Time Lag Phenomenon Research Articles

Exploring a spatiotemporal hetero graph-based long short-term memory model for multi-step-ahead flood forecasting

Operational flood prevention platforms and systems rely upon the advance notice provided by flood forecasts to formulate efficient measures for flood mitigation. Capturing complex spatial heterogeneity and correlation of hydro-meteorological variables is fundamentally challenging for artificial neural networks. This challenge becomes even more significant when the complexity involved introduces systematic biases and time-lag phenomena in flood forecasts. For the first time, this study proposed a Spatiotemporal Hetero Graph-based Long Short-term Memory (SHG-LSTM) model for multi-step-ahead flood forecasting. The case study focused on the Jianxi basin in China. 25,341 hydro-meteorological data, with a temporal resolution of three hours, collected during flood events were divided into training and test datasets for model construction purpose. The model was fed with 3-h streamflow and precipitation data from 23 gauge stations, covering a time span of the preceding 21 h, for generating flood forecasts at 1 up to 7 horizons. To make a comparative analysis, both LSTM and the Spatiotemporal Graph Convolutional Network (S-GCN) were constructed. This study conducted multiple rounds of model training with varying initial parameters to assess the accuracy, stability, and reliability of the LSTM, S-GCN, and SHG-LSTM models. The results demonstrated that the SHG-LSTM model outperformed LSTM and S-GCN models, with an average reduction in the volume error (VE) of 6.5% and 11.1%, respectively, a decrease in the Mean Absolute Error (MAE) of 6.7% and 8.1%, respectively, and a reduction in the Root Mean Square Error (RMSE) of 5.0% and 12.9%, respectively. Furthermore, the SHG-LSTM model not only could efficiently overcome the under-prediction bottleneck, but also could largely mitigate the time-lag phenomenon in flood forecasts, even during the testing stages. These findings indicate that the proposed SHG-LSTM model can provide a general framework for modelling the spatial heterogeneity and correlation of hydro-meteorological variables and achieve accurate and reliable flood forecasts, thereby enhancing the model’s applicability in flood prevention platforms and systems.

Ecological threshold of phosphorus load in Baiyangdian Lake based on a PCLake model and ecological network analysis

Ecological thresholds are a useful indicator for implementing ecological management. Many studies determine the thresholds for nutrient loads in lakes based on the maximum allowable concentration of chlorophyll a (Chla), although this neglects the overall performance of the ecosystem. A PCLake model of Baiyangdian (BYD) Lake in northern China was constructed with six ecological network analysis (ENA) indicators that characterized the ecosystem function, system maturity, and food web structure to quantify the overall status of the BYD ecosystem. To my knowledge, this is the first study on the system level responses of the BYD Lake to phosphorus load interference. Different phosphorus load scenarios were designed to simulate the ecological responses of BYD Lake. The simulated results were employed to calculate the ENA indicators. Ecological thresholds were determined through the driving response relationship between the phosphorus load gradient and the ENA indicators. The results show a non-linear transition response of ENA indicator under phosphorus load gradient. As phosphorus load increases, D/H, SOI, and FCI decreases while A/DC, TPP/TR, and TPP/TB increases. This indicates that the overall structure and function of the ecosystem will deteriorate if phosphorus load increases. The phosphorus load thresholds for the overall performance of BYD Lake were 0.50–1.32 mg m−2 d−1, slightly wider than that of Chla (0.53–1.26 mg m−2 d−1). The model results clearly indicate that there is a time-lag phenomenon at the switch points in the response of ENA indicators compared to that of single functional group. In addition, the A/DC, TPP/TR, SOI, and FCI present more time-lag than that of other ENA indicators. These time-lag effects provide a particular opportunity for biodiversity conservation. Therefore, a possible management strategy is proposed to combine system-level and function group-level thresholds, with the ENA-based threshold as the bottom line and the phytoplankton's threshold as the early-warning indicator. This design is expected to be more precise and efficient, by exploiting the advantages of two thresholds, and may benefit for ecological management practices.

Understanding the Time-Lag Behavior of the Breakdown-Discharge Voltage.

As the world enters the era of the Internet of Things (IoT), wireless devices and their networks become essential fundamental components. Recently, with the rapid development of the triboelectric nanogenerator (TENG), breakdown discharge has become an emerging hot topic in the field since it is the key limiting factor of the output performance, and it may also trigger new applications such as self-powered wireless sensing. However, understandings of the discharge behaviors in TENG are still limited. This study proposed a method to study the breakdown discharge with a large serial resistance and discovered the time-lag behavior of the breakdown discharge. A model based on the Eyring equation is demonstrated to explain this time-lag phenomenon. A convenient method to adjust the breakdown-discharge voltage is developed through this study. As an application, a wireless spark switch being modulated by a series-connected resistance is designed, which may be potentially utilized in wireless applications.

Development of rill erosion on bare sloping farmland under natural rainfall conditions

Rill erosion plays an important role in soil erosion, and studying this process can provide a basis for controlling soil loss on sloping farmland. The objectives of this study were to observe runoff and sediment transport processes during two continuous and two intermittent natural rainfall events and to monitor the changing morphological characteristics of rills within a standard runoff plot of bare soil (20 m length, 5 m width, and slope of 10°) at five successive observation times. We found that the processes of runoff and sediment transport presented a pattern with multiple peaks during continuous rainfall events and with a single or two peaks during intermittent rainfall events. The peak runoff and sediment yield rates exhibited a time-lag phenomenon of 1‒12 min compared with instantaneous rainfall intensity. Rills occurred as strip-shapes, V-shapes, and with a tree-branch-like distribution; their widths were mainly 5–20 cm and their depths 0–10 cm. Compared to our initial rill observation, the mean rill length, width, and depth increased by 227%, 26%, and 6%, respectively, after four subsequent rill observations over a period of almost one month. Side-wall collapse erosion was greater than downcutting erosion on the middle slope (section II; 6.67–13.34 m), while rill depth reached a minimum value on the lower slope (section III; 13.34–20 m). These findings help us to understand bare slope runoff and erosion mechanisms and provide a scientific basis for soil erosion modeling of sloping farmland.

Dynamic response analysis of isolated curved beam bridge under multi-dimensional non-stationary random excitation considering the torsion component

The coupling effect of bending and torsion caused by plane irregularity of the isolated curved beam bridge makes its seismic response more complex than that of the isolated straight beam bridge. In order to study the influence of multi-dimensional non-stationary random excitation considering torsion component on seismic response of tqiongw@mls.sinanet.com he isolated curved beam bridge. The classical Bouc-Wen model was used to simulate the hysteretic characteristics of the curved beam bridge, and the nonlinear dynamic equation considering the eccentricity of superstructure was established. The pseudo excitation was transformed into harmonic external load by Euler formula, and combining with the precise integration method, the precise integration forms of the special solution under different modulation functions were derived. By using these integral forms to solve the response at each time, the time-varying variance of displacement of the isolated curved beam bridge under multi-dimensional non-stationary random excitation was obtained, and the law of time-varying variance of displacement, including the upper and lower structures of the isolated curved beam bridge, was analyzed with different deck width, curvature radius and yield ratio of bearing. The results show that the multi-dimensional non-stationary random excitation with torsion component has significant influence on the seismic response of the isolated curved beam bridge. Under the rare non-stationary random excitation, the dynamic response of the isolated curved beam bridge presents strong non-stationarity, and the time-lag phenomenon is apparent. For the isolated curved beam bridge with large deck width and small yield ratio of bearing, the influence of non-stationary random excitation on the structure is particularly obvious. The influence of non-stationary random excitation considering torsion component on dynamic response of the isolated curved beam bridge with large deck width, small curvature radius and large yield ratio of bearing is more significant.

Moving Ship Optimal Association for Maritime Surveillance: Fusing AIS and Sentinel-2 Data

Nowadays, a variety of different sources can be combined together to measure and monitor maritime human activities. Reliable data fusion techniques are essential to associate the targets from different systems for maritime surveillance. In particular, the fusion of data from Sentinel-2 satellites and the Automatic Identification System (AIS) has attracted wide attention due to their public availability and complementarity. However, most traditional methods for target association are not suitable for this particular case, due to the time lag phenomenon of Sentinel-2 data. In this study, we first construct two new datasets for the detection of moving ships and their wakes based on Sentinel-2 images. Combined with the detection results obtained by the You Only Look Once (YOLOv5) model, the position and course information of the detected ships are first extracted. After carefully analyzing the time lag phenomenon of Sentinel-2 data, we develop a new domain adaptation-based method for target association based on the fusion of Sentinel-2 and AIS data, called Moving Ship Optimal Association (MSOA). Different from standard domain adaptation methods only for representation alignment, the proposed MSOA is able to align representation, time and position simultaneously. A case study is provided in which the newly proposed method is tested over the Port of Long Beach, USA. Experimental results demonstrate that both moving ships and wakes are well detected. Specifically, our newly proposed MSOA exhibits more accurate and robust performance when compared to traditional methods, and the detected ships without corresponding AIS tracks can also be detected by our MSOA. Moreover, the real sensing time and time lag of Sentinel-2 data are deduced with high accuracy. Overall, it can be concluded that our MSOA provides a new perspective for accurate target association based on heterogeneous data fusion.

An Interpretable Interflow Simulated Graph Neural Network for Reservoir Connectivity Analysis

SummaryReservoir connectivity analysis plays an essential role in controlling water cut in the middle and later stages of reservoir development. The traditional analysis methods, such as well test and tracer, may result in interruption and high reservoir development costs. Analyzing connectivity through history data is an advisable alternative method because the fluctuation of data reflects interwell interference. However, most of the former data-driven methods, such as capacitance and resistance model (CRM), estimate connectivity using formulas in relatively simple forms, leading to inadequate expression for underground interwell flow. In this paper, an interpretable recurrent graph neural network (GNN) is proposed to construct an interacting process imitating the real interwell flow regularity and overcoming the weakness in previous methods. In contrast, it is formed by a deep enough neural network structure with a relatively larger number of parameters when compared with the CRM model. In detail, this method makes the first use of both rate information and bottomhole pressure (BHP) to completely describe the hidden state of wells and the energy information exchanged among them, which are then continually updated in spatial and temporal ways.Meanwhile, a self-defined recurrent structure deals with the time lag and attenuation phenomenon as it records the residual energy from past timestamps. Finally, it calculates BHP for each production well with the manually specified production rate as extra input data. Detailed results are presented in two examples. Our proposed method shows significant advantages to other methods due to its reasonable structure and great ability to fit nonlinear mapping.

Origin of the Time Lag Phenomenon and the Global Signal in Resting-State fMRI.

The global mean signal of resting-state fMRI (rs-fMRI) shows a characteristic spatiotemporal pattern that is closely related to the pattern of vascular perfusion. Although being increasingly adopted in the mapping of the flow of neural activity, the mechanism that gives rise to the BOLD signal time lag remains controversial. In the present study, we compared the time lag of the global mean signal with those of the local network components obtained by applying temporal independent component analysis to the resting-state fMRI data, as well as by using simultaneous wide-field visual stimulation, and demonstrated that the time lag patterns are highly similar across all types of data. These results suggest that the time lag of the rs-fMRI signal reflects the local variance of the hemodynamic responses rather than the arrival or transit time of the stimulus, whether the trigger is neuronal or non-neuronal in origin as long as it is mediated by local hemodynamic responses. Examinations of the internal carotid artery signal further confirmed that the arterial signal is tightly inversely coupled with the global mean signal in accordance with previous studies, presumably reflecting the blood flow or blood pressure changes that are occurring almost simultaneously in the internal carotid artery and the cerebral pial/capillary arteries, within the low-frequency component in human rs-fMRI.

Data Processing Techniques for Real-Time Traveler Information: Use of Dedicated Short-Range Communications Probes on Suburban Arterial

Background:As wireless communication technologies evolve, probe-based travel-time collection systems are becoming popular around the globe. However, two problems generally arise in probe-based systems: one is the outlier and the other is time lag. To resolve the problems, methods for outlier removal and travel-time prediction need to be applied.Methods:In this study, data processing methods for addressing the two issues are proposed. After investigating the characteristic of the travel times on the test section, the modified z-score was suggested for censoring outliers contained in probe travel times. To mitigate the time-lag phenomenon, a recurrent neural network, a class of deep learning where temporal sequence data are normally treated, was applied to predict travel times.Results:As a result of evaluation with ground-truth data obtained through test-car runs, the proposed methods showed enhanced performances with prediction errors lower than 13% on average compared to current practices.Conclusion:The suggested methods can make drivers to better arrange their trip schedules with real-time travel-time information with improved accuracy.

Time-Frequency and Energy Correlations of the Transient Voltages Triggered by Cloud to Cloud Discharges

This paper presents a study performed on time, frequency, and energy correlations of transient voltages generated by the cloud to cloud discharges. It revealed that the energy embedded in transient voltages have been lumped over few segments of time domain voltage profile than uniquely scattering over the time span. The study further determined that the energy concentration becomes higher in and around the vicinity of the time domain voltage maxima or minima, and such high energy-concentrated segments confined to a minute time span in comparison to the total time span of the transient voltage. The study also established that there is a small time lead or lag between the time domain voltage maxima or minima and the time of energy maximize. Moreover, the analysis deduced that the time lead or time lag phenomenon, is not sensitive to the orientation of the time domain voltage profile, but fuelled by the pulse type. The response time of surge protective devices can become crucial if the stipulated clamping voltages of the protection devices fall close to local peaks of the transient voltages.

Time-Lag Effect Between Sap Flow and Environmental Factors of Larix principis-rupprechtii Mayr

A time lag between sap flux density (Js) and meteorological factors has been widely reported, but the controlling factors of the time lag are poorly understood. To interpret the time lag phenomenon systematically, thermal dissipation probes were placed into each of eight trees to measure the Js of Larix principis-rupprechtii Mayr. in the Liupan Mountains in Northwest China. Meteorological factors, including vapor pressure deficit (VPD), solar radiation (Rs) and air temperature (Ta), were synchronously measured with Js, and the dislocation contrast method was used to analyze the time lag between Js and the meteorological factors. The analysis indicated the following for the whole experimental period. (1) The time lag between Js and VPD (TLV) and the time lag between Js and Rs (TLR) both exhibited different patterns under different weather conditions, and Js could precede Rs on dry days. (2) Both TLV and TLR varied with the day of the year (DOY) throughout the experimental period; namely, both exhibited a decreasing tendency in September. (3) Reference crop evapotranspiration (ETref) had a greater influence on the time lag than the other meteorological factors and directly controlled the length and direction of TLV and TLR; relative extractable water (REW) modified the relationship between ETref and time lag. (4) The regression analysis results showed differences between the time lags and the environmental factors (ETref and REW) within different ranges of REW. Namely, TLR was better determined by ETref and REW when REW < 0.38, while TLV was better correlated with ETref and REW in the absence of soil water limitations (REW > 0.38). This project provided an important opportunity to advance the understanding of the interaction between plant transpiration and meteorological factors in a changing climate.

Study on nonlinear parametric vibration of footbridge considering time-lag effect

Under the action of pedestrian dynamic load, a pedestrian bridge with large span and light flexibility will show the nonlinear characteristics of the structure, and there is a time lag phenomenon in the feedback of the pedestrian’s force on the pedestrian bridge. Therefore, based on the derivation of the nonlinear dynamic model of the parametric vibration of pedestrian bridge, the time lag effect is introduced. Taking the Millennium Bridge of London as an example, the influence of time-lag on parametric vibration of pedestrian bridge is analyzed. By using Galerkin method and multi-scale perturbation method, theoretical and numerical analysis of large vibration induced by parametric vibration and forced vibration of pedestrian bridge is carried out. The amplitude frequency curve of nonlinear parametric vibration with time-lag effect is obtained, and it is concluded that the time-lag of nonlinear parametric vibration in Millennium Bridge has no effect on the amplitude of the structure, but only affects the peak arrival time and the time of stable amplitude. And the conclusion is proved by the numerical analysis.

Prediction model of Cooling Load considering time-lag for preemptive action in buildings

As interest in automation technologies for maintaining occupants' comfort and reducing building energy consumption increases, Energy Management Systems (EMS) and Building Energy Management Services (BEMS) are gradually receiving more attention. However, the conventional methods associated with these systems cannot predict the future thermal load based on real time thermal load and climatic factors. This study shows that the external environment and building thermal load may not be the same due to the time-lag phenomenon. Consequently, prediction models that take the time-lag phenomenon into consideration are developed. In order to create the prediction models, meteorological data (mixed humidity) over 4 years (2011–2014) in Seoul were consolidated using the collected data by KMA (Korea Meteorological Administration) and mathematical equations used in energy analysis simulations. A cooling load prediction model per building size considering the time-lag phenomenon was proposed based on multiple regression analysis. It was found that there are some cases where energy could not be predicted as there is a different time-lag due to architectural characteristics and building thermal load conditions.

Use of an Energy Balance Model for Studying Urban Surface Temperature at Microscale

Urban surface temperature is a major diagnostic parameter to describe the urban environment in cross-scale urban climatic studies. Modeling of urban surface temperature at microscale is fundamental to advances in understanding the nature of urban microclimate, and it is essential for diverse studies related to urban pollution dispersion, pedestrian thermal comfort and building energy consumption. This paper focuses on the use of an urban canopy model (Town Energy Balance model, TEB) to study urban surface energy balance and surface temperature evolution. TEB is run in an offline mode with atmospheric forcing data from continuous observation above the canopy layer of Toulouse city center, France from February 2004 to February 2005. The surface temperatures derived from TEB present both the correct temporal course and diurnal amplitude. Simulation results show different patterns exist between urban roof, wall, and road assemble-averaged estimates in diurnal and annual temperature cycles. The time lag phenomenon and amplitude attenuation between surface temperature cycle and canyon air temperature cycle indicate that TEB can reproduce the urban thermal responses and the temporal evolution of diagnostic parameters in urban microclimate studies. TEB and other microclimate model have the potential to be important tools for the deterministic analysis of urban microclimate and hence for the analysis of adaptation measures in mitigating UHI for urban design.

Sapflow characteristics of Kandelia obovata and their controlling factors in Zhangjiang estuary, China.

In this study, the Grainer's thermal dissipation probe method was applied to monitor sap flux density (SFD) of a mangrove species Kandelia obovata over a period of one year (2010-10-2011-10) in Zhangjiangkou Mangrove National Nature Reserve, Fujian, China. The results showed that both season and diameter class exerted significant effects on the SFD of K. obovata trees. In summer, when the diameter at breast height (DBH) reached 8-10 cm, the highest SFD was found at a depth of 2 cm with a value of 38.21 g·m-2·s-1, which was comparable with those for other mangrove tree species and forested wetland tree species. The mean whole tree transpiration (i.e. daily water use) of all stem size classes demonstrated large changes from winter to summer, increased from 0.14 to 0.19 kg·d-1 in small trees (S, DBH=2-4 cm), from 0.94 to 1.45 kg·d-1 in medium trees (M, DBH=4-8 cm) and from 1.96 to 3.43 kg·d-1 in large ones (L, DBH=8-10 cm). The daily transpiration of K. obovata stand was calculated by summing all size classes, which was then summed up for entire year to estimate annual transpiration of entire K. obovata forest, which was about 100.38 mm, less than 6% of local annual precipitation. Key environmental factors all had significant effects (all P<0.001) on the stand transpiration rate (Es) of K. obovata forest, and photosynthetically active radiation (PAR) and vapor pressure deficit (VPD) were the main driving factors, which explained 60%-92% seasonal variation of Es. The PAR and VPD had larger effects on the Es in summer than that in winter. In addition, we observed an obvious time lag phenomenon in the relationship between Es and PAR or VPD, which should be taken into account when explaining seasonal variation of Es in K. obovata forest.

An Empirical Study on Time Lag Phenomenon Regarding Summertime Indoor Thermal Environments in the Domestic Buildings of Different Construction Types in Hot-Humid Climate Zone

In the empirical case studies of the seven detached house buildings situated in Yilan, Taiwan in a hot and humid climate, this research conducted the actual measurements and analysis of the Summertime Indoor and Outdoor thermal environment parameters in order to accomplish the research of Time Lag Phenomenon of Summertime Indoor Temperature and Humidity in the Buildings of Light (Composite) Constructions and Heavy (Reinforced Concrete) Constructions. Firstly, it indicated that given the condition of doors and windows in closed positions, there would be Time Lag Phenomenon for both of the indoor Temperature and Humidity measurements in domestic buildings. The Temperature Time Lag for Heavy Construction Buildings had a duration of around three hours, almost as twice that of the figure for Light Construction Buildings. There was a significant correlation between Quantity of Interior Finishes and Humidity Time Lag inside domestic buildings, whereas the bigger the Quantity of Interior Finishes, the longer the Humidity Time Lag. Secondly, it also showed that given the condition of doors and windows in opened positions, there was almost zero Time Lag for both of the domestic indoor Temperature and Humidity measurements. Last but not least, generally speaking, the Ratio of Indoor/Outdoor Diurnal Temperature Range of Light Construction Buildings were higher than that of Heavy Construction Buildings. In particular, given the condition of doors and windows in opened positions with natural ventilation in summertime, it was slightly cooler inside the Light Construction Domestic Buildings than the Heavy Construction Domestic Buildings.

창호 블라인드와 상변화물질 적용에 의한 냉방 에너지 사용량 절감효과에 대한 검토 연구

This study looks into changing building energy use by application of phase change material (PCM). PCM does not need extra energy for operation and is used for reducing building energy use and, CO2 output by displaying semi-permanent effects after installation. It also is able to avoid the maximum electric power time-zone by inducing a time lag phenomenon of cooling and heating loads with high thermal capacity using latent heat. To verify the efficiency of blinds and PCM, tests about the PCM operation mechanism using air conditioning machinery and nocturnal panel cooling were done. In the test results of the case using PCM installation, a blind angle with machinery air conditioning and nocturnal panel cooling at the same time shows a 22 percent energy saving effect against general space. The test results of each case were compared and analyzed based on the blind and window opening settings. Finally, the energy reduction of existing buildings using PCM application was reviewed based on the final measurement results.

Spatial Effect Analysis on Shaking Table Tests of Subway Station Structure in Liquefiable Ground

Based on the test data of shaking table tests of subway station structure in liquefiable ground under both near-field and far-field earthquakes, the spatial effects of dynamic pore water pressure (PWP)and peak ground acceleration (PGA)of liquefiable ground as well as peak strain response of the subway station structure are analyzed. The results show that there exists time-lag phenomenon of dynamic PWP ratio of each measuring point on different observation planes. The characteristic of input ground motion has a noticeable influence on the spatial effect of dynamic PWP ratio. The PWP ratio obtained on the major observation plane presents to be larger than that on the minor one when under far-field Songpan wave. Meanwhile, the peak acceleration of measuring points on both major and minor planes increase with the growing peak acceleration of earthquake. The law of PGA and frequency spectral character of measuring points on different observation planes or at different depth varies with each other, and there present remarkable spatial effect. The peak strain of central cylinders at the top and middle floors on the major plane appear larger than that on the minor planes. However, the peak strain of central cylinders at the bottom floor are more remarkable than that of the top and middle floors, There are sharp contrasts among the peak strain responses in different spatial positions of the station structure.

Gastroesophageal Reflux Disease (GERD) in the East—Same as the West

Gastroesophageal reflux disease (GERD) is basically the same disease in the East as in the West. Although it is one of the most common illnesses in Western patients, GERD is still comparatively uncommon in the East. Furthermore, Asian patients with GERD often exhibit milder disease with lower prevalence of complications including Barrett esophagus. Recent data, however, indicate that it is an emerging disease in Asia and its increase in prevalence seem to be a time lag phenomenon when compared with the West. Pathophysiologic factors in Asian patients have been noted to be the same as in Western patients except on a lower magnitude. A lower acid secreting capacity has been reported in Chinese patients and low dietary fat and reduced obesity may account for better gastric emptying and decreased transient lower sphincter relaxations. The high Helicobacter pylori prevalence in the East may also account for lower acid secretion and consequent milder GERD. Heartburn, which is the cardinal symptom of GERD in the West may not be present in Asian patients who may in fact, complain with nonspecific chest discomfort and labeled as having noncardiac chest pains. Extra esophageal manifestations in Asian patients have not been well studied but available data suggest that it is not uncommon. Treatment practices in the East are similar to the West. Proton pump inhibitors are widely prescribed, but its use is often limited by cost as patients are often not insured and are self paying. Surgery and endoscpic therapy for GERD are not commonly carried out.

Management consensus of inflammatory bowel disease for the Asia–Pacific region

At the present there are no large-scale epidemiologic data on inflammatory bowel disease (IBD) in the Asia-Pacific region, but several studies have shown an increased incidence and prevalence of IBD in this region. Compared to the West, there appears to exist a time lag phenomenon. With regard to the two main forms of IBD, ulcerative colitis (UC) is more prevalent than Crohn's disease (CD). In addition to geographic differences, ethnic differences have been observed in the multiracial Asian countries. Moreover, the genetic backgrounds are different in the Asian compared to Western patients. For instance, NOD2/CARD15 variants have not been found in Asian CD patients. In general, the clinical course of IBD seems to be less severe in the Asia-Pacific region than in Western countries. Diagnosis of IBD in this region poses special problems. The lack of a gold standard for the diagnosis of IBD, and the existence of a variety of infectious enterocolitis with similar manifestations to those of IBD make the differential diagnosis particularly difficult. So far, Western diagnostic criteria have been introduced for the diagnosis of IBD. A stepwise approach to exclude non-IBD enterocolitis also must be introduced, and a definite diagnosis must include typical histological features. In some patients, follow up and therapeutic trials might be necessary to obtain a definitive diagnosis. A better understanding of the pathogenesis of IBD will allow the development of better diagnostic markers. The management of IBD also poses some special problems in the Asia-Pacific Region. There is often a delay in using proper medications for IBD, and alternative local remedies are still widely used. With a combination of Western guidelines and regional experiences, similar principles can be used for induction and maintenance of remission. A stepwise selection of medications is advocated depending on the extent, activity and severity of the disease. Comprehensive and individualized approaches are suggested for different IBD patients. Deeper understanding of disease pathogenesis and the unique characteristics of IBD in the Asia-Pacific region, combined with reasonable and practical guidelines for drug management and the future use of biological agents would improve the therapeutic outlook of IBD in this region.