Hoang Le - Academia.edu (original) (raw)

Papers by Hoang Le

Economic Annals-ХХI, 2019

Over the past decade, Africa and other developing regions have been in the midst of tremendous ch... more Over the past decade, Africa and other developing regions have been in the midst of tremendous changes. Market liberalisation and governmental decentralisation policies have interfaced with globalisation and urbanisation trends to dramatically transform social, political, economic and cultural lives. Agriculture can no longer remain behindserving only to meet subsistence food needs. Agriculture has to become a dynamic and integral part of the market economy. If African agriculture is bypassed by the economic transformation going on world wide, then large numbers of Africans and perhaps all of Africa will remain poor and food insecure. The fundamental purpose behind the FAO initiative to strengthening farmagribusiness linkages is to help transform the agricultural sector in order to accelerate productivity growth, increase income and employment generation, improve food security, and increase competitiveness in regional and international trade. In 2001 and 2002 five country case studies on farm-agribusiness linkages were undertaken in Ghana, Nigeria, Kenya, Uganda and South Africa. The main purpose of the studies was to get an insight into current farm-agribusiness linking arrangements. This included identifying and analysing successful linkages highlighting different methods and practices as well as exploring key factors that have led to successful partnerships. The country studies also contained a brief agribusiness sector overview. The work in Africa began with preparation of five case studies which are presented as summary results as well as individually. FAO work on farm-agribusiness linkages emerged from a broader cross-regional study on farm-agribusiness linkages launched in 2000. The first stage was a series of country studies and a regional consultation in Asia. During 2001 and 2002, case studies and a regional workshop on agribusiness linkages were carried out in Latin America. This was followed by a workshop on strategies for improving negotiation and compliance capabilities, held in November 2002 in Peru. An expert consultation on strengthening farm-agribusiness linkages in Africa was held in March 2003 in Nairobi, Kenya.

Computer Vision – ECCV 2018, 2018

Journal of Computational and Graphical Statistics, 2020

Many problems in statistics and machine learning can be formulated as an optimization problem of ... more Many problems in statistics and machine learning can be formulated as an optimization problem of a finite sum of non-smooth convex functions. We propose an algorithm to minimize this type of objective functions based on the idea of alternating linearization. Our algorithm retains the simplicity of contemporary methods without any restrictive assumptions on the smoothness of the loss function. We apply our proposed method to solve two challenging problems: overlapping group Lasso and convex regression with sharp partitions (CRISP). Numerical experiments show that our method is superior to the state-of-the-art algorithms, many of which are based on the accelerated proximal gradient method.

Journal of Materials Processing Technology, 2020

High aspect ratio micro holes are very important functional features in many products, in particu... more High aspect ratio micro holes are very important functional features in many products, in particular in electronics industry. Especially, the critical requirements that such holes in electronic devices should satisfy, concern their morphology and quality that can impact directly the products' functional performance. At the same time, ultra-short lasers have shown that they have the capabilities to match such tight requirements due to their unique processing characteristics. The typical beam spatial profile of the laser sources used for drilling is Gaussian and this entails some constraints and limitations. In this study, a beam shaping system for laser micro drilling has been designed and implemented to achieve a top-hat spatial profile. The morphology of the high aspect ratio holes in terms of cylindricity, circularity, tapering angle, heat affected zone (HAZ) and penetration depth was investigated by a high resolution X-Ray Computed Tomography (XCT). The capabilities and limitations of such beam shaping solutions for producing micro-scale high aspect ratio holes has been discussed, i.e. their sensitivity to defocusing, and compared to Gaussian beam spatial distribution. Conclusions were made regarding the effects of top-had beams on morphology of high aspect ratio holes and trade-offs when deploying them for laser micro drilling.

Molecular neurobiology, Nov 5, 2016

Over the last few decades, molecular neurobiology has uncovered many genes whose deficiency in mi... more Over the last few decades, molecular neurobiology has uncovered many genes whose deficiency in mice results in behavioral traits associated with human neuropsychiatric disorders such as autism, obsessive-compulsive disorder (OCD), and schizophrenia. However, the etiology of these common diseases remains enigmatic with the potential involvement of a battery of genes. Here, we report abnormal behavioral phenotypes of mice deficient in a cell adhesion molecule Ninjurin 1 (Ninj1), which are relevant to repetitive and anxiety behaviors of neuropsychiatric disorders. Ninj1 knockout (KO) mice exhibit compulsive grooming-induced hair loss and self-made lesions as well as increased anxiety-like behaviors. Histological analysis reveals that Ninj1 is predominantly expressed in cortico-thalamic circuits, and neuron-specific Ninj1 conditional KO mice manifest aberrant phenotypes similar to the global Ninj1 KO mice. Notably, the brains of Ninj1 KO mice display altered synaptic transmission in tha...

Objective : Expandable cage used for spinal reconstruction after corpectomy has several advantage... more Objective : Expandable cage used for spinal reconstruction after corpectomy has several advantages over nonexpendable cages. Here we present our clinical experience with the use of this cage after anterior column corpectomy with an average of one year follow up. Methods : Ten patients underwent expandable cage reconstruction of the anterior column after single-level or multilevel corpectomy for various cervical spinal disorders. Anterior plating with or without additional posterior instrumentation were performed in all patients. Functional outcomes, complications, and radiographic outcomes were determined. Results : There was no cage-related complication. Functionally, neurological examination revealed improvement in 7 of 10 patients and no patient had neurological deterioration after the surgery. Immediate stability was achieved and maintained throughout the period of follow-up. There was minimal subsidence (2mm) noticeable in three of the cases that underwent a two-level corpectom...

Five ecdysteroids, makisterone A (1), 24-epi-makisterone A (2), 24-methylene-shidasterone (3), po... more Five ecdysteroids, makisterone A (1), 24-epi-makisterone A (2), 24-methylene-shidasterone (3), polypodine B (4), and 20-hydroxy-ecdysone (5), were isolated from the methanol extract of Achyranthes bidentata by various chromatographic methods. Their structures were elucidated by spectroscopic methods including nuclear magnetic resonance (NMR) and electrospray ionization mass spectrometry (ESI-MS), and comparison of their spectral data with reported values. Compounds 1-4 were isolated from A. bidentata for the first time.

2010 Proceedings IEEE INFOCOM, 2010

Dictionary-Based String Matching (DBSM) is used in network Deep Packet Inspection (DPI) applicati... more Dictionary-Based String Matching (DBSM) is used in network Deep Packet Inspection (DPI) applications virus scanning [1] and network intrusion detection [2]. We propose the Pipelined Affix Search with Tail Acceleration (PASTA) architecture for solving DBSM with guaranteed worst-case performance. Our PASTA architecture is composed of a Pipelined Affix Search Relay (PASR) followed by a Tail Acceleration Finite Automaton (TAFA). PASR consists of one or more pipelined Binary Search Tree (pBST) modules arranged in a linear array. TAFA is constructed with the Aho-Corasick goto and failure functions [3] in a compact multi-path and multi-stride tree structure. Both PASR and TAFA achieve good memory efficiency of 1.2 and 2 B/ch (bytes per character) respectively and are pipelined to achieve a high clock rate of 200 MHz on FPGAs. Because PASTA does not depend on the effectiveness of any hash function or the property of the input stream, its performance is guaranteed in the worst case. Our prototype implementation of PASTA on an FPGA with 10 Mb on-chip block RAM achieves 3.2 Gbps matching throughput against a dictionary of over 700K characters. This level of performance surpasses the requirements of next-generation security gateways for deep packet inspection.

The Spine Journal, 2004

CONCLUSIONS: This study demonstrates that even mildly positive sagittal balance is detrimental, b... more CONCLUSIONS: This study demonstrates that even mildly positive sagittal balance is detrimental, but that the severity of symptoms increases in a linear fashion with progressive sagittal imbalance. The results also show that kyphosis is favorable in the upper thoracic region but poorly tolerated in the lumbar spine. These findings emphasize the importance of thoroughly assessing sagittal balance in the treatment of adults with spinal deformity.

2011 21st International Conference on Field Programmable Logic and Applications, 2011

Most current SRAM-based high-speed Internet Protocol (IP) packet classification implementations u... more Most current SRAM-based high-speed Internet Protocol (IP) packet classification implementations use tree traversal and pipelining. However, these approaches result in inefficient memory utilization. Due to the limited amount of on-chip memory of the state-of-the-art Field Programmable Gate Arrays (FPGAs), existing designs cannot support large filter databases arising in backbone routers and intrusion detection systems. Hierarchical search structures for packet classification exhibit good memory performance and support quick rule update. However, pipelined hardware implementation of these algorithms suffer from inefficient resource and memory usage due to variation in the size of the trie nodes and backtracking. We propose a memory efficient organization denoted Clustered Hierarchical Search Structure (CHSS) for packet classification. We present a clustering algorithm that partitions a given filter database to reduce the memory requirement. We show that, using the resulting structure, backtracking is not needed to perform a search. We introduce two parameters (NRtrie, NRtree), which can be chosen based on the given filter database to achieve good memory efficiency. Our algorithm demonstrates substantial reduction in the memory footprint compared with the state-ofthe-art. For all publicly available filter databases, the achieved memory efficiency is between 21.54 and 41.25 bytes per rule. We map the proposed data structure onto a linear pipeline architecture to achieve high throughput. Post place and route result using a state-of-the-art FPGA device shows that the design can sustain a throughput of 408 million packets per second, or 130.5 Gbps (for the minimum packet size of 40 Bytes).

2012 International Conference on Reconfigurable Computing and FPGAs, 2012

ABSTRACT Memory efficiency with compact data structures for Internet Protocol (IP) lookup has rec... more ABSTRACT Memory efficiency with compact data structures for Internet Protocol (IP) lookup has recently regained much interest in the research community. In this paper, we revisit the classic trie-based approach for solving the longest prefix matching (LPM) problem used in IP lookup. Among all existing implementation platforms, Field Programmable Gate Array (FPGA) is a prevailing platform to implement SRAM-based pipelined architectures for high-speed IP lookup because of its abundant parallelism and other desirable features. However, due to the available on-chip memory and the number of I/O pins of FPGAs, state-of-the-art designs cannot support large routing tables consisting of over 350K prefixes in backbone routers. We propose a search algorithm and data structure denoted Compact Trie (CT) for IP lookup. Our algorithm demonstrates a substantial reduction in the memory footprint compared with the state-of-the-art solutions. A parallel architecture on FPGAs, named Compact Trie Forest (CTF), is introduced to support the data structure. Along with pipelining techniques, our optimized architecture also employs multiple memory banks in each stage to further reduce memory and resource redundancy. Implementation on a state-of-the-art FPGA device shows that the proposed architecture can support large routing tables consisting up to 703K IPv4 or 418K IPv6 prefixes. The post place-and-route result shows that our architecture can sustain a throughput of 420 million lookups per second (MLPS), or 135 Gbps for the minimum packet size of 40 Bytes. The result surpasses the worst-case 150 MLPS required by the standardized 100GbE line cards.

2012 Proceedings IEEE INFOCOM, 2012

ABSTRACT Hierarchical search structures for packet classification offer good memory performance a... more ABSTRACT Hierarchical search structures for packet classification offer good memory performance and support quick rule updates when implemented on multi-core network processors. However, pipelined hardware implementation of these algorithms has two disadvantages: (1) backtracking which requires stalling the pipeline and (2) inefficient memory usage due to variation in the size of the trie nodes. We propose a clustering algorithm that can partition a given rule database into a fixed number of clusters to eliminate back-tracking in the state-of-the-art hierarchical search structures. Furthermore, we develop a novel ternary trie data structure (T∈). In T∈ structure, the size of the trie nodes is fixed by utilizing ∈-branch property, which overcomes the memory inefficiency problems in the pipelined hardware implementation of hierarchical search structures. We design a two-stage hierarchical search structure consisting of binary search trees in Stage 1, and T∈ structures in Stage 2. Our approach demonstrates a substantial reduction in the memory footprint compared with that of the state-of-the-art. For all publicly available databases, the achieved memory efficiency is between 10.37 and 22.81 bytes of memory per rule. State-of-the-art designs can only achieve the memory efficiency of over 23 byte/rule in the best case. We also propose a SRAM-based linear pipelined architecture for packet classification that achieves high throughput. Using a state-of-the-art FPGA, the proposed design can sustain a 418 million packets per second throughput or 134 Gbps (for the minimum packet size of 40 Bytes). Additionally, our design maintains packet input order and supports in-place non-blocking rule updates.

Lecture Notes in Computer Science, 2006

A novel portable hardware architecture for the Elliptic Curve Method of factoring, designed and o... more A novel portable hardware architecture for the Elliptic Curve Method of factoring, designed and optimized for application in the relation collection step of the Number Field Sieve, is described and analyzed. A comparison with an earlier proof-of-concept design by Pelzl,Šimka, et al. has been performed, and a substantial improvement has been demonstrated in terms of both the execution time and the area-time product. The ECM architecture has been ported across three different families of FPGA devices in order to select the family with the best performance to cost ratio. A timing comparison with a highly optimized software implementation, GMP-ECM, has been performed. Our results indicate that low-cost families of FPGAs, such as Xilinx Spartan 3, offer at least an order of magnitude improvement over the same generation of microprocessors in terms of the performance to cost ratio.

Most high-speed Internet Protocol (IP) lookup implementations use tree traversal and pipelining. ... more Most high-speed Internet Protocol (IP) lookup implementations use tree traversal and pipelining. However, this approach results in inefficient memory utilization. Due to available on-chip memory and pin limitations of FPGAs, stateof-the-art designs on FPGAs cannot support large routing tables arising in backbone routers. Therefore, ternary content addressable memory (TCAM) is widely used. We propose a novel SRAM-based linear pipeline architecture, named DuPI. Using a single Virtex-4, DuPI can support a routing table of up to 228K prefixes, which is 3× the state-of-the-art. Our architecture can also be easily partitioned, so as to use external SRAM to handle even larger routing tables (up to 2 M prefixes), while maintaining a 324 MLPS throughput. The use of SRAM (instead of TCAM) leads to orders of magnitude of reduction in power dissipation. Employing caching to exploit Internet traffic locality, we can achieve a throughput of 1.3 GLPS (billion lookups per second). Our design also maintains packet input order, and supports in-place nonblocking route updates.

$Research paper thumbnail of Cauda equina syndrome in patients with low lumbar fractures$

Neurosurgical focus, Jan 15, 2004

Symptoms of cauda equina syndrome (CES) can include low-back pain, sciatica, lower-extremity weak... more Symptoms of cauda equina syndrome (CES) can include low-back pain, sciatica, lower-extremity weakness, sensory deficit, perineal hypesthesia or anesthesia, and loss of bowel or bladder function. Several causes of the syndrome are recognized, but its optimal treatment remains controversial and has been broadly based on data gathered from series involving herniated discs. Information on the treatment of CES caused by low lumbar traumatic injuries has not been well documented. Between January 2000 and December 2003, 17 consecutive cases of CES caused by low lumbar traumatic injuries at L2-5 were identified. The traumatic injuries consisted of gun shot wound in two cases, motor vehicle accident in 11, and a fall from height in four. Conus medullaris injuries causing CES were excluded from this review. Presenting symptoms, mechanisms of injury, radiographic images, timing of surgery, surgical approaches, and neurological status at the final follow up were documented. All patients underwe...

The Journal of biological chemistry, Jan 8, 2014

Ninjurin1 is involved in the pathogenesis of experimental autoimmune encephalomyelitis, an animal... more Ninjurin1 is involved in the pathogenesis of experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis, by mediating leukocyte extravasation, a process that depends on homotypic binding. However, the precise regulatory mechanisms of Ninjurin1 during inflammation are largely undefined. We therefore examined the pro-migratory function of Ninjurin1 and its regulatory mechanisms in macrophages. Interestingly, Ninjurin1-deficient bone marrow-derived macrophages exhibited reduced membrane protrusion formation and dynamics, resulting in the impairment of cell motility. Furthermore, exogenous Ninjurin1 was distributed at the membrane of filopodial structures in Raw264.7 macrophage cells. In Raw264.7 cells, RNA interference of Ninjurin1 reduced the number of filopodial projections, whereas overexpression of Ninjurin1 facilitated their formation and thus promoted cell motility. Ninjurin1-induced filopodial protrusion formation required the activation of Rac1. In Raw264....

2011 IEEE International Symposium on Multimedia, 2011

The rule of thirds is one of the most important composition rules used by photographers to create... more The rule of thirds is one of the most important composition rules used by photographers to create high-quality photos. The rule of thirds states that placing important objects along the imagery thirds lines or around their intersections often produces highly aesthetic photos. In this paper, we present a method to automatically determine whether a photo respects the rule of thirds. Detecting the rule of thirds from a photo requires semantic content understanding to locate important objects, which is beyond the state of the art. This paper makes use of the recent saliency and generic objectness analysis as an alternative and accordingly designs a range of features. Our experiment with a variety of saliency and generic objectness methods shows that an encouraging performance can be achieved in detecting the rule of thirds from photos.