• 산경연구논집
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• 제11권2호
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• pp.7-16
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• 2020

Purpose: This study explores how demographic transitions with workforce implications taking place in South Korea are affecting the job market, and proposes a novel conceptual model to analyze the increased role that migrant workers will play as the changes progress in the medium term. Research design, data and methodology: A qualitative approach based on the available published data is used in order to create a conceptual model that could be used to determine the order in which job sector strata will be gradually taken over by migrant workers, as the demographic transitions will create an increasing need for workforce reforms. Results: The study determines that migrant workers will replace domestic Korean workers in a stratified manner, initially in rural areas, followed by regional cities and then in the industrial areas on the edges of big cities, and the strata can be analyzed based on a proposed four-category model to determine where the opportunities will open. Conclusion: It is possible to use a conceptual model for this phenomenon. Extensive Government planning is needed to avoid possible social exclusion problems and to determine how to keep the economies of rural and regional Korean cities economically viable while they are becoming increasingly depopulated.

• 수산해양기술연구
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• 제32권3호
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• pp.266-272
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• 1996

The distribution and abundance of fish in the Cheju southeastern area was studied by the combined hydroacoustic and bottom trawl surveys in April 1994 and in July 1995, respectively. The main purpose of these investigations was to provide the basic data for this management and the biomass estimation of commercially important demersal fish stocks in this area. The hydroacoustic surveys were performed by using a 50 kHz scientific echo sounder system with a microcomputer-based echo integrator. Acoustical measurements of fish abundance and distribution were conducted along the cruise tracks of research vessel and during all trawl hauls by continuous echo sounding. The average weight-normalized target strength for demersal fish aggregations was derived from the relationship between the mean volume backscattering strength for the depth strata of trawl hauls and the weight per cubic meter of trawl catches. The geographical distribution of fish stocks in the 1994 survey area was investigated in relation to oceanographic conditions. The results obtained can be summarized as follows: 1. From the 1994 and 1995 survey data, the relationship between the mean volume backscattering strength (, dB) for the depth strata of trawl hauls and the weight (W, kg/$m^3$) per cubic meter of trawl catches was expressed by the following equation = - 32.8+ lOlog(W) The average weighted-target strength value at 50 kHz derived from this equation was .. 32.8 dB/kg. 2. In 1994 and 1995, both surveys showed a trend of decreasing fish abundance toward the southern area of the Cheju Island with high densities offish along the west coast ofth.e Tsushima Island. The highest demersal concentrations in the southern area of the CheJu Island appeared in bottom waters colder than $12^{\circ}C.$. . 3. From the results of combined bottom trawl and hydroacoustic surveys, the estunated fish densities in the southeastern area of the Cheju Island were 1.5488 x $10^-4$kg/$m^3$ in the 1994 surveyand 1.9498 x $10^-4$kg/$m^3$ in the 1995 survey, respectively.

• 한국해양학회지
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• 제9권1_2호
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• pp.1-9
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• 1974

The vertical distribution and diurnal migration of Evadne nordmanii has been studied at different stations in the Irish Sea. There are many reports that the migrations of planktonic animals tend to be hampered by thermoclines and haloclines. Physical and chemical factors were compared with vertical distribution and diurnal migrations of the animal. Evadne must be essentially an epiplanktonic form with the ability to endure strong light intensity. The animals generally migrated to the very surface layer from their shallow day strata with the decreased of light intensity. During the night their distribution seems rather random or even throughout all the layers, with a tendency to concentrate at the bottom layers, when the water was homogeneous physically and chemically. E. nordmanii may penetrate minor thermoclines and haloclines, but they may avoid chemically distinct waters or possibly currents.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2005년도 학술발표논문집
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• pp.423-428
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• 2005

If the load of constructing vehicles during the construction work acts on the road or the ground surface on the soft ground, due to the excess stresses in soils the trafficability of the vehicles influences the constructing efficiency, constructing period and so on. Stress distribution in soils is the very important element to design and to solve the problems of settlement, safety of foundations and trafficability of constructing vehicle in civil engineering. This research represents the comparative estimation of the actual and theoretical measurement on the underground stress of outer layer for each soil after the observation of each top soil layer for its vertical and horizontal stress in (1)homogeneous sand ground (2) weak stratum with the sand soil (3) weak stratum with gravel of the soil model, and it also investigates the effect of subsidence of ground by the repeated load. The underground stress turn out to be different in the value of theoretical and actual measurement after the trial examination of model.

• Geomechanics and Engineering
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• 제37권3호
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• pp.293-306
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• 2024

Influenced by the alternating effects of dynamic and static pressure during the mining process of close range coal seams, the surrounding rock support of cross mining roadway is difficult and the deformation mechanism is complex, which has become an important problem affecting the safe and efficient production of coal mines. The paper takes the inclined longwall mining of the 10304 working face of Zhongheng coal mine as the engineering background, analyzes the key strata fracture mechanism of the large inclined right-angle trapezoidal mining field, explores the stress distribution characteristics and transmission law of the surrounding rock of the roadway affected by the mining of the inclined coal seam, and proposes a segmented and hierarchical support method for the cross mining roadway affected by the mining of the close range coal seam group. The research results indicate that based on the derived expressions for shear and tensile fracture of key strata, the ultimate pushing distance and ultimate suspended area of a right angle trapezoidal mining area can be calculated and obtained. Within the cross mining section, along the horizontal direction of the coal wall of the working face, the peak shear stress is located near the middle of the boundary. The cracks on the floor of the cross mining roadway gradually develop in an elliptical funnel shape from the shallow to the deep. The dual coupling support system composed of active anchor rod support and passive U-shaped steel shed support proposed in this article achieves effective control of the stability of cross mining roadways, which achieves effective control of floor by coupling active support and preventive passive support to improve the strength of the surrounding rock itself. The research results are of great significance for guiding the layout, support control, and safe mining of cross mining roadways, and to some extent, can further enrich and improve the relevant theories of roof movement and control.

• 한국지반공학회지:지반
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• 제9권3호
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• pp.77-90
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• 1993

얕은기초의 침하해석에 관련된 토질정수, 하중 및 지층구조는 많은 불확실성을 내포하고 있어 확률적 특성을 고려한 해석이 필요하다. 본 연구는 Monte Carlo Method를 이용하여 독립후팅들로 구성된 얕은기초의 침하에 관한 확률론적 해석을 하였다. 변수의 불확실성을 고려하기 위하여 토질정수와 하중은 정규분포의 확률변수로 가정하여 독립후팅의 침하평균 및 변동계수를 구하고 각 독립후팅의 침하도 정규분포하는 것으로 가정하였다. 또한 지반내에 존재할 수 있는 연약토질 포켓 (soft soil pocket)의 확률을 고려한 각 독립후팅의 침하는 Markov process를 따르는 것으로 하였다. 이와같은 각 변수들의 변화에 따라 최대침하와 부등칭하의 허용한계 초과확률에 대한 민감도분석을 하였으며, 얕은기초의 침하해석은 각 변수의 불확실성과 지반조건을 고려하는 것이 타당하다고 판단된다.

• 한국수산과학회지
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• 제57권1호
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• pp.60-68
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• 2024

The size distribution, maturation, and molting stages of the snow crab Chionoecetes opilio in the coastal sea of Gyeongbuk were investigated to understand its monthly and bathymetric occurrence patterns. C. opilio was collected from three depth strata (A1, 100-120 m; A2, 120-180 m; A3, 180-220 m) from May to November 2020. The average sex ratio was 0.8. The mean carapace width was largest in females in October, and in males in November. The occurrence rate of small immature crabs was the highest in A1. The ratio of ovigerous females at 75-80 mm was highest at A2 and A3. There was a significant difference in carapace width in females and depth in both sexes in September and October. The occurrence rate of immature crabs was the highest in A1, whereas that ovigerous and spawned females was higher in A2 and A3 than in A1. Very old-shelled females occurred highly in September and October. The occurrence rate of newly shelled males was higher throughout the study period. This research indicated that the size distribution, maturation conditions, and molting stages of C. opilio varied with water depth strata in the coastal sea of Gyeongbuk, Korea.

• 자원환경지질
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• 제27권1호
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• pp.65-80
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• 1994

The Tertiary $Ch{\check{o}}ngja$ basin is located in the southeastern coastal area of the Korean Peninsula. It is a lozenge shaped fault-bounded basin with circa $5{\times}5km$ areal extent, isolated from other Tertiary basins by the Cretaceous Ulsan Formation in-between. The northwestern boundary of the basin is a domino/listric type normal fault trending $N30^{\circ}E$, whereas its southwestern boundary is a dextral strike-slip fault (trending $N20^{\circ}W$) with a lateral offset of more than 1 km. The basin is bounded by the East Sea on the eastern margin. Basin-fills consist of extrusive volcanic rock (Tangsa Andesites) of Early Miocene (16~22 Ma in radiometric age), unconsolidated fluviatile conglomerate (Kangdong Formation) and shallow brackish-water sandstone ($Sinhy{\check{o}}n$ Formation). The latter yields abundant Vicarya-Anadara molluscan fossils of early Middle Miocene age. The Tertiary strata become younger toward the northwestern boundary-fault of the basin, showing a zonal distribution pattern parallel to the fault: the younger sedimentary formations occupy a narrow zone of 2 km width along the northwestern boundary-fault, whereas the older Tangsa Andesites underlie them unconformably in the eastern and southeastern portions of the basin. The strata in the basin, including the Tangsa Andesites, are tilted (about $20^{\circ}$) toward the northwestern boundary-fault Sedimentary strata thicken toward the boundary-fault, forming a wedge shaped half-graben structure. A number of small-scale syndepositional normal growth faults and graben structures are observed in the sedimentary strata. These extensional structures have the same trend as the normal northwestern boundary-fault which we interpret as a pull-apart detachment fault. These characteristics imply persistent extension during the basin evolution, caused by a NW-SE directed tensional force. The $Ch{\check{o}}ngja$ basin is, thus, a kind of syndepositional tectonic basin evolved in a strike-slip (pull-apart) regime. The latter was caused by a dextral simple shear associated with the NNW-SSE opening of the East Sea. In view of the fact that the normal growth faults do not cut through the uppermost portion of the youngest $Sinhy{\check{o}}n$ Formation, it is inferred that the tensional force came to be inactive in the early Middle Miocene. This is coincident in timing with the termination of the East Sea opening (15 Ma).

• 한국방재안전학회논문집
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• 제10권1호
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• pp.47-53
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• 2017

지반 굴착에 따른 주변 지반의 함몰 문제를 예측하고 평가하기 위해서는 지반함몰 위험인자의 정확한 탐사가 필요하다. 이 연구에서는 지반굴착현장 주변의 거동 분석을 통하여 지반이완영역 분포를 분석하고 여러 가지 조건에서 GPR 탐사를 시뮬레이션 한 결과, 함수율에 따라 다소 차이는 있으나 불포화 지반에서는 지층의 분포 및 이완영역 분포를 확인할 수 있었으며, 포화 지반에서는 GPR 탐사의 어려움이 있는 것으로 나타났다.

• Geomechanics and Engineering
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• 제14권4호
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• pp.337-344
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• 2018

The study of the mining effect influenced by a normal fault has great significance concerning the prediction and prevention of fault rock burst. According to the occurrence condition of a normal fault, the stress evolution of the working face and fault plane, the movement characteristics of overlying strata, and the law of fault slipping when the working face advances from footwall to hanging wall are studied utilizing UDEC numerical simulation. Then the inducing-mechanism of fault rock burst is revealed. Results show that in pre-mining, the in situ stress distribution of two fault walls in the fault-affected zone is notably different. When the working face mines in the footwall, the abutment stress distributes in a "double peak" pattern. The ratio of shear stress to normal stress and the fault slipping have the obvious spatial and temporal characteristics because they vary gradually from the higher layer to the lower one orderly. The variation of roof subsidence is in S-shape which includes slow deformation, violent slipping, deformation induced by the hanging wall strata rotation, and movement stability. The simulation results are verified via several engineering cases of fault rock burst. Moreover, it can provide a reference for prevention and control of rock burst in a fault-affected zone under similar conditions.