Korea District Heating Corporation

Abstract BACKGROUND: Biological conversion of CO 2 to useful carbonic compounds such as methane is a potentially attractive technology for reducing its concentration in the atmosphere. One of the advantages of this technology over chemical conversion is that it requires much lower energy for reduction of CO 2 . In this article, biological conversion of CO 2 to CH 4 using hydrogenotrophic methanogens was examined in a fixed bed reactor inoculated with anaerobic mixed culture from the anaerobic digestor of a sewage treatment plant. RESULTS: Methane formation commenced on the first day of operation of the fixed bed reactor. CO 2 fed to the reactor was reduced with H 2 by hydrogenotrophic methanogens. The feed ratio of CO 2 to H 2 is an important factor in determining the conversion rate of CO 2 . When the feed ratio is 4, methane is produced at the expected rate according to the chemical equation. The CO 2 conversion rate was 100% when the gas retention time was 3.8 h in the fixed bed reactor. CONCLUSIONS: The results show that the fixed bed reactor employing hydrogentrophic methanogens has the potential to be effective in converting CO 2 to CH 4 with a conversion rate of 100% at 3.8 h retention time. Copyright © 2012 Society of Chemical Industry

Protein- and sugar-rich food products processed at high temperatures contain large amounts of dietary advanced glycation endproducts (dAGEs). Our earlier studies have shown that specifically protein-bound dAGEs induce a pro-inflammatory reaction in human macrophage-like cells. To what extent these protein-bound dAGEs survive the human gastrointestinal (GI) tract is still unclear. In this study we analysed gastric and small intestinal digestion of dAGEs using the validated, standardised TNO in vitro gastroIntestinal digestion model (TIM-1), a dynamic in vitro model which mimics the upper human GI tract. This model takes multiple parameters into account, such as: dynamic pH curves, peristaltic mixing, addition of bile and pancreatic digestive enzymes, and passive absorption. Samples of different digested food products were collected at different time points after (i) only gastric digestion and (ii) after both gastric plus small intestinal digestion. Samples were analysed for dAGEs using UPLC-MS/MS for the lysine derived Nε-carboxymethyllysine (CML) and Nε-carboxyethyllysine (CEL), and the arginine derived methylglyoxal-derived hydroimidazolone-1 (MG-H1), and glyoxal-derived hydroimidazolone-1 (G-H1). All AGEs were quantified in their protein-bound and free form. The results of this in vitro study show that protein-bound dAGEs survive gastrointestinal digestion and are additionally formed during small intestinal digestion. In ginger biscuits, the presence MG-H1 in the GI tract increased with more than 400%. This also indicates that dAGEs enter the human GI tract with potential pro-inflammatory characteristics.

The combinatorial approach of anthropogenic activities and CO2 sequestration is becoming a global research trend to alleviate the average global temperature. Although microalgae have been widely used to capture CO2 from industrial flue gas, the application of bioproducts was limited to bioenergy due to the controversy over the quality and safety of the products in the food and feed industry. Herein, the waste CO2 emitted from large point sources was directly captured using astaxanthin-hyperproducing microalgae Haematococcus pluvialis. Astaxanthin production was successfully carried out using the hypochlorous acid water-based axenic culture process under highly contamination-prone outdoor conditions. Consequently, after 36 days of autotrophic induction, the productivity of biomass and astaxanthin of H. pluvialis (the mutant) reached 0.127 g L−1 day−1 and 5.47 mg L−1 day−1 under high summer temperatures, respectively, which was 38% and 48% higher than that of wild type cell. After grinding the wet astaxanthin-enriched biomass, the extract was successfully approved by compliance validation testing from Korea Food and Drug Administration. The assorted feed improved an immune system of the poultry without causing any side effects. The flue gas-based bioproducts could certainly be used for health functional food for animals in the future.

Abstract A polyurethane (PU)/clay nanocomposite was synthesized from polyol, polymeric 4,4′‐diphenyl methane diisocyanate (PMDI), and modified clay with PMDI. To achieve the modified clay with PMDI, the silanol group of the clay and the NCO group of the PMDI were reacted for 24 h at 50°C to form urethane linkage. Fourier transform IR analysis of the clay modified with the PMDI demonstrated that the NCO characteristic peak was observed in the clay after a modification reaction with PMDI. The results of the X‐ray pattern suggested that the clay layers were exfoliated from the PU/clay nanocomposite. From the results of the mechanical properties, the maximum values of the flexural and tensile strength were observed when 3 wt % clay based on PMDI was added into the PU/clay nanocomposites. The glass‐transition temperature and change in the heat capacity at glass transition temperature (Δ C p ) of the PU/clay nanocomposite decreased with an increase in the modified clay content. We suggested that the decrease in the Δ C p with the modified clay content might be due to the increase of steric hindrance by the exfoliated clay layers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2879–2883, 2006

We present a new concept of a structured surface for enhanced boiling heat transfer that is capable of self-adapting to the local thermal conditions. An array of freestanding nanoscale bimorphs, a structure that consists of two adjoining materials with a large thermal expansion mismatch, is able to deform under local temperature change. Such a surface gradually deforms as the nucleate boiling progresses due to the increase in the wall superheat. The deformation caused by the heated surface is shown to be favorable for boiling heat transfer, leading to about 10% of increase in the critical heat flux compared to a regular nanowire surface. A recently developed theoretical model that accounts for the critical instability wavelength of the vapor film and the capillary wicking force successfully describes the critical heat flux enhancement for the nanobimorph surface with a good quantitative agreement.

External damage to buried pipelines is mainly caused by corrosive components in soil solution. The reality that numerous agents are present in the corrosive environment simultaneously makes it troublesome to study. To solve that issue, this study aims to determine the influence of the combination of pH, chloride, and sulfate by using a statistical method according to the design of experiment (DOE). Response surface methodology (RSM) using the Box-Behnken design (BBD) was selected and applied to the design matrix for those three factors. The input corrosion current density was evaluated by electrochemical tests under variable conditions given in the design matrix. The output of this method is an equation that calculates the corrosion current density as a function of pH, chloride, and sulfate concentration. The level of influence of each factor on the corrosion current density was investigated and response surface plots, contour plots of each factor were created in this study.

The aim of the present study was to determine whether a disintegrin and metalloproteinase (ADAM)-8, -9, -10, -12, -15 and -17 and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-1 are involved in the remodelling process of the mouse uterus during the oestrous cycle. The mRNA expression of ADAM was observed in all uterine tissues throughout the entire cycle. The levels of ADAM-8 mRNA were maximal at pro-oestrus, whereas the expression of ADAM-9 and ADAMTS-1 mRNA was maximal at oestrus. The minimum mRNA level of all ADAM genes always occurred at dioestrus. The mRNA levels of ADAM-10, -12, -15 and -17 did not vary significantly, regardless of the stage of the oestrous cycle. Immunoblot analyses demonstrated the presence of all ADAM proteins throughout the cycle. In terms of protein intensities, ADAM-8, -12 and -17 were maximal at pro-oestrus, whereas ADAM-10 and ADAMTS-1 were maximal at metoestrus and ADAM-9 was maximal at oestrus. Regardless of the ADAM species, minimal protein expression always occurred at dioestrus. Immunohistochemical studies showed ADAM protein expression in luminal and glandular epithelial layers, but not in the stromal layer. Moreover, ADAM proteins were found to be heterogeneously localised and their individual localisations depended on the stage of the oestrous cycle. From these observations, we suggest that the ADAM genes play an important role in mouse uterine tissue remodelling during the oestrous cycle.

Economically feasible photosynthetic cultivation of microalgal and cyanobacterial strains is crucial for the biological conversion of CO 2 and potential CO 2 mitigation to challenge global warming. To overcome the economic barriers, the production of value-added chemicals was desired by compensating for the overall processing cost. Here, we engineered cyanobacteria for photosynthetic squalene production and cultivated them in a scalable photobioreactor using industrial flue gas. First, an inducer-free gene expression system was developed for the cyanobacteria to lower production const. Then, the recombinant cyanobacteria were cultivated in a closed photobioreactor (100 L) using flue gas (5% CO 2 ) as the sole carbon source under natural sunlight as the only energy source. Seasonal light intensities and temperatures were analyzed along with cyanobacterial cell growth and squalene production in August and October 2019. As a result, the effective irradiation hours were the most critical factor for the large-scale cultivation of cyanobacteria. Thus, an automated photobioprocess system will be developed based on the regional light sources.

The present study was conducted to evaluate the total cooling effectiveness in combined full-coverage film cooling and impingement jet using an infrared thermographic technique. The effect of film cooling hole angle, blowing ratio, and height to diameter ratio between the film cooling and impingement jet plates was discussed. The total cooling effectiveness increased as impingement jet cooling was added. The angled film cooling holes had approximately 4.6% higher total cooling effectiveness than the normal film cooling holes. The total cooling effectiveness was almost constant regardless of height to diameter ratio, but enhanced as the blowing ratio was increased.

In this study, the cause of failure of a low-carbon steel pipe meeting standard KS D 3562 (ASTM A135), in a district heating system was investigated. After 6 years of operation, the pipe failed prematurely due to pitting corrosion, which occurred both inside and outside of the pipe. Pitting corrosion occurred more prominently outside the pipe than inside, where water quality is controlled. The analysis indicated that the pipe failure occurred due to aluminum inclusions and the presence of a pearlite inhomogeneous phase fraction. Crevice corrosion occurred in the vicinity around the aluminum inclusions, causing localized corrosion. In the large pearlite fraction region, cementite in the pearlite acted as a cathode to promote dissolution of surrounding ferrite. Therefore, in the groundwater environment outside of the pipe, localized corrosion occurred due to crevice corrosion by aluminum inclusions, and localized corrosion was accelerated by the large fraction of pearlite around the aluminum inclusions, leading to pipe failure.

In this letter, we propose an efficient algorithm which reduces the complexity of conventional vector perturbation schemes by searching the real and imaginary components of a perturbation vector individually. To minimize a performance loss induced from the decoupled joint search, we apply diagonal precoding at the transmitter whose parameters are iteratively optimized to maximize the chordal distance between subspaces spanned by the real and imaginary components. We also propose a simple non-iterative method with a slight performance loss which can achieve a significant complexity reduction compared to the conventional vector perturbation schemes.

This paper proposes a method of detecting the number of persons in an area, along with their locations and breath patterns, using ultra-wideband (UWB) radars. A time-of-arrival type of location estimation was performed in this study not only using techniques introduced in the existing study results of detecting biomedical signals using a UWB radar but also by applying an initial screening method for redundancy reduction and a maximum likelihood observation-target association technique. This paper also introduces radar measurements conducted under a variety of scenarios and presents the results of applying the proposed algorithm to the measured data. The test results showed that the number of targets was accurately estimated with an average positioning accuracy of 12.7 cm.

BACKGROUND/AIMS: Recent outbreak of hepatitis A in Korea is clearly related to the epidemiological shift of hepatitis A virus (HAV). However, nationwide seroprevalence data have been limited. This study estimated the nationwide, age- and area-adjusted anti-HAV prevalence from 2005 to 2009. METHODS: Retrospective analysis of the results of total anti-HAV test in 25,140 cases which were requested by 1,699 medical institutions throughout the nation to Seoul Clinical Laboratory from Jan. 1 2005 to Dec. 31 2009 was performed. The estimated seroprevalence was adjusted by area and age of the standard population based on the 2005 Census data from Korea National Statistical Office. RESULTS: The area-adjusted anti-HAV prevalence in the children younger than 10 years were 33.4% in 2005 and 69.9% in 2009. The most susceptible age groups to HAV infection during the last 5 years were teenagers and the young adults in their age of twenties. The area-adjusted seroprevalence in 2009 were 11.9% in the age group of 20-29 years, 23.4% in the age group of 10-19 years, 48.4% in the age group of 30-39 years. The population in 40-49 years showed geographically different seroprevalence with the lowest rate in Seoul (80%). CONCLUSIONS: The most susceptible age group to HAV infection is 10-29 years, while the young children less than 10 years showed about 70% seropositivity. The changing seroepidemiology should be monitored continuously for the proper vaccination and patient care.

As it is known, there is a pandemic that is growing rapidly and affecting almost the entire world, including Turkey. Following the announcement of the isolation of a new type of Coronavirus (SARS CoV-2) by the Chinese government on January 7, 2020, as of March 15, 2020, 168 834 Verified cases and 6492 deaths were reported due to this pandemic (COVID-19 pandemic) (1,2). However, it is noteworthy that children are less affected by this viral pandemic in terms of both the number of cases and the incidence of serious illnesses. So far, it has been shown that children aged 0-9 years generally have a mild infection, but there are no reported fatalities (2,3). It is not new for children to experience some viral diseases mildly (4). However, given the seriousness of the current pandemic, clarifying the cause of this situation may reveal crucial information regarding the outbreak control. The fact that the clinical picture in children is seriously different from adults may be that their immune system responds more quickly than adults, or it may depend on the immunity they have gained through the extended immunization program. In other words, some antibodies that exist in children thanks to vaccination but disappear in adults over the years may protect children. In a study conducted in 2008, the measles vaccine has been shown to provide neutralizing antibodies against SARS CoV (5). In addition, studies revealed that whooping cough outbreaks have been observed in China in recent years (6,7). In one study, Bordetella spp. were isolated in 4.51% of pediatric patients followed for respiratory tract infection (8). There are similarities between SARS CoV-2 and transmission dynamics of Bordetella species. Both pathogens are transmitted at a high secondary attack rate via respiration and droplet. The incubation and clinical time of both pathogens are similar. Prior antibiotic use facilitates the placement of Bordetella species. Bordetella species actively interact with other pathogens or flora members (9,10). In the clinic of both pathogens, there are asymptomatic carrier cases, cough is dominant, as well as the complaint of dry cough. It is noteworthy that the number of CD4 T lymphocytes has decreased in the laboratory findings of whooping cough, and that some medicines used in treatment (Chloroquine, erythromycin) can also be used in Bordetella species. The absence of death in the 0-9 age group who with a strong titer of whooping cough antibodies also brought to mind the possibility of an overlooked co-infection in the pandemic (7). Pathogens that may co-infect with SARS CoV-2 such as whooping cough and different clinical manifestations seen among children and adults are considered to be examined in this respect. In this sense we developed two hypotheses: <b>Hypothesis 1:</b> Could childhood vaccines be the reason for a milder infection in children? <b>Hypothesis 2:</b> In cases of severe pneumonia and ARDS, can there be a bacterial co-infection, such as bordatella pertussis, that has been vaccinated in childhood but whose antibody titer has declined over the years?

Global demand for plastics has increased steadily alongside industrial development. Despite their versatility and convenience, environmental pollution caused by plastics are a major issue. With a reduction in the market size of plastics being seemingly impossible, bioplastics may become key to tackle this issue. Among a wide range of sources of bioplastics, microalgae have come into the limelight. While abundant and valuable components in microalgae have the potential to replace preexisting plastics, complex processes and low cost performances have prevented them from entering the market. In this study, we examined techniques for biocomposites in which polymers are blended with microalgae. We focused on microalgae-based biocomposite blending processed from the perspective of functionality and cost performance.

Many research studies have been conducted on the corrosion inhibition performance of imidazole in acidic environments such as in the piping of a petrochemical plant. However, there has been no study on the effect of imidazole in alkaline conditions such as a local district water heating environment. Therefore, in this study, the effect of imidazole as a corrosion inhibitor on carbon steel weldment was investigated in alkaline district heating water. Inhibition efficiency and electrochemical properties were investigated by potentiodynamic polarization test and electrochemical impedance spectroscopy. As the concentration of imidazole increased up to 500 ppm, inhibition efficiency increased up to 91.7%. At 1000 ppm, inhibition efficiency decreased. Atomic force microscopy showed that surface coverage of imidazole at 1000 ppm is lower than that of imidazole at 500 ppm. X-ray photoelectron spectroscopy showed that with 500 ppm of imidazole, the amount of pyrrole type interaction is 4.8 times larger than pyridine type interaction. At 1000 ppm of imidazole, the amount of pyridine type interaction is 3.49 times larger than pyrrole type interaction. Depending on the concentration of imidazole, the ratio of interaction between carbon steel and imidazole affected inhibition efficiency.

Repeated loading in district heating networks is occurring inconstantly. There are small and great load amplitudes in the system. As small load amplitudes are usually observed more frequently than great load amplitudes, their accumulation with respect to great load amplitudes is of common interest. A growing share of renewable energy can be noted in energy markets. Because of this, flexible operation of combined heat and power plants is necessary. For the connected district heating network this means additional temperature amplitudes in the system, causing higher stresses for the network. Repeated loading in the system has to be considered in the fatigue analysis. For a suggested lifetime of a district heating network of 30 years, an estimated number of cycles for the temperature load were accumulated for standardization. Nevertheless a longer lifetime than 30 years for district heating pipes is expected in the district heating sector, which also means higher cyclic loading. Due to individual operation parameters and individual network conditions, the equivalent action cycles are expected to be different at every element in the network. The paper is based on a review on damage accumulation theories that may be used for district heating systems regarding future developments. Some examples are shown for equivalent full load cycles for different locations in district heating networks.

The present study aimed to investigate the effect of an unsteady wake on the heat transfer for the endwall surface of a linear of cascade turbine blade. A naphthalene sublimation method was implemented to obtain the detailed heat/mass transfer distributions on the endwall surface. Tests were conducted on a five-passage linear cascade in a low-speed wind tunnel. The effects of unsteady wakes were simulated in the facility by a wake generator consisting of circular rods that were traversed across the inlet flow. The test conditions were fixed at a Reynolds number of 70,000 based on the inlet velocity and chord length. The flow coefficients were varied from 1.3 to 4.2 and the range of Strouhal number was 0.1–0.3. The results showed that the heat transfer distributions differed between steady and unsteady cases. The overall heat transfer for the unsteady cases was higher, and the heat transfer was enhanced with increasing the Strouhal number due to the resulting thin boundary layer and high turbulence intensity. Therefore, a cooling system for the endwall of a rotor should focus on reducing the high temperatures on the endwall surface induced by the unsteady wakes.

District heating has been widely implemented in residences because of its environmental and economic advantages. The hot water load of residences generally peaks in the morning and at night because of the lifestyle of the residents. An imbalance in the heat load presents high capital costs and low operating efficiency of the district heating facilities. In this study, a latent heat storage system using a solid-liquid phase change material was developed for the peak load shifting control of hot water supplied from district heating in an apartment complex. The latent heat storage system was designed using a shell-tube structure and can store heat for more than 100 h using an insulation of 50 mm. A field demonstration was performed by installing the developed latent heat storage system in a machinery room in the basement of the apartment complex. The demonstration showed that the total heat flow of hot water during a day and its standard deviation with the latent heat storage are lower than those without latent heat storage by 2.69% and 59.9%, respectively. Therefore, the latent heat storage system is crucial in the peak load shifting of hot water in the apartment complex.

Heat accounts for about one-third of the final energy use and it is mostly produced using fossil fuels in South Korea. Thus, heat production is an important source of greenhouse gas emissions. However, using renewable heat that is directly produced from renewable energy, such as bioenergy, geothermal, or solar heat can save energy and reduce greenhouse gas emissions, rather than transforming conventional fuel into heat. Therefore, an energy policy for renewable heat urgently needs to be established. It is such situations that this paper attempts to assess the consumers’ additional willingness to pay (WTP) or the price premium for renewable heat over heat that is produced from fossil fuels for residential heating. To that end, a nationwide contingent valuation survey of 1000 households was conducted during August 2018. Employing the model allowing for zero WTP values, the mean of the additional WTP or premium for one Gcal of heat produced using renewable energy rather than fossil fuels was estimated to be KRW 3636 (USD 3.2), which is statistically meaningful at the 1% level. This value represents the price premium for renewable heat over heat that is based on fossil fuels. Given that the heat price for residential heating was approximately KRW 73,000 (USD 65.1) per Gcal at the time of the survey, the additional WTP or the price premium corresponds to about 5% of that. When considering that the cost of producing renewable heat is still significantly higher than the cost of producing fossil fuels-based heat, more efforts to lower the production costs of renewable heat as well as financial support of the government for producing and supplying renewable heat are needed to ensure residential consumers’ acceptance of renewable heat.