• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.1199-1205
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• 1993

It has been well known that the assumption of full state availability is one of the most important restrictions to the practical realization of VSCS. And several attempts to alleviate the assumption had been made. However, it is not easy to find a positive scheme among them. Recently, an output feedback variable structure control system(OFVSCS) was proposed and the effectiveness of the scheme was validated for the disturbance free systems. The purpose of this study is to propose a robust OFVSCS that have the robust properties against process parameter variations and external distrubances by extending the basic OFVSCS and to evaluate its control performances through power system stabilizer design example. The ROFVSCS is composed of dynamic switching function and output feedback switching control inputs that are constructed by the use of the unknown vector modeling technique. With the proposed scheme, existence of sliding mode is guaranteed and any nonzero bias can be suppressed in the face of disturbances and process parameter variations as far as well-known matching condition is satisfied. Due to the fact that the ROFVSCS is driven by small number of measured informations, the practical application of VSCS for the systems with unmeasurable states and for high order systems that conventional schemes cannot be applied, is possible with the proposed scheme. It is noticeable that the implementation cost of VSCS can be considerably reduced without sacrifice of control performances by adopting ROFVSCS since there is no need measure the states with high measurement cost.

• Safety and Health at Work
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• 제13권3호
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• pp.261-262
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• 2022

Globally, it is estimated that the number of people living outside of their country of origin reached 281 million in 2020. The primary drive of those migrants when migrating voluntarily is work to increase their income and provide for their families left behind in their home countries. Those who migrate immediately seek means of income to sustain themselves through a perilous process as currently evidenced in the war in Ukraine and not too long ago in Syria and Venezuela. Unfortunately, migrant workers are globally known to predominantly be working in "4-D jobs"- dirty, dangerous, and difficult and discriminatory; the fourth D was recently added to acknowledge the discriminatory aspect and other social determinants of health migrant workers face in their host country while exposed to precarious work. Consequently, migrant workers are at considerable risk of work-related illnesses and injury but their health needs are critically overlooked in research and policy. Recognizing the UN Universal Declaration of Human Rights "Everyone has the right to work, to free choice of employment, to just and favourable conditions of work and to protection against unemployment", we cannot consider any human life - thus, the life of migrant workers - as dispensable through a structural discriminatory process that undervalues their occupational safety and health, livelihood and the contribution these workers bring to their host countries. This was seen during the preparation for the upcoming world cup in Qatar where migrant workers were exposed to a multiplicity of serious hazards including deadly heat hazards.

• Archives of Plastic Surgery
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• 제51권5호
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• pp.480-486
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• 2024

Many failures in total or subtotal nasal reconstruction result from an underestimation of the amount of skin required for an adequate result, especially for sufficient lining. Such planning errors usually lead to poor results, with exposure of structural grafts, infection, scar retraction, airway obstruction, and finally loss of projection and shape of the reconstructed nose. Reconstruction options for cases in which previous attempts have failed are always limited, as well as in cases of trauma or burns affecting the soft tissues of the forehead and face. In such complex situations, one may employ free flaps or tissue expansion, but such resources may not be always available. We describe a technique indicated for salvage surgeries in patients whose previous nasal reconstructions have failed, allowing a generous amount of tissue transfer for the nasal region. The technique combines the use of supraclavicular and submental flaps, with simple execution, not requiring microsurgical skills or devices such as tissue expanders. Done in three stages, the described technique provides enough skin for a total nasal reconstruction. The final result is obtained after subsequent refinements, and the total number of procedures is equivalent to when more sophisticated techniques are employed, such as tissue expansion or microsurgery.

• Advances in aircraft and spacecraft science
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• 제6권1호
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• pp.31-49
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• 2019

Flutter is a dangerous phenomenon encountered in flexible structures subjected to aerodynamic forces. This includes aircraft, helicopter blades, engine rotors, buildings and bridges. Flutter occurs as a result of interactions between aerodynamic, stiffness and inertia forces on a structure. The conventional method for designing a rotor blade to be free from flutter instability throughout the helicopter's flight regime is to design the blade so that the aerodynamic center (AC), elastic axis (EA) and center of gravity (CG) are coincident and located at the quarter-chord. While this assures freedom from flutter, it adds constraints on rotor blade design which are not usually followed in fixed wing design. Periodic Structures have been in the focus of research for their useful characteristics and ability to attenuate vibration in frequency bands called "stop-bands". A periodic structure consists of cells which differ in material or geometry. As vibration waves travel along the structure and face the cell boundaries, some waves pass and some are reflected back, which may cause destructive interference with the succeeding waves. In this work, we analyze the flutter characteristics of a helicopter blades with a periodic change in their sandwich material using a finite element structural model. Results shows great improvements in the flutter forward speed of the rotating blade obtained by using periodic design and increasing the number of periodic cells.

• Wind and Structures
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• 제23권2호
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• pp.127-142
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• 2016

Aerodynamic effects, such as drag force and flow-induced vibration (FIV), on civil engineering structures can be minimized by optimally modifying the structure shape. This work investigates the turbulent wake of a square prism with its faces modified into a sinusoidal wave along the spanwise direction using three-dimensional large eddy simulation (LES) and particle image velocimetry (PIV) techniques at Reynolds number $Re_{Dm}$ = 16,500-22,000, based on the nominal width ($D_m$) of the prism and free-stream velocity ($U_{\infty}$). Two arrangements are considered: (i) the top and bottom faces of the prism are shaped into the sinusoidal waves (termed as WSP-A), and (ii) the front and rear faces are modified into the sinusoidal waves (WSP-B). The sinusoidal waves have a wavelength of $6D_m$ and an amplitude of $0.15D_m$. It has been found that the wavy faces lead to more three-dimensional free shear layers in the near wake than the flat faces (smooth square prism). As a result, the roll-up of shear layers is postponed. Furthermore, the near-wake vortical structures exhibit dominant periodic variations along the spanwise direction; the minimum (i.e., saddle) and maximum (i.e., node) cross-sections of the modified prisms have narrow and wide wakes, respectively. The wake recirculation bubble of the modified prism is wider and longer, compared with its smooth counterpart, thus resulting in a significant drag reduction and fluctuating lift suppression (up to 8.7% and 78.2%, respectively, for the case of WSP-A). Multiple dominant frequencies of vortex shedding, which are distinct from that of the smooth prism, are detected in the near wake of the wavy prisms. The present study may shed light on the understanding of the underlying physical mechanisms of FIV control, in terms of passive modification of the bluff-body shape.

• Steel and Composite Structures
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• 제49권3호
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• pp.307-323
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• 2023

In this research, the study of the thermoelastic flexural analysis of silicon carbide/Aluminum graded (FG) sandwich 2D uniform structure (plate) under harmonic sinusoidal temperature load over time is presented. The plate is modeled using a simple two dimensional integral shear deformation plate theory. The current formulation contains an integral terms whose aim is to reduce a number of variables compared to others similar solutions and therefore minimize the computation time. The transverse shear stresses vary according to parabolic distribution and vanish at the free surfaces of the structure without any use of correction factors. The external load is applied on the upper face and varying in the thickness of the plates. The structure is supposed to be composed of "three layers" and resting on nonlinear visco-Pasternak's-foundations. The governing equations of the system are deduced and solved via Hamilton's principle and general solution. The computed results are compared with those existing in the literature to validate the current formulation. The impacts of the parameters (material index, temperature exponent, geometry ratio, time, top/bottom temperature ratio, elastic foundation type, and damping coefficient) on the dynamic flexural response are studied.

• 한국가금학회지
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• 제46권1호
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• pp.47-53
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• 2019

The aim of this study was to investigate the difficulties that Korean farmers and processors currently experience with respect to the market for Korean native chicken (KNC). This study also provides suggestions by which they can overcome these difficulties. In all, sixty-nine farmers and sixty-two processors participated in our investigation, which addressed 1) the current difficulties that KNC farmers face, 2) the current importance-satisfaction measures among KNC farmers and processors, and 3) the future direction of the KNC market: farmer and processor opinions. The respondents stated that the limited number of sales stores was the most difficult market condition they faced in raising KNC, followed by feed cost, animal disease, and poor production environment. Regarding issues of importance and satisfaction, origin in raising step and slaughtering in the processing and distribution step were considered the areas most in urgent need of improvement, given farmers' and processors' high levels of dissatisfaction with these. Both the free-range farming system and the concept of animal welfare are growing in importance, given consumers' interests in these areas. As to opinions on the direction of KNC development, menu development was cited as most important, followed by public advertisement, accessibilities, business aid, and breed development. Consequently, the results show that well-organized support from both the government and related industries is needed, as chicken farmers and processors cannot resolve certain limitations inherent in the KNC industry on their own.

• Journal of Preventive Medicine and Public Health
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• 제42권6호
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• pp.403-407
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• 2009

Objectives : The amount of medical utilization by Medical Aid recipients was 3.7 times that of patients with Korean Medical Insurance. This study aims to describe the surplus medicine and the medication-related utilization, and to determine factors contributing to surplus medicine. Methods : Among those who used copayment-free Class I Medical Aid in 2005, 146,880 subjects who were $\geq19$ year-old and received >365 days medical treatment per year were studied with their case managers by conducting face-to-face interviews. The analytic methods were description, chi-square, t-tests, ANCOVA and multiple logistic regressions. Results : Most subjects were female (68.6%), the elderly (62.5%), and the separated (61.6%), had an elementary graduation or less (74.8%), and had disabilities (33.2%). The percentage of subjects with surplus medicine was 18.5%. However, the percentage of females, the elderly, those with non-disabilities, the separated, the uneducated, those with a very poor perceived health status and those with an economical burden for medical treatment was 19.3%, 18.9%, 19.0%, 19.3%, 19.0%, 20.2% and 24.3%, respectively. For subjects with surplus medicine, averages for the number of used pharmacies, the pharmacy-visit days and the medication costs were 4.6 drugstores, 34.9 days and approximately 1,124 thousand Won(￦). These values were higher than those without surplus medicine (4.4 drugstores, 33.8 days, and ￦1,110 thousand, respectively). The odds ratios of the contributing factors to surplus medicine were female 1.11 (95% CI=1.07-1.14), the elderly 1.06 (95% CI=1.02-1.10), those with non-disabilities 1.08 (95% CI=1.05-1.12), the separated 1.14 (95% CI=1.10-1.18), the unmarried 1.12 (95% CI=1.07-1.18), the uneducated 1.03 (95% CI=1.01-1.08), those with a very poor perceived health status 1.04 (95% CI=1.01-1.08) and experiencing an economical burden for medical treatment 2.33 (95% CI=2.26-2.40). Conclusions : 18.5% of subjects had surplus medicine with a higher mean of medication cost. Therefore, health education and health promotion programs to prevent surplus medicine and to improve the appropriate usage of medication are necessary.

• 화약ㆍ발파
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• 제42권3호
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• pp.49-57
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• 2024

선행이완발파는 본 굴착 전에 대상 암반에 균열을 유도하는 발파이고, 선행이완발파의 일종으로 터널내 기계굴착을 위해 막장을 사전 취약화하는 프리프랙쳐링발파가 개발되었다. 본 연구는 일반 발파 설계의 절반의 장약을 이용하여 프리프랙쳐링발파의 효과를 검증하고자 하였다. 가평에 위치한 채석장에서 시험 시공한 결과, 일반 발파에 비해 소음이 공당 장약량 감소로 인해 2.7 dB 줄어들었고 정밀진동제어발파 수준으로 진동이 제어되었다. 암반 취약화는 표면 및 코어 관찰에서 유도된 균열을 통해 확인되었으며, 저항선 증가에 따라 발파에 의한 취약화 효과가 감소함을 관찰하였다. 시험 시공에서 일반 발파의 진동이 프리프랙쳐링발파보다 작게 측정되었으나, 장약량, 저항선, 자유면 등의 발파 설계 요인보다 절리와 같은 지반 조건이 진동 저감에 더 큰 영향을 미쳤기 때문으로 분석되었다.

• Architectural research
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• 제8권1호
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• pp.1-7
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• 2006

Various housing measures are needed for the rapidly aging society of Korea. In particular, the welfare policy for the elderly has changed towards the community care. Taking this fact into consideration, it is necessary to have the establishment of a system that offers the elderly appropriate welfare services at their appropriate residence (ageing in place) for the effectiveness of the community care. In this aspect, there are a number of implications to Korea to study merits and demerits of the Health Facilities for the Aged (HFA) in Japan. The society of Japan has been rapidly aging since 1970, and Korea is to face the same situation. As for the data of this study, a total of 2,393 facilities (as of November 1999) mentioned in the annual report of the Japanese Ministry of Health, Labor and Welfare were classified based on types of their establishment: (1) free-standing structures (603 facilities); (2) annexes to hospitals (981 facilities); (3) annexes to welfare facilities (511 facilities); and (4) annexes to clinics (298 facilities). Next, 239 facilities were selected through taking a sample of 10 percent from each type of the HFA mentioned above. This was done through the random sampling method with the computer program of MS EXCEL. The Implications of the results of analyses are as follows. First, most of the health facilities were planned with the scale that was larger than the scale of standard special nursing homes in terms of the total floor area. Precise equations that were to obtain precise results of the scale of the HFA and the appropriate number of residents were obtained through the method of the regression analysis. Korea and Japan have similarities in terms of culture, society and family relations; however, the two countries also have differences in terms of the application of laws on the establishment of houses, hospitals, and welfare facilities. As for planning the scale of the HFA, the realities of Korea should be considered. Second, as for the functional aspect of the HFA with a condition of returning home, the place before and after the HFA showed the pattern of 'from a residential place to a residential place' and 'from a hospital to a hospital.' This reveals a close correlation with the types of the HFAs and operational ways of the facilities. Its cause is considered to be the aspect of the operation and management of the HFA rather than the aspect of its function of providing services in association with medical and health facilities. Therefore, when intermediate welfare facilities are considered in Korea, it is strongly advised to consider the problem of annexes to other facilities and efficiency of sharing of the facilities in terms of its operation and management.