한국통신학회 2013 한국통신학회 학술대회논문집 Vol.2013 No.1

As network traffic is dramatically increasing, classification of application traffic becomes important for the effective use of network resources. Classification of network traffic using port-based or payload-based analysis is becoming increasingly difficult because of many peer-to-peer (P2P) applications using dynamic port numbers, masquerading techniques, and encryption. An alternative approach is to classify traffic by exploiting the distinctive characteristics of applications. In this letter, we propose a classification method of application traffic using statistic signatures based on SVM (Support Vector Machine). The statistic signatures, defined as a directional sequence of packet size in a flow, are collected for each application, and applications are classified by SVM mechanism.

Parameter Identification of a Synchronous Reluctance Motor by using a Synchronous PI Current Regulator at a Standstill

Hwang, Seon-Hwan,Kim, Jang-Mok,Khang, Huynh Van,Ahn, Jin-Woo The Korean Institute of Power Electronics 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.5

This paper proposes an estimation algorithm for the electrical parameters of synchronous reluctance motors (SynRMs) by using a synchronous PI current regulator at standstill. In reality, the electrical parameters are only measured or estimated in limited conditions without fully considering the effects of the switching devices, connecting wires, and magnetic saturation. As a result, the acquired electrical parameters are different from the real parameters of the motor drive system. In this paper, the effects of switching devices, connecting wires, and the magnetic saturation are considered by simultaneously using the short pulse and closed loop equations of resistance and synchronous inductances. Therefore, the proposed algorithm can be easily and safely implemented with a reduced measuring time. In addition, it does not need any external or additional measurement equipment, information on the motor's dimensions, and material characteristics as in the case of FEM. Several experimental results verify the effectiveness of the proposed algorithm.

DC Offset Error Compensation of Current Sensor for Single-phase Permanent Magnet Synchronous Motor Drives

Hwang Seon-Hwan 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.1

In this paper, a compensation algorithm for DC ofset error in the current measurement path of a single-phase permanent magnet synchronous motor (SP-PMSM) is proposed. In general, current information is necessary to perform vector control of the SP-PMSM based on the synchronous reference frame. However, the nonideal nature of the current measurement process causes the DC ofset and scaling errors in the current path. Especially, the DC ofset error generates a fundamental frequency ripple in the synchronous reference frame dq-axis currents. As a result, the speed ripple of the SP-PMSM drives is the same as the dq-axis current ripples. Therefore, the DC ofset error is compensated using an integral controller and detected by the low-pass flter to obtain the dc component in the integral output of stator fux estimator. The efectiveness of the proposed method is verifed through several experimental results.

Signal Compensation for Analog Rotor Position Errors due to Nonideal Sinusoidal Encoder Signals

Seon-Hwan Hwang,Dong-Youn Kim,Jang-Mok Kim,Do-Hyun Jang 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.1

This paper proposes a compensation algorithm for the analog rotor position errors caused by nonideal sinusoidal encoder output signals including offset and gain errors. In order to achieve a much higher resolution, position sensors such as resolvers or incremental encoders can be replaced by sinusoidal encoders. In practice, however, the periodic ripples related to the analog rotor position are generated by the offset and gain errors between the sine and cosine output signals of sinusoidal encoders. In this paper, the effects of offset and gain errors are easily analyzed by applying the concept of a rotating coordinate system based on the dq transformation method. The synchronous d-axis signal component is used directly to detect the amplitude of the offset and gain errors for the proposed compensator. As a result, the offset and gain errors can be well corrected by three integrators located on the synchronous d-axis component. In addition, the proposed algorithm does not require any additional hardware and can be easily implemented by a simple integral operation. The effectiveness of the proposed algorithm is verified through several experimental results.

DC Offset Error Compensation for Synchronous Reference Frame PLL in Single-Phase Grid-Connected Converters

Seon-Hwan Hwang,Liming Liu,Hui Li,Jang-Mok Kim IEEE 2012 IEEE TRANSACTIONS ON POWER ELECTRONICS - Vol.27 No.8

<P>This letter proposes a dc offset error compensation algorithm for synchronous reference frame phase-locked loop (PLL) in single-phase grid-connected converters. The errors generated from the grid voltage measurement circuits can be divided into dc offset and scaling errors. These errors may cause the undesirable periodic ripples with grid frequency in the synchronous reference frame PLL. As a result, the performance of the power conversion systems is degraded. In this letter, the effects of the dc offset and scaling errors are comprehensively analyzed based on the synchronous dq frame PLL. In particular, the dc offset error can be estimated and compensated by controlling the synchronous d-axis voltage in a PLL system to be zero. The proposed algorithm does not require any additional hardware and can be implemented by a simple proportional-integral controller and an integral operation. Experimental results are presented to demonstrate the effective- ness of the proposed dc offset error compensation algorithm.</P>

Dead Time Compensation Method for Voltage-Fed PWM Inverter

Seon-Hwan Hwang,Jang-Mok Kim IEEE 2010 IEEE transactions on energy conversion Vol.25 No.1

<P>A new dead time compensation method for a pulsewidth modulation (PWM) inverter is proposed. In the PWM inverter, voltage distortion due to the dead time effects produces fifth and seventh harmonics in the phase currents of the stationary reference frame, and a sixth harmonic in the <I>d</I>- and <I>q</I>-axis currents of the synchronous reference frame, respectively. In this paper, the sixth harmonic of the integrator output of the synchronous <I>d</I>-axis proportional-integral (PI) current regulator is used to compensate the output voltage distortion due to the dead time effects, since the integrator output has ripple corresponding to six times the stator fundamental frequency. The proposed method can be easily implemented by feedforwardly adding compensation voltages to the output reference voltage of the synchronous PI current regulator. The proposed method, therefore, has some significant advantages such as simple implementation without additional hardware, easy mathematical computation, no offline experimental measurements, and application in both the steady state and the transient state. The validity of the proposed compensation algorithm is shown through several experiments.</P>

Signal Compensation for Analog Rotor Position Errors due to Nonideal Sinusoidal Encoder Signals

Hwang, Seon-Hwan,Kim, Dong-Youn,Kim, Jang-Mok,Jang, Do-Hyun The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.1

This paper proposes a compensation algorithm for the analog rotor position errors caused by nonideal sinusoidal encoder output signals including offset and gain errors. In order to achieve a much higher resolution, position sensors such as resolvers or incremental encoders can be replaced by sinusoidal encoders. In practice, however, the periodic ripples related to the analog rotor position are generated by the offset and gain errors between the sine and cosine output signals of sinusoidal encoders. In this paper, the effects of offset and gain errors are easily analyzed by applying the concept of a rotating coordinate system based on the dq transformation method. The synchronous d-axis signal component is used directly to detect the amplitude of the offset and gain errors for the proposed compensator. As a result, the offset and gain errors can be well corrected by three integrators located on the synchronous d-axis component. In addition, the proposed algorithm does not require any additional hardware and can be easily implemented by a simple integral operation. The effectiveness of the proposed algorithm is verified through several experimental results.