• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.20 no.1
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• pp.49-59
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• 1984

Optimizing investigation of characteristics of underwater welding by a gravity type arc welding process was experimentally carried out by using six types of domestic coated welding electrodes for welding of domestic marine structural steel plates (KR Grade A-1, SWS41A, SWS41B,) in order to develop the underwater welding techniques in practical use. Main results obtained are summarized as follows: 1. The absorption speed of the coating of domestic coated lime titania type welding-electrode became constant at about 60 minutes in water and it was about 0.18%/min during initial 8 minutes of absorption time. 2. Thus, the immediate welding electrode could be used in underwater welding for such a short time in comparison with the joint strength of in-atmosphere-and on-water-welding by dry-, wet-or immediate-welding-electrode. 3. By bead appearance and X-ray inspection, ilmenite, limetitania and high titanium oxide types of electrodes were found better for underwater-welding of 10 mm KR Grade A-1 steel plates, while proper welding angle, current and electrode diameter were 6$0^{\circ}C$, above 160A and 4mm respectively under 28cm/min of welding speed. 4. The weld metal tensile strength or proof stress of underwater-welded-joints has a quadratic relationship with the heat input, and the optimal heat input zone is about 13 to 15KJ/cm for 10mm SWS41A steel plates, resulting from consideration upon both joint efficiency of above-100% and recovery of impact strength and strain. Meanwhile, the optimal heat input zone resulting from tension-tension fatigue limit above the base metal's of SWS41A plates is 16 to 19KJ/cm. Reliability of all the empirical equations reveals 95% confidence level. 6. The microstructure of the underwater welds of SES41A welded in such a zone has no weld defects such as hydrogen brittleness with supreme high hardness, since the HAZ-bond boundary area adjacent to both surface and base metal has only Hv400 max with the microstructure of fine martensite, bainite, pearlite and small amount of ferrite.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.85-95
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• 2018

In this research, a biofilter system equipped with a biofilter process and a humidifier composed of a fluidized aerobic and an anoxic reactor, was constructed to treat odorous waste air containing hydrogen sulfide, ammonia and VOC, frequently generated from pig and poultry housing facilities, compost manufacturing factories and publicly owned facilities. Its optimum operating condition was revealed and discussed. In the experiment of complex feed, the ammonia of fed-waste air was removed by ca. 75% and more than 20% at the stage of the humidifier and the biofilter, respectively. The toluene of the fed-waste air was removed by ca. 20% and more than 70% at the stage of the humidifier and the biofilter, respectively. Therefore the water-soluble ammonia and the water-insoluble toluene were treated mainly at the stage of the humidifier and the biofilter, respectively. In addition, hydrogen sulfide was almost absorbed at the stage of the humidifier so that it was not detected at the biofilter process. In the experiment of ammonia-containing feed, the ammonia of fed-waste air was removed by ca. 65% and 35% at the stage of the humidifier and the biofilter, respectively. Its removal efficiency of ammonia at the stage of the humidifier was 10% less than that in the experiment of complex feed, due to no supply of such carbon source as toluene required in the process of denitrification. In the experiments of complex feed, ammonia-containing feed with and without (instead, glucose) the addition of yeast extract, the absorption rates of ammonia-nitrogen were ca. 0.28 mg/min, 0.23 mg/min and 0.27 mg/min, respectively. The corresponding denitrification rates in the anoxic reactor were 0.42 mg/min, 0.55 mg/min and 0.27 mg/min, respectively. In addition, in the modeling of bubble column(the fluidized aerobic reactor of the humidifier) process, the value of specific surface area(a) of bubbles multiplied by enhanced mass transfer coefficient (E $K_y$) was evaluated to be 0.12/hr.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.31 no.4
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• pp.70-83
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• 2013

To widen prospect of villa as Korea traditional garden, the result of the research about constructional characteristics of Seogo-jeongsa and Sameun-jeong of Yeoju Lee family at Toero-ri, Miryang-si, Gyeongsangnam-do, Korea, is abstracted as below. Seogo-jeongsa(西皐精舍) and Sameun-jeong(三隱亭) was intended to practise retirement with sense of unity with the head residence, since Seogo-jeongsa was 340m far and sameun-jeong was 630m far away from head residence, which set within 1km. Although Seogo-jeongsa's basic prop, Sameun-jeong's timber, which are both from designer's pen name and head residence name, "Hangjae(恒齋)" and "Yongjae(庸齋)," and Hanseoam have each different exposure, it is homogeneous as space configurational side in order to optimize the gaze leading effect and appreciated domestic trees from the pond, which is center of the garden and the significant facility. Method of direction of Seogo-jeongsa's Hwalsudang(活水塘) and Sameunjeong's pond of Sameun-ji(三隱 池) gets attention by distinction. Especially, directing of 3 step water flow from behind to front and traditional pond method, called Bangji-Bangdo(方池方島), were very unique that any other place can be found. Also, the middle islet on the pond at both villa, which isn't more supper, but more for the symbolic molding that seek a stone pagoda(石假山), is more interesting directing method as considering the relationship of the 3 stone pagoda imageries on the surface of Ghwayukchon(果肉泉) At the same time, Seogo-jeongsa and Sameun-jeong shows very different characteristics from traditional villa that adopted both domestic trees and foreign trees. Particularly, it is extremely exceptional case to plant vigorous needleleaf tree, such as Chamaecyparis pisifera, C. obtusa, Pinus bungeana, P. palustris, Sciadopitys verticillata, Metasequoia glyptostroboides and Cedrus deodara, on Sameun-jeong. Moreover, adopting foreign wild needleleaf trees for landscaping trees, such as a Torreya nucifera, Taxus cuspidata, P. parviflora, and foreign landsacping trees, such as P. bungeana, Cryptomeria japonica and C. obtusa tells planting trend of the late Joseon dysnasty era. Also, as we can know from 2 Jipgyeong(集景), which is 'Seogo-jabyoung 17 young(西皐雜詠十七詠)', and 'Sameun-jeong 12 Gyoung(三隱亭十二景)' which are set on both villa, the intend to expand the garden area is strongly shown by the natural forest directing. As a result, Seogo-jeongsa and Sameun-jeong, located at Toero-li Miryang, are sharing the traditional Joseon dynasty era's custom, such as space and visual composition; however, it is different and attractive garden remains as a point of view of water directing, stone pagodas, and adopting foreign landscaping trees.

• Korean Journal of Remote Sensing
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• v.37 no.6_1
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• pp.1657-1667
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• 2021

Anthropogenic activities and natural processes have been causes of land subsidence which is sudden sinking or gradual settlement of the earth's solid surface. Mexico City, the capital of Mexico, is one of the most severe land subsidence areas which are resulted from excessive groundwater extraction. Because groundwater is the primary water resource occupies almost 70% of total water usage in the city. Traditional terrestrial observations like the Global Navigation Satellite System (GNSS) or leveling survey have been preferred to measure land subsidence accurately. Although the GNSS observations have highly accurate information of the surfaces' displacement with a very high temporal resolution, it has often been limited due to its sparse spatial resolution and highly time-consuming and high cost. However, space-based synthetic aperture radar (SAR) interferometry has been widely used as a powerful tool to monitor surfaces' displacement with high spatial resolution and high accuracy from mm to cm-scale, regardless of day-or-night and weather conditions. In this paper, advanced interferometric approaches have been applied to get a time-series of land subsidence of Mexico City using four-year-long twenty ALOS PALSAR L-band observations acquired from Feb-11, 2007 to Feb-22, 2011. We utilized persistent scatterer interferometry (PSI) and small baseline subset (SBAS) techniques to suppress atmospheric artifacts and topography errors. The results show that the maximum subsidence rates of the PSI and SBAS method were -29.5 cm/year and -27.0 cm/year, respectively. In addition, we discuss the different subsidence rates where the study area is discriminated into three districts according to distinctive geotechnical characteristics. The significant subsidence rate occurred in the lacustrine sediments with higher compressibility than harder bedrock.

• Korean Journal of Environment and Ecology
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• v.33 no.5
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• pp.525-538
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• 2019

The purpose of this study was to analyze the habitat status and species diversity of benthic diatoms and estimate the applicability of TDI (Trophic Diatom Index) to obtain the basic data for the identification and management of created wetlands in the Nakdong River. We observed a total of 38 families and 173 species of benthic diatom during the survey period, and spring and autumn showed a similar number of species of 156 and 154, respectively. The result of the SOM (Self-Organizing Map) analysis showed that the distribution of benthic diatom was sensitive to environmental factors such as nutrient concentration and rainfall in each wetland. The cluster 1 was characterized by the survey sites of autumn mostly and consisted of points of high TDI, although the nutrients such as total phosphorus and total nitrogen were low, and the species number and abundance of diatoms were low. Conversely, cluster 4 was characterized by the survey sites of spring mostly and consisted of points of low TDI, even though total nitrogen was high. Considering that most of the created wetlands had the reduced inflow and outflow, the increased flow rate in the summer lowers nutrient values in autumn, and the species number and abundance of benthic diatom decreases due to the increase of turbidity, which reduces the light penetrations to the substrates. On the contrary, the TDI value is low in spring because the low water level causes insufficient substrate surface to the benthic diatoms, and it is too early for the establishment and development of saprophilous species. Although various studies have used TDI as an indicator for evaluating the habitat environment and water quality, it is not a good evaluation indicator in this study since the nutrient concentration in the wetlands mostly high as they have a low flow rate and are close to the stagnant area. Nevertheless, additional periodic surveys that comprehensively reflect the fact that the summer rainfall and inflow/outflow regulating function might affect the species diversity and distribution of benthic diatoms are necessary.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.4
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• pp.241-253
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• 2021

Manganese nodules have been found in the shallow water depth of the Arctic Ocean as well as in the abyssal plains of the Pacific and Indian Oceans, but detailed study for them were rarely investigated. Manganese nodules, collected from the East Siberian Sea through the Arctic Expedition using Araon ice braking vessel, have a high potential for Mn mineral resources because they have high Mn content with high Mn/Fe ratio. This study investigated the external form, size and weight, internal texture for the non-spherical manganese nodule, which has about 7 % of total nodule from the East Siberian Sea. This study also researched the relative Mn-oxide mineral composition using the peak area ratio of X-ray diffraction pattern and their chemical composition. All data obtained from non-spherical nodules were compared with the spherical ones. Ellipsoidal, platy and irregular types are common among 5 groups of non-spherical manganese nodule based on the external form, and major axis and weight have positive relationship. All non-spherical manganese nodules have core mainly composed of mud sediments. The average Mn oxide mineral contents in nodules are birnessite, buserite and todorokite in descending order. Although mineral composition does not show any correlation with the external form, kind of core or internal structure, todorokite and buserite contents tend to increase and birnessite content decrease from the surface to the core in the nodule. Non-spherical manganese nodules have higher Mn content and Mn/Fe ratio than those from the shallow water depth of the Arctic Sea and even in the deep-sea of the Pacific and Indian Ocean. Although non-spherical nodule is larger and heavier, and has lower Mn content and Mn/Fe ratio than spherical nodule, there are not any differences in mineral composition and internal structure between them. Almost all manganese nodules collected from the East Siberian Sea are attributed to diagenetic process, because they are higher than 5 in Mn/Fe ratio.

• The Korean Journal of Air & Space Law and Policy
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• v.29 no.2
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• pp.3-54
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• 2014

The Republic of Korea enacted the Air Transport Act in Commercial Law which was entered into force in November, 2011. The Air Transport Act in Korean Commercial Law was established to regulate domestic carriage by air and damages to the third party which occur within the territorial area caused by aircraft operations. There are some problems to be reformed in the Provisions of Korean Commercial Law for the aircraft operator's liability of compensation for damages to the third party caused by aircraft operation as follows. First, the aircraft operator's liability of compensation for damages needs to be improved because it is too low to compensate adequately to the third party damaged owing to the aircraft operation. Therefore, the standard of classifying per aircraft weight is required to be detailed from the current 4-tier into 10-tier and the total limited amount of liability is also in need of being increased to the maximum 7-hundred-million SDR. In addition, the limited amount of liability to the personal damage is necessary to be risen from the present 125,000 SDR to 625,000 SDR according to the recent rate of prices increase. This is the most desirable way to improve the current provisions given the ordinary insurance coverage per one aircraft accident and various specifications of recent aircraft in order to compensate the damaged appropriately. Second, the aircraft operator shall be liable without fault to damages caused by terrorism such as hijacking, attacking an aircraft and utilizing it as means of attack like the 9 11 disaster according to the present Air Transport Act in Korean Commercial Law. Some argue that it is too harsh to aircraft operators and irrational, but given they have also some legal duties of preventing terrorism and in respect of helping the third party damaged, it does not look too harsh or irrational. However, it should be amended into exempting aircraft operator's liability when the terrorism using of an aircraft by well-organized terrorists group happens like 9 11 disaster in view of balancing the interest between the aircraft operator and the third party damaged. Third, considering the large scale of the damage caused by the aircraft operation usually aircraft accident, it is likely that many people damaged can be faced with a financial crisis, and the provision of advance payment for air carrier's liability of compensation also needs to be applied to the case of aircraft operator's liability. Fourth, the aircraft operator now shall be liable to the damages which occur in land or water except air according to the current Air Transport Act of Korean Commercial Law. However, because the damages related to the aircraft operation in air caused by another aircraft operation are not different from those in land or water. Therefore, the term of 'on the surface' should be eliminated in the term of 'third parties on the surface' in order to make the damages by the aircraft operation in air caused by another aircraft operation compensable by Air Transport Act of Korean Commercial Law. It is desired that the Air Transport Act in Commercial Law including the clauses related to the aircraft operator's liability of compensation for damages to the third party be developed continually through the resolutions about its problems mentioned above for compensating the third party damaged appropriately and balancing the interest between the damaged and the aircraft operator.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.2
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• pp.148-156
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• 2008

Statement of problems: Self-etch adhesives exhibit some clinical benefits such as ease of manipulation and reduced technique-sensitivity. Nevertheless, some concern remains regarding the bonding effectiveness of self-etch adhesives to enamel, in particular when so-called 'mild' self-etch adhesives are employed. This study compared the microtensile bond strengths to ground enamel of the two-step self-etch adhesive Clearfil SE Bond (Kuraray) to the three-step etch-and- rinse adhesive Scotchbond Multi-Purpose (3M ESPE) and the one-step self-etch adhesive iBond (Heraeus Kulzer). Purpose: The purpose of this study was to determine the effect of a preceding phosphoric acid conditioning step on the bonding effectiveness of a two-step self-etch adhesive to ground enamel. Material and methods: The two-step self-etch adhesive Clearfil SE Bond non-etch group, Clearfil SE Bond etch group with prior 35% phosphoric acid etching, and the one-step self-etch adhesive iBond group were used as experimental groups. The three-step etch-and-rinse adhesive Scotchbond Multi-Purpose was used as a control group. The facial surfaces of bovine incisors were divided in four equal parts cruciformly, and randomly distributed into each group. The facial surface of each incisor was ground with 800-grit silicon carbide paper. Each adhesive group was applied according to the manufacturer's instructions to ground enamel, after which the surface was built up using Light-Core (Bisco). After storage in distilled water at $37^{\circ}C$ for 1 week, the restored teeth were sectioned into enamel beams approximately 0.8*0.8mm in cross section using a low speed precision diamond saw (TOPMET Metsaw-LS). After storage in distilled water at $37^{\circ}C$ for 1 month, 3 months, microtensile bond strength evaluations were performed using microspecimens. The microtensile bond strength (MPa) was derived by dividing the imposed force (N) at time of fracture by the bond area ($mm^2$). The mode of failure at the interface was determined with a microscope (Microscope-B nocular, Nikon). The data of microtensile bond strength were statistically analyzed using a one-way ANOVA, followed by Least Significant Difference Post Hoc Test at a significance level of 5%. Results: The mean microtensile bond strength after 1 month of storage showed no statistically significant difference between all adhesive groups (P>0.05). After 3 months of storage, adhesion to ground enamel of iBond was not significantly different from Clearfil SE Bond etch (P>>0.05), while Clearfil SE Bond non-etch and Scotchbond Multi-Purpose demonstrated significantly lower bond strengths (P<0.05), with no significant differences between the two adhesives. Conclusion: In this study the microtensile bond strength to ground enamel of two-step self-etch adhesive Clearfil SE Bond was not significantly different from three-step etch-and-rinse adhesive Scotchbond Multi-Purpose, and prior etching with 35% phosphoric acid significantly increased the bonding effectiveness of Clearfil SE Bond to enamel at 3 months.

• Journal of Korean Society of Forest Science
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• v.54 no.1
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• pp.1-24
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• 1981

Kangweon-Do is rich in sightseeing resources. There are three sightseeing areas;first, mountain area including Seolak and Ohdae National Parks, and chiak Provincial Park; second eastern coastal area; third lake area including the watersheds of North Han River. In this paper, several methods of forestation were studied for landscaping the North Han River watersheds centering around Chounchon. In Chunchon lake complex, there are four lakes; Uiam, Chunchon, Soyang and Paro from down to upper stream. The total surface area of the above four lakes is $14.4km^2$ the total pondage of them 4,155 million $m^3$, the total generation of electric power of them 410 thousand Kw, and the total forest area bordering on them $1,208km^2$. The bordering forest consists of planned management forest ($745km^2$) and non-planned management forest ($463km^2$). The latter is divided into green belt zone, natural conservation area, and protection forest. The forest in green belt amounts to $177km^2$ and centers around the 10km radios from Chunchon. The forest in natural conservation area amounts to $165km^2$, which is established within 2km sight range from the Soyang-lake sides. Protection forest surrounding the lakes is $121km^2$ There are many scenic places, recreation gardens, cultural goods and ruins in this lake complex, which are the same good tourist resources as lakes and forest. The forest encirelng the lakes has the poor average growing stock of $15m^3/ha$, because 70% of the forest consists of the young plantation of 1 to 2 age class. The ration of the needle-leaved forest, the broad-leaved forest and the mixed forest in 35:37:28. From the standpoint of ownership, the forest consists of national forest (36%), provincial forest (14%), Gun forest (5%) and private forest(45%). The greater part of the forest soil, originated from granite and gneiss, is much liable to weathering. Because the surface soil is mostly sterile, the fertilization for improving the soil quality is strongly urged. Considering the above-mentioned, the forestation methods for improving landscape of the North Han River Watersheds are suggested as follows: 1) The mature-stage forest should be induced by means of fertilizing and tendering, as the forest in this area is the young plantation with poor soil. 2) The bare land should be afforested by planting the rapid growing species, such as rigida pine, alder, and etc. 3) The bare land in the canyon with moderate moist and comparatively rich soil should be planted with Korean-pine, larch, ro fir. 4) Japaness-pine stand should be changed into Korean-pine, fir, spruce or hemlock stand from ravine to top gradually, because the Japanese-pine has poor capacity of water conservation and great liability to pine gall midge. 5) Present hard-wood forest, consisting of miscellaneous trees comparatively less valuable from the point of wood quality and scenerity, should be change into oak, maple, fraxinus-rhynchophylla, birch or juglan stand which is comparatively more valuable. 6) In the mountain foot within the sight-range, stands should be established with such species as cherry, weeping willow, white poplar, machilus, maiden-hair tree, juniper, chestnut or apricot. 7) The regeneration of some broad-leaved forests should be induced to the middle forest type, leading to the harmonious arrangement of the two storied forest and the coppice. 8) For the preservation of scenery, the reproduction of the soft-wood forest should be done under the selection method or the shelter-wood system. 9) Mixed forest should be regenerated under the middle forest system with upper needle-leaved forest and lower broad-leaved forest. In brief, the nature's mysteriousness should be conserved by combining the womanly elegance of the lakes and the manly grandeur of the forest.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.1
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• pp.1-8
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• 2015

To evaluate accuracy and precision of determination of total alkalinity ($Alk_T$) and carbon dioxide ($TCO_2$) derived from present study, experiment was applied with $CO_2$ CRM (Batch 132, Scripps Institution of Oceanography; $Alk_T=2229.24{\pm}0.39{\mu}mol/kg$, $TCO_2=2032.65{\pm}0.45{\mu}mol/kg$). As the result, average concentration of $Alk_T$ and $TCO_2$ was $2354.09{\mu}mol/kg$ (~5.6% difference with $CO_2$ CRM) and $2089.60{\mu}mol/kg$ (~2.3% difference with $CO_2$ CRM), respectively. For previous method (Gran Titration) by addition $NaHCO_3$ to deionized water($Alk_T$ $2023.33{\mu}mol/kg$), average concentration was $2193.39{\mu}mol/kg$ (sd=57.15, n=7). Whereas, average concentration was $2017.02{\mu}mol/kg$ (sd=10.98, n=7) for the present study. Recovery yield experiments of total alkalinity in deionized water and seawater were implemented by addition of $NaHCO_3$. The recovery yield of deionized water in the range 0 to $4952.39{\mu}mol/kg$ was 100.8% ($R^2$=0.999), and seawater in the range 0 to $2041.32{\mu}mol/kg$ was 102.3% ($R^2$=0.999). Comparison of $pCO_2$ sensor (PSI $CO_2-Pro^{TM}$) with present method showed very meaningful correlation coefficient ($R^2$=0.977) in the range of 427 to $705{\mu}atm$ and 9.16 to $15.24{\mu}mol/kg$ throught elapsed time for two weeks. Field experiment of diurnal variation of total carbon dioxide was accomplished at Sachon harbor in the coastal waters of East Sea of Korea. Concentration of $Alk_T$ and $TCO_2$ was increased during night, and decreased during daylight hours. The results showed mirror type between $TCO_2$ and dissolved oxygen, which was attributable to photosynthesis and respiration of phytoplankton. Also, open ocean field study was performed to obtain vertical profile of $Alk_T$ and $TCO_2$ in C-C zone (Clarion-Clipperton Fracture Zone), Northeastern Pacific. Average concentrations of $Alk_T$ in the surface mixed layer (0~60 m) and deeper layer below 200 m were $2422.38{\mu}mol/kg$ (sd=78.73, n=20) and $2465.87{\mu}mol/kg$ (sd=57.68, n=103), respectively. And average concentrations of $TCO_2$ were $2134.47{\mu}mol/kg$ (sd=65.4, n=20) and $2431.87{\mu}mol/kg$ (sd=65.02, n=103) in the same depth ranges such as $Alk_T$. Vertical distributions of $Alk_T$ and $TCO_2$ concentrations tended to increase with depth, and analyzed concentrations showed slightly higher than those of previous studies in this area.