• Journal of the Korean Institute of Telematics and Electronics
• /
• v.8 no.3
• /
• pp.1-14
• /
• 1971

A relay servo, one of the nonlinear sytsems, is inherently compact compared to a linear system for an equivalent control problem. The power element or actuator is not adjusted proportionally in accordance with an error signals but rather is switched abruptly between several discrete conditions. Usually switched conditions are off, full, forward or full reverse. The relay system is a particularly simple and compact one, but probably more effort has been expended on its analysis and design than on all other systems together. Early studies in the art were made by Goldfarb, austin, Oppelt and Kochenburger on the describing function method, which can be used as an approximate check on the stability of the system. The describing function method is based on the assumption that any periodic wave could be approximated as a fundamental one in wide ranges of practical applications. A relay servo system usually operates on a limit cycle condition as the loop gain increases. The stability analysis compensation or any improvement effort based on the describing function method sometimes may present considerable discrepancies on physically realized practical systems. An approach to exact periodic solutions of a relay servo system is much important for the analysis, design and system improvement. This paper dells with periodic solutions of a relay servo system on the basis of describing function and generalized chopper wave form which is composed of infinite number of harmonic series. Various ways of graphical representation were attempted to get periodic solutions, some of which have shown its validity in rapid approach to exact solutions and also in judgement of system behavior.

• Journal of Sensor Science and Technology
• /
• v.8 no.1
• /
• pp.69-79
• /
• 1999

The research and implementation was preformed on high-resolution CCTV camera with CCD exclusive DSP conventional analog signal processor CCTV camera has its limit on auto exposure(AE), auto white balance(AWB), back light compensation(BLC) processing, severe distortion and noise of image, manual control parameter setting, etc. In our study, to resolve the problems in conventional CCTV camera, we made it possible to control AE, AWB, BLC automatically by the use of the DSP, which are used exclusively in the CCD camera produced domestically, and the microcontroller. And we utilized the function of screen display of microcontroller for the user-friendly interface to control CCD camera. And the electronic variable resister(EVR) was used to avoid setting parameters manually in the level of manufacturing process. As the result, It became possible to control parameters of the camera by program. And the cost-down effect was accomplished by improving the reliability of parameter values and reducing the efforts in setting parameters.

• The Korean Journal of Health Service Management
• /
• v.4 no.1
• /
• pp.145-156
• /
• 2010

The purpose of this study is one of high price medical equipment wished to grasp propriety factor about the MRI introduction, analyzing payability through cost accounting into compensation. It was investigated from January 1 to December 31, 2007 about the MRI of a General Hospital. Expectation availability was 23.2 cases, but actual availability did achievement more than 196.1% with 45.5 items. It is estimated that there are a lot of occurrence cases because great reasons that actual availability increases more than expectation availability is excellent resolving power than a CT, and is device that prefer to reason back that radiation damage is less in person body. The followings show the main results of this study. 1. The MRI was construed in order of cost accounting, wave and personnel expenses 45.4%, administrative expenses 53.0%, and material costs 1.6%. 2. According to CVP (Cost-volume-profit) analysis, BEP (Break Even Point) profit is 173,931,428 won for 11 months, and break even usage number of items are 37.5 cases, and separation usage number of items were confirmed by 1.4 cases. Therefore, was construed that can achieve BEP within 11 months though usage number of items keeps 1.4 items day to create the MRI's hospital operation profit. 3. Estimated limit profitability appears high by 96.7%, exceed fixed charges even if when is non-benefit and when it is benefit consider variable, is judged that the MRI's addition induction helps in hospital management enhancing earning rates.

• Journal of Environmental Policy
• /
• v.3 no.2
• /
• pp.31-57
• /
• 2004

Attempts were made to compare and analyze the policies of the United States, the United Kingdom, the Netherlands, Germany and Denmark concerning Korea's major problems associated with legal liability of the contaminated sites. These countries were chosen from a feasible preliminary analysis of 18 countries of the EU and the U. S. The major problems were revealed based on the analysis of Korean legacy and legislation, which are summarized as follows i) lack of clear detailed technical and legal guidance to determine the responsible party or parties of contaminated sites, ii) no distinction between the strict and non strict legal liability of innocent land owners, iii) no clearly set limit on retroactive legal liability. Comparison of the policies of countries chosen suggested improvements regarding these major problems as follows: i) activating national and international research on soil contamination prevention policy, ii) arranging distinct legal regulation between strict and non strict liability criteria, iii) establishing the limits on innocent and non strict liability, iv) establishing methodology and process of legal liability distribution and compensation, and v) establishing a legal process to redeem any benefit derived from remediation of contaminated sites with the public budget. Our policy suggestions above are not yet conclusive due to a lack of policy implementation simulation. Additional research is needed on aspects of social, economic and long term effects of the proposed policy directions. Nevertheless, application of the policy suggestions of this research would increase the efficacy of Korean policy regarding the survey and remediation of the potentially contaminated sites.

• Journal of the Microelectronics and Packaging Society
• /
• v.20 no.4
• /
• pp.25-30
• /
• 2013

Pb-free ferroelectric $(Na_{0.5}Bi_{0.5})TiO_3$ (NBT) thin films were prepared by a modified sol-gel process. Their structural, dielectric and pyroelectric properties were investigated as a function of the excess Na/Bi ratio and the annealing temperature. In the case of thin films containing no excess Na and Bi, only partial amounts of the perovskite NBT were crystallized, where the films consisted mainly of the pyrochlore phase of $Bi_2Ti_2O_7$ for annealing conditions of $600{\sim}800^{\circ}C$. With increasing excess Na/Bi ratio, the proportion of the perovskite phase effectively increased due to the compensation of the volatile Na and Bi components. For a Na/Bi ratio of 2.0, the thin film with single NBT perovskite phase was obtained within XRD detection limit after annealing at $700^{\circ}C$ for 10 min and it showed the excellent dielectric properties, ${\varepsilon}r$ of ~550 and tan ${\delta}$ of 0.03. While these properties were degraded for Na/Bi ratio of 2.5 despite the existence of pure perovskite phase. The NBT thin film with Na/Bi ratio of 2.0 are also promising candidates for applications requiring pyroelectric devices because it was found to have pyroelectric coefficients of $1.3{\sim}7nC/cm^2K$ in the temperature range of $30{\sim}100^{\circ}C$.

• Journal of the Ergonomics Society of Korea
• /
• v.29 no.4
• /
• pp.465-471
• /
• 2010

Work-related musculoskeletal disorders (WMSDs) have been the most common health problem covered by worker's accident compensation insurance for several years in Korea. Korean government has strengthened related regulations since 2003. People looked forward to decreasing the incidence and prevalence of WMSDs. At first, the expectation could be realized. However, we were bumped against to limit at present. The authors think it is due to the negligence of psychosocial factors for WMSDs. Many researchers reported that the various psychosocial factors were associated with WMSDs or symptoms. Job demand, social support, job satisfaction and decision latitude are the major risk factors in job stress aspect. Work pressure, lack of rest, qualified workload, workload variability and monotonous job are the significant risk factors in work context of work organization. Employment flexibility, downsizing, lean production, contingent work and pay for by the piece are also the risk factors in an organizational context. Furthermore, these risk factors are associated with each other across different dimensions of work organization. Suggestive possible pathways between these risks and WMSDs have been taken note of increasing muscle strain or ergonomic stress and of a cognitive aspect. The authors suggest these risk factors could explain the limitation of the regulation system for WMSDs. In conclusion, the strategy to manage psychosocial factors is the one of the essential approach to prevent WMSDs.

• Journal of the Korean Society for Railway
• /
• v.9 no.6 s.37
• /
• pp.761-765
• /
• 2006

At present, harmonic currents cause serious problems in power conversion system using the semiconductor switching device. Also some of the conversion system provokes harmonic currents against to the main power supply system and causes hindrances for the system. Main power impedance of the traditional LC passive filter method, influences on the filter characteristics and amplifies the harmonics when resonance phenomenon is occurred. And the traditional existing 2 level inverter systems show the limit in capacity of voltage and current in case of occurring sudden load change. So, to solve this problem active filter which uses cascaded H-bridge multi level inverter has been designed and ex-filter system circuits were totally investigated. With multi level active filtering system not only the size of filter but also the size of filter for transformer can be reduced by half and so as to the weight, while the capacity of inverter can be double sized and wave forms can be compensated exactly and precisely. Also by the benefit of the increase in rating capacity, the various currents owing to the load fluctuation can be dealt more steadily. In order to simulate the wave form of harmonics based on the measured data on the AC 25kV high speed Domestic Commercial railway, it was simulated with PSCAD/EMTDC and PSIM. Based on the results of this demonstration, the power supply system and inverter system would be more stable and also promoting its efficiency.

• The Korean Society of Law and Medicine
• /
• v.14 no.2
• /
• pp.143-172
• /
• 2013

In order to achieve the purpose of treatment for patients by a doctor, the instruction explanation obligation, which means that he should give patients the description in more details to prepare for postoperative sequelae or complications, is common with the advice explanation obligation as a doctor should ex-plain some information to patients. Since the advice explanation obligation is the benefit and protection of the law for self determination right, but the instruction explanation obligation is one for the integrity of body and life, one can be distinct from the other. Judgments giving the instruction on the concept of instruction explanation obligation, specific methods of implementation and a range of compensation for damage are recently being made by courts at all levels including the Supreme Court. It is the time to systematize them. The contents which have been mainly discussed so far include the essence of above mentioned instruction explanation obligation. However, when the tendency of practice is considered, the efforts are required to admit the organic relevance between instruction explanation obligation and advice explanation obligation and to explain the relationship without any contradiction. For whereabouts of li-ability of proof, patients theoretically demonstrate the failure to implement it. However, when the theoretical consistency is maintained, it is likely to fail the intent to recognize the instruction explanation obligation and it may ask patients to prove something impossible to be proven. Thus, these things should be considered. Moreover, as the instruction explanation obligation is associated with medicine instruction obligation of a pharmacist and the coverage is being extended, it is the time to require the systematic study on the theoretical limit.

• The korean journal of orthodontics
• /
• v.33 no.3 s.98
• /
• pp.141-150
• /
• 2003

The purposes of this study were to classify the anteroposterior and vertical skeletal pattern of normal occlusion samples into specific types with factor and hierarchical cluster analysis, and to evaluate the range and limit of skeletal relationships that permit the establishment of normal occlusion via natural dentoalveolar compensation. Lateral cephalograms of 294 normal occlusion samples were measured, as selected from 15,836 persons through a community dental health survey who cooperated in record taking. Using a factor analysis, two factors representing anteroposterior and vertical skeletal relationships were extracted from 18 skeletal measurements. Then cluster analysis classified the skeletal patterns into nine types. The means and the standard deviations of 8 anteroposterior skeletal measurements and 10 vertical skeletal measurements were determined and comparisons of these measurements among the types were performed. The results obtained in this study showed that the range of normal occlusion included very diverse anteroposterior and vertical skeletal relationships.

• Journal of Korean Neurosurgical Society
• /
• v.45 no.5
• /
• pp.293-296
• /
• 2009

Objective : Pain has long been regarded as a subjective symptom. Recently, however, some regard a type of intractable chronic pain as a disease. Furthermore, chronic persistent pain becomes a cause of permanent impairment (PI) In 6th edition, the American Medical Association (AMA) Guides has rated the pain as a PI. In Korea, pain has been already been rated as a PI. Here, we examined the present status and the prospect of disability evaluation for the pain in Korea. Methods : Pain can be rated as a PI by the Workmen's Compensation Insurance Act (WCIA) and Patriots and Veterans Welfare Corporation Act (PVWCA) in Korea. We examined the definition, diagnostic criteria and grades of the pain related disability (PRD) in these two acts. We also examined legal judgments, which were made in 2005 for patients with severe pain. We also compared the acts and the judgments to the criteria of the 6th AMA Guides. Results : The PRD can berated as one of the 4 grades according to the WCIA. The provisions of the law do not limit the pain only for the complex regional pain syndrome (CRPS). The PRD can berated as one of the 3 grades by the PVWCA. If there were objective signs such as osteoporosis, joint contracture and muscle atrophy corresponding to the CRPS, the grade is rated as 6. When the pain always interferes with one's job except easy work,the grade is rated as high as 5. In Korea, judicial precedents dealt the pain a sa permanent disability in 2005. Conclusion : Although there were no objective criteria for evaluation of the PRD, pain has been already rated as a PI by the laws or judicial precedents, in Korea. Thus, we should regulate the Korean criteria of PRD like the AMA 6th edition. We also should develop the objective tools for evaluation of the PRD near in future.