2,034 research outputs found
Solving bilevel programs based on lower-level Mond-Weir duality
This paper focuses on developing effective algorithms for solving bilevel
program. The most popular approach is to replace the lower-level problem by its
Karush-Kuhn-Tucker conditions to generate a mathematical program with
complementarity constraints (MPCC). However, MPCC does not satisfy the
Mangasarian-Fromovitz constraint qualification (MFCQ) at any feasible point. In
this paper, inspired by a recent work using the lower-level Wolfe duality
(WDP), we apply the lower-level Mond-Weir duality to present a new
reformulation, called MDP, for bilevel program. It is shown that, under mild
assumptions, they are equivalent in globally or locally optimal sense. An
example is given to show that, different from MPCC, MDP may satisfy the MFCQ at
its feasible points. Relations among MDP, WDP, and MPCC are investigated.
Furthermore, in order to compare the new MDP approach with the MPCC and WDP
approaches, we design a procedure to generate 150 tested problems randomly and
comprehensive numerical experiments showed that MDP has evident advantages over
MPCC and WDP in terms of feasibility to the original bilevel programs, success
efficiency, and average CPU time.Comment: arXiv admin note: text overlap with arXiv:2302.0683
Stochastic mathematical programs with hybrid equilibrium constraints
AbstractThis paper considers a stochastic mathematical program with hybrid equilibrium constraints (SMPHEC), which includes either “here-and-now” or “wait-and-see” type complementarity constraints. An example is given to describe the necessity to study SMPHEC. In order to solve the problem, the sampling average approximation techniques are employed to approximate the expectations and smoothing and penalty techniques are used to deal with the complementarity constraints. Limiting behaviors of the proposed approach are discussed. Preliminary numerical experiments show that the proposed approach is applicable
Service selection strategic analysis for selfoperated e-commerce platforms under settlement
In order to study whether e-commerce platforms carry out service
cooperation after settlement in-depth, this paper focuses on service
selection strategic analysis for agent channels on some self-operated
e-commerce platforms settled in hybrid e-commerce platforms. We
present multi-leader-follower models in two different scenarios with
the platforms as leaders and the manufacturers as followers and give
some numerical experiments to analyze the impacts of service selection
strategies for self-operated platforms on all supply chain members.
Our finding shows that if the service cost efficiency is moderate
or low, the self-operated platform prefers to provide its service for
the agent; otherwise, its selection mainly depends on the unit product
service fee. In addition, fierce service competition and high unit
service fee are unfavorable to all members, while high service cost
efficiency may hurt both the platform and the manufacturer
A novel approach for bilevel programs based on Wolfe duality
This paper considers a bilevel program, which has many applications in
practice. To develop effective numerical algorithms, it is generally necessary
to transform the bilevel program into a single-level optimization problem. The
most popular approach is to replace the lower-level program by its KKT
conditions and then the bilevel program can be reformulated as a mathematical
program with equilibrium constraints (MPEC for short). However, since the MPEC
does not satisfy the Mangasarian-Fromovitz constraint qualification at any
feasible point, the well-developed nonlinear programming theory cannot be
applied to MPECs directly. In this paper, we apply the Wolfe duality to show
that, under very mild conditions, the bilevel program is equivalent to a new
single-level reformulation (WDP for short) in the globally and locally optimal
sense. We give an example to show that, unlike the MPEC reformulation, WDP may
satisfy the Mangasarian-Fromovitz constraint qualification at its feasible
points. We give some properties of the WDP reformulation and the relations
between the WDP and MPEC reformulations. We further propose a relaxation method
for solving WDP and investigate its limiting behavior. Comprehensive numerical
experiments indicate that, although solving WDP directly does not perform very
well in our tests, the relaxation method based on the WDP reformulation is
quite efficient
Dimethyl 3,5-diethyl-1H-pyrrole-2,4-dicarboxylate
The title pyrrole derivative, C12H17NO4, consists of a pyrrole ring with two diagonally attached methoxycarbonyl groups and two diagonally attached ethyl groups. The two carbonyl groups are approximately in the same plane as the pyrrole ring, making dihedral angles of 3.50 (19) and 6.70 (19)°. In the crystal, adjacent molecules are assembled into dimers in a head-to-head mode by pairs of intermolecular N—H⋯O hydrogen bonds
Bis(2-aminopyridine-κN 1)bis(benzoato-κO)cobalt(II)
In the title compound, [Co(C7H5O2)2(C5H6N2)2], the CoII atom is hexacoordinated by four O atoms from two benzoate anions, and two N atoms from two 2-aminopyridine molecules, resulting in a distorted octahedral geometry. Both benzoate anions act as bidentate ligands and both 2-aminopyridine molecules are coordinated to the metal through their pyridyl N atoms. The crystal packing is stabilized by intermolecular N—H⋯O hydrogen bonds, C—H⋯π, and π–π stacking interactions involving benzoate anions and 2-aminopyridine molecules
Novel insights into bacterial dimethylsulfoniopropionate catabolism in the East China Sea
The compatible solute Dimethylsulfoniopropionate (DMSP), made by many marine organisms, is one of Earth’s most abundant organosulfur molecules. Many marine bacteria import DMSP and can degrade it as a source of carbon and/or sulfur via DMSP cleavage or DMSP demethylation pathways, which can generate the climate active gases dimethyl sulfide (DMS) or methanthiol (MeSH), respectively. Here we used culture-dependent and -independent methods to study bacteria catabolising DMSP in East China Sea (ECS). Of bacterial isolates, 42.11% showed DMSP-dependent DMS (Ddd+) activity, and 12.28% produced detectable levels of MeSH. Interestingly, although most Ddd+ isolates were Alphaproteobacteria (mainly Roseobacters), many gram-positive Actinobacteria were also shown to cleave DMSP producing DMS. The mechanism by which these Actinobacteria cleave DMSP is unknown, since no known functional ddd genes have been identified in genome sequences of Ddd+ Microbacterium and Agrococcus isolates or in any other sequenced Actinobacteria genomes. Gene probes to the DMSP demethylation gene dmdA and the DMSP lyase gene dddP demonstrated that these DMSP-degrading genes are abundant and widely distributed in ECS seawaters. dmdA was present in relatively high proportions in both surface (19.53% ± 6.70%) and bottom seawater bacteria (16.00% ± 8.73%). In contrast, dddP abundance positively correlated with chlorophyll a, and gradually decreased with the distance from land, which implies that the bacterial DMSP lyase gene dddP might be from bacterial groups that closely associate with phytoplankton. Bacterial community analysis showed positive correlations between Rhodobacteraceae abundance and concentrations of DMS and DMSP, further confirming the link between this abundant bacterial class and the environmental DMSP cycling
Limonoids and triterpenoids from the twigs and leaves of Dysoxylum hainanense
Four new limonoids, dysohainanins A–D (1–4), and two new triterpenoids, dysohainanins E and F (5 and 6), together with seven known ones were isolated from the twigs and leaves of Dysoxylum hainanense Merr. The structures of the new compounds were determined by a variety of spectroscopic methods. The cytotoxic activities of these compounds were evaluated, and the known compound ent-19-nor-4,16,18-trihydroxy-8(14)-pomaren-15-one (13) showed in vitro cytotoxicity against HL-60, A-549, MCF-7, and SW480 cells, with IC(50) values of 24.3, 28.1, 30.7, and 22.5 µM, respectively. Compounds 2 and 3 were tested their insecticidal activities using brine shrimp and both of them were inactive. [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: Supplementary material is available for this article at 10.1007/s13659-011-0030-8 and is accessible for authorized users
Mutation of SLC35D3 causes metabolic syndrome by impairing dopamine signaling in striatal D1 neurons
We thank Dr. Ya-Qin Feng from Shanxi Medical University, Dr. Tian-Yun Gao from Nanjing University and Dr. Yan-Hong Xue from Institute of Biophysics (CAS) for technical assistance in this study. We are very thankful to Drs. Richard T. Swank and Xiao-Jiang Li for their critical reading of this manuscript and invaluable advice. Funding: This work was partially supported by grants from National Basic Research Program of China (2013CB530605; 2014CB942803), from National Natural Science Foundation of China 1230046; 31071252; 81101182) and from Chinese Academy of Sciences (KSCX2-EW-R-05, KJZD-EW-L08). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD
- …