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Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013 (설비공학 분야의 최근 연구 동향 : 2013년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.26 no.12
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    • pp.605-619
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    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.

Universal Service and Public Service Broadcasting -In the Age of Media Convergence (융합미디어 시대 보편적 서비스와 공영방송)

  • Kang, Hyung Cheol
    • Korean journal of communication and information
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    • v.67
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    • pp.35-61
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    • 2014
  • This article argues that public service broadcasting (PSB) should be transformed into public service media (PSM) in order to accommodate the concept of universal service in this media convergence age. If we utilize the universal service concept of telecommunications in this purpose, it inevitably constrains the concept to "access to general information" and has a limitation in its scope. In contrast, the application of the broadcast perspective leads to only examine the possibility of expanding the universal service obligation to new platforms, which has been applied to terrestrial broadcasting. As a result, these two approaches have no choice but to stay in limited area such as low-income assistance. Thus, in conclusion, it is necessary to convert PSB to the PSM as a means of providing the socially required content universally, which commercial market cannot easily produce.

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A Study on Product Liability of Aircraft Manufacturer (항공기제조업자(航空機製造業者)의 책임(責任)에 관한 연구)

  • Song, S.H.
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.12 no.3
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    • pp.41-63
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    • 2004
  • The area covered by product liability in broadest sense is so vast that an attempt to analyse all its impact on the aviation world risk. Every effort has been made to confine our review of subject a closely as possible to its influence on aircraft manufacturers, airlines and passengers, in spite of strong connections with other spheres of commercial. Product Liability in aviation is the liability of aircraft's manufacturer, processor or non-manufacturing seller for injury to the person or property of a buyer or third party caused by a product which has been sold. Here-in a product is aircraft, third party is passengers who suffered damage by defective design, defective construction, inadequate instructions for handling in aircraft. Whenever a product turns out to be defective after it has been sold, there are under Anglo-American law three remedies available against the aircraft's manufacturer (1) liability for negligence (2) breach of warranty (3) strict liability in tort. There are Under continental law Three remedies available against the aircraft's manufacturer (1) liability for defective warranty (2) liability for non-fulfillment of obligation (3) liability in tort. It is worth pointing out here an action for breach of warranty or for defective warranty, for non-fulfillment of obligation is available only to direct purchaser on the basis of his contract with the aircraft's manufacturer, which of course weakness its range and effectiveness. An action for tort offers the advantage of being available also to third parties who have acquired the defective product at a later stage. In tort, obligations are constituted not only by contract, but also by stature and common law. In conclusion, There in no difference in principle of law. In conclusion I would like to make few suggestions regarding the product liability for aircraft's manufacturer. Firstly, current general product liability code does not specify whether government offices(e.g. FAA) inspector conducted the inspection and auditory certificate can qualify as conclusive legal evidence. These need to be clarified. Secondly, because Korea is gaining potential of becoming aircraft's manufacturer through co-manufacturing and subcontracting-manufacturing with the US and independent production, there needs legislation that can harmonize the protection of both aircraft's manufacturers and their injured parties. Since Korea is in primary stage of aviation industry, considerate policy cannot be overlooked for its protection and promotion. Thirdly, because aircraft manufacturers are risking restitution like air-carriers whose scope of restitution have widened to strict and unlimited liability, there needs importation of mandatory liability insurance and national warranty into the product liability for aircraft's manufacturers. Fourthly, there needs domestic legislation of air transportation law that clearly regulates overall legal relationship in air transportation such as carrier & aircraft manufacturer's liability, and aviation insurance.

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Equivalent Design Parameter Determination for Effective Numerical Modeling of Pre-reinforced Zones in Tunnel (터널 사전보강 영역의 효과적 수치해석을 위한 등가 물성치 결정 기법)

  • Song, Ki-Il;Cho, Gye-Chun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.8 no.2
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    • pp.151-163
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    • 2006
  • Although various methods for effective modeling of pre-reinforced zones have been suggested for numerical analysis of large section tunnels, tunnel designers refer to empirical cases and literature reviews rather than engineering methods because ones who use commercial programs are unfamiliar with a macro-scale approach in general. Therefore, this paper suggests a simple micro-scale approach combined with the macro-scale approach to determine equivalent design parameters for effective numerical modeling of pre-reinforced zones in tunnel. This new approach is to determine the equivalent stiffness of pre-reinforced zones with combination of ground, bulb, and steel in series or/and parallel. For verification, 3-D numerical results from the suggested approach are compared with those of a realistic model. The comparison suggests that two cases make best approximation to a realistic solution: One is related to the series-parallel stiffness system (hereafter SPSS) in which bulb and steel are coupled in parallel and then connected to the ground in series, and the other is the series stiffness system (hereafter SSS) in which only bulb and steel are coupled in series. The SPSS is recommended for stiffness calculation of pre-reinforced zones because the SSS is inconvenient and time-consuming. The SPSS provides slightly bigger vertical displacement at tunnel crown in weathered rock than other cases and give almost identical results to a realistic model for horizontal displacement at tunnel spring line and ground surface settlement. Displacement trends on weathered rock and weathered soil are similar. The SPSS which is suggested in this paper represents the behavior mechanism of pre-reinforced area effectively.

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Development of Reliability-Based Optimum Design of High-Speed Railway Bridges Considering Structure-Rail Longitudinal Interaction and Structure-Vehicle Interaction Using Heuristic Decision Method (Heuristic Decision Method를 이용하여 구조물-궤도 종방향 상호작용 및 구조물-차량 상호작용을 고려한 고속철도 교량의 신뢰성 최적설계 기법 개발)

  • Ihm, Yeong-Rok
    • Journal of the Korean Society of Hazard Mitigation
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    • v.10 no.3
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    • pp.31-38
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    • 2010
  • In this study, it is suggested that it has to reliability-based design methodology with respect to bridge structure-rail longitudinal interaction and bridge structure-vehicle interaction. For the structural analysis, commercial package, ABAQUS, are used for a three-dimensional finite element analysis. The optimization process utilizes a well-known optimizer, ADS(Automated Design Synthesis). Optimization technique is utilized the ALM-BFGS method for global area search and Golden Section Method for 1-D search. In general, ALM-BFGS method don't need the 1-D search, and that algorithm converge a 0.1~0.2 of Push-Off factor. But in this study, value of Push-Off factor is used 90, therefore 1-D search should be needed for effective convergency. That algorithm contains the "heuristic decision method". As a result of optimum design of 2-main steel girder birdge with 5${\times}$(1@50m), design methodology suggested in this study was demonstrated more economic and efficient than existing design and LCC optimization not considering bridge-rail longitudinal interaction and bridge-vehicle interaction.

The Effect of Floating Location on Goodwill and Rent of Retail Shop -Focused on Seocho·Gangnam Commercial Area- (유동인구가 상가권리금과 임대료에 미치는 영향 -서초·강남구 상권을 중심으로-)

  • Lee, Se-won;Noh, Seung-Chul;Park, Yong-Beom;Kim, Hyun-Deok
    • Journal of Cadastre & Land InformatiX
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    • v.48 no.1
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    • pp.229-244
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    • 2018
  • The purpose of this study is to analyze the factors affecting the influence of the size and composition of the floating population on goodwill and Rent. First, the conceptual difference between location value and rent is clearly distinguished. Second, the value of land price is divided into fixed land value and floating land value. The empirical analysis utilized consulting data from 188 shops in Seocho and Gangnam-gu in 2013 ( restaurants, resting restaurants, drinking places, general stores, entertainment and sports). The results using linear regression analysis are as follows. Goodwill and rent have a positive correlation, but the evaluation system and factors are different. Especially the influence of the floating location factor is larger than the rent. And the fixed location factors such as building deterioration bus stops, were found to be significant influencing factors in the rents, but they did not affect goodwill. This result implies that the value of location of goodwill should be taken into consideration of a temporal and spatial concept. Since, in order to resolve disputes between the landlord and the tenant, it is necessary to accumulate data continuously and to study the objective evaluation system in the future.

A Study of the Relationship on the Perceived Family Support and the Level of Depression among Adolescents (청소년이 지각한 가족지지와 우울과의 상관관계 연구)

  • Park Myung Hee;Kim Chang Sook;Suh Young Sook;Suh Hee Sook;No Hyun Shin
    • Journal of Korean Public Health Nursing
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    • v.12 no.2
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    • pp.67-88
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    • 1998
  • Present study was attempt to explore the relationship between perceived family support and depression and to emphasize the importance or needs of family support in psychological care especially among adolescents. Study subjects comprized of 308 high school students including vocational students in part, and data collection was done in the Kwangju City area in April. 1998. The Moos Family Environment Scale and the Zung's Self-Rating Depression Scale modified by investigators were used as measurement tools of 59 item questionnaire and in data analysis, statistical methods of T-test, ANOVA. and Pearson Correlation Coefficient were utilized. The study findings are as follows 1. The hypothesis of the study, 'the higher the degree of perceived family support among adolescents, the lower the level of depression', was supported (r=-0.4469, p<.001). 2. Some variables in demographic characteristics related to the degree of family support with statistical significance were school division of vacational vs non-vocational(t=-2.02, p<.05), age(f=5.47, p<.01), family monthly income (f=2.49, p<.05), mother's level of education (f=3.01. p<.05), residence at developmental stage (f=2.87, p<.05), personal problem of highest priority at present(f=7.73, p<.001), and family problem perceived by adolescents(f=7.38, p< .001). 3. Items In general characteristics related to the level of depression with statistical significance were sex(t=-2.91, p<.0l). mother's level of education(f=2.53. p<.05). residence at developmental stage (f=3.95. p<.0l). present personal problem of highest priority (f=3.68. p<.1l). and perceived in-family problem (f=4.58. p<.001). 4. The mean score of the degree of perceived family support was 61.26 $(SD=\pm14.45)$ in a range of 21.00 to 96.00 ; that of the level of depression. 43.74 $(SD=\pm8.04)$ in a range of 23.00 to 67.00. which demonstrated that the higher the degree of perceived family support, the lower the level of depression. In conclusion. it was found that the degree of family support perceived by adolescents is a variable affecting the level of depression. Based on the study outcome, further research suggestions can be made as such that repeated studies are needed in order to delineate the various factors affecting family support and depression, and a study involving family support implementation program is required as a nursing intervention for the development of emotional security among adolescents, perceived family support, depression, adolescence.

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REPLACEMENT OF A PHOTOMULTIPLIER TUBE IN A 2-INCH THALLIUM-DOPED SODIUM IODIDE GAMMA SPECTROMETER WITH SILICON PHOTOMULTIPLIERS AND A LIGHT GUIDE

  • KIM, CHANKYU;KIM, HYOUNGTAEK;KIM, JONGYUL;LEE, CHAEHUN;YOO, HYUNJUN;KANG, DONG UK;CHO, MINSIK;KIM, MYUNG SOO;LEE, DAEHEE;KIM, YEWON;LIM, KYUNG TAEK;YANG, SHIYOUNG;CHO, GYUSEONG
    • Nuclear Engineering and Technology
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    • v.47 no.4
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    • pp.479-487
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    • 2015
  • The thallium-doped sodium iodide [NaI(Tl)] scintillation detector is preferred as a gamma spectrometer in many fields because of its general advantages. A silicon photomultiplier (SiPM) has recently been developed and its application area has been expanded as an alternative to photomultiplier tubes (PMTs). It has merits such as a low operating voltage, compact size, cheap production cost, and magnetic resonance compatibility. In this study, an array of SiPMs is used to develop an NaI(Tl) gamma spectrometer. To maintain detection efficiency, a commercial NaI(Tl) $2^{\prime}{\times}2^{\prime}$ scintillator is used, and a light guide is used for the transport and collection of generated photons from the scintillator to the SiPMs without loss. The test light guides were fabricated with polymethyl methacrylate and reflective materials. The gamma spectrometer systems were set up and included light guides. Through a series of measurements, the characteristics of the light guides and the proposed gamma spectrometer were evaluated. Simulation of the light collection was accomplished using the DETECT 97 code (A. Levin, E. Hoskinson, and C. Moison, University of Michigan, USA) to analyze the measurement results. The system, which included SiPMs and the light guide, achieved 14.11% full width at half maximum energy resolution at 662 keV.

An Investigation on Gridline Edges in Screen-Printed Crystalline Silicon Solar Cells

  • Kim, Seongtak;Park, Sungeun;Kim, Young Do;Kim, Hyunho;Bae, Soohyun;Park, Hyomin;Lee, Hae-Seok;Kim, Donghwan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.490.2-490.2
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    • 2014
  • Since the general solar cells accept sun light at the front side, excluding the electrode area, electrons move from the emitter to the front electrode and start to collect at the grid edge. Thus the edge of gridline can be important for electrical properties of screen-printed silicon solar cells. In this study, the improvement of electrical properties in screen-printed crystalline silicon solar cells by contact treatment of grid edge was investigated. The samples with $60{\Omega}/{\square}$ and $70{\Omega}/{\square}$ emitter were prepared. After front side of samples was deposited by SiNx commercial Ag paste and Al paste were printed at front side and rear side respectively. Each sample was co-fired between $670^{\circ}C$ and $780^{\circ}C$ in the rapid thermal processing (RTP). After the firing process, the cells were dipped in 2.5% hydrofluoric acid (HF) at room temperature for various times under 60 seconds and then rinsed in deionized water. (This is called "contact treatment") After dipping in HF for a certain period, the samples from each firing condition were compared by measurement. Cell performances were measured by Suns-Voc, solar simulator, the transfer length method and a field emission scanning electron microscope. According to HF treatment, once the thin glass layer at the grid edge was etched, the current transport was changed from tunneling via Ag colloids in the glass layer to direct transport via Ag colloids between the Ag bulk and the emitter. Thus, the transfer length as well as the specific contact resistance decreased. For more details a model of the current path was proposed to explain the effect of HF treatment at the edge of the Ag grid. It is expected that HF treatment may help to improve the contact of high sheet-resistance emitter as well as the contact of a high specific contact resistance.

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Analysis of an internal flow with multi-perforated tube geometry in an integrated Urea-SCR muffler (다공튜브 형상변화에 따른 촉매 삽입형 Urea-SCR 머플러 내부유동 해석)

  • Moon, Namsoo;Lee, Sangkyoo;Lee, Jeekeun
    • Journal of Advanced Marine Engineering and Technology
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    • v.37 no.5
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    • pp.500-509
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    • 2013
  • This study reports a numerical analysis of the internal flow characteristics of the integrated urea-SCR muffler system with the various geometries of the multi-perforated tube which is set up between the muffler inlet and in front of SCR catalysts. The multi-perforated tube is generally used to disperse uniformly the urea-water solution spray and to make better use of the SCR catalyst, resulting in the increased $NO_x$ reduction and decreased ammonia slip. The effects of the multi-perforated tube orifice area ratios on the velocity distributions in front of the SCR catalyst, which is ultimately quantified as the uniformity index, were investigated for the optimal muffler system design. The steady flow model was applied by using a general-purpose commercial software package. The air at the room temperature was used as a working fluid, instead of the exhaust gas and urea-water solution spray mixture. From the analysis results, it was clarified that the multi-perforated tube geometry sensitively affected to the formation of the bulk swirling motion inside the plenum chamber set in front of the SCR catalyst and to the uniformity index of the velocity distribution produced at the inlet of the catalyst.