Influence of pore structure heterogeneity on channeling channels during hot water flooding in heavy oil reservoir based on CT scanning

Hot water flooding is an effective way to develop heavy oil reservoirs.However,local channeling channels may form,possibly leading to a low thermal utilization efficiency and high water cut in the reservoir.The pore structure heterogeneity is an important factor in forming these channels.This study proposes a method that mixes quartz sand with different particle sizes to prepare weakly heterogeneous and strongly heterogeneous models through which hot water flooding experiments are conducted.During the experiments,computer tomography(CT)scanning identifies the pore structure and micro remaining oil saturation distribution to analyze the influence of the pore structure heterogeneity on the channeling channels.The oil saturation reduction and average pore size are divided into three levels to quantitatively describe the relationship between the channeling channel distribution and pore structure heterogeneity.The zone where oil saturation reduction exceeds 20%is defined as a channeling channel.The scanning area is divided into 180 equally sized zones based on the CT scanning images,and threedimensional(3D)distributions of the channeling channels are developed.Four micro remaining oil distribution patterns are proposed,and the morphology characteristics of micro remaining oil inside and outside the channeling channels are analyzed.The results show that hot water flooding is more balanced in the weakly heterogeneous model,and the oil saturation decreases by more than 20%in most zones without narrow channeling channels forming.In the strongly heterogeneous model,hot water flooding is unbalanced,and three narrow channeling channels of different lengths form.In the weakly heterogeneous model,the oil saturation reduction is greater in zones with larger pores.The distribution range of the average pore size is larger in the strongly heterogeneous model.The network remaining oil inside the channeling channels is less than outside the channeling channels,and the hot water converts the network remaining oil into cluster,film,and droplet remaining oil.

Experimental research and application of cold cutting to hot stamping parts based on multiphase microstructure

Among the bottlenecks that hinder the improvement of the production efficiency of hot stamping are high strength and difficulty in edge cutting and hole punching.Starting from the preparation of hot stamping multiphase microstructure materials,this paper developed a plate quenching die system with controllable surface temperature and prepared four types of hot stamping plates with different martensite volume fractions.Then,straight edge cold cutting experiments were performed to study the influence of cutting clearance and cutting force on fracture quality.The results show that the bright zone is the largest when the cutting clearance is 0.14 mm,and the cutting experience coefficient of the hot stamping sheet with each martensite volume fraction is obtained when the cutting clearance is 0.14 mm.The research results of this paper were applied to the production of hot stamping parts.

Large-scale physical simulation of injection and production of hot dry rock in Gonghe Basin,Qinghai Province,China

Based on the independently developed true triaxial multi-physical field large-scale physical simulation system of in-situ injection and production,we conducted physical simulation of long-term multi-well injection and production in the hot dry rocks of the Gonghe Basin,Qinghai Province,NW China.Through multi-well connectivity experiments,the spatial distribution characteristics of the natural fracture system in the rock samples and the connectivity between fracture and wellbore were clarified.The injection and production wells were selected to conduct the experiments,namely one injection well and two production wells,one injection well and one production well.The variation of several physical parameters in the production well was analyzed,such as flow rate,temperature,heat recovery rate and fluid recovery.The results show that under the combination of thermal shock and injection pressure,the fracture conductivity was enhanced,and the production temperature showed a downward trend.The larger the flow rate,the faster the decrease.When the local closed area of the fracture was gradually activated,new heat transfer areas were generated,resulting in a lower rate of increase or decrease in the mining temperature.The heat recovery rate was mainly controlled by the extraction flow rate and the temperature difference between injection and production fluid.As the conductivity of the leak-off channel increased,the fluid recovery of the production well rapidly decreased.The influence mechanisms of dominant channels and fluid leak-off on thermal recovery performance are different.The former limits the heat exchange area,while the latter affects the flow rate of the produced fluid.Both of them are important factors affecting the long-term and efficient development of hot dry rock.

Cold snare polypectomy:A closer look at the efficacy and limitations for polyps 10-20 mm in size

Current guidelines recommend cold snare polypectomy for polyps less than 10 mm in size.Conversely,endoscopic mucosal resection is still the preferred technique for larger polyps.Concerns regarding cold snare polypectomy for larger polyps revolve around the difficulty in conducting en-bloc resection(resulting in piecemeal removal),and the potential for local residual polyp tissue and a high rate of recurrence.On the other hand,cold snare technique has the advantages of shortening procedure time,reducing delayed bleeding risks and lowering cost of treatment.Numerous ongoing and recent studies are focused on evaluating the risks and benefits of this technique for polyps larger than 10 mm,with the goal of providing clear guidelines in the near future.The aim of this editorial is to provide our readers with an overview regarding this subject and the latest developments surrounding it.

Microstructural evolution during hot and cold deformation of Ti-36Nb-2Ta-3Zr-0.35O alloy

The Ti-36Nb-2Ta-3Zr-0.350 （mass fraction, %） （TNTZO） alloy was produced by cold isostatic pressing and sintering from elemental powders, followed by hot and cold deformation. The effects of deformation process on microstructures and mechanical properties were investigated using the SEM, TEM, OM and the universal material testing machine. Results show that the alloy can be easily hot forged and cold swaged due to the fine-grained microstructure. Only after cold swaging by 85%, the alloy shows the typical ＂marble-like＂ structure. And thecold deformation is accompanied by stress-induced a＂ phase transformations. Moreover, both the strength and the ductility of the alloy are significantly improved by hot and cold working.

Removal of diminutive colorectal polyps: A prospective randomized clinical trial between cold snare polypectomy and hot forceps biopsy

AIMTo compare the efficacy and safety of cold snare polypectomy (CSP) and hot forceps biopsy (HFB) for diminutive colorectal polyps.METHODSThis prospective, randomized single-center clinical trial included consecutive patients ≥ 20 years of age with diminutive colorectal polyps 3-5 mm from December 2014 to October 2015. The primary outcome measures were en-bloc resection (endoscopic evaluation) and complete resection rates (pathological evaluation). The secondary outcome measures were the immediate bleeding or immediate perforation rate after polypectomy, delayed bleeding or delayed perforation rate after polypectomy, use of clipping for bleeding or perforation, and polyp retrieval rate. Prophylactic clipping after polyp removal wasn’t routinely performed.RESULTSTwo hundred eight patients were randomized into the CSP (102), HFB (106) and 283 polyps were evaluated (CSP: 148, HFB: 135). The en-bloc resection rate was significantly higher with CSP than with HFB [99.3% (147/148) vs 80.0% (108/135), P < 0.0001]. The complete resection rate was significantly higher with CSP than with HFB [80.4% (119/148) vs 47.4% (64/135), P < 0.0001]. The immediate bleeding rate was similar between the groups [8.6% (13/148) vs 8.1% (11/135), P = 1.000], and endoscopic hemostasis with hemoclips was successful in all cases. No cases of perforation or delayed bleeding occurred. The rate of severe tissue injury to the pathological specimen was higher HFB than CSP [52.6% (71/135) vs 1.3% (2/148), P < 0.0001]. Polyp retrieval failure was encountered CSP (7), HFB (2).CONCLUSIONCSP is more effective than HFB for resecting diminutive polyps. Further long-term follow-up study is required.

Efficacy and adverse events of cold vs hot polypectomy: A meta-analysis

AIM: To compare previously reported randomized controlled studies (RCTs) of cold and hot polypectomy, we systematically reviewed and clarify the utility of cold polypectomy over hot with respect to efficacy and adverse events.METHODS: A meta-analysis was conducted to evaluate the predominance of cold and hot polypectomy for removing colon polyps. Published articles and abstracts from worldwide conferences were searched using the keywords “cold polypectomy”. RCTs that compared either or both the effects or adverse events of cold polypectomy with those of hot polypectomy were collected. The patients’ demographics, endoscopic procedures, No. of examined lesions, lesion size, macroscopic and histologic findings, rates of incomplete resection, bleeding amount, perforation, and length of procedure were extracted from each study. A forest plot analysis was used to verify the relative strength of the effects and adverse events of each procedure. A funnel plot was generated to assess the possibility of publication bias.RESULTS: Ultimately, six RCTs were selected. No significant differences were noted in the average lesion size (less than 10 mm) between the cold and hot polypectomy groups in each study. Further, the rates of complete resection and adverse events, including delayed bleeding, did not differ markedly between cold and hot polypectomy. The average procedural time in the cold polypectomy group was significantly shorter than in the hot polypectomy group.CONCLUSION: Cold polypectomy is a time-saving procedure for removing small polyps with markedly similar curability and safety to hot polypectomy.

Comment on 'Efficacy and adverse events of cold vs hot polypectomy: A meta-analysis'

This is a comment on a meta-analysis of published studies comparing cold vs hot polypectomy. We believe that the conclusion of this meta-analysis that "cold polypectomy is a time-saving procedure for removing small polyps with markedly similar curability and safety to hot polypectomy" needs more rigorous evidence.

Chemical Properties of Pectin from Industry Hot and Cold Break Tomato Products

Tomato processing includes a break step, which involves rapid heating of freshly chopped tomatoes to >90°C for hot break, or 60°C to 77°C for cold break. Pectolytic enzyme deactivation is believed to be the key element in the hot break step;therefore, pectin content of different products should be qualitatively distinct. The objective of this study was to investigate the effect of hot break versus cold break on the cell-wall pectin of tomato. Cell-wall pectin from hot and cold break tomato products was isolated and analyzed for carbohydrate composition, degree of polymerization, and degree of esterification. The results showed no observable differences in the cell-wall pectin isolated from the two products, indicating that there was no significant pectolytic breakdown of the tomato in the cold break product, and the pectin might not, by itself, contribute to the differences in the final product viscosity resulting from the two processing techniques.

Internal oxidation of hot-rolled ultra-high strength steel and its effect on the surface quality of cold-rolled sheets

In this study,the scale and internal oxidation of hot-rolled ultra-high strength steel sheets were characterized.It was found that both the formation of the scale and the internal oxidation of Si and Mn depended on the coiling temperature and position of the steel sample on the strip coil.At a relatively high coiling temperature,a large amount of internal oxidation was observed on the samples cut from the middle of the coil.The depth of the internal oxidation zone exceeded 10 μm and a thin iron layer covering the scale was observed in some cases.Pickling and cold-rolling experiments were conducted on selected samples.Scale pickling was found to be greatly delayed by the formation of an iron layer,which frequently resulted in under-pickled defects.In addition,pickling of the entire internal oxidation zone was difficult,except at the grain boundaries,where the degree of internal Si and Mn oxidation was enriched.The surface of the cold-rolled steel sheet was ruined by the remaining oxidation zone in the subsurface of the pickled steel.The internal oxidation of hot-rolled ultra-high strength steel must be precisely controlled to improve the subsequent surface quality of cold-rolled steel.

Ventilated Double Skin Facades in Hot-Summer and Cold-Winter Zones in China

Double-skin facades(DSF)are a technique developed for colder climates,so few people think about whether or not it can also be used for hot-summer and cold-winter zones in China.After analyzing the problems of using DSF for hot-summer zones,this paper explored on the possibility of applying DSF in hot-summer and cold-winter zones in China.The main existing research methods for DSF were also collected and commented.If properly managed,the ventilated DSF with controlled shading devices can be used even in hot summer in China.

THE COLD AND HOT DAMAGES TO THE CITRUS IN THE THREE GORGES AREA OF THE CHANGJIANG RIVER

Starting from the research on and collection of the damaging factors andindex of the cold and hot damages to citrus, this peper systematically studies the apparent properties in temporal and spatial distribution, differences, relationship of the twokinds of disasters and their impact on citrus production in the Three Gorges area inHubei. It also reveals the important faCt that it is warmer in winter and hotter in springsince the 1980s, which is the cause of departing to two poles of the cold and hot damages, and discusses the alleviating effect to the disasters by the Three Gorges Project.Finally some countermeasures are proposed.

The mechanism of hot crack formation in Ti-6Al-4V during cold crucible continuous casting

Hot crack is one of common defects in castings, which often results in failure of castings. This work studies the formation of hot crack during cold crucible continuous casting by means of experiments and theoretical analysis. The results show that hot crack occurs on the surface and in the circumference of ingots, where the solidified shell and the solidification front meet each other. The tendency of hot cracking decreases with the increase of withdrawal velocities in some extent. The hot crack is caused mainly by the friction force between the shell and the crucible inner wall, and it takes place when the stress resulting from friction exceeds the tensile strength of the shell. The factors of μ_m, η_t, η_s and η_m, affecting hot cracks are analyzed and verified. In order to decrease the tendency of hot cracks, technical parameters should be optimized by decreasing μ_m, η_t, η_s and η_m.

Suitability and Construction of Self-Insulation Walls in the Hot Summer and Cold Winter Zone of Southern Shaanxi

In this paper, the suitability and construction technology of self-insulation walls were studied under the specific climatic conditions and regional resources of Hanzhong and Ankang in the hot summer and cold winter zone of Southern Shaanxi. Through the calculation of heat transfer coefficient and thermal inertia index, combined with the specifications of the shale hollow brick and aerated concrete block of Hanzhong and Ankang in southern Shaanxi, the thermal performance and suitable thickness of the external wall using self-insulation materials that meet the Design Standard for Energy Efficiency of Residential Buildings(DBJ61-65-2011) in Shaanxi Province were obtained. The results showed that the self-insulation wall had technical suitability in the hot summer and cold winter zone. The research results provide not only a theoretical basis for the external wall insulation design of urban residential buildings in the hot summer and cold winter zone of southern Shaanxi, but also a reference for designers to carry out energy-saving design of external walls of residential buildings in other similar climate zones.

Verification of Hazard Analysis and Critical Control Point in Hotels and Catering Units: Evaluation of the Cleaning and Disinfection Procedures and Microbiological Monitoring of Hot and Cold Meals

The aim of the present study is to assess the efficacy of the methods used in a HACCP system by measuring the Total Viable Count (TVC) and Coliforms, after cleaning and disinfecting the surfaces used and also by monitoring TVC and enterobacteriaceae of hot and cold meals. In order to evaluate the appropriateness of the surfaces used, samples were obtained from kitchens of 37 Greek hotels/resorts, all of which operated a documented HACCP safety management scheme, while the samples of hot and cold meals were selected from the menu of a catering unit and collected from the actual point of hot and cold dishes banquette at the start time (time 0) and after 4 hours. The developed colonies were counted. The results showed that only 13.5% of the hotels presented surfaces without any TVC or coliforms and 86.5% of the hotels had surfaces with TVC or coliforms or both above the limits. However, 75.8% of the total surfaces examined were acceptable for TVC and 81.9% of the surfaces examined were coliforms. Our microbiological monitoring of food showed that the TVC content of hot meal samples after 4 hours of display (above 60℃) was not significantly different from the TVC content of the aforementioned samples at time 0, while in cold meals TVC and enterobacteriaceae content had significantly risen after 4 hours of display (below 5℃).Conclusively, insufficient application of disinfection and ineffective surface and equipment cleaning programs were found. Additionally, cold meals are more vulnerable than hot meals in developing TVC and enterobacteriaceae.

The Theoretically Studies and Field Testing of Self-Insulation Exterior Wall in the Hot Summer and Cold Winter Zone

The energy efficiency design of the exterior wall in the buildings of the hot summer and cold winter zone of China should consider the heat prevention in summer and the heat insulation in winter. The self-insulation of the exterior?wall is a more feasible design to satisfy the energy efficiency of buildings in the?zone. However, the systematic research is urgently needed for the self-insulation of the exterior wall in the hot summer and cold winter zone of China. The paper tested the thermal performance of the common non-clay materials such as shale sintered hollow brick, sand autoclaved aerated concrete block, etc. by means of indoor experiments. The energy efficiency effect of the common materials was verified using dynamic calculation soft PKPM and several constitutions of exterior wall with different main bricks and insulation materials on the heat bridge were simulated, too. Besides, the tests of the thermal performance of exterior wall in real constructions were carried out to testify the practical effect of the recommended constitutions of exterior wall with different main bricks and insulation materials on the heat bridge. The conclusions are: the physical and thermal properties of the six non-clay wall material are better than the clay porous brick;the thermal performance of the non-clay brick can be improved obviously through the rational arrangement of the holes;shale sintered hollow brick after increasing the holes and rationalizing the hole arrangement and sand autoclaved aerated concrete block are recommended for buildings in the hot summer and cold winter area of China. The dynamic calculation results show that the thermal performances?of the non-clay materials are all satisfied with the energy efficiency;The heat transfer coefficient of the exterior wall with composition?③,?in which?the main wall was sand autoclaved aerated concrete block and the material on the heat bridge was sand autoclaved aerated concrete plate, is the smallest among the three recommended compositions.

High Temperature Oxidation and Hot Corrosion Behaviour of 9Cr 1Mo Ferritic Cold Rolled Steel in Air at 900°C under Cyclic Condition

The oxidation behaviour of 10%, 30%, and 50% cold rolled and unprocessed 9Cr 1Mo ferritic steels in air have been studied under isothermal conditions at a temperature of 900°C in a cyclic manner. Oxidation kinetics was established for all samples on which experiment was conducted in air at 900°C under cyclic conditions for 50 cycles by thermogravimetric technique. Each cycle consisted of 1 hour heating at 900°C followed by 20 min of cooling in air. 10% cold rolled sample followed parabolic rate of oxidation while 30% cold rolled sample showed accelerated rate of weight gain. X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive X-ray (SEM/EDAX) techniques were used to characterise the oxidized sample and their scales. 10% cold rolled steel was found to be more corrosion resistance than other in air oxidation for 50 cycles.

Performance on Power,Hot and Cold Water Generation of a Hybrid Photovoltaic Thermal Module

This paper proposed a new function of photovoltaic thermal(PVT)module to produce nocturnal cool water not just only generating electrical power and hot water during daytime.Experimental tests were carried out under Chiang Mai tropical climate with a 200 Wp monocrystalline PVT module having dimensions of 1.601 m×0.828 m connected with two water tanks each of 60 L taken for hot and cool water storages.The module was facing south with 18o inclination.The electrical load was a 200 W halogen lamp.From experiments,by taking the module as a nocturnal radiative cooling surface,the cool water temperature in the cool storage tank could be reduced 2℃–3℃each night and the temperature could be reduced from 31.5℃to 22.1℃within 4 consecutive days.The cool water at approximately 23℃was also used to cool down the PVT module from noon when the PVT module temperature was rather high,and then the module temperature immediately dropped around 5℃and approximately 10%increase of electrical power could be achieved.A set of mathematical models was also developed to predict the PVT module temperature and the hot water temperature including the cool water temperature in the storage tanks during daytime and nighttime.The simulated results agreed well with the experimental data.

Research on Passive Design Optimization about an Experimental Rural Residence in Hot Summer and Cold Winter Region of China

In China, rural residential environment under the poor construction measures has not been satisfactory due to the backward infrastructure of countryside and the lacking of professional planning, which will result in considerable amount of energy consumption in the future. The economy of rural residences in the hot summer and cold winter region of China is relative developed, but the indoor thermal environmental quality is not so good. In this paper, the design strategies directed by passive design ideas for a small experimental rural residential building located in Hangzhou city was introduced and researched in response to hot summer and cold winter climate. Through modeling solution undertaken by Ecotect software, the building performance was simulated and analyzed for the optimization of design factors, such as shape, roof angle, insulation system, shading devices, as well as day-lighting system. Based on the above study, a set of appropriate energy-saving technologies were provided for improving the new rural residences construction in Hangzhou, which should also be recommended to other projects constructed in the same climate region.

Effective Channel Length Degradation under Hot-Carrier Stressing

This article describes the effective channel length degradation under hot carrier stressing. The extraction is based on the IDs-Vcs characteristics by maximum transconductance （maximum slope of IDs ＆ VGS） in the linear region. The transconductance characteristics are determine for the several devices of difference drawn channel length. The effective channel length of submicron LDD （Lightly Doped Drain） NMOSFETs （Metal Oxide Semiconductor Field Effect Transistor） under hot carrier stressing was measured at the stress time varying from zero to 10,000 seconds. It is shown that the effective channel length was increased with time. This is caused by charges trapping in the oxide during stress. The increased of effective channel length （△Leff） is seem to be increased sharply as the gate channel length is decrease.