Small Buffer Research Articles

Polling-Based Memory Interface

Non-volatile memory has been extensively researched as the alternative for a DRAM-based system; however, the traditional memory controller cannot efficiently track and schedule operations for all the memory devices in heterogeneous systems due to different timing requirements and complex architecture supports of various memory technologies. To address this issue, we propose a hybrid memory architecture framework called POMI (POlling-based Memory Interface). It uses a small buffer chip inserted on each DIMM (Dual In-line Memory Module) to decouple operation scheduling from the controller to enable the support for diverse memory technologies in the system. Unlike the conventional DRAM-based system, POMI uses a polling-based memory bus protocol for communication and to resolve any bus conflicts between memory modules. The buffer chip on each DIMM will provide feedback information to the main memory controller so that the polling overhead is trivial. We propose two unique designs. The first one adds additional bus lines for sending the feedback information, and the second one utilizes the Command/Address bus. The framework provides several benefits: a technology-independent memory system, higher parallelism, and better scalability. Our experimental results show that POMI can efficiently support both homogeneous and heterogeneous systems. Compared with the conventional DDR4-2400 implementation, our scheme improves the performance of memory-intensive workloads by 3.7% on average. Compared with an existing interface for hybrid memory systems, Twin-Load, it also improves performance by 22.0% on average for memory-intensive workloads.

Preparation and property studies of enteric-soluble oral nattokinase microcapsules with halloysite nanotubes

Eudragit L100-55-halloysite nanotubes (EL100-55, HNTs) nanocomposite microcapsules were introduced to release nattokinase (NK) and avoid the limitations of oral and systemic administration of NK while increasing the entrapment efficiency and stability of NK. The drug loading capacity, stability, and shapes of the NK microcapsules (NK@HNTs-EL) were characterized with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The maximum loading rate of NK was 82.63%, and the encapsulation efficiency of NK was 31.6%. The formulation conditions did not adversely affect the NK tertiary structure. The maximum in vitro drug release in the simulated small intestine buffer was 93.3%, and the NK@HNTs-EL exhibited pH-dependent drug release. The drug release data were analyzed with different kinetic models, which showed that the NK@HNTs-EL drug-release mechanism involved erosion and osmotic pressure on the EL100-55. After 90 days of storage, the NK@HNTs-EL maintained an enzymatic activity greater than 95%. Hemolysis analyses indicated that NK@HNTs-EL was not cytotoxic at concentrations below 500 FU/mL. These findings indicate that NK@HNTs-EL is a promising oral thrombolytic agent.

Sustainable and Highly Reactive Nerve-Agent Simulant Detoxification: Effective Amine Buffers for Metal–Organic Framework Catalysts

The appropriate treatment of chemical warfare agents (CWAs) is essential because of their toxicity and lethality. Metal–organic framework (MOF) catalysts, with the assistance of a volatile small molecule buffer, have been reported to be effective for the destruction of CWAs. However, employing small molecular volatile buffers not only contaminates the catalysts and causes them to lose their activity but also prevents their practical application. In this study, we report a novel polymeric buffer that can enhance the catalytic ability of MOFs without contamination of the catalyst. The macromolecular chain can provide non-flowability to buffer, as well as inhibit catalyst contamination by steric hindrance while maintaining activity as a buffer. The optimized polymer buffer [P(MEMA)43] can effectively degrade nerve-agent simulants (7.7 min of t1/2) in the presence of UiO-66 and preserve its catalytic activity by more than 90% even after three cycles. In addition, the polymeric composite with MOFs coated on a cotton substrate shows excellent detoxification performance in humidified conditions (RH 99%). This fundamental study on a sustainable CWA destruction catalytic system is anticipated to be promising for developing chemical protective textiles against CWAs.

2D vanadium oxide inverse opal films: cycling stability exploration as an electrochromic active electrode

2D V2O5 IO films with various pore sizes and phases are fabricated, in which small pores buffer stress-induced pulverization but fasten chemical dissolution, while introducing a small amount of V6O13+y into V2O5 improves electrochromic and electrochemical cycling stability.

Scheduling model for simultaneous update of multiple service function chains with state consistency

Network function virtualization (NFV) enables network providers to provide functions of network services as virtual machines. Software-defined network (SDN) enables the network providers to control a network quickly and flexibly in a centralized manner. Service chaining is realized by utilizing NFV and SDN. Service chaining concatenates virtual network functions (VNFs) in the network to automatically process packets in an appropriate order. Routes of service function chains (SFCs) need to be updated to achieve users’ requirements, such as keeping the VNFs up-to-date, suppressing packet losses and processing delays, and continuing to provide services in case of VNF failure. States of VNF instances that make up the SFC need to be kept consistent when updating the SFC routes; otherwise, the accuracy of the processing in the VNF instance after the update can be reduced. Multiple SFCs need to be updated at the same time in some situations, such as security updates of VNFs. Existing models update SFCs one by one. If these models are adopted to the update of multiple SFCs, the total time required to update all SFCs can be long; problems such as leaving VNFs out-of-date can occur. This paper proposes a model that determines the update schedule of multiple SFCs guaranteeing state consistency. SFCs to be updated and where to update them are given in this model. The proposed model is formulated as an integer linear programming (ILP) problem. The objective function is minimizing the total time required to update all SFCs. The decision problem of the proposed model is proved to be NP-complete. We develop a heuristic algorithm since the optimal solution may not be obtained in a practical time when the number of requests increases. Numerical results show that the total time required to update all SFCs can be shortened by updating multiple SFCs at the same time. The numerical results also show that the total time can be shortened by dividing a large buffer into an adequate number of small buffers. The heuristic algorithm can reduce the computation time compared to the ILP approach with suppressing the total update time.

The Influence of Small Biomolecules, Salts and Buffers on the Molecular Recognition of Amide Naphthotube in Aqueous Solutions.

We found the binding affinities of amide naphthotube to neutral organic molecules in water are not influenced by most of small biomolecules, inorganic salts, and PBS and Tris buffers but are reduced in HEPES buffer through competitive binding. Nevertheless, salts do change the binding affinities of amide naphthotube to charged molecules through a screening effect.

Forested riparian buffer environmental variables are more important than size for species functional diversity in production forests

Retention of forested buffers around streams following forest cutting operations is a common management technique used to protect aquatic resources and conserve the surrounding ecosystem services. Species richness, or α-diversity, is commonly used as an indicator of the effects of forestry management although it provides very little information about those effects on ecosystem processes and function. Functional diversity links species traits and ecosystem function incorporating species diversity, community composition, and functional guild and is more suitable to investigate the direct and indirect effects of forestry on ecosystem function. We sampled spiders and vascular plants in buffered and unbuffered stream-forest systems in southern Sweden and used a trait-based approach to assess the effects of buffer size and environmental variables on functional diversity. We used structural equation modeling (SEM) to explore the effects of buffer size and condition on spider and vascular plant diversity. We found no effect of buffer size on the functional richness or functional redundancy for spiders or vascular plants. Buffer size had a slight effect on the α-diversity of spiders within small buffers and fully forested sites but the effect was small. Other buffer variables including canopy closure, buffer density, bare ground coverage, and soil fertility had direct effects on spider and vascular plant functional diversity. The main driver of functional richness was α-diversity, but our SEM analysis illustrated other environmental variables working jointly to drive functional diversity. Using a trait-based approach, we showed that forested buffers have a minimal overall impact on spider and vascular plant functional diversity. However, it is important to maintain high levels of α-diversity to preserve and promote both spider and plant functional richness in production forests and we suggest that forest management conserves and encourages high levels of α-diversity to increase overall functional diversity.

Buffered Streaming Graph Partitioning

Partitioning graphs into blocks of roughly equal size is a widely used tool when processing large graphs. Currently, there is a gap observed in the space of available partitioning algorithms. On the one hand, there are streaming algorithms that have been adopted to partition massive graph data on small machines. In the streaming model, vertices arrive one at a time including their neighborhood, and then have to be assigned directly to a block. These algorithms can partition huge graphs quickly with little memory, but they produce partitions with low solution quality. On the other hand, there are offline (shared-memory) multilevel algorithms that produce partitions with high-quality but also need a machine with enough memory to partition huge networks. In this work, we make a first step to close this gap by presenting an algorithm that computes significantly improved partitions of huge graphs using a single machine with little memory in a streaming setting. First, we adopt the buffered streaming model which is a more reasonable approach in practice. In this model, a processing element can store a buffer of nodes alongside with their edges before making assignment decisions. When our algorithm receives a batch of nodes, we build a model graph that represents the nodes of the batch and the already present partition structure. This model enables us to apply multilevel algorithms and in turn, on cheap machines, compute much higher quality solutions of huge graphs than previously possible. To partition the model graph, we develop a multilevel algorithm that optimizes an objective function that has previously been shown to be effective for the streaming setting. Surprisingly, this also removes the dependency on the number of blocks k from the running time compared to the previous state-of-the-art. Overall, our algorithm computes, on average, 75.9% better solutions than Fennel [ 35 ] using a very small buffer size. In addition, for large values of k our algorithm becomes faster than Fennel .

A Low-Delay Hybrid Half/Full-Duplex Link Selection Scheme for Cooperative Relaying Networks

In this paper, we propose a hybrid half-duplex (HD)/full-duplex (FD) link selection scheme for cooperative buffer-aided (BA) relaying networks with small buffers. FD BA relaying offers high spectral efficiency but it does not change the buffer states, while HD relaying offers the ability to change the buffer states, which can be exploited to minimize the outage probability and the average delay by controlling the queue length of the relays. Unlike the existing hybrid BA relaying schemes and opportunistic relying schemes, the proposed scheme considers the average buffering delay and uses probabilistic relay selection (RS) instead of using a fixed RS policy. It probabilistically prioritizes the selection of one of the FD and HD modes over the other. Markov chain (MC) theory is used to model the considered system and derive the throughput, average delay and outage probability as functions of the prioritizing probabilities. Based on the buffer and average channel states, the prioritizing probabilities are determined such that the overall average delay is minimized using the accelerated proximal gradient method. As compared to the existing HD, opportunistic, and hybrid BA relaying schemes, simulation results show that the proposed scheme offers higher throughput and lower average delay.

A kilometer or a mile? Does buffer size matter when it comes to car ownership?

When modeling car ownership, the scale at which built environment (BE) and accessibility indicators are measured are often overlooked. Most existing research use “fixed neighborhood” (zonal) or “sliding neighborhoods” (buffers around households) of the same distance (e.g., 1-km or 1 mile) to estimate the impact of various neighborhood features. However, it is likely that 1) different features have different ranges of influence on behavior and 2) that the impact of some variables are highly scale sensitive. Our study builds a series of Gradient Boosting Machines decision trees and uses partial dependence plots to examine potential threshold effects of various built environment characteristics and accessibility to resources when measured at different scales. Household-specific walking-distance buffers ranging from 400 to 1600 m are tested. Results indicate that BE measures of population density, land-use diversity, and design have consistent impacts across the tested buffer-sizes and show mostly linear relationships with the probability of households being fully motorized below or above a threshold value. Accessibility to transit, bikesharing, carsharing, and local amenities, however, appear to be very sensitive to the size of the neighborhood considered. Their relative influence within the models and the shape of their partial dependence function can change drastically as buffer sizes vary. Furthermore, smaller buffers (≤ 800 m) for accessibility measures exhibit clear threshold effects on car ownership, suggesting that shorter distances have more influence on car ownership. Further research is needed to validate the observed access distances and how many of each opportunity types are necessary for a significant impact on household car ownership decisions.

Spectroscopy and laser gain measurements of CaF2: Nd, X3+, Z3+ (X, Z = Gd, La, Ce, Y, Lu, Sc) crystals for broadband lasers applications

An efficient approach to avoid Nd3+ clustering in CaF2:Nd3+ is the co-doping with non-optically active buffer (Bu) ions creating Nd-Bu emitting clusters for laser applications around 1050 nm (4F3/2 → 4I11/2) taking advantage of their unique large absorption and emission bands. A detailed spectroscopic investigation of buffer codoping with Gd3+, La3+, Ce3+, Y3+, Lu3+ and Sc3+ ions is presented. The codoping with large buffer ions compared to Nd3+ like Gd3+, La3+, Ce3+ leads to one type of dominant Nd-Bu cluster, while the codoping with smaller ions like Y3+, Lu3+ and Sc3+ involves the formation of two types of Nd-Bu clusters, which can be discriminated in absorption/excitation/luminescence spectra and which further exhibit two different lifetimes. The laser gain performance of these codoped crystals with one or two buffer ions is investigated using a dedicated double modulation pump-probe setup allowing the tuning of both pump and probe wavelengths. As an example, a laser gain of 35% is measured in a 5 mm long CaF2: 0.5%Nd, 5%Lu crystal at 1054 nm for 400 mW of absorbed pump power at 797 nm. This direct measurement of the laser gain is particularly interesting for crystals codoped with small buffer ions where the presence of two Nd emitting centers complicates the calculation of the laser gain. For large buffer ions, a direct calculation of the laser gain is shown to be in good agreement with the experimental gain values.

Adaptive Coexistence of Delay-Sensitive and Delay-Tolerant MTC Devices: A Control-Theoretic Approach

We consider future cellular networks and study the coexistence of delay-sensitive (DS) and delay-tolerant (DT) devices in machine-type communication (MTC). DS devices require to minimize access delay for their low delay requirements; in contrast, DT devices have flexible delay constraints. For reducing access delay, we extend fast retrial idea in the data transmissions when a group of preambles is divided into two subsets to support the time-varying nature of the traffic from DS devices. We focus on the stability dynamics by design—we derive convergence conditions by using a control-theoretic approach in terms of variation in the 1) arrival rates; 2) buffer sizing at the devices; 3) number of preambles; and 4) number of DS devices. More importantly, we discover a novel adaptive algorithm that dynamically allocates the number of preambles for DS, thus guaranteeing stability by design. We validate our findings with extensive simulations. Besides, we develop a novel framework that describes how the control theory idea can be applied to address the issue of tracking the buffers and handling coexistence in such a diverse network environment under realistic application constraints. Our extension to the control-theoretic idea predicts whether the overall system is stable, i.e., whether data flows are desynchronized. Given the data flows are desynchronized, small buffers are always sufficient. Our approach shows that a smaller DS buffer often promotes desynchronization—a virtuous cycle.

Higher proportion of agricultural land use around the residence is associated with higher urinary concentrations of AMPA, a glyphosate metabolite.

Pesticides, including herbicides, are widely used for agricultural and sanitary reasons and concerns have been raised about their various health effects. Little research has been done into the extent to which agricultural land use in the residential surroundings contributes to (internal) exposure of pesticides. We investigated the associations between the proportion of agricultural land use around the residence and the exposure to pesticides in adolescents in Flanders (Belgium). We included 424 adolescents participating in the fourth Flemish Environment and Health Study (FLEHS IV) between 2016 and 2020. The residential address of all participants was geocoded and the proportion of agricultural land use around the residence was estimated in several buffers (300m, 500m, 1000m and 2000 m). The concentrations of the following biomarkers of pesticides were measured in urine and adjusted for the specific gravity: glyphosate and its metabolite, aminomethyl-phosphonic acid (AMPA); 3-phenoxybenzoic acid (3-PBA); 3,5,6-trichloro-2-pyridinol (TCPy) and 2,4-dichlophenoxy-acetic acid (2,4-D). We categorized the pesticide biomarkers in three categories according to the exposure levels and used ordinal logistic regression models adjusted for sex, season and household education to estimate the odds ratio for an increase in an interquartile range (IQR) of proportion of agricultural land use. We also used binary logistic regression models in which the category of highest exposure was compared to the category of lowest exposure. In addition, we explored potential effect modification by sex and season. We found a significant association between the proportion of agricultural land use in a buffer of 2000 m around the residence and the levels of urinary AMPA divided into three categories (OR=1.35 for an IQR increase in the proportion of agricultural land use around residence; 95% CI: 1.00-1.83). This association was less pronounced and not statistically significant for the other studied pesticides (OR ranging between 0.95 and 1.16). Stratified analysis showed the strongest association of the proportion of agricultural land use within 2000 m buffers for AMPA among boys (OR=1.89; 95% CI: 1.19-3.04). Results using smaller buffers were comparable, but did not reach statistical significance. Our findings suggest that a higher proportion of agricultural land use around the residence might increase exposure to AMPA.

Determination of Flood Susceptibility Index Using Overlay-Scoring Data Method based on Geographic Information System (GIS) in Semarang City, Central Java, Indonesia

Semarang City is the capital of the Central Java Province, located in the lowlands and directly adjacent to the north side of the Java Sea. This geographical condition makes this city very vulnerable to being affected by floods. This study aims to determine the distribution of flood-prone locations and classify the level of flood susceptibility that occurs in the Semarang City. Quantitative descriptive is the type of research with an overlay method based on scoring parameters related to environmental conditions. These parameters include slope, soil type, rainfall, altitude, land use and river flow buffers. The scored parameters are then entered into the overlay stage with other parameters in the geographic information system (GIS) application to form a map of the flood susceptibility level. The data analysis technique used the descriptive method. The level of flood susceptibility map resulting from this study is in one area of the Pemali-Juana Sub-watershed. The results also show that the scattered highly vulnerable areas in the northern part of Semarang City are areas with low elevations and flat slopes, then dominated by settlement land use that lacks infiltration areas, small river buffer sizes. These are what make the area classified as an area that is very prone to flooding.

A Classy Memory Management System (CyM2S) using an Isolated Dynamic Two-Level Memory Allocation (ID2LMA) Algorithm for the Real Time Embedded Systems

Due to an increased scalability, flexibility, and reduced cost complexity, the dynamic memory allocation models are highly preferred for the real-time embedded systems. For this purpose, the different types of dynamic models have been developed in the conventional works, which are highly focused on allocating the memory blocks with increased searching capability. However, it faced some of the problems and issues related to the factors of complex operations, high time consumption, memory overhead, and reduced speed of processing. Thus, this research work objects to design an advanced and intelligent dynamic memory allocation mechanism for the real-time embedded systems. Here, a Classy Memory Management System (CyM2S) is developed by using an Isolated Dynamic Two-Level Memory Allocation (ID2LMA) algorithm for efficiently allocating the memory blocks with simple searching. The CyM2S helps to reduce the fragmentation rate and time consumption by optimally allocating the memory blocks. In this model, the small buffer has been maintained for surplus pointers, and the allocated blocks comprise the metadata and payload data. During evaluation, the performance of the proposed CyM2S- ID2LMA technique is validated and compared by using the measures of memory allocation time, release time, execution, and processing speed.

Impact of Land Use Types at Different Scales on Surface Water Environment Quality and Its Driving Mechanism

As an important carrier of human activities, the spatial type of land use has an important impact on the surface water environment. Taking the Ruoergai wetland as an example, based on object-oriented remote sensing interpretation of land use types combined with water quality examination data, this study analyzed the impact and driving mechanism of land use types at different scales on the surface water environment at the small watershed and buffer scale. ① It was found that the water quality of the Ruoergai wetland could been classified as water grade V, and it was slightly eutrophic as a whole. The main pollutants were total nitrogen(TN) and phosphorus(TP), and the pollution originated from domestic sewage and grazing. ② The environmental quality of surface water was closely related to land use types. There was a negative correlation between chemical oxygen demand(COD) and the proportion of water area, a positive correlation between TN and the proportion of swamp area, and a negative correlation between total TP. ③ There was a significant correlation between spatial land use types at different scales and surface water environment. The land use type within a buffer of 1000 m had the highest interpretation degree for all factors, the land use type within a buffer of 200 m had the greatest interpretation degree for COD, the land use type within a buffer of 500 m zone had the greatest interpretation degree for TP and TN, and the land use type within a buffer of 800 m had the greatest explanation for Chl-a. The results of this study showed that the Ruoergai wetland wetland had a certain purification effect on pollutants and eutrophication. However, different land use types had different effects on different pollutants. The water body had a purification effect on Fe2+, COD, and Chl-a, and the swamp had a purification effect on TP but a cumulative effect on TN. Thus, the small-buffer zone(≤ 1000 m) land use type should be controlled, the water body and swamp areas should be controlled, the self-purification capacity of wetland waters should be improved, and the surface water environment of the Ruoergai wetland should be further protected and repaired.

Buffer State Based Relay Selection for Half-Duplex Buffer-Aided Serial Relaying Systems

This work investigates multi-hop serial relaying half-duplex (HD) networks comprising one source, one destination and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> decode-and-forward (DF) relays. Buffer-aided (BA) relays are considered where finite size buffers are added to relays. For this setup, we propose a novel BA relaying strategy that selects the node that must transmit over one epoch in a block fading environment. Selecting a node depends on the buffer state information of all relays and on the availability of the hops. Moreover, the proposed relaying scheme is controlled by an adjustable parameter that allows the system to achieve multiple levels of tradeoff between the average packet delay (APD) and the outage probability (OP). A Markov chain model is adopted to evaluate the system’s performance and simple closed-form expressions were derived for the APD and OP based on an asymptotic analysis. The performance analysis proves the ability of the suggested relaying scheme to achieve significant OP and APD gains with small buffer sizes. Two variants of the proposed relaying scheme are particularly appealing. The APD-prioritizing variant achieves the smallest APD of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2K$ </tex-math></inline-formula> without improving the diversity order. The second OP-prioritizing variant reaches the full diversity order of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K+1$ </tex-math></inline-formula> while increasing the asymptotic APD to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K(K+3)$ </tex-math></inline-formula> .

Children's Lived Experiences in Poverty in Hong Kong as a High-Income Asian Society.

Child poverty situated in different socioeconomic and environmental contexts has long been a central concern for practitioners, researchers, and policy makers. However, concerned research studies are predominantly adult-centric, confined to specific areas, or seldom found in Asian developed economies. Against the backdrop of this research gap, this study examines children’s experiences of poverty in relation to economic and material aspects, social relationships and participation, and psychological and emotional wellbeing, and their ways of coping with the effects of poverty. Using a purposive sampling method, a total of 40 children participants aged 8–14 living in or near poverty were recruited for an individual interview. The study showed that children experienced a range of deprivations in relation to falling short of the resources, opportunities, and activities that are commanded by average young persons. Limited living space also stands out as a more severe problem that is difficult to cope with. The various coping strategies include small spending savvy tactics, parental buffering, compensation, and mental coping. Proximity to schools and NGOs can help children in poverty to cope with problems caused by deprivations in different aspects. Implications for research studies and practice for working with children in or near poverty are discussed accordingly.

An experimental evaluation of LEDBAT++

LEDBAT++ is the evolution of LEDBAT, a congestion control algorithm originally designed to provide less-than-best-effort transport on the Internet. LEDBAT++ aims to address a number of shortcomings present in LEDBAT, including late-comer advantage, latency drift, competition on equal grounds with best effort traffic in the presence of small buffers and difficulties experienced while measuring the variations on the delay.In this paper, we perform an experimental evaluation of LEDBAT++ using the Windows Server’s LEDBAT++ implementation. We find that while LEDBAT++ overcomes all the limitations identified in LEDBAT, the change introduced in LEDBAT++ to do so results in a performance penalty that prevents LEDBAT++ flows to seize all the available capacity when there is no competing traffic. We propose two simple modifications to the LEDBAT++ algorithm that would address the identified issues and reduce the penalty.

Proportional–integral–derivative-based intra rate controller for low-delay applications of high efficiency video coding screen content coding

Most screen content (SC) video applications are real time, and a low-delay transmission is needed. An effective low-delay transmission requires a precise video rate controller to fit the video bit rate to the capacity of the transmission channel. The rate controller has to support the unique standard coding tools of SC video. We propose a unique intra rate controller based on a unique content-based rate-distortion model for low delay applications of high efficiency video coding SC coding. The proposed model supports the unique SC coding tools and different modes and sizes of coding tree units. The proportional–integral–derivative control concept is used for frame-level bit allocation and rate control. The rate controller utilizes a small size virtual buffer to provide low-delay buffering constraints for the bit stream. Experimental results show that the proposed rate controller can control the bit rate of test sequences with a low buffering delay (about 20 ms) while the rate-distortion performance is maintained.