The ongoing pandemic has transformed communication modes globally. Especially in the case of higher education, where countermeasures against coronavirus disease 2019 (COVID-19) have affected students’ learning experience. This study emphasized the case of business simulation games, where critical factors were underlined to define learners’ intention to use an online learning environment through the lens of task technology fit (TTF) as a theoretical stance. This study considered the statistical analysis of 523 students who attended the business simulation module online at the tertiary level of education. Findings conclude that flow experience is the most critical factor to define learners’ perceived TTF in the case of an online learning experience. However, the learners’ self-efficacy is significant enough to map learners’ intentions to use an online environment for learning. The study discussed several theoretical and practical implications for learners’ educators and policymakers. Business simulation games (BSGs) have been used to bridge the gulf between practice and theory in scientific studies . These gImproved communication skills, problem-solving, teamwork, and adaptability to new conditions have also been spurred from the interaction and learning of respective games . CorrespThis study aims to underline the following two research questions. RQ1: How interactivity and flow experience help to define students’ perceived task technology fit (TTF) in the case of an online learning environment (a case of BSG) . RQ2: HoBy having insights into the existing pool of literature about business simulation, this study takes a deep overview of the origin, development, and evolution. It also entails the definitional framework and the varying definition of business simulation games. Furthermore, this study has been laid on TTF and frames the hypothesis on the basis of the postulates remarked by TTF. It also differentiates measurements of TTF at the organizational level and explains why it has been measured at the individual level in the present context. The study proposes the hypothesis of flow experience, real-time interactivity, and active control.Online business games have emerged as the alternative and effective means of learning globally. With innovation, creativity, and improved learning, they are meant to change the landscape of education . For eduThe origin of the BSG can be traced back to the 1950s when games were designed in the military war games. Business associations, industrial firms, and educational institutes have designed several business games in the following decades. Consequently, the University of Washington has been using BSG in classrooms since 1957. Perhaps BSG has been used as an educational tool for the past 50 years and has gained an important place from the supplemental exercise to the key method of business instructions . GreenlaContrarily, A surge to map out the TTF theory in the spectrum of Information Systems (ISs) literature is notable . The theThe fundamental postulate of the TTF narrates that consequences or results are based on the alignment or extent of fit between the information and the executed task. Eventually, IT significantly affects the individual’s performance and matches the particular task to be performed . GoodhueTask technology fit digs out that technology is apprehended as a tool by individuals to accomplish their particular tasks. Somehow, in the context of this model of the study, technology refers to BSG, different software, and support services that are meant to provide ease in the learning process within the academic circle . The modThe graphical attraction has been a determining factor in academic performance because it increases students’ exposure and confidence. Graphs become vicarious to understand particular scientific concepts. H1: A higher degree of graphical attraction increases the perceived TTF among online learners (a case of BSG).Real-time interactivity is captioned as the users’ perception or the social indication regarding the connection. Interactivity is a much-prioritized matter for companies. H2: The higher degree of real-time interactivity increases the perceived TTF among online learners in the case of BSG adoption.Flow refers to individuals’ overall sensation when they execute an action with their optimum output. It is the individual experience to exert their best effort. In case of the high state of flow, users indulge in their respective activities. They become unaware of their surrounded environment by elapsing time at a higher pace . IndividH3: The media enriched flow experience increases the perceived TTF among online learners in the case of BSG adoption.Active control is defined as an individual’s ability to participate voluntarily and technically exert an impact on communication. This communication is a two-way communication between users and the messages on the Internet and between users and other users . Active H4: The higher degree of active control increases the perceived TTF among online learners in the case of BSG adoption.Business simulation games have inferred TTF in the context of the current mapped out model. It has been designed as a mediator with reference to different variables leading toward academic performance. BSG has attained concertation by educators, managers, and practitioners in recent years. They are categorized as education games, digital game-based learning, serious games, and applied games . The simAs far as the relationship between the flow and the BSG is concerned, the existence indicates that flow has been an influential construct to determine the relationship between human and computer interactions . FurtherActive control has an interesting association with BSG in academic performance. Active control spurs students’ engagement by providing them with fun and entertainment. It led toward knowledge construction and escalated academic performance . NeverthH5: The higher degree of perceived TTF increases online learners’ intentions to use the digital environment (as a case of BSG).Scientific inquiry has been much debated among the academic circles in the previous two decades. It refers to the manifold process, which comprises of doing observations, raising the questions, enquiring the books and relevant information sources to determine what is already present in the body of knowledge, planning the research through several tools, analyzing, interpreting, and generalizing the data with the assistance of explanations and descriptions . The defSelf-efficacy has been narrated as an individual perception of their abilities to execute an action successfully. It is not the concrete criteria to measure abilities, rather it is a perception of the capability to perform the tasks . Self-efH6: Simulation games’ self-efficacy positively moderates the relationship between the perceived TTF and online learners’ intentions to use BSG.This study used structural equation modeling to examine the proposed model because the study includes several exogenous factors with multidimensional interactions. The following subsection discussed instrument development and the data collection process, followed by the descriptive profile of the collected response set.To avoid instrumental reliability issues, the authors adapted the items for each construct from existing sources and literature. Furthermore, the instrument was adopted in the context of the current research. Particularly, the four items scale to examine real-time interactivity and inquiry-based simulation games’ self-efficacy adapted from the research contribution by via online classes were approached. The researchers collected samples from the affiliated universities and through referral networks only. The authors assumed that the response would be taken anonymously to keep the data confidential and address privacy concerns. The data were collected during the first and second quarters of 2020 from mainland China. A total of 523 complete responses were collected, whereas the descriptions of the collected sample are given in To address the hygiene concerns and safety precautions during coronavirus disease 2019 (COVID-19), the authors used the online questionnaire survey method to collect the survey. Particularly, the convenience sampling method was adopted, where students attending a business simulation course (at undergraduate and postgraduate level) SPSS-Statistics (version 26) and AMOS (version 24) were employed to examine the proposed model of the research. The analysis comprised of (1) data normality and common method bias testing, (2) the constructs’ internal and external validity and reliability testing by examining confirmatory factor analysis, (3) structural path analysis, and (4) moderation effect as proposed in Section 3.Data skewness measured by a kurtosis marker was calculated to examine data normality and biases in the collected data. Multicollinearity (variance inflation factor) was checked in the skewness measure. All the markers and checks were counted under the upper limit, as The confirmatory factor analysis was performed to compute the external and internal validity of the data. The factor loadings of the surveyed data at a saturated and model level were calculated. Furthermore, Cronbach alpha was also calculated to check data reliability. Satisfactory results are noted, as shown in Apart from factor loadings and Cronbach alpha-based analysis, average variance, composite reliability, the interaction effect of average variance extracted with interconstruct correlation, and hetro/mono trait are also measures, as shown in Given that the study comprises adapted instruments, the authors adopted Harmans’ single factor analysis to examine the risk of common method bias, as suggested by The model fit indices for the structured model were computed. Particularly, the model fit measured the discrepancy between sigma and unrestricted sigma (CMIN), population discrepancy (by measuring RMSEA), comparing baseline model (by computing TLI and NFI), and the goodness-of-fit (GFI). The acceptable score was reported as advised by Furthermore, all the proposed hypotheses in Section 3 (H1-H5) recorded significance. Each of the proposed hypotheses is discussed in Section 6. Furthermore, the variance explained by the perceived TTF and by the perceived intentions to use business simulation games is.295 and.200, respectively. The pictorial view of the structural path analysis is shown in The SPSS process macro (model 1) was used, where the bootstrapping method was adopted, to measure the moderation effect of the simulation games self-efficacy over the relationship between the perceived TTF and the perceived intentions to use BSG. The findings concluded that the perceived simulation games self-efficacy, which is fundamentally designed based on individuals’ scientific inquiry, strengthened the positive relationship between the learners’ perceived TTF, and intention to use BSG. The graphical interaction plot of the proposed moderator is shown in This study has been conducted in the context of the students’ intention to use BSG to increase their academic performance. Regarding the demographic characteristics, particularly the gender distribution, males constituted 60.61% of the total participants, and females were 39.39%. Regarding education, 6.69% possess a diploma, 59.85% are undergraduate, and 33.46% are postgraduate. Concerning disciplines, BSG constituted 49.91% of the total participants, management had 46.27%, and engineering had 3.82%. However, the study put forward that simulation games’ self-efficacy has been identified as a scientific inquiry that fosters a stronger association between TTF and the intention to use BSG.via immersive media learning, which remarked interesting results through findings that can be bifurcated on the basis of underlined research questions of the study in the first segment discussed later. While addressing and exploring RQ1, that is, how interactivity and flow experience help define students’ perception toward TTF, the study articulated a surprising fact that flow experience possesses the strongest exogenous compared with the rest of the factors  to define the perceived TTF among learners in the case of BSG adoption . It is followed by the role of interactivity, which includes active control and real-time interactivity  and . In addition, the richness appears as a fragile factor to predict the mapped-out model. Its least significance in the construct can be depicted by H2  while determining the perceived TTF among learners in the case of BSG adoption. These findings have contributed in a manner that can be observed in existing literature  characteristics of learners’ cognition can help to improve learning through BSG for learners. It concludes that self-efficacy to inquire and digitally seek information can be critical in formulating learners’ self-regulated learning. Furthermore, the domination of flow experience also highlights the potential risk where flow experience can be accounted for limited learning outcomes and leads to cognitive-behavioral outcomes . The level of effort educators is giving in online BSG-based learning needs to be examined qualitatively. It can underline the challenges educators experience because of the virtual learning environment. Future studies can examine how task characteristics (in the view of TTF) can affect technology characteristics concerning BSG.The present model of the study entails several limitations that indicate the need to bridge these academic gaps in the context of intentions to use BSG. This study is survey-based, which is a limitation. Future studies can find basis from an experimental research design to determine the intentions to use BSG. Future studies can have qualitative examinations of this particular phenomenon. Similarly, flow experience can be enquired with reference to the human-computer interaction, which can yield novel contributions. At last, the readiness of the technology has been studied as the moderator in the underlined model. It can be further studied as the exogenous factor to dig out its impact on the students or the general population. The current venture encompasses the interesting outcomes that indicate the learners’ intentions to adopt the business simulation games. Our study concludes that flow experience has been the most influential factor to determine the use of business simulation games. On the other hand, media richness has been a low-affective factor to measure the concerned model. However, the scientific efficacy has been essential to shaping individual behavior for enhanced learning through BSG.In the recent pandemic, the significant role of BSG has increased. Nevertheless, technological advancement has motivated learners to engage and learn through the games. The present construct concluded that, to use BSG, learners have a significant role in the flow experience that derives their behavior more than any other factor. The rationale may be embedded in the motivation and the engagement that learners seek during engagement with these games. Thus, BSG is evolving as an alternative mode of learning owing to its interesting features.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The studies involving human participants were reviewed and approved by the Ethical Committee of the Affiliated University . The patients/participants provided their written informed consent to participate in this study.HH initially drafted the manuscript. YW significantly contributed to each section of the manuscript at the time of revision. Both authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


A 48-year old woman was diagnosed with metastatic pancreatic acinar cell carcinoma (PACC) and with a marked elevation in alpha-fetoprotein (AFP), this being a recognized but uncommon feature of PACC. As she refused chemotherapy, the combined therapy of lenvatinib and sintilimab  was given, which conferred significant tumor shrinkage and long progression-free survival (>21 months). This study is the first report and description of a PACC demonstrating favorable response to the combination therapy of an antiangiogenic agent and immunotherapy. Acinar cell carcinoma (ACC) is an epithelial tumor similar to the acinar cells of the exocrine gland . It can Since PACC is generally asymptomatic in the early stages, clinical presentation is often delayed, and about 50% of cases already have metastatic disease at diagnosis. The liver is the most commonly affected site . There aA 48-year-old female underwent right total hip replacement because of right hip trauma on December 4, 2019. Pathological findings showed that local tissue of the femoral head was necrotic with a heterogeneous epithelial infiltration between the trabeculae, consistent with a metastatic adenocarcinoma Figure 1Despite the elevated AFP, the lack of rapid filling and rapid washout of contrast in the liver lesions in CT and absence of antecedents such as hepatitis or alcohol consumption goes against the liver lesions being hepatocellular carcinoma (HCC). After multidisciplinary discussion and literature retrieval, the patient was eventually diagnosed with PACC clinically based on her radiographic data: large diameter, common internal necrosis, exophytic growth, and a well-defined margin with enhanced capsule, often invading peripheral blood vessels, which are the typical radiographic features of PACC .There is no standard treatment for PACC due to its rarity, and the patient refused chemotherapy for fear of chemotherapy-related side effects. Abdominal CT showed multiple masses in the liver and a solitary 3.7-cm mass in the pancreatic tail with a rich blood supply to the tumor, which is the key point to choose antiangiogenic agents. And through literature review, we also found synergy effects of antiangiogenic agents combined with anti-PD-1 antibody. After discussion, the patient consented to undergo a combination therapy of sintilimab (a multitargeted tyrosine kinase inhibitor (TKI)) and lenvatinib . Three weeks into the treatment, her AFP levels  , neutropIn summary, to the best of our knowledge, this is the first report of favorable response to the combination of antiangiogenic agents and immunotherapy in a PACC patient, which provides a new therapeutic approach for many tumors that have reached the treatment bottleneck or rare tumors that have no standard treatment.The original contributions presented in the study are included in the article/supplementary material. Further inquiries can be directed to the corresponding author.Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.LQ and JS contributed equally. All authors contributed to the article and approved the submitted version.This study was supported by the National Natural Science Foundation of China (Nos. 81872484 and 82073365).The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


The least absolute shrinkage and selection operator (lasso) and principal component regression (PCR) are popular methods of estimating traits from high-dimensional omics data, such as transcriptomes. The prediction accuracy of these estimation methods is highly dependent on the covariance structure, which is characterized by gene regulation networks. However, the manner in which the structure of a gene regulation network together with the sample size affects prediction accuracy has not yet been sufficiently investigated. In this study, Monte Carlo simulations are conducted to investigate the prediction accuracy for several network structures under various sample sizes. When the gene regulation network is a random graph, a sufficiently large number of observations are required to ensure good prediction accuracy with the lasso. The PCR provided poor prediction accuracy regardless of the sample size. However, a real gene regulation network is likely to exhibit a scale-free structure. In such cases, the simulation indicates that a relatively small number of observations, such as  For example, RNA sequencing quantifies expression levels of thousands of genes. Such omics data is useful in predicting organismal traits, with empirical applications including diagnosis and classification of diseases and prediction of patient survival8 and possible future applications in predicting crop yields9, insecticide resistance10, and environmental adaptation11.Technological advancements have enabled the collection of highly multidimensional data from biological systemsA common challenge in predicting traits from omics data is the dimension of the data far exceeding that of the sample size . For example, if one is to apply least-squares estimation in multiple regression (e.g. 12) is one of the most frequently used methods for high-dimensional regression. It simultaneously achieves variable selection and parameter estimation. Theoretically, the prediction accuracy of the lasso is highly dependent on the correlation structure among exploratory variables; it is high under certain strong conditions, such as the compatibility condition13. However, in practice, it is not easy to check whether the compatibility condition holds. Another popular estimation method for high-dimensional regression is principal component regression (PCR14). PCR is a two-stage procedure: first, principal component analysis is conducted for predictors, following which the regression model on which the principal components are used as predictors is fitted. This method may perform well when the exploratory variables are highly correlated.The least absolute shrinkage and selection operator . When a random vector of exploratory variables follows a multivariate normal distribution, two variables are conditionally independent if and only if the corresponding element of the inverse covariance matrix is zero. Essentially, the networks are characterized by the nonzero pattern of the inverse covariance matrix.It is reasonable to assume that gene regulation networks will result in conditional independence among the levels of gene expression20. Empirical studies suggest that biological networks are often scale-free23, although exceptions have also been found24. Therefore, it is reasonable to consider the problem of high-dimensional regression when the networks of exploratory variables are scale-free. Here, it should be noted that the relative performance of different high-dimensional regression techniques may depend on sample sizes. However, to the best of our knowledge, the effect of the gene regulation network structure together with sample size on prediction accuracy has not yet been sufficiently investigated.One of the most notable characteristics of biological networks is their scale-free nature, that is, the degree distribution of the network follows a power-law expressed as 25, is considered. It should be noted that the implementation of the proposed procedure is independent of the empirical data25; the proposed framework may be applied to predict any consequence of gene expression differences. The proposed framework is based on the Monte Carlo simulations. Three datasets of transcriptome and their traits are generated. The datasets are characterized by the covariance structure of exploratory variables; one of the covariance structures corresponds to the scale-free gene regulation network. Both lasso and PCR are applied to these simulated datasets to investigate the prediction accuracy with different types of gene regulation networks. The sample size is also varied to examine its effect on the prediction accuracy.This paper provides a general simulation framework to study the effects of correlation structure in explanatory variables. As an example, the prediction of ambient temperature from the transcriptome, for which good empirical data is availableThe remainder of this paper is organized as follows. Section “n observations p-dimensional vector of explanatory variables and Suppose that we have The lasso minimizes a loss function that consists of quadratic loss with a penalty based on an 26). In such a case, the lasso may not function effectively in terms of both prediction accuracy and consistency in model selection, because the conditions for its effective performance  may not be satisfied. This issue could be addressed using PCR because it transforms data with a large number of highly correlated variables into a few principal components. In the first stage of PCR, principal component analysis is applied to predictors. The ith observation of predictor, A is a A is obtained by the following least squares optimization problem28:d, was chosen such that d principle components collectively explain 90% or more variance  can be considerably large . Detail of setting of these parameters will be presented in the next subsection.The performance of the estimation procedure is investigated by the following expected prediction error:X. Then, I being an identity matrix. The test data, N  matrix. In other words, the network structure is characterized by the inverse covariance matrix of predictors.S be the sample covariance matrix of predictors, that is, 29, and there exists several efficient algorithms to obtain the solution33. The estimator of  using .Get entclass1pt{minimaTo obtain 30, 37)q is the number of nonzero parameters of the upper triangular matrix of 38. We set 37. As a result, the EBIC selected Because the log-penalty  is noncop = 17205 results in The upper triangular matrix Figure X, Y) are divided into ten datasets, j  is again randomly divided into two datasets: test data The values of mentclass2pt{minimmentclass2pt{minimIn addition, the root mean squared error (RMSE) is calculated as follows:N (the number of observations of training data) and the vertical axis is the RMSE or The box and whisker plot of the RMSE and the coefficient of determination (N increased. The poor performance of the PCR can be attributed to the predictors associated with small eigenvalues; these predictors affected the prediction performance. Figure We compared the performance of the lasso with that of the PCR. When N. Further, The prediction accuracy was compared among the three covariance structures. In all the cases except PCR with https://github.com/keihirose/simrnet. Below is a sample code of the simrnet in R: The proposed simulation is implemented in R package simrnet, which is available at p = 17,205, which was used in the simulation presented in this paper, several days were required to complete the simulation task.When In a gene regulation network, a gene regulates a small portion of a genome, not all the genes in a genome. This indicates that gene regulation network is expected to be a sparse network rather than a complete graph. Therefore, two covariance matrices indicating sparse networks (39. However, omics data, which is rapidly being accumulated, results in high dimensional data with strong correlations. Thus, our simulation study considered more complicated settings than the traditional ones. Our simulation, or its extension, may be used in the future to find clues about theoretical aspects that may ultimately lead to the development of a sample size determination technique for omics data.Conventional theory on the relationship between RMSE and sample size has been developed under the assumption that the sample size exceeds the number of exploratory variables40. The definition of the small-word networks is that the shortest path length between two randomly chosen variables is proportional to 43. Some statistical properties of the small-world networks have also been studied46. The investigation of the prediction accuracy in the small-world networks would be interesting but beyond the scope of this research. We would like to take this as a future research topic. The development of methods that provides better prediction accuracy than the lasso in various network structures with small sample sizes would also be an important future research topic.Other than the scale-free network, the small-world network is another notable property in the networks literature


One of the main advantages of information-centric networking (ICN) is that a requested piece of content can be retrieved from a content store (CS) at any intermediate node, instead of its original content producer. In existing ICN designs, nodes forward Interest packets mainly based on forwarding information base (FIB). FIB is constructed from name prefixes registered by content producers with a list of next hops to the name prefixes. The ICN forwarding engine uses those information to forward Interest packets towards corresponding content producers. CS information of a node is currently used only for checking the availability of cached content objects at the node and is not considered in the data plane of existing ICN forwarding mechanisms. This paper highlights the importance of CS information in an ICN forwarding mechanism and enables neighbor CS information in the data plane to improve the cache hit ratio and forwarding efficiency, especially for resource-constraint Internet of Things (IoT). We propose an efficient CS-based forwarding scheme for IoT. The proposed forwarding scheme exploits CS information of neighbors to find efficient routes to forward Interest packets toward nearby nodes with corresponding cached content. For that, we carefully design an efficient way for CS information sharing using counting bloom filter. We implement the proposed scheme and compare with state-of-the-art ICN forwarding schemes in IoT. Experimental results indicate that the proposed forwarding scheme achieves a significant improvement in terms of cache hit ratio, energy efficiency, content retrieval latency, and response rate. This paper extends our preliminary version  to develICN is considered as a potential networking architecture for Internet of Things (IoT)  which coIn particular, ICN decouples the content location and the content producer from content Interest packet forwarding. Based on the location decoupling and content naming features, ICN implements in-network caching ,9 at intIn the current design of ICN in general and named data networking (NDN), specifically ,3, CS ofThis paper highlights the importance of CS information in an ICN forwarding mechanism. We propose to enable neighbor CS information in the data plane for Interest packet forwarding purposes. The idea is to exploit the CS information of nodes to improve the network performance. For the purpose, we design an efficient CS-based forwarding scheme to improve the cache hit ratio and forwarding efficiency, especially for resource-constraint Internet of Things (IoT)  where foThe rest of this paper is organized as follows: Information-centric networking (ICN) names content objects and exploits content names for routing. In its core design, ICN decouples the content location and the content producer from content Interest packet forwarding. Relying on the location decoupling and content naming, ICN is designed with in-network caching ,11 in whIn the current design of ICN ,6, CS ofCC-WSN  is a ligIn , the autTo address the above limitations, Muhammad et al.  proposedIn existing ICN design ,3, nodesThe limitation of the existing design is that the cached content is exploited only if it is cached at a node on the forwarding path toward the corresponding content producer. If a sender requests the same content C in the former and the content is cached at a node  that is not on the path from S to P, the cached content C at Y does not benefit the request of S, although Y is close to S. This is inefficient packet forwarding, especially for resource-constraint IoT devices. In addition, as CS information is not shared among neighbor nodes, several neighbor nodes may cache the same content objects. As a result, this lowers the number unique content objects can be cached within a neighborhood of a node because the storage capacity of IoT device is limited. This paper proposes an efficient design to make CS information of a node available in the data plane to share with neighbor nodes. Based on that, we implement an efficient forwarding mechanism to improve the cache hit ratio, reduce the hit distance, network delay, and increase energy efficiency for IoT devices.As we discuss above, CS information of a node can help improve the efficiency of forwarding mechanism and caching policy of its neighbor nodes. However, the amount of CS information is normally quite large and inefficient for exchanging among IoT nodes. Transmitting the whole CS information can lead to another inefficient problem. Therefore, an efficient design for CS information exchange is required to take benefits of CS information in the data plane.For that, we use the counting bloom filter (CBF)  in our dLocal CS information of a node is summarized using a CBF, namely a local CBF. Note that all CBFs have the same size. Local CBF of a node is updated when a content is added or deleted. Each node advertises its local CS information summary through a compressed local CBF  to the nIn addition to existing data structures of ICN ,7 includThe detailed procedures for Interest packet forwarding of the proposed scheme are presented in The node then checks its neighbor CS. If the requested content is cached at the neighborhood, the node forwards the Interest packet to the corresponding face toward the neighbor having the cached content object. The neighbor node receiving the Interest packet responds with its cached content object. Otherwise, the node forwards the Interest packet to the next hop using FIB toward the content producer. The above operations are processed recursively until the Interest is satisfied.In this paper, we implement one hop CS based forwarding, but it can be extended for multiple hop neighbors . For multi-hop cases, we also use the neighbor CS table for each node and a CBF is used for an interface. However, a CBF is used to summarize a compact set of representing lists of content names cached by its N hop neighbors, instead of one hop neighbors. For that, the CS information summarized using CBF of a node is propagated to multiple hop neighbors instead of one hop neighbors. Other operations remain the same.For Interest packet forwarding, after the phase in which a node A checks PIT for Interest packet forwarding, the node then checks if the packet forwarding distance using FIB is smaller than N , and the node forwards the Interest packet using FIB for efficiency. Otherwise, in the phase in which a node checks its neighbor CS table for Interest packet forwarding, if the requested content name exists in a CBF of an interface in the neighbor CS table, the node adds a hop counter to the Interest packet and forwards the Interest to next hops through the corresponding interface until it is satisfied by CS of a neighbor. At each hop, the hop counter is increased by one. When the Interest packet is received by a node containing the cached content object, the node returns to the sender with its cached content object. In cases of errors when the requested content is not found within N hops, a fall-back recovery is performed by sending a notification ACK back to node A. FIB-based NFD forwarding is then executed at node A. The above operations are processed recursively until the Interest is satisfied.We implement the proposed CS-based forwarding scheme in Contiki . We thenDue to resource constraints, we conduct experiments using nodes with light-weight sensing information and limited storage capacity. As implemented in our prior study , we reusWe use the following metrics for the performance evaluation and comparison.Average radio duty cycle: We use average radio duty cycle as an indicator for energy efficiency [i is calculated using (1) by simply adding duty cycles for each radio operation: listening (ficiency . We cons (DCadd) :(1)DCi=DTo measure the radio duty cycle, we record changes in the radio’s states and use a counter to accumulate the time period used in each state. At the end of simulation, we calculate the average radio duty cycle and report average results.n is the total number of IoT nodes.Average duty cycle of nodes in a network is calculated as follows:Average cache hit ratio: measures the percentage of content interest that are satisfied by cached content objects (COs) in the CS of IoT nodes. This metric implies that the higher the cache hit ratio, the higher the energy efficiency of IoT nodes that is achieved. As a result, this metric also reflects the network performance of the forwarding mechanism. We calculate the average cache hit ratio as follows:i and Average content retrieval latency: indicates the average time needed for interest packet get satisfied whether from an original content publisher or from a cache. A good forwarding decision should reduce the content retrieval latency. The average content retrieval latency is calculated as follows:p is the total number of content objects provided by nodes responding to content interests.Response ratio R: measures the ratio between the total number of content objects responded p and the total number of Interest packet sent by nodes I in the network. This metric shows the reliability of the network. The response ratio is calculated as follows:The previous figure also indicates that the proposed scheme should have another benefit of average content retrieval latency because it improves the cache hit ratio significantly. We also measure the response rate of Interest packets to understand the quality of service under different schemes. This paper proposes to enable neighbor CS information in the data plane of ICN to improve the Interest packet forwarding, especially in IoT environments. For that purpose, we carefully design an efficient way for CS information sharing using CBF. We extend the existing ICN forwarding based on FIB with neighbor CS information to optimize the forwarding efficiency for Interest packets. In comparison with existing approaches, the proposed scheme exploits CS to increase the cache hit ratio, thus improving the network performance instead of using only FIB. We implement the proposed scheme and compare with state-of-the-art forwarding schemes in IoT. Obtained results show that the proposed scheme achieves a significant improvement in terms of energy efficiency, cache hit ratio, content retrieval latency, and response rate. In future works, we plan to collaborate various caching mechanisms with the forwarding scheme to enhance the network performance and perform experiments with edge cloud computing to integrate the forwarding scheme with our existing systems.


Controlling the motion of macroscopic oscillators in the quantum regime has been the subject of intense research in recent decades. In this direction, opto-mechanical systems, where the motion of micro-objects is strongly coupled with laser light radiation pressure, have had tremendous success. In particular, the motion of levitating objects can be manipulated at the quantum level thanks to their very high isolation from the environment under ultra-low vacuum conditions. To enter the quantum regime, schemes using single long-lived atomic spins, such as the electronic spin of nitrogen-vacancy (NV) centers in diamond, coupled with levitating mechanical oscillators have been proposed. At the single spin level, they offer the formidable prospect of transferring the spins’ inherent quantum nature to the oscillators, with foreseeable far-reaching implications in quantum sensing and tests of quantum mechanics. Adding the spin degrees of freedom to the experimentalists’ toolbox would enable access to a very rich playground at the crossroads between condensed matter and atomic physics. We review recent experimental work in the field of spin-mechanics that employ the interaction between trapped particles and electronic spins in the solid state and discuss the challenges ahead. Our focus is on the theoretical background close to the current experiments, as well as on the experimental limits, that, once overcome, will enable these systems to unleash their full potential. The unique control offered by single quantum systems, such as atoms or ions, has enabled an immense boost in the development of quantum technologies. Extending these technologies to larger masses is important both for fundamental questions on the nature of quantum physics at larger scales, and for the development of innovative devices such as ultra-high precision force sensors and accelerometers .Electro-, magneto- or opto- mechanically controlled levitating objects in vacuum are fascinating in this regard and have been at the focus of intense recent research activity . This at− center for short) in diamond centers stands out because of the ease with which one can optically polarize and read-out its electronic spin under ambient conditions. Most of the proposals initially designed for clamped oscillators coupled with NV− centers ≠0 .In the following, we will restrict the study to one librational mode that is assumed to be in the y axis. Moving to the particle frame through the unitary transformation The Hamiltonian of the simplified system readsy axis. It is the sum of the particle and the NV-spin angular momentum. This modified angular momentum could cause precession of the particle. Such a precession is predicted to be observable in levitated hard ferromagnetic nano-particles [In this frame, articles ,81, with− excited states, which is satisfied under the condition The remaining step is to diagonalize the spin part of the Hamiltonian. Apart from in ref. , experimThe expression of the new eigenstates − center. This is also manifest in It was shown in  that theSimilar to the calculation for the center of mass (CoM), we obtain the Hamiltonian see :(11)H^NVHere − ground state is populated and can be interpreted as a consequence of van Vleck paramagnetism. The mixing between the ground and excited states induced by the transverse magnetic field indeed generates a non-zero magnetic moment in the NV− center [The second term − center ,83. ThisAt this point, a word of caution is in order if one wishes to translate the above description to ensembles of NV centers. We indeed need to check for the consistency of our initial assumptions about independent NV directions in the presence of strong van Vleck paramagnetism. This paramagnetism is present in the absence of microwave excitation, so all NV orientations contribute to give a spin-torque in the ground state, the extent of which depends upon the transverse magnetic field amplitude for each orientation. When including the four orientations, the first-order effect is a slight reduction of the van Vleck paramagnetic susceptibility that can be estimated for a single orientation. This is due to an overall spatial averaging of the magnetizations from the four NV orientations, which should be recast in ation in .Let us redefine the center of the mechanical resonator to be around the equilibrium angular position when the population is in the Equation ), when rD.The optimum coupling strength − centers can then be used as a marker of the center of mass motion of diamonds or distant ferromagnetic particles, as pioneered in experiments with tethered oscillators [As we just described, the ESR frequencies depend strongly on the angle of the homogeneous magnetic field with respect to the NV axis, and on the center of mass in a magnetic field gradient. In the presence of a microwave drive on the diamond, the change in the photoluminescence from the NVillators ,17. With− centers from a diamond containing about 1000 NV− centers. Eight ODMR lines were observed due to the four projections of the magnetic field onto the four possible NV axes in the diamond cristalline structure and thanks to the efficient particle angular confinement. Assuming thermalization with a gas at a temperature close to T = 300 K, the angular standard deviation is Note that, additionally, control of the trapping laser polarisation allows tuning the NV angles . In 54,,54,86, Omrad see . The expters see .− centers in the diamond were employed to read-out the librational motion. In the second experiment [− center was brought in the vicinity of the magnet to read-out its center of mass motion.Two recent experiments have even shown read out of the harmonic motion of a trapped particle using NV centers ,70. In tperiment , a magneIn order for NV centers to efficiently detect the center of mass motion, Gieseler et al.  used broSimilarly, Huillery et al.  reportedThese studies open a path towards the NV read-out of the Brownian motion of trapped harmonic oscillators. To reach this limit, more involved dynamical decoupling (DDC) techniques  could ben motion . Rabi osn motion  using anWe have discussed experiments where the trapped particle motion was read-out by NV spin states. In order to strongly couple a mechanical oscillator to spins, however, not only should the mechanical motion affect the spin state, but the spin should also alter the motion.In this section, we review work on the reverse process where NV centers act on the motion. We start by a discussion on optimum sensing of the force and the torque induced by NV centers.Presently, direct optical read-out of the motion of trapped particles using scattered light is more efficient than using embedded NV centers. Most experiments that use optical read-out are currently in the regime where the influence of collisions with the background gas dominates. The detection noise is thus determined by the resulting Brownian motion of the levitating object. Note that the ultimate sensitivity should be given by the quantum back-action of the measurement under low vacuum. This limited was recently reached in experiments with trapped nano-spheres ,89.The most sensitive way to detect an external torque, with current technology, is to use optical interferometric detection and to modulate the torque at the mechanical frequency of the oscillator. Modulation of the amplitude of the NV induced spin-torque can be done straightforwardly by modulating the microwave tone that excites them. The minimum torque Tethered torque sensors with sensitivities in the illators . The larillators . The autained in  using soeratures .Q with I by m. Sensitivities in the zeptonewtonA similar formula can be obtained for the smallest detectable force acting on the center of mass mode, by replacing mentally ,92,93. Vmentally . AmongstHz range ,44. NoteThese last achievements not only show the capabilities of levitating systems, close to the sensing capabilities of MEMS, but also offer immediate perspectives for entering the quantum regime by coupling magnets to distant NV centers.− centers have a lifetime that is greater than the typical time required to shift the angle or the center of mass. The latter is typically on the order of the period of the potential.In this section, we discuss the parameters required for observing spin-dependent forces and torques on a trapped particle. We focus on the expected static shifts, assuming that the NVUsing Equation , one finThe optimum shift will be found for Let us consider a particle with a diameter of 15 m undergoing Brownian motion in a harmonic trap under 0.1 mbar. Stable harmonic confinement is readily attainted at 300 K in a Paul trap with these parameters , enablineference  reportedken from ), revealQ factor of In order to approach the single spin torque level, particles with much smaller moment of inertia must be used. A levitating particle with a diameter of 100 nm and a modest A similar discussion can be made to estimate the magnitude of the magnetic force on the CoM of a trapped diamond subjected to a magnetic field gradientUnder a gradient of − centers to the best of our knowledge, even with large ensembles of spins. Even if strong magnetic field gradients can be achieved, it may induce a large inhomogeneous broadening when using ensembles, which will forbid efficient microwave excitation of the whole ensemble of NV− centers in the selected orientation. The magnetic field gradient will thus be bounded by the microwave excitation Fourier width d is the diameter of the probed spin-ensemble. Note that The spin-dependent force has not been observed thus far using NVctronics .One further difficulty with NV centers coupled with trapped particles is to distinguish the center of mass motion from spin-induced torques. Indeed, a magnetic field offset is required in order to magnetize the NVLet us conclude by adding that single-spin forces were measured using Magnetic Resonance Force Microscopy (MRFM) in . AcquisiSpin–mechanical systems can show richer physics than just static torques and forces. When calculating the torque and force in Further, when the spin-torque resulting from the combined laser and microwave induced magnetization is lagging behind the motion, exchange of heat between the spin and the mechanical oscillator can take place. Experiments have recently entered this regime .We provide a simplified analytical theory of such spin dynamical back-action. We focus on the angular degree of freedom, but the calculation can be straightforwardly carried out for the center of mass by making the replacement As in opto-mechanics, bistability and modified spring constants can occur. We first describe these two effects, in the limit where the microwave magnetization and the laser polarisation rates are faster than the mechanical oscillator frequency. This means that no energy exchange between the motion and the spin can take place.The torque Equation . We obtaIn the dispersive limit where This spin torque can be added to the restoring torque of the levitating system. The new angular stable position can be found by solving the equation In the very same way as in opto-mechanics, two stable solutions for Linearizing about an equilibrium position In the presence of the green laser light, transitions from the dressed spin states will alter this predicted shift. We will estimate it together with the spin-cooling effect using a density matrix formulation in the following.In the above estimation, we assumed that the spins react immediately to a change in the motion. When the spin torque lags behind the motion, friction forces can alter the motional temperature and lead to spin-cooling, as calculated in  and obseWe will again assume that the microwave is tuned to the Equation .The von Neumann equation for the reduced two-by-two spin density matrix The above equations are coupled with the equation of motion of the particle viaWe introduce the steady-state quantities Using Equation , one finThis last equation gives a third degree polynomial equation for Writing each spin and angle parameters in Equations –24) as  as 24) aThe quantity The modified damping and frequency of the mechanical oscillator have been estimated in the limit In the adiabatic limit We now linearize this equation around the steady states and move to the Fourier space. We find:Finally, using Equation , we obtaAs manifest in Equation , when ωθT of the gas molecules surrounding the particle, in the regime where T of the gas. One indeed has The change in damping induces a change in the oscillator temperature. Using For large quality factors and negative detunings, that is with a microwave tuned to the red, a pronounced cooling can take place. This effect is strongly analogous to Raman cooling or cavity cooling and was observed in  using diThe SRR regime has not been attained so far using trapped particles coupled with NVen atoms  to make en atoms . If all Levitated spin-mechanics offers prospects for a wide range of applications in quantum science. The negatively charge NVressures , while ear range ,36. To gThe diamonds that are employed for research purposes are almost always of artificial origin. They are produced mainly using three methods, detailed in the  centers . When stAs discussed previously, thanks to the development of CVD grown diamonds and implantation techniques, it is possible to finely control the purity, and the number of hosted NVructures . Pillarsructures .The development of coated diamond initially intended for biology applications may also increase the achievable control of the properties of trapped diamond. A typical example is silica embedded diamonds, which allows obtaining spherical particles, and that have been shown to favor the NVdiamonds .Spin-mechanics with trapped objects will thus benefit from the tremendous progress in diamond material science and continuously improved knowledge about diamond and NVmpulsion ,101, or mpulsion , are verWe have seen that increasing the number of NVFor concentrations that are larger than ∼1 ppm (corresponding to a mean distance between spins of ≈15 nm or a dipolar coupling strength of ≈15 kHz), the dipolar coupling amongst NV spins plays an important role. One important effect is the modification of the spin lifetime  centers ,102,103. centers .Other collective effects between NVribed in ,72,73, aribed in .Numerous studies have reported an increase in levitated diamond internal temperature under vacuum conditions ,104,105.This heating was shown to be induced by laser absorption by the particle. The final temperature is the result of a competition between absorption, heat conduction to the surrounding residual gas, and black-body radiative exchange. Studies conducted on high purity CVD bulk diamonds have shown that a very low laser absorbance is achievable , even beD, between The spin of the NVperature ,104,108 cterized . One canit hosts ,104, seeNote that instead of improving the properties of trapped diamonds that are destined to be trapped under a magnetic field produced by a fixed magnet, the roles of the diamond and the magnet can be reversed. Schemes already discussed in this review ,70 involThe present review focused on NVesonance . SiC canesonance , even siIn this review, we presented recent levitated spin-mechanics experiments, focusing specifically on NV


The spatial resolution and light detected in fluorescence imaging for small animals are limited by light scattering, absorption and autofluorescence. To address this, novel near-infrared fluorescent contrast agents and imaging configurations have been investigated. In this paper, the influence of the light wavelength and imaging configurations (full-field illumination system and scanning system) on fluorescence imaging are compared quantitatively. The surface radiance for both systems is calculated by modifying the simulation tool Near-Infrared Fluorescence and Spectral Tomography. Fluorescent targets are embedded within a scattering medium at different positions. The surface radiance and spatial resolution are obtained for emission wavelengths between 620 nm and 1000 nm. It was found that the spatial resolution of the scanning system is independent of the tissue optical properties, whereas for full-field illumination, the spatial resolution degrades at longer wavelength. The full width at half maximum obtained by the scanning system is 25% lower than that obtained by the full-field illumination system when the targets are located in the middle of the phantom. The results indicate that although imaging at near-infrared wavelength can achieve a higher surface radiance, it may produce worse spatial resolution. Recent advances in molecular imaging technologies allow detection of physiological and pathological processes in molecular sensitivities from micromolar to picomolar level . Among tThe spatial resolution and light detected by the in vivo fluorescence imaging are however limited by light scattering, absorption and autofluorescence in tissue. Scattering acts on both the excitation and emission light and introduces an intrinsic blurring in fluorescence images . AnotherDevelopment of near-infrared (NIR) contrast agents for fluorescence imaging has attracted much interest ,7,8,9, bPlanar imaging is a simple, inexpensive and rapid way to image the fluorescence. Generally planar fluorescence imaging configurations for small animals can be divided into two categories based on source arrangements. The most widely used system is full-field illumination imaging, in which an excitation light source , lamp or laser) supplies a full field excitation and the images are captured with a camera . An alternative imaging configuration is a scanning laser system in which a galvonometer-based scanner scans across and illuminates the sample, and the emission light is captured by a photomultiplier tube (PMT), an avalanche photodiode (APD) or a charge-coupled device (CCD) camera . In geneSpatial frequency domain imaging (SFDI) is a full-field illumination method that can enhance the spatial resolution of fluorescence imaging . In SFDIThere have also been several techniques based on scanning illumination beam proposed to enhance resolution and depth of fluorescence imaging. In Laminar Optical Tomography , a focusAlthough contrast and resolution of images are improved in ,15, therIn this paper, a fast modelling technique based on the finite element method (FEM) for a point scanning fluorescence imaging system is developed. The influence of the two aspects, light wavelength and imaging configuration, on the fluorescence imaging surface radiance and spatial resolution are studied quantitatively. Surface radiance for the scanning imaging system is calculated and compared with a full-field illumination system. The ability to resolve two fluorescent targets using these two imaging systems in both reflection and transmission mode are compared.To obtain the imaging resolution and surface radiance of the full-field and scanning mode imaging, it is necessary to obtain the photon fluence distribution within the simulated tissue first. This is achieved numerically by modifying the tool Near Infrared Fluorescence and Spectral Tomography (NIRFAST) . As an ocreat mesh function of NIRFAST. The surface radiances  with the centre located at  mm and radius Specifically, the surface radiance is calculated in three steps: (a) calculate the photon fluence all over the regions where the QDs are located using the forward model of NIRFAST, (b) convert the photon fluence at the QDs regions to their emission strength and (c) calculate the surface radiance at the detector for both the reflection mode and transmission mode with the previously calculated fluorescence emission as the new source for the forward model of the NIRFAST. The emission strength Sfl and 24 GB memory is ~ 35 min for the geometry described in b is the scattering power.The reduced scattering coefficient (ed using (2)μs′μa(λ)It can be seen from Equations  and 3)  3) that quations  and (3) 1, S=0.8 . μa,oxy thors of . Only bl 1000 nm  and is n 1000 nm .The spatial resolution is defined as the minimum separation of two targets that can still be perceived as separate by an observer. The spatial resolution is estimated by the Sparrow criterion : the minWithin the 200–650 nm excitation wavelength range, the autofluorescence from tissue also confounds fluorescence measurements. In this paper, the autofluorescence is simulated by treating the intrinsic fluorophores that are responsible for generating autofluorescence similarly to QDs. The intrinsic fluorophores have an intrinsic fluorescence coefficient (fined as (4)β is simulated with a fixed emission wavelength of 1000 nm. Point spread function (PSF) is calculated for each of the excitation wavelength and FWHM of the PSF is used to estimate the resolution. The PSF here is defined as the detected image when the quantum dot is a point target. Example PSFs for the scanning system is shown in The surface radiance of the full-field illumination system is calculated when autofluorescence is considered, as shown in For the scanning system, when the scanning source is located directly opposite to the detector, the photon intensity due to autofluorescence detected is at its maximum. The maximum intensity due to autofluorescence in transmission mode and reflection mode are calculated to be Much attention has been focused on developing novel probes emitting light in the NIR spectral window, because tissue has minimal absorbance in the wavelength range between 650 nm and 1000 nm, allowing for deep penetration depth and higher sensitivity . The finerent μa . HoweverImprovement of spatial resolution can be obtained by using a scanning system, which has a much better spatial resolution than the full-field illumination system. For example, for the case when the targets are located in the middle of the phantom, the FWHM obtained by the full-field illumination system is 8 mm, whereas that obtained by the scanning system is 6 mm which is 25% lower. The spatial probability distribution of photons entering tissue at a source location, scattering through the tissue, and being emitted at a particular detector location, defines the spatial sensitivity profile for that source-detector pair . A typicIt was found that for the scanning system, the same spatial resolution is obtained for reflection mode and transmission mode. The emission wavelength of the fluorescent probe also has no effect on the spatial resolution. The spatial resolution is only dependent on the distance between the excitation source and the targets. This is because the In the simulation, the resolution is estimated as the average value of the FWHMs of the two fluorescent targets with an arbitrary separation of 16 mm. A change of the separation will not influence on the resolution. To demonstrate that this method of estimating resolution is accurate within the Born approximation, the light distribution of the two fluorescent targets are calculated separately and then superimposed, followed by an image of two targets. The fluorescence light distribution of the first target, the second target, the superposition of the two images of the single targets and the fluorescence light distribution of the two targets are shown in Some recent research has indicated that fluorophores emitting light at longer wavelength at first or second NIR window can achieve a better spatial resolution , and so The signal-to-noise ratio (SNR) of a practical system will depend on the surface radiance and the choice of photodetector . Given the wide range of available commercial detectors, surface radiance is plotted to provide general results that can be utilised for specific detectors. A small animal fluorescence imaging system which can provide scanning illumination can be built based on the simulation. Two galvanometer mirrors can be used to deflect a laser beam to provide the scanning capability. The fluorescent emission will be captured by a photon detector  mounted in a fixed position. Note that, although it is time-consuming to obtain a scanned image from the simulation (~6 h depending on the computing capability), the speed to obtain one image from the setup will be fast. The scan rate of a galvanometer mirror is approximately 1–100 kHz . To obtaIn summary, this study numerically investigated the influence of the optical properties and imaging configurations on the surface radiance and spatial resolution of fluorescence imaging in tissue. For the full-field illumination system, a lower


This study describes the development of a landslide monitoring system for the purpose of reducing damages caused by landslides in natural terrain. The system was developed to analyze the effects of landslide-inducing rainfall and the behavior of slopes through 12 monitoring stations that are distributed across eight national parks in Korea. Several sensors and a data acquisition equipment to monitor landslide were installed in each station. The composition of the system and its operating program were designed to efficiently manage the sizeable amounts of real-time monitoring data that are collected from the various stations. To test the potential of the developed system for reliable landslide hazard evaluations, data measured over a five-year period by the two monitoring stations in Jirisan National Park were analyzed. Subsequently, the suction stress of the soil over the monitoring period was calculated by applying laboratory test result of the geotechnical and unsaturated soil properties in the analysis domain area. The infinite slope stability analysis combined with an effective stress concept based on the suction stress was applied to calculate the factor of safety. This method also enabled the temporal and quantitative evaluation of slope stability in natural terrain. In addition, based on the monitoring and slope stability analysis results, an analysis for the spatial classification of landslide hazards was conducted. The analysis results quantitatively and statistically demonstrated that 98% of historical landslide initiation areas were classified as high hazard levels. Many areas are becoming exposed to multiple landslide hazards due to extreme rainfall conditions. Global climate change has introduced significantly higher rainfall intensity and cumulative rainfall than those from past records in Korea. This has directly resulted in greater casualties and property damage than in the past ,2,3. ThuThe prediction of where landslides occur requires the evaluations of spatially varying rainfall conditions and the intrinsic factors of natural slopes, such as topographic, geological, and geotechnical properties. However, to predict when landslides occur, one must understand how such conditions and properties vary over time. Namely, it is vital to determine how the hydro-mechanical properties within slope soil mass change over time as rainfall infiltrates into the soil, which helps clearly understand critical conditions leading to the moment of actual landslide events. For this purpose, researchers must go further than analyzing fixed and intrinsic factors and observe in real time the changes in slope soil mass properties according to variations in rainfall conditions. To achieve this task, real-time monitoring of natural slopes is essential.To detect landslide occurrences in advance, it is necessary to observe rainfall conditions and the resulting response characteristics within slopes. Based on the observations, the changes in rainfall and soil conditions upon landslide occurrence should be analyzed. For instance, some studies adopted modeling approaches based on either experiments  or statiOne of the most crucial element of landslide early warning technology for natural slopes is in-situ monitoring in areas with the potential for landslide occurrence; it is related to comprehensive measurements of various geological and geotechnical factors related to landslides. With this as a basis, landslide monitoring systems for natural slopes should be capable of detecting the potential of landslide occurrence in advance and issue alerts to local citizens.Currently, the Korea Institute of Geoscience and Mineral Resources (hereafter referred to as KIGAM) is in the process of establishing and operating LAndslide MOnitoring Systems (hereafter referred to as KIGAM-LAMOS) for natural slopes in national parks in Korea. While numerous state-of-the-art landslide monitoring systems have been oriented to detecting long-term mass displacements using various remote sensing techniques ,18,19,20To fully understand the changes in rainfall and soil properties leading to the moment of landslide occurrence, the relevant in-situ measurements should first be conducted, followed by in-depth consideration and accurate judgement. This paper first presents a technical note describing the principles, development, operational architecture, and techniques of KIGAM-LAMOS that mainly aims to monitor geo-hydraulic processes leading to the initiations of shallow landslides. Subsequently, the results of landslide hazard evaluation analyses based on monitored data are provided and discussed to verify the effectiveness of the developed system in determining the landslide potential. The monitored parameters consist of rainfall and matric suction that were measured at two monitoring stations in Jirisan National Park from 2015 to 2019. Using the five-year monitoring data, the analyses were conducted in the following two interconnected but independent categories: (1) temporal evaluations of suction stress of soil and slope stability; (2) spatial classifications of landslide hazards for the analysis domain area. To verify the effectiveness of the spatial classification results, a comparative analysis was performed with historical landslide areas that were found to have occurred in the analysis domain area.In general, rainfall-induced landslides are initiated in the form of slope failure caused by an increase in pore water pressure as the groundwater level rises or wetting front advances in soils. However, Fredlund and Rahardjo  reportedTherefore, the KIGAM-LAMOS monitoring sensors were installed in a manner to measure changes in effective stress at various depths during rainfall that may contribute to the triggering of shallow landslides in natural terrain. The effective stress in an unsaturated state of soil can be calculated by measuring both volumetric water content and matric suction. Accordingly, sensors that are suitable for natural slopes in Korea were selected based on previous unsaturated slope monitoring studies and experience. In addition, a data acquisition system capable of wireless communication was established to enable real-time data transmission.The diagrams in Decagon 5TM sensors from ICT International  were installed to observe changes in volumetric water content in the direction of gravity as rainfall infiltrates into the soil layers from the surface. As rainfall infiltrates into the soil, the wetting front descends from the soil surface, and in this process, saturation takes place as a wetting band is formed. The expansion of the wetting band causes shallow failure in the upper soil layer. To measure matric suction, MPS-6 sensors from Decagon were installed. The upper soil layers of natural slopes exist in an unsaturated state, and as rainfall infiltrates, the changing saturation state results in a change in suction stress that eventually leads to failure in the upper soil layer.On the other hand, tiltmeters, specifically MV-5B sensors from NGI , were installed to measure the displacement of natural slopes. In addition, rain gauges were installed to measure the rainfall amount and intensity of the monitoring area. WDR-205 sensors from Wedaen  were used for the rain gauges, which are based on the tipping bucket method.An electronic wire sensor  was installed at a lower point of each monitoring station to detect movements and measure velocities of debris flows. An electronic signal is induced and transmitted to a data logger as the wire is cut by loads larger than 150 kgf.In the stage of deciding the locations for landslide monitoring stations, the potential for landslide occurrence should be considered above others. As such, various factors related to landslides should be comprehensively determined. From this perspective, geological conditions should be considered with the highest priority when selecting sites for landslide monitoring. Locations that exhibit representative geological conditions of Korea with a distribution of granite, gneiss, and sedimentary rocks were selected. In addition, the following types of areas were considered with higher priority: areas with suitable conditions  for the installation of monitoring systems; areas that allow for the sustainable and efficient maintenance of monitoring systems after installation; history of large-scale landslides; the influence areas and paths of typhoons and heavy rainfall, which are key causes of landslides; factors that influence landslides such as soil layers and soil distribution characteristics; the risks of human casualties and property damage in the event of landslides. Furthermore, the ease of licensing for the installation of landslide monitoring systems, convenience in terms of long-term operation and maintenance of monitoring systems, and soil and forest type distributions/terrain conditions that allow for various field tests (in tandem with landslide monitoring) were also considered.Candidate installation locations were selected by comprehensively considering the aforementioned factors. The final installation locations were selected after conducting site surveys and considering the installation conditions of each candidate location.Korea National Park Service and KIGAM have been engaged in a mutual working-level cooperation to mitigate natural disasters since the memorandum of understanding was signed in November 2014. Based on this cooperation between the two organizations and following the aforementioned selection process for the landslide monitoring station locations, a total of 12 landslide monitoring stations have been installed across eight national parks in Korea thus far. A cloud server is useful as it enables administrators and developers to continuously operate the system with greater convenience and efficiency. This is due to the fact that a cloud server remotely provides computing resources to the user, ensuring efficient use of resources. In addition, it allows for the stable storage and supply of monitoring data by gathering scattered resources to a central hub, removing the need for complex management by individual users. Based on such advantages, a cloud server was established as shown in The detailed transfer route of the data is as follows: the measurement values  obtained from the 12 landslide monitoring stations and the sensor status information  are stored in real time by the data logger and are transferred via an LTE modem to a DAQ computer installed in KIGAM-LAMOS for storage, as shown in As the data of landslide monitoring instruments are transferred via a virtual server port, industrial PCs require a static IP to access the data. In addition, as web services are only available with a static web address during monitoring, and as an address is required for monitoring, the cloud server was set with a static IP. As the current LTE modem was assigned with a dynamic IP, filtering with a firewall is not possible, and as the LTE modem itself cannot connect to a VPN, the data were obtained using an industrial PC. The system was configured to allow data to be stored in the DB by establishing a VPN between an industrial PC and the cloud server.For a case study to test the proposed KIGAM-LAMOS in terms of its capability in detecting the potential of landslide hazards, measurement data from two selected landslide monitoring stations in Jirisan National Park  were used. The analysis was performed for a five-year period from 2015 to 2019. The area surrounding the Jeseokbong station has steep slopes from the peak of Jirisan Mountain (1915 m above sea level) and consists of a shallow soil layer with depths of up to 2 m covering the bedrock. The area has a robust history of landslide occurrences, and is located on the path of typhoons as they first pass over the Korean Peninsula from the south. Such typhoons pass over this area with a substantial amount of energy, bringing heavy rainfall and strong winds, which results in multiple large-scale landslides and debris flows. In the event of a landslide in this area, the hiking trails that extend from the lower areas to Cheonwangbong Peak are affected by debris flows, causing direct damage to various facilities. In particular, as shown in In addition to the monitoring data from the Jeseokbong station in the analysis domain area, data from the nearby Jungsalli station were also used in this study for analysis. In contrast to the other three stations in Jirisan that use solar energy for power, the Jungsalli station has a stable power supply through cables; this allows the Jungsalli station to transfer and store real-time measurement data with relative stability. Therefore, it is possible to supplement data that are missing in the Jeseokbong station data using the measurement data from the Jungsalli station.To apply the real-time monitoring data to the slope stability analysis, the suction stress of the unsaturated soil according to the wet condition of the slope was considered. Lu and Likos  expandedσ′ is effective normal stress; σ is normal stress; sσ is suction stress; au is pore air pressure; wu is pore water pressure; (au − wu) is matric suction; eS is effective saturation; and α, n, m are the fitting coefficients of the soil-water characteristic curve of the van Genuchten [Here, enuchten  equationssH is the depth from the ground surface to the sliding surface, β is the slope angle, τ is shear stress, and fτ is shear strength. Based on the diagram, the factor of safety equation for general infinite slopes can be expressed as Equation (4):In recent years, Lu and Godt  proposedc′ is effective cohesion, σ′ is effective vertical stress, φ′ is effective angle of internal friction, and γ is the unit weight of the sliding mass.Here, By substituting Equation (1), which expresses effective stress considering the aforementioned suction stress into Equation (4), Equation (5) can be obtained:As shown in Equation (5), the infinite slope factor of safety equation that considers suction stress can be divided into angle of internal friction, cohesion, and suction stress elements.α, n, and m of Equation (3) were derived. Field surveys, sampling, and various soil and unsaturated property tests were conducted to produce data for input parameters required for slope stability analysis of the analysis domain area. Based on the test results and the assumption of near-homogeneous geotechnical properties within the area, input parameter data required for slope stability analysis were determined as shown in Effective cohesion was set as zero as previous researches reported that effective cohesion has insignificant effects on slope stability analysis involving Korean weathered residual soil, and have thus been set as zero in multiple studies ,41,42. IThe data from the Jungsalli station were used for the analysis domain area. This was because the rainfall data were measured and stored with stability at the Jungsalli station, and this data did not show significant deviations from those of the Jeseokbong station. To examine the reliability of the rainfall data collected by the rain gauges installed at the Jungsalli station, the data were compared with the rainfall data measured by a weather observatory (observatory name: Jirisan) of the Korea Meteorological Administration (KMA) in the vicinity of the analysis domain area. In contrast to the rain gauges of the monitoring station, which are located near the peak of Jirisan Mountain, the KMA weather observatory is located at the middle and lower parts of the mountain. Landslides that occur in Korea are caused as rainfall infiltrates the ground surface during heavy rainfall and reduces the shear strength of the soil below a certain threshold, resulting in sliding. Such decreases in shear strength that lead to landslides are mainly due to an increase in soil saturation and the resulting decrease in unsaturated suction stress. Therefore, matric suction, an unsaturated property of natural slope soils, is measured in real time to enable the calculation of suction stress. This in turn enables the calculation of the factor of safety through infinite slope stability analysis.The upper graph in The lower graph of As a result, it is possible to evaluate slope stability according to real-time rainfall by monitoring the unsaturated properties of the slope soil. Furthermore, the evaluation results highlight the potential of the monitoring system for landslide forecasting. By establishing landslide prognosis thresholds, which are indices of how unstable a slope is, warnings can be issued depending on the calculated factor of safety value relative to the thresholds. Notably, as such landslide early warning methods based on real-time monitoring do not use prediction data, it will be crucial to determine a set of conservative landslide occurrence thresholds to ensure adequate lead time.β) becomes the only spatially variable parameter for the infinite slope stability equation (Equation (5)) at a particular time. In other words, all slopes in the analysis domain area are characterized by the data in Assuming near-homogeneous conditions in geotechnical and unsaturated soil properties within the analysis domain area, the slope angle  with a resolution of 10 m was produced for the 2 km × 2 km analysis domain area, and thus a total of 40,000 grid cells constituted the analysis domain area. Moreover, approximately 98% of the historical landslide areas were confirmed to be classified with the “High” or “Very high” hazard levels. Considering that almost all historical landslide areas were located in areas with high landslide hazard levels, the proposed method for the spatial classification of landslide hazards based on long-term monitored data is expected to be effectively utilized as a reliable fundamental resource for decision making in disaster management policies and future land-use planning. However, it should be noted that the validity of the proposed spatial classification method is restricted to shallow depth planar landslide types. From a theoretical perspective, if the factor of safety is less than 1, this indicates that the shear stress has exceeded the shear strength, meaning there is a high chance that a slope failure or landslide has occurred.However, landslides have yet to actually occur in a significant portion of areas under the “Very high” hazard level due to various factors: spatial uncertainty of soil engineering properties or unsaturated characteristics, including increased strength due to the effective cohesion of soil or root cohesion effects from vegetation, and exposure of bedrock or soil depths of less than 1 m due to the loss of soil in case of steep slope angles. The idealization of problems, simplification processes, and conservative designs are inevitable issues when applying modelling techniques for landslide prediction. Therefore, areas with high landslide hazard levels that have yet to experience landslides should not be considered as overestimated predictions, but rather as areas with a high potential for landslide occurrence that can be triggered by minute variables at any moment in the future.An integrated landslide monitoring system, denominated as KIGAM-LAMOS, was developed to measure rainfall and the resulting unsaturated soil behaviors in real time that cause shallow landslides in natural slopes. Based on the long-term monitoring results, it was possible to quantitatively evaluate landslide hazards in the analysis domain area. These include temporal variations of suction stress in unsaturated soil and slope stability and spatial classifications of landslide hazard levels.Monitoring stations of KIGAM-LAMOS were installed at 12 natural slopes across eight national parks in Korea. Each station had various sensors to measure rainfall and unsaturated soil properties in real time in addition to various equipment for the collection and transmission of the measurement data. The monitoring stations were installed in areas that exhibited representative geological conditions of Korea, namely those of granite, gneiss, and sedimentary rock lithology. In addition, a cloud server-based landslide monitoring operation program was developed to provide a user-friendly interface that allowed users to effectively store and manage the sizeable amounts of data being transferred from the multiple monitoring stations.To test the potential of the landslide monitoring system for detecting and forecasting landslides, a 2 km × 2 km landslide-prone area around the Jeseokbong monitoring station in Jirisan National Park was set as the analysis domain area. Then, the analyses for landslide hazard evaluations based on infinite slope stability analysis were conducted by analyzing monitored data gathered over a five-year period from 2015 to 2019. The data missing from the Jeseokbong station were supplemented by data monitored at the nearby Jungsalli station. The time-series variations in the suction stress of slope soil layers could be calculated using the monitored matric suction data and unsaturated soil laboratory test data. The calculated suction stress data were subsequently used to calculate the factor of safety within the monitoring period. With this as a basis, the slope factor of safety according to real-time rainfall was calculated, which highlighted the temporal capability of the monitoring system for detecting landslide hazards. As such landslide detecting (or forecasting) methods based on real-time measurements do not use prediction data, it will be crucial to set multiple conservative thresholds to ensure adequate lead time.By assuming that the analysis domain area has spatially uniform soil properties and unsaturated characteristics, the spatial classification analysis of landslide hazards was conducted using the long-term factor of safety calculation results. Upon comparing the historical landslide areas that occurred in the analysis domain area with the spatial classification results, it was found that almost all of the historical landslide areas were located in areas with high hazard levels. As such, the reliability of the proposed landslide hazard classification method was validated.The present study covers the establishment of a landslide monitoring system and shows the beginning stage of its applications. We are sustaining our monitoring system to keep collecting the measurement data as well as future landslide events. Based on such cumulated dataset, we expect that even more valuable findings could be published in the future to contribute to landslide community.Although KIGAM-LAMOS was verified in its effectiveness in landslide hazard evaluations, a monitoring-based shallow landslide management method cannot stand alone. This is mainly because its effectiveness is limited to the local area of sensing. Therefore, further studies should be directed towards the integration of the developed monitoring system with analytical methods that can cover regional-scale areas.